The interaction of iopanoic and iophenoxic acids with human serum albumin.

Iopanoic and iophenoxic acids are strongly bound to human serum albumin, as revealed from ultracentrifugation experiments. About two or three high affinity binding sites were found for both drugs. Within the concentration range investigated iopanoic acid is stronglier bound than iophenoxic acid. The binding to only one of the high affinity binding sites produces extrinsic Cotton effects. Further saturation of the high affinity binding sites decreases the extrinsic Cotton effects, possibly due to a binding induced change of the protein conformation.