Electronic devices assembled by protein building blocks
Electronic devices assembled by protein building blocks Hodgkiss, Gerrard, Plank, et al Natural proteins have evolved amino acid sequences that adhere to each other with exceptional strength and specificity. In a highlight publication this month,1 a team of biologists, chemists, and physicists exploited such sequences to encode the assembly of electronic devices from hybrid materials. The concept is illustrated in Figure 1. By tethering sticky amino acid sequences called peptides to electronically semiconducting molecules, hybrid nanowires self assemble and are then used as the active components of transistor devices. Figure 1. Electronic device assembly using naturally aggregating peptides (reproduced from ref 1). In their previous attempts at semiconductor self-assembly, Hodgkiss’ team explored the use of synthetic peptides.2,3 The peptide sequences affected self-assembly, but lacked the finesse to align neighboring molecules sufficiently well for electrons to hop between them. Meanwhile, Gerrard’s team had been approaching a similar problem from the other direction. They first looked to nature to identify peptide sequences that evolved to stick protein units together.4 The short sequences they found in protein-protein interfaces of the peroxiredoxin family (Figure 2) were ideal tectons to assemble electronic devices. Figure 2. Crystal structures of A) Peroxiredoxin III homodecamer and B) b-loctoglobulin homodimer, highlighting the peptide interfaces identified in each (adapted from ref 4). Natural 8-mer peptide sequences were then synthesized and grafted to organic semiconductor molecules to create new hybrid materials. Under the right conditions, the hybrid materials were found to assemble into nanofibers, whereby the semiconducting units are brought into electronic communication with each other in a way that strongly depends on the peptide interactions (Figure 3). Figure 3. A) Atomic force micrograph and B) Transmission electron micrograph of various peptide assembled conductive nanofibres. Scale bar 25 nm and 100 nm, respectively (adapted from ref 1). The final key challenge was to transform these novel materials into functioning devices. Plank’s nanoelectronics device team led this aspect of the work. They used the new hybrid materials as the active components of field-effect transistors that act as electronic switches like those found in computer processors. This research breakthrough, published this month in Advanced Functional Materials,1 highlights the possibilities of exploiting natural peptides to drive the water-based assembly of other functional materials and devices. References
- Eakins, G. L. et al. Functional Organic Semiconductors Assembled via Natural Aggregating Peptides. Adv. Funct. Mater. (2015). doi:10.1002/adfm.201502255
- Gallaher, J. K., Aitken, E. J., Keyzers, R. A. & Hodgkiss, J. M. Controlled aggregation of peptide-substituted perylene-bisimides. Chem. Commun. (Camb.) 48, 7961 (2012).
- Eakins, G. L. et al. Thermodynamic Factors Impacting the Peptide-Driven Self-Assembly of Perylene Diimide Nanofibers. J Phys Chem B 118, 8642–8651 (2014).
- Valéry, C., Pandey, R. & Gerrard, J. A. Protein β-interfaces as a generic source of native peptide tectons. Chem. Commun. (Camb.) 49, 2825 (2013).