SEA Ligation Is Accelerated at Mildly Acidic pH. Application to the Formation of Difficult Peptide Junctions

23 December 2019, Version 1
This content is a preprint and has not undergone peer review at the time of posting.


The bis(2-sulfanylethyl)amido (SEA)-mediated ligation has been introduced in 2010 as a novel chemoselective peptide bond forming reaction. SEA ligation is a useful reaction for protein total synthesis that is complementary to the native chemical ligation (NCL). In particular, SEA ligation proceeds efficiently in a wide range of pH, from neutral pH to pH 3-4. Thus, the pH can be chosen to optimize the solubility of the peptide segments or final product. It can be also chosen to facilitate the formation of difficult junctions, since the rate of SEA ligation increases significantly by decreasing the pH from 7.2 to 4.0. Here we describe a protocol for SEA ligation at pH 5.5 in the presence of 4-mercaptophenylacetic acid (MPAA) or at pH 4.0 in the presence of a newly developed diselenol catalyst. The protocols describe the formation of a valyl-cysteinyl peptide bond between two model peptides.


SEA-mediated ligation
acid catalysis
N,S-acyl shift
peptide ligation
Protein chemical synthesis


Comments are not moderated before they are posted, but they can be removed by the site moderators if they are found to be in contravention of our Commenting Policy [opens in a new tab] - please read this policy before you post. Comments should be used for scholarly discussion of the content in question. You can find more information about how to use the commenting feature here [opens in a new tab] .
This site is protected by reCAPTCHA and the Google Privacy Policy [opens in a new tab] and Terms of Service [opens in a new tab] apply.