Time-resolved fluorescence anisotropy of labeled plasma proteins adsorbed on polymer surfaces

The rotational motion of a pyrene sulfonyl group covalently bonded to plasma proteins was studied at the solution/polymer interface by a technique combining total internal reflection (TIR) with time-resolved fluorescence anisotropy. Assuming the time dependence of fluorescence anisotropy to be one exponential decay, the rotational correlation time (φ) was obtained. The values of φ varied with the polymer surfaces, whose hydrophobicities differ. It was presumed that the adsorbed proteins change conformation or orient particularly as if the fragmental motion of the protein molecules became dominant, in addition the interference of the protein rotation due to the surface adhesion.