Abstract
DNA binding and photocleavage characteristics of a series of mixed ligand complexes of the type [M(bpy)2qbdp](PF6)n·xH2O (where M = Co(III) or Ni(II), bpy = 2.2′-bipryidine, qbdp = Quinolino[3,2-b]benzodiazepine, n = 3 or 2 and x = 5 or 2) have been investigated. The DNA binding property of the complexes with calf thymus DNA has been investigated by using absorption spectra, viscosity measurements, as well as thermal denaturation studies. Intrinsic binding constant (K b) has been estimated under similar set of experimental conditions. Absorption spectral studies indicate that the Co(III) and Ni(II) complexes intercalate between the base pairs of the CT-DNA tightly with intrinsic DNA binding constant of 1.3 × 106 and 3.1 × 105 M−1 in Tris-HCl buffer containing 50 mM NaCl, respectively. The proposed DNA binding mode supports the large enhancement in the relative viscosity of DNA on binding to quinolo[3,2-b]benzodiazepine. The oxidative as well as photo-induced cleavage reactions were monitered by gel electrophoresis for both complexes. The photocleavage experiments showed that the cobalt(III) complex can cleave pUC19 DNA effectively in the absence of external additives as an effective inorganic nuclease.
Highlights
The interaction and reaction of metal complexes with DNA have long been the subject of intense investigation in relation to the development of new reagents for biotechnology and medicine
DNA interactions of number of mixed ligand complexes have previously appeared in the literature, still there is scope to design and study small molecules containing mixed ligand with the same or different metal ions as new chemical nucleases
These new complexes are insoluble in water, but they are soluble in DMF, DMSO, and in buffer solution
Summary
The interaction and reaction of metal complexes with DNA have long been the subject of intense investigation in relation to the development of new reagents for biotechnology and medicine. A number of metal complexes have been used as probes of DNA structure in solution, as agents for mediation of strand scission of duplex DNA and as chemotherapeutic agents [1–7]. In this regard, mixed-ligand metal complexes have been found to be useful because of their potential to bind DNA via a multitude of interactions and to cleave the duplex by virtue of their intrinsic chemical, electrochemical, and photochemical reactivities [8–15]. DNA interactions of number of mixed ligand complexes have previously appeared in the literature, still there is scope to design and study small molecules containing mixed ligand with the same or different metal ions as new chemical nucleases. In continuation of our work on studies of nuclease activity of mixed-ligand complexes, we wish to explore the binding and oxidative as well as photocleavage activities of mixed ligand complexes of Co(III) and Ni(II) containing bipyridine and condensed quinoline derivative ligand
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