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https://www.readbyqxmd.com/read/27913292/structural-basis-for-catalysis-at-the-membrane-water-interface
#1
REVIEW
Meagan Belcher Dufrisne, Vasileios I Petrou, Oliver B Clarke, Filippo Mancia
The membrane-water interface forms a uniquely heterogeneous and geometrically constrained environment for enzymatic catalysis. Integral membrane enzymes sample three environments - the uniformly hydrophobic interior of the membrane, the aqueous extramembrane region, and the fuzzy, amphipathic interfacial region formed by the tightly packed headgroups of the components of the lipid bilayer. Depending on the nature of the substrates and the location of the site of chemical modification, catalysis may occur in each of these environments...
November 29, 2016: Biochimica et Biophysica Acta
https://www.readbyqxmd.com/read/27911722/dawn-of-the-in-vivo-rna-structurome-and-interactome
#2
REVIEW
Chun Kit Kwok
RNA is one of the most fascinating biomolecules in living systems given its structural versatility to fold into elaborate architectures for important biological functions such as gene regulation, catalysis, and information storage. Knowledge of RNA structures and interactions can provide deep insights into their functional roles in vivo For decades, RNA structural studies have been conducted on a transcript-by-transcript basis. The advent of next-generation sequencing (NGS) has enabled the development of transcriptome-wide structural probing methods to profile the global landscape of RNA structures and interactions, also known as the RNA structurome and interactome, which transformed our understanding of the RNA structure-function relationship on a transcriptomic scale...
October 15, 2016: Biochemical Society Transactions
https://www.readbyqxmd.com/read/27911042/orderly-layered-zr-benzylphosphonate-nanohybrids-for-efficient-acid-base-mediated-bifunctional-cascade-catalysis
#3
Hu Li, Zhen Fang, Jian He, Song Yang
The development of functional metal-organic materials being robust and active for bifunctional/cascade catalysis is of great significance. Herein, a series of mesoporous and orderly layered nanohybrids were synthesized for the first time via simple and template-free assembly of ortho-, meta-, or para-xylylenediphosphonates (o-, p-, or m-PhP) with zirconium. It was found that m-PhPZr nanoparticles (20-50 nm) with mesopores centered at 7.9 nm and high Lewis acid/base site ratio (1:0.7) showed prominent performance under mild conditions (as low as 82 ºC) in transfer hydrogenation of carbonyl compounds including bio-aldehydes to alcohols with near quantative yields and little Zr leaching...
December 2, 2016: ChemSusChem
https://www.readbyqxmd.com/read/27910968/designing-hierarchical-hollow-nanostructures-of-cu2mos4-for-improved-hydrogen-evolution-reaction
#4
Ke Zhang, Yongli Zheng, Yunxiang Lin, Changda Wang, Hengjie Liu, Daobin Liu, Chuanqiang Wu, Shuangming Chen, Yanxia Chen, Li Song
Layered Cu2MoS4, consisting of earth-abundant elements, is regarded as a potential catalyst for the hydrogen evolution reaction (HER). Herein, we demonstrate a Cu2O-based template strategy to synthesise hierarchical hollow nanostructures of Cu2MoS4. The characterizations reveal that the electrochemically active surface of the hollow Cu2MoS4 is largely enhanced, in contrast to the nanosheet or nanoparticle structures. As the direct outcome, the designed hierarchical hollow structures display excellent HER activities with a low overvoltage and small Tafel slope...
December 2, 2016: Physical Chemistry Chemical Physics: PCCP
https://www.readbyqxmd.com/read/27910847/efficiency-limits-for-photoelectrochemical-water-splitting
#5
Katherine T Fountaine, Hans Joachim Lewerenz, Harry A Atwater
Theoretical limiting efficiencies have a critical role in determining technological viability and expectations for device prototypes, as evidenced by the photovoltaics community's focus on detailed balance. However, due to their multicomponent nature, photoelectrochemical devices do not have an equivalent analogue to detailed balance, and reported theoretical efficiency limits vary depending on the assumptions made. Here we introduce a unified framework for photoelectrochemical device performance through which all previous limiting efficiencies can be understood and contextualized...
December 2, 2016: Nature Communications
https://www.readbyqxmd.com/read/27910601/combined-scanning-probe-microscopy-and-x-ray-scattering-instrument-for-in-situ-catalysis-investigations
#6
Willem G Onderwaater, Peter C van der Tuijn, Rik V Mom, Matthijs A van Spronsen, Sander B Roobol, Amirmehdi Saedi, Jakub Drnec, Helena Isern, Francesco Carla, Thomas Dufrane, Raymond Koehler, Bert Crama, Irene M N Groot, Roberto Felici, Joost W M Frenken
We have developed a new instrument combining a scanning probe microscope (SPM) and an X-ray scattering platform for ambient-pressure catalysis studies. The two instruments are integrated with a flow reactor and an ultra-high vacuum system that can be mounted easily on the diffractometer at a synchrotron end station. This makes it possible to perform SPM and X-ray scattering experiments in the same instrument under identical conditions that are relevant for catalysis.
November 2016: Review of Scientific Instruments
https://www.readbyqxmd.com/read/27910578/liquid-phase-catalytic-reactor-combined-with-measurement-of-hot-electron-flux-and-chemiluminescence
#7
Ievgen I Nedrygailov, Changhwan Lee, Song Yi Moon, Hyosun Lee, Jeong Young Park
Understanding the role of electronically nonadiabatic interactions during chemical reactions on metal surfaces in liquid media is of great importance for a variety of applications including catalysis, electrochemistry, and environmental science. Here, we report the design of an experimental apparatus for detection of the highly excited (hot) electrons created as a result of nonadiabatic energy transfer during the catalytic decomposition of hydrogen peroxide on thin-film metal-semiconductor nanodiodes. The apparatus enables the measurement of hot electron flows and related phenomena (e...
November 2016: Review of Scientific Instruments
https://www.readbyqxmd.com/read/27910186/diverse-activation-modes-in-the-hydroboration-of-aldehydes-and-ketones-with-germanium-tin-and-lead-lewis-pairs
#8
Julia Schneider, Christian P Sindlinger, Sarah M Freitag, Hartmut Schubert, Lars Wesemann
Intramolecular germylene, stannylene, and plumbylene Lewis pairs were reacted with hexanal and yielded the cyclic addition products only with the germanium and tin reagents. In further reactivity studies, the hydroboration of aldehydes and ketones catalyzed by intramolecular germylene, stannylene, and plumbylene Lewis pairs was studied. In the case of the cyclic germylene Lewis pair, the product of the oxidative addition of pinacolborane at the germylene moiety was observed. According to stoichiometric as well as catalytic experiments, the intramolecular germylene Lewis pair acts as a catalyst in the hydroboration of aldehydes and ketones...
December 2, 2016: Angewandte Chemie
https://www.readbyqxmd.com/read/27908729/structural-and-biochemical-characterization-of-fabk-from-thermotoga-maritima
#9
Byung Hak Ha, Sang Chul Shin, Jin Ho Moon, Gyochang Keum, Chan-Wha Kim, Eunice EunKyeong Kim
TM0800 from Thermotoga maritima is one of the hypothetical proteins with unknown function. The crystal structure determined at 2.3 Å resolution reveals a two domain structure: the N-terminal domain forming a barrel and the C-terminal forming a lid. One FMN is bound between the two domains with the phosphate making intricate hydrogen bonds with protein and three tightly bound water molecules, and the isoalloxazine ring packed against the side chains of Met22 and Met276. The structure is almost identical to that of FabK (enoyl-acyl carrier protein (ACP) reductase, ENR II), a key enzyme in bacterial type II fatty-acid biosynthesis that catalyzes the final step in each elongation cycle; and the enzymatic activity confirms that TM0800 is an ENR...
November 28, 2016: Biochemical and Biophysical Research Communications
https://www.readbyqxmd.com/read/27906391/large-area-growth-of-vertically-aligned-luminescent-mos2-nanosheets
#10
G Deokar, N S Rajput, P Vancsó, F Ravaux, M Jouiad, D Vignaud, F Cecchet, J-F Colomer
Vertically aligned MoS2 nanosheets (NSs) with exposed edges were successfully synthesized over a large area (∼2 cm(2)). The NSs were grown using an ambient pressure chemical vapor deposition technique via rapid sulfurization of sputter deposited thick molybdenum films. Extensive characterization of the grown MoS2 NSs has been carried out using high resolution scanning and transmission electron microscopy (SEM & TEM). A special care was given to the TEM lamella preparation process by means of a focused ion beam to preserve the NS growth direction...
December 1, 2016: Nanoscale
https://www.readbyqxmd.com/read/27906387/hierarchically-porous-materials-synthesis-strategies-and-structure-design
#11
REVIEW
Xiao-Yu Yang, Li-Hua Chen, Yu Li, Joanna Claire Rooke, Clément Sanchez, Bao-Lian Su
Owing to their immense potential in energy conversion and storage, catalysis, photocatalysis, adsorption, separation and life science applications, significant interest has been devoted to the design and synthesis of hierarchically porous materials. The hierarchy of materials on porosity, structural, morphological, and component levels is key for high performance in all kinds of applications. Synthesis and applications of hierarchically structured porous materials have become a rapidly evolving field of current interest...
December 1, 2016: Chemical Society Reviews
https://www.readbyqxmd.com/read/27905606/a-qm-mm-study-of-the-reaction-mechanism-of-human-%C3%AE-ketoacyl-reductase
#12
Fabiola E Medina, Rui P P Neves, Maria J Ramos, Pedro A Fernandes
Human fatty acid synthase (hFAS) is a multifunctional enzyme involved in a wide diversity of biological functions. For instance, it is a precursor of phospholipids and other complex processes such as the de novo synthesis of long chain fatty acid. Human FAS is also a component of biological membranes and it is implicated in the overexpression of several types of cancers. In this work, we describe the catalytic mechanism of β-ketoreductase (KR), which is a catalytic domain of the hFAS enzyme that catalyzes the reduction of β-ketoacyl to β-hydroxyacyl with the concomitant oxidation of the NADPH cofactor...
December 1, 2016: Physical Chemistry Chemical Physics: PCCP
https://www.readbyqxmd.com/read/27905505/surface-protonics-promotes-catalysis
#13
R Manabe, S Okada, R Inagaki, K Oshima, S Ogo, Y Sekine
Catalytic steam reforming of methane for hydrogen production proceeds even at 473 K over 1 wt% Pd/CeO2 catalyst in an electric field, thanks to the surface protonics. Kinetic analyses demonstrated the synergetic effect between catalytic reaction and electric field, revealing strengthened water pressure dependence of the reaction rate when applying an electric field, with one-third the apparent activation energy at the lower reaction temperature range. Operando-IR measurements revealed that proton conduction via adsorbed water on the catalyst surface occurred during electric field application...
December 1, 2016: Scientific Reports
https://www.readbyqxmd.com/read/27903763/enzyme-activation-through-the-utilization-of-intrinsic-dianion-binding-energy
#14
REVIEW
T L Amyes, M M Malabanan, X Zhai, A C Reyes, J P Richard
We consider 'the proposition that the intrinsic binding energy that results from the noncovalent interaction of a specific substrate with the active site of the enzyme is considerably larger than is generally believed. An important part of this binding energy may be utilized to provide the driving force for catalysis, so that the observed binding energy represents only what is left over after this utilization' [Jencks,W.P. (1975) Adv. Enzymol. Relat. Areas. Mol. Biol., 43: , 219-410]. The large ~12 kcal/mol intrinsic substrate phosphodianion binding energy for reactions catalyzed by triosephosphate isomerase (TIM), orotidine 5'-monophosphate decarboxylase and glycerol-3-phosphate dehydrogenase is divided into 4-6 kcal/mol binding energy that is expressed on the formation of the Michaelis complex in anchoring substrates to the respective enzyme, and 6-8 kcal/mol binding energy that is specifically expressed at the transition state in activating the respective enzymes for catalysis...
November 29, 2016: Protein Engineering, Design & Selection: PEDS
https://www.readbyqxmd.com/read/27903293/personalized-medicine-approach-confirms-a-milder-case-of-abat-deficiency
#15
A Besse, A K Petersen, J V Hunter, V Appadurai, S R Lalani, P E Bonnen
ABAT deficiency (OMIM 613163) is a rare inborn error of metabolism caused by recessive variants in the gene 4-aminobutyric acid transaminase (ABAT), which is responsible for both the catalysis of GABA and maintenance of nucleoside pools in the mitochondria. To date, only a few patients have been reported worldwide. Their clinical presentation has been remarkably consistent with primary features of severe psychomotor retardation, encephalopathy, hypotonia, and infantile-onset refractory epilepsy. We report a new case of ABAT deficiency that marks an important departure from previous clinical findings...
December 1, 2016: Molecular Brain
https://www.readbyqxmd.com/read/27902861/thioaldehydes-from-aldehyde-hydrogen-sulfide-interaction-under-organocatalysis
#16
Joseph S Francisco, Manoj Kumar
Thioaldehydes are an important class of sulfur compounds involved in atmospheric, synthetic organic and biological chemistry. Traditionally, they are believed to be formed by the nucleophilic attack of bisulfide anion on the carbonyl compounds. Herein we suggest a novel mechanism that does not require the formation of bisulfide anion, but rather involves an interaction between hydrogen sulfide and an aldehyde. Though the uncatalyzed or the water-catalyzed reactions involve high barriers, the formic acid-catalyzed reactions involve moderate barriers that should be accessible in planetary atmospheres...
November 30, 2016: Chemistry: a European Journal
https://www.readbyqxmd.com/read/27901528/au-i-ag-i-co-operative-catalysis-interception-of-ag-bound-carbocations-with-%C3%AE-gold-i-enals-in-the-imino-alkyne-cyclizations-with-n-allenamides
#17
Pradip N Bagle, Manoj V Mane, K Vanka, Dinesh R Shinde, Samir R Shaikh, Rajesh G Gonnade, Nitin T Patil
A co-operative Au(i)/Ag(i) catalyst system has been developed to utilize N-allenamides as nucleophilic enal equivalents for the interceptive capturing of incipient carbocations generated through π-acid-triggered imino-alkyne cyclization. The salient features include the in situ generation of silver-bound carbocations (from iminoalkynes), α-gold(i) enals (from N-allenamides) and union of these two species to form indolizines with the regeneration of Au and Ag catalysts.
November 30, 2016: Chemical Communications: Chem Comm
https://www.readbyqxmd.com/read/27901152/an-atomic-level-insight-into-the-basic-mechanism-responsible-for-the-enhancement-of-the-catalytic-oxidation-of-carbon-monoxide-on-a-cu-ceo2-surface
#18
Kenichi Koizumi, Katsuyuki Nobusada, Mauro Boero
The reaction mechanisms of CO molecules interacting with a Cu/CeO2 surface and related morphological modifications occurring upon removal of O atoms to generate CO2 are investigated by first-principles dynamical simulations complemented by a free-energy sampling technique. We show that the reactivity of oxygen atoms located in the first layer in the vicinity of the Cu site is remarkably high because of a reduction of the O coordination number. Moreover, we evidence that the doped Cu atoms are responsible for an enhancement of the exposure of other surrounding O atoms, even below the first surface layer, which can then easily react with CO and are gradually removed from the system in the oxidation process...
November 30, 2016: Physical Chemistry Chemical Physics: PCCP
https://www.readbyqxmd.com/read/27901129/platinum-single-atom-and-cluster-catalysis-of-the-hydrogen-evolution-reaction
#19
Niancai Cheng, Samantha Stambula, Da Wang, Mohammad Norouzi Banis, Jian Liu, Adam Riese, Biwei Xiao, Ruying Li, Tsun-Kong Sham, Li-Min Liu, Gianluigi A Botton, Xueliang Sun
Platinum-based catalysts have been considered the most effective electrocatalysts for the hydrogen evolution reaction in water splitting. However, platinum utilization in these electrocatalysts is extremely low, as the active sites are only located on the surface of the catalyst particles. Downsizing catalyst nanoparticles to single atoms is highly desirable to maximize their efficiency by utilizing nearly all platinum atoms. Here we report on a practical synthesis method to produce isolated single platinum atoms and clusters using the atomic layer deposition technique...
November 30, 2016: Nature Communications
https://www.readbyqxmd.com/read/27900807/highly-ortho-selective-chlorination-of-anilines-using-a-secondary-ammonium-salt-organocatalyst
#20
Xiaodong Xiong, Ying-Yeung Yeung
An organocatalytic, highly facile, efficient, and regioselective ortho-chlorination of anilines is described. A secondary ammonium chloride salt has been employed as the catalyst and the reaction can be conducted at room temperature without protection from air and moisture. In addition, the reaction is readily scalable and the catalyst can be recycled and reused. This catalytic protocol has been applied to the efficient synthesis of a highly potent c-Met kinase inhibitor. Mechanistic studies revealed that unique structural features of the secondary ammonium chloride salt are important for both the catalysis and regioselectivity of the electrophilic ortho-chlorination...
November 30, 2016: Angewandte Chemie
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