Background: Green fluorescent protein (GFP), originally isolated from the jellyfish Aequorea victoria, is one of the best visual reporters for monitoring gene expression in vivo and in situ. GFP is a also convenient marker for use in flow cytometry because it eliminates the need to incubate with a secondary reagent (such as dyes or antibodies) for detection. However, anti-GFP antibody is also widely used for co-immunipreciapitation, co-localization or western blotting for the confirmation of specificity when a GFP fusion protein is expressed in cells. Abgent's anti-GFP monoclonal antibody provides a simple solution to detect the expression of a GFP-tagged protein in cells. Because of its ability to spontaneously generate its own fluorophore, the green fluorescent protein (GFP) from the jellyfish Aequorea victoria is used extensively as a fluorescent marker in molecular and cell biology. The yellow fluorescent proteins (YFPs) have the longest wavelength emissions of all GFP variants examined to date. This shift in the spectrum is the result of a T203Y substitution (single-letter amino acid code), a mutation rationally designed on the basis of the X-ray structure of GFP S65T. Abgent's anti-GFP monoclonal antibody can detect both GFP and YFP but not BFP (Blue fluorescent protein) by western blotting.