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Arabidopsis halleri shows hyperbioindicator behaviour for Pb and leaf Pb accumulation spatially separated from Zn
Stephan Höreth, Paula Pongrac, Marta Debeljak, Katarina Vogel-Mikuš, Matic Pečovnik, Primož Vavpetič, Iztok Arčon, izvirni znanstveni članek

Opis: Lead (Pb) ranks among the most problematic environmental pollutants. Background contamination of soils is nearly ubiquitous, yet plant Pb accumulation is barely understood. In a survey covering 165 European populations of the metallophyte Arabidopsis halleri, several field samples had indicated Pb hyperaccumulation, offering a chance to dissect plant Pb accumulation. Accumulation of Pb was analysed in A. halleri individuals from contrasting habitats under controlled conditions to rule out aerial deposition as a source of apparent Pb accumulation. Several elemental imaging techniques were employed to study the spatial distribution and ligand environment of Pb. Regardless of genetic background, A. halleri individuals showed higher shoot Pb accumulation than A. thaliana. However, dose–response curves revealed indicator rather than hyperaccumulator behaviour. Xylem sap data and elemental imaging unequivocally demonstrated the in planta mobility of Pb. Highest Pb concentrations were found in epidermal and vascular tissues. Distribution of Pb was distinct from that of the hyperaccumulated metal zinc. Most Pb was bound by oxygen ligands in bidentate coordination. A. halleri accumulates Pb whenever soil conditions render Pb phytoavailable. Considerable Pb accumulation under such circumstances, even in leaves of A. thaliana, strongly suggests that Pb can enter food webs and may pose a food safety risk.
Ključne besede: Pb accumulation, XANES, EXAFS, Arabidopsis halleri
Objavljeno v RUNG: 16.01.2020; Ogledov: 3116; Prenosov: 0
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68.
A consensus protocol for the in silico optimisation of antibody fragments
Miguel Soler, Barbara Medagli, Marta S. Semrau, Paola Storici, Gregor Bajc, Ario De Marco, Alessandro Laio, Sara Fortuna, 2019, izvirni znanstveni članek

Ključne besede: nanobodies, in silico design, Her2
Objavljeno v RUNG: 21.11.2019; Ogledov: 3314; Prenosov: 0
Gradivo ima več datotek! Več...

69.
Localization, ligand environment, bioavailability and toxicity of mercury in Boletus spp. and Scutiger pes-caprae mushrooms
Anja Kavčič, Klemen Mikuš, Marta Debeljak, Johannes Teun van Elteren, Iztok Arčon, Alojz Kodre, Peter Kump, Andreas-Germanos Karydas, Alessandro Migliori, Mateusz Czyzycki, Katarina Vogel-Mikuš, 2019, izvirni znanstveni članek

Opis: This study provides information on mercury (Hg) localization, speciation and ligand environment in edible mushrooms: Boletus edulis, B. aereus and Scutiger pes-caprae collected at non-polluted and Hg polluted sites, by LA-ICP-MS, SR-μ-XRF and Hg L3-edge XANES and EXAFS. Mushrooms (especially young ones) collected at Hg polluted sites can contain more than 100 μg Hg g−1 of dry mass. Imaging of the element distribution shows that Hg accumulates mainly in the spore-forming part (hymenium) of the cap. Removal of hymenium before consumption can eliminate more than 50% of accumulated Hg. Mercury is mainly coordinated to di-thiols (43–82%), followed by di-selenols (13–35%) and tetra-thiols (12–20%). Mercury bioavailability, as determined by feeding the mushrooms to Spanish slugs (known metal bioindicators owing to accumulation of metals in their digestive gland), ranged from 4% (S. pes-caprae) to 30% (B. aereus), and decreased with increasing selenium (Se) levels in the mushrooms. Elevated Hg levels in mushrooms fed to the slugs induced toxic effects, but these effects were counteracted with increasing Se concentrations in the mushrooms, pointing to a protective role of Se against Hg toxicity through HgSe complexation. Nevertheless, consumption of the studied mushroom species from Hg polluted sites should be avoided.
Ključne besede: edible mushrooms, HgSe complex, imaging of elemental distribution, LA-ICP-MS, alpha-XRF, XAS
Objavljeno v RUNG: 24.10.2019; Ogledov: 4638; Prenosov: 0
Gradivo ima več datotek! Več...

70.
SEARCH FOR NEUTRINOS AT EXTREME ENERGIES WITH THE PIERRE AUGER OBSERVATORY
Marta Trini, 2019, doktorska disertacija

Opis: The detection of Ultra-High-Energy (UHE) neutrinos around and above 10 18 eV (1 EeV) can be the key to answering the long-standing question of the origin of the UHE cosmic rays. The Pierre Auger Observatory is the largest experiment that can detect the extensive air showers produced when the cosmic rays and neutrinos interact in the earth’s atmosphere. In particular, with the Infilled array of the Surface Detector of the Pierre Auger Observatory we can detect sub-EeV neutrino-induced particle showers. In this thesis we demonstrate that it is possible to discriminate neutrino-induced showers from the background showers produced by the more numerous nucleonic cosmic rays. The sensitivity to neutrinos is enhanced in the inclined directions with respect to the vertical to the ground, where cosmic ray-induced showers starting in the upper layers of the atmosphere are dominated by the muonic component of the shower, while deeply- penetrating neutrino showers in contrast exhibit a large electromagnetic component. Based on this idea in this thesis we have developed a search procedure for UHE neutrinos that consists on selecting inclined events in the Infilled array of the Pierre Auger Observatory in which the signals in the water-Cherenkov stations are spread in time, characteristic of the presence of electromagnetic component in the shower. We have established a complete chain of criteria to first select the inclined events among the sample of all events triggering the Infilled array, and then identifying those that have a large electromagnetic component at ground, and hence can be considered as neutrino candidates. We have identified a single variable, the so-called area-over-peak averaged over all of the stations in each event, as a suitable observable for neutrino identification purposes. The neutrino selection was established using extensive Monte Carlo simulations of the neutrino-induced showers in the Infilled array of Auger as well as a fraction of the data assumed to be totally constituted of background nucleonic cosmic rays. Using these neutrino simulations we have also computed the exposure of the Infilled array to UHE neutrinos in the period 1 January 04 - 31 December 2017. Associated systematic uncertainties on the exposure are also described. Expecting no candidate neutrinos in the period up to 31 December 2017, and adopting a differential neutrino diffuse flux dN ν /dE ν = k E ν −2 in the energy range from 0.05 to 1 EeV, we have obtained a 90% C.L. upper limit on the all neutrino flavor, k 90 < 7.97 × 10 −8 GeV cm −2 s −1 sr −1 .
Ključne besede: astroparticles, astrophysical neutrinos, cosmic rays showers, Pierre Auger Observatory, Infilled array
Objavljeno v RUNG: 03.10.2019; Ogledov: 4877; Prenosov: 147
.pdf Celotno besedilo (6,02 MB)

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