Membrane water-penetration profiles from spin labels.
Spin label hyperfine splittings in mixtures of protic and aprotic solvents are used to obtain association constants K(A,h) for hydrogen bonding to oxazolidine nitroxides. With the Onsager approach to account for the variation in local dielectric constant, these results are used to determine the effective penetration profile of water into fluid phospholipid membranes, from recent electron paramagnetic resonance (EPR) studies on phospholipids spin-labelled systematically down the sn-2 chain. Water penetration is appreciable, depends on chain unsaturation, and is strongly affected by cholesterol.
Marsh
Derek
D
Max-Planck-Institut für biophysikalische Chemie, Abteilung Spektroscopie, 37070 Göttingen, Germany. dmarsh@gwdg.de
D015060:1,2-Dipalmitoylphosphatidylcholine / Q000737:chemistry; D002463:Cell Membrane Permeability; D003198:Computer Simulation; D003497:Cyclic N-Oxides / Q000737:chemistry; D004058:Diffusion; D004578:Electron Spin Resonance Spectroscopy / Q000379:methods*; D006860:Hydrogen Bonding; D008051:Lipid Bilayers / Q000737:chemistry*; D008563:Membrane Lipids / Q000737:chemistry*; D008567:Membranes, Artificial; D008956:Models, Chemical; D008958:Models, Molecular; D010713:Phosphatidylcholines / Q000737:chemistry; D012996:Solutions / Q000737:chemistry; D012997:Solvents / Q000737:chemistry; D013113:Spin Labels; D013229:Stearic Acids / Q000737:chemistry; D014867:Water / Q000737:chemistry*
C116482:5-(N-oxyl-4,4-dimethyloxazolodine)stearic acid; D003497:Cyclic N-Oxides; D008051:Lipid Bilayers; D008563:Membrane Lipids; D008567:Membranes, Artificial; D010713:Phosphatidylcholines; D012996:Solutions; D012997:Solvents; D013113:Spin Labels; D013229:Stearic Acids; D014867:Water; D015060:1,2-Dipalmitoylphosphatidylcholine; C017251:1,2-oleoylphosphatidylcholine; C028694:1-palmitoyl-2-oleoylphosphatidylcholine