Electronic Decay Length in a Protein Molecule.

Antibodies have two identical binding domains and can therefore form a well-defined conducting bridge by binding a pair of electrodes functionalized with an epitope. The conductance measured between these two fixed points on the antibody does not change with the size of the electrode gap. A second conduction path is via one specific attachment to an epitope and a second nonspecific attachment to the surface of the antibody. In this case, the conductance does change with gap size, yielding an estimated electronic decay length >6 nm, long enough that it is not possible to distinguish between an exponential or a hyperbolic distance dependence. This decay length is substantially greater than that measured for hopping transport in an organic molecular wire.