2.5. Determination of thiol group content

The Ellman reagent was prepared as follows: 4 mg DTNB (5, 5-dithionitrobenzoic acid) was accurately weighed in 1 mL tris–glycine buffer. 3 mg sample was dissolved in 1 mL tris–glycine buffer. 10 μL of Ellman reagent was added. After kept at room temperature for 1 h, the mixture was diluted five times. The absorbance value was measured at 412 nm.