The crystal structure of mono-ethylenediamine β-chitin from synchrotron X-ray fiber diffraction

The crystal structure of a complex of β-chitin with ethylenediamine (EDA) was determined by synchrotron X-ray fiber diffraction. Data were collected from a sample prepared from the bathophilous tubeworm Lamellibrachia satsuma. The unit cell contains one chain having one N-acetylglucosamine residue in the asymmetric unit with the hydroxymethyl group in gt conformation (a = 4.682 Å, b = 14.351 Å, c = 10.275 Å and γ = 96.24° in space group P21). The complexed EDA molecule has a trans conformation with one amino group tightly bound to the primary alcohol hydroxyl group O6 atom of the N-acetylglucosamine residue in an arrangement similar to that found in the EDA–cellulose I complex. The other amino group has no detectible hydrogen bonding and higher thermal displacement. This common interaction between EDA and O6 would appear to be the dominant driving interaction for complex formation with both β-chitin and cellulose.