Electrochemistry of LB films of mixed MGDG:UQ on ITO.
The electrochemical behaviour of biomimetic monolayers of monogalactosyldiacylglycerol (MGDG) incorporating ubiquinone-10 (UQ) has been investigated. MGDG is the principal component in the thylakoid membrane and UQ seems a good substitute for plastoquinone-9, involved in photosynthesis chain. The monolayers have been performed using the Langmuir and Langmuir-Blodgett (LB) techniques and the redox behaviour of the LB films, transferred at several surface pressures on a glass covered with indium-tin oxide (ITO), has been characterized by cyclic voltammetry. The cyclic voltammograms show that UQ molecules present two redox processes (I and II) at high UQ content and high surface pressures, and only one redox process (I) at low UQ content and low surface pressures. The apparent rate constants calculated for processes I and II indicate a different kinetic control for the reduction and the oxidation of UQ/UQH2 redox couple, being k(Rapp)(I) = 2.2 · 10(-5) s(-1), k(Rapp)(II) = 5.1 · 10(-14) k(Oapp)(I) = 3.3 · 10(-3) s(-1) and k(Oapp)(II) = 6.1 · 10(-6) s(-1), respectively. The correlation of the redox response with the physical states of the LB films allows determining the positions of the UQ molecules in the biomimetic monolayer, which change with the surface pressure and the UQ content. These positions are known as diving and swimming.
Universitat Politècnica de Catalunya, Dpt. of Chemical Engineering, 08222 Terrassa, Barcelona, Spain.
Javier
J
Hoyo
Universitat Politècnica de Catalunya, Dpt. of Chemical Engineering, 08222 Terrassa, Barcelona, Spain. Electronic address: ester.guaus@upc.edu.
Ester
E
Guaus
Universitat Politècnica de Catalunya, Dpt. of Chemical Engineering, 08222 Terrassa, Barcelona, Spain; Institut de Bioenginyeria de Catalunya (IBEC), 08028 Barcelona, Spain.
Juan
J
Torrent-Burgués
Institut de Bioenginyeria de Catalunya (IBEC), 08028 Barcelona, Spain; Universitat de Barcelona, Dpt. of Physical-Chemistry, 08028 Barcelona, Spain.
Fausto
F
Sanz
D004563:Electrochemistry; D004566:Electrodes; D038983:Galactolipids / Q000737:chemistry*; D017971:Tin Compounds / Q000737:chemistry*; D014451:Ubiquinone / Q000737:chemistry*
D038983:Galactolipids; D017971:Tin Compounds; C009909:monogalactosyldiacylglycerol; D014451:Ubiquinone; C109984:indium tin oxide; C025204:Ubiquinone Q2
Cyclic voltammetry; Electron transfer; Langmuir–Blodgett film; Modified ITO electrode; Monogalactosyldiacylglycerol; Ubiquinone