Microgravimetric quartz-crystal microbalance analysis of cytochrome c interactions with pyridine and pyridine-nitrospiropyran monolayer electrodes: characterization of inter-protein complexes at the functionalized surfaces

Abstract

The association of cytochrome c (Cyt. c) to a pyridine monolayer assembled onto Au electrodes associated with a quartz crystal is followed microgravimetrically using a quartz-crystal microbalance (QCM). The association constant of Cyt. c to the monolayer corresponds to K 1 = 8.5 × 10 3 M −1. The inter-protein binding of cytochrome oxidase (COx) to a pyridine-Cyt. c monolayer assembled on the electrode is similarly characterized by the QCM method. The association constant of COx to Cyt. c is K 2 = 1.67 × 10 6 M −1. A mixed monolayer consisting of pyridine and nitrospiropyran units was assembled on Au electrodes associated with a quartz crystal. The functionalized monolayer was used to photostimulate the association and dissociation of Cyt. c to the monolayer. The system provides a means for the piezoelectric microgravimetric transduction of optical signals recorded by the monolayer-modified surface.