ELECTROCHEMICAL DIFFERENTIATION OF PROTEIN AGGREGATE STATE
Joseph Kotarek and Napoleon Tercero
Macromolecular Structure and Function Group, NIST Division 631
Protein aggregation is a phenomenon of great interest in pharmaceuticals, biology, and medicine. A host of techniques including sedimentation velocity, size exclusion chromatography, and light scattering have been developed to characterize aggregation state on a size basis, each possessing advantages and limitations. We demonstrate an electrochemical method for probing perturbations in higher order protein structure. Using a rotating disk electrode, an analyte's diffusive and electrochemical properties can be measured, and by generating Damk÷hler coefficients for each sample a fingerprint for samples of a particular conformation can be defined. Here the time course of amyloid beta (Ab) aggregation is observed, and there is clear differentiation in the signal for monomeric and aggregated forms of the peptide. Ab is of particular interest as its spontaneous aggregation is widely believed to be causative in Alzheimer's disease. It is hoped that this analysis could be expanded to other peptides or proteins of biopharmaceutical interest, such as monoclonal antibodies. Future efforts will be directed toward evaluating Ab aggregation kinetics and determining measurement sensitivity, as well as expanding the platform to evaluate other biomolecules of interest.