The dichotomy in the DNA-binding behaviour of ruthenium(II) complexes bearing benzoxazole and benzothiazole groups |
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Authors: | Spillane Catriona B Dabo Marième N V Fletcher Nicholas C Morgan Joy L Keene F Richard Haq Ihtshamul Buurma Niklaas J |
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Institution: | The School of Chemistry and Chemical Engineering, Queen's University Belfast, Belfast BT9 5AG, Northern Ireland, United Kingdom. |
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Abstract: | The substituted tris(bipyridine)ruthenium(II) complexes {Ru(bpy)(2)(4,4'-bbob)](2+) and Ru(bpy)(2)(5,5'-bbob)](2+) where bpy=2,2'-bipyridine and bbob=bis(benzoxazol-2-yl)-2,2'-bipyridine] have been prepared and compared to the previously studied complex Ru(bpy)(2)(4,4'-bbtb)](2+) where bbtb=bis(benzothiazol-2-yl)-2,2'-bipyridine]. From the UV/VIS titration studies, Delta-Ru(bpy)(2)(4,4'-bbob)](2+) displays a stronger association than the Lambda-isomer with calf-thymus DNA (ct-DNA). For Ru(bpy)(2)(5,5'-bbob)](2+), there appears to be minimal interaction with ct-DNA. The results of fluorescence titration studies suggest that Ru(bpy)(2)(4,4'-bbob)](2+) gives an increase in emission intensity with increasing ct-DNA concentrations, with an enantiopreference for the Delta isomer, confirmed by membrane dialysis studies. The fluorescent intercalation displacement studies revealed that Ru(bpy)(2)(4,4'-bbob)](2+) and Ru(bpy)(2)(5,5'-bbob)](2+) display a preference for more open DNA structures such as bulge and hairpin sequences. While Lambda-Ru(bpy)(2)(4,4'-bbtb)](2+) has shown the most significant affinity for all the oligonucleotides sequences screened in previous studies, it is the Delta isomer of the comparable benzoxazole ruthenium(II) complex (Delta-Ru(bpy)(2)(4,4'-bbob)](2+)) that preferentially binds to DNA. |
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Keywords: | Ruthenium 2 2′-bipyridine Benzothiazole Benzoxazole Enantioselectivity DNA-binding |
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