Cytochrome c (Cyt c) was immobilized at the surface of a silver electrode through the formation of host-guest complexes between adamantane (A) units located at the protein surface (Cyt c-A) and chemisorbed thiolated beta-cyclodextrin(CDSH). The voltammetric response of immobilized Cyt c-A is quasi-reversible and very stable with time. Addition of competitive guests, such as 1-adamantamol, results in the disappearance of the signal. In the presence of 4,4'-bipyridine, the quasi-reversible redox response changed to give the characteristic signal of a surface confined redox couple. Experiments in the presence of electroactive probes such as Ru(NH3)(6)(3+) and 1,2-naphthoquinone resulted in a decrease of the signal intensity of the probe and shifted the half-wave potential to more positive values. These results demonstrated the adsorption of Cyt c-A molecules at the electrode surface.