![Fig. 1. CVs obtained at 50 mV s 1 in tris–HCl pH 9.0 after: (a) immersion of dA21CPE in a superoxide radical generating solution ([XOD] = 0.3 U mL 1, [xanthine] = 4.4 10 5M) for 15 min and (b) subsequent electrochemical oxidation of the undamaged adenine bases adsorbed on the dA21-CPE.](/figures/fig-1-cvs-obtained-at-50-mv-s-1-in-tris-hcl-ph-9-0-after-a-196vvky1.webp)
![Fig. 2. CVs obtained with a dA21-CPE at 50 mV s 1 in tris–HCl pH 9.0 containing 0.5 mM NADH + 0.01 M CaCl2 after; immersion in O 2 generating solution ([XOD] = 0.1 U mL 1, [xanthine] = 4.4 10 5 M) for 10 min (a) in the absence of antioxidant (b) in the presence of 10 lM of AA; and further complete electrochemical oxidation in both cases.](/figures/fig-2-cvs-obtained-with-a-da21-cpe-at-50-mv-s-1-in-tris-hcl-rwthlvd9.webp)
![Fig. 4. CVs at 50 mV s 1 obtained in tris–HCl at pH 9 containing 0.5 mM NADH + 0.01 M CaCl2 after immersion of DNA-CPE in O 2 generating solution ([XOD] = 0.1 U mL 1, [xanthine] = 4.4 10 5 M) containing a standard solution of AA: (a) 10, (b) 30, (c) 50, (d) 80 and (e) 100 lM for 10 min. Inset panel: relationship between Ia and AA concentration.](/figures/fig-4-cvs-at-50-mv-s-1-obtained-in-tris-hcl-at-ph-9-3klmlxo8.webp)
Q2. What is the major scavenger of this radical in vivo?
The major scavenger of this radical in vivo is the superoxide dismutase enzyme (SOD) that catalyzes its disproportionation to H2O2.
Q3. What was used to measure the electrocatalytic current after the subsequent immersion of the damaged C?
CV was used to measure the electrocatalytic current after the subsequent immersion of the damaged DNA-modified CPE in a NADH–Ca2+ containing solution.
Q4. What was the effect of the antioxidants on the DNA?
In the presence of antioxidant compounds a diminution in the damage was expected along with an increase in the electrocatalytic current.
Q5. What is the role of phenolic compounds in antioxidant activity?
In general, phenolic compounds content correlates with antioxidant activity and seems to have an important role in stabilizing lipid oxidation.
Q6. Why is a low potential advantageous for analytical purposes?
A low potential is advantageous for analytical purposes because of the diminution of potential oxidizable interferent compounds present in real food samples.
Q7. What are the common methods of quantification of antioxidant capacity?
chemiluminescent, fluorimetric, chromatographic and electrochemical methods have been proposed for in vitro quantification of the antioxidant capacity (AOC) in biological and food samples [6].
Q8. What was used to remove the gas from the sample?
Two lemon sparkling flavored water samples corresponding to two different brands were purchased in a supermarket and stored in the dark at +4 C. Sonication was used to eliminate gas from the sample.
Q9. What are the common immobilization strategies for cytochrome c?
To enhance the electrical contact between cytochrome c and the electrode and to increase the surface coverage of this compound, several immobilization strategies have been proposed mostly based on SAMs of thiols of different length [2–4,15] and hemin modified electrodes [17].
Q10. What is the way to detect hydroxyl radical?
To the best of their knowledge, all electrochemical DNA-based antioxidant sensors developed so far used the hydroxyl radical as a damaging agent, which caused strand scission or oxidative lesions in nucleobases (guanine or adenine).
Q11. What is the common antioxidant mechanism used to control the biological effects of highly reactive ROS?
XanthineþH2Oþ O2 ! XOD uric acidþ 2Hþ þ O 2 ð1ÞThe biological effects of highly reactive ROS are controlled in vivo by a variety of non-enzymatic and enzymatic antioxidant mechanisms.
Q12. What is the method for determining antioxidant capacity?
the composition of both samples was different because brand B had green tea in addition to vitamin C.Among the methods used for antioxidant capacity assessment, the Folin–Ciocalteu method for the quantification of the phenolic content is widely used because its robustness, simplicity and cost-effectiveness [24].
Q13. What was the expected behavior of the antioxidants?
This anticipated behavior was related to the ability of antioxidant compounds to scavenge or inactivate the ROS and prevent the damage on DNA.
Q14. What is the reaction time between the superoxide radical and dA21 layer?
The reaction time between the superoxide radical and dA21 layer depends on the half-time on the generated ROS, so, this parameter is an important feature to select.
Q15. What was the effect of the electrocatalytic current on the concentration of antioxidant in the damaged?
A dependence of the electrocatalytic current on the concentration of antioxidant in the damaging solution was found, which allowed the development of a voltammetric method for the determination of AOC in flavored waters.
Q16. Why was the oxidation of the remaining adenines not observed?
It is worth mentioning that the oxidation current of the remaining adenines was not observed because it was overlapped by the rising background current at the high potential at which it takes place.