Fig 1. Chemical structure formula (a) and three-dimensional structure (b) of 5,5'-Dithiobis(2-nitrobenzoic acid)

5,5'-Dithiobis(2-nitrobenzoic acid) (DTNB)is an organic disulfide that results from the formal oxidative dimerisation of 2-nitro-5-thiobenzoic acid. An indicator used to quantify the number or concentration of thiol groups. 5,5'-Dithiobis(2-nitrobenzoic acid) has a role as an indicator. 5,5'-Dithiobis(2-nitrobenzoic acid) can be used to quantitate thiols in proteins, cells and plasma by absorption measurements. It readily forms a mixed disulfide with thiols, liberating the chromophore 5-merapto-2-nitrobenzoic acid (absorption maximum 410 nm). Only protein thiols that are accessible to this water-soluble reagent are modified.It is a nitrobenzoic acid and an organic disulfide.

A standard reagent for the determination of reactive sulfhydryl groups by absorbance measurements. 5,5'-Dithiobis(2-nitrobenzoic acid) is used primarily for the determination of sulfhydryl and disulfide groups in proteins. The color produced is due to the formation of a thio anion, 3-carboxyl-4-nitrothiophenolate. 5,5'-Dithiobis(2-nitrobenzoic Acid), also known as Elman's reagent or Dithionitrobenzoic acid, is used as a chemical to quantify the concentration or number of thiol groups in a sample. Ungraded products supplied by Spectrum are indicative of a grade suitable for general industrial use or research purposes and typically are not suitable for human consumption or therapeutic use. 5,5'-dithiobis(2-nitrobenzoic acid) has found extensive use in the estimation of free thiol groups in native and denatured proteins[1].

Reagent for determination of sufhydryl groups. 5,5'-dithiobis-(2-nitrobenzoic acid) is widely utilized as a non-fluorescent probe to quantify the number or the concentration of thiol groups in a sample. 5,5'-dithiobis-(2-nitrobenzoic acid) acts as a cleavable cross-linking agent. It finds an important application as a sensitive reagent for determining free sulfhydryl content in proteins, peptides, and tissues. 5,5'-dithiobis-(2-nitrobenzoic acid) is also employed in high-performance liquid chromatography (HPLC) to determine the alkylthiol content[2]. Keep the container tightly closed in a dry and well-ventilated place. Incompatible with strong oxidizing agents and strong bases. 5,5'-dithiobis-(2-nitrobenzoic acid)is an membrane-impermeant thiol/disulfide exchange blocker. 5,5'-dithiobis-(2-nitrobenzoic acid) is also used to quantify the number or concentration of thiol groups in a sample.

References

[1] Ellman, G. L. (1959) Arch. Biochem. Biophys.82, 70-77.
[2] Li, Z. G. Chapter Six - Quantification of Hydrogen Sulfide Concentration Using Methylene Blue and 5,5'-Dithiobis(2-Nitrobenzoic Acid) Methods in Plants. Methods Enzymol. 2015, 554, 101-110.