In this module:

The helix-turn-helix motif shown here is called an EF hand. This structure is often used to bind metal ions (like the Ca²⁺ ion shown here) and hold them in a specific orientation.

helices often pack against each other at angles of +20 or -50º, so that the ridges of one can fit into the grooves of another.

The strands of a parallel ß sheet are often linked by an helix in a ßß motif.

Several ß strands together can form a ß barrel.