Molecules or parts of molecules that have low or no affinity for water are called hydrophobic. These are usually composed of hydrocarbons that lack O or N or other polar groups and therefore cannot hydrogen bond or interact easily with water.

• Water forces hydrophobic groups together in order to minimize their disruptive impact on the hydrogen-bonded aqueous network. This is often referred to as hydrophobic bonding although it is not bonding but merely an exclusionary force. This force, however, is one of the major driving factors in the initial stages of protein folding.

• The water molecules adjacent to hydrophobic domains form icelike cages that surround the hydrophobic region (Fig. A.).