Search Results - (Author, Cooperation:G. Witte)

2013-06-01

Nature Publishing Group (NPG)

0028-0836

1476-4687

Biology

Chemistry and Pharmacology

Medicine

Natural Sciences in General

Physics

Adenosine Triphosphate/chemistry/metabolism ; Animals ; Base Sequence ; Catalytic Domain ; Crystallography, X-Ray ; *Cytosol ; DNA/chemistry/*metabolism/pharmacology ; Guanosine Triphosphate/chemistry/metabolism ; HEK293 Cells ; Humans ; Membrane Proteins/genetics/metabolism ; Mice ; Models, Biological ; Models, Molecular ; Mutation ; Nucleotidyltransferases/*chemistry/genetics/metabolism ; Protein Conformation/drug effects ; Structure-Activity Relationship ; Substrate Specificity ; Swine ; Uridine Triphosphate/chemistry/metabolism ; Zinc/chemistry/metabolism

2018-10-05

American Association for the Advancement of Science (AAAS)

0036-8075

1095-9203

Biology

Chemistry and Pharmacology

Geosciences

Computer Science

Medicine

Natural Sciences in General

Physics

Medicine, Diseases

2013-06-01

Nature Publishing Group (NPG)

0028-0836

1476-4687

Biology

Chemistry and Pharmacology

Medicine

Natural Sciences in General

Physics

Adenosine Monophosphate/chemistry ; Animals ; Biocatalysis ; Cell Line ; Cyclic GMP/chemistry ; Cyclization ; HEK293 Cells ; Humans ; Magnetic Resonance Spectroscopy ; Membrane Proteins/*metabolism ; Mice ; Models, Molecular ; Molecular Structure ; Nucleotidyltransferases/genetics/*metabolism ; Oligoribonucleotides/biosynthesis/chemistry/*metabolism ; Second Messenger Systems/*physiology

2013-01-19

American Association for the Advancement of Science (AAAS)

0036-8075

1095-9203

Biology

Chemistry and Pharmacology

Computer Science

Medicine

Natural Sciences in General

Physics

Adenosine Triphosphate/metabolism ; Amino Acid Motifs ; Amino Acid Sequence ; Animals ; Crystallography, X-Ray ; DEAD-box RNA Helicases/*chemistry/genetics/*metabolism ; HEK293 Cells ; Humans ; Hydrolysis ; Immunity, Innate ; Mice ; Models, Molecular ; Molecular Sequence Data ; Mutation ; *Parainfluenza Virus 5/immunology ; Protein Binding ; Protein Folding ; Protein Structure, Tertiary ; RNA, Double-Stranded/*metabolism ; Signal Transduction ; Sus scrofa ; Viral Proteins/*chemistry/genetics/*metabolism

2011-07-08

Nature Publishing Group (NPG)

0028-0836

1476-4687

Biology

Chemistry and Pharmacology

Medicine

Natural Sciences in General

Physics

Binding Sites ; Crystallization ; Crystallography, X-Ray ; DNA/chemistry/genetics/metabolism/ultrastructure ; Encephalitozoon cuniculi/*chemistry ; Fungal Proteins/*chemistry/*metabolism/ultrastructure ; Microscopy, Electron ; Models, Biological ; Models, Molecular ; Promoter Regions, Genetic/genetics ; Protein Conformation ; Protein Structure, Tertiary ; Structure-Activity Relationship ; Substrate Specificity ; TATA-Box Binding Protein/*chemistry/*metabolism/ultrastructure ; Transcription Factor TFIIB/chemistry/metabolism

1089-7623

AIP Digital Archive

Physics

Electrical Engineering, Measurement and Control Technology

Micrometer-sized nozzles and skimmers made from drawn glass tubes are described and tested for the production of highly monoenergetic He atom beams. Glass nozzles with diameters between 1 μm and 4 μm when operated at He source stagnation pressures of up to 1000 atm provide intense beams with measured speed ratios of S=50–100, in good agreement with the predicted behavior scaled from nozzles with larger openings. Miniature glass skimmers with diameters as small as 3 μm were also successfully tested with conventional 10 μm diameter nozzles. These miniature nozzle-beam sources can be used to greatly reduce the size of present-day He-atom surface-scattering time-of-flight spectrometers and to reduce the number of vacuum stages and the size of vacuum pumps. They also open up new experimental possibilities as illustrated by measurements of the spatial profiles of seeded nozzle beams. © 1997 American Institute of Physics.

Electronic Resource

1077-3118

AIP Digital Archive

Physics

We report the preparation of periodic nanostripes on vicinal copper surfaces. For the investigated Cu(n,n,n−1) surfaces [n=4,3,2], an oxygen-induced mesoscopic faceting of the regular monoatomic stepped surfaces into periodic nanostripes consisting of Cu(111) and Cu(110)–O(2×1) facets is observed. The width and thermal stability of these nanostripes increase with the terrace length of the initial vicinal surfaces. Stripe widths of 50, 20, and 12 nm were obtained for Cu(443), Cu(332), and Cu(221), respectively. Whereas on Cu(221) the nanostripes disappear above 450 K, they are stable up to 800 K on Cu(443). For the latter surface, the nanostructures are found to be unusually stable and could be observed ex situ by atomic force microscopy under ambient conditions. © 2000 American Institute of Physics.

Electronic Resource

1089-7690

AIP Digital Archive

Physics

Chemistry and Pharmacology

A search for external vibrations of hydrocarbons physisorbed on Cu(100) has been carried out with high-resolution inelastic He-atom scattering. For the saturated hydrocarbons n-hexane, cyclohexane, n-octane, and n-decane, the frustrated translation normal to the surface could be detected with energies of 6.8 meV, 7.3 meV, 7.0 meV, and 7.0 meV, respectively. A very similar value of 7.3 meV for the same vibration is observed for the unsaturated hydrocarbon benzene. No vibrational modes corresponding to frustrated translations parallel to the surface could be detected. © 1995 American Institute of Physics.

Electronic Resource

1089-7690

AIP Digital Archive

Physics

Chemistry and Pharmacology

The structure and vibrational modes of CO adsorbed on Cu(001) have been investigated by helium atom scattering (HAS). Below coverages of θ=0.13, CO adsorbs as isolated molecules, and the time of flight (TOF) spectra of helium atoms scattered from the surface are characterized by energy losses and gains of 3.94 ± 0.07 meV. With the aid of isotope shift measurements, this mode is unambiguously assigned to the frustrated translation mode of the adsorbed CO. In the c(2×2) structure (θ=0.5) this mode is found to show dispersion in both the 〈100〉 and 〈110〉 azimuths with frequencies ranging from 3.9 meV at the zone origin to 5.6 meV at the zone boundary. A simple force constant model with a single nearest neighbor force constant within the layer is found to be sufficient to describe the dispersion. For coverages slightly less than θ=0.5 the angular distributions of scattered helium atoms show features characteristic of vacancies in the overlayer. In the TOF spectra an additional nondispersive mode at about 4 meV is also seen and assigned to the frustrated translation of CO molecules adjacent to the vacancies in the c(2×2) overlayer. The Rayleigh mode is clearly observed in the c(2×2) structure but is found to decrease slightly in frequency while the longitudinal resonance, which is especially prominent on the clean surface, disappears completely. The results are interpreted with the aid of slab calculations. © 1995 American Institute of Physics.

Electronic Resource

1089-7690

AIP Digital Archive

Physics

Chemistry and Pharmacology

Ordered phases of CO on a Ru(0001) surface have been characterized with regard to structural and dynamical properties using high resolution helium atom scattering. In the energy regime below 10 meV a vibrational mode corresponding to a frustrated translation parallel to the surface (FTx) could be identified, the energy amounts to 5.9 meV for isolated CO molecules and to 5.75 meV for the ((square root of 3)×(square root of 3))R30°CO structure. The formation of the more compressed (2(square root of 3)×2(square root of 3))R30°CO and (5(square root of 3)×5(square root of 3))R30°CO structures is accompanied by significant changes of the low energy external vibrations, in pronounced contrast to the gradual frequency increase of the CO internal ν1-vibration. Coadsorption of hydrogen or oxygen was found to result in substantially larger FTx energies. Implications of these findings on the character of the molecule-surface interaction will be discussed, as well as the connection between the FTx-dispersion and the strength and type of the adsorbate-adsorbate interaction. © 1997 American Institute of Physics.

Electronic Resource

1089-7690

AIP Digital Archive

Physics

Chemistry and Pharmacology

The adsorption of benzene, naphthalene, and anthracene on Cu(111) and its vicinal Cu(221) and Cu(443) surfaces has been studied by means of thermal desorption spectra (TDS) and low energy electron diffraction. For each of the studied acenes (C4n+2H2n+4, n=1,2,3) two distinct binding states were observed in the TDS corresponding to adsorption on terraces and at step edges. The binding energies of both states are found to increase linearly with the number of aromatic rings n. In contrast to the Cu(111) surface where these acenes form disordered adlayers only, ordered films of naphthalene and anthracene with an alignment of the molecular axis along the steps could be prepared on the vicinal surfaces. © 2001 American Institute of Physics.

Electronic Resource

0040-4020

Elsevier Journal Backfiles on ScienceDirect 1907 - 2002

Chemistry and Pharmacology

Electronic Resource

0022-328X

Elsevier Journal Backfiles on ScienceDirect 1907 - 2002

Chemistry and Pharmacology

Electronic Resource

0368-2048

Elsevier Journal Backfiles on ScienceDirect 1907 - 2002

Physics

Electronic Resource

0368-2048

Elsevier Journal Backfiles on ScienceDirect 1907 - 2002

Physics

Electronic Resource

0368-2048

Elsevier Journal Backfiles on ScienceDirect 1907 - 2002

Physics

Electronic Resource

0368-2048

Elsevier Journal Backfiles on ScienceDirect 1907 - 2002

Physics

Electronic Resource

0368-2048

Elsevier Journal Backfiles on ScienceDirect 1907 - 2002

Physics

Electronic Resource

1432-0630

34.50 ; 79.60

Springer Online Journal Archives 1860-2000

Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics

Physics

Abstract The adsorption of N2 molecules on Ni(110) has been investigated by high-resolution He-atom energy-loss spectroscopy. Two external vibrations in the subthermal (〈 30 meV) energy regime at 5.75 and 4.5 meV have been observed and are shown to imply the existence of two different adsorption sites, which are assigned to an on-top and a bridge-site. This finding is at variance with the interpretation of data from electron energy loss spectroscopy and InfraRed (IR) spectroscopy, where only one mode of the internal stretch vibration v1 at frequencies is observed for the chemisorbed nitrogen molecules. A reanalysis of previously published high-resolution IR data reveals that the presence of the second unexpected adsorbate species correlates with a feature in the IR spectra, which previously has been assigned to N2 molecules adsorbed at defect sites. These findings reveal that in this case the external vibrations are significantly more sensitive to different adsorption sites than the internal vibration, the latter exhibiting a difference between on-top and bridge sites of less than 6 cm−1.

Electronic Resource

1432-0630

PACS:  34.50; 79.60

Springer Online Journal Archives 1860-2000

Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics

Physics

Abstract.  The adsorption of N2 molecules on Ni(110) has been investigated by high-resolution He-atom energy-loss spectroscopy. Two external vibrations in the subthermal (〈30 meV) energy regime at 5.75 and 4.5 meV have been observed and are shown to imply the existence of two different adsorption sites, which are assigned to an on-top and a bridge-site. This finding is at variance with the interpretation of data from electron energy loss spectroscopy and InfraRed (IR) spectroscopy, where only one mode of the internal stretch vibration ν1 at frequencies is observed for the chemisorbed nitrogen molecules. A reanalysis of previously published high-resolution IR data reveals that the presence of the second unexpected adsorbate species correlates with a feature in the IR spectra, which previously has been assigned to N2 molecules adsorbed at defect sites. These findings reveal that in this case the external vibrations are significantly more sensitive to different adsorption sites than the internal vibration, the latter exhibiting a difference between on-top and bridge sites of less than 6 cm-1.

Electronic Resource