Browsing by Author "Aspee, Alexis"
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- ItemAggregation of alpha- and beta- caseins induced by peroxyl radicals involves secondary reactions of carbonyl compounds as well as di-tyrosine and di-tryptophan formation(2018) Fuentes Lemus, Eduardo Felipe; Silva, Eduardo; Barrias, Pablo; Aspee, Alexis; Escobar Álvarez, Elizabeth; Lorentzen, Lasse G.; Carroll, Luke; Leinisch, Fabian; Davies, Michael J.; López Alarcón, Camilo Ignacio
- ItemAntioxidant capacity of phenolic compounds in acidic medium : a pyrogallol red-based ORAC (oxygen radical absorbance capacity) assay(2013) Atala, Elias; Aspee, Alexis; Speisky, Hernán; Lissi, Eduardo; López Alarcón, Camilo Ignacio
- ItemAntioxidant reactivity toward nitroxide probes anchored into human serum albumin. A new model for studying antioxidant repairing capacity of protein radicals(2009) Aspee, Alexis; Orrego, Alejandra; Alarcón Abarzúa, Emilio Isaac; López Alarcón, Camilo Ignacio; Poblete, Horacio; Gonzalez-Nilo, Danilo
- ItemAtypical antioxidant activity of non-phenolic amino-coumarins(2018) Zuniga-Nunez, Daniel; Barrias, Pablo; Cardenas-Jiron, Gloria; Soledad Ureta-Zanartu, M.; López Alarcón, Camilo Ignacio; Moran Vieyra, F. Eduardo; Borsarelli, Claudio D.; Alarcon, Emilio I.; Aspee, Alexis
- ItemChemiluminescence associated with singlet oxygen reactions with amino acids, peptides and proteins(WILEY, 2007) Alarcon, Emilio; Henriquez, Carola; Aspee, Alexis; Lissi, Eduardo A.Low level chemiluminescence (CL) is observed after protein oxidation mediated by singlet oxygen produced in Rose Bengal (RB) irradiation. This CL lasts for several minutes after the end of the photolysis. In this work, the mechanism of the process was assessed from the spectral characteristics of the CL and the effect of antioxidants (Trolox or ascorbate), Ebselen (a compound with peroxidase-like activity), azide (a singlet oxygen scavenger) and D2O, added prior to or after RB irradiation. It is concluded that most of the light emission is due to formation of excited states generated in the decomposition of peroxides and/or hydroperoxides accumulated during the photolysis. Experiments carried out in the presence of several amino acids (Cys, Met, His, Tyr and Trp) and di- and tripeptides suggest that peroxides (and/or hydroperoxides) of Trp residues are mainly responsible for the CL observed after singlet oxygen-mediated protein oxidation. The much weaker CL observed after the oxidation of proteins without Trp residues supports this conclusion. A comparison of the results obtained employing free Trp, Ala-Trp and Trp-Ala dipeptides, Ala-Trp-Ala tripeptide and Trp-containing proteins supports the conclusion that blocking the amino group of the Trp moiety strongly increases the efficiency of the chemilummescent process, producing approximate to 2.5x10(-8) photons per oxidized Trp group in Alla-Trp. A mechanism comprising two chemiluminescent oxidation pathways of Trp residues is proposed to explain the results.
- ItemCompetitive kinetics in free radical reactions of cinnamic acid derivatives. Influence of phenoxyl radicals reactions(2007) López Alarcón, Camilo Ignacio; Aspee, Alexis; Lissi, Eduardo
- ItemCover Picture: Electron Spin-Dependent Electrocatalysis for the Oxygen Reduction Reaction in a Chiro-Self-Assembled Iron Phthalocyanine Device (Angew. Chem. Int. Ed. 4/2024)(2024) Scarpetta-Pizo, Laura; Venegas, Ricardo; Barrias, Pablo; Munoz-Becerra, Karina; Vilches-Labbe, Nayareth; Mura, Francisco; Mendez-Torres, Ana Maria; Ramirez-Tagle, Rodrigo; Toro-Labbe, Alejandro; Hevia, Samuel; Zagal, Jose H.; Onate, Ruben; Aspee, Alexis; Ponce, Ingrid
- ItemDistribution and reactivity of gallates toward galvinoxyl radicals in SDS micellar solutions - Effect of the alkyl chain length(2011) Bridi, Raquel; Aliaga, Carolina; Aspee, Alexis; Abuin, Elsa; Lissi, Eduardo
- ItemElectrochemical and Spectroscopic Study of Pyranine Fluorescent Probe: Role of Intermediates in Pyranine Oxidation(2011) Velasquez, Gabriela; Ureta-Zanartu, M. Soledad; López Alarcón, Camilo Ignacio; Aspee, Alexis
- ItemElectrodes based on zeolites modified with cobalt and/or molybdenum for pesticide degradation: part II-2,4,6-trichlorophenol degradation(2021) Castro, Jorge; Fernandez, Francisco; Olivares, Felipe; Berrios, Cristhian; Garrido-Ramirez, Elizabeth; Blanco, Elodie; Escalona, Nestor; Aspee, Alexis; Barrias, Pablo; Soledad Ureta-Zanartu, M.2,4,6-trichlorophenol (TCP) is a persistent pollutant introduced in water by industrial processes and pesticides. We have studied the electrooxidation of TCP on glassy carbon (GC) electrodes drop-coated with a suspension containing Mo- and/or Co-modified zeolite, graphite, and Nafion (R) perfluorinated ion-exchange resin in distilled water. Three zeolites, Linde type A (ZA), Faujasite (ZY) and MFI (ZSM-5), of different hydrophilic/hydrophobic character, were modified with molybdenum and/or cobalt by the wet impregnation method and characterized by Fourier-transform infrared spectroscopy with attenuated total reflection and temperature programmed reduction. The electrochemical study included cyclic voltammetry, electrochemical impedance spectroscopy, and electrolysis at controlled potential. High performance liquid chromatography and mass spectrometry allowed detecting the following reaction products: 2,6-dichloro-1,4-benzoquinone, 2,6-dichloro-1,4-hydroquinone, 3,5-dichloro-2-hydroxy-1,4-benzoquinone, and malic, maleic, picric, and acetic acids. A maximum degradation of about 90% was reached after 4 h of electrolysis at 0.83 V vs Ag/AgCl/KCl 3 M, using a GC/graphite-ZSM5(Mo) electrode. The electrodes modified with Mo, and especially that with ZSM5, the most hydrophobic zeolite, were active for the degradation of TCP. We conclude that the main role of the Mo species is to catalyze the hydrogen peroxide decomposition yielding reactive singlet oxygen, as evidenced by the pink color of 3,5-dichloro-2-hydroxy-1,4-benzoquinoneand confirmed by mass spectrometry.
- ItemElectron Spin-Dependent Electrocatalysis for the Oxygen Reduction Reaction in a Chiro-Self-Assembled Iron Phthalocyanine Device(2023) Scarpetta-Pizo, Laura; Venegas, Ricardo; Barrias, Pablo; Munoz-Becerra, Karina; Vilches-Labbe, Nayareth; Mura, Francisco; Mendez-Torres, Ana Maria; Ramirez-Tagle, Rodrigo; Toro-Labbe, Alejandro; Hevia, Samuel; Zagal, Jose H.; Onate, Ruben; Aspee, Alexis; Ponce, IngridThe chiral-induced spin selectivity effect (CISS) is a breakthrough phenomenon that has revolutionized the field of electrocatalysis. We report the first study on the electron spin-dependent electrocatalysis for the oxygen reduction reaction, ORR, using iron phthalocyanine, FePc, a well-known molecular catalyst for this reaction. The FePc complex belongs to the non-precious catalysts group, whose active site, FeN4, emulates catalytic centers of biocatalysts such as Cytochrome c. This study presents an experimental platform involving FePc self-assembled to a gold electrode surface using chiral peptides (L and D enantiomers), i.e., chiro-self-assembled FePc systems (CSAFePc). The chiral peptides behave as spin filters axial ligands of the FePc. One of the main findings is that the peptides ' handedness and length in CSAFePc can optimize the kinetics and thermodynamic factors governing ORR. Moreover, the D-enantiomer promotes the highest electrocatalytic activity of FePc for ORR, shifting the onset potential up to 1.01 V vs. RHE in an alkaline medium, a potential close to the reversible potential of the O2/H2O couple. Therefore, this work has exciting implications for developing highly efficient and bioinspired catalysts, considering that, in biological organisms, biocatalysts that promote O2 reduction to water comprise L-enantiomers.
- ItemExploring the photophysics of cinnamoyl-coumarin derivatives in cucurbit [7]uril complexes and assessing phototoxicity in HeLa cells(2024) Zuniga-Nunez, Daniel; Mura, Francisco; Marino-Ocampo, Nory; Zuniga, Benjamin; Robinson-Duggon, Jose; Zamora, Ricardo A.; Poblete, Horacio; Aspee, Alexis; Fuentealba, DenisCinnamoyl-coumarin derivatives containing 5 or 12 carbon aliphatic chains were evaluated as photosensitizers and their photophysical properties were studied in detail. Moreover, these compounds were encapsulated in cucurbit[7]uril macrocycle with relatively high binding affinities in aqueous media. Fluorescence quantum yields, fluorescence lifetimes and singlet oxygen quantum yields were measured upon encapsulation. Computational DFT calculations and molecular dynamics simulations allowed the visualization of the binding modes of both derivatives inside the macrocycle. In particular, the free energy profiles for the insertion of the molecules into the macrocycle were determined to assess the most probable conformations of the complexes in water. In vitro phototoxicity assays were carried out in HeLa cells showed significant decreases in cell viability upon illumination of the 5 carbon aliphatic chain derivative at 460 nm with an LED source at different concentrations and enhanced by cucurbit[7]uril. However, the one with 12 carbon aliphatic chain did not display any phototoxicity regardless of the presence of cucurbit[7]uril. This behavior is related to the high lipophilicity introduced by a 12 carbon aliphatic chain conditioning its distribution on hydrophobic compartments and decreasing its phototoxicity. The enhanced phototoxicity elicited by cucurbit[7]uril on the 5 carbon aliphatic chain derivative but not in the 12 carbon derivative remark that there is a balance between hydrophobicity of these probes with the carrier properties of cucurbit[7]uril to be reach for effective phototoxicity properties.
- ItemFree radical scavenging capacity of hydroxycinnamic acids and related compounds(2006) Pino, Eduardo; Campos, Ana M.; López Alarcón, Camilo Ignacio; Aspee, Alexis; Lissi, Eduardo
- ItemGeneration, spectroscopic characterization by EPR, and decay of a pyranine-derived radical(2007) Aliaga, Carolina; Arenas Lissi, Andrea Beatriz; Aspee, Alexis; López Alarcón, Camilo Ignacio; Lissi, Eduardo A.
- ItemInfluence of the Target Molecule on the ORAC Index(2012) López Alarcón, Camilo Ignacio; Aspee, Alexis; Lissi, Eduardo
- ItemInteraction and reactivity of urocanic acid towards peroxyl radicals(2005) López Alarcón, Camilo Ignacio; Aspee, Alexis; Henriquez, C.; Campos, A.M.; Lissi, E.A.
- ItemPhotobehavior of merocyanine 540 bound to human serum albumin(2010) Alarcón Abarzúa, Emilio Isaac; Aspee, Alexis; González Bejar, María; EdwardsM., Ana M; Lissi, E. A.; Scaiano, J. C.
- ItemPhotophysics and photochemistry of dyes bound to human serum albumin are determined by the dye localization(2010) Alarcón Abarzúa, Emilio Isaac; EdwardsM., Ana M; Aspee, Alexis; Moran Vieyra, Faustino Eduardo; Borsarelli, Claudio D.; Lissi, Eduardo A.; González Nilo, Fernando Danilo; Poblete, Horacio; Scaiano, J. C.
- ItemPhotophysics and photochemistry of rose bengal bound to human serum albumin(2009) Alarcón Abarzúa, Emilio Isaac; EdwardsM., Ana M; Aspee, Alexis; Borsarelli, Claudio D.; Lissi, Eduardo A.
- ItemPhotophysics and photochemistry of zinc phthalocyanine bovine serum albumin adducts(2009) Alarcón Abarzúa, Emilio Isaac; EdwardsM., Ana M; García Torres, Angélica María; Muñoz Figueroa, Marcelo Alejandro; Aspee, Alexis; Borsarelli, Claudio D.; Lissi, Eduardo A.