Search results for "Nuclear magnetic resonance spectroscopy"
showing 10 items of 843 documents
Base-assisted synthesis of 4-pyridinate gold(I) metallaligands: a study of their use in self-assembly reactions
2021
Made available in DSpace on 2021-06-25T12:16:58Z (GMT). No. of bitstreams: 0 Previous issue date: 2021-05-06 Ministerio de Economia y Competitividad (MINECO/FEDER) of Spain Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq) Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES) The synthesis of di- and tritopic gold(I) metallaligands of the type [(Au4-py)(2)(mu(2)-diphosphane)] (diphosphane = bis(diphenylphosphanyl)isopropane or dppip (1), 1,2-bis(diphenylphosphanyl)ethane or dppe (2), 1,3-bis(diphenylphosphanyl)propane or dppp (3) and 1,4-bis(diphenylphosphanyl)butane or dppb (4)) and [(Au4-py)(3)(mu(3)-triphosphane)] (triphosphane = 1,1,1-tris(diphenylphosph…
Increased conformational rigidity of humic substances by oxidative biomimetic catalysis
2005
A synthetic water-soluble meso-tetra(2,6-dichloro-3-sulfonatophenyl)porphyrinate of iron(III) chloride, Fe(TDCPPS)Cl, was employed as a biomimetic catalyst in the oxidative coupling of terrestrial humic materials. High-performance size-exclusion chromatography (HPSEC), solid-state nuclear magnetic resonance (CPMAS-(13)C NMR), electron paramagnetic resonance (EPR), and diffuse reflectance infrared spectroscopy (DRIFT) were used to follow conformational and structural changes brought about in different humic materials by the oxidative coupling. Increase in apparent weight-average molecular weight (Mw(a)) occurred invariably for all humic substances with the oxidative polymerization catalyzed …
Novel 2,6-disubstituted phenylboronic compounds - Synthesis, crystal structures, solution behaviour and reactivity
2015
Abstract 2,6-Diformylphenylboronic acid has been synthesized and characterized both in the solid state as well as in solution. In crystal, an unusual structural pattern has been found with the formation of intermolecular hydrogen bonds by B(OH) 2 and CHO groups as well as water molecules. In solution tautomeric equilibrium with the formation of oxaborole ring by one of the formyl groups was proved on the basis of multinuclear NMR spectroscopy. The title compound reacts with secondary mono- and diamines to form various types of substituted benzoxaboroles, which have been characterized by XRD and spectroscopic methods.
Spontaneous Resolution of an Electron‐Deficient Tetrahedral Fe4L4cage
2015
A highly electron-deficient C3-symmetric tris(bipyridyl) ligand was prepared in four steps and used for the coordination of Fe(OTf)2, thereby resulting in the homochiral assembly of a new family of robust tetrahedral M4L4 cages. This homochiral T-symmetric cage containing a relatively large cavity of 330 A(3) is capable of encapsulating an anionic guest, as was determined by mass spectrometry, (19)F NMR spectroscopy, and finally shown from its crystal structure. Moreover, crystallization of the cage from CH3CN led to crystals containing both (ΔΔΔΔ and ΛΛΛΛ) enantiomers, while crystallization from CH3 OH resulted in crystals containing only the right-handed (ΔΔΔΔ) cage. The difference in the…
A new member of the fusaricidin family – structure elucidation and synthesis of fusaricidin E
2017
Two hitherto unknown fusaricidins were obtained from fermentation broths of three Paenibacillus strains. After structure elucidation based on tandem mass spectrometry and NMR spectroscopy, fusaricidin E was synthesized to confirm the structure and the suggested stereochemistry. The synthesis was based on a new strategy which includes an efficient access to the 15-guanidino-3-hydroxypentadecanoyl (GHPD) side chain from erucamide.
Preparation and physico-chemical study of inclusion complexes between idebenone and modified beta-cyclodextrins
1996
The inclusion properties of modifiedβ-cyclodextrins (trimethyl-β-cyclodextrin, dimethyl-β-cyclodextrin and hydroxypropyl-β-cyclodextrin) towards idebenone were compared with naturalβ-cyclodextrin. The inclusion complexes were prepared by different methods (coprecipitation, kneading, and freeze-drying) and characterized by differential scanning calorimetry, X-ray diffractometry, UV, CD and NMR spectroscopy. The results obtained by CD and NMR spectroscopy indicate a different orientation of idebenone in dimethyl-β-cyclodextrin with respect to other cyclodextrins. Stability constants of the complexes were determined in water at various temperatures and consequently thermodynamic parameters wer…
Localization and interactions of melatonin in dry cholesterol/lecithin mixed reversed micelles used as cell membrane models
2005
The state of melatonin confined in dry cholesterol/lecithin mixed reversed micelles dispersed in CCl4 was investigated using 1H-NMR and FT-IR spectroscopies as a function of the melatonin to lecithin molar ratio (R(MLT)) and of the cholesterol to lecithin molar ratio (R(CHL)). An analysis of experimental results leads to the hypothesis that, independent of R(MLT) and as a consequence of anisotropic melatonin/lecithin, melatonin/cholesterol and cholesterol/lecithin interactions, melatonin is totally solubilized in reversed micelles. Melatonin is mainly located in and oriented in the nanodomain constituted by the hydrophilic groups of cholesterol and lecithin. A competition of melatonin and c…
1H, 13C and 15N NMR chemical shift assignments of cAMP-regulated phosphoprotein-19 and -16 (ARPP-19 and ARPP-16)
2020
Protein Phosphatase 2A, PP2A, the principal Serine/threonine phosphatase, has major roles in broad range of signaling pathways that include regulation of cell cycle, cell proliferation and neuronal signaling. The loss of function of PP2A is linked with many human diseases, like cancer and neurodegenerative disorders. Protein phosphatase 2A (PP2A) functions as tumor suppressor and its tumor suppressor activity is inhibited by the overexpression of PP2A inhibitor proteins in most of the cancers. ARPP-19/ARPP-16 has been identified as one of the potential PP2A inhibitor proteins. Here, we report the resonance assignment of backbone 1H, 13C and 15N atoms of human ARPP-19 and ARPP-16 proteins. T…
Synthesis and characterization of a novel high luminescent gold-2-mercapto-1-methyl-imidazole complex
2010
Synthesis and characterization of a new gold-2-mercapto-1-methyl imidazole are reported. This new organic material shows an extraordinary fluorescence activity (superfluorescence) up to 220°C with an unusual quantum yield of 0.2. Both fluorescence and NMR spectroscopy were applied to understand the behavior of the gold-2-mercapto-1-methylimidazole complex. Results suggest that the superfluorescence activity can be attributed to the shrinking of the HOMO-LUMO band gap energy following complexation of the organic imidazole system with gold. Copyright © 2010 John Wiley & Sons, Ltd.
High Resolution-magic Angle Spinning NMR Study of Olive Leaves
2013
In recent years HR-MAS 1H NMR spectroscopy has proven to be a useful tool for the rapid determination of the metabolic profile of several solid and semisolid foods, such as fruits and vegetables, cheese and meat. Olive leaves are today recognized as direct sources of bioactive compounds and natural antioxidants (flavonoids, secoiridoids) suitable as food additives, and their extracts form the basis of beauty care products and pharmaceutical supplements. Thus, olive leaves are emerging as a new and potentially important product for olive tree growing regions. In this report we present the application of 1H and 13C HR-MAS 1D and 2D NMR spectroscopy for the characterization and analysis of tri…