Cholesterol versus alpha-tocopherol: effects on properties of bilayers made from heteroacid phosphatidylcholines.
The techniques of differential scanning calorimetry, fluorescence of merocyanine 540, fluorescence polarization of 1,6-diphenyl-1,3,5-hexatriene, proton permeability, and lipid peroxidation are used to compare the perturbations of cholesterol and alpha-tocopherol on lipid bilayer membranes composed of different phosphatidylcholines containing stearic acid in the sn-1 position and an unsaturated fatty acid (either oleic, alpha-linolenic, gamma-linolenic, or docosahexaenoic acid) in the sn-2 position. It is concluded that the structural roles of cholesterol and alpha-tocopherol may be similar with membranes composed of some phosphatidylcholines but are clearly different with membranes composed of other related phosphatidylcholines. alpha-Tocopherol exerts a much larger effect than cholesterol on membranes rich in polyunsaturated fatty acids that have their initial double bond before the delta 9 position. Cholesterol interacts more favorably with fatty acids that do not have an double bond before the delta 9 position. The membrane structural effects are explained in terms of the larger size of the sterol ring structure of cholesterol compared to the smaller chromanol ring of the alpha-tocopherol.
Stillwell
W
W
Department of Biology, Indiana University, Purdue University at Indianapolis 46202-5132, USA.
Dallman
T
T
Dumaual
A C
AC
Crump
F T
FT
Jenski
L J
LJ
D002152:Calorimetry, Differential Scanning; D002784:Cholesterol / Q000737:chemistry*; D004161:Diphenylhexatriene; D004281:Docosahexaenoic Acids / Q000737:chemistry; D005454:Fluorescence Polarization; D005456:Fluorescent Dyes; D008051:Lipid Bilayers / Q000737:chemistry*; D015227:Lipid Peroxidation; D046911:Macromolecular Substances; D015394:Molecular Structure; D019301:Oleic Acid / Q000737:chemistry; D010539:Permeability; D010713:Phosphatidylcholines / Q000737:chemistry*; D011522:Protons; D011744:Pyrimidinones; D013050:Spectrometry, Fluorescence; D013816:Thermodynamics; D014810:Vitamin E / Q000737:chemistry*
D005456:Fluorescent Dyes; D008051:Lipid Bilayers; D046911:Macromolecular Substances; D010713:Phosphatidylcholines; D011522:Protons; D011744:Pyrimidinones; D014810:Vitamin E; D004161:Diphenylhexatriene; D004281:Docosahexaenoic Acids; D019301:Oleic Acid; C003954:merocyanine dye; D002784:Cholesterol