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First Structural Characterization (first + structural_characterization)
Selected AbstractsFirst Structural Characterization of a Protactinium(V) Single Oxo Bond in Aqueous Media.CHEMINFORM, Issue 9 2006Claire Le Naour Abstract ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 200 leading journals. To access a ChemInform Abstract, please click on HTML or PDF. [source] Structural and biochemical characterization of gentisate 1,2-dioxygenase from Escherichia coli O157:H7MOLECULAR MICROBIOLOGY, Issue 6 2006Melanie A. Adams Summary Gentisic acid (2,5-dihydroxybenzoic acid) is a key intermediate in aerobic bacterial pathways that are responsible for the metabolism of a large number of aromatic compounds. The critical step of these pathways is the oxygen-dependent reaction catalysed by gentisate 1,2-dioxygenase which opens the aromatic ring of gentisate to form maleylpyruvate. From gentisic acid, the cell derives carbon and energy through the conversion of maleylpyruvate to central metabolites. We have confirmed the annotation of a gentisate 1,2-dioygenase from the pathogenic O157:H7 Escherichia coli strain and present the first structural characterization of this family of enzymes. The identity of the reaction product was revealed using tandem mass spectroscopy. The operon responsible for the degradation of gentisate in this organism exhibits a high degree of conservation with the gentisate-degrading operons of other pathogenic bacteria, including the Shiga toxin-producing E. coli O103:H2, but does not appear to be present in non-pathogenic strains. The acquisition of the gentisate operon may represent a special adaptation to meet carbon source requirements under conditions of environmental stress and may provide a selective advantage for enterohaemorrhagic E. coli relative to their non-pathogenic counterparts. [source] Coordination polymers and hydrogen-bonded assemblies of 2,2,-[2,5-bis(carboxymethoxy)-1,4-phenylene]diacetic acid with ammonium, lanthanum and zinc cationsACTA CRYSTALLOGRAPHICA SECTION C, Issue 9 2010Hatem M. Titi We report the synthesis of the 2,2,-[2,5-bis(carboxymethoxy)-1,4-phenylene]diacetic acid (TALH4) ligand and the structures of its adducts with ammonium, namely diammonium 2,2,-[2,5-bis(carboxymethyl)-1,4-phenylenedioxy]diacetate, 2NH4+·C14H12O102,, (I), lanthanum, namely poly[[aquabis[,4 -2,2,-(2-carboxylatomethyl-5-carboxymethyl-1,4-phenylenedioxy)diacetato]dilanthanum(III)] monohydrate], {[La2(C14H11O10)2(H2O)]·H2O}n, (II), and zinc cations, namely poly[[{,4 -2,2,-[2,5-bis(carboxymethyl)-1,4-phenylenedioxy]diacetato}zinc(II)] trihydrate], {[Zn(C14H12O10)]·3H2O}n, (III), and poly[[diaqua(,2 -4,4,-bipyridyl){,4 -2,2,-[2,5-bis(carboxymethyl)-1,4-phenylenedioxy]diacetato}dizinc(II)] dihydrate], {[Zn2(C14H10O10)(C10H8N2)(H2O)2]·2H2O}n, (IV), the formation of all four being associated with deprotonation of TALH4. Adduct (I) is a diammonium salt of TALH22,, with the ions located on centres of crystallographic inversion. Its crystal structure reveals a three-dimensional hydrogen-bonded assembly of the component species. Reaction of TALH4 with lanthanum trinitrate hexahydrate yielded a two-dimensional double-layer coordination polymer, (II), in which the LaIII cations are nine-coordinate. With zinc dinitrate hexahydrate, TALH4 forms 1:1 two-dimensional coordination polymers, in which every ZnII cation is linked to four neighbouring TALH22, anions and each unit of the organic ligand is coordinated to four different tetrahedral ZnII cation connectors. The crystal structure of this compound accommodates molecules of disordered water at the interface between adjacent polymeric layers to give (III), and it has been determined with low precision. Another polymer assembly, (IV), was obtained when zinc dinitrate hexahydrate was reacted with TALH4 in the presence of an additional 4,4,-bipyridyl ligand. In the crystal structure of (IV), the bipyridyl and TAL4, entities are located on two different inversion centres. The ternary coordination polymers form layered arrays with corrugated surfaces, with the ZnII cation connectors revealing a tetrahedral coordination environment. The two-dimensional polymers in (II),(IV) are interconnected with each other by hydrogen bonds involving the metal-coordinated and noncoordinated molecules of water. TALH4 is doubly deprotonated, TALH22,, in (I) and (III), triply deprotonated, viz. TALH3,, in (II), and quadruply deprotonated, viz. TAL4,, in (IV). This report provides the first structural characterization of TALH4 (in deprotonated form) and its various supramolecular adducts. It also confirms the potential utility of this tetraacid ligand in the formulation of coordination polymers with metal cations. [source] Coordination and hydrogen-bonding assemblies in hybrid reaction products between 5,10,15,20-tetra-4-pyridylporphyrin and dysprosium trinitrate hexahydrateACTA CRYSTALLOGRAPHICA SECTION C, Issue 8 2010Sophia Lipstman Reactions of the title free-base porphyrin compound (TPyP) with dysprosium trinitrate hexahydrate in different crystallization environments yielded two solid products, viz. [,-5,15-bis(pyridin-1-ium-4-yl)-10,20-di-4-pyridylporphyrin]bis[aquatetranitratodysprosium(III)] benzene solvate, [Dy2(NO3)8(C40H28N8)(H2O)2]·C6H6, (I), and 5,10,15,20-tetrakis(pyridin-1-ium-4-yl)porphyrin pentaaquadinitratodysprosate(III) pentanitrate diethanol solvate dihydrate, (C40H30N8)[Dy(NO3)2(H2O)5](NO3)5·2C2H6O·2H2O, (II). Compound (I) represents a 2:1 metal,porphyrin coordinated complex, which lies across a centre of inversion. Two trans -related pyridyl groups are involved in Dy coordination. The two other pyridyl substituents are protonated and involved in intermolecular hydrogen bonding along with the metal-coordinated water and nitrate ligands. Compound (II) represents an extended hydrogen-bonded assembly between the tetrakis(pyridin-1-ium-4-yl)porphyrin tetracation, the [Dy(NO3)2(H2O)5]+ cation and the free nitrate ions, as well as the ethanol and water solvent molecules. This report provides the first structural characterization of the exocyclic dysprosium complex with tetrapyridylporphyrin. It also demonstrates that charge balance can be readily achieved by protonation of the peripheral pyridyl functions, which then enhances their capacity in hydrogen bonding as H-atom donors rather than H-atom acceptors. [source] Hydrogen-bonded assemblies of 5,10,15,20-tetrakis(4-hydroxyphenyl)porphyrin with dimethylformamide, dimethylacetamide and waterACTA CRYSTALLOGRAPHICA SECTION C, Issue 1 2009Sophia Lipstman The title free base porphyrin compound forms hydrogen-bonded adducts with N,N -dimethylformamide, C44H30N4O4·4C3H7NO, (I), a mixture of N,N -dimethylformamide and water, C44H30N4O4·4C3H7NO·H2O, (II), and a mixture of N,N -dimethylacetamide and water, C44H30N4O4·6C3H7NO·2H2O, (III). Total solvation of the four hydroxy functions of the porphyrin molecules characterizes all three compounds, thus preventing its supramolecular association into extended network architectures. In (I), the asymmetric unit consist of two five-component adduct species, while in (III), the nine-component entities reside on centres of inversion. This report provides the first structural characterizations of the free base tetra(hydroxyphenyl)porphyrin. It also demonstrates that the presence of strong Lewis bases, such as dimethylformamide or dimethylacetamide, in the crystallization mixture prevents direct supramolecular networking of the porphyrin ligands via O,H...O,H hydrogen bonds, due to their competing O,H...N(base) interaction with the hydroxy functions. The crystal packing of compounds (I),(III) resembles that of other hydrogen-bonding-assisted tetraarylporphyrin clathrates. [source] | ||||||||||