35C) 



RADIATION BIOLOGY 



photosynthesis. In some species it has been definitely demonstrated that 

 certain carotenoids function in photosynthesis by the absorption of fight, 

 which is then transferred to chlorophyll. Absorption curves of a few of 

 the more common carotenoids of particular significance in photosynthesis 

 are presented in Fig. 6-5; the bacterial carotenoids will be discussed in a 

 later section of this chapter. 



o 



Q. 



a: 

 o 

 in 

 m 

 <i 



o 

 <_> 



UJ 



300 



200 



100 





 500 



400 

 300 

 200 

 1 00 



I — I — I — I — I" 



fa) 



"r~n" 



a'-CAROTENE 



300 



(6) 



/3-CAROTENE 



(r) 



UJ 



< 

 o 





400 



500 



400 



LUTEIN 



500 



FUCOXANTHIN 



i~rT 



200 



300 



LU 



_l 

 < 



I 

 I- 



o 

 o 



u. 



140 



120 



100 



80 



60 



40 



20 



400 

 WAVE LENGTH , m^ 



Fig. 6-5. The absorption spectra of a few common carotenoids in hexane. 

 a-Carotene. (Zscheile et al, 1942.) (6) /3-Carotene. {Zscheile et al, 1942.) 

 Lutein (xanthophyll) and fucoxanthin. (Karrer and Jucker, 1950.) 



(a) 

 (c) 



Phycohilins. The water-soluble phycobilins have not been investigated 

 so thoroughly as the chlorophylls, since they are not so common, being 

 restricted to red algae, blue-green algae, flagellates, dinoflagellates, and 

 diatoms. Some of these pigments are extractable as water-soluble 

 chromoproteins. Therefore the absorption curves of their extracts do 

 not differ appreciably from those within the living organisms. These 

 chromoproteins have the characteristics of plant globulins (Lemberg and 

 Legge, 1949, p. 184). The prosthetic groups can be split off by drastic 

 action of acid (Lemberg, 1929, 1930a) and have been identified as meso- 

 bili violin for phycocyanin and mesobilierythrin for phycoerythrin (ibid.; 



