Chitin

(→4)-β-2-acetamido-2-deoxy-D-glucose(1→). Some degree of N-deacetylation may be found. Complete N-deacetylation is chitosan [1].

In chrystallography there are two polymorphic chitin forms: α and β: α-chitin, the most abundant of the two chitins. The helix repeats after 10.3 Å, analogous to the formation of cellulose. The α and β conformations depend on hydrogen bonds [4]. Crystallographic data in [2] and [5].