Specific staining of sialic acid components on sodium dodecyl sulfate polyacrylamide gel

Specific staining of sialic acid components after sodium dodecyl sulfate polyacrylamide gel electrophoresis can be carried out as follows: 1) extract glycoprotein of erythrocyte membranes or serum by the phenol-saline method, 2) electrophorese the extract on 5% polyacrylamide gel containing 0.1% sodium dodecyl sulfate at constant current, 3) treat the gel with chilled 0.04 M HIO4 for 45 minutes, 4) replace the periodic acid solution with one containing resorcinol 0.6 g, conc. HCl 50 ml, 0.1 M CuSO4 0.5 ml and H2O 50 ml, 5) warm the container in boiling water until blue violet sialic acid bands become clear, 6) replace the staining solution with a mixture of equal parts water and concentrated HCl and observe at once.