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Naturally Occurring Polymers—Animals 327
H O R H O R
N N
R 1 N N R 1
R H O R H
: :
: :
H O R H O R
N N
R 1 N N R 1
R H O R H
: :
: :
H O R H O R
N N
R 1 N N R 1
R H O R H
FIGURE 10.3 A beta arrangement or pleated-sheet conformation of proteins.
FIGURE 10.4 α-Keratine helix for the copolymer derived from glycine and leucine.
configuration is described as an l-configuration, with the helix being a “right-handed” helix. This
right-handed helix is referred to as an alpha helix.
10.2.3 KERATINES
Keratines are structural proteins. As noted above, two basic “ordered” secondary structures pre-
dominate in synthetic and natural polymers. These are the helices and the pleated sheet structures.
These two structures are illustrated by the group of proteins called the keratines. It is important to
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