Complexation of Curium(III) by Adenosine 5’-triphosphate (ATP): A Time-resolved Laser-induced Fluorescence Spectroscopy (TRLFS) Study.

The complex formation of curium(III) with adenosine 5’-triphosphate (ATP) was determined by time-resolved laser-induced fluorescence spectroscopy (TRLFS). The interaction between soluble species of curium(III) with ATP was studied at trace Cm(III) concentrations (3x10-7 M). The concentrations of ATP are varied between 6x10-7 and 1.5x10-4 M in the pH range of 1.5 to 7.0 using 0.154 M NaCl as background electrolyte.
Three Cm-ATP species, MpHqLr, could be identified from the fluorescence emission spectra: (i) CmH2ATP+ with a peak maximum at 598.6 nm, (ii) CmHATP with a peak maximum at 600.3 nm, and (iii) CmATP- with a peak maximum at 601.0 nm. The formation constants of these complexes were calculated from TRLFS measurements to be log β121 = 16.86 ± 0.09, log β111 = 13.23 ± 0.10, and log β101 = 8.19 ± 0.16. The hydrated Cm-ATP species showed fluorescence lifetimes between 88 and 96 µs; whereas the CmATP- complex has a significantly longer fluorescence lifetime of 187 ± 7 µs.