Scanning probe technology in metalloprotein and biomolecular electronics

The interfacing of man-made electronic components with specifically-folded biomacromolecules lies central not only to the development of sensory interfaces and potential new molecular-scale devices, but also enables us to analyse processes of great biological importance in a refined and controllable manner. Recent advances in both available technology, most notably optical and scanning probes in nature, and our understanding of suitable methodologies, have led us to the point where the characteristics of single biological molecules can be interrogated with good levels of reproducibility. We review here the application of scanning probe microscopy to the analysis of and experimentation on biological redox systems. Within this paper the tunnel transport characteristics, as assayed by both scanning tunnelling microscopy (STM) and conducting probe atomic force microscopy (AFM), of single metalloproteins are discussed. In a specific case study the electron transfer characteristics of the blue copper metalloprotein, azurin, are reported. The modulation of these properties under the influence of calibratable compressional force has also been examined in some detail. Work such as this enables one to reproducibly establish the conductance, barrier height, environmental sensitivity and electromechanical properties of these molecules.