Determination of trace chelating carboxylic acids in rice by green extraction combined with liquid chromatography-mass spectrometry analysis and its application in the evaluation of old and new rice.

RATIONALE: Accurate identification of old rice samples from new ones benefits their market circulation and consumers. However, the current detection methods are still not satisfactory because of their insufficient accuracy or (and) time-consuming process. METHODS: Chelating carboxylic acids (CCAs) were selectively extracted from rice, by stirring with chelating resin and a dilute Na2CO3 solution. The green analytical chemistry guidelines for sample preparation were investigated by using the green chemistry calculator AGREE prep. The extractant was determined by liquid chromatography-mass spectrometry (LC/MS), and statistical analysis of the analytical data was carried out to evaluate the significance of the difference by ChiPlot. RESULTS: The limit of quantitation for the CCAs is in the range of 1 to 50 ng/mL, with a reasonable reproducibility. The CCAs in 23 rice samples were determined within a wide concentration range from 0.03 to 1174 µg/g. Intriguingly, the content of citric acid, malonic acid, α-ketoglutaric acid and cis-aconite acid in new rice was each found to be distinctively higher than that in old rice by several times. Even mixtures of old and new rice were found to show much difference in the concentration of citric acid and malic acid. CONCLUSION: A green analytical method has been developed for the simultaneous determination of CCAs by LC/MS analysis, and the identification of old rice samples from new ones was easily carried out according to their CCA content for the first time. The results indicated that the described method has powerful potential for the accurate identification of old rice samples from new ones.

Integrated Transcriptome and Proteome Analysis Reveals the Regulatory Mechanism of Root Growth by Protein Disulfide Isomerase in Arabidopsis.

Protein disulfide isomerase (PDI, EC 5.3.4.1) is a thiol-disulfide oxidoreductase that plays a crucial role in catalyzing the oxidation and rearrangement of disulfides in substrate proteins. In plants, PDI is primarily involved in regulating seed germination and development, facilitating the oxidative folding of storage proteins in the endosperm, and also contributing to the formation of pollen. However, the role of PDI in root growth has not been previously studied. This research investigated the impact of PDI gene deficiency in plants by using 16F16 [2-(2-Chloroacetyl)-2,3,4,9-tetrahydro-1-methyl-1H-pyrido[3,4-b]indole-1-carboxylic acid methyl ester], a small-molecule inhibitor of PDI, to remove functional redundancy. The results showed that the growth of Arabidopsis roots was significantly inhibited when treated with 16F16. To further investigate the effects of 16F16 treatment, we conducted expression profiling of treated roots using RNA sequencing and a Tandem Mass Tag (TMT)-based quantitative proteomics approach at both the transcriptomic and proteomic levels. Our analysis revealed 994 differentially expressed genes (DEGs) at the transcript level, which were predominantly enriched in pathways associated with "phenylpropane biosynthesis", "plant hormone signal transduction", "plant-pathogen interaction" and "starch and sucrose metabolism" pathways. Additionally, we identified 120 differentially expressed proteins (DEPs) at the protein level. These proteins were mainly enriched in pathways such as "phenylpropanoid biosynthesis", "photosynthesis", "biosynthesis of various plant secondary metabolites", and "biosynthesis of secondary metabolites" pathways. The comprehensive transcriptome and proteome analyses revealed a regulatory network for root shortening in Arabidopsis seedlings under 16F16 treatment, mainly involving phenylpropane biosynthesis and plant hormone signal transduction pathways. This study enhances our understanding of the significant role of PDIs in Arabidopsis root growth and provides insights into the regulatory mechanisms of root shortening following 16F16 treatment.

Design, Synthesis and Biological Evaluation of Novel Phenyl-Substituted Naphthoic Acid Ethyl Ester Derivatives as Strigolactone Receptor Inhibitor.

Strigolactones (SLs) are plant hormones that regulate several key agronomic traits, including shoot branching, leaf senescence, and stress tolerance. The artificial regulation of SL biosynthesis and signaling has been considered as a potent strategy in regulating plant architecture and combatting the infection of parasitic weeds to help improve crop yield. DL1b is a previously reported SL receptor inhibitor molecule that significantly promotes shoot branching. Here, we synthesized 18 novel compounds based on the structure of DL1b. We performed rice tillering activity assay and selected a novel small molecule, C6, as a candidate SL receptor inhibitor. In vitro bioassays demonstrated that C6 possesses various regulatory functions as an SL inhibitor, including inhibiting germination of the root parasitic seeds Phelipanche aegyptiaca, delaying leaf senescence and promoting hypocotyl elongation of Arabidopsis. ITC analysis and molecular docking experiments further confirmed that C6 can interact with SL receptor proteins, thereby interfering with the binding of SL to its receptor. Therefore, C6 is considered a novel SL receptor inhibitor with potential applications in plant architecture control and prevention of root parasitic weed infestation.

Nationwide distribution of perfluoroalkyl ether carboxylic acids in Chinese diets: An emerging concern.

With the phase-out of perfluorooctanoic acid (PFOA) and its replacement by perfluoroalkyl ether carboxylic acids (PFECAs), there is a potential for increased exposure to various new PFECAs among the general population in China. While there are existing studies on dietary exposure to legacy perfluoroalkyl and polyfluoroalkyl substances (PFASs), research on dietary exposure to PFECAs, especially among the general Chinese populace, remains scarce. In the present study, we investigated the distribution of PFECAs in dietary sources from 33 cities across five major regions in China, along with the associated dietary intake. Analysis indicated that aquatic animal samples contained higher concentrations of legacy PFASs compared to those from terrestrial animals and plants. In contrast, PFECAs were found in higher concentrations in plant and terrestrial animal samples. Notably, hexafluoropropylene oxide dimer (HFPO-DA) was identified as the dominant compound in vegetables, cereals, pork, and mutton across the five regions, suggesting widespread dietary exposure. PFECAs constituted the majority of PFAS intake (57 %), with the estimated daily intake (EDI) of HFPO-DA ranging from 2.33 to 3.96 ng/kg bw/day, which corresponds to 0.78-1.32 times the reference dose (RfD) (3.0 ng/kg bw/day) set by the United States Environmental Protection Agency. Given the ubiquity of HFPO-DA and many other PFECAs in the nationwide diet of China, there is an urgent need for further research into these chemicals to establish relevant safety benchmarks or consumption advisory values for the diet.

Independent Mutation of Two Bridging Carboxylate Ligands Stabilizes Alternate Conformers of the Photosynthetic O2-Evolving Mn4CaO5 Cluster in Photosystem II.

The O2-evolving Mn4CaO5 cluster in photosystem II is ligated by six carboxylate residues. One of these is D170 of the D1 subunit. This carboxylate bridges between one Mn ion (Mn4) and the Ca ion. A second carboxylate ligand is D342 of the D1 subunit. This carboxylate bridges between two Mn ions (Mn1 and Mn2). D170 and D342 are located on opposite sides of the Mn4CaO5 cluster. Recently, it was shown that the D170E mutation perturbs both the intricate networks of H-bonds that surround the Mn4CaO5 cluster and the equilibrium between different conformers of the cluster in two of its lower oxidation states, S1 and S2, while still supporting O2 evolution at approximately 50% the rate of the wild type. In this study, we show that the D342E mutation produces much the same alterations to the cluster's FTIR and EPR spectra as D170E, while still supporting O2 evolution at approximately 20% the rate of the wild type. Furthermore, the double mutation, D170E + D342E, behaves similarly to the two single mutations. We conclude that D342E alters the equilibrium between different conformers of the cluster in its S1 and S2 states in the same manner as D170E and perturbs the H-bond networks in a similar fashion. This is the second identification of a Mn4CaO5 metal ligand whose mutation influences the equilibrium between the different conformers of the S1 and S2 states without eliminating O2 evolution. This finding has implications for our understanding of the mechanism of O2 formation in terms of catalytically active/inactive conformations of the Mn4CaO5 cluster in its lower oxidation states.

Bioisoteres for carboxylic acids: From ionized isosteres to novel unionized replacements.

Carboxylic acids are key pharmacophoric elements in many molecules. They can be seen as a problem by some, due to perceived permeability challenges, potential for high plasma protein binding and the risk of forming reactive metabolites due to acyl-glucuronidation. By others they are viewed more favorably as they can decrease lipophilicity by adding an ionizable center which can be beneficial for solubility, and can add enthalpic interactions with the target protein. However, there are many instances where the replacement of a carboxylic acid with a bioisosteric group is required. This has led to the development of a number of ionizable groups which sufficiently mimic the carboxylic acid functionality whilst improving, for example, the metabolic profile of the molecule in question. An alternative strategy involves replacement of the carboxylate by neutral functional groups. This review initially details carefully selected examples whereby tetrazoles, acyl sulfonamides or isoxazolols have been beneficially utilized as carboxylic acid bioisosteres altering physicohemical properties, interactions with the target and metabolism and/or pharmacokinetics, before delving further into the binding mode of carboxylic acid derivatives with their target proteins. This analysis highlights new ways to consider the replacement of carboxylic acids by neutral bioisosteric groups which either rely on hydrogen bonds or cation-π interactions. It should serve as a useful guide for scientists working in drug discovery.

Application of the intramolecular Diels-Alder vinylarene (IMDAV) reaction for the synthesis of benzo-, carbocyclo-, thienothiopheneisoindolecarboxylic acids and its limitations.

Thienylallylamines, readily accessible from the corresponding thienyl aldehydes, react with maleic and trifluoromethylmaleic anhydrides leading to the formation of acids with a thieno[2,3-f]isoindole core. The reaction sequence involves two successive steps: acylation of the nitrogen atom of the initial allylamine and the intramolecular Diels-Alder vinylarene (IMDAV) reaction. The scope and limitations of the proposed method were thoroughly investigated. It has been revealed with the aid of X-ray analysis and DFT calculations that the key step, the IMDAV reaction, proceeds through an exo-transition state, giving rise to the exclusive formation of a single diastereomer of the target heterocycle. The obtained functionally substituted thieno[2,3-f]isoindole carboxylic acids are potentially useful substrates for further transformations and bioscreening. The antimicrobial evaluation of the obtained compounds revealed that 1-oxo-2-(3-(trifluoromethyl)phenyl)hexahydrobenzo[4,5]thieno[2,3-f]isoindole-10-carboxylic acid is the most active sample in the synthesized library. It exhibits antibacterial activity against sensitive strains of Gram-positive bacteria, including S. aureus, Enterococcus faecium, Bacillus cereus, and Micrococcus luteus, as well as the Gram-negative bacteria E. coli and Pseudomonas fluorescens, with MIC values ranging from 4 to 64 µg mL-1. 9-Oxo-8-phenyloctahydronaphtho[2,1-d]thieno[2,3-f]isoindole-10-carboxylic acid showed antifungal activity against yeast culture C. albicans with a MIC value of 32 µM.

Nanopore analysis of cis-diols in fruits.

Natural fruits contain a large variety of cis-diols. However, due to the lack of a high-resolution sensor that can simultaneously identify all cis-diols without a need of complex sample pretreatment, direct and rapid analysis of fruits in a hand-held device has never been previously reported. Nanopore, a versatile single molecule sensor, can be specially engineered to perform this task. A hetero-octameric Mycobacterium smegmatis porin A (MspA) nanopore modified with a sole phenylboronic acid (PBA) adapter is prepared. This engineered MspA accurately recognizes 1,2-diphenols, alditols, α-hydroxy acids and saccharides in prune, grape, lemon, different varieties of kiwifruits and commercial juice products. Assisted with a custom machine learning program, an accuracy of 99.3% is reported and the sample pretreatment is significantly simplified. Enantiomers such as DL-malic acids can also be directly identified, enabling sensing of synthetic food additives. Though demonstrated with fruits, these results suggest wide applications of nanopore in food and drug administration uses.

Carboxylated Nanoparticle Surfaces Enhance Association with Mucoid Pseudomonas aeruginosa Biofilms.

Pseudomonas aeruginosa biofilms comprise three main polysaccharides: alginate, psl, and pel, which all imbue tolerance against exogenous antimicrobials. Nanoparticles (NPs) are an exciting new strategy to overcome the biofilm matrix for therapeutic delivery applications; however, zero existing FDA approvals for biofilm-specific NP formulations can be attributed to the complex interplay of physiochemical forces at the biofilm-NP interface. Here, we leverage a set of inducible, polysaccharide-specific, expressing isogenic P. aeruginosa mutants coupled with an assembled layer-by-layer NP (LbL NP) panel to characterize biofilm-NP interactions. When investigating these interactions using confocal microscopy, alginate-layered NPs associated more than dextran-sulfate-layered NPs with biofilms that had increased alginate production, including biofilms produced by mucoid P. aeruginosa isolates from people with cystic fibrosis. These differences were further confirmed in LbL NPs layered with polysaccharide- or hydrocarbon-based polymers with pendent carboxylate or sulfate functional groups. These data suggest carboxylated NP surfaces have enhanced interactions specifically with mucoid biofilms as compared to sulfated surfaces and lay the foundation for their inclusion as a design element for increasing biofilm-NP interactions and efficacious drug delivery.

Mechanistic studies to understand peak tailing due to sulfinic acid- and carboxylic acid-silanophilic interactions in reversed-phase liquid chromatography.

Silanophilic interactions are a primary contributor to peak tailing of acidic pharmaceutical compounds, thus a thorough understanding is especially important for reversed-phase liquid chromatography (RPLC) method development. Herein, a sulfinic acid compound that exhibited severe peak tailing in RPLC with acidic mobile phases was carefully studied. Results indicated that the neutral protonated form of the sulfinic acid is involved in the strong interaction that leads to peak tailing, but that tailing can be mitigated with a blocking effect achieved through use of acetic acid modifier in the mobile phase. Peak tailing was also observed with other structurally-similar sulfinic acids and carboxylic acids but was, in general, less severe with the latter. The Hydrophobic Subtraction Model (HSM) was applied to six commercial C18 columns that exhibited different tailing behaviors for the sulfinic acid compound in attempts to identify key sites of interaction within the stationary phase. A combination of heated acid column wash experiments and density functional theory (DFT) calculations indicate that the differential interactions of the acids with vicinal silanol pairs in the stationary phase play a major role in peak tailing.

Discovery of GLPG2737, a Potent Type 2 Corrector of CFTR for the Treatment of Cystic Fibrosis in Combination with a Potentiator and a Type 1 Co-corrector.

Cystic fibrosis (CF) is caused by mutations in the CF transmembrane conductance regulator (CFTR) protein. This epithelial anion channel regulates the active transport of chloride and bicarbonate ions across membranes. Mutations result in reduced surface expression of CFTR channels with impaired functionality. Correctors are small molecules that support the trafficking of CFTR to increase its membrane expression. Such correctors can have different mechanisms of action. Combinations may result in a further improved therapeutic benefit. We describe the identification and optimization of a new pyrazolol3,4-bl pyridine-6-carboxylic acid series with high potency and efficacy in rescuing CFTR from the cell surface. Investigations showed that carboxylic acid group replacement with acylsulfonamides and acylsulfonylureas improved ADMET and PK properties, leading to the discovery of the structurally novel co-corrector GLPG2737. The addition of GLPG2737 to the combination of the potentiator GLPG1837 and C1 corrector 4 led to an 8-fold increase in the F508del CFTR activity.

Removal of perfluoroalkyl acids (PFAAs) from aqueous solution by water hyacinth (Eichhornia crassipes): Uptake, accumulation, and translocation.

Although Eichhornia crassipes, commonly known as water hyacinth, has been widely used in wastewater treatment, further investigations are still needed to explore the removal efficiency of perfluoroalkyl acids (PFAAs) from the aqueous environment using this floating aquatic plant. In this study, a hydroponic experiment was conducted to assess accumulation, bioconcentration factors (BCFs), translocation factors (TFs), and removal rates of eight PFAAs by water hyacinth. The obtained results indicated that all PFAAs, including five perfluoroalkyl carboxylic acids (PFCAs) with chain lengths C4-C8 and three perfluoroalkyl sulfonic acids (PFSAs) with C4, C6, and C8, were readily accumulated in water hyacinth. Throughout the duration of the experiment, there was a noticeable increase in PFAA concentrations and BCF values for different plant parts. For the root, PFAAs with more carbon numbers showed a higher uptake than the shorter homologues, with PFSAs being more readily accumulated compared to PFCAs with the same carbon number in the molecules. In contrast, the levels of long-chain PFAAs were comparatively lower than those of short-chain substances in the stem and leaf. Notably, PFAAs with less carbon numbers, like PFPeA, PFBA, and PFBS, showed a remarkable translocation from the root to the stem and leaf with TFs >1. For the whole plant, no significant correlation was found between BCFs and organic carbon-water partition coefficients (Koc), octanol-water partition coefficients (Kow), membrane-water distribution coefficients (Dmw), or protein-water distribution coefficients (Dpw). The removal rates of PFAAs ranged from 40.3 to 63.5 % throughout the three weeks of the experiment while the removal efficiencies varied from 48.9 % for PFHxS to 82.6 % for PFPeA in the last week.

Development and validation of a simple and efficient method for the analysis of commercial formulations containing clopyralid, picloram and aminopyralid as active ingredients.

Liquid chromatography plays a pivotal role in evaluating pesticide formulations as it enables the determination of multiple active substances in plant protection products. An adaptable separation technique has been developed, enabling the qualitative and quantitative analysis of clopyralid, picloram, and aminopyralid within pesticide formulations in line with SANCO/3030/99 rev. 5 guidelines. This article offers an insight into the validation procedure encompassing key aspects such as selectivity, linearity, accuracy, precision, and recovery. It places emphasis on critical stages, including sample preparation, chromatographic separation, detection, quantification, and data analysis. The active ingredients are separated using chromatography with isocratic elution, utilizing a mobile phase consisting of a mixture of water, acetonitrile, and acetic acid in a specific ratio (83:15:2 v/v/v). This separation is carried out on a YMC-Pack ODS-AQ column (250 mm x 4.6 mm, 5 µm) at a flow rate of 1.5 mL/min. The method's validation parameters have produced satisfactory outcomes. The recovery rates for each individual compound were found to be in the range of 98.6% to 101.0%. Precision, as indicated by the relative standard deviation (%RSD), was lower than the values predicted by the modified Horwitz equation. Furthermore, the correlation coefficients assessing the linearity of the response exceeded 0.99.

Single-cell RNA sequencing reveals the heterogeneity of hepatic non-parenchymal cell responses to chronic PFO5DoDA exposure in male mice.

Perfluoroalkyl ether carboxylic acids (PFECA) have emerged as novel alternatives to legacy per- and polyfluoroalkyl substances (PFAS). Existing research has revealed hepatoxicity induced by various PFAS, including PFECA. However, these studies have primarily focused on overall changes in whole liver tissue, particularly in hepatocytes, with the impact of PFAS on diverse liver non-parenchymal cells (NPCs) still inadequately understood. In the present study, we examined the heterogeneous responses of hepatic NPCs following exposure to perfluoro-3,5,7,9,11-pentaoxadodecanoic acid (PFO5DoDA), a type of PFECA, by administering PFO5DoDA (5 µg/L)-contaminated water to male mice for one year. Single-cell RNA sequencing (scRNA-seq) of 15 008 cells from the liver identified 10 distinct NPC populations. Notably, although relative liver weight remained largely unchanged following exposure to 5 µg/L PFO5DoDA, there was an observed increase in proliferating cells, indicating that proliferating NPCs may contribute to the hepatomegaly frequently noted in PFAS-exposed livers. There was also a considerable alteration in the composition of hepatic NPCs. Specifically, the total number of B cells decreased substantially, while many other cells, such as monocytes and macrophages, increased after PFO5DoDA exposure. In addition, interactions among the hepatic NPC populations changed variously after PFO5DoDA exposure. The findings emphasize the heterogeneity in the responses of hepatic NPCs to PFO5DoDA exposure. Taken together, the changes in immune cell populations and their intercellular interactions suggest that PFO5DoDA disrupts immune homeostasis in the liver. These findings offer new insights into the cellular mechanisms of PFAS-induced liver damage.

Distinctive biotransformation and biodefluorination of 6:2 versus 5:3 fluorotelomer carboxylic acids by municipal activated sludge.

Fluorotelomer carboxylic acids (FTCAs) represent an important group of per- and polyfluoroalkyl substances (PFAS) given their high toxicity, bioaccumulation potential, and frequent detection in landfill leachates and PFAS-impacted sites. In this study, we assessed the biodegradability of 6:2 FTCA and 5:3 FTCA by activated sludges from four municipal wastewater treatment plants (WWTPs) in the New York Metropolitan area. Coupling with 6:2 FTCA removal, significant fluoride release (0.56∼1.83 F-/molecule) was evident in sludge treatments during 7 days of incubation. Less-fluorinated transformation products (TPs) were formed, including 6:2 fluorotelomer unsaturated carboxylic acid (6:2 FTUCA), perfluorohexanoic acid (PFHxA), perfluoropentanoic acid (PFPeA), and perfluorobutanoic acid (PFBA). In contrast, little fluoride (0.01∼0.09 F-/molecule) was detected in 5:3 FTCA-dosed microcosms, though 25∼68% of initially dosed 5:3 FTCA was biologically removed. This implies the dominance of "non-fluoride-releasing pathways" that may contribute to the formation of CoA adducts or other conjugates over 5:3 FTCA biotransformation. The discovery of defluorinated 5:3 FTUCA revealed the possibility of microbial attacks of the C-F bond at the γ carbon to initiate the transformation. Microbial community analysis revealed the possible involvement of 9 genera, such as Hyphomicrobium and Dechloromonas, in aerobic FTCA biotransformation. This study unraveled that biotransformation pathways of 6:2 and 5:3 FTCAs can be divergent, resulting in biodefluorination at distinctive degrees. Further research is underscored to uncover the nontarget TPs and investigate the involved biotransformation and biodefluorination mechanisms and molecular basis.

Life cycle sustainability assessment of short chain carboxylic acid produced from municipal bio-wastes.

Bio-based products are a fast-growing market due to increasing consumer consciousness for sustainability. Although this is per se a positive trend, it leads to a higher demand for organic feedstocks which normally comes from primary agricultural sources and can lead to undesired deforestation or other land use changes to farmland. At the same time, Europe is facing another challenge related with the treatment of organic wastes. In this context, the project CAFIPLA developed an integrated process to convert heterogeneous organic materials to building blocks for the bio-based economy. This study performs a life cycle sustainability assessment (life cycle assessment, life cycle costing and social life cycle assessment) of the production of short chain carboxylic acids (SCCA) employing municipal bio-wastes as a feedstock. In addition to a hot-spot identification to detect the main sources of impact, a comparison of the novel technology with the current benchmark is carried out applying a cradle-to-gate approach and using 1 kg of SCCA as a functional unit. Results show the great performance of CAFIPLA in all the environmental categories analysed. Furthermore, the profitability of the plant is also verified, reaching a payback period below 6 years as long as the product is sold above 0.49 €/kg. Finally, the potential social risk associated to the supply chain is also improved with CAFIPLA technology.

Oxidative Transformation of Nafion-Related Fluorinated Ether Sulfonates: Comparison with Legacy PFAS Structures and Opportunities of Acidic Persulfate Digestion for PFAS Precursor Analysis.

The total oxidizable precursor (TOP) assay has been extensively used for detecting PFAS pollutants that do not have analytical standards. It uses hydroxyl radicals (HO•) from the heat activation of persulfate under alkaline pH to convert H-containing precursors to perfluoroalkyl carboxylates (PFCAs) for target analysis. However, the current TOP assay oxidation method does not apply to emerging PFAS because (i) many structures do not contain C-H bonds for HO• attack and (ii) the transformation products are not necessarily PFCAs. In this study, we explored the use of classic acidic persulfate digestion, which generates sulfate radicals (SO4-•), to extend the capability of the TOP assay. We examined the oxidation of Nafion-related ether sulfonates that contain C-H or -COO-, characterized the oxidation products, and quantified the F atom balance. The SO4-• oxidation greatly expanded the scope of oxidizable precursors. The transformation was initiated by decarboxylation, followed by various spontaneous steps, such as HF elimination and ester hydrolysis. We further compared the oxidation of legacy fluorotelomers using SO4-• versus HO•. The results suggest novel product distribution patterns, depending on the functional group and oxidant dose. The general trends and strategies were also validated by analyzing a mixture of 100000- or 10000-fold diluted aqueous film-forming foam (containing various fluorotelomer surfactants and organics) and a spiked Nafion precursor. Therefore, (1) the combined use of SO4-• and HO• oxidation, (2) the expanded list of standard chemicals, and (3) further elucidation of SO4-• oxidation mechanisms will provide more critical information to probe emerging PFAS pollutants.

Application of electron beam technology to decompose per- and polyfluoroalkyl substances in water.

The widespread detection of per- and polyfluoroalkyl substances (PFAS) in environmental compartments across the globe has raised several health concerns. Destructive technologies that aim to transform these recalcitrant PFAS into less toxic, more manageable products, are gaining impetus to address this problem. In this study, a 9 MeV electron beam accelerator was utilized to treat a suite of PFAS (perfluoroalkyl carboxylates: PFCAs, perfluoroalkyl sulfonates, and 6:2 fluorotelomer sulfonate: FTS) at environmentally relevant levels in water under different operating and water quality conditions. Although perfluorooctanoic acid and perfluorooctane sulfonic acid showed >90% degradation at <500 kGy dose at optimized conditions, a fluoride mass balance revealed that complete defluorination occurred only at/or near 1000 kGy. Non-target and suspect screening revealed additional degradation pathways differing from previously reported mechanisms. Treatment of PFAS mixtures in deionized water and groundwater matrices showed that FTS was preferentially degraded (∼90%), followed by partial degradation of long-chain PFAS (∼15-60%) and a simultaneous increase of short-chain PFAS (up to 20%) with increasing doses. The increase was much higher (up to 3.5X) in groundwaters compared to deionized water due to the presence of PFAS precursors as confirmed by total oxidizable precursor (TOP) assay. TOP assay of e-beam treated samples did not show any increase in PFCAs, confirming that e-beam was effective in also degrading precursors. This study provides an improved understanding of the mechanism of PFAS degradation and revealed that short-chain PFAS are more resistant to defluorination and their levels and regulation in the environment will determine the operating conditions of e-beam and other PFAS treatment technologies.

Molecular and metabolic characterization of petroleum hydrocarbons degrading Bacillus cereus.

Hydrocarbon constituents of petroleum are persistent, bioaccumulated, and bio-magnified in living tissues, transported to longer distances, and exert hazardous effects on human health and the ecosystem. Bioaugmentation with microorganisms like bacteria is an emerging approach that can mitigate the toxins from environmental sources. The present study was initiated to target the petroleum-contaminated soil of gasoline stations situated in Lahore. Petroleum degrading bacteria were isolated by serial dilution method followed by growth analysis, biochemical and molecular characterization, removal efficiency estimation, metabolites extraction, and GC-MS of the metabolites. Molecular analysis identified the bacterium as Bacillus cereus, which exhibited maximum growth at 72 hours and removed 75% petroleum. Biochemical characterization via the Remel RapID™ ONE panel system showed positive results for arginine dehydrolase (ADH), ornithine decarboxylase (ODC), lysine decarboxylase (LDC), o-nitrophenyl-ß-D-galactosidase (ONPG), p-nitrophenyl-ß-D-glucosidase (ßGLU), p-nitrophenyl-N-acetyl-ß-D-glucosaminidase (NAG), malonate (MAL), adonitol fermentation (ADON), and tryptophane utilization (IND). GC-MS-based metabolic profiling identified alcohols (methyl alcohol, o-, p- and m-cresols, catechol, and 3-methyl catechol), aldehydes (methanone, acetaldehyde, and m-tolualdehyde), carboxylic acid (methanoic acid, cis,cis-muconic acid, cyclohexane carboxylic acid and benzoic acid), conjugate bases of carboxylic acids (benzoate, cis,cis-muconate, 4-hydroxybenzoate, and pyruvate) and cycloalkane (cyclohexene). It suggested the presence of methane, methylcyclohexane, toluene, xylene, and benzene degradation pathways in B. cereus.

Pinpointing Acidic Residues in Proteins.

It is of great importance to pinpoint specific residues or sites of a protein in biological contexts to enable desired mechanism of action for small molecules or to precisely control protein function. In this regard, acidic residues including aspartic acid (Asp) and glutamic acid (Glu) hold great potential due to their great prevalence and unique function. To unlock the largely untapped potential, great efforts have been made recently by synthetic chemists, chemical biologists and pharmacologists. Herein, we would like to highlight the remarkable progress and particularly introduce the electrophiles that exhibit reactivity to carboxylic acids, the light-induced reactivities to carboxylic acids and the genetically encoded noncanonical amino acids that allow protein manipulations at acidic residues. We also comment on certain unresolved challenges, hoping to draw more attention to this rapidly developing area.