The same characteristics that make misfolded proteins known as prions such a pernicious medical threat in neurodegenerative diseases may offer a construction toolkit for manufacturing nanoscale electrical circuits.
Scientists working at Whitehead Institute for Biomedical Research and the University of Chicago have used self-assembling fibres formed by prions as a template on which to deposit electricity-bearing gold and silver, creating nanoscale electrical wire.
‘Most of the people working on nanocircuits are trying to build them using ‘top-down’ fabrication techniques’ used in conventional electrical engineering, said Whitehead Institute Director Susan Lindquist. ‘We thought we’d try a ‘bottom-up’ approach, and let molecular self-assembly do the hard work for us.’
Lindquist and her colleagues let prions build a very thin fibrous template and then coaxed gold and silver to bond to the protein fibres. By themselves, the fibres are insulators but when coated with gold and silver particles, they are said to become effective electrical wires.
The choice of prions to build this template was a natural one for Lindquist and her colleagues at the University of Chicago, where she started work on this project before joining Whitehead Institute. Proteins are the cell’s workhorses, and they need to fold into complex and precise shapes to do their jobs. Prions are misfolded proteins.
Prions have another characteristic that makes them ideal for the mass-manufacturing jobs researchers have in mind: They can attract properly folded proteins into misforming along with them, a process Lindquist calls a ‘conformational cascade.’
In the test tube, conformational cascade is said to generate strings and strings of tough, durable and heat-resistant protein fibres called amyloids.
In humans, amyloids are best known as the plaque that clogs up neurons in people with Alzheimer’s, mad cow disease and other neurodegenerative illnesses. However, yeast prions used as the source of protein in these experiments are reportedly harmless, making them safe to work with in manufacturing.
Lindquist and her colleagues used a genetic variant of yeast, which they modified to produce fibres capable of bonding with gold particles. They then coated these fibre strings with enough metal to make a working electrical wire.
In all important respects, these nanowires possess the characteristics of conventional solid metal wire, Lindquist explained, such as low resistance to electrical current.
‘With materials like these,’ she noted, ‘it should be possible to harness the extraordinary diversity and specificity of protein functions to nanoscale electrical circuitry.’