Performance information

• Low magnetic field effects on a photoinduced electron transfer reaction in an ionic liquid　　　　　　　　　　　　　　　
  Nanshi Harada; Taisuke Matsuo; Tomoaki Yago; Kiminori Maeda; Masanobu Wakasa
  Chemical Physics Letters, Volume：773, First page：138569, Last page：138569, Jun. 2021
  Elsevier {BV}, English, Scientific journal
  DOI：https://doi.org/10.1016/j.cplett.2021.138569
  DOI ID：10.1016/j.cplett.2021.138569, ISSN：0009-2614, ORCID：106571386
• Gigantic Magnetic Field Effect on the Long-Lived Intermolecular Charge-Separated State Created at the Nonionic Bilayer Membrane
  Tomoaki Miura; Kiminori Maeda; Yoshimi Oka; Tadaaki Ikoma
  The Journal of Physical Chemistry B, Volume：122, Number：50, First page：12173, Last page：12183, Dec. 2018, [Reviewed]
  American Chemical Society ({ACS}), Scientific journal
  DOI：https://doi.org/10.1021/acs.jpcb.8b08389
  DOI ID：10.1021/acs.jpcb.8b08389, ISSN：1520-6106, eISSN：1520-5207, ORCID：51231052
• Millitesla magnetic field effects on the photocycle of an animal cryptochrome　　　　　　　　　　　　　　　
  Dean M. W. Sheppard; Jing Li; Kevin B. Henbest; Simon R. T. Neil; Kiminori Maeda; Jonathan Storey; Erik Schleicher; Till Biskup; Ryan Rodriguez; Stefan Weber; P. J. Hore; Christiane R. Timmel; Stuart R. Mackenzie
  SCIENTIFIC REPORTS, Volume：7, Feb. 2017, [Reviewed]
  Drosophila have been used as model organisms to explore both the biophysical mechanisms of animal magnetoreception and the possibility that weak, low-frequency anthropogenic electromagnetic fields may have biological consequences. In both cases, the presumed receptor is cryptochrome, a protein thought to be responsible for magnetic compass sensing in migratory birds and a variety of magnetic behavioural responses in insects. Here, we demonstrate that photo-induced electron transfer reactions in Drosophila melanogaster cryptochrome are indeed influenced by magnetic fields of a few millitesla. The form of the protein containing flavin and tryptophan radicals shows kinetics that differ markedly from those of closely related members of the cryptochrome-photolyase family. These differences and the magnetic sensitivity of Drosophila cryptochrome are interpreted in terms of the radical pair mechanism and a photocycle involving the recently discovered fourth tryptophan electron donor.
  NATURE PUBLISHING GROUP, English, Scientific journal
  DOI：https://doi.org/10.1038/srep42228
  DOI ID：10.1038/srep42228, ISSN：2045-2322, Web of Science ID：WOS:000393575500001
• Long-Distance Sequential Charge Separation at Micellar Interface Mediated by Dynamic Charge Transporter: A Magnetic Field Effect Study　　　　　　　　　　　　　　　
  Miura Tomoaki; Maeda Kiminori; Murai Hisao; Ikoma Tadaaki
  JOURNAL OF PHYSICAL CHEMISTRY LETTERS, Volume：6, Number：2, First page：267, Last page：271, Jan. 2015, [Reviewed]
  American Chemical Society (ACS), Scientific journal
  DOI：https://doi.org/10.1021/jz502495u
  DOI ID：10.1021/jz502495u, ISSN：1948-7185, Web of Science ID：WOS:000348093300010
• Sensitive fluorescence-based detection of magnetic field effects in photoreactions of flavins　　　　　　　　　　　　　　　
  Emrys W. Evans; Jing Li; Jonathan G. Storey; Kiminori Maeda; Kevin B. Henbest; Charlotte A. Dodson; P. J. Hore; Stuart R. Mackenzie; Christiane R. Timmel
  PHYSICAL CHEMISTRY CHEMICAL PHYSICS, Volume：17, Number：28, First page：18456, Last page：18463, 2015, [Reviewed]
  Magnetic field effect studies have been conducted on a variety of flavin-based radical pair systems chosen to model the magnetosensitivity of the photoinduced radical pairs found in cryptochrome flavoproteins. Cryptochromes are blue-light photoreceptor proteins which are thought to mediate avian magnetoreception, an hypothesis supported by recent in vitro observations of magnetic field-dependent reaction kinetics for a light-induced radical pair in a cryptochrome from the plant Arabidopsis thaliana. Many cryptochromes are difficult to express in large quantities or high concentrations and are easily photodegraded. Magnetic field effects are typically measured by spectroscopic detection of the transient radical (pair) concentrations. Due to its low sensitivity, single-pass transient absorption spectroscopy can be of limited use in such experiments and much recent work has involved development of other methodologies offering improved sensitivity. Here we explore the use of flavin fluorescence as the magnetosensitive probe and demonstrate the exceptional sensitivity of this technique which allows the detection of magnetic field effects in flavin samples at sub-nanomolar concentrations and in cryptochromes.
  ROYAL SOC CHEMISTRY, English, Scientific journal
  DOI：https://doi.org/10.1039/c5cp00723b
  DOI ID：10.1039/c5cp00723b, ISSN：1463-9076, eISSN：1463-9084, Web of Science ID：WOS:000357808500028
• Fluorescence-detected magnetic field effects on radical pair reactions from femtolitre volumes　　　　　　　　　　　　　　　
  C. A. Dodson; C. J. Wedge; M. Murakami; K. Maeda; M. I. Wallace; P. J. Hore
  CHEMICAL COMMUNICATIONS, Volume：51, Number：38, First page：8023, Last page：8026, 2015, [Reviewed]
  We show that the effects of applied magnetic fields on radical pair reactions can be sensitively measured from sample volumes as low as similar to 100 femtolitres using total internal reflection fluorescence microscopy. Development of a fluorescence-based microscope method is likely to be a key step in further miniaturisation that will allow detection of magnetic field effects on single molecules.
  ROYAL SOC CHEMISTRY, English, Scientific journal
  DOI：https://doi.org/10.1039/c5cc01099c
  DOI ID：10.1039/c5cc01099c, ISSN：1359-7345, eISSN：1364-548X, Web of Science ID：WOS:000353639600007
• Probing a chemical compass: novel variants of low-frequency reaction yield detected magnetic resonance　　　　　　　　　　　　　　　
  Kiminori Maeda; Jonathan G. Storey; Paul A. Liddell; Devens Gust; P. J. Hore; C. J. Wedge; Christiane R. Timmel
  PHYSICAL CHEMISTRY CHEMICAL PHYSICS, Volume：17, Number：5, First page：3550, Last page：3559, 2015, [Reviewed]
  We present a study of a carotenoid-porphyrin-fullerene triad previously shown to function as a chemical compass: the photogenerated carotenoid-fullerene radical pair recombines at a rate sensitive to the orientation of an applied magnetic field. To characterize the system we develop a time-resolved Low-Frequency Reaction Yield Detected Magnetic Resonance (tr-LF-RYDMR) technique; the effect of varying the relative orientation of applied static and 36 MHz oscillating magnetic fields is shown to be strongly dependent on the strength of the oscillating magnetic field. RYDMR is a diagnostic test for involvement of the radical pair mechanism in the magnetic field sensitivity of reaction rates or yields, and has previously been applied in animal behavioural experiments to verify the involvement of radical-pair-based intermediates in the magnetic compass sense of migratory birds. The spectroscopic selection rules governing RYDMR are well understood at microwave frequencies for which the so-called 'high-field approximation' is valid, but at lower frequencies different models are required. For example, the breakdown of the rotating frame approximation has recently been investigated, but less attention has so far been given to orientation effects. Here we gain physical insights into the interplay of the different magnetic interactions affecting low-frequency RYDMR experiments performed in the challenging regime in which static and oscillating applied magnetic fields as well as internal electron-nuclear hyperfine interactions are of comparable magnitude. Our observations aid the interpretation of existing RYDMR-based animal behavioural studies and will inform future applications of the technique to verify and characterize further the biological receptors involved in avian magnetoreception.
  ROYAL SOC CHEMISTRY, English, Scientific journal
  DOI：https://doi.org/10.1039/c4cp04095c
  DOI ID：10.1039/c4cp04095c, ISSN：1463-9076, eISSN：1463-9084, Web of Science ID：WOS:000348203200067
• Broadband Cavity-Enhanced Detection of Magnetic Field Effects in Chemical Models of a Cryptochrome Magnetoreceptor　　　　　　　　　　　　　　　
  Simon R. T. Neil; Jing Li; Dean M. W. Sheppard; Jonathan Storey; Kiminori Maeda; Kevin B. Henbest; P. J. Hore; Christiane R. Timmel; Stuart R. Mackenzie
  JOURNAL OF PHYSICAL CHEMISTRY B, Volume：118, Number：15, First page：4177, Last page：4184, Apr. 2014, [Reviewed]
  Broadband cavity-enhanced absorption spectroscopy (BBCEAS) is shown to be a sensitive method for the detection of magnetic field effects (MFEs) in two flavin-based chemical reactions which are simple models for cryptochrome magnetoreceptors. The advantages of optical cavity-based detection and (pseudo-white-light) super-continuum radiation have been combined to provide full spectral coverage across the whole of the visible spectrum (425 < lambda < 700 nm). This region covers the absorbance spectra of Flavin mononucleotide (FMN) and flavin adenine dinucleotide (FAD) as well as their photogenerated radicals. To illustrate the power of this technique, BBCEAS has been used to record the spectral dependence of MFEs for photoinduced radical pairs formed in the intermolecular reaction of FMN with lysozyme and the intramolecular photochemistry of FAD. These reactions have been chosen for their photochemical similarities to cryptochrome proteins which have been proposed as key to the magnetic compass sense of many animals including birds. In experiments performed using low protein concentrations (10 mu M) and 1 mm optical path-lengths, absorbance changes as small as 1 x 10(-7) (representing <0.1% MFEs) have been detected with good signal-to-noise offering the prospect of sensitive MFE detection in cryptochrome.
  AMER CHEMICAL SOC, English, Scientific journal
  DOI：https://doi.org/10.1021/jp500732u
  DOI ID：10.1021/jp500732u, ISSN：1520-6106, Web of Science ID：WOS:000334731300015
• Spin-selective recombination reactions of radical pairs: Experimental test of validity of reaction operators　　　　　　　　　　　　　　　
  Kiminori Maeda; Paul Liddell; Devens Gust; P. J. Hore
  JOURNAL OF CHEMICAL PHYSICS, Volume：139, Number：23, Dec. 2013, [Reviewed]
  Spin-selective reactions of radical pairs are conventionally modelled using an approach that dates back to the 1970s [R. Haberkorn, Mol. Phys. 32, 1491 (1976)]. An alternative approach based on the theory of quantum measurements has recently been suggested [J. A. Jones and P. J. Hore, Chem. Phys. Lett. 488, 90 (2010)]. We present here the first experimental attempt to discriminate between the two models. Pulsed electron paramagnetic resonance spectroscopy has been used to investigate intramolecular electron transfer in the radical pair form of a carotenoid-porphyrin-fullerene molecular triad. The rate of spin-spin relaxation of the fullerene radical in the triad was found to be inconsistent with the quantum measurement description of the spin-selective kinetics, and in accord with the conventional model when combined with spin-dephasing caused by rotational modulation of the anisotropic g-tensor of the fullerene radical. (C) 2013 AIP Publishing LLC.
  AMER INST PHYSICS, English, Scientific journal
  DOI：https://doi.org/10.1063/1.4844355
  DOI ID：10.1063/1.4844355, ISSN：0021-9606, eISSN：1089-7690, Web of Science ID：WOS:000329191300024
• Electron Tunneling in Lithium-Ammonia Solutions Probed by Frequency-Dependent Electron Spin Relaxation Studies　　　　　　　　　　　　　　　
  Kiminori Maeda; Matthew T. J. Lodge; Jeffrey Harmer; Jack H. Freed; Peter P. Edwards
  JOURNAL OF THE AMERICAN CHEMICAL SOCIETY, Volume：134, Number：22, First page：9209, Last page：9218, Jun. 2012, [Reviewed]
  Electron transfer or quantum tunneling dynamics for excess or solvated electrons in dilute lithium-ammonia solutions have been studied by pulse electron paramagnetic resonance (EPR) spectroscopy at both X- (9.7 GHz) and W-band (94 GHz) frequencies. The electron spin-lattice (T-1) and spin-spin (T-2) relaxation data indicate an extremely fast transfer or quantum tunneling rate of the solvated electron in these solutions which serves to modulate the hyperfine (Fermi-contact) interaction with nitrogen nuclei in the solvation shells of ammonia molecules surrounding the localized, solvated electron. The donor and acceptor states of the solvated electron in these solutions are the initial and final electron solvation sites found before, and after, the transfer or tunneling process. To interpret and model our electron spin relaxation data from the two observation EPR frequencies requires a consideration of a multiexponential correlation function. The electron transfer or tunneling process that we monitor through the correlation time of the nitrogen Fermi-contact interaction has a time scale of (1-10) x 10(-12) s over a temperature range 230-290 K in our most dilute solution of lithium in ammonia. Two types of electron-solvent interaction mechanisms are proposed to account for our experimental findings. The dominant electron spin relaxation mechanism results from an electron tunneling process characterized by a variable donor-acceptor distance or range (consistent with such a rapidly fluctuating liquid structure) in which the solvent shell that ultimately accepts the transferring electron is formed from random, thermal fluctuations of the liquid structure in, and around, a natural hole or Bjerrum-like defect vacancy in the liquid. Following transfer and capture of the tunneling electron, further solvent-cage relaxation with a time scale of similar to 10(-13) s results in a minor contribution to the electron spin relaxation times. This investigation illustrates the great potential of multifrequency EPR measurements to interrogate the microscopic nature and dynamics of ultrafast electron transfer or quantum-tunneling processes in liquids. Our results also impact on the universal issue of the role of a host solvent (or host matrix, e.g. a semiconductor) in mediating long-range electron transfer processes and we discuss the implications of our results with a range of other materials and systems exhibiting the phenomenon of electron transfer.
  AMER CHEMICAL SOC, English, Scientific journal
  DOI：https://doi.org/10.1021/ja212015b
  DOI ID：10.1021/ja212015b, ISSN：0002-7863, J-Global ID：201202208927395107, Web of Science ID：WOS:000304837800042
• Magnetically sensitive light-induced reactions in cryptochrome are consistent with its proposed role as a magnetoreceptor　　　　　　　　　　　　　　　
  Kiminori Maeda; Alexander J. Robinson; Kevin B. Henbest; Hannah J. Hogben; Till Biskup; Margaret Ahmad; Erik Schleicher; Stefan Weber; Christiane R. Timmel; P. J. Hore
  PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF THE UNITED STATES OF AMERICA, Volume：109, Number：13, First page：4774, Last page：4779, Mar. 2012, [Reviewed]
  Among the biological phenomena that fall within the emerging field of "quantum biology" is the suggestion that magnetically sensitive chemical reactions are responsible for the magnetic compass of migratory birds. It has been proposed that transient radical pairs are formed by photo-induced electron transfer reactions in cryptochrome proteins and that their coherent spin dynamics are influenced by the geomagnetic field leading to changes in the quantum yield of the signaling state of the protein. Despite a variety of supporting evidence, it is still not clear whether cryptochromes have the properties required to respond to magnetic interactions orders of magnitude weaker than the thermal energy, k(B)T. Here we demonstrate that the kinetics and quantum yields of photo-induced flavin-tryptophan radical pairs in cryptochrome are indeed magnetically sensitive. The mechanistic origin of the magnetic field effect is clarified, its dependence on the strength of the magnetic field measured, and the rates of relevant spin-dependent, spin-independent, and spin-decoherence processes determined. We argue that cryptochrome is fit for purpose as a chemical magnetoreceptor.
  NATL ACAD SCIENCES, English, Scientific journal
  DOI：https://doi.org/10.1073/pnas.1118959109
  DOI ID：10.1073/pnas.1118959109, ISSN：0027-8424, J-Global ID：201202204192769240, Web of Science ID：WOS:000302164200021
• Following Radical Pair Reactions in Solution: A Step Change in Sensitivity Using Cavity Ring-Down Detection　　　　　　　　　　　　　　　
  Kiminori Maeda; Simon R. T. Neil; Kevin B. Henbest; Stefan Weber; Erik Schleicher; P. J. Hore; Stuart R. Mackenzie; Christiane R. Timmel
  JOURNAL OF THE AMERICAN CHEMICAL SOCIETY, Volume：133, Number：44, First page：17807, Last page：17815, Nov. 2011, [Reviewed]
  The study of radical pair intermediates biological. systems has been hampered by the low sensitivity of the optical techniques usually employed to investigate these highly reactive species. Understanding the physical principles governing the spin-selective and magneto-sensitive yields and kinetics of their reactions is essential in identifying the mechanism governing bird migration, and might have significance in the discussion of potential health hazards of electromagnetic radiation. Here, we demonstrate the powerful capabilities of optical cavity-enhanced techniques, such as cavity ring-down spectroscopy (CRDS) in monitoring radical recombination reactions and associated magnetic field effects (MFEs). These include submicrosecond time-resolution, high sensitivity (baseline noise on the order of 10(-6) absorbance units) and small (mu L) sample volumes. Combined, we show that these represent significant advantages over the single pass flash photolysis techniques conventionally applied. The studies described here focus on photoinduced radical pair reactions involving the protein lysozyme and one of two possible photosensitizers: anthraquinone-2,6-disulphonate and flavin mononucleotide CRDS-measured MFEs are observed; in pump probe experiments and discussed in terms of the sensitivity gains and sample volume minimization afforded by CRDS when compared with flash photolysis method's. Finally, CRDS is applied to an in vitro MFE study of intramolecular electron transfer in the DNA repair enzyme, Escherichia coli photolyase, a protein closely related to cryptochrome which has been proposed to mediate animal magnetoreception,
  AMER CHEMICAL SOC, English, Scientific journal
  DOI：https://doi.org/10.1021/ja206783t
  DOI ID：10.1021/ja206783t, ISSN：0002-7863, J-Global ID：201102206317486429, Web of Science ID：WOS:000296312200049
• Following Radical Pair Reactions in Solution: A Step Change in Sensitivity Using Cavity Ring-Down Detection　　　　　　　　　　　　　　　
  Kiminori Maeda; Simon R. T. Neil; Kevin B. Henbest; Stefan Weber; Erik Schleicher; P. J. Hore; Stuart R. Mackenzie; Christiane R. Timmel
  JOURNAL OF THE AMERICAN CHEMICAL SOCIETY, Volume：133, Number：44, First page：17807, Last page：17815, Nov. 2011, [Reviewed]
  The study of radical pair intermediates biological. systems has been hampered by the low sensitivity of the optical techniques usually employed to investigate these highly reactive species. Understanding the physical principles governing the spin-selective and magneto-sensitive yields and kinetics of their reactions is essential in identifying the mechanism governing bird migration, and might have significance in the discussion of potential health hazards of electromagnetic radiation. Here, we demonstrate the powerful capabilities of optical cavity-enhanced techniques, such as cavity ring-down spectroscopy (CRDS) in monitoring radical recombination reactions and associated magnetic field effects (MFEs). These include submicrosecond time-resolution, high sensitivity (baseline noise on the order of 10(-6) absorbance units) and small (mu L) sample volumes. Combined, we show that these represent significant advantages over the single pass flash photolysis techniques conventionally applied. The studies described here focus on photoinduced radical pair reactions involving the protein lysozyme and one of two possible photosensitizers: anthraquinone-2,6-disulphonate and flavin mononucleotide CRDS-measured MFEs are observed; in pump probe experiments and discussed in terms of the sensitivity gains and sample volume minimization afforded by CRDS when compared with flash photolysis method's. Finally, CRDS is applied to an in vitro MFE study of intramolecular electron transfer in the DNA repair enzyme, Escherichia coli photolyase, a protein closely related to cryptochrome which has been proposed to mediate animal magnetoreception,
  AMER CHEMICAL SOC, English, Scientific journal
  DOI：https://doi.org/10.1021/ja206783t
  DOI ID：10.1021/ja206783t, ISSN：0002-7863, PubMed ID：21932826, Web of Science ID：WOS:000296312200049
• Reaction operators for spin-selective chemical reactions of radical pairs　　　　　　　　　　　　　　　
  J. A. Jones; Kiminori Maeda; P. J. Hore
  CHEMICAL PHYSICS LETTERS, Volume：507, Number：4-6, First page：269, Last page：273, May 2011
  Spin-selective reactions of radical pairs have traditionally been modelled theoretically by adding phenomenological rate equations to the quantum mechanical equation of motion of the radical pair spin density matrix. More recently an alternative set of rate expressions, based on a quantum measurement approach, has been suggested. Here we show how these two reaction operators can be seen as limiting cases of a more general reaction scheme. (C) 2011 Elsevier B.V. All rights reserved.
  ELSEVIER SCIENCE BV, English, Scientific journal
  DOI：https://doi.org/10.1016/j.cplett.2011.03.082
  DOI ID：10.1016/j.cplett.2011.03.082, ISSN：0009-2614, J-Global ID：201102253022965099, Web of Science ID：WOS:000290018500013
• Reply to Comment on 'Spin-selective reactions of radical pairs act as quantum measurements'　　　　　　　　　　　　　　　
  J. A. Jones; Kiminori Maeda; U. E. Steiner; P. J. Hore
  CHEMICAL PHYSICS LETTERS, Volume：508, Number：1-3, First page：184, Last page：185, May 2011, [Reviewed]
  In his Comment on a recent paper by two of us Kominis claims that the recently proposed quantum measurement model for spin-selective reactions of radical pairs leads to ambiguous predictions in a simple case. Here we show that this claim is based on a confusion between the unreacted and unrecombined portions of the radical pairs, and to an incorrect interpretation of the improper density matrices used in both our model and the conventional Haberkorn model of such reactions. We further show that if this error is corrected then the supposed ambiguity is resolved. (C) 2011 Elsevier B.V. All rights reserved.
  ELSEVIER SCIENCE BV, English
  DOI：https://doi.org/10.1016/j.cplett.2011.04.022
  DOI ID：10.1016/j.cplett.2011.04.022, ISSN：0009-2614, eISSN：1873-4448, Web of Science ID：WOS:000290298200037
• Spin-selective recombination kinetics of a model chemical magnetoreceptor　　　　　　　　　　　　　　　
  Kiminori Maeda; Christopher J. Wedge; Jonathan G. Storey; Kevin B. Henbest; Paul A. Liddell; Gerdenis Kodis; Devens Gust; P. J. Hore; Christiane R. Timmel
  CHEMICAL COMMUNICATIONS, Volume：47, Number：23, First page：6563, Last page：6565, 2011, [Reviewed]
  We determine the spin-selective kinetics of a carotenoid-porphyrin-fullerene triad that has previously been used to establish the principle that a photochemical reaction could form the basis of the magnetic compass sensor of migratory birds and show that its magnetic sensitivity can be understood without invoking quantum Zeno effects.
  ROYAL SOC CHEMISTRY, English, Scientific journal
  DOI：https://doi.org/10.1039/c1cc11625h
  DOI ID：10.1039/c1cc11625h, ISSN：1359-7345, Web of Science ID：WOS:000291113000010
• Consistent Treatment of Spin-Selective Recombination of a Radical Pair Confirms the Haberkorn Approach　　　　　　　　　　　　　　　
  Konstantin L. Ivanov; Marina V. Petrova; Nikita N. Lukzen; Kiminori Maeda
  JOURNAL OF PHYSICAL CHEMISTRY A, Volume：114, Number：35, First page：9447, Last page：9455, Sep. 2010, [Reviewed]
  In the present work, we have shown that consistent derivation of the kinetic equations describing the electron spin-selective recombination of radical pairs confirms the conventional Haberkorn approach. The derivation has been based on considering the interaction of the reactive system (radical pair and product state) with. the thermal bath. The consistency of this approach has also been substantiated by numerical simulations performed for the purely quantum mechanical model of the recombining radical pair. Finally, we have shown that the quantum Zeno effect on radical pair recombination is not an exclusive feature of the approach recently proposed by Kominis, as it should be present at any rate of the singlet-triplet dephasing in the radical pair, which always accompanies the recombination process.
  AMER CHEMICAL SOC, English, Scientific journal
  DOI：https://doi.org/10.1021/jp1048265
  DOI ID：10.1021/jp1048265, ISSN：1089-5639, CiNii Articles ID：80021269496, PubMed ID：20704353, Web of Science ID：WOS:000281404400005
• Entangling Remote Nuclear Spins Linked by a Chromophore　　　　　　　　　　　　　　　
  M. Schaffry; V. Filidou; S. D. Karlen; E. M. Gauger; S. C. Benjamin; H. L. Anderson; A. Ardavan; G. A. D. Briggs; K. Maeda; K. B. Henbest; F. Giustino; J. J. L. Morton; B. W. Lovett
  PHYSICAL REVIEW LETTERS, Volume：104, Number：20, First page：200501, Last page：200504, May 2010, [Reviewed]
  Molecular nanostructures may constitute the fabric of future quantum technologies, if their degrees of freedom can be fully harnessed. Ideally one might use nuclear spins as low-decoherence qubits and optical excitations for fast controllable interactions. Here, we present a method for entangling two nuclear spins through their mutual coupling to a transient optically excited electron spin, and investigate its feasibility through density-functional theory and experiments on a test molecule. From our calculations we identify the specific molecular properties that permit high entangling power gates under simple optical and microwave pulses; synthesis of such molecules is possible with established techniques.
  AMER PHYSICAL SOC, English, Scientific journal
  DOI：https://doi.org/10.1103/PhysRevLett.104.200501
  DOI ID：10.1103/PhysRevLett.104.200501, ISSN：0031-9007, Web of Science ID：WOS:000277945900004
• Protein Surface Interactions Probed by Magnetic Field Effects on Chemical Reactions　　　　　　　　　　　　　　　
  Kiminori Maeda; Alexander J. Robinson; Kevin B. Henbest; Emma J. Dell; Christiane R. Timmel
  JOURNAL OF THE AMERICAN CHEMICAL SOCIETY, Volume：132, Number：5, First page：1466, Last page：+, Feb. 2010
  Here we have employed the effects of weak static magnetic fields (not exceeding 46 mT) on radical recombination reactions to investigate protein-substrate interactions. Pulsed laser excitation of an aqueous solution of anthraquinone-2,6-disulfonate (AQDS(2-)) and either hen egg white lysozyme (HEWL) or bovine serum albumin (BSA) produces the triplet state of the radical pair (T)[AQDS(3-center dot) Trp(center dot)] by a photoinduced electron transfer reaction from tryptophan residues. Time-resolved absorption techniques were employed to study the recombination characteristics of these radical pairs at different static magnetic fields and ionic strengths. The experimental data in connection with the simulated curves unequivocally show that the radical pair has a lifetime of the order of microseconds in both systems (HEWL and BSA). However, the radical pair is embedded within a binding pocket of the BSA protein, while the (otherwise identical) radical pair, being subject to attractive Coulomb forces, resides on the protein surface in the HEWL system.
  AMER CHEMICAL SOC, English, Scientific journal
  DOI：https://doi.org/10.1021/ja908988u
  DOI ID：10.1021/ja908988u, ISSN：0002-7863, Web of Science ID：WOS:000275084900011
• Protein Surface Interactions Probed by Magnetic Field Effects on Chemical Reactions　　　　　　　　　　　　　　　
  Kiminori Maeda; Alexander J. Robinson; Kevin B. Henbest; Emma J. Dell; Christiane R. Timmel
  JOURNAL OF THE AMERICAN CHEMICAL SOCIETY, Volume：132, Number：5, First page：1466, Last page：+, Feb. 2010, [Reviewed]
  Here we have employed the effects of weak static magnetic fields (not exceeding 46 mT) on radical recombination reactions to investigate protein-substrate interactions. Pulsed laser excitation of an aqueous solution of anthraquinone-2,6-disulfonate (AQDS(2-)) and either hen egg white lysozyme (HEWL) or bovine serum albumin (BSA) produces the triplet state of the radical pair (T)[AQDS(3-center dot) Trp(center dot)] by a photoinduced electron transfer reaction from tryptophan residues. Time-resolved absorption techniques were employed to study the recombination characteristics of these radical pairs at different static magnetic fields and ionic strengths. The experimental data in connection with the simulated curves unequivocally show that the radical pair has a lifetime of the order of microseconds in both systems (HEWL and BSA). However, the radical pair is embedded within a binding pocket of the BSA protein, while the (otherwise identical) radical pair, being subject to attractive Coulomb forces, resides on the protein surface in the HEWL system.
  AMER CHEMICAL SOC, English, Scientific journal
  DOI：https://doi.org/10.1021/ja908988u
  DOI ID：10.1021/ja908988u, ISSN：0002-7863, PubMed ID：20085319, Web of Science ID：WOS:000275084900011
• Effect of magnetic fields on cryptochrome-dependent responses in Arabidopsis thaliana　　　　　　　　　　　　　　　
  Sue-Re Harris; Kevin B. Henbest; Kiminori Maeda; John R. Pannell; Christiane R. Timmel; P. J. Hore; Haruko Okamoto
  JOURNAL OF THE ROYAL SOCIETY INTERFACE, Volume：6, Number：41, First page：1193, Last page：1205, Dec. 2009, [Reviewed]
  The scientific literature describing the effects of weak magnetic fields on living systems contains a plethora of contradictory reports, few successful independent replication studies and a dearth of plausible biophysical interaction mechanisms. Most such investigations have been unsystematic, devoid of testable theoretical predictions and, ultimately, unconvincing. A recent study, of magnetic responses in the model plant Arabidopsis thaliana, however, stands out; it has a clear hypothesis-that seedling growth is magnetically sensitive as a result of photoinduced radical-pair reactions in cryptochrome photoreceptors-tested by measuring several cryptochrome-dependent responses, all of which proved to be enhanced in a magnetic field of intensity 500 mu T. The potential importance of this study in the debate on putative effects of extremely low-frequency electromagnetic fields on human health prompted us to subject it to the 'gold standard' of independent replication. With experimental conditions chosen to match those of the original study, we have measured hypocotyl lengths and anthocyanin accumulation for Arabidopsis seedlings grown in a 500 mu T magnetic field, with simultaneous control experiments at 50 mu T. Additionally, we have determined hypocotyl lengths of plants grown in 50 mu T, 1 mT and approximately 100 mT magnetic fields (with zero-field controls), measured gene (CHS, HY5 and GST) expression levels, investigated blue-light intensity effects and explored the influence of sucrose in the growth medium. In no case were consistent, statistically significant magnetic field responses detected.
  ROYAL SOC, English, Scientific journal
  DOI：https://doi.org/10.1098/rsif.2008.0519
  DOI ID：10.1098/rsif.2008.0519, ISSN：1742-5689, PubMed ID：19324677, Web of Science ID：WOS:000271464500008
• 2SA1-07 Does a migrating bird watch the earth magnetic field?(2SA1 Electron Spin Resonance on Biophysics -The Next Generation-,The 47th Annual Meeting of the Biophysical Society of Japan)　　　　　　　　　　　　　　　
  Maeda Kiminori
  Biophysics, Volume：49, Number：1, First page：S10, Last page：S11, Sep. 2009
  The Biophysical Society of Japan, English
  DOI：https://doi.org/10.2142/biophys.49.S10_6
  DOI ID：10.2142/biophys.49.S10_6, ISSN：0582-4052, CiNii Articles ID：110008100996
• Refolding of ribonuclease A monitored by real-time photo-CIDNP NMR spectroscopy　　　　　　　　　　　　　　　
  Iain J. Day; Kiminori Maeda; Howard J. Paisley; K. Hun Mok; P. J. Hore
  JOURNAL OF BIOMOLECULAR NMR, Volume：44, Number：2, First page：77, Last page：86, Jun. 2009, [Reviewed]
  Photo-CIDNP NMR spectroscopy is a powerful method for investigating the solvent accessibility of histidine, tyrosine and tryptophan residues in a protein. When coupled to real-time NMR, this technique allows changes in the environments of these residues to be used as a probe of protein folding. In this paper we describe experiments performed to monitor the refolding of ribonuclease A following dilution from a high concentration of chemical denaturant. These experiments provide a good example of the utility of this technique which provides information that is difficult to obtain by other biophysical methods. Real-time photo-CIDNP measurements yield residue-specific kinetic data pertaining to the folding reaction, interpreted in terms of current knowledge of the folding of bovine pancreatic ribonuclease A.
  SPRINGER, English, Scientific journal
  DOI：https://doi.org/10.1007/s10858-009-9322-2
  DOI ID：10.1007/s10858-009-9322-2, ISSN：0925-2738, eISSN：1573-5001, PubMed ID：19436956, Web of Science ID：WOS:000266140600003
• Radiofrequency polarization effects in zero-field electron paramagnetic resonance　　　　　　　　　　　　　　　
  Christopher T. Rodgers; C. J. Wedge; Stuart A. Norman; Philipp Kukura; Karen Nelson; Neville Baker; Kiminori Maeda; Kevin B. Henbest; P. J. Hore; C. R. Timmel
  PHYSICAL CHEMISTRY CHEMICAL PHYSICS, Volume：11, Number：31, First page：6569, Last page：6572, 2009
  Optically detected zero-field electron paramagnetic resonance spectroscopy is used to show that weak linearly and circularly polarized radiofrequency magnetic fields affect the recombination reactions of spin-correlated radical pairs to different extents; the spectra are shown to be consistent with the radical pair mechanism.
  ROYAL SOC CHEMISTRY, English, Scientific journal
  DOI：https://doi.org/10.1039/b906102a
  DOI ID：10.1039/b906102a, ISSN：1463-9076, Web of Science ID：WOS:000268481200003
• Radiofrequency polarization effects in low-field electron paramagnetic resonance　　　　　　　　　　　　　　　
  C. J. Wedge; Christopher T. Rodgers; Stuart A. Norman; Neville Baker; Kiminori Maeda; Kevin B. Henbest; C. R. Timmel; P. J. Hore
  PHYSICAL CHEMISTRY CHEMICAL PHYSICS, Volume：11, Number：31, First page：6573, Last page：6579, 2009
  Low-field optically detected EPR spectra of photochemically formed transient radical ion pairs are reported for weak circularly and linearly polarized radiofrequency (RF) fields. The spectra are found to be strongly dependent on the polarization and frequency of the RF field and on the angle between the static magnetic field and the plane containing the RF field. The spectra are discussed in terms of resonances arising from Zeeman and hyperfine interactions; the conditions for validity of the rotating frame approximation are determined. Knowledge of the latter is important when using low-field EPR as a diagnostic test for the operation of the radical pair mechanism.
  ROYAL SOC CHEMISTRY, English, Scientific journal
  DOI：https://doi.org/10.1039/b907915g
  DOI ID：10.1039/b907915g, ISSN：1463-9076, Web of Science ID：WOS:000268481200004
• SQUID magnetometry as a tool for following a clock reaction in solution　　　　　　　　　　　　　　　
  Robert Evans; Kevin B. Henbest; Michael A. Hayward; Melanie M. Britton; Kiminori Maeda; Christiane R. Timmel
  DALTON TRANSACTIONS, Number：14, First page：2467, Last page：2469, 2009, [Reviewed]
  SQUID magnetometry, normally used to characterise the properties of solids, was used to follow a clock reaction in solution, namely the auto-catalytic oxidation of [Co(II) EDTA](2-) by H(2)O(2), in real time and it was shown that, in combination with other methods (e. g., magnetic resonance proton relaxation studies and UV-vis absorption analysis), SQUID magnetometry can be a powerful method in elucidating and interpreting the time-profile of chemical reactions so as long as reactants, intermediates and products have suitably large differences in their respective magnetic susceptibilities.
  ROYAL SOC CHEMISTRY, English, Scientific journal
  DOI：https://doi.org/10.1039/b819977a
  DOI ID：10.1039/b819977a, ISSN：1477-9226, CiNii Articles ID：80020372064, PubMed ID：19319389, Web of Science ID：WOS:000264555200002
• Quenching Mechanisms and Diffusional Pathways in Micellar Systems Unravelled by Time-Resolved Magnetic-Field Effects　　　　　　　　　　　　　　　
  Martin Goez; Kevin B. Henbest; Emma G. Windham; Kiminori Maeda; Christiane R. Timmel
  CHEMISTRY-A EUROPEAN JOURNAL, Volume：15, Number：24, First page：6058, Last page：6064, 2009, [Reviewed]
  WILEY-V C H VERLAG GMBH, English, Scientific journal
  DOI：https://doi.org/10.1002/chem.200802502
  DOI ID：10.1002/chem.200802502, ISSN：0947-6539, CiNii Articles ID：80020387734, PubMed ID：19405051, Web of Science ID：WOS:000267278900024
• Radiofrequency polarization effects in zero-field electron paramagnetic resonance　　　　　　　　　　　　　　　
  Christopher T. Rodgers; C. J. Wedge; Stuart A. Norman; Philipp Kukura; Karen Nelson; Neville Baker; Kiminori Maeda; Kevin B. Henbest; P. J. Hore; C. R. Timmel
  PHYSICAL CHEMISTRY CHEMICAL PHYSICS, Volume：11, Number：31, First page：6569, Last page：6572, 2009, [Reviewed]
  Optically detected zero-field electron paramagnetic resonance spectroscopy is used to show that weak linearly and circularly polarized radiofrequency magnetic fields affect the recombination reactions of spin-correlated radical pairs to different extents; the spectra are shown to be consistent with the radical pair mechanism.
  ROYAL SOC CHEMISTRY, English, Scientific journal
  DOI：https://doi.org/10.1039/b906102a
  DOI ID：10.1039/b906102a, ISSN：1463-9076, PubMed ID：19639131, Web of Science ID：WOS:000268481200003
• Radiofrequency polarization effects in low-field electron paramagnetic resonance　　　　　　　　　　　　　　　
  C. J. Wedge; Christopher T. Rodgers; Stuart A. Norman; Neville Baker; Kiminori Maeda; Kevin B. Henbest; C. R. Timmel; P. J. Hore
  PHYSICAL CHEMISTRY CHEMICAL PHYSICS, Volume：11, Number：31, First page：6573, Last page：6579, 2009, [Reviewed]
  Low-field optically detected EPR spectra of photochemically formed transient radical ion pairs are reported for weak circularly and linearly polarized radiofrequency (RF) fields. The spectra are found to be strongly dependent on the polarization and frequency of the RF field and on the angle between the static magnetic field and the plane containing the RF field. The spectra are discussed in terms of resonances arising from Zeeman and hyperfine interactions; the conditions for validity of the rotating frame approximation are determined. Knowledge of the latter is important when using low-field EPR as a diagnostic test for the operation of the radical pair mechanism.
  ROYAL SOC CHEMISTRY, English, Scientific journal
  DOI：https://doi.org/10.1039/b907915g
  DOI ID：10.1039/b907915g, ISSN：1463-9076, Web of Science ID：WOS:000268481200004
• Magnetic-field effect on the photoactivation reaction of Escherichia coli DNA photolyase　　　　　　　　　　　　　　　
  Kevin B. Henbest; Kiminori Maeda; P. J. Hore; Monika Joshi; Adelbert Bacher; Robert Bittl; Stefan Weber; Christiane R. Timmel; Erik Schleicher
  PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF THE UNITED STATES OF AMERICA, Volume：105, Number：38, First page：14395, Last page：14399, Sep. 2008, [Reviewed]
  One of the two principal hypotheses put forward to explain the primary magnetoreception event underlying the magnetic compass sense of migratory birds is based on a magnetically sensitive chemical reaction. It has been proposed that a spin-correlated radical pair is produced photochemically in a cryptochrome and that the rates and yields of the subsequent chemical reactions depend on the orientation of the protein in the Earth's magnetic field. The suitability of cryptochrome for this purpose has been argued, in part, by analogy with DNA photolyase, although no effects of applied magnetic fields have yet been reported for any member of the cryptochrome/photolyase family. Here, we demonstrate a magnetic-field effect on the photochemical yield of a flavin-tryptophan radical pair in Escherichia coli photolyase. This result provides a proof of principle that photolyases, and most likely by extension also cryptochromes, have the fundamental properties needed to form the basis of a magnetic compass.
  NATL ACAD SCIENCES, English, Scientific journal
  DOI：https://doi.org/10.1073/pnas.0803620105
  DOI ID：10.1073/pnas.0803620105, ISSN：0027-8424, PubMed ID：18799743, Web of Science ID：WOS:000259592400032
• Chemical compass model of avian magnetoreception　　　　　　　　　　　　　　　
  Kiminori Maeda; Kevin B. Henbest; Filippo Cintolesi; Ilya Kuprov; Christopher T. Rodgers; Paul A. Liddell; Devens Gust; Christiane R. Timmel; P. J. Hore
  NATURE, Volume：453, Number：7193, First page：387, Last page：U38, May 2008, [Reviewed]
  Approximately 50 species, including birds, mammals, reptiles, amphibians, fish, crustaceans and insects, are known to use the Earth's magnetic field for orientation and navigation(1). Birds in particular have been intensively studied, but the biophysical mechanisms that underlie the avian magnetic compass are still poorly understood. One proposal, based on magnetically sensitive free radical reactions(2,3), is gaining support(4-11) despite the fact that no chemical reaction in vitro has been shown to respond to magnetic fields as weak as the Earth's (similar to 50 mu T) or to be sensitive to the direction of such a field. Here we use spectroscopic observation of a carotenoid-porphyrin-fullerene model system to demonstrate that the lifetime of a photochemically formed radical pair is changed by application of <= 50 mu T magnetic fields, and to measure the anisotropic chemical response that is essential for its operation as a chemical compass sensor. These experiments establish the feasibility of chemical magnetoreception and give insight into the structural and dynamic design features required for optimal detection of the direction of the Earth's magnetic field.
  NATURE PUBLISHING GROUP, English, Scientific journal
  DOI：https://doi.org/10.1038/nature06834
  DOI ID：10.1038/nature06834, ISSN：0028-0836, PubMed ID：18449197, Web of Science ID：WOS:000255868400051
• Radical cation stabilization in a cucurbituril oligoaniline rotaxane　　　　　　　　　　　　　　　
  Rienk Eelkema; Kinninori Maeda; Barbara Odell; Harry L. Anderson
  JOURNAL OF THE AMERICAN CHEMICAL SOCIETY, Volume：129, Number：41, First page：12384, Last page：+, Oct. 2007, [Reviewed]
  A cucurbituril-encapsulated oligoaniline rotaxane is synthesized in high yield by reductive amination in aqueous acid. Spectroscopic and electrochemical measurements show that encapsulation by cucurbit[7]uril increases the thermodynamic and kinetic stability of the radical cation of the threaded oligoaniline. This radical cation has a stoichiometry similar to that of the conducting emeraldine salt form of polyaniline, which implies that cucurbituril insulation of polyaniline might drastically alter the oxidation potential of the threaded conjugated polymer chain.
  AMER CHEMICAL SOC, English, Scientific journal
  DOI：https://doi.org/10.1021/ja074997i
  DOI ID：10.1021/ja074997i, ISSN：0002-7863, PubMed ID：17887677, Web of Science ID：WOS:000250105500022
• Chemical Magnetoreception: Bird Cryptochrome 1a Is Excited by Blue Light and Forms Long-Lived Radical-Pairs　　　　　　　　　　　　　　　
  Miriam Liedvogel; Kiminori Maeda; Kevin Henbest; Erik Schleicher; Thomas Simon; Christiane R. Timmel; P. J. Hore; Henrik Mouritsen
  PLOS ONE, Volume：2, Number：10, First page：e1106, Oct. 2007, [Reviewed]
  Cryptochromes (Cry) have been suggested to form the basis of light-dependent magnetic compass orientation in birds. However, to function as magnetic compass sensors, the cryptochromes of migratory birds must possess a number of key biophysical characteristics. Most importantly, absorption of blue light must produce radical pairs with lifetimes longer than about a microsecond. Cryptochrome 1a (gwCry1a) and the photolyase-homology-region of Cry1 (gwCry1-PHR) from the migratory garden warbler were recombinantly expressed and purified from a baculovirus/Sf9 cell expression system. Transient absorption measurements show that these flavoproteins are indeed excited by light in the blue spectral range leading to the formation of radicals with millisecond lifetimes. These biophysical characteristics suggest that gwCry1a is ideally suited as a primary light-mediated, radical-pair-based magnetic compass receptor.
  PUBLIC LIBRARY SCIENCE, English, Scientific journal
  DOI：https://doi.org/10.1371/journal.pone.0001106
  DOI ID：10.1371/journal.pone.0001106, ISSN：1932-6203, PubMed ID：17971869, Web of Science ID：WOS:000207458700023
• The spin mixing process of a radical pair in low magnetic field observed by transient absorption detected nanosecond pulsed magnetic field effect　　　　　　　　　　　　　　　
  Tomoaki Miura; Kiminori Maeda; Tatsuo Arai
  Journal of Physical Chemistry A, Volume：110, Number：12, First page：4151, Last page：4156, Mar. 2006, [Reviewed]
  The spin mixing process of the radical pair in the sodium dodecyl sulfate (SDS) micelle is studied by using a novel technique nanosecond pulsed magnetic field effect on transient absorption. We have developed the equipment for a nanosecond pulsed magnetic field and observed its effect on the radical pair reaction. A decrease of the free radical yield by a reversely directed pulsed magnetic field that cancels static field is observed, and the dependence on its magnitude, which is called pulsed MARY (magnetic field effect on reaction yield) spectra, is studied. The observed spectra reflect the spin mixing in 50-200 ns and show clear time evolution. Theoretical simulation of pulsed MARY spectra based on a single site modified Liouville equation indicates that the fast spin dephasing processes induced by the modulation of electron-electron spin interaction by molecular reencounter affect to the coherent spin mixing by a hyperfine interaction in a low magnetic field. © 2006 American Chemical Society.
  12, English, Scientific journal
  DOI：https://doi.org/10.1021/jp056488d
  DOI ID：10.1021/jp056488d, ISSN：1089-5639, CiNii Articles ID：80019269619, PubMed ID：16553365, SCOPUS ID：33645834369
• Spin dynamics of the radical pair in a low magnetic field studied by the transient absorption detected magnetic field effect on the reaction yield and switched external magnetic field　　　　　　　　　　　　　　　
  Toshiaki Suzuki; Tomoaki Miura; Kiminori Maeda; Tatsuo Arai
  Journal of Physical Chemistry A, Volume：109, Number：44, First page：9911, Last page：9918, Nov. 2005, [Reviewed]
  xxThe spin dynamics of the radical pair generated from the photocleavage reaction of (2,4,6-trimethylbenzoyl)-diphenylphosphine oxide (TMDPO) in micellar solutions was studied by the time-resolved magnetic field effect (MFE) on the transient absorption (TA) and by a novel technique, absorption detected switched external magnetic field (AD-SEMF). Thanks to the large hyperfine coupling constant (A -38 mT), a characteristic negative MFE on the radical yield was observed at a magnetic field lower than 60 mT whereas a positive effect due to the conventional hyperfine (HFM) and relaxation mechanisms (RM) was observed at higher magnetic field. The negative effect can be assigned to the mechanism "so-called" low field effect (LFE) mechanism and has been analyzed thoroughly using a model calculation incorporating a fast spin dephasing process. The time scale of the spin mixing process of LFE studied by AD-SEMF is shorter than the lifetime of the recombination kinetics of the radical pair. These results indicate that the LFE originates from the coherent spin motion. This can be interfered from the fast spin dephasing caused by electron spin interaction fluctuations. © 2005 American Chemical Society.
  44, English, Scientific journal
  DOI：https://doi.org/10.1021/jp053989q
  DOI ID：10.1021/jp053989q, ISSN：1089-5639, CiNii Articles ID：80017727100, SCOPUS ID：28144433162
• Dynamics of intramolecular electron transfer reaction of FAD studied by magnetic field effects on transient absorption spectra　　　　　　　　　　　　　　　
  M Murakami; K Maeda; T Arai
  JOURNAL OF PHYSICAL CHEMISTRY A, Volume：109, Number：26, First page：5793, Last page：5800, Jul. 2005, [Reviewed]
  The kinetics of intermediates generated from intramolecular electron-transfer reaction by photo irradiation of the flavin adenine dinucleotide (FAD) molecule was studied by a magnetic field effect (MFE) on transient absorption (TA) spectra. Existence time of MFE and MFE action spectra have a strong dependence on the pH of solutions. The MFE action spectra have indicated the existence of interconversion between the radical pair and the cation form of the triplet excited state of flavin part. All rate constants of the triplet and the radical pair were determined by analysis of the MFE action spectra and decay kinetics of TA. The obtained values for the interconversion indicate that the formation of cation radical promotes the back electron-transfer reaction to the triplet excited state. Further, rate constants of spin relaxation and recombination have been studied by the time profiles of MFE at various pH. The drastic change of those two factors has been obtained and can be explained by SOC (spin-orbit coupling) induced back electron-transfer promoted by the formation of a stacking conformation at pH > 2.5.
  AMER CHEMICAL SOC, English, Scientific journal
  DOI：https://doi.org/10.1021/jp0519722
  DOI ID：10.1021/jp0519722, ISSN：1089-5639, CiNii Articles ID：80017406565, Web of Science ID：WOS:000230225000004
• 電子-核スピン分極移動と中間体ラジカルの分子内運動　　　　　　　　　　　　　　　
  前田 公憲
  Volume：28, Number：1, First page：47, Last page：48, Aug. 1998
  Japanese
  ISSN：0913-4689, CiNii Articles ID：10020427159, CiNii Books ID：AN10131680
• CIDNP AND CIDEP STUDIES ON INTRAMOLECULAR HYDROGEN ABSTRACTION REACTION OF POLYMETHYLENE-LINKED XANTHONE AND XANTHENE - DETERMINATION OF THE EXCHANGE INTEGRAL OF THE INTERMEDIATE BIRADICALS　　　　　　　　　　　　　　　
  K MAEDA; M TERAZIMA; T AZUMI; Y TANIMOTO
  JOURNAL OF PHYSICAL CHEMISTRY, Volume：95, Number：1, First page：197, Last page：204, Jan. 1991, [Reviewed]
  Hydrogen abstraction reaction of a polymethylene-linked system is investigated by using chemically induced dynamic nuclear and electron polarization (CIDNP and CIDEP) methods. The reaction scheme is determined from the CIDNP and CIDEP spectra of the unlinked xanthene and xanthone system. The exchange integral J between the two terminal radicals of the system is obtained from the simulation process by using the spin-correlated CIDEP theory modified with (a) the fast population relaxation between the central S-T0 mixed states, (b) the contribution from the triplet mechanism, and (c) hyperfine line dependent line width. The mechanism of the fast population relaxation and the dependence of the J value on the temperature and polymethylene chain length are discussed.
  AMER CHEMICAL SOC, English, Scientific journal
  DOI：https://doi.org/10.1021/j100154a040
  DOI ID：10.1021/j100154a040, ISSN：0022-3654, CiNii Articles ID：80005650242, Web of Science ID：WOS:A1991ER47300040
• CIDNP and CIDEP Studies on Hydrogen Abstruction of 9, 10 - Authraquinone from Xanthene　　　　　　　　　　　　　　　
  TERAZIMA M; MAEDA K; SUGAWARA M; TAKAHASHI S; AZUMI T
  Journal of the Chemical Society. Faraday Transactions, Volume：86, Number：2, First page：253, Last page：256, 1990, [Reviewed]
  English
  DOI：https://doi.org/10.1039/ft9908600253
  DOI ID：10.1039/ft9908600253, ISSN：0956-5000
• CIDEP Studies on the Intramolecular Hydrogen Abstruction Reaction of Polymethylene Linked System Population Relaxation Between the S-To Mixed States　　　　　　　　　　　　　　　
  TERAZIMA M; MAEDA K; AZUMI T; TANIMOTO Y; OKADA N; ITOH M
  Chemical Physics Letters, Volume：164, Number：5, First page：562, Last page：566, 1989, [Reviewed]
  English
  DOI：https://doi.org/10.1016/0009-2614(89)85258-3
  DOI ID：10.1016/0009-2614(89)85258-3, ISSN：0009-2614, CiNii Articles ID：80004965430

• 超分子的アプローチによる段階的電荷分離系の構築および電荷分離状態のスピンダイナミクス　　　　　　　　　　　　　　　
  三浦智明; 前田公憲; 村井久雄
  電子スピンサイエンス学会年会講演要旨集, Volume：51st, First page：274, Last page：275, 01 Nov. 2012
  Japanese
  J-Global ID：201202216198121614
• Spectroscopic techniques for exploring the photochemical magnetic compass of migrating birds　　　　　　　　　　　　　　　
  MAEDA KIMINORI
  分光研究, Volume：61, Number：5, First page：177, Last page：189, 15 Oct. 2012
  Japanese
  ISSN：0038-7002, J-Global ID：201202205998468394, CiNii Articles ID：10031079495, CiNii Books ID：AN00222531
• Following radical pair reactions to understand the mechanism of the animal magnetoreception.-a step change in sensitivity.　　　　　　　　　　　　　　　
  MAEDA Kiminori; NEIL Simon R. T; HENBEST Kevin B; WEBER Stefan; SCHLEICHER Erik; HORE P. J; MACKENZIE Stuart R; TIMMEL Christiana R
  電子スピンサイエンス学会年会講演要旨集, Volume：50th, First page：4, Last page：5, 16 Nov. 2011
  English
  J-Global ID：201102205878064780
• ポリビニルカルバゾ‐ル薄膜の光電導における低磁場効果　　　　　　　　　　　　　　　
  駒形圭亮; 生駒忠昭; 生駒忠昭; 前田公憲; HENBEST Kevin B
  電子スピンサイエンス学会年会講演要旨集, Volume：49th, First page：52, Last page：53, 11 Nov. 2010
  Japanese
  J-Global ID：201002256369501167
• タンパク質中の電子移動反応の磁場効果　　　　　　　　　　　　　　　
  前田公憲; HENBEST Kevin; ROBINSON Alexander; DELL Ema; NEIL Simon; MACKENZIE Stuart; TIMMEL Christiane
  電子スピンサイエンス学会年会講演要旨集, Volume：49th, First page：278, Last page：279, 11 Nov. 2010
  Japanese
  J-Global ID：201002259725553079
• ポリビニルカルバゾール薄膜の光電導におけるキャリアダイナミクスの低磁場効果　　　　　　　　　　　　　　　
  駒形圭亮; 生駒忠昭; 前田公憲; HENBEST Kevin B
  光化学討論会講演要旨集, Volume：2010, First page：96, 08 Sep. 2010
  Japanese
  J-Global ID：201002280630206273
• Consistent Treatment of Spin-Selective Recombination of a Radical Pair Confirms the Haberkorn Approach　　　　　　　　　　　　　　　
  Konstantin L. Ivanov; Marina V. Petrova; Nikita N. Lukzen; Kiminori Maeda
  JOURNAL OF PHYSICAL CHEMISTRY A, Volume：114, Number：35, First page：9447, Last page：9455, Sep. 2010
  In the present work, we have shown that consistent derivation of the kinetic equations describing the electron spin-selective recombination of radical pairs confirms the conventional Haberkorn approach. The derivation has been based on considering the interaction of the reactive system (radical pair and product state) with. the thermal bath. The consistency of this approach has also been substantiated by numerical simulations performed for the purely quantum mechanical model of the recombining radical pair. Finally, we have shown that the quantum Zeno effect on radical pair recombination is not an exclusive feature of the approach recently proposed by Kominis, as it should be present at any rate of the singlet-triplet dephasing in the radical pair, which always accompanies the recombination process.
  AMER CHEMICAL SOC, English
  DOI：https://doi.org/10.1021/jp1048265
  DOI ID：10.1021/jp1048265, ISSN：1089-5639, J-Global ID：201002262197337769, Web of Science ID：WOS:000281404400005
• Protein Surface Interactions Probed by Magnetic Field Effects on Chemical Reactions　　　　　　　　　　　　　　　
  Kiminori Maeda; Alexander J. Robinson; Kevin B. Henbest; Emma J. Dell; Christiane R. Timmel
  JOURNAL OF THE AMERICAN CHEMICAL SOCIETY, Volume：132, Number：5, First page：1466, Last page：+, Feb. 2010
  Here we have employed the effects of weak static magnetic fields (not exceeding 46 mT) on radical recombination reactions to investigate protein-substrate interactions. Pulsed laser excitation of an aqueous solution of anthraquinone-2,6-disulfonate (AQDS(2-)) and either hen egg white lysozyme (HEWL) or bovine serum albumin (BSA) produces the triplet state of the radical pair (T)[AQDS(3-center dot) Trp(center dot)] by a photoinduced electron transfer reaction from tryptophan residues. Time-resolved absorption techniques were employed to study the recombination characteristics of these radical pairs at different static magnetic fields and ionic strengths. The experimental data in connection with the simulated curves unequivocally show that the radical pair has a lifetime of the order of microseconds in both systems (HEWL and BSA). However, the radical pair is embedded within a binding pocket of the BSA protein, while the (otherwise identical) radical pair, being subject to attractive Coulomb forces, resides on the protein surface in the HEWL system.
  AMER CHEMICAL SOC, English
  DOI：https://doi.org/10.1021/ja908988u
  DOI ID：10.1021/ja908988u, ISSN：0002-7863, J-Global ID：201002294807892807, Web of Science ID：WOS:000275084900011
• Cavity enhanced detection methods for probing the dynamics of spin correlated radical pairs in solution　　　　　　　　　　　　　　　
  Simon R. T. Neil; Kiminori Maeda; Kevin B. Henbest; Martin Goez; Robert Hemmens; Christiane R. Timmel; Stuart R. Mackenzie
  MOLECULAR PHYSICS, Volume：108, Number：7-9, First page：993, Last page：1003, 2010
  Cavity enhanced absorption spectroscopy (CEAS) combined with phase-sensitive detection is employed to study the effects of static magnetic fields on radical recombination reactions. The chemical system comprises the photochemically generated thionine semiquinone radical and a 1,4-diazabicyclo [2.2.2]octane (DABCO) cationic radical in a micellar solution of sodium dodecyl sulphate. Data obtained using the modulated CEAS technique, describing the magnetic field effect (MFE) on reaction yields, are shown to be superior to those obtained using conventional transient absorption (TA) flash photolysis methods typically employed for these measurements. The high sensitivity afforded by modulated CEAS detection is discussed in terms of the new possibilities it offers such as the measurement of magnetic field effects in real biological systems which have hitherto been largely beyond the detection capabilities of existing techniques.
  TAYLOR & FRANCIS LTD, English
  DOI：https://doi.org/10.1080/00268971003614368
  DOI ID：10.1080/00268971003614368, ISSN：0026-8976, J-Global ID：201102225630289310, Web of Science ID：WOS:000278110600017
• Effect of magnetic fields on cryptochrome-dependent responses in Arabidopsis thaliana　　　　　　　　　　　　　　　
  Sue-Re Harris; Kevin B. Henbest; Kiminori Maeda; John R. Pannell; Christiane R. Timmel; P. J. Hore; Haruko Okamoto
  JOURNAL OF THE ROYAL SOCIETY INTERFACE, Volume：6, Number：41, First page：1193, Last page：1205, Dec. 2009
  The scientific literature describing the effects of weak magnetic fields on living systems contains a plethora of contradictory reports, few successful independent replication studies and a dearth of plausible biophysical interaction mechanisms. Most such investigations have been unsystematic, devoid of testable theoretical predictions and, ultimately, unconvincing. A recent study, of magnetic responses in the model plant Arabidopsis thaliana, however, stands out; it has a clear hypothesis-that seedling growth is magnetically sensitive as a result of photoinduced radical-pair reactions in cryptochrome photoreceptors-tested by measuring several cryptochrome-dependent responses, all of which proved to be enhanced in a magnetic field of intensity 500 mu T. The potential importance of this study in the debate on putative effects of extremely low-frequency electromagnetic fields on human health prompted us to subject it to the 'gold standard' of independent replication. With experimental conditions chosen to match those of the original study, we have measured hypocotyl lengths and anthocyanin accumulation for Arabidopsis seedlings grown in a 500 mu T magnetic field, with simultaneous control experiments at 50 mu T. Additionally, we have determined hypocotyl lengths of plants grown in 50 mu T, 1 mT and approximately 100 mT magnetic fields (with zero-field controls), measured gene (CHS, HY5 and GST) expression levels, investigated blue-light intensity effects and explored the influence of sucrose in the growth medium. In no case were consistent, statistically significant magnetic field responses detected.
  ROYAL SOC, English
  DOI：https://doi.org/10.1098/rsif.2008.0519
  DOI ID：10.1098/rsif.2008.0519, ISSN：1742-5689, Web of Science ID：WOS:000271464500008
• 鳥の化学コンパスモデルの電子スピン共鳴　　　　　　　　　　　　　　　
  前田公憲; HENBEST K.B; WEDGE C; LIDDEL P.A; GUST D; TIMMEL C.R; HORE P.J
  電子スピンサイエンス学会年会講演要旨集, Volume：48th, First page：50, Last page：51, 10 Nov. 2009
  Japanese
  J-Global ID：200902288581357570
• リチウムアンモニア,エチルアミンの電子スピン緩和と電子ダイナミクス　　　　　　　　　　　　　　　
  前田公憲; LODGE M; HARMER J; JONES M.O; EDWARDS P.P
  電子スピンサイエンス学会年会講演要旨集, Volume：48th, First page：146, Last page：147, 10 Nov. 2009
  Japanese
  J-Global ID：200902297688361308
• ポリビニルカルバゾール薄膜における光キャリアダイナミクスの低磁場効果　　　　　　　　　　　　　　　
  駒形圭亮; 生駒忠昭; 生駒忠昭; 前田公憲; HENBEST Kevin
  光化学討論会講演要旨集, Volume：2009, First page：90, 16 Sep. 2009
  Japanese
  J-Global ID：200902278489714582
• ENDOR of photo-excited fullerene derivatives　　　　　　　　　　　　　　　
  Steven D. Karlen; Vasileia Filidou; Kiminori Maeda; Kevin Henbest; John J. L. Morton; Harry L. Anderson
  ABSTRACTS OF PAPERS OF THE AMERICAN CHEMICAL SOCIETY, Volume：238, Aug. 2009
  AMER CHEMICAL SOC, English, Summary international conference
  ISSN：0065-7727, Web of Science ID：WOS:000207861909462
• Refolding of ribonuclease A monitored by real-time photo-CIDNP NMR spectroscopy　　　　　　　　　　　　　　　
  Iain J. Day; Kiminori Maeda; Howard J. Paisley; K. Hun Mok; P. J. Hore
  JOURNAL OF BIOMOLECULAR NMR, Volume：44, Number：2, First page：77, Last page：86, Jun. 2009
  Photo-CIDNP NMR spectroscopy is a powerful method for investigating the solvent accessibility of histidine, tyrosine and tryptophan residues in a protein. When coupled to real-time NMR, this technique allows changes in the environments of these residues to be used as a probe of protein folding. In this paper we describe experiments performed to monitor the refolding of ribonuclease A following dilution from a high concentration of chemical denaturant. These experiments provide a good example of the utility of this technique which provides information that is difficult to obtain by other biophysical methods. Real-time photo-CIDNP measurements yield residue-specific kinetic data pertaining to the folding reaction, interpreted in terms of current knowledge of the folding of bovine pancreatic ribonuclease A.
  SPRINGER, English
  DOI：https://doi.org/10.1007/s10858-009-9322-2
  DOI ID：10.1007/s10858-009-9322-2, ISSN：0925-2738, eISSN：1573-5001, Web of Science ID：WOS:000266140600003
• SQUID magnetometry as a tool for following a clock reaction in solution　　　　　　　　　　　　　　　
  Robert Evans; Kevin B. Henbest; Michael A. Hayward; Melanie M. Britton; Kiminori Maeda; Christiane R. Timmel
  DALTON TRANSACTIONS, Number：14, First page：2467, Last page：2469, 2009
  SQUID magnetometry, normally used to characterise the properties of solids, was used to follow a clock reaction in solution, namely the auto-catalytic oxidation of [Co(II) EDTA](2-) by H(2)O(2), in real time and it was shown that, in combination with other methods (e. g., magnetic resonance proton relaxation studies and UV-vis absorption analysis), SQUID magnetometry can be a powerful method in elucidating and interpreting the time-profile of chemical reactions so as long as reactants, intermediates and products have suitably large differences in their respective magnetic susceptibilities.
  ROYAL SOC CHEMISTRY, English
  DOI：https://doi.org/10.1039/b819977a
  DOI ID：10.1039/b819977a, ISSN：1477-9226, CiNii Articles ID：80020372064, PubMed ID：19319389, Web of Science ID：WOS:000264555200002
• Quenching Mechanisms and Diffusional Pathways in Micellar Systems Unravelled by Time-Resolved Magnetic-Field Effects　　　　　　　　　　　　　　　
  Martin Goez; Kevin B. Henbest; Emma G. Windham; Kiminori Maeda; Christiane R. Timmel
  CHEMISTRY-A EUROPEAN JOURNAL, Volume：15, Number：24, First page：6058, Last page：6064, 2009
  WILEY-V C H VERLAG GMBH, English
  DOI：https://doi.org/10.1002/chem.200802502
  DOI ID：10.1002/chem.200802502, ISSN：0947-6539, CiNii Articles ID：80020387734, PubMed ID：19405051, Web of Science ID：WOS:000267278900024
• Magnetic-field effect on the photoactivation reaction of Escherichia coli DNA photolyase　　　　　　　　　　　　　　　
  Kevin B. Henbest; Kiminori Maeda; P. J. Hore; Monika Joshi; Adelbert Bacher; Robert Bittl; Stefan Weber; Christiane R. Timmel; Erik Schleicher
  PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF THE UNITED STATES OF AMERICA, Volume：105, Number：38, First page：14395, Last page：14399, Sep. 2008
  One of the two principal hypotheses put forward to explain the primary magnetoreception event underlying the magnetic compass sense of migratory birds is based on a magnetically sensitive chemical reaction. It has been proposed that a spin-correlated radical pair is produced photochemically in a cryptochrome and that the rates and yields of the subsequent chemical reactions depend on the orientation of the protein in the Earth's magnetic field. The suitability of cryptochrome for this purpose has been argued, in part, by analogy with DNA photolyase, although no effects of applied magnetic fields have yet been reported for any member of the cryptochrome/photolyase family. Here, we demonstrate a magnetic-field effect on the photochemical yield of a flavin-tryptophan radical pair in Escherichia coli photolyase. This result provides a proof of principle that photolyases, and most likely by extension also cryptochromes, have the fundamental properties needed to form the basis of a magnetic compass.
  NATL ACAD SCIENCES, English
  DOI：https://doi.org/10.1073/pnas.0803620105
  DOI ID：10.1073/pnas.0803620105, ISSN：0027-8424, CiNii Articles ID：80019800180, PubMed ID：18799743, Web of Science ID：WOS:000259592400032
• Chemical compass model of avian magnetoreception　　　　　　　　　　　　　　　
  Kiminori Maeda; Kevin B. Henbest; Filippo Cintolesi; Ilya Kuprov; Christopher T. Rodgers; Paul A. Liddell; Devens Gust; Christiane R. Timmel; P. J. Hore
  NATURE, Volume：453, Number：7193, First page：387, Last page：U38, May 2008
  Approximately 50 species, including birds, mammals, reptiles, amphibians, fish, crustaceans and insects, are known to use the Earth's magnetic field for orientation and navigation(1). Birds in particular have been intensively studied, but the biophysical mechanisms that underlie the avian magnetic compass are still poorly understood. One proposal, based on magnetically sensitive free radical reactions(2,3), is gaining support(4-11) despite the fact that no chemical reaction in vitro has been shown to respond to magnetic fields as weak as the Earth's (similar to 50 mu T) or to be sensitive to the direction of such a field. Here we use spectroscopic observation of a carotenoid-porphyrin-fullerene model system to demonstrate that the lifetime of a photochemically formed radical pair is changed by application of <= 50 mu T magnetic fields, and to measure the anisotropic chemical response that is essential for its operation as a chemical compass sensor. These experiments establish the feasibility of chemical magnetoreception and give insight into the structural and dynamic design features required for optimal detection of the direction of the Earth's magnetic field.
  NATURE PUBLISHING GROUP, English
  DOI：https://doi.org/10.1038/nature06834
  DOI ID：10.1038/nature06834, ISSN：0028-0836, CiNii Articles ID：80019473435, PubMed ID：18449197, Web of Science ID：WOS:000255868400051
• Chemical Magnetoreception: Bird Cryptochrome 1a Is Excited by Blue Light and Forms Long-Lived Radical-Pairs　　　　　　　　　　　　　　　
  Miriam Liedvogel; Kiminori Maeda; Kevin Henbest; Erik Schleicher; Thomas Simon; Christiane R. Timmel; P. J. Hore; Henrik Mouritsen
  PLOS ONE, Volume：2, Number：10, First page：e1106, Oct. 2007
  Cryptochromes (Cry) have been suggested to form the basis of light-dependent magnetic compass orientation in birds. However, to function as magnetic compass sensors, the cryptochromes of migratory birds must possess a number of key biophysical characteristics. Most importantly, absorption of blue light must produce radical pairs with lifetimes longer than about a microsecond. Cryptochrome 1a (gwCry1a) and the photolyase-homology-region of Cry1 (gwCry1-PHR) from the migratory garden warbler were recombinantly expressed and purified from a baculovirus/Sf9 cell expression system. Transient absorption measurements show that these flavoproteins are indeed excited by light in the blue spectral range leading to the formation of radicals with millisecond lifetimes. These biophysical characteristics suggest that gwCry1a is ideally suited as a primary light-mediated, radical-pair-based magnetic compass receptor.
  PUBLIC LIBRARY SCIENCE, English
  DOI：https://doi.org/10.1371/journal.pone.0001106
  DOI ID：10.1371/journal.pone.0001106, ISSN：1932-6203, Web of Science ID：WOS:000207458700023
• Radical cation stabilization in a cucurbituril oligoaniline rotaxane　　　　　　　　　　　　　　　
  Rienk Eelkema; Kinninori Maeda; Barbara Odell; Harry L. Anderson
  JOURNAL OF THE AMERICAN CHEMICAL SOCIETY, Volume：129, Number：41, First page：12384, Last page：+, Oct. 2007
  A cucurbituril-encapsulated oligoaniline rotaxane is synthesized in high yield by reductive amination in aqueous acid. Spectroscopic and electrochemical measurements show that encapsulation by cucurbit[7]uril increases the thermodynamic and kinetic stability of the radical cation of the threaded oligoaniline. This radical cation has a stoichiometry similar to that of the conducting emeraldine salt form of polyaniline, which implies that cucurbituril insulation of polyaniline might drastically alter the oxidation potential of the threaded conjugated polymer chain.
  AMER CHEMICAL SOC, English
  DOI：https://doi.org/10.1021/ja074997i
  DOI ID：10.1021/ja074997i, ISSN：0002-7863, CiNii Articles ID：80018128640, PubMed ID：17887677, Web of Science ID：WOS:000250105500022
• Photoionization of TMPD in DMSO solution: mechanism and magnetic field effects　　　　　　　　　　　　　　　
  K. B. Henbest; E. Athanassiades; K. Maeda; I. Kuprov; P. J. Hore; C. R. Timmel
  MOLECULAR PHYSICS, Volume：104, Number：10-11, First page：1789, Last page：1794, May 2006
  Photoionization of N, N, N', N'-tetramethyl-p-phenylenediamine ( TMPD) in alcoholic solution produces the radical ion pair [TMPD center dot+ e(-)]. However, the identity of the negatively charged counter-radical formed by photolysis of TMPD in DMSO (dimethylsulphoxide)/toluene mixtures, for which unusually large effects of weak applied magnetic fields have been observed, is unclear. Modulated MARY (Magnetically Affected Reaction Yield) experiments on solutions containing different isotopomers of TMPD, DMSO and toluene show that the counter-radical is likely to be the solvated electron. This result supports the idea that large effects of weak fields on radical recombination yields can be expected for radical pairs in which the electron-nuclear hyperfine interactions are concentrated in one of the radicals, rather than being distributed more evenly between the two radicals.
  TAYLOR & FRANCIS LTD, English
  DOI：https://doi.org/10.1080/00268970600611017
  DOI ID：10.1080/00268970600611017, ISSN：0026-8976, eISSN：1362-3028, Web of Science ID：WOS:000238118900030
• A practical simulation and a novel insight to the magnetic field effect on a radical pair in a micelle　　　　　　　　　　　　　　　
  K. Maeda; T. Miura; T. Arai
  MOLECULAR PHYSICS, Volume：104, Number：10-11, First page：1779, Last page：1788, May 2006
  The spin mixing process of a radical pair in a micelle in a low magnetic field is investigated by transient absorption detected MARY spectra. In a system comprising the radical pair generated by photoreaction of 2-methyl-1,4-naphthoquinone in sodium dodecylsulfate micelle, two techniques were applied: time resolved MARY spectra and pulsed MARY spectra. In order to analyse the results, a practical calculation method that lends itself to the simulation of experimental results has been developed. In the calculation, a semi-classical model was used for the evaluation of the hyperfine mechanism (HFM) in the single-site Liouville equation in which one can take spin relaxation and dephasing phenomena into account. The interrelation between the HFM and relaxation mechanism (RM) was discussed. A new insight into the HFM induced spin mixing process, which is assisted by fast spin dephasing phenomena, is proposed. This mechanism is important for the MARY spectral shape and connects the HFM and RM smoothly.
  TAYLOR & FRANCIS LTD, English
  DOI：https://doi.org/10.1080/14767050600588106
  DOI ID：10.1080/14767050600588106, ISSN：0026-8976, Web of Science ID：WOS:000238118900029
• Measurement of magnetic field effects on radical recombination reactions using triplet-triplet energy transfer　　　　　　　　　　　　　　　
  KB Henbest; K Maeda; E Athanassiades; PJ Hore; CR Timmel
  CHEMICAL PHYSICS LETTERS, Volume：421, Number：4-6, First page：571, Last page：576, Apr. 2006
  Previously, the effect of applied magnetic fields on the yield of the reaction of the radical ions of pyrene and 1,3-dicyanobenzene (DCB) has been measured by monitoring the emission of the pyrene/1,3-DCB exciplex formed from the singlet state of the spin-correlated radical pair (SCRP). This Letter describes an alternative approach that relies on energy transfer from the excited triplet state of pyrene to the tris(2,2'-bipyridyl)ruthenium(II) ion, Ru(bpy)(3)(2+), allowing the recombination of the triplet SCRP to be monitored by emission spectroscopy. Measurements of magnetic field effects in combination with time-resolved flash photolysis and luminescence experiments confirm triplet-triplet energy transfer as the reaction mechanism. (c) 2006 Elsevier B.V. All rights reserved.
  ELSEVIER SCIENCE BV, English
  DOI：https://doi.org/10.1016/j.cplett.2006.01.106
  DOI ID：10.1016/j.cplett.2006.01.106, ISSN：0009-2614, Web of Science ID：WOS:000236789800052
• ラジカル対における電子スピン操作による反応ダイナミクスの研究　　　　　　　　　　　　　　　
  前田公憲
  電子スピンサイエンス, Number：6, First page：43, Last page：49, 06 Mar. 2006
  Japanese
  J-Global ID：201002274762752137
• The spin mixing process of a radical pair in low magnetic field observed by transient absorption detected nanosecond pulsed magnetic field effect　　　　　　　　　　　　　　　
  T Miura; K Maeda; T Arai
  JOURNAL OF PHYSICAL CHEMISTRY A, Volume：110, Number：12, First page：4151, Last page：4156, Mar. 2006
  The spin mixing process of the radical pair in the sodium dodecyl sulfate (SDS) micelle is studied by using a novel technique nanosecond Pulsed magnetic field effect oil transient absorption. We have developed the equipment for a nanosecond pulsed magnetic field and observed its effect on the radical pair reaction. A decrease of the free radical yield by a reversely directed pulsed magnetic field that cancels static field is observed, and the dependence on its magnitude, which is called pulsed MARY (magnetic field effect on reaction yield) spectra, is studied. The observed spectra reflect the spin mixing in 50-200 ns and show clear time evolution. Theoretical simulation of pulsed MARY spectra based on a single site modified Liouville equation indicates that the fast spin dephasing processes induced by the modulation of electron -electron spin interaction by molecular reencounter affect to the coherent spin mixing by a hyperfine interaction in a low magnetic field.
  AMER CHEMICAL SOC, English
  DOI：https://doi.org/10.1021/jp056488d
  DOI ID：10.1021/jp056488d, ISSN：1089-5639, Web of Science ID：WOS:000236407000002
• The spin mixing process of a radical pair in low magnetic field observed by transient absorption detected nanosecond pulsed magnetic field effect　　　　　　　　　　　　　　　
  Volume：110, 12号,4151-4156, 2006
  DOI：https://doi.org/10.1021/jp056488d
  DOI ID：10.1021/jp056488d
• 超低磁場における光誘起電子移動反応に対する磁場効果の観測　　　　　　　　　　　　　　　
  前田公憲; HENBEST K. B; CINTOLESI F; TIMMEL C. R; HORE P. J
  電子スピンサイエンス学会年会講演要旨集, Volume：44th, First page：96, Last page：97, 24 Oct. 2005
  Japanese
  J-Global ID：200902255986326561
• Dynamics of intramolecular electron transfer reaction of FAD studied by magnetic field effects on transient absorption spectra　　　　　　　　　　　　　　　
  Masaaki Murakami; Kiminori Maeda; Tatsuo Arai
  Journal of Physical Chemistry A, Volume：109, Number：26, First page：5793, Last page：5800, 07 Jul. 2005
  The kinetics of intermediates generated from intramolecular electron-transfer reaction by photo irradiation of the flavin adenine dinucleotide (FAD) molecule was studied by a magnetic field effect (MFE) on transient absorption (TA) spectra. Existence time of MFE and MFE action spectra have a strong dependence on the pH of solutions. The MFE action spectra have indicated the existence of interconversion between the radical pair and the cation form of the triplet excited state of flavin part. All rate constants of the triplet and the radical pair were determined by analysis of the MFE action spectra and decay kinetics of TA. The obtained values for the interconversion indicate that the formation of cation radical promotes the back electron-transfer reaction to the triplet excited state. Further, rate constants of spin relaxation and recombination have been studied by the time profiles of MFE at various pH. The drastic change of those two factors has been obtained and can be explained by SOC (spin-orbit coupling) induced back electron-transfer promoted by the formation of a stacking conformation at pH >
  2.5. © 2005 American Chemical Society.
  English
  DOI：https://doi.org/10.1021/jp0519722
  DOI ID：10.1021/jp0519722, ISSN：1089-5639, PubMed ID：16833913, SCOPUS ID：22344442809
• Dynamics of intramolecular electron transfer reaction of FAD studied by magnetic field effects on transient absorption spectra　　　　　　　　　　　　　　　
  M Murakami; K Maeda; T Arai
  JOURNAL OF PHYSICAL CHEMISTRY A, Volume：109, Number：26, First page：5793, Last page：5800, Jul. 2005
  The kinetics of intermediates generated from intramolecular electron-transfer reaction by photo irradiation of the flavin adenine dinucleotide (FAD) molecule was studied by a magnetic field effect (MFE) on transient absorption (TA) spectra. Existence time of MFE and MFE action spectra have a strong dependence on the pH of solutions. The MFE action spectra have indicated the existence of interconversion between the radical pair and the cation form of the triplet excited state of flavin part. All rate constants of the triplet and the radical pair were determined by analysis of the MFE action spectra and decay kinetics of TA. The obtained values for the interconversion indicate that the formation of cation radical promotes the back electron-transfer reaction to the triplet excited state. Further, rate constants of spin relaxation and recombination have been studied by the time profiles of MFE at various pH. The drastic change of those two factors has been obtained and can be explained by SOC (spin-orbit coupling) induced back electron-transfer promoted by the formation of a stacking conformation at pH > 2.5.
  AMER CHEMICAL SOC, English
  DOI：https://doi.org/10.1021/jp0519722
  DOI ID：10.1021/jp0519722, ISSN：1089-5639, Web of Science ID：WOS:000230225000004
• Spin dynamics of the radical pair in low magnetic field studied by transient absorption detected MARY and SEMF.　　　　　　　　　　　　　　　
  Volume：109, 44号, 9911-9988, 2005
  DOI：https://doi.org/10.1021/jp053989q
  DOI ID：10.1021/jp053989q
• Spin dynamics of the radical pair in low magnetic field studied by transient absorption detected MARY and SEMF.　　　　　　　　　　　　　　　
  The Journal of Physical Chemistry A, Volume：109, 44号, 9911-9988, 2005
  DOI：https://doi.org/10.1021/jp053989q
  DOI ID：10.1021/jp053989q
• Dynamic process of the photo-chemically produced flavin radicals in a neutral micelle studied by a magnetic field effect　　　　　　　　　　　　　　　
  M Horiuchi; K Maeda; T Arai
  CHEMICAL PHYSICS LETTERS, Volume：394, Number：4-6, First page：344, Last page：348, Aug. 2004
  The dynamics of the free radicals generated from the photo-induced electron transfer reaction from the phenyl ether group of Triton X-100 micelle to flavin derivatives has been studied by transient absorption (TA) spectra and its magnetic field effect (MFE). By the MFE on TA spectrum, one can selectively observe radical species avoiding the overlap of the TA signal of the triplet state. By virtue of this, the protonation kinetics from the anion radical to the neutral radical has been able to be analyzed. The dynamic process of the anion radicals depends on the hydrophobic character of flavin derivatives. (C) 2004 Elsevier B.V. All rights reserved.
  ELSEVIER SCIENCE BV, English
  DOI：https://doi.org/10.1016/j.cplett.2004.06.143
  DOI ID：10.1016/j.cplett.2004.06.143, ISSN：0009-2614, Web of Science ID：WOS:000223463500023
• Effect of halogen atom on electron spin polarization studied by CIDEP, using halogen substituted aromatic acyl compounds　　　　　　　　　　　　　　　
  T Suzuki; K Maeda; T Arai; K Akiyama; S Tero-Kubota
  MOLECULAR PHYSICS, Volume：101, Number：22, First page：3341, Last page：3348, Nov. 2003
  The reaction and spin dynamics of the photocleavage reaction of 2-chloro-2'-acetylnaphthalene were studied by time-resolved FT-EPR and transient absorption (TA) spectroscopy. The photocleavage reaction from both singlet and triplet states was observed by TA and EPR experiments, although the radical cleavage reaction in the excited triplet state is energetically unfavourable. This feature has been explained by the ionic cleavage reaction due to the electro-negativity of the chlorine atoms. The time-resolved FT-EPR spectra were similar to those observed in the bromine substituted compound, 2-BAN, reported in a previous paper. The origin of the electron spin polarization was assigned to the radical triplet pair mechanism (RTPM) and free radical pair mechanism (F-pair RPM) from analysis of the time profiles of the spin polarization.
  TAYLOR & FRANCIS LTD, English
  DOI：https://doi.org/10.1080/00268970310001640193
  DOI ID：10.1080/00268970310001640193, ISSN：0026-8976, Web of Science ID：WOS:000188515000010
• Dimerization by hydrogen bonding and photochemical properties of dipyridone　　　　　　　　　　　　　　　
  A Matsumoto; K Maeda; T Arai
  JOURNAL OF PHYSICAL CHEMISTRY A, Volume：107, Number：47, First page：10039, Last page：10045, Nov. 2003
  The ground state and the excited state of dipyridones are studied by various spectroscopic methods: absorption spectra, fluorescence spectra, time resolved fluorescence measurements, and nanosecond transient absorption spectra. In the system of 3-, where bhq(-) is the C-deprotonated forms of benzo[h]quinoline (bhqH) and L is either PEt(3), p-toluidine, or piperidine. The lowest singlet states of the Ru(II) complexes are metal-to-ligand charge-transfer (1)d pi(*) states. Vibrational structures of the phosphorescence spectra observed in the crystalline states at 4.2 K are similar to the structures of the phosphorescence spectra and the magnitude of the free bhqH ligand. Zero-field splittings indicate that the lowest triplet states of all the Ru(II) complexes are mainly characterized as ligand-localized (3) pi pi* states. However, the phosphorescence lifetimes are significantly shorter for Ru(II) complexes as compared with free bhqH. This result suggests that the lowest triplet state of the Ru(II) complex includes (3)d pi* character due to configurational mixing with the bhq-localized 3 pi pi* state. By intersystem crossing from the singlet excited state, the in-plane y sublevel is the most populated for bhqH, whereas the out-of-plane x sublevel is the most populated for the Ru(II) complexes. This dramatic change of the intersystem crossing route is satisfactorily interpreted within the framework of the theory of the intersystem crossing by considering the difference of the character of the lowest singlet state.
  AMER CHEMICAL SOC, English
  DOI：https://doi.org/10.1021/jp961018s
  DOI ID：10.1021/jp961018s, ISSN：1089-5639, CiNii Articles ID：80009515575, Web of Science ID：WOS:A1997WL08500004
• Contolling of Radical-Ion Pair Reactions with Microwave radiation : Photoconductivity-detected Magnetic Resonance.　　　　　　　　　　　　　　　
  MURAI H; MATSUYAMA A; ISHIDA T; IWASAKI Y; MAEDA K; AZUMI T
  Volume：264, Number：6, First page：619, Last page：622, 1997
  DOI：https://doi.org/10.1016/S0009-2614(96)01383-8
  DOI ID：10.1016/S0009-2614(96)01383-8, ISSN：0009-2614, CiNii Articles ID：80009418688
• The time-resolved ADMR in the photolysis of the polymethylene-linked system of xanthone and xanthene: Power dependence　　　　　　　　　　　　　　　
  K Maeda; Y Araki; K Enjo; T Etoh; H Murai; T Azumi
  APPLIED MAGNETIC RESONANCE, Volume：12, Number：4, First page：431, Last page：439, 1997
  The time-resolved ADMR (absorption-detected magnetic resonance) spectrum of the polymethylene linked biradical generated in the photolysis of alpha-(xanthene-2-carbonyloxy)-omega-(xanthene-2-carbonyloxy) dodecane is observed at various microwave power. When the lower microwave power is low, the ADMR spectrum is totally negative (the absorbance of xanthyl radical decreases by the microwave irradiation) and is interpreted in terms of the hyperfine structure of the terminal radicals. In contrast with this, the ADMR spectrum obtained at high microwave field consists of two components: central component and wing component. The central component is positive and is interpreted in terms of the deceleration of the intersystem crossing by microwave, which is known as the spin locking. The wing component is negative and the linewidth is much larger than that of the central one. It is ascribed to the transitions from \T+1] and \T-1] states to singlet state having a slight \T-0] character. It is proposed that the width of the time resolved spectrum is due to the fluctuation of the exchange integral (modulated exchange integral) by the motion of the polymethylene chain. The time dependence of the central and wing components and the conditions for observation of them are discussed.
  SPRINGER VERLAG, English
  DOI：https://doi.org/10.1007/BF03164124
  DOI ID：10.1007/BF03164124, ISSN：0937-9347, Web of Science ID：WOS:A1997XP82200006
• The SNP Measurement of the Elecrton Transfer Reaction from Quadricyclane to Tetrafluoro-P-Benzoquinone　　　　　　　　　　　　　　　
  Applied Magnetic Resonance, Volume：11, First page：441, Last page：447, 1997
• Reaction-Yield-Detected Magnetic Resonance in the Intra-and Intermolecular Electron Transfer Reactions　　　　　　　　　　　　　　　
  Applied Magnetic Resonance, Volume：11, First page：423, Last page：430, 1997
• Several RYDMR Studies on the Radical-Ion Pair Formed in the Photolysis of TMPD : Photoconductivity, Transient-Absorption and Fluorescence Detected Methods　　　　　　　　　　　　　　　
  Applied Magnetic Resonance, Volume：11, First page：411, Last page：422, 1997
• Excited-state properties of the ligand-localized (3)pi pi* state of cyclometalated ruthenium(II) complexes　　　　　　　　　　　　　　　
  S Kimachi; R Satomi; H Miki; K Maeda; T Azumi; M Onishi
  JOURNAL OF PHYSICAL CHEMISTRY A, Volume：101, Number：4, First page：345, Last page：349, Jan. 1997
  We report the results of an investigation on the absorption spectra, phosphorescence spectra, phosphorescence lifetimes, and magnetic properties of [Ru(bhq)(CO)(2)Cl(L)], where bhq(-) is the C-deprotonated forms of benzo[h]quinoline (bhqH) and L is either PEt(3), p-toluidine, or piperidine. The lowest singlet states of the Ru(II) complexes are metal-to-ligand charge-transfer (1)d pi(*) states. Vibrational structures of the phosphorescence spectra observed in the crystalline states at 4.2 K are similar to the structures of the phosphorescence spectra and the magnitude of the free bhqH ligand. Zero-field splittings indicate that the lowest triplet states of all the Ru(II) complexes are mainly characterized as ligand-localized (3) pi pi* states. However, the phosphorescence lifetimes are significantly shorter for Ru(II) complexes as compared with free bhqH. This result suggests that the lowest triplet state of the Ru(II) complex includes (3)d pi* character due to configurational mixing with the bhq-localized 3 pi pi* state. By intersystem crossing from the singlet excited state, the in-plane y sublevel is the most populated for bhqH, whereas the out-of-plane x sublevel is the most populated for the Ru(II) complexes. This dramatic change of the intersystem crossing route is satisfactorily interpreted within the framework of the theory of the intersystem crossing by considering the difference of the character of the lowest singlet state.
  AMER CHEMICAL SOC, English
  DOI：https://doi.org/10.1021/jp961018s
  DOI ID：10.1021/jp961018s, ISSN：1089-5639, Web of Science ID：WOS:A1997WL08500004
• Contolling of Radical-Ion Pair Reactions with Microwave radiation : Photoconductivity-detected Magnetic Resonance.　　　　　　　　　　　　　　　
  Chemical Physics Letters, Volume：264, Number：6, First page：619, Last page：622, 1997
  DOI：https://doi.org/10.1016/S0009-2614(96)01383-8
  DOI ID：10.1016/S0009-2614(96)01383-8, ISSN：0009-2614, CiNii Articles ID：80009418688
• Spin-correlated radical pairs in micellar systems: Mechanism of CIDEP and the micelle size dependence　　　　　　　　　　　　　　　
  VF Tarasov; H Yashiro; K Maeda; T Azumi; IA Shkrob
  CHEMICAL PHYSICS, Volume：212, Number：2-3, First page：353, Last page：361, Dec. 1996
  A new model of time-resolved EPR in micellized radical pairs is introduced. The model is based on numerical integration of the master Liouville equation for spin-correlated (micellized) pairs and free (escaped) radicals. The diffusion of radicals is considered in terms of a supercage model. This approach is used to analyze data on laser flash photolysis of C-13-carbonyl labelled ketone alpha-deoxybenzoin in aqueous sodium alkyl(10-12) sulphate solutions. EPR lines of C-13-benzoyl radicals exhibit antiphase structure (APS) typical of spin-correlated pairs. Due to very large APS splitting, 0.8-1.5 mT, the ST0 polarized lines from free benzoyl radicals can be isolated spectrally. The observed line shape of the APS cannot be accounted for in the standard model of effective exchange potential. The shape of the APS is shown to be controlled by spin exchange relaxation in micellized pairs.
  ELSEVIER SCIENCE BV, English
  DOI：https://doi.org/10.1016/S0301-0104(96)00145-0
  DOI ID：10.1016/S0301-0104(96)00145-0, ISSN：0301-0104, CiNii Articles ID：80009327419, Web of Science ID：WOS:A1996VV61700007
• The time-resolved absorption-detected magnetic resonance spectrum of the polymethylene linked biradical: Effect of the exchange integral　　　　　　　　　　　　　　　
  K Maeda; Y Araki; Y Kamata; K Enjo; H Murai; T Azumi
  CHEMICAL PHYSICS LETTERS, Volume：262, Number：1-2, First page：110, Last page：114, Nov. 1996
  The time-resolved absorption-detected magnetic resonance spectrum of the polymethylene linked biradical generated in the photolysis of alpha-(xanthene-2-carbonyloxy)-omega-(xanthene-2-carbonyloxy)dodecane was observed. The central part of the spectrum shows an increase in the absorbance by applying high microwave power. This is rationalized by the deceleration of the intersystem crossing due to the state locking that serves to slow down the intramolecular recombination reaction. Both wing portions show an increase in the recombination rate by microwave radiation, i.e. acceleration of the intersystem crossing. This is ascribed to transitions from the \T-+1> and \T--1> states to a singlet state having a slight \T-0> character. We propose that the broadness of the time resolved spectrum is due to the wide distribution of the exchange integral and its fluctuation (modulated exchange integral) by the motion of the polymethylene chain.
  ELSEVIER SCIENCE BV, English
  DOI：https://doi.org/10.1016/0009-2614(96)01047-0
  DOI ID：10.1016/0009-2614(96)01047-0, ISSN：0009-2614, CiNii Articles ID：80009259650, Web of Science ID：WOS:A1996VR36800017
• SNP studies on the structure of the short-lived radical pair generated in the hydrogen abstraction reaction of anthraquinone from xanthene　　　　　　　　　　　　　　　
  K Shindo; K Yamamoto; K Maeda; T Azumi
  BULLETIN OF THE CHEMICAL SOCIETY OF JAPAN, Volume：69, Number：10, First page：2731, Last page：2734, Oct. 1996
  Nuclear-polarization-detected ESR (NP-detected ESR) spectra were measured in the hydrogen abstraction reaction of anthraquinone from xanthene for the purpose of assigning of the radical pair and the geminate product generated from the radical pair. By properly choosing of the nuclear spin of the product, we can obtain the SNP spectra of the two component radicals individually. The sign of the hyperfine coupling constant is discussed and the SNP spectra are assigned as 9-xanthenyl radical and 10-hydroxy-9-anthryloxyl radical from the spectrum simulated by the radical pair theory. Additionally, the features of the cross relaxation process in the intermediate free radical are discussed by examining the DNP components of spectra.
  CHEMICAL SOC JAPAN, English
  DOI：https://doi.org/10.1246/bcsj.69.2731
  DOI ID：10.1246/bcsj.69.2731, ISSN：0009-2673, eISSN：1348-0634, CiNii Articles ID：10008909140, Web of Science ID：WOS:A1996VQ50900005
• Time-Resolved CIDNP-Detected ESR Spectrum in the Photochemical Hydrogen Abstraction Reaction of Benzoquinone　　　　　　　　　　　　　　　
  Volume：6, First page：393, Last page：395, 1995
• Low field CIDNP-Detected ESR Spectrwn of Intermedicate Radicul Pair in Photoinduced Hydrogen Abstraction Reaction　　　　　　　　　　　　　　　
  Volume：6, First page：407, 1995
• Photochemical Hydrogen Abstraction Reaction of 2,6-dichloro-P-benzoguinone as Studied by Nuclear-Spin-Dolarization-Detected ESR Spectroscopy　　　　　　　　　　　　　　　
  Volume：107, First page：831, 1995
• CIDNP-Detected ESR Spectrum in the Photoinduced Electron Transfer Reaction　　　　　　　　　　　　　　　
  Volume：6, 1995
• CIDNP Studies on the Photochemical Reaction of 4-Methyl-2-quinolinecarbonitrile with Optically Active (S)- or (R)-2-Phenylpropionic Acid. No evidence for the Chiral Symmetry Breaking　　　　　　　　　　　　　　　
  Volume：227, 1995
  DOI：https://doi.org/10.1246/cl.1995.227
  DOI ID：10.1246/cl.1995.227
• Time-Resolved CIDNP-Detected ESR Spectrum in the Photochemical Hydrogen Abstraction Reaction of Benzoquinone　　　　　　　　　　　　　　　
  Magnetic Resonance in Medicine, Volume：6, First page：393, Last page：395, 1995
• Low field CIDNP-Detected ESR Spectrwn of Intermedicate Radicul Pair in Photoinduced Hydrogen Abstraction Reaction　　　　　　　　　　　　　　　
  Magnetic Resonance in Medicine, Volume：6, First page：407, 1995
• Photochemical Hydrogen Abstraction Reaction of 2,6-dichloro-P-benzoguinone as Studied by Nuclear-Spin-Dolarization-Detected ESR Spectroscopy　　　　　　　　　　　　　　　
  Proceeding of Indian Academy of Science, Volume：107, First page：831, 1995
• CIDNP-Detected ESR Spectrum in the Photoinduced Electron Transfer Reaction　　　　　　　　　　　　　　　
  Magnetic Resonance in Medicine, Volume：6, 1995
• CIDNP Studies on the Photochemical Reaction of 4-Methyl-2-quinolinecarbonitrile with Optically Active (S)- or (R)-2-Phenylpropionic Acid. No evidence for the Chiral Symmetry Breaking　　　　　　　　　　　　　　　
  Chemistry Letters, Volume：227, 1995
  DOI：https://doi.org/10.1246/cl.1995.227
  DOI ID：10.1246/cl.1995.227
• Direct Analysis of Hydrogen Transfer Reaction from P-Benzosemiquinone Radical to P-Benzoquinone hy Time Resolved CIDNP Method.　　　　　　　　　　　　　　　
  Volume：50A, First page：1943, 1994
• Direct Analysis of Hydrogen Transfer Reaction from P-Benzosemiquinone Radical to P-Benzoquinone hy Time Resolved CIDNP Method.　　　　　　　　　　　　　　　
  Spectrochim. Acta, Volume：50A, First page：1943, 1994
• ELECTRON-NUCLEAR CROSS-RELAXATION EFFECT ON THE PHOTOCHEMICAL-REACTION OF BENZALDEHYDE AS STUDIED BY CIDNP AND DNP　　　　　　　　　　　　　　　
  Y YAMAKAGE; QX MENG; SS ALI; K MAEDA; T AZUMI
  PROCEEDINGS OF THE INDIAN ACADEMY OF SCIENCES-CHEMICAL SCIENCES, Volume：105, Number：6, First page：629, Last page：636, Dec. 1993
  The magnetic field dependence of CIDNP was measured for the photolysis of benzaldehyde. At high and low fields, respectively, the CIDNP behavior is satisfactorily interpreted by the S-T0 and S-T- mixing of radical pair mechanism (RPM). At around 325mT the CIDNP of the aldehyde proton is emissive, which cannot be interpreted by RPM. In order to understand this anomalous behavior, we observe the dynamic nuclear polarization.
  The DNP sign shows that the cross-relaxation mechanism of the intermediate free radical is DELTAm = 2. With this result, the emissive CIDNP at 325 mT is interpreted by the triplet mechanism (TM) with cross-relaxation-induced polarization transfer from electron spin to nuclear spin.
  Further, the time-resolved DNP is observed with laser excitation and switching of microwaves. With pulse excitation, the features of CIDNP and DNP are different (rom that with continuous light excitation. This is interpreted as due to the associated increase of the initial concentration of the ketyl radical. From the time dependence of the DNP intensity, the lifetime of the ketyl radical is estimated to be of the order of hundreds of nanoseconds.
  INDIAN ACADEMY SCIENCES, English
  ISSN：0253-4134, Web of Science ID：WOS:A1993NJ59100031
• STUDIES OF PHOTOCHEMICAL-REACTION BY CIDNP-DETECTED ESR-SPECTRUM　　　　　　　　　　　　　　　
  Q MENG; Y YAMAKAGE; T AIZAWA; K MAEDA; T AZUMI
  PROCEEDINGS OF THE INDIAN ACADEMY OF SCIENCES-CHEMICAL SCIENCES, Volume：105, Number：6, First page：619, Last page：628, Dec. 1993
  CIDNP-detected ESR spectroscopy was applied to the study of photochemical reaction. In the CIDNP-detected ESR spectroscopy, the spectrum due to intermediate radical pairs and the spectrum due to free (escaped) radicals can be separately observed. The spectrum due to radical pairs is called stimulated nuclear polarization (SNP), and the spectrum due to free radicals is called dynamic nuclear polarization (DNP). The method was applied to the study of photochemical reaction of 2,6-dichlorobenzoquinone and the isomerization of quadricyclane assisted by photoinduced electron transfer, and the chemical species of the intermediate radical pair and of the radical were clarified.
  INDIAN ACADEMY SCIENCES, English
  ISSN：0253-4134, Web of Science ID：WOS:A1993NJ59100030
• PHOSPHORESCENCE FROM THE DELOCALIZED TRIPLET-STATE OF POLYSILYLENES　　　　　　　　　　　　　　　
  K MAEDA; K SHIMIZU; T AZUMI; M YOSHIDA; K SAKAMOTO; H SAKURAI
  JOURNAL OF PHYSICAL CHEMISTRY, Volume：97, Number：47, First page：12144, Last page：12146, Nov. 1993
  Fairly sharp phosphorescence is observed at 4.2 K for several polysilylenes synthesized by an anion polymerization method. No broad phospho rescence was observed in the spectral region where the phosphorescence was previously reported to exist. The small bandwidth and the small fluorescence-phosphorescence energy separation are in accord with our previous idea that the phosphorescence is from the delocalized triplet state of the polymers. The temperature dependence of the phosphorescence intensity is interpreted by a model in which a quenching level exists approximately 60 cm-1 above the emitting level.
  AMER CHEMICAL SOC, English
  DOI：https://doi.org/10.1021/j100149a007
  DOI ID：10.1021/j100149a007, ISSN：0022-3654, CiNii Articles ID：30011588119, Web of Science ID：WOS:A1993MH93900007
• SPIN DYNAMICS AND CHAIN DYNAMICS OF BIRADICALS GENERATED BY THE PHOTOCLEAVAGE OF CYCLOALKANONE　　　　　　　　　　　　　　　
  K MAEDA; N SUZUKI; T AZUMI
  JOURNAL OF PHYSICAL CHEMISTRY, Volume：97, Number：38, First page：9562, Last page：9565, Sep. 1993
  The magnetic field dependence of the low-field chemically induced dynamic nuclear polarization (CIDNP) on the photocleavage of cyclodecanone and cyclododecanone was measured at various temperatures. The magnetic field effect at which CIDNP intensity is maximum is shifted to larger magnetic field as temperature increases. This is interpreted as due to the increase of the effective exchange integral of the intermediate biradicals at higher temperatures. The observed magnetic field dependence is simulated with a theoretical model based on the stochastic Liouville equation. The observed temperature dependence of the effective exchange integral is interpreted as due to the shrinking of the effective alkyl chain at higher temperature.
  AMER CHEMICAL SOC, English
  DOI：https://doi.org/10.1021/j100140a005
  DOI ID：10.1021/j100140a005, ISSN：0022-3654, CiNii Articles ID：80007276896, Web of Science ID：WOS:A1993LY49500005
• DYNAMIC NUCLEAR-POLARIZATION STUDIES OF ANOMALOUS CIDNP BEHAVIOR OF BENZALDEHYDE　　　　　　　　　　　　　　　
  Y YAMAKAGE; QX MENG; K MAEDA; T AZUMI
  CHEMICAL PHYSICS LETTERS, Volume：204, Number：5-6, First page：411, Last page：414, Mar. 1993
  The magnetic field dependence of CIDNP observed during the photolysis of benzaldehyde was measured. At high and low magnetic field limits, respectively, the CIDNP polarization is satisfactorily interpreted in terms of S-T0 and S-T_ mixing of radical pair theory. The CIDNP polarization observed at around 300 mT, however, cannot be interpreted in terms of radical pair theory. In order to understand this anomalous CIDNP behavior, dynamic nuclear polarization (DNP) was observed. From the observed emissive DNP and the known emissive CIDEP polarization, we conclude that the anomalous CIDNP is due to the transfer of electron spin polarization created by the triplet mechanism to the nuclear spin by cross relaxation.
  ELSEVIER SCIENCE BV, English
  DOI：https://doi.org/10.1016/0009-2614(93)89178-K
  DOI ID：10.1016/0009-2614(93)89178-K, ISSN：0009-2614, CiNii Articles ID：80006971816, Web of Science ID：WOS:A1993KU02600004
• TRIPLET MECHANISM OF CIDNP IN THE PHOTOLYSIS OF BENZOQUINONES AS STUDIED BY DYNAMIC NUCLEAR-POLARIZATION　　　　　　　　　　　　　　　
  QX MENG; K SUZUKI; K MAEDA; M TERAZIMA; T AZUMI
  JOURNAL OF PHYSICAL CHEMISTRY, Volume：97, Number：7, First page：1265, Last page：1269, Feb. 1993
  CIDNP and CIDNP-detected ESR spectra are observed in the photolysis of benzoquinone and its methyl derivatives. In low concentrations of solutions, the sign of the CIDNP of the ring and methyl protons of benzoquinones is in accord with the prediction from the Kaptein rule; however, at high concentrations, the sign is reversed. From the sign of the dynamic nuclear polarization that is observed as a component of the CIDNP-detected ESR spectrum, the mechanism of the cross-relaxation in free radicals is determined. From the correlation between the sign of the dynamic nuclear polarization and the sign of the CIDNP, the anomalous sign of the CIDNP observed at high concentrations is ascribed to generation of an electron spin polarization by the anisotropy in the intersystem crossing (triplet mechanism) and subsequent transfer of this polarization to the nuclei by the cross-relaxation in free radicals. Thus, the triplet mechanism of CIDNP is well substantiated.
  AMER CHEMICAL SOC, English
  DOI：https://doi.org/10.1021/j100109a005
  DOI ID：10.1021/j100109a005, ISSN：0022-3654, CiNii Articles ID：80006934400, Web of Science ID：WOS:A1993KM69400005
• CIDNP-Detected ESR Spectrometer　　　　　　　　　　　　　　　
  Volume：76, First page：7, Last page：15, 1993
• X-band CIDNP detected ESR spectron in the hydrogen abstraction reaction of the carbonyl compounds　　　　　　　　　　　　　　　
  Volume：182, First page：99, 1993
• DNP Spectrum observed in the Photolysis of Benzoquinone and Some of Its Methyl Derivatives. The Triplet Mechanism in CIDNP　　　　　　　　　　　　　　　
  Volume：180,95, 1993
• CIDNP-Detected ESR Spectrometer　　　　　　　　　　　　　　　
  Science Reports Tohoku Universuty, First Series,, Volume：76, First page：7, Last page：15, 1993
• X-band CIDNP detected ESR spectron in the hydrogen abstraction reaction of the carbonyl compounds　　　　　　　　　　　　　　　
  Zeitschcrift f(]E88DB[)r Physikalish Chemie, Volume：182, First page：99, 1993
• TIME-RESOLVED ELECTRON-SPIN-RESONANCE SPECTRA OF LINKED RADICAL PAIRS ON LASER EXCITATION OF ZINC TETRAPHENYLPORPHYRIN VIOLOGEN SYSTEMS　　　　　　　　　　　　　　　
  H NAKAMURA; S USUI; Y MATSUDA; T MATSUO; K MAEDA; T AZUMI
  JOURNAL OF PHYSICAL CHEMISTRY, Volume：97, Number：3, First page：534, Last page：536, Jan. 1993
  Photoinduced electron transfer from the zinc tetraphenylporphyrin moiety to the viologen unit in linked compounds in reversed micelles generated radical pairs, which afforded chemically induced dynamic electron polarization (CIDEP) spectra at room temperature. The CIDEP spectra varied with the number of methylene groups (n) in the alkyl spacer of the linked compounds. In the case of longer spacers (n = 6 and 8), common E/A/E/A patterns were observed throughout the measurement (0.7-5 mus). The signal pattern could be simulated by a formula for the well-known spin-correlated radical pair mechanism, and the corresponding exchange coupling (J) was evaluated (-0.4mT). In the case of ZP4V, the CIDEP signals rapidly changed with elapsed time (O.5-3 mus) from the absorptive to emissive mode. The observation was explained on the basis of a strong contribution of the triplet mechanism in the photogeneration of the radical pair in the early period of measurement.
  AMER CHEMICAL SOC, English, Report scientific journal
  DOI：https://doi.org/10.1021/j100105a002
  DOI ID：10.1021/j100105a002, ISSN：0022-3654, CiNii Articles ID：80006890053, Web of Science ID：WOS:A1993KH92900002
• DNP Spectrum observed in the Photolysis of Benzoquinone and Some of Its Methyl Derivatives. The Triplet Mechanism in CIDNP　　　　　　　　　　　　　　　
  Zeitschcrift fur Physikalish Chemie, Volume：180,95, 1993
• Time-resolved DNP study on the hydrogen abstraction reaction of benzaldehyde　　　　　　　　　　　　　　　
  Applied Magnetic Resonance, Volume：5,177, 1993
• Time-resolved DNP study on the hydrogen abstraction reaction of benzaldehyde　　　　　　　　　　　　　　　
  Volume：5,177, 1993
• THE EFFECT OF THE COULOMB FORCE ON THE DIFFUSIONAL MOTION OF RADICALS AS STUDIED BY THE SOLVENT PERMITTIVITY DEPENDENCE OF THE CIDNP INTENSITY　　　　　　　　　　　　　　　
  T AIZAWA; T SAKATA; S ITOH; K MAEDA; T AZUMI
  CHEMICAL PHYSICS LETTERS, Volume：195, Number：1, First page：16, Last page：20, Jul. 1992
  The diffusional motion of radical ions in the photoisomerization of trans-stilbene in the presence of triphenylamine is studied by the solvent permittivity dependence of the CIDNP intensity. The CIDNP intensity is analyzed with a stochastic Liouville equation that includes the effect of the Coulomb force on the diffusional motion of radicals. The Coulomb force greatly affects the diffusional motion. The increase of the Coulomb force enhances the reaction yield in the high-permittivity region (epsilon(r) > 12), and suppresses the reaction yield in the low-permittivity region (epsilon(r) < 12).
  ELSEVIER SCIENCE BV, English
  DOI：https://doi.org/10.1016/0009-2614(92)85903-N
  DOI ID：10.1016/0009-2614(92)85903-N, ISSN：0009-2614, CiNii Articles ID：80006590524, Web of Science ID：WOS:A1992JF88000004
• DETERMINATION OF THE EXCHANGE INTEGRAL BY THE LOW-FIELD CIDNP IN INTRAMOLECULAR HYDROGEN ABSTRACTION REACTION OF POLYMETHYLENE-LINKED XANTHONE AND XANTHENE　　　　　　　　　　　　　　　
  K MAEDA; QX MENG; T AIZAWA; M TERAZIMA; T AZUMI; Y TANIMOTO
  JOURNAL OF PHYSICAL CHEMISTRY, Volume：96, Number：12, First page：4884, Last page：4889, Jun. 1992
  The intramolecular hydrogen abstraction reaction in a series of polymethylene-linked xanthone and xanthene systems is investigated from the viewpoint of the magnetic field effect of the low-field chemically induced dynamic nuclear polarization (CIDNP) spectra. The magnetic field effect can be successfully simulated with the stochastic Liouville equation, and the effective exchange integral J between the two terminal radicals is determined from the peak of the magnetic field dependence. The effective J values thus determined are much larger than those obtained by the CIDEP method. The difference in the J values obtained by the CIDEP and CIDNP is discussed.
  AMER CHEMICAL SOC, English
  DOI：https://doi.org/10.1021/j100191a030
  DOI ID：10.1021/j100191a030, ISSN：0022-3654, CiNii Articles ID：80006537856, Web of Science ID：WOS:A1992HY32200030
• CIDNP AND CIDEP STUDIES ON INTRAMOLECULAR HYDROGEN ABSTRACTION REACTION OF POLYMETHYLENE-LINKED XANTHONE AND XANTHENE - DETERMINATION OF THE EXCHANGE INTEGRAL OF THE INTERMEDIATE BIRADICALS　　　　　　　　　　　　　　　
  K MAEDA; M TERAZIMA; T AZUMI; Y TANIMOTO
  JOURNAL OF PHYSICAL CHEMISTRY, Volume：95, Number：1, First page：197, Last page：204, Jan. 1991
  Hydrogen abstraction reaction of a polymethylene-linked system is investigated by using chemically induced dynamic nuclear and electron polarization (CIDNP and CIDEP) methods. The reaction scheme is determined from the CIDNP and CIDEP spectra of the unlinked xanthene and xanthone system. The exchange integral J between the two terminal radicals of the system is obtained from the simulation process by using the spin-correlated CIDEP theory modified with (a) the fast population relaxation between the central S-T0 mixed states, (b) the contribution from the triplet mechanism, and (c) hyperfine line dependent line width. The mechanism of the fast population relaxation and the dependence of the J value on the temperature and polymethylene chain length are discussed.
  AMER CHEMICAL SOC, English
  DOI：https://doi.org/10.1021/j100154a040
  DOI ID：10.1021/j100154a040, ISSN：0022-3654, CiNii Articles ID：80005650242, Web of Science ID：WOS:A1991ER47300040
• CIDNP and CIDEP Studies on Hydrogen Abstruction of 9, 10 - Authraquinone from Xanthene　　　　　　　　　　　　　　　
  Journal of Chemical Society Faraday Transaction, Volume：86, Number：2, First page：253, Last page：256, 1990
  DOI：https://doi.org/10.1039/ft9908600253
  DOI ID：10.1039/ft9908600253, ISSN：0956-5000
• CIDEP Studies on the Intramolecular Hydrogen Abstruction Reaction of Polymethylene Linked System Population Relaxation Between the S-To Mixed States　　　　　　　　　　　　　　　
  Chemical Physics Letters, Volume：164, Number：5, First page：562, Last page：566, 1989
  DOI：https://doi.org/10.1016/0009-2614(89)85258-3
  DOI ID：10.1016/0009-2614(89)85258-3, ISSN：0009-2614, CiNii Articles ID：80004965430
• Magnetic field effect on electron transfer reaction of flavin derivatives associated with micelles. Makoto Horiuchi, Kiminori Maeda, Tatsuo Arai　　　　　　　　　　　　　　　
  Applied Magnetic Ressonance, in press.

• 核スピン分極からみた分子磁性の動的挙動　　　　　　　　　　　　　　　
  1996
• Temperature Dependence of the Magnetic Field Effect of the CIDNP in the Photocleavage of Cycloalkanone.　　　　　　　　　　　　　　　
  1992
• Temperature Dependence of the Magnetic Field Effect of the CIDNP in the Photocleavage of Cycloalkanone.　　　　　　　　　　　　　　　
  Spin Chemistry, 1992
• Effect of Colomb Force on Diffusion as Studied by CIDNP Intensities of Photo-Induced Electron Transter Reactions of trans-Stilbene.　　　　　　　　　　　　　　　
  1991
• CIDNP and CIDEP Studies on Intramolecular Hydrogen Abstruction Reaction of Polyrethylene Linked System　　　　　　　　　　　　　　　
  1991
• Effect of Colomb Force on Diffusion as Studied by CIDNP Intensities of Photo-Induced Electron Transter Reactions of trans-Stilbene.　　　　　　　　　　　　　　　
  Spin Chemistry, 1991
• CIDNP and CIDEP Studies on Intramolecular Hydrogen Abstruction Reaction of Polyrethylene Linked System　　　　　　　　　　　　　　　
  Spin Chemistry, 1991

• Electron dynamics in Lithium Ammonia Solution Probed by X and W-band Pulse EPR　　　　　　　　　　　　　　　
  2010
• Magnetic Field Effects on the photochemical reactions in protein systems　　　　　　　　　　　　　　　
  2009
• Does a migrating bird watch the earth magnetic field?　　　　　　　　　　　　　　　
  2009
• Quantum Spin dynamics appears in the chemical reaction of radical pairs　　　　　　　　　　　　　　　
  2009
• Spin dynamics of the model system of a chemical compass using pulsed EPR and transient absorption techniques　　　　　　　　　　　　　　　
  2009
• “Magnetic Field Effects in Biological Systems”　　　　　　　　　　　　　　　
  2007
• ”A photochemical compass”　　　　　　　　　　　　　　　
  2007
• Anisotropic magnetic field effect observed in the model system of the photochemical compass　　　　　　　　　　　　　　　
  2007
• Oscillating magnetic field effects on photochemical reactions studied by time-resolved laser flash photolysis　　　　　　　　　　　　　　　
  2006
• “Extremely low magnetic field effects towards a photochemical compass”　　　　　　　　　　　　　　　
  2006
• Probing the spin mixing process of radical pairs by nano-second pulsed magnetic fields　　　　　　　　　　　　　　　
  2005
• Probing the dynamics of flavin radical and its radical pair in confined systems by magnetic field effects on transient absorption　　　　　　　　　　　　　　　
  2004
• “A contribution of the Magnetic Field Effects to Flavin Photochemistry”　　　　　　　　　　　　　　　
  2003
• Spin Chemistry in the electron transfer reaction of flavin derivatives　　　　　　　　　　　　　　　
  2003
• Application of the Magnetic Spin Effect to Exploring Photochemical Reactions of Flavin Derivatives　　　　　　　　　　　　　　　
  2003
• Effects of the various environments on the radical pair dynamics in electron transfer reactions of flavin derivatives　　　　　　　　　　　　　　　
  2002
• “Applications of magnetic spin effect on the electron transfer reactions of flavin derivatives”　　　　　　　　　　　　　　　
  2002

• International EPR Society

• マイクロ波とラジオ波を用いたスピン化学の手法による選択的同位体濃縮　　　　　　　　　　　　　　　
  30 Jul. 2020 - 31 Mar. 2024
  Grant amount(Total)：25740000, Direct funding：19800000, Indirect funding：5940000
  Grant number：20K20557
• 3 dimensional imaging of photochemical quantum magnetic compasses.　　　　　　　　　　　　　　　
  Japan Society for the Promotion of Science, Grants-in-Aid for Scientific Research, Grant-in-Aid for Scientific Research (B), 01 Apr. 2018 - 31 Mar. 2023
  Saitama University
  Grant amount(Total)：15990000, Direct funding：12300000, Indirect funding：3690000
  Grant number：18H01184
• Does protein clustering play a role in biological magnetoreception?　　　　　　　　　　　　　　　
  Japan Society for the Promotion of Science, Grants-in-Aid for Scientific Research, Grant-in-Aid for JSPS Fellows, 12 Oct. 2018 - 31 Mar. 2020
  Saitama University
  Grant amount(Total)：2200000, Direct funding：2200000
  Grant number：18F18789
• Quantum interference to charge recombination reactions by strong magnetic fields　　　　　　　　　　　　　　　
  Japan Society for the Promotion of Science, Grants-in-Aid for Scientific Research, Grant-in-Aid for Challenging Exploratory Research, 01 Apr. 2015 - 31 Mar. 2017
  MAEDA Kiminori, Saitama University
  Grant amount(Total)：3250000, Direct funding：2500000, Indirect funding：750000
  In order to clarify the quantum mechanical effect in radical pair mechanism, which is considered to be the cause of magnetic compass of migratory birds, we built a new setup for measurement of magnetic field effects (MFEs) with high sensitivity and stability that allows the precise analysis of the magnetic field effect on reaction yield (MARY) spectrum in time resolved manner. In the flavin system, we succeeded in measuring the magnetic field effect with very high stability, and discovered the time evolution of the MARY spectral shape. We calculated these phenomena based on quantum mechanics and could explain the time evolution of the spectra by an effect of the spin dephasing. The spin dephasing is one of the most important phenomena in the discussion of the magnetoreception of the very small magnetic field. This result should have an impact on the discussion of the relationship of the spin dynamic and the molecular magnetoreceptions.
  Grant number：15K13547
• スピン選択的化学反応の量子ダイナミクス　　　　　　　　　　　　　　　
  29 Aug. 2014 - 31 Mar. 2015
  Grant amount(Total)：1300000, Direct funding：1000000, Indirect funding：300000
  Grant number：26888004
• 疎水的環境場を持つ分子集合系と生体高分子を利用した光化学反応制御　　　　　　　　　　　　　　　
  2002 - 2002
  Grant amount(Total)：2900000, Direct funding：2900000
  Grant number：14050018
• 超分子システム中における低磁場中でのスピンダイナミクス操作による化学反応制御　　　　　　　　　　　　　　　
  2001 - 2002
  Grant amount(Total)：2100000, Direct funding：2100000
  Grant number：13740320
• 局所的反応場とスピン対の量子制御に基づく化学反応制御　　　　　　　　　　　　　　　
  1999 - 2000
  Grant amount(Total)：2300000, Direct funding：2300000
  Grant number：11740304
• SPIN CHEMISTRY OF MEMBRANE INTERFACE　　　　　　　　　　　　　　　
  Japan Society for the Promotion of Science, Grants-in-Aid for Scientific Research, Grant-in-Aid for Scientific Research (B)., 1999 - 2000
  MURAI Hisao; MAEDA Kiminori, TOHOKU UNIVERSITY
  Grant amount(Total)：4300000, Direct funding：4300000
  We used this grant project mainly for the purpose of exchange of scientists and discussion of scientific information about the spin chemical phenomena of membrane interface. Our final aim of this project is the investigation of biological active membrane, but the basic physical understanding of the interface is much more important to start the studies. During the project period, we invited several scientists who were experts of spin effect and membrane phenomenon. Murai visited University of North Carolina and Oxford University to discuss and obtain information concerning membranes. Maeda also visited Oxford University to discuss the application of magnetic resonance to the investigation of biological systems. In this project we employed several different micellar and bilayer systems. The methods of the observation of the spin effects in the membrane interface were 1) time-resolved ESR and 2) reaction yield detected magnetic resonance. Especially, method 2) was newly developed technique and a transient optical absorption detection was mainly used to monitor the reaction change by the irradiation of microwave under the conditions of electron spin resonance. Using method 2), we studied a singlet born radical pair system in an SDS micelle employing tetraphenylhydrazine. In this study we succeeded in effective spin flip operation and chemical reaction control in the micellar solution. Method 2) was also applied to the photoreduction system of xanthone and t-butylphenol derivatives in an SDS micelle. We discovered a quantum beat phenomenon of two-spin simultaneous excitation by microwave. From the data of the quantum beat we concluded that the decay of the beat is mainly due to the triplet-triplet dephasing that is a new concept of spin-phase relaxation in radical pair systems. Our recent aim of the project is photochemical electron labeling of a bilayer system and the investigation using method 1) is underway.
  Grant number：11694052
• OBSERVATION OF QUANTUM COHERENCE OF PARAMAGNETIC SPECIES BY MEANS OF SUDDEN MAGNETIC FIELD JUMP　　　　　　　　　　　　　　　
  Japan Society for the Promotion of Science, Grants-in-Aid for Scientific Research, Grant-in-Aid for Scientific Research (B)., 1998 - 2000
  MURAI Hisao; MAEDA Kiminori, TOHOKU UNIVERSITY
  Grant amount(Total)：15300000, Direct funding：15300000
  This project aims at the observation and deep investigation of the spin coherent phenomenon of radical pairs formed transiently by photochemical method. We employed two different methods under the existence of radical pairs : 1) sudden jumping of the external magnetic field, 2) quick switching of the electromagnetic field (microwave field) under the conditions of the electron spin resonance. The radical pairs are prepared using a laser pulse irradiation to several solutions. The systems we employed were a) polymethylene-linked biradical, b) radical-ion pairs formed by photoinduced electron transfer reaction, c) micellar systems that include transiently formed radical pairs. Method 1) was applied to the the system b) and it showed the controlled reaction by the magnetic field jump, but we realized the difficulty of the theoretical handling of low magnetic field phenomenon. This study is still under investigation. Method 2) provided many new discoveries about the spin dynamics of radical pair and radical-ion pair systems. First of all, we succeeded in observing the different spin quantum beats of several radical pair systems. The beat data showed the double tequency signal due to simultaneous excitation of the component radicals of radical pairs by microwave field. The decay of the beat signal was proved to be due to the triplet-triplet dephasing phenomenon probably induced by anisotropic dipole-dipole interaction in the radical pair. Another important finding is the appearance of a broadened spectral pattern under the strong microwave field, that was also rationalized by the spin dephasing effect. This project apparently demonstrated that the switching of the external field and/or the electromagnetic alternating field can control the chemical reaction pathways and it also provides a lot of important information about the spin and chemical dynamics of photochemical systems.
  Grant number：10440164
• 局所的反応場とスピン対の量子制御に基づく化学反応制御　　　　　　　　　　　　　　　
  1998 - 1998
  Grant amount(Total)：1300000, Direct funding：1300000
  Grant number：10740262
• Photochemically formed contact radical pair and its unusual spin polarization　　　　　　　　　　　　　　　
  Japan Society for the Promotion of Science, Grants-in-Aid for Scientific Research, Grant-in-Aid for Scientific Research (B), 1996 - 1997
  MURAI Hisao; OKADA Keiji; MAEDA Kiminori, TOHOKU UNIVERSITY
  Grant amount(Total)：7600000, Direct funding：7600000
  The aim of this project is to clarify the dynamics of the radical-ion pairs and contact radical pairs formed transiently in photochemical reactions using new detection techniques of a photoconductivity detected magnetic resonance (PCDMR) and a transient absorption detected magnetic resonance (ADMR).
  1996 : The photoionization process of TMPD in alcohol by way of the radical-ion pair was investigated by PCDMR and ADMR methods. The sample solutions previously deoxygenated were photolyzed in the ESR cavity, and the conductivity change was monitored under the ESR conditions by applying strong microwave power. We finally succeeded in the observation of the transient radical-ion pair. This was the first report of the observation of the radical-ion pair using PCDMR method in the world. The trial of the observation of the transient absorption (optical) under ESR conditions proved that the PCDMR spectrum was the observation of the real radical-ion pair. The spectrum was broadened probably due to the dynamic properties of the radical-ion pair, and the formation of the contact radical pair having short lifetime was the main cause of the broadening. Theoretical analysis was also performed.
  1997 : We investigated a system of the photoinduced electron transfer reaction using the PCDMR technique. The deoxygenated solution of xanthone and N,N-diethylaniline in 2-propanol was used as the sample. This system is known to show large external magnetic field effect contrary to its homogeneous conditions. Finally, we succeeded in observing the PCDMR spectrum of the radical-ion pair composed of xanthone anion and diethylaniline cation radicals. We also succeeded in determining the lifetime of the radical-ion pair to be about 200 ns. That is extremely long comparing with the ordinary radical pair in 2-propanol under the same conditions. This long lifetime is the main cause of the large external magnetic field effect. This Iong lifetime may be due to the network formation between the radical-ion pair and alcohol molecules. The spectrum showed a forbidden transition of ESR under very strong microwave radiation. This implies that two radical ions are fluctuating and frequently they encounter in close distance such as the contact radical pair.
  Grant number：08454172
• ラジカル対におけるスピン対相関のダイナミクスおよび緩和現象の高速観測　　　　　　　　　　　　　　　
  1996 - 1996
  Grant amount(Total)：1100000, Direct funding：1100000
  Grant number：08740437
• Reaction control by the accerelation and the decerelation of the intersystem crossing by microwave irradiation.　　　　　　　　　　　　　　　
  Japan Society for the Promotion of Science, Grants-in-Aid for Scientific Research, Grant-in-Aid for Scientific Research (A), 1995 - 1996
  AZUMI Tohru; FUJII Kanae; MAEDA Kiminori, Tohoku University
  Grant amount(Total)：4300000, Direct funding：4300000
  In this project we have tried to clear the effect of the microwave irradiation on the spin correlation of the radical pair (RP), and to control the photochemical reaction by this effect. For these purpose, we performed the investigation on the following subjects. (1) Construction of the new time-resolved RYDMR (Reaction Yield Detected Magnetic Resonance) and SNP (Stimulate Nuclear Polarization) detection system. For the investigation of the spin correlation of the radical pair, we need a method to observe the spin correlation in fast time resolution (-ns). We apply the various techniques (detection of emission, transient absorption, nuclear polarization, and photo-conductivity) for the observation of the microwave effect on the dynamics of the radical pair. (2) Discussion of the time-resolved ADMR spectra observed in the polymethylene-linked xanthone and xanthene. (3) Observation of the effect of the pulsed microwave on the spin dynamics of RP.(4) The spin dynamics of the RP in the micellar supercage studied by the time-resolved ESR and the stimulated nuclear polarization (SNP) spectra.
  Grant number：07554064
• マイクロ波パルスによるラジカル対スピンダイナミクスの量子制御　　　　　　　　　　　　　　　
  1995 - 1995
  Grant amount(Total)：2100000, Direct funding：2100000
  Grant number：07228206
• スピン相関操作を利用した光化学反応制御　　　　　　　　　　　　　　　
  1994 - 1994
  Grant amount(Total)：2200000, Direct funding：2200000
  Grant number：06239207
• 強いマイクロ波パルス照射による光反応制御　　　　　　　　　　　　　　　
  1993 - 1993
  Grant amount(Total)：900000, Direct funding：900000
  Grant number：05740345
• Development of the CIDNP-detected Electron Spin Resonance Apparatus for the Aid of Investigation of Radical Pairs　　　　　　　　　　　　　　　
  Japan Society for the Promotion of Science, Grants-in-Aid for Scientific Research, Grant-in-Aid for Developmental Scientific Research (B), 1991 - 1993
  AZUMI Tohru; FUJII Kanae; MAEDA Kiminori, TOHOKU UNIVERSITY
  Grant amount(Total)：10100000, Direct funding：10100000
  In most of chemical reactions in solution, the whole fate of the reaction path is governed by the small interaction that is operative within a short lifetime of radical pairs. In this respect one whishes to observe the spectrum of radical pairs and analyze it to fully understand chemical reactions. However, in any conventional spectroscopy, the spectrum due to radical pairs and that due to free radicals cannot be separately observed.
  The CIDNP-detected ESR spectroscopy has been developed in order to separately obseve the ESR spectrum of radical pairs and that of free radicals. We have further tried to extend this spectroscopy to time-resolved spectroscopy.
  By this new spectroscopy, a lot of chemical reactions have been investigated. As an example, the photo-induced hydrogen abstraction reaction of dichlorobenzoquinone has been investigated. It has found that the hydroxybenzoquinone radical that exists as a radical pair and that exists as a free radical are different. This amazing conclusion can never be obtained by any other spectroscopic means. Further, the lifetime of radical pairs was determined as 20 ns.
  Grant number：03554013
• 低磁場中における光化学反応中間体のスピンダイナミクスに関する研究　　　　　　　　　　　　　　　
  1992 - 1992
  Grant amount(Total)：900000, Direct funding：900000
  Grant number：04740271
• 閉殻配置をもつ金属イオンの錯体におけるd-π相互作用　　　　　　　　　　　　　　　
  1992 - 1992
  Grant amount(Total)：2000000, Direct funding：2000000
  Grant number：04640466
• Opto-magnetic studies of metal-ligand interactions in transition metal complexes having closed shell configurations　　　　　　　　　　　　　　　
  Japan Society for the Promotion of Science, Grants-in-Aid for Scientific Research, Grant-in-Aid for international Scientific Research, 1990 - 1992
  AZUMI Tohru; IKEYAMA Takeshi; MAEDA kiminori; CROSBY Glenn A., Tohoku University
  Grant amount(Total)：7900000, Direct funding：7900000
  Spectroscopic and magnetic properties have been investigated for complexes of d^<10> closed shell metal ions, and the results of significance are summarized as follows.
  (1) Mixed ligand complexes of the type Zn(X-PhS)_2(phen)
  The triplet sublevels associated with the lowest ligand charge transfer (LLCT) triplet excited state have been investigated for a series of the complexes of the type Zn(X-PhS)_2(phen), where X is a substituent on the benzenthiol ligand and phen is 1,10-phenanthroline. The zero field splitting parameters D* are significantly larger than the values calculated quantum mechanically based on a model of pure charge transfer state. This discrepany suggests that the phen localized pipi* states mixes with the LLCT state. The degree of mixing is obtained based on this mixing mechanism from the results of both the lifetime and the zero field splitting. The mixing coefficients determined show a good and expected correlation with the electron donating ability of the substituent X on benzenethiol. Thus, the participation of LLCT to phen localized pipi* state is well substantiated.
  (2) Complexes of the type MX_2(phen)
  Fluorescence and the triplet sublevel properties have been investigated for a series of complexes of the type MX_2(phen), where M is Zn(II) or Cs(II) and X is C1, Br, or I. The fluorescence lifetime, zero field splittings,and the radiative rate constants for sublevels are all interpreted satisfactorily by a theoretical model in which the phen localized pipi* state mixes with charge transfer state arising from the electron promotion from p orbital of halogen to pi* orbital phen.
  Grant number：02044011
• CIDNP検出ESR法によるラジカル対内の構造変化と反応　　　　　　　　　　　　　　　
  1991 - 1991
  Grant amount(Total)：2100000, Direct funding：2100000
  Grant number：03640422
• 光化学反応、反応中間体のスピンダイナミクス、動物の地磁気感受システム、化学コンパス、電子スピン共鳴　　　　　　　　　　　　　　　
  Competitive research funding
• Photochemical reactions　　　　　　　　　　　　　　　
  Competitive research funding

• 磁場応答性分子固体物質および該分子固体を用いた磁場測定方法ならびに磁場測定装置　　　　　　　　　　　　　　　
  Patent right
  P08P005642