AVS 51st International Symposium
    Nanometer-scale Science and Technology Tuesday Sessions
       Session NS-TuA

Paper NS-TuA5
Atomic Force Microscope Conductivity Measurements of Single Ferritin Molecules

Tuesday, November 16, 2004, 2:40 pm, Room 213D

Session: Nanostructures and Biology
Presenter: D. Xu, Brigham Young University
Authors: D. Xu, Brigham Young University
G.D. Watt, Brigham Young University
J.N. Harb, Brigham Young University
R.C. Davis, Brigham Young University
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We will present electrical measurements on the conductivity of ferritin molecules by conductive atomic force microscope (c-AFM). The high structural stability of ferritin molecules, relative to other proteins, makes them attractive for nanotechnology applications such as nanoscale batteries. Ferritin is an iron-storage protein that functions as an iron reservoir in animals, plants, fungi and bacteria. Ferritin consists of 24 protein subunits that are arranged to form a spherical molecule with an external diameter of 12nm. The hollow ferritin interior with a diameter of ~8nm can hold up to 4500 iron atoms as Fe(OH)@sub 3@. For battery applications the electron transfer rate through the ferritins is a critically important parameter; it will affect the internal resistance and limit the maximum current. Ferritin molecules were self-assembled on gold surfaces to form sub-monolayer films and characterized by AFM prior to electrical measurements. Electrical conductivity measurements were performed on both single apoferritin and holoferritin molecules by c-AFM. The conductivity of monolayer films (~ 1 µm@super 2@) of ferritin molecules on atomically flat gold surfaces was measured for comparison. Holoferritin was 5-15 times more conductive than apoferritin, indicating that for holoferritin most electron transfer occurs through the ferrihydrite core. With 1 volt applied, the average electrical current through single holoferritins and single apoferritins was 2.58 pA and 0.188 pA respectively.