Read by QxMD icon Read

Magnetic Resonance in Chemistry: MRC

M Hahn, E von Elert, L Bigler, M D Díaz Hernández, N E Schloerer
No abstract text is available yet for this article.
July 13, 2018: Magnetic Resonance in Chemistry: MRC
Kazuo Furihata, Mitsuru Tashiro
Natural products such as polyketides often possess various spin systems, consisting of a methine group directly bonded to a methyl group (e.g. -CHA -CHB (CH3 )-CHC -). The methine proton HB splits into a broadened multiplet by coupling with several vicinal protons, rendering analysis difficult of n JH-H with respect to HB in DQF-COSY or E-COSY. For the purpose of measuring n JH-H in the aforesaid spin system, we have developed new techniques, named MDEC-J-resolved COSY and DPFGSE-MDEC-J-resolved COSY. This method incorporates MDEC (multi-frequency-homo-decoupling) pulse scheme into J-resolved COSY for the selective decouple of individual methyl groups, avoiding decoupling of the target protons resonating in methyl region...
July 11, 2018: Magnetic Resonance in Chemistry: MRC
Luca Fusaro
17 O-enriched complexes between oxydiacetate (ODA) ligand and several diamagnetic and paramagnetic lanthanide-(III) metal ions (Ln) were investigated by solution-state 17 O NMR spectroscopy. The bound-state signals of chelating (Oin ) and nonchelating (17 Out) oxygen atoms of the carboxylate groups were observed for all the samples investigated. The data indicate that the 17 O line width is dominated by contributions from both quadrupole relaxation and chemical exchange in the case of Pr and Nd complexes. Dissection of the chemical shift induced by metal ions on Oin into Fermi contact and pseudocontact contributions was performed and the hyperfine coupling constant (A/ℏ) was estimated...
July 10, 2018: Magnetic Resonance in Chemistry: MRC
Bin-Bin Gu, Yu-Han Gui, Li Liu, Zhi-You Su, Wei-Hua Jiao, Lei Li, Fan Sun, Shu-Ping Wang, Fan Yang, Hou-Wen Lin
A new asymmetric diketopiperazine dimer, Asperflocin (1), has been isolated from the fungus Aspergillus versicolor 16F-11. It's structure was determined by virtue of detailed spectroscopic analysis, Marfey's method, and 13 C NMR chemical shifts, [α]25 D , and TDDFT/ECD calculations. Cytotoxic activity test showed that 1 has moderate cytotoxic activity against A375 cell line with IC50 value of 10.29 ± 2.37 μM.
July 7, 2018: Magnetic Resonance in Chemistry: MRC
Aida R Contreras, Vladimir I Bakhmutov, Douglas W Elliott, Abraham Clearfield
For the first time, pore spaces in the Zr (IV) phosphonate (1) as a representative of layered metal (IV) phosphonate materials have been investigated by studying mobility of guest molecules, benzene-d6 and toluene-d8 . Guest molecules located in micro pores of 1 have been characterized by solid-state 13 C{1 H} and 2 H NMR spectra in static samples with varying temperatures. At moderately low temperatures, the benzene and toluene molecules experience fast isotropic reorientations, and show the motionally averaged liquid-like carbon and deuterium line shapes in the NMR spectra...
July 5, 2018: Magnetic Resonance in Chemistry: MRC
Youngshim Lee, Dongsoo Koh, Yoongho Lim
No abstract text is available yet for this article.
June 27, 2018: Magnetic Resonance in Chemistry: MRC
Paolo Sabatino, Min Gao, Jianbo Hou
13 C-NMR is a powerful tool for the detailed characterization and structure elucidation of polymeric samples. The low natural abundance and sensitivity of the 13 C isotope, however, lead to very long acquisition time, therefore limiting the use of such technique. We report here the implementation of a quantitative method, QA-RINEPT, for the characterization of polyol samples. The method, based on the well-known INEPT sequence, allows the boost in sensitivity of the carbon resonances without sacrificing the quantitative aspects of the analysis...
June 27, 2018: Magnetic Resonance in Chemistry: MRC
Teodor Parella
The development of new tools to improve the quality of NMR spectra is a challenging task. The concept of "perfect NMR" includes the design of robust pulse sequences that allow an investigator to obtain undistorted pure in-phase signals, with pure absorption lineshapes that are free of phase anomalies derived from undesired J modulations. The spin-echo is a fundamental tool in NMR spectroscopy allowing J evolution while δ effects are refocused and, therefore, potentially contributing to these phase distortions...
June 21, 2018: Magnetic Resonance in Chemistry: MRC
Huong Giang Thi Nguyen, Vinh Ngoc Nguyen, Fadhil S Kamounah, Poul Erik Hansen
In a conventional Mannich reaction using piperidine, hydroxypiperidines, morpholine and N-methylpiperazine with usnic acid a deacetylation was observed resulting in a substitution at C-2, loss of an acetyl group and a Mannich base with a stabilized enol. The enol has a hydrogen bond to the nitrogen of the secondary amine. The structure was investigated by NMR and deuterium isotope effects on 13 C chemical shifts as well as with DFT calculations to study the changed hydrogen bond pattern. It was found that the hydrogen bond involving the OH-9 group in chloroform forms a strong hydrogen bond than in usnic acid itself and that this hydrogen bond becomes even stronger in the more polar solvent, dimethylsulfoxide...
June 19, 2018: Magnetic Resonance in Chemistry: MRC
Kenji Tomita, Sho Miyazaki, Kazuo Furihata, Masatoshi Nakajima, Tadao Asami
No abstract text is available yet for this article.
June 15, 2018: Magnetic Resonance in Chemistry: MRC
Durgesh Dubey, Smriti Chaurasia, Anupam Guleria, Sandeep Kumar, Dinesh Raj Modi, Ramnath Misra, Dinesh Kumar
Currently, there are no reliable clinical biomarkers available that can aid early differential diagnosis of reactive arthritis (ReA) from other inflammatory joint diseases. Metabolic profiling of synovial fluid (SF) -obtained from joints affected in ReA- holds great promise in this regard and will further aid monitoring treatment and improving our understanding about disease mechanism. As a first step in this direction, we report here the metabolite specific assignment of 1 H and 13 C resonances detected in the NMR spectra of SF samples extracted from human patients with established ReA...
June 15, 2018: Magnetic Resonance in Chemistry: MRC
Peter Bigler, Julien Furrer
Long-Range Heteronuclear Single Quantum Correlation (LR-HSQC) experiments may be applied as an alternative to Heteronuclear Multiple-Bond correlation (HMBC) experiments for detecting long-range correlations, but has never enjoyed popularity for that purpose. To the best of our knowledge, the exact reasons have not yet been fully established. For both experiments it is widely accepted that the evolution of proton-proton homonuclear couplings JHH' during the polarization transfer delays Δ leads to significant losses, and that the intensity of the observable coherence is zero when JHH' matches the condition Δ = 0...
June 15, 2018: Magnetic Resonance in Chemistry: MRC
Maryam Tabatabaei Anaraki, Myrna J Simpson, André J Simpson
No abstract text is available yet for this article.
June 15, 2018: Magnetic Resonance in Chemistry: MRC
Laura Castañar
No abstract text is available yet for this article.
June 8, 2018: Magnetic Resonance in Chemistry: MRC
Julian Ilgen, Lukas Kaltschnee, Christina M Thiele
Pure shift techniques have recently attracted much attention, as they have the ability to reduce spectral overlap and thus to simplify the analysis of complex and congested spectral regions. For peptides, band-selective pure shift approaches are often the most reasonable choice amongst these, when spectra need to be simplified along proton dimensions. Band-selective approaches, usually offer the highest sensitivity of all pure shift methods, albeit at the cost that signals can only be acquired in a single frequency region of the spectrum, in which protons are well isolated in the proton spectrum...
June 8, 2018: Magnetic Resonance in Chemistry: MRC
Keunhong Jeong, Sein Min, Heelim Chae, Sung Keon Namgoong
Parahydrogen is a potentially significant source of hyperpolarization. However, a heat exchanger at an ultralow temperature, which is normally sustained wastefully using liquid nitrogen, is essential for the generation of hyperpolarized parahydrogen. In order to cut down on the use of liquid nitrogen, we employed a cryogenic storage dewar as the key component of our home-built parahydrogen generator, which lasted over 20 days with a single filling. Small concentrations of an unsaturated compound in a mixture were identified by hydrogenation in a principle-based experiment involving the use of hyperpolarization and phase difference...
June 1, 2018: Magnetic Resonance in Chemistry: MRC
Vadim V Bardin
No abstract text is available yet for this article.
May 30, 2018: Magnetic Resonance in Chemistry: MRC
Chengchen Guo, Jeffery L Yarger
Gold nanoparticles have attracted considerable attention in recent research because of their wide applications in various fields such as material science, electrical engineering, physical science, and biomedical engineering. Researchers have developed many methods for synthesizing different kinds of gold nanoparticles, where the sizes and surface chemistry of the nanoparticles are considered to be the two key factors. Traditionally, the sizes of nanoparticles are determined by electron microscopy whereas the surface chemistry is characterized by optical spectroscopies such as infrared spectroscopy and Raman spectroscopy...
May 29, 2018: Magnetic Resonance in Chemistry: MRC
Carla I Nieto, Pilar Cabildo, M Ángeles García, Rosa M Claramunt, José Elguero, Ibon Alkorta
The X-ray crystal structure of 2-benzyl-1H-benzimidazole, 2BnBzIm, was determined at 293 K showing no dynamic phenomena (disorder) of any class. On the other hand, some 13 C NMR signals were absent in the CPMAS spectrum (100 MHz, 300 K). We decided to carry out variable-temperature SSNMR and discovered that the missing signals are ortho and meta carbons of the phenyl ring of the benzyl group. Line-shape analysis and the Eyring equation were used to determine the barrier, which was compared with the calculated DFT for the gas phase that it is much lower...
May 28, 2018: Magnetic Resonance in Chemistry: MRC
Reika Masuda, Abhishek Gupta, Tim Stait-Gardner, Gang Zheng, Allan Torres, William S Price
Conventionally, arrayed nuclear magnetic resonance experiments, such as diffusion and relaxation, are performed with the same number of scans (NS) at each iteration despite the signal-to-noise ratio being more than sufficient for many of the iterations. Here, we propose a simple yet effective approach that significantly shortens experimental times by varying NS through the arrayed experiments while keeping the signal-to-noise ratio essentially the same and retaining experimental accuracy.
May 19, 2018: Magnetic Resonance in Chemistry: MRC
Fetch more papers »
Fetching more papers... Fetching...
Read by QxMD. Sign in or create an account to discover new knowledge that matter to you.
Remove bar
Read by QxMD icon Read

Search Tips

Use Boolean operators: AND/OR

diabetic AND foot
diabetes OR diabetic

Exclude a word using the 'minus' sign

Virchow -triad

Use Parentheses

water AND (cup OR glass)

Add an asterisk (*) at end of a word to include word stems

Neuro* will search for Neurology, Neuroscientist, Neurological, and so on

Use quotes to search for an exact phrase

"primary prevention of cancer"
(heart or cardiac or cardio*) AND arrest -"American Heart Association"