An alpha helix can be formed by making a rope coil in a
left handed direction. In the case of a protein the rope would be represented
by the N-C-C-N-C-C-N .... backbone of the polypeptide chain.
Pauling and Corey built models of proteins. They found that by using the information they had gained concerning bond angles, lenghts and rotations to make their models, proteins could form an alpha helix.
In addition they found that the alpha helix could be
a very stable structure because intrachain hydrogen bonds could be formed
that stabilized the helix.
The alpha helix is one of the structures that are called
the secondary structures of proteins.
The other structure that is a part of the secondary
structure is the beta pleated sheat.
Some proteins like keratin and collagen are almost
entirely alpha helical in structure.
Most globular proteins have alpha helical and beta
pleated sheat regions in addition to regions that are neither alpha helical
or beta pleated sheats.
Charge amino acid side chains have a tendency to destabilize the alpha helical or beta pleated sheat structures.
amino acids with hydrophobic side chains are compatiable with the formation of alpha helices and beta pleated sheats.
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