Ramasamy Karvembu

Bio: Ramasamy Karvembu is an academic researcher from National Institute of Technology, Tiruchirappalli. The author has contributed to research in topics: Catalysis & Transfer hydrogenation. The author has an hindex of 27, co-authored 139 publications receiving 2025 citations.

Half-sandwich RuCl2(η6-p-cymene) core complexes containing sulfur donor aroylthiourea ligands: DNA and protein binding, DNA cleavage and cytotoxic studies

Abstract: A series of Ru(II)(η6-p-cymene) complexes (1–4) bearing the general formula [RuCl2(η6-p-cymene)L] (L = monodentate aroylthiourea ligand) has been synthesized and characterized by analytical and various spectroscopic techniques. The neutral monodentate coordination of aroylthiourea with Ru via an S atom was confirmed by single crystal X-ray diffraction study. The complexes were tested for their ability to interact with DNA and protein. The complexes bound with calf thymus DNA (CT DNA) with the intrinsic binding constant value in the order of 104 M−1. The intercalative mode of binding was confirmed by the ethidium bromide (EB) displacement study. The interaction of the complexes with CT DNA was further supported by viscosity measurements and circular dichroic (CD) spectra. The Ru(II) complexes cleaved the supercoiled DNA without the need of any external agent. The spectroscopic evidence showed good binding efficacy of the complexes with BSA (Bovine Serum Albumin). The alterations in the secondary structure of BSA by the Ru(II) complexes were confirmed by synchronous fluorescence spectra. Cytotoxicity examination by MTT assay was carried out in two cancer cell lines (MCF7 and A549) and one non-cancerous cell line (L929). Complex 4 showed significant activity [IC50 = 52.3 (MCF7) and 54.6 (A549) μM] which was comparable with that of similar known complexes. The morphological changes assessed by Hoechst staining revealed that the cell death occurred by apoptosis.

Synthesis of Ni(II) complexes bearing indole-based thiosemicarbazone ligands for interaction with biomolecules and some biological applications

Abstract: A series of new Ni(II) complexes containing indole-based thiosemicarbazone ligands was synthesized and characterized by elemental analyses, and UV-visible, FT-IR, 1H & 13C NMR and mass spectroscopic techniques. The Ni(II) complexes (1-4) bear the general formula [Ni{C10H9N2NHCSNH(R)}2] where R = hydrogen (1), 4-methyl (2), 4-phenyl (3) and 4-cyclohexyl (4). Molecular structure of ligands (L3 and L4) and complexes (2, 3 and 4) was confirmed by single crystal X-ray crystallography. Four coordinated Ni(II) complexes showed square planar geometry. The interaction of the Ni(II) complexes with calf thymus DNA (CT-DNA) has been evaluated by absorption spectroscopic and ethidium bromide (EB) competitive binding studies, which revealed the intercalative interaction of the complexes with CT-DNA. Gel electrophoresis experiments showed the cleavage of DNA by the complexes without any external agent. Further, the interaction of the complexes with bovine serum albumin (BSA) was investigated using UV-visible, fluorescence and synchronous fluorescence spectroscopic methods, which showed that the complexes could bind strongly with BSA. Molecular docking was employed to understand the binding of the Ni(II) complexes with the molecular target B-DNA, human DNA topoisomerase I and BSA. All the Ni(II) complexes possess high antioxidant activity against 2-2-diphenyl-1-picrylhydrazyl (DPPH) radical and antihaemolytic activity. In addition, in vitro cytotoxicity of the Ni(II) complexes against lung cancer (A549), human breast cancer (MCF7) and mouse embryonic fibroblasts (L929) cell lines was investigated. Complex 4 has high cytotoxicity. The mode of cell death effected by complex 4 has been explored using Hoechst 33258 staining. Nickel(II) complexes of thiosemicarbazone ligands were synthesized and their DNA/protein binding, DNA cleavage and cytotoxicity abilities were studied.

DNA/protein binding, DNA cleavage, cytotoxicity, superoxide radical scavenging and molecular docking studies of copper(II) complexes containing N-benzyl-N′-aryl-N′′-benzoylguanidine ligands

Abstract: Five copper(II) complexes containing N,N′,N′′-trisubstituted guanidine ligands were synthesized and characterized by elemental analyses and UV-Visible, FT-IR, EPR and mass spectroscopic techniques. The synthesized copper(II) complexes (1–5) bear the general formula [Cu{C6H5CONC(NR)NHCH2C6H5}2] where R = phenyl (1), 4-methylphenyl (2), 4-ethoxyphenyl (3), 2-methoxyphenyl (4) or 1-naphthyl (5). The four coordinated square planar geometry of the complexes was confirmed by the single crystal X-ray diffraction study. The interaction of the Cu(II) complexes with calf thymus DNA (CT DNA) was explored using absorption and fluorescence spectroscopic methods. The results revealed that the complexes have an affinity constant for DNA in the order of 104 M−1 and the mode of interaction is non-covalent intercalation. The DNA cleavage study showed that the complexes cleaved DNA without any external agent. The interaction of Cu(II) complexes with bovine serum albumin (BSA) was also studied using absorption and fluorescence techniques. The cytotoxic activity of the Cu(II) complexes was probed in vitro against human breast (MCF7) and lung (A549) cancer cell lines. The complexes were also tested against mouse embryonic fibroblast (NIH 3T3) cell lines. Complexes 1 and 3 have good cytotoxic activity which is comparable with the cyclophosphamide drug. The complexes were less cytotoxic towards normal cell lines showing that they affect only cancer cell lines. Superoxide radical scavenging property of the complexes was assessed using the NBT assay. Copper(II) complexes showed appreciable superoxide radical scavenging activity with IC50 values ranging from 1.53 to 5.62 μM. A further molecular docking technique was employed to understand the binding of the complexes toward the molecular target DNA and human DNA topoisomerase I.

Ab initio calculation of vibrational absorption and circular dichroism spectra using density functional force fields

Abstract: : The unpolarized absorption and circular dichroism spectra of the fundamental vibrational transitions of the chiral molecule, 4-methyl-2-oxetanone, are calculated ab initio. Harmonic force fields are obtained using Density Functional Theory (DFT), MP2, and SCF methodologies and a 5S4P2D/3S2P (TZ2P) basis set. DFT calculations use the Local Spin Density Approximation (LSDA), BLYP, and Becke3LYP (B3LYP) density functionals. Mid-IR spectra predicted using LSDA, BLYP, and B3LYP force fields are of significantly different quality, the B3LYP force field yielding spectra in clearly superior, and overall excellent, agreement with experiment. The MP2 force field yields spectra in slightly worse agreement with experiment than the B3LYP force field. The SCF force field yields spectra in poor agreement with experiment.The basis set dependence of B3LYP force fields is also explored: the 6-31G* and TZ2P basis sets give very similar results while the 3-21G basis set yields spectra in substantially worse agreements with experiment. jg

Antitumour metal compounds: more than theme and variations

Abstract: Triggered by the resounding success of cisplatin, the past decades have seen tremendous efforts to produce clinically beneficial analogues. The recent achievement of oxaliplatin for the treatment of colon cancer should, however, not belie the imbalance between a plethora of investigated complexes and a very small number of clinically approved platinum drugs. Strategies opening up new avenues are increasingly being sought using complexes of metals other than platinum such as ruthenium or gallium. Based on the chemical differences between these metals, the spectrum of molecular mechanisms of action and potential indications can be broadened substantially. Other approaches focus on complexes with tumour-targeting properties, thereby maximizing the impact on cancer cells and minimizing the problem of adverse side effects, and complexes with biologically active ligands.