We have investigated the formation of supported model membranes via the adsorption of phospholipid-surfactant mixtures at the Si water interface by specular neutron reflection. The adsorption of mixed micelles of the nonionic surfactant beta-D-dodecyl maltoside and DOPC or POPC was determined as a function of bulk concentration, and using d(25)-beta-D-dodecyl maltoside, the composition of DOPC and POPC bilayers was determined. Bilayer thicknesses of 39 +/- 3 (A) dot over for DOPC and 41 +/- 3 A for POPC agree well with data from bulk lamellar phases for both lipids, and the average area per lipid molecule can be varied from 62 to 115 (A) dot over (2) by varying the bulk concentrations used. The amount of surfactant in the bilayer is very sensitive to the bulk volume-to-surface area ratio, but it can be fully eliminated by ensuring a sufficiently large dilution/rinsing volume of the solution. (C) 2004 Elsevier B.V. All rights reserved.
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