Partial Analysis of the Bands Seen in Circular Dichroism Spectra of Green and Blue-Green Algal Cells and Thylakoids

Abstract

A comparison was made of the circular dichroism (C.D.) spectra of Chlorella, Eugkna, and Anacystis cells and thylakoids. Analyses of the spectra reveal that these C.D. bands are similar to those observed previously in whole spinach choloroplasts and subchloroplast particles. C.D. spectra of Euglena chloroplasts show bands at longer wavelengths than previously reported. From comparisons of circular dichroism spectra and fine structure, it was concluded that: (a) bands seen in circular dichroism spectra were not ihe result of light scattering from thylakoid membranes; and (b) bands seen in the C.D. spectra of nonmembranous systems (previously reported) could account for circular dichroism of algae. We also concluded that comparisons would have to be made with model systems in order to correct for effects of absorption flattening, concentration obscuring, and differential light scattering of membranous systems.Studies have been reported using circular dichroism techniques to elucidate chloroplast structure by comparison of the C.D.' spectra of Chl a in solution and as organized into membranes (particulate Chl). Dratz et al. (10) linolenic acid to a suspension of intact spinach chloroplasts (1, 21) resulted in the disappearance of the 683 nm band and a shift in the negative band from 672 nm back to 679 nm. Brody and Nathanson (1) and Nathanson (21) concluded that the 683 and 672 nm bands could be correlated with one species of Chl a and the 679 nm and 665 bands with another.