MONTE-CARLO SIMULATION STUDY ON THE CONFORMATION AND INTERACTION OF THE GLYCINE ZWITTERION IN AQUEOUS-SOLUTION

A Monte Carlo simulation with the statistical perturbation method has been employed to determine the relative stabilities among four represe ntative conformations of the glycine zwitterion (GLYZ) in aqueous solu tion. The (phi,theta)=(0,0) and (60,0) conformations, in which the dih edral angle theta between the NCC and CCO planes is 0 degrees, were fo und to be more stable than the (0,90) and (60,90) conformations, in wh ich theta=90 degrees. The relative stabilities of these four conformat ions are well elucidated on the basis of solvent-solute interactions u sing two-dimensional radial distribution functions. Ab initio MO/GB ca lculations including the solvent effect via the generalized Born formu la gave similar results for the relative stabilities of the four confo rmations in solution. (C) 1997 Elsevier Science B.V.