Fluorescence studies of dye displacement from DNA by chromium(III) complexes: Evidence for cation induced DNA condensations |
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| Authors: | A Kortenkamp P O'Brien D Beyersmann |
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| Institution: | 1. The School of Pharmacy , University of London , 29/39 Brunswick Square, London, WC1N 1AX, UK;2. Department of Chemistry, Queen Mary and Westfield College , University of London , Mile end Road, London, E1 4NS, UK;3. University of Bremen, Department of Chemistry and Biology , NW2, Leobener Str., D 2800, Bremen 33, Germany |
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| Abstract: | The interactions of 10 different chromium(III) complexes with isolated calf thymus DNA have been analysed by studying the electronic and fluoresence spectra of intercalated ethidiumbromide. Triply charged cationic complexes including: Cr(urea)6]Cl3.3H2O, Cr(1,10‐phenanthroline)3](ClO4)3.2H2O, Cr(2,2'‐bipyridyl)3] (ClO4)3.2H2O, Cr(ethylendiamine)3]Cl3.3.5H2O and Cr(NH3)6](NO3)3 displaced the dye from DNA. Similar effects were observed in experiments using the non‐intercalating dye bisbenzimidazole ("Hoechst 33258"). However, singly charged cationic, anionic and uncharged chromium(III) complexes such as: cis‐Cr(1,10‐phenanthroline)2Cl2]Cl.2H2O, cis‐Cr(2,2'‐bipyridyl)2Cl2]Cl.2H2O, Cr(glutathione)2]Na2, Cr(cysteine)2]Na.2H2O and Cr(glycine)3] were unable to displace both ethidiumbromide and bisbenzimidazole from DNA. There was no evidence for the formation of co‐ordinate bonds between chromium(III) and DNA for any of the above complexes. The charge and type of ligand are important in controlling the interaction of chromium(III) with isolated DNA in vitro. Our findings indicate that the outer sphere interaction of a chromium(III) complex with DNA is weak and unlikely to be the mechanism by which chromate causes DNA impairments in vivo and in vitro. |
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| Keywords: | Chromium(III) complexes chromium(III) genotoxicity speciation DNA binding fluorochromes |
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