Role of secondary structure on the stress relaxation processes in rat tail tendon (RTT) collagen fibre

One of the important physical properties of collagen is viscoelasticity. The molecular and the matrix stability of collagen arises from the interplay of wide range of forces, namely covalent and hydrogen bonding, ionic interactions, hydrophobic interactions, van der Waals forces and weak interactions. Therefore, the stress relaxation behaviour of native rat tail tendon (RTT) collagen fibre has been studied in water, saline media, 1, 3 and 6 M urea solutions, 0.02 M tris(maleate) buffer at pH 4-8 and 7 mol-% of methanol, ethanol and propanol at various temperatures. Experimental values of fractional stress change σ/σο as a function of time have been fitted to one-, two-and three-term models. The results show that the two-term model is the best fit for the experimental data. Two different rates of relaxation (fast and slow) have been computed using a non-linear least-squares fit. Arrhenius plots of the temperature dependence of the rates constant are non-linear. The activation energy values at absolute zero have been computed using the rates of relaxation under different experimental conditions. Thermodynamic parameters have also been calculated using the rates of relaxation