Rayleigh scattering properties of small polyglycine molecules

Density-functional theory calculations of the Rayleigh optical activities of small isolated polyglycine molecules are reported. Fully extended beta-sheet-like conformations of polypeptides of glycine, (Gly)(n) (with n = 1-5) are considered. After geometry optimizations, dipole moments and dipole polarizabilities (both the mean and the anisotropic components) are calculated using the B3LYP and B3P86 functionals in three basis sets. The polarizabilities are used to analyze the Rayleigh scattering activities and depolarization ratios. The convergence of the average dipole polarizability per monomer is analyzed. The differences in activity and depolarization for Rayleigh scattered radiation between the extended beta-sheet-like and the folded alpha-helix-like forms of tetraglycine are analyzed and found to be relevant, suggesting its possible use in experimental characterization. (c) 2005 Elsevier B.V. All rights reserved.