How do actinyls interact with hyperphosphorylated yolk protein Phosvitin ?

We carried out a multi-techniques spectroscopic investigation to reveal the coordination geometry of actinyl ions (U(VI), Np(V)) in speciation with phosvitin protein. Like other protein molecules, phosvitin has carboxylic, phosphoryl and amide functional groups, but it has clustered serine residues and all the serine residues are phosphorylated to make it a hyperphosphorylated protein. IR spectroscopic study revealed phosphoryl groups as the main functional group interacting with uranyl ions. This was confirmed in the U(VI)-phosvitin fluorescence spectroscopic investigation and Np(V)-phosvitin UV-visible studies. Further, the existence of U(VI)-phosvitin system in a single speciation was found by the analysis of uranyl ion fluorescence decay data. Interestingly, X-ray absorption fine structure spectroscopic data for U/Np LIII edge revealed small contribution of bidentate binding present along with predominantly monodentate binding of phosphoryl groups in speciation of Uranyl ions with phosvitin protein. Signature of only bidentate binding was found in speciation of Np(V)-phosvitin system. In view of (de)phosphorylation as an important step of functional expression of various human body proteins, this study adds significant details to the molecular description of the toxicity of actinyl ions in biosphere.