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  • 1
    Electronic Resource
    Electronic Resource
    Electron-energy-loss spectroscopy of the low-lying triplet states of styrene (1994)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 100 (1994), S. 70-77 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: Low-energy electron-energy-loss spectra of styrene deposited on a thin film of solid argon are measured at a temperature of 15 K. The spectra show vibrationally resolved bands in the region of the lowest valence transitions thus allowing to locate the 0–0 transition to the lowest triplet state at 2.69 eV. The second triplet state of styrene is detected for the first time with a 0–0 transition at 3.98 eV. Semiempirical calculations are performed to characterize the bands observed in the spectrum considering the nomenclature of Platt. They suggest that the lowest triplet state has the same spacial wave function as the second singlet state and is closely related to 3La benzene. The second triplet state which has most likely Ba character cannot directly be related to a specific singlet state because the Ba and Bb states are found to mix strongly in the singlet manifold whereas among the triplets they do not.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.466936
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  • 2
    Electronic Resource
    Electronic Resource
    Vitamin B 12 and Protein Biosynthesis: Vitamin B 12 and Biosynthesis in Chick Liver (1959)
    [s.l.] : Nature Publishing Group
    Nature 183 (1959), S. 519-523 
    Details
    ISSN: 1476-4687
    Source: Nature Archives 1869 - 2009
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
    Notes: [Auszug] IN recent years evidence has been produced that the steps of incorporation of amino-acids into proteins include: (i) an activation dependent on adenosine triphosphate of the amino-acids through the COOH group, with the formation of an amino-acid-adenosine monophosphate complex by means of enzymes ...
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1038/183519a0
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  • 3
    Electronic Resource
    Electronic Resource
    Optimal Protein Synthesis by Ascites Tumour Cells in vitro (1960)
    [s.l.] : Nature Publishing Group
    Nature 187 (1960), S. 1114-1115 
    Details
    ISSN: 1476-4687
    Source: Nature Archives 1869 - 2009
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
    Notes: [Auszug] Since the incorporations of different amino-acids were not stimulated to the same extent by rat serum under identical conditions (for example, glycine by 187 per cent, valine by 133 per cent, leucine and glutamic acid by less than 10 per cent), great care was taken to show that the stimulated ...
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1038/1871114a0
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  • 4
    Electronic Resource
    Electronic Resource
    Formation of Fibres from Protein Monolayers (1953)
    [s.l.] : Nature Publishing Group
    Nature 171 (1953), S. 559-560 
    Details
    ISSN: 1476-4687
    Source: Nature Archives 1869 - 2009
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
    Notes: [Auszug] WHEN a monomolecular film of protein at an VV air/water interface is compressed beyond a certain critical surface pressure it can no longer be re-expanded to its original area, due to the formation of intermolecular linkages by the unfolded film protein. As the film is further compressed, more such ...
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1038/171559a0
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  • 5
    Electronic Resource
    Electronic Resource
    A single, phosphate-repressible deoxyribonuclease, DNase A, secreted inAspergillus nidulans (1989)
    Springer
    Biochemical genetics 27 (1989), S. 153-166 
    Details
    ISSN: 1573-4927
    Keywords: Aspergillus nidulans ; DNase A ; deoxyribonuclease secretion ; phosphate repression ; regulator genepalcA
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology
    Notes: Abstract High levels of nuclease activities were identified in filtrates ofAspergillus cultures after growth in low- but not in high-phosphate media. Deoxyribonuclease activities, characterized extensively by column chromatography, showed a coincident single peak for ss- and ds-DNase which was distinct from the peak for RNase. Both ss-DNase and ds-DNase are endonucleolytic and showed the highest activity in the presence of Ca2+ and Mn2+ (atpH 8.0). They also showed identical heat sensitivities suggesting that a single, phosphate-repressible DNase was secreted. This enzyme, therefore, corresponds to the well-characterized extracellular DNase A ofNeurospora. However, theAspergillus DNase A did not cross-react with antisera to secretedNeurospora nucleases and showed different chromatographic properties, and active peptides of different sizes were visualized on DNA activity gels. The increasing derepression ofAspergillus DNase A by decreasing phosphate levels was similar to that of secreted alkaline phosphatase and these increases were both abolished by the regulatory mutantpalcA.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02401798
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  • 6
    Electronic Resource
    Electronic Resource
    A single, phosphate-repressible deoxyribonuclease, DNase A, secreted inAspergillus nidulans (1989)
    Springer
    Biochemical genetics 27 (1989), S. 153-166 
    Details
    ISSN: 1573-4927
    Keywords: Aspergillus nidulans ; DNase A ; deoxyribonuclease secretion ; phosphate repression ; regulator genepalcA
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology
    Notes: Abstract High levels of nuclease activities were identified in filtrates ofAspergillus cultures after growth in low- but not in high-phosphate media. Deoxyribonuclease activities, characterized extensively by column chromatography, showed a coincident single peak for ss- and ds-DNase which was distinct from the peak for RNase. Both ss-DNase and ds-DNase are endonucleolytic and showed the highest activity in the presence of Ca2+ and Mn2+ (atpH 8.0). They also showed identical heat sensitivities suggesting that a single, phosphate-repressible DNase was secreted. This enzyme, therefore, corresponds to the well-characterized extracellular DNase A ofNeurospora. However, theAspergillus DNase A did not cross-react with antisera to secretedNeurospora nucleases and showed different chromatographic properties, and active peptides of different sizes were visualized on DNA activity gels. The increasing derepression ofAspergillus DNase A by decreasing phosphate levels was similar to that of secreted alkaline phosphatase and these increases were both abolished by the regulatory mutantpalcA.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00552989
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  • 7
    Electronic Resource
    Electronic Resource
    Caspase-3-dependent and caspase-3-independent pathways leading to chromatin DNA fragmentation in HL-60 cells (2000)
    Springer
    Apoptosis 5 (2000), S. 61-67 
    Details
    ISSN: 1573-675X
    Keywords: Apoptosis ; caspase ; etoposide ; hydroxychloroquine ; nuclease.
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract Apoptosis induced by etoposide (VP-16) in HL-60 cells was confirmed to be caspase-dependent. It was fully inhibited by the broad-spectrum caspase inhibitor Z-VAD-fmk. However, the caspase-3-specific inhibitor Z-DEVD-fmk only partially inhibited apoptosis. This indicated that a second caspase is required in vivo for full activation of the apoptotic nucease CAD. Aurin tricarboxylic acid (ATA) did not inhibit VP-16-induced apoptosis. In contrast, apoptosis induced by hydroxychloroquine (HCQ) in HL-60 cells was caspase-3 independent and was fully inhibited by ATA. Thus, CAD does not appear to be involved in chromatin DNA degradation in this case. A second apoptotic nuclease is postulated to degrade the DNA, likely endo-exonuclease, an abundant nuclear enzyme that acts on both DNA and RNA and is present in latent form. HCQ, but not VP-16, stimulated DNA degradation (“laddering”) in isolated nuclei. This indicates that the drug can act directly in the nuclei to trigger activation of the second latent apoptotic nuclease.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1009689710184
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  • 8
    Electronic Resource
    Electronic Resource
    Caspase-3 activates endo-exonuclease: Further evidence for a role of the nuclease in apoptosis (2000)
    Springer
    Apoptosis 5 (2000), S. 243-254 
    Details
    ISSN: 1573-675X
    Keywords: apoptosis ; caspase-3 ; nuclease ; endo-exonuclease
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract Single-strand DNase and poly rAase, activities characteristic of endo-exonuclease, were co-activated in nuclear fractions of HL-60 cells by caspase-3. Activation was accompanied by cleavages of large soluble polypeptides (130–185 kDa) and a 65 kDa inactive chromatin-associated polypeptide related to the endo-exonuclease of Neurospora crassa as detected on immunoblots. The major products seen in vitro were a 77 kDa soluble polypeptide and an active chromatin-associated 34 kDa polypeptide. When HL-60 cells were induced to undergo apoptosis by treating with 50 μM etoposide (VP-16) for 4 hours, 77 kDa and 40 kDa polypeptides accumulated in nuclear fractions. Chromatin DNA fragmentation activity was also activated in cytosol and nuclear extract either by pre-treating the cells in vivo with VP-16 or by treating the cytosol in vitro with caspase-3 or dATP and cytochrome c. Endo-exonuclease activated by caspase-3 in cytosol-derived fractions augmented chromatin DNA fragmentation activity in vitro. Endo-exonuclease is proposed to act in vivo in conjunction with the caspase-activated DNase (CAD) to degrade chromatin DNA during apoptosis of HL-60 cells.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1009604529237
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  • 9
    Electronic Resource
    Electronic Resource
    An investigation of a possible role for mitochondrial nuclease in apoptosis (1998)
    Springer
    Apoptosis 3 (1998), S. 395-405 
    Details
    ISSN: 1573-675X
    Keywords: Apoptosis ; etoposide ; hydroxychloroquine ; mitochondria ; nuclease ; transmembrane potential.
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract Since mitochondrial factors have been implicated in apoptosis, experiments were designed to assess whether or not the potent mitochondrial nuclease could be one of these factors. Nuclei isolated by two different methods were found to contain mitochondrial nuclease in masked form. This nuclease was released by treatment with the non-ionic detergent NP-40 and rendered trypsin-sensitive. It was not removed appreciably from the nuclei by washing and sedimentation of the nuclei through a sucrose cushion. Levels of the mitochondrial nuclease were followed during drug-induced apoptosis. Time courses of apoptosis in cultures of HL-60 cells were monitored by flow cytometry of propidium iodide-stained cells and by agarose gel electrophoresis of extracted DNA. Changes in the inner mitochondrial transmembrane potential were monitored by flow cytometry of chloromethyl-X-Rosamine-stained cells. Apoptosis was induced by treatment with either the chemotherapeutic agent etoposide (VP-16 at 10 μM) over an 8 h period or with the anti-rheumatic agent hydroxychloroquine (HCQ at 0.28 mM) over a 24 h period. These two drugs likely act in different pathways of apoptosis. VP-16 caused loss of the mitochondrial transmembrane potential 1.0–1.5 h before apoptosis was detected. On the other hand, treatment with HCQ caused these processes to occur in parallel possibly indicating that the mitochondrial changes are secondary events. No losses of masked mitochondrial nuclease were detected with either drug treatment during the course of apoptosis. HL-60 mitochondrial DNA was also not degraded during apoptosis induced by either agent. These observations likely explain why the mitochondrial DNA is not degraded and make it unlikely that mitochondrial nuclease plays any role in vivo in chromatin DNA fragmentation.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1009654418089
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  • 10
    Electronic Resource
    Electronic Resource
    Excision of the piggyBac transposable element in vitro is a precise event that is enhanced by the expression of its encoded transposase (1996)
    Springer
    Genetica 98 (1996), S. 33-41 
    Details
    ISSN: 1573-6857
    Keywords: piggyBac ; Lepidopteran ; transposable element
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The piggyBac Lepidopteran transposable element moves from the cellular genome into infecting baculovirus genomes during passage of the virus in cultured TN-368 cells. We have constructed genetically tagged piggyBac elements that permit analysis of excision when transiently introduced on plasmids into the piggyBac-deficient Spodoptera frugiperda IPLB-SF21AE cell line. Precise excision of the element from these plasmids occurs at a higher frequency in the presence of a helper plasmid that presumably supplies the piggyBac transposase. The results suggest that the piggyBac transposon encodes a protein that functions to facilitate not only insertion, but precise excision as well. This is the first demonstration of piggyBac mobility from plasmid sources in uninfected Lepidopteran cells.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00120216
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