Kinetic Silver Staining of Proteins

Abstract

Silver staining methods have long been know to provide highly sensitive detection of proteins and nucleic acids following electrophoresis in agarose and polyacrylamide gels (1,2). Silver staining technologies can be extended to other media such as blots, thin-layer chromatography (TLC), and microtiter plates. The quantification of proteins adsorbed to microtiter plate wells provides quantitative information for enzyme-linked immunosorbent assay (ELISA) and protein interaction assays. One nonradioactive procedure, copper iodide staining, is described in Chapter 51 (3). The kinetic silver staining method for measuring the amount of adsorbed protein in a microtiter plate has been developed recently. The microtiter plate assay has a sensitivity similar to copper iodide staining (5-150 ng/well) but higher precision (<5%; 4). When quantification is based on the time required for staining to reach a fixed optical density, very little protein-to-protein variation is observed, so a standard protein for calibration can be selected (such as bovine albumin) that is free of interfering substances to which the assay is sensitive (4). Furthermore, this kinetic silver staining assay is found to be most sensitive for the detection of proteins on cellulose such as is commonly used for TLC (see Chapter 51 for a comparison with other solid-phase stains).