A PARTIALLY UNFOLDED STATE OF LYSOZYME WI TH DEVELOPED SECONDARY STRUCTURE IN DIMETHYLSULFOXIDE

The conformation of a chicken egg lysozyme molecule (dimensions, stoic hiometry of its associates, and the degree of helicity) in DMSO was st udied by small-angle neutron scattering, dynamic light scattering, and optical rotatory dispersion in the visible region of the spectrum, At high DMSO concentrations (70%), the protein was shown to exist as a d imer. The monomer molecules in the dimer adapt a partially unfolded co nformation, with dimensions substantially greater than those in the na tive state and a high content of secondary structure (the degree of he licity is close to that of native lysozyme). This approach provides a unique possibility to assess the compactness of molecules in associate s, which may be very useful in studying protein self-organization.