Vibrational circular dichroism of polypeptides. III. Film studies of several α‐helical and β‐sheet polypeptides

Abstract

Abstract Vibrational CD (VCD) of amides A, I, and II vibrations of a variety of polypeptide films have been measured. VCD of films of α‐helical and β‐sheet structures are compared in the three regions. Reproducible spectra could only be obtained for thin films free of orientation dependence. The sign and band shape of the VCD of films are not always the same as that in solution. However, the magnitude of the observed VCD seems to correlate with the secondary structure such that α‐helical molecules typically have much larger Δε/ε values than do β‐sheet molecules. The possibility of interference by artifacts owing to light‐scattering effects is discussed.