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81.
Anna D. Ilyina José L. Martínez Hernández César Estrada Badillo María G. Sena Maldonado Sara Carrillo Galindo María Hernández González Jesús Rodríguez Martínez 《Applied biochemistry and biotechnology》2000,88(1-3):33-44
This article presents a novel method of arachidonic acid (AA) determination based on the reaction catalyzed by prostaglandin
H synthase (PGHs). The deoxygenated and nondeoxygenated (as control) buffers were used to obtain the PGHs preparations from
bovine vesicular glands by two different methods. The higher specific activity was observed for solubilized preparations obtained
by ultracentrifugation and deoxygenated buffers. The preparations obtained by Ca2+ treatment demonstrated higher stability of PGHs during its storage at −15°C. To record the initial rate of AA transformation,
a spectrophotometric assay of PGHs cyclo-oxygenase and peroxidase activities was developed using adrenaline and ABTS as electron
donors. No oxidation of A BTS was observed in the reaction of AA transformation catalyzed by the PGHs from bovinevesicular
glands. However, this electron donor was successfully used in the reaction catalyzed by PGHs from sheep vesicular glands.
No chemilum inescence was recorded in the reaction of AA transformation catalyzed by PGHs from bovine vesicular glands in
the presence of luminol. The chemiluminescent intensity was measured after addition of hydrogen peroxide allowing quantitative
assay of AA to be performed. 相似文献
82.
Barros Itana Sena Oliveira Antonia Soares dos Santos Arnaud Victor Carvalho Luciene Santos das Virgens Cesário Francisco 《Journal of Thermal Analysis and Calorimetry》2019,138(2):869-878
Journal of Thermal Analysis and Calorimetry - Lucina pectinata, popularly called Lambreta, is a delicacy very consumed in Bahian cuisine. The shell is composed of nacreous layers formed by keratin,... 相似文献
83.
Interactions between the moieties responsible for the conformations and hydrophobic microdomains in poly(styrene-4-sulphonate)
(PSS) and its copolymers with n-butylvinylether (BVE) were studied by their emission spectra and the lifetimes of the phenyl groups and pyrene used as a
photochemical probe. The emission spectra of PSS shows bands due to dimers and higher aggregates as well as the characteristic
excimer band. At low concentrations, the random copolymers have spectra similar to that of the free monomer, whereas the block
copolymers have spectra like that of PSS. At higher concentrations, the random copolymer also shows these excimer bands, due
to interchain interactions. Results from the emission of pyrene prove that the behaviour of the copolymers with approximately
40% BVE seems to be relatively independent of having random or block configurations. Except at low concentrations (<0.05 g/dl),
where the block copolymer already has a conformation with “stable” hydrophobic microdomains, both types of copolymers behave
similarly. There is an initial aggregate equilibrium between individual chains and aggregates, associated with a relocation
of the probes. At higher concentrations, both copolymers suffer a severe change in conformation, due to the formation of “stable”
hydrophobic microdomains, resulting from interchain interactions. In both cases the lifetimes of pyrene are of the order of
240 ± 10 ns.
Received: 27 August 1998 Accepted: 11 January 1999 相似文献
84.
An analysis of the role of nonreactive plasticizers in the crosslinking reactions of a rigid resin
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Jigneshkumar P. Patel Subrajeet Deshmukh Caixia Zhao Onyenkachi Wamuo Shaw Ling Hsu Andrew B. Schoch Sena Ada Carleen Dean Matsumoto 《Journal of Polymer Science.Polymer Physics》2017,55(2):206-213
A uniform dispersion of reactants is necessary to achieve a complete reaction involving multiple components. Using a combination of infrared spectroscopy, thermal analysis, and low field NMR, we have elucidated the role of a new class of nonreactive plasticizers on the crosslinking reaction between hexamethylenetetramine (HMTA) and phenol formaldehyde resin. These two seemingly dissimilar reactants are responsible for the exceptionally high mechanical strength in a number of organic–inorganic composites. The efficiency of the curing reaction is characterized by the changing functionality of HMTA. Infrared active vibrations are used to characterize the changing molecular structures as a function of temperature. The T1 spin‐lattice relaxation time is used for the characterization of segmental dynamics of the chains in the formation of the crosslinked product. The segmental mobility depends on the amount of crosslinking and the stiffness of the chain. This study shows that this new class of nonreactive plasticizer can induce highly crosslinked structures without any of the environmental impact of the current technology. An efficient crosslinking reaction in phenolic resin can be achieved by using methyl benzoate as a nonreacting plasticizer. Low field NMR, in conjunction with infrared spectroscopy (mid and near) and DSC, clarified the crosslinking reaction mechanism and the ensuing structure. © 2016 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2017 , 55, 206–213 相似文献
85.
Dipaloy Datta Özge Kerkez Kuyumcu Şahika Sena Bayazit 《Journal of Dispersion Science and Technology》2017,38(11):1556-1562
This study demonstrates the adsorption experiments of toxic dyes malachite green (MG) and Rhodamine B (RB) on Fe3O4-loaded activated carbon (AC). AC, which is known to be a high-capacity adsorbent, was aimed to be easily separated from aqueous media by loading it with Fe3O4. Fe3O4-loaded AC was prepared by the coprecipitation method and named magnetic activated carbon (M-AC), and the produced M-AC was characterized by x-ray diffraction (XRD), thermogravimetric analysis (TGA), and pHpzc analyses. MG and RB adsorption by the M-AC was performed separately by batch technique and the effects of adsorbent amount, solution pH, and initial dye concentration on the adsorption were explored. Maximum removal efficiencies were found to be 96.11% for MG and 98.54% for RB, and the Langmuir isotherm model was the most fitted isotherm model for the adsorption. The kinetic and thermodynamic studies showed that the adsorption proceeded via the pseudo-second-order kinetic model and endothermic in-nature for both dyes. 相似文献
86.
Valfredo Azevedo Lemos Leonardo Sena Gomes Teixeira Marcos de Almeida Bezerra Antonio Celso Spínola Costa Jacira Teixeira Castro Luiz Augusto Martins Cardoso 《应用光谱学评论》2013,48(4):303-334
Abstract The development of new sorbents and their application in preconcentration methods for determination of trace elements is a subject of great interest. This review summarizes and discusses several analytical methods involving the preparation and use of new solid‐phase materials. The performance and general properties of sorbents such as carbon nanotubes, imprinted ions, biosorbents, nanoparticles, and fullerene are discussed in detail. The perspective and future trends in the use of these materials are also considered. 相似文献
87.
Dr. Roberta Tesch Dr. Christian Becker Dr. Matthias Philipp Müller Dr. Michael Edmund Beck M. Sc. Lena Quambusch Dr. Matthäus Getlik M. Sc. Jonas Lategahn M. Sc. Niklas Uhlenbrock Dr. Fanny Nascimento Costa M. Sc. Marcelo D. Polêto M. Sc. Pedro de Sena Murteira Pinheiro M. Sc. Daniel Alencar Rodrigues Prof. Carlos Mauricio R. Sant'Anna Prof. Fabio Furlan Ferreira Prof. Hugo Verli Prof. Carlos Alberto Manssour Fraga Prof. Daniel Rauh 《Angewandte Chemie (International ed. in English)》2018,57(31):9970-9975
PIK‐75 is a phosphoinositide‐3‐kinase (PI3K) α‐isoform‐selective inhibitor with high potency. Although published structure–activity relationship data show the importance of the NO2 and the Br substituents in PIK‐75, none of the published studies could correctly determine the underlying reason for their importance. In this publication, we report the first X‐ray crystal structure of PIK‐75 in complex with the kinase GSK‐3β. The structure shows an unusual U‐shaped conformation of PIK‐75 within the active site of GSK‐3β that is likely stabilized by an atypical intramolecular Br???NO2 halogen bond. NMR and MD simulations show that this conformation presumably also exists in solution and leads to a binding‐competent preorganization of the PIK‐75 molecule, thus explaining its high potency. We therefore suggest that the site‐specific incorporation of halogen bonds could be generally used to design conformationally restricted bioactive substances with increased potencies. 相似文献
88.
Karina Penedo Carvalho Nathalia Balthazar Martins Ana Rosa Lopes Pereira Ribeiro Taliria Silva Lopes Rodrigo Caciano de Sena Pascal Sommer José Mauro Granjeiro 《Journal of nanoparticle research》2016,18(8):244
Nanoparticles agglomerate when in contact with biological solutions, depending on the solutions’ nature. The agglomeration state will directly influence cellular response, since free nanoparticles are prone to interact with cells and get absorbed into them. In sunscreens, titanium dioxide nanoparticles (TiO2-NPs) form mainly aggregates between 30 and 150 nm. Until now, no toxicological study with skin cells has reached this range of size distribution. Therefore, in order to reliably evaluate their safety, it is essential to prepare suspensions with reproducibility, irrespective of the biological solution used, representing the above particle size distribution range of NPs (30–150 nm) found on sunscreens. Thus, the aim of this study was to develop a unique protocol of TiO2 dispersion, combining these features after dilution in different skin cell culture media, for in vitro tests. This new protocol was based on physicochemical characteristics of TiO2, which led to the choice of the optimal pH condition for ultrasonication. The next step consisted of stabilization of protein capping with acidified bovine serum albumin, followed by an adjustment of pH to 7.0. At each step, the solutions were analyzed by dynamic light scattering and transmission electron microscopy. The final concentration of NPs was determined by inductively coupled plasma-optical emission spectroscopy. Finally, when diluted in dulbecco’s modified eagle medium, melanocytes growth medium, or keratinocytes growth medium, TiO2–NPs displayed a highly reproducible size distribution, within the desired size range and without significant differences among the media. Together, these results demonstrate the consistency achieved by this new methodology and its suitability for in vitro tests involving skin cell cultures. 相似文献
89.
Trans-resveratrol (RVT) is an antioxidant found in red grapes and their derivatives, which has been related to the reduction of cardiovascular diseases and cancer incidence.This work developed a new spectrofluorimetric-chemometric method for the direct determination of RVT in human plasma. For each measurement, excitation-emission matrices were obtained from 280 to 360 nm (excitation) and from 380 to 550 nm (emission). The strategy adopted in this work combined data treatment with parallel factor analysis (PARAFAC), for extracting the pure analyte signal, using the standard addition method, which permits determinations in the presence of a strong matrix effect caused by plasma analyte-protein binding. Plasma samples were diluted 10 times and, for each, four standard additions of RVT were performed, in triplicate. A specific PARAFAC model was built for the three replicates of each sample, from three-way arrays formed by five measurements (initial sample plus four additions), 17 excitation wavelengths and 86 emission wavelengths. The best models were selected with four factors and accounted for more than 99.90% of the data variance. The loadings obtained were related to RVT and three interferences. The scores related to the analyte were used for linear regressions and all standard addition curves presented correlation coefficients equal or greater than 0.99. Good results were obtained in the concentration range from 0.10 to 5.00 μg mL−1, with recoveries between 94.0 and 110.0%. The proposed method was also validated through the estimates of several figures of merit: sensitivity, analytical sensitivity, selectivity, precision, and limits of detection and quantitation. 相似文献
90.
Two simple, rapid and reproducible spectrophotometric methods have been described for the assay of olmesartan (OLM) in pharmaceutical formulation. The methods are based on the formation of ion associates in the reactions between the studied
drug substance and ion-pair agents [bromocresol green (BCG) and bromophenol blue (BPB)]. By the extraction with dichloromethane and chloroform, yellow-colored ion associates were formed in acidic medium and
absorbances were measured at 409 (BCG) and 412 nm (BPB). Optimizations of the reaction conditions were performed. Beer’s law
was obeyed within the concentration range from 1–40 μg/mL and 10–120 μg/mL, respectively, for BCG and BPB. The molar absorptivity,
detection and quantification limits were also determined. The developed methods were applied successfully to the determination
of this drug in tablets. 相似文献