BINDING OF SULFONAMIDES TO SERUM PROTEINS: PHYSICO-CHEMICAL AND IMMUNOCHEMICAL STUDIES

¹ Neurochemical Institute, Copenhagen, Denmark

Immunoelectrophoresis combined with autoradiography revealed that radioactive S³⁵-labeled 3-sulfamido-6-methoxypyridazine (Lederkyn) is bound in vitro to plasma prealbumin, albumin, ₁ (S_r 3.5)-glycoprotein and ₂-macroglobulin. Sephadex filtration made it possible to determine quantitatively the thermodynamic binding data of plasma albumin for 3-sulfamido-6-methoxy-pyridazine. By means of a Sephadex column, stepwise equilibrated with different concentrations of sulfonamides at different temperatures, it was possible to determine quantitatively the total amount of binding sites per molecule of albumin, as well as the intrinsic and individual binding constant for the binding of sulfonamide to albumin. The free energy change, the change in enthalpy and change in entropy of the binding were also estimated by Sephadex filtration. The data are discussed on the basis of previous binding experiments.