Browsing by Subject "Redox reactions"

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    Investigating comproportionation in multielectron transfers via UV–visible spectroelectrochemistry: the electroreduction of anthraquinone-2-sulfonate in aqueous media
    (ACS Publications, 2022-08-22) Romay García, Luis; González Sánchez, Joaquín; Molina Gómez, Ángela; Laborda Ochando, Eduardo; Química Física; Facultad de Química
    UV–vis spectroelectrochemistry is assessed as a tool for the diagnosis and quantitative in situ investigation of the incidence of comproportionation in multielectron transfer processes. Thus, the sensitivity of the limiting current chronoabsorptometric signals related to the different redox states to the comproportionation kinetics is studied theoretically for different working modes (normal and parallel light beam arrangements) and mass transport regimes (from semi-infinite to thin layer diffusion). The theoretical results are applied to the spectroelectrochemical study of the two-electron reduction of the anthraquinone-2-sulfonate in alkaline aqueous solution, tuning the thermodynamic favorability of the comproportionation reaction through the electrolyte cation. The quantitative analysis of the experimental results reveals the occurrence of comproportionation in the three media examined, showing different kinetics depending on the cationic species in solution.
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    Structure and Enzymatic Properties of an Unusual Cysteine Tryptophylquinone-Dependent Glycine Oxidase from Pseudoalteromonas luteoviolacea
    (ACS Publications, 2018) Andreo-Vidal, Andres; Mamounis, Kyle J.; Sehanobish, Esha; Avalos, Dante; Campillo-Brocal, Jonatan C.; Sanchez-Amat, Antonio; Yukl, Erik T.; Davidson, Victor L.; Genética y Microbiología
    Glycine oxidase from Pseudoalteromonas luteoviolacea (PlGoxA) is a cysteine tryptophylquinone (CTQ)-dependent enzyme. Sequence and phylogenetic analysis place it in a newly designated subgroup (Group IID) of a recently identified family of LodA-like proteins, which are predicted to possess CTQ. The crystal structure of PlGoxA reveals that it is a homo-tetramer. It possesses an N-terminal domain with no close structural homologues in the Protein Data Bank. The active site is quite small due to intersubunit interactions, which may account for the observed cooperativy towards glycine. Steady-state kinetic analysis yielded values of kcat=6.0±0.2 s−1, K0.5=187±18 μM and h=1.77±0.27. In contrast to other quinoprotein amine dehydrogenases and oxidases that exhibit anomalously large primary kinetic isotope effects on the rate of reduction of the quinone cofactor by the amine substrate, no significant primary kinetic isotope effect was observed for this reaction of PlGoxA. The absorbance spectrum of the glycine-reduced PlGoxA exhibits features in the 400-650 nm range that have not previously been seen in other quinoproteins. Thus, in addition to the unusual structural features of PlGoxA, the kinetic and chemical reaction mechanisms of the reductive half-reaction of PlGoxA appear to be distinct from those of other amine dehydrogenases and amine oxidases that use tryptophylquinone and tyrosylquinone cofactors.