Characterization of the thermal denaturation of Bence-Jones proteins by ultracentrifugation at elevated temperatures.

The unusual thermosolubility properties of BenceJones proteins have been investigated by the technique of ultracentrifugation at elevated temperature. Study of several purified Bence-Jones proteins has allowed description of the molecular changes that occur upon heating. Although the proteins participate in a common phenomenon, individual difIerences in their ultracentrifugal properties at high temperatures were observed. In certain cases an initial polymerization, followed by a depolymerization to an unfolded molecule, occurred as the temperature was raised. Sulfhydryl-binding reagents had little effect on the high temperature reactions, whereas ethanol, urea, detergents, or salts had a large effect. Therefore, the precipitation and redissolution phenomenon is attributed to alterations in the noncovalent bonding and tertiary structure of the BenceJones protein.