Membrane incorporated synthetic a-helical polypeptides labelled with Dy(III) chelate complexes and nitroxide radicals were studied by the inversion recovery (IR) technique and Dy(III)-nitroxide distances were obtained. A comparison of obtained distances with the previously reported Gd(III)-nitroxide double electron–electron resonance (DEER) calibration data was performed and revealed reliability of the IR-based technique for the distance determination in membrane-incorporated biomacromolecules. The presented distance determination technique is ‘spectroscopically orthogonal’ to DEER-based distance measurements and can be potentially combined with DEER to study multiply spin-labelled biomacromolecules. The key steps of the data processing, the types of obtained distance information and the areas of possible application of the technique are discussed.
- pulsed dipolar esr
- epr spectroscopy