TY - JOUR
T1 - Calculation of solvation free energy utilizing a constrained QM/MM approach combined with a theory of solutions
AU - Takahashi, Hideaki
AU - Kambe, Hiroyuki
AU - Morita, Akihiro
N1 - Funding Information:
This work was supported by the Grant-in-Aid for Scientific Research on Innovative Areas (Grant No. 23118701) from the Ministry of Education, Culture, Sports, Science, and Technology (MEXT), by the Grant-in-Aid for Challenging Exploratory Research (Grant No. 25620004), and the Grant-in-Aid for Scientific Research(C) (Grant No. 17K05138) from the Japan Society for the Promotion of Science (JSPS). The calculations were performed partly using computational resources of the HPCI systems provided by SX-ACE at Osaka University and at Tohoku University, and Cray XC30 and XC40 at Kyoto University through the HPCI System Research Project (Project Nos. hp150131, hp160007, hp170046, and hp180032).
Publisher Copyright:
© 2019 Author(s).
PY - 2019/3/21
Y1 - 2019/3/21
N2 - In an extended QM/MM (quantum mechanical/molecular mechanical) description of a solution, the solvent molecules surrounding the solute are incorporated into the QM region besides the solute. In a recent development, we introduced a simple and efficient method, referred to as boundary constraint with correction (BCC), to prevent the diffusion of the QM solvent into the bulk. The major purpose of the present work is to develop a method to compute the solvation free energy of a QM solute in an extended QM/MM simulation by means of the BCC method. The strategy of our development is to utilize the QM/MM-ER method which combines the QM/MM simulation and the theory of solutions termed energy representation (ER) to expedite the free energy calculation. A theory is, then, formulated to couple QM/MM-ER and the BCC method on the basis of the statistical mechanics. A notable feature of our method is that the effect of the constraint potentials on the free energy completely vanishes when the force field of the QM solvent coincides with that of the MM solvent. The method is applied to the calculations of the solvation free energies of a water molecule and a hydronium ion in water solutions. It turns out that the present method can offer a significant improvement in describing the free energy Δν of the hydronium ion, in particular, as compared with the conventional QM/MM approach. Explicitly, Δν is obtained as -98.0 kcal/mol showing a good agreement with an experimental value of -103.5 kcal/mol, while -86.1 kcal/mol by the conventional method.
AB - In an extended QM/MM (quantum mechanical/molecular mechanical) description of a solution, the solvent molecules surrounding the solute are incorporated into the QM region besides the solute. In a recent development, we introduced a simple and efficient method, referred to as boundary constraint with correction (BCC), to prevent the diffusion of the QM solvent into the bulk. The major purpose of the present work is to develop a method to compute the solvation free energy of a QM solute in an extended QM/MM simulation by means of the BCC method. The strategy of our development is to utilize the QM/MM-ER method which combines the QM/MM simulation and the theory of solutions termed energy representation (ER) to expedite the free energy calculation. A theory is, then, formulated to couple QM/MM-ER and the BCC method on the basis of the statistical mechanics. A notable feature of our method is that the effect of the constraint potentials on the free energy completely vanishes when the force field of the QM solvent coincides with that of the MM solvent. The method is applied to the calculations of the solvation free energies of a water molecule and a hydronium ion in water solutions. It turns out that the present method can offer a significant improvement in describing the free energy Δν of the hydronium ion, in particular, as compared with the conventional QM/MM approach. Explicitly, Δν is obtained as -98.0 kcal/mol showing a good agreement with an experimental value of -103.5 kcal/mol, while -86.1 kcal/mol by the conventional method.
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U2 - 10.1063/1.5089199
DO - 10.1063/1.5089199
M3 - Article
C2 - 30902001
AN - SCOPUS:85063356934
VL - 150
JO - Journal of Chemical Physics
JF - Journal of Chemical Physics
SN - 0021-9606
IS - 11
M1 - 114109
ER -