Abstract
Electrophoretic separation of discrete protein bands from solutions of crystalline pepsin or pepsinogen was accomplished in a system incorporating pH discontinuity and using standard, glass microslides to support thin (0.25-mm) sheets of 15% polyacrylamide gel. Adherence of gel films to a glass support during fixation and staining with crystal violet not only prevented distortion of gels as a result of swelling, but also provided preparations that could be readily scanned with a microspectrophotometer. A number of discrete peptide bands were identified from different samples of purified pepsin. Among the several heterogeneous components found in commercially available samples of crystalline pepsinogen, there was a characteristic impurity, the mobility of which was directly comparable to that of pepsin run under the same conditions of electrophoresis. Specific details of methodology are presented.