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61.
Christa H. Oberth A. Daniel Jonescor 《Journal of the American Society for Mass Spectrometry》1997,8(7):727-736
The protonated mercapturic acid conjugate of acrolein, S-(3-oxopropyl)-N-acetyl-L-cysteine (I), undergoes facile retro-Michael loss of acrolein in the gas phase. To determine whether extensive loss of acrolein would impede structural characterization of acrolein-peptide adducts, fragmentation reactions of a series of conjugates, formed by 1,4-Michael addition of acrolein to peptides and cysteine derivatives, were investigated at collision cell potentials up to ?50 V using a triple quadrupole mass spectrometer. Differences in fragmentation dynamics suggest protonation at the sulfur of the N-acetylcysteine conjugate I facilitates retro-Michael elimination of acrolein with a low activation energy relative to other fragmentations. Analogous fragmentation was eliminated after borohydride reduction of the aldehyde to an alcohol. Retro-Michael fragmentation was not significant for acrolein conjugates of glutathione derivatives, suggesting that proton sequestration occurs in peptides with multiple amide linkages even when the peptide does not contain a basic amino group. An unexpected outcome of these experiments was the observation of a facile gas-phase cleavage of peptides on the N-terminal side of S-(3-oxopropyl)cysteine residues. Such fragmentation behavior may prove useful for locating cysteine residues in peptides. 相似文献
62.
Katarzyna Kie-Kononowicz Ewa Szymaska Janina Karolak-Wojciechowska Waldemar Ksiazek Christa E. Müller Uli Geis 《Journal of heterocyclic chemistry》1999,36(1):257-263
A series of arylidene imidazo[2,1-b]thiazoles was synthesized, in order to investigate the influence of different spatial arrangements of the arylidene substituent towards the bicyclic structure of imidazo[2,1-b]-thiazole on benzodiazepine receptor affinity. 1,2- And 2,3-cyclized derivatives of mono- and di-substituted Z-5-arylidene-2-thiohydantoins were investigated. As an example of E isomers E-5-benzylidene-2,3-dihydroimidazo[2,1-b]thiazol-6(5H)-one was obtained. The spatial arrangement of the arylidene sub stituent toward the bicyclic structure as well as the character of isomers had little influence on the benzo diazepine receptor affinity of the compounds. It seems that the greatest influence on biological activity has the nature and the number of substituents on the phenyl ring. All investigated imidazo[2,1-b]thiazoles were less active than previously described arylidene imidazo[2,1-b]thiazepinones. 相似文献
63.
64.
Caterina Brandmayr Mirko Wagner Tobias Brückl Daniel Globisch David Pearson Andrea Christa Kneuttinger Veronika Reiter Antje Hienzsch Susanne Koch Ines Thoma Peter Thumbs Stylianos Michalakis Markus Müller Martin Biel Thomas Carell 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2012,124(44):11324-11328
65.
Dr. Kai Fredriksson Dr. Philip Lottmann Dr. Sonja Hinz Iounut Onila Dr. Aliaksei Shymanets Prof. Christian Harteneck Prof. Christa E. Müller Prof. Christian Griesinger Dr. Thomas E. Exner 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2017,129(21):5844-5848
G-protein-coupled-receptors (GPCRs) are of fundamental importance for signal transduction through cell membranes. This makes them important drug targets, but structure-based drug design (SBDD) is still hampered by the limitations for structure determination of unmodified GPCRs. We show that the interligand NOEs for pharmacophore mapping (INPHARMA) method can provide valuable information on ligand poses inside the binding site of the unmodified human A2A adenosine receptor reconstituted in nanodiscs. By comparing experimental INPHARMA spectra with back-calculated spectra based on ligand poses obtained from molecular dynamics simulations, a complex structure for A2AR with the low-affinity ligand 3-pyrrolidin-1-ylquinoxalin-2-amine was determined based on the X-ray structure of ligand ZM-241,358 in complex with a modified A2AR. 相似文献
66.
M. Chem. Caterina Brandmayr Dipl.‐Chem. Mirko Wagner Dr. Tobias Brückl Dr. Daniel Globisch Dr. David Pearson M. Sc. Andrea Christa Kneuttinger Dipl.‐Chem. Veronika Reiter Dr. Antje Hienzsch Dipl.‐Biol. Susanne Koch M. Sc. Ines Thoma Dipl.‐Chem. Peter Thumbs Dr. Stylianos Michalakis Dr. Markus Müller Prof. Dr. Martin Biel Prof. Dr. Thomas Carell 《Angewandte Chemie (International ed. in English)》2012,51(44):11162-11165
67.
Nicole A. Rice William J. Bodnaryk Isaac Tamblyn Zygmunt J. Jakubek Jacques Lefebvre Greg Lopinski Alex Adronov Christa M. Homenick 《Journal of polymer science. Part A, Polymer chemistry》2020,58(13):1889-1902
To fully actualize the potential of boron nitride nanotubes (BNNTs), it is necessary to overcome the inherent insolubility of this nanomaterial. Drawing on the successes realized in the analogous carbon nanotube field, noncovalent functionalization with conjugated polymers offers a simple, scalable route toward the production of stable dispersions of BNNTs. 2,7-carbazoles were chosen as our core monomer based on density functional theory (DFT) predictions, which suggest superior interactions with BNNTs when compared to fluorene-BNNT interactions. Homo poly(2,7-carbazole)s and copolymers with fluorenes were synthesized and used successfully to disperse BNNTs into organic solvents. Thermogravimetric analysis and atomic force microscopy results confirm the proficiency of these polymers to disperse large amounts (> 80% by weight) of individualized BNNTs. Analysis of absorbance data shows that the choice of solvent is critical, with stability enhanced in THF compared to CHCl3 due to the more efficient planarization of polymer chains on the surface of BNNTs, particularly for the homopolymers. The utility of these highly-soluble poly(2,7-carbazole)-BNNT complexes for printed electronics and transparent composites was demonstrated by the fabrication of simple capacitors and incorporation into poly(methyl methacrylate) composites, respectively. 相似文献
68.
Large‐volume sample stacking with polarity switching for monitoring of nucleotide pyrophosphatase/phosphodiesterase 1 (NPP1) reactions by capillary electrophoresis
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Nucleotide pyrophosphatase/phosphodiesterase 1 (NPP1) is a membrane glycoprotein involved in the hydrolysis of extracellular nucleotides. Its main substrate is ATP yielding AMP and pyrophosphate. NPP1 has been proposed as a novel drug target, for diabetes type 2 and the treatment of calcium pyrophosphate dihydrate deposition disease leading to inflammatory arthritis. The monitoring of NPP1 reactions is difficult because its velocity is very slow requiring highly sensitive analytical procedures. In this study, a method of large‐volume sample stacking with polarity switching was developed, and separations were optimized. Large sample volumes were loaded by hydrodynamic injection (5 psi, 13 s) followed by removal of a large plug of sample matrix from the capillary using polarity switching (?10 kV). The stacked analytes were subsequently separated in phosphate buffer (100 mM, pH 9.2) at 20 kV. The validated method was found to be linear (R2 = 0.9927) in the concentration range of 0.05–50 μM of AMP, with high accuracy and precision. The determined LOD and LOQ of AMP were 18 nM and 60 nM, respectively. Compared to a previously reported CE procedure using sweeping technique, a fivefold improvement of sensitivity was achieved. Moreover, the new technique was faster, and reproducibility of migration times was improved (RSD value = 1.2%). Importantly, adenine nucleotide analogs and derivatives tested as NPP1 inhibitors could be completely separated from the substrate ATP and the enzymatic product AMP. The method was applied to NPP1 inhibition assays investigating nucleotide‐derived inhibitors in the presence of ATP. 相似文献
69.
Christa Cuchiero 《Stochastic Processes and their Applications》2019,129(5):1829-1872
We introduce polynomial processes in the context of stochastic portfolio theory to model simultaneously companies’ market capitalizations and the corresponding market weights. These models substantially extend volatility stabilized market models considered in Fernholz and Karatzas (2005), in particular they allow for correlation between the individual stocks. At the same time they remain remarkably tractable which makes them applicable in practice, especially for estimation and calibration to high dimensional equity index data. In the diffusion case we characterize the polynomial property of the market capitalizations and their weights, exploiting the fact that the transformation between absolute and relative quantities perfectly fits the structural properties of polynomial processes. Explicit parameter conditions assuring the existence of a local martingale deflator and relative arbitrages with respect to the market portfolio are given and the connection to non-attainment of the boundary of the unit simplex is discussed. We also consider extensions to models with jumps and the computation of optimal relative arbitrage strategies. 相似文献
70.
The aim of this study is to quantify the effectivity of the depletion of human high-abundance serum and plasma proteins for improved protein identification and disease marker candidate discovery and to assess the risk of concomitant removal of relevant marker proteins. 2-DE and bottom-up shotgun MS combining 2-D capillary chromatography with MS/MS were applied in parallel for the analysis of fractions resulting from the depletion procedure. For many proteins the factors of enrichment by the depletion were obvious allowing their enhanced detection and identification upon high-abundance protein depletion. Nano-liquid chromatography linked MS allowed the efficient identification of several low-abundant proteins that were not identified on the 2-DE gels. Resolving the fractions that were eluted from the matrix upon depletion indicated unspecific binding of disease relevant proteins in plasma samples from acute myocardial infarction patients. The unspecific binding to the depletion matrix of inflammatory markers spiked into the serum was found to depend on the type of capturing agent used. Polyclonal avian antibodies (IgY) displayed the least unspecific binding due to the high immunogenicity of mammalian proteins in avian hosts. 相似文献