Binding of iodide to bovine serum albumin and protamine studied with an ion-selective electrode

Binding of iodide ion to bovine serum albumin and protamine was studied using an iodide ion-selective electrode. Binding was found to be significant with bovine serum albumin but insignificant with protamine. The data for the iodide-bovine serum albumin system were treated according to the Klotz equation and the fit was found to be quite good. Number of iodide ions bound per bovine serum albumin molecule was calculated as one and the equilibrium constant for this binding was determined to be 5.3 × 103. Insignificant binding to protamine and single binding to each bovine serum albumin molecule were explained in terms of the amino acid compositions and secondary structures of these proteins.