A novel post-ligation thioesterification device enables peptide ligation in the N to C direction: synthetic study of human glycodelin

Analysis of carbohydrates and glycoconjugates by matrix-assisted laser desorption/ionization mass spectrometry: An update for 2013-2014

This review is the eighth update of the original article published in 1999 on the application of Matrix-assisted laser desorption/ionization mass spectrometry (MALDI) mass spectrometry to the analysis of carbohydrates and glycoconjugates and brings coverage of the literature to the end of 2014. Topics covered in the first part of the review include general aspects such as theory of the MALDI process, matrices, derivatization, MALDI imaging, fragmentation, and arrays. The second part of the review is devoted to applications to various structural types such as oligo- and poly- saccharides, glycoproteins, glycolipids, glycosides, and biopharmaceuticals. Much of this material is presented in tabular form. The third part of the review covers medical and industrial applications of the technique, studies of enzyme reactions, and applications to chemical synthesis. © 2018 Wiley Periodicals, Inc. Mass Spec Rev 37:353-491, 2018.

A new method of N to C sequential ligation using thioacid capture ligation and native chemical ligation

Sequential peptide ligation strategy becomes more and more important in large protein or long peptides chemical synthesis due to the limited peptide/protein size obtained by solid phase synthesis of individual peptides or even one-step peptide ligation. Herein, we developed an alternative method which could perform the sequential peptide ligation of several segments from N to C direction based on the combined use of thioacid capture ligation and native chemical ligation. The sweet protein monellin was produced through this strategy on a scale of multi-milligrams.

Removal of the 5-nitro-2-pyridine-sulfenyl protecting group from selenocysteine and cysteine by ascorbolysis

We previously reported on a method for the facile removal of 4-methoxybenzyl and acetamidomethyl protecting groups from cysteine (Cys) and selenocysteine (Sec) using 2,2'-dithiobis-5-nitropyridine dissolved in trifluoroacetic acid, with or without thioanisole. The use of this reaction mixture removes the protecting group and replaces it with a 2-thio(5-nitropyridyl) (5-Npys) group. This results in either a mixed selenosulfide bond or disulfide bond (depending on the use of Sec or Cys), which can subsequently be reduced by thiolysis. A major disadvantage of thiolysis is that excess thiol must be used to drive the reaction to completion and then removed before using the Cys-containing or Sec-containing peptide in further applications. Here, we report a further advancement of this method as we have found that ascorbate at pH 4.5 and 25 °C will reduce the selenosulfide to the selenol. Ascorbolysis of the mixed disulfide between Cys and 5-Npys is much less efficient but can be accomplished at higher concentrations of ascorbate at pH 7 and 37 °C with extended reaction times. We envision that our improved method will allow for in situ reactions with alkylating agents and electrophiles without the need for further purification, as well as a number of other applications. Copyright © 2016 European Peptide Society and John Wiley & Sons, Ltd.

Facile preparation of the N-acetyl-glucosaminylated asparagine derivative with TFA-sensitive protecting groups useful for solid-phase glycopeptide synthesis

In this study, a novel N-acetyl-glucosaminylated asparagine derivative was developed. This derivative carried TFA-sensitive protecting groups and was derived from commercially available compounds only in three steps. It was applicable to the ordinary 9-fluorenylmethoxycarbonyl (Fmoc)-based solid-phase peptide synthesis (SPPS) method, and the protecting groups on the carbohydrate moiety could be removed by a single step of TFA cocktail treatment generally used for the final deprotection step in Fmoc-SPPS.