Page 58 - The Miracle of Protein

56 THE MIRACLE OF PROTEIN

with the peptide bond that every amino acid forms with the
amino acid next to it, hydrogen bonds also form. How these
bonds form determines the shape and position that amino acids
will assume along the sequence. Under some circumstances—
for instance, when hydrogen bonds form within the chain—the

amino acid forms a spiral structure. When amino acids estab-
lish weak bonds with an amino acid outside that chain, then lay-
ered structures form that are reminiscent of the steps on a stair-
case.
Proteins whose chains assume a spiral form resemble the

springs in mattress or automobile seat and, just like them they
twist around a central axis. The proteins in hair, and myosin, a
protein in muscles, possess this spiral structure and, as a result,
are elastic because hydrogen bonds can easily break and reform
just as easily.

The discovery of the effects of hydrogen bonds on body
proteins has resulted in various applications in daily life. For ex-
ample, to straighten curly hair or put curls into straight hair, the
hydrogen bonds between the amino acids in hair proteins must
be broken and reconstituted. 9
Proteins in layered form with a secondary staircase struc-

ture are not as flexible as those arranged in a spiral structure.
They do, however, permit the formation of structures that bend,
one very important requirement of living things. For example,
proteins like the silk fibers in cocoons and spider webs are set

out in parallel and form chains bound to one another with hy-
drogen bonds. Because the silk atoms are bound perpendicular-
ly to the protein chain, the spine of these proteins bends up and
10
down like a strand of yarn. For this reason, the proteins with
this model display flat and pliant features. In living things, the
folds in proteins are always exactly where they need to be. If fi-