Uranium is an abundant natural element found in many ores and seawater. Despite its omnipresence, uranium does not play an essential role in living organisms. The molecular mechanisms responsible for its radiological and chemical toxicity are still poorly understood.

In vivo, the most stable uranium ion is uranyl cation UO₂²⁺ which preferentially interacts with four to six oxygen atoms in the plane perpendicular to the O=U=O bonds. Chemists from INAC have chosen short peptide sequences to mimic protein/metal interactions to determine their structural and thermodynamic characteristics. A cyclic peptide structure constraining electron-donating oxygen atoms in the equatorial plane of uranyl has been found to be particularly effective in producing a supramolecular edifice in which the peptide interacts with uranyl (uranyl complex).

By combining synthesis, chemical analysis, X-ray absorption spectroscopy and theoretical calculations, the researchers managed to correlate the amino acid sequence of the cyclic structure and the stability of the resulting uranyl complex. Phosphate groups (PO₄^3-) were found to significantly enhance the affinity of biomimetic peptides with uranyl. Phosphoproteins such as osteopontin must therefore be considered as potential targets for uranyl in vivo.