Atomic Force Microscope Conductivity Measurements of Single Ferritin Molecules

• Main Author: Xu, Degao
• Format: Others
• Published: BYU ScholarsArchive 2004
• Subjects: horse spleen ferritin; protein; conductive atomic force microscope; c-AFM; I-V measurement; molecular electronics; conductivity; conduction; resistivity; resistance; Astrophysics and Astronomy; Physics
• Online Access: https://scholarsarchive.byu.edu/etd/227; https://scholarsarchive.byu.edu/cgi/viewcontent.cgi?article=1226&context=etd

Conductive Atomic Force Microscope (c-AFM) was used to measure the conductivity of single horse spleen ferritin (HoSF) and azotobacter vinelandii bacterial ferritin (AvBF) molecules deposited on flat gold surfaces. A 500 micron diameter gold ball was also used as a contact probe to measure the conductivity of a thin film of ferritin molecules. The average current measured for holo HoSF was 13 and 5 times larger than that measured for apo HoSF as measured by c-AFM at 1V and gold ball at 2V and respectively, which indicates that the core of ferritin is more conductive than the protein shell and that conduction through the shell is likely the main factor limiting electron transfer. With 1 volt applied, the average electrical currents through single holo HoSF and single apo HoSF molecules were 2.6 pA and 0.19 pA respectively. Measurements on holo AvBF showed it was more than 10 times as conductive as holo HoSF, indicating that the protein shell of AvBF is more conductive than that of HoSF. The increased conductivity of AvBF is attributed to heme groups in the protein shell.