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Magnetic Resonance in Chemistry: MRC

Aikaterini Koutsaviti, Efstathia Ioannou, Maria Couladis, Olga Tzakou, Vassilios Roussis
No abstract text is available yet for this article.
February 16, 2017: Magnetic Resonance in Chemistry: MRC
Ēriks Kupče, Ole W Sørensen
Two new related methods for tracking out the backbone of protonated (13) C nuclei are presented. 2BOB extracts an H2BC and an HSQC-type spectrum from one and the same data set, and the combined information of these two spectra tracks out the molecular backbone. The faster method, H2OBC, typically requiring only a few minutes of instrument time, yields a single spectrum with distinct and different phases imposed on the H2BC and one-bond peaks thus obviating the need to separate them in the absence of complicating spectral overlap...
February 16, 2017: Magnetic Resonance in Chemistry: MRC
David Soulsby, Jeryl A M Chica
We have developed a simple, direct and novel method for the determination of partition coefficients and partitioning behavior using (1) H NMR spectroscopy combined with time domain complete reduction to amplitude-frequency tables (CRAFT). After partitioning into water and 1-octanol using standard methods, aliquots from each layer are directly analyzed using either proton or selective excitation NMR experiments. Signal amplitudes for each compound from each layer are then extracted directly from the time domain data in an automated fashion and analyzed using the CRAFT software...
February 9, 2017: Magnetic Resonance in Chemistry: MRC
Alexander K Osipov, Alexander A Aniskov, Vyacheslav S Grinev, Alevtina Yu Yegorova
The structure and configuration of the series of previously unknown arylaminomethylidenefuran-2(3H)-ones have been determined in solution by (1) H, (13) C, (15) N NMR spectroscopy including two-dimensional experiments such as (1) H-(1) H COSY, dqCOSY, (1) H-(13) C HSQC, (1) H-(13) C HMBC. It was found, that synthesized substances exist as an equilibrium mixture of E- and Z-enamines in solution. It was established on the basis of DFT calculations, that the exchange between the two push-pull enamines is a simple rotation around exocyclic partial double bond which depends on the effect of the solvents...
February 8, 2017: Magnetic Resonance in Chemistry: MRC
Gray Martin
No abstract text is available yet for this article.
January 23, 2017: Magnetic Resonance in Chemistry: MRC
Raine Garrido, Jean Pierre Soubal, Leonid Torres, Ubel Ramirez, Vicente Vérez
The polysaccharides modification via carbodiimide reaction is one of most applied method for obtaining conjugated vaccines against Salmonella enterica. However, N-acylurea carbodiimide adduct generated in the process is a critical impurity in carbohydrate-based vaccines. A quantitative NMR method was developed for assessing the N-acylurea carbodiimide adduct impurity. The procedure was based on line-fitting facilities for processing the NMR signals on complex spectra. The method showed good linearity, accuracy and precision under inter-operator variation (relative standard deviation <5%)...
January 14, 2017: Magnetic Resonance in Chemistry: MRC
Rubria Marlen Martínez-Casares, Herminia Inés Pérez Méndez, Norberto Manjarrez Alvarez, Ernesto Sánchez Mendoza, Aida Solís Oba, Liliana Hernández Vázquez
No abstract text is available yet for this article.
January 14, 2017: Magnetic Resonance in Chemistry: MRC
E Etienne, N Le Breton, M Martinho, E Mileo, V Belle
Site Directed Spin Labeling (SDSL) combined with continuous wave Electron Paramagnetic Resonance (cw EPR) spectroscopy is a powerful technique to reveal, at the residue level, structural transitions in proteins. SDSL-EPR is based on the selective grafting of a paramagnetic label on the protein under study, followed by cw EPR analysis. To extract valuable quantitative information from SDSL-EPR spectra and thus give reliable interpretation on biological system dynamics, numerical simulations of the spectra are required...
January 12, 2017: Magnetic Resonance in Chemistry: MRC
Louis Evelyne, Francois-Xavier Cantrelle, Liesbet Mesotten, Gunter Reekmans, Liene Bervoets, Karolien Vanhove, Michiel Thomeer, Guy Lippens, Peter Adriaensens
Accurate identification and quantification of human plasma metabolites can be challenging in crowded regions of the NMR spectrum with severe signal overlap. Therefore, this study describes metabolite spiking experiments on the basis of which the NMR spectrum can be rationally segmented into well-defined integration regions, and this for spectrometers having magnetic field strengths corresponding to (1) H resonance frequencies of 400 MHz and 900 MHz. Subsequently, the integration data of a case-control dataset of 69 lung cancer patients and 74 controls were used to train a multivariate statistical classification model for both field strengths...
January 6, 2017: Magnetic Resonance in Chemistry: MRC
D David Jebaraj, Hideo Utsumi, A Milton Franklin Benial
The Electron Spin Resonance studies were carried out for 2 mM concentration of (14) N and (15) N -labeled 3-carbamoyl-2,2,5,5-tetramethyl-pyrrolidine-1-oxyl, 3-carboxy-2,2,5,5-tetramethyl-pyrrolidine-1-oxyl, 3-methoxycarbonyl-2,2,5,5-tetramethyl-pyrrolidine-1-oxyl and their deuterated nitroxyl radicals using X-band Electron Spin Resonance spectrometer. The ESR Line shape analysis was carried out. The Electron Spin Resonance parameters such as, linewidth, Lorentzian component, signal intensity ratio, rotational correlation time, hyperfine coupling constant and g-factor were estimated...
January 4, 2017: Magnetic Resonance in Chemistry: MRC
Núria Marcó, Roberto R Gil, Teodor Parella
A fast RDC-assisted strategy involving the simultaneous determination of scalar and total coupling constants from a single (1) JCH /(2) JHH -resolved NMR spectrum is reported. It is shown that the concerted use of the directly measured (1) DCH (for all CHn multiplicities) and (2) DHH residual dipolar couplings allows an on-the-fly assignment of diastereotopic CH2 protons, as well as of an efficient discrimination between all eight possible diastereoisomeric structures of strychnine, which contains six stereocenters...
January 2, 2017: Magnetic Resonance in Chemistry: MRC
Shiva Kalantari, Mohsen Nafar, Shiva Samavat, Mahmoud Parvin
The severity of IgA nephropathy (IgAN), the most common primary glomerulonephritis, is judged on the basis of histologic and clinical features. A limited number of studies have considered molecular signature of IgAN for this issue and no reliable biomarkers have been presented non-invasively for use in patient evaluations. This study aims to identify metabolite markers excreted in the urine and impaired pathways that are associated with a known marker of severity (proteinuria) to predict mild and severe stages of IgAN...
January 1, 2017: Magnetic Resonance in Chemistry: MRC
Hyeji Shin, Yeeun Park, Ji Hoon Choi, Young Ho Jeon, Youngjoo Byun, Sang Hyun Sung, Ki Yong Lee
No abstract text is available yet for this article.
January 1, 2017: Magnetic Resonance in Chemistry: MRC
Pau Nolis André Fredi, Teodor Parella
Selective Refocusing (GSERF or the recent PSYCHEDELIC) experiments were originally designed to determine all proton-proton coupling constants (JHH ) for a selected proton resonance. They work for isolated signals on which selective excitation can be successfully applied but, as happens in other selective experiments, fail for overlapped signals. To circumvent this limitation, a doubly-selective TOCSY-GSERF scheme is presented for the measurement of JHH in protons resonating in crowded regions. This new experiment takes advantage of the editing features of an initial TOCSY transfer to uncover hidden resonances that become accessible to perform the subsequent frequency-selective refocusing...
December 27, 2016: Magnetic Resonance in Chemistry: MRC
Wilson C Brooks, Noemi D Paguigan, Huzefa A Raja, Franklin J Moy, Nadja B Cech, Cedric J Pearce, Nicholas H Oberlies
Analysis of complex mixtures is a common challenge in natural products research. Quantitative nuclear magnetic resonance spectroscopy (qNMR) offers analysis of complex mixtures at early stages and with benefits that are orthogonal to more common methods of quantitation, including ultraviolet absorption spectroscopy (UV) and mass spectrometry (MS). Several experiments were conducted to construct a methodology for use in analysis of extracts of fungal cultures. A broadly applicable method was sought for analysis of both pure and complex samples through use of an externally calibrated method...
December 26, 2016: Magnetic Resonance in Chemistry: MRC
Athanassios C Tsipis, Ioannis N Karapetsas
Highly predictive one parameter Quantitative Structure-Activity Relationship (QSAR) models have been developed for platinum based anticancer drugs using the (195) Pt NMR parameters as strong descriptors. The developed QSAR models were applied in diverse homogeneous sets of antiproliferative Pt(II) and Pt(IV) compounds. These observations form the basis for making predictions of cytotoxicity for a broad range of platinum based antitumor compounds just from inspection of calculated or experimentally determined (195) Pt NMR parameters...
December 21, 2016: Magnetic Resonance in Chemistry: MRC
Raffaele Lamanna, Giovanna Imparato, Paola Tano, Angela Braca, Mario D'Ercole, Giovanni Ghianni
Proton NMR profiling is nowadays a consolidated technique for the identification of geographical origin of food samples. The common approach consists in correlating NMR spectra of food samples to their territorial origin by multivariate classification statistical algorithms. In the present work, we illustrate an alternative perspective to exploit territorial information, contained in the NMR spectra, which is based on the implementation of a geographic information system (GIS). Nuclear magnetic resonance spectra are used to build a GIS map permitting the identification of territorial regions having strong similarities in the chemical content of the produced food (terroir units)...
December 17, 2016: Magnetic Resonance in Chemistry: MRC
Carla Rigling, Marc-Olivier Ebert
Residual dipolar couplings (RDCs) are a rich source of structural information that goes beyond the range covered by the nuclear Overhauser effect or scalar coupling constants. They can only be measured in partially oriented samples. RDC studies of peptides in organic solvents have so far been focused on samples in chloroform or DMSO. Here we show that stretched poly(vinyl acetate) can be used for the partial alignment of a linear β-peptide with proteinogenic side-chains in methanol. (1) DCH , (1) DNH , and (2) DHH RDCs were collected with this sample and included as restraints in a simulated annealing calculation...
December 15, 2016: Magnetic Resonance in Chemistry: MRC
Yan Guo, Meng Li, Peng Chen, Qiong Wu, Chun Gao, Yuxuan Lu, Liangren Zhang, Dan Yuan, Hongzheng Fu
No abstract text is available yet for this article.
December 14, 2016: Magnetic Resonance in Chemistry: MRC
Vladimir I Bakhmutov, Yuwei Kan, Javeed Ahmad Sheikh, Julissa González-Villegas, Jorge L Colón, Abraham Clearfield
Several layered zirconium phosphates treated with Zr(IV) ions, modified by monomethoxy-polyethyleneglycol-monophosphate and intercalated with doxorubicin hydrochloride have been studied by solid-state MAS NMR techniques. The organic components of the phosphates have been characterized by the (13) C{(1) H} CP MAS NMR spectra compared with those of initial compounds. The multinuclear NMR monitoring has provided to establish structure and covalent attachment of organic/inorganic moieties to the surface and interlayer spaces of the phosphates...
December 14, 2016: Magnetic Resonance in Chemistry: MRC
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