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  • 1
    Electronic Resource
    Electronic Resource
    Isolation, characterization and crystallization of an iron-superoxide dismutase from the crenarchaeon Sulfolobus acidocaldarius (1996)
    Oxford, UK : Blackwell Publishing Ltd
    FEMS microbiology letters 138 (1996), S. 0 
    Details
    ISSN: 1574-6968
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: Abstract An iron containing Superoxide dismutase from the cytosol of the thermoacidophilic crenarchaeon Sulfolobus acidocaldarius (DSM 639) has been purified to electrophoretic homogeneity. It comprises at least 11% of the cytosolic protein. The isolated protein consists of two identical subunits with an apparent molecular mass of 22.4 kDa. It contains one iron atom per dimer. The protein shows the typical EPR spectrum of a S = 3 / 2, rhombic high-spin iron center. It is extremely resistant against thermal and chemical denaturation. Simultaneous treatment with heat and detergent resulted in the conversion into a more active tetrameric form. Similar enzymes appear to be present in the cytosol of other members of the Sulfolobaceae. The dimeric form of the protein from S. acidocaldarius has been crystallized.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1574-6968.1996.tb08136.x
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  • 2
    Electronic Resource
    Electronic Resource
    Coalescing neutron stars as gamma ray bursters? (1995)
    Springer
    Astrophysics and space science 231 (1995), S. 423-426 
    Details
    ISSN: 1572-946X
    Keywords: Hydrodynamics ; Binaries: Close ; Stars: neutron ; Gamma rays: bursts
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract We investigate the dynamics and evolution of coalescing neutron stars. The three-dimensional Newtonian equations of hydrodynamics are integrated by the “Piecewise Parabolic Method” on an equidistant Cartesian grid. The code is purely Newtonian, but does include the emission of gravitational waves and their back-reaction. The properties of neutron star matter are described by the equation of state of Lattimer and Swesty (1991). Energy loss by all types of neutrinos and changes of the electron fraction due to the emission of electron neutrinos and antineutrinos are taken into account by an elaborate “neutrino leakage scheme”. We simulate the coalescence of two identical, cool neutron stars with a baryonic mass of ≈ 1.6M ⊙ and a radius of ≈ 15 km and with an initial center-to-center distance of 42 km. The initial distributions of density and electron concentration are given from a model of a cold neutron star in hydrostatic equilibrium. We investigate three cases which differ by the initial velocity distribution in the neutron stars. The orbit decays due to gravitational-wave emission and after one revolution the stars are so close that dynamical instability sets in. Within 1 ms the neutron stars merge into a rapidly spinning (P ≈ 1 ms), high-density body (ρ ≈ 1014 g/cm3) with a surrounding thick disk of material with densitiesρ ≈ 1010 − 1012 g/cm3 and orbital velocities of 0.3-0.5 c. The peak emission of gravitational waves has a maximum luminosity of a few times 1055 erg/s and is reached for about 1 ms. The amplitudes of the gravitational waves are close to 3 ⋅ 10−23 at a distance of 1 Gpc and the typical frequency is near the dynamical value of the orbital motion of the merging neutron stars of 2 KHz. In a post-processing step, the rate of neutrino-antineutrino annihilation is calculated from the neutrino luminosities generated during the hydrodynamical simulations. We find the integral annihilation rate to be a few 1050 erg/s during the phase of strongest neutrino emission, which is too small to generate the observed bursts considering the fact that the merged object of about 3M⊙ will most likely collapse to a black hole within milliseconds.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00658662
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  • 3
    Electronic Resource
    Electronic Resource
    Studies of the Electron Transport Chain of the Euryarcheon Halobacterium salinarum: Indications for a Type II NADH Dehydrogenase and a Complex III Analog (1998)
    Springer
    Journal of bioenergetics and biomembranes 30 (1998), S. 443-453 
    Details
    ISSN: 1573-6881
    Keywords: Archea ; inhibitors ; NADH dehydrogenase ; complex III ; cytochromes ; Rieske iron–sulfur cluster ; terminal oxidase
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology , Physics
    Notes: Abstract The components involved in the respiratory system of the euryarcheon Halobacterium salinarum were investigated by spectroscopic and polarographic techniques. Previous results about the cytochrome composition could be verified. However, under low oxygen tension, the expression of a d-type cytochrome was detected. Membranes exerted an NADH– and succinate–cytochrome-c oxidoreductase as well as an NADH and succinate oxidase activity. These activities could be blocked by the following inhibitors: 7-jodocarboxylic acid, giving evidence for the presence of a type II NADH dehydrogenase, antimycin A, and myxothiazol, indicating the presence of a complex III analog, and the typical succinate dehydrogenase (SDH) and terminal oxidase inhibitors. Complex I inhibitors like rotenone and annonine were inactive, clearly excluding the presence of a coupled NADH dehydrogenase. In addition, no [Fe-S] resonances in the region of the NADH dehydrogenase (NDH) clusters could be observed after NADH addition. One of the terminal oxidases could be shown to act as a cytochrome-c oxidase with a K m value of 37 μM and an activation energy of 23.7 kJ/mol. The relative molecular mass of the endogenous c-type cytochrome could be determined as 14.1 kD. The complex III analog could be enriched after detergent extraction with Triton X-100 and hydroxylapatite (HTP) chromatography. The partially purified complex contained a Rieske iron–sulfur cluster, b- and c-type cytochromes, and was catalytically active in the decylubiquinone–cytochrome-c oxidoreductase assay.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1020538129400
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  • 4
    Electronic Resource
    Electronic Resource
    A Novel Rieske Iron-Sulfur Protein from the Hyperthermophilic Crenarchaeon Pyrobaculum aerophilum: Sequencing of the Gene, Expression in E. coli and Characterization of the Protein (1999)
    Springer
    Journal of bioenergetics and biomembranes 31 (1999), S. 119-128 
    Details
    ISSN: 1573-6881
    Keywords: pyrobaculum aerophilum ; archaea ; hyperthermophile ; rieske protein ; sequence ; expression ; redox potential ; pH-dependence
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology , Physics
    Notes: Abstract The crenarchaeon Pyrobaculum aerophilum is with an optimalgrowth temperature of 100 °C one of the most thermophilic organisms knownto possess an aerobic respiratory chain. The analysis of DNA sequences fromthe Pyrobaculum genome project lead to the identification of an openreading frame potentially coding for a Rieske iron-sulfur protein. Thecomplete gene (named parR) was cloned and sequenced. The deducedamino acid sequence displays unusual amino acid exchanges and a so farunknown sequence insertion. The N-terminus shows similarities to bacterialsignal sequences. Several forms of the gene were expressed in E.coli in order to verify the classification as a Rieske protein and tofacilitate biophysical studies. Soluble, thermo-stable proteins withcorrectly inserted iron-sulfur clusters were expressed from two versions ofthe gene. The Δ1–23 truncated holo-protein is redox active. Itdisplays the typical spectroscopic properties of a Rieske protein. The redoxpotential was determined to be +215 mV at pH 6.5 and is pH dependentabove pH 7.5 revealing the influence of two protonation equilibria with pKavalues of 8.1 and 9.8. Phylogenetic analysis demonstrates that the parRprotein clusters together with the two other available archaeal Rieskesequences from Sulfolobus on a separate branch of the phylogenetictree apart from the proteins from thermophilic bacteria like Aquifexand Thermus.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1005447710894
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  • 5
    Electronic Resource
    Electronic Resource
    Expression of 72 kDa and 92 kDa type IV collagenases from human giant-cell tumor of bone (1995)
    Springer
    Clinical & experimental metastasis 13 (1995), S. 420-426 
    Details
    ISSN: 1573-7276
    Keywords: invasion ; metalloproteinases ; metastasis ; tissue inhibitors of metalloproteinases
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract Basement membrane forms widespread barriers to tumor invasion. It has been shown that tumor-secreted, basement membrane-degrading enzymes, namely metalloproteinases (MMPs) play an important role in tumor invasion and metastasis. In this study, we determined the enzymatic activity, content, and mRNA of both the 72 kDa (MMP-2) and 92 kDa (MMP-9) MMPs in primary cultures of human giant-cell tumor of bone (GCT)in vitro and in tissue extracts (in vivo). Gelatin zymography showed the presence of lytic bands at Mr 121000, 92000, and 72000, and these enzymatic activities were inhibited by EDTA, an inhibitor of MMPs. Western blots with antibodies specific for MMP-2 and MMP-9 confirmed the presence of MMP-2 and MMP-9 bothin vitro andin vivo, but GCT cells at late passage showed only MMP-2. Northern blots using labeled cDNA probes specific for these molecules revealed the presence of 3.1 kb transcript for MMP-2 and a 2.9 kb transcript for MMP-9. Using specific antibodies to 72 kDa and 92 kDa type IV collagenases, we studied their cellular distribution by immunohistochemical means. Stronger immunoreactivity was found for 92 kDa type IV collagenase than 72 kDa type IV collagenase in the giant cells. It appears, therefore, that MMP-9 may play an important role in the malignant behavior of GCTs and suggests a potential therapeutic role for protease inhibitors in attempting to minimize the invasive behavior of GCTs.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00118181
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  • 6
    Electronic Resource
    Electronic Resource
    Regulation of MMP-9 (92 kDa type IV collagenase/gelatinase B) expression in stromal cells of human giant cell tumor of bone (1997)
    Springer
    Clinical & experimental metastasis 15 (1997), S. 400-409 
    Details
    ISSN: 1573-7276
    Keywords: cytokines ; giant cell tumor ; metalloproteinases ; stromal cells
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract Matrix metalloproteinases (MMPs) play an important regulatory role in tissue morphogenesis, cell differentiation, tumor invasion and metastasis. Several authors have reported a direct correlation between the production of 72 kDa (MMP-2) and 92 kDa (MMP-9) type IV collagenases/gelatinases and the metastatic potential of cancer cells. Recently, we have identified the expression of both MMP-2 and MMP-9 in primary cultures of human giant cell tumor (GCT) of bone in vitro, and in tissue extracts in vivo. Interestingly, MMP-9 is not secreted by late-passaged GCT cells. It is possible that the production of MMP-9 is regulated by certain factor(s) secreted by the multinucleated giant cells in the primary culture. In order to test this hypothesis, the effect of primary-culture-conditioned medium on the expression of MMP-9 by late-passaged mononuclear stromal cells was examined. Adding conditioned medium from the primary GCT culture to the late-passaged stromal cells induced MMP-9, as evidenced by the presence of lytic bands at Mr 92000 and 72000 on a gelatin zymogram. These enzyme activities were inhibited by EDTA, a well-known inhibitor of the MMPs. We confirmed these results by Western blotting using specific antibodies and RT-PCR for MMP-2 and MMP-9. Immunofluorescence studies with specific antibodies to MMP-9 further confirmed its expression by the passaged stromal cells cultured in the primary-culture-conditioned medium. The data indicate that MMP-2 and MMP-9 are produced by the mononuclear stromal cells when cultured in GCT primary-culture-conditioned medium. This suggests that multinucleated giant cells in primary cultures secrete a factor(s) that stimulates stromal cells to produce MMP-9, which, in turn, may contribute to the aggressive behavior of GCT.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1018450204980
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  • 7
    Electronic Resource
    Electronic Resource
    Highly Substituted Anthraquinones by Anionic Cyclization Reactions (1996)
    New York, NY : Wiley-Blackwell
    Journal für Praktische Chemie/Chemiker-Zeitung 338 (1996), S. 349-354 
    Details
    ISSN: 0941-1216
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Highly substituted anthraquinone esters (3a/b, 6, 20) and acids (12, 21) are synthesized by base induced anionic cyclizations starting from bisalkylated naphthalenes (e.g. 10) or monoalkylated naphthoquinones (e.g. 19).
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/prac.19963380168
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  • 8
    Electronic Resource
    Electronic Resource
    Biologen in unserer Zeit (1996)
    Weinheim : Wiley-Blackwell
    Biologie in unserer Zeit 26 (1996), S. 81-95 
    Details
    ISSN: 0045-205X
    Keywords: Life and Medical Sciences
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/biuz.19960260612
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