Studies on Synthetic and Natural Melanin and Its Affinity for Fe(III) Ion

Table 1

Equilibrium constants for the interactions of DHI melanin-Fe(III) systems*.

Equilibria	log𝐾 (SD)
[Fe(OH)(CatH2Cat)][H^+]/[Fe^3+][CatH2Cat^2−]	42.52 (1.03)
[Fe(OH)2(CatH2Cat)]^−[H^+]/[Fe(OH)(CatH2Cat)]	−8.63 (0.11)
[Fe(OH)2(CatHCat)^2−[H^+]/[Fe(OH)2(CatH2Cat)^−]	−10.80 (0.09)
[Fe(OH)2(Qi^−)(CatHCat)]^3−/[Fe(OH)2(CatH2Cat)^2−][Qi^−]	5.0 (0.2)

*Obtained by fitting the average of three or more titrations. SD is standard deviation.