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  • 4.2 ka BP event  (1)
  • Analytical ultracentrifugation  (1)
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  • 1
    ISSN: 1432-1017
    Keywords: Key words Glutamate dehydrogenase ; Analytical ultracentrifugation ; Allostery ; Quaternary structure ; Subunit communication
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Physics
    Notes: Abstract X-ray crystallographic studies have previously shown that glutamate dehydrogenase from Clostridium symbiosum is a homohexamer. Mutation of the active-site aspartate-165 to histidine causes an alteration in the structural properties of the enzyme. The mutant enzyme, D165H exists predominantly as a single species of lower molecular mass than the wild-type enzyme as indicated by gel filtration and sedimentation velocity analysis. The latter technique gives an s20,w value for D165H of (6.07 ± 0.01)S which compares with (11.08 ± 0.01)S for the wild-type, indicative of alteration of the homohexameric quaternary structure of the native enzyme to a dimeric form, a result confirmed by sedimentation equilibrium experiments. Further support for this is provided by chemical modification by Ellman's reagent of cysteine-144 in the mutant, a residue which is buried at the dimer-dimer interface in the wild-type enzyme and is normally inaccessible to modification. The results suggest a possible structural route for communication between the active sites and subunit interfaces which may be important for relaying signals between subunits in allosteric regulation of the enzyme.
    Type of Medium: Electronic Resource
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  • 2
    Publication Date: 2019-10-11
    Description: The Mediterranean region and the Levant have returned some of the clearest evidence of a climatically dry period occurring around 4200 years ago. However, some regional evidence is controversial and contradictory, and issues remain regarding timing, progression, and regional articulation of this event. In this paper, we review the evidence from selected proxies (sea-surface temperature, precipitation, and temperature reconstructed from pollen, 18O on speleothems, and 18O on lacustrine carbonate) over the Mediterranean Basin to infer possible regional climate patterns during the interval between 4.3 and 3.8 ka. The values and limitations of these proxies are discussed, and their potential for furnishing information on seasonality is also explored. Despite the chronological uncertainties, which are the main limitations for disentangling details of the climatic conditions, the data suggest that winter over the Mediterranean involved drier conditions, in addition to already dry summers. However, some exceptions to this prevail – where wetter conditions seem to have persisted – suggesting regional heterogeneity in climate patterns. Temperature data, even if sparse, also suggest a cooling anomaly, even if this is not uniform. The most common paradigm to interpret the precipitation regime in the Mediterranean – a North Atlantic Oscillation-like pattern – is not completely satisfactory to interpret the selected data.
    Description: Monica Bini and Giovanni Zanchetta are indebted to the University of Pisa and Earth Science Department for the support in organizing the workshop “The 4.2 ka BP Event”. Monica Bini and Giovanni Zanchetta’s contribution have also been developed within the frame of the project “Climate and alluvial event in Versilia: integration of Geoarcheological, Geomorphological, Geochemical data and numerical simulations” awarded to Monica Bini and funded by the Fondazione Cassa di Risparmio di Lucca. Leszek Marks and Fabian Welc were funded by the National Science Centre in Poland (decision no. DEC-2013/09/B/ST10/02040). Aurel Per¸soiu was funded by UEFISCDI Romania, trough grant no. PN-III-P1-1.1-TE-2016-2210.
    Description: Published
    Description: 555-557
    Description: 5A. Ricerche polari e paleoclima
    Description: JCR Journal
    Keywords: 4.2 ka BP event ; Mediterranean Basin ; Paleoclimate
    Repository Name: Istituto Nazionale di Geofisica e Vulcanologia (INGV)
    Type: article
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