Figure 4.

Model of the silk spinning process. The highly concentrated spider silk protein solution is secreted and stored inside the spinning gland. Upon initiation of thread formation, the solution is directed through a narrow ion exchange channel, in which a phase separation process takes place. Mechanical drawing of the silk thread (hind legs/gravity) results in rapid assembly of the silk fiber. Two theories exist concerning the molecular process inside the spinning duct. The first theory supports a liquid-crystalline behavior of the silk proteins, whereas the other theory favors a micellar organization of the proteins, before elongation (through laminar force) finally leads to thread assembly.