Fluorophore-labeled, Peptide-based Glycoclusters: Synthesis, Binding Properties for Lectins, and Detection of Carbohydrate-Binding Proteins in Cells

Efficient Preparation and Bioactivity Evaluation of Glycan-Defined Glycoproteins

Owing to the generation of heterogeneous glycoproteins in cells, it is highly difficult to study glycoprotein-mediated biological events and to develop biomedical agents. Thus, general and efficient methods to prepare homogeneous glycoproteins are in high demand. Herein, we report a general method for the efficient preparation of homogeneous glycoproteins that utilizes a combination of genetic code expansion and chemoselective ligation techniques. In the protocol to produce glycan-defined glycoproteins, an alkyne tag-containing protein, generated by genetic encoding of an alkynylated unnatural amino acid, was quantitatively coupled via click chemistry to versatile azide-appended glycans. The glycoproteins produced by the present strategy were found to recognize mammalian cell-surface lectins and enter the cells through lectin-mediated internalization. Also, cell studies exhibited that the glycoprotein containing multiple mannose-6-phosphate residues enters diseased cells lacking specific lysosomal glycosidases by binding to the cell-surface M6P receptor, and subsequently migrates to lysosomes for efficient degradation of stored glycosphingolipids.

Bacterial Lectin-Targeting Glycoconjugates for Selective Elimination of Pathogenic Bacteria

Herein we report a strategy to eradicate pathogenic bacteria selectively, which utilizes bacterial lectin-targeting glycoconjugates that contain an epitope or a photosensitizer to promote antibody-dependent cellular cytotoxicity (ADCC) or photodynamic therapy (PDT), respectively. Our results show that death promoted by using the designed synthetic glycoconjugates coupled with ADCC or PDT takes place selectively in pathogenic bacteria expressing lectins on their surfaces.

Analysis of carbohydrates and glycoconjugates by matrix-assisted laser desorption/ionization mass spectrometry: An update for 2011-2012

This review is the seventh update of the original article published in 1999 on the application of MALDI mass spectrometry to the analysis of carbohydrates and glycoconjugates and brings coverage of the literature to the end of 2012. General aspects such as theory of the MALDI process, matrices, derivatization, MALDI imaging, and fragmentation are covered in the first part of the review and applications to various structural types constitute the remainder. The main groups of compound are oligo- and poly-saccharides, glycoproteins, glycolipids, glycosides, and biopharmaceuticals. Much of this material is presented in tabular form. Also discussed are medical and industrial applications of the technique, studies of enzyme reactions, and applications to chemical synthesis. © 2015 Wiley Periodicals, Inc. Mass Spec Rev 36:255-422, 2017.

Cyclometalated Ir(iii) complexes incorporating a photoactive anthracene-based ligand: syntheses, crystal structures and luminescence switching by light irradiation

Compound aip and its Ir(iii) complexes [Ir(dfppy)₂(aip)](PF₆) (1) and [Ir(ppy)₂(aip)](PF₆) (2) show light-irradiation-induced luminescence switching behaviors.

Heteroleptic Ir(iii) and Pt(ii) complexes based on 2-(2,4-difluorophenyl)-pyridine and bisthienylethene BrLH: the influence of the metal center on structures, luminescence and photochromism

Based on bisthienylethene BrLH, [Ir(dfppy)₂(BrL)]·3CH₃OH (1) and [Pt(dfppy)(BrL)]·CH₃OH (2) have been prepared. The two complexes are significantly different in structure, luminescence and photochromic behavior, due to their different metal centers.

Probing cell-surface carbohydrate binding proteins with dual-modal glycan-conjugated nanoparticles

Dual-modal fluorescent magnetic glyconanoparticles have been prepared and shown to be powerful in probing lectins displayed on pathogenic and mammalian cell surfaces. Blood group H1- and Le(b)-conjugated nanoparticles were found to bind to BabA displaying Helicobacter pylori, and Le(a)- and Le(b)-modified nanoparticles are both recognized by and internalized into DC-SIGN and SIGN-R1 expressing mammalian cells via lectin-mediated endocytosis. In addition, glyconanoparticles block adhesion of H. pylori to mammalian cells, suggesting that they can serve as inhibitors of infection of host cells by this pathogen. It has been also shown that owing to their magnetic properties, glyconanoparticles are useful tools to enrich lectin expressing cells. The combined results indicate that dual-modal glyconanoparticles are biocompatible and that they can be employed in lectin-associated biological studies and biomedical applications.

Functionalization of DNA-dendron supramolecular fibers and application in regulation of Escherichia coli association

Specific carbohydrate recognition in biology is a dynamic process. Thus, supramolecular multivalent scaffolds with dynamic features have been applied to mimic this process. Herein, we prepared DNA-dendron supramolecular fibers and synthesized carbohydrate-oligonucleotide conjugates (C18-mannose). Via DNA hybridization, the C18-mannose could be guided onto the fiber platform and form multiple mannose-functionalized fibers, which can be utilized to agglutinate E. coli because of high affinity among multivalent mannose ligands and receptors on E. coli. In addition, via chain exchange reaction of DNAs, the E. coli could be dissociated by replacing multivalent mannose ligands with competitive unmodified DNA sequences. The association and dissociation processes of E. coli are confirmed by fluorescent microscope and transmission electron microscope (TEM). These results not only demonstrate the ability of DNA-dendron fibers in reversibly associating E. coli but also illustrate their potential to be an easily modified multivalent supramolecular platform.

Glyco-regioisomerism Effect on Lectin-Binding and Cell-Uptake Pathway of Glycopolymer-Containing Nanoparticles

Sugar regioisomerism (glycosidic linkage on different hydroxyl groups of the same sugar) widely exists in various polysaccharides and glycans with a significant contribution to their biological functions. However, the effects of this regioisomersim in glycopolymers and their self-assembled nanoparticles on such functions were almost not investigated previously. In this paper, this regioisomersim effect is studied for self-assembled nanoparticles NP-1-Gal and NP-6-Gal from triblock copolymers carrying different constitutional isomers of the pendent sugar species (1 and 6 denote the glycosidic linkage from the anomeric position and 6 position of the galactose unit, respectively). NP-1-Gal shows strong binding to lectins of Peanut (Arachis hypogea) agglutinin (PNA) and Erythrina cristagalli agglutinin (ECA), while NP-6-Gal does not. More importantly, they show binding behavior similar to the asialoglycoprotein receptor (ASGPR) but different internalization pathways in the Hep G2 cell after ASGPR-mediated endocytosis; i.e., NP-1-Gal can reach the early endosome, late endosome, as well as lysosome, while NP-6-Gal enters the early endosome only but not the others.

Carbohydrate microarrays

In the last decade, carbohydrate microarrays have been core technologies for analyzing carbohydrate-mediated recognition events in a high-throughput fashion. A number of methods have been exploited for immobilizing glycans on the solid surface in a microarray format. This microarray-based technology has been widely employed for rapid analysis of the glycan binding properties of lectins and antibodies, the quantitative measurements of glycan-protein interactions, detection of cells and pathogens, identification of disease-related anti-glycan antibodies for diagnosis, and fast assessment of substrate specificities of glycosyltransferases. This review covers the construction of carbohydrate microarrays, detection methods of carbohydrate microarrays and their applications in biological and biomedical research.

Synthetic glycopeptides and glycoproteins with applications in biological research

Over the past few years, synthetic methods for the preparation of complex glycopeptides have been drastically improved. The need for homogenous glycopeptides and glycoproteins with defined chemical structures to study diverse biological phenomena further enhances the development of methodologies. Selected recent advances in synthesis and applications, in which glycopeptides or glycoproteins serve as tools for biological studies, are reviewed. The importance of specific antibodies directed to the glycan part, as well as the peptide backbone has been realized during the development of synthetic glycopeptide-based anti-tumor vaccines. The fine-tuning of native chemical ligation (NCL), expressed protein ligation (EPL), and chemoenzymatic glycosylation techniques have all together enabled the synthesis of functional glycoproteins. The synthesis of structurally defined, complex glycopeptides or glyco-clusters presented on natural peptide backbones, or mimics thereof, offer further possibilities to study protein-binding events.