排序方式: 共有41条查询结果,搜索用时 156 毫秒
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Marc B. Taraban Daniel J. Deredge Margaret E. Smith Katharine T. Briggs Yu Li Zhong-Xing Jiang Patrick L. Wintrode Yihua Bruce Yu 《Magnetic resonance in chemistry : MRC》2019,57(10):861-872
The conformational transition of a fluorinated amphiphilic dendrimer is monitored by the 1H signal from water, alongside the 19F signal from the dendrimer. High-field NMR data (chemical shift δ, self-diffusion coefficient D, longitudinal relaxation rate R1, and transverse relaxation rate R2) for both dendrimer (19F) and water (1H) match each other in detecting the conformational transition. Among all parameters for both nuclei, the water proton transverse-relaxation rate R2(1H2O) displays the highest relative scale of change upon conformational transition of the dendrimer. Hydrogen/deuterium-exchange mass spectrometry reveals that the compact form of the dendrimer has slower proton exchange with water than the extended form. This result suggests that the sensitivity of R2(1H2O) toward dendrimer conformation originates, at least partially, from the difference in proton exchange efficiency between different dendrimer conformations. Finally, we also demonstrated that this conformational transition could be conveniently monitored using a low-field benchtop NMR spectrometer via R2(1H2O). The 1H2O signal thus offers a simple way to monitor structural changes of macromolecules using benchtop time-domain NMR. 相似文献
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In this study,the three dimensional nanoscale organization in the photoactive layers of poly(3-hexylthiophene) (P3HT) and a methanofullerene derivative (PCBM) is revealed by transmission electron tomography.After annealing treatment,either at elevated temperature or during slow solvent evaporation,nanoscale interpenetrating networks are formed with high crystalline order and favorable concentration gradients of both components through the thickness of the photoactive layer.Such a tailored morphology acco... 相似文献
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Márcio AF Belo-Filho Franklina MB Toledo Bernardo Almada-Lobo 《The Journal of the Operational Research Society》2014,65(11):1735-1747
Setup operations are significant in some production environments. It is mandatory that their production plans consider some features, as setup state conservation across periods through setup carryover and crossover. The modelling of setup crossover allows more flexible decisions and is essential for problems with long setup times. This paper proposes two models for the capacitated lot-sizing problem with backlogging and setup carryover and crossover. The first is in line with other models from the literature, whereas the second considers a disaggregated setup variable, which tracks the starting and completion times of the setup operation. This innovative approach permits a more compact formulation. Computational results show that the proposed models have outperformed other state-of-the-art formulation. 相似文献
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Afanasyeva MS Taraban MB Polyakov NE Purtov PA Leshina TV Grissom CB 《The journal of physical chemistry. B》2006,110(42):21232-21237
The elementary steps of the enzymatic oxidation of nifedipine (NF) catalyzed by horseradish peroxidase (HRP) have been described based on analysis of kinetic magnetic field effects (MFEs). It has been shown that the first step of the catalytic cycle is single electron transfer resulting in formation of NF*(+) radical cation and ferroperoxidase (Per(2+)). As a result, comparison with an earlier studied oxidation reaction of NADH catalyzed by HRP evidenced that the enzymatic oxidations of two substrates-native, NADH, and its synthetic analogue, NF-catalyzed by HRP in the absence of H(2)O(2) follow identical mechanisms. 相似文献
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Polyakov NE Khan VK Taraban MB Leshina TV Luzina OA Salakhutdinov NF Tolstikov GA 《Organic & biomolecular chemistry》2005,3(5):881-885
CIDNP techniques were applied to the investigation of the elementary mechanism of photoinduced interaction between anti-arrhythmic drug lappaconitine and amino acids tyrosine and tryptophan. It has been shown that the reactions involve the formation of lappaconitine radical anion. Lappaconitine radical anion is unstable and rapidly eliminates N-acetyl anthranilic acid via protonation and ether bond cleavage. The rate constant of ether bond cleavage was estimated to be equal to 4 x 10(5) s(-1). The role of single electron transfer is discussed in the light of the model of drug-receptor interactions. 相似文献
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Photoinduced dispersion polymerization of styrene in the presence of dibenzyl ketone as a photoinitiator, with or without magnetic field, has been followed with time. The experiments were carried out at low degrees of conversion of monomer. Since the conditions of the polymerization reaction (viscosity of the medium, reagents concentration, etc.) were approximately unchanged, the results were explained on the basis of a simplified model of dispersion polymerization. The normal growth of the polymerization rates with temperature was registered, and the activation energy of the polymerization was estimated to be about 12 kJ/mol in the temperature range from 20 to 60 °C. The magnetic field effect was best seen at low temperature. The maximum yield of the polymerization product increases by 20% when the magnetic field of 1000 G was applied at the temperature of 20 °C. 相似文献
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Polyakov NE Khan VK Taraban MB Leshina TV Salakhutdinov NF Tolstikov GA 《The journal of physical chemistry. B》2005,109(51):24526-24530
NMR and UV-vis spectroscopy have been used to study the complexation of antiarrhythmic alkaloid lappaconitine with an efficient complexing agent from licorice, glycyrrhizic acid, which is known to profoundly influence the therapeutic activity of the alkaloid in the complex. In MeOH, DMSO, or aqueous solutions, lappaconitine has been shown to form a stable complex with glycyrrhizic acid with 1:1 stoichiometry over a broad concentration range from 1 microM to 300 microM. The stability constant K(11) equals 2.0 x 10(5) M(-1) in aqueous solution. A similar complex of lappaconitine hydrobromide--the pharmaceutical formulation used in the treatment of arrhythmia--is 2 orders of magnitude less stable than pure lappaconitine. A notable decrease in the rate of the photoinduced electron-transfer reaction between lappaconitine in a complex with glycyrrhizic acid and tyrosine allows the suggestion of an explicit interrelation between the suppressed chemical reactivity of the bound alkaloid and the changes of its therapeutic efficiency. 相似文献