Differential mechanism between Listeria monocytogenes strains with different virulence contaminating ready-to-eat sausages during the simulated gastrointestinal tract.

Listeria monocytogenes exhibits varying levels of pathogenicity when entering the host through contaminated food. However, little is known regarding the stress response and environmental tolerance mechanism of different virulence strains to host gastrointestinal (GI) stimuli. This study analyzed the differences in the survival and genes of stress responses among two strains of L. monocytogenes 10403S (serotype 1/2a, highly virulent strain) and M7 (serotype 4a, low-virulence strain) during simulated gastrointestinal digestion. The results indicated that L. monocytogenes 10403S showed greater acid and bile salt tolerance than L. monocytogenes M7, with higher survival rates and less cell deformation and cell membrane permeability during the in vitro digestion. KEGG analysis of the transcriptomes indicated that L. monocytogenes 10403S displayed significant activity in amino acid metabolism, such as glutamate and arginine, associated with acid tolerance. Additionally, L. monocytogenes 10403S demonstrated a higher efficacy in promoting activities that preserve bacterial cell membrane integrity and facilitate flagellar protein synthesis. These findings will contribute valuable practical insights into the tolerance distinctions among different virulence strains of L. monocytogenes in the GI environment.

Visible-Light-Promoted C3-Sulfenylindoles with Arylsulfonyl Chlorides via Electron Donor-Acceptor Complex.

In this study, we present an efficient approach for the synthesis of 3-sulfenyl indoles through an electron donor-acceptor (EDA) complex-promoted photoreaction. This sulfenylation reaction leverages sulfonyl chlorides as the sulfur source and employs PPh3 as the reductant without the need for any transition-metal catalyst or photocatalyst. At the same time, the relaxation process of the excited EDA complex was theoretically investigated at the method and multiconfiguration second-order perturbation//complete active space self-consistent field/PCM level of theory, which involves the π bond of indoles injecting an electron to the antibonding orbital of the S-Cl bond in arylsulfonyl chlorides.

Once daily cediranib and weekly paclitaxel to prevent malignant bowel obstruction in at-risk patients with platinum-resistant ovarian cancer (CEBOC): a single-arm, phase II safety trial.

OBJECTIVE: Cytotoxic chemotherapy for ovarian cancer can be augmented by co-administration of vascular endothelial growth factor inhibitors but these are contraindicated in patients with bowel obstruction due to the risk of gastrointestinal perforation. We evaluated the safety and feasibility of paclitaxel plus cediranib to treat patients with platinum-resistant ovarian cancer at risk of malignant bowel obstruction. METHODS: A phase II trial included eligible patients between March 2018 and February 2021, identified by clinical symptoms and radiographic risk factors for malignant bowel obstruction. Cediranib (20 mg/day) was added to paclitaxel (70 mg/m2/week) within 9 weeks of starting paclitaxel if pretreatment bowel symptoms had improved. The primary endpoint was the number of patients treated for ≥5 days with cediranib that were free of grade 3-5 gastrointestinal perforation or fistula. Secondary endpoints were hospitalization for bowel obstruction, grade ≥3 adverse events, treatment compliance assessed by relative dose intensity, objective response, progression-free survival, and overall survival. RESULTS: Thirty patients were recruited. Of these, 12 received paclitaxel alone and 17 received paclitaxel and cediranib in combination. One patient died before starting treatment. No patient developed a grade 3-5 gastrointestinal perforation or fistula (one sided 95% confidence interval (CI) upper limit 0.16). One patient required hospitalization for bowel obstruction but recovered with conservative management. The most common cediranib-related grade ≥3 adverse events were fatigue (3/17), diarrhorea (2/17), and hypomagnesemia (2/17). Relative dose intensity for paclitaxel was 90% (interquartile range (IQR) 85-100%; n=29) and for cediranib 88% (IQR 76-93%; n=17). The objective response in patients who received paclitaxel and cediranib was 65.0% (one complete and 10 partial responses). Median progression-free survival was 6.9 months (95% CI 4.4-11.5 months; n=17) and overall survival was 19.4 months (95% CI 10.1-20.4 months; n=17). Median follow-up was 12.4 months (8.9-not reached; n=17). CONCLUSIONS: The unexpectedly high withdrawal rate during paclitaxel alone, before introducing cediranib, meant we were unable to definitely conclude that paclitaxel plus cediranib did not cause gastrointestinal perforation or fistula. The regimen was however tolerated. TRIAL REGISTRATION NUMBER: EudraCT 2016-004618-93.

Magnetic Seeding of SPIO-BMSCs Into a Biphasic Scaffold Can Promote Tendon-Bone Healing After Rotator Cuff Repair.

BACKGROUND: The tendon-bone interface (TBI) in the rotator cuff has a poor intrinsic capacity for healing, which increases the risk of retear after rotator cuff repair (RCR). However, facilitating regeneration of the TBI still remains a great clinical challenge. Herein, the authors established a novel strategy based on magnetic seeding to enhance the TBI regeneration. HYPOTHESIS: Magnetic seeding bone marrow mesenchymal stem cells labeled with superparamagnetic iron oxide (SPIO-BMSCs) into a biphasic scaffold can promote tendon-bone healing after RCR. STUDY DESIGN: Controlled laboratory study. METHODS: BMSCs were labeled with SPIOs. Prussian blue staining, CCK-8 tests, Western blot, and quantitative reverse transcription polymerase chain reaction (PCR) were used to determine the optimal effect concentration of SPIOs on cell bioactivities and abilities. Then SPIO-BMSCs were magnetically seeded into a biphasic scaffold under a magnetic field. The seeding efficacy was assessed by a scanning electron microscope, and the potential mechanism in chondrogenic differentiation after seeding SPIO-BMSCs into the scaffold was evaluated by Western blot and PCR. Furthermore, the effect of SPIO-BMSC/biphasic scaffold on tendon-bone healing after RCR using a rat model was examined using histological analysis, enzyme-linked immunosorbent assay, and biomechanical evaluation. RESULTS: BMSCs labeled with 100 µg/mL SPIO had no effect on cell bioactivities and the ability of chondrogenic differentiation. SPIO-BMSCs were magnetically seeded into a biphasic scaffold, which offered a high seeding efficacy to enhance chondrogenic differentiation of SPIO-BMSCs via the CDR1as/miR-7/FGF2 pathway for TBI formation in vitro. Furthermore, in vivo application of the biphasic scaffold with magnetically seeded SPIO-BMSCs showed their regenerative potential, indicating that they could significantly accelerate and promote TBI healing with superior biomechanical properties after RCR in a rat rotator cuff tear model. CONCLUSION: Magnetically seeding SPIO-BMSCs into a biphasic scaffold enhanced seeding efficacy to promote cell distribution and condensation. This construct enhanced the chondrogenesis process via the CDR1as/miR-7/FGF2 pathway and further promoted tendon-bone healing after RCR in a rat rotator cuff tear model. CLINICAL RELEVANCE: This study provides an alternative strategy for improving TBI healing after RCR.

Profiling the interplay and coevolution of Microcystis aeruginosa and cyanosiphophage Mic1.

The cyanosiphophage Mic1 specifically infects the bloom-forming Microcystis aeruginosa FACHB 1339 from Lake Chaohu, China. Previous genomic analysis showed that its 92,627 bp double-stranded DNA genome consists of 98 putative open reading frames, 63% of which are of unknown function. Here, we investigated the transcriptome dynamics of Mic1 and its host using RNA sequencing. In the early, middle, and late phases of the 10 h lytic cycle, the Mic1 genes are sequentially expressed and could be further temporally grouped into two distinct clusters in each phase. Notably, six early genes, including gp49 that encodes a TnpB-like transposase, immediately reach the highest transcriptional level in half an hour, representing a pioneer cluster that rapidly regulates and redirects host metabolism toward the phage. An in-depth analysis of the host transcriptomic profile in response to Mic1 infection revealed significant upregulation of a polyketide synthase pathway and a type III-B CRISPR system, accompanied by moderate downregulation of the photosynthesis and key metabolism pathways. The constant increase of phage transcripts and relatively low replacement rate over the host transcripts indicated that Mic1 utilizes a unique strategy to gradually take over a small portion of host metabolism pathways after infection. In addition, genomic analysis of a less-infective Mic1 and a Mic1-resistant host strain further confirmed their dynamic interplay and coevolution via the frequent horizontal gene transfer. These findings provide insights into the mutual benefit and symbiosis of the highly polymorphic cyanobacteria M. aeruginosa and cyanophages. IMPORTANCE: The highly polymorphic Microcystis aeruginosa is one of the predominant bloom-forming cyanobacteria in eutrophic freshwater bodies and is infected by diverse and abundant cyanophages. The presence of a large number of defense systems in M. aeruginosa genome suggests a dynamic interplay and coevolution with the cyanophages. In this study, we investigated the temporal gene expression pattern of Mic1 after infection and the corresponding transcriptional responses of its host. Moreover, the identification of a less-infective Mic1 and a Mic1-resistant host strain provided the evolved genes in the phage-host coevolution during the multiple-generation cultivation in the laboratory. Our findings enrich the knowledge on the interplay and coevolution of M. aeruginosa and its cyanophages and lay the foundation for the future application of cyanophage as a potential eco-friendly and bio-safe agent in controlling the succession of harmful cyanobacterial blooms.

Third-generation sequencing identified a novel complex variant in a patient with rare alpha-thalassemia.

BACKGROUND: Thalassemias represent some of the most common monogenic diseases worldwide and are caused by variations in human hemoglobin genes which disrupt the balance of synthesis between the alpha and beta globin chains. Thalassemia gene detection technology is the gold standard to achieve accurate detection of thalassemia, but in clinical practice, most of the tests are only for common genotypes, which can easily lead to missing or misdiagnosis of rare thalassemia genotypes. CASE PRESENTATION: We present the case of an 18-year-old Chinese female with abnormal values of routine hematological indices who was admitted for genetic screening for thalassemia. Genomic DNA was extracted and used for the genetic assays. Gap polymerase chain reaction and agarose gel electrophoresis were performed to detect HBA gene deletions, while PCR-reverse dot blot hybridization was used to detect point mutations in the HBA and HBB genes. Next-generation sequencing and third-generation sequencing (TGS) were used to identify known and potentially novel genotypes of thalassemia. We identified a novel complex variant αHb WestmeadαHb Westmeadαanti3.7/-α3.7 in a patient with rare alpha-thalassemia. CONCLUSIONS: Our study identified a novel complex variant that expands the thalassemia gene variants spectrum. Meanwhile, the study suggests that TGS could effectively improve the specificity of thalassemia gene detection, and has promising potential for the discovery of novel thalassemia genotypes, which could also improve the accuracy of genetic counseling. Couples who are thalassemia carriers have the opportunity to reduce their risk of having a child with thalassemia.

AgNPs loaded adenine-modified chitosan composite POSS-PEG hybrid hydrogel with enhanced antibacterial and cell proliferation properties for promotion of infected wound healing.

Wound healing is a dynamic and complex process, it's urgent to develop new wound dressings with excellent performance to promote wound healing at the different stages. Here, a novel composite hydrogel dressing composed by silver nanoparticles (AgNPs) impregnated adenine-modified chitosan (CS-A) and octafunctionalized polyhedral oligomeric silsesquioxane (POSS) of benzaldehyde-terminated polyethylene glycol (POSS-PEG-CHO) solution was presented to solve the problem of wound infection. Modification of chitosan with adenine, not only can improve the water solubility of chitosan, but also introduce bioactive substances to promote cell proliferation. CS-A and POSS-PEG-CHO were cross-linked by Schiff-base reaction to form the injectable self-healing hydrogel. On this basis, AgNPs were added into the hydrogel, which endows the hydrogel with better antibacterial activity. Moreover, this kind of hydrogel exhibits excellent cell proliferation properties. Studies demonstrated that the hydrogel can significantly accelerate the closure of infected wounds. The histological analysis and immunofluorescence staining demonstrated that the wounds treated with the composite hydrogel exhibited fewer inflammatory cells, more collagen deposition and angiogenesis, faster regeneration of epithelial tissue. Above all, adenine-modified chitosan composite hydrogel with AgNPs loaded was considered as a dressing material with great application potential for promoting the healing of infected wounds.

Screening for thalassemia carriers among the Han population of childbearing age in Southwestern of China.

Purpose: Thalassemia is a severe hereditary blood disorder that poses a significant threat to human health and leads to mortality and disability. It is one of the most prevalent monogenic diseases worldwide. The aim of this study was to analyze the molecular epidemiological data of individuals of childbearing age from the Han ethnic group with thalassemia in Southwest China and to explore the application of next-generation sequencing (NGS) technology in screening thalassemia carriers. Methods: The participants were Han males and females of childbearing age who sought medical advice at the West China Second University Hospital, Sichuan University from June 2022 to June 2023. We detected α- and ß-thalassemia mutations using full-length capture of the thalassemia genes and NGS technology. Results: In a cohort of 1,093 participants, 130 thalassemia carriers were identified, with an overall detection rate of 11.89% (130/1,093). Among these, 0.91% (10/1,093) had mutations that could not be detected using traditional PCR techniques. The proportions of carriers with α-, ß-, and α-complexed ß-thalassemia gene mutations were 7.68% (84/1,093), 3.93% (43/1,093), and 0.27% (3/1,093), respectively. We identified a novel HBA2 c.166del variant that has not been previously reported. Conclusion: Using NGS technology, we found that the mutation-carrying rate of thalassemia genes was 11.89% in the Han population of childbearing age in Southwest China. Compared with the results of traditional PCR techniques, NGS detected an additional 0.91% (10/1,093) rare genetic variants. NGS technology should be utilized as the primary screening method for thalassemia carriers among Han nationality people of childbearing age in Southwest China.

Structure and assembly of the α-carboxysome in the marine cyanobacterium Prochlorococcus.

Carboxysomes are bacterial microcompartments that encapsulate the enzymes RuBisCO and carbonic anhydrase in a proteinaceous shell to enhance the efficiency of photosynthetic carbon fixation. The self-assembly principles of the intact carboxysome remain elusive. Here we purified α-carboxysomes from Prochlorococcus and examined their intact structures using single-particle cryo-electron microscopy to solve the basic principles of their shell construction and internal RuBisCO organization. The 4.2 Å icosahedral-like shell structure reveals 24 CsoS1 hexamers on each facet and one CsoS4A pentamer at each vertex. RuBisCOs are organized into three concentric layers within the shell, consisting of 72, 32 and up to 4 RuBisCOs at the outer, middle and inner layers, respectively. We uniquely show how full-length and shorter forms of the scaffolding protein CsoS2 bind to the inner surface of the shell via repetitive motifs in the middle and C-terminal regions. Combined with previous reports, we propose a concomitant 'outside-in' assembly principle of α-carboxysomes: the inner surface of the self-assembled shell is reinforced by the middle and C-terminal motifs of the scaffolding protein, while the free N-terminal motifs cluster to recruit RuBisCO in concentric, three-layered spherical arrangements. These new insights into the coordinated assembly of α-carboxysomes may guide the rational design and repurposing of carboxysome structures for improving plant photosynthetic efficiency.

Preserving multi-dimensional information: A hypersphere method for parameter space analysis.

Background: Physiological modelling often involves models described by large numbers of variables and significant volumes of clinical data. Mathematical interpretation of such models frequently necessitates analysing data points in high-dimensional spaces. Existing algorithms for analysing high-dimensional points either lose important dimensionality or do not describe the full position of points. Hence, there is a need for an algorithm which preserves this information. Methods: The most-distant uncovered point (MDUP) hypersphere method is a binary classification approach which defines a collection of equidistant N-dimensional points as the union of hyperspheres. The method iteratively generates hyperspheres at the most distant point in the interest region not yet contained within any hypersphere, until the entire region of interest is defined by the union of all generated hyperspheres. This method is tested on a 7-dimensional space with up to 35.8 million points representing feasible and infeasible spaces of model parameters for a clinically validated cardiovascular system model. Results: For different numbers of input points, the MDUP hypersphere method tends to generate large spheres away from the boundary of feasible and infeasible points, but generates the greatest number of relatively much smaller spheres around the boundary of the region of interest to fill this space. Runtime scales quadratically, in part because the current MDUP implementation is not parallelised. Conclusions: The MDUP hypersphere method can define points in a space of any dimension using only a collection of centre points and associated radii, making the results easily interpretable. It can identify large continuous regions, and in many cases capture the general structure of a region in only a relative few hyperspheres. The MDUP method also shows promise for initialising optimisation algorithm starting conditions within pre-defined feasible regions of model parameter spaces, which could improve model identifiability and the quality of optimisation results.

Genome-wide association study and genomic prediction for resistance to brown planthopper in rice.

The brown planthopper (BPH) is the most destructive insect pest that threatens rice production globally. Developing rice varieties incorporating BPH-resistant genes has proven to be an effective control measure against BPH. In this study, we assessed the resistance of a core collection consisting of 502 rice germplasms by evaluating resistance scores, weight gain rates and honeydew excretions. A total of 117 rice varieties (23.31%) exhibited resistance to BPH. Genome-wide association studies (GWAS) were performed on both the entire panel of 502 rice varieties and its subspecies, and 6 loci were significantly associated with resistance scores (P value < 1.0e-8). Within these loci, we identified eight candidate genes encoding receptor-like protein kinase (RLK), nucleotide-binding and leucine-rich repeat (NB-LRR), or LRR proteins. Two loci had not been detected in previous study and were entirely novel. Furthermore, we evaluated the predictive ability of genomic selection for resistance to BPH. The results revealed that the highest prediction accuracy for BPH resistance reached 0.633. As expected, the prediction accuracy increased progressively with an increasing number of SNPs, and a total of 6.7K SNPs displayed comparable accuracy to 268K SNPs. Among various statistical models tested, the random forest model exhibited superior predictive accuracy. Moreover, increasing the size of training population improved prediction accuracy; however, there was no significant difference in prediction accuracy between a training population size of 737 and 1179. Additionally, when there existed close genetic relatedness between the training and validation populations, higher prediction accuracies were observed compared to scenarios when they were genetically distant. These findings provide valuable resistance candidate genes and germplasm resources and are crucial for the application of genomic selection for breeding durable BPH-resistant rice varieties.

Structure of the intact tail machine of Anabaena myophage A-1(L).

The Myoviridae cyanophage A-1(L) specifically infects the model cyanobacteria Anabaena sp. PCC 7120. Following our recent report on the capsid structure of A-1(L), here we present the high-resolution cryo-EM structure of its intact tail machine including the neck, tail and attached fibers. Besides the dodecameric portal, the neck contains a canonical hexamer connected to a unique pentadecamer that anchors five extended bead-chain-like neck fibers. The 1045-Å-long contractile tail is composed of a helical bundle of tape measure proteins surrounded by a layer of tube proteins and a layer of sheath proteins, ended with a five-component baseplate. The six long and six short tail fibers are folded back pairwise, each with one end anchoring to the baseplate and the distal end pointing to the capsid. Structural analysis combined with biochemical assays further enable us to identify the dual hydrolytic activities of the baseplate hub, in addition to two host receptor binding domains in the tail fibers. Moreover, the structure of the intact A-1(L) also helps us to reannotate its genome. These findings will facilitate the application of A-1(L) as a chassis cyanophage in synthetic biology.

Allosteric regulation of nitrate transporter NRT via the signaling protein PII.

Coordinated carbon and nitrogen metabolism is crucial for bacteria living in the fluctuating environments. Intracellular carbon and nitrogen homeostasis is maintained by a sophisticated network, in which the widespread signaling protein PII acts as a major regulatory hub. In cyanobacteria, PII was proposed to regulate the nitrate uptake by an ABC (ATP-binding cassette)-type nitrate transporter NrtABCD, in which the nucleotide-binding domain of NrtC is fused with a C-terminal regulatory domain (CRD). Here, we solved three cryoelectron microscopy structures of NrtBCD, bound to nitrate, ATP, and PII, respectively. Structural and biochemical analyses enable us to identify the key residues that form a hydrophobic and a hydrophilic cavity along the substrate translocation channel. The core structure of PII, but not the canonical T-loop, binds to NrtC and stabilizes the CRD, making it visible in the complex structure, narrows the substrate translocation channel in NrtB, and ultimately locks NrtBCD at an inhibited inward-facing conformation. Based on these results and previous reports, we propose a putative transport cycle driven by NrtABCD, which is allosterically inhibited by PII in response to the cellular level of 2-oxoglutarate. Our findings provide a distinct regulatory mechanism of ABC transporter via asymmetrically binding to a signaling protein.

Effects of hypo-osmotic stress on osmoregulation, antioxidant response, and energy metabolism in sea cucumber Holothuria moebii under desalination environment.

With global climate changing, hypo-salinity events are increasing in frequency and duration because of continuous rainfall and freshwater inflow, which causes reduced cytosolic osmolarity and cellular stress responses in aquatic animals. Sea cucumbers are considered stenohaline because they lack osmoregulatory organs and are vulnerable to salinity fluctuations. In this study, we performed multiple biochemical assays, de novo transcriptomics, and widely targeted metabolomics to comprehensively explore the osmoregulatory mechanisms and physiological responses of sea cucumber Holothuria moebii to hypo-osmotic stress, which is a representative specie that is frequently exposed to hypo-saline intertidal zones. Our results found that H. moebii contracted their ambulacral feet and oral tentacles, and the coelomic fluid ion concentrations were reduced to be consistent with the environment. The microvilli of intestines and respiratory trees underwent degeneration, and the cytoplasm exhibited swelling and vacuolation. Moreover, the Na+, K+, and Cl- concentrations and Na+/K+-ATPase activity were significantly reduced under hypo-osmotic stress. The decrease in protein kinase A activity and increase in 5'-AMP level indicated a significant inhibition of the cAMP signaling pathway to regulate ion concentrations. And small intracellular organic molecules (amino acids, nucleotides and their derivatives) also play crucial roles in osmoregulation through oxidative deamination of glutamate, nucleotide catabolism, and nucleic acid synthesis. Moreover, lysosomes and peroxisomes removed oxidative damage, whereas antioxidant metabolites, such as N-acetyl amino acids and glutathione, were increased to resist oxidative stress. With prolonged hypo-osmotic stress, glycerophospholipid metabolism was enhanced to maintain membrane stability. Furthermore, acyl-CoA-binding protein activity was significantly inhibited, and only a small amount of acylcarnitine was significantly accumulated, which indicated a disruption in energy metabolism. PPAR signaling pathway and choline content were up-regulated to promote fatty acid metabolism under hypo-osmotic stress. Overall, our results provide new insights into the osmoregulatory mechanisms and physiological responses of sea cucumbers to hypo-osmotic stress.

Bioinformatics and LC-QTOF-MS based discovery of pharmacodynamic and Q-markers of Pitongshu against functional dyspepsia.

ETHNOPHARMACOLOGICAL RELEVANCE: Pitongshu (PTS) is a clinically effective empirical formula for the treatment of FD. The efficacy and safety of PTS have been demonstrated in randomized, controlled, double-blind trials, but there is a lack of understanding of the systematic evaluation of the efficacy of PTS and its material basis. OBJECTIVE: To investigate the efficacy of PTS in Functional dyspepsia (FD) mice and possible Q-markers. METHOD: In this study, we used "irregular feeding + chronic unpredictable chronic stimulation" to establish a mice model of FD with hepatogastric disharmony. The efficacy of PTS was assessed from hair condition, behavioral, pain, gastrointestinal function, and serum 5-HT, GAS, MTL levels in mice by instillation of different doses of PTS. In addition, the composition of drugs in blood was analyzed by LC-QTOF-MS and potential Q-markers were selected by combining network pharmacology, molecular docking and actual content. RESULT: Our study showed that different doses of PTS increased pain threshold and writhing latency, decreased the number of writhings, increased gastric emptying rate and small intestinal propulsion rate, decreased total acidity of gastric contents and gastric acid secretion, and increased serum levels of 5-HT, GAS, and MTL in mice to different degrees. Enrichment analysis showed that PTS may be anti-FD through multiple pathways such as Serotonergic synapse, thyroid hormone signaling pathway, cholinergic synapse, and dopaminergic synapse. In addition, potential active ingredient substances were explored by LC-QTOF-MS combined with bioinformatics. Combined with the actual contentselected six constituents, hesperidin, neohesperidin, naringin, paeoniflorin, magnolol and honokiol, possible as Q-markers. CONCLUSION: PTS may exert its anti-FD effects through multi-component, multi-target and multi-pathway". Constituents, hesperidin, neohesperidin, naringin, paeoniflorin, magnolol and honokiol may be the Q-markers of its anti-FD effects.

Heterogeneous Photocatalytic Ring Expansion of Cyclic Ketones for the Construction of Medium-Sized Lactams.

Construction of medium-sized ring compounds remains challenging in synthetic chemistry. Herein, we describe the synthesis of medium-sized lactams via a photoinduced ring expansion of benzo-fused cyclic ketones using graphitic carbon nitride (g-C3N4) as a photocatalyst. The ring expansion protocol provided an efficient access to 8-10-membered lactams in good yields and displayed good tolerance to a range of functional groups. The mechanism studies revealed that the photochemical reaction proceeds via an intermediary of a nitrogen radical, which is generated through an oxidative hydrogen atom transfer (HAT) process.

Modular catalytic activity of nonribosomal peptide synthetases depends on the dynamic interaction between adenylation and condensation domains.

Nonribosomal peptide synthetases (NRPSs) are large multidomain enzymes for the synthesis of a variety of bioactive peptides in a modular and pipelined fashion. Here, we investigated how the condensation (C) domain and the adenylation (A) domain cooperate with each other for the efficient catalytic activity in microcystin NRPS modules. We solved two crystal structures of the microcystin NRPS modules, representing two different conformations in the NRPS catalytic cycle. Our data reveal that the dynamic interaction between the C and the A domains in these modules is mediated by the conserved "RXGR" motif, and this interaction is important for the adenylation activity. Furthermore, the "RXGR" motif-mediated dynamic interaction and its functional regulation are prevalent in different NRPSs modules possessing both the A and the C domains. This study provides new insights into the catalytic mechanism of NRPSs and their engineering strategy for synthetic peptides with different structures and properties.

The development of aesthetic experience through virtual and augmented reality.

Emerging technological innovations offer the potential for experiential engagement through virtual scenarios, yet the viability of this approach for educational purposes remains significantly underexplored. This study aims to assess the feasibility of Augmented Reality (AR) and Virtual Reality (VR) technologies in providing users with aesthetic experiences when visiting digital exhibitions. A total of 190 students participated in this investigation. The control group visited traditional exhibits at the Palace Museum in Beijing. This group underwent a survey to evaluate their acquired aesthetic experience. In contrast, the experimental group, comprising 96 students, engaged with VR/AR scenarios at the Palace Museum in Beijing. Accordingly, students in the experimental group were also surveyed to evaluate both their aesthetic experiences and, additionally, their user experiences. The survey results unveiled significant distinctions in aesthetic experiences between students in the control and experimental groups. Moreover, there were notable correlations between individual variables related to user and aesthetic experiences within the experimental group. Furthermore, the study revealed disparities in both user and aesthetic experiences among male and female students. The findings have implications for aesthetic education teachers and officials in the context of developing sound strategies for providing aesthetic experiences to their students. This information is also of interest to employees of museums, exhibitions, and other cultural facilities, who are interested in holding or hold digital exhibitions.

Transport mechanism of human bilirubin transporter ABCC2 tuned by the inter-module regulatory domain.

Bilirubin is mainly generated from the breakdown of heme when red blood cells reach the end of their lifespan. Accumulation of bilirubin in human body usually leads to various disorders, including jaundice and liver disease. Bilirubin is conjugated in hepatocytes and excreted to bile duct via the ATP-binding cassette transporter ABCC2, dysfunction of which would lead to Dubin-Johnson syndrome. Here we determine the structures of ABCC2 in the apo, substrate-bound and ATP/ADP-bound forms using the cryo-electron microscopy, exhibiting a full transporter with a regulatory (R) domain inserted between the two half modules. Combined with substrate-stimulated ATPase and transport activity assays, structural analysis enables us to figure out transport cycle of ABCC2 with the R domain adopting various conformations. At the rest state, the R domain binding to the translocation cavity functions as an affinity filter that allows the substrates of high affinity to be transported in priority. Upon substrate binding, the R domain is expelled from the cavity and docks to the lateral of transmembrane domain following ATP hydrolysis. Our findings provide structural insights into a transport mechanism of ABC transporters finely tuned by the R domain.

Discovery of Potential Neonicotinoid Insecticides by an Artificial Intelligence Generative Model and Structure-Based Virtual Screening.

The identification of neonicotinoid insecticides bearing novel scaffolds is of great importance for pesticide discovery. Here, artificial intelligence-based tools and virtual screening strategy were integrated to discover potential leads of neonicotinoid insecticides. A deep generative model was successfully constructed using a recurrent neural network combined with transfer learning. The model evaluation showed that the pretrained model could accurately grasp the SMILES grammar of drug-like molecules and generate potential neonicotinoid compounds after transfer learning. The generated molecules were evaluated by hierarchical virtual screening, hits were subjected to a similarity search, and the most similar structures were purchased for the bioassay. Compounds A2 and A5 displayed 52.5 and 50.3% mortality rates against Aphis craccivora at 100 mg/L, respectively. The docking study indicated that these two compounds have similar binding modes to neonicotinoids, which were verified by further molecular dynamics simulations.