REFRACTIVE-INDEX AND LAYER THICKNESS OF AN ADSORBING PROTEIN AS REPORTERS OF MONOLAYER FORMATION

A method is presented for a separate real-time determination of refrac tive index and layer thickness of an adsorbing thin layer, The changin g angular deflections of TE and TM modes in a dedicated planar wavegui de structure are measured. A resolution of 0.01 in the refractive inde x and 0.5 nm in the average thickness is obtained. The method is illus trated with experimental results on the binding of an antibody to the substrate, both in a physisorption and in an immunoreaction. In the la tter, results are consistent with an end-on binding of the antibody to the surface.