Rates of spontaneous exchange of synthetic radiolabeled sterols between lipid vesicles

Journal Article · Tue Feb 18 00:00:00 EST 1992 · Biochemistry; (United States)

DOI:https://doi.org/10.1021/bi00121a040· OSTI ID:5687672

Kan, Chucheng; Yan, Jiasheng; Bittman, R ^[1]

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1. City Univ. of New York, Flushing (United States)

{sup 14}C-labeled sterols with structural variation in the polar function (3{alpha}-OH, 3-O(CH{sub 2}){sub 2}O-(CH{sub 2}){sub 2}O(CH{sub 2}){sub 2}OH, 3 {alpha}-NH{sub 2}, 3{beta}-NH{sub 2}, and 3-OC(O)CHN{double bond}N) and at the 7 position (7-oxo, 7{alpha}-OH, and 7{beta}-OH) were synthesized and incorporated into unilamellar vesicles for studies of the rates of transfer to an excess of acceptor vesicles. Cholesterol, cholestanol, and epicholesterol underwent full exchange in a single kinetic pool, and 90% of the 3{alpha}-triethoxycholesterol was exchangeable in one pool. Biphasic kinetics with full exchangeability were observed for cholesterylamines, which bear a positive charge at the 3 position; the slow phase reflects the high activation energy for inner-to-outer leaflet movement of the charged lipid. Biphasic kinetics were also found for cholesteryl diazoacetate, indicating that this photoaffinity probe and cholesterol have different mechanisms of transfer. Sterols that are more hydrophilic than cholesterol as estimated by reversed-phase high-performance chromatography gave faster exchange rates than cholesterol, whereas sterols that are more hydrophobic gave slower exchange rates. However, the rates of ({sup 14}C)sterol desorption from the lipid-water interface are not correlated with the relative sterol hydrophobicity as estimated by the logarithm of the capacity factors using acetonitrile-2-propanol-water as the mobile phase. These studies suggest that the interaction of sterols with phospholipids provides the principal physical-chemical basis for determining the rates of spontaneous exchange of sterols between bilayers.

• OSTI ID: 5687672
• Journal Information: Biochemistry; (United States), Vol. 31:6; ISSN 0006-2960
• Country of Publication: United States
• Language: English

Related Subjects

59 BASIC BIOLOGICAL SCIENCES
CARBON 14 COMPOUNDS
BIOSYNTHESIS
CHOLESTEROL
MOLECULAR STRUCTURE
STEROLS
MEMBRANE TRANSPORT
CELL MEMBRANES
PHOSPHOLIPIDS
TIME DEPENDENCE
CARBON COMPOUNDS
CELL CONSTITUENTS
ESTERS
HYDROXY COMPOUNDS
LABELLED COMPOUNDS
LIPIDS
MEMBRANES
ORGANIC COMPOUNDS
ORGANIC PHOSPHORUS COMPOUNDS
STEROIDS
SYNTHESIS
550201* - Biochemistry- Tracer Techniques