Electrocatalytic reduction of S-nitrosoglutathione at electrodes modified with an electropolymerized film of a pyrrole-derived viologen system and their application to cellular S-nitrosoglutathione determinations

Abstract

The preparation, electrochemical characterization, and analytical applications of glassy carbon (GC) electrodes modified with electropolymerized films of the cation N,N'-di(3-pyrrol-1-yl-propyl)-4,4'- bipyridine (DPPB) are described. Electropolymerized films of DPPB on GC electrodes exhibit two one-electron redox processes centered at -0.45 and - 0.85 V, respectively. S-Nitrosoglutathione (GSNO) can be electrocatalytically reduced at electrodes modified with electropolymerized films of DPPB at approximately -0.4 V vs sodium-saturated calomel electrode, which represents a dramatic diminution of about 600 mV in the overpotential in comparison with the reaction carried out at a bare GC electrode. The kinetics of the catalytic reaction have been characterized using cyclic voltammetry and rotated disk electrode techniques from which a value of (1.3 ± 0.2) x 103 M-1 s-1 was obtained. Using electrodes modified with an electropolymerized film of DPPB we have carried out preliminary studies of the determination of intracellular GSNO concentrations in two strains of the bacterium Rhodobacter sphaeroides.