54 



SUBCELLULAR PARTICLES 



0.4 



03 



0.2 



o 



J3 



J3 

 < 



02M p-Benzoquinone 

 24° C. 75 hrs. 

 ( Supernatant) 



• With fibrin 



o Control 



\ 



c 



\ 



\y 



pH 5.5 



Xo:^ 



pH 8.8 





Fig. 



400 500 600 400 500 600 



Effect of fibrin and pH on spectral features of quinone reaction products. 



unique products or mixtures are associated with each of the proteins used, and 

 with specific fractions as well. 



Relation of Synthetic Polyquinones to Melanins. The absorption curves of sev- 

 eral polyquinone fractions resembled the spectrum of pigment extracted from a 

 poriferan, Eiispongia, the similarity prompting a broader comparison of poly- 

 quinones with natural melanins. The spectrum of the sponge pigment is distinct 

 from polyquinones formed in matrix-free systems and all fractions formed under 

 the influence of fibrin, but is approximated in varying degrees by three fractions 

 from the collagen system (fig. 9), a finding of interest in view of the occurrence 

 of collagen in the porifera (27). All of the synthetic products appear to be less 

 homogeneous than the natural product, a condition also to be met with in com- 

 parison of natural and synthetic lignins. 



Other similarities noted were: ^7) between an ethanol fraction formed with 

 fibrin at pH 8.8 and black guinea pig melanin (13); and b) between aqueous 

 fractions formed with fibrin at pH 5.5 and the pigment from the endoskeleton 

 of the alcyonarian, Pterogonia (fig. 10). 



In no instance has it been claimed that exact replication of a native melanin 

 has been accomplished. Nevertheless, when the several kinds of analytical and 

 comparative evidence are taken together it is clear that substances fitting the 

 generic concept of melanins (13, 23, 7) can be formed, particularly under the 

 influence of proteins. It is further gratifying to note that the possible significance 

 of a polymerization-ordering protein surface has already been recognized in rela- 

 tion to the question of pigment granule formation (21), and it is perhaps not 

 unreasonable to suggest that a biologically meaningful model of the melanin 



