Specific Anion Effects with Antibenzoate Antibody

Open Access
Publisher Website
Google Scholar
Abstract
Summary: Inorganic salts affect the binding of p-iodobenzoate by anti-p-azobenzoate antibody. The effects observed were due to the anion whereas the nature of the cation was unimportant. Except for fluoride, univalent anions decreased binding of p-iodobenzoate whereas nearly all of the polyvalent anions increased binding. The magnitude of the decrease for univalent anions was in the order CNS- > NO3- > I- > Br- > Cl-. It appears that the anions at high concentration compete with p-iodobenzoate for the antibody site if they are small enough to be accommodated in the site. It is proposed that the increase observed with polyvalent anions is due to increased ionic strength, which tends to decrease electrostatic repulsion between the negatively charged hapten and antibody; and that, in the case of univalent anions, this effect of ionic strength is more than overcome by direct competition with hapten for the antibody site. Further evidence for the presence of a positive charge in the antibody site of anti-p-azobenzoate antibody is given. The heat of reaction of p-iodobenzoate with antibody was determined from the temperature variation of the binding equilibrium constant to give a value of ΔH° = -4.1 ± 0.4 kcal/mole.