An Yb(OTf)₃-Mediated Indirect Activation Strategy for the Stereoselective Synthesis of α-Sialosides from 2-Fluorosialyl Donors.

Most of chemical sialylation reactions are conducted at extremely low temperatures to achieve the formation of challenging sialic acid linkages with high stereoselectivities. Performing chemical sialylation at room temperature independent of enzymatic methods represents an effective approach, particularly significant in biological and biochemical research. Our study aims to develop a convenient method of providing α-sialyl glycosides.

Investigating a Boronate-Affinity-Guided Acylation Reaction for Labelling Native Antibodies.

The excellent molecular recognition capabilities of monoclonal antibodies (mAbs) have opened up exciting opportunities for biotherapeutic discovery. Taking advantage of the full potential of this tool necessitates affinity ligands capable of conjugating directly with small molecules to a defined degree of biorthogonality, especially when modifying natural Abs. Herein, a bioorthogonal boronate-affinity-based Ab ligand featuring a 4-(dimethylamino)pyridine and an S-aryl thioester to label full-length Abs is reported.

Acceptor-mediated regioselective enzyme catalyzed sialylation: chemoenzymatic synthesis of GAA-7 ganglioside glycan.

Herein, we applied PmST1 (a sialyltransferase) to achieve acceptor-mediated regioselective sialylation (AMRS) on the nonreducing end GalNH or GalAz (2-azido-2-deoxy galactose). Thus, C5 and C8-modified sialic acid was efficiently assembled on GalNH (or GalAz) to achieve the synthesis of the GAA-7 (one of the echinodermatous gangliosides with higher neuritogenic activity) glycan moiety.

Regioselective S2-Type Reaction for the Oriented and Irreversible Immobilization of Antibodies to a Glass Surface Assisted by Boronate Formation.

Antibodies have exquisite specificities for molecular recognition, which have led to their incorporation into array sensors that are crucial for research, diagnostic, and therapeutic applications. Many of these platforms rely heavily on surface-bound reactive groups to covalently tether antibodies to solid substrates; however, this strategy is hindered by a lack of orientation control over antibody immobilization. Here, we report a mild electrophilic phenylsulfonate (tosylate) ester-containing boronic acid affinity ligand for attaching antibodies to glass slides.

A Modular Chemoenzymatic Synthesis of Disialosyl Globopentaosylceramide (DSGb5Cer) Glycan.

The total synthesis of the oligosaccharide moiety of disialosyl globopentaosylceramide (DSGb5 Cer), a dominant ganglioside isolated from malignant renal cell carcinoma tissues, is reported. The synthetic strategy relies on a chemical α(2,6)-sialylation at the internal GalNAc unit of a Gb5 pentasaccharide backbone that furnishes a Neu5Acα(2,6)GalNAc-linked hexasaccharide, suitable for an enzymatic α(2,3)-sialylation of the terminal Gal residue to construct a heptasaccharide glycan. Convergent access to this key α(2,6)-sialylated hexasaccharide was also achieved through a [3+3] glycosylation building upon a Galβ(1,3)[Neu5Acα(2,6)]GalNAc-based trisaccharide donor and a Gb3 acceptor.

Fluorescence "Turn-on" Lectin Sensors Fabricated by Ligand-Assisted Labeling Probes for Detecting Protein-Glycoprotein Interactions.

Elucidation of protein-protein interactions (PPIs) is often very challenging and yields complex and unclear results. Lectin-glycoprotein interactions are especially difficult to study due to the noncovalent nature of the interactions and inherently low binding affinities of proteins to glycan ligands on glycoproteins. Here, we report a "ligand-directed labeling probe (LLP)"-based approach to fabricate protein probes for elucidating protein-glycoprotein interactions.

Chemoenzymatic Synthesis of DSGb5 and Sialylated Globo-series Glycans.

Sialic-acid-binding, immunoglobulin-type lectin-7 (Siglec-7) is present on the surface of natural killer cells. Siglec-7 shows preference for disialylated glycans, including α(2,8)-α(2,3)-disialic acids or internally branched α(2,6)-NeuAc, such as disialosylglobopentaose (DSGb5). Herein, DSGb5 was synthesized by a one-pot multiple enzyme method from Gb5 by α2,3-sialylation (with PmST1) followed by α2,6-sialylation (with Psp2,6ST) in 23 % overall yield.

A photo-cleavable biotin affinity tag for the facile release of a photo-crosslinked carbohydrate-binding protein.

The use of photo-crosslinking glycoprobes represents a powerful strategy for the covalent capture of labile protein complexes and allows detailed characterization of carbohydrate-mediated interactions. The selective release of target proteins from solid support is a key step in functional proteomics. We envisaged that light activation can be exploited for releasing labeled protein in a dual photo-affinity probe-based strategy.