6533b82cfe1ef96bd128ea1e

RESEARCH PRODUCT

Pressure dependent arrangement of a protein in two-dimensional crystals specifically bound to a monolayer

subject

description

Abstract The arrangement of streptavidin bound to a biotinylated monolayer of a polymeric amphiphile at the air-water interface is studied as a function of lateral pressure or ligand density. Closely packed domains are observed by fluorescence microscopy. The arrangement of the protein in these domains is sensitively detected by X-ray reflectivity and an especially thorough data analysis yields the following: the distance of the protein from the air-monolayer interface varies with lateral pressure by 10 A; the interfaces involving the protein are much rougher than expected due to capillary waves; the electron density of the protein layer increases considerably on compression, which can be understood as a squeezing of about 1000 water molecules per protein out of the protein slab. The results indicate that the two-dimensional crystals are much more compressible than classical crystals and suggest an arrangement with low positional order. Concerning the surface-sensitive sensor fabrication, the results point to the necessity of controlling the lipid structure, which considerably influences the distances along the surface normal.