X-ray diffraction studies of lipid phase transitions in cholesterol-rich membranes at sub-zero temperatures.
In X-ray diffraction studies of hydrated (greater than 60%) cholesterol/dioleoylphosphatidylcholine mixtures the lipid packing band showed an abrupt transition from liquid crystal-type to gel-type position and definition at a temperature which decreased progressively to almost -50 degrees C as the proportion of cholesterol was increased to a saturation level of about 50 mol%. Plots of transition temperature against composition (mol% cholesterol) and of peak position against composition provided evidence of a significant change in phospholipid configuration at about 20 mol% cholesterol. However, the data overall suggested a uniform dispersion of the cholesterol molecules in the phospholipid bilayer at all concentrations up to the saturation point. Parallel studies of hydrated lipid extract of erythrocyte membranes and of several cholesterol-rich membrane preparations showed a similar overall change from liquid crystal-type packing at +20 degrees C to a gel-type packing at -30 degrees C to -40 degrees C but without displaying a defined transition temperature.
Finean
J B
JB
Department of Biochemistry, University of Birmingham, U.K.
Hutchinson
A L
AL
D000818:Animals; D002784:Cholesterol; D004910:Erythrocyte Membrane / Q000032:analysis; D006801:Humans; D008563:Membrane Lipids / Q000097:blood*; D008968:Molecular Conformation; D009186:Myelin Sheath / Q000032:analysis; D010713:Phosphatidylcholines; D051381:Rats; D011919:Rats, Inbred Strains; D012584:Sciatic Nerve; D013816:Thermodynamics; D014961:X-Ray Diffraction / Q000379:methods
D008563:Membrane Lipids; D010713:Phosphatidylcholines; D002784:Cholesterol; C017251:1,2-oleoylphosphatidylcholine