DEER Sensitivity between Iron Centers and Nitroxides in Heme-Containing Proteins Improves Dramatically Using Broadband, High-Field EPR
- Resource Type
- Authors
- Motion, Claire L.; Lovett, Janet E.; Bell, Stacey; Cassidy, Scott L.; Cruickshank, Paul A.S.; Bolton, David R.; Hunter, Robert I.; El Mkami, Hassane; Van Doorslaer, Sabine; Smith, Graham M.
- Source
- The Journal of Physical Chemistry Letters
The journal of physical chemistry letters
- Subject
- Models, Molecular
Letter
Myoglobin
Protein Conformation
Physics
Iron
Electron Spin Resonance Spectroscopy
Neuroglobin
Nerve Tissue Proteins
Globins
Animals
Humans
Nitrogen Oxides
Spin Labels
- Language
- English
- ISSN
- 1948-7185
This work demonstrates the feasibility of making sensitive nanometer distance measurements between Fe(III) heme centers and nitroxide spin labels in proteins using the double electron−electron resonance (DEER) pulsed EPR technique at 94 GHz. Techniques to measure accurately long distances in many classes of heme proteins using DEER are currently strongly limited by sensitivity. In this paper we demonstrate sensitivity gains of more than 30 times compared with previous lower frequency (X-band) DEER measurements on both human neuroglobin and sperm whale myoglobin. This is achieved by taking advantage of recent instrumental advances, employing wideband excitation techniques based on composite pulses and exploiting more favorable relaxation properties of low-spin Fe(III) in high magnetic fields. This gain in sensitivity potentially allows the DEER technique to be routinely used as a sensitive probe of structure and conformation in the large number of heme and many other metalloproteins.