Raman spectroscopy of secondary structure of elastinlike polymer poly(GVGVP)

Raman spectra of the elastinlike polypentapeptide poly(GVGVP) were measured in H(2)O and D(2)O as solutions and, after increasing the temperature, as suspensions and sediments. In addition, spectra of the polypentapeptide in the solutions of increasing concentration and in the solid state were also investigated by gradually evaporating the water. Significant changes in band frequencies, intensities, and shapes were found for selected Raman bands in the measured spectra, particularly for the C-H stretching, the glycine CH(2) wagging, and some amide vibrations. The C-H stretching vibrations are influenced predominantly by the presence of water, the glycine CH(2) wagging vibrations are associated with conformational transitions. Three possible types of poly(GVGVP)s in the presence of water were indicated: polymer chains in a relatively extended state in the solution, a beta-spiral structure in the suspension, and irregularly bent chains in the sediment.