排序方式: 共有24条查询结果,搜索用时 31 毫秒
1.
Elisabeth Siebert Marius Horch Yvonne Rippers Johannes Fritsch Stefan Frielingsdorf Oliver Lenz Francisco VelazquezEscobar Friedrich Siebert Lars Paasche Uwe Kuhlmann Friedhelm Lendzian Maria‐Andrea Mroginski Ingo Zebger Peter Hildebrandt 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2013,125(19):5267-5270
2.
Lars Lauterbach Hongxin Wang Marius Horch Leland B. Gee Yoshitaka Yoda Yoshihito Tanaka Ingo Zebger Oliver Lenz Stephen P. Cramer 《Chemical science》2015,6(2):1055-1060
Hydrogenases are complex metalloenzymes that catalyze the reversible splitting of molecular hydrogen into protons and electrons essentially without overpotential. The NAD+-reducing soluble hydrogenase (SH) from Ralstonia eutropha is capable of H2 conversion even in the presence of usually toxic dioxygen. The molecular details of the underlying reactions are largely unknown, mainly because of limited knowledge of the structure and function of the various metal cofactors present in the enzyme. Here, all iron-containing cofactors of the SH were investigated by 57Fe specific nuclear resonance vibrational spectroscopy (NRVS). Our data provide experimental evidence for one [2Fe2S] center and four [4Fe4S] clusters, which is consistent with the amino acid sequence composition. Only the [2Fe2S] cluster and one of the four [4Fe4S] clusters were reduced upon incubation of the SH with NADH. This finding explains the discrepancy between the large number of FeS clusters and the small amount of FeS cluster-related signals as detected by electron paramagnetic resonance spectroscopic analysis of several NAD+-reducing hydrogenases. For the first time, Fe–CO and Fe–CN modes derived from the [NiFe] active site could be distinguished by NRVS through selective 13C labeling of the CO ligand. This strategy also revealed the molecular coordinates that dominate the individual Fe–CO modes. The present approach explores the complex vibrational signature of the Fe–S clusters and the hydrogenase active site, thereby showing that NRVS represents a powerful tool for the elucidation of complex biocatalysts containing multiple cofactors. 相似文献
3.
S. Horch P. Zeppenfeld G. Comsa 《Applied Physics A: Materials Science & Processing》1995,60(2):147-153
The adsorption of Xe on Pt(111) has been investigated from the arrival of the very first atoms up to completion of the monolayer using a variable-temperature Scanning Tunneling Microscope (STM). Surprisingly, in the initial stages of the adsorption Xe preferentially binds to a low coordination site, theupper edge of the platinum steps. The strong binding to these sites leads to a local repulsive interaction with further Xe atoms. Therefore, the Xe atoms located at the upper edge of the steps do not serve as nuclei for 2D Xe islands, which, instead, form on the terraces and at thelower edges of the platinum steps. Only during completion of the monolayer do these islands make contact with the atoms adsorbed at the beginning in the upper-edge positions. The full monolayer exhibits the Hexagonal Incommensurate Rotated (HIR) phase already known from earlier helium-diffraction experiments. 相似文献
4.
Background
Earlier observations in our lab had indicated that large, time-varying magnetic fields could elicit action potentials that travel in only one direction in at least some of the myelinated axons in peripheral nerves. The objective of this study was to collect quantitative evidence for magnetically induced unidirectional action potentials in peripheral nerves of human subjects. A magnetic coil was maneuvered to a location on the upper arm where physical effects consistent with the creation of unidirectional action potentials were observed. 相似文献5.
6.
K Horch 《The Journal of the Acoustical Society of America》1991,89(6):2827-2836
Psychophysical and electrophysiological techniques were used to study the encoding and processing of information about the frequency content of vibrational stimuli applied to glabrous skin in humans and cats. Trained human subjects were asked to discriminate changes in stimulus frequency and harmonic content for pairs of mono- and diharmonic sinusoidal vibrations applied to the fingertips. These psychophysical tests supplied data on what information is available to the central nervous system about the frequency components of vibratory stimuli. Electrophysiological recordings from nerves innervating the glabrous skin of the paw in cats during presentation of the same stimuli used in the psychophysical study provided data on how the peripheral nervous system encodes information about the physical parameters of cutaneous vibratory stimuli. The two sets of data indicated that the subjects derived information about the frequency of vibrotactile stimuli from the mean interval between action potentials in afferent nerve fibers activated by the stimulus. 相似文献
7.
S. Helveg H. T. Lorensen S. Horch E. L gsgaard I. Stensgaard K. W. Jacobsen J. K. N rskov F. Besenbacher 《Surface science》1999,430(1-3):L533-L539
From an interplay between scanning tunneling microscopy (STM) experiments and density functional theory (DFT) calculations, a comprehensive picture is obtained for oxygen adsorption on the Pt(110)-(1×2) surface, from single isolated oxygen atoms chemisorbed in FCC sites along the platinum ridges to the formation of a new high-coverage oxide-like structure with a local coverage of two oxygen atoms per platinum surface atom. We find that the repulsive O–O interactions for the O/Pt(110) system are compensated by an effective O–O attractive interaction originating from a strong coupling between oxygen adsorption and platinum lattice distortions. 相似文献
8.
Hinnemann B Moses PG Bonde J Jørgensen KP Nielsen JH Horch S Chorkendorff I Nørskov JK 《Journal of the American Chemical Society》2005,127(15):5308-5309
The electrochemical hydrogen evolution reaction is catalyzed most effectively by the Pt group metals. As H2 is considered as a future energy carrier, the need for these catalysts will increase and alternatives to the scarce and expensive Pt group catalysts will be needed. We analyze the ability of different metal surfaces and of the enzymes nitrogenase and hydrogenase to catalyze the hydrogen evolution reaction and find a necessary criterion for high catalytic activity. The necessary criterion is that the binding free energy of atomic hydrogen to the catalyst is close to zero. The criterion enables us to search for new catalysts, and inspired by the nitrogenase active site, we find that MoS2 nanoparticles supported on graphite are a promising catalyst. They catalyze electrochemical hydrogen evolution at a moderate overpotential of 0.1-0.2 V. 相似文献
9.
Elisa A. Paoli Federico Masini Rasmus Frydendal Davide Deiana Christian Schlaup Mauro Malizia Thomas W. Hansen Sebastian Horch Ifan E. L. Stephens Ib Chorkendorff 《Chemical science》2015,6(1):190-196
Oxygen evolution was investigated on model, mass-selected RuO2 nanoparticles in acid, prepared by magnetron sputtering. Our investigations include electrochemical measurements, electron microscopy, scanning tunneling microscopy and X-ray photoelectron spectroscopy. We show that the stability and activity of nanoparticulate RuO2 is highly sensitive to its surface pretreatment. At 0.25 V overpotential, the catalysts show a mass activity of up to 0.6 A mg–1 and a turnover frequency of 0.65 s–1, one order of magnitude higher than the current state-of-the-art. 相似文献
10.
Elisabeth Siebert Marius Horch Yvonne Rippers Dr. Johannes Fritsch Dr. Stefan Frielingsdorf Prof. Dr. Oliver Lenz Francisco Velazquez Escobar Prof. Dr. Friedrich Siebert Lars Paasche Dr. Uwe Kuhlmann Dr. Friedhelm Lendzian Prof. Dr. Maria‐Andrea Mroginski Dr. Ingo Zebger Prof. Dr. Peter Hildebrandt 《Angewandte Chemie (International ed. in English)》2013,52(19):5186-5186