1H NMR studies on lanthanides substituted transferrins.

The binding of lanthanide(III) ions to human serum apotransferrin has been investigated through 1H NMR spectroscopy. Several well resolved isotropically shifted signals have been observed between 100/-100 ppm for the Tm, Tb, Yb and Dy derivatives. Significant spectroscopic inequivalence of the two metal binding sites has been revealed. Differences in the behavior of signals assigned to the C- and to the N-terminal site have been observed upon titration with sodium perchlorate.