The three dimension folding of proteins is the result of specific interactions between side chains. Globular proteins fold with most hydrophobic side changes on the inside and most hydrophilic side changes on the inside. But, globular proteins inserted in membranes often have a band of hydrophobic side chains on the outside of the molecule. This equatorial band fits in the hydrophobic interior of the cell membrane. Hydrogen bonds help stabilize the three-dimensional structure of many types of globular and structural proteins.
Proteins tend to fold into the lowest energy conformation.
The RNAase became inactive as an enzyme and didn't work anymore. Then the Urea was removed by dialysis and the disulfide bonds reformed by oxidation by oxygen in the air. The enzyme worked once again, indicating that it had refolded into the original three-dimensional structure. These were first discovered as heat shock proteins, which are produced in response to stress - Heat shock proteins were first discovered in 1962 by Ferruccio Ritossa. Most of these were shown to form hydrophobic bonds with proteins and help move the hydrophobic regions to the inside when hydrogen bonds had been disrupted by stress.