Figure 4.

Effect of ${\text{O}}_{\text{2}}^{-*}$ on Fe bioavailability in a system containing a single Fe complexing ligand. (A) Steady-state $\left[{\text{O}}_2^{-*}\right]=0$ (B) Steady-state $\left[{\text{O}}_2^{-*}\right]=100\text{\hspace{0.17em}pM}$ (C) Steady-state $\left[{\text{O}}_2^{-*}\right]=100\text{\hspace{0.17em}pM}$ (D) Steady-state $\left[{\text{O}}_2^{-*}\right]=1\text{\hspace{0.17em}nM}$. Panels show the resulting pFe′ [= −log[Fe′] _T = −log([Fe(II)′] + [Fe(III)′]) at steady-state. The contours shown in each panel represent constant pFe′ values, as indicated by the numbers marked on the contour lines. The region to the bottom right of the dashed lines in each panel approximately indicates conditions where the strength of the Fe(II) complex relative to that of the Fe(III) complex is sufficiently high that the presence of ${\text{O}}_2^{-*}$ decreases Fe bioavailability.