Chapter 6: Are There Distinguishable Roles for the Different Oxidation States of Manganese in Manganese Toxicity?

The transition metal, manganese (Mn), has a complex chemistry and multiple oxidation states. Only three of these oxidation states, Mn²⁺, Mn³⁺, and Mn⁴⁺, have been found in living cells. Although Mn²⁺ is relatively stable and Mn⁴⁺ largely restricted to an insoluble precipitate or a role in photosynthesis, Mn³⁺ is a strong oxidizing agent and has been suggested to be the cause of the initial damage seen in manganese toxicity. In this review, we consider the chemistry and biology of these manganese oxidation states, some of the physical techniques that can be used to distinguish them, and the evidence found in the literature for differing effects of the different oxidation states.