Photosynthetic Activities of Membrane Preparations of the Blue‐Green Alga Phormidium luridum

Techniques have been developed for the isolation of whole spheroplaste and membrane preparations from the blue-green alga Phormidium luridum which are active in photosystem-II-sensitized and photosystem-I-sensitized electron-transport reactions and in photophosphorylation. Attention is called to the necessity of supplying magnesium and phosphate throughout the preparative and assay procedures for obtaining active membranes. Selective washing of a proper membrane preparation is shown to remove a new protein factor, termed protein factor 1, which restores the ability of the preparation ot catalyze photosystem-I-sensitized reactions.