CIRCULAR DICHROISM OF VISUAL PIGMENTS IN THE VISIBLE AND ULTRAVIOLET SPECTRAL REGIONS

Abstract

Solutions of visual pigments displayed circular dichroism (CD) in association with the main absorption ([alpha]-band) in the visible region and, in rhodopsin as distinct from porphyropsin, also in the 0 -band. These CD-bands vanish upon bleaching. The ultraviolet CD was that of proteins with a predominantly [alpha]-helical conformation, and the CD in this region became reduced upon bleaching. The findings are discussed in comparison with the views of Hubbard and Wald on conformational changes in the visual pigments.