[Thermal characteristics of a collagen-water system. II. Conformationalmobility of macromolecules in native and...

By calorimetric study of the collagen-water systems with 10-100% content of protein in the temperature range 20 + 90 degrees C we have measured the proper heat capacity of protein in native and denatured state. It is shown that S-like dependence of heat capacity on the water content for both native and denatured samples is caused by glass transition. At temperatures above the glass transition in moist collagen or above the denaturation of native collagen the translational mobility of segments in protein molecules appears. This mobility is most probably the cause of the increments in the temperature dependence of heat capacity. According to our results, for the denatured collagen the value of heat capacity in solution exceeds that for dry samples at least by the magnitude of heat capacity increment at glass transition.