Studying Biomolecular Complexes with Pulsed Electron-Electron Double Resonance Spectroscopy

The function of biomolecules is intrinsically linked to their structure and the complexes they form during function. Techniques for the determination of structures and dynamics of these nanometer assemblies are therefore important for an understanding on the molecular level. Pulsed Electron-Electron Double resonance (PELDOR) is a pulsed Electron Paramagnetic Resonance (EPR) method that can be used to reliably and precisely measure distances in the range of 1.5 - 8 nm, to unravel orientations and to determine the number of monomers in complexes. In conjunction with site-directed spin labeling it can be applied to biomolecules of all sizes in aqueous solutions or membranes. PELDOR is therefore complementary to the methods of X-ray crystallography, NMR and FRET and is becoming a powerful method for structural determination of biomolecules. In this review, the methods of PELDOR are discussed and examples where PELDOR has been used to obtain structural information on biomolecules are summarized.