Groove Binding Mode Research Articles

Synthesis, Crystal Structure and DNA-Binding Study of a New Zinc(II) Complex Based on 2,6-Bis(imino)pyridyl Ligand

A new zinc complex [Zn(L1)Cl2]2‧CH3OH‧2H2O (complex 1), where L1 stands for 2,6-Bis{[(4-ethylphenyl)imino]ethyl}pyridine (L1) has been synthesized and characterized. The crystal structure of L1 and complex 1 have been determined by single-crystal X-ray diffraction. Both compounds crystallize in the monoclinic P21/c space group. For the ligand L1, the crystal parameters are a = 16.7487(7) A, b = 5.8177(3) A, c = 21.8427(10) A, β = 104.1350(10)° and Z = 4. For complex 1, the crystal parameters are a = 8.0216(14) A, b = 13.433(2) A, c = 24.640(4) A, β = 90.223(3)° and Z = 2. In the crystal structure of complex 1, L1 acts as a tridentate ligand and coordinated with Zn1 with three nitrogen atoms. Together with two chlorine atoms, Zn1 atom is five-coordinated in a trigonal bipyramidal geometry. Hydrogen bonds play great role in the crystal structure of complex 1 and form a two-dimensional network. Furthermore, the DNA-binding property of complex 1 with fish sperm DNA (FS-DNA) has been investigated by electronic absorption titration. The result suggests that complex 1 might interact with FS-DNA via groove binding mode. The single crystals of 2,6-Bis{[(4-ethylphenyl)imino]ethyl}pyridine (L1) and it’s Zinc(II) complex [Zn(L1)Cl2]‧CH3OH‧H2O (1) were determined. In the crystal structure of complex 1, Zn1 atom is five-coordinated in a trigonal bipyramidal geometry. A two-dimensional network is formed by hydrogen bonds. DNA-binding study indicated that complex 1 interact with FS-DNA via groove binding mode.

Elucidation of DNA binding interaction of new Cu(II)/Zn(II) complexes derived from Schiff base and L-tryptophan amino acid: a multispectroscopic and molecular docking approach.

Herein, we describe the synthesis, structural elucidation, and DNA interaction of newly synthesized Cu(II) and Zn(II) complexes, i.e., [Cu(SB)(L-trp)(H2O)2]NO3 (1) and [Zn(SB)(L-trp)(H2O)2]NO3 (2) (SB = Schiff base obtained from the reaction between o-vanillin and 2-amino-2-methylpropane-1,3-diol; L-trp = L-tryptophan). From the analysis, a six-coordinated environment around the Cu(II) or Zn(II) center is proposed. The ability of the complexes to bind with calf thymus DNA was examined by optical spectroscopy (UV-vis titrations and steady-state fluorescence emission) and viscosity measurements. The vivid experimental results revealed that complexes 1 and 2 avidly bind to DNA through surface and groove binding modes, albeit with dissimilar intrinsic binding constants (1.54 × 104 and 1.36 × 104 M-1 for 1 and 2, respectively). Both complexes can displace ethidium bromide (EB) to some extent from the intercalated EB-DNA system, resulting in fluorescence quenching. Additional experiments such as [Fe(CN)6]4--induced quenching and thermal melting confirmed the electrostatic and groove binding mode. Furthermore, molecular docking studies verified that both complexes locate in the DNA minor groove by surface binding and were stabilized through weak intermolecular forces. The binding affinity of the lowest energy docked pose was found to be -5.37 kcal/mol for complex 1 and - 5.18 kcal/mol for complex 2. The present work is expected to pave the way for the synthesis of DNA-targeting Cu(II)/Zn(II) metal complexes for the development of chemotherapeutic agents.

In–Vitro Anticancer and Antibacterial Activities of Brominated Indeno[1,2‐b]qinoline Amines Supported with Molecular Docking and MCDM**

AbstractThe present study describes mono substituted indeno[1,2‐b]quinolines (3 a–c and 5) have much more antiproliferative potentials than positive controls against A549, HeLa, MCF7 and Hep3B cell lines (IC50 values 1.1–29.6 μg/mL) and show similar cytotoxicity (14.3 % to 19.8 %) to cells such as controls. Moreover, the mono substituted indeno[1,2‐b]quinoline amines (3 a–c and 5) exhibit significant antimicrobial activity with MIC values between 15.62 μg/mL and 250 μg/mL. The compounds can also bind to DNA in the groove binding mode with a binding constant range of 1.1×103–1.1×105 M−1. The anticancer and antibacterial properties of compounds were confirmed with the molecular docking simulation for their pharmacokinetic. As a result, the preliminary experimental data and a multi‐criteria decision‐making methodology (MCDM) indicated that the mono substituted indeno[1,2‐b]quinoline amine derivatives, especially 3 a and 5, exhibit effective pharmacological properties. parameters and their interaction with related cells at the molecular level.

Tailoring, structural inspection of novel oxy and non-oxy metal-imine chelates for DNA interaction, pharmaceutical and molecular docking studies

A green synthetic pathway for two mononuclear M(II)-complexes (M = Ni2+ as a non-oxy-metal ion and ZrO2+ as an oxy-metal ion, NiLig and ZrOLig, respectively) of an imino-naphthalenol sodium sulfonate ligand (H2Lig) was followed. Using various physico-chemical tools, their chemical compositions were elucidated. The material-studio package was applied to confirm the structures of NiLig and ZrOLig via the DFT method. The biological potential of the ligand (H2Lig) and its NiLig and ZrOLig complexes was investigated for different microbial strains as well as different cancer cell lines. The redox potential of the newly synthesized complexes was evaluated using different biochemical assays, e.g. DPPH and SOD assays. The NiLig and ZrOLig complexes exhibited improved antimicrobial and anticancer activities as compared to the free ligand (H2Lig). Accordingly, the ZrOLig complex was the most active biological reagent. The binding nature of the M2+ complexes to calf thymus DNA (ctDNA) was examined by UV–Vis. spectrophotometry and viscosity measurements. Both the Ni2+ and ZrO2+ complexes interestingly demonstrated anti-proliferative action against the human cancer cell lines. Such ctDNA interactions were examined theoretically by molecular docking. The approaches between the exported in-silico drug-likeness and the considered DNA interaction study were explored. The binding action between the M2+ complex and DNA would be within the electrostatic minor groove, intercalation and replacement binding modes.

Structural investigation, DNA interactions and in vitro anticancer studies of transition metal complexes of 3-(2-(2, 4-dihydroxy benzylidene) hydrazinyl) quinoxalin-2(1H) -one

The Schiff base ligand, 3-(2-(2, 4-dihydroxybenzylidene) hydrazinyl) quinoxalin-2(1H)-one (RHQO) has been synthesized and characterized by spectral and single crystal X-ray analysis. The Mn(II), Ni(II) and Cu(II) complexes of RHQO have been synthesized and characterized by FT-IR, UV-VIS, mass, EPR spectra, CHN, thermo gravimetric analysis, magnetic susceptibility and conductivity measurements. The morphology of the ligand and complexes is studied by Scanning Electron Microscopy. The metal complexes formed were found to be polymeric in nature. The abilities of the ligand and its metal complexes to interact and bind with calf thymus DNA (CT-DNA) has been studied by electronic absorption spectroscopy and their quantitative binding strength was evaluated in terms of their intrinsic binding constant (Kb). The cleavage interaction of the ligand and its metal complexes with super coiled pBR 322 DNA has been investigated by agarose gel electrophoresis. Cytotoxicity of the Cu(II) and Ni(II) complexes was evaluated using various cancer cell lines, Human cervical cancer cell line (Hela), B16 melanoma F10(B16-F10), Human ovarian cancer cell (SKOV3) and Breast cancer cell line (MCF7) by MTT assay. The results indicated that the ligand and its metal complexes bind with CT-DNA by groove binding mode and cleaved the supercoiled pBR 322 DNA in to nicked form. The Ni(II) and Cu(II) complexes exhibited anticancer activity without affecting the normal CHO-K1 cell lines. Communicated by Vsevolod Makeev

Synthesis, TDDFT Calculations and Biological Evaluation of Dicationic Porphyrins as Groove Binders and Antimicrobial Agents

AbstractA2B2 porphyrin bearing 2/3‐thienyl and 2‐pyridyl moieties (P1a, P3a) and its dicationic derivatives (P2a, P4a) were synthesized in reasonably good yield. The corresponding Copper (II) (P1‐4 b) and Zinc (II) metallated (P1‐4 c) analogs were obtained by conventional methods. The synthesized compounds were characterized by various spectroscopic techniques, electrochemical studies and thermogravimetric analysis. The Copper (II) porphyrin, P1b is structurally characterized by single‐crystal X‐ray structure analysis. The ground state electronic structure and geometry optimizations are carried out by DFT calculations. The computed TD‐DFT results validate the observed optical bands and spectral features. DNA interaction studies of trans‐dicationic porphyrins were performed using spectroscopic titrations, docking studies, and gel electrophoresis experiments. All porphyrins interact with the calf thymus DNA by outside groove binding mode with self‐stacking, and the highest intrinsic binding constant of 1.29 ± 0.14×106 M‐1 is observed for P4a. Molecular docking studies reveal that the binding energy of porphyrins with DNA is around −10 kcal/mol. The antimicrobial properties of the dicationic derivatives (P2,4 a, b, c) were investigated against E. Coli and S. aureus under light and dark conditions, and the growth inhibitory effect is found to be negligible when unilluminated.

Novel 1-methoxyindole- and 2-alkoxyindole-based chalcones: design, synthesis, characterization, antiproliferative activity and DNA, BSA binding interactions

Indole-based chalcones have been identified as interesting compounds with anticancer properties. In the present study, we report the synthesis and evaluation of new 1-methoxyindole and 2-alkoxyindole chalcone hybrids as antiproliferative agents active against colorectal carcinoma cell line. Among the 19 investigated molecules, four inhibit the proliferation of colorectal cancer cells HCT-116 with IC50 values <8 µM and display low cytotoxicity to fibroblast cell line 3T3. The UV–visible, CD and fluorescence competitive displacement assays with ethidium bromide and Hoechst 33258 performed with two active chalcones demonstrated that investigated chalcones interact with calf thymus (CT) DNA through the groove binding mode. Likewise, the quenching interaction of chalcones with bovine serum albumin (BSA) was studied in vitro under optimal physiological condition (pH = 7.4). The Stern–Volmer constant for chalcone-BSA system was found in the range of 105 M−1.

Multispectroscopic and molecular docking studies on DNA binding of guaifenesin drug

The interaction mechanism of guaifenesin drug; (RS)-3-(2-methoxyphenoxy)propane-1,2-diol; and calf thymus DNA was characterized by multiple spectroscopic and molecular docking approaches. The changes in drug electronic absorption with increasing DNA concentration and also the observed significant quenching of guaifenesin emission in the presence of DNA proved the complex formation between guaifenesin and DNA during the interactions. Both the binding constant and thermodynamic parameters for the interaction have been calculated in 283, 298, and 310 K at pH 7.4. The results = 17.87 kJ/mol and = 143.31 J/mol.K confirmed the role of hydrophobic force in the guaifenesin–DNA interaction. Circular dichroism study showed that guaifenesin causes decrease in the negative band of CT-DNA and at the same time the positive band increases which indicated the transition of DNA conformation from B to A. KI quenching experiment specifies that guaifenesin binds to DNA via nonintercalative mode. The competitive studies based on known Hoechst 33258 and methylene blue probes proved the groove binding mode in guaifenesin-DNA adduct. Further, full agreement of molecular docking simulation with the experimental results of binding constant and interaction mode, support high accuracy of the results.

Spectroscopic Studies on the Interaction of Naphthyridines with DNA and Fluorescent Detection of DNA in Agarose Gel.

Four new naphthyridine derivatives (R1-R4) possessing amino acid or boronic acid moieties have been synthesized and characterized using 1H and 13C NMR, FT-IR, and mass spectral techniques. The mechanism of binding of these probes with calf thymus DNA (CT-DNA) has been delineated through UV-Vis, fluorescence, and circular dichroism (CD) spectral techniques along with thermodynamic and molecular docking studies. Small hypochromicity in absorption maximum of the probes without any shift in wavelength of absorption suggests groove binding mode of interaction of these probes with CT-DNA, confirmed by CD and 1H NMR spectral data competitive binding assay with ethidium bromide (EB). CT-DNA quenches the fluorescence of these probes via a static quenching mechanism. In the case of R1 and R4, the observed ΔHo < 0 and ΔSo > 0suggest that these probes interact with CT-DNA through H-bonding and hydrophobic interactions, while in the interaction of R2 and R3, van der Walls and H-boding forces are found to be dominant (ΔHo < 0 and ΔSo < 0). Results of molecular docking investigations corroborate well with that of spectral studies, and these probes bind in the minor groove of DNA. These probes are found to be effective fluorescent staining agents for DNA in agarose gel in gel electrophoresis experiment with sensitivity comparable to that of EB, and DNA amounts as low as 37.5ng are visually detectable in the gel.

Chromium (III) Complexes of 4,5-diazafluoren-9-one Ligand as Potential Anti-proliferative Agents: Synthesis, Characterization, DNA Binding, Molecular Docking and In-vitro Cytotoxicity Evaluation.

Three novel Cr(III) complexes, [Cr(dafone)2(H2O)2](NO3)3 (1), [Cr(opd) (dafone)2](NO3)3 (2) and [Cr (phen-dione) (dafone) (H2O)2].(NO3)3 (3) were synthesized and characterized by different techniques. Fluorescence spectroscopy, gel electrophoresis, viscosity measurement, and circular dichroism (CD) were applied to explore the interaction of Cr complexes with FS-DNA. The binding constant (Kb) was obtained from UV–Vis measurements. The obtained results exhibited the effective binding of target complexes to DNA double-strand. The fluorescence data appraised both binding and thermodynamic constants of complexes-DNA interactions. The measured thermodynamic factors (∆S˚, ∆H˚, ∆G˚) revealed that hydrogen bonding and van der Waals forces for DNA- Cr(III) complexes bear the most important roles. As well, the Stern–Volmer quenching constants (Ksv) and the binding constants (Kb) of synthesized compounds and DNA were calculated. The results of thermodynamic parameters showed that the binding of synthesized Cr(III) compounds to DNA was driven mainly through hydrogen bonds and van der Waals interactions. Viscosity measurement results showed that increasing the concentration of synthesized compounds, did not make any major changes in specific viscosity of FS-DNA. The data of viscosity and circular dichroism (CD) support the groove binding mode.

Synthesis, antiproliferative and antitrypanosomal activities, and DNA binding of novel 6-amidino-2-arylbenzothiazoles

A series of 6-amidinobenzothiazoles, linked via phenoxymethylene or directly to the 1,2,3-triazole ring with a p-substituted phenyl or benzyl moiety, were synthesised and evaluated in vitro against four human tumour cell lines and the protozoan parasite Trypanosoma brucei. The influence of the type of amidino substituent and phenoxymethylene linker on antiproliferative and antitrypanosomal activities was observed, showing that the imidazoline moiety had a major impact on both activities. Benzothiazole imidazoline 14a, which was directly connected to N-1-phenyl-1,2,3-triazole, had the most potent growth-inhibitory effect (IC50 = 0.25 µM) on colorectal adenocarcinoma (SW620), while benzothiazole imidazoline 11b, containing a phenoxymethylene linker, exhibited the best antitrypanosomal potency (IC90 = 0.12 µM). DNA binding assays showed a non-covalent interaction of 6-amidinobenzothiazole ligands, indicating both minor groove binding and intercalation modes of DNA interaction. Our findings encourage further development of novel structurally related 6-amidino-2-arylbenzothiazoles to obtain more selective anticancer and anti-HAT agents.

From groove binding to intercalation: unravelling the weak interactions and other factors modulating the modes of interaction between methylated phenanthroline-based drugs and duplex DNA.

Several antitumor drugs base their cytotoxicity on their capacity to intercalate between base pairs of DNA. Nevertheless, it has been established that the mechanism of intercalation of drugs in DNA starts with the prior groove binding mode of interaction of the drug with DNA. Sometimes, for some kind of flat small molecules, groove binding does not produce any cytotoxic effect and the fast transition of such flat small molecules to the cytotoxic intercalation mode is desirable. This is the case of methylated phenanthroline (phen) derivatives, where, changes in the substitution in the position and number of methyl groups determine their capability as cytotoxic compounds and, therefore, it is a way for the modulation of cytotoxic effects. In this work, we studied this modulation by means of the interaction of the [Pt(en)(phen)]2+ complex and several derivatives by methylation of phen in different number and position and the d(GTCGAC)2 DNA hexamer via groove binding using PM6-DH2 and DFT-D methods. The analysis of the geometries, electronic structure and energetics of the studied systems was compared to experimental works to gain insight into the relation structure-interaction for the studied systems with cytotoxicity. The trends are explained by means of the Non-Covalent Interaction (NCI) index, the Energy Decomposition Analysis (EDA) and solvation contributions. Our results are in agreement with the experiments, in which the methylation of position 4 of phen seems to favour the interaction via groove binding thus making the transition to the intercalation cytotoxic mode difficult. Looking at the NCI results, these interactions come not only from the CH/π and CH/n interactions of the methyl group in position 4 but also from the ethylenediamine (en) ligand, whose orientation in the Pt complex was found in such a way that it produces a high number of weak interactions with DNA, especially with the sugar and phosphate backbone.

Binding behaviour of aminoglycoside drug kanamycin with calf thymus DNA: Thermodynamic, spectroscopic and molecular modelling studies

In this work, the binding mode of antibiotic drug kanamycin with Calf thymus DNA (ctDNA) was assessed using thermodynamic, spectroscopic and molecular docking studies. Isothermal Titration Calorimetry (ITC) studies suggest that the binding is enthalpically favored with a small entropic change and a binding constant of the order of 104 mol−1 dm3, which remains almost same in the studied temperature range. Studies in the presence of osmolytes tetraethylene glycol and sucrose show no appreciable change in the binding behaviour as well as on the stability of the DNA-kanamycin complex. These finding suggests that the number of water molecule released or taken up is not significant in the binding process. Competitive fluorescence displacement assay and circular dichroism studies show that kanamycin follows groove binding mode of interaction. Molecular docking studies also supports that kanamycin prefers groove binding mode, stabilized by hydrogen bonding.

Fluorescent Visualization of Nucleolar G-Quadruplex RNA and Dynamics of Cytoplasm and Intranuclear Viscosity

The nucleolus, the locus of ribosome biogenesis, was found to be the predominant intracellular target of a new fluorescent probe, V-P1. In solution, the probe demonstrated both a selectivity to RNA...

Antimicrobial, cytotoxicity, molecular modeling and DNA cleavage/binding studies of zinc-naproxen complex: switching DNA binding mode of naproxen by coordination to zinc ion

The intercalation DNA binding mode of the naproxen, a non-steroidal anti-inflammatory drug, has been reported previously. In this study, calf thymus deoxyribonucleic acid (CT-DNA) binding of zinc-naproxen complex, [Zn(naproxen)2(MeOH)2], at physiological pH has been investigated by multi-spectroscopic techniques and molecular docking. Zinc-naproxen complex displays significant binding property to the CT-DNA (Kb = 0.2 105 L.mol−1). All of the experimental results; relative increasing in viscosity of CT-DNA and fluorimetric studies using ethidium bromide (EB) and Hoechst 33258 probes, are indicative of groove binding mode of zinc-naproxen complex to CT-DNA. These results show that the coordination of naproxen to zinc metal switches the mode of binding from intercalation to groove. The molecular modeling also shows that the complex binds to the AT-rich region of minor groove of DNA. Structural and topography changes of DNA in interaction with the complex by atomic force microscopy (AFM) indicated that CT-DNA becomes swollen after interaction. The pUC18 plasmid DNA cleavage ability of zinc-naproxen complex by gel electrophoresis experiments revealed that zinc-naproxen complex cleaved supercoiled pUC18 plasmid DNA to nicked DNA. The cytotoxicity of the zinc complex performed by MTT method on HT29 and MCF7 cancer cell lines and on HEK 293 normal cell lines indicates that zinc complex has no cytotoxic effect on both HT29 and MCF7 cell lines but has better cytotoxicity effect on HEK 293 cell lines compared to cisplatin standard drug. The antimicrobial activity of the complex against Staphylococcus aureus and Escherichia coli bacteria revealed the high antimicrobial activity of the complex. Communicated by Ramaswamy H. Sarma

Divalent zinc complex of succinylsulfathiazole: Synthesis, spectral, molecular structure, DNA interaction profile and Hirshfeld surface analysis

The zinc complex of succinylsulfathiazole with coordinated 3-methyl pyridine (Zn-SST) was successfully synthesized using reflux method. Its chemical component and properties were determined by FT-IR technique. The crystal structure of the complex, [{Zn(SST)(3-methyl pyridine)2}(3-methyl pyridine)(H2O)] has been successfully explored through single crystal X-ray diffraction technique. An asymmetric unit of the complex consists of one molecule of SST ligand, two molecules of coordinated secondary ligand, 3-methyl pyridine along with one water molecule and one free molecule of 3-methyl pyridine. The metal Zn exhibits distorted tetrahedral coordination in the molecular complex being coordinated to two nitrogen atoms of two 3-methyl pyridine molecules, to carbonyl oxygen O1 of the tail end of bidentate SST ligand and the fourth coordination is due to hetero N3 of the thiazolate ring of inversely related SST ligand at -x + 1, -y + 1, -z. To have a better visualization of the intermolecular interactions within the crystal, the Hirshfeld surface (HS) analysis has been performed. Furthermore, lipophilicity index represents significant biological activity (log P = 3.75) of the molecule, correlates well with the contribution of C…H/H…C (17%) interactions. Additionally, the DNA interaction studies revealed that complex is exhibited groove binding mode interactions with ct-DNA and this interaction is nicely visualized by docking studies.

Synthesis and interaction of thiazolo [2, 3-a] isoquinoline analog with DNA

A reaction between 1-(furan-2-yl)-3,4-dihydroisoquinoline and thioglycolic acid using DCC at 00-50C will give 10b-(furan-2-yl)-5,6-dihydro-2H-thiazolo[2,3-a]isoquinolin-3(10bH)-one [FUIQTGA]. The interaction between FUIQTGA and DNA was studied using UV Visible spectroscopy, fluorescence and Circular Dichroism (CD) techniques. Static quenching mechanism was observed from fluorescence measurements of interaction between FUIQTGA and DNA. Circular Dichroism reveals the minor groove binding mode between FUIQTGA and DNA.

Synthesis, Characterization and Biological Application of Pyrazolo[1,5-a]pyrimidine Based Organometallic Re(I) Complexes

The neutral rhenium(I) complexes (I-VI) of type [ReCl(CO)3Ln-] where L1 = 7-phenyl-5-(pyridin-2-yl)pyrazolo[1,5-a]pyrimidine, L2 = 7-(4-bromophenyl)-5-(pyridin-2-yl)pyrazolo[1,5-a]pyrimi- dine, L3 = 7-(4-chlorophenyl)-5-(pyridin-2-yl)pyrazolo[1,5-a]pyrimidine, L4 = 7-(2-chlorophenyl) -5-(pyridin-2-yl)pyrazolo[1,5-a]pyrimidine, L5 = 7-(4-methoxyphenyl)-5-(pyridin-2-yl)pyrazolo [1,5-a]pyrimidine, L6 = 5-(pyridin-2-yl)-7-(p-tolyl)pyrazolo[1,5-a]pyrimidine were synthesized and characterized by 13C-APT, 1H-NMR, IR, electronic spectra, magnetic moment and conductance measurement. The anti-proliferative activity on HCT116 cells by MTT assay suggests potent cytotoxic nature of complexes, even some complexes have better activity than standard drug cisplatin, oxaliplatin, and carboplatin. The complexes found to have better antimicrobial activity compare to pyrazolo pyrimidine ligands. The theoretical study of compounds-DNA interactions was examined by molecular docking as a supportive tool to the experimental data, which suggests the groove mode of binding. The values of docking energy for compounds-DNA interaction were found in the range of -230.31 to -288.34 kJ/mol. The intrinsic binding constant values of complexes (1.1-3.5×105 M-1) were found higher than the ligands (0.32-1.8×105 M-1).

Interaction of memantine with calf thymus DNA: an in-vitro and in-silico approach and cytotoxic effect on the cancerous cell lines

Memantine belongs to the class of cognition enhancers that functions as NMDA receptor antagonist, used to treat Alzheimer's disease. The interaction of memantine with DNA was not investigated. In the present study, the interaction of memantine with ct-DNA, as well as its cytotoxicity on cancer cells, was evaluated. UV-visible spectroscopy, steady-state fluorescence spectroscopic studies revealed the interaction between memantine and ct-DNA. The quenching studies, chemical denaturation, (CD), and DNA melting studies showed the groove binding mode of memantine with ct-DNA. The thermodynamic parameters revealed that the interaction between memantine and ct-DNA is enthalpically driven, and the stabilizing forces involved were hydrogen bonding and van der Waals interaction. The groove-binding was also observed by molecular docking studies, which corroborated the findings of spectroscopic investigations. Density function theory calculations confirmed the existence of electron donor and recipient groups. The stability of memantine and DNA interaction, as well as the critical residues involved in the interaction, was identified by molecular dynamics simulations. Memantine showed cytotoxicity towards the cancer cells as compared to normal cells, as observed by MTT assay. Inverted compound microscopy analysis of memantine treated cancer cell lines further confirmed the results obtained by MTT assay. Communicated by Ramaswamy H. Sarma

Water soluble Cu(II) and Zn(II) complexes of bidentate-morpholine based ligand: synthesis, spectral, DFT calculation, biological activities and molecular docking studies

Copper(II) and zinc(II) complexes of the type [ML(AcO)2.H2O] were synthesized from bidentate-morpholine based Schiff base ligand (L - morpholinopropylimino)methyl)-6-methoxyphenol). The prepared ligand, copper(II) and zinc(II) complexes were characterized by elemental analysis, ESI-MS, 1H-NMR, FT-IR, UV-Visible, ESR and spectrometric methods. The elemental and ESI-MS results have been established that the prepared ligand and complexes possess 1:1 stoichiometric ratio. 1H-NMR and FT-IR results have been suggested that azomethine nitrogen and morpholine ring nitrogen atoms are coordinated with Cu(II) and Zn(II) metal ions. UV-Visible, ESI-MS and ESR spectroscopic results have been supported that the proposed structure of Cu(II) and Zn(II) complexes possess square pyramidal geometry. In order to confirm the proposed square pyramidal geometry of prepared complexes by DFT calculation has been studied. DNA binding ability of Cu(II) and Zn(II) complexes have been studied by electronic absorption and viscometric methods. These results reveal that Cu(II) and Zn(II) complexes interact with CT-DNA by the way of groove binding mode. Molecular docking studies result shows that synthesized compounds has better binding ability. The in vitro antioxidant activities of ligand, Cu(II) and Zn(II) complexes have been investigated by using the DPPH assay. The result shows that synthesized compounds have good radical scavenging activity against DPPH radical. Antimicrobial activities of synthesized ligand and its complexes have been tested against selected bacterial (gram positive & gram negative) and fungal species. The results reveal that Cu(II) and Zn(II) have good antimicrobial activity than ligand. Communicated by Ramaswamy H. Sarma