Yazar "Mendez, Manuel A." seçeneğine göre listele

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    Melittin Adsorption and Lipid Monolayer Disruption at Liquid-Liquid Interfaces
    (AMER CHEMICAL SOC, 2011) Mendez, Manuel A.; Nazemi, Zahra; Uyanik, Ibrahim; Lu, Yu; Girault, Hubert H.
    Melittin, a membrane-active peptide with antimicrobial activity, was investigated at the interface formed between two immiscible electrolyte solutions (ITIES) supported on a metallic electrode. Ion-transfer voltammetry showed well-defined semi-reversible transfer peaks along with adsorptive peaks. The reversible adsorption of melittin at the liquid-liquid interface is qualitatively discussed from voltammetric data and experimentally confirmed by real-time image analysis of video snapshots. It is also demonstrated that polarization of the water/1,2-DCE interface results in drastic drop shape variations caused by large variations of the interfacial tension. The experimental data also confirmed that maximum adsorption occurs near the ion transfer potential. Finally, the interaction of melittin with a monolayer of L-alpha-dipalmitoyl phosphatidylcholine (DPPC) was also investigated showing that melittin destabilizes the lipidic monolayer facilitating its desorption. The non-covalent complex formation between melittin and DPPC was confirmed by mass spectrometry.
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    Oxygen Reduction by Decamethylferrocene at Liquid/Liquid Interfaces Catalyzed by Dodecylaniline
    (Elsevier Science Sa, 2010) Su, Bin; Hatay, İmren; Li, Fei; Partovi-Nia, Raheleh; Mendez, Manuel A.; Samec, Zdenek; Ersöz, Mustafa; Girault, Hubert H.
    Molecular oxygen (O-2) reduction by decamethylferrocene (DMFc) was investigated at a polarized water/1,2-dichloroethane (DCE) interface. Electrochemical results point to a mechanism similar to the EC type reaction at the conventional electrode/solution interface, in which an assisted proton transfer (APT) by DMFc across the water/DCE interface via the formation of DMFcH(+) corresponds to the electrochemical step and O-2 reduction to hydrogen peroxide (H2O2) represents the chemical step. The proton transfer step can also be driven using lipophilic bases such as 4-dodecylaniline. Finally, voltammetric data shows that lipophilic DMFc can also be extracted to the aqueous acidic phase to react homogeneously with oxygen.
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    Oxygen Reduction Catalyzed by a Fluorinated Tetraphenylporphyrin Free Base at Liquid/Liquid Interfaces
    (Amer Chemical Soc, 2010) Hatay, İmren; Su, Bin; Mendez, Manuel A.; Corminboeuf, Clemence; Khoury, Tony; Gros, Claude P.; Bourdillon, Melanie; Meyer, Michel; Barbe, Jean-Michel; Ersöz, Mustafa; Zális, Stanislav; Samec, Zdenek; Girault, Hubert H.
    The diprotonated form of a fluorinated free base porphyrin, namely 5-(p-aminophenyl)-10,15,20-tris(pentafluorophenyl)porphyrin (H(2)FAP), can catalyze the reduction of oxygen by a weak electron donor, namely ferrocene (Fc). At a water/1,2-dichloroethane interface, the interfacial formation of H(4)FAP(2+) is observed by UV-vis spectroscopy and ion-transfer voltammetry, due to the double protonation of H(2)FAP at the imino nitrogen atoms in the tetrapyrrole ring. H(4)FAP(2+) is shown to bind oxygen, and the complex in the organic phase can easily be reduced by Fc to produce hydrogen peroxide as studied by two-phase reactions with the Galvani potential difference between the two phases being controlled by the partition of a common ion. Spectrophotometric measurements performed in 1,2-dichloroethane solutions clearly evidence that reduction of oxygen by Fc catalyzed by H(4)FAP(2+) only occurs in the presence of the tetrakis(pentafluorophenyl)borate (TB(-)) counteranion in the organic phase. Finally, ab initio computations support the catalytic activation of H(4)FAP(2+) on oxygen.