Optimization and degradation studies of cellulose transesterification to palmitate esters in superbase ionic liquid

Cellulose palmitates (CPs) were synthesized with varying degrees of substitution (DS) via a catalyst-free, homogeneous transesterification of cellulose in a novel superbase ionic liquid (SB-IL) system, specifically 5-methyl-1,5,7-triaza-bicyclo[4.3.0]non-6-enium acetate [mTBNH][OAc], combined with dimethyl sulfoxide (DMSO) as a co-solvent, using vinyl palmitate as the acylating agent. We examined the influence of reaction temperature, reaction time, and the molar ratio of vinyl palmitate to anhydroglucose unit (AGU) on the DS, which ranged from 0.5 to 2.3 under the given conditions. Notably, the reaction order of the three hydroxy groups was C6-OH > C2-OH > C3-OH. To elucidate the chemical structure of CPs and confirm the transesterification process, various spectroscopic techniques including 1H nuclear magnetic resonance (NMR), 13C NMR, heteronuclear single quantum correlation (HSQC), and solid-state NMR were employed. Higher reaction temperatures and extended reaction times led to a decrease in the DS of CPs, potentially due to the degradation of some of the involved chemicals during the transesterification process. We also investigated the stability of the pure ionic liquid (IL) and the IL + DMSO solvent system at elevated temperatures by heating them at 100 °C for 5 h, confirming their chemical integrity through 1H NMR analysis. Additionally, we assessed the compatibility between the solvent system and cellulose by subjecting a mixture of cellulose and the solvent system to 100 °C for 5 h. To compare the structures of untreated cellulose and regenerated cellulose, Fourier transform infrared (FT-IR) spectroscopy was employed. Furthermore, we determined the molar mass of both untreated cellulose and regenerated cellulose, as well as CPs synthesized at higher reaction temperatures and longer durations, using intrinsic viscosity measurements. Lastly, we examined the solubility properties of CPs.

Parahydrogen hyperpolarized NMR detection of underivatized short oligopeptides

Parahydrogen hyperpolarization has evolved into a versatile tool in NMR, allowing substantial sensitivity enhancements in analysis of biological samples. Herein we show how its application scope can be extended from small metabolites to underivatized oligopeptides in solution. Based on a homologous series of alanine oligomers, we report on an experimental and DFT study on the structure of the oligopeptide and hyperpolarization catalyst complexes formed in the process. We demonstrate that alanine oligomers coordinate to the iridium carbene-based catalyst in three different ways, each giving rise to distinctive hydride signals. Moreover, the exact structures of the transient oligopeptide-catalyst complexes are oligomer-specific. This work gives a first insight into how the organometallic iridium-N-heterocyclic carbene-based parahydrogen hyperpolarization catalyst interacts with biopolymers that have multiple catalyst binding sites. A preliminary application example is demonstrated for oligopeptide detection in urine, a complex biological mixture.

Preparation of Thermoplastic Cellulose Esters in [mTBNH][OAC] Ionic Liquid by Transesterification Reaction

The transesterification of cellulose with vinyl esters in ionic liquid media is suggested as a prospective environmentally friendly alternative to conventional esterification. In this study, various long-chain cellulose esters (laurate, myristate, palmitate, and stearate) with a degree of substitution (DS) up to 1.8 have been synthesized in novel distillable ionic liquid, [mTBNH][OAC]. This IL has high dissolving power towards cellulose, which can improve homogeneous transesterification. Additionally, [mTBNH][OAC] has durability towards recycling and can be regenerated and re-used again for the next cycles of esterification. DMSO is used as a co-solvent because of its ability to speed up mass transport due to lower solvent viscosity. The optimization of the reaction parameters, such as co-solvent content, temperature (20-80 °C), reaction time (1-5 h), and a molar ratio of reactants (1-5 eq. AGU) is reported. It was found that within studied reaction conditions, DS increases with increasing reaction time, temperature, and added vinyl esters. Structure analysis using FTIR, 1H, and 13C NMR after acylation revealed the introduction of the alkyl chains into cellulose for all studied samples. The results also suggested that the substitution order of the OH group is C7-O6 > C7-O2 > C7-O3. Unique, complex thermal and rheological investigation of the cellulose esters shows the growth of an amorphous phase upon the degree of substitution. At the same time, the homogeneous substitution of cellulose with acyl chains increases the melt viscosity of a material. Internal plasticization in cellulose esters was found to be the mechanism for the melt processing of the material. Long-chain cellulose esters show the potential to replace commonly used externally plasticized cellulose derivatives.

Stable Isotope Tracing Uncovers Reduced γ/β-ATP Turnover and Metabolic Flux Through Mitochondrial-Linked Phosphotransfer Circuits in Aggressive Breast Cancer Cells

Changes in dynamics of ATP γ- and β-phosphoryl turnover and metabolic flux through phosphotransfer pathways in cancer cells are still unknown. Using ¹⁸O phosphometabolite tagging technology, we have discovered phosphotransfer dynamics in three breast cancer cell lines: MCF7 (non-aggressive), MDA-MB-231 (aggressive), and MCF10A (control). Contrary to high intracellular ATP levels, the ¹⁸O labeling method revealed a decreased γ- and β-ATP turnover in both breast cancer cells, compared to control. Lower β-ATP[¹⁸O] turnover indicates decreased adenylate kinase (AK) flux. Aggressive cancer cells had also reduced fluxes through hexokinase (HK) G-6-P[¹⁸O], creatine kinase (CK) [CrP[¹⁸O], and mitochondrial G-3-P[¹⁸O] substrate shuttle. Decreased CK metabolic flux was linked to the downregulation of mitochondrial MTCK1A in breast cancer cells. Despite the decreased overall phosphoryl flux, overexpression of HK2, AK2, and AK6 isoforms within cell compartments could promote aggressive breast cancer growth.

Process Optimization for Catalytic Oxidation of Dibenzothiophene over UiO-66-NH2 by Using a Response Surface Methodology

This research investigates the catalytic performance of a metal-organic framework (MOF) with a functionalized ligand-UiO-66-NH₂-in the oxidative desulfurization of dibenzothiophene (DBT) in n-dodecane as a model fuel mixture (MFM). The solvothermally prepared catalyst was characterized by XRD, FTIR, ¹H NMR, SEM, TGA, and MP-AES analyses. A response surface methodology was employed for the experiment design and variable optimization using central composite design (CCD). The effects of reaction conditions on DBT removal efficiency, including temperature (X ₁), oxidant agent over sulfur (O/S) mass ratio (X ₂), and catalyst over sulfur (C/S) mass ratio (X ₃), were assessed. Optimal process conditions for sulfur removal were obtained when the temperature, O/S mass ratio, and C/S mass ratio were 72.6 °C, 1.62 mg/mg, and 12.1 mg/mg, respectively. Under these conditions, 89.7% of DBT was removed from the reaction mixture with a composite desirability score of 0.938. From the results, the temperature has the most significant effect on the oxidative desulfurization reaction. The model F values gave evidence that the quadratic model was well-fitted. The reusability of the MOF catalyst in the ODS reaction was tested and demonstrated a gradual loss of activity over four runs.

Understanding Parahydrogen Hyperpolarized Urine Spectra: The Case of Adenosine Derivatives

Parahydrogen hyperpolarization has emerged as a promising tool for sensitivity-enhanced NMR metabolomics. It allows resolution and quantification of NMR signals of certain classes of low-abundance metabolites that would otherwise be undetectable. Applications have been implemented in pharmacokinetics and doping drug detection, demonstrating the versatility of the technique. Yet, in order for the method to be adopted by the analytical community, certain limitations have to be understood and overcome. One such question is NMR signal assignment. At present, the only reliable way to establish the identity of an analyte that gives rise to certain parahydrogen hyperpolarized NMR signals is internal standard addition, which can be laborious. Herein we show that analogously to regular NMR metabolomics, generating libraries of hyperpolarized analyte signals is a viable way to address this limitation. We present hyperpolarized spectral data of adenosines and give an early example of identifying them from a urine sample with the small library. Doing so, we verify the detectability of a class of diagnostically valuable metabolites: adenosine and its derivatives, some of which are cancer biomarkers, and some are central to cellular energy management (e.g., ATP).

Extraction and Fractionation of Bioactives from Dipsacus fullonum L. Leaves and Evaluation of Their Anti-Borrelia Activity

Lyme disease (LD) is a tick-borne bacterial disease that is caused by Borrelia burgdorferi. Although acute LD is treated with antibiotics, it can develop into relapsing chronic form caused by latent forms of B. burgdorferi. This leads to the search for phytochemicals against resistant LD. Therefore, this study aimed to evaluate the activity of Dipsacus fullonum L. leaves extract (DE) and its fractions against stationary phase B. burgdorferi in vitro. DE showed high activity against stationary phase B. burgdorferi (residual viability 19.8 ± 4.7%); however, it exhibited a noticeable cytotoxicity on NIH cells (viability 20.2 ± 5.2%). The iridoid-glycoside fraction showed a remarkable anti-Borrelia effect and reduced cytotoxicity. The iridoid-glycoside fraction was, therefore, further purified and showed to contain two main bioactives—sylvestrosides III and IV, that showed a considerable anti-Borrelia activity being the least toxic to murine fibroblast NIH/3T3 cells. Moreover, the concentration of sylvestrosides was about 15% of DE, endorsing the feasibility of purification of the compounds from D. fullonum L. leaves.

Parahydrogen hyperpolarization of minimally altered urine samples for sensitivity enhanced NMR metabolomics

Parahydrogen hyperpolarization has been shown to enhance NMR sensitivity in urine analysis by several orders of magnitude if urine samples are prepared by solid phase extraction (SPE). We present a different approach, developed for minimal sample alteration before analysis. Removing SPE from the workflow allows to retain a wider range of metabolites and paves the way towards more universal hyperpolarized NMR metabolomics of low abundance metabolites.

Correction: A line-broadening free real-time 31P pure shift NMR method for phosphometabolomic analysis

Correction for 'A line-broadening free real-time ³¹P pure shift NMR method for phosphometabolomic analysis' by Karl Kristjan Kaup et al., Analyst, 2021, 146, 5502-5507, DOI: 10.1039/D1AN01198G.

A line-broadening free real-time 31P pure shift NMR method for phosphometabolomic analysis

Phosphometabolomics by ³¹P NMR can be challenging, since overlapping multiplets of homonuclear coupled phosphorus nuclei complicate spectral analysis. Pure shift NMR allows to simplify such spectra by collapsing multiplets into singlets, but most pure shift methods require substantially elongated measurement times or cause disturbing spectral line broadening. Herein, we combine established pure shift NMR and artefact suppression techniques to record ³¹P pure shift NMR spectra without penalties in measurement time or line width. Examples are demonstrated in resolution of a mixture of nucleotide triphosphates and a biological sample of ¹⁸O labelled ATP isotopomers.

Developing Analytical Applications for Parahydrogen Hyperpolarization: Urinary Elimination Pharmacokinetics of Nicotine

Nuclear magnetic resonance spectroscopy (NMR) is a valuable analytical tool with applications in a vast array of research fields from chemistry and biology to medicine and beyond. NMR is renowned for its straightforward data interpretation and quantitative properties, making it attractive for pharmacokinetic applications, where drug metabolism pathways, concentrations, and kinetics need to be evaluated. However, pharmacologically active compounds and their metabolites in biofluids often appear in minute concentrations, well below the detection limit of NMR. Herein, we demonstrate how parahydrogen hyperpolarization overcomes this sensitivity barrier, allowing us to detect mid-nanomolar concentrations of a drug and a drug metabolite in a biofluid matrix. The performance of the method is demonstrated by monitoring nicotine and cotinine urinary elimination, reflected by their concentrations in urine during the onset and withdrawal from nicotine consumption. An NMR limit of detection of 0.1 μM and a limit of quantitation of 0.7 μM is achieved in a practical pharmacokinetics scenario where precise quantitative and qualitative analysis is desired.

Adaptation of striated muscles to Wolframin deficiency in mice: Alterations in cellular bioenergetics

BACKGROUND

Wolfram syndrome (WS), caused by mutations in WFS1 gene, is a multi-targeting disease affecting multiple organ systems. Wolframin is localized in the membrane of the endoplasmic reticulum (ER), influencing Ca²⁺ metabolism and ER interaction with mitochondria, but the exact role of the protein remains unclear. In this study we aimed to characterize alterations in energy metabolism in the cardiac and in the oxidative and glycolytic skeletal muscles in Wfs1-deficiency.

METHODS

Alterations in the bioenergetic profiles in the cardiac and skeletal muscles of Wfs1-knock-out (KO) male mice and their wild type male littermates were determined using high resolution respirometry, quantitative RT-PCR, NMR spectroscopy, and immunofluorescence confocal microscopy.

RESULTS

Oxygen consumption without ATP synthase activation (leak) was significantly higher in the glycolytic muscles of Wfs1 KO mice compared to wild types. ADP-stimulated respiration with glutamate and malate was reduced in the Wfs1-deficient cardiac as well as oxidative and glycolytic skeletal muscles.

CONCLUSIONS

Wfs1-deficiency in both cardiac and skeletal muscles results in functional alterations of energy transport from mitochondria to ATP-ases. There was a substrate-dependent decrease in the maximal Complex I -linked respiratory capacity of the electron transport system in muscles of Wfs1 KO mice. Moreover, in cardiac and gastrocnemius white muscles a decrease in the function of one pathway were balanced by the increase in the activity of the parallel pathway.

GENERAL SIGNIFICANCE

This work provides new insights to the muscle involvement at early stages of metabolic syndrome like WS as well as developing glucose intolerance.

Parahydrogen induced hyperpolarization provides a tool for NMR metabolomics at nanomolar concentrations

Sensitivity enhancement by parahydrogen hyperpolarization allows NMR detection and quantification of hundreds of urinary metabolites at down to nanomolar concentrations.

NMR detection in biofluid extracts at sub-μM concentrations via para-H2 induced hyperpolarization

NMR spectroscopy is one of the most powerful techniques to simultaneously obtain qualitative and quantitative information in chemical analysis. Despite its versatility, the applications of NMR in the study of biofluids are often limited by the insensitivity of the technique, further aggravated by the poor signal dispersion in the (1)H spectra. Recent advances in para-H2 induced hyperpolarization have proven to address both these limitations for specific classes of compounds. Herein, this approach is for the first time applied for quantitative determination in biofluid extracts. We demonstrate that a combination of solid phase extraction, para-hydrogen induced hyperpolarization and selective NMR detection quickly reveals a doping substance, nikethamide, at sub-μM concentrations in urine. We suggest that this method can be further optimized for the detection of different analytes in various biofluids, anticipating a wider application of hyperpolarized NMR in metabolomics and pharmacokinetics studies in the near future.

A quantitative method for analysis of mixtures of homologues and stereoisomers of hemicucurbiturils that allows us to follow their formation and stability

Cyclic and linear oligomers of hemicucurbiturils have large difference in UV absorbance.

A New Ir-NHC Catalyst for Signal Amplification by Reversible Exchange in D2 O

NMR signal amplification by reversible exchange (SABRE) has been observed for pyridine, methyl nicotinate, N‐methylnicotinamide, and nicotinamide in D₂O with the new catalyst [Ir(Cl)(IDEG)(COD)] (IDEG=1,3‐bis(3,4,5‐tris(diethyleneglycol)benzyl)imidazole‐2‐ylidene). During the activation and hyperpolarization steps, exclusively D₂O was used, resulting in the first fully biocompatible SABRE system. Hyperpolarized ¹H substrate signals were observed at 42.5 MHz upon pressurizing the solution with parahydrogen at close to the Earth's magnetic field, at concentrations yielding barely detectable thermal signals. Moreover, 42‐, 26‐, 22‐, and 9‐fold enhancements were observed for nicotinamide, pyridine, methyl nicotinate, and N‐methylnicotinamide, respectively, in conventional 300 MHz studies. This research opens up new opportunities in a field in which SABRE has hitherto primarily been conducted in CD₃OD. This system uses simple hardware, leaves the substrate unaltered, and shows that SABRE is potentially suitable for clinical purposes.

Template-controlled synthesis of chiral cyclohexylhemicucurbit[8]uril

Enantiomerically pure cyclohexylhemicucurbit[8]uril (cycHC[8]), possessing a barrel-shaped cavity, has been prepared in high yield on a gram scale from either (R,R,N,N')-cyclohex-1,2-diylurea and formaldehyde or cycHC[6]. In either case, a dynamic covalent library is first generated from which the desired cycHC can be amplified using a suitable anion template.

Excess of threonine compared with serine promotes threonine aldolase activity in Lactococcus lactis IL1403

Lactococcus lactis is an important lactic acid starter for food production as well as a cell factory for production of food grade additives, among which natural flavour production is one of the main interests of food producers. Flavour production is associated with the degradation of amino acids and comprehensive studies are required to elucidate mechanisms behind these pathways. In this study using chemically defined medium, labelled substrate and steady-state cultivation, new data for the catabolism of threonine in Lc. lactis have been obtained. The biosynthesis of glycine in this organism is associated with the catabolic pathways of glucose and serine. Nevertheless, if threonine concentration in the growth environment exceeds that of serine, threonine becomes the main source for glycine biosynthesis and the utilization of serine decreases. Also, the conversion of threonine to glycine was initiated by a threonine aldolase and this was the principal pathway used for threonine degradation. As in Streptococcus thermophilus, serine hydroxymethyltransferase in Lc. lactis may possess a secondary activity as threonine aldolase. Other catabolic pathways of threonine (e.g. threonine dehydrogenase and threonine dehydratase) were not detected.