Modified two-dimensional electrophoresis for identification and autoradiography of ribosomal proteins reacted withp-chloromercuribenzoate

Ribosomal proteins labelled with [¹⁴C]PCMB, a reversibly reacting sulfhydryl reagent, lose most of their radioactivity when separated by the conventional two-dimensional polyacrylamide gel electrophoresis. Therefore, the two-dimensional method was modified to insure stability of the PCMB-protein complex during the procedure. Proteins ofEscherichia coli ribosomes were separated by the modified method, and those which reacted with [¹⁴C]PCMB were identified by counting of stained spots and by autoradiography of dried gels.