H-2-NMR STUDY OF MEMBRANES COMPOSED OF DI ACYL, ALKYLACYL, ACYLALKYL AND DIALKYL PHOSPHATIDYLCHOLINES

A comparative study of model membranes formed from 1-12-H-2(2)] mitoyl -rac-glycero-3-phospho-[gamma-H-2(3)]choline (H-2(5)-DPPC), 1-O-[2-H-2 (2)] mitoyl-rac-glycero-3-phospho-[gamma-H-2(3)]choline (H-2(5)-HPPC), adecyl-rac-glycero-3-phospho-[gamma-H-2(3)]choline (H-2(5)-PHPC), and mitoyl-rac-glycero-3-phospho-]gamma-H-2(3)]choline (H-2(5)-PHPC) in e xcess of water has been performed by H-2-NMR. The dynamics and conform ation of the labelled molecular segments have been estimated on the ba sis of the spin-lattice relaxation time and residual quadrupolar split ting. The mobility of the N-(CH3)-H-2 group has been shown to be the s ame in all membranes studied in both liquid crystalline and gel state. Quadrupolar splitting of N-(CH3)-H-2 groups increases in the order H- 2(5)-DPPC < H-2(5)-HPPC almost-equal-to H-2(5)-PHPC < H-2(5)-DHPC in g el and liquid crystalline membranes. The orientation of the 2-(CH2)-H- 2 segment in liquid crystalline membranes is the same for all lipids i nvestigated. The mobility of this fragment is lower in the membranes f ormed from H-2(5)-DPPC and H-2(5)-PHPC.