ABSTRACT
The protective properties of nonwoven materials (Spandbond, SMS) used to manufacture 3-5-layer medical masks, by using model physical and bacterial test aerosols, were experimentally assessed. It was shown that the more layers of the materials, the less permeable they became for test aerosols. Three-five-layer masks made from SMS at a density of 42 g/m2 were found to have higher protective properties for oil mist and fine aerosol than those made from Spandbond at a density of 25 g/m2. Five-layer SMS materials at a density of 42 g/m2 have the highest values of bacterial aerosol retention.
Subject(s)
Masks/standards , Occupational Medicine/methods , Polypropylenes , Respiratory Protective Devices/microbiology , Respiratory Protective Devices/standards , Respiratory Tract Diseases/prevention & control , Equipment Design , Filtration , Humans , Infection Control , Occupational Medicine/instrumentation , Serratia marcescens/isolation & purificationABSTRACT
Experimental evaluation of the biological risks of introducing the genetically modified microorganism (GMM) B. subtilis VKPM B-7092, an active ingredient of the probiotic VETOM 1.1, into an open system was performed. The following features of the GMM were studied: the survival rate of the GMM in bovine gastroenteric tract; its influence on the microbiocenosis; the species composition of microflora of the gastroenteric tract of the animal species; the possibility of transfer of the DNA fragment cloned in the B. subtilis bacterium and containing the gene of human leukocyte alpha2 interferon to the representatives of intestinal microflora of animals fed on the probiotic VETOM 1.1, as well as the GMM transfer to other microorganism species spread in the areas of potential getting of the GMM into the environment (soil). The study revealed no negative effects of the GMM on the animal organism and the environment, including remote aftereffects.
Subject(s)
Bacillus subtilis/growth & development , Bacillus subtilis/genetics , Cattle/microbiology , Environment , Interferon-alpha/genetics , Animals , Bacillus subtilis/isolation & purification , Gastrointestinal Tract/microbiology , Gene Transfer, Horizontal , Genetic Engineering , Humans , RiskABSTRACT
The structural and catalytic properties of the phage T4 DNA-(adenine-N6)-methyltransferase (EC 2.1.1.72) were studied at different enzyme-substrate concentration ratios by chemical cross-linking of the protein subunits and by measuring the presteady state kinetics of the reactions. Various structural states of the methyltransferase were correlated with its catalytic activity, and it was shown that the oligomeric forms of the enzyme are catalytically active but are characterized by the reaction parameters different from those of the monomer.
Subject(s)
Bacteriophage T4/enzymology , Biopolymers/chemistry , Site-Specific DNA-Methyltransferase (Adenine-Specific)/metabolism , Base Sequence , Catalysis , DNA PrimersABSTRACT
Conjugates of the distamycin tetrapyrrole analogue containing four pyrrolecaboxamide fragments (MGB) with inosine-containing oligodeoxyribonucleotides were synthesized. The stability of duplexes formed by these conjugates depends on the composition of inosine-containing pairs and decreases in the order: IC > IA > > IT. For the duplexes (d(TTTATATA)p(MGB))2, (d(TTCICICI)p(MGB))2, and (d(TTAIAIAI)p(MGB))2, the melting temperatures are 68, 54, and 35-45 degrees C, respectively; (d(TTTITITI)p(MGB))2 forms no duplexes at temperatures above 4 degrees C. The binding was shown to be highly specific: in the duplex d(GGCATCTA)p(MGB).d(GGTAIATI)p(MGB), the substitution of only one A.T pair by A.A decreases the binding constant by almost three orders of magnitude.
Subject(s)
Distamycins/chemical synthesis , Inosine Nucleotides/chemistry , Oligodeoxyribonucleotides/chemistry , Base Composition , DNA/chemistry , Distamycins/chemistry , Ligands , Nucleic Acid Denaturation , Pyrroles/chemistry , Structure-Activity Relationship , ThermodynamicsABSTRACT
Diastereomers of oligonucleotide ethyl phosphotriesters were separated by high-performance complementary (affinity) chromatography on a column with the immobilized complementary oligonucleotide. The elution buffer contained 0.18 M K2HPO4, pH 7.5, and 30% acetonitrile. The temperature of the separation was a few degrees lower than Tm of corresponding oligonucleotide complexes. The diastereomers separated completely or partially were: d[GCC(Et)AAACA], d[GCCA(Et)AACA], d[GCAA(Et)ACA], d[GCC(Et)A(Et)AACA], d[GCC(Et)AA(Et)ACA], d[GCCA(Et)A(Et)ACA], d[GCC(Et)A(Et)A(Et)ACA].
Subject(s)
Oligonucleotides/chemistry , Organophosphorus Compounds/chemistry , Chromatography, Affinity , Chromatography, High Pressure Liquid , Stereoisomerism , TemperatureABSTRACT
The hemagglutinin gene primary structure of influenza virus A/Riga/9977/86 (H3N2) belonging to the "Coen/84" antigenic subgroup was determined by primer sequencing. A comparative analysis confirmed that the reversions of amino acids in the late stages of the H3 influenza virus subtype antigenic drift became more frequent and the antigenic variants remained in epidemic circulation longer. The possible role of some mutations is discussed.
Subject(s)
Antigenic Variation/genetics , Genes, Viral/genetics , Hemagglutinins, Viral/genetics , Influenza A Virus, H3N2 Subtype , Influenza A virus/genetics , Base Sequence , Molecular Sequence DataABSTRACT
The specificity of DNA methylase M. FokI towards oligonucleotides containing sequence 5'...GGATG.../3'...CCTAC... was investigated, and N6-methyladenine in the GGATG chain was shown to be the only product of the modification.
Subject(s)
DNA Modification Methylases/metabolism , Flavobacterium/enzymology , Base Sequence , Kinetics , Molecular Sequence Data , Substrate SpecificityABSTRACT
The interaction of Eco dam methylase with various synthetic oligonucleotide substrates was investigated. The "imperfect" duplexes contained a normal GATC recognition sequence in one chain of the enzyme recognition site and had some defects in the complementary chain, i.e., the absence of one or several nucleotide residues or the presence of S-methyl thiophosphate groups at the 3'-termini. The 3'-S-methyl thiophosphate residue has the same effect on the methylation of oligonucleotide complexes as does the absence of internucleotide phosphate in the analogous complexes. The presence of both GA dinucleotides in the recognition site is necessary for a productive enzyme-substrate interaction. The experimental data suggest that Eco dam methylase does form a symmetrical enzyme-substrate complex which is similar to that formed by type II restriction enzymes.
Subject(s)
Methyltransferases/metabolism , Oligodeoxyribonucleotides/metabolism , Site-Specific DNA-Methyltransferase (Adenine-Specific) , Base Sequence , Electrophoresis, Polyacrylamide Gel , Methylation , Nucleic Acid Conformation , Oligodeoxyribonucleotides/chemical synthesis , Substrate SpecificityABSTRACT
Kinetic values of the BamHI endonuclease interaction with synthetic oligonucleotides, containing some defects, have been determined. These defects were: the absence of the one internucleotide phosphate in the GGATCC sequence; substitution of a phosphate linkage by a methylphosphonate one; 5'-protruding end of the double-stranded oligonucleotide substrate. Some modifications resulted in the increase of the initial rates of cleavage due to higher Vmax values for these substrates. Several structural defects in the oligonucleotide substrates have been shown to intensity the formation of productive complexes with the enzyme, which can be explained by the significant role of the polynucleotide chain kinks in the recognition process. Studies on oligonucleotides with different defects made it possible to reveal the phosphate groups essential for the interaction with BamHI endonuclease.
Subject(s)
DNA Restriction Enzymes/metabolism , Oligodeoxyribonucleotides/metabolism , Base Sequence , Deoxyribonuclease BamHI , Kinetics , Substrate SpecificityABSTRACT
Oligodeoxyribonucleotides which form a number of duplexes, containing the recognition sequences for endonuclease BamHI and DNA methylase Eco dam, were synthesised by the phosphotriester approach. Furthermore, synthesis of 3'-phosphorylated oligodeoxyribonucleotides from corresponding S-methyl phosphorothioate triester oligomers is described. The synthetic duplexes are characterized by some defects in the recognition sequences for endonuclease BamHI and methylase Eco dam, viz. nick, absence of an internucleotide phosphate, modifications (including partial single-strandedness) of the recognition site. Interaction of the enzymes with these synthetic substrates was investigated.
Subject(s)
DNA Restriction Enzymes/metabolism , Methyltransferases/metabolism , Oligodeoxyribonucleotides/metabolism , Base Sequence , Chromatography, High Pressure Liquid , Deoxyribonuclease BamHI , Oligodeoxyribonucleotides/chemical synthesis , Site-Specific DNA-Methyltransferase (Adenine-Specific) , Substrate SpecificityABSTRACT
Synthetic oligodeoxyribonucleotides, containing one or two ribonucleotides in the recognition sequence, and RNA--DNA hybrids were tested for their activity in cleavage with BamH1 and Sau3A endonucleases. The replacement of dG with G in the first position of BamH1-site (GGATCC) of one of the chains does not affect the rate of the BamH1 hydrolysis. The similar heteroduplex, containing G residue in the second position, displays a decreased rate of the BamH1 hydrolysis of the modified strand and, to a lesser extent, of the unmodified complementary strand. Oligodeoxyribonucleotides in complex with oligoribonucleotides can be cleaved with the excess of BamH1 and Sau3A, oligoribonucleotides remaining intact.
Subject(s)
DNA Restriction Enzymes , DNA , Deoxyribonucleases, Type II Site-Specific , Nucleic Acid Hybridization , RNA , Base Sequence , Deoxyribonuclease BamHI , Hydrolysis , Oligodeoxyribonucleotides/chemical synthesis , Substrate SpecificityABSTRACT
Interaction of Ecodam methylase (E.C. 2.1.1) with synthetic oligonucleotide substrates of various primary structure was studied by the small angle X-ray scattering method. Complex formation between the enzyme and substrates occurs after addition of double-stranded oligonucleotides to the methylase. In the presence of 1 M NaC1 (when the enzyme is inactive) addition of the synthetic substrates does not result in complex formation. Comparison of the experimental scattering parameters with the calculated ones has been made. The best coincidence of these data is obtained for the model which proposed Ecodam methylase dimer formation in the course of its interaction with the substrates.
