Crystalline Phycobilin Ghromoproteids Obtained from a Blue-Green Alga, Tolypothrix Tenuis

Abstract

There is an extensive literature dealing with the physical and chemical nature of phycobilin pigments —phycocyanin, phycoerythrin and allophy–cocyanin— which represent, besides chlorophylls and carotenoids, important colored constituents of red and blue-green algae. From various red algae, which had mostly been used as materials in earlier studies of these pigments, phycoerythrin and phycocyanin have been isolated in crystalline state (1-3). Using a blue-green alga, Aphanizomenon flos aquae, as a material, Svedberg and K a t s u r a i (4) obtained phycocyanin, but not phycoerythrin, in crystalline form. In contrast to these substances, allophycocyanin has never been isolated in pure form, and consequently little has been known about its physicochemical properties. The data reported on the physicochemical nature of the crystalline preparations of phycoerythrin and phycocyanin also seem to require reconsideration, since the sample studied by earlier workers were those obtained by simple repetition of salting-out procedures and, therefore, could not fully claim their chemical purity. Recently, H a x o et al. (5) applied for separating the pigments the chromatographic technique using tricalcium phosphate-gel as originally attempted by S w in gel and T i s e 1 i u s (6). By this method H a x o et al. succeeded in separating the three pigments in a clear-cut manner, although they did not proceed to the crystllization of each component. The present work is concerned with the isolation and crystallization of the three phycobilin pigments by combined use of salting-out method and adsorption method. The algal material used was Tolypothrix tenuis, a fresh water bluegreen alga having the capacity of nitrogen fixation. Using the purified samples, the physical and chemical properties of each pigment were investigated in detail, and based on the results obtained, a critical appraisal was made of the reported by earlier workers.