616 research outputs found
Характеристика механизма функционирования форм хозяйствования с иностранными инвестициями
Механизм функционирования предприятия с иностранными инвестициями неразрывно связан с понятиями "хозяйственный механизм" и "механизм
функционирования предприятия". В экономической науке советского периода
широко применялся термин "хозяйственный механизм". Рассматривался хозяйственный механизм отдельного предприятия, отрасли, экономики страны в целом, то есть рассматривался хозяйственный механизм экономических систем
различного уровня
Holo-like and Druggable Protein Conformations from Enhanced Sampling of Binding Pocket Volume and Shape
Understanding molecular recognition of small molecules by proteins in atomistic detail is key for drug design. Molecular docking is a widely used computational method to mimic ligand-protein association in silico. However, predicting conformational changes occurring in proteins upon ligand binding is still a major challenge. Ensemble docking approaches address this issue by considering a set of different conformations of the protein obtained either experimentally or from computer simulations, e.g., molecular dynamics. However, holo structures prone to host (the correct) ligands are generally poorly sampled by standard molecular dynamics simulations of the apo protein. In order to address this limitation, we introduce a computational approach based on metadynamics simulations called ensemble docking with enhanced sampling of pocket shape (EDES) that allows holo-like conformations of proteins to be generated by exploiting only their apo structures. This is achieved by defining a set of collective variables that effectively sample different shapes of the binding site, ultimately mimicking the steric effect due to the ligand. We assessed the method on three challenging proteins undergoing different extents of conformational changes upon ligand binding. In all cases our protocol generates a significant fraction of structures featuring a low RMSD from the experimental holo geometry. Moreover, ensemble docking calculations using those conformations yielded in all cases native-like poses among the top-ranked ones
kt Effects in Direct-Photon Production
We discuss the phenomenology of initial-state parton-kt broadening in
direct-photon production and related processes in hadron collisions. After a
brief summary of the theoretical basis for a Gaussian-smearing approach, we
present a systematic study of recent results on fixed-target and collider
direct-photon production, using complementary data on diphoton and pion
production to provide empirical guidance on the required amount of kt
broadening. This approach provides a consistent description of the observed
pattern of deviation of next-to-leading order QCD calculations relative to the
direct-photon data, and accounts for the shape and normalization difference
between fixed-order perturbative calculations and the data. We also discuss the
uncertainties in this phenomenological approach, the implications of these
results on the extraction of the gluon distribution of the nucleon, and the
comparison of our findings to recent related work.Comment: LaTeX, uses revtex and epsf, 37 pages, 15 figure
Weak Hyperon Decays: Quark Sea and SU(3) Symmetry Breaking
An explanation of the difference in the values of the apparent ratios
for the S- and P- wave amplitudes of nonleptonic hyperon decays is proposed.
The argument is formulated in the framework of the standard pole model with
ground-state and excited baryons as intermediate
states for the P- and S- waves respectively. Under the assumption that the
dominant part of the deviation of from is due to large
quark sea effects, symmetry breaking in energy denominators is shown to
lead to a prediction for which is in excellent agreement with
experiment. This corroborates our previous unitarity calculations which
indicated that the matrix elements of the parity
conserving weak Hamiltonian between the ground-state baryons are characterized
by or more. A brief discussion of the problem of the
relative size of S- and P- wave amplitudes is given. Finally, implications for
weak radiative hyperon decays are also discussed.Comment: 26 pages, LATEX, 1647/PH IFJ Krako
A multichamber fluidic device for 3D cultures under interstitial flow with live imaging: Development, characterization, and applications
Interstitial flow is an important biophysical cue that can affect capillary morphogenesis, tumor cell migration, and fibroblast remodeling of the extracellular matrix, among others. Current models that incorporate interstitial flow and that are suitable for live imaging lack the ability to perform multiple simultaneous experiments, for example, to compare effects of growth factors, extracellular matrix composition, etc. We present a nine-chamber radial flow device that allows simultaneous 3D fluidic experiments for relatively long-term culture with live imaging capabilities. Flow velocity profiles were characterized by fluorescence recovery after photobleaching (FRAP) for flow uniformity and estimating the hydraulic conductivity. We demonstrate lymphatic and blood capillary morphogenesis in fibrin gels over 10 days, comparing flow with static conditions as well as the effects of an engineered variant of VEGF that binds fibrin via Factor XIII. We also demonstrate the culture of contractile fibroblasts and co-cultures with tumor cells for modeling the tumor microenvironment. Therefore, this device is useful for studies of capillary morphogenesis, cell migration, contractile cells like fibroblasts, and multicellular cultures, all under interstitial flow. © 2009 Wiley Periodicals, Inc
Quark and Pole Models of Nonleptonic Decays of Charmed Baryons
Quark and pole models of nonleptonic decays of charmed baryons are analysed
from the point of view of their symmetry properties. The symmetry structure of
the parity conserving amplitudes that corresponds to the contribution of the
ground-state intermediate baryons is shown to differ from the one hitherto
employed in the symmetry approach. It is pointed out that the "subtraction" of
sea quark effects in hyperon decays leads to an estimate of -exchange
contributions in charmed baryon decays that is significantly smaller than
naively expected on the basis of . An constraint questioning
the reliability of the factorization technique is exhibited. Finally, a
successful fit to the available data is presented.Comment: 25 pages, LATEX, 1643/PH IFJ Krako
3D-DART: a DNA structure modelling server
There is a growing interest in structural studies of DNA by both experimental and computational approaches. Often, 3D-structural models of DNA are required, for instance, to serve as templates for homology modeling, as starting structures for macro-molecular docking or as scaffold for NMR structure calculations. The conformational adaptability of DNA when binding to a protein is often an important factor and at the same time a limitation in such studies. As a response to the demand for 3D-structural models reflecting the intrinsic plasticity of DNA we present the 3D-DART server (3DNA-Driven DNA Analysis and Rebuilding Tool). The server provides an easy interface to a powerful collection of tools for the generation of DNA-structural models in custom conformations. The computational engine beyond the server makes use of the 3DNA software suite together with a collection of home-written python scripts. The server is freely available at http://haddock.chem.uu.nl/dna without any login requirement
1H, 13C and 15N assignment of the GNA1946 outer membrane lipoprotein from Neisseria meningitidis
GNA1946 (Genome-derived Neisseria Antigen 1946) is a highly conserved exposed outer membrane lipoprotein from Neisseria meningitidis bacteria of 287 amino acid length (31 kDa). Although the structure of NMB1946 has been solved recently by X-Ray crystallography, understanding the behaviour of GNA1946 in aqueuos solution is highly relevant for the discovery of the antigenic determinants of the protein that will possibly lead to a more efficient vaccine development against virulent serogroup B strain of N.meningitidis. Here we report almost complete 1H, 13C and 15N resonance assignments of GNA1946 (residues 10–287) in aqueous buffer solution
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