Thermal Stability of Serum Thyroxine-Binding Proteins

The thyroxine-binding capacity of normal human blood serum after heating to 60 C was determined by paper electrophoresis. The denaturation of TBG by heat resulted in decrease of its binding capacity. The process of denaturation is strictly a reaction of the first order. The temperature dependence of the velocity constant obeys Arrhenius' law, the calculated apparent energy of activation being 89867.2±33.4 cal/mole of TBG. The binding capacity of TBPA was unaltered by heating in the range measured.