Effect of chemical modification of sunflower 11S protein on the binding of chlorogenic acid.

Binding of chlorogenic acid by sunflower 11S protein and succinylated and N-ethylmaleimide-treated protein was measured at pH 4.0 in 0.1M acetate buffer. Succinylation reduced binding, whereas N-ethylmaleimide treatment did not. Analysis of the binding data showed that succinylation reduced the number of binding sites without affecting the binding affinity. N-Ethylmaleimide treatment reduced neither the number of binding sites nor the binding affinity. Succinylation dissociated the 11S protein, whereas N-ethylmaleimide treatment did not. The secondary structure of N-ethylmaleimide-treated protein was different from that of the unmodified protein.