Biomedical subjects

M Kanthimathi

Publications and source records attributed to M Kanthimathi.

6 recordsLinked to original sources

PubMed2006

A new dinuclear biphenylene bridged copper(II) complex: DNA cleavage under hydrolytic conditions.

The dinucleating ligand, tpbpd (tetrapyridyl biphenylenediamine) forms a dicopper complex with practically no electronic coupling between the two copper (II) centres. The EPR spectrum of the complex is consistent with coordination of each copper ion to two nitrogens of the binuclear ligand. Cyclic voltammogram of the complex also reveals that the two copper (II) centres have identical ligating environment. This dimeric copper (II) complex is found to be a very efficient catalyst for the cleavage of plasmid DNA in the absence of any added cofactor. The amount of conversion of supercoiled form (Form I) of plasmid to the open circular form (Form II) depends on the concentration of the complex as well as the duration of incubation of the complex with DNA. The maximum rate of conversion of the supercoiled form to the nicked circular form at pH 7.5 in the presence of 150 microM of the complex is found to be 1.8 x 10(-3) s(-1).

DNA, Superhelical↗

PubMed2005

Oxidative DNA cleavage mediated by a new copper (II) terpyridine complex: crystal structure and DNA binding studies.

The copper (II) complex [Cu(Itpy)(2)](ClO(4))(2) (1), (Itpy=imidazole terpyridine) has been synthesized and structurally characterized. Crystal structure of the complex shows the complex to be a monomeric copper (II) species with two Itpy ligands coordinated to the metal ion to give a six coordinate complex. The complex has a distorted octahedral geometry with axial elongation. Variable temperature crystal structure data shows dynamic nature of the Jahn-Teller distortion. The complex is an avid DNA binder with a binding constant of 4.26+/-0.20x10(3)M(-1). Observed changes in the viscosity and circular dichroic spectrum of calf thymus DNA solution in the presence of complex 1 suggests intercalative binding of complex 1 to DNA. The complex cleaves supercoiled pBR322 DNA oxidatively in the presence of hydrogen peroxide.

Animals↗

PubMed2004

Oxidation of benzaldehyde in films by Oxo-Cr(V) salen derivatives at solid/liquid interface.

The oxidation of benzaldehyde as a film on a solid surface by various substituted oxochromium(V) salen in solution has been studied by monitoring the change in contact angle of the oxidant at the film/liquid interface utilizing a Teflon cell of known hydrodynamics and controlled convection/diffusion. The kinetics of the redox reaction in bulk has been monitored by measuring the change in absorbance of the oxidant solution. The interfacial study permits analysis of adsorption of the oxidant followed by the oxidation of the substrate under pseudo-first-order conditions. A comparison of the independent surface-averaged kinetic data with those obtained in the solution phase oxidation reaction is made and a model is presented for the mechanism of the interfacial reaction. The kinetic investigation shows that the rate of oxidation is accelerated in the presence of an electron-withdrawing group and is faster at the solid/liquid interface compared to the bulk. The probable mechanism of the redox reaction is discussed.

Journal Article↗

PubMed2000

Interaction of DNA with [Cr(Schiff base)(H(2)O)(2)]ClO(4).

The binding of Schiff base complexes of chromium(III) of the type [Cr(salen)(H(2)O)(2)](+) and [Cr(salprn)(H(2)O)(2)](+), where salen denotes 1,2-bis(salicylideneamino)ethane and salprn denotes 1,3-bis(salicylideneamino)propane to calf thymus DNA has been investigated by absorption, emission, circular dichroism, melting temperature and viscosity measurements. These chromium(III) complexes showed absorption hyperchromicity accompanied by red shift in charge transfer band, fluorescence enhancement, increase in melting temperature, some structural changes in CD spectra and changes in specific viscosity when bound to calf thymus DNA. The binding constant K(b) has been determined from absorption measurements for both the complexes and found to be (2.5+/-0. 4)x10(3) M(-1) for [Cr(salen)(H(2)O)(2)](+) and (1.7+/-0.3)x10(4) M(-1) for [Cr(salprn)(H(2)O)(2)](+). From the binding stoichiometry of DNA-[Cr(salprn)(H(2)O)(2)](+), the number of binding site size has been determined and found to be ten base pairs per bound complex molecule. The chromium(III) complexes also bring about single strand cleavage in plasmid DNA. The experimental results show that the chromium(III) complexes bind to DNA by non-intercalative mode. Major groove binding is the preferred mode of interaction for these Schiff base complexes of chromium(III).

Binding Sites↗

PubMed2000

DNA cleavage by a Chromium(III) complex.

A new Cr(III) complex with the empirical formula [Cr(Schiff base) (H(2)O)(2)]ClO(4), where the Schiff base is 2, 3-bis¿[(2-hydroxy-4-diethylamino) (phenyl) (methylene)]amino¿2-butenedinitrile has been synthesized and characterized spectroscopically. Binding of this complex to DNA has been studied using UV-visible spectroscopy. The complex has been found to bind to the major groove of DNA with a binding constant, K = (1.3 +/- 0.2) x 10(3) M(-1). The induced CD spectrum of the complex in the presence of DNA is also indicative of major groove binding. Gel electrophoresis of plasmid DNA in the presence of the complex shows that the complex brings about nicking of the DNA.

Chromium Compounds↗

PubMed1999

Interaction of Schiff base with bovine serum albumin: site-specific photocleavage.

A Schiff-base ligand with donor/acceptor substituents viz. 2, 3-bis¿[(2-hydroxy-4-diethylamino) (phenyl) (methylene)]amino¿-2-butenedinitrile was synthesized, its binding properties with bovine serum albumin (BSA) and its site-specific photocleavage in the presence of cobaltous chloride have been evaluated. The Schiff-base ligand showed increase in absorption with a 5-nm red shift in the absorption maximum consistent with the binding of Schiff-base ligand to hydrophobic sites on the protein. The binding plot obtained from the absorption titration gives a binding constant of 6.4 +/- 0.3 x 10(4) M(-1). The CD spectrum of BSA in presence of the ligand shows that binding of the ligand leads to a change in the helicity of the protein. This ligand has been found to induce site-specific photocleavage of the protein in the presence of cobaltous chloride. The gel electrophoresis pattern of a photolyzed sample of BSA/Schiff-base ligand/cobaltous chloride shows that protein is cleaved into two polypeptide fragments, indicating site-specific binding for the ligand to the protein.

Animals↗