118 IV. BILE PIGMENTS 



compared with that in the visible part of the spectrum, but low if 

 compared with the Soret band of porphyrins or hematin compounds. 

 Complex salts. Although the zinc complex salts of bilatrienes do 

 not fluoresce (possibly they fluoresce in the infrared) and have the 

 same color as the free biliverdins, there is nevertheless a change of 

 the absorption spectrum with shift of the maximum toward the red 

 (mesobiliverdin-zinc, 685 m/x). By a spectrophotometric study of 

 the complex salt formation, it could be shown that one atom of zinc 

 combines with one molecule of biliverdin {1680,1688). This is only 

 possible if the biliverdin reacts in cyclic form and if one of the hydroxy- 

 lated pyrrole rings is in lactim, the other in lactam, form; probably 

 the whole molecule is in resonance through a hydrogen bond between 

 the OH group and the doubly linked oxygen atom : 



HC 



The formula is supported by the observation of Fischer and collab- 

 orators (864) that bilatrienes with methoxyl instead of hydroxyl 

 groups did not form zinc complex salts. The significance of this 

 observation for the problem of the structure of verdohemochrome 

 will be discussed in Chapter X. 



Bivalent copper forms a similar complex of olive color (1680). The 

 absorption bands of the copper complexes usually lie nearer the infra- 

 red than those of the corresponding zinc complexes, and in this 

 instance the absorption band lies partly in the infrared (3556). 

 Excess bivalent copper oxidizes the copper biliverdins to copper 

 bilipurpurins. 



4. BILADIENES-(a,c). RUBINS 

 4.1. Structure 



This structure of the bilirubins was established by Fischer and his 

 co-workers, both from the study of the degradation products of meso- 

 bilirubin in the resorcinol melt (Section 1.2.) and by synthesis (Section 



