High yield coupling of peptides to protein carriers

Coupling of peptides to protein carriers has been achieved at a high level of peptide incorporation. Bovine serum albumin was used as the model carrier protein and several peptides were tested in the coupling reaction. The peptides were coupled to succinylated bovine serum albumin after conversion of its caroxyl side chains to the reactive $\text{p-}\text{nitrophenyl}$ ester groups by reaction with $\text{p-}\text{nitrophenol}\text{/N,N′-}\text{dicyclohexylcarbodiimide}$ in anhydrous dimethylformamide. The reaction afforded succinyl-albumin-peptide conjugates that had high levels of peptide incorporation (18–35 mol peptide/mol albumin). In addition to the high level of peptide coupling, the reaction avoids the production of polymeric forms of peptide, protein or conjugate.