Quantitative analysis of the molecular sliding mechanisms in native tendon collagen — time-resolved dynamic studies using synchrotron radiation

Abstract

The stretching of native fibres from rat tail tendons (RTT) was monitored in time-resolved X-ray measurements using synchotron radiation, by registering one meridional small angle diffraction pattern every second. The time course of this dynamic molecular process was analyzed quantitatively with the help of model calculations based on the amino acid sequence. The results show that two mechanisms contribute to the elongation of fibrils, namely the stretching of the collagen triple helices and their sliding relative to each other (increase of the D stagger). The results further show that these two processes do not take place simultaneously. The first increase of the D period from 67.0 nm to about 67.6 nm is correlated with a stretching of the triple helices. The further increase of the D period is due to a continuous increase of the D stagger. This succession is independent of the age of the animals and also independent of the stretching velocity. The stretching process is shown to be reversible at the molecular level up to a D period of about 68.4 nm.