Solvent Effects in Calculated Vibrational Raman Optical Activity Spectra of α-Helices

We study the influence of solvation effects on vibrational Raman optical activity spectra of a-helices by means of quantum chemical calculations. Solvent effects are considered in the calculations via the conductor-like screening model COSMO and, in addition, via explicit water molecules. The so-called external type of hydration is employed. In this hydration pattern, the water molecules form hydrogen bonds to the carbonyl groups of the alpha-helical (Ala)(20) model. It is found that the amide I bands are significantly shifted to lower wavenumbers if solvent effects are incorporated into the calculations. These computational results, obtained within the static picture employed in this work, suggest that the amide I bands may serve as a signature for the hydration of alpha-helices.