CONSTANT-PRESSURE MOLECULAR-DYNAMICS INVESTIGATION OF CHOLESTEROL EFFECTS IN A DIPALMITOYLPHOSPHATIDYLCHOLINE BILAYER

Citation
Kc. Tu et al., CONSTANT-PRESSURE MOLECULAR-DYNAMICS INVESTIGATION OF CHOLESTEROL EFFECTS IN A DIPALMITOYLPHOSPHATIDYLCHOLINE BILAYER, Biophysical journal, 75(5), 1998, pp. 2147-2156
Citations number
37
Language
INGLESE
art.tipo
Article
Categorie Soggetti
Biophysics
Journal title
ISSN journal
0006-3495
Volume
75
Issue
5
Year of publication
1998
Pages
2147 - 2156
Database
ISI
SICI code
0006-3495(1998)75:5<2147:CMIOCE>2.0.ZU;2-J
Abstract
We report a 1.4-ns constant-pressure molecular dynamics simulation of cholesterol at 12.5 mol% in a dipalmitoylphosphatidylcholine (DPPC) bi layer at 50 degrees C and compare the results to our previous simulati on of a pure DPPC bilayer. The interlamellar spacing was increased by 2.5 Angstrom in the cholesterol-containing bilayer, consistent with x- ray diffraction results, whereas the bilayer thickness was increased b y only 1 Angstrom. The bilayer/water interface was more abrupt because the lipid headgroups lie flatter to fill spaces left by the cholester ol molecules. This leads to less compensation by the lipid headgroups of the oriented water contribution to the membrane dipole potential an d could explain the experimentally observed increase in the magnitude of the dipole potential by cholesterol, Our calculations suggested tha t 12.5 mol% cholesterol does not significantly affect the conformation s and packing of the hydrocarbon chains and produces only a slight red uction in the empty free volume. However, cholesterol has a significan t: influence on the subnanosecond time scale lipid dynamics: the diffu sion constant for the center-of-mass ''rattling'' motion was reduced b y a factor of 3, and the reorientational motion of the methylene group s was slowed along the entire length of the hydrocarbon chains.