Griesinger's Group @ The MPIBPC
NMR-based Structural Biology
For our molecular inventory, the structure of a molecule is just as important as its composition. The lethal consequences of misfolding are evidenced by such medical conditions as Alzheimer's or Creutzfeld-Jacob diseases. For both diseases, misfolded protein molecules precipitate in the brain and cause extensive damage. Only properly shaped (folded) proteins fulfill their biological function. Therefore, we are interested in the connections between structure and function.
Our method of choice is nuclear magnetic resonance (NMR) spectroscopy. NMR spectroscopy uses a common property of most atomic nuclei, i.e., that they are magnetic and therefore tend to align either in a parallel or an antiparallel manner with respect to an external magnetic field. Electromagnetic radiation with an energy that matches exactly the energy difference of the two states is absorbed. The corresponding frequency is determined by the nucleus under investigation as well as by the chemical environment. Thus, each atom in a given molecule provides a signal with a slightly different frequency. This phenomenon accounts for the atomic resolution that NMR can provide. Extracting the structural information from the NMR spectrum, however, is an art in itself. In fact, the larger the molecules we deal with, the more difficult the task becomes. Nonetheless, three dimensional triple resonance experiments have made it possible to push the limit of structural investigation to proteins of some 200 amino acids. However, we are trying to push these limits even further.
Pushing the limits:
One of our prime methods for approaching this problem is the partial (or segmental) incorporation of active isotopes into molecules by NMR. This allows us to focus on the resonances of the incorporated isotope and thus to simplify spectra as well as to analyze molecules one by one. In order to perform this approach, we first have to generate the molecules in an adequate form by manipulating bacteria. Feeding bacteria or also other "expression systems" with the appropriate sources is the approach that ultimately yields sufficient amounts of these molecules.
In addition to providing static structures, NMR spectroscopy is also able to trace the motion or "action" of molecules. This is due to the fact that NMR spectroscopy permits the investigation of objects of interest in a nearly physiological environment, either in solution or in a membrane environment. Changes in three-dimensional structure are very rapid, the fastest motions to be observed by NMR occurring on a time scale of one millionth of a millionth of a second. Other conformational changes may take hours to occur. In both cases, NMR permits the observation of conformational changes with atomic resolution.
Focus on drug molecules:
NMR spectroscopy is especially powerful when it comes to the interaction of molecules with each other, whether it is a small molecule as in a drug (?) or two larger molecules, e.g. two proteins. We study such interactions in various systems, such as tubulin and epothilon, as discussed in more detail in the contribution by Teresa Carlomagno, or drug molecules binding to GPCR's as discussed in the contribution by Marc Baldus.
Last modification Fri Jan 9 14:55:35 2004
mantained by Dirk Bockelmann