Improving the Performance of the Coupled Reference Interaction Site Model-Hyper-netted Chain (RISM-HNC)/Simulation Method for Free Energy of Solvation

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• 作者：Holly Freedman ; Ly Le ; Jack A. Tuszynski ; Thanh N. Truong
• 刊名：Journal of Physical Chemistry B
• 出版年：2008
• 出版时间：February 28, 2008
• 年：2008
• 卷：112
• 期：8
• 页码：2340 - 2348
• 全文大小：110K
• 年卷期：v.112,no.8(February 28, 2008)
• ISSN：1520-5207

文摘

The coupled reference interaction site model-hyper-netted chain (RISM-HNC)/ simulation methodologydetermines solvation free energies as a function of the set of all radial distribution functions of solvent atomsabout atomic solute sites. These functions are determined from molecular dynamics (MD) or Monte Carlo(MC) simulations rather than from solving the RISM and HNC equations iteratively. Previous applications ofthe method showed that it can predict relative free energies of solvation for small solutes accurately. However,the errors scale with the system size. In this study, we propose the use of the hard-sphere free energy as thereference and a linear response approximation to improve the performance, i.e., accuracy and robustness, ofthe method, particularly removing the size dependency of the error. The details of the new formalism arepresented. To validate the proposed formalism, solvation free energies of N-methylacetamide and methylamineare computed using the new RISM-HNC-based expressions in addition to a linear response expression,which are compared to previous thermodynamic integration and thermodynamic perturbation results performedwith the same force field. Additionally, free energies of solvation for cyclohexane, pyridine, benzene andderivatives, and other small organic molecules are calculated and compared to experimental values.