2.3.4. Free and total sulphydrylsFree and total sulphydryl groups of protein samples weredetermined using the method developed by Beveridge et al.(1974) and Thannauser et al. (1984), respectively. Samples(1 mg/mL) were suspended in 0.086 mol/L Tris-HCl–0.09 mol/Lglycine–4 mmol/L EDTA–8 mol/L urea–pH 8 buffer. Disper-sions were stirred at 25◦C during 10 min at 500 rpm ina thermomixer and then centrifuged at 15,000×g (10 min,10◦C). Supernatant was incubated with Ellman’s reagent (4 mgDTNB/mL methanol) and 1 mL NTSB was used in the caseof the total sulphydryls. Absorbance at 412 nm was mea-sured in a Genesys-20 spectrophotometer (Thermo Scientific,Waltham, MA, USA). The molar extinction coefficient of 3-thio-6-nitrobenzoate (TNB; 13,600 L mol−1cm−1) was used. Proteinconcentration of extracts was determined by the Bradfordmethod (Bradford, 1976).