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 2
Exemplary fluorescence titration of the Anticalin CL31d with (a) Ho³⁺·DTPA-NH₂ and (b) Bi³⁺·DTPA-NH₂. The ligand solution was added stepwise to an approximately 1 µM protein solution in PBS, and the protein Tyr/Trp fluorescence upon excitation at 280 nm was measured at 340 nm. Data were subjected to curve fitting according to the law of mass action for bimolecular complex formation. The equivalence point (0.85 or 1.10 µM, respectively, resulting from the curve fit) is indicated by a small vertical arrow. Fluorescence titration of CL31d was also performed with DTPA-NH₂ in complex with Sm³⁺, Gd³⁺, Tb³⁺, Dy³⁺, Y³⁺, Lu³⁺, In³⁺, Sc³⁺ and Ga³⁺, and without metal ion (for the resulting K_d values, see Table 2

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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