The Adsorption and Aggregation Properties of Biological Systems

grantor: University of TorontoThe adsorption and aggregation properties of two diverse biological systems have been examined. Adsorption of Bovine Serum Albumin (BSA) onto mica and highly-ordered pyrolytic graphite (HOPG) surfaces has been studied at molecular length scales through Atomic Force Microscopy (AFM). It was found that BSA tended to adsorb to mica in multimolecular aggregates, aligned end-on with the solid surface. Aggregate formation has been discussed in terms of interparticle capillary forces and cooperative adsorption effects. While BSA adsorption on mica showed no particular preference for surface site defects, it was found to adsorb exclusively to step defects on HOPG. This preferential adsorption is explained in terms of oxidized carbon species known to exist on the step defects. The general utility of the AFM for generating adsorption isotherms was also examined, and a preliminary room-temperature isotherm for BSA on mica was produced. Dynamic light-scattering experiments and AFM have been used to study the self-assembly of Type I calf-skin collagen. Non-sigmoidal light-scattering curves which have not previously been reported in the literature were found at high collagen concentrations (2-5 mg/mL). The non-sigmoidal light-scattering curves could be produced over a range of temperatures. AFM analysis of the assembly mixture sampled at different stages in the process showed typical assembly intermediates, but did not provide further insight into the nature of the non-sigmoidal curves. It is proposed that the non-sigmoidal curves are the result of an assembly mechanism different than that found at low concentrations, though the nature of the new mechanism remains unclear.M.Sc