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Journal of the American Chemical Society

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https://www.readbyqxmd.com/read/28086264/structural-insights-into-the-redox-sensing-mechanism-of-marr-type-regulator-abfr
#1
Guijie Liu, Xing Liu, Hongjiao Xu, Xichun Liu, Hu Zhou, Zhen Huang, Jianhua Gan, Hao Chen, Lefu Lan, Cai-Guang Yang
As a master redox-sensing MarR-family transcriptional regulator, AbfR participates in oxidative stress responses and virulence regulations in Staphylococcus epidermidis. Here, we present structural insights into the DNA-binding mechanism of AbfR in different oxidation states by determining the X-ray crystal structures of a reduced-AbfR/DNA complex, an overoxidized (Cys13-SO2H and Cys13-SO3H) AbfR/DNA, and 2-disulfide cross-linked AbfR dimer. Together with biochemical analyses, our results suggest that the redox regulation of AbfR-sensing displays two novel features: i) the reversible disulfide modification, but not the irreversible overoxidation, significantly abolishes the DNA-binding ability of the AbfR repressor; ii) either 1-disulfide cross-linked or 2-disulfide cross-linked AbfR dimer is biologically significant...
January 13, 2017: Journal of the American Chemical Society
https://www.readbyqxmd.com/read/28085268/effect-of-interlayer-spacing-on-the-activity-of-layered-manganese-oxide-bilayer-catalysts-for-the-oxygen-evolution-reaction
#2
Qing Kang, Loranne Vernisse, Richard C Remsing, Akila C Thenuwara, Samantha L Shumlas, Ian G McKendry, Michael L Klein, Eric Borguet, Michael J Zdilla, Daniel R Strongin
We investigated the dependence of the electrocatalytic activity for the oxygen evolution reaction (OER) on the interlayer distance of five compositionally distinct layered manganese oxide nanostructures. Each individual electrocatalyst was assembled with a different alkali metal intercalated between two nanosheets (NS) of manganese oxide to form a bilayer structure. Manganese oxide NS were synthesized via the exfoliation of a layered material, birnessite. Atomic force microscopy (AFM) was used to determine the heights of the bilayer catalysts...
January 13, 2017: Journal of the American Chemical Society
https://www.readbyqxmd.com/read/28085263/structure-and-dynamics-of-the-huntingtin-exon-1-n-terminus-a%C3%A2-solution-nmr-perspective
#3
Maria Baias, Pieter E S Smith, Koning Shen, Lukasz A Joachimiak, Szymon Żerko, Wiktor Koźmiński, Judith Frydman, Lucio Frydman
Many neurodegenerative diseases are characterized by misfolding and aggregation of an expanded polyglutamine tract (polyQ). Huntington's Disease, caused by expansion of the polyQ tract in exon 1 of the Huntingtin protein (Htt), is associated with aggregation and neuronal toxicity. Despite recent structural progress in understanding the structures of amyloid fibrils, little is known about the solution states of Htt in general, and about molecular details of their transition from soluble to aggregation-prone conformations in particular...
January 13, 2017: Journal of the American Chemical Society
https://www.readbyqxmd.com/read/28085260/surface-coordination-chemistry-of-metal-nanomaterials
#4
Pengxin Liu, Ruixuan Qin, Gang Fu, Nanfeng Zheng
Surface coordination chemistry of nanomaterials deals with the chemis-try on how ligands are coordinated on their surface metal atoms and influence their properties at the molecular level. This Perspective demonstrates that there is a strong link between surface coordination chemistry and the shape-controlled synthesis, and many intriguing sur-face properties of metal nanomaterials. While small adsorbates intro-duced in the synthesis can control the shapes of metal nanocrystals by minimizing their surface energy via preferential coordination on specif-ic facets, surface ligands properly coordinated on metal nanoparticles readily promote their catalysis via steric interactions and electronic modifications...
January 13, 2017: Journal of the American Chemical Society
https://www.readbyqxmd.com/read/28085258/new-insight-into-the-synthesis-of-large-pore-ordered-mesoporous-materials
#5
Jing Wei, Zhenkun Sun, Wei Luo, Yuhui Li, Ahmed A Elzatahry, Abdullah M Al-Enizi, Yonghui Deng, Dongyuan Zhao
Ordered mesoporous materials (OMMs) have received increasing interest due to their uniform pore size, high surface area, various compositions and wide applications in energy conversion and storage, biomedicine and environmental remediation, etc. The soft templating synthesis using surfactants or amphiphilic block copolymers is the most efficient method to produce OMMs with tailorable pore structure and surface property. However, due to the limited choice of commercially-available soft templates, the common OMMs usually show small pore size and amorphous (or semi-crystalline) frameworks...
January 13, 2017: Journal of the American Chemical Society
https://www.readbyqxmd.com/read/28084735/real-time-screening-of-biocatalysts-in-live-bacterial-colonies
#6
Cunyu Yan, Fabio Parmeggiani, Emrys A Jones, Emmanuelle Claude, Shaneela A Hussain, Nicholas J Turner, Sabine L Flitsch, Perdita E Barran
Screening of bacterial colonies to identify new biocatalytic activities is a widely adopted tool in biotechnology, but is constrained by the requirements for colorimetric or tag-based detection methods. Herein we report a label-free screening platform using desorption electrospray ionization coupled with ion mobility mass spectrometry imaging (DESI-IM-MS). The screening method is demonstrated for both ammonia lyases and P450 monooxygenases expressed within live bacterial colonies and is shown to enable multiplexing of enzyme variants and substrate libraries simultaneously...
January 13, 2017: Journal of the American Chemical Society
https://www.readbyqxmd.com/read/28084734/macrocyclized-extended-peptides-inhibiting-the-substrate-recognition-domain-of-tankyrase
#7
Wenshu Xu, Yu Heng Lau, Gerhard Fischer, Yaw Sing Tan, Anasuya Chattopadhyay, Marc de la Roche, Marko Hyvonen, Chandra S Verma, David R Spring, Laura S Itzhaki
We report a double-click macrocyclization approach for the constraint of peptide inhibitors in non-helical or extended conformations. Our targets are the tankyrase proteins (TNKS), poly(ADP-ribose) polymerases that regulate Wnt signaling by targeting Axin for degradation. TNKS are deregulated in many different cancer types, and inhibition of TNKS therefore represents an attractive therapeutic strategy. However, the clinical development of TNKS-specific PARP inhibitors is challenging due to off-target effects and cellular toxicity...
January 13, 2017: Journal of the American Chemical Society
https://www.readbyqxmd.com/read/28084731/luminescent-cdse-superstructures-a-nanocluster-superlattice-and-a-nanoporous-crystal
#8
Tetyana I Levchenko, Christian Kübel, Bahareh Khalili Najafabadi, Paul D Boyle, Carolyn Cadogan, Lyudmila V Goncharova, Alexandre Garreau, François Lagugné-Labarthet, Yining Huang, John F Corrigan
Superstructures, combining nanoscopic constituents into micrometer-size assemblies, have a great potential for utilization of the size-dependent quantum-confinement properties in multifunctional electronic and optoelectronic devices. Two diverse superstructures of nanoscopic CdSe were prepared using solvothermal conversion of the same cadmium selenophenolate precursor (Me4N)2[Cd(SePh)4]: the first is a superlattice of monodisperse [Cd54Se32(SePh)48(dmf)4](4-) nanoclusters; the second is a unique porous CdSe crystal...
January 13, 2017: Journal of the American Chemical Society
https://www.readbyqxmd.com/read/28084075/a-two-dimensional-polymer-synthesized-through-topochemical-2-2-cycloaddition-on-the-multigram-scale
#9
Ralph Z Lange, Gregor Hofer, Thomas Weber, A Dieter Schlüter
The single-crystal-to-single-crystal (scsc) synthesis of a 2D polymer based on photochemically triggered [2+2]-cycloaddition is reported. Both monomer and polymer single crystals are analyzed by X-ray diffraction, which is the first case of a scsc two-dimensional polymerization based on this cycloaddition and the third ever case for a scsc synthesis of a 2D polymer. The product crystals at quantitative conversion are wet-exfoliated under mild conditions and afford countless features which are single and double layers as judged by their AFM heights hAFM ≈ 1...
January 13, 2017: Journal of the American Chemical Society
https://www.readbyqxmd.com/read/28071048/solvent-free-strategy-yields-size-and-shape-uniform-capsules
#10
Ana M S Costa, João F Mano
Capsules with a liquefied core were fabricated via the assembly of polymeric droplets induced by superamphiphobic surfaces. These highly repellent substrates exhibit distinct features such as (i) an easy and precise control over the particle size and shape, (ii) a high encapsulation efficiency, (iii) mild processing conditions, and (iv) the possibility to include any object in either a water or oil-based liquid core, which are not found on the current available strategies. As proof of concept, a photo-cross-linkable derivative of chitosan was used to produce the polymeric shell while a wealth variety of template cores were tested using a reversible cross-linking mechanism, interfacial gelation process or ice...
January 13, 2017: Journal of the American Chemical Society
https://www.readbyqxmd.com/read/28013539/time-resolved-ir-spectroscopy-reveals-a-mechanism-with-tio2-as-a-reversible-electron-acceptor-in-a-tio2-re-catalyst-system-for-co2-photoreduction
#11
Mohamed Abdellah, Ahmed M El-Zohry, Liisa J Antila, Christopher D Windle, Erwin Reisner, Leif Hammarström
Attaching the phosphonated molecular catalyst [Re(I)Br(bpy)(CO)3](0) to the wide-bandgap semiconductor TiO2 strongly enhances the rate of visible-light-driven reduction of CO2 to CO in dimethylformamide with triethanolamine (TEOA) as sacrificial electron donor. Herein, we show by transient mid-IR spectroscopy that the mechanism of catalyst photoreduction is initiated by ultrafast electron injection into TiO2, followed by rapid (ps-ns) and sequential two-electron oxidation of TEOA that is coordinated to the Re center...
January 13, 2017: Journal of the American Chemical Society
https://www.readbyqxmd.com/read/28081603/metal-chalcogenide-clusters-with-closed-electronic-shells-and-the-electronic-properties-of-alkalis-and-halogens
#12
Vikas Chauhan, Arthur C Reber, Shiv N Khanna
Clusters with filled electronic shells and a large gap between the Highest Occupied Molecular Orbital (HOMO) and the Lowest Unoccupied Molecular Orbital (LUMO) are generally energetically and chemically stable. Enabling clusters to become electron donors with low ionization potentials or electron acceptors with high electron affinities usually requires changing the valence electron count. Here we demonstrate that a metallic cluster may be transformed from an electron donor to an acceptor by exchanging ligands while the neutral form of the clusters has closed electronic shells...
January 12, 2017: Journal of the American Chemical Society
https://www.readbyqxmd.com/read/28081597/a-new-wide-band-gap-donor-for-efficient-fullerene-free-all-small-molecule-organic-solar-cells
#13
Liyan Yang, Shaoqing Zhang, Chang He, Jianqi Zhang, Huifeng Yao, Yang Yang, Yun Zhang, Wenchao Zhao, Jianhui Hou
A new organic small molecule, DRTB-T, that incorporates a two-dimensional tri-alkylthienyl-substituted benzodithiophene core building block was designed and synthesized. DRTB-T has a band gap (Egopt) of 2.0 eV with a low-lying highest occupied molecular orbital (HOMO) level of -5.51 eV. Non-fullerene small-molecule solar cells consisting of DRTB-T and a non-fullerene acceptor (IC-C6IDT-IC) were constructed, and the morphology of the active layer was fine-tuned by solvent vapor annealing (SVA). The device showed a record 9...
January 12, 2017: Journal of the American Chemical Society
https://www.readbyqxmd.com/read/28080045/crystal-engineering-of-hand-twisted-helical-crystals
#14
Subhankar Saha, Gautam R Desiraju
A strategy is outlined for the design of hand-twisted helical crystals. The starting point in the exercise is the one-directional (1D) plastic crystal, 1,4-dibromobenzene, which is then changed to a 1D elastic crystal, exemplified by 4-bromophenyl 4'-chlorobenzoate, by introduction of a molecular synthon -O-CO- in lieu of the supramolecular synthon Br•••Br in the precursor. The 1D elastic crystals are next modified to two-directional (2D) elastic crystals, of the type 4-bromophenyl 4'-nitrobenzoate where the halogen bonding and C-H•••O hydrogen bonding are well matched...
January 12, 2017: Journal of the American Chemical Society
https://www.readbyqxmd.com/read/28080042/relative-stability-of-empty-exohedral-fullerenes-%C3%AF-delocalization-versus-strain-and-steric-hindrance
#15
Yang Wang, Sergio Díaz-Tendero, Manuel Alcami, Fernando Martin
Predicting and understanding the relative stability of exohedral fullerenes is an important aspect of fullerene chemistry, since the experimentally formed structures do not generally follow the rules that govern addition reactions and/or the making of pristine fullerenes. First-principles theoretical calculations are of limited applicability due to the large number of possible isomeric forms, e.g., more than 50 billion for C60X8. Here we propose a simple model, exclusively based on topological arguments, that allows one to predict the relative stability of exohedral fullerenes without the need for electronic structure calculations or geometry optimizations...
January 12, 2017: Journal of the American Chemical Society
https://www.readbyqxmd.com/read/28080040/insights-into-thiol-aromatic-interactions-a-stereoelectronic-basis-for-s-h-%C3%AF-interactions
#16
Christina R Forbes, Sudipta Kumar Sinha, Himal Kanti Ganguly, Shi Bai, Glenn P A Yap, Sandeep Patel, Neal J Zondlo
Thiols can engage favorably with aromatic rings in S-H/π interactions, within abiological systems and within proteins. However, the underlying bases for S-H/π interactions are not well understood. The crystal structure of Boc-L-4-thiolphenylalanine tert-butyl ester revealed crystal organization centered on the interaction of the thiol S-H with the aromatic ring of an adjacent molecule, with a through-space Hthiol...Caromatic distance of 2.71 Å, below the 2.90 Å sum of the van der Waals radii of H and C...
January 12, 2017: Journal of the American Chemical Society
https://www.readbyqxmd.com/read/28080038/tracking-catalyst-redox-states-and-reaction-dynamics-in-ni-fe-oxyhydroxide-oxygen-evolution-reaction-oer-electrocatalysts-the-role-of-catalyst-support-and-electrolyte-ph
#17
Mikaela Goerlin, Jorge Ferreira de Araújo, Henrike Schmies, Denis Bernsmeier, Soeren Dresp, Manuel Gliech, Zenonas Jusys, Petko Chernev, Ralph Kraehnert, Holger Dau, Peter Strasser
Ni-Fe oxyhydroxides are the most active known electrocatalysts for the oxygen evolution reaction (OER) in alkaline electrolytes and are therefore of great scientific and technological importance in the context of electrochemical energy conversion. Here we uncover, investigate, and discuss previously unaddressed effects of conductive supports and the electrolyte pH on the Ni-Fe oxide catalyst redox behavior and catalytic OER activity, combining operando UV-vis spectro-electrochemistry, operando electrochemical mass spectrometry (DEMS), and in-situ cryo X-ray absorption spectroscopy (XAS)...
January 12, 2017: Journal of the American Chemical Society
https://www.readbyqxmd.com/read/28080036/lithium-hexamethyldisilazide-mediated-enolization-of-acylated-oxazolidinones-solvent-cosolvent-and-isotope-effects-on-competing-monomer-and-dimer-based-pathways
#18
Gabriel J Reyes-Rodríguez, Russell F Algera, David B Collum
Lithium hexamethyldisilazide (LiHMDS)-mediated enolization of (+)-4-benzyl-3-propionyl-2-oxazolidinone in THF-hydrocarbon mixtures shows unusual sensitivity to the choice of hydrocarbon cosolvent (hexane versus toluene) and to isotopic labeling. Four mechanisms corresponding to monosolvated monomers, trisolvated dimers, octasolvated monomers, and octasolvated dimers were identified. Even under conditions in which the LiHMDS monomer was the dominant observable form, dimer-based metalation was significant. The mechanism-dependent isotope and cosolvent effects are discussed in the context of ground-state stabilization and transition-state tunneling...
January 12, 2017: Journal of the American Chemical Society
https://www.readbyqxmd.com/read/28080035/fluorescence-turn-on-sensing-of-dna-duplex-formation-by-a-tricyclic-cytidine-analogue
#19
Dillon D Burns, Kristine L Teppang, Raymond W Lee, Melissa Eleanor Lokensgard, Byron W Purse
Most fluorescent nucleoside analogues are quenched when base stacked and some maintain their brightness, but there has been little progress towards developing nucleoside analogues that markedly increase their fluorescence upon duplex formation. Here, we report on the design and synthesis of a new tricyclic cytidine analogue, 8-diethylamino-tC (8-DEA-tC), that responds to DNA duplex formation with up to a 20-fold increase in fluorescent quantum yield as compared with the free nucleoside, depending on neighboring bases...
January 12, 2017: Journal of the American Chemical Society
https://www.readbyqxmd.com/read/28080033/solvent-templated-folding-of-perylene-bisimide-macrocycles-into-coiled-double-string-ropes-with-solvent-sensitive-optical-signatures
#20
Peter Spenst, Ryan M Young, Brian T Phelan, Michel Keller, Jakub Dostál, Tobias Brixner, Michael R Wasielewski, Frank Würthner
A series of semi-rigid perylene bisimide (PBI) macrocycles with varied ring size containing two to nine PBI chromophores were synthesized in a one-pot reaction and their photophysical properties were characterized by fluorescence, steady-state and transient absorption spectroscopy as well as femtosecond stimulated Raman spectroscopy. These macrocycles show solvent-dependent conformational equilibria and excited-state properties. In dichloromethane the macrocycles prevail in wide-stretched conformations and exhibit upon photoexcitation symmetry-breaking charge separation followed by charge recombination to triplet states, which photosensitize singlet oxygen formation...
January 12, 2017: Journal of the American Chemical Society
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