ABSTRACT

Biological macromolecules and surfaces interact through different nonspecic and specic forces. These interactions, which can be highly complex, affect the organization and morphology of biological systems at different length scales. Since biological systems are not at thermodynamic equilibrium, the interactions are best described as processes that evolve in time and space. Static and dynamic forces between surfaces functionalized with

biomolecules can be directly measured with the surface force apparatus. The general principles of such measurements are described, and examples are shown of measured forces and lm thickness transitions associated with hemifusion of supported bilayers, interactions between end-adsorbed glycoproteins and between ligands and receptors, and forces generated due to polymerization of conned actin.