(571ay) Urea-Induced Dissociation of Non-Native Aggregates of α-Chymotrypsinogen: Kinetics, Thermodynamics, and Competing Pathways

Non-native aggregation is problematic during the development of protein-based pharmaceuticals, and is commonly implicated in several neurodegenerative diseases. A comprehensive understanding of the specific interactions that lead to the stabilization or destabilization of protein aggregates relative to free monomers is important to help alleviate these issues. This work focuses on the effects of urea on the dissociation of pre-formed aggregates of α-Chymotrypsinogen A. The primary experimental results are the kinetics of monomer recovery and changes in aggregate structure, size, and morphology during urea-promoted dissociation as a function of initial aggregate size, overall protein concentration, urea concentration, and salt concentration. Biphasic kinetics are observed where extent of monomer recovery and aggregate dissociation is primarily controlled by the final urea concentration and the initial size of the aggregates. Final monomer recovery is independent of the overall protein concentration, indicating kinetic control of the process. Light scattering measurements indicate aggregate weight-average molecular weight decreases, morphology is conserved, and polydispersity increases during dissociation. A number of candidate models are presented and evaluated to quantitatively and qualitatively capture all of the experimental results.