Modeling of drug molecule orientation within a receptor cavity in the BiS algorithm framework

The BiS algorithm is suggested for modeling the drug molecule orientation within a receptor cavity. It is based on the assumption of complementarity of the field created by biologically active compounds and the field of the responsive receptor. The comparison of predicted orientations of various biologically active compounds on the relevant receptors with the data of X-ray structural studies (Protein Data Bank) reveals that the results obtained with this approach surpasses those reported in the literature. The suggested technique made it possible to elucidate the details of the action mechanism of DNA antimetabolites, dihydrofolate reductase inhibitors. The dependence of the activity on the structural parameters of “ligand-receptor” complexes is determined.     

A new method for predicting conduction anesthesia

A new method for predicting conduction anesthesia has been suggested. The method is based on calculation of theP matrix probabilities of interatomic contacts for each molecule of the compounds considered. TheP matrix enables one to evaluate the main tendencies of atoms and atomic groups to interact in biochemical sorption on the nerve fiber surface. The minimum effective concentrations calculated for 25 compounds are in good agreement with the experimental data. The correlation coefficient between the experimental and calculated values is 0.98 when the standard deviation is 0.1 mmol L⁻¹. Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 10, pp. 1781–1784, October, 1997.     

Numerical simulation of natural convection in a sessile liquid droplet

Heat transfer in a sessile liquid droplet was studied with numerical methods. A computer code was developed for solving the problem of convection in an axisymmetric hemispherical droplet and in a spherical layer as well. The problem of establishing an equilibrium state in a droplet was solved using several variables: temperature, stream function, and vorticity. Simulation was performed for droplets of water, ethyl alcohol, and model liquids. Variable parameters: intensity of heat transfer from droplet surface, Rayleigh and Marangoni dimensionless criteria, and the characteristic temperature difference. It was revealed that the curve of convective flow intensity versus heat transfer intensity at droplet surface has a maximum. A dual-vortex structure was obtained in a stationary hemispherical profile of liquid droplet for the case of close values for thermocapillary and thermogravitational forces. Either thermocapillary or thermogravitational vortex might be dominating phenomena in the flow structure.     

Pre-organization of diarylideneacetonyl crownophanes in single crystals to photochemical transformations

Specific features of crystal packings and pre-organization of diarylideneacetonyl crownophane molecules to solid-phase photochemical transformations were studied on the basis of X-ray diffraction data using methods of simulation of molecular crystal packings. The tendency of the most part of the synthesized macrocyclic E,E-isomers to the formation of homochiral crystals (P2₁2₁2₁) was revealed, while (23E,26E)-11,12,14,15-tetrahydro-8H-dinaphtho-[2,1-k:1′,2′-r][1,4,7,10]tetraoxacyclononadecine-23,26-dien-25(9H)-one is prone to polymorphism. A phenomenon of solid-phase stereospecific photochemical dimerization of molecules according to the syn-head-to-tail type without crystal destruction (single crystal—single crystal transformation) was found for one of the modifications of this crownophane.     

Structure and properties of 4-phenyl-5H-1,2,3-dithiazole-5-thione polyiodide with S−I+−S bridged complex

Structural Chemistry - Treatment of 4-phenyl-5H-1,2,3-dithiazole-5-thione with iodine in acetonitrile yielded crystalline product with thione-iodonium three-center halogen bond and triiodide anion...     

Energy properties and structure of 2- and 8-allylthioquinoline complexes with iodine

The study focuses on the energy and quantum topological properties of substituted 2- and 8-allylthioquinoline complexes with iodine, which are assumed to correspond to prereaction states in the iodocyclization reaction leading to the formation of thiazolo- and tiazinoquinoline systems. The structures of the complexes and the corresponding atomic interactions are modeled considering the different conformational states of allyl-substituted quinolinethiols (thioquinolines). The energy values are analyzed for the interactions between the iodine molecule and different donor centers of the substituted quinoline system: the nitrogen heteroatom, sulfur, and π-system of the allyl group. It is shown that the formation of stable complexes with the nitrogen of the quinoline ring is complicated by steric hindrances posed by the S-allyl group at positions 2 and 8 of the quinoline system, which in turn contributes to the convergence of the cyclization centers.     

The features of iodine loss at high temperatures

Journal of Thermal Analysis and Calorimetry - A series of crystalline thiazoloquinolinium iodides has been studied using a combination of thermal analysis, mass and Raman spectroscopy techniques....     

Intermolecular interactions and structural dichotomy in 1,3,2,4-benzodithiadiazine crystals

The intermolecular interactions and structural dichotomy in 1,3,2,4-benzodithiadiazine crystals (1) (the heterocycle is planar for one derivative, but bent for another) were studied in terms of topological analysis of electron density (ED) using QTAIM theory and crystal packing modeling in an OPiX approximation. The intermolecular interactions in crystals 1 can be detected and quantified by means of the critical points (CPs) of ED with (3, ?1). The total value of ED at all CPs of a molecule can be correlated with the torsion angle that defines the bending of its heterocycle; the larger the total ED at intermolecular CPs, the smaller the bending of the heterocycle. Thus, under the conditions of weak intermolecular interactions in crystal, molecules 1 preserve the bent conformations typical of the gas phase; strong intermolecular interactions lead to planar conformations.     

Dynamics of a finite-width liquid film in a co-current microchannel gas flow

The velocity fields and the parameters of a finite-width liquid film moving along the bottom of a mini- and a microchannel under the action of a gas flow are calculated. The investigations are performed for different levels of gravity. It is found that the thin liquid film distorts the velocity field in the gaseous phase. In contrast to the minichannel flow, in the microchannel the film surface is not leveled with increase in the gravity force.     

Magnetic Moments,Electronic Structure,and Optical Spectroscopy of Cobalt-Based Intermetallic Compounds YCo3, Y2Co7, and LaCo5

Journal of Experimental and Theoretical Physics - We report on the results of analysis of magnetic properties and electronic structure, which were obtained by self-consistent ab initio...