Evidence for C?Cl/C?Br⋅⋅⋅π Interactions as an Important Contribution to Protein–Ligand Binding Affinity

Attractive chlorine : Noncovalent interactions between chlorine or bromine atoms and aromatic rings in proteins open up a new method for the manipulation of molecular recognition. Substitution at distinct positions of two factor Xa inhibitors improves the free energy of binding by interaction with a tyrosine unit. The generality of this motif was underscored by multiple crystal structures as well as high‐level quantum chemical calculations (see picture).

     

MHD boundary-layer flow of a micropolar fluid past a wedge with constant wall heat flux

The steady laminar magnetohydrodynamic (MHD) boundary-layer flow past a wedge with constant surface heat flux immersed in an incompressible micropolar fluid in the presence of a variable magnetic field is investigated in this paper. The governing partial differential equations are transformed into a system of ordinary differential equations using similarity variables, and then they are solved numerically by means of an implicit finite-difference scheme known as the Keller-box method. Numerical results show that micropolar fluids display drag reduction and consequently reduce the heat transfer rate at the surface, compared to the Newtonian fluids. The opposite trends are observed for the effects of the magnetic field on the fluid flow and heat transfer characteristics.     

Explicit series solutions of some linear and nonlinear Schrodinger equations via the homotopy analysis method

In this paper, by means of the homotopy analysis method (HAM), the solutions of some Schrodinger equations are exactly obtained in the form of convergent Taylor series. The HAM contains the auxiliary parameter ?, that provides a convenient way of controlling the convergent region of series solutions. This analytical method is employed to solve linear and nonlinear examples to obtain the exact solutions. HAM is a powerful and easy-to-use analytic tool for nonlinear problems.     

Bounds for the number of points on curves over finite fields

Let U be a bounded open subset of ?^d, d ≥ 2 and f ∈ C(?U). The Dirichlet solution f^CU of the Dirichlet problem associated with the Laplace equation with a boundary condition f is not continuous on the closure ū of U in general if U is not regular but it is always Baire-one.Let H(U) be the space of all functions continuous on the closure ū and harmonic on U and F(H(U)) be the space of uniformly bounded absolutely convergent series of functions in H(U). We prove that f^CU can be obtained as a uniform limit of a sequence of functions in F(H(U)). Thus f^CU belongs to the subclass B_1/2 of Baire-one functions studied for example in [8]. This is not only an improvement of the result obtained in [10] but it also shows that the Dirichlet solution on the closure ū can share better properties than to be only a Baire-one function. Moreover, our proof is more elementary than that in [10].A generalization to the abstract context of simplicial function space on a metrizable compact space is provided.We conclude the paper with a brief discussion on the solvability of the abstract Dirichlet problem with a boundary condition belonging to the space of differences of bounded semicontinuous functions complementing the results obtained in [17].     

Synthesis,characterization, preliminary biological screening,and interaction studies of the bis(pyridinium)amine compound, 4,4'-[(2-aminophenyl)azanediyl]bis(1-methylpyridin-1-ium)triflate with biological macromolecules

Russian Journal of General Chemistry - Bis(pyridinium)amine 4,4'-[(2-aminophenyl)azanediyl]bis(1-methylpyridin-1-ium)triflate ([H2L][TfO]2) was synthesized and characterized by elemental...     

Synthesis and characterization of ZnO thin films by thermal evaporation

ZnO thin films have been successfully synthesized by thermal evaporation of pure zinc at 900 °C under the flow of different percentages of argon and oxygen gases. The films were characterized by X-ray diffraction (XRD), variable pressure scanning electron microscopy (VPSEM), energy dispersive X-ray spectroscopy (EDS) and UV–vis spectroscopy. The aim of this paper is to study the influence of the oxygen percentage on the structural and morphological properties of the ZnO films. VPSEM results show that very thick needle structures were produced at high oxygen percentages. EDS results revealed that only Zn and O are present in the sample, indicating a composition of pure ZnO. XRD results showed that the ZnO synthesized under different quantities of oxygen were crystalline with the hexagonal wurtzite structure. UV–vis spectroscopy results indicated that the optical band gap energies from the transmission spectrum are between 3.62 and 3.69 eV for ZnO thin films.     

Charge ordering in lithium vanadium phosphates: electrode materials for lithium-ion batteries

The delithiation process in monoclinic Li3V2(PO4)3 has been determined by powder neutron diffraction coupled with 7Li solid-state NMR techniques. Charge ordering of vanadium (V3+/V4+) was observed in Li2V2(PO4)3 as shown by the gray and blue V-O octahedra, respectively, indicating that the electrons are pinned in this phase and hence transport is limited.     

Electrochemical property: Structure relationships in monoclinic Li(3-y)V2(PO4)3

Monoclinic lithium vanadium phosphate, alpha-Li(3)V(2)(PO(4))(3), is a highly promising material proposed as a cathode for lithium-ion batteries. It possesses both good ion mobility and high lithium capacity because of its ability to reversibly extract all three lithium ions from the lattice. Here, using a combination of neutron diffraction and (7)Li MAS NMR studies, we are able to correlate the structural features in the series of single-phase materials Li(3-y)V(2)(PO(4))(3) with the electrochemical voltage-composition profile. A combination of charge ordering on the vanadium sites and lithium ordering/disordering among lattice sites is responsible for the features in the electrochemical curve, including the observed hysteresis. Importantly, this work highlights the importance of ion-ion interactions in determining phase transitions in these materials.     

Novel antifoam for fermentation processes: fluorocarbon-hydrocarbon hybrid unsymmetrical bolaform surfactant

As foaming appears as a problem in chemical and fermentation processes that inhibits reactor performance, the eminence of a novel fluorocarbon-hydrocarbon unsymmetrical bolaform (FHUB: OH(CH2)11N+(C2H4)2(CH2)2(CF2)5CF3 I-) surfactant as an antifoaming agent as well as a foam-reducing agent was investigated and compared with other surfactants and a commercial antifoaming agent. The surface elasticity of FHUB was determined as 4 mN/m, indicating its high potential on thinning of the foam film. The interactions between FHUB and the microoganism were investigated in a model fermentation process related with an enzyme production by recombinant Escherichia coli, in V = 3.0 dm3 bioreactor systems with V(R) = 1.65 dm3 working volume at air inlet rate of Q(o)/V(R) = 0.5 dm3 dm(-3) min(-1) and agitation rate of N = 500 min(-1) oxygen transfer conditions, at T = 37 degrees C, pH(o) = 7.2, and C(FHUB) = 0 and 0.1 mM, in a glucose-based defined medium. As FHUB did not influence the metabolism, specific enzyme activity values obtained with and without FHUB were close to each other; however, because of the slight decrease in oxygen transfer coefficient, slightly lower volumetric enzyme activity and cell concentrations were obtained. However, when FHUB is compared with widely used silicon oil based Antifoam A, with the use of the FHUB, higher physical oxygen transfer coefficient (K(L)a) values are obtained. Moreover, as the amount required for the foam control is very low, minute changes in the working volume of the bioreactor were obtained indicating the high potential of the use of FHUB as an antifoaming agent as well as a foam-reducing agent.