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1.
Cadmium associates with oxalate in calcium oxalate crystals and competes with calcium for translocation to stems in the cadmium bioindicator Gomphrena claussenii
Paula Pongrac, Tania Serra, Hiram Castillo Michel, Katarina Vogel-Mikuš, Iztok Arčon, Mitja Klemen, Boštjan Jencic, Anja Kavčič, Mina T. Villafort Carvalho, Mark G. M. Aarts, 2018, izvirni znanstveni članek

Opis: Cadmium (Cd) was shown to co-localise with calcium (Ca) in oxalate crystals in the stems and leaves of Cd tolerant Gomphrena claussenii, but Cd binding remained unresolved. Using synchrotron radiation X-ray absorption near edge spectroscopy we demonstrate that in oxalate crystals of hydroponically grown G. claussenii the vast majority of Cd is bound to oxygen ligands in oxalate crystals (488%; Cd–O–C coordination) and the remaining Cd is bound to sulphur ligands (Cd–S–C coordination). Cadmium binding to oxalate does not depend on the amount of Ca supplied or from which organs the crystals originate (stems and mature leaves). By contrast, roots contain no oxalate crystals and therein Cd is bound predominantly by S ligands. The potential to remove Cd by extraction of Cd-rich oxalate crystals from plant material should be tested in phytoextraction or phytomining strategies.
Ključne besede: Cd XANES, Cd oxalate, Gomphrena claussenii
Objavljeno v RUNG: 06.09.2018; Ogledov: 3232; Prenosov: 0
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2.
Biotransformation of copper oxide nanoparticles by the pathogenic fungus Botrytis cinerea
Eva Kovačec, Marjana Regvar, Johannes Teun van Elteren, Iztok Arčon, Tamás Papp, Darko Makovec, Katarina Vogel-Mikuš, 2017, izvirni znanstveni članek

Opis: Two plant pathogenic fungi, Botrytis cinerea and Alternaria alternata, isolated from crop plants, were exposed to Cu in ionic (Cu2þ), microparticulate (MP, CuO) or nanoparticulate (NP, Cu or CuO) form, in solid and liquid culturing media in order to test fungal response and toxic effects of the mentioned compounds for the potential use as fungicides. B. cinerea has shown pronounced growth and lower levels of lipid peroxidation compared to A. alternata. Its higher resistance/tolerance is attributed mainly to biotransformation of CuO and Cu NPs and CuO MPs into a blue compound at the fungal/culturing media interface, recognized by Cu K-edge EXAFS analysis as Cu-oxalate complex. The pronounced activity of catechol-type siderophores and organic acid secretion in B. cinerea induce leaching and mobilization of Cu ions from the particles and their further complexation with extracellularly secreted oxalic acid. The ability of pathogenic fungus to biotransform CuO MPs and NPs hampers their use as fungicides. However the results show that B. cinerea has a potential to be used in degradation of Cu(O) nanoparticles in environment, copper extraction and purification techniques.
Ključne besede: copper, metal oxide nanoparticles, detoxification mechanisms, metal pollution, Cu-oxalate
Objavljeno v RUNG: 23.08.2017; Ogledov: 4267; Prenosov: 0
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3.
Oxalic acid adsorption states on the clean Cu(110) surface
Sara Fortuna, 2016, izvirni znanstveni članek

Opis: Carboxylic acids are known to assume a variety of configurations on metallic surfaces. In particular oxalic acid on the Cu(110) surface has been proposed to assume a number of upright configurations. Here we explore with DFT calculations the possible structures that oxalic acid can form on copper 110 at different protonation states, with particular attention at the possibility of forming structures composed of vertically standing molecules. In its fully protonated form it is capable of anchoring itself on the surface thanks to one of its hydrogen-free oxygens. We show the monodeprotonated upright molecule with two oxygens anchoring it on the surface to be the lowest energy conformation of a single oxalic molecules on the Cu(110) surface. We further show that it is possible for this configuration to form dense hexagonally arranged patterns in the unlikely scenario in which adatoms are not involved.
Ključne besede: oxalic acid, oxalate, cu(110), copper, surface, adsorption, density functional theory, DFT
Objavljeno v RUNG: 11.10.2016; Ogledov: 4440; Prenosov: 0
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