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101.
Sugar–Edge Interactions in a DNA–RNA G‐Quadruplex: Evidence of Sequential C−H⋅⋅⋅O Hydrogen Bonds Contributing to RNA Quadruplex Folding
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Jonathan Dickerhoff Dr. Bettina Appel Prof. Dr. Sabine Müller Prof. Dr. Klaus Weisz 《Angewandte Chemie (International ed. in English)》2016,55(48):15162-15165
DNA G‐quadruplexes were systematically modified by single riboguanosine (rG) substitutions at anti‐dG positions. Circular dichroism and NMR experiments confirmed the conservation of the native quadruplex topology for most of the DNA–RNA hybrid structures. Changes in the C8 NMR chemical shift of guanosines following rG substitution at their 3′‐side within the quadruplex core strongly suggest the presence of C8?H???O hydrogen‐bonding interactions with the O2′ position of the C2′‐endo ribonucleotide. A geometric analysis of reported high‐resolution structures indicates that such interactions are a more general feature in RNA quadruplexes and may contribute to the observed preference for parallel topologies. 相似文献
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A divalent europium chloride-bromide phase, EuBr1.56(7)Cl0.46(2) has been prepared and identified on the basis of analytical, X-ray powder diffraction and single-crystal data. Although the phase is considered isostructural with EuCl2 (PbCl2 structure type, a = 0.9230 (5), b = 0.7890 (4), c = 0.4613 (3) nm, space group Pbnm), the single-crystal data indicate long-range order in the form of a superstructure which doubles the b parameter. In the pseudocell the square pyramidal anion sites are occupied principally by bromide ions, the tetrahedral sites almost equally by bromide and chlorine ions. Structural details and the long-range order are discussed. Evidence is presented for the existence of another europium(II) mixed halide phase, EuBr1.8(2)Cl0.16(2). 相似文献
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Coclass theory can be used to define infinite families of finite p-groups of a fixed coclass. It is conjectured that the groups in one of these infinite families all have isomorphic mod-p cohomology rings. Here we prove that almost all groups in one of these infinite families have equivalent Quillen categories. We also show how the Quillen categories of the groups in an infinite family are connected to the Quillen category of their associated infinite pro-p-group of finite coclass. 相似文献
108.
Zoran Andjelkovic Shailen Bharadia Bettina Sommer Manuel Vogel Wilfried N?rtersh?user 《Hyperfine Interactions》2010,196(1-3):81-91
The extremely strong fields that exist around the nuclei of few-electron heavy ions drastically change the properties of the electronic system such as energy level spacings, lifetimes and magnetic moments. In turn, the electrons serve as sensitive probes for nuclear properties such as size, magnetic moment and spatial distribution of charge and magnetization. The energies of their forbidden fine and hyperfine structure transitions strongly depend on the nuclear charge and shift from microwave domains in or close to the optical domain. Thus, they become accessible for laser spectroscopy and its potentially high precision. A number of such measurements have been performed in storage rings and electron beam ion traps, and have yielded results with relative accuracies in the permille region. We present here an experiment under development at GSI Darmstadt which aims to significantly increase the accuracy by employing charged particle traps which allow to slow the ion motion nearly to rest, thus reducing Doppler effects and increasing the possible accuracy to the more than ppm region. 相似文献
109.
Schausberger SE Heise B Maurer C Bernet S Ritsch-Marte M Stifter D 《Optics letters》2010,35(24):4154-4156
We propose a full-field low-coherence interference (LCI) microscope that can provide different contrast modes using Fourier-plane filtering by means of a spatial light modulator. By altering the phase and spatial frequencies of the backreflected wavefront from the sample arm of the interferometer, we are able to change the contrast in the depth-resolved LCI images. We demonstrate that different types of contrast modes, such as, e.g., spiral phase contrast, can successfully be emulated to provide specific enhancement of internal structures and edges and to reveal complementary details within the samples under investigation. 相似文献
110.
Bomke S Seiwert B Dudek L Effkemann S Karst U 《Analytical and bioanalytical chemistry》2009,393(1):247-256
A liquid chromatography (LC)/mass spectrometry method was developed for the determination of selected biogenic amines in various
fish and other food samples. It is based on a precolumn derivatization of the amines with succinimidylferrocenyl propionate
under formation of the respective amides and their reversed-phase liquid-chromatographic separation with subsequent electrospray
ionization mass-spectrometric detection. Deuterated putescine, cadaverine, and histamine are added prior to the derivatization
as internal standards that are coeluted, thus allowing excellent reproducibility of the analysis to be achieved. Depending
on the analyte, the limits of detection were between 1.2 and 19.0 mg/kg, covering between 2 and 3 decades of linearity. The
limit of detection and the linear range for histamine are suitable for the surveillance of the only defined European threshold
for biogenic amines in fish samples. Compared with the established ortho-phthalaldehyde (OPA)/LC/fluorescence method, the
newly developed method allows an unambiguous identification of the biogenic amines by their mass spectra in addition to only
retention times, a fivefold acceleration of the separation, and independency from the sample matrix owing to the isotope-labeled
internal standards. Various fish, calamari, and salami samples were successfully analyzed with the new method and validated
with an independent OPA/LC/fluorescence method. 相似文献