Cyclo-addition of perfluoroisobutylene to azomethines

Conclusions Perfluoroisobutylene can participate in cyclo-addition with azomethines.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 11, pp. 2621–2623, November, 1968.     

Diamond monochromator-splitter with enhanced reflectivity for synchrotron radiation

It has been shown that a damaged surface layer can enhance the reflectivity of a diamond monochromator-splitter for synchrotron radiation. The X-ray diffraction analysis with the use of asymmetric Bragg reflections allowed the determination of the layer thickness and its mosaicity dispersion equal to 3 μm and 19″, respectively. In this case, the observed integrated intensity of a quasisymmetric 422 Laue reflection ( $Mo_{K_\alpha } $ radiation) exceeds its calculated value by a factor of 2.5 at a sufficiently high energy resolution (δE/E = 1.1 × 10^?5). The perspectives of the practical use of a diamond monochromator-splitter with enhanced reflectivity are also discussed.     

15N HYSCORE characterization of the fully deprotonated, reduced form of the archaeal Rieske [2Fe-2S] center

The hyperfine couplings for strongly and weakly coupled 15N nuclei around a reduced Rieske [2Fe-2S] center of uniformly 15N-labeled, hyperthermostable archaeal Rieske protein at pH 13.3 were determined by hyperfine sublevel correlation (HYSCORE) spectroscopy and compared with those at physiological pH. Significant changes in the hyperfine couplings of the terminal histidine Ndelta ligands and Nepsilon nuclei were observed between them, which can be explained by not only the redistribution of the unpaired electron spin density over the ligands but also the difference in the mixed-valence state of the fully deprotonated, reduced cluster. These quantitative data can be used in theoretical analysis for the selection of an appropriate model of the mixed-valence state of the reduced Rieske center at very alkaline pH.     

ENDOR study of anthraquinone paramagnetic complexes with Lewis acid centers of aluminium oxide

Paramagnetic complexes with charge transfer formed upon adsorption of anthraquinone on the surface of aluminium oxide were studied with EPR and ENDOR methods. A hyper-fine structure due to the interaction of unpaired electron with one and two²⁷Al nuclei of surface Lewis acid centers was observed. The process of complex decomposition in the presence of water on the surface was studied.     

Epr Spectroscopy of Adsorbed Spin-Labeled Peptides: Immobilization of Trichogin on the Titanium Oxide

The TOAC-spin-labeled peptide Trichogin GA IV adsorbed on the TiO₂ surface is studied. It is shown that the continuous wave (CW) electron paramagnetic resonance (EPR) spectrum does not depend on temperature in a wide range of 77–300 K. A pulsed EPR method of electron spin echo (ESE) utilizing a two-pulse sequence (π/2-τ-π) is used to study temperature dependence of the phase relaxation time, T_F. The T_F values are found to change from 750 ns to 100 ns in the interval of 77–300 K. The pulsed electronelectron double resonance (PELDOR) measurements utilizing the pulse sequence((π/2)_A,-T-π_B,-(τ-T)-π_A) show that the space distribution of spin labels on the surface remains uniform irrespective of the temperature, and provide the fractal dimension of the surface of 2.7±0.1. The obtained results testify that EPR pulse experiments can be used to study adsorbed spin-labeled molecules at room temperatures, i.e. not only at cryogenic temperatures.     

Investigation of the formation of secondary radicals in the reduction of fluoranil with alcoholate in ethanol by ESR and EPR

The coupling constants have been measured of secondary radicals, formed in the reduction of fluoranil with sodium alcoholate in anhydrous ethanol. Structures for the anions formed have been proposed.Institute of Chemical Kinetics and Combustion, Siberian Branch, Russian Academy of Sciences, Novosibirsk. Institute of Kinetics and Catalysis, Bulgarian Academy of Sciences, Sofia. Translated from Teoreticheskaya i Éksperimental'naya Khimiya, Vol. 27, No. 6, pp. 698–702, November-December, 1991. Original article submitted December 17,1990.     

Complexation of chitosan with maleic acid copolymers

The complexation of chitosan with alternating copolymers of maleic acid with N-vinylpyrrolidone, ethylene, or styrene is studied. It is found that the process is of a cooperative character and that the binding constants and the Hill parameters are dependent on the nature of a nonionogenic comonomer maleic acid in the synthetic polyanion and on the conditions of complexation. The data of atomic force microscopy and turbidimetric titration confirm the effect of temperature on the conformation of interacting macromolecules and the size of macromolecular aggregates. It is shown that the composition and yield of insoluble interpolyelectrolyte complexes at constant pH are determined by the reactant ratio, the temperature, and the initial concentration of polyelectrolytes.