Nuclear Physics meets Biophysics: New Insights into Macromolecules

Frank Heinrich, Institut für Experimentelle Physik II, Universität Leipzig

In order to study biochemical systems under physiological conditions an extremely sensitive spectroscopy technique, like time differential perturbed angular correlations (TDPAC), is required. TDPAC spectroscopy monitors the hyperfine interaction (nuclear quadrupole or magnetic interaction) of a radioactive isotope integrated in a molecule during a γ-γ-coincidence experiment. In the case of a nuclear quadrupole interaction the electric field gradient (EFG) at the position of the radioactive probe is determined and provides information about the chemical coordination and the molecular dynamics of the probe. Due to recent developments of density functional theory (DFT) software for molecules the interpretation of EFGs by means of theoretical calculations has become applicable even for larger molecules. In this talk TDPAC experiments and DFT calculations performed on the .molecular families. of Hg-mercaptides, Ag-crown-thioethers and azurin are presented. Experiments with the reanimated isomeric TDPAC isotope ^204mPb are introduced and special demands on the data analysis of this TDPAC probe are discussed. The DFT package "ADF" has been successfully employed for EFG calculations in these molecules including solvation effects. A strong influence of solvation effects on the EFG has been proved and lead to new insights into the interpretation of experimental data.

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