Byssal threads are produced in the foot of mussels and used to attach to the rocks, piers, or other large, generally immobile objects that they live on. Just like spider silk they can serve as an inspiration for biomimetic materials.
- They can be up to 6cm in length.
- They exhibit the greatest hysteresis of any extracellular marine biomaterial.
- They exhibit recoverable strain softening when put in tension. This is a form of self healing.
- There is a gradient of elasticity along their long axis. This gradient in elasticity is related to complimentary gradients in two proteins. One of which is collagen like, the other, elastin like. The threads are stiffest on the end furthest from the mussel.
A third protein has a somewhat uniform concentration throughout the thread.
- They are held at one end by a retractor muscle within the mussel and at the other end an adhesive plaque allows them to attach to nearly any surface, even wet ones.
- The surface of the distal side of each thread is rough. The surface of the proximal side is comparatively smooth.
- To form a thread, glands in a mussel's foot secrete liquid crystalline precursor proteins into a long channel. The precursors react to form a solid thread. This process is very similar to reaction injection molding.
- The attachment plaque at the tip of the distal end could possibly be used as a medical glue to quickly fix severely
broken bones or to seal up cut or torn tissue.
- A special garment for a Roman Centurion, three sheets found in King Tutankhamen's tomb, and the golden fleece of Jason were made from byssal threads.
- A thin protective protein coating, dubbed Mefp-1, or Mytilus edulis foot protein 1, protects the threads from degradation by bacteria and other microorganisms. This protein could possibly be mass produced and used as an antimicrobial coating. Mass production may be difficult though because of the need for post-translational modifications.