Distance determination from dysprosium induced relaxation enhancement: a case study on membrane-inserted WALP23 polypeptides

Abstract

Membrane incorporated synthetic α-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.

Keywords:

• lanthanide ions
• EPR/ESR
• inversion recovery
• biomacromolecules
• dipolar spectroscopy
• distance measurements

Acknowledgements

This work was supported by the SNF (Grant No. 200021_121579) and by the European Community Activity Large-Scale Facility Wageningen NMR Center (FP6-2004-026164 (2006–2009)).