Thermal (In)Stability of Type I Collagen Fibrils

We measured the Young's modulus at temperatures ranging from 20 to 100 ^∘C for a collagen fibril that is taken from a rat's tendon. The hydration change under heating and the damping decrement were measured as well. At physiological temperatures 25 to 45 ^∘C, the Young's modulus decreases, which can be interpreted as an instability of the collagen. For temperatures between 45 and 80 ^∘C, the Young's modulus first stabilizes and then increases when the temperature is increased. The hydrated water content and the damping decrement have strong maximums in the interval 70 to 80 ^∘C indicating complex intermolecular structural changes in the fibril. All these effects disappear after heat-denaturation of the sample at 120 ^∘C. Our main achievement is a five-stage mechanism by which the instability of a single collagen at physiological temperatures is compensated by the interaction between collagen molecules.