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  • 1
    Electronic Resource
    Electronic Resource
    THE CHLOROPLAST ATP SYNTHASE: A Rotary Enzyme? (2000)
    Palo Alto, Calif. : Annual Reviews
    Annual Review of Plant Physiology and Plant Molecular Biology 51 (2000), S. 83-109 
    Details
    ISSN: 1040-2519
    Source: Annual Reviews Electronic Back Volume Collection 1932-2001ff
    Topics: Biology
    Notes: Abstract The chloroplast adenosine triphosphate (ATP) synthase is located in the thylakoid membrane and synthesizes ATP from adenosine diphosphate and inorganic phosphate at the expense of the electrochemical proton gradient formed by light-dependent electron flow. The structure, activities, and mechanism of the chloroplast ATP synthase are discussed. Emphasis is given to the inherent structural asymmetry of the ATP synthase and to the implication of this asymmetry to the mechanism of ATP synthesis and hydrolysis. A critical evaluation of the evidence in support of and against the notion that one part of the enzyme rotates with respect to other parts during catalytic turnover is presented. It is concluded that although rotation can occur, whether it is required for activity of the ATP synthase has not been established unequivocally.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1146/annurev.arplant.51.1.83
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  • 2
    Electronic Resource
    Electronic Resource
    Prior exposure to a behaviorally sensitizing regimen of d-methamphetamine does not alter the striatal dopaminergic damage induced by a neurotoxic regimen (2000)
    Oxford, UK : Blackwell Publishing Ltd
    Addiction biology 5 (2000), S. 0 
    Details
    ISSN: 1369-1600
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: Repeated exposure to psychostimulant drugs such as d-methamphetamine (d-METH) and cocaine can be associated with extremely long-lived changes in dopamine systems at the behavioral, cellular and molecular level. Sensitization or an enhanced response to drug exposure is one such change. Investigations of these phenomena at the cellular and molecular levels are being conducted in the hope that this will aid in understanding how such adaptations might contribute to drug addition. Repeated exposure to certain amphetamines can also result in damage to dopaminergic pathways. Although some of the same molecular adaptations and mechanisms are suspected to occur or play a role in the neurotoxic sequelae associated with psychostimulant exposure, there has been little attempt to examine the relationship among these phenomena. Here we utilized C57BL/6J female mice to examine whether exposure to a sensitizing regimen of d-METH would impact the degree of neural injury induced by a subsequent exposure to a neurotoxic regimen of the same psychostimulant. Every other day exposure to d-METH (1.0 or 2.0 mg/kg) for 11 days produced a behavioral sensitization, as evidenced by a significant increase in the degree of locomotor activity induced by each subsequent exposure to d-METH. Following a 5-day period of no drug exposure sensitized mice were given a neurotoxic regiment of d-METH (a total of four injections of 10.0 mg/kg, one every 2 hours) and striatal tissue examined 72 hours later. All groups, whether drug-naive or sensitized previously to d-METH, showed exactly the same degree of dopaminergic striatal damage induced by a neurotoxic regimen. This was evidenced by equivalent reductions in dopamine and elevations in GFAP protein, a marker of astrocytic response to injury, GFAP. The inability of a sensitizing regimen to either exacerbate or lessen the neurotoxic actions of the same compound suggests that the molecular and cellular control of these two aspects of psychostimulant exposure may differ.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1369-1600.2000.tb00203.x
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  • 3
    Electronic Resource
    Electronic Resource
    Direct, high throughput LIGA for commercial applications: a progress report (2000)
    Springer
    Microsystem technologies 6 (2000), S. 103-105 
    Details
    ISSN: 1432-1858
    Source: Springer Online Journal Archives 1860-2000
    Topics: Electrical Engineering, Measurement and Control Technology , Technology
    Notes: Abstract Direct LIGA; LIGA without injection molding; has the potential to become a cost effective, high throughput form of LIGA. The process requires high energy photons; near 20,000 eV; which are best produced in facilities such as the X-ray ring at Brookhaven National Laboratory. The increased absorption lengths over lower energy photons eliminates the need for a membrane type X-ray mask. This in turn facilitates very large area X-ray masks fabricated from standard silicon wafers with 20 μm gold absorbers. The absorption length increase in PMMA to 2 cm is used to implement stacked PMMA exposures in which 1 mm thick PMMA layers are used to produce exposed PMMA sheets. These sheets are eventually solvent bonded to working substrates with plating bases. New high energy X-ray masks have been developed. Two exposure stations at Brookhaven are operational. The recently commissioned manufacturing exposure station which uses a 22 inch scanner which can expose four separate PMMA-mask combination is in the testing phase.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s005420050007
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  • 4
    Electronic Resource
    Electronic Resource
    SUMO conjugation and deconjugation (2000)
    Springer
    Molecular genetics and genomics 263 (2000), S. 771-786 
    Details
    ISSN: 1617-4623
    Keywords: Key wordsSaccharomyces cerevisiae ; Ubiquitin-like protein ; ULP ; SUMO/SMT3 ; UBA2
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Ligation of the ubiquitin-like protein SUMO (Smt3p) to other proteins is essential for viability of the yeast Saccharomyces cerevisiae. Like ubiquitin (Ub), SUMO undergoes ATP-dependent activation by a specific activating enzyme. SUMO-activating enzyme is a heterodimer composed of Uba2p and Aos1p, polypeptides with sequence similarities, respectively, to the C- and N-terminal parts of Ub-activating enzyme. To study the function of SUMO conjugation, we isolated uba2 mutants that were temperature-sensitive for growth. In these mutants conjugation of SUMO to other proteins was drastically reduced, even at the temperature permissive for growth. In a screen for spontaneous suppressors of the temperature-sensitive growth phenotype of the mutant uba2-ts9, we isolated a strain with a null mutation (sut9) in a gene of hitherto unknown function (SUT9/YIL031W/SMT4). This gene encodes a protein with similarities to Ulp1p, a dual-function protease that processes the SUMO precursor and deconjugates SUMO from its substrates. The novel protein was therefore termed Ulp2p. Inactivation of ULP2 in a strain expressing wild-type SUMO-activating enzyme resulted in slow and temperature-sensitive growth, and accumulation of SUMO conjugates. Thus, mutations in SUMO-activating enzyme and mutations in Ulp2p suppress each other, indicating that SUMO conjugation and deconjugation must be in balance for cells to grow normally. Other phenotypes of ulp2 mutants include a defect in cell cycle progression, hypersensitivity to DNA damage, and chromosome mis-segregation. Ulp2p is predominantly located within the nucleus, whereas Ulp1p colocalizes with nuclear pore complex proteins, indicating that the apparently distinct functions of the two SUMO deconjugating enzymes are spatially separated.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s004380000254
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  • 5
    Electronic Resource
    Electronic Resource
    Magnetisation of isolated single crystalline Fe-nanoparticles measured by a ballistic Hall micro-magnetometer (2000)
    Springer
    The European physical journal 10 (2000), S. 259-263 
    Details
    ISSN: 1434-6079
    Keywords: PACS. 07.55.Jg Magnetometers for susceptibility, magnetic moment, and magnetization measurements - 36.40.Cg Electronic and magnetic properties of clusters - 61.46.+w Clusters, nanoparticles, and nanocrystalline materials
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract: We present here the first magnetisation measurements on isolated single crystalline Fe-nanoparticles performed with a ballistic Hall micro-magnetometer. The measurements have a sensitivity of and thus provide us the possibility to study the mechanisms of magnetisation reversal in a single nanoparticle. The magnetic properties of the nanoparticles are influenced by their crystal structure and shape, and the presence of an oxide surface layer. They exhibit curling of the magnetic moments, but also a novel hysteresis behaviour. The spin configurations found for the system agree well with numerical calculations based on a Heisenberg Hamiltonian including the exchange and dipole interaction and surface anisotropy.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s100530050547
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