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Solid state NMR

Dominik Suter, Luuk T C G van Summeren, Olivier Blacque, Koushik Venkatesan
C^C cyclometalated platinum(II) triplet emitters bearing electronically different N-heterocyclic carbenes-(1,3-diisopropyl-4-(trifluoromethyl)-imidazol-2-ylidene (d), 1,3-diisopropyl-benzimidazol-2-ylidene (e), and 1,3-diisopropyl-imidazol-2-ylidene (f))-as neutral ligands and biphenyl (bph) as well as its fluorinated derivative octafluorobiphenyl (oFbph) as dianionic cyclometalating ancillary ligand were synthesized and structurally characterized by 1 H, 13 C, 19 F, and 195 Pt NMR, single crystal X-ray diffraction, and HR-ESI-MS studies...
June 22, 2018: Inorganic Chemistry
H E Mason, E C Uribe, J A Shusterman
The development of multi-dimensional statistical methods has been demonstrated on variable contact time (VCT) 29Si{1H} cross-polarization magic angle spinning (CP/MAS) data sets collected using Carr-Purcell-Meiboom-Gill (CPMG) type acquisition. These methods utilize the transformation of the collected 2D VCT data set into a 3D data set and use tensor-rank decomposition to extract the spectral components that vary as a function of transverse relaxation time (T2) and CP contact time. The result is a data dense spectral set that can be used to reconstruct CP/MAS spectra at any contact time with a high signal to noise ratio and with an excellent agreement to 29Si{1H} CP/MAS spectra collected using conventional acquisition...
June 22, 2018: Physical Chemistry Chemical Physics: PCCP
Ieva Goldberga, Rui Li, Melinda J Duer
The extracellular matrix of a tissue is as important to life as the cells within it. Its detailed molecular structure defines the environment of a tissue's cells and thus their properties, including differentiation and metabolic status. Collagen proteins are the major component of extracellular matrices. Self-assembled collagen fibrils provide both specific mechanical properties to handle external stresses on tissues and, at the molecular level, well-defined protein binding sites to interact with cells. How the cell-matrix interactions are maintained against the stresses on the tissue is an important and as yet unanswered question...
June 22, 2018: Accounts of Chemical Research
Susanne Penzel, Albert A Smith, Matthias Ernst, Beat H Meier
Fast magic-angle spinning, coupled with 1 H detection is a powerful method to improve spectral resolution and signal to noise in solid-state NMR spectra. Commercial probes now provide spinning frequencies in excess of 100 kHz. Then, one has sufficient resolution in the 1 H dimension to directly detect protons, which have a gyromagnetic ratio approximately four times larger than 13 C spins. However, the gains in sensitivity can quickly be lost if the rotation angle is not set precisely. The most common method of magic-angle calibration is to optimize the number of rotary echoes, or sideband intensity, observed on a sample of KBr...
June 15, 2018: Journal of Magnetic Resonance
Brice J Albert, Chukun Gao, Erika L Sesti, Edward P Saliba, Nicholas Alaniva, Faith J Scott, Snorri Th Sigurdsson, Alexander B Barnes
Solid-state nuclear magnetic resonance (NMR) enables atomic resolution characterization of molecular structure and dynamics within complex heterogeneous samples, but it is typically insensitive. Dynamic nuclear polarization (DNP) increases NMR signal intensity by orders of magnitude and can be performed in combination with magic angle spinning (MAS) for sensitive, high-resolution spectroscopy. Here we report MAS DNP experiments, for the first time, within intact human cells with >40-fold DNP enhancement and a sample temperature below 6 K...
June 20, 2018: Biochemistry
Yue Wu, David M Halat, Fengxia Wei, Trevor Binford, Ieuan D Seymour, Michael W Gaultois, Sammy Shaker, John Wang, Clare P Grey, Anthony K Cheetham
Following the recent discovery of a new family of hybrid ABX3 perovskites where X = (H2POO)- (hypophosphite), we show a facile synthesis for mixed X-site formate perovskites of composition [GUA]Mn(HCOO)3-x(H2POO)x. We report two crystallographically distinct, partially ordered intermediate phases with x = 0.84 and 1.53, corresponding to ca. 30 and 50 mole % hypophosphite respectively. These phases are characterised by single-crystal XRD and solid-state NMR spectroscopy, and their magnetic properties are reported...
June 19, 2018: Chemistry: a European Journal
Maximilian Zinke, Pascal Fricke, Sascha Lange, Sophie Zinn-Justin, Adam Lange
Proton detection and fast magic-angle spinning have advanced biological solid-state NMR, allowing for the backbone assignment of complex protein assemblies with high sensitivity and resolution. However, so far no method has been proposed to detect intermolecular interfaces in these assemblies by proton detection. Here, we introduce a concept based on methyl-labeling that allows for the assignment of these moieties and for the study of protein-protein interfaces at atomic resolution.
June 19, 2018: Chemphyschem: a European Journal of Chemical Physics and Physical Chemistry
Margaret Phillips, Janet To, Toshio Yamazaki, Toshio Nagashima, Jaume Torres, Konstantin Pervushin
Aquaporins are integral membrane proteins that facilitate water flow across biological membranes. Their involvement in multiple physiological functions and disease states has prompted intense research to discover water channel activity modulators. However, inhibitors found so far are weak and/or lack specificity. For organic compounds, which lack of high electron-dense atoms, the identification of binding sites is even more difficult. Nuclear magnetic resonance spectroscopy (NMR) requires large amounts of the protein, and expression and purification of mammalian aquaporins in large quantities is a difficult task...
June 18, 2018: Journal of Biomolecular NMR
Jasmina Radoicic, Sang Ho Park, Stanley J Opella
Macrodiscs, which are magnetically alignable lipid bilayer discs with diameters of >30 nm, were obtained by solubilizing protein-containing liposomes with styrene-maleic acid copolymers. Macrodiscs provide a detergent-free phospholipid bilayer environment for biophysical and functional studies of membrane proteins under physiological conditions. The narrow resonance linewidths observed from membrane proteins in styrene-maleic acid macrodiscs advance structure determination by oriented sample solid-state NMR spectroscopy...
June 15, 2018: Biophysical Journal
Patrick C A van der Wel
Various recent developments in solid-state nuclear magnetic resonance (ssNMR) spectroscopy have enabled an array of new insights regarding the structure, dynamics, and interactions of biomolecules. In the ever more integrated world of structural biology, ssNMR studies provide structural and dynamic information that is complementary to the data accessible by other means. ssNMR enables the study of samples lacking a crystalline lattice, featuring static as well as dynamic disorder, and does so independent of higher-order symmetry...
April 20, 2018: Emerging Topics in Life Sciences
Long Wang, Gerald Kehr, Constantin G Daniliuc, Melanie Brinkkötter, Thomas Wiegand, Anna-Lena Wübker, Hellmut Eckert, Lei Liu, Jan Gerit Brandenburg, Stefan Grimme, Gerhard Erker
In solution the PCy3 /B(C6 F5 )3 pair is rapidly deactivated by nucleophilic aromatic substitution. In the solid state deactivation is effectively suppressed and the active frustrated phosphane/borane Lewis pair splits dihydrogen or adds to sulfur dioxide. A variety of phosphane/B(C6 F5 )3 pairs have been used to carry out active FLP reactions in the solid state. The reactions were analyzed by DFT calculations and by solid state NMR spectroscopy. The solid state dihydrogen splitting reaction was also carried out under near to ambient conditions with suspensions of the non-quenched phosphane/borane mixtures in the fluorous liquid perfluoromethylcyclohexane...
June 7, 2018: Chemical Science
Pavlo Bielytskyi, Daniel Gräsing, Kaustubh R Mote, Karthick Babu Sai Sankar Gupta, Shimon Vega, P K Madhu, A Alia, Jörg Matysik
In the present study, we exploit the light-induced hyperpolarization occurring on 13 C nuclei due to the solid-state photochemically induced dynamic nuclear polarization (photo-CIDNP) effect to boost the NMR signal intensity of selected protons via inverse cross-polarization. Such hyperpolarization transfer is implemented into 1 H-detected two-dimensional 13 C-1 H correlation magic-angle-spinning (MAS) NMR experiment to study protons in frozen photosynthetic reaction centers (RCs). As a first trial, the performance of such an experiment is tested on selectively 13 C labeled RCs from the purple bacteria of Rhodobacter sphaeroides...
June 8, 2018: Journal of Magnetic Resonance
Xiangyan Shi, Chinmayi Prasanna, Toshio Nagashima, Toshio Yamazaki, Konstantin Pervushin, Lars Nordenskiöld
Eukaryotic chromatin structure and dynamics play key roles in genomic regulation. In the current study, the secondary structure and intramolecular dynamics of human histone H4 (hH4) in the nucleosome core particle (NCP) and in a nucleosome array are determined by solid-state NMR (SSNMR). Secondary structure elements are successfully localized in the hH4 in the NCP precipitated with Mg2+. In particular, dynamics on nanosecond to microsecond and microsecond to millisecond timescales are elucidated, revealing diverse internal motions in the hH4 protein...
June 14, 2018: Angewandte Chemie
Ahmed S Abdel-Razek, Abdelaaty Hamed, Marcel Frese, Norbert Sewald, Mohamed Shaaban
Penicisteroid C , a new polyoxygenated steroid was isolated from co-cultivation of Streptomyces piomogenus AS63D and Aspergillus niger using solid-state fermentation on rice medium. Additional diverse eleven known metabolites were identified: Fumigaclavine C, fumiquinazoline C, physcion, methylsulochrin, methyllinoleate, glycerol linoleate, cerebroside A, thymine, adenine, thymidine and adenosine. The structure of penicisteroid C was determined by HRESIMS, 1D and 2D NMR data. The antimicrobial and in vitro cytotoxic activities of the microbial extract and penicisteroid C were reported as well...
June 11, 2018: Steroids
Pavel A Zhizhko, Andrey V Pichugov, Nikolai S Bushkov, Florian Allouche, Anton A Zhizhin, Dmitry N Zarubin, Nikolai A Ustynyuk
Grafting Ti(=NtBu)(Me2Pyr)2(py)2 (Me2Pyr = 2,5-dimethylpyrrolyl, py = pyridine) onto the surface of silica partially dehydroxylated at 700 °C gives a well-defined silica-supported Ti imido complex (≡SiO)Ti(=NtBu)(Me2Pyr)(py)2 fully characterized by IR, solid-state NMR, elemental and mass balance analyses. While stoichiometric imido-transfer reactivity is typical for Ti imides, the obtained surface complex is unique in that it enables catalytic transformations involving Ti imido and oxo intermediates. In particular, it efficiently catalyzes imidation of carbonyl compounds with N-sulfinylamines via oxo/imido heterometathesis...
June 14, 2018: Angewandte Chemie
Hyun Ho Lee, Jae Bin Lee, Yuwon Park, Kern Ho Park, Mahmut Sait Okyay, Dong-Seon Shin, Sunghwan Kim, Jongnam Park, Noejung Park, Byeong-Kwan An, Yoon Seok Jung, Hyun-Wook Lee, Kyu Tae Lee, Sung You Hong
Electrode materials exploiting multi-electron transfer processes are essential components for large scale energy storage systems. Organic-based electrode materials undergoing distinct molecular redox transformations can intrinsically circumvent the structural instability issue of conventional inorganic-based host materials associated with lattice volume expansion and pulverization. Yet, the fundamental mechanistic understanding of metal-organic coordination polymers toward the reversible electrochemical processes is still lacking...
June 14, 2018: ACS Applied Materials & Interfaces
Wenzheng Li, Qiang Wang, Jun Xu, Fabien Aussenac, Guodong Qi, Xingling Zhao, Pan Gao, Chao Wang, Feng Deng
γ-Al2O3 is an important catalyst and catalyst support of industrial interest. Its acid/base characteristics are correlated to the surface structure, which has always been an issue of concern. In this work, the complex (sub-)surface oxygen species on surface-selectively labelled γ-Al2O3 were probed by 17O dynamic nuclear polarization surface-enhanced NMR spectroscopy (DNP-SENS). Direct 17O MAS and indirect 1H-17O cross-polarization (CP)/MAS DNP experiments enable observation of the (sub-)surface bare oxygen species and hydroxyl groups...
June 14, 2018: Physical Chemistry Chemical Physics: PCCP
M G Montalbán, G Víllora, P Licence
Data presented in this article are related with the research paper entitled "Ecotoxicity assessment of dicationic versus monocationic ionic liquids as a more environmentally friendly alternative" [1]. The present article describes the synthesis steps and characterization data of a set of twenty-six imidazolium, pyrrolidinium and pyridinium-based ionic liquids (ILs) or molten salts: nine monocationic and seventeen dicationic. Specifically, the chemical structure of the compounds was confirmed by 1 H NMR, 13 C NMR and 19 F NMR spectroscopy and mass spectrometry (MS)...
August 2018: Data in Brief
P Cerreia Vioglio, P M J Szell, M R Chierotti, R Gobetto, D L Bryce
Despite the applicability of solid-state NMR to study the halogen bond, the direct NMR detection of 79/81 Br covalently bonded to carbon remains impractical due to extremely large spectral widths, even at ultra-high magnetic fields. In contrast, nuclear quadrupole resonance (NQR) offers comparatively sharp resonances. Here, we demonstrate the abilities of 79/81 Br NQR to characterize the electronic changes in the C-Br···N halogen bonding motifs found in supramolecular assemblies constructed from 1,4-dibromotetrafluorobenzene and nitrogen-containing heterocycles...
May 28, 2018: Chemical Science
Roc Matheu, Abolfazl Ghaderian, Laia Francas, Petko Chernev, Mehmed Ertem, Jordi Benet-Buchholz, Victor Batista, Michael Haumann, Carolina Gimbert-Suriñach, Xavier Sala, Antoni Llobet
The Ru complex [RuII(bda-κ-N2O2)(N-NH2)2], 1, (bda2- = (2,2'-bipyridine)-6,6'-dicarboxylate; N-NH2 = 4-(pyridin-4-yl)aniline) is used as a synthetic intermediate to prepare Ru-bda complexes that contain the NO+, acetonitrile (MeCN) or H2O ligands at oxidation states II and III. Complex 1 reacts with excess NO+ to form a Ru complex where the aryl amine ligands N-NH2 in 1 are transformed into diazonium salts (N-N2+ = 4-(pyridin-4-yl)benzenediazonium)) together with the formation of a new Ru-NO group at the equatorial zone, to generate [RuII(bda-κ-N2O)(NO)(N-N2)2]3+, 23+...
June 13, 2018: Chemistry: a European Journal
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