Your email was sent successfully. Check your inbox.

An error occurred while sending the email. Please try again.

Proceed reservation?

Export
  • 1
    ISSN: 1434-601X
    Keywords: 21.60.Ev ; 27.90.+b
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract TheK π=0− bands in even uranium nuclei were studied in the compound reactions231Pa(p, 2n)230U,230, 232Th(α,2n)232, 234U and236U(d, pn)236U. In-beamγ-rays were measured in coincidence with conversion-electrons, which were detected with an iron-free orange spectrometer. The negative-parity levels are observed up to intermediate spins (I〈13−). In addition, the 1− and 3− levels in230U were confirmed by a decay study with an isotope separated230Pa source. For the heavier isotopes (A≥232) the properties of theK π=0− bands (energies andγ-branchings) are consistent with a vibrational character of these bands. For230U theK π=0− band lies at rather low energy (E(1−)=367 keV), and the level spacings within this band are very similar to those of the isotones228Th and226Ra, which might indicate the onset of a stable octupole deformation.
    Type of Medium: Electronic Resource
    Signatur Availability
    BibTip Others were also interested in ...
  • 2
    ISSN: 1434-601X
    Keywords: 21.60.Ev ; 27.90.+b
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract Positive and negative parity bands have been followed up to 10+ (possibly 12+) and 11− in224Ra and are compared to the corresponding bands in the isotone226Th. If a constant value of the intrinsic quadrupole moment is assumed for allE2 transitions in224Ra theE1/E2 branching ratios are consistent with an intrinsic dipole moment of ¦Q1¦=0.032(3)e·fm. This small value, as compared to ¦Q1¦=0.30(2)e·fm for226Th, can be explained by an almost complete cancellation of large positive liquid-drop and negative shell-model contributions.
    Type of Medium: Electronic Resource
    Signatur Availability
    BibTip Others were also interested in ...
  • 3
    ISSN: 1434-601X
    Keywords: 21.60.Ev ; 23.60.+e ; 27.90.+b
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract The nuclei221Ra and217Rn have been investigated in the α-decay chain225Th→221Ra →217Rn through γ-ray and conversion-electron studies. The short-lived225Th nuclei (T 1/2=8min) were produced in the226Ra(α, 5n) reaction, and γ-rays and conversion electrons were measured — between the irradiation periods — in coincidence with αparticles. In221Ra the five lowest levels are interpreted as members of aK=5/2 paritydoublet with ΔEπ=104 keV. These levels, as well as a higher-lying Kπ=3/2+ band, are consistent with an octupole deformation of221Ra, as expected from theoretical considerations. In217Rn only three excited levels are observed, with a favoured α-decay to a 5/2+ excited level thus establishing positive parity for the ground state of221Ra.
    Type of Medium: Electronic Resource
    Signatur Availability
    BibTip Others were also interested in ...
  • 4
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Yeast 6 (1990), S. 87-97 
    ISSN: 0749-503X
    Keywords: Hansenula polymorpha ; methylotrophic yeast ; microbodies ; peroxisome-deficient mutants ; alcohol oxidase ; Life and Medical Sciences ; Genetics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology
    Notes: As a first step in a genetic approach towards understanding peroxisome biogenesis and function, we have sought to isolate mutants of the methylotrophic yeast Hansenula polymorpha which are deficient in peroxisomes. A collection of 260 methanol-utilization-defective strains was isolated and screened for the ability to utilize a second compound, ethanol, the metabolism of which involves peroxisomes. Electron microscopical investigations of ultrathin sections of selected pleiotropic mutants revealed two strains which were completely devoid of peroxisomes. In both, different peroxisomal matrix enzymes were active but located in the cytosol; these included catalase, alcohol oxidase, malate synthase and isocitrate lyase.Subsequent backcrossing experiments revealed that for all crosses involving both strains, the methanol- and ethanol utilizing-deficient phenotypes segregated independently of each other, indicating that different gene mutations were responsible for these phenotypes. The phenotype of the backcrossed peroxisome-deficient derivates was identical: defective in the ability to utilize methanol but capable of growth on other carbon sources, including ethanol.The mutations complemented and therefore were recessive mutations in different genes.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
    Signatur Availability
    BibTip Others were also interested in ...
  • 5
    ISSN: 0749-503X
    Keywords: Hansenula polymorpha ; alcohol oxidase ; amine oxidase ; choline ; peroxisome-deficient mutant ; enzyme assembly ; Life and Medical Sciences ; Genetics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology
    Notes: We have studied the expression of alcohol oxidase (AO) in a peroxisome-deficient mutant strain of Hansenula polymorpha. High levels of octameric, active AO (up to 3·0 U/mg protein) were detected in cells grown at low dilution rates in a glucose-limited chemostat in the presence of choline as the sole nitrogen source. Monomeric or other intermediate forms of AO were not detected in the mutant strain. This indicated that assembly of the protein into active octameric molecules in the cytosol was as efficient as in wild-type cells where this process is confined to the peroxisomal matrix. At relatively low rates of expression (less than 1 U/mg protein) AO was localized throughout the cytosol and, surprisingly, was also present inside the nucleus. However, at enhanced levels large crystalloids were formed. Generally one crystalloid was observed per cell, whereas smaller ones were occasionally found in developing buds. Also large crystalloids have been observed inside the nucleus. These crystalloids were not surrounded by a membrane. Based on the morphology of the molecules that constituted these crystalloids and the results of (immuno)cytochemical experiments we conclude that the crystalloids are composed of octameric AO molecules, arranged in a regular lattice, identical to the 3-dimensional architecture previously described for the crystalline matrix of peroxisomes in methanol-grown wild type cells of H. polymorpha. Attempts to purify the crystalloids by conventional fractionation methods failed, due to their apparent fragility; however, (immuno)cytochemical experiments revealed that catalase and dihydroxyacetone synthase were also associated with these structures.
    Additional Material: 15 Ill.
    Type of Medium: Electronic Resource
    Signatur Availability
    BibTip Others were also interested in ...
  • 6
    ISSN: 0749-503X
    Keywords: alcohol oxidase ; flavin adenine dinucleotide ; peroxisomes ; Hansenula polymorpha ; protein translocation ; protein assembly ; Life Sciences ; Life Sciences (general)
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology
    Notes: We have studied the role of flavin adenine dinucleotide (FAD) in the in vivo assembly of peroxisomal alcohol oxidase (AO) in the yeast Hansenula polymorpha. In previous studies, using a riboflavin (Rf) autotrophic mutant, an unequivocal judgement could not be made, since Rf-limitation led to a partial block of AO import in this mutant. This resulted in the accumulation of AO precursors in the cytosol where they remained separated from the putative peroxisomal AO assembly factors. In order to circumvent the peroxisomal membrane barrier, we have now studied AO assembly in a peroxisome-deficient/Rf-autotrophic double mutant (Δper1.rif1) of H. polymorpha. By sucrose density centrifugation and native gel electrophoresis, three conformations of AO were detected in crude extracts of Δper1.rif1 cells grown under Rf-limitation, namely active octameric AO and two inactive, monomeric forms. One of the latter forms lacked FAD; this form was barely detectable in extracts wild-type and Δper1 cells, but had accumulated in the cytosol of rif1 cells. The second form of monomeric AO contained FAD; this form was also present in Δper1 cells but absent/very low in wild-type and rif1 cells. In vivo only these FAD-containing monomers associate into the active, octameric protein. We conclude that in H. polymorpha FAD binding to the AO monomer is mediated by a yet unknown peroxisomal factor and represents the crucial and essential step to enable AO oligomerization; the actual octamerization and the eventual crystallization in peroxisomes most probably occurs spontaneously.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
    Signatur Availability
    BibTip Others were also interested in ...
Close ⊗
This website uses cookies and the analysis tool Matomo. More information can be found here...