Comparative investigation of the reactivity of the ignored radical HO2* with that of HO* in the case of guanine/cytosine complex

The two distinct methods in which the free radicals HO* and HO2* attack the purine/pyrimidine complex were investigated using DFT and TDDFT calculations. AIM calculations and orbital analysis are used to explain the covalent contribution to the N2-H-N3 hydrogen bond between cytosine and guanine. All of these strategies result in a nucleophilic/electrical attack mechanism with a high radical fraction. The thermodynamic parameters determined for HO* and HO2* radicals using the classical and CBS-QB3 techniques define the free radical attack as exothermic or endothermic. HO2* has been investigated to see if it interacts with guanine and cytosine to impact the integrity of DNA. This was not, however, the only biological structure that it might affect.