Proton and deuteron relaxation study of molecular dynamics in lysozyme solutions

A nuclear magnetic resonance spin-lattice relaxation dispersion study of the relaxation of several magnetization components in both natural and deuterated lysozyme solutions was undertaken at 20 degrees C. Proton and deuteron resonances were employed. The two-dimensional time evolution of the magnetization and the spin-spin relaxation were analyzed. In addition, an isotopic dilution study was performed at 5 and 30.6 MHz. The results indicate that the water proton spin-lattice relaxation rate which arises from intermolecular relaxation between the water protons and the lysozyme protons represents a relatively strong relaxation mechanism. A model for the dynamics of the water molecules, consistent with the proton and deuteron dispersions as well as with the isotopic dilution results, is presented.