Efficient and exceptionally selective semireduction of alkynes using a supported gold catalyst under a CO atmosphere.

A new efficient method for chemo- and regio-selective semireduction of alkynes using CO/H2O as the hydrogen source catalyzed by gold supported on high surface area TiO2 was developed. A facile and practical synthesis of 1,2-dideuterioalkenes was also realized by using CO/D2O as the reducing agent.

Propylene from renewable resources: catalytic conversion of glycerol into propylene.

Propylene, one of the most demanded commodity chemicals, is obtained overwhelmingly from fossil resources. In view of the diminishing fossil resources and the ongoing climate change, the identification of new efficient and alternative routes for the large-scale production of propylene from biorenewable resources has become essential. Herein, a new selective route for the synthesis of propylene from bio-derived glycerol is demonstrated.

Solvent feedstock effect: the insights into the deactivation mechanism of Cu/SiO2 catalysts for hydrogenation of dimethyl oxalate to ethylene glycol.

The variation of the supports on the Cu/SiO2 catalyst plays an important role in the catalytic performance for hydrogenation of dimethyl oxalate. The loss of silica in the form of tetramethoxysilane from the support under the reaction conditions is responsible for the deactivation of the Cu/SiO2 catalyst.

Extended Energy Divide-and-Conquer Method Based on Charge Conservation.

The divide-and-conquer (DC) scheme, the most popular linear-scaling method, is very important in the quantum mechanics computation of large systems. However, when a chemical system is divided into subsystems, its covalent bonds are often broken and then capped by complementary atoms/groups. In this paper, we show that the charge transfer between subsystems and the complementary atoms/groups causes the nonconservation of the total charge of the whole system, and this is the main source of error for the computed total energy.

C-C cross-coupling of primary and secondary benzylic alcohols using supported gold-based bimetallic catalysts.

Clean alcohol-alcohol cross-coupling: A clean and efficient one-pot direct C-C cross-coupling of equimolar amounts of primary and secondary alcohols by a facile hydrogen autotransfer pathway is achieved over a robust and easily recovered hydrotalcite-supported Au-Pd bimetallic catalyst system. A variety of primary and secondary alcohols have been selectively converted into the corresponding β-alkylated ketones in good yields.

A versatile aqueous reduction of bio-based carboxylic acids using syngas as a hydrogen source.

Syngas as a versatile hydrogen source: Using readily available and economically favorable syngas as a convenient hydrogen source, an efficient and sustainable aqueous reduction of bio-based carboxylic acids has been achieved over a highly robust catalyst system consisting of gold nanoparticles supported on acid-tolerant single-phase monoclinic zirconia (Au/m-ZrO(2)). A range of bio-based multifunctional carboxylic acids have been selectively converted into their corresponding lactones or diols in high to excellent yields.

An unusual chemoselective hydrogenation of quinoline compounds using supported gold catalysts.

The pursuit of modern sustainable chemistry has stimulated the development of innovative catalytic processes that enable chemical transformations to be performed under mild and clean conditions with high efficiency. Herein, we report that gold nanoparticles supported on TiO(2) catalyze the chemoselective hydrogenation of functionalized quinolines with H(2) under mild reaction conditions. Our results point toward an unexpected role for quinolines in gold-mediated hydrogenation reactions, namely that of promoter; this is in stark contrast to what prevails in the traditional noble metal Pd-, Pt-, and Ru-based catalyst systems, in which quinolines and their derivatives typically act as poisons.

Efficient subnanometric gold-catalyzed hydrogen generation via formic acid decomposition under ambient conditions.

Formic acid (FA) has tremendous potential as a safe and convenient source of hydrogen for sustainable chemical synthesis and renewable energy storage, but controlled and efficient dehydrogenation of FA by a robust solid catalyst under ambient conditions constitutes a major challenge. Here, we report that a previously unappreciated combination of subnanometric gold and an acid-tolerant oxide support facilitates the liberation of CO-free H(2) from FA. Applying an ultradispersed gold catalyst comprising TEM-invisible gold subnanoclusters deposited on zirconia to a FA-amine mixture affords turnover frequencies (TOFs) up to 1590 per hour and a turnover number of more than 118,400 at 50 °C.

Matrix isolation spectroscopic and theoretical study of carbon dioxide activation by titanium oxide molecules.

The reactions of titanium monoxide and dioxide molecules with carbon dioxide were investigated by matrix isolation infrared spectroscopy. It was found that the titanium monoxide molecule is able to activate carbon dioxide to form the titanium dioxide-carbon monoxide complex upon visible light excitation via a weakly bound TiO(η(1)-OCO) intermediate in solid neon. In contrast, the titanium dioxide molecule reacted with carbon dioxide to form the titanium monoxide-carbonate complex spontaneously on annealing.

Highly efficient heterogeneous gold-catalyzed direct synthesis of tertiary and secondary amines from alcohols and urea.

Urea, the white gold: The efficient synthesis of tertiary and secondary amines is achieved by heterogeneous gold-catalyzed direct amination of stoichiometric alcohols with urea in good to excellent yields. Via a hydrogen autotransfer pathway, the reactions of primary alcohols with urea give tertiary amines exclusively, while secondary alcohols selectively afford secondary amines.

Interdomain flexibility and pH-induced conformational changes of AcrA revealed by molecular dynamics simulations.

The membrane fusion protein (MFP) AcrA is proposed to link the inner membrane transporter AcrB and outer membrane protein TolC, forming the tripartite AcrAB-TolC efflux pump, and was shown to be functionally indispensible. Structural and EPR studies showed that AcrA has high conformational flexibility and exhibited pH-induced conformational change. In this study, we built the complete structure of AcrA through homology modeling and performed atomistic simulations of AcrA at different pH values.

The conformational transition pathways of ATP-binding cassette transporter BtuCD revealed by targeted molecular dynamics simulation.

BtuCD is a member of the ATP-binding cassette transporters in Escherichia coli that imports vitamin B(12) into the cell by utilizing the energy of ATP hydrolysis. Crystal structures of BtuCD and its homologous protein HI1470/1 in various conformational states support the "alternating access" mechanism which proposes the conformational transitions of the substrate translocation pathway at transmembrane domain (TMD) between the outward-facing and inward-facing states. The conformational transition at TMD is assumed to couple with the movement of the cytoplasmic nucleotide-binding domains (NBDs) driven by ATP hydrolysis/binding.

Highly stable and efficient Ag/AgCl@TiO2 photocatalyst: preparation, characterization, and application in the treatment of aqueous hazardous pollutants.

A new plasmonic photocatalyst of Ag-AgCl@TiO(2) was prepared by deposition-precipitation and photoreduction. This photocatalyst exhibited efficient photocatalytic activity for the degradation of 4-chlorophenol and photoreduction of Cr(VI) ion under visible light irradiation. Its high photocatalytic activity can be attributed to the surface plasmon resonance effect of Ag nanoparticles, which were highly dispersed on the surface of Ag-AgCl@TiO(2).

Conversion of biomass-derived levulinate and formate esters into γ-valerolactone over supported gold catalysts.

The utilization of biomass has recently attracted tremendous attention as a potential alternative to petroleum for the production of liquid fuels and chemicals. We report an efficient alcohol-mediated reactive extraction strategy by which a hydrophobic mixture of butyl levulinate and formate esters, derived from cellulosic biomass, can be converted to valuable γ-valerolactone (GVL) by a simple supported gold catalyst system without need of an external hydrogen source. The essential role of the supported gold is to facilitate the rapid and selective decomposition of butyl formate to produce a hydrogen stream, which enables the highly effective reduction of butyl levulinate into GVL.

Carbon dioxide coordination and activation by niobium oxide molecules.

Carbon dioxide coordination and activation by niobium oxide molecules were studied by matrix isolation infrared spectroscopy. It was found that the niobium monoxide molecule reacted with carbon dioxide to form the niobium dioxide carbonyl complex NbO(2)(η(1)-CO) spontaneously on annealing in solid neon. The observation of the spontaneous reaction is consistent with theoretical predictions that this carbon dioxide activation process is both thermodynamically exothermic and kinetically facile.

Elastic network model-based normal mode analysis reveals the conformational couplings in the tripartite AcrAB-TolC multidrug efflux complex.

The AcrAB-TolC drug efflux system, energized by proton movement down the transmembrane electrochemical gradient, is responsible for the resistance of the organism to a wide range of drugs. Experimental data suggest functional roles of each part of the assembly, but the detailed working mechanism of this machinery remains elusive. We used elastic network-based normal mode analysis (NMA) to explore the conformational dynamics of the AcrAB-TolC complex.

A hybrid sol–gel synthesis of mesostructured SiC with tunable porosity and its application as a support for propane oxidative dehydrogenation.

Porous silicon carbide (SiC) is of great potential as catalyst support in several industrially important reactions because of its unique thermophysical characteristics. Previously porous SiC was mostly obtained by a simple sol–gel or reactive replica technique which can only produce a material with low or medium surface area (< 50 m2 g(−1)). Here we report a new hybrid sol–gel approach to synthesize mesostructured SiC with high surface area (151–345 m2 g(−1)) and tunable porosity.

Detailed regulatory mechanism of the interaction between ZO-1 PDZ2 and connexin43 revealed by MD simulations.

The gap junction protein connexin43 (Cx43) binds to the second PDZ domain of Zonula occludens-1 (ZO-1) through its C-terminal tail, mediating the regulation of gap junction plaque size and dynamics. Biochemical study demonstrated that the very C-terminal 12 residues of Cx43 are necessary and sufficient for ZO-1 PDZ2 binding and phosphorylation at residues Ser (-9) and Ser (-10) of the peptide can disrupt the association. However, only a crystal structure of ZO-1 PDZ2 in complex with a shorter 9 aa peptide of connexin43 was solved experimentally.

CO oxidation catalyzed by a single gold atom: benchmark calculations and the performance of DFT methods.

Quantum chemical calculations were carried out on CO oxidation catalyzed by a single gold atom. To investigate the performance of density functional theory (DFT) methods, 42 DFT functionals have been evaluated and compared with high-level wavefunction based methods. It was found that in order to obtain accurate results the functionals used must treat long range interaction well.

Titanium oxide complexes with dinitrogen. Formation and characterization of the side-on and end-on bonded titanium oxide-dinitrogen complexes in solid neon.

The reactions of titanium oxide molecules with dinitrogen have been studied by matrix isolation infrared spectroscopy. The titanium monoxide molecule reacts with dinitrogen to form the TiO(N(2))(x) (x = 1-4) complexes spontaneously on annealing in solid neon. The TiO(η(1)-NN) complex is end-on bonded and was predicted to have a (3)A'' ground state arising from the (3)Δ ground state of TiO.

Highly chemoselective hydrogenation of crotonaldehyde over Ag-In/SBA-15 fabricated by a modified "two solvents" strategy.

In the challenging crotonaldehyde hydrogenation to crotyl alcohol, an Ag-In/SBA-15 catalyst fabricated by a modified "two solvents" strategy shows an unprecedentedly high yield of 86% at a selectivity of 87%, which exceeds the best results on Pt-, Au- and other Ag-based heterogeneous catalysts reported so far.