Koichi Hiramatsu

Bovine serum albumin exposed to high pressure

Abstract Pressures of 1000–6000 kg/cm 2 were applied to a solution of bovine serum albumin for 15–60 min at 15–40°. The bovine serum albumin solution at pH 8.9 was compressed, for instance, at 3000 kg/cm 2 for 60 min at 35°. The product was resolved into five zones by acrylamide gel electrophoresis, and into two main and a trace boundaries by the ultracentrifuge. When results by the ultracentrifuge and those by gel electrophoresis at various gel concentrations were combined, it was found that a modified monomer, a dimer and probably higher aggregates were formed. A pressure-temperature curve was constructed; the pressure denaturation occurred in the upper region of the curve. The heat-denatured bovine serum albumin and pressure-denatured bovine serum albumin gave similar patterns in the ultracentrifuge, and gave zones with the same mobilities in gel electrophoresis. The mechanism of heat denaturation is interpreted to be identical with that of pressure denaturation, at least in the initial steps. High pressure lowered the temperature at which heat denaturation began to occur. The dimerization was irreversible. Direct measurement of the electric conductivity under high pressure revealed that another kind of aggregation, which is reversible, occurred at higher pressures than 4000 kg/cm 2 at 25–30°.