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National Research Foundation, South Africa, (DIB, Grant number 76226; JCS, Grant number 81829), and by the Spanish MICINN and CAM (IF, Grants CTQ2010-20714-CO2-01/BQU, Consolider-Ingenio 2010, CSD2007-00006, S2009/PPQ-1634).

The interaction of Fe(III) and Cu(II) with Aspergillus awamori-derived recombinant human lactoferrin was studied by means of UV–Vis and electron paramagnetic resonance spectroscopy. Results are interpreted as to indicate that non-specific metal binding occurs after a 2:1 stoichiometric metal uptake at the two specific binding sites of lactoferrin has taken place. Like wild-type lactoferrin from human milk, the expressed protein also coordinates the metal at the two specific binding sites to two deprotonated tyrosil and one histidine side chain, one aspartate and a bidentate sinergistic anion, here carbonate. Results of the cobalt(III), manganese(III), cerium(III) and cerium(IV) lactoferrin complexes are also presented and differences induced by the medium (Tris–HCl, phosphate and Hepes buffers) are explained.