Computed molecular surface electrostatic potentials of the nonionic and zwitterionic forms of glycine, histidine, and tetracycline

Abstract

Three different procedures (HF/STO-3G, HF/3-21G, and B3P86/6-31+G**) were used to compute the electrostatic potentials on the molecular surfaces of glycine, histidine, tetracycline, and their zwitterions. These surface potentials were characterized in terms of a group of statistically defined quantities, which include the average deviation, the positive and negative average potentials, variances and extremes, and a balance parameter. The results were found to be qualitatively reasonably independent of the computational procedure. The zwitterions have much greater internal charge separations than the nonionic forms, although this is progressively diluted as the system increases in size. The statistical properties of the surface potentials permitted the determination of the solvation energetics of both the nonionic forms and the zwitterions. © 2000 John Wiley & Sons, Inc. Int J Quant Chem 80: 1216–1223, 2000