Lanmodulin (LanM) is the first identified macrochelator
that has
naturally evolved to sequester ions of rare earth elements (REEs)
such as Y and all lanthanides, reversibly. This natural protein showed
a 106times better affinity for lanthanide cations than
for Ca, which is a naturally abundant and biologically relevant element.
Recent experiments have shown that its metal ion binding activity
can be further extended to some actinides, like Np, Pu, and Am. For
this reason, it was thought that LanM could be adopted for the separation
of REE ions and actinides, thus increasing the interest in its potential
use for industry-oriented applications. In this work, a systematic
study of the affinity of LanM for lanthanides and actinides has been
carried out, taking into account all trivalent ions belonging to the
4f (from La to Lu) and 5f (from Ac to Lr) series, starting from their
chemistry in solution. On the basis of a recently published nuclear
magnetic resonance structure, a model of the LanM-binding site was
built and a detailed structural and electronic description of initial
aquo– and LanM–metal ion complexes was provided. The
obtained binding energies are in agreement with the available experimental
data. A possible reason that could explain the origin of the affinity
of LanM for these metal ions is also discussed.