Optical rotatory dispersion of poly‐<scp>L</scp>‐tyrosine in solution

Abstract

Abstract This paper consists of a theoretical discussion of exciton band contributions to the optical rotatory dispersion of polypeptides in a specific context, namely that of poly‐ L ‐tyrosine in solution in α‐helix form. The calculated results when compared with existing data suggest that poly‐ L ‐tyrosine in aqueous solution at pH &lt; 11.2 as studied by Fasman et al. and Beychok et al. is of right‐handed α‐helix conformation. Poly‐β‐ L ‐aspartate esters on the other hand are shown definitely to be of left‐handed conformation. Although there are undoubtedly interactions between neighboring side groups there is no evidence in optical rotatory dispersion data of existence of a stable helical arrangement of the side groups in poly‐ L ‐tyrosine. The NV 1 exciton contributions below 1900 A. should provide reliable measures of the helix content and handed ness of the helix in polypeptides, and experimental techniques for the wavelengths below 1900 A. should be developed.