COMPOSITION AND PHASE-BEHAVIOR OF POLAR LIPIDS ISOLATED FROM SPIRULINA-MAXIMA CELLS GROWN IN A PERDEUTERATED MEDIUM

The lipid composition of Spirulina maxima cells grown in a perdeuterat ed medium was determined by using nuclear magnetic resonance spectrosc opy, fast atom-bombardment-mass spectroscopy, gas chromatography, gas- chromatography-mass spectroscopy as well as conventional chemical meth ods. The extent of deuteration ws determined by mass spectrometry and was superior to 97.5%. The major lipids identified in the strain were: non-polar lipids (9%), monogalactosyldiacylglycerol (5%), digalactosy ldiacylglycerol (22%), phosphatidylglycerol (31%), sulfoquinovosyldiac ylglycerol (32%), phosphatidylinositol (traces). The major fatty acids were 16:0 (80%) and 18:1 (15%). These results demonstrate that the ad aptation of the cells to D2O did not imply a profound modification of the lipid composition. The perdeuterated polar lipid mixture dispersed into an excess of water organises spontaneously in a lamellar phase a s seen by P-31 and deuterium solid state NMR and can therefore be used to prepare perdeuterated model membranes with a well defined composit ion. Liposomes made using these lipids have a gel to liquid-crystallin e phase transition in the range 15-27 degrees and are in a fluid L(alp ha) phase above this temperature.