An improved method for the analysis of low molecular weight polypeptides (<molecular weight 10, 000) by SDS-polyacrylamide gel electrophoresis was described. Linear gradient polyacrylamide gels, 10-20% [1:20(w/w) bisacrylamide: acrylamide], with a stacking gel gave good resolution. Separation gels also contained 0.45M Tris-HCl (pH 8.8), 0.1% SDS and 7M urea, as well as a 0-10% linear gradient of sucrose. Polypeptides having molecular weights from 1, 400 to 100, 000 could be analyzed by this gel system. Moreover, leakage of low molecular weight polypeptides from gels in the staining procedure had been lowered by using the relatively high concentration of bisacrylmaide. This method could be applied for the analysis and detection of low molecular weight polypeptides from complex biological sources.
