The structure of antigen-antibody layers adsorbed on silica surfaces: a scanning angle reflectometry study

摘要

Scanning Angle Reflectometry (SAR) is used to investigate the structure of protein layers deposited sequentially,first the antigen and then the antibody, on a silica surface. The reflectivity curves are analyzed by means of the optical invariants, a general description valid in the thin film limit which permits the determination of three and only three structural parameters for a dielectric layer, independent of any model of the layer. The three parameters can be related to the first two moments of the mass density in the layer, or to an average film thickness and density. In addition, a new invariant is constructed which directly yields information about the distribution of mass in the layer, and thus goes beyond the usual uniform layer model.