Electron transfer reactions between molecules at interfaces play a central role in all living systems. In respiration and in
photosynthesis, sequential electron transfer at and across biological membranes is the central process in the generation
of the proton motive force, an essentially electrochemical phenomenon, which is used to drive the thermodynamically
uphill synthesis of adenosine triphosphate (ATP) from inorganic phosphate and adenosine diphosphate (ADP). ATP is
the essential energy carrier which is used in a wide range of biological processes where the energy produced by the
hydrolysis of ATP back to ADP and inorganic phosphate is used to drive many different and essential reactions in living
cells. Thus electrochemical processes, that is electron transfer at interfaces and the build up of potential differences at
and across interfaces, are central processes in life.
Bioelectrochemistry is the study and application of biological electron transfer processes. Over the last 25 years
there have been enormous advances in bioelectrochemistry and in the study of electrochemical reactions of biological
molecules both large, such as redox proteins and redox enzymes, and small, such as NADH and quinones. Over this
time we have learnt some of the important factors which control the interaction between biological redox partners.We
have learnt how to apply this knowledge and to start to design electrode surfaces, through deliberate chemical
modification, so that the biological molecules will interact in a productive way with the electrode surface and facilitate
efficient electron transfer. Over the same period, significant parallel developments in physical electrochemistry have
meant that the tools and techniques, such as in situ infrared spectroscopy, SERS, EQCM, STM and AFM, now exist to
study the electrode solution interface in situ at the molecular level. These techniques are now being used to characterise
chemically modified electrode surfaces and to study their interactionwith biological molecules. This has led to increasing
sophistication in the approaches to the assembly of molecules on electrode surfaces, including methods for the
immobilisation and orientation of enzymes at the electrode surface and the use of techniques from molecular biology
to produce mutant enzymes modified to facilitate electrochemical applications. At the same time electrochemical
approaches have been developed and successfully applied to study the electron transfer behaviour of complexmulticentre
redox enzymes and to investigate the gating of electron transfer, thus using electrochemical techniques to address
fundamental biological questions.