Calorimetric Methods

The Institute of Resource Ecology is the only European research site that provides access to life cell metabolic monitoring of naturally and genetically engineered organisms in the presence of radionuclides covering a large variety of radioisotopes. We use state of the art microcalorimetry within an S1-lab as part of a controlled area. This allows studying the metabolic effects evoked by heavy metals and radionuclides in the radioecologically most relevant low dose regime. In contrast to other facilities, where doses are typically limited to external gamma radiation, all scenarios of the interaction of ionizing radiation with living organisms, ranging from external to internal exposure, can be addressed and monitored in real time from hours to weeks. The combination of metabolic monitoring with genetics is a particularly powerful tool to address mechanisms of metal toxicity at the level of molecule-specific biochemical pathways as has been demonstrated for the protective role of glutathione (GSH) against uranyl toxicity (Obeid et al. 2016).

Uranyl dependence of the metabolic heat flow of Lactococcus lactis in the absence of GSH. (A) Heat flow plotted versus time.The arrow indicates the metabolic transition from the first phase (I) to the second phase (II) of exponential growth, characterized by the rate constants k1 and k2, respectively. Dotted lines show the corresponding exponential fits. (B) Total heat-versus-time plot approximating the change in cell number. (C) Heat flow versus total heat.

UComparison of growth rates during first and second phases of logarithmic growth. (A) Copper sensitivity of growth rates (determined in duplicates in identical culture media). (B) Uranyl sensitivity of growth rates (determined from two sets of duplicates in different batches of medium). All rates were determined from the linear stretches of the heat flow-versus-heat diagrams. Red, without GSH induction; blue, with GSH induction.

In the field of surface science, the equipment is used to determine the energetics of adsorption processes of heavy metals and radionuclides to mineral surfaces using Isothermal Titration Calorimetry (ITC). The derived energetics complements the structural picture of metal mineral interactions obtained from spectroscopic methods and quantumchemical calculations.

Finally, the experiments enable material investigations that address the chemical aspects of reactor safety (Willms et al. 2017).