Chloramine immobilized

Iodobeads (Thermo Fisher) is an immobilized preparation of a chloramine-T analog, consisting of nonporous, polystyrene beads of diameter 1/8" that have been derivatized to contain N-chlorobenzenesulfonamide groups (as the sodium salt) (refer to US patents 4,448,764 and 4,436,718). During the manufacturing process, the hydrophobic nature of the polystyrene is changed to a rather hydrophilic surface due to the chlorosulfonamide modifications. The surface... 

Figure 12.4 IODO-BEADS contains immobilized chloramine-T groups that can react with radioactive iodide in...

Figure 265 IODO-BEADS contains immobilized Chloramine-T functional groups that can react with radioactive iodide in aqueous solution to form a highly reactive intermediate. The active species may be an iodosulfonamide derivative, which then can iodinate tyrosine or histidine residues in proteins.

IODO-GEN (Pierce), first described by Fraker and Speck in 1978, is 1,3,4,6-tetrachloro-3a,6a-diphenylglycouril, an N-haloamine derivative with oxidizing properties similar to those of IODO-BEADS and chloramine-T. The compound is insoluble in aqueous solution, therefore making it a type of solid-phase radioiodination reagent. However, unlike IODO-BEADS, wherein the oxidizing group is immobilized on an-... 

Under these conditions, radioiodine incorporation of up to 99% can be achieved at labeled protein recovery rates of >90%. The reaction is more gentle than soluble Chloramine-T because there is less contact between the protein and the immobilized oxidizing agent. If the reaction is conducted at pH values above 8, it is possible to radioiodinate histidine residues. The reaction is believed to proceed in the close proximity of the surface of the polymer beads. An electrophilic iodosulfonamide intermediate species that reacts with either tyrosine or histidine residues of the protein to be labeled is formed. 

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