4-chlorobenzoic Acid Research Articles

Degradation of P-Nitrobenzoic Acid and 4-Chlorobenzoic Acid by Catalytic Ozonation with Modified Birnessite-Type MnO2 as Catalyst

Degradation of P-Nitrobenzoic Acid and 4-Chlorobenzoic Acid by Catalytic Ozonation with Modified Birnessite-Type MnO2 as Catalyst

Heterogeneous Catalytic Ozonation of Pharmaceuticals: Optimization of the Process by Response Surface Methodology.

Batch heterogeneous catalytic ozonation experiments were performed using commercial and synthesized nanoparticles as catalysts in aqueous ozone. The transferred ozone dose (TOD) ranged from 0 to 150 μM, and nanoparticles were added in concentrations between 0 and 1.5 g L-1, with all experiments conducted at 20 °C and a total volume of 240 mL. A Ce-doped TiO2 catalyst (1% molar ratio of Ce/Ti) was synthesized via the sol-gel method. Response surface methodology (RSM) was applied to identify the most significant factors affecting the removal of selected pharmaceuticals, with TOD emerging as the most critical variable. Higher TOD resulted in greater removal efficiencies. Furthermore, it was found that the commercially available metal oxides α-Al2O3, Mn2O3, TiO2, and CeO2, as well as the synthesized CeTiOx, did not increase the catalytic activity of ozone during the degradation of ibuprofen (IBF) and para-chlorobenzoic acid (pCBA). Carbamazepine (CBZ) and diclofenac (DCF) are compounds susceptible to ozone oxidation, thus their complete degradation at 150 μM transferred ozone dose was attained. The limited catalytic effect was attributed to the rapid consumption of ozone within the first minute of reaction, as well as the saturation of catalyst active sites by water molecules, which inhibited effective ozone adsorption and subsequent hydroxyl radical generation (●OH).

Mechanochemical oxidative complexation of copper(I) chloride with acetic acid, benzoic acid, their chloro derivatives and l-histidine affording anhydrous copper(II) complexes

This work reports solvent-free synthesis of copper(II)-carboxylates by grinding the reactants in solid state (the mechanochemical method). Here we used copper(I) salt to synthesize copper(II) complexes to demonstrate the potential of oxidative synthesis of the mechanochemical technique. The complexes were synthesized by grinding copper(I) chloride with a carboxylic acid together in 1:2 molar ratio in mortar and pestle. The carboxylic acids used were acetic acid, benzoic acid, 2-chloroacetic acid, 2-chlorobenzoic acid and l-histidine. The oxidative complexation occurred in the solid state producing anhydrous dimeric copper(II)-carboxylates (except that of l-histidine) in quantitative yield (>96%) having 1:2 metal to ligand ratio. The first evidence to oxidation of copper(I) to copper(II) ion was a change in color (pale to greenish blue) and a change in magnetic susceptibility from diamagnetic to paramagnetic value. The complexes were also characterized by elemental analysis, electronic absorption spectroscopy, FT-IR spectra, mass spectrometry, powder X-ray diffraction and thermal analysis. The electronic absorption, magnetic susceptibility, ESR and X-ray diffraction data supported a distorted square-planer geometry. This study provided for a distinct test in the form of magnetic susceptibility for the formation of copper(II)-complexes from a copper(I) salt. The dimeric nature of the complexes, except that of bis(histidinato)copper(II), was confirmed by the lower magnetic-moments (1.40–1.50 BM) than the spin only value (1.73 BM).

Aliphatic Ketone Claisen Rearrangement: Troubleshooting the Transetherification Step by Identifying a Stable Acid Catalyst.

After optimization for retention of catalytic activity, 4-chlorobenzoic acid emerged as the optimal catalyst for the aliphatic ketone Claisen rearrangement. The optimal catalyst enables a one-pot, metal-free, catalytic protocol from allylic alcohols to γ,δ-unsaturated ketones. The optimized process tolerates a range of substrates, including substituents with acid-labile protecting groups. Reaction monitoring and DFT studies of the aliphatic ketone Claisen process agree that the ultimate rearrangement step typically has the highest activation barrier.

Application of tryptophan-like fluorescence index to quantify the trace organic compounds removal in wastewater ozonation

The effectiveness of ozonation, one of the techniques known for destroying organic contaminants from wastewater, depends on the composition of the wastewater matrix. The required ozone (O3) dose is determined based on the target compounds during ozonation. Hydroxyl radicals are quantified using a probe compound. The para-chlorobenzoic acid (pCBA) is typically used as a probe compound to measure hydroxyl radicals. However, real-time measurement is impossible, as the analysis process consumes time and resources. This study aimed to evaluate the spectroscopic characteristics of various organic substances in wastewater ozonation through fluorescence excitation-emission matrix and parallel factor analysis. The study also demonstrated that real-time analyzable tryptophan-like fluorescence (TLF) can be used as a hydroxyl radical index. Importantly, the correlation between para-chlorobenzoic acid and TLF was derived, and the results showed a high correlation (R2 = 0.91), confirming the reliability of our findings. Seven trace organic compounds, classified based on their reactivity with O3 and hydroxyl radicals, were selected as target compounds and treated with O3. The TLF index was used as a model factor for the removal rate of the target compounds. The experimental and model values matched when the O3 dose was below 1.0 g O3/g DOC (RMSE: 0.0445–0.0895).

Ni–Ca metastable–nonmetastable bimetallic sites induced ·OH directed generation and efficient water purification

AbstractStrongly oxidizing ·OH can non‐selectively degrade various organic pollutants, but how to selectively generate ·OH is a great challenge. In this study, the directed generation of ·OH was achieved based on Ni–Ca metastable–nonmetastable bimetallic sites, Ni2+/Ni3+ valence cycling provided electrons for ·OH generation induced by the non‐variable Ca‐based sites, which constructed a nearly 100% selective generation pathway of ·OH (O3 → HO3/HO2 → OH). The antibiotic pefloxacin could be completely removed in 15 min, and the COD removal efficiency for other hard‐to‐degrade pollutants such as oxalic acid and chlorobenzoic acid could reach more than 90%. Ni doping significantly increased the oxygen vacancy and Lewis acid content, and DFT calculations showed that Ni–Ca dual‐site had a lower reaction energy barrier and the complexed hydroxyl radical intermediate *OO had a higher spin density (−0.6), which was more favorable for the generation of ·OH. Therefore, this study provides new ideas for efficient treatment of actual wastewater.

Analysis of the steady-state concentrations of reactive species and their role in contaminant degradation by the iron-biochar/persulfate advanced oxidation process: Comparison of probe compound and quenching agent methods

Reactive species, including hydroxyl radicals (OH), sulfate radicals (SO4−), singlet oxygen (1O2), superoxide radicals (O2−), and Fe(IV), are generated by the iron-biochar activated persulfate (Fe-BC/PS) process. These reactive species can be leveraged for treatment of micropollutants, such as the sulfamethoxazole antibiotic. In this study, the steady-state concentrations and contributions of OH, SO4−, 1O2, O2−, and Fe(IV) to sulfamethoxazole degradation were calculated for different operating conditions in the iron-biochar/persulfate (Fe-BC/PS advanced oxidation process. Electron paramagnetic resonance was employed to confirm the production of each reactive species. The nitrobenzene, benzoic acid, furfuryl alcohol, p-chlorobenzoic acid or p-benzoquinone, and phenyl methyl sulfoxide probe compounds were added to experimental solutions in isolation, as mixtures, and at different concentrations to calculate the steady-state concentrations of OH, SO4−, 1O2, O2−, and Fe(IV) and determine their contributions to sulfamethoxazole degradation at variable pH conditions. The results not only informed the primary mechanisms of sulfamethoxazole degradation by the Fe-BC/PS system, but also highlighted best practices for the use of probe compounds and quenching agents in persulfate-based advanced oxidation processes. In particular, the initial concentration of the probe compounds should be as low as possible to avoid impacts on target contaminant degradation and misinterpretation of the role of each reactive species. Furthermore, quenching-based approaches to determination of the key reactive species were less consistent than evaluation by probe compounds. The overall outcomes of this work inform sulfamethoxazole treatment by the Fe-BC/PS system and emphasize the need for internal validation of kinetics results using a multi-pronged approach.

Unveiling Competitive Adsorption in TiO2 Photocatalysis through Machine-Learning-Accelerated Molecular Dynamics, DFT, and Experimental Methods.

The efficient harnessing of solar power for water treatment via photocatalytic processes has long been constrained by the challenge of understanding and optimizing the interactions at the photocatalyst surface, particularly in the presence of nontarget cosolutes. The adsorption of these cosolutes, such as natural organic matter, onto photocatalysts can inhibit the degradation of pollutants, drastically decreasing the photocatalytic efficiency. In the present work, computational methods are employed to predict the inhibitory action of a suite of small organic molecules during TiO2 photocatalytic degradation of para-chlorobenzoic acid (pCBA). Specifically, tryptophan, coniferyl alcohol, succinic acid, gallic acid, and trimesic acid were selected as interfering agents against pCBA to observe the resulting competitive reaction kinetics via bulk and surface phase reactions according to Langmuir-Hinshelwood adsorption dynamics. Experiments revealed that trimesic and gallic acids were most competitive with pCBA, followed by succinic acid. Density functional theory (DFT) and machine learning interatomic potentials (MLIPs) were used to investigate the molecular basis of these interactions. The computational findings showed that while the type of functional group did not directly predict adsorption affinity, the spatial arrangement and electronic interactions of these groups significantly influenced adsorption dynamics and corresponding inhibitory behavior. Notably, MLIPs, derived by fine-tuning models pretrained on a vastly larger dataset, enabled the exploration of adsorption behaviors over substantially longer periods than typically possible with conventional ab initio molecular dynamics, enhancing the depth of understanding of the dynamic interaction processes. Our study thus provides a pivotal foundation for advancing photocatalytic technology in environmental applications by demonstrating the critical role of molecular-level interactions in shaping photocatalytic outcomes.

Abraham General Solvation Parameter Model: Predictive Expressions for Solute Transfer into Isobutyl Acetate

Mole fraction of solubilities are reported for the: o-acetoacetanisidide, anthracene, benzoin, 4-tert-butylbenzoic acid, 3-chlorobenzoic acid, 3-chlorobenzoic acid, 2-chloro-5-nitrobenzoic acid, 4-chloro-3-nitrobenzoic acid, 3,4-dichlorobenzoic acid, 2,3-dimethoxybenzoic acid, 3,4-dimethoxybenzoic acid, 3,5-dimethoxybenzoic acid, 3,5-dinitrobenzoic acid, diphenyl sulfone, 2-ethylanthraquinone, 2-methoxybenzoic acid, 4-methoxybenzoic acid, 2-methylbenzoic acid, 3-methylbenzoic acid, 2-methyl-3-nitrobenzoic acid, 3-methyl-4-nitrobenzoic acid, 4-methyl-3-nitrobenzoic acid, 2-naphthoxyacetic acid, 3-nitrobenzoic acid, 4-nitrobenzoic acid, salicylamide, thioxanthene-9-one, 3,4,5-trimethoxybenzoic acid, and xanthene dissolved in isobutyl acetate at 298.15 K. The results of our experimental measurements, combined with the published literature data, were used to obtain Abraham model equations for isobutyl acetate. The mathematical correlations presented in the current study describe the observed molar solubility ratios of the solutes dissolved in isobutyl acetate to within an overall standard deviation of 0.12 log units or less.

Supramolecular Assemblies in Mn(II) and Zn(II) Metal–Organic Compounds Involving Phenanthroline and Benzoate: Experimental and Theoretical Studies

Two new Mn(II) and Zn(II) metal–organic compounds of 1,10-phenanthroline and methyl benzoates viz. [Mn(phen)2Cl2]2-ClBzH (1) and [Zn(4-MeBz)2(2-AmPy)2] (2) (where 4-MeBz = 4-methylbenzoate, 2-AmPy = 2-aminopyridine, phen = 1,10-phenanthroline, 2-ClBzH = 2-chlorobenzoic acid) were synthesized and characterized using elemental analysis, TGA, spectroscopic (FTIR, electronic) and single crystal X-ray diffraction techniques. The crystal structure analysis of the compounds revealed the presence of various non-covalent interactions, which provides stability to the crystal structures. The crystal structure analysis of compound 1 revealed the formation of a supramolecular dimer of 2-ClBzH enclathrate within the hexameric host cavity formed by the neighboring monomeric units. Compound 2 is a mononuclear compound of Zn(II) where flexible binding topologies of 4-CH3Bz are observed with the metal center. Moreover, various non-covalent interactions, such as lp(O)-π, lp(Cl)-π, C–H∙∙∙Cl, π-stacking interactions as well as N–H∙∙∙O, C–H∙∙∙O and C–H∙∙∙π hydrogen bonding interactions, are found to be involved in plateauing the molecular self-association of the compounds. The remarkable enclathration of the H-bonded 2-ClBzH dimer into a supramolecular cavity formed by two [Mn(phen)2Cl2] complexes were further studied theoretically using density functional theory (DFT) calculations, the non-covalent interaction (NCI) plot index and quantum theory of atoms in molecules (QTAIM) computational tools. Synergistic effects were also analyzed using molecular electrostatic potential (MEP) surface analysis.

Dimerization and Dissociation: The Rate-Controlling steps of molecular Self-Assembly during solution nucleation determined by variation of gas media

To further probe into the link between solution chemistry and nucleation processes experimental and computational data are presented on unsaturated, saturated, and supersaturated solutions and in situ monitoring of nucleation chemistry of p-chlorobenzoic acid (PCBA), p-methoxybenzoic acid (PMBA) and p-nitrobenzoic acid (PNBA), three benzoic acid derivatives with different properties of para-substituents. By variation of the gas media, we were able to establish that hydrogen-bonded dimers (HD) are the basic building unite in solution for clusters and nucleuses despite of the gases and solvents, and there is a strong link between the supersaturated solution chemistry and the intrinsic supersaturation ratio, and the nucleation kinetics. Two different molecular self-assembly pathways and the rate-controlling steps were discussed, which paves new aspects for understanding the role of solution chemistry in directing nucleation processes.

Development of a Five-Chemical-Probe Method to Determine Multiple Radicals Simultaneously in Hydroxyl and Sulfate Radical-Mediated Advanced Oxidation Processes.

Advanced oxidation processes (AOPs), such as hydroxyl radical (HO•)- and sulfate radical (SO4•-)-mediated oxidation, are attractive technologies used in water and wastewater treatments. To evaluate the treatment efficiencies of AOPs, monitoring the primary radicals (HO• and SO4•-) as well as the secondary radicals generated from the reaction of HO•/SO4•- with water matrices is necessary. Therefore, we developed a novel chemical probe method to examine five key radicals simultaneously, including HO•, SO4•-, Cl•, Cl2•-, and CO3•-. Five probes, including nitrobenzene, para-chlorobenzoic acid, benzoic acid, 2,4,6-trimethylbenzoic acid, and 2,4,6-trimethylphenol, were selected in this study. Their bimolecular reaction rate constants with diverse radicals were first calibrated under the same conditions to minimize systematic errors. Three typical AOPs (UV/H2O2, UV/S2O82-, and UV/HSO5-) were tested to obtain the radical steady-state concentrations. The effects of dissolved organic matter, Br-, and the probe concentration were inspected. Our results suggest that the five-probe method can accurately measure radicals in the HO•- and SO4•--mediated AOPs when the concentration of Br- and DOM are less than 4.0 μM and 15 mgC L-1, respectively. Overall, the five-probe method is a practical and easily accessible method to determine multiple radicals simultaneously.

Synthesis of New Benzoxazole Derivatives and Evaluation of their Antifungal and Antibacterial Activities

Analytical chemistry aims to synthesize some novel benzoxazole derivatives with lower side effects and more efficacy. In this research, we synthesized the target compound’s reaction of 2- aminophenol in methanol and added carbon disulfide to obtain benzo[d] oxazole-2-thiol. This obtained compound again reacts with 4-chlorobenzoic acid to form 4-(benzo [d]oxazol-2-ylthio) benzoic acid. 4-(benzo[d]oxazol-2-ylthio) benzoic acid was further treated with substituted esters to give the crude product (4a-4e). The structures of derivatives are characterized with the help of IR, 1H NMR, TLC Spectroscopy, and melting point. The derivatives of the compounds were tested for antibacterial & antifungal activities. Antimicrobial evaluation was performed individually with gram-positive and gram-negative bacteria S. aureus and Pseudomonas aeruginosa. Aspergillus niger and Candida albicans were the two types of fungi on which antifungal activities were conducted. The outcomes were compared to those of the common medications Amphotericin B and Ciprofloxacin. It was discovered that the produced compounds have considerable antibacterial and antifungal activity. Four synthesized derivatives are named as 4 (d, b, e, c). The 4 d showed a good antimicrobial activity against the S. aureus. The 4 c showed good antifungal activities against the Candida albicans MTCC3541. The order of antifungal activity of these synthesized compounds is 4c >4e > 4b >4d. The standard. The 4 c showed a good antifungal activity against the C. albicans.

Selective sensing of picric acid using a Zn(II)-metallacycle: experimental and theoretical validation of the sensing mechanism and quantitative analysis of sensitivity in contact mode detection.

A combination of N,N',N''-tris(3-pyridyl)-1,3,5-benzenetricarboxamide (L1) and p-chlorobenzoic acid (HL2) with Zn(NO3)2·6H2O resulted in the formation of a dinuclear metallacycle [ZnL1(L2)2(DMF)2]2 (1(DMF)4). In 1(DMF)4, the Zn(II) centre adopts a square pyramidal geometry, while one of the pyridyl N out of the three pyridyl groups in L1 remained uncoordinated. Solvated DMF molecules are present in 1(DMF)4. The structural and chemical nature of 1(DMF)4 is effective for it to act as a potential fluorescent probe for the detection of nitroaromatic compounds. It is observed that the probe, 1(DMF)4, could selectively detect picric acid (PA) among various aromatic compounds in solution (DMSO), while the solid state (contact mode) detection showed a positive sensing response for the nitrophenols (PA: 87% quenching efficiency, 2,4-dinitrophenol (2,4-DNP): 57% quenching efficiency and 4-nitrophenol (4-NP): 40% quenching efficiency). The limit of detection (LOD) of PA by the probe in DMSO was found to be 6.8 × 10-11 M while the LOD in contact mode detection was estimated to be 0.49 ng cm-2. The mechanism of selective detection of PA by 1(DMF)4 in DMSO was analyzed through photophysical studies, 1H-NMR experiments and also by density functional theory (DFT) calculations. The effective overlap of the absorption spectrum of 1(DMF)4 and emission spectrum of PA in DMSO suggests that the Förster resonance energy transfer (FRET) is responsible for quenching phenomena in DMSO. The DFT calculations and molecular docking studies showed the adduct formation due to the favorable interactions between 1(DMF)4 and PA in DMSO, while negligible interactions were observed between 1(DMF)4 with other aromatic compounds. The experimental and DFT studies showed that the efficient sensing ability of PA by 1(DMF)4 in the solid-state was due to photoelectron transfer (PET) and FRET phenomena described herein.

Uncovering the mesoporous secrets of Ti/γAl2O3 3-D gels: Fine-tuning morphology engineering for enhancing catalytic ozonation efficacy of environmental contaminants

Herein, we optimized the catalytic ozonation process (COP) by engineering the morphology of versatile mesoporous Ti-doped γAl2O3 materials. Ti/γAl2O3 catalysts were synthesized as xerogels, ambigels, and aerogels for p-chlorobenzoic acid (pCBA) degradation by catalytic ozonation. The roles of Lewis acids and basic sites in Ti/γAl2O3 were investigated along with the synthesis parameters affecting the morphology, structure, and surface acidity. The incorporation of Ti4+ increased the surface acidity, resulting in an effective COP. Full characterization confirmed the uniform Ti distribution and well-defined acidic properties. The sole ozonation process was insufficient, while 0.5 g/L catalyst addition rapidly degraded 50 mg/L pCBA (xerogel: 30 min, ambigel/aerogel: 60 min) while showing excellent reusability and robustness under ions’ presence. EPR analysis suggested that pCBA removal occurs via bulk HO• and less by O3 and O2•--mediated reactions, without 1O2 generation. Based on the above findings, we proposed an integrated pCBA degradation pathway, providing insights into enhancing the COP for organic pollutant degradation via novel, cheap, and sustainable mesoporous materials.

Supramolecular Assemblies of 3/4-Chlorobenzoic Acid and Amino-Chloropyridine Derivatives: Synthesis, X-ray Diffraction, DFT Calculations, and Biological Screening

Organic acids (3-chlorobenzoic acid and 4-chlorobenzoic acid) were treated with 4-amino-2-chloropyridine and 2-amino-4-chloropyridine as coformers for cocrystallization. Acid/base pairs afforded a cocrystal (3-chlorobenzoic acid and 4-amino-2-chloropyridine, compound 1) and molecular salts (2-amino-4-chloropyridinium 3-chlorobenzoate, 2; 2-amino-4-chloropyridinium 4-chlorobenzoate, 3). The products were characterized with the help of FT-IR, UV/visible spectroscopy, PXRD, and SC-XRD. The position of the Cl-substituent on the phenyl ring was explored with respect to proton transfer between acid/base pairs, and its role in supramolecular chemistry is discussed in detail. The existence of supramolecular assemblies was further reproduced using DFT calculations. Further, frontier molecular orbital (FMO), molecular electrostatic potential (MEP), and noncovalent interaction index (NCI) analyses were performed to gain insight into the electronic properties and nature of noncovalent interactions. The prepared compounds were examined for their biological activities against selected Gram-positive and Gram-negative bacterial strains and were also tested as antioxidant agents (DPPH free radical scavenging). Structural parameters determined experimentally and theoretically are within the expected range, and the biological activities of the resultant compounds are moderate.

Mass Balance Studies of Robenidine Hydrochloride in the Body of Channel Catfish (Ictalurus punctatus).

This study aims to determine the mass balance of robenidine hydrochloride (ROBH) in the body of Channel catfish (Ictalurus punctatus). ROBH was administered orally at a dose of 20 mg/kg; following drug administration, the water samples were collected at predetermined time points (12, 24, 48, 72, 96, 120, 144, and 168 h), the experimental fish were executed after the water samples were obtained at 168 h, and the tissue samples were collected separately from the bones. The water and tissue samples were analyzed by high-performance liquid chromatography coupled with tandem mass spectrometry (HPLC-MS/MS) for concentrations of ROBH and its potential major metabolites, 4-chlorohippuric acid (PCHA) and 4-chlorobenzoic acid (PCBA). The tissue samples were prepared using a modified QuEChERS procedure; the water samples were prepared using a liquid-liquid extraction (LLE) procedure. The results show that the recovery rate of ROBH in fish is very low, less than 2% of the total amount of the drug, and the recovery in water can reach 80.7% of the total amount of the drug. The content of PCBA accounted for 42.4% of the total amount of the drug; the content of ROBH accounted for 38.3% of the total amount of the drug. The content of PCHA accounted for less than 1% of the total amount of the drug. The results show that, after a single administration, ROBH is rapidly metabolized in vivo and excreted in the form of ROBH as well as metabolite PCBA. ROBH and PCBA can be used as the main targets for the metabolism detection of ROBH in Channel catfish.

Kinetic constants and transformation products of ornidazole during ozonation

Ornidazole (ONZ), a nitroimidazole antibiotic detected in water bodies, may negatively impact the aquatic ecosystem. Its reaction kinetics during ozonation which is a feasible and applicable technology to control the contamination of emerging contaminants, however, has not been reported in literature. In this study, we measured the apparent second-order kinetic constant of ONZ with ozone molecules via the excessive ozone method and the competing method which led to an average value of 103.8 ± 2.7 M−1 s−1 at pH 7. The apparent second-order kinetic constant of ONZ with HO• was calculated to be 4.65 × 109 M−1 s−1 with the concept of Rct measured via para-chlorobenzoic acid as a probe. The transformation products (TPs) of ONZ during ozonation at pH 3 and pH 11 were separately analyzed with HPLC-MS/MS and some unique products were found at pH 11, reflecting the influence of HO•. The toxicity of individual TPs was predicted with the tool of T.E.S.T. It was found that 62% of 21 identified TPs could be more toxic than ONZ in terms of at least one acute toxicity endpoint, including chlorinated amines and N-oxides. The analysis with a respirometer further revealed that the toxicity of mixing TPs generated at HO• rich conditions was slightly lower than O3 dominated conditions. In general, this study provides the basic kinetic data for designing ozonation processes to eliminate ONZ and the important reference for understanding the toxicity evolution of ONZ during ozonation.

Whole-cell biosensor engineering based on the transcription factor XylS/Pm for sensitive detection of PCB intermediate chlorobenzoic acid

Chlorobenzoic acids (Cba) are toxic chloride pollutants commonly released by chemical industries or formed during the degradation pathway of organic chlorides, such as polychlorinated biphenyls (PCBs). Here, we successfully developed a highly sensitive Escherichia coli whole-cell Cba biosensor, named XyF10 (MG1655(DE3)-Ps-XylS (Step13)-Pm1-EGFP), by comprehensive engineering the elements of Cba sensing genetic circuit from Pseudomonas putida. Compared to the native sensing system, XyF10 exhibited a significantly reduced detection limit (<1 μM vs. 50 μM) and an increased signal-to-noise ratio (11.7-fold vs. 4.4-fold), making it a highly efficient whole-cell sensor with the lowest detection limit for Cba reported to date. Structural analysis and molecular dynamics simulations of XylS and its variants revealed that the increased flexibility of a ring structure in XylS (Step13) variant promoted the sensing efficiency of XyF10 system by fascinating the formation of active dimers and enabled more stable binding with inducer. Furthermore, the XyF10 system displayed an obvious preference for meta-substituted Cba (3-Cba) as substrates, which was attributed by the stronger interaction between 3-Cba and the active site of XylS. Overall, our research not only advanced the Cba detection techniques for large-scale detection of Cba in the environment, but also provided potential tools for high-throughput screening of PCB degradation pathways and enzymes.

Updated Abraham model correlations for describing solute transfer into both 2-Pentanol and 3-Methyl-1-butanol based on much larger data sets

ABSTRACT Mole fraction solubilities of 4-tert-butylbenzoic acid, 3-chlorobenzoic acid, 2-methyl-3-nitrobenzoic acid, 3-methyl-4-nitrobenzoic acid, 3,4,5-trimethoxybenzoic acid, isophthalic acid, 3-hydroxybenzoic acid, o-acetoacetaniside, 2,4-dihydroxybenzophenone, benzoin, paracetamol, and 1,4-dichloro-2-nitrobenzene in 2-pentanol at 298.15 K. Results of the experimental measurements, combined with published literature data, were used to calculated revised equation coefficients for the Abraham model correlations for the 2-pentanol solvent. Revised equation coefficients are also reported for the 3-methyl-1-butanol Abraham model correlations based on much larger data sets containing 95 experimental data points.