Abstact

Lysozyme structures at six different temperatures in the range 95-295 K have been determined using X-ray crystallography at a resolution of 1.7 A. The crystals at lower temperatures had a 7.4% decrease in the unit-cell volume. The volume change was discontinuous with the volume being near 238 000 A(3) from 295 to 250 K and about 220 200 A(3) below 180 K. The thermal expansion of the protein has been analyzed and shows anisotropy, which is correlated with local atomic packing and secondary-structure elements. The lysozyme structure at low temperature is nearly the same as that at high temperature, with only small relative translations and rotations of structure elements including a hinge-bending rearrangement of two domains. Because of a considerable increase of lattice disorder at low temperature dynamical analysis of internal motion is difficult. The analysis of structural and dynamical properties of well ordered protein-bound water has been carried out.