Synthesis Characterization and DNA Interaction Studies of a New Zn(II) Complex Containing Different Dinitrogen Aromatic Ligands

The crucial role of stability of intercalating agent for DNA binding studies in DMSO/water system

In recent years, extensive research has been directed towards understanding the interactions between various zinc complexes with DNA, specifically delving into their intercalation and binding behaviors. The binding of zinc complexes to DNA is particularly intriguing due to their distinctive intercalating capabilities. This study unveils a remarkable phenomenon observed with a specific Zn complex, ([B-Zn-N3], where B is a Schiff base ligand), during DNA intercalation investigations in the popular DMSO-Water binary solvent mixture. An unanticipated observation revealed time-dependent changes in the UV-visible absorption spectroscopic studies, coupled with the existence of an isosbestic point. This observation questions the stability of the intercalating agent itself during the intercalation process. The emergence of a decomposed product during the intercalation study has been confirmed through various analytical techniques, including CHN analysis, MALDI mass, XPS, Raman spectroscopy, and Powder XRD. The change in the chemical species on intercalation is further substantiated by theoretical studies, adding depth to our understanding of the intricate dynamics at play during DNA intercalation with the [B-Zn-N3] complex in the DMSO-Water system.

Ternary Cobalt (II)-Metformin-Glycine/Histidine/Proline Complexes: Multispectroscopic DNA, HSA, and BSA Interaction and Cytotoxicity Studies

The synthesized water-soluble ternary complexes [Co(met)(gly)(Cl)2] (1), [Co(met)(hist)(Cl)2] (2), and [Co(met)(pro)(Cl)2] (3), (met = metformin, gly = glycine, hist = histidine, and pro = proline) were evaluated using spectro-analytical techniques, and the stereochemistry of the complexes was determined to be octahedral. UV-Vis absorption, competitive DNA-binding experiments using ethidium bromide (EB) by fluorescence, fluorescence emission studies, viscosity studies, and gel electrophoresis techniques were all employed to explore the binding characteristics of the cobalt (II) complexes with CT-DNA and groove-binding mechanism established. The salt-dependent association of the complexes to CT-DNA was investigated using UV-Vis spectrophotometric analysis. The association of the cobalt (II) complexes with BSA and HSA was explored by utilizing UV-Vis absorption and fluorescence spectroscopy approaches. The findings show that the complexes exhibit adequate capacity to quench BSA and HSA fluorescence and that the binding response is mostly a static quenching mechanism. The cytotoxicity of the complexes has also been appraised with the human breast adenocarcinoma cell lines (MCF-7) and (MDA-MB-231) by utilizing the MTT assay. For each cell line, the IC50 values were computed. In both cell lines, all the complexes were active.

GSH resistant, luminescent 2-(pyren-1-yl)-1H-imidazo[4,5-f][1,10]phenanthroline-based Ru(II)/Ir(III)/Re(I) complexes for phototoxicity in triple-negative breast cancer cells

Selective chemotherapeutic strategies necessitate the emergence of a photosensitive scaffold to abate the nuisance of cancer. In the current context, photo-activated chemotherapy (PACT) has, therefore, appeared to be very effective to vanquish the vehemence of triple-negative breast cancer (TNBC). Metal complexes have been identified to act well against cancer cell microenvironment (high GSH content, low pH, and hypoxia), and thus they have been employed in the treatment of various types of cancer. As TNBC is very challenging to treat owing to its poor prognosis, lack of a specific target, high chance of relapse, and strong metastatic ability, herein we have aspired to design GSH-resistant phototoxic Ru(II)/Ir(III)/Re(I) based pyrene imidazophenathroline complexes to selectively avert the triple-negative breast cancer. The application of complexes, [RuL], [IrL], and [ReL] in the absence and in the presence of GSH against MDA-MB-231TNBC cells, has revealed that they are very active upon irradiation of visible light compared to dark due to the creation of copious singlet oxygen (1O2) as reactive oxygen species (ROS). Among three synthesized complexes, [IrL] has shown outstanding potency (IC50 = 3.70 in the absence of GSH and IC50 = 3.90 in the presence of GSH). Also, the complex, [IrL] is capable of interacting with DNA with the highest binding constant (Kb = 0.023 × 106 M-1) along with higher protein binding affinity (KBSA = 0.0321 × 106 M-1). Here, it has been unveiled that all the complexes have been entitled to involve DNA covalent interaction through the available sites of both adenine and guanine bases.

DNA Binding and Cleavage, Stopped-Flow Kinetic, Mechanistic, and Molecular Docking Studies of Cationic Ruthenium(II) Nitrosyl Complexes Containing “NS4” Core

This work aimed to evaluate in vitro DNA binding mechanistically of cationic nitrosyl ruthenium complex [RuNOTSP]+ and its ligand (TSPH2) in detail, correlate the findings with cleavage activity, and draw conclusions about the impact of the metal center. Theoretical studies were performed for [RuNOTSP]+, TSPH2, and its anion TSP−2 using DFT/B3LYP theory to calculate optimized energy, binding energy, and chemical reactivity. Since nearly all medications function by attaching to a particular protein or DNA, the in vitro calf thymus DNA (ctDNA) binding studies of [RuNOTSP]+ and TSPH2 with ctDNA were examined mechanistically using a variety of biophysical techniques. Fluorescence experiments showed that both compounds effectively bind to ctDNA through intercalative/electrostatic interactions via the DNA helix’s phosphate backbone. The intrinsic binding constants (Kb), (2.4 ± 0.2) × 105 M−1 ([RuNOTSP]+) and (1.9 ± 0.3) × 105 M−1 (TSPH2), as well as the enhancement dynamic constants (KD), (3.3 ± 0.3) × 104 M−1 ([RuNOTSP]+) and (2.6 ± 0.2) × 104 M−1 (TSPH2), reveal that [RuNOTSP]+ has a greater binding propensity for DNA compared to TSPH2. Stopped-flow investigations showed that both [RuNOTSP]+ and TSPH2 bind through two reversible steps: a fast second-order binding, followed by a slow first-order isomerization reaction via a static quenching mechanism. For the first and second steps of [RuNOTSP]+ and TSPH2, the detailed binding parameters were established. The total binding constants for [RuNOTSP]+ (Ka = 43.7 M−1, Kd = 2.3 × 10−2 M−1, ΔG0 = −36.6 kJ mol−1) and TSPH2 (Ka = 15.1 M−1, Kd = 66 × 10−2 M, ΔG0 = −19 kJ mol−1) revealed that the relative reactivity is approximately ([RuNOTSP]+)/(TSPH2) = 3/1. The significantly negative ΔG0 values are consistent with a spontaneous binding reaction to both [RuNOTSP]+ and TSPH2, with the former being very favorable. The findings showed that the Ru(II) center had an effect on the reaction rate but not on the mechanism and that the cationic [RuNOTSP]+ was a more highly effective DNA binder than the ligand TSPH2 via strong electrostatic interaction with the phosphate end of DNA. Because of its higher DNA binding affinity, cationic [RuNOTSP]+ demonstrated higher cleavage efficiency towards the minor groove of pBR322 DNA via the hydrolytic pathway than TSPH2, revealing the synergy effect of TSPH2 in the form of the complex. Furthermore, the mode of interaction of both compounds with ctDNA has also been supported by molecular docking.

Study of Interactions Between 3-benzoyl-4-hydroxy-2-methyl-2H-1, 2-benzothiazine and Human DNA by Theoretical, Spectroscopic and Viscometric measurements

From the last few years mode of interactions between drugs and DNA is an attractive research area as it bridges chemistry, molecular biology and medicinal science. Interactions between small heterocyclic molecules and human DNA is a noteworthy feature in pharmacology for investigation of drugs mechanism and designing of more effective and target specific drugs with fewer side effects. The present research work focuses on the theoretical investigations of 3-benzoyl-4-hydroxy-2-methyl-2H-1, 2-benzothiazine (SASA) by using Gaussian (16 W) software to predict optimized geometry, HOMO-LUMO gap, bond length, bond angle, dihedral angle, electronic and vibrational spectra. Possible reaction site observed in SASA was C_7, C₉ and C₁₈ as these atoms show maximum charge density. Later the interactions of SASA with human DNA was explored spectroscopic investigations and viscometric investigations at physiological buffers of pH of 4.7 (stomach pH) and 7.4 (blood pH) respectively. Maximum absorbance between SASA-DNA complex was observed in buffer solution of pH 3.4 at wavelength of 370 nm, whereas at 7.4 has maximim absorbance between. Spectroscopic results reflects the bathochromic and hyperchromic shift succeeding the addition of human DNA. During viscosity measurement, intercalation and electrostatic mode of interaction were detected at low and high concentration of drug in solution respectively. Increase in the value of rate constant was observed with the increase in concentration of drug. Larger values of rate constant were observed at pH 7.4 in comparison to pH 3.5. Rate constant, thermodynamic parameters and viscometric analysis prefers the intake of SASA via blood.

Response of Ancillary Azide Ligand in Designing a 1D Copper(II) Polymeric Complex along with the Introduction of High DNA- and HAS-Binding Efficacy, Leading to Impressive Anticancer Activity: A Compact Experimental and Theoretical Approach

A new versatile azide-bridged polymeric Cu(II) complex, namely, [Cu(L)(μ_1,3-N₃)]_∞ (1), was synthesized utilizing an N,N,O-donor piperidine-based Schiff base ligand (E)-4-bromo-2-((2-(-1-yl)imino)methyl)phenol (HL), obtained via the condensation reaction of 1-(2-aminoethyl) piperidine and 5-bromo salicylaldehyde. The single-crystal X-ray diffraction analysis reveals that complex 1 consists of an end-to-end azido-bridged polymeric network, which is further rationalized with the help of a density functional theory (DFT) study. After routine characterization with a range of physicochemical studies, complex 1 is exploited to evaluate its biomedical potential. Initially, theoretical inspection with the help of a molecular docking study indicated the ability of complex 1 to effectively bind with macromolecules such as DNA and the human serum albumin (HSA) protein. The theoretical aspect was further verified by adopting several spectroscopic techniques. The electronic absorption spectroscopic analysis indicates a remarkable binding efficiency of Complex 1 with both DNA and HSA. The notable fluorescence intensity reduction of the ethidium bromide (EtBr)-DNA adduct, 4',6-diamidino-2-phenylindole (DAPI)-DNA adduct, and HSA after the gradual addition of complex 1 authenticates its promising binding potential with the macromolecules. The retention of the canonical B form of DNA and α form of HSA during the association of complex 1 was confirmed by implementing a circular dichroism spectral study. The association ability of complex 1 with macromolecules further inspired us to inspect its impact on different cell lines such as HeLa (cervical cancer cell), PA1 (ovarian cancer cell), and HEK (normal cell). The dose-dependent and time-dependent in vitro 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay suggests an effective antiproliferative property of complex 1 with low toxicity toward the normal cell line. Finally, the anticancer activity of complex 1 toward carcinoma cell lines was analyzed by nuclear and cellular staining techniques, unveiling the cell death mechanism.

The Significant Influence of a Second Metal on the Antiproliferative Properties of the Complex [Ru(η6 -C10 H14 )(Cl2 )(dmoPTA)]

Complexes [Ru(η⁶−C₁₀H₁₄)(Cl₂)(HdmoPTA)](OSO₂CF₃) (1), [Ru(η⁶−C₁₀H₁₄)(Cl₂)(dmoPTA)] (2) and [Ru(η⁶−C₁₀H₁₄)(Cl₂)‐μ‐dmoPTA‐1κP:2κ²N,N’‐MCl₂] (M=Zn (3), Co (4), Ni (5), dmoPTA=3,7‐dimethyl‐1,3,7‐triaza‐5‐phosphabicyclo[3.3.1]nonane) have been synthesized and characterized by elemental analysis and spectroscopic techniques. The crystal structures of 1, 3 and 5 were obtained by single‐crystal X‐ray diffraction. The antiproliferative activity of the complexes was evaluated against colon cancer cell line Caco‐2/TC7 by using the MTT protocol. The monometallic ruthenium complexes 1 and 2 were found to be inactive, but the bimetallic complexes 3, 4 and 5 display an increased activity (IC₅₀3: 9.07±0.27, 4: 5.40±0.19, 5: 7.15±0.30 μM) compared to cisplatin (IC₅₀=45.6±8.08 μM). Importantly, no reduction in normal cell viability was observed in the presence of the complexes. Experiments targeted to obtain information on the possible action mechanism of the complexes, such as cell cycle, ROS and gene expression studies, were performed. The results showed that the complexes display different properties and action mechanism depending on the nature of metal, M, bonded to the CH₃N_dmoPTA atoms.

Synthesis, X-ray, Hirshfeld surface analysis, exploration of DNA binding, urease enzyme inhibition and anticancer activities of novel adamantane-naphthyl thiourea conjugate

1-(adamantane-1-carbonyl-3-(1-naphthyl)) thiourea (C₂₂H₂₄N₂OS (4), was synthesized by the reaction of freshly prepared adamantane-1-carbonyl chloride from corresponding acid (3) with ammonium thiocyanate in 1:1 M ratio in dry acetone to afford the adamantane-1-carbonyl isothiocyanate (2) in situ followed by treatment with 1-naphthyl amine (3). The structure was established by elemental analyses, FTIR, ¹H, ¹³C NMR and mass spectroscopy. The molecular and crystal structure were determined by single crystal X-ray analysis. It belongs to triclinic system P - 1 space group with a = 6.7832(5) Å, b = 11.1810(8) Å, c = 13.6660(10) Å, α = 105.941(6)°, β = 103.730(6)°, γ = 104.562(6)°, Z = 2, V = 910.82(11) ų. The naphthyl group is almost planar. In the crystal structure, intermolecular CH···O hydrogen bonds link the molecules into centrosymmetric dimers, enclosing R₂²(14) ring motifs, while the intramolecular NH···O hydrogen bonds enclose S(6) ring motifs, in which they may be effective in the stabilization of the structure. The Hirshfeld surface analysis of the crystal structure indicates that the most important contributions for the crystal packing are from H … H (59.3%), H … C/C … H (19.8%) and H … S/S … H (10.1%) interactions. Hydrogen bonding and van der Waals interactions are the dominant interactions in the crystal packing. DFT, molecular docking and urease inhibition studies revealed stability and electron withdrawing nature of 4 as compared to DNA base pairs and residues of urease. The DNA binding results from docking, UV- visible spectroscopy, and viscosity studies indicated significant binding of 4 with the DNA via intercalation and groove binding. Further investigation of the compound was done on hepatocellular carcinoma; Huh-7 cell line as well as normal human embryonic kidney; Hek-293 cell line. The compound showed significant cytotoxic activity against Huh-7 cells in comparison to normal Hek-293 cells indicating selective cytotoxicity towards cancer cells.

Active Bromoaniline-Aldehyde Conjugate Systems and Their Complexes as Versatile Sensors of Multiple Cations with Logic Formulation and Efficient DNA/HSA-Binding Efficacy: Combined Experimental and Theoretical Approach

Two fluorescence active bromoaniline-based Schiff base chemosensors, namely, (E)-4-bromo-2-(((4-bromophenyl)imino)methyl)phenol (HL1 ) and (E)-2-(((4-bromophenyl)imino)methyl)phenol (HL2 ), have been employed for the selective and notable detection of Cu2+ and Zn2+ ions, respectively, with the simultaneous formation of two new metal complexes [Cu(L1)2] (1) and [Zn(L2)2] (2). X-ray single crystal analyses indicate that complexes 1 and 2 are tetra-coordinated systems with substantial CH...π/π...π stacking interactions in the solid-state crystal structures. These two complexes are exploited for the next step detection of Al3+ and Hg2+ where complex 2 exhibits impressive results via turn-off fluorescence quenching in (DMSO/H2O) HEPES buffer medium. The sensing phenomena are optimized by UV-vis spectral analyses as well as theoretical calculations (density functional theory and time-dependent density functional theory). The combined detection phenomena of the ligand (HL2 ) and complex 2 are exclusively utilized for the first time to construct a molecular memory device, intensifying their multisensoric properties. Furthermore, the DNA- and human serum albumin (HSA)-binding efficacies of these two complexes are examined by adopting electronic and fluorometric titration methods. Complex 2 shows a higher DNA-binding ability in comparison with complex 1, whereas in the case of HSA, the reverse situation is observed. Finally, the binding modes of both the complexes with DNA and HSA have been investigated through molecular docking studies, suggesting good agreement with the experimental results.

Insight into the binding mechanism of macrolide antibiotic; erythromycin to calf thymus DNA by multispectroscopic and computational approaches

In the present study, the interactions between Erythromycin drug and calf thymus deoxyribonucleic acid (ct-DNA) were explored by multi spectroscopic techniques (UV-Visible, fluorescence, circular dichroism spectroscopies), viscosity, molecular docking simulation, and atomic force microscopy (AFM). In addition, the values of binding constant were calculated by the UV-Visible and fluorescence spectroscopy. Competitive fluorescence study with methylene blue (MB), acridine orange (AO), and Hoechst 33258 were indicated that the Erythromycin drug could displace the DNA-bound Hoechst, which displays the strong competition of Erythromycin with Hoechst to interact with the groove binding site of DNA. In addition, the observed complexes in AFM analysis comprise the chains of ct-DNA and Erythromycin with an average size of 314.05 nm. The results of thermodynamic parameter calculations (ΔS° = -332.103 ± 14 J mol^-1 K^-1 and ΔH° = -115.839 ± 0.02 kJ mol^-1) approved the critical role of van der Waals forces and hydrogen bonds in the complexation of Erythromycin-DNA. Fluorescence spectroscopy results demonstrate the existence of a static enhancement mechanism in the interaction of Erythromycin-DNA. According to the obtained results, Erythromycin drug interacts with the major groove of ct-DNA. These consequences were further supported by the molecular docking study, and it could be determined that DNA-Erythromycin docked model was in a rough correlation with our experimental results.Communicated by Ramaswamy H. Sarma.

DNA Electrochemical Biosensor Based on Iron Oxide/Nanocellulose Crystalline Composite Modified Screen-Printed Carbon Electrode for Detection of Mycobacterium tuberculosis

Death from tuberculosis has resulted in an increased need for early detection to prevent a tuberculosis (TB) epidemic, especially in closed and crowded populations. Herein, a sensitive electrochemical DNA biosensor based on functionalized iron oxide with mercaptopropionic acid (MPA-Fe3O4) nanoparticle and nanocellulose crystalline functionalized cetyl trimethyl ammonium bromide (NCC/CTAB) has been fabricated for the detection of Mycobacterium tuberculosis (MTB). In this study, a simple drop cast method was applied to deposit solution of MPA-Fe3O4/NCC/CTAB onto the surface of the screen-printed carbon electrode (SPCE). Then, a specific sequence of MTB DNA probe was immobilized onto a modified SPCE surface by using the 1-ethyl-3-(3-dimethylaminopropyl) carbodiimide/N-hydroxysuccinimide (EDC/NHS) coupling mechanism. For better signal amplification and electrochemical response, ruthenium bipyridyl Ru(bpy)32+ was assigned as labels of hybridization followed by the characteristic test using differential pulse voltammetry (DPV). The results of this biosensor enable the detection of target DNA until a concentration as low as 7.96 × 10-13 M with a wide detection range from 1.0 × 10-6 to 1.0 × 10-12 M. In addition, the developed biosensor has shown a differentiation between positive and negative MTB samples in real sampel analysis.

Nanostructured Polyelectrolyte Complexes Based on Water-Soluble Thiacalix[4]Arene and Pillar[5]Arene: Self-Assembly in Micelleplexes and Polyplexes at Packaging DNA

Controlling the self-assembly of polyfunctional compounds in interpolyelectrolyte aggregates is an extremely challenging task. The use of macrocyclic compounds offers new opportunities in design of a new generation of mixed nanoparticles. This approach allows creating aggregates with multivalent molecular recognition, improved binding efficiency and selectivity. In this paper, we reported a straightforward approach to the synthesis of interpolyelectrolytes by co-assembling of the thiacalix[4]arene with four negatively charged functional groups on the one side of macrocycle, and pillar[5]arene with 10 ammonium groups located on both sides. Nanostructured polyelectrolyte complexes show effective packaging of high-molecular DNA from calf thymus. The interaction of co-interpolyelectrolytes with the DNA is completely different from the interaction of the pillar[5]arene with the DNA. Two different complexes with DNA, i.e., micelleplex- and polyplex-type, were formed. The DNA in both cases preserved its secondary structure in native B form without distorting helicity. The presented approach provides important advantage for the design of effective biomolecular gene delivery systems.

Study on the substitution effects of zinc benzoate terpyridine complexes on photoluminescence, antiproliferative potential and DNA binding properties

Six zinc(II) complexes, [Zn(OCOPh)₂L^R] (R = 1, 2, 3, 4, 5, 6) were synthesized by the reaction of zinc benzoate and six para-substituted 4-phenyl-terpyridine complexes and their structures were confirmed by elemental analysis, FT-IR, ¹H NMR and X-ray single crystal diffraction analysis. Their photoluminescent properties in solid and in solutions of DMSO were studied. Three human cancer cell lines were used for antiproliferative potential: human lung cancer cell line (A549), human esophageal cancer cell line (Eca-109) and human breast cancer cell line (MCF-7). The results have shown that these zinc complexes have good inhibitory effects on cancer cells, which are better than that of the commonly used clinical drug cisplatin. The ability of the complexes to binding to CT-DNA was studied by UV spectroscopy and fluorescence titration, while the interaction between the complexes and CT-DNA, AT6, GC6 short-chain DNA sequences and G-quadruplex were analyzed by circular dichroism (CD). It is found that these complexes can bind to DNA, and the binding mode is mainly intercalator. The docking of the complexes with the DNA fragment was simulated using molecular docking software. All the results clearly display that the substituents at these ligands of the complexes have the substitution effects on the properties of photoluminescence, antiproliferative potential and DNA binding study.

Developing novel zinc(ii) and copper(ii) Schiff base complexes: combined experimental and theoretical investigation on their DNA/protein binding efficacy and anticancer activity

Zn(ii) and Cu(ii) Schiff base complexes having DNA and HSA binding efficacy have been exploited as cancer therapeutic agents.

Design, synthesis, and DNA interaction studies of furo-imidazo[3.3.3]propellane derivatives: Potential anticancer agents

A large number of natural products containing the propellane scaffold have been reported to exhibit cytotoxicity against several cancers; however, their mechanism of action is still unknown. Anticancer drugs targeting DNA are mainly composed of small planar molecule/s that can interact with the DNA helix, causing DNA malfunction and cell death. The aim of this study was to design and synthesize propellane derivatives that can act as DNA intercalators and/or groove binders. The unique structure of the propellane derivatives and their ability to display planar ligands with numerous possible geometries, renders them potential starting points to design new drugs targeting DNA in cancer cells. New substituted furo-imidazo[3.3.3]propellanes were synthesized via the reaction of substituted alkenylidene-hydrazinecarbothioamides with 2-(1,3-dioxo-2,3-dihydro-1H-2-ylidene)propanedinitrile in tetrahydrofuran at room temperature. The structures of the products were confirmed by a combination of elemental analysis, NMR, ESI-MS, IR and single crystal X-ray analysis. Interestingly, 5c, 5d and 5f showed an ability to interact with Calf Thymus DNA (CT-DNA). Their DNA-binding mode was investigated using a combination of absorption spectroscopy, DNA melting, viscosity, CD spectroscopy measurements, as well as competitive binding studies with several dyes. Their cytotoxicity was evaluated against the NCI-60 panel of cancer cell lines. 5c, 5d and 5f exhibited similar anti-proliferative activity against the A549 non-small cell lung cancer (NSCLC) cell line. Further mechanistic studies revealed their ability to induce DNA damage in the A549 cell line, as well as apoptosis, evidenced by elevated Annexin V expression, enhanced caspase 3/7 activation and PARP cleavage. In this study, we present the potential for designing novel propellanes to provoke cytotoxic activity, likely through DNA binding-induced DNA damage and apoptosis.

Biomolecular interactions of amphotericin B nanomicelles with serum albumins: A combined biophysical and molecular docking approach

In this work, we investigated the interaction of amphotericin B (AmB) nanomicelles on the binding affinity and conformational change of human serum albumin (HSA) in comparison with bovine serum albumin (BSA) under physiological conditions by conducting several spectroscopic techniques further confirmed through molecular docking approaches. The experimental results showed that AmB nanomicelles could bind to both HSA and BSA to form protein/drug complexes with one binding site, and the binding process was spontaneous under physiological conditions. Fluorescence studies revealed that the quenching mechanism of these complexes was static quenching rather than dynamic quenching and exhibited strong binding between serum albumin and AmB nanomicelles. The results from UV-Visible spectra, FT-IR spectra, and CD spectra revealed that the AmB formulations affected the structure of both HSA and BSA proteins by changing the microenvironment around the tryptophan residues of protein and caused a secondary structure change of the protein with the loss of helical stability. The molecular docking experiments also supported the above results and effectively proved the binding and changes in the conformation of serum albumins by AmB micelles. This finding provides information of in vitro drug-plasma protein interactions for further study on the AmB binding mechanism and the pharmacodynamics and pharmacokinetics.

Nonionic but water soluble, [Glycine-Pd-Alanine] and [Glycine-Pd-Valine] complexes. Their synthesis, characterization, antitumor activities and rich DNA/HSA interaction studies

Two novel, neutral and water soluble Pd(II) complexes of formula [Pd(Gly)(Ala)] (1) and [Pd(Gly)(Val)] (2) (Gly, Ala, and Val are anionic forms of glycine, alanine, and valine amino acids, respectively) have been synthesized and characterized by FT-IR, UV-Vis, ¹H-NMR, elemental analysis, and molar conductivity measurement. The data revealed that each amino acid binds to Pd(II) through the nitrogen of -NH₂ and the oxygen of -COO^- groups and acts as a bidentate chelate. These complexes have been assayed against leukemia cells (K₅₆₂) using MTT method. The results indicated that both of the complexes display more cytotoxicity than the well-known anticancer drug, cisplatin. The interaction of the compounds with calf thymus DNA (CT-DNA) and human serum albumin (HSA) were assayed by a series of experimental techniques including electronic absorption, fluorescence, viscometry, gel electrophoresis, and FT-IR. The results indicated that the two complexes have interesting binding propensities toward CT-DNA as well as HSA and the binding affinity of (1) is more than (2). The fluorescence data indicated that both complexes strongly quench the fluorescence of ethidium bromide-DNA system as well as the intrinsic fluorescence of HSA via static quenching procedures. The thermodynamic parameters (ΔH°, ΔS°, and ΔG°) calculated from the fluorescence studies showed that hydrogen bonds and van der Waals interactions play a major role in the binding of the complexes to DNA and HSA. We suggest that both of the Pd(II) complexes exhibit the groove binding mode with CT-DNA and interact with the main binding pocket of HSA. Communicated by Ramaswamy H. Sarma.

Self-Assembled Novel BODIPY-Based Palladium Supramolecules and Their Cellular Localization

Four new palladium metal supramolecules with triangular/square architectures derived from boron dipyrromethane (BODIPY) ligands were synthesized by self-assembly and fully characterized by ¹H and ³¹P NMR, electrospray ionization mass spectrometry, and single-crystal X-ray diffraction. These supramolecules were more cytotoxic to brain cancer (glioblastoma) cells than to normal lung fibroblasts. Their cytotoxicity to the glioblastoma cells was higher than that of a benchmark metal-based chemotherapy drug, cisplatin. The characteristic green fluorescence of the BODIPY ligands in these supramolecules permitted their intracellular visualization using confocal microscopy, and the compounds were localized in the cytoplasm and on the plasma membrane.

Synthesis, characterization and biological evaluation of novel α, β unsaturated amides

Three derivatives of α,β unsaturated amides have been successfully synthesized via Ugi-four component (U-4CR) reaction. The interactions of the amides with calf thymus deoxyribonucleic acid (ct-DNA) have been investigated in the Tris-HCl buffer (pH=7.4) using viscometric, spectroscopic, thermal denaturation studies, and also molecular docking. By UV-Vis absorption spectroscopy studies, adding CT-DNA to the compound solution caused the hypochromism indicates that there are interactions between the compounds and DNA base pairs. In competitive fluorescence with methylene blue as an intercalator probe, adding compounds to DNA-MB solution caused an increase in emission spectra of the complex. This could be because of compound replacing, with similar binding mode of MB, between the DNA base pairs due to release of bonded MB molecules from DNA-MB complex. Thermal denaturation studies and viscometric experiments also indicated that all three investigated compounds bind to CT-DNA by non-classical intercalation mode. Additionally, molecular docking technique predicted partial intercalation binding mode for the compounds. Also, the highest binding energy was obtained for compound 5a. These results are in agreement with results obtained by empirical methods.

Novel BODIPY-based Ru(ii) and Ir(iii) metalla-rectangles: cellular localization of compounds and their antiproliferative activities

The synthesis and antiproliferative activities of novel BODIPY-based Ru and Ir rectangles are presented.

Novel bio-essential metal based complexes linked by heterocyclic ligand: Synthesis, structural elucidation, biological investigation and docking analysis

New series of bio-essential metal based complexes linked by Schiff base ligand (L) and 2,2'-bipyridine (bpy) have been synthesized and characterized by diverse spectral techniques such as elemental analysis, magnetic susceptibility, molar conductivity measurements, FT-IR, UV-Vis., (1)H NMR, (13)C NMR, EPR and Mass. The spectral data suggest that the metal complexes espouse octahedral geometry around the metal ions. Interactions of the complexes with CT DNA have been explored by electronic absorption, ethidium bromide displacement assay, viscosity measurements, cyclic voltammetry and differential pulse voltammetry in order to evaluate the possible DNA-binding mode and to calculate the corresponding DNA-binding constants. The DNA interaction studies propose that the intercalative mode of interaction and the complexes exhibit oxidative cleavage of pUC19 DNA in the presence of hydrogen peroxide as activator. The synthesized Schiff base ligand and its metal complexes have been screened for anti-microbial activity by micro dilution method against two Gram-positive bacteria (Staphylococcus aureus and Bacillus subtilis), two Gram-negative bacteria (Escherichia coli and Salmonella typhi) and three fungi strains (Fusarium solani, Aspergillus niger and Candida albicans) revealing that the complexes are good anti-pathogenic agents than the ligand. Moreover, molecular docking analysis has been performed to confirm the nature of binding of the complexes with DNA.