Ab initio self-consistent field and potential-dependent partial equalization of orbital electronegativity calculations of hydration properties of N-acetyl-N'-methyl-alanineamide.
Ab initio self-consistent field and potential-dependent partial equalization of orbital electronegativity calculations of hydration properties of N-acetyl-N'-methyl-alanineamide.
复制标题
N-乙酰基-N-甲基-丙氨酸酰胺水合性质的从头算自洽场和轨道电负性的电势相关部分均衡计算。
DOI：
10.1002/bip.360300908
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发表时间：
1990
期刊：
影响因子：
2.9
通讯作者：
Scheraga,HA
中科院分区：
文献类型：
--
作者：
Grant,JA;Williams,RL;Scheraga,HA
采用一种新的并行计算方法，对N-乙酰基-N′-甲基-丙氨酸酰胺的12种低能构象的相对水化能进行了从头算自洽场（SCF）计算.所需的SCF计算使用6 - 31 G和6 - 31 G * 基组进行，在不存在和存在由模型溶剂引起的扰动势的情况下。αR，αL，聚脯氨酸II（PII）和π螺旋构象优先稳定的溶剂势，而分子内氢键C5和C7的构象在气相中是首选。平均邻位核磁共振耦合常数（J），使用各种溶剂化构象的总能量计算，与水溶液中观察到的该肽的耦合常数一致。当分子从低介电常数的介质转移到高介电常数的介质时，在与反应场平衡时发生溶质电荷密度的实质性改变，如分子偶极矩和原子中心多极的变化所示。为了用经验方案模拟电荷密度的这些变化，我们基于轨道电负性部分均衡的势依赖形式（PDPEOE）实现了溶质电荷密度的新型单极表示。在原子中心点电荷PDPEOE表示中，电荷如何响应于外部场从溶质的一个区域移动到另一个区域。使用PDPEOE表示法计算的水合能与SCF程序计算的水合能相似。此外，PDPEOE计算得到的分子偶极矩溶剂化后，同意密切从头计算SCF偶极矩的变化。
Using a recently developed parallel computation algorithm, ab initio self‐consistent field (SCF) calculations were carried out to estimate the relative hydration energies for 12 low‐energy conformations of N‐acetyl‐N′‐methyl‐alanineamide. The requisite SCF calculations were carried out using 6‐31G and 6‐31G* basis sets, both in the absence and presence of a perturbing potential arising from a model solvent. The αR, αL, polyproline II (PII), and π helical conformations were preferentially stabilized by the solvent potential, whereas conformations with intramolecular hydrogen‐bonding C5and C7were preferred in the gas phase. Average vicinal nmr coupling constants (J), calculated using the total energies of the various solvated conformations, were consistent with observed coupling constants for this peptide in aqueous solution. Substantial alteration of the solute charge density occurred upon equilibration with the reaction field, as was exemplified in changes both in the molecular dipole moments and in atom‐centered multipoles, when the molecule was transferred from a medium of low dielectric constant to one of high dielectric constant. In order to model these changes in charge density with an empirical scheme, we have implemented a novel monopolar representation of the solute charge density based on a potential‐dependent form of partial equalization of orbital electronegativities (PDPEOE). In the atom‐centered point charge PDPEOE representation, charge Hows from one region of the solute to another in response to external fields. Hydration energies calculated using the PDPEOE representation are similar to those calculated by the SCF procedure. Also, the PDPEOE calculations yielded changes in molecular dipole moments upon solvation that agreed closely with the changes in the calculated ab initio SCF dipole moments.