The specificity of biomolecular particle adhesion

Life as we know it could scarcely exist in the absence of specific interactions between its molecular and supramolecular components. At every stage in the existence of a living organism, specificity intervenes to ensure that chance encounters are selectively guided towards further interaction. This applies to the reactions directing the development of a complex multicellular organism, enzyme catalysis, the immune response, etc. The efficiency of searching for specific interaction partners can be greatly increased by reducing the dimensionality of the search space. Selectivity is enhanced by imposing a requirement for multiple binding events, within constraints of either time or space, in order to actuate a response. Most biological macromolecules can exist in several stable conformational states, and switching between them (conformational change) following the initial encounter between two biomolecules enables specificity to be further enhanced. The experimental determination of the parameters governing biomolecular interactions needs high resolution binding assays carried out under well defined hydrodynamic conditions. Optical waveguide lightmode spectrosmetry (OWLS) is well able to fulfil these requirements. Illustrative examples using this technique are presented, demonstrating the enzymatic decomposition of polylysine, the lipid head group selectivity of actin filament polymerization and the influence of both head group and internal bilayer membrane structure on perforin binding.