Electrochemical investigation of the interaction of different mediators with the photosynthetic reaction center from Rhobobacter sphaeroides

In this paper the electrochemical techniques (chronoamperometry, cyclic vol tammetry and linear sweep voltammetry) have been employed in order to study the interactions between different mediators and the reaction center of th e photosynthetic bacterium Rhodobacter sphaeroides. The experimental data a re interpreted in view of the competitive occurring of an electrochemical r eaction of the mediators at the electrode and their chemical reaction with the cofactors of the reaction center. The overall process is modelled by a set of differential equations, integrated using the Runge-Kutta method, tha t allow the calculation of k(ch) and k(el), the kinetic constant of the che mical and electrochemical reactions, respectively. The redox species used a s mediators are the ferricyanide and 2,3,5,6-tetramethyl-p-phenylenediamine (DAD), both reductants of the photooxidized dimer, the Ubiquinone-0, which is able to reduce the quinones in the site A (Q(A)) and B (Q(B)) of the pr otein and the TMPD, an oxidant of the semiquinone anion. (C) 2000 Elsevier Science Ltd. All rights reserved.