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Thermo Scientific™ DTNB (Ellman's Reagent) (5,5-dithio-bis-(2-nitrobenzoic acid)

Measure peptide cysteines or other free, reduced sulfhydryls (-SH groups) in solution using this thiol-reactive, colored compound (Amax 412nm).

Manufacturer:  Thermo Scientific™ 22582

Catalog No. PI22582

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Thermo Scientific™ Pierce DTNB (Ellman's Reagent) reacts with sulfhydryl groups to yield a colored product, which provides a reliable method for measure free reduced cysteines and other free sulfhydryls in solution.

A solution of this compound produces a measurable yellow-colored product when it reacts with sulfhydryls. Consequently, Ellman's Reagent is very useful as a sulfhydryl assay reagent because of its specificity for –SH groups at neutral pH, high molar extinction coefficient and short reaction time. Sulfhydryl groups may be estimated in a sample by comparison to a standard curve composed of known concentrations of a sulfhydryl-containing compound such as cysteine. Alternatively, sulfhydryl groups may be quantitated by reference to the extinction coefficient of TNB.


  • Sulfhydryl detection– reacts quantitatively with free (reduced) sulfhydryl groups

  • Colorimetric–yields colored product to enable spectrophotemetric measurement in tubes or microplates

  • Proven assay method– well-characterized chemistry enables quantitation of peptide or protein sulfhydryl groups using extinction coefficient calculation or by comparison to a cysteine standard



5 g


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