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Chemical Science

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https://www.readbyqxmd.com/read/30210776/microwave-assisted-cvd-like-synthesis-of-dispersed-monolayer-few-layer-n-doped-graphene-encapsulated-metal-nanocrystals-for-efficient-electrocatalytic-oxygen-evolution
#1
Fanxing Bu, Wenshu Chen, Jiajun Gu, Phillips O Agboola, Najeeb Fuad Al-Khalli, Imran Shakir, Yuxi Xu
Herein a novel and general microwave-assisted chemical vapor deposition (CVD)-like synthetic strategy was developed to realize the ultrafast synthesis of a series of well-dispersed monolayer/few-layer N-doped graphene shell encapsulated metal nanocrystals (M@NC) by using a metal-organic framework (MOF) on graphene as precursors for the first time. Unlike traditional programmed heat treatment, this microwave-assisted method decomposed the MOF into separated metal and carbon- and nitrogen-containing gases rather than aggregated metal and carbon composites during the initial thermal transformation stages...
September 14, 2018: Chemical Science
https://www.readbyqxmd.com/read/30210775/probing-key-elements-of-teixobactin-lipid-ii-interactions-in-membranes
#2
Po-Chao Wen, Juan M Vanegas, Susan B Rempe, Emad Tajkhorshid
Teixobactin (Txb) is a recently discovered antibiotic against Gram-positive bacteria that induces no detectable resistance. The bactericidal mechanism is believed to be the inhibition of cell wall biosynthesis by Txb binding to lipid II and lipid III. Txb binding specificity likely arises from targeting of the shared lipid component, the pyrophosphate moiety. Despite synthesis and functional assessment of numerous chemical analogs of Txb, and consequent identification of the Txb pharmacophore, the detailed structural information of Txb-substrate binding is still lacking...
September 14, 2018: Chemical Science
https://www.readbyqxmd.com/read/30210774/electric-field-induced-bistability-in-single-molecule-conductance-measurements-for-boron-coordinated-curcuminoid-compounds
#3
Ignacio José Olavarría-Contreras, Alvaro Etcheverry-Berríos, Wenjie Qian, Cristian Gutiérrez-Cerón, Aldo Campos-Olguín, E Carolina Sañudo, Diana Dulić, Eliseo Ruiz, Núria Aliaga-Alcalde, Monica Soler, Herre S J van der Zant
We have studied the single-molecule conductance of a family of curcuminoid molecules (CCMs) using the mechanically controlled break junction (MCBJ) technique. The CCMs under study contain methylthio (MeS-) as anchoring groups: MeS-CCM ( 1 ), the free-ligand organic molecule, and two coordination compounds, MeS-CCM-BF2 ( 2 ) and MeS-CCM-Cu ( 3 ), where ligand 1 coordinates to a boron center (BF2 group) and to a CuII moiety, respectively. We found that the three molecules present stable molecular junctions allowing detailed statistical analysis of their electronic properties...
September 14, 2018: Chemical Science
https://www.readbyqxmd.com/read/30210773/a-simple-label-free-electrochemical-dna-parity-generator-checker-for-error-detection-during-data-transmission-based-on-aptamer-nanoclaw-modulated-protein-steric-hindrance
#4
Daoqing Fan, Yongchao Fan, Erkang Wang, Shaojun Dong
Versatile DNA logic devices have exhibited magical power in molecular-level computing and data processing. During any type of data transmission, the appearance of erroneous bits (which have severe impacts on normal computing) is unavoidable. Luckily, the erroneous bits can be detected via placing a parity generator (pG) at the sending module and a parity checker (pC) at the receiving module. However, all current DNA pG/pC systems use optical signals as outputs. In comparison, sensitive, facilely operated, electric-powered electrochemical outputs possess inherent advantages in terms of potential practicability and future integration with semiconductor transistors...
September 14, 2018: Chemical Science
https://www.readbyqxmd.com/read/30210772/rapid-non-invasive-characterization-of-the-dispersity-of-emulsions-via-microwaves
#5
Yuqiang Yan, Sergio Gonzalez-Cortes, Benzhen Yao, Daniel R Slocombe, Adrian Porch, Fahai Cao, Tiancun Xiao, Peter P Edwards
A rapid and non-invasive method to determine the dispersity of emulsions is developed based on the interrelationship between the droplet size distribution and the dielectric properties of emulsions. A range of water-in-oil emulsions with different water contents and droplet size distributions were analysed using a microwave cavity perturbation technique together with dynamic light scattering. The results demonstrate that the dielectric properties, as measured by non-invasive microwave cavity analysis, can be used to characterise the dispersity of emulsions, and is also capable of characterizing heavy oil emulsions...
September 14, 2018: Chemical Science
https://www.readbyqxmd.com/read/30210771/bifunctional-iminophosphorane-catalysed-enantioselective-sulfa-michael-addition-of-alkyl-thiols-to-alkenyl-benzimidazoles
#6
Michele Formica, Geoffroy Sorin, Alistair J M Farley, Jesús Díaz, Robert S Paton, Darren J Dixon
The first enantioselective sulfa-Michael addition of alkyl thiols to alkenyl benzimidazoles, enabled by a bifunctional iminophosphorane (BIMP) organocatalyst, is described. The iminophosphorane moiety of the catalyst provides the required basicity to deprotonate the thiol nucleophile while the chiral scaffold and H-bond donor control facial selectivity. The reaction is broad in scope with respect to the thiol and benzimidazole reaction partners with the reaction proceeding in up to 98% yield and 96 : 4 er...
September 14, 2018: Chemical Science
https://www.readbyqxmd.com/read/30210770/quasi-single-crystalline-coo-hexagrams-with-abundant-defects-for-highly-efficient-electrocatalytic-water-oxidation
#7
Zuozhong Liang, Zhehao Huang, Haitao Yuan, Zhiyuan Yang, Chaochao Zhang, Yang Xu, Wei Zhang, Haoquan Zheng, Rui Cao
Defects and structural long-range ordering have been recognized as two crucial characters for advanced electrocatalysts. However, these two features have rarely been achieved together. Herein, we report the preparation of single-crystalline CoO hexagrams and demonstrate their exceptional electrocatalytic properties for water oxidation. The quasi-single-crystalline CoO hexagrams, prepared at the critical phase transition point of β-Co(OH)2 /Co(OH)F hexagrams, possess both abundant oxygen vacancies as defects and structural long-range ordering...
September 14, 2018: Chemical Science
https://www.readbyqxmd.com/read/30210769/a-mononuclear-nonheme-feno-6-complex-synthesis-and-structural-and-spectroscopic-characterization
#8
Seungwoo Hong, James J Yan, Deepika G Karmalkar, Kyle D Sutherlin, Jin Kim, Yong-Min Lee, Yire Goo, Pradip K Mascharak, Britt Hedman, Keith O Hodgson, Kenneth D Karlin, Edward I Solomon, Wonwoo Nam
While the synthesis and characterization of {FeNO}7,8,9 complexes have been well documented in heme and nonheme iron models, {FeNO}6 complexes have been less clearly understood. Herein, we report the synthesis and structural and spectroscopic characterization of mononuclear nonheme {FeNO}6 and iron(iii)-nitrito complexes bearing a tetraamido macrocyclic ligand (TAML), such as [(TAML)FeIII (NO)]- and [(TAML)FeIII (NO2 )]2- , respectively. First, direct addition of NO(g) to [FeIII (TAML)]- results in the formation of [(TAML)FeIII (NO)]- , which is sensitive to moisture and air...
September 14, 2018: Chemical Science
https://www.readbyqxmd.com/read/30210768/nanowell-mediated-two-dimensional-liquid-chromatography-enables-deep-proteome-profiling-of-1000-mammalian-cells
#9
Maowei Dou, Ying Zhu, Andrey Liyu, Yiran Liang, Jing Chen, Paul D Piehowski, Kerui Xu, Rui Zhao, Ronald J Moore, Mark A Atkinson, Clayton E Mathews, Wei-Jun Qian, Ryan T Kelly
Multidimensional peptide separations can greatly increase the depth of coverage in proteome profiling. However, a major challenge for multidimensional separations is the requirement of large biological samples, often containing milligram amounts of protein. We have developed nanowell-mediated two-dimensional (2D) reversed-phase nanoflow liquid chromatography (LC) separations for in-depth proteome profiling of low-nanogram samples. Peptides are first separated using high-pH LC and the effluent is concatenated into 4 or 12 nanowells...
September 14, 2018: Chemical Science
https://www.readbyqxmd.com/read/30210767/divergent-ring-opening-coupling-between-cyclopropanols-and-alkynes-under-cobalt-catalysis
#10
Junfeng Yang, Yixiao Shen, Yang Jie Lim, Naohiko Yoshikai
Cobalt-diphosphine catalysts promote ring-opening coupling reactions between cyclopropanols and unactivated internal alkynes, affording either β-alkenyl ketones or multisubstituted cyclopentenol derivatives in good yields with good to excellent regioselectivities. The chemoselectivity between these β-alkenylation and [3 + 2] annulation reactions, which likely share a cobalt homoenolate as a key catalytic intermediate, is exquisitely controlled by the reaction conditions, with the solvent being a major controlling factor...
September 14, 2018: Chemical Science
https://www.readbyqxmd.com/read/30210766/combining-traditional-2d-and-modern-physical-organic-derived-descriptors-to-predict-enhanced-enantioselectivity-for-the-key-aza-michael-conjugate-addition-in-the-synthesis-of-prevymis%C3%A2-letermovir
#11
Toni T Metsänen, Katrina W Lexa, Celine B Santiago, Cheol K Chung, Yingju Xu, Zhijian Liu, Guy R Humphrey, Rebecca T Ruck, Edward C Sherer, Matthew S Sigman
Quantitative structure-activity relationships have an extensive history for optimizing drug candidates, yet they have only recently been applied in reaction development. In this report, the predictive power of multivariate parameterization has been explored toward the optimization of a catalyst promoting an aza-Michael conjugate addition for the asymmetric synthesis of letermovir. A hybrid approach combining 2D QSAR and modern 3D physical organic parameters performed better than either approach in isolation...
September 14, 2018: Chemical Science
https://www.readbyqxmd.com/read/30210765/hydrogen-bonded-perylene-bisimide-j-aggregate-aqua-material
#12
Vincenzo Grande, Bartolome Soberats, Stefanie Herbst, Vladimir Stepanenko, Frank Würthner
A new twelvefold methoxy-triethyleneglycol-jacketed tetraphenoxy-perylene bisimide ( MEG-PBI ) amphiphile was synthesized that self-assembles into two types of supramolecular aggregates in water: red-coloured aggregates of low order and with weak exciton coupling among the PBIs and blue-coloured strongly coupled J-aggregates consisting of a highly ordered hydrogen-bonded triple helix of PBIs. At room temperature this PBI is miscible with water at any proportions which enables the development of robust dye aggregates in solution, in hydrogel states and in lyotropic liquid crystalline states...
September 14, 2018: Chemical Science
https://www.readbyqxmd.com/read/30210764/-o-2-3-aminopropyl-diazeniumdiolates-suppress-the-progression-of-highly-metastatic-triple-negative-breast-cancer-by-inhibition-of-microvesicle-formation-via-nitric-oxide-based-epigenetic-regulation
#13
Fenghua Kang, Jiayi Zhu, Jianbing Wu, Tian Lv, Hua Xiang, Jide Tian, Yihua Zhang, Zhangjian Huang
Currently, there is no effective therapy for the treatment of highly metastatic triple-negative breast cancer (TNBC). Microvesicle (MV) formation is crucial for the metastasis of TNBC. Here we report a novel strategy to inhibit the generation of MVs for the intervention of TNBC. O 2 -3-Aminopropyl diazeniumdiolates 3a-f are designed and synthesized, which can be activated by lysyloxidase over-expressed in TNBC cells. The most active compound 3f is able to selectively release high levels of NO in TNBC cells, inhibit the cell proliferation, and reduce the adhesion, invasion and migration of TNBC cells in vitro ...
September 14, 2018: Chemical Science
https://www.readbyqxmd.com/read/30123486/correction-the-enhancement-and-suppression-of-immersion-mode-heterogeneous-ice-nucleation-by-solutes
#14
Thomas F Whale, Mark A Holden, Theodore W Wilson, Daniel O'Sullivan, Benjamin J Murray
[This corrects the article DOI: 10.1039/C7SC05421A.].
August 7, 2018: Chemical Science
https://www.readbyqxmd.com/read/30123485/catalytic-asymmetric-synthesis-of-geminal-dicarboxylates
#15
Nisha Mistry, Stephen P Fletcher
Stereogenic acetals, spiroacetals and ketals are well-studied stereochemical features that bear two heteroatoms at a common carbon atom. These stereocenters are normally found in cyclic structures while linear (or acyclic) analogues bearing two heteroatoms are rare. Chiral geminal-dicarboxylates are illustrative, there is no current way to access this class of compounds while controlling the stereochemistry at the carbon center bound to two oxygen atoms. Here we report a rhodium-catalysed asymmetric carboxylation of ester-containing allylic bromides to form stereogenic carbon centers bearing two different carboxylates with high yields and enantioselectivities...
August 7, 2018: Chemical Science
https://www.readbyqxmd.com/read/30123484/similar-ligand-metal-bonding-for-transition-metals-and-actinides-5f-1-u-c-7-h-7-2-versus-3d-n-metallocenes
#16
Dumitru-Claudiu Sergentu, Frédéric Gendron, Jochen Autschbach
U(C7 H7 )2 - is a fascinating 5f1 complex whose metal-ligand bonding was assigned in the literature as being very similar to 3d7 cobaltocene, based on a crystal-field theoretical interpretation of the experimental magnetic resonance data. The present work provides an in-depth theoretical study of the electronic structure, bonding, and magnetic properties of the 5f1 U(C7 H7 )2 - vs. 3d metallocenes with V, Co, and Ni, performed with relativistic wavefunction and density functional methods. The ligand to metal donation bonding in U(C7 H7 )2 - is strong and in fact similar to that in vanadocene, in the sense that the highest occupied arene orbitals donate electron density into empty metal orbitals of the same symmetry with respect to the rotational axis (3dπ for V, 5fδ for U), but selectively with α spin (↑)...
August 7, 2018: Chemical Science
https://www.readbyqxmd.com/read/30123483/modular-o-2-electroreduction-activity-in-triphenylene-based-metal-organic-frameworks
#17
Elise M Miner, Lu Wang, Mircea Dincă
Triphenylene ligands hexasubstituted with amino or phenol groups afford two phases of electrically conductive layered two-dimensional metal-organic frameworks upon reaction with various metals. Regardless of the identity of the metal or chelating atom, π-stacking within the MOF layers is essential to achieve high electrical conductivity, redox activity, and catalytic activity.
August 7, 2018: Chemical Science
https://www.readbyqxmd.com/read/30123482/membrane-glycomics-reveal-heterogeneity-and-quantitative-distribution-of-cell-surface-sialylation
#18
Diane Dayoung Park, Gege Xu, Maurice Wong, Chatchai Phoomak, Mingqi Liu, Nathan E Haigh, Sopit Wongkham, Pengyuan Yang, Emanual Maverakis, Carlito B Lebrilla
Given that unnatural sugar expression is metabolically achieved, the kinetics and disposition of incorporation can lend insight into the temporal and localization preferences of sialylation across the cell surface. However, common detection schemes lack the ability to detail the molecular diversity and distribution of target moieties. Here we employed a mass spectrometric approach to trace the placement of azido sialic acids on membrane glycoconjugates, which revealed substantial variations in incorporation efficiencies between N -/ O -glycans, glycosites, and glycosphingolipids...
August 7, 2018: Chemical Science
https://www.readbyqxmd.com/read/30123481/electrophile-promoted-fe-to-n-2-hydride-migration-in-highly-reduced-fe-n-2-h-complexes
#19
Meaghan M Deegan, Jonas C Peters
One of the emerging challenges associated with developing robust synthetic nitrogen fixation catalysts is the competitive formation of hydride species that can play a role in catalyst deactivation or lead to undesired hydrogen evolution reactivity (HER). It is hence desirable to devise synthetic systems where metal hydrides can migrate directly to coordinated N2 in reductive N-H bond-forming steps, thereby enabling productive incorporation into desired reduced N2 -products. Relevant examples of this type of reactivity in synthetic model systems are limited...
August 7, 2018: Chemical Science
https://www.readbyqxmd.com/read/30123480/dynamically-imaging-collision-electrochemistry-of-single-electrochemiluminescence-nano-emitters
#20
Cheng Ma, Wanwan Wu, Lingling Li, Shaojun Wu, Jianrong Zhang, Zixuan Chen, Jun-Jie Zhu
The quest for new techniques to measure single nanomaterials is a great impetus to research efforts to understand individual behaviours. Here, we develop an electrochemiluminescence (ECL) microscopy for visualization of stochastic collision electrochemistry of single nano-emitters without the interference of current and optical background. This design uses a water-immersion objective to capture the ECL emission of nanoparticles near the specular electrode surface for enhancing light collection efficiency. The approach enables us to trace the collision trajectory of multiple nanoparticles and spatially distinguish simultaneous collisions...
August 7, 2018: Chemical Science
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