九州大学 研究者情報
論文一覧
秋山 良(あきやま りょう) データ更新日:2021.06.14

准教授 /  理学研究院 化学部門 複合領域化学講座


原著論文
1. Farhana Afroze, Daisuke Inoue, Tamanna Farhana, Tetsuya Hiraiwa, Ryo Akiyama, Arif MD. Rashedul Kabir, Kazuki Sada, Akira Kakugo, Monopolar flocking of microtubules in collective motion, Biochemical and Biophysical Research Communications,
, https://doi.org/10.1016/j.bbrc.2021.05.037, 563, 73-78, 2021.05, [URL].
2. Keiju Suda, Ayumi Suematsu, and Ryo Akiyama, Lateral depletion effect on two-dimensional ordering of bacteriorhodopsins in a lipid bilayer: A theoretical study based on a binary hard-disk model, Journal of Chemical Physics, https://doi.org/10.1063/5.0044399, 154, 204904-1-204904-11, 2021.05, [URL].
3. Nakamura, Yuka; Yoshimori, Akira; Akiyama, Ryo, Solvation effects on diffusion processes of a macromolecule: Accuracy required for radial distribution function to calculate diffusion coefficient, Journal of Chemical Physics, https://doi.org/10.1063/5.0038894, 154, 8, 084501-1-084501-10, 2021.02, [URL].
4. Suematsu, Ayumi; Akiyama, Ryo, Solvent effect for an effective attraction between like-charged macroions immersed in an electrolyte solution: The intensification mechanism of the effective attraction caused by the translational motion of solvent particles, Journal of Chemical Physics, https://doi.org/10.1063/5.0033874, 154, 3, 034902-1-034902-8, 2021.01, [URL].
5. Y. Tamura1, A. Yoshimori, A. Suematsu and R. Akiyama, Reentrant crystallization of like-charged colloidal particles in an electrolyte solution: Relationship between the shape of the phase diagram and the effective potential of colloidal particles, EPL (Europhys Letter), 10.1209/0295-5075/129/66001, 129, 66001-p1-66001-p7, 2020.04, The reentrant crystallization of like-charged colloidal particles in electrolyte solutions was studied to clarify the relationship between the shape of the phase diagram and the particle-particle effective potential. Coexisting densities were calculated at various electrolyte concentrations using the thermodynamic perturbation expansion method with effective one-component models. The effective potentials were obtained using an integral equation theory for liquids. Some model effective potentials were examined. The calculated results indicated that the reentrant behaviors of various acidic protein solutions observed in the experiments required not only the nonmonotonic dependence of the short-range attraction on the electrolyte concentration, but also the absence of a long repulsive tail..
6. Ayano Chiba, Akio Oshima, Ryo Akiyama, Confined Space Enables Spontaneous Liquid Separation by Molecular Size
Selective Absorption of Alkanes into a Polyolefin Cast Film, Langmuir, 10.1021/acs.langmuir.9b02509, 35, 52, 17177-17184, 2019.12, [URL], The depletion force has been used to explain phase separation phenomena in colloidal systems. Here, we showed that depletion force can explain not only phase separation of large and small colloidal particles but also preferential absorption of larger molecules from a mixture of large and small molecules in a liquid state. When a polyolefin cast film was immersed in a mixture of long and short normal alkanes, the longer molecules were selectively absorbed into the film. This experimental result was explained from the viewpoint of depletion force. The main finding was the use of confined space to emphasize the separation tendency caused by the force. In general, the increase in entropy may serve as a driving force to mix molecules. However, if sufficiently narrow pores are present, large and small molecules are separated naturally by size as the entropy increases. This finding will lead to size exclusion chromatography of low-mass molecules, similar to gel permeation chromatography of macromolecules. In order to demonstrate the effect of depletion force, we selected and experimented with a system based on a polyolefin isotactic poly(4-methyl-1-pentene) (P4MP1) film and a normal alkane mixture and realized high molecular selectivity. The P4MP1 film we used can be prepared simply by evaporating the solvent from the solution and casting the film. On the basis of the Asakura-Oosawa theory, we concluded that spontaneous and high molecular selectivity is attributed to the depletion force provided by the small sub-nanopores with uniform size in the film..
7. Ken Tokunaga, Ryo Akiyama, Molecular dynamics study of a solvation motor in a Lennard-Jones solvent, Physical Review E, 10.1103/PhysRevE.100.062608, 100, 6, 062608-1-062608-8, 2019.12, [URL], The motions of a solvation motor in a Lennard-Jones solvent were calculated by using molecular dynamics simulation. The results were analyzed considering the large spatial scale effects caused by the motion of the solvation motor. A reaction site was located on the surface of the solvation motor and the attraction between the reaction site and the solvent molecules was varied for 100 fs. The motion of the motor was driven by solvation changes near the reaction site on the motor. Two finite-size effects were observed in the motion. One was the hydrodynamic effect and the other was the increase in solvent viscosity caused by heat generation. The latter affected not only the displacement of the motor caused by the reaction but also the wave propagation phenomena. Both effects reduced the motor displacement. Heat generation affects the displacement, in particular for small systems. By contrast, the hydrodynamic effect remained even for large systems. An extrapolation method was proposed for the displacement..
8. Yuka Nakamura, Shota Arai, Masahiro Kinoshita, Akira Yoshimori, Ryo Akiyama, Reduced density profile of small particles near a large particle
Results of an integral equation theory with an accurate bridge function and a Monte Carlo simulation, Journal of Chemical Physics, 10.1063/1.5100040, 151, 4, 044506-1-044506-10, 2019.07, [URL], Solute-solvent reduced density profiles of hard-sphere fluids were calculated by using several integral equation theories for liquids. The traditional closures, Percus-Yevick (PY) and the hypernetted-chain (HNC) closures, as well as the theories with bridge functions, Verlet, Duh-Henderson, and Kinoshita (named MHNC), were used for the calculation. In this paper, a one-solute hard-sphere was immersed in a one-component hard-sphere solvent and various size ratios were examined. The profiles between the solute and solvent particles were compared with those calculated by Monte Carlo simulations. The profiles given by the integral equations with the bridge functions were much more accurate than those calculated by conventional integral equation theories, such as the Ornstein-Zernike (OZ) equation with the PY closure. The accuracy of the MHNC-OZ theory was maintained even when the particle size ratio of solute to solvent was 50. For example, the contact values were 5.7 (Monte Carlo), 5.6 (MHNC), 7.8 (HNC), and 4.5 (PY), and the first minimum values were 0.48 (Monte Carlo), 0.46 (MHNC), 0.54 (HNC), and 0.40 (PY) when the packing fraction of the hard-sphere solvent was 0.38 and the size ratio was 50. The asymptotic decay and the oscillation period for MHNC-OZ were also very accurate, although those given by the HNC-OZ theory were somewhat faster than those obtained by Monte Carlo simulations..
9. Ayumi Suematsu, Takuto Sawayama, and Ryo Akiyama, Effective potential between negatively charged patches on acidic proteins immersed in various electrolyte solutions, The Journal of Chemical Physics, doi: 10.1063/1.5038912, 149, 074105-1-8, 2018.08, Effective interactions between O-sized anions in various electrolyte solutions were calculated by using
the integral equation theory with some simple models. The results indicated that only multivalent
cations mediated a strong effective attraction between O-sized anions at a certain concentration. The
effective interaction turned from repulsive to attractive as the electrolyte concentration increased,
and the effective attraction decreased when more electrolyte was added. Moreover, the effective interactions between O-sized anions in the electrolyte solution did not present a long repulsive tail, although the effective attraction caused by the divalent cations appeared. By contrast, the effective attraction mediated by monovalent cations and the reentrant behavior did not appear and the effective interaction was basically repulsive. These behaviors agree with the experimental results for reentrant condensation of acidic proteins in various electrolyte solutions. The calculated results suggest that the dissociated carboxylic acidic groups on the proteins form attractive patches between proteins under certain concentration conditions..
10. Yuka Nakamura, Akira Yoshimori, Ryo Akiyama, and Tsuyoshi Yamaguchi , Stick boundary condition at large hard sphere arising from effective attraction in binary hard-sphere mixtures , The Journal of Chemical Physics, doi: 10.1063/1.5025202 , 148, 124502-1-12, 2018.03.
11. Ken Tokunaga, and Ryo Akiyama, Basic cell size dependence of displacement for a solvation motor in a Lennard-Jones solvent , J. Comp. Chem. Jpn., 10.2477/jccj.2018-0004 , 17, 80-84, 2018.03.
12. Mafumi Hishida, Yoko Nomura, Ryo Akiyama, Yasuhisa Yamamura, and Kazuya Saito, Electrostatic double-layer interaction between stacked charged bilayers, Phys. Rev. E, https://doi.org/10.1103/PhysRevE.96.040601, 96, 040601(R)-1-5, 2017.08.
13. Ayano Chiba, Masanori Inui, Yukio Kajihara, Kazuhiro Fuchizaki, Ryo Akiyama, Isotactic poly(4-methyl-1-pentene) melt as a porous liquid: Reduction of compressibility due to penetration of pressure medium, J. Chem. Phys. , 10.1063/1.4983508, 146, 194503-1-5, 2017.05.
14. Ayumi Suematsu, Akira Yoshimori, Ryo Akiyama, Effects of interactions between depletants in phase diagrams of binary hard-sphere systems, Europhys Letters(EPL), https://doi.org/10.1209/0295-5075/116/38004, 116, 38004-1-7, 2016.12.
15. Yuichi Kawabata, 秋山 良, Choice of the center of water molecules in calculations of partial molar volume of single ions immersed in water: A molecular simulation study, JOURNAL OF MOLECULAR LIQUIDS, 10.1016/j.molliq.2014.05.022, 200, 67-71, 2014.12.
16. Yuka Nakamura, 吉森 明, 秋山 良, Effects of the solvation structure on diffusion of a large particle in a binary mixture studied by perturbation theory, JOURNAL OF MOLECULAR LIQUIDS, 10.1016/j.molliq.2014.06.021, 200, 85-88, 2014.12.
17. Shingo Fujihara, 秋山 良, Attractive interaction between macroanions mediated by multivalent cations in biological fluids, JOURNAL OF MOLECULAR LIQUIDS, 10.1016/j.molliq.2014.06.022, 200, 89-94, 2014.12.
18. 秋山 良, Takumi Yamashita, Shingo Fujihara, Hidden peak of radial distribution function and effective attraction between like-charged proteins caused by translational motion of solvent molecules, JOURNAL OF MOLECULAR LIQUIDS, 10.1016/j.molliq.2014.06.004, 200, 72-76, 2014.12.
19. Yuka Nakamura, 吉森 明, 秋山 良, Perturbation Theory of Large-Particle Diffusion in a Binary Solvent Mixture, JOURNAL OF THE PHYSICAL SOCIETY OF JAPAN, 10.7566/JPSJ.83.064601, 83, 6, 064601-1-064601-9, 2014.06.
20. 久保田 陽二, Akira Yoshimori, Nobuyuki Matubayasi, Makoto Suzuki, Ryo Akiyama, Molecular dynamics study of fast dielectric relaxation of water around a molecular-sized ion, JOURNAL OF CHEMICAL PHYSICS, 10.1063/1.4769972, 137, 22, 224502-1-224502-4, 2012.12.
21. Yuko Inayoshi, 吉森 明, 秋山 良, Perturbation Theory of Large-Particle Diffusion, JOURNAL OF THE PHYSICAL SOCIETY OF JAPAN, 10.1143/JPSJ.81.114603, 81, 11, 114603-1-114603-10, 2012.11.
22. 久保田 陽二, Ryo Akiyama, Assessment of Three- Dimensional Distribution Functions and Triplet Distribution Functions for Hard Spheres Calculated using a Three- Dimensional Ornstein- Zernike Equation with Hypernetted- Chain Closure, JOURNAL OF THE PHYSICAL SOCIETY OF JAPAN, 10.1143/ JPSJS.81SA.SA017, 81, Supplement A, SA017-1-SA017-7, 2012.09.
23. 久保田 陽二, Ryo Akiyama, Model dependence of the electrostatic response to a molecular- sized ion in water, JOURNAL OF THE PHYSICAL SOCIETY OF JAPAN, 10.1143/ JPSJS.81SA.SA012, 81, Supplement A, SA012-1-SA012-6, 2012.09.
24. Yukio Kawashima, Satoshi Yamamoto, Tetsuya Sakata, Haruyuki Nakano, Katsura Nishiyama, Ryo Akiyama, Solvent Effect on the Fluorescence Spectra of Coumarin 120 in Water: A Combined Quantum Mechanical and Molecular Mechanical Study, JOURNAL OF THE PHYSICAL SOCIETY OF JAPAN, 10.1143/ JPSJS.81SA.SA024, 81, Supplement A, SA024-1-SA024-8, 2012.09.
25. Ken Tokunaga, Ryo Akiyama, A Model Study of the Conversion of Energy froma Chemical Reaction into Motion through a Solvation Motor, JOURNAL OF THE PHYSICAL SOCIETY OF JAPAN, 10.1143/ JPSJS.81SA.SA019, 81, Supplement A, SA019-1-SA019-9, 2012.09.
26. Yuka Nakamura, Akira Yoshimori, Ryo Akiyama, A Perturbation Theory for Friction of a Large Particle Immersed in a Binary Solvent, JOURNAL OF THE PHYSICAL SOCIETY OF JAPAN, 10.1143/ JPSJS.81SA.SA026, 81, Supplement A, SA026-1-SA026-7, 2012.09.
27. Ryo Akiyama, and Ryo Sakata , An Integral Equation Study of Reentrant Behavior in Attractive Interactions between Like-Charged Macroions Immersed in an Electrolyte Solution, J. Phys. Soc. Jpn., 10.1143/JPSJ.80.123602, 80, 123602, 2011.12.
28. Yasuhito Karino, Ryo Akiyama, and Masahiro Kinoshita , A Simple Theory for Entropic Interaction Induced between Large Spheres in a Binary Mixture of Small and Medium Spheres, J. Phys. Soc. Jpn., 10.1143/JPSJ.80.114802, 80, 114802, 2011.11.
29. Yoji Kubota and Ryo Akiyama, Fine Structure of the Dielectric Response to a Molecular-Sized Ion in Water, J. Phys. Chem. Lett., 10.1021/jz200571f, 2, 13, 1588–1591, 2011.06, [URL].
30. Ryo Akiyama, Yasuhito Karino, Hokuto Obama, Ayako Yoshifuku, Adsorption of xenon on a protein arising from the translational motion of solvent molecules, Phys. Chem. Chem. Phys. , 10.1039/b921314g, 12, 3096-3101, 12, 3096-3101 (Communication), 2010.03, [URL].
31. Yasuhito Karino, Ryo Akiyama, Effect of Solvent Granularity on the Activity Coefficient of Macromolecules, Chem. Phys. Lett., 478, 180-184 , 2009.08, [URL].
32. Yasuhito Karino, Ryo Akiyama, and Masahiro Kinoshita , Three-Dimensional Density Profiles of Small and Medium Spheres near a Pair of Large Spheres: Relevance to Entropic Interaction Induced between Large Spheres, J. Phys. Soc. Jpn., 78, 044801-1-6 , 2009.04.
33. Ryo Akiyama, Naohiko Fujino, Kouhei Kaneda, and Masahiro Kinoshita, Interaction between like-charged colloidal particles in aqueous electrolyte solution:
Attractive component arising from solvent granularity, Cond. Matt. Phys., 10, 587-596 , 2007.12, [URL].
34. Masahiro Kinoshita, Yuichi Harano, and Ryo Akiyama, Changes in thermodynamic quantities upon contact of two solutes in solvent under isochoric and isobaric conditions, J. Chem. Phys., 125, 244504-1-7 , 2006.12.
35. Ryo Akiyama, Yasuhito Karino, Yasuhiro Hagiwara, Masahiro Kinoshita, Remarkable Solvent Effects on Depletion Interaction in Crowding Media:
Analyses by the Integral Equation Theories, J. Phys. Soc. Jpn., 75, 064804-1-7 , 2006.05.
36. 早川洋一、秋山良、宗原弘幸, ヨコスジカジカHemilepidotus gilberti の異型精子による卵塊への正型精子輸送機能に関するモデル的検証, 魚類学雑誌, 51巻1号 33-42, 2004.05.
37. Merchant, K.A.; Noid, W.G.; Akiyama, R; Finkelstein, I.; Goun, A.; McClain, B.L.; Loring, R.F.; Fayer,M.D., Myoglobin-CO Substate Structures and Dynamics: Spectrally Resolved Stimulated Vibrational Echoes and Molecular Dynamics Simulations, J. Am. Chem. Soc., (2003) Vol.125, p.13804., 2003.11.
38. Ryo Akiyama and Roger F. Loring, Quantum Solvent and Solute Effects in the Infrared Vibrational echo, J. Phys. Chem. A, (2003) Vol.107, p.8024, 2003.10.
39. Kusai A. Merchant, W. G. Noid, David E. Thompson, Ryo Akiyama, Roger F. Loring, and M. D. Fayer, Structural Assignments and Dynamics of the A Substates of MbCO: Spectrally
Resolved Vibrational Echo Experiments and Molecular Dynamics Simulations, J. Phys. Chem. B, Vol.107, p.4 (2003)., 2003.01.
40. Ryo Akiyama and Roger F. Loring, Vibrational Echoes for Classical and Quantum Solutes,, J. Chem. Phys., Vol. 116, p.4655(2002)., 2002.01.
41. Youichi Hayakawa, Ryo Akiyama, Hiroyuki Munehara and Akira Komaru, Dimorphic sperm influence semen distribution in a non-copulatory
sculpin Hemilepidotus gilberti,, Environmental Biology of Fishes., Vol.65, p.311(2002)., 2002.01.
42. Ryo Akiyama, Masahiro Kinoshita, and Fumio Hirata:, Free energy profiles of electron transfer at water-electrode interface
studied by the reference interaction site model theory, Chem. Phys. Lett., Vol.305, p.251(1999)., 1999.01.
43. Ryo Akiyama and Fumio Hirata, Theoretical Study for Water Structure at Highly Ordered Surface: Effect of
Surface Structure, J. Chem. Phys., Vol.108, p.4904 (1998)., 1998.01.
44. T. Kakitani, R. Akiyama, Y. Hatano, Y. Imamoto, Y. Shichida, P. Verdegem and J. Lugtenburg, Deuterium Substitution Effect on the Excited State Dynamics of Rhodopsin, J. Phys. Chem. B, Vol.102, p.1334 (1998) ., 1998.01.
45. Ryo Akiyama, Akira Yoshimori, Toshiaki Kakitani, Yasushi Imamoto, Yoshinori Shichida and Yasuyo Hatano, Analysis of Excited State Dynamics of 13-trans-Locked-Bacteriorhodopsin, J. Phys. Chem. A, Vol. 101, p.412 (1997)., 1997.01.
46. R. Akiyama, A. Yoshimori, T. Kakitani, Y. Imamoto, Y. Shichida and Y. Hatano:, Analysis of the temperature dependence of femtosecond excited state
dynamics of bacteriorhodopsin by spin-boson model,, Chem. Phys. Lett., Vol. 256, 165(1996)., 1996.01.
47. Ryo Akiyama, Toshiaki Kakitani, Yasushi Imamoto, Yoshinori Shichida and Yasuyo Hatano, Bacteriorhodopsin Analyzed by the Fourier Transform of Optical Absorption Spectra,, J. Phys. Chem., Vol. 99, 7147(1995)., 1995.01.
48. Ryo Akiyama, Masatoshi Kitaichi, Tomoharu Fujiwara and Sadashi Sawamura:, Short Lived Species Produced in Pulse Irradiaded Melts of LiF-KF and
LiF-NaF-KF Eutectic Mixtures, J. Nuc. Sci. Tech., Vol.31, p.250(1994), 1994.01.

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