Browsing by Author "Silva, E."

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    Alpha- and beta-casein aggregation induced by riboflavin-sensitized photo-oxidation occurs via di-tyrosine cross-links and is oxygen concentration dependent
    (2018) Fuentes Lemus, Eduardo Felipe; Silva, E.; Leinisch, F.; Dorta Pérez, Eva; Lorentzen, L. G.; Davies, M. J.; López Alarcón, Camilo Ignacio
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    Apoptosis induction in nonirradiated human HL-60 and murine NSO/2 tumor cells by photoproducts of indole-3-acetic acid and riboflavin
    (1999) EdwardsM., Ana M; Barredo, F.; Silva, E.; De Ioannes I., Alfredo E.; Becker C., María Inés
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    Giant spin-charge conversion driven by nanoscopic particles of Ag in Pt
    (2017) Alves, O.; Silva, E.; Gamino, M.; Cunha, R.; Mendes, J.; Rodríguez Suárez, Roberto; Rezende, S.; Azevedo, A.
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    Isolation and photo-oxidation of lysozyme fragments
    (1981) Ferrer Meli, Irene del Carmen; Silva, E.
    Reduction of the four disulfide bonds and further carboxymethylation of lysozyme followed by its reaction with CNBr brings about L-I, (aa 1 12) and L-II-III (aa 13 129) peptides. When breaking the polypeptidic chain by CNBr action and freeing the peptides formed through S-S bonds reduction and carboxymethylation three peptides are obtained corresponding to L-I (aa 1 12), L-II (aa 13 105) and L-III (aa 106 129). L-II-III, L-III and L-II peptides were separately subjected to photo-oxidation in presence of riboflavin, in 0.05 M phosphate buffer, pH 7.0. The kinetic analysis of Trp photo-oxidation in L-II-III peptides shows that these residues keep, to a great extent, the degree of exposition they had in native lysozyme. L-II peptide also presents Trp residues with a different degree of exposition. Presence of Tyr photo-oxidation in L-II and L-II-III peptides - what does not take place in native lysozyme - suggests a relationship between photo-oxidation selectivity and the degree of exposition of certain amino acid residues in spatial configuration.Reduction of the four disulfide bonds and further carboxymethylation of lysozyme followed by its reaction with CNBr brings about L-I, (aa 1 12) and L-II-III (aa 13 129) peptides. When breaking the polypeptidic chain by CNBr action and freeing the peptides formed through S-S bonds reduction and carboxymethylation three peptides are obtained corresponding to L-I (aa 1 12), L-II (aa 13 105) and L-III (aa 106 129). L-II-III, L-III and L-II peptides were separately subjected to photo-oxidation in presence of riboflavin, in 0.05 M phosphate buffer, pH 7.0. The kinetic analysis of Trp photo-oxidation in L-II-III peptides shows that these residues keep, to a great extent, the degree of exposition they had in native lysozyme. L-II peptide also presents Trp residues with a different degree of exposition. Presence of Tyr photo-oxidation in L-II and L-II-III peptides - what does not take place in native lysozyme - suggests a relationship between photo-oxidation selectivity and the degree of exposition of certain amino acid residues in spatial configuration.Reduction of the four disulfide bonds and further carboxymethylation of lysozyme followed by its reaction with CNBr brings about L-I, (aa 1 12) and L-II-III (aa 13 129) peptides. When breaking the polypeptidic chain by CNBr action and freeing the peptides formed through S-S bonds reduction and carboxymethylation three peptides are obtained corresponding to L-I (aa 1 12), L-II (aa 13 105) and L-III (aa 106 129). L-II-III, L-III and L-II peptides were separately subjected to photo-oxidation in presence of riboflavin, in 0.05 M phosphate buffer, pH 7.0. The kinetic analysis of Trp photo-oxidation in L-II-III peptides shows that these residues keep, to a great extent, the degree of exposition they had in native lysozyme. L-II peptide also presents Trp residues with a different degree of exposition. Presence of Tyr photo-oxidation in L-II and L-II-III peptides - what does not take place in native lysozyme - suggests a relationship between photo-oxidation selectivity and the degree of exposition of certain amino acid residues in spatial configuration.
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    Light pollution reduces activity, food consumption and growth rates in a sandy beach invertebrate
    (2016) Luarte, T.; Bonta, C.; Silva, E.; Quijon, P.; Miranda, C.; Farias Piccolini, Ariel Alejandro; Duarte, C.
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    Oxidation of free, peptide and protein tryptophan residues mediated by AAPH-derived free radicals: role of alkoxyl and peroxyl radicals
    (2016) Fuentes Lemus, Eduardo Felipe; Dorta Pérez, Eva; Escobar Álvarez, Elizabeth; Aspée, A.; Pino, E.; Abasq, M. L.; Speisky, Hernán; Silva, E.; Lissi, E.; Davies, M. J.; López Alarcón, Camilo Ignacio
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    Photo -oxidation of lysozyme triggered by riboflavin is O 2-dependent, occurs via mixed type 1 and type 2 pathways, and results in inactivation, site-specific damage and intra- and inter -molecular crosslinks
    (2020) Fuentes Lemus, Eduardo Felipe; Mariotti, M.; Reyes Martinez, Juan; Leinisch, F.; Hagglund, P.; Silva, E.; Davies, M. J.; López Alarcón, Camilo Ignacio
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    Study of a photo-induced lysozyme-riboflavin bond
    (1985) Ferrer Meli, Irene del Carmen; Silva, E.
    Irradiation of lysozyme in the presence of riboflavin results in the formation of a lysozyme-riboflavin adduct. Reduction and carboxymethylation of the four disulfide bonds as well as the chemical modification of the Tyr residues and the photochemical alteration of the His residue in lysozyme, do not affect the formation of the photo-induced lysozyme-riboflavin bond. When the lysozyme-riboflavin adduct was subjected to mild acid hydrolysis and ion exchange chromatography, the retention of a compound containing14C-riboflavin was observed. Free14C-riboflavin, on the contrary is not retained by the column. The photo-oxidation of free Trp in the presence of14C-riboflavin, gave a compound which bound to the ion exchange resin like the above-mentioned derivative. The photo-oxidation of the Trp residues in lysozyme and in peptides obtained from lysozyme showed very high quantum yields, and these values were directly related to the incorporation of14C-riboflavin in these samples.
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    The riboflavin-sensitized photooxidation of horseradish apoperoxidase
    (1985) Silva, E.; Barrera, M.
    Native horseradish peroxidase, as well as its reduced and carboxymethylated form, and the apoenzyme, showed resistance to photodynamic action. Sensitivity to this action was detected only in reduced and carboxymethylated apoenzyme, when the photooxidation of its histidine residues was observed. When analyzing the bulk hydrophobic character (Hf) and the accessibility coefficients (Br) in those amino acid residues which can be subjected to photooxidation in horseradish peroxidase, it was found that all of them are situated in hydrophobic zones with low accessibility coefficients. This could justify the high resistance of this enzyme to photodynamic action. The only exception is tryptophan-117, which has low values of Hf and Br, and therefore its resistance to photodynamic action can only be explained in terms of its location and environment. Tryptophan-117 would be situated in a zone of antiparallel?-structure, according to Chou and Fasman's predictive method for protein conformation.
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    The role of protein-derived free radicals as intermediaries of oxidative processes
    (2014) López Alarcón, Camilo Ignacio; Arenas, A.; Lissi, E.; Silva, E.