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Pusch A.,University of Bonn | Boeckenhoff A.,University of Bonn | Glaser T.,Institute For Rekonstruktive Neurobiologie | Kaminski T.,University of Bonn | And 8 more authors.
Biochimica et Biophysica Acta - Molecular Cell Research | Year: 2010

Hyaluronan and its receptor CD44 are known to contribute to the invasive growth of different tumors of the central nervous system. It is not known, however, if CD44 is sufficient to activate invasive growth into the brain tissue. This study examines how CD44 regulates the motility and invasive growth of B35 neuroblastoma cells into a hyaluronan-rich environment. A comprehensive experimental approach was used encompassing biochemical techniques, single molecule microscopy, correlative confocal and scanning electron microscopy, morphometry of cellular extensions, live-cell imaging and tracking, transplantation onto organotypic brain slices, two-photon imaging and invasion assays. We found that CD44-GFP fusion protein was localized in filopodia and in focal bleb-like protrusions where it provided binding sites for hyaluronan. Transient expression of CD44-GFP was sufficient to increase the length of filopodia, to enhance cell migration and to promote invasive growth into hyaluronan-rich brain tissue. Thus, CD44 controls molecular devices localized in filopodia and bleb-like specializations of the cell surface that enhance cell migration and invasive growth. © 2010 Elsevier B.V. All rights reserved. Source

Anoop A.,Institute For Physikalische Und Theoretische Chemie | Thiel W.,Max-Planck-Institut fur Kohlenforschung | Neese F.,Institute For Physikalische Und Theoretische Chemie
Journal of Chemical Theory and Computation | Year: 2010

The recently developed local pair natural orbital coupled cluster theory with single and double excitations (LPNO-CCSD) was used to study the rhodium-catalyzed asymmetric hydrogenation of two prochiral enamides. The method was carefully calibrated with respect to its accuracy. According to calculations on a truncated model system, the effects of perturbative triples (T) on the reaction energetics are very limited, the LPNO approximation is accurate, and complete basis set extrapolation (CBS) causes only minor changes in the relative energies computed with a standard basis set (def2-TZVP). The results for the full system are thus believed to be within 1-2 kcal/mol of the CCSD(T)/CBS limit for the present systems. Relativistic effects were treated by a scalar relativistic Hamiltonian using the zeroth order regular approximation (ZORA). The results of the study were compared to density functional calculations on the same systems and with calculations available in the literature. All calculations predict the correct stereochemical outcome of the reaction that is determined by the relative energies of the transition states in the early stages of the catalytic cycle. In general, DFT calculations using the B3LYP functional are in reasonable agreement with the LPNO-CCSD results, although deviations of 3-5 kcal/mol exist that are also not entirely systematic in the minor and major reaction branches. The present case study thus demonstrates that catalytic reactions, which are well described by single-reference electronic structure theory, can now be routinely studied with confidence in systems with 50-100 atoms applying local correlation methods that are as easy to use as DFT methods. © 2010 American Chemical Society. Source

Rota J.-B.,Ecole Normale Superieure de Lyon | Knecht S.,CNRS Strasbourg Institute of Chemistry | Fleig T.,CNRS Laboratory for Quantum Chemistry and Physics | Ganyushin D.,Institute For Physikalische Und Theoretische Chemie | And 5 more authors.
Journal of Chemical Physics | Year: 2011

The spectrum arising from the ()2 configuration of the chalcogen dimers, namely, the X21, a2, and b0 states, is calculated using wave-function theory based methods. Two-component (2c) and four-component (4c) multireference configuration interaction (MRCI) and Fock-space coupled cluster (FSCC) methods are used as well as two-step methods spin-orbit complete active space perturbation theory at 2nd order (SO-CASPT2) and spin-orbit difference dedicated configuration interaction (SO-DDCI). The energy of the X21 state corresponds to the zero-field splitting of the ground state spin triplet. It is described with high accuracy by the 2-and 4-component methods in comparison with experiment, whereas the two-step methods give about 80 of the experimental values. The b0 state is well described by 4c-MRCI, SO-CASPT2, and SO-DDCI, but FSCC fails to describe this state and an intermediate Hamiltonian FSCC ansatz is required. The results are readily rationalized by a two-parameter model; , the spinor splitting by spin-orbit coupling and K, the exchange integral between the 1* and the-1* spinors with, respectively, angular momenta 1 and-1. This model holds for all systems under study with the exception of Po2. © 2011 American Institute of Physics. Source

Serrano G.,University of Rome Tor Vergata | Bonanni B.,University of Rome Tor Vergata | Kosmala T.,University of Rome Tor Vergata | Kosmala T.,Institute For Physikalische Und Theoretische Chemie | And 5 more authors.
Beilstein Journal of Nanotechnology | Year: 2015

Despite the rising technological interest in the use of calcium-modified TiO2 surfaces in biomedical implants, the Ca/TiO2 interface has not been studied in an aqueous environment. This investigation is the first report on the use of in situ scanning tunneling microscopy (STM) to study calcium-modified rutile TiO2(110) surfaces immersed in high purity water. The TiO2 surface was prepared under ultrahigh vacuum (UHV) with repeated sputtering/annealing cycles. Low energy electron diffraction (LEED) analysis shows a pattern typical for the surface segregation of calcium, which is present as an impurity on the TiO2 bulk. In situ STM images of the surface in bulk water exhibit one-dimensional rows of segregated calcium regularly aligned with the [001] rystal direction. The in situ-characterized morphology and structure of this Ca-modified TiO2 surface are discussed and compared with UHV-STM results from the literature. Prolonged immersion (two days) in the liquid leads to degradation of the overlayer, resulting in a disordered surface. X-ray photoelectron spectroscopy, performed after immersion in water, confirms the presence of calcium. © 2015 Serrano et al. Source

Hader K.,Institute For Physikalische Und Theoretische Chemie | Engel V.,Institute For Physikalische Und Theoretische Chemie
Chemical Physics Letters | Year: 2011

We study fragmentation processes induced by femtosecond laser pulses. Within an adiabatic treatment of the nuclear motion, the interaction with two identical but time-delayed pulses leads to interference structures in the momentum distribution which are related to the pulse delay. These structures are modified if an electronic degree of freedom is included in the wave-packet propagation. Additional time-dependent patterns are found in the electron momentum distributions which are also present for a single-pulse excitation. They are related to the delocalization of the electron density over the different charge centers. © 2011 Elsevier B.V. All rights reserved. Source

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