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User:Stephen Mills/Sandbox 4 Secondary Structure: Helices XU
From Proteopedia
The α-helix
α-helices are the most common type of regular helix found in proteins. They are characterized by the following helix parameters:
- Dihedral angles: Φ ~ -60o, φ ~ -45o
- Repeat (number of residues per turn) = 3.6
- Rise (translation along axis per amino acid residue) = 1.5 Angstroms (0.15 nm)
- Twist (rotation around axis per amino acid residue) = 100o (= 360o/repeat)
- Pitch (translation along axis per turn) = 5.4 Angstroms (= 0.54 nm = Repeat x Rise)
The helix shown below is a 19 amino acid chain in α-helical conformation.
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All the atoms are shown in this initial orientation (C = green; N = blue; O = red; S = yellow; H = white). The helix axis runs vertically, approximately parallel to the plane of the screen.
