Although proteins are usually electrically insulating, hair-like nanoscale filaments (called pili) on the surface of Geobacter bacteria exhibit metallic-like conductivity. To understand why pili are conductive, scientists from the University of Massachusetts at Amherst, Holy Cross, and Brookhaven National Laboratory recently used X-ray diffraction to analyze the structure of the filaments. They found that the electronic arrangement and the small molecular separation distances (~0.3 nanometers) give the pili an electrical conductivity comparable to that of copper.
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