Solid-state NMR and FTIR studies on bilayer membranes from 1,2-dioctadec-(14-ynoyl)-sn-glycero-3-phosphatidylcholine

Multilamellar dispersions from a new model phospholipid, 1,2-dioctadec-(14- ynoyl)-sn-glycero-3-phosphatidylcholine (DO(14-yne)PC), bearing a triple bo nd in the fatty acid chains are studied by H-2, P-31 NMR and Fourier transf orm infrared (FTIR) spectroscopy. The investigations are focused on the eva luation of the molecular properties of the lipid molecules as function of t emperature and sample composition. Information about the fatty acid chain c onformations are obtained from FTIR measurements by analysing the CH2 waggi ng and stretching modes. H-2 NMR studies are performed on two selectively d euterated compounds that provide further insights into the molecular charac teristics at two specific positions along the fatty acid chains. These stud ies demonstrate that the introduction of the triple bond is accompanied by a reduction of fatty acid chain order which holds for both the conformation al and the orientational order. Likewise, P-31 NMR spectroscopy is used for the determination of the dynamics and ordering in the head group region. H ere, particular emphasis is given to the evaluation of the lipid lateral mo tions that are quantified over a large temperature range within the liquid crystalline phase. It is found that the lateral mobility of the lipid molec ules is almost unaffected by the triple bond in the fatty acid chains. The addition of cholesterol gives rise to a reduction in lateral mobility for D O(14-yne)PC, as can be followed by spin echo, 2D-exchange NMR and stimulate d echo experiments. (C) 1999 Elsevier Science B.V. All rights reserved.