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Conformational changes of proteins are tightly coupled to rearrangements of the water molecules surrounding them. When spin-labeled proteins are investigated to extract changes in dynamics at each labeled site, or in the interspin distances during protein functions, it would be desirable to directly monitor also the water molecules surrounding each label in the different stages of the protein cycle. Several experimental techniques are available to extract water accessibility around spin-labeled sites, among others are CW power saturation, ESEEM, high field CW spectra analysis.
To this aim we want to focus on Overhauser dynamic nuclear polarization (ODNP) at a magnetic field of 0.33 T. Via ODNP it is possible to measure the transfer of the electron spin polarization to nuclear spins via cross-relaxation. The change in the intensity of the proton NMR spectrum of water at a Larmor frequency of 14 MHz contains information on the water accessibility of the labeled site. We will explore the potential of ODNP to monitor protein conformational changes, rearrangements of water cavities within biomolecules, membrane binding events, water retardation at specific interfaces.

Collaboration partners:
- Song-I Han, UCSB, California, US
- Lars Schäfer, Ruhr University of Bochum, Germany
- Christian Herrmann, Ruhr University of Bochum, Germany