keyword
MENU ▼
Read by QxMD icon Read
search

NMR

keyword
https://www.readbyqxmd.com/read/28732341/chirp-excitation
#1
Navin Khaneja
The paper describes the design of broadband chirp excitation pulses. We first develop a three stage model for understanding chirp excitation in NMR. We then show how a chirp π pulse can be used to refocus the phase of the chirp excitation pulse. The resulting magnetization still has some phase dispersion in it. We show how a combination of two chirp π pulses instead of one can be used to eliminate this dispersion, leaving behind a small residual phase dispersion. The excitation pulse sequence presented here allows exciting arbitrary large bandwidths without increasing the peak rf-amplitude...
July 13, 2017: Journal of Magnetic Resonance
https://www.readbyqxmd.com/read/28732012/multi-approach-metabolomics-analysis-and-artificial-simplified-phytocomplexes-reveal-cultivar-dependent-synergy-between-polyphenols-and-ascorbic-acid-in-fruits-of-the-sweet-cherry-prunus-avium-l
#2
Mauro Commisso, Martino Bianconi, Flavia Di Carlo, Stefania Poletti, Alessandra Bulgarini, Francesca Munari, Stefano Negri, Matteo Stocchero, Stefania Ceoldo, Linda Avesani, Michael Assfalg, Gianni Zoccatelli, Flavia Guzzo
Fruits of the sweet cherry (Prunus avium L.) accumulate a range of antioxidants that can help to prevent cardiovascular disease, inflammation and cancer. We tested the in vitro antioxidant activity of 18 sweet cherry cultivars collected from 12 farms in the protected geographical indication region of Marostica (Vicenza, Italy) during two growing seasons. Multiple targeted and untargeted metabolomics approaches (NMR, LC-MS, HPLC-DAD, HPLC-UV) as well as artificial simplified phytocomplexes representing the cultivars Sandra Tardiva, Sandra and Grace Star were then used to determine whether the total antioxidant activity reflected the additive effects of each compound or resulted from synergistic interactions...
2017: PloS One
https://www.readbyqxmd.com/read/28731714/total-synthesis-and-structural-revision-of-chaetoviridins-a
#3
Mehdi Makrerougras, Romain Coffinier, Samuel Oger, Arnaud Chevalier, Cyrille Sabot, Xavier Franck
The first synthesis of the proposed structures of chaetoviridins A 1-4 has been achieved in 10 steps by controlling the syn- or anti-aldol side chain. The angular lactone has been regioselectively introduced by condensation of a chiral dioxin-4-one to cazisochromene. Comparison of the NMR and circular dichroism data of the synthesized and reported natural products led to the complete reassignment and renaming of the chaetoviridins.
July 21, 2017: Organic Letters
https://www.readbyqxmd.com/read/28731703/natural-poly-and-oligosaccharides-as-novel-delivery-systems-for-plant-protection-compounds
#4
Olga Selyutina, Irina Apanasenko, Salavat Khalikov, Nikolay E Polyakov
To increase the bioavailability of plant protection products we have applied new approach based on non-covalent association with natural water soluble polysaccharides and oligosaccharides as delivery systems (DSs). The mechanochemical technique has been applied to prepare the solid state nano-dispersed compositions of antidote 1,8-naphthalic anhydride (NA) with arabinogalactan, sodium salt of carboxymethylcellulose, and glycyrrhizin as DSs. The effect of DSs on the solubility and the penetration of NA into the seeds of barley and wheat has been investigated by various physicochemical techniques...
July 21, 2017: Journal of Agricultural and Food Chemistry
https://www.readbyqxmd.com/read/28731702/drude-polarizable-force-field-for-molecular-dynamics-simulations-of-saturated-and-unsaturated-zwitterionic-lipids
#5
Hui Li, Janamejaya Chowdhary, Lei Huang, Xibing He, Alexander D MacKerell, Benoît Roux
Additive force fields are designed to account for induced electronic polarization in a mean-field average way using effective empirical fixed charges. The limitation of this approximation is cause for serious concerns, particularly in the case of lipid membranes, where the molecular environment undergoes dramatic variations over microscopic length scales. A polarizable force field based on the classical Drude oscillator offers a practical and computationally efficient framework for an improved representation of electrostatic interactions in molecular simulations...
July 21, 2017: Journal of Chemical Theory and Computation
https://www.readbyqxmd.com/read/28731689/dinuclear-coordination-compounds-based-on-a-5-nitropicolinic-carboxylate-ligand-with-single-molecule-magnet-behavior
#6
Álvaro Raya-Barón, Itziar Oyarzabal, Francisco M Arrabal-Campos, José Manuel Seco, Antonio Rodríguez-Diéguez, Ignacio Fernández
Isostructural dinuclear dysprosium and yttrium coordination compounds based on the 5-nitropicolinic carboxylate ligand were synthesized and characterized. The formation of these air-stable complexes is achieved via solvothermal routes employing water as the reaction solvent. The dysprosium-based complex exhibits single-molecule magnet behavior with frequency dependence of the out-of-phase susceptibility at zero direct-current field. High-resolution mass spectrometry (electrospray ionization) experiments and advanced NMR methods including diffusion NMR techniques were applied on the diamagnetic yttrium analogue and established that these species retained their solid-state structure in solution with hydrodynamic radii of 6...
July 21, 2017: Inorganic Chemistry
https://www.readbyqxmd.com/read/28731688/the-%C3%AF-configuration-of-the-www-motif-of-a-short-trp-rich-peptide-is-critical-for-targeting-bacterial-membranes-disrupting-preformed-biofilms-and-killing-methicillin-resistant-staphylococcus-aureus
#7
D Zarena, Biswajit Mishra, Tamara Lushnikova, Fangyu Wang, Guangshun Wang
Tryptophan-rich peptides, being short and suitable for large-scale chemical synthesis, are attractive candidates for developing a new generation of antimicrobials to combat antibiotic-resistant bacteria (superbugs). Although there are numerous pictures for membrane-bound structure of a single tryptophan (W), how multiple Trp amino acids assemble themselves and interact with bacterial membranes are poorly understood. This communication presents the three-dimensional structure for an eight-residue Trp-rich peptide (WWWLRKIW-NH2 with 50% W) determined by the improved 2D NMR method, which includes the measurements of 13C and 15N chemical shifts at natural abundance...
July 21, 2017: Biochemistry
https://www.readbyqxmd.com/read/28731593/synthesis-characterization-and-efficient-catalytic-activities-of-a-nickel-ii-porphyrin-remarkable-solvent-and-substrate-effects-on-participation-of-multiple-active-oxidants
#8
Cheal Kim, Hye Ahn, Jeong Bae, Min Kim, Kwon Bok, Ha Jeong, Suk Lee
A new nickel(II) porphyrin complex, [NiII(porp)] (1) has been synthesized and characterized by 1H NMR, 13C NMR and mass spectrometry analysis. This NiII porphyrin complex 1 catalyzed quantitatively the epoxidation reaction of a wide range of olefins with meta-chloroperoxybenzoic acid (MCPBA) under mild conditions. Reactivity and Hammett studies, H218O-exchange experiments, and the use of PPAA (peroxyphenylacetic acid) as a mechanistic probe suggested that participation of multiple active oxidants NiII-OOC(O)R 2, NiIV-Oxo 3, and NiIII-Oxo 4 in olefin epoxidation reactions by nickel porphyrin complex is markedly affected by solvent polarity and concentration and type of substrate...
July 21, 2017: Chemistry: a European Journal
https://www.readbyqxmd.com/read/28731348/proton-transport-in-hierarchical-structured-nafion-membranes-a-nmr-study
#9
Hengrui Yang, Jin Zhang, Jingliang Li, San Ping Jiang, Maria Forsyth, Haijin Zhu
It is known that hierarchical structure plays a key role in many unique material properties such as self-cleaning effect of lotus leaves and the anti-fogging property of the compound eyes of mosquitoes. This study reports a series of highly ordered meso-porous Nafion membranes with unique hierarchical structural features at the nanometre scale. Using NMR, we show for the first time that at low RH conditions, the proton in the ionic domains migrates via a surface diffusion mechanism and exhibits approximately two orders of magnitude faster transport than that in the nano-pores, whereas the nano-pores play a role of reservoir and maintain water and thereby conductivity at higher temperature and lower humidities...
July 21, 2017: Journal of Physical Chemistry Letters
https://www.readbyqxmd.com/read/28731305/the-role-of-lead-ii-in-nucleic-acids
#10
Joana Palou-Mir, Miquel Barceló-Oliver, Roland K O Sigel
Although lead(II) is naturally not associated with nucleic acids, this metal ions has been applied with DNA and RNA in various contexts. Pb2+ is an excellent hydrolytic metal ion for nucleic acids, which is why it is mainly used as probing agent for secondary structure and to determine metal ion binding sites both in vitro and in vivo. A further application of lead(II) is in structural studies, i.e., NMR, but also in X-ray crystallography, mostly using this heavy metal to solve the phase problem in the latter method...
April 10, 2017: Metal Ions in Life Sciences
https://www.readbyqxmd.com/read/28731303/lead-ii-binding-in-natural-and-artificial-proteins
#11
Virginia Cangelosi, Leela Ruckthong, Vincent L Pecoraro
This article describes recent attempts to understand the biological chemistry of lead using a synthetic biology approach. Lead binds to a variety of different biomolecules ranging from enzymes to regulatory and signaling proteins to bone matrix. We have focused on the interactions of this element in thiolate-rich sites that are found in metalloregulatory proteins such as Pbr, Znt, and CadC and in enzymes such as δ-aminolevulinic acid dehydratase (ALAD). In these proteins, Pb(II) is often found as a homoleptic and hemidirectic Pb(II)(SR)3- complex...
April 10, 2017: Metal Ions in Life Sciences
https://www.readbyqxmd.com/read/28731268/-13-c-metabolic-flux-profiling-of-pichia-pastoris-grown-in-aerobic-batch-cultures-on-glucose-revealed-high-relative-anabolic-use-of-tca-cycle-and-limited-incorporation-of-provided-precursors-of-branched-chain-amino-acids
#12
Meng Zhang, Xiao-Wei Yu, Yan Xu, Paula Jouhten, G V T Swapna, Ralf W Glaser, John F Hunt, Gaetano T Montelione, Hannu Maaheimo, Thomas Szyperski
Carbon metabolism of Crabtree negative yeast Pichia pastoris was profiled using (13) C NMR to delineate regulation during exponential growth and to study the import of two precursors for branched-chain amino acid biosynthesis, α-ketoisovalerate and α-ketobutyrate. Cells were grown in aerobic batch cultures containing (i) only glucose, (ii) glucose along with the precursors, or (iii) glucose and Val. The study provided the following new insights. First, (13) C flux ratio analyses of central metabolism reveal an unexpectedly high anaplerotic supply of the tricarboxylic acid cycle for a Crabtree negative yeast, and show that a substantial fraction of glucose catabolism proceeds through the pentose phosphate pathway...
July 21, 2017: FEBS Journal
https://www.readbyqxmd.com/read/28731123/lasiodiplactone-a-a-novel-lactone-from-the-mangrove-endophytic-fungus-lasiodiplodia-theobromae-zj-hq1
#13
Senhua Chen, Zhaoming Liu, Hongju Liu, Yuhua Long, Dongni Chen, Yongjun Lu, Zhigang She
Lasiodiplactone A (1), an unprecedented lactone, was obtained from the mangrove endophytic fungus Lasiodiplodia theobromae ZJ-HQ1. The structure of 1 was established by analysis of NMR spectroscopic data and electronic circular dichroism (ECD) spectra. Lasiodiplactone A (1) was the first example of lactone that possesses a unique tetracyclic system (12/6/6/5) of RAL12 (12-membered β-resorcylic acid lactone) with a pyran ring and a furan ring. A possible biogenetic pathway for 1 was proposed. Compound 1 showed anti-inflammatory activity by inhibiting nitric oxide (NO) production in lipopolysaccharide activated in RAW264...
July 21, 2017: Organic & Biomolecular Chemistry
https://www.readbyqxmd.com/read/28731100/the-15-n-nmr-chemical-shift-in-the-characterization-of-weak-halogen-bonding-in-solution
#14
Sebastiaan B Hakkert, Jürgen Gräfenstein, Mate Erdelyi
We have studied the applicability of (15)N NMR spectroscopy in the characterization of the very weak halogen bonds of nonfluorinated halogen bond donors with a nitrogenous Lewis base in solution. The ability of the technique to detect the relative strength of iodine-, bromine- and chlorine-centered halogen bonds, as well as solvent and substituent effects was evaluated. Whereas computations on the DFT level indicate that (15)N NMR chemical shifts reflect the diamagnetic deshielding associated with the formation of a weak halogen bond, the experimentally observed chemical shift differences were on the edge of detectability due to the low molar fraction of halogen-bonded complexes in solution...
July 21, 2017: Faraday Discussions
https://www.readbyqxmd.com/read/28731076/simple-gd-3-neu5nac-complexation-results-in-nmr-chemical-shift-asymmetries-of-structurally-equivalent-complex-type-n-glycan-branches
#15
Konstantin Usachev, Yoshiki Yamaguchi, Masayuki Takamatsu, Nataliya Pavlova, Vladimir Klochkov, Almira Kurbangalieva, Takefumi Murase, Taiji Shimoda, Katsunori Tanaka
In the present Communication, we propose a quite simple but previously overlooked approach for conveniently analyzing, assigning, and extracting sialic acid-containing N-glycan structures using high-resolution NMR spectroscopy without pre-installing metal chelators. Paramagnetic metals, such as Gd(3+), appear to bind to the carboxyl groups of N-acetylneuraminic acid when introduced at room temperature, leading to the measurement of nonequivalent proton and carbon NMR spectral signals among otherwise "identical" glycan branched structures...
July 21, 2017: Analyst
https://www.readbyqxmd.com/read/28730816/multi-functional-octamethyltetrasila-2-2-cyclophanes-conformational-variations-circularly-polarized-luminescence-and-organic-electroluminescence
#16
Masaki Shimada, Yoshinori Yamanoi, Tatsuhiko Ohto, Song-Toan Pham, Ryo Yamada, Hirokazu Tada, Kenichiro Omoto, Shohei Tashiro, Mitsuhiko Shionoya, Mineyuki Hattori, Keiko Jimura, Shigenobu Hayashi, Hikaru Koike, Munetaka Iwamura, Koichi Nozaki, Hiroshi Nishihara
Both symmetrical and unsymmetrical cyclophanes containing disilane units, tetrasila[2.2]cyclophanes 1-9, were synthesized. The syn and anti conformation and the kinetics of inversion between two anti-isomers were investigated by X-ray diffraction and variable-temperature NMR analysis, respectively. The flipping motion of two aromatic rings was affected by the bulkiness of the aromatic moiety (1 vs 6), the phase (solid vs solution), and the inclusion by host molecules (1 vs 1⊂[Ag2L](2)(+)). The photophysical, electrochemical, and structural properties of the compounds were thoroughly investigated...
July 21, 2017: Journal of the American Chemical Society
https://www.readbyqxmd.com/read/28730621/multiple-homonuclear-band-selective-decoupling-nmr-fast-and-unambiguous-determination-of-diastereomeric-excess
#17
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
https://www.readbyqxmd.com/read/28730431/protocols-for-molecular-dynamics-simulations-of-rna-nanostructures
#18
Taejin Kim, Wojciech K Kasprzak, Bruce A Shapiro
Molecular dynamics (MD) simulations have been used as one of the main research tools to study a wide range of biological systems and bridge the gap between X-ray crystallography or NMR structures and biological mechanism. In the field of RNA nanostructures, MD simulations have been used to fix steric clashes in computationally designed RNA nanostructures, characterize the dynamics, and investigate the interaction between RNA and other biomolecules such as delivery agents and membranes.In this chapter we present examples of computational protocols for molecular dynamics simulations in explicit and implicit solvent using the Amber Molecular Dynamics Package...
2017: Methods in Molecular Biology
https://www.readbyqxmd.com/read/28730214/palladium-ii-complexes-of-n-n-diphenylacetamide-based-thio-selenoethers-and-flower-shaped-pd16s7-and-prismatic-pd17se15-nano-particles-tailored-as-catalysts-for-c-c-and-c-o-coupling
#19
Poornima Singh, Ajai K Singh
2-Bromo-N,N-diphenylacetamide (P1) prepared by reacting diphenylamine with α-bromoacetyl bromide, on treatment with Na2S and Na2Se generated in situ, has resulted in thio and selenoether ligands, L1 ((Ph2NCOCH2)2S) and L2 ((Ph2NCOCH2)2Se), respectively. Reacting these ligands with Na2PdCl4 in ethanol at room temperature resulted in their complexes [Pd(L1/L2)2Cl2] (C1/C2). P1, L1, L2, C1 and C2 were characterized by (1)H, (13)C{(1)H} and (77)Se{(1)H} NMR spectroscopy, IR spectroscopy and High resolution mass spectrometry (HR-MS)...
July 21, 2017: Dalton Transactions: An International Journal of Inorganic Chemistry
https://www.readbyqxmd.com/read/28729737/direct-binding-to-gabarap-family-members-is-essential-for-hiv-1-nef-plasma-membrane-localization
#20
Alexandra Boeske, Melanie Schwarten, Peixiang Ma, Markus Tusche, Jessica Mötter, Christina Möller, Philipp Neudecker, Silke Hoffmann, Dieter Willbold
HIV-1 Nef is an important pathogenic factor for HIV/AIDS pathogenesis. Studies have shown that the association of Nef with the inner leaflet of the plasma membrane and with endocytic and perinuclear vesicles is essential for most activities of Nef. Using purified recombinant proteins in pull-down assays and by co-immunoprecipitation assays we demonstrate that Nef binds directly and specifically to all GABARAP family members, but not to LC3 family members. Based on nuclear magnetic resonance (NMR) experiments we showed that Nef binds to GABARAP via two surface exposed hydrophobic pockets...
July 20, 2017: Scientific Reports
keyword
keyword
5983
1
2
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"