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crystal structure

Ki-Young Lee, Bong-Jin Lee
Fourteen well-defined ribozyme classes have been identified to date, among which nine are site-specific self-cleaving ribozymes. Very recently, small self-cleaving ribozymes have attracted renewed interest in their structure, biochemistry, and biological function since the discovery, during the last three years, of four novel ribozymes, termed twister, twister sister, pistol, and hatchet. In this review, we mainly address the structure, biochemistry, and catalytic mechanism of the novel ribozymes. They are characterized by distinct active site architectures and divergent, but similar, biochemical properties...
April 24, 2017: Molecules: a Journal of Synthetic Chemistry and Natural Product Chemistry
Yingjie Sun, Zhiwen Zhuo, Xiaojun Wu, Jinlong Yang
Searching experimental feasible two-dimensional (2D) ferromagnetic crystals with large spin-polarization ratio, high Curie temperature and large magnetic anisotropic energy is one key to develop next-generation spintronic nano-devices. Here, 2D Fe2Si nanosheet, one counterpart of Hapkeite mineral discovered in meteorite, with novel magnetism is proposed on the basis of first-principles calculations. 2D Fe2Si crystal has a slightly buckled triangular lattice with planar hexacoordinated Si and Fe atoms. The spin-polarized calculations with hybrid HSE06 function method indicate that 2D Fe2Si is a ferromagnetic half metal at its ground state with 100% spin-polarization ratio at Fermi energy level...
April 25, 2017: Nano Letters
Andrea Hadjikyriacou, Steven Gerard Clarke
Caenorhabditis elegans protein arginine methyltransferases PRMT-7 and PRMT-9 are two evolutionarily conserved enzymes, with distinct orthologs in plants, invertebrates, and vertebrates. Biochemical characterization of these two enzymes reveals that they share much in common with their mammalian orthologs. C. elegans PRMT-7 produces only monomethyl arginine (MMA) and preferentially methylates R-X-R motifs in a broad collection of substrates, including human histone peptides and RG-rich peptides. In addition, the activity of the PRMT-7 enzyme is dependent on temperature, the presence of metal ions, and the reducing agent dithiothreitol (DTT)...
April 25, 2017: Biochemistry
M Mansurova, J von der Haar, J Panke, Jakob Walowski, Henning Ulrichs, M Münzenberg
The discovery of ultrafast magnetization dynamics 20 years ago has led to a broad variety of experimental techniques to explore phenomena in magnetic materials with high temporal resolution. In the current article we present a study dealing with broadband excitation of spin-wave packets at different magnonic crystal continuous magnetic film interfaces. Similar to protected conducting states on the surfaces of topological band insulators, these interfaces exhibit surface spin-wave modes that propagate out of the crystal into the continuous film...
April 25, 2017: Journal of Physics. Condensed Matter: An Institute of Physics Journal
Satya K Kushwaha, Karoline Stolze, Zhijun Wang, Max Hirschberger, Jingjing Lin, B Andrei Bernevig, N Phuan Ong, Robert J Cava
We report the growth of high quality bulk crystals, through crystallization from molten Sn flux, of the predicted ferromagnetic Weyl metal ZrCo2-x Sn with the L21 Heusler phase structure. The concentration of Co vacancies in the single crystals is found to be dependent on the initial concentration of Co in the flux. The saturation magnetization increases approximately linearly with decreasing Co deficiency and the ferromagnetic transition temperature changes significantly. p-type carrier conduction and an anomalous Hall effect are observed...
April 25, 2017: Journal of Physics. Condensed Matter: An Institute of Physics Journal
Brian J Sobieski, Isao Noda, John F Rabolt, D Bruce Chase
In this work, we describe polymer-solvent interactions in biosynthesized and biodegradable poly[(R)-3-hydroxybutyrate- co-(R)-3-hydroxyhexanoate] (PHBHx) and the atactic homopolymer, poly(3-hydroxybutyrate) (a-PHB), which were studied both as neat polymers and in solutions of chloroform and 1,1,1,3,3,3-hexafluoro-2-propanol (HFIP). Specifically, infrared frequency shifts of the carbonyl band were observed in semi-crystalline PHBHx, but not in a-PHB, because it cannot form the helical conformation required for crystallization...
January 1, 2017: Applied Spectroscopy
Benoît Bertrand, Julio Fernandez-Cestau, Jesus Angulo, Marco M D Cominetti, Zoë A E Waller, Mark Searcey, Maria A O'Connell, Manfred Bochmann
The synthesis of a series of cyclometalated gold(III) complexes supported by pyrazine-based (C^N^C)-type pincer ligands is reported, including the crystal structure of a cationic example. The compounds provide a new platform for the study of antiproliferative properties of gold(III) complexes. Seven complexes were tested: the neutral series (C^N(pz)^C)AuX [X = Cl (1), 6-thioguanine (4), C≡CPh (5), SPh (6)] and an ionic series that included the N-methyl complex [(C^N(pzMe)^C)AuCl]BF4 (7) and the N-heterocyclic carbene complexes [(C^N(pz)^C)AuL](+) with L = 1,3-dimethylbenzimidazol-2-ylidene (2) or 1,3,7,9-tetramethylxanthin-8-ylidene (3)...
April 25, 2017: Inorganic Chemistry
Safwan Aroua, Tanya K Todorova, Paul Hommes, Lise-Marie Chamoreau, Hans-Ulrich Reissig, Victor Mougel, Marc Fontecave
Terpyridine ligands are widely used in chemistry and material sciences owing to their ability to form stable molecular complexes with a large variety of metal ions. In that context, variations of the substituents on the terpyridine ligand allow modulation of the material properties. Applying the Stille cross-coupling reaction, we prepared with good yields a new series of terpyridine ligands possessing quinoline-type moieties in ortho, meta, and para positions and dimethylamino substituents at central or distal positions...
April 25, 2017: Inorganic Chemistry
Mattia Sist, Carlo Gatti, Peter Nørby, Simone Cenedese, Hidetaka Kasai, Kenichi Kato, Bo B Iversen
The discovery of the ultra-high thermoelectric figure of merit of 2.6 in SnSe has drawn attention to other lead-free IV-VI orthorhombic semiconductors. GeSe has been predicted to possess thermoelectric performances comparable to SnSe. Here, a complete structural study is reported of GeSe with temperature by means of high-resolution synchrotron powder X-ray diffraction. In the orthorhombic phase, the evolution of the bond distances with temperature is shown to deviate significantly with respect to SnSe. Analysis of the chemical bonding within the Quantum Theory of Atoms in Molecules shows that GeSe is ionic with van der Waals interlayer interactions...
April 25, 2017: Chemistry: a European Journal
Shota Fujino, Minoru Yamaji, Hideki Okamoto, Toshiki Mutai, Isao Yoshikawa, Hirohiko Houjou, Fumito Tani
We studied the photoproducts of 1-(n-phenanthryl)-2-(m-phenanthryl)ethenes (nEm; n, m = 1, 3 and 9) for understanding photocyclization patterns based on NMR spectroscopy. The crystal structures of the photoproducts were analyzed by X-ray crystallography, and the photophysical features of the photocyclized molecules were investigated based on emission and transient absorption measurements. Phenanthrene derivatives substituted at the 1- and 3-positions were prepared for synthesizing nEm by photocyclization of stilbene derivatives...
April 25, 2017: Photochemical & Photobiological Sciences
Chun Hong Yoon, Hasan DeMirci, Raymond G Sierra, E Han Dao, Radman Ahmadi, Fulya Aksit, Andrew L Aquila, Alexander Batyuk, Halilibrahim Ciftci, Serge Guillet, Matt J Hayes, Brandon Hayes, Thomas J Lane, Meng Liang, Ulf Lundström, Jason E Koglin, Paul Mgbam, Yashas Rao, Theodore Rendahl, Evan Rodriguez, Lindsey Zhang, Soichi Wakatsuki, Sébastien Boutet, James M Holton, Mark S Hunter
We provide a detailed description of selenobiotinyl-streptavidin (Se-B SA) co-crystal datasets recorded using the Coherent X-ray Imaging (CXI) instrument at the Linac Coherent Light Source (LCLS) for selenium single-wavelength anomalous diffraction (Se-SAD) structure determination. Se-B SA was chosen as the model system for its high affinity between biotin and streptavidin where the sulfur atom in the biotin molecule (C10H16N2O3S) is substituted with selenium. The dataset was collected at three different transmissions (100, 50, and 10%) using a serial sample chamber setup which allows for two sample chambers, a front chamber and a back chamber, to operate simultaneously...
April 25, 2017: Scientific Data
Dong Chen, Shuai Zhang, Yang Huaixin, Jianqi Li, Gen-Fu Chen
Ce<sub>2</sub>Te<sub>5</sub> single crystals were successfully grown using RbCl/LiCl flux method. The structure of Ce<sub>2</sub>Te<sub>5</sub> can be viewed as a combination of CeTe<sub>2</sub> and CeTe<sub>3</sub>. The experimental results of magnetic susceptibility <i>χ</i>(<i>T</i>), isothermal magnetization <i>M</i>(<i>H</i>), electrical resistivity <i>ρ</i>(<i>T</i>), and heat capacity <i>C</i>(<i>T</i>) show two clear anomalies at 5...
April 25, 2017: Journal of Physics. Condensed Matter: An Institute of Physics Journal
Minfeng Lü, Hongil Jo, Seung-Jin Oh, Suheon Lee, Kwang-Yong Choi, Yang Yu, Kang Min Ok
Three new quaternary lithium metal tellurites, Li3MTe4O11 (M = Al, Ga, and Fe), have been synthesized through hydrothermal and solid-state reactions by heating a mixture of LiOH·H2O, TeO2, and M2O3. The structures of the title compounds have been determined by single-crystal and powder X-ray diffraction. Li3MTe4O11 reveal three-dimensional (3D) frameworks that consist of MO6 octahedra, TeO3 trigonal pyramids, and TeO4 polyhedra. The variable coordination mode of Te(4+) within the framework leads to the formation of 1D channels that host Li(+) cations on both tetrahedral and octahedral sites...
April 25, 2017: Inorganic Chemistry
Lalit A Darunte, Yuri Terada, Christopher R Murdock, Krista S Walton, David S Sholl, Christopher W Jones
The potential of using an amine-functionalized MOF, mmen-M2(dobpdc) (M = Mg, Mn), supported on a structured monolith contactor for CO2 capture from simulated flue gas is explored. The stability of the unsupported MOF powders under humid conditions is explored using nitrogen physisorption and X-ray diffraction analysis before and after exposure to humidity. Based on its superior stability to humidity, mmen-Mg2(dobpdc) is selected for further growth on a honeycomb cordierite monolith that is washcoated with α-alumina...
April 25, 2017: ACS Applied Materials & Interfaces
Billel Salhi, David Troadec, Rabah Boukherroub
The work presented in this paper concerns the synthesis of silicon (Si) 2D and 3D nanostructures using the delayed effect, caused by implanted Ga ions, on the dissolution of Si in aqueous solutions of tetramethylammonium hydroxide (TMAH). The crystalline silicon substrates (100) are first cleaned and then hydrogenated by immersion in an aqueous solution of hydrofluoric acid. The ion implantation is then carried out by a focused ion beam by varying the dose and the exposure time. Chemical etching in aqueous solutions of TMAH at 80 °C leads to the selective dissolution of the Si planes not exposed to the ions...
April 25, 2017: Nanotechnology
Kaori Noridomi, Go Watanabe, Melissa N Hansen, Gye Won Han, Lin Chen
The nicotinic acetylcholine receptor (nAChR) is a major target of autoantibodies in myasthenia gravis (MG), an autoimmune disease that causes neuromuscular transmission dysfunction. Despite decades of research, the molecular mechanisms underlying MG have not been fully elucidated. Here, we present the crystal structure of the nAChR α1 subunit bound by the Fab fragment of mAb35, a reference monoclonal antibody that causes experimental MG and competes with ~65% of antibodies from MG patients. Our structures reveal for the first time the detailed molecular interactions between MG antibodies and a core region on nAChR α1...
April 25, 2017: ELife
Matthew S Beyersdorf, Ria Sircar, Daniel B Lookadoo, Cory Bottone, Michael J Lynch, Brian R Crane, Christopher J Halkides
Phosphorylation of CheY promotes association with the flagellar motor and ultimately controls the directional bias of the motor. However, biochemical studies of activated CheY-phosphate have been challenging due to the rapid hydrolysis of the aspartyl-phosphate in vitro. An inert analog of Tm CheY-phosphate, phosphono-CheY, was synthesized by chemical modification and purified by cation-exchange chromatography. Changes in HPLC retention times, chemical assays for phosphate and free thiol, and mass spectrometry experiments demonstrate modification of Cys54 with a phosphonomethyl group...
April 25, 2017: Protein Science: a Publication of the Protein Society
Rui Zhang, Michihisa Murata, Atsushi Wakamiya, Takafumi Shimoaka, Takeshi Hasegawa, Yasujiro Murata
Dissociation of an acid molecule in aqueous media is one of the most fundamental solvation processes but its details remain poorly understood at the distinct molecular level. Conducting high-pressure treatments of an open-cage fullerene C70 derivative with hydrogen fluoride (HF) in the presence of H2O, we achieved an unprecedented encapsulation of H2O·HF and H2O. Restoration of the opening yielded the endohedral C70s, that is, (H2O·HF)@C70, H2O@C70, and HF@C70 in macroscopic scales. Putting an H2O·HF complex into the fullerene cage was a crucial step, and it would proceed by the synergistic effects of "pushing from outside" and "pulling from inside...
April 2017: Science Advances
Taku Fukuzawa, Zenjiro Sampei, Kenta Haraya, Yoshinao Ruike, Meiri Shida-Kawazoe, Yuichiro Shimizu, Siok Wan Gan, Machiko Irie, Yoshinori Tsuboi, Hitoshi Tai, Tetsushi Sakiyama, Akihisa Sakamoto, Shinya Ishii, Atsuhiko Maeda, Yuki Iwayanagi, Norihito Shibahara, Mitsuko Shibuya, Genki Nakamura, Takeru Nambu, Akira Hayasaka, Futa Mimoto, Yuu Okura, Yuji Hori, Kiyoshi Habu, Manabu Wada, Takaaki Miura, Tatsuhiko Tachibana, Kiyofumi Honda, Hiroyuki Tsunoda, Takehisa Kitazawa, Yoshiki Kawabe, Tomoyuki Igawa, Kunihiro Hattori, Junichi Nezu
Dysregulation of the complement system is linked to the pathogenesis of a variety of hematological disorders. Eculizumab, an anti-complement C5 monoclonal antibody, is the current standard of care for paroxysmal nocturnal hemoglobinuria (PNH) and atypical hemolytic uremic syndrome (aHUS). However, because of high levels of C5 in plasma, eculizumab has to be administered biweekly by intravenous infusion. By applying recycling technology through pH-dependent binding to C5, we generated a novel humanized antibody against C5, SKY59, which has long-lasting neutralization of C5...
April 24, 2017: Scientific Reports
Minghao Chen, Shin-Ichi Asai, Shun Narai, Shusuke Nambu, Naoki Omura, Yuriko Sakaguchi, Tsutomu Suzuki, Masao Ikeda-Saito, Kimitsuna Watanabe, Min Yao, Naoki Shigi, Yoshikazu Tanaka
Two-thiouridine (s(2)U) at position 54 of transfer RNA (tRNA) is a posttranscriptional modification that enables thermophilic bacteria to survive in high-temperature environments. s(2)U is produced by the combined action of two proteins, 2-thiouridine synthetase TtuA and 2-thiouridine synthesis sulfur carrier protein TtuB, which act as a sulfur (S) transfer enzyme and a ubiquitin-like S donor, respectively. Despite the accumulation of biochemical data in vivo, the enzymatic activity by TtuA/TtuB has rarely been observed in vitro, which has hindered examination of the molecular mechanism of S transfer...
April 24, 2017: Proceedings of the National Academy of Sciences of the United States of America
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