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Magnetic Resonance in Chemistry: MRC

Martin R M Koos, Hannes Feyrer, Burkhard Luy
Pulse sequences in NMR spectroscopy sometimes require the application of pulses with effective flip angles different from 90˚ and 180˚ Previously (Magn. Reson. Chem.), offset-compensated broadband excitation pulses with rf-amplitude-dependent effective flip angles (RADFA) were introduced that are applicable in such cases. However, especially rf-amplitude-restricted RADFA pulses turned out to perform not as good as desired in terms of achievable bandwidths. Here, a class of rf-amplitude-restricted RADFA pulses with linear phase slope is introduced that allows excitation over much larger bandwidths with better performance...
March 20, 2017: Magnetic Resonance in Chemistry: MRC
Bruno Guigas
SpecPad is a new device-independent software program for the visualization and processing of one- and two-dimensional NMR time domain (FID) and frequency domain (spectrum) data. It is the result of a project to investigate whether the novel programming language DART, in combination with Html5 Web technology, forms a suitable base to write an NMR data evaluation software which runs on modern computing devices such as Android, iOS, and Windows tablets as well as on Windows, Linux, and Mac OS X desktop PCs and notebooks...
March 12, 2017: Magnetic Resonance in Chemistry: MRC
Yulia B Monakhova, Bernd W K Diehl
Quantitative nuclear magnetic resonance (qNMR) is considered as a powerful tool for measuring the absolute amount of small molecules in complex mixtures. However, verification of the accuracy of such quantification is not a trivial task. In particular, preprocessing and integration steps are particularly challenging and potentially erroneous.A script was developed in Matlab environment to automate qNMR analysis. Verification of the results is based on two evolving integration profiles. The analysis of binary mixtures of internal standards as well as pharmaceutical products has shown that all common artifacts (phase and baseline distortion, impurities) can be easily recognized in routine qNMR experiments...
March 10, 2017: Magnetic Resonance in Chemistry: MRC
Rongfu Zhang, Indra D Sahu, Raven G Comer, Sergey Maltsev, Carole Dabney-Smith, Gary A Lorigan
KCNE1 is known to modulate the voltage-gated potassium channel α subunit KCNQ1 to generate slowly activating potassium currents. This potassium channel is essential for the cardiac action potential that mediates a heartbeat as well as the potassium ion homeostasis in the inner ear. Therefore it is important to know the structure and dynamics of KCNE1 to better understand its modulatory role. Previously the Sanders group solved the three-dimensional structure of KCNE1 in LMPG micelles, which yielded a better understanding of this KCNQ1/KCNE1 channel activity...
February 23, 2017: Magnetic Resonance in Chemistry: MRC
Esa Haapaniemi
The (1) H, (13) C{(1) H}, and (31) P NMR spectral parameters of some pyrophosphates were determined in CDCl3 . The most complicated (1) H spectrum can be solved fully only as (A3 MN)R6 XX'R6 '(MNA3 )', where R6 (= -N(CH3 )2 ) is coupled only to phosphorus (X). Second order coupling between phosphorus was found and solved with iterative analysis. A signal shape of one of the carbon resonance cannot be explained only with couplings. Explanation for exceptional shape was searched from molecular modeling results...
February 22, 2017: Magnetic Resonance in Chemistry: MRC
Jaspal Singh, Vineeta Rustagi, Shanrong Zhang, A Dean Sherry, D Gomika Udugamasooriya
The rate of water exchange between the inner-sphere of a paramagnetic ion and bulk water is an important parameter in determining the magnitude of the chemical exchange saturation transfer signal from paramagnetic CEST agents (paraCEST). This is governed by various geometric, steric, and ligand field factors created by macrocyclic ligands surrounding the paramagnetic metal ion. Our previous on-bead combinatorial studies of di-peptoid-europium(III)-DOTA-tetraamide complexes revealed that negatively charged groups in the immediate vicinity of the metal center strongly enhances the CEST signal...
February 21, 2017: Magnetic Resonance in Chemistry: MRC
Indrek Reile, Ruud L E G Aspers, Martin C Feiters, Floris P J T Rutjes, Marco Tessari
DOSY analysis can resolve analytes according to their molecular size, offering a complementary way to traditional 2D NMR spectroscopy in the study of chemical mixtures. Applications are, however, limited if analytes have similar shape and size, as is the case in isomer mixtures. Herein we show how solvent effects in methanol-d4 , a common solvent in NMR laboratories, allow to overcome this limitation and provide increased separation of isomeric compounds. Clear NMR signal separation of eight structurally related analytes within a molecular weight (MW) range of three units is demonstrated, allowing unambiguous analysis of a mixture that would have otherwise been unsuitable for DOSY...
February 20, 2017: Magnetic Resonance in Chemistry: MRC
Vadim Zorin, Michael A Bernstein, Carlos Cobas
The trends towards rapid NMR data acquisition, automated NMR spectrum analysis, and data processing and analysis by more naïve users combine to place a higher burden on data processing software to automatically process these data. Downstream data analysis is compromised by poor processing, and the automated processing algorithms must therefore be robust and accurate. We describe a new algorithm for automatic phase correction of frequency-domain, high-resolution NMR spectra. We show this to be reliable for data derived from a wide variety of typical NMR usages...
February 20, 2017: 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
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
A structural study of new diastereoisomeric 5'(R and S)-cyanohydrins nucleosides that are important intermediates for antibiotics and antimycotics, such as polyoxins and nikkomycins, was performed using experimental NMR, theoretical methods and 3D analysis. The structures of these compounds were elucidated, and modeling was based on the conformer with the local minimized energy. The calculated and experimentally determined values are in good agreement (Supporting Information).
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-labeled 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 electron spin resonance 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
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