Enhanced solid-state electron transport via tryptophan containing peptide networks.

The electrical conductivity via peptide networks was measured using conductive probe atomic force microscopy, where the tryptophan-containing peptide network (composed of Phe-Trp dipeptides) exhibited a superior (5 fold) conductivity in comparison to an all phenylalanine network (composed of Phe-Phe dipeptides). These results are in line with previous spectroscopic measurements exploring intramolecular electron transfer in proteins. Bias-scaling factors (instead of the more commonly used transition voltage spectroscopy method) were calculated for the two peptide networks. These calculations showed substantial differences between the two peptide networks, suggesting different electron transport characteristics. While the factor for the tryptophan-containing network is similar to conjugated molecules with a low electron-tunneling barrier, the one for the all phenylalanine network can be ascribed as an 'intermediate' factor between conjugated and saturated molecules.