Theoretical and experimental study of DNA helix-coil transition in acidic and alkaline medium.

The theoretical approach to the calculation of the influence of selective binding of small ligands on DNA helix-coil transition has been described in the previous paper (Lando D. Yu., J. Biomol. Struct. Dyn., (1994)). In the present paper that method is used for the study of DNA protonation and deprotonation in acidic and alkaline medium by theoretical analysis of pH effect on DNA heat denaturation. The mechanism of DNA protonation in acidic medium and pK values of nucleotides are well known. It gave us an opportunity to check the theory without any fitting of pK values. A good agreement between experimental and calculated functions Tm(pH) and delta T(pH) (melting temperature and melting range width) obtained for acidic medium proved the validity of the theory. However, for alkaline medium there was not even qualitative agreement when the agreed-upon mechanism of deprotonation was considered. Looking into the cause of the discrepancy, we have studied the DNA melting for different mechanisms of deprotonation by calculation of Tm(pH) and delta T(pH). As a result, it has been established that the discrepancy is due to deprotonation of bonded GC base pairs of helical DNA regions (pK = 11). It was shown that the early known protonation and newly found deprotonation of helical DNA essentially stabilised double helix in alkaline and acidic medium.

[Dependence of the melting temperature of phage DNA on the GC pair content in a solvent with low ionic strength]. / Zavisimost' temperatury plavleniia fagovykh DNK v rastvoritele s nizkoi ionnoi siloi ot soderzhaniia GC-par.

Base ratio of DNA from 21 bacteriophage of Pseudomonas was determined by chemical hydrolysis and paper chromatography. Obtained values of the GC pair content were compared with melting temperature of DNA in 0,1 X SSC. The content of GC pairs correlates with melting temperature by equation %GC = 2,53 (Tm - 53,4). The content of GC pair for DNA from 30 bacteriophages of Pseudomonas was calculated. Some speculations concerning the distribution in DNA base ratio of bacteriophages of Pseudomonas are discussed.

[Restriction analysis of DNA from phage SM of Pseudomonas aeruginosa]. / Restrictaznyi analiz DNK faga SM Pseudomonas aeruginosa.

The DNA of temperate phage SM P. aeruginosa has one PvuII site, two BamHI sites, three HindIII sites and five EcoRI sites. Using these restrictases the physical map of the phage genome has been constructed. The DNA of phage SM has in their structure cohesive ends similar to cos-sites of phage lambda DNA. EcoRI-fragments with cohesive ends have molecular masses 2.9 and 4.9 MDa.

[Effect of selectively reacting ligands on the helix-coil transition of DNA. IV. Heat denaturation of DNA in an acid medium]. / Vliianie ligandov s izbiratel'nym kharakterom vzaimodeistviia na perekhod spiral'-klubok DNK. IV. Teplovaia denaturatsiia DNK v kisloi srede.

The DNA thermal denaturation in acidic medium has been investigated experimentally and theoretically. The formulae describing a dependence of the helix--coil transition parameters (melting temperature (Tm) and melting range width (delta T) on ionisation constants values of all kinds of DNA bases in the helix and coil regions and medium acidity have been obtained. Dependences Tm (pH) and delta T (pH) have been determined experimentally and calculated for different models of protonation. Based on the comparison of theoretical and experimental dependences Tm (pH) and delta T (pH) a strict examination of the theory is conducted. The mechanism of DNA protonation is discussed.

[Isolation and characteristics of plasmids from Aeromonas]. / Vydelenie i kharakteristika plazmid bakterii Aeromonas.

Fourteen out of fifty-two examined strains of Aeromonas contain plasmids. One of them determines the resistance to tetracycline, streptomycin, and chloramphenicol. The pAs30 plasmid, 53 t. n. p. in size, is capable of conjugative transfer to bacteria of different genera, which permits us to consider it a broad host range plasmid. Using 12 restriction endonucleases, the physical map of the plasmid was plotted, on which the genes responsible for transporting functions and streptomycin resistance were tentatively located.

[Conjugative R-plasmid of facultative methylotrophic bacteria Pseudomonas sp. M]. / Kon''iugativnaia R-plazmida fakul'tativnykh metilotrofnykh bakterii Pseudomonas sp. M.

50 Md conjugative plasmid, designated pM3, has been found in the cells from natural isolates of Pseudomonas sp M. The plasmid determines the resistance to tetracycline and streptomycin and is capable of conjugative transfer between the cells of Pseudomonas and Escherichia coli. The conjugative derivatives of pM3 deleted for 14 Md of molecular mass were isolated after acridine dyes treatment of cells harbouring plasmid pM3. The discovered plasmid was not shown to belong to IncP1 incompatibility group.

[The effect of R-plasmids on the reproduction of Pseudomonas aeruginosa phage SM]. / Vliianie R-plazmid na reproduktsiiu faga SM Pseudomonas aeruginosa.

The inheritance of plasmids Rms163 and R74 by Pseudomonas aeruginosa strain PAO hs been shown to effect the reproduction of a temperature bacteriophage SM. The decrease in plating efficiency of bacteriophage on Pseudomonas aeruginosa PAO (rms163) lawn is explained by the high degree of cell lysogenization by bacteriophage. Plasmid R74 inhibits bacteriophage SM propagation ultimately, evidently due to interruption of definite stages in vegetative development of bacteriophage by the products of plasmid specific genes.

[Temperate SM phage from Pseudomonas aeruginosa as a vector for cloning genetic information]. / Umerennyi fag SM Pseudomonas aeruginosa kak vektor dlia klonirovaniia geneticheskoi informatsii.

The recombinant bacteriophages with the genomes containing the DNA fragments of bacteria Erwinia chrysanthemi, including the pectatelyase gene, were constructed on the base of Pseudomonas aeruginosa temperate bacteriophage SM. The gene transferred into Pseudomonas aeruginosa PAO1 cells by transfection is expressed in the new bacterial host. The restriction maps of the recombinant bacteriophages are constructed and the position of an insert is defined. Bacteriophage SM was found to be capable of reproducing in Pseudomonas aeruginosa PAO1 cells when its DNA was shortened to 88% or increased to 111% of the normal genome length. Except for bacteriophage SM, the recombinant bacteriophage SM-2 with an unique restriction endonuclease site for XbaI can also be used as a vector for cloning. Bacteriophage SM capacity in cloning of heterological DNA at HindIII sites is not less than 8 Md, capacity of bacteriophage SM-2 is not less than 5 and 8 Md at XbaI and HindIII sites respectively.

[Localization of prophage SM of Pseudomonas aeruginosa in the chromosome of host cells]. / Lokalizatsiia profaga SM Pseudomonas aeruginosa v khromosome kletok-khoziaev.

Pseudomonas aeruginosa PAO SM-prophage was localized on the chromosome between thr-9001 and pur-66 locuses on 42-43 min of chromosomal genetic map. The location of prophage was identified on the basis of prophage linkage with the above-mentioned markers and confirmed by the purine, hypoxanthine and threonine deletions in course of thermoinduction of SM cts6 prophage from lysogens. The decrease for two orders in lysogenization frequency of thr mutants by SM bacteriophage suggests the integration of SM prophage in these cells into some other region of chromosome.

[Transducing activity of the temperate SM bacteriophage of Pseudomonas aeruginosa]. / Transdutsiruiushchaia aktivnost' umerennogo bakteriofaga SM Pseudomonas aeruginosa.

The temperate bacteriophage SM is not serologically related to the known transducing phages F116, G101, B3 of Pseudomonas aeruginosa. The strains with auxotrophic mutations within the wide ranges of the genetic map of P. aeruginosa strain PAO1 were used for studying the transducing activity of the SM phage. All of the 7 bacterial markers tested are transduced with SM phage grown on a prototrophic donor strain. The frequency of transduction of separate bacterial markers using the wild type SM phage is 2.3 to 4.6 X 10(-8). Linked ilv202+ - met28+ markers are cotransduced with SM phage at a frequency of about 1.5%.

[The role of te transposition of Tn1000 from Flac+-plasmid into chromosome of Erwinia chrysanthemi in the formation of Hfr-type donors]. / Rol' transpozitsii Tn1000 iz Flac+-plazmidy v khromosomu Erwinia chrysanthemi v formirovanii donorov Hfr-tipa.

Based on the data of stability of the donor state of Hfr-like strain Erwinia chrysanthemi VY1-10 in RecA+ and RecA- cells, it can be suggested that the donor properties of the strain are mediated by the presence of the genetic homology region which occurred as a result of transposition of the Tn1000 from the Flac+ plasmid into the chromosome of E. chrysanthemi. Tn1000 may be transposed into several sites on the chromosome of E. chrysanthemi ENA49. This leads to the appearance of donors transferring their chromosome from several fixed points oriT and in opposite directions. The location of these points and the direction of transfer are determined by Tn1000 insertion sites and their orientation.

[Complementation and the physiological characteristics of the ts mutants of Pseudomonas aeruginosa phage SM]. / Komplementatsiia i fiziologicheskaia kharakteristika ts-mutantov faga SM Pseudomonas aeruginosa.

Seventy three temperature-sensitive mutants of Pseudomonas aeruginosa SM phage have been obtained using different mutagens and assigned to thirteen complementation groups. Representative mutants of each group have been studied with the aim of characterizing tentatively the time of genes expression in infected bacteria. Two genes appear to function during the first minutes after infection, whereas the remaining genes are needed for late functions. Most of the temperature-sensitive functions in the different mutants are reversible, i.e. they become active when the infected cells are shifted-down to the permissive temperature.

[Control of lysogeny and a genetic map of the temperate phage SM of Pseudomonas aeruginosa]. / Kontrol' lizogenizatsii i geneticheskaia karta umerennogo faga SM Pseudomonas aeruginosa.

76 mutants with impaired ability to lysogenize host cells were isolated in SM phage after mutagenesis using several chemical mutagens. By means of complementation test, these mutants were distributed into two groups, cI and cII. The mutants of the cI group were similar phenotypically to the cI mutants of phage lambda defective in synthesis of repressor. The mutants of the cII group establish and support the lysogenic state in infected cells with very low frequency. Temperature-sensitive mutants belonging to 13 complementation groups and nonlysogenizing mutants of the cI and cII groups were used in genetic mapping of SM phage. Mutual positions of markers and relative distances between them were determined by the method of two-factorial crosses. The greatest distance equal to 20 units of recombination was determined between ts 88 marker and one of early genes marked with ts 105 mutation. The genes cI and cII are closely linked to each other and also to ts 105 marker and are situated at one end of the genetic map.

[Pseudomonas putida PpG1 resistance to different bacteriophages]. / Izuchenie ustoichivosti Pseudomonas putida PgG1 k razlichnym bakteriofagam.

Cris-cross resistance analysis has been accomplished for some Pseudomonas putida PpG1 mutants resistant to pf16, af, tf and PMW phages. On the basis of the results, a formal scheme of the receptor sites for these phages on the bacterial cell surface was drawn. Study of the sensitivity of P. putida PpG1 phage-resistant mutants an unexpected phenomenon. Some of the phages specific to P. putida B-21 and B-31 which did not adsorb on the PpG1 strain acquired the ability on certain types of the PpG1 phage resistant mutants. Mutants of P. putida B-21 and B-21 resistant to specific phages did not maintain the growth of pf16, af, tf or PMW phages.

[Spectroscopic and photochemical properties of pigments bound to proteins]. / Spektroskopicheskie i fotokhimicheskie svoistva pigmentov, sviazannykh s belkom.

Using gel-filtration and spectral-luminescent analysis properties of artificial chlorophyll-protein and chlorine-protein complexes on the basis of human serum albumin (HSA) were analysed. It has been shown that formation of joint complexes pigments - HSA does not induce essential changes in the spectral and energetic parameters of the pigment part of the complex. A change in the rate of photosensitized reduction of methylviologen (sensitizer-pigment) was found during the variation of the relative content of the pigment mixed with HSA. An increase of the photoreaction rate during maximal filling of the protein globule with pigment molecules is explained by different pattern of incorporation of these molecules into protein matrix.

[Biological properties and DNA nucleotide makeup of Pseudomonas bacteriophages]. / Biologicheskie svoistva i nukleotidnyi sostav DNK bakteriofagov Pseudomonas.

Fifty-two bacteriophages active against Pseudomonas bacteria were isolated from nautral sources and their following properties were studied: the morphology of negative colonies, the spectrum of lytic action, and the susceptibility to certain chemical and physical factors. One phage was shown to contain lipids. The content of GC pairs in the DNA of the phages determined from the melting temperature varied within the range of 46 to 67%.