User:Stephen Mills/Sandbox 4 Secondary Structure: Helices XU

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(New page: '''Bold text'''==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 ~ -...)
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Revision as of 17:47, 27 August 2015

Bold text==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.

Drag the structure with the mouse to rotate

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.

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Drag the structure with the mouse to rotate

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