Speaker
Prof.
Tilman Butz
(University of Leipzig)
Description
The understanding of the function of metalloproteins and metal-containing enzymes is
usually based on the detailed knowledge of the structure of these macromolecules
obtained by X-ray diffraction. In many cases, crystals of sufficient quality are not
available and one has to rely on spectroscopy such as, e.g., Nuclear Magnetic
Resonance (NMR) or Electron Paramagnetic Resonance EPR). Another particularly
interesting technique is Time Differential Perturbed Angular Correlation of -Rays
(TDPAC) which has the highest possible sensitivity due to the use of radioactive -
emitters. Experiments under physiological conditions with picomolar concentrations
are feasible.
The nuclear quadrupole interaction (NQI) turns out to be an extremely sensitive tool
to study, e.g., the structure and dynamics at metal ion binding sites, protein-
protein interactions in solutions, and the metal binding site structure during
catalytic action. The basic reason for this sensitivity is the strong inverse cubed
dependence of the NQI on nearest-neighbour distance. Very subtle changes in
rigidity/flexibility in isomorphous replacements of metal ions are detectable.
A drawback is the fact that only a limited number of suitable radioisotopes is
available which happen to be rather short-lived. In all cases an extremely high
specific activity is required. Therefore an on-line isotope separator such as ISOLDE
is indispensable.
Examples from recent work at ISOLDE and from the group of the late Rogert Bauer in
Copenhagen will be presented. Future applications such as, e.g., the combination of
freeze-quench techniques with TDPAC for the study of enzymatic reactions will be
discussed.
Primary author
Prof.
Tilman Butz
(University of Leipzig)
