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https://www.readbyqxmd.com/read/28327766/phosphorescent-platinum-ii-alkynyls-end-capped-with-benzothiazole-units
#1
Rebeca Lara, Elena Lalinde, M Teresa Moreno
Symmetric trans-bis(alkynyl)bis(phosphine) Pt(II) complexes based on the 2-phenylbenzothiazole (pbt) unit [trans-Pt(C[triple bond, length as m-dash]C-pbt)2L2] [L = PPh31, PEt32, 1,3,5-triaza-7-phosphaadamantane (PTA) 3] and the mixed alkynyl-cyanide anionic complex (NBu4)2[trans-Pt(C[triple bond, length as m-dash]C-pbt)2(CN)2] (4) were synthesized. The complexes have been fully characterized including X-ray crystallography for 2 and 4. All complexes display long-lived emission with moderate quantum yields (ϕ 6...
March 22, 2017: Dalton Transactions: An International Journal of Inorganic Chemistry
https://www.readbyqxmd.com/read/28326781/the-berkeleylactones-antibiotic-macrolides-from-fungal-coculture
#2
Andrea A Stierle, Donald B Stierle, Daniel Decato, Nigel D Priestley, Jeremy B Alverson, John Hoody, Kelly McGrath, Dorota Klepacki
A carefully timed coculture fermentation of Penicillium fuscum and P. camembertii/clavigerum yielded eight new 16-membered-ring macrolides, berkeleylactones A-H (1, 4, 6-9, 12, 13), as well as the known antibiotic macrolide A26771B (5), patulin, and citrinin. There was no evidence of the production of the berkeleylactones or A26771B (5) by either fungus when grown as axenic cultures. The structures were deduced from analyses of spectral data, and the absolute configurations of compounds 1 and 9 were determined by single-crystal X-ray crystallography...
March 22, 2017: Journal of Natural Products
https://www.readbyqxmd.com/read/28326773/germanium-compounds-containing-ge%C3%A2-e-double-bonds-e-s-se-te-as-single-source-precursors-for-germanium-chalcogenide-materials
#3
Hyo-Suk Kim, Eun Ae Jung, Seong Ho Han, Jeong Hwan Han, Bo Keun Park, Chang Gyoun Kim, Taek-Mo Chung
New germanium chalcogenide precursors, S═Ge(dmamp)2 (3), S═Ge(dmampS)2 (4), Se═Ge(dmamp)2 (5), Se═Ge(dmampS)2 (6), Te═Ge(dmamp)2 (7), and Te═Ge(dmampS)2 (8), were synthesized from Ge(dmamp)2 (1) and Ge(dmampS)2 (2) using sulfur, selenium, and tellurium powders (dmamp = 1-dimethylamino-2-methyl-2-propanolate, dmampS = 1-dimethylamino-2-methylpropane-2-thiolate). Complexes 1 and 2 were synthesized from metathesis reactions of GeCl2·dioxane with 2 equiv of aminoalkoxide or aminothiolate ligands. Thermogravimetric analysis of complex 1 displayed good thermal stability and volatility...
March 22, 2017: Inorganic Chemistry
https://www.readbyqxmd.com/read/28324508/in-vitro-preparation-and-crystallization-of-vertebrate-telomerase-subunits
#4
Jing Huang, Christopher J Bley, Dustin P Rand, Julian J L Chen, Ming Lei
Telomerase is a unique reverse transcriptase that replicates the telomeric DNA at most eukaryotic chromosomal ends. The telomerase consists of the catalytic protein subunit TERT and the RNA component TR that provides the template for telomeric DNA synthesis. In vitro reconstitution of telomerase core components in large quantity is the prerequisite to studying the catalytic mechanisms of telomerase at the structural level; however, large-scale preparation of recombinant telomerase, especially that of higher eukaryotes, has been a big challenge for a long time...
2017: Methods in Molecular Biology
https://www.readbyqxmd.com/read/28323293/atomic-scale-investigation-of-a-new-phase-transformation-process-in-tio2-nanofibers
#5
Yimin Lei, Jian Li, Zhan Wang, Jun Sun, Fuyi Chen, Hongwei Liu, Xiaohua Ma, Zongwen Liu
Crystallography of phase transformation combining transmission electron microscopy (TEM) with in situ heating techniques and X-ray diffraction (XRD) can provide critical information regarding solid-state phase transitions and the transition-induced interfaces in TiO2 nanomaterials theoretically and experimentally. Two types of reduced titanium oxides (Ti3O5, Ti6O11) are found during ex situ and in situ heating of TiO2 (B) nanofibers with a specific morphology of the {100} single form (SF) in air and vacuum...
March 21, 2017: Nanoscale
https://www.readbyqxmd.com/read/28322546/diverse-bonding-activations-in-the-reactivity-of-a-pentaphenylborole-toward-sodium-phosphaethynolate-heterocycle-synthesis-and-mechanistic-studies
#6
Yan Li, Rahul Kumar Siwatch, Totan Mondal, Yongxin Li, Rakesh Ganguly, Debasis Koley, Cheuk-Wai So
The reaction of the pentaphenylborole [(PhC)4BPh] (1) with sodium phosphaethynolate·1,4-dioxane (NaOCP(1,4-dioxane)1.7) afforded the novel sodium salt of phosphaboraheterocycle 2. It comprises anionic fused tetracyclic P/B-heterocycles that arise from multiple bond activation between the borole backbone and [OCP](-)anion. Density functional theory calculations indicate that the [OCP](-) anion prefers the form of phosphaethynolate (-)O-C≡P over phosphaketenide O═C═P(-) to interact with two molecules of 1, along with various B-C, C-P, and C-C bond activations to form 2...
March 21, 2017: Inorganic Chemistry
https://www.readbyqxmd.com/read/28319659/improving-computational-predictions-of-single-stranded-rna-tetramers-with-revised-%C3%AE-%C3%AE-torsional-parameters-for-the-amber-force-field
#7
David J Wales, Ilyas Yildirim
With current advancements in RNA based therapeutics, it is becoming crucial to utilize theoretical and computational methods to describe properly the physical properties of RNA molecules. NMR and X-ray crystallography are two powerful techniques for investigating structural properties. However, if the RNA molecules are complex or dynamic, these methods might not be adequate. For computational approaches, the quality of the force field will determine accuracy of our predictions. In this contribution, we revise the α/γ torsional parameters of RNA for amber force field using a model system representing an RNA dimer backbone...
March 20, 2017: Journal of Physical Chemistry. B
https://www.readbyqxmd.com/read/28319372/3d-printed-micrometre-scale-polymer-mounts-for-single-crystal-analysis
#8
Niall P Macdonald, Grace L Bunton, Ah Young Park, Michael C Breadmore, Nathan Laird Kilah
3D printed micrometre-scale polymer mounts for single crystal analysis have been prepared by photo polymerization using digital light projection stereolithography (DLP-SLA), with a commercially available digital light projection stereolithography printer (US$4000) and 3DM-ABS resin (US$150 per litre). The polymer mounts were prepared in batches of 49 in 1 hour 15 minutes, which allowed for rapid prototyping and testing of new crystal mounting designs, with a resin cost of 0.2¢ US per mount. The suitability of the 3D printed mounts for single crystal crystallography has been demonstrated through their use in Cu Kα X-ray diffraction experiments of Rochelle salt (sodium potassium tartrate), the protein lysozyme, and has been employed for routine crystallographic analysis of organic and inorganic materials...
March 20, 2017: Analytical Chemistry
https://www.readbyqxmd.com/read/28319294/activation-of-sf6-at-platinum-complexes-formation-of-sf3-derivatives-and-their-application-in-deoxyfluorination-reactions
#9
Claudia Berg, Thomas Braun, Mike Ahrens, Philipp Wittwer, Roy Herrmann
The activation of SF6 at [Pt(PR3 )2 ] R=Cy, iPr complexes in the presence of PR3 led selectively and in an unprecedented reaction route to the generation of the SF3 complexes trans-[Pt(F)(SF3 )(PR3 )2 ]. These can also be synthesized from SF4 and the SF2 derivative trans-[Pt(F)(SF2 )(PCy3 )2 ][BF4 ] was characterized by X-ray crystallography. trans-[Pt(F)(SF3 )(PR3 )2 ] complexes are useful tools for deoxyfluorination reactions and novel fluorido complexes bearing a SOF ligand are formed. Based on these studies a process for the deoxyfluorination of ketones was developed with SF6 as fluorinating agent...
March 20, 2017: Angewandte Chemie
https://www.readbyqxmd.com/read/28318239/trapping-experiments-on-a-trichlorosilanide-anion-a-key-intermediate-of-halogenosilane-chemistry
#10
Julian Teichmann, Markus Bursch, Benedikt Köstler, Michael Bolte, Hans-Wolfram Lerner, Stefan Grimme, Matthias Wagner
Treatment of Si2Cl6 with [Et4N][BCl4] in CH2Cl2 furnished the known products of a chloride-induced disproportionation reaction of the disilane, such as SiCl4, [Si(SiCl3)3](-), and [Si6Cl12·2Cl](2-). No Si-B-bonded products were detectable. In contrast, the addition of Si2Cl6 to [Et4N][BI3Cl] afforded the Si-B adduct [Et4N][I3SiBI3]. Thus, a quantitative Cl/I exchange at the silicon atom accompanies the trihalogenosilanide formation. [Et4N][I3SiBI3] was also accessible from a mixture of Si2I6, [Et4N]I, and BI3...
March 20, 2017: Inorganic Chemistry
https://www.readbyqxmd.com/read/28317198/dinuclear-complexes-formed-by-hydrogen-bonds-synthesis-structure-and-magnetic-and-electrochemical-properties
#11
Alan Francis Williams, Matteo Granelli, Alan M Downward, Robin Huber, Laure Guenée, Céline Besnard, Karl W Krämer, Silvio Decurtins, Shi-Xia Liu, Laurence K Thompson
The synthesis is reported of a series of homo- and hetero-dinuclear octahedral complexes of the ligand 1, 1,2-bis(1-methyl-benzimidazol-2-yl) ethanol, where the two metal centres are linked by hydrogen bonds between coordinated alcohols and coordinated alkoxides. Homonuclear divalent M(II)M(II), mixed valent M(II)M(III) and heteronuclear M(II)M'(III) species are prepared. The complexes have been characterised by X-ray crystallography and show unusually short O…O distances for the hydrogen bonds. Magnetic measurements show the hydrogen bond bridges can lead to ferromagnetic or antiferromagnetic coupling...
March 20, 2017: Chemistry: a European Journal
https://www.readbyqxmd.com/read/28317076/an-experimental-tool-to-estimate-the-probability-of-a-nucleotide-presence-in-the-crystal-structures-of-the-nucleotide-protein-complexes
#12
Maria Nemchinova, Vitaly Balobanov, Ekaterina Nikonova, Natalia Lekontseva, Alisa Mikhaylina, Svetlana Tishchenko, Alexey Nikulin
A correlation between the ligand-protein affinity and the identification of the ligand in the experimental electron density maps obtained by X-ray crystallography has been tested for a number of RNA-binding proteins. Bacterial translation regulators ProQ, TRAP, Rop, and Hfq together with their archaeal homologues SmAP have been used. The equilibrium dissociation constants for the N-methyl-anthraniloyl-labelled adenosine and guanosine monophosphates titrated by the proteins have been determined by the fluorescent anisotropy measurements...
March 20, 2017: Protein Journal
https://www.readbyqxmd.com/read/28315749/integrated-structural-biology-to-unravel-molecular-mechanisms-of-protein-rna-recognition
#13
REVIEW
Andreas Schlundt, Jan-Niklas Tants, Michael Sattler
Recent advances in RNA sequencing technologies have greatly expanded our knowledge of the RNA landscape in cells, often with spatiotemporal resolution. These techniques identified many new (often non-coding) RNA molecules. Large-scale studies have also discovered novel RNA binding proteins (RBPs), which exhibit single or multiple RNA binding domains (RBDs) for recognition of specific sequence or structured motifs in RNA. Starting from these large-scale approaches it is crucial to unravel the molecular principles of protein-RNA recognition in ribonucleoprotein complexes (RNPs) to understand the underlying mechanisms of gene regulation...
March 15, 2017: Methods: a Companion to Methods in Enzymology
https://www.readbyqxmd.com/read/28315011/the-exocyclic-amino-group-of-adenine-in-pt-ii-and-pd-ii-complexes-a-critical-comparison-of-the-x-ray-crystallographic-structural-data-and-gas-phase-calculations
#14
Radu Silaghi-Dumitrescu, Béla Mihály, Timea Mihály, Amr A A Attia, Pablo J Sanz Miguel, Bernhard Lippert
A detailed computational (DFT level of theory) study regarding the nature of the exocyclic amino group, N6H2, of the model nucleobase 9-methyladenine (9MeA) and its protonated (9MeAH(+)) and deprotonated forms (9MeA-H), free and metal-complexed, has been conducted. The metals are Pt(II) and Pd(II), bonded to nitrogen-containing co-ligands (NH3, dien, bpy), with N1, N6, and N7 being the metal-binding sites, individually or in different combinations. The results obtained from gas phase calculations are critically compared with X-ray crystallography data, whenever possible...
March 17, 2017: Journal of Biological Inorganic Chemistry: JBIC
https://www.readbyqxmd.com/read/28314102/unique-four-electron-metal-to-cage-charge-transfer-of-th-to-a-c82-fullerene-cage-complete-structural-characterization-of-th-c3v-8-c82
#15
Yaofeng Wang, Roser Morales-Martínez, Xingxing Zhang, Wei Yang, Yaxing Wang, Antonio Rodriguez-Fortea, Josep M Poblet, Lai Feng, Shuao Wang, Ning Chen
Endohedral metallofullerenes (EMFs) containing lanthanides have been intensively studied in recent years. By contrast, actinide endohedral fullerenes remain largely unexplored. Herein, for the first time, we report the single crystal structure and full characterization of an actinide endohedral fullerene, Th@C82, which exhibits remarkably different electronic and spectroscopic properties compared to those of lanthanide EMFs. Single crystal X-ray crystallography unambiguously established the molecular structure as Th@C3v(8)-C82...
March 17, 2017: Journal of the American Chemical Society
https://www.readbyqxmd.com/read/28304041/hydrogen-bridged-bis-silylene-complexes-of-ruthenium-and-iron-synthesis-structures-and-multi-centre-bonding-interactions-at-the-m-si-h-si-four-membered-ring
#16
Hisako Hashimoto, Katsuto Komura, Takatoshi Ishizaki, Yuto Odagiri, Hiromi Tobita
Hydrogen-bridged bis(silylene) complexes of ruthenium and iron were synthesized as the first examples of this type containing Group 8 metals and their rare four-membered ring structures and multi-center bonding interactions at the M-Si-H-Si moiety were clarified by NMR spectroscopy, X-ray crystallography and theoretical calculations.
March 17, 2017: Dalton Transactions: An International Journal of Inorganic Chemistry
https://www.readbyqxmd.com/read/28301773/progress-and-potential-of-electron-cryotomography-as-illustrated-by-its-application-to-bacterial-chemoreceptor-arrays
#17
Ariane Briegel, Grant Jensen
Electron cryotomography (ECT) can produce three-dimensional images of biological samples such as intact cells in a near-native, frozen-hydrated state to macromolecular resolution (∼4 nm). Because one of its first and most common applications has been to bacterial chemoreceptor arrays, ECT's contributions to this field illustrate well its past, present, and future. Although X-ray crystallography and nuclear magnetic resonance spectroscopy have revealed the structures of nearly all the individual components of chemoreceptor arrays, ECT has revealed the mesoscale information about how the components are arranged within cells...
February 23, 2017: Annual Review of Biophysics
https://www.readbyqxmd.com/read/28301148/synthesis-and-photobiological-activity-of-ru-ii-dyads-derived-from-pyrrole-2-carboxylate-thionoesters
#18
Deborah A Smithen, Huimin Yin, Michael H R Beh, Marc Hetu, T Stanley Cameron, Sherri A McFarland, Alison Thompson
The synthesis and characterization of a series of heteroleptic ruthenium(II) dyads derived from pyrrole-2-carboxylate thionoesters are reported. Ligands bearing a conjugated thiocarbonyl group were found to be more reactive toward Ru(II) complexation compared to analogous all-oxygen pyrrole-2-carboxylate esters, and salient features of the resulting complexes were determined using X-ray crystallography, electronic absorption, and NMR spectroscopy. Selected complexes were evaluated for their potential in photobiological applications, whereupon all compounds demonstrated in vitro photodynamic therapy effects in HL-60 and SK-MEL-28 cells, with low nanomolar activities observed, and exhibited some of the largest photocytotoxicity indices to date (>2000)...
March 16, 2017: Inorganic Chemistry
https://www.readbyqxmd.com/read/28300169/double-flow-focused-liquid-injector-for-efficient-serial-femtosecond-crystallography
#19
Dominik Oberthuer, Juraj Knoška, Max O Wiedorn, Kenneth R Beyerlein, David A Bushnell, Elena G Kovaleva, Michael Heymann, Lars Gumprecht, Richard A Kirian, Anton Barty, Valerio Mariani, Aleksandra Tolstikova, Luigi Adriano, Salah Awel, Miriam Barthelmess, Katerina Dörner, P Lourdu Xavier, Oleksandr Yefanov, Daniel R James, Garrett Nelson, Dingjie Wang, George Calvey, Yujie Chen, Andrea Schmidt, Michael Szczepek, Stefan Frielingsdorf, Oliver Lenz, Edward Snell, Philip J Robinson, Božidar Šarler, Grega Belšak, Marjan Maček, Fabian Wilde, Andrew Aquila, Sébastien Boutet, Mengning Liang, Mark S Hunter, Patrick Scheerer, John D Lipscomb, Uwe Weierstall, Roger D Kornberg, John C H Spence, Lois Pollack, Henry N Chapman, Saša Bajt
Serial femtosecond crystallography requires reliable and efficient delivery of fresh crystals across the beam of an X-ray free-electron laser over the course of an experiment. We introduce a double-flow focusing nozzle to meet this challenge, with significantly reduced sample consumption, while improving jet stability over previous generations of nozzles. We demonstrate its use to determine the first room-temperature structure of RNA polymerase II at high resolution, revealing new structural details. Moreover, the double flow-focusing nozzles were successfully tested with three other protein samples and the first room temperature structure of an extradiol ring-cleaving dioxygenase was solved by utilizing the improved operation and characteristics of these devices...
March 16, 2017: Scientific Reports
https://www.readbyqxmd.com/read/28299734/using-small-angle-x-ray-scattering-saxs-to-characterize-the-solution-conformation-and-flexibility-of-matrix-metalloproteinases-mmps
#20
Louise E Butt, Robert A Holland, Nikul S Khunti, Debra L Quinn, Andrew R Pickford
Small angle X-ray scattering (SAXS) provides information about the conformation and flexibility of proteins in solution, and hence provides complementary structural information to that obtained from X-ray crystallography and nuclear magnetic resonance spectroscopy. In this chapter, we describe the methods for the preparation of matrix metalloproteinase (MMP) samples for SAXS analyses, and for the acquisition, processing and interpretation of the SAXS data.
2017: Methods in Molecular Biology
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