β‐STRUCTURE OF POLYPEPTIDES IN NON‐AQUEOUS SOLUTIONS: I. Spectral Characteristics of the Polypeptide Backbone

The optical rotatory features of the β‐structure of the polypeptides in nonaqueous solutions and films cast from these solutions have been investigated. The β‐structure of poly‐S‐benzyl‐L‐cysteine, poly‐S‐carbobenzoxy‐L‐cysteine and poly‐S‐benzyl‐L‐cysteine, poly‐S‐carbobenzoxy‐L‐cysteine and poly‐O‐carbo‐bands of their films. The optical rotatory dispersion (ORD) and circular dichroism (CD) spectra of these polypeptides are found to be very similar in both film and solution. In solvents promoting the β‐structure, the polypeptides are characterized by CD troughs in the n‐±* transition region of the peptide chromophore. The ORD spectra are found to be positive in sign throughout the visible and accessible ultraviolet regions and are interpreted in terms of the possible existence of a relatively much larger positive π‐π* CD band as compared with the negative π‐π* band. The rotatory data obtained in the non‐aqueous solution are compared with those obtained for other poly peptides in aqueous solutions, with respect to the type and extent of β‐structure present.

β‐STRUCTURE OF POLYPEPTIDES IN NON‐AQUEOUS SOLUTIONS: I. Spectral Characteristics of the Polypeptide Backbone Journal Articles