Fig. 11.

A) Single subfilaments (tropocollagen) arranged in a left helical array form single rope filaments (microfibrils composed by left-handed helices of tropocollagens) which twisting rightwards form a rope (single fibril composed by microfibrils arranged in a rightward helix). When the rope (fibril) twists leftwards of about 180° in a local region, the single rope filaments (microfibrils) appear swelled also changing their handedness. B) When the rope (fibril) is stretched at the ends the portion of the rope, twisting leftward, acts like a knot (fibrillar crimp). (Compare it with tendon fibrils stretched in vivo in Fig. 10).