[Mechanical denaturation of lysozyme in a crystal and film]

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 tension, sigma cr, is reached, the protein molecules in the sample denature and become greatly extended. Depending on crystal type and crystallographic direction the sample length increases 2 to 4 times. The sample deformation accompanying denaturation is reversible: when the sample is kept at high temperature it restores completely its initial length. The critical stress is essentially dependent on temperature, hydration level, urea concentration, the factors affecting intra- and intermolecular interactions.