THE VISUAL PIGMENTS 



400 500 



Wavelength in mju 



Fig. 5.9. Comparison between the regeneration and bleaching difference 

 spectra of the carp pigment (523). Full-line curve, bleaching difference 

 spectrum; dashed-line curve, regeneration difference spectrum: O, 

 measurements made from 380 to 620 m/x; 0, return measurements 

 from 590 to 390 m/n. T = 20°C. 

 {Crescitelli and Dartnall, 1954) 



resynthesizing porphyropsin.' But no experimental details are given 

 and the species from which 'porphyropsin' was obtained is not 

 stated. 



CIS-TRANS ISOMERISM IN OTHER VISUAL 

 PIGMENTS 



We have seen (p. 144 et seq.) that for the synthesis of cattle 

 rhodopsin, a specific isomer of retinenej — «eo-retinenei b — is required. 



150 



