(Figure Presented). The adventures of titin: in vertebrates, titin filaments control the extendibility of the muscle sarcomere. The titin immunoglobulin 27 unfolds through an intermediate (see structure; arrow: hydrogen bonds ruptured to reach intermediate) that it is highly independent of the force load applied. It is shown that this intermediate acts as a "force buffer" that protects immunoglobulin from unfolding at physiologically applied forces.