Bis(alkyl) scandium and yttrium complexes coordinated by an amidopyridinate ligand: synthesis, characterization and catalytic performance in isoprene polymerization, hydroelementation and carbon dioxide hydrosilylation.

New neutral bis(alkyl) Sc and Y complexes [N,Npy,N-]Ln(CH2SiMe3)2(THF)n [n = 0, Ln = Sc (1Sc), Y (1Y); n = 1, Ln = Y (1YTHF)] stabilized by a tridentate monoanionic amidopyridinate ligand were straightforwardly prepared by alkane elimination, upon mixing ligand [N,Npy,N-]H and metal precursor Ln(CH2SiMe3)3(THF)2 in toluene at 0 °C. Depending on the work-up conditions, yttrium bis(alkyl)s were isolated as either a pentacoordinate Lewis base free complex [N,Npy,N-]Y(CH2SiMe3)2 (1Y) or as a hexacoordinate THF adduct [N,Npy,N-]Y(CH2SiMe3)2THF (1YTHF). For the smaller Sc ion the only solvent-free complex [N,Npy,N-]Y(CH2SiMe3)2 (1Sc) was isolated as a pentacoordinate species irrespective of the reaction/work-up/crystallization conditions applied. Complexes 1Ln (Ln = Y, Sc) and 1YTHF were scrutinized as pre-catalysts in ternary catalytic systems Ln/borate/AliBu3 (borate = [HNMe2Ph][B(C6F5)4] or [Ph3C][B(C6F5)4]), applied to isoprene (IP) polymerization, providing moderate activity albeit high selectivity with predominant formation of 1,4-cis polyisoprene (up to 99%). The same complexes proved to be effcient catalysts also for the intermolecular hydrolelementation of styrene with various EH sustrates (pyrrolidine, morpholine, Ph2PH, PhPH2, PhSH) affording linear anti-Markovnikov addition products exclusively. After a preliminary activation by B(C6F5)3, selected bis(alkyl) complexes from this series have been finally used as valuable pre-catalysts for the CO2 hydrosylilation to CH4 in the presence of organosilanes as reducing agents (PhMe2SiH, PhSiH3, Et2MeSiH).

Ln3I5(S2N2)(S2)(THF)10 - a new type of molecular compounds.

Unprecedented complexes of the composition Ln3I5(S2N2)(S2)(THF)10 were obtained in the reactions of neodymium and dysprosium iodide-nitrides with sulfur. The inorganic core of the molecules contains the cyclic fragments Ln(µ-S2)Ln, LnSNSN and LnSN. Ten of the fourteen atoms of the core are coplanar, the remaining four S2 and I2 atoms lie in the other two orthogonal planes. The dysprosium complex upon excitation with UV light exhibits the metal-centered luminescence characteristic of the Dy(3+) ion. Geometric parameters of the molecules, computational data, electron spectroscopy and fluorescence suggest the existence of some conjugation in the mentioned heterocycles.

[Analysis of the Nucleotide Sequence of a Cryptic Plasmid from Yersinia pestis Strains in the Central Caucasian High-Mountain Plague Focus].

An analysis of a 5.4-kbp cryptic plasmid detected in the course of whole-genome sequencing of the Yersinia pestis medieval biovar isolated in the Russian Central Caucasian high-mountain plague focus was performed. The identification of the nucleotide sequence of this cryptic plasmid and its structural and functional analysis revealed that it contained eight open reading frames, among which the following genes were identified: the rep gene of a replication protein, the virB6 gene of a type-IV secretion system inner membrane protein, the virB5gene of the type-IV secretion system minor pilin, and a number of genes probably associated with secretion and transport. A general analysis of the pCKF plasmid DNA showed that the adenine content was 28.34%, the cytosine content was 20.5%, the guanine content was 17.87%, and that of thymine was 33.28%, while the total G+C content appeared to be 38.38%. The G+C content of the chromosome of the Y pestis strain C-627 is 47.6%, which indicates that the pCKF plasmid was obtained from a microorganism equally-phylogenetically distant from the Yersinia bacteria andany other bacteria from the Enterobacteriaceae family. A comparison of the amino acid sequences.of hypothetical proteins encoded by pCKF plasmid with analogous proteins encoded by other bacteria was carried out. The possible contribution of the pCKF plasmid to the maintenance of the most ancient known phylogenetic line of Y. pestis medieval biovar, 2.MEDO, was discussed.

[Algorithm of toxigenic genetically altered Vibrio cholerae El Tor biovar strain identification].

AIM: Development of an algorithm of genetically altered Vibrio cholerae biovar El Tor strai identification that ensures determination of serogroup, serovar and biovar of the studied isolate based on pheno- and genotypic properties, detection of genetically altered cholera El Tor causative agents, their differentiation by epidemic potential as well as evaluation of variability of key pathogenicity genes. MATERIALS AND METHODS: Complex analysis of 28 natural V. cholerae strains was carried out by using traditional microbiological methods, PCR and fragmentary sequencing. RESULTS: An algorithm of toxigenic genetically altered V. cholerae biovar El Tor strain identification was developed that includes 4 stages: determination of serogroup, serovar and biovar based on phenotypic properties, confirmation of serogroup and biovar based on molecular-genetic properties determination of strains as genetically altered, differentiation of genetically altered strains by their epidemic potential and detection of ctxB and tcpA key pathogenicity gene polymorphism. The algorithm is based on the use of traditional microbiological methods, PCR and sequencing of gene fragments. CONCLUSION: The use of the developed algorithm will increase the effectiveness of detection of genetically altered variants of the cholera El Tor causative agent, their differentiation by epidemic potential and will ensure establishment of polymorphism of genes that code key pathogenicity factors for determination of origins of the strains and possible routes of introduction of the infection.

[Genovariants of the cholera agent biovar El Tor: construction, molecular-genetic, and proteomic analysis].

Experimental modeling of origination of the virulent Vibrio cholerae El Tor genovariants is presented. It was demonstrated that the genovariants obtained did not differ from the natural genetically modified strains emerged in a natural population of the agent, either in phenotypical or genotypic properties. Using the PCR assay and sequencing techniques it was proved that the constructed genovariants carried a CTX(Class phi) prophage genome region with ctxBl gene of the V. cholerae classical biovar in the chromosome. It is shown that the prophage structure alterations lead to the increase in the toxigenicity and virulence in the genovariants compared to the typical strain-recipient. Moreover, as regards proteomics, changes in the expression of 26 proteins that perform various functions in the cell, such as metabolism, energy exchange, transportation, etc., were demonstrated. The data are indicative of the impact that a new DNA region in the genome of the genovariants has on the expression level of different house-keeping genes. The results obtained testify to the fact that one of the mechanisms of the genovariant emergence in the natural populations of the agent can be horizontal gene transfer.

[Comparative molecular-genetic analysis of mobile elements in natural strains of cholera agent].

The molecular-genetic peculiarities of the prophage CTXφ genome, the VPI-1 pathogenicity island, and the VSP-II pandemicity island in recently emerged, genetically altered Vibrio cholerae El Tor strains have been studied. The genome of the prophage CTXφ, which contains the ctxAB operon, which codes cholera toxin (CT), was shown to be unstable. A comparative analysis of the nucleotide sequences of the two phage genome regions (the ctxB gene and ctxAB operon promoter region) among 23 genovariant strains allowed us to reveal the presence of distinct ctxB gene alleles (ctxB1 or ctxB7) that differed in single-nucleotide substitutions and the polymorphism of the ctxAB operon promoter region. An analysis of the VPI-1 structure showed that tcpA gene that encodes the basic protein of the toxin-coregulated pilli (TCP) was represented in the genovariants by four alleles. The variability of the VSP-II was also revealed. It was manifested in the occurence of the deletions of varying length (2069 or 13 105 bp).

[ANSA analysis. IV. Specificity spectra in characterizing proteases and mixtures of them]. / ANSA-analiz. IV. Spektry spetsifichnosti v kharakteristike proteaz i ikh smesei.

ANSA-analysis was used for characterization of proteases and their mixtures, such as snake venoms. The method is based on the cleavage by proteases of mixtures of competing chromogenic substrates containing substituted aminonaphtalenesulfonamide (ANSA) detectable groups. All detectable ANSA groups in the substrate mixtures have non-identical modifiers, one or two substituents in the sulfonamide fragment and can be determined by chromatographic methods. To identify venoms, a mixture of six peptide substrates cleaved at the Arg-ANSA bond was proposed. Hydrolysis of this substrate mixture catalyzed by the venoms of different Crotalidae and Viperidae species gave characteristic chromatograms (ANSA spectra) for each tested sample. A method for quantitative description of differences in ANSA spectra has been proposed. Each ANSA spectrum can be presented as a vector going from the origin of the coordinated axes to a point in an n-dimensional space (n is the number of assayed ANSA products of proteolysis) with peak squares of corresponding ANSA as coordinates. The similarity between two ANSA spectra will then be characterized by angle between their vectors.

[ANSA analysis. V. Secondary specificity of peptidases to the structure of detected groups of aminonaphthalenesulfamide chromogenic substrates]. / ANSA-analiz. V. Vtorichnaia spetsifichnost' peptidaz k strukture detektiruemykh grupp aminonaftalinsul'famidnykh khromogennykh substratov.

Mixtures of competing aminonaphthalenesulfonamide (ANSA) substrates can be used for identifying secondary substrate specificity of peptidases and their mixtures. All substrates in the mixture had identical amino acid residues; however, cleaved ANSA differed in chromatographic mobilities due to differences in the substituent in the sulfonamide residue. ANSA generated by limited proteolysis of the substrate mixture by the enzyme preparation were detected chromatographically. The chromatogram obtained (the ANSA spectrum) was characteristic of each enzyme or enzyme-containing preparation. Using arginyl-ANSA mixtures, informative ANSA spectra suitable for enzyme identification were obtained. The correlations between the structure of the substituents in the SONR1R2 group of ANSA and the efficiency of substrate hydrolysis were studied. The method was used to identify snake venoms.

[ANSA analysis. VI. Activation, inhibition and interaction of proteases in enzyme mixtures]. / ANSA-analiz. VI. Aktivatsiia, ingibirovanie i vzaimodeistviia proteaz v smesiakh fermentov.

A new accurate method (ANSA-analysis) is used for studying the interactions of proteases with their inhibitors or other proteases. The method is based on the cleavage by proteases of mixtures of competing chromogenic substrates containing aminonaphthalenesulfonamide (ANSA) detectable groups. Each substrate contained a specifically substituted ANSA group which showed its specific retention time during chromatographic separation. For the analysis of blood coagulation, mixtures of blood-clotting factor substrates were used. Hydrolysis of the substrate mixture catalyzed by blood samples gave characteristic chromatograms (ANSA spectra) for each sample. The activation time before injection of the blood sample into the substrate mixture and the pool of clotting factors and inhibitors both had influence upon the ANSA spectrum. The ANSA spectra of mixtures of trypsin and/or chymotrypsin with snake venoms are described as A x (the ANSA spectrum of a protease) + B x (the ANSA spectrum of a venom) + C x (the ANSA spectrum of catalytically active interaction products). They are additive (A = B = 1, C = 0), if no proteolysis, inhibition or activation takes place. ANSA spectra analysis shows deviations from additivity for some mixtures of Viperidae, (including E. carinatus), Naja naja, Agkistrodon contortrix and A. halys venoms. Explanations for the inability to detect inhibitors in venoms having a high protease activity by previously used methods are given.

[Effect of laser and non-laser radiation on the brain (experimental study)]. / O vozdeistvii lazernym i nelazernym izlucheniem na mozg (éksperimental'noe issledovanie).

It has been established in a study on animals and human cadavers that light can penetrate the brain through the intact skin and eyes. Quantitative optical characteristics of the brain and internal organs are presented.

[Measurement of the optical parameters of animal and human tissues in exposure to lasers]. / Izmerenie opticheskikh parametrov tkanei zhivotnykh i cheloveka pri lazernom vozdeistvii.

A new method for calculation of low laser-energy exposure in biological tissues has been worked out. This method allows to determine the exposition of laser-treatment in each laser exposure more exactly.