Electrochemical approach to the dynamics of molecular recognition of redoxenzyme sites by artificial cosubstrates in solution and in integrated systems

Application of antigen-antibody technology allows the attachment to an elec trode surface of an enzyme monolayer structure to which both the enzyme and the mediator are bound. As illustrated with the example of glucose oxidase and a ferrocene mediator, the enzyme preserves its full activity in such s tructures, which may be easily reproduced. In spite of their fixation to th e structure, the mobility of the ferrocene heads is sufficient to ensure th at its transport to the enzyme prosthetic group is not rate determining. Th e reaction is rather controlled by the prior formation of a complex between the ferrocenium ion and the flavin required for electron transfer to occur . The efficiency of this step is affected by steric hindrance and the vario us observations made with free-moving and attached ferrocene-ended poly(eth ylene glycol) chains may be rationalized by the interplay of factors contro lling their distribution and shape. Analyzing the dynamics of this system, in comparison with previous systems, was thus an occasion to shed further l ight on the recognition phenomenon. The enzyme monolayer integrated system is a good starting point for the step-by-step construction of spatially ord ered multilayered assemblies with strong catalytic efficiencies. Fast respo nding systems are expected both in terms of electron transport and electron transfer between the mediator and the enzyme. The spatial order resulting from the step-by-step construction should allow a much more precise analysi s of electron transport and electron transfer than in conventional assembli es of redox centers. Mastering both the construction and the functioning of such systems should help the design of more complex systems, integrating a dditional functionalities electrically controlled by means of their electro n transport/electron transfer connection to the electrode surface.