Azide-alkyne Cycloaddition Reaction Research Articles

Alkyne-Tagged Apigenin, a Chemical Tool to Navigate Potential Targets of Flavonoid Anti-Dengue Leads.

A flavonoid is a versatile core structure with various cellular, immunological, and pharmacological effects. Recently, flavones have shown anti-dengue activities by interfering with viral translation and replication. However, the molecular target is still elusive. Here we chemically modified apigenin by adding an alkyne moiety into the B-ring hydroxyl group. The alkyne serves as a chemical tag for the alkyne-azide cycloaddition reaction for subcellular visualization. The compound located at the perinuclear region at 1 and 6 h after infection. Interestingly, the compound signal started shifting to vesicle-like structures at 6 h and accumulated at 24 and 48 h after infection. Moreover, the compound treatment in dengue-infected cells showed that the compound restricted the viral protein inside the vesicles, especially at 48 h. As a result, the dengue envelope proteins spread throughout the cells. The alkyne-tagged apigenin showed a more potent efficacy at the EC50 of 2.36 ± 0.22, and 10.55 ± 3.37 µM, respectively, while the cytotoxicities were similar to the original apigenin at the CC50 of 70.34 ± 11.79, and 82.82 ± 11.68 µM, respectively. Molecular docking confirmed the apigenin binding to the previously reported target, ribosomal protein S9, at two binding sites. The network analysis, homopharma, and molecular docking revealed that the estrogen receptor 1 and viral NS1 were potential targets at the late infection stage. The interactions could attenuate dengue productivity by interfering with viral translation and suppressing the viral proteins from trafficking to the cell surface.

Universal activity-based labeling method for ammonia- and alkane-oxidizing bacteria

The advance of metagenomics in combination with intricate cultivation approaches has facilitated the discovery of novel ammonia-, methane-, and other short-chain alkane-oxidizing microorganisms, indicating that our understanding of the microbial biodiversity within the biogeochemical nitrogen and carbon cycles still is incomplete. The in situ detection and phylogenetic identification of novel ammonia- and alkane-oxidizing bacteria remain challenging due to their naturally low abundances and difficulties in obtaining new isolates from complex samples. Here, we describe an activity-based protein profiling protocol allowing cultivation-independent unveiling of ammonia- and alkane-oxidizing bacteria. In this protocol, 1,7-octadiyne is used as a bifunctional enzyme probe that, in combination with a highly specific alkyne-azide cycloaddition reaction, enables the fluorescent or biotin labeling of cells harboring active ammonia and alkane monooxygenases. Biotinylation of these enzymes in combination with immunogold labeling revealed the subcellular localization of the tagged proteins, which corroborated expected enzyme targets in model strains. In addition, fluorescent labeling of cells harboring active ammonia or alkane monooxygenases provided a direct link of these functional lifestyles to phylogenetic identification when combined with fluorescence in situ hybridization. Furthermore, we show that this activity-based labeling protocol can be successfully coupled with fluorescence-activated cell sorting for the enrichment of nitrifiers and alkane-oxidizing bacteria from complex environmental samples, enabling the recovery of high-quality metagenome-assembled genomes. In conclusion, this study demonstrates a novel, functional tagging technique for the reliable detection, identification, and enrichment of ammonia- and alkane-oxidizing bacteria present in complex microbial communities.

Synthesis, in vitro antimicrobial evaluation, and molecular docking studies of new isatin-1,2,3-triazole hybrids

Antibiotic resistance is rapidly evolving at an alarming rate, posing a severe threat to humanity. In an effort to develop compounds with antimicrobial activity, we synthesized a series of isatin-1,2,3-triazole hybrids 12–21 using the copper(I)-catalyzed azide-alkyne cycloaddition (CuAAC) reactions. Structural verification of the new isatin-1,2,3-triazole hybrids was accomplished using a variety of spectroscopic characterization techniques. The novel hybrids were evaluated for their in vitro antimicrobial activity against different pathogenic bacteria and fungi species using both agar well and disc-diffusion assays. Ampicillin and Nystatin were used as standard reference antimicrobial drugs. The antimicrobial evaluation revealed that the most active derivative is isatin-1,2,3-triazole 21. Moreover, the tested compounds are more active against Gram-negative bacteria than Gram-positive bacteria. Molecular docking revealed that compound 21 could bind to the active sites of d-alanine-d-alanine ligase and dihydrofolate reductase via multiple H-bonds, π-π, and CH-π interactions.

Design and Synthesis of Oleanolic Acid Trimers to Enhance Inhibition of Influenza Virus Entry.

Influenza is a major threat to millions of people worldwide. Entry inhibitors are of particular interest for the development of novel therapeutic strategies for influenza. We have previously discovered oleanolic acid (OA) to be a mild influenza hemagglutinin (HA) inhibitor. In this work, inspired by the 3D structure of HA as a homotrimeric receptor, we designed and synthesized 15 OA trimers with different linkers and central region via the copper-catalyzed azide-alkyne cycloaddition reaction. All of the OA trimers were evaluated for their antiviral activities in vitro, and 12c, 12e, 13c, and 13d were observed to exhibit robust potency (IC50 in the submicromolar range) against influenza A/WSN/33 (H1N1) virus that was stronger than that observed with oseltamivir. In addition, these compounds also displayed strong biological activity against A/Hong Kong/4801/2014 and B/Sichuan/531/2018 (BV). The results of hemagglutination inhibition assays and surface plasmon resonance binding assays suggest that these OA trimers may interrupt the interaction between the HA protein of influenza virus and the host cell sialic acid receptor, thus blocking viral entry. These findings highlight the utility of multivalent OA conjugates to enhance the ligand-target interactions in anti-influenza virus drug design and are also helpful for studying antiviral drugs derived from natural products.

A Facile, Efficient Step-Wise and Alternative Synthesis of Indolyl Triazoles via “Click” Chemistry

series of new 1,2,3 triazoles hybrids were synthesized using a Cu-catalysed azide-alkyne cycloaddition reaction. Thus, a remarkable rapid click reaction of aryl azides with terminal alkynes at room temperature in DMF afforded new 4-((1-((1-(4-methoxy-3-nitrophenyl)-1H-1,2,3-triazol-4- yl)methyl)-1H-indol-3-yl)methylene)-3-methyl-1-phenyl-1H-pyrazol-5(4H)-ones in good to excellent yields. The reaction provides a safe, efficient and economic approach for the synthesis of various 1,2,3 triazoles. The reaction has many advantages like shorter reaction times, good yields of products and isolation of the products without the need for column chromatography. By using knoevenagel reaction under physical grinding with alkylating agents prepared various 1,2,3 triazoles.

Synthesis of a Novel Series of Cu(I) Complexes Bearing Alkylated 1,3,5-Triaza-7-phosphaadamantane as Homogeneous and Carbon-Supported Catalysts for the Synthesis of 1- and 2-Substituted-1,2,3-triazoles.

The N-alkylation of 1,3,5-triaza-7-phosphaadamantane (PTA) with ortho-, meta- and para-substituted nitrobenzyl bromide under mild conditions afforded three hydrophilic PTA ammonium salts, which were used to obtain a new set of seven water-soluble copper(I) complexes. The new compounds were fully characterized and their catalytic activity was investigated for the low power microwave assisted one-pot azide–alkyne cycloaddition reaction in homogeneous aqueous medium to obtain disubstituted 1,2,3-triazoles. The most active catalysts were immobilized on activated carbon (AC), multi-walled carbon nanotubes (CNT), as well as surface functionalized AC and CNT, with the most efficient support being the CNT treated with nitric acid and NaOH. In the presence of the immobilized catalyst, several 1,4-disubstituted-1,2,3-triazoles were obtained from the reaction of terminal alkynes, organic halides and sodium azide in moderate yields up to 80%. Furthermore, the catalyzed reaction of terminal alkynes, formaldehyde and sodium azide afforded 2-hydroxymethyl-2H-1,2,3-triazoles in high yields up to 99%. The immobilized catalyst can be recovered and recycled through simple workup steps and reused up to five consecutive cycles without a marked loss in activity. The described catalytic systems proceed with a broad substrate scope, under microwave irradiation in aqueous medium and according to “click rules”.

A minireview of 1,2,3-triazole hybrids with O-heterocycles as leads in medicinal chemistry.

Over the past few decades, the dynamic progress in the synthesis and screening of heterocyclic compounds against various targets has made a significant contribution in the field of medicinal chemistry. Among the wide array of heterocyclic compounds, triazole moiety has attracted the attention of researchers owing to its vast therapeutic potential and easy preparation via copper and ruthenium-catalyzed azide-alkyne cycloaddition reactions. Triazole skeletons are found as major structural components in a different class of drugs possessing diverse pharmacological profiles including anti-cancer, anti-bacterial, anti-fungal, anti-viral, anti-oxidant, anti-inflammatory, anti-diabetic, anti-tubercular, and anti-depressant among various others. Furthermore, in the past few years, a significantly large number of triazole hybrids were synthesized with various heterocyclic moieties in order to gain the added advantage of the improved pharmacological profile, overcoming the multiple drug resistance and reduced toxicity from molecular hybridization. Among these synthesized triazole hybrids, many compounds are available commercially and used for treating different infections/disorders like tazobactam and cefatrizine as potent anti-bacterial agents while isavuconazole and ravuconazole as anti-fungal activities to name a few. In this review, we will summarize the biological activities of various 1,2,3-triazole hybrids with copious oxygen-containing heterocycles as lead compounds in medicinal chemistry. This review will be very helpful for researchers working in the field of molecular modeling, drug design and development, and medicinal chemistry.

Naphthalen-2-yl 1-(benzamido(diethoxyphosphoryl)methyl)-1H-1,2,3-triazole-4-carboxylate

We have previously published new biheterocyclic phospohonic α-amino esters of the 1,2,3-triazole-benzimidazole and 1,2,3-triazole-carbazole type. The aim of the present paper was to describe a new phosponic aminoester bearing a triazole ring substituted in position 5 by an ester group. Thus, according to the same catalytic process used previously, the compound naphthalen-2-yl 1-(benzamido(diethoxyphosphoryl)methyl)-1H-1,2,3-triazole-4-carboxylate was synthesized with an excellent yield and high regioselectivity via the copper (I)-catalyzed alkyne–azide cycloaddition reaction (CuAAC), using diethyl (α-azido(benzamido)methyl)phosphonate (1) as a dipole and 2- naphthyl propiolate as a dipolarophile (2). The structure of the new compound was fully characterized by 1D (31P, 1H-, 13C-) and 2D (1H-1H and 1H-, 13C-) NMR spectroscopy, IR, and HRMS.

Unraveling the conformational properties of comb-like Poly(propargyl acrylate)-graft-poly(2-ethyl-2-oxazoline) chains in dilute solutions

We report the preparation and conformational property in solution of a library of comb-like poly(propargyl acrylate)-graft-poly(2-ethyl-2-oxazoline) (PPANb-g-PEtOx47-σg) samples with varied grafting densities (σg) ranging from 0 to 0.68. An azido end-functionalized linear poly(2-ethyl-2-oxazoline) (PEtOx-N3) as grafting side chain with a molar mass of 4700 g mol−1 was synthesized by the living cationic ring opening polymerization (CROP) of 2-ethyl-2-oxazoline (EtOx), followed by the sequential post-polymerization azidation modification at the living chain end of PEtOx. Poly(propargyl acrylate) (PPA) as the backbone was prepared by the chemical transformation from the ATRP-made poly(tert-butyl acrylate) (PtBA). Comb-like PPANb-g-PEtOx47-σg samples with different σg were eventually obtained by grafting PEtOx-N3 onto PPA backbone via the copper(I)-catalyzed alkyne-azide cycloaddition (CuAAC) reaction under varied [PEtOx-N3]0/[alkyne]0 ratios. Quadruple-detection size-exclusion chromatography (QD-SEC) system was used to extract the molecular parameters of the obtained comb-like polymers, including molar mass (M), viscometric radius (Rη), and intrinsic viscosity ([η]), etc. The comb-like chain showing a scaling-law of Rη ∼ σg0.34 was confirmed in the shortest backbone, which is fairly accordant with our previous results in polystyrene system. In addition, a transition of polymer shape from star-like to comb-like, and further to branched comb-like structure was observed as the backbone length increases. The transition from star-like to comb-like could be attributed to the continuous increase of length-diameter ratio, which would lead to that the comb-like chain changes its molecular feature from isotropic to anisotropic. On the other hand, the transition from comb-like to branched comb-like should be due to the presence of the intermolecular Glasser-Hay coupling side reactions in comb-like polymers.

Novel poly(azoamide triazole)s containing twin azobenzene units in the backbone. Synthesis, characterization, and in vitro degradation studies

We describe the synthesis and characterization of four new light and reduction sensitives poly(azoamide triazole)s, in which the azobenzene units are found along the main chain of the macromolecule. These polymers were prepared by the azide-alkyne cycloaddition reaction catalyzed with copper (I) (CuAAC). They were obtained in high yield and with apparent molecular weights in the range from 95 to 148 kDa. All poly(azoamide triazole)s are soluble in polar aprotic solvents, and two of them are also soluble in chloroform showing good coating and film-forming properties. They were characterized by Fourier transform infrared, nuclear magnetic resonance (NMR), ultraviolet-visible spectroscopy and gel permeation chromatography (GPC). The photoisomerization study of the synthesized polymers has been carried out by UV–Vis spectroscopy, as well as their trans-cis-trans reversibility behavior. Differential scanning calorimetry (DSC) and themogravimetric analysis (TGA) were used to investigate their thermal properties. Results show that the polymers were amorphous and stable up to 300 °C under nitrogen. The hydrolytic degradation of films of these polymers has been studied in vitro under various conditions of pH and temperature and was monitored by GPC. Furthermore, the presence of azo units along the polymer backbone as cleavable groups provides access to their degradation by reduction. In this sense, the degradation of polymers has also been studied using sodium dithionite as a mimic of the enzyme azoreductase. The results of these studies show that the polymers are stable enough under hydrolytic physiological conditions, but they degrade rapidly when sodium dithionite is used. A preliminary study of biocompatibility of polymers PAAT1 and PAAT4 has been carried out. A hemolysis study with human red blood cells (hRBC) and a cytotoxicity study with human gingival fibroblasts (HGnF) have been carried out. The results obtained suggest that these polymers could be good candidates to be used as drug coating materials.

Catalytic Enantioselective Construction of Chiroptical Boron-Stereogenic Compounds.

The construction of main group heteroatom-stereogenic compounds is of great importance due to their intriguing chemical, physical, biological, and stereoelectronic properties. Despite that organoboron compounds are widely used in organic chemistry, the creation of a tetrahedral boron-stereogenic center in one enantiomeric form remains highly challenging. Given the labile nature of ligands attached to the tetracoordinate boron atom, only a handful of enantioenriched boron-stereogenic compounds have been reported via resolution or a chiral substrate-induced diastereoselective approach. To date catalytic asymmetric synthesis of boron-stereogenic compounds has remained unknown. Here, we demonstrate the first catalytic enantioselective construction of boron-stereogenic compounds via an asymmetric copper-catalyzed azide-alkyne cycloaddition (CuAAC) reaction. This enantioselective CuAAC reaction not only gives access to a wide range of novel highly functionalized boron-stereogenic heterocycles in high yields with good to excellent enantioselectivities but also produces optically active terminal alkyne and triazole moieties with various potential application prospects. Further transformation of the chiral tetracoordinate boron compounds delivers several complex heterocyclic entities bearing boron-stereogenic centers without the loss of enantiopurity. Moreover, the X-ray structure, the barrier to racemization, and the HOMO/LUMO gap of selected tetracoordinate boron compounds are investigated. Notably, these novel N,N π-conjugated boron-stereogenic compounds exhibit bright fluorescence. The optical properties, including circular dichroism, quantum yield, and circular polarized luminescence spectroscopies, are examined. These features expand the chemical space of the chiroptical boron-based dye platform, which could have great potential applications in chiral optoelectronic materials.

Highly Efficient Modular Construction of Functional Drug Delivery Platform Based on Amphiphilic Biodegradable Polymers via Click Chemistry.

Amphiphilic copolymers with pendant functional groups in polyester segments are widely used in nanomedicine. These enriched functionalities are designed to form covalent conjugates with payloads or provide additional stabilization effects for encapsulated drugs. A general method is successfully developed for the efficient preparation of functional biodegradable PEG-polyester copolymers via click chemistry. Firstly, in the presence of mPEG as initiator, Sn(Oct)2-catalyzed ring-opening polymerization of the α-alkynyl functionalized lactone with D,L-lactide or ε-caprolactone afforded linear mPEG-polyesters bearing multiple pendant alkynyl groups. Kinetic studies indicated the formation of random copolymers. Through copper-catalyzed azide-alkyne cycloaddition reaction, various small azido molecules with different functionalities to polyester segments are efficiently grafted. The molecular weights, polydispersities and grafting efficiencies of azido molecules of these copolymers were investigated by NMR and GPC. Secondly, it is demonstrated that the resulting amphiphilic functional copolymers with low CMC values could self-assemble to form nanoparticles in aqueous media. In addition, the in vitro degradation study and cytotoxicity assays indicated the excellent biodegradability and low cytotoxicity of these copolymers. This work provides a general approach toward the preparation of functional PEG-polyester copolymers in a quite efficient way, which may further facilitate the application of functional PEG-polyesters as drug delivery materials.

Click and Cut: a click chemistry approach to developing oxidative DNA damaging agents.

Metallodrugs provide important first-line treatment against various forms of human cancer. To overcome chemotherapeutic resistance and widen treatment possibilities, new agents with improved or alternative modes of action are highly sought after. Here, we present a click chemistry strategy for developing DNA damaging metallodrugs. The approach involves the development of a series of polyamine ligands where three primary, secondary or tertiary alkyne-amines were selected and ‘clicked’ using the copper-catalysed azide-alkyne cycloaddition reaction to a 1,3,5-azide mesitylene core to produce a family of compounds we call the ‘Tri-Click’ (TC) series. From the isolated library, one dominant ligand (TC1) emerged as a high-affinity copper(II) binding agent with potent DNA recognition and damaging properties. Using a range of in vitro biophysical and molecular techniques—including free radical scavengers, spin trapping antioxidants and base excision repair (BER) enzymes—the oxidative DNA damaging mechanism of copper-bound TC1 was elucidated. This activity was then compared to intracellular results obtained from peripheral blood mononuclear cells exposed to Cu(II)–TC1 where use of BER enzymes and fluorescently modified dNTPs enabled the characterisation and quantification of genomic DNA lesions produced by the complex. The approach can serve as a new avenue for the design of DNA damaging agents with unique activity profiles.

Synthesis, characterization, DFT-TDDFT calculations and optical properties of a novel pyrazole-1,2,3-triazole hybrid thin film

Aiming to construct active photosensitizer agents, a novel 1-((3-(3-(3,5-diphenyl-4,5-dihydro-1H-pyrazol-1-yl)-5-methyl-1H-1,2,4-triazol-1-yl)-1-phenyl-1H-pyrazol-4-yl)methyl)-4-(4-methoxy phenyl)-1H-1,2,3-triazole (4MOTZ), was efficiently synthesized using click chemistry, through Cu-catalyzed azide-alkyne cycloaddition reactions. The experimental and simulation investigations were used for the analysis of the structure and the unique optical characteristics for [4MOTZ]TF thin films. The newly synthesized compound was fully examined by elemental analysis, FTIR, mass spectrometry, and (1H, 13C)-NMR analysis. XRD studies were performed to investigate the crystallinity of the deposited films. XRD patterns for thin films and gas-phase showed the polycrystalline structure of [4MOTZ]TF with a monoclinic 2 space group. The average crystallite size was 70.26 nm. The optical properties of the thin film were examined, and substantial straight transitions with bandgaps of 2.60 and 3.02 eV were confirmed. The optical gap predicted theoretically using DFT-TDDFT matched the optical gap observed experimentally. Also, the dispersion parameters of [4MOTZ]TF thin film were determined. The obtained results recommended that [4MOTZ]TF thin film can be utilized for prospective optoelectronic devices such as solar cells.

Coumarin bearing asymmetrical zinc(II) phthalocyanine functionalized SWCNT hybrid nanomaterial: Synthesis, characterization and investigation of bifunctional electrocatalyst behavior for water splitting

A novel asymmetrical zinc(II) phthalocyanine (Coum-Pc) bearing three 7-ethynyl-3-(3,4,5-trimethoxyphenyl) coumarin and one ethyloxy azido groups was synthesized and characterized for the first time. This novel asymmetric Coum-Pc was covalently attached to single walled carbon nanotube (SWCNT) containing terminal ethynyl groups via the azide-alkyne Huisgen cycloaddition (Click) reaction for preparation of coumarin bearing zinc(II) phthalocyanine functionalized SWCNT hybrid nanomaterial (SWCNT-Coum-Pc). Hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) electrocatalyst for water splitting behavior of SWCNT-Coum-Pc hybrid nanomaterial were evaluated. The SWCNT-Coum-Pc hybrid reduced the onset potential required for HER by approximately 200 mV compared to SWCNT catalyst in acidic medium. The SWCNT-Coum-Pc catalyst reduced the HER overpotential of 570 mV at a current density of 10 mA cm−2 in alkaline medium. It also exhibited outstanding activity in OER, required only an overpotential of 330 mV at a current density of 10 mA cm−2. Heterogeneous rate constants of the electrodes from impedance analysis were used to calculate the value of charge transfer resistance and the conductivity of the composite film. The presence of Coum-Pc groups on the SWCNT surface increased for both the conductivity and electron transfer rate of the SWCNT. Therefore, SWCNT-Coum-Pc hybrid significantly improved the performance of OER and HER for water splitting. The present work provided a promising ground for the of SWCNT-Coum-Pc hybrid as a bifunctional electrocatalyst for water splitting.

Acetylene Dicarboxylic Acid Diallyl Ester: A Versatile Monomer for Thiol–Ene Photocured Networks

AbstractThiol–ene photopolymerization (TEP) is a highly advantageous method for the curing of unsaturated monomers, and the design of novel monomers to be used in TEP is an active area of research. The feasibility and the versatility of novel acetylene dicarboxylic acid diallyl ester (ACDAE)‐based monomers are synthesized and demonstrated. The electron deficient acetylenic core in ACDAE allows to apply three different click reactions, aza‐Michael, thio‐Michael, and metal‐free azide–alkyne cycloaddition reactions, efficiently on it. Thus, three novel allylic monomers are synthesized and are used to prepare thiol–ene photopolymerized networks. All monomers are synthesized in good yields and structurally characterized by 1H NMR and Fourier‐transform infrared spectroscopy (FTIR) measurements. Thermal, thermomechanical, and mechanical properties, flame retardancy, transmittance, and the wettability of the networks are determined.

VvComplexation of copper ion-containing immobilized ionic liquid in designed hierarchical-functionalized layered double hydroxide nanoreactor for azide–alkyne cycloaddition reaction

A novel nanoreactor containing Cu (II) ions which are well distributed throughout the ionic liquid-based designed layered double hydroxide is applied for azide–alkyne cycloaddition reaction. The synthesized nanocatalyst was fully characterized by thermogravimetry analysis, scanning electron microscopy, X-ray powder diffraction, Fourier transform infrared spectroscopy and Brunauer–Emmett–Teller analysis. The high surface area and the appropriate pore size of the synthesized-nanocatalyst make metal active centers accessible. On the other hand, the presence of ionic liquid in the inner layer of designed hierarchical-functionalized layered double hydroxide nanostructure creates a good environment for the leaching protection and stabilization of extremely dispersed copper ion-containing that results in good reusable features of the nanocatalyst for the synthesis of 1,4-disubstituted-1,2,3-triazole derivatives with excellent yields (75–96%) through an azide-alkyne [3 + 2] cycloaddition reaction.

Poly(hydrophobic amino acid) Conjugates for the Delivery of Multiepitope Vaccine against Group A Streptococcus.

Peptide-based vaccines are composed of small, defined, antigenic peptide epitopes. They are designed to induce well-controlled immune responses. Multiple epitopes are often employed in these vaccines to cover strain variability of a pathogen. However, peptide epitopes cannot stimulate adequate immune responses on their own and require an adjuvant (immune stimulant) and/or delivery system. Here, we designed and synthesized a multiepitope vaccine candidate against Group A Streptococcus (GAS) composed of several B-cell epitopes (J8, PL1, and 88/30) derived from GAS M-protein, universal PADRE T-helper cell epitope, and a polyleucine self-adjuvanting unit. The vaccine components were conjugated together (using mercapto-maleimide and azide-alkyne Huisgen cycloaddition reactions) or delivered as a mixture. The conjugated multiepitope vaccine candidate self-assembled into small nanoparticles and chain-like aggregated nanoparticles (CLANs) that were able to induce the production of J8-, PL1-, and 88/30-specific antibodies in mice. The multiepitope conjugate and the physical mixture of conjugates bearing the individual epitopes produced similar nanoparticles and induced comparable immune responses. Hence, simple physical mixing can replace complex chemical conjugation to produce multiepitope nanoparticles with equivalent morphology and immunological efficacy. This greatly simplifies vaccine production.

Significant effect of intra-chain distribution of catalytic sites on catalytic activity in “clickase” single-chain nanoparticles

“Clickase” single-chain nanoparticles (Ck-SCNPs) are folded, enzyme-mimetic unimolecular polymeric nano-objects containing copper (Cu) ions able to catalyze the azide-alkyne Huisgen cycloaddition reaction in water and/or selected organic solvents often in the presence of a reductant. Herein, we investigate the effect of morphology on catalytic activity of identical Ck-SCNPs either containing a homogeneous distribution of Cu catalytic sites (Ck-SCNPs1) or showing intra-chain clustering of Cu ions (Ck-SCNPs2). A model fluorogenic “click” reaction between 9-(azidomethyl)anthracene and phenylacetylene, which was catalyzed either by Ck-SCNPs1 or Ck-SCNPs2, was used to unravel the effect of intra-chain clustering on catalytic activity. This work paves the way to improve the catalytic activity of other metallo-folded SCNPs through control of the intra-chain distribution of catalytic sites.

Use of NAD-Seq to Profile NAD+-Capped RNAs in Plants.

A 7-methylguanosine (m7G) cap in the 5′ end of eukaryotic mRNA transcript to protect mRNAs from degradation and regulate gene expression has been well characterized. Recently, some RNAs were found to contain a NAD+ cap, which is a different type of 5′ cap structure in eukaryotic organisms, including bacteria, yeast, mammalian cells, and Arabidopsis thaliana (arabidopsis) plant. NAD captureSeq was the first method to label NAD+-capped RNAs (NAD-RNAs) and uses ADP ribose cyclase (ADPRC)-catalyzed replacement of the nicotinamide of NAD+ with an alkynyl alcohol followed by copper-catalyzed azide-alkyne cycloaddition (CuAAC) to biotinylate NAD-RNA. In the next step, the eluted RNAs are subjected to library preparation and sequencing, followed by determination of NAD+-capped RNA in the transcriptome. Improved methods are emerging to determine NAD-RNAs, such as NAD tagSeq and strain-promoted azide–alkyne cycloaddition reaction (SPAAC)-NAD-Seq. Commonly, those methods use an enzymatic reaction followed by a click chemistry reaction to label NAD-RNAs with biotin or synthetic RNA tag (TagRNA).