THE STRUCTURE OF VISUAL PURPLE (RHODOPSIN) 



ferment, the chromophores of which are based on the carotenoids 

 astaxanthene and flavin, respectively. 



Visual purple solutions of a high standard of purity have now been 

 prepared, notably by wald (1949) and by collins, love and 

 MORTON (1952). The density spectrum of visual purple (Fig. 4.1) is 

 characterized by three bands. The most important of these is the 



_| I I I I I I I I I I I I I I I I i I I I I I I i I I I I I I I I i I, 



250 



300 



350 400 450 



Wavelength in mp 



500 



550 



600 



Fig. 4.1. Analysis of the density spectrum of visual purple. O O O, 

 density spectrum of a pure solution of cattle visual purple (pH 9-2) ; 

 # # #, ditto after bleaching (the C-band is unaffected) ; x x x 

 Goodeve, Lythgoe and Schneider's photosensitivity data for frog visual 

 purple, equated at 500 m/u to the density spectrum. The non-photo- 

 sensitive C-band can be accounted for by tyrosine and tryptophan, as 



indicated. 



(Modified after Collins, Love and Morton, 1952) 



97 



