Search results for "resonance spectroscopy"
showing 10 items of 1478 documents
Paramagnetic NMR investigations of Co(II) and Ni(II) amicyanin.
1999
The paramagnetic 1H NMR spectra of the Co(II) and Ni(II) substituted forms of the type 1 blue copper protein (cupredoxin) amicyanin have been assigned. This is the first such analysis of a cupredoxin, which has a distorted tetrahedral active site with the ligands provided by two histidines, a cysteine and a methionine. The isotropic shifts of the resonances in these spectra are compared with those of Co(II) and Ni(II) azurin. A number of interesting similarities and differences are found. The coordination of the metal by the two equatorial histidine ligands is very similar in both proteins. The interaction between the introduced metal and the thiolate sulfur of the equatorial cysteine ligan…
Identification of a new series of amides as non-covalent proteasome inhibitors
2014
Proteasome inhibition has emerged as an important therapeutic strategy for the treatment of multiple myeloma (MM) and some forms of lymphoma, with potential application in other types of cancers. 20S proteasome consists of three different catalytic activities known as chymotrypsin-like (ChT-L), trypsin-like (T-L), and, post-glutamyl peptide hydrolyzing (PGPH) or caspase-like (C-L), which are located respectively on the β5, β2, and β1 subunits of each heptameric β rings. Currently a wide number of covalent proteasome inhibitors are reported in literature; however, the less widely investigated non-covalent inhibitors might be a promising alternative to employ in therapy, because of the lack o…
Triterpene saponins from the roots ofAmpelozizyphus amazonicus
1992
A new triterpene saponin was isolated from the roots of Ampelozizyphus amazonicus together with the known 3-O-beta-D-glucopyranosyl-20-O-alpha-L-rhamnopyranosyljujubogenin and the known triterpenes melaleucic acid, 3 beta,27 alpha-dihydroxylup-20(29)-en-28 beta-oic acid, betulinic acid, betulin, lupeol. The structure of this saponin was elucidated as 3-O-[beta-D-glucopyranosyl(1----2)alpha-L-arabinopyranosyl]- 20-O-alpha-L-rhamnopyranosyljujubogenin by spectral analysis and chemical transformations.
Thioflavin T Hydroxylation at Basic pH and Its Effect on Amyloid Fibril Detection
2008
The fluorescent dye thioflavin T (ThT) is commonly used for in situ amyloid fibril detection. In this work, we focused on the spectroscopic properties and chemical stability of ThT in aqueous solution as a function of pH, temperature, and dye concentration. A reversible hydroxylation process occurs in alkaline solutions, which was characterized using a combination of UV-vis absorption spectroscopy, proton NMR, and density functional theory (DFT). On the basis of these studies, we propose a chemical structure for the hydroxylated form. Finally, by means of fluorescence spectroscopy, ThT hydroxylation effects on in situ amyloid detection have been investigated, providing new insights on the e…
H2-Antihistaminika, 36. Mitt. Isolamtidin und Analoge
1987
Isolamtidin (9a), ein Stellungsisomer des Lamtidins (8a), sowie die analogen N3-substituierten 1-Methyl-1H-1,2,4-triazol-3,5-diamine 9e-i, k wurden durch spezifische Synthese dargestellt und am isolierten Meerschweinchenvorhof und an der histaminstimulierten Sauresekretion der narkotisierten Ratte auf H2-antagonistische Wirkung untersucht. H2-Antihistaminics, XXXVI: Isolamitidine and Analogues Isolamitidine (9a), a position isomer of lamtidine (8a), as well as the analogous N3-substituted 1-methyl-1H-1,2,4-triazole-3,5-diamines 9e-i, k were prepared and tested for H2-antagonistic activity on the isolated guinea-pig atrium and towards the histamine-stimulated acid secretion of the anaestheti…
Stimulated Raman and Cars Spectroscopy of ν1 and 2ν2 (A1) Bands of 12CF4
1994
Two experimental coherent Raman techniques, stimulated Raman and coherent anti-Stokes Raman spectroscopy (CARS), were employed to study the Raman spectrum of CF 4 in the 900 cm −1 region. The stimulated Raman and CARS spectra of the ν 1 band of CF 4 were recorded at high resolution. The analysis of these spectra enabled some spectroscopic constants of this band to be refined and higher order constants to be determined for the first time. The first high-resolution CARS spectrum of the 2ν 2 (A 1 ) harmonic band is also presented. The rotational transitions of this band up to J = 40 were assigned and the first set of spectroscopic constants for this sub-level were determined. These results imp…
Influence of Amorphous TiO2-x on Titania Nanoparticle Growth and Anatase-to-Rutile Transformation
2012
Amorphous TiO2-x formed together with precursors and anatase nuclei, during TiCl4 hydrolysis at soft conditions, influences both crystal growth and phase stability. The highly defective nanoparticles of anatase grow by reaction of their basic hydroxyls with acidic ones of TiO2 precursor species. The growth of anatase crystals, however, is affected by their interactions with simultaneously formed amorphous TiO2-x which increasingly covers the particles hindering the anatase-precursor contact. The interactions among anatase and amorphous and precursor components have been studied by H-1-MAS (magic angle spinning) NMR spectroscopy. The interaction between acid and basic hydroxyls favors the fo…
Protection by extra virgin olive oil against oxidative stress in vitro and in vivo. Chemical and biological studies on the health benefits due to a m…
2017
Abstract We report the results of in vivo studies in Caenorhabditis elegans nematodes in which addition of extra virgin olive oil (EVOO) to their diet significantly increased their life span with respect to the control group. Furthermore, when nematodes were exposed to the pesticide paraquat, they started to die after two days, but after the addition of EVOO to their diet, both survival percentage and lifespans of paraquat-exposed nematodes increased. Since paraquat is associated with superoxide radical production, a test for scavenging this radical was performed using cyclovoltammetry and the EVOO efficiently scavenged the superoxide. Thus, a linear correlation (y = -0.0838x +19.73, regres…
Simultaneous endo and exo Complex Formation of Pyridine[4]arene Dimers with Neutral and Anionic Guests
2017
The formation of complexes between hexafluorophosphate (PF6- ) and tetraisobutyloctahydroxypyridine[4]arene has been thoroughly studied in the gas phase (ESI-QTOF-MS, IM-MS, DFT calculations), in the solid state (X-ray crystallography), and in chloroform solution (1 H, 19 F, and DOSY NMR spectroscopy). In all states of matter, simultaneous endo complexation of solvent molecules and exo complexation of a PF6- anion within a pyridine[4]arene dimer was observed. While similar ternary complexes are often observed in the solid state, this is a unique example of such behavior in the gas phase.
NMR Spectroscopic Evidence for the Intermediacy of XeF3− in XeF2/F− Exchange, Attempted Syntheses and Thermochemistry of XeF3− Salts, and Theoretical…
2010
The existence of the trifluoroxenate(II) anion, XeF(3)(-), had been postulated in a prior NMR study of the exchange between fluoride ion and XeF(2) in CH(3)CN solution. The enthalpy of activation for this exchange, ΔH(⧧), has now been determined by use of single selective inversion (19)F NMR spectroscopy to be 74.1 ± 5.0 kJ mol(-1) (0.18 M) and 56.9 ± 6.7 kJ mol(-1) (0.36 M) for equimolar amounts of [N(CH(3))(4)][F] and XeF(2) in CH(3)CN solvent. Although the XeF(3)(-) anion has been observed in the gas phase, attempts to prepare the Cs(+) and N(CH(3))(4)(+) salts of XeF(3)(-) have been unsuccessful, and are attributed to the low fluoride ion affinity of XeF(2) and fluoride ion solvation in…