Conducting polymers as antennas for probing biophysical activities

Conducting polymers can serve as soft electrode substrates for anchoring and orientating functional membrane proteins. We utilize this possibility to orient bacteriorhodopsin (bR), a membrane protein that functions as a light-driven proton pump, on these substrates. The underlying polymer substrate becomes optoelectronically active with the spectral and temporal characteristics corresponding to that of the adjacent bR molecular layer. We demonstrate the concept of passive and active biomolecular signal transduction using model conducting polymers. The photoinduced current modulation in the conducting polymer layer can be explained in terms of the charge displacements within the proximal bR layer or charge-transfer processes across the interface. We explore the implications of this strong coupling between the photophysical processes in bR and electrical processes in the conducting polymer layer.