THERMAL GELATION OF GLOBULAR-PROTEINS - WEIGHT-AVERAGE MOLECULAR-WEIGHT DEPENDENCE OF GEL STRENGTH

Thermal gelation of various globular proteins in the presence and absence of N-ethylmaleimide (NEM) and cysteine was studied. For the proteins that did not contain intersubunit disulfide bonds, the relative hardness of the gels at any given protein concentration followed the order no additive <Cys <NEM. However, for the proteins that contained intersubunit disulfide bonds, the relative order was no additive <NEM <Cys. Despite the differences among the proteins, the square root of the hardness of gels of various proteins exhibited a linear relationship with the weight-average molecular weight of the polypeptides in the gel network. Evidences are presented which indicate that the hardness or gel strength of typical globular protein gels is fundamentally related to the size and shape of the polypeptides in the gel network rather than to their chemical nature such as the amino acid composition and distribution. It is also shown that the globular proteins having a weight-average molecular weight less than 23 000 cannot form a self-supporting gel network at any reasonable concentration. © 1990, American Chemical Society. All rights reserved.