業績情報

• Distinct Solubilization Mechanisms of Medroxyprogesterone in Gemini Surfactant Micelles: A Comparative Study with Progesterone　　　　　　　　　　　　　　　
  Hiromichi Nakahara; Kazutaka Koga; Keisuke Matsuoka
  Molecules, 巻：29, 号：20, 2024年10月, ［査読有り］
  The solubilization behavior of medroxyprogesterone (MP) within gemini surfactant micelles (14-6-14,2Br−) was investigated and compared with that of progesterone to uncover distinct solubilization mechanisms. We employed 1H-NMR and 2D ROESY spectroscopy to elucidate the spatial positioning of MP within the micelle, revealing that MP integrates more deeply into the micellar core. This behavior is linked to the unique structural features of MP, particularly its 17β-acetyl group, which promotes enhanced interactions with the hydrophobic regions of the micelle, while the 6α-methyl group interacts with the hydrophilic regions of the micelle. The 2D ROESY correlations specifically highlighted interactions between the hydrophobic chains of the surfactant and two protons of MP, H22 and H19. Complementary machine learning and electron density analyses supported these spectroscopic findings, underscoring the pivotal role of the molecular characteristics of MP in its solubilization behavior. These insights into the solubilization dynamics of MP not only advance our understanding of hydrophobic compound incorporation in gemini surfactant micelles but also indicate the potential of 14-6-14,2Br− micelles for diverse drug delivery applications.
  研究論文（学術雑誌）
  DOI：https://doi.org/10.3390/molecules29204945
  Scopus：https://www.scopus.com/inward/record.uri?partnerID=HzOxMe3b&scp=85207674635&origin=inward
  Scopus Citedby：https://www.scopus.com/inward/citedby.uri?partnerID=HzOxMe3b&scp=85207674635&origin=inward
  DOI ID：10.3390/molecules29204945, eISSN：1420-3049, PubMed ID：39459313, SCOPUS ID：85207674635
• Solubilization of polycyclic aromatic compounds into supralong-chain surfactants with double quaternary ammonium micelles　　　　　　　　　　　　　　　
  Keisuke Matsuoka; Rina Sekiguchi; Tomokazu Yoshimura; Hiromichi Nakahara; Kazutaka Koga
  Journal of Molecular Liquids, 巻：405, 2024年07月, ［査読有り］
  The dissolution of poorly water-soluble compounds in micelles via hydrophobic interactions is termed solubilization. The solubilization of polycyclic aromatic compounds, namely, naphthalene, anthracene, and pyrene, was studied using supralong-chain surfactants with two consecutive cationic hydrophilic groups [CnH2n+1N+(CH3)2-(CH2)2-N+(CH3)3 2Br-: Cn-2Am (n = 18, 20, and 22)] and typical cationic surfactants [CnH2n+1N+(CH3)3 Br-: Cn-Am (n = 12, 14, and 16)]. Long alkyl chains in hydrophobic surfactants are advantageous for forming a large micellar core. The maximum quantity of solubilized polycyclic aromatic compounds increased as the alkyl chain length of the surfactant increased. Therefore, the molar solubilization ratio (MSR), which represents the solubilization ability of the surfactant, was maximized when the alkyl chain length was C22-2Am. Similarly, the Gibbs free energy (ΔG0) associated with the solubilization of polycyclic aromatic compounds was also lowest for C22-2Am. Surfactants with long alkyl chains functioned as excellent solubilizers. The solubilization sites of the polycyclic aromatic compounds were determined using two-dimensional NMR and small-angle X-ray scattering (SAXS) measurements. As the molecular size of the polycyclic aromatic compounds increased, the solubilization positions in the micelles shifted from the palisade layer to the vicinity of the hydrophilic groups. Extension of the alkyl chain length of the surfactant resulted in an increase in the palisade region of the micelles, which was advantageous for solubilization.
  研究論文（学術雑誌）
  DOI：https://doi.org/10.1016/j.molliq.2024.125109
  Scopus：https://www.scopus.com/inward/record.uri?partnerID=HzOxMe3b&scp=85194340088&origin=inward
  Scopus Citedby：https://www.scopus.com/inward/citedby.uri?partnerID=HzOxMe3b&scp=85194340088&origin=inward
  DOI ID：10.1016/j.molliq.2024.125109, ISSN：0167-7322, SCOPUS ID：85194340088
• Micelle formation of sodium taurolithocholate　　　　　　　　　　　　　　　
  Keisuke Matsuoka; Rina Sekiguchi; Tomokazu Yoshimura
  Chemistry and Physics of Lipids, 巻：259, 開始ページ：105378, 終了ページ：105378, 2024年03月, ［査読有り］
  Elsevier BV, 研究論文（学術雑誌）
  DOI：https://doi.org/10.1016/j.chemphyslip.2024.105378
  DOI ID：10.1016/j.chemphyslip.2024.105378, ISSN：0009-3084
• Solubilization of progesterone into Gemini surfactant solutions: 2D ROESY spectroscopy　　　　　　　　　　　　　　　
  Hiromichi Nakahara; Kazutaka Koga; Keisuke Matsuoka
  Journal of Molecular Liquids, 巻：395, 2024年02月, ［査読有り］
  We investigate the capabilities of micellar systems, specifically their role as solubilizing agents for hydrophobic substances. Our focus is on interaction of a Gemini surfactant of 14-6-14,2Br− with progesterone, a hydrophobic bioactive compound. Through the application of 1H NMR and 2D ROESY spectroscopic techniques, we provide a detailed analysis of the proton environments within the surfactant and their spatial organization within the micellar structure. Our results indicate that the integration of progesterone into the system does not significantly disrupt the micellar structure, highlighting the stability of the 14-6-14,2Br− micelles. Additionally, we present compelling evidence suggesting that progesterone is situated near the micellar surface, a critical insight into the positioning of solubilized molecules within micellar structures. The structural fingerprint and electron density map of progesterone further support this conclusion, indicating a potential interaction between the acetyl group of progesterone and the positively charged -N(CH3)2 headgroups of the surfactant near the micelle surface. This study enhances our understanding of micellar systems and their potential use in the solubilization of hydrophobic compounds, paving the way for advancements in drug delivery systems and related fields.
  研究論文（学術雑誌）
  DOI：https://doi.org/10.1016/j.molliq.2023.123841
  Scopus：https://www.scopus.com/inward/record.uri?partnerID=HzOxMe3b&scp=85180969731&origin=inward
  Scopus Citedby：https://www.scopus.com/inward/citedby.uri?partnerID=HzOxMe3b&scp=85180969731&origin=inward
  DOI ID：10.1016/j.molliq.2023.123841, ISSN：0167-7322, SCOPUS ID：85180969731
• Micelle Formation of Dodecanoic Acid with Alkali Metal Counterions
  Keisuke Matsuoka; Aiko Sato; Yukino Ogawa; Kana Okazaki; Shiho Yada; Tomokazu Yoshimura
  Journal of Oleo Science, 巻：72, 号：9, 開始ページ：831, 終了ページ：837, 2023年06月, ［査読有り］
  Japan Oil Chemists' Society, 研究論文（学術雑誌）
  DOI：https://doi.org/10.5650/jos.ess23086
  DOI ID：10.5650/jos.ess23086, ISSN：1345-8957, eISSN：1347-3352
• Preferential Removal of Alkali Metal Using Dodecanoic Acid and Sodium Dodecyl Sulfate in Foam Separation System.　　　　　　　　　　　　　　　
  Keisuke Matsuoka; Daichi Asamoto
  Journal of oleo science, 巻：72, 号：5, 開始ページ：543, 終了ページ：548, 2023年02月, ［査読有り］, ［国内誌］
  The selectivity of adsorption between alkali metal ions (Li+, Na+, K+, Rb+, and Cs+) based on the ionic functional groups of the surfactants was studied using two types of surfactants, dodecanoic acid (DA) and sodium dodecyl sulfate (SDS), in the foam separation system. The results showed that Li+ was preferably removed by foam separation using DA. The removal rates of other alkali metal ions were relatively low, and there were no significant differences among other alkali metal ions (Na+, K+, Rb+, and Cs+). However, Cs+ exhibited the highest removal rate among the mixed alkali metals by foam separation using SDS. From these results, the selectivity of the alkali metal in foam separation was dependent on the type of surfactant.
  英語, 研究論文（学術雑誌）
  DOI：https://doi.org/10.5650/jos.ess22422
  DOI ID：10.5650/jos.ess22422, PubMed ID：37121679
• Solubilization of fullerene in polyoxyethylene tetradecyl ether type nonionic surfactants　　　　　　　　　　　　　　　
  Hikaru Kuroki; Erika Aida; Takuya Komine; Keisuke Matsuoka
  Journal of Molecular Liquids, 巻：335, 2021年08月, ［査読有り］
  Fullerene is insoluble in water owing to its bulky spherical structure composed of 60 carbons. Herein, polyoxyethylene tetradecyl ether-type nonionic surfactants with a varying number of oxyethylene groups, i.e., C14En (n = 5, 6, and 7), were used to solubilize fullerene. In addition, a solubilization experiment was conducted using the aromatic compound naphthalene as a reference substance. Fullerene tended to solubilize in aqueous solutions of surfactants bearing long EO chains. Particularly, the maximum solubilization quantities of fullerene increased with an increasing number of EO chains in 100 mmol L−1 C14En solutions ranging from 43.2 (n = 5) to 76.9 (n = 6) and 115.6 μmol L−1 (n = 7). In contrast, naphthalene was well solubilized in surfactants bearing relatively shorter EO chains and showing an opposite tendency to that of fullerene. The Gibbs free energy change (ΔG0) per EO chain for the solubilization of fullerene and naphthalene was –1.51 and +0.27 kJ mol−1, respectively. These results indicated that the extension of EO chain of nonionic surfactants is thermodynamically advantageous for achieving the solubilization of fullerene. In addition, the solubilization site of fullerene in the micelles was studied by analyzing its absorption spectrum in four types of solvents with different polarities. The peak wavelength of fullerene suggested that the surrounding environment possessed an intermediate polarity between water and organic solvents. According to the 1H NMR measurements, the waveform of the EO groups in the NMR spectra significantly split upon solubilization of fullerene. From these results, it was concluded that fullerene located in the vicinity of the EO chains (shell area) in the micelles.
  研究論文（学術雑誌）
  DOI：https://doi.org/10.1016/j.molliq.2021.116236
  Scopus：https://www.scopus.com/inward/record.uri?partnerID=HzOxMe3b&scp=85105693362&origin=inward
  Scopus Citedby：https://www.scopus.com/inward/citedby.uri?partnerID=HzOxMe3b&scp=85105693362&origin=inward
  DOI ID：10.1016/j.molliq.2021.116236, ISSN：0167-7322, SCOPUS ID：85105693362
• Removal of period 4 transition metals by foam separation　　　　　　　　　　　　　　　
  Keisuke Matsuoka; Nana Yamaguchi
  JOURNAL OF MOLECULAR LIQUIDS, 巻：325, 2021年03月, ［査読有り］
  Anionic surfactants that form floating bubbles can adsorb metal ions and change foams at the gas-liquid interface. The final rate of ion removal by foam separation determines the selectivity or priority of adsorption of ions. Foam separation was conducted to remove multi-component chlorides of period 4 transition metals (Mn, Fe, Co, Ni, Cu, and Zn) by using sodium decyl sulfate (SDeS) and sodium dodecyl sulfate (SDS) as surfactants. The first-order ion-removal rate constant (k) did not completely change with an increase the atomic number of transition metals. The difference in removal rate constant (k) between the elements was not significant in multi-component chlorides of transition metals. On the other hand, the foam separation was performed in a one-component of period 4 transition metal (Mn, Fe, Co, Ni, Cu, and Zn) using SDeS (8 mmol L-1) for comparing k from alkaline earth metals having different ionic radii, respectively. The transition metal was continuously removed over time, whereas the counter ion (sodium) of the surfactant was not efficiently removed. The results also showed that the k in the one-component 4 transition metal system also slightly increased with increasing ionic radius in 5 h of foam separation. A linear relationship was observed between the first-order ion-removal rate constant (k) by foam separation and the ionic radius of the divalent metal ion. These results indicated that the selectivity of cation adsorption on the soluble monolayer is closely related to the ionic radius of the metal ion. (C) 2020 Elsevier B.V. All rights reserved.
  ELSEVIER, 英語, 研究論文（学術雑誌）
  DOI：https://doi.org/10.1016/j.molliq.2020.115185
  DOI ID：10.1016/j.molliq.2020.115185, ISSN：0167-7322, eISSN：1873-3166, Web of Science ID：WOS:000636695200104
• Micelle Formation of Monoammonium Glycyrrhizinate　　　　　　　　　　　　　　　
  Keisuke Matsuoka; Mamoru Arima; Yusuke Goto; Shiho Yada; Tomokazu Yoshimura
  JOURNAL OF OLEO SCIENCE, 巻：70, 号：7, 開始ページ：911, 終了ページ：918, 2021年, ［査読有り］
  Monoammonium glycyrrhizinate is produced by the neutralization of glycyrrhizic acid from plant licorice with ammonia. In this study, the physicochemical properties of aqueous monoammonium glycyrrhizinate were investigated from the viewpoint of surface chemistry. The structure of the amphiphilic molecule is bola type, comprising two glucuronic acid moieties having two carboxylic acids groups and an aglycone part having a carboxylic acid at the opposite end of the molecule from the glucuronic acids. We found that the physicochemical properties of aqueous monoammonium glycyrrhizinate are dependent on the ionization of the carboxylic acid groups. The solubility of monoammonium glycyrrhizinate gradually increased above pH 4 in the buffer solution. The critical micelle concentration (CMC) and surface tension at the CMC (gamma CMC) of monoammonium glycyrrhizinate were determined by the surface tension method to be 1.5 mmol L-1 and 50 mN m-1 in pH 5 buffer and 3.7 mmol L-1 and 51 mN m-1 in pH 6 buffer, respectively. The surface tension gradually decreased with increasing concentration of monoammonium glycyrrhizinate in the pH 7 buffer, but the CMC was not defined by the curve. Light scattering measurements also did not reveal a clear CMC in the pH 7 buffer. The ionization of the carboxylic acid groups in the bola-type amphiphilic molecule with increasing pH is disadvantageous for micelle formation. Cryo-transmission electron microscopy showed that monoammonium glycyrrhizinate forms rod-like micelles in pH 5 buffer, and small angle X-ray scattering experiments confirmed that the average micellar structure was rod-like in pH 5 buffer. Thus, it was found that monoammonium glycyrrhizinate can form micelles only in weakly acidic aqueous solutions.
  JAPAN OIL CHEMISTS SOC, 英語, 研究論文（学術雑誌）
  DOI：https://doi.org/10.5650/jos.ess21046
  DOI ID：10.5650/jos.ess21046, ISSN：1345-8957, eISSN：1347-3352, Web of Science ID：WOS:000670011000004
• Foam Separation of Dyes Using Anionic, Cationic, and Amphoteric Surfactants.　　　　　　　　　　　　　　　
  Yusuke Goto; Yuya Nema; Keisuke Matsuoka
  Journal of oleo science, 巻：69, 号：6, 開始ページ：549, 終了ページ：555, 2020年, ［査読有り］, ［国内誌］
  Foam separation can selectively remove a target substance from a solution via adsorption of the substance with the surfactant at the surface of the bubble. A cationic dye, methylene blue, and an anionic dye, Fast Green FCF, were prepared as substances to be removed via foam separation. Anionic (sodium dodecyl sulfate, SDS), cationic (dodecyltrimethylammonium chloride, DTAC), and amphoteric (3-(dodecyldimethylammonio)propane-1-sulfonate, SB-12) surfactants were used in the foam separation process. The effectiveness of the surfactants for removing the cationic methylene blue increased as follows: DTAC < SB-12 < SDS. On the other hand, the effectiveness of the surfactants for removing the anionic Fast Green FCF was in the opposite order. The dyes were effectively adsorbed by the foams via electrostatic interactions between the oppositely charged surfactant and the dye molecules. Since amphoteric surfactants have both anionic and cationic charges in a molecule, they could effectively remove both dyes in the foam separation process. Therefore, it was found that the amphoteric surfactant was highly versatile. Analysis of the kinetics of the removal rate showed that the aqueous solutions of monomers could remove the dyes more effectively than micellar solutions in foam separation.
  英語, 研究論文（学術雑誌）
  DOI：https://doi.org/10.5650/jos.ess20004
  DOI ID：10.5650/jos.ess20004, PubMed ID：32522916
• Removal of Zwitterionic Rhodamine B Using Foam Separation.　　　　　　　　　　　　　　　
  Yusuke Goto; Yuya Nema; Keisuke Matsuoka
  Journal of oleo science, 巻：69, 号：6, 開始ページ：563, 終了ページ：567, 2020年, ［査読有り］, ［国内誌］
  Foam separation promotes the removal of dissolved materials from solutions by adsorbing the molecules onto a surfactant. The zwitterion of rhodamine B was removed by using both anionic (sodium dodecyl sulfate: SDS) and cationic (dodecyltrimethylammonium chloride: DTAC) surfactants through foam separation. However, rhodamine B could not be removed from a strongly acidic DTAC solution (pH 2), because the molecular form changes from the zwitterion to cation. Moreover, the cationic dye of rhodamine 6G could not be removed from the DTAC solution. Therefore, these results demonstrate that the electrostatic interaction between a surfactant and target ion is an important factor in foam separation.
  英語, 研究論文（学術雑誌）
  DOI：https://doi.org/10.5650/jos.ess20005
  DOI ID：10.5650/jos.ess20005, PubMed ID：32522917
• Application of foam separation method for removal of alkaline earth metal ions from solution
  Keisuke Matsuoka; Satomi Hasegawa; Taiyo Yuma; Yusuke Goto
  Journal of Molecular Liquids, 巻：294, 2019年11月, ［査読有り］
  © 2019 Elsevier B.V. Foam separation was used to separate dissolved alkaline earth metal ions from aqueous solution. The mechanism is based on anionic surfactant adsorption onto the bubbles generated in the aqueous alkaline earth metal solution. The negatively charged bubbles rise while adsorbing the positive metal ions and change to foam at the surface. The foam in the glass tube drains excess water as it rises and is finally turned into dry foam. The foam separation method with sodium decyl sulfate (SDeS) (8 mmol L−1, below the critical micelle concentration (CMC)) was used to remove alkaline earth metal (Mg, Ca, and Sr) chlorides in the respective systems. The initial concentrations of the surfactant and alkaline earth metal chloride were 8 mmol L−1 (below the CMC) and 2.5 mmol L−1 in 250 mL of solution, respectively. The results showed that the removal rate in the one-component alkaline earth metal system increased with increasing atomic number: Mg (46%) < Ca (58%) < Sr (77%) in 5 h of foam separation. A similar trend was observed in the foam separation in a mixed system of alkaline earth metals. However, the concentration of the surfactant counterion (Na+) remained almost constant after the operation, indicating that the divalent ions, rather than the monovalent surfactant counterions, were preferentially adsorbed onto the sulfate group of the anionic surfactant. The changes in the concentration of the alkaline earth metal ions were analyzed using kinetics. The plot of the first-order rate constant against the ionic radius of each metal suggested a linear relationship in each series of alkaline earth metals or alkali metals. The present study indicates that foam separation using SDeS can be used to effectively remove large alkaline earth metal ions from contaminated water.
  DOI：https://doi.org/10.1016/j.molliq.2019.111663
  DOI ID：10.1016/j.molliq.2019.111663, ISSN：0167-7322, SCOPUS ID：85071718760
• Solubilization ability of star-shaped trimeric quaternary ammonium bromide surfactant
  Keisuke Matsuoka; Naohiro Takahashi; S. Yada; Tomokazu Yoshimura
  Journal of Molecular Liquids, 巻：291, 2019年10月, ［査読有り］
  © 2019 Elsevier B.V. The solubilization ability of surfactants is closely related to their molecular design. The number of alkyl chains in a surfactant molecule accordingly affects the forming of micellar structures. In the present study, the solubilization ability of cationic surfactants was studied by changing number of alkyl chains by using one of these three types of surfactants: star-shaped trimeric quaternary ammonium bromides (tris(N-alkyl-N,N-dimethyl-2-ammoniumethyl)amine bromides (3CntrisQ, n = 10, 12, and 14 is the number of carbon atoms in the alkyl chains)), dimeric surfactants (1,2-bis(alkyldimethylammonio)ethane dibromide (n-2-n, n = 10, 12, and 14)), and dodecyltrimethylammonium bromide (DTAB). The solubilization abilities of the above surfactants were studied using naphthalene and stearic acid at 298.2 K. Judging from the value of the molar solubilization ratios (MSR) for naphthalene and stearic acid, the solubilization ability generally improved as the number of alkyl chains of the surfactant molecules increased, as follows: DTAB <12-2-12 < 3C12trisQ. The Gibbs free energy change (ΔG0) values for the solubilization of naphthalene and stearic acid into 3C12TrisQ solutions were relatively large negative numbers, −28.3 and −59.4 kJ mol−1, respectively. Moreover, small angle X-ray scattering analysis indicated that electron density at the ellipsoidal micellar surface of 3C12trisQ was decreased by solubilizing naphthalene and stearic acid, however, the micellar shape was not drastically changed from ellipsoidal micelle. These results indicated that the trimeric surfactant presented better potential as solubilizer compared to typical monomeric surfactants.
  DOI：https://doi.org/10.1016/j.molliq.2019.111254
  DOI ID：10.1016/j.molliq.2019.111254, ISSN：0167-7322, SCOPUS ID：85068251951
• Superoxide Scavenging Activity of Gold, Silver, and Platinum Nanoparticles Capped with Sugar-based Nonionic Surfactants　　　　　　　　　　　　　　　
  Keisuke Matsuoka; Yuka Nakatani; Tomokazu Yoshimura; Tsubasa Akasaki
  Journal of oleo science, 巻：68, 開始ページ：847, 終了ページ：854, 2019年09月, ［査読有り］
  Metal nanoparticles have the ability to remove superoxide via changes in the surface electronic states at the large surface area. Gold, silver, and platinum nanoparticles were prepared in the presence of three sugar-based nonionic surfactants using NaBH4 as a reducing agent. The surfactants (glycosyloxyethyl methacrylate: xGEMA) contain sugar oligomers of various lengths (x), are biodegradable, and act as protecting groups for the nanoparticles. Three types of xGEMA were used: dodecyl and hexadecyl chains containing amphiphilic oligomers (C12-3.0GEMA and C16-3.2GEMA) and multi-dodecyl chain with multiple sugar side chains (1.8C12-4.7GEMA). We found that the type of nonionic surfactant affected the size of the nanoparticles. The average size of the gold, silver, and platinum nanoparticles ranged from 1.9 to 6.6 nm depending on the surfactant. The trend in the size of gold nanoparticles in relation to the chosen surfactants was different from that for the silver and platinum nanoparticles. Moreover, the gold nanoparticles did not show effective antioxidant activity for superoxide, whereas the silver and platinum nanoparticles removed superoxide to a certain extent. The general order for superoxide scavenging activity increased in the following order: gold < platinum < silver. In particular, the largest size of silver nanoparticles capped with C16-3.2GEMA had a similar ability for the removal of superoxide as superoxide dismutase (ca. 3999 unit/mg) on the basis of the mass concentration.
  DOI：https://doi.org/10.5650/jos.ess19079
  DOI ID：10.5650/jos.ess19079, PubMed ID：31484901, SCOPUS ID：85071739601
• Emulsification, solubilization, and detergency behaviors of homogeneous polyoxypropylene-polyoxyethylene alkyl ether type nonionic surfactants　　　　　　　　　　　　　　　
  Yada Shiho; Matsuoka Keisuke; Kanasaki Yu Nagai; Gotoh Keiko; Yoshimura Tomokazu
  COLLOIDS AND SURFACES A-PHYSICOCHEMICAL AND ENGINEERING ASPECTS, 巻：564, 開始ページ：51, 終了ページ：58, 2019年03月, ［査読有り］
  DOI：https://doi.org/10.1016/j.colsurfa.2018.12.030
  DOI ID：10.1016/j.colsurfa.2018.12.030, ISSN：0927-7757, Web of Science ID：WOS:000455389200006
• Removal of alkali metal ions from aqueous solution by foam separation method　　　　　　　　　　　　　　　
  Keisuke Matsuoka; Hiroaki Miura; Shiho Karima; Chiharu Taketaka; Shota Ouno; Yoshikiyo Moroi
  Journal of Molecular Liquids, 巻：263, 開始ページ：89, 終了ページ：95, 2018年08月, ［査読有り］
  Foam separation method can effectively remove alkali metal ions from anionic surfactant solution by a combination of an air bubble generator and the flotation system. The alkali metal ions in the solution electrostatically adsorb onto the many bubbles by bubbling ionic surfactant solution and they transfer to the air/water interface. These bubbles change to the foam state that is removed using a long glass tube. The typical experimental system was composed of sodium dodecyl sulfate (SDS) as an anionic surfactant and the target alkali ions (Li, K, Rb, and Cs). Therefore, selective competition for air bubbles exists between the sodium (counterion of the surfactant) and target alkali ions. The removal rate of the alkali metal was noticeably dependent on surfactant concentration. The surfactant was effective in removing the alkali metal below the critical micelle concentration (CMC). The removal rate increased with increasing atomic number or crystal ion radius: Li <
  K <
  Rb <
  Cs. The best removal rate of the alkali metals involved 80% Cs elimination by using a microbubble generator (5 h) at the initial SDS concentration of 4 mmol/L and Cs 2.5 mmol/L. On the other hand, the removal rates of dodecylsulfate and counterion (Na) respectively decreased to 25% and 42% for the system. These results indicated that Cs was more selectively adsorbed onto the bubble than Na. A smaller hydration radius can easily bind the surfactant sulfate ions. This study showed that the foam separation method could selectively remove hazardous metals from contaminated water.
  Elsevier B.V., 英語, 研究論文（学術雑誌）
  DOI：https://doi.org/10.1016/j.molliq.2018.04.136
  DOI ID：10.1016/j.molliq.2018.04.136, ISSN：0167-7322, SCOPUS ID：85046779753, Web of Science ID：WOS:000436911300011
• Solubilization ability of N,N-dimethyl-N-alkyladamantylammonium bromide　　　　　　　　　　　　　　　
  Keisuke Matsuoka; Rinpei Omori; Shiho Yada; Tomokazu Yoshimura; Hiroki Iwase
  Journal of Molecular Liquids, 巻：260, 開始ページ：131, 終了ページ：137, 2018年06月, ［査読有り］
  Adamantane is difficult to dissolve in water owing to its bulky steric hydrocarbon structure. We designed a novel amphiphilic molecule by introducing an alkyl chain and a cation group into an adamantyl group. N,N-dimethyl-N-alkyladamantylammonium bromide (CnAdAB
  n is the alkyl chain length, where n = 10, 12, and 14) dissolves easily in water by forming micelles above the critical micelle concentration. Aggregates of this surfactant series form small nonspherical micelles several nanometers in size with relative small aggregation number
  53 (n = 10), 59 (n = 12), and 63 (n = 14) at the typical concentration. Small-angle X-ray scattering measurement showed that the micellar structure of C12AdAB was changed slightly by solubilization of naphthalene and stearic acid. Moreover, the solubilization ability of the aggregates was studied using naphthalene and long-alkyl-chain fatty acids (myristic, palmitic, and stearic acids). The same solubilization experiments were performed using typical cationic surfactants (dodecyltrimethylammonium bromide and a gemini surfactant) for comparison. The molar solubilization ratios indicate that the CnAdAB series can solubilize the aromatic compound naphthalene as well as the other surfactants, whereas they can barely solubilize the long-alkyl-chain fatty acids. The solubilization stability can be analyzed by estimating the Gibbs free energy change (ΔG0) for the transfer of solubilizate molecules to the aggregate phase. The gemini surfactant system showed the largest negative value of ΔG0 for both naphthalene and the fatty acids. On the other hand, solubilization of fatty acids into CnAdAB micelles was not advantageous energetically. These results indicate that the solubilization ability of CnAdAB surfactants is not generally suitable for solubilization of long-alkyl-chain fatty acids owing to the smallness of the micelles.
  Elsevier B.V., 英語, 研究論文（学術雑誌）
  DOI：https://doi.org/10.1016/j.molliq.2018.03.078
  DOI ID：10.1016/j.molliq.2018.03.078, ISSN：0167-7322, SCOPUS ID：85044527704, Web of Science ID：WOS:000433645500013
• Study on Micelle Formation of Bile Salt Using Nuclear Magnetic Resonance Spectroscopy　　　　　　　　　　　　　　　
  Keisuke Matsuoka; Atsushi Yamamoto
  JOURNAL OF OLEO SCIENCE, 巻：66, 号：10, 開始ページ：1129, 終了ページ：1137, 2017年10月, ［査読有り］
  H-1-nuclear magnetic resonance (H-1-NMR) measurements can identify the specific protons that contribute to interactions between molecules. Using this technique, micelles formed by four bile salts: sodium taurocholate (NaTC), taurodeoxycholate (NaTDC), taurochenodeoxycholate (NaTCDC), and tauroursodeoxycholate (NaTUDC) were measured and compared in viewpoint of molecular interactions. Rotating-frame nuclear Overhauser effect and exchange spectroscopy (ROESY) analysis of the four bile salts showed differences with respect to the type of micelle formation. For all four bile salts, the key protons contributing to hydrophobic interactions were found to be the methyl protons at positions 18 and 19. The cross-peak patterns for the four bile salt species indicated pairs of characteristic proton depending on a bile salt species. The spin-lattice relaxation time (T-1) of the alkyl side-chain in NaTC was relatively long compared to that of the three other bile salts, even when the concentration was higher than the critical micelle concentration (cmc). This unique behavior indicates that the hydrophilic region of NaTC molecules is flexible within their micelles. Moreover, T-1 values for the typically hydrophobic methyl protons at sites C18 and C19 of NaTC were almost constant above the cmc. These results may suggest that NaTC micelles remain as small primary structures in solution unlike the three other bile salt molecules investigated in the study.
  JAPAN OIL CHEMISTS SOC, 英語, 研究論文（学術雑誌）
  DOI：https://doi.org/10.5650/jos.ess17063
  DOI ID：10.5650/jos.ess17063, ISSN：1345-8957, eISSN：1347-3352, Web of Science ID：WOS:000412263900007
• Role of the spacer of Gemini surfactants in solubilization into their micelles　　　　　　　　　　　　　　　
  Hiromichi Nakahara; Hiroaki Nishizaka; Kensuke Iwasaki; Yu Otsuji; Mika Sato; Keisuke Matsuoka; Osamu Shibata
  JOURNAL OF MOLECULAR LIQUIDS, 巻：244, 開始ページ：499, 終了ページ：505, 2017年10月, ［査読有り］
  We report the role of a spacer chain in gemini surfactants for solubilization of poor soluble compounds to the aqueous medium. Solubilization of n-alkylbenzenes into micellar solutions of alkanediy1-1,s-bis(dimethyltetradecylammonium bromide) (14-s-14,2Br(-), s = 2, 6, and 12) has been studied in the temperature range from 288.2 to 308.2 K. The equilibrium concentrations of all the solubilizates are determined spectrophotometrically. The solubility of the solubilizates remains constant below the critical micelle concentration (cmc) and increases linearly with an increase in the surfactant concentration above the cmc. The hydrodynamic diameter of the micellar aggregates with or without the solubilizates is measured by means of dynamic light scattering (DLS). The enthalpy, entropy, and Gibbs energy changes for the solubilization of n-alkylbenzenes have been calculated to evaluate a driving force of a transfer of the solubilizates into the micelle. These results indicate that the driving force and solubilization site in the aggregates are changed depending on the spacer chain length of surfactants. Furthermore, the inner core of the solubilized aggregates has been investigated by Fourier transform infrared (FTIR) spectra and two-dimensional nuclear Overhauser effect spectroscopy (2-D NOESY). (C) 2017 Elsevier B.V. All rights reserved.
  ELSEVIER SCIENCE BV, 英語, 研究論文（学術雑誌）
  DOI：https://doi.org/10.1016/j.molliq.2017.09.014
  DOI ID：10.1016/j.molliq.2017.09.014, ISSN：0167-7322, eISSN：1873-3166, Web of Science ID：WOS:000413391000057
• Aggregate Formation of Glycyrrhetic Acid 3-O-Glucuronide　　　　　　　　　　　　　　　
  Keisuke Matsuoka; Ryusuke Miyajima; Seigo Karasawa
  JOURNAL OF SURFACTANTS AND DETERGENTS, 巻：20, 号：5, 開始ページ：1153, 終了ページ：1159, 2017年09月, ［査読有り］
  The molecular structure of glycyrrhetic acid 3-O-glucuronide consists of an aglycone and glucuronic acid as hydrophobic and hydrophilic groups, respectively. In general, this amphiphile is obtained from glycyrrhizic acid (a major component of licorice root) by hydrolysis of the terminal glucuronic acid. Glycyrrhetic acid 3-O-glucuronide is used as a substitute for glycyrrhizic acids, which are potent sweeteners. In this work, the surface and aggregation properties of glycyrrhetic acid 3-O-glucuronide were studied using general surface chemistry techniques. The surface tension of a glycyrrhetic acid 3-O-glucuronide solution (pH 7) gradually decreased with increasing concentration and the critical micelle concentration (CMC) was determined to be 1.6 mmol L-1 (gamma (CMC) = 54 mN m(-1)). Similar values of CMC were further confirmed by the pyrene fluorescent probe method and light scattering measurements. According to the dynamic light scattering method, the average radius of aggregate was 200 nm over a concentration of 3 mmol L-1. Transmission electron microscopy showed that glycyrrhetic acid 3-O-glucuronide forms large spherical aggregates. These results suggested that its potential for surface activity is almost equivalent to that of glycyrrhizic acid, even though the two amphiphiles have a different number of hydrophilic groups in them. The removal of one glucuronic acid group significantly influenced the shape of the aggregate formed by glycyrrhetic acid 3-O-glucuronide. Furthermore, it was confirmed that glycyrrhetic acid 3-O-glucuronide can also be used as a plant-derived surfactant, similar to glycyrrhetic acid.
  SPRINGER HEIDELBERG, 英語, 研究論文（学術雑誌）
  DOI：https://doi.org/10.1007/s11743-017-2001-5
  DOI ID：10.1007/s11743-017-2001-5, ISSN：1097-3958, eISSN：1558-9293, Web of Science ID：WOS:000407391500016
• Single-alkyl and multi-alkyl chain-containing amphiphilic oligomers with several sugar side chains: solution properties and nanostructural analysis of aggregates by SANS　　　　　　　　　　　　　　　
  Tomokazu Yoshimura; Yuka Nakatani; Keisuke Matsuoka; Kazuhiro Akutsu; Hiroki Iwase
  COLLOID AND POLYMER SCIENCE, 巻：295, 号：5, 開始ページ：793, 終了ページ：802, 2017年05月, ［査読有り］
  Single-alkyl chain-containing amphiphilic oligomers with a terminal alkyl chain and several sugar side chains (i.e., C (n) -mGEMA, where n represents alkyl chain lengths of 12 or 16 and m represents the polymerization degree of glycosyloxyethyl methacrylate (GEMA) units of 3.0-7.1), and multi-alkyl chain-containing amphiphilic oligomers with several sugar side chains (i.e., xC(12)-mGEMA, where x represents the average number of alkyl chains and x-m is 0.2-6.6, 1.8-4.7, and 3.4-3.7), were synthesized via the radical oligomerization of one or two monomers in the presence of alkanethiol or 2-aminoethanethiol hydrochloride. Surface tension, pyrene fluorescence, and small-angle neutron scattering (SANS) measurements were used to characterize the solution properties of the oligomers and the nanostructures of their aggregates. Both amphiphilic oligomers are highly efficient in reducing the surface tension of water (42-48 mN m(-1) for C (n) -mGEMA and 36-46 mN m(-1) for xC(12)-mGEMA), despite the relatively large structures of the hydrophilic parts in sugar GEMA units. The critical micelle concentration (CMC) of C (n) -mGEMA and xC(12)-mGEMA increased with an increase in the degree of polymerization for hydrophilic GEMA units and a decrease in the alkyl chain length. The results of SANS determined that C (n) -mGEMA formed prolate ellipsoid micelles with a radius of 1.96 nm and an axial ratio of 1.58 for a low degree of polymerization (m = 3.0) in solution. However, the radius decreased to 1.33 nm and the axial ratio increased to 5.04 as the degree of polymerization of the amphiphilic oligomers increased to m = 7.1, indicating structural transformation to an asymmetric ellipsoid. On the other hand, the structure of the aggregates formed by xC(12)-mGEMA changed from ellipsoidal to an ellipsoidal cylinder shape with increasing number of alkyl chains, i.e., decreasing the number of GEMA units.
  SPRINGER, 英語, 研究論文（学術雑誌）
  DOI：https://doi.org/10.1007/s00396-017-4063-3
  DOI ID：10.1007/s00396-017-4063-3, ISSN：0303-402X, eISSN：1435-1536, Web of Science ID：WOS:000399706800007
• Synthesis and Solution Properties of Adamantane-Containing Quaternary Ammonium Salt-type Cationic Surfactants: Hydrocarbon-based, Fluorocarbon-based and Bola-type　　　　　　　　　　　　　　　
  Tomokazu Yoshimura; Mari Okada; Keisuke Matsuoka
  JOURNAL OF OLEO SCIENCE, 巻：65, 号：10, 開始ページ：843, 終了ページ：852, 2016年10月, ［査読有り］
  Quaternary ammonium salt-type cationic surfactants with an adamantyl group (hydrocarbon-type; C(n)AdAB, fluorocarbon-type; C(m)(F)C(3)AdAB, bola-type; Ad-s-Ad, where n, m and s represent hydrocarbon chain lengths of 8-16, fluorocarbon chain lengths of 4-8, and spacer chain length of 10-12) were synthesized via quaternization of N, N-dimethylaminoadamantane and n-alkyl bromide or 1, n-dibromoalkane. Conductivity and surface tension were measured to characterize the solution properties of the synthesized adamantyl group-containing cationic surfactants. In addition, the effects of hydrocarbon and fluorocarbon chain lengths and spacer chain length between headgroups on the measured properties were evaluated by comparison with those of conventional cationic surfactants. The critical micelle concentration (CMC) of C(n)AdAB and Ad-s-Ad was 2/5 of that for the corresponding conventional surfactants C(n)TAB and bola-type surfactants with similar number of carbons in the alkyl or alkylene chain; this was because of the increased hydrophobicity due to the adamantyl group. A linear relationship between the logarithm of CMC and the hydrocarbon chain length for C(n)AdAB was observed, as well as for C(n)TAB. The slope of the linear correlation for both surfactants was almost the same, indicating that the adamantyl group does not affect the CMC with variations in the hydrocarbon chain length. Similar to conventional surfactants C(n)TAB, the hydrocarbon-type C(n)AdAB is highly efficient in reducing the surface tension of water, despite the large occupied area per molecule resulting from the relatively bulky structure of the adamantane skeleton. On the other hand, the bola-type Ad-s-Ad resulted in increased surface tension compared to C(n)AdAB, indicating that the curved chain between adamantyl groups leads to poor adsorption and orientation at the air-water interface.
  JAPAN OIL CHEMISTS SOC, 英語, 研究論文（学術雑誌）
  DOI：https://doi.org/10.5650/jos.ess16095
  DOI ID：10.5650/jos.ess16095, ISSN：1345-8957, eISSN：1347-3352, Web of Science ID：WOS:000384705400005
• Aggregate formation of glycyrrhizic acid　　　　　　　　　　　　　　　
  Keisuke Matsuoka; Ryusuke Miyajima; Yudai Ishida; Seigo Karasawa; Tomokazu Yoshimura
  COLLOIDS AND SURFACES A-PHYSICOCHEMICAL AND ENGINEERING ASPECTS, 巻：500, 開始ページ：112, 終了ページ：117, 2016年07月, ［査読有り］
  Glycyrrhizic acid is derived from the licorice root. The compound is amphiphilic with a large hydrophobic aglycone group, and two glucuronic acids and a carboxyl group constituting the hydrophilic part. Therefore, glycyrrhizic acid can form aggregates or lower the surface tension of aqueous solutions owing to its specific amphiphilic structure. The aqueous solubility of glycyrrhizic acid is relatively low (0.15 mM) and dependent on the solvent pH due to the weak acidity resulting from the carboxylic groups. Glycyrrhizic acid is quite soluble in a buffer solution at pH 4.5, and its ability to affect the surface tension of the buffer solution increases from pH 5. The critical micelle concentration (cmc) was estimated to be 2.9 mM (gamma(CMC) = 55.2 mN/m) and 5.3 mM (gamma(CMC) = 56.8 mN/m) at pH 5 and 6, respectively. The surface tension also decreased gradually at pH 7, but the critical point was not observed in the curve. At pH 7, the pyrene fluorescent probe method and light scattering measurements did not show a clear cmc. Small angle X-ray scattering experiments revealed that the aggregates were rod-like micelles with an estimated radius and length of 1.5 nm and 21 nm, respectively, at 5 mM in a pH 5 solvent. Transmission electron microscopy confirmed that glycyrrhizic acid forms rod-like micelles. These results suggest that glycyrrhizic acid has potential applications as a biosurfactant in various fields. (C) 2016 Elsevier B.V. All rights reserved.
  ELSEVIER SCIENCE BV, 英語, 研究論文（学術雑誌）
  DOI：https://doi.org/10.1016/j.colsurfa.2016.04.032
  DOI ID：10.1016/j.colsurfa.2016.04.032, ISSN：0927-7757, eISSN：1873-4359, Web of Science ID：WOS:000375860100014
• Competitive Solubilization of Cholesterol/Cholesteryl Oleate and Seven Species of Sterol/Stanol in Model Intestinal Solution System　　　　　　　　　　　　　　　
  Keisuke Matsuoka; Asumi Kase; Takashi Matsuo; Yusuke Ashida
  JOURNAL OF OLEO SCIENCE, 巻：64, 号：7, 開始ページ：783, 終了ページ：791, 2015年07月, ［査読有り］
  The addition of plant sterols/stanols (sterols or stanols) can reduce the solubilization of cholesterol in a model intestinal solution system. We studied the molecular structure of seven different sterols/stanols and the effect they had on the solubilization of cholesterol or cholesterol ester in a model intestinal solution. The differences in the molecular structures of the sterol/stanol species influenced their abilities to reduce the solubility of cholesterol in the competitive solubilization experiments. Cholestanol whose molecular structure resembled cholesterol was the most effective at reducing the solubilization of cholesterol and cholesterol ester, with the solubilities of cholesterol and cholesteryl oleate being 41% and 39% respectively of the values observed for the single solubilizate systems. beta-Sitosterol was also able to reduce the solubilities of cholesterol and cholesteryl oleate to 43% and 45% of those observed in a single solubilizate system. Both, stigmasterol and brassicasterol have an unsaturated double bond in a steroid side chain and did not exhibit major cholesterol-lowering effects. These results were reflected by the Gibbs free energy change values (Delta G(0)) for solubilization, where the sterol/stanol species with cholesterol-lowering effects had similar or larger negative Delta G(0) values than those observed for cholesterol.
  JAPAN OIL CHEMISTS SOC, 英語, 研究論文（学術雑誌）
  DOI：https://doi.org/10.5650/jos.ess15044
  DOI ID：10.5650/jos.ess15044, ISSN：1345-8957, eISSN：1347-3352, Web of Science ID：WOS:000357348400011
• Solubilization of naphthalene and octafluoronaphthalene in ionic hydrocarbon and fluorocarbon surfactants　　　　　　　　　　　　　　　
  Keisuke Matsuoka; Rika Yamashita; Miki Ichinose; Maiko Kondo; Tomokazu Yoshimura
  COLLOIDS AND SURFACES A-PHYSICOCHEMICAL AND ENGINEERING ASPECTS, 巻：456, 開始ページ：83, 終了ページ：91, 2014年08月, ［査読有り］
  The solubilization abilities of various kinds of surfactants are clarified through a systematic solubilization study. Naphthalene and octafluoronaphthalene have similar molecular structures and can be used as solubilizates in hydrocarbon and fluorocarbon surfactant systems. The solubilizaton quantities are measured for typical anionic, cationic, and cationic gemini surfactants with different alkyl chain lengths (nine hydrocarbon and six fluorocarbon surfactants). The maximum solubilization quantities of naphthalene and octafluoronaphthalene in aqueous solutions of hydrocarbon or fluorocarbon surfactant are measured as a function of surfactant concentration at 318.2 K. There are four solubilization systems regarding hydrocarbons and fluorocarbons. Judging from the molar solubilization ratio (MSR), naphthalene is solubilized most in typical gemini surfactant solution (12-2-12), whereas hardly any naphthalene is solubilized in fluorocarbon surfactants. On the other hand, the maximum MSR of octafluoronaphthalene is found for the gemini type of fluorocarbon surfactant, whereas the minimum value is recorded in the C9H19COONa system. Therefore, gemini surfactants reveal excellent solubilization abilities in homogeneous combination systems. The solubilization stability can be analyzed by estimating the Gibbs free energy change (Delta G degrees) for the transfer of solubilizate molecules to the aggregate phase. The largest negative value of Delta G degrees is estimated to be -34.8 kJ mol(-1) for the homogeneous system of octafluoronaphthalene and the gemini-type fluorocarbon surfactant, whereas smaller values are obtained for the heterogeneous systems of naphthalene and fluorocarbon surfactants. These results indicate that fluorocarbon surfactants are not generally suitable for the solubilization of naphthalene. (C) 2014 Elsevier B.V. All rights reserved.
  ELSEVIER SCIENCE BV, 英語, 研究論文（学術雑誌）
  DOI：https://doi.org/10.1016/j.colsurfa.2014.04.060
  DOI ID：10.1016/j.colsurfa.2014.04.060, ISSN：0927-7757, eISSN：1873-4359, Web of Science ID：WOS:000340318000012
• Solubilization of polycyclic aromatic hydrocarbons in C16E7 nonionic surfactant solutions　　　　　　　　　　　　　　　
  Emi Takeuchi; Keisuke Matsuoka; Shigeaki Ishii; Sho Ishikawa; Chikako Honda; Kazutoyo Endo
  COLLOIDS AND SURFACES A-PHYSICOCHEMICAL AND ENGINEERING ASPECTS, 巻：441, 開始ページ：133, 終了ページ：139, 2014年01月, ［査読有り］
  Polycyclic aromatic hydrocarbons (PAHs), namely, naphthalene, phenanthrene, and pyrene, were solubilized in nonionic surfactant micelles formed from heptaoxyethylene monohexadecyl ether (C16E7). The sizes of the PAH-incorporated micelles, and the location of the solubilized molecules, were studied using dynamic light scattering, transmission electron microscopy (TEM), and H-1 nuclear magnetic resonance (NMR) spectroscopy. The solubilization of the PAHs increased significantly above a C16E7 concentration of 1 mM, which corresponded to the point at which the morphology of the micelles changed from globular to string-like, as demonstrated by TEM imaging. The string-like micelles then grew with increasing incorporation of PAHs (naphthalene, phenanthrene, and pyrene). The H-1 NMR chemical shifts of the discrete groups of the C16E7 micelles shifted upfield with increasing naphthalene concentration as a result of the ring current and/or local anisotropic effects of the PAH. The H-1 peak of the oxyethylene segment at 3.7 ppm clearly split with increasing naphthalene concentration in the C16E7 solution. The rotating frame nuclear Overhauser and exchange spectroscopy of naphthalene solubilized in C16E7 micelles showed a cross peak between the oxyethylene segment and the H-1 naphthalene peaks. The NMR spectral measurements showed that the solubilized naphthalene molecules were located in the palisade region of the micelles rather than in the core. (C) 2013 Elsevier B.V. All rights reserved.
  ELSEVIER SCIENCE BV, 英語, 研究論文（学術雑誌）
  DOI：https://doi.org/10.1016/j.colsurfa.2013.09.011
  DOI ID：10.1016/j.colsurfa.2013.09.011, ISSN：0927-7757, eISSN：1873-4359, Web of Science ID：WOS:000329260800018
• Micelle formation of sodium hyodeoxycholate　　　　　　　　　　　　　　　
  Keisuke Matsuoka; Kaede Takagi; Chikako Honda
  Chemistry and Physics of Lipids, 巻：172-173, 開始ページ：6, 終了ページ：13, 2013年, ［査読有り］
  Sodium hyodeoxycholate (NaHDC) is the main component of hog bile salts, which play a role in the absorption of sparingly soluble materials in the intestinal solution. The biosurfactant has an amphiphilic molecular structure, similar to that of ursodeoxycholate from bear gallbladder. Micelle formation from hyodeoxycholate was studied at 308.2 K using pyrene fluorescence probe to determine critical micelle concentrations (cmc) at various NaCl concentrations. The change in the fluorescence spectrum peak ratios with NaHDC concentration indicated two steps for bile salt aggregation. The first step was the formation of small micelles (cmc) at 5 mM, and the second step was the formation of stable aggregates at 14 mM in aqueous solution. The aggregation of hyodeoxycholate, analyzed using the stepwise association model, was found to grow its aggregation number from 4 to 7 with increasing concentration. The aggregation number in aqueous solution was also confirmed by the static light scattering method. The average measured aggregation number of the micelles was 6.7. The micellar size was relatively small as measured by either method, but it was covered by general aggregation number of human bile salts. The degree of counterion binding to the micelles, determined using a sodium ion-selective electrode, was ca. 0.5 for the NaHDC micelles. This value was relatively high among typical bile salts. Moreover, the solubilization capacity of the NaHDC micelles was assessed using cholesterol. It became clear that NaHDC micelles hardly solubilized cholesterol compared to typical human bile salts. The maximum solubilization by NaHDC was equivalent only to that by sodium ursodeoxycholate. © 2013 Elsevier Ireland Ltd. All rights reserved.
  Elsevier Ireland Ltd, 英語, 研究論文（学術雑誌）
  DOI：https://doi.org/10.1016/j.chemphyslip.2013.04.003
  DOI ID：10.1016/j.chemphyslip.2013.04.003, ISSN：1873-2941, SCOPUS ID：84878148253, Web of Science ID：WOS:000322415100002
• Aggregation properties of supralong-chain surfactants with double or triple quaternary ammonium head groups　　　　　　　　　　　　　　　
  Keisuke Matsuoka; Nagisa Chiba; Tomokazu Yoshimura
  JOURNAL OF COLLOID AND INTERFACE SCIENCE, 巻：379, 開始ページ：72, 終了ページ：77, 2012年08月, ［査読有り］
  Double or triple quaternary ammonium head groups were designed to improve the solubility of supralong alkyl chain surfactants. In the surfactant head group, quaternary ammonium groups are connected by an ethylene spacer. Micellar shapes of divalent surfactants [CH2n+1N+(CH3)(2)-(CH2)(2)-N(CH3)(3) 2Br(-): C-n-2Am (n = 18, 20, and 22)] and trivalent surfactants [CnH2n+1N+(CH3)(2)-(CH2)(2)-N+(CH3)(2)-(CH2)(2)-N+(CH3)(3) 3Br(-): C-n-3Am (n = 18, 20, and 22)] were studied in aqueous solutions by means of dynamic light scattering (DLS) and transmission electron microscopy (TEM). Changes in the surfactant concentration have a small influence on the apparent hydrodynamic radii (r(h)) of the molecular aggregates in both surfactant series. Average values of r(h) of aggregates are 60-90 nm for C-n-2Am (n= 18, 20, and 22) and 2-40 nm for C-n-3Am (n = 18, 20, and 22). TEM micrographs showed that aggregates of C-n-2Am (n = 18, 20, and 22) typically formed rod-like micelles. In contrast, trivalent surfactants of C-n-3Am (n = 18, 20, and 22) formed spherical (C-18-3Am) or ellipsoidal micelles (C-20-3Am and C-22-3Am). Moreover, the degree of micellar counterion binding for these surfactants was determined by using a bromide ion-selective electrode, which indicated relatively high values (0.8-0.9) for C-n-2Am (n = 18, 20, and 22) and more common values (0.5-0.8) for C-n-3Am (n = 18, 20, and 22). The size of the aggregates is closely related to the degree of counterion binding. (C) 2012 Elsevier Inc. All rights reserved.
  ACADEMIC PRESS INC ELSEVIER SCIENCE, 英語, 研究論文（学術雑誌）
  DOI：https://doi.org/10.1016/j.jcis.2012.04.043
  DOI ID：10.1016/j.jcis.2012.04.043, ISSN：0021-9797, Web of Science ID：WOS:000305592000011
• Supra-long chain surfactants with double or triple quaternary ammonium headgroups　　　　　　　　　　　　　　　
  Tomokazu Yoshimura; Nagisa Chiba; Keisuke Matsuoka
  JOURNAL OF COLLOID AND INTERFACE SCIENCE, 巻：374, 開始ページ：157, 終了ページ：163, 2012年05月, ［査読有り］
  Novel supra-long chain surfactants with double or triple quaternary ammonium salts (C-n-2Am, C-n-3Am, in which n represents a hydrocarbon chain length of 18, 20, and 22) were synthesized, and electrical conductivity and surface tension were used to characterize their properties depending on both the hydrocarbon chain length and number of hydrophilic groups. The Krafft temperatures decreased remarkably with an increase in the quaternary ammonium headgroups, resulting in a high solubility in water. The critical micelle concentration (cmc) increased with an increase in the number of quaternary ammonium moieties in the hydrophilic group, and the difference in the cmc was smaller for C-n-2Am and C-n-3Am than for C-n-2Am and C-n-Am of alkyltrimethylammonium bromide. The surface tension at the cmc was approximately 45 and 48 mN m(-1) for C-n-2Am and C-n-3Am with n = 18-22, respectively. This indicated that the supra-long chain surfactants could not efficiently adsorb at the air/water interface and orient by themselves, as is known for conventional surfactants. (C) 2012 Elsevier Inc. All rights reserved.
  ACADEMIC PRESS INC ELSEVIER SCIENCE, 英語, 研究論文（学術雑誌）
  DOI：https://doi.org/10.1016/j.jcis.2012.01.033
  DOI ID：10.1016/j.jcis.2012.01.033, ISSN：0021-9797, Web of Science ID：WOS:000302446900022
• Competitive solubilization of cholesterol and beta-sitosterol with changing biliary lipid compositions in model intestinal solution　　　　　　　　　　　　　　　
  Keisuke Matsuoka; Ebisawa Rie; Saori Yui; Chikako Honda; Kazutoyo Endo
  CHEMISTRY AND PHYSICS OF LIPIDS, 巻：165, 号：1, 開始ページ：7, 終了ページ：14, 2012年01月, ［査読有り］
  We used a model intestinal solution to understand the mechanisms of cholesterol lowering by the addition of plant sterols. The experimental results of the competitive solubilization of cholesterol and beta-sitosterol in vitro give useful information about these mechanisms. The states of the model intestinal solution as a solubilizer were analyzed by transmission electron microscopy (TEM) and dynamic light scattering (DLS) by changing the number of components, and the bile salt and phosphatidylcholine concentrations. There were aggregates of different sizes: liposomes and mixed micelles depending on their components and concentrations. The maximum solubilization of cholesterol increased from 0.2 mM to 1.3 mM when adding fatty compounds in the pure bile salts system, which is almost the same as the full components model intestinal solution. Therefore, an excessive intake of fatty compounds may also increase cholesterol absorption in vivo. Even if the components of the model intestinal solution were modified from the standard condition, there were not remarkable differences in the selectivity of cholesterol and beta-sitosterol in competitive solubilization. With the addition of beta-sitosterol, the maximum solubilization of cholesterol decreases to almost half of that in the system with only cholesterol, except for PC-rich systems. In general, the different structures of aggregates considerably influence the maximum solubilization of sterols but not the selectivity of cholesterol and beta-sitosterol in the competitive solubilization. The Gibbs energy change (Delta G degrees) of the solubilization of beta-sitosterol showed a more negative value than cholesterol by -4 to -6 kJ mol(-1), which indicates that beta-sitosterol is energetically favored relative to cholesterol in the model intestinal solution, regardless of the different systems. (C) 2011 Elsevier Ireland Ltd. All rights reserved.
  ELSEVIER IRELAND LTD, 英語, 研究論文（学術雑誌）
  DOI：https://doi.org/10.1016/j.chemphyslip.2011.10.004
  DOI ID：10.1016/j.chemphyslip.2011.10.004, ISSN：0009-3084, Web of Science ID：WOS:000299580000002
• Biliary excretion of essential trace elements in rats under oxidative stress caused by selenium deficiency　　　　　　　　　　　　　　　
  Kosuke Yamasaki; Yasunobu Sakuma; Junya Sasaki; Ken-ichiro Matsumoto; Kazunori Anzai; Keisuke Matsuoka; Chikako Honda; Masamichi Tsukada; Kazutoyo Endo; Shuichi Enomoto
  ANALYTICAL AND BIOANALYTICAL CHEMISTRY, 巻：401, 号：8, 開始ページ：2531, 終了ページ：2538, 2011年11月, ［査読有り］
  The excretion of essential trace elements, namely, Se, Sr, As, Mn, Co, V, Fe, and Zn into the bile of Se-deficient (SeD) Wistar male rats was studied using the multitracer (MT) technique, and instrumental neutron activation analysis (INAA). Normal and Se-control (SeC) rat groups were used as reference groups to compare the effects of Se levels on the behaviors of the essential trace elements. The excretion (% dose) of Se, Sr, As, Mn, Co, and V increased with Se levels in the liver. The biliary excretion of Mn and As dramatically enhanced for SeC rats compared with SeD rats, while that of V accelerated a little for SeC rats. The radioactivity levels of Fe-59 and Zn-65 in the MT tracer solution were insufficient to measure their excretion into bile. The role of glutathione and bilirubin for biliary excretion of the metals was discussed in relation to Se levels in rat liver.
  SPRINGER HEIDELBERG, 英語, 研究論文（学術雑誌）
  DOI：https://doi.org/10.1007/s00216-011-5333-4
  DOI ID：10.1007/s00216-011-5333-4, ISSN：1618-2642, Web of Science ID：WOS:000295508600021
• Effect of double quaternary ammonium groups on micelle formation of partially fluorinated surfactant　　　　　　　　　　　　　　　
  Keisuke Matsuoka; Nagisa Chiba; Tomokazu Yoshimura; Emi Takeuchi
  JOURNAL OF COLLOID AND INTERFACE SCIENCE, 巻：356, 号：2, 開始ページ：624, 終了ページ：629, 2011年04月, ［査読有り］
  To investigate the effect of divalency on the micelle properties, we synthesized divalent cationic surfactants composed of fluorocarbons and double quaternary ammonium groups N,N-dimethyl-N-[2-(N'-trimethylammonium)ethyl]-1-(3-perfluoroalkyl-2-hydroxypropyl) ammonium bromide [C(n)(F)C(3)-2Am; where n (=8 or 10) represents the number of carbon atoms in the fluorocarbon chain]. The double quaternary ammonium groups are continuously combined by the ethylene spacer in the surfactant head group, which clearly distinguishes the molecular design of the surfactant from those of the other typical divalent surfactants, bolaform and gemini types. The presence of the divalent head group results in an advantageous increase in their solubility [i.e., rise in the critical micelle concentration (cmc)]; however, the extra electrostatic repulsion between divalent cations decreases the surface activity in comparison with monovalent homologous fluorinated surfactants. The cmc, surface tension at cmc, and area occupied by a surfactant molecule in aqueous solution at 298.2 K are 4.32 mM, 30.6 mN m(-1), and 0.648 nm(2) molecule(-1), respectively, for C(8)(F)C(3)-2Am, and 1.51 mM, 30.4 mN m(-1), and 0.817 nm(2) molecule(-1), respectively, for C(10)(F)C(3)-2Am. The micellar size and shape were investigated by dynamic light scattering and freeze-fracture transmission electron microscopy (TEM). The TEM micrographs show that C(n)(F)C(3)-2Am (n = 8 and 10) mainly forms ellipsoidal micelles approximately 10-100 nm in size for n = 8 and approximately 10-20 nm in size for n = 10. The degree of counterion binding to micelle was determined by selective electrode potential measurements, and the results of 0.7-0.8 agree with the average values for conventional monovalent ionic surfactants. (C) 2011 Elsevier Inc. All rights reserved.
  ACADEMIC PRESS INC ELSEVIER SCIENCE, 英語, 研究論文（学術雑誌）
  DOI：https://doi.org/10.1016/j.jcis.2011.01.030
  DOI ID：10.1016/j.jcis.2011.01.030, ISSN：0021-9797, Web of Science ID：WOS:000288527800032
• Competitive solubilization of cholesterol and six species of sterol/stanol in bile salt micelles　　　　　　　　　　　　　　　
  Keisuke Matsuoka; Eriko Kajimoto; Maho Horiuchi; Chikako Honda; Kazutoyo Endo
  CHEMISTRY AND PHYSICS OF LIPIDS, 巻：163, 号：4-5, 開始ページ：397, 終了ページ：402, 2010年05月, ［査読有り］
  Slight differences in the molecular structures of a category of sterol/stanol species affect the solubility of cholesterol in a bile salt solution. We systematically studied the preferential solubilization of cholesterol and sterol/stanol in sodium taurodeoxycholate solutions using relatively minor plant species of sterol/stanol (brassicasterol and stigmasterol) and a non-plant sterol (cholestanol). As relatively major sterol/stanol species (beta-sitosterol, beta-sitostanol, and campesterol) have already been examined using nearly identical procedures to that used in our system, we were able to sufficiently discuss the cholesterol-lowering effects resulting from the molecular structures of six sterol/stanol species. The results of competitive solubilization revealed that cholestanol has the largest cholesterol-lowering effect, decreasing cholesterol solubility to 33% of that in a single solubilizate system. The molecular structure of cholestanol is also most similar to that of cholesterol. In contrast, brassicasterol and stigmasterol have little ability to decrease cholesterol solubility in a mixed binary system. Both have an unsaturated double bond at the side chain of the steroid ring. By applying thermodynamic analyses to these results, we found that the Gibbs energy changes (Delta G degrees) of solubilization for sterol/stanol species with cholesterol-lowering effects show larger negative values than that for cholesterol. (C) 2010 Elsevier Ireland Ltd. All rights reserved.
  ELSEVIER IRELAND LTD, 英語, 研究論文（学術雑誌）
  DOI：https://doi.org/10.1016/j.chemphyslip.2010.03.006
  DOI ID：10.1016/j.chemphyslip.2010.03.006, ISSN：0009-3084, eISSN：1873-2941, Web of Science ID：WOS:000278169400010
• Micellization of bile salts and solubilization into the micelles　　　　　　　　　　　　　　　
  松岡 圭介
  Journal of Surface Science and Technology, 巻：26, 開始ページ：105, 終了ページ：136, 2010年, ［査読有り］
  英語, 研究論文（学術雑誌）
• Surface properties and aggregate morphology of partially fluorinated carboxylate-type anionic gemini surfactants　　　　　　　　　　　　　　　
  Tomokazu Yoshimura; Miri Bong; Keisuke Matsuoka; Chikako Honda; Kazutoyo Endo
  JOURNAL OF COLLOID AND INTERFACE SCIENCE, 巻：339, 号：1, 開始ページ：230, 終了ページ：235, 2009年11月, ［査読有り］
  Three anionic homologues of a novel partially fluorinated carboxylate-type anionic gemini surfactant, N, N'-di(3-perfluoroalkyl-2-hydroxypropyl)-N, N'-diacetic acid ethylenediamine (2C(n)(F) edda, where n represents the number of carbon atoms in the fluorocarbon chain (4, 6, and 8)) were synthesized. In these present gemini surfactants, the relatively small carboxylic acid moieties form hydrophilic head groups. The surface properties or structures of the aggregates of these surfactants are strongly influenced by the non-flexible fluorocarbons and small head groups; this is because these surfactants have a closely packed molecular structure. The equilibrium surface tension properties of these surfactants were measured at 298.2 K for various fluorocarbon chain lengths. The plot of the logarithm of the critical micelle concentration (cmc) against the fluorocarbon chain lengths for 2C(n)(F) edda (n = 4, 6, and 8) showed a minimum for n = 6. Furthermore, the lowest surface tension of 2C(6)(F) edda at the cmc was 16.4 mN m (1). Such unique behavior has not been observed even in the other fluorinated surfactants. Changes in the shapes and sizes of these surfactant aggregate with concentration were investigated by dynamic light scattering and transmission electron microscopy (TEM). The TEM micrographs showed that in an aqueous alkali solution, 2C(n)(F) edda mainly formed aggregates with stringlike (n = 4), cagelike (n = 6), and distorted bilayer structures (n = 8). The morphological changes in the aggregates were affected by the molecular structure composed of nonflexible fluorocarbon chains and flexible hydrocarbon chains. (C) 2009 Elsevier Inc. All rights reserved.
  ACADEMIC PRESS INC ELSEVIER SCIENCE, 英語, 研究論文（学術雑誌）
  DOI：https://doi.org/10.1016/j.jcis.2009.07.054
  DOI ID：10.1016/j.jcis.2009.07.054, ISSN：0021-9797, Web of Science ID：WOS:000272262900029
• Solubilization of n-alkylbenzene and n-perfluoroalkylbenzene in hydrogenated and fluorinated surfactants micelles　　　　　　　　　　　　　　　
  Keisuke Matsuoka; Emi Takeuchi; Megumi Takahashi; Satomi Kitsugi; Chikako Honda; Kazutoyo Endo
  JOURNAL OF COLLOID AND INTERFACE SCIENCE, 巻：333, 号：2, 開始ページ：641, 終了ページ：645, 2009年05月, ［査読有り］
  The maximum solubilities of homologous Series of n-alkylbenzene and n-perfluoroalkylbenzene in aqueous solutions of surfactants n-tetradecyltrimethylammonium chloride (TTAC) and N-(1,1-dihydroperfluorodecyl)-N,N,N-trimethylammonium chloride (C10F-TAC) were measured as a function of the surfactant concentration at 298.2 K. There are four solubilization systems in viewpoints of hydrocarbons and fluorocarbons. In general, in all systems, the maximum solubility decreased with an increase in the alkyl carbon length of the solubilizates. The homogeneous combinations of solubilizates and solubilizers have higher affinity than heterogeneous combinations. The affinity between a hydrocarbon and a fluorocarbon can be clarified by determining the Gibbs free energy (Delta G(0)) on solubilization by thermodynamic analysis. The largest negative value of Delta G(0) was obtained for the homogeneous system of n-perfluoroalkylbenzene and C10F-TAC, whereas the smallest value was obtained for the heterogeneous system of n-perfluoroalkylbenzene and TTAC. The contributions of methylene and perfluoromethylene to Gibbs energy, namely, Delta G(CH2)(0) and Delta G(CF2)(0), were found to be -2.6 and -2.9 kJ mol(-1), respectively, for the TTAC solution, whereas the respective values for the C10F-TAC solution were -2.0 and -3.3 kJ mol(-1). (C) 2009 Elsevier Inc. All rights reserved.
  ACADEMIC PRESS INC ELSEVIER SCIENCE, 英語, 研究論文（学術雑誌）
  DOI：https://doi.org/10.1016/j.jcis.2009.02.009
  DOI ID：10.1016/j.jcis.2009.02.009, ISSN：0021-9797, Web of Science ID：WOS:000265121500029
• Dynamics of redox related elements (Fe, Co, Zn, and Se) and oxidative stress caused by Se-deficiency in rats　　　　　　　　　　　　　　　
  Y. Sakuma; K. Matsuoka; C. Honda; K. Matsumoto; K. Endo
  JOURNAL OF RADIOANALYTICAL AND NUCLEAR CHEMISTRY, 巻：278, 号：3, 開始ページ：591, 終了ページ：594, 2008年12月, ［査読有り］
  The dynamics of redox related elements (Fe, Co, Zn, and Se) were studied using instrumental neutron activation analysis as a function of rat age in the range of 4 to 16 weeks. Activity levels of glutathione peroxidase (GSH-Px), thiobarbituric acid reactive substance (TBARS) were assayed, and hydrogen peroxide (H(2)O(2)) concentrations were measured for the same liver homogenates using an X-band ESR spectrometer. The oxidative stress, the aging effect, and the mineral valance are discussed.
  SPRINGER, 英語, 研究論文（学術雑誌）
  DOI：https://doi.org/10.1007/s10967-008-1011-1
  DOI ID：10.1007/s10967-008-1011-1, ISSN：0236-5731, Web of Science ID：WOS:000261262500011
• Study of thermodynamic parameters for solubilization of plant sterol and stanol in bile salt micelles　　　　　　　　　　　　　　　
  Keisuke Matsuoka; Tomomi Nakazawa; Ai Nakamura; Chikako Honda; Kazutoyo Endo; Masamichi Tsukada
  CHEMISTRY AND PHYSICS OF LIPIDS, 巻：154, 号：2, 開始ページ：87, 終了ページ：93, 2008年08月, ［査読有り］
  We investigated the difference between the molecular structures of plant sterols and stanols that affect the solubilization of cholesterol in bile salt micelles (in vitro study). First, the aqueous solubility of beta-sitosterol, beta-sitostanol, and campesterol was determined by considering the specific radioactivity by using a fairly small quantity of each radiolabeled compound. The order of their aqueous solubilities was as follows: cholesterol > campesterol > beta-sitostanol > beta-sitosterol. The maximum solubility of cholesterol and the above mentioned sterol/stanol in sodium taurodeoxycholate and sodium taurocholate solutions (single solubilizate system) was measured. Moreover, the preferential solubilization of cholesterol in bile salt solutions was systematically studied by using different types of plant sterols/stanols. The solubilization results showed that the cholesterol-lowering effect was similar for sterols and stanol. Thermodynamic analysis was applied to these experimental results. The Gibbs energy change (Delta G degrees) for the solubilization of plant sterols/stanols showed a negative value larger than that for cholesterol. (C) 2008 Elsevier Ireland Ltd. All rights reserved.
  ELSEVIER IRELAND LTD, 英語, 研究論文（学術雑誌）
  DOI：https://doi.org/10.1016/j.chemphyslip.2008.05.002
  DOI ID：10.1016/j.chemphyslip.2008.05.002, ISSN：0009-3084, eISSN：1873-2941, Web of Science ID：WOS:000258369200002
• Nanocage aggregates composed of bilayer sheets　　　　　　　　　　　　　　　
  Keisuke Matsuoka; Tomokazu Yoshimura; Miri Bong; Chikako Honda; Kazutoyo Endo
  LANGMUIR, 巻：24, 号：11, 開始ページ：5676, 終了ページ：5678, 2008年06月, ［査読有り］
  A partially fluorinated carboxylate-type anionic gemini surfactant, N,N'-di(3-perfluorohexyl-2-hydroxypropyl)-N,N'-diacetic acid-ethylenediamine (2C(6)(F)edda), formed aggregates with a cagelike structure in an aqueous alkali solution. These aggregates were composed of several bilayer sheets. The TEM micrograph showed that the bilayer sheets were produced from a condensed self-assembly core. The leaflike bilayer sheets-can form folds and link to each other at their edges. The typical size of the spherical cage ranged from ca. 200 to 1500 nm.
  AMER CHEMICAL SOC, 英語, 研究論文（学術雑誌）
  DOI：https://doi.org/10.1021/la800618v
  DOI ID：10.1021/la800618v, ISSN：0743-7463, Web of Science ID：WOS:000256232900010
• Indomethacin solubilization induced shape transition in CnE7 (n=14,16) nonionic micelles　　　　　　　　　　　　　　　
  Shigeaki Ishii; Sho Ishikawa; Nozomi Mizuno; Keisuke Matsuoka; Chikako Honda; Kazutoyo Endo
  JOURNAL OF COLLOID AND INTERFACE SCIENCE, 巻：317, 号：1, 開始ページ：115, 終了ページ：120, 2008年01月, ［査読有り］
  Shape transitions were examined with regard to the solubilization of the poorly water-soluble drug indomethacin (IMC) in the nonionic surfactants heptaethylene oxide tetradecyl (C14E7) and hexadecyl (C16E7) ethers by means of a dynamic light scattering technique. The cloud points of the pure C14E7 and C16E7 micelles ranged from 58 to 62 degrees C and from 52.1 to 55.6 degrees C, respectively, at surfactant concentrations of 1 to 10 mM. The cloud points of IMC-solubilized micelles increased by approximately 1 to 5 degrees. The sizes of the pure C14E7 micelles were 4 to 14 nm at 20 to 40 degrees C at a concentration of 2 to 20 mM. The apparent hydrodynamic radius (R-happ) of pure C16E7 micelles varied with temperature and concentration. C16E7 surfactant formed small spherical micelles at 20 and 25 degrees C at concentrations below 5 mM; the size of the micelles was approximately 5 nm. On the other hand, from 30 to 40 degrees C and at a higher concentration, C16E7 formed elongated cylindrical micelles, and these elongated micelles entangled or overlapped each other. The Rhapp of the IMC-solubilized C14E7 micelles at 20 to 40 degrees C and Of C16E7 micelles at 20 degrees C increased compared to that of pure micelles. On the other hand, the cylindrical micelles of C16E7 decreased in size and turned into spherical ones because of the hydrophobicity between the micelles caused by solubilization of IMC. This phenomenon was confirmed by transmission electron microscope (TEM) images. (c) 2007 Elsevier Inc. All rights reserved.
  ACADEMIC PRESS INC ELSEVIER SCIENCE, 英語, 研究論文（学術雑誌）
  DOI：https://doi.org/10.1016/j.jcis.2007.09.021
  DOI ID：10.1016/j.jcis.2007.09.021, ISSN：0021-9797, Web of Science ID：WOS:000251283100014
• NMR study on solubilization of sterols and aromatic compounds in sodium taurodeoxycholate micelles　　　　　　　　　　　　　　　
  Keisuke Matsuoka; Shigeaki Ishii; Chikako Honda; Kazutoyo Endo; Akio Saito; Yoshikiyo Moroi; Osamu Shibata
  BULLETIN OF THE CHEMICAL SOCIETY OF JAPAN, 巻：80, 号：12, 開始ページ：2334, 終了ページ：2341, 2007年12月, ［査読有り］
  The solubility of cholesterol in the binary solubilizates system (cholesterol and, beta-sitosterol) of a sodium taurodeoxycholate solution decreased to almost half of that in the single cholesterol system. On the other hand, the cholesterol solubilities in other binary other systems (cholesterol and certain aromatics) of those solutions were the same as that of the single cholesterol system. The results of competitive solubilization between sterols and aromatics suggested that both were solubilized at different solubilization sites of a micelle. Their molecular dynamics and solubilization sites were measured by the H-1 NMR method. The rotating-frame nuclear Overhauser effect and exchange spectroscopy (ROESY) contour plot of aromatics solubilized micellar solution exhibited direct cross-peaks between the aromatics and bile salt of 19-methyl protons. The observed ROESY spectra of the sterol-solubilized solutions were almost identical to those of the pure micellar solution. The spin-lattice relaxation time (T-1) for aromatics solubilized in the micellar solutions increased for 18-, 19-, and 21-methyl protons of the bile salt in comparison with those of a pure micellar solution, which indicated that the micellar core changed to a loosely packed state owing to the penetration of aromatics. On the other hand, the T-1 values for sterols solubilized in micelles were lesser than those for pure micellar solutions for almost all proton positions, which suggested that the sterols were compatible with the micelle. These results indicated that the aromatics were solubilized in micellar palisade layer interacting with bile salt of methyl protons, whereas, the sterols were solubilized to match the micellar structure via the steroids interaction.
  CHEMICAL SOC JAPAN, 英語, 研究論文（学術雑誌）
  DOI：https://doi.org/10.1246/bcsj.80.2334
  DOI ID：10.1246/bcsj.80.2334, ISSN：0009-2673, eISSN：1348-0634, Web of Science ID：WOS:000252141000009
• Molecular aggregates of partially fluorinated quaternary ammonium salt gemini surfactants　　　　　　　　　　　　　　　
  Keisuke Matsuoka; Tomokazu Yoshimura; Takashi Shikimoto; Juri Hamada; Mika Yamawaki; Chikako Honda; Kazutoyo Endo
  LANGMUIR, 巻：23, 号：22, 開始ページ：10990, 終了ページ：10994, 2007年10月, ［査読有り］
  The size and shape of novel partially fluorinated gemini surfactant 1,2-bis[dimethyl-(3-perfluoroalkyl-2F hydroxypropyl) ammonium] ethane bromide ((CnC3)-C-F-2-C3CnF, where n = 4, 6, and 8) were investigated in aqueous solution by means of light scattering and transmission electron microscopy (TEM). The sizes of these molecular aggregates changed with increasing carbon number of the alkyl chain and concentration. For example, the apparent hydrodynamic radius by dynamic light scattering was 18 nm at a concentration of cmc x 5 for n = 4, 115 urn at the cmc x 15 for it = 6, and 62 nm at the cmc x 30 for it = 8, at 298.2 K. The shapes of C-n(F) C-3-2-C3 C-n(F) aggregates drastically changed with the alkyl chain length; the aggregates were mainly in the form of large or irregular small auureaates (n = 4), string-like aggregates (n = 6), and vesicles (n = 8). The bromide-ion activity was measured using a bromide-ion-selective electrode to determine the degree of counterion binding to the aggregates. The degree of counterion binding to aggregate was very small compared with that in the typical hydrogenated gemini surfactants. These results indicated that the small curvature of large aggregates was not influenced by an electrostatic repulsion between the cationic head groups in the case of the bulky molecular volume of fluorinated gemini surfactants.
  AMER CHEMICAL SOC, 英語, 研究論文（学術雑誌）
  DOI：https://doi.org/10.1021/la701525c
  DOI ID：10.1021/la701525c, ISSN：0743-7463, Web of Science ID：WOS:000250228100023
• Changes in the components of biliary and plasma lipids in selenium-deficient rats　　　　　　　　　　　　　　　
  Yasunobu Sakuma; Junya Sasaki; Aya Futami; Kousuke Yamasaki; Keisuke Matsuoka; Chikako Honda; Kazutoyo Endo; Masarnichi Tsukada
  CHEMISTRY AND PHYSICS OF LIPIDS, 巻：148, 号：2, 開始ページ：70, 終了ページ：76, 2007年08月, ［査読有り］
  We constructed a chronic oxidative stress model in which Se-deficient diet was fed to male Wister rats for 8 weeks. As expected, effects of oxidative damage, including Fe accumulation and increase in peroxidized lipids, were identified in the liver owing to the lack of glutathione peroxidase. Although the oxidative stress caused Fe accumulation in the liver, the Fe concentration in bile of the SeD rat was almost the same as that in the control rats. The constant excretion of Fe into bile supported the Fe accumulation in the liver. No differences were observed in the principal components of biliary lipids, i.e., bile acids, phospholipids, and cholesterol, between the two groups; moreover, these trends were also reflected in the plasma. Due to the trapping of reactive oxygen species, only bilirubin concentrations in the bile and plasma were decreased in the SeD group, when compared with those in the control group. Measurement of bilirubin concentration may be used as a supplemental oxidative stress marker. (c) 2007 Elsevier Ireland Ltd. All rights reserved.
  ELSEVIER IRELAND LTD, 英語, 研究論文（学術雑誌）
  DOI：https://doi.org/10.1016/j.chemphyslip.2007.04.005
  DOI ID：10.1016/j.chemphyslip.2007.04.005, ISSN：0009-3084, Web of Science ID：WOS:000248433600003
• Thermodynamic study on competitive solubilization of cholesterol and P-sitosterol in bile salt micelles　　　　　　　　　　　　　　　
  Keisuke Matsuoka; Takashi Hirosawa; Chikako Honda; Kazutoyo Endo; Yoshikiyo Moroi; Osamu Shibata
  CHEMISTRY AND PHYSICS OF LIPIDS, 巻：148, 号：1, 開始ページ：51, 終了ページ：60, 2007年07月, ［査読有り］
  Differences in the preferential solubilization of cholesterol and competitive solubilizates (P-sitosterol and aromatic compounds) in bile salt micelles was systematically studied by changing the molar ratio of cholesterol to competitive solubilizates. The cholesterol solubility in a mixed binary system (cholesterol and P-sitosterol) was almost half that of the cholesterol alone system, regardless of the excess-sitosterol quantity added. On the other hand, the mutual solubilities of cholesterol and pyrene were not inhibited by their presence in binary mixed crystals. Finally, the cholesterol solubility was measured by changing the alkyl chain length of n-alkylbenzenes. When tetradecylbenzene was added to the bile solution, the cholesterol solubility decreased slightly and was below the original cholesterol solubility. Based on Gibbs energy change (Delta G degrees) for solubilization, chemicals that inhibit cholesterol solubility in their combined crystal systems showed a larger negative Delta G degrees value than cholesterol alone. (C) 2007 Elsevier Ireland Ltd. All rights reserved.
  ELSEVIER IRELAND LTD, 英語, 研究論文（学術雑誌）
  DOI：https://doi.org/10.1016/j.chemphyslip.2007.04.007
  DOI ID：10.1016/j.chemphyslip.2007.04.007, ISSN：0009-3084, Web of Science ID：WOS:000248174500003
• Aggregate structure of N-(perfluoroalkylmethyl)-N,N,N-trimethylammonium chloride by transmission electron microscopy　　　　　　　　　　　　　　　
  Keisuke Matsuoka; Mariko Ishii; Aki Yonekawa; Chikako Honda; Kazutoyo Endo; Yoshikiyo Moroi; Yutaka Abe; Takamitsu Tamura
  BULLETIN OF THE CHEMICAL SOCIETY OF JAPAN, 巻：80, 号：6, 開始ページ：1129, 終了ページ：1131, 2007年06月, ［査読有り］
  The size and shape of aggregates were investigated for four fluorinated amphiphiles with different alkyl chain lengths: Cn-1F2n-1CH2N+(CH3)(3)Cl- (Cn-TAC; n = 8, 10, 12, and 14) by TEM. The micrographs showed that Cn-TACs were mostly disc-like or ellipsoid-shaped lamella, which exponentially grew up their size from 10 nm (C8-TAC) to 500 nm (C14-TAC).
  CHEMICAL SOC JAPAN, 英語, 研究論文（学術雑誌）
  DOI：https://doi.org/10.1246/bcsj.80.1129
  DOI ID：10.1246/bcsj.80.1129, ISSN：0009-2673, eISSN：1348-0634, Web of Science ID：WOS:000248256600011
• Antibacterial activity of long-chain fatty alcohols against Staphylococcus aureus　　　　　　　　　　　　　　　
  Naoko Togashi; Akiko Shiraishi; Miki Nishizaka; Keisuke Matsuoka; Kazutoyo Endo; Hajime Hamashima; Yoshihiro Inoue
  MOLECULES, 巻：12, 号：2, 開始ページ：139, 終了ページ：148, 2007年02月, ［査読有り］
  The antibacterial activity against Staphylococcus aureus of long-chain fatty alcohols was investigated, with a focus on normal alcohols. The antibacterial activity varied with the length of the aliphatic carbon chain and not with the water/octanol partition coefficient. 1-Nonanol, 1-decanol and 1-undecanol had bactericidal activity and membrane-damaging activity. 1-Dodecanol and 1-tridecanol had the highest antibacterial activity among the long-chain fatty alcohols tested, but had no membrane-damaging activity. Consequently, it appears that not only the antibacterial activity but also the mode of action of long-chain fatty alcohols might be determined by the length of the aliphatic carbon chain.
  MOLECULAR DIVERSITY PRESERVATION INTERNATIONAL, 英語, 研究論文（学術雑誌）
  DOI：https://doi.org/10.3390/12020139
  DOI ID：10.3390/12020139, ISSN：1420-3049, Web of Science ID：WOS:000244767600002
• Micellar size, shape and counterion binding of N-(1,1-Dihydroperfluoroalkyl)-N,N,N-trimethylammonium chloride in aqueous solutions　　　　　　　　　　　　　　　
  Keisuke Matsuoka; Aki Yonekawa; Mariko Ishii; Chikako Honda; Kazutoyo Endo; Yoshikiyo Moroi; Yutaka Abe; Takamitsu Tamura
  COLLOID AND POLYMER SCIENCE, 巻：285, 号：3, 開始ページ：323, 終了ページ：330, 2006年12月, ［査読有り］
  Under the limiting conditions, light-scattering method was applied to determine the size and shape of fluorinated micellar structure in aqueous solution. The hydrodynamic radii (r(h)) of molecular aggregates were investigated for four amphiphiles with different alkyl chain length: N-(1,1-dihydroperfluorooctyl)-, N-(1,1-dihydroperfluorodecyl)-, N-(1,1-dihydroperfluorododecyl)-, and N-(1,1-dihydroperfluorotetradecyl)-N,N,N-trimethylammonium chloride by dynamic light scattering. Size of these molecular aggregates drastically increased with increasing carbon number of alkyl chain and the concentration. For example, the r(h) values were 35, 63, 95, and 136 nm for C8, C10, C12, and C14 of the alkyl chain, respectively, at the concentration of 15x critical micelle concentration (cmc) and at 298.2 K. On the other hand, the mean radius of gyration (r(g)) and the apparent molecular weight of these aggregates were measured using static light scattering. The r(g) value was found to be 34, 73, and 125 nm for C8, C10, and C12 of the alkyl chain, respectively, at the same condition above. The shape of aggregate was analyzed by comparing the dependence of r(g)/r(h) with theoretical values. The plots of r(g) against r(h) almost corresponded with the theoretical line of oblate ellipsoid (disk-like), and which was also expected from calculation of packing parameter value. The measurement for chloride ion activity was made by a chloride ion selective electrode to know the degree of counterion binding to the aggregates, whose values increased with increasing total concentration and with the carbon number of alkyl chain. The chloride ion binding to aggregates neutralized cationic head groups under their electrostatic repulsion and partly promoted the growth of aggregates.
  SPRINGER, 英語, 研究論文（学術雑誌）
  DOI：https://doi.org/10.1007/s00396-006-1574-8
  DOI ID：10.1007/s00396-006-1574-8, ISSN：0303-402X, Web of Science ID：WOS:000242146000008
• Temperature dependence of pyrene fluorescence spectra in aqueous solutions of CnEm (C14E7, C16E7, and C16E6) nonionic surfactant micelles　　　　　　　　　　　　　　　
  Chikako Honda; Yumi Katsumata; Risa Yasutome; Sanae Yamazaki; Shigeaki Ishii; Keisuke Matsuoka; Kazutoyo Endo
  JOURNAL OF PHOTOCHEMISTRY AND PHOTOBIOLOGY A-CHEMISTRY, 巻：182, 号：2, 開始ページ：151, 終了ページ：157, 2006年08月, ［査読有り］
  Apparent hydrodynamic radii (Rh pp) of nonionic surfactant micelles in aqueous solutions of hepta- and hexa-ethyleneoxide monoalkylether (C14E7, C16E7, and C16E6) were measured at 20-40 degrees C. Fluorescence spectra of pyrene in aqueous solutions of the nonionic surfactants were measured as a function of surfactant concentration and temperature. The cloud point of C16E6 was about 35 degrees C at concentration range of 10(-3) to 10(-2) M. However, even at a higher temperature than the cloud point, the fluorescence intensity ratio of pyrene monomer, I-m1/I-m3, in C16E6 solution behaves similarly to other surfactants (C16E7 and C(14)EA indicating that the pyrene molecules reside in a similar location of surfactants. The slope for the temperature dependence of the I-m1/I-m3 ratio also changed with the surfactant concentration, and the micelle size differed among the surfactants (C16E6, C16E7, and C14E7). The activation enthalpy of pyrene diffusion was evaluated using Stevens-Ban plot, and the value of 20-30 KJ mol(-1) was obtained for surfactant concentrations of 5 x 10(-4) to 10(-2) M. The results were compared with those reported for ionic and nonionic surfactant micelles. (c) 2006 Elsevier B.V All rights reserved.
  ELSEVIER SCIENCE SA, 英語, 研究論文（学術雑誌）
  DOI：https://doi.org/10.1016/j.jphotochem.2006.02.003
  DOI ID：10.1016/j.jphotochem.2006.02.003, ISSN：1010-6030, Web of Science ID：WOS:000239874600005
• Micellization of conjugated chenodeoxy- and ursodeoxycholates and solubilization of cholesterol into their micelles: comparison with other four conjugated bile salts species　　　　　　　　　　　　　　　
  K Matsuoka; M Suzuki; C Honda; K Endo; Y Moroi
  CHEMISTRY AND PHYSICS OF LIPIDS, 巻：139, 号：1, 開始ページ：1, 終了ページ：10, 2006年01月, ［査読有り］
  Micelle formations of soclium glyco- and taurochenodeoxychol ate (NaGCDC and NaTCDC) and sodium glyco- and tauroursodeoxycholates (NaGUDC and NaTUDC) was Studied at 308.2 K for their critical micelle concentrations at various NaCl concentrations by pyrene fluorescence probe, and the degree of counterion binding to micelle was determined using the Corrin-Harkins plots. The degree of counterion binding was found to be 0.37-0.38 for chenodeoxycholate Conjugates, while the determination of the degree was quite difficult for ursodeoxycholate conjugates. The change of I-1/I-3 values on the fluorescence spectrum with the conjugate bile salt concentration suggested two steps for their bile salt aggregation. The first step is a commencement of smaller aggregates, the first cmc, and the second one is a starting of stable aggregates, the second cmc. The aggregation number was determined at 308.2 K and 0.15 M NaCl concentration by static light scattering: 16.3 and 11.9 for sodium NaGCDC and NaTCDC, and 7.9 and 7.1 for NaGUDC and NaTUDC, respectively. The solubilization of cholesterol into the bile salt micelles in the presence of coexisting cholesterol phase and the maximum additive concentration (MAC) of cholesterol was determined against the bile salt concentration. The standard Gibbs energy change for the solubilization was evaluated, where the micelles were regarded as a chemical species. The solubilization was stabilized in the order of NaGUDC congruent to NaTUDC < NaTC < NaGC < NiTCDC < NaGCDC < NaTDC < NaGDC, where the preceding results were taken into the order. (c) 2005 Elsevier Ireland Ltd. All rights reserved.
  ELSEVIER IRELAND LTD, 英語, 研究論文（学術雑誌）
  DOI：https://doi.org/10.1016/j.chemphyslip.2005.08.006
  DOI ID：10.1016/j.chemphyslip.2005.08.006, ISSN：0009-3084, PubMed ID：16256096, Web of Science ID：WOS:000234822000001
• Spontaneous membrane fusion induced by chemical formation of ceramides in a lipid bilayer　　　　　　　　　　　　　　　
  Kunishima, Munetaka; Tokaji, Masafumi; Matsuoka, Keisuke; Nishida, Jin; Kanamori, Masanori; Hioki, Kazuhito; Tani, Shohei
  Journal of the American Chemical Society, 巻：128, 号：45, 開始ページ：14452, 終了ページ：14453, 2006年, ［査読有り］
  研究論文（学術雑誌）
  DOI：https://doi.org/10.1021/ja0652969
  DOI ID：10.1021/ja0652969, ISSN：0002-7863, ORCID：42933560, PubMed ID：17090016, Web of Science ID：WOS:000241857200018
• Micelle formation and surface adsorption of octaethylene glycol monoalkyl ether (CnE8)　　　　　　　　　　　　　　　
  M Rusdi; Y Moroi; T Hlaing; K Matsuoka
  BULLETIN OF THE CHEMICAL SOCIETY OF JAPAN, 巻：78, 号：4, 開始ページ：604, 終了ページ：610, 2005年04月
  The surface tension was measured against the concentration of CnE8 (n = 14, 16, and 18) at temperatures of 298.2, 303.2, 308.2, 313.2, and 318.2 K, from which the critical micelle concentration (CM was determined. The CNC decreased with increasing carbon number at lower temperatures, where the decreasing rate became much smaller at higher temperatures. The CMC values were examined by pyrene fluorescence, and the I,/I-3 ratio of the pyrene spectrum steeply decreased below the CMC, and finally reached a plateau at higher surfactant concentrations. The I-1/I-3 ratios indicate that the microenvironment of: pyrene in the micellar region becomes more hydrophobic with increasing the alkyl chain of CnE8. The aggregation number by a static light-scattering method increased with increasing the alkyl chain at a definite temperature and with raising the temperature for all of the surfactants. The thermodynamic parameters (Delta G degrees, Delta H degrees, T Delta S degrees) of the micelle formation were calculated from the temperature dependence of CMC and the aggregation number, and the micellization was found to be entropy-driven. The surface excess concentration (F) was also determined from the change in the surface tension with the concentration from which the molecular surface area (A) below the CMC was evaluated. The molecular surface areas suggest that longer monoalkyl ethers form a bi-molecular layer with the hydrophobic tail intruding inwards. The positive entropy change (As) for the surface adsorption decreased and stayed almost constant with increasing concentration for C14E8 and C16E8, while the change remained almost zero for C18E8 at whole concentrations below the CMC. These results suggest that the non-fully extended alkyl chain in the bulk could not well contribute to a positive entropy change upon adsorption, which results in a smaller decreasing rate in CMC with increasing carbon number of alkylchain for C16E8 and C18E8 compared with the decreasing rate for CnE8 with n less than 14.
  CHEMICAL SOC JAPAN, 英語, 研究論文（学術雑誌）
  DOI：https://doi.org/10.1246/bcsj.78.604
  DOI ID：10.1246/bcsj.78.604, ISSN：0009-2673, eISSN：1348-0634, SCOPUS ID：18744387421, Web of Science ID：WOS:000228912900006
• Micelle formation and surface adsorption of octaethylene glycol monoalkyl ether (CnE8)　　　　　　　　　　　　　　　
  M Rusdi; Y Moroi; T Hlaing; K Matsuoka
  BULLETIN OF THE CHEMICAL SOCIETY OF JAPAN, 巻：78, 号：4, 開始ページ：604, 終了ページ：610, 2005年04月, ［査読有り］
  The surface tension was measured against the concentration of CnE8 (n = 14, 16, and 18) at temperatures of 298.2, 303.2, 308.2, 313.2, and 318.2 K, from which the critical micelle concentration (CM was determined. The CNC decreased with increasing carbon number at lower temperatures, where the decreasing rate became much smaller at higher temperatures. The CMC values were examined by pyrene fluorescence, and the I,/I-3 ratio of the pyrene spectrum steeply decreased below the CMC, and finally reached a plateau at higher surfactant concentrations. The I-1/I-3 ratios indicate that the microenvironment of: pyrene in the micellar region becomes more hydrophobic with increasing the alkyl chain of CnE8. The aggregation number by a static light-scattering method increased with increasing the alkyl chain at a definite temperature and with raising the temperature for all of the surfactants. The thermodynamic parameters (Delta G degrees, Delta H degrees, T Delta S degrees) of the micelle formation were calculated from the temperature dependence of CMC and the aggregation number, and the micellization was found to be entropy-driven. The surface excess concentration (F) was also determined from the change in the surface tension with the concentration from which the molecular surface area (A) below the CMC was evaluated. The molecular surface areas suggest that longer monoalkyl ethers form a bi-molecular layer with the hydrophobic tail intruding inwards. The positive entropy change (As) for the surface adsorption decreased and stayed almost constant with increasing concentration for C14E8 and C16E8, while the change remained almost zero for C18E8 at whole concentrations below the CMC. These results suggest that the non-fully extended alkyl chain in the bulk could not well contribute to a positive entropy change upon adsorption, which results in a smaller decreasing rate in CMC with increasing carbon number of alkylchain for C16E8 and C18E8 compared with the decreasing rate for CnE8 with n less than 14.
  CHEMICAL SOC JAPAN, 英語, 研究論文（学術雑誌）
  DOI：https://doi.org/10.1246/bcsj.78.604
  DOI ID：10.1246/bcsj.78.604, ISSN：0009-2673, eISSN：1348-0634, Web of Science ID：WOS:000228912900006
• O/W emulsion of n-alkylbenzene/ionic surfactant/water systems　　　　　　　　　　　　　　　
  Y Doi; Y Kawashima; K Matsuoka; Y Moroi
  JOURNAL OF PHYSICAL CHEMISTRY B, 巻：108, 号：8, 開始ページ：2594, 終了ページ：2599, 2004年02月, ［査読有り］
  The maximum additive concentration of benzene, toluene, ethylbenzene, n-propylbenzene, n-butylbenzene, and n-pentylbenzene into two kinds of ionic micelles, 1-dodecanesulfonic acid and n-tetradecyltrimethylammonium bromide micelles, was determined at 298.2 K, where these volatile solubilizates were solubilized, not by direct contact of the liquid solubilizate with micellar solution but by molecular transfer through their own gaseous phase. The aggregation number of micelles is ca. 60 and their size is 5 urn in diameter in the aqueous solution in the case of no solubilizate in the system. In the presence of the above solubilizates, however, the micellar aggregates greatly grow in size up to more than 150 nm in diameter for 1-dodecanesulfonic acid micelle and 200 nm for n-tetradecyltrimethylammonium bromide micelle, where the micelles or the aggregates accommodate the volatile solubilizates as much as possible or the maximum additive concentration. The solubilization was analyzed by partition equilibrium of the solubilizates between aqueous phase and micellar phase, because the micelles are so large in size. The contribution per ethylene group in the alkyl chain to the Gibbs energy change was calculated to be -2.35 and -2.78 U mol(-1) for 1-dodecanesulfonic acid and n-tetradecyltrimethylammonium bromide micelles, respectively. The larger negative value for the latter is due to more hydrophobic solubilization site by hydrocarbon head of the latter.
  AMER CHEMICAL SOC, 英語, 研究論文（学術雑誌）
  DOI：https://doi.org/10.1021/jp0304879
  DOI ID：10.1021/jp0304879, ISSN：1520-6106, Web of Science ID：WOS:000189152000016
• Characteristics of conjugate bile salt-phosphatidylcholine-cholesterol-water systems　　　　　　　　　　　　　　　
  K Matsuoka; M Maeda; Y Moroi
  COLLOIDS AND SURFACES B-BIOINTERFACES, 巻：33, 号：2, 開始ページ：101, 終了ページ：109, 2004年01月, ［査読有り］
  Solubilization of L-alpha-phosphatidylcholine (PC) to micelles of conjugate bile salts, sodium glycocholate (NaGC), sodium taurocholates (NaTC), and sodium glycodeoxycholate (NaGDC), was studied at different bile salt concentrations by enzymatic method and by transmittance of the suspension system at 308.2 K. The solubility of PC increased in the order of NaTC < NaGC < NaGDC. An average molar ratio of PC/NaTC decreased with increasing bile salt concentration at different temperatures. Hydrodynamic diameters (d(h)) of PC-saturated conjugate bile salt aggregates were measured by dynamic light scattering (DLS or QELS) as a function of the bile salt concentration at 308.2 K. Change of the d(h) values with increasing bile salt concentration indicated shape transition from vesicle (d(h): 150 nm) to micelle (d(h): 10 nm). The maximum additive concentrations of cholesterol into the aqueous micellar solutions of PC-conjugate bile salt mixtures were spectrophotometrically determined using enzymatic analysis. The cholesterol solubility increased in the order of NaTC < NaGC at the same concentration, and in addition, cholesterol can be more solubilized at higher molar ratio of PC/bile salt. An addition of cholesterol to the PC-bile salt systems was found to become a trigger that gave rise to generation of polydisperse distribution of larger aggregates or vesicle formation for PC-bile salt systems. The critical cholesterol concentration of vesicle formation was 1.2 mM for NaTC (47.5 mM)-PC (36.5 mM) system and 0.7 mM for NaTC (47.5 mM)-PC (23.8 mM) system. (C) 2003 Elsevier B.V. All rights reserved.
  ELSEVIER SCIENCE BV, 英語, 研究論文（学術雑誌）
  DOI：https://doi.org/10.1016/j.colsurfb.2003.09.002
  DOI ID：10.1016/j.colsurfb.2003.09.002, ISSN：0927-7765, Web of Science ID：WOS:000188863300005
• Micelle formation of sodium chenodeoxycholate and solubilization into the micelles: comparison with other unconjugated bile salts　　　　　　　　　　　　　　　
  R Ninomiya; K Matsuoka; Y Moroi
  BIOCHIMICA ET BIOPHYSICA ACTA-MOLECULAR AND CELL BIOLOGY OF LIPIDS, 巻：1634, 号：3, 開始ページ：116, 終了ページ：125, 2003年11月, ［査読有り］
  Micellization of sodium chenodeoxycholate (NaCDC) was studied for the critical micelle concentration (CMC), the micelle aggregation number, and the degree of counterion binding to micelle at 288.2, 298.2, 308.2, and 318.2 K. They were compared with those of three other unconjugated bile salts; sodium cholate (NaC), sodium deoxycholate (NaDC), and sodium ursodeoxycholate (NaUDC). The I-1/I-3, ratio of pyrene fluorescence and the solubility dependence of solution pH were employed to determine the CMC values. As the results, a certain concentration range for the CMC and a stepwise molecular aggregation for micellization were found reasonable. Using a stepwise association model of the bile salt anions, the mean aggregation number (n) over bar of NaCDC micelles was found to increase with the total anion concentration, while the (n) over bar values decreased with increasing temperature; 9.1, 8.1, 7.4, and 6.3 at 288.2, 298.2, 308.2, and 318.2 K, respectively, at 50 mmol dm(-3). The results from four unconjugated bile salts indicate that the number, location, and orientation of hydroxyl groups in the steroid nucleus are quite important for growth of the micelles. Activity of the counterion (Na+) was determined by a sodium ion selective electrode in order to confirm the low counterion binding to micelles. The solubilized amount of cholesterol into the aqueous bile salt solutions increased in the order of NaUDC < NaC < NaCDC < NaDC. The first stepwise association or solubilization constants ((K) over bar)(1) between a cholesterol monomer and a vacant micelle were evaluated at different bile salt concentrations. The constants were also determined for polycyclic aromatic compounds (benzene, naphthalene, anthracene, and pyrene). The corresponding DeltaG(0) value was most negative for cholesterol among the solubilizates studied, which indicated that cholesterol was thermodynamically stabilized most by solubilization into the bile salt micelles. (C) 2003 Elsevier B.V. All rights reserved.
  ELSEVIER SCIENCE BV, 英語, 研究論文（学術雑誌）
  DOI：https://doi.org/10.1016/j.bbalip.2003.09.003
  DOI ID：10.1016/j.bbalip.2003.09.003, ISSN：1388-1981, Web of Science ID：WOS:000186987500007
• Micelle formation of sodium chenodeoxycholate and solubilization into the micelles: comparison with other unconjugated bile salts.　　　　　　　　　　　　　　　
  Ninomiya R; Matsuoka K; Moroi Y
  Biochimica et biophysica acta, 巻：1634, 号：3, 開始ページ：116, 終了ページ：125, 2003年11月, ［査読有り］
  DOI：https://doi.org/10.1016/j.bbalip.2003.09.003
  DOI ID：10.1016/j.bbalip.2003.09.003, ISSN：0006-3002, PubMed ID：14643799
• Micelle formation of sodium glyco- and taurocholates and sodium glyco- and taurodeoxycholates and solubilization of cholesterol into their micelles　　　　　　　　　　　　　　　
  K Matsuoka; M Maeda; Y Moroi
  COLLOIDS AND SURFACES B-BIOINTERFACES, 巻：32, 号：2, 開始ページ：87, 終了ページ：95, 2003年10月, ［査読有り］
  Micelle formation of sodium glyco- and taurocholates and sodium glyco- and taurodeoxycholates was studied at 308.2 K for the critical micelle concentration at various NaCl concentrations by pyrene fluorescence and scattered light intensity, and the degree of counterion binding to micelle was calculated using the Corrin-Harkins plots. The change of I-1/I-3 values of the fluorescence spectrum with the conjugate bile salt concentration suggested two steps for the bile salt aggregation, which was supported by the scattered light intensity. The first step is a commencement of smaller aggregates, the first CMC, and the second one is a beginning of stable aggregates, the second CMC. Between the first and the second CMCs, the aggregates grow in size with the conjugate concentration. The aggregation number above the second CMC was determined at 308.2 K and 0.15 mol dm(-3) NaCl concentration by the static light scattering: 8.7 and 6.0 for sodium glyco- and taurocholate, respectively, and 15.7 and 15.9 for sodium glyco- and taurodeoxycholate, respectively. The solubilization of cholesterol into the bile salt micelles in the presence of coexisting cholesterol phase or the maximum additive concentration (MAC) of cholesterol was determined against the bile salt concentration, and then, the standard Gibbs energy change for the solubilization was evaluated, where the micelles were regarded as a chemical species. The solubilization was stabilized in the order of sodium taurocholate < sodium glyco-cholate < sodiun taurodeoxycholate < sodium glycodeoxycholate. (C) 2003 Elsevier B.V. All rights reserved.
  ELSEVIER SCIENCE BV, 英語, 研究論文（学術雑誌）
  DOI：https://doi.org/10.1016/S0927-7765(03)00148-6
  DOI ID：10.1016/S0927-7765(03)00148-6, ISSN：0927-7765, Web of Science ID：WOS:000185549100001
• Micellization of fluorinated amphiphiles　　　　　　　　　　　　　　　
  K Matsuoka; Y Moroi
  CURRENT OPINION IN COLLOID & INTERFACE SCIENCE, 巻：8, 号：3, 開始ページ：227, 終了ページ：235, 2003年08月, ［査読有り］
  New cationic fluorinated surfactants and new types of fluorinated surfactants having fluorocarbon-hydrocarbon hybrids, dimeric and polymeric structure have been synthesized recently. Their synthesis requires many steps and consequently requires much time and high expense. Since the fluorinated surfactants have unusual molecular aggregation properties, F-19-NMR, novel fluorescence probes and cryo-transmission electron microscope techniques have been applied to study their aggregation behaviour in aqueous systems. Their unique characteristics are summarized as follows: (1) the dissolution process from solid state to dissolved aggregate state requires a very long time for the long chain fluorinated surfactants under thermodynamic equilibrium. The equilibration time can be reduced at higher temperatures; (2) interfacial properties and critical micelle concentration (CMC) are influenced by the nature of the hydrophobic terminal groups (CF3 - or H-CF2 -); (3) the fluorocarbon functionality can make it possible even for single-chain amphiphiles to form vesicles or lamellar structures; (4) the hybrid surfactant made of both hydrocarbon and fluorocarbon chains showed a life time of 2.0 x 10(-3) s for the exchange rate between the monomeric and the micellar states at the CMC and moreover, these detergents can cosolubilize fluorocarbon-hydrocarbon mixed solubilizates. (C) 2003 Elsevier Ltd. All rights reserved.
  ELSEVIER SCIENCE LONDON, 英語
  DOI：https://doi.org/10.1016/S1359-0294(03)00056-6
  DOI ID：10.1016/S1359-0294(03)00056-6, ISSN：1359-0294, Web of Science ID：WOS:000184757000004
• Temperature effect on formation of sodium cholate micelles　　　　　　　　　　　　　　　
  H Sugioka; K Matsuoka; Y Moroi
  JOURNAL OF COLLOID AND INTERFACE SCIENCE, 巻：259, 号：1, 開始ページ：156, 終了ページ：162, 2003年03月, ［査読有り］
  The micellization of sodium cholate (NaC) at 293.2, 298.2 303.2 308.2, and 313.2 K by cholate anion concentration was studied over the pH range from 6.0 to 7.2. Using a stepwise association model of cholate anions without bound sodium counterions, the aggregation number ((n) over bar) of the cholate micelles was evaluated and found to increase with the total concentration, indicating that the stepwise association model is applicable. The n values go up and down with increasing temperature: 17 at 298.2 and 12 at 313.2 K and at 60 mM of the sodium cholate. The fluorescence of pyrene was measured in sodium cholate solution to determine the critical micelle concentration (CMC), indicating a narrow concentration range for CMC. A sodium-ion-specific electrode was used to determine a relatively low degree of counterion binding to micelles, supporting the validity of the present association model of cholate anions. The aggregation numbers evaluated at a constant ionic strength of 0.15 and at lower but variable ionic strengths were similar except for higher cholate concentrations. (C) 2003 Elsevier Science (USA). All rights reserved.
  ACADEMIC PRESS INC ELSEVIER SCIENCE, 英語, 研究論文（学術雑誌）
  DOI：https://doi.org/10.1016/S0021-9797(02)00191-1
  DOI ID：10.1016/S0021-9797(02)00191-1, ISSN：0021-9797, PubMed ID：12651144, Web of Science ID：WOS:000181864700017
• Micelle formation of sodium deoxycholate and sodium ursodeoxycholate (Part 1)　　　　　　　　　　　　　　　
  K Matsuoka; Y Moroi
  BIOCHIMICA ET BIOPHYSICA ACTA-MOLECULAR AND CELL BIOLOGY OF LIPIDS, 巻：1580, 号：2-3, 開始ページ：189, 終了ページ：199, 2002年02月, ［査読有り］
  Micellization of sodium deoxycholate (NaDC) and sodium ursodeoxycholate (NaUDC) was studied for the critical micelle concentration (CMC), the micelle aggregation number, and the degree of counterion binding to micelle, where sodium cholate (NaC) was used as a reference. The fluorescence probe technique of pyrene was employed to determine accurately the CMC values for the bile salts, which indicated that a certain concentration range of CMC and a stepwise aggregation for micellization were reasonable. The temperature dependences of micellization for NaDC and NaUDC were studied at 288.2, 298.2, 308.2, and 318.2 K by aqueous solubility change with solution pH. Aggregations of the bile salt anions were analyzed using the stepwise association model and found to grow in size with increasing concentration, which confirmed that the mass action model worked quite well. The average aggregation number was found to be 2.5 (NaUDC) and 10.5 (NaDC) at the concentration of 20 mM and at 308.2 K. The aggregation number determined by static light scattering also agreed well with those by the solubility method in the order of size: NaUDC < NaC < NaDC at 308.2 K. The results indicated that the location of the OH group at C-7 and its orientation were the most important factors from the viewpoint of chemical structure for the growth of micelles. The activity measurement for sodium ions was made by a sodium ion selective electrode in order to confirm the low counterion binding to micelles and the validity of the present association model of bile salts, but the model did not hold good for NaDC at higher concentrations. (C) 2002 Elsevier Science B.V. All rights reserved.
  ELSEVIER SCIENCE BV, 英語, 研究論文（学術雑誌）
  DOI：https://doi.org/10.1016/S1388-1981(01)00203-7
  DOI ID：10.1016/S1388-1981(01)00203-7, ISSN：1388-1981, PubMed ID：11880243, Web of Science ID：WOS:000174494600009
• Solubilization of cholesterol and polycyclic aromatic compounds into sodium bile salt micelles (Part 2)　　　　　　　　　　　　　　　
  K Matsuoka; Y Kuranaga; Y Moroi
  BIOCHIMICA ET BIOPHYSICA ACTA-MOLECULAR AND CELL BIOLOGY OF LIPIDS, 巻：1580, 号：2-3, 開始ページ：200, 終了ページ：214, 2002年02月, ［査読有り］
  The aqueous solubility of cholesterol was determined over the temperature range from 288.2 to 318.2 K with intervals Of 5 K by the enzymatic method. The solubility was (3.7 +/- 0.3) X 10(-8) mol dm(-3) (average +/- S.D.) at 308.2 K. The maximum additive concentrations of cholesterol into the aqueous micellar solutions of sodium deoxycholate (NaDC). sodium ursodeoxycholate (NaUDC), and sodium cholate (NaC) were spectrophotometrically determined at different temperatures. The cholesterol solubility increased in the order of NaUDC < NaC < NaDC; for example, 0.10 for NaUDC 0.61 for NaC, and 2.99 mmol dm(-3) for NaDC at the concentration of 60 mmol dm(-3) and at 308.2 K. The same solubilization experiments were made at 308.2 K using polycyclic aromatic compounds (benzene, naphthalene. anthracene. pyrene) as a reference. Their solubility increase for the bile salts was in the same order as above. Thermodynamic analysis was made for the solubilization, where a micelle was regarded as a chemical species. The average number of solubilizate per micelle was less than unity throughout the experiments. From the Gibbs energy change for solubilization at the different mean aggregation numbers, the function of bile salt micelles was discussed from the viewpoint of molecular structure of solubilizates. The DeltaG(0) value for cholesterol was most negative among the solubilizates studied, which reflected that solubilization of cholesterol into bile salt micelles brought about largest thermodynamic stabilization. (C) 2002 Published by Elsevier Science B.V.
  ELSEVIER SCIENCE BV, 英語, 研究論文（学術雑誌）
  DOI：https://doi.org/10.1016/S1388-1981(01)00204-9
  DOI ID：10.1016/S1388-1981(01)00204-9, ISSN：1388-1981, PubMed ID：11880244, Web of Science ID：WOS:000174494600010
• Micelle formation of n-decyltrimethylammonium perfluorocarboxylates　　　　　　　　　　　　　　　
  N Yoshida; K Matsuoka; Y Moroi
  JOURNAL OF COLLOID AND INTERFACE SCIENCE, 巻：187, 号：2, 開始ページ：388, 終了ページ：395, 1997年03月, ［査読有り］
  Critical micelle concentrations (CMCs) of three ionic surfactants that contain n-decyltrimethylammonium ion as a surfactant cation and bromide, perfluoroacetate, and perfluoropropionate anions as a counterion, respectively, were determined by electrical conductivity at several temperatures. The degrees of counterion binding to micelle were obtained at the same temperatures as the change in CMC with total counterion concentration. Molecular weights of micelles were determined by static light scattering. The change in monomeric surfactant ion concentration with total surfactant concentration was determined by membrane potential measurement. The mass-action model was applied to micelle formation to calculate the three micellization parameters: micellization constant, micelle aggregation number, and number of counterions per micelle. Thermodynamic parameters (Delta G(0), Delta H-0, Delta S-0) of the micelle formations were calculated from the temperature dependence of these parameters. At lower temperatures micellization has been found to be entropy driven, whereas it is enthalpy driven at higher temperatures. For n-decyltrimethylammonium perfluoropropionate, however, the tendency is quite different from those of other surfactants. The micellization parameters also made it possible to evaluate the concentration change of monomeric surfactant ion with total surfactant concentration. The evaluated concentration explains the results from the membrane potential measurement. (C) 1997 Academic Press.
  ACADEMIC PRESS INC JNL-COMP SUBSCRIPTIONS, 英語, 研究論文（学術雑誌）
  DOI：https://doi.org/10.1006/jcis.1996.4691
  DOI ID：10.1006/jcis.1996.4691, ISSN：0021-9797, Web of Science ID：WOS:A1997WQ33200014
• ELECTRIC-CONDUCTIVITY ANALYSIS OF MICELLAR SOLUTION OF SODIUM DODECYL-SULFATE　　　　　　　　　　　　　　　
  Y MOROI; K MATSUOKA
  BULLETIN OF THE CHEMICAL SOCIETY OF JAPAN, 巻：67, 号：8, 開始ページ：2057, 終了ページ：2061, 1994年08月, ［査読有り］
  Electric conductivities at 298.2 K of sodium dodecyl sulfate solution above the cmc were analyzed from the concentrations of counterion, surfactant ion, and micelle based upon the mass action model of monodisperse micelle formation, where the three micellization parameters (log K(n) = 230, n = 64, and m = 46.7) were employed. The ionic conductivity of micelle was found to be inconsistent not only with the micellar size of the identical charge but also with the conductivity of the dynamic radius of micelle of the identical charge. The inconsistencies could be solved by the hopping reaction of counterions between micelles through the overlapping of ionic diffuse double layers around micelle that takes place when two micelles come close together. The hopping reaction was found to start when the distance between micelles becomes less than 5 times the Debye length.
  CHEMICAL SOC JAPAN, 英語, 研究論文（学術雑誌）
  ISSN：0009-2673, eISSN：1348-0634, Web of Science ID：WOS:A1994PG24200010
• Thermodynamics of micelle formation of 1-dodecanesulfonic acid
  Keisuke Matsuoka; Yoshikiyo Moroi; Masahiko Saito
  Journal of Physical Chemistry, 巻：97, 開始ページ：13006, 終了ページ：13010, 1993年01月, ［査読有り］
  The critical micelle concentrations (cmc's) of 1-dodecanesulfonic acid in aqueous solution were precisely determined over the temperature range 278.2-323.2 K by an electrical conductivity method. The degrees of counterion binding to micelle were obtained over the above temperature range by cmc change with total counterion concentration. Molecular weights of micelles were determined by static light scattering. Activity change of the counterion H+ with total surfactant concentration was estimated by pH values of the solutions. The mass action model was applied to the micelle formation in order to enumerate the three micellization parameters from these values: micellization constant, micelle aggregation number, and the number of counterions per micelle. Thermodynamic parameters (ΔG°, ΔH°, ΔS°) of micelle formation were then calculated from the temperature change of these parameters. At lower temperatures, the micellization was found to be entropy-driven, while at higher temperatures it was enthalpy-driven. The micellization parameters also made it possible to evaluate the concentration change of every chemical species with total surfactant concentration, and the total conductivity was divided into the contribution of each chemical species. The activity coefficient of the counterion started to increase above the cmc due to its excess concentration in the intermicellar bulk phase. ? 1993 American Chemical Society.
  DOI：https://doi.org/10.1021/j100151a059
  DOI ID：10.1021/j100151a059

• 泡沫分離による水溶液からの物質の除去—Removal of Materials from Aqueous Solution by Foam Separation—特集 泡の最新研究動向 : 構造・性能・機能の応用　　　　　　　　　　　　　　　
  松岡 圭介
  オレオサイエンス / オレオサイエンス編集委員会 編, 巻：24, 号：7, 開始ページ：305, 終了ページ：310, 2024年07月
  東京 : 日本油化学会, 日本語
  ISSN：1345-8949, CiNii Books ID：AA11503417
• 分析化学と材料物性 表面張力と界面張力
  松岡圭介
  ぶんせき, 号：3, 開始ページ：97‐98, 2016年03月05日
  日本語
  ISSN：0386-2178, J-Global ID：201602207697098950
• 植物ステロール/スタノールによるコレステロールの吸収抑制機構に関する研究　　　　　　　　　　　　　　　
  松岡圭介
  オレオサイエンス, 巻：11, 号：4, 開始ページ：119, 終了ページ：125, 2011年04月01日
  日本油化学会, 日本語
  DOI ID：10.5650/oleoscience.11.119, ISSN：1345-8949, J-Global ID：201102289084616354, CiNii Articles ID：40018765807, CiNii Books ID：AA11503417
• マルチトレーサー法と放射化分析法によるSe欠乏ラット胆汁中の微量元素の動態の解析　　　　　　　　　　　　　　　
  山崎 公輔; 塚田 正道; 遠藤 和豊; 本田 智香子; 松岡 圭介; 松本 謙一郎; 安西 和紀; 榎本 秀一
  日本薬学会年会要旨集, 巻：130年会, 号：4, 開始ページ：127, 終了ページ：127, 2010年03月
  (公社)日本薬学会, 日本語
  ISSN：0918-9823, 医中誌Web ID：2011238918
• 胆汁酸塩ミセルへのコレステロール及び植物ステロール/スタノールの競争的可溶化
  松岡圭介
  Colloid & Interface Communication, 巻：34, 号：2, 開始ページ：14, 終了ページ：15, 2009年05月10日
  日本語
  J-Global ID：201002220477410963
• Mouse Abcg5/Abcg8発現系におけるステロール輸送に関するin vitro機能解析
  前田和哉; 浅野静佳; 杉山雄一; 高田龍平; 松岡圭介
  薬理と治療, 巻：34, 号：Suppl.2, 開始ページ：S.101-S.105, 2006年12月15日
  日本語
  ISSN：0386-3603, J-Global ID：200902225116084981
• 胆汁酸塩のミセル形成とミセルヘの可溶化(コレステロール及びホスファチジルコリン)―その2　　　　　　　　　　　　　　　
  松岡圭介; 師井義清
  表面(表面談話会・コロイド懇話会), 巻：41, 号：10, 開始ページ：357, 終了ページ：369, 2003年10月01日
  広信社, 日本語
  ISSN：0367-648X, J-Global ID：200902264003962139, CiNii Articles ID：40006262202, CiNii Books ID：AN00211091
• 胆汁酸塩のミセル形成とミセルへの可溶化　　　　　　　　　　　　　　　
  松岡圭介; 師井義清
  表面(表面談話会・コロイド懇話会), 巻：41, 号：7, 開始ページ：242, 終了ページ：252, 2003年07月01日
  広信社, 日本語
  ISSN：0367-648X, J-Global ID：200902203529972024, CiNii Articles ID：40006015858, CiNii Books ID：AN00211091

• 日本化学会
• 日本油化学会

• イオン性ポリマーをベシクルキャリアに吸着させた新しい泡沫分離法による金属の除去　　　　　　　　　　　　　　　
  日本学術振興会, 科学研究費助成事業, 基盤研究(C), 2022年04月01日 - 2025年03月31日
  松岡 圭介, 埼玉大学
  配分額（総額）：3380000, 配分額（直接経費）：2600000, 配分額（間接経費）：780000
  課題番号：22K05185
• 放射性金属の除去を目的とした泡沫分離法の確立　　　　　　　　　　　　　　　
  日本学術振興会, 科学研究費助成事業, 基盤研究(C), 2016年04月01日 - 2019年03月31日
  松岡 圭介, 埼玉大学
  配分額（総額）：4290000, 配分額（直接経費）：3300000, 配分額（間接経費）：990000
  泡沫分離は陰イオン性界面活性剤と金属イオンの静電相互作用に基づいて、水溶液からアルカリ金属やアルカリ土類金属の除去を可能とした。その両系列を除去するために最適な界面活性剤濃度は臨界ミセル濃度以下であった。ドデシル硫酸ナトリウム界面活性剤系では、アルカリ金属の除去率はLi < K < Rb < Csの順に増大した。一方、アルカリ土類金属の除去率はMg < Ca < Srの順に増大した。その順番は原子番号順である。除去に関する一次の反応速度定数は結晶イオン半径と比例関係である。泡沫分離法は水溶液中の金属を効果的に除去できることから、原子力発電所の汚水や工場排水の浄化に応用できる。
  課題番号：16K00582
• 医薬品の乳化剤とコレステロールの吸収抑制剤としてのグリチルリチン酸の可能性　　　　　　　　　　　　　　　
  日本学術振興会, 科学研究費助成事業, 基盤研究(C), 2013年04月01日 - 2016年03月31日
  松岡 圭介, 埼玉大学
  配分額（総額）：4290000, 配分額（直接経費）：3300000, 配分額（間接経費）：990000
  グリチルリチン酸の弱酸基は緩衝水溶液のpHに依存して、表面及び会合体の物性に大きな影響を与えた。水への溶解度は強酸性領域では極めて低いことが分かった(0.15mM)。ミセルを形成できる領域はpH5-6の限られた領域だけであった。その会合体は棒状ミセルと判明した。会合体の形成は乳化剤や可溶化剤として応用できる可能性を示唆した。中性以上ではグリチルリチン酸はモノマー分子としてしか存在できない。故に、グリチルリチン酸を生体界面活性剤として、実在系に適用するには水溶液のpHに注意を払う必要がある。その分子構造と会合構造の関係はグチリルリチン酸の類似化合物の会合体形成を明らかにすることで理解できる。
  課題番号：25460043
• 植物ステロールによるコレステロール吸収抑制機構の解明と新しい吸収抑制方法　　　　　　　　　　　　　　　
  日本学術振興会, 科学研究費助成事業, 若手研究(B), 2009年 - 2011年
  松岡 圭介, 昭和薬科大学
  配分額（総額）：4030000, 配分額（直接経費）：3100000, 配分額（間接経費）：930000
  数種の植物ステロール/スタノール種の添加に伴うコレステロール低下機構をモデル腸液中で研究を行った。その植物ステロール/スタノール種の僅かな分子構造の違いはモデル腸液中でのコレステロールの溶解度に影響を及ぼした。その競争的可溶化の結果、コレスタノールが最もコレステロールの溶解度を低下させた。そのコレステロールの最大溶解度はコレステロールだけ溶解させた時に対して、35%まで低下する。コレステロールの溶解度低下効果は次の順であることが分かった。ブラシカステロール<スティグマステロール<フコステロール<カンペステロール<シトスタノール<シトステロール<コレスタノール。
  課題番号：21790043
• セレン欠乏による酸化ストレスと微量元素の動態変化　　　　　　　　　　　　　　　
  日本学術振興会, 科学研究費助成事業, 基盤研究(C), 2005年 - 2007年
  遠藤 和豊; 本田 智香子; 松岡 圭介; 榎本 秀一, 昭和薬科大学
  配分額（総額）：3680000, 配分額（直接経費）：3500000, 配分額（間接経費）：180000
  1)低線量β線照射による肝臓中でのフリーラジカル生成をEPRを用いて評価した。β線照射のラット肝臓からの胆汁の方が、ニトロキシルスピンプローブのシグナルの減衰は、照射しないラットのそれよりも速かった。in vitro実験と組み合わせて組織の酸素濃度が高いときには、ヒドロキシルアミンの過酸化水素由来の酸化が優先することが示された。
  2)胆汁脂質の主要な成分である胆汁酸、リン脂質、コレステロールにはSe欠乏群とコントロール群での違いは認められなかった。活性酸素種を補足するために、コントロール群と比べると胆汁と血漿中のビリルビン濃度が、Se欠乏群で減少した。ビリルビン濃度測定は補助的な酸化ストレスマーカーとしての可能性が示唆することができた。
  3)マルチトレーサー(MT)法を用いてSe, Sr, As, Mn, Co, V, Fe, and Znの胆汁排泄を比較検討した。Mn, AsはSe濃度に依存して胆汁排泄が大きくなった。V, CoはSe濃度により幾分、大きくなるがSeの効果は少なかった。放射性のFe-59, Zn-65は投与後少なくとも2時間以内は検出されなかった。Se欠乏と体内で産生されるグルタチオン(GSH)量、GSHに依存する金属イオンの錯形成、メチル化、またメタロチオネインなどと関連づけて各微量元素の胆汁排泄を説明することができた。
  4)Se欠乏としてはその程度の低いけれど、その期間を長期に継続するとこにより肝臓中のGSH-Px活性、GSH濃度、SOD活性、TBARS量、過酸化水素濃度の週齢に伴う酸化ストレスの変化を評価した。
  5)セレン欠乏ラットの肝臓、腎臓、脾臓中のSe, Fe, Zn量を8週間にわたり放射化分析法により分析した。その結果をラット血漿中のaspatate aminotransferase(AST), alanie aminotransferase(ALT), blood urea nitrogen(BUN)など生化学的データと比較しSe-欠乏に由来する酸化ストレスを評価した。
  課題番号：17590040

• 横型高耐圧トランジスタ　　　　　　　　　　　　　　　
  渡邉 君則; 松岡 圭介; 伊藤 隆夫, 特許権
  J-Global ID：200903061428636966