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1.
Artigo em Inglês | MEDLINE | ID: mdl-33591587

RESUMO

We herein report the synthesis, structures, coordination ability, and mechanism of formation of silicon analogs of crown ethers. An oligomerization of 2 D2 (I) (2 Dn ,=(Me4 Si2 O)n ) was achieved by the reaction with GaI3 and MIx (M=Li, Na, Mg, Ca, Sr). In these reactions the metal cations serve as template and the anions (I- /[GaI4 ]- ) are required as nucleophiles. In case of MIx =LiI, [Li(2 D3 )GaI4 ] (1) is formed. In case of MIx =NaI, MgI2 , CaI2 , and SrI2 the compounds [M(2 D4 )(GaI4 )x ] (M=Mg2+ (3), Ca2+ (4), Sr2+ (5) are obtained. Furthermore the proton complex [H(2 D3 )][Ga2 I7 ] (6) was isolated and structurally characterized. All complexes were characterized by means of multinuclear NMR spectroscopy, DOSY experiments and, except for compound 3, also by single crystal X-ray diffraction. Quantum chemical calculations were carried out to compare the affinity of M+ to 2 Dn and other ligands and to shed light on the formation of larger rings from smaller ones.

2.
Inorg Chem ; 59(23): 17565-17572, 2020 Dec 07.
Artigo em Inglês | MEDLINE | ID: mdl-33197182

RESUMO

The syntheses and XRD molecular structures of a complete series of silylsulfido metalates Cat[M(SSiMe3)2] (M = Cu, Ag, Au) and corresponding silylselenido metalates Cat[M(SeSiMe3)2] (M = Cu, Ag, Au) comprising lattice stabilizing organic cations (Cat = Ph4P+ or PPN+) are reported. Much to our surprise these homoleptic cuprates, argentates, and aurates are stable enough to be isolated even in the absence of any strongly binding phosphines or N-heterocyclic carbenes as coligands. Their metal atoms are coordinated by two silylchalcogenido ligands in a linear fashion. The silyl moieties of all anions show an unexpected gauche conformation of the silyl substituents with respect to the central axis Si-[E-M-E]-Si in the solid state. The energetic preference for the gauche conformation is confirmed by quantum chemical calculations and amounts to about 2-6 kJ/mol, thus revealing a rather shallow potential mainly depending on electronic effects of the metal. Furthermore, 2D HMQC methods were applied to detect the otherwise nonobservable NMR shifts of the 29Si and 77Se nuclei of the silylselenido compounds. Preliminary investigations reveal that these thermally and protolytically labile chalcogenido metalates are valuable precursors for the precipitation of binary coinage metal chalcogenide nanoparticles from organic solution and for coinage metal cluster syntheses.

3.
Org Lett ; 22(16): 6653-6656, 2020 08 21.
Artigo em Inglês | MEDLINE | ID: mdl-32806187

RESUMO

A ring-closing aminooxygenation of alkenes with N-benzoyloxycarbamates occurs with very high diastereoselectivity (typically >20:1 d.r.) and very high enantioselectivity (up to 99% ee). The reaction is catalyzed by a recently developed chiral-at-metal ruthenium complex at catalyst loadings of 0.5-1.0 mol %. The reaction is proposed to proceed through a ruthenium nitrenoid intermediate that depending on the nature of the substrate undergoes either an aminooxygenation (1,2-disubstituted alkenes) or stops at the stage of the aziridination (trisubstituted alkenes), which can then be ring opened with benzoic acid. The resulting chiral cyclic carbamates can be hydrolyzed under basic conditions to provide versatile chiral 2-amino-1,3-diols with vicinal stereocenters.

4.
Chem Commun (Camb) ; 56(75): 11042-11045, 2020 Sep 22.
Artigo em Inglês | MEDLINE | ID: mdl-32808942

RESUMO

Genome mining revealed the presence of two cdps-p450 operons in Saccharopolyspora antimicrobica. Heterologous expression, biochemical characterisation and structure elucidation proved that the two P450 enzymes catalyse distinct regio- and stereospecific dimerizations of cyclo-(l-Trp-l-Trp), which significantly expands the repertoire of diketopiperazine-tailoring enzymes. TtpB1 connects the monomers via C3-C3', both from the opposite side of H-11/H-11', while TtpB2 is characterised as the first P450 to mainly catalyse the unusual linkage between N1' and C3 from the H-11 side.

5.
Angew Chem Int Ed Engl ; 59(32): 13552-13556, 2020 Aug 03.
Artigo em Inglês | MEDLINE | ID: mdl-32488954

RESUMO

A transformation of fluxional into configurationally stable axially chiral N-arylpyrroles was achieved with a highly atroposelective electrophilic aromatic substitution catalyzed by a chiral-at-metal rhodium Lewis acid. Specifically, N-arylpyrroles were alkylated with N-acryloyl-1H-pyrazole electrophiles in up to 93 % yield and with up to >99.5 % ee, and follow-up conversions reveal the synthetic utility of this new method. DFT calculations elucidate the origins of the observed excellent atroposelectivity.

6.
Org Biomol Chem ; 18(14): 2646-2649, 2020 04 08.
Artigo em Inglês | MEDLINE | ID: mdl-32207506

RESUMO

The attachment of a dimethylallyl moiety to C4 of 1,3-dihydroxynaphthalene led to spontaneous oxidative cyclisations, resulting in the formation of two tetrahydrobenzofuran and one bicyclo[3.3.1]nonane derivatives. Incubation under an 18O-rich atmosphere proved that both the incorporated oxygen atoms originated from O2. A radical-involved mechanism is proposed for these cyclisations.

7.
Trop Anim Health Prod ; 52(3): 915-926, 2020 May.
Artigo em Inglês | MEDLINE | ID: mdl-32026291

RESUMO

For further understanding the genetic control mechanisms of growth and development in Tan sheep, and culturing good traits on meat performance, which is very important to both in developing local species and improving economic efficaciously. In our study, we recruited a total of 250 Tan sheep and 174 healthy Hu sheep to detect 32 SNPs in GH, GHR, NPY, Leptin, H-FABP, MSTN, and CAST by using direct sequencing techniques, in order to explore genetic marking loci which were an association with growth characters. From the results, we found different SNPs with an obvious difference for the growth traits. In the different genetic model analysis, we found SNP12, SNP29, SNP41, SNP8, SNP34, SNP35, SNP9, SNP10, SNP36, SNP45, and SNP39 were a significantly negative association with the two kinds of sheep. And SNP46, SNP42, and SNP69 with the positive association between the different trait in sheep were analyzed. From the LD and haplotype analysis, we found three blocks with the positive association in growth traits between Tan sheep and Hu sheep. The block of SNP29, SNP32, SNP34, SNP35, SNP36, SNP39, SNP41, SNP42, SNP45, and SNP46 with the genotype "AATCTACTTA" is the most significantly association with the traits. In summary, the study initially explored the genes for growth and reproduction between Tan sheep and Hu sheep and found some statistically significant results which demonstrate that there are genetic differences. These differential molecular markers may provide a scientific theoretical basis for the preferred species of Tan sheep which with good meat performance and better utilization of species resources.


Assuntos
Genótipo , Polimorfismo de Nucleotídeo Único , Ovinos/genética , Animais , Conservação dos Recursos Naturais , Marcadores Genéticos , Fenótipo
8.
Int Immunopharmacol ; 81: 106026, 2020 Apr.
Artigo em Inglês | MEDLINE | ID: mdl-31759863

RESUMO

Diet is one of the factors contributing to symptom of Helicobacter pylori (H. pylori) infection. Trimethylamine N-oxide (TMAO), a diet-related microbial metabolite, is associated with inflammatory and metabolic diseases. The aim of this study is to investigate the effects of TMAO intake on inflammation and gut microbiota composition in H. pylori-infected mice via 16S rRNA sequencing and biochemical analyses. The in vitro experiments showed that TMAO not only increased the expression of growth- and metabolism-associated genes and the urease activity of H. pylori, but increased the production of virulence factors. Moreover, TMAO intake increased the production of inflammatory markers and reduced the richness and diversity of the gut microbiota in H. pylori-infected mice. Further analysis showed that TMAO increased the relative abundance of Escherichia_Shigella in H. pylori-infected mice, which had positive correlation with the levels of LPS, CRP, and CXCL1. Collectively, our results suggest that TMAO may aggravate H. pylori-induced inflammation by increasing the viability and virulence of H. pylori and may aggravate inflammation in association with the gut microbiota in H. pylori-infected mice. This study may provide a novel insight into the mechanism for the effect of diet-derived metabolites such as TMAO on H. pylori-induced disease development.

9.
Org Lett ; 21(22): 9142-9146, 2019 Nov 15.
Artigo em Inglês | MEDLINE | ID: mdl-31680528

RESUMO

With the synthesis of N,N',N″,N‴-tetrakis(3-(dimethylamino)propyl)triaminophosphazene (TDMPP, 1), we present the first phosphazene superbase with enhanced basicity through the effect of multiple intramolecular hydrogen bonding (IHB). Due to intramolecular solvation of four NH protons, the proton affinity is even higher than that of second-order phosphazene (dma)P2-tBu. X-ray structural proof, NMR titration experiments, and computational investigations provide a more detailed quantitative description of the IHB influence on the superbasicity of 1 in solid-state, solution, and the gas-phase.

10.
Org Lett ; 21(22): 9104-9108, 2019 11 15.
Artigo em Inglês | MEDLINE | ID: mdl-31663761

RESUMO

The cyclo-l-Trp-l-Trp (cWW, 1) tailoring P450 GutD2774 from Streptomyces lavendulae was characterized by expression in Streptomyces coelicolor, precursor feeding and enzyme assays. GutD2774 catalyzes mainly the transfer of hypoxanthine to C2 and C3 of the indole ring of 1. cWW adducts with guanine were detected as minor products. An orthologous cluster was identified in Streptomyces xanthophaeus. These results expand the spectrum of cyclodipeptide derivatives by involvement of an additional nucleobase and identification of new coupling patterns.


Assuntos
Dipeptídeos/química , Hipoxantina/química , Peptídeos Cíclicos/química , Transferases/química , Catálise , Sistema Enzimático do Citocromo P-450/química , Estrutura Molecular , Streptomyces/genética , Streptomyces/metabolismo , Transferases/genética , Transferases/metabolismo
11.
Food Chem ; 299: 125163, 2019 Nov 30.
Artigo em Inglês | MEDLINE | ID: mdl-31319344

RESUMO

Citrus fruit postharvest degreening is a critical stage in marketing, carried out by exposure to ethylene or ethephon. Genome-wide screening of the AP2/ERF superfamily indicated that a novel ERF-II (CitERF6) was shown to trans-activate the CitPPH promoter. Expression of CitERF6 is associated with both developmental and postharvest degreening in citrus fruit. Transient and stable over-expression of CitERF6 in Nicotiana tabacum leaves and 'Ponkan' fruit also results in rapid chlorophyll degradation. Auto- and mutual-regulation was also found between CitERF6 and the previously characterized CitERF13 using the dual-luciferase and yeast one-hybrid assays. Moreover, substitution of the 35S promoter for endogenous promoters showed that both pCitERF6::CitERF6 and pCitERF13::CitERF13 were effective in trans-activating their promoters or triggering chlorophyll degradation. It is proposed that ethylene is one of the triggers activating promoters of CitERF6 and CitERF13, and subsequent auto- and mutual-regulation between CitERF6 and CitERF13 might facilitate the effect of ethylene, leading to fruit degreening.


Assuntos
Citrus/fisiologia , Etilenos/metabolismo , Frutas/fisiologia , Proteínas de Plantas/metabolismo , Clorofila/genética , Clorofila/metabolismo , Armazenamento de Alimentos , Regulação da Expressão Gênica de Plantas , Proteínas de Plantas/genética , Plantas Geneticamente Modificadas , Regiões Promotoras Genéticas , Tabaco/genética
12.
Biomed Res Int ; 2019: 9732325, 2019.
Artigo em Inglês | MEDLINE | ID: mdl-31205950

RESUMO

Exposure to a variety of environmental factors such as salinity, drought, metal toxicity, extreme temperature, air pollutants, ultraviolet-B (UV-B) radiation, pesticides, and pathogen infection leads to subject oxidative stress in plants, which in turn affects multiple biological processes via reactive oxygen species (ROS) generation. ROS include hydroxyl radicals, singlet oxygen, and hydrogen peroxide in the plant cells and activates signaling pathways leading to some changes of physiological, biochemical, and molecular mechanisms in cellular metabolism. Excessive ROS, however, cause oxidative stress, a state of imbalance between the production of ROS and the neutralization of free radicals by antioxidants, resulting in damage of cellular components including lipids, nucleic acids, metabolites, and proteins, which finally leads to the death of cells in plants. Thus, maintaining a physiological level of ROS is crucial for aerobic organisms, which relies on the combined operation of enzymatic and nonenzymatic antioxidants. In order to improve plants' tolerance towards the harsh environment, it is vital to reinforce the comprehension of oxidative stress and antioxidant systems. In this review, recent findings on the metabolism of ROS as well as the antioxidative defense machinery are briefly updated. The latest findings on differential regulation of antioxidants at multiple levels under adverse environment are also discussed here.


Assuntos
Antioxidantes/metabolismo , Meio Ambiente , Estresse Oxidativo/fisiologia , Fenômenos Fisiológicos Vegetais , Espécies Reativas de Oxigênio/metabolismo
13.
Angew Chem Int Ed Engl ; 58(33): 11534-11540, 2019 08 12.
Artigo em Inglês | MEDLINE | ID: mdl-31206992

RESUMO

Mining microbial genomes including those of Streptomyces reveals the presence of a large number of biosynthetic gene clusters. Unraveling this genetic potential has proved to be a useful approach for novel compound discovery. Here, we report the heterologous expression of two similar P450-associated cyclodipeptide synthase-containing gene clusters in Streptomyces coelicolor and identification of eight rare and novel natural products, the C3-guaninyl indole alkaloids guanitrypmycins. Expression of different gene combinations proved that the cyclodipeptide synthases assemble cyclo-l-Trp-l-Phe and cyclo-l-Trp-l-Tyr, which are consecutively and regiospecifically modified by cyclodipeptide oxidases, cytochrome P450 enzymes, and N-methyltransferases. In vivo and in vitro results proved that the P450 enzymes function as key biocatalysts and catalyze the regio- and stereospecific 3α-guaninylation at the indole ring of the tryptophanyl moiety. Isotope-exchange experiments provided evidence for the non-enzymatic epimerization of the biosynthetic pathway products via keto-enol tautomerism. This post-pathway modification during cultivation further increases the structural diversity of guanitrypmycins.


Assuntos
Vias Biossintéticas , Sistema Enzimático do Citocromo P-450/metabolismo , Guanina/química , Streptomyces/metabolismo , Dipeptídeos/química
14.
Fungal Genet Biol ; 130: 91-97, 2019 09.
Artigo em Inglês | MEDLINE | ID: mdl-31103599

RESUMO

Mannosylerythritol lipids (MELs) are surface active molecules produced by many basidiomycetous fungi. MELs consist of a mannosylerythritol disaccharide, which is acylated with short and medium chain fatty acids at the mannosyl moiety. A gene cluster composed of five genes is required for MEL biosynthesis. Here we show that the plant pathogenic fungus Ustilago hordei secretes these glycolipids under nitrogen starvation conditions. In contrast to MELs produced by the closely related fungus Ustilago maydis those secreted by U. hordei are mostly mono-acetylated and contain a different mixture of acyl groups. Cross-species complementation between these fungi revealed that these differences result from different catalytic activities of the acetyltransferase Mat1 and the acyltransferases Mac1 and Mac2. U. maydis mat1 mutants expressing the homologous mat1 gene from U. hordei produced mostly mono-acetylated variants and lack di-acetylated MELs normally produced by U. maydis. Furthermore, we determined that the acyltransferase Mac1 acylates the mannosylerythritol moiety at position C2 while Mac2 acylates C3. The identification of decorating enzymes with different substrate specificities will allow the tailor-made production of novel subsets of MELs.


Assuntos
Glicolipídeos/biossíntese , Ustilaginales/enzimologia , Ustilaginales/metabolismo , Acetilação , Acetiltransferases/genética , Acetiltransferases/metabolismo , Aciltransferases/genética , Aciltransferases/metabolismo , Ácidos Graxos/metabolismo , Proteínas Fúngicas/genética , Regulação Fúngica da Expressão Gênica , Família Multigênica , Nitrogênio/metabolismo , Especificidade por Substrato , Transcriptoma , Ustilaginales/genética
15.
Angew Chem Int Ed Engl ; 58(30): 10335-10339, 2019 Jul 22.
Artigo em Inglês | MEDLINE | ID: mdl-31037821

RESUMO

It was discovered that phosphazenyl phosphines (PAPs) can be stronger P-superbases than the corresponding Schwesinger type phosphazene N-superbases. A simple synthetic access to this class of PR3 derivatives including their homologization is described. XRD structures, proton affinities (PA), and gas-phase basicities (GB) as well as calculated and experimental pK BH + values in THF are presented. In contrast to their N-basic counterparts, PAPs are also privileged ligands in transition metal chemistry. In fact, they are currently the strongest uncharged P-donors known, exceeding classical and more recently discovered ligands such as PtBu3 and imidazolin-2-ylidenaminophosphines (IAPs) with respect to their low Tolman electronic parameters (TEPs) and large cone angles.

16.
ACS Chem Biol ; 13(10): 2949-2955, 2018 10 19.
Artigo em Inglês | MEDLINE | ID: mdl-30226371

RESUMO

Prenylation of cyclodipeptides contributes largely to the structure diversification and biological activity. The prenylated products can be further metabolized by modifications like hydroxylation with cytochrome P450 enzymes or nonheme FeII/2-oxoglutarate-dependent oxygenases. Herein, we cloned and overexpressed NFIA_045530 from Neosartorya fischeri, which shares high sequence similarity with the nonheme FeII/2-oxoglutarate-dependent oxygenase FtmOx1Af from Aspergillus fumigatus on the amino acid level. FtmOx1Af is a member of the biosynthetic enzymes for fumitremorgin-type mycotoxins and catalyzes the conversion of fumitremorgin B to verruculogen by insertion of an oxygen molecule into the two prenyl moieties. The recombinant protein EAW25734 encoded by NFIA_045530 was purified to apparent homogeneity and then was used for incubation with intermediates of the fumitremorgin biosynthetic pathway. LC-MS analysis revealed no consumption of fumitremorgin B but good conversion with its biosynthetic precursor tryprostatin B in the presence of FeII and 2-oxoglutarate. Structure elucidation confirmed 22-hydroxylisotryprostatin B and 14α, 22-dihydroxylisotryprostatin B as the major enzyme products. Further detailed biochemical characterization led to the identification of a novel enzyme, which catalyzes a double bond migration within the dimethylallyl moiety of tryprostatin B with concomitant hydroxylation. Incubation with 18O2-enriched atmosphere confirmed O2 as the major origin of the hydroxyl groups. Solvent exchange was also observed for that at C22. LC-MS analysis confirmed the presence of 22-hydroxylisotryprostatin B in a Neosartorya fischeri extract, highlighting the role of this enzyme in the metabolism of intermediates of the fumitremorgin/verruculogen pathway. A plausible reaction mechanism implementing a radical rearrangement prior to accepting a hydroxyl radical from FeIII is discussed.


Assuntos
Alcaloides Indólicos/química , Oxigenases/química , Piperazinas/química , Catálise , Cromatografia Líquida , Hidroxilação , Ferro/química , Isomerismo , Ácidos Cetoglutáricos/química , Espectrometria de Massas , Modelos Químicos , Neosartorya/enzimologia , Isótopos de Oxigênio/química
17.
Org Lett ; 20(16): 4921-4925, 2018 08 17.
Artigo em Inglês | MEDLINE | ID: mdl-30074809

RESUMO

A cyclo-l-Trp-l-Trp tailoring P450 with novel function from Streptomyces purpureus was identified by heterologous expression in S. coelicolor and in vitro assays the recombinant protein. Structural elucidation revealed that this enzyme catalyzes the transfer of a guanine moiety to the indole ring of the cyclodipeptide via a C-N bond. Adduct products of CDP and guanine are unprecedented in nature, and CDP modification by coupling with guanine has not been reported prior to this study.


Assuntos
Proteínas de Bactérias/metabolismo , Sistema Enzimático do Citocromo P-450/metabolismo , Dipeptídeos/química , Guanina/química , Peptídeos Cíclicos/química , Streptomyces/metabolismo , Proteínas de Bactérias/genética , Sistema Enzimático do Citocromo P-450/genética , Indóis/química , Indóis/metabolismo , Oxirredução , Conformação Proteica , Proteínas Recombinantes/química , Proteínas Recombinantes/genética , Proteínas Recombinantes/metabolismo , Streptomyces/enzimologia , Streptomyces/genética
18.
Angew Chem Int Ed Engl ; 57(35): 11193-11197, 2018 08 27.
Artigo em Inglês | MEDLINE | ID: mdl-29714818

RESUMO

ß-Substituted chiral γ-aminobutyric acids feature important biological activities and are valuable intermediates for the synthesis of pharmaceuticals. Herein, an efficient catalytic enantioselective approach for the synthesis of ß-substituted γ-aminobutyric acid derivatives through visible-light-induced photocatalyst-free asymmetric radical conjugate additions is reported. Various ß-substituted γ-aminobutyric acid analogues, including previously inaccessible derivatives containing fluorinated quaternary stereocenters, were obtained in good yields (42-89 %) and with excellent enantioselectivity (90-97 % ee). Synthetically valuable applications were demonstrated by providing straightforward synthetic access to the pharmaceuticals or related bioactive compounds (S)-pregabalin, (R)-baclofen, (R)-rolipram, and (S)-nebracetam.


Assuntos
Ácido gama-Aminobutírico/análogos & derivados , Ácido gama-Aminobutírico/síntese química , Aminobutiratos/síntese química , Aminobutiratos/química , Catálise , Halogenação , Luz , Oxirredução , Processos Fotoquímicos , Estereoisomerismo , Ácido gama-Aminobutírico/química
19.
Angew Chem Int Ed Engl ; 57(21): 6242-6246, 2018 05 22.
Artigo em Inglês | MEDLINE | ID: mdl-29624849

RESUMO

A novel method for the catalytic asymmetric dearomatization by visible-light-activated [2+2] photocycloaddition with benzofurans and one example of a benzothiophene is reported, thereby providing chiral tricyclic structures with up to four stereocenters including quaternary stereocenters. The benzofurans and the benzothiophene are functionalized at the 2-position with a chelating N-acylpyrazole moiety which permits the coordination of a visible-light-activatable chiral-at-rhodium Lewis acid catalyst. Computational molecular modeling revealed the origin of the unusual regioselectivity and identified the heteroatom in the heterocycle to be key for the regiocontrol.

20.
Chem Commun (Camb) ; 54(12): 1421-1424, 2018 Feb 06.
Artigo em Inglês | MEDLINE | ID: mdl-29303170

RESUMO

The novel binary P4 analogue (Ge2P2)2- proved to be a suitable precursor for heteroatomic cluster synthesis. Over time in solution, it rearranges to form (Ge7P2)2-, as shown by NMR studies and X-ray diffraction. Reactions of (Ge2P2)2- with CdPh2 afford [K(crypt-222)]3[Cd3(Ge3P)3], containing an unprecedented ternary cluster anion with a triangular Cd3 moiety.

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