[Isoelectric focusing with silver impregnation of proteins]

Silver impregnation of polyacrylamide gel sheets after isoelectrofocusing is described. This method of staining allows to increase the sensitivity of the traditional isoelectrofocusing 5 to 10 times, as compared with staining of gels by Coumassi brilliant-blue R-250 (in case of analysis of complex protein mixtures). When analyzing individual protein preparations, the sensitivity of isoelectrofocusing with silver staining is within the range of several dozens of ng per sample. A special attention is paid to methods permitting to decrease the non-specific background staining of gel by silver.