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•Green synthesis of Pd/RGO/Fe3O4 nanocomposite using Withania coagulans leaf extract.•Reduction of 4-nitrophenol in water at room temperature.•Characterization of catalyst by XRD, ...FE-SEM, EDS, VSM, TEM, FT-IR and UV–vis.•The catalyst can be recovered and reused for further catalytic reactions with almost no loss in activity.
A reduced graphene oxide (RGO)/Fe3O4 based nanocomposite with palladium nanoparticles (Pd NPs) has been synthesized via a green route by Withania coagulans leaf extract as a reducing and stabilizing agent and its catalytic activity has been tested for the reduction of 4-nitrophenol (4-NP) in water at room temperature. The hydroxyl groups of phenolics in W. coagulans leaf extract is directly responsible for the reduction of Pd2+, Fe3+ ions and GO. The nanocomposite was characterized by X-ray diffraction (XRD), fourier transformed infrared (FT-IR) spectroscopy, field emission scanning electron microscopy (FE-SEM), energy dispersive X-ray spectroscopy (EDS), Vibrating sample magnetometer (VSM) and transmission electron microscopy (TEM). Furthermore, due to the magnetic separability and high stability of the composite the catalyst can be recovered and recycled several times without marked loss of activity.
Calixarenes and related macrocycles have been shown to have antimicrobial effects since the 1950s. This review highlights the antimicrobial properties of almost 200 calixarenes, resorcinarenes, and ...pillararenes acting as prodrugs, drug delivery agents, and inhibitors of biofilm formation. A particularly important development in recent years has been the use of macrocycles with substituents terminating in sugars as biofilm inhibitors through their interactions with lectins. Although many examples exist where calixarenes encapsulate, or incorporate, antimicrobial drugs, one of the main factors to emerge is the ability of functionalized macrocycles to engage in multivalent interactions with proteins, and thus inhibit cellular aggregation.
A molecularly imprinted polymer (MIP) was developed for the electrochemical determination of the antiviral drug sofosbuvir (SOF). The MIP was obtained by polymerization of p-aminothiophenol (p-ATP) ...on N,S co-doped graphene quantum dots (N,S@GQDs) in the presence of gold nanoparticles to form gold-sulfur covalent network. The presence of quantum dots improves the electron transfer rate, enhances surface activity and amplifies the signal. The nanocomposites were characterized by FTIR, TEM, EDX, and SEM. The electrochemical performance of the electrode was investigated by differential pulse voltammetry and cyclic voltammetry. The sensor uses hexacyanoferrate as the redox probe and is best operated at a potential of around 0.36 V vs. Ag/AgCl. It has a linear response over the concentration range of 1–400 nM SOF, with a detection limit of 0.36 nM. Other features include high selectivity, good reproducibility and temporal stability. The sensor was applied to the determination of SOF in spiked human plasma.
Graphical abstract
Novel sofosbuvir imprinted p-ATP polymer was synthesized by the aid of gold nanoparticles on N,S co-doped graphene quantum dots as a good conductive support. The imprinted polymer was used for detection of sofosbuvir in real samples by using the ferri/ferrocyanide redox probe.
•Cell wall polysaccharide fractions were isolated from Chinese quince fruits.•Chelator-soluble pectins exhibited a high DPPH radical scavenging activity.•1 mol/L KOH soluble hemicelluloses showed a ...high reducing power.
To investigate the composition and structural characteristics of cell wall polysaccharides, three pectic fractions and two hemicellulose fractions, namely water-soluble pectin (WSP), chelator-soluble pectin (CSP), sodium carbonate-soluble pectin (NSP), 1 mol/L KOH soluble hemicellulose (KSH-1) and 4 mol/L KOH soluble hemicellulose (KSH-2), were isolated from Chinese quince fruits. The five fractions exhibited structural and compositional variation. The results showed NSP was the predominant cell wall polysaccharide fraction in the fruit. All pectic fractions had a low degree of esterification (31.7–42.4%). WSP fraction had the highest thermal stability among the five fractions. The polysaccharide chain lengths ranged from 19.4 nm to 121.4 nm. CSP had the highest molecular weight, giving it also the highest solution viscosity. NMR spectra revealed that NSP was composed of RG-I and galacturonic acid main chains, KSH-1 was composed of 1,4-β-D-Xylp backbone attached to 1,5-α-L-Araf units. Among the five fractions, CSP has the highest DPPH radical scavenging activity while KSH-1 has the highest reducing power. This study can contribute to the applications of Chinese quince fruit polysaccharides in food and pharmaceutical industries.
•An alternating filtration method has been developed to prepare sandwich-like composite paper for oil/water separation.•The addition of CNF improved significantly the emulsions’ separation ...efficiency.•The thiol-mediated in situ immobilization of Ag NPs on pulp fibers endowed excellent non-leaching property.•The resulting Ag-Pulp/CNF showed efficient emulsions’ separation and anti-bacterial property.
Bio-based membranes for emulsion separation are sustainable, low-cost, renewable, biodegradable, and nontoxic. Herein, an antibacterial sandwich-like composite paper was fabricated by a facile process using Ag nanoparticles (Ag NPs)-coated pulp fibers and cellulose nanofibrils (CNFs). The obtained Ag-Pulp/CNF composite paper was superhydrophilic, allowing a 96 % separation efficiency for various oil-in-water emulsions. This outstanding separation efficiency was maintained over 20 separation cycles. The composite paper also showed satisfactory separation performance for water-in-oil emulsions after modification to render the surface hydrophobic. The CNFs provided the composite a nanoscale pore, which rejected nearly 100 % of bacteria when used to filter bacteria-contaminated emulsions due to a physical barrier effect. Attributed to the intrinsic antibacterial capability of Ag NPs, the composite paper exhibited strong antibacterial performance against Escherichia coli. Thus, the composite paper that was mainly derived from sustainable pulp fibers exhibited potential performance for oil/water separation and water purification.
Employing ethyl 2-oxocyclohexanecarboxylate as a novel, efficient, and versatile ligand, the copper-catalyzed coupling reactions of various N/O/S nucleophilic reagents with aryl halides could be ...successfully carried out under mild conditions. A variety of products including N-arylamides, N-arylimidazoles, aryl ethers, and aryl thioethers were synthesized in good to excellent yields.
The nucleocapsid (N) protein is one of the four structural proteins of the SARS-CoV-2 virus and plays a crucial role in viral genome organization and, hence, replication and pathogenicity. The ...N-terminal domain (NNTD) binds to the genomic RNA and thus comprises a potential target for inhibitor and vaccine development. We determined the atomic-resolution structure of crystalline NNTD by integrating solid-state magic angle spinning (MAS) NMR and X-ray diffraction. Our combined approach provides atomic details of protein packing interfaces as well as information about flexible regions as the N- and C-termini and the functionally important RNA binding, β-hairpin loop. In addition, ultrafast (100 kHz) MAS 1H-detected experiments permitted the assignment of side-chain proton chemical shifts not available by other means. The present structure offers guidance for designing therapeutic interventions against the SARS-CoV-2 infection.
We describe a novel manifestation of rigidochromic behavior in a series of tetranuclear Cu(I)–pyrazolate (Cu4pz4) macrocycles, with implications for solid-state luminescence at deep-blue wavelengths ...(<460 nm). The Cu4pz4 emissions are remarkably sensitive to structural effects far from the luminescent core: when 3,5-di-tert-butylpyrazoles are used as bridging ligands, adding a C4 substituent can induce a blue shift of more than 100 nm. X-ray crystal and computational analyses reveal that C4 units influence the conformational behavior of adjacent tert-butyl groups, with a subsequent impact on the global conformation of the Cu4pz4 complex. Emissions are mediated primarily through a cluster-centered triplet (3CC) state; compression of the Cu4 cluster into a nearly close-packed geometry prevents the reorganization of its excited-state structure and preserves the 3CC energy at a high level. The remote steric effect may thus offer alternative strategies toward the design of phosphors with rigid excited-state geometries.
Recent advances related to catalytic enantioselectice fluorination are examined. Catalytic enantioselective monofluoromethylation and catalytic enantioselective difluoromethylation are among the ...topics discussed.
A method for conjugation of ligands to the surface of exosomes was developed using click chemistry. Copper-catalyzed azide alkyne cycloaddition (click chemistry) is ideal for biocojugation of small ...molecules and macromolecules to the surface of exosomes, due to fast reaction times, high specificity, and compatibility in aqueous buffers. Exosomes cross-linked with alkyne groups using carbodiimide chemistry were conjugated to a model azide, azide-fluor 545. Conjugation had no effect on the size of exosomes, nor was there any change in the extent of exosome adherence/internalization with recipient cells, suggesting the reaction conditions were mild on exosome structure and function. We further investigated the extent of exosomal protein modification with alkyne groups. Using liposomes with surface alkyne groups of a similar size and concentration to exosomes, we estimated that approximately 1.5 alkyne groups were present for every 150 kDa of exosomal protein.
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