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  • Springer  (51)
  • Institute of Physics  (20)
  • Wiley-Blackwell  (3)
  • American Physical Society (APS)  (2)
  • Blackwell Science Ltd  (2)
  • American Association for the Advancement of Science (AAAS)  (1)
  • 1
    Electronic Resource
    Electronic Resource
    RdgB acts to avoid chromosome fragmentation in Escherichia coli (2003)
    Oxford, UK : Blackwell Science Ltd
    Molecular microbiology 48 (2003), S. 0 
    Details
    ISSN: 1365-2958
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology , Medicine
    Notes: Bacterial RecA protein is required for repair of two-strand DNA lesions that disable whole chromosomes. recA mutants are viable, suggesting a considerable cellular capacity to avoid these chromosome-disabling lesions. recA-dependent mutants reveal chromosomal lesion avoidance pathways. Here we characterize one such mutant, rdgB/yggV, deficient in a putative inosine/xanthosine triphosphatase, conserved throughout kingdoms of life. The rdgB recA lethality is suppressed by inactivation of endonuclease V (gpnfi) specific for DNA-hypoxanthines/xanthines, suggesting that RdgB either intercepts improper DNA precursors dITP/dXTP or works downstream of EndoV in excision repair of incorporated hypoxathines/xanthines. We find that DNA isolated from rdgB mutants contains EndoV-recognizable modifications, whereas DNA from nfi mutants does not, substantiating the dITP/dXTP interception by RdgB. rdgB recBC cells are inviable, whereas rdgB recF cells are healthy, suggesting that chromosomes in rdgB mutants suffer double-strand breaks. Chromosomal fragmentation is indeed observed in rdgB recBC mutants and is suppressed in rdgB recBC nfi mutants. Thus, one way to avoid chromosomal lesions is to prevent hypoxanthine/xanthine incorporation into DNA via interception of dITP/dXTP.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1046/j.1365-2958.2003.03540.x
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  • 2
    Electronic Resource
    Electronic Resource
    Chromosomal fragmentation in dUTPase-deficient mutants of Escherichia coli and its recombinational repair (2004)
    Oxford, UK : Blackwell Science Ltd
    Molecular microbiology 51 (2004), S. 0 
    Details
    ISSN: 1365-2958
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology , Medicine
    Notes: Recent findings suggest that DNA nicks stimulate homologous recombination by being converted into double-strand breaks, which are mended by RecA-catalysed recombinational repair and are lethal if not repaired. Hyper-rec mutants, in which DNA nicks become detectable, are synthetic-lethal with recA inactivation, substantiating the idea. Escherichia coli dut mutants are the only known hyper-recs in which presumed nicks in DNA do not cause inviability with recA, suggesting that nicks stimulate homologous recombination directly. Here, we show that dut recA mutants are synthetic-lethal; specifically, dut mutants depend on the RecBC–RuvABC recombinational repair pathway that mends double-strand DNA breaks. Although induced for SOS, dut mutants are not rescued by full SOS induction if RecA is not available, suggesting that recombinational rather than regulatory functions of RecA are needed for their viability. We also detected chromosomal fragmentation in dut rec mutants, indicating double-strand DNA breaks. Both the synthetic lethality and chromosomal fragmentation of dut rec mutants are suppressed by preventing uracil excision via inactivation of uracil DNA-glycosylase or by preventing dUTP production via inactivation of dCTP deaminase. We suggest that nicks become substrates for recombinational repair after being converted into double-strand DNA breaks.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1365-2958.2003.03924.x
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  • 3
    Electronic Resource
    Electronic Resource
    Precise measurement of 14C beta spectrum by using a wall-less proportional counter (2000)
    Springer
    Physics of atomic nuclei 63 (2000), S. 1292-1296 
    Details
    ISSN: 1063-7788
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract The technique and results of a precise measurement of the 14C beta spectrum in the energy range 10–160 keV by using a wall-less proportional counter are presented. The results of analysis and the inclusion of possible factors that distort the spectrum in the calculation of the detector response function are reported. Considerable deviations from the distribution expected for an allowed transition are found.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1134/1.855786
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  • 4
    Electronic Resource
    Electronic Resource
    New limit on the half-life of 78Kr with respect to the 2K(2ν)-capture decay mode (2000)
    Springer
    Physics of atomic nuclei 63 (2000), S. 2201-2204 
    Details
    ISSN: 1063-7788
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract The features of data accumulated for 1817 h in an experimental search for the 2K(2ν)-capture mode of 78Kr decay are discussed. A new limit on the half-life for this decay is found: T 1/2≥2.3×1020 yr (at a 90% C.L.).
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1134/1.1333889
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  • 5
    Electronic Resource
    Electronic Resource
    Resonant formation of ddµ molecular ions (1996)
    Springer
    Hyperfine interactions 101-102 (1996), S. 197-205 
    Details
    ISSN: 1572-9540
    Keywords: mesomolecule ; resonance ; ddµ ; fusion rate ; spin flip
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract Calculations of the ddµ formation rate were performed beyond the dipole approximation. In the temperature rangeT=25–150 K the results are in good agreement with the Vienna-PSI fusion rate data. The calculated spin flip rate is also closer to experiment than in the dipole approximation. New experiments for the verification of the finite width theory are discussed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02227623
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  • 6
    Electronic Resource
    Electronic Resource
    Intense thermal neutron source based on MCF (1996)
    Springer
    Hyperfine interactions 101-102 (1996), S. 655-659 
    Details
    ISSN: 1572-9540
    Keywords: muon ; fusion ; thermal neutrons ; reactor
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract The conceptual scheme of an ecologically clean thermal neutron source (TNS) based on muon-catalyzed fusion (MCF) is proposed. The preliminary design shows that an MCF-based TNS can produce the maximum value of unperturbed thermal neutron flux 1015 n/cm2 s using for muon production a beam power of about 14 MW supplied by an accelerator of the next generation.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02227679
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  • 7
    Electronic Resource
    Electronic Resource
    Fuel breeding in a hybrid muon catalyzed fusion reactor (1993)
    Springer
    Hyperfine interactions 82 (1993), S. 445-458 
    Details
    ISSN: 1572-9540
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract We discuss the processes of nuclear fuel burnup and plutonium breeding in the uranium blanket of a hybrid mesocatalytic reactor. The time dependence of the nuclear fuel isotopic concentrations was calculated by the BURNFL code. Using a three-dimensional Monte Carlo MORSE-H code the plutonium and tritium breeding coefficients, the fission rates of uranium and plutonium and a specific power distribution in the blanket were computed. The total fusion energy multiplication factor was obtained as a function of the fuel residence time using results of a detailed calculation of the mesocatalytic channel and estimations of the electronuclear channel.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01027979
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  • 8
    Electronic Resource
    Electronic Resource
    Repair of uracil residues closely spaced on the opposite strands of plasmid DNA results in double-strand break and deletion formation (1991)
    Springer
    Molecular genetics and genomics 225 (1991), S. 448-452 
    Details
    ISSN: 1617-4623
    Keywords: Plasmid DNA ; Uracil repair ; Doublestrand breaks ; Deletions
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary The role of closely spaced lesions on both DNA strands in the induction of double-strand breaks and formation of deletions was studied. For this purpose a polylinker sequence flanked by 165 by direct repeats was inserted within the tet gene of pBR327. This plasmid was used to construct DNA containing one or two uracil residues which replaced cytosine residues in the Kpnl restriction site of the polylinker. Incubation of the plasmid DNA construct with Escherichia coli cell-free extracts showed that double-strand breaks occurred as a result of excision repair of the opposing uracil residues by uracil-DNA glycosylase (in extracts from ung + but not in extracts from ung − E. coli strains). Recombination of direct repeats, induced by double-strand breakage of plasmid DNA, can lead to the deletion of the polylinker and of one of the direct repeats, thus restoring the tet + gene function which can be detected by the appearance of tetracycline-resistant colonies of transformants. Transformation of E. coli cells with single or double uracil-containing DNAs demonstrated that DNA containing two closely spaced uracil residues was tenfold more effective in the induction of deletions than DNA containing only a single uracil residue. The frequency of deletions is increased tenfold in an ung + E. coli strain in comparison with an ung − strain, suggesting that deletions are induced by double-strand breakage of plasmid DNA which occurs in vivo as a result of the excision of opposing uracil residues.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00261686
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  • 9
    Electronic Resource
    Electronic Resource
    Molecular mechanisms of deletion formation in Escherichia coli plasmids (1991)
    Springer
    Molecular genetics and genomics 228 (1991), S. 153-159 
    Details
    ISSN: 1617-4623
    Keywords: Deletion ; Direct repeats ; Plasmid recombination ; Unequal crossing-over ; RecA-dependence
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary Derivatives of plasmid pBR327 with the tet gene interrupted by 165 pb or 401 by direct repeats were constructed. In cells harboring these plasmids, deletions which restored the wild-type tet gene gave rise to tetracycline-resistant colonies, thereby allowing a simple phenotypic test for deletion formation. The frequencies of deletions in these plasmids were measured in Escherichia coli strains proficient or deficient in general recombination. The structure of plasmid DNA isolated from tetracycline-resistant transformants was analyzed by agarose gel electrophoresis, restriction mapping and sequencing. The data presented here demonstrate that deletion formation is always associated with dimerization of plasmid DNA. Dimeric plasmids were of two types. Those which carried both a deletion and a compensating duplication were the major type in a Rec+ background and were rare in recA, recF, recJ and recO backgrounds. Dimers of the second type contained deletions, but no compensating duplications, and their formation was RecA-independent. The data presented demonstrate that deletion formation mediated by long direct repeats is mainly the result of unequal crossing-over between two plasmid molecules.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00282460
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  • 10
    Electronic Resource
    Electronic Resource
    Mechanisms of deletion formation in Escherichin coli plasmids (1991)
    Springer
    Molecular genetics and genomics 228 (1991), S. 209-214 
    Details
    ISSN: 1617-4623
    Keywords: Deletion ; Direct repeats ; Escherichia coli plasmids ; Plasmid recombination
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary A set of plasmids containing 42, 21 and 13 bp direct repeats was used to analyze the effect of repeat length on the frequencies of deletion formation and the structure of the deleted derivatives of different recombination-deficient Escherichia coli strains. Agarose gel electrophoresis of plasmid DNA demonstrated that the formation of deletions in these plasmids was associated with dimerization of plasmid DNA. Restriction analysis of the dimers showed that deletions at short direct repeats arose non-conservatively, that is, the formation of a deletion in one monomeric plasmid unit was not associated with a duplication in the other. Mutations in the recA, recF, recJ and recO genes had no marked effect on either the frequencies of deletion formation or the structure of dimers. In contrast, recB recC mutations greatly increased the frequencies of deletion formation, 6-fold for 42 bp, and 115-fold for 21 by direct repeats. Conversion of DNA replication to the rolling circle mode in a recB recC strain, resulting in the formation of double-stranded ends, is suggested as the stimulatory effector.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00282467
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