Search results for "Molecules"
showing 10 items of 1147 documents
Efficient and accurate modeling of electron photoemission in nanostructures with TDDFT
2017
We derive and extend the time-dependent surface-flux method introduced in [L. Tao, A. Scrinzi, New J. Phys. 14, 013021 (2012)] within a time-dependent density-functional theory (TDDFT) formalism and use it to calculate photoelectron spectra and angular distributions of atoms and molecules when excited by laser pulses. We present other, existing computational TDDFT methods that are suitable for the calculation of electron emission in compact spatial regions, and compare their results. We illustrate the performance of the new method by simulating strong-field ionization of C60 fullerene and discuss final state effects in the orbital reconstruction of planar organic molecules.
Dynamics of myoglobin in confinement: An elastic and quasi-elastic neutron scattering study
2008
In order to clarify the role of hard confinement on protein dynamics, elastic and quasi-elastic neutron scattering experiments have been performed on ferric horse myoglobin in two different systems: the protein embedded in a porous silica matrix, and the corresponding hydrated protein powder. Elastic data have been analysed using two different models (dynamical heterogeneity and anharmonic double-well potential) that take into account deviations of elastic intensity from Gaussian behaviour. The profile of quasi-elastic spectra has been approximated by a combination of Lorentzian and Gaussian components. Comparison between the data relative to the two different samples indicates that geometr…
Levels of self-consistency in the GW approximation
2009
We perform $GW$ calculations on atoms and diatomic molecules at different levels of self-consistency and investigate the effects of self-consistency on total energies, ionization potentials and on particle number conservation. We further propose a partially self-consistent $GW$ scheme in which we keep the correlation part of the self-energy fixed within the self-consistency cycle. This approximation is compared to the fully self-consistent $GW$ results and to the $G W_0$ and the $G_0W_0$ approximations. Total energies, ionization potentials and two-electron removal energies obtained with our partially self-consistent $GW$ approximation are in excellent agreement with fully self-consistent $…
Etude théorique de spectres de molécules toupies sphériques à l'aide du formalisme d'ensembles tensoriels irréductibles
2022
Vibrational-rotational spectroscopy of molecules of the spherical top type, in particular, SiH4 and GeH4 molecules, as well as their isotopologues, is of interest in various fields of science and technology, especially in astrophysics and planetology. One of the most important discoveries in the study of the atmospheres of giant planets is the discovery of german and silane gases in the atmospheres of Saturn, Titan, and Jupiter. Despite many years of research on the vibrational-rotational spectra of molecules of german, silane, and their deuterated modifications, many spectral ranges are still unexplored. However, a complete study of the atmospheres of giant planets is possible only in the …
β1-Integrin Cytoplasmic Subdomains Involved in Dominant Negative Function
1998
The beta1-integrin cytoplasmic domain consists of a membrane proximal subdomain common to the four known isoforms ("common" region) and a distal subdomain specific for each isoform ("variable" region). To investigate in detail the role of these subdomains in integrin-dependent cellular functions, we used beta1A and beta1B isoforms as well as four mutants lacking the entire cytoplasmic domain (beta1TR), the variable region (beta1COM), or the common region (beta1 deltaCOM-B and beta1 deltaCOM-A). By expressing these constructs in Chinese hamster ovary and beta1 integrin-deficient GD25 cells (Wennerberg et al., J Cell Biol 132, 227-238, 1996), we show that beta1B, beta1COM, beta1 deltaCOM-B, a…
Targeting the JAK/STAT Pathway: A Combined Ligand- and Target-Based Approach
2021
Janus kinases (JAKs) are a family of proinflammatory enzymes able to mediate the immune responses and the inflammatory cascade by modulating multiple cytokine expressions as well as various growth factors. In the present study, the inhibition of the JAK-signal transducer and activator of transcription (STAT) signaling pathway is explored as a potential strategy for treating autoimmune and inflammatory disorders. A computationally driven approach aimed at identifying novel JAK inhibitors based on molecular topology, docking, and molecular dynamics simulations was carried out. For the best candidates selected, the inhibitory activity against JAK2 was evaluated in vitro. Two hit compounds with…
Can aromaticity be connected with molecular polarizability? A theoretical study of benzene isomers and five-membered heterocyclic molecules
2004
Extended calculations of molecular electric dipole polarizability tensor, at Hartree-Fock and correlated level of accuracy (MP2, CCS, CC2, CCSD, and CCSD(T)) have been carried out to investigate whether aromaticity could be related to the electric dipole polarizability of planar ring systems. The calculations prove the exaltation of the average property of conjugated molecules, which is possibly due to their easily polarizable π-electron cloud. On the other hand, theoretical out-of-plane polarizability components are smaller in benzene than in any other C$_6$H$_6$ isomer. The aromatic stabilization energies of monosubstituted five-membered conjugated cyclic molecules increase in the same di…
Encapsulation of xenon by bridged resorcinarene cages with high 129Xe NMR chemical shift and efficient exchange dynamics
2023
Functionalized cages encapsulating xenon atoms enable highly sensitive, background-free molecular imaging through a technique known as HyperCEST 129Xe MRI. Here, we introduce a class of potential biosensor cage structures based on two resorcinarene macrocycles bridged either by aliphatic carbon chains or piperazines. First-principles-based modeling predicts a high chemical shift (about 345 ppm) outside the typical experimental observation window for 129Xe encapsulated by the aliphatically bridged cage and two 129Xe resonances for the piperazine-bridged cages corresponding to single and double loading. Based on the computational predictions as well as 129Xe chemical exchange saturation trans…
Specific phosphorylation of proteins in pore complex-laminae from the sponge Geodia cydonium by the homologous aggregation factor and phorbol ester. …
1987
We have recently shown that the aggregation factor (AF) from the sponge Geodia cydonium stimulates DNA synthesis in quiescent, dissociated cells from the same organism; this event was correlated with the release of the two second messengers: inositol trisphosphate and diacylglycerol. Here we describe that after binding of the AF to the plasma membrane-bound aggregation receptor, a rapid and drastic increase in the incorporation of 32Pi into a series of proteins in the pore complex-lamina fraction occurs. Addition of the tumor promoter, 12-O-tetradecanoylphorbol-13-acetate, to quiescent cells resulted in a similar stimulation of phosphorylation of nuclear proteins. Among them we have selecte…
Electrochemical properties of crystallized dilithium squarate: insight from dispersion-corrected density functional theory.
2012
International audience; The stacking parameters, lattice constants, and bond lengths of solvent-free dilithium squarate (Li(2)C(4)O(4)) crystals were investigated using density functional theory with and without dispersion corrections. The shortcoming of the GGA (PBE) calculation with respect to the dispersive forces appears in the form of an overestimation of the unit cell volume up to 5.8%. The original Grimme method for dispersion corrections has been tested together with modified versions of this scheme by changing the damping function. One of the modified dispersion-corrected DFT schemes, related to a rescaling of van der Waals radii, provides significant improvements for the descripti…