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51.
R. Zimny H. Hagedorn H. Winter J. Kirschner 《Applied Physics A: Materials Science & Processing》1988,47(1):77-81
We observe the emission of circularly polarized light after grazing scattering of fast ions at a magnetized Fe(110) surface. Changing the state of magnetization of the target affects the polarization of the emitted light due to capture of spin polarized electrons. Some aspects of atom-surface interaction and investigations of surface magnetism are discussed. 相似文献
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Understanding the conformational flexibility of amino acid zwitterions (ZWs) and their associated conformational energies is crucial for predicting their interactions in biological systems. Gas-phase ab initio calculations of ZWs are intractable. Molecular mechanics (MM), on the other hand, is able to handle large systems but lacks the necessary force field parameters to model ZWs. To develop force field parameters that are able to correctly model ZW geometries and energetics we used a novel combinatorial approach: amino acid ZWs were broken down structurally into key functional components, which were parameterized separately. M?ller-Plesset second-order perturbation calculations on small carboxylates, on the glycine cation, and on novel hydrogen bonded systems, coupled with available experimental data, were used to generate MM3(2000) ZW parameters (Allinger N. L.; Yuh, Y. H.; Lii, J.-H. J Am Chem Soc 1989, 111, 8551). The MM3 results from this combinatorial approach gave geometries that are in good agreement with neutron diffraction experiments, plus their frequencies and energies appear to be reasonably modeled. Current limitations and future development of MM force fields are discussed briefly. 相似文献
55.
Rainer Schobert Anett Mangold Wolfgang Milius 《Journal of organometallic chemistry》2004,689(3):575-584
Ferracyclic (1-3-η3)pentadienyl complexes with electronically decoupled allyl and vinyl moieties were reacted with various heteroatom and carbon nucleophiles. Primary amines selectively attacked neutral (4-6-η3-pentadienyl)ferralactones 2 on the end of the allyl ligand to give 3-(endo-vinyl)-(4-6-η3-allyl)ferralactams 4 and by a similar reaction of the latter eventually 6-(exo-vinyl)-(4-6-η3-allyl)ferralactams 5. -like attack on the conjugated coplanar vinyl residue of 2 was not observed. The cationic η3-allyl complex 3 was attacked by nucleophiles either on the allylic terminus furnishing free (1Z, 3E)-dienes 8, or on the vinyl residue which is part of an activated Michael system to give η4-1,3-diene complexes 9. η4-1,3,5-Triene complex 10 was obtained with basic nucleophiles. 相似文献
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Marcus W. Jurema Karl N. Kirschner George C. Shields 《Journal of computational chemistry》1993,14(11):1326-1332
The PM3 quantum-mechanical method is able to model the magic water clusters (H2O)20 and (H2O)21H+. Results indicate that the H3O+ ion is tightly bound within the (H2O)20 cluster by multiple hydrogen bonds, causing deformation to the symmetric (H2O)20 pentagonal dodecahedron structure. The structures, energetics, and hydrogen bond patterns of six local minima (H2O)21H+ clusters are presented. © John Wiley & Sons, Inc. 相似文献
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Feczk Tivadar Muskotl Adl Gl Lornd Szpvlgyi Jnos Sebestyn Anett Vonderviszt Ferenc 《Journal of nanoparticle research》2008,10(1):227-232
Superparamagnetic Ni–Zn ferrite nanoparticles were synthesized in radiofrequency thermal plasma reactor from aqueous solutions of Ni- and Zn-nitrates. The nanoparticles were studied for protein purification performance in both quantitative and qualitative terms. For comparison, experiments were also performed by Ni-charged affinity chromatography. It was proved that the Ni–Zn ferrite nanoparticles effectively purified histidine-tagged proteins with a maximum protein binding capacity of about 7% (w/w). Gel electrophoresis demonstrated better purification characteristics for magnetic nanoparticles than for affinity chromatography.
相似文献60.
Jennifer Solarczek Dr. Felix Kaspar Pia Bauer Prof. Anett Schallmey 《Chemistry (Weinheim an der Bergstrasse, Germany)》2022,28(72):e202202343
Halohydrin dehalogenases are promiscuous biocatalysts, which enable asymmetric ring opening reactions of epoxides with various anionic nucleophiles. However, despite the increasing interest in such asymmetric transformations, the substrate scope of G-type halohydrin dehalogenases toward cyclic epoxides has remained largely unexplored, even though this subfamily is the only one known to display activity with these sterically demanding substrates. Herein, we report on the exploration of the substrate scope of the two G-type halohydrin dehalogenases HheG and HheG2 and a newly identified, more thermostable member of the family, HheG3, with a variety of sterically demanding cyclic epoxides and anionic nucleophiles. This work shows that, in addition to azide and cyanide, these enzymes facilitate ring-opening reactions with cyanate, thiocyanate, formate, and nitrite, significantly expanding the known repertoire of accessible transformations. 相似文献