Positional Isomers Research Articles

Revisiting Butafulvene formation by Thermal Dimerization of Fluorene-Based Dialkynes - Effects of Aromatic Substitutents.

Butafulvenes, together with pentafulvenes and [3]radialenes, form a series of constitutional benzene isomers in which aromaticity changes significantly and can be strongly substituent dependent. Butafulvene, as a member of this series, is frequently proposed to be antiaromatic. Based on butafulvenes Hopf, Zimmerman and coworkers first time described, derivatives thereof were synthesized and the effects of substituents on both the stability of the intermediate isobenzenes and on their optoelectronic and (anti)aromatic properties are discussed.

Accelerating Additive-Assisted Defect Passivation via the Structural Isomer Effect for Highly Efficient and Stable Perovskite Solar Cells.

Defects in hybrid perovskites have hindered the development of highly efficient and stable hybrid perovskite solar cells (PSCs). Therefore, researchers have used additives to passivate defects in hybrid perovskites; however, detailed studies on multifunctional group additives with structural isomers are limited. In this letter, we report the improved defect passivation ability of additives through the structural isomer effect and enhanced photovoltaic performance using this effect. l-Alanine methyl ester hydrochloride (l-AMECl) and its structural isomer, β-AMECl, were used to understand the influence of structural variations in functional groups. The structural isomer β-AMECl effectively reduced the trap density in the hybrid perovskite, thereby enhancing the photovoltaic parameters. Consequently, we achieved a power conversion efficiency of 24.25% with β-AMECl, which is the best result among PSCs using additives. Additionally, the PSCs with β-AMECl maintained an initial efficiency of 94% over 2500 h at 25 °C and 25% relative humidity, showing improved long-term stability.

Contamination in LIB Pouch Cells Promoting Self‐Discharge and Crosstalk

AbstractStorage studies of lithium‐ion battery electrolyte within bags made of commercial pouch foils, commonly used as encasing material of battery cells, revealed the presence of contamination leaching from the pouch foil material into the electrolyte. By analyzing the stored electrolyte via GC‐MS the appearing compound was identified as 2,4‐di‐tert‐butylphenol (2,4‐DTBP). To investigate the influence of DTBP on the battery cell performance, full cells employing commercial LiNi1/3Mn1/3Co1/3O2 based cathodes and graphite‐type anodes were assembled using 1 M LiPF6 in ethylene carbonate/ dimethyl carbonate mixture as the electrolyte with/out the intentional addition of either 2,4‐DTBP or its constitutional isomer 2,6‐DTBP. Furthermore, dimethyl terephthalate (DMT), a literature known redox shuttle triggering impurity leaching from PET‐based fixing tape used in LIBs, was added to compare the effect of DMT to DTBPs. It was revealed that either DTBP contaminations have a significant impact on the self‐discharge behavior of the studied cells, which exceed the effect of present DMT. Moreover, all contaminants heavily increase transition metal dissolution‐migration‐deposition (TM DMD) processes and irreversible capacity loss. When vinylene carbonate, an SEI forming additive, is added to the electrolyte mixtures self‐discharge, as well as TM DMD are suppressed to a different degree depending on the type of contaminant added.

Acyclic sesquiterpenes nerolidol and farnesol: mechanistic insights into their neuroprotective potential.

Sesquiterpenes are a class of organic compounds found in plants, fungi, and some insects. They are characterized by the presence of three isoprene units, resulting in a molecular formula that typically contains 15 carbon atoms (C₁₅H₂₄). Nerolidol and farnesol are both sesquiterpene alcohols present in the essential oils of numerous plants. They have drawn attention due to their potential neuroprotective properties. Nerolidol and farnesol are structural isomers, specifically geometric isomers, haring the same molecular formula (C₁₅H₂₄O) but differing in the spatial arrangement of their atoms. This variation in structure may contribute to their distinct biological activities. Scientific evidence suggests that nerolidol and farnesol exhibit antioxidant and anti-inflammatory characteristics which are crucial for neuroprotection. Nerolidol has been specifically noted for its ability to alleviate conditions such as Alzheimer's disease, Parkinson's disease, encephalomyelitis, depression, and anxiety by modulating inflammatory and oxidative stress pathways. Moreover, research indicates that both nerolidol and farnesol may modulate the Nrf-2/HO-1 antioxidant signaling pathway to mitigate oxidative stress-induced neurological damage. Activation of Nrf-2/HO-1 signaling cascade promotes cell survival and enhances the brain's ability to resist various insults. Nerolidol has also been reported to alleviate neuroinflammation by inhibiting the TLR-4/NF-κB and COX-2/NF-κB inflammatory signaling pathway. Besides, this nerolidol also modulates BDNF/TrkB/CREB signaling pathway to improve neuronal health. To date, limited research has delved into the anti-inflammatory properties of farnesol concerning neurodegenerative diseases. Further investigation is warranted to comprehensively elucidate the mechanisms underlying its action and potential therapeutic uses in neuroprotection. Initial observations indicate that farnesol exhibits promising prospects as a natural agent for safeguarding brain functions. Henceforth, drawing upon existing literature elucidating the neuroprotective attributes of nerolidol and farnesol, the current review endeavors to provide a detailed analysis of their mechanistic underpinnings in neuroprotection.

Novel Strategies for Synthesis and Assessment of Dextran Conjugated 9Z,11E Linoleic Acid on Cancer Cell Lines Viability via Wnt/Beta‐Catenin Signaling Pathway and Apoptosis

AbstractConjugated linoleic acid (CLA) is one of the positional and structural isomers of linoleic acid. Ninety percent of the CLA contained in natural foods is the cis‐9(9Z), trans‐11(11E) isomer. CLA also has anti‐carcinogenic, anti‐adipogenic, and anti‐inflammatory properties. Limited studies aim to elucidate the impact of 9Z,11E‐CLA on Wnt/beta‐catenin signaling.In this study, we have selected MDA‐MB‐231, T98G, and SAOS‐2 cell lines of various cancer origins and investigate the impact of dextran conjugated 9Z,11E CLA (Dex‐9Z,11E‐CLA) using cell proliferation assay and immunocytochemical methods. Cytotoxic effects of Dex conjugated 9Z,11E CLA are assessed with the MTT method. It analyzed Wnt/beta‐catenin signaling changes using target molecule beta‐catenin, Dickkopf‐1 (Dkk‐1) as a negative regulator, and active caspase3 (CC3) as an apoptotic marker.Dex‐9Z,11E‐CLA is shown to suppress cell viability in three different types of cancer cells, and the most effective concentration is 200 µm. 9Z,11E‐CLA and Dex‐9Z,11E‐CLA affect the Wnt/beta‐catenin signaling pathway negatively in all cell lines. Beta‐catenin expression is decreased, Dkk‐1 expression is increased, and CC3 positivity is increased significantly compared to the control group. In conclusion, the data suggest that Dex‐9Z,11E‐CLA suppresses cell viability and causes apoptosis in cells via the Wnt/beta‐catenin signaling pathway. Lastly, Dex‐9Z,11E‐CLA harbors novel anticancer potential and exhibits uncontrolled activation of Wnt/beta‐catenin signaling.

Positional Isomerism Toward Tunable Organic Afterglow and Reversible Photoactivation Behavior for Anti‐Counterfeiting and Encryption

AbstractAchieving amorphous polymers with ultralong room‐temperature phosphorescence (RTP), tunable organic afterglow, and reversible photoactivation behavior is highly desirable for practical applications but challenging. Herein, simple positional isomers with three carboxyl groups located in the ortho, meta, and para positions of the triphenylamine skeleton are designed and synthesized. By physically blending with the poly(vinyl alcohol) matrix, these isomers show ultralong RTP properties, among which the meta‐isomer has the longest RTP lifetime (620.1 ms). Theoretical calculations reveal that the more efficient intersystem crossing, the slower radiative decay rate of the lowest triplet excitons, and stronger intermolecular hydrogen‐bonding interactions should be responsible for the superior RTP property of meta‐isomer. Furthermore, the tunable organic afterglow is readily realized via a triplet‐to‐singlet energy transfer process. More impressively, the meta and para isomers exhibit reversible photoactivated ultralong RTP properties after embedding into the rigid poly(methyl methacrylate) matrix. Finally, amorphous and flexible polymer films prepared from these positional isomers show potential applications in advanced anti‐counterfeiting and multilevel encryption through subtly combining ultralong RTP lifetime, tunable organic afterglow, and reversible photoactivation behavior.

Elucidation of the influence of trinitro-diazinotriazine isomerism on the energetic properties and stability: Insights from DFT approach

The exploration of isomeric energetic molecules with high nitrogen content and the examination of their structure–property relationships remains compelling areas of interest within the field of energetic materials. Energetic isomers comprising the same molecular composition but distinct molecular structures potentially lead to notable variations in performance and properties. This study focused on designing and evaluating different forms of diazinotriazine using two molecular compositions: C5H3N5 and C5N8O6, aiming to generate various isomeric structures and to guide the rational design of new molecules. The electronic configurations, energetic properties, and sensitivity prediction of the optimized structures were investigated using the M06-2X/def2-TZVPP level of theory. The trinitro-diazinotriazine isomers exhibit high heat of formation (>486 kJ/mol), high detonation properties (D > 8.7 km/s, P > 34 GPa), high density (>1.81 g/cm3), and better thermal stability (BDE > 230 kJ/mol) making them promising explosive contenders. Among the designed diazinotriazine backbones, the pyridazine-1,2,3-triazine framework is favourable for the heat of formation and detonation properties. The heats of formation, detonation velocity, pressure, and heats of detonation of A4 and B4 outperform the other trinitro-diazinotriazine isomers.

Rapid evaluation of vegetable oil varieties and geographical origins by ambient corona discharge ionization mass spectrometry

The composition and ratio of unsaturated fatty acids in vegetable oils play a crucial role in determining their overall quality. In this study, we present a corona discharge ionization mass spectrometry (MS) method for the rapid differentiation of vegetable oil varieties and their geographical origins under environmental conditions. Abundant water dimer radical cations, (H2O)2+•, were generated by the ionization setup, which effectively activated carbon‑carbon double bonds (C=C) to form epoxidized products. These epoxidation products were analyzed using tandem MS, generating diagnostic fragment ions that precisely identified CC bond positions. Statistical analysis models were subsequently developed using the resulting MS fingerprint data, revealing significant differences between various vegetable oils and olive oils from different origins. Key advantages of this method include minimal sample preparation, rapid analysis, and easily interpretable spectra. This study provides a new MS-based strategy for food quality assessment and offers a promising tool for identifying CC positional isomers in complex systems.

Online, Bottom-up Characterization of Histone H4 4-17 Isomers.

The "Histone Code" is comprised of specific types and positions of post-translational modifications (PTMs) which produce biological signals for gene regulation and have potential as biomarkers for medical diagnostics. Previous work has shown that electron-based fragmentation improves the sequence coverage and confidence of labile PTM position assignment. Here, we evaluated two derivatization methods (e.g., irreversible - propionylation and reversible-citraconylation) for bottom-up analysis of histone H4 4-17 proteoforms using online liquid chromatography (LC), trapped ion mobility spectrometry (TIMS), and electron-based dissociation (ExD) in tandem with mass spectrometry. Two platforms were utilized: a custom-built LC-TIMS-q-ExD-ToF MS/MS based on a Bruker Impact and a commercial μLC-EAD-ToF MS/MS SCIEX instrument. Complementary LC-TIMS preseparation of H4 4-17 0-4ac positional isomer standards showed that they can be resolved in their endogenous form, while positional isomers cannot be fully resolved in their propionylated form; online LC-ExD-MS/MS provided high sequence coverage (>90%) for all H4 4-17 (0-4ac) proteoforms in both instrumental platforms. When applied to model cancer cells treated with a histone deacetylase inhibitor (HeLa + HDACi), both derivatization methods and platforms detected and confirmed H4 4-17 (0-4ac) proteolytic peptides based on their fragmentation pattern. Moreover, a larger number of HeLa + HDACi H4 4-17 proteoforms were observed combining LC-TIMS and LC-q-ExD-ToF MS/MS due to the positional isomer preseparation in the LC-TIMS domain of citraconylated H4 4-17 (0-4ac) peptides.

Orientational Compatibility Modulation of Ligands in Low-Symmetry Multi-Cavity Discrete Coordination Cages by Neighbouring Cage Participation.

Complexation of Pd(II) with a designer unsymmetrical bis-monodentate ligand (2:4 ratio) yielded a specific Pd2L4 type "single-cavity discrete coordination cage" (SCDCC), from a pool of 4 isomeric structures. The observed selctivity is attributed to inherent orientational preference of the ligand strands around the metal centers. Crafting a short coordinating arm at either ends of the bis-monodentate ligand (i.e the longer-arm) produced a pair of unsymmetrical isomeric tris-monodentate ligands; whereas crafting the same short-arm at both ends of the ligand gives an unsymmetrical tetrakis-monodentate ligand. Complexation of Pd(II) with either of the isomeric tris-monodenate ligands (3:4 ratio) resulted in corresponding low-symmetry "multi-cavity discrete coordination cage" MCDCC having two conjoined cavities, though the inherent relative orientational preference of the longer arms is not achievable in these cages. The enforced orientation is sustained by "Neighbouring Cage Participation" (NCP). However, one-pot combination of Pd(II), with a mixture of isomeric tris-monodenate ligands in 3:2:2 ratio produced an integratively self-sorted mixed-ligated MCDCC from a pool of 31 structures. Also, mixing Pd(II) with the tetrakis-monodentate ligand produced a MCDCC having three conjoined cavities. The inherent orientational preference of longer-arm of the ligand strands is retained in the mixed-ligated double-cavity and the homo-ligated triple cavity cages.

Orientational Compatibility Modulation of Ligands in Low‐Symmetry Multi‐Cavity Discrete Coordination Cages by Neighbouring Cage Participation

Complexation of Pd(II) with a designer unsymmetrical bis‐monodentate ligand (2:4 ratio) yielded a specific Pd2L4 type “single‐cavity discrete coordination cage” (SCDCC), from a pool of 4 isomeric structures. The observed selctivity is attributed to inherent orientational preference of the ligand strands around the metal centers. Crafting a short coordinating arm at either ends of the bis‐monodentate ligand (i.e the longer‐arm) produced a pair of unsymmetrical isomeric tris‐monodentate ligands; whereas crafting the same short‐arm at both ends of the ligand gives an unsymmetrical tetrakis‐monodentate ligand. Complexation of Pd(II) with either of the isomeric tris‐monodenate ligands (3:4 ratio) resulted in corresponding low‐symmetry “multi‐cavity discrete coordination cage” MCDCC having two conjoined cavities, though the inherent relative orientational preference of the longer arms is not achievable in these cages. The enforced orientation is sustained by “Neighbouring Cage Participation” (NCP). However, one‐pot combination of Pd(II), with a mixture of isomeric tris‐monodenate ligands in 3:2:2 ratio produced an integratively self‐sorted mixed‐ligated MCDCC from a pool of 31 structures. Also, mixing Pd(II) with the tetrakis‐monodentate ligand produced a MCDCC having three conjoined cavities. The inherent orientational preference of longer‐arm of the ligand strands is retained in the mixed‐ligated double‐cavity and the homo‐ligated triple cavity cages.

Forging 1,1'-Bicyclopropenyls by Synergistic Au/Ag Dual-Catalyzed Cyclopropenyl Cross-Coupling.

1,1'-Bicyclopropenyl is a constitutional isomer of benzene comprising two coupled cyclopropene units with the endocyclic double bonds in conjugation. Due to the intrinsic high strain energy, it remains a long-standing challenge to prepare 1,1'-bicyclopropenyl derivatives, particularly multisubstituted, nonsymmetrical ones, in an efficient and modular manner. Herein a straightforward Au/Ag bimetallic-catalyzed cyclopropenyl cross-coupling has been developed, providing a robust and versatile strategy for the rapid assembly of symmetrical and unsymmetrical 1,1'-bicyclopropenyl derivatives from cyclopropenyl benziodoxoles (CpBXs) and terminal cyclopropenes. Advantages of this strategy include tolerance to a wide range of synthetically useful functional groups, mild reaction conditions, and a simple catalytic system. The obtained 1,1'-bicyclopropenyl derivatives were shown to be valuable synthetic intermediates through selective downstream manipulations.

Trehalulose: Exploring its benefits, biosynthesis, and enhanced production techniques

The increasing concern over sugar-related health issues has sparked research interest in seeking alternatives to sucrose. Trehalulose, a beneficial structural isomer of sucrose, is a non-cariogenic sugar with a low glycemic and insulinemic index. Besides its potential as a sugar substitute, trehalulose exhibits high antioxidant properties, making it attractive for various industrial applications. Despite its numerous advantages and potential application in various sectors, the industrial adoption of trehalulose has yet to be established due to lack of studies on its characteristics and practical uses. This review aims to provide a comprehensive overview of the properties of trehalulose, emphasizing its health benefits. The industrial prospects of trehalulose as sweetener and reducing agent, particularly in food and beverages pharmaceutical, and cosmeceutical sectors, are explored. Additionally, the review delves into the sources of trehalulose and the diverse organisms capable of producing trehalulose. The biosynthesis of this sugar primarily involves an enzyme-mediated process. Thus, these enzymes' properties, mechanisms, and the heterologous expression of genes associated with trehalulose production are explored. The strategies discussed in this review can be improved and applied to establish trehalulose bio-factories for efficient synthesis of trehalulose in the future. With further research and development, trehalulose holds promise as a valuable component across various industries.

Sergeant-and-Soldier Effect in an Organic Room-Temperature Phosphorescent Host-Guest System.

Host-guest systems have emerged as an efficient strategy for promoting organic room temperature phosphorescence (RTP). Despite the advantages of doping guest molecules into a host matrix, the complexity of these systems and the lack of techniques to visualize host-guest interactions at the molecular scale pose significant challenges in understanding the underlying mechanisms. Here, a novel host-guest RTP system is developed by incorporating low concentrations (1-10 mol%) of TPP-4C-BI (guest) into crystalline TPP-4C-Cz (host). Utilizing structural isomerism, the guest molecules are regularly incorporated into the host crystal lattice, resulting in phosphorescence quantum yields almost ten times higher than the pure compounds. The system enabled resolution of the molecular packing of the single crystal through X-ray diffraction, providing unprecedented visualization of host-guest interactions. A "sergeant-and-soldier" effect, where the minority dopant molecules (sergeants) significantly influence the packing arrangement of the host molecules (soldiers), enhances RTP is identified. Further analyses revealed that due to the host molecule's inefficient phosphorescence pathway, its long-lived dark triplets are channeled to the guest via triplet-triplet energy transfer (TTET), allowing the excited energy to radiatively decay more efficiently. These insights advance the understanding of RTP mechanisms and offer practical implications for designing high-efficiency phosphorescent materials.

Isomeric diammonium passivation for perovskite-organic tandem solar cells.

In recent years, perovskite has been widely adopted in series-connected monolithic tandem solar cells (TSCs) to overcome the Shockley-Queisser limit of single-junction solar cells. Perovskite/organic TSCs, comprising a wide-bandgap (WBG) perovskite solar cell (pero-SC) as the front cell and a narrow-bandgap organic solar cell (OSC) as the rear cell, have recently drawn attention owing to the good stability and potential high power conversion efficiency (PCE)1,2,3,4. However, WBG pero-SCs usually exhibit higher voltage losses than regular pero-SCs, which limits the performance of TSCs5,6. One of the major obstacles comes from interfacial recombination at the perovskite/C60 interface, and it is important to develop effective surface passivation strategies to pursue higher PCE of perovskite/organic TSCs7. Here we exploit a new surface passivator cyclohexane 1,4-diammonium diiodide (CyDAI2), which naturally contains two isomeric structures with ammonium groups on the same or opposite sides of the hexane ring (denoted as cis-CyDAI2 and trans-CyDAI2, respectively), and the two isomers demonstrate completely different surface interaction behaviors. The cis-CyDAI2 passivation treatment reduces the Quasi-Fermi level splitting (QFLS)-open circuit voltage (Voc) mismatch of the WBG pero-SCs with a bandgap of 1.88 eV and enhanced its Voc to 1.36 V. Combining the cis-CyDAI2 treated perovskite and the organic active layer with a narrow-bandgap of 1.24 eV, the constructed monolithic perovskite/organic TSC demonstrates a PCE of 26.4% (certified as 25.7%).

Heterometallic Molecular and Ionic Isomers.

Numerous descriptions of structural isomerism in metal complexes do not list any molecular vs ionic isomers. At the same time, one of the most striking examples of structural isomerism in organic chemistry is molecular urea, which has the same atomic composition as the chemically distinct ionic ammonium cyanate. This iconic organic couple now meets its inorganic heterometallic counterpart. We introduce a new class of structural isomers, molecular vs ionic, that can be consummated in complex and coordinatively unsaturated polynuclear/heterometallic compounds. We report inorganic molecular and ionic isomers of the composition [NaCrFe (acac)3(hfac)3] (acac = acetylacetonate; hfac = hexafluoroacetylacetonate). Heterometallic molecular [CrIII(acac)3-Na-FeII(hfac)3] (1m) and ionic {[CrIII(acac)3-Na-CrIII(acac)3]+[FeII(hfac)3-Na-FeII(hfac)3]-} (1i) isomers have been isolated in pure form and characterized. While both ions are heterobimetallic trinuclear entities, the neutral counterpart is a heterotrimetallic trinuclear molecule. The two isomers exhibit distinctly different characteristics in terms of solubility, volatility, mass spectrometry ionization, and thermal behavior. Unambiguous assignment of the positions and oxidation/spin states of the Periodic Table neighbors, Fe and Cr, in both isomers have been made by a combination of characterization techniques that include synchrotron X-ray resonant diffraction, synchrotron X-ray fluorescence spectroscopy, Mössbauer spectroscopy, and DART mass spectrometry. The transformation between the two isomers that does take place in solutions of noncoordinating solvents has also been tested.

Isotope Encoded chemical Imaging Identifies Amyloid Plaque Age Dependent Structural Maturation, Synaptic Loss, and Increased Toxicity.

It is of critical importance to our understanding of Alzheimer's disease (AD) pathology to determine how key pathological factors are interconnected and implicated in nerve cell death, clinical symptoms, and disease progression. The formation of extracellular beta-amyloid (Aβ) plaques is the major pathological hallmark of AD and Aβ has been suggested to be a critical inducer of AD, driving disease pathogenesis. Exactly how Aβ plaque formation begins and how ongoing plaque deposition proceeds and initiates subsequent neurotoxic mechanisms is not well understood. The primary aim of our research is to elucidate the biochemical processes underlying early Aβ plaque formation in brain tissue. We recently introduced a chemical imaging paradigm based on mass spectrometry imaging (MSI) and metabolic isotope labelling to follow stable isotope labelling kinetics (iSILK) in vivo to track the in vivo build-up and deposition of Aβ. Herein, knock-in Aβ mouse models ( App NL-F ) that develop Aβ pathology gradually are metabolically labeled with stable isotopes. This chemical imaging approach timestamps amyloid plaques during the period of initial deposition allowing the fate of aggregating Aβ species from before and during the earliest events of plaque pathology through plaque maturation to be tracked. To identify the molecular and cellular response to plaque maturation, we integrated iSILK with single plaque transcriptomics performed on adjacent tissue sections. This enabled changes in gene expression to be tracked as a function of plaque age (as encoded in the Aβ peptide isotopologue pattern) distinct from changes due to the chronological age or pathological severity. This approach identified that plaque age correlates negatively with gene expression patterns associated with synaptic function as early as in 10-month-old animals but persists into 18 months. Finally, we integrated hyperspectral confocal microscopy into our multiomic approach to image amyloid structural isomers, revealing a positive correlation between plaque age and amyloid structural maturity. This analysis identified three categories of plaques, each with a distinct impact on the surrounding microenvironment. Here, we identified that older, more compact plaques were associated with the most significant synapse loss and toxicity. These data show how isotope-encoded MS imaging can be used to delineate Aβ toxicity dynamics in vivo. Moreover, we show for the first time a functional integration of dynamic MSI, structural plaque imaging and whole genome-wide spatial transcriptomics at the single plaque level. This multiomic approach offers an unprecedented combination of temporal and spatial resolution enabling a description of the earliest events of precipitating amyloid pathology and how Aβ modulates synaptotoxic mechanisms.

Phonon Transport in Supramolecular Polymers Regulated by Hydrogen Bonds.

Supramolecular polymers hold promise in thermal management applications due to their multistability, high responsiveness, and cost-effectiveness. In this work, we successfully regulate phonon transport at the molecular level in supramolecular polymers by adjusting the strength of intermolecular hydrogen bonding. We synthesized three supramolecular polymer fibers with thermal conductivity differences of up to 289% based on melamine (M) and three simple positional isomers of hydroxybenzoic acid. Differential Scanning Calorimetry (DSC) measurement revealed discrepancies in thermal stability of the polymers, where structures with higher stability exhibited enhanced thermal conductivity. Fourier Transform Infrared Spectroscopy (FTIR) measurement and Density Functional Theory (DFT) calculations indicate that these differences arise from variations in hydrogen-bonding strengths at different bonding sites. Higher hydrogen-bonding strength leads to more stable thermal pathways, reduces phonon scattering, and increases thermal conductivity. Our findings provide valuable insights into controlling the thermal conductivity of polymer fibers, paving the way for applications in phonon-based thermal devices.

Synthesis of Nanocarbons from Isomeric Structures of Toluidine for the Removal of Organochlorine Pesticides

Synthesis of Nanocarbons from Isomeric Structures of Toluidine for the Removal of Organochlorine Pesticides

Quantification of Total Ketone Bodies in Biological Matrices Using Stable Isotope-Labeled Internal Standards and RP-UHPLC-MS/MS.

Acetoacetate (AcAc) and D-beta-hydroxybutyrate (D-βOHB), the two major ketone bodies found in circulation, are linked to multiple physiological and pathophysiological states. Therefore, analytical methodologies surrounding the quantification of total ketone body (TKB) concentrations in biological matrices are paramount. Traditional methods to quantify TKBs relied on indirect spectrophotometric assays with narrow dynamic ranges, which have been significantly improved upon by modern mass spectrometry (MS)-based approaches. However, the lack of stable isotope-labeled internal standards (ISs) for AcAc and the need to distinguish D-βOHB from its closely related structural and enantiomeric isomers pose significant obstacles. Here, we provide a protocol to synthesize and quantify a [13C] stable isotope-labeled IS for AcAc, which, in conjunction with a commercially available [2H] stable isotope-labeled IS for βOHB, allows TKBs to be measured across multiple biological matrices. This rapid (7min) analysis employs reverse phase ultra-high performance liquid chromatography (RP-UHPLC) coupled to tandem MS (MS/MS) to distinguish βOHB from three structural isomers using parallel reaction monitoring (PRM), providing excellent specificity and selectivity. Finally, a method is provided that distinguishes D-βOHB from L-βOHB using a simple one-step derivatization to produce the corresponding diastereomers, which can be chromatographically resolved using the same rapid RP-UHPLC separation with new PRM transitions. In summary, this method provides a rigorous analytical pipeline for the analysis of TKBs in biological matrices via leveraging two authentic stable isotope-labeled ISs and RP-UHPLC-MS/MS.