Xyl II

Glycosylation of biomolecules can greatly alter their physicochemical properties, cellular recognition, subcellular localization, and immunogenicity. Glycosylation reactions rely on the stepwise addition of sugars using nucleotide diphosphate (NDP)-sugars. Making these substrates readily available will greatly accelerate the characterization of new glycosylation reactions, elucidation of their underlying regulation mechanisms, and production of glycosylated molecules. In this work, we engineered Saccharomyces cerevisiae to heterologously express nucleotide sugar synthases to access a wide variety of uridine diphosphate (UDP)-sugars from simple starting materials (i...

We present a new synthetic strategy for obtaining mixed-valence triiron complexes where the metal centers are bridged by a novel, highly functionalized hydrocarbyl ligand. The alkynyl-vinyliminium complexes [Fe2 Cp2 (CO)(μ-CO){μ-η1 :η3 -C(X-CCH)CHCNMe2 }]CF3 SO3 (X = 4-C6 H4 , [2a1]CF3SO3; X = (CH2 )3 , [2a2]CF3SO3) were synthesized in almost quantitative yields from the aminocarbyne precursor [Fe2 Cp2 (CO)2 (μ-CO){μ-CNMe2 }]CF3 SO3 , [1a]CF3SO3, and the di-alkynes HCC-X-CCH...

BACKGROUND: UDP-glucuronate decarboxylase (also named UXS) converts UDP-glucuronic acid (UDP-GlcA) to UDP-xylose (UDP-Xyl) by decarboxylation of the C6-carboxylic acid of glucuronic acid. UDP-Xyl is an important sugar donor that is required for the synthesis of plant cell wall polysaccharides. RESULTS: In this study, we first carried out the genome-wide identification of NtUXS genes in tobacco. A total of 17 NtUXS genes were identified, which could be divided into two groups (Group I and II), and the Group II UXSs can be further divided into two subgroups (Group IIa and IIb)...

In this study, three acidic polysaccharides from different plant parts of Codonopsis pilosula var. Modesta (Nannf.) L. T. Shen were obtained by ion exchange chromatography and gel filtration chromatography, and the yields of these three polysaccharides were different. According to the preliminary experimental results, the antioxidant activities of the polysaccharides from rhizomes and fibrous roots (CLFP-1) were poor, and was thus not studied further. Due to this the structural features of polysaccharides from roots (CLRP-1) and aerial parts (CLSP-1) were the object for this study and were structurally characterized, and their antioxidant activities were evaluated...

Palladium(II) and platinum(II) complexes featuring metalla-N-heterocyclic carbenes (7-12) were synthesised via metal-mediated coupling between equimolar cis -[MCl2 (CNR)2 ] (R = 2,6-Me2 C6 H3 (Xyl), 2,4,6-Me3 C6 H3 (Mes)) and 2-aminopyridine or 2-aminopyrazine. Thiocyanate complexes 13-18 with two thiocyanate ligands were obtained through the ligand exchange in the parent compounds 7-12 with NH4 CNS in acetone/CH2 Cl2 . Complexes 7-18 were isolated and characterised by HRESI+ -MS, IR, 1 H and 13 C{1 H} NMR spectroscopy and single-crystal X-ray diffraction (in the case of 11, 16, and 18)...

Alpha-1,6-mannosyl-glycoprotein 2-β- N -acetylglucosaminyltransferase [EC 2.4.1.143, N -acetylglucosaminyltransferase II (GnTII)] catalyzes the transfer of N-acetylglucosamine (GlcNAc) residue from the nucleotide sugar donor UDP-GlcNAc to the α1,6-mannose residue of the di-antennary N-glycan acceptor GlcNAc(Xyl)Man3 (Fuc)GlcNAc2 in the Golgi apparatus. Although the formation of the GlcNAc2 (Xyl)Man3 (Fuc)GlcNAc2 N-glycan is known to be associated with GnTII activity in Arabidopsis thaliana , its physiological significance is still not fully understood in plants...

To create bacterial transcription "circuits" for biotechnology, one approach is to recombine natural transcription factors, promoters, and operators. Additional novel functions can be engineered from existing transcription factors such as the E. coli AraC transcriptional activator, for which binding to DNA is modulated by binding L-arabinose. Here, we engineered chimeric AraC/XylS transcription activators that recognized ara DNA binding sites and responded to varied effector ligands. The first step, identifying domain boundaries in the natural homologs, was challenging because (i) no full-length, dimeric structures were available and (ii) extremely low sequence identities (≤10%) among homologs precluded traditional assemblies of sequence alignments...

A series of group 11 m -terphenyl complexes have been synthesized via a metathesis reaction from the iron(II) complexes (2,6-Mes2 C6 H3 )2 Fe and (2,6-Xyl2 C6 H3 )2 Fe (Mes = 2,4,6-Me3 C6 H2 ; Xyl = 2,6-Me2 C6 H3 ). [2,6-Mes2 C6 H3 M]2 ( 1 , M = Cu; 2 , M = Ag; 6 , M = Au) and [2,6-Xyl2 C6 H3 M]2 ( 3 , M = Cu; 4 , M = Ag) are dimeric in the solid state, although different geometries are observed depending on the ligand. These complexes feature short metal-metal distances in the expected range for metallophilic interactions...

Even though homoatomic nine-atom germanium clusters are known for two decades, their chemical properties are still rarely investigated. We now discovered that Zintl ion main group-element clusters possess a reactive lone pair of electrons, and we show a new pathway to bind ligands with functional groups to the [Ge9 ] cluster core through Ge-C bond formation. We report on the reactivity of [Ge9 {Si(TMS)3 }2 ]2- (TMS = trimethylsilyl) towards a series of Lewis acidic bromo-boranes. The reaction of [Ge9 {Si(TMS)3 }2 ]2- and DAB o -tol -Br (DAB = 1,3,2-diazaborolidine; o -tol = 2-methylphenyl) resulted, depending on the reaction protocol, either in the formation of [Ge9 {Si(TMS)3 }2 DAB o -tol ]- ( 1a ) with direct Ge-B interactions, or in [Ge9 {Si(TMS)3 }2 (CH2 )4 O-DAB o -tol ]- ( 2a ) featuring a ring-opened thf moiety...

Reactions of the hindered N-heterocyclic carbene, :C{(MesNCH)2 } (IMes; Mes = mesityl), with a series of β-diketiminatomagnesium(II) hydride and dimagnesium(I) complexes were carried out at 80 °C. The reactions involving the magnesium hydrides, [{(Ar Nacnac)Mg(μ-H)}2 ] [Ar Nacnac = [(ArNCMe)2 CH]- , where Ar = 2,6-diethylphenyl (Dep) or 2,6-diisopropylphenyl (Dip)], proceeded via activation of an exocyclic C-N bond of IMes, giving magnesium imidazolyl compounds [(Ar Nacnac)Mg(μ-H)(μ-Imid)Mg(Ar Nacnac)] (Imid = [NC2 H2 N(Mes)C]- ) and mesitylene...

The aim of this study was to develop optimized enzyme cocktails, containing native and recombinant purified enzymes from five fungal species, for the saccharification of alkali- and acid-pretreated sugarcane bagasse (SCB), soybean hulls (SBH) and oil palm empty fruit bunches (EFB). Basic cellulases were represented by cellobiohydrolase I (CBH) and endo-glucanase II (EG) from Penicillium verruculosum and β-glucosidase (BG) from Aspergillus niger. Auxiliary enzymes were represented by endo-xylanase A (Xyl), pectin lyase (PNL) and arabinoxylanhydrolase (AXH) from Penicillium canescens, β-xylosidase (BX) from Aspergillus japonicus, endo-arabinase (ABN) from A...

Pectins are a major dietary nutrient source for the human gut microbiota. The prominent gut microbe Bacteroides thetaiotaomicron was recently shown to encode the founding member (BT1017) of a new family of pectin methylesterases essential for the metabolism of the complex pectin rhamnogalacturonan-II (RG-II). However, biochemical and structural knowledge of this family is lacking. Here, we showed that BT1017 is critical for the metabolism of an RG-II-derived oligosaccharide ΔBT1017oligoB generated by a BT1017 deletion mutant (ΔBT1017) during growth on carbohydrate extract from apple juice...

Pectins are a major dietary nutrient source for the human gut microbiota. The prominent gut microbe Bacteroides thetaiotaomicron was recently shown to encode the founding member (BT1017) of a new family of pectin methylesterases essential for the metabolism of the complex pectin rhamnogalacturonan-II (RG-II). However, biochemical and structural knowledge of this family is lacking. Here, we showed that BT1017 is critical for the metabolism of an RG-II-derived oligosaccharide ΔBT1017oligoB generated by a BT1017 deletion mutant (ΔBT1017) during growth on carbohydrate extract from apple juice...

A 91 kDa heteropolysaccharide (F2) was isolated from Mangifera indica fruit via extraction with H2 O, purification by C2 H5 OH, starch removal and ion exchange chromatography. This polymer was made up mostly of Ara, Gal, Glc, Rha, Xyl, and GalA in a 37: 29: 9:3:2:19 molar proportion. It inherited a small backbone containing GalpA and Rhap units substituted with very large side chains containing differently linked Ara and Gal units plus esterified gallic acid (GA) residue. Several enzymes generated oligosaccharides including (i) Ara2-10 Ac6 - 22 , (ii) Gal1-8 Ac5 - 26 and (iii) GA1 Gal1 Ac7 were characterized...

Rhamnogalacturonan-II (RG-II) is structurally the most complex glycan in higher plants, containing 13 different sugars and 21 distinct glycosidic linkages. Two monomeric RG-II molecules can form an RG-II-borate diester dimer through the two apiosyl (Api) residues of side chain A to regulate cross-linking of pectin in the cell wall. But the relationship of Api biosynthesis and RG-II dimer is still unclear. In this study we investigated the two homologous UDP-D-apiose/UDP-D-xylose synthases (AXSs) in Arabidopsis thaliana that synthesize UDP-D-apiose (UDP-Api)...

A straightforward method for the preparation of trisphosphinite ligands in one step, using only commercially available reagents (1,1,1-tris(4-hydroxyphenyl)ethane and chlorophosphines) is described. We have made use of this approach to prepare a small family of four trisphosphinite ligands of formula [CH3 C{(C6 H4 OR2 )3 ], where R stands for Ph ( 1a ), Xyl ( 1b , Xyl = 2,6-Me2 -C6 H3 ), i Pr ( 1c ), and Cy ( 1d ). These polyfunctional phosphinites allowed us to investigate their coordination chemistry towards a range of late transition metal precursors...

The Pseudomonas putida transcriptional activator XylS induces transcription from the Pm promoter in the presence of several benzoic acid effectors, with m -toluic acid being the most effective and p -toluic acid being much less effective. To alter the effector specificity of XylS, we developed a dual selection system in Escherichia coli , which consists of (i) an artificial operon of an ampicillin resistance gene and tetR under Pm promoter control and (ii) a chloramphenicol resistance gene under tetR promoter control...

In this work, the aromatic hydroxylation mechanism of the [Cu2 (H-XYL)O2 ]2+ complex mediated by a peroxo dicopper core and Cu-ligand effects are investigated by using hybrid density functional theory (DFT) and the broken symmetry B3LYP method. Based on the calculated free-energy profiles, we proposed two available mechanisms. The first reaction steps of both mechanisms involve concerted O-O bond cleavage and C-O bond formation and the second step involves the Wagner-Meerwein rearrangement of the substrate by a [1,2] H shift (HA shift from CA to CC ) or (HA shift from CA to OA ) across the phenyl ring to form stable dienone intermediates, and this is followed by the protonation of bridging oxygen atoms to produce the final hydroxylated dicopper(ii) product...

Structures and spectroscopic characterization of the divalent complexes cis-dibromidotetrakis(2,6-dimethylphenyl isocyanide)iron(II) dichloromethane 0.771-solvate, [FeBr2 (C9 H9 N)4 ]·0.771CH2 Cl2 or cis-FeBr2 (CNXyl)4 ·0.771CH2 Cl2 (Xyl = 2,6-dimethylphenyl), trans-dibromidotetrakis(2,6-dimethylphenyl isocyanide)iron(II), [FeBr2 (C9 H9 N)4 ] or trans-FeBr2 (CNXyl)4 , trans-dibromidotetrakis(2,6-dimethylphenyl isocyanide)cobalt(II), [CoBr2 (C9 H9 N)4 ] or trans-CoBr2 (CNXyl)4 , and trans-dibromidobis(2,6-dimethylphenyl isocyanide)nickel(II), [NiBr2 (C9 H9 N)2 ] or trans-NiBr2 (CNXyl)2 , are presented...

The one-electron reduction of a diiron cationic complex revealed unique features: cleavage of the diiron structure occurred despite a multidentate bridging C3 ligand and was accompanied by the clean dissociation of one η5 -cyclopentadienyl ring and one iron as isolated units. Thus, the iron(II)-iron(II) μ-vinyliminium complex [Fe2 Cp2 (CO)(μ-CO){μ-η1 :η3 -C3 (Et)C2 HC1 N(Me)(Xyl)}][SO3 CF3 ] ([1a]SO3 CF3 ) reacted with cobaltocene in tetrahydrofuran (THF), affording the iron(II) vinylaminoalkylidene [FeCp(CO){C1 N(Me)(Xyl)C2 HC3 (Et)C(═O)}] (2a) in 77% yield relative to the C3 ligand...