On the Numerical Calculation of Frustrations in the Ising Model

JETP Letters - A quantitative measure of magnetic frustration is defined as a thermodynamically averaged relative number of excited pair interactions in the Hamiltonian of a system. The Metropolis...     

Substructure of Intermetallic Thin-Film Cu3Sn

Technical Physics - The crystalline structure of intermetallic Cu3Sn synthesized by successively condensing thin layers of copper and tin on a substrate at 150°C has been studied. Cu3Sn...     

Generalization of Resonant Equations for the Laguerre- and Legendre-Type Polynomials to Equations of the Fourth Order

Ukrainian Mathematical Journal - A recurrence algorithm for finding particular solutions of the resonant equation of the fourth order connected with the generalization of Laguerre and Legendre...     

A Voltage-Responsive Synthetic Cl−-Channel Regulated by pH

Transmembrane protein channels are an important inspiration for the design of artificial ion channels. Their dipolar structure helps overcome the high energy barrier to selectively translocate water and ions sharing one pathway, across the cell membrane. Herein, we report that the amino-imidazole (Imu) amphiphiles self-assemble via multiple H-bonding to form stable artificial Cl⁻-channels within lipid bilayers. The alignment of water/Cl⁻ wires influences the conduction of ions, envisioned to diffuse along the hydrophilic pathways; at acidic pH, Cl⁻/H⁺ symport conducts along a partly protonated channel, while at basic pH, higher Cl⁻/OH⁻ antiport translocate through a neutral channel configuration, which can be greatly activated by applying strong electric field. This voltage/pH regulated channel system represents an unexplored alternative for ion-pumping along artificial ion-channels, parallel to that of biology.     

Biomimetic Approach for Highly Selective Artificial Water Channels Based on Tubular Pillar[5]arene Dimers

Artificial water channels mimicking natural aquaporins (AQPs) can be used for selective and fast transport of water. Here, we quantify the transport performances of peralkyl-carboxylate-pillar[5]arenes dimers in bilayer membranes. They can transport ≈10⁷ water molecules/channel/second, within one order of magnitude of the transport rates of AQPs, rejecting Na⁺ and K⁺ cations. The dimers have a tubular structure, superposing pillar[5]arene pores of 5 Å diameter with twisted carboxy-phenyl pores of 2.8 Å diameter. This biomimetic platform, with variable pore dimensions within the same structure, offers size restriction reminiscent of natural proteins. It allows water molecules to selectively transit and prevents bigger hydrated cations from passing through the 2.8 Å pore. Molecular simulations prove that dimeric or multimeric honeycomb aggregates are stable in the membrane and form water pathways through the bilayer. Over time, a significant shift of the upper vs. lower layer occurs initiating new unexpected water permeation events through toroidal pores.     

A noncanonical binding site of linezolid revealed via molecular dynamics simulations

Linezolid, an antibiotic of oxazolidinone family, is a translation inhibitor. The mechanism of its action that consists in preventing the binding of aminoacyl-tRNA to the A-site of the large subunit of a ribosome was embraced on the basis of the X-ray structural analysis of the linezolid complexes with vacant bacterial ribosomes. However, the known structures of the linezolid complexes with bacterial ribosomes poorly explain the linezolid selectivity in suppression of protein biosynthesis, depending on the amino acid sequence of the nascent peptide. In the present study the most probable structure of the linezolid complex with a E. coli ribosome in the A,A/P,P-state that is in line with the results of biochemical studies of linezolid action has been obtained by molecular dynamics simulation methods.     

An Approach to Paracyclophane-Based Tetrathiafulvalenes: Synthesis and Characterization of a Pseudo-Geminal [2.2]Paracyclophane 1,3-Dithia-2-Thione

The synthesis of paracyclophane-based tetrathiafulvalene precursors is described in the context of the importance of these compounds in the field of material chemistry. Pseudo-geminal bis(1,3-dithia-2-thione) was synthesized via the corresponding 1,3-dithiol-2-ylium salt. The latter was obtained by a synthetic procedure that involves 4,15-bis(acetyl)[2.2]paracyclophane, a new compound of interest for many researchers.     

Application of Isothermal Upset for Megaplastic Deformation of Cu–Al–Ni β Alloys

Technical Physics - Cu–14 wt% Al–4 wt% Ni alloy demonstrating the shape memory effect has been subjected to plastic deformation by means of uniaxial compression (upset). The process has...     

Comparative Study of Redox Reactions of Aqua- and Thiocyanatocobalamin

The interaction of aqua- and thiocyanatocobalamin with sodium hydroxymethanesulfinate in neutral aqueous solution has been studied, and the kinetic as well as activation parameters of the reactions have been determined. The reduction of the aqua complex is faster in comparison with the thiocyanato one. In contrast to the earlier studied reaction of hydroxymethanesulfinate with cyanocobalamin, reduction of aquaand thiocycnatocobalamins occurs via the associative mechanism.     

Crystal Structure of the Intermetallic Thin-Film Cu–Sn Condensate

The synthesis of intermetallic compounds in multilayer Cu–Sn films is confined within reaction islands, which can attain 100 nm in size. X-ray diffraction analysis reveals the predominance of one intermetallic Cu₆Sn₅ phase, while electron microscopy evidences a high crystallographic orientation of its islands. They have the same orientation to the film surface, but are rotated with respect to each other at different angles and randomly oriented to the axis, which is perpendicular to the film plane and coincide with the crystallographic axis [100] of individual single crystals.