Detection of PEGylated proteins in polyacrylamide gels by reverse staining with zinc and imidazole salts.

The reverse staining, with imidazole-SDS-zinc, of PEG-linked proteins separated by SDS-PAGE was studied. Using model conjugates (interferon-alpha 2b (IFN-alpha2b) reacted with either a branched-chain (40,000) PEG (PEG2,40) or a linear monomethoxy PEG polymer (Mr of 12,000) and chromatographically purified monoPEG2,40-IFN-alpha2b), conventional small-format analytical gels (<1 mm thick) showed typical detection patterns (i.e.