プロトンの水和自由エネルギー: 酸解離定数および標準水素電極電位の高精度計算  [in Japanese] Solvation Energy of Proton: a Consistent Calculation Schemefor Acid Dissociation Constantsand Standard Hydrogen Electrode Potentials  [in Japanese]

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Author(s)

    • 松井 亨 MATSUI Toru
    • 筑波大学大学院数理物質科学研究科 Graduate School of Pure and Applied Sciences, University of Tsukuba.Center for Computational Sciences, University of Tsukuba. 1-1-1 Tennodai, Tsukuba, Ibaraki 305-8577, Japan
    • 喜屋武 茜 KIYAN Akane
    • 筑波大学大学院数理物質科学研究科 Graduate School of Pure and Applied Sciences, University of Tsukuba.Center for Computational Sciences, University of Tsukuba. 1-1-1 Tennodai, Tsukuba, Ibaraki 305-8577, Japan
    • 庄司 光男 SHOJI Mitsuo
    • 筑波大学大学院数理物質科学研究科|筑波大学計算科学研究センター Graduate School of Pure and Applied Sciences, University of Tsukuba.Center for Computational Sciences, University of Tsukuba. 1-1-1 Tennodai, Tsukuba, Ibaraki 305-8577, Japan
    • 重田 育照 SHIGETA Yasuteru
    • 筑波大学大学院数理物質科学研究科|筑波大学計算科学研究センター Graduate School of Pure and Applied Sciences, University of Tsukuba.Center for Computational Sciences, University of Tsukuba. 1-1-1 Tennodai, Tsukuba, Ibaraki 305-8577, Japan

Abstract

<p>本総説では,分極誘電体モデルと量子化学計算に基づく酸解離定数(p<i>K</i><sub>a</sub>)の計算手法について述べる.この手法では,参照分子に対して計算により得られる自由エネルギー差と実験により得られるp<i>K</i><sub>a</sub>値から官能基毎の線形関係を導くことで,アミノ酸の側鎖のp<i>K</i><sub>a</sub>の半定量的な計算が可能になる.ペプチド3量体の計算においては,周囲のアミノ酸の水素結合の効果によってp<i>K</i><sub>a</sub>が単量体とくらべ大きく(3 p<i>K</i><sub>a</sub>単位)異なることがわかる.また本手法は標準水素電極電位の計算にも適用可能であり,いくつかの酸化還元反応の誤差はCCSD (T)/aug-cc-pVDZでは0.1V以内であり,B3LYPでも同程度の精度で酸化還元電位が計算される.</p>

<p>We here review a scheme for estimating the acid dissociation constant (p<i>K</i><sub>a</sub>) based on quantum-chemical calculations combined with a polarizable continuum model, where a parameter is determined for small reference molecules. This scheme enabled us to derive a semiquantitative p<i>K</i><sub>a</sub> value of specific chemical groups and discuss the influence of the surroundings on the p<i>K</i><sub>a</sub> values. As applications, we have derived the p<i>K</i><sub>a</sub> value of the side chain of an amino acid and almost reproduced the experimental value. By using our computing schemes, we showed the influence of hydrogen bonds on the p<i>K</i><sub>a</sub> values in the case of tripeptides, which decreases the p<i>K</i><sub>a</sub> value by 3.0 units for serine in comparison with those of the corresponding monopeptides. The same procedure is also applicable to estimate the standard hydrogen electrode (SHE) potential in aqueous solution. With our computational scheme, the CCSD (T)/aug-cc-pVDZ method provides the SHE potential of 4.52 V, which is almost the same as the experimental SHE potential. This scheme also reproduces well the redox potentials of several typical reactions within almost 0.1 V. B3LYP also gives excellent redox potentials of the same reactions with almost the same accuracy with our new computational scheme.</p>

Journal

  • Journal of Computer Chemistry, Japan

    Journal of Computer Chemistry, Japan 15(5), 184-191, 2016

    Society of Computer Chemistry, Japan

Codes

  • NII Article ID (NAID)
    130005239564
  • Text Lang
    JPN
  • ISSN
    1347-1767
  • Data Source
    J-STAGE 
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