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Structures of dipeptides: the head-to-tail story

Acta Cryst. (2010). B66, 84–93 (

[Hydrogen-bonded dipeptide chains] The simultaneous presence of two crystallographically independent hydrogen-bonded chains, highlighted in blue (with yellow H atoms) and red, in a dipeptide structure. Peptide side chains have been omitted.

Hydrogen bonding in crystal structures of unprotected, zwitterionic dipeptides is dominated by head-to-tail chains involving the amino and carboxylate groups. Of special interest are patterns with two concomitant chains that generate a hydrogen-bonded layer. A comprehensive survey shows that these can conveniently be divided into only four groups, differing not only in the symmetry of the chains and amide hydrogen bonding, but also in peptide conformation and the propensity to include guest molecules. The pattern observed for a specific dipeptide follows from the amino-acid sequence.

C. H. Görbitz