Footprinting molecular electrostatic potential surfaces for calculation of solvation energies
Footprinting molecular electrostatic potential surfaces for calculation of solvation energies
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DOI：
10.1039/c3cp53158a
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发表时间：
2013-01-01
影响因子：
3.3
通讯作者：
Vinter, Jeremy G.
中科院分区：
文献类型：
--
作者：
Calero, Christian Solis;Farwer, Jochen;Vinter, Jeremy G.
液体是由一系列分子组成的，这些分子占据了大量不同的状态，因此计算溶液中分子的溶剂化能需要一种方法来总结所有这些状态与环境的相互作用。平衡液体性质的表面位点相互作用模型（SSIMPLE）将分子表面简化为离散的特定相互作用位点（SSIP）。这些相互作用位点的热力学性质可以通过实验来表征，例如，通过测量形成简单复合物的缔合常数来表征，所述简单复合物具有单个氢键相互作用。实验确定的溶液相H-键参数与气相从头计算的最大值和最小值的分子静电势表面（MEPS）的相关性提供了一种方法，用于转换气相计算孤立分子的参数，可用于估计溶液相相互作用的自由能。这种方法已经使用足迹技术进行了推广，该足迹技术将MEPS转换为一组离散的SSIP（每个SSIP由极性相互作用参数描述）。这些SSIP代表了分子整个表面的分子识别特性。例如，水由四个SSIP、两个氢键供体位点和两个氢键受体位点描述。液体混合物被描述为代表适当浓度的混合物组分的SSIP的集合。假设各个SSIP是独立的，因此可以基于各个SSIP相互作用的性质来计算SSIP接触的物种形成，所述性质由极性（E（i）E（j））和非极性（E-vdW）相互作用项的总和给出。计算了一系列有机分子从纯液体到水，从纯液体到正十六烷，从正十六烷到水，从正辛醇到水的转移自由能，以及水从纯水到一系列有机液体的转移自由能。与实验的协议是准确的1.6-3.9 kJ mol（-1）的均方根差，这表明，SSIMPLE方法是一个有前途的方法，在更复杂的系统中的溶剂化能估计。
A liquid is composed of an ensemble of molecules that populate a large number of different states, so calculation of the solvation energy of a molecule in solution requires a method for summing the interactions with the environment over all of these states. The surface site interaction model for the properties of liquids at equilibrium (SSIMPLE) simplifies the surface of a molecule to a discrete number of specific interaction sites (SSIPs). The thermodynamic properties of these interaction sites can be characterised experimentally, for example, through measurement of association constants for the formation of simple complexes that feature a single H-bonding interaction. Correlation of experimentally determined solution phase H-bond parameters with gas phase ab initio calculations of maxima and minima on molecular electrostatic potential surfaces (MEPS) provides a method for converting gas phase calculations on isolated molecules to parameters that can be used to estimate solution phase interaction free energies. This approach has been generalised using a footprinting technique that converts an MEPS into a discrete set of SSIPs (each described by a polar interaction parameter, epsilon(i)). These SSIPs represent the molecular recognition properties of the entire surface of the molecule. For example, water is described by four SSIPs, two H-bond donor sites and two H-bond acceptor sites. A liquid mixture is described as an ensemble of SSIPs that represent the components of the mixture at appropriate concentrations. Individual SSIPs are assumed to be independent, so speciation of SSIP contacts can be calculated based on properties of the individual SSIP interactions, which are given by the sum of a polar (epsilon(i)epsilon(j)) and a non-polar (E-vdW) interaction term. Results are presented for calculation the free energies of transfer of a range of organic molecules from the pure liquid into water, from the pure liquid into n-hexadecane, from n-hexadecane into water, from n-octanol into water, and for the transfer of water from pure water into a range of organic liquids. The agreement with experiment is accurate to within 1.6-3.9 kJ mol(-1) root mean square difference, which suggests that the SSIMPLE approach is a promising method for estimation of solvation energies in more complex systems.