We show the possibility of realizing a hybrid system composed of a semiconductor nanoparticle (NP) and a metalloprotein, in which the photophysical properties of the two species can be exploited to elicit fluorescence resonance energy transfer mechanisms from the biomolecule to the NP. A specific conjugation process between CdSe/ZnS core/shell water soluble NPs, functionalized with surface exposed thiol groups (-SH), and the apo form of the metalloprotein azurin (Az) has been achieved, resulting in a fixed distance in the donor-acceptor pairs. The increase in the NP fluorescence intensity was found to be dependent on the Az to NP molar ratio. (c) 2005 Elsevier B.V. All rights reserved.