A modified silver staining protocol for visualization of proteins compatible with matrix-assisted laser desorption/ionization and electrospray ionization-mass spectrometry

The growing availability of genomic sequence information, together with imp rovements in analytical methodology, have enabled high throughput, high sen sitivity protein identification. Silver staining remains the most sensitive method for visualization of proteins separated by two-dimensional gel elec trophoresis (2-D PAGE). Several silver staining protocols have been develop ed which offer improved compatibility with subsequent mass spectrometric an alysis. We describe a modified silver staining method that is available as a commercial kit (Silver Stain PlusOne; Amersham Pharmacia Biotech, Amersha m, UK). The 2-D patterns obtained with this modified protocol are comparabl e to those from other silver staining methods. Omitting the sensitizing rea gent allows higher loading without saturation, which facilitates protein id entification and quantitation. We show that tryptic digests of proteins vis ualized by the modified stain afford excellent mass spectra by both matrix- assisted laser desorption/ionization and tandem electrospray ionization. We conclude that the modified silver staining protocol is highly compatible w ith subsequent mass spectrometric analysis.