Münster 1997 – wissenschaftliches Programm

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CP: Chemische Physik

CP 11: Poster zur Sitzung CP1

CP 11.20: Poster

Montag, 17. März 1997, 18:30–21:15, FBH

TDPAC–Studies of Macrocyclic Ag–Thiocrownethers: Molecular Stability of Radiopharmaceuticals — •B. Ctortecka¹, W. Tr"oger¹, T. Butz¹, R. Alberto², D. Angst², and P. Schubiger² — ¹Institut f"ur Experimentelle Physik II, Nukleare Festk"orperphysik, Linnéstr. 5, 04103 Leipzig — ²Radiopharmazie, Paul-Scherrer-Institut, Villigen, Switzerland

The almost pure β⁻ emitter ¹¹¹Ag (τ_1/2 = 7.5 d) would be a promissing alternative to the known isotopes (e.g. ³²P, ⁶⁷Cu etc.) for systemic targeted radiotherapy. Since ¹¹¹Ag exhibits no tissue selectivity suitable tumour seeking agents have to be labelled by strong ¹¹¹Ag complexes. We use derivatized hexadendate macrocyclic thioethers (...18S6(OH), 19S6(OH), 20S6(OH)...) for this purpose. In order to monitor the complexation of ¹¹¹Ag by these ligands the 95–247 keV γ–γ–cascade in ¹¹¹Cd (populated by less than 0.2% of the decays) is used to detect the nuclear quadrupole interaction (NQI) via time differential perturbed angular correlation (TDPAC). Besides structural information the molecular stability of the complexes at physiological conditions (concentration, pH, various body liquids or tissue) can be monitored. Up to now, only the 18S6(OH) thioether shows a distinct Ag(I)-coordination. Furthermore, a pH dependency of the complexation was observed. Dissolving the crystallized complex leads to a significant change in the Ag(I)-coordination sphere. Temperature dependent studies reveal intramolecular dynamics in these complexes.