Loading effects on the photoelectric response of dry bacteriorhodopsin sensors

Photoactive biomolecules have been proposed for several technical applications including optoelectronics. Wild-type bacteriorhodopsin is used as an example molecule to study the photoelectric measurements of dry sensor films and problems related to the implementation and interpretation of the measurement results. Thick bacteriorhodopsin films have high electrical impedance which makes the photoelectric response very sensitive to the loading of the electrical interfaces and the measurement equipment. A measurement circuit featuring a standard instrumentation amplifier was built and connected to a wild-type bacteriorhodopsin sensor for measurements. Our measurements and simulations show how the response shape depends on the sensor-to-instrumentation interface. The results emphasise how the photoelectric response is affected by sensor-amplifier RC time constants and time constants of the instrumentation.