Effect of thermal denaturation on water-collagen interactions: NMR relaxation and differential scanning calorimetry analysis

The dependence of the proton spin-lattice relaxation rate, and of the entha lpy and temperature of denaturation on water content, were studied hp nmr a nd differential scanning calorimetry (DSC) in native and denatured collagen . Collagen was as first heated at four different temperatures ranging from 40 to 70 degrees C. The percentage of denatured collagen induced by these p reheating treatments was determined from DSC measurements. The DSC results are discussed in terms of heat-induced structural changes. A two-exponentia l behavior for the spin-lattice relaxation was observed with the appearance of denatured collagen. This was attributed to the presence of a noncollage n protein fraction. The variations in the different longitudinal relaxation rates as a function of the moisture content and of the denatured collagen percentage are described within the multiphase water proton exchange model. This study highlights the complementarity of the information obtained from the two analytical tools used. (C) 1999 John Wiley & Sons, Inc.