These enzymes cleave the phosphodiester bond of double helix DNA. Hydrophobic leucine amino acids are located along the inner edge of the alpha helix. DNA normally exists as a double-stranded molecule, coiled into the shape of a double helix. DNA is made up of a double helix of two complementary strands. Its structure comprises a single alpha helix. Linus Pauling proposed that DNA might be a triple helix. Typically it consists of a wire wound into a coil or helix. These two long strands coil around each other, in the shape of a double helix. A coil forming the shape of a straight tube (a helix) is called a solenoid. These hydrophobic residues pack together in the interior of the helix bundle. The spherical core consists of an alpha helix and a beta sheet. These two lobes are connected through a single bridge helix. Hybridization is the process of complementary base pairs binding to form a double helix. This sequence is highly degenerate and is capable of folding into amphiphilic helix. They permit the sharp twisting of the collagen helix.