Methyl Formate Research Articles

Spatial distribution and temporal evolution of wall-stabilized DME/O2 premixed cool flames

The low-temperature oxidation of dimethyl ether (DME) was investigated in premixed wall-stabilized cool flames at two equivalence ratios (ϕ) of 0.2 and 0.5. Using a time-of-flight mass spectrometry (TOF-MS) coupled with gas chromatography (GC), the spatial distributions of major intermediate species, including DME, CH2O (formaldehyde), CO, CO2, and CH3OCHO (methyl formate), were quantified under well-controlled boundary conditions. Moreover, the temporal evolutions of multiple intermediate species in the wall-stabilized cool flame ignition process were measured via TOF-MS, while the wall temperature was gradually ramped up from 550 K to 730 K. Several kinetic models were examined herein to assess the estimated low-temperature reactivity of DME by comparing the one-dimensional axisymmetric simulation results with the experimental data. Wall-stabilized cool flame structures at equivalence ratios ϕ of 0.2 and 0.5 were quantitatively examined with the major intermediate species. It is found that the kinetic models reasonably predict the onset of the reaction zone near the wall. Among these models, Kurimoto et al.’s model gives better predictions for the distributions of CH2O and CO, which are characteristic species of cool flames. In addition, time-resolved measurements of the unsteady cool flames identified the negative temperature coefficient (NTC) turnover points for different species across various temperature regions. It is also found that the Kurimoto et al. model still indicates a slightly higher reactivity of DME in the low-temperature range, resulting in earlier DME consumption and a shift of NTC window to lower temperatures at ϕ = 0.2.

Epigenetic Explorations of Neurological Disorders, the Identification Methods, and Therapeutic Avenues

Neurodegenerative disorders are major health concerns globally, especially in aging societies. The exploration of brain epigenomes, which consist of multiple forms of DNA methylation and covalent histone modifications, offers new and unanticipated perspective into the mechanisms of aging and neurodegenerative diseases. Initially, chromatin defects in the brain were thought to be static abnormalities from early development associated with rare genetic syndromes. However, it is now evident that mutations and the dysregulation of the epigenetic machinery extend across a broader spectrum, encompassing adult-onset neurodegenerative diseases. Hence, it is crucial to develop methodologies that can enhance epigenetic research. Several approaches have been created to investigate alterations in epigenetics on a spectrum of scales—ranging from low to high—with a particular focus on detecting DNA methylation and histone modifications. This article explores the burgeoning realm of neuroepigenetics, emphasizing its role in enhancing our mechanistic comprehension of neurodegenerative disorders and elucidating the predominant techniques employed for detecting modifications in the epigenome. Additionally, we ponder the potential influence of these advancements on shaping future therapeutic approaches.

Cold plasma-activated Ni-Co tandem catalysts with CN vacancies for enhancing CH4 electrocatalytic to methyl formate

The direct electrooxidation of methane (CH4OR) into high value-added liquid products has been considered an effective method to efficient and clean utilization of methane. However, this process is mainly limited by CH4 activation and subsequent intermediate regulation. Here, we report the first successful achieve methyl formate from CH4OR on Ni-Co tandem catalysts with CN vacancies prepared by H2 cold plasma. The faradaic efficiency of CH4OR into methyl formate reaches 56.7 % at 2.0 V vs. RHE with remained stability for 160 h. In situ ATR-SEIRAS and DFT calculations suggest that the CN vacancies can shift the d-band center of the active Ni sites upwards to enhance the chemisorption of CH4 over Ni atom near CN vacancy, generating the key intermediates of *CH3 and *CH2. *CH2 further overflows onto the Co atom around the same CN vacancy, providing favorable conditions for esterification reaction to obtain methyl formate. This work opens a new avenue for the development of efficient electrocatalytic systems for the clean utilization of methane and the electrosynthesis of methyl formate under ambient conditions.

Trimetallic Alloys as an Electrocatalyst for Fuel Cells: The Case of Methyl Formate on Pt3Pd3Sn2.

The shift toward renewable energy sources plays a central role in the quest for a circular economy. In this context, methyl formate (MF) has garnered attention as a compelling hydrogen carrier and alternative fuel, because of its remarkable characteristics (energy density, ease of storage and transport, and low boiling point). In this study, DFT calculations supported by online electrochemical mass spectroscopy (OE-MS) were performed to investigate the MF electro-oxidation (MFEO) on Pt3Pd3Sn2 (111). The DFT calculations provide insight into the role of Pt, Pd, and Sn atoms in MFEO. Pt and Pd together provide a preferred active site for initiating MFEO through the O-H bond scission, and Sn plays an essential role in the mitigation of CO through oxygenation or water activation. By comparing the reaction energies and activation barriers for all possible reactions in MFEO, the suggested path necessitates a minimum energy of 0.14 eV to initiate the MFEO. This value was supported by the experimental results, showing that the oxidation wave of MF starts at 0.15 V (70 °C). Density functional theory (DFT) results, supported by OE-MS, indicate that the hydrolysis of MF prior to MFEO is not preferred on Pt3Pd3Sn2 (111) surfaces, although the formation of methanol is plausible via a CH3O intermediate. Among the three small organic molecules (SOMs) studied─MF, methanol, and formic acid─MF has the lowest activation energy for the initial bond breaking that starts the whole oxidation process (0.13 eV), compared to formic acid (0.45 eV) and methanol (0.61 eV); thus, MF is the preferred fuel on Pt3Pd3Sn2 (111).

Meiosis as a mechanism for epigenetic reprogramming and cellular rejuvenation.

Meiosis is a hallmark of sexual reproduction because it represents the transition from one life cycle to the next and, in animals, meiosis produces gametes. Why meiosis evolved has been debated and most studies have focused on recombination of the parental alleles as the main function of meiosis. However, 40 years ago, Robin Holliday proposed that an essential function of meiosis is to oppose the consequence of successive mitoses that cause cellular aging. Cellular aging results from accumulated defective organelles and proteins and modifications of chromatin in the form of DNA methylation and histone modifications referred to collectively as epigenetic marks. Here, recent findings supporting the hypothesis that meiosis opposes cellular aging are reviewed and placed in the context of the diversity of the life cycles of eukaryotes, including animals, yeast, flowering plants and the bryophyte Marchantia.

Exploring the catalytic conversion of aromatic model compounds of coal pyrolysis over Ca(OH)2

The distribution of pyrolysis products from aromatic model compounds in coal catalyzed by Ca(OH)2 was investigated at the molecular level. The composition and relative abundance of the pyrolysis products from coal were analyzed using Py-GC/MS. The rapid pyrolysis products of coal at 600 °C consisted of phenols (15.94 %), non-phenolic oxygenated compounds (25.31 %), aliphatics (49.03 %), aromatic compounds (21.74 %), and other compounds (0.03 %). Six representative aromatic model compounds (2-methoxy-4-methylphenol, p-cresol, 2,4-dimethylphenol, o-cresol, guaiacol, and catechol) were selected. The pyrolysis process of model compounds was primarily the cleavage of C-O and C-C bonds, which resulted in the formation of methoxy and methyl radicals. The results revealed that Ca(OH)2 undergoes acid-base reactions with -OH, thereby increasing the stability of the model compounds. Notably, the impact of Ca(OH)2 on the composition and distribution of pyrolysis products was significantly more pronounced in aromatic compounds containing both -OCH3 and -OH compared to those containing solely -OH. The formation pathways of pyrolysis products involving guaiacol and Ca(OH)2 were elucidated through density functional theory (DFT) calculations, demonstrating that Ca(OH)2 could facilitate more free radicals release and the conversion of model compounds. This study contributes to the understanding of the transformation of aromatic compounds during coal pyrolysis at the molecular level.

Methanol steam reforming over copper supported on apatites

Low-temperature methanol steam (MSR) reforming over Cu is an efficient process for releasing H2 from this promising liquid hydrogen carrier but the Cu contents of commercial catalysts are often exceedingly high. Here we show that Sr-exchanged fluoro and hydroxyapatites with 1wt.% Cu exhibit very high methanol turnover frequencies up to 386h-1 and H2 production rates up to 6569mol H2 kgCu-1 h-1 with CO selectivity as low as ~0.25% at 250 °C. Formaldehyde and methyl formate are the only other byproducts which are especially observed over catalysts with low Sr/P ratio in the hydroxyapatite. The reforming proceeds through methoxy, formaldehyde and formate species according to in situ FTIR and mass spectrometric measurements. The spectroscopic analyses further reveal the involvement of apatitic HPO42- ions in the catalytic sequence. Thus, the catalytic synergy between Cu and apatites provides a basis for highly efficient, bifunctional MSR catalysts with low copper content.

A dTDP-L-rhamnose 4-epimerase required for glycopeptidolipid biosynthesis in Mycobacterium abscessus

Mycobacterium abscessus causes severe lung infections in cystic fibrosis patients and exhibits smooth (S) or rough (R) morphotypes. Disruption of glycopeptidolipid (GPL) production results in the S-to-R transition but the underlying molecular mechanisms of this transition remain incompletely understood. Herein, we characterized MAB_4111c in relation to GPL synthesis and investigated the effects of MAB_4111c deletion in M. abscessus pathogenicity. An enzymatic assay indicated that MAB_4111c, also designated Tle for Talose epimerase, is converting dTDP-L-Rhamnose into dTDP-6-deoxy-L-Talose. A tle deletion mutant was constructed in the S variant of M. abscessus and relative areas of Rhamnose and 6-deoxy-Talose and their methylated forms expressed as ratios of total monosaccharides, showed an altered GPL profile lacking 6-deoxy-Talose. Thus, Tle provides dTDP-6-deoxy-L-Talose, subsequently used by the glycosyltransferase Gtf1 to transfer 6-deoxy-Talose to the GPL backbone. Strikingly, the tle mutant exhibited a R morphotype, showed impaired sliding motility and biofilm formation, and these phenotypes were rescued upon functional complementation. Moreover, deletion of tle in M. abscessus results in increased pathogenicity and killing in zebrafish embryos. Together, our results underscore the importance of the dTDP-L-Rhamnose 4-epimerase activity in GPL biosynthesis and in influencing M. abscessus virulence.

Overview of Methylation and Demethylation Mechanisms and Influencing Factors of Mercury in Water.

Mercury, particularly in its methylated form, poses a significant environmental and health risk in aquatic ecosystems. While the toxicity and bioaccumulation of mercury are well documented, there remains a critical gap in our understanding of the mechanisms governing mercury methylation and demethylation in aquatic environments. This review systematically examines the complex interplay of chemical, biological, and physical factors that influence mercury speciation and transformation in natural water systems. We provide a comprehensive analysis of methylation and demethylation processes, specifically focusing on the dominant role of methanogenic bacteria. Our study highlights the crucial function of hgcAB genes in facilitating mercury methylation by anaerobic microorganisms, an area that represents a frontier in current research. By synthesizing the existing knowledge and identifying key research priorities, this review offers novel insights into the intricate dynamics of mercury cycling in aquatic ecosystems. Our findings provide a theoretical framework to inform future studies and guide pollution management strategies for mercury and its compounds in aquatic environments.

Online FTIR and Mass Spectrometry Study of Direct Methyl Formate Electro-oxidation for Fuel-Cells Application

Online FTIR and Mass Spectrometry Study of Direct Methyl Formate Electro-oxidation for Fuel-Cells Application

Single-cell DNA methylation analysis tool Amethyst reveals distinct noncanonical methylation patterns in human glial cells.

Single-cell sequencing technologies have revolutionized biomedical research by enabling deconvolution of cell type-specific properties in highly heterogeneous tissue. While robust tools have been developed to handle bioinformatic challenges posed by single-cell RNA and ATAC data, options for emergent modalities such as methylation are much more limited, impeding the utility of results. Here we present Amethyst, a comprehensive R package for atlas-scale single-cell methylation sequencing data analysis. Amethyst begins with base-level methylation calls and expedites batch integration, doublet detection, dimensionality reduction, clustering, cell type annotation, differentially methylated region calling, and interpretation of results, facilitating rapid data interaction in a local environment. We introduce the workflow using published single-cell methylation human peripheral blood mononuclear cell (PBMC) and human cortex data. We further leverage Amethyst on an atlas-scale brain dataset to describe a noncanonical methylation pattern in human astrocytes and oligodendrocytes, challenging the notion that this form of methylation is principally relevant to neurons in the brain. Tools such as Amethyst will increase accessibility to single-cell methylation data analysis, catalyzing research progress across diverse contexts.

Survey of complex organic molecules in starless and pre-stellar cores in the Perseus molecular cloud

ABSTRACT Cold ($\sim$10 K) and dense ($\sim 10^{5}$ cm$^{-3}$) cores of gas and dust within molecular clouds, known as starless and dynamically evolved pre-stellar cores, are the birthplaces of low-mass (M$\le$ few M$_\odot$) stars. As detections of interstellar complex organic molecules, or COMs, in starless cores has increased, abundance comparisons suggest that some COMs might be seeded early in the star formation process and inherited to later stages (i.e. protostellar discs and eventually comets). To date observations of COMs in starless cores have been limited, with most detections reported solely in the Taurus molecular cloud. It is therefore still a question whether different environments affect abundances. We have surveyed 35 starless and pre-stellar cores in the Perseus molecular cloud with the Arizona Radio Observatory (ARO) 12 m telescope detecting both methanol, CH$_3$OH, and acetaldehyde, CH$_3$CHO, in 100 per cent and 49 per cent of the sample, respectively. In the sub-sample of 15 cores where CH$_3$CHO was detected at $\gt 3\sigma$ ($\sim$18 mK) with the ARO 12 m, follow-up observations with the Yebes 40 m telescope were carried out. Detections of formic acid, t-HCOOH, ketene, H$_2$CCO, methyl cyanide, CH$_3$CN, vinyl cyanide, CH$_2$CHCN, methyl formate, HCOOCH$_3$, and dimethyl ether, CH$_3$OCH$_3$, are seen in at least 20 per cent of the cores. We discuss detection statistics, calculate column densities, and compare abundances across various stages of low-mass star formation. Our findings have more than doubled COM detection statistics in cold cores and show COMs are prevalent in the gas before star and planet formation in the Perseus molecular cloud.

Arsenic, selenium, and mercury speciation in hypersaline lakes of the Andean Altiplano: Link between extreme levels and biodiversity repartition

Arsenic (As) and mercury (Hg) are highly toxic contaminants whereas selenium (Se) is both an essential trace element and potentially harmful at higher concentrations. The hyper-saline lakes of southern Bolivian Altiplano, which are ecological niches for endemic species, are also expected to be enriched in these toxic trace elements. The biogeochemistry of As, Hg, and Se in such high-altitude extreme environments (e.g., high UV radiation and salt content) remains poorly understood. In this study, we investigated the concentrations and chemical forms (speciation) of As, Hg, and Se in sediment, water, and air samples of Lagunas Colorada (LC), Verde (LV), and Blanca (LB) in the South Lipez region (>4200 m a.s.l.). We compared them with the repartition of biodiversity (invertebrates, algae, and bacteria). Extreme As concentrations were found in water (up to 82 mg L−1), and the main As species was inorganic As(V), with neither biogenic methylated As nor volatile As forms being detected in water and air, respectively. Se concentrations in water were of 0.1 to 1.4 μg L−1, and Se existed under different redox states, i.e., Se(IV), Se(VI), and reduced Se (0, -II), including biogenic methylated Se(-II) (trimethyl selenonium). Volatile Se compounds (e.g., dimethyl selenide) were detected in water and air samples. Hg was enriched in the surface water (6 to 30 ng L−1) compared to other regional water bodies, and a significant amount of methyl-Hg and gaseous Hg(0) was detected. The drastic disparity between As, Se and Hg concentrations and speciation between lakes has important implications for their cycling in these extreme aquatic systems. While As mostly accumulated in its oxidized and non-volatile form, Hg and Se concentrations can be controlled by significant conversion to reduced and methylated forms, allowing efficient evasion to the atmosphere. Finally, the salinity, including major ions, and high levels of As were among the main drivers of biodiversity repartition between lakes.

Interstellar Glycolaldehyde, Methyl Formate, and Acetic Acid. II. Chemical Modeling of the Bimodal Abundance Pattern in NGC 6334I

Gas-phase abundance ratios between C2H4O2 isomers methyl formate (MF), glycolaldehyde (GA), and acetic acid (AA) are typically on the order of 100:10:1 in star-forming regions. However, an unexplained divergence from this neat relationship was recently observed toward a collection of sources in the massive protocluster NGC 6334I; some sources exhibited extreme MF:GA ratios, producing a bimodal behavior between different sources, while the MF:AA ratio remained stable. Here, we use a three-phase gas-grain hot-core chemical model to study the effects of a large parameter space on the simulated C2H4O2 abundances. A combination of high gas densities and long timescales during ice-mantle desorption (∼125–160 K) appears to be the physical cause of the high MF:GA ratios. The main chemical mechanism for GA destruction occurring under these conditions is the rapid adsorption and reaction of atomic H with GA on the ice surfaces before it has time to desorb. The different binding energies of MF and GA on water ice are crucial to the selectivity of the surface destruction mechanism; individual MF molecules rapidly escape the surface when exposed by water loss, while GA lingers and is destroyed by H. Moderately elevated cosmic-ray ionization rates can increase absolute levels of “complex organic molecule” (COM) production in the ices and increase the MF:GA ratio, but extreme values are destructive for gas-phase COMs. We speculate that the high densities required for extreme MF:GA ratios could be evidence of COM emission dominated by COMs desorbing within a circumstellar disk.

Selective Oxidation of Methanol to Methyl Formate on Gold: The Role of Low-Coordinated Sites Revealed by Isothermal Pulsed Molecular Beam Experiments and AIMD Simulations.

To elucidate the role of low-coordinated sites in the partial methanol oxidation to methyl formate (MeFo), the isothermal reactivity of flat Au(111) and stepped Au(332) in pulsed molecular beam experiments was compared for a broad range of reaction conditions. Low-coordinated step sites were found to enhance MeFo selectivity, especially at low coverage conditions, as found at higher temperatures. The analysis of the transient kinetics provides evidence for the essential role of Au x O y phases for MeFo formation and the complex interplay of different oxygen species for the observed selectivity. Ab initio molecular dynamic simulations yielded microscopic insights in the formation of Au x O y phases on flat and stepped gold surfaces emphasizing the role of low-coordinated sites in their formation. Moreover, associated surface restructuring provides atomic-scale insights which align with the experimentally observed transient kinetics in MeFo formation.

Knockdown of nicotinamide N-methyltransferase ameliorates renal fibrosis caused by ischemia-reperfusion injury and remodels sphingosine metabolism.

CKD currently affects 8.2% to 9.1% of the global population and the CKD mortality rate has increased during recent decades, making it necessary to identify new therapeutic targets. This study investigated the role of nicotinamide N-methyltransferase (NNMT) in renal fibrosis following ischemia-reperfusion injury (IRI), a key factor in chronic kidney disease (CKD) progression. We established a mouse model with a knockdown of NNMT to investigate the impact of this enzyme on renal fibrosis after unilateral IRI. We then utilized histology, immunohistochemistry, and metabolomic analyses to investigate fibrosis markers and sphingolipid metabolism in NNMT-deficient mice. We also utilized an Nnmt lentivirus interference vector or an Nnmt overexpression plasmid to transfect mouse kidney proximal tubule cells, stimulated these cells with TGF-β1, and then measured the pro-fibrotic response and the expression of the methylated and unmethylated forms of Sphk1. The results demonstrated that reducing NNMT expression mitigated fibrosis, inflammation, and lipid deposition, potentially through the modulation of sphingolipid metabolism. Histology, immunohistochemistry, and metabolomic analyses provided evidence of decreased fibrosis and enhanced sphingolipid metabolism in NNMT-deficient mice. NNMT mediated the TGF-β1-induced pro-fibrotic response, knockdown of Nnmt decreased the level of unmethylated Sphk1 and increased the level of methylated Sphk1 in renal tubular epithelial cells. Our findings suggest that NNMT functions in sphingolipid metabolism and has potential as a therapeutic target for CKD. Further research is needed to elucidate the mechanisms linking NNMT to sphingolipid metabolism and renal fibrosis.

Theoretical study on reaction kinetics of the absent HO2 concerted addition reaction on ester group of methyl esters: Case studies of methyl formate and methyl propanoate

In this work, a comprehensive study is performed to specify the contributions of H-abstraction, addition and addition-dissociation reactions of methyl esters + HO2, particularly to the low temperature oxidation. It is imperative to investigate these reactions in detail despite the generally higher bond strength of C=O compared to C=C. The two representative methyl esters, methyl formate (MF, HC(=O)OCH3) and methyl propanoate (MP, CH3CH2C(=O)OCH3), are chosen to theoretically explore the reaction kinetics of the C=O of ester group and HO2. The reaction pathways and potential energy profiles including H-abstraction, addition and addition-dissociation of MF+HO2 and MP+HO2 are investigated at the CCSD(T)/cc-pVxZ(x = T, Q)//M062X/6–311+G(2df,2p) and DLPNO-CCSD(T)/cc-pVxZ(x = T, Q)//M062X/6–311+G(2df,2p) level of theory, respectively. The rate constants of MF/MP + HO2 are determined by using the RRKM/master equation coupled with the 1-D hindered rotor approximation and Eckart tunneling correction. This work delves into the temperature and pressure-dependence of these reaction pathways, as well as the competition relationship among of them. The results indicate that for small ester (MF), the H-abstraction is more competitive across all reaction pathways, but under low temperature (≤ 700 K) and high pressure (≥ 10 atm) conditions, the collisional stabilization of peroxy-alcohol radicals (MF+HO2 = HO-ROO) becomes predominant. For larger ester (MP), this is not necessarily the case as such reactions are unimportant for combustion conditions (rates only appear at 400 K, 100 atm). Furthermore, to assess the impact of these reactions on kinetic modeling, the new rate constants of MF/MP + HO2 are incorporated into the kinetic models of MF and MP, respectively. The updated kinetic models reveal the significant role of H-abstraction reactions in ignition delay time and fuel consumption and the formation of peroxy-alcohol radicals is favorable for decomposition pathways, notably affecting fuel consumption at low temperatures. Consequently, this study highlights the important role of the HO2 addition to the C=O of ester group in the low temperature oxidation mechanism of methyl esters, which has been overlooked in previous studies.

Electrochemical Conversion of CO2 to Methyl Formate in a Flow Electrolyzer with Mixed Propylene Carbonate/Methanol Catholyte

Electrochemical Conversion of CO₂ to Methyl Formate in a Flow Electrolyzer with Mixed Propylene Carbonate/Methanol Catholyte

Highly Efficient Catalyst for Methyl Formate Decomposition Through KOH Activation of Carbon Material Supports

AbstractIn this research, we utilized potassium hydroxide (KOH) to re‐activate activated carbon and subsequently loaded zinc oxide to obtain a more efficient catalyst for the decomposition of methyl formate. The objective of KOH activation was to augment the catalytic activity of the original ZnO/AC catalyst. Various techniques were used to characterize the prepared catalyst samples, including BET, FT‐IR, SEM, XRD, XPS, and CO2‐TPD. We found that KOH re‐activation of AC can increase the carrier's specific surface area and alkaline sites, significantly improving the catalyst's performance.

Correlations of Methyl Formate (CH3OCHO), Dimethyl Ether (CH3OCH3) and Ketene (H2CCO) in High-mass Star-forming Regions

Correlations of Methyl Formate (CH3OCHO), Dimethyl Ether (CH3OCH3) and Ketene (H2CCO) in High-mass Star-forming Regions