There is an increasing interest in the use of lanthanides in medicine. However, themechanismof their accumulation in cells isnotwell are similar to ferric ions with regard to transferrin binding, suggesting transferrin-receptormediated transport is possible; however, this has not yet been confirmed. In order to clarify this mechanism, we investigated the binding of Yb 3+ to apo-transferrin by UV-Vis spectroscopy and stopped-flow spec-trophotometry, and found that Yb 3+ binds to apotransferrin at the specific iron sites in the presence of bicarbonate. .
