Double Electron-Electron Resonance Measured Between Gd3+ Ions and Nitroxide Radicals

Double electron electron resonance has attracted growing attention as a technique to study structure and conformational changes of biomacromolecules. Here, a new combination of paramagnetic labels is experimentally tested, one being a commonly used nitroxide radical, and the other being a Gd3+ ion. The Gd3+-nitroxide spin pair can serve as a good substitute for the nitroxide-nitroxide pair of spin labels and potentially provides a link to other experimental approaches dealing with structural information.