524 



Eiji Fujimori and Kenneth Quinlan 



chlorophylls in the light reactions of photosynthesis. 



When the cells of Porphyridium cruentum and Anacystis nidulans are 

 ruptured by sonic oscillation and treated with PCMB, the change of 

 absorption occurs only at the phycobilin band. The absorption and 

 fluorescence spectra of the phycobilins undergo the same changes as the 

 purified phycobilins. The fluorescence of chlorophyll excited by the 

 phycobilins also decreases. This decrease in fluorescence of chlorophyll 

 can be explained by the decrease in efficiency of the energy transfer from 

 the phycobilins to chlorophyll, since the longest wave-length chromophore 

 becomes inactive. 



The effects of PCMB on intact cells of both algae are different. Fig. 5 

 shows the gradual increase of fluorescence of phycoerythrin in Porphy- 

 ridium cruentum and the initial increase of chlorophyll fluorescence 

 followed by a subsequent decrease when phycoerythrin was excited. 

 Fig. 6 exhibits the continuous decrease of phycocyanin fluorescence and 

 the increase of chlorophyll fluorescence in Anacystis nidulans. The 

 increase in fluorescence of the phycoerythrin in Porphyridium cruentum 

 has been found to be due to the release of a modified fluorescent phy- 

 coerythrin from the cell by PCMB. This modified fluorescent phycoery- 

 thrin is different from the non-fluorescent one formed in isolated phy- 

 coerythrin treated with PCMB. Anacystis nidulans does not release any 

 pigment. The modified phycoerythrin exhibits only the 545 mpi band with 

 the inactive 565 m|jiband. The 500 m|ji chromophore component was 

 found to remain in the cell. The studies of modified fluorescent phycoery- 

 thrin will be reported elsewhere. The separation of modified phycoery- 

 thrin from the cell explains the subsequent decrease of energy transfer 

 from phycoerythrin to chlorophyll. The initial increase of the fluores- 

 cence of chlorophyll in Porphyridium cruentum and the continuous increase 

 in Anacystis nidulans may be the result of an efficient direct energy 

 transfer from the shorter wave-length chromophores to chlorophyll. It is 

 also suspected that the structural environment or arrangement of chloro- 

 phyll may have been changed, since a continuous increase in chlorophyll 

 fluorescence is observed in the PCMB-treated whole cells when chloro- 

 phyll is directly excited with blue light. 



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