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11.
A flow-injection—conductimetric method was applied to the determination of ammonia, nitrate and nitrite at concentrations down to 5, 20 and 20 ng ml?1, respectively. Ammonia was determined by merging the injected sample with an alkaline solution (NaOHEDTA) and passing the mixture through a diffusion cell. The ammonia released was collected by a flowing stream of deionized water that passed through a conductance flow cell. Nitrate and nitrite concentrations were determined after reduction to ammonia in alkaline medium using a column filled with metallic zinc. The ammonia produced was then measured as described above. About 60 samples per hour can be processed with a relative standard deviation of about 1%. Satisfactory agreement was observed between results for ammonia in samples of natural water and nitrate in tap and mineral water determined by the proposed method and by standard spectrophotometric procedures. Speciation can be achieved by adding sulphanilic acid to remove nitrite from the sample and determining the ammonia without the use of the column. 相似文献
12.
Vânia G. Zuin Aylon M. Stahl Karine Zanotti Mateus L. Segatto 《Current Opinion in Green and Sustainable Chemistry》2020
Green (and sustainable?) frame around ‘Inverted America’ (adapted from Torres García, 1943, Museo Juan Manuel Blanes, Montevideo, CC BY 4.0). 相似文献
13.
Immobilized purine nucleoside phosphorylase from Schistosoma mansoni for specific inhibition studies
Marcela Cristina de Moraes Carmen L. Cardoso Quezia B. Cass 《Analytical and bioanalytical chemistry》2013,405(14):4871-4878
The parasite Schistosoma mansoni (Sm) depends exclusively on the salvage pathway for its purine requirements. The enzyme purine nucleoside phosphorylase (PNP) is, therefore, a promising target for development of antischistosomal agents and an assay for screening of inhibitors. To enable this, immobilized SmPNP reactors were produced. By quantification of hypoxanthine by liquid chromatography, kinetic constants (K M) for the substrate inosine were determined for the free and immobilized enzyme as 110 ± 6.90 μmol?L ?1 and 164 ± 13.4 μmol?L ?1 , respectively, indicating that immobilization did not affect enzyme activity. Furthermore, the enzyme retained 25 % of its activity after four months. Non-Michaelis kinetics for the phosphate substrate, and capacity for Pi-independent hydrolysis were also demonstrated, despite the low rate of enzymatic catalysis. Use of an SmPNP immobilized enzyme reactor (IMER) for inhibitor-screening assays was demonstrated with a small library of 9-deazaguanine analogues. The method had high selectivity and specificity compared with screening by use of the free enzyme by the Kalckar method, and furnished results without the need for verification of the absence of false positives. Figure
A cartoon illustrating the online SmPNP-IMER activity assay 相似文献
14.
André Luís Branco de Barros Saulo Fernandes de Andrade José Dias de Souza Filho Valbert Nascimento Cardoso Ricardo José Alves 《Journal of Radioanalytical and Nuclear Chemistry》2013,298(1):605-609
Glycodendrimers are neoglycoconjugates that can be considered as bioisosters of glycoproteins, since they can mimic the multivalent interactions of lectin-carbohydrate. The ability of glycodendrimers to present multivalent interactions with lectins as compared to a monovalent ligand is referred to as “cluster effect”. It is expected that, because of the cluster effect, glycodendrimers would result in a better association with lectins than mono-carbohydrate anchored systems. Radioisotopes are useful to evaluate biodistribution of molecules. This study is important to obtain information about molecule–receptor interactions. Indeed, such study can provide an exquisite tool to evaluate the affinity of certain molecules to specific areas in the body, leading to the development of new radiopharmaceuticals and/or drug delivery systems. Herein, we describe a d-galactose coated low molecular weight PAMAM G0 dendrimer that was successfully radiolabeled with technetium-99m. Biodistribution studies and scintigraphic images were performed in healthy mice. It was observed high liver uptake which was significantly reduced in blocking studies, indicating hepatic specificity. Therefore, low molecular weight glycodendrimer can be considered as useful platform for selective targeting of drugs to the liver and to assess hepatic function. 相似文献
15.
Lóren C.C. Gonçalves Francine N. Victória David B. Lima Pedro M.Y. Borba Gelson Perin Lucielli Savegnago Eder J. Lenardão 《Tetrahedron letters》2014
(E)-1,2-Bis-chalcogen alkenes were stereoselectively prepared in good yields by the addition of diorganyl dichalcogenides to terminal alkynes using CuI/Zn/glycerol as a recyclable catalytic system. The antioxidant activity in vitro of four (E)-1,2-bis-chalcogen alkenes synthesized was evaluated and (E)-1,2-bis-(4-methoxyphenylselanyl)styrene 3b presented excellent activity. The catalytic system used in the synthesis was recovered and used directly up to 5 cycles without loss of activity. 相似文献
16.
Aleksandra Borisova Mario De Bruyn Vitaliy L. Budarin Peter S. Shuttleworth Jennifer R. Dodson Mateus L. Segatto James H. Clark 《Macromolecular rapid communications》2015,36(8):774-779
Bio‐derived polysaccharide aerogels are of interest for a broad range of applications. To date, these aerogels have been obtained through the time‐ and solvent‐intensive procedure of hydrogel fomation, solvent exchange, and scCO2 drying, which offers little control over meso/macropore distribution. A simpler and more versatile route is developed, using freeze drying to produce highly mesoporous polysaccharide aerogels with various degrees of macroporosity. The hierarchical pore distribution is controlled by addition of different quantities of t‐butanol (TBA) to hydrogels before drying. Through a systematic study an interesting relationship between the mesoporosity and t‐butanol/water phase diagram is found, linking mesoporosity maxima with eutectic points for all polysaccharides studied (pectin, starch, and alginic acid). Moreover, direct gelation of polysaccharides in aqueous TBA offers additional time savings and the potential for solvent reuse. This finding is a doorway to more accessible polysaccharide aerogels for research and industrial scale production, due to the widespread accessibility of the freeze drying technology and the simplicity of the method.
17.
Machado Poliana A. L. Cavalcanti Marcello H. S. Silva Fábio A. B. de Almeida Eduardo T. Cardoso Marcus V. C. Mesquita Anderson F. Lemes Nelson H. T. Virtuoso Luciano S. 《Journal of solution chemistry》2022,51(3):320-344
Journal of Solution Chemistry - Liquid–liquid equilibrium (LLE) data and phase diagrams for new aqueous two-phase systems (ATPSs) containing 1-butyl-3-methylimidazolium chloride... 相似文献
18.
Poliana Cristina Spricigo Banny Silva Barbosa Correia Karla Rodrigues Borba Isabela Barroso Taver Guilherme de Oliveira Machado Renan Ziemann Wilhelms Luiz Henrique Keng Queiroz Junior Angelo Pedro Jacomino Luiz Alberto Colnago 《Molecules (Basel, Switzerland)》2021,26(12)
The cambuci is a native Brazilian fruit from the Atlantic Forest biome. A soft and astringent pulp, a green color, and a sweet aroma are its main characteristics. Classical food quality attributes (fresh fruit mass, fruit height, diameters, total soluble solid, titratable acidity, and ratio) and the metabolic profile from ten accessions from three different locations were analyzed herein by analytical methods (refractometry and neutralization titration) and nuclear magnetic resonance spectroscopy. Concerning sugar content, sucrose was the predominant compound, with glucose and fructose alternating in second, depending on the accession. Citric acid was the most relevant acid, followed by shikimic and quinic acids in quite variable amounts. These three main acids vary in amounts for each accession. Ascorbic acid content emerges as an important quality attribute and makes this fruit nutritionally attractive, due to values comparable to those contained in citric fruits. The main amino acids identified in cambuci were glutamic acid individually or in comprising the tripeptide glutathione (glutamic acid, cysteine, glycine). The quality diversity of the evaluated accessions suggests the potentiality of cambuci use in future breeding programs. 相似文献
19.
20.
Noelia Cambeiro-Prez Xiana Gonzlez-Gmez Carmen Gonzlez-Barreiro María Rosa Prez-Gregorio Iva Fernandes Nuno Mateus Victor de Freitas Borja Snchez Elena Martínez-Carballo 《Molecules (Basel, Switzerland)》2021,26(4)
Dihydrochalcones, phlorizin (PZ) and its aglycone phloretin (PT), have evidenced immunomodulatory effects through several mechanisms. However, the differential metabolic signatures that lead to these properties are largely unknown. Since macrophages play an important role in the immune response, our study aimed to characterise human THP-1 macrophages under PZ and PT exposure. A multiplatform-based untargeted metabolomics approach was used to reveal metabolites associated with the anti-inflammatory mechanisms triggered by the dihydrochalcones in LPS-stimulated macrophages, for the first time. Results showed differential phenotypic response in macrophages for all treatments. Dihydrochalcone treatment in LPS-stimulated macrophages mimics the response under normal conditions, suggesting inhibition of LPS response. Antagonistic effects of dihydrochalcones against LPS was mainly observed in glycerophospholipid and sphingolipid metabolism besides promoting amino acid biosynthesis. Moreover, PT showed greater metabolic activity than PZ. Overall, the findings of this study yielded knowledge about the mechanisms of action PZ and PT at metabolic level in modulating inflammatory response in human cells. 相似文献