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ONPG Substrate

Detect beta-galactosidase probes in ELISA applications.

ONPG for beta-galactosidase detection

Thermo Scientific Pierce ONPG is the preferred colorimetric substrate for ELISA applications involving beta-galactosidase (b-Gal) as the reporter enzyme.

When using beta-Galactosidase as the label for proteins in ELISA studies, a wide variety of substrates are available, including: o-Nitrophenyl-beta-D-galactopyranosidase (ONPG), Naphthol-AS-Bl-beta-D-galactopyranosidase (Nap-Gal), and 4-Methyl-umbelliferyl-beta-D-galactopyranosidase (MUm-Gal). However, it is important to choose a substrate with adequate solubility, that uses readily available equipment, and that gives a significant reading over the background. ONPG is a superior beta-Galactosidase substrate option.(1) The product formed is completely soluble and has a high extinction coefficient at 405nm. The substrate yields a yellow product that is easily detectable in the visual range after stopping the reaction with 1M Sodium Carbonate.


  1. Craven, G.R., Steers, Jr., E., and Anfinsen, C.B.,(1965). Purification, composition and molecular weight of the beta-Galactosidase of Escherichia coli K12. J. Biol. Chem. 240, 2468-2477.

Related Resources:

Assay development and ELISA technical guide
ELISA substrate selection guide

Ordering Information
Product # Description Pkg. Size Instructions MSDS CofA Price
34055 ONPG
Formulation: o-nitrophenyl-β-D-galactopyranoside; powder
Sufficient For: At least 5L of typical 1X (3mM) substrate solution
5g Product Instructions for product #34055 ONPG MSDS for product #34055 ONPG Certificate of Analysis for product #34055 ONPG $84.00

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Instructions | MSDS | CofA
Product Instructions | MSDS | CofA  

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