EXPERIMENTAL AND COMPUTATIONAL INFRARED CD STUDIES OF PROTOTYPICAL PEPTIDE CONFORMATIONS

The infrared vibrational circular dichroism (VCD) spectral features of prototypical peptide secondary structures were reported previously by Yasui and Keiderling [Yasui, S. C., & Keiderling, T. A. (1986) Biopolymers 25, 51. These results demonstrated that the "random coil' peptide conformation exhibits VCD signals which are approximately mirror-image features of those exhibited by alpha-helical conformers. We report here a comparison of observed VCD spectra with those computed for several secondary structures, using the extended coupled oscillator formalism employed previously to compute VCD spectra of model DNA [Zhong et al. (1990) Biochemistry 29, 7485]. These studies suggest that the so-called random-coil peptide conformation has distinct short-range order and appears to be a left-handed, helical structure.