A peptide–sugar crystalline complex containing a very strong hydrogen bond

Abstract

The X-ray crystal structure of a complex of galacturonic acid and tryptophan methyl ester shows a laminar packing arrangement in which hydrophobic bilayers of amino acid sandwich hexapyranose monolayers; the lattice allows 50 : 50 occupancy of α- and β-galactopyranose anomers and dimer pairs of galacturonic and molecules are formed by means of a very strong hydrogen bond of 2.43 Å between the hemiprotonated carboxy groups.