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411.
Eduardo J. Crevelin Fernanda H. Salami Marcela N. R. Alves Bruno S. De Martinis Antônio E. M. Crotti Luiz A. B. Moraes 《Journal of the American Society for Mass Spectrometry》2016,27(5):944-947
Amphetamine-type stimulants (ATS) are among illicit stimulant drugs that are most often used worldwide. A major challenge is to develop a fast and efficient methodology involving minimal sample preparation to analyze ATS in biological fluids. In this study, a urine pool solution containing amphetamine, methamphetamine, ephedrine, sibutramine, and fenfluramine at concentrations ranging from 0.5 pg/mL to 100 ng/mL was prepared and analyzed by atmospheric solids analysis probe tandem mass spectrometry (ASAP-MS/MS) and multiple reaction monitoring (MRM). A urine sample and saliva collected from a volunteer contributor (V1) were also analyzed. The limit of detection of the tested compounds ranged between 0.002 and 0.4 ng/mL in urine samples; the signal-to-noise ratio was 5. These results demonstrated that the ASAP-MS/MS methodology is applicable for the fast detection of ATS in urine samples with great sensitivity and specificity, without the need for cleanup, preconcentration, or chromatographic separation. Thus ASAP-MS/MS could potentially be used in clinical and forensic toxicology applications. 相似文献
412.
Marcela Holl Aneta Bílkov Pavel Jakubec Stanislava Kokov Hana Ko
ov Vl
kov Dalibor atínský Frantiek vec Hana Sklenov 《Molecules (Basel, Switzerland)》2021,26(11)
The new screening method for rapid evaluation of major phenolic compounds in apples has been developed. Suitability of coupling HPLC/UHPLC separation with the diode-array detection and universal charged aerosol detection with respect to the presence of interfering substances was tested. Characteristics of both detection techniques were compared and method linearity, limits of detection and quantitation, and selectivity of them determined. Student t-test based on slopes of calibration plots was applied for the detailed comparison. The diode-array detection provided the best results regarding sensitivity and selectivity of the developed method in terms of evaluation of phenolics profiles. The response of the charged aerosol detector was negatively affected by co-eluting substances during rapid-screening analyses. Coulometric detection was used for advanced characterization of extracts in terms of antioxidant content and strength to obtain more complex information concerning sample composition. This detection also allowed evaluation of unidentified compounds with antioxidant activity. HPLC/UHPLC separation using a combination of diode-array and coulometric detectors thus represented the best approach enabling quick, yet complex characterization of bioactive compounds in apples. 相似文献
413.
Nicolae Dan Tesloianu Lucian Dobreci Vlad Ghizdovat Andrei Zala Adrian Valentin Cotirlet Alina Gavrilut Maricel Agop Decebal Vasincu Igor Nedelciuc Cristina Marcela Rusu Irina Iuliana Costache 《Entropy (Basel, Switzerland)》2021,23(4)
By assimilating biological systems, both structural and functional, into multifractal objects, their behavior can be described in the framework of the scale relativity theory, in any of its forms (standard form in Nottale’s sense and/or the form of the multifractal theory of motion). By operating in the context of the multifractal theory of motion, based on multifractalization through non-Markovian stochastic processes, the main results of Nottale’s theory can be generalized (specific momentum conservation laws, both at differentiable and non-differentiable resolution scales, specific momentum conservation law associated with the differentiable–non-differentiable scale transition, etc.). In such a context, all results are explicated through analyzing biological processes, such as acute arterial occlusions as scale transitions. Thus, we show through a biophysical multifractal model that the blocking of the lumen of a healthy artery can happen as a result of the “stopping effect” associated with the differentiable-non-differentiable scale transition. We consider that blood entities move on continuous but non-differentiable (multifractal) curves. We determine the biophysical parameters that characterize the blood flow as a Bingham-type rheological fluid through a normal arterial structure assimilated with a horizontal “pipe” with circular symmetry. Our model has been validated based on experimental clinical data. 相似文献
414.
Suelem D. Ramalho Lorena R. F. de Sousa Marcela C. M. Burger Maria Inês S. Lima M. Fátima das G. F. da Silva João B. Fernandes 《Natural product research》2015,29(23):2212-2214
Cathepsin B (catB) is a cysteine protease involved in tumour progression and represents a potential therapeutic target in cancer. Among the 15 evaluated extracts from cerrado biome, Myrcia lingua Berg. (Myrtaceae) extract demonstrated to be a source of compounds with potential to inhibit catB. Using bioactivity-guided fractionation, we have found flavonols as inhibitors and also some other derivatives were obtained. From the evaluated compounds, myricetin (5) and quercetin (6) showed the most promising results with IC50 of 4.9 and 8.2 μM, respectively, and mode of inhibition as uncompetitive on catB. The results demonstrated polyhydroxylated flavonols as promising inhibitors of catB. 相似文献
415.
This study aims to evidence the influence of polyelectrolytes structure and the number of double layers on the properties
of some new nanostructured architectures formed by layer-by-layer self-assembly of complementary weak polyelectrolytes on
planar surfaces. For this purpose, we used chitosan and poly(allylamine hydrochloride) as polycations, and poly(acrylic acid)
and poly(2-acrylamido-2-methylpropanesulfonic acid–co-acrylic acid) as polyanions. To get a direct image on the polyelectrolyte
multilayers formation and properties, gravimetry, infrared spectroscopy, and atomic force microscopy have been used. The capacity
of the polyions to overcompensate the complementary polyions charges, and thus to influence the swelling degree in water of
thin films, was strongly influenced by the chain structure and flexibility. A special attention was paid to the responsiveness
of the new composite materials to the pH of the swelling environment. 相似文献
416.
Carolina V. Barra Fillipe V. Rocha Adelino V. G. Netto Regina C. G. Frem Antonio E. Mauro Iracilda Z. Carlos Sandra R. Ananias Marcela B. Quilles 《Journal of Thermal Analysis and Calorimetry》2011,106(2):489-494
This study describes the synthesis, IR, 1H, and 13C{1H} NMR spectroscopic as well the thermal characterization of the new palladium(II) pyrazolyl complexes [PdCl2(HmPz)2] 1, [PdBr2(HmPz)2] 2, [PdI2(HmPz)2] 3, [Pd(SCN)2(HmPz)2] 4 {HmPz = 4-methylpyrazole}. The residues of the thermal decomposition were identified as Pd0 by X-ray powder diffraction. From the initial decomposition temperatures, the thermal stability of the complexes can be ordered
in the sequence: 1 > 2 > 4 ≈ 3. The cytotoxic activities of the complexes and the ligand were investigated against two murine cancer cell lines: mammary
adenocarcinoma (LM3) and lung adenocarcinoma (LP07) and compared to cisplatin under the same experimental conditions. 相似文献
417.
Luís M. Magalhes Joana P.N. Ribeiro Marcela A. Segundo Salette Reis Jos L.F.C. Lima 《Trends in analytical chemistry : TRAC》2009,28(8):952-960
Conventionally, measuring antioxidant capacity is time consuming, laborious and costly, especially in routine work. These limitations can be overcome using multi-syringe flow-injection analysis (MSFIA), which has succeeded in automating the most widely applied antioxidant-capacity assays that use chromogen radicals or reactive species found in vivo. We highlight the features of MSFIA and improved methodologies in using MSFIA to measure antioxidant capacity. 相似文献
418.
Dilek I Madrid M Singh R Urrea CP Armitage BA 《Journal of the American Chemical Society》2005,127(10):3339-3345
Optical spectroscopy and molecular dynamics simulations have been used to study the interaction between a cationic cyanine dye and peptide nucleic acid (PNA)-DNA duplexes. This recognition event is important because it leads to a visible color change, signaling successful hybridization of PNA with a complementary DNA strand. We previously proposed that the dye recognized the minor groove of the duplex, using it as a template for the assembly of a helical aggregate. Consistent with this, we now report that addition of isobutyl groups to the PNA backbone hinders aggregation of the dye when the substituents project into the minor groove but have a weaker effect if directed out of the groove. UV-Visible and circular dichroic spectroscopy were used to compare aggregation on the different PNA-DNA duplexes, while molecular dynamics simulations were used to confirm that the substituents block the minor groove to varying degrees, depending on the configuration of the starting amino acid. In addition to a simple steric blockage effect of the substituent, the simulations suggest that directing the isobutyl group into the minor groove causes the groove to narrow and the duplex to become more rigid, structural perturbations that are relevant to the growing interest in backbone-modified PNA for applications in the biological and materials sciences. 相似文献
419.
Multi-Syringe Flow Injection System with In-Line Pre-Concentration for the Determination of Total Phenolic Compounds 总被引:1,自引:0,他引:1
Hugo M.?Oliveira Marcela A.?SegundoEmail author Salette?Reis José L. F. C.?Lima 《Mikrochimica acta》2005,150(2):187-196
A multi-syringe flow injection system for the determination of total phenolics based on the 4-aminoantipyrine reaction is proposed. In-line preconcentration using solid-phase extraction was implemented, offering an environmentally friendly alternative to organic solvent extraction performed in the batch procedure and in previously described flow methodologies. Therefore, phenolic compounds were retained in Amberlite XAD4 resin using acidic conditions. The elution was carried out using 0.10molL–1 NaOH solution, promoting the ionisation of the retained phenolic compounds, and thus their desorption.Since different elution profiles were obtained for several phenol derivatives, the calibration curves were established using the peak area as analytical signal. Moreover, a dynamic calibration range was applied by using a variable sample volume (0.500–6.00mL) and calibration curves based on the mass of phenol retained in the pre-concentration column. A methodology based on a fixed sample volume (24.0mL) was also proposed for determination at concentration levels below 50µgL–1. A limit of detection of 52ng of phenol (9 or 2µgL–1) was achieved with a sampling frequency of 10–16h–1 for the variable volume method and 4h–1 for the fixed volume method. The application of the proposed methodology to reference material provided results that were within the certified acceptance limits. 相似文献
420.
The total synthesis of (S)-(+)-imperanene, a natural product found in Chinese medicine, has been completed in 12 steps from a commercially available cinnamic acid. The key step is highly enantioselective carbon-hydrogen insertion from a diazoacetate using a chiral dirhodium(II) carboxamidate catalyst. An elimination process essential to the construction has been optimized to avoid intramolecular Friedel-Crafts alkylation. 相似文献