Involvement of disulfide bands in bovine beta-lactoglobulin B gels set thermally at various pH

To obtain information on forces important for maintenance of the structure of heat-set beta-lactoglobulin gels, gels set from pure beta-lactoglobulin at pH 3.0, 5.0, and 7.0 were solubilized in dissociating buffers, and solub ilized material was characterized by sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) and size exclusion high performance liquid c hromatography. The gel formed at pH 7.0 was largely soluble in urea (or SDS ), and this gel seemed to be built from covalently linked soluble aggregate s, associating into a gel network mainly by strong noncovalent interactions . The gel set at pH 5.0 was solubilized only in the presence of a reducing agent, indicating that this gel structure was supported mainly by covalent disulfide bonds. The gel set at pH 3.0 was almost completely solubilized in SDS or urea without a reducing agent, showing the importance of noncovalen t interactions in maintaining the gel structure.