Site Specific Hydration Contributes to the Thermal Stability of Proteins and Protein-Complexes

Replacing H2O with D2O increases the thermal transition temperature by approximately 3 {degrees}C for CI-2 and the barnase-barstar (Bn-B*) complex, favoring compact conformations.

• Why it matters: Ensemble measurements often miss which hydration interactions stabilize proteins, leaving solvent-dependent conformational thermodynamics unresolved.
• What they did: Variable-temperature electrospray ionization ion mobility mass spectrometry with conformation-resolved thermodynamic analysis and molecular dynamics simulations compared H2O versus D2O for CI-2 and Bn-B*.
• The result: D2O reduces thermodynamic accessibility of extended states and shifts enthalpy-entropy compensation differently for CI-2 versus Bn-B*, while simulations show site-specific, longer water residence times.