X-RAY AND NEUTRON REFLECTIVITY STUDIES OF A PROTEIN MONOLAYER ADSORBED TO A FUNCTIONALIZED AQUEOUS SURFACE

We report the structural organization of a protein, streptavidin, spec ifically bound at aqueous surfaces to lipid monolayers functionalized by biotinylated head groups. X-ray and neutron reflectivity data with H2O and D2O as subphases are consistent with the formation of homogene ous monomolecular protein layers (thickness d(pr) almost-equal-to 42 /- 2 angstrom) directly underneath the lipid. A new approach of analyz ing all four data sets in terms of one general model reveals the dry v olume of the protein, its average lateral density at the interface, an d the amount of water interpenetrating the protein film.