ENERGY-TRANSFER AMONG THE CHROMOPHORES IN PHYCOCYANINS MEASURED BY PICOSECOND KINETICS

Energy-transfer processes in the algal light-harvesting proteins, the phycocyanins, have been studied by means of picosecond absorption spectroscopy. After excitation at 530 nm, the absorption at several wavelengths in the range 480-669 nm decayed with a short time constant (picosecond) and a long time constant (>1 ns). For C-phycocyanin, energy transfer from the β to the α subunits is interpreted as being a likely candidate for the short time constant; the long time constant probably is the excitation lifetime of the chromophore on the α subunits. The time constants for energy transfer in monomers, trimers, and hexamers of C-phycocyanin extracted from a blue-green alga, Phormidium luridum, were measured as ~85, ~56, and ~32 ps, respectively. The corresponding time constant in the cryptomonad phycocyanin 645 from Chroomonas species was found to be less than 8 ps. © 1979, American Chemical Society. All rights reserved.