Steady-state fluorescence emissions spectra of metalated DTPA.

Fluorescence emission spectrum observed upon metalation of DTPA by Tb3+. Fluorescence intensity, in counts per second (cps), of 100 mM MES, pH 5.5 (MES) (light blue arrow), 10 mM DTPA in 100 mM MES, pH 5.5 (DTPA) (dark blue arrow), 40 mM terbium trichloride in 100 mM MES, pH 5.5 (gray arrows), and 10 mM DTPA, 40 mM terbium trichloride in 100 mM MES, pH 5.5 (black arrows). The excitation wavelength was 350 nm; emission was monitored from 400–800 nm. The water Raman is evident at 702 nm. Peaks at 489, 544, 584, and 621 correspond to terbium fluorescence emission.