  The dependence of the structure of a phospholipid layer (DSPC and SOPC)
adsorbed on a hydrosol substrate on the concentration of NaOH in a solution of
5-nm silica particles has been studied by X-ray reflectrometry with the use of
synchrotron radiation. Profiles of the electron density (polarizability) have
been reconstructed from the experimental data within a model-independent
approach. According to these profiles, the thickness of the lipid film can vary
from a monolayer (~ 35 Angstrom) to several bilayers (~ 450 Angstrom). At the
volume concentration of NaOH of ~ 0.5 mol/L, the film on the hydrosol surface
is a macroscopically flat phospholipid membrane (bilayer) with a thickness of ~
60 Angstrom and with areas of 45 +/- 2 and 49 +/- 3 Angstrom^2 per DSPC and
SOPC molecule, respectively.
