二水合甘氨酸两性离子复合体的结构和性能的理论研究

采用理论计算方法B3LYP, 在6-31++G**基组水平研究使甘氨酸质子化所需的最少水分子数目, 然后讨论水合两性离子复合体的结构和性能, 进而计算了二水合甘氨酸中性分子复合体(2W-GN)到二水合甘氨酸两性离子复合体(2W-GZ)的过渡态, 得到如下结论: (1)两个水分子可以使甘氨酸质子化, 能够形成稳定的二水合两性离子复合体. (2)甘氨酸与水分子之间通过氢键相互作用, 结合能较大, 复合体稳定; 在二水合甘氨酸复合体中, 水合甘氨酸中性分子比水合甘氨酸两性离子稳定. (3)由2W-GN到2W-GZ过程的反应活化能和氢键键能相近.

Theoretical Study on Structures and Properties of Dihydrated Zwitterionic Glycine Complexes

The number of water molecules necessary to stabilize the glycine zwitterions was studied, then the structures and properties of dihydrated zwitterionic glycine complexes were discussed. At the same time, the transition state of dihydrated neutral glycine (2W-GN) to dihydrated zwitterionic glycine (2W-GZ) was calculated . Three conclusions were drawn as below, (1) Two water molecules are necessary to stabilize the glycine zwitterions; (2) It is hydrogen bond which combines the glycine with two water molecules, the bonding energy is relatively large and the complexes are stable; (3) The activation energy of 2W-GN to 2W-GZ is close to the energy of hydrogen bond. All the tasks were calculated by B3LYP, at the 6-31 G** basis set level with the Gaussian98 program.