Intercalative DNA binding, protein binding, antibacterial activities and cytotoxicity studies of a mononuclear copper(II) complex

Abstract

A mononuclear copper(II) complex, [CuL2] (Complex 1) where HL = 4-chloro-2-((cyclohexylmethylimino)methyl)phenol), has been synthesized and characterized by standard methods including single crystal X-ray diffraction analysis. UV–vis spectral studies have been carried out to establish the intercalative binding affinity of complex 1 with DNA and the corresponding intrinsic binding constant has been determined to be 1.68 × 105 M−1. Several other studies such as competitive binding experiment, fluorescence quenching spectra, CV and CD also support intercalative binding ability of complex 1. Agarose gel electrophoresis technique has been employed to study the DNA cleavage. Interaction of complex 1 with a protein, human serum albumin (HSA) has been analyzed by UV–vis and fluorescence quenching spectra. The intrinsic binding constant (K) of complex 1 for HSA has been determined to be 1.91 × 104 M−1. HSA shows strong fluorescence at 344 nm (λex: 295 nm). But the intensity decreases in the presence of complex 1 signifying binding of 1 with HSA. Quenching of fluorescence occurs by fluorescence energy transfer mechanism. FT-IR, 3D fluorescence spectral and CD analyses also show the considerable interaction between HSA and 1. Remarkable degration of HSA has been observed in the presence of hydrogen peroxide when it is incubated with complex 1. On the other hand, complex 1 shows excellent antibacterial activity towards both gram positive and gram negative bacteria. To observe nuclear changes, HeLa cells have been treated with complex 1 and it shows apoptosis of the cell as predicted by the morphological changes in the cell nucleus.