Air-coupled ultrasonic transducer based on lead-free piezoceramics prepared by digital light processing 3D printing.

Piezoelectric composite ceramics, as the key components of ultrasonic transducers, have their vibration modes, electromechanical coupling performance, and acoustic impedance closely related to the volume fraction of ceramics. This study employed a novel digital light processing 3D printing technique (DLP) to fabricate 0.5Ba(Zr0.2Ti0.8)O3-0.5(Ba0.7Ca0.3)TiO3 (BCZT)-based 1-3 piezoelectric composite ceramics with different ceramic volume fractions (15.6 %, 23.5 %, 36.2 %, 48.4 %, 59.5 %). It demonstrates the suitability of the DLP process for the fabrication of 1-3 piezoelectric composite ceramics and investigates the influence of ceramic volume fraction on the performance of these ceramics. When the piezoelectric ceramic volume fraction was 59.5 %, the piezoelectric coefficient effective d33 of the 1-3 piezoelectric composite device reached 315 pC/N, demonstrating excellent piezoelectric performance. The acoustic impedance Z was 16.3 MRayl, and the thickness electromechanical coupling coefficient kt was 0.55, indicating high energy conversion efficiency. The air-coupled ultrasonic transducer prepared from the 1-3 piezoelectric composite ceramics with a ceramic volume fraction of 59.5 % exhibited a round-trip insertion loss (IL) of -70.32 dB and a -6 dB bandwidth (BW-6dB) of 7.42 %. This work provides a more convenient and new method for the preparation of lead-free piezoelectric ceramic ultrasonic transducers.

LncRNA MEG9 Promotes Inflammation and Liver Fibrosis Through S100A9 in Biliary Atresia.

BACKGROUND: The pathogenesis of biliary atresia (BA) remains elusive. We aimed to investigate the role of long noncoding RNA (lncRNA) MEG9 in BA. METHODS: LncRNA microarray was conducted to identify differentially expressed lncRNAs in three BA and three para-hepatoblastoma liver tissues. RT-qPCR validated the results. Human intrahepatic bile duct epithelial cells (HIBECs) were stably transfected with lncRNA MEG9 knockdown/overexpression to investigate its cellular localization and function. RNA sequencing (RNA-seq), differentially expressed genes (DEGs) analysis and gene set enrichment analysis were applied to MEG9-overexpresed HIBECs. RNA pull-down and mass spectrometry explored the interacting protein of MEG9, while clinical information was reviewed. RESULTS: 436 differentially expressed lncRNAs were identified, with MEG9 highly upregulated in BA. RT-qPCR further confirmed MEG9's overexpression in BA and diagnostic potential (AUC = 0.9691). MEG9 was predominantly located in the nucleus and significantly promoted cell proliferation and migration. RNA-seq revealed inflammation- and extracellular matrix-related pathways enriched in MEG9-overexpressing HIBECs, with upregulated cytokine genes like CXCL6 and IL6. MMP-7 and collagen I were also overexpressed. Furthermore, 38 proteins were identified to specifically interact with MEG9, and S100A9 was highly expressed in cell models. S100A9 was also significantly upregulated in BA liver tissue and correlated with MEG9 expression (r = 0.313, p < 0.05), albumin level (r = -0.349, p < 0.05), and platelet level (r = -0.324, p < 0.05). CONCLUSION: MEG9 influences cholangiocyte proliferation, migration, and cytokine production, potentially regulating BA inflammation and fibrosis via S100A9 interaction.

Structurally Diverse Secondary Metabolites from a Deep-sea Derived Cladosporium sp. SCSIO 41318 and Their Biological Evaluation.

Four new compounds, including one drimane sesquiterpene lactone (1), one isocoumarin (2), one coumarin (3), and a new natural product (4), as well as fourteen known compounds were obtained from a deep-sea derived Cladosporium sp. SCSIO 41318. The structures of the new compounds were determined using extensive NMR and HRESIMS spectroscopic analysis, electronic circular dichroism calculations, and single-crystal X-ray diffraction measurements. Biological assays showed that compounds (1, 6, 7, 9-12, 14, 15, 17, 18) exhibited varying degrees of antimicrobial activity against the tested human pathogenic bacteria and plant pathogenic fungi. Besides, penicitrinone A (11) and penicitrinol A (12) displayed weak antitumor activities against the 22Rv1 cell line.

Refined composite multiscale slope entropy and its application in rolling bearing fault diagnosis.

Rolling bearing is the key component of rotating machinery, and its vibration signal usually exhibits nonlinear and nonstationary characteristics when failure occurs. Multiscale permutation entropy (MPE) is an effective nonlinear dynamics analysis tool, which has been successfully applied to rolling bearing fault diagnosis in recent years. However, MPE ignores the deep amplitude information when measuring the complexity of the time series and the original multiscale coarse-graining is insufficient, which requires further research and improvement. In order to protect the integrity of information structure, a novel nonlinear dynamic analysis method termed refined composite multiscale slope entropy (RCMSlE) is proposed in this paper, which introduced the concept of refined composite to further boost the performance of MPE in nonlinear dynamical complexity analysis. Furthermore, RCMSlE utilizes a novel symbolic representation that takes full account of mode and amplitude information, which overcomes the weaknesses in describing the complexity and regularity of bearing signals. Based on this, a GWO-SVM multi-classifier is introduced to fulfill mode recognition, and then a new intelligent fault diagnosis method for rolling bearing based on RCMSlE and GWO-SVM is proposed. The experimental results show that the proposed method can not only accurately identify different fault types and degrees of rolling bearing, but also has a short computation time and better performance than other comparative methods.

Borate bioactive glass enhances 3D bioprinting precision and biocompatibility on a sodium alginate platform via Ca2+ controlled self-solidification.

Sodium alginate (SA) has gained widespread acclaim as a carrier medium for three-dimensional (3D) bioprinting of cells and a diverse array of bioactive substances, attributed to its remarkable biocompatibility and affordability. The conventional approach for fabricating alginate-based tissue engineering constructs entails a post-treatment phase employing a calcium ion solution. However, this method proves ineffectual in addressing the predicament of low precision during the 3D printing procedure and is unable to prevent issues such as non-uniform alginate gelation and substantial distortions. In this study, we introduced borate bioactive glass (BBG) into the SA matrix, capitalizing on the calcium ions released from the degradation of BBG to incite the cross-linking reaction within SA, resulting in the formation of BBG-SA hydrogels. Building upon this fundamental concept, it unveiled that BBG-SA hydrogels greatly enhance the precision of SA in extrusion-based 3D printing and significantly reduce volumetric contraction shrinkage post-printing, while also displaying certain adhesive properties and electrical conductivity. Furthermore, in vitro cellular experiments have unequivocally established the excellent biocompatibility of BBG-SA hydrogel and its capacity to actively stimulate osteogenic differentiation. Consequently, BBG-SA hydrogel emerges as a promising platform for 3D bioprinting, laying the foundation for the development of flexible, biocompatible electronic devices.

Role of water in the formation of low-temperature coal oxidation products: An experimental isotope tracer study.

The interaction between water and coal is of great significance to the study of coal spontaneous combustion (CSC) in humid mine environments. Here, using an isotope tracing method to trace oxygen atoms in water, the role of water in the formation of CO, CO2, product water, and other substances during CSC was quantitatively studied through thermogravimetry coupled with mass spectrometry (TG-MS). In addition, Pearson correlation analysis was used to evaluate the relationships between the amounts of CO and CO2 generated during CSC and the different functional groups. The migration and transformation paths of oxygen atoms in water were analyzed. The results showed that water participated in the CSC reaction to produce CO, CO2, and product water in a dynamic, temperature-dependent process. CO and CO2 were formed through different reaction paths involving reactions between water and aldehyde and carboxyl groups. Further, carboxyl groups were also involved in the reaction with coal to form product water. The results from this study are helpful for understanding the influence of water in each stage of CSC, thereby aiding in its prevention and control.

Transition Layer Assisted Synthesis of Defect Free Amine-Phosphine Based InP QDs.

Environmentally friendly InP-based quantum dots (QDs) are promising for light-emitting diodes (LEDs) and display applications. So far, the synthesis of highly emitting InP-based QDs via safe and economically viable amine-phosphine remains a challenge. Herein, we report the synthesis of amine-phosphine based InP/ZnSe/ZnS QDs by introducing an alloyed oxidation-free In-ZnSe transition layer (TL) at the core-shell interface. The TL not only has the essential function of preventing oxidation of the core and relieving interfacial strain but also results in oriented epitaxial growth of shell. The alloyed TL significantly mitigates the nonradiative recombination at core-shell interfacial trap states, thereby boosting the photoluminescence (PL) efficiency of the QDs up to 98%. Also, the Auger recombination is suppressed, extending the biexciton lifetime from 60 to 100 ps. The electroluminescence device based on the InP-based QDs shows a high external quantum efficiency over 10%, further demonstrating high quality QDs synthesized by this process.

Taraxasterol exhibits dual biological effects on anti-aging and anti-cancer in lung cells.

As numerous countries around the world have entered an aging society currently, understanding the impact of aging on human health becomes critically important. Notably, aging is associated with increased prevalence of age-related diseases, with the lungs being particularly susceptible. Aging contributes to a decline in lung function, including respiratory disorders, inflammation, and oxidative stress. Therefore, it is a very important to identify and develop active substances that can mitigate lung cell aging. In current study, we evaluated the impact of Taraxasterol on lung cell senescence, showing that Taraxasterol can alleviate lung cell senescence, as evidenced by reductions in senescence-related marker molecules, including p16 and p21. Additionally, Taraxasterol was found to ameliorate inflammation and oxidative stress in lung cells. Further mechanistic studies indicated that Taraxasterol exerts anti-aging effects through the PGC1α/NRF1 signaling pathway in lung cell models. Since aging is also closely related to lung cancer, we also explored the potential anti-tumor effect of taraxasterol. Utilizing non-small cell lung cancer cells (NSCLC) as a model, we systematically study the anti-tumor effect of Taraxasterol both in vivo and in vitro. Our findings suggest that Taraxasterol exhibited anti-cancer effect through EGFR-mediated signaling. Taken together, Taraxasterol shows dual biological activities, offering promising anti-aging and anti-lung cancer benefits.

The 6-hour lactate clearance rate in predicting 30-day mortality in cardiogenic shock.

Background: Early evaluation of prognosis in cardiogenic shock (CS) is crucial for tailored treatment selection. Both lactate clearance and lactate levels are considered useful prognostic biomarkers in patients with CS. However, there is yet no literature comparing the 6-hour lactate clearance rate (Δ6Lac) with lactate levels measured at admission (L1) and after 6 h (L2) to predict 30-day mortality in CS. Methods: In this observational cohort study, 95 patients with CS were treated at Department of Intensive Care Unit, Yiwu Central Hospital between January 2020 and December 2022. Of these, 88 patients met the eligibility criteria. The lactate levels were measured after admission (L1) as the baseline lactate value, and were measured after 6 h (L2) following admission. The primary endpoint of the study was survival rate at 30 days. A receiver operating characteristic curve was used for data analysis. Univariate and multivariate Cox regression analyses were performed based on Δ6Lac. Kaplan-Meier (KM) survival curves were generated to compare the 30-day survival rates among L1, L2, and Δ6Lac. Results: The Δ6Lac model showed the highest area under the curve value (0.839), followed by the L2 (0.805) and L1 (0.668) models. The Δ6Lac model showed a sensitivity of 84.2% and specificity of 75.4%. The L1 and L2 models had sensitivities of 57.9% each and specificities of 89.9% and 98.6%, respectively. The cut-off values for Δ6Lac, L1, and L2 were 18.2%, 6.7 mmol/L, and 6.1 mmol/L, respectively. Univariate Cox regression analysis revealed a significant association between Δ6Lac and 30-day mortality. After adjusting for five models in multivariate Cox regression, Δ6Lac remained a significant risk factor for 30-day mortality in patients with CS. In our fifth multivariate Cox regression model, Δ6Lac remained a risk factor associated with 30-day mortality (hazard ratio [HR]=5.14, 95% confidence interval [CI]: 1.48 to 17.89, P=0.010) as well as L2 (HR=8.42, 95% CI: 1.26 to 56.22, P=0.028). The KM survival curve analysis revealed that L1 >6.7 mmol/L (HR=8.08, 95% CI: 3.23 to 20.20, P <0.001), L2 >6.1 mmol/L (HR=25.97, 95% CI: 9.76 to 69.15, P <0.001), and Δ6Lac ≤18.2% (HR=8.92, 95% CI: 2.95 to 26.95, P <0.001) were associated with a higher risk of 30-day mortality. Conclusions: Δ6Lac is a better predictor for 30-day mortality in CS than lactate levels at admission. It has a predictive value equivalent to that of lactate level at 6 h after admission, making it an important surrogate indicator for evaluating the suitability as well as poor prognosis after CS treatment. We found that a cut-off value of 18.2% for Δ6Lac provided the most accurate assessment of early prognosis in CS.

Multi-Component Lithiophilic Alloy Film Modified Cu Current Collector for Long-Life Lithium Metal Batteries by a Novel FCVA Co-Deposition System.

Surface modification of Cu current collectors (CCs) is proven to be an effective method for protecting lithium metal anodes. However, few studies have focused on the quality and efficiency of modification layers. Herein, a novel home-made filtered cathode vacuum arc (FCVA) co-deposition system with high modification efficiency, good repeatability and environmental friendliness is proposed to realize the wide range regulation of film composition, structure and performance. Through this system, ZnMgTiAl quaternary alloy films, which have good affinity with Li are successfully constructed on Cu CCs, and the fully enhanced electrochemical performances are achieved. Symmetrical cells constructed with modified CCs maintained a fairly low voltage hysteresis of only 13 mV after 2100 h at a current density of 1 mA cm-2. In addition, the capacity retention rate is as high as 75.0% after 100 cycles in the full cells. The influence of alloy films on the dynamic evolution process of constructing stable artificial solid electrolyte interphase (SEI) layer is revealed by in situ infrared (IR) spectroscopy. This work provides a promising route for designing various feasible modification films for LMBs, and it displays better industrial application prospects than the traditional chemical methods owing to the remarkable controllability and scale-up capacity.

Structural basis for the dynamic chaperoning of disordered clients by Hsp90.

Molecular chaperone heat shock protein 90 (Hsp90) is a ubiquitous regulator that fine-tunes and remodels diverse client proteins, exerting profound effects on normal biology and diseases. Unraveling the mechanistic details of Hsp90's function requires atomic-level insights into its client interactions throughout the adenosine triphosphate-coupled functional cycle. However, the structural details of the initial encounter complex in the chaperone cycle, wherein Hsp90 adopts an open conformation while engaging with the client, remain elusive. Here, using nuclear magnetic resonance spectroscopy, we determined the solution structure of Hsp90 in its open state, bound to a disordered client. Our findings reveal that Hsp90 uses two distinct binding sites, collaborating synergistically to capture discrete hydrophobic segments within client proteins. This bipartite interaction generates a versatile complex that facilitates rapid conformational sampling. Moreover, our investigations spanning various clients and Hsp90 orthologs demonstrate a pervasive mechanism used by Hsp90 orthologs to accommodate the vast array of client proteins. Collectively, our work contributes to establish a unified conceptual and mechanistic framework, elucidating the intricate interplay between Hsp90 and its clients.

(-) - Epicatechin regulates LOC107986454 by targeting the miR-143-3p/EZH2 axis to enhance the radiosensitivity of non-small cell lung cancer.

BACKGROUND AND OBJECTIVE: Non-small cell lung cancer (NSCLC) is a pernicious tumor with high incidence and mortality rates. The incidence rate of NSCLC increases with age and poses a serious danger to human health. The aim of this study was to determine the mechanism by which (-)-epicatechin (EC) alleviates NSCLC. METHODS: Twenty-four pairs of NSCLC tissues and cancer-adjacent tissues were collected, and A549 and H460 radiotherapy-resistant strains were generated by repeatedly irradiating A549 and H460 cells with dose-gradient X-rays. Radiotherapy-resistant H460 cells were successfully injected subcutaneously into the left dorsal side of nude mice at a dose of 1 × 105 to establish an NSCLC animal model. The levels of interrelated genes and proteins were detected by RT‒qPCR and Western blotting, and cell proliferation and apoptosis were evaluated by CCK‒8 assay, Transwell assay, flow cytometry, and TUNEL staining. RESULTS: LOC107986454 was highly expressed in NSCLC patients, while miR-143-3p was expressed at low levels and was negatively correlated with LOC107986454. Functionally, EC promoted autophagy and apoptosis induced by radiotherapy, restrained cell proliferation and migration, and ultimately enhanced the radiosensitivity of NSCLC cells. A downstream mechanistic study showed that EC facilitated miR-143-3p expression by inhibiting LOC107986454 and then restraining the expression of EZH2, which ultimately facilitated autophagy and apoptosis in cancer cells, inhibited proliferation and migration, and enhanced the radiosensitivity of NSCLC cells. CONCLUSION: EC can enhance the radiosensitivity of NSCLC cells by regulating the LOC107986454/miR-143-3p/EZH2 axis.

Lipid droplet accumulation mediates macrophage survival and Treg recruitment via the CCL20/CCR6 axis in human hepatocellular carcinoma.

Metabolic changes play a crucial role in determining the status and function of macrophages, but how lipid reprogramming in macrophages contributes to tumor progression is not yet fully understood. Here, we investigated the phenotype, contribution, and regulatory mechanisms of lipid droplet (LD)-laden macrophages (LLMs) in hepatocellular carcinoma (HCC). Enriched LLMs were found in tumor tissues and were associated with disease progression in HCC patients. The LLMs displayed immunosuppressive phenotypes (with extensive expression of TREM2, PD-L1, CD206, and CD163) and attenuated the antitumor activities of CD8+ T cells. Mechanistically, tumor-induced reshuffling of cellular lipids and TNFα-mediated uptake of tumoral fatty acids contribute to the generation of triglycerides and LDs in macrophages. LDs prolong LLM survival and promote CCL20 secretion, which further recruits CCR6+ Tregs to HCC tissue. Inhibiting LLM formation by targeting DGAT1 and DGAT2, which catalyze the synthesis of triglycerides, significantly reduced Treg recruitment, and delayed tumor growth in a mouse hepatic tumor model. Our results reveal the suppressive phenotypes and mechanisms of LLM enrichment in HCC and suggest the therapeutic potential of targeting LLMs for HCC patients.

Formaldehyde exacerbates inflammation and biases T helper cell lineage commitment through IFN-γ/STAT1/T-bet pathway in asthma.

The correlation between formaldehyde (FA) exposure and prevalence of asthma has been widely reported. However, the underlying mechanism is still not fully understood. FA exposure at 2.0 mg/m3 was found to exacerbate asthma in OVA-induced murine models. IFN-γ, the cytokine produced by T helper 1 (Th1) cells, was significantly induced by FA in serum and bronchoalveolar lavage fluid (BALF) of asthmatic mice, which was different from cytokines secreted by other Th cells. The observation was also confirmed by mRNA levels of Th marker genes in CD4+ T cells isolated from BALF. In addition, increased production of IFN-γ and expression of T-bet in Jurkat T cells primed with phorbol ester and phytohaemagglutinin were also observed with 100 µM FA treatment in vitro. Upregulated STAT1 phosphorylation, T-bet expression and IFN-γ production induced by FA was found to be restrained by STAT1 inhibitor fludarabine, indicating that FA promoted Th1 commitment through the autocrine IFN-γ/STAT1/T-bet pathway in asthma. This work not only revealed that FA could bias Th lineage commitment to exacerbate allergic asthma, but also identified the signaling mechanism of FA-induced Th1 differentiation, which may be utilized as the target for development of interfering strategies against FA-induced immune disorders.

Enhancement of silicon vacancy fluorescence intensity in silicon carbide using a dielectric cavity.

Over the past decades, spin qubits in silicon carbide (SiC) have emerged as promising platforms for a wide range of quantum technologies. The fluorescence intensity holds significant importance in the performance of quantum photonics, quantum information process, and sensitivity of quantum sensing. In this work, a dual-layer Au/SiO2 dielectric cavity is employed to enhance the fluorescence intensity of a shallow silicon vacancy ensemble in 4H-SiC. Experimental results demonstrate an effective fourfold augmentation in fluorescence counts at saturating laser power, corroborating our theoretical predictions. Based on this, we further investigate the influence of dielectric cavities on the contrast and linewidth of optically detected magnetic resonance (ODMR). There is a 1.6-fold improvement in magnetic field sensitivity. In spin echo experiments, coherence times remain constant regardless of the thickness of dielectric cavities. These experiments pave the way for broader applications of dielectric cavities in SiC-based quantum technologies.

Antitumor aspochalasin and antiviral benzofuran derivatives from a marine-derived fungus Aspergillus sp. SCSIO41032.

Chemical investigation of the EtOAc extract of a deep-sea derived fungus Aspergillus sp. SCSIO41032 resulted in the isolation of ten known compounds, including eight aspochalasins. Their structures were elucidated by using extensive NMR spectroscopic, mass spectrometric and single crystal X-ray diffraction analysis. The detailed crystallographic data for structures 1, 2, and 4, along with the relative configurations of aspochalasin E (3) determined by its acetonide derivative were reported for the first time. The results of antitumor and antiviral activities showed that 3 displayed moderate antitumor activities against 22Rv1, PC-3, A549, and HCT-15 cell lines with IC50 values ranged from 5.9 ± 0.8 to 19.0 ± 7.7 µM, and 9 exhibited moderate antiviral activities against HSV-1/2 with EC50 values of 9.5 ± 0.5 and 5.4 ± 0.6 µM, respectively. Plate clone formation assays results indicated that 3 inhibited the 22Rv1, PC-3 cells growth in a dose-dependent manner.

Fouling behavior of nanofiltration membrane during the refining treatment of morphlines-dominant reverse osmosis concentrate.

Nanofiltration (NF) has been proven to be with great potential for the separation of morpholines with molecular weight less than 200 Da in refining reverse osmosis concentrate (ROC), but its application is significantly restricted by the membrane fouling, which can reduce the rejection and service time. To enable the long-term operation stability of nanofiltration, this work focuses on the fouling behavior of each substance in the hydrosaline organic solution on nanofiltration membrane, aiming to give insight into the fouling mechanism. To this end, in this work, the effects of salts (i.e NaCl and Na2SO4), organic substances (including N-(2-hydroxypropyl)morpholine(NMH) and 4-morpholineacetate(MHA)) and representative divalent ions (Ca2+ and Mg2+) on the performance and physicochemical properties of DK membrane were systematically investigated. The results show that both salts and organics can induce DK membrane swelling, leading to an increase of the mean effective pore size. After the filtration of Na2SO4-NaCl-H2O, the mean pore size increased by 0.002 nm, resulting in the decrease of the removal ratio of NMH and MHA for 3.82% and 13.10%, respectively. With static adsorption of NMH and MHA, the mean pore size of DK membrane increased by 0.005 and 0.003 nm. The swelling slowed the entrance of more organic molecules into membrane pores. Among them, MHA led to the terrible irreversible pore blocking. As the concentration of Ca2+ increased, gypsum scaling was formed on the membrane surface. During this process, NMH and MHA played different roles, i.e. NMH accelerated the CaSO4 crystallization while MHA inhibited. As a conclusion, the fouling behavior of substances in the high saline organic wastewater on DK membrane were systematically revealed with the fouling mechanisms proposed, which could provide an insightful guidance for membrane fouling control and cleaning in the treatment of high salinity and organic wastewater.

Energy Band Specific to Injected Li-Ion-Induced Formation of Lithium Dendrites in Garnet Solid Electrolytes.

As one of the most significant challenges in solid-state batteries, thorough investigation is necessary on the formation process of lithium dendrites in solid-state electrolytes. Here, we reveal that the growth of lithium dendrites in solid electrolytes is a physical-electrochemical reaction process caused by injected lithium ions and electron carriers, which requires a low electrochemical potential. A unique energy band specific to injected Li ions is identified at the bottom of the conduction band, which can be occupied by electron carriers from low-potential electrodes, leading to dendrite formation. In this case, it is quantitatively determined that the employed anodes with higher working voltages (>0.2 V versus Li/Li+) can effectively prevent dendrite formation. Moreover, lithium dendrite formation exclusively occurs during the charging process (i.e., lithium plating), where lithium ions meet electrons at mixed conductive grain boundaries under highly reductive potentials. The proposed model has significant scientific significance and application value.

ß-Terrecyclene synthase constructs the quadrane backbone in terrecyclic acid biosynthesis.

Quadrane sesquiterpenes featuring a distinctive tricyclic skeleton exhibit potent antimicrobial and anticancer activities. Although extensive studies have attempted to reveal the multistep carbocation rearrangement involved in the formation of the tricyclic quadrane scaffold, the exact biosynthetic pathway and chemical logic to generate the quadrane structure remains mysterious. Here we identified a novel sesquiterpene synthase that is capable of generating ß-terrecyclene possessing the quadrane scaffold and characterized the biosynthetic pathway of a representative fungal quadrane terrecyclic acid. Further mutagenesis coupled with isotopically sensitive branching studies of this ß-terrecyclene synthase provided insight into the mechanism involved in the formation of the quadrane scaffold.