Influence of Dibenzyl-o-carborane on Radiation Aging of Polymethyl Methacrylate

Radiation aging of polymethyl methacrylate produced in the presence of dibenzyl-o-carborane was studied. The influence of dibenzyl-o-carborane addition on the thermomechanical properties of the resulting polymer was analyzed.     

Analytical model of drift and diffusion of charge carriers in organic light-emitting diodes in the presence of a space charge

A relatively simple analytical model taking into account energy disorder and space charge effects is proposed for calculating the current-voltage characteristics for the monopolar regime of charge transfer in thin layers of disordered organic materials. The dependence of the minimal energy barrier height for injection, for which the space charge effects can be disregarded, is determined as a function of the layer thickness and the Gaussian energy distribution width.     

Some Properties of Crystalline Polyacetylenes of Various Density

The resistance of crystalline polyacetylenes of various density to oxidants and high temperatures was studied. The electrophysical and magnetic properties of these polymers and of the products of their thermolysis were determined.     

Glycoside hydrolase stabilization of transition state charge: new directions for inhibitor design

Carbasugars are structural mimics of naturally occurring carbohydrates that can interact with and inhibit enzymes involved in carbohydrate processing. In particular, carbasugars have attracted attention as inhibitors of glycoside hydrolases (GHs) and as therapeutic leads in several disease areas. However, it is unclear how the carbasugars are recognized and processed by GHs. Here, we report the synthesis of three carbasugar isotopologues and provide a detailed transition state (TS) analysis for the formation of the initial GH-carbasugar covalent intermediate, as well as for hydrolysis of this intermediate, using a combination of experimentally measured kinetic isotope effects and hybrid QM/MM calculations. We find that the α-galactosidase from Thermotoga maritima effectively stabilizes TS charge development on a remote C5-allylic center acting in concert with the reacting carbasugar, and catalysis proceeds via an exploded, or loose, S_N2 transition state with no discrete enzyme-bound cationic intermediate. We conclude that, in complement to what we know about the TS structures of enzyme-natural substrate complexes, knowledge of the TS structures of enzymes reacting with non-natural carbasugar substrates shows that GHs can stabilize a wider range of positively charged TS structures than previously thought. Furthermore, this enhanced understanding will enable the design of new carbasugar GH transition state analogues to be used as, for example, chemical biology tools and pharmaceutical lead compounds.

Positive charge stabilized on remote C5-allylic center with catalysis occurring via a loose S_N2 transition state.     

Extraction-chromatographic determination of sulfonated azo dyes in aqueous solutions

The extraction of sulfonated azo dyes E102, E110, E122, E124, and E129 from aqueous solutions using hydrophilic solvents and their mixtures in the presence of a salting-out agent (ammonium sulphate) has been studied. Some regularities of extraction have been revealed. The composition of the mobile phase has been optimized and a procedure has been proposed for the identification and determination of the dyes in aqueous solutions by thin-layer chromatography in concentrations of 0.1–0.01 μg/L. An office scanner and a personal computer have been used to process the results of the separate determination of the dyes.     

An Improved Apparatus for Determining Microgram Amounts of Arsenic by the Gutzeit Method Using Computer-Assisted Data Processing

An improved version of the determination of arsenic traces by the Gutzeit method was proposed. The determination error was decreased by changing the design of the apparatus and using a computer with a scanner for processing the experimental data. Arsenic in model solutions containing from 0.05 to 0.6 g As per a sample volume of 2 mL can be determined with a relative standard deviation of no higher than 10%. The detection limit is 0.01 mg/L (1 × 10^–7 M, which is equal to 0.3 MPC in water).     

Investigation of the reaction of furfural with o-phenylenediamines

1,2-Disubstituted benzimidazoles were synthesized by the reaction of furfural and 5-methylfurfural with o-phenylenediamines in an alcoholic acidic medium.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 6, pp. 816–819, June, 1981.     

Stability of ZIF-8 Nanoparticles in Most Common Cell Culture Media

Zeolite imidazolate framework-8 (ZIF-8) is a promising platform for drug delivery, and information regarding the stability of ZIF-8 nanoparticles in cell culture media is essential for proper interpretation of in vitro experimental results. In this work, we report a quantitative investigation of the ZIF-8 nanoparticle’s stability in most common cell culture media. To this purpose, ZIF-8 nanoparticles containing sterically shielded nitroxide probes with high resistance to reduction were synthesized and studied using electron paramagnetic resonance (EPR). The degradation of ZIF-8 in cell media was monitored by tracking the cargo leakage. It was shown that nanoparticles degrade at least partially in all studied media, although the degree of cargo leakage varies widely. We found a strong correlation between the amount of escaped cargo and total concentration of amino acids in the environment. We also established the role of individual amino acids in ZIF-8 degradation. Finally, 2-methylimidazole preliminary dissolved in cell culture media partially inhibits the degradation of ZIF-8 nanoparticles. The guidelines for choosing the proper cell culture medium for the in vitro study of ZIF-8 nanoparticles have been formulated.     

Refinement of the Theory of Electrodissolution of Difficultly-Soluble Compounds from Metal Surfaces: Taking into Account Nonuniform Film Thickness Along the Electrode Surface

An equation that describes the electrodissolution of a film of a difficultly-soluble compound from the surface of metallic electrode during a linear potential scan is derived and solved numerically. The model accounts for a nonuniform deposit distribution over the electrode surface and for the diffusion of the deposit particles through the film. Voltammograms for the compound electroreduction display peaks whose shape is dependent on the deposit distribution over thickness. The obtained results are analyzed.     

2-Phenyl-5-(4-Biphenylyl)-1,3,4-Oxadiazole and 2-(4'-tert-Butylphenyl-5)-(4'biphenylyl)-1,3,4-Oxadiazole in a Polymethyl Methacrylate Based Plastic Scintillator

The fluorescence intensity was studied for the scintillation formulation including 1,1,3-trimethyl-3-phenylindan and 2-phenyl-5-(4-biphenylyl)-1,3,4-oxadiazole, 2-(4'-tert-butylphenyl-5-(4"-biphenylyl)-1,3,4-oxadiazole, and 1,4-di(5-phenyl-2-oxazolyl)benzene. The scintillation efficiency was determined for the polymethyl methacrylate based plastic scintillator containing the above-listed compounds as luminescent additives.