Abstract
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.
Highlights
A well known characteristic of elastin, an insoluble protein that is responsible for the elasticity of vertebrate tissues, is that the complex microscopic solvent-protein relationship dictates its macroscopic behavior
The and values measured from the Inverse Laplace Transform (ILT) maps are tabulated in Table 1; the waters of hydration in and around elastin may be separated into four groups indicated in Fig
We investigated the exchange of water in hydrated elastin by using 2D T1-T2 and T2-T2 correlation experiments
Summary
A well known characteristic of elastin, an insoluble protein that is responsible for the elasticity of vertebrate tissues, is that the complex microscopic solvent-protein relationship dictates its macroscopic behavior. Fundamental to the mechanical property of elastin is the inverse temperature transition — a process pointed out by D.W. Urry in numerous experimental studies of a poly(GVGVP) peptide [1] [11] [12] [13]. During the inverse temperature transition there is an increase in order of the backbone upon raising the temperature - microscopically a hydrophobic association of β turns occur, resulting in a macroscopic volumetric contraction. During the phase transition, structured hydration becomes less ordered bulk water due to the hydrophobic association of elastin β turns [1]. The goal of this work is to quantify in detail the exchange of waters of hydration in elastin and shed light on the complex water-protein association
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