The ribosome, the molecular machine that translates our genetic code to build the body’s proteins, is a mechanical marvel. Now, chemists have invented a nanomachine that can achieve a similar feat.
The artificial system is not about to displace nature’s ribosome, a complex of proteins and RNA. It is much simpler, and only about about one-tenth of the size — and, it is achingly slow, destroys the code it reads and can produce only very short chunks of protein, known as peptides. It does, however, show that some of the tactics of biology’s molecular machines can be adopted to make useful chemicals.
“We were inspired by the ribosome,” says synthetic chemist Dave Leigh at the University of Manchester, UK, who led the team behind the development. “But our machine is extremely primitive compared to the ribosome.”
Leigh’s system relies on a rotaxane — a large molecular ring threaded onto another molecule that acts as an axle. The axle is lined with three amino acids, and a chain of three more amino acids hangs from the outer edge of the ring. One of the amino acids attached to the ring is cysteine, which contains a crucial sulphur-containing thiol group.
Heating the system prompts the thiol group to pluck an amino acid from the axle and transfer it to the end of the chain of amino acids attached to the ring. The ring can then move along the axle and repeat the same trick with the next two amino acids. Unthreading the ring and breaking off the newly-formed chain delivers a perfectly formed peptide made from all six amino acids.