(D) Specificity of glucan-Fe2+ interaction. Purified Xcc β-(1, 2)-glucan was incubated with 100 µM FeSO4 and increasing concentrations of Ca2+, Co2+, Ni2+, Mn2+, Mg2+ or Zn2+, and free or unbound iron was measured by Fe2+-ferrozine colorimetric assay. Data shown are mean ± SD (n=3). 