The effect of a low strength oscillating electric field on the conformation of Bovine Serum Albumin (BSA) and Lysozyme in solution has been measured. A purpose built cell has been used to measure the real time autofluorescence and Circular Dichroism of the protein solutions exposed to electric fields of differing strength and frequency. Exposure to the electric fields results in protein unfolding for both Lysozyme and BSA. The applied field strengths are extremely small compared to the protein inter-chain intra-molecular forces. We propose a model whereby the electrophoretic motion of the proteins leads to a frictional force that results in protein unfolding. For BSA and Lysozyme in the electric fields used in this study, the shear rates at the protein surface under electrophoretic motion are of order 10³ and 10⁴ s⁻¹ respectively. Prolonged electric field exposure results in significant frictional energy dissipation in the proteins. The energy dissipated in the proteins results in protein unfolding, which is a critical initial step for protein aggregation and potentially amyloid fibril formation.

Direct measurements of the effect of hydrodynamic forces generated in Couette flow on the secondary and tertiary structure of bovine serum albumin (BSA) are reported. Real time measurements were made using both fluorescence and circular dichroism spectroscopy as complementary measures of protein structure. Our results demonstrate that BSA, a medium sized, predominantly α-helical protein, unfolds irreversibly in simple shear flow. The shear rates used in this study are comparable to those encountered in bioprocessing and in physiology. Flow-induced unfolding of BSA occurs in simple Couette flow where both exposure time and shear rate increase the degree of irreversible unfolding.