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  • 1
    Online Resource
    Online Resource
    Exponential Gain and Saturation of a Self-Amplified Spontaneous Emission Free-Electron Laser
    American Association for the Advancement of Science (AAAS) ; 2001
    In:  Science Vol. 292, No. 5524 ( 2001-06-15), p. 2037-2041
    Details
    In: Science, American Association for the Advancement of Science (AAAS), Vol. 292, No. 5524 ( 2001-06-15), p. 2037-2041
    Abstract: Self-amplified spontaneous emission in a free-electron laser has been proposed for the generation of very high brightness coherent x-rays. This process involves passing a high-energy, high-charge, short-pulse, low-energy-spread, and low-emittance electron beam through the periodic magnetic field of a long series of high-quality undulator magnets. The radiation produced grows exponentially in intensity until it reaches a saturation point. We report on the demonstration of self-amplified spontaneous emission gain, exponential growth, and saturation at visible (530 nanometers) and ultraviolet (385 nanometers) wavelengths. Good agreement between theory and simulation indicates that scaling to much shorter wavelengths may be possible. These results confirm the physics behind the self-amplified spontaneous emission process and forward the development of an operational x-ray free-electron laser.
    Type of Medium: Online Resource
    ISSN: 0036-8075 , 1095-9203
    URL: Article
    DOI: 10.1126/science.1059955
    RVK:
    TA 1000
    RVK:
    WA 15000
    Language: English
    Publisher: American Association for the Advancement of Science (AAAS)
    Publication Date: 2001
    detail.hit.zdb_id: 128410-1
    detail.hit.zdb_id: 2066996-3
    detail.hit.zdb_id: 2060783-0
    SSG: 11
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  • 2
    Online Resource
    Online Resource
    Blockade of the granzyme B/perforin pathway through overexpression of the serine protease inhibitor PI-9/SPI-6 constitutes a mechanism for immune escape by tumors
    Proceedings of the National Academy of Sciences ; 2001
    In:  Proceedings of the National Academy of Sciences Vol. 98, No. 20 ( 2001-09-25), p. 11515-11520
    Details
    In: Proceedings of the National Academy of Sciences, Proceedings of the National Academy of Sciences, Vol. 98, No. 20 ( 2001-09-25), p. 11515-11520
    Abstract: The concept for cellular immunotherapy of solid tumors relies heavily on the capacity of class I MHC-restricted cytotoxic T lymphocytes (CTLs) to eliminate tumor cells. However, tumors often have managed to escape from the cytolytic machinery of these effector cells. Therefore, it is very important to chart the mechanisms through which this escape can occur. Target-cell killing by CTLs involves the induction of apoptosis by two major mechanisms: through death receptors and the perforin/granzyme B (GrB) pathway. Whereas tumors previously were shown to exhibit mechanisms for blocking the death receptor pathway, we now demonstrate that they also can resist CTL-mediated killing through interference with the perforin/GrB pathway. This escape mechanism involves expression of the serine protease inhibitor PI-9/SPI-6, which inactivates the apoptotic effector molecule GrB. Expression of PI-9 was observed in a variety of human and murine tumors. Moreover, we show that, indeed, expression results in the resistance of tumor cells to CTL-mediated killing both in vitro and in vivo . Our data reveal that PI-9/SPI-6 is an important parameter determining the success of T cell-based immunotherapeutic modalities against cancer.
    Type of Medium: Online Resource
    ISSN: 0027-8424 , 1091-6490
    URL: Article
    DOI: 10.1073/pnas.201398198
    RVK:
    TA 1000
    RVK:
    WA 15000
    Language: English
    Publisher: Proceedings of the National Academy of Sciences
    Publication Date: 2001
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    detail.hit.zdb_id: 1461794-8
    SSG: 11
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  • 3
    Online Resource
    Online Resource
    Activation of Fas by FasL induces apoptosis by a mechanism that cannot be blocked by Bcl-2 or Bcl-x L
    Proceedings of the National Academy of Sciences ; 1999
    In:  Proceedings of the National Academy of Sciences Vol. 96, No. 26 ( 1999-12-21), p. 14871-14876
    Details
    In: Proceedings of the National Academy of Sciences, Proceedings of the National Academy of Sciences, Vol. 96, No. 26 ( 1999-12-21), p. 14871-14876
    Abstract: Fas activation triggers apoptosis in many cell types. Studies with anti-Fas antibodies have produced conflicting results on Fas signaling, particularly the role of the Bcl-2 family in this process. Comparison between physiological ligand and anti-Fas antibodies revealed that only extensive Fas aggregation, by membrane bound FasL or aggregated soluble FasL consistently triggered apoptosis, whereas antibodies could act as death agonists or antagonists. Studies on Fas signaling in cell lines and primary cells from transgenic mice revealed that FADD/MORT1 and caspase-8 were required for apoptosis. In contrast, Bcl-2 or Bcl-x L did not block FasL-induced apoptosis in lymphocytes or hepatocytes, demonstrating that signaling for cell death induced by Fas and the pathways to apoptosis regulated by the Bcl-2 family are distinct.
    Type of Medium: Online Resource
    ISSN: 0027-8424 , 1091-6490
    URL: Article
    DOI: 10.1073/pnas.96.26.14871
    RVK:
    TA 1000
    RVK:
    WA 15000
    Language: English
    Publisher: Proceedings of the National Academy of Sciences
    Publication Date: 1999
    detail.hit.zdb_id: 209104-5
    detail.hit.zdb_id: 1461794-8
    SSG: 11
    SSG: 12
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  • 4
    Online Resource
    Online Resource
    Isolation of a condensed, intracellular form of the 2-micrometer DNA plasmid of Saccharomyces cerevisiae.
    Proceedings of the National Academy of Sciences ; 1979
    In:  Proceedings of the National Academy of Sciences Vol. 76, No. 8 ( 1979-08), p. 3727-3731
    Details
    In: Proceedings of the National Academy of Sciences, Proceedings of the National Academy of Sciences, Vol. 76, No. 8 ( 1979-08), p. 3727-3731
    Abstract: We have initiated an investigation of the proteins bound in vivo to the 2-micrometer DNA plasmid found in the yeast Saccharomyces cerevisiae by examining its intracellular form. To isolate 2-micrometer DNA without disturbing proteins bound to the plasmid, an extract was prepared from a strain lacking mitochondrial DNA and the nuclear chromatin was removed from the extract by centrifugation. When the DNA in this extract was sedimented through a sucrose gradient containing 0.15 M NaCl, plasmid DNA had a sedimentation coefficient of approximately 70. This S value is greater than the S value of 25 for naked, superhelical 2-micrometer DNA. Cosedimenting with the DNA were proteins of the same size as the histone proteins associated with yeast nuclear chromatin. Digestion of the plasmid DNA with micrococcal nuclease and electrophoresis of the resulting DNA fragments revealed that segments of discrete sizes are protected from degradation. Examination of the plasmid DNA protein complex by electron microscopy showed nucleosome structures. We conclude that 2-micron DNA exists as a condensed chromosome body within the cell.
    Type of Medium: Online Resource
    ISSN: 0027-8424 , 1091-6490
    URL: Article
    DOI: 10.1073/pnas.76.8.3727
    RVK:
    TA 1000
    RVK:
    WA 15000
    Language: English
    Publisher: Proceedings of the National Academy of Sciences
    Publication Date: 1979
    detail.hit.zdb_id: 209104-5
    detail.hit.zdb_id: 1461794-8
    SSG: 11
    SSG: 12
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  • 5
    Online Resource
    Online Resource
    Evidence for phosphorylation and oligomeric assembly of presenilin 1
    Proceedings of the National Academy of Sciences ; 1997
    In:  Proceedings of the National Academy of Sciences Vol. 94, No. 10 ( 1997-05-13), p. 5090-5094
    Details
    In: Proceedings of the National Academy of Sciences, Proceedings of the National Academy of Sciences, Vol. 94, No. 10 ( 1997-05-13), p. 5090-5094
    Abstract: Pathogenic mutations in presenilin 1 (PS1) are associated with ≈50% of early-onset familial Alzheimer disease. PS1 is endoproteolytically cleaved to yield a 30-kDa N-terminal fragment (NTF) and an 18-kDa C-terminal fragment (CTF). Using COS7 cells transfected with human PS1, we have found that phorbol 12,13-dibutyrate and forskolin increase the state of phosphorylation of serine residues of the human CTF. Phosphorylation of the human CTF resulted in a shift in electrophoretic mobility from a single major species of 18 kDa to a doublet of 20–23 kDa. This mobility shift was also observed with human PS1 that had been transfected into mouse neuroblastoma (N2a) cells. Treatment of the phosphorylated CTF doublet with phage λ protein phosphatase eliminated the 20- to 23-kDa doublet while enhancing the 18-kDa species, consistent with the interpretation that the electrophoretic mobility shift was due to the addition of phosphate to the 18-kDa species. The NTF and CTF eluted from a gel filtration column at an estimated mass of over 100 kDa, suggesting that these fragments exist as an oligomerized species. Upon phosphorylation of the PS1 CTF, the apparent mass of the NTF- or CTF-containing oligomers was unchanged. Thus, the association of PS1 fragments may be maintained during cycles of phosphorylation/dephosphorylation of the PS1 CTF.
    Type of Medium: Online Resource
    ISSN: 0027-8424 , 1091-6490
    URL: Article
    DOI: 10.1073/pnas.94.10.5090
    RVK:
    TA 1000
    RVK:
    WA 15000
    Language: English
    Publisher: Proceedings of the National Academy of Sciences
    Publication Date: 1997
    detail.hit.zdb_id: 209104-5
    detail.hit.zdb_id: 1461794-8
    SSG: 11
    SSG: 12
    Location Call Number Limitation Availability
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