Monoclonal Anti-polyHistidine (mouse IgG2a isotype) is derived from the HIS-1 hybridoma produced by the fusion of mouse myeloma cells and splenocytes from a BALB/c mouse immunized with a recombinant His-tagged fusion protein. The antibody is purified from culture supernatant of hybridoma cells grown in a bioreactor. Monoclonal anti-polyHistidine recognizes native as well as denatured, reduced forms of synthetic polyHistidine or polyhistidine-tagged fusion proteins. The product is reactive with fusion protein expressed by prokaryotic pET, pRSET, and pTrc expression vectors. The antibody preferentially recognizes N-terminal tagged fusion proteins.