Somalactams A-D: Anti-inflammatory Macrolide Lactams with Unique Ring Systems from an Arctic Actinomycete Strain.

Four new PKS-NRPS-derived macrolide lactams with three unique ring fusion types were discovered from the Arctic sponge associated actinomycete Streptomyces somaliensis 1107 using a genome mining strategy. Their structures were elucidated by a combination of MS, NMR spectroscopic analysis, and single-crystal X-ray diffraction. Biosynthetically, a novel gene cluster sml consisting of three polyketide synthases and one hybrid polyketide synthase-nonribosomal peptide synthetase together with cytochrome P450s and flavin-containing monooxygenases and oxidoreductases was demonstrated to assemble the unique skeleton. Pharmacological studies revealed that compound 1 displayed a potent anti-inflammatory effect without cytotoxicity. It inhibited IL-6 and TNF-α release in the serum of LPS-stimulated RAW264.7 macrophage cells with IC50 values of 5.76 and 0.18 µM, respectively, and modulated the MAPK pathway. Moreover, compound 1 alleviated LPS-induced systemic inflammation in our transgenic fluorescent zebrafish model.

Magnetically controlled capsule endoscopy in one-time gastro-small intestinal joint examination: a two-centre experience.

BACKGROUND: The lesions of certain diseases are widely distributed in both stomach and small intestine, while the step-by-step strategy of gastroscopy followed by enteroscopy can be burdensome and costly. We aimed to determine if magnetically controlled capsule endoscopy (MCE) could be used in one-time gastro-small intestine (GSI) joint examination. METHODS: In this study, data of patients in Chinese PLA General Hospital and Changhai Hospital who underwent MCE GSI examination from January 2020 to August 2021 were retrospectively analysed. The primary outcome of this study was the success rate of one-time GSI joint examination, and secondary outcomes included visualization and cleanliness of gastrointestinal tract, gastrointestinal transit times, diagnostic yield and safety of MCE examination. RESULTS: A total of 768 patients were included. The success rate of one-time GSI joint examination was 92.58%. There were 94.92% MCEs observed > 90% gastric mucosa in the 6 anatomic landmarks. The rate of complete small bowel examination was 97.40%. The median gastric examination time, gastric transit time and small intestine transit time were 8.18 min, 63.89 min and 4.89 h, respectively. Magnetic steering of MCE significantly decreased gastric transit time (8.92 min vs. 79.68 min, P = 0.001) and increased duodenal lesion detection rate (13.47% vs. 6.26%, P = 0.001) when compared with non-magnetic steering group. Two capsules were retained and were removed by enteroscopy or spontaneously excreted. CONCLUSIONS: MCE is feasible to complete GSI joint examination and the detection of both gastric and small intestinal diseases can be achieved simultaneously. Trial registration Clinical Trial Registration ClinicalTrials.gov, ID: NCT05069233.

Use of glioma to assess the distribution patterns of perfluoroalkyl and polyfluoroalkyl substances in human brain.

Human brain has a complex structure and is able to perform powerful functions. Blood-brain barrier blocks the entry of foreign substances and maintains the homeostasis of the brain. However, some exogenous substances are still able to pass through the blood-brain barrier, with distribution patterns yet to be clarified. Perfluoroalkyl and polyfluoroalkyl substances (PFASs), including perfluoroalkyl carboxylic acids (PFCAs), perfluoroalkyl sulfonic acids (PFSAs), a precursor (perfluorooctane sulfonamide that can be degraded to other substances), and emerging PFASs, were analyzed for the first time in living human brain glioma. The target compounds were detected and quantified in 25 out of 26 glioma samples. The concentration range of ∑PFAS was < RL-51 ng g-1 wet weight (applied to all reported concentrations), with a median of 2.9 ng g-1. The most abundant compound was PFCAs (40%), followed by PFSAs (28%), emerging PFASs (22%), and perfluorooctane sulfonamide (10%). Abundant alternatives PFASs, including short-chain PFCAs, short-chain PFSAs, and emerging PFASs (52% of ∑PFAS), were found in the glioma samples, supporting the notion that low molecular weight exogenous compounds have high permeability to cross the blood-brain barrier and accumulate in brain tissue. Gender difference was not significant (p > 0.05) in the concentrations of PFASs in the glioma samples. Concentrations of PFASs increased with increasing age, from 0.61 ng g-1 (0-14 years old) to 1.6 ng g-1 (>48 years old), with no significant linear correlation with age. The present study suggested that glioma is an effective indicator for monitoring exogenous contaminants in brain tissues.

PLAC8, a new marker for human interstitial extravillous trophoblast cells, promotes their invasion and migration.

Proper differentiation of trophoblast cells in the human placenta is a prerequisite for a successful pregnancy, and dysregulation of this process may lead to malignant pregnancy outcomes, such as preeclampsia. Finding specific markers for different types of trophoblast cells is essential for understanding trophoblast differentiation. Here, we report that placenta-specific protein 8 (PLAC8) is specifically expressed in the interstitial extravillous trophoblast cells (iEVTs) on the fetomaternal interface. Using model systems, including placental villi-decidua co-culture, iEVTs induction by using primary trophoblast cells or explants, etc., we found that PLAC8 promotes invasion and migration of iEVTs. Mechanistically, time-lapse imaging, GTPase activity assay, co-immunoprecipitation and RNA-seq studies show that PLAC8 increases the Cdc42 and Rac1 activities, and further induces the formation of filopodia at the leading edge of the migratory trophoblast cells. More interestingly, PLAC8 is significantly upregulated under hypoxia and expression of PLAC8 is higher in iEVTs from preeclamptic placentas when compared with those from the normal control placentas. Together, PLAC8 is a new marker for iEVTs and plays an important role in promoting trophoblast invasion and migration.

Adverse events of video capsule endoscopy over the past two decades: a systematic review and proportion meta-analysis.

BACKGROUND: A full spectrum of video capsule endoscopy (VCE) adverse events over the past two decades has not been evaluated. We aimed to determine pooled rates, predictors and temporal-trend of VCE adverse events over the past two decades. METHODS: Systematic search of PubMed and EMBASE for English-language publications reporting VCE adverse events (January 1, 2000 to March 31, 2019). Data were extracted independently by two investigators. Pooled VCE adverse event rates were calculated using the random or fixed model as appropriate. Predictors and temporal-trend of each adverse event were performed by meta-regression analyses. RESULTS: In total, 402 studies were identified, including 108,079 VCE procedures. Rate of retention, swallow disorder, aspiration, technical failure, and procedural adverse events were 0.73% (95% confidence interval [CI] 0.59-0.89%), 0.75% (95% CI 0.43-1.13%), 0.00% (95% CI 0.00-0.00%), 0.94% (95% CI 0.65-1.28%), 0.67% (95% CI 0.32-1.10%), respectively; incomplete examination rate of esophagus, stomach, small bowel, and colon were 9.05%, 7.69%, 12.08%, 19.19%, respectively. Patency capsule reduced retention rate by 5.04%, whereas known inflammatory bowel disease increased retention rate by 4.29%. Elder was the risk and protective factor for small bowel incomplete examination (0.30%) and swallow disorder (- 0.72%), respectively. Rates of retention and small bowel incomplete examination significantly declined over time (P = .0006 and P < .0001).. CONCLUSIONS: VCE adverse event rates were generally low, and retention and small bowel incomplete examination rates declined over the past two decades. Patients with known inflammatory bowel disease or elder should be alerted to high risk of retention or small bowel incomplete examination (PROSPERO: CRD42019139595).

An investigation of the anomalous asymptotic behavior of elastic electron scattering of helium.

For the inelastic electron scattering of atoms and molecules, a consensus has been reached that the first Born approximation is easily approached by decreasing the momentum transfer at the same impact electron energy or increasing the impact electron energy at the same momentum transfer. Although this consensus is applicable for the elastic electron scattering of most atoms and molecules, it is violated for helium where the experimental differential cross sections deviate from the first Born approximation prediction gradually with the decrease of squared momentum transfer at the same impact electron energy. Since this anomalous phenomenon was observed more than 40 years ago, the intrinsic mechanism is not explicit. In the present work, using the high-resolution x-ray scattering, we isolate the scattering contribution from the nucleus and directly obtain the pure electronic structure of helium. Then, the anomalous asymptotic behavior of the elastic electron scattering of helium has been elucidated, i.e., in the small squared momentum transfer region, the scattering contribution from the target's electrons is counteracted by the one from the atomic nucleus, which results in the residual contribution beyond the first Born approximation being drastically enlarged.

Oscillator strengths and integral cross sections of the valence-shell excitations of HCl studied by fast electron scattering.

The oscillator strengths and integral cross sections of the valence-shell excitations of HCl have significant applications in the studies of planetary atmospheres and interstellar gases. In the present work, the generalized oscillator strengths of the valence-shell excitations of HCl have been measured at an incident electron energy of 1500 eV and an energy resolution of 70 meV, and their momentum transfer dependence behaviors have been elucidated. It is observed that the generalized oscillator strength ratios of the b3Π1(ν' = 0) state to the C1Π(ν' = 0) state are a constant and independent of the squared momentum transfer, and this typical behavior in the momentum space is explained by the intraconfiguration mixing of the b3Π1 and C1Π states due to the spin-orbital interaction. The optical oscillator strengths of the valence-shell excitations have been obtained by extrapolating the generalized oscillator strengths to the limit of zero squared momentum transfer. The present optical oscillator strengths give an independent cross-check to the previous experimental and theoretical results, and it is found that most of the photoabsorption measurements are limited by the line saturation effect. The integral cross sections of the valence-shell excitations of HCl have been obtained systematically from the threshold to 5000 eV with the aid of the BE-scaling method.

Oscillator strengths and integral cross sections of the ÃA2″1← X̃1A1 excitation of ammonia studied by fast electron impact.

The vibrationally resolved generalized oscillator strengths of the first and strongest singlet excitation ÃA2″1← X̃1A1 of ammonia have been determined at an impact electron energy of 1500 eV with an energy resolution of 80 meV. The comprehensive comparison of the present results with the previous experimental and theoretical ones shows that the high-energy limit, where the first Born approximation holds, has been reached at an impact electron energy of 1500 eV in K2 < 1 a.u., while it is still not satisfied in the K2 > 1 a.u. even at 1500 eV. It is also observed that the minimum position of the generalized oscillator strength of the vibronic state shifts toward the larger squared momentum transfer with the increasing vibrational quantum number. By extrapolating the generalized oscillator strength to the zero momentum transfer, the optical oscillator strength of the ÃA2″1 state has been obtained, which gives an independent cross check to the previous results. The integral cross sections of the ÃA2″1 state have been obtained systematically from the threshold to 5000 eV with the aid of the BE-scaling method.

Generalized oscillator strengths of the low-lying valence-shell excitations of N2, O2, and C2H2 studied by fast electron and inelastic x-ray scattering.

The generalized oscillator strengths of the low-lying valence-shell excitations of N2, O2, and C2H2 have been studied by the high-energy electron scattering, the high-resolution inelastic X-ray scattering, and the multireference single- and double-excitation configuration-interaction methods. Good agreement between the present electron-scattering results and the X-ray-scattering ones for the a''1Σg +v'=0 and a''1Σg +v'=1+b1Πuv'=0 excitations of N2 and the A'3Δu excitation of O2 is achieved in the small squared momentum transfer region, while obvious discrepancies among them are observed in the large squared momentum transfer region. This phenomenon indicates that the first Born approximation is satisfied in the small squared momentum transfer region, while it does not hold in the large squared momentum transfer region at an incident electron energy of 1500 eV, in view of the fact that the first Born approximation is satisfied in the X-ray scattering. In addition, the present calculation for the a''1Σg + excitation shows that the traditional assigned v' = 0 and 1 of the a″1Σg + excitation correspond to v' = 9 and 13 of the 21Σg + excitation and reproduces the X-ray-scattering results of the a''1Σg +v'=0 excitation very well except the ones in the small squared momentum transfer region. We also report the generalized oscillator strengths of the à + B̃ excitations of C2H2, and its profile shows that the bending geometry has great influence on the transition feature.

Proteomic analysis of the effects of cell culture density on the metastasis of breast cancer cells.

Cancer cell progression and proliferation increase cell density, resulting in changes to the tumour site, including the microenvironment. What is not known is if increased cell density influences the aggressiveness of cancer cells, especially their proliferation, migration, and invasion capabilities. In this study, we found that dense cell culture enhances the aggressiveness of the metastatic cancer cell lines, 4T1 and ZR-75-30, by increasing their proliferation, migration, and invasion capabilities. However, a less metastatic cell line, MCF-7, did not show an increase in aggressiveness, following dense cell culture conditions. We conducted a differential proteomic analysis on 4T1 cells cultured under dense or sparse conditions and identified an increase in expression for proteins involved in migration, including focal adhesion, cytoskeletal reorganization, and transendothelial migration. In contrast, 4T1 cells grown under sparse conditions had higher expression levels for proteins involved in metabolism, including lipid and phospholipid binding, lipid and cholesterol transporter activity, and protein binding. These results suggest that the high-density tumour microenvironment can cause a change in cellular behaviour, leading towards more aggressive cancers. SIGNIFICANCE OF THE STUDY: Metastasis of cancer cells is an obstacle to the clinical treatment of cancer. We found that dense cultures made metastatic cancer cells more potent in terms of proliferation, migration, and invasion. The proteomic and bioinformatic analyses provided some valuable clues for further intensive studies about the effects of cell density on cancer cell aggressiveness, which were associated with events such as pre-mRNA splicing and RNA transport, focal adhesion and cytoskeleton reorganization, ribosome biogenesis, and transendothelial migration, or associated with proteins, such as JAM-1 and S100A11. This investigation gives us new perspectives to investigate the metastasis mechanisms related to the microenvironment of tumour sites.

Oscillator strengths and integral cross sections for the valence-shell excitations of nitric oxide studied by fast electron impact.

The generalized oscillator strengths for the valence-shell excitations of A2Σ+, C2Π, and D2Σ+ electronic-states of nitric oxide have been determined at an incident electron energy of 1500 eV with an energy resolution of 70 meV. The optical oscillator strengths for these transitions have been obtained by extrapolating the generalized oscillator strengths to the limit that the squared momentum transfer approaches to zero, which give an independent cross-check to the previous experimental and theoretical results. The integral cross sections for the valence-shell excitations of nitric oxide have been determined systematically from the threshold to 2500 eV with the aid of the newly developed BE-scaling method for the first time. The present optical oscillator strengths and integral cross sections of the valence-shell excitations of nitric oxide play an important role in understanding many physics and chemistry of the Earth's upper atmosphere such as the radiative cooling, ozone destruction, day glow, aurora, and so on.

Investigations of the valence-shell excitations of molecular ethane by high-energy electron scattering.

The differential cross sections and generalized oscillator strengths for the low-lying excitations of the valence-shell 1eg orbital electron in ethane have been measured for the first time at a high incident electron energy of 1500 eV and a scattering angular range of 1.5°-10°. A weak feature, termed X here, with a band center of about 7.5 eV has been observed, which was also announced by the previous experimental and theoretical studies. The dynamic behaviors of the generalized oscillator strengths for the 3s (8.7 eV), 3s+3p (9.31 eV, 9.41 eV), and X (∼7.5 eV) transitions on the momentum transfer squared have been obtained. The integral cross sections of these transitions from their thresholds to 5000 eV have been obtained with the aid of the BE-scaling (B is the binding energy and E is the excitation energy) method. The optical oscillator strengths of the above transitions determined by extrapolating their generalized oscillator strengths to the limit of the squared momentum transfer K2 → 0 are in good agreement with the ones from the photoabsorption spectrum [J. W. Au et al., Chem. Phys. 173, 209 (1993)], which indicates that the present differential cross sections, generalized oscillator strengths, and integral cross sections can serve as benchmark data.

A novel urinary long non-coding RNA transcript improves diagnostic accuracy in patients undergoing prostate biopsy.

BACKGROUND: Long non-coding RNA (LncRNA) PCA3 has been a well-established urine biomarker for the detection of prostate cancer (PCa). Our previous study showed a novel LncRNA FR0348383 is up-regulated in over 70% of PCa compared with matched benign tissues. The aim of this study was to evaluate the diagnostic value of urinary FR0348383 for men undergoing prostate biopsy due to elevated PSA (PSA > 4.0 ng/ml) and/or abnormal digital rectal examination (DRE). METHODS: Post-DRE first-catch urine specimens prior to prostate biopsies were prospectively collected. After the whole transcriptome amplification, quantitative real time polymerase chain reaction was applied to quantify urine FR0348383 and PSA levels. The FR0348383 score was calculated as the ratio of PSA and FR0348383 mRNA (PSA mRNA/FR0348383 mRNA × 1000). The diagnostic value of FR0348383 score was evaluated by logistic regression and decision curve analysis. RESULTS: 213 cases with urine samples containing sufficient mRNA were included, 94 cases had serum PSA level 4.0-10.0 ng/ml. PCa was identified in 72 cases. An increasing FR0348383 score was correlated with an increasing probability of a positive biopsy (P < 0.001). Multivariable logistic analysis indicated FR0348383 score (P < 0.001), PSA (P = 0.004), age (P = 0.007), prostate volume (P < 0.001) were independent predictors of PCa. ROC analysis demonstrated FR0348383 score outperformed PSA, %free PSA, and PSA Density in the prediction of PCa in the subgroup of patients with grey area PSA (AUC: 0.815 vs. 0.562 vs. 0.599 vs. 0.645). When using a probability threshold of 30% in the grey zone cohort, The FR0348383 score would save 52.0% of avoidable biopsies without missing any high grade cancers. CONCLUSIONS: FR0348383 transcript in post-DRE urine may be a novel biomarker for detection of PCa with great diagnostic value, especially in the grey zone cohort. The application of FR0348383 score in clinical practice might avoid unnecessary prostate biopsies and increase the specificity of PCa diagnosis.

Osthole ameliorates hepatic fibrosis and inhibits hepatic stellate cell activation.

BACKGROUND: Hepatic fibrosis is a dynamic process which ultimately leads to cirrhosis in almost patients with chronic hepatic injury. However, progressive fibrosis is a reversible scarring response. Activation of hepatic stellate cells (HSCs) is the prevailing process during hepatic fibrosis. Osthole is an active component majorly contained in the fruit of Cnidium monnieri (L.) Cusson. This present study investigated the therapeutic effects of osthole on rat liver fibrosis and HSC activation. RESULTS: We established the thioacetamide (TAA)-model of Sprague-Dawley (SD) rats to induce hepatic fibrosis. Rats were divided into three groups: control, TAA, and TAA + osthole (10 mg/kg). In vivo, osthole significantly reduced liver injury by diminishing levels of plasma AST and ALT, improving histological architecture, decreasing collagen and α-SMA accumulation, and improving hepatic fibrosis scores. Additionally, osthole reduced the expression of fibrosis-related genes significantly. Osthole also suppressed the production of fibrosis-related cytokines and chemokines. Moreover, nuclear translocation of p65 was significantly suppressed in osthole-treated liver. Osthole also ameliorated TAA-induced injury through reducing cellular oxidation. Osthole showed inhibitory effects in inflammation-related genes and chemokines production as well. In vitro, we assessed osthole effects in activated HSCs (HSC-T6 and LX-2). Osthole attenuated TGF-ß1-induced migration and invasion in HSCs. Furthermore, osthole decreased TNF-α-triggered NF-κB activities significantly. Besides, osthole alleviated TGF-ß1- or ET-1-induced HSCs contractility. CONCLUSIONS: Our study demonstrated that osthole improved TAA-caused liver injury, fibrogenesis and inflammation in rats. In addition, osthole suppressed HSCs activation in vitro significantly.

Periostin: a novel prognostic predictor for meningiomas.

The expression and role of periostin in meningiomas remains unknown. Tissue specimens of 175 convexity meningiomas were immunohistochemically examined with antibodies against periostin and Ki67. The expression levels of periostin and Ki67 were compared among different WHO groups. The role of periostin and Ki67 in postoperative prognosis of meningiomas was also analyzed. Negative (-) expression of Ki67 was observed in 101 (57.7 %) cases of all the surgical tissue samples. The Ki67 expressions differed significantly among the WHO groups (P < 0.001) and correlated positively with the WHO grade (r = 0.673, P < 0.001). Low/negative staining of periostin was observed in 116 (66.3 %) cases. The periostin expressions differed significantly among the WHO groups (P < 0.001). Periostin expression correlated positively with the WHO grade (r = 0.742, P < 0.001). There was a positive correlation between Ki67 expression and periostin (r = 0.513, P < 0.001). Both Ki67 expression and periostin expression was found statistically different between brain invasion tumor and non-invasion tumor (p < 0.001). The recurrence rate and PFS rate in both varied Ki67 expression groups and periostin expression groups was statistically different (P < 0.001). The survival time and PFS time in both varied Ki67 expression groups and periostin expression groups was also statistically different (P < 0.001). Periostin was expressed in tumor stroma of meningiomas. Both periostin and Ki67 may behave as a maker in predicting the grade and prognosis in meningiomas. Drugs that targets periostin aims at reducing invasion of meningioma patients should be further researched.

Investigation of Compton profiles of molecular methane and ethane.

The Compton profiles of methane and ethane molecules have been determined at an incident photon energy of 20 keV based on the third generation synchrotron radiation, and the statistical accuracy of 0.2% is achieved near pz = 0. The density functional theory with aug-cc-pVTZ basis set was used to calculate the Compton profiles of methane and ethane. The present experimental Compton profiles are in better agreement with the theoretical calculations in the whole pz region than the previous experimental results, which indicates that the present experimental Compton profiles are accurate enough to serve as the benchmark data for methane and ethane molecules.

Proteomic analysis on effectors involved in BMP-2-induced osteogenic differentiation of beagle bone marrow mesenchymal stem cells.

OBJECTIVE: To identify the protein regulation profile of recombinant human bone morphogenetic protein-2 (rhBMP-2)-induced osteogenic differentiation in beagle bone marrow stem cells (BMSCs). METHODS: Beagle BMSCs were isolated and cultured with or without rhBMP-2. Two-dimensional gel electrophoresis was used to determine the differences in protein expression in rhBMP-2-induced and non-induced BMSCs. Real-time PCR and western blotting analyses were used to verify the expression patterns of selected proteins. RESULTS: After the induction, the osteogenic differentiation of beagle BMSCs was activated successfully. Nine and 11 proteins were found to be down- and up-regulated by rhBMP-2, respectively. The increase in Lim and SH3 domain protein 1(LASP1) and the decrease in ferritin were verified by real-time PCR and western blotting analyses. CONCLUSIONS: Among the 20 rhBMP-2-regulated factors, there is empirical evidence supporting the involvement of LASP1 and ferritin in osteogenic differentiation. LASP1 plays an important role in the regulation of the activity of the cytoskeleton, and ferritin is an important molecule in cellular iron homeostasis. Further studies focused on these 20 proteins will help elucidate the molecular mechanism(s) through which rhBMP-2 induces osteogenic differentiation of BMSCs.

Per- and polyfluoroalkyl substances (PFAS) exposure in plasma and their blood-brain barrier transmission efficiency-A pilot study.

Per- and polyfluoroalkyl substances (PFAS) have been shown to penetrate the blood-brain barrier (BBB) and accumulate in human brain. The BBB transmission and accumulation efficiency of PFAS, as well as the potential health risks from human co-exposure to legacy and emerging PFAS due to differences in transport efficiency, need to be further elucidated. In the present pilot study, 23 plasma samples from glioma patients were analyzed for 17 PFAS. The concentrations of PFAS in six paired brain tissue and plasma samples were used to calculate the BBB transmission efficiency of PFAS (RPFAS). This RPFAS analysis was conducted with utmost care and consideration amid the limited availability of valuable paired samples. The results indicated that low molecular weight PFAS, including short-chain and emerging PFAS, may have a greater potential for accumulation in brain tissue than long-chain PFAS. As an alternative to perfluorooctane sulfonic acid (PFOS), 6:2 chlorinated polyfluorinated ether sulfonate (6:2 Cl-PFESA) exhibited brain accumulation potential similar to that of PFOS, suggesting it may not be a suitable substitute concerning health risk in brain. The BBB transmission efficiencies of perfluorooctanoic acid, PFOS, and 6:2 Cl-PFESA showed similar trends with age, which may be an important factor influencing the entry of exogenous compounds into the brain. A favorable link between perfluorooctane sulfonamide (FOSA) and the development and/or progression of glioma may be implicated by a strong positive correlation (r2 = 0.94; p < 0.01) between RFOSA and Ki-67 (a molecular marker of glioma). However, a causal relationship between RFOSA and glioma incidence were not established in the present study. The present pilot study conducted the first examination of BBB transmission efficiency of PFAS from plasma to brain tissue and highlighted the importance of reducing and/or controlling exposure to PFAS.

Guanidine-Based Covalent Organic Frameworks: Cooperation between Cores and Linkers for Chromic Sensing and Efficient CO2 Conversion.

C(sp)-H carboxylation with CO2 is an attractive route of CO2 utilization and is traditionally promoted by transition metal catalysts, and organocatalysis for the conversion remains rarely explored and challenging. In this article, triaminoguanidine-derived covalent organic frameworks (COFs) were used as platforms to develop heterogeneous organocatalysts for the reaction. We demonstrated that the COFs with guanidine cores and pyrazine linkers show high catalytic performance as a result of the cooperation between cores and linkers. The core is vitally important, which is deprotonated to the guanidinato group that binds and activates CO2. The pyrazine linker collaborates with the core to activate the C(sp)-H bond through hydrogen bonding. In addition, the COFs show acid- and base-responsive chromic behaviors thanks to the amphoteric nature of the core and the auxochromic effect of the pyrazine linker. The work opens up new avenues to organocatalysts for C-H carboxylation and chromic materials for sensing and switching applications.

Insufficient evidence to link human exposure to heavy metals with biomarkers of glioma.

Information on molecular mechanisms has implicated potential association between the concentrations of heavy metals and incidences of glioma, but experimental data on human brain tissue remain sparse. To address this data gap, 13 heavy metals were measured in 137 glioma and 35 non-glioma samples collected from 161 alive patients in Guangdong Province, China in 2019 - 2020. All target heavy metals were detected, suggesting they could cross the blood-brain barrier. Concentrations of Mn, Cu, and Zn were higher in glioma than in non-glioma samples, while those of Ni and Se were higher in non-glioma samples, probably suggesting that these five heavy metals are more prone to be altered by changing pathological conditions. In addition, Cu/Zn, Cr/Mn, Cr/Se, Ni/Se, Pb/Mn, and Pb/Se were statistically different between glioma and non-glioma samples by a difference test and a multiple logistic regression model. These concentration ratios may serve as chemical markers to assist pathological analysis for differentiating between tumor and healthy tissues. However, no direct link between heavy metal concentrations or concentration ratios and biomarkers of glioma (i.e., tumor grade, P53, and Ki-67) was observed. No sufficient evidence was obtained to implicate the role of heavy metals in inducing glioma, largely caused by the limited number of samples. Different concentrations and concentration ratios of heavy metals may be the consequence rather than the cause of pathological changes in brain tumors.