Hydration dynamics of proteins in reverse micelles probed by 1H-NOESY/1H-ROESY NMR and 17O-nuclear quadrupole resonance (NQR)

Abstract

This study is based on extensive MD simulations of a protein in a reverse micelle to mimic the effect of confinement on biomolecules. This permits the calculation of measurable quantities appearing in NQR and Nuclear Overhauser-NMR despite the high computational effort. We address the long-standing debate about the intermolecular NOE showing that absolute quantities derived from NOESY and ROESY spectra do indeed contain considerable long-range contributions, while ratios thereof are effectively short-ranged due to almost perfect compensation effects. Based on NQR relaxation times, we predict strong rotational retardation of interstitial water between the protein and the surfactant surface. The computed NOE to ROE ratio correlates fairly with experimental results. The solvation dynamics mapped onto the protein surface reflects the spatial heterogeneity of a cell-like system with slow water dynamics in proximity to the cell wall and almost bulk-like behaviour in the water core.