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 representative conformations of the glycine zwitterion (GLYZ) in aqueous solution. The (phi,theta)=(0,0) and (60,0) conformations, in which the dihedral angle theta between the NCC and CCO planes is 0 degrees, were found to be more stable than the (0,90) and (60,90) conformations, in which theta=90 degrees. The relative stabilities of these four conformations are well elucidated on the basis of solvent-solute interactions using two-dimensional radial distribution functions. Ab initio MO/GB calculations including the solvent effect via the generalized Born formula gave similar results for the relative stabilities of the four conformations in solution. (C) 1997 Elsevier Science B.V.