FLUORESCENCE, ENERGY TRANSFER, AND SH-GROUPS IN PHOTO- 

 SYNTHETIC PIGMENTS OF RED AND BLUE-GREEN ALGAE 



Eiji Fujimori and Kenneth Quinlan 



The phycobilins of the red and blue-green algae have been shown to 

 have the unique property of utilizing light energy more efficiently in 

 photosynthesis than chlorophyll a. Duysens ^ ' has shown that the energy 

 absorbed by phycoerythrin in red algae is transferred mainly to fluorescent 

 chlorophyll, with a smaller amount to the weakly or non-fluorescent 

 chlorophyll. Spectral studies of the phycobilins show that more than one 

 type of chromophore exist in the chromoproteins ^ K Phycoerythrins and 

 phycocyanins exhibit various numbers of absorption maxima in the visible 

 which are due to different types of chromophore. At present time, the 

 energy interactions of the chromophores within the same pigment-protein 

 complexes as well as those between the different types of chromophore in 

 the phycobilins and the different forms of chlorophyll are not clear. A 

 spectral study of the phycobilins in vivo and in vitro may shed light on the 

 function of the different chromophores in photosynthesis and their rela- 

 tionship to the chlorophylls. 



Modifying the structure of the protein associated with the photosynthe- 

 tic pigments may induce changes in the spectral and photochemical pro- 

 perties of the chromophores. These changes may elucidate the types of 

 energy interaction between the different pigments. This paper reports the 

 results of a study of the effect of the sulfhydryl blocking agent, p-chloro- 

 mercuribenzoate (PCMB), on purified phycoerythrin and phycocyanin. 

 These results are correlated with the changes induced by PCMB on the 

 ruptured and whole cells of red and blue-green algae. Newton '^ has 

 shown that disulfide and sulfhydryl groups play a role in the energetics of 

 photosynthetic bacteria. 



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