Anomalous behavior of electrical conductivity of solubilized collagen solutions with thermal denaturation

The temperature dependence of the electrical conductivity, σ, for a collagen solution was measured in the temperature region including the thermal denaturation temperature, t_d. The σ increased with temperature, t, but decreased at ca. 40°C, and then again increased. In this temperature region, a change of optical rotation, α_D, was observed. The change is due to the thermal denaturation. The differential curve of σ vs. t gave clear deflection points and a large peak at ca. 40°C. The t_d could be estimated from the peak temperature. The t_d decreased with the increase in the concentration of collagen and with the decrease in the heating rate. These measurements were carried out for the collagen prepared by various methods. Some of them showed one peak; others had two peaks. The t_d obtained by the measurement of σ correlated with that obtained by the measurement of α_D. The activation energy of σ, ΔE_a, obtained from the linear relationship between log σ and 1/T, increased with the concentration of collagen, but was unchanged for the heating rate. The ΔE_a obtained for various types of collagen showed a constant value. © 1993 John Wiley & Sons, Inc.