A Closed Cavity Strategy for Selective Dipeptide Binding by a Polyaromatic Receptor in Water
Mayu Shuto, Ryuki Sumida, Mana Yuasa, Tomohisa Sawada, Michito Yoshizawa
Abstract
High Resolution Image Download MS PowerPoint Slide Precise recognition of peptides is a daunting task owing to the substantial number of available amino acids and their combination into various oligo/polymeric structures in addition to the high hydration of their flexible frameworks. Here, we report the selective recognition of a dipeptide through a closed cavity strategy, in contrast to previous synthetic receptors with open cavities. A polyaromatic receptor with a virtually isolated, hydrophobic cavity exclusively binds one molecule of phenylalanine dipeptide from a mixture with its amino acid and tripeptide in water via multiple CH−π and hydrogen-bonding interactions in the complementary cavity. The binding selectivity persists even in the presence of other dipeptides, such as leucine–leucine, leucine–phenylalanine, tyrosine–phenylalanine, tryptophan–tryptophan, and aspartame, revealed by NMR/MS-based competitive binding experiments. ITC studies reveal that the selective binding of the phenylalanine dipeptide is relatively strong ( K a = 1.1 × 10 5 M –1 ) and an enthalpically and entropically favorable process (Δ H = −11.7 kJ mol –1 and T Δ S = 17.0 kJ mol –1 ). In addition, the present receptor can be used for the emission detection of the dipeptide through a combination with a fluorescent dye in water.