A Novel Natural Siderophore Antibiotic Conjugate Reveals a Chemical Approach to Macromolecule Coupling.

Inspired by natural sideromycins, the conjugation of antibiotics to siderophores is an attractive strategy to facilitate "Trojan horse" delivery of antibiotics into bacteria. Genome analysis of a soil bacterium, found a "hybrid" biosynthetic gene cluster responsible for the production of both an antibiotic, pyridomycin, and a novel chlorocatechol-containing siderophore named chlorodactyloferrin. While both of these natural products were synthesized independently, analysis of the culture supernatant also identified a conjugate of both molecules.

Pt -N-Heterocyclic Carbene Complexes in Solvent-Free Alkene Hydrosilylation.

Herein, we report the catalytic activity of a series of platinum(II) pre-catalysts, bearing N-heterocyclic carbene (NHC) ligands, in the alkene hydrosilylation reaction. Their structural and electronic properties are fully investigated using X-ray diffraction analysis and nuclear magnetic resonance spectroscopy (NMR). Next, our study presents a structure-activity relationship within this group of pre-catalysts and gives mechanistic insights into the catalyst activation step.

Dactylosporolides: Glycosylated Macrolides from .

A series of novel macrolides were discovered from the culture supernatant of the rare soil actinobacteria and named dactylosporolides A-C. The structure and absolute configuration of these dactylosporolides were defined using a combination of NMR structural elucidation and analysis of the dactylosporolide biosynthetic gene cluster. Together these data revealed dactylosporolides to be composed of a central 22-membered macrolactone with an internal hemiketal ring and a protruding ketide tail that were (poly)glycosylated at two distal parts.

Structural Variety of Niobium(V) Polyoxo Clusters Obtained from the Reaction with Aromatic Monocarboxylic Acids: Isolation of {Nb O}, {Nb O } and {Nb O } Cores.

The reactivity of aryl monocarboxylic acids (benzoic, 1- or 2-naphtoic, 4'-methylbiphenyl-4-carboxylic, and anthracene-9-carboxylic acids) as complexing agents for the ethoxide niobium(V) (Nb(OEt) precursor has been investigated. A total of eight coordination complexes were isolated with distinct niobium(V) nuclearities as well as carboxylate complexation states. The use of benzoic acid gives a tetranuclear core Nb (μ -O) (L) (OEt) ] (L=benzoate (1)) with four Nb-(μ -O)-Nb linkages in a square plane configuration.

Glycopeptidolipid glycosylation controls surface properties and pathogenicity in Mycobacterium abscessus.

Mycobacterium abscessus is an emerging and difficult-to-manage mycobacterial species that exhibits smooth (S) or rough (R) morphotypes. Disruption of glycopeptidolipid (GPL) production results in transition from S to R and severe lung disease. A structure-activity relationship study was undertaken to decipher the role of GPL glycosylation in morphotype transition and pathogenesis.

H, C and N chemical shift backbone resonance NMR assignment of tobacco calmodulin 2.

Calcium is a ubiquitous second messenger regulating numbers of cellular processes in living organisms. It encodes and transmits information perceived by cells to downstream sensors, including calmodulin (CaM), that initiate cellular responses. In plants, CaM has been involved in the regulation of plant responses to biotic and abiotic environmental cues.

Phosphorylation and -GlcNAcylation of the PHF-1 Epitope of Tau Protein Induce Local Conformational Changes of the C-Terminus and Modulate Tau Self-Assembly Into Fibrillar Aggregates.

Phosphorylation of the neuronal microtubule-associated Tau protein plays a critical role in the aggregation process leading to the formation of insoluble intraneuronal fibrils within Alzheimer's disease (AD) brains. In recent years, other posttranslational modifications (PTMs) have been highlighted in the regulation of Tau (dys)functions. Among these PTMs, the -β-linked N-acetylglucosaminylation (-GlcNAcylation) modulates Tau phosphorylation and aggregation.

Isonitrile ruthenium and iron PNP complexes: synthesis, characterization and catalytic assessment for base-free dehydrogenative coupling of alcohols.

Neutral and ionic ruthenium and iron aliphatic PNHP-type pincer complexes (PNHP = NH(CH2CH2PiPr2)2) bearing benzyl, n-butyl or tert-butyl isocyanide ancillary ligands have been prepared and characterized. Reaction of [RuCl2(PNHP)]2 with one equivalent CN-R per ruthenium center affords complexes [RuCl2(PNHP)(CNR)] (R = benzyl, 1a, R = n-butyl, 1b, R = t-butyl, 1c), with cationic [RuCl(PNHP)(CNR)2]Cl 2a-c as side-products. Dichloride species 1a-c react with excess NaBH4 to afford [RuH(PNHP)(BH4)(CN-R)] 3a-c, analogues to benchmark Takasago catalyst [RuH(PNHP)(BH4)(CO)].

Rubrolone production by Dactylosporangium vinaceum: biosynthesis, modulation and possible biological function.

Rare actinomycetes are likely treasure troves for bioactive natural products, and it is therefore important that we enrich our understanding of biosynthetic potential of these relatively understudied bacteria. Dactylosporangium are a genus of such rare Actinobacteria that are known to produce a number of important antibacterial compounds, but for which there are still no fully assembled reference genomes, and where the extent of encoded biosynthetic capacity is not defined. Dactylosporangium vinaceum (NRRL B-16297) is known to readily produce a deep wine red-coloured diffusible pigment of unknown origin, and it was decided to define the chemical identity of this natural product pigment, and in parallel use whole genome sequencing and transcriptional analysis to lay a foundation for understanding the biosynthetic capacity of these bacteria.

Heteroleptic Ruthenium(II) Complexes with Bathophenanthroline and Bathophenanthroline Disulfonate Disodium Salt as Fluorescent Dyes for In-Gel Protein Staining.

The in-gel detection of proteins for various proteomic experiments is commonly done with the fluorescent Ru tris(bathophenanthroline disulfonate) complex (Ru(BPS)), which is more cost-effective compared to commercial Ru-based formulations but requires tedious procedures for its preparation and strongly acidic staining conditions. Herein, we report the synthesis and characterization of heteroleptic Ru complexes Ru(BPS)(BP) and Ru(BPS)(BP) containing bathophenanthroline (BP) and bathophenanthroline disulfonate disodium salt (BPS) in comparison with Ru(BPS). It was shown by fluorescent and UV-vis measurements that novel Ru complexes were excitable in both UV and visible light, close to emission bands of classical lasers, which is important for successful in-gel protein detection.

Direct conversion of uranium dioxide UO to uranium tetrafluoride UF using the fluorinated ionic liquid [Bmim][PF].

The industrial fluorination of UO2 to UF4 is based on a complex process involving the manipulation of a large amount of HF, a very toxic and corrosive gas. We present here a safer way to accomplish this reaction utilizing ionic liquid [Bmim][PF6] as a unique reaction medium and fluoride source.

Gold(i) catalysed regio- and stereoselective intermolecular hydroamination of internal alkynes: towards functionalised azoles.

Gold(i) catalysed regio- and stereoselective intermolecular hydroamination of internal alkynes was developed for the effective synthesis of a series of (Z)-functionalised vinylazoles under solvent free conditions. The catalytic hydrogenation of the resulting enamines leads to substituted saturated azoles in good yields.

Polymerization of rac-Lactide Using Achiral Iron Complexes: Access to Thermally Stable Stereocomplexes.

Enantiopure poly(lactic acid) (PLA) can form stereocomplexes when enantiomeric PLA chains are mixed in equivalent amounts. Such materials provide interesting features that might be suitable for numerous applications. Despite several advantages, the main drawback of PLA is its narrow window of processing, thus limiting its use for industrial applications.

Uranyl Cation Incorporation in the [PWO] Macrocycle Phosphopolytungstate.

Association of uranyl nitrate with the macrocycle [PWO] in formate buffered aqueous solution leads to the formation of a new compound (KLiNa)[(UO)(HCOO)(PWO)Cl]·89HO (1). Its characterization by XRD reveals a high disorder of the uranyl cations and the formation of monodimensional chains of anionic [(UO)(HCOO)(PWO)Cl] entities linked through formate ligands. The uranyl species are located either in the coordinating sites of the macrocycle [PWO] or at its surface.

Formation of β-Lactoglobulin Aggregates from Quite, Unfolded Conformations upon Heat Activation.

In presence of calcium ions, β-lactoglobulin (BLG) unfolds and subsequently aggregates after heating. This process has important pharmaceutical and agroalimentary applications. Nowadays, the molecular mechanism of unfolding and BLG aggregation, and the role of calcium in the mechanism, is poorly understood.

Formation of a new type of uranium(iv) poly-oxo cluster {U} based on a controlled release of water esterification reaction.

A new strategy for the synthesis of large poly-oxo clusters bearing 38 tetravalent uranium atoms {U} has been developed by controlling the water release from the esterification reaction between a carboxylic acid and an alcohol. The molecular entity [UOCl(HO)(ipa)]·(ipa) (ipa = isopropanol) was crystallized from the solvothermal reaction of a mixture of UCl and benzoic acid in isopropanol at temperature ranging from 70 to 130 °C. Its crystal structure reveals the molecular assembly of the UO fluorite-like inner core {U} with oxo groups bridging the uranium centers.

On the use of solid-state Sc NMR for structural investigations of molecular and silica-supported scandium amide catalysts.

Tris- and tetra-coordinated scandium amides were grafted onto silica and probed as catalysts for alkyne dimerization. Sc NMR was carried out, providing information about the metal coordination sphere. The increasing number of coordinated ligands was correlated with decreased catalytic activity.

Gold(I)-Catalysed Asymmetric Hydroamination of Alkenes: A Silver- and Solvent-Dependent Enantiodivergent Reaction.

In the present study, we report the first silver-dependent enantiodivergent gold-catalysed reaction. The asymmetric intramolecular hydroamination of alkenes catalysed by the combination of a single chiral binuclear gold(I) chloride complex and silver perchlorate can afford both enantiomers of the products by a simple solvent change from toluene to methanol. Such an enantiodivergent reaction is strictly independent of the reaction temperature or of the nature of the catalyst anion and displays the same first-order kinetic rate law with respect to substrate concentration in both solvents.

Mechanistic Aspects of the Polymerization of Lactide Using a Highly Efficient Aluminum(III) Catalytic System.

We report here a unique example of an in situ generated aluminum initiator stabilized by a C-symmetric salen ligand which shows a hitherto unknown high activity for the ROP of rac-lactide at room temperature. Using a simple and robust catalyst system, which is prepared from a salen complex and an onium salt, this convenient route employs readily available reagents that afford polylactide in good yields with narrow polydispersity indices, without the need for time-consuming and expensive processes that are typically required for catalyst preparation and purification. In line with the experimental evidence, DFT studies reveal that initiation and propagation proceed via an external alkoxide attack on the coordinated monomer.

NMR Reveals the Interplay among the AMSH SH3 Binding Motif, STAM2, and Lys63-Linked Diubiquitin.

AMSH [associated molecule with a Src homology 3 domain of signal transducing adaptor molecule (STAM)] is one of the deubiquitinating enzymes associated in the regulation of endocytic cargo trafficking. It shows an exquisite selectivity for Lys63-linked polyubiquitin chains that are the main chains involved in cargo sorting. The first step requires the ESCRT-0 complex that comprises the STAM and hepatocyte growth factor-regulated substrate (Hrs) proteins.

Mycobacterium lutetiense sp. nov., Mycobacterium montmartrense sp. nov. and Mycobacterium arcueilense sp. nov., members of a novel group of non-pigmented rapidly growing mycobacteria recovered from a water distribution system.

From our recent survey of non-pigmented rapidly growing mycobacteria in the Parisian water system, three groups of isolates (taxons 1-3) corresponding to possible novel species were selected for taxonomic study. The three taxa each formed creamy white, rough colonies, had an optimal growth temperature of 30 °C, hydrolyzed Tween 80, were catalase-positive at 22 °C and expressed arylsulfatase activity. All three were susceptible to amikacin, ciprofloxacin and tigecycline.

Catalytic Conversion of Alcohols into Carboxylic Acid Salts in Water: Scope, Recycling, and Mechanistic Insights.

The catalytic conversion of alcohols into carboxylic acid salts in water was performed in the presence of ruthenium complexes supported by aliphatic PNP pincer ligands preformed or formed in situ. High activity toward a wide substrate scope was achieved with turnover number values of up to 4000. The air-stable catalytic system can be recycled by using toluene as a catalyst-immobilizing phase; the activity is maintained after five consecutive runs.

Glycosylation of BclA Glycoprotein from Bacillus cereus and Bacillus anthracis Exosporium Is Domain-specific.

The spores of the Bacillus cereus group (B. cereus, Bacillus anthracis, and Bacillus thuringiensis) are surrounded by a paracrystalline flexible yet resistant layer called exosporium that plays a major role in spore adhesion and virulence. The major constituent of its hairlike surface, the trimerized glycoprotein BclA, is attached to the basal layer through an N-terminal domain.

Stabilization of Tetravalent 4f (Ce), 5d (Hf), or 5f (Th, U) Clusters by the [α-SiW9O34](10-) Polyoxometalate.

The reaction of Na10[α-SiW9O34] with tetravalent metallic cations such as 4f ((NH4)2Ce(NO3)6), 5d (HfCl4), or 5f (UCl4 and Th(NO3)4) in a pH 4.7 sodium acetate buffer solution leads to the formation of four sandwich-type polyoxometalates [Ce4(μ(3)-O)2(SiW9O34)2(CH3COO)2](10-) (1), [U4(μ(3)-O)2(SiW9O34)2(CH3COO)2](10-) (2), [Th3(μ(3)-O)(μ(2)-OH)3(SiW9O34)2](13-) (3), and [Hf3(μ(2)-OH)3(SiW9O34)2](11-) (4). All four compounds consist of a polynuclear cluster fragment stabilized by two [α-SiW9O34](10-) polyanions.