Hydration Dynamics at Biomolecular Interfaces via Low-Field Overhauser Dynamic Nuclear Polarization (ODNP) Relaxometry

Gail E Fanucci, Afnan M. Jaufer, Mingwei Zhou, Katie M. Dunleavy, Mahsa Moshari

University of Florida

By utilizing site-directed spin-labeling strategies, a nitroxide radical can be utilized to probe the local hydration diffusivity within 5-15 Å of the probe through the Overhauser effect. Specifically at X-band frequency and field (9.5 GHz e^-/ 14.6 MHz ¹H) ODNP relaxometry provides quantitative metrics to characterize the local hydration dynamics in two different time regimes, those “slower-bound” water molecules that interact with the surface in the millisecond to nanosecond regime (aka tumble with the biomolecule) and those “faster” diffusive waters in the picosecond time regime. In this presentation we will introduce the methodology, summarize prior results of the Han lab and provide examples where our lab is utilizing these methods to answer question related to how charge distribution in intrinsically disordered proteins can modulate hydration behavior and be coupled with disordered conformations and possibly liquid-liquid phase separation. We are also using ODNP to understand how polymer conjugation to protein and lipid surfaces alters the local hydration dynamics, with goals of obtaining insights into how these surface modifications allow for enzyme function in organic solvents, ionic liquids and biofluids.