  We review the status of protein-based molecular electronics. First we discuss
fundamental concepts of electron transfer and transport in and across proteins
and proposed mechanisms for these processes. We then describe the
immobilization of proteins to solid-state surfaces in both nanoscale and
macroscopic approaches, and highlight how different methodologies can alter
protein electronic properties. Because immobilizing proteins while retaining
biological activity is crucial to the successful development of bioelectronic
devices, we discuss this process at length. We briefly discuss computational
predictions and their link to experimental results. We then summarize how the
biological activity of immobilized proteins is beneficial for bioelectronics
devices, and how conductance measurements can shed light on protein properties.
Finally, we consider how the research to date could influence the development
of future bioelectronics devices.
