Protective action of copper (II) complex of a Schiff base against DNA damage induced by m-chloroperbenzoic acid using a novel DNA unwinding technique

Abstract

DNA strand breaks can be detected with great sensitivity by exposing calf thymus DNA to alkaline solutions and monitoring the rate of strand unwinding. Fluorometric analysis of DNA unwinding (FADU) is a reliable method for detecting single-strand DNA breaks as an index of DNA damage induced by photosensitizer. m-Chloroperbenzoic acid (CPBA) was used as a photosensitizer in the photodamage of calf thymus DNA. When DNA is exposed to ionizing radiation, the radicals produced in the irradiated sample modify the base-pair regions of the double strands. The protective action of copper salt, Schiff base [ethylene diamine with ethyl acetate](L) and its Cu(II) complex (Cu 7 L Cl 14) against DNA damage photoinduced by CPBA was studied using ethidium bromide as a fluorescent probe. Treatment of DNA with 5, 10, 50, 100, or 200 μM CPBA produced 75%, 48%, 38%, 32% and 30% double-stranded DNA remaining, respectively after 30 min of alkaline treatment at 15 °C. Treatment of calf thymus DNA irradiated with CPBA with a dose of 1 mM [Cu 7 L Cl 14] produced 96% double-stranded remaining protection under the same conditions compared with irradiated DNA without addition of Cu(II) complex of Schiff base.