[Fractionation of phycobilisomes from the blue-green alga Nostoc muscorum]

Phycobilisomes (PBS) isolated from Nostoc muscorum contain eight spectral forms of phycobiliproteins. PBS partially dissociated by osmotic or temperature shock, were separated into 42S and 34S particles by centrifugation in sucrose density gradient. The 42S particles are enriched with phycocyanin, the 34S ones--with allophycocyanin. The 42S particles dissociate to free pigments by repeated osmotic or temperature shock and the 34S ones dissociate to subparticles I and II having the constant pigments composition. The integrity of PBS and isolated substructures is controlled by the yield of energy transfer between pigment molecules. PBS from Nostoc muscorum was found to contain the rods of three different types. The model PBS containing different spectral forms of biliproteins is proposed.