ABSTRACT
A great deal of effort has been expended in trying to understand the folding of soluble proteins, the tertiary structures of which have been determined in many cases. Hydrophobic interactions tend to reduce the nonpolar surface area in contact with water. Their approximate magnitude has been obtained by measuring the partitioning of compounds between water and nonpolar solvents. Nucleic acid sequencing has led to knowledge of the amino acid sequences of membrane proteins for which little structural or topological information exists. Since globular proteins fold in aqueous solutions in response to the driving energy provided by the hydrophobic effect, one is led to question the basis of stability of proteins in a nonaqueous membrane environment. During subsequent synthesis of the polypeptide chain, additional hairpins would be formed and inserted in a similar way. Helices containing polar groups would orient first at the lipid-water interface with their polar groups toward the water and nonpolar sides toward the lipid.
