title: Lateral diffusion rates of lipid, water, and a hydrophobic drug in a multilamellar liposome.
abstract: The lateral diffusion constants of 1-palmitoyl-2-oleoyl-sn-glycero-3 phosphocholine (POPC), water, and ibuprofen were measured in multilamellar liposomes using pulsed field gradient magic-angle spinning (PFG-MAS) (1)H NMR. The analysis of diffusion data obtained in powder samples and a method for liposome curvature correction are presented. At 322 K POPC has a diffusion constant of (8.6 +/- 0.2) x 10(-12) m(2)/s when dehydrated (8.2 waters/lipid) and (1.9 +/- 0.1) x 10(-11) m(2)/s in excess water. The diffusion constant of water in dehydrated POPC was found to be (4.7 +/- 0.1) x 10(-10) m(2)/s. The radius of curvature is 21 +/- 2 microm for the dehydrated sample and 4.5 +/- 0.5 microm for POPC sample containing excess water. The activation energies of diffusion are 40.6 +/- 0.4 kJ/mole for dehydrated POPC, 30.7 +/- 0.9 kJ/mole for POPC with excess water, and 28.6 +/- 1.5 kJ/mole for water in dehydrated POPC. The diffusion constants and activation energies for a sample of POPC/ibuprofen/water (1:0.56:15) were also measured. The ibuprofen, which locates in the lipid-water interface, diffuses faster than POPC but has a slightly higher activation energy of lateral diffusion. Within certain restrictions, PFG-MAS NMR provides a useful method for characterizing membrane organization and mobility.
authors.affiliation: Laboratory of Membrane Biochemistry and Biophysics, National Institute on Alcohol Abuse and Alcoholism, National Institutes of Health, Rockville, Maryland 20852, USA.
authors.forename: Holly C
authors.initials: HC
authors.lastname: Gaede
authors.forename: Klaus
authors.initials: K
authors.lastname: Gawrisch
mesh_terms: D000894:Anti-Inflammatory Agents, Non-Steroidal / Q000494:pharmacology; D055592:Biophysical Phenomena; D001703:Biophysics; D002138:Calibration; D004058:Diffusion; D007052:Ibuprofen / Q000494:pharmacology; D008051:Lipid Bilayers / Q000737:chemistry*; D008055:Lipids / Q000737:chemistry*; D008081:Liposomes / Q000737:chemistry*; D009682:Magnetic Resonance Spectroscopy; D008956:Models, Chemical; D010713:Phosphatidylcholines / Q000737:chemistry*; D013696:Temperature; D013997:Time Factors; D014867:Water / Q000737:chemistry*
chemical_list: D000894:Anti-Inflammatory Agents, Non-Steroidal; D008051:Lipid Bilayers; D008055:Lipids; D008081:Liposomes; D010713:Phosphatidylcholines; D014867:Water; C028694:1-palmitoyl-2-oleoylphosphatidylcholine; D007052:Ibuprofen