The pathogenic R5L mutation disrupts formation of Tau complexes on the microtubule by altering local N-terminal structure.

The microtubule-associated protein (MAP) Tau is an intrinsically disordered protein (IDP) primarily expressed in axons, where it functions to regulate microtubule dynamics, modulate motor protein motility, and participate in signaling cascades. Tau misregulation and point mutations are linked to neurodegenerative diseases, including progressive supranuclear palsy (PSP), Pick's disease, and Alzheimer's disease. Many disease-associated mutations in Tau occur in the C-terminal microtubule-binding domain of the protein. Effects of C-terminal mutations in Tau have led to the widely accepted disease-state theory that missense mutations in Tau reduce microtubule-binding affinity or increase Tau propensity to aggregate. Here, we investigate the effect of an N-terminal arginine to leucine mutation at position 5 in Tau (R5L), associated with PSP, on Tau-microtubule interactions using an in vitro reconstituted system. Contrary to the canonical disease-state theory, we determine that the R5L mutation does not reduce Tau affinity for the microtubule using total internal reflection fluorescence microscopy. Rather, the R5L mutation decreases the ability of Tau to form larger-order complexes, or Tau patches, at high concentrations of Tau. Using NMR, we show that the R5L mutation results in a local structural change that reduces interactions of the projection domain in the presence of microtubules. Altogether, these results challenge both the current paradigm of how mutations in Tau lead to disease and the role of the projection domain in modulating Tau behavior on the microtubule surface.

Genome-wide DNA N6-methyladenosine in Aeromonas veronii and Helicobacter pylori.

BACKGROUND: DNA N6-methyladenosine (6mA), as an important epigenetic modification, widely exists in bacterial genomes and participates in the regulation of toxicity, antibiotic resistance, and antioxidant. With the continuous development of sequencing technology, more 6mA sites have been identified in bacterial genomes, but few studies have focused on the distribution characteristics of 6mA at the whole-genome level and its association with gene expression and function. RESULTS: This study conducted an in-depth analysis of the 6mA in the genomes of two pathogenic bacteria, Aeromonas veronii and Helicobacter pylori. The results showed that the 6mA was widely distributed in both strains. In A. veronii, 6mA sites were enriched at 3' end of protein-coding genes, exhibiting a certain inhibitory effect on gene expression. Genes with low 6mA density were associated with cell motility. While in H. pylori, 6mA sites were enriched at 5' end of protein-coding genes, potentially enhancing gene expression. Genes with low 6mA density were closely related to defense mechanism. CONCLUSIONS: This study elucidated the distribution characteristics of 6mA in A. veronii and H. pylori, highlighting the effects of 6mA on gene expression and function. These findings provide valuable insights into the epigenetic regulation and functional characteristics of A. veronii and H. pylori.

Photoinduced Pd-Catalyzed Enantioselective Carboamination of Dienes via Aliphatic C-H Bond Elaboration.

Three-component diene carboaminations offer a potent means to access synthetically valuable allylic amines with rapid molecular complexity escalation. The existing literature primarily discloses racemic examples, necessitating the use of halides/pseudohalides as substrates. This paper introduces a photoinduced Pd-catalyzed enantioselective three-component carboamination of aryl-substituted 1,3-dienes, leveraging aliphatic C-H bonds for rapid synthesis. The reaction employs 10 mol % of chiral palladium catalyst and an excess aryl bromide as the HAT reagent. This approach yields diverse chiral allylamines with moderate to excellent enantioselectivities. Notably, it stands as the first instance of an asymmetric three-component diene carboamination reaction, directly utilizing abundant C(sp3)-H bearing partners, such as toluene-type substrates, ethers, amines, esters, and ketones. The protocol exhibits versatility across amines, encompassing aliphatic, aromatic, primary, and secondary derivatives. This method could serve as a versatile platform for stereoselective incorporation of various nucleophiles, dienes, and C(sp3)-H bearing partners.

Local Management for Diabetic Foot Ulcers: A Systematic Review and Network Meta-analysis of Randomized Controlled Trials.

OBJECTIVE: This study evaluated the efficacy of various local management strategies for diabetic foot ulcers (DFUs). BACKGROUND: Several surgical and non-surgical local interventional approaches are available for the treatment of DFUs. The comparative effectiveness of different treatments is unknown, and it remains unclear which approach is the optimal choice for DFUs treatment due to limited direct comparisons. METHODS: We did a systematic review and meta-analysis to select the optimal approach to DFUs local management. We searched Medline, Embase, Web of Science, and ClinicalTrials.gov from inception to September 1, 2023, to identify relevant randomized controlled trials (RCTs). We analysed data by pairwise meta-analyses with a random-effects model. A network meta-analysis using the surface under the cumulative ranking curve (SUCRA) was performed to evaluate the comparative efficacy of different interventional approaches in the early (within 12 wk) and late stages (over 12 wk). RESULTS: 141 RCTs involving 14076 patients and exploring 14 interventional strategies were eligible for inclusion. Most studies (102/141) had at least one risk-of-bias dimension. Good consistency was observed during the analysis. Local pairwise comparisons demonstrated obvious differences in the early-stage healing rate and early- and late-stage healing times, while no significant difference in the late-stage healing rate or adverse events were noted. SUCRAs identified the standard of care (SOC) + decellularized dressing (DD), off-loading (OL), and autogenous graft (AG) as the three most effective interventions within 12 weeks for both healing rate (97%, mean rank: 1.4; 90%, mean rank: 2.3; 80.8%, mean rank: 3.5, respectively) and healing time (96.7%, mean rank: 1.4; 83.0%, mean rank: 3.0; 76.8%, mean rank: 3.8, respectively). After 12 weeks, local drug therapy (LDT) (89.5%, mean rank: 2.4) and OL (82.4%, mean rank: 3.3) ranked the highest for healing rate, and OL (100.0%, mean rank: 1.0) for healing time. With respect to adverse events, moderate and high risks were detected in the SOC + DD (53.7%, mean rank: 7.0) and OL (24.4%, mean rank: 10.8) groups, respectively. CONCLUSION: The findings suggest that OL provided considerable benefits for DFU healing in both the early and late stages, but the high risk of adverse events warrants caution. SOC+DD may be the preferred option in the early stages, with an acceptable risk of adverse events.

Fabrication of Hollow and Hierarchical CuO Micro-Nano Cubes Wrapped by Reduced Graphene Oxide as a Prospective Anode for SIBs.

In this study, hollow and hierarchical CuO micro-nano cubes wrapped by reduced graphene oxide (H-CuO MNCs@rGO) were designed and successfully fabricated via a novel three-step wet-chemical method. Benefiting from its unique hollow and hierarchical micro-nano structures, H-CuO MNCs@rGO exhibited significantly enhanced electrochemical Na+ storage performance when utilized as anode material for sodium-ion batteries (SIBs). Specifically, H-CuO MNCs@rGO demonstrated a specific capacity of 380.9 mAh g-1 in the initial reversible cycle and a capacity retention of 218.9 mAh g-1 after 150 cycles at a current density of 300 mA g-1. Furthermore, through the dominant pseudocapacitive behavior, an optimized rate capability of 221.2 mAh g-1 at 800 mA g-1 can be obtained for H-CuO MNCs@rGO. The comprehensive Na+ storage properties of H-CuO MNCs@rGO obviously exceeded those of hollow CuO cubes (H-CuO MNCs) and bulk CuO anodes. Such enhanced Na+ storage performances of H-CuO MNCs@rGO can be attributed to its reasonable hollow and hierarchical micro-nano structures, which provide abundant redox active sites, shorten Na+ migration pathway, buffer volume expansion, and improve electronic/ionic conductivity during sodiation/desodiation process. Our strategy provides a facile and innovative approach for the design of CuO with rational micro-nano structure as a high-performance anode for SIBs, which would also be a guiding way for tailoring transition metal oxides in other scalable and functional applications.

Microstructural and functional alterations of the ventral pallidum are associated with levodopa-induced dyskinesia in Parkinson's disease.

BACKGROUND AND PURPOSE: The ventral pallidum (VP) regulates involuntary movements, but it is unclear whether the VP regulates the abnormal involuntary movements in Parkinson's disease (PD) patients who have levodopa-induced dyskinesia (LID). To further understand the role of the VP in PD patients with LID (PD-LID), we explored the structural and functional characteristics of the VP in such patients using multimodal magnetic resonance imaging (MRI). METHODS: Thirty-one PD-LID patients, 39 PD patients without LID (PD-nLID), and 28 healthy controls (HCs) underwent T1-weighted MRI, quantitative susceptibility mapping, multi-shell diffusion MRI, and resting-state functional MRI (rs-fMRI). Different measures characterizing the VP were obtained using a region-of-interest-based approach. RESULTS: The left VP in the PD-LID group showed significantly higher intracellular volume fraction (ICVF) and isotropic volume fraction (IsoVF) compared with the PD-nLID and HC groups. Rs-MRI revealed that, compared with the PD-nLID group, the PD-LID group in the medication 'off' state had higher functional connectivity (FC) between the left VP and the left anterior caudate, left middle frontal gyrus and left precentral gyrus, as well as between the right VP and the right posterior ventral putamen and right mediodorsal thalamus. In addition, the ICVF values of the left VP, the FC between the left VP and the left anterior caudate and left middle frontal gyrus were positively correlated with Unified Dyskinesia Rating Scale scores. CONCLUSION: Our multimodal imaging findings show that the microstructural changes of the VP (i.e., the higher ICVF and IsoVF) and the functional change in the ventral striatum-VP-mediodorsal thalamus-cortex network may be associated with pathophysiological mechanisms of PD-LID.

Rational modification of melatonin for broad-spectrum antifungal agents discovery.

Natural products, known for their environmental safety, are regarded as a significant basis for the modification and advancement of fungicides. Melatonin, as a low-cost natural indole, exhibits diverse biological functions, including antifungal activity. However, its potential as an antifungal agent has not been fully explored. In this study, a series of melatonin derivatives targeting the mitogen-activated protein kinase (Mps1) protein of fungal pathogens were synthesized based on properties of melatonin, among which the trifluoromethyl-substituted derivative Mt-23 exhibited antifungal activity against seven plant pathogenic fungi, and effectively reduced the severity of crop diseases, including rice blast, Fusarium head blight of wheat and gray mold of tomato. In particular, its EC50 (5.4 µM) against the rice blast fungus Magnaporthe oryzae is only one-fourth that of isoprothiolane (22 µM), a commercial fungicide. Comparative analyzes revealed that Mt-23 simultaneously targets the conserved protein kinase Mps1 and lipid protein Cap20. Surface plasmon resonance assays showed that Mt-23 directly binds to Mps1 and Cap20. In this study, we provide a strategy for developing antifungal agents by modifying melatonin, and the resultant melatonin derivative Mt-23 is a commercially valuable, eco-friendly and broad-spectrum antifungal agent to combat crop disease.

The effects of pks+ Escherichia coli and bile acid in colorectal tumorigenesis among people with cholelithiasis or cholecystectomy.

BACKGROUND AND AIM: Patients with cholelithiasis (CL) or cholecystectomy (CE) would have more chances of getting colorectal adenoma (CRA) or cancer (CRC). We aimed to figure out the effects of gut microbiota and bile acid on colorectal neoplasm in CL and CE patients. METHODS: This was a retrospective observational study that recruited 514 volunteers, including 199 people with normal gallbladders (normal), 152 CL, and 163 CE patients. Discovery cohort was established to explore the difference in gut microbiota through 16S rRNA and metagenomics sequencing. Validation cohort aimed to verify the results through quantitative polymerase chain reaction (qPCR). RESULTS: Significant enrichment of Escherichia coli was found in patients with cholelithiasis or cholecystectomy both in the discovery cohort (16S rRNA sequencing, PNormal-CL = 0.013, PNormal-CE = 0.042; metagenomics sequencing, PNormal-CE = 0.026) and validation cohort (PNormal-CL < 0.0001, PNormal-CE < 0.0001). Pks+ E. coli was found enriched in CL and CE patients through qPCR (in discovery cohort: PNormal-CE = 0.018; in validation cohort: PNormal-CL < 0.0001, PNormal-CE < 0.0001). The differences in bile acid metabolism were found both through Tax4Fun analysis of 16S rRNA sequencing (Ko00120, primary bile acid biosynthesis, PNormal-CE = 0.014; Ko00121, secondary bile acid biosynthesis, PNormal-CE = 0.010) and through metagenomics sequencing (map 00121, PNormal-CE = 0.026). The elevation of serum total bile acid of CE patients was also found in validation cohort (PNormal-CE < 0.0001). The level of serum total bile acid was associated with the relative abundance of pks+ E. coli (r = 0.1895, P = 0.0012). CONCLUSIONS: E. coli, especially pks+ species, was enriched in CL and CE patients. Pks+ E. coli and bile acid metabolism were found associated with CRA and CRC in people after cholecystectomy.

Development of PEG-mediated genetic transformation and gene editing system of Bryum argenteum as an abiotic stress tolerance model plant.

KEY MESSAGE: To establish a sterile culture system and protoplast regeneration system for Bryum argenteum, and to establish and apply CRISPR/Cas9 system in Bryum argenteum. Bryum argenteum is a fascinating, cosmopolitan, and versatile moss species that thrives in various disturbed environments. Because of its comprehensive tolerance to the desiccation, high UV and extreme temperatures, it is emerging as a model moss for studying the molecular mechanisms underlying plant responses to abiotic stresses. However, the lack of basic tools such as gene transformation and targeted genome modification has hindered the understanding of the molecular mechanisms underlying the survival of B. argenteum in different environments. Here, we reported the protonema of B. argenteum can survive up to 95.4% water loss. In addition, the genome size of B. argenteum is approximately 313 Mb by kmer analysis, which is smaller than the previously reported 700 Mb. We also developed a simple method for protonema induction and an efficient protoplast isolation and regeneration protocol for B. argenteum. Furthermore, we established a PEG-mediated protoplast transient transfection and stable transformation system for B. argenteum. Two homologues of ABI3(ABA-INSENSITIVE 3) gene were successfully cloned from B. argenteum. To further investigate the function of the ABI3 gene in B. argenteum, we used the CRISPR/Cas9 genetic editing system to target the BaABI3A and BaABI3B gene in B. argenteum protoplasts. This resulted in mutagenesis at the target in about 2-5% of the regenerated plants. The isolated abi3a and abi3b mutants exhibited increased sensitivity to desiccation, suggesting that BaABI3A and BaABI3B play redundant roles in desiccation stress. Overall, our results provide a rapid and simple approach for molecular genetics in B. argenteum. This study contributes to a better understanding of the molecular mechanisms of plant adaptation to extreme environmental.

Annotation Query (AnnoQ): an integrated and interactive platform for large-scale genetic variant annotation.

The Annotation Query (AnnoQ) (http://annoq.org/) is designed to provide comprehensive and up-to-date functional annotations for human genetic variants. The system is supported by an annotation database with ∼39 million human variants from the Haplotype Reference Consortium (HRC) pre-annotated with sequence feature annotations by WGSA and functional annotations to Gene Ontology (GO) and pathways in PANTHER. The database operates on an optimized Elasticsearch framework to support real-time complex searches. This implementation enables users to annotate data with the most up-to-date functional annotations via simple queries instead of setting up individual tools. A web interface allows users to interactively browse the annotations, annotate variants and search variant data. Its easy-to-use interface and search capabilities are well-suited for scientists with fewer bioinformatics skills such as bench scientists and statisticians. AnnoQ also has an API for users to access and annotate the data programmatically. Packages for programming languages, such as the R package, are available for users to embed the annotation queries in their scripts. AnnoQ serves researchers with a wide range of backgrounds and research interests as an integrated annotation platform.

PACSIN1 promotes immunosuppression in gastric cancer by degrading MHC-I.

Gastric cancer (GC) is a common gastrointestinal system malignancy. PACSIN1 functions as an oncogene in various cancers. This study aims to investigate the potential of PACSIN1 as a target in GC treatment. Gene expression is determined by RT-qPCR, immunofluorescence staining, and immunohistochemistry assay. FISH is performed to determine the colocalization of PACSIN1 and the major histocompatibility complex (MHC-I). Cytokine release and cell functions are analyzed by flow cytometry. In vivo assays are also conducted. Histological analysis is performed using H&E staining. The results show that PACSIN1 is overexpressed in GC patients, especially in those with immunologically-cold tumors. A high level of PACSIN1 is associated with poor prognosis. PACSIN1 deficiency inhibits autophagy but increases antigen presentation in GC cells. Moreover, PACSIN1 deficiency inhibits the lysosomal fusion and selective autophagy of MHC-I, increases CD8 + T-cell infiltration, and suppresses tumor growth and liver metastasis in vivo. Additionally, PACSIN1 knockout enhances the chemosensitivity of cells to immune checkpoint blockade. In summary, PACSIN1 mediates lysosomal fusion and selective autophagy of MHC-I and suppresses antigen presentation and CD8 + T-cell infiltration, thus inhibiting antitumor immunity in GC.

Societal shifts due to COVID-19 reveal large-scale complexities and feedbacks between atmospheric chemistry and climate change.

The COVID-19 global pandemic and associated government lockdowns dramatically altered human activity, providing a window into how changes in individual behavior, enacted en masse, impact atmospheric composition. The resulting reductions in anthropogenic activity represent an unprecedented event that yields a glimpse into a future where emissions to the atmosphere are reduced. Furthermore, the abrupt reduction in emissions during the lockdown periods led to clearly observable changes in atmospheric composition, which provide direct insight into feedbacks between the Earth system and human activity. While air pollutants and greenhouse gases share many common anthropogenic sources, there is a sharp difference in the response of their atmospheric concentrations to COVID-19 emissions changes, due in large part to their different lifetimes. Here, we discuss several key takeaways from modeling and observational studies. First, despite dramatic declines in mobility and associated vehicular emissions, the atmospheric growth rates of greenhouse gases were not slowed, in part due to decreased ocean uptake of CO2 and a likely increase in CH4 lifetime from reduced NO x emissions. Second, the response of O3 to decreased NO x emissions showed significant spatial and temporal variability, due to differing chemical regimes around the world. Finally, the overall response of atmospheric composition to emissions changes is heavily modulated by factors including carbon-cycle feedbacks to CH4 and CO2, background pollutant levels, the timing and location of emissions changes, and climate feedbacks on air quality, such as wildfires and the ozone climate penalty.

Uncertainty-based saltwater intrusion prediction using integrated Bayesian machine learning modeling (IBMLM) in a deep aquifer.

Data-driven machine learning approaches are promising to substitute physically based groundwater numerical models and capture input-output relationships for reducing computational burden. But the performance and reliability are strongly influenced by different sources of uncertainty. Conventional researches generally rely on a stand-alone machine learning surrogate approach and fail to account for errors in model outputs resulting from structural deficiencies. To overcome this issue, this study proposes a flexible integrated Bayesian machine learning modeling (IBMLM) method to explicitly quantify uncertainties originating from structures and parameters of machine learning surrogate models. An Expectation-Maximization (EM) algorithm is combined with Bayesian model averaging (BMA) to find out maximum likelihood and construct posterior predictive distribution. Three machine learning approaches representing different model complexity are incorporated in the framework, including artificial neural network (ANN), support vector machine (SVM) and random forest (RF). The proposed IBMLM method is demonstrated in a field-scale real-world "1500-foot" sand aquifer, Baton Rouge, USA, where overexploitation caused serious saltwater intrusion (SWI) issues. This study adds to the understanding of how chloride concentration transport responds to multi-dimensional extraction-injection remediation strategies in a sophisticated saltwater intrusion model. Results show that most IBMLM exhibit r values above 0.98 and NSE values above 0.93, both slightly higher than individual machine learning, confirming that the IBMLM is well established to provide better model predictions than individual machine learning models, while maintaining the advantage of high computing efficiency. The IBMLM is found useful to predict saltwater intrusion without running the physically based numerical simulation model. We conclude that an explicit consideration of machine learning model structure uncertainty along with parameters improves accuracy and reliability of predictions, and also corrects uncertainty bounds. The applicability of the IBMLM framework can be extended in regions where a physical hydrogeologic model is difficult to build due to lack of subsurface information.

Beneficial In Vitro Effects of Polysaccharide and Non-Polysaccharide Components of Dendrobium huoshanense on Gut Microbiota of Rats with Type 1 Diabetes as Opposed to Metformin.

The extract of Dendrobium huoshanense, a traditional Chinese medicinal and food homologous plant belonging to the family Orchidaceae, was previously reported to have hypoglycemic and antioxidant effects. In this study, the direct effects of polysaccharide (DHP) and non-polysaccharide (NDHP) components of D. huoshanense, as well as its water extract (DHWE) were compared with that of metformin (an antidiabetic drug) on the gut microbiota (collected from fecal flora) of rats with streptozotocin-induced type 1 diabetes (T1D) using an in vitro fermentation method. The results showed that DHWE, DHP, and NDHP reduced pH and increased bacterial proliferation and short-chain fatty acid (SCFA) content in fermentation broth. DHWE, DHP, NDHP and metformin promoted the production of acetic and propionic acid, acetic acid, propionic acid and butyric acid, and propionic acid, respectively. DHWE, DHP, and NDHP reduced the abundance of Proteobacteria (subdominant pathogenic bacteria) and increased the abundance of Firmicutes (dominant beneficial gut bacteria). NDHP also reduced the abundance of Bacteroidetes (beneficial and conditional pathogenic). Metformin increased the abundance of Proteobacteria and reduced the abundance of Firmicutes and Bacteroidetes. At the genus level, NDHP promoted the proliferation of Megamonas and Megasphaera and decreased harmful bacteria (e.g., Klebsiella), and DHP increased the abundance of Prevotellaceae (opportunistic and usually harmless). By contrast, metformin increased the abundance of harmful bacteria (e.g., Citrobacter) and reduced the abundance of beneficial bacteria (e.g., Oscillospira). Our study indicates that DHWE, DHP, and NDHP are potentially more beneficial than metformin on the gut microbiota of T1D rats in vitro.

Effects of predictive nursing interventions on pressure ulcer in older bedridden patients: A meta-analysis.

To evaluate the effect of predictive nursing interventions on pressure ulcers in elderly bedridden patients by meta-analysis. Applied computer searches of PubMed, Embase, Google Scholar, Cochrane Library, China National Knowledge Infrastructure and Wanfang databases for randomised controlled trials (RCTs) on the effect of predictive nursing in preventing pressure ulcers in elderly bedridden patients from the database inception to November 2023. Two researchers independently screened the literature, extracted data and performed quality assessment based on inclusion and exclusion criteria. Stata 17.0 software was utilised for data analysis. Eighteen RCTs involving 6504 patients were finally included. The analysis revealed the implementation of predictive nursing interventions had a significant advantage in reducing the incidence of pressure ulcers in elderly bedridden patients compared with conventional nursing (odds ratio [OR] = 0.20, 95% confidence interval [CI]: 0.15-0.28, p < 0.001), while the patients' satisfaction with nursing care was higher (OR = 3.70, 95% CI: 2.99-4.57, p < 0.001). This study shows that the implementation of a predictive nursing interventions for elderly bedridden patients can effectively reduce the occurrence of pressure ulcers and significantly improve patients' satisfaction with nursing care, which is worthy of clinical promotion and application.

Effect of quality nursing intervention on wound healing in patients with burns: A meta-analysis.

This meta-analysis aimed to explore the effects of quality nursing intervention on wound healing in patients with burns. A computerised search was conducted for randomised controlled trials (RCTs) on the effect of quality nursing intervention on wound healing in patients with burns in the PubMed, Embase, Google Scholar, Cochrane Library, China National Knowledge Infrastructure and Wanfang databases from the date of database inception to November 2023. Two researchers independently screened the literature, extracted data and performed quality assessment based on the inclusion and exclusion criteria. Stata 17.0 software was used for the data analysis. Twenty-nine RCTs involving 2637 patients with burns were included. The meta-analysis revealed that compared with conventional nursing, the implementation of quality nursing intervention in patients with burns significantly shortened the wound healing time (standardised mean difference [SMD] = -2.93, 95% confidence interval [CI]: -3.44 to -2.42, p < 0.001). The incidence of wound infections (odds ratio [OR] = 0.14, 95% CI: 0.07-0.27, p < 0.001) and complications (OR = 0.16, 95% CI: 0.11-0.23, p < 0.001) was also reduced significantly. This meta-analysis shows that applying quality nursing interventions in patients with burns can significantly shorten the wound healing time and reduce the incidence of wound infection and complications, thus promoting early patient recovery.

Enantio- and Diastereodivergent N-Heterocyclic Carbene/Nickel Dual-Catalyzed Umpolung Propargylic Substitutions of Enals.

The creation of full stereoisomers of an organic compound comprising multiple contiguous stereocenters with simultaneous control over both relative and absolute configurations remains a significant challenge in synthetic chemistry. Using a cooperative catalysis strategy, we established an N-heterocyclic carbene/nickel-catalyzed enantio- and diastereodivergent propargylation reaction to access 3,3'-disubstituted oxindoles, enabling the incorporation of internal alkyne functionality and the introduction of a single quaternary or vicinal quaternary/tertiary stereogenic center. By selecting the appropriate combination of catalyst chirality, all four potential stereoisomers of α-quaternary propargylated oxindoles were synthesized in a predictable and precise way with remarkable yields, diastereoselectivities, and enantioselectivities from identical starting materials. The synthetic utility of this method was demonstrated in the concise asymmetric total synthesis of (-)-debromoflustramine B and (-)-C(ß-Me)-debromoflustramine B.

Diastereodivergent Desymmetric Annulation to Access Spirooxindoles: Chemical Probes for Mitosis.

Spirooxindoles have emerged as promising architectures for engineering biologically active compounds. The diastereodivergent construction of unique scaffolds of this type with full control of continuous chiral centers including an all-carbon quaternary stereogenic center is yet to be developed. Here, we report an unprecedented diastereodivergent desymmetric [3 + 3] annulation of oxabicyclic alkenes with enals enabled by N-heterocyclic carbene (NHC)/Rh cooperative catalysis, leading to a series of enantiomerically enriched spirooxindole lactones with excellent enantioselectivities (up to >99% ee) and diastereoselectivities (up to >95:5 dr). The combined catalyst system comprises a rhodium complex that controls the configuration at the electrophilic carbon and an NHC catalyst that controls the configuration at the nucleophilic oxindole-containing carbon; thus, four stereoisomers of the spirooxindole products can be readily obtained simply by switching the configurations of the two chiral catalysts. Transformations of the chiral spirooxindoles delivered synthetically useful compounds. Importantly, those chiral spirooxindoles arrested mammalian cells in mitosis and exhibited potent antiproliferative activities against HeLa cells. Significantly, both absolute and relative configurations exert prominent effects on the bioactivities, underscoring great importance of catalytic asymmetric diastereodivergent synthesis beyond creating useful tools for the exploration of structure-activity relationships.

Atom Transfer Radical Coupling Enables Highly Enantioselective Carbo-Oxygenation of Alkenes with Hydrocarbons.

The selective functionalization of C(sp3)-H bonds has emerged as a transformative approach for streamlining synthetic routes, offering remarkable efficiency in the preparation and modification of complex organic molecules. However, the direct enantioselective transformation of hydrocarbons to medicinally valuable chiral molecules remains a significant challenge that has yet to be addressed. In this study, we adopt an atom transfer radical coupling (ATRC) strategy to achieve the asymmetric functionalization of C(sp3)-H bonds in hydrocarbons. This approach involves intermolecular H atom transfer (HAT) between a hydrocarbon and an alkoxy radical, leading to the formation of a carbon-centered radical. The resulting radical adds to alkenes, generating a new radical species that is intercepted by a chiral copper-mediated C-O bond coupling. By employing this method, we can directly access valuable chiral lactones bearing a quaternary stereocenter with high efficiency and excellent enantioselectivity. Importantly, ATRC exhibits great potential as a versatile platform for achieving stereoselective transformations of hydrocarbons.

Local Regulator AcrR Regulates Persister Formation by Repression of AcrAB Efflux Pump during Exponential Growth in Aeromonas veronii.

Bacterial persisters refer to a small fraction of dormant variants that survive treatment with high concentrations of antibiotics. Increasing research indicates that multidrug efflux pumps play a major role in persister formation in many Gram-negative organisms. In the present study, the roles of the repressor of the AcrAB efflux pump, AcrR, in the regulation of the activity and function of the efflux, as well as in the production of persisters, were investigated in the pathogen Aeromonas veronii, which causes huge economic losses in the aquatic industry and threatens human health. We observed that exclusively in exponential-phase cells, not in stationary-phase cells, the deletion of the acrR gene significantly (P < 0.05) promoted the expression of the acrA and acrB genes and reduced the intracellular accumulation of the efflux substrate Hoechst 33342. Moreover, overexpression of acrR triggered decreased transcription of the promoter of the acrAB operon. The persister assay indicated that the loss of the AcrAB pump decreased the formation of persisters under challenge with all tested antibiotic types of chloramphenicol, fluoroquinolone, tetracycline, and ß-lactam, while deletion of acrR caused an exponential-phase-specific increase in persister formation against chloramphenicol, tetracycline, and ß-lactam. Our results provide molecular insights into the mechanism of bacterial persistence by demonstrating for the first time that the local regulator AcrR is involved in the modulation of persister formation in A. veronii through its repressive activity on the function of the AcrAB efflux pump during the exponential growth period.