Metal‐Ion‐Mediated Tuning of Duplex DNA Binding by Bis(2‐(2‐pyridyl)‐1H‐benzimidazole) |
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Authors: | Santanu Bhattacharya Prof. Padmaparna Chaudhuri |
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Affiliation: | 1. Department of Organic Chemistry, Indian Institute of Science, Bangalore 560012, India, Fax: (+91)?80‐2360‐0529;2. Chemical Biology Unit, Jawaharlal Nehru Centre of Advanced Scientific Research, Bangalore 560012, India |
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Abstract: | Studies of double‐stranded‐DNA binding have been performed with three isomeric bis(2‐(n‐pyridyl)‐1H‐benzimidazole)s (n=2, 3, 4). Like the well‐known Hoechst 33258, which is a bisbenzimidazole compound, these three isomers bind to the minor groove of duplex DNA. DNA binding by the three isomers was investigated in the presence of the divalent metal ions Mg2+, Co2+, Ni2+, Cu2+, and Zn2+. Ligand–DNA interactions were probed with fluorescence and circular dichroism spectroscopy. These studies revealed that the binding of the 2‐pyridyl derivative to DNA is dramatically reduced in the presence of Co2+, Ni2+, and Cu2+ ions and is abolished completely at a ligand/metal‐cation ratio of 1:1. Control experiments done with the isomeric 3‐ and 4‐pyridyl derivatives showed that their binding to DNA is unaffected by the aforementioned transition‐metal ions. The ability of 2‐(2‐pyridyl)benzimidazole to chelate metal ions and the conformational changes of the ligand associated with ion chelation probably led to such unusual binding results for the ortho isomer. The addition of ethylenediaminetetraacetic acid (EDTA) reversed the effects completely. |
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Keywords: | benzimidazoles chelates divalent metal ions DNA fluorescence |
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