Effect of Superoxide Dismutase on the DNA Damage by TiO2 under UV

DNA damage in the photocatalysis system of TiO2 and the effect of SOD were studied using calf thymus DNA as research object. The degree of DNA damage was detected by gel electrophoresis and high performance liquid chromatography (HPLC) analysis. 8-Hydroxy-2'-deoxyguanosine (8-OHdG) was used as an internal standard, HPLC-ESI-MS/MS were employed to analyze products of DNA damage. Peroxidase catalytic spectrophotometry and electron spin resonance (ESR) were used to determine the content of H2O2 and the change of reactive oxygen species, the mechanism of DNA damage was studied. The results indicated that the degree of DNA damage in different systems was in the order of UV/TiO2>UV>Dark/TiO2, the degree of DNA damage reached 99% after 260 min and the reaction kinetic constants K was equal to 7.82X 10(-3) min(-1). SOD used as an antioxidant had the ability of removing free radicals and inhibiting DNA damage, the reaction kinetic constants K was equal to 2.27 x 10(-3) min(-1) in the system with SOD. 8-OHdG was the special product of guanine damage. DNA damage process was predominated mainly by the hydroxyl radical (center dot OH) and superoxide radical (center dot O-2(-)) generated in the system. Besides, photocatalytic damage was with the mineralization of DNA and mineralization rate reached 75.06% after 12 h.