Nuclear Overhauser Effect , hydration

By measurement of nuclear Overhauser effects for pancreatic trypsin inhibitor in solution, Otting and Wuethrich (1989) identified the four structural water molecules found in the crystal by diffraction measurements. Other hydration waters exchanged rapidly with bulk solvent, that is, with a proton-exchange lifetime shorter than 3 x 10" ° sec. 

The use of NMR in hydration studies is based on two complementary approaches. In one approach, nuclear Overhauser effect (NOE) cross-peaks between DNA protons and hydration water are used to gain insight into the dynamics of localized water... 

Nuclear Overhauser effect (NOE) is another techiuque used to study the dynamics of water near a heterogeneous surface. NOE intensities are modulated by dipole-dipole interactions between protons of protein and water in the hydration layer. This interaction varies as where R is the separation between the two protons. Measurements of magnetization transfer using NOE have been used to obtain the residence time of the hydration water. The residence time of water molecules in the hydration layer immediate to the protein is not easily available by other techniques and is valuable information in quantifying the rigidity of the layer. 

A special NMR technique, H NOES Y, using the nuclear Overhauser effect, was applied by Bagno et al. [57] to Me NCl and Bu NI in A=W and B = MeCN mixtures, the ions of the former salt being preferentially hydrated and those of the latter one preferentially solvated by the organic component. Both ions of NaGHjCO are preferentially solvated by DMSO in its aqueous mixtures according to this technique. 

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