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Solid-state NMR

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https://www.readbyqxmd.com/read/28225610/intramolecular-energy-and-electron-transfer-within-a-diazaperopyrenium-based-cyclophane
#1
Xirui Gong, Ryan M Young, Karel J Hartlieb, Claire Miller, Yilei Wu, Hai Xiao, Peng Li, Nema Hafezi, Jiawang Zhou, Lin Ma, Tao Cheng, William A Goddard, Omar K Farha, Joseph T Hupp, Michael R Wasielewski, J Fraser Stoddart
Molecules capable of performing highly efficient energy transfer and ultrafast photo-induced electron transfer in well-defined multichromophoric structures are indispensable to the development of artificial photosynthetic systems. Herein, we report on the synthesis, characterization and photophysical properties of a rationally designed multichromophoric tetracationic cyclophane, DAPPBox(4+), containing a diazaperopyrenium (DAPP(2+)) unit and an extended viologen (ExBIPY(2+)) unit, which are linked together by two p-xylylene bridges...
February 22, 2017: Journal of the American Chemical Society
https://www.readbyqxmd.com/read/28225158/solid-state-17-o%C3%A2-nmr-reveals-hydrogen-bonding-energetics-not-all-low-barrier-hydrogen-bonds-are-strong
#2
Jiasheng Lu, Ivan Hung, Andreas Brinkmann, Zhehong Gan, Xianqi Kong, Gang Wu
While NMR and IR spectroscopic signatures and structural characteristics of low-barrier hydrogen bond (LBHB) formation are well documented in the literature, direct measurement of the LBHB energy is difficult. Here, we show that solid-state (17) O NMR spectroscopy can provide unique information about the energy required to break a LBHB. Our solid-state (17) O NMR data show that the HB enthalpy of the O⋅⋅⋅H⋅⋅⋅N LBHB formed in crystalline nicotinic acid is only 7.7±0.5 kcal mol(-1) , suggesting that not all LBHBs are particularly strong...
February 22, 2017: Angewandte Chemie
https://www.readbyqxmd.com/read/28225091/phase-separation-in-ceramide-np-containing-lipid-model-membranes-neutron-diffraction-and-solid-state-nmr
#3
Annett Schroeter, Sören Stahlberg, Barbora Školová, Stefan Sonnenberger, Adina Eichner, Daniel Huster, Kateřina Vávrová, Thomas Hauß, Bodo Dobner, Reinhard H H Neubert, Alexander Vogel
The stratum corneum is the outermost layer of the skin and protects the organism against external influences as well as water loss. It consists of corneocytes embedded in a mixture of ceramides, fatty acids, and cholesterol in a molar ratio of roughly 1 : 1 : 1. The unique structural and compositional arrangement of these stratum corneum lipids is responsible for the skin barrier properties. Many studies investigated the organization of these barrier lipids and, in particular, the exact conformation of ceramides...
February 22, 2017: Soft Matter
https://www.readbyqxmd.com/read/28224161/f-element-metalated-dipyrrins-synthesis-and-characterization-of-a-family-of-uranyl-bis-dipyrrinate-complexes
#4
Duer Bolotaulo, Alejandro Metta-Magaña, Skye Fortier
Using an improved, chromatography-free dipyrrin synthesis, the α,β-unsubstituted dipyrrins [RC(C4H2N)2H] (2) (R = tolyl (2toly(l)), p-OMe-C6H4 (2anis), mesityl (2mes), ferrocenyl (2Fc)) were isolated in good to excellent yields. Deprotonation of 2 with Na[N(SiMe3)2] gives the alkali metal salts [Na(DME)n][RC(C4H2N)2] (3) which reacts with UO2Cl2(THF)3 to give the uranyl bis(dipyrrinates) UO2[RC(C4H2N)2]2(L) (L = THF (4R-THF); DMAP (4R-DMAP)) (R = tolyl, p-OMe-C6H4, mesityl, ferrocenyl). The THF adducts, 4R-THF, are unstable in aromatic and nonpolar solvents and rapidly decompose to 2 and an intractable uranium-containing solid...
February 22, 2017: Dalton Transactions: An International Journal of Inorganic Chemistry
https://www.readbyqxmd.com/read/28224130/-1-h-nmr-spectra-dataset-and-solid-state-nmr-data-of-cowpea-vigna-unguiculata
#5
Elenilson G Alves Filho, Lorena M A Silva, Elizita M Teofilo, Flemming H Larsen, Edy S de Brito
In this article the NMR data from chemical shifts, coupling constants, and structures of all the characterized compounds were provided, beyond a complementary PCA evaluation for the corresponding manuscript (E.G. Alves Filho, L.M.A. Silva, E.M. Teofilo, F.H. Larsen, E.S. de Brito, 2017) [3]. In addition, a complementary assessment from solid-state NMR data was provided. For further chemometric analysis, numerical matrices from the raw (1)H NMR data were made available in Microsoft Excel workbook format (.xls)...
April 2017: Data in Brief
https://www.readbyqxmd.com/read/28221772/desleucyl-oritavancin-with-a-damaged-d-ala-d-ala-binding-site-inhibits-the-transpeptidation-step-of-cell-wall-biosynthesis-in-whole-cells-of-staphylococcus-aureus
#6
Sung Joon Kim, Manmilan Singh, Shasad Sharif, Jacob Schaefer
We have used solid-state NMR to characterize the exact nature of the dual mode of action of oritavancin in preventing cell-wall assembly in Staphylococcus aureu. Measurements performed on whole cells labeled selectively in vivo have established that des-N-methylleucyl-N-4-(4-fluorophenyl)benzyl-chloroeremomycin, an Edman degradation product of [19F]oritavancin, which has a damaged D-Ala-D-Ala binding aglycon, is a potent inhibitor of the transpeptidase activity of cell-wall biosynthesis. The desleucyl-drug binds to partially cross-linked peptidoglycan by a cleft formed between the drug aglycon and its biphenyl hydrophobic sidechain...
February 21, 2017: Biochemistry
https://www.readbyqxmd.com/read/28220918/cadmium-complexes-bearing-me2-n-e-o-e-s-se-organochalcogenoalkoxides-and-their-zinc-and-mercury-analogues
#7
Alexandra Pop, Clément Bellini, Răzvan Şuteu, Vincent Dorcet, Thierry Roisnel, Jean-François Carpentier, Anca Silvestru, Yann Sarazin
Heteroleptic zinc and cadmium complexes of the type [{(Me2)N^E^O(R2)}M-Nu]n (M = Zn, Cd; E = S, Se; R = CH3, CF3; Nu = N(SiMe3)2, I, Cl; n = 1-2) were prepared by reacting the alcohol proteo-ligands {(Me2)N^E^O(R2)}H with [M(N(SiMe3)2)2] (M = Zn, Cd) or [XMN(SiMe3)2] (M = Zn, X = Cl; M = Cd, X = I) in an equimolar ratio. These group 12 metal complexes were characterised in solution by multinuclear NMR spectroscopy and their solid-state structures were determined by X-ray diffractometry. The ligands {(Me2)N^E^O((CH3)2)}(-) bearing CH3 groups in α position to the alkoxide behave as κ(2)-O,E-bidentate moieties (E = S, Se) and form centro-symmetric dinuclear O-bridged heteroleptic alkoxo-amido complexes both with zinc and cadmium, with four-coordinate metal centres resting in tetrahedral environments...
February 21, 2017: Dalton Transactions: An International Journal of Inorganic Chemistry
https://www.readbyqxmd.com/read/28219822/ultrafast-acquisition-of-1-h-1-h-dipolar-correlation-experiments-in-spinning-elastomers
#8
Laetitia Rouger, Maxime Yon, Vincent Sarou-Kanian, Franck Fayon, Jean-Nicolas Dumez, Patrick Giraudeau
We show that two widely used 2D solid-state NMR (ssNMR) pulse sequences can be implemented in an ultrafast (UF) manner, and yield 2D spectra of elastomers in a single scan, under magic-angle spinning. UF 2D ssNMR provides an acceleration of one to several orders of magnitude for classic experiments.
February 9, 2017: Journal of Magnetic Resonance
https://www.readbyqxmd.com/read/28218526/dinuclear-metallacycles-with-single-m-x-m-bridges-x-cl-br-m-fe-ii-co-ii-ni-ii-cu-ii-zn-ii-cd-ii-strong-antiferromagnetic-superexchange-interactions
#9
Daniel L Reger, Andrea E Pascui, Elizabeth A Foley, Mark D Smith, Julia Jezierska, Agnieszka Wojciechowska, Sebastian A Stoian, Andrew Ozarowski
A series of monochloride-bridged, dinuclear metallacycles of the general formula [M2(μ-Cl)(μ-L)2](ClO4)3 have been prepared using the third-generation, ditopic bis(pyrazolyl)methane ligands L = m-bis[bis(1-pyrazolyl)methyl]benzene (Lm), M = Cu(II), Zn(II), and L = m-bis[bis(3,5-dimethyl-1-pyrazolyl)methyl]benzene (Lm*), M = Fe(II), Co(II), Ni(II), Cu(II), Zn(II), Cd(II). These complexes were synthesized from the direct reactions of M(ClO4)2·6H2O, MCl2, and the ligand, Lm or Lm*, in the appropriate stoichiometric amounts...
February 20, 2017: Inorganic Chemistry
https://www.readbyqxmd.com/read/28217261/affinity-of-rimantadine-enantiomers-against-influenza-a-m2-protein-revisited
#10
Antonios Drakopoulos, Christina Tzitzoglaki, Chulong Ma, Kathrin Freudenberger, Anja Hoffmann, Yanmei Hu, Günter Gauglitz, Michaela Schmidtke, Jun Wang, Antonios Kolocouris
Recent findings from solid state NMR (ssNMR) studies suggested that the (R)-enantiomer of rimantadine binds to the full M2 protein with higher affinity than the (S)-enantiomer. Intrigued by these findings, we applied functional assays, such as antiviral assay and electrophysiology (EP), to evaluate the binding affinity of rimantadine enantiomers to the M2 protein channel. Unexpectedly, no significant difference was found between the two enantiomers. Our experimental data based on the full M2 protein function were further supported by alchemical free energy calculations and isothermal titration calorimetry (ITC) allowing an evaluation of the binding affinity of rimantadine enantiomers to the M2TM pore...
February 9, 2017: ACS Medicinal Chemistry Letters
https://www.readbyqxmd.com/read/28216999/solution-and-structural-binding-studies-of-phosphate-with-thiophene-based-azamacrocycles
#11
Syed A Haque, Rainier S Berkley, Frank R Fronczek, Md Alamgir Hossain
Two thiophene-based monocyclic receptors L1 and L2 have been studied for phosphate binding in solutions (D2O and DMSO-d6 ) by (1)H NMR and (31)P NMR titrations, and in the solid state by single crystal X-ray analysis. Results from (1)H NMR titrations suggest that the ligands bind phosphate anions in a 1:2 binding mode in DMSO-d6 , with the binding constants of 5.25 and 4.20 (in log K), respectively. The binding of phosphate to L1 and L2 was further supported by (31)P NMR in D2O at pH = 5.2. The crystal structure of the phosphate complex of L1 reveals unambiguous proof for the formation of a ditopic complex via multiple hydrogen bonds from NH···O and CH···O interactions...
August 2016: Inorganic Chemistry Communications
https://www.readbyqxmd.com/read/28215068/comprehensive-ms-and-solid-state-nmr-metabolomic-profiling-reveals-molecular-variations-in-native-periderms-from-four-solanum-tuberosum-potato-cultivars
#12
Wenlin Huang, Olga Serra, Keyvan Dastmalchi, Liqing Jin, Lijia Yang, Ruth E Stark
The potato (Solanum tuberosum L.) ranks third in worldwide consumption among food crops. Whereas disposal of potato peels poses significant challenges for the food industry, secondary metabolites in these tissues are also bioactive and essential to crop development. The diverse primary and secondary metabolites reported in whole tubers and wound-healing tissues prompted a comprehensive profiling study of native periderms from four cultivars with distinctive skin morphologies and commercial food uses. Polar and nonpolar soluble metabolites were extracted concurrently, analyzed chromatographically, and characterized with mass spectrometry; the corresponding solid interfacial polymeric residue was examined by solid-state 13C NMR...
February 18, 2017: Journal of Agricultural and Food Chemistry
https://www.readbyqxmd.com/read/28214103/tracking-the-evolution-and-differences-between-guest-induced-phases-of-ga-mil-53-via-ultra-wideline-69-71-ga-solid-state-nmr-spectroscopy
#13
Yue Zhang, Bryan E G Lucier, Victor V Terskikh, Renlong Zheng, Yining Huang
Ga-MIL-53 is a metal-organic framework (MOF) that exhibits a "breathing effect," in which the pore size and overall MOF topology can be influenced by temperature, pressure, and host-guest interactions. The phase control afforded by this flexible framework renders Ga-MIL-53 a promising material for guest storage and sensing applications. In this work, the structure and behavior of four Ga-MIL-53 phases (as, ht, enp and lt), along with CO2 adsorbed within Ga-MIL-53 at various loading levels, has been investigated using (69/71)Ga solid-state NMR (SSNMR) experiments at 21...
January 31, 2017: Solid State Nuclear Magnetic Resonance
https://www.readbyqxmd.com/read/28209384/non-homogeneous-distribution-of-al-3-in-doped-phosphate-glasses-revealed-by-27-al-31-p-solid-state-nmr
#14
G Tricot, B Doumert, B Revel, M Bria, J Trebosc, H Vezin
Solid state NMR is applied in this contribution on the xAl2O3-(50-x/2)Na2O-(50-x/2)P2O5 composition line (with 0<x<5mol%) in order to investigate the distribution of Al(3+) ions in Al2O3-doped sodium phosphate glasses. The structure was analysed by (i) (27)Al 1D-, 3Q-, DQ- MAS-NMR analysis and (ii) 1D (31)P, (27)Al((31)P) 2D D-HMQC MAS-NMR and 2D (31)P R-INADEQUATE technique. The (27)Al NMR results confirm the presence of six-coordinated aluminate as major aluminate species and indicate that Al(3+) ions are fully dissociated in the glass network...
February 9, 2017: Solid State Nuclear Magnetic Resonance
https://www.readbyqxmd.com/read/28205016/sensitivity-enhancement-for-membrane-proteins-reconstituted-in-parallel-and-perpendicular-oriented-bicelles-obtained-by-using-repetitive-cross-polarization-and-membrane-incorporated-free-radicals
#15
Sophie N Koroloff, Deanna M Tesch, Emmanuel O Awosanya, Alexander A Nevzorov
Multidimensional separated local-field and spin-exchange experiments employed by oriented-sample solid-state NMR are essential for structure determination and spectroscopic assignment of membrane proteins reconstituted in macroscopically aligned lipid bilayers. However, these experiments typically require a large number of scans in order to establish interspin correlations. Here we have shown that a combination of optimized repetitive cross polarization (REP-CP) and membrane-embedded free radicals allows one to enhance the signal-to-noise ratio by factors 2...
February 15, 2017: Journal of Biomolecular NMR
https://www.readbyqxmd.com/read/28201894/manipulating-and-probing-the-polarisation-of-a-methyl-tunnelling-system-by-field-cycling-nmr
#16
Bo Zhang, Sabah M M Abu-Khumra, Abdellah Aibout, Anthony J Horsewill
In NMR the polarisation of the Zeeman system may be routinely probed and manipulated by applying resonant rf pulses. As with spin-1/2 nuclei, at low temperature the quantum tunnelling states of a methyl rotor are characterised by two energy levels and it is interesting to consider how these tunnelling states might be probed and manipulated in an analogous way to nuclear spins in NMR. In this paper experimental procedures based on magnetic field-cycling NMR are described where, by irradiating methyl tunnelling sidebands, the polarisations of the methyl tunnelling systems are measured and manipulated in a prescribed fashion...
February 14, 2017: Journal of Chemical Physics
https://www.readbyqxmd.com/read/28201885/nmr-shieldings-from-density-functional-perturbation-theory-gipaw-versus-all-electron-calculations
#17
G A de Wijs, R Laskowski, P Blaha, R W A Havenith, G Kresse, M Marsman
We present a benchmark of the density functional linear response calculation of NMR shieldings within the gauge-including projector-augmented-wave method against all-electron augmented-plane-wave+local-orbital and uncontracted Gaussian basis set results for NMR shieldings in molecular and solid state systems. In general, excellent agreement between the aforementioned methods is obtained. Scalar relativistic effects are shown to be quite large for nuclei in molecules in the deshielded limit. The small component makes up a substantial part of the relativistic corrections...
February 14, 2017: Journal of Chemical Physics
https://www.readbyqxmd.com/read/28197589/an-unusual-nitride-network-of-aluminum-centered-octahedra-and-phosphorus-centered-tetrahedra-and-structure-determination-from-microcrystalline-samples
#18
Lukas Neudert, Frank Heinke, Thomas Bräuniger, Florian J Pucher, Gavin B Vaughan, Oliver Oeckler, Wolfgang Schnick
A new imidooxonitridophosphate AlP6O3x(NH)3-3xN9 with x ≈ 0.33 was synthesized under high-pressure high-temperature conditions. The crystal structure determination of the microcrystalline product involved a combination of electron microscopy, synchrotron X-ray diffraction and solid-state NMR. In the solid there are discrete AlN6 octahedra that interconnect imidophosphate layers. The network topology is unprecedented but is related to other nitride structures.
February 15, 2017: Chemical Communications: Chem Comm
https://www.readbyqxmd.com/read/28195721/gallium-iii-and-indium-iii-complexes-with-meso-monophosphorylated-porphyrins-synthesis-and-structure-a-first-example-of-dimers-formed-by-the-self-assembly-of-meso-porphyrinylphosphonic-acid-monoester
#19
Yulia Yu Enakieva, Marina V Volostnykh, Sergey E Nefedov, Gayane A Kirakosyan, Yulia G Gorbunova, Aslan Yu Tsivadze, Alla G Bessmertnykh-Lemeune, Christine Stern, Roger Guilard
The synthesis and structural characterization, both in solution by means of (1)H and (31)P NMR and UV-vis spectroscopies and in the solid state by X-ray diffraction on single crystal, of a series of gallium(III) and indium(III) meso-mono(diethoxyphosphoryl)porphyrins bearing different peripheral substituents as well as the corresponding monoesters and phosphonic acids are reported. This work describes the first example of the X-ray structure of a self-assembled dimer formed via strong binding between the oxygen atom of the phosphonate substituent and the gallium(III) cations of adjacent porphyrin molecules [Ga-O = 1...
February 14, 2017: Inorganic Chemistry
https://www.readbyqxmd.com/read/28195488/surface-sensitive-nmr-detection-of-the-sei-layer-on-reduced-graphene-oxide
#20
Michal Leskes, Gunwoo Kim, Tao Liu, Alison L Michan, Fabien Aussenac, Patrick Dorffer, Subhradip Paul, Clare P Grey
The solid electrolyte interphase (SEI) is detrimental for rechargeable batteries' performance and lifetime. Understanding its formation requires analytical techniques that provide molecular level insight. Here dynamic nuclear polarization (DNP) is utilized for the first time for enhancing the sensitivity of solid state NMR (ssNMR) spectroscopy to the SEI. The approach is demonstrated on reduced-graphene oxide (rGO) cycled in Li-ion cells in natural abundance and 13C-enriched electrolyte solvents. Our results indicate that DNP enhances the signal of outer SEI layers, enabling detection of natural abundance 13C spectra from this component of the SEI at reasonable timeframes...
February 14, 2017: Journal of Physical Chemistry Letters
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