Metal–Peptide Nonafoil Knots and Decafoil Supercoils

Abstract

Despite the frequent occurrence of knotted frameworks in protein structures, the latent potential of peptide strands to form entangled structures is rarely discussed in peptide chemistry. Here we report the construction of highly entangled molecular topologies from Ag(I) ions and tripeptide ligands. The efficient entanglement of metal−peptide strands and the wide scope for design of the amino acid side chains in these ligands enabled the construction of metal−peptide 9 1 torus knots and 10 1 2 torus links. Moreover, steric control of the peptide side chain induced ring opening and twisting of the torus framework, which resulted in an infinite toroidal supercoil nanostructure.

Knotting matters: orderly molecular entanglements

“…Fujita and coworkers have reported a number of higher-order metalla-entanglements based on the coordination of Ag I ions to pyridyl-capped polypeptide ligands. 102–104 Examples include a series of topoisomeric [4]catenanes 102 and the divergent synthesis of 7 1 and 8 2 1 metalla-knots (Fig. 26).…”

Distinctive features and challenges in catenane chemistry

“…For example, a Hopf link (2 2 1 ), a Solomon link (4 2 1 ), a Star of David catenane (6 2 1 ), and an 8-crossing Torus link (8 2 1 ) are topological isomers of a [2]catenane with different number of crossings between the two interlocked macrocycles. 14,15 Similarly, molecular knots that have the same covalent structure but different topologies (different number of crossings) are also topological isomers. Due to their different topologies, topological isomers are not interconvertible.…”

Unsymmetrical Metallosupramolecular Polycondensation of Expanded l-Amino Acid Containing Platinum(II) Complex in Nonpolar Solvents

“…In contrast, natural polymers, namely, proteins, consist of chiral amino acids and form well-defined three-dimensional structures, which are constructed elaborately from structural motifs including α-helices, β-sheets, and turns, depending on amino acid sequences. , These sophisticated structures exhibit outstanding functions such as enzymatic activities, which have not been realized using only artificial catalysts. , Conversely, elaborate designs of molecules have been believed to endow polymers with excellent functions. This has inspired several researchers to develop chiral oligomers such as foldamers − and polymers. − In recent years, soluble metal–peptide rings containing silver–pyridine bonds have been reported, which are referred to as metallosupramolecular cyclic oligomers. − …”