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Xyl II

Alexander S Mikherdov, Mikhail A Kinzhalov, Alexander S Novikov, Vadim P Boyarskiy, Irina A Boyarskaya, Dmitry V Dar'in, Galina L Starova, Vadim Yu Kukushkin
The reaction of cis-[PdCl2(CNXyl)2] (Xyl = 2,6-Me2C6H3) with various 1,3-thiazol- and 1,3,4-thiadiazol-2-amines in chloroform gives a mixture of two regioisomeric binuclear diaminocarbene complexes. For 1,3-thiazol-2-amines the isomeric ratio depends on the reaction conditions and kinetically (KRs) or thermodynamically (TRs) controlled regioisomers were obtained at room temperature and on heating, respectively. In CHCl3 solutions, the isomers are subject to reversible isomerization accompanied with the cleavage of Pd-N and С-N bonds in the carbene fragment XylNCN(R)Xyl...
October 4, 2016: Journal of the American Chemical Society
Jimmy Omony, Astrid R Mach-Aigner, Gerrit van Straten, Anton J B van Boxtel
BACKGROUND: Transcription of genes coding for xylanolytic and cellulolytic enzymes in Aspergillus niger is controlled by the transactivator XlnR. In this work we analyse and model the transcription dynamics in the XlnR regulon from time-course data of the messenger RNA levels for some XlnR target genes, obtained by reverse transcription quantitative PCR (RT-qPCR). Induction of transcription was achieved using low (1 mM) and high (50 mM) concentrations of D-xylose (Xyl). We investigated the wild type strain (Wt) and a mutant strain with partial loss-of-function of the carbon catabolite repressor CreA (Mt)...
2016: BMC Systems Biology
Joan Serrano-Plana, Isaac Garcia-Bosch, Anna Company, Miquel Costas
Dioxygen is widely used in nature as oxidant. Nature itself has served as inspiration to use O2 in chemical synthesis. However, the use of dioxygen as an oxidant is not straightforward. Its triplet ground-state electronic structure makes it unreactive toward most organic substrates. In natural systems, metalloenzymes activate O2 by reducing it to more reactive peroxide (O2(2-)) or superoxide (O2(-)) forms. Over the years, the development of model systems containing transition metals has become a convenient tool for unravelling O2-activation mechanistic aspects and reproducing the oxidative activity of enzymes...
August 18, 2015: Accounts of Chemical Research
Jesús Campos, Laura Ortega-Moreno, Salvador Conejero, Riccardo Peloso, Joaquín López-Serrano, Celia Maya, Ernesto Carmona
This paper describes the formation of new platinacyclic complexes derived from the phosphine ligands PiPr2 Xyl, PMeXyl2 , and PMe2 Ar Xyl 2 (Xyl=2,6-Me2 C6 H3 and Ar Xyl 2=2,6-(2,6-Me2 C6 H3 )2 -C6 H3 ) as well as reactivity studies of the trans-[Pt(C^P)2 ] bis-metallacyclic complex 1 a derived from PiPr2 Xyl. Protonation of compound 1 a with [H(OEt2 )2 ][BArF ] (BArF =B[3,5-(CF3 )2 C6 H3 ]4 ) forms a cationic δ-agostic structure 4 a, whereas α-hydride abstraction employing [Ph3 C][PF6 ] produces a cationic platinum carbene trans-[Pt{PiPr2 (2,6-CH(Me)C6 H3 }{PiPr2 (2,6-CH2 (Me)C6 H3 }][PF6 ] (8)...
June 8, 2015: Chemistry: a European Journal
Liudmila V Kozlova, Oleg V Gorshkov, Natalia E Mokshina, Tatyana A Gorshkova
Specific α- l -arabinofuranosidases are involved in the realisation of elongation growth process in cells with type II cell walls. Elongation growth in a plant cell is largely based on modification of the cell wall. In type II cell walls, the Ara/Xyl ratio is known to decrease during elongation due to the partial removal of Ara residues from glucuronoarabinoxylan. We searched within the maize genome for the genes of all predicted α-L-arabinofuranosidases that may be responsible for such a process and related their expression to the activity of the enzyme and the amount of free arabinose measured in six zones of a growing maize root...
May 2015: Planta
Yuan Zhi Shi, Xiao Fang Zhu, Janice G Miller, Timothy Gregson, Shao Jian Zheng, Stephen C Fry
Xyloglucan plays an important structural role in primary cell walls, possibly tethering adjacent microfibrils and restraining cell expansion. There is therefore considerable interest in understanding the role of xyloglucan endotransglucosylase/hydrolases (XTHs), which are encoded in Arabidopsis by a 33-member gene family. We compared the key catalytic properties of two very different Arabidopsis XTHs (heterologously produced in Pichia), both of which are aluminium-repressed. Reductively tritiated oligosaccharides of xyloglucan were used as model acceptor substrates...
April 2015: Phytochemistry
Joan Serrano-Plana, Isaac Garcia-Bosch, Ryosuke Miyake, Miquel Costas, Anna Company
The bis(μ-oxo)dicopper(III) species [Cu(III) 2 (μ-O)2 (m-XYL(MeAN) )](2+) (1) promotes the electrophilic ortho-hydroxylation-defluorination of 2-fluorophenolates to give the corresponding catechols, a reaction that is not accomplishable with a (η(2) :η(2) -O2 )dicopper(II) complex. Isotopic labeling studies show that the incoming oxygen atom originates from the bis(μ-oxo) unit. Ortho-hydroxylation-defluorination occurs selectively in intramolecular competition with other ortho-substituents such as chlorine or bromine...
September 1, 2014: Angewandte Chemie
Mengmeng Zhao, Wanfang Li, Xiaoming Li, Kai Ren, Xiaoming Tao, Xiaomin Xie, Tahar Ayad, Virginie Ratovelomanana-Vidal, Zhaoguo Zhang
A series of γ-hydroxy amides were synthesized with high enantioselectivities (up to 99%) using asymmetric hydrogenation of the corresponding γ-ketoamides in the presence of Ru-Xyl-SunPhos-Daipen catalyst providing key building blocks for a variety of naturally occurring and biologically active compounds.
July 3, 2014: Journal of Organic Chemistry
B K Rana, B N Johri, I S Thakur
A thermophilic fungus, Humicola grisea var thermoidea, produced in liquid culture two endoxylanases (1,4-β-D-xylan-xylanohydrolase, EC with M r of 95 (Xyl I) and 13 (Xyl II) kDa. PAGE of the crude culture filtrate and of each fraction obtained by gel filtration produced three and one band, respectively. Cross-reaction of the culture filtrate and each fraction with polyclonal antibodies prepared against Xyl II produced two and one precipitin bands, respectively. Hydrolysis of wheat straw and rice husk xylan was maximal using a combination of Xyl I and Xyl II...
January 1996: World Journal of Microbiology & Biotechnology
Sueharu Horinouchi, Teruhiko Beppu
Streptomyces griseus, a well-known industrial producer of streptomycin, is a member of the genus Streptomyces, which shows a complex life cycle resembling that of fungi. A-factor, a C13 γ-butyrolactone compound, was discovered as a self-regulatory factor or a bacterial hormone to induce morphological differentiation and production of secondary metabolites, including streptomycin, in this organism. Accumulating evidence has revealed an A-factor-triggered signal cascade, which is composed of several key steps or components...
December 2007: Proceedings of the Japan Academy. Series B, Physical and Biological Sciences
Zhiliang Wu, Mingliang Zhang, Lingqiang Wang, Yuanyuan Tu, Jing Zhang, Guosheng Xie, Weihua Zou, Fengcheng Li, Kai Guo, Qing Li, Chunbao Gao, Liangcai Peng
BACKGROUND: Wheat and rice are important food crops with enormous biomass residues for biofuels. However, lignocellulosic recalcitrance becomes a crucial factor on biomass process. Plant cell walls greatly determine biomass recalcitrance, thus it is essential to identify their key factors on lignocellulose saccharification. Despite it has been reported about cell wall factors on biomass digestions, little is known in wheat and rice. In this study, we analyzed nine typical pairs of wheat and rice samples that exhibited distinct cell wall compositions, and identified three major factors of wall polymer features that affected biomass digestibility...
December 16, 2013: Biotechnology for Biofuels
Rebecca A Musgrave, Robert S P Turbervill, Mark Irwin, Radovan Herchel, Jose M Goicoechea
Reaction of dimesityliron(II) (Fe2(mes)4) with the N-heterocyclic carbenes 1,3-bis(2,6-diisopropylphenyl)-imidazol-2-ylidene (IPr) and 1,3-bis(2,6-dimethylphenyl)hexahydropyrimidin-2-ylidene (6-Xyl) afforded the novel trigonal planar complexes [Fe(IPr)(mes)2] (1) and [Fe(6-Xyl)(mes)2] (2), respectively. Both species were structurally characterized by single crystal X-ray diffraction and display structures and magnetic responses consistent with a quintet ground state (S = 2). Reaction of 1 with KC8 in THF afforded K(+) salts of the anionic complex [{:C[N(2,6-(i)Pr2C6H3)]2(CH)C}2Fe(mes)](-) (3) and the homoleptic organometallic anion [Fe(mes)3](-) (4)...
March 21, 2014: Dalton Transactions: An International Journal of Inorganic Chemistry
Munzarin F Qayyum, Ritimukta Sarangi, Kiyoshi Fujisawa, T Daniel P Stack, Kenneth D Karlin, Keith O Hodgson, Britt Hedman, Edward I Solomon
The hydroxylation of aromatic substrates catalyzed by coupled binuclear copper enzymes has been observed with side-on-peroxo-dicopper(II) (P) and bis-μ-oxo-dicopper(III) (O) model complexes. The substrate-bound-O intermediate in [Cu(II)2(DBED)2(O)2](2+) (DBED = N,N'-di-tert-butyl-ethylenediamine) was shown to perform aromatic hydroxylation. For the [Cu(II)2(NO2-XYL)(O2)](2+) complex, only a P species was spectroscopically observed. However, it was not clear whether this O-O bond cleaves to proceed through an O-type structure along the reaction coordinate for hydroxylation of the aromatic xylyl linker...
November 20, 2013: Journal of the American Chemical Society
Jekaterina Jutkina, Lars Hestbjerg Hansen, Lili Li, Eeva Heinaru, Eve Vedler, Merike Jõesaar, Ain Heinaru
In the present study we report the complete nucleotide sequence of the toluene catabolic plasmid pD2RT of Pseudomonas migulae strain D2RT isolated from Baltic Sea water. The pD2RT is 129,894 base pairs in size with an average G+C content of 53.75%. A total of 135 open reading frames (ORFs) were predicted to encode proteins, among them genes for catabolism of toluene, plasmid replication, maintenance and conjugative transfer. ORFs encoding proteins with putative functions in stress response, transposition and site-specific recombination were also predicted...
November 2013: Plasmid
Nadja Graf, Josef Altenbuchner
A methyl ethyl ketone (MEK)-inducible system based on the broad-host-range plasmid pBBR1MCS2 and on the P mekA promoter region of the MEK degradation operon of Pseudomonas veronii MEK700 was characterized in Escherichia coli JM109 and Pseudomonas putida KT2440. For validation, β-galactosidase (lacZ) was used as a reporter. The novel system, which is positively regulated by MekR, a member of the AraC/XylS family of regulators, was shown to be subject to carbon catabolite repression by glucose, which, however, could not be attributed to the single action of the global regulators Crc and PtsN...
September 2013: Applied Microbiology and Biotechnology
Kenneth D Karlin, Christiana Xin Zhang, Arnold L Rheingold, Benedikt Galliker, Susan Kaderli, Andreas D Zuberbühler
Copper-dioxygen interactions are of intrinsic importance in a wide range of biological and industrial processes. Here, we present detailed kinetic/thermodynamic studies on the O(2)-binding and arene hydroxylation reactions of a series of xylyl-bridged binuclear copper(I) complexes, where the effects of ligand electronic and structural elements on these reactions are investigated. Ligand 4-pyridyl substituents influence the reversible formation of side-on bound μ-η(2):η(2)-peroxodicopper(II) complexes, with stronger donors leading to more rapid formation and greater thermodynamic stability of product complexes [Cu(II) (2)((R)XYL)(O(2) (2-))](2+)...
July 1, 2012: Inorganica Chimica Acta
Wenhui Zhang, Allen G Oliver, Henry M Vu, John G Duman, Anthony S Serianni
Methyl β-D-mannopyranosyl-(1→4)-β-D-xylopyranoside, C(12)H(22)O(10), (I), crystallizes as colorless needles from water, with two crystallographically independent molecules, (IA) and (IB), comprising the asymmetric unit. The internal glycosidic linkage conformation in molecule (IA) is characterized by a ϕ' torsion angle (O5'(Man)-C1'(Man)-O1'(Man)-C4(Xyl); Man is mannose and Xyl is xylose) of -88.38 (17)° and a ψ' torsion angle (C1'(Man)-O1'(Man)-C4(Xyl)-C5(Xyl)) of -149.22 (15)°, whereas the corresponding torsion angles in molecule (IB) are -89...
December 2012: Acta Crystallographica. Section C, Crystal Structure Communications
Maija Tenkanen, Mária Vršanská, Matti Siika-aho, Dominic W Wong, Vladimír Puchart, Merja Penttilä, Markku Saloheimo, Peter Biely
A minor xylanase, named XYN IV, was purified from the cellulolytic system of the fungus Trichoderma reesei Rut C30. The enzyme was discovered on the basis of its ability to attack aldotetraohexenuronic acid (HexA-2Xyl-4Xyl-4Xyl, HexA(3)Xyl(3)), releasing the reducing-end xylose residue. XYN IV exhibited catalytic properties incompatible with previously described endo-β-1,4-xylanases of this fungus, XYN I, XYN II and XYN III, and the xylan-hydrolyzing endo-β-1,4-glucanase EG I. XYN IV was able to degrade several different β-1,4-xylans, but was inactive on β-1,4-mannans and β-1,4-glucans...
January 2013: FEBS Journal
Juan Forniés, Violeta Sicilia, Pilar Borja, José M Casas, Alvaro Díez, Elena Lalinde, Carmen Larraz, Antonio Martín, M Teresa Moreno
The neutral compounds [Pt(bzq)(CN)(CNR)] (R = tBu (1), Xyl (2), 2-Np (3); bzq = benzoquinolate, Xyl = 2,6-dimethylphenyl, 2-Np = 2-napthyl) were isolated as the pure isomers with a trans-C(bzq),CNR configuration, as confirmed by (13)C{(1)H} NMR spectroscopy in the isotopically marked [Pt(bzq)((13)CN)(CNR)] (R = tBu (1'), Xyl (2'), 2-Np (3')) derivatives (δ(13)C(CN) ≈ 110 ppm; (1) J(Pt,(13)C) ≈ 1425 Hz]. By contrast, complex [Pt(bzq)(C≡CPh)(CNXyl)] (4) with a trans-N(bzq),CNR configuration, has been selectively isolated from [Pt(bzq)Cl(CNXyl)] (trans-N(bzq),CNR) using Sonogashira conditions...
December 2012: Chemistry, An Asian Journal
Wen Zhou, Linus Chiang, Brian O Patrick, Tim Storr, Kevin M Smith
Paramagnetic CpCr(III) complexes with antiferromagnetically-coupled anionic radical diimine and pyridine-imine ligands were prepared and characterized. The diimine chloro CpCr[(ArNCR)(2)]Cl complexes (1: Ar = 2,6-iPr(2)C(6)H(3) (Dpp), R = H; 2: Ar = 2,6-Me(2)C(6)H(3) (Xyl), R = Me; 3: Ar = 2,4,6-Me(3)C(6)H(2) (Mes), R = Me) were synthesized by treatment of previously reported Cr(diimine)(THF)(2)Cl(2) precursors with NaCp. Reduction of 1 with Zn gives CpCr[(DppNCH)(2)], 4, resulting from reduction of Cr(III) to Cr(II) with retention of the ligand-based radical...
July 14, 2012: Dalton Transactions: An International Journal of Inorganic Chemistry
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