High Specific Activity Iodination of v-Globulin with Iodine-131 Monochloride*

A technic, efficient in use ~ of I TM, has been developed for introducing I TM into 4-mg. amounts of antibody or 3,-globulin protein at a level of 10 me. I ~al per mg. protein with a resulting iodine content of ~-S atoms per protein molecule of 160,000 molecular weight. Oak Ridge I TM was adjusted to pH 8 with borate buffer and the requisite amount of hydrochloric acid. To this solution was added Na2SOa to destroy H20: produced by I TM B-radiation. Excess sulfite was oxidized by aerating the solution in a boiling water bath. On the addition of iodine monochloride to the cooled solution, Ila~C1 (or HOI TM) was produced by exchange, and following the rapid addition of this solution to protein, also in pH 8 buffer, coupling of approximately 60 per cent of the I TM to protein occurred. When 10 inc. or less of Oak Ridge I ~al was used, the addition of Na2SOa and the aeration could be omitted, and a yield of about 60 per cent of I ~31 attached to protein was still obtained.