Alpha Helix

Introduction to Protein Structure

Secondary Structure -- Alpha Helix

The backbone of an alpha helix (shown in color below) is arranged in a spiral similar to that seen on a cork screw. Notice how the sidechains (shown in dark grey) stick more-or-less straight out from the backbone.

The alpha helix is stabilized by hydrogen bonds between the carbonyl oxygen of one amino acid and the backbone nitrogen of a second amino acid located four positions away. Turn on the "highlight" in the figure below to color every fourth residue the same color.

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H-bonds
Highlight
Sidechains

This alpha helix consists of residues 4 to 15 in lysozyme isolated from chicken egg white.