164 



LIGHT AND LIFE 



Changes in the Absorption Spectra of Flavins and Flavoproteins 



Due to Specific Interactions 



Fig. 1 shows schematically a flavin or flavoprotein spectrum (dotted 

 line) and the various solid lines, appearing in different regions of the 

 spectrum, indicate the approximate shapes and positions of new ab- 

 sorption bands which have been observed under specific conditions 

 or with certain flavin compounds. The intensities of these bands 

 relative to the main flavin band at about 450 mjx are approximately 

 correct, except for the bands at 560 and 900 m^x, which are of much 



200 



400 



600 



800 



1000 



Fig. 1. .Schematic representation of flavin or flavoprotein spectrum (dotted line) 

 and spectral changes which occur on speciflc interactions or vvitii certain flavin com- 

 pounds (solid lines). 



lower intensity with free flavin compounds (1) . The bands observed 

 in the region between 500 and 1000 ni/x are all rather broad, extend- 

 ing over 100-200 ni/x, whereas those shown at shorter wavelengths 

 are more narrow and fall within about 20 m^x. Broad bands in the 

 latter region cannot be readily recognized because of the absorption 

 of the flavin itself. 



The 400-500 m^ Region 



It has long been known that a spectral shift toward longer wave- 

 lengths and a slight decrease of absorption occurs when flavin is 

 attached to adenine, as it is in flavin adenine dinucleotide (FAD) 



