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81.
The solvolysis of N-acetoxy-4-acetylaminobiphenyl in 40% buffered aqueous acetone has been studied. Two processes have been identified, both leading exclusively to the formation of hydroxamic acid. By the use of 0-18 labeling, both have been shown to involve the intermediacy of nitrenium ions. 相似文献
82.
A. Ruebner D. Kirsch S. Andrees W. Decker B. Roeder B. Spengler R. Kaufmann J.G. Moser 《Journal of inclusion phenomena and macrocyclic chemistry》1997,27(1):69-84
The aim of our investigation was to develop carrier systems for an application of inert drugs in photodynamic cancer therapy. -Cyclodextrin dimers linked at their primary and secondary faces by spacers of varying lengths were synthesized as carrier systems. The binding constants of the inclusion complexes of these cyclodextrin dimers and porphyrinoid photosensitizers were determined by competitive spectrofluorometry. Particularly the secondary face linked dimers exhibited extremely high binding constants with values of 106-107 L/mol. Theoretical studies were carried out on these inclusion complexes to confirm the influence of spacer length and connecting side on complex stability. 相似文献
83.
84.
Kirsch M Lehnig M Korth HG Sustmann R de Groot H 《Chemistry (Weinheim an der Bergstrasse, Germany)》2001,7(15):3313-3320
Peroxynitrite (ONOO-/ONOOH) is assumed to react preferentially with carbon dioxide in vivo to produce nitrogen dioxide (NO2*) and trioxocarbonate(1-) (CO3*-) radicals. We have studied the mechanism by which glutathione (GSH) inhibits the NO2*/CO3*--mediated formation of 3-nitrotyrosine. We found that even low concentrations of GSH strongly inhibit peroxynitrite-dependent tyrosine consumption (IC50 = 660 microM) as well as 3-nitrotyrosine formation (IC50) = 265 microM). From the determination of the level of oxygen produced or consumed under various initial conditions, it is inferred that GSH inhibits peroxynitrite-induced tyrosine consumption by re-reducing (repairing) the intermediate tyrosyl radicals. An additional protective pathway is mediated by the glutathiyl radical (GS*) through reduction of dioxygen to superoxide (O2*-) and reaction with NO2* to form peroxynitrate (O2NOOH/O2NOO-), which is largely unreactive towards tyrosine. Thus, GSH is highly effective in protecting tyrosine against an attack by peroxynitrite in the presence of CO2. Consequently, formation of 3-nitrotyrosine by freely diffusing NO2* radicals is highly unlikely at physiological levels of GSH. 相似文献
85.
Diarylamines in the benzo[b]thiophene series bearing electron donating or withdrawing groups, were prepared by Buchwald-Hartwig C-N coupling in moderate to high yields. The conditions used were Pd(OAc)2 (3 mol%), BINAP as ligand (4 mol%) and Cs2CO3 as base (1.4 equiv.), in toluene at 100°C, being 6-bromo or amino benzo[b]thiophenes coupled, respectively, with substituted anilines or phenylbromides. The 6-aminobenzo[b]thiophene derivatives were also prepared by palladium catalyzed C-N coupling of the corresponding 6-bromo compounds with benzophenone imine, followed by acidic hydrolysis of the imino derivatives. When 4-nitrobromobenzene and 4-bromobenzonitrile were used as coupling components, triarylamines were also isolated in small amounts. The presence of a fluorine atom on the phenylbromide highly increases the diarylamine yields. 相似文献
86.
P. Aufmuth R. Kirsch A. Steudel E. Wöbker 《Zeitschrift für Physik D Atoms, Molecules and Clusters》1987,7(2):153-159
The isotope shift in the arc spectrum of hafnium was studied in 10 lines for the isotopes176Hf,178Hf, and180Hf by means of a photoelectric recording Fabry-Perot spectrometer with digital data processing. The observed shifts together with results from an earlier study were analyzed by means of the parametric method. The field shift difference between the terms 5d 3(4 F) 6s 5 F and3 F resulted in 17(2) mK for the isotope pair178,180Hf. This reflects the influence of a second-order effect which is described by the parameterg 2=?4.4(6) mK. The parameterz 5d , displaying the magnitude of spin-dependent effects in the isotope shift of 5d 36s, was found to be 0.8(2) mK for the same isotope pair. The experimental data are compared with results obtained from the non-relativistic Hartree-Fock method. The calculated electron densities describe the experimental field shifts with good accuracy. Hartree-Fock screening ratios for various types of transitions were used to evaluate changes in mean-square nuclear charge radii. The mean value ofλ 178,180≈δ〈r 2〉178,180 equals 0.069(10) fm2. 相似文献
87.
The most convenient spectral regions for dye laser excitation are presented for seven lanthanide ions. Fluorescence lifetimes are given for 0.5 M sulphuric acid and 3 M potassium carbonate media. With the excimer-pumped dye laser, the detection limits are in the range 0.1 μg 1?1 (Eu) to 50 μg 1?1 (Gd). Examples of the resolution of mixtures are given. 相似文献
88.
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90.