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排序方式: 共有398条查询结果,搜索用时 15 毫秒
101.
Willems AV Deforce DL Van den Eeckhout EG Lambert WE Van Peteghem CH De Leenheer AP Van Bocxlaer JF 《Electrophoresis》2002,23(24):4092-4103
Benzo[a]pyrene diol epoxide (BPDE) was reacted in vitro with (2'-deoxy)nucleotides and with calf thymus DNA. The modified DNA was enzymatically hydrolyzed to the 5'-monophosphate nucleotides using deoxyribonuclease I (DNA-ase I), nuclease P1 and snake venom phosphodiesterase (SVP). Most of the unmodified nucleotides were removed using solid phase extraction (SPE) in a polystyrene divinylbenzene copolymer. Three adducts could be detected and identified using capillary zone electrophoresis(negative)-ion electrospray ionization-mass spectrometry (CZE-(-)-ESI-MS) in conjunction with sample stacking. This way, not only a BPDE-dGMP adduct [(M-H)(-) at m/z 648], a well-known nucleotide adduct, could be retrieved, but also a BPDE-dAMP [(M-H)(-) at m/z 632] and a BPDE-dCMP adduct [(M-H)(-) at m/z 608] could be detected for the first time. The presence of the prominent ion at m/z 195 (the deoxyribose-phosphate ion) in the three low-energy collision-activated decomposition (CAD) spectra indicated that the adducts were formed through base-alkylation. CZE-positive ion ESI-MS/MS experiments were performed to obtain further information on base-alkylation. The absence of the loss of NH(3) from the nucleobase in each CAD spectrum points to an alkylated exocyclic NH(2) position of the nucleobase. So, the three adducts could be identified as BPDE-N(2)-dGMP, BPDE-N(6)-dAMP and BPDE-N(4)-dCMP using CZE-ESI-MS and CZE-ESI-MS/MS. 相似文献
102.
When hydroxide ions are added to a solution of Cr(H2O)63+ ions at low temperature a well crystallized chromium hydroxide hydrate is formed, corresponding to the formula [Cr(OH)3-(H2O)3]∞. Its structure is the inverse of bayerite type, two thirds of the octahedral M3+ positions being vacant. It loses water easily and turns into a totally amorphous hydroxide of variable water content. An amorphous hydroxide is also obtained when solutions are alkalized at higher temperatures or when aged solutions (containing polynuclear complexes) are used. 相似文献
103.
Morelle W Slomianny MC Diemer H Schaeffer C van Dorsselaer A Michalski JC 《Rapid communications in mass spectrometry : RCM》2005,19(14):2075-2084
Oligosaccharides were derivatized by reductive amination using 2-aminobenzamide (2-AB) and analyzed by matrix-assisted laser desorption/ionization two-stage time-of-flight (MALDI-TOF/TOF) tandem mass spectrometry (MS/MS) in the positive ion mode. The major signals were obtained under these conditions from the [M+Na]+ ions for all 2-AB-derivatized oligosaccharides. A systematic study was conducted on a series of 2-AB-derivatized oligosaccharides to allow rationalization of the fragmentation processes. The MALDI-TOF/TOF-MS/MS spectra of the [M+Na]+ ions of 2-AB-derivatized oligosaccharides were dominated by glycosidic cleavages. These fragments originating both from the reducing and the non-reducing ends of the oligosaccharide yield information on sequence and branching. Moreover, the MALDI-TOF/TOF-MS/MS spectra were also characterized by abundant cross-ring fragments which are very informative on the linkages of the monosaccharide residues constituting these oligosaccharides. MALDI-TOF/TOF-MS/MS analysis of 2-AB-derivatized oligosaccharides, by providing structural information at the low-picomole level, appears to be a powerful tool for carbohydrate structural analysis. 相似文献
104.
The various stages of procedures based on particle-induced x-ray emission spectrometry are discussed. These include standardization (calibration of the equipment), sample and target preparation, contamination (blank) control, target bombardment, spectral data processing, and correction for matrix effects. Aspects requiring particular attention are indicated and optimization of these stages is outlined. Examples are given to demonstrate that optimized procedures can provide precise and accurate concentration data for trace elements in biological, environmental and geological samples. 相似文献
105.
Franz A. Pohl und Willy Bonsels 《Fresenius' Journal of Analytical Chemistry》1958,161(2):108-114
Zusammenfassung Es wird eine spurenanalytische Methode zur Bestimmung von Verunreinigungen in hochreinem Indium beschrieben. Die Elemente Blei, Eisen, Cadmium, Kupfer, Thallium, Wismut und Zink werden durch Isopropylätherextraktion aus Halogensäuren angereichert und polarographisch bestimmt. Die Bedingungen zur extraktiven Anreicherung werden eingehend behandelt. Zur Vermeidung von Einschleppungen wird weitgehend im geschlossenen System gearbeitet. Die Bestimmung der genannten Elemente ist bis 10–6% mit einer Genauigkeit von besser als ± 10% möglich. 相似文献
106.
Alain Krief Thierry Van Wemmel Martine Redon Willy Dumont Cathy Delmotte 《Angewandte Chemie (International ed. in English)》1999,38(15):2245-2248
The addition of elemental selenium to organolithium compounds 1 or organic selenates 2 gives organic diselenolates 3 . The reactions proceed by the insertion of two selenium atoms into the carbon–metal bonds or of one selenium atom into a selenolate. Evidence for the existence of n-butyldisilenol has also been obtained. 相似文献
107.
108.
109.
Willy Haas 《Mikrochimica acta》1930,8(1):83-119
Ohne Zusammenfassung 相似文献
110.
Willy Hartman 《Fresenius' Journal of Analytical Chemistry》1925,67(4):152-155
Ohne Zusammenfassung 相似文献