Conductance of single thiolated poly(GC)-poly(GC) DNA molecules

We use ultrahigh vacuum scanning tunneling microscopy∕spectroscopy (UHV-STM∕STS) to investigate the electronic properties of single thiolated 12-base-pair poly(GC)-poly(GC) DNA molecules on a Au(111) surface at room temperature. Reproducible current-voltage curves of the DNA are obtained at variable sample-tip separations. The normalized conductance, which can be interpreted as the density of states, shows a well-defined wide band gap. UHV-STM∕STS opens up a novel technique to probe the electronic properties of biomolecules on surfaces at the atomic level.