295 research outputs found
Bare carbon electrodes as simple and efficient sensors for the quantification of caffeine in commercial beverages
This work has been supported by the European Union's Horizon 2020 research and innovation programme under the Marie Sklodowska-Curie grant agreement no. 642014 (IPCOS). Ĺ.Š. would like to acknowledge the Grant Agency of the Slovak Republic (grant no. 1/0489/16)
Simultaneous quantification of antioxidants paraxanthine and caffeine in human saliva by electrochemical sensing for CYP1A2 phenotyping
The enzyme CYP1A2 is responsible for the metabolism of numerous antioxidants in the body, including caffeine, which is transformed into paraxanthine, its main primary metabolite. Both molecules are known for their antioxidant and pro-oxidant characteristics, and the paraxanthine-to-caffeine molar ratio is a widely accepted metric for CYP1A2 phenotyping, to optimize dose\u2013 response effects in individual patients. We developed a simple, cheap and fast electrochemical based method for the simultaneous quantification of paraxanthine and caffeine in human saliva, by differential pulse voltammetry, using an anodically pretreated glassy carbon electrode. Cyclic voltammetry experiments revealed for the first time that the oxidation of paraxanthine is diffusion controlled with an irreversible peak at ca. +1.24 V (vs. Ag/AgCl) in a 0.1 M H2 SO4 solution, and that the mechanism occurs via the transfer of two electrons and two protons. The simultaneous quantification of paraxanthine and caffeine was demonstrated in 0.1 M H2 SO4 and spiked human saliva samples. In the latter case, limits of detection of 2.89 \ub5M for paraxanthine and 5.80 \ub5M for caffeine were obtained, respectively. The sensor is reliable, providing a relative standard deviation within 7% (n = 6). Potential applicability of the sensing platform was demonstrated by running a small scale trial on five healthy volunteers, with simultaneous quantification by differential pulse voltammetry (DPV) of paraxanthine and caffeine in saliva samples collected at 1, 3 and 6 h postdose administration. The results were validated by ultra-high pressure liquid chromatography and shown to have a high correlation factor (r = 0.994)
Synthesis of p-coumaroylquinic acids and analysis of their interconversion
The synthesis of four isomers of p-coumaroylquinic acids was performed by esterification of p-acetylcoumaroylchloride with a suitably protected (-)-quinic acid. All isomers have been characterized by means of NMR spectroscopy and circular dichroism. Acyl migration was observed in the synthesis of 3-0-p-coumaroylquinic acid and 4-O-p-coumaroylquinic acid. Calculations on the most stable conformations of all isomers have also been performed to explain the acyl migration observed during the synthesis procedure
Prediction of self-assembly of adenosine analogues in solution: a computational approach validated by isothermal titration calorimetry.
The recent discovery of the role of adenosine-analogues as neuroprotectants and cognitive enhancers has sparked interest in these molecules as new therapeutic drugs. Understanding the behavior of these molecules in solution and predicting their ability to self-assemble will accelerate new discoveries. We propose a computational approach based on density functional theory, a polarizable continuum solvation description of the aqueous environment, and an efficient search procedure to probe the potential energy surface, to determine the structure and thermodynamic stability of molecular clusters of adenosine analogues in solution, using caffeine as a model. The method was validated as a tool for the prediction of the impact of small structural variations on self-assembly using paraxanthine. The computational results were supported by isothermal titration calorimetry experiments. The thermodynamic parameters enabled the quantification of the actual percentage of dimer present in solution as a function of concentration. The data suggest that both caffeine and paraxanthine are present at concentrations comparable to the ones found in biological samples
Kinds of tags: progress report for the DC-Social tagging community
Apresentação efectuada na DC-2007 International Conference on Dublin Core and Metadata Applications - "Application profiles : theory and practice", Singapura, 27 - 31 Ag. 2007
NEU3 sialidase role in activating HIF-1α in response to chronic hypoxia in cyanotic congenital heart patients
Background Hypoxia is a common feature of many congenital heart defects (CHDs) and significantly contributes to their pathophysiology. Thus, understanding the mechanism underlying cell response to hypoxia is vital for the development of novel therapeutic strategies. Certainly, the hypoxia inducible factor (HIF) has been extensively investigated and it is now recognized as the master regulator of cell defense machinery counteracting hypoxic stress. Along this line, we recently discovered and reported a novel mechanism of HIF activation, which is mediated by sialidase NEU3. Thus, aim of this study was to test whether NEU3 played any role in the cardiac cell response to chronic hypoxia in congenital cyanotic patients. Methods Right atrial appendage biopsies were obtained from pediatric patients with cyanotic/non-cyanotic CHDs and processed to obtain mRNA and proteins. Real-Time PCR and Western Blot were performed to analyze HIF-1\uce\ub1 and its downstream targets expression, NEU3 expression, and the NEU3 mediated effects on the EGFR signaling cascade. Results Cyanotic patients showed increased levels of HIF-1\uce\ub1, NEU3, EGFR and their downstream targets, as compared to acyanotic controls. The same patients were also characterized by increased phosphorylation of the EGFR signaling cascade proteins. Moreover, we found that HIF-1\uce\ub1 expression levels positively correlated with those recorded for NEU3 in both cyanotic and control patients. Conclusions Sialidase NEU3 plays a central role in activating cell response to chronic hypoxia inducing the up-regulation of HIF-1\uce\ub1, and this represent a possible novel tool to treat several CHD pathologies
Serum prolactin concentrations as risk factor of metabolic syndrome or type 2 diabetes?
Epigenetic modifications and glucocorticoid sensitivity in Myalgic Encephalomyelitis/Chronic Fatigue Syndrome (ME/CFS)
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