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Magnetic Resonance in Chemistry: MRC

Amin Ordikhani Seyedlar, Siegfried Stapf, Carlos Mattea
The molecular dynamics of the room-temperature ionic liquid 1-butyl-3-methylimidazolium bis (trifluoromethylsulphonyl)imide (Bmim Tf2N) confined in porous glass is studied by NMR relaxometry and diffusometry, and is compared to its bulk dynamics over a wide temperature range. The molecular reorientation processes for anions and cations alike are found to be significantly affected by the presence of the glass interface at high temperatures. In this respect, the ionic liquid behaves similar to polar liquids where proton NMR relaxation is governed by reorientations mediated by translational displacements (RMTD)...
February 15, 2019: Magnetic Resonance in Chemistry: MRC
Valentin A Semenov, Dmitry O Samultsev, Leonid B Krivdin
A systematic DFT study of the accuracy factors (functionals, basis sets, solvent effects) for the computation of 15 N NMR chemical shifts has been performed in the series of condensed nitrogen containing heterocycles. The behavior of the most representative functionals was examined based on the benchmark calculations of 15 N NMR chemical shifts in the reference set of compounds. It was found that the best agreement with experiment was achieved with OLYP functional in combination with aug-pcS-3(N)//pc-2 locally dense basis set scheme providing MAE of 5...
February 15, 2019: Magnetic Resonance in Chemistry: MRC
Ajay Verma, Rashmi Parihar, Bikash Baishya
NMR is a fast method for obtaining a holistic snapshot of the metabolome and also offers quantitative information without separating the compounds present in a complex mixture. Identification of the metabolites present in a plant extract sample is a crucial step for all plant metabolomics studies. In the present work, we used various two dimensional (2D) NMR methods such as J-Resolved NMR, TOCSY, and HSQC NMR spectroscopy for the identification of thirty-six common metabolites present in Coriandrum sativum L...
February 14, 2019: Magnetic Resonance in Chemistry: MRC
Marc B Taraban, Daniel J Deredge, Margaret E Smith, Katharine T Briggs, Yu Li, Zhong-Xing Jiang, Patrick Wintrode, Yihua Bruce Yu
The conformational transition of a fluorinated amphiphilic dendrimer is monitored by the 1 H signal from water, alongside the 19 F signal from the dendrimer. High-field NMR data (chemical shift δ, self-diffusion coefficient D, longitudinal relaxation rate R1 , and transverse relaxation rate R2 ) for both dendrimer (19 F) and water (1 H) match each other in detecting the conformational transition. Among all parameters for both nuclei, water proton transverse relaxation rate R2 (1 H2 O) displays the highest relative scale of change upon conformational transition of the dendrimer...
February 11, 2019: Magnetic Resonance in Chemistry: MRC
Pierre Thureau, Simone Sturniolo, Miri Zilka, Fabio Ziarelli, Stéphane Viel, Jonathan Yates, Giulia Mollica
Structure determination of functional organic compounds remains a formidable challenge when the sample exists as a powder. NMR crystallography approaches based on the comparison of experimental and DFT-computed 1H chemical shifts have already demonstrated great potential for structure determination of organic powders, but limitations still persist. In this study we discuss the possibility of using 13C-13C dipolar couplings quantified on powdered theophylline at natural isotopic abundance with the help of dynamic nuclear polarisation, to realize a DFT-free, rapid, screening of a pool of structures predicted by AIRSS...
February 8, 2019: Magnetic Resonance in Chemistry: MRC
Qinghu Wang, Biligetu Pa, Juhua Gong, Wenqing Bao, Junsheng Hao, Yanhua Xu
From the CH2 Cl2 extract of Artemisia ordosica, two new phenylpropanoids, ordosicin A (9) and ordosicin B (10), was obtained in addition to two known phenylpropanoids [dihydroconiferyl alcohol (3) and coniferyl alcohol (4)]. Moreover, five flavonoids [5-hydroxy-7,4'-dimethoxyflavanone (5), 3,5-dihydroxy-7,4'-dimethoxyflavone (6), 5,4'-dihydroxy-7-methoxyflavanone (7), 5,4'-dihydroxy-7,3'-dimethoxyflavanone (8) and acacetin (11)] and two terpenoids [spathulenol (1) and uvaol (2)] were isolated and identified...
February 7, 2019: Magnetic Resonance in Chemistry: MRC
Pelin Pocan, Esmanur Ilhan, Mecit Halil Oztop
Confectionary gels are considered as composite gel systems composed of high amount of sugar and gelling agent such as gelatin or starch. D-Psicose is classified as a type of rare sugar which is a C-3 epimer of fructose and has 70% of the sweetness of sucrose with a caloric value of 0.39 kcal/g. Utilization of D-Psicose in food products is gaining particular interest due to its low caloric value. In this study, gelatin based soft candies were formulated and the effect of D-Psicose substitution was explored on the quality of the products...
February 7, 2019: Magnetic Resonance in Chemistry: MRC
Steven Parslow, Najlaa Almazrouei, Michael Newton, Elizabeth Dye, Robert Morris
Moisture content of foodstuffs are typically assessed by Titration or Near Infrared Spectroscopy which are labour intensive as a manual measurement or costly when automated. Magnetic Resonance offers a method for moisture evaluation but is also normally costly. In this work we revisit Look and Locker's "Tone Burst" experiment with a marginal oscillator to evaluate moisture content of powdered skimmed milk subjected to increased humidity. We refer to this technique as the Transient Effect Determination of Spin-Lattice (TEDSpiL) relaxation times...
February 1, 2019: Magnetic Resonance in Chemistry: MRC
Dennis Weidener, Kawarpal Singh, Bernhard Blümich
For optimization and control of pharmaceutically and industrially important reactions chemical information is required in real time. Instrument size, handling and operation costs are important criteria to be considered when choosing a suitable analytical method apart from sensitivity and resolution. This present study explores the use of a robust and compact NMR spectrometer to monitor the stereo-selective formation of α-fluoro-α,β-unsaturated esters from α-fluoro-β-keto esters via deprotonation and deacylation in real-time...
January 31, 2019: Magnetic Resonance in Chemistry: MRC
Raheel Ahmed, Hina Siddiqui, M Iqbal Choudhary, Ioannis P Gerothanassis
The radical-dependent oxidation of unsaturated fatty acids is a fundamental reaction in lipid chemistry, biochemistry and technology. We report herein the first successful application of 1 H-13 C HMBC NMR experiment for the identification and quantification of complex and minor (3.9 to 0.85 -per-cent) components of cis and trans primary hydroperoxide isomers of oxidized oleate and linoleate methyl esters in solution, without the need of laborious isolation of the individual components.
January 31, 2019: Magnetic Resonance in Chemistry: MRC
Federica Rossi, Nghia Tuan Duong, Manoj Kumar Pandey, Michele R Chierotti, Roberto Gobetto, Yusuke Nishiyama
Chemical shift anisotropy (CSA) is a sensitive probe of electronic environment at a nucleus and thus, it offers deeper insights into detailed structural and dynamics properties of different systems: e.g. chemical, biological and materials. Over the years, massive efforts have been made to develop recoupling methods that reintroduce CSA interaction under magic angle spinning (MAS) conditions. Most of them require slow or moderate MAS (≤ 20 kHz) and isotopically enriched samples. On the other hand, to the best of the authors' knowledge, no 13 C or 15 N CSA recoupling schemes at ultrafast MAS (≥60 kHz) suitable for cost-effective natural abundant samples have been developed...
January 26, 2019: Magnetic Resonance in Chemistry: MRC
Lien Vermeir, Arnout Declerck, Chak Ming To, Barbara Kerkaert, Paul Van der Meeren
A time-domain 1 H NMR relaxometry method was elaborated for the rapid microstructural characterization of mozzarella cheese. For this purpose, there is a strong need to know how the experimentally determined T2 relaxation time distribution can be related to specific constituents in mozzarella. In this study, a detailed investigation is offered for fresh and aged low-moisture mozzarella cheese, often applied as a pizza cheese, by application of both a conventional CPMG sequence and a FID-CPMG sequence. The relaxation behavior was further elucidated by addition of deuterium oxide and by mild heat treatment of samples...
January 24, 2019: Magnetic Resonance in Chemistry: MRC
Svenja M Ackermann, Dirk W Lachenmeier, Thomas Kuballa, Birk Schütz, Manfred Spraul, Mirko Bunzel
Both the German and European organic food markets are growing fast, and there is also a rising demand for organic chicken eggs. Consumers are willing to pay higher prices for organic eggs produced in an animal appropriate environment considering animal welfare. Strict labelling requirements do not prevent chicken eggs from being a subject of food fraud. Conventionally produced (barn/free-range) eggs can easily be mislabeled as organic eggs. Especially since the demand for organically produced chicken eggs is likely to exceed supply in the future, mislabeling appears to be a realistic scenario...
January 24, 2019: Magnetic Resonance in Chemistry: MRC
Pau Nolis, Teodor Parella
The practical aspects of some NMR experiments designed for the simultaneous acquisition of 2D COSY and 2D TOCSY spectra are presented and discussed. Several techniques involving afterglow-based, CTP-based and NOAH-based strategies for the collection of different FIDs within the same scan are evaluated and compared. These methods offer a faster recording of these spectra in small-molecule NMR when sensitivity is not a limiting factor, with a reduction in spectrometer time about 45%-60% when compared to the conventional sequential acquisition of the parent experiments...
January 24, 2019: Magnetic Resonance in Chemistry: MRC
Ronna Delgado-Altamirano, A Rojas, Esturau-Escofet Nuria
No abstract text is available yet for this article.
January 24, 2019: Magnetic Resonance in Chemistry: MRC
Simona Baroni, Maria Rosaria Ruggiero, Silvio Aime, Simonetta Geninatti Crich
1 H Fast-Field Cycling NMR relaxometry is proposed as a powerful method to investigate tumour stroma in vivo upon the administration of a Gd based contrast agent. To perform this study, a FFC-NMR equipment endowed with a wide bore magnet was used for the acquisition of Nuclear Magnetic Resonance Dispersion (NMRD) profiles on healthy muscle and tumour tissue in living mice. At magnetic field strengths < of ca. 1 MHz the differences in the relaxation rates of the intra- and extra- cellular compartment become of the same order of magnitude of the exchange rate across the cellular membranes...
January 24, 2019: Magnetic Resonance in Chemistry: MRC
Veronique Nelis, Arnout Declerck, Lien Vermeir, Mathieu Balcaen, Koen Dewettinck, Paul Van der Meeren
Water-in-oil-in-water (W/O/W) double emulsions are a promising technology for encapsulation applications of water soluble compounds with respect to functional food systems. Yet, molecular transport through the oil phase is a well-known problem for liquid-oil based double emulsions. The influence of network crystallization in the oil phase of W/O/W globules was evaluated by NMR- and laser light scattering experiments on both a liquid-oil based double emulsion and a solid-fat based double emulsion. Water transport was assessed by low resolution NMR-diffusometry and by an osmotically-induced swelling/shrinking experiment, whereas manganese ion permeation was followed by means of T2 -relaxometry...
January 22, 2019: Magnetic Resonance in Chemistry: MRC
Benjamin Radel, Edme Hardy, Zorana Djuric, Markus Mahlbacher, Michael Haist, Harald Müller
Not only in Low-Field NMR, Laplace inversion is a relevant and challenging topic. Considerable conceptual and technical progress has been made, especially for the inversion of data encoding two decay dimensions. Distortion of spectra by overfitting of even moderate noise is counteracted requiring a priori smooth spectra. In this contribution, we treat the case of simple and fast one-dimensional decay experiments which are repeated many times in a series in order to study the evolution of a sample or process...
January 22, 2019: Magnetic Resonance in Chemistry: MRC
Laura Febvay, Erwann Hamon, Raphaël Recht, Nicolas Andres, Mathilde Vincent, Dalal Aoudé-Werner, Hervé This
Roasting of Coffea arabica L. seeds gives rise to chemical reactions that produce more than 800 compounds, some being responsible for the desired organoleptic properties for which the beverage called "coffee" is known. In the industry, the "roasting profile", i.e. the times and temperatures applied, is key to influence the composition of roasted coffee beans and the flavour of the beverage made from them. The impact of roasting on the chemical composition of coffee has been the subject of numerous studies, including by NMR spectroscopy...
January 21, 2019: Magnetic Resonance in Chemistry: MRC
Niels de Roo, Sanne Wilmsen, Velitchka Mihaleva, Doris Jacobs, John van Duynhoven
The health benefits of black tea have been linked to polyphenol metabolites that target specific modes of action in the human body. A major bottleneck in unravelling the underlying mechanisms is the preparative isolation of these metabolites which hampers their structural elucidation and assessment of in vitro bioactivity. A SPE-prepLC-MS-LC-MS-NMR workflow was implemented for preparative isolation of conjugated valerolactone metabolites of catechin-based polyphenols from urine of black tea consumers. First, the urine was cleaned and pre-concentrated using an SPE method...
January 18, 2019: Magnetic Resonance in Chemistry: MRC
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