Fig. 3.

Detection of the reduced (free) thiol content. (A) The Ellman assay is based on the susceptibility of a double bond in Ellman’s reagent 5,5′-dithiobis-2-nitrobenzoic acid (DTNB) to be chemically reduced by a free thiol group. The reaction products are a mixed disulfide and a yellow-colored 5-Thio-2-NitroBenzoic acid (TNB). The amount of TNB generated correlates with the reduced thiol content and can be measured spectrophotometrically. (B) Monobromobimane (mBrB) reacts with the thiols resulting in a fluorescent thiol-mBrB adduct formation which can be measured.