Role of polyhydroxybutyrate and glycogen as carbon storage compounds in pea and bean bacteroids

Rhizobium leguminosarum synthesizes polyhydroxybutyrate and glycogen as its main carbon storage compounds. To examine the role of these compounds in bacteroid development and in symbiotic efficiency, single and double mutants of R. legumosarum bv. viciae were made which lack polyhydroxybutyrate synthase (phaC), glycogen synthase (glgA), or both. For comparison, a single phaC mutant also was isolated in a bean-nodulating strain of R. leguminosarum bv. phaseoli. In one large glasshouse trial, the growth of pea plants inoculated with the R. leguminosarum bv. viciae phaC mutant were significantly reduced compared with wild-type-inoculated plants. However, in subsequent glasshouse and growth-room studies, the growth of pea plants inoculated with the mutant were similar to wildtype-inoculated plants. Bean plants were unaffected by the loss of polyhydroxybutyrate biosynthesis in bacteroids. Pea plants nodulated by a glycogen synthase mutants or the glgA/phaC double mutant, grew as well as the wild type in growth-room experiments. Light and electron micrographs revealed that pea nodules infected with the glgA mutant accumulated large amounts of starch in the II/III interzone. This suggests that glycogen may be the dominant carbon storage compound in pea bacteroids. Polyhydroxybutyrate was present in bacteria in the infection thread of pea plants but was broken down during bacteroid formation. In nodules infected with a phaC mutant of R. leguminosarum bv. viciae, there was a drop in the amount of starch in the II/III interzone, where bacteroids form. Therefore, we propose a carbon burst hypothesis for bacteroid formation, where polyhydroxybutyrate accumulated by bacteria is degraded to fuel bacteroid differentiation.

In vitro antioxidant activity of coffee compounds and their metabolites

In this paper we report the antioxidant activity of different compounds which are present in coffee or are produced as a result of the metabolism of this beverage. In vitro methods such as the ABTS(center dot+) [ABTS = 2,2'-azinobis(3-ethylbenzothiazoline-6-sulfonic acid)] decolorization assay and the oxygen radical absorbance capacity assay (ORAC) were used to assess the capacity of coffee compounds to scavenge free radicals. The importance of caffeine metabolites and colonic metabolites in the overall antioxidant activity associated with coffee consumption is shown. Colonic metabolites such as m-coumaric acid and dihydroferulic acid showed high antioxidant activity. The ability of these compounds to protect human low-density lipoprotein (LDL) oxidation by copper and 2,2'-azobis(2-amidinopropane) dihydrochloride was also explored. 1-Methyluric acid was particularly effective at inhibiting LDL oxidative modification. Different experiments showed that this caffeine metabolite is not incorporated into LDL particles. However, at physiologically relevant concentrations, it was able to delay for more than 13 h LDL oxidation by copper.

Metalloestrogens: an emerging class of inorganic xenoestrogens with potential to add to the oestrogenic burden of the human breast

Many compounds in the environment have been shown capable of binding to cellular oestrogen receptors and then mimicking the actions of physiological oestrogens. The widespread origin and diversity in chemical structure of these environmental oestrogens is extensive but to date such compounds have been organic and in particular phenolic or carbon ring structures of varying structural complexity. Recent reports of the ability of certain metal ions to also bind to oestrogen receptors and to give rise to oestrogen agonist responses in vitro and in vivo has resulted in the realisation that environmental oestrogens can also be inorganic and such xenoestrogens have been termed metalloestrogens. This report highlights studies which show metalloestrogens to include aluminium, antimony, arsenite, barium, cadmium, chromium (Cr(II)), cobalt, copper, lead, mercury, nickel, selenite, tin and vanadate. The potential for these metal ions to add to the burden of aberrant oestrogen signalling within the human breast is discussed. Copyright (c) 2006 John Wiley & Sons, Ltd.

Role of polyhydroxybutyrate and glycogen as carbon storage compounds in pea and bean bacteroids

Rhizobium leguminosarum synthesizes polyhydroxybutyrate and glycogen as its main carbon storage compounds. To examine the role of these compounds in bacteroid development and in symbiotic efficiency, single and double mutants of R. legumosarum bv. viciae were made which lack polyhydroxybutyrate synthase (phaC), glycogen synthase (glgA), or both. For comparison, a single phaC mutant also was isolated in a bean-nodulating strain of R. leguminosarum bv. phaseoli. In one large glasshouse trial, the growth of pea plants inoculated with the R. leguminosarum bv. viciae phaC mutant were significantly reduced compared with wild-type-inoculated plants. However, in subsequent glasshouse and growth-room studies, the growth of pea plants inoculated with the mutant were similar to wildtype-inoculated plants. Bean plants were unaffected by the loss of polyhydroxybutyrate biosynthesis in bacteroids. Pea plants nodulated by a glycogen synthase mutants or the glgA/phaC double mutant, grew as well as the wild type in growth-room experiments. Light and electron micrographs revealed that pea nodules infected with the glgA mutant accumulated large amounts of starch in the II/III interzone. This suggests that glycogen may be the dominant carbon storage compound in pea bacteroids. Polyhydroxybutyrate was present in bacteria in the infection thread of pea plants but was broken down during bacteroid formation. In nodules infected with a phaC mutant of R. leguminosarum bv. viciae, there was a drop in the amount of starch in the II/III interzone, where bacteroids form. Therefore, we propose a carbon burst hypothesis for bacteroid formation, where polyhydroxybutyrate accumulated by bacteria is degraded to fuel bacteroid differentiation.

Growth of copper nanoparticles within VOx nanotubes

The synthesis of new Cu-VOx nanotubes has been achieved by exchanging a Cu(II) salt against the protonated template in the parent dodecylamine-VOx nanotubes. The intercalation of Cu(II) species induces some significant morphological and structural changes within the material, but the tubular shape is still well preserved. Controlled thermolysis under nitrogen of the Cu(II) species initially dispersed within the multiwalls induces the growth and sintering of copper nanoparticles, which are formed without destroying the tubular morphology of the host carrier. (C) 2002 Elsevier Science B.V. All rights reserved.

Construction of coordination polymers of cadmium(II) with mixed hexamethylenetetramine and terephthalate or thiocyanate ligands

Three new polymeric complexes [Cd(hmt)(SCN)(2)(H2O)(2)](n) (1), [Cd-3(mu(2)-hmt)(2)(SCN)(6)(H2O)(2)](n) (2), and [Cd-2(hmt)(2)(tP)(2)(H2O)(6)](n) (3) [hmt = hexamethylenetetramine, tp = terephthalate] have been synthesized and characterized by single crystal X-ray diffraction. Both the compounds 1 and 2 are 1-D polymers where Cd units are linked by double end-to-end thiocyanate bridges but in 2 the chain is wider containing three cadmium atoms instead of one as found in 1. In both compounds the coordination environment around cadmium atom is distorted octahedral. Compound 3 is a three-dimensional polymer having water-filled microporous channels. Both tp and brut are mu(2)-bridged. One of the acid groups of tp is coordinated in chelating bidentate and the other in monodentate fashion. Half of its Cd atoms are hexa-coordinated and the rest are hepta-coordinated. Thermogravimetric analysis and X-ray diffraction study of 3 show that its framework remains intact upon removal of water molecules. The flexibility of coordination number around cadmium atoms (six or seven) probably plays an important role in establishing the rigidity of the framework. (C) 2003 Elsevier Ltd. All rights reserved.

Anion-pi, Lone-Pair-pi, pi-pi and Hydrogen-Bonding Interactions in a Cu-II Complex of 2-Picolinate and Protonated 4,4 '-Bipyridine: Crystal Structure and Theoretical Studies

A Cu-II complex of protonated 4,4'-bipyridine (Hbyp) and 2-picolinate (pic), [Cu-2(pic)(3)(Hbyp)(H2O)(ClO4)(2)], has been synthesised and characterised by single-crystal X-ray analysis. The structure consists of two copper atoms that have different environments, bridged by a carboxylate group. The equatorial plane is formed by the two bidentate picolinate groups in one Cu-II, and one picolinate, one monodentate 4,4'-bipyridyl ligand and a water molecule in the other. Each copper atom is also weakly bonded to a perchlorate anion in an axial position. One of the coordinated perchlorate groups displays anion-pi interaction with the coordinated pyridine ring. The noncoordinated carboxylate oxygen is involved in lone-pair (l.p.)-pi interaction with the protonated pyridine ring. In addition there are pi-pi and H-bonding interactions in the structure. Bader's theory of "atoms in molecules" (AIM) is used to characterise the anion-pi and l.p.-pi interactions observed in the solid state. A high-level ab initio study (RI-MP2/aug-cc-pVTZ level of theory) has been performed to analyse the anion-pi binding affinity of the pyridine ring when it is coordinated to a transition metal and also when the other pyridine ring of the 4,4'-bipyridine moiety is protonated. Theoretical investigations support the experimental findings of an intricate network of intermolecular interactions, which is characterised in the studied complex, and also indicate that protonation as well as coordination to the transition metal have important roles in influencing the pi-binding properties of the aromatic ring. ((C) Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2009)

Nickel(II) complexes of terdentate or symmetrical tetradentate Schiff bases: Evidence of the influence of the counter anions in the hydrolysis of the imine bond in Schiff base complexes

Two sets of ligands, set-1 and set-2, have been prepared by mixing 1,3-diaminopentane and carbonyl compounds (2-acetylpyridine or pyridine-2-carboxaldehyde) in 1:1 and 1:2 ratios, respectively, and employed for the synthesis of complexes with Ni(II) perchlorate, Ni(II) thiocyanate and Ni(II) chloride. Ni(II) perchlorate yields the complexes having general formula [NiL2](ClO4)(2)(L = L-1 [N-3-(1-pyridin-2-yl-ethylidene)-pentane-1,3-diamine] for complex 1 or L-2[N-3-pyridin-2-ylmethylene-pentane-1,3-diamine] for complex 2) in which the Schiff bases are monocondensed terdentate, whereas Ni(II) thiocyanate results in the formation of tetradentate Schiff base complexes, [NiL(SCN)(2)] (L = L-3[N,N'-bis-(1-pyridin-2- yl-ethylidine)-pentane-1,3-diamine] for complex 3 or L-4 [N,N'-bis(pyridin-2-ylmethyline)-pentane-1,3- diamine] for complex 4) irrespective of the sets of ligands used. Complexes 5 {[NiL3(N-3)(2)]} and 6 {[NiL4(N-3)(2)]} are prepared by adding sodium azide to the methanol solution of complexes 1 and 2. Addition of Ni(II) chloride to the set-1 or set-2 ligands produces [Ni(pn)(2)]Cl-2, 7, as the major product, where pn = 1,3-diaminopentane. Formation of the complexes has been explained by the activation of the imine bond by the counter anion and thereby favouring the hydrolysis of the Schiff base. All the complexes have been characterized by elemental analyses and spectral data. Single crystal X-ray diffraction studies con. firm the structures of three representative members, 1, 4 and 7; all of them have distorted octahedral geometry around Ni(II). The bis-complex of terdentate ligands, 1, is the mer isomer, and complexes 4 and 7 possess trans geometry. (C) 2008 Elsevier B. V. All rights reserved.

Anion directed templated synthesis of mono- and di-Schiff base complexes of Ni(II)

Two sets of Schiff base ligands, set-1 and set-2 have been prepared by mixing the respective diamine (1,2-propanediamine or 1,3-propanediamine) and carbonyl compounds (2-acetylpyridine or pyridine-2-carboxaldehyde) in 1:1 and 1:2 ratios, respectively and employed for the synthesis of complexes with Ni(II) perchlorate and Ni(II) thiocyanate. Ni(II) perchlorate yields the complexes having general formula [NiL2](ClO4)(2) (L = L-1 [N-1-(1-pyridin-2-yl-ethylidine)-propane-1,3-diamine] for complex 1, L-2 [N-1-pyridine-2-ylmethylene-propane1,3-diamine] for complex 2 or L-3 [N-1-(1-pyridine-2-yl-ethylidine)-propane-1,2-diamine] for complex 3) in which the Schiff bases are mono-condensed terdentate whereas Ni(II) thiocyanate results in the formation of tetradentate Schiff base complexes, [NiL](SCN)(2) (L=L-4 [N,N'-bis-(1-pyridine-2-yl-ethylidine)-propane-1,3-diamine] for complex 4, L-5 [NN'-bis(pyridine-2-ylmethyline)-propane-1, 3-diamine] for complex 5 or L-6 [NN'-bis-(1-pyridine-2-yl-ethylidine)-propane- 1, 2-diamine] for complex 6) irrespective of the sets of ligands used. Formation of the complexes has been explained by anion modulation of cation templating effect. All the complexes have been characterized by elemental analyses, spectral and electrochemical results. Single crystal X-ray diffraction studies confirm the structures of four representative members, 1, 3, 4 and 5; all of them have distorted octahedral geometry around Ni(II). The bis-complexes of terdentate ligands, I and 3 are the mer isomers and the complexes of tetradentate ligands, 4 and 5 possess trans geometry. (c) 2007 Elsevier Ltd. All rights reserved.

Helices, chirality and interpenetration: the versatility and remarkable interconversion of silver-copper cyanide frameworks

The structural transformations between cesium silver-copper cyanides under modest conditions, both in solution and in the solid state, are described. Three new cesium silver(I) copper(I) cyanides with three-dimensional (3-D) framework structures were prepared as single crystals from a one-pot reaction initially heated under hydrothermal conditions. The first product to appear, Cs3Ag2Cu3(CN)(8) (I), when left in contact with the supernatant produced CsAgCu(CN)(3) (II) and CsAgCu(CN)(3)center dot 1/3H(2)O (III) over a few months via a series of thermodynamically controlled cascade reactions. Crystals of the hydrate (III) can be dehydrated to polycrystalline CsAgCu(CN)(3) (II) on heating at 100 degrees C in a remarkable solid-state transformation involving substantial breaking and reconnection of metal-cyanide linkages. Astonishingly, the conversion between the two known polymorphs of CsAg2Cu(CN)(4), which also involves a major change in connectivity and topology, occurs at 180 degrees C as a single-crystal to single-crystal transformation. Structural features of note in these materials include the presence of helical copper-cyanide chains in (I) and (II), which in the latter compound produce a chiral material. In (II) and (III), the silver-copper cyanide networks are both self- and interpenetrating, features also seen in the known polymorphs of CsAg2Cu(CN)(4).

A DFT study of free radicals formed from artemisinin and related compounds

Ab initio calculations using density functional theory have shown that the reactions that occur between artemisinin, 1, a cyclic trioxane active against malaria, and some metal ions and complexes lead to a series of radicals which are probably responsible for its therapeutic activity. In particular it has been shown that the interaction of Fe(H) with artemisinin causes the O-O bond to be broken as indeed does Fe(III) and Cu(I), while Zn(II) does not. Calculations were carried out with Fe(II) in several different forms including the bare ion, [Fe(H2O)(5)](2+) and [FeP(Im)] (P, porphyrin; Im, imadazole) and similar results were obtained. The resulting oxygen-based radicals are readily converted to more stable carbon-based radicals and/or. stable products. Similar radicals and products are also formed from two simple model trioxanes 2 and 3 that show little or no therapeutic action against malaria although some subtle differences were obtained. This suggests that the scaffold surrounding the pharmacophore may be involved in molecular recognition events allowing efficient uptake of this trioxane warhead into the parasite. (C) 2004 Elsevier B.V. All rights reserved.

Synthesis, structural analysis, and magnetic behaviour of three fumarate bridged coordination polymers: five-fold interpenetrated diamond-like net of Ni-II, sheets of Ni-II and Co-II

The hydrothermal reactions of Ni(NO3)(2).6H(2)O, disodium fumarate (fum) and 1,2-bis(4-pyridyl)ethane (bpe)/1,3-bis(4-pyridyl) propane (bpp) in aqueous-methanol medium yield one 3-D and one 2-D metal-organic hybrid material, [Ni(fum)(bpe)] (1) and [Ni(fum)(bpp)(H2O)] (2), respectively. Complex 1 possesses a novel unprecedented structure, the first example of an "unusual mode" of a five-fold distorted interpenetrated network with metal-ligand linkages where the four six-membered windows in each adamantane-type cage are different. The structural characterization of complex 2 evidences a buckled sheet where nickel ions are in a distorted octahedral geometry, with two carboxylic groups, one acting as a bis-chelate, the other as a bis-monodentate ligand. The metal ion completes the coordination sphere through one water molecule and two bpp nitrogens in cis position. Variable-temperature magnetic measurements of complexes 1 and 2 reveal the existence of very weak antiferromagnetic intramolecular interactions and/or the presence of single-ion zero field splitting (D) of isolated Ni-II ions in both the compounds. Experimentally, both the J parameters are close, comparable and very small. Considering zero-field splitting of Ni-II, the calculated D values are in agreement with values reported in the literature for Ni-II ions. Complex 3, [{Co(phen)}(2)(fum)(2)] (phen=1,10-phenanthroline) is obtained by diffusing methanolic solution of 1,10-phenanthroline on an aqueous layer of disodium fumarate and Co(NO3)(2).6H(2)O. It consists of dimeric Co-II(phen) units, doubly bridged by carboxylate groups in a distorted syn-syn fashion. These fumarate anions act as bis-chelates to form corrugated sheets. The 2D layer has a (4,4) topology, with the nodes represented by the centres of the dimers. The magnetic data were fitted ignoring the very weak coupling through the fumarate pathway and using a dimer model.

Syntheses, characterization and X-ray crystal structures of Ni(II) complexes of tridentate monocondensed and tetradentate dicondensed Schiff bases

Two octahedral complexes [Ni(HL1)(2)](ClO4)(2) (1) and [Ni(HL2)(2)](ClO4)(2) (2) and a square planar complex [Ni(HL3)]ClO4 (3) have been prepared, where [HL1 = 3-(2-amino-ethylimino)-butan-2-one oxime, HL2 = 3-(2-amino-propylimino)butan-2-one oxime] and H2L3 = 3-[2-(3-hydroxy-1-methyl-but-2-enylideneamino)-1-methyl-ethylimino]-buta n-2-one oxime. All the complexes have been characterized by elemental analyses, spectral studies and room temperature magnetic moment measurements. The molecular structures of all three compounds were elucidated on the basis of X-ray crystallography: complexes 1 and 2 are seen to be the met isomers. (C) 2008 Elsevier Ltd. All rights reserved.

Structural and spectroscopic properties of Ru(II) complexes of 4-(aryl)thiosemicarbazones of thiophen-2-carbaldehyde

Six Ru(II) complexes of formula [Ru(L)(2)(PPh3)(2)] have been prepared where LH = 4-(aryl)thiosemicarbazones of thiophen-2-carbaldehyde. X-ray crystal structures of five of the complexes are reported. In all the complexes ruthenium is six coordinate with a distorted octahedral cis-P-2, cis-N-2, trans-S-2 donor environment, and each of the two thiosemicarbazone ligands are coordinated in a bidentate fashion forming a four membered chelate ring. The complexes undergo a one-electron oxidation at similar to 0.5 V vs. Ag/AgCl. The EPR spectrum of the electrochemically oxidized solution at 100 K shows a rhombic signal, with transitions at g(1) = 2.27, g(2) = 2.00 and g(3) = 1.80. DFT calculations on one of the complexes suggest that there is 35% ruthenium and 17% sulfur orbital contribution to the HOMO. These results suggest that the assignment of metal atom oxidation states in these compounds is not unambiguous. (C) 2009 Elsevier Ltd. All rights reserved.

Mixed ligand binuclear copper(I) complexes containing (Cu2N8)-N-I chromophores. Observation of emissions from MLCT excited states involving two different ligands

Using the 1:2 condensate (L) of diethylenetriamine and benzaldehyde as the main ligand, binuclear copper(l) complexes [Cu2L2(4,4'-bipyridine)](CIO4)(2).0.5H(2)O (1a) and [Cu2L2(1,2-bis(4-pyridyl)ethane)](CIO4)(2) (1b) are synthesised. The two metal ions in la are bridged by 4,4'-bipyridine and those in 1b by 1,2-bis(4-pyridyl)ethane, From the X-ray crystal structure of la, each metal ion is found to be bound to three N atoms of L and one of the two N atoms of the bridging ligand in a distorted tetrahedral fashion. The Cu(I)-N bond lengths in la lie in the range of 1.998(5)-2.229(6) Angstrom. Electrochemical studies in dichloromethane (DCM) show that the (Cu2N8)-N-I moieties in la and 1b are composed of two essentially non-interacting (CuN4)-N-I cores with Cu-II/I potential of 0.44 V vs. SCE. While la displays metal induced quenching of the inherent emission of 4,4'-bipyridine in DCM solution, 1b exhibits two weak emission bands in DCM solution at 425 and 477 nm (total quantum yield = 3.59 x 10(-5)) originating from MLCT excited states. With the help of Extended Huckel calculations it is established that the higher energy emission in 1b is from Cu(I) --> bridging-ligand charge transfer excited state and the lower energy one in 1b from Cu(I) --> L charge transfer excited state.