Studies on the genotoxic effect of chromium oxide (Cr VI): interaction with deoxyribonucleic acid in solution.

Chromium is a toxic and carcinogenic compound widely distributed in environment. In the present study we have investigated the interaction of chromium oxide with DNA employing UV/vis and fluorescence spectroscopy as well as Circular dichroism, thermal denaturation, retardation polyacrylamide gel electrophoresis and DNA-cellulose affinity techniques. The results showed that the binding of chromium oxide to DNA is concentration dependent; at low concentration shows a little effect but ant higher concentrations (>100μg/ml) reduced the absorbance at 260 and 210nm producing hypochromicity. Also λ(max) of the metal at 210, 260 and 350nm was reduced. DNA chromophores quenched with the chromium oxide and decreased fluorescence emission intensity. Upon binding of the metal to DNA the elliplicity at positive extreme was decreased (275nm) and increased the ellipticity of the DNA at negative extreme 245nm. Thermal denaturation profile of DNA shifted to higher degrees upon chromium oxide binding which accompanied by hypochromicity. Also, affinity of chromium oxide to double stranded DNA was higher than single stranded DNA. From the result it is concluded that chromium oxide interacts with DNA via two modes of interaction inducing structural changes and DNA compaction evidence providing chromium oxide genotoxicity.