Charge storage in nanoscaled monolayer of recombinant azurin by using direct self-assembly method was investigated for the construction of bioelectronic devices. Recombinant azurin having a cysteine residue was utilized to enhance the stability of the self-assembled protein on the gold surface without any chemical linker. We investigated the immobilization of protein by surface plasmon resonance and scanning tunneling microscopy. The electrochemical properties of recombinant azurin immobilized on the surface were confirmed by cyclic voltammetry. The memory device characteristics, including the "Read", "Write", and "Erase" functions of the self-assembled azurin layer, were obtained with three distinct electrical states of the azurin layers by cyclic voltammetry. It was concluded that the proposed device had a memory function and could be used for the construction of a nanobiochip with memory function. (C) 2009 Elsevier B. V. All rights reserved.