Glassy state of native collagen fibril

TL;DR

This study demonstrates that native collagen fibrils exhibit glassy state features at physiological temperatures, with a softening transition influenced by heating rate and frequency-dependent internal friction, marking a novel biopolymer glassiness observation.

Contribution

It provides the first evidence of biopolymer glassiness at physiological temperatures, highlighting collagen fibrils' unique mechanical properties and transition behaviors.

Findings

Collagen fibrils show glassy features at 20-30°C.

Softening transition depends on heating rate.

Internal friction peaks at specific oscillation frequencies.

Abstract

Our micromechanical experiments show that at physiological temperatures type I collagen fibril has several basic features of the glassy state. The transition out of this state [softening transition] essentially depends on the speed of heating v, e.g., for v=1 C/min it occurs around 70 C and is displayed by a peak of the internal friction and decreasing Young's modulus. The softening transition decreases by 45 C upon decreasing the heating speed to v=0.1 C/min. For temperatures 20-30 C the native collagen fibril demonstrates features of mechanical glassines at oscillation frequencies 0.1-3 kHz; in particular, the internal friction has a sharp maximum as a function of the frequency. This is the first example of biopolymer glassines at physiological temperatures, because well-known glassy features of DNA and globular proteins are seen only for much lower temperatures (around 200 K).