A Discrete Four-Stranded β-Sheet through Catenation of ML Metal-Peptide Rings.

Methods for precisely constructing a β-sheet assembly with number-defined strands in solution remains quite limited due to its intense aggregation property. Here, we report the precise construction of a four-stranded anti-parallel β-sheet by utilizing a non-covalent approach. This was achieved by folding and assembly of Ag and a pentapeptide (1) with the Ala-3pa-Gly-3pa-Val (3pa: β-(3-pyridyl)-alanine) sequence, which was designed to form an interlocking Ag(1) ring through metal cross-linking of the side chains. NMR analyses and X-ray crystallographic studies characterized the structure of the discrete β-sheet assembly as well as the remarkable structural selectivity in terms of strands' number, orientation and the sheet type.