Solubility and diffusion of oxygen in phospholipid membranes.
The transport of oxygen and other nonelectrolytes across lipid membranes is known to depend on both diffusion and solubility in the bilayer, and to be affected by changes in the physical state and by the lipid composition, especially the content of cholesterol and unsaturated fatty acids. However, it is not known how these factors affect diffusion and solubility separately. Herein we measured the partition coefficient of oxygen in liposome membranes of dilauroyl-, dimiristoyl- and dipalmitoylphosphatidylcholine in buffer at different temperatures using the equilibrium-shift method with electrochemical detection. The apparent diffusion coefficient was measured following the fluorescence quenching of 1-pyrenedodecanoate inserted in the liposome bilayers under the same conditions. The partition coefficient varied with the temperature and the physical state of the membrane, from below 1 in the gel state to above 2.8 in the liquid-crystalline state in DMPC and DPPC membranes. The partition coefficient was directly proportional to the partial molar volume and was then associated to the increase in free-volume in the membrane as a function of temperature. The apparent diffusion coefficients were corrected by the partition coefficients and found to be nearly the same, with a null dependence on viscosity and physical state of the membrane, probably because the pyrene is disturbing the surrounding lipids and thus becoming insensitive to changes in membrane viscosity. Combining our results with those of others, it is apparent that both solubility and diffusion increase when increasing the temperature or when comparing a membrane in the gel to one in the fluid state.
Laboratorio de Fisicoquímica Biológica, Instituto de Química Biológica, Facultad de Ciencias, and Center for Free Radical and Biomedical Research, Universidad de la República, Montevideo, Uruguay. Electronic address: mmoller@fcien.edu.uy.
Matías N
MN
Möller
Department of Anesthesiology, Center for Free Radical Biology, The University of Alabama at Birmingham, Birmingham, AL, USA. Electronic address: qianli@uab.edu.
Qian
Q
Li
Department of Biochemistry and Molecular Genetics, The University of Alabama at Birmingham, Birmingham, AL, USA. Electronic address: mathicraj@gmail.com.
Mathivanan
M
Chinnaraj
Department of Biochemistry and Molecular Genetics, The University of Alabama at Birmingham, Birmingham, AL, USA. Electronic address: hccheung@uab.edu.
Herbert C
HC
Cheung
Departments of Pharmacology and Chemical Biology, Medicine, and Surgery, University of Pittsburgh School of Medicine, Pittsburgh, PA, USA. Electronic address: doctorno@pitt.edu.
Jack R
JR
Lancaster
Laboratorio de Fisicoquímica Biológica, Instituto de Química Biológica, Facultad de Ciencias, and Center for Free Radical and Biomedical Research, Universidad de la República, Montevideo, Uruguay. Electronic address: denicola@fcien.edu.uy.
Ana
A
Denicola
D015060:1,2-Dipalmitoylphosphatidylcholine / Q000737:chemistry*; D002021:Buffers; D002784:Cholesterol / Q000737:chemistry*; D004058:Diffusion; D004134:Dimyristoylphosphatidylcholine / Q000737:chemistry*; D055664:Electrochemical Techniques; D005456:Fluorescent Dyes / Q000737:chemistry; D007848:Laurates / Q000737:chemistry; D008051:Lipid Bilayers / Q000737:chemistry; D008081:Liposomes / Q000737:chemistry*; D010100:Oxygen / Q000737:chemistry*; D044367:Phase Transition; D010713:Phosphatidylcholines / Q000737:chemistry*; D011721:Pyrenes / Q000737:chemistry; D013696:Temperature; D013816:Thermodynamics; D014783:Viscosity
D002021:Buffers; D005456:Fluorescent Dyes; D007848:Laurates; D008051:Lipid Bilayers; D008081:Liposomes; D010713:Phosphatidylcholines; D011721:Pyrenes; C061646:pyrenemethyl laurate; C015153:1,2-dilauroylphosphatidylcholine; D015060:1,2-Dipalmitoylphosphatidylcholine; D002784:Cholesterol; D010100:Oxygen; D004134:Dimyristoylphosphatidylcholine
Diffusion; Free volume; Partition; Permeability; Phospholipid membranes