Role of solvation in the energy stabilization inside the hydrophobic core of the protein rubredoxin.

There are many forces that contribute to the stability of a protein; among these are dispersion interactions, hydrogen bonding, and solvation effects. In a recent work, Vondrasek et al. estimated the in vacuo stabilization energy of the hydrophobic core of the protein rubredoxin using high level ab initio methods (Vondrasek, J.; et al. J. Am. Chem. Soc. 2005, 127, 2615). In this work, we evaluate the effects of solvation on the stability of the hydrophobic core of this protein. Solvation calculations are made using the polarizable continuum method at the MP2/aug-cc-pVDZ level of theory. It is found that, in a protein-like environment (mimicked by a continuum solvent with a dielectric constant of approximately 4), the stability of rubredoxin's hydrophobic core is decreased by 40-50%. We also observed that the stabilization energy of the hydrophobic core is only slightly lower in a protein-like medium than in an aqueous one (DeltaGether-DeltaGwater approximately 1.0-3.5 kcal/mol).