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 bond in the fatty acid chains are studied by (2)H, (31)P NMR and Fourier transform infrared (FTIR) spectroscopy. The investigations are focused on the evaluation of the molecular properties of the lipid molecules as function of temperature and sample composition. Information about the fatty acid chain conformations are obtained from FTIR measurements by analysing the CH(2) wagging and stretching modes. (2)H NMR studies are performed on two selectively deuterated compounds that provide further insights into the molecular characteristics at two specific positions along the fatty acid chains. These studies demonstrate that the introduction of the triple bond is accompanied by a reduction of fatty acid chain order which holds for both the conformational and the orientational order. Likewise, (31)P NMR spectroscopy is used for the determination of the dynamics and ordering in the head group region. Here, particular emphasis is given to the evaluation of the lipid lateral motions that are quantified over a large temperature range within the liquid crystalline phase. It is found that the lateral mobility of the lipid molecules 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 DO(14-yne)PC, as can be followed by spin echo, 2D-exchange NMR and stimulated echo experiments.