ABSTRACT
Polypeptides that are characterized by helical structures are, at the molecular level, noncentrosymmetric. However, in randomly oriented polypeptide films such as might be obtained by solvent evaporation, noncentrosymmetry is lost and the sample does not exhibit nonlinear optical (NLO) properties such second harmonic generation (SHG). Alignment of the molecular helices by application of an electric field across the solution with simultaneous evaporation of the solvent yields SHGactive films with relaxation times reported to be at least 6 months [1].
