1H Nuclear Magnetic Resonance Spectroscopy Research Articles

From the end to the beginning: Obtaining and evaluation of flexible PVC produced via chemical recycling of post-consumer PET

Di(2-ethylhexyl) terephthalate (DEHTP) is a promising substitute for dioctyl phthalate (DOP, banned in certain countries) as a polyvinyl chloride (PVC) plasticizer. This research endeavors to present findings about the synthesis of DEHTP through the depolymerization of polyethylene terephthalate (PET) with 2-ethyl-1-hexanol, the production and assessment of PVC formulated with this plasticizer, and a comparative analysis with PVC compounded using commercial plasticizers (DOP and DEHTP). Approximately 200 post-consumer PET bottles underwent chemical recycling under various conditions, leading to complete depolymerization (99%) following a six-hour reaction at 300°C. The plasticizers were characterized by infrared spectroscopy, 1H nuclear magnetic resonance spectroscopy, and gas chromatography coupled to mass spectrometry. The flexible PVCs were tensile and hardness tested and submitted to dynamic mechanical and thermogravimetric analyses. The resulting plasticizer exhibited properties analogous to commercial DEHTP, producing flexible PVC with even better properties. For instance, the activation energy of the dehydrochlorination reaction of the flexible PVC produced with DHETP from depolymerization was 3.3% to 16.2% higher than those produced with commercial plasticizers.

In-cell NMR reveals metabolic adaptations in central carbon pathways driving antibiotic tolerance in Salmonella Typhimurium.

Antibiotic tolerance presents a significant challenge in eradicating bacterial infections, as tolerant strains can survive antibiotic treatment, contributing to the recurrence of infections and the development of resistance. However, unlike antibiotic resistance, tolerance is not detectable by standard susceptibility assays such as minimal inhibitory concentration (MIC) tests. Consequently, antibiotic tolerance often goes unnoticed in clinical settings. Bacterial metabolism is closely linked to antibiotic efficacy, and thus presents as a potential target for novel diagnostic methods. Recent advancements in nuclear magnetic resonance (NMR) spectroscopy, including dynamic nuclear polarization (DNP-NMR), enable a non-invasive real-time approach to analyzing bacterial metabolism. In this study, we applied both 1H and in-cell 13C NMR spectroscopy to investigate metabolic adaptations in a tolerance-evolved Salmonella Typhimurium strain, C10, developed through ten cycles of ampicillin treatment. Our results demonstrated that despite similar MICs and growth rates, the C10 strain exhibited a 25-fold increase in tolerance compared to the wild-type, while exhibiting lower metabolic activity. Under ampicillin stress, however, the C10 strain maintained higher metabolic activity and demonstrated greater resilience in glucose consumption and metabolite production relative to the wild-type. Using DNP-NMR, rapid metabolic shifts in the C10 strain were identified within 10 minutes of exposure to high concentrations of ampicillin, characterized by accumulation of key metabolites such as pyruvate and acetate. Overall, our findings underscore the potential of real-time NMR-based analyses to provide deeper insights into antibiotic tolerance and distinguish between susceptible and tolerant bacterial strains.

One-Pot Synthesis of Benzopinacolone Derivatives from Acetophenones

Pinacolone and benzopinacolone derivatives are an important class of organic compounds due to their uses in polymer synthesis and more recently as biologically active compounds. The conventional synthesis of such molecules is generally done in two steps, the pinacol coupling followed by the pinacol/pinacolone rearrangement. Aiming to prepare benzopinacolone derivatives in a greener fashion, we present here a one-step synthesis from acetophenones in the presence of zinc and tert-butyl chloride. To develop the methodology, conditions to prepare 3,3-diphenyl-2-butanone from acetophenone were optimized. To assess the scope, different substituted acetophenones were tested, resulting in the corresponding benzopinacolones at moderate yields (20-50%) with high purity. Structural elucidations were performed by 1H and 13C NMR (nuclear magnetic resonance spectroscopy) and GC-MS (gas chromatography-mass spectrometry).

Multi-biofluid metabolomics analysis of allergic respiratory rhinitis and asthma in early childhood.

Childhood rhinitis and asthma are allergic respiratory diseases triggered by common allergens, but they affect different parts of the respiratory system, leading to distinct symptoms. However, a comprehensive multi-biofluid metabolomics-based approach to uncover valuable insights into childhood allergies and allergen sensitization remains unaddressed. Seventy-six children, comprising 26 with rhinitis, 26 with asthma, and 24 healthy controls, were enrolled. Fecal, blood, and urine metabolomic analyses using 1H nuclear magnetic resonance (NMR) spectroscopy were conducted. An integrative analysis of their associations with allergen-specific IgE levels in the context of allergic rhinitis and asthma were also assessed. The analysis of 228 various biofluid samples revealed strong positive correlations between stool and blood metabolites, while blood metabolites exhibited negative correlations with most urine metabolites. Five and 19 metabolites were significantly different in children with rhinitis and asthma, respectively (P<0.05). Among them, blood isovaleric acid correlated positively with stool IgE levels in rhinitis, while stool butyric acid and acetic acid in asthma exhibited strong negative correlations with total serum and mite allergen-specific IgE levels (P<0.01). Blood metabolic profiles appeared to have the highest area under the curve (AUC) of 0.732 for rhinitis, whereas stool metabolic profiles had the highest AUC of 0.799 for asthma. Multiple biofluid metabolomics provides comprehensive insights into childhood allergies, with blood profiles associated with allergic rhinitis and fecal profiles linked to asthma. Their short-chain fatty acid metabolites related to IgE levels emphasize the significant role of the gut microbiota in childhood rhinitis and asthma.

Characterization of 1,8-diazabicyclo(5.4.0)undec-7-ene-hydroxyl-based ionic liquid for CO2 capture.

Six 1,8-diazabicyclo(5.4.0)undec-7-ene-based ionic liquids (ILs) linked with ethyl or propyl hydroxyl cations, coupled with thiocyanate, dicyanamide and bistriflimide anions, were synthesized through a two-step reaction: quaternization and ion exchange. The characterization of the ILs was carried out using 1H and 13C nuclear magnetic resonance spectroscopy (NMR) and Fourier-transform infrared spectroscopy (FTIR). The NMR results confirmed the structures of all the ILs, and these were supported by the FTIR results. In addition, the physicochemical properties, namely thermal stability, density and refractive index, were determined. The effects of the chain length in the cation and the identity of the anion on CO2 absorption were studied in a pressure drop equipment at different pressures. It was found that CO2 sorption increased with increasing pressure and the number of nitrile groups present. The highest CO2 sorption is reported to be 0.96 mol CO2 mol-1 IL at 20 bar.

Evaluation of hydrogen storage in sandstone reservoirs using 1H nuclear magnetic resonance spectroscopy.

Evaluation of the hydrogen storage capacity of porous rocks is crucial for underground hydrogen storage. Using 1H nuclear magnetic resonance (NMR) spectroscopy, we successfully characterized the hydrogen responses and identified storage mechanisms in Berea sandstone under varying water saturation. The results indicate that the injected hydrogen behaves as a free gas phase and is capable of occupying the empty pore volume regardless of the saturation state. No hysteresis was observed during injection and production cycles.

Maximizing yields of furfural and 5‐hydroxymethylfurfural in side streams from steam explosion of lignocellulosic residues

AbstractThe demand for renewable energy and chemicals from biomass resources has led to the development of methods for biorefining lignocellulosic materials into pellets and value‐added chemicals. This has, in turn, driven a search for alternative raw materials to use as feedstock in such biorefineries. This study proposes the inclusion of low‐grade lignocellulosic residues from agriculture and forestry, such as straw and woody biomass with a high bark content, in the feedstock mix for steam explosion (STEX) based biorefineries. It focuses on exploring how the use of low‐grade residues affects the yield of value‐added chemicals that arise as side streams during the steam explosion of lignocellulosic biomass and if acetic acid impregnation of the biomass prior to STEX pretreatment will further improve yields of valuable side stream chemicals. The raw materials were impregnated with water/acetic acid before being subjected to STEX pretreatment, using high temperatures (190 °C–223 °C), and a reaction time of 8 min before pressure release. Value‐added chemicals were identified in two separate aqueous side streams. In the condensed process effluents, the most abundant compounds were acetic acid (1.2 g*kg−1 dry input biomass) and furfural (1.4 g*kg−1 dry input biomass), and the highest yields were found in the samples from mixed spruce and branches and tops (BRAT) at high temperatures. Filtrate samples produced from washing the steam‐exploded biomass contained acetic acid (53.6 g*kg−1 dry input biomass), furfural (4.1–7.9 g*kg−1 dry input biomass) and 5‐hydroxymethylfurfural (5‐HMF) (9.0 g*kg−1 dry input biomass) as the most abundant compounds and highest yields of target compounds were found in samples of spruce alone and of spruce mixed with BRAT. All compounds in the side streams were identified and quantified using quantitative 1H nuclear magnetic resonance spectroscopy (qNMR). This study demonstrates that high yields of valuable chemicals are present in the aqueous side streams of pellet production using alternative feedstocks such as forestry and agricultural residues.

Structural and Serological Characterization of Yet Another New O Antigen, O86, in Proteus mirabilis Clinical Strains.

Bacteria from the genus Proteus are facultative human pathogens, primarily attacking the urinary tract and wounds. A total of 85 O serogroups have been identified so far among these bacilli. P. mirabilis Bprz 86 was isolated from the fistula of a patient in Łódź, Poland. Enzyme-Linked Immunosorbent Assay (ELISA) and Western blotting studies involving the P. mirabilis Bprz 86 lipopolysaccharide (LPS) and the strain-specific rabbit antiserum indicated that the strain, which does not belong to any of the O1-O85 serogroups, shares a common epitope with Proteus O17 antigens and is identical to another clinical P. mirabilis strain, Sm 120, isolated from the urine of a patient in the area. The O-specific polysaccharide (O antigen) was obtained from P. mirabilis Bprz 86 LPS through mild acid degradation, and the six-constituent structure of its repeating unit was determined using chemical analyses and 1D and 2D 1H and 13C Nuclear Magnetic Resonance (NMR) spectroscopy. It includes (R)-3-hydroxybutanoyl, which, along with fucosamine and glucose residues, forms a fragment also present in the O17 antigens. Based on the obtained serological and chemical data, the two studied P. mirabilis isolates were proposed as candidates for a new successive O serogroup in the genus Proteus, O86.

Crystallization of n-Alkanes under Anisotropic Nanoconfinement in Lipid Bilayers.

Understanding crystallization behavior is integral to the design of pharmaceutical compounds for which the pharmacological properties depend on the crystal forms achieved. Very often, these crystals are based on hydrophobic molecules. One method for delivering crystal-forming hydrophobic drugs is by means of lipid nanoparticle carriers. However, so far, a characterization of the potential crystallization of fully hydrophobic molecules in a lipid environment has never been reported. In this work we investigate the crystallization behavior of two model hydrophobic chains, n-eicosane (C20) and n-triacontane (C30), in phospholipid bilayers. We combine static 2H nuclear magnetic resonance (NMR) spectroscopy and differential scanning calorimetry (DSC) and show that C30 molecules can indeed crystallize inside DMPC and POPC bilayers. The phase transition temperatures of C30 are slightly reduced inside DMPC, and rotator phase formation becomes a two-step process: Preorganized n-alkane chains assemble in rotator-phase crystallites just as fast as bulk C30, but further addition of molecules is notably slower. Under the same isothermal conditions, different crystal forms can be obtained by crystallization in the membrane and in bulk. In excess water conditions, homogeneous nucleation of C30 is observed. The initial anisotropic molecular arrangement of C30 molecules in the membrane is readily recovered upon reheating, showing reversibility. The shorter C20 molecules on the other hand become trapped in the DMPC membrane gel-phase upon cooling and do not crystallize. This work marks the first observation of the crystallization of hydrophobic chains inside a lipid bilayer environment. As such, it defines a fundamental starting point for studying the crystallization characteristics of various hydrophobic molecules in lipid membranes.

Application of 1H NMR Metabolic Profiling of Serum in Canine Multicentric Lymphoma.

Canine lymphoma represents a biologically and metabolically heterogeneous group of neoplasms that arise from malignant transformation of lymphoid cells. An accurate diagnosis is crucial because of its impact on survival. Current diagnostic methods include clinical laboratory tests and imaging, most of which are invasive and lack sensitivity and specificity. Interestingly, recent work in cancer patients focuses on the search for biomarkers for diagnosis, investigation of treatment response mechanisms, treatment efficacy and prognosis and the discovery of tumour metabolic pathways using metabolomic analysis. In this study, we compare the metabolite profiles in serum from 37 dogs with multicentric lymphoma (22 B-cell lymphomas/LB, 9 CD45+ T-cell lymphomas/LTCD45+, 6 CD45- T-cell lymphomas/LTCD45-) and 25 healthy dogs using 1H nuclear magnetic resonance spectroscopy (NMR). 1H NMR-based metabolite profiling analysis recognised lipids and 22 metabolites, with 16 of them altered, and was shown to be an effective approach for differentiating samples from dogs with lymphoma and healthy controls based on principal component analysis of the NMR data. We also investigated variations in the serum metabolome between immunophenotypes and the control group through pairwise comparisons of the healthy against the LB, LTCD45+ and LTCD45- groups, respectively which showed similar metabolomic profiles. In addition, there were significant differences in the levels of five individual metabolites based on the univariate statistical analysis. Our results showed alterations in energy, protein and lipid metabolism, suggesting glucose, lactate, N-acetyl glycoproteins (NAGs), scyllo-inositol and choline as possible new candidate biomarkers in canine multicentric lymphoma.

Design, synthesis, X-ray crystal structure, and antifungal evaluation of new acetohydrazide derivatives containing a 4-thioquinazoline moiety.

To find efficient agricultural fungicides, 29 new 4-thioquinazoline-containing acetohydrazide derivatives were prepared and tested for their fungicidal properties. All of the target compounds were characterized by 1H and 13C nuclear magnetic resonance and high-resolution mass spectrometry techniques, and the molecular structure of compound A2 was verified by single-crystal X-ray diffraction measurement. The experimental results revealed that many compounds from this series had impressive inhibition efficacies in vitro against the tested fungi. For example, compound A25 was identified as the best fungicidal agent against Rhizoctonia solani with an EC50 (half-maximal effective concentration) value of 0.66 μg mL-1, superior to those of the commercial fungicides chlorothalonil, carbendazim and boscalid. Additionally, this compound displayed favorable protection and curative activities in vivo against rice sheath blight caused by R. solani. Antifungal mechanistic studies on compound A25 indicated that this compound exerted its strong anti-R. solani effects probably through an effective inhibition of fungal succinate dehydrogenase activity [half-maximal inhibitory concentration (IC50) = 4.88 μm] and the impairment of cell membrane integrity, based on the results from enzymatic bioassays, molecular docking studies, and scanning and transmission electron microscopy observations. Acetohydrazide derivatives containing the 4-thioquinazoline moiety had the potential to be employed as lead compounds for developing more efficient agricultural fungicides in the near future. © 2024 Society of Chemical Industry.

Structure and Biosynthetic Gene Cluster of Sulfated Capsular Polysaccharide from the Marine Bacterium Vibrio sp. KMM 8419.

Vibrio sp. KMM 8419 (=CB1-14) is a Gram-negative bacterium isolated from a food-net mucus sample of marine polychaete Chaetopterus cautus collected in the Sea of Japan. Here, we report the structure and biosynthetic gene cluster of the capsular polysaccharide (CPS) from strain KMM 8419. The CPS was isolated and studied by one- and two-dimensional 1H and 13C nuclear magnetic resonance (NMR) spectroscopy. The molecular weight of the CPS was about 254 kDa. The CPS consisted of disaccharide repeating units of D-glucose and sulfated and acetylated L-rhamnose established as →2)-α-L-Rhap3S4Ac-(1→6)-α-D-Glcp-(1→. To identify the genes responsible for CPS biosynthesis, whole-genome sequencing of KMM 8419 was carried out. Based on the genome annotations together with the Interproscan, UniProt and AntiSMASH results, a CPS-related gene cluster of 80 genes was found on chromosome 1. This cluster contained sets of genes encoding for the nucleotide sugar biosynthesis (UDP-Glc and dTDP-Rha), assembly (glycosyltransferases (GT)), transport (ABC transporter) and sulfation (PAPS biosynthesis and sulfotransferases) of the sulfated CPS. A hypothetical model for the assembly and transportation of the sulfated CPS was also proposed. In addition, this locus included genes for O-antigen biosynthesis. Further studies of biological activity, the structure-activity relationship in the new sulfated polysaccharide and its biosynthesis are necessary for the development of potent anticancer agents or drug delivery systems.

Synthesis of Chalcones, Screening In silico and In vitro and Evaluation of Helicobacter pylori Adhesion by Molecular Docking.

We synthetized 10 hydroxylated and methoxylated chalcones and evaluated them targeting MMP-9 inhibition, looking for the rate of adhesion of H. pylori in gastric cells, and then, reduction of the inflammatory response as alternative therapeutic agents for controlling the infection. Helicobacter pylori is a Gram-negative bacterium that chronically infects the human stomach, a risk factor for the development of inflammatory gastrointestinal diseases, including cancer, and is classified as a group I carcinogen. It is estimated that it infects around 45% of the global population and that the persistence of the infection is related to the adhesion of the bacteria in the gastric epithelium. The progression of gastric lesions to cancer is connected to the activation of the NF-κB and MAPK pathways, especially in cagA+ strains, which are related to increased expression of MMP-9. The activation of these metalloproteinases (MMPs) contributes to the adhesion of the bacterium in gastric cells and the evolving stages of cancer, such as enabling metastasis. Due to the increasing resistance to the current therapy protocols, the search for alternative targets and candidate molecules is necessary. In this way, controlling adhesion seems to be a suitable option since it is a crucial step in the installation of the bacterium in the gastric environment. Synthetize ten hydroxylated and methoxylated chalcones. Assess their anti-H. pylori potential, minimum inhibitory concentration (MIC), and minimum bactericidal concentration (MBC). Evaluate their cytotoxicity in AGS cells and selectivity with L-929 cells. Analyze the results and correlate them with in silico predictions to evaluate potential anti-adhesive properties for the chalcones against H. pylori. The chalcones were synthetized by Claisen-Schmidt condensation using Ba(OH)2 or LiOH as catalysts. Predictive in silico assays in PASS Online, tanimoto similarity, ADME properties and molecular docking in MMP-9 (PDB code: 6ESM) were performed. The in vitro assays carried out were the cell viability in gastric adenocarcinoma cells (AGS) and fibroblasts (L-929) by the MMT method and anti-H. pylori, by the broth microdilution method, through the minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC). Ten chalcones were synthesized through Claisen-Schimdt condensation with yields of 10 to 52% and characterized by 1H and 13C nuclear magnetic resonance (NMR) and mass spectrometry (MS). in silico data revealed the possibility of anti-H. pylori, anti-inflammatory, and MMP-9 inhibition for the chalcones. Chalcone 9 showed the best growth inhibition values for MIC and MBC, at 1 μg/mL and 2 μg/mL, respectively. Chalcones 14 and 15 likewise demonstrated excellent inhibitory results, being 2 μg/mL for both MIC and MBC. Additionally, 15 had the best MMP-9 inhibition score. Despite not corroborating the in silico findings, chalcones 10, 13, and 18 showed good cytotoxicity and the best selectivity indices. All compounds exhibited strong activity against H. pylori, specially 15. The predicted MMP-9 inhibition by molecular docking added to the reasonable SI and CI50 values for 15 and the satisfactory reduction in the rate of survival of the bacteria, reveals that it may be acting synergically to reduce the inflammatory response and the possibilities for developing a tumor by inhibiting both bacteria and malignant cells.

Rhamnolipid-Enriched PA3 Fraction from Pseudomonas aeruginosa SWUC02 Primes Chili Plant Defense Against Anthracnose.

Chili anthracnose, caused by Colletotrichum truncatum, causes significant yield loss in chili production. In this study, we investigated the elicitor properties of a rhamnolipid (RL)-enriched PA3 fraction derived from Pseudomonas aeruginosa SWUC02 in inducing systemic resistance in yellow chili seedlings and antifungal activity against C. truncatum CFPL01 (Col). Fractionation of the ethyl acetate extract yielded 12 fractions, with PA3 demonstrating the most effective disease suppression, reducing the disease severity index to 4 ± 7.35% at 7 days post-inoculation compared with Col inoculation alone (83 ± 23.57%). PA3 also exhibited direct antifungal activity, inhibiting Col mycelial growth by 41 ± 0.96% at 200 µg/mL. Subfractionation revealed PA3 as a mixture of mono- and di-RLs, confirmed by 1H nuclear magnetic resonance and electrospray ionization mass spectrometry data. Additionally, PA3 enhanced seed germination and promoted plant growth without causing phytotoxicity. Transcriptomics revealed that PA3 pre-treatment prior to Col infection primed the defense response, upregulating defense-related genes involved in the phenylpropanoid, flavonoid, and jasmonic acid biosynthesis pathways, as well as those associated with cell wall reinforcement. Our findings highlight the potential of RL-enriched PA3 as both an antifungal agent and a plant defense elicitor, with transcriptome data providing new insights into defense priming and resistance pathways in chili, offering an eco-friendly solution for sustainable anthracnose management.

Silver Nanocluster Assemblies As Electrocatalyst for Electrochemical Carbon Dioxide Reduction Reaction

Recent rise in the consumption of fossil fuels have raised the levels of carbon dioxide (CO2) in the atmosphere causing global warming1. Electrochemical reduction of carbon dioxide (CO2RR) to value-added chemicals at low temperature and ambient pressure using green renewable energy sources has emerged as a propitious technology to realize carbon neutrality and mitigate global warming2.Supramolecular assembly of noble metal nanoclusters (NMNC) is one of the alluring areas of modern material science. Nanocluster assemblies formed by integrating NMNC using a crosslinking ligand, are reported to be applied in various applications such as nanodevices and as luminescent sensor materials3. Silver nanocluster assemblies (Ag-CAM) are composed of regularly crosslinked silver nanoclusters4 and were evaluated as cathodic electrocatalysts for CO2RR. In this study, we evaluated the reaction selectivity and structural stability of an Ag-CAM ([Ag12(StBu)6(CF3COO)6(2EB)3]n; Ag12-2EB) crosslinked by linker with triple bonds5 when used as a cathode electrocatalyst (Figure 1).Synthesized Ag-CAMs were supported onto the surface of commercially available gas diffusion electrode (GDE) by spray coating method (Figure 2). The catalyst-loaded electrodes were attached to a self-fabricated GDE flow cell, and electrocatalytic properties were evaluated. Ag/AgCl was used as the reference electrode, and Pt mesh was taken as the counter electrode for the electrochemical reactions. Single crystal-XRD and powder-XRD were measured to determine the exact crystal structure, while SEM-EDS was used to characterize the electrode surface to determine the structural stability. We used gas chromatography (GC) and 1H-nuclear magnetic resonance (NMR) spectroscopy to calculate the reaction selectivity and quantify the product concentration. The CO2RR products in outlet gas streams from the gas chamber and electrolytes from the catholyte room were analyzed using GC and 1H-NMR spectroscopy.For silver nanocluster assembly cross-linked with 4,4`-bipyridine ([Ag12(StBu)8(CF3COO)4(BPY)4]n; Ag12-BPY) most of the constituent elements of the aggregate (S, N, F, etc.) were eluted out after performing the electrochemical (EC) reactions up to a voltage of 3.2V. The catalyst structure underwent significant transformations and was confirmed by SEM-EDS analysis with samples before and after EC analysis. However, in EC experiments using Ag12-2EB as the cathode electrocatalyst, the structural decompositions were suppressed and the electrocatalyst could withstand long-term use. Figure 3 shows the Faraday selectivity (%) of CO2RR products against the applied potential for Ag12-2EB/GDE in 0.1M KHCO3. Carbon monoxide (CO) was the main product obtained from electrochemical CO2RR of Ag12-2EB and hydrogen evolution reaction (HER) could be suppressed when the applied potential was shifted to the negative side. Additionally, regarding the reaction selectivity, it was found that the selectivity was approximately the same regardless of the structure of the crosslinking agent. Knowledge obtained from this study will help to bridge the gap for utilizing Ag-CAMs as novel cathode catalyst materials for electrochemical CO2RR experiments.References(1) Liu, Y. Y., Huang, J. R., Zhu, H. L., Liao, P. Q., & Chen, X. M. (2023). Simultaneous Capture of CO2 Boosting Its Electroreduction in the Micropores of a Metal–organic Framework. Angewandte Chemie, 135(52), e202311265.(2) Kawawaki, T., Okada, T., Hirayama, D., & Negishi, Y. (2024). Atomically precise metal nanoclusters as catalysts for electrocatalytic CO 2 reduction. Green Chemistry, 26(1), 122-163.(3) Nag, A., & Pradeep, T. (2022). Assembling atomically precise noble metal nanoclusters using supramolecular interactions. ACS Nanoscience Au, 2(3), 160-178.(4) Huang, R. W., Wei, Y. S., Dong, X. Y., Wu, X. H., Du, C. X., Zang, S. Q., & Mak, T. C. (2017). Hypersensitive dual-function luminescence switching of a silver-chalcogenolate cluster-based metal–organic framework. Nature chemistry, 9(7), 689-697.(5) Das, S., Sekine, T., Mabuchi, H., Hossain, S., Das, S., Aoki, S., Takahashi, S & Negishi, Y. (2023). Silver cluster-assembled materials for label-free DNA detection. Chemical Communications, 59(27), 4000-4003. Figure 1

Highly Potent Fluorenone Azine-based ESIPT Active Fluorophores for Cellular Viscosity Detection and Bioimaging Applications.

Herein, synthesizes of fluorenone azine-based Schiff fluorescence probes: (E)-2-(((9H-fluoren-9-ylidene)hydrazineylidene)methyl)-5-(diethylamino)phenol (3a), (E)-9-(((9H-fluoren-9-ylidene)hydrazineylidene) methyl)-2,3,6,7-tetrahydro-1H,5H-pyrido[3,2,1-ij]quinolin-8-ol (3b), and (E)-1-(((9H-fluoren-9-ylidene)hydrazineylidene)methyl) naphthalen-2-ol (3c). The probes were structurally characterized using Fourier-transform infrared spectroscopy (FTIR), 1H and 13C nuclear magnetic resonance (NMR) spectroscopy and high-resolution mass spectrometry(HRMS) analysis. The probes exhibit hydrogen bonding between phenolic -OH and imine nitrogen, enabling excited state intramolecular proton transfer (ESIPT) and free rotation in the azine (> C = N-N = C <) functional, facilitating twisted intramolecular charge transfer (TICT), and a positive solvatochromism in solvent-dependent emission studies. Further, density functional theory (DFT) based calculations accounted for the observed photophysical TICT and ESIPT processes, revealing a non-covalent interaction between phenolic -OH and imine nitrogen. Furthermore, the fluorescence intensity (log I) showed good linearity (R2 = 0.999) with the viscosity (log η) with Förster-Hoffmann coefficient (X) values of 2.238, 1.405 and 3.121 for 3a, 3b and 3c, respectively. The study established the probes toxicity and fluorescence imaging in the Caenorhabditis elegans model. Probe 3a, the first azine-based probe for micro viscosity detection, demonstrated exceptional efficacy in detecting intercellular viscosity and facilitating bioimaging applications.

Non-Targeted Metabolomics of White Rhinoceros Colostrum and Its Changes During Early Lactation by 1H Nuclear Magnetic Resonance Spectroscopy.

Dynamic changes in components from colostrum to mature milk occur in any mammal. However, the time it takes to reach the mature milk stage differs between taxa and species, as do the final concentrations of all the components. The white rhinoceros belongs to the family Perissodactyla, of which the milk and milk metabolome of the domesticated Equidae have been studied to some detail. Metabolomic information on the colostrum and milk of the Rhinocerotidae is lacking. Colostrum and milk were obtained from seven white rhinoceroses. Of note is that it was their first parturition and all followed the same diet, two factors known to affect colostrum composition and its changes during early lactation in domesticated mammals. Milk serum was prepared by the ultrafiltration of the milk samples. Untargeted 1N NMR spectra were processed with Topspin 3.2, calibration was carried out according to the alanine signal and the identification of signals was carried out with Chenomx and assignments in the literature. Statistical analysis of the data was carried out using MetaboAnalyst 6.0. The changes in the metabolites were followed during the first 7 days of lactation as well as on day 20. The amounts of amino acids and their derivatives, organic acids and lipid metabolites decreased over lactation, while carbohydrates and their derivatives increased. The colostrum phase ended on day 2, while the transition to mature milk seemed to be complete by day 7. From day 3 to 7, galactose metabolism and tyrosine metabolism were uprated. Of interest is the presence of the oligosaccharide 3'-sialyllactose on days 3 and 4 of lactation. Mainly the content of carbohydrates increased over lactation, specifically lactose. The 3'-sialyllactose content peaked on days 3 and 4 of lactation. The colostrum phase ended on day 2. The mature milk stage was reached by day 7. The galactose metabolism and tyrosine metabolism were uprated after day 3 of lactation.

Analysis of Poly(ethylene glycol) from the conservation of 17th century shipwreck Vasa and associated wooden objects

Vasa, a Swedish warship that sunk in 1628 and was excavated in 1961, and associated wooden objects underwent a preservation process using various low molecular weights (600, 1500, and 4000 Mn) of poly(ethylene glycol) (PEG) to gradually displace the water within the wooden structure, preventing the collapse of the waterlogged wood upon drying. However, after six decades of aging after application, to what extent are these polymers degraded? To investigate this, a Soxhlet apparatus was used to extract PEG from wooden samples of Vasa, and lyophilization was used to dry aqueous PEG solutions, these samples being the runoff accumulated during the application of different molecular weights of PEG to Vasa and other associated wooden objects. These samples underwent analysis via matrix-assisted laser desorption/ionization – time-of-flight mass spectrometry (MALDI-TOF MS), gel permeation chromatography (GPC), and 1H and 13C nuclear magnetic resonance (NMR) spectroscopy.The primary discovery was that the PEG within Vasa exhibited minimal degradation, with the dominant identified species, as determined by MALDI-TOF MS and NMR spectroscopy, being HO-PEG-OH. However, small quantities of HO-PEG-OH had undergone degradation, resulting in the formation of PEG chains with distinct end groups, notably a range of carbonyl-based compounds, including aldehydes, carboxylic acids, and esters, as observed through MALDI-TOF MS, 1H, and 13C NMR spectroscopy. These mass spectrometry product peaks could be confirmed by the expected mass difference through various end-group functionalizations, such as oxidations, esterifications, or ether formations. In addition to the carbonyl-based degradation products, some PEG chains had completely cleaved into two separate lower molecular weight HO-PEG-OH polymers, each approximately half of their original molecular weight, as revealed by GPC analysis.

Synthesis, Biological Evaluation, and Molecular Docking Studies of Indole-Based Heterocyclic Scaffolds as Potential Antibacterial Agents.

Indole-based heterocyclic scaffolds have become increasingly important in medicinal chemistry due to their notable pharmacological and biological properties. Their role in the discovery and development of innovative drugs for treating various diseases highlights their value. This study aimed to synthesize C3-indole derivatives linked to various heterocyclic scaffolds, including thiophenes, thiazolidine-4-ones, and 1,3,4-thiadiazoles, via the reaction of ethylthioacetanilide 2 with different α-haloketones.The structures of the target compounds were established using 1H and 13C nuclear magnetic resonance spectroscopy, mass spectrometry, infrared spectroscopy, and elemental analysis. The synthesized compounds were tested for antimicrobial activity against different microbes: S. aureus ATCC 6538 (Gram-positive bacteria), E. coli ATCC 25933 (Gram-negative bacteria), C. albicans ATCC 10231 (yeast), and fungi (A. niger NRRL-A326). Thiophene 6a, thiazolidine-4-one 8, and compound 10d exhibited the highest antimicrobial activities. The molecular docking study showed that compounds 2, 4, 6a, and 6c had good binding energy and favorable binding modes of interactions with the DNA gyrase B enzymes (PDB: 3 U2D) and (PDB: 1S14). The results showed that the NH group of the indole in compounds 2 and 4, together with the nitrile group (CN), played an important role in inhibiting DNA gyrase B of S. aureus, PDB: 3 U2D. Furthermore, the NH of the indole ring, together with the ethylamino group of compound 2, was crucial in inhibiting DNA gyrase B of E. coli, PDB: 1S14. These findings may encourage researchers to develop more effective C3-indole derivatives in their search for antimicrobial drugs.

Use of a hydrosilylation reaction for the preparation of structure-controlled boroxine-based polyborosiloxanes

The structure of organosilicon vinyl-containing boroxine was confirmed by 1H nuclear magnetic resonance (NMR) spectroscopy, infrared (IR) spectroscopy and matrix-assisted laser desorption/ionization (MALDI) mass spectrometry. Its thermal properties were studied using thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC) methods. The ability of boroxine to undergo hydrosilylation using the Karstedt's catalyst was investigated on various organosilicon substrates. Boroxine was shown to be involved in these reactions as a cross-linking agent. The formation of dynamic boroxine cross-links allowed the analysis of the reaction products by NMR spectroscopy, including the use of polyfunctional hydride-containing reagents. In all cases the addition proceeds selectively to the β-position and with complete conversion. The structure of the resulting polyborosiloxane containing 1.4 mol% of modified units was also confirmed by 1H NMR spectroscopy, and its thermal and rheological properties were studied.