Search results for "acids"
showing 10 items of 3520 documents
Hepatic farnesyl diphosphate synthase expression is suppressed by polyunsaturated fatty acids
2005
Dietary vegetable oils and fish oils rich in PUFA (polyunsaturated fatty acids) exert hypocholesterolaemic and hypotriglyceridaemic effects in rodents. The plasma cholesterol-lowering properties of PUFA are due partly to a diminution of cholesterol synthesis and of the activity of the rate-limiting enzyme HMG-CoA reductase (3-hydroxy-3-methylglutaryl-CoA reductase). To better understand the mechanisms involved, we examined how tuna fish oil and individual n−3 and n−6 PUFA affect the expression of hepatic FPP synthase (farnesyl diphosphate synthase), a SREBP (sterol regulatory element-binding protein) target enzyme that is subject to negative-feedback regulation by sterols, in co-ordination …
An unusually high substitution rate in transplant-associated BK polyomavirus in vivo is further concentrated in HLA-C-bound viral peptides
2018
Infection with human BK polyomavirus, a small double-stranded DNA virus, potentially results in severe complications in immunocompromised patients. Here, we describe the in vivo variability and evolution of the BK polyomavirus by deep sequencing. Our data reveal the highest genomic evolutionary rate described in double-stranded DNA viruses, i.e., 10−3–10−5 substitutions per nucleotide site per year. High mutation rates in viruses allow their escape from immune surveillance and adaptation to new hosts. By combining mutational landscapes across viral genomes with in silico prediction of viral peptides, we demonstrate the presence of significantly more coding substitutions within predicted cog…
An Experimental and Computational Study on the Effect of Al(OiPr)3 on Atom-Transfer Radical Polymerization and on the Catalyst-Dormant Chain Halogen …
2005
International audience; Compound Al(OiPr)3 is shown to catalyze the halide-exchange process leading from [Mo(Cp)Cl2(iPrN=CH-CH=NiPr)] and CH3CH(X)COOEt (X=Br, I) to the mixed-halide complexes [Mo(Cp)ClX(iPrN=CH-CH=NiPr)]. On the other hand, no significant acceleration is observed for the related exchange between [MoX3(PMe3)3] (X=Cl, I) and PhCH(Br)CH3, by analogy to a previous report dealing with the RuII complex [RuCl2(PPh3)3]. A DFT computation study, carried out on the model complexes [Mo(Cp)Cl2(PH3)2], [MoCl3(PH3)3], and [RuCl2(PH3)3], and on the model initiators CH3CH(Cl)COOCH3, CH3Cl, and CH3Br, reveals that the 16-electron RuII complex is able to coordinate the organic halide RX in a…
Conformational preferences and synthesis of isomers Z and E of oxazole-dehydrophenylalanine
2016
Dehydrophenylalanine, ΔPhe, is the most commonly studied α,β-dehydroamino acid. In nature, further modifications of the α,β-dehydroamino acids were found, for example, replacement of the C-terminal amide group by oxazole ring. The conformational properties of oxazole-dehydrophenylalanine residue (ΔPhe-Ozl), both isomers Z and E, were investigated. To determine all possible conformations, theoretical calculations were performed using Ac-(Z/E)-ΔPhe-Ozl(4-Me) model compounds at M06-2X/6-31++G(d,p) level of theory. Ac-(Z/E)-ΔPhe-Ozl-4-COOEt compounds were synthesized and the conformational preferences of each isomer, Z and E, were investigated using FTIR and NMR-NOE in solutions of increasing p…
Meat quality of commercial chickens reared in different production systems: industrial, range and organic
2020
Abstract Meat is an important part of the human diet since it provides several nutrients. However, the amount of these nutrients can differ according to several factors. With this in mind, the present research was designed with the main objective of evaluating the effect of production system of broiler chickens (industrial, range and organic) on meat quality. The physicochemical, chemical and nutritional characteristics were determined in breast and drumstick meat. The organic chickens presented the lowest amounts of fat and cholesterol and the highest amounts of protein. The colour was also influenced by the production system, where organic and range chickens had the highest values of redn…
Detection of lactobacillic acid in low erucic rapeseed oil--A note of caution when quantifying cyclic fatty acid monomers in vegetable oils.
2010
International audience; The purpose of this work was to identify an unknown component which has been detected during the analysis of cyclic fatty acid monomers (CFAMs) in low erucic acid rapeseed oils (LEAR). A sample of crude LEAR was transformed into fatty acid methyl esters (FAMEs) and hydrogenated using PtO2. The hydrogenated sample was fractionated by reversed-phase high-performance liquid chromatography (RP-HPLC) and the fraction containing the CFAMs transformed into picolinyl esters. Analysing these picolinyl derivatives by gas-liquid chromatography coupled to mass spectrometry (GC-MS) showed that the unknown product observed in LEAR is the 11,12-methylene-octadecanoic acid. This cyc…
N-Glycosyl Amides as Glycosyl Donors in Stereoselective Glycosylation Reactions
2004
Due to their high stability, N-glycosyl amides have so far not been considered as glycosyl donors for glycosylation reactions. Two new procedures for the cleavage of the anomeric amide functionality under mild reaction conditions and further stereoselective in situ conversions of the activated glycosyl donors with alcohols and amines to give β-configured O- and N-glycosides are described in this article.
Diels-Alder Reactions of 2-Azabutadienes with Aldehydes: Ab Initio and Density Functional Theoretical Study of the Reaction Mechanism, Regioselectivi…
1997
The Diels−Alder reaction of 2-azabutadiene with aldehydes has been studied using high level ab initio molecular orbital and density functional methods. Multiconfigurational calculations were carried out on the concerted and stepwise mechanisms. At the CASPT2F/6-31G*//CASSCF/6-31G* level of theory, the [π4s + π2s]-cycloaddition of 2-azabutadiene with formaldehyde is predicted to be a concerted reaction, in good agreement with the experimental evidence. The regio- and stereoselectivity of the reaction was studied at the HF/6-31G*, MP2/6-31G*, and Becke3LYP/6-31G* levels of theory. The density functional calculations appears to give a good description of the basic features of the reaction. The…
Unveiling the reaction mechanism of novel copper N-alkylated tetra-azacyclophanes with outstanding superoxide dismutase activity.
2020
Quantum chemical and multiscale calculations reveal the mechanistic pathway of two superoxide dismutase mimetic N-alkylated tetra-azacyclophane copper complexes with remarkable activity. The arrangement of the binding site afforded by the bulky alkyl substituents and the coordinated water molecule as a proton source play key roles in the reaction mechanism.
Synthesis, Reactivity and Theoretical Study of B3H8−and Related Derivatives
1996
Abstract Octahydrotriborate salts, B3H8 −, have been prepared by the reaction of NaBH4 with Lewis acids such as BX3·BDMA (BDMA = benzyldimethylamine, × = Cl,Br) or C2H5I in diglyme. The presence of BH3·BDMA as a by-product in the former reaction provides new insight into the reaction mechanism of B11H14 − formation. In acetonitrile-water solutions of HCl or CH3CO2H, the B3H8 − anion reacted to give B3H7CH3CN or B3H7CH3CO2 − characterized by 11B NMR spectroscopy. Their kinetic hydrolysis study was consistent with NMR analysis. Reaction of Bu4NB3H8 and CuCl2 at 0°C produced pure B3H6Cl2 −. An AM1 theoretical study of the substituted derivatives B3H7L (L = Cl−, CH3CN, CH3CO2 −, OH−) and B3H6L2…