Investigating the Physicochemical Properties of Oxoanion Doped Iron Mineral: Implication in Understanding the Ferritin Iron Core

Abstract

Iron, a crucial element, is inextricably intertwined in various stages of living and non-living systems. Its existence in two different oxidation states (Fe 2+ /Fe 3+ ) is not only a virtue but also troublesome (low solubility of Fe3+ at neutral pH and Fenton’s reaction by Fe 2+ ). As a solution to this essentiality and toxicity dilemma, nature devised a globular multimeric protein nanocage: ferritin, to detoxify and store iron in soluble ferrihydrite (Fh) bio-mineral form. Native ferritin bio-minerals are associated with variable amounts of phosphate depending upon their source (animals Pi: Fe ~0.1 & plant and bacteria Pi: Fe ~0.5 -1.0) which possibly contributes to their physicochemical properties. Whether the occurrence of a high Pi : Fe ratio in plant/bacterial ferritins is just a coincidence or a consequence of favorable ferritin pore electrostatics is not well understood. Similar to phosphate other oxoanions may stabilize Fe 3+ to modulate the redox and optoelectronic properties of bare and ferritin-encapsulated ferrihydrite minerals. Therefore, a comparison of bare and protein-encapsulated oxoanion-doped iron minerals may give insights into the impact of oxoanion on the structure, stability, and reactivity of iron bio-mineral. So a detailed investigation was performed on a number of oxoanion-doped Ferrihydrite which closely resembles, the iron mineral found in nature. Hence, the current work justifies the % incorporation of oxoanion by natural selection.