  The mechanism by which silver staining of proteins in polyacrylamide gels
interferes with mass spectrometry of peptides produced by proteolysis has been
investigated. It was demonstrated that this interference increases with time
between silver staining and gel processing, although the silver image is
constant. This suggested an important role of the formaldehyde used in silver
staining development in this interference process. Consequently, a
formaldehyde-free staining protocol has been devised, using carbohydrazide as
the developing agent. This protocol showed much increased peptide coverage and
retained the sensitivity of silver staining. These results were however
obtained at the expense of an increased background in the stained gels and of a
reduced staining homogeneity.
