Incorporation of fatty acids containing photosensitive groups into phospholipids of Escherichia coli.

A series of new fatty acids containing photosensitive groups at different positions on the paraffin chains supported the growth of an auxotroph of E. coli requiring unsaturated fatty acids. The derivatives were 6-, 9-, 11-, and 12-azidostearic acids, 12-azido-oleic acid, 16-azidopalmitelaidic acid, and 12-(4-azido-2-nitrophenoxy)-stearic and -oleic acids. Analyses of the phospholipids from cultures grown in the presence of the first six compounds showed that these derivatives accounted for 16-43% of the total fatty acids. Further analysis of phospholipids from cultures grown with 12-azido-oleic acid, 11-azidostearic acid, or 16-azidopalmitelaidic acid indicated that the azido fatty acids were at the 2-position of the glycerol moieties. The incorporation of these fatty acid derivatives offers a new approach to the study of membrane structure and, in particular, phospholipid-protein interactions by photolysis-induced crosslinking of the fatty acids to the structures in their immediate vicinity.