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Dynamics of Chromium in the soil-root interface and role of humic and phenolic acids in the chromium detoxification process
No full textTransfer of Metal Ions at the Soil-Root Interface: Role of VO2+ on Fe3+ Mobilization from a Fe(III)-Network
No full textPrime valutazioni degli effetti della protezione sull’ittiofauna di fondo roccioso nella costa occidentale dell’Isola dell’Asinara
No full textCoastal fish fauna from a recently established Mediterranean MPA and from an adjacent non-protected zone near its boundary were compared to evaluate the effects of protection. A remarkable “reserve effect” was detected for the whole assemblage in terms of both species richness and abundance. Moreover, a moderate spillover effect outside the MPA was observed for several target species
Interaction of Ca2+ and Na+ ions with polygalacturonic chains: a molecular dinamics study
No full textPartially esterified polygalacturonic acid is the main component of pectin in higher plants. The carboxylic groups and their methyl esters markedly affect the ability of the pectin molecules to bind oppositely charged ions and to form gels. In order to make a contribution to the understanding of the mechanisms which regulate the ionic transfer at the soil root interface and in the apoplast, we report the results of a set of molecular dynamics experiments in which the interactions of four fully deprotonated fragments of polygalacturonic acid, each counting 12 units, 300 water molecules and 48 or 24 Na+ and Ca2+ ions were studied.
We observed the formation of Ca2+ bridges between the polygalacturonate chains. The forces driving the aggregation processes are characterized by the formation of strong coulombic interactions between the metal ions and the carboxylate groups. The results are consistent with experiment evidence of the formation of Ca polygalacturonate organized gels. The Ca polygalacturonate complex exhibits a lower energy compared to that of Na polygalacturonate. The ratio of the Na+ and Ca2+ diffusion coefficients agree well with experimental reports
Molecular dynamics study of polygalacturonic acid chains in aqueous solution
No full textMolecular dynamics (MD) simulations were performed on a system consisting of polygalacturonic acid (PGA) chains. MD experiments were conducted both in vacuo and in the presence of water. The PGA chains were formed by 12 GalA units and each chain had a molecular weight of 2132. Three chains were enclosed in the simulation cells. NPT runs, carried out either in the absence and in the presence of water molecules, evidenced the collapse of the chains which aggregate due to the formation of hydrogen bonds. NVT trajectories performed in the presence of water molecules show that the solvent moves in channels which separate the PGA aggregates, These findings well agree with experimental results about gel formation by PGA and other pectins in strong acid media. (C) 1997 Elsevier Science Ltd.Molecular dynamics (MD) simulations were performed on a system consisting of polygalacturonic acid (PGA) chains. MD experiments were conducted both in vacuo and in the presence of water. The PGA chains were formed by 12 GalA units and each chain had a molecular weight of 2132. Three chains were enclosed in the simulation cells. NPT runs, carried out either in the absence and in the presence of water molecules, evidenced the collapse of the chains which aggregate due to the formation of hydrogen bonds. NVT trajectories performed in the presence of water molecules show that the solvent moves in channels which separate the PGA aggregates, These findings well agree with experimental results about gel formation by PGA and other pectins in strong acid media
Mechanism and stoichiometry of the redox reaction between iron(III) and caffeic acid
No full textThe stoichiometry of the redox reaction of caffeic acid with iron(III) was determined at pH 2.5. A linear increase in the yield of iron(II) was found with increasing iron(III) concentration until reached constant values when iron(III)/caffeic acid molar ratios were higher than 9. The reaction proceeds through two steps each having different rates, and involving intermediates with different redox activities. A mechanism of the redox reaction consistent with our results is proposed.The stoichiometry of the redox reaction of caffeic acid with iron(III) was determined at pH 2.5. A linear increase in the yield of iron(II) was found with increasing iron(III) concentration until reached constant values when iron(III)/caffeic acid molar ratios were higher than 9. The reaction proceeds through two steps each having different rates, and involving intermediates with different redox activities. A mechanism of the redox reaction consistent with our results is proposed
Detoxification processes from vanadate at the root apoplasm activated by caffeic and polygalacturonic acids
Get PDFIn the root apoplasm, V(V) and V(IV) toxicity can be alleviated through redox and complexation reactions involving phenolic substances and the polyuronic components. In such context we report the role of polygalacturonic acid (PGA) on the reducing activity of caffeic acid (CAF) towards V(V). The redox reaction was particularly effective at pH 2.8 leading to the formation of oxidation products with redox activity towards V(V). An o-quinone was identified as the first product of the reaction which is further involved in the formation of CAF dimers. At pH ≥ 3.6 the redox activity decreased and a yield in V(IV) equal to 38, 31, 21 and 14% was found at pH 3.6, 4.0. 5.0 and 6.0 respectively compared with that obtained at pH 2.8. The redox reaction was faster in the presence of PGA and a higher yield of V(IV) was found in the 4.0–6.0 pH range with respect to the CAF-V(V) binary system. The higher efficiency of the redox reaction in the presence of PGA was related with the ability of PGA to bind V(IV). The biological significance of the redox reaction between CAF and V(V), as well as the role of PGA in such reaction, was established “in vivo” using triticale plants. Results showed that PGA reduced significantly the phytotoxic effects of the V(V)-CAF system.In the root apoplasm, V(V) and V(IV) toxicity can be alleviated through redox and complexation reactions involving phenolic substances and the polyuronic components. In such context we report the role of polygalacturonic acid (PGA) on the reducing activity of caffeic acid (CAF) towards V(V). The redox reaction was particularly effective at pH 2.8 leading to the formation of oxidation products with redox activity towards V(V). An o-quinone was identified as the first product of the reaction which is further involved in the formation of CAF dimers. At pH - 3.6 the redox activity decreased and a yield in V(IV) equal to 38, 31, 21 and 14% was found at pH 3.6, 4.0. 5.0 and 6.0 respectively compared with that obtained at pH 2.8. The redox reaction was faster in the presence of PGA and a higher yield of V(IV) was found in the 4.0-6.0 pH range with respect to the CAF-V(V) binary system. The higher efficiency of the redox reaction in the presence of PGA was related with the ability of PGA to bind V(IV). The biological significance of the redox reaction between CAF and V(V), as well as the role of PGA in such reaction, was established "in vivo" using triticale plants. Results showed that PGA reduced significantly the phytotoxic effects of the V(V)-CAF system. © 2015 Garau et al. This is an open access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited
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