Staining Nucleic Acids with Silver: An Alternative to Radioisotopic and Fluorescent Labeling

Silver staining was introduced more than a decade ago as a sensitive procedure to detect trace amounts of proteins in polyacrylamide gels (1). Since then, silver staining has been perfected and extended to the study of other biological molecules that have been separated by electrophoresis in a variety of supports (2,3). Silver staining follows generally one of two methods. One uses diamine or ammoniacal silver solutions for gel impregnation and dilute acid solutions of formaldehyde for image development. The other method impregnates with silver nitrate in a weakly acidic milieu and uses formaldehyde to reduce silver under alkaline conditions. Reportedly, diamine alkaline methods are less sensitive but better suited for thicker gels, while acidic methods are fast and work best with thin gels (2).