Self-assembled monolayer fabrication of cysteine-modified ferredoxin

Rhodobacter sphaeroides ferredoxin is a metalloprotein with ferric ion in its active site. Ferredoxin has redox property and it can transfer the electron. These molecules can be applied to the bioelectronics by fabricating them as a self-assembled bio-film. The significant key of film fabrication is the immobilization method of bio-molecule. In our previous works, it has been reported that metalloprotein film can be fabricated by using chemical linker material that have thiol-group to assemble it on gold substrate. However, the chemical linker can interfere with electron transfer because it is acted as an insulator of the system. So, we used recombinant protein with cysteine functional residue at the end of the protein which can be directly immobilized on the gold (Au) surface. It could be confirmed the immobilization of the protein and surface morphology of thin film by surface plasmon resonance (SPR) and scanning tunneling microscope (STM). These results show that cysteine-modified ferredoxin can be used for making high quality protein film, and applied to the fabrication of nano-scale bioelectronics.