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The prepn. of gadolinium complexes of peptide conjugates as contrast agents for use in NMR (MRI) is described. This novel class of contrast agents may be used to identify and locate primary human tumors and their metastases which over-express type CCK A and/or type B cholecystokinin receptors, and/or type SSTR 1-5 somatostatin receptors (no data). Thus, gadolinium DTPA-peptide deriv. conjugates with Gly-CCK8 or vapreotide were prepd. (DTPA = diethylenetriaminepentaacetic acid, Gly-CCK8 = H-Gly-Asp-Tyr-Met-Gly-Trp-Met-Asp-Phe-NH2).

A two-component ligand system (1) containing 1,4,7,10-tetraazacyclododecane-1,4,7-triacetic acid (DO3A)as the hosting unit for the lanthanide cations and an appended asymmetrically functionalized 1,10-phenanthroline (phen) as the chromophore was synthesized. The 1:1 complexes with Eu3 +,Gd3+,Tb3+, and Yb3+ have been prepared and studied in aqueous solution. For Gd‚1, a relaxivity value of 2.4 mM-1 s-1 has been measured at 20 MHz and 25 °C, which indicates that there are no water molecules in the first coordination sphere of the metal ion. The analysis of high resolution 1H NMR spectra of Yb‚1 supports this view and suggests the direct involvement of the phen moiety in the coordination of the metal ion. For Eu‚1 and Tb‚1, the absorption and luminescence spectra, the overall luminescence efficiencies, and the metal-centered (MC) lifetimes were obtained; coordination features were also determined by comparing luminescence properties in water and deuterated water. For Eu‚1 and Tb‚1, the overall emission sensitization (se) process in air-equilibrated water was found to be notably effective with ?se= 0.21 and 0.11, respectively. A detailed study of the steps originating from light absorption at the phen unit and leading to MC sensitized emission was performed.

A two-component ligand system (1) containing 1,4,7,10-tetraazacyclododecane-1,4,7-triacetic acid (DO3A) as the hosting unit for the lanthanide cations and an appended asymmetrically functionalized 1,10-phenanthroline (phen) as the chromophore was synthesized, The 1:1 complexes with Eu3+, Gd3+, Tb3+, and Yb3+ have been prepared and studied in aqueous solution. For Gd.1, a relaxivity value of 2.4 mM(-1) s(-1) has been measured at 20 MHz and 25degreesC, which indicates that there are no water molecules in the first coordination sphere of the metal ion. The analysis of high resolution H-1 NMR spectra of Yb.1 supports this view and suggests the direct involvement of the phen moiety in the coordination of the metal ion. For Eu.1 and Tb.1, the absorption and luminescence spectra, the overall luminescence efficiencies, and the metal-centered (MC) lifetimes were obtained; coordination features were also determined by comparing luminescence properties in water and deuterated water. For Eu.1 and Tb.1, the overall emission sensitization (se) process in air-equilibrated water was found to be notably effective with phi(se) = 0.21 and 0.11, respectively. A detailed study of the steps originating from light absorption at the phen unit and leading to MC sensitized emission was performed.