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

Abstract

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 UO2 2+ and the non- and phosphorylated amino acid L-threonine. The complex formation constants for a 1:1 and 1:2 complex in the case of L-threonine were determined to be log β 111=10.33 ± 0.26 at ionic strength I=0.1 M, log β 111=10.25 ± 0.25 and log β 122=19.94 ± 0.24 at ionic strength I=0.5 M. The calculated constants of the different 1:1 uranyl complexes with O-phospho-L-threonine are log β 131=0.28 ± 0.11, log β 121=18.94 ± 0.29 and log β 111=15.02 ± 0.23 at I=0.1 M.