Sequence recognition and self-sorting of a dipeptide by cucurbit[6]uril and cucurbit[7]uril

Cucurbit[7]uril forms very strong complex with zwitterionic dipeptide Phe–Gly with affinity exceeding 107 M−1 and effectively recognizes peptide sequence of Phe–Gly over Gly–Phe as well as Tyr–Gly over Gly–Tyr and Trp–Gly over Gly–Trp with relative affinities of 23 000, 18 000 and 2000, respectively.