Studies on DNA Binding of a Double-chain Surfactant Cobalt(III) Complex Containing 2,2′-Bipyridine Ligand

Abstract

The critical micelle concentration (CMC) value of the double chain surfactant-cobalt(III) complex, cis-[Co(bpy) 2 (DA) 2 ](ClO 4 ) 3 (bpy = 2,2 -bipyridine, DA = dodecyl amine) in aqueous β-cyclodextrin medium was obtained from conductance measurements at 303, 308 and 313 K. The CMC value was found to be higher in β-cyclodextrin medium compared to that in aqueous medium containing no β-cyclodextrin. These results indicate that the surfactant complex has been incorporated into the cavity of β-cyclodextrin through its two aliphatic chains thereby reduce the capacity of our complex to form micelles. This strong interaction between β-cyclodextrin and our complex has been confirmed by the changes occurred in the UV-Visible absorption spectrum of the complex in β-cyclodextrin. The surfactant complex has been found to bind strongly to CT DNA with apparent binding constants at below and above CMC are 1.69 × 10 5 , 2.1× 10 6 M −1 respectively. Binding of this surfactant-cobalt(III) complex with CT DNA was through intercalative mode via the long aliphatic chains present in the ligands. The binding was investigated by various techniques, UV-Visible absorption, fluorescence spectroscopy, circular dichroism, and viscosity measurements. This binding of the surfactant cobalt(III) complex with CT DNA has been reduced in presence of β-cyclodextrin medium due to the combined effect of incorporation of the aliphatic chains into the cavity of β-cyclodextrin and trapping of a base from within the DNA by β-cyclodextrin. The cytotoxic activity of the surfactant cobalt(III) complex was tested in vitro on human tumor cell lines (HepG2 liver carcinoma) using different cell death indicator stains and MTT assay and found to be active. The experiments suggest that the complex suffered loss of viability and death mostly through apoptosis.

Effect of hydrophobicity on intercalative binding of some surfactant copper(II) complexes with tRNA

“…This observed strong hypochromism along with red shift may be due to vast drastic hydrophobic interaction between the modified phenanthroline along with the long aliphatic chain amine ligands of the surfactant copper(II) complexes and base pairs of tRNA leading to strong intercalative binding mode. This affinity is basically consistent with data found for bipyridine-and phenanthroline-based metal complexes reported by us earlier [14,16,18]. Our results may suggest that the ligands (modified phenanthroline ligand ip, dpqc, and dppn) structurally provide aromatic moiety extending from the metal center to overlap with the base pairs by intercalation.…”

“…In our laboratory, we have been focusing on designing, development, and interaction of surfactant metal complexes with DNA and RNA [14][15][16][17][18]. Surfactant metal complexes with chelating ligands are of interest for metallobiomolecules in the search for appropriate systems for binding and activating simple molecules, catalysis, and magnetic interactions [19].…”

Nucleic acid binding study of surfactant copper(ii) complex containing dipyrido[3,2-a:2′-3′-c]phenazine ligand as an intercalator: in vitro antitumor activity of complex in human liver carcinoma (HepG2) cancer cells

“…42,43 This affinity is basically consistent with data found for phenanthroline-based complexes of copper. 19 Our results may suggest that the ligand, dppz, structurally provides one aromatic moiety extending from the metal center to overlap with the DNA base pairs by intercalation. The long aliphatic chain present in the surfactant copper(II) complex enhances this intercalation with the base pairs of DNA through a strong hydrophobic effect.…”

“…In our laboratory, we have been focusing on the design, development, and interaction of surfactant metal complexes with nucleic acids. 18,19 Surfactant metal complexes with chelating ligands are attractive for metallobiomolecules that can be used with the appropriate systems for binding and activating simple molecules, catalysis, and magnetic interactions. 20 In these surfactants, the metal complex containing the central metal ion with its primary coordination sphere acts as the head group, and the hydrophobic part of one or more ligands acts as the tail.…”

Biophysical insights into the intercalative interaction of surfactant cobalt(III) complexes of certain diimine ligands bound to yeast tRNA: Effects of hydrophobicity

“…Modeling of electrostatic, hydrophobic, and hydration forces in such interactions has also been widely studied [20]. We have been interested in synthesis and micelle forming properties of cationic surfactant cobalt(III) complexes with DNA and RNA [21][22][23][24][25][26][27]. In these surfactants, the metal complex containing the central metal ion with its primary coordination sphere acts as the head group and the hydrophobic part of one or more ligands acts as the tail.…”