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UNIVERSITY OF BUCHAREST
FACULTY OF PHYSICS Guest
2024-11-22 1:23 |
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Conference: Bucharest University Faculty of Physics 2010 Meeting
Section: Biophysics and Medical Physics;Electricity and Magnetism
Title:
Redox Mechanism of Lumazine at Glassy Carbon Electrode
Authors:
Andra Militaru 1, V. C. Diculescu 2, A. Shah 3, R. Qureshi 3, Ana Maria Oliveira Brett 2 , Laura Tugulea 4
Affiliation:
1National Institute for Laser, Plasma and Radiation Physics, Magurele, Romania
2Departamento de Química, Faculdade de Ciências e Tecnologia, Universidade de Coimbra, 3004-535 Coimbra, Portugal
3Department of Chemstry, Quaid-i-Azam University, 45320, Islamabad, Pakistan
4Faculty of Physics, University of Bucharest, 077125, Magurele-Bucharest, Romania
E-mail
andra.militaru@inflpr.ro
Keywords:
lumazine, voltammetry, redox mechanism, diffusion coefficient
Abstract:
Lumazine is a pterin compound which acts as substrate for the lumazine synthase/riboflavin synthase complex. Since lumazine may participate in vivo in several redox reactions, the clarification of its redox mechanisms using electrochemical techniques, namely voltammetric methods, seems timely.
The electrochemical behaviour of lumazine has been studied at a glassy carbon electrode using cyclic, differential pulse and square wave voltammetry. The oxidation of lumazine was possible only in electrolytes with pH > 7.0 since it occurred at very high potential values, near the glassy carbon positive potential limit in aqueous solutions. It is an irreversible, pH-dependent process that occurred with the transfer of 2 electrons and 2 protons and did not involve the formation of any electroactive lumazine oxidation product.
The reduction of lumazine was studied over a wide pH range and occurred in a cascade mechanism with the transfer of 4 electrons and 4 protons. In acid electrolytes the reduction was quasi-reversible and occurred with the formation of several reduction products that were oxidized at the glassy carbon surface. Increasing the pH, the reduction of lumazine became a reversible process. The diffusion coefficient of lumazine was calculated in pH 7.0 0.1 M phosphate buffer to be DLMZ = 9.1 x 10-6 cm2 s-1. The electroanalytical determination of lumazine was carried out in pH 7.0 0.1 M phosphate buffer using differential pulse voltammetry with a detection limit LOD = 0.76 x 10-6 M. A mechanism for both oxidation and reduction of lumazine is proposed.
The investigation of the electrochemical behaviour of lumazine has the potential for providing valuable insights into biological redox reactions of this class of molecules, resulting in a better understanding of the data described for biological systems and increasing the overall knowledge of lumazines’ physiological mechanism of action.
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