From the moss Erythrodontium julaceum Paris growing in Vietnam, julacelide, a new 3-benzylphthalide compound, along with methyl orsellinate, ethyl orsellinate, 4-O-methylhaematommic acid, and zeorin, were isolated and structurally elucidated. Their chemical structures were elucidated through extensive 1D and 2D NMR analysis and high-resolution mass spectroscopy as well as through comparisons to the existing literature. Compound 4-O-methylhaematommic acid was a new natural product. The absolute configuration of julacelide was defined using time-dependent density functional theory (TDDFT) calculations. Julacelide was evaluated for alpha-glucosidase inhibition.
Monthly Archives: September 2023
Glycolipids from Sargassum filipendula, a Natural Alternative for Overcoming ABC Transporter‐Mediated MDR in Cancer
Chemotherapy is a widely used strategy to treat cancer, a disease that causes millions of deaths each year. However, its efficacy is reduced by the overexpression of ABC transporters, which are proteins that expel the drugs used in chemotherapy and involved in the multidrug resistance (MDR). Glycolipids have been identified as potential inhibitors of ABC transporters. Algae of the genus Sargassum contain high levels of glycolipids, being a promising therapeutic alternative against the MDR phenotype. Sargassum filipendula glycolipids were obtained by exhaustive maceration with chloroform/methanol, purified by column and thin layer chromatography, and then characterized by FTIR, NMR, and LC-MS. Cell viability by PI labeling and inhibition of ABC transporters were analyzed by flow cytometry. Assessment of resistance reversal was determined by MTT assay. Ten sulfoquinovosylglycerol-type compounds were found, and six of them are reported for the first time. Moiety 4 (GL-4) showed strong and moderate inhibitory activity against ABCC1 and ABCB1 transporters, respectively. Treatment of GL-4 in combination with the antineoplastic drug vincristine sensitized Lucena-1 cell model to drug and reversed the MDR phenotype. This is the first report of glycolipids isolated from S. filipendula capable of inhibiting ABC transporters and thus overcoming acquired drug resistance.
[ASAP] Novel MCP-Windowed EUV Light Source and Its Mass Spectrometric Application for Detecting Chlorinated Methanes
Analytical Chemistry
DOI: 10.1021/acs.analchem.3c02365
Prebiotic synthesis of 3’,5’ cyclic adenosine and guanosine monophosphates via carbodiimide‐assisted cyclization
3’,5’ cyclic nucleotides play a fundamental role in modern biochemical processes and have been suggested to play a central role at the origin of terrestrial life. In the current work we suggest that a formamide-based systems chemistry may account for their availability on the early Earth. In particular, we demonstrate that in a liquid formamide environment at elevated temperatures 3’,5’ cyclic nucleotides are obtained in good yield and selectivity upon intramolecular cyclization of 5’ phosphorylated nucleosides in the presence of carbodiimides.
The stability of oxygen‐centered radicals and its response to hydrogen bonding interactions
The thermodynamic stability of various alkoxy/aryloxy/peroxy radicals, as well as TEMPO and triplet dioxygen has been explored at a variety of theoretical levels. The effects of hydrogen bonding interactions on the stability of oxygen-centered radicals have been probed by addition of a single solvating water molecule.
Abstract
The stability of various alkoxy/aryloxy/peroxy radicals, as well as TEMPO and triplet dioxygen (3O2) has been explored at a variety of theoretical levels. Good correlations between RSEtheor and RSEexp are found for hybrid DFT methods, for compound schemes such as G3B3-D3, and also for DLPNO-CCSD(T) calculations. The effects of hydrogen bonding interactions on the stability of oxygen-centered radicals have been probed by addition of a single solvating water molecule. While this water molecule always acts as a H-bond donor to the oxygen-centered radical itself, it can act as a H-bond donor or acceptor to the respective closed-shell parent.
Study on the Turbulent Vortex Structure Characteristics of a Two‐Layer Impinging Stream Reactor
The intensity of the vortex structure in a two-layer impinging stream reactor was quantitatively analyzed according to the Liutex method. The bound vortex, trapped vortex, and longitudinal vortex in the reactor were studied for the first time. The formation of vortices is related to the velocity field and pressure field. In this paper, the field synergy theory is used to evaluate their synergy.
Abstract
The structure of the turbulent vortex in a two-layer impinging stream reactor was studied by large eddy simulation. The distributions of vortex intensity, turbulent kinetic energy, and shear stress at different Reynolds numbers Re, nozzle spacings L, and nozzle layer spacings are discussed. The relationship between vortex structure and mixing effect in the flow field is revealed. The effects of longitudinal swirls and shear flow characteristics are analyzed. Finally, the field synergy theory is used for evaluation. With increasing Re, the vortex intensity and average shear stress increase. The nozzle spacing and layer spacing affect the mixing effect in the reactor by controlling the change of vortex structure in the flow field. When L/D = 3, where D is the nozzle diameter, the energy loss is the smallest and the mixing effect is the best. The research results provide a theoretical reference for the structural optimization of the impinging stream reactor.
[ASAP] Role and Function of Polymer Binder Thickeners in Carbon Pastes for Multiporous-Layered-Electrode Perovskite Solar Cells
Chemistry of Materials
DOI: 10.1021/acs.chemmater.3c01483
Ionic‐Liquid‐Based Nanofluids and Their Heat‐Transfer Applications: A Comprehensive Review
One of the emerging study areas to boost the heat transfer rates of the thermal devices is the further improvement of the thermophysical properties and thermal performance of ionic liquids (IL) by dispersing nanoparticles. This work provides a summary of the most recent research on the use of ionic liquid nanofluids as heat transfer fluids. Additionally, the methods for analyzing the thermophysical properties and creating IL nanofluids are discussed.
Abstract
Due to the improved thermophysical characteristics of ionic liquids (ILs), such as their strong ionic conductivity, negligible vapor pressure, and thermal stability at high temperatures, they are being looked at viable contender for future heat transfer fluids. Additionally, the dispersing nanoparticles can further improve the thermophysical characteristics and thermal performance of ionic liquids, which is one of the emerging research interests to increase the heat transfer rates of the thermal devices. The latest investigations about the utilization of ionic liquid nanofluids as a heat transfer fluid is summarized in this work. These summaries are broken down into three types: (a) the thermophysical parameters including thermal conductivity, viscosity, density, and specific heat of ionic liquids (base fluids), (b) the thermophysical properties like thermal conductivity, viscosity, density, and viscosity of ionic liquids based nanofluids (IL nanofluids), and (iii) utilization of IL nanofluids as a heat transfer fluid in the thermal devices. The techniques for measuring the thermophysical characteristics and the synthesis of IL nanofluids are also covered. The suggestions for potential future research directions for IL nanofluids are summarized.
Structural and Electronic Properties of Two‐Dimensional Materials: A Machine‐Learning‐Guided Prediction
For the purpose of predicting the structural and electronic properties of two-dimensional materials, a universal machine learning approach is reported.
Abstract
The growing number of studies and interest in two-dimensional (2D) materials has not yet resulted in a wide range of material applications. This is a result of difficulties in getting the properties, which are often determined through numerical experiments or through first-principles predictions, both of which require lots of time and resources. Here we provide a general machine learning (ML) model that works incredibly well as a predictor for a variety of electronic and structural properties such as band gap, fermi level, work function, total energy and area of unit cell for a wide range of 2D materials derived from the Computational 2D Materials Database (C2DB). Our predicted model for classification of samples works extraordinarily well and gives an accuracy of around 99 %. We are able to successfully decrease the number of studied features by employing a strict permutation-based feature selection method along with the sure independence screening and sparsifying operator (SISSO), which further supports the design recommendations for the identification of novel 2D materials with the desired properties.
Organometallic Allene [(μ‐C)(Fe(CO)4)2]: Bridging Carbon Showing Transformation from Classical Electron‐Sharing Bonding to Double σ‐Donor and Double π‐Acceptor Ligation
![Organometallic Allene [(μ-C)(Fe(CO)4)2]: Bridging Carbon Showing Transformation from Classical Electron-Sharing Bonding to Double σ-Donor and Double π-Acceptor Ligation](https://chemistry-europe.onlinelibrary.wiley.com/cms/asset/690d5856-85ca-4067-9925-eb138d459b33/cphc202300528-toc-0001-m.png)
Diversity in organometallic allenes: A structure-bonding study on two isomeric organometallic allenes [(μ-C)(Fe(CO)4)2] reveals a bis-pseudoallylic anionic delocalisation, similar to organic allene C(CH2)2, in the first case, and a typical three-center bis-allylic anionic delocalisation in the second one. A quantitative bonding analysis shows the transformation of the central carbon atom from a classical tetravalent coordinating center to a double σ-donor double π-acceptor ligand.
Abstract
Allenes (R2C=C=CR2) have been traditionally perceived to feature localized orthogonal π-bonds between the carbon centres. We have carried out quantum-mechanical studies of the organometallic allenes envisioned by the isolobal replacement of the terminal CH2 groups by the d8 Fe(CO)4 fragment. Our studies have identified two organometallic allenes viz. D2d symmetric [(μ-C)(Fe(CO)4)2] (2) and D3 symmetric [(μ-C)(Fe(CO)4)2] (3) with trigonal bipyramidal coordination at the Fe atoms. Compound 2 features the bridging carbon atom in an equatorial position with respect to the ligands on the TM centre, while 3 features the central carbon atom in an axial position. The bis-pseudoallylic anionic delocalisation proposed in the C2-C1-C3 spine of organic allene is retained in the organometallic allene 2, and is transformed to a typical three-centre bis-allylic anionic delocalisation in the organometallic allene 3. The topological analysis of electron density also indicates a bis-allylic anionic type delocalisation in the organometallic allenes. The quantitative bonding analysis using the EDA-NOCV method suggests a transition from classical electron-sharing bonding between the central carbon atom and the terminal groups in 1 to donor-acceptor bonding in 3. Meanwhile, both electron-sharing and donor-acceptor bonding models are found to be probable heuristic bonding representations in the organometallic allene 2.