Studies On The Properties Of GLY(H₂O)_n(n=1-8) Clusters In Terms Of ABEEM/MM Fluctuating Charge Molecular Force Field

As the simplest amino acid and essential living nutrition, glycine (GLY) plays an important role in biological systems. So it is of great interest to study the glycine-water interaction energies.We present a new glycine-water potential model by compiling and debugging the related programs based on the atom-bond electronegativity equalization fluctuating charge molecular force field (ABEEM/MM), in conjunction with the ABEEM-7P water model. The potential was applied to study Glycine-water clusters and to reproduce gas-phase state properties of GLY(H2O)n(n=1-8). The structures and vibrational frequencies of the GLY(H2O)n (n=1-8) were examined using the B3LYP/6-311++G(d,p) method. The M?ller-Plesset (second order) theory with 6-311++G(3d,3p) basis set was used to calculate the binding energy, and the BSSE (basis set superposition error) was corrected by the counterpoise correction method. First, we studied the structure of glycine, and the results are in good agreement with the experimental results. According to the study of charge distribution of N and O atom and their isolated charge distribution in glycine by using ABEEM model, we can explain the intensity of the H-bond interaction. In addition, the potential was applied to study Glycine-water clusters and reproduce gas-phase state properties of GLY(H2O)n (n=1-3), including structures, dipole moments, ABEEM charge distributions, interaction energies, and hydrogen bonding cooperative effects, and so on. These results show a good agreement with those calculated by the ab initio methods. The larger Glycine-water clusters, GLY(H2O)n (n=4-8), were also studied to further test the reasonableness of this potential, the correctness and transferability of the parameters of the ABEEM/MM. including structures, interaction energies, and successive bonding energies. The results also show good consistency with those of ab initio calculations.