Redox Chemistry of Ca-Transporter 2-Palmitoylhydroquinone in an Artificial Thin Organic Film Membrane

Mirceski, Valentin and Gulaboski, Rubin and Bogeski, Ivan and Hoth, Markus (2007) Redox Chemistry of Ca-Transporter 2-Palmitoylhydroquinone in an Artificial Thin Organic Film Membrane. Journal of Physical Chemistry C, 111 (16). pp. 6068-6076. ISSN 1932-7447

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Official URL: http://dx.doi.org/10.1021/jp068600t

Abstract

The redox chemistry of 2-palmitoylhydroquinone (H2Q), a recently introduced synthetic transmembrane Ca2+ transporter, was studied with cyclic and square-wave voltammetry in an artificial thin organic-film membrane sandwiched between a pyrolytic graphite electrode and an aqueous solution. The membrane has a micrometer dimension and consists of the water immiscible organic solvent nitrobenzene, which contains suitable electrolyte and H2Q as a redox active compound. The potential drop at the electrode/membrane interface is controlled by the potentiostat, whereas the potential drop at the membrane/water interface is dependent on the ClO4 - concentration, which is present in a large excess in both liquid phases. The redox transformation of H2Q at the electrode/membrane interface is accompanied by a corresponding ion-transfer reaction at the other side of the membrane. Proton transfer at the membrane/water interface is critical for the redox transformation of H2Q in the interior of the membrane, as a strong dependence of the voltammetric response on the pH of the aqueous medium was observed. H2Q undergoes two oxidation processes due to existence of two distinctive redox forms of H2Q. The electrochemical mechanism can be explained with two tautomer forms of H2Q formed by migration of a proton between the 1-hydroxyl group and the adjacent carbonyl group of the palmitoyl residue. Both tautomers undergo 2e/2H+ distinctive redox transformations to form the quinone form of the studied compound. In the presence of Ca2+ in the aqueous phase, voltammetric experiments confirmed the capability of both tautomers to form 1:1 complexes with Ca2+ and to extract it into the organic membrane. Upon the oxidation of the complexes, Ca2+ is expelled back to the aqueous phase. The studied compound exhibits very similar complexing affinity toward Mg2+, implying that it is not highly selective for transmembrane Ca2+ transport.

Item Type: Article
Uncontrolled Keywords: calcium transporter, quinones, ion transfer, complexation, liquid-liquid interface, voltammetry
Subjects: Medical and Health Sciences > Basic medicine
Natural sciences > Biological sciences
Natural sciences > Chemical sciences
Natural sciences > Physical sciences
Divisions: Faculty of Agriculture
Depositing User: Rubin Gulaboski
Date Deposited: 31 Oct 2012 13:14
Last Modified: 15 Aug 2013 13:54
URI: http://eprints.ugd.edu.mk/id/eprint/156

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