Search results for "Spectroscopy"
showing 10 items of 10293 documents
Cytotoxic eudesmane sesquiterpenes from Crepis sancta
2019
Abstract Chemical exploration of Crepis sancta (L.) Bornm. (Asteraceae) aerial parts afforded two new eudesmane sesquiterpenes (1 and 2) together with three known congeners (3-5) and two known methylated flavonoids (6 and 7). Structure elucidation of the new compounds was unambiguously performed based on HRESIMS, 1D and 2D NMR spectroscopic analyses. All isolated compounds were subjected to an in vitro cytotoxicity assay against mouse lymphoma (L5178Y) cells, revealing moderate activities with IC50 ranging from 7.9 to 21.0 μM.
Prodrugs of sulfacetamide: Synthesis, X-ray structure, Hirshfeld analysis, antibacterial assessment, and docking studies
2022
Abstract New prodrugs of sulfacetamide as azo compounds were synthesized and have been evidenced through elemental and spectral analyses. Their synthesis was carried out by coupling the diazonium salt of sulfacetamide with activated carbanion salt of ethyl acetoacetate at 0 ˚C to afford the hydrazono derivative 3. Other prodrugs as sulfacetamide-pyrazoles, 5a, 5b and 5c were furnished via cyclocondensation of 3 with aryl/heteroaryl hydrazines. X-ray diffraction for single crystal was used to confirm the molecular and supramolecular structures of 3. In addition, DFT studies were performed to analyze the geometric parameters and compute the electronic properties of 3 and 5a-c. Hirshfeld analy…
New umbelliferone sesquiterpene ethers from roots ofLigularia persica
1991
An extract of roots of Ligularia persica yielded thirteen umbelliferone sesquiterpene ethers, among them the new ones ligupersin A (11) and ligupersin B (13).
Recent advances of electrochemical and optical biosensors for detection of C-reactive protein as a major inflammatory biomarker
2020
Abstract Early detection of inflammatory mediators including C-reactive protein (CRP) is of great diagnostic importance in many human diseases. CRP elevates very fast in conditions such as tissue injuries, infections, cancers, and renal and cardiovascular diseases. Conventional techniques for detecting CRP are based on antigen–antibody, agglutination, and precipitation reactions. Newer methods based on immunoturbidimetry and immunonephelometry are also time-consuming and relatively expensive. For solving these problems, highly efficient techniques based on CRP-biosensors have been introduced. Here, our aim was to summarize the features of recent biosensors for detection of CRP in biological…
Excitation energy transfer in isolated chlorosomes from Chloroflexus aurantiacus
2009
Abstract Chlorosomes from green photosynthetic bacteria Chloroflexus aurantiacus have been studied by time-resolved femtosecond transient absorption spectroscopy. The fastest kinetics of 200–300 fs resolved, was interpreted to stem for intra-chlorosomal excitation energy transfer. Energy transfer from the antenna to the baseplate appeared as a major 9.2 ps rise component detected at the baseplate probe wavelength. Excitation energy transfer rates were evaluated for a model chlorosome. Calculated rod to rod, and rods to baseplate rate constants of 200–400 fs and 10–20 ps, respectively, are in accord with the experimental results.
Excitation Energy Transfer in Isolated Chlorosomes from Chlorobaculum tepidum and Prosthecochloris aestuarii
2012
Excitation energy transfer in chlorosomes from photosynthetic green sulfur bacteria, Chlorobaculum (Cba.) tepidum and Prosthecochloris (Pst.) aestuarii, have been studied at room temperature by time-resolved femtosecond transient absorption spectroscopy. Bleach rise times from 117 to 270 fs resolved for both chlorosomes reflect extremely efficient intrachlorosomal energy transfer. Bleach relaxation times, from 1 to 3 ps and 25 to 35 ps, probed at 758 nm were tentatively assigned to intrachlorosomal energy transfer based on amplitude changes of the global fits and model calculations. The anisotropy decay constant of about 1 ps resolved at 807 nm probe wavelength for the chlorosomes from Chlo…
COBALT SUBSTITUTED PROTEINS
1995
Cobalt(II) has been extensively used as a spectroscopic probe in many proteins, mainly replacing zinc, but also substituting iron, manganese and copper ions. The relatively short electronic relaxation times of high spin cobalt(II) makes this ion suitable as a paramagnetic probe for Nuclear Magnetic Resonance spectroscopy. A survey of the NMR studies performed in cobalt substituted proteins is shown. In the zinc enzymes Carboxypeptidase A, Carbonic Anhydrase and Superoxide Dismutase the implications of these studies on their catalytic mechanisms are commented. Finally, a further insight in the research of the blue copper protein Azurin by applying NMR to its cobalt derivative is also reporte…
Chapter 6 Contribution of NMR Spectroscopy to Flavour Release and Perception
2008
Abstract The control of flavouring of a food product as well as the flavour perception during consumption is a great challenge for improving food quality. However, the various ingredient composition and the different textural properties of foods can significantly affect the release of aroma compounds or sapid molecules. It is thus of major importance to determine physicochemical factors that govern diffusion and binding phenomena of these small solutes in food products. In this way, NMR spectroscopy is an efficient tool to characterize these mechanisms at a molecular scale. Diffusion rates of small solutes in aqueous, viscous and gel solutions can be extracted from relaxation or diffusion N…
Influence of K on the transport of Cs-137 in soil–plant root and root-leaf systems in sugar beet
2015
The main aim of this study was to determine the influence of K-40 activity in the soil on the transport of Cs-137 from the soil to plants and the impact of its activity on the internal transport of Cs-137 between anatomical parts of the sugar beet. The activity concentration of Cs-137 in the soil was bigger than that in the beet. The highest activity concentration of K-40 was observed in beet leaves, while its content in roots and the soil were comparable.