Observation of Charge Separation Enhancement in Plasmonic Photocatalysts under Coupling Conditions.

Surface plasmon resonance-induced charge separation plays key roles in plasmon-related applications, especially in photocatalysis and photovoltaics. Plasmon coupling nanostructures exhibit extraordinary behaviors in hybrid states, phonon scattering, and ultrafast plasmon dephasing, but plasmon-induced charge separation in these materials remains unknown. Here, we design Schottky-free Au nanoparticle (NP)/NiO/Au nanoparticles-on-a-mirror plasmonic photocatalysts to support plasmon-induced interfacial hole transfer, evidenced by surface photovoltage microscopy at the single-particle level. In particular, we observe a nonlinear increase in charge density and photocatalytic performance with an increase in excitation intensity in plasmonic photocatalysts containing hot spots as a result of varying the geometry. Such charge separation increased the internal quantum efficiency by 14 times at 600 nm in catalytic reactions as compared to that of the Au NP/NiO without a coupling effect. These observations provide an improved understanding of charge transfer management and utilization by geometric engineering and interface electronic structure for plasmonic photocatalysis.

Antcin A, a phytosterol regulates SARS-CoV-2 spike protein-mediated metabolic alteration in THP-1 cells explored by the 1 H-NMR-based metabolomics approach.

The mechanism of SARS-CoV-2 spike protein-mediated perturbations of metabolic pathways and modulation of antcin A, a steroid-like compound isolated from Taiwanofungus camphoratus, are not studied. Here, we investigated the metabolic alteration by SARS-CoV-2 spike protein and the regulatory effect of antcin A on SARS-CoV-2 spike protein-induced metabolic changes in the Phorbol 12-myristate 13-acetate (PMA)-induced human monocytes (THP-1) using proton nuclear magnetic resonance (1 H-NMR) and MetaboAnalyst 5.0 software. The cytotoxic potential of SARS-CoV-2 spike protein, antcin A, and dexamethasone was assessed by MTT assay. The metabolomic perturbations and their relation to human coronaviruses' receptors were evaluated by qPCR. This study indicated that the altered metabolites mediated by SARS-CoV-2 protein, such as methionine, phosphoenolpyruvic acid, canadine, glutamine, ethanolamine, and phenylalanine, were significantly reversed by antcin A. In addition, antcin A significantly inhibited SARS-CoV-2 spike protein-mediated up-regulation of TLR-4 and ACE2 receptors, while GRP78 inhibition was not statistically significant. This is the first study to use 1 H-NMR to investigate SARS-CoV-2 spike protein-induced metabolomic changes in PMA-induced THP-1 cells. Antcin A significantly reversed metabolomic alters while dexamethasone failed to fix them. Therefore, we believe that antcin A could be a potential candidate for therapeutic agents for viral infections related to a metabolic abnormality.

Recent advances and perspectives for solar-driven water splitting using particulate photocatalysts.

The conversion and storage of solar energy to chemical energy via artificial photosynthesis holds significant potential for optimizing the energy situation and mitigating the global warming effect. Photocatalytic water splitting utilizing particulate semiconductors offers great potential for the production of renewable hydrogen, while this cross-road among biology, chemistry, and physics features a topic with fascinating interdisciplinary challenges. Progress in photocatalytic water splitting has been achieved in recent years, ranging from fundamental scientific research to pioneering scalable practical applications. In this review, we focus mainly on the recent advancements in terms of the development of new light-absorption materials, insights and strategies for photogenerated charge separation, and studies towards surface catalytic reactions and mechanisms. In particular, we emphasize several efficient charge separation strategies such as surface-phase junction, spatial charge separation between facets, and polarity-induced charge separation, and also discuss their unique properties including ferroelectric and photo-Dember effects on spatial charge separation. By integrating time- and space-resolved characterization techniques, critical issues in photocatalytic water splitting including photoinduced charge generation, separation and transfer, and catalytic reactions are analyzed and reviewed. In addition, photocatalysts with state-of-art efficiencies in the laboratory stage and pioneering scalable solar water splitting systems for hydrogen production using particulate photocatalysts are presented. Finally, some perspectives and outlooks on the future development of photocatalytic water splitting using particulate photocatalysts are proposed.

Correction: Recent advances and perspectives for solar-driven water splitting using particulate photocatalysts.

Correction for 'Recent advances and perspectives for solar-driven water splitting using particulate photocatalysts' by Xiaoping Tao et al., Chem. Soc. Rev., 2022, 51, 3561-3608, https://doi.org/10.1039/d1cs01182k.

Lucidone inhibits autophagy and MDR1 via HMGB1/RAGE/PI3K/Akt signaling pathway in pancreatic cancer cells.

Gemcitabine (GEM) drug resistance remains a difficult challenge in pancreatic ductal adenocarcinoma (PDAC) treatment. Therefore, identifying a safe and effective treatment strategy for PDAC is urgent. Lucidone is a natural compound extracted from the fruits of Lindera erythrocarpa Makino. However, the role of lucidone in PDAC inhibition remains unclear. In addition, high-mobility group box 1 (HMGB1) and receptor for advanced glycation end products (RAGE) are involved in multidrug resistance protein 1 (MDR1) regulation and GEM resistance. Thus, this study aimed to explore the function of lucidone in tumor cytotoxicity and chemosensitivity through the suppression of RAGE-initiated signaling in PDAC cells. The data showed that lucidone significantly promoted apoptotic cell death and inhibited the expression of autophagic proteins (Atg5, Beclin-1, LC3-II, and Vps34) and MDR1 by inhibiting the HMGB1/RAGE/PI3K/Akt axis in both MIA Paca-2 cells and MIA Paca-2GEMR cells (GEM-resistant cells). Notably, convincing data were also obtained in experiments involving RAGE-specific siRNA transfection. In addition, remarkable cell proliferation was observed after treatment with lucidone combined with GEM, particularly in MIA Paca-2GEMR cells, indicating that lucidone treatment enhanced chemosensitivity. Collectively, this study provided the underlying mechanism by which lucidone treatment inhibited HMGB1/RAGE-initiated PI3K/Akt/MDR1 signaling and consequently enhanced chemosensitivity in PDAC.

Limonene protects human skin keratinocytes against UVB-induced photodamage and photoaging by activating the Nrf2-dependent antioxidant defense system.

Long term exposure to solar ultraviolet B (UVB) radiation is one of the primary factors of premature skin aging and is referred to as photoaging. Also, mammalian skin exposed to UVB triggers an increase in production of α-melanocyte-stimulating hormone (α-MSH), which is critically involved in the pathogenesis of hyperpigmentary skin diseases. This study investigated the protective effect of limonene on UVB-induced photodamage and photoaging in immortalized human skin keratinocytes (HaCaT) in vitro. Initially, we determined cell viability and levels of reactive oxygen species (ROS) in UVB-irradiated HaCaT cells. Pretreatment with limonene increased cell viability followed by inhibition of intracellular ROS generation in UVB-irradiated HaCaT cells. Interestingly, the antioxidative activity of limonene was directly correlated with an increase in expression of endogenous antioxidants, including heme oxygenase 1 (HO-1), NAD(P)H:quinone oxidoreductase 1 (NQO-1), and γ-glutamylcysteine synthetase (γ-GCLC), which was associated with enhanced nuclear translocation and activation of NF-E2-related factor-2 (Nrf2). Indeed, Nrf2 knockdown reduced limonene's protective effects. Additionally, we observed that limonene treatment inhibited UVB-induced α-MSH secretion followed by inhibition of proopiomelanocortin (POMC) via suppression of p53 transcriptional activation. Moreover, limonene prevented UVB-mediated depletion of tight junction regulatory proteins, including occludin and zonula occludens-1. On the other hand, limonene treatment significantly decreased matrix metalloproteinase-2 levels in UVB-irradiated HaCaT cells. Based on these results, limonene may have a dermato-protective effect in skin cells by activating the Nrf2-dependent cellular antioxidant defense system.

Characterization of Virus-Inducible Orchid Argonaute 5b Promoter and Its Functional Characterization in Nicotiana benthamiana during Virus Infection.

Plant ARGONAUTES (AGOs) play a significant role in the defense against viral infection. Previously, we have demonstrated that AGO5s encoded in Phalaenopsis aphrodite subsp. formosana (PaAGO5s) took an indispensable part in defense against major viruses. To understand the underlying defense mechanism, we cloned PaAGO5s promoters (pPaAGO5s) and analyzed their activity in transgenic Nicotiana benthamiana using ß-glucuronidase (GUS) as a reporter gene. GUS activity analyses revealed that during Cymbidium mosaic virus (CymMV) and Odontoglossum ringspot virus (ORSV) infections, pPaAGO5b activity was significantly increased compared to pPaAGO5a and pPaAGO5c. Analysis of pPaAGO5b 5'-deletion revealed that pPaAGO5b_941 has higher activity during virus infection. Further, yeast one-hybrid analysis showed that the transcription factor NbMYB30 physically interacted with pPaAGO5b_941 to enhance its activity. Overexpression and silencing of NbMYB30 resulted in up- and downregulation of GUS expression, respectively. Exogenous application and endogenous measurement of phytohormones have shown that methyl jasmonate and salicylic acid respond to viral infections. NbMYB30 overexpression and its closest related protein, PaMYB30, in P. aphrodite subsp. formosana reduced CymMV accumulation in P. aphrodite subsp. formosana. Based on these discoveries, this study uncovers the interaction between virus-responsive promoter and the corresponding transcription factor in plants.

Enhancement of Plasmon-Induced Photoelectrocatalytic Water Oxidation over Au/TiO2 with Lithium Intercalation.

Plasmon-induced chemical reaction is an emerging field but its development faces huge challenges because of low quantum efficiency. Herein, we report that the solar energy conversion efficiency of Au/TiO2 in plasmon-induced water oxidation is greatly enhanced by intercalating Li+ into TiO2 . An incident photon-to-current efficiency as high as 2.0 %@520 nm is achieved by Au/Li0.2 TiO2 in photoelectrocatalytic water oxidation, realizing a 33-fold enhancement in photocurrent density compared with Au/TiO2 . The superior photoelectrocatalytic performance is mainly ascribed to the enhanced electric conductivity and higher catalytic activity of Li0.2 TiO2 . Furthermore, the ultrafast transient absorption spectroscopy suggests that lithium intercalation into TiO2 could change the dynamics of hot electron relaxation in Au nanoparticles. This work demonstrates that intercalation of alkaline ions into semiconductors can promote the charge separation efficiency of the plasmonic effect of Au/TiO2 .

Solving the Structural Puzzles of Amipurimycin and Miharamycins Enabled by Stereodivergent Total Synthesis.

The efforts toward the synthesis of amipurimycin and miharamycin A/B, two peptidyl nucleoside antibiotics bearing a unique nine carbon C3-branched pyranosyl amino acid core, are accounted. Highlighted is our stereodivergent total synthesis of all the possible diastereoisomers of amipurimycin, which has enabled us to solve the structural puzzles of amipurimycin and miharamycin A/B after ∼50 years of their discovery.

Color variation in young and senescent leaves of Formosan sweet gum (Liquidambar formosana) by the gene regulation of anthocyanidin biosynthesis.

In certain plants, leaf coloration occurs in young and senescent leaves; however, it is unclear whether these two developmental stages are controlled by the same regulatory mechanisms. Formosan sweet gum (Liquidambar formosana Hance) is a subtropical deciduous tree species that possesses attractive autumnal leaf coloration. The color of young leaves is closer to purplish red, while senescent leaves are more orange-red to dark red. It was confirmed that delphinidin and cyanidin are the two anthocyanidins that contribute to the color of Formosan sweet gum leaves, and the content of different anthocyanins influences the appearance of color. To elucidate the regulation of anthocyanidin biosynthesis, recombinant DIHYDROFLAVONOL-4-REDUCTASEs (LfDFR1 and LfDFR2) (EC 1.1.1.234) were produced, and their substrate acceptability was investigated both in vitro and in planta. The functions of flavanones and dihydroflavonols modification by FLAVONOID 3' HYDROXYLASE (LfF3'H1) (EC 1.14.14.82) and FLAVONOID 3'5' HYDROXYLASE (LfF3'5'H) (EC 1.14.14.81) were verified using a transient overexpression experiment in Nicotiana benthamiana. The results showed that LfMYB5 induced LfF3'5'H and LfMYB123 induced both LfF3'H1 and LfDFR1 in spring when the leaves were expanding, whereas LfMYB113 induced LfF3'H1, LfDFR1, and LfDFR2 in late autumn to winter when the leaves were undergoing leaf senescence. In conclusion, the color variation of Formosan sweet gum in young and senescent leaves was attributed to the composition of anthocyanidins through the transcriptional regulation of LfF3'H1 and LfF3'5'H by LfMYB5, LfMYB113, and LfMYB123.

Biochemical characterization of diterpene synthases of Taiwania cryptomerioides expands the known functional space of specialized diterpene metabolism in gymnosperms.

Taiwania cryptomerioides is a monotypic gymnosperm species, valued for the high decay resistance of its wood. This durability has been attributed to the abundance of terpenoids, especially the major diterpenoid metabolite ferruginol, with antifungal and antitermite activity. Specialized diterpenoid metabolism in gymnosperms primarily recruits bifunctional class-I/II diterpene synthases (diTPSs), whereas monofunctional class-II and class-I enzymes operate in angiosperms. In this study, we identified a previously unrecognized group of monofunctional diTPSs in T. cryptomerioides, which suggests a distinct evolutionary divergence of the diTPS family in this species. Specifically, five monofunctional diTPS functions not previously observed in gymnosperms were characterized, including monofunctional class-II enzymes forming labda-13-en-8-ol diphosphate (LPP, TcCPS2) and (+)-copalyl diphosphate (CPP, TcCPS4), and three class-I diTPSs producing biformene (TcKSL1), levopimaradiene (TcKSL3) and phyllocladanol (TcKSL5), respectively. Methyl jasmonate (MeJA) elicited the accumulation of levopimaradiene and the corresponding biosynthetic diTPS genes, TcCPS4 and TcKSL3, is consistent with a possible role in plant defense. Furthermore, TcCPS4 and TcKSL3 are likely to contribute to abietatriene biosynthesis via levopimaradiene as an intermediate in ferruginol biosynthesis in Taiwania. In conclusion, this study provides deeper insight into the functional landscape and molecular evolution of specialized diterpenoid metabolism in gymnosperms as a basis to better understand the role of these metabolites in tree chemical defense.

Characterization of Miharamycin Biosynthesis Reveals a Hybrid NRPS-PKS to Synthesize High-Carbon Sugar from a Complex Nucleoside.

Miharamycins are peptidyl nucleoside antibiotics with a unique branched C9 pyranosyl amino acid core and a rare 2-aminopurine moiety. Inactivation of 19 genes in the biosynthetic gene cluster and identification of several unexpected intermediates suggest an alternative biosynthetic pathway, which is further supported by feeding experiments and in vitro characterization of an unusual adenylation domain recognizing a complex nucleoside derivative as the substrate. These results thereby provide an unprecedented biosynthetic route of high-carbon sugar catalyzed by atypical hybrid nonribosomal peptide synthetase-polyketide synthase.

Effects of the interfacial defects in Au/ TiO2 on plasmon-induced water oxidation.

In the plasmonic metal-semiconductor systems, the interfacial structure is vital for both charge separation and photocatalytic reaction. However, the role of interfacial defects, a ubiquitous phenomenon in the metal-semiconductor heterostructure, is not well understood, especially for the hot hole-involved water oxidation reaction. Herein, we studied the effect of interfacial defects, derived from oxygen vacancies, on plasmonic photocatalytic water oxidation. In addition, we found that the plasmon-induced water oxidation activity decreased with the increase in the oxygen vacancies present at the interface, and the activity of Au/TiO2 can be restored after eliminating the defects via a post-oxidation treatment. It is elucidated that a defect state appeared below the conduction band of TiO2 as a result of interfacial defects, which acts as the electron traps and backward transfer channel for electrons to combine with the holes left at the interface. The charge recombination at defect sites leads to the shorter lifetime of hot holes, which is harmful for the kinetics-sluggish water oxidation. This work emphasizes the significance of the interface structure for the plasmon-based photocatalytic process.

Sinensol-C Isolated from Spiranthes sinensis Inhibits Adipogenesis in 3T3-L1 Cells through the Regulation of Adipogenic Transcription Factors and AMPK Activation.

Obesity is an abnormal medical condition caused by accumulation of body fat that presents negative health impacts. Adipocyte hyperplasia, also known as adipogenesis, is one of the major manifestations of obesity. In the present study, we isolated six phenanthrene derivatives (compounds 1-6) from the ethyl acetate fraction of Spiranthes sinensis and investigated their anti-adipogenic activity. We found that among the six phenanthrene derivatives, compound 6 (sinensol-C) exhibited strong inhibitory activity against intracellular lipid accumulation in 3T3-L1 adipocytes, with an IC50 value of 12.67 µM. Sinensol-C remarkably suppressed the accumulation of lipid droplets and adipogenesis, via down-regulation of adipogenic transcription factors, including peroxisome proliferator-activated receptor γ (PPARγ), CCAAT/enhancer binding protein α (C/EBPα), sterol regulatory element binding protein-1 (SREBP-1c), fatty acid synthase (FAS), and fatty acid binding protein 4 (FABP4), during adipocyte differentiation in 3T3-L1 cells. In addition, treatment with sinensol-C significantly increased the adenosine monophosphate-activated protein kinase (AMPK) activity in 3T3-L1 cells. Taken together, these data strongly suggest that sinensol-C regulates adiogenesis via down-regulation of adipogenic transcription factors and up-regulation of AMPK. Furthermore, this is the first study that demonstrates that sinensol-C has the capacity to modulate adipogenesis.

The Polarization Effect in Surface-Plasmon-Induced Photocatalysis on Au/TiO2 Nanoparticles.

Controlling the interaction of polarization light with an asymmetric nanostructure such as a metal/semiconductor heterostructure provides opportunities for tuning surface plasmon excitation and near-field spatial distribution. However, light polarization effects on interfacial charge transport and the photocatalysis of plasmonic metal/semiconductor photocatalysts are unclear. Herein, we reveal the polarization dependence of plasmonic charge separation and spatial distribution in Au/TiO2 nanoparticles under 45° incident light illumination at the single-particle level using a combination of photon-irradiated Kelvin probe force microscopy (KPFM) and electromagnetic field simulation. We quantitatively uncover the relationship between the local charge density and polarization angle by investigating the polarization-dependent surface photovoltage (SPV). The plasmon-induced photocatalytic activity is enhanced when the polarization direction is perpendicular to the Au/TiO2 interface.

MicroRNA-708 activation by glucocorticoid receptor agonists regulate breast cancer tumorigenesis and metastasis via downregulation of NF-κB signaling.

Therapeutic administration of glucocorticoids (GCs) is frequently used as add-on chemotherapy for palliative purposes during breast cancer treatment. Recent studies have shown that GC treatment induces microRNA-708 in ovarian cancer cells, resulting in impaired tumor cell proliferation and metastasis. However, the regulatory functions of GCs on miR-708 and its downstream target genes in human breast cancer cells (BCCs) are poorly understood. In this study, we found that treatment with either the synthetic GC dexamethasone (DEX) or the natural GC mimic, antcin A (ATA) significantly increased miR-708 expression by transactivation of glucocorticoid receptor alpha (GRα) in MCF-7 and MDA-MB-231 human BCCs. Induction of miR-708 by GR agonists resulted in inhibition of cell proliferation, cell-cycle progression, cancer stem cell (CSC)-like phenotype and metastasis of BCCs. In addition, GR agonist treatment or miR-708 mimic transfection remarkably inhibited IKKß expression and suppressed nuclear factor-kappaB (NF-κB) activity and its downstream target genes, including COX-2, cMYC, cyclin D1, Matrix metalloproteinase (MMP)-2, MMP-9, CD24, CD44 and increased p21CIP1 and p27KIP1 that are known to be involved in proliferation, cell-cycle progression, metastasis and CSC marker protein. BCCs xenograft models indicate that treatment with GR agonists significantly reduced tumor growth, weight and volume. Overall, our data strongly suggest that GR agonists induced miR-708 and downstream suppression of NF-κB signaling, which may be applicable as a novel therapeutic intervention in breast cancer treatment.

Antcin-A Modulates Epithelial-to-Mesenchymal Transition and Inhibits Migratory and Invasive Potentials of Human Breast Cancer Cells via p53-Mediated miR-200c Activation.

Antcin-A (ATA) is a steroid-like phytochemical isolated from the fruiting bodies of a precious edible mushroom Antrodia cinnamomea. We previously showed that ATA has strong anti-inflammatory and anti-tumor effects; however, other possible bioactivities of this unique compound remain unexplored. In the present study, we aimed to investigate the modulation of epithelial-to-mesenchymal transition (EMT), anti-migration, and anti-invasive potential of ATA against human breast cancer cells in vitro. Human breast cancer cell lines, MCF-7 and MDA-MB-231, were incubated with ATA for 24 h. Wound healing, trans-well invasion, western blot, q-PCR, F-actin staining, and immunofluorescence assays were performed. We found that treatment with ATA significantly blocked EMT processes, as evidenced by upregulation of epithelial markers (E-cadherin and occludin) and downregulation of mesenchymal markers (N-cadherin and vimentin) via suppression of their transcriptional repressor ZEB1. Next, we found that ATA could induce miR-200c, which is a known player of ZEB1 repression. Further investigations revealed that ATA-mediated induction of miR-200c is associated with transcriptional activation of p53, as confirmed by the fact that ATA failed to induce miR-200c or suppress ZEB1 activity in p53 inhibited cells. Further in vitro wound healing and trans-well invasion assays support that ATA could inhibit migratory and invasive potentials of breast cancer cells, and the effect was likely associated with induced phenotypic modulation. Taken together, the present study suggests that antcin-A could be a lead phyto-agent for the development of anti-metastatic drug for breast cancer treatment.

The Miharamycins and Amipurimycin: their Structural Revision and the Total Synthesis of the Latter.

The structural puzzle of amipurimycin, a peptidyl nucleoside antibiotic, is solved by total synthesis and X-ray diffraction analysis, with the originally proposed configurations at C3' and C8' inverted and those at C6', C2'', and C3'' corrected. A similar structural revision of the relevant miharamycins is proposed via chemical transformations and then validated by X-ray diffraction analysis. The miharamycins bear an unusual trans-fused dioxabicyclo[4.3.0]nonane sugar scaffold, which was previously assigned as being in the cis configuration.

Palladium and Lewis-Acid-Catalyzed Intramolecular Aminocyanation of Alkenes: Scope, Mechanism, and Stereoselective Alkene Difunctionalizations.

An expansion of methodologies aimed at the formation of versatile organonitriles, via the intramolecular aminocyanation of unactivated alkenes, is herein reported. Importantly, the need for a rigid tether in these reactions has been obviated. The ease-of-synthesis and viability of substrates bearing flexible backbones has permitted for diastereoselective variants as well. We demonstrated the utility of this methodology with the formation of pyrrolidones, piperidinones, isoindolinones, and sultams. Furthermore, subsequent transformation of these motifs into medicinally relevant molecules is also demonstrated. A double crossover 13C-labeling experiment is consistent with a fully intramolecular cyclization mechanism. Deuterium labeling experiments support a mechanism involving syn-addition across the alkene.

Identification, Functional Characterization, and Seasonal Expression Patterns of Five Sesquiterpene Synthases in Liquidambar formosana.

Terpenoids are a large group of important secondary metabolites that are involved in a variety of physiological mechanisms, and many are used commercially in the cosmetics and pharmaceutical industries. During the past decade, the topic of seasonal variation in terpenoid biosynthesis has garnered increasing attention. Formosan sweet gum ( Liquidambar formosana Hance) is a deciduous tree species. The expression of terpene synthase and accumulation of terpenoids in leaves may vary in different seasons. Here, four sesquiterpene synthases (i.e., LfTPS01, LfTPS02, LfTPS03, and LfTPS04) and a bifunctional mono/sesquiterpene synthase ( LfTPS05) were identified from Formosan sweet gum. The gene expression of LfTPS01, LfTPS02, and LfTPS03 showed seasonal diversification, and, in addition, expression of LfTPS04 and LfTPS05 was induced by methyl jasmonate treatment. The major products LfTPS01, LfTPS02, LfTPS04, and LfTPS05 are hedycaryol, α-selinene, trans-ß-caryophyllene, α-copaene/δ-cadinene, and nerolidol/linalool, respectively. The data indicated that the sesquiterpenoid content in the essential oil of Formosan sweet gum leaves shows seasonal differences that were correlated to the sesquiterpene synthase gene expression.