Chiral recognition of a guest amino acid by a host peptide nanoring (PNR) is studied by ab initio calculations. The intermolecular hydrogen bonds (HBs) between the present host and the guest force the guest amino acid to land into the host PNR, and also the side chain of the host PNR to hold the guest amino acid. Thus, the host PNR captures the guest amino acid and gives a distinct energy difference in accordance with the chirality of the captured guest D/L-SerH+. The calculated energy difference of 18 kJ/mol in Gibbs free energy is comparable to that by the host crown ether, by which Moreno et al. have succeeded in experimentally recognizing the chirality of the guest D/L-SerH+ [J. R. A. Moreno, M. M. Q. Moreno, J. J. L. González, and B. M. Haya, J. Phys. Chem. B 117, 9362 (2013)]. The PNRs could be unique biomolecular materials from the perspective that the chirality of an amino acid is recognized by the PNR consisting of amino acid residues.
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