Polycondensation of N-substituted borazoles with the bis-β, β′ -aminodiethyl ester of trimethylenediboric acid

Conclusions N-Triphenylborazole and B-methyl-N-triphenylborazole enter into a condensation reaction with the bis-, '-aminodiethyl ester of trimethylenediboric acid, forming polymers with reticular and linear structures, respectively.The authors would like to thank L. I. Zakharkin and A. I. Kovredov for providing the bis-, '-aminodiethyl ester of trimethylenediboric acid.     

Mechanism of Reaction of Flavone Derivatives with Hydroxyl Radical by Semiempirical Methods

Semiempirical quantum-chemical calculations were used to study the reactivity of the C² = C³ bond in flavones in reaction with hydroxyl radical. The preferred pathway was found to be addition of the radical by C³. Increased reactivity in the reaction in question of the hydroxy groups on C³ and C⁴' in polyhydroxyflavones was revealed.     

Phosphorylated Allylchlorides: A Source of new Structures and Transformations

Abstract

General methods have been elaborated for the synthesis of O (or S)-phosphorylated vinylcholines, including the corresponding betaines of mono-, bis- and polymer structures, 5-membered heterocycles with P, O, S, N atoms in the cycle and exo- CHX= (X=H, C1) bond. The key substances, O-phos- phorylated allylchlorides, were obtained either by the well known Perkov reaction or according to scheme (I), worked out by us. The scheme is based on the reactions of 3- or 4-coordinated phosphorus with substituted ketones in the presence of triethylamine (B:).     

Study of Retention Ability of Nucleopore Membranes

The influence of pore sizes of nucleopore membranes and their shapes on the retention of polystyrene particles of 40–100 nm in size was studied. The interrelation between structural parameters of the nucleopore membranes found by various methods and the efficiency of filtration of calibrated particles were analyzed. The potential and limitations of the procedure for determining the efficiency of filtration of nanosized latex particles was demonstrated; the procedure was based on UV absorption spectroscopy.     

A new promising method for processing of serpentinites

A new thermal-acid method for processing of serpentinized ultrabasic rocks was developed. The method makes it possible to recover, in a very short time and in good yield, magnesium and iron(III) in the form of salts (hydroxides or oxides) and two varieties of SiO₂ as an aqua silica gel and light silica.     

A general approach for prediction of motional EPR spectra from Molecular Dynamics (MD) simulations: application to spin labelled protein

A general approach for the prediction of EPR spectra directly and completely from single dynamical trajectories generated from Molecular Dynamics (MD) simulations is described. The approach is applicable to an arbitrary system of electron and nuclear spins described by a general form of the spin-Hamiltonian for the entire motional range. It is shown that for a reliable simulation of motional EPR spectra only a single truncated dynamical trajectory generated until the point when correlation functions of rotational dynamics are completely relaxed is required. The simulation algorithm is based on a combination of the propagation of the spin density matrix in the Liouville space for this initial time interval and the use of well defined parameters calculated entirely from the dynamical trajectory for prediction of the evolution of the spin density matrix at longer times. A new approach is illustrated with the application to a nitroxide spin label MTSL attached to the protein sperm whale myoglobin. It is shown that simulation of the EPR spectrum, which is in excellent agreement with experiment, can be achieved from a single MD trajectory. Calculations reveal the complex nature of the dynamics of a spin label which is a superposition of the fast librational motions within dihedral states, of slow rotameric dynamics among different conformational states of the nitroxide tether and of the slow rotational diffusion of the protein itself. The significance of the slow rotameric dynamics of the nitroxide tether on the overall shape of the EPR spectrum is analysed and discussed.