ABTS (diammonium salt)

ABTS diammonium salt (AzBTS-(NH4)2) is a substrate for horseradish peroxidase (HRP) conjugate. ABTS diammonium salt can be used to evaluate antioxidant capacity^[1][2]. In Vitro: In vitro free radical scavenging experiment
1. Dissolve ABTS in ultrapure water (7.4 mM, 0.4 mL);
2. K2S2O8 stock solution (2.6 mM, 1.43 mL);
3. Mix the two solutions and let stand at room temperature in the dark for 12 hours;
4. Dilute 50 times with anhydrous ethanol;
5. Detect the absorbance at 734 nm.

A micro-technique of enzyme-linked immunosorbent assay (ELISA) using ABTS, as a substrate for HRP conjugate is studied. In a comparative study among 4 substrates, namely; 5-aminosalicylic acid (5AS), O-phenylenediamine (OPD), O-tolidine (OT) and ABTS, for HRP in terms of sensitivity, ABTS is the most sensitive, stable and the best in visuality by its bluish-green color^[1]. ABTS is a typical peroxidase substrate. For purification and characterization peroxidase positive transformants are cultivated in large scale (XL) under conditions that yield active protein in the culture supernatant. After 160 h cultivation an activity of 55,000 U/L in relation to the substrate ABTS is achieved and the supernatant containing the peroxidase is harvested. With ABTS as substrate the peroxidase activity falls significantly when the H₂O₂ concentration rose above 0.125 mM, indicating that the enzyme is inhibited by H₂O₂. Maximum reaction rates depending upon substrate tested reache values between 31.2 and 125 μM^[2].