A study of structure and dynamics of water and lysozyme protein in aqueous solution by pulsed-high-field-gradient spin-echo 1>H NMR and 17>O NMR methods

Abstract

The self-diffusion coefficients of water and lysozyme in aqueous solution have been measured over a wide range of the protein concentration and over a wide range of temperature by means of the pulsed-high-field-gradient spin-echo 1>H NMR method, and also the 17>O NMR spectra of water in the protein solutions have been measured by means of a solution 17>O NMR method, in order to elucidate the structure and dynamics of water and the protein, and intermolecular interactions between water and the protein. From these experimental results, it is found that there exist two types of water molecules with different diffusion components in the lysozyme solution. One of them is mobile water with a relatively large diffusion coefficient, and the other is immobile water with a relatively small diffusion coefficient which comes from strong intermolecular interactions between water and the protein. The 17>O NMR experiments support such experimental results. Further, detailed discussion on the aggregation of lysozyme molecules is through the diffusion coefficients determined as functions of the protein concentration and temperature.