Molecular Interactions in an α‑Chitin/Hydrazine Complex: Dynamic Hydrogen Bonds and Improvement of Polymeric Crystallinity

The
high-resolution structure of an α-chitin/hydrazine complex
has been determined to reveal the molecular interactions between hydrazine
molecules and chitin chains. The complexation with guest hydrazine
molecules improves the crystallinity of α-chitin from the original
form, so that the primary hydroxyl group is clearly located in the gt position on the chitin chains arranged in an antiparallel
manner in contrast to the original α-chitin structure which
has the disorder between gt and gg positions. During the complexation process, α-chitin chains
translate by c/4 to incorporate hydrazine molecules.
Molecular dynamics calculations based on the refined structure show
that hydrazine nitrogen atoms are disordered with competing hydrogen
bonds. These observations suggest a mechanism for the structural conversion
of polysaccharides to their crystal solvate forms during penetration
by amine molecules.