Radioiodination service

Peptides, proteins and other small molecules can be radioiodinated by us for use in our in vivo or in vitro assays.  We have experience with the following radioiodination approaches:

IODO-GEN reagent:  Iodo-gen is a simple and effective method for labeling a variety of proteins and peptides.  This oxidative method involves exposure of the substrate to iodo-gen in the presence of sodium 125-iodide followed by HPLC or other separation techniques.  It produces high specific activity proteins or peptides in good yields.  However, a drawback is that cysteine and methionine residues in the peptide may be partially oxidized during the procedure.

Lactoperoxidase:  Lactoperoxidase catalyzes the oxidation of iodine using hydrogen peroxide as a substrate.  It is a milder oxidative method than iodo-gen and leaves methionine residues intact.

Reaction with [125I]iodobenzoate:  The active ester of [125I]iodobenozoate can be used to label terminal amino groups with a radioiodinated phenyl residue, effectively introducing radioactive iodine into proteins and peptides.  Since it is a non-oxidative technique, it is less harsh to proteins than alternative methods.   Labeled proteins and peptides retain a high degree of binding activity to receptors.  Additionally, since the radioiodine is in the 3' position on a non-activated phenyl ring, it is resistant to the action of in vivo deiodinating enzymes (Garg et al., 1995, Bioconjugate Chem. 6: 493-501).