Electroelution of nonfluorescent stacked proteins detected by fluorescenceoptics from gel electrophoretic bands for transfer into mass spectrometry

The extreme accuracy of spectrometrically determined masses of proteins has opened the possibility to identify proteins separated as gel electrophoret ic bands in the absence of specific immunologic ways of identification. For the purpose of protein transfer from gel electrophoretic bands to mass spe ctrometer, electroelution from the intact get has advantages, in particular when apparatus with capacity for fluorescent scanning allows one to direct the electroelution cell over the band under computer control. To avoid flu orescent labeling of the protein which is incompatible with mass spectromet ric identification, it is proposed to selectively stack the unlabeled prote in and detect it by comigrating tracking dye prior to electroelution. The f easibility of the approach is exemplified in case of a single protein, but still remains to be demonstrated in conjunction with the selective stacking or unstacking of a single protein from a mixture of several proteins.