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RATIONALE: Electron Affinity (EA) is one of the fundamental properties of a molecule. EA values can be measured with various experimental methods, although their availability is still relatively limited. We make an attempt to use Dissociative Electron Attachment Spectroscopy (DEAS) data for evaluation of the EAs of twelve naphthoquinone (NQ) derivatives. METHODS: Naphthoquinone (NQ) and eleven of its hydroxyl derivatives were investigated by means of DEAS. A combined investigation of NQ and juglone by means of the Electron Transmission Spectroscopy (ETS) and DEAS techniques, with the support of density functional theory (DFT) calculations, allowed us to elucidate the empty-level structures of NQ and its hydroxyl derivatives. RESULTS: All molecules under investigation form extremely long-lived molecular anions associated with three resonant states (except for NQ, where only two long-lived resonances were observed). The hydroxyl substituents of NQ cause an increase in EA and number of internal degrees of freedom (N), and, as a result, an increase in the mean electron autodetachment lifetimes of the molecular negative ions (NIs). Evaluation of the EAs from the measured lifetimes of the molecular NIs through a simple Arrhenius approximation gives results in reasonable agreement with those obtained with DFT calculations. CONCLUSIONS: NI lifetime measurements by means of a modified DEAS instrumentation can provide quantitative data of EA. A simple Arrhenius approximation seems to be adequate to describe the process of electron detachment from molecular anions. Copyright © 2014 John Wiley & Sons, Ltd.

A micro-Raman study of optical phonons in GaAs/InGaAs and InGaAs/InAs bilayer microtubes is presented. From the analysis of optical phonon frequencies the built-in mechanical strain in the microtubes was estimated and compared with theoretical predictions. (© 2009 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)

An unusual cleavage of the Cpy–Cpy bond in the reaction of 2,2′-bipyridine N,N′-diimine and its C-methyl substituted derivatives with acetylenes is described. The effect of the solvent on the yield of 7,7′-bipyrazolo[1,5-a]pyridine-2,2′,3,3′-tetracarboxylates and the products of cleavage of the Cpy–Cpy bond has been studied. The mechanism of the cleavage reaction is discussed on the basis of DFT calculations.

A tendency to form multiferroic states with a spatially modulated antiferromagnetic structure and electric polarization in pure orthorhombic manganites RMnO 3 upon decreasing of the rare-earth ionic radii has been realized in single crystals of substituted compounds Eu 1x- Y x MnO 3 (0.2 ≤ x ≤ 0.5) and Gd 1-y Y y MnO 3 (0 < y ≤ 0.2). While the parent pure and slightly substituted (x ≤ 0,1) compounds exhibited a spontaneous transition from the incommensurate (IC) to the canted antiferromagnetic (CAF) state at T CA < T N = 45-50 K, the transitions from IC to commensurate ferroelectric (C/FE) phase were observed at T lock < T N for x ≥ 0.3 and y ≥ 0.05 accompanied by dielectric anomalies. Various phase transitions were observed in magnetic fields up to 250 kOe along the a-, b-, c-axes by magnetization, magnetostriction and electric polarization measurements. The latter indicate the existence of a spontaneous electric polarization below T lock .

We study the broadening of deuterium spectral lines and radiative transfer under conditions typical for a plasma edge of a divertor tokamak, such as Alcator C-Mod. A model for emission of Lyman and Balmer spectral lines by a plane layer of deuterium plasma is considered taking into account the Zeeman, Stark and Doppler effects. The dependence of the line profiles and intensities on the layer thickness and on the direction of the magnetic field is presented.

Apparent rate constants of tryptic hydrolysis of amide bonds containing Arg and Lys residues in beta-casein were determined by the analysis of kinetics of accumulation of 17 major peptide components revealed by high performance liquid chromatography. When studying pH influence on Arg/Lys bond cleavage preference, averaged rate constants over several ArgbX and LysbX bonds were used for analysis of kinetics of wild-type trypsin, K188H, K188F, K188Y, K188W, and of K188D/D189K mutants. The pK(a1) value of 6.5 was found for all studied trypsins. For wild-type trypsin and its K188D/D189K mutant, pK(a2) was found to be 10. The lowest among studied engineered trypsins pK(a2) = 9.3 was determined for K188Y mutant. Considerable preference for the cleavage of Arg over Lys containing peptide bonds was demonstrated for all trypsins with engineered S2 site except for K188H and K188F. The comparison of individual rate constants for various bonds showed that during the hydrolysis by wild-type trypsin, the probabilities of splitting depend on secondary specificity and local hydrophobicity of amino acid residues, which are nearest to the hydrolyzed peptide bond (P2 site). The improvement of prediction of hydrolysis rates performed by the used program was achieved after considering the presence of hydrophobic neighborhood of Lys48--Ile49 and Arg202--Gly203 bonds.

Indium gas-phase nucleation is suggested as a possible mechanism responsible for low indium incorporation during InGaN MOVPE. Indium generated due to trimethylindium (TMIn) decomposition provides significant supersaturation in the gas phase. This results in nucleation and subsequent formation of In clusters carried away from the reactor by the gas stream and not participating in InGaN growth. 2D model of gas flow, heat transfer and mass transport accounting for gas-phase pyrolysis of group III precursors and indium nucleation is applied to evaluate this effect on indium incorporation into InGaN during MOVPE in a horizontal tube reactor. It is shown that the nonlinear dependence of indium composition in the epitaxial layer on In/(In + Ga) input ratio is caused by the interplay between precursor pyrolysis and nucleation.

In order to find which of the electron structure features of benzodiazepine molecules control their biological activity, a series of benzodiazepine derivatives was investigated by means of negative ion mass spectrometry with resonance electron capture. The resonance curves for negative ion effective yields are presented. Comparison within a series demonstrates a significant (0.6–1.5 eV) shift of curve maxima towards high electron energies (destabilization) for inactive compounds. It is concluded that the destabilization of resonances reflects an increase in energy of several first electronic transitions in the neutral benzodiazepine molecules, and is related to the second (inactive) conformer, the pseudo-chair. It is suggested that the energies of the electronic transitions are the sought feature of the electron structure of a benzodiazepine molecule which correlates with its activity, and that the stereospecific structure of the benzodiazepine conformers affect the activity via this feature. Copyright © 1998 John Wiley & Sons, Ltd.

Computer assistance was used for simulation of proteolysis of partially demasked β-Lactoglobulin by pepsin. Total proteolysis kinetics and kinetics for intermediate peptides were computed by PROTEOLYSIS program for different rates of demasking. The increase of demasking rate by a factor of 100 gives twofold increase in the total hydrolysis rate. The identification of cleavage sites on the basis of limited number of peptides was found to depend on the depth of hydrolysis. When the number of identified peptides was only 10, the computer simulation has allowed to predict a half of experimentally determined cleavage sites. The influence of the dimension of enzyme active site and of the secondary structure of substrate on the efficiency of prediction of cleavage sites was analysed.

The data obtained on the regioselectivity of amination are interpreted in terms of DFT/PBE/3Z quantum-chemical calculations.

Basic chromosomal proteins were extracted from the sperm of fertile and infertile human males. The relative proportions of protamine 1, 2, and 3 were determined by scanning microdensitometry following electrophoresis of total protamine in polyacrilamide gels. The findings were as follows: (1) The proportion of protamine P(2 + 3) in sperm obtained from infertile males was lower than that in fertile males. (2) Protamine P(2 + 3) in infertile human males showed reduced affinity to DNA. The possibility that some cases of human male infertility may be due to mutation within the protamine P2 gene is discussed. © 1993 Wiley-Liss, Inc.

Reactions of phenylenediamines with sodium azide and triethyl orthoformate provides the title bis(tetrazoles), which suffer tetrazole opening under basic conditions.

The ability of Rhodococcus bacteria to transform dehydroabietic and isopimaric acids with a high degree of conversion (up to 95%) was detected.

Selective method of reduction of the ortho-nitro groups in 2,4,6-trinitrotoluene by hydrazine hydrate in the presence of FeCl3 and charcoal has been elaborated. This method allows obtaining either ...

Electrodeposited Fe–P alloys with P concentration up to 45 at% are studied by Mossbauer spectroscopy. The concentration dependences of average hyperfine magnetic fields H(x) and isomer shifts H(x) are measured. The values of local hyperfine magnetic fields HK depending on the P-atom numbers in the nearest Fe-atom environment are determined. Conclusions about changes in the local atomic structure of Fe–P alloys with P concentration increasing from 7 up to 25 at% are drawn. From the H(x) dependence the possibility of describing integral macrophysical properties of Fe–P alloys using local atomic environment characteristics, is illustrated. [Russian Text Ignored].

O-(3,5-Dinitrophenyl) ketoximes obtained in the reactions of ketoximes with 1,3,5-trinitrobenzene undergo acid-catalyzed cyclization into 2-substituted or 2,3-disubstituted 4,6-dinitrobenzo[b]furans. In analogous cyclization, products of selective reduction of a nitro group in O-(3,5-dinitrophenyl) ketoximes unexpectedly yield, along with 6-amino-4-nitrobenzofurans, 4-hydroxy-6-nitroindoles. The 4-NO2 group is displaced from 4,6-dinitrobenzo[b]furans in reactions with thiols in the presence of K2CO3. Conditions for nitration and sulfochlorination of 4,6-dinitrobenzo[b]furans in position 3 were found. Condensation of a 2-methyl derivative with dimethylformamide acetal was accomplished.

Disordered FeP alloys are produced by electrochemical deposition in a wide concentration range from 0 up to 20 at% of P. The form of the concentration dependences of the structural and magnetic parameters is determined by X-ray diffraction, Mossbauer spectroscopy, and magnetic measurements. The observed anomaly is explained by changes in the character of interatomic bonds and by the existence of the transition from a microcrystalline b.c.c. structure to an amorphous state. The results obtained are compared with analogous data for disordered alloys of iron with Al and Si. [Russian Text Ignored].

7H-Pyrrolo[3,2-e][1,2,4]triazolo[1,5-c]pyrimidines were synthesized by the reactions of 2-ethoxymethyleneamino-1H-pyrrole-3-carbonitriles with acid hydrazides and by the reactions of aminoiminopyrimidines (prepared based on the above-mentioned carbonitriles) with acid chlorides.

1,3-Dinitrophenoxazine and 1,3-dinitrophenothiazine derivatives were prepared by the reactions of ortho -aminophenols and ortho -aminothiophenols with 1,3,5-trinitrobenzene.

It has been shown that amino derivatives of sulfanilamide, and also some functionally substituted primary arylamines and cycloalkylamines, undergo heterocyclization with triethyl orthoformate and sodium azide with the formation of 1-monosubstituted tetrazoles. Primary amines of the azole series, 5-aminotetrazole, 5-amino-1-methyltetrazole, 4-amino-1,2,4-triazole, and also less basic arylamines (4-fluoro-3-nitroaniline, 2,6-dibromo-4-nitroaniline) did not react. An efficient method of introducing an amino group into position C(5) of the tetrazole ring of 1-aryltetrazoles is proposed, based on alkaline decomposition of the tetrazole ring and heterocyclization of the resulting N-arylcyanamides on interaction with ammonium azide generated in situ.

O -3,5-Dinitrophenylketoximes obtained by treatment of ketoximes with 1,3,5-trinitrobenzene undergo acid-catalysed cyclization to give 4,6-dinitrobenzo[ b ]furans substituted at the 2- or 2- and 3-positions.

Analysis of experimental data on the formation of β-sialon (β-Si6 – zAlzOzN8 – z) at high temperatures (1300–1500°C) indicates that two morphological forms—fibers and spherical particles—differ in chemical composition:z = 3.58 in the fibers and 2.60 in the spherical particles. The formation of fibers is assumed to follow the whisker growth mechanism, while the spherical particles are likely to grow via diffusion.