Finally, exposure of a protein to an organic solvent, such as an alcohol, may also cause denaturation. Recall the hydrophobic effect in tertiary structure. The surface of the protein, in contact with water, will bristle with lots of hydrophilic (polar) amino acid side chains, while the hydrophobic (nonpolar) amino acid side chains tend to be tucked away toward the protein's interior. That interaction with the surrounding solvent (water) is an important factor in determining the ultimate stability of the folded protein. When an organic solvent such as an alcohol is mixed with the aqueous solution, the amino acid side chains on the surface don't dissolve in the water-alcohol mixture as well. The protein molecule twists and flexes (through free bond rotations within) as the hydrophilic side chains shun the alcohol. At the same time some interior hydrophobic side chains twist to the surface where they interact favorably with the organic solvent. The net effect is as though the protein molecule were trying to turn itself inside out in response to the change in the surrounding solvent. In the process H bonds and ionic interactions will be broken. The result is a structurally altered, perhaps unraveled, protein molecule.