서강대학교

초록/요약

Since 2000, the molecular electronics have been researched to overcome the current limitation of silicon-based electronic device such as increasing integration, shorting problem, efficiency, and etc. However, the molecular electronics has some problems. For example, organic-based electronic based only focused on miniaturizing their element size and trying to operate similar function compared to silicon-based electronic device. This can be hard to develop the single-molecular based computing system in the future. To solve this problem, herein, author suggested some biomolecular device which emphasized ‘diverse functionality’ compared to current molecular electronic device. This effort enabled to make the various-type of biomolecular-based bioelectronic device. Moreover, this thesis suggested the new-concept of biomemory modulator for perform the multi-function which can’t perform the current oranic molecular-based electronic device. A multi-level biomemory device using a hetero protein film consisting of two metallo-proteins, a recombinant azurin and a cytochrome c was developed for storage of 4 kinds of information at one device. As a result, Multi-level information was successfully stored in hetero protein layers contained in a bioelectronics device and were read out from identical positions of the protein layers. To fabricate the hetero protein layer, azurin was modified for direct immobilization on the Au surface by genetic mutagenesis and cytochrome c was adsorbed on the azurin layer by electrostatic attraction. These well-defined hetero protein layers showed superior electrochemical properties when compared to random hetero protein layers consisting of well-mixed proteins. The adsorption properties of the hetero proteins layers were investigated by surface tunneling microscopy and surface plasmon resonance. The multi-state electrochemical properties of the hetero protein layer were readily achieved when its specific oxidation, reduction and open circuit potentials were applied as signals for ‘write’, ‘erase’ and ‘read’ functions, respectively. The multi-state writing, reading, and erasing processes achieved in this biodevice, which is based on the incorporation of a hetero protein layer, indicate that biomemory devices may be eventually utilized as a potential alternative to silicon based memory device when measuring single electrons from single proteins on an electrode. We developed a multi-functional 4-bit biomemory chip that consisted of recombinant azurin variants to perform the various ‘biomemory function’. 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 comfirm 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 amperomemtry. 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. A signal-enhanced biomemory device was developed by introducing cysteine-modified azurin/gold nanoparticle (GNP) heterolayers. The proposed recombinant azurin/GNP heterolyers provided an enhanced electron transfer between recombinant azurin/GNP and the Au surface, which stored the charges in the fabricated heterolayer. The fabricated recombinant azurin/GNP heterolayers was investigated by atomic force microscopy (AFM) and surface plasmon resornance (SPR) spectroscopy. Cyclic voltamemmtry (CV) was performed to examine the current signal-amplified electrochemical property. In this analysis, the recombinant azurin/GNP heterolayers produced current that was 5 times greater than the recombinant azurin monolayer. These redox potentials were then used to obtain the ''write step'' and ''erase step''. Using these parameters, the biomemory function of the device was verified by chronoamperometry (CA). The conventional molecular electronics just focused on miniaturization of their size and realizing a simple function to alter the silicon-based electronics. It is hard to develop the single molecular-based computing system. Because molecular-based computing system is need to develop the complex functionality at single molecule. They must compete with functionality. To solve the functionality problem of molecular electronics, herein, we firstly demonstrated the biomemory modulator that consisted of recombinant azurin/DNA/nanoparticle hybrid to perform the various functions. It is based on the recombinant azurin/DNA hybrid material, defined as biomemory modulator platform. And its properties could be operated by commanding materials (metal ions, conducting nanoparticles and semiconducting nanoparticles) for three individual functions ‘information reinforcement’, ‘information regulation’, and ‘information amplification’, respectively. This demonstration of the biomemory modulating functions based on single hybrid biomolecule would be a foundation stone to develop single biomolecular-based computing system.