Vacklin HP, Tiberg F, Fragneto G, Thomas RK. Composition of supported model membranes determined by neutron reflection.
LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2005;
21:2827-2837. [PMID:
15779955 DOI:
10.1021/la047389e]
[Citation(s) in RCA: 52] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/24/2023]
Abstract
We have investigated the formation of supported bilayers by coadsorption of dipalmitoyl phosphatidylcholine (DPPC) with the nonionic surfactant beta-D-dodecyl maltoside. The adsorption of mixed phospholipid-surfactant micelles on hydrophilic silica surfaces at 25 degrees C was followed as a function of bulk concentration by neutron reflection. Using chain-deuterated d(25)-beta-D-dodecyl maltoside and d(62)-DPPC, we demonstrate that it is possible to determine the composition of the bilayers at each stage of a sequential dilution process, which enriches the adsorbed layer in phospholipid and leads to complete elimination of the surfactant. The final supported bilayers have thicknesses of 51 +/- 3 A and are stable to heating to 37 degrees C once all surfactant has been removed, and the structures agree well with other published data on DPPC supported bilayers. The coadsorption of cholesterol in a DPPC-surfactant mixture was also achieved, and the location and volume fraction of cholesterol in the DPPC bilayer was determined. Cholesterol is located in a 18 +/- 1 A thick layer below the lipid headgroup region and leads to an increased bilayer thickness of 58 +/- 2 A at 26 mol % of cholesterol.
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