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  • release processes  (2)
  • sediments  (2)
  • Mn superoxide dismutase  (1)
  • 1
    ISSN: 1432-1017
    Keywords: Mn superoxide dismutase ; NMR relaxation ; pH influence on enzyme structure
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Physics
    Notes: Abstract The dependence of the magnetic relaxation rates of1H and19F on temperature, frequency, pH and N 3 - concentration, were measured in solutions of Manganese-containing superoxide dismutase ofBacillus stearothermophilus, and were compared to activity measurements, in order to obtain some information on the structure and dynamics at Mn(III) present in the active site of the enzyme. The experimental data lead us to hypothesize the presence of two binding sites in the coordination sphere of the enzyme bound Mn(III), which are accessible to water and anions and have different chemical and spectroscopic properties. NMR measurements carried out in the presence of competitive inhibitors and the pH dependence of both NMR relaxation rates suggest that F-, N 3 - and OH- ions bind to one site, while a water molecule binds to the other one. The stability constant values of the complexes between these anions and the enzyme are reported. The influence of the anions on activity and the pH dependence of NMR parameters are discussed.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    Springer
    Water, air & soil pollution 99 (1997), S. 255-263 
    ISSN: 1573-2932
    Keywords: heavy metals ; sediments ; pollution ; resuspension ; release processes ; bioavailability ; anthropogenic ; metal ; residual inetal ; geochemical phases
    Source: Springer Online Journal Archives 1860-2000
    Topics: Energy, Environment Protection, Nuclear Power Engineering
    Notes: Abstract The space-time distribution of some pollutants (Cu, Ph, Zn, Cd, Fe, Mn, V, Ni, Cr) in the sludge of the canals of Venice was studied. The contamination levels were comparable to, or higher, than those measured in the most polluted sediments of the Lagoon of Venice Sediments were collected by two different sampling techniques I ) collection of sediment cores (upper 5 cm) by a syringe-type corer, 2) collection by traps, placed on the bottom of the canal Traps pennitted the sampling of sediments essentially resuspended by overlying water turbulence This sediment fraction is subjected to variations of its physicochemical parameters (principally change of redox conditions) and therefore to pollutant exchange at the water/sediment interface The metals principally exchanged during sediment resuspension were Cd, Pb, Zn and Cu These metals have principally an anthropogenic origin and are bound to the most labile geochemical phases of the sediment (such as sulphides), which can be oxidised during sediment resuspension, releasing metals into the water Fe, Cr and Ni were only partially exchanged, while Mn and V were generally not exchanged, a significant fraction of these metals is of natural origin and is bound to the most refractory phases of the sediment.
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    Springer
    Water, air & soil pollution 99 (1997), S. 255-263 
    ISSN: 1573-2932
    Keywords: heavy metals ; sediments ; pollution ; resuspension ; release processes ; bioavailability ; anthropogenic metal ; residual metal ; geochemical phases
    Source: Springer Online Journal Archives 1860-2000
    Topics: Energy, Environment Protection, Nuclear Power Engineering
    Notes: Abstract The space-time distribution of some pollutants (Cu, Pb, Zn, Cd, Fe, Mn, V, Ni, Cr) in the sludge of the canals of Venice was studied. The contamination levels were comparable to, or higher, than those measured in the most polluted sediments of the Lagoon of Venice. Sediments were collected by two different sampling techniques: 1) collection of sediment cores (upper 5 cm) by a syringe-type corer; 2) collection by traps, placed on the bottom of the canal. Traps permitted the sampling of sediments essentially resuspended by overlying water turbulence. This sediment fraction is subjected to variations of its physicochemical parameters (principally change of redox conditions) and therefore to pollutant exchange at the water/sediment interface. The metals principally exchanged during sediment resuspension were Cd, Pb, Zn and Cu. These metals have principally an anthropogenic origin and are bound to the most labile geochemical phases of the sediment (such as sulphides), which can be oxidised during sediment resuspension, releasing metals into the water. Fe, Cr and Ni were only partially exchanged, while Mn and V were generally not exchanged; a significant fraction of these metals is of natural origin and is bound to the most refractory phases of the sediment.
    Type of Medium: Electronic Resource
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
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