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1.
Herein, we report an addition to the toolbox for the monitoring and quantification of the hydrolytic decay of pentose-1-phosphates, which are known to be elusive and difficult to quantify. This communication describes how apparent equilibrium shifts of a nucleoside phosphorolysis reaction can be employed to calculate hydrolytic loss of pentose-1-phosphates based on the measurement of post-hydrolysis equilibrium concentrations of a nucleoside and a nucleobase. To demonstrate this approach, we assessed the stability of the relatively stable ribose-1-phosphate at 98 °C and found half-lives of 1.8–11.7 h depending on the medium pH. This approach can be extended to other sugar phosphates and related reaction systems to quantify the stability of UV-inactive and hard-to-detect reaction products and intermediates. 相似文献
2.
H. Neubauer 《Fresenius' Journal of Analytical Chemistry》1904,43(1):14-36
Ohne Zusammenfassung(Mitteilung aus der agrikulturchemischen Versuchsstation Breslau.) 相似文献
3.
In this paper we prove for several classes of ideals in regular local rings of equicharacteristic 0 that the symbolic square
of the ideal contains no minimal generator of the ideal. Our techniques come from residual intersections, integral closures
of ideals, and differentials.
Received January 14, 1997; in final form March 20, 1997 相似文献
4.
Reversed-phase LC-MS/MS is used to determine major estrogenic alkylphenol ethoxylates (APEOs) and their biotransformation products. It allows the simultaneous analysis of eight APEOs, alkylphenoxy carboxylates (APECs) and alkylphenols (APs) in sewage treatment plant (STP) effluents in the same extract after solid-phase enrichment on polymeric Oasis HLB. As precursor ions, [APEO + NH4]+, [APEC - H]- and [AP - H]- were monitored. Instrumental limits of detection (LOD) were 2-600 pg, corresponding to sample concentrations of 0.04-12 ng l(-1), without correction for overall method recoveries. Matrix-induced signal suppression during electrospray ionisation (ESI) and extraction as well as overall method recoveries were assessed and the suitability of deuterated surrogates as internal standards was evaluated. 相似文献
5.
Biener MM Biener J Friend CM 《Langmuir : the ACS journal of surfaces and colloids》2005,21(5):1668-1671
The Au-S interaction is probably the most intensively studied interaction of Au surfaces with nonmetals, as, for example, it plays an important role in Au ore formation(1) and controls the structure and dynamics of thiol-based self-assembled monolayers (SAMs). Various S-induced surface structures on Au(111) were recently reported for different conditions and predominantly interpreted in terms of a static Au surface. Here, we demonstrate that the Au(111) surface exhibits a very dynamic character upon interaction with adsorbed sulfur: large-scale surface restructuring and incorporation of Au atoms into a growing 2D AuS phase were observed in situ. These results provide new insight into the Au-S surface chemistry. 相似文献
6.
Starting from activated benzoxazines 1 and 2 new synthetic pathways to the tricyclic compounds 4, 9, 12 and 16 are described. Reaction of the hydrazides 17a,b with thionylchloride leads to the novel thiatriazolo-benzoxazines 18a,b . 相似文献
7.
The following substances could be prepared by Grignard reactions or by conversions with trichlorosilane: C6F5CH2CHCH2, C6F5(CH2)3SiCl3, CF3(CF2)9CH2CHCH2, CF3(CF2)7(CH2)2SiCl3, CF3(CF2)11(CH2)3CHCH2 und CF3(CF2)11(CH2)5SiCl3.They were characterized by spectroscopical and microanalytical methods. 相似文献
8.
The hindered rotor transitions of H(2) adsorbed in the chemically related and prototypical porous metal-organic frameworks IRMOF-1, IRMOF-8, IRMOF-11, and MOF-177 were studied by inelastic neutron scattering to gain information on the specifics of H(2) binding in this class of adsorbents. Remarkably sharp and complex spectra of these materials signify a diversity of well-defined binding sites. Similarities in the spectral features as a function of H(2) loading and correlations with recent crystallographic studies were used to assign transitions ranging in rotational barrier from <0.04 to 0.6 kcal/mol as corresponding to localized adsorption sites on the organic and inorganic components of these frameworks. We find that binding of H(2) at the inorganic cluster sites is affected by the nature of the organic link and is strongest in IRMOF-11 in accord with our adsorption isotherm data. The sites on the organic link have lower binding energies, but a much greater capacity for increases in H(2) loading, which demonstrates their importance for hydrogen uptake by these materials. 相似文献
9.
Hedin N Graf R Christiansen SC Gervais C Hayward RC Eckert J Chmelka BF 《Journal of the American Chemical Society》2004,126(30):9425-9432
The structure of a novel molecularly ordered two-dimensional (2D) silicate framework in a surfactant-templated mesophase has been established by using a combination of solid-state nuclear magnetic resonance (NMR) spectroscopy, X-ray diffraction, and quantum chemical and empirical force-field modeling. These materials are unusual in their combination of headgroup-directed 2D crystalline framework ordering, zeolite-like ring structures within the layers, and long-range mesoscopic organization without three-dimensional (3D) atomic periodicity. The absence of registry between the silicate sheets, resulting from the liquidlike disorder of the alkyl surfactant chains, has presented significant challenges to the determination of framework structures in these and similar materials lacking 3D crystalline order. Double-quantum (29)Si NMR correlation experiments establish the interactions and connectivities between distinct intra-sheet silicon sites from which the structure of the molecularly ordered inorganic framework is determined. 相似文献
10.
Summary In the manufacture of aero-engine components, auxiliary materials are used which impair mechanical properties if they are not completely removed afterwards. Taking the manufacture of turbine blades and vanes as an example, this investigation shows how the inclusion of an analysis stage in the fully-automatic production cycle makes it possible to monitor the thoroughness of the cleaning process. As indicator, the element Bi is used; the matrix consists of concentrated nitric acid with a high nickel content. Because of the imposition of a limiting value, it must be possible to determine differences in the Bi-content of 20 g/l. The main part of the paper concerns the selection of the most optimum process. The results using two types of AAS coupled with hydride generation are presented. The success of the complete system is illustrated by the summarized results. 相似文献