Specific inhibitory reactions of herbicides with photosynthetic reaction centers bound
to working electrodes were monitored in a conventional electrochemical cell and a
newly designed microfluidic electrochemical flow cell. In both cases, the bacterial
reaction centers were bound to a transparent conductive metal oxide, indium-tin-oxide,
electrode through carbon nanotubes. In the conventional cell, photocurrent densities
of up to a few muA/cm2 could be measured routinely. The photocurrent could be blocked
by the photosynthetic inhibitor terbutryn (I 50 = 0.38 +/- 0.14 muM) and o-phenanthroline
(I 50 = 63.9 +/- 12.2 muM). The microfluidic flow cell device enabled us to reduce
the sample volume and to simplify the electrode arrangement. The useful area of the
electrodes remained the same (ca. 2 cm2), similar to the classical electrochemical
cell; however, the size of the cell was reduced considerably. The microfluidic flow
control enabled us monitoring in real time the binding/unbinding of the inhibitor
and cofactor molecules at the secondary quinone site.
