Peptide Cyclisations Disulfide Bridge Cyclisation Mass Spectrum

There are two types of cyclisations that can be performed:

1. N-terminal to C-terminal cyclisation
2. Disulfide bridge cyclisation

N-terminal to C-terminal cyclisation is confirmed by a molecular weight shift of 18 mass units in the Maldi-Tof mass spectrum. A disulfide bridge cyclisation is confirmed by MS and HPLC before and after the cyclisation step. Although a mass shift of 2 mass units can be difficult to detect for certain peptides, an HPLC shift helps confirm the completion of the reaction.