Iron and oxygen: a biologically damaging mixture.

Iron is a remarkably useful metal in Nature, but iron ions not safely sequestered in storage or transport proteins are hazardous because they can stimulate damaging free radical reactions. Biological examples of these are Fenton Chemistry leading to the formation of highly reactive species, such as the hydroxyl radical (.OH) and the ferryl ion (FeO2+), and lipid peroxidation. The need to conserve body iron stores has closely evolved with an essential requirement for antioxidant protection and, several 'acute-phase' proteins involved in iron metabolism such as caeruloplasmin, haptoglobins and haemopexin in collaboration with the iron binding proteins transferrin and lactoferrin contribute to our defense against oxidative damage.