Collect. Czech. Chem. Commun. 1982, 47, 2077-2086

Kinetics and thermodynamics of the reaction between thyroxine and antithyroxine antiserum under the conditions of radioimmunoanalysis

Peter Talán and Juraj Mucha

Institute of Radioecology and Application of Nuclear Techniques, 040 61 Košice


Thermodynamics and kinetics of the reaction between thyroxine and antithyroxine antiserum has been studied using the concentration and temperature conditions usual in the radioimmunoanalysis. The reaction is assumed to be homogeneous and of the second order. Because of the initial concentrations of thyroxine and of the free bonds of the heterogeneous population of antibodies present in the used antiserum the rate constant equation for second-order reaction has been used in the integrated form. The relative rate constants have been obtained and the activation energy of the reaction in absence of the serum proteins in the reaction mixture or, respectively, in the presence of the euthyroidic serum has been calculated. The nature of the effect of so-called deblockators (J) (8-anilino-1-naphthalene sulphonic acid and tiomersal) on the reaction rate and on the change of the reaction enthalpy (or entropy) has also been investigated. The association constant of this reaction has been evaluated from the radioimmunoanalytical data transformed by the Scatchard relation, modified for the conditions of thyroxine radioimmunoanalysis.