Effect of dynamic high pressure on functional and structural properties of bovine serum albumin

Dynamic high pressure (DHP) has been investigated as an innovative suitable method to induce protein modifications. This work evaluated the effect of DHP (up to three passes at 100, 150 and 200MPa, with an inlet temperature of 20°C) on functional and structural properties of bovine serum albumin (BSA). Results indicated that DHP process applied up to an energy limit of 100MPa increased the protein foaming capacity (FC) (p<0.05 - increase up to 63% after 1 pass at 100MPa) and the utilization of multiple passes at high pressure promoted a reduction in this property (p<0.05 - reduction up to 31.6% after 3 passes at 200MPa). Similar results were observed for sulfhydryl group, indicating an influence of free thiol groups on FC. Complementarily, DHP process promoted an increase of proteins particles size, suggesting a new rearrangement of their conformational structure. DHP did not affect tryptophan microenvironment in BSA; however, this process induced the rearrangement of secondary structure elements. In the first cycle, the pressure increase resulted in a loss of secondary structure, while in the second and third cycles the DHP process resulted in the gain of secondary structure elements. These results indicated that the second and third passes triggered a molecular rearrangement of the protein structure, giving rise to a novel and more stable conformational state. This conclusion was also supported by thermal unfolding studies (melting temperature reduction from 67.5 to 54.6°C after 1 pass at 200MPa), in which the additional cycles of DHP caused the occurrence of an initial denaturation at high temperatures, compared to the first cycle.