Double-strand hydrolysis of plasmid DNA by dicerium complexes at 37 degrees C

Nuclease-Mimetic Nanomaterials: From Fundamentals to Bioapplications

With the rapid development of nanozymes and nanomedicine, designing novel nanostructures directly acting on deoxyribonucleic acid (DNA) has great therapeutic potential because DNA is the carrier of genetic information and plays a vital role on life activities of the organism. Specifically, DNA cleavage is an important step in most of these DNA engineering technologies. While nucleases play crucial roles in the cell metabolism by efficient DNA cutting, the practical applications of natural nucleases suffer from some intrinsic shortcomings such as high cost and intolerance to harsh environments. In the past 20 years, great varieties of engineered nanostructures with DNA cleavage (nuclease-mimetic nanomaterials, abbreviated as nuclease mimics) have been developed rapidly and widely used in biomedical fields. In view of the significant progress of nuclease-mimetic nanomaterials, the possible DNA cleavage mechanism mediated by nuclease-mimetic nanomaterials is systematically discussed in this review, and the classification of nuclease-mimetic nanomaterials is illustrated. Their potential biomedical applications, especially in anti-biofilms and cancer treatment, are also comprehensively summarized. Finally, the current opportunities and challenges are discussed to stimulate the research of understanding and development of nuclease-mimetic nanomaterials.

Recent Development of Nanozymes for Combating Bacterial Drug Resistance: A Review

The World Health Organization has warned that without effective action, deaths from drug-resistant bacteria can exceed 10 million annually, making it the leading cause of death. Conventional antibiotics are becoming less effective due to rapid bacterial drug resistance and slowed new antibiotic development, necessitating new strategies. Recently, materials with catalytic/enzymatic properties, known as nanozymes, have been developed, inspired by natural enzymes essential for bacterial eradication. Unlike recent literature reviews that broadly cover nanozyme design and biomedical applications, this review focuses on the latest advancements in nanozymes for combating bacterial drug resistance, emphasizing their design, structural characteristics, applications in combination therapy, and future prospects. This approach aims to promote nanozyme development for combating bacterial drug resistance, especially towards clinical translation.

Efficient Cleavage of pUC19 DNA by Tetraaminonaphthols

In an attempt to create models of phosphodiesterases, we previously investigated bis(guanidinium) naphthols. Such metal-free anion receptors cleaved aryl phosphates and also plasmid DNA. Observed reaction rates, however, could not compete with those of highly reactive metal complexes. In the present study, we have replaced the guanidines by ethylene diamine side chains which accelerates the plasmid cleavage by compound 13 significantly (1 mM 13: t1/2=22 h). Further gains in reactivity are achieved by azo coupling of the naphthol unit. The electron accepting azo group decreases the pKa of the hydroxy group. It can also serve as a dye label and a handle for attaching DNA binding moieties. The resulting azo naphthol 17 not only nicks (1 mM 17: t1/2~1 h) but also linearizes pUC19 DNA. Although the high reactivity of 17 seems to result in part from aggregation, in the presence of EDTA azo naphthol 17 obeys first order kinetics (1 mM 17: t1/2=4.8 h), reacts four times faster than naphthol 13 and surpasses by far the former bis(guanidinium) naphthols 4 and 5.

Gene identification and enzymatic characterization of the initial enzyme in pyrimidine oxidative metabolism, uracil-thymine dehydrogenase

Uracil-thymine dehydrogenase (UTDH), which catalyzes the irreversible oxidation of uracil to barbituric acid in oxidative pyrimidine metabolism, was purified from Rhodococcus erythropolis JCM 3132. The finding of unusual stabilizing conditions (pH 11, in the presence of NADP+ or NADPH) enabled the enzyme purification. The purified enzyme was a heteromer consisting of three different subunits. The enzyme catalyzed oxidation of uracil to barbituric acid with artificial electron acceptors such as methylene blue, phenazine methosulfate, benzoquinone, and α-naphthoquinone; however, NAD+, NADP+, flavin adenine dinucleotide, and flavin mononucleotide did not serve as electron acceptors. The enzyme acted not only on uracil and thymine but also on 5-halogen-substituted uracil and hydroxypyrimidine (pyrimidone), while dihydropyrimidine, which is an intermediate in reductive pyrimidine metabolism, and purine did not serve as substrates. The activity of UTDH was enhanced by cerium ions, and this activation was observed with all combinations of substrates and electron acceptors.

Ce-based solid-phase catalysts for phosphate hydrolysis as new tools for next-generation nanoarchitectonics

This review comprehensively covers synthetic catalysts for the hydrolysis of biorelevant phosphates and pyrophosphates, which bridge between nanoarchitectonics and biology to construct their interdisciplinary hybrids. In the early 1980s, remarkable catalytic activity of Ce4+ ion for phosphate hydrolysis was found. More recently, this finding has been extended to Ce-based solid catalysts (CeO2 and Ce-based metal-organic frameworks (MOFs)), which are directly compatible with nanoarchitectonics. Monoesters and triesters of phosphates, as well as pyrophosphates, were effectively cleaved by these catalysts. With the use of either CeO2 nanoparticles or elegantly designed Ce-based MOF, highly stable phosphodiester linkages were also hydrolyzed. On the surfaces of all these solid catalysts, Ce4+ and Ce3+ coexist and cooperate for the catalysis. The Ce4+ activates phosphate substrates as a strong acid, whereas the Ce3+ provides metal-bound hydroxide as an eminent nucleophile. Applications of these Ce-based catalysts to practical purposes are also discussed.

A Ce-MOF as an alkaline phosphatase mimic: Ce-OH2 sites in catalytic dephosphorylation

For the first time, a metal–organic framework (Ce-MOF) bearing a Ce–OH2–Ce motif was used to mimic the active sites of alkaline phosphatase.

One-pot crystallization of two 1,4-cyclohexanedicarboxylate-based tetranuclear Cu(ii) compounds and their DNA binding affinities

Two new tetranuclear Cu(ii) compounds have been synthesized using flexible linker 1,4-cyclohexanedicarboxylic acid in an one-pot crystallization which exhibit dissimilar affinities to DNA binding.

Cerium oxide nanoparticles: properties, biosynthesis and biomedical application

Cerium oxide nanoparticles have revolutionized the biomedical field and is still in very fast pace of development. Hence, this work elaborates the physicochemical properties, biosynthesis, and biomedical applications of cerium oxide nanoparticles.

A biomimetic cerium-based biosensor for the direct visual detection of phosphate under physiological conditions

An indicator displacement assay (IDA) was used to probe phosphate ions in an aqueous medium at neutral pH using a dinuclear cerium based complex [Ce2(HXTA)]3+. The homoleptic complex can be used to detect phosphate ions with nanomolar affinity either spectrophotometrically or with the naked-eye. To our knowledge, this is the first dinuclear cerium biomimetic IDA detection system with the highest affinity known to date for selective, naked-eye based phosphate recognition under physiological conditions (pH = 5-7) and even in pure water and complex samples such as sea water.

Evaluation of cytotoxic activity and genotoxicity of structurally well characterized potent cobalt(II) phen-based antitumor drug entities: An in vitro and in vivo approach

Cobalt (II) phen-based drug candidates of the formulation Co(phen)2Cl2,1, Co(phen)2L, 2 where L = 1H-pyrazole-3,5-dicarboxylic acid were synthesized and thoroughly characterized by spectroscopic methods and single X-ray crystallography. DNA binding interaction of 1 and 2 was carried out employing biophysical techniques {UV-visible, fluorescence, thermal denaturation and cyclic voltammetry} to validate their potential to act as antitumor agents. The interpretations of these biophysical studies of 1 and 2 supported the non-covalent intercalative binding mode; furthermore, a higher binding trend of 2 was observed as compared to 1, phen and 1H-pyrazole-3,5-dicarboxylic acid alone. Cleavage studies of 1 and 2 with pBR322 were assessed by gel electrophoresis and it was observed that both drug candidates cleave DNA by hydrolytic pathway involving hydroxyl radical (OH). Cytotoxic activity of 1 and 2 against human cancer cell lines [MCF-7 (breast), HeLa (cervical), MIA-PA-CA 2 (pancreatic), A-498 (kidney), Hep-G2 (hepatoma)] was evaluated by SRB assay. The obtained results showed that drug candidate 1 showed significantly low GI50 value (<10 µg/ml) against MCF-7 and HeLa cell lines. However, candidate 2 revealed excellent cytotoxicity (<10 µg/ml) against all the tested cancer cell lines. The in vivo genotoxicity of 2 was evaluated by micronucleus (MN) test and chromosomal aberration (CA) in bone marrow cells of the Wistar rats to check cobalt(II)-induced systemic toxicity. The results showed that no significant chromosomal aberrations and micronucleus formation was observed at 5 mg/kg and 10 mg/kg in presence of drug candidate 2 implicating that it could be administered safely at a low dosage. However, an elevated percentage of chromosomal aberration and micronucleated polychromatic erythrocytes (MNPCE) was observed only at higher doses (20 mg/kg and 40 mg/kg) of drug candidate 2.

A series of MOF/Ce-based nanozymes with dual enzyme-like activity disrupting biofilms and hindering recolonization of bacteria

Notorious bacterial biofilms are becoming severe threats to public health worldwide. As the important component in biofilm extracellular polymeric substances (EPS), extracellular DNA (eDNA) has been manifested to connect different EPS components and bacteria together, leading biofilms hard to eliminate. Herein a series of MOF/Ce-based nanozymes with deoxyribonuclease (DNase) and peroxidase mimetic activities have been designed and synthesized for combating biofilms. The cerium (IV) complexes (DNase mimics) are capable of hydrolyzing eDNA and disrupting established biofilms, while the MOF with peroxidase-like activity can kill bacteria exposed in dispersed biofilms in the presence of H₂O₂. This can avoid the recolonization of bacteria and recurrence of biofilms. Given the fact that single-modal antibacterial agent is difficult to drastically eradicate biofilms, the marriage of two kinds of nanozymes is a rational strategy to acquire enhanced performance in combating biofilms. Besides, the utilization of nanozymes circumvents drawbacks of natural enzymes which are costly and vulnerable. Further studies have demonstrated that this kind of artificial enzyme with dual enzyme-mimetic activities can penetrate the biofilms, and inhibit bacterial biofilm formation intensively. Consistently, in vivo anti-biofilm application in treating subcutaneous abscess exhibits commendable wound healing and admirable bactericidal effect. To the best of our knowledge, it is the first time to devise an integrated nanozyme based on the peroxidase-like activity of MOF to eliminate biofilms and kill bacteria on site. This work may promote the application of MOF in the antibacterial field.

Carbohydrate-based heteronuclear complexes as topoisomerase Iα inhibitor: approach toward anticancer chemotherapeutics

Due to the critical role of cellular enzymes necessary for cell proliferation by deciphering topological hurdles in the process of DNA replication, topoisomerases have been one of the major targets in the anticancer drug development area. A need, therefore, arises for new metallodrugs that specifically recognizes DNA and inhibits the activity of topoisomerase enzymes, herein, we report the synthesis and characterization of new metal-based glycoconjugate entities containing heterobimetallic core CuII-SnIV (1) and NiII-SnIV (2) derived from N-glycoside ligand (L). The optimized structure of complex 1 and other significant vibrational modes have been explained using dispersion corrected B3LYP/DFT calculations. In vitro DNA binding profile of the L and both the complexes 1 and 2 were done by various biophysical studies. Complex 1 breaks pBR322 DNA via a hydrolytic means which was validated by T4 DNA enzymatic assay. To get a mechanistic insight of mode of action topoisomerase I (Topo I) inhibition assay was carried out. Also, we have taken the help of molecular modeling studies in accordance with experimental findings. In vitro cytotoxicity of the complex 1 was evaluated against a panel of cancer cells which exhibited remarkably good anticancer activity (GI50 values <10 μg/ml). Moreover, intracellular localization of the complex 1 was visualized by confocal microscopy against HeLa cells.

Dinuclear Lanthanide(III)-m-ODO2A-dimer Macrocyclic Complexes: Solution Speciation, DFT Calculations, Luminescence Properties, and Promoted Nitrophenyl-Phosphate Hydrolysis Rates

Potentiometric speciation studies, mass spectrometry, and DFT calculations helped to predict the various structural possibilities of the dinuclear trivalent lanthanide ion (Ln^III , Ln=La, Eu, Tb, Yb, Y) complexes of a novel macrocyclic ligand, m-ODO2A-dimer (H₄ L), to correlate with their luminescence properties and the promoted BNPP and HPNP phosphodiester bond hydrolysis reaction rates. The stability constants of the dinuclear Ln₂ (m-ODO2A-dimer) complexes and various hydrolytic species confirmed by mass spectrometry were determined. DFT calculations revealed that the Y₂ LH_-1 and the Y₂ LH_-2 species tended to form structures with the respective closed- and open-form conformations. Luminescence lifetime data for the heterodimetallic TbEuL system confirmed the fluorescence resonance energy transfer from the Tb^III to Eu^III ion. The internuclear distance R_TbEu values were estimated to be in the range of 9.4-11.3 Å (pH 6.7-10.6), which were comparable to those of the DFT calculated open-form conformations. Multiple linear regression analysis of the k_obs data was performed using the equation: k_obs,corr. =k_obs -k_obs,OH =kLn2LHM->1 [Ln₂ LH_-1 ]+kLn2LH-2 [Ln₂ LH_-2 ] for the observed Ln₂ L-promoted BNPP/HPNP hydrolysis reactions in solution pH from 7 to 10.5 (Ln=Eu, Yb). The results showed that the second-order rate constants for the Eu₂ LH_-2 and Yb₂ LH_-2 species were about 50-400 times more reactive than the structural analogous Zn₂ (m-12 N₃ O-dimer) system.

Tuning the MnII2/MnIII2 redox cycle of a phenoxo-bridged diMn catalase mimic with terminal carboxylate donors

A new phenoxo-bridged diMn^III complex, Na[Mn₂L(OH)₂(H₂O)₂]·5H₂O (1), obtained with the ligand L^5- = 5‑methyl‑2‑hydroxo‑1,3‑xylene‑α,α‑diamine‑N,N,N',N'‑tetraacetato, has been prepared and characterized. Mass spectrometry, conductivity, UV-visible, EPR and ¹H NMR spectroscopic studies showed that the complex exists in solution as a monoanionic diMn^III complex. Complex 1 catalyzes H₂O₂ disproportionation with second-order rate constant k_cat = 305(9) M^-1 min^-1 and without a time-lag phase. Based on spectroscopic results, the catalase activity of complex 1 in methanol involves a Mn^III₂/Mn^II₂ redox cycle, which distinguishes this catalyst from other phenoxo-bridged diMn complexes that cycle between Mn^IIMn^III/Mn^IIIMn^IV species. Addition of base stabilizes the catalyst, restrains demetallation during catalysis and causes moderate enhancement of catalase activity. The terminal carboxylate donors of 1 not only contribute as internal bases to assist deprotonation of H₂O₂ but also favor the formation of active homovalent diMn species, just as observed for the enzyme.

Polyoxometalates as artificial nucleases: hydrolytic cleavage of DNA promoted by a highly negatively charged ZrIV-substituted Keggin polyanion

A highly negatively charged binuclear Zr^IV-substituted Keggin polyoxometalate [{α-PW₁₁O₃₉Zr(μ-OH)(H₂O)}₂]^8- (ZrK 2 : 2) has been shown to promote the hydrolytic cleavage of phosphoester bonds in the supercoiled plasmid pUC19 DNA under physiological pH and temperature, giving relaxed and linear forms of pUC19 as hydrolysis products. The interaction between ZrK 2 : 2 and DNA was experimentally proven by circular dichroism (CD) spectroscopy and ³¹P diffusion ordered NMR spectroscopy.

The large terminase DNA packaging motor grips DNA with its ATPase domain for cleavage by the flexible nuclease domain

Many viruses use a powerful terminase motor to pump their genome inside an empty procapsid shell during virus maturation. The large terminase (TerL) protein contains both enzymatic activities necessary for packaging in such viruses: the adenosine triphosphatase (ATPase) that powers DNA translocation and an endonuclease that cleaves the concatemeric genome at both initiation and completion of genome packaging. However, how TerL binds DNA during translocation and cleavage remains mysterious. Here we investigate DNA binding and cleavage using TerL from the thermophilic phage P74-26. We report the structure of the P74-26 TerL nuclease domain, which allows us to model DNA binding in the nuclease active site. We screened a large panel of TerL variants for defects in binding and DNA cleavage, revealing that the ATPase domain is the primary site for DNA binding, and is required for nuclease activity. The nuclease domain is dispensable for DNA binding but residues lining the active site guide DNA for cleavage. Kinetic analysis of DNA cleavage suggests flexible tethering of the nuclease domains during DNA cleavage. We propose that interactions with the procapsid during DNA translocation conformationally restrict the nuclease domain, inhibiting cleavage; TerL release from the capsid upon completion of packaging unlocks the nuclease domains to cleave DNA.

Coumarin centered copper(ii) complex with appended-imidazole as cancer chemotherapeutic agents against lung cancer: molecular insight via DFT-based vibrational analysis

Synthesis and structural characterization of the novel copper complex, DFT based vibrational analysis, DNA binding studies.In vitrocytotoxicity against A549 cancer cell lines and estimation of GSH, ROS, LPO levels, have been reported.

A Multinuclear Metal Complex Based DNase-Mimetic Artificial Enzyme: Matrix Cleavage for Combating Bacterial Biofilms

Extracellular DNA (eDNA) is an essential structural component during biofilm formation, including initial bacterial adhesion, subsequent development, and final maturation. Herein, the construction of a DNase-mimetic artificial enzyme (DMAE) for anti-biofilm applications is described. By confining passivated gold nanoparticles with multiple cerium(IV) complexes on the surface of colloidal magnetic Fe3 O4  /SiO2 core/shell particles, a robust and recoverable artificial enzyme with DNase-like activity was obtained, which exhibited high cleavage ability towards both model substrates and eDNA. Compared to the high environmental sensitivity of natural DNase in anti-biofilm applications, DMAE exhibited a much better operational stability and easier recoverability. When DMAE was coated on substratum surfaces, biofilm formation was inhibited for prolonged periods of time, and the DMAE excelled in the dispersion of established biofilms of various ages. Finally, the presence of DMAE remarkably potentiated the efficiency of traditional antibiotics to kill biofilm-encased bacteria and eradiate biofilms.

Enzyme Mimics: Advances and Applications

Enzyme mimics or artificial enzymes are a class of catalysts that have been actively pursued for decades and have heralded much interest as potentially viable alternatives to natural enzymes. Aside from having catalytic activities similar to their natural counterparts, enzyme mimics have the desired advantages of tunable structures and catalytic efficiencies, excellent tolerance to experimental conditions, lower cost, and purely synthetic routes to their preparation. Although still in the midst of development, impressive advances have already been made. Enzyme mimics have shown immense potential in the catalysis of a wide range of chemical and biological reactions, the development of chemical and biological sensing and anti-biofouling systems, and the production of pharmaceuticals and clean fuels. This Review concerns the development of various types of enzyme mimics, namely polymeric and dendrimeric, supramolecular, nanoparticulate and proteinic enzyme mimics, with an emphasis on their synthesis, catalytic properties and technical applications. It provides an introduction to enzyme mimics and a comprehensive summary of the advances and current standings of their applications, and seeks to inspire researchers to perfect the design and synthesis of enzyme mimics and to tailor their functionality for a much wider range of applications.

Characterization of antiproliferative potential and biological targets of a copper compound containing 4'-phenyl terpyridine

Several copper complexes have been assessed as anti-tumor agents against cancer cells. In this work, a copper compound [Cu(H2O){OS(CH3)2}L](NO3)2 incorporating the ligand 4'-phenyl-terpyridine antiproliferative activity against human colorectal, hepatocellular carcinomas and breast adenocarcinoma cell lines was determined, demonstrating high cytotoxicity. The compound is able to induce apoptosis and a slight delay in cancer cell cycle progression, probably by its interaction with DNA and induction of double-strand pDNA cleavage, which is enhanced by oxidative mechanisms. Moreover, proteomic studies indicate that the compound induces alterations in proteins involved in cytoskeleton maintenance, cell cycle progression and apoptosis, corroborating its antiproliferative potential.

Tuning Cerium(IV)-Assisted Hydrolysis of Phosphatidylcholine Liposomes under Mildly Acidic and Neutral Conditions

With the goal of designing a lysosomal phospholipase mimic, we optimized experimental variables to enhance Ce(IV) -assisted hydrolysis of phosphatidylcholine (PC) liposomes. Our best result was obtained with the chelating agent bis-tris propane (BTP). Similar to the hydrolytic enzyme, Ce(IV) -assisted hydrolysis of PC phosphate ester bonds was higher at lysosomal pH (∼4.8) compared to pH 7.2. In the presence of BTP, the average cleavage yield at ∼pH 4.8 and 37 °C was: 67±1 %, 5.7-fold higher than at ∼pH 7.2 and roughly equivalent to the percent of phospholipid found on the metal-accessible exo leaflet of small liposomes. No Ce(IV) precipitation was observed. When BTP was absent, there was significant turbidity, and the amount of cleavage at ∼pH 4.8 (69±1 %) was 2.1-fold higher than the yield obtained at ∼pH 7.2. Our results show that BTP generates homogenous solutions of Ce(IV) that hydrolyze phosphatidylcholine with enhanced selectivity for lysosomal pH.

Nuclear blebbing of biologically active organoselenium compound towards human cervical cancer cell (HeLa): in vitro DNA/HSA binding, cleavage and cell imaging studies

New pharmacophore organoselenium compound (1) was designed, synthesized and characterized by various spectroscopic methods (IR, ESI-MS, (1)H, (13)C and (77)Se NMR) and further confirmed by X-ray crystallography. Compound 1 consists of two 3,5-bis(trifluoromethyl)phenyl units which are connected to the selenium atom via the organometallic C-Se bond. In vitro DNA binding studies of 1 was investigated by absorption and emission titration methods which revealed that 1 recognizes the minor groove of DNA in accordance with molecular docking studies with the DNA duplex. Gel electrophoretic assay demonstrates the ability of 1 to cleave pBR322 DNA through hydrolytic process which was further validated by T4 religation assay. To understand the drug-protein interaction of which ultimate molecular target was DNA, the affinity of 1 towards HSA was also investigated by the spectroscopic and molecular modeling techniques which showed hydrophobic interaction in the subdomain IIA of HSA. Furthermore, the intracellular localization of 1 was evidenced by cell imaging studies using HeLa cells.

Luminescent europium and terbium complexes of dipyridoquinoxaline and dipyridophenazine ligands as photosensitizing antennae: structures and biological perspectives

Luminescent europium and terbium complexes of quinoxaline and phenazine ligands were studied for their structures, luminescence properties, interaction with DNA, and photo-induced DNA cleavage activity.

Synthesis, hydrolytic DNA-cleaving activities and cytotoxicities of EDTA analogue-tethered pyrrole-polyamide dimer-based Ce(IV) complexes

Two EDTA analogue-tethered C2-symmetrical dimeric monopyrrole-polyamide 5 and dipyrrole-polyamide 6, and their corresponding Ce(IV) complexes Ce-5 and Ce-6 were synthesized and fully characterized. Agarose gel electrophoresis studies on pBR322 DNA cleavage indicate that complexes Ce-5 and Ce-6 exhibited potent DNA-cleaving activities under physiological conditions. The maximal first-order rate constants (kmax's) were (0.42 ± 0.02) h(-1) for Ce-5 and (0.52 ± 0.02) h(-1) for Ce-6, respectively, suggesting that both complexes catalyzed the cleavage of supercoiled DNA by up to approximately 10(8)-fold. Complex Ce-6 exhibited ca 10-fold higher overall catalytic activity (kmax/KM) than Ce-5, which may be ascribed to its higher DNA-binding affinity. Inhibition experiments and a model study convincingly suggest that both complexes Ce-5 and Ce-6 functioned as hydrolytic DNA-cleavers. In addition, both complexes were found to display moderate inhibitory activity toward A549 and HepG-2 cells.

New modulated design, docking and synthesis of carbohydrate-conjugate heterobimetallic CuII-SnIV complex as potential topoisomerase II inhibitor: in vitro DNA binding, cleavage and cytotoxicity against human cancer cell lines

New carbohydrate-conjugate heterobimetallic complexes [C₂₂H₅₀N₆O₁₃CuSnCl₂] (3) and [C₂₂H₅₈N₆O₁₇NiSnCl₂] (4) were synthesized from their monometallic analogs [C₂₂H₅₂N₆O₁₃Cu] (1) and [C₂₂H₆₀N₆O₁₇Ni] (2) containing N-glycoside ligand (L). In vitro DNA binding studies of L and complexes (1-4) with CT DNA were carried out by employing various biophysical and molecular docking techniques which revealed that heterobimetallic complex 3 strongly binds to DNA in comparison to 4, monometallic complexes (1 and 2) and the free ligand. Complex 3 cleaves pBR322 DNA via hydrolytic pathway (confirmed by T4 DNA ligase assay) and inhibited Topo-II activity in a dose-dependent manner. Furthermore, complex 3 was docked into the ATPase domain of human-Topo-II in order to probe the possible mechanism of inhibition.

Poly[[μ-bis-(4-nitro-phen-yl) phosphato-κ(2) O,O']sodium]

The title compound, [Na(C₁₂H₈N₂O₈P)], consists of one Na⁺ cation and one bis­(p-nitro­phen­yl)phosphate anion with a considerable distortion of the phosphate tetra­hedron due to the presence of two P—O ester bonds. The anion bridges five Na⁺ cations whereby each cation is chelated by the nitro O atoms of one anion and bonded via a nitro O atom and phosphate O atoms to four other anions. This bridging arrangement leads to the formation of double layers parallel to (001). Adjacent layers are linked through weak C—H⋯O hydrogen bonds.

Zinc(II) complexes of Pro-Gly and Pro-Leu dipeptides: synthesis, characterization, in vitro DNA binding and cleavage studies

Dipeptide (Pro-Gly and Pro-Leu) Zinc(II) complexes 1 and 2 were designed and synthesized for potential use as cancer chemotherapeutic agents. In order to augment the DNA recognition of metallonuclease activity, zinc metal ion was tethered to peptide motif to carry out DNA site specific hydrolytic cleavage. The structural formulation of the complexes 1 and 2 was done by elemental analysis, spectroscopic methods (IR, NMR, electronic) and molar conductance measurements. Their in vitro DNA binding profile was investigated by UV-vis titrations, fluorescence titrations and circular dichroism which revealed that these complexes bind to CT DNA by electrostatic interactions via groove binding mode. Zn(II) Pro-Gly complex 1 showed greater binding affinity to CT DNA as compared to the Zn(II) Pro-Leu complex 2 due to steric constraints in the latter. The supercoiled pBR322 DNA cleavage activity of complex 1, ascertained by gel electrophoresis demonstrated efficient DNA cleaving ability via hydrolytic mechanistic pathway. Further, the molecular docking studies confirmed that complex 1 bind to the minor groove of DNA having AT-rich sequences with relative binding energy of -196.72kJmol(-1).

2-Hydroxynaphthalene-1-carbaldehyde- and 2-(aminomethyl)pyridine-based Schiff base Cu(II) complexes for DNA binding and cleavage

Three mononuclear Cu(II) complexes, [CuCl(naph-pa)] (1), [Cu(bipy)(naph-pa)]Cl (2), and [Cu(naph-pa)(phen)]Cl (3) ((naph-pa)=Schiff base derived from the condensation of 2-hydroxynaphthalene-1-carbaldehyde and 2-picolylamine (=2-(aminomethyl)pyridine), bipy=2,2'-bypiridine, and phen=1,10-phenanthroline) were synthesized and characterized. Complex 1 exhibits square-planar geometry, and 2 and 3 exhibit square pyramidal geometry, where Schiff base and bipy/phen act as NNO and as NN donor ligands, respectively. CT (Calf thymus)-DNA-binding studies revealed that the complexes bind through intercalative mode and show good binding propensity (intrinsic binding constant K(b): 0.98×10(5), 2.22×10(5), and 2.67×10(5) M(-1) for 1-3, resp.). The oxidative and hydrolytic DNA-cleavage activity of these complexes has been studied by gel electrophoresis: all the complexes displayed chemical nuclease activity in the presence and absence of H(2)O(2). From the kinetic experiments, hydrolytic DNA cleavage rate constants were determined as 2.48, 3.32, and 4.10 h(-1) for 1-3, respectively. It amounts to (0.68-1.14)×10(8)-fold rate enhancement compared to non-catalyzed DNA cleavage, which is impressive. The complexes display binding and cleavage propensity to DNA in the order of 3>2>1.