Rapid sodium periodate cleavage of an unnatural amino acid enables unmasking of a highly reactive α-oxo aldehyde for protein bioconjugation

The α-oxo aldehyde is a highly reactive aldehyde for which many protein bioconjugation strategies exist. Here, we explore the genetic incorporation of a threonine-lysine dipeptide into proteins, harbouring a “masked” α-oxo aldehyde that is rapidly unveiled in four minutes. The reactive aldehyde could undergo site-specific protein modification by SPANC ligation

Bioorthogonal, Bifunctional Linker for Engineering Synthetic Glycoproteins

Post-translational glycosylation of proteins results in complex mixtures of heterogeneous protein glycoforms. Glycoproteins have many potential applications from fundamental studies of glycobiology to potential therapeutics, but generating homogeneous recombinant glycoproteins using chemical or chemoenzymatic reactions to mimic natural glycoproteins or creating homogeneous synthetic neoglycoproteins is a challenging synthetic task. In this work, we use a site-specific bioorthogonal approach to produce synthetic homogeneous glycoproteins. We develop a bifunctional, bioorthogonal linker that combines oxime ligation and strain-promoted azide–alkyne cycloaddition chemistry to functionalize reducing sugars and glycan derivatives for attachment to proteins. We demonstrate the utility of this minimal length linker by producing neoglycoprotein inhibitors of cholera toxin in which derivatives of the disaccharide lactose and GM1os pentasaccharide are attached to a nonbinding variant of the cholera toxin B-subunit that acts as a size- and valency-matched multivalent scaffold. The resulting neoglycoproteins decorated with GM1 ligands inhibit cholera toxin B-subunit adhesion with a picomolar IC50

Correction: Rapid sodium periodate cleavage of an unnatural amino acid enables unmasking of a highly reactive α-oxo aldehyde for protein bioconjugation

Correction for ‘Rapid sodium periodate cleavage of an unnatural amino acid enables unmasking of a highly reactive α-oxo aldehyde for protein bioconjugation’ by Robin L. Brabham et al., Org. Biomol. Chem., 2020, 18, 4000–4003, DOI: 10.1039/D0OB00972E. The authors regret that the Acknowledgements section included below was accidentally omitted from the published article

A ‘glyco-fluorine’ code revealing differential recognition by glycan binding partners

Biosensing or diagnostics using glycan sequences as targets is limited by glycan cross-reactivities. As binding sites of different proteins that all recognise a given glycan will not be identical, we introduce application of a library of synthetic analogues of a single glycan ligand as a powerful approach to obtain fingerprint binding profiles. We report the enzymatic synthesis of a 150-member library of fluorinated Lewisx analogues (‘glycofluoroforms’) using naturally occurring enzymes and fluorinated monosaccharide building blocks, and the incorporation of a subset into lipid-linked glycan probes or into glyconanoparticles for probing protein binding both in solid-phase high-throughput glycan microarray screening analyses and in solution-phase nanoparticle-based interaction studies. These fluorinated Lewisx analogues, which NMR studies showed to have very similar 3D structures compared to the nonfluorinated Lewisx, gave variously increased or decreased binding with a set of proteins, the different proteins having different preferences and tolerances for binding