Complexation of Cm(iii) with the recombinant N-lobe of human serum XXXX studied by time-resolved laser fluorescence spectroscopy (TRLFS).

@entity596 @entity6445 @entity535 @entity69 @entity2507
The complexation of Cm(iii) with the recombinant N-lobe of human serum @entity69 (hTf/2N) is investigated in the pH range from 4.0 to 11.0 using TRLFS. At pH >=  7.4 a Cm(iii) hTf/2N species is formed with Cm(iii) bound at the @entity596 binding site. The results are compared with Cm(iii) @entity69 interaction at the C-lobe and indicate the similarity of the coordination environment of the C- and N-terminal binding sites with four @entity535 residues of the protein, two @entity2507 molecules and three additional ligands (e.g. synergistic anions such as @entity6445 ) in the first coordination sphere. Measurements at c( @entity6445 )tot = 0.23 mM (ambient @entity6445 concentration) and c(carbonate)tot = 25 mM (physiological @entity6445 concentration) show that an increase of the total @entity6445 concentration suppresses the formation of the Cm(iii) hTf/2N species significantly. Additionally, the three Cm(iii) carbonate species Cm(CO3)(+), Cm(CO3)2(-) and Cm(CO3)3(3-) are formed successively with increasing pH. In general, @entity6445 complexation is a competing reaction for both Cm(iii) complexation with @entity69 and hTf/2N but the effect is significantly higher for the half molecule. At c( @entity6445 )tot = 0.23 mM the complexation of Cm(iii) with @entity69 and hTf/2N starts at pH >=  7.4. At physiological @entity6445 concentration the Cm(iii) @entity69 species II forms at pH >=  7.0 whereas the Cm(iii) hTf/2N species is not formed until pH > 10.0. Hence, our results reveal significant differences in the complexation behavior of the C-terminal site of @entity69 and the recombinant N-lobe (hTf/2N) towards trivalent actinides.
