MP2 Study on the Proton Transfer Mechanism of Glycine Assisted by Water

The geometries of glycine-nH2O (n=1～5) complexes and the transition states of proton transfer in glycine-H2O system were calculated at the MP216-31++G**IIMP216-31G* level,upon which we discovered the proton transfer mechanisms,including the number of water molecules necessary for the stabilization of zwitterions and the effect of increasing water molecules on the proton transfer.To our interest,we found that only one water molecule can stabilize the zwitterions;in addition,with the increment of water molecules,the activation energy of positive reaction decreases and that of reverse reaction increases gradually.Glycine will be ionized com-pletely while the water molecules reach to a certain number.