In this paper, proton transfer mechanism of alanine induced by Zn2＋ was investiga- ted by the CCSD/6-31＋＋G＊＊//B3LYP/6-31＋＋G＊＊ method. Six neutral complexes and one ampho- teric complex were optimized, among w...In this paper, proton transfer mechanism of alanine induced by Zn2＋ was investiga- ted by the CCSD/6-31＋＋G＊＊//B3LYP/6-31＋＋G＊＊ method. Six neutral complexes and one ampho- teric complex were optimized, among which the amphoteric complex was the most stable with binding energy of 201.92 kcal·mol-1. In addition, the rotation of intramolecular single bond leads to the neutral configuration conversion, in which the rotation energy barriers of C–C single bonds are lower than 10.51 kcal·mol-1, and those of C–O single bonds range among 9.53~17.50 kcal·mol-1. On the other hand, the proton transfers among the carboxylic oxygen atoms can also result in the neutral configuration conversion, whose energy barriers of forward/back reaction are 53.90 and 32.46 kcal·mol-1, respectively. In detail, the proton transfers from carboxylic group to amino lead to their configuration conversion from neutral to amphoteric. Furthermore, under the catalysis of Zn2＋, there was no energy barrier in this reaction. The conversion route from the most stable neutral configuration Ⅱ to the most stable amphoteric configuration I was： Ⅱ→Ⅱ-Ⅲ→Ⅲ→Ⅲ-Ⅵ→Ⅵ→Ⅴ-Ⅵ→Ⅴ→Ⅰ-Ⅴ→Ⅰ,with the energy barrier to be 64.64 kcal·mol-1.展开更多
基金supported by New Biological and Chemical Technology Key Laboratory of Tangshan(12150224B-2)Science Foundation of Tangshan Normal University(2013D02)
文摘In this paper, proton transfer mechanism of alanine induced by Zn2＋ was investiga- ted by the CCSD/6-31＋＋G＊＊//B3LYP/6-31＋＋G＊＊ method. Six neutral complexes and one ampho- teric complex were optimized, among which the amphoteric complex was the most stable with binding energy of 201.92 kcal·mol-1. In addition, the rotation of intramolecular single bond leads to the neutral configuration conversion, in which the rotation energy barriers of C–C single bonds are lower than 10.51 kcal·mol-1, and those of C–O single bonds range among 9.53~17.50 kcal·mol-1. On the other hand, the proton transfers among the carboxylic oxygen atoms can also result in the neutral configuration conversion, whose energy barriers of forward/back reaction are 53.90 and 32.46 kcal·mol-1, respectively. In detail, the proton transfers from carboxylic group to amino lead to their configuration conversion from neutral to amphoteric. Furthermore, under the catalysis of Zn2＋, there was no energy barrier in this reaction. The conversion route from the most stable neutral configuration Ⅱ to the most stable amphoteric configuration I was： Ⅱ→Ⅱ-Ⅲ→Ⅲ→Ⅲ-Ⅵ→Ⅵ→Ⅴ-Ⅵ→Ⅴ→Ⅰ-Ⅴ→Ⅰ,with the energy barrier to be 64.64 kcal·mol-1.
