NUMBER AND DISTRIBUTION OF CHROMOPHORE TYPES IN NATIVE PHYCOBILIPROTEINS

Abstract

Abstract— Fluorescence lifetimes and absolute quantum yields of a number of chromatographically pure phycobiliproteins have been determined. In conjunction with absorption, fluorescence emission and polarization spectra, these data were used to calculate the number of different types of chromophore, sensitizing and fluorescing, per chromoprotein. To characterize the spatial distributions of the chromophores, the observed emission anisotropies were compared with those calculated from models, using the Förster transfer mechanism and the Jablonski ‘active sphere’ approximation. The experimental values are more consistent with surface locations for the fluorescing chromophores rather than with their distribution throughout the volume. Theoretical efficiencies of transfer between sensitizing and fluorescing chromophores on the same macromolecule are consistent with those observed. The transfer efficiency from phycoerythrin prosthetic groups to chlorophyll a compared with that for transfer via phycocyanin indicates that the latter process is probably the favoured migration route.