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91.
Alma Viso Roberto Fernández de la Pradilla Ana García Carlos Guerrero-Strachan Marta Alonso Mariola Tortosa 《Phosphorus, sulfur, and silicon and the related elements》2013,188(5-6):1229-1234
Abstract Readily available p-tolylsulfinimines undergo highly stereoselective [3 + 2] cycloadditions with azomethine ylides generated from α -iminoesters and LDA to produce N-sulfinylimidazolidines. In the presence of Lewis acids, p-tolylsulfinimines react with glycine iminoester enolates to produce N-sulfinylimidazolidines, after cyclization of open chain intermediates. These mechanistically diverse processes take place with excellent regio-, stereo-, and facial selectivities, and the latter is opposite to most known reactions involving sulfinimines. Some of the resulting imidazolidines have been transformed into examples of a novel class of nonsymmetrical vicinal diamines using reductive and/or hydrolytic protocols. 相似文献
92.
93.
The effect of certain chemicals known as singlet oxygen quenchers on the photoreaction between 8-MOP and DNA has been studied in vitro; sodium azide, l,4-diazabicyclo-(2,2,2)-octane, p-carotene and dimethylsolfoxide (used as a solvent) appeared to be capable of reducing significantly the 8-MOP ability to induce both monoadducts and cross-links in DNA. Therefore, these chemicals seem to be not useful in studying the singlet oxygen implication in the induction of biological effects of 8-MOP sensitization. 相似文献
94.
Pardes Habib Jennifer Jung Gina Maria Wilms Alma Kokott-Vuong Shahin Habib Jrg B. Schulz Aaron Voigt 《Experimental & molecular medicine》2021,53(2):264
Hypoxia is an underlying pathophysiological condition of a variety of devastating diseases, including acute ischemic stroke (AIS). We are faced with limited therapeutic options for AIS patients, and even after successful restoration of cerebral blood flow, the poststroke mortality is still high. More basic research is needed to explain mortality after reperfusion and to develop adjunct neuroprotective therapies. Drosophila melanogaster (D.m.) is a suitable model to analyze hypoxia; however, little is known about the impacts of hypoxia and especially of the subsequent reperfusion injury on the behavior and survival of D.m. To address this knowledge gap, we subjected two wild-type D.m. strains (Canton-S and Oregon-R) to severe hypoxia (<0.3% O2) under standardized environmental conditions in a well-constructed hypoxia chamber. During posthypoxic reperfusion (21% O2), we assessed fly activity (evoked and spontaneous) and analyzed molecular characteristics (oxidative stress marker abundance, reactive oxygen species (ROS) production, and metabolic activity) at various timepoints during reperfusion. First, we established standard conditions to induce hypoxia in D.m. to guarantee stable and reproducible experiments. Exposure to severe hypoxia under defined conditions impaired the climbing ability and reduced the overall activity of both D.m. strains. Furthermore, a majority of the flies died during the early reperfusion phase (up to 24 h). Interestingly, the flies that died early exhibited elevated activity before death compared to that of the flies that survived the entire reperfusion period. Additionally, we detected increases in ROS and stress marker (Catalase, Superoxide Dismutase and Heat Shock Protein 70) levels as well as reductions in metabolic activity in the reperfusion phase. Finally, we found that changes in environmental conditions impacted the mortality rate. In particular, decreasing the temperature during hypoxia or the reperfusion phase displayed a protective effect. In conclusion, our data suggest that reperfusion-dependent death might be associated with elevated temperatures, predeath activity, and oxidative stress.Subject terms: Stroke, Molecular neuroscience 相似文献
95.
Optimal control theory (OCT) including nonresonant multiphoton transitions (NMT) in the femtosecond time regime has been implemented. The NMT process is modelled using an effective time-dependent Schrödinger equation, which considers a reduced space of the two levels which are involved in the transition, coupled to a density of high-lying off-resonant states. The specification of OCT to two-photon transitions is done within the rotating wave approximation. As an application, the transfer and displacement of a wavepacket in the organometallic system CpMn(CO)3, from the ground to an electronically excited state using two nonresonant photons, is simulated. 相似文献
96.
97.
Z. Leppert Z. Majewska K. Ho C. S. Wan S. H. Wen F. W. Cheng G. Lunde F. Stiebel L. M. Labaune A. Jermakow W. Leithe F. Fritz W. F. Geddes F. H. Lehberg A. Afanassjew M. Podolskaja M. Sserga K. Höll E. Delvaux N. N. Godbole A. M. Se P. S. Varma G. M. Garde M. Procopio H. Levin Alma Tomingas M. E. Marks C. H. Lea G. S. Fawcett F. M. Biffen und F. D. Snell 《Fresenius' Journal of Analytical Chemistry》1938,113(5-6):235-240
Ohne Zusammenfassung 相似文献
98.
Beraldo Heloisa Nacif Wanderlene F. Teixeira Leticia R. Rebouças Julio S. 《Transition Metal Chemistry》2002,27(1):85-88
CoII and NiII complexes of N(4)-methyl and N(4)-ethyl thiosemicarbazones derived from 3- and 4-acetylpyridine have been prepared and characterized by microanalyses, magnetic susceptibility and molar conductivity measurements and by their electronic, i.r. and n.m.r. (in the case of NiII complexes) spectra. 相似文献
99.
100.
Gustavo Crdenas Ivan Trentin Ludwig Schwiedrzik David Hernndez-Castillo Grace A. Lowe Julian Kund Christine Kranz Sarah Klingler Robert Stach Boris Mizaikoff Philipp Marquetand Juan J. Nogueira Carsten Streb Leticia Gonzlez 《Chemical science》2021,12(39):12918
Despite their technological importance for water splitting, the reaction mechanisms of most water oxidation catalysts (WOCs) are poorly understood. This paper combines theoretical and experimental methods to reveal mechanistic insights into the reactivity of the highly active molecular manganese vanadium oxide WOC [Mn4V4O17(OAc)3]3− in aqueous acetonitrile solutions. Using density functional theory together with electrochemistry and IR-spectroscopy, we propose a sequential three-step activation mechanism including a one-electron oxidation of the catalyst from [Mn23+Mn24+] to [Mn3+Mn34+], acetate-to-water ligand exchange, and a second one-electron oxidation from [Mn3+Mn34+] to [Mn44+]. Analysis of several plausible ligand exchange pathways shows that nucleophilic attack of water molecules along the Jahn–Teller axis of the Mn3+ centers leads to significantly lower activation barriers compared with attack at Mn4+ centers. Deprotonation of one water ligand by the leaving acetate group leads to the formation of the activated species [Mn4V4O17(OAc)2(H2O)(OH)]− featuring one H2O and one OH ligand. Redox potentials based on the computed intermediates are in excellent agreement with electrochemical measurements at various solvent compositions. This intricate interplay between redox chemistry and ligand exchange controls the formation of the catalytically active species. These results provide key reactivity information essential to further study bio-inspired molecular WOCs and solid-state manganese oxide catalysts.Combined theoretical and experimental studies shed light on the initial steps of redox-activation of a molecular manganese vanadium oxide water oxidation catalyst. 相似文献