Hetero-Cross-Linking of Peptides Enabled by Solvent-Regulated Diazo-Type Esterification of Carboxylic Acids

Abstract We have designed a cross-linker with a more reactive diazoamide attached to one end and a less reactive diazoacetate attached to the other end. In normal solvent acetonitrile, the more reactive diazoamide portion of the cross-linker reacts readily with one carboxylic acid residue. Subsequent buffer exchange into a solvent system containing 1,1,1,3,3,3-hexafluoro-2-propanol (HFIP) promotes the reaction between the less reactive diazoacetate portion of the cross-linker and a second carboxylic acid. This method can be used to join two different carboxylic acid-containing molecules, such as two different peptides, a peptide and a small-molecule carboxylic acid, or several peptides and a protein.