Download MendeleyEngineered Recognition of Tetravalent Zirconium and Thorium by Chelator-Protein Systems: Toward Flexible Radiotherapy and Imaging Platforms.
Captain, I., Deblonde, G.J., Rupert, P.B., An, D.D., Illy, M.C., Rostan, E., Ralston, C.Y., Strong, R.K., Abergel, R.J.(2016) Inorg Chem 55: 11930-11936
- PubMed: 27802058
- DOI: https://doi.org/10.1021/acs.inorgchem.6b02041
- Primary Citation of Related Structures:
5KHP, 5KID - PubMed Abstract:
Targeted α therapy holds tremendous potential as a cancer treatment: it offers the possibility of delivering a highly cytotoxic dose to targeted cells while minimizing damage to surrounding healthy tissue. The metallic α-generating radioisotopes 225 Ac and 227 Th are promising radionuclides for therapeutic use, provided adequate chelation and targeting. Here we demonstrate a new chelating platform composed of a multidentate high-affinity oxygen-donating ligand 3,4,3-LI(CAM) bound to the mammalian protein siderocalin. Respective stability constants log β 110 = 29.65 ± 0.65, 57.26 ± 0.20, and 47.71 ± 0.08, determined for the Eu III (a lanthanide surrogate for Ac III ), Zr IV , and Th IV complexes of 3,4,3-LI(CAM) through spectrophotometric titrations, reveal this ligand to be one of the most powerful chelators for both trivalent and tetravalent metal ions at physiological pH. The resulting metal-ligand complexes are also recognized with extremely high affinity by the siderophore-binding protein siderocalin, with dissociation constants below 40 nM and tight electrostatic interactions, as evidenced by X-ray structures of the protein:ligand:metal adducts with Zr IV and Th IV . Finally, differences in biodistribution profiles between free and siderocalin-bound 238 Pu IV -3,4,3-LI(CAM) complexes confirm in vivo stability of the protein construct. The siderocalin:3,4,3-LI(CAM) assembly can therefore serve as a "lock" to consolidate binding to the therapeutic 225 Ac and 227 Th isotopes or to the positron emission tomography emitter 89 Zr, independent of metal valence state.
Organizational Affiliation:
Chemical Sciences Division, Lawrence Berkeley National Laboratory , Berkeley, California 94720, United States.
