Cyclization with Multiple S-S Bonds
When peptides contain multiple cysteine residues, challenges arise due to the random formation of disulfide bridges between them. Pepmic is able to build disulfide bridges regiospecifically between cysteines at specified positions. We are able to introduce up to four customized disulfide bridges on one peptide, by applying either native folding or a variety site-specific orthogonal chemistries.

A common method for this kind of reactions is native folding. This thermodynamic stability strategy requires to precisely mimic the ideal conditions required for the species to fold, which are very specific for each peptide. However, in several cases isomers may appear in the reaction mixture, which are difficult to remove with prep-HPLC and results in poor yields. Therefore Pepmic has developed various methods to couple cysteine-pairs regioselectively at specified positions. We are capable to introduce up to four customized disulfide bridges on one peptide, via site-specific orthogonal chemistry.

Using a defined combination of cysteine protecting groups we are able to de-protect and oxidize the cysteine couples individually. This leads not only to regiospecific disulfide bridge formation, but also relative high yield and purity compared with traditional methods.

Cys-Cys Cyclization

Peptide Name

Peptide Sequence

Disulfide bonds

alpha Defensin 1 (human)


C2-C30, C4-C19, C9-C29

alpha Defensin 2 (human)


C1-C29, C3-C18, C8-C28

alpha Defensin 3 (human)


C2-C30, C4-C19, C9-C29

alpha Defensin 4 (human)


C2-C30, C4-C19, C9-C29

alpha Defensin 5 (human)


C3-C31, C5-C20, C10-C30

alpha Defensin 6 (human)


C4-C31, C6-C20, C10-C30

beta Defensin 1 (human)


C5-C34, C12-C27, C17-C35

beta Defensin 2 (human)


C8-C37, C15-C30, C20-C38

beta Defensin 3 (human)


C11-C40, C18-C33, C23-C41

beta Defensin 4 (human)


C6-C33, C13-C27, C17-C34