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Cu(2+) ions are used to follow the sol-gel transition in amino-modified TEOS mixtures. In contrast to unmodified TEOS gels, fixation of the spin probe (Cu(2+)) to the sol particle surface takes place and changes in mobility are detectable. Furthermore, we find changes in the coordination sphere of the copper ions and a temporary loss of EPR intensity. By using a simple kinetic model it is possible to estimate the rate constants of the condensation and syneresis processes. 相似文献
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Theodor Breyer 《Fresenius' Journal of Analytical Chemistry》1889,28(1):438-440
Ohne Zusammenfassung 相似文献
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This paper reviews the use of lipid vesicles as model membranes in capillary electrophoresis (CE). The history and utility of CE in the characterization of microparticles is summarized, focusing on the application of colloidal electromigration theories to lipid vesicles. For instance, CE experiments have been used to characterize the size, surface properties, enclosed volumes, and electrophoretic mobilities of lipid vesicles and of lipoprotein particles. Several techniques involving small molecules or macromolecules separated in the presence of lipid vesicles are discussed. Interactions between the analytes and the lipid vesicles - acting as a pseudostationary phase or coated stationary phase in electrokinetic chromatography (EKC) - can be used to obtain additional information on the characteristics of the vesicles and analytes, and to study the biophysical properties of membrane-molecule interactions in lipid vesicles and lipoproteins. Different methods of determining binding constants by EKC are reviewed, along with the relevant binding constant calculations and a discussion of the application and limitations of these techniques as they apply to lipid vesicle systems. 相似文献
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Daniel S. Breyer 《Acta Analytica》2013,28(2):253-256
In this article, I respond to Jennifer Duke-Yonge’s (2012) discussion of my article ‘Reflective Luck and Belief Ownership’ (Breyer, Acta Analytica, 25:133–154, 2010) and defend my Taking Responsibility account of belief ownership against her insightful criticisms. 相似文献
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Tian C Breyer RM Kim HJ Karra MD Friedman DB Karpay A Sanders CR 《Journal of the American Chemical Society》2005,127(22):8010-8011
The seven-transmembrane-spanning G protein-coupled receptor (GPCR) superfamily plays many important roles in basic biology, human health, and human disease. Here, well-resolved solution NMR spectra are presented for a human GPCR, the vasopressin V2 receptor in detergent micelles. The quality of the NMR spectra indicates that backbone resonance assignments for a majority of resonances are feasible. The key to obtaining high quality spectra appears to be the coupling of methods for expressing the receptor into membranes rather than into inclusion bodies, with use of a biochemically mild lysolipid detergent for membrane extraction, protein purification, and NMR sample preparation. 相似文献
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The energy spectra of electrons detached from O? and S? ions by 488.0 nm and 514.5 nm photons have been measured with high electron energy resolution (5 meV) in order to determine the branching ratios for the various2 P 3/2, 1/2 →3P2, 1, 0 fine-structure transitions together with their respective angular distributions. Detailed information on the relative importance of thes- andd-wave continuum is obtained. 相似文献
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Christian Schmidt Felicitas Breyer Marc-Michael Blum Horst Thiermann Franz Worek Harald John 《Analytical and bioanalytical chemistry》2014,406(21):5171-5185
Toxic organophosphorus compounds (e.g., pesticides and nerve agents) are known to react with nucleophilic side chains of different amino acids (phosphylation), thus forming adducts with endogenous proteins. Most often binding to serine, tyrosine, or threonine residues is described as being of relevance for toxicological effects (e.g., acetylcholinesterase and neuropathy target esterase) or as biomarkers for post-exposure analysis (verification, e.g., albumin and butyrylcholinesterase). Accordingly, identification of novel protein targets might be beneficial for a better understanding of the toxicology of these compounds, revealing new bioanalytical verification tools, and improving knowledge on chemical reactivity. In the present study, we investigated the reaction of ubiquitin (Ub) with the V-type nerve agents Chinese VX, Russian VX, and VX in vitro. Ub is a ubiquitous protein with a mass of 8564.8 Da present in the extra- and intracellular space that plays an important physiological role in several essential processes (e.g., proteasomal degradation, DNA repair, protein turnover, and endocytosis). Reaction products were analyzed by matrix-assisted laser desorption/ionization-time-of-flight- mass spectrometry (MALDI-TOF MS) and μ-high-performance liquid chromatography online coupled to UV-detection and electrospray ionization MS (μHPLC-UV/ESI MS). Our results originally document that a complex mixture of at least mono-, di, and triphosphonylated Ub adducts was produced. Surprisingly, peptide mass fingerprint analysis in combination with MALDI and ESI MS/MS revealed that phosphonylation occurred with high selectivity in at least 6 of 7 surface-exposed lysine residues that are essential for the biological function of Ub. These reaction products were found not to age. In addition, we herein report for the first time that phosphonylation induced intramolecular cyclization by formation of an isopeptide bond between the ε-amino group of a formerly phosphonylated lysine and the side chain of an adjacent acidic glutamic acid residue.
Lysine residues in ubiquitin are phosphonylated by nerve agents and undergo intramolecular cyclization 相似文献
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P. Frey M. Lawen F. Breyer H. Klar H. Hotop 《Zeitschrift für Physik A Hadrons and Nuclei》1982,304(2):155-165
A crossed ion-laser beam apparatus has been used to measure accurate relative total and partial cross sections for photodetachment from Rb? ions with high photon energy resolution (0.1–0.6 cm?1) in the region of the Rb(5p 2 P 1/2,3/2) thresholds (photon energy range 16,350–16,820 cm?1). Satisfactory fits to these data by multichannel quantum defect theory (MQDT) have been obtained, resulting in a reliable set of seven MQDT parameters. The electron angular distribution parameter for the Rb(5s) channel was found to beβ(5s)=2, independent of photon energy. MQDT predicts a sharp, window-type variation of?(5s) around the minimum of the 5s-cross section below the Rb(5p 2 P 1/2) threshold (where an accurate experimental measurement ofβ(5s) was not possible) and a similar behaviour ofβ(6s) in the case of Cs?photodetachment below the Cs(6p 2 P 1/2) threshold. 相似文献