Malonic Acid Research Articles

Third-order nonlinear optical properties of choline chloride based deep eutectic solvents: Theoretical and experimental studies

In this work, the preparation of three deep eutectic solvents (DES) based on choline chloride as hydrogen bond acceptor and urea, malonic acid, and phenylpropionic acid as hydrogen bond donor is reported. These series of DES were used as models to measure, for the first time, the third-order optical nonlinearities in eutectic solvents. The nonlinear refractive index (n2) originated from the fast electronic response was determined by the close aperture Z-scan technique under excitation of laser ultrafast pulses at 800 nm, resulting in values of the order of ∼3 × 10-16 cm2 W−1, which are similar to those reported recently for ionic liquids. These values are also similar to those exhibited by some traditional polar protic organic solvents such as water and ethanol. At relatively low energy pulses, the DES presented only pure refractive response, but at high energies two of them exhibited nonlinear absorption. On the other hand, ab initio theoretical calculations using density functional theory (DFT) allowed to determine the static and dynamic second hyperpolarizabilities for the DES with M11/6-311G(d,p) level of theory. The tendency of the theoretical results agrees satisfactorily with the values of n2 obtained experimentally. Our results suggest that the presence of aromatic cloud makes that choline chloride:phenylpropionic acid contributes to produce relatively high n2 values. This study provides relevant information to be considered when DES are intended as an alternative to standard organic solvents in the development of photonic materials.

Changes in the Size Distributions of Oxalic Acid and Related Polar Compounds Over Northern Japan During Spring

AbstractSize distributions of chemical species provide evidence for their sources and formation mechanisms. Size‐segregated aerosols with 12 sizes were collected over Northern Japan (Sapporo: 43.07°N and 141.35°E) during the spring (9 April–21 May) of 2001 and analyzed for water‐soluble organic and inorganic species. The dominances of SO42– and NH4+ in submicron (Da < 1.1 μm) and Na+ and Ca2+ in supermicron (Da > 1.1 μm) aerosols suggest substantial contributions from anthropogenic sources, sea‐salt and dust particles via long‐range atmospheric transport. Oxalic acid (C2) is the dominant organic species followed by malonic (C3) and succinic (C4) acid. A supermicron mode enrichment of C2 is heavily involved with the long‐range transport of dust particles, whereas submicron mode C2 was influenced by anthropogenic sources from the East Asian continent. The size distributions of shorter‐chain diacids (C3–C6), phthalic (Ph) and glyoxylic acid are consistent with those of C2, whereas azelaic acid (C9) is enriched in submicron and supermicron modes by the influences of continental and marine air masses. The mass concentration ratios of C3/C4 in submicron (1.5–2.3) and supermicron (1.2–1.8) mode demonstrated that water‐soluble organic aerosols in Sapporo were photochemically processed during long‐range transport. The Ph/C9 ratios show that the influence of anthropogenic sources on 9–28 April samples was pronounced in supermicron (2.5–2.9) than the submicron (1.1–1.2) particles, and vice‐versa on 6–21 May samples. These contrast distributions suggest that the continental air masses from East Asia and marine air masses from the surrounding ocean likely control the chemical composition of aerosols over Northern Japan.

Synthesis of (E)‐α,β‐Unsaturated Thioesters from Malonic Acid Half Thioesters and Aldehydes

AbstractA decarboxylative condensation of malonic acid half thioesters (MAHTs) with aldehydes catalyzed by benzylammonium trifluoroacetate has been developed for the synthesis of (E)‐α,β‐unsaturated thioesters. The reaction of aromatic aldehydes and sterically non‐demanding aliphatic aldehydes proceeded smoothly at room temperature in DMF in a stereo‐ and regioselective manner. Besides the unsubstituted malonate, 2‐fluoro‐ and 2‐methylmalonates could be employed as a nucleophile. Use of the present catalyst could avoid nonproductive protiodecarboxylation of MAHTs.

A Non-Systemic Phosphodiesterase-5 Inhibitor Suppresses Colon Proliferation in Mice.

Phosphodiesterase-5 inhibitors (PDE5i) are under investigation for repurposing for colon cancer prevention. A drawback to conventional PDE5i are their side-effects and drug-drug interactions. We designed an analog of the prototypical PDE5i sildenafil by replacing the methyl group on the piperazine ring with malonic acid to reduce lipophilicity, and measured its entry into the circulation and effects on colon epithelium. This modification did not affect pharmacology as malonyl-sildenafil had a similar IC50 to sildenafil but exhibited an almost 20-fold reduced EC50 for increasing cellular cGMP. Using an LC-MS/MS approach, malonyl-sildenafil was negligible in mouse plasma after oral administration but was detected at high levels in the feces. No bioactive metabolites of malonyl-sildenafil were detected in the circulation by measuring interactions with isosorbide mononitrate. The treatment of mice with malonyl-sildenafil in the drinking water resulted in a suppression of proliferation in the colon epithelium that is consistent with results previously published for mice treated with PDE5i. A carboxylic-acid-containing analog of sildenafil prohibits the systemic delivery of the compound but maintains sufficient penetration into the colon epithelium to suppress proliferation. This highlights a novel approach to generating a first-in-class drug for colon cancer chemoprevention.

Differentiation of obese and healthy mice by analyzing the carboxylic acids in the TCA cycle in their feces

The tricarboxylic acid cycle is an important metabolic route in almost all living bodies, yet current analytical methods for the detection of the relevant tricarboxylic acids (TCAs) in biological samples are still unsatisfactory due to their complex matrix and physicochemical properties. In this work, a sample method based on solid phase extraction (SPE) in conjunction with liquid chromatography-mass spectrometry (LC-MS) analysis has been developed for the simultaneous determination of 7 TCAs, including α-ketoglutaric acid, malic acid, malonic acid, aconitic acid, citric acid, succinic acid and fumaric acid, in mice faeces. By treatment with macroporous styrene chelate resin and solid phase extraction, the matrix in mice feces was selectively and efficiently removed. Under optimized parameters, the limit of quantitation for the TCAs was in the range of 1-50 ng/mL, and the content of the TCAs in mice feces was determined with a recovery range of 76.2 % to 128.4 %. Interestingly, the content of malic acid, malonic acid, succinic acid and fumaric acid in the normal mice's feces was found to be 2-10 times higher than that of obese mice, indicating a new potential method for the diagnosis of obesity.

Electrified interfaces of deep eutectic solvents

Many theoretical and experimental studies have been focused on the physicochemical properties of dense ionic fluids such as ionic liquids (ILs). However, less attention has been given to interfacial properties involving deep eutectic solvents (DES). The impact of the DES composition, hydrogen bond donor (HBD) structure, temperature, and electrode nature material on the DES-electrode vertical interactions remain vague. The lack of knowledge imposes significant constraints in proposing a suitable Electrical Double Layer model (EDL) to describe the DES at electrified interfaces. Measuring differential capacitance-potential curves is a strategy to assess the EDL structure and understand how ions interact with the electrode surface, which knowledge is fundamental to designing and optimizing electrochemical systems for various applications (e.g., energy storage devices). Accordingly, a set of choline chloride-based DESs was assessed containing distinct HBD at their eutectic composition (the polyalcohol's 1,2-ethanediol, 1,2-propylene glycol, 1,3-propylene glycol, and the amide urea) against glassy carbon (GC), gold (Au), and the platinum (Pt) electrode at different temperatures.The differential capacitance-potential curves were found to vary significantly in shape in the three different electrode surfaces studied, ranging from camel shape (Au electrode), U-shape (GC), and asymmetric bell shape (polycrystalline Pt). The carboxylic malonic and oxalic acids were also assessed for a proper comparison to understand better the role of the HBD's functional group in shaping the electrode-electrolyte structure against the trend found with diol isomers. A suitable EDL model must inevitably accommodate interfacial properties assessed at the capacitive region, namely the influence of the surface chemistry, potential dependence, DES structure molecules, and temperature in shaping the electrified interfacial anatomy.

On Fractional-Order Discrete-Time Reaction Diffusion Systems

Reaction–diffusion systems have a broad variety of applications, particularly in biology, and it is well known that fractional calculus has been successfully used with this type of system. However, analyzing these systems using discrete fractional calculus is novel and requires significant research in a diversity of disciplines. Thus, in this paper, we investigate the discrete-time fractional-order Lengyel–Epstein system as a model of the chlorite iodide malonic acid (CIMA) chemical reaction. With the help of the second order difference operator, we describe the fractional discrete model. Furthermore, using the linearization approach, we established acceptable requirements for the local asymptotic stability of the system’s unique equilibrium. Moreover, we employ a Lyapunov functional to show that when the iodide feeding rate is moderate, the constant equilibrium solution is globally asymptotically stable. Finally, numerical models are presented to validate the theoretical conclusions and demonstrate the impact of discretization and fractional-order on system dynamics. The continuous version of the fractional-order Lengyel–Epstein reaction–diffusion system is compared to the discrete-time system under consideration.

Study of thioacetazone in aqueous mixtures of choline chloride/carboxylic acids deep eutectic solvents: Solubility and density measurements

The solubility of thioacetazone was measured in aqueous mixtures of deep eutectic solvents (DESs) with choline chloride as the hydrogen bond acceptor within the temperature range (298.15–313.15) K. The drug solubility in the neat DESs was found to be higher than that in water: by 53 times when malonic acid was used as the hydrogen bond donor, by 37 times with tartaric acid and by 33 times with citric acid in this role. The density of the water, neat DESs and their mixtures was determined at different temperatures. The density of the solvents under study was higher if the molecules of the acids contained in them had a bigger number of active functional groups. However, their solvating capacity was lower. The experimental data of the drug solubility in DES mixtures were shown to agree with the Hansen solubility parameters. The thermodynamic functions of thioacetazone dissolution were calculated and the intermolecular interactions in the systems with DESs were discussed.

Chemical characteristics and spatiotemporal variation of marine fine particles for clustered channels of air masses transporting toward remote background sites in East Asia

This study investigated the chemical characteristics, spatiotemporal distribution, and source apportionment of marine fine particles (PM2.5) for clustered transport channels/routes of air masses moving toward three remote sites in East Asia. Six transport routes in three channels were clustered based on backward trajectory simulation (BTS) in the order of: West Channel > East Channel > South Channel. Air masses transported toward Dongsha Island (DS) came mainly from the West Channel, while those transported toward Green Island (GR) and Kenting Peninsula (KT) came mostly from the East Channel. High PM2.5 commonly occurred from late fall to early spring during the periods of Asian Northeastern Monsoons (ANMs). Marine PM2.5 was dominated by water-soluble ions (WSIs) which were predominated by secondary inorganic aerosols (SIAs). Although the metallic content of PM2.5 was predominated by crustal elements (Ca, K, Mg, Fe, and Al), enrichment factor clearly showed that trace metals (Ti, Cr, Mn, Ni, Cu, and Zn) came mainly from anthropogenic sources. Organic carbon (OC) was superior to elemental carbon (EC), while OC/EC and SOC/OC ratios in winter and spring were higher than those in other two seasons. Similar trends were observed for levoglucosan and organic acids. The mass ratio of malonic acid and succinic acid (M/S) was commonly higher than unity, showing the influences of biomass burning (BB) and secondary organic aerosols (SOAs) on marine PM2.5. We resolved that the main sources of PM2.5 were sea salts, fugitive dust, boiler combustion, and SIAs. Boiler combustion and fishing boat emissions at the site DS had higher contribution than those at the sites GR and KT. The highest/lowest contribution ratios of cross-boundary transport (CBT) were 84.9/29.6% in winter and summer, respectively.

Structure-Based Analysis of Transient Interactions between Ketosynthase-like Decarboxylase and Acyl Carrier Protein in a Loading Module of Modular Polyketide Synthase.

Ketosynthase-like decarboxylase (KSQ) domains are widely distributed in the loading modules of modular type I polyketide synthases (PKSs) and catalyze the decarboxylation of the (alkyl-)malonyl unit bound to the acyl carrier protein (ACP) in the loading module for the construction of the PKS starter unit. Previously, we performed a structural and functional analysis of the GfsA KSQ domain involved in the biosynthesis of macrolide antibiotic FD-891. We furthermore revealed the recognition mechanism for the malonic acid thioester moiety of the malonyl-GfsA loading module ACP (ACPL) as a substrate. However, the exact recognition mechanism for the GfsA ACPL moiety remains unclear. Here, we present a structural basis for the interactions between the GfsA KSQ domain and GfsA ACPL. We determined the crystal structure of the GfsA KSQ-acyltransferase (AT) didomain in complex with ACPL (ACPL=KSQAT complex) by using a pantetheine crosslinking probe. We identified the key amino acid residues involved in the KSQ domain-ACPL interactions and confirmed the importance of these residues by mutational analysis. The binding mode of ACPL to the GfsA KSQ domain is similar to that of ACP to the ketosynthase domain in modular type I PKSs. Furthermore, comparing the ACPL=KSQAT complex structure with other full-length PKS module structures provides important insights into the overall architectures and conformational dynamics of the type I PKS modules.

Green Fractionation and Structural Characterization of Lignin Nanoparticles via Carboxylic-Acid-Based Deep Eutectic Solvent (DES) Pretreatment

Green fractionation and a comprehensive overview of lignin molecular structures during the DES (deep eutectic solvent) pretreatment are very important for lignin valorization and the whole biorefinery process. Herein, intractable woody biomass (poplar wood) was pretreated with five types of carboxylic-acid-based DESs (acetamide served as an HBA (hydrogen bond acceptor), propanedioic acid, tartaric acid, malic acid, glutaric acid, and succinic acid served as HBDs (hydrogen bond donors)) under the optimized pretreatment conditions. Results showed that the optimal delignification ratio was achieved for tartaric-acid-based DES at 140 °C for 20 min under microwave-assisted heating. Two-dimensional HSQC NMR data demonstrated that the isolated poplar DES lignin consisted mainly of β-β, β-O-4 (normal and acylated forms), β-5, and esterified p-hydroxybenzoates (PBs) in different contents. Especially, the contents of β-O-4 in the isolated DES lignin fractions varied based on the pretreatment temperature and different chemical compositions of the DES. The antioxidant activity (2,2-diphenyl-1-picrylhydrazyl, DPPH analysis), microstructure (scanning electron microscope, SEM), and molecular weights (gel permeation chromatography, GPC) of the DES lignin fractions demonstrated that the DES delignification promoted the rapid assembly of lignin nanoparticles (LNPs) and could yield homogeneous lignin (1.23 < PDI < 1.58) with controlled nanometer size (30–170 nm) and good antioxidant activity. This study will improve the knowledge of structural changes of lignin during the different carboxylic-acid-based DES pretreatments and maximize the lignin valorization.

Limited Role of Malonic Acid in Sulfuric Acid-Dimethylamine New Particle Formation.

Aerosols play an important role in climate and air quality; however, the mechanisms behind aerosol particle formation in the atmosphere are poorly understood. Studies have identified sulfuric acid, water, oxidized organics, and ammonia/amines as key precursors for forming aerosol particles in the atmosphere. Theoretical and experimental investigations have indicated that other species, such as organic acids, may be involved in atmospheric nucleation and growth of freshly formed aerosol particles. Organic acids, such as dicarboxylic acids, which are abundant in the atmosphere, have been measured in ultrafine aerosol particles. These observations suggest that organic acids may contribute to new particle formation in the atmosphere but their role remains ambiguous. This study examines how malonic acid interacts with sulfuric acid and dimethylamine to form new particles at warm boundary layer conditions using experimental observations from a laminar flow reactor and quantum chemical calculations coupled with cluster dynamics simulations. Observations reveal that malonic acid does not contribute to the initial steps (formation of <1 nm diameter particle) of nucleation with sulfuric acid-dimethylamine. In addition, malonic acid was found to not participate in the subsequent growth of the freshly nucleated 1 nm particles from sulfuric acid-dimethylamine reactions to diameters of 2 nm.

Copper-Catalyzed Synthesis of Propanedioic Acid Derivatives via a Carbene Carbonylation

Key words copper catalysis - carbenes - carbonylation - diazo compounds

Cannabis sativa L. modulates altered metabolic pathways involved in key metabolisms in human breast cancer (MCF-7) cells: A metabolomics study

The present study investigated the ability of Cannabis sativa leaves infusion (CSI) to modulate major metabolisms implicated in cancer cells survival, as well as to induce cell death in human breast cancer (MCF-7) cells. MCF-7 cell lines were treated with CSI for 48 h, doxorubicin served as the standard anticancer drug, while untreated MCF-7 cells served as the control. CSI caused 21.2% inhibition of cell growth at the highest dose. Liquid chromatography–mass spectroscopy (LC-MS) profiling of the control cells revealed the presence of carbohydrate, vitamins, oxidative, lipids, nucleotides, and amino acids metabolites. Treatment with CSI caused a 91% depletion of these metabolites, while concomitantly generating selenomethionine, l-cystine, deoxyadenosine triphosphate, cyclic AMP, selenocystathionine, inosine triphosphate, adenosine phosphosulfate, 5'-methylthioadenosine, uric acid, malonic semialdehyde, 2-methylguanosine, ganglioside GD2 and malonic acid. Metabolomics analysis via pathway enrichment of the metabolites revealed the activation of key metabolic pathways relevant to glucose, lipid, amino acid, vitamin, and nucleotide metabolisms. CSI caused a total inactivation of glucose, vitamin, and nucleotide metabolisms, while inactivating key lipid and amino acid metabolic pathways linked to cancer cell survival. Flow cytometry analysis revealed an induction of apoptosis and necrosis in MCF-7 cells treated with CSI. High-performance liquid chromatography (HPLC) analysis of CSI revealed the presence of cannabidiol, rutin, cinnamic acid, and ferulic. These results portray the antiproliferative potentials of CSI as an alternative therapy for the treatment and management of breast cancer as depicted by its modulation of glucose, lipid, amino acid, vitamin, and nucleotide metabolisms, while concomitantly inducing cell death in MCF-7 cells.

Tetraparesis as an initial manifestation of biotinidase deficiency: a case report.

The authors present a case of 2.5-year-old boy complained of progressive weakness in all four limbs, with difficulties in breathing. Abdominal examination revealed hepatomegaly and splenomegaly. Also, her parents were first-degree cousins. Therefore, tandem mass spectroscopy and urine organic acid analysis were planned to exclude metabolic disorders. Urinary organic acid analysis revealed elevated levels of methylmalonic acid and 3-hydroxyisovaleric acid. Serum biotinidase activity was found to be 3.9nmol/min/ml. Oral biotin at a dose of 1mg/kg daily was initiated. A marked improvement of his neurological deficit was noted over a period of 15 days after treatment and cutaneous manifestations resolved within 3 weeks. Myelopathy due to BTD is a challenging diagnosis. Spinal cord impairment is a rare complication of this disease and is frequently unrecognized. BTD should be included in the differential diagnosis of children presenting with demyelinating spinal cord disease.

A Comprehensive Study on DES Pretreatment Application to Microalgae for Enhanced Lipid Recovery Suitable for Biodiesel Production: Combined Experimental and Theoretical Investigations

Cell wall disturbance is an important step in the downstream process of improving the efficiency of lipid extraction from microalgae. Surfactants have been proven to be efficient alternatives to organic solvents in the extraction process. In this study, an effective approach involving deep eutectic solvent (DES) (choline chloride and carboxylic acids) treatment supplemented with surfactants has been developed to disrupt the cell walls of microalgae and increase the extraction of lipids suitable for biodiesel production. A combination of polar and non-polar solvents (ethyl acetate and n-butanol) was used for the lipid extraction process. Microalgae biomass pretreated with choline chloride malonic acid supplemented with the surfactant hexadecyl trimethylammonium chloride (HTAC) showed the best results, improving lipid extraction by 12.365%. Further elucidation of the detailed mechanism behind the cell disruption of the microalga wall by DES was achieved using density functional theory (DFT) methods. The DFT calculations revealed that hydrogen bonds between the chloride ion of the DES and hydrogen bond donor (HBD) molecules are key factors dominating the destruction of the cell wall structure of Chlorella pyrenoidosa. The optimization of lipid extraction was performed through a single-factor experiment, which included the effects of different variables (time, temperature, dosage of surfactant, and ratio of n-butanol to ethyl acetate). An extraction period of 60 min at 80 °C with a surfactant concentration of 0.5% at a 1:2 ratio of n-butanol to ethyl acetate was found to produce the maximum lipid yield (16.97%). Transesterification reactions were used to obtain fatty acid methyl esters from the optimized extracted lipids. Thus, it was determined that C16:0 (20.04%), C18:2 (29.95%), and C18:3 (21.21%) were the most prevalent fatty acids. The potential for producing biodiesel from C. pyrenoidosa was validated by the high yields of C18 fatty acid methyl esters, and the properties of biodiesel are within the European and US standards.

Phosphate Solubilization and Plant Growth Promotion by Pantoea brenneri Soil Isolates.

Phosphate solubilizing microorganisms (PSMs) in soil have been shown to reduce mineral phosphate fertilizer supplementation and promote plant growth. Nevertheless, only several P-solubilizing microorganisms capable of solubilizing both organic and mineral sources of soil phosphorus have been identified up to now. The aim of this study was to evaluate the inorganic soil phosphate solubilizing activity of phytate-hydrolyzing Pantoea brenneri soil isolates. We showed that the strains efficiently solubilize a variety of inorganic phosphates. We optimized the media composition and culturing conditions to improve the solubilization efficiency of the strains and investigated the mechanisms of their phosphate solubilization. Through HPLC analysis, it was determined that P. brenneri produce oxalic, malic, formic, malonic, lactic, maleic, acetic, and citric acids as well as acid and alkaline phosphatases while growing on insoluble phosphate sources. Finally, we analyzed the influence of P. brenneri strains with multiple PGP-treats on plant growth in greenhouse experiments and showed their ability to promote growth of potato.

Simultaneous ozonation of ethylbenzene and fluorene in water, soil, and air

Most of the studies regarding aromatic hydrocarbon degradation by ozone focus on individual treatment. Hence, two aromatic hydrocarbons, ethylbenzene (ETB) presented in water and fluorene (FL) distributed in soil, were selected to be eliminated simultaneously in water, soil, and air using ozone. In this study, the effect of the physicochemical properties of ETB and FL, the distribution of FL on sandy and agricultural soils, and the influence of the presence of moisture in both soils were analyzed. The chemical composition of the agricultural soil (mainly metal oxides) enhanced the FL degradation by the possible catalytic ozone decomposition into reactive species, such as •OH, O2•−, H2O2, O3•−, and O•, which reduced its treatment time 4.5-fold in this solid matrix compared to the sandy soil. Moreover, the moisture liberated from water by the gas flow and adsorbed on the soil bed (up to 0.33% at 180 min) reduced the ozonation time 2-fold in the agricultural and sandy soils, due to the •OH formation. Contrary to FL, the rapid elimination of ETB (< 20 min) in both soils did not allow to observe the possible effect of reactive species generation on ETB decomposition due to the low amount of moisture accumulated during this time (<0.06%). The proposed simultaneous ozonation scheme permitted to achieve up to 96% and 100% of the ETB and FL decomposition. Some identified by-products, such as maleic, malonic, oxalic, and formic acids, suggest that ozone and possible reactive species formed on the soil surfaces reacted with both compounds, leading to non-toxic simple by-products with their partial mineralization (≈80%), which was proven by a toxicity evaluation (phytotoxicity and eco-toxicity). The rapid and efficient simultaneous ozonation of aromatic hydrocarbons in water, soil, and air (only ETB) proves the feasibility of ozone to treat different organic pollutants in more than one phase.

Route-based chemical significance and source origin of marine PM2.5 at three remote islands in East Asia: Spatiotemporal variation and long-range transport

We explored the route-based chemical significance, spatial distribution, temporal variation, and source origin of fine particles (PM2.5) in East Asia. Marine PM2.5 was sampled at three remote islands in the Taiwan Strait (TS) and the South China Sea (SCS) to identify their chemical significance. High PM2.5 concentrations concurred with LRT of northerly polluted air. Moreover, daytime PM2.5 levels were mostly greater than nighttime. Secondary inorganic aerosols (SIAs) accounted for 42.4–79.9% of water-soluble ions (WSIs) in PM2.5, which were commonly higher in spring and winter. Although crustal elements suppressed the metallic contents of PM2.5, trace elements (V, Cr, Mn, Ni, Zn, and Cd) came dominantly from anthropogenic origins. Additionally, OC/EC ratios >2.0 were observed due to higher organic carbon (OC) than elemental carbon (EC) during the Asian Northeastern Monsoons (ANMs) commonly in spring and winter. Levoglucosan and oxalic acid were, respectively, the most abundant anhydrosugars (ASs) and organic acids (OAs) in PM2.5, and both descended from the north to the south. The mass ratios of malonic and succinic acids (M/S) were in the range of 0.95–1.41, suggesting a high correlation of marine PM2.5 with secondary organic aerosols (SOAs). Source resolution of PM2.5 showed that sea salts, fugitive dust, mobile sources, secondary sulfate and nitrate were the major sources of PM2.5. In particular, anthropogenic origins and biomass burning (BB) contributed notably to PM2.5 during the ANMs. Overall, compared to natural sources (21–48%), anthropogenic sources (25–57%) contributed more to marine PM2.5 in East Asia.

ROS-mediated TCA cycle is greatly related to the UV resistance of Bacillus thuringiensis

Bacillus thuringiensis (Bt) is a popular and environment-friendly biopesticide. However, similar to other microbial pesticides, Bt is limited by ultraviolet (UV) radiation during its application, which greatly reduces its toxicity and persistence. To further know the mechanism of Bt against UV radiation, metabolomic profiles between Bt LLP29 and its UV-resistant mutant LLP29-M19 were compared, analyzed, and annotated in this study, and then a total of 61 metabolites with different abundances were detected. With P < 0.05 as the standard, a total of 12 metabolic pathways were enriched, including the TCA cycle. According to the result of RT-qPCR, the expression levels of the TCA cycle key genes in Bt LL29-M19, such as icd1 citZ, citB, sdhA, sdhB, sdhC, fumA, and mdh, were found down-regulated for 85.58%, 37.02%, 70.87%, 85.97%, 76.33%, 83.15%, 87.28%, and 35.77% than those in Bt LLP29. It was consistent with the down-regulation trend of the TCA cycle key enzymes activity in Bt LLP29-M19. Consistently, the enzyme activities of ICDH, SDH, and PDH in LLP29-M19 were detected 86.28%, 43.93%, and 83.03% lower than those in Bt LLP29. It was revealed that the reduced TCA cycle was required for Bt UV radiation resistance, which was also demonstrated by the addition of inhibitors furfural and malonic acid, respectively. Based on the result of RT-qPCR, the gene transcription levels of the main reactive oxygen species (ROS) generation pathways were down-regulated, such as EMP, however, the activity of the main degrading enzymes was up-regulated, which showed the reduction of ROS generation rate was a way for the TCA cycle to regulate the anti-ultraviolet resistance of Bt. All of these provide solid evidence for reprogramming metabolomics to strengthen Bt UV radiation resistance.