Figure 1

(a) Structure of the siderophores desferrioxamine-B (DFOB) and desferrioxamine-D (DFOD). The terminating group R of DFOB is an amine group with a pK_a of 8.4. The three hydroxyl groups have pK_a values of 8.73, 8.99, and 10.1, respectively [11]. The terminating group R of DFOD is acetylated and has no charge. The stability constant for Fe-DFOB and Fe-DFOD are 10^30.7 and 10^30.76, respectively (I=0.1M) [7]. (b) Structure of EDTA with pK_a values of 2, 2.69, 6.13, and 9.52 [31]. The dominant species under the experimental conditions is doubly negatively charged. (c) Structure of the sodium salt of the anionic surfactant dodecyl sulfate (SDS) with a pK_a of 2.3 [22].