The conjunction of the chemical properties of zinc underlies its biological significance. It is a relatively small ion (with an atomic number of 30) and carries a positive charge of two. It attracts electrons as a strong Lewis acid, and this property can be important in its catalytic functions. It has relatively flexible coordination geometry and, while binding its ligands with high affinity, exhibits rapid rates of exchange, which can facilitate chemical reactions and biological processes. All this is coupled with its single redox state, in contrast to the multiple redox states of iron and copper, which eliminates the danger of oxidative damage. While other trace elements may share some of these properties, none share them all. This is what makes zinc so valuable for protein structure and function.
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