The affinity of the maltose binding protein-nitro reductase fusion (MBP-NR) to electropolymerized films of N-(3-pyrrol-l-ylpropyl)-4,4'-bipyridinium (PPB) has been studied in aqueous medium by the quartz crystal microbalance (QCM) technique. It was found that the MBP domain of MBP-N-R exhibits specific binding toward PPB films through the maltose binding site and that the immobilized MBP-NR retains its enzymatic activity toward trinitrotoluene (TNT) reduction. Although some MBP-NR was nonspecifically adsorbed onto a maltose-covered PPB film as well as to a bare Au electrode, in both cases the adsorbed enzyme exhibited no catalytic activity. Nitro reductase (NR) also appeared to adsorb onto the PPB films but did not exhibit any enzymatic activity. The electropolymerization of N-(3-pyrrol-1-ylpropyl)-4,4'bipyridinium (PPB) onto a Au electrode in acetonitrile solution was studied by electrochemical quartz crystal microbalance (EQCM). It was found that the extent of polymerization upon pyrrole-centered oxidation decreased with continuous potential scanning. The bipyridinium-localized (quaternized nitrogen) redox reaction appeared to be of the anion-exchange type.