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Stimuli‐responsive materials based on π‐conjugated donor‐acceptor systems have great potential for sensing applications in solution and solid state. The photophysical properties of an oligo(p‐phenylenevinylene) series consisting of five push‐pull type molecules were systematically investigated to switch their absorption and emission properties by using trifluoroacetic acid as a specific external analyte. During the trifluoracetic acid sensing, the terminal pyridine units of the molecules undergo the protonation and lead to the broader absorption band at a longer wavelength region owing to the π‐π* characteristics of molecules. Upon exposing solid samples to the trifluoracetic acid vapors, the initial color of solid samples changed from yellow to orange for three‐ring system‐based molecules and brick red to wine red color for five‐ring system‐based molecules with the shifting of emission band to the longer wavelength region. Furthermore, exposing the trifluoracetic acid‐fumed solid samples to triethylamine vapors, the color of the solid samples reverted to their original colors and emission properties. The DFT analysis indicated a decreased energy band gap for the protonated molecules compared to the neutral molecules, suggesting a redshift in both the absorption and emission spectra of the protonated molecules. Thus, all the molecules of an Oligo(p‐phenylenevinylene) series can be utilized effectively for volatile acid detection. [ABSTRACT FROM AUTHOR]

Per‐ and polyfluoroalkyl substances (PFAS) are emerging as bioaccumulative and toxic water pollutants, posing a large threat to human and aquatic organisms. This threat is aggravated by their extreme persistence to common degradation methods. Adsorption is regarded as the most conventional method to treat these contaminants, however, existing sorbents present considerable limitations on performance. The development of more efficient PFAS adsorbents is therefore of urgent need. The class of metal‐organic frameworks (MOFs) can hold great promise for these purposes, featuring porous materials with high tailoring potential. Herein, a series of functionalized Zr‐MOFs have been designed with boosted capacities for the adsorption of short‐ and long‐chain perfluorinated carboxylic acids of environmental interest. The approach relies on chemistry‐based concepts to introduce targeted post‐synthetic modifications that promote PFAS···MOF interactions, specifically through coordinative bonding and hydrophobic effects. In particular, the framework TFA‐MOF‐808 (TFA = trifluoroacetic acid) displays the highest capture capacities reported for MOF materials in this pollutant class. Mechanistic studies, assisted by advanced synchrotron characterization techniques and theoretical calculations, support a ligand exchange process occurring during the adsorption phenomena. The results demonstrate the potential of this design approach in developing advanced PFAS sorbents with optimal performance. [ABSTRACT FROM AUTHOR]

Simultaneous determination of a tandem of drugs like perindopril and rosuvastatin with differences in water and organic solvent solubilities, hydrophobicity, polarities, and UV‐absorbing possibilities between them necessitates careful selection of chromatographic conditions. The four specified and different bonded reversed‐phase columns were tested with running mobile phases containing various composition contents concepts; the concept of using diluted trifluoroacetic acid in mobile phase composition with acetonitrile enabled simultaneous acidification and weak ion‐pairing with protonized molecules of analytes, yielding appropriate, short, reasonable run times and resolutions of analytes, satisfying UV‐transparency, and good peak symmetries. These facts especially stand for the peak of perindopril, as a member of the group of proline‐containing moiety in its structure, often and easily prone to peak‐tailing, skewing, or splitting on the high‐performance liquid chromatography chromatograms, which is usually solved by using alkyl‐sulfonate base and ion pairs on higher concentrations of buffering salts with low pH values and with column temperatures increasing by 50°C–60°C. Linearity range was 0.002/004–0.5 mg/mL. The score for method AGREE was 0.73–0.77. The method development approaches, with all columns employing our concepts in mobile phases and experimental conditions, can cover the complete needs and demands of quality control departments and laboratories as simple high‐throughput analysis methods. [ABSTRACT FROM AUTHOR]

Real-time measurements of short-chain (C < 8) per- and polyfluoroalkyl substances (PFAS) were performed in Central New Jersey air using chemical ionization mass spectrometry (CIMS). The CIMS was calibrated for C2–C6 perfluorinated carboxylic acids, and 4:2 and 6:2 fluorotelomer alcohols. Of these, only trifluoroacetic acid (TFA) was detected in ambient air above instrumental detection limits. However, instrumental sensitivities (and thus ambient mixing ratios) were estimated for other detected PFAS including C3H2F6O and C6HF11O3. TFA mixing ratios reached up to 0.7 parts-per-trillion by volume (pptv). Estimated C3H2F6O and C6HF11O3 mixing ratios reached the single pptv level. These latter two formulas are consistent with hexafluoroisopropanol (HFIP) and hexafluoropropylene oxide dimer acid (HFPO-DA), respectively, though they may potentially represent multiple isomers. Diel profiles of detected PFAS along with local meteorological data can provide information on potential local sources of these compounds. However, only limited discussion of potential sources was provided here given the sparse detection of these compounds above instrument detection limits. These results demonstrate the potential of online CIMS instrumentation for measuring certain PFAS in ambient outdoor air in real time at or below the pptv level. This technique also has potential for fenceline monitoring and other near-source applications. Implications: Online chemical ionization mass spectrometry (CIMS) has potential for fast, real-time measurements of certain airborne per- and polyfluoroalkyl substances (PFAS). Three short-chain (C < 8) PFAS were detected by CIMS in Central New Jersey ambient air near or above the parts-per-trillion by volume (pptv) level. This technique also has potential for fenceline monitoring and other near-source applications for airborne PFAS. [ABSTRACT FROM AUTHOR]

Pollen collected by pollinators can be used as a marker of the foraging behavior as well as indicate the botanical species present in each environment. Pollen intake is essential for pollinators' health and survival. During the foraging activity, some pollinators, such as honeybees, manipulate the collected pollen mixing it with salivary secretions and nectar (corbicular pollen) changing the pollen chemical profile. Different tools have been developed for the identification of the botanical origin of pollen, based on microscopy, spectrometry, or molecular markers. However, up to date, corbicular pollen has never been investigated. In our work, corbicular pollen from 5 regions with different climate conditions was collected during spring. Pollens were identified with microscopy-based techniques, and then analyzed in MALDI-MS. Four different chemical extraction solutions and two physical disruption methods were tested to achieve a MALDI-MS effective protocol. The best performance was obtained using a sonication disruption method after extraction with acetic acid or trifluoroacetic acid. Therefore, we propose a new rapid and reliable methodology for the identification of the botanical origin of the corbicular pollens using MALDI-MS. This new approach opens to a wide range of environmental studies spanning from plant biodiversity to ecosystem trophic interactions. [ABSTRACT FROM AUTHOR]

The radiolysis of liquid and boiling hexafluoroacetylacetone has been studied. The structure of the main radiolysis products indicates the predominance of C–CF3 and C–F bond cleavages. Ten compounds including monoketones, trifluoroacetic acid, keto alcohols, and tautomeric tetraketones were formed. Carbon monoxide was the main gaseous product, and its yield increased under boiling conditions. The initial yields of hexafluoroacetylacetone degradation were 0.29 ± 0.2 and 0.32 ± 0.2 µmol/J at 293 and 343 K, respectively. No accumulation of free HF was observed at low doses. The products of radiolysis are less diverse than those in acetylacetone; this is due to enhancement of the cage effect and to an increase the Onsager radius and the ability of trifluoromethyl groups to dissipate excitation energy. [ABSTRACT FROM AUTHOR]

Chemical ligation of peptides is increasingly used to generate proteins not readily accessible by recombinant approaches. However, a robust method to ligate "difficult" peptides remains to be developed. Here, we report an enhanced native chemical ligation strategy mediated by peptide conjugation in trifluoroacetic acid (TFA). The conjugation between a carboxyl-terminal peptide thiosalicylaldehyde thioester and a 1,3-dithiol-containing peptide in TFA proceeds rapidly to form a thioacetal-linked intermediate, which is readily converted into the desired native amide bond product through simple postligation treatment. The effectiveness and practicality of the method was demonstrated by the successful synthesis of several challenging proteins, including the SARS-CoV-2 transmembrane Envelope (E) protein and nanobodies. Because of the ability of TFA to dissolve virtually all peptides and prevent the formation of unreactive peptide structures, the method is expected to open new opportunities for synthesizing all families of proteins, particularly those with aggregable or colloidal peptide segments. [ABSTRACT FROM AUTHOR]

As the least abundant residue in proteins, tryptophan widely exists in peptide drugs and bioactive natural products and contributes to drug-target interactions in multiple ways. We report here a clickable tryptophan modification for late-stage diversification of native peptides, via catalyst-free C2-sulfenylation with 8-quinoline thiosulfonate reagents in trifluoroacetic acid (TFA). A wide range of groups including trifluoromethylthio (SCF3), difluoromethylthio (SCF2H), (ethoxycarbonyl)difluoromethylthio (SCF2CO2Et), alkylthio, and arylthio were readily incorporated. The rapid reaction kinetics of Trp modification and full tolerance with other 19 proteinogenic amino acids, as well as the super dissolving capability of TFA, render this method suitable for all kinds of Trp-containing peptides without limitations from sequences, hydrophobicity, and aggregation propensity. The late-stage modification of 15 therapeutic peptides (1.0 to 7.6 kilodaltons) and the improved bioactivity and serum stability of SCF3- and SCF2Hmodified melittin analogs illustrated the effectiveness of this method and its potential in pharmacokinetic property improvement. [ABSTRACT FROM AUTHOR]

Based on the prior observation of the trifluoroacetate hypoiodite, CF3C(O)OI, demonstrating the largest σ‐hole of a neutral halogen bond donor, a series of mono‐ and bis‐carbonyl hypoiodites utilising trifluoromethyl or fluorine substituents at various positions of a parent benzoyl skeleton have been synthesised. The carbonyl hypoiodite complexes were prepared via cation exchange of the silver(I) cations with iodine(I) from the respective silver(I) carboxylates and dicarboxylates as the synthetic precursors. A range of pyridinic Lewis bases of varying nucleophilicities were used to stabilise the carbonyl hypoiodites to further probe their properties. The silver(I) intermediates with these Lewis bases were also isolated for silver(I) pentafluorobenzoate, providing additional insight into the cation exchange reaction. All complexes were characterised both in solution (1H, 1H‐15N HMBC, 19F) and in the solid state (SCXRD), permitting insights into the formation of the elusive pyridine‐iodine(I) cation. [ABSTRACT FROM AUTHOR]

Polyester plastics, constituting over 10% of the total plastic production, are widely used in packaging, fiber, single‐use beverage bottles, etc. However, their current depolymerization processes face challenges such as non‐broad spectrum recyclability, lack of diversified high‐value‐added depolymerization products, and crucially high energy consumption. Herein, an efficient strategy is developed for dismantling the compact structure of polyester plastics to achieve diverse monomer recovery. Polyester plastics undergo swelling and decrystallization with a low depolymerization energy barrier via synergistic effects of polyfluorine/hydrogen bonding, which is further demonstrated via density functional theory calculations. The swelling process is elucidated through scanning electron microscopy analysis. Obvious destruction of the crystalline region is demonstrated through X‐ray crystal diffractometry curves. PET undergoes different aminolysis efficiently, yielding nine corresponding high‐value‐added monomers via low‐energy upcycling. Furthermore, four types of polyester plastics and five types of blended polyester plastics are closed‐loop recycled, affording diverse monomers with exceeding 90% yields. Kilogram‐scale depolymerization of real polyethylene terephthalate (PET) waste plastics is successfully achieved with a 96% yield. [ABSTRACT FROM AUTHOR]

The use of non–precious metals for electrocatalytic hydrogen reaction (HER) is particularly important for energy conservation and environmental protection. In this work, three new cobalt corroles containing o−, m−, and p−nitrobenzyl (1, 2, 3) at the meso 10−position of the corrole macrocycle were synthesized, and their electrocatalytic hydrogen evolution reaction in organic and neutral aqueous systems was also investigated. The results show that these three cobalt corroles have significant catalytic HER activity in both systems, and the catalytic efficiency follows 1 > 3 > 2, which indicates that the position of the nitro group can affect the catalytic property of the complexes. In the organic phase, when using trifluoroacetic acid or p−toluenesulfonic acid as the proton source, the electrocatalytic HER may undergo an EECC (E: electron transfer, C: proton coupling) pathway. In a neutral aqueous system, the HER turnover frequency value of 1 is up to 137.4 h−1 at 938 mV overpotential. [ABSTRACT FROM AUTHOR]

The unique physicochemical properties of PEG-400 were imparted to (L)-prolinamide to afford a homogeneous, solvent-free, recyclable organocatalyst for scalable enantioselective aldol reaction between acetone and benzaldehyde to afford (R)-4-hydroxy-4-phenylbutan-2-one. The reaction was scaled up to afford 41 g of ketol in 95% yield and an ee of 91% using 30 mol% catalyst, 10 mol% trifluoroacetic acid (TFA), and 135 equivalent moles of acetone with respect to benzaldehyde. The catalyst was recycled 4 times with no obvious loss of activity. The role of PEG is discussed at the molecular level. This type of catalyst may provide new possibilities for the so-far-thwarted attempts at large-scale application of proline organocatalysis to asymmetric aldol reactions. [ABSTRACT FROM AUTHOR]

A simple, efficient, and reversible fluorescent sensor probe, PBA (2,6-dimethyl pyrone barbituric acid conjugate), comprised of a pro-aromatic donor conjugated with a barbituric acid, was developed for the detection of highly toxic mercuric ions. The probe showed high selectivity and "Turn-On" fluorescence response towards Hg2+ among various metal cations such as Na+, Mg2+, Ca2+, Mn2+, Fe2+, Co2+, Ni2+, Cu2+, Zn2+, Cd2+, Ba2+, Hg2+, and Pb2+, in both homogeneous and microheterogeneous micelle medium sodium dodecyl sulphate (SDS). The binding stoichiometry, limit of detection (LOD), and binding constant for the PBA-Hg complex were determined. The mechanism of binding was ascertained using the N,N'-dimethylbarbituric acid conjugate of 2,6-dimethylpyran (PDMBA), where no binding interaction by deprotonation is possible. In the presence of cysteamine hydrochloride and trifluoroacetic acid (TFA), the complexation of Hg2+ with PBA was demonstrated to be reversible, indicating its potential for the development of reusable sensors. Moreover, the practical applicability of PBA in monitoring Hg2+ in living cells was also evaluated. [ABSTRACT FROM AUTHOR]

Host‐guest chemistry, a pivotal branch of supramolecular chemistry, plays an essential role in understanding and constructing complex structures through non‐covalent interactions. Organic molecular cages, characterized by their intrinsic confined cavities, can selectively bind a variety of guest molecules. Their host–guest chemistry has been well studied in the solution phase, and several attempts have been made to encode well‐defined molecular architectures into solid‐state polymeric materials. However, only limited studies have explored their potential in the solid state, where their lack of robustness and less ordered networks significantly hinder practical applications. Herein, we report the synthesis of a single‐crystal cage framework and a systematic study of its host–guest chemistry, spanning from the solution state to the solid state. Our studies reveal that the host–guest interactions inherent to the cage are successfully maintained in the solid‐state polymeric material. Furthermore, the framework's robustness allows for the guest molecules (fullerene) to be released triggered by an organic acid (trifluoroacetic acid), with subsequent regeneration of the framework through an organic base (triethylamine) treatment. Our findings represent the first synthesis of a robust, single‐crystal cage framework exhibiting highly selective and reversible host–guest chemistry, thus showing great potential towards molecular separation application. [ABSTRACT FROM AUTHOR]

The production of jet-fuel precursors from furfural via aldol-condensation with methyl-isobutyl ketone (MIBK) over defect-engineered UiO-66(Zr) catalysts is presented. The catalysts are prepared using formic acid (FA), trifluoroacetic acid (TFA) and HCl as synthesis modulators, leading to the incorporation of defects on the microcrystalline structure of the metalorganic framework (MOF) material, which dramatically boosts the catalytic performance. An extensive characterization of the modified catalysts by means of X-ray diffraction (XRD), argon adsorption isotherm, thermogravimetry (TGA), transmission electron microscopy, and FTIR spectroscopy of adsorbed acetonitrile, confirmed the incorporation of missing-linker and missing-node defects within the MOF structure, enabling the explanation of the enhancement in the catalytic process. The analysis of the reaction kinetics evidences that, working under moderate temperature conditions, conversion of furfural and selectivity to the desired adduct (FuMe) close to 100% can be achieved, avoiding the formation of degradation and bulkier compounds. Finally, despite the generation of defects within the UiO-66(Zr) structure, the resultant catalyst displays good reusability in low furfural concentration mediums. [ABSTRACT FROM AUTHOR]

We report two methods for selective morpholinomethylation and formylation of C1 − H bonds in pyrrolo[1,2-a]quinoxalines. Reaction of pyrrolo[1,2-a]quinoxalines and morpholine using CuI catalyst, (bis(trifluoroacetoxy)iodo)benzene oxidant, and DMSO solvent yielded the morpholinomethylation products. Meanwhile, formylation of C1 − H bonds in pyrrolo[1,2-a]quinoxalines progressed in the presence of CuI catalyst, trifluoroacetic acid, and DMSO solvent. Compounds bearing halogen, methylsulfonyl, pyridine, and thiophene groups were isolated in moderate yields. [ABSTRACT FROM AUTHOR]

The electrophilic activation of various substrates via double or even triple protonation in superacidic media enables reactions with extremely weak nucleophiles. Despite the significant progress in this area, the utility of organophosphorus compounds as superelectrophiles still remains limited. Additionally, the most common superacids require a special care due to their high toxicity, exceptional corrosiveness and moisture sensitivity. Herein, we report the first successful application of the "Brønsted acid assisted Brønsted acid" concept for the superelectrophilic activation of 2-hydroxybenzo[e][1,2]oxaphosphinine 2-oxides (phosphacoumarins). The pivotal role is attributed to the tendency of the phosphoryl moiety to form hydrogen-bonded complexes, which enables the formation of dicationic species and increases the electrophilicity of the phosphacoumarin. This unmasks the reactivity of phosphacoumarins towards non-activated aromatics, while requiring only relatively non-benign trifluoroacetic acid as the reaction medium. [ABSTRACT FROM AUTHOR]

The reaction of Pd(OAc)2 with (Z)-5-arylidene-4-(4H)-imidazolones (2a-e) and (Z)-4-arylidene-5(4H)- thiazolones (3a-e) in trifluoroacetic acid results in the corresponding orthopalladated dinuclear complexes (4a-e, imidazolones; 11a-d, thiazolones) with trifluoroacetate bridges through regioselective C-H activation at the ortho position of the 4-arylidene group. Compound 4e, which contains an imidazolone substituted at 2- and 4-positions of the arylidene ring with methoxide groups and exhibits strong push-pull charge transfer, is an excellent precursor for the synthesis of fluorescent complexes with green yellowish emission and remarkable quantum yields. Breaking the bridging system with pyridine yields the mononuclear complex 5e (ΦF = 5%), while metathesis of trifluoroacetate ligands with chloride leads to the dinuclear complex 6e, also a precursor of fluorescent complexes by breaking the chloride bridging system with pyridine (7e, ΦF = 7%), or by substitution of chloride ligands with pyridine (8e, ΦF = 15%) or acetylacetonate (9e, ΦF = 2%). In addition to notable photophysical properties, dinuclear complexes 4 and 11 also exhibit significant photochemical reactivity. Thus, irradiation of orthopalladates 4a-c and 11a-c in CH2Cl2 with blue light (465 nm) proceeds via [2 + 2] photocycloaddition of the CvC double bonds of imidazolone and thiazolone ligands, yielding the corresponding cyclobutane-bridging diaminotruxillic derivatives 10a-c and 12a-c, respectively. [ABSTRACT FROM AUTHOR]

The aim of this study was to develop and validate a robust reversed‐phase high‐performance liquid chromatography (RP‐HPLC) method for the simultaneous estimation of neomycin sulfate (NEO) and beclomethasone dipropionate (BECLO) in both bulk drug and pharmaceutical dosage forms. The analysis was conducted using the Box‐Behnken design. The separation of NEO and BECLO was conducted on a Phenomenex Luna C‐18 column (4.6 × 150 mm, 5 µm), employing a mobile phase comprising a mixture of methanol and trifluoroacetic acid in a ratio of 88:12% v/v. The separation was performed at a flow rate of 0.6 mL/min. NEO and BECLO were analyzed at a wavelength of 240 nm employing a photodiode array detector. The validation of the methodology followed the guidelines outlined in the International Council for Harmonization Q2 R (1). The validation process involved assessing critical parameters such as linearity, accuracy, system suitability, precision, and robustness. The results for each parameter were found to be within the acceptable range. The results indicate that the established RP‐HPLC method can effectively be employed for the routine analysis of NEO and BECLO in bulk drug and pharmaceutical dosage forms. [ABSTRACT FROM AUTHOR]

A facile synthesis of novel 5-hydroxy-6,6-dimethyl-6,7-dihydrobenzo[d]isoxazol-4(5H)-ones and 5-hydroxy-6,6-dimethyl-6,7-dihydrobenzo[c]isoxazol-4(5H)-ones starting from the corresponding 6,6-dimethyl-6,7-dihydrobenzisoxazol-4(5H)-ones was developed. The approach includes an oxidation of methylene group adjacent to carbonyl to ketone with selenium dioxide in acetic acid followed by regioselective reduction of the formed carbonyl to hydroxyl group with triethyl silane in trifluoroacetic acid. A series of 14 target compounds were prepared using developed method with yield of 50–87% in two steps. The synthesized α-hydroxy ketones were tested as potential antiproliferative agents against BT-474 breast carcinoma cell line, however at concentration of 50 µM they showed no negative effect on the growth of these cancer cells. [ABSTRACT FROM AUTHOR]

Various methods of introducing deuterium into dopamine using isotope exchange are considered. The best result is achieved by isotope exchange with deuterated water at 190°C for 30 min using (a) trifluoroacetic acid as a catalyst and (b) 5% Pd/Al2O3 catalyst presaturated with deuterium gas. In the first case, the yield of deuterated dopamine was 65–70%, and the average deuterium content was 2.4–2.5 at./molecule. In the second case, the yield decreased to 35–40%, but the deuterium content increased to 3.50–3.60 at./molecule. The obtained result highlights the effectiveness of an integrated approach to introducing hydrogen isotopes into organic molecules, when activated hydrogen isotope species are formed on the catalyst and the substance deposited on it, which contribute to increasing the efficiency of isotope exchange with deuterated water at heating. [ABSTRACT FROM AUTHOR]

The new palladium(II) complex, [Pd(C16H16N4O3)2](CF3COO)2·2CF3COOH, crystallizes in the triclinic space group P⥘ with the asymmetric unit containing half the cation (PdII site symmetry Ci), one tri­fluoro­actetate anion and one co-crystallized tri­fluoro­acetic acid mol­ecule. Two neutral chelating 2-[5-(3,4,5-tri­meth­oxy­phen­yl)-4H-1,2,4-triazol-3-yl]pyridine ligands coordinate to the PdII ion through the triazole-N and pyridine-N atoms in a distorted trans-PdN4 square-planar configuration [Pd—N 1.991 (2), 2.037 (2) Å; cis N—Pd—N 79.65 (8), 100.35 (8)°]. The complex cation is quite planar, except for the methoxo groups (δ = 0.117 Å for one of the C atoms). The planar configuration is supported by two intra­molecular C—H⋯N hydrogen bonds. In the crystal, the π–π-stacked cations are arranged in sheets parallel to the ab plane that are flanked on both sides by the tri­fluoro­acetic acid–tri­fluoro­acetate anion pairs. Apart from classical N/O—H⋯O hydrogen-bonding inter­actions, weak C—H⋯F/N/O contacts consolidate the three-dimensional architecture. Both tri­fluoro­acetic moieties were found to be disordered over two resolvable positions with a refined occupancy ratio of 0.587 (1):0.413 (17) and 0.530 (6):0.470 (6) for the protonated and deprotonated forms, respectively. [ABSTRACT FROM AUTHOR]

Dynamic nuclear polarization (DNP) offers significant signal enhancement compared to conventional nuclear magnetic resonance (NMR) in measuring the nuclear Overhauser effect. Owing to this enhancement, DNP enables the quantitative analysis of solvent–solute interactions, which are typically challenging to assess using standard NMR techniques. However, current experimental setups generally require the use of samples with relatively high solute concentrations because of large dilution factors. This limits the studies on solvent–solute interactions for bio‐related molecules, particularly those with low solubility. In such cases, the concentration of solute post‐dilution often falls below the detection limits. Herein, we introduce a novel dual injection system designed to considerably increase the dilution factor, thereby enabling the use of samples with lower solute concentrations while maintaining detectable signal levels. The effectiveness of this system was demonstrated in experiments using trifluoroacetic acid at concentrations 50 times lower than those used in the conventional method. [ABSTRACT FROM AUTHOR]

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Hydrophobins are small amphiphilic extracellular proteins produced by filamentous fungi; they are surface-active proteins, and their functions are mainly related to their ability to self-assemble into amphipathic monolayers at hydrophobic-hydrophilic interfaces. Depending on their hydropathy patterns and purification requirements, they are classified into class I and class II; both present eight conserved cysteines throughout their sequence, forming four disulfide bridges, which generate four loops that give stability to the protein in its monomeric and folded forms. Class I hydrophobin loops are more extended than class II hydrophobin loops, resulting in differences in assembly on divergent surfaces, additionally accompanied by conformational changes in the protein structure. In the monomer hydrophobin glycosylated form, hydrophobins are rich in ß-sheet structure, while being assembled at the water-air interface increases the content of the ß-sheet in their structure and is at the interface with water, and a hydrophobic solid such as Teflon also induces the formation of an a-helix structure. The monolayers generated by class I are stable structures called fibrils or rodlets, and class II only produces aggregates. Class I presents a glycosylated chain in its sequence; this causes the formation of the a-helix structure, promoting ordered assemblies, which entails their stability and high insolubility. Fibrils could be dissociated with trifluoroacetic acid and formic acid, which unfolds the protein, while 60% ethanol and 2% sodium dodecyl sulfate solutions dissociate class II aggregates. [ABSTRACT FROM AUTHOR]

Electrochemistry offers a sustainable synthesis route to value-added fine chemicals but is often constrained by competing electron transfer between the electrode and redox-sensitive functionalities distinct from the target site. Here, we describe an ion-shielding heterogeneous photoelectrocatalysis strategy to impose mass-transfer limitations that invert the thermodynamically determined order of electron transfer. This strategy is showcased to enable decarboxylative trifluoromethylation of sensitive (hetero)arenes by using trifluoroacetate, an inexpensive yet relatively inert trifluoromethyl group (CF3) source. An ion-shielding layer, formed by trifluoroacetate anions electrostatically adsorbed on a positive molybdenum-doped tungsten trioxide (WO3) photoanode, prevents undesired electron transfer between substrates and photogenerated holes. The practicality of the developed method was demonstrated with robust photoanode stability (approximately 380 hours), a good substrate scope, and scaling capability to achieve 100-gram synthesis by using photoelectrochemical flow cells. [ABSTRACT FROM AUTHOR]

Herein, we reported a selective, mild method for the visible‐light‐photocatalyzed trifluoromethylation and cyclization of unactivated tethered alkenes to provide tri‐ and tetracyclic quinazolinones. Trifluoroacetic acid and anhydride are inexpensive and readily available reagents for the process that proceeds without the addition of a strong oxidant. The wide substrate scope and the formation of 5‐ and 6‐membered rings are demonstrated in 44–82 % yields. Control experiments provide the basis for a proposed mechanism involving photocatalyzed SET from fac‐Ir(ppy)3 to TFAA and trifluoromethyl radical‐mediated regioselective cyclization. The practicality of the protocol was illustrated by a gram‐scale synthesis in 76 % yield. [ABSTRACT FROM AUTHOR]

[Display omitted] Reactions between 4-(propargyloxy)benzaldehyde with anthracene-9-carbaldehyde oxime or pyrene-1-carbaldehyde oxime in the presence of chloramine T in ethanol lead to new isoxazole-containing derivatives of benzaldehyde. The subsequent acid-catalyzed condensation of these compounds with 2-methylresorcinol in chloroform/trifluoroacetic acid mixtures affords novel calix[4]resorcinols with anthaceneand pyrene-ended isoxazole-containing fragments as all– cis (rccc) and cis–trans–trans (rctt) diastereoisomers, their ratios being dependent on the CF 3 CO 2 H percentage in the medium. The crystal structures of pyrene-ended isoxazole-containing benzaldehyde and corresponding calix[4]resorcinol rctt isomer have been established by single crystal X-ray diffraction. [ABSTRACT FROM AUTHOR]

Three new antimony corroles bearing nitro group at ortho-, meta-, and para-position of 10-phenyl 2-NBPC-Sb(1), 3-NBPC-Sb(2) and 4-NBPC-Sb(3), respectively, were prepared. The application of antimony corrole in the electrocatalytic hydrogen evolution reaction (HER) was explored for the first time. The results demonstrate that antimony corrole has good electrocatalytic activity in the HER with acetonitrile and neutral buffer solvents; the catalytic efficacy follows the order 1 > 2 > 3. Specifically, complex 1 exhibited a remarkable turnover frequency (TOF) of 17.65 s−1 in acetonitrile when using trifluoroacetic acid (TFA) served as the proton source at an overpotential of 642 mV. The HER electrocatalyzed with antimony corrole may occur via ECEC pathways. [ABSTRACT FROM AUTHOR]

A series of 5-alkoxy-1,3-benzenedicarbaldehydes and related dimers were prepared in three steps from dimethyl 5-hydroxyisophthalate. Acid catalyzed condensation of the dialdehydes with a tripyrrane dicarboxylic acid, followed by oxidation with 2,3-dichloro-5,6-dicyano-1,4-benzoquinone, afforded good yields of 3-alkoxybenziporphyrins, although dimeric tetraaldehydes failed to give isolatable porphyrinoid products. Proton NMR spectroscopy gave no indication of an aromatic ring current, but addition of trifluoroacetic acid resulted in the formation of dications that exhibited weakly diatropic characteristics. Spectroscopic titration with TFA demonstrated that stepwise protonation took place, generating monocationic and dicationic species. 3-Alkoxybenziporphyrins reacted with nickel(II) or palladium(II) acetate to give the related nickel(II) or palladium(II) complexes. These stable organometallic derivatives showed increased diatropic properties that were most pronounced for the palladium(II) complexes. These unique porphyrinoids provide further insights into the properties of benziporphyrins. [ABSTRACT FROM AUTHOR]

Ginkgo biloba leaves (GBLs), which comprise many phytoconstituents, also contain a toxic substance named ginkgolic acid (GA). Our previous research showed that heating could decarboxylate and degrade GA into ginkgols with high levels of bioactivity. Several methods are available to measure GA in GBLs, but no analytical method has been developed to measure ginkgols and GA simultaneously. Hence, for the first time, an HPLC-DAD method was established to simultaneously determine GA and ginkgols using acetonitrile (0.01% trifluoroacetic acid, v/v) as mobile phase A and water (0.01% trifluoroacetic acid, v/v) as mobile phase B. The gradient elution conditions were: 0–30 min, 75–90% phase A; 30–35 min, 90–90% phase A; 35–36 min, 90–75% phase A; 36–46 min, 75–75% phase A. The detection wavelength of GA and ginkgol were 210 and 270 nm, respectively. The flow rate and injection volume were 1.0 mL/min and 50 μL, respectively. The linearity was excellent (R2 > 0.999), and the RSD of the precision, stability, and repeatability of the total ginkgols was 0.20%, 2.21%, and 2.45%, respectively, in six parallel determinations. The recoveries for the low, medium, and high groups were 96.58%, 97.67%, and 101.52%, respectively. The limit of detection of ginkgol C13:0, C15:1, and C17:1 was 0.61 ppm, 0.50 ppm, and 0.06 ppm, respectively. The limit of quantification of ginkgol C13:0, C15:1, and C17:1 was 2.01 ppm, 1.65 ppm, and 0.20 ppm, respectively. Finally, this method accurately measured the GA and ginkgol content in ginkgo leaves and ginkgo tea products (ginkgo black tea, ginkgo dark tea, ginkgo white tea, and ginkgo green tea), whereas principal component analysis (PCA) was performed to help visualize the association between GA and ginkgols and five different processing methods for GBLs. Thus, this research provides an efficient and accurate quantitative method for the subsequent detection of GA and ginkgols in ginkgo tea. [ABSTRACT FROM AUTHOR]

This study aimed to isolate actinomycetes that exhibit strong herbicidal activity, identify compounds active against weeds, and researching methods to improve the production of these compounds through culture optimization to establish a foundation for the development of environmentally friendly bioherbicides. 334-W4, one of the herbicidal active substances isolated from the culture broth of Streptomyces sp. KRA16-334, exhibited herbicidal activity against various weeds. The molecular formula of 334-W4 was determined to be C16H26N2O6, based on ESI-MS (m/z) and 1H and 13C NMR spectral data. It had molecular weight 365.1689 [M+Na] and 343.1869 [M+H], indicating the presence of the epoxy-β-aminoketone moiety based on HMBC correlations. Additionally, selective culture was possible depending on the addition of trifluoroacetic acid (TFA) during culture with GSS medium. Experiments confirmed that exposure of the KRA16-334 strain to UV irradiation (254 nm, height 17 cm) for 45 seconds improved the yield of the active substance (334-W4) by over 200%. As a result of examining yields of active materials of four mutants selected through optimization of culture conditions such as temperature, agitation, and initial pH, the yield of one mutant 0723–8 was 264.7 ± 12.82 mg/L, which was 2.8-fold higher than that of wild-type KRA16-334 at 92.8 ± 5.48 mg/L. [ABSTRACT FROM AUTHOR]

A simple and robust high‐performance liquid chromatography (HPLC) method was developed for organic impurities of hydroxyzine hydrochloride in pharmaceuticals. The developed method was designed to estimate all organic impurities of hydroxyzine. The HPLC separation was achieved using C18 column (150 × 3.9 mm, 5 μm) along with a binary gradient consisting of mobile phases A (0.1%, trifluoroacetic acid in purified water) and B (0.05%, trifluoroacetic acid in acetonitrile), a flow rate of 0.7–mL/min, a column temperature of 30°C and a sample temperature of 25°C. The detection wavelength used was 230 nm for the estimation of impurity‐A, impurity‐B, and all unspecified impurities and degradation products, whereas impurity‐C was quantitated using 254 nm. The stability‐indicating property of the developed HPLC technique was assessed using stress testing conditions of hydrolysis, oxidation, thermal, photo‐light, and humidity. The validation study was performed for the limit of detection and limit of quantification, linearity, and recoveries were 0.03%, 0.05%, and 0.1132–2.9920 μg/mL (R2 > 0.999), and 84.09%–109.74%, respectively. The proposed method is highly suitable for the determination of assay, organic impurities, and degradation products of the hydroxyzine. The chemical structure of degradation product 1 (hydroxyzine N‐Oxide) and degradation product 2 (O‐Acetyl hydroxyzine) were identified with the supporting data of LC‐mass spectrometry (LC‐MS) and high‐resolution MS. [ABSTRACT FROM AUTHOR]

C18H18N2O3S⋅C2HF3O2, monoclinic, P21 (no. 4), a = 6.0979(2) Å, b = 32.3052(9) Å, c = 11.0805(3) Å, β = 99.5620(10)°, V = 2152.46(11) Å3, Z = 4, Rgt(F) = 0.0570, wRref(F2) = 0.1470, T = 200(1) K. [ABSTRACT FROM AUTHOR]

Abstract Polyester plastics, constituting over 10% of the total plastic production, are widely used in packaging, fiber, single‐use beverage bottles, etc. However, their current depolymerization processes face challenges such as non‐broad spectrum recyclability, lack of diversified high‐value‐added depolymerization products, and crucially high energy consumption. Herein, an efficient strategy is developed for dismantling the compact structure of polyester plastics to achieve diverse monomer recovery. Polyester plastics undergo swelling and decrystallization with a low depolymerization energy barrier via synergistic effects of polyfluorine/hydrogen bonding, which is further demonstrated via density functional theory calculations. The swelling process is elucidated through scanning electron microscopy analysis. Obvious destruction of the crystalline region is demonstrated through X‐ray crystal diffractometry curves. PET undergoes different aminolysis efficiently, yielding nine corresponding high‐value‐added monomers via low‐energy upcycling. Furthermore, four types of polyester plastics and five types of blended polyester plastics are closed‐loop recycled, affording diverse monomers with exceeding 90% yields. Kilogram‐scale depolymerization of real polyethylene terephthalate (PET) waste plastics is successfully achieved with a 96% yield.

The article provides an overview of the ongoing debate surrounding trifluoroacetic acid (TFA) in the environment. It explains that TFA is a byproduct of certain ozone-depleting chlorofluorocarbon replacements and can accumulate in water bodies. However, current concentrations of TFA in the oceans are below toxic levels, and the risks to environmental health are considered minimal. The article suggests further research to address knowledge gaps in TFA production, transport, and toxicity. Additionally, it mentions two scientific articles that delve into the chemistry and environmental impact of certain compounds, providing valuable information for researchers in the field. [Extracted from the article]

Four different isomeric azadibenzo[a,e]pyrenes (benzo[4,10]anthra[9,1‐gh]isoquinolines and benzo[4,10]anthra[1,9‐fg]isoquinolines) were prepared by combination of Pd‐catalyzed Sonogashira and Suzuki cross‐coupling, Brønsted acid mediated cycloisomerization and Pd‐catalysed CH‐activation reactions. The optical properties have been studied by steady‐state absorption and emission spectroscopy in different solvents and during acid titration. Trifluoroacetic acid protonation strongly affects absorption and emission properties, with variations depending on the position of the nitrogen atom of the specific compound. Electrochemical analysis showed distinct oxidation and reduction potentials. DFT calculations provided further insights into electronic properties. [ABSTRACT FROM AUTHOR]

The article shows, for the first time, an example of the manifestation of electrocatalytic activity in the hydrogen evolution reaction (HER) in a new class of organic, metal-free electrocatalysts called "organic hydrides." These organic hydrides are derivatives of the compound 4,4′-dihydropyridine - 1,1'-(2,6-dimethyl-1,4-dihydropyridin-3,5-diyl)bis(ethan-1-one). The electrocatalytic activity of the organic hydride was studied in the presence of acetic and trifluoroacetic acid. It has been shown that the pK value of the acid used determines the HER mechanism. Based on kinetic data, isotope exchange data, as well as density functional theory (DFT)-based calculations, it is shown that the formation of molecular hydrogen proceeds through three different mechanisms depending on the nature of the acid: in the case of using acetic acid, the process goes through the stage of bimolecular elimination; when using trifluoroacetic acid at potential E = −1.0 V, it goes through the stage of intramolecular elimination; whereas at E = −1.6 V, it proceeds through a heterogeneous mechanism. The first example of electrocatalytic hydrogen evolution (HER) from organic 'hydrides'. [Display omitted] • HER of new members of the family of metal-free electrocatalysts studied. • The TOF value strongly depends on potential and pK of the acid. • The destruction of the radical as a key factor influencing the HER mechanisms. • The pK value of the acid used determines the HER mechanism. [ABSTRACT FROM AUTHOR]

The oxidation of cage compounds derived from quinopimaric acid, namely γ-diketone, oxa-"bird cage," 18-chloro-15-oxa-"bird cage," and 16-sulfanyl-15-oxa-"bird cage," was studied using a number of oxidating agents, including sodium percarbonate in trifluoroacetic acid at 0°C, 36% hydrogen peroxide in acetone at room temperature, and tert-butyl hydroperoxide in the presence of MoCl5 in boiling benzene. It was shown for the first time that the oxidation of diterpene oxa-"bird cages" led to the formation of mixtures of keto lactones (Baeyer–Villiger oxidation products), in which 7,10-dioxo-6-oxaheptacyclo[11.8.0.03,8.04,12.05,11.09,13.016,21]heneicosane was the major component. [ABSTRACT FROM AUTHOR]

Cyclic adenosine monophosphate (cAMP) is an important second messenger in cells, mediating various stimulation signals such as the growth and development of organisms and stress and participating in regulating various biological processes of cells. This article explores the quantitative determination of cAMP in plants using High-Performance Liquid Chromatography (HPLC) and applies this method to analyzing the changes in cAMP content during the process of plant response to the bacterial quorum sensing signal N-acyl homoserine lactone (AHL). Research has shown that the optimal detection conditions for HPLC are as follows: the chromatographic column is Venusil MP C18 (2), the mobile phase is methanol–water (0.1% trifluoroacetic acid) (v:v, 10:90), the detection wavelength is 259 nm, the column temperature is 35 °C, and the flow rate is 0.8 mL/min. The precision of the standard sample of this method is 98.21%, the precision of the sample is 98.87%, and the recovery rate is 101.067%. The optimal extraction conditions for cAMP in Arabidopsis are to use 15% methanol ultrasonic extraction for 10 min, followed by a 40 °C water bath for 4 h. Bacterial AHL signal processing can significantly stimulate an increase in cAMP levels in Arabidopsis leaves and roots. The establishment of HPLC detection methods for the cAMP content in plants is of great significance for in-depth research on the signal transduction mechanisms of plant–bacterial interactions. [ABSTRACT FROM AUTHOR]

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Due to the high C–H bond dissociation energy of alkanes, the utilization of alkanes as alkyl radical precursors for C–H functionalization of heteroarenes is synthetically captivating but practically challenging, especially under metal- and photocatalyst-free conditions. We report herein a mild and practical visible-light-mediated method for C–H alkylation of quinoxalin-2(1H)-ones using trifluoroacetic acid as a hydrogen atom transfer reagent and air as an oxidant. This mild protocol was performed under metal- and photocatalyst-free circumstances and presented good functional-group tolerance as well as a broad substrate scope. [ABSTRACT FROM AUTHOR]

The reaction of 2‐alkynylanilines with phenyliodonium bis(trifluoroacetate) (PIFA) and diaryl ditellurides was found to conveniently afford the corresponding 3‐aryltelluroindoles via oxidative cyclization/tellurolation. A plausible mechanism involving the in situ formation of the reactive ArTeOCOCF3 from the reaction of PIFA and diaryl ditellurides, and the subsequent oxidative C−N/C−Te bond formations was postulated. [ABSTRACT FROM AUTHOR]

The efficiency of incorporating deuterium into 4-aminobutanoic acid (GABA) has been studied. The use of D2O at 200°C makes it possible to introduce into GABA an average of about 0.5 deuterium atoms, D2O with trifluoroacetic acid (1 : 1) at 250°C, an average 1.49 deuterium atoms with a yield of 15%. The solid-phase method permits introducing about 3 deuterium atoms per GABA molecule. During isotopic exchange with D2O, the use of a palladium–rhodium mixture pretreated with deuterium gas made it possible to produce [D]GABA with the deuterium content of 4.5–4.6 atoms. But in both cases, the yields of [D]GABA were low. Preparative amounts of [D]GABA were produced engaging additional supports. The best result was obtained when applying GABA to zeolite. Using D2O with 5% Pd/BaSO4–GABA–zeolite pretreated with deuterium gas, allows producing [D]GABA with an average content of 1.5–2.0 deuterium atoms and a yield of about 30%. [ABSTRACT FROM AUTHOR]

The urea cycle has been found to be closely associated with certain types of cancers and other diseases such as cardiovascular disease and chronic kidney disease. An analytical method for the precise quantification of urea cycle amino acids (arginine, ornithine, citrulline, and argininosuccinate) by off-line two-dimensional liquid chromatography (2D-LC) combined with fluorescence-based detection was developed. Before analysis, the amino acids were derivatised with 4-fluoro-7-nitro-2,1,3-benzoxadiazole (NBD-F) to obtain NBD-amino acids. The first dimension involved the reversed-phase separation, in which NBD derivatives of urea cycle amino acids were completely separated from each other and mostly separated from the 18 NBD-proteinogenic amino acids. The samples were eluted with stepwise gradient using 0.02% trifluoroacetic acid in water–acetonitrile as the mobile phase. In the second dimension, an amino column was used for the separation of NBD-ornithine, -citrulline, and -argininosuccinate, while a sulfonic acid column was used to separate NBD-arginine. The developed 2D-LC system was used to analyse human plasma samples. The fractions of NBD-urea cycle amino acids obtained in the first dimension were collected manually and introduced into the second dimension. By choosing appropriate mobile phases for the second dimension, each NBD-urea cycle amino acid eluted in the first dimension was well separated from the other proteinogenic amino acids and interference from endogenous substance. This could not be achieved in the first dimension. The urea cycle amino acids in human plasma sample were quantified, and the method was well validated. The calibration curves for each NBD-urea cycle amino acid showed good linearity from 3 (ASA) or 15 (Orn, Cit, and Arg) to 600 nM, with correlation coefficients higher than 0.9969. The intraday and interday precisions were less than 7.9% and 15%, respectively. The 2D-LC system is expected to be useful for understanding the involvement of the urea cycle in disease progression. [ABSTRACT FROM AUTHOR]

Objective: Convolvulus arvensis is one of the world's top noxious weeds and is commonly known as field bindweed. The objective of research work was separation and identification of flavonoids and to check the anthelmintic activity of this plant. Methods: The flavonoids were analyzed by High-Performance Liquid Chromatography (HPLC) method from alcoholic, hydroalcoholic and aqueous extract of aerial parts of Convolvulus arvensis. Acetonitrile:water (containing 0.05% Trifluoroacetic Acid (TFA) each) was used as mobile phase and isolation was done by using RP-18 column with UV variable wavelength detector (254 nm). Chromatogram of standards was compared with sample. Anthelmintic activity also was performed on prepared extracts of various concentrations. Results: The presence of flavonoids like rutin, kaemferol, quercetin and quercetrin in crude extract was revealed. Significant anthelmintic activity in ethanolic extract was also reported. [ABSTRACT FROM AUTHOR]

"Hot spot" 19F magnetic resonance imaging (MRI) has garnered significant attention recently for its ability to image various disease markers quantitatively. Unlike conventional gadolinium-based MRI contrast agents, which rely on proton signal modulation, 19F-MRI's direct detection has a unique advantage in vivo, as the human body exhibits a negligible background 19F-signal. However, existing perfluorocarbon (PFC) or PFC-based contrast materials suffer from several limitations, including low longitudinal relaxation rates and relatively low imaging efficiency. Hence, we designed a macromolecular contrast agent featuring a high number of magnetically equivalent 19F-nuclei in a single macromolecule, adequate fluorine nucleus mobility, and excellent water solubility. This design utilizes superfluorinated polyphosphazene (PPz) polymers as the 19F-source; these are modified with sodium mercaptoethanesulfonate (MESNa) to achieve water solubility exceeding 360 mg/mL, which is a similar solubility to that of sodium chloride. We observed substantial signal enhancement in MRI with these novel macromolecular carriers compared to non-enhanced surroundings and aqueous trifluoroacetic acid (TFA) used as a positive control. In conclusion, these novel water-soluble macromolecular carriers represent a promising platform for future MRI contrast agents. [ABSTRACT FROM AUTHOR]

A simple, fast, and accurate high-performance liquid chromatographic (HPLC) method is developed, optimized, and validated for a fixed-dose combination of apixaban (APX) and clopidogrel (CLOP) tablets according to ICH guidelines. Chromatographic separation of the drugs was performed on a BDS Hypersil C18 (4.6 ∗ 150 mm, 5 μm), with acetonitrile (ACN) and trifluoroacetic acid (TFA) in the ratio 48 : 52 (v/v) as a mobile phase, at a flow rate of 0.9 ml/min., injection volume of 5 μL, and column temperature 45°C. The proposed method was linear over the level 25–200% for a concentration of APX 5 μg/ml and CLOP 75 μg/ml (R2 > 0.999). The detection limit for APX and CLOP was found to be 0.3465 and 3.8496 μg/ml, whereas the quantification limit was 1.0499 and 11.6656 μg/ml, respectively. The recovery was more than 99% using the standard addition method. The developed method was found to be specific, accurate, precise, and robust against changes in column temperature (±5°C) and mobile phase composition (±5% ACN); hence, it can be used for the determination of APX and CLOP in the fixed-dose combination tablets. [ABSTRACT FROM AUTHOR]

This article presents a study on the tert-butylation reaction of amino acids, carboxylic acids, and alcohols using bis(trifluoromethanesulfonyl)imide (Tf2NH) as a reagent. The study found that this method resulted in faster reactions and higher yields compared to conventional methods. The authors suggest that this information could be valuable to synthetic organic chemists as an alternative to using perchloric acid, as it offers safer conversions and improved reaction rates and yields. [Extracted from the article]