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Magnetic Resonance in Chemistry: MRC

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https://www.readbyqxmd.com/read/28921712/a-review-of-nmr-methods-used-in-the-study-of-the-structure-and-dynamics-of-ionic-liquids
#1
Raju Nanda, Krishnan Damodaran
Recently, NMR spectroscopy has been emerging out as a powerful tool to study the structure and dynamics of ionic liquids (ILs) and ILs-Li(+) salt mixtures. This mini-review primarily focuses on the applications of various NMR spectroscopic techniques such as self-diffusion measurements, NMR relaxometry, two-dimensional NMR and other novel NMR approaches to study the structure and dynamics of ILs and its mixtures with lithium salts.
September 18, 2017: Magnetic Resonance in Chemistry: MRC
https://www.readbyqxmd.com/read/28921691/quantitative-determination-and-validation-of-octreotide-acetate-using-1-h-nmr-spectroscopy-with-internal-standard-method
#2
Chen Yu, Qian Zhang, Peng-Yao Xu, Yin Bai, Wen-Bin Shen, Bin Di, Meng-Xiang Su
Quantitative nuclear magnetic resonance (qNMR) is a well-established technique in quantitative analysis. We presented a validated (1) H quantitative nuclear magnetic resonance ((1) H-qNMR) method for assay of octreotide acetate (OCT-Ac), a kind of cyclic octopeptide. Deuterium oxide was used to remove the undesired exchangeable peaks, which was referred to as proton exchange, in order to make the quantitative signals isolated in the crowded spectrum of the peptide and ensure precise quantitative analysis. Gemcitabine hydrochloride was chosen as the suitable internal standard (IS)...
September 15, 2017: Magnetic Resonance in Chemistry: MRC
https://www.readbyqxmd.com/read/28913938/application-of-craft-complete-reduction-to-amplitude-frequency-table-in-non-uniformly-sampled-nus-two-dimensional-nmr-data-processing
#3
Krish Krishnamurthy, Natarajan Hari
The recently published CRAFT (Complete Reduction to Amplitude Frequency Table) technique converts the raw FID data (i.e., time domain data) into a table of frequencies, amplitudes, decay rate constants and phases. It offers an alternate approach to decimate time-domain data, with minimal pre-processing step. It has been shown that application of CRAFT technique to process the t1 dimension of the 2D data, significantly improved the detectable resolution by it ability to analyze without the use of ubiquitous apodization of extensively zero-filled data...
September 15, 2017: Magnetic Resonance in Chemistry: MRC
https://www.readbyqxmd.com/read/28879664/fast-simulations-of-multidimensional-nmr-spectra-of-proteins-and-peptides
#4
Thomas Vosegaard
To simulate full multidimensional NMR spectra of peptides and proteins in a reasonable time frame, a strategy for separating the time-consuming full-density matrix calculations from the chemical shift prediction and calculation of coupling patterns is presented. The simulation setup uses SIMPSON to calculate TOCSY transfer amplitudes and average distances as a source for NOESY transfer amplitudes. Simulated (1) H 1D, 2D TOCSY, and 2D NOESY NMR spectra of peptides with sequence PAGYN and NFGAIL and of ubiquitin are presented...
September 6, 2017: Magnetic Resonance in Chemistry: MRC
https://www.readbyqxmd.com/read/28876470/structure-elucidation-of-new-fusarielins-from-fusarium-sp-and-their-antimicrobial-activity
#5
Abdou Tchoukoua, Ryosuke Hasegawa, Kurniawan Andreas Hendracipta, Satoru Sato, Takuya Koseki, Yoshihito Shiono
Three new fusarielins, 3-epi-fusarielin H (1), 3-O-methyl-fusarielin H (2) and 3-O-methyl-epi-fusarielin H (3), were isolated from the fungus Fusarium sp. together with the known analogues, fusarielins F (4) and G (5). The structures of these compounds were elucidated by analysis of their MS, 1D and 2D NMR spectroscopic data. The new compounds exhibited weak antibacterial effect against Staphylococcus aureus.
September 6, 2017: Magnetic Resonance in Chemistry: MRC
https://www.readbyqxmd.com/read/28875542/analysis-on-the-local-structures-for-3d-1-impurities-ti-3-and-v-4-in-ktipo4
#6
C C Ding, S Y Wu, L J Zhang, Y Q Xu, Z H Zhang, M H Wu, B H Teng
Making use of the perturbation formulae for 3d(1) ions (Ti(3+) and V(4+) ) under orthorhombically compressed octahedra, the spin Hamiltonian parameters (SHPs) (g factors: gx , gy , gz and hyperfine structure constants: Ax , Ay , Az ) and local structures of the 3d(1) impurity centres C1 , C2 and C3 in KTP crystals are theoretically analyzed in a consistent way. The remarkable local distortions (i.e., the relative axial compression ratios 11.2%, 7.0% and 5.5% along Z axis and the relative planar bond length variation ratios 15...
September 6, 2017: Magnetic Resonance in Chemistry: MRC
https://www.readbyqxmd.com/read/28873503/large-scale-nmr-simulations-in-liquid-state-a-tutorial
#7
Ilya Kuprov
Liquid state NMR is the only class of magnetic resonance experiments for which the simulation problem is solved comprehensively for spin systems of any size. This paper contains a practical walkthrough for one of the many available simulation packages - Spinach. Its unique feature is polynomial complexity scaling: the ability to simulate large spin systems quantum mechanically and with accurate account of relaxation, diffusion, chemical processes and hydrodynamics. This paper is a gentle introduction written with a PhD student in mind...
September 5, 2017: Magnetic Resonance in Chemistry: MRC
https://www.readbyqxmd.com/read/28847042/fatty-acid-derivatives-from-the-halotolerant-fungus-cladosporium-cladosporioides
#8
Xiaoping Peng, Yi Wang, Guoliang Zhu, Weiming Zhu
Halotolerant fungus Cladosporium cladosporioides OUCMDZ-187 was isolated from mangrove plant Rhizophora stylosa collected in Shankou, Guangxi province of China. Three new fatty acid esters cladosporesters A-C (1-3), and five new fatty acids cladosporacids A-E (4-8), were isolated from the ethyl acetate extract of the fermentation broth of OUCMDZ-187 in a hypersaline (10% salt) medium. Their structures were elucidated by UV, IR, MS, specific rotation, 1D and 2D NMR data.
August 28, 2017: Magnetic Resonance in Chemistry: MRC
https://www.readbyqxmd.com/read/28847040/metabolic-effects-of-hedyotis-diffusa-on-rats-bearing-walker-256-tumor-revealed-by-nmr-based-metabolomics
#9
Zhiyong Wang, Kuo Gao, Can Xu, Jian Gao, Yujing Yan, Yingfeng Wang, Zhongfeng Li, Jianxin Chen
Hedyotis diffusa, a traditional Chinese herbal medicine, is widely used for oncotherapy and shows a positive effect in the clinical treatment. But its mechanism of anticancer activities is complicated and unclear. This study was undertaken to assess the therapeutic effects and reveal detailed mechanisms of H. diffusa for oncotherapy. A Walker 256 tumor-bearing rat model was established, and metabolomic profiles of plasma and urine were obtained from (1) H NMR technique. Multivariate statistical analysis methods were used to characterize the discriminating metabolites between control (C), Walker 256 tumor-bearing rats model (M), and H...
August 28, 2017: Magnetic Resonance in Chemistry: MRC
https://www.readbyqxmd.com/read/28833470/towards-unbiased-and-more-versatile-nmr-based-structure-elucidation-a-powerful-combination-of-case-algorithms-and-dft-calculations
#10
Alexei V Buevich, Mikhail E Elyashberg
Computer-Assisted Structure Elucidation (CASE) is comprised of two steps: 1) generation of all possible structural isomers for a given molecular formula and 2D NMR data (COSY, HSQC and HMBC), and 2) selection of the correct isomer based on empirical chemical shift predictions. This method has been very successful in solving structural problems of small organic molecules and natural products. However, CASE applications are generally limited to structural isomer problems and can sometimes be inconclusive due to insufficient accuracy of empirical shift predictions...
August 18, 2017: Magnetic Resonance in Chemistry: MRC
https://www.readbyqxmd.com/read/28809056/spindynamica-symbolic-and-numerical-magnetic-resonance-in-a-mathematica-environment
#11
Christian Bengs, Malcolm H Levitt
SpinDynamica is a set of Mathematica packages for performing numerical and symbolic analysis of a wide range of magnetic resonance experiments and phenomena. An overview of the SpinDynamica architecture and functionality is given, with some simple representative examples.
August 15, 2017: Magnetic Resonance in Chemistry: MRC
https://www.readbyqxmd.com/read/28806857/structure-elucidation-total-assignment-of-the-1-h-and-13-c-chemical-shifts-and-absolute-configuration-by-nmr-techniques-of-dammarane-type-triterpenes-from-hippocratea-volubilis
#12
LETTER
María L Kennedy, Atteneri López-Arencibia, María Reyes-Batlle, Jacob Lorenzo-Morales, José E Piñero, Isabel L Bazzocchi, Ignacio A Jiménez
No abstract text is available yet for this article.
August 14, 2017: Magnetic Resonance in Chemistry: MRC
https://www.readbyqxmd.com/read/28783883/a-theoretical-and-nmr-lanthanide-induced-shift-lis-investigation-of-the-conformations-of-lactams
#13
Raymond J Abraham, Marco Filippi, Giovanni Petrillo, Paola Piaggio, Chiara Vladiskovic, Fernando Sancassan
Molecular mechanics (MM) with MMFF94 and MMX force-fields and ab initio (RHF/6-31G*,RHF/6-311G** and B3LYP/6-311G** ) calculations are used with LIS to investigate the conformations of N-methyl-2-pyrrolidone 1, N-methyl-2-piperidone 2, ε-caprolactam 3, γ-valerolactam (1,5-dimethyl-2-pyrrolidone) 4, 2-azetidinone 5, 4-methyl azetidinone 6, 4-phenyl azetidinone 7, and N-methyl-4-phenyl azetidinone 8. The Yb(fod)3 paramagnetic induced shifts of all the (1) H and (13) C nuclei are measured and the corresponding diamagnetic complexation shifts obtained by the addition of Lu(fod)3 ...
August 7, 2017: Magnetic Resonance in Chemistry: MRC
https://www.readbyqxmd.com/read/28778115/new-cyclic-2-3-sulfite-ester-derivatives-of-poststerone-discriminating-diastereomers-and-probing-spatial-proximities-by-nmr-and-dft-calculations
#14
LETTER
Attila Balázs, Attila Hunyadi, József Csábi, L M Viranga Tillekeratne, Ana Martins, Gábor Tóth
No abstract text is available yet for this article.
August 4, 2017: Magnetic Resonance in Chemistry: MRC
https://www.readbyqxmd.com/read/28762528/-19-f-nmr-isotropic-chemical-shift-for-efficient-screening-of-fluorinated-fragments-which-are-racemates-and-or-display-multiple-conformers
#15
Claudio Dalvit, Stefan Knapp
Fluorine ligand-based NMR spectroscopy is now an established method for performing binding screening against a macromolecular target. Typically, the transverse relaxation rate of the fluorine signals is monitored in the absence and presence of the target. However, useful structural information can sometimes be obtained from the analysis of the fluorine isotropic chemical shift. This is particularly relevant for molecule that are racemates and/or display multiple conformers. The large difference in fluorine isotropic chemical shift between free and bound state deriving mainly from the breaking and/or making of intramolecular and/or intermolecular hydrogen bonds allows the detection of very weak affinity ligands...
August 1, 2017: Magnetic Resonance in Chemistry: MRC
https://www.readbyqxmd.com/read/28755418/a-13-c-nmr-method-for-determining-secondary-nitroxide-substrate-associations
#16
Nicholas A Eddy, Michael S Martin, Pranjali Ichalkaranje, Martha D Morton
The major effects of nitroxides on substrates in proton spectra is well studied, while the effect on carbon spectra has received less attention. Present knowledge relies on chemical shift differences between diamagnetic and paramagnetic solutions of the substrates to propose interactions. Changes in scalar coupling constants (JCH ) would, however, provide better insight. Herein, we present a method of utilizing coupled (13) C NMR spectra where differences in (1) JCH coupling show alternate modes of association between nitroxides and test substrates...
July 28, 2017: Magnetic Resonance in Chemistry: MRC
https://www.readbyqxmd.com/read/28752526/dynamic-properties-of-imidazolium-orthoborate-ionic-liquids-mixed-with-polyethylene-glycol-studied-by-nmr-diffusometry-and-impedance-spectroscopy
#17
Andrei Filippov, Nail Azancheev, Amal Gibaydullin, Shubhankar Bhattacharyya, Oleg N Antzutkin, Faiz Ullah Shah
We used (1) H pulsed field gradient (PFG) NMR to study the self-diffusion of polyethylene glycol (PEG) with average molecular mass of 200 and ions in mixtures of PEG with imidazolium bis(mandelato)borate (BMB) and imidazolium bis(oxalato)borate (BOB) ionic liquids (ILs). The ionic liquid was mixed with PEG in the concentration range of 0-100 wt%. Within the temperature range of 295 to 353 K, the diffusion coefficient of BMB is slower than that of the imidazolium cation. The diffusion coefficients of PEG, as well as the imidazolium cation and BMB anions, differ under all experimental conditions tested...
July 27, 2017: Magnetic Resonance in Chemistry: MRC
https://www.readbyqxmd.com/read/28736823/distinct-alignment-of-benzene-derivatives-in-stretched-polystyrene-and-polybutylacrylate-gels-specific-polymer-solute-interactions
#18
T Niklas, C Steinmetzger, F Rüttger, D Stalke, M John
We have measured the alignment of a range of benzene derivatives in cross-linked polystyrene and poly(butyl acrylate) using a small number of residual dipolar couplings and simple geometric considerations. For apolar solutes in polystyrene and protic solutes in poly(butyl acrylate), the preferred molecular orientation does not coincide with the longest molecular axis (steric aligment). This behavior may be explained by specific π-π and hydrogen bonding interactions between solute and polymer, respectively, the latter being confirmed by molecular dynamics simulations...
July 23, 2017: Magnetic Resonance in Chemistry: MRC
https://www.readbyqxmd.com/read/28731512/fast-and-simultaneous-determination-of-1-h-1-h-and-1-h-19-f-scalar-couplings-in-complex-spin-systems-application-of-psyche-homonuclear-broadband-decoupling
#19
Veera Mohana Rao Kakita, Kavitha Rachineni, Ramakrishna V Hosur
The present manuscript focuses on fast and simultaneous determination of (1) H-(1) H and (1) H-(19) F scalar couplings in fluorinated complex steroid molecules. Incorporation of broadband PSYCHE homonuclear decoupling in the indirect dimension of zero-quantum filtered diagonal experiments (F1-PSYCHE-DIAG) suppresses (1) H-(1) H scalar couplings, however it retains (1) H-(19) F scalar couplings (along F1-dimension) for the (19) F coupled protons while preserving the pure-shift nature for (1) H resonances uncoupled to (19) F...
July 21, 2017: Magnetic Resonance in Chemistry: MRC
https://www.readbyqxmd.com/read/28730621/multiple-homonuclear-band-selective-decoupling-nmr-fast-and-unambiguous-determination-of-diastereomeric-excess
#20
Kavitha Rachineni, Veera Mohana Rao Kakita, Ramakrishna V Hosur
Discrimination and quantification of chiral stereoisomers have been studied by different analytical methods and NMR has emerged as a powerful one with the advancements in pure-shift NMR methods. In the present manuscript, an al-F1F2-MHOBS-DIAG NMR method for the quantification of diastereomeric excess ratio (dr) has been proposed and demonstrated, using Hesperidin and Naringin mixtures. This method enables simultaneous quantification of dr at multiple resonances, in a single experiment, and it takes only ~10 min to record...
July 20, 2017: Magnetic Resonance in Chemistry: MRC
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