MONOLAYER INTERACTION OF CHOLESTEROL WITH PHOSPHATIDYLCHOLINES - EFFECTS OF PHOSPHOLIPID ACYL CHAIN LENGTH

A1 Journal article (refereed)


Internal Authors/Editors


Publication Details

List of Authors: MATTJUS P, HEDSTRÖM G, SLOTTE JP
Publication year: 1994
Journal: Chemistry and Physics of Lipids
Journal acronym: CHEM PHYS LIPIDS
Volume number: 74
Issue number: 2
Start page: 195
End page: 203
Number of pages: 9
ISSN: 0009-3084
eISSN: 1873-2941


Abstract

The degree of association of cholesterol with phosphatidylcholines having symmetric acyl chains from 10 to 20 carbons in length have been examined in monolayers at the air/water interface using cholesterol oxidase as a probe. Mixed monolayers having three different cholesterol/phospholipid (C/PL) molar ratios (0.9:1.0, 1.0:1.0, and 1.5:1.0 C/PL) were prepared. In these monolayers (at a lateral surface pressure of 20 mN/m), cholesterol was most readily available for oxidation in monolayers having phosphatidylcholines with short (di-10-PC and di-12-PC) or long (di-18-PC and di-20-PC) acyl chains, whereas the oxidation susceptibility was lower in monolayers having phosphatidylcholines with intermediate length acyl chains (di-14-PC, di-15-PC, di-16-PC and di-17-PC). Mixed monolayers having a C/PL of 0.9:1.0 were prepared to include 0.5 mol% NBD-cholesterol, and the monolayer surface texture at 20 mN/m was examined using epifluorescence microscopy. It was clearly revealed that monolayers containing di-10-PC and di-12-PC were laterally heterogeneous (containing both liquid-expanded and liquid-condensed lateral domains). With intermediate chain phosphatidylcholines (14-17 carbons), there was no surface texture (dominantly dark monolayer areas), whereas occasional bright NBD-cholesterol-rich inclusions again began to appear in di-18-PC and di-20-PC monolayers. The increased oxidation susceptibility of cholesterol in di-18-PC and di-20-PC could possibly result from a partial lateral phase separation of cholesterol-rich phases in these monolayers, since cholesterol can be expected to be less readily soluble in a long chain than in intermediate chain phosphatidylcholine matrix, and since cholesterol-rich phases are expected to be oxidized more readily than cholesterol-poor phases. We conclude that the susceptibility of cholesterol to oxidation by cholesterol oxidase was most pronounced in monolayers containing phosphatidylcholines with acyl chain lengths that did not match the length of the sterol molecule.


Keywords

ACYL CHAIN LENGTH, CHOLESTEROL, CHOLESTEROL OXIDASE, FLUORESCENCE MICROSCOPY, LIPID INTERACTION, MONOLAYER MEMBRANES, PHASE SEPARATION, PHOSPHATIDYLCHOLINE

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