Calorimetric study of thermal denaturation of type I human placenta collagen

The thermal denaturations of type I human placenta collagen were studied in different aqueous solutions in the temperature range from 274 to 345 K by differential scanning calorimetry. The thermodynamic parameters of denaturational process were accurately. The average temperature of denaturation of the collagen Td is 47.1 degrees C, and the denaturational enthalpy delta Hd is 8.43 kJ per mole of residue in salt-free aqueous solution at pH 3.7. The linear relationship of delta Hd with Td has been obtained for the various collagens studied. The various factors concerning the stabilization of collagen structure of the Sigma collagen have been demonstrated. The dominant factors are hydrogen bonding and the participation of water molecules in the collagen structure. It is concluded from the thermodynamic evidence obtained that the water-carbonyl model is preferable to other models. By means of calculating the van't Hoff enthalpy of the collagen denaturation, the number and the size of cooperative blocks of the Sigma collagen have been evaluated. Its molecule contains five cooperative blocks, each having 600 residues or so. The type I human placenta collagen is a multi-domain protein.