304 



RADIATION BIOLOGY 



cells. Recent observations on sensitized fluorescence suggest that, never- 

 theless, in the intact cell a close connection exists between chlorophyllin 

 and phycocyanin. 



H,C 



/ 



CH:CH2 HjC 



Mg _ 



CoH 



2^5 



CH 



H:.C 



H.C 



_^N <' 





CH:CH2 H3C 



Mg, 



CH2 



CH, 



H,C 



CH 



2 I 



H39C2o02C COgCHj 



C55H7005N4Mg 



(a) 



H3C 



I • CHp .-N. 



H H CHg I ^ 



H39 CaoOgC CO2CH3 



C55H72 05N4Mg 

 ib) 



f 



H 



CHCHj 0- C 



H 



C?Hr 



HC 



H3C 



_Mg_ 

 = c- 



\ 



CH 



/ 



H H 



CHj 

 CHp 



CH, 



H39C2o02C C02CH3 



(c) 



^2^5 



N ^\ 



C 



CH, 



H,C 



C 



H,C 



COCH, 



Mg , 



/ 



CH, 



H 



CH, 



H,C 



H "r"? I 



H39C2QO2C C02CH3 

 C55H7206N4 Mg 



CpH 



2"5 



H3C 





CH 





CH, 



H3C1 



COCH3 H3C 



H 

 C 



C2H5 



Mg 



/ch' l^c 



H H CH2 I ■■ 



'\ 



( 



CH, 



•^39^2002^ 



CO2 CH3 

 C55H7406N4Mg 



Fig. 5-6. Formulas of various chlorophylls, (a) Protochlorophyll; (6) chlorophyll a; 

 (c) chlorophyll b; (rf) bacterioviridin; (e) bacteriochlorophyll. (After Fischer and 

 Orth, 1940.) 



The energy absorbed by some carotenoids (as will be discussed later) 

 is active in photosynthesis. As far as is known, these carotenoids act 

 through chlorophyll as an intermediate since they also give rise to 

 chlorophyll fluorescence (Button and Manning, 1941; Button et al., 1943; 

 Wassink and Kersten, 1946-1948). An important question is whether 



