Search results for "Amide"
showing 10 items of 3119 documents
NovelAmycolatopsis balhimycinabiochemical abilities unveiled by proteomics
2014
Amycolatopsis balhimycina DSM5908 is an actinomycete producer of balhimycin, an analogue of vancomycin, the antibiotic of ‘last resort’ against multidrug-resistant Gram-positive pathogens. Most knowledge on glycopeptide biosynthetic pathways comes from studies on A. balhimycina as this strain, among glycopeptide producers, is genetically more amenable. The recent availability of its genome sequence allowed to perform differential proteomic analyses elucidating key metabolic pathways leading to antibiotic production in different growth conditions. To implement proteomic data on A. balhimycina derived from 2-DE approaches and to identify novel components, a combined approach based on protein …
Effect of carboxymethyl cellulose on tartrate salt, protein and colour stability of red wine
2014
Background and Aims Recent studies have confirmed a long-term effect of carboxymethyl cellulose (CMC) for tartrate salt stabilisation in white wine. It has been argued that CMC is not only less effective in red wine but also interacts with proteins and polyphenols generating turbidity and change in colour. In order to explain these effects, we studied in detail the impact of CMC on haze formation and colour stability of red wine. Methods and Results The influence of CMC concentration was tested with ten samples of red wine produced from several grape cultivars. The haze-forming material was analysed by sodium dodecyl-sulfate polyacrylamide electrophoresis and the protein composition by high…
Combined effect of solvent content, temperature and pH on the chromatographic behaviour of ionisable compounds.
2008
The organic solvent content and the pH in the mobile phase are the usual main factors in reversed-phase liquid chromatographic separations, owing to their strong effects on retention and/or selectivity. Temperature is often neglected. However, even in cases where the impact of this factor on selectivity is minor, the reduction in analysis time is still an interesting reason to consider it. In addition, ionisable compounds may exhibit selectivity changes, owing to the interaction of organic solvent and/or temperature with pH. The separation of ionisable compounds (nine diuretics: bendroflumethiazide, benzthiazide, bumetanide, chlorthalidone, furosemide, piretanide, probenecid, trichloromethi…
Testing experimental designs in liquid chromatography (I): Development and validation of a method for the comprehensive inspection of experimental de…
2020
The basis of interpretive optimisation in liquid chromatography is the prediction of resolution, from appropriate solute retention models. The reliability of the process depends critically on the quality of the experimental design. This work develops, validates and applies a general methodology aimed to evaluate the quality of any training experimental design, which will be applied in Part II to design optimisation. The methodology is based on the systematic evaluation of the uncertainties associated to the prediction of retention times in comprehensive scans of both isocratic and gradient experimental conditions. It is able to evaluate comprehensively experimental designs of arbitrary comp…
Comparison of two serially coupled column systems and optimization software in isocratic liquid chromatography for resolving complex mixtures.
2012
Although there is a great deal of stationary phases having different selectivities (even practically orthogonal selectivities), these very rarely are taken as a factor to be optimized during method development. The chromatographer selects the stationary phase usually in a trial-and-error fashion (or based on the solute nature and expected interactions), and then optimizes continuous factors as the mobile phase composition, pH, temperature and flow-rate. However, the optimization of the stationary phase nature and column length (which are discrete factors) may be interesting. In this regard, the optimization of the coupling of individual columns may yield separations that are not possible wi…
Cyclic tetraureas with variable flexibility--synthesis, crystal structures and properties.
2008
Macrocyclic molecules containing several amide or urea functions may serve as anion receptors. We describe the synthesis of 32-membered macrocycles, in which four rigid xanthene units (X) and/or diphenyl ether units (D) as flexible analogues are linked via urea groups. All six possible combinations of these units (XXXX, XXXD, XXDD, XDXD, XDDD and DDDD) were synthesized and two examples were characterised by single-crystal X-ray analyses (DDDD and two structures for XXXD). Both macrocycles showed distinct differences in their overall conformation and consequently in their hydrogen-bonding pattern. Hydrogen-bonded solvent molecules are found for both compounds and intramolecular hydrogen bond…
2,7-Di-tert-butyl-9,9-dimethyl-4,5-bis(4-tritylanilinocarbonyl)-9H-xanthene methanol trisolvate monohydrate
2006
The title compound, C75H68N2O3·3CH3OH·H2O, was synthesized starting from the corresponding acid and p-tritylaniline. Single crystals were obtained from a methanol solution as a solvate, with three methanol molecules and one water molecule. The solid-state structure proves the existence of an intramolecular bifurcated hydrogen bond between one amide H atom and the carbonyl and xanthene O atoms. The packing is stabilized by intermolecular hydrogen bonds.
Evaluation of Fused Pyrrolothiazole Systems as Correctors of Mutant CFTR Protein.
2021
Cystic fibrosis (CF) is a genetic disease caused by mutations that impair the function of the CFTR chloride channel. The most frequent mutation, F508del, causes misfolding and premature degradation of CFTR protein. This defect can be overcome with pharmacological agents named “correctors”. So far, at least three different classes of correctors have been identified based on the additive/synergistic effects that are obtained when compounds of different classes are combined together. The development of class 2 correctors has lagged behind that of compounds belonging to the other classes. It was shown that the efficacy of the prototypical class 2 corrector, the bithiazole corr-4a, could be impr…
Sulfur Dioxide Oxidation Catalyzed by Photosensitized Ytterbium Diphthalocyanine
2008
Oxidation of SO2 into SO3 was found effectively catalyzed by photosensitized ytterbium diphthalocyanine, YbPc2 (Pc = phthalocyanine ligand, C32H16N8) when performed in air-saturated dimethylformamide (DMF) solution at 20 °C. The process follows according to a multi-step complex mechanism involving chemical induction as its driving force. Excitation energy of the sandwich molecular system in YbPc2 is used to promote the reaction by creating a reactive intermediate form of the ytterbium complex hosting up to eight SO2 molecules. The conversion of SO2 proved complete.
Harvesting canthinones: identification of the optimal seasonal point of harvest of Zanthoxylum chiloperone leaves as a source of 5-methoxycanthin-6-o…
2015
This article is focused on the seasonal variation in the contents of 5-methoxycanthin-6-one from the leaves of Zanthoxylum chiloperone (Rutaceae). Based on the pharmacological interest presented by 5-methoxycanthin-6-one, its seasonal variation in Z. chiloperone leaves was analysed in order to determine the best time for harvesting, optimising the 5-methoxycanthin-6-one content. The seasonal dynamics of canthinone alkaloids can be the key to improve the isolation from natural sustainable sources, such as leaves. Complementarily, this study describes the phytochemistry of leaf from this Ruraceae species.