Plasmid vectors for the expression of coding regions of eukaryotic genes in bacterial, insect and mammalian hosts are in common usage; such expression vectors frequently encode hybrid fusion proteins consisting in part of prokaryotic and in part, eukaryotic specified proteins. One such system utilizes maltose binding protein (MBP), the 370 amino acid product of the E. coli mal E gene. Plasmid vectors have been constructed utilizing the MBP domain that allow the synthesis of high levels of MBP-fusion proteins that can be Purified in a one step procedure by affinity chromatography crosslinked amylose resin. Once bound to amylose, the MBP protein can then be separated from the target protein by cleavage by coagulation factor Xa at a specific four residue site. Alternatively, the intact fusion protein can be specifically eluted from the resin by the addition of excess free maltose. Subsequent to elution, MBP fusion protein can be visualized either by western blot analysis or immunoprecipitation using antibodies specific for the MBP-tag. Expression systems utilizing the MBP fusion tag include pCG-806fx and pMal vectors. Primary antibodies are available purified, or with a selection of fluorescent CF® Dyes and other labels. CF® Dyes offer exceptional brightness and photostability. Note: Conjugates of blue fluorescent dyes like CF®405S and CF®405M are not recommended for detecting low abundance targets, because blue dyes have lower fluorescence and can give higher non-specific background than other dye colors.