OBSERVATION OF ANOMALOUS DIFFUSION OF PROTEINS NEAR SURFACES

The kinetics of deposition of various extracellular matrix and other proteins on solid substrates is studied by letting the molecules adsorb onto planar optical waveguides and measuring the changes in the effective refractive indices of the guided modes. At low concentrations (approximately 5-mu-g/cm3), fibronectin, tenascin, and integrin confirm the expected t1/2 kinetics. At higher concentrations (approximately 20-mu-g/cm3), tenascin and serum fibronectin exhibit anomalous behavior with exponents 0.6 and 0.28, respectively, whereas tissue fibronectin adsorbs with normal kinetics at intermediate times, but deposition declerates and stops before full monolayer coverage is reached. The method also provides a convenient way for determining translational diffusion coefficients of the proteins.