Nuclear Magnetic Resonance Spectrometer Research Articles

Calcium ions do not influence the Aβ(25–35) triggered morphological changes of lipid membranes

We have studied the effect of calcium ions (Ca2+) at various concentrations on the structure of lipid vesicles in the presence of amyloid-beta peptide Aβ(25–35). In particular, we have investigated the influence of calcium ions on the formation of recently documented bicelle-like structures (BLSs) emerged as a result of Aβ(25–35) triggered membrane disintegration. First, we have shown by using small-angle X-ray and neutron scattering that peptide molecules rigidify the lipid bilayer of gel phase DPPC unilamellar vesicles (ULVs), while addition of the calcium ions to the system hinders this effect of Aβ(25–35). Secondly, the Aβ(25–35) demonstrates a critical peptide concentration at which the BLSs reorganize from ULVs due to heating and cooling the samples through the lipid main phase transition temperature (Tm). However, addition of calcium ions does not affect noticeably the Aβ-induced formation of BLSs and their structural parameters, though the changes in peptide's secondary structure, e.g. the increased α-helix fraction, has been registered by circular dichroism spectroscopy. Finally, according to 31P nuclear magnetic resonance (NMR) measurements, calcium ions do not affect the lipid-peptide arrangement in BLSs and their ability to align in the magnetic field of NMR spectrometer. The influences of various concentrations of calcium ions on the lipid-peptide interactions may prove biologically important because their local concentrations vary widely in in-vivo conditions. In the present work, calcium ions were investigated as a possible tool aimed at regulating the lipid-peptide interactions that demonstrated the disruptive effect of Aβ(25–35) on lipid membranes.

Study on the Effect of Sorghum Flour Particle Size on the Storage Quality of Leavened Pancakes.

Pancakes prepared with sorghum flour possess a high nutritional value, yet their quality is unstable and prone to degradation during storage. This instability can be attributed to the particle size of coarse cereal powder, which significantly influences the quality of flour products during storage. In this study, changes in the quality of these pancakes, prepared with varying particle sizes of sorghum flour, were meticulously analyzed during cold storage using advanced instruments such as a texture analyzer, nuclear magnetic resonance spectrometer, differential scanning calorimeter, X-ray diffractometer, and Fourier transform infrared spectrometer. Findings revealed that the hardness of leavened pancakes significantly increased over time. After a refrigeration period of 7 days, the hardness of wheat flour leavened pancakes increased by 56.60%. However, with a decrease in the particle size of sorghum flour, the increase in hardness diminished, thereby delaying the aging process of the pancakes. As the storage duration was extended, moisture migration within the pancakes occurred, and the sorghum flour pancakes with a smaller particle size exhibited a reduced moisture change rate, indicating an enhanced water holding capacity. In comparison to their wheat flour counterparts, sorghum flour leavened pancakes exhibited a substantial reduction in retrogradation enthalpy and crystallinity. The inclusion of sorghum flour effectively inhibited amylopectin recrystallization, thus slowing down the aging process of the pancakes. This inhibitory effect was more evident with decreasing sorghum flour particle sizes. Fourier transform infrared data indicated no significant alterations in absorption peaks across various wavelengths during cold storage. Although starch short-range orderliness increased with storage time, the use of sorghum flour with smaller particles reduced the degree of short-range orderliness in starch molecules throughout the cold storage period. Sorghum flour with a smaller particle size can inhibit water migration and amylopectin recrystallization, which subsequently delays pancake aging and enhances its quality stability during storage.

Effect of Dicarboxylic Acid Chain Length on the Tribological Properties of Aqueous Polyether Esters

ABSTRACTThis article presents the preparation of environmentally friendly water‐soluble lubricant additives. Adipic acid (AA), sebacic acid (SA) and dodecanedioic acid (DA) were individually subjected to esterification reactions with polyethylene glycol 1500 (PEG1500) to prepare a class of water‐soluble polyether esters (AAPEE1500, SAPEE1500 and DAPEE1500) (referred to as XAPEE1500s) that exhibit excellent water solubility and do not contain environmentally harmful elements. First, the molecular structure characterisation and functional group analysis of these additives will be conducted using an infrared spectrometer and a nuclear magnetic resonance spectrometer. Subsequently, the frictional properties of the additives in the base liquid (deionised water) will be investigated using an SRV‐V tribometer, Falex pin‐on‐disc tribometer and screw torque tester. The surface morphology of wear scars will be characterised and analysed using scanning electron microscopy (SEM) and a non‐contact 3D profilometer. Finally, the lubrication mechanism of the DAPEE1500 additive will be analysed using X‐ray photoelectron spectroscopy (XPS). The results indicate that the optimal lubrication performance is achieved when the added mass fraction of DAPEE1500 is at 3%. Compared with 0.5 wt% DAPEE1500, the average friction coefficient of 3 wt% DAPEE1500 decreased from 0.285 to 0.122, and the wear volume decreased from 25.52 × 10−5 μm3 to 10.96 × 10−5 μm3. The lubrication mechanism of polyether ester is the result of the combined action of its polar ester functional groups and long carboxylic acid chains in the structure. These polar functional groups can form a relatively firm adsorption film on the friction surface, while the long carboxylic acid chains act as a brush‐like isolating layer, thus demonstrating superior anti‐wear and anti‐friction performance.

Analysis of <i>cis</i>-isomer-enriched dihydroquercetin sample by 1D and 2D NMR spectroscopy

Introduction. The structure of dihydroquercetin (DHQ) is characterized by two chiral centers at positions 2 and 3 of the benzopyran cycle, resulting in possible diastereomers: trans- and cis-isomers. Therefore, the development of methods for qualitative and quantitative control of DHQ diastereomers in analyzed samples is essential for patient safety management. Nuclear magnetic resonance (NMR) spectroscopy is one of the physicochemical methods that can be used for this purpose.Aim. The study objective was to accumulate the analytical and structural characteristics of cis-DHQ by NMR spectroscopy of the spheroidal form of this flavonoid (DHQs).Materials and Methods. 1D 1H, 1H,1H-COSY, 1H,1H-NOESY, and 1H,13C-HSQC NMR spectra were acquired at 298 K on an 800 MHz NMR spectrometer equipped with a TXI triple resonance probe. The number of scans was 32. The mixing time in the NOESY experiment was 400 ms. The 1H and 13C were analyzed using CcpNmr software. The dihedral angles were calculated by applying the Karplus equation.Results and discussion. In trans-DHQ, the chemical shift values for H2 and H3 are 4.93 ppm and 4.52 ppm, respectively, and in cis-DHQ they are 5.31 ppm and 4.20 ppm, respectively. The spin-spin coupling constants between H2 and H3 of trans- and cis-DHQ are 12.00 Hz and 2.40 Hz, respectively. Thus, the dihedral angles for the trans- and cis-isomers are 154° and 64°, respectively. We found that DHQs contains 12.5 % of the cis-isomer.Conclusion. Our experiments confirmed that NMR spectroscopy can discriminate between trans- and cis-DHQ based on the chemical shift values for the cross-peaks of H2 and H3. The second major finding was that this method can be considered as a more selective quantitative analysis than HPLC with UV detection without reference. One of the most important results of this study for drug development is the updated information on the structural parameters of DHQ diastereomers in the liquid phase.

Benchtop NMR Coupled with Chemometrics: A Workflow for Unveiling Hidden Drug Ingredients in Honey-Based Supplements.

Recently, benchtop nuclear magnetic resonance (NMR) spectrometers utilizing permanent magnets have emerged as versatile tools with applications across various fields, including food and pharmaceuticals. Their efficacy is further enhanced when coupled with chemometric methods. This study presents an innovative approach to leveraging a compact benchtop NMR spectrometer coupled with chemometrics for screening honey-based food supplements adulterated with active pharmaceutical ingredients. Initially, fifty samples seized by French customs were analyzed using a 60 MHz benchtop spectrometer. The investigation unveiled the presence of tadalafil in 37 samples, sildenafil in 5 samples, and a combination of flibanserin with tadalafil in 1 sample. After conducting comprehensive qualitative and quantitative characterization of the samples, we propose a chemometric workflow to provide an efficient screening of honey samples using the NMR dataset. This pipeline, utilizing partial least squares discriminant analysis (PLS-DA) models, enables the classification of samples as either adulterated or non-adulterated, as well as the identification of the presence of tadalafil or sildenafil. Additionally, PLS regression models are employed to predict the quantitative content of these adulterants. Through blind analysis, this workflow allows for the detection and quantification of adulterants in these honey supplements.

Efficient extraction of Au(Ⅲ) by a piperidine-based ionic liquid and exploration of the mechanism driving force

Efficient gold extraction is of paramount importance, but how to improve the extraction efficiency and enhance the driving force of the extraction process is still to be explored. This study introduces an innovative approach using versatility ionic liquids (ILs) to overcome existing challenges. A tailored IL was synthesized and employed computational tools, including the Interaction Region Indicator, to predict its effectiveness in gold extraction. Quantum chemical calculations elucidated the interplay between hydrogen bonding capability and ion exchange properties of the ILs. Subsequent optimization of experimental conditions (0.1 mol/L HCl, 10.6 mg IL) yielded a remarkable 98.4 % extraction efficiency at 45 °C. Molecular dynamics simulations affirmed the IL's exceptional selectivity for Au(III) extraction, with analysis revealing that the extraction mechanism primarily hinged on electrostatic attraction and van der Waals interactions between ionic liquid cations and [AuCl4]−. This mechanism aligns with the established anion exchange mechanism, validated through Ultraviolet–visible spectrometer (UV–Vis), Nuclear Magnetic Resonance spectrometer (NMR), and Liquid Chromatograph Mass Spectrometer (LC-MS) analyzes. To complete the extraction cycle, 1.0 mol/L K2C2O4 was employed as a stripping agent for efficient Au(III) recovery from the loaded IL phase, facilitating repeated extraction cycles. This study underscores the sustainability of the IL-based Au(III) extraction process, maintaining consistently high extraction rates even after five cycles. In summary, this method does not use solvent, enabling environmentally friendly Au(III) extraction.

Chloride ion permeability of concrete containing recycled composite powder from building demolition waste

Buildings in the marine environment are vulnerable to chloride ion erosion, which threatens the service life of concrete structures. To facilitate the application of concrete containing construction demolition waste in the marine environment, recycled composite powder concrete (RCPC) was prepared using recycled composite powder as cement substitute. The chloride ion permeability of RCPC was evaluated by chloride ion diffusion test and rapid chloride ion migration test (RCM). The chloride ion permeability of RCPC continued to enhance with growing content of recycled composite powder. During the immersion age, the surface chloride ion content of the samples containing recycled composite powder increased by an average of 18.3–65.3% over the control group, with a corresponding average increase in chloride ion diffusion coefficients ranging from 17.0% to 31.5%. The chloride ion migration coefficients in the RCM test raised by 9.5–24.7%. A series of microscopic tests such as nuclear magnetic resonance (NMR), X-ray diffraction (XRD) and scanning electron microscope-energy dispersive spectrometer (SEM-EDS) suggested that the total porosity increased by 11.9–29.5% with the addition of recycled composite powder. The chloride ion diffusion coefficients exhibited a linear increase with growing total porosity and porosity of capillary pores, whereas an exponential increase with the porosity of transitional pores. The poor reactivity of the recycled composite powder resulted in a looser microstructure and weakened chloride binding capacity, and these factors boosted chloride ion transport. A chloride ion diffusion model of RCPC considering the time dependence of chloride ion transport was developed, and the reliability of the model was verified by experimental data.

Noncontact In Situ Multidiagnostic NMR/Dielectric Spectroscopy.

Introduction of a dielectric material in a nuclear magnetic resonance (NMR) probe head modifies the frequency response of the probe circuit, a phenomenon revealed by detuning of the probe. For NMR spectroscopy, this detuning is corrected for by tuning and matching the probe head prior to the NMR measurement. The magnitude of the probe detuning, "the dielectric shift", provides direct access to the dielectric properties of the sample, enabling NMR spectrometers to simultaneously perform both dielectric and NMR spectroscopy. By measuring sample dielectric permittivity as a function of frequency, dielectric permittivity spectroscopy can be performed using the new methodology. As a proof of concept, this was evaluated on methanol, ethanol, 1-propanol, 1-pentanol, and 1-octanol using a commercial cross-polarization magic angle spinning (CPMAS) NMR probe head. The results accurately match the literature data collected by standard dielectric spectroscopy techniques. Subsequently, the method was also applied to investigate the solvent-surface interactions of water confined in the micropores of an MFI-type, hydrophilic zeolite with a Si/Al ratio of 11.5. In the micropores, water adsorbs to Bro̷nsted acid sites and defect sites, resulting in a drastically decreased dielectric permittivity of the nanoconfined water. Theoretical background for the new methodology is provided using an effective electric circuit model of a CPMAS probe head with a solenoid coil, describing the detuning resulting from the insertion of dielectric samples in the probe head.

Removal of rubidium from brine by an integrated film of sulfonated polysulfone/graphene/potassium copper ferricyanide

A novel integrated film of sulfonated polysulfone/graphene/potassium copper ferricyanide (KCuFC/SPSG) was used for selectively extracting rubidium ion (Rb+) from brine. To form KCuFC/SPSG, the precursor film of sulfonated polysulfone/graphene (SPSG) was synthesized by phase conversion process, which was alternately immersed in 0.1 mol·L–1 CuSO4/K4[Fe(CN)6] by in-situ adsorption coupled co-precipitation method. Various data such as nuclear magnetic resonance spectrometer, Fourier transform infrared spectroscope, X-ray photoelectron spectroscope, X-ray diffraction, scanning electron microscope and energy dispersive spectroscopy all verified that abundant KCuFC were uniformly located on the film. The resulting KCuFC/SPSG was used in film separation system. As the solution was fed into the system, the Rb+ could be selectively adsorption by KCuFC/SPSG. After the saturation adsorption, 0.5 mol·L–1 NH4Cl/HCl was fed into the film cell, Rb+ could be quickly desorbed by ion-exchange between Rb+ and NH4+ in the lattice of KCuFC. The purpose of separating and recovering Rb+ from the brine can be achieved after the repeated operation. The effects of pH, adsorption time and interferential ions on the adsorption capacity of Rb+ were investigated by batch experiments. The adsorption behavior fits the pseudo-second order kinetic process, while KCuFC has a higher adsorption capacity (Langmuir maximum sorption 165.4 mg∙g–1). In addition, KCuFC/SPSG shows excellent selectivity for Rb+ even in complex brine systems. KCuFC/SPSG could maintain 93.5% extraction efficiency after five adsorption/desorption cycles.

Unraveling Metabolic Changes following Stroke: Insights from a Urinary Metabolomics Analysis.

The neuropathological sequelae of stroke and subsequent recovery are incompletely understood. Here, we investigated the metabolic dynamics following stroke to advance the understanding of the pathophysiological mechanisms orchestrating stroke recovery. Using a nuclear magnetic resonance (NMR)-driven metabolomic profiling approach for urine samples obtained from a clinical group, the objective of this research was to (1) identify novel biomarkers indicative of severity and recovery following stroke, and (2) uncover the biochemical pathways underlying repair and functional recovery after stroke. Urine samples and clinical stroke assessments were collected during the acute (2-11 days) and chronic phases (6 months) of stroke. Using a 700 MHz 1H NMR spectrometer, metabolomic profiles were acquired followed by a combination of univariate and multivariate statistical analyses, along with biological pathway analysis and clinical correlations. The results revealed changes in phenylalanine, tyrosine, tryptophan, purine, and glycerophospholipid biosynthesis and metabolism during stroke recovery. Pseudouridine was associated with a change in post-stroke motor recovery. Thus, NMR-based metabolomics is able to provide novel insights into post-stroke cellular functions and establish a foundational framework for future investigations to develop targeted therapeutic interventions, advance stroke diagnosis and management, and enhance overall quality of life for individuals with stroke.

Analysis of complex mixtures with benchtop nuclear magnetic resonance: Solvent suppression with T2 and diffusion filters.

Benchtop nuclear magnetic resonance (NMR) spectrometers are being employed in a wide variety of applications from undergraduate teaching and research in academia to quality control and process monitoring in industrial settings. Incorporating benchtop NMR in some of these applications presents opportunities for new practical uses of the technology and challenges that truly test the capabilities of compact NMR spectrometers. For instance, the use of protonated solvents in manufacturing or process monitoring requires separating and quantitating the analyte signals of interest from the strong (overwhelming) response from the solvents. Furthermore, due to the lower field strength available with permanent magnet spectrometers, the NMR spectra of complex mixtures can be more difficult to analyze due to partial or complete signal overlap. To address some of these challenges and to extend the range of applications of benchtop NMR, we investigate NMR techniques that enable quantitative analysis of different components in mixtures. These pulse sequences can be used to suppress one or multiple solvent peaks, to filter out signals by spin-spin relaxation time (T2), or to separate signal components by a molecule's diffusion coefficient (NMR diffusometry). In this paper, we discuss quantitative analysis of excipients in buffers for therapeutic proteins to highlight the usefulness of these NMR pulse sequences in the analysis of complex samples with benchtop NMR spectrometers.

Cryogen-free 400-MHz nuclear magnetic resonance spectrometer as a versatile tool for pharmaceutical process analytical technology.

The discovery of new ceramic materials containing Ba-La-Cu oxides in 1986 that exhibited superconducting properties at high temperatures in the range of 35 K or higher, recognized with the Nobel Prize in Physics in 1987, opened a new world of opportunities for nuclear magnetic resonance (NMRs) and magnetic resonance imaging (MRIs) to move away from liquid cryogens. This discovery expands the application of high temperature superconducting (HTS) materials to fields beyond the chemical and medical industries, including electrical power grids, energy, and aerospace. The prototype 400-MHz cryofree HTS NMR spectrometer installed at Amgen's chemistry laboratory has been vital for a variety of applications such as structure analysis, reaction monitoring, and CASE-3D studies with RDCs. The spectrometer has been integrated with Amgen's chemistry and analytical workflows, providing pipeline project support in tandem with other Kinetic Analysis Platform technologies. The 400-MHz cryofree HTS NMR spectrometer, as the name implies, does not require liquid cryogens refills and has smaller footprint that facilitates installation into a chemistry laboratory fume hood, sharing the hood with a process chemistry reactor. Our evaluation of its performance for structural analysis with CASE-3D protocol and for reaction monitoring of Amgen's pipeline chemistry was successful. We envision that the HTS magnets would become part of the standard NMR and MRI spectrometers in the future. We believe that while the technology is being developed, there is room for all magnet options, including HTS, low temperature superconducting (LTS) magnets, and low field benchtop NMRs with permanent magnets, where utilization will be dependent on application type and costs.

MaDDOSY (Mass Determination Diffusion Ordered Spectroscopy) using an 80MHz Bench Top NMR for the Rapid Determination of Polymer and Macromolecular Molecular Weight.

Measurement of molecular weight is an integral part of macromolecular and polymer characterization which usually has limitations. Herein, this article presents the use of a bench-top 80MHz Nuclear Magnetic Resonance (NMR) spectrometer for diffusion-ordered spectroscopy as a practical and rapid approach for the determination of molecular weight/size using a novel solvent and polymer-independent universal calibration.

Automated self-optimization, intensification, and scale-up of photocatalysis in flow.

The optimization, intensification, and scale-up of photochemical processes constitute a particular challenge in a manufacturing environment geared primarily toward thermal chemistry. In this work, we present a versatile flow-based robotic platform to address these challenges through the integration of readily available hardware and custom software. Our open-source platform combines a liquid handler, syringe pumps, a tunable continuous-flow photoreactor, inexpensive Internet of Things devices, and an in-line benchtop nuclear magnetic resonance spectrometer to enable automated, data-rich optimization with a closed-loop Bayesian optimization strategy. A user-friendly graphical interface allows chemists without programming or machine learning expertise to easily monitor, analyze, and improve photocatalytic reactions with respect to both continuous and discrete variables. The system's effectiveness was demonstrated by increasing overall reaction yields and improving space-time yields compared with those of previously reported processes.

Investigation of Nearest Neighbor Interactions in Nickel Substituted Cobalt Using 59Co IFNMR

Co100-x Nix (x = 10, 20, 30, 40) alloys were synthesized via the chemical method by reducing nitrates of cobalt and nickel using hydrazine as a reducing agent. The proportion of solvents, ethanol, and water was maintained constant for all the samples in the series. The structure and morphology of the samples were examined based on X-Ray diffraction (XRD) data and Scanning Electron Microscope (SEM) images. From XRD it was evident that the system had a mixture of hexagonal close packed (hcp) and face centered cubic (fcc) phases. The amount of hcp phase in the composition gradually reduced as the concentration of nickel increased. The effect of substitution of nickel on cobalt was studied using a home built 59Co internal field nuclear magnetic resonance (IFNMR) spectrometer. Further, the saturation magnetization and hence magnetic field anisotropy values, obtained from M vs H loops, are found to vary with nickel concentration. The NMR results show a broadening of the NMR signals in comparison with the pure phase of cobalt. The NMR spectra and the number of peaks were assigned to possible cobalt-nickel neighbors, and the percentage of such combinations is interpreted in terms of the frequency and intensity of the peaks. This percentage of different nickel-cobalt combinations was compared with the random distribution obtained using the binomial distribution function. This comparison shows a clear trend compared to that analysed by the IFNMR experiment.

Antibacterial activity of five Indonesian medicinal plants and the isolation of compounds from Plectranthus scutellarioides

The purpose of this study is to investigate the antibacterial properties of five Indonesian medicinal plant extracts, namely Physalis angulata, Loranthus parasiticus, Plectranthus scutellarioides, Cyperus rotundus, and Terminalia catappa. The isolation of compounds from P. scutellarioides against pathogenic bacteria was also investigated. The assessment of the antibacterial activity of the extracts was conducted using the microdilution-3-(4,5-dimethylthiazol- 2-yl)-2,5-diphenyltetrazolium bromide method against Gram-positive bacteria (Bacillus subtilis and Staphylococcus aureus) and Gram-negative bacteria (Escherichia coli). The plant extract with the highest antibacterial activity was further purified using various chromatographic assays to isolate bioactive compounds. High Resolution-Electron Ionization Mass Spectroscopy/Electrospray Ionization Mass Spectroscopy (HR-ESIMS/EIMS) and Nuclear Magnetic Resonance (NMR) spectrometers were used to elucidate the structure of isolated compounds. Among all the plants tested, P. scutellarioides showed the strongest antibacterial activity against S. aureus [minimum inhibitory concentration (MIC 100 μg/ml)] and B. subtilis (MIC 200 μg/ml). Three compounds were isolated from P. scutellarioides including an abietane diterpene, 2,16-diacetoxy-6,11,12,14,17-pentahydroxy-abieta-5,8,11,13- tetraene-7-one (1), 5,6,7,3′,4′,5′-hexamethoxy flavone (2), and 5,6,7,8,3′,4′,5′-heptamethoxy flavone (3). Compounds 2 and 3 were recognized to be first isolated from this plant. Compound 1 exerted antibacterial activity against S. aureus with a MIC value of 60 μM, but was inactive against B. subtilis and E. coli (MIC > 200 μM). Compounds 2 and 3 were inactive against S. aureus, B. subtilis, and E. coli (MIC > 200 μM).

Spectroscopic Characterization And Antimicrobial Studies Of Synthesized N-Benzyl-1h-Indole-3-Carboxamide

A four step synthetic approach afforded N-benzyl-1H-indole-3-carboxamide in a moderate yield. The process involved formylation with Vismeier-Haack reagents, followed by disproportionation through the Cannizzaro reaction, chlorination using thionyl chloride, and subsequent substitution with benzylamine, ultimately generating the target compound. The compound was analysed using, 1H NMR (Proton nuclear magnetic resonance), 13C NMR (carbon nuclear magnetic resonance) and FTIR (fourier transform infrared) spectrophotometry. The FT-IR spectrum of the compound show characteristics peaks at 1540 cm-1 for C=C of benzene ring, at 1660 cm-1 for C=O of amide, sp3 C-H stretching frequency, that is, the methylene bonded to the nitrogen of the amide at 2900 cm-1, N-H. The proton and carbon data were obtained using the aforementioned nuclear magnetic resonance spectrometers, and the corresponding spectrum displaced chemical shifts that align with the proposed structure of the target molecule.

Understanding the Reaction Mechanism and Kinetics of Mediated Li-O2 Batteries Using Flow Set-Ups and Cyclic Voltammetry

Li-O2 batteries are very promising candidates for electromobility because of their very high theoretical energy density. Moreover, they are composed of abundant materials, as opposed to Li-ion batteries, which would make them a greener and cheaper alternative. The principal reaction in Li-O2 batteries is the formation of lithium peroxide during discharge via the oxygen reduction reaction (ORR), that is then oxidised during the charge by the oxygen evolution reaction (OER). One of the major challenges of Li-O2 batteries is related to the insulating nature of their discharge product, that significantly limits the capacity and hinders performance. A strategy to overcome this is by using redox mediators (RMs), which shuttle electrons from the electrode surface to the solution and thus facilitate a solution-based mechanism for the formation of large crystals. Understanding the reaction kinetics of these RMs can therefore aid in increasing the battery performance.Quinones, specifically 2,5-Di-tert-butyl-1,4-benzoquinone (DBBQ),is a commonly used discharge RM in this type of batteries. However, their reaction kinetics and how these vary with different electrolyte conditions are not yet well understood. DBBQ undergoes two single electron reductions, whose potentials and kinetics vary with salt concentrations and solvent having a direct effect on its ability to mediate the ORR.In this work, we have developed a Li-O2 flow cell to study the reaction mechanism and kinetics of DBBQ, and performed cyclic voltammetry (CV) studies to better understand how these vary with changing solvent and salt conditions. In the Li-O2 flow set-up the battery is positioned outside the nuclear magnetic resonance (NMR) magnet and plastic tubing then runs through the NMR and electron paramagnetic resonance (EPR) spectrometers. In this way, the reduction of the DBBQ can be monitored while the battery is cycling. In the proton NMR, the neutral DBBQ signals disappear on discharge as the singly reduced DBBQ semiquinone monoanion is a radical. The fast electron exchange between the neutral and radical species broaden out the NMR signals on discharge as the EPR signal grows. On charge, the neutral DBBQ signal reappears and the EPR signal disappears. The Li-O2 flow set-up is very sensitive to air and moisture exposure as the tubing is not perfectly impermeable to them. Therefore, having the CVs as a complementary method to study the reaction mechanisms and kinetics is very useful.We have developed a theoretical framework of Li-coupled electron transfer reactions that can predict the electrochemical kinetics in the presence of high and low donor number solvents and used to quantify thermodynamic and kinetic parameters. We define E0 app and k0 app as the apparent thermodynamic and kinetic parameters that describe the overall system and can be derived from the Nernst equation and Butler Volmer kinetics. These overall descriptors depend on the pathway the reaction takes (Figure 1). The different pathways in different solvents/salts are due to changes in the Li+ solvation strength as well as the competing ionic association of the counter anion.Experimentally, we have shown that in three different solvents, DME, tetraglyme and DMSO the behaviour of DBBQ can be explained by this theoretical framework. In DME, the DBBQ behaviour is most reminiscent of pathway 1 where the kinetics slow down with increasing Li+ concentration. In DMSO the kinetics present a maximum at Li+ concentrations around 1M. Simulations and fitting of the CV experiments in DMSO for the first reduction are in good agreement with pathways 2 and 3, while in tetraglyme it is harder to explain the trends as they do not fit into just one of the pathways.In conclusion we have studied the mechanism and kinetics of DBBQ as a RM for Li-O2 batteries with an in-situ flow set up and CVs and build a theoretical framework to understand how these vary in different electrolyte conditions. This method can be extended to study both the second reduction of DBBQ and other discharge and charge RMs for Li-O2 batteries. Figure 1

A reliable external calibration method for reaction monitoring with benchtop NMR.

Nuclear magnetic resonance (NMR) spectroscopy is a powerful analytical technique with the ability to acquire both quantitative and structurally insightful data for multiple components in a test sample. This makes NMR spectroscopy a desirable tool to understand, monitor, and optimize chemical transformations. While quantitative NMR (qNMR) approaches relying on internal standards are well-established, using an absolute external calibration scheme is beneficial for reaction monitoring as resonance overlap complications from an added reference material to the sample can be avoided. Particularly, this type of qNMR technique is of interest with benchtop NMR spectrometers as the likelihood of resonance overlap is only enhanced with the lower magnetic field strengths of the used permanent magnets. The included study describes a simple yet robust methodology to determine concentration conversion factors for NMR systems using single- and multi-analyte linear regression models. This approach is leveraged to investigate a pharmaceutically relevant amide coupling batch reaction. An on-line stopped-flow (i.e., interrupted-flow or paused-flow) benchtop NMR system was used to monitor both the 1,1'-carbonyldiimidazole (CDI) promoted acid activation and the amide coupling. The results highlight how quantitative measurements in benchtop NMR systems can provide valuable information and enable analysts to make decisions in real time.

Study of 1-Formyl-2-Pyrazolines as Anticancer Drug Candidates

The development of novel anticancer agents is essential in cancer prevention. One versatile group of compounds, known for their significant bioactivity and several of its derivatives that have been clinically approved, is the group of pyrazolines. This study aimed to synthesize 1-formyl-2-pyrazoline derivatives (pyrazolines 1-2) using chalcone 1-2, hydrazine hydrate, and formic acid via cyclo-condensation. The synthesized compounds were characterized using Fourier Transform Infrared (FTIR), Gas Chromatography-Mass Spectrometry (GC-MS), and Nuclear Magnetic Resonance (1H- and 13C-NMR) spectrometers. Pyrazolines 1-2 were found to be drug-like compounds, satisfying Lipinski’s Rule of Five and possessing favourable absorption, distribution, metabolism, and excretion (ADME) properties, including good gastrointestinal absorption, blood-brain barrier permeability, and no interaction with P-glycoprotein. Furthermore, they were inactive against several toxicity endpoints in a normal body condition, such as immunotoxicity, mutagenicity, and cytotoxicity. In vitro cytotoxic evaluation of the pyrazolines 1-2 against HeLa and MCF7 cancer cell lines demonstrated moderate activity, with IC50 values of 25.01 µM and 82.87 µM, respectively. Pyrazolines 1-2 also showed good selectivity with selectivity index (SI) values of 8.92 and 14.45. The molecular docking study on epidermal growth factor receptor tyrosine kinase (EGFR-TK) (PDB ID: 4HJO) revealed that pyrazolines 1-2 had a binding affinity of -7.9 and -8.0 kcal/mol, respectively. The compounds interacted with Lys721 residue through hydrogen bonds and hydrophobic interactions due to the presence of the pyrazoline ring and the formyl group in their structures. These findings suggest that pyrazolines 1-2 scaffold has the potential to be further studied as a lead compound for anticancer drug candidates.