为了探讨"几个水分子导致甘氨酸两性离子复合体与其中性分子复合体等能",采用mp2/6-31++g//b31yp/6-31++g方法研究了甘氨酸水化的微观机理,发现答案是5个水分子,并证实了实验结果.最稳定的5水合甘氨酸两性离子复合体具有双链结构,与最稳定的5水合甘氨酸中性分子复合体能量接近(仅相差2.26 kJ/mol),能够共存;中性复合体和两性复合体之间可以通过直接质子迁移和桥助质子迁移等两种途径相互转化,双链结构的甘氨酸复合体中质子迁移的能垒较低甚至无垒,能够自发进行.%To investigate how many water molecules may induce the zwitterionic glycine isoenergetic with respect to the neutral form, mp2/6-31 ++g**//b31yp/6-31 + +g** method has been applied to study the micromechanism of the glycine-H20 interaction. It is found that the answer is five water molecules which confirms the experimental result. The most stable conformation of pentahydrated zwitterionic glycine complexes is a pair-chains structure, whose energy is near to the energy of the most stable pentahydrated neutral glycine conformation (the error is only 2.26 k J/mol), so they can coexist. Via proton transfering, a pentahydrated neutral glycine complex can convert into the corresponding pentahydrated zwitterionic glycine complex. There are two kinds of proton transfer route in glycine-H2O system, one is “direct proton transfer” and the other is “water-assisted proton transfer”. In the proton transfer process of the corresponding pair-chains structures, there is a lower energy barrier or no barrier, and the reaction can proceed spontaneously.
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