Fig. 4.

AGP Ca²⁺ binding: titration of Ca²⁺-depleted gum arabic with Ca²⁺ at pH 5. (A) Saturation binding data (black squares) with theoretical curve (line). (B) Scatchard analysis of binding data with best-fit line giving a K_d of 6·5 μm. Y_GlcA is the fraction of glucuronic acid bound. (C) pH-dependent cation release from Ca²⁺-saturated gum arabic: Ca²⁺ (dashed line) and Mg²⁺ (solid line). (D) Release of Ca²⁺ from gum arabic (dashed line) compared with pectin (solid line). [Reprinted from Lamport and Varnai (2013).]