CONFORMATION OF POLYMERIZABLE DIACETYLENIC LECITHIN, DC8,9PC, BY H-1-NMR SPECTROSCOPY

Diacetylenic phospholipid, 1,2 tricosa-10,12-diynoyl)-sn-glycero-3-pho sphocholine (DC8,9PC), forms helices and tubules in addition to liposo mes. The diacetylenic moiety responsible for the transformation is pro bed by 2-D NMR correlated spectroscopy. Chemical shift assignments and the analysis of 2D-COSY measurements were done on the lipid in chloro form-d solution. Based on this analysis, a model for the lipid is prop osed. The geometry of the headgroup, glycerol backbone and acyl chains up to three methylenes from glycerol backbone [-(CH2)(3)-] is similar to that of dipalmitoyl phosphatidylcholine. The estimated torsional a ngle for methylene groups adjacent to diacetylenic moieties suggested an overall tilt of the diacetylenic lipid molecule from the bilayer ax is of 25-30 degrees. This tilt could be negative or positive depending on the handedness of the resultant microstructures.