Complexation of U(VI) with highly phosphorylated protein, phosvitin. A vibrational spectroscopic approach

The complexation of uranium(VI) to variant functional groups of the highly phosphorylated protein phosvitin in aqueous solution was investigated by Attenuated Total Reflection Fourier-transform Infrared (ATR FT-IR) spectroscopy. For the verification of the affinity of the actinyl ions to carboxyl and phosphate groups of the amino acid side chains, samples with different phosphate to uranium(VI) (P/U) ratios were investigated under denaturing conditions and as well as aqueous complexes. From a comparative study with other heavy metal ions, i.e. Ba2+ and Pb2+, a strong coordination of U(VI) to carboxyl and phosphoryl groups can be derived. Furthermore, the spectra indicate a preferential binding to phosphate groups at deficient U(VI) concentrations. These findings are confirmed by spectra of aqueous U(VI)-phosvitin complexes reflecting an explicit coordination of the uranyl ions to phosphate groups at a high P/U ratio. Our study provides a deeper insight into the molecular interactions between actinyl ions and basic biomolecules such as proteins, polysaccharides, nucleic acids.