Nitrite-assisted peptide iodination and conjugation

In this study, a simple method for selective iodination of peptides and proteins is established. Using angiotensin It as the model system, we demonstrate that nitrite catalyzed the selective iodination of the peptide at the N-terminus in an acidic solution. The N-terminal-iodinated peptides alkylated thiol-containing molecules such as N-acetyleysteine and glutathione to form peptide conjugates in a basic solution. Reactive species formed by increasing the pH of the reaction mixture of sodium nitrite and sodium iodide from 4 to 8 selectively iodinated peptides and proteins at tyrosine and histidine residues. These results show that nitrite is a useful catalyst for peptide and protein ligation. Copyright (c) 2006 European Peptide Society and John Wiley & Sons, Ltd.