DNA targeting polyaza macrobicyclic dizinc(II) complexes promoting high in vitro caspase dependent anti-proliferative activity against human carcinoma cancer cells

A series of macrobicyclic dizinc(II) complexes Zn2L1-2B](ClO4)(4) (1-6) have been synthesized and characterized (L1-2 are polyaza macrobicyclic binucleating ligands, and B is the N,N-donor heterocyclic base (viz. 2,2'-bipyridine (bipy) and 1,10-phenanthroline (phen)). The DNA and protein binding, DNA hydrolysis and anticancer activity of these complexes were investigated. The interactions of complexes 1-6 with calf thymus DNA were studied by spectroscopic techniques, including absorption, fluorescence and CD spectroscopy. The DNA binding constant values of the complexes were found to range from 2.80 x 10(5) to 5.25 x 10(5) M-1, and the binding affinities are in the following order: 3 > 6 > 2 > 5 > 1 > 4. All the dizinc(II) complexes 1-6 are found to effectively promote the hydrolytic cleavage of plasmid pBR322 DNA under anaerobic and aerobic conditions. Kinetic data for DNA hydrolysis promoted by 3 and 6 under physiological conditions give observed rate constants (k(obs)) of 5.56 +/- 0.1 and 5.12 +/- 0.2 h(-1), respectively, showing a 10(7)-fold rate acceleration over the uncatalyzed reaction of dsDNA. Remarkably, the macrobicyclic dizinc(II) complexes 1-6 bind and cleave bovine serum albumin (BSA), and effectively promote the caspase-3 and caspase-9 dependent deaths of HeLa and BeWo cancer cells. The cytotoxicity of the complexes was further confirmed by lactate dehydrogenase enzyme levels in cancer cell lysate and content media.

Design and Synthesis of a Functional Derivative of the Triazinium Cation and Its Rhodium Complex that Shows Photoinduced DNA Cleavage Activity and Photocytotoxicity

The design and synthesis of an intensely blue rhodium(III) complex 3]+ of a new N,N-donor ligand, 8-(quinolin-8-ylamino)pyrido2,1-c]1,2,4]benzotriazin-11-ium, 2]+, which contains a planar pendant triazinium arm, is described. Structural characterization for 3]+ was carried out by using various spectroscopic techniques and single-crystal X-ray crystallography. The organometallic rhodium(III) compound shows a ligand-based reversible reduction at 0.65 V. The electrochemically reduced compound displays a single-line EPR spectrum that signifies the formation of ligand-based free radicals. Compound 3]+ shows a binding propensity to calf thymus DNA to give a Kapp value of 6.05X105 M1. The parent triazinium salt, pyrido2,1-c]1,2,4]benzotriazin-11-ium 1]+ and the ligand salt 2]+ exhibit photoinduced cleavage of DNA in UV-A light, whereas the reference Rh complex 3]+ photocleaves DNA with red light (647.1 nm). The compounds show photonuclease activities under both aerobic and anaerobic conditions. Mechanistic investigations under aerobic conditions with several inhibitors indicate the formation of hydroxyl radicals by means of a photoredox pathway. Under anaerobic conditions, it is believed that a photoinduced oxidation of DNA mechanism is operative. Compound 3]+ exhibits photocytotoxicity in HeLa cervical cancer cells to give IC50 values of (12+/-0.9) mu M in UV-A light at 365 nm and (31.4+/-1.1) mu M in the dark.

Caryophyllene-Rich Essential Oil of Didymocarpus tomentosa: Chemical Composition and Cytotoxic Activity

The essential oil from the leaves of Didymocarpus tomentosa was extracted by hydrodistillation and analyzed by GC/FID and GC/MS. Twenty five constituents amounting to 81.6% of the oil were identified. The leaf oil contained 78.7% sesquiterpenes and 2.9% monoterpenes. The leaf essential oil of D. tomentosa is a unique caryophyllene-rich natural source containing beta-caryophyllene, caryophyllene oxide, alpha-humulene and humulene oxide. The cytotoxic activity of the oil was determined by the BSLT using shrimp larva and the MTT assay using HeLa tumor cell line. The oil showed significant cytotoxic activity with LC50 and IC50 values of 12.26 and 11.4 mu g/mL, respectively. This is the first report on the chemical composition and cytotoxic activity of the essential oil of D. tomentosa.

TURBULENT PUMPING OF MAGNETIC FLUX REDUCES SOLAR CYCLE MEMORY AND THUS IMPACTS PREDICTABILITY OF THE SUN'S ACTIVITY

Prediction of the Sun's magnetic activity is important because of its effect on space environment and climate. However, recent efforts to predict the amplitude of the solar cycle have resulted in diverging forecasts with no consensus. Yeates et al. have shown that the dynamical memory of the solar dynamo mechanism governs predictability, and this memory is different for advection- and diffusion-dominated solar convection zones. By utilizing stochastically forced, kinematic dynamo simulations, we demonstrate that the inclusion of downward turbulent pumping of magnetic flux reduces the memory of both advection- and diffusion-dominated solar dynamos to only one cycle; stronger pumping degrades this memory further. Thus, our results reconcile the diverging dynamo-model-based forecasts for the amplitude of solar cycle 24. We conclude that reliable predictions for the maximum of solar activity can be made only at the preceding minimum-allowing about five years of advance planning for space weather. For more accurate predictions, sequential data assimilation would be necessary in forecasting models to account for the Sun's short memory.

Urea-based constructs readily amplify and attenuate nonlinear optical activity in response to H-bonding and anion recognition

Urea-based molecular constructs are shown for the first time to be nonlinear optically (NLO) active in solution. We demonstrate self-assembly triggered large amplification and specific anion recognition driven attenuation of the NLO activity. This orthogonal modulation along with an excellent nonlinearity-transparency trade-off makes them attractive NLO probes for studies related to weak self-assembly and anion transportation by second harmonic microscopy.

Characterization of DNA topoisomerase I from Mycobacterium tuberculosis: DNA cleavage and religation properties and inhibition of its activity

Type I DNA topoisomerases from bacteria catalyse relaxation of negatively supercoiled DNA in a Mg2+ dependent manner. Although topoisomerases of distinct classes have been subjected for anti-cancer and anti-infective drug development, bacterial type I enzymes are way behind in this regard. Our studies with Mycobacterium smegmatis topoisomerase I (MstopoI) revealed several of its distinct properties compared to the well studied Escherichia coli topoisomerase I (EctopoI) suggesting the possibility of targeting the mycobacterial enzyme for inhibitor development. Here, we describe Mycobacterium tuberculosis topoisomerase I (MttopoI) and compare its properties with MstopoI and EctopoI. The enzyme cleaves DNA at preferred sites in a pattern similar to its ortholog from M. smegmatis. Oligonucleotides containing the specific recognition sequence inhibited the activity of the enzyme in a manner similar to that of MstopoI. Substitution of the acidic residues, D111 and E115 which are involved in Mg2+ co-ordination, to alanines affected the DNA relaxation activity. Unlike the wild type enzyme, D111A was dependent on Mg2+ for DNA cleavage and both the mutants were compromised in religation. The monoclonal antibody (mAb), 2F3G4, developed against MstopoI inhibited the relaxation activity of MttopoI. These studies affirm the characteristics of MttopoI to be similar to MstopoI and set a stage to target it for the development of specific small molecule inhibitors. (C) 2012 Elsevier Inc. All rights reserved.

Stability of Adult Emergence and Activity/Rest Rhythms in Fruit Flies Drosophila melanogaster under Semi-Natural Condition

Here we report the results of a study aimed at examining stability of adult emergence and activity/rest rhythms under seminatural conditions (henceforth SN), in four large outbred fruit fly Drosophila melanogaster populations, selected for emergence in a narrow window of time under laboratory (henceforth LAB) light/dark (LD) cycles. When assessed under LAB, selected flies display enhanced stability in terms of higher amplitude, synchrony and accuracy in emergence and activity rhythms compared to controls. The present study was conducted to assess whether such differences in stability between selected and control populations, persist under SN where several gradually changing time-cues are present in their strongest form. The study revealed that under SN, emergence waveform of selected flies was modified, with even more enhanced peak and narrower gate-width compared to those observed in the LAB and compared to control populations in SN. Furthermore, flies from selected populations continued to exhibit enhanced synchrony and accuracy in their emergence and activity rhythms under SN compared to controls. Further analysis of zeitgeber effects revealed that enhanced stability in the rhythmicity of selected flies under SN was primarily due to increased sensitivity to light because emergence and activity rhythms of selected flies were as stable as controls under temperature cycles. These results thus suggest that stability of circadian rhythms in fruit flies D. melanogaster, which evolved as a consequence of selection for emergence in a narrow window of time under weak zeitgeber condition of LAB, persists robustly in the face of day-to-day variations in cycling environmental factors of nature.

Curcumin reduces the antimicrobial activity of ciprofloxacin against Salmonella Typhimurium and Salmonella Typhi

Typhoidal and non-typhoidal infection by Salmonella is a serious threat to human health. Ciprofloxacin is the last drug of choice to clear the infection. Ciprofloxacin, a gyrase inhibitor, kills bacteria by inducing chromosome fragmentation, SOS response and reactive oxygen species (ROS) in the bacterial cell. Curcumin, an active ingredient from turmeric, is a major dietary molecule among Asians and possesses medicinal properties. Our research aimed at investigating whether curcumin modulates the action of ciprofloxacin. We investigated the role of curcumin in interfering with the antibacterial action of ciprofloxacin in vitro and in vivo. RTPCR, DNA fragmentation and confocal microscopy were used to investigate the modulation of ciprofloxacin-induced SOS response, DNA damage and subsequent filamentation by curcumin. Chemiluminescence and nitroblue tetrazolium reduction assays were performed to assess the interference of curcumin with ciprofloxacin-induced ROS. DNA binding and cleavage assays were done to understand the rescue of ciprofloxacin-mediated gyrase inhibition by curcumin. Curcumin interferes with the action of ciprofloxacin thereby increasing the proliferation of Salmonella Typhi and Salmonella Typhimurium in macrophages. In a murine model of typhoid fever, mice fed with curcumin had an increased bacterial burden in the reticuloendothelial system and succumbed to death faster. This was brought about by the inhibition of ciprofloxacin-mediated downstream signalling by curcumin. The antioxidant property of curcumin is crucial in protecting Salmonella against the oxidative burst induced by ciprofloxacin or interferon (IFN), a pro-inflammatory cytokine. However, curcumin is unable to rescue ciprofloxacin-induced gyrase inhibition. Curcumins ability to hinder the bactericidal action of ciprofloxacin and IFN might significantly augment Salmonella pathogenesis.

Tertiary amine-based glutathione peroxidase mimics: some insights into the role of steric and electronic effects on antioxidant activity

In this work, several tertiary amine-based diaryl diselenides were synthesized and evaluated for their glutathione peroxidase (GPx)-like antioxidant activities using hydrogen peroxide, tert-butyl hydroperoxide and cumene hydroperoxide as substrates and thiophenol (PhSH) and glutathione (GSH) as co-substrates. A comparison of the GPx-like activity of 4-methoxy-substituted N,N-dialkylbenzylamine-based diselenides with that of the corresponding 6-methoxy-substituted compounds indicates that the activity highly depends on the position of the methoxy substituent. Although the methoxy group at 4- and 6-position alters the electronic properties of selenium, the substitution at the 6-position provides the required steric protection for some of the key intermediates in the catalytic cycle. A detailed experimental and theoretical investigation reveals that the 6-methoxy substituent prevents the undesired thiol exchange reactions at the selenium centers in the selenenyl sulfide intermediates. The 6-methoxy substituent also prevents the formation of seleninic and selenonic acids. When PhSH is used as the thiol co-substrate, the 4-methoxy-substituted diselenides exhibit GPx-like activity similar to that of the parent compounds as the 4-methoxy substituent does not block the selenium center in the selenenyl sulfide intermediates from thiol exchange reactions. In contrast, the 4-methoxy substituent significantly enhances the GPx-like activity of the diselenides when glutathione (GSH) is used as the co-substrate. (C) 2012 Elsevier Ltd. All rights reserved.

Photo-induced anticancer activity of polypyridyl platinum(II) complexes

Polypyridyl platinum(II) complexes (1-5), viz., Pt(pyphen)Cl]Cl (1), Pt(pyphen)(C CFc)]Cl (2), Pt(pydppz)Cl]Cl (3), Pt(pydppz)(C CPh)]Cl (4) and Pt(pydppz)(C CFc)]Cl (5), where pyphen is 6-(2-pyridyl)-1,10-phenanthroline, pydppz is 6-(2-pyridyl)-dipyrido-3,2-a:2',3'-c]-phenazine, FcC CH is ferrocenyl acetylene and PhC CH is phenyl acetylene, were synthesized, characterized and their DNA binding and photocytotoxic properties studied. The complexes showed strong binding affinity to calf-thymus DNA giving K-app of similar to 10(6)-10(7) M-1. Complexes 4 and 5 showed dual mode of binding to ct-DNA. The pydppz complexes 3-5 having a photoactive phenazine moiety showed photocytotoxicity in HeLa and MCF-7 cells in UV-A light of 365 nm with apoptotic cell death as evidenced from the acridine orange/ethidium bromide dual staining and the FACS data. (C) 2012 Elsevier Masson SAS. All rights reserved.

Cobalt(II), Nickel(II) and Copper(II) complexes of a tetradentate Schiff base as photosensitizers: Quantum yield of O-1(2) generation and its promising role in anti-tumor activity

In the present investigation, a Schiff base N'(1),N'(3)-bis(E)-(5-bromo-2-hydroxyphenyl)methylidene]benzene-1,3-d icarbohydrazide and its metal complexes have been synthesized and characterized. The DNA-binding studies were performed using absorption spectroscopy, emission spectra, viscosity measurements and thermal denatuaration studies. The experimental evidence indicated that, the Co(II), Ni(II) and Cu(II) complexes interact with calf thymus DNA through intercalation with an intrinsic binding constant K-b of 2.6 x 10(4) M-1, 5.7 x 10(4) M-1 and 4.5 x 10(4) M-1, respectively and they exhibited potent photo-damage abilities on pUC19 DNA, through singlet oxygen generation with quantum yields of 0.32, 0.27 and 0.30 respectively. The cytotoxic activity of the complexes resulted that they act as a potent photosensitizers for photochemical reactions. (C) 2012 Elsevier B.V. All rights reserved.

Catalytic activity of Peptidase N is required for adaptation of Escherichia coli to nutritional downshift and high temperature stress

Peptidase N (PepN), the sole M1 family member in Escherichia coli, displays broad substrate specificity and modulates stress responses: it lowers resistance to sodium salicylate (NaSal)-induced stress but is required during nutritional downshift and high temperature (NDHT) stress. The expression of PepN does not significantly change during different growth phases in LB or NaSal-induced stress; however, PepN amounts are lower during NDHT stress. To gain mechanistic insights on the roles of catalytic activity of PepN in modulating these two stress responses, alanine mutants of PepN replacing E264 (GAMEN motif) and E298 (HEXXH motif) were generated. There are no major structural changes between purified wild type (WT) and mutant proteins, which are catalytically inactive. Importantly, growth profiles of Delta pepN upon expression of WT or mutant proteins demonstrated the importance of catalytic activity during NDHT but not NaSal-induced stress. Further fluorescamine reactivity studies demonstrated that the catalytic activity of PepN is required to generate higher intracellular amounts of free N-terminal amino acids; consequently, the lower growth of Delta pepN during NDHT stress increases with high amounts of casamino acids. Together, this study sheds insights on the expression and functional roles of the catalytic activity of PepN during adaptation to NDHT stress. (C) 2012 Elsevier GmbH. All rights reserved.

Synthesis, characterization and phosphotriesterase mimetic activity of some Zn(II) and Cu(II) complexes

We report here the synthesis and characterization of a few phenolate-based ligands bearing tert- amino substituent and their Zn(II) and Cu(II) metal complexes. Three mono/binuclear Zn(II) and Cu(II) complexes Zn(L1)(H2O)].CH3OH.H2O (1) (H (2) L1 = 6,6(')-(((2-dimethylamino)ethylazanediyl)bis(methylene))bis(2, 4-dimethylphenol), Zn-2(L2)(2)] (2) (H (2) L2 = 2,2(')-(((2-dimethylamino)ethyl)azanediyl)bis(methylene)bis(4- methylphenol) and Cu-2(L3)(2).CH2 Cl-2] (3) (H (2) L3 = (6,6(')-(((2-(diethylamino)ethyl)azanediyl)bis(methylene)) bis(methylene))bis(2,4-dimethylphenol) were synthesized by using three symmetrical tetradendate ligands containing N2O2 donor sites. These complexes are characterized by a variety of techniques including; elemental analysis, mass spectrometry, H-1, C-13 NMR spectroscopic and single crystal X-ray analysis. The new complexes have been tested for the phosphotriesterase (PTE) activity with the help of P-31 NMR spectroscopy. The P-31 NMR studies show that mononuclear complex Zn(L1)(H2O)].CH3OH.H2O (1) can hydrolyse the phosphotriester i.e., p-nitrophenyl diphenylphosphate (PNPDPP), more efficiently than the binuclear complexes Zn-2(L2)(2)] (2) and Cu-2(L3)(2).CH2Cl2] (3). The mononuclear Zn(II) complex (1) having one coordinated water molecule exhibits significant PTE activity which may be due to the generation of a Zn(II)-bound hydroxide ion during the hydrolysis reactions in CHES buffer at pH 9.0.

Discovery of novel glitazones incorporated with phenylalanine and tyrosine: Synthesis, antidiabetic activity and structure-activity relationships

We report a series of new glitazones incorporated with phenylalanine and tyrosine. All the compounds were tested for their in vitro glucose uptake activity using rat-hemidiaphragm, both in presence and absence of insulin. Six of the most active compounds from the in vitro screening were taken forward for their in vivo triglyceride and glucose lowering activity against dexamethazone induced hyperlipidemia and insulin resistance in Wistar rats. The liver samples of rats that received the most active compounds, 23 and 24, in the in vivo studies, were subjected to histopathological examination to assess their short term hepatotoxicity. The investigations on the in vitro glucose uptake, in vivo triglyceride and glucose lowering activity are described here along with the quantitative structure-activity relationships. (C) 2012 Elsevier Inc. All rights reserved.

DNA Binding and Oxidative Cleavage Activity of Ternary (alpha-Lipoic Acid) Copper(II) Complex of Heterocyclic Base

Ternary copper(II) complex Cu(a-lipo)(phen)(Cl)](NO3) where a-lipo = a-lipoic acid, phen is N, N-donor heterocyclic base, 1,10-phenanthroline was synthesized, characterized, and its DNA binding and cleavage activity were studied. Binding interactions of the complex with calf thymus (CT) DNA has been investigated by emission, viscosity, and DNA melting studies. The complex shows efficient oxidative cleavage of SC-DNA in the presence of 3-mercaptopropionic acid involving hydroxyl radical species, and results of control experiments exhibit the inhibition of DNA cleavage in the presence of hydroxyl radical scavengers, viz. DMSO and KI.