Measurement of the exchange rate of waters of hydration in elastin by 2D T₂–T₂ correlation nuclear magnetic resonance spectroscopy

We report on a direct measurement of the exchange rate of waters of hydration in elastin by T₂–T₂ exchange spectroscopy. The exchange rates in bovine nuchal ligament elastin and aortic elastin at temperatures near, below and at the physiological temperature are reported here. Using an inverse Laplace transform (ILT) algorithm, we are able to identify four components in the relaxation times. While three of the components are in good agreement with previous measurements that used multi-exponential fitting, the ILT algorithm distinguishes a fourth component having relaxation times close to that of free water and is identified as water between fibers. With the aid of scanning electron microscopy, a model is proposed that allows for the application of a two-site exchange analysis between any two components for the determination of exchange rates between reservoirs. The results of the measurements support a model (described by Urry and Parker 2002 J. Muscle Res. Cell Motil. 23 543–59) wherein the net entropy of waters of hydration should increase with increasing temperature in the inverse temperature transition.