Open Circular Form Research Articles

Analytical and Functional Characterization of Plasmid DNA Topological Forms and Multimers.

Plasmid DNA (pDNA) is an essential tool in genetic engineering that has gained prevalence in cell and gene therapies. Plasmids exist as supercoiled (SC), open circular (OC), and linear forms. Plasmid multimerization can also occur during the manufacturing process. Even though the SC forms are thought to provide optimal knock-in (KI) efficiency, there is no strong consensus on the effect of the topological forms and multimers on the functional activity. In addition, the results obtained for conventional pDNAs (>5 kbp) do not necessarily translate to smaller pDNAs (∼3 kbp). In this study, a workflow was developed for the analytical and functional characterization of pDNA topological forms and multimers. An anion exchange chromatography (AEC) method was first developed to quantify the topological forms and multimers. Four AEC columns were initially compared, one of which was found to provide superior chromatographic performance. The effect of mobile phase pH, various salts, column temperature, and acetonitrile content on the separation performance was systematically studied. The method performance, including precision and accuracy, was evaluated. The final AEC method was compared to capillary gel electrophoresis (CGE) by analyzing several pDNA sequences and lots. A forced degradation study revealed unexpectedly high degradation of the SC forms. Finally, the KI efficiency was compared for the SC and OC forms, and the multimers.

First Report of Tomato Leaf Curl Bangladesh Virus Associated with Leaf Yellowing Symptoms in Lablab purpureus in Bangladesh

First Report of Tomato Leaf Curl Bangladesh Virus Associated with Leaf Yellowing Symptoms in <i>Lablab purpureus</i> in Bangladesh

Phenolic furanochromene hydrazone derivatives: Synthesis, antioxidant activity, ferroptosis inhibition, DNA cleavage and DNA molecular docking studies

Twenty-four phenolic furanochromene hydrazone derivatives were designed and synthesized in order to evaluate structure–activity relationships in a series of antioxidant-related assays. The derivatives have varying substitution patterns on the phenol ring, with some compounds having one, two or three hydroxy groups, and others containing one hydroxy group in combination with methoxy, methyl, bromo, iodo and/or nitro groups. Antioxidant activity was determined using the DPPH free radical scavenging and CUPRAC assays. Compounds containing ortho-dihydroxy and para-dihydroxy patterns had the highest free radical scavenging activity, with IC50 values ranging from 5.0 to 28 μM. Similarly, derivatives with ortho-dihydroxy and para-dihydroxy patterns, together with a 4-hydroxy-3,5‑dimethoxy pattern, displayed strong copper (II) ion reducing capacity, using Trolox as a standard. Trolox equivalent antioxidant capacity (TEAC) coefficients for these derivatives ranged from 1.75 to 3.97. As further evidence of antioxidant potential, greater than half of the derivatives reversed erastin-induced ferroptosis in HaCaT cells. In addition, twenty-three of the derivatives were effective at cleaving supercoiled plasmid DNA in the presence of copper (II) ions at 1 mM, with the 3,4‑dihydroxy derivative showing cleavage to both the linear and open circular forms at 3.9 uM. The interaction of the phenolic furanochromene derivatives with DNA was confirmed by molecular docking studies, which revealed that all the derivatives bind favorably in the minor groove of DNA.

First Report of Squash leaf curl China virus Associated with Mosaic and Mild Leaf Curl Disease of Pumpkin in Bangladesh

First Report of <i>Squash leaf curl China virus</i> Associated with Mosaic and Mild Leaf Curl Disease of Pumpkin in Bangladesh

Enzymatic Supercoiling of Bacterial Chromosomes Facilitates Genome Manipulation.

The physical stability of bacterial chromosomes is important for their in vitro manipulation, while genetic stability is important in vivo. However, extracted naked chromosomes in the open circular form are fragile due to nicks and gaps. Using a nick/gap repair and negative supercoiling reaction (named SCR), we first achieved the negative supercoiling of the whole genomes extracted from Escherichia coli and Vibrio natriegens cells. Supercoiled chromosomes of 0.2–4.6 megabase (Mb) were separated by size using a conventional agarose gel electrophoresis and served as DNA size markers. We also achieved the enzymatic replication of 1–2 Mb chromosomes using the reconstituted E. coli replication-cycle reaction (RCR). Electroporation-ready 1 Mb chromosomes were prepared by a modified SCR performed at a low salt concentration (L-SCR) and directly introduced into commercial electrocompetent E. coli cells. Since successful electroporation relies on the genetic stability of a chromosome in cells, genetically stable 1 Mb chromosomes were developed according to a portable chromosome format (PCF). Using physically and genetically stabilized chromosomes, the democratization of genome synthetic biology will be greatly accelerated.

Elite Zingiber extracts as potential free radical scavengers and radioprotectors

ABSTRACT Fresh rhizome extracts of four elite Zingiber species, viz., Zingiber kangleipakense, Zingiber montanum, Zingiber officinale, and Zingiber zerumbet, prepared in 60% aqueous ethanol/60% aqueous methanol solutions were used for assessing their comparative free radical scavenging and radioprotective properties. Various methods, such as ferric ion reducing power assay, DPPH ion scavenging assay, nitric oxide scavenging assay, metal chelating assay, thiyl/sulfur free radical reactivity assay, and hydroxyl ion scavenging assay, were employed for radical scavenging capabilities. Bio-active principles, such as total phenolic, flavonoid, and ascorbic acid contents, were also assessed. Z. officinale showed the highest TPC, TFC, and ascorbic acid content of 650 mg GAE/100 g, 889 mg QE/100 g, and 3.19 mg/100 g, respectively, as well as the greatest efficacy in ferric ion reducing and DPPH scavenging ability having lowest IC50 value of 0.22 mg/mL. Z. montanum showed the lowest IC50 value of 0.91 mg/mL in NO scavenging assay and also exhibited the highest curcumin protection in thiyl free radical scavenging assay. Z. kangleipakense showed the lowest IC50 value of 0.24 mg/mL and 0.25 mg/mL in metal ion chelating assay and hydroxyl radical assay, respectively. 60% aqueous ethanol extracts of Z. officinale and Z. kangleipakense were used for radioprotective assays both for in vitro and in vivo using plasmid pBR322 DNA and bone marrow cells of albino rats, respectively, based on their significant free radical scavenging properties. At the same concentration of 0.25 mg/mL, Z. officinale and Z. kangleipakense showed 71.50% and 56.54% protection, respectively, of DNA from exposure to 6 Gy gamma radiation. Also, Z. officinale and Z. kangleipakense exhibited 51.16% and 38.96% protection from radiation-induced chromosomal damages in rats, respectively, when exposed to 2 Gy. Reduction in the DNA open circular form as well as the chromosomal aberrations in treatments with plant extracts compared to the controls confirmed the radioprotective potentials of the extracts. The results showed that the extracts possessed potential antioxidant compounds having capacities to scavenge radiation-induced free radical species. The accessibility of the extracts in radiation countermeasures can provide immense nutraceutical potentials.

Evaluation of Leea rubra Leaf Extract for Oxidative Damage Protection and Antitumor and Antimicrobial Potential.

Background The leaves of Leea rubra contain an abundance of phenolic constituents and have medicinal uses as antipyretic and diaphoretic agents and are also used in the treatment of stomach ache, rheumatism, arthritis etc. In spite of the traditional uses, data on the scientific evaluation of the plant are not sufficient. So, the present study was designed to evaluate the protective role of the extract against oxidative damage to DNA and human erythrocytes as well as antitumor and antibacterial activities against some resistant bacteria. Methods The protective activity of the ethyl acetate fraction (EAF) of the extract was investigated by evaluating the inhibition of oxidative damage of pUC19 plasmid DNA as well as hemolysis and lipid peroxidation damage to human erythrocytes induced by 2,2′-azobis-2-amidinopropane (AAPH). Antitumor activity was assessed by evaluating the percentage inhibition of cell growth, morphological changes of Ehrlich's ascites carcinoma (EAC) cells, and hematological parameters. Antimicrobial activity was determined by the disc diffusion method against different resistant microorganisms. Results EAF effectively inhibited AAPH-induced oxidative damage to DNA because it can inhibit the transformation of the supercoiled form of plasmid DNA to open circular and further linear form. The oxidative hemolysis caused by AAPH in human erythrocytes was inhibited by EAF extract in a time-dependent manner, and the production of malondialdehyde (MDA) was significantly reduced, which indicates the prevention of lipid peroxidation. In antitumor assay, 76% growth of inhibition of EAC was observed compared with the control mice (p < 0.05) at a dose of 100 mg/kg body weight. Antimicrobial activity was evaluated against two pathogenic resistant microorganisms (Escherichia coli and Pseudomonas aeruginosa), and the highest antimicrobial activity was observed against Pseudomonas spp. Conclusion EAF may have great importance in preventing oxidative damage to DNA, erythrocytes, and other cellular components as well as can be a good candidate in cancer chemotherapy and treating infectious diseases caused by antibiotic-resistant bacteria.

Use of Ganoderma lucidum (Ganodermataceae, Basidiomycota) as Radioprotector.

For millennia, naturopaths and physicians have used Ganoderma lucidum (reishi mushroom) for its diverse therapeutic properties, as recorded in the oldest Chinese herbal encyclopedia. Indeed, a radioprotective effect has been reported in the isolated components of its extracts. A systematic review and meta-analyses (PRISMA) was conducted in March 2020, searching databases including PubMed, Scopus, Embase, and Google Scholar, along with Clinical Trials. The inclusion criteria were ex vivo, in vitro, and in vivo studies, with full texts in English, conducted to determine the radioprotective benefits of G. lucidum, or reports in which ionizing radiation was used. From a total number of 1109 records identified, 15 full text articles were eligible, none of them were clinical trials. In vivo studies reveal the efficiency of G. lucidum aqueous extracts of polysaccharides and triterpenes in mice exposed to γ-rays. In plasmid, they can reduce radiation damage as an increment of the open circular form, as well as increase the DNA extension, as shown in vitro studies. Ex vivo studies conducted in human blood cells show the radioprotective effect of β-glucan of aqueous extract of G. lucidum, nevertheless, its implementation as radioprotector to humans is in need of further clinical research studies.

Grape extract protect against ionizing radiation-induced DNA damage

Grape extracts of different cultivars (Flame seedless, Kishmish chorni, Red globe and Thompson seedless) were investigated for in vitro antioxidant activity by ABTS assay, and compared protective efficacy against radiation-induced DNA damage. Seed extract showed the highest scavenging activity, followed by skin extract. Among different cultivars, ‘flame seedless’ skin extract showed higher scavenging activity followed by ‘Kishmish chorni’ skin extract. Grape extracts significantly prevented radiation-induced plasmid DNA damage. Super-coiled pBR 322 plasmid DNA (~93%) is completely converted to open circular (~97%) and linear (~2%) form at a dose of 150 Gy γ-radiation. Pretreatment with different grape extracts showed various degree of protection against radiation-induced DNA damage. Pretreatment with 1.6 µg grape skin extract of ‘Thompson seedless’ cultivar or grape flesh extract of any tested cultivar diminished the DNA strand breaks, and there was an increase in the super coiled form of DNA against 150 Gy of γ-radiation. However, pretreated pBR 322 DNA with the skin of ‘Kishmish chorni’ cultivars or seed of ‘red globe’ grape cultivars remained static during electrophoresis and confined in the groove on exposure to 150 Gy γ-radiation treatment. Co-treatment with the skin of red globe cultivar also partially confined plasmid DNA in the groove. The same trend was observed when plasmid DNA was exposed to 1.2 kGy γ-radiation. Our investigation revealed that anthocyanin present in grape skin was probably involved in radio protective activities through the formation of co-pigmentation with DNA.

Investigation of the protection efficacy of Thai medicinal plants on irradiation-induced plasmid DNA damage

Extracts of Thai medicinal plants have been reported to be natural sources of antioxidants which can inhibit free radicals and have potential for radiation protection. In this study, we investigated the efficacy of five medicinal plant extracts, cinnamon, ginger, white kwao krua, black pepper, and moringa compared to gallic acid, which served as a positive control in the protection of plasmid pET-15b DNA after exposure to gamma irradiation. pET-15b plasmid DNA was irradiated by gamma radiation at 100 Gy with various concentrations of medicinal plant extracts and DNA damage was measured by using gel electrophoresis. The results showed that exposure of pET-15b plasmid DNA to 100 Gy of gamma radiation induced DNA strand breakage and plasmid DNA alteration from a supercoiled to open circular form. Extracts of moringa, cinnamon and ginger significantly reduced plasmid DNA damage by gamma radiation. While black pepper and white kwao krua extracts did not show observable radioprotective effects. The presence of moringa, cinnamon and ginger extracts during irradiation can protect pET-15b plasmid against radiation-induced DNA damage.

Fluorescence and Absorption Titrations of Bio-relevant Imidazole Based Organometallic Pd(II) Complexes with DNA: Synthesis, Characterization, DNA Interaction, Antimicrobial, Cytotoxic and Molecular Docking Studies

Organometallic Pd(II) complexes(4a–4f) of type Na[Pd(3n)Cl2]; where 3n = imidazole ligands (3a–3f), were synthesized. The complexes have been characterized by elemental analysis, thermogravimetric analysis, conductance measurement, mass spectrometry, UV–visible absorption spectroscopy, IR, 1H NMR, 13C APT NMR and Energy-dispersive X-ray spectroscopy. The compounds were screened for various biological activities such as nucleolytic, DNA binding, bacteriostatic (MIC) and cytotoxicity. DNA binding aptitude has been studied by UV–visible absorption titration, fluorescence spectroscopy, molecular modelling and viscosity measurement, which suggests Pd(II) complexes as DNA intercalating agents. Gibb’s free energy, enthalpy and entropy change parameters were evaluated for DNA–complex interaction by UV–visible absorption titration at different temperature, in which negative value of all the thermodynamic parameters suggests that the ligand–DNA complex is stabilized by hydrogen bonding and van der Waals forces. The gel electrophoresis of pUC19 DNA in presence of Pd(II) complexes showed the conversion of supercoiled DNA into open circular and linear form of DNA. Compounds were screened against different pathogens for evaluating their bacteriostatic activity in terms of MIC. In vitro cytotoxicity on Artemia cysts and in vivo cytotoxicity on S. pombe cells propose potent cytotoxic nature of Pd(II) complexes.

DNA Strand Breaks Induced by Fast and Thermal Neutrons from YAYOI Research Reactor in the Presence and Absence of Boric Acid.

It is well known that neutrons have more damaging effects, with high relative biological effectiveness or a radiation weighting factor depending on neutron energy, compared to low-LET ionizing radiations. In the current work, we evaluated the contribution of the indirect effect induced by radicals for the purpose of studying the mechanisms of fast neutron effects or mechanisms of boron neutron capture therapy (BNCT) using relatively lower energy neutrons. Plasmid pBR322 DNA with a supercoiled structure was irradiated with fast neutrons (1-10 MeV) in the reactor core of the YAYOI research reactor at the University of Tokyo, and with thermalized neutrons passing through a phantom made of acrylic resin to simulate a human body. The single- and double-strand breaks (SSBs and DSBs) of the plasmid were evaluated from the numbers of its open circular and linear forms, respectively, detected using agarose gel electrophoresis. The number of supercoiled forms decreased exponentially with the absorbed dose of fast neutrons. The decrease was inhibited by dimethyl sulfoxide (DMSO) in a concentration-dependent manner. The contributions of the indirect effect to DNA strand breaks by fast neutrons and thermalized neutrons were calculated to be 50-65% which, while lower than the value for X rays, still accounts for the majority of the DNA strand breaks. In the case of thermalized neutrons, SSB and DSB yields were increased by the addition of boric acid. Moreover, an increased 10B isotope concentration was found to increase the DSB/SSB ratio.

Study of the interaction of Co(III) polypyridyl complexes with DNA: an experimental and computational approach

Three new cobalt(III) polypyridyl complexes, [Co(L - L)2IIP]3+ where IIP = 2-(2H-isoindol-1-yl)-2H-imidazo[4,5-f][1, 10]phenanthroline, L = 1) phen (1,10-phenanthroline), 2) bpy (2,2’bipyridyl), 3) dmb (4, 4-dimethyl 2, 2’-bipyridine) have been synthesized, characterized (UV –VIS, IR, 1HNMR and 13C NMR spectroscopy) and screened for their in vitro antibacterial activity against E.coli, Staphylococcus aureus and Bacillus subtilis. The binding of these complexes with calf-thymus DNA (CT-DNA) has been investigated by absorption and fluorescence spectroscopy, viscosity measurements. The experimental studies indicate that complexes bind to CT-DNA by means of intercalation, but with different binding affinities due to differences in the planarity of the ancillary ligand. The complexes promote photocleavage of plasmid DNA from super coiled form I to the open circular form II. The antibacterial activities suggest that the metal complexes are more active as compared to the prepared un-complexed IIP ligand.In addition, a conformational search was carried out by Molecular Dynamics Simulations, and docking revealed that complexes intercalate between base pairs of DNA. The experimental and computational approaches reveal that the length of the intercalator and the nature of ancillary ligand are highly important factors for DNA binding.

Synthesis and Characterisation of Transition Metal Complexes Derived from 4-Aminoantipyrine and Thiosemicarbazide Based Schiff Base

Abstract A novel Schiff base ligand was synthesized through the condensation of 4-Aminoantipyrine with 1, 3-isophthaldehyde and Thiosemicarbazide. The Schiff base ligand and its metal complexes of Co(II), Ni(II), Cu(II) and Zn(II) were synthesized and characterized by elemental analyses, molar conductance, magnetic susceptibility measurement , IR, UV-Vis, 1 H NMR, Mass and EPR spectral studies. The data showed that the complexes have composition of [ML]Cl 2 stoichiometry. The conductivity data confirmed the electrolytic nature of the complexes. The metal complexes of Co (II), Ni (II), and Zn (II) were showed an octahedral configuration. The electronic absorption spectra of the Cu (II) complex suggested a square- planar geometry around the central metal ion further it was confirmed by the EPR spectrum. The IR spectral data suggest the involvement of sulphur and azomethine nitrogen in coordination to the central metal ion. The interaction of the complexes with calf thymus (CT) DNA has been studied using absorption spectra and Cyclic Voltammetric measurement. The metal complexes exhibit effective cleavage of pBR 322 DNA from the super coiled form to the open circular form. The synthesized complexes have been subjected to antimicrobial study. The antimicrobial results indicated that the antimicrobial activity of the complexes show the enhanced activity in comparison to free ligand. These findings are giving suitable support for developing new anti cancer and antimicrobial agent and expand our scope for applications.

Exploiting the biological efficacy of benzimidazole based Schiff base complexes with l-Histidine as a co-ligand: Combined molecular docking, DNA interaction, antimicrobial and cytotoxic studies

Four new metal complexes were synthesized and screened for their cytotoxic activity after sufficient assertion from the preliminary DNA binding studies. The metal complexes could bind to CT-DNA through intercalation binding mode. This has also been confirmed by the molecular docking studies. The DNA cleavage efficiencies of these complexes with pBR322 DNA were investigated by gel electrophoresis. The complexes were found to promote the cleavage of pBR322 DNA from the supercoiled form I to the open circular form II in the presence of an oxidizing agent (H2O2). The in vitro chemosensitivity of the studied complexes exhibits significant cytotoxic effects, compared to those reported for cisplatin. These findings represent a prompting to search for the probable interaction of these complexes with other cellular elements of fundamental consequence in cell proliferation. The in vitro anticancer activities indicate that the Cu(II) complex is active against the selected human tumor cell lines, and the order of in vitro anticancer activities is consistent with the DNA-binding affinities. Towards noncancerous cell line, Cu(II) complex exhibits very low toxicity. On the other hand all the complexes have been found to exhibit cytotoxic effects against cancerous cell lines with potency more than that of the widely used drug cisplatin and hence they have the potential to act as promising anticancer agents. Captivatingly, they are non-toxic to normal cell lymphocytes revealing that they are selective in killing only the cancer cells.

Synthesis, Spectroscopic Characterization, DNA Binding Ability and Biological Activities of Transition Metal Complexes Containing Tridentate Schiff base

A new series of transition metal complexes of Cu(II),Ni(II),Co(II),and Zn(II) have been synthesized from the Schiff base (L) derived from1,3- isopthaldehyde with 2-amino phenol and 4-Nitroaniline. Its Cu(II), Co(II), Ni(II), Zn(II) complexes have also been synthesized in ethanol medium. The structural features have arrived from their elemental analyses, molar conductance, magnetic susceptibility, IR, UV–Vis, mass, ESR and 1H NMR spectral studies. The data show that the complexes have composition of ML2 type. The electronic absorption spectral data of the complexes suggest an octahedral geometry around the central metal ion. The interaction of the complexes with calf thymus (CT) DNA has been studied using absorption spectra, and Cyclic Voltammetric measurement. The metal complexes exhibit effective cleavage of pBR 322 DNA from the super coiled form to the open circular form. These complexes also show enhanced antifungal and antibacterial activities compared with the free ligand

Antioxidant and Cytoprotective Activities of Enzymatic Extracts from Rhizoid of Laminaria japonica.

Rhizoid of Laminaria japonica was hydrolyzed with proteases and carbohydrases to obtain antioxidant materials. Oxygen radical absorbance capacity (ORAC) of the enzymatic extracts was evaluated and the Protamex extract (PE) exhibited the highest ORAC value. PE also potently scavenged 2,2-diphenyl-1-picrylhydrazyl radical, 2,2′-azino-bis(3-ethylbenzthiazoline-6-sulphonic) acid cation radical, and hydrogen peroxide (H2O2) and had good reducing power. PE inhibited hydroxyl radical-induced DNA scission by measuring the conversion of supercoiled pBR322 plasmid DNA to the open circular form. The cytoprotective effect of PE against H2O2-induced hepatic cell damage was also investigated. PE showed a dose-dependent cytoprotective effect in cultured hepatocytes by inhibiting intracellular reactive oxygen species scavenging activity. In addition, PE up-regulated the expression of heme oxygenase-1, which is a cytoprotective enzyme, by activating translocation of nuclear factor-erythroid 2-related factor 2. Taken together, the enzymatic extract of rhizoid of L. japonica, particularly PE, may be useful for antioxidant additives.

Evolution of palladium(II) complexes as DNA intercalator and artificial metallonuclease

New complexes of Pd(II) with only thiophene derivatives and also thiophene derivatives with benzene-1,2-dithiol (bdt) were synthesized and deliberately investigated. All synthesized complexes were characterized by elemental analysis, conductivity measurements, thermogravimetric analysis, magnetic moment measurements, electronic spectra, 1H NMR, FT-IR and LC–MS. Antibacterial study was carried out against pathogenic bacteria like Staphylococcus aureus, Escherichia coli, Bacillus subtilis, Serratia marcescens, and Pseudomonas aeruginosa. Toxic property of synthesized complexes was determined using in vitro brine shrimp (Artemia cysts) lethality bioassay technique. The complexes were screened for DNA-binding study using UV–Vis absorption titration and relative viscosity measurement study. Hypochromism with bathochromic shift in absorption titration and increase in viscosity indicate the intercalative binding of the complexes with CT-DNA. Intercalative mode of binding of the complex with CT-DNA was also shown by molecular modelling. DNA cleavage study of the complexes was performed by gel electrophoresis experiment using pUC19 DNA. All complexes are very effective artificial metallonuclease, which promote the cleavage of DNA from supercoil to open circular form. Anti-tuberculosis activity was tested using Mycobacterium tuberculosis H37RV bacteria by LJ medium conventional method.

DNA interaction and cleavage studies of ancillary chiral ligand and N,N‐donor ligands coordinated platinum(II) complexes

Four new platinum(II) complexes [Pt(dpen)(bpy)](ClO4)2 (1), [Pt(dpen)(phen)](ClO4)2 (2), [Pt(dpen)(dpq)](ClO4)2 (3) and [Pt(dpen)(dppz)](ClO4)2 (4) comprising of different N,N‐donor ligands, viz., 2,2′‐bipyridine (bpy), 1,l0‐phenanthroline (phen), dipyridoquinoxaline (dpq), dipyrido‐[3,2‐d:2¢,3¢‐f–phenazine] (dppz), and chiral ancillary ligand 1R,2R‐1,2‐diphenylethylenediamine (dpen) have been synthesized and characterized. The interaction of these complexes 1–4 with calf‐thymus DNA (CT‐DNA) has been explored using absorption, circular dichroism spectral and cyclic voltammetric studies. The absorption spectrum of complex 4 with dppz ligand exhibits a major red shift with an overall hypochromic as well as a hyperchromic effect in the presence of DNA, other complexes (1–3) show only hypochromism. From these absorption spectral studies, the intercalative ability of the complexes follows the order as, 4 &gt; 3 &gt; 2 &gt; 1, which is further confirmed by CD and cyclic voltammetry measurements. CD spectral studies show that DNA becomes more A‐like upon interaction with the complexes 1 &amp; 2 but the complexes 3 &amp; 4 bring about B‐form to Z‐ form DNA conformational transition. The DNA cleavage study of these Pt(II) complexes 1–4 carried out by gel electrophoresis revealed that complexes 1–4 can cleave super coiled (SC) pUC18 DNA efficiently into open circular form (form II) under hydrolytic and oxidative conditions.

Mixed ligand N4O2 type metal(II) complexes as metallointercalators: Preliminary investigation of DNA-binding/cleavage and antimicrobial

ABSTRACTFew N4O2-type mixed ligand complexes (metallointercalators) were synthesized using benzene-1,2-diamine-derived Schiff base as primary ligand and 8-hydroxyquinoline as co-ligand. They were characterized by physicochemical and spectral techniques. The binding properties with DNA explored by different techniques indicate that the complexes have the ability to interact with DNA by intercalative mode. Gel electrophoresis technique reveals that the complexes have been found to promote cleavage of pUC19 DNA from the supercoiled form to the open circular form in the presence of ascorbic acid. The biological screening data exhibit that the complexes show growth inhibitory activity against various microorganisms.