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showing 10 items of 1921 documents
Redox reaction between amino-(3,4-dihydroxyphenyl)methyl phosphonic acid and dopaquinone is responsible for the apparent inhibitory effect on tyrosin…
2002
Amino-(3,4-dihydroxyphenyl)methyl phosphonic acid, the phosphonic analog of 3,4-dihydroxyphenylglycine, had been previously reported as a potent inhibitor of tyrosinase. The mechanism of the apparent enzyme inhibition by this compound has now been established. Amino-(3,4-dihydroxyphenyl)methyl phosphonic acid turned out to be a substrate and was oxidized to o-quinone, which evolved to a final product identified as 3,4-dihydroxybenzaldehyde, the same as for 3,4-dihydroxyphenylglycine. Monohydroxylated compounds (amino-(3-hydroxyphenyl)methyl phosphonic acid and amino-(4-hydroxyphenyl)methyl phosphonic acid) were not oxidized, neither was 4-hydroxy-l-phenylglycine. However, the relatively hig…
Nucleophilic benzoylation using a mandelic acid dioxolanone as a synthetic equivalent of the benzoyl carbanion. Oxidative decarboxylation of α-hydrox…
2004
The synthesis of alkyl aryl ketones using a mandelic acid dioxolanone as a synthetic equivalent (Umpolung) of the benzoyl carbanion is reported. The methodology involves alkylation of the mandelic acid dioxolanone, hydrolysis of the dioxolanone moiety in the alkylated products and oxidative decarboxylation of the resulting alpha-hydroxyacids. The last step is carried out in a catalytic aerobic way using a Co (III) complex in the presence of pivalaldehyde under very mild conditions.
Reaktionen an Aluminiumoxiden. 5. Mitt.: Umsetzungen von Cyclohexanon an Aluminiumoxid
1974
Die Umsetzungen von Cyclohexanon (1) an verschiedenen Aluminiumoxiden wurden bei unterschiedlichen Bedingungen untersucht. Die dabei entstandenen Stoffe wurden durch Vergleichssubstanzen mit Hilfe der DC und GC nachgewiesen. Reactions on Aluminium Oxides The reactions of cyclohexanone (1) on various aluminium oxides were investigated under different conditions. The resulting products were identified using synthesized compounds by aid of TLC and GLC.
ENANTIOSELECTIVE REDUCTION OF PROCHIRAL KETONES PROMOTED BY AMINO AMIDE RUTHENIUM COMPLEXES: A DFT STUDY
2021
International audience; The origin of enantioselectivity in the reaction of chiral Ru amino amide complexes in the asymmetric transfer hydrogenation of acetophenone was investigated using DFT calculations. For the most stable active catalysts, the full free energy profiles for the reaction were calculated according to the concerted hydrogen transfer mechanism. We succeeded in reproducing the experimentally observed enantioselectivity for the studied Ru amino amide complexes. Our results indicate that the high enantioselectivity can be explained by a stabilizing CH-π interaction existing between the phenyl group of acetophenone and the aromatic substituent of the catalyst, which plays a sign…
CyaC, a redox-regulated adenylate cyclase of Sinorhizobium meliloti with a quinone responsive diheme-B membrane anchor domain.
2019
The nucleotide cyclase CyaC of Sinorhizobium meliloti is a member of class III adenylate cyclases (AC), a diverse group present in all forms of life. CyaC is membrane-integral by a hexahelical membrane domain (6TM) with the basic topology of mammalian ACs. The 6TM domain of CyaC contains a tetra-histidine signature that is universally present in the membrane anchors of bacterial diheme-B succinate-quinone oxidoreductases. Heterologous expression of cyaC imparted activity for cAMP formation from ATP to Escherichia coli, whereas guanylate cyclase activity was not detectable. Detergent solubilized and purified CyaC was a diheme-B protein and carried a binuclear iron-sulfur cluster. Single poin…
Alternative respiratory pathways of Escherichia coli: energetics and transcriptional regulation in response to electron acceptors
1997
AbstractThe electron-transport chains of Escherichia coli are composed of many different dehydrogenases and terminal reductases (or oxidases) which are linked by quinones (ubiquinone, menaquinone and demethylmenaquinone). Quinol:cytochrome c oxido-reductase (`bc1 complex') is not present. For various electron acceptors (O2, nitrate) and donors (formate, H2, NADH, glycerol-3-P) isoenzymes are present. The enzymes show great variability in membrane topology and energy conservation. Energy is conserved by conformational proton pumps, or by arrangement of substrate sites on opposite sides of the membrane resulting in charge separation. Depending on the enzymes and isoenzymes used, the H+/e− rat…
Anal canal mixed adenoneuroendocrine carcinoma in a young patient misdiagnosed as anal abscess.
2021
Mixed neuroendocrine non-neuroendocrine neoplasms (MiNENs) are rare tumours of gastrointestinal tract, extremely rare in anal canal. We report a case of misdiagnosed MiNEN in a 38-year-old woman initially conservatively treated for a supposed anal fistula. In a second proctological evaluation, biopsy of the anal neoformation was performed and the histological specimen diagnosed a MiNEN. The complete staging showed a disseminate disease and the patient started a chemotherapy schedule. After 6 months, stable disease was revealed at the last imaging performed and radical surgery was offered to the patient that is actually on oncological follow-up without recurrence at 1 year.
Ready Access to Proquinazid Haptens via Cross-Coupling Chemistry for Antibody Generation and Immunoassay Development.
2015
17 pages, 4 tables, 5 figures.-- Publisher's PDF
Determination of trichothecenes and zearalenones in grain cereal, flour and bread by liquid chromatography tandem mass spectrometry
2012
Although analytical methods have been already reported for legislated mycotoxins as trichothecenes and zearalenone (ZON) separately, we describe the optimization of a simple and rapid multimycotoxin method for the determination of a total of 12 mycotoxins simultaneously, nine trichothecenes (NIV, DON, FUS-X, DAS, 15-AcDON, 3-AcDON, NEO, HT-2, T-2 T2), and zearalenone and its metabolites (ZON, a-ZOL, b-ZOL), of different origin (wheat, oat, barley and spelt) and in three different products where these substance can be present (grain, flour and bread) reach the food chain and cause toxic effect either in humans or animals. The extraction procedure was based on a mixture of acetonitrile/water …
Amphetamine-type stimulants analysis in oral fluid based on molecularly imprinting extraction
2018
Abstract A methamphetamine-based molecularly imprinted polymer (MIP) has been prepared by bulk polymerization to recognize new psychoactive substances (NPS) of the amphetamine, cathinones and 2C families in oral fluid samples, being the first precedent of a synthetized MIP for the extraction and preconcentration 32 NPS including amphetamine type substances and synthetic cathinones from oral fluids. Pre-polymerization complex and resulting materials were appropriately characterized by infrared spectroscopy, scanning electron microscopy, and nitrogen adsorption-desorption isotherms. Appropriateness of the material for the specific recognition of the target analytes was also evaluated through …