Electrical transport through ordered self-assembled protein monolayer measured by constant force conductive atomic force microscopy

This paper addresses some of the challenges met in electrical characterization of biomolecules, namely, the control of the orientation of molecules and the control of the force exerted on these soft molecules. We investigate the transport properties of small proteins called hydrophobins using conductive atomic force microscopy. The proteins have a property that they form a well ordered monolayer in which the orientation of the molecules is known. We introduce an active compensation for the electrostatic force induced by the bias voltage, which often hamper the measurements. Results suggest that the electrical transport through the hydrophobins protein monolayer occurs mainly via tunneling.