Extended chain with secondary structure predictions.

Some Foldit puzzles start with an Extended Chain, where the entire protein is arranged in a straight line. The first segment is normally on the right.

In Foldit design puzzles, each segment in the extended chain is usually the same amino acid. Often isoleucine is used as the starting amino acid. Part of the design process involves mutating the segments to different amino acids.

The extended chain in a design puzzle generally has no secondary structure defined, so every segment starts as loop.

In Foldit de-novo puzzles, the primary structure is fixed, so no mutations are allowed. The extended chain usually has a secondary structure prediction based on the sequence of amino acids.

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