DIAMINODURENE AS A MEDIATOR OF A PHOTOCURRENT USING INTACT-CELLS OF CYANOBACTERIA

A mediator for the measurement of a photocurrent generated by intact c ells of cyanobacteria immobilized onto the working electrode in an ele ctrochemical cell is described. The efficiency of diaminodurene (DAD) as an electron shuttle between the photosynthetic electron transport c hain (PET) within the cells and the electrode was compared with ferroc yanide and p-benzoquinone. A simple Synechococcus-carbon-paste electro de containing DAD as the mediator in the electrode material and the ph otosynthetic cells immobilized in a polymer matrix was constructed. Th e device required no addition of further reagents to the bulk solution for the generation of a photocurrent. Using cyclic voltammetry the se cond-order rate constant for the reaction of DAD with the PET was dete rmined. Diaminodurene compared favorably with p-benzoquinone in that t he overpotential was reduced to 0.2 V. The deterioration of the PET by the DAD was significantly decreased compared with p-benzoquinone, res ulting in a prolonged lifetime of the electrode. A possible mechanism for the reaction of DAD with the PET is discussed.