Date of Award


Degree Type


Degree Name

Doctor of Philosophy


Interactions between biological surfaces are central events in a wide variety of biological processes, including ligand-receptor binding, adsorption of molecules from suspension onto interfaces, and adhesive interactions between whole cells or subcellular particles. Despite the chemical diversity of these reactions--for example, the wide range of ligand structures and binding behaviour--it is believed that the underlying physicochemical forces do not differ between all of these surface phenomena.;In this study, an approach based on classical equilibrium capillarity has been adapted to estimate the magnitude of the macroscopically observable resultant of these surface forces (the surface affinity or work of adhesion) between several biological surfaces under various biochemically or pharmacologically defined conditions. Phase separated aqueous polymer solutions of dextran and poly (ethylene glycol) have been used to provide the necessary sensitivity (ca. 10{dollar}\sp{lcub}-6{rcub}{dollar} J.m{dollar}\sp{lcub}-2{rcub}{dollar}) and relative freedom from measurement-induced perturbation of the biological structures.;We have used these approaches to characterise the surface behaviour of several cell surfaces (including human peripheral blood erythrocytes and neutrophils, pig alveolar macrophages and a variety of mouse cells, both freshly isolated and maintained in culture) and non-cellular surfaces (pulmonary surfactant and model cell membranes).;The results indicate that these estimates of the surface affinities of biological surfaces vary in a reproducible way between different surfaces, and between the same surface under different conditions. The analysis of the relationships between thermodynamics and structure indicates that several molecular factors are responsible for the observed macroscopic potential energies: these factors include the amount, molecular weight, conformation and last (but not least) the solvation of the polymeric components of the biological surfaces.;Future applications of this approach may encompass such areas as interactions of cellular components with biomaterials or the detailed analysis of the surface effects of ligand-receptor interactions. The surface thermodynamic approach unites these diverse phenomena by stressing their common dependence on free energy minimisation.



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