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Per- and polyfluoroalkyl substances (PFAS) are widely used in industry, residential, and consumer products. Studies have shown associations between high PFAS exposure and adverse health effects. In 2022, the National Academies of Science, Engineering, and Medicine (NASEM) published Guidance on PFAS Exposure, Testing, and Clinical Follow-up providing laboratory and clinical direction. The Guidance suggests nine PFAS should be measured in serum or plasma specimens and summed to provide a total PFAS concentration using a NASEM-recommended method. Follow-up clinical recommendations are based on the calculated PFAS NASEM summation. We developed and validated a liquid chromatography-tandem mass spectrometry (LC–MS/MS) method in accordance with NASEM recommendations but distinguished by the ability to separate closely related structural isomers. As part of our validation, PFAS prevalence was evaluated in a population survey comprised of clinical donor and remnant specimens (n = 1023 in total). In this study, 82.2% of the specimens had PFAS NASEM summations of 2 to < 20 ng/mL and 2.5% had a summation ≥ 20 ng/mL. The median PFAS NASEM summation was 4.65 ng/mL in this study, lower than the 7.74 ng/mL median observed in the 2017–2020 Centers for Disease Control and Prevention, National Health and Nutrition Examination Survey (n = 3072). This lower median PFAS NASEM summation may reflect a decline in PFAS population levels over time or sample population exposure differences. [ABSTRACT FROM AUTHOR]

This study reports the development of new probes RR1 ((1E)-1-(1-(6-bromo-2-oxo-2H-chromen-3-yl)ethylidene)ethyl thiosemicarbazone) and RR2 ((1E)-1-(1-(6-bromo-2-oxo-2H-chromen-3-yl)ethylidene)phenyl thiosemicarbazone), which selectively showed fluorescence turn 'OFF' response towards Cu2+ and Al3+. Further, complexes of RR1-Cu2+ and RR2-Al3+ acted as chemosensors for the detection of L -amino acids. RR1-Cu2+ selectively detected L -arginine (fluorescence turn 'ON'), and RR2-Al3+ selectively detected L -glutamic acid (fluorescence turn 'ON'). The existence of the fluorophore–quencher complexes RR1-Cu2+ and RR2-Al3+ was confirmed by theoretical studies. Further, the chemosensors RR1-Cu2+ and RR2-Al3+ have three possible structural isomers (RR1-Cu2+- L -arginine – A, B and C) and (R2-Al3+- L -glutamic acid – D, E and F), as confirmed by theoretical studies. In vitro bio-imaging of the probes (RR1 and RR2), complexes (RR1-Cu2+ and RR2-Al3+) and complexes associated with L -arginine (RR1-Cu2+- L -arginine) and L -glutamic acid (R2-Al3+- L -glutamic acid) was performed in the MDA-MB-231 cell line using their IC50 concentrations. In addition, in vivo live cell imaging studies were conducted using C. elegans as the model organism. [ABSTRACT FROM AUTHOR]

This research delves into a comprehensive investigation of a specific group of alkanes, with the primary objective of establishing meaningful associations between their inherent physical attributes and a set of graphical parameters ranging from topological indices to their associated graphical entropies. Though there are countless techniques to relate molecular structure and physical properties of chemical compounds, the pursuit has often been pricey and arduous. With a view to curb the expense and intense labour, this work focuses on attaining some of these properties using graphical interpretations and statistical interventions. Driven by this objective, we compute Sombor index, a recently developed topological tool and some of its variants for all structural isomers of alkanes with carbon range four to nine. Furthermore, our study employs multiple regression analysis to explore their connections with some physical attributes of alkanes while concurrently addressing the challenge posed by multicollinearity. We have adopted the technique of robust regression to scale down the impact of outliers in the dataset, while generating regression models. Further, the established results are justified with a 10-fold cross validation process and a comparison with the results obtained from different topological indices. The results of this research contribute a valuable insight to the fields of chemical informatics and structural analysis, offering an enhanced comprehension of the interplay between molecular structure and physical attributes within alkanes. [ABSTRACT FROM AUTHOR]

Acanthopanax senticosus belongs to Araliaceae family and is traditionally used as a tonic. The roots and stems are mainly used as treatments for hypodynamia, rheumatism, and hypertension, but their frequent use may lead to extinction. However, comprehensive and simultaneous analysis of the remaining parts were still limited. There is a need to reorganize them for standardization of functional foods. In this study, 50 phenolic compounds and 82 triterpenoid saponins from the shoots, leaves, fruits, and stems of were characterized using UPLC-QTOF-MS and UPLC-QTRAP-MS/MS. Among them, 52 compounds were newly determined as the cis and malonyl-bound phenolic acids and were found to be structural isomers of Acanthopanax flavonoids and saponins. All compounds were absolutely/relatively quantified, and shoots had the highest content. Peroxynitrite and α-glucosidase inhibitory activities were performed, followed by evaluation of structure-activity relationships. Particularly, hederasaponin B and ciwujianoside B showed remarkable efficacy, which were affected by the C-23 hydroxylation, the C-20(29) double bond, and the presence of rhamnose. These detailed profiling can be used as fundamental data for increasing the utilization of A. senticosus and developing them into functional foods. [ABSTRACT FROM AUTHOR]

Dinuclear Re(I) complexes have proportionally been much less studied than mononuclear analogues. In particular, very little information is available about their solid-state emission properties. In this work, two structural isomers of dinuclear complexes (Bi-Re-metaPhe and Bi-Re-paraPhe), which differ by the relative position of the coordination spheres on a central phenyl ring, were synthesized and compared with each other and with the parent mononuclear compound (Mono-Re-Phe), from a theoretical and experimental point of view. In solution, the electronic, electrochemical and spectroscopic properties of the dinuclear complexes were almost identical, and rather close to those of the monomer. In the solid state, the photoluminescence (PL) efficiency of dimers was not higher than that of the monomer, but a clear mechanoresponsive luminescence (MRL) effect appeared only for the former ones. The positional isomerism influenced the amplitude of this effect, as well as the aggregation-induced emission (AIE) properties in a water-acetonitrile mixture. This study reveals the importance of positional isomerism to modulate the emission properties in the solid state. It also shows the advantage of dinuclear structures to access new MRL-active materials. [ABSTRACT FROM AUTHOR]

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We report a synthesis of the trans and cis isomers of 1,4‐di‐tert‐butyl‐2,2,3,3,5,5,6,6‐octamethyl‐1,4‐diphenylcyclohexasilane (3), together with the solid‐state structure of cis‐3. Both isomers were characterized using multinuclear NMR and UV spectroscopies and were compared based on these data, together with DFT calculations. Remarkably, we found that both isomers of 3 showcase redshifted UV maxima when compared with other known cyclosilanes. To explain this, the theoretical calculations show that the transitions involved in the excited states of trans‐3 and cis‐3 have, in addition to the expected σ conjugation component of the Si6 ring, significant π contributions of phenyl substituents. The results presented herein show the effect of the substituent's electronic properties regarding reactivity of intermediates, reaction yield, identity, and electronic properties of novel silicon‐containing molecules. [ABSTRACT FROM AUTHOR]

Structurally flexible organic porous molecular arrays are promising for the development of vapochromic materials with superior detection performance. Exploring the photophysical control of vapochromic materials using these molecular arrays is important for the design of new vapochromic materials. However, difficulties arise in the formation and control of organic porous molecular arrays owing to weak and less‐oriented noncovalent forces and their tendency to arrange into energetically preferred high‐density configurations. Herein, an efficient strategy is presented to control molecular arrays by manipulating the shapes of donor–acceptor–donor system‐based molecular building blocks using positional isomerism and report on the correlation between controlled molecular arrays and vapochromic behavior. Depending on their shape (Z‐shaped, quasi‐Z‐shaped, or linear shape), the building blocks formed different molecular arrays that controlled the intermolecular interactions and void volumes. This led to differences in the final microstructural morphologies. Consequently, they exhibited different vapochromic behaviors, and an in‐depth understanding of the correlation between the molecular arrays and vapochromism/vapofluorochromism is obtained. [ABSTRACT FROM AUTHOR]

For many years, natural products have been recognised as an essential source of active components for medicinal medicines. Specifically, the application of active substances originated from plants and utilised in microbial natural goods dates back to a time before modern medicine. Natural product chemistry, biochemistry, and synthetic activities have long been linked to the effectiveness of natural products. Hence, the special qualities of these natural products are being utilised in light of scientific advancements in contemporary molecular and cellular biology, analytical chemistry, and pharmacology. The goal is to take advantage of the chemical and structural diversity, as well as the biodiversity, of these types of products in relation to their potential therapeutic effects. Rearranging chemical entities or structural isomers of naturally existing products to create new compounds is a common strategy used by drug design units to create novel molecules of interest that may be developed into therapeutics with potential. [ABSTRACT FROM AUTHOR]

Isoguanosine (isoG) is a natural structural isomer of guanosine (G) with significant potential for applications in ionophores, genetics, gel formation, and cancer therapy. However, the cost of commercially available isoG on a gram scale is relatively high. To date, a detailed method for the large‐scale preparation of high‐purity isoG has not been reported. This study presented a simple and convenient approach for the large‐scale synthesis of isoG through the diazotization of 2,6‐diaminopurine riboside with sodium nitrite and acetic acid at room temperature. Further, this method could synthesize isoG derivatives (2'‐fluoro‐isoguanosine (1) and 2'‐deoxy‐isoguanosine (2)) from 2,6‐diaminopurine nucleoside derivatives using diazotization. The structural information of natural and modified nucleosides is crucial for the modification and substitution of DNA/RNA. This study obtained the single‐crystal structure of isoG for the first time and analyzed it in detail using microcrystal electron diffraction. The three‐dimensional supramolecular structure of isoG adopted similarly base‐pair motifs from π‐π stacking interaction of diverse layers, intramolecular hydrogen bonding, and distinct hydrogen bonding interactions from sugar residues. This study has contributed to further isoG modification and its applications in medicinal chemistry and materials. [ABSTRACT FROM AUTHOR]

A synergetic interaction between two or more photochromic chromophores has a potential to achieve advanced photochemical properties beyond conventional photochromic molecules and to realize photochemical control of complex systems using only a single molecule. Herein, we report a hybrid photochromic molecule consisting of hexaarylbiimidazole (HABI) and terarylene that exhibits multi‐state photochromism. The biphotochrome hybrid shows four‐state photochromic reaction involving sequentially proceeding photoreactions. The UV or visible light irradiation to the biphotochrome leads to the C−N bond breaking reaction of the HABI in preference to the ring‐closing reaction of the 6π‐electron system in the terarylene unit, leading to two terarylene radical molecules. The photogenerated terarylene radical further exhibits the 6π‐electrocyclization reaction by UV irradiation. The delocalized π‐radical on the closed‐ring form of the terarylene is efficient to enhance the photosensitivity to the NIR−I and ‐II region. Furthermore, a recombination reaction of radicals between the open‐ and closed‐ring isomers of terarylene affords an unprecedented photochromic dimer as a structural isomer of the initial molecule. This is a consequence of the sequential hybrid photochromic system involving the HABI and terarylene units. [ABSTRACT FROM AUTHOR]

Conjugated linolenic acid (CLnA) is a mixture of octadecenoic acid with multiple positional and geometric isomers (including four 9, 11, 13-C18:3 isomers and three 8, 10, 12-C18:3 isomers) that is mainly present in plant seeds. In recent years, CLnA has shown many promising health benefits with the deepening of research, but the metabolic characteristics, physiological function differences and mechanisms of different isomers are relatively complex. In this article, the metabolic characteristics of CLnA were firstly reviewed, with focus on its conversion, catabolism and anabolism. Then the possible mechanisms of CLnA exerting biological effects were summarized and analyzed from its own chemical and physical characteristics, as well as biological receptor targeting characteristics. In addition, the differences and mechanisms of different isomers of CLnA in anticancer, lipid-lowering, anti-diabetic and anti-inflammatory physiological functions were compared and summarized. The current results show that the position and cis-trans conformation of conjugated structure endow CLnA with unique physical and chemical properties, which also makes different isomers have commonalities and particularities in the regulation of metabolism and physiological functions. Corresponding the metabolic characteristics of different isomers with precise nutrition strategy will help them to play a better role in disease prevention and treatment. CLnA has the potential to be developed into food functional components and dietary nutritional supplements. The advantages and mechanisms of different CLnA isomers in the clinical management of specific diseases need further study. [ABSTRACT FROM AUTHOR]

The synthesis of amides holds great promise owing to their impeccable contributions as building blocks for highly valued functional derivatives. Herein, we disclose the design, synthesis and crystal structure of a mixed-ligand ruthenium(II) complex, [Ru(η6-Cym)(O,O-PLY)Cl], (1) where Cym = 1-isopropyl-4-methyl-benzene and O,O-PLY = deprotonated form of 9-hydroxy phenalenone (HO,O-PLY). The complex catalyzes the aerobic oxidation of various primary amines (RCH2NH2) to value-added amides (RCONH2) with excellent selectivity and efficiency under relatively mild conditions with common organic functional group tolerance. Structural, electrochemical, spectroscopic, and computational studies substantiate that the synergism between the redox-active ruthenium and π-Lewis acidic PLY moieties facilitate the catalytic oxidation of amines to amides. Additionally, the isolation and characterization of key intermediates during catalysis confirm two successive dehydrogenation steps leading to nitrile, which subsequently transform to the desired amide through hydration. The present synthetic approach is also extended to substitution-dependent tuning at PLY to tune the electronic nature of 1 and to assess substituent-mediated catalytic performance. The effect of substitution at the PLY moiety (5th position) leads to structural isomers, which were further evaluated for the catalytic transformations of amine to amides under similar reaction conditions. [ABSTRACT FROM AUTHOR]

The gelation of two TADF positional isomers, 4BPy-mDTC and BPy-DTC, was explored. Among these emitters, only 4BPy-mDTC forms stable organogels due to the optimized intermolecular interactions. Interestingly, the morphology of the gel can be tuned from fibre to fettuccine by changing the solvents. The electrical conductivity of the self-assembly can also be increased from 8.05 × 10−4 S m−1 to 6.05 × 10−3 S m−1 by tuning the morphology. [ABSTRACT FROM AUTHOR]

This article discusses the use of lignocellulose, a renewable source of chemical products, for the production of high-value compounds. The authors focus on the nitration of lignin-derived monomeric products, such as vanillin, to produce 5-nitrovanillin. They explore the use of acetyl nitrate as a nitrating agent and highlight its advantages over other methods. The study demonstrates that the nitration of vanillin is highly selective and can be carried out in a simple and efficient manner. The authors hope that this research will contribute to the practical applications of lignin-derived structures and enhance our understanding of their reactivities. [Extracted from the article]

In this study, we successfully employed a 19F‐labeled cyclopalladium probe to achieve simultaneous differentiation and detection of various amines and N‐heterocyclic compounds. This method features a broad detection window, facilitating the discrimination and multi‐component analysis of structural analogs and isomers through the generation of characteristic 19F NMR signals with distinct chemical shifts. The utility of this approach is demonstrated in monitoring chemical reactions and identifying components in food, beverages, and cosmetics. [ABSTRACT FROM AUTHOR]

Goji, a renowned traditional Chinese medicine and food source, is characterized by a long fruiting period. This study was conducted to investigate the variations in nutritional quality of goji berries across different harvest stages by utilizing widely targeted metabolome and transcriptome. The results showed that goji berries of the first harvest stage had advantages in terms of size and metabolic levels, and there was little difference in sugars and organic acids levels. Within significantly enriched phenylpropanoid and flavonoid pathways, chlorogenic acid, and its positional isomers (neochlorogenic acid and cryptochlorogenic acid) increased significantly along with P‐coumaroyl quinic acid as the harvest stages progressed, while the other bioactive DEMs including scopoletin, scopolin, naringenin, and pruning exhibited a decreasing trend. The key DEGs encoding PAL, HCT, 4CL, C4H, TOGT1, and C12RT1 were suggested to regulate the variations of these DEMs. Furthermore, six oxidative metabolites enriched in alpha‐linolenic acid and linoleic acid metabolism pathways all peaked at the second harvest stage. Climate or plant weakening is suggested as potential factors influencing the metabolic and transcriptomic changes in goji berries. This study provides a fresh perspective on understanding the accumulation of metabolites and their molecular mechanisms in goji at different harvest stages in the Qaidam Basin and can be used to guide goji production and processing. [ABSTRACT FROM AUTHOR]

4-[(S)-2-Methyl-3-hydroxypropyloxy]-4'-formylazobenzene, 4-(3-hydroxypropyloxy)-4'-formylazobenzene and µ-oxodimer of iron 2,8,12,18-tetramethyl-3,7,13,17-tetra-n-amylporphine were synthesized using known methods. A mixture with a certain concentration of components was prepared from the synthesized compounds. The resulting mixture was used as an impregnation of the wide-porous adsorbent Chromaton N-AW. The degree of impregnation was 10%. The prepared adsorbent was used as a stationary phase for inverse gas-mesophase chromatography. In this work, the sorption redistribution of a number of volatile organic compounds—isomers of methyl and dimethylpyridines, weakly polar xylenes and enantiomers from the gas phase on the prepared adsorbent was studied using inverse gas chromatography. During the experiment, the specific retention volumes of sorbates, characterizing the sorption activity of the prepared stationary phase were calculated. For structural isomers, activity coefficients for the distribution of sorbates in the liquid layer of the liquid crystal were obtained. To confirm the data on the sorption activity of sorbates, the thermodynamic parameters of the dissolution of specific isomers were found. Conclusions were drawn about the influence of enthalpy and entropy factors on the retention ability of sorbates. The influence of structure, isomerism, intermolecular interactions, and the addition of a macrocycle on the sorption properties of sorbates is discussed. Data on the analytical features of sorption were obtained, namely, the maximum values of separation factors for structural and optical isomers and compounds of different structures, but with similar boiling points, were calculated. It was experimentally established that the prepared adsorbent exhibits a fairly high ability to separate close-boiling structural isomers and a moderate ability to separate enantiomers. Emphasis is placed on the maximum value of the separation factor of 3,4- and 3,5-lutidines, which is the highest in value among the previously developed stationary phases of similar structure. In conclusion, the use of the resulting adsorbent in a unified system of chemical analysis is justified. [ABSTRACT FROM AUTHOR]

Pidotimod is a chiral drug that possesses two chiral centers, resulting in three isomeric impurities (analytes, A). This study employs electrospray ionization ion trap mass spectrometry (ESI‐MS) through collision‐induced dissociation (CID) to investigate the chiral recognition of pidotimod and its three isomers to eliminate chromatographic separation. Three approaches were explored: (1) Protonated molecules in CID exhibited discriminative potential for diastereomers, with the ability to distinguish between S,S and R,R configurations, albeit with an Rchiral value of ~1.8. However, differentiation between R,S and S,R configurations was not achievable. (2) Alkali adductions (lithium and sodium) only discerned diastereomers. The Rchiral values of the diastereomers obtained from alkali adduct ions were significantly lower than those obtained from protonated ions. (3) Therefore, a third approach was used to address the challenge of distinguishing between R,S and S,R configurations, including the introduction of chiral references (ref) and transition metals (MII) to form metal‐bound complexes [MII(A)(ref)‐H]+. Additionally, we synthesized a novel ligand, 4‐(N‐tert‐butoxycarbonyl [Boc]‐L‐prolinamido)phenol (denoted as ligand A), by modifying N‐t‐Boc‐L‐Pro with 2‐aminophenol, which, in combination with CuII and NiII, enabled simultaneous differentiation of all four isomers. CuII complexes exhibited significant chiral selectivity between R,S and S,R configurations. Density functional theory calculations were performed to further elucidate the stereodynamic behavior and stoichiometry of these ions in the gas phase. These calculations revealed the interaction energy and coordination sites of the precursor ions in the gas phase, correlating well with MS/MS experiment results. Additionally, the logarithm of the CuII complexes' characteristic fragment ion abundance ratio demonstrated a strong linear relationship with enantiomeric excess (ee). This study presents a novel strategy for chiral drug quality control that eliminates chromatographic separation. [ABSTRACT FROM AUTHOR]

Bile acids (BAs) currently occupy the research hotspot because of their unreplaceable physiological functions as well as their unique abilities to reflect the physiopathological status. It is always challenging to characterize BAs‐submetabolome using LC–MS/MS, primarily attributing to the high‐level structural diversity. The key obstructing confirmative identification is isomeric identification because of the inherent "isomer‐blind" disadvantage of MS/MS. The isomerism styles of BAs are broadly divided into: type‐I, 5α‐H and 5β‐H epimers; type‐II, α‐OH and β‐OH epimers; type‐III, C‐OH positional isomers; and type‐IV, hybrid isomers bearing two or more isomerism fashions. Herein, we aim to comprehensively pursue isomer‐selective clues for BAs through constructing three‐dimensional MS2 (3D‐MS2) spectrum that was accomplished by fortifying energy‐resolved MS (ER‐MS) program as the new dimension. The breakdown graphs of primary MS2 spectral signals composed of 3D‐MS2 spectrum namely full collision energy ramp (FCER)‐MS2 spectrum for each BA species after appropriate normalization, and seven isomeric BAs covering all isomerism styles were utilized as representative cases. After recording MS2 spectra with progressive CE levels, differences were observed for their FCER‐MS2 spectra. Diagnostic fragment ions (DFIs) occurred within type‐I, type‐II, type‐III or type‐IV isomers, and noteworthily, 2.02 Da neutral loss discriminated BAs containing cis‐6,7‐diol and trans‐6,7‐diol functional groups. Notably, the features such as the maximal relative ion intensity (RIImax) and optimal CE (OCE) enabled isomeric differentiation for all types, even type‐II and type‐III isomers. Above all, it is feasible to acquire in‐depth isomer‐selective MS/MS clues for BAs using FCER‐MS2 spectrum, regardless of the isomerism manner. [ABSTRACT FROM AUTHOR]

Cancer is a global health problem, with the incidence rate estimated to reach 40% of the population by 2030. Although there are currently several therapeutic methods, none of them guarantee complete healing. Plant-derived natural products show high therapeutic potential in the management of various types of cancer, with some of them already being used in current practice. Among different classes of phytocompounds, pentacyclic triterpenoids have been in the spotlight of research on this topic. Ursolic acid (UA) and its structural isomer, oleanolic acid (OA), represent compounds intensively studied and tested in vitro and in vivo for their anticancer and chemopreventive properties. Since natural compounds can rarely be used in practice as such due to their characteristic physico-chemical properties, to tackle this problem, their derivatization has been attempted, obtaining compounds with improved solubility, absorption, stability, effectiveness, and reduced toxicity. This review presents various UA and OA derivatives that have been synthesized and evaluated in recent studies for their anticancer potential. It can be observed that the most frequent structural transformations were carried out at the C-3, C-28, or both positions simultaneously. It has been demonstrated that conjugation with heterocycles or cinnamic acid, derivatization as hydrazide, or transforming OH groups into esters or amides increases anticancer efficacy. [ABSTRACT FROM AUTHOR]

Pure aromatic hydrocarbon materials (PHCs) represent a new generation of host materials for phosphorescent OLEDs (PhOLEDs), free of heteroatoms. They reduce the molecular complexity, can be easily synthesized and are an important direction towards robust devices. As heteroatoms can be involved in bonds dissociations in operating OLEDs through exciton induced degradation processes, developing novel PHCs appear particularly relevant for the future of this technology. In the present work, we report a series of extended PHCs constructed by the assembly of three spirobifluorene fragments. The resulting positional isomers present a high triplet energy level, a wide HOMO/LUMO difference and improved thermal and morphological properties compared to previously reported PHCs. These characteristics are beneficial for the next generation of host materials for PhOLEDs and provide relevant design guidelines. When used as a host in blue‐emitting PhOLEDs, which are still the weakest link of the field, a very high EQE of 24 % and low threshold voltage of 3.56 V were obtained with a low‐efficiency roll‐off. This high performance strengthens the position of PHC strategy as an efficient alternative for OLED technology and opens the way to a more simple electronic. [ABSTRACT FROM AUTHOR]

The ability of thermoresponsive polymers to respond to temperature with a reversible conformational change makes them promising 'smart' materials for solutions in medical and biotechnological applications. In this work, two such polymers and structural isomers were studied: poly(N-isopropyl acrylamide) (PNiPAm) and poly(2-isopropyl-2-oxazoline) (PiPOx). We compare the critical solution temperatures (CST) of these polymers in D2O and H2O in the presence of Hofmeister series salts, as results obtained under these different solvent conditions are often compared. D2O has a higher dipole moment and electronegativity than H2O, which could significantly alter the CST transition. We used two complementary methods to measure the CST, dynamic light scattering (DLS) and differential scanning calorimetry (DSC) and found that the CST decreased significantly in D2O compared to H2O. In the presence of highly concentrated kosmotropes, the CST of both polymers decreased in both solvents. The influence of the kosmotropic anions was smaller than the water isotope effect at low ionic strengths but considerably higher at physiological ionic strengths. However, the Hofmeister anion effect was quantitatively different in H2O than in D2O, with the largest relative differences observed for Cl−, where the CSTs in D2O decreased more than in H2O measured by DLS but less by DSC. PiPOx was more sensitive than PNiPAm to the presence of chaotropes. It exhibited much higher transition enthalpies and multistep transitions, especially in aqueous solutions. Our results highlight that measurements of thermoresponsive polymer properties in D2O cannot be compared directly or quantitatively to application conditions or even measurements performed in H2O. [ABSTRACT FROM AUTHOR]

Glycosphingolipids (GSLs) are essential components of cell membranes, particularly enriched in the nervous system. Altered molecular distributions of GSLs are increasingly associated with human diseases, emphasizing the significance of lipidomic profiling. Traditional GSL analysis methods are hampered by matrix effect from phospholipids and the difficulty in distinguishing structural isomers. Herein, we introduce a highly sensitive workflow that harnesses magnetic TiO2 nanoparticle-based selective enrichment, charge-tagging Paternò–Büchi reaction, and liquid chromatography-tandem mass spectrometry. This approach enables mapping over 300 distinct GSLs in brain tissues by defining sugar types, long chain bases, N-acyl chains, and the locations of desaturation and hydroxylation. Relative quantitation of GSLs across multiple structural levels provides evidence of dysregulated gene and protein expressions of FA2H and CerS2 in human glioma tissue. Based on the structural features of GSLs, our method accurately differentiates human glioma with/without isocitrate dehydrogenase genetic mutation, and normal brain tissue. The molecular profiling of glycosphingolipids (GSLs) is hindered by the coexistence of abundant phospholipids and diverse isomers. The authors introduce a highly sensitive workflow that maps out the structural atlas of neutral GSLs, previously deemed a "dark space" within the lipidome. [ABSTRACT FROM AUTHOR]

Two structural isomeric porphyrin-based triads (Zn(II)porphyrin−Sn(IV)porphyrin−Zn(II)porphyrin) denoted as T1 and T2 were prepared from the reaction of meso-[5-(4-hydroxyphenyl)-10,15,20-tris(3,5-di-tert-butylphenyl)porphyrinato]zinc(II) (ZnL) with trans-dihydroxo-[5,10-bis(3-pyridyl)-15,20-bis(phenyl)porphyrinato]tin(IV) (SnP1) and trans-dihydroxo-[5,15-bis(3-pyridyl)-10,20-bis(phenyl)porphyrinato]tin(IV) (SnP2), respectively. All the compounds were characterized using UV–vis spectroscopy, emission spectroscopy, ESI−MS, 1H NMR spectroscopy, and FE-SEM. Most importantly, the two structurally isomeric porphyrin-based triads supramolecularly self-assembled into completely different nanostructures. T1 exhibits a nanosphere morphology, whereas T2 exhibits a nanofiber morphology. The amplified geometric feature in the structural isomeric porphyrin-based triads dictates the physical and chemical properties of the two triads. Both compounds showed the morphology-dependent visible light catalytic photodegradation of rhodamine B dye (74–97% within 90 min) and tetracycline antibiotic (44–71% within 45 min) in water. In both cases, the photodegradation efficiency of T2 was higher than that of T1. The present investigation can significantly contribute to the remediation of wastewater by tuning the conformational changes in porphyrin-based photocatalysts. [ABSTRACT FROM AUTHOR]

Diisopentyl phthalate (DiPeP) is primarily used as a plasticizer or additive within the production of polyvinyl chloride (PVC), and has many additional industrial applications. Its metabolites were recently found in urinary samples of pregnant women; thus, this substance is of concern as relates to human exposure. Depending upon the nature of the alcohol used in its synthesis, DiPeP may exist either as a mixture consisting of several branched positional isomers, or as a single defined structure. This article investigates the skin sensitization potential and immunomodulatory effects of DiPeP CAS No. 84777-06-0, which is currently marketed and classified as a UVCB substance, by in silico and in vitro methods. Our findings showed an immunomodulatory effect for DiPeP in LPS-induced THP-1 activation assay (increased CD54 expression). In silico predictions using QSAR TOOLBOX 4.5, ToxTree, and VEGA did not identify DiPeP, in the form of a discrete compound, as a skin sensitizer. The keratinocyte activation (Key Event 2 (KE2) of the adverse outcome pathway (AOP) for skin sensitization) was evaluated by two different test methods (HaCaT assay and RHE assay), and results were discordant. While the HaCaT assay showed that DiPeP can activate keratinocytes (increased levels of IL-6, IL-8, IL-1α, and ILA gene expression), in the RHE assay, DiPeP slightly increased IL-6 release. Although inconclusive for KE2, the role of DiPeP in KE3 (dendritic cell activation) was demonstrated by the increased levels of CD54 and IL-8 and TNF-α in THP-1 cells (THP-1 activation assay). Altogether, findings were inconclusive regarding the skin sensitization potential of the UVCB DiPeP—disagreeing with the results of DiPeP in the form of discrete compound (skin sensitizer by the LLNA assay). Additional studies are needed to elucidate the differences between DiPeP isomer forms, and to better understand the applicability domains of non-animal methods in identifying skin sensitization hazards of UVCB substances. [ABSTRACT FROM AUTHOR]

Herein we reported the synthesis of three positional isomeric (o-, m-, and p-) π-conjugated polyyne chromophores, in which three diethynylbenzene positional isomers were used as π-conjugated bridges, respectively. Subsequently, the structural characterization of the above positional isomers was accomplished by NMR, MS, IR, etc. Then, their electronic absorption, photoluminescence (PL) emissions, and electrochemiluminescence (ECL) properties were further investigated. The PL emissions of three π-conjugated polyyne chromophores were observed in the wavelength of ~325–510 nm. Interestingly, the para-isomer with a rigid planar π-conjugated structure exhibits the strongest UV-Vis absorption and fluorescence emission. Finally, the ECL measurements indicated that the three π-conjugated polyyne chromophores exhibited stable cathode ECL emission, providing excellent candidate materials for the future design and manufacturing of ECL emitters. [ABSTRACT FROM AUTHOR]

A method was developed for obtaining positional isomers—2-[6-aryl-4-trifluoromethyl-3-cyanopyridin-2(1H)-ylidene]malononitriles and 2-[4-aryl-6-trifluoromethyl-3-cyanopyridin-2(1H)-ylidene]malononitriles, which differ in the opposite positioning of the aryl and trifluoromethyl substituents. These compounds exhibit photoluminescence in solutions ranging from the violet to the yellow region of the visible spectrum (λemmax = 418–577 nm). The strongest photoluminescence was observed in low-polarity solvents, where the quantum yield of photoluminescence reached 46%. It was shown that a basic medium leads to a significant red shift due to the formation of the anionic form. [ABSTRACT FROM AUTHOR]

Developing aggregation‐induced emission luminogens (AIEgens) is a unique strategy for alleviating concentration quenching of π‐conjugated organic compounds. This AIE behaviour can be induced not only in organic dyes with rotors but also in invertible π‐conjugated systems. Herein, intramolecular Ullmann coupling was used to synthesize π‐twisted triskelion‐shaped AIEgens (2F, 2G, and 2H), in which benzo[f], [g], and [h] coumarins were fused into the benzene core to form a helical propeller shape. These structural isomers had unique molecular thicknesses and planarities depending on the fusion mode of the benzocoumarin. The racemic crystals, PPP and MMM, had different overlapping molecular configurations because of their twisted molecular frameworks. Compounds 2F, 2G and 2H demonstrated weak fluorescence emission in diluted solutions resulting from molecular motions caused by the isomerization process during molecular inversion. By comparison, aggregates exhibited enhanced emission intensity. These π‐twisted triskelions exhibited the characteristics of AIEgens. [ABSTRACT FROM AUTHOR]

Enantioseparation of nineteen liquid crystalline racemic mixtures obtained based on (R,S)-2-octanol was studied in reversed-phase mode on an amylose tris(3-chloro-5-methylphenylcarbamate) (ReproSil Chiral-MIG) and a cellulose tris(3,5-dichlorophenylcarbamate) (ReproSil Chiral-MIC). These polysaccharide-based chiral stationary phase (CSP) columns for High-Performance Liquid Chromatography (HPLC) were highly effective in recognizing isomers of minor structural differences. The mobile phase (MP), which consists of acetonitrile (ACN)/water (H2O) at different volume ratios, was used. The mobile phases were pumped at a flow rate of 0.3, 0.5, or 1 mL·min−1 with a column temperature of 25 °C, using a UV detector at 254 nm. The order of the elution was also determined. The chromatographic parameters, such as resolution (Rs), selectivity (α), and the number of theoretical plates, i.e., column efficiency (N), were determined. The polysaccharide-based CSP columns have unique advantages in separation technology, and this study has shown the potential usefulness of the CSP columns in separating liquid crystalline racemic mixtures belonging to the same homologous series. [ABSTRACT FROM AUTHOR]

Conjugated linoleic acid (CLA) is a class of naturally occurring octadecadienoic acid in humans and animals and is a general term for a group of conformational and positional isomers of linoleic acid. In order to obtain the development of excellent lactic acid strains with a high production of conjugated linoleic acid, 32 strains with a possible CLA conversion ability were obtained by initial screening using UV spectrophotometry, and then the strains were re-screened by gas chromatography, and finally, the strain with the highest CLA content was obtained. The strains were optimized for cultivation by changing the amount of substrate addition, inoculum amount, and fermentation time. The results showed that the yield of the experimentally optimized strain for the conversion of conjugated linoleic acid could reach 94.68 ± 3.57 μg/mL, which was 74.4% higher than the initial yield of 54.28 ± 2.12 μg/mL of the strain. The results of this study can provide some basis for the application of conjugated linoleic acid production by Lactobacillus paracasei in the fermentation of lactic acid bacteria. [ABSTRACT FROM AUTHOR]

The thermally stable zirconium-based MOF, UiO-66, was employed for the preparation of bonded porous-layer open-tubular (PLOT) GC columns. The synthesis included the in situ growth of the UiO-66 film on the inner wall of the capillary through a one-step solvothermal procedure. SEM–EDX analysis revealed the formation of a thin, continuous, uniform, and compact layer of UiO-66 polycrystals on the functionalized inner wall of the column. The average polarity (ΔIav = 700) and the McReynolds constants reflected the polar nature of the UiO-66 stationary phase. Several mixtures of small organic compounds and real samples were used to evaluate the separation performance of the fabricated columns. Linear alkanes from n-pentane to n-decane were baseline separated within 1.35 min. Also, a series of six n-alkylbenzenes (C3–C8) were separated within 3 min with a minimum resolution of 3.09, whereas monohalobenzene mixtures were separated at 220 °C within 14s. UiO-66 PLOT columns are ideally suited for the isothermal separation of chlorobenzene structural isomers at 210 °C within 45 s with Rs ≥ 1.37. The prepared column featured outstanding thermal stability (up to 450 °C) without any observed bleeding or significant impact on its performance. This feature enabled the analysis of various petroleum-based samples. [ABSTRACT FROM AUTHOR]

3-hydroxy-3-(3′-hydroxyphenyl)propanoic acid (CID: 102959) (3,3'-HPHPA) is one of several phenolic molecules that are generated by a process involving gut microbiota and have been implicated in autism and schizophrenia. The structural isomers of 3,3′-HPHPA have been challenging to separate chromatographically. Accordingly, their distribution across brain and other compartments in humans and experimental animals remains poorly characterized. We describe a modified liquid chromatography mass spectroscopy method for the detection and separation of seven commercially available structural isomers of 3,3′-HPHPA. We used the method to screen different compartments in the mouse and demonstrate its utility in identifying multiple structural isomers and conjugates of 3,3′-HPHPA in biological matrices. Characterizing the diversity and complexity of this family of structural isomers will advance studies of their bioactivity and clinical relevance. [ABSTRACT FROM AUTHOR]

Molecular fingerprints are indispensable tools in cheminformatics. However, stereochemistry is generally not considered, which is problematic for large molecules which are almost all chiral. Herein we report MAP4C, a chiral version of our previously reported fingerprint MAP4, which lists MinHashes computed from character strings containing the SMILES of all pairs of circular substructures up to a diameter of four bonds and the shortest topological distance between their central atoms. MAP4C includes the Cahn-Ingold-Prelog (CIP) annotation (R, S, r or s) whenever the chiral atom is the center of a circular substructure, a question mark for undefined stereocenters, and double bond cis–trans information if specified. MAP4C performs slightly better than the achiral MAP4, ECFP and AP fingerprints in non-stereoselective virtual screening benchmarks. Furthermore, MAP4C distinguishes between stereoisomers in chiral molecules from small molecule drugs to large natural products and peptides comprising thousands of diastereomers, with a degree of distinction smaller than between structural isomers and proportional to the number of chirality changes. Due to its excellent performance across diverse molecular classes and its ability to handle stereochemistry, MAP4C is recommended as a generally applicable chiral molecular fingerprint. Scientific contribution: The ability of our chiral fingerprint MAP4C to handle stereoisomers from small molecules to large natural products and peptides is unprecedented and opens the way for cheminformatics to include stereochemistry as an important molecular parameter across all fields of molecular design. [ABSTRACT FROM AUTHOR]

Helical nanographenes with high quantum yields and strong chiroptical responses are pivotal for developing circularly polarized luminescence (CPL) materials. Here, we present the successful synthesis of novel π‐extended double [7]helicenes (ED7Hs) where two helicene units are fused at the meta‐ or para‐position of the middle benzene ring, respectively, as the structural isomers of the reported ortho‐fused ED7H. The structural geometry of these ED7Hs is clearly characterized by single‐crystal X‐ray analysis. Notably, this class of ED7Hs exhibits bright luminescence with high quantum yields exceeding 40 %. Through geometric regulation of two embedded [7]helicene units from ortho‐, meta‐ to para‐position, these ED7Hs display exceptional amplification in chiroptical responses. This enhancement is evident in a remarkable approximate fivefold increase in the absorbance and luminescence dissymmetry factors (gabs and glum), respectively, along with a boosted CPL brightness up to 176 M−1 cm−1, surpassing the performance of most helicene‐based chiral NGs. Furthermore, DFT calculations elucidate that the geometric adjustment of two [7]helicene units allows the precise alignment of electric and magnetic transition dipole moments, leading to the observed enhancement of their chiroptical responses. This study offers an effective strategy for magnifying the CPL performance in chiral NGs, promoting their expanded application as CPL emitters. [ABSTRACT FROM AUTHOR]

This contribution reports extensive studies on structure–property correlations of two isoelectronic betaine metamers (positional isomers). These zwitterions differ from each other with respect to bonding modes of pyridinium acceptors (Reichardt's mode: through N‐atom versus Brooker's mode: through C‐atom) with the p‐phenylene bridged phenolate donors. Various quantum chemical methodologies are used in this investigation, with time‐dependent (TD) and coupled perturbed (CPHF) theories for computations of many molecular response properties. Analysis of first hyperpolarizabilities (β) indicates that Reichardt's metamer (ωB97xD: β = 349.5 × 10−30 esu) is more efficient chromophore (~5‐fold enhanced) than Brooker's metamer (ωB97xD: β = 69.4 × 10−30 esu). The gyratory abilities of the bridge junctions resulted in a cohort of metastable conformations, in the rotational potential energy surfaces (PES) of the two metamers. Moreover, rotational PES establishes that intermediary torsions are suitable for optimal chromophore design strategies (Reichardt's metamer: β = 956.5 × 10−30 esu, and Brooker's metamer: β = 1104.7 × 10−30 esu), Thus suitable conformational manipulations, can be used to obtain more efficient zwitterionic molecular chromophores. Compared unbridged prototype molecules, p‐phenylene bridged zwitterions showed ~6–9 times enhanced values of β. In addition, important aspects of suitable chromophore design strategies are suggested. [ABSTRACT FROM AUTHOR]

Filgrastim was pegylated by acylation with a linear 20-kDa pegylating agent (PEG agent) to search for conjugates characterized by biological activity comparable to or exceeding that of commercial drugs. The pegylation kinetics were studied at different pH values taking into account the contribution of the hydrolysis kinetics of the PEG agent. The optimal time for pegylation to a required protein conversion and the method of adding the PEG agent to the reaction mixture (once or fractionally) at a given pH value and ratio between the PEG agent and protein were calculated using a proposed equation based on previously obtained pegylation and hydrolysis rate constants. Various mixtures of pegylated positional isomers were obtained. Their contents in the mixtures depended on the pH value because of the different pKa values of the amino-acid residues involved in the reaction. The estimated specific biological activity of the obtained monopegylated forms of Filgrastim appeared comparable with that of the product Neulastim. [ABSTRACT FROM AUTHOR]

Organic electrodes have gained great interest for batteries. Conducting polymers have the merits of high conductivity, and hence are attempted as electrode materials in batteries as soon as their discoveries. However, conducting polymers showe poor electrochemical performance and are baring vague charge storage mechanisms. Here, a strategy is reported to reveal the charge storage mechanisms of conducting polymers by constructing isomers and using polypyridines as a proof‐of‐concept. Polypyridines are rarely studied and its redox activity is still not clear. The results indicate that every pyridine ring can accept one electron and the dimer unit with adjacent C═N groups can gain one more electron through chelation effects with Li ions. The electron transferred number and the chelation effects can be quantified by the matrix‐assisted laser desorption/ionization time‐of‐flight (MALDI‐TOF) mass spectroscopy and verified by density functional theory (DFT) calculations. As a result, one of the polypyridine isomers delivers the highest capacity of 504 mAh g−1 after deducting the contribution of conductive additives. This work provides a universal way to reveal the charge storage mechanism and highlights the significance of adjacent active centers to form chelation with Li ions and hence enhance the performance of organic batteries. [ABSTRACT FROM AUTHOR]

Each year, new psychoactive substances appear on the global drug market leading to constant changes. Most of these compounds with stimulating effect possess a chiral center, thus leading to two enantiomers with presumably different pharmacological properties. Among them, synthetic cathinones, often misleadingly traded as "bath salts," play an important role. There is little knowledge about the distinct effect of the enantiomers. The aim of this study was to test a commercially available Lux® i‐Amylose‐3 column by HPLC‐UV for enantiorecognition of cathinone derivatives. Overall, 80 compounds were tested in normal phase mode, where 75 substances were separated under initial conditions. After method optimization, at least partial separation was achieved for the remaining compounds. The same set of substances was measured in polar‐organic mode, where 63 analytes were resolved into their enantiomers under initial conditions with very short retention times. Both modes showed complementary results for the individual compounds. Furthermore, the tested methods proved to be suitable for differentiation of positional isomers, which can be useful for drug checking programs. All measurements were carried out under isocratic conditions, and intraday and interday repeatability tests were performed. [ABSTRACT FROM AUTHOR]

Summary: Biosynthesis of flavonoid aglycones and glycosides is well established. However, key genes involved in their catabolism are poorly understood, even though the products of hydrolysis and oxidation play important roles in plant resistance to biotic stress.Here, we report on catabolism of dihydrochalcones (DHCs), the most abundant flavonoids in domesticated apple and wild Malus. Two key genes, BGLU13.1 and PPO05, were identified by activity‐directed protein purification. BGLU13.1‐A hydrolyzed phlorizin, (the most abundant DHC in domesticated apple) to produce phloretin which was then oxidized by PPO05. The process differed in some wild Malus, where trilobatin (a positional isomer of phlorizin) was mainly oxidized by PPO05.The effects of DHC catabolism on apple resistance to biotic stresses was investigated using transgenic plants. Either directly or indirectly, phlorizin hydrolysis affected resistance to the phytophagous pest two‐spotted spider mite, while oxidation of trilobatin was involved in resistance to the biotrophic fungus Podosphaera leucotricha. DHC catabolism did not affect apple resistance to necrotrophic pathogens Valsa mali and Erwinia amylovara.These results suggest that different DHC catabolism pathways play different roles in apple resistance to biotic stresses. The role of DHC catabolism on apple resistance appeared closely related to the mode of invasion/damage used by pathogen/pest. [ABSTRACT FROM AUTHOR]

The unique organizational framework for polycyclic aromatic hydrocarbons developed by us has led to the discovery of number patterns for their number of isomers. Constant-isomer series are generated by repetitive circumscribing of a given set of isomers. Benzenoid, fluoranthenoid, indacenoid, and primitive coronoid constant isomer series possess twin isomer numbers with members having corresponding topologies. The concepts of strictly pericondensed, strain-free, Clar's aromatic sextet, and symmetry are interconnected in the topological correspondence between strictly pericondensed and total resonant sextet (TRS) benzenoid hydrocarbons. In a plot of TRS isomer numbers on the Formula Periodic Table for Total Resonant Sextet Benzenoids [Table PAH6(TRS)] which is a subset of Table PAH6 for ordinary benzenoids, structural correlations in isomer numbers, symmetry distributions, and empty rings between various strain-free TRS benzenoids are presented. These chemical graph theoretical results belong to the branch of mathematics called number theory. [ABSTRACT FROM AUTHOR]

Objective: The conventional method for the characterization of volatile compounds has been mostly limited to the use of gas chromatography. This work offers an alternative method to address the limitations that might be encountered with the use of the gas chromatography method. Furthermore, this work addresses the scarcity of the analysis of these materials in the far infrared/terahertz region as previous studies have been focused mainly on the mid-infrared region. Methods: The far infrared/terahertz spectra of carvacrol and thymol were analyzed using the Fourier transform infrared (FTIR) and gas chromatography-mass spectroscopy (GC-MS). Density function theory (DFT) calculations were employed for the interpretation of the FTIR experimental spectra. Results: Thymol and carvacrol spectra were characterized by distinct absorption bands in the 200-600 cm−1 (6-18 THz). There were appearances of bands at similar energies for these isomers. These bands appeared at 320.7 cm−1 (9.6 THz), 439.2 cm−1 (13.2 THz), 525.2 cm−1 (15.8 THz), and 586.8 cm−1 (17.6 THz) for thymol and at 313.6 cm−1 (9.4 THz), 419.8 cm−1 (12.6 THz), 521.2 cm−1 (15.7 THz), and 566.9 cm−1 (17.0 THz) for carvacrol. Despite these similarities, there were also significant differences in the spectra of these materials. The theoretical peak frequencies were in agreement with the experimental absorption band frequencies. Two seemingly common absorption bands were observed in the spectra of thymol and carvacrol. However, peak assignments revealed that these bands have different vibrational modes. The GC-MS results show that the retention time of thymol and carvacrol are very close at 18.5 and 18.8 respectively. Conclusion: This work underscores the ability of far infrared/terahertz waves in identifying materials with similar structural features. Furthermore, it supplements the limited studies of these isomers in the far infrared/terahertz region. The GC-MS results emphasize the need for a complementary method that can improve the characterization of these materials. [ABSTRACT FROM AUTHOR]

Ion mobility mass spectrometry (ESI-tims-ToF–MS, syringe pump infusion) has been applied to glucose and oligosaccharide ethers derived from hydroxyethyl-methyl celluloses (HEMC) and hydroxyethyl celluloses (HEC) after permethylation and partial depolymerization: by hydrolysis without or with subsequent reductive amination with m-amino benzoic acid (mABA) or by reductive cleavage. As model compounds without tandem substitution methoxyethylated methylcellulose was used. Regioisomeric glucose ethers were separated according to their ion mobility, and positions of substitution could be assigned. Glucose ethers including isomers with tandem substitution showed additional signals with a smaller collision cross-section (CCS) than core-substituted isomers. Positional isomers of cellobiose ethers were only partly resolved due to too high complexity but showed a characteristic fingerprint that might allow classifying samples. Relative intensities of signals of glucose ether isomers could only be quantified in case of ABA derivatives with its fixed charge, while sodium adducts of methoxyethyl ethers showed an influence of the MeOEt position on ion yield. Results were in very good agreement with reference analysis. [M + Na]+ adducts of α- and β-anomers of glucose derivatives were separated in IM, complicating position assignment. This could be overcome by reductive cleavage of the permethylated HE(M)C yielding 1,5-anhydroglucitol-terminated oligosaccharides, showing the best resolved fingerprints of the cellobiose ethers of a particular cellulose ether. With this first application of ion mobility MS to the analysis of complex cellulose ethers, the promising potential of this additional separation dimension in mass spectrometry is demonstrated and discussed. [ABSTRACT FROM AUTHOR]

The current work demonstrates the reversible control of substantial molecular motion in 'nano-sized' molecules, where two structural isomers can 'open' and 'close' their cavities in response to light or heat. The isomers differ widely in their photophysical properties, including colour, polarity, two-photon absorption and π-conjugation, and can easily be separated through column chromatography and thus have wide applicability. [ABSTRACT FROM AUTHOR]

Anthraimidazoledione-based optical sensors have been designed by varying the position of the nitro functional group. All three positional isomers showed highly colored, photostable optical signals owing to intramolecular charge transfer interactions. Despite having the same anion-binding site (imidazole unit), the selectivity and sensitivity of the compounds depend on the positioning of the nitro group. The selectivity was fairly good for the meta isomer, followed by the ortho and para isomers, respectively. In contrast, the sensitivity towards anions followed a completely opposite trend, with the para isomer being the most sensitive one towards anions. Interestingly, the color changing response along the turn-on fluorescence signal was observed only with CN-ions in a semi-aqueous environment. Though the introduction of water as a co-solvent could improve the selectivity, the sensitivity was found to be slightly less than that observed in pure organic medium. Mechanistic studies indicated hydrogen bonding interactions between the imidazole -NH proton and cyanide, which further facilitated the extent of intramolecular charge transfer. [ABSTRACT FROM AUTHOR]

A semi-flexible imidazole-based urea ligand, 1-(3-(1H-imidazol-1-yl)propyl)-3-phenylurea, and three zincdicarboxylate coordination polymers possessing the ligand were synthesized and characterized. The stoichiometry and coordination number of the zinc(II) ions in the coordination polymers were found to be dependent on the positional isomers of the benzene dicarboxylate. The 1,3-benzenedicarboxylate-based coordination polymer has a one-dimensional structure, whereas, the one possessing 1,4-benzenedicarboxylate has a two-dimensional architecture. The solvent used in the synthesis of the zinc-1,3-benzenedicarboxylate coordination polymer with the ligand played a decisive role on the solvation and conformation of the ligand. The anhydrous form was obtained from a reaction in methanol in which one of the urea moieties has a puckered geometry and the assembly has layers from one-dimensional bunches of coordination chains. However, the same reaction in ethanol provided a solvate having water and ethanol as the solvents of crystallization and it has the two ligands with a stretched geometry forming a cleft-like geometry to include the ethanol molecules. The two forms were not inter-convertible. The coordination polymer with 1,4-benzenedicarboxylate has a 2-dimensional structure with 2 × 2 grids having self-included urea that held DMF molecules by hydrogen bonds. [ABSTRACT FROM AUTHOR]

Food intoxications evoked by emetic Bacillus cereus strains constitute a serious threat to public health, leading to emesis and severe organ failure. The emetic peptide toxin cereulide, assembled by the non-ribosomal peptide synthetase CesNRPS, cannot be eradicated from contaminated food by usual hygienic measures due to its molecular size and structural stability. Next to cereulide, diverse chemical variants have been described recently that are produced concurrently with cereulide by CesNRPS. However, the contribution of these isocereulides to the actual toxicity of emetic B. cereus, which produces a cocktail of these toxins in a certain ratio, is still elusive. Since cereulide isoforms have already been detected in food remnants from foodborne outbreaks, we aimed to gain insights into the composition of isocereulides and their impact on the overall toxicity of emetic B. cereus. The amounts and ratios of cereulide and isocereulides were determined in B. cereus grown under standard laboratory conditions and in a contaminated sample of fried rice balls responsible for one of the most severe food outbreaks caused by emetic B. cereus in recent years. The ratios of variants were determined as robust, produced either under laboratory or natural, food-poisoning conditions. Examination of their actual toxicity in human epithelial HEp2-cells revealed that isocereulides A-N, although accounting for only 10% of the total cereulide toxins, were responsible for about 40% of the total cytotoxicity. An this despite the fact that some of the isocereulides were less cytotoxic than cereulide when tested individually for cytotoxicity. To estimate the additive, synergistic or antagonistic effects of the single variants, each cereulide variant was mixed with cereulide in a 1:9 and 1:1 binary blend, respectively, and tested on human cells. The results showed additive and synergistic impacts of single variants, highlighting the importance of including not only cereulide but also the isocereulides in routine food and clinical diagnostics to achieve a realistic toxicity evaluation of emetic B. cereus in contaminated food as well as in patient samples linked to foodborne outbreaks. Since the individual isoforms confer different cell toxicity both alone and in association with cereulide, further investigations are needed to fully understand their cocktail effect. [ABSTRACT FROM AUTHOR]

The present work describes the synthesis of two cholesterol appended cyanostyryl thiophene positional isomers CS-1 and CS-2 and their stimuli responsive solid state emission and liquid crystalline properties. Both compounds showed enhanced emission in the solid state due to their aggregation-induced emission (AIE). Interestingly, CS-1 and CS-2 showed emission switching under the influence of thermal and/or mechanical stimuli. The difference in emission properties of pristine CS-1 and its melt processed sample CS-1M is attributed to the formation of two different crystalline phases. The powder X-ray diffractogram simulated from the single crystal X-ray diffraction data of CS-1 and CS-1M showed similar features indicating that the molecules in the melt cooled phase adopt a packing similar to the one observed in the single crystal. In addition to heat-induced changes in fluorescence properties, compound CS-2 showed mechanofluorochromism and methanol vapour-induced reversible emission switching. The observed emission switching in CS-2 under thermal and shear stress was due to crystalline to amorphous transition. The emission recovery from the ground sample of CS-2 under methanol vapours was attributed to the reversible transition from amorphous to a crystalline phase similar to pristine CS-2. A detailed analysis of various photophysical parameters of the compounds under different stimuli is reported. The liquid crystalline properties of the compounds were studied using polarizing optical microscopy (POM), differential scanning calorimetry (DSC), and X-ray diffraction (XRD) measurements. Both CS-1 and CS-2 showed the formation of an enantiotropic cholesteric (N*) liquid crystalline phase. Interestingly, the N* phase in CS-1 and CS-2 was stabilized down to room temperature in a glassy state. [ABSTRACT FROM AUTHOR]

The identification of the synthetic cannabinoids receptor agonists (SCRAs) has always posed a great challenge to drug testing laboratories with slight structural modifications aimed at evading drug legislation. In addition, the most prevalent synthetic cannabinoids have valine and tert‐leucine amino acid moieties where re‐arrangement of the carbon chains can result in structural isomers that are very similar to the parent synthetic cannabinoids. This makes their analysis and identification challenging, and the problem is compounded with the difficulty in purchasing reference standards quickly and a lack of literature for comparison. Therefore, in this investigation, four series of synthetic cannabinoids (AB‐PINACA, AB‐CHMINACA, MMB‐FUBINACA and 5‐fluoro‐MDMB‐PINACA) and their alkyl chain structural isomers at the amino acid moieties were synthesized and characterized using various analytical techniques—gas chromatography–mass spectrometry (GC–MS), gas chromatography–infrared detection (GC–IRD) and nuclear magnetic resonance (NMR) spectroscopy to evaluate the ability of each analytical technique to differentiate the respective isomers for their identification. A total of 12 isomers were synthesized and analysed together with the four parent synthetic cannabinoids. NMR was able to differentiate between all the compounds, whereas GC–IRD was able to discern between most of the synthetic cannabinoids and their isomers. GC–MS had the least discriminating power and was not able to differentiate some of the compounds that has very similar mass spectra. The results from this work will be useful to other drug testing laboratories that are facing the identification of related synthetic cannabinoids. [ABSTRACT FROM AUTHOR]