Biphasic Interaction of Γ-Globulin with Copper Cations

Interactions of human serum γ-globulin with copper cations in solution were studied by differential ultraviolet spectrophotometry. Copper in supraphysiological concentrations increases optical density of protein solution, reflecting the effect of γ-globulin saturation with metal. In physiological and lower concentrations of copper cations we observed hypochromia in the protein absorption spectrum. Conformational changes in γ-globulin molecule during interactions with copper by the surface and intramolecular binding sites and possible role of bivalent metal cations in the maintenance of certain conformations of immunoactive serum proteins are discussed.