Quantification of proteins in sample buffer for sodium dodecyl sulfate-polyacrylamide gel electrophoresis using colloidal silver.

A rapid and simple assay for quantification of proteins in sodium dodecyl sulfate-sample buffer is described. Proteins are bound to a nitrocellulose membrane, stained with colloidal silver, and quantified by transmission densitometry. The staining requires 1 microL of protein sample and takes less than 20 min. Good linearity between the staining intensity and amount of proteins is in the range of 5-100 ng.