2026-04-13T19:55:17Zhttps://recercat.cat/oai/request

oai:recercat.cat:2445/2244242026-04-07T22:42:34Zcom_2072_1057col_2072_478917col_2072_478933

00925njm 22002777a 4500 dc Sánchez Campillo, Iván author Blanco Canosa, Juan B. author 2025-11-21T11:30:17Z 2025-11-21T11:30:17Z 2024-10-30 Native chemical ligation (NCL) ligates two unprotected peptides in an aqueous buffer. One of the fragments features a C-terminal α-thioester functional group, and the second bears an N-terminal cysteine. The reaction mechanism depicts two steps: an intermolecular thiol–thioester exchange resulting in a transient thioester, followed by an intramolecular S-to-N acyl shift to yield the final native peptide bond. Although this mechanism is well established, the direct observation of the transient thioester has been elusive because the fast intramolecular rearrangement prevents its accumulation. Here, the use of α-selenoester peptides allows a faster first reaction and an early buildup of the intermediate, enabling its quantification and the kinetic monitoring of the first and second steps. The results show a correlation between the steric hindrance in the α-thioester residue and the rearrangement rate. In bulky residues, the S-to-N acyl shift has a significant contribution to the overall reaction rate. This is particularly notable for valine and likely for other similar β-branched amino acids. Cinètica química Síntesi proteica Pèptids Chemical kinetics Protein synthesis Peptides Kinetic and Mechanistic Studies of Native Chemical Ligation with Phenyl α-Selenoester Peptides