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  • Key words Manganese nodules  (1)
  • Protease  (1)
  • 1995-1999  (2)
  • 1
    ISSN: 0016-7835
    Keywords: Key words Manganese nodules ; Thorium dating ; Uranium isotopes ; Peru basin ; TIMS
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences
    Notes: Abstract  Thorium- and uranium isotopes were measured in a diagenetic manganese nodule from the Peru basin applying alpha- and thermal ionization mass spectrometry (TIMS). Alpha-counting of 62 samples was carried out with a depth resolution of 0.4 mm to gain a high-resolution 230Thexcess profile. In addition, 17 samples were measured with TIMS to obtain precise isotope concentrations and isotope ratios. We got values of 0.06–0.59 ppb (230Th), 0.43-1.40 ppm (232Th), 0.09–0.49 ppb (234U) and 1.66–8.24 ppm (238U). The uranium activity ratio in the uppermost samples (1–6 mm) and in two further sections in the nodule at 12.5±1.0 mm and 27.3–33.5 mm comes close to the present ocean water value of 1.144±0.004. In two other sections of the nodule, this ratio is significantly higher, probably reflecting incorporation of diagenetic uranium. The upper 25 mm section of the Mn nodule shows a relatively smooth exponential decrease in the 230Thexcess concentration (TIMS). The slope of the best fit yields a growth rate of 110 mm/Ma up to 24.5 mm depth. The section from 25 to 30.3 mm depth shows constant 230Thexcess concentrations probably due to growth rates even faster than those in the top section of the nodule. From 33 to 50 mm depth, the growth rate is approximately 60 mm/Ma. Two layers in the nodule with distinct laminations (11–15 and 28–33 mm depth) probably formed during the transition from isotopic stage 8 to 7 and in stage 5e, respectively. The Mn/Fe ratio shows higher values during interglacials 5 and 7, and lower ones during glacials 4 and 6. A comparison of our data with data from adjacent sediment cores suggests (a) a variable supply of hydrothermal Mn to sediments and Mn nodules of the Peru basin or (b) suboxic conditions at the water sediment interface during periods with lower Mn/Fe ratios.
    Type of Medium: Electronic Resource
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  • 2
    ISSN: 0173-0835
    Keywords: Two-dimensional zymography ; Photorhabdus luminescens ; Protease ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Chemistry and Pharmacology
    Notes: Two-dimensional zymography which combines two-dimensional electrophoresis with zymography was used to analyze proteases and other proteins produced by different phase variants of two strains of Photorhabdus luminescens. Both the primary and secondary phases of P. luminescens strains Hp and Hm secreted proteases. The protease in P. luminescens Hp has a molecular weight (Mr) of 57 000 and an isoelectric point (pI) of 4.4 whereas that in P. luminescens Hm has an Mr of 59 000 and pI of 4.9. Several putative protease degradation products were clearly visible in the zymograms from both bacterial strains. Two-dimensional zymography also showed that several secretory proteins were present only in particular phase variants and therefore could be used as specific markers. Unexpectedly, the two-dimensional zymography revealed that a nonsecretory protease with an Mr of 47 000 and a pI of 4.0 was present in the cell extracts of all phases of both P. luminescens Hp and Hm. The application of the two-dimensional zymography for the identification of other enzymes was also discussed.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
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