Mechanical denaturation of globular protein in the solid state.

A method for taking stress-strain diagrams in microsamples prepared from glutaraldehyde-treated monocrystals and amorphous films of hen egg-white lysozyme has been developed. Analysis of the diagrams has shown that the deformation obeys Hooke's law within 0-2%. Upon further deformation of a crystalline sample (up to 6-10%), when a critical stress, sigma(cr), is reached, the protein molecules in the sample denature and become greatly extended. Depending on the crystal type and crystallographic direction, the sample length increases 2-4 times. The critical stress is essentially dependent on the factors affecting intra- and intermolecular interactions: temperature, hydration level and urea concentration. Mechanisms for mechanical denaturation are proposed.