• M Adinarayana

      Articles written in Journal of Chemical Sciences

    • Kinetics and mechanism of protection of thymine from sulphate radical anion under anoxic conditions

      M Sudha Swaraga M Adinarayana

      More Details Abstract Fulltext PDF

      The rates of photooxidation of thymine in presence of peroxydisulphate (PDS) have been determined by measuring the absorbance of thymine at 264 nm spectrophotometrically. The rates and the quantum yields (φ) of oxidation of thymine by sulphate radical anion have been determined in the presence of different concentrations of caffeic acid. Increase in [caffeic acid] is found to decrease the rate of oxidation of thymine suggesting that caffeic acid acts as an efficient scavenger of SO4•- and protects thymine from it. Sulphate radical anion competes for thymine as well as for caffeic acid. The rate constant of sulphate radical anion with caffeic acid has been calculated to be 1.24 x 1010 dm3 mol-1s-1. The quantum yields of photooxidation of thymine have been calculated from the rates of oxidation of thymine and the light intensity absorbed by PDS at 254 nm, the wavelength at which PDS is activated to sulphate radical anion. From the results of experimentally determined quantum yields (φexpt1) and the quantum yields calculated (φcl) assuming caffeic acid acting only as a scavenger of SO4•- radicals show that φexpt1 values are lower than φcl values. The φ ’ values, which are experimentally found quantum yield values at each caffeic acid concentration and corrected for SO4•- scavenging by caffeic acid, are also found to be greater than φexpt1 values. These observations suggest that the thymine radicals are repaired by caffeic acid in addition to scavenging of sulphate radical anions.

    • Mechanism of protection of adenosine from sulphate radical anion and repair of adenosine radicals by caffeic acid in aqueous solution

      M Sudha Swaraga L Charitha M Adinarayana

      More Details Abstract Fulltext PDF

      The photooxidation of adenosine in presence of peroxydisulphate (PDS) has been studied by spectrophotometrically measuring the absorbance of adenosine at 260 nm. The rates of oxidation of adenosine by sulphate radical anion have been determined in the presence of different concentrations of caffeic acid. Increase in [caffeic acid] is found to decrease the rate of oxidation of adenosine suggesting that caffeic acid acts as an efficient scavenger of SO4 and protects adenosine from it. Sulphate radical anion competes for adenosine as well as for caffeic acid. The quantum yields of photooxidation of adenosine have been calculated from the rates of oxidation of adenosine and the light intensity absorbed by PDS at 254 nm, the wavelength at which PDS is activated to sulphate radical anion. From the results of experimentally determined quantum yields (Φexpt¹) and the quantum yields calculated (Φcal) assuming caffeic acid acting only as a scavenger of SO4 show that Φexpt¹ values are lower than Φexpt¹ values. The ǵf values, which are experimentally found quantum yield values at each caffeic acid concentration and corrected for4 scavenging by caffeic acid, are also found to be greater than Φexpt¹ values. These observations suggest that the transient adenosine radicals are repaired by caffeic acid in addition to scavenging of sulphate radical anions.

  • Journal of Chemical Sciences | News

    • Editorial Note on Continuous Article Publication

      Posted on July 25, 2019

      Click here for Editorial Note on CAP Mode

© 2017-2019 Indian Academy of Sciences, Bengaluru.