局部软度、软度偶极和官能团的极化率：应用于二十种氨基酸的侧链
Local softness, softness dipole and polarizabilities of functional groups: application to the side chains of the twenty amino acids
摘要：
用从头计算法（MP 2）计算了20种氨基酸的分子极化率和软度。通过使用迭代Hirshfeld方案划分分子的电子性质，我们证明了20个氨基酸的侧链的柔软度的值聚集在反映其生化分类的组中，即：脂肪族，碱性，酸性，含硫和芳香族氨基酸。目前的研究结果是在协议与以前的结果，使用不同的近似和分割方案[P. Senet和F。Aparicio，J.Chem.Phys.126，145105（2007）]。此外，我们表明，一个氨基酸的侧链的极化率主要取决于它的电子数（反映其大小），因此不能被用来集群的氨基酸在不同的生化组，在当地的柔软性。我们的研究结果还表明，整体软度不是简单地成正比的整体极化率在不同意的直觉，“一个软的部分也是更极化”。具有相同柔软度的氨基酸可具有相差高达1.7倍的极化率。这种差异可以从第一原理理解，因为我们表明，分子的极化率取决于“软偶极子矢量”，而不仅仅是在全球的软。
英文摘要：
The values of molecular polarizabilities and softnesses of the twenty amino acids were computed ab initio (MP2). By using the iterative Hirshfeld scheme to partition the molecular electronic properties, we demonstrate that the values of the softness of the side chain of the twenty amino acid are clustered in groups reflecting their biochemical classification, namely: aliphatic, basic, acidic, sulfur containing, and aromatic amino acids . The present findings are in agreement with previous results using different approximations and partitioning schemes [P. Senet and F. Aparicio, J. Chem. Phys. 126,145105 (2007)]. In addition, we show that the polarizability of the side chain of an amino acid depends mainly on its number of electrons (reflecting its size) and consequently cannot be used to cluster the amino acids in different biochemical groups, in contrast to the local softness. Our results also demonstrate that the global softness is not simply proportional to the global polarizability in disagreement with the intuition that "a softer moiety is also more polarizable". Amino acids with the same softness may have a polarizability differing by a factor as large as 1.7. This discrepancy can be understood from first principles as we show that the molecular polarizability depends on a "softness dipole vector" and not simply on the global softness.
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