keyword
MENU ▼
Read by QxMD icon Read
search

NMR

keyword
https://www.readbyqxmd.com/read/28231561/structural-analysis-of-rebaudioside-a-derivatives-obtained-by-lactobacillus-reuteri-180-glucansucrase-catalyzed-trans-%C3%AE-glucosylation
#1
Gerrit J Gerwig, Evelien M Te Poele, Lubbert Dijkhuizen, Johannis P Kamerling
The wild-type Gtf180-ΔN glucansucrase enzyme from Lactobacillus reuteri 180 was found to catalyze the α-glucosylation of the steviol glycoside rebaudioside A, using sucrose as glucosyl donor in a transglucosylation process. Structural analysis of the formed products by MALDI-TOF mass spectrometry, methylation analysis and NMR spectroscopy showed that rebaudioside A is specifically α-d-glucosylated at the steviol C-19 β-d-glucosyl moiety (55% conversion). The main product is a mono-(α1 → 6)-glucosylated derivative (RebA-G1)...
January 31, 2017: Carbohydrate Research
https://www.readbyqxmd.com/read/28231530/identification-of-a-novel-low-level-impurity-in-fungicide-pyraclostrobin-by-high-performance-liquid-chromatography-tandem-mass-spectrometry
#2
Kaimin Xia, ShanShan Shen, Qun Gao, Wei Shang, Yuanjiang Pan, Jun Wu
Pyraclostrobin is one kind of new type methoxy acrylate fungicides that has been widely used in agriculture at present, with a lot of advantages including broad spectrum, high efficiency and high selectivity. In this work, a novel low-level impurity in the pyraclostrobin at about 0.2% was separated and characterized by high-performance liquid chromatography/tandem mass spectrometry (HPLC-MS). Firstly, the impurity was speculated to possess the same skeleton structure as the main product pyraclostrobin while the methyl group on the methyl ester was substituted to be CH2CH2Cl on the basis of the on-line multi-stage mass spectrometric behaviors compared with that of pyraclostrobin...
February 17, 2017: Journal of Pharmaceutical and Biomedical Analysis
https://www.readbyqxmd.com/read/28231528/identification-of-uv-absorbing-extractables-from-rubber-closures-used-in-containers-of-injectable-powder-and-safety-assessment-of-leachables-in-the-drug
#3
Yulei Wei, Ying Wu, Tingli Zhu, Zhiyan Li, Yilan Zhang
Rubber closures have been of great concern to regulatory authorities on account of their potential safety risks to patients. The aim of our work is to provide part of data about the compatibility of the injectable powder and its packaging materials for the drug registration. In this report, methodologies were established to study the system of the preparation. Firstly, three major extractables were isolated by semi-preparative HPLC method combined with silica gel-based chromatographic methods. NMR spectra including 1D NMR ((1)H, (13)C, DEPT135) and 2D NMR (COSY, HSQC, HMBC) were introduced to identify the extractables, besides HPLC, GC-MS, ESI-MS/MS and HRMS...
February 16, 2017: Journal of Pharmaceutical and Biomedical Analysis
https://www.readbyqxmd.com/read/28231455/synthetic-investigation-physicochemical-characterization-and-antibacterial-evaluation-of-ternary-bi-iii-systems-with-hydroxycarboxylic-acid-and-aromatic-chelator-substrates
#4
C M Nday, E Halevas, A Tsiaprazi-Stamou, D Eleftheriadou, A Hatzidimitriou, G Jackson, D Reid, A Salifoglou
Due to its physical and chemical properties, bismuth (Bi(III)) is widely used in the treatment of several gastrointestinal and skin diseases, and infections caused by bacteria. Herein, its known antimicrobial potential was taken into consideration in the synthesis of two new hybrid ternary materials of Bi(III) with the physiological α-hydroxycarboxylic glycolic acid and 1,10-phenanthroline (phen), [Bi2(C2H2O3)2(C2H3O3)(NO3)]n(.) nH2O (1) and [Bi(C12H8N2)(NO3)4](C10H8N4) (2), aiming at improving its antibacterial properties...
February 11, 2017: Journal of Inorganic Biochemistry
https://www.readbyqxmd.com/read/28231388/structural-characterization-and-antifatigue-effect-in-vivo-of-maca-lepidium-meyenii-walp-polysaccharide
#5
Weimin Tang, Lu Jin, Lianghua Xie, Juqing Huang, Nan Wang, Bingquan Chu, Xulin Dai, Yu Liu, Rui Wang, Ying Zhang
Maca (Lepidium meyenii Walp) polysaccharides (MP) with purity of 99.2% were obtained to investigate their structural characteristics and antifatigue effect in vivo. The physicochemical properties of MP were analyzed through high-performance gel filtration chromatography, IR, monosaccharide composition, methylation, GC-MS, and NMR analyses. The antifatigue effect of MP was evaluated by using a mouse weight-loaded swimming model. MP is an acidic heteropolysaccharide with an average molecular weight (Mw ) of 793...
February 23, 2017: Journal of Food Science
https://www.readbyqxmd.com/read/28231145/recent-advances-in-techniques-for-starch-esters-and-the-applications-a-review
#6
REVIEW
Jing Hong, Xin-An Zeng, Charles S Brennan, Margaret Brennan, Zhong Han
Esterification is one of the most important methods to alter the structure of starch granules and improve its applications. Conventionally, starch esters are prepared by conventional or dual modification techniques, which have the disadvantages of being expensive, have regent overdoses, and are time-consuming. In addition, the degree of substitution (DS) is often considered as the primary factor in view of its contribution to estimate substituted groups of starch esters. In order to improve the detection accuracy and production efficiency, different detection techniques, including titration, nuclear magnetic resonance (NMR), Fourier transform infrared spectroscopy (FT-IR), thermal gravimetric analysis/infrared spectroscopy (TGA/IR) and headspace gas chromatography (HS-GC), have been developed for DS...
July 9, 2016: Foods (Basel, Switzerland)
https://www.readbyqxmd.com/read/28230995/synthesis-of-high-quality-biodiesel-using-feedstock-and-catalyst-derived-from-fish-wastes
#7
Devarapaga Madhu, Rajan Arora, Shalini Sahani, Veena Singh, Yogesh Chandra Sharma
A low cost and high purity calcium oxide (CaO) was prepared from waste crab shells which were extracted from the dead crabs, used as efficient solid base catalyst in the synthesis of biodiesel. Raw fish oil was extracted from the waste parts of fish through mechanical expeller followed by solvent extraction. Physical as well as chemical properties of raw fish oil were studied and FFA's composition was analysed with GC-MS. Stable and high purity calcium oxide (CaO) was obtained when the material was calcined at 800 °C for 4 h...
February 23, 2017: Journal of Agricultural and Food Chemistry
https://www.readbyqxmd.com/read/28230990/a-comparative-study-of-the-synthesis-structural-and-physicochemical-properties-of-diketopiperazines-vs-aza-diketopiperazines
#8
Pierre Regenass, Damien Bosc, Stéphanie Riché, Patrick Gizzi, Marcel Hibert, Lydia Brelot, A Ganesan, Dominique Bonnet
Aza-diketopiperazines (Aza-DKP) represent an underprivileged motif obtained by scaffold hopping of 2,5-diketopiperazines (2,5-DKP). Herein, we compare the synthesis but also the structural and the physicochemical properties of aza-DKP 4 vs 2,5-DKP 7. Thus, X-ray and 1H NMR studies show that aza-DKP 4 is a rigid and non-flat scaffold like the 2,5-DKP 7. Moreover, the replacement of one Calpha-stereogenic center by a nitrogen atom results in a significant improvement of both the water solubility and the microsomal stability...
February 23, 2017: Journal of Organic Chemistry
https://www.readbyqxmd.com/read/28230982/synthesis-of-%C3%AE-1-2-linked-6-deoxy-l-altropyranose-oligosaccharides-via-gold-i-catalyzed-glycosylation-of-a-ortho-hexynylbenzoate-donor
#9
Zhengnan Shen, Hani Mobarak, Wei Li, Göran Widmalm, Biao Yu
The β-(1-2)-linked 6-deoxy-L-altropyranose di- to penta-saccharides 2-5, relevant to the O-antigen of the infectious Yersinia enterocolitica O:3, were synthesized for the first time. The challenging 1,2-cis-altropyranosyl linkage was assembled effectively via glycosylation with 2-O-benzyl-3,4-di-O-benzoyl-6-deoxy-L-altropyranosyl ortho-hexynylbenzoate (7) under the catalysis of PPh3AuNTf2. NMR and molecular modeling studies showed that the pentasaccharide (5) adopted a left-handed helical conformation.
February 23, 2017: Journal of Organic Chemistry
https://www.readbyqxmd.com/read/28230901/-1-h-nmr-with-multivariate-analysis-for-automobile-lubricant-comparison
#10
Siwon Kim, Dahye Yoon, Dong-Kye Lee, Changshin Yoon, Suhkmann Kim
Identification of suspected automobile-related lubricants could provide valuable information in forensic cases. We examined that automobile lubricants might exhibit the chemometric characteristics to their individual usages. To compare the degree of clustering in the plots, we co-plotted general industrial oils that were highly dissimilar with automobile lubricants in additive compositions. (1) H-NMR spectroscopy was used with multivariate statistics as a tool for grouping, clustering, and identification of automobile lubricants in laboratory conditions...
February 23, 2017: Journal of Forensic Sciences
https://www.readbyqxmd.com/read/28230756/synthesis-and-structural-evaluation-of-organo-ruthenium-complexes-with-%C3%AE-diketonates
#11
Matija Uršič, Tanja Lipec, Anton Meden, Iztok Turel
Four novel ruthenium organometallic complexes: [(η⁶-p-cymene)Ru(4,4,4-trifluoro-1-(4-bromophenyl)-1,3-butanedione)Cl] (1), [(η⁶-p-cymene)Ru(4,4,4-trifluoro-1-(4-bromophenyl)-1,3-butanedione)pta]PF₆ (2), [(η⁶-p-cymene)Ru(4,4,4-trifluoro-1-(4-iodophenyl)-1,3-butanedione)Cl] (3) and [(η⁶-p-cymene)Ru(4,4,4-trifluoro-1-(4-iodophenyl)-1,3-butanedione)pta]PF₆ (4) were synthesized and characterized by elemental analysis, infrared (IR), UV-Vis, NMR and mass spectroscopy and single-crystal X-ray diffraction...
February 20, 2017: Molecules: a Journal of Synthetic Chemistry and Natural Product Chemistry
https://www.readbyqxmd.com/read/28230755/three-chalconoids-and-a-pterocarpene-from-the-roots-of-tephrosia-aequilata
#12
Yoseph Atilaw, Sandra Duffy, Matthias Heydenreich, Lois Muiva-Mutisya, Vicky M Avery, Máté Erdélyi, Abiy Yenesew
In our search for new antiplasmodial agents, the CH₂Cl₂/CH₃OH (1:1) extract of the roots of Tephrosia aequilata was investigated, and observed to cause 100% mortality of the chloroquine-sensitive (3D7) strain of Plasmodium falciparum at a 10 mg/mL concentration. From this extract three new chalconoids, E-2',6'-dimethoxy-3',4'-(2'',2''-dimethyl)pyranoretrochalcone (1, aequichalcone A), Z-2',6'-dimethoxy-3',4'-(2'',2''-dimethyl)pyranoretrochalcone (2, aequichalcone B), 4''-ethoxy-3''-hydroxypraecansone B (3, aequichalcone C) and a new pterocarpene, 3,4:8,9-dimethylenedioxy-6a,11a-pterocarpene (4), along with seven known compounds were isolated...
February 20, 2017: Molecules: a Journal of Synthetic Chemistry and Natural Product Chemistry
https://www.readbyqxmd.com/read/28230365/catalytic-enantioselective-2-3-rearrangements-of-allylic-ammonium-ylides-a-mechanistic-and-computational-study
#13
Thomas H West, Daniel M Walden, James E Taylor, Alexander C Brueckner, Ryne C Johnston, Paul H-Y Cheong, Guy C Lloyd-Jones, Andrew D Smith
A mechanistic study of the isothiourea-catalysed enantioselective [2,3]-rearrangement of allylic ammonium ylides is described. Reaction kinetic analyses using 19F NMR and density functional theory computations have elucidated a reaction profile and allowed identification of the catalyst resting state and turnover-rate limiting step. A catalytically-rele- vant catalyst-substrate adduct has been observed, and its constitution elucidated unambiguously by 13C and 15N isotopic labelling. Isotopic entrainment has shown the observed catalyst-substrate adduct to be a genuine intermediate on the pro- ductive cycle towards catalysis...
February 23, 2017: Journal of the American Chemical Society
https://www.readbyqxmd.com/read/28230363/inhibition-and-stabilization-cucurbituril-induced-distinct-effects-on-the-schiff-base-reaction
#14
Wanjun Gong, Jun Ma, Zhiyong Zhao, Fang Gao, Feng Liang, Haijun Zhang, Simin Liu
The different effects of cucurbit[7]uril (CB[7]) on the Schiff base reactions in aqueous solution were explored by 1H NMR spectroscopy and single X-ray crystallography. With CB[7] the condensation reaction of aldehyde and primary amine is dramatically inhibited. In contrast the presence of CB[7] does tremendously stabilize iminium cation in water through ion-dipole interactions. A single crystal structure of the complex of iminium ion 7 with CB[7] grown in water is reported.
February 23, 2017: Journal of Organic Chemistry
https://www.readbyqxmd.com/read/28230361/10-gingerol-a-phytochemical-derivative-from-tongling-white-ginger-inhibits-cervical-cancer-insights-into-the-molecular-mechanism-and-inhibitory-targets
#15
Fang Zhang, Kiran Thakur, Fei Hu, Jian-Guo Zhang, Zhao-Jun Wei
With an aim to evaluate anti-cancerous activities of 10-gingerol (10-G) against Hela cells, it was purified and identified from Tongling White Ginger by HSCCC, UPLC-TOF-MS/MS and NMR analysis, respectively. 10-G inhibited the proliferation of HeLa cells at IC50 (29.19 μM) and IC80 (50.87 μM) with altered cell morphology, increased cytotoxicity and arrested cell cycle in G0/G1-phase. The most cell cycle related genes and proteins expression significantly decreased, followed by slight decrease in few and without affecting cyclin B1 and cyclin E1 (protein)...
February 23, 2017: Journal of Agricultural and Food Chemistry
https://www.readbyqxmd.com/read/28230348/nmr-structures-of-gcn4p-are-largely-conserved-when-ion-pairs-are-disrupted-at-acidic-ph-but-show-a-relaxation-of-the-coiled-coil-superhelix
#16
Anne R Kaplan, Megan R Brady, Mark W Maciejewski, Richard A Kammerer, Andrei T Alexandrescu
To understand the roles ion pairs play in stabilizing coiled coils we determined NMR structures of GCN4p at three pH values. At pH 6.6 all acidic residues are fully charged, at pH 4.4 they are half-charged, and at pH 1.5 they are protonated and uncharged. The α-helix monomer and coiled coil structures of GCN4p are largely conserved, except for a loosening of the coiled coil quaternary structure with decreasing pH. Differences going from neutral to acidic pH include (i) an unwinding of the coiled coil superhelix due to the loss of inter-chain ion pair contacts, (ii) a small increase in the separation of the monomers in the dimer, (iii) a loosening of knobs-into-holes packing motifs, and (iv) an increased separation between oppositely charged residues that participate in ion pairs at neutral pH...
February 23, 2017: Biochemistry
https://www.readbyqxmd.com/read/28230201/relapsing-remitting-multiple-sclerosis-patients-display-an-altered-lipoprotein-profile-with-dysfunctional-hdl
#17
Winde Jorissen, Elien Wouters, Jeroen F Bogie, Tim Vanmierlo, Jean-Paul Noben, Denis Sviridov, Niels Hellings, Veerle Somers, Roland Valcke, Bart Vanwijmeersch, Piet Stinissen, Monique T Mulder, Alan T Remaley, Jerome J A Hendriks
Lipoproteins modulate innate and adaptive immune responses. In the chronic inflammatory disease multiple sclerosis (MS), reports on lipoprotein level alterations are inconsistent and it is unclear whether lipoprotein function is affected. Using nuclear magnetic resonance (NMR) spectroscopy, we analysed the lipoprotein profile of relapsing-remitting (RR) MS patients, progressive MS patients and healthy controls (HC). We observed smaller LDL in RRMS patients compared to healthy controls and to progressive MS patients...
February 23, 2017: Scientific Reports
https://www.readbyqxmd.com/read/28229941/dual-high-resolution-inhibition-profiling-and-hplc-hrms-spe-nmr-analysis-for-identification-of-%C3%AE-glucosidase-and-radical-scavenging-inhibitors-in-solanum-americanum-mill
#18
Eder L Silva, Rita C Almeida-Lafetá, Ricardo M Borges, Dan Staerk
Solanum americanum is one of the most prominent species used to treat type 2 diabetes in Guatemala. In our ongoing efforts to find antidiabetic and antioxidative compounds from natural sources, an ethyl acetate extract of this medicinal herb was investigated using dual high-resolution α-glucosidase/radical scavenging inhibition profiling. The high-resolution biochromatograms obtained by this technique were used to target subsequent structural elucidation by HPLC-HRMS-SPE-NMR analysis towards the bioactive constituents...
February 13, 2017: Fitoterapia
https://www.readbyqxmd.com/read/28229939/chenopodium-bonus-henricus-l-a-source-of-hepatoprotective-flavonoids
#19
Zlatina Kokanova-Nedialkova, Paraskev Nedialkov, Magdalena Kondeva-Burdina, Rumyana Simeonova, Virginia Tzankova, Denitsa Aluani
Three new flavonoid glycosides (7-9) named patuletin-3-O-(5″'-О-Е-feruloyl)-β-d-apiofuranosyl(1→2)[β-d-glucopyranosyl (1→6)]-β-d-glucopyranoside (7), spinacetin-3-O-(5″'-О-Е-feruloyl)-β-d-apiofuranosyl (1→2)[β-d-glucopyranosyl(1→6)]-β-d-glucopyranoside (8) and 6-methoxykaempferol-3-O-(5″'-О-Е-feruloyl)-β-d-apiofuranosyl(1→2)[β-d-glucopyranosyl (1→6)]-β-d-glucopyranoside (9) together with six known flavonoid glycosides of patuletin, spinacetin and 6-methoxykaempferol (1-6) were isolated from the aerial parts of C...
February 14, 2017: Fitoterapia
https://www.readbyqxmd.com/read/28229598/dipicolylamine-functionalized-polyfluorene-based-gel-with-lower-critical-solution-temperature-preparation-characterization-and-application
#20
Chunlan Xiang, Hao Wan, Mingjing Zhu, Yijing Chen, Juan Peng, Gang Zhou
A thermoresponsive fluorescent polymer gel with lower critical solution temperature (LCST) phase transition has been prepared by cooperating conjugated fluorene homopolymer poly(2,7-(9,9-di(8-di(2-picolyl)aminooctyl))fluorene) (PPAOF) and small organic dye sulforhodamine B (SRB) or its sodium salt (SRB-Na). The sol-gel phase transition originates from the electrostatic interactions between the protonated pyridyl/amino groups in PPAOF and the sulfonic groups in the organic dye molecules, as revealed by FTIR, variable-temperature 1H NMR spectroscopies, and cyclic voltammetry measurements...
February 23, 2017: ACS Applied Materials & Interfaces
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"