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Chemical Science

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https://www.readbyqxmd.com/read/28507725/metal-free-c-h-alkylation-of-heteroarenes-with-alkyltrifluoroborates-a-general-protocol-for-1%C3%A2-2%C3%A2-and-3%C3%A2-alkylation
#1
Jennifer K Matsui, David N Primer, Gary A Molander
A photoredox-catalyzed C-H functionalization of heteroarenes using a variety of primary, secondary, and tertiary alkyltrifluoroborates is reported. Using Fukuzumi's organophotocatalyst and a mild oxidant, conditions amenable for functionalizing complex heteroaromatics are described, providing a valuable tool for late-stage derivatization. The reported method addresses the three major limitations of previously reported photoredox-mediated Minisci reactions: (1) use of superstoichiometric amounts of a radical precursor, (2) capricious regioselectivity, and (3) incorporation of expensive photocatalysts...
May 1, 2017: Chemical Science
https://www.readbyqxmd.com/read/28507724/deep-learning-and-3d-desi-imaging-reveal-the-hidden-metabolic-heterogeneity-of-cancer
#2
Paolo Inglese, James S McKenzie, Anna Mroz, James Kinross, Kirill Veselkov, Elaine Holmes, Zoltan Takats, Jeremy K Nicholson, Robert C Glen
Visual inspection of tumour tissues does not reveal the complex metabolic changes that differentiate cancer and its sub-types from healthy tissues. Mass spectrometry imaging, which quantifies the underlying chemistry, represents a powerful tool for the molecular exploration of tumour tissues. A 3-dimensional topological description of the chemical properties of the tumour permits the formulation of hypotheses about the biological composition and interactions and the possible causes of its heterogeneous structure...
May 1, 2017: Chemical Science
https://www.readbyqxmd.com/read/28507723/p-doping-of-graphene-in-hybrid-materials-with-3-10-diazapicenium-dications
#3
Alexandra Roth, Tobias A Schaub, Ute Meinhardt, Dominik Thiel, Jan Storch, Vladimír Církva, Pavel Jakubík, Dirk M Guldi, Milan Kivala
N,N'-Didodecyl-substituted 3,10-diazapicenium salts featuring bromide and hexafluorophosphate counterions have been designed as novel dopants to realize individualized graphene sheets in a series of cutting edge experiments and to intrinsically stabilize them via p-doping. Importantly, electrochemical studies revealed two consecutive irreversible one-electron reductions of the N,N'-didodecyl-substituted 3,10-diazapicenium salts to yield the corresponding radical cation and neutral quinoidal species. Formation of both species was accompanied by characteristic changes in the absorption spectra...
May 1, 2017: Chemical Science
https://www.readbyqxmd.com/read/28507722/novel-bright-emission-small-molecule-nir-ii-fluorophores-for-in-vivo-tumor-imaging-and-image-guided-surgery
#4
Yao Sun, Mingmin Ding, Xiaodong Zeng, Yuling Xiao, Huaping Wu, Hui Zhou, Bingbing Ding, Chunrong Qu, Wei Hou, Aga Er-Bu, Yejun Zhang, Zhen Cheng, Xuechuan Hong
Though high brightness and biocompatible small NIR-II dyes are highly desirable in clinical or translational cancer research, their fluorescent cores are relatively limited and their synthetic processes are somewhat complicated. Herein, we have explored the design and synthesis of novel NIR-II fluorescent materials (H1) without tedious chromatographic isolation with improved fluorescence performance (QY ≈ 2%) by introducing 2-amino 9,9-dialkyl-substituted fluorene as a donor into the backbone. Several types of water-soluble and biocompatible NIR-II probes: SXH, SDH, and H1 NPs were constructed via different chemical strategies based on H1, and then their potential to be used in in vivo tumor imaging and image-guided surgery in the NIR-II region was explored...
May 1, 2017: Chemical Science
https://www.readbyqxmd.com/read/28507721/mo-6-activated-multimetal-oxygen-evolving-catalysts
#5
Peng Fei Liu, Shuang Yang, Li Rong Zheng, Bo Zhang, Hua Gui Yang
Water splitting is key to electrically-powered chemical fuel synthesis, but the slow kinetics of the oxygen evolution reaction (OER) hinder the wider promotion of such technology. Several first-row (3d) transition metal-based catalysts have been developed for the OER; however, these catalysts still require operating voltages that lie well above the fundamental thermodynamic potential. Here, we report high-valence metal molybdenum (Mo(6+)) modulated 3d metal (oxy)hydroxides. The obtained multimetal FeCoMo based OER catalysts require an overpotential of 277 mV to reach the current density of 10 mA cm(-2) on the glassy carbon electrode, and there was no evidence of degradation for about 40 hours of stability testing...
May 1, 2017: Chemical Science
https://www.readbyqxmd.com/read/28507720/in-vivo-imaging-of-leucine-aminopeptidase-activity-in-drug-induced-liver-injury-and-liver-cancer-via-a-near-infrared-fluorescent-probe
#6
Xinyuan He, Lihong Li, Yu Fang, Wen Shi, Xiaohua Li, Huimin Ma
The liver, a main detoxification organ, has evolved a complex enzymatic system to respond to multiple pathological conditions, in which leucine aminopeptidase (LAP) has been reported to participate in detoxifying cisplatin in hepatoma cells and contribute to the intrinsic drug resistance. In vivo imaging of LAP activity in liver disease models is thus helpful to further understand the function of LAP in detoxification and medicine, but such an imaging approach is still lacking. Herein, we develop a selective and sensitive near-infrared fluorescent probe (HCAL) for this purpose...
May 1, 2017: Chemical Science
https://www.readbyqxmd.com/read/28507719/broad-substrate-tolerance-of-tubulin-tyrosine-ligase-enables-one-step-site-specific-enzymatic-protein-labeling
#7
Dominik Schumacher, Oliver Lemke, Jonas Helma, Lena Gerszonowicz, Verena Waller, Tina Stoschek, Patrick M Durkin, Nediljko Budisa, Heinrich Leonhardt, Bettina G Keller, Christian P R Hackenberger
The broad substrate tolerance of tubulin tyrosine ligase is the basic rationale behind its wide applicability for chemoenzymatic protein functionalization. In this context, we report that the wild-type enzyme enables ligation of various unnatural amino acids that are substantially bigger than and structurally unrelated to the natural substrate, tyrosine, without the need for extensive protein engineering. This unusual substrate flexibility is due to the fact that the enzyme's catalytic pocket forms an extended cavity during ligation, as confirmed by docking experiments and all-atom molecular dynamics simulations...
May 1, 2017: Chemical Science
https://www.readbyqxmd.com/read/28507718/copper-catalyzed-direct-alkylation-of-heteroarenes
#8
Cédric Theunissen, Jianjun Wang, Gwilherm Evano
An efficient and broadly applicable process is reported for the direct alkylation of C-H bonds in heteroarenes, privileged scaffolds in many areas of science. This reaction is based on the copper-catalyzed addition of alkyl radicals generated from activated secondary and tertiary alkyl bromides to a wide range of arenes, including furans, thiophenes, pyrroles, and their benzo-fused derivatives, as well as coumarins and quinolinones.
May 1, 2017: Chemical Science
https://www.readbyqxmd.com/read/28507717/dynamic-structural-and-thermodynamic-basis-of-insulin-like-growth-factor-1-kinase-allostery-mediated-by-activation-loop-phosphorylation
#9
Yaozong Li, Kwangho Nam
Despite the importance of kinases' catalytic activity regulation in cell signaling, detailed mechanisms underlying their activity regulation are poorly understood. Herein, using insulin-like growth factor 1 receptor kinase (IGF-1RK) as a model, the mechanisms of kinase regulation by its activation loop (A-loop) phosphorylation were investigated through molecular dynamics (MD) and alchemical free energy simulations. Analyses of the simulation results and free energy landscapes determined for the entire catalytic cycle of the kinase revealed that A-loop phosphorylation affects each step in the IGF-1RK catalytic cycle, including conformational change, substrate binding/product release and catalytic phosphoryl transfer...
May 1, 2017: Chemical Science
https://www.readbyqxmd.com/read/28507716/chemistry-in-nanoconfined-water
#10
Daniel Muñoz-Santiburcio, Dominik Marx
Nanoconfined liquids have extremely different properties from the bulk, which profoundly affects chemical reactions taking place in nanosolvation. Here, we present extensive ab initio simulations of a vast set of chemical reactions within a water lamella that is nanoconfined by mineral surfaces, which might be relevant to prebiotic peptide formation in aqueous environments. Our results disclose a rich interplay of distinct effects, from steric factors typical of reactions occurring in small spaces to a charge-stabilization effect in nanoconfined water at extreme conditions similar to that observed in bulk water when changing from extreme to ambient conditions...
May 1, 2017: Chemical Science
https://www.readbyqxmd.com/read/28507715/a-quantitative-mechanistic-pk-pd-model-directly-connects-btk-target-engagement-and-in-vivo-efficacy
#11
Fereidoon Daryaee, Zhuo Zhang, Kayla R Gogarty, Yong Li, Jonathan Merino, Stewart L Fisher, Peter J Tonge
Correlating target engagement with in vivo drug activity remains a central challenge in efforts to improve the efficiency of drug discovery. Previously we described a mechanistic pharmacokinetic-pharmacodynamic (PK/PD) model that used drug-target binding kinetics to successfully predict the in vivo efficacy of antibacterial compounds in models of Pseudomonas aeruginosa and Staphylococcus aureus infection. In the present work we extend this model to quantitatively correlate the engagement of Bruton's tyrosine kinase (Btk) by the covalent inhibitor CC-292 with the ability of this compound to reduce ankle swelling in an animal model of arthritis...
May 1, 2017: Chemical Science
https://www.readbyqxmd.com/read/28507714/targeting-the-tumour-microenvironment-with-an-enzyme-responsive-drug-delivery-system-for-the-efficient-therapy-of-breast-and-pancreatic-cancers
#12
Brigitte Renoux, Florian Raes, Thibaut Legigan, Elodie Péraudeau, Balkis Eddhif, Pauline Poinot, Isabelle Tranoy-Opalinski, Jérôme Alsarraf, Oleksandr Koniev, Sergii Kolodych, Stéphanie Lerondel, Alain Le Pape, Jonathan Clarhaut, Sébastien Papot
The development of novel therapeutic strategies allowing the destruction of tumour cells while sparing healthy tissues is one of the main challenges of cancer chemotherapy. Here, we report on the design and antitumour activity of a low-molecular-weight drug delivery system programmed for the selective release of the potent monomethylauristatin E in the tumour microenvironment of solid tumours. After intravenous administration, this compound binds covalently to plasmatic albumin through Michael addition, thereby enabling its passive accumulation in tumours where extracellular β-glucuronidase initiates the selective release of the drug...
May 1, 2017: Chemical Science
https://www.readbyqxmd.com/read/28507713/white-light-emission-from-discrete-heterometallic-lanthanide-directed-self-assembled-complexes-in-solution
#13
Oxana Kotova, Steve Comby, Christophe Lincheneau, Thorfinnur Gunnlaugsson
White-light-emitting materials have attracted significant interest in recent years due to their potential applications in solid-state lighting and flat-panel displays. Design of such materials is challenging and often relies on the use of multiple fluorophores despite the fact that single component systems yield materials with enhanced stability and reproducibility. Herein, we have developed a white-light-emitting system based on the formation of discrete lanthanide-based self-assembled complexes using a newly-designed ligand...
May 1, 2017: Chemical Science
https://www.readbyqxmd.com/read/28507712/redox-non-innocence-permits-catalytic-nitrene-carbonylation-by-dadi-ti-0000000000000000000000000000000000-0000000000000000000000000000000000-0000000000000000000000000000000000-0000000000000000000000000000000000-0000000000000000000000000000000000-0000000000000000000000000000000000
#14
Spencer P Heins, Peter T Wolczanski, Thomas R Cundari, Samantha N MacMillan
Application of the diamide, diimine {-CHN(1,2-C6H4)N(2,6-(i)Pr2-C6H3)}2(m) ((dadi) (m) ) ligand to titanium provided adducts (dadi)TiL x (1-L x ; L x = THF, PMe2Ph, (CNMe)2), which possess the redox formulation [(dadi)(4-)]Ti(iv)L x , and 22 πe(-) (4n + 2). Related complexes containing titanium-ligand multiple bonds, (dadi)TiX (2 X; X = O, NAd), exhibit a different dadi redox state, [(dadi)(2-)]Ti(iv)X, consistent with 20 πe(-) (4n). The Redox Non-Innocence (RNI) displayed by dadi (m) impedes binding by CO, and permits catalytic conversion of AdN3 + CO to AdNCO + N2...
May 1, 2017: Chemical Science
https://www.readbyqxmd.com/read/28507711/interfacial-engineering-of-renewable-metal-organic-framework-derived-honeycomb-like-nanoporous-aluminum-hydroxide-with-tunable-porosity
#15
Ye-Tang Pan, Lu Zhang, Xiaomin Zhao, De-Yi Wang
Novel honeycomb-like mesoporous aluminum hydroxide (pATH) was synthesized via a facile one-step reaction by employing ZIF-8 as a template. This self-decomposing template was removed automatically under acidic conditions without the need for any tedious or hazardous procedures. Meanwhile, the pore size of pATH was easily modulated by tuning the dimensions of the ZIF-8 polyhedrons. Of paramount importance was the fact that the dissolved ZIF-8 in solution was regenerated upon deprotonation of the ligand under mild alkali conditions, and was reused in the preparation of pATH, thus forming a delicate synthesis cycle...
May 1, 2017: Chemical Science
https://www.readbyqxmd.com/read/28507710/semiconducting-polymer-dots-with-bright-narrow-band-emission-at-800-nm-for-biological-applications
#16
Dandan Chen, I-Che Wu, Zhihe Liu, Ying Tang, Haobin Chen, Jiangbo Yu, Changfeng Wu, Daniel T Chiu
The development of near-infrared (NIR) fluorescent probes is critical for in vivo exploration of the fundamental and complex processes in living systems by noninvasive fluorescence imaging techniques. Semiconducting polymer dots (Pdots) are emerging as important probes that exhibit several advantages, such as high brightness and biocompatibility. However, NIR-emitting Pdots are very rare, particularly at the center (∼800 nm) of the first optical window of biological tissues (between 650 nm and 950 nm). In this paper, we describe the synthesis of a semiconducting polymer with bright and narrow-band emission at 800 nm...
May 1, 2017: Chemical Science
https://www.readbyqxmd.com/read/28507709/first-total-synthesis-of-concavine
#17
François Saint-Dizier, Nigel S Simpkins
The synthesis of the unusual alkaloid concavine, isolated from Clitocybe concava (Basidiomycetae), has been accomplished. The synthetic route features regio- and stereoselective manipulation of polycyclic imide intermediates via enolate substitution and Grignard addition, along with a key bridge-forming step involving a new method for sulfenylative radical cyclisation. The NMR data for synthetic concavine demonstrate that the original data reported for the natural product refer to the derived acetic acid salt, probably formed as an artefact of isolation or purification...
May 1, 2017: Chemical Science
https://www.readbyqxmd.com/read/28507708/manganese-catalyzed-allylation-via-sequential-c-h-and-c-c-c-het-bond-activation
#18
Qingquan Lu, Felix J R Klauck, Frank Glorius
Manganese-catalyzed sequential C-H and C-C/C-Het bond activation to synthesize allylic alcohols, allylated arenes, functionalized cyclopentenes and skipped dienes is reported. This protocol can be readily scaled up and various coupling partners are applied in manganese catalysis for the first time. Moreover, manganese-catalyzed alkenyl C(sp(2))-H activation is also shown. Complimentary to the standard solution-based protocols, these reactions also proceed efficiently under neat conditions, which is unprecedented for abundant metal catalyzed C-H activation reactions...
May 1, 2017: Chemical Science
https://www.readbyqxmd.com/read/28507707/nanophase-separated-ni3nb-as-an-automobile-exhaust-catalyst
#19
Toyokazu Tanabe, Tsubasa Imai, Tomoharu Tokunaga, Shigeo Arai, Yuta Yamamoto, Shigenori Ueda, Gubbala V Ramesh, Satoshi Nagao, Hirohito Hirata, Shin-Ichi Matsumoto, Takeshi Fujita, Hideki Abe
Catalytic remediation of automobile exhaust has relied on precious metals (PMs) including platinum (Pt). Herein, we report that an intermetallic phase of Ni and niobium (Nb) (i.e., Ni3Nb) exhibits a significantly higher activity than that of Pt for the remediation of the most toxic gas in exhaust (i.e., nitrogen monoxide (NO)) in the presence of carbon monoxide (CO). When subjected to the exhaust-remediation atmosphere, Ni3Nb spontaneously evolves into a catalytically active nanophase-separated structure consisting of filamentous Ni networks (thickness < 10 nm) that are incorporated in a niobium oxide matrix (i...
May 1, 2017: Chemical Science
https://www.readbyqxmd.com/read/28507706/ph-and-ligand-induced-release-of-loads-from-dna-acrylamide-hydrogel-microcapsules
#20
Wei-Ching Liao, Sivan Lilienthal, Jason S Kahn, Marianna Riutin, Yang Sung Sohn, Rachel Nechushtai, Itamar Willner
Herein, a method to construct stimuli-responsive DNA-acrylamide-based hydrogel microcapsules has been presented. This method involves the use of polyacrylamide chains modified with predesigned nucleic acid hairpin units and optionally single-strand tethers that provide the required hybridization and recognition functions to yield substrate-loaded stimuli-responsive hydrogel-based microcapsules. The synthesis of the microcapsules involves the loading of CaCO3 microparticles with the respective load substrates and the functionalization of the CaCO3 template particles with nucleic acid promoter units...
May 1, 2017: Chemical Science
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