Quantitative kinetic analyses of adsorption and desorption processes at the liquid-solid interface with surface plasmon resonance
Jung, Linda Suna, 1970-
MetadataShow full item record
Surface Plasmon Resonance (SPR) spectroscopy is one of the few techniques that can directly detect adsorption onto a surface immersed in liquid with high time resolution and sensitivity to <5% of a monolayer. By modifying the sensing surface with a proper terminal receptor group, SPR provides a surface analytical tool for studying the kinetics of surface adsorption and desorption reactions in situ. Methods for extracting quantitative information as well as kinetic parameters from such experiments are presented here. First, a simple but quantitative mathematical formalism for interpretation of SPR signals from adsorbed films is presented. This provides a way of estimating adsorbed film thicknesses, surface coverages or surface concentrations from the SPR response over the entire range of film thicknesses without relying on calibration curves of response versus known thicknesses or surface concentrations. Next, a method for estimating sticking probabilities (rate per collision) and intrinsic rate constants for adsorption from liquid solutions is described, where a simple numerical solution to Fick's Law is used to calculate the adsorbate concentrations at incremental distances from the surface as adsorption occurs. The resulting concentration nearest the surface is needed to calculate both the intrinsic rate constant for adsorption and the collision frequency of the adsorbate with the surface versus time or coverage. These methods are applied to alkylthiol adsorption on the Au SPR surface and streptavidin (SA) adsorption on mixed biotin-containing alkylthiolate monolayers. The sticking probability of alkylthiols on gold shows that its transition state is stabilized by ∼0.7 kJ/mol per CH2 group, or about half of that of the product thiolate. The kinetics of the competitive desorption of SA and SA mutants from the biotin-containing monolayers; reveal the nature of the SA monolayer. Finally, a method for quantifying binding of proteins and other ligands to the surfaces of phospholipid bilayered vesicles (attached intact to the SPR surface via the SA layer) is demonstrated, and applied to determine the dissociation equilibrium constant for phospholipase A2 binding to membranes.
- Chemistry