| Electron transfer (ET) in protein has attracted much attention because it is extremely important in the bioenergetics reaction pathways. Furthermore, the study on the electron transfer of protein could help investigations into the utilization of biomolecule based on electric components. Metalloprotein, with the intrinsic properties such as nanometer dimension, electrochemical activity, robust structure, ease being engineered and comparably high resistivity, is a good candidate for next generation of electronic material. Study on its topography, orientation and electrical property on the surface of electrode is very necessary and attractive. In this thesis, the atomic force microscopy is used to investigate the topography and the surface binding interaction of protein on the annealed gold. The use of mutagenesis as a method of controlling the orientation of azurin on gold surfaces was studied. Two kinds of azurin, wild type and one genetically altered azurin mutant K27C were investigated here. Wild type azurin is immobilized using a disulphide bridge to form a covalent bond with gold surfaces. The mutant, K27C, has residues at their surface converted into cysteine residues, as it is known that thiol groups form strong covalent bonds with gold. The surface coverage and height of the adsorbed protein molecules were observed using atomic force microscopy. It is found that the density of height distribution of K27C azurin is different from that of the wild type distribution, which is possibly a result of a different orientation on the surface. It is concluded that binding of K27C mutant azurin to gold surfaces occurs preferentially through surface cysteine rather than the disulphide bridge.Electron transfer through the azurin, metalloprotein molecule has also been explored using the conducting atomic force microscopy by assembling the protein on conducting tip, which is then in conduct with the conductive substrate. The I-V curves under different force loads were collected to estimate the resistance of protein at molecular level. When reliable electrical contact between electrodes and protein is achieved under a force greater than 5 nN, well-behaved current-voltage characters are revealed, and dependent on the force load. Increasing the force from 5 to 70nN, the electrical resistance of protein is measurable, and found to be decreased with the force. However, the resistance could not return to the original value correspondingly as the force is withdrawn, indicating the protein deformation in this situation is not elastic.To explore the possibility and reliability of azurin being a biomolecular electrical component, study on its strengths, including the dielectric strength and mechanical strength, is also necessary. Here, the strength of azurin, has been studied at real molecular level by using conducting atomic force microscopy (C-AFM). Under a force lower than 2 nN, dielectric breakdown has been observed at a bias higher than a critical value at either positive or negative polarization. The mechanical strength of protein has been elucidated on basis of the fact that the extremely high force ranging from 60 to 100 nN leads to collapse of the protein molecular structure.In this thesis the theory of electron transfer of protein was also studied. Recent progress of study on theoretical approaches on electron transfer (ET) through organic monolayer junctions has been summarized. Metal-insulator-metal junctions have been constructed by sandwiching chemisorbed protein molecules between a conducting AFM tip and the conducting substrate. Asymmetric current curves have been observed within the confined bias region from -1 to 1 V. Due to the original Simmons model only predict the symmetric I-V behaviour, a modified Simmons model, which considered the observed spectra asymmetry in terms of inequivalent Fermi level shifts of the two contacts, was proposed to describe the I-V behaviour of azurin. A comparison of the theoretical fitting with original Simmons model and the modified model showed the modified model f...
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