Complex formation of U(VI) with the amino acid L-threonine and the corresponding phophate ester O-Phopho-L-threonine

The complex formation of uranium(VI) with L-threonine and O-Phospho-L-threonine was studied by time-resolved laser-induced fluorescence spectroscopy (TRLFS). An increase in fluorescence emission intensity and a corresponding red shift of the bands in the spectra compared to the free uranyl cation indicate a complex formation between UO22+ and the non- and phosphorylated amino acid threonine. The complex formation constants for a 1:1 and 1:2 complex in the case of L-threonine were determined to be logß111 = 10.33 ± 0.26 at ionic strength I = 0.1 M, logß111 = 10.25 ± 0.25 and logß122 = 19.94 ± 0.01 at ionic strength I = 0.5 M. The calculated constants of the different 1:1 uranyl complexes with O-Phospho-L-threonine are logß113 = 20.28 ± 0.11, logß112 = 18.94 ± 0.29 and logß111 = 15.02 ± 0.23 at I = 0.1 M.