LAUSR

Electron Paramagnetic Resonance is a spectroscopic technique which, in combination with site-directed spin-labeling, provides structural and dynamic information about proteins in conditions similar to those of their physiological environment. The information is sequence-resolved as it is based on probing the local dynamics of a paramagnetic label incorporated as a side chain of a selected amino acid. This technique does not impose a limit on the size of the protein or protein complex, as long as it is amenable to site-directed mutagenesis. Reliable distance distributions between two or more labels (identical or different) can also be obtained. The mean value, width and shape of distance distributions, as well as their dependence upon the state of the protein or interactions with physiological partners, provides insight into order-disorder transitions and the roles of protein flexibility. The main potentialities of the technique are revised and illustrated with examples of proteins for which order-disorder play an important role.