5,5-Dithiobis(2-nitrobenzoic acid), also known as DTNB or Ellman’s reagent, is a chemical compound commonly used in biochemical and pharmaceutical research. It is a yellow, crystalline powder that is highly soluble in water and organic solvents.
DTNB is primarily used to measure the concentration of sulfhydryl (-SH) groups in proteins and peptides. The compound reacts with thiols, resulting in the formation of a mixed disulfide and releasing 2-nitro-5-thiobenzoate, which has a yellow color that can be measured spectrophotometrically. By quantifying the intensity of the yellow color, it is possible to estimate the concentration of thiols in a sample. This technique is often used to study protein-protein interactions, protein folding, and enzymatic reactions that involve thiol groups.
In addition to thiol quantification, DTNB has been employed in other applications, such as evaluating the redox state of cells, studying the stability of metal-sulfur compounds, and measuring the activity of various enzymes.