Single Molecule Manipulation and Self-Assembly of Amyloid $\beta $/A4 Precursor Protein on Ag(111)*

We perform a single molecule level study of the RERMS sequence of amyloid $\beta $/A4 precursor protein fragment on a clean Ag(111) surface using a low-temperature scanning-tunneling-microscope (STM) system at 5K. The mechanical stability of individual protein fragments are checked by laterally manipulating them with the STM tip. Moreover, we are able to form a well ordered two-dimensional layer of the protein fragment by increasing the deposition time. A unit cell has been assigned and a model for the molecular arrangement inside the structure is proposed. This work opens possibilities of using well ordered protein structures on inorganic surfaces for future bimolecular electronic and nano-bio applications.