Deuterium nuclear magnetic resonance studies of bile salt/phosphatidylcholine mixed micelles.
Mixed micelles of deoxycholate (DOC) and 1-palmitoyl-2-oleoylphosphatidylcholine (POPC) have been prepared in which the POPC was specifically deuterated in the 2-, 6-, 10-, or 16-position of the palmitoyl chain or in the N-methyl position of the choline head group. The deuterium nuclear magnetic resonance (2H NMR) spectrum of each of these specifically deuterated mixed micelles consists of a singlet whose line width depends upon the position of deuteration. Spin-spin relaxation times indicate a gradient of mobility along the POPC palmitoyl chain in the mixed micelle, with a large increase in mobility on going from the 10- to the 16-position. Spin-lattice relaxation times (T1's) demonstrate a similar gradient of mobility. Both trends in NMR relaxation behavior are consistent with a bilayer arrangement for the solubilized POPC. 2H T1 times for DOC/POPC micelles are significantly shorter than those measured in other bilayer systems, indicating unusually tight phospholipid acyl chain packing in the mixed micelle.
D003840:Deoxycholic Acid; D006801:Humans; D008051:Lipid Bilayers; D009682:Magnetic Resonance Spectroscopy; D008823:Micelles; D008954:Models, Biological; D008968:Molecular Conformation; D010713:Phosphatidylcholines
D008051:Lipid Bilayers; D008823:Micelles; D010713:Phosphatidylcholines; D003840:Deoxycholic Acid; C028694:1-palmitoyl-2-oleoylphosphatidylcholine