5,5'-二硫双(2-硝基苯甲酸) MSDS3-Carboxy-4-nitrophenyl disulfide
• 巯基测定 — 与游离（还原）巯基基团 (—SH) 定量反应，以生成可检测的 TNB 产物
• 比色检测 — 有色产物可在比色皿或微孔板中进行分光光度测量
• 成熟的分析方法 — 可利用消光系数计算或通过与半胱氨酸标准进行比较，对肽或蛋白巯基基团进行定量测定
DTNB reacts with the free sulfhydryl side chain of cysteine to form an S-S bond between the protein and a thionitrobenzoic acid (TNB) residue. The main advantage of DTNB over alternative reagents (e.g., N-ethylmaleimide or iodoacetamide) is in the selectivity of this reagent and in the ability to follow the course of the reaction spectrophotometrically. Modification of Enzyme with DTNB: Modification of the SH groups of the enzyme is carried out by reacting 10 μL of 10 mM DTNB solution (about a 20-fold molar excess) at room temperature with 0.6 mL of enzyme solution (0.807 mg/mL) in 80 mM phosphate buffer, pH 8.0, containing 1 mM EDTA, which has been dialyzed previously against the same buffer solution for 24 h. The number of SH groups is estimated from the increase of absorbance at 410 nm using a molar extinction coefficient of 13,600 M -1 cm -1 for thionitrobenzoate ions liberated.