Browsing by Author "Droguett Muñoz, Kevin Arturo"

Now showing 1 - 2 of 2
  • Thumbnail Image
    Item
    A comparative study on the cucurbit[7]uril-based indicator displacement assay for methyl Viologen. A theoretical and experimental perspective
    Pavez Guerrero, Paulina; Fierro Huerta, Angelica Maria; Rojas Guerrero, Mabel Natalia; Garcia-Rio, Luis; Dinamarca-Villarroel, Luis; Fuentealba Patino, Denis Alberto; Droguett Muñoz, Kevin Arturo; Santos Blanco, José Guillermo; Aliaga Miranda, Margarita Elly
    One colorimetric and one fluorescent-indicator displacement assay (IDA) were studied to assess their interaction with methyl viologen (MV), an herbicide commercially known as paraquat. The host–guest complexes formed by cucurbit[7]uril (CB[7]) and the 4-nitroaniline (NA) or Berberine (Be) dyes function as colorimetric- and fluorescent-IDA for MV, respectively. The CB[7]@NA and CB[7]@Be complexes were characterized by UV–vis, fluorescence spectroscopy, and dynamic simulations. Isothermal titration calorimetry (ITC) experiments and dynamic simulations were employed to obtain thermodynamic data for the formation of the 1:1 inclusion complexes. Finally, NA is proposed as a reference colorimetric dye for determining CB[7]-binding affinities using competitive host–guest titrations, and the fluorescent-IDA as the best assay proposed, as it exhibits a high binding constant, a good detection limit of 2.7 × 10−6 mol L-1, good linearity in the range from 4 × 10−6 mol L-1 to 3.5 × 10−5 mol L-1, in aqueous solution.
  • Thumbnail Image
    Item
    Complexes between 2,20-azobis(2methylpropionamidine) dihydrochloride (AAPH) and cucurbit[n]uril hosts modulate the yield and fate of photolytically-generated AAPH radicals
    (Royal Society of Chemistry, 2024) Forero Girón, Angie; Oyarzún Alfaro, Mauricio Sebastián; Droguett Muñoz, Kevin Arturo; Fuentealba Patiño, Denis Alberto; Gutiérrez Oliva, Soledad; Herrera Pisani, Bárbara Andrea; Toro Labbé, Alejandro; Fuentes Lemus, Eduardo Felipe; Davies, Michael J.; López Alarcón, Camilo Ignacio; Aliaga Miranda, Margarita Elly
    Using theoretical and experimental tools we investigated the recognition of AAPH (2,2′-azobis(2-methylpropionamidine) dihydrochloride), a well-known water-soluble azo-compound employed as a source of peroxyl radicals, by cucurbit[6]uril (CB[6]), and cucurbit[8]uril (CB[8]). Density functional theory calculations and isothermal titration calorimetry experiments demonstrated that AAPH was not included in the cavity of CB[6], however, an exclusion complex was generated. Inclusion of AAPH in the CB[8] cavity was favored, forming stable inclusion complexes at 1 : 1 and 2 : 1 stoichiometries; AAPH@CB[8] and 2AAPH@CB[8], respectively. Radical formation upon photolytic cleavage of AAPH was examined theoretically, and by spin trapping with electron paramagnetic resonance. The radical yields detected with uncomplexed (free) AAPH and the AAPH-CB[6] (exclusion) complex were identical, whereas a marked decrease was shown for AAPH@CB[8]. Lower decreases were seen with a bimolecular (2 : 1) AAPH-CB[8] inclusion complex (2AAPH@CB[8]). This modulation was corroborated by the consumption of pyrogallol red (PGR), an oxidizable dye that does not associate with CB[6] or CB[8]. AAPH-CB[6] and 2AAPH@CB[8] did not significantly modify the initial consumption rate (Ri) of PGR, whereas AAPH@CB[8] decreased this. The oxidative consumption of free Trp, Gly-Trp and Trp-Gly by radicals derived from AAPH in the presence of CB[8] showed a dependence on the association of the targets with CB[8].