Sub-terahertz spectroscopy as a probe for protein stability in an ionic environment

The sub-terahertz (sub-THz) absorption properties of bovine serum albumin (BSA) protein solutions, are investigated at different concentrations of sodium chloride (NaCl). Initially the proposed technique is validated by tracking the unfolding process of BSA in the concentrated solution of strong denaturant - GdmCl. Measurements are performed on a quasi-optical table with frequency multiplier heads covering 0.22-0.325 GHz. Results show a minimum THz absorption for a 100 mM concentration of NaCl, indicating the most stable protein conformation. Sub-THz spectroscopy, therefore, facilitates identification of the salt buffer concentration that enables the least dynamically active protein conformation.