[Distribution of small hydrophobic molecules in membranes. II. Heterogeneity of binding centers on a phospholipid bilayer surface].

4-dimethylaminochalcone (DMC), a hydrophobic uncharged fluorescent probe, was bound to a phospholipid bilayer surface and was distributed in different binding sites. Sites whose polar groups of phospholipid and hydration shell molecules were the least mobile had the greatest affinity to DMC. The increase DMC/phospholipid ratio resulted in DMC molecules getting bound to sites of a lesser affinity whose polar groups were more mobile. Cholesterol presence caused DMC binding to the first type of sites only.