The role of conformational changes in the mechanism of cryoprecipitation of human monoclonal immunoglobulin M (IgM) was studied. It was demonstrated that the variable moiety of the Fab-region of cryo-IgM has a site which comprises 5 to 6 charged amino acid residues. This site is responsible for intermolecular electrostatic interactions which lead to the formation of a precipitate with a decrease in temperature. This interaction is cooperative and stabilized by dipole molecules of H2O. The chain growth during aggregation is nuclear. The primary nucleus contains three IgM macromolecules. stability of the three-molecule nucleus is provided for by 16--17 intermolecular links. Using circular dichroism and fluorescent methods, it was found that the formation of a cryoprecipitate is accompanied by ionic pair release and conformational changes.
Calorimetry, Differential Scanning Chemical Phenomena