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61.
Stability and Conversion of Tin Zintl Anions in Liquid Ammonia Investigated by NMR Spectroscopy
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Franziska Fendt Dr. Carina Koch Dr. Maria Neumeier Dr. Stefanie Gärtner Prof. Dr. Ruth M. Gschwind Prof. Dr. Nikolaus Korber 《Chemistry (Weinheim an der Bergstrasse, Germany)》2015,21(41):14539-14544
Homoatomic polyanions of post‐transition main‐group metals, namely, Zintl anions, are precast in analogous Zintl phases and can react in solution to form new materials. Despite comprehensible reaction approaches, the formed products cannot be planned in advance, as hitherto undetected and therefore disregarded side reactions take place. The outcomes and interpretations of the reactions of Zintl anions are so far based mainly on crystal structures, which only allow characterization of the product that has the lowest solubility. Here we present the results of our investigation of the stability of highly charged tin Zintl anions in liquid ammonia, which is not exclusively based on solution effects but also on the oxidative influence of the solvent. This allows for a deeper understanding of the ongoing processes in solution and opens doors to the directed synthesis of transition metal complexes of Sn44?, here shown by its reactivity towards MesCu. 相似文献
62.
Nikolaus Bck Gerhard A. Holzapfel 《International Journal of Solids and Structures》2004,41(26):7459-7469
Starting from the issue of what is the correct form for a Legendre transformation of the strain energy in terms of Eulerian and two-point tensor variables we introduce a new two-point deformation tensor, namely H=(F−F−T)/2, as a possible deformation measure involving points in two distinct configurations. The Lie derivative of H is work conjugate to the first Piola–Kirchhoff stress tensor P. The deformation measure H leads to straightforward manipulations within a two-point setting such as the derivation of the virtual work equation and its linearization required for finite element implementation. The manipulations are analogous to those used for the Lagrangian and Eulerian frameworks. It is also shown that the Legendre transformation in terms of two-point tensors and spatial tensors require Lie derivatives. As an illustrative example we propose a simple Saint Venant–Kirchhoff type of a strain-energy function in terms of H. The constitutive model leads to physically meaningful results also for the large compressive strain domain, which is not the case for the classical Saint Venant–Kirchhoff material. 相似文献
63.
Weise K Kapoor S Denter C Nikolaus J Opitz N Koch S Triola G Herrmann A Waldmann H Winter R 《Journal of the American Chemical Society》2011,133(4):880-887
The K-Ras4B GTPase is a major oncoprotein whose signaling activity depends on its correct localization to negatively charged subcellular membranes and nanoclustering in membrane microdomains. Selective localization and clustering are mediated by the polybasic farnesylated C-terminus of K-Ras4B, but the mechanisms and molecular determinants involved are largely unknown. In a combined chemical biological and biophysical approach we investigated the partitioning of semisynthetic fully functional lipidated K-Ras4B proteins into heterogeneous anionic model membranes and membranes composed of viral lipid extracts. Independent of GDP/GTP-loading, K-Ras4B is preferentially localized in liquid-disordered (l(d)) lipid domains and forms new protein-containing fluid domains that are recruiting multivalent acidic lipids by an effective, electrostatic lipid sorting mechanism. In addition, GDP-GTP exchange and, thereby, Ras activation results in a higher concentration of activated K-Ras4B in the nanoscale signaling platforms. Conversely, palmitoylated and farnesylated N-Ras proteins partition into the l(d) phase and concentrate at the l(d)/l(o) phase boundary of heterogeneous membranes. Next to the lipid anchor system, the results reveal an involvement of the G-domain in the membrane interaction process by determining minor but yet significant structural reorientations of the GDP/GTP-K-Ras4B proteins at lipid interfaces. A molecular mechanism for isoform-specific Ras signaling from separate membrane microdomains is postulated from the results of this study. 相似文献
64.
Owschimikow N Schmidt B Schwentner N 《Physical chemistry chemical physics : PCCP》2011,13(19):8671-8680
We numerically investigate the post-pulse alignment of rotationally excited diatomic molecules upon nonresonant interaction with a linearly polarized laser pulse. In addition to the simulations, we develop a simple model which qualitatively describes the shape and amplitude of post-pulse alignment induced by a laser pulse of moderate power density. In our treatment we take into account that molecules in rotationally excited states can interact with a laser pulse not only by absorbing energy but also by stimulated emission. The extent to which these processes are present in the interaction depends, on the one hand, on the directionality of the molecular angular momentum (given by the M quantum number), and on the other hand on the ratio of transition frequencies and pulse duration (determined by the J number). A rotational wave packet created by a strong pulse from an initially pure state contains a broad range of rotational levels, over which the character of the interaction can change from non-adiabatic to adiabatic. Depending on the laser pulse duration and amplitude, the transition from the non-adiabatic to the adiabatic limit proceeds through a region with dominant rotational heating, or alignment, for short pulses and a large region with rotational cooling, and correspondingly preferred anti-alignment, for longer pulses. 相似文献
65.
Joseph K. Rugutt Nikolaus H. Fischer Marcus A. Nauman Thomas J. Schmidt Dana K. Berner 《光谱学快报》2013,46(5):799-818
The two known cadinanes 2-hydroxy-8α-hydroxycalamenene and 2-hydroxy-8α-angeloyloxycalamenene were isolated from a Louisiana population of Heterotheca subaxillaris. Their 13C NMR spectra were fully assigned by the application of HETCOR, COLOC, COSY, NOESY and DEPT experiments. It was shown on the basis of NOESY experiments that both cadinanes require revision at the stereogenic centre C-7. 相似文献
66.
67.
J. Radon W. Nöbauer N. Hofreiter K. Prachar L. Schmetterer H. Hornich J. Laub L. Hofmann W. Gröbner W. Wunderlich Th. Sexl E. Hlawka 《Monatshefte für Mathematik》1956,60(4):337-358
Ohne Zusammenfassung 相似文献
68.
Nikolaus Seiler Herbert Schneider und Klaus-Dieter Sonnenberg 《Fresenius' Journal of Analytical Chemistry》1970,252(2-3):127-136
Zusammenfassung Von etwa 80 1-Dimethylamino-naphthalin-5-sulfonyl-(DANS-)Derivaten biogener Amine und verwandter Verbindungen mit unterschiedlichen strukturellen Elementen wurden die durch Elektronenstoß induzierten Fragmentierungen untersucht. Die Prinzipien dieser Fragmentierungen und die Brauchbarkeit der Massenspektrometrie bei niedrigem Auflösungsvermögen für die Identifizierung dünnschicht-chromatographisch getrennter DANS-Derivate biogener Amine aus Gewebsextrakten werden diskutiert.
Mass spectrometric identification of biogenic amines as 1-dimethylamino-naphthalene-5-sulphonyl derivatives
The fragmentation by electron impact of approximately 80 1-dimethylamino-naphthalene-5-sulphonyl (DANS) derivatives of biogenic amines and related substances of different structural features has been studied. The principles of these fragmentations and the suitability of low resolution mass spectrometry for the identification of thin-layer chromatographically separated DANS-derivatives of biogenic amines from tissue extracts are discussed.相似文献
69.
P. Schmitt E. Hlawka H. Reiter H. G. Feichtinger N. Hofreiter S. Grosser H. Rindler E. Kotzmann P. Michor F. Haslinger H. Mitsch H. -C. Reichel 《Monatshefte für Mathematik》1976,81(2):169-176
Ohne Zusammenfassung 相似文献