PHYCOBILINS 1789 



Legge suggested, for phycoerythrobilin, the structure III, with only five 

 conjugated double bonds. This seems, however, too short for a compound 

 with a strong absorption band in the green. (Lemberg and Legge said 

 that the spectroscopic properties of erythrobihn are similar to those of 

 mesobilin b — a compound with a structure of type III — but mesobilin h 

 is yellow and its first aljsorption band lies at 452 m/i in dioxane, and at 

 450 m/x in HCl + alcohol, while those of the red-violet erythrobilin lie 

 at about 530 and 560 ni/x, respectively.) (Only one band, at 498 m/x, 

 was listed in our table on p. 665; but Lemberg and Legge give, for erythro- 

 bilin in 5% HCl, two bands — at 560 and 495 m/x, respectively.) 



Lemberg and Legge refer to one difficulty, pointed out on p. 666 (Vol. II, 

 1): the implausibly high absolute values (3 X 10^) calculated for the molar 

 extinction coefficients of the phycolnlins. They suggest that the estimate 

 of 8 chromophores (ii/ = 536) per chromoproteid molecule {M = about 

 200,000) used in this calculation (about 2% phycobilin by weight !) has been 

 too low, and that the number of chromophores per chromoproteid molecule 

 may be as high as 16; the previously calculated molar extinction coef- 

 ficients will then have to be halved. 



The phycocyanin of Oscillatoria was hydrolyzed at 100° C. in 6 N HCl, 

 and subjected to fractionation by paper chromatography by Wassink and 

 Ragetli (1952). Sixteen amino acids were found, and 13 of them identi- 

 fied, one of the "unknowns" was a major component. Non-occurrence of 

 arginine is the only notable difference of the phycocyanin protein from the 

 proteins of Chlorella, or leaf chloroplasts, or hemoglobin. 



Swingle and Tiselius (1951) developed a chromatographic method for 

 the separation of phycochromoproteins. Its application led to the dis- 

 covery of several new pigments of this class. 



Koch (1953) found a new phycoenjthrin (in addition to the two or three 

 varieties encountered in Rhodophyceae and Cyanophijccae) in one of the 

 Bangiales, a rather primiti\'e red algal group; it is characterized by the 

 absence of the 495 myu absorption peak (c/. Fig. 21.39). 



A new phycocyanin was isolated chromatographically, from l)oth blue- 

 green and red algae, by Haxo, O'hEocha and Strout (1954), and tentatively 

 named "P-phycocyanin." It has a single absorption peak at 650 m/x, as 

 contrasted to the "R-phycocyanin" from red algae (which has peaks at 

 555 and 617 m^t), and the "C-phycocyanin" from blue-green algae (which 

 has a single peak at 615 m/tx, cf. Fig. 21.40). 



BUnks (1954) suggested that "R-phycocyanin" may be a complex of 

 C-phycocyanin (X^ax. 617 m/x) with phycoerythrin (A^ax. -555 m^u). The 

 evidence is electrophoretic and chromatographic ; in both types of experi- 

 ments, a mixture of the two pigments is observed to behave, under certain 

 conditions, as a single, anionic entity. 



