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Blue light photoredox decarboxylation and tin-free Barton-McCombie reactions in the stereoselective synthesis of (+)-muscarine
摘要： Starting from a 1,2-O-isopropylidene-D-xylofuranose derivative, a non-toxic free-radical approach for the synthesis of (+)-muscarine is reported. To this end, a stereoselective allylation reaction at the anomeric position of a respective xylofuranose derivative was employed as a new synthetic strategy for the installation of the methyl group at the C-5 position of (+)-muscarine. Accordingly, the allyl group was transformed into the methyl group in three sequential steps highlighting a blue-light photoredox decarboxylation reaction. Additionally, a tin-free Barton-McCombie deoxygenation reaction of the respective C-methyl glycoside allowed the completion of this free-radical approach to (+)-muscarine.
关键词： C-glycosylation,chiron approach,free radicals,Photoredox reaction
更新于2025-09-23 15:23:52
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Matrix-Assisted Laser Desorption/Ionization Mass Spectrometry to Detect Diagnostic Glycopeptide Markers of Congenital Disorders of Glycosylation
摘要： Congenital disorders of glycosylation (CDG), an increasingly recognized group of diseases affecting glycosylation, comprise the largest known subgroup involving approximately 100 responsible genes related to N-glycosylation. This subgroup presents as various molecular abnormalities, of either the CDG-I or the CDG-II type, attributable to lack of glycans or abnormal glycoform profiles, respectively. The most effective approach to identifying N-glycosylation disorders is mass spectrometry (MS) using either released glycans, intact glycoproteins or proteolytic peptides as the analyte. Among these, MS of tryptic peptides of transferrin reliably identifies the signature peptides characteristic of CDG-I and II. In the present study, matrix-assisted laser desorption/ionization (MALDI) MS was applied to various N-glycosylation disorders including ALG1-CDG, B4GALT1-CDG, SLC35A2-CDG, ATP6V0A2-CDG, TRAPPC11-CDG and MAN1B1-CDG. This method does not require prior enrichment of glycopeptides or chromatographic separation, and thus serves as a practical alternative to liquid chromatography-electrospray ionization MS. The signature peptides are biomarkers of CDG.
关键词： diagnosis,congenital disorder of glycosylation,glycopeptide,screening
更新于2025-09-23 15:19:57
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N-glycosylation state of TRPM8 protein revealed by terahertz spectroscopy and molecular modelling
摘要： TRPM8 member of the TRP superfamily of membrane proteins participates to various cellular processes ranging from Ca2+ uptake and cold sensation to cellular proliferation and migration. TRPM8 is a large tetrameric protein with more than 70% of its residues located in the cytoplasm. TRPM8 is N-glycosylated, with a single site per subunit. This work focuses on the N-glycosylation of TRPM8 channel that was previously studied by our group in relation to proliferation and migration of tumoral cells. Here, experimental data performed with deglycosylating agents assess that the sole glycosylation site contains complex glycans with a molecular weight of 2.5 kDa. The glycosylation state of TRPM8 in cells untreated and treated with a deglycosylating agent was addressed with Terahertz (THz) spectroscopy. Results show a clear difference between cells comprising glycosylated and deglycosylated TRPM8, the first presenting an increased THz absorption. Human TRPM8 was modelled using as templates the available TRPM8 and other TRPM channels structures. Glycosylations were modelled by considering two glycan structures with molecular weight close to the experiment: shorter and branched at the first sugar unit (glc1) and longer and unbranched (glc2). Simulation of THz spectra based on the molecular dynamics of unglycosylated and the two glycosylated TRPM8 models in lipid membrane and solvation box showed that glycan structure strongly influences the THz spectrum of the channel and of other components from the simulation system. Only spectra of TRPM8 with glc1 glycans were in agreement with the experiment, leading to the validation of glc1 glycan structure.
关键词： N-glycosylation,Terahertz spectroscopy,TRPM8,Molecular modelling,Membrane proteins
更新于2025-09-19 17:13:59
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Fluorometric visualization of mucin 1 glycans on cell surfaces based on rolling-mediated cascade amplification and CdTe quantum dots
摘要： A rolling-mediated cascade (RMC) amplification strategy is described for improved visualization of profiling glycans of mucin 1 (MUC 1) on cell surfaces. CdTe quantum dots (QDs) are used as fluorescent labels. The RMC based amplification allows even distinct glycoforms of MUC1 to be visualized on the surface of MCF-7 cell via an amplified F?rster resonance energy transfer (FRET) imaging strategy that works at excitation/emission wavelengths of 345/610 nm. This is achieved by utilizing antibody against MUC1 modified with the fluorescent label 7-amino-4-methylcoumarin-3-acetic acid (AMCA) as the energy donor in FRET. The QDs (used to label surface glycans) act as acceptors. N-Azidoacetylgalactosamine-Acetylated (Ac4GalNAz) as a non-natural azido sugar, can be incorporated into the glycans of the cell surface, which can promote further labeling. The method has the advantage of only requiring a small amount of non-natural sugar to be introduced in metabolic glycan labeling since too much of an artificial sugar will interfere with the physiological functions of cells.
关键词： Cancer marker,Azide polysaccharide,FRET,Glycosylation,Glycoprotein,DNA probe,Quantum dots,Click reaction,Metabolic labeling,Rolling-mediated cascade amplification
更新于2025-09-19 17:13:59
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Orthogonal dual molecularly imprinted polymer-based plasmonic immunosandwich assay: A double characteristic recognition strategy for specific detection of glycoproteins
摘要： Sensitive and specific detection methods are critical to the detection of glycoproteins. Immunoassay has been a powerful tool for this purpose, in which antibodies or their mimics particularly molecularly imprinted polymers (MIPs) are used for specific recognition. Epitope and glycan are two structure features of a glycoprotein. However, immunoassays based on simultaneous recognition towards the two characteristics have been scarcely explored so far. Herein we present a new strategy called orthogonal dual molecularly imprinted polymer-based plasmonic immunosandwich assay (odMIP-PISA). It relies on double recognition towards a target glycoprotein by two different types of MIPs, using epitope-imprinted gold nanoparticles (AuNPs)-coated slide as capturing substrate to recognize the peptide epitope and glycans-imprinted Raman-active silver nanoparticles as labeling nanotags to recognize the glycans. Carcinoembryonic antigen (CEA), a routinely used marker for colon cancer, was used as a test glycoprotein. The orthogonal double recognition apparently improved the specificity, reducing the maximum cross-reactivity from 14.4% for epitope recognition and 15.2% for glycan recognition to 8.2% for double recognition. Meanwhile, the plasmonic nanostructure-based Raman detection provided ultrahigh sensitivity, yielding a limit of detection of 5.56×10-14 M (S/N = 10). Through measuring the CEA level in human serum, this method permitted differentiation of colon cancer patient from healthy individual. Compared with the traditional immunoassay, odMIP-PISA exhibited multiple advantages, including simplified procedure (6 steps), speed (30 min), reduced cost, and so on. Therefore, this new approach holds great promise in many applications particularly clinical diagnosis.
关键词： Raman spectroscopy,glycoprotein,plasmonic immunosandwich assay,molecularly imprinted polymer,epitope,glycosylation
更新于2025-09-12 10:27:22