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Solid-state NMR

Bethany G Caulkins, Robert P Young, Ryan A Kudla, Chen Yang, Thomas J Bittbauer, Baback Bastin, Eduardo Hilario, Li Fan, Michael J Marsella, Michael F Dunn, Leonard J Mueller
Carbanionic intermediates play a central role in the catalytic transformations of amino acids performed by pyridoxal-5'-phosphate (PLP)-dependent enzymes. Here, we make use of NMR crystallography - the synergistic combination of solid-state nuclear magnetic resonance, X-ray crystallography, and computational chemistry - to interrogate a carbanionic/quinonoid intermediate analogue in the β-subunit active site of the PLP-requiring enzyme tryptophan synthase. The solid-state NMR chemical shifts of the PLP pyridine ring nitrogen and additional sites, coupled with first principles computational models, allow a detailed model of protonation states for ionizable groups on the cofactor, substrates, and nearby catalytic residues to be established...
October 25, 2016: Journal of the American Chemical Society
Tomasz Mroczek, Tomasz Plech, Monika Wujec
Till now, three major spectroscopic techniques, fourier transform infrared (FT-IR), nuclear magnetic resonance (NMR) spectroscopy and X-ray crystallography, have been used for determination of thiol-thione tautomeric forms. Therefore, a novel analytical concept of discrimination of 1,2,4-triazole-3-thione and 3-thiol tautomers using two high-resolution mass spectrometers has been proposed. It comprises the high-performance liquid chromatography (HPLC) hyphenated with electrospray ionization (ESI)-time-of-flight mass spectrometry (ESI-TOF-MS, positive ion mode) followed by in-source collision-induced dissociation (CID) and low-energy CID-tandem mass spectrometry (MS/MS) analysis measured with a Quadruple-TOF-MS instrument...
October 24, 2016: Journal of Chromatographic Science
Shrikant S Maktedar, Gopal Avashthi, Man Singh
The new sonochemical approach for simultaneous reduction and direct functionalization of graphene oxide (GrO) has been developed. The GrO was functionalized with 2-Aminobenzoxazole (2-ABOZ) in twenty min with complete deletion of hazardous steps. The significance of ultrasound was exemplified with the comparative conventional methods. The newly prepared f-(2-ABOZ)GrO was extensively characterized with near edge X-ray absorption fine structure (NEXAFS) spectroscopy, (13)C solid state NMR, XPS, XRD, HRTEM, SAED, AFM, Raman, UV-vis, FTIR and TGA...
January 2017: Ultrasonics Sonochemistry
Shrikant S Maktedar, Shantilal S Mehetre, Gopal Avashthi, Man Singh
The rapid, robust, scalable and non-hazardous sonochemical approach for in situ reduction and direct functionalization of graphene oxide has been developed for non-toxic biomedical applications. The graphene oxide (GrO) was directly functionalized with tryptamine (TA) without using any hazardous acylating and coupling reagents. The reaction was completed within 20min. An impact of ultrasound was inferred for a direct functionalization with other conventional methods. The evolved electronic states were confirmed with near edge X-ray absorption fine structure (NEXAFS)...
January 2017: Ultrasonics Sonochemistry
R Rohaizu, W D Wanrosli
Highly stable and dispersible nanocrystalline cellulose (NCC) was successfully isolated from oil palm empty fruit bunch microcrystalline cellulose (OPEFB-MCC), with yields of 93% via a sono-assisted TEMPO-oxidation and a subsequent sonication process. The sono-assisted treatment has a remarkable effect, resulting in an increase of more than 100% in the carboxylate content and a significant increase of approximately 39% in yield compared with the non-assisted process. TEM images reveal the OPEFB-NCC to have rod-like crystalline morphology with an average length and width of 122 and 6nm, respectively...
January 2017: Ultrasonics Sonochemistry
Dennis W Piehl, Luis M Blancas-Mejía, Marina Ramirez-Alvarado, Chad M Rienstra
Light chain (AL) amyloidosis is a systemic disease characterized by the formation of immunoglobulin light-chain fibrils in critical organs of the body. The light-chain protein AL-09 presents one severe case of cardiac AL amyloidosis, which contains seven mutations in the variable domain (VL) relative to its germline counterpart, κI O18/O8 VL. Three of these mutations are non-conservative-Y87H, N34I, and K42Q-and previous work has shown that they are responsible for significantly reducing the protein's thermodynamic stability, allowing fibril formation to occur with fast kinetics and across a wide-range of pH conditions...
October 22, 2016: Biomolecular NMR Assignments
Joel Jerushan Thevarajah, Matthew Paul Van Leeuwen, Herve Cottet, Patrice Castignolles, Marianne Gaborieau
Chitosan is often characterized by its average degree of acetylation. To increase chitosan's use in various industries, a more thorough characterization is necessary as the acetylation of chitosan affects properties such as dissolution and mechanical properties of chitosan films. Despite the poor solubility of chitosan, free solution capillary electrophoresis (CE) allows a robust separation of chitosan by the degree of acetylation. The distribution of degrees of acetylation of various chitosan samples was characterized through their distributions of electrophoretic mobilities...
October 19, 2016: International Journal of Biological Macromolecules
Lei Zhou, Shenhui Li, Guodong Qi, Yongchao Su, Jing Li, Anmin Zheng, Xianfeng Yi, Qiang Wang, Feng Deng
The carbonylation of methanol with carbon monoxide to generate methyl acetate over Cu-H-MOR and H-MOR zeolites is studied using solid-state NMR spectroscopy. It is found that the catalytic activity of Cu-H-MOR zeolite is much higher than that of H-MOR zeolite. The presence of Cu(+) species enables the stabilization of dimethyl ether, which efficiently suppresses the hydrocarbon formation during carbonylation process over Cu-H-MOR zeolite. In addition, the carbon monoxide adsorbed on Cu(+) site is not an active species to produce either methyl acetate or acetic acid...
October 6, 2016: Solid State Nuclear Magnetic Resonance
Martin Heberle, Stefanie Tschierlei, Nils Rockstroh, Mark Ringenberg, Wolfgang Frey, Henrik Junge, Matthias Beller, Stefan Lochbrunner, Michael Karnahl
A series of heteroleptic copper(I) photosensitizers of the type [(P^P)Cu(N^N)]+ with an extended π-system in the backbone of the diimine ligand have been prepared. The structures of all complexes are completely characterized by NMR spectroscopy, mass spectrometry and X-ray crystallography. These novel photosensitizers were assessed with respect to the photocatalytic reduction of protons in the presence of triethylamine and [Fe3(CO)12]. While the solid state structures and computational results show no significant impact of the π-extension on the structural properties decreased activities were observed...
October 21, 2016: Chemistry: a European Journal
Hongwei Yao, Myungwoon Lee, Shu Y Liao, Mei Hong
The fusion peptide (FP) and transmembrane domain (TMD) of viral fusion proteins play important roles during virus-cell membrane fusion, by inducing membrane curvature and transient dehydration. The structure of the water-soluble ectodomain of viral fusion proteins has been extensively studied crystallographically, but the structures of the FP and TMD bound to phospholipid membranes are not well understood. We recently investigated the conformations and lipid interactions of the separate FP and TMD peptides of the parainfluenza virus 5 (PIV5) fusion protein F using solid-state NMR...
October 21, 2016: Biochemistry
Alexander S Falk, Ansgar B Siemer
Several amyloid fibrils have cores framed by highly dynamic, intrinsically disordered, domains that can play important roles for function and toxicity. To study these domains in detail using solid-state NMR spectroscopy, site-specific resonance assignments are required. Although the rapid dynamics of these domains lead to considerable averaging of orientation-dependent NMR interactions and thereby line-narrowing, the proton linewidths observed in these samples is far larger than what is regularly observed in solution...
October 20, 2016: Journal of Biomolecular NMR
Jean-Marie E P Cols, Cameron E Taylor, Kevin J Gagnon, Simon J Teat, Ruaraidh D McIntosh
The synthesis and full characterisation of four discrete tetrametallic titanium complexes is reported. These well-defined compounds are isostructural in the solid state and share the same general formula: Ti4(μ-O)2L4 (L = 1, 2, 3 or 4). Using a combination of NMR techniques the complexes are found to be stable in solution, even at elevated temperatures. Further studies show that the carboxylate moieties of the supporting amine bis(phenolate) ligands can be displaced by a more strongly coordinating solvent...
October 21, 2016: Dalton Transactions: An International Journal of Inorganic Chemistry
Sujin Seo, Huiyeong Ju, Seulgi Kim, In-Hyeok Park, Eunji Lee, Shim Sung Lee
Homo- and heteronuclear group 12 metal (Zn(2+), Cd(2+), and Hg(2+)) complexes 1-6 containing a newly designed 18-membered N2O2S2 macrocycle incorporating two pyridine subunits (L) were prepared and structurally characterized. The individual complexes isolated exhibit unusual stoichiometries, geometries, oxidation states, and structural topologies and include an infinite mercurous complex and a heteronuclear dumbbell-shaped complex. Both the Zn(II) complex [Zn(L)][ZnBr4] (1) and the Cd(II) complex [Cd(L)Br2] (2) are mononuclear, with the metal ion located inside the macrocyclic cavity...
October 20, 2016: Inorganic Chemistry
Oleg M Michurin, Sergii Afonin, Marina Berditsch, Constantin G Daniliuc, Anne S Ulrich, Igor V Komarov, Dmytro S Radchenko
Conformationally constrained non-racemizing trifluoromethyl-substituted lysine isosteres [(E)- and (Z)-TCBLys] with charged side chains are presented as a new type of (19) F-NMR labels for peptide studies. Design of the labels, their synthesis, incorporation into peptides and experimental demonstration of their application for solid state NMR studies of membrane-active peptides are described. A series of fluorine-labeled analogues of the helical amphipathic antimicrobial peptide PGLa(Nle) was obtained, in which different lysine residues in the original peptide sequence were replaced, one at a time, by either (E)- or (Z)-TCBLys...
October 20, 2016: Angewandte Chemie
Matthias Lehmann, Philipp Maier, Matthias Grüne, Markus Hügel
The molecular design of crowded hexasubstituted star mesogens based on a benzene core and alternating substitution with oligo(phenylenevinylene) arms and aryl units generates free space between the conjugated arm scaffolds. Various arylcarboxy building blocks, decorated with alkoxy chains have been incorporated in the void by mixing, hydrogen bonding or covalent bonds to the aryl groups. The mesogens assemble in columnar stacks ranging from soft crystals to rectangular and hexagonal columnar liquid crystals, revealed by polarized optical microscopy, differential scanning calorimetry, X-ray scattering and modelling...
October 20, 2016: Chemistry: a European Journal
Han-Xiao Wang, Shu-Zhen Hu, Qiang Shi, Chuan-Feng Chen
With an expanded electron-rich cavity and a fixed conformation, macrocycle H was found to encapsulate π-extended viologens G1-G4 to form the first case of pseudo[3]rotaxanes based on oxacalixarenes. The complexation was investigated in detail both in solution and in the solid state using NMR spectroscopy and X-ray crystallography. Due to the three-dimensional nonsymmetric structure of H, three orientational isomers of the pseudorotaxanes could be expected theoretically. However, as the crystal structure analysis revealed, only one of the three isomers was obtained with either G1 or G3...
October 20, 2016: Organic & Biomolecular Chemistry
Yuanrong Xin, Junji Sakamoto, André J van der Vlies, Urara Hasegawa, Hiroshi Uyama
This data article provides supplementary figures to the research article entitled, "Phase separation approach to a reactive polycarbonate monolith for "click" modifications" (Xin et al., Polymer, 2015, doi:10.1016/j.polymer.2015.04.008). Here, the nitrogen adsorption/desorption isotherms of the prepared porous polycarbonate monolith are shown to classify its inner structure and calculate the specific surface area. The monoliths were modified by using the thiol-ene click chemistry and the olefin metathesis, which was examined by contact angle measurements, FT-IR, solid state (13)C NMR spectroscopy as well as thermogravimetric analysis...
June 2016: Data in Brief
Stephan Ingmar Brückner, Sergii Donets, Arezoo Dianat, Manfred Bobeth, Rafael Gutierrez, Gianaurelio Cuniberti, Eike Brunner
Understanding the molecular interactions between inorganic phases such as silica and organic material is fundamental for chromatographic applications, for tailoring silica-enzyme interactions, and for elucidating the mechanisms of biomineralization. The formation, structure, and properties of the organic/inorganic interface is crucial in this context. Here, we investigate the interaction of selectively (13)C-labeled choline with (29)Si-labeled monosilicic acid/silica at the molecular level. Silica/choline nanocomposites were analyzed by solid-state NMR spectroscopy in combination with extended molecular dynamics (MD) simulations to understand the silica/organic interface...
October 19, 2016: Langmuir: the ACS Journal of Surfaces and Colloids
Dipankar Sahoo, Mihai Peterca, Emad Aqad, Benjamin E Partridge, Paul A Heiney, Robert Graf, Hans W Spiess, Xiangbing Zeng, Virgil Percec
Perylene bisimide derivatives (PBIs) are known to form only columnar or lamellar assemblies. There is no known example of a PBI self-assembling into a supramolecular sphere. Therefore, periodic and quasiperiodic arrays generated from spherical assemblies produced from PBIs are also not known. Here, a PBI functionalized at its imide groups with a second generation self-assembling dendron is reported to self-assemble into supramolecular spheres. These spheres self-organize in a body-centered cubic (BCC) periodic array, rarely encountered for self-assembling dendrons but often encountered in block copolymers...
October 19, 2016: Journal of the American Chemical Society
D Han, M Joksch, M Klahn, A Spannenberg, H-J Drexler, W Baumann, H Jiao, R Knitsch, M R Hansen, H Eckert, T Beweries
The synthesis of 3,5-disubstituted cyclometalated iridium(iii) hydrido complexes of the type [3,5-R2(POCOP)IrHX] (3,5-R2(POCOP) = κ(3)-C5HR2-2,6-(OPtBu2)2 with R = t-Bu, COOMe; X = Cl, H) is described. All complexes were investigated in the catalytic dehydrogenation of hydrazine borane and compared with the unsubstituted compounds [(POCOP)IrHX] (X = Cl, H). All catalysts are highly active and recyclable, clearly maintaining hydrogen production activity. The dehydrogenation products were structurally characterised by solid state NMR and FTIR spectroscopy...
October 19, 2016: Dalton Transactions: An International Journal of Inorganic Chemistry
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