Metal-Peptide Torus Knots from Flexible Short Peptides

Summary Entanglements of strings are regularly encountered on the macroscale yet rarely utilized in nanoscale construction. Here, we report highly entangled peptide-mimic structures created through folding and assembly of silver(I) ions and a triglycine ligand (L). The highly flexible triglycine strand assembled into a septafoil knot ([Ag⋅L]7) and its eight-crossing link analog ([Ag⋅L]8), both of which were formed for the first time by chemical synthesis. The two structures result from circular oligomerization of the same 1-crossing Ag⋅L motif. We also obtained poly[n]catenane [Ag⋅L]n from a topologically isomeric 2-crossing motif. Our observations reveal that dynamic linkages of short peptides enable easy access to knotted structures, which are restricted in protein structures because of the entropic (and/or kinetic) disadvantage of self-threading processes in long peptide chains, with remarkable stereoselectivity in the self-assembly process.