Language：English   Publishing type：Research paper (scientific journal)   Publisher：AIP Publishing  

To gain quantitative insight into how the overall strength of the hydrophobic interaction varies with the molecular size, we calculate osmotic second virial coefficients B for hydrophobic spherical molecules of different diameters σ in water based on molecular simulation with corrections to the finite-size and finite-concentration effects. It is shown that B (<0) changes by two orders of magnitude greater as σ increases twofold and its solute-size dependence is best fit by a power law B ∝ σ ^α with the exponent α ≃ 6, which contrasts with the cubic power law that the second virial coefficients of gases obey. It is also found that values of B for the solutes in a nonpolar solvent are positive but they obey the same power law as in water. A thermodynamic identity for B derived earlier [K. Koga, V. Holten, and B. Widom, J. Phys. Chem. B 119, 13391 (2015)] indicates that if B is asymptotically proportional to a power of σ, the exponent α must be equal to or greater than 6.

DOI： 10.1063/5.0097547

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：American Chemical Society (ACS)  

DOI： 10.1021/acs.biochem.2c00166

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Authorship：Lead author,　Corresponding author   Language：English   Publishing type：Research paper (scientific journal)   Publisher：Springer Science and Business Media LLC  

<title>Abstract</title>The origin of life is believed to be chemoautotrophic, deriving all biomass components from carbon dioxide, and all energy from inorganic redox couples in the environment. The reductive tricarboxylic acid cycle (rTCA) and the Wood–Ljungdahl pathway (WL) have been recognized as the most ancient carbon fixation pathways. The rTCA of the chemolithotrophic <italic>Thermosulfidibacter takaii</italic>, which was recently demonstrated to take place via an unexpected reverse reaction of citrate synthase, was reproduced using a kinetic network model, and a competition between reductive and oxidative fluxes on rTCA due to an acetyl coenzyme A (ACOA) influx upon acetate uptake was revealed. Avoiding ACOA direct influx into rTCA from WL is, therefore, raised as a kinetically necessary condition to maintain a complete rTCA. This hypothesis was confirmed for deep-branching bacteria and archaea, and explains the kinetic factors governing elementary processes in carbon metabolism evolution from the last universal common ancestor.

DOI： 10.1038/s42004-021-00585-0

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Other Link： https://www.nature.com/articles/s42004-021-00585-0

Authorship：Lead author,　Corresponding author   Language：English   Publishing type：Research paper (scientific journal)   Publisher：Wiley  

DOI： 10.1002/pro.4168

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Other Link： https://onlinelibrary.wiley.com/doi/full-xml/10.1002/pro.4168

Language：English   Publishing type：Research paper (scientific journal)   Publisher：Elsevier BV  

Myoglobin (Mb) is highly concentrated in the myocytes of diving mammals such as whales and seals, in comparison with land animals, and its molecular evolution has played a crucial role in their deep-sea adaptation. We previously resurrected ancestral whale Mbs and demonstrated the evolutional strategies for higher solubility under macromolecular crowding conditions. Pinnipeds, such as seals and sea lions, are also expert diving mammals with Mb-rich muscles. In the present study, we resurrected ancestral pinniped Mbs and investigated their biochemical and structural properties. Comparisons between pinniped and whale Mbs revealed the common and distinctive strategies for the deep-sea adaptation. The overall evolution processes, gaining precipitant tolerance and improving thermodynamic stability, were commonly observed. However, the strategies for improving the folding stability differed, and the pinniped Mbs exploited the shielding of hydrophobic surfaces more effectively than the whale Mbs.

DOI： 10.1016/j.isci.2021.102920

PubMed

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：American Chemical Society (ACS)  

DOI： 10.1021/acs.jpcb.1c03388

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Publishing type：Research paper (scientific journal)   Publisher：Springer Science and Business Media LLC  

DOI： 10.1007/s10015-020-00664-w

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Other Link： https://link.springer.com/article/10.1007/s10015-020-00664-w/fulltext.html

Authorship：Last author,　Corresponding author   Publishing type：Research paper (scientific journal)   Publisher：American Chemical Society (ACS)  

DOI： 10.1021/acs.nanolett.0c03978

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Authorship：Corresponding author   Publishing type：Research paper (scientific journal)   Publisher：Royal Society of Chemistry (RSC)  

<p>Solvent fluctuation (<italic>G</italic>_TFE-TFE) of 2,2,2-trifluoroethanol (TFE)–H₂O mixture was determined by small-angle X-ray scattering investigation. Protein’s coil–helix transition can be induced by preferential binding of TFE (Δ<italic>Γ</italic>₂₃) without aggregation of TFE.</p>

DOI： 10.1039/d0cp05103a

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Authorship：Lead author,　Corresponding author   Publishing type：Research paper (scientific journal)   Publisher：Springer Science and Business Media LLC  

<title>Abstract</title>N-methyl-D-aspartate (NMDA) receptor-dependent long-term potentiation (LTP) and long-term depression (LTD) of signal transmission form neural circuits and thus are thought to underlie learning and memory. These mechanisms are mediated by AMPA receptor (AMPAR) trafficking in postsynaptic neurons. However, the regulatory mechanism of bidirectional plasticity at excitatory synapses remains unclear. We present a network model of AMPAR trafficking for adult hippocampal pyramidal neurons, which reproduces both LTP and LTD. We show that the induction of both LTP and LTD is regulated by the competition between exocytosis and endocytosis of AMPARs, which are mediated by the calcium-sensors synaptotagmin 1/7 (Syt1/7) and protein interacting with C-kinase 1 (PICK1), respectively. Our result indicates that recycling endosomes containing AMPAR are always ready for Syt1/7-dependent exocytosis of AMPAR at peri-synaptic/synaptic membranes. This is because molecular motor myosin V_b constitutively transports the recycling endosome toward the membrane in a Ca²⁺-independent manner.

DOI： 10.1038/s41598-020-71528-3

PubMed

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Other Link： https://www.nature.com/articles/s41598-020-71528-3

Publishing type：Research paper (scientific journal)   Publisher：The Chemical Society of Japan  

Small-angle X-ray and neutron scatterings can measure the structure factor of dispersed particles (macromolecules or colloidal particles), which can estimate the pair distribution function and the pair potential between the particles. However, the assumption of a model pair potential is usually necessary in the estimations. Especially when the system condition is complicated, one cannot prepare a plausible model pair potential. Hence, we propose a model-potential-free method. The new method does not require the assumptions of rigid particle surface and random phase approximation unlike the conventional model-potential-free method.

DOI： 10.1246/cl.200292

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Authorship：Lead author,　Corresponding author   Publishing type：Research paper (scientific journal)   Publisher：American Chemical Society (ACS)  

DOI： 10.1021/acs.nanolett.9b01181

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© 2019 the Owner Societies. A novel Raman scattering enhancement was discovered using colloid nanoparticles conjugated with an amine-based copolymer. The interaction potential surface between Raman scattering enhancing nanoparticles was clarified by combining a small-angle scattering method and a model-potential-free liquid-state theory as an in situ observation in the solution state. The potential surface indicates that the most stable position is located around 0.9 nm from the particle surface, suggesting the existence of a nanogap structure between the nanocomposites. The change in Raman scattering enhancement was also acquired during the dispersion process of the aggregated nanocomposites through a glutathione-triggered nanosensing reaction.

DOI： 10.1039/C9CP01946D

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Authorship：Lead author,　Corresponding author   Language：English   Publishing type：Research paper (scientific journal)   Publisher：NATURE PUBLISHING GROUP  

Understanding the dominant factor in thermodynamic stability of proteins remains an open challenge. Kauzmann's hydrophobic interaction hypothesis, which considers hydrophobic interactions between nonpolar groups as the dominant factor, has been widely accepted for about sixty years and attracted many scientists. The hypothesis, however, has not been verified or disproved because it is difficult, both theoretically and experimentally, to quantify the solvent effects on the free energy change in protein folding. Here, we developed a computational method for extracting the dominant factor behind thermodynamic stability of proteins and applied it to a small, designed protein, chignolin. The resulting free energy profile quantitatively agreed with the molecular dynamics simulations. Decomposition of the free energy profile indicated that intramolecular interactions predominantly stabilized collapsed conformations, whereas solvent-induced interactions, including hydrophobic ones, destabilized them. These results obtained for chignolin were consistent with the site-directed mutagenesis and calorimetry experiments for globular proteins with hydrophobic interior cores.

DOI： 10.1038/s41598-019-41518-1

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Authorship：Lead author,　Corresponding author   Language：English   Publishing type：Research paper (scientific journal)   Publisher：WILEY  

Recently, we proposed a reference-modified density functional theory (RMDFT) to calculate solvation free energy (SFE), in which a hard-sphere fluid was introduced as the reference system instead of an ideal molecular gas. Through the RMDFT, using an optimal diameter for the hard-sphere reference system, the values of the SFE calculated at room temperature and normal pressure were in good agreement with those for more than 500 small organic molecules in water as determined by experiments. In this study, we present an application of the RMDFT for calculating the temperature and pressure dependences of the SFE for solute molecules in water. We demonstrate that the RMDFT has high predictive ability for the temperature and pressure dependences of the SFE for small solute molecules in water when the optimal reference hard-sphere diameter determined for each thermodynamic condition is used. We also apply the RMDFT to investigate the temperature and pressure dependences of the thermodynamic stability of an artificial small protein, chignolin, and discuss the mechanism of high-temperature and high-pressure unfolding of the protein. (c) 2017 Wiley Periodicals, Inc.

DOI： 10.1002/jcc.25101

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Language：English   Publishing type：Research paper (scientific journal)  

Extant cetaceans, such as sperm whale, acquired the great ability to dive into the ocean depths during the evolution from their terrestrial ancestor that lived about 50 million years ago. Myoglobin (Mb) is highly concentrated in the myocytes of diving animals, in comparison with those of land animals, and is thought to play a crucial role in their adaptation as the molecular aqualung. Here, we resurrected ancestral whale Mbs, which are from the common ancestor between toothed and baleen whales (Basilosaurus), and from a further common quadrupedal ancestor between whale and hippopotamus (Pakicetus). The experimental and theoretical analyses demonstrated that whale Mb adopted two distinguished strategies to increase the protein concentration in vivo along the evolutionary history of deep sea adaptation; gaining precipitant tolerance in the early phase of the evolution, and increase of folding stability in the late phase.

DOI： 10.1038/s41598-018-34984-6

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Authorship：Lead author,　Corresponding author   Language：English   Publishing type：Research paper (scientific journal)   Publisher：AMER PHYSICAL SOC  

A two-step subdiffusion behavior of lateral movement of transmembrane proteins in plasma membranes has been observed by using single-molecule experiments. A nested double-compartment model where large compartments are divided into several smaller ones has been proposed in order to explain this observation. These compartments are considered to be delimited by membrane-skeleton "fences" and membrane-protein "pickets" bound to the fences. We perform numerical simulations of a master equation using a simple two-dimensional lattice model to investigate the heterogeneous diffusion dynamics behavior of transmembrane proteins within plasma membranes. We show that the experimentally observed two-step subdiffusion process can be described using fence and picket models combined with decreased local diffusivity of transmembrane proteins in the vicinity of the pickets. This allows us to explain the two-step subdiffusion behavior without explicitly introducing nested double compartments.

DOI： 10.1103/PhysRevE.96.042410

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Authorship：Lead author,　Last author,　Corresponding author   Language：English   Publishing type：Research paper (scientific journal)   Publisher：NATURE PUBLISHING GROUP  

A chemomechanical-network model for myosin V is presented on the basis of both the nucleotide-dependent binding affinity of the head to an actin filament (AF) and asymmetries and similarity relations among the chemical transitions due to an intramolecular strain of the leading and trailing heads. The model allows for branched chemomechanical cycles and takes into account not only two different force-generating mechanical transitions between states wherein the leading head is strongly bound and the trailing head is weakly bound to the AF but also load-induced mechanical-slip transitions between states in which both heads are strongly bound. The latter is supported by the fact that ATP-independent high-speed backward stepping has been observed for myosin V, although such motility has never been for kinesin. The network model appears as follows: (1) the high chemomechanical-coupling ratio between forward step and ATP hydrolysis is achieved even at low ATP concentrations by the dual mechanical transitions; (2) the forward stepping at high ATP concentrations is explained by the front head-gating mechanism wherein the power stroke is triggered by the inorganic-phosphate (Pi) release from the leading head; (3) the ATP-binding or hydrolyzed ADP.Pi-binding leading head produces a stable binding to the AF, especially against backward loading.

DOI： 10.1038/s41598-017-13661-0

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：ROYAL SOC CHEMISTRY  

We demonstrate by molecular dynamics simulation that co-nonsolvency manifests itself in the solvent-induced interaction between three hydrophobes, methane, propane and neopentane, inmethanol-water mixtures. Decomposition of the potential of mean force, based on the potential distribution theorem, clearly shows that the solute-solvent entropic change is responsible for stabilizing the aggregation of these hydrophobic molecules. Furthermore, we show that the entropic change pertains to the excluded volume effect.

DOI： 10.1039/c7cp04152g

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Authorship：Lead author,　Last author,　Corresponding author   Language：English   Publishing type：Research paper (scientific journal)   Publisher：NATURE PUBLISHING GROUP  

A systematic chemomechanical network model for the molecular motor kinesin is presented in this report. The network model is based on the nucleotide-dependent binding affinity of the heads to an microtubule (MT) and the asymmetries and similarities between the chemical transitions caused by the intramolecular strain between the front and rear heads. The network model allows for multiple chemomechanical cycles and takes into account all possible mechanical transitions between states in which one head is strongly bound and the other head is weakly bound to an MT. The results obtained from the model show the ATP-concentration dependence of the dominant forward stepping cycle and support a gated rear head mechanism in which the forward step is controlled by ATP hydrolysis and the resulting ADP-bound state of the rear head when the ATP level is saturated. When the ATP level is saturated, the energy from ATP hydrolysis is used to concentrate the chemical transition flux to a force-generating state that can produce the power stroke. In contrast, when the ATP level is low, the hydrolysis energy is consumed to avoid states in which the leading head is weakly bound to an MT and to inhibit frequent backward steps upon loading.

DOI： 10.1038/s41598-017-01328-9

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：AMER CHEMICAL SOC  

A simple model of a hydrophobic polymer in water is studied. The model polymer, a chain of Lennard-Jones particles with a fixed bond length, is designed in such a way that it undergoes a coil-to-globule conformational change near room temperature upon heating in liquid water. At low temperatures (less than or similar to 270 K), the polymer chain under vacuum takes a globular conformation, whereas in water, it adopts an extended form. At higher temperatures (greater than or similar to 320 K), the polymer has a more compact conformation in water than under vacuum. The same polymer chain in a nonpolar solvent is always extended and shows no sign of a coil-to-globule transformation up to 360 K. The heat-induced collapse of the polymer uniquely observed in water is not attributed to the hydrophobic effect on individual monomers, but it is correlated with the temperature dependence of the potential of mean force between two monomers at contact distance.

DOI： 10.1021/acs.jpcb.6b08347

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Authorship：Last author   Language：English   Publishing type：Research paper (scientific journal)   Publisher：AMER CHEMICAL SOC  

Biological sensing technology utilizing nanoparticles extends through a diverse range of fields. The nanosensing is controlled using the assembly/disassembly of nanoparticles dominated by interaction forces between them. Although the interaction potential surface gives decisive information on the sensing mechanism, evaluating the quantitative profile has been impossible due to extremely complicated interactions of conjugated soft matter. In this study, a model-potential-free determination of the interaction potential surfaces was devised by combining small-angle scattering and liquid-state theory. The model-potential-free liquid theory was developed for colloidal nanoparticles inherently with strong van der Waals attraction forces by their nanoscopic size. The present method extracts interaction potential between nanoparticles even in systems with complicated interactions due to conjugated soft matter. By applying this determination method to a glutathione-triggered biosensing reaction, interaction potential curves between biosensing nanoparticles were realized for the first time. The analysis revealed peculiar potential surfaces of the sensing nanoparticles. The mechanism of colorimetric nanosensing function based on surface plasmon resonance is discussed from the viewpoint of the assembly/disassembly of nanoparticles in nanocomposites dominated by the interaction potential surfaces.

DOI： 10.1021/acs.jpcc.6b06487

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Authorship：Lead author,　Corresponding author   Language：English   Publishing type：Research paper (scientific journal)   Publisher：AMER INST PHYSICS  

In the conventional classical density functional theory (DFT) for simple fluids, an ideal gas is usually chosen as the reference system because there is a one-to-one correspondence between the external field and the density distribution function, and the exact intrinsic free-energy functional is available for the ideal gas. In this case, the second-order density functional Taylor series expansion of the excess intrinsic free-energy functional provides the hypernetted-chain (HNC) approximation. Recently, it has been shown that the HNC approximation significantly overestimates the solvation free energy (SFE) for an infinitely dilute Lennard-Jones (LJ) solution, especially when the solute particles are several times larger than the solvent particles [T. Miyata and J. Thapa, Chem. Phys. Lett. 604, 122 (2014)]. In the present study, we propose a reference-modified density functional theory as a systematic approach to improve the SFE functional as well as the pair distribution functions. The second-order density functional Taylor series expansion for the excess part of the intrinsic free-energy functional in which a hard-sphere fluid is introduced as the reference system instead of an ideal gas is applied to the LJ pure and infinitely dilute solution systems and is proved to remarkably improve the drawbacks of the HNC approximation. Furthermore, the third-order density functional expansion approximation in which a factorization approximation is applied to the triplet direct correlation function is examined for the LJ systems. We also show that the third-order contribution can yield further refinements for both the pair distribution function and the excess chemical potential for the pure LJ liquids. Published by AIP Publishing.

DOI： 10.1063/1.4953191

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：NATURE PUBLISHING GROUP  

We investigate driving forces of the liquid-liquid phase separation of N-isopropylpropionamide (NiPPA) aqueous solutions above the lower critical solution temperature using molecular dynamics simulations. Spontaneous phase separations of the model aqueous solution with a modified OPLS-AA force field are observed above the experimentally determined cloud point. The destabilization toward the phase separation is confirmed by temperature dependence of the long-wavelength limit of the concentration-concentration structure factor, the dominant component of which is found to be an increasing effective attraction between NiPPA molecules. At varying temperatures, the potentials of mean force (PMFs) between a pair of NiPPA molecules at infinite dilution are obtained and decomposed into the nonpolar and Coulombic contributions. The nonpolar contribution, arising essentially from molecular volume, promotes association of NiPPA molecules with increasing temperature while the Coulombic one antagonizes the association. Thus, our analysis leads to a conclusion that the driving force of thermally induced aggregation of NiPPA molecules is the temperature dependence of the nonpolar contribution in PMF between NiPPA molecules, not the temperature dependence of the number or strength of hydrogen bonds between NiPPA and water molecules.

DOI： 10.1038/srep24657

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：AMER CHEMICAL SOC  

A mean-field approximation to the solvation of nonpolar solutes in the liquid vapor interface of aqueous solutions is proposed. It is first remarked with a numerical illustration that the solvation of a methane like solute in bulk liquid water is accurately described by the mean-field theory of liquids, the main idea of which is that the probability (P-cav) of finding a cavity in the solvent that can accommodate the solute molecule and the attractive interaction energy (watt) that the solute would feel if it is inserted in such a cavity are both functions of the solvent density alone. It is then assumed that the basic idea is still valid in the liquid vapor interface, but Pcav and watt are separately functions of different coarse-grained local densities, not functions of a common local density. Validity of the assumptions is confirmed for the solvation of the methane-like particle in the interface of model water at temperatures between 253 and 613 K. With the mean-field approximation extended to the inhomogeneous system the local solubility profiles across the interface at various temperatures are calculated from P-cav and u(att) obtained at a single temperature. The predicted profiles are in excellent agreement with those obtained by the direct calculation of the excess chemical potential over an interfacial region where the solvent local density varies most rapidly.

DOI： 10.1021/acs.jpcb.5b10169

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：ROYAL SOC CHEMISTRY  

Driving forces for the pressure-induced aggregation of poly(N-isopropylacrylamide) (PNiPA) in water are investigated by performing extensive molecular dynamics simulations. First, we observe that the model short oligomer of PNiPA with a modified OPLS-AA force field in water shrinks with increasing pressure. At varying pressures, the potentials of mean force (PMFs) between a pair of N-isopropylpropionamide (NiPPA) molecules, the repeating unit of PNiPA, are obtained and decomposed into the nonpolar and Coulombic contributions. The nonpolar contribution is the PMF between the hypothetical nonpolar NiPPA molecules in the solvent, which is mainly due to the molecular volume effect. The attractive force between NiPPA molecules is enhanced at higher pressures in agreement with the behavior of PNiPA. This pressure dependence of the PMF is caused by the growing nonpolar contribution at higher pressures. In contrast, the Coulombic contribution to the PMF becomes higher overall, making the mean force less attractive or more repulsive, with increasing pressure. The strength of the aggregation and its pressure dependence of the nonpolar contribution in water are closely reproduced even in nonpolar solvents. The degree of the pressure dependence is explained by the isothermal compressibility or the tightness of the solvation shell around an isolated solute, without regard to the existence and variation of hydrogen bond networks in a solvent. The role of hydrogen bonds in the aggregation of NiPPA and PNiPA molecules is also discussed.

DOI： 10.1039/c5cp07674a

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：Society of Computer Chemistry, Japan  

<p>As a refinement of the fluid mosaic model for explaining cell membrane functions, membrane-skeleton fence model and anchored membrane protein picket model have been proposed according to the tracing experiment of a single molecule in plasma membrane. In addition, the experimental observation that the diffusive motion of a transmembrane protein in plasma membrane leads to a normal diffusion through two-step relaxation has suggested that there are two types of nested compartments, large and small. In this paper, we propose a virtual nested two-dimensional lattice model that can express a nested compartment structure of plasma membrane using three parameters in order to represent such a single molecule diffusion movement. Using this 2D lattice model, various diffusive motion simulations of one particle random walks were performed and their trajectories were analyzed by Detrended fluctuation analysis. As a result, we have confirmed that both plasma membrane models, "fence" and "picket," can be represented by our virtual nested 2D lattice model.</p>

DOI： 10.2477/jccj.2016-0069

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Authorship：Lead author,　Corresponding author   Language：English   Publisher：WILEY-BLACKWELL  

DOI： 10.1002/jcc.24035

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Authorship：Lead author,　Corresponding author   Language：English   Publishing type：Research paper (scientific journal)   Publisher：WILEY-BLACKWELL  

The three-dimensional reference interaction site model (3D-RISM) theory, which is one of the most applicable integral equation theories for molecular liquids, overestimates the absolute values of solvation-free-energy (SFE) for large solute molecules in water. To improve the free-energy density functional for the SFE of solute molecules, we propose a reference-modified density functional theory (RMDFT) that is a general theoretical approach to construct the free-energy density functional systematically. In the RMDFT formulation, hard-sphere (HS) fluids are introduced as the reference system instead of an ideal polyatomic molecular gas, which has been regarded as the appropriate reference system of the interaction-site-model density functional theory for polyatomic molecular fluids. We show that using RMDFT with a reference HS system can significantly improve the absolute values of the SFE for a set of neutral amino acid side-chain analogues as well as for 504 small organic molecules. (c) 2015 Wiley Periodicals, Inc.

DOI： 10.1002/jcc.23942

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Authorship：Lead author   Language：English   Publishing type：Research paper (scientific journal)   Publisher：ELSEVIER SCIENCE BV  

A small-angle X-ray scattering has been used to probe protein-protein interaction in solution. Conventional methods need to input modeled potentials with variable/invariable parameters to reproduce the experimental structure factor. In the present study, a model-free method for extracting the excess part of effective interaction potential between protein molecules in solutions over an introduced hard-sphere potential by using experimental data of small-angle X-ray scattering is presented on the basis of liquid-state integral equation theory. The reliability of the model-free method is tested by the application to experimentally derived structure factors for dense lysozyme solutions with different solution conditions [Javid et al., Phys. Rev. Lett. 99, 028101 (2007), Schroer et al., Phys. Rev. Lett. 106, 178102 (2011)]. The structure factors calculated from the model-free method agree well with the experimental ones. The model-free method provides the following picture of the lysozyme solution: these are the stabilization of contact-pair configurations, large activation barrier against their formations, and screened Coulomb repulsion between the charged proteins. In addition, the model-free method will be useful to verify whether or not a model for colloidal system is acceptable to describing protein-protein interaction. (C) 2014 Elsevier B.V. All rights reserved.

DOI： 10.1016/j.molliq.2014.03.014

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：AMER INST PHYSICS  

One important aspect of the hydrophobic effect is that solubility of small, nonpolar molecules in liquid water decreases with increasing temperature. We investigate here how the characteristic temperature dependence in liquid water persists or changes in the vicinity of the liquid-vapor interface. From the molecular dynamics simulation and the test-particle insertion method, the local solubility Sigma of methane in the liquid-vapor interface of water as well as Sigma of nonpolar solutes in the interface of simple liquids are calculated as a function of the distance z from the interface. We then examine the temperature dependence of Sigma under two conditions: variation of Sigma at fixed position z and that at fixed local solvent density around the solute molecule. It is found that the temperature dependence of Sigma at fixed z depends on the position z and the system, whereas Sigma at fixed local density decreases with increasing temperature for all the model solutions at any fixed density between vapor and liquid phases. The monotonic decrease of Sigma under the fixed-density condition in the liquid-vapor interface is in accord with what we know for the solubility of nonpolar molecules in bulk liquid water under the fixed-volume condition but it is much robust since the solvent density to be fixed can be anything between the coexisting vapor and liquid phases. A unique feature found in the water interface is that there is a minimum in the local solubility profile Sigma(z) on the liquid side of the interface. We find that with decreasing temperature the minimum of Sigma grows and at the same time the first peak in the oscillatory density profile of water develops. It is likely that the minimum of Sigma is due to the layering structure of the free interface of water. (C) 2014 AIP Publishing LLC.

DOI： 10.1063/1.4896236

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Authorship：Lead author,　Corresponding author   Language：English   Publishing type：Research paper (scientific journal)   Publisher：ROYAL SOC CHEMISTRY  

To extract protein-protein interaction from experimental small-angle scattering of proteins in solutions using liquid state theory, a model potential consisting of a hard-sphere repulsive potential and the excess interaction potential has been introduced. In the present study, we propose a model-potential-free integral equation method that extracts the excess interaction potential by using the experimental small-angle scattering data without specific model potential such as the Derjaguin-Landau-Verwey-Overbeek (DLVO)-type model. Our analysis of experimental small-angle X-ray scattering data for lysozyme solution shows both the stabilization of contact configurations of protein molecules and a large activation barrier against the formation of the contact configurations in addition to the screened Coulomb repulsion. These characteristic features, which are not well-described by the DLVO-type model, are interpreted as solvent effects.

DOI： 10.1039/c4cp03606a

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Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：AMER INST PHYSICS  

Detrended fluctuation analysis (DFA) was originally developed for the evaluation of DNA sequence and interval for heart rate variability (HRV), but it is now used to obtain various biological information. In this study we perform DFA on artificially generated data where we already know the relationship between signal and the physical event causing the signal. We generate artificial data using molecular dynamics. The Brownian motion of a polymer under an external force is investigated. In order to generate artificial fluctuation in the physical properties, we introduce obstacle pillars fixed to nanostructures. Using different conditions such as presence or absence of obstacles, external field, and the polymer length, we perform DFA on energies and positions of the polymer.

DOI： 10.1063/1.4866638

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：WILEY-BLACKWELL  

Toward understanding intermolecular interactions governing self-association of proteins, the present study investigated a model protein, myoglobin, using a small-angle X-ray scattering technique. It has been known that removal of the heme makes myoglobin aggregation-prone. The interparticle interferences of the holomyoglobin and the apomyoglobin were compared in terms of the structure factor. Analysis of the structure factor using a model potential of Derjaguin-Laudau-Verwey-Overbeek (DLVO) suggests that the intermolecular interaction potential of apomyoglobin is more attractive than that of holomyoglobin at short range from the protein molecule.

DOI： 10.1107/S0909049513022772

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Authorship：Lead author,　Corresponding author   Language：English   Publishing type：Research paper (scientific journal)  

A multiscale simulation of a hydrophobic polymer chain immersed in water including the supercooled region is presented. Solvent effects on the polymer conformation were taken into account via liquid-state density functional theory in which a free-energy functional model was constructed using a density response function of bulk water, determined from a molecular dynamics (MD) simulation. This approach overcomes sampling problems in simulations of high-viscosity polymer solutions in the deeply supercooled region. Isobars determined from the MD simulations of 4000 water molecules suggest a liquid-liquid transition in the deeply supercooled region. The multiscale simulation reveals that a hydrophobic polymer chain exhibits swelling upon cooling along isobars below a hypothesized second critical pressure
no remarkable swelling is observed at higher pressures. These observations agree with the behavior of a polymer chain in a Jagla solvent model that qualitatively reproduces the thermodynamics and dynamics of liquid water. A theoretical analysis of the results obtained from the multiscale simulation show that a decrease in entropy due to the swelling arises from the formation of a tetrahedral hydrogen bond network in the hydration shell. © The Royal Society of Chemistry 2013.

DOI： 10.1039/c3ra41320a

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Authorship：Last author,　Corresponding author   Language：English   Publishing type：Research paper (scientific journal)   Publisher：ELSEVIER SCI LTD  

By using in-situ neutron reflectivity, we have investigated swelling isotherms of solvophilic and solvophobic end-grafted/non-grafted polymer chains on solid substrates in supercritical carbon dioxide and supercritical ethane. It was found that anomalous expansion of the polymer chains associated with excess absorption of the fluid molecules occurs in the large compressible regions of both supercritical fluids (SCFs) regardless of the polymer-fluid interactions. In addition, we found that the excess expansion of the solvophobic polymer chains in both SCFs collapse onto one master curve under the same magnitude of density fluctuations in the fluids. A simple thermodynamic two-state model along with the experimental results proposes that polymer chains are expanded independently of the polymer fluid interactions to further change solvent density fluctuations around the polymer chains, thereby lowering the free energy of the polymer/SCF systems. (C) 2011 Elsevier Ltd. All rights reserved.

DOI： 10.1016/j.polymer.2011.07.039

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Authorship：Lead author,　Corresponding author   Language：English   Publishing type：Research paper (scientific journal)   Publisher：ROYAL SOC CHEMISTRY  

Hydration effects on high-pressure unfolding of a hydrophobic polymer chain are investigated through a multiscale simulation based on density-functional theory. The results strongly suggest the following: a thermodynamic origin for high-pressure denaturation, i.e., the decrease in volume due to the unfolding can be explained by the formation of a short-period high-density hydration shell.

DOI： 10.1039/c1cp21347d

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A thermodynamic analysis of high-temperature and low-pressure unfolding of proteins using a coarse-grained multiscale simulation combined with a liquid-state density-functional theory is presented. In this study, a hydrophobic polymer chain is employed as a probe molecule for investigating qualitative changes in a hydration free energy surface acting on proteins with changes in temperature and pressure. When water is heated so that its vapor pressure is equal to the atmospheric pressure, it boils. Long-ranged dewetting or drying caused by a hydrophobic planar wall and a large hydrophobic solute surface is significantly enhanced as it approaches the liquid-vapor coexistence curve of water. In this study, we demonstrate that high-temperature and low-pressure unfolding of the polymer chain is interpreted as dewetting-induced unfolding that occurs as it approaches the liquid-vapor coexistence. The unfolding of proteins due to high-temperature and low-pressure denaturation enhances the long-ranged dewetting or drying around them. The long-ranged dewetting phenomenon is considered to be originating from positive changes in both volume and entropy due to the high-temperature and low-pressure denaturation of the proteins. (C) 2010 American Institute of Physics. [doi: 10.1063/1.3394864]

DOI： 10.1063/1.3394864

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Authorship：Lead author,　Corresponding author   Language：English   Publishing type：Research paper (scientific journal)   Publisher：AMER INST PHYSICS  

A thermodynamic analysis of high-temperature and low-pressure unfolding of proteins using a coarse-grained multiscale simulation combined with a liquid-state density-functional theory is presented. In this study, a hydrophobic polymer chain is employed as a probe molecule for investigating qualitative changes in a hydration free energy surface acting on proteins with changes in temperature and pressure. When water is heated so that its vapor pressure is equal to the atmospheric pressure, it boils. Long-ranged dewetting or drying caused by a hydrophobic planar wall and a large hydrophobic solute surface is significantly enhanced as it approaches the liquid-vapor coexistence curve of water. In this study, we demonstrate that high-temperature and low-pressure unfolding of the polymer chain is interpreted as dewetting-induced unfolding that occurs as it approaches the liquid-vapor coexistence. The unfolding of proteins due to high-temperature and low-pressure denaturation enhances the long-ranged dewetting or drying around them. The long-ranged dewetting phenomenon is considered to be originating from positive changes in both volume and entropy due to the high-temperature and low-pressure denaturation of the proteins. (C) 2010 American Institute of Physics. [doi: 10.1063/1.3394864]

DOI： 10.1063/1.3453654

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Hydrophobic effects on multivalent-salt-induced self-condensation of a single polyelectrolyte chain such as DNA are investigated through a multiscale coarse-grained simulation based on density functional theory. We show that the water-mediated hydrophobic effect that was enhanced by hydration of multivalent salts plays an essential role in self-condensation of DNA. The self-condensation is interpreted as an entropy-driven compaction due to the hydration entropy gain. (C) 2009 American Institute of Physics. [doi:10.1063/1.3256982]

DOI： 10.1063/1.3256982

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Authorship：Lead author,　Corresponding author   Language：English   Publishing type：Research paper (scientific journal)   Publisher：AMER PHYSICAL SOC  

Density fluctuation effects on the conformation of a polymer chain in a supercritical solvent were investigated by performing a multiscale simulation based on the density-functional theory. We found (a) a universal swelling of the polymer chain near the critical point, irrespective of whether the polymer chain is solvophilic or solvophobic, and (b) a characteristic collapse of the polymer chain having a strong solvophilicity at a temperature slightly higher than the critical point, where the isothermal compressibility becomes less than the ideal one.

DOI： 10.1103/PhysRevE.79.030801

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Authorship：Lead author,　Corresponding author   Language：English   Publishing type：Research paper (scientific journal)   Publisher：PHYSICAL SOC JAPAN  

A self-consistent density-functional theory (DFT) for homogeneous and inhomogeneous classical fluids is presented using the density-functional Taylor expansion of an effective density that is introduced to describe the intrinsic excess free-energy functional. The first-order density expansion of the effective density around the uniform bulk density provides the same intrinsic excess chemical potential as the weighted density-functional approach proposed by Patra and Ghosh [J. Chem. Phys. 116 (2002) 8509]. The density-expansion coefficient is determined in a self-consistent manner by using Percus' relation between the pair correlation function and the density distribution function. The pair correlation functions for hard-sphere (HS) and Lennard-Jones (U) fluids as well as one-component plasma obtained from the self-consistent DFT are compared with the simulation results. The DFr with the self-consistent expansion coefficient is applied to calculate density distribution functions for the inhomogeneous fluids, interacting via the HS and LJ potentials, under external fields such as confinement in several geometries.

DOI： 10.1143/JPSJ.77.034605

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The density dependence of the fluid structure and electrical resistivity of dense fluid hydrogen are studied along an isotherm of T=10(4) K using a density-functional theory for an electron-proton binary mixture. A metal-nonmetal (M-NM) transition is estimated to occur around the dimensionless density value of r(s)=2.19. The electrical resistivity rapidly increases around this value with a decrease in the hydrogen density. Simultaneously, the density dependence of the fluid structure reveals a significant jump near the M-NM transition. The character of the effective interaction potential between protons is qualitatively changed after the M-NM transition. The pressure variation suggests that the M-NM transition is a discontinuous phase transition under coexistence conditions with regard to the phase equilibrium between the metal and the nonmetal phases. (C) 2008 American Institute of Physics.

DOI： 10.1063/1.2824930

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The behavior of a polymer chain immersed in a binary solvent mixture is investigated via a single-polymer simulation using an effective Hamiltonian, where the solvent effects are taken into account through a density-functional theory for polymer-solvent admixtures. The liquid-liquid phase separation of the binary solvent mixture is modeled as that of a Lennard-Jones binary fluid mixture with weakly attractive interactions between the different components. Two types of energetic preferences of the polymer chain for the better solvent - (A) no preferential solvophilicity and (B) strong preferential solvophilicity - are employed as polymer-solvent interaction models. The radius of gyration and the polymer-solvent radial distribution functions are determined from the simulations of various molar fractions along an isotherm slightly above the critical temperature of the liquid-liquid phase separation. These quantities near the critical point conspicuously depend on the strength of the preferential solvophilicity. In the case where the polymer exhibits a strong preferential solvophilicity, a remarkable expansion of the polymer chain is observed near the critical point. On the other hand, in the case where the polymer has no preferential solvophilicity, no characteristic variation of the polymer conformation is observed even near the critical point. These results indicate that the expansion of a polymer chain enhances the local phase separation around it, acting as a nucleus of demixing in the vicinity of the critical point. This phenomenon in binary solvents near the liquid-liquid critical point is similar to the expansion of the polymer chain in one-component supercritical solvents near the liquid-vapor critical point, which we have reported. (C) 2007 American Institute of Physics.

DOI： 10.1063/1.2793778

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The hydrophobic interaction that is characterized by a potential of mean force (PMF) between spherical apolar solutes immersed in the simple point charge (SPCE) model for water was studied using an interaction site model integral equation based on a density-functional theory for molecular fluids. For comparison with the PMFs for various size solutes in the SPCE model, the PMFs in a Lennard-Jones (LJ) model for a solvent whose diameter is same as the SPCE model were also studied using a hypernetted chain integral equation. It is noted in the LJ model that the hydrogen bond and its network structure are completely ignored, but the translational entropy is taken into account. Both PMFs obtained from the SPCE model and from the LJ model have a large first minimum at a contact distance of solutes. In the case that the solute size is about three times larger than water, these PMFs also have a large maximum at a longer distance than the contact position. The strong attraction is attributed to the translational entropy of the solvent, and that the large activation barrier is arising from the weak attraction between the solute and the solvent. The comparison between the SPCE model and the LJ solvent model suggests that the qualitative description of the hydrophobic interaction is possible by using the LJ solvent model. On the other hand, the dewetting tendency on the surface of the apolar solute in a room condition is observed only on the SPCE model. These results indicate that the characteristics of water such as the hydrogen bond affect rather the hydrophobic hydration than the hydrophobic interaction. (c) 2007 American Institute of Physics.

DOI： 10.1063/1.2718520

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Thermodynamic properties in dense fluid hydrogen are studied by using a density-functional theory for electron-proton binary mixtures that is called quantal hypernetted-chain (QHNC) integral equation. A nonlocal approximation for the exchange-correlation potential in a finite-temperature Kohn-Sham equation is presented. Results obtained from the QHNC with the nonlocal approximation are compared with those obtained from the QHNC with a local density approximation. Temperature variation of thermodynamic quantities between 10(4) and 10(6) K are investigated along an isochor specified by a dimensionless density parameter of r(s)=0.5. These quantities obtained from the QHNCs show that a crossover from metal to plasma occurs around a temperature of T=1.78x10(5) K. Electrical resistivity R-e of the dense fluid hydrogen evaluated from a Ziman formula [The Properties of Liquid Metals, edited by S. Takenohi (Wiley, New York, 1973)] extended to finite temperature is about 0.7 mu Omega cm at T=10(4) K. The dense fluid hydrogen at the temperature can be considered as a metallic fluid, because the value is smaller than typical values of R-e in alkali metals at room temperature. The R-e slightly increases with the temperature increase, and the temperature valuation of R-e is monotonic. We clearly show that the contribution from the electronic excited states plays an important role for the sharp crossover from the metal to the plasma, and that the crossover is interpreted as a crossover from degenerate electron gas to nondegenerate electron gas. (c) 2006 American Institute of Physics.

DOI： 10.1063/1.2390704

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We implemented an interaction site model integral equation for rigid molecules based on a density-functional theory where the molecular orientation is explicitly considered. In this implementation of the integral equation, multiple integral of the degree of freedom of the molecular orientation is performed using efficient quadrature methods, so that the site-site pair correlation functions are evaluated exactly in the limit of low density. We apply this method to Cl-2, HCl, and H2O molecular fluids that have been investigated by several integral equation studies using various models. The site-site pair correlation functions obtained from the integral equation are in good agreement with the one from a simulation of these molecules. Rotational invariant coefficients, which characterize the microscopic structure of molecular fluids, are determined from the integral equation and the simulation in order to investigate the accuracy of the integral equation.

DOI： 10.1063/1.2215603

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We applied a simulation method [T. Sumi and H. Sekino, J. Chem. Phys. 122, 194910 (2005)] to an infinitely dilute polyelectrolyte immersed in one-component charged fluids in order to investigate salt effects on its collapse. In this model system, the degree of freedom of the counterion (or the coion) is considered using a density-functional theory for polymer-solvent admixtures, while the oppositely charged ions are treated as a structureless background having the opposite charge. Results obtained by these simulations show that not only the counterion but also the coion makes the polymer chain collapsed. The effects by the coion are stronger than that by the counterion. Temperature variation of the gyration radius of the polymer chain immersed in the counterion is opposite to that in the coion: while the radius of gyration decreases as the temperature decreases in the case of the counterion, it decreases as the temperature increases in the case of the coion. From these results we conclude that the former is interpreted as an enthalpy-driven collapse caused by the screening effects of the counterion, whereas the latter is interpreted as an entropy-driven one due to the translational entropy of the coion.

DOI： 10.1063/1.2110007

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We propose a simulation method for infinitely dilute polymer solutions. In this method, an effective Hamiltonian of the solvated polymer chain is introduced to eliminate the degree of freedom of the solvent particle. The effective Hamiltonian is coupled with the density-functional theory (DFT) that we have developed for a polymer-solvent pair correlation function. All the equations proposed in this paper are derived from the first principle. This simulation method was applied to polymer chains in supercritical solvents. We observed anomalous behaviors of polymer chains near the liquid-vapor critical point: both solvophilic and solvophobic polymers expand significantly near the critical point; this is in contrast to the behavior of polymer chains in vacuum. This expansion can be interpreted as a cooperative phenomenon, which enhances the large long-wavelength density fluctuation of the solvent. (c) 2005 American Institute of Physics.

DOI： 10.1063/1.1900728

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Authorship：Lead author,　Corresponding author   Language：English   Publishing type：Research paper (scientific journal)   Publisher：ELSEVIER SCIENCE BV  

An anomalous increase of positron annihilation rare caused by a decrease of the temperature has been observed in supercritical fluid He-4 along isochors by an experiment. By using a molecular simulation, we demonstrate the similar increase in supercritical fluid xenon at the temperature that is far away from the liquid-vapor phase transition. The phenomenon can be interpreted as a sudden clustering of xenon atom that is induced by a self-trapping of the positron. (c) 2005 Elsevier B.V. All rights reserved.

DOI： 10.1016/j.cplett.2005.03.106

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Conformational change of a solvophobic polymer along an isotherm slightly above critical temperature of solvent is studied by using a simulation with an effective Hamiltonian of the solvated polymer chain, where solvent effects are taken into account. We observe an expansion of the solvophobic polymer in the vicinity of the critical density. The anomalous behavior can be understood only through the large fluctuation of solvent density near the critical point. (c) 2005 Elsevier B.V. All rights reserved.

DOI： 10.1016/j.cplett.2005.03.094

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We have used a density-functional theory based on the interaction site model to predict the liquid-vapor coexistence curve of nitrogen fluid. The pressure and chemical potential were calculated from thermodynamic integrations. The different paths of thermodynamic integration provide slightly different predictions for the liquid-vapor coexistence curve. However, these critical points and coexistence curves evaluated by the theory are in qualitative agreement with the experimental data. The theoretical coexistence curves scaled to critical constants agree with the experimental data quantitatively. (C) 2004 American Institute of Physics.

DOI： 10.1063/1.1759618

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In paper, we propose a path integral influence functional from a solvent to determine a self-correlation function of a quantum particle in classical simple fluid. It is shown that the influence functional is related to a grand potential functional of the pure solvent under a three-dimensional external field arising from a classical isomorphic polymer, on which the quantum particle is mapped. The influence functional can be calculated from the self-correlation function, the solute-solvent and the solvent-solvent pair correlation function. The obtained equation of the self-correlation function is applied to an excess electron problem in fluid helium. The Fourier path-integral Monte Carlo method is employed to perform the path integral of the electron. The solute-solvent pair correlation function is estimated from a reference interaction site model integral equation. These results obtained form our proposed influence functional and from that proposed by Chandler, Singh, and Richardson are compared with those provided by a path integral Monte Carlo simulation with the explicit helium solvent. (C) 2004 American Institute of Physics.

DOI： 10.1063/1.1695324

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The density-functional theory (DFT) for molecular fluids [J. Chem. Phys. 115, 6653 (2001)] is extended to the case of polymer liquids. A system consisting of the ideal chains is employed as a reference system for the DFT, where many-body effects are considered as an effective field that acts on each site of the ideal chains. We derived a relation between the site-site pair distribution functions and the site-density distribution functions under a mean field arising from a single polymer molecule. An integral equation for the site-site pair distribution functions is obtained by the DFT, where the external field is taken to be the mean field. We propose an approximate expression of the intramolecular correlation functions for isolated single-polymer chains to take account for the excluded volume effects inside a polymer chain. The intramolecular correlation function considering the excluded volume effects was in qualitative agreement with those obtained from a simulation for liquid consisting of freely jointed tangent-soft-core chains. The site-density integral equation under the mean field, using the intramolecular correlation function, reproduces the simulation results for site-site pair distribution functions of the system of freely jointed tangent-soft-core chains. (C) 2003 American Institute of Physics.

DOI： 10.1063/1.1533784

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An integral equation for rigid-body molecules with respect to site-density distribution function under arbitrary external fields is derived by the density-functional theory. Using a grand canonical partition function of molecular systems, we extend original Percus' idea to molecular fluids. The extended Percus' idea provides a relation between the site-site pair distribution function and site-density distribution function under an external field composed of the site-site interaction potentials of a molecule fixed at the origin. The site-density integral equation combined with the extended Percus' relation to molecular fluids gives a closure relation of reference interaction site model equation. The site-site pair distribution functions of homonuclear diatomic Lennard-Jones fluids obtained by the integral equation agree well with those of Monte Carlo simulation. (C) 2001 American Institute of Physics.

DOI： 10.1063/1.1401824

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Molecular dynamics (MD) calculations of expanded liquid mercury in the density region between metal and nonmetal were made using the potential energy curve of dimeric mercury (Formula presented) determined from molecular orbital calculations. The density dependence of the thermal pressure coefficient and the internal pressure, which were observed experimentally in the density region that included the metal-nonmetal transition range, were qualitatively demonstrated with our MD calculations. The change of calculated pair distribution function and structure factor from a metallic to a nonmetallic state also explained qualitatively the change of experimental ones. The temperature dependence of the isochoric electrical conductivity was discussed using quantities obtained from the calculated pair distribution functions. It was shown that the increase of the isochoric electrical conductivity accompanying an increase in temperature, which was experimentally observed in the strong-scattering metallic region, can be realized through the increase of the density of states at the Fermi energy arising from the decrease of interatomic distance. © 1999 The American Physical Society.

DOI： 10.1103/PhysRevB.59.6153

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A potential curve and spectroscopic constants of (Formula presented) were calculated using multireference single- and double-excitations configuration interaction calculations, where (Formula presented) and (Formula presented) electrons were correlated. The calculated constants were consistent with experimental data. Using the potential curves of (Formula presented) we performed molecular-dynamics (MD) calculations to identify the melting point of mercury. A characteristic feature of liquid metal, cooperative motion, was observed in the MD calculations. On the other hand, MD calculations using a Lennard-Jones potential gave the cooperative motion only in very short time intervals (Formula presented). © 1998 The American Physical Society.

DOI： 10.1103/PhysRevB.57.914

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Ab initio complete active space self-consistent field (CASSCF) and multireference singly and doubly excited configuration interaction (MRSDCI) calculations were performed for the (C6H6)(2)(+) radical. The calculations revealed that the global minima of the ground state of(C6H6)(2)(+) are at distorted C-2h geometries. Sandwich (D-6h) and T-shaped (C-2v) structures are higher in energy than the minima by 0.4 and 3.7 kcal/mol, respectively. The calculated binding energy is 15.0 kcal/mol compared with an observed value of 20.6 +/- 1.0 kcal/mol. The excitation energies of low-lying excited states are discussed. (C) 1997 Elsevier Science B.V.

DOI： 10.1016/S0009-2614(97)00773-2

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Hartree-Fock and configuration-interaction calculations were performed for (Formula presented) Li and (Formula presented) LiOH, as models of Li/Cu(001) and LiOH/Cu(001), respectively. To take into account the dielectric-response effect of the metal surface to external point charges, we used cluster models with image charges. For (Formula presented) Li, the calculated vibrational frequency was almost the same as that given by a cluster model without image charges, and both values agreed well with the experimental value. Image charges improved the Li-OH vibrational frequency for (Formula presented) LiOH. On the other hand, simple cluster calculations without image charges gave poor results for work-function changes upon Li and LiOH adsorption
however, by considering image charges, we obtained excellent results, were comparable to the observed values. © 1997 The American Physical Society.

DOI： 10.1103/PhysRevB.55.4755

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Authorship：Lead author,　Corresponding author   Language：Japanese   Publishing type：Article, review, commentary, editorial, etc. (scientific journal)   Publisher：日本化学会コロイドおよび界面化学部会  

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DOI： 10.11436/mssj.14.206

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