Protein and peptide drugs has the advantages of action site specificity, and clear effect. In recent years, the research and development of protein and peptide drugs has become a hot spot in the field of bio- medicine research. Disulfide bond is the S-S bond protein or polypeptide molecules in two different loci forming by Cys thiol(- SH) oxidized .
Regarding disulfide modification, reaction conditions have a variety of options,
Regarding disulfide modification, reaction conditions have a variety of options, such as air oxidation, DMSO oxidation etc. these mild oxidation process,as well as the hydrogen peroxide (H2O2 and I2, mercury salt ,etc. fierce reaction conditions).Reaction product relatively easy separation and purification, then high purity and yielding. Air oxidation forming disulfide bond is the classical method in peptide synthesis . By air oxidation method is that usually thiol are dissolved in water in the reduction state of the peptides under the condition of near neutral or weak alkaline conditions (pH 6.5 to 10), reacting more than 24 hours. In order to reduce the possibility of inter molecular disulfide bond formation, the method usually need to be done under the condition of low concentration. Iodine oxidation method also widely applies in peptide synthesis . Generally peptide solubles in 25% of the methanol water solution or 30% aqueous solution of acetic acid, dropping in 10 ~ 15mol/L iodine drop by drop , reacting 15 ~ 40min. Please control the oxidation conditions accurately When the peptide contains Tyr, Trp, Met and His residues which are more sensitive to iodine. After oxidation,join the vitamin C or sodium thiosulfate to remove excess iodine immediately .

Commonly TRT, ACM, Mmt, TBU, Bzl, mob, Tmob etc ,a variety of groups, are used as thiol protecting group.Please see below multi-disulfide bond forming routes in peptides synthesis using 2-Cl and rink resins as the carrier :
Successful case :
Sequence : DC*TSHNGAC*NHHSHC*C*SNVC*NTWAHLC*T (three disulfide bonds)
HPLC analysis:
MS analysis: