  The primary building block of the body is collagen, which is found in the
extracellular matrix and in many stress-bearing tissues such as tendon and
cartilage. It provides elasticity and support to cells and tissues while
influencing biological pathways including cell signaling, motility and
differentiation. Collagen's unique triple helical structure is thought to
impart mechanical stability. However, detailed experimental studies on its
molecular mechanics have been only recently emerging. Here, we review the
treatment of the triple helix as a homogeneous flexible rod, including bend
(standard worm-like chain model), twist, and stretch deformations, and the
assumption of backbone linearity. Additionally, we discuss protein-specific
properties of the triple helix including sequence dependence, and relate
single-molecule mechanics to collagen's physiological context.
