Diverse DTPA-chelated lanthanides with relevance for nuclear medicine bound to an engineered lipocalin reveal conserved ligand geometry

Mirwald, A.; Eichinger, A.; Skerra, A.

doi:10.1107/S2053230X26007624

Figure 5
Correlation between the radius of the central ion and the overall geometry of the Anticalin-bound metal-chelate complex. (a) Superposition of the six different M^III·DTPA-NH₂ complexes via the central ion to illustrate the minute structural influence of the ionic radius: Bi³⁺·DTPA-NH₂ (cyan C atoms), Tb³⁺·DTPA-NH₂ (green), Dy³⁺·DTPA-NH₂ (orange), Y³⁺·DTPA-NH₂ (white), Lu³⁺·DTPA-NH₂ (yellow) and uncomplexed DTPA (purple). (b) Sum of the metal–ligand distances to eight donor atoms (5 O + 3 N) plotted against the ionic radii (CN = 6). (c, d) Superposition of the Sc³⁺·DTPA-NH₂ complex (salmon) and of the empty DTPA-NH₂ chelator (purple; harboring a central water molecule, which is obscured here, and one peripherally associated water molecule), respectively, with the published In³⁺·DTPA complex (light blue) from the Cambridge Structural Database (CSD entry MOQVOD). Contacts with the coordinating N and O atoms and the water molecule are indicated by dashed black lines.

STRUCTURAL BIOLOGY
COMMUNICATIONS

ISSN: 2053-230X

Volume 82| Part 9| September 2026| Pages 301-311

https://doi.org/10.1107/S2053230X26007624

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