-
Bioconjugate Chemistry May 2022Glycan binding often mediates extracellular macromolecular recognition events. Accurate characterization of these binding interactions can be difficult because of...
Glycan binding often mediates extracellular macromolecular recognition events. Accurate characterization of these binding interactions can be difficult because of dissociation and scrambling that occur during purification and analysis steps. Use of photocrosslinking methods has been pursued to covalently capture glycan-dependent interactions ; however, use of metabolic glycan engineering methods to incorporate photocrosslinking sugar analogs is limited to certain cell types. Here, we report an exo-enzymatic labeling method to add a diazirine-modified sialic acid (SiaDAz) to cell surface glycoconjugates. The method involves the chemoenzymatic synthesis of diazirine-modified CMP-sialic acid (CMP-SiaDAz), followed by sialyltransferase-catalyzed addition of SiaDAz to desialylated cell surfaces. Cell surface SiaDAzylation is compatible with multiple cell types and is facilitated by endogenous extracellular sialyltransferase activity present in Daudi B cells. This method for extracellular addition of α2-6-linked SiaDAz enables UV-induced crosslinking of CD22, demonstrating the utility for covalent capture of glycan-mediated binding interactions.
Topics: Diazomethane; Glycoproteins; N-Acetylneuraminic Acid; Polysaccharides; Sialic Acids; Sialyltransferases
PubMed: 35437982
DOI: 10.1021/acs.bioconjchem.2c00037 -
RSC Advances Feb 2022A series of quinolizinium-based fluorescent reagents were prepared by visible light-mediated gold-catalyzed -difunctionalization between quinolinium diazonium salts and...
A series of quinolizinium-based fluorescent reagents were prepared by visible light-mediated gold-catalyzed -difunctionalization between quinolinium diazonium salts and electron-deficient alkyne-linked phenylethynyl trimethylsilanes. The electron-deficient alkynyl group of the quinolizinium-based fluorescent reagents underwent nucleophilic addition reaction with the sulfhydryl group on cysteine-containing peptides and proteins. The quinolizinium-based fluorescent reagents were found to function as highly selective reagents for the modification of cysteine-containing peptides and proteins with good to excellent conversions (up to 99%). Moreover, the modified BCArg mutants bearing cationic quinolizinium compounds 1b, 1d, 1e and 1h exhibit comparable activity in enzymatic and cytotoxicity assays to the unmodified one.
PubMed: 35424586
DOI: 10.1039/d1ra08329e -
Advanced Science (Weinheim,... Jul 2022Covalent functionalization of graphene (CFG) has shown attractive advantages in tuning the electronic, mechanical, optical, and thermal properties of graphene. However,...
Covalent functionalization of graphene (CFG) has shown attractive advantages in tuning the electronic, mechanical, optical, and thermal properties of graphene. However, facile, large-scale, controllable, and highly efficient CFG remains challenging and often involves highly reactive and volatile compounds, requiring complex control of the reaction conditions. Here, a diazonium-based grafting ink consisting of only two components, i.e., an aryl diazonium salt and the solvent dimethyl sulfoxide (DMSO) is presented. The efficient functionalization is attributed to the combination of the solvation of the diazonium cations by DMSO and n-doping of graphene by DMSO, thereby promoting electron transfer (ET) from graphene to the diazonium cations, resulting in the generation of aryl radicals which subsequently react with the graphene. The grafting density of CFG is controlled by the reaction time and very high levels of functionalization, up to the failing of the Tuinstra-Koenig (T-K) relation, while the functionalization layer remains at monolayer height. The grafting ink, effective for days at room temperature, can be used at ambient conditions and renders the patterning CFG by direct writing as easy as writing on paper. In combination with thermal sample treatment, reversible functionalization is possible by subsequent writing/erasing cycles.
PubMed: 35419972
DOI: 10.1002/advs.202105017 -
Analytical and Bioanalytical Chemistry Jul 2022Electrochemical, aptamer-based (E-AB) sensors uniquely enable reagentless, reversible, and continuous molecular monitoring in biological fluids. Because of this ability,...
Electrochemical, aptamer-based (E-AB) sensors uniquely enable reagentless, reversible, and continuous molecular monitoring in biological fluids. Because of this ability, E-AB sensors have been proposed for therapeutic drug monitoring. However, to achieve translation from the bench to the clinic, E-AB sensors should ideally operate reliably and continuously for periods of days. Instead, because these sensors are typically fabricated on gold surfaces via self-assembly of alkanethiols that are prone to desorption from electrode surfaces, they undergo significant signal losses in just hours. To overcome this problem, our group is attempting to migrate E-AB sensor interfaces away from thiol-on-gold assembly towards stronger covalent bonds. Here, we explore the modification of carbon electrodes as an alternative substrate for E-AB sensors. We investigated three strategies to functionalize carbon surfaces: (I) anodization to generate surface carboxylic groups, (II) electrografting of arenediazonium ions, and (III) electrografting of primary aliphatic amines. Our results indicate that electrografting of primary aliphatic amines is the only strategy achieving monolayer organization and packing densities closely comparable to those obtained by alkanethiols on gold. In addition, the resulting monolayers enable covalent tethering of DNA aptamers and support electrochemical sensing of small molecule targets or complimentary DNA strands. These monolayers also achieve superior stability under continuous voltammetric interrogation in biological fluids relative to benchmark thiol-on-gold monolayers when a positive voltage scan window is used. Based on these results, we postulate the electrografting of primary aliphatic amines as a path forward to develop carbon-supported E-AB sensors with increased operational stability.
Topics: Amines; Aptamers, Nucleotide; Biosensing Techniques; Carbon; Electrochemical Techniques; Electrodes; Gold; Sulfhydryl Compounds
PubMed: 35352164
DOI: 10.1007/s00216-022-04015-5 -
Nature Communications Mar 2022π-Extended tetrasubstituted olefins are widely found motifs in natural products, leading drugs, and agrochemicals. Thus, development of modular strategies for the...
π-Extended tetrasubstituted olefins are widely found motifs in natural products, leading drugs, and agrochemicals. Thus, development of modular strategies for the synthesis of complex all-carbon-substituted olefins always draws attention. The difunctionalization of unsymmetrical alkynes is an attractive approach but it has remained faced with regioselectivity issues. Here we report the discovery of a regio- and stereoselective syn-1,2-dicarbofunctionalization of unsymmetrical internal alkynes. A cationic Pd-catalyzed three-component coupling of aryl diazonium salts, aryl boronic acids (or olefins) and yne-acetates enables access to all-carbon substituted unsymmetrical olefins. The transformation features broad scope with labile functional group tolerance, building broad chemical space of structural diversity (94 molecules). The value of this synthetic method is demonstrated by the direct transformation of natural products and drug candidates containing yne-acetates, to enable highly substituted structurally complex allyl acetate analogues of biologically important compounds. Synthetic versatility of the carboxylate bearing highly substituted olefins is also presented. The reaction outcome is attributed to the in situ formation of stabilized cationic aryl-Pd species, which regulates regioselective aryl-palladation of unsymmetrical yne-acetates. Control experiments reveal the synergy between the carboxylate protecting group and the cationic Pd-intermediate in the regioselectivity and reaction productivity; density functional theory (DFT) studies rationalize the selectivity of the reaction.
Topics: Alkenes; Alkynes; Boronic Acids; Catalysis; Palladium
PubMed: 35296641
DOI: 10.1038/s41467-022-28949-7 -
Journal of the American Chemical Society Feb 2022α-Alkynyldiazomethanes, generated in situ from the corresponding sulfonyl hydrazones in the presence of a base, can serve as effective metalloradicophiles in...
α-Alkynyldiazomethanes, generated in situ from the corresponding sulfonyl hydrazones in the presence of a base, can serve as effective metalloradicophiles in Co(II)-based metalloradical catalysis (MRC) for asymmetric cyclopropanation of alkenes. With -symmetric chiral amidoporphyrin 2,6-DiMeO-QingPhyrin as the optimal supporting ligand, the Co(II)-based metalloradical system can efficiently activate different α-alkynyldiazomethanes at room temperature for highly asymmetric cyclopropanation of a broad range of alkenes. This catalytic radical process provides a general synthetic tool for stereoselective construction of alkynyl cyclopropanes in high yields with high both diastereoselectivity and enantioselectivity. Combined computational and experimental studies offer several lines of evidence in support of the underlying stepwise radical mechanism for the Co(II)-catalyzed olefin cyclopropanation involving a unique α-metalloradical intermediate that is associated with two resonance forms of α-Co(III)-propargyl radical and γ-Co(III)-allenyl radical. The resulting enantioenriched alkynyl cyclopropanes, as showcased with several stereospecific transformations, may serve as valuable chiral building blocks for stereoselective organic synthesis.
Topics: Alkenes; Cobalt; Cyclization; Diazonium Compounds; Molecular Structure
PubMed: 35099966
DOI: 10.1021/jacs.1c13154 -
Molecules (Basel, Switzerland) Jan 2022A family of oxazaborines, diazaborinones, triazaborines, and triazaborinones was prepared by reaction of polarized ethylenes, such as β-enaminoamides, with...
A family of oxazaborines, diazaborinones, triazaborines, and triazaborinones was prepared by reaction of polarized ethylenes, such as β-enaminoamides, with 4-methylbenzenediazonium tetraphenylborates. The reaction conditions (stirring in CHCl at room temperature (Method A) or stirring with CHCOONa in CHCl at room temperature (Method B) or refluxing in the CHCl/toluene mixture (Method C)) controlled the formation and relative content of these compounds in the reaction mixtures from one to three products. Substituted oxazaborines gradually rearranged into diazaborinones at 250 °C. The prepared compounds were characterized by H NMR, C NMR, IR, and UV-Vis spectroscopy, HRMS, or microanalysis. The structure of individual compounds was confirmed by B NMR, N NMR, 1D NOESY, and X-ray analysis. The mechanism of reaction of enaminoamides with 4-methylbenzenediazonium tetraphenylborate was proposed.
PubMed: 35056681
DOI: 10.3390/molecules27020367 -
Beilstein Journal of Organic Chemistry 2021We describe the synthesis of so far synthetically not accessible 3,6-substituted-4,6-dihydro-3-pyrazolo[3,4-][1,2,3]triazines as nitrogen-rich heterocycles. The target...
We describe the synthesis of so far synthetically not accessible 3,6-substituted-4,6-dihydro-3-pyrazolo[3,4-][1,2,3]triazines as nitrogen-rich heterocycles. The target compounds were obtained in five steps, including an amidation and a cyclative cleavage reaction as key reaction steps. The introduction of two side chains allowed a variation of the pyrazolo[3,4-][1,2,3]triazine core with commercially available building blocks, enabling the extension of the protocol to gain other derivatives straightforwardly. Attempts to synthesize 3,7-substituted-4,7-dihydro-3-pyrazolo[3,4-][1,2,3]triazines, the regioisomers of the successfully gained 3,6-substituted 4,6-dihydro-3-pyrazolo[3,4-][1,2,3]triazines, were not successful under similar conditions due to the higher stability of the triazene functionality in the regioisomeric precursors and thus, the failure of the removal of the protective group.
PubMed: 34900007
DOI: 10.3762/bjoc.17.187 -
Nature Chemical Biology Dec 2021Oxysterols (OHCs) are hydroxylated cholesterol metabolites that play ubiquitous roles in health and disease. Due to the non-covalent nature of their interactions and...
Oxysterols (OHCs) are hydroxylated cholesterol metabolites that play ubiquitous roles in health and disease. Due to the non-covalent nature of their interactions and their unique partitioning in membranes, the analysis of live-cell, proteome-wide interactions of OHCs remains an unmet challenge. Here, we present a structurally precise chemoproteomics probe for the biologically active molecule 20(S)-hydroxycholesterol (20(S)-OHC) and provide a map of its proteome-wide targets in the membranes of living cells. Our target catalog consolidates diverse OHC ontologies and demonstrates that OHC-interacting proteins cluster with specific processes in immune response and cancer. Competition experiments reveal that 20(S)-OHC is a chemo-, regio- and stereoselective ligand for the protein transmembrane protein 97 (Tmem97/the σ2 receptor), enabling us to reconstruct the 20(S)-OHC-Tmem97 binding site. Our results demonstrate that multiplexed, quantitative analysis of cellular target engagement can expose new dimensions of metabolite activity and identify actionable targets for molecular therapy.
Topics: 3T3 Cells; Animals; Cell Communication; Cell Membrane; Click Chemistry; Diazomethane; HEK293 Cells; Humans; Hydroxycholesterols; Ligands; Mice; Proteome; Pyridinium Compounds; Streptavidin
PubMed: 34799735
DOI: 10.1038/s41589-021-00907-2 -
Analytical Methods : Advancing Methods... Nov 2021For electrochemical immunosensors, inexpensive electrodes with fast redox kinetics, and simple stable methods of electrode functionalization are vital. However, many...
For electrochemical immunosensors, inexpensive electrodes with fast redox kinetics, and simple stable methods of electrode functionalization are vital. However, many inexpensive and easy to fabricate electrodes suffer from poor redox kinetics, and functionalization can often be difficult and/or unstable. Diazonium tosylates are particularly stable soluble salts that can be useful for electrode functionalization. Recently developed thermoplastic electrodes (TPEs) have been inexpensive, moldable, and highly electroactive carbon composite materials. Herein, the synthesis and grafting of diazonium tosylate salts were optimized for modification of TPEs and used to develop the first TPE immunosensors. With diazonium tosylates, TPEs were amine functionalized either directly through grafting of -aminophenyl diazonium salt or indirectly through grafting -nitrophenyl diazonium salt followed by electrochemical reduction to an amine. Diazonium tosylates were synthesized as a paste in 6 min. Once the reaction paste was spread over the electrodes, near monolayer coverage (1.0 ± 0.2 nmol cm) was achieved for -nitrophenyl diazonium salt within 5 min. Amine functionalized electrodes were conjugated to C-reactive protein (CRP) antibodies. Antibody-modified TPEs were applied for the sensitive detection of CRP, a biomarker of cardiovascular disease using electrochemical enzyme-linked immunosorbent assays (ELISA). LODs were determined to be 2 ng mL in buffer, with high selectivity against interfering species for both functionalization methods. The direct -aminophenyl modification method had the highest sensitivity to CRP and was further tested in spiked serum with an LOD of 10 ng mL. This low-cost and robust TPE immunosensor platform can be easily adapted for other analytes and multiplexed detection.
Topics: Biosensing Techniques; Diazonium Compounds; Electrochemical Techniques; Electrodes; Immunoassay
PubMed: 34651620
DOI: 10.1039/d1ay00965f