In vitro study of the interaction between neptunium ions and aposerumtransferrin by absorption spectrophotometry and ultrafiltration : the case of Np(V)
Racine, R., Moisy, Ph., Paquet, F., Métivier, H., and Madic, C.
Radiochim. Acta 90, 1-8
The interaction between Np(V) and human aposerumtransferrin (apoTf) was studied in vitro under simulated physiological conditions (37°C, pH 7.4, [NaCl] = 0.15 M, [HEPES] = 5 × 10-2 M) by UV-visible and near-IR absorption spectrophotometry and by ultrafiltration. It was found that Np(V) was bound in small fraction (< 12%) to apoTf, and that the role of carbonate and citrate anions in binding is more competitive than synergistic. The complexes NpO2CO3- and NpO2Cit2- tend to form rather than the Np(V)-apoTf complex. Np(V) binding on apotransferrin appears to be pH-dependent and reversible. Displacement experiments with FeIIINTA showed non-specific binding, suggesting a weak interaction between Np(V) and apotransferrin different from the reactions involving transferrin-specific sites with other metallic ions, such as Fe(III). The low overall charge, the size and the geometry of the linear di-oxocation NpO2+ could account for the weak interaction between Np(V) and human transferrin.