Multifunctional 4-bit biomemory chip consisting of recombinant azurin variants

We developed a multi-functional 4-bit biomemory chip that consisted of recombinant azurin variants. The azurin was modified to introduce cysteine-residues. In addition, the Cu ion in this recombinant azurin protein was substituted with various other metal ions such as Co, Mn, Fe and Ni ion to allow the protein to perform various memory functions. Each metal-substituted recombinant protein was directly self-assembled attached onto Au surface via the thiol group of the cysteine. UV–VIS spectroscopy was performed to confirm the metal substitution. Atomic force microscopy was used to measure the film organization. Also, the 4 different azurin variants were investigated to assess the electrochemical behavior. Cyclic voltammetry and an open circuit potential indicated that the azurin variants had different redox peaks and specific open circuit potential values. Using these parameters, memory function was verified by chronoamperometry and open circuit potential amperometry. Therefore, a multi-bit biomemory chip was successfully developed. The results presented here provide a new approach, concept and material combination for the development of biomemory systems using recombinant protein. If a low electrochemical signal from a few single proteins could be achieved, it may be possible to substitute silicon-based memory devices with biological-based memory devices.