The magnetic coupling between solid components and liquid components of a dynamically heterogeneous system provides a means for studying the H-1 nuclear magnetic resonance spectrum of the solid by observation of the liquid proton signal response to an off-resonance preparation pulse that partially saturates the solid spin population. The efficiency of the transfer of the saturation to the liquid spins depends on atom-exchange effects, whole molecule exchanges with solid component binding sites, and through-space dipole-dipole coupling. In a mixed solvent system, the magnitude of the cross-relaxation response depends on the efficiency of all three of these contributions; however, in cases where there are no exchangeable protons, the short-range nature of the dipole dipole coupling and exchange of buried solvent molecules provides an efficient way to study preferential solvation. This study demonstrates that, in the solvent mixture of water, methanol, and acetone, the acetone and methanol compete for protein binding sites and that neither perturbs significantly the water-protein coupling.