Understanding the Reshaping of Fluorinated Polyester Vitrimers by Kinetic and DFT Studies of the Transesterification Reaction

Vitrimers are a third class of polymers gathering the mechanical properties and solvent resistance of 3D thermosets and the reprocessability of thermoplastics. This unique behaviour is due to the triggering of certain covalent exchange reactions that allow the network to rearrange upon application of a stimulus. The constitutive feature of vitrimers is the adoption of a glass-like viscosity during the rearrangement of the network, often due to an associative mechanism for the exchange reaction. Transesterification networks are one of the most studied type of vitrimers that usually require the incorporation of a catalyst, implying the associated drawbacks. Following up on a recent report on catalyst-free transesterification vitrimers in which the ester functions are particularly reactive thanks to the presence of fluorine atoms in α- or β-position, parallel DFT calculations and an experimental kinetic study on model molecules are presented in order to quantitatively assess the effect of neighbouring fluorinated groups on the transesterification reaction rate.     

CPMD Simulation of a Bimolecular Chemical Reaction: Nucleophilic Attack of a Disulfide Bond under Mechanical Stress

Previous single‐molecule atomic force microscopy (AFM) experiments showed a change in the reactivity of a bimolecular substitution reaction with a definite force acting on a protein containing disulfide bonds. Using Car–Parrinello molecular dynamics (CPMD) simulations, we analyse the relevant reaction pathways for the breaking of a disulfide bond in the presence of nucleophiles.     

Parallel computations in drilling process

Methods for decision-making formalization at all stages of drilling process have been developed. They include methods for efficient use of drilling fluids with grounded technological parameters, prediction of troubles during drilling process and construction of optimal well profiles. Software implementing them makes it possible to optimize drilling parameters, improve tailing-in quality and in general to increase technical and economic indices of drilling. Use of parallel computations allows reducing time of computations and increasing their accuracy.     

Modern information technologies in construction of kinetic models for reactions of metal complex catalysis

For detailed study of complex chemical reactions mechanisms experiment is conducted for selected private reactions. This causes a problem of kinetic parameters getting—the same set of rate constants must describe both public and private reaction stages, and also a general mechanism. In this paper, solution of this problem for a reaction of olefins hydroalumination is proposed. To optimize the computational process a methodology of parallelization is elaborated. On the base of parallel computations, a kinetic model for the reaction assigned is constructed, and on its base, the physical and chemical conclusions about reaction mechanism are done.     

Structural Basis for Copper–Oxygen Mediated C−H Bond Activation by the Formylglycine-Generating Enzyme

The formylglycine-generating enzyme (FGE) is a unique copper protein that catalyzes oxygen-dependent C−H activation. We describe 1.66 Å- and 1.28 Å-resolution crystal structures of FGE from Thermomonospora curvata in complex with either Ag^I or Cd^II providing definitive evidence for a high-affinity metal-binding site in this enzyme. The structures reveal a bis-cysteine linear coordination of the monovalent metal, and tetrahedral coordination of the bivalent metal. Similar coordination changes may occur in the active enzyme as a result of Cu^I/II redox cycling. Complexation of copper atoms by two cysteine residues is common among copper-trafficking proteins, but is unprecedented for redox-active copper enzymes or synthetic copper catalysts.     

Time and frequency domain finite element implementation of a fully anisotropic linear visco-elastic model

Consistent time and frequency domain formulations for a fully anisotropic, linear visco-elastic material model are presented. The finite element implementation leads to a complex valued stiffness matrix in the frequency domain. A homogenisation procedure based on unit-cell analyses in the frequency domain is presented to derive input parameters for the material model. (© 2016 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim)