苯丙氨酸电荷转移百分数的理论计算

Theoretical Calculation of Charge Transfer Percentage of Phenylalanine

采用密度泛函理论中的CAM-B3LYP方法,在6-31G(d)基组水平上优化不同条件下左旋体苯丙氨酸(S-Phe)分子的几何构型.结果表明:在隐式溶剂甲醇与气相条件下,S-Phe分子体系电荷转移的定性结果基本一致,定量结果略有差别,其中各片段的S2激发态基本一致,仅COOH片段的S2激发态差别为2.2%,S4激发态差别为0.4%～2.8%;在不同环境下,定性分析缺少一个S5激发态,由Becke方法计算的激发态S2和S4电荷转移相差分别约为2.5%～8%.

Using the CAM-B3LYP method of density functional theory,we optimized the geometric configuration of S-phenylalanine(S-Phe)molecule at 6-31G(d)basis set under different conditions.The results show that,under the conditions of implicit methanol solvent and the gas phase,the qualitative results of charge transfer in S-Phe molecular system are basically consistent,the quantitative results are slightly different,the S2 excited states of each fragment are basically consistent,only the difference of S2 excited state of COOH fragment is 2.2%,and the difference of S4 excited state is 0.4%-2.8%.The qualitative analysis lacks an S5 excited state in different environments.The difference of charge transfer of S2 and S4 excited states calculated by Becke method is about 2.5%-8%.