[TiO2-DNA nanocomposites capable of penetrating into cells].

Methods of noncovalent immobilization of DNA fragments onto titanium dioxide nanoparticles (TiO2) were developed, which led to TiO2-DNA nanocomposites capable of penetrating through cell membranes. TiO2 nanoparticles of different forms (amorphous, anatase, brookit) with enhanced agglomeration stability were synthesized. The particles were characterized by X-ray diffraction, small angle X-ray scattering, infrared spectroscopy and atomic force microscopy. Three approaches to the preparation of nanocomposites are described: (1) sorption of polylysine-containing oligonucleotides onto TiO2-nanoparticles, (2) the electrostatic binding of oligonucleotides to TiO2 nanoparticles bearing immobilized polylysine, and (3) sorption of oligonucleotides on TiO2 nanoparticles in the presence of cetavlon. All three methods provide an efficient and stable immobilization of DNA fragments onto nanoparticles, which leads to nanocomposites with a density for an oligonucleotide up to 40 nmol/mg. It is shown that DNA fragments in nanocomposites retain their ability to form complementary complexes and can be delivered into cells without transfection agents and other methods of exposure.

[Cloning of Escherichia coli K12 xylose isomerase (glucose isomerase) and studying the enzymatic properties of its expression product].

The coding region of Escherichia coli K12 xylose (glucose) isomerase gene was inserted into the pRAC expression vector and cloned in E. coli BL21 (DE3) cells. After induction of expression of the cloned gene, the proportion of recombinant xylose isomerase accounted for 40% of the total protein content. As a result of one-stage purification by affinity chromatography, a protein preparation of 90% purity was obtained. The recombinant enzyme catalyzed the isomerization of glucose to fructose and exhibited maximum activity (0.8 U/mg) at 45 degrees C and pH 6.8. The enzyme required Mg2+ ions as a cofactor. When Mg2+ and Co2+ ions were simultaneously present in the reaction medium, the enzyme activity increased by 15-20%. Complete replacement of Mg2+ with Co2+ decreased the enzyme activity. In the presence of Ca2+ at concentrations comparable to the concentration of Mg2+, the enzyme was not inhibited, although published data reported inhibition of similar enzymes by Ca2+. The recombinant enzyme exhibited a very low thermostability: it underwent a slow inactivation when incubated at 45 degrees C and was completely inactivated after incubation at 65 degrees C for 1 h.

[Consumption of hydrocarbons by psychrotolerant degrader strains].

Oil-oxidizing microorganisms have been sampled in various regions of Siberia and used in strain associations, which degrade n-alkanes of oil from various fields by 64-92% after 6 days of growth in a wide temperature range. These strains are salt-tolerant and psychrotolerant. They are compatible with aboriginal soil microflora. Promising results have been obtained in experiments on growing plants on oil-polluted soil purified with a biodegrader of this series.

[Isolation of total RNA from baker's yeast].

A simple method of production of total RNA from baker's yeast was developed. Total RNA was isolated from yeast (Saccharomyces cerevisiae) biomass using lysis with sodium dodecyl sulfate at 100 degrees C for 40-60 min and subsequent precipitation of the target product with 3 M NaCl. The preparation obtained was characterized in detail: yield of total RNA from 1 kg of pressed yeast, 9.25 g; optical density at 260 nm of 1 mg of RNA dissolved in 1 ml of water, 20.2 U; content of the acid-soluble fraction, 2.02%; and protein content, 1.8%. Total tRNA was isolated from total RNA by fractional precipitation with ethanol followed by gel filtration.

[Antigenic determinants of proteins. The humoral immune response]. / Antigennye determinanty belkov. Gumoral'nyi immunnyi otvet.

There exist two opposing points of view on the organization of antigenic determinants of proteins: 1) the determinants are stringently predetermined regions of the protein molecule; 2) all the surface of the protein globule is potentially antigenic, and the immune response is generated occasionally in every individual, although some sites of the protein surface could be preferable for eliciting the immune response. In this work, taking into account the results of recent investigations, we propose some reconciliation: a correlation between the rigidity of the protein architecture and the antigenicity of the particular sites of the antigen molecule. Some general principles of the antigenic determinants of proteins are formulated.

[Mechanism of reaction catalyzed by RNA-ligase from bacteriophage T4]. / Izuchenie mekhanizma reaktsii, kataliziruemoi RNK-ligazoi bakteriofaga T4.

The dissociation constants of the complexes of RNA-ligase with acceptors, donors and the adenylylated donor A(5')ppAp have been determined on the basis of the inhibition of ATP-pyrophosphate exchange reaction. The dissociation constants of the complexes of the enzyme with "poor" acceptors (oligouridilates) have been shown to be slightly different from those with "good" acceptors (oligoadenylates). The dependence of the reaction velocity of the formation of ligation products on the concentration of acceptors (pA)4, (pU)4 and the adenylylated donor A(5)ppAp has been studied. On the basis of the data obtained the conclusion about the random addition mechanism has been drawn. The reaction takes place in the steady-state conditions in the case of (pA)4 and in the equilibrium conditions--in the case of (pU)4.

[Study of ATP-independent stages of reaction catalyzed by phage T4 RNA-ligase]. / Izuchenie ATP-nezavisimykh stadii reaktsii, kataliziruemoi RNK-ligazoi bakteriofaga T4.

The isotope exchange between [5'-32P]pAP and A(5')ppAp catalyzed by enzyme was shown not to take place in the absence of the acceptor; i. e. the necessity of the acceptor presence during the second step of the process was demonstrated. The isotope exchange reaction between [5'32P]pAp and (pA)5p was studied. It was demonstrated that acceptor (pA)4, slightly whereas the acceptor (pU)4 completely inhibits the isotope reaction. The isotope reaction exchange between [5'-32P]pAp and (pU)4pAp does not take place. The question of existence of adenylated donor elimination mechanism in the presence of "poor" acceptors is considered on the basis of the data obtained.

[Kinetic characteristics of the ATP-pyrophosphate isotope exchange catalyzed by RNA ligase from T4 bacteriophage]. / Kineticheskie kharakteristiki izotopnogo obmena ATP-pirofosfat, kataliziruemogo RNK-ligazoi bakteriofaga T4.

The dependence of initial rate v0 of ATP--PPi exchange reaction catalyzed by RNA-ligase of bacteriophage T4 on the concentration of ATP(s), pyrophosphate (z) and Mgcl2 has been determined. The dependence of v0 on s and z described by the equation v0 = k-1k2E0/(k-1 + K2) (1 + K1/s + k2/z) has been obtained for the reaction of E + S in equilibrium ES in equilibrium E1 + Z, where E--enzyme, E1--adenylylenzyme, S--ATP, Z--pyrophosphate, K1 and K2--constants of equilibrium, k-1, k2--velocity constants of transition of ES to E + S and E1 + Z, E0--complete concentration of enzyme. The low inhibition of the ATP--PPi exchange by the acceptor A(pA)2 and donors pAp, p(Ap)3, pCp has been shown. The dependence of v0 on the concentration of MgCl2 is consent with the incorporation of only dimagnesium salts of substrates in the isotope-exchange reaction.

[Reiterative poly(A) synthesis on oligonucleotide templates in an Escherichia coli RNA-polymerase system]. / Rei terativnyi sintez poli(A) na oligonukleotidnykh matritsakh v sisteme RNK-polimerazy Escherichia coli.

The poly(A) synthesis in the E. coli RNA-polymerase system on the oligothymidilates, oligouridilates and oligonucleotides d(5'-OH-CCATCTTTT-3'-OH) and d(5'-HO-TCTTTT-3'-OH) as templates was studied. The reaction was shown to proceed more intensively on the oligothymidilates compared to oligouridilates. The insertion of phosphate residues into 3' end of oligouridilates deteriorates properties of their templates though the length of the synthesized poly(A) is not changed in this case. The synthesis of poly(A) on the nonanucleotide d(CCATCTTTT) proceeds intensively, but there is no AMP incorporation on the hexanucleotide of similar structure. The author's data combined with certain literature results suppose that the template activity of the oligonucleotides containing homopolymer sequences is determined in the RNA-polymerase system in reiterative regime by two factors: by the total amount of oligonucleotide links and by the homopolymer block size. The total amount of links seems to be important for the oligonucleotide enzyme bind stability and must comprise not less than 6 charges of the phosphate groups. The homopolymer block size must be no less than of 4 links.

[Circular transcription map of the plasmid pBR322]. / Kol'tsevaia transkriptsionnaia karta plazmidy pBR322.

The plasmid pBR322 transcription in the isolated E. coli DNA-dependent RNA-polymerase system was studied. Transcription regions as well as transcripts orientation were defined using both the technique of "criss-cross" hybridization and the annealing of RNA-products with L- and H-strands of plasmid. Summing up obtained data together with available data on promoter localization a circular transcription map of plasmid pBR322 was constructed. Effects of heparin, ion strength and E. coli S-30 system on in vitro transcripts were also studied. The 110-long RNA transcript synthesized in Ori region of pBR322 was found to be the most sensitive to all these factors. RNA-transcripts obtained in in vitro system are able to direct protein synthesis in cell-free S-30 system.

[Termination of DNA transcription by a poly(dA).poly(dT) fragment inserted into pBR325 plasmid]. / Terminatsiia transkriptsii DNK fragmentom poli(dA).poli(dT), vstroennym v plazmidu pBR325.

A recombinant DNA was constructed by inserting polynucleotide (dA).(dT) of 80-100 base pairs long into EcoRI site of the pBR325 plasmid DNA. Transcription of this DNA was studied in E. coli RNA polymerase system in vitro. Some transcripts obtained with the recombinant plasmid were shown to have poly(U) clusters at the 3'-ends. Obtained data indicate that poly(dA).poly(dT) sequence acts as a terminator of RNA synthesis. Orientation of this sequence in recombinant DNA was also established.

[Transcription of synthetic oligonucleotides]. / Transkriptsiia sinteticheskikh oligonukleotidov.

The decadeoxynucleotides d(pTTC)3 and d(CCATCTTTT) transcription by E. coli RNA-polymerase was studied. The nucleotide composition of d(pTTC)3 transcript was shown to be consistent with that of the template, but RNA-product was several times longer than the template. With nonanucleotide d(CCATCTTTT) the poly(A) synthesis was observed. This fact may be attributed to the reiteration on the TTTT-cluster. When using the oligonucleotide primers d(pGGA) and r(pAAAA) complementary to the templates d(pTTC)3 and d(CCATCTTTT), accordingly, the nucleosidetriphosphates concentration being reduced and the RNA-polymerase "holo" being replaced by "core", the considerable decrease in the unhomogeneity of the transcript length and in the length itself was found. With d(pTTC)3 as a template the length of RNA-product was found to be of 24-25 nucleotides and with d(CCATCTTTT) it was of 18-19 nucleotides. The sequence of RNA transcribed from both templates in the presence of primers was in accordance with the structure of templates.

[Template properties of the decadeoxynucleotide d(pCCACGAAACC) in the RNA polymerase system of Escherichia coli]. / Issledovanie matrichnykh svoistv dekadezoksinukleotida d(pCCACGAAACC) v sisteme RNK-polimerazy Escherichia coli.

The decadeoxynucleotide d(pCCACGAAACC) transcription by E. coli RNA-polymerase was studied. The transcript was shown to be several times longer than the template. The oligonucleotide GpGpGpGpUp complementary to the "contact" of two neighbouring template molecules was found in the pancreatic RNase digest of the RNA-product. This fact is consistent with our hypothesis reported recently. Pentanucleotide d(pGGTTT) may funtion as a primer in the decadeoxynucleotide transcription being incorporated into RNA.

[Conversion of nucleoside triphosphates in an RNA polymerase system]. / O prevrashcheniiakh nukleozidtrifosfatov v RNK-polimeraznoi sisteme.

The behavior of nucleoside triphosphates (NTP) in the RNA-polymerase system from E. coli was studied. The conversion of NTP to the corresponding nucleoside diphosphate (NDP) was observed. This phenomenon was accounted for a contaminating enzyme activity in the RNA-polymerase preparations. The possibility to remove such a contamination was demonstrated, the best technique being the DNA-cellulose affinity chromatography. The purified enzyme does not catalyze the intermediate formation of NDP's from NTP's during RNA synthesis with poly(U) and poly(dG)-poly(dC) as templates.

[Col E1 DNA transcription in Escherichia coli RNA-polymerase system in vitro]. / Issledovanie transkriptsii DNK plazmidy ColEI v sisteme RNK-polimerazy Escherichia coli.

The ColEI plasmid DNA transcription in E. coli RNA-polymerase system in vitro was studied. Three RNA types: of 110-140 residues long, 1700 residues long and of the length similar to that of DNA-template were synthesized in the reaction, containing 10 mM MgCl2, 50 mM KCl and 15% glycerol. The transcription was shown to be asymmetric, the DNA H-chain being transcribed. The ColEI DNA region transcribed in vitro was located by the blotting techniques. This region comprised most of the ColEI genome except the colicin EI gene. The addition of mitomycin C to the reaction mixture caused only a little stimulation of colicin EI gene transcription. Four fragments of HaeIII digest of ColEI DNA were shown to have affinity to RNA-polymerase in the absence of NTPs and two fragments to have it in the presence of 3 NTPs (in the RNA initiation conditions). These two fragments seem to contain two strong promoters. One of them is in the HaeIIIA fragment, where the colicin EI gene origin is situated, and another one is the HaeIIIB fragment (in the immunity region).

[Effectiveness of the promoter Ptac' in vitro and in mini-cells]. / Izuchenie éffektivnosti promotora Ptac' in vitro i v mini-kletkakh.

The efficiency of hybrid promotor Ptac', comprising a synthetic trp-promoter and lacUV5 "-10" sequence, was studied. By means of electrophoresis and hybridization of RNA-products obtained in vitro and in minicells, with promotor-containing plasmids; the hybrid promotor was found to be 6 times and 3-4 times as efficient as trp and lacUV5 promoters, respectively.

[Effect of poly(dA).poly(dT) sequence inserted into EcoR1 site of pBr322 plasmid on the expression of tet and bla genes]. / Vliianie posledovatel'nosti poli(dA).poli(dT), vstroennoi v EcoR1-uchastok plazmidy pBR322, na ékspressiiu genov tet i bla.

The 99 base pair poly(dA).poly(dT) stretch was inserted into EcoRI site of pBR plasmid. The effect of this insertion on tet-gene expression from P2 promoter, and bla-gene expression from P1 and P3 promoters was studied. The insertion results in a slight enhancement of the resistance of the cells to tetracycline and a decreased sensitivity to ampicillin. It is suggested that these findings reflect the effect of insertion on the transcription of the corresponding genes.

[Expression of the gene for hybrid beta-lactamase pBR322 with C-terminal fragment containing tuftsin (Thr-Lys-Pro-Arg)]. / Izuchenie ékspressii gena gibridnoi beta-laktamazy pBR322 s C-kontsevym fragmentom, soderzhashchim taftsin (Thr-Lys-Pro-Arg).

A hybrid beta-lactamase gene with a synthetic tuftsin-coding DNA fragment inserted at the Pst I-site of pBR322 plasmid has been obtained and its expression has been studied. Radioactive amino acids have been used to show that in E. coli chi 925 minicells up to 30% of newly synthesized chimeric protein is secreted into periplasm providing the tuftsin transport. After hybrid protein cleavage with CNBr, tuftsin has been isolated using ion-exchange and thin-layer chromatography.

[Construction of an expression plasmid vector for accomplishing in vivo delivery of recombinant biologically active proteins. 2. Synthesis of HBcAG in a vaccine strain of Salmonella choleraesuis]. / Konstruirovanie ékspressionnogo plazmidnoto vektora dlia osushchestvleniia dostavki in vivo rekombinantnykh biologicheski aktivnykh belkov. 2. Sintez HBcAg v vaktsinnom shtamme Salmonella choleraesuis.

The capacity of a previously described plasmid vector pAZ to deliver bioactive proteins to targets in vivo has been studied. This vector molecule has a strong constitutive promoter, is extremely stable in cells of vaccinal S. choleraesuis strain, and encodes the synthesis of marker protein beta-galactosidase which helps monitor the vector's fate in the host. The gene encoding hepatitis B virus core antigen (HBcAg) has been inserted into pAZ under its constitutive promoter. The resultant recombinant plasmid p19-24 has been used to transform Enterobacteriaceae (E. coli and S. choleraesuis) cells. Transformed cells produce immunologically active HBcAg. p19-24 was stable in S. choleraesuis cells during their culturing and during this strain persistence in mice. Triple oral immunization of rabbits in a dose of 1 x 10(9) S. choleraesuis cells TC177 induced the production of virus-specific antibodies. Successful transformation of cells of another vaccinal strain S. abortus ovis by this plasmid extends the potentialities of the vector. The results demonstrate good prospects of using pAZ vector for the construction of live oral vaccines.

[The principles of creating standard serum panels with a low concentration of HIV-1 antibodies for the quality control of commercial immunoenzyme test systems]. / Printsipy sozdaniia standartnykh panelei syvorotok s nizkoi kontsentratsiei antitel k VICh-1 dlia kontrolia kachestva kommercheskikh immunofermentnykh test-sistem.

The main approaches are defined to the production of sera with the required concentration of antibodies to HIV by the dilution method and to formation on their basis of serum panels according to theoretical distribution of optic density (OD) values. It was shown to be principally possible to prepare panels of positive sera with low concentration of HIV-specific antibodies in a dry stable form, and their practical importance in the evaluation of the sensitivity of enzyme immunoassays was demonstrated. The evaluation of the quality of commercial test systems is based on the position and shape of the histogram of OD values distribution for panel sera for the controlled test systems.