排序方式: 共有49条查询结果,搜索用时 46 毫秒
31.
Shujing Ding Inez Schoenmakers Kerry Jones Albert Koulman Ann Prentice Dietrich A. Volmer 《Analytical and bioanalytical chemistry》2010,398(2):779-789
Vitamin D is an important determinant of bone health at all ages. The plasma concentrations of 25-hydroxy vitamin D (25-OH
D) and other metabolites are used as biomarkers for vitamin sufficiency and function. To allow for the simultaneous determination
of five vitamin D metabolites, 25-OH D3, 25-OH D2, 24,25-(OH)2 D3, 1,25-(OH)2 D3, and 1,25-(OH)2 D2, in low volumes of human plasma, an assay using ultra-high-performance liquid chromatography–tandem mass spectrometry (UHPLC-MS/MS)
was established. Plasma samples were spiked with isotope-labeled internal standards and pretreated using protein precipitation,
solid-phase extraction (SPE) and a Diels–Alder derivatization step with 4-phenyl-1,2,4-triazoline-3,5-dione. The SPE recovery
rates ranged from 55% to 85%, depending on the vitamin D metabolite; the total sample run time was <5 min. Mass spectrometry
was conducted using positive ion electrospray ionization in the multiple reaction monitoring mode on a quadrupole–quadrupole-linear
ion trap instrument after pre-column addition of methylamine to increase the ionization efficiency. The intra- and inter-day
relative standard deviations were 1.6–4.1% and 3.7–6.8%, respectively. The limit of quantitation for these compounds was determined
to be between 10 and 20 pg/mL. The 25-OH D results were compared with values obtained for reference materials (DEQAS). In
addition, plasma samples were analyzed with two additional Diasorin antibody assays. All comparisons with conventional methods
showed excellent correlations (r
2 = 0.9738) for DEQAS samples, demonstrating the high degree of comparability of the new UHPLC-MS/MS technique to existing
methods. 相似文献
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33.
Ditaranto N Loperfido S van der Werf I Mangone A Cioffi N Sabbatini L 《Analytical and bioanalytical chemistry》2011,399(1):473-481
Biological agents play an important role in the deterioration of cultural heritage causing aesthetic, biogeophysical and biogeochemical
damages. Conservation is based on the use of preventive and remedial methods. The former aims at inhibiting biological attack,
and the latter aims at eradicating the biological agents responsible for biodeterioration. Here, we propose the preparation
and the analytical characterisation of copper-based nanocoating, capable of acting both as a remedy and to prevent microbial
proliferation. Core–shell CuNPs are mixed with a silicon-based product, commonly used as a water-repellent/consolidant, to
obtain a combined bioactive system to be applied on stone substrates. The resulting coatings exert a marked biological activity
over a long period of time due to the continuous and controlled release of copper ions acting as biocides. To the best of
our knowledge, this is the first time that a multifunctional material is proposed, combining the antimicrobial properties
of nanostructured coatings with those of the formulations applied to the restoration of stone artworks. A complete characterisation
based on a multi-technique analytical approach is presented. 相似文献
34.
Ktia Cristina Sibin Melo Terezinha Inez Estivalet Svidzinski Mariana Cristina Vicente Umada Zapater Thiago Honrio Dutra da Silva Gutierrez Rodrigues de Morais Francielle Sato Mauro Luciano Baesso Luzmarina Hernandes 《Journal of Raman spectroscopy : JRS》2014,45(10):873-878
Fusarium is an emerging pathogen with high levels of morbidity and mortality. A significant tissue response is observed in infected patients, and the condition has been associated with the production of toxic metabolites. The aim of the present study was to identify a major fraction of crude metabolic extract of Fusarium oxysporum and investigate its effects on the skin of healthy rats. Fraction F1 was obtained from the cultivation of F. oxysporum in Czapek–Dox. In the treatment groups, fraction F1 (0.05 mg/ ml) was injected intradermally, while (50 µl) 0.9% of saline solution was injected in the control groups. The animals were killed 3, 6, 12, and 24 h after inoculation. The skin was fixed for inclusion in paraffin to obtain histological sections and stained with hematoxylin and eosin, Sirius red, and terminal deoxynucleotidyl transferase‐mediated dUTP nick‐end labeling. Samples were analyzed using Fourier transform Raman spectroscopy. The tissue reactions were classified and compared over time and by treatment. In the treatment group, inflammatory reaction peaked at 6 h, being classified as moderate, with infiltrate composed mainly of neutrophils. terminal deoxynucleotidyl transferase‐mediated dUTP nick‐end labeling staining was negative. The area occupied by types I and III collagen in the treatment group increased over time. There was a change in the area occupied by amide I and the ratios of the –CH2 and –CH3 molecules. It can be argued that the fraction F1 contains elements that contribute to the invasion of Fusarium in the skin, destructurizing the organization of the extracellular matrix. Copyright © 2014 John Wiley & Sons, Ltd. 相似文献
35.
Inez van der Werf Francesco Palmisano Luigia Sabbatini 《Journal of Analytical and Applied Pyrolysis》2009,86(1):233-238
The thermal decomposition process and pyrolysis products of poly(vinyl phenyl ketone) (PVPK) were investigated by thermogravimetric analysis (TGA) and on-line pyrolysis-gas chromatography–mass spectrometry (Py-GC–MS). TGA showed a largest weight loss rate around 380 °C. Py-GC–MS was used for the qualitative analysis of the pyrolysis products at 350, 500, 600, 700 and 850 °C. The major volatile thermal decomposition product was found to be 1-phenyl-2-propenone, which dominated all other volatile species especially under the least severe pyrolysis conditions (<600 °C). At higher temperatures a much wider range of pyrolysis products was obtained. The results have been interpreted assuming that primary random chain scission reactions occur followed by typical unzipping mainly producing monomer units; detachment of the side-group occurs only under more severe pyrolysis conditions. Py-GC–MS showed to be effective in PVPK detection in ink and paint formulations. 相似文献
36.
Kalász H Klebovich I Balogh-Nemes K Szilágyi A Tihanyi M Szarvas T Lengyel J 《Analytical and bioanalytical chemistry》2005,382(3):760-764
Administration of radiolabelled deprenyl to rats resulted in the urinary elimination of a 14C-labelled N-monomethyl-lysine. An increased level of N-monomethyl-lysine was found following an oral dose of another drug, also containing an N-methyl group. The urine sample was treated with 9-fluorenylmethoxycarbonyl chloride and then subjected to high-performance liquid chromatography (HPLC); the radioactive fraction was identified as N-monomethyl-lysine by using HPLC-MS in electrospray mode. Identification of N-monomethyl-lysine in the radioactive fraction gives experimental proof of transmethylation from a well-known drug to an endogenous compound. 相似文献
37.
Christine Joy Querebillo Ibrahim Halil Öner Prof. Dr. Peter Hildebrandt Dr. Khoa Hoang Ly Prof. Dr. Inez M. Weidinger 《Chemistry (Weinheim an der Bergstrasse, Germany)》2019,25(70):16048-16053
Herein, the enhanced visible-light-induced degradation of the azo-dye benzidine-p-aminothiophenolate immobilized on TiO2 nanotube electrodes is reported. Exploiting the reported photonic properties of the TiO2 support and the strong electronic absorption of the dye allowed for employing surface-enhanced resonance Raman spectroscopy at 413 nm to simultaneously trigger the photoreaction and follow the time-dependent decay process. Degradation rate constants of up to 25 s−1 were observed, which stand among the highest reported values for laser-induced degradation of immobilized dyes on photonically active supports. Contrast experiments with two differently light-enhancing TiO2 nanotube electrodes establish the direct correlation of the material's optical response, that is, electromagnetic field enhancement, on the interfacial photocatalytic reaction. 相似文献
38.
The Ramanujan Journal - Computing the reciprocal sum of sparse integer sequences with tight upper and lower bounds is far from trivial. In the case of Carmichael numbers or twin primes even the... 相似文献
39.
Luís A. S. A. De Prado Iris L. Torriani Inez V. P. Yoshida 《Journal of polymer science. Part A, Polymer chemistry》2010,48(5):1220-1229
Self‐supported translucent films constituted of poly(n‐octylsilsesquioxane) or poly(n‐dodecylsilsesquioxane) were obtained from the hydrolysis and condensation of n‐octyltriethoxysilane (OTES) or n‐dodecyltriethoxysilane (DTES), respectively. Dense films were obtained in the absence of organic solvents, with dibutyltin diacetate as catalyst. These films exhibited good optical transparency and thermal stability. The incorporation of oligomeric dimethylsiloxane units (DMe,Me) in these materials, derived from silanol‐terminated poly(dimethylsiloxane) (PDMS) or 1,1,3,3‐tetramethyl‐1,3‐diethoxydisiloxane (TMDES), was carried out during the hydrolysis and condensation of OTES and DTES and was confirmed by solid‐state 29Si NMR. Poly(n‐octylsilsesquioxane) showed a glass‐transition temperature at ?65 °C, due to the increase in the free volume, promoted by the bulky n‐octyl groups. The differential scanning calorimetric (DSC) curves of the polymer derived from DTES were characterized by first‐order transitions at temperatures ranging from ?15.8 to ?0.7 °C. Further studies of these networks by low‐temperature XRD evidenced narrowing of the diffraction halos suggesting a partial order–disorder transition for these materials at lower temperatures. Good thermal stability up to 350 °C and the solvent‐free production process make these polymers potential candidates for the development of self‐supported hydrophobic protective coatings. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 48: 1220–1229, 2010 相似文献
40.
Larissa Reis Brandão Inez Valéria Pagotto Yoshida Maria Isabel Felisberti Maria do Carmo Gonçalves 《Cellulose (London, England)》2013,20(6):2791-2802
Composites of cellulose acetate and polysiloxane were prepared using 3-isocyanatepropyltriethoxysilane, as a coupling agent. The structure, the thermal and dynamic-mechanical behaviors, and the morphology of the obtained composites were investigated. The composites showed phase separation which was confirmed by the presence of siloxane micro- and nano-domains dispersed in the cellulose acetate matrix, with good interfacial adhesion between the phases. The results demonstrated that the incorporation of a polysiloxane phase on a cellulose acetate matrix caused a decrease in the glass transition temperature, storage modulus and hardness. The proposed methodology was seen to be convenient for the preparation of cellulose acetate/polysiloxane composites with useful properties. 相似文献