The ribosome is a molecular machine found in all living cells that can stitch together amino acids to form proteins. David Leigh and colleagues at the University of Manchester and the University of Edinburgh have now created an artificial molecular machine with similar, although distinctly more primitive, capabilities.
The machine is based on a rotaxane — a mechanically interlocked molecule that has a molecular ring threaded onto a molecular axle — and can synthesize a short oligopeptide. The ring of the rotaxane is functionalized with a thiol-protected molecular arm, whereas the axle has an unreactive stopper on one end and three consecutive stoppers bearing the amino acids to be added to the ring's arm on the other.
The oligopeptide synthesis is activated by deprotecting the thiol group on the ring's arm, which then detaches the first amino acid from the axle and positions it at the end of the arm. This reaction also regenerates the reactive thiol group, and the ring can proceed autonomously along the axle, picking up the other two peptides in the order that they appear on the thread. When the last peptide is removed, the ring is free to slip off, and the final oligopeptide sequence can be recovered from the ring by simple hydrolysis.