Molecular order and dynamics of phosphatidylcholine bilayer membranes in the presence of cholesterol, ergosterol and lanosterol: a comparative study using 2H-, 13C- and 31P-NMR spectroscopy. 1995

J A Urbina, and S Pekerar, and H B Le, and J Patterson, and B Montez, and E Oldfield
Department of Chemistry, University of Illinois at Urbana-Champaign 61801, USA.

We report the results of a comparative study of the molecular order and dynamics of phosphatidylcholine (PC) bilayer membranes in the absence and presence of cholesterol, ergosterol and lanosterol, using deuterium (2H) nuclear magnetic resonance (NMR) of deuterated phospholipid molecules, in addition to solid state 13C and 31P-NMR. Using dimyristoylphosphatidylcholines (DMPCs) specifically labeled at positions 2', 3', 4', 6', 8', 10' and 12' of the sn-2 chain together with the perdeuterated 2-[2H27]DMPC derivative, the order profile for 9 of the 13 methylene groups of the sn-2 chain was established at 25 degrees C for DMPC, DMPC/cholesterol, DMPC/ergosterol and DMPC/lanosterol membranes, at a fixed sterol/phospholipid mol ratio of 30%, and in the presence of excess water. The overall ordering effects were found to be ergosterol > cholesterol >> lanosterol. Transverse relaxation (T2e) studies of these systems indicated that while for DMPC, DMPC/cholesterol and DMPC/ergosterol the relative relaxation rates were in qualitative agreement with models which assume cooperative motions of the bilayer molecules as the main relaxation mechanism, those in DMPC/lanosterol were anomalously high, suggesting alterations of lipid packing. Using dipalmitoylphosphatidylcholine (DPPC) deuterated at the trimethylammonium group of the choline moiety, we found that the differential ordering and motional effects induced by the sterols in the acyl chains were also reflected in the headgroup, both in the gel (L beta) and liquid-crystalline phases. 13C and 1H spin dynamics studies of these systems, including cross-polarization, rotating frame longitudinal relaxation and dipolar echo relaxation rates showed that the mobility of the different regions of the phospholipid molecules in the binary lipid systems were inversely correlated with the ordering effects induced by the sterols. A novel combination of C-D bond order parameters (obtained by 2H-NMR) and 13C-1H cross polarization rates confirmed these results. The effects of the same sterols at the same molar proportion on the unsaturated lipid 1-[2H31]palmitoyl-2-oleoyl-sn-glycero-3-phosphatidylcholine (2H31-POPC) at 25 and 35 degrees C were different from those observed on DMPC and showed ordering effects which are largest for cholesterol, while ergosterol and lanosterol produced significantly smaller effects. Transverse relaxation studies indicate that while cholesterol does not perturb cooperative motions in POPC, both ergosterol and lanosterol do. Again, high-resolution solid state 13C-NMR studies support the conclusions of the 2H-NMR experiments.(ABSTRACT TRUNCATED AT 400 WORDS)

UI MeSH Term Description Entries
D007810 Lanosterol A triterpene that derives from the chair-boat-chair-boat folding of 2,3-oxidosqualene. It is metabolized to CHOLESTEROL and CUCURBITACINS. Kryptosterol,4,4,14 alpha-trimethyl-5 alpha-cholesta-8,24-dien-3 beta-ol
D008051 Lipid Bilayers Layers of lipid molecules which are two molecules thick. Bilayer systems are frequently studied as models of biological membranes. Bilayers, Lipid,Bilayer, Lipid,Lipid Bilayer
D009682 Magnetic Resonance Spectroscopy Spectroscopic method of measuring the magnetic moment of elementary particles such as atomic nuclei, protons or electrons. It is employed in clinical applications such as NMR Tomography (MAGNETIC RESONANCE IMAGING). In Vivo NMR Spectroscopy,MR Spectroscopy,Magnetic Resonance,NMR Spectroscopy,NMR Spectroscopy, In Vivo,Nuclear Magnetic Resonance,Spectroscopy, Magnetic Resonance,Spectroscopy, NMR,Spectroscopy, Nuclear Magnetic Resonance,Magnetic Resonance Spectroscopies,Magnetic Resonance, Nuclear,NMR Spectroscopies,Resonance Spectroscopy, Magnetic,Resonance, Magnetic,Resonance, Nuclear Magnetic,Spectroscopies, NMR,Spectroscopy, MR
D010713 Phosphatidylcholines Derivatives of PHOSPHATIDIC ACIDS in which the phosphoric acid is bound in ester linkage to a CHOLINE moiety. Choline Phosphoglycerides,Choline Glycerophospholipids,Phosphatidyl Choline,Phosphatidyl Cholines,Phosphatidylcholine,Choline, Phosphatidyl,Cholines, Phosphatidyl,Glycerophospholipids, Choline,Phosphoglycerides, Choline
D010759 Phosphorus Isotopes Stable phosphorus atoms that have the same atomic number as the element phosphorus, but differ in atomic weight. P-31 is a stable phosphorus isotope. Isotopes, Phosphorus
D002247 Carbon Isotopes Stable carbon atoms that have the same atomic number as the element carbon but differ in atomic weight. C-13 is a stable carbon isotope. Carbon Isotope,Isotope, Carbon,Isotopes, Carbon
D002784 Cholesterol The principal sterol of all higher animals, distributed in body tissues, especially the brain and spinal cord, and in animal fats and oils. Epicholesterol
D003903 Deuterium The stable isotope of hydrogen. It has one neutron and one proton in the nucleus. Deuterons,Hydrogen-2,Hydrogen 2
D004875 Ergosterol A steroid occurring in FUNGI. Irradiation with ULTRAVIOLET RAYS results in formation of ERGOCALCIFEROL (vitamin D2). Lumisterol,Pro-Vitamin D2,Provitamin D 2,D2, Pro-Vitamin,Pro Vitamin D2

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