Polarization Effects on Amino-Acid Conformation

A modified CNDO/2 method was used to calculate the conformational energy surface of zwitterionic glycine in a simulated polarizable environment. While the calculated global minimum for the in vacuo glycine zwitterion corresponds to an eclipsed conformation, the allowance of even a small degree of environmental polarisability inverts the relative stabilities of the staggered and eclipsed forms. The results indicate that in vacuo models may be unreliable, even for supposedly 'inert' media, and that the significance of environmental polarizability should be considered in the calculation of short-range potentials.