Characterization of Bound Water at Protein Surfaces the First Hydration Shell

1 Characterization of Bound Water at Protein Surfaces -the First Hydration Shell 

If a protein is dissolved in water and the water is gradually removed, there remains a residual amount of water bound to the protein. The quantity of this bound water per gram of protein can be measured by the different methods described in Thble 23.1a. It is immediately obvious that the results vary considerably, depending on the method used, with 0.25 to 0.52 g water g-1 lysozyme and 0.32 to 0.75 g water g-1 hemoglobin. 

This corresponds to a hydration level of 0.31 g water g-1 protein, a value very close to that obtained experimentally for lysozyme (see Ihble 23.1). If we add another 130-150 water molecules to cover the lysozyme surface completely, a value of 0.46 g water g-1 protein is reached. In this range, IR and NMR experiments indicate a discontinuity suggestive of another kind of more mobile and less tightly bound water. 

The hydration of a protein can be described in several steps [622, 810, 827-829]. If the molar ratio water/lysozyme is gradually increased, a number of discrete levels of hydration are observed [810, 828], as established by a variety of methods summarized in Fig. 23.1 and in Ihble 23.2  

Method Viscosity Diffusion Sedimentation NMR DSC Dielectric Isopiestic Range 

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