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The cleavage of a disulfide bond and the redox equilibrium of thiol/disulfide are strongly related to the levels of glutathione (GSH)/oxidized glutathione (GSSG) or mixed disulfides in vivo. In this work, the cleavage of a disulfide bond in GSSG induced by a platinum(II) complex [Pt(Met)Cl2] (where Met = methionine) was studied and the cleavage fragments or their platinated adducts were identified by means of electrospray mass spectrometry, high-performance liquid chromatography, and ultraviolet techniques. The second-order rate constant for the reaction between [Pt(Met)Cl2] and GSSG was determined to be 0.4 M(-1) s(-1) at 310 K and pH 7.4, which is 100- and 12-fold faster than those of cisplatin and its monoaqua species, respectively. Different complexes were formed in the reaction of [Pt(Met)Cl2] with GSSG, mainly mono- and dinuclear platinum complexes with the cleavage fragments of GSSG. This study demonstrated that [Pt(Met)Cl2] can promote the cleavage of disulfide bonds. The mechanistic insight obtained from this study may provide a deeper understanding on the potential involvement of platinum complexes in the intracellular GSH/GSSG systems. 相似文献
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A series of spiropyrans with a polyaromatic or heteroaromatic pendant was synthesized conveniently.Their photochromic behaviors were investigated with the aid of absorption spectral measurements.The results indicated that the compounds with the same parent spiropyran but different aromatic pendant show significantly different photochromic properties.This may be due to the π-π orbital interaction between the polyaromatic pendant and the open photomerocyanine form of spiropyran.The results obtained are very useful in the molecule design area. 相似文献
87.
A. S. Aynacioglu A. -H. Meißner F. Walachowicz G. v. Oppen 《Zeitschrift für Physik D Atoms, Molecules and Clusters》1991,18(1):85-91
The magnetic depolarization of the impact radiation at λ(41 D?21 P)=492 nm and λ(31 D?21 P) = 668 nm as well as the splitting of the magnetic depolarisation signals in electric fields were investigated for 10–25 keV H 2 + (D 2 + )-He collisions (only 492 nm line) and for 5-22.5 keV He-He collisions (both lines). The results are compared with analogous measurements for He+- He and Ne+ - He collisions and the dynamics of the excitation process are qualitatively discussed. In particular, we emphasize the importance of inertia for the evolution of the electron cloud during the final phase of the collision process. 相似文献
88.
An ab initio-based kinetic Monte Carlo algorithm was developed to simulate the direct decomposition of NO over Pt and different PtAu alloy surfaces. The algorithm was used to test the influence of the composition and the specific atomic surface structure of the alloy on the simulated activity and selectivity to form N2. The apparent activation barrier found for the simulation of lean NO decomposition over Pt(100) was 7.4 kcal/mol, which is lower than the experimental value of 11 kcal/mol that was determined over supported Pt nanoparticles. Differences are likely due to differences in the surface structure between the ideal (100) surface and supported Pt particles. The apparent reaction orders for lean NO decomposition over the Pt(100) substrate were calculated to be 0.9 and -0.5 for NO and O2, respectively. Oxygen acts to poison Pt. Simulations on the different Pt-Au(100) surface alloys indicate that the turnover frequency goes through a maximum as the Au composition in the surface is increased, and the maximum occurs near 44% Au. Turnover frequencies, however, are dictated by the actual arrangements of Pt and Au atoms in the surface rather than by their overall composition. Surfaces with similar compositions but different alloy arrangements can lead to very different activities. Surfaces composed of 50% Pt and 50% Au (Pt4 and Au4 surface ensembles) showed very little enhancement in the activity over that which was found over pure Pt. The Pt-Pt bridge sites required for NO adsorption and decomposition were still effectively poisoned by atomic oxygen. The well-dispersed Pt(50%)Au(50%) alloy, on the other hand, increased the TOF over that found for pure Pt by a factor of 2. The most active surface alloy was one in which the Pt was arranged into "+" ensembles surrounded by Au atoms. The overall composition of this surface is Pt(56.2%)Au(43.8%). The unique "+" ensembles maintain Pt bridge sites for NO to adsorb on but limit O2 as well as NO activation by eliminating next-nearest neighbor Pt-bridge sites. The repulsive interactions between two adatoms prevent them from sharing the same metal atoms. The decrease in the oxygen coverage leads to a greater number of vacant sites available for NO adsorption. This increases the NO coupling reaction and hence N2 formation. The inhibition of the rate of N2 formation by O2 is therefore suppressed. The coverage of atomic oxygen decreases from 53% on the Pt(100) surface down to 19% on the "+" ensemble surface. This increases the rate of N2 formation by a factor of 4.3 over that on pure Pt. The reaction kinetics over the "+" ensemble Pt(56.2%)Au(43.8%) surface indicate apparent reaction orders in NO and oxygen of 0.7 and 0.0, respectively. This suggests that oxygen does not poison the PtAu "+" alloy ensemble. The activity and selectivity of the PtAu ensembles significantly decrease for alloys that go beyond 60% Au. Higher coverages of Au shut down sites for NO adsorption and, in addition, weaken the NO and O bond strengths, which subsequently promotes desorption as well as NO oxidation. The computational approach identified herein can be used to more rapidly test different metal compositions and their explicit atomic arrangements for improved catalytic performance. This can be done "in silico" and thus provides a method that may aid high-throughput experimental efforts in the design of new materials. The synthesis and stability of the metal complexes suggested herein still ultimately need to be tested. 相似文献
89.
Joseph Lee Mei Wang Goutam Mondal Ikhlas A. Khan Charles R. Yates 《Molecules (Basel, Switzerland)》2022,27(21)
Sample preparation remains both a challenging and time-consuming process in the field of bioanalytical chemistry. Many traditional techniques often require multi-step processes, which can introduce additional errors to the analytical method. Given the complexity of many biological matrices, thorough analyte extraction presents a major challenge to researchers. In the present study, a headspace solid-phase microextraction (HS-SPME) coupled with a GC/Q-ToF-MS method, was developed to quantify in vitro metabolism of β-caryophyllene by both human liver microsome (HLM) and S9 liver fractions. Validation of the method was demonstrated both in terms of linearity (R2 = 0.9948) and sensitivity with a limit of detection of 3 ng/mL and a limit of quantitation of 10 ng/mL. In addition, the method also demonstrated both inter- and intra-day precision with the relative standard deviation (RSD) being less than 10% with four concentrations ranging from 50–500 ng/mL. Since this method requires no solvents and minimal sample preparation, it provides a rapid and economical alternative to traditional extraction techniques. The method also eliminates the need to remove salts or buffers, which are commonly present in biological matrices. Although this method was developed to quantify in vitro metabolism of one analyte, it could easily be adapted to detect or quantify numerous volatiles and/or semi-volatiles found in biological matrices. 相似文献
90.
在无水乙醇溶液中合成了以铕及铕掺人不同比例的Y2 或Tb3 为中心,以β萘基甲酰三氟丙酮(β-NTA)和邻菲咯啉(phen)为配体的配合物;对其进行了元素分析、摩尔电导、核磁共振氢谱、差热-热重、红外光谱分析及荧光性能的研究.其化学组成式为(EuxY1-x)(β-NTA)3 PJlen及(EuxTb1-x)(p-NTA)3Phen(x=0.1;0.3;0.5;0.7;0.9);摩尔电导测试数据表明,所有配合物均为非电解质;核磁共振氢谱和红外光谱表明,配体β-NTA通过烯醇式氧负离子采用双齿配位的形式与稀土离子配位,Phen的两个氮原子也与稀土离子双齿配位;荧光光谱实验结果表明,所有激发光谱都为一宽带峰,配体能很好的吸收能量,在惰性不发光Y3 的含量工小于0.3,发光Tb3 的含量小于0.5时,可以使Eu3 的特征荧光发射得到一定程度增强,这表明两种不同的离子都可以敏化Eu3 . 相似文献