Comparison of dynamic denaturation temperature of collagen with its static denaturation temperature and the configuration characteristics in collagen denaturation processes

Exposing collagen to a sinusoidally fluctuating strain, dynamic denaturation temperature (Tdd) of collagen was obtained by measuring its dynamic viscoelasticity changes depended on temperature using a dynamic rheometer, and it was compared with static denaturation temperature (Tsd), which was determined both by differential scanning calorimeter (DSC) and measuring specific viscosity changes of collagen only depended on temperature using an Ubbelohde viscosimeter. The results showed that Tdd was 31.1 °C and was about 4 °C lower than Tsd. The changes of apparent viscosity caused by increasing shear rate were reversible when collagen was sheared at 28.5 °C, but they were irreversible when sheared at 33 °C. The results of sodium dodecyl sulphate-polyacrylamide gel electrophoresis (SDS-PAGE), circular dichroism (CD) and fibril formation experiments showed collagen sheared at 28.5 °C could keep its triple helical structure but the triple helix of collagen sheared at 33 °C was transformed to random coils, indicating it was heat-denatured. However collagen only heated at 33 °C did not denature and kept its native configuration. The results revealed that shearing could induce a decrease of denaturation temperature of collagen.