Isolation and characterization of the bioligands secreted by P. fluorescens (CCUG 32456 A) and Complexation of uranium(VI) with aromatic acids having different functionalities studied by different spectroscopic techniques (UV-vis spectroscopy and time-resolved laser-induced fluorescence spectroscopy (TRLFS))

The FZD/IRC contributions within the microbe project as part of the international co-operation of the Äspö HRL (Sweden) with the BMWi (Germany) are concentrated in a project addressing the indirect interaction mechanism of a mobilization of actinides by released bioligands in the aquifer system from relevant Äspö bacteria. The ongoing study is focused on: (i) isolation and characterization of microbial ligands produced from a subsurface strain of Pseudomonas fluorescence isolated at Äspö, (ii) interaction of U(VI), Np(V), and Cm(III) with the microbial ligands including compounds simulating the functionality of the microbial ligands and the surface of the bacteria and (iii) spectroscopic characterization of the formed actinide complexes/compounds. The formation constants determined will be used directly in speciation and transport models. This project should help to identify the dominating process of the interaction between actinides and microbes (direct or indirect ones). The research performed in our project improves the understanding of the behavior of colloids and microbes and their respective interaction with radionuclides.

The activities in 2006 were concentrated on a) the isolation and characterization of bioligands secreted by a subsurface strain of P. fluorescence found at Äspö HRL and b) complexation studies of actinides with relevant model compounds to explain the interactions of actinides in biologically systems on a molecular level. Main results of these subjects will be reported here.