Abstract: Electrodes carrying FAD-dependent enzymes on their surface are enclosed. The FAD is modified to include a functional group or moiety which affects the properties of the enzyme. The functional group or moiety can be a binding moiety through which the FAD-enzyme complex is immobilized onto the electrode; it can be an electron mediator group for transferring electrons between the electrode and the FAD; or it can be a photoisomerizable group which can undergo photoisomerization which yields a change in the rate of the electrically induced catalytic activity of the enzyme. The electrodes can be used in electrochemical systems for deforming analytes in liquid medium or for recordal of optical signals.

Abstract: Electrochemical determination of the presence, and optionally concentration of an analyte utilizes an electrode having immobilized thereon one member of a recognition pair, the recognition pair consisting of said analyte. In the presence of the analyte medium pair complexes, which are complexes between the analyte and the immobilized member are formed. The electrode forms part of an electrochemical system which includes also redox molecules comprising at least one first redox molecule and at least one second redox molecule, the former transferring electrons between the electrode and the latter. Upon formation of a pair complex the electron transfer is inhibited and the change in the electrical response then indicates the presence of said analyte in the medium.

Abstract: An elcctrobiochemical system for the determination of the presence and optionally concentration of an analyte in a liquid medium, the system comprising an electrode having immobilized thereon a member of a recognition pair, the other member of said pair being said analyte, the presence of said analyte in the medium resulting in formation of a pair complex, being a complex between said immobilized member and said analyte; the system further comprising redox molecules capable of changing their redox state by accepting electrons from or donating electrons to the electrode; the formation of the pair complex on the electrode bringing a change in the electrical response of the system, whereby the presence and optionally the concentration of said analyte in the medium can be determined.