EPR
Electron Paramagnetic Resonance (EPR)[1] gives access to magnetic properties of isolated molecules or it my give insight into local environment of a given paramagnetic site within the object under study. Such object possessing magnetic properties may be nano-object synthesized through bottom up strategy (supra molecular chemistry)[2] or top down nanostructures. Interest of EPR relies on its great sensitivity, which allows studying isolated molecules and/or nano-objects.
With regards to structural biology, it is worth noting that EPR requires paramagnetic spin probes (spin labels and/or metallic centers) to investigate: (i) local environment (local dynamic, access to solvent) and (ii) local conformation when having two spin probes within the sensitivity range of the technique (up to 7nm). Nowadays, thanks to mutagenesis and Site Directed Spin Labeling advanced techniques, spin probe can be easily covalently bound to biological molecules. Upon successive multiple graftings the conformational map of the proteins may be fully generated at relevant sites.[3]
Specific needs of EPR with respect to the study of complex systems:
- increase sensitivity: high-field/high frequency spectrometers are demanded (e.g. pulse Q-band, ca. 32 GHz); development of optically detected EPR would be much relevant
- development of methodological tools: new pulse sequences, increasing the distance range to be explored; efficient algorithms for data filtering are still required.
References
- Spectroscopie de résonance paramagnétique électronique, Patrick Bertrand, EDP Sciences, 2010
- Parizel N, Ramírez J, Burg C, Choua S, Bernard M, Gambarelli S, Maurel V, Brelot L, Lehn J-M, Turek P, Stadler A-M. CHEMICAL COMMUNICATIONS, 2011
- Vileno B, Chamoun J, Liang H, Brewer P, Haldeman BD, Facemyer FC, Salzameda B, Song L, Li HC, Cremo CR, Fajer PG. PNAS, 2011