Figure 1.

(a) α-L-guluronate (G), and (b) β-D-mannuronate (M), form the anionic polysaccharides that make up alginate. (c) Alginate (indicated by the bold lines) is known to order into an “egg box” formation when a divalent cation is introduced, forming a gel. The cation, such as Ca²⁺, will covalently bond (indicated by the dashed lines) with the negative charges on the deprotanated carboxyl groups (indicated by the (−)) of the G units in the alginate chain.