  Protein detection on SDS gels or on 2-D gels must combine several features,
such as sensitivity, homogeneity from one protein to another, speed, low cost,
and user-friendliness. For some applications, it is also interesting to have a
nonfixing stain, so that proteins can be mobilized from the gel for further use
(electroelution, blotting). We show here that coelectrophoretic staining by
fluorophores of the oxacarbocyanine family, and especially
diheptyloxacarbocyanine, offers several positive features. The sensitivity is
intermediate between the one of colloidal CBB and the one of fluroescent
ruthenium complexes. Detection is achieved within 1 h after the end of the
electrophoretic process and does not use any fixing or toxic agent. The
fluorescent SDS-carbocyanine-protein complexes can be detected either with a
laser scanner with an excitation wavelength of 488 nm or with a UV table
operating at 302 nm. Excellent sequence coverage in subsequent MS analysis of
proteolytic peptides is also achieved with this detection method.
