Catalysis

We demonstrated an unconventional polymerization route to synthesize hydrophilic fluorescent organic nanoparticles (FONs) for multicolor cellular bioimaging in this contribution. Actually, it benefits from our unexpected discovery of a rapid polymerization reaction between 1, 6-hexanediol dipropiolate and 2, 4, 6-triazide-1, 3, 5-triazine under the catalysis of N, N, N', N", N"-pentamethyldiethylenetriamine (PMDETA). Interestingly, the 2, 4, 6-triazide-1, 3, 5-triazine and PMDETA system can also induce rapid free radical polymerization at room temperature...

The "replacement" of noble metals by earth abundant metals is a desirable aim in catalysis and a possible way of conserving rare elements. The "replacement" is especially attractive if novel selectivity patterns are observed permitting the development of novel coupling reactions. Herein, we report on a novel, robust and reusable iron catalyst, which permits the selective hydrogenation of nitroarenes in the presence of hydrogenation-sensitive functional groups. Based on the selectivity pattern observed, the direct iron catalyzed synthesis of imines and benzimidazoles from nitroarenes and aldehydes becomes feasible...

Nanoparticles comprising three or more different metals are challenging to prepare. General methods that tackle this challenge are highly sought after as multicomponent metal nanoparticles display favorable properties in applications such as catalysis, biomedicine, and imaging. Herein, we report a practical and versatile approach for the synthesis of nanoparticles composed of up to four different metals. This method relies on the thermal decomposition of nanostructured composite materials assembled from platinum nanoparticles, a metal-organic framework (ZIF-8), and a tannic acid coordination polymer...

An iron-catalysed intermolecular vicinal aminoazidation of alkenes, using N-fluorobenzenesulfonimide (NFSI) and trimethylsilyl azide (TMSN3) as the imidating and azidating reagents, respectively, is described, which could potentially provide a valuable route toward diverse vicinal diamine derivatives of great significance in medicinal chemistry and organic synthesis. Such iron-catalysed aminative bisfunctionalization of alkenes with NFSI has not been reported yet. Comparing to previously employed copper or palladium catalysts, the iron catalyst, FeCl2, was demonstrated to be a good alternative for its comparable efficiency and broad alkene scope...

Cell surface Fc receptors activate inflammation and are tightly controlled to prevent autoimmunity. Antibodies also simulate potent immune signalling from inside the cell via the cytosolic antibody receptor TRIM21, but how this is regulated is unknown. Here we show that TRIM21 signalling is constitutively repressed by its B-Box domain and activated by phosphorylation. The B-Box occupies an E2 binding site on the catalytic RING domain by mimicking E2-E3 interactions, inhibiting TRIM21 ubiquitination and preventing immune activation...

Although iron-catalyzed cross-coupling of Grignard reagents with alkyl halides has been well established, the adoption of the reaction for fluoroalkylations has not been reported because traditional catalytic systems often lead to defluorination reactions. Here, we describe our investigation of an iron-catalyzed cross-coupling between arylmagnesium and difluoroalkyl bromides with steric modified N,N,N',N'-tetramethyl-ethane-1,2-diamine (TMEDA) (L4) as a ligand. The use of a bulky diamine ligand (L4), in which a butylene is substituted at one carbon atom of ethylene backbone in TMEDA, enables the iron-catalyzed difluoroalkylation under mild reaction conditions with a wide range of difluoroalkyl bromides including vulnerable bromodifluoromethane, thus providing a general and cost-efficient route for application in medicinal chemistry...

The chemistry of group 14 element(ii) hydride complexes has rapidly expanded since the first stable example of such a compound was reported in 2000. Since that time it has become apparent that these systems display remarkable reactivity patterns, in some cases mimicking those of late transition-metal (TM) hydride compounds. This is especially so for the hydroelementation of unsaturated organic substrates. Recently, this aspect of their reactivity has been extended to the use of group 14 element(ii) hydrides as efficient, "TM-like" catalysts in organic synthesis...

Graphene and fullerene, two types of C allotropes with very different structures and properties, have attracted considerable attention from the scientific community as new forms of carbon for several decades. It will be a great advantage to combine the geometrical features of the two. Herein, we report a series of novel two-dimensional carbon allotropes that possess fullerene-like hollow structures (bubbles) embedded in a graphene sheet. These carbon allotropes are both thermally and dynamically stable. Calculations using hybrid functionals show that these two-dimensional carbon allotropes could be metals or semiconductors depending on the size and the pattern of the bubbles...

In the last decades many efforts have been devoted to design supramolecular organocatalysts able to work in water as the reaction medium. The use of water as solvent provides promising benefits with respect to environmental impact. In this context, macrocyclic compounds played a role of primary importance thanks to their ease of synthesis and their molecular recognition abilities toward the reactants. The aim of this review is to give an overview of the recent advances in the field of supramolecular organocatalysis in water, focusing the attention on calixarene and cyclodextrins derivatives...

The occurrence of Cladosporium in cold ecosystems has been evidenced long before, and most of the knowledge about nutrient utilization of this genus is sporadic. An alpine soil isolate C. neopsychrotolerans SL-16, showing great cold tolerance and significant lignocellulose-degrading capability, was sequenced to form a 35.9 Mb genome that contains 13,456 predicted genes. Functional annotation on predicted genes revealed a wide array of proteins involved in the transport and metabolism of carbohydrate, protein and lipid...

Asn-linked oligosaccharides are extensively modified during transit through the secretory pathway, first by trimming of the nascent glycan chains and subsequently by initiating and extending multiple oligosaccharide branches from the trimannosyl glycan core. Trimming and branching pathway steps are highly ordered and hierarchal based on the precise substrate specificities of the individual biosynthetic enzymes. A key committed step in the synthesis of complex-type glycans is catalyzed by N -acetylglucosaminyltransferase II (MGAT2), an enzyme that generates the second GlcNAcβ1,2- branch from the trimannosyl glycan core using UDP-GlcNAc as the sugar donor...

Metabolic engineering has facilitated the production of pharmaceuticals, fuels, and soft materials but is generally limited to optimizing well-defined metabolic pathways. We hypothesized that the reaction space available to metabolic engineering could be expanded by coupling extracellular electron transfer to the performance of an exogenous redox-active metal catalyst. Here we demonstrate that the electroactive bacterium Shewanella oneidensis can control the activity of a copper catalyst in atom-transfer radical polymerization (ATRP) via extracellular electron transfer...

Although branchpoint recognition is an essential component of intron excision during the RNA splicing process, the branchpoint itself is frequently assumed to be a basal, rather than regulatory, sequence feature. However, this assumption has not been systematically tested due to the technical difficulty of identifying branchpoints and quantifying their usage. Here, we analyzed ∼1.31 trillion reads from 17,164 RNA sequencing data sets to demonstrate that almost all human introns contain multiple branchpoints...

Porphyrin-based metal-organic networks on surfaces are a new class of planar materials with promising features for applications in chemical sensing, catalysis and organic optoelectronics at nanoscale. Herein we studied systematically a series of the SURMOFs assembled from variously meso-carboxyphenyl/pyridyl substituted porphyrins and zinc acetate on template monolayers of graphene oxide via layer-by-layer deposition. This microscopically flat template can initiate the growth of macroscopically uniform SURMOF films exhibiting well-resolved X-ray diffraction...

Biomass combustion under the oxy-fuel conditions (Oxy-biomass combustion) is one of the approaches achieving negative CO2 emissions. KCl, K2 CO3 and K2 SO4 , as the major potassium species in biomass ash, can catalytically affect biomass combustion. In this paper, the catalysis of the representative potassium salts on oxy-biomass combustion was studied using a thermogravimetric analyzer (TGA). Effects of potassium salt types (KCl, K2 CO3 and K2 SO4 ), loading concentrations (0, 1, 3, 5, 8 wt%), replacing N2 by CO2 , and O2 concentrations (5, 20, 30 vol%) on the catalysis degree were discussed...

The ten-eleven translocation (TET) protein family, consisting of three isoforms (TET1/2/3), have been found in mammalian cells and have a crucial role in 5-methycytosine demethylation in genomic DNA through the catalysis of oxidation reactions assisted by 2-oxoglutarate (2OG). DNA methylation/demethylation contributes to the regulation of gene expression at the transcriptional level, and recent studies have revealed that TET1 is highly elevated in malignant cells of various diseases and related to malignant alteration...

Hypervalent iodine(V) reagents, such as Dess-Martin periodinane (DMP) and 2-iodoxybenzoic acid (IBX), are broadly useful oxidants in chemical synthesis. Development of strategies to access these reagents from O₂ would immediately enable use of O₂ as a terminal oxidant in a broad array of substrate oxidation reactions. Recently we disclosed the aerobic synthesis of I(III) reagents by intercepting reactive oxidants generated during aldehyde autoxidation. Here, we couple aerobic oxidation of iodobenzenes with disproportionation of the initially generated I(III) compounds to generate I(V) reagents...

Pd/Norbornene cocatalyzed tandem C-H activation/annulation reactions of free NH-sulfoximines with aryl iodides to produce diverse polyheterocyclic sulfoximines in highly chemoselective models are reported. The reaction tolerated a broad range of functional groups under external oxidant-free conditions. The preliminary mechanistic studies using density functional theory (DFT) calculations highlighted the key role of a PdIV intermediate.

An iridium photoredox catalyst in combination with phenanthroline-supported palladium catalyst catalyzes decarboxylative alkenylation of tertiary and secondary aliphatic carboxylic acids with vinyl arenes to deliver β-alkylated styrenes with Z-selectivity. A broad scope of aliphatic carboxylic acids, including amino acids, exhibit as amenable substrates, and external oxidant is not required. The reaction proceeds by synergistic utilization of both energy-transfer and electron-transfer reactivity of iridium photoredox catalyst merging with palladium-catalyzed hydride elimination and insertion...

Metals have been increasingly used as substrates in devices based on two-dimensional (2D) materials. However, the high reflectivity of bulk metals results in low optical contrast (<3%) and therefore poor visibility of transparent mono- and few-layer 2D materials on these surfaces. Here we demonstrate that by engineering the complex reflectivity of a purpose-designed multilayer heterostructure composed of thin Au films (2 - 8 nm) on SiO<sub>2</sub>/Si substrate, the optical contrast of graphene and graphene oxide (GO) can be significantly enhanced in comparison to bulk Au, up to about 3 and 5 times, respectively...