Site-specifically engineered disulphide or surface cysteine residues have been introduced into two blue copper proteins, Pseudomonas aeruginosa azurin and Populus nigra plastocyanin, in order to facilitate protein chemisorption on gold electrodes. The subsequently formed well-defined protein monolayers gave rise to robust electrochemical responses and electron transfer rates comparable to those observed at modified electrode surfaces. Proximal probe characterisation confirms the presence, at high coverage, of well-ordered protein adlayers. Additionally, gold-metalloprotein affinity is such that molecular-level tunnelling and topographic analyses can be carried out under aqueous solution. The approaches outlined in this work can, in principal, be extended to the generation of arrays of any redox-active biomolecule. (C) 2003 Elsevier B.V. All rights reserved.