Browsing by Author "Mura, Francisco"

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    Cover 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
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    Electron 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, Ingrid
    The 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.
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    Exploring 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, Denis
    Cinnamoyl-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.
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    Time-resolved fluorescence and anisotropy-sensitive 1,2-dimyristoyl-sn-glycero-3-(7-aminocoumarin) phosphoetanolamide probe for studying membrane lipid domains
    (ELSEVIER SCI LTD, 2023) Zúñiga Núñez, Daniel; Mura, Francisco; Mariño-Ocampo, Nory; Briones-Rebolledo, Patricio; Poblete, Horacio; Mallet, Jean-Maurice; Fuentealba Patino, Denis Alberto; Aspee, Alexis
    A fluorescent probe C-DMPE was synthesised to monitor interfacial membrane properties by conjugating coumarin-343 and 1,2-dimyristoyl-sn-glycero-3-phosphorylethanolamine (DMPE), anchoring the 7-aminocou-marin moiety close to the phospholipid polar head at the membrane interface. Large unilamellar vesicles (LUV) of 1,2-dipalmitoyl-sn-glycero-3-phosphatidylcholine (DPPC), of 1,2-dioleyl-sn-glycero-3-phosphatidyl-choline (DOPC) and cholesterol were employed as a model of lipid bilayer. Time-resolved fluorescence developed an emissive Internal Charge Transfer excited state with a long fluorescence lifetime (T1), a Locally Excited state with an intermediate fluorescence lifetime (T2), and a short lifetime (T3) associated with an intermolecular quenching by interaction with a phosphate group of neighbour phospholipids, as is clearly shown by molecular dynamics simulations. Shorter values of fluorescence lifetimes T1 and T3 were observed in DOPC with respect to DPPC, responding to a more fluid membrane with more significant water accessibility in DOPC than DPPC. However, in DPPC:DOPC vesicles, these fluorescence lifetimes are even shorter, allowing to be attributed to favourable sensing of boundary limit lipid domains. In similitude, time-resolved anisotropy showed shorter rotational correlation times phi 1, in DPPC: DOPC vesicles than in DOPC associated with a faster internal rotational movement of the 7-aminocoumarin group in domains than in fluid a DOPC membrane. In addition, shorter rotational correlation times, (P2, were also observed in DPPC:DOPC vesicles compared to DPPC, suggesting a faster lateral diffusion of the probe in the presence of domains.