A perspective essay on the use of Ga as a proxy for Fe in bioinorganic model studies and its successful use for therapeutic purposes.

The use of Ga as a structural mimic for Fe in model bioinorganic investigations is usually based on a common assumption that Ga and Fe should form bioligand complexes of similar stabilities due to their similar charge/radius ratio (z/r). However, the literature survey presented here is contrary to this notion, showing that under laboratory conditions often Ga forms weaker bioligand complexes than Fein aqueous medium. We hypothesize that this is because Ga is more aquaphilic than Fe as suggested by their relative heats of hydration (ΔH). The successful use of Ga as a therapeutic agent is also briefly reviewed, showing this success often stems from the redox inertness as well as different pharmacokinetics of Ga than Fe, but similar metabolic pathways as Fe in human serum.