An example of a symmetric trimer, provided by Foldit player skippysk8s. The colorful main chain is on the right, with the two grey symmetric chains on the left.
Symmetric chains are a feature of Foldit symmetry puzzles a type of design puzzle.
In a symmetry puzzle, there is a main chain, also known as "the monomer". Foldit players can design the main chain freely. There are also one or more symmetric chains, which are exact duplicates of the main chain.
The goal of a symmetry is to arrange the chains into a a stable oligomer, a protein consisting of a few identical copies of one chain.
In Foldit, symmetric chains typically appear in shades of gray, while the main chain is more colorful. The exact coloring depends on the View Options selected.
Players can draw bands that start on the main chain, and end on one of the symmetric chains. Recipes can now do the same thing, a feature added in 2019.