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71.
Many carbohydrate compounds undergo electro-oxidation at modest positive potentials at chemically modified electrodes (CMEs) made by adding cobalt phthalocyanine (CoPC) electrocatalyst to a conventional carbon paste mixture. The active carbohydrates which were oxidized at the CME at +0.4 to 0.5 V vs. Ag/AgCl under the very basic pH conditions required, included not only monosaccharides but also oligosaccharides, deoxy sugars, and even simple polyalcohols such as glycerol. When used for carbohydrate detection after liquid chromatography, the CoPC CME yielded detection limits in the 10–50 pmol range. Electrode stability and selectivity was such that no sample preparation other than dilution and particulate filtration was required for carbohydrate determinations in sample matrices including food products and physiological fluids. 相似文献
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G. C. Baldwin 《Journal of Quantitative Spectroscopy & Radiative Transfer》1988,40(6):685-691
The central problem to developing a graser—that pumping can inhibit or destroy the Mössbauer and Borrmann effects—can conceivably be mitigated by a superlattice geometry, into which collimated coherent transfer radiation is introduced to form a multiwave Borrmann (or anti-Borrmann) mode. Such a geometry is introduced, and its effects on pump intensity and lattice heating are discussed. 相似文献
74.
A practical, efficient and diastereoselective synthesis of the cytotoxic and antiprotozoal compound aculeatin D (1) is described, employing a biomimetic oxidative cyclisation cascade reaction to generate the tricyclic system of the natural product. The synthesis proceeds in ten steps from commercially available 1-tetradecanol. 相似文献
75.
Nuclear gamma resonance spectroscopy, also known as M?ssbauer spectroscopy, is a technique that probes transitions between the nuclear ground state and a low-lying nuclear excited state. The nucleus most amenable to M?ssbauer spectroscopy is 57Fe, and 57Fe M?ssbauer spectroscopy provides detailed information about the chemical environment and electronic structure of iron. Iron is by far the most structurally and functionally diverse metal ion in biology, and 57Fe M?ssbauer spectroscopy has played an important role in the elucidation of its biochemistry. In this article, we give a brief introduction to the technique and then focus on two recent exciting developments pertaining to the application of 57Fe M?ssbauer spectroscopy in biochemistry. The first is the use of the rapid freeze-quench method in conjunction with M?ssbauer spectroscopy to monitor changes at the Fe site during a biochemical reaction. This method has allowed for trapping and subsequent detailed spectroscopic characterization of reactive intermediates and thus has provided unique insight into the reaction mechanisms of Fe-containing enzymes. We outline the methodology using two examples: (1) oxygen activation by the non-heme diiron enzymes and (2) oxygen activation by taurine:alpha-ketoglutarate dioxygenase (TauD). The second development concerns the calculation of M?ssbauer parameters using density functional theory (DFT) methods. By using the example of TauD, we show that comparison of experimental M?ssbauer parameters with those obtained from calculations on model systems can be used to provide insight into the structure of a reaction intermediate. 相似文献
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R. M. Baldwin T. H. Lin G. Harris H. S. Winchell M. B. Winstead 《Journal of Radioanalytical and Nuclear Chemistry》1981,65(1-2):189-193
Synthesis of α-(p-iodoanilino)phenylacetonitrile (IAPAN), an amygdalin analog, labeled with I-123 (t1/2 13.3 hr) in a carrier-free
state (i.e. no-carrier-added) was made possible by virtue of the high speed, sensitivity, and resolving power of HPLC. Aniline
was iodinated by the action of no-carrier-added Na123I in the presence of Cu(II), and the resulting iodaniline was reacted with benzaldehyde followed by the addition of HCN to
yield the title compound. The radioactive IAPAN was separated from α-anilinophenylacetonitrile and other byproducts by reversed
phase partition chromatography on an octadecylsilane column using 50% ethanol/H2O as eluent. The product was correlated with authentic, classically characterized IAPAN, and with123I IAPAN prepared by electrophilic exchange of IAPAN and ICl iodination of α-anilinophenylacetonitrile. 相似文献
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