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排序方式: 共有793条查询结果,搜索用时 15 毫秒
31.
Lina Hudhud David R. Chisholm Andrew Whiting Anita Steib Krisztina Pohczky Angla Kecsks va Szke Zsuzsanna Helyes 《Molecules (Basel, Switzerland)》2022,27(3)
All-trans-retinoic acid (ATRA), the active metabolite of vitamin A, plays a pivotal role in cell differentiation, proliferation and embryonic development. It is an effective therapy for dermatological disorders and malignancies. ATRA is prone to isomerization and oxidation, which can affect its activity and selectivity. Novel diphenylacetylene-based ATRA analogues with increased stability can help to overcome these problems and may offer significant potential as therapeutics for a variety of cancers and neurodegenerative diseases, including amyotrophic lateral sclerosis. Here, we investigated the effects of these retinoids on cell viability and genotoxicity in the widely used model system of the rapidly proliferating Chinese hamster ovary cell line. DC360 is a fluorescent ATRA analogue and DC324 is a non-active derivative of DC360. EC23, DC525, DC540, DC645, and DC712 are promising analogues with increased bioactivity. The cytotoxic activity of the compounds was evaluated by ATP assay and DNA damage was tested by comet assay. No cytotoxicity was observed in the 10−6–10−5 M concentration range. All compounds induced DNA migration similar to ATRA, but DC324, DC360 and EC23 did so to a greater extent, particularly at higher concentrations. We believe that retinoid receptor-independent genotoxicity is a general characteristic of these compounds; however, further studies are needed to identify the molecular mechanisms and understand their complex biological functions. 相似文献
32.
Eva Hoffmann GyÖrgy Marko-Varga Istvan Csiky Jan Årke JÖnsoon 《International journal of environmental analytical chemistry》2013,93(1-3):161-171
Abstract A three-column ion chromatographic system for the removal of humic substances from natural waters, and subsequent on-line concentration and determination of nitrate and sulfate using non-suppressed ion chromatography is presented. Humic substances are removed using disposable adsorption columns packed with chemically bonded amine silica material. The sample is directly transfered to an ion exchange column where the anions are concentrated ca 10 times. After reversing the flow, the ions are transferred to a third column where they are separated and quantified. The detection limit is less than 1 mg L?1 of nitrate or sulfate in water containing 45mgL?1 of humic acid. 相似文献
33.
毛细管电泳在线化学发光分离及检测铬(Ⅲ)与钒(Ⅴ) 总被引:3,自引:0,他引:3
基于在碱性介质中 Cr( )和 V( )对鲁米诺和过氧化氢的催化化学发光反应 ,研究了毛细管电泳在线化学发光分离和检测 Cr( )和 V( )。方法简便、快速、灵敏、进样量少。 Cr( )和 V( )的检出限分别为 7.8× 1 0 - 8mol/L和 5.0× 1 0 - 6mol/L ,线性范围分别是 32~ 80 ng/m L和 0 .55~ 3.0μg/m L 相似文献
34.
The electronpoor double-bond of cyclic vinylphosphine oxides (1, 3 and 4) is easily reduced by borane in a selective manner to give the corresponding saturated derivatives (2, 4 and 5, respectively) Under forcing conditions, change of the functionality may also take place. 相似文献
35.
36.
Erik Allard Rikard Åslund Tröger Björn Arvidsson Per Johan Ragnar Sjöberg 《Rapid communications in mass spectrometry : RCM》2010,24(4):429-435
Precision, reproducibility and lower limit of quantitation (LLOQ) are important characteristics of a quantitative method. We have investigated these properties for Ximelagatran (Xi), which has a high tendency to form doubly charged ions in electrospray ionization (ESI), by studying the percentage of doubly charged species formed when varying the formic acid (FA) concentration, analyte concentration, amount of organic modifier and flow rate. It was found that the percentage of [Xi + 2H]2+ can be controlled to be more than 90% or less than 10% by varying the amount of FA present, and that the change between these values is dramatic. Furthermore, the percentage of [Xi + 2H]2+ formed decreases with increased analyte concentration and increased flow rate. No apparent relationship with the amount of organic modifier was found. The results have the implication that, by carefully controlling the selected parameters, the LLOQ, precision and reproducibility can be improved. We have compared the fragmentation of the singly and doubly charged species and concluded that the [Xi + 2H]2+ ion is more inclined to undergo fragmentation than [Xi + H]+. As a consequence, unusual instrumental settings had to be used for the experiments. The fragmentation patterns are to a great extent similar, but the doubly charged species is more inclined to generate low‐mass product ions. Copyright © 2010 John Wiley & Sons, Ltd. 相似文献
37.
38.
Jan-ke Schweitz 《International journal of quantum chemistry》1980,18(3):811-817
The concepts of “open assembly” is defined, and the hypervirial theorem is derived in three steps: (i) An equation of motion of the reduced density matrix of the first order is derived. (ii) This equation is utilized to derive a general equation of continuity for single-particle properties. (iii) The hypervirial equation for open assemblies is obtained as a long-time average of the continuity equation. The hypervirial theorem is shown to be equivalent to a simple postulate: no physical property can keep on accumulating for ever in a limited volume. Finally, the hypervirial theorem is applied to the problems of force, torque, and virial balance in open dynamical assemblies, and the results are compared with the corresponding classical results. 相似文献
39.
A hybrid method of order five (eight) which uses three (four) function evaluations per step is presented together with an algorithm which ensures global convergence. The method is compared with its closest competitors (among globally convergent methods which do not use derivatives) in a series of numerical examples. An ALGOL procedure of the method is included. 相似文献
40.
A controlled temperature controlled atmosphere atomization system is described. The sample is placed on a tungsten wire provided with temperature-controlled heating. After thermal pretreatment of the sample the wire is inserted into a hot quartz tube and rapid vaporization is accomplished by separate electrothermal heating. The pyrolysis products formed are mixed with a gas buffer and are passed through two equilibrium zones. The residence time of the analyte in the system is of the order of seconds so that the probability of attaining a state close to equilibrium is high for high temperatures. A third zone is placed perpendicularly to the others and constitutes the atomic absorption measuring cell. The usefulness of the system is illustrated for the determination of lead, bismuth, cadmium and zinc. The system provides unique possibilities in controlling interference effects in complex matrices. Examples are given for lead in concentrated chloride and sulphate solutions. Good agreement between the experimental results and high-temperature equilibrium calculations was obtained for a large variation in the composition of the gas phase. 相似文献