Evolution of sea-surfing plant propagule as revealed by the genomes of Heritiera mangroves.

Coastal forests, such as mangroves, protect much of the tropical and subtropical coasts. Long-distance dispersal via sea-surfing propagules is essential for coastal plants, but the genomic and molecular basis of sea-surfing plant propagule evolution remains unclear. Heritiera fomes and Heritiera littoralis are two coastal plants with typical buoyant fruits. We de novo sequenced and assembled their high-quality genomes. Our phylogenomic analysis indicates H. littoralis and H. fomes originated (at ~6.08 Mya) just before the start of Quaternary sea-level fluctuations. Whole-genome duplication occurred earlier, permitting gene copy gains in the two species. Many of the expanded gene families are involved in lignin and flavonoid biosynthesis, likely contributing to buoyant fruit emergence. It is repeatedly revealed that one duplicated copy to be under positive selection while the other is not. By examining H. littoralis fruits at three different developmental stages, we found that gene expression levels remain stable from young to intermediate. However, ~1000 genes are up-regulated and ~ 3000 genes are down-regulated as moving to mature. Particularly in fruit epicarps, the upregulation of WRKY12 and E2Fc likely constrains the production of p-Coumaroyl-CoA, the key internal substrate for lignin biosynthesis. Hence, to increase fruit impermeability, methylated lignin biosynthesis is shut down by down-regulating the genes CCoAOMT, F5H, COMT, and CSE, while unmethylated lignins are preferentially produced by upregulating CAD and CCR. Similarly, cutin polymers and cuticular waxes accumulate with high levels before maturation in epicarps. Overall, our genome assemblies and analyses uncovered the genomic evolution and temporal transcriptional regulation of sea-surfing propagule.

Recent advances in the chemistry of isolable carbene analogues with group 13-15 elements.

Carbenes (R2C:), compounds with a divalent carbon atom containing only six valence shell electrons, have evolved into a broader class with the replacement of the carbene carbon or the RC moiety with main group elements, leading to the creation of main group carbene analogues. These analogues, mirroring the electronic structure of carbenes (a lone pair of electrons and an empty orbital), demonstrate unique reactivity. Over the last three decades, this area has seen substantial advancements, paralleling the innovations in carbene chemistry. Recent studies have revealed a spectrum of unique carbene analogues, such as monocoordinate aluminylenes, nitrenes, and bismuthinidenes, notable for their extraordinary properties and diverse reactivity, offering promising applications in small molecule activation. This review delves into the isolable main group carbene analogues that are in the forefront from 2010 and beyond, spanning elements from group 13 (B, Al, Ga, In, and Tl), group 14 (Si, Ge, Sn, and Pb) and group 15 (N, P, As, Sb, and Bi). Specifically, this review focuses on the potential amphiphilic species that possess both lone pairs of electrons and vacant orbitals. We detail their comprehensive synthesis and stabilization strategies, outlining the reactivity arising from their distinct structural characteristics.

Correction: Recent advances in the chemistry of isolable carbene analogues with group 13-15 elements.

Correction for 'Recent advances in the chemistry of isolable carbene analogues with group 13-15 elements' by Mian He et al., Chem. Soc. Rev., 2024, https://doi.org/10.1039/D3CS00784G.

Post-hybridization introgression and natural selection promoted genomic divergence of Aegilops speltoides and the four S*-genome diploid species.

Understanding how different driving forces have promoted biological divergence and speciation is one of the central issues in evolutionary biology. The Triticum/Aegilops species complex contains 13 diploid species belonging to the A-, B- and D-lineages and offers an ideal system to address the evolutionary dynamics of lineage fusion and splitting. Here, we sequenced the whole genomes of one S-genome species (Aegilops speltoides) of the B-lineage and four S*-genome diploid species (Aegilops bicornis, Aegilops longissima, Aegilops sharonensis and Aegilops searsii) of the D-lineage at the population level. We performed detailed comparisons of the five species and with the other four representative A-, B- and D-lineage species. Our estimates identified frequent genetic introgressions from A- and B-lineages to the D-lineage species. A remarkable observation is the contrasting distributions of putative introgressed loci by the A- and B-lineages along all the seven chromosomes to the extant D-lineage species. These genetic introgressions resulted in high levels of genetic divergence at centromeric regions between Ae. speltoides (B-lineage) and the other four S*-genome diploid species (D-lineage), while natural selection is a potential contributor to divergence among the four S*-genome species at telomeric regions. Our study provides a genome-wide view on how genetic introgression and natural selection acted together yet chromosome-regionally divided to promote genomic divergence among the five S- and S*-genome diploid species, which provides new and nuanced insights into the evolutionary history of the Triticum/Aegilops species complex.

Carbene-Stabilized Phosphagermylenylidene: A Heavier Analog of Isonitrile.

Phosphagermylenylidenes (R-P═Ge), as heavier analogs of isonitriles, whether in their free state or as complexes with a Lewis base, have not been previously identified as isolable entities. In this study, we report the synthesis of a stable monomeric phosphagermylenylidene within the coordination sphere of a Lewis base under ambient conditions. This species was synthesized by Lewis base-induced dedimerization of a cyclic phosphagermylenylidene dimer or via Me3SiCl elimination from a phosphinochlorogermylene framework. The deliberate integration of a bulky, electropositive N-heterocyclic boryl group at the phosphorus site, combined with coordination stabilization by a cyclic (alkyl)(amino)carbene at the low-valent germanium site, effectively mitigated its natural tendency toward oligomerization. Structural analyses and theoretical calculations have demonstrated that this unprecedented species features a P═Ge double bond, characterized by conventional electron-sharing π and σ bonds, complemented by lone pairs at both the phosphorus and germanium atoms. Preliminary reactivity studies show that this base-stabilized phosphagermylenylidene demonstrates facile release of ligands at the Ge atom, coordination to silver through the lone pair on P, and versatile reactivity including both (cyclo)addition and cleavage of the P═Ge double bond.

Genome-wide association and Mendelian randomization analysis provide insights into the shared genetic architecture between high-dimensional electrocardiographic features and ischemic heart disease.

Observational studies have revealed that ischemic heart disease (IHD) has a unique manifestation on electrocardiographic (ECG). However, the genetic relationships between IHD and ECG remain unclear. We took 12-lead ECG as phenotypes to conduct genome-wide association studies (GWAS) for 41,960 samples from UK-Biobank (UKB). By leveraging large-scale GWAS summary of ECG and IHD (downloaded from FinnGen database), we performed LD score regression (LDSC), Mendelian randomization (MR), and polygenic risk score (PRS) regression to explore genetic relationships between IHD and ECG. Finally, we constructed an XGBoost model to predict IHD by integrating PRS and ECG. The GWAS identified 114 independent SNPs significantly (P value < 5 × 10-8/800, where 800 denotes the number of ECG features) associated with ECG. LDSC analysis indicated significant (P value < 0.05) genetic correlations between 39 ECG features and IHD. MR analysis performed by five approaches showed a putative causal effect of IHD on four S wave related ECG features at lead III. Integrating PRS for these ECG features with age and gender, the XGBoost model achieved Area Under Curve (AUC) 0.72 in predicting IHD. Here, we provide genetic evidence supporting S wave related ECG features at lead III to monitor the IHD risk, and open up a unique approach to integrate ECG with genetic factors for pre-warning IHD.

Relaxation of Spring Festival Firework Regulations Leads to a Deterioration in Air Quality.

The relaxation of restrictions on Chinese Spring Festival (SF) firework displays in certain regions has raised concerns due to intensive emissions exacerbating air quality deterioration. To evaluate the impacts of fireworks on air quality, a comparative investigation was conducted in a city between 2022 (restricted fireworks) and 2023 SF (unrestricted), utilizing high time-resolution field observations of particle chemical components and air quality model simulations. We observed two severe PM2.5 pollution episodes primarily triggered by firework emissions and exacerbated by static meteorology (contributing approximately 30%) during 2023 SF, contrasting with its absence in 2022. During firework displays, freshly emitted particles containing more primary inorganics (such as chloride and metals like Al, Mg, and Ba), elemental carbon, and organic compounds (including polycyclic aromatic hydrocarbons) were predominant; subsequently, aged particles with more secondary components became prevalent and continued to worsen air quality. The primary emissions from fireworks constituted 54% of the observed high PM2.5 during the displays, contributing a peak hourly PM2.5 concentration of 188 µg/m3 and representing over 70% of the ambient PM2.5. This study underscores that caution should be exercised when igniting substantial fireworks under stable meteorological conditions, considering both the primary and potential secondary effects.

Associations of multimorbidity with body pain, sleep duration, and depression among middle-aged and older adults in China.

BACKGROUND: Multimorbidity, body pain, sleep disturbance, and depression are major clinical and public health challenges. This paper aimed to examine the associations of multimorbidity with body pain, sleep duration, and depression; and whether the associations varied by socioeconomic status. METHODS: Data was derived from four waves of the nationally representative China Health and Retirement Longitudinal Study (CHARLS), including participants aged 45 years and older in 2011. 12 physical non-communicable diseases and 1 mental chronic disease were used to measure multimorbidity. Educational attainment and annual per-capita household consumption expenditure were employed as proxies for socioeconomic status. RESULTS: Of the 16,931 participants aged 45 + years old, the proportion of people with multimorbidity was 37.87% at baseline. The number of multimorbidity increased with older age and higher socioeconomic status. Multimorbidity was associated with more body pain (incidence rate ratio (IRR) = 1.53, 95% CI = 1.45-1.61), and decreased sleep duration (ß = -0.26, 95% CI = -0.36--0.15). Furthermore, multimorbidity was associated with increased depression risks (odds ratio (OR) = 1.54, 95% CI = 1.44-1.64, adjusted for sociodemographic variables), with the mediating effects of the number of body pain and sleep duration. The associations between multimorbidity and depression persisted among different socioeconomic groups. CONCLUSIONS: Multimorbidity was associated with increased body pain, decreased sleep duration, and further led to increased depression risks. It is necessary to pay attention to the multimorbidity of middle-aged and older adults, relieve their body pain, guarantee sufficient sleep, so as to reduce depression risks.

Spatial variation in iodine content with relation to soil physicochemical properties in lower Himalayan region.

Topography of a place has a significant impact on soil characteristics that ultimately influence soil iodine levels. Lower Himalayan region (LHR) in Pakistan has a wide range of climatic and geological variations. Hence, an investigation was conducted to analyze the iodine concentration and other physicochemical properties of soils in two LHR districts, Haripur and Mansehra. Spatial analysis indicated a decrease in iodine levels in the mountainous regions in comparison to the flat portions of LHR. Soil samples obtained from different locations across Haripur had a stronger affinity for iodine due to variations in solubility and adsorption of iodine to soil clay components, which can be attributed to lower pH, higher organic matter, and a higher cation exchange capacity (CEC). In contrast to the plains of Haripur, elevated locations in the Mansehra district had decreased levels of iodine, along with a higher soil pH and reduced soil organic matter. The soil erosion and depletion of soil micronutrients in the hilly region of Mansehra may be attributed to the unfavorable soil conditions and excessive precipitation. Presence of clay, iron (Fe), and aluminum (Al) in the soil led to a rise in iodine levels. Iodine concentrations exhibited an inverse relationship with soil acidity. Study revealed a direct correlation between soil iodine levels and their cation exchange capacity (CEC) and clay content. This study aims to gather fundamental data for the chosen regions of LHR to address illnesses caused by iodine deficiency.

Evolutionary roles of polyploidization-derived structural variations in the phenotypic diversification of Panax species.

Genomic structural variations (SVs) are widespread in plant and animal genomes and play important roles in phenotypic novelty and species adaptation. Frequent whole genome duplications followed by (re)diploidizations have resulted in high diversity of genome architecture among extant species. In this study, we identified abundant genomic SVs in the Panax genus that are hypothesized to have occurred through during the repeated polyploidizations/(re)diploidizations. Our genome-wide comparisons demonstrated that although these polyploidization-derived SVs have evolved at distinct evolutionary stages, a large number of SV-intersecting genes showed enrichment in functionally important pathways related to secondary metabolites, photosynthesis and basic cellular activities. In line with these observations, our metabolic analyses of these Panax species revealed high diversity of primary and secondary metabolites both at the tissue and interspecific levels. In particular, genomic SVs identified at ginsenoside biosynthesis genes, including copy number variation and large fragment deletion, appear to have played important roles in the evolution and diversification of ginsenosides. A further herbivore deterrence experiment demonstrated that, as major triterpenoidal saponins found exclusively in Panax, ginsenosides provide protection against insect herbivores. Our study provides new insights on how polyploidization-derived SVs have contributed to phenotypic novelty and plant adaptation.

Active quasi-BIC metasurfaces assisted by epsilon-near-zero materials.

Active devices play a critical role in modern electromagnetic and photonics systems. To date, the epsilon (ε)-near-zero (ENZ) is usually integrated with the low Q-factor resonant metasurface to achieve active devices, and enhance the light-matter interaction significantly at the nanoscale. However, the low Q-factor resonance may limit the optical modulation. Less work has been focused on the optical modulation in the low-loss and high Q-factor metasurfaces. Recently, the emerging optical bound states in the continuum (BICs) provides an effective way for achieving high Q-factor resonators. In this work, we numerically demonstrate a tunable quasi-BICs (QBICs) by integrating a silicon metasurface with ENZ ITO thin film. Such a metasurface is composed of five square holes in a unit cell, and hosts multiple BICs by engineering the position of centre hole. We also reveal the nature of these QBICs by performing multipole decomposition and calculating near field distribution. Thanks to the large tunability of ITO's permittivity by external bias and high-Q factor enabled by QBICs, we demonstrate an active control on the resonant peak position and intensity of transmission spectrum by integrating ENZ ITO thin films with QBICs supported by silicon metasurfaces. We find that all QBICs show excellent performance on modulating the optical response of such a hybrid structure. The modulation depth can be up to 14.8 dB. We also investigate how the carrier density of ITO film influence the near-field trapping and far-field scattering, which in turn influence the performance of optical modulation based on this structure. Our results may find promising applications in developing active high-performance optical devices.

The performance of interferon gamma release assays in patients with nontuberculous mycobacterial infection: a systematic review and meta-analysis.

BACKGROUND: The actual positive rate of interferon gamma release assays (IGRAs) in patients with nontuberculous mycobacteria (NTM) infections remains unclear. This review and meta-analysis present the prevalence of positive IGRAs (T-SPOT.TB and QuantiFERON [QFT] tests) among patients infected with NTM isolates (with or without ESAT-6/CFP-10). METHODS: Several databases, including PubMed, Scopus, Embase, and Web of Science were searched (until June 18th, 2022). Studies that had the following data were included: (1) results of T-SPOT.TB, QuantiFERON (QFT) test, or both, (2) NTM species, and (3) NTM diseases, or NTM colonization. The metaprop command that incorporates a Freeman-Tukey double arcsine transformation is used for pooling proportions. RESULTS: A total of 11 articles (n = 929) were deemed eligible for inclusion. Meta-analysis identified that the overall pooled positive and indeterminate rates of IGRA results in patients with NTM infections was 16% and 5%, respectively. Subgroup analysis showed that the positive rate of IGRAs in patients infected with NTM (without ESAT-6/CFP-10) was 7% (95% CI, 1%-18%), and 44% (95%CI, 22%-68%) in patients infected with NTM (with ESAT-6/CFP-10). In addition, the indeterminate rate of QFT (7%, 95% CI: 4%-12%) was higher than that of T-SPOT.TB (0%; 95% CI, 0%-2%) among the overall population with NTM infections. CONCLUSIONS: The IGRAs have a moderate positive rate for the diagnosis of NTM (expressing ESAT-6/CFP-10) infections, and a significant indeterminate rate is observed among the overall population infected with NTM. However, these findings should be interpreted with caution because of the high heterogeneity among studies.

Antibacterial MccM as the Major Microcin in Escherichia coli Nissle 1917 against Pathogenic Enterobacteria.

Probiotic Escherichia coli Nissle 1917 (EcN) possesses excellent antibacterial effects on pathogenic enterobacteria. The microcins MccM and MccH47 produced in EcN played critical roles, but they are understudied and poorly characterized, and the individual antibacterial mechanisms are still unclear. In this study, three EcN mutants (ΔmcmA, ΔmchB, and ΔmcmAΔmchB) were constructed and compared with wild-type EcN (EcN wt) to test for inhibitory effects on the growth of Escherichia coli O157: H7, Salmonella enterica (SE), and Salmonella typhimurium (ST). The antibacterial effects on O157: H7 were not affected by the knockout of mcmA (MccM) and mchB (MccH47) in EcN. However, the antibacterial effect on Salmonella declined sharply in EcN mutants ΔmcmA. The overexpressed mcmA gene in EcN::mcmA showed more efficient antibacterial activity on Salmonella than that of EcN wt. Furthermore, the EcN::mcmA strain significantly reduced the abilities of adhesion and invasion of Salmonella to intestinal epithelial cells, decreasing the invasion ability of ST by 56.31% (62.57 times more than that of EcN wt) while reducing the adhesion ability of ST by 50.14% (2.41 times more than that of EcN wt). In addition, the supernatant of EcN::mcmA culture significantly decreased the mRNA expression and secretion of IL-1ß, TNF-α, and IL-6 on macrophages induced by LPS. The EcN::mcmA strain generated twice as much orange halo as EcN wt by CAS agar diffusion assay by producing more siderophores. MccM was more closely related to the activity of EcN against Salmonella, and MccM-overproducing EcN inhibited Salmonella growth by producing more siderophores-MccM to compete for iron, which was critical to pathogen growth. Based on the above, EcN::mcmA can be developed as engineered probiotics to fight against pathogenic enterobacteria colonization in the gut.

Investigation of Immune Responses in Giant African Snail, Achatina immaculata, against a Two-Round Lipopolysaccharide Challenge.

As one of the 100 most-threatening invasive alien species, the giant African snail (Achatina immaculata) has successfully invaded and established itself in most areas of southern China. Protection against recurrent pathogen infections is vital to biological invasion. Enhanced immune protection has been previously found in other invertebrates, but not in the unique immune system of the giant African snail. In the present study, the survival rate of the giant African snail was recorded following a second infection with lethal doses of Escherichia coli after a previous first injection using lipopolysaccharide (LPS), and the mechanism of immune enhancement was investigated by examining the cellular and transcriptomic response of the giant African snail after two successive stimuli using LPS. Snails injected first with LPS, sterilized physiologic (0.9%) saline (SPS), phosphate-buffered saline (PBS) or untreated (Blank) were rechallenged at 7d with E. coli (Ec), and were named as LPS + Ec, SPS + Ec, PBS + Ec, Ec, and Blank. The log-rank test shows the survival rate of the LPS + Ec group as significantly higher than that of other control groups after the second injection (p < 0.05). By performing cell counting and BrdU labeling on newly generated circulating hemocytes, we found that the total hemocyte count (THC) and the ratio of BrdU-positive cells to total cells increased significantly after primary stimulation with LPS and that they further increased after the second challenge. Then, caspase-3 of apoptosis protease and two antioxidant enzyme activities (CAT and SOD) increased significantly after infection, and were significantly higher in the second response than they had been in the first round. Moreover, transcriptome analysis results showed that 84 differentially expressed genes (DEGs) were expressed at higher levels in both the resting and activating states after the second immune response compared to the levels observed after the first challenge. Among them, some DEGs, including Toll-like receptor 4 (TLR4) and its downstream signaling molecules, were verified using qRT-PCR and were consistent with the transcriptome assay results. Based on gene expression levels, we proposed that these genes related to the TLR signaling cascade participate in enhanced immune protection. All results provide evidence that enhanced immune protection exists in the giant African snail.

[Ferroptosis:Mechanism and Role in Malignant Tumors].

Ferroptosis is a new type of programmed cell death different from other cell death pathways such as apoptosis,autophagy,necrosis,and pyroptosis in terms of initiation,mechanisms,and molecular characteristics.As the accumulation of phospholipid hydroperoxides is the hallmark of ferroptosis,the balance between oxidative damage and antioxidant defense is critical to the regulatory mechanism of ferroptosis.In cancer,the upregulation of antioxidant defense pathways can inhibit ferroptosis,thereby promoting cancer cells to survive the oxidative stress and develop drug resistance.This review systematically introduces the main features and regulatory mechanisms of ferroptosis.In addition,we summarize the role of ferroptosis in the progression and drug resistance of malignant tumors,providing novel implications for further research on the pathogenesis of malignant tumors and discovery of new targets for anti-cancer therapy.

Stable Ketenyl Anions via Ligand Exchange at an Anionic Carbon as Powerful Synthons.

Under an atmosphere of carbon monoxide (CO), a (phosphino)diazomethyl anion salt [[P]-CN2 ][K(18-C-6)(THF)] (1) ([P]=[(CH2 )(NDipp)]2 P; 18-C-6=18-crown-6; Dipp=2,6-diisopropylphenyl) undergoes a facile N2 /CO exchange reaction giving the (phosphino)ketenyl anion salt [[P]-CCO][K(18-C-6)] (2). Oxidation of 2 with elemental Se affords the (selenophosphoryl)ketenyl anion salt [P](Se)-CCO][K(18-C-6)] (3). These ketenyl anions feature a strongly bent geometry at the P-bound carbon and this carbon atom is highly nucleophilic. The electronic structure of the ketenyl anion [[P]-CCO]- of 2 is examined by theoretical studies. Reactivity investigations demonstrate 2 as a versatile synthon for derivatives of ketene, enolate, acrylate and acrylimidate moieties.

Phenotypic and transcriptomic responses of the shade-grown species Panax ginseng to variable light conditions.

BACKGROUND AND AIMS: Elucidating how plant species respond to variable light conditions is important to understand the ecological adaptation to heterogeneous natural habitats. Plant performance and its underlying gene regulatory network have been well documented in sun-grown plants. However, the phenotypic and molecular responses of shade-grown plants under variable light conditions have remained largely unclear. METHODS: We assessed the differences in phenotypic performance between Panax ginseng (shade-grown) and Arabidopsis thaliana (sun-grown) under sunlight, shade and deep-shade conditions. To further address the molecular bases underpinning the phenotypic responses, we compared time-course transcriptomic expression profiling and candidate gene structures between the two species. KEY RESULTS: Our results show that, compared with arabidopsis, ginseng plants not only possess a lower degree of phenotypic plasticity among the three light conditions, but also exhibit higher photosynthetic efficiency under shade and deep-shade conditions. Further comparisons of the gene expression and structure reveal that differential transcriptional regulation together with increased copy number of photosynthesis-related genes (e.g. electron transfer and carbon fixation) may improve the photosynthetic efficiency of ginseng plants under the two shade conditions. In contrast, the inactivation of phytochrome-interacting factors (i.e. absent and no upregulation of the PIF genes) are potentially associated with the observed low degree of phenotypic plasticity of ginseng plants under variable light conditions. CONCLUSIONS: Our study provides new insights into how shade-grown plants respond to variable light conditions. Candidate genes related to shade adaptation in ginseng provide valuable genetic resources for future molecular breeding of high-density planting crops.

Chemical composition, sources and optical properties of nitrated aromatic compounds in fine particulate matter during winter foggy days in Nanjing, China.

Functionalized aromatic compounds are one of the most important light-absorbing organic chromophores - so-called brown carbon (BrC) - in fine particulate matter (PM2.5). In this study, we conducted a wintertime field campaign to measure eight nitrated aromatic compounds (NACs) in PM2.5 with offline analysis techniques, including liquid chromatograph mass spectrometer (LC-MS) and aerodyne high-resolution aerosol mass spectrometer (AMS) measurements, during foggy and nonfoggy days in suburban Nanjing in the Yangtze River Delta region, China. On average, 4-nitrophenol could be one of the most important light absorbing materials in the observed BrC, which accounted for over 40% of the mass concentration of identified chromophores. The mass concentration of 2-methyl-4-nitrophenol and 2,6-dimethyl-4-nitrophenol were evidently increased during foggy days, contribution of which to total NACs were increased by 10% and 5%, respectively. Positive matrix factorization analysis of combining LC-MS and AMS dataset was performed to identify the primary and secondary sources of NACs. Primary sources, e.g., traffic and solid-fuel combustion, accounted for 71% of the sum of 4-nitrophenol, 2,6-dimethyl-4-nitrophenol and 3-nitrosalicylic acid, suggesting important contribution of primary emissions to these NACs. The contribution of secondary sources, associated with two oxygenated organic aerosols, could contribute 66% to 4-nitrophenol, reflecting the link of such nitrated aromatic compounds to secondary organic aerosol source. Together with optical measurements, 4-nitrophenol presented a high contribution (>50%) to the identified BrC absorbance in the light range 250 and 550 nm was observed. This could highlight an important role of such NACs in ambient BrC light absorption, despite its mass contribution to total organic carbon was negligible. Our work could improve the understanding of the links between optical properties and chemical composition of BrC, and the difference between BrC chromophores from nonfoggy days and foggy days under the typical polluted atmospheric conditions.

Particulate organic nitrates at Mount Tai in winter and spring: Variation characteristics and effects of mountain-valley breezes and elevated emission sources.

Particulate organic nitrates, among the major components of secondary organic aerosols and fine particles, play important roles in regional nitrogen cycle, ozone budget, and cloud condensation nuclei formation. However, the pollution characteristics of particulate organic nitrates at mountain areas and the effects of anthropogenic pollutant transport remain poorly understood. In this study, field sampling and measurements were conducted at a high-elevation mountain site over North China Plain in winter and spring. Total five kinds of particulate organic nitrates in fine particles were determined by ultra-high performance liquid chromatography-electrospray mass spectrometry. The average total concentrations of particulate organic nitrates were 330 ± 121 ng m-3 and 247 ± 63 ng m-3 in winter and spring. The monoterpene-derived organic nitrates were the dominant components in both seasons with their contribution higher than 70%, accounting for 1.2 ± 0.8% and 2.0 ± 1.0% in organic aerosols in winter and spring, respectively. The significantly higher levels of particulate organic nitrates in winter than spring was ascribed to the strong effects of mountain-valley breezes and coal combustion plumes. The increasing concentrations of NOx and particulate matters brought by the valley breeze at daytime facilitated the formation of MHN215, OAKN359, and OAHN361, while the rising SO2 abundance and the sulfate aerosols transported by elevated emission sources affected the formation of MDCN247 at nighttime.

Asymmetric Total Synthesis of Taxol.

Taxol is one of the most famous natural diterpenoids and an important anticancer medicine. Taxol represents a formidable synthetic challenge and has prompted significant interest from the synthetic community. However, in all the previous syntheses of Taxol, there have been no reports of closing the desired eight-membered ring through C1-C2 bond formation. Furthermore, the existence of Taxol-resistant tumors and side effects of Taxol make the development of new approaches to synthesize Taxol and its derivatives highly desirable. Here, we report the asymmetric total synthesis of Taxol using a concise approach through 19 isolated intermediates. The synthetically challenging eight-membered ring was constructed efficiently by a diastereoselective intramolecular SmI2-mediated pinacol coupling reaction to form the C1-C2 bond. The unique biomimetic oxygen ene reaction and the newly developed facile tandem C2-benzoate formation and C13 side chain installation improved the efficiency of the synthesis. The mild oxygen ene reaction under light conditions would be an alternative reaction involved in Taxol biosynthesis. This new convergent approach will allow the diverse creation of Taxol derivatives to enable further biological research.