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  • 1
    Electronic Resource
    Electronic Resource
    Aspects of the reproductive ecology of four australian Hakea species (Proteaceae) in South Africa (1987)
    Springer
    Oecologia 71 (1987), S. 345-354 
    Details
    ISSN: 1432-1939
    Keywords: Hakea ; Invasion ; Reproduction ; Germination ; Seed dispersal ; Fire
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary Four shrub species of the Australian Proteaceae (Hakea sericea, H. gibbosa, H. suaveolens and H. salicifolia) were introduced to South African fynbos shrublands between 1840 and 1860. H. sericea is highly invasive, H. gibbosa and H. suaveolens are moderately invasive and H. salicifolia is not invasive. The allocation of reproductive energy, germinability, the ability to survive fires and to germinate in burnt and unburnt areas, and the nutrient content of seeds were assessed for the four species. The information was used to investigate whether the success of H. sericea relative to the other three species could be explained by the superior expression of any trait. The most important trait which separates H. sericea from the other species is its ability to produce a large seed bank in its adopted environment in the absence of seed predators. Seed production in H. sericea shrubs with an above-ground dry mass of 8 kg is four times greater than H. gibbosa and more than 16 times that of H. suaveolens. Although H. salicifolia also produces a large seed bank, its seeds are unable to survive fires due to inadequate insulation by the small follicles. The results are compared to dispersal and seed bank data for indigenous South African Proteaceae, which have low dispersal and suffer high pre-dispersal seed predation. We suggest that potential invasives in the fynbos can be identified as species that have: (i) a potentially high seed production that is limited by specialized predators; (ii) an ability to disperse over long distances; and (iii) are pre-adapted to frequent fires and low soil nutrients. The data also support the current strategy of combatting H. sericea using specialized insect seed predators.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00378706
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  • 2
    Electronic Resource
    Electronic Resource
    ATR/ATM-mediated phosphorylation of human Rad17 is required for genotoxic stress responses (2001)
    [s.l.] : Macmillian Magazines Ltd.
    Nature 411 (2001), S. 969-974 
    Details
    ISSN: 1476-4687
    Source: Nature Archives 1869 - 2009
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
    Notes: [Auszug] Genotoxic stress triggers the activation of checkpoints that delay cell-cycle progression to allow for DNA repair. Studies in fission yeast implicate members of the Rad family of checkpoint proteins, which includes Rad17, Rad1, Rad9 and Hus1, as key early-response elements during the activation ...
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1038/35082110
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  • 3
    Electronic Resource
    Electronic Resource
    Isolation of transposon Tn5 insertion mutants of Rhodobacter capsulatus unable to reduce trimethylamine-N-oxide and dimethylsulphoxide (1988)
    Springer
    Archives of microbiology 150 (1988), S. 138-144 
    Details
    ISSN: 1432-072X
    Keywords: Photosynthetic bacteria (Rhodobacter capsulatus) ; Transposon mutagenesis ; TMAO reduction ; DMSO reduction ; Anaerobic respiration ; Electron transport
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract 1) Rhodobacter capsulatus (formerly Rhodopseudomonas capsulata) strain 37b4 was subjected to transposon Tn5 mutagenesis. 2) Kanamycin-resistant transconjugants were screened for their inability to reduce trimethylamine-N-oxide (TMAO) as judged by the lack of alkali production during anaerobic growth on plates containing glucose as carbon source and cresol red as pH indicator. 3) Of 6 mutants examined, all were found to have considerably decreased levels of methylviologen-dependent TMAO reductase activity and dimethylsulphoxide (DMSO) reductase activity. 4) Periplasmic fractions of one of these mutants (DK9) and of the parent strain were subjected to sodium dodecylsulphate polyacrylamide gel electrophoresis. The gels were stained for TMAO-reductase and DMSO-reductase. With the wild-type strain, only a single polypeptide band, Mr=46,000, stained for TMAO and DMSO reductase activity. In mutant DK9 this band was not detectable. 5) In contrast to the parent strain, harvested washed cells of mutant DK9 were unable to generate a cytoplasmic membrane potential in the presence of TMAO or DMSO under dark anaerobic conditions. 6) In contrast to the parent strain, DK9 was unable to grow in dark anaerobic culture with fructose as the carbon source and TMAO as oxidant.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00425153
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  • 4
    Electronic Resource
    Electronic Resource
    Inhibitory effects of myxothiazol and 2-n-heptyl-4-hydroxyquinoline-N-oxide on the auxiliary electron transport pathways of Rhodobacter capsulatus (1986)
    Springer
    Archives of microbiology 146 (1986), S. 159-165 
    Details
    ISSN: 1432-072X
    Keywords: Rhodobacter capsulatus ; Nitrate reduction ; Auxiliary electron transport ; Myxothiazol ; 2-n-heptyl-4-hydroxyquinoline-N-oxide ; Ubiquinone pool
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The effects of various electron transport inhibitors upon the rates of reduction NO 3 - , dimethyl sulphoxide (DMSO) and N2O in anaerobic suspensions of Rhodobacter capsulatus have been studied. A new method for the determination of the rates of reduction of these auxiliary oxidants in intact cells is presented, based on the proportionality observed between the concentration of oxidant and the duration of the electrochromic carotenoid bandshift. For NO 3 - and N2O good agreement was found between rates of reduction determined using electrodes and those determined by the electrochromic method. Myxothiazol and antimycin A had no effect on the rates of reduction of NO 3 - and DMSO suggesting that the cytochrome b/c 1complex is not involved in electron transport to these oxidants. 2-n-heptyl-4-hydroxyquinoline-N-oxide (HOQNO) inhibited at two sites, one within the cytochrome b/c 1complex and the other on the nitrate reducing pathay, but had no effect on electron transport to N2O or DMSO. In both intact cells and cell free extracts, HOQNO had no effect on the nitrate dependent re-oxidation of reduced methylviologen (MVH2), a direct electron donor to nitrate reductase. Our data are consistent with a branch point for the auxiliary electron transport pathways at the level of the ubiquinone pool.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00402344
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  • 5
    Electronic Resource
    Electronic Resource
    Identification of an assimilatory nitrate reductase in mutants of Paracoccus denitrificans GB17 deficient in nitrate respiration (1997)
    Springer
    Archives of microbiology 167 (1997), S. 61-66 
    Details
    ISSN: 1432-072X
    Keywords: Key words Nitrate assimilation ; Nitrate reductase ; Paracoccus denitrificans ; Thiosphaera pantotropha
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract A Paracoccus denitrificans strain (M6Ω) unable to use nitrate as a terminal electron acceptor was constructed by insertional inactivation of the periplasmic and membrane-bound nitrate reductases. The mutant strain was able to grow aerobically with nitrate as the sole nitrogen source. It also grew anaerobically with nitrate as sole nitrogen source when nitrous oxide was provided as a respiratory electron acceptor. These growth characteristics are attributed to the presence of a third, assimilatory nitrate reductase. Nitrate reductase activity was detectable in intact cells and soluble fractions using nonphysiological electron donors. The enzyme activity was not detectable when ammonium was included in the growth medium. The results provide an unequivocal demonstration that P. denitrificans can express an assimilatory nitrate reductase in addition to the well-characterised periplasmic and membrane-bound nitrate reductases.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s002030050417
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  • 6
    Electronic Resource
    Electronic Resource
    Low Reynolds number flow inside straight micro channels with irregular cross sections (2000)
    Springer
    Heat and mass transfer 36 (2000), S. 187-193 
    Details
    ISSN: 1432-1181
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Abstract This paper presents an analysis of the compound effect of finite temperature differences and fluid friction on the existence of an optimum laminar flow regime in singly connected micro channels with complex free flow area cross sections. A widespread conviction has been established that the two competing irreversibility sources in a channel flow with heat transfer lead to the existence of an optimum flow regime. The results presented in this paper clearly shows the opposite. When an objective function is represented by the entropy generation rate per unit heat capacity rate of the fluid stream, the thermodynamic optimum flow regime represents a rather rare occurrence in the laminar region of irregularly shaped ducts. The presence of an extremum is more probable for very small diameters, the ones of an order of magnitude of O(≤10−3 m). The analysis is performed for selected ranges of relevant geometric, flow, and thermal parameters of a set of straight micro channels with irregular free flow area cross-sections. The following geometries of the free flow area cross section were investigated: (i) sine duct, (ii) circular duct, (iii) elliptical duct, (iv) moon-shaped ducts, and (v) four-cuspped duct. The range of Reynolds numbers has been established between O(102) and O(104). The existence of the objective function minimum is confirmed for ducts with an irregular cross section only for very small hydraulic diameters. These minima are relatively weak, and as a general rule, the sets of optimum parameters are close to the onset of turbulence or possibly even in the transitional or turbulent regions.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s002310050383
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  • 7
    Electronic Resource
    Electronic Resource
    Hydroxylamine oxidation in heterotrophic nitrate-reducing soil bacteria and purification of a hydroxylamine-cytochrome c oxidoreductase from a Pseudomonas species (1997)
    Springer
    Archives of microbiology 166 (1997), S. 421-424 
    Details
    ISSN: 1432-072X
    Keywords: Key words Nitrification ; Hydroxylamine-cytochrome c oxidoreductase ; Ammonia monooxygenase ; Denitrification ; Pseudomonas sp.
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Hydroxylamine oxidation was measured in four recently isolated heterotrophic nitrate-reducing bacteria belonging to the genera Pseudomonas, Moraxella, Arthrobacter and Aeromonas. A hydroxylamine-cytochrome c oxidoreductase activity was detected in periplasmic fractions of the Pseudomonas and Aeromonas spp. and in total soluble fractions of the Arthrobacter sp. A monomeric 19-kDa non-haem iron hydroxylamine-cytochrome c oxidoreductase was purified from the Pseudomonas species and shown to be similar to hydroxylamine-cytochrome c oxidoreductase of Paracoccus denitrificans.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01682991
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  • 8
    Electronic Resource
    Electronic Resource
    Dimethylsulphoxide and trimethylamine-N-oxide as bacterial electron transport acceptors: use of nuclear magnetic resonance to assay and characterise the reductase system in Rhodobacter capsulatus (1987)
    Springer
    Archives of microbiology 149 (1987), S. 47-51 
    Details
    ISSN: 1432-072X
    Keywords: Rhodobacter capsulatus ; Nuclear magnetic resonance assay ; Dimethyl sulphoxide ; Dimethyl sulphide ; Trimethylamine-N-oxide ; Trimethylamine ; Electron transport
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Nuclear magnetic resonance is established as a sensitive and specific method for following the reduction of dimethylsulphoxide and trimethylamine-N-oxide by bacteria. Using this method it has been shown that cells of Rhodobacter capsulatus reduce both dimethylsulphoxide and trimethylamine-N-oxide at linear rates at all concentrations of these acceptors that can be conveniently detected during a continuous assay. The rate of reduction of trimethylamine-N-oxide was eightfold higher than the rate of dimethylsulphoxide reduction. An upper limit of approximately 0.1 mM may be placed upon the apparent K m value for each acceptor, but the value for dimethylsulphoxide is deduced to be lower than that for trimethylamine-N-oxide on the basis of the strong inhibitory effect of the former on the reduction of the latter. Reduction of trimethylamine-N-oxide by Rb. capsulatus was inhibited by illumination and by oxygen, but only the former effect was relieved following dissipation of the proton electrochemical gradient across the cytoplasmic membrane. Rotenone inhibited the reduction of trimethylamine-N-oxide whereas myxothiazol did not, consistent with a pathway of electrons to the reductase from NADH dehydrogenase that does not involve the cytochrome bc 1complex.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00423135
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  • 9
    Electronic Resource
    Electronic Resource
    Crystal and molecular structure of 2-hydroxy-1-naphthaldehyde isonicotinoyl hydrazone (NIH) and its iron(III) complex: an iron chelator with anti-tumour activity (1999)
    Springer
    JBIC 4 (1999), S. 266-273 
    Details
    ISSN: 1432-1327
    Keywords: Key words Crystal structure ; Iron chelators ; Anti-tumour agent
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology
    Notes: Abstract  Previous studies have demonstrated that 2-hydroxy-1-naphthaldehyde isonicotinoyl hydrazone (NIH) and several other aroylhydrazone chelators possess anti-neoplastic activity due to their ability to bind intracellular iron. In this study we have examined the structure and properties of NIH and its FeIII complex in order to obtain further insight into its anti-tumour activity. Two tridentate NIH ligands deprotonate upon coordination to FeIII in a meridional fashion to form a distorted octahedral, high-spin complex. Solution electrochemistry of [Fe(NIH–H)2]+ shows that the trivalent oxidation state is dominant over a wide potential range and that the FeII analogue is not a stable form of this complex. The fact that [Fe(NIH–H)2]+ cannot cycle between the FeII and FeIII states suggests that the production of toxic free-radical species, e.g. OH . or O2 . –, is not part of this ligand's cytotoxic action. This suggestion is supported by cell culture experiments demonstrating that the addition of FeIII to NIH prevents its anti-proliferative effect. The chemistry of this chelator and its FeIII complex are discussed in the context of understanding its anti-tumour activity.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s007750050312
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  • 10
    Electronic Resource
    Electronic Resource
    An analytical theory for the orbit of nereid (1996)
    Springer
    Celestial mechanics and dynamical astronomy 66 (1996), S. 321-344 
    Details
    ISSN: 1572-9478
    Keywords: Nereid ; Lie transformation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract A complete analytical dynamic theory for the motion of Nereid has been constructed, accurate to approximately 0.01 arc second over several hundred years. The solution uses the Lie transform approach advanced by Deprit and is consistent with respect to the magnitudes of the disturbing functions, including all perturbations to an accuracy of 10−8 relative to the two-body potential (oblateness and third-body). Multiple short-period variables in the third-body perturbations are related via the ratio of their mean motions, reducing the number of independent variables. Extensive use is made of expansions giving trigonometric functions of the true anomaly as analytical Fourier series in the mean anomaly. Initial constants and mass parameters come from the data obtained during the Voyager II encounter with Neptune in 1989.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00049385
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