Compressibility of the protein-water interface.

摘要: The compressibility of a protein relates to its stability, flexibility, and hydrophobic interactions, but the measurement, interpretation, computation this important thermodynamic parameter present technical conceptual challenges. Here, we theoretical analysis apply it molecular dynamics simulations four globular proteins. Using additively weighted Voronoi tessellation, decompose solution into contributions from hydration shells. We find that positively cross-correlated protein-water volume fluctuations account for more than half governs protein's pressure response, while self correlations correspond small (∼0.7%) volume. is nearly same as ice, whereas total compressibility, including cross correlations, ∼45% bulk-water value. Taking inhomogeneous solvent density account, experimentally accessible partial intrinsic, hydration, exchange show how they can be computed with good statistical accuracy despite dominant contribution. contribution describes responds an applied by redistributing water molecules lower higher density; negligibly native proteins, potentially non-native states. Because shell open system, conventional closed-system definitions yield pseudo-compressibility. define intrinsic unaffected occupation number fluctuations, approaches value exponentially decay "length" one shell, less correlation length. In first 25%-30% in bulk water, part 15%-20% lower. These large reductions are caused mainly proximity rigid not consequence perturbed structure.