Osteopontin: A Uranium Phosphorylated Binding‐Site Characterization

Abstract

Herein, we describe the structural investigation of one possible uranyl binding site inside a nonstructured protein. This approach couples spectroscopy, thermodynamics, and theoretical calculations (DFT) and studies the interaction of uranyl ions with a phosphopeptide, thus mimicking a possible osteopontin (OPN) hydroxyapatite growth-inhibition site. Although thermodynamical aspects were investigated by using time-resolved laser fluorescence spectroscopy (TRLFS) and isothermal titration calorimetry (ITC), structural characterization was performed by extended X-ray absorption fine structure (EXAFS) at the U LIII -edge combined with attenuated total reflection Fourier transform infrared (ATR-FTIR) spectroscopy. From the vibrational and fluorescence spectra, several structural models of a UO2 (2+) /peptide complex were developed and subsequently refined by using theoretical calculations to fit the experimental EXAFS obtained. The structural effect of the pH value was also considered under acidic to moderately acidic conditions (pH 1.5-5.5). Most importantly, the uranyl/peptide coordination environment was similar to that of the native protein.

Intracellular uranium distribution: Comparison of cryogenic fixation versus chemical fixation methods for SIMS analysis

“…In the literature, speciation studies have shown that actinides, especially uranium, could bind to several biological ligands: proteins, lipids or amino acids and DNA (Ansoborlo et al, ; Bresson, Ansoborlo, & Vidaud, ; Carrière et al, ; Dedieu et al, ; Hartsock, Cohen, & Segal, ; Huynh, Bourgeois, Basset, Vidaud, & Hagège, ; Safi et al, ). Moreover, previous studies have displayed, in cytotoxic uranium conditions ( U > 300 µM), uranyl phosphate precipitates in the cytoplasm of cells (Carrière et al, ; Ghadially et al, ; Mirto et al, ).…”

Phosphate‐Rich Biomimetic Peptides Shed Light on High‐Affinity Hyperphosphorylated Uranyl Binding Sites in Phosphoproteins

“…Once dephosphorylated, its affinity toward UO 2 2+ drops 10‐ to 100‐fold . A phosphorylated group was confirmed to be involved in the complexation of UO 2 2+ by an OPN fragment by extended X‐ray absorption fine structure (EXAFS) analyses …”

Adsorption characteristics of Cr (III) onto starch‐graft‐poly(acrylic acid)/organo‐modifed zeolite 4A composite: A novel path to the adsorption mechanisms

“…The degeneracy for single scattering paths were all fixed as obtained from the theoretical model during the fitting procedure, but the degeneracy for the double and triple scattering paths were initially set to 7.4 and 9.5 (Table ), respectively, based on the scattering amplitude of each multiple scattering paths. The Debye‐Waller factors ( σ ) for the Cr–O eq/ax multiple scattering path was constrained to twice that of the corresponding single scattering path of Cr–O eq ( σ 1 ) . However, for the double Cr–C–O eq scattering path, we defined a different σ because the bond angle was not linear ( σ 5 ) .…”

“…The Debye‐Waller factors ( σ ) for the Cr–O eq/ax multiple scattering path was constrained to twice that of the corresponding single scattering path of Cr–O eq ( σ 1 ) . However, for the double Cr–C–O eq scattering path, we defined a different σ because the bond angle was not linear ( σ 5 ) . Within the resolution limit of EXAFS, the scattering distance for the six scattering paths were chosen from those values provided by FEFF calculations (Table ).…”

“…S2 and Table S3). Thus, the co‐existence of two kinds of oxygen atoms at different distance to the center Cr 3+ , just like the uranium complexes , and copper complexes , would be preferred to return good fit of the collected data.…”