22] Iodine monochloride (ICI) iodination techniques

Abstract

This chapter describes iodine monochloride (ICI) iodination techniques. The chapter explains that, for labeling proteins and related substances in solution with 131 I or 125 I, the use of the ICI isotopic exchange procedure may often be the method of choice. In this technique, the total amount of iodine incorporated into the iodinated material is known and can be controlled and it avoids the use of oxidizing agents that may damage protein. The basic method, as it is most widely used today, is 131 I or 125 I in the form of iodide ions are mixed with the protein solution to be iodinated, buffered to a pH of approximately eight. As the only oxidizing agent present during the iodination procedure is the ICI itself, no harm can come to protein that would be produced by other oxidizing agents. Also, the ICI method has not been found to be a useful procedure for directly labeling cells or cell membranes; it is useful in preparing reagents for other types of 131 I or 125 I labeling, for example, the preparation of diazotized diodosulfonilic acid for labeling of cell membranes.