Diffusion NMR spectroscopy: folding and aggregation of domains in p53

Protein interactions and aggregation phenomena are probably amongst the most ubiquitous types of interactions in biological systems; they play a key role in many cellular processes. The ability to identify weak intermolecular interactions is a unique feature of NMR spectroscopy. In recent years, pulsed-field gradient NMR spectroscopy has become a convenient method to study molecular diffusion in solution. Since the diffusion coefficient of a certain molecule under given conditions correlates with its effective molecular weight, size, and shape, it is evident that diffusion can be used to map intermolecular interactions or aggregation events. Complex models can be derived from comparison of experimental diffusion data with those predicted by hydrodynamic simulations. In this review, we will give an introduction to pulsed-field gradient NMR spectroscopy and the hydrodynamic properties of proteins and peptides. Furthermore, we show examples for applying these techniques to a helical peptide and its hydrophobic oligomerization, as well as to the dimerization behavior and folding of p53.