Metal complexes of a new class of polydentate Mannich bases: Synthesis and spectroscopic characterisation

A new class of polydentate Mannich bases featuring an N₂S₂ donor system, bis((2-mercapto-N-phenylacetamido)methyl)phosphinic acid H₃L¹ and bis((2-mercapto-N-propylacetamido)methyl)phosphinic acid H₃L², has been synthesised from condensation of phosphinic acid and paraformaldehyde with 2-mercaptophenylacetamide W1 and 2-mercaptopropylacetamide W2, respectively. Monomeric complexes of these ligands, of general formula K₂[Cr^III(Lⁿ)Cl₂], K₃[M′^II(Lⁿ)Cl₂] and K[M(Lⁿ)] (M′ = Mn(II) or Fe(II); M = Co(II), Ni(II), Cu(II), Zn(II), Cd(II) or Hg(II); n = 1, 2) are reported. The structures of new ligands, mode of bonding and overall geometry of the complexes were determined through IR, UV–Vis, NMR, and mass spectral studies, magnetic moment measurements, elemental analysis, metal content, and conductance. These studies revealed octahedral geometries for the Cr(III), Mn(II) and Fe(II) complexes, square planar for Ni(II) and Cu(II) complexes and tetrahedral for the Co(II), Zn(II), Cd(II) and Hg(II) complexes. Complex formation studies via molar ratio in DMF solution were consistent to those found in the solid complexes with a ratio of (M:L) as (1:1).     

Dicopper(II) complexes showing DNA hydrolase activity and monomeric adduct formation with bis(4-nitrophenyl)phosphate

Ferromagnetic dicopper(II) complexes [Cu₂(μ-O₂CCH₃)(μ-OH)(L)₂(μ-L¹)](PF₆)₂, where L = 1,10-phenanthroline (phen), L¹ = H₂O in 1 and L = dipyrido[3,2-d:2′,3′-f]quinoxaline (dpq), L¹ = CH₃CN in 2, are prepared and structurally characterized. Crystals of 1 and 2 belong to the monoclinic space group of P2₁/n and P2₁/m, respectively. The copper(II) centers display distorted square-pyramidal geometry having a phenanthroline base and two oxygen atoms of the bridging hydroxo and acetate group in the basal plane. The fifth coordination site has weak axially bound bridging solvent molecule H₂O in 1 and CH₃CN in 2. The Cu···Cu distances are 3.034 and 3.046 Å in 1 and 2, respectively. The complexes show efficient hydrolytic cleavage of supercoiled pUC19 DNA as evidenced from the mechanistic studies that include T4 DNA ligase experiments. The binuclear complexes form monomeric copper(II) adducts [Cu(L)₂(BNPP)](PF₆) (L = phen, 3; dpq, 4) with bis(4-nitrophenyl)phosphate (BNPP) as a model phosphodiester. The crystal structures of 3 and 4 reveal distorted trigonal bipyramidal geometry in which BNPP binds through the oxygen atom of the phosphate. The kinetic data of the DNA cleavage reactions of the binuclear complexes under pseudo- and true-Michaelis-Menten conditions indicate remarkable enhancement in the DNA hydrolysis rate in comparison to the control data.     

Influence of the geometry around the manganese ion on the peroxidase and catalase activities of Mn(III)-Schiff base complexes

The peroxidase and catalase activities of eighteen manganese-Schiff base complexes have been studied. A correlation between the structure of the complexes and their catalytic activity is discussed on the basis of the variety of systems studied. Complexes 1-18 have the general formulae [MnLⁿ(D)₂](X)(H₂O/CH₃OH)_m, where Lⁿ = L¹-L¹³; D = H₂O, CH₃OH or Cl; m = 0-2.5 and X = NO₃⁻, Cl⁻, ClO₄⁻, CH₃COO⁻, C₂H₅COO⁻ or C₅H₁₁COO⁻. The dianionic tetradentate Schiff base ligands H₂Lⁿ are the result of the condensation of different substituted (OMe-, OEt-, Br-, Cl-) hydroxybenzaldehyde with diverse diamines (1,2-diaminoethane for H₂L¹-H₂L²; 1,2-diamino-2-methylethane for H₂L³-H₂L⁴; 1,2-diamino-2,2-dimethylethane for H₂L⁵; 1,2-diphenylenediamine for H₂L⁶-H₂L⁷; 1,3-diaminopropane for H₂L⁸-H₂L¹¹; 1,3-diamino-2,2-dimethylpropane for H₂L¹²-H₂L¹³). The new Mn(III) complexes [MnL¹(H₂O)Cl](H₂O)_2.5 (2), [MnL²(H₂O)₂](NO₃)(H₂O) (4), [MnL⁶(H₂O)₂][MnL⁶(CH₃OH)(H₂O)](NO₃)₂(CH₃OH) (8), [MnL⁶(H₂O)(OAc)](H₂O) (9) and [MnL⁷(H₂O)₂](NO₃)(CH₃OH)₂ (12) were isolated and characterised by elemental analysis, magnetic susceptibility and conductivity measurements, redox studies, ESI spectrometry and UV, IR, paramagnetic ¹H NMR, and EPR spectroscopies. X-ray crystallographic studies of these complexes and of the ligand H₂L⁶ are also reported. The crystal structures of the rest of the complexes have been previously published and herein we have only revised their study by those techniques still not reported (EPR and ¹H NMR for some of these compounds) and which help to establish their structures in solution. Complexes 1-12 behave as more efficient mimics of peroxidase or catalase in contrast with 13-18. The analysis between the catalytic activity and the structure of the compounds emphasises the significance of the existence of a vacant or a labile position in the coordination sphere of the catalyst.     

Binding of oxindole-Schiff base copper(II) complexes to DNA and its modulation by the ligand

Previous studies on copper(II) complexes with oxindole-Schiff base ligands have shown their potential antitumor activity towards different cells, inducing apoptosis through a preferential attack to DNA and/or mitochondria. Herein, we better characterize the interactions between some of these copper(II) complexes and DNA. Investigations on its binding ability to DNA were carried out by fluorescence measurements in competitive experiments with ethidium bromide, using plasmidial or calf-thymus DNA. These results indicated an efficient binding process similar to that observed with copper(II)-phenanthroline species, [Cu(o-phen)₂]²⁺, with binding constants in the range 3 to 9 × 10² M^− 1. DNA cleavage experiments in the presence and absence of distamycin, a recognized binder of DNA, indicated that this binding probably occurs at major or minor groove, leading to double-strand DNA cleavage, and being modulated by the imine ligand. Corroborating these data, discrete changes in EPR spectra of the studied complexes were observed in the presence of DNA, while more remarkable changes were observed in the presence of nucleotides (AMP, GMP, CMP or UMP). Additional evidence for preferential coordination of the copper centers to the bases guanine or cytosine was obtained from titrations of these complexes with each nucleotide, monitored by absorption spectral changes. Therefore, the obtained data point out to their action as groove binders to DNA bases, rather than as intercalators or covalent cross-linkers. Further investigations by SDS PAGE using ³²P-ATP or ³²P-oligonucleotides attested that no hydrolysis of phosphate linkage in DNA or RNA occurs, in the presence of such complexes, confirming their main oxidative mechanism of action.     

Synthesis and biological evaluation of novel oxadiazole derivatives: A new class of thymidine phosphorylase inhibitors as potential anti-tumor agents

Based on the fact that the thymidine phosphorylase inhibitors are considered potential anti-tumor agents, a range of novel oxadiazole derivatives 3a–3u was designed and synthesized by a simple and facile synthetic route. The biological assay revealed that majority of compounds displayed modest inhibitory activity against thymidine phosphorylase at low micromolar concentrations (IC₅₀ 173.23 ± 3.04 to 14.40 ± 2.45 μM). In the current study the most active compounds were 3h and 3q with IC₅₀ values 14.40 ± 2.45 and 17.60 ± 1.07 μM, respectively. Molecular docking studies were performed on the most active compounds (3h, 3k, 3o–3q) to show their binding mode.     

我国大型煤炭基地建设的生态恢复技术研究综述

煤炭能源是我国的主体能源,在我国经济社会发展中具有重要的战略地位。煤炭工业是关系我国经济发展和能源供应安全的重要基础产业。由于受传统发展观的影响,煤炭工业一直存在生产粗放、安全事故频发、资源浪费严重、环境治理和管理滞后等问题。我国大型煤炭基地的建设对提高煤炭供应保障能力起到了关键支撑作用。因此,从区域可持续发展的角度出发,加强矿区的生态恢复,深化煤炭资源的开发利用和环境保护,对促进国家和区域生态环境与社会经济的可持续发展,构建和谐矿区,确保区域乃至全国的生态安全特别是能源安全具有重要的意义。介绍了国家大型煤炭基地的发展历程、分布和开发现状,以及煤炭开采利用带来的一系列生态环境问题,重点阐述了当前我国煤炭基地建设的关键生态恢复技术体系,并从生态恢复与环境管理的角度提出我国大型煤炭基地的可持续发展建议。     

东部草原区煤电基地开发生态修复技术研究

本项目为"十三五"国家重点研发计划批复项目(2016YFC0501100)。针对我国东部草原区大型煤电基地开发生态修复技术需求和工程实施难题,聚焦煤炭开发对草原生态(水、土壤、植被)的影响机理及累积效应、区域生态稳定性与生态安全协调机制两大科学问题,运用生态学、采矿学、环境科学、草叶科学等多学科方法,采用理论分析、调查监测、试验研究相结合的综合手段,厘清煤炭开发对地下水和植被种群的影响边界、程度及累计效应,研发生态效应评价、区域水资源动态监测、水资源保护利用、煤矿土地整治、微生物联合修复、景观生态恢复等15项关键技术,形成基础理论、关键技术和工程示范一体化体系,创立东部草原区生态修复模式,在呼盟和锡盟煤炭开发基地进行集中工程示范,为我国东部草原区煤炭开发与生态修复提供理论和技术支撑。     

Non-Watson-Crick base associations in DNA and RNA revealed by single crystal x-ray diffraction methods: Mismatches,modified bases,and nonduplex DNA

Single crystal x-ray diffraction methods have been used to characterize numerous oligonucleotide structures, providing valuable information on the fine structure of DNA, oligonucleotide hydration, interactions with small molecule ligands and proteins. There has been a particular focus on nonstandard base associations and a number of groups have sought to characterize different non-Watson-Crick base pairs to further the understanding of their influence on the structure of duplex DNA and RNA, and to investigate which structural features might be utilized by enzymes in recognition and repair of these errors in DNA. Bases that have been chemically damaged by mutagenic or carcinogenic agents have distinctive modified hydrogen-bonding patterns and these have been investigated. The structure determination of a series of nonduplex DNA structures including examples of a triplex, quadruplexes, and a novel DNA loop have recently been published. In this article we survey the structures of a series of non-Watson-Crick base associations in duplex DNA and RNA. We show how nonstandard base pairs, base triads, and tetrads play an important role in stabilizing nonduplex structures. © 1997 John Wiley & Sons, Inc. Biopoly 44: 91–103, 1997     

Synthesis and SAR studies of potent H+/K+-ATPase inhibitors of quinazolinone-Schiff’s base analogues

A series of quinazolinone derived Schiff base derivatives 7–36 were synthesized and characterized by analytical and spectroscopic techniques. The synthesized analogues were screened for their in vitro H⁺/K⁺-ATPase inhibition. Most of the compounds showed excellent activity, compared to that of omeprazole, a reference drug. In particular, hydroxy and methoxy derivatives 13–24 were the most active compounds possessing a significant increase for different substituents on the benzene ring thus, contributing positively to gastric H⁺/K⁺-ATPase inhibition. Preliminary structure-activity relationship revealed that the compounds 13–24 with electron donating moiety (OH, OCH₃) were found to be excellent activity and compounds 9–12 and 25–36 with electron withdrawing moiety (Cl, F, NO₂ and Br) were found to be least antiulcer agents.     

Feeding preferences of eastern spruce budworm larvae in two-choice tests with combinations of host-plant extracts

Three extracts were obtained from each of four host plants: sugars/glycosides; amino acids/bases; and organic acids. The four hosts studied were balsam fir, black spruce, red spruce, and white spuce. The effects of recombined host plant extracts on the feeding behaviour of eastern spruce budworm larvae were examined in two-choice tests. Results compare feeding preferences as well as feeding rates between combinations of extracts. The importance of each class of polar compounds is discussed.

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Préférences des larves de la tordeuse des bourgeons de l'épinette envers extraits combinés de leurs plantes-hôtes

Résumé Trois extraits ont été obtenus de chacune de quatre plantes-hôtes: sucres/glycosides; acides aminées/bases organiques; acides organiques. Les quatre plantes-hôtes étudiées furent le sapin baumier, et les épinettes blanc, noir, et rouge. Le comportement gustatoire des larves a été étudié en raison de l'effet de combinaisons d'extraits de chaque plantehôte. Les résultats comparent la préférence des larves ainsi que leur consommation totale envers ces extraits.