Effect of monomeric binding affinity on scaffold mediated protein aggregation

Abstract

The intermolecular interactions that occur in a system determine the degree and duration of the contact. They govern processes from signaling and recognition to aggregation and tumor formation. The ability to control and affect intermolecular processes requires an understanding of the assembly process and factors modulating the assembly, such as the strength of individual interactions (binding affinity) and the number of interactions between molecules (valency). Functionalized PAMAM dendrimers were used as nucleating scaffolds to study the significance of intermolecular interactions on aggregate assembly. Dendrimers functionalized with biotin, lactose and mannose units spontaneously aggregated when added to the appropriate protein binding partner (streptavidin, galectin-3, and Concanavalin A, respectively). Aggregates were characterized to provide insight regarding the effects of binding affinity, protein valency and concentration on the average diameter, regularity (polydispersity) and kinetics of aggregate formation. A number of tools were used in this investigation, including dynamic light scattering (DLS), fluorescence microscopy (FM) and fluorescence lifetime spectroscopy (FLS). FLS instrumentation was reconfigured to enable high thoughput formats. A discussion of the validation and re-design of the FLS instrumentation is included.