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81.
Martin Barner 《Archiv der Mathematik》1956,7(3):204-213
Ohne Zusammenfassung 相似文献
82.
Shaban E. A. Saad Donald J. L. Jones Leonie M. Norris Emma Horner‐Glister Ketan R. Patel Robert G. Britton William P. Steward Andreas J. Gescher Karen Brown Stewart Sale 《Biomedical chromatography : BMC》2012,26(12):1559-1566
3′,4′,5′‐Trimethoxyflavonol (TMFol) is a synthetic flavonol with preclinical cancer chemopreventive properties. The hypothesis was tested that, in mice, p.o. administration of TMFol results in measureable levels of the parent in target tissues. A single oral dose (240 mg/kg) was administered to mice (n = 4 per time point) with time points ranging from 5 to 1440 min. TMFol and its metabolites were identified and quantitated in all tissues by high‐performance liquid chromatography (HPLC). Plasma levels of TMFol were at the limit of quantification or below, although metabolites were identified. Peak levels of TMFol in the gastrointestinal tract and the prostate averaged 1671 ± 265 µg/g (5.3 µmol/g) and 6.0 ± 1.6 µg/g (18.4 nmol/g), and occurred 20 and 360 min post‐dose, respectively. The area under the tissue concentration–time curve (AUC) for TMFol was greater than those of the metabolites, indicating that TMFol is relatively metabolically stable. Micromolar TMFol levels are easily achieved in the prostate and gastrointestinal tract, suggesting that TMFol might exert chemopreventive efficacy at these tissue sites. Further investigations are warranted to elucidate the potential chemopreventive potency of TMFol. Copyright © 2012 John Wiley & Sons, Ltd. 相似文献
83.
Kayte Ranieri Guillaume Delaittre Christopher Barner‐Kowollik Thomas Junkers 《Macromolecular rapid communications》2014,35(23):2023-2028
The β‐scission rate coefficient of tert‐butyl radicals fragmenting off the intermediate resulting from their addition to tert‐butyl dithiobenzoate—a reversible addition–fragmentation chain transfer (RAFT) agent—is estimated via the recently introduced electron spin resonance (ESR)‐trapping methodology as a function of temperature. The newly introduced ESR‐trapping methodology is critically evaluated and found to be reliable. At 20 °C, a fragmentation rate coefficient of close to 0.042 s−1 is observed, whereas the activation parameters for the fragmentation reaction—determined for the first time—read EA = 82 ± 13.3 kJ mol−1 and A = (1.4 ± 0.25) × 1013 s−1. The ESR spin‐trapping methodology thus efficiently probes the stability of the RAFT adduct radical under conditions relevant for the pre‐equilibrium of the RAFT process. It particularly indicates that stable RAFT adduct radicals are indeed formed in early stages of the RAFT polymerization, at least when dithiobenzoates are employed as controlling agents as stipulated by the so‐called slow fragmentation theory. By design of the methodology, the obtained fragmentation rate coefficients represent an upper limit. The ESR spin‐trapping methodology is thus seen as a suitable tool for evaluating the fragmentation rate coefficients of a wide range of RAFT adduct radicals.
84.
Joachim Laun Mariia Vorobii Andres de los Santos Pereira Ognen Pop‐Georgievski Vanessa Trouillet Alexander Welle Christopher Barner‐Kowollik Cesar Rodriguez‐Emmenegger Thomas Junkers 《Macromolecular rapid communications》2015,36(18):1681-1686
Surface‐initiated photo‐induced copper‐mediated radical polymerization is employed to graft a wide range of polyacrylate brushes from silicon substrates at extremely low catalyst concentrations. This is the first time that the controlled nature of the reported process is demonstrated via block copolymer formation and re‐initiation experiments. In addition to unmatched copper catalyst concentrations in the range of few ppb, film thicknesses up to almost 1 μm are achieved within only 1 h.
85.
Dr. Ozcan Altintas Dr. Mathias Glassner Dr. Cesar Rodriguez‐Emmenegger Dr. Alexander Welle Vanessa Trouillet Prof. Dr. Christopher Barner‐Kowollik 《Angewandte Chemie (International ed. in English)》2015,54(19):5777-5783
The efficient trapping of photogenerated thioaldehydes with functional shelf‐stable nitrile oxides in a 1,3‐dipolar cycloaddition is a novel and versatile photochemical strategy for polymer end‐group functionalization and surface modification under mild and equimolar conditions. The modular ligation in solution was followed in detail by electrospray ionization mass spectrometry (ESI‐MS). X‐ray photoelectron spectroscopy (XPS) was employed to analyze the functionalized surfaces, whereas time‐of‐flight secondary‐ion mass spectrometry (ToF‐SIMS) confirmed the spatial control of the surface functionalization using a micropatterned shadow mask. Polymer brushes were grown from the surface in a spatially confined regime by surface‐initiated atom transfer radical polymerization (SI‐ATRP) as confirmed by TOF‐SIMS, XPS as well as ellipsometry. 相似文献
86.
Jan O. Mueller Dr. Friedrich G. Schmidt Dr. James P. Blinco Prof. Christopher Barner‐Kowollik 《Angewandte Chemie (International ed. in English)》2015,54(35):10284-10288
A rapid and catalyst‐free cycloaddition system for visible‐light‐induced click chemistry is reported. A readily accessible photoreactive 2H‐azirine moiety was designed to absorb light at wavelengths above 400 nm. Irradiation with low‐energy light sources thus enables efficient small‐molecule synthesis with a diverse range of multiple‐bond‐containing compounds. Moreover, in order to demonstrate the efficiency of the current approach, quantitative ligation of the photoactivatable chromophore with functional polymeric substrates was performed and full conversion with irradiation times of only 1 min at ambient conditions was achieved. The current report thus presents a highly efficient method for applications involving selective cycloaddition to electron‐deficient multiple‐bond‐containing materials. 相似文献
87.
Philipp Vana Luca Albertin Leonie Barner Thomas P. Davis Christopher Barner‐Kowollik 《Journal of polymer science. Part A, Polymer chemistry》2002,40(22):4032-4037
Electrospray ionization mass spectrometry was performed to identify the structure of polymeric methyl acrylates generated via the cumyl dithiobenzoate (CDB), cumyl p‐fluorodithiobenzoate (CPFDB), and 1‐phenylethyl dithiobenzoate (PEDB) mediated reversible addition–fragmentation chain‐transfer (RAFT) polymerizations. The relatively simple spectra clearly demonstrate the end groups of this living free‐radical polymerization technique. Only polymeric chains carrying one leaving group of the RAFT agent and the dithiobenzoate end group as the active RAFT center were discovered. Multiple‐stage mass spectrometric experiments and oxidation of the dithioester end group confirmed the structure of the generated polymers. © 2002 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 40: 4032–4037, 2002 相似文献
88.
Alexander P. Haehnel Benjamin Wenn Katrin Kockler Tobias Bantle Andrea M. Misske Friederike Fleischhaker Thomas Junkers Christopher Barner‐Kowollik 《Macromolecular rapid communications》2015,36(22):1984-1986
A recent response on a publication from our team investigating solvent effects on propagation rate coefficients is commented. Among other issues, we point to the fact that the response interprets only a subset of the data provided in our original contribution.
89.
Federica Cavalli Fabian R. Bloesser Prof. Dr. Christopher Barner-Kowollik Prof. Dr. Leonie Barner 《Chemistry (Weinheim an der Bergstrasse, Germany)》2019,25(43):10049-10053
We introduce a protecting-group-free concept for the powerful para-fluoro-thiol reaction (PFTR) employing a source of fluoride ions as base. The reaction is shown to be self-propagating, with under-stoichiometric amounts of base, thus effectively foregoing the need for high base concentrations. Careful tuning of the solvent–thiol combination allows for quantitative conversion, in some cases within a short timeframe, when only minimal amounts of base are used, allowing the PFTR reaction to essentially proceed base-free. 相似文献