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排序方式: 共有396条查询结果,搜索用时 20 毫秒
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The VO3?4 and Eu3+ luminescence in compounds with ordered β-K2SO4 structure is reported. The ratio of the Eu3+ and vandate emission intensity depends on the excitation energy. 相似文献
93.
The amino acid selenocysteine represents the major biological form of selenium. Both the synthesis of selenocysteine and its co-translational incorporation into selenoproteins in response to an in-frame UGA codon, require a complex molecular machinery. To decode the UGA Sec codon in eubacteria, this machinery comprises the tRNASec, the specialized elongation factor SelB and the SECIS hairpin in the selenoprotein mRNAs. SelB conveys the Sec-tRNASec to the A site of the ribosome through binding to the SECIS mRNA hairpin adjacent to the UGA Sec codon. SelB is thus a bifunctional factor, carrying functional homology to elongation factor EF-Tu in its N-terminal domain and SECIS RNA binding activity via its C-terminal extension. In archaea and eukaryotes, selenocysteine incorporation exhibits a higher degree of complexity because the SECIS hairpin is localized in the 3' untranslated region of the mRNA. In the last couple of years, remarkable progress has been made toward understanding the underlying mechanism in mammals. Indeed, the discovery of the SECIS RNA binding protein SBP2, which is not a translation factor, paved the way for the subsequent isolation of mSelB/EFSec, the mammalian homolog of SelB. In contrast to the eubacterial SelB, the specialized elongation factor mSelB/EFSec the SECIS RNA binding function. The role is carried out by SBP2 that also forms a protein-protein complex with mSelB/EFSec. As a consequence, an important difference between the eubacterial and eukaryal selenoprotein synthesis machineries is that the functions of SelB are divided into two proteins in eukaryotes. Obviously, selenoprotein synthesis represents a higher degree of complexity than anticipated, and more needs to be discovered in eukaryotes. In this review, we will focus on the structural and functional aspects of the SelB and SBP2 factors in selenoprotein synthesis. 相似文献
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Martin Bröring Carsten Milsmann Silke Ruck Silke Köhler 《Journal of organometallic chemistry》2009,694(7-8):1011-1015
Superstructured corrole ligands related to the picket-fence porphyrins were obtained from (2,6-dichlorophenyl)dipyrromethane in two steps. Condensation with an aryl aldehyde followed by oxidative ring closure yields A2B corroles with four peripheral bromine atoms. Palladium-catalyzed fourfold amidation at these positions results in the formation of the desired sterically encumbered species, accompanied mainly by disubstituted by-products. The insertion of iron ions into the blocked cavity of the new corrole ligands proves successful when directed towards the nitrosyl derivative. The X-ray crystallographic investigation of such an iron complex allows a detailed view of the steric restraints imposed by the bulky amido substituents. 相似文献
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The results of the Monte Carlo simulation of the LORD experiment are presented for two types of antenna systems with various parameters. The effect of possible polarization mismatch and galactic noise “percolation” are taken into consideration. 相似文献
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Margherita Disertori Franz Merkl Silke W. W. Rolles 《Communications in Mathematical Physics》2014,332(2):783-825
We study a lattice sigma model which is expected to reflect Anderson localization and delocalization transition for real symmetric band matrices in 3D, but describes the mixing measure for a vertex reinforced jump process too. For this model we prove exponential localization at any temperature in a strip, and more generally in any quasi-one dimensional graph, with pinning (mass) at only one site. The proof uses a Mermin–Wagner type argument and a transfer operator approach. 相似文献
100.
Markus Gellesch Franziska Hammerath Vicky Süß Marcel Haft Silke Hampel Sabine Wurmehl Bernd Büchner 《Journal of nanoparticle research》2017,19(9):307
The increasing interest in nanoscale materials goes hand in hand with the challenge to reliably characterize the chemical compositions and structural features of nanosized objects in order to relate those to their physical properties. Despite efforts, the analysis of the chemical composition of individual multi-element nanoparticles remains challenging—from the technical point of view as well as from the point of view of measurement statistics. Here, we demonstrate that zero-field solid-state nuclear magnetic resonance (NMR) complements local, single particle transmission electron microscopy (TEM) studies with information on a large assembly of chemically complex nanoparticles. The combination of both experimental techniques gives information on the local composition and structure and provides an excellent measurement statistic through the corresponding NMR ensemble measurement. This analytical approach is applicable to many kinds of magnetic materials and therefore may prove very versatile in the future research of particulate magnetic nanomaterials. 相似文献