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San Sebastián de los Reyes, Spain

Mujika J.I.,Donostia International Physics Center | Rezabal E.,Ecole Polytechnique - Palaiseau | Mercero J.M.,Donostia International Physics Center | Ruiperez F.,Polymat | And 3 more authors.
Computational and Structural Biotechnology Journal | Year: 2014

The increased availability of aluminium in biological environments, due to human intervention in the last century, raises concerns on the effects that this so far "excluded from biology" metal might have on living organisms. Consequently, the bioinorganic chemistry of aluminium has emerged as a very active field of research. This review will focus on our contributions to this field, based on computational studies that can yield an understanding of the aluminum biochemistry at a molecular level. Aluminium can interact and be stabilized in biological environments by complexing with both low molecular mass chelants and high molecular mass peptides. The speciation of the metal is, nonetheless, dictated by the hydrolytic species dominant in each case and which vary according to the pH condition of the medium. In blood, citrate and serum transferrin are identified as the main low molecular mass and high molecular mass molecules interacting with aluminium. The complexation of aluminium to citrate and the subsequent changes exerted on the deprotonation pathways of its tritable groups will be discussed along with the mechanisms for the intake and release of aluminium in serum transferrin at two pH conditions, physiological neutral and endosomatic acidic. Aluminium can substitute other metals, in particular magnesium, in protein buried sites and trigger conformational disorder and alteration of the protonation states of the protein's sidechains. A detailed account of the interaction of aluminium with proteic sidechains will be given. Finally, it will be described how alumnium can exert oxidative stress by stabilizing superoxide radicals either as mononuclear aluminium or clustered in boehmite. The possibility of promotion of Fenton reaction, and production of hydroxyl radicals will also be discussed. © 2014 Mujika et al.

Cadena F.,National Polytechnic School of Ecuador | Irusta L.,Polymat | Fernandez-Berridi M.J.,Polymat
Progress in Organic Coatings | Year: 2013

The performance of alkyd based coatings exposed in two different sites in Ecuador, urban and industrial locations, for corrosion protection was evaluated. Atmospheric test sites and corrosion resistance of coatings were examined using mainly ISO and ASTM standards. The alkyd resin degradation was characterized by different methods such as FTIR-ATR, DSC, TGA and SEM. The studies showed that the corrosion resistance and chemical structural changes were more evident for those samples exposed in the industrial environment although the sun radiation was lower than that measured in the urban location. © 2013 Elsevier B.V. All rights reserved.

Agirre A.,Polymat | Santos J.I.,University of the Basque Country | Leiza J.R.,Polymat
Macromolecular Chemistry and Physics | Year: 2013

The architecture of crosslinked acrylic latexes of 2-ethylhexyl acrylate, methacrylic acid, and a crosslinker agent are investigated. These polymers contain a significant amount of gel content. Branching is obtained by liquid- and melt-state 13C NMR spectroscopy. For the first time, the branching densities (long and short chains) of the soluble and gel fractions are measured independently. Branching is higher for the polymers produced with the most-efficient crosslinkers, namely those which yield a higher crosslinking density. The branching (long chains) and the molecular-weight distribution (MWD) of the soluble fraction are characterized by size-exclusion chromatography (SEC) coupled with triple detection. Coelution of branched chains at large elution volumes is observed in the SEC chromatograms indicating the highly branched nature of the sol fractions of the latexes. Copyright © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Hamzehlou S.,Polymat | Ballard N.,Polymat | Carretero P.,Polymat | Paulis M.,Polymat | And 4 more authors.
Polymer (United Kingdom) | Year: 2014

A detailed kinetic Monte Carlo simulation was used to predict the characteristics of the batch miniemulsion polymerization of an isocyanate and an acrylic monomer mixture that contains a hydroxyl functional monomer (HEMA). The simulation takes into account the simultaneous polyaddition of the polyurethane prepolymer with the hydroxyl group of HEMA and the free radical polymerization of the acrylic monomers and all reactions in aqueous and polymer particle phases. The model has been assessed by batch miniemulsion polymerizations carried out using an aliphatic isocyanate prepolymer, n-butyl acrylate, 2-hydroxyethyl methacrylate monomers and potassium persulfate as an initiator. It was found that partitioning of water had a significant effect on both kinetics and microstructure of the resulting polymer. Evolution of different species of PU prepolymer produced in the reaction and the sol and gel fractions revealed that the terminal pendent double bond of the HEMA in polymer chains has significantly lower reactivity than that of the HEMA free monomer. Detailed information on gel microstructure has been derived in the model by both distribution of molecular weight between crosslinking points in acrylic chains and distribution of chain extension of PU prepolymers. These crosslinking density distributions can be related to mechanical and adhesive properties of the polymer. © 2014 Elsevier Ltd.

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