Theoretical Studies on the Proton Transfer Mechanism in Four-water Hydrated Glycine Complexes

The mp2/6-31＋＋g^＊＊//b3lyp/6-31＋＋g^＊＊ method has been employed to study the proton transfer mechanism in 4H2O-glycine complexes（4W-G）.Compared with bare glycine the four-water hydrated neutral glycine complexes（4W-GN） can turn into the corresponding zwitterionic glycine（4W-GZ） through proton transfer.The most stable conformation of 4W-GZ has a ＂double water-chain＂ structure and is more stable than its corresponding precursor 4W-GN by 0.97 KJ/mol though it is less stable than the most stable 4W-GN by 7.80 KJ/mol.It is a spontaneous reaction to form the most stable conformation of 4W-GZ,and the potential barrier is only 1.97 KJ/mol,so the probability of this reaction is very high and the most stable 4W-GZ may be detected in experiment or in the early stage of experiment.