Monthly Archives: September 2023

Biochemical and Structural Characterization of a Uronic Acid Oxidase from Citrus sinensis

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Biochemical and Structural Characterization of a Uronic Acid Oxidase from Citrus sinensis

Aldaric acids are attractive diacids that can be prepared by selective oxidation of carbohydrates. The discovery, biochemical and structural characterization of a VAO-type flavin-containing carbohydrate oxidase from Citrus sinensis: URAOCs3 is reported. The selective oxidation of D-galacturonic acid in a complex mixture is demonstrated.


Abstract

Aldaric acids are attractive diacids that can be prepared by selective oxidation of carbohydrates. For this, effective biocatalysts are in demand. This work reports on the discovery, biochemical and structural characterization of a VAO-type flavin-containing carbohydrate oxidase from Citrus sinensis: URAOCs3. URAOCs3 could be overexpressed using prokaryotic and eukaryotic expression systems. Extensive biochemical characterization revealed that the enzyme displays a high thermostability and an exquisite selectivity for uronic acids, galacturonic acid and glucuronic acid. The enzyme was further investigated by determining the crystal structure. The selective oxidation of D-galacturonic acid in a complex mixture was demonstrated, showing how URAOCs3 was found to be highly effective in selectively producing galactaric acid while leaving other carbohydrates untouched. In addition to the specific discovery of URAOCs3, these findings suggest that plant proteomes can be an interesting source for new biocatalysts.

Virus‐Bionic Mesoporous Silica Nanoplatform for Malignant Tumor Inhibition via Effective Cellular Uptake and Precise Drug Delivery

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Virus-Bionic Mesoporous Silica Nanoplatform for Malignant Tumor Inhibition via Effective Cellular Uptake and Precise Drug Delivery

Virus-bionic mesoporous-silica-based nanocarriers can be successfully prepared for precise programmed drug delivery. These unique viral mimic nanovesicles not only present virus bionic counterparts and nanostructures, but also have infectious virus-like properties toward tumor cells and tumor tissues, showing rapid cell uptake.


Abstract

Over the past few decades, sophisticated nanomaterials have been used as carries for the targeted delivery of therapeutics to solid tumors. However, the low efficiency of intracellular internalization of nanocarriers in current use restricts their biomedical application. In this work, we demonstrate that novel virus-bionic mesoporous-silica-based nanocarriers can be successfully prepared for programmed precise drug delivery. These unique viral mimic nanovesicles not only present virus bionic counterparts and nanostructures, but also have infectious virus-like properties toward tumor cells and tumor tissues. Encouragingly, their large surface area (322.1 m2/g) endows them with high loading capacity for therapeutic agents, especially, they have more effective gene transfection properties than the commercially available LipoGeneTM transfection reagent. Thanks to their virus-inspired morphology, they exhibit outstanding cellular uptake efficiency with living tumor cells and the ability to invade cells in large quantities with incubation times as short as 5 min, which is much faster than traditional mesoporous silica nanoparticles (mSN) with smooth appearance. Importantly, after doxorubicin (DOX) loading and surface modification of tumor recognition motifs, RGD (Arg-Gly-Asp, vMN@DOX-RGD), the bionic drug-loaded viral mimics elicit potent tumor cell elimination both in vitro and in vivo, greatly exceeding the mSN-based group. Our work paves the way toward virus bionic nanocarrier design for malignant tumor suppression in the clinic.

Repurposing Salicylamides to Combat Phytopathogenic Bacteria and Induce Plant Defense Responses

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Based on the research strategy of "drug repurposing", a series of derivatives and marketed drugs that containing salicylic acid skeleton were tested for their antibacterial activities against phytopathogens. Salicylic acid can not only regulate some important growth metabolism of plants, but also induce plant disease resistance. The bioassay results showed that the salicylamides exhibited excellent antibacterial activity. Especially, oxyclozanide showed the best antibacterial effect against Xanthomonas oryzae, Xanthomonas axonopodis pv. citri and Pectobacterium atroseptica with MICs of 0.78, 3.12 and 12.5 μg.mL-1, respectively. In vivo experiments with rice bacterial leaf blight had further demonstrated that oxyclozanide exhibited stronger antibacterial activity than the commercial bactericide, thiodiazole copper. Oxyclozanide could induce plant defense responses through the determination of salicylic acid content and the activities of defense-related enzymes including CAT, POD, and SOD in rice. The preliminarily antibacterial mechanism study indicated that oxyclozanide exhibited the antibacterial activity by disrupting cell integrity and reducing bacterial pathogenicity. Additionally, oxyclozanide could induce plant defense responses through the determination of salicylic acid content.

Piano‐stool dinuclear ruthenium (II) complexes of pyrazine‐carboxylate/carboxamide ligands: Structural studies and catalytic transfer hydrogenation of ketones

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Piano-stool dinuclear ruthenium (II) complexes of pyrazine-carboxylate/carboxamide ligands: Structural studies and catalytic transfer hydrogenation of ketones

Dinuclear piano-stool ruthenium (II) complexes anchored on pyrazine-based carboxylic carboxamide ligands catalyse transfer hydrogenation of a wide of ketones at low catalyst loadings.


Reactions of ligand pyrazine-2-carboxylic acid (HL1) with [Ru(η6-p-cymene)Cl2]2 precursor gave the dinuclear piano-stool ruthenium (II) complex [{Ru(η6-p-cymene)Cl2}-μ-(L1)-{Ru(p-cymene)Cl}] (Ru1). Separately, reactions of N-(quinolin-8-yl) pyrazine-2-carboxamide (HL2), 5-methyl-N-(−(quinolin-8-yl) pyridine-2-carboxamide (HL3) and 5-chloro-N-(quinolin-8-yl) pyridine-2-carboxamide (HL4) with [Ru(η6-p-cymene)Cl2]2 dimer in the presence of KPF6 afforded the cationic dinuclear complexes [{Ru(η6-p-cymene)Cl}2-μ-(L2)][PF6] (Ru2), [{Ru(η6-p-cymene)Cl}2-μ-(L3)][Ru(L3)Cl3] (Ru3) and [{Ru(η6-p-cymene)Cl}2-μ-(L4)][PF6] (Ru4). The Ru (II) complexes were analysed using FT-IR, 1H, 13C{1H}, 31P{1H} (Ru2 and Ru4) and 19F (Ru2 and Ru4) NMR spectroscopic techniques, micro-analyses and mass spectrometry. Molecular structures of complexes Ru1 and Ru3 were confirmed to display piano-stool coordination nature using single-crystal X-ray crystallography analyses. All the complexes (Ru1–Ru4) mediated the transfer hydrogenation (TH) of a broad spectrum of ketones in isopropanol in the presence of a base and demonstrated high catalytic activities (TON of 24,000) at catalyst concentrations of 0.002 mol%. In general, the catalytic performance of these Ru (II) complexes depended on the identity of the ligands, coordination chemistry and ketone substrates.

Chiroptical Generation, Switching, and Long‐Term Memory in Supramolecular Azobenzene‐Pendant Polymer: Regulation by Cellulose Peralkyl Esters, D‐/L‐Glucose Permethyl Esters, Solvents, UV Light Irradiation, and Thermal Annealing Process

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Chiroptical Generation, Switching, and Long-Term Memory in Supramolecular Azobenzene-Pendant Polymer: Regulation by Cellulose Peralkyl Esters, D-/L-Glucose Permethyl Esters, Solvents, UV Light Irradiation, and Thermal Annealing Process†

The chirality transfer from a natural chiral biosource to achiral azobenzene polymers is developed based on the simple and efficient spin-coated film. The annealing treatment, the content of chiral inducer and the molecular weight of the Azo polymer are key to the induction of supramolecular chirality by cellulose derivatives. The corresponding chirality-inducing mechanism was demonstrated to arise from the aggregation chirality induced by the C-H/O=C and C-H/π interactions between the glucose repeating units and the PMMAzo polymer side-chains.


Comprehensive Summary

Various optically active polymers are known to afford sophisticated chirality-related functionalities, i.e., asymmetric catalysis, chiroptical switching and memory in UV-vis-NIR region, chromatographic separation of enantiomers, and sensors for molecular chirality. Recently, material researchers have paid much attention to the design of chiral supramolecular architectures from achiral polymers upon intermolecular interactions with help of greener biosources. The present article reports an instantaneous generation of ambidextrous supramolecules revealing light-driven chiroptical switching/memory in UV-vis region when achiral azobenzene-containing vinylpolymers are non-covalently interacted with alkyl ester derivatives of natural cellulose and D-/L-glucose. It was recognized that the semi-synthetic biomaterials efficiently work as chirality-inducing scaffoldings to several achiral and optically inactive molecules, oligomers, and polymers. Our successful results shed light on a new approach of how inexpensive poly-/mono-saccharide derivatives can afford supramolecular chiroptical systems with the azobenzene pendant polymer as aggregates in suspension and liquid-crystalline films with minimal energy, time, and cost.

Manganese Exacerbates Seasonal Health Declines in a Suicidally‐Breeding Mammal

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Abstract

Reproductive costs must be balanced with survival to maximise lifetime reproductive rates; however, some organisms invest in a single, suicidal bout of breeding known as semelparity. The northern quoll (Dasyurus hallucatus) is an endangered marsupial in which males, but not females, are semelparous. Northern quolls living near mining sites on Groote Eylandt, Northern Territory, Australia, accumulate manganese (Mn) in their brains, testes, and hair, and elevated Mn impacts motor performance. Whether Mn is associated with other health declines is yet unknown. Here, we show that male and female northern quolls with higher Mn accumulation had a 20% reduction in immune function and a trend toward reduced cortisol concentrations in hair. The telomere lengths of male quolls did not change pre- to post-breeding, but those with higher Mn levels had longer telomeres; in contrast, the telomeres of females shortened during the breeding season but recovered between the first year and second year of breeding. In addition, the telomeres of quolls that were re-captured declined at significantly higher rates in quolls with higher Mn between pre-breeding, breeding, and/or post-breeding seasons. Future work should determine whether changes in cortisol, immune function, or telomere length affect reproductive output or survival—particularly for semelparous males.

Acidic Electrocatalytic Semihydrogenation of Alkynols to Alkenols on Copper Phosphide at Industrial‐Level Current Density

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Acidic Electrocatalytic Semihydrogenation of Alkynols to Alkenols on Copper Phosphide at Industrial-Level Current Density

We demonstrate a novel electrocatalytic strategy for selectively hydrogenating alkynols to corresponding high-value-added alkenols under ambient temperature and pressure. In acidic solution, the as-fabricated Cu3P nanoarrays on Cu foam exhibit high alkynol conversion, high alkenol selectivity, and superior long-term stability at an industrial-level current density.


Comprehensive Summary

Alkenols are important intermediates for the industrial manufacture of various commodities and fine chemicals. At present, alkenols are produced via thermocatalytic semihydrogenation of corresponding alkynols using precious metal Pd-based catalysts in pressurized hydrogen atmosphere. In this work, we highlight an efficient electrocatalytic strategy for selectively reducing alkynols to alkenols under ambient conditions. Using 2-methyl-3-butyn-2-ol as a model alkynol, Cu3P nanoarrays anchored on Cu foam remarkably deliver an industrial-level partial current density of 0.79 A·cm–2 and a specific selectivity of 98% for 2-methyl-3-buten-2-ol in acidic solution. Over a 40-runs stability test, Cu3P nanoarrays maintain 90% alkynol conversion and 90% alkenol selectivity. Even in a large two-electrode flow electrolyser, the single-pass alkynol conversion and alkenol selectivity of Cu3P nanoarrays exceed 90%. Moreover, this selective electrocatalytic hydrogenation approach is broadly feasible for the production of various water-soluble alkenols. Electrochemical analyses, theoretical simulation and electrochemical in-situ infrared investigations together reveal that exothermic alkynol hydrogenation, facile alkenol desorption and formation of active H on Cu3P surfaces account for the excellent electrocatalytic performance.

Sensitivity of the Neotropical Solitary Bee Centris analis F. (Hymenoptera, Apidae) to the Reference Insecticide Dimethoate for Pesticide Risk Assessment

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Abstract

Currently, only Apis mellifera is used in environmental regulation to evaluate the hazard of pesticides to pollinators. The low representativeness of pollinators and bee diversity in this approach may result in insufficient protection for the wild species. This scenario is intensified in tropical environments, where little is known about the effects of pesticides on solitary bees. We aimed to calculate the medium lethal dose (LD50) and medium lethal concentration (LC50) of the insecticide dimethoate in the Neotropical solitary bee Centris analis, a cavity-nesting, oil-collecting bee distributed from Brazil to Mexico. Males and females of C. analis were exposed orally to dimethoate for 48 h under laboratory conditions. Lethality was assessed every 24 h until 144 h after the beginning of the test. After the LD50 calculation, we compared the value with available LD50 values in the literature of other bee species using the species sensitivity distribution curve. In 48 h of exposure, males showed an LD50 value 1.33 times lower than females (32.78 and 43.84 ng active ingredient/bee, respectively). Centris analis was more sensitive to dimethoate than the model species A. mellifera and the solitary bee from temperate zones, Osmia lignaria. However, on a body weight basis, C. analis and A. mellifera had similar LD50 values. Ours is the first study that calculated an LD50 for a Neotropical solitary bee. Besides, the results are of crucial importance for a better understanding of the effects of pesticides on the tropical bee fauna and will help to improve the risk assessment of pesticides to bees under tropical conditions, giving attention to wild species, which are commonly neglected. Environ Toxicol Chem 2023;00:1–10. © 2023 SETAC

Laboratory Determination of Particulate‐Matter–Bound Agrochemical Toxicity among Honeybees, Mason Bees, and Painted Lady Butterflies

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Abstract

Pollinator population declines are global phenomena with severe consequences for native flora and agriculture. Many factors have contributed to pollinator declines including habitat loss, climate change, disease and parasitism, reductions in abundance and diversity of foraging resources, and agrochemical exposure. Particulate matter (PM) serves as a carrier of toxic agrochemicals, and pollinator mortality can occur following exposure to agrochemical-contaminated PM. Therefore, laboratory-controlled experiments were conducted to evaluate impacts of individual PM-bound agrochemicals. Honeybees (Apis mellifera), blue orchard mason bees (Osmia lignaria), and painted lady butterfly (Vanessa cardui) larvae were exposed to bifenthrin, permethrin, clothianidin, imidacloprid, abamectin, and ivermectin via suspended, airborne PM. Agrochemical concentrations in PM to which pollinators were exposed were based on concentrations observed in fugitive beef cattle feedyard PM including a “mean” treatment and a “max” treatment reflective of reported mean and maximum PM-bound agrochemical concentrations, respectively. In general, pollinators in the mean and max treatments experienced significantly higher mortality compared with controls. Honeybees were most sensitive to pyrethroids, mason bees were most sensitive to neonicotinoids, and painted lady butterfly larvae were most sensitive to macrocyclic lactones. Overall, pollinator mortality was quite low relative to established toxic effect levels derived from traditional pollinator contact toxicity tests. Furthermore, pollinator mortality resulting from exposure to individual agrochemicals via PM was less than that reported to occur at beef cattle feedyards, highlighting the importance of mixture toxicity to native and managed pollinator survival and conservation. Environ Toxicol Chem 2023;00:1–9. © 2023 SETAC

Ionothermal Synthesis and Photoactivity of Ti17 and Ti19‐Oxo Clusters Functionalized by Sulfate and 1,10‐Phenanthroline Ligands

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Ionothermal Synthesis and Photoactivity of Ti17 and Ti19-Oxo Clusters Functionalized by Sulfate and 1,10-Phenanthroline Ligands

Sulfate and 1,10-phenanthroline ligands decorated Ti17 and Ti19-oxo clusters are prepared by ionothermal synthesis and show structure dependent photocatalytic MB dye degradation and photoelectrochemical photocurrent behaviors.


Comprehensive Summary

In this study, we successfully synthesized two titanium-oxo clusters, namely Ti19(μ3-O)19(μ2-O)10(1,10-phn)2(OiPr)18] (PTC-178) and (EMIm)3[Ti17(μ4-O)4(μ3-O)16(μ2-O)4(SO4)3(μ2-OiPr)4(OiPr)13] (PTC-179). These clusters were synthesized using an ionothermal reaction and possess similar nuclearity (Ti19 vs. Ti17) moieties. Additionally, we observed that these complexes exhibit varying activities for photocatalytic degradation of Methylene Blue (MB) dye and distinct photocurrent responses for photoelectrochemical studies due to their different surface-decorated ligands. This study provides valuable insights into the design of Ti-oxo molecular clusters with similar nuclearity but different surface environments, allowing for the establishment of critical structure-property relationships. Furthermore, our research contributes to the exploration of sustainable synthetic methods for high nuclearity TOCs using ionic liquids.