Binding of antibodies onto the thylakoid membrane. I. Maximal antibody binding and adsorption of antibodies to lipids.

The binding of antibodies onto the lamellar system of Antirrhinum majus was determined in dependence on the serum addition. The unspecific adsorption of serum proteins was taken into account or eliminated. The binding of antibodies as a function of the amount of serum added is seem from a saturation curve. From an antiserum obtained by hyperimmunization with stroma-freed chloroplasts, the chloroplasts bind maximally 1 gram antibodies per gram stroma-freed chloroplasts. From an antiserum to the proteins of the thylakoid membrane prepared in the same way an equal amount of antibodies is adsorbed. It is assumed that with this amount the surfaces of the lamellar system accessible to antibodies is completely covered by antibodies. For an antiserum to monogalactosyl diglyceride a maximal antibody binding of 0.16 g, for sulphoquinovosyl diglyceride 0.12 g and for phosphatidyl glycerol 0.13 of antibodies per gram stroma-freed chloroplasts are obtained. The significance of these results with respect to the molecular surface structure of the thylakoid membrane is discussed.