At Last: Erythropoietin as a Single Glycoform

A PEGylated photocleavable auxiliary mediates the sequential enzymatic glycosylation and native chemical ligation of peptides

Research aimed at understanding the specific role of glycosylation patterns in protein function would greatly benefit from additional approaches allowing direct access to homogeneous glycoproteins. Herein the development and application of an efficient approach for the synthesis of complex homogenously glycosylated peptides based on a multifunctional photocleavable auxiliary is described. The presence of a PEG polymer within the auxiliary enables sequential enzymatic glycosylation and straightforward isolation in excellent yields. The auxiliary-modified peptides can be directly used in native chemical ligations with peptide thioesters easily obtained by direct hydrazinolysis of the respective glycosylated peptidyl resins and subsequent oxidation. The ligated glycopeptides can be smoothly deprotected by UV irradiation. We apply this approach to the preparation of variants of the epithelial tumor marker MUC1 carrying one or more Tn, T, or sialyl-T antigens.

Patchwork protein chemistry: a practitioner's treatise on the advances in synthetic peptide stitchery

With the study of peptides and proteins at the heart of many scientific endeavors, the omics era heralded a multitude of opportunities for chemists and biologists alike. Across the interface with life sciences, peptide chemistry plays an indispensable role, and progress made over the past decades now allows proteins to be treated as molecular patchworks stitched together through synthetic tailoring. The continuous elaboration of sophisticated strategies notwithstanding, Merrifield's solid-phase methodology remains a cornerstone of chemical protein design. Although the non-practitioner might misjudge peptide synthesis as trivial, routine, or dull given its long history, we comment here on its many advances, obstacles, and prospects from a practitioner's point of view. While sharing our perspectives through thematic highlights across the literature, this treatise provides an interpretive overview as a guide to novices, and a recap for specialists.

Engineered fluorescence tags for in vivo protein labelling

In vivoprotein labelling with a peptide tag–fluorescent probe system is an important chemical biology strategy for studying protein distribution, interaction and function.

The winding pathway to erythropoietin along the chemistry-biology frontier: a success at last

The total synthesis of a homogeneous erythropoietin (EPO), possessing the native amino acid sequence and chitobiose glycans at each of the three wild-type sites of N glycosylation, has been accomplished in our laboratory. We provide herein an account of our decade-long research effort en route to this formidable target compound. The optimization of the synergy of the two bedrock sciences we now call biology and chemistry was central to the success of the synthesis of EPO.