ELLIPSOMETRIC CHARACTERIZATION OF STREPTAVIDIN BINDING TO BIOTIN-FUNCTIONALIZED LIPID MONOLAYERS AT THE WATER AIR INTERFACE

Ellipsometric studies of the streptavidin binding to a biotin-functionalized phospholipid monolayer at the water/air interface have been performed as a function of the lateral pressure of the monolayer. It is found that the protein monolayer formation upon specific binding is characterized by a ''spontaneous'' (diffusion-limited) thickness increase followed by a slow reorganization process with a further thickness increase. The kinetic parameters as well as the final thicknesses are strongly dependent on the phase state of the lipid monolayer. Strong evidence is given that the binding is completely blocked if the lipid is in a solid-condensed phase.