PERMEABILITY OF LYSOZYME TETRAGONAL CRYSTALS TO WATER

Diffusion of water within cross-linked tetragonal crystals of hen egg- white lysozyme has been measured and simulated on a computer using the X-ray structure of water-filled channels within the crystal lattice. Relative to the self-diffusion coefficient of bulk water molecules, th e experimental diffusion coefficient of water within the crystal was f ound to be 13 times reduced in the (001) crystallographic plane and 5 times reduced in the [001] direction. Comparison of the experimental a nd computer simulated diffusion coefficients shows that steric limitat ions for water diffusion are mostly responsible for this reduction of the water diffusion in the crystal, with the self-diffusion coefficien t of intracrystalline water reduced by no more than 30-40% as compared to that of bulk water.