Ellman's reagent reacts with free thiol groups (-SH) to produce a mixed disulfide and 2-nitro-5-thiobenzoic acid (TNB), a compound that exhibits a strong yellow color. This color change can be quantitatively measured using a spectrophotometer at an absorbance of 412 nm, providing a direct correlation to the concentration of thiol groups in the sample. The reaction is highly specific, making it a reliable method for detecting thiols in complex biological matrices.
