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Chemistry: a European Journal

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https://www.readbyqxmd.com/read/28092417/dense-semi-clathrates-at-high-pressure-a-study-of-the-water-tert-butylamine-system
#1
Rubén Granero-García, Andrzej Falenty, Francesca Paola Anna Fabbiani
In situ high-pressure crystallization and diffraction techniques have been applied to obtain two very structurally-distinct semi-clathrates of the tert-butylamine-water system with hydration numbers 5.65 and 5.8, respectively, thereby considerably reducing a notable hydration gap between the monohydrate and the 7¼-hydrate that results when crystallization space is explored by temperature alone. Both structures can be considered as an intriguing solid-state example of hydrophobic hydration in which the water network creates wide tert-butylamine-filled channels stabilized by cross-linking hydrogen bonds...
January 16, 2017: Chemistry: a European Journal
https://www.readbyqxmd.com/read/28092124/active-site-mapping-of-xylan-deconstructing-enzymes-with-arabinoxylan-oligosaccharides-produced-by-automated-glycan-assembly
#2
Deborah Senf, Colin Ruprecht, Goswinus de Kruijff, Sebastian Simonetti, Frank Schuhmacher, Peter Seeberger, Fabian Pfrengle
Xylan-degrading enzymes are crucial for the deconstruction of hemicellulosic biomass, making the hydrolysis products available for various industrial applications such as biofuel production. To determine the substrate specificities of these enzymes, we prepared a collection of complex xylan oligosaccharides by automated glycan assembly. Seven differentially protected building blocks provided the basis for the modular assembly of 2-substituted, 3-substituted, and 2-/3-substituted arabino- and glucuronoxylan oligosaccharides...
January 16, 2017: Chemistry: a European Journal
https://www.readbyqxmd.com/read/28090694/graphene-oxide-wrapped-sio2-tio2-hollow-nanoparticles-loaded-with-photosensitizer-for-photothermal-and-photodynamic-combination-therapy
#3
Yoonsun Jang, Sojin Kim, Seungae Lee, Chang-Min Yoon, Inkyu Lee, Jyongsik Jang
Graphene oxide (GO) enwrapped SiO2/TiO2 hollow nanoparticles (GO-HNP) are synthesized by stöbber method and used as a nanocarrier for loading protoporphyrin IX (PpIX). The synthesized nanoparticle has high dispersibitliy and high uniformity in diameter (ca. 50 nm). . Furthermore, this nanoparticle shows 808 nm laser induced PpIX release property (photo-induced "on-off" drug release system). The GO-HNP-PpIX is employed for inducing both photothermal therapy (PTT) and photodynamic therapy (PDT). The synergic effect of the PTT and PDT exhibits powerful anti-cancer property...
January 16, 2017: Chemistry: a European Journal
https://www.readbyqxmd.com/read/28090689/%C3%AE-aminoxy-peptoids-a-unique-peptoid-backbone-with-a-preference-for-cis-amide-bonds
#4
Viktoria Krieger, Emanuele Ciglia, Roland Thoma, Vera Vasylyeva, Benedikt Frieg, Nader de Sousa Amadeu, Thomas Kurz, Christoph Janiak, Holger Gohlke, Finn Kristian Hansen
α-Peptoids, or N-substituted glycine oligomers, are an important class of peptidomimetic foldamers with proteolytic stability. Nevertheless, the presence of cis-/trans-amide bond conformers, which contribute to the high flexibility of α-peptoids, is considered as a major drawback. A modified peptoid backbone with an improved control of the amide bond geometry could therefore help to overcome this limitation. Here we have performed the first thorough analysis of the folding propensities of α-aminoxy peptoids (or N-substituted 2-aminoxyacetic acid oligomers)...
January 16, 2017: Chemistry: a European Journal
https://www.readbyqxmd.com/read/28087882/cooperatively-interlocked-2-1-type-%C3%AF-system-anion-complexes
#5
Ryohei Yamakado, Yukina Ashida, Ryuma Sato, Yasuteru Shigeta, Nobuhiro Yasuda, Hiromitsu Maeda
As fascinating examples of closely connected multiple π-electronic systems involving noncovalent interactions, the cooperatively interlocked [2+1]-type anion complexes of well-designed π-electronic molecules are reported. The anion-responsive π-electronic molecules investigated in this study are the boron complexes of dipyrrolyldiketones bearing arylethynyl moieties at the pyrrole α-positions. Diverse substituents were introduced at the terminal aryl moieties, thus controlling the cooperativity to form [2+1]-type complexes...
January 14, 2017: Chemistry: a European Journal
https://www.readbyqxmd.com/read/28087880/direct-synthesis-of-highly-designable-hybrid-metal-hydroxide-nanosheets-using-tripodal-ligands-as-one-size-fits-all-modifiers
#6
Yoshiyuki Kuroda, Tatsuyuki Koichi, Keisuke Muramatsu, Kazuya Yamaguchi, Noritaka Mizuno, Atsushi Shimojima, Hiroaki Wada, Kazuyuki Kuroda
Brucite-type layered metal hydroxides are prepared from diverse metallic elements and have outstanding functions; however, their poor intercalation ability significantly limits their chemical designability and the use of their potentially ultrahigh surface areas and unique properties as two-dimensional nanosheets. Here, we demonstrate that tripodal ligands (R-C(CH2OH)3, R = NH2, CH2OH, or NHC2H4SO3H) are useful as "one-size-fits-all" modifiers for the direct synthesis of hybrid metal hydroxide nanosheets with various constituent metallic elements (M = Mg, Mn, Fe, Co, Ni, or Cu) and surface functional groups...
January 14, 2017: Chemistry: a European Journal
https://www.readbyqxmd.com/read/28084659/mixed-linkage-glucan-oligosaccharides-produced-by-automated-glycan-assembly-serve-as-tools-to-determine-the-substrate-specificity-of-lichenase
#7
Pietro Dallabernardina, Frank Schuhmacher, Peter H Seeberger, Fabian Pfrengle
The mixed-linkage (1→3),(1→4)-D-glucan (MLG) specific glycosyl hydrolase lichenase is an important biochemical tool for the structural characterization of MLGs. It holds potential for application in the brewery, animal feed, and biofuel industries. Several defined MLG oligosaccharides obtained by automated glycan assembly are used to analyze the substrate specificities of Bacillus subtilis lichenase. Two glucose building blocks (BBs), equipped with a temporary Fmoc protecting group in the C-3 or C-4 position, served to assemble different oligosaccharides using an automated oligosaccharide synthesizer...
January 13, 2017: Chemistry: a European Journal
https://www.readbyqxmd.com/read/28084055/small-molecule-activation-with-n-nr-mic-platinum-complexes
#8
Ekkehardt Hahn, Hanpeng Jin, Alexander Hepp, Christian Mück-Lichtenfeld, Douglas Stepahn
The reaction of platinum complex trans-[1] bearing an N,NEt-imidazolide ligand with bis(diphenylphosphino)ethane (dppe) or bis(dicyclohexylphosphino)ethane (dchpe) yields the dinuclear MIC complexes [2]I2 or the mononuclear MIC complex [3]I, respectively. While dinuclear [2]I2 does not react with elemental hydrogen, the mononuclear complex [3]I splits elemental hydrogen under mild reaction conditions with formation of hydride complex [4]I and N-ethylimidazole. Dinuclear complex [3]I activates CS2 with formation of complex [5]I featuring the CS2 molecule bound via the carbon atom to the MIC nitrogen atom and one sulphur atom coordinating to the platinum center...
January 13, 2017: Chemistry: a European Journal
https://www.readbyqxmd.com/read/28084031/direct-and-autocatalytic-reductive-elimination-from-gold-complexes-ph3p-au-ar-cf3-x-x-f-cl-br-i-the-key-role-of-halide-ligands
#9
Rameswar Bhattacharjee, Abdulrahiman Nijamudheen, Ayan Datta
Kinetic and thermodynamic preferences for the reductive elimination of Caryl-CF3, Caryl-X, Caryl-P, and CF3-X bonds and competitive phosphine dissociation from a series of Au(III) complexes, (Ph3P)Au(Ar)(CF3)(X), (1X, Ar = 4-Me-C6H4, X = F, Cl, Br, I) are studied computationally. Kinetically, most favorable pathways consist of an initial phosphine dissociation from 1X, furnishing respective three coordinate Au(III) complexes Au(Ar)(CF3)(X), 2X. The computed barriers for various reductive elimination reactions from 2X via a direct (or uncatalyzed) mechanism showed Caryl-CF3 bond formation as the most favorable fate for any X...
January 13, 2017: Chemistry: a European Journal
https://www.readbyqxmd.com/read/28083988/breaking-the-gordian-knot-in-the-structural-chemistry-of-polyoxometalates-copper-ii-oxo-hydroxo-clusters
#10
Kirill Monakhov, Aleksandar Kondinski
This Concept article provides insights into the molecular design and construction aspects of polyoxocuprates (POCus), an emerging class of polyoxometalate (POM)-like architectures featuring low-to-high nuclearity copper(II)-oxo/hydroxo skeletons. POCus have been identified to adopt the structural principles of classical POMs consisting of early transition metals. Their potential to afford motifs of the noble metal-based POMs is exploited. "Cross-structural topological transformation" is introduced to generalize skeletal relationships between POCus and POMs...
January 13, 2017: Chemistry: a European Journal
https://www.readbyqxmd.com/read/28083957/synthesis-and-oxidation-of-a-paddlewheel-shaped-rhodium-antimony-complex-featuring-pyridine-2-thiolate-ligands
#11
Erik Wächtler, Luis A Oro, Manuel Iglesias, Birgit Gerke, Rainer Pöttgen, Robert Gericke, Jörg Wagler
The paddlewheel-shaped complex [Sb(µ-pyS)4Rh]2 (1) (pyS-: 2-S-C5H4N-) was synthesized from [Rh(pyS)(cod)]2 (cod = 1,5-cyclooctadiene) and Sb(pyS)3. Upon oxidation with ONMe3, the complex [(µ-O)Sb(µ-pyS)3Rh(κ2-pyS)]2 (2) is formed. Both 1 and 2 form dimers and feature short Rh-Sb bonds and bridging pyS ligands. 121Sb Mössbauer spectroscopy and computational studies were employed to elucidate the Rh-Sb bonding in 1 and 2. Both covalent (Rh-Sb, X-type Sb ligand) and dative (Rh→Sb, Z-type; Rh←Sb L-type Sb ligand) interactions have to be considered for the description of their bonding situations...
January 13, 2017: Chemistry: a European Journal
https://www.readbyqxmd.com/read/28081291/a-bioorganometallic-approach-to-the-study-histidine-kinase-auto-phosphorylation
#12
Nan Wang, Zhe She, Zakiyya Ingar, Sanela Martic, Heinz-Bernhard Kraatz
Auto-phosphorylation of bacterial histidine kinases PhoR, PhoQ and EnvZ have been investigated using Adenosine-5'-[γ-ferrocene] triphosphate (Fc-ATP) as a co-substrate for the first time. The study has been carried out in solution and on surface. Results from biochemical multiplex assay and surface electrochemical/optical methods are consistent, which successfully demonstrates Fc-ATP is an efficient co-substrate for histidine kinase auto-phosphorylations. The study also has discovered that the concentration of Fc-ATP influences the auto-phosphorylation efficiency...
January 12, 2017: Chemistry: a European Journal
https://www.readbyqxmd.com/read/28079952/regioselectivity-change-in-the-organocatalytic-enantioselective-3-2-cycloaddition-with-nitrones-through-cooperative-h-bonding-catalysis-iminium-activation
#13
Liher Prieto, Veronica Juste-Navarro, Uxue Uria, Ignacio Delso, Efraim Reyes, Tomas Tejero, Luisa Carrillo, Pedro Merino, Jose L Vicario
The reaction of nitrones with enals under iminium activation can be modulated by using cooperative H-bonding catalysis to induce the participation of a nitrone ylide (C-N-C) instead of the classical C-N-O dipole. As a consequence, N-hydroxypyrrolidines, rather than the expected isoxazolidines, are obtained. The reaction proceeds smoothly and high enantioselectivities are observed in all cases. By using the appropriate substrate, polysubstituted pyrrolidines incorporating quaternary stereocenters can be efficiently prepared...
January 12, 2017: Chemistry: a European Journal
https://www.readbyqxmd.com/read/28079948/induction-of-antibodies-directed-against-branched-core-o-mannosyl-glycopeptides-selectivity-complimentary-to-the-cona-lectin
#14
Jin Yu, Oliver C Grant, Christian Pett, Sabine Strahl, Robert J Woods, Ulrika Westerlind
Mammalian protein O-mannosylation comprise a group of post-translational modifications (PTMs) involved in muscle and brain development. Despite the enormous progress made, to date the biological impact of the mammalian O-mannosyl glycoproteome remains largely unknown. Tools are still needed to investigate the structure, role and abundance of O-mannosyl glycans. While O-mannosyl branching has been shown to be of relevance in integrin-dependent cell-migration, and also plays a role in demyelinating diseases, a broader understanding of the biological roles of branched O-mannosyl glycans is lacking in part due to the paucity of detection tools...
January 12, 2017: Chemistry: a European Journal
https://www.readbyqxmd.com/read/28079287/triarylmethane-dyes-for-artificial-repellent-cotton-fibers
#15
Adelina Vallribera, Ana Maria Montagut, Erik Gálvez, Rosa María Sebastián, Alexandr Shafir
Families of new hydrophobic and/or oleophobic triarylmethane dyes possessing long hydrocarbon or polyfluorinated chains have been prepared. When covalently grafted upon cotton fabric, these dyes give rise to a new type of colored superhydrophobic fibers.
January 12, 2017: Chemistry: a European Journal
https://www.readbyqxmd.com/read/28078753/photoredox-catalysed-decarboxylative-alkylation-of-n-heteroarenes-with-n-acyloxy-phthalimides
#16
Yao Fu, Wan-Min Cheng, Rui Shang, Ming-Chen Fu
An iridium-photoredox catalyst in combination with either a stoichiometric amount of Brønsted acid or a catalytic amount of Lewis acid is capable of catalysing regioselective alkylation of N-heteroarenes with N-(acyloxy)phthalimides at room temperature under irradiation. A broad range of N-heteroarenes can be alkylated using a variety of secondary, tertiary, and quaternary carboxylates. Mechanistic studies suggest that an Ir(II)/Ir(III) redox catalytic cycle is responsible for the observed reactivity.
January 12, 2017: Chemistry: a European Journal
https://www.readbyqxmd.com/read/28078752/two-new-copperoborates-with-mesoscale-cubic-supramolecular-cages-assembled-from-cu4-b20-clusters
#17
Guo-Yu Yang, Jia-Jia Wang, Qi Wei, Bai-Feng Yang
Two new copper borates with 3D supramolecular framework with mesoscale cavities have been made under solvothermal conditions, showing novel cubic supramolecular cages assembled by [(µ4-O)Cu4@B20O32(OH)8] ({Cu4@B20}) clusters with different point-group symmetry.
January 12, 2017: Chemistry: a European Journal
https://www.readbyqxmd.com/read/28078726/dissecting-the-cytochrome-p450-1a2-and-3a4-mediated-metabolism-of-aflatoxin-b1-in-ligand-and-protein-contributions
#18
Lars Olsen, Flemming S Jørgensen, Silvia Bonomo
Aflatoxin B1 (AFB1) is a chemically intriguing compound because it has several potential sites of metabolism (SOMs) while only some of them are observed experimentally. Cytochrome P450 (CYP) 3A4 and 1A2 are the major isoforms involved in its metabolism. Here, we systematically investigate reactivity and accessibility of all possible SOMs in these two CYPs to elucidate AFB1 metabolism. Density functional theory (DFT) calculations were used to determine activation energies for each possible reaction. Aliphatic hydroxylation on position 9A and 3α are energetically favored, whereas position 9 is the preferred site for epoxidation...
January 12, 2017: Chemistry: a European Journal
https://www.readbyqxmd.com/read/28078725/chiral-amplification-by-self-assembly-of-neutral-luminescent-platinum-ii-complexes
#19
Alessandro Aliprandi, Christelle M Croisetu, Matteo Mauro, Luisa De Cola
Two novel enantiomerically pure chiral ligands and the corresponding neutral Pt(II) complexes have been synthetized and characterized. The self-assembly properties of the complexes have been investigated using different morphological and photophysical techniques. The two enantiomeric complexes, 4 a and 4 b, show high tendency to self-assemble into chiral supramolecular aggregates with right (P) and left-handed (M) helical configurations, respectively, as proven by SEM and absorption circular dichroism. The formation of such organized structures is driven by the formation of metallophilic and π-π interactions between spatially close Pt complexes with an enhancement of the chiro-optical properties in the solid state...
January 12, 2017: Chemistry: a European Journal
https://www.readbyqxmd.com/read/28078805/three-dimensional-mos2-cnt-rgo-network-composites-for-high-performance-flexible-supercapacitors
#20
Shouzhi Wang, Jiayan Zhu, Yongliang Shao, Weiran Li, Yongzhong Wu, Xiaopeng Hao
Two-dimensional atomically thick materials, reduced graphene oxide (RGO) and layered molybdenum disulphide (MoS2) have been potentially investigated as novel energy storage materials because of their distinct physicochemical properties. However, these materials suffer from rapid capacity decay and low rate capability. This study describes a facile binder-free approach to fabricate large-scale 3D network structure MoS2@carbon nanotube (CNT)/RGO composites for application in flexible supercapacitor devices. The as-obtained composites possess a hierarchical porosity and an interconnected framework...
January 11, 2017: Chemistry: a European Journal
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