CEITEC Central European Institute of Technology

Kamenice, Czech Republic

CEITEC Central European Institute of Technology

Kamenice, Czech Republic

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Mouralova K.,Brno University of Technology | Kovar J.,Brno University of Technology | Zahradnicek R.,Brno University of Technology | Man O.,CEITEC Central European Institute of Technology
Proceedings of the 2016 17th International Conference on Mechatronics - Mechatronika, ME 2016 | Year: 2016

Finishing technologies of machining such as grinding or wire electrical discharge machining (WEDM) represent the most frequently used applications when mechanical engineering components that are subject to high requirements for the accuracy of shapes and dimensions as well as quality of machined areas. The study was focused on the evaluation of the machined surface contamination due to grinding and WEDM elements of tool material. In addition, the machined surface morphology was studied using light microscopy, atomic force microscopy (AFM) technique and 3D profile meter. Both area and profile parameters of the surfaces were evaluated by means of two different contactless profilometers based on the principle of coherence correlation interferometry. © 2016 Czech Technical University in Prague.


Mouralova K.,Brno University of Technology | Karpisek Z.,Brno University of Technology | Kovar J.,Brno University of Technology | Klakurkova L.,CEITEC Central European Institute of Technology
Proceedings of the 2016 17th International Conference on Mechatronics - Mechatronika, ME 2016 | Year: 2016

Wire electrical discharge machining (WEDM) is an unconventional technology of machining that applies physical principles to material removal. The morphology of WEDM surface is characterized by a great number of craters caused by electrical discharges occurring during the process of cutting. The study deals with the evaluation of surface morphology of titanium alloy Ti-6Al-4V after WEDM as well as total height of profile Rt by means of mathematical and statistical techniques of fitting (estimation) of discrete probability distributions using pseudoquasi-norms under side moment conditions. Here, the new Freeman-Tukey pseudoquasi-norm is presented, the characteristics of which are based on an already studied term of quasi-norm'. © 2016 Czech Technical University in Prague.


Drsata T.,Czech Institute of Organic Chemistry And Biochemistry | Drsata T.,Academy of Sciences of the Czech Republic | Spackova N.,Academy of Sciences of the Czech Republic | Jurecka P.,Palacky University | And 4 more authors.
Nucleic Acids Research | Year: 2014

A-tracts are functionally important DNA sequences which induce helix bending and have peculiar structural properties. While A-tract structure has been qualitatively well characterized, their mechanical properties remain controversial. A-tracts appear structurally rigid and resist nucleosome formation, but seem flexible in DNA looping. In this work, we investigate mechanical properties of symmetric AnTn and asymmetric A2n tracts for n = 3, 4, 5 using two types of coarse-grained models. The first model represents DNA as an ensemble of interacting rigid bases with non-local quadratic deformation energy, the second one treats DNA as an anisotropically bendable and twistable elastic rod. Parameters for both models are inferred from microsecond long, atomic-resolution molecular dynamics simulations. We find that asymmetric A-tracts are more rigid than the control G/C-rich sequence in localized distortions relevant for nucleosome formation, but are more flexible in global bending and twisting relevant for looping. The symmetric tracts, in contrast, are more rigid than asymmetric tracts and the control, both locally and globally. Our results can reconcile the contradictory stiffness data on A-tracts and suggest symmetric A-tracts to be more efficient in nucleosome exclusion than the asymmetric ones. This would open a new possibility of gene expression manipulation using A-tracts. © 2014 The Author(s) 2014.


Hernandez-Hernandez V.,National Autonomous University of Mexico | Niklas K.J.,Cornell University | Newman S.A.,New York Medical College | Benitez M.,National Autonomous University of Mexico | Benitez M.,CEITEC Central European Institute of Technology
International Journal of Developmental Biology | Year: 2012

Broad comparative studies at the level of developmental processes are necessary to fully understand the evolution of development and phenotypes. The concept of dynamical patterning modules (DPMs) provides a framework for studying developmental processes in the context of wide comparative analyses. DPMs are defined as sets of ancient, conserved gene products and molecular networks, in conjunction with the physical morphogenetic and patterning processes they mobilize in the context of multicellularity. The theoretical framework based on DPMs originally postulated that each module generates a key morphological motif of the basic animal body plans and organ forms. Here, we use a previous definition of the plant multicellular body plan and describe the basic DPMs underlying the main features of plant development. For each DPM, we identify characteristic molecules and molecular networks, and when possible, the physical processes they mobilize. We then briefly review the phyletic distribution of these molecules across the various plant lineages. Although many of the basic plant DPMs are significantly different from those of animals, the framework established by a DPM perspective on plant development is essential for comparative analyses aiming to provide a truly mechanistic explanation for organic development across all plant and animal lineages. © 2012 UBC Press.


Stadlbauer P.,Academy of Sciences of the Czech Republic | Krepl M.,Academy of Sciences of the Czech Republic | Cheatham III T.E.,University of Utah | Koca J.,CEITEC Central European Institute of Technology | And 2 more authors.
Nucleic Acids Research | Year: 2013

Explicit solvent molecular dynamics simulations have been used to complement preceding experimental and computational studies of folding of guanine quadruplexes (G-DNA). We initiate early stages of unfolding of several G-DNAs by simulating them under no-salt conditions and then try to fold them back using standard excess salt simulations. There is a significant difference between G-DNAs with all-anti parallel stranded stems and those with stems containing mixtures of syn and anti guanosines. The most natural rearrangement for all-anti stems is a vertical mutual slippage of the strands. This leads to stems with reduced numbers of tetrads during unfolding and a reduction of strand slippage during refolding. The presence of syn nucleotides prevents mutual strand slippage; therefore, the antiparallel and hybrid quadruplexes initiate unfolding via separation of the individual strands. The simulations confirm the capability of G-DNA molecules to adopt numerous stable locally and globally misfolded structures. The key point for a proper individual folding attempt appears to be correct prior distribution of syn and anti nucleotides in all four G-strands. The results suggest that at the level of individual molecules, G-DNA folding is an extremely multi-pathway process that is slowed by numerous misfolding arrangements stabilized on highly variable timescales. © The Author(s) 2013. Published by Oxford University Press.


Zgarbova M.,Palacky University | Luque F.J.,University of Barcelona | Sponer J.,Academy of Sciences of the Czech Republic | Sponer J.,CEITEC Central European Institute of Technology | And 3 more authors.
Journal of Chemical Theory and Computation | Year: 2013

We present a refinement of the backbone torsion parameters ε and ζ of the Cornell et al. AMBER force field for DNA simulations. The new parameters, denoted as εζOL1, were derived from quantum-mechanical calculations with inclusion of conformation-dependent solvation effects according to the recently reported methodology (J. Chem. Theory Comput.2012, 7 (9), 2886-2902). The performance of the refined parameters was analyzed by means of extended molecular dynamics (MD) simulations for several representative systems. The results showed that the εζ OL1 refinement improves the backbone description of B-DNA double helices and the G-DNA stem. In B-DNA simulations, we observed an average increase of the helical twist and narrowing of the major groove, thus achieving better agreement with X-ray and solution NMR data. The balance between populations of BI and BII backbone substates was shifted toward the BII state, in better agreement with ensemble-refined solution experimental results. Furthermore, the refined parameters decreased the backbone RMS deviations in B-DNA MD simulations. In the antiparallel guanine quadruplex (G-DNA), the εζOL1 modification improved the description of noncanonical α/γ backbone substates, which were shown to be coupled to the ε/ζ torsion potential. Thus, the refinement is suggested as a possible alternative to the current ε/ζ torsion potential, which may enable more accurate modeling of nucleic acids. However, long-term testing is recommended before its routine application in DNA simulations. © 2013 American Chemical Society.


Sponer J.,Academy of Sciences of the Czech Republic | Sponer J.,CEITEC Central European Institute of Technology | Banas P.,Palacky University | Jurecka P.,Palacky University | And 7 more authors.
Journal of Physical Chemistry Letters | Year: 2014

We present a brief overview of explicit solvent molecular dynamics (MD) simulations of nucleic acids. We explain physical chemistry limitations of the simulations, namely, the molecular mechanics (MM) force field (FF) approximation and limited time scale. Further, we discuss relations and differences between simulations and experiments, compare standard and enhanced sampling simulations, discuss the role of starting structures, comment on different versions of nucleic acid FFs, and relate MM computations with contemporary quantum chemistry. Despite its limitations, we show that MD is a powerful technique for studying the structural dynamics of nucleic acids with a fast growing potential that substantially complements experimental results and aids their interpretation. © 2014 American Chemical Society.


Krepl M.,Academy of Sciences of the Czech Republic | Otyepka M.,Palacky University | Banas P.,Academy of Sciences of the Czech Republic | Banas P.,Palacky University | And 2 more authors.
Journal of Physical Chemistry B | Year: 2013

Guanine to inosine (G → I) substitution has often been used to study various properties of nucleic acids. Inosine differs from guanine only by loss of the N2 amino group, while both bases have similar electrostatic potentials. Therefore, G → I substitution appears to be optimally suited to probe structural and thermodynamics effects of single H-bonds and atomic groups. However, recent experiments have revealed substantial difference in free energy impact of G → I substitution in the context of B-DNA and A-RNA canonical helices, suggesting that the free energy changes reflect context-dependent balance of energy contributions rather than intrinsic strength of a single H-bond. In the present study, we complement the experiments by free energy computations using thermodynamics integration method based on extended explicit solvent molecular dynamics simulations. The computations successfully reproduce the basic qualitative difference in free energy impact of G → I substitution in B-DNA and A-RNA helices although the magnitude of the effect is somewhat underestimated. The computations, however, do not reproduce the salt dependence of the free energy changes. We tentatively suggest that the different effect of G → I substitution in A-RNA and B-DNA may be related to different topologies of these helices, which affect the electrostatic interactions between the base pairs and the negatively charged backbone. Limitations of the computations are briefly discussed. © 2013 American Chemical Society.


Kuhrova P.,Palacky University | Otyepka M.,Palacky University | Otyepka M.,Academy of Sciences of the Czech Republic | Sponer J.,Academy of Sciences of the Czech Republic | And 3 more authors.
Journal of Chemical Theory and Computation | Year: 2014

Hydrating water molecules are believed to be an inherent part of the RNA structure and have a considerable impact on RNA conformation. However, the magnitude and mechanism of the interplay between water molecules and the RNA structure are still poorly understood. In principle, such hydration effects can be studied by molecular dynamics (MD) simulations. In our recent MD studies, we observed that the choice of water model has a visible impact on the predicted structure and structural dynamics of RNA and, in particular, has a larger effect than type, parametrization, and concentration of the ions. Furthermore, the water model effect is sequence dependent and modulates the sequence dependence of A-RNA helical parameters. Clearly, the sensitivity of A-RNA structural dynamics to the water model parametrization is a rather spurious effect that complicates MD studies of RNA molecules. These results nevertheless suggest that the sequence dependence of the A-RNA structure, usually attributed to base stacking, might be driven by the structural dynamics of specific hydration. Here, we present a systematic MD study that aimed to (i) clarify the atomistic mechanism of the water model sensitivity and (ii) discover whether and to what extent specific hydration modulates the A-RNA structural variability. We carried out an extended set of MD simulations of canonical A-RNA duplexes with TIP3P, TIP4P/2005, TIP5P, and SPC/E explicit water models and found that different water models provided a different extent of water bridging between 2′-OH groups across the minor groove, which in turn influences their distance and consequently also inclination, roll, and slide parameters. Minor groove hydration is also responsible for the sequence dependence of these helical parameters. Our simulations suggest that TIP5P is not optimal for RNA simulations. © 2013 American Chemical Society.


Kruse H.,CEITEC Central European Institute of Technology | Havrila M.,CEITEC Central European Institute of Technology | Havrila M.,Academy of Sciences of the Czech Republic | Sponer J.,CEITEC Central European Institute of Technology | Sponer J.,Academy of Sciences of the Czech Republic
Journal of Chemical Theory and Computation | Year: 2014

A set of conformations obtained from explicit solvent molecular dynamics (MD) simulations of the Sarcin-Ricin internal loop (SRL) RNA motif is investigated using quantum mechanical (QM, TPSS-D3/def2-TZVP DFT-D3) and molecular mechanics (MM, AMBER parm99bsc0+πol3 force field) methods. Solvent effects are approximated using implicit solvent methods (COSMO for DFT-D3; GB and PB for MM). Large-scale DFT-D3 optimizations of the full 11-nucleotide motif are compared to MM results and reveal a higher flexibility of DFT-D3 over the MM in the optimization procedure. Conformational energies of the SRL motif expose significant differences in the DFT-D3 and MM energy descriptions that explain difficulties in MD simulations of the SRL motif. The TPSS-D3 data are in excellent agreement with results obtained by the hybrid functionals PW6B95-D3 and M06-2X. Computationally more efficient methods such as PM6-D3H and HF-3c show promising but partly inconsistent results. It is demonstrated that large-scale DFT-D3 computations on complete nucleic acids building blocks are a viable tool to complement the picture obtained from MD simulations and can be used as benchmarks for faster computational methods. Methodological challenges of large-scale QM computations on nucleic acids such as missing solvent-solute interactions and the truncation of the studied systems are discussed. © 2014 American Chemical Society.

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