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A full-dimensional analytical potential energy surface (PES) is developed for the Cl + CH3CN reaction following our previous work on the benchmark ab initio characterization of the stationary points. The spin–orbit-corrected PES is constructed using the Robosurfer program and a fifth-order permutationally invariant polynomial method for fitting the high-accuracy energy points determined by a ManyHF-based coupled-cluster/triple-zeta-quality composite method. Quasi-classical trajectory simulations are performed at six collision energies between 10 and 60 kcal mol−1. Multiple low-probability product channels are found, including isomerization to isonitrile (CH3NC), but out of the eight possible channels, only the H-abstraction has significant reaction probability; thus, detailed dynamics studies are carried out only for this reaction. The cross sections and opacity functions show that the probability of the H-abstraction reaction increases with increasing collision energy (Ecoll). Scattering angle, initial attack angle, and product relative translational energy distributions indicate that the mechanism changes with the collision energy from indirect/rebound to direct stripping. The distribution of initial attack angles shows a clear preference for methyl group attack but with different angles at different Ecoll values. Post-reaction energy distributions show that the energy transfer is biased toward the products' relative translational energy instead of their internal energy. Rotational and vibrational energy have about the same amount of contribution to the internal energy in the case of both products (HCl and CH2CN), i.e., both of them are formed with high rotational excitations. HCl is produced mostly in the ground vibrational state, while a notable fraction of CH2CN is formed with vibrational excitation. [ABSTRACT FROM AUTHOR]

In this study, peptides designed using fragments of an antifreeze protein (AFP) from the freeze-tolerant insect Tenebrio molitor, TmAFP, were evaluated as inhibitors of clathrate hydrate formation. It was found that these peptides exhibit inhibitory effects by both direct and indirect mechanisms. The direct mechanism involves the displacement of methane molecules by hydrophobic methyl groups from threonine residues, preventing their diffusion to the hydrate surface. The indirect mechanism is characterized by the formation of cylindrical gas bubbles, the morphology of which reduces the pressure difference at the bubble interface, thereby slowing methane transport. The transfer of methane to the hydrate interface is primarily dominated by gas bubbles in the presence of antifreeze peptides. Spherical bubbles facilitate methane migration and potentially accelerate hydrate formation; conversely, the promotion of a cylindrical bubble morphology by two of the designed systems was found to mitigate this effect, leading to slower methane transport and reduced hydrate growth. These findings provide valuable guidance for the design of effective peptide-based inhibitors of natural-gas hydrate formation with potential applications in the energy and environmental sectors. [ABSTRACT FROM AUTHOR]

The lifetime of a hydrogen bond between water and dimethyl sulfoxide (DMSO) is found to be considerably longer than that between two water molecules in neat water. This is counter-intuitive because the charge on the oxygen in DMSO is considerably less than that in water. Additionally, the strength of the water–dimethyl sulfoxide (w–D) hydrogen bond is found to be strongly composition dependent; the lifetime of the hydrogen bond is ten times larger at 30% than at very low concentrations. Using computer simulations, we perform microscopic structural and dynamic analysis to find that these anomalies arise at least partly from an "action-at-a-distance" effect where the attraction between the hydrophobic methyl groups results in the self-aggregation of DMSO molecules that "cages" both the rotational and linear motions of the molecules involved. This is reflected in the observed strong correlation of the lifetime with the local coordination number of the associated methyl groups. The elongated w–D h-bond lifetime causes a slowdown of collective dynamics and affects the lifetime of the w–w h-bond. This nonlinear feedback mechanism explains the strong composition dependence of viscosity and is anticipated to play a dominant role in many self-assemblies. Furthermore, the w–D hydrogen bond breaking mechanism changes from low to high DMSO concentration, a phenomenon not anticipated a priori. We introduce a new order parameter-based free energy surface of the bond breaking pathway. A two-dimensional transition state rate theory calculation is performed for the lifetime of the w–D h-bond that is found to be semi-quantitatively accurate. [ABSTRACT FROM AUTHOR]

We investigated the rotational spectrum of 2,5-dimethylfluorobenzene containing coupled large amplitude motions of two methyl groups in the frequency range from 2 to 26.5 GHz using a pulsed molecular jet Fourier transform microwave spectrometer. The internal rotation of two inequivalent methyl groups with low torsional barriers (around 16 and 226 cm−1) causes splittings of all rotational transitions into quintets with separations of up to hundreds of MHz between the torsional components. Spectral analysis and modeling of the observed splittings were performed using the programs XIAM and BELGI-Cs-2Tops, whereby the latter achieved measurement accuracy. The methyl internal rotation can be used to examine the electronic and steric environments around the methyl group because they affect the methyl torsional barrier. Electronic properties play a particularly important role in aromatic molecules in the presence of a π-conjugated double bond system. The experimental results were compared with those of quantum chemistry. Benchmark calculations resulted in the conclusion that the B3LYP-D3BJ/6-311++G(d,p) level of theory can be recommended for predicting rotational constants to guide the microwave spectral assignment of dimethylfluorobenzenes in particular and toluene derivatives in general. [ABSTRACT FROM AUTHOR]

In this study, the total ion yield near-edge x-ray absorption fine structure spectra of four similar peptoid molecules, which differ in the numbers and positions of methyl groups, were investigated experimentally and theoretically. At each excitation energy, the intensity and branching ratio of each ionic product were measured. At a few resonant excitation energies, a specific dissociation of the C–CO bond at the nitrogen and oxygen K-edges and of the N–CO bond at the carbon K-edge was dominant, which correlated well with the predicted destination antibonding orbitals of the core electron excitation. These specific dissociation mechanisms of small peptoid molecules could provide insights into similar phenomena that occur in peptide molecules. [ABSTRACT FROM AUTHOR]

Two routes leading to thiosemicarbazone-based complexes are reported with the view of developing ionic titanium complexes as cytotoxic metallodrugs. The reaction of bis(π-η5:σ-η1-pentafulvene)titanium complexes with most thiosemicarbazones gives κ2N,S thiosemicarbazonido complexes via deprotonation of the acidic N–H bond by the pentafulvene ligand. The use of an o-cresyl TSCN revealed a κ2N,O coordination mode by deprotonation of the O–H bond. The protonolysis of the remaining pentafulvene unit in these complexes with Brønsted acids and further functionalization with multiple bond substrates were attempted. The reaction of titanocene(III) triflate with TSCN reveals an unprecedented reactivity and leads to Ti(III) thiosemicarbazone complexes. The Ti(IV) complexes were characterized using NMR experiments and the nitrogen cores were identified via1H,15N HMBC experiments by coupling with the adjacent aldimine proton or the methyl group of the thiosemicarbazone. These are the first structural examples of thiosemicarbazone-based titanium complexes obtained from single-crystal X-ray diffraction. [ABSTRACT FROM AUTHOR]

Two dumbbell‐shaped building blocks (TMB and TMBT), featuring methyl benzoate groups as hydrogen bond units, are selected to construct heterostructures of HOFs, aiming to achieve multiple functions including white luminescence, stimulus‐response behavior, as well as application in information encryption. TMB molecules are self‐assembled to form a flexible HOF (X‐HOF‐8) in p‐xylene, containing solvent channels and blue fluorescence. Upon removal of guests, it can transform into a nonporous crystal with gray fluorescence. In contrast, TMBT forms a guest‐free HOF (X‐HOF‐9) displaying orange fluorescence. They could form bulk heterojunction (BHJ) HOFs with energy transfer from TMB to TMBT, exhibiting composition‐dependent fluorescent color. Notably, white emission can be achieved in BHJ HOFs and can be converted to gray fluorescence upon guest removal; subsequently, white fluorescence is restored upon re‐capturing guests. Furthermore, rod‐like triblock heterojunction (THJ) HOFs can also be constructed, which exhibit regulatory behavior in response to gaining or losing guests. The unique luminescent characteristics and stimulus responsiveness of these HOFs make them an excellent platform for applications in anticounterfeit. This represents the pioneering achievement of white light emission in a BHJ HOF, as well as the groundbreaking realization of a THJ HOF with remarkable exciting response characteristics. [ABSTRACT FROM AUTHOR]

Targeting pour point depressants of low-molecular weight and branched polyethylenes, a series of 9-[2,4-bis(benzhydryl)-6-R-phenylimino]-5,6,7,8-tetrahydro-cycloheptapyridine-nickel complexes (Ni1–Ni10) were developed as efficient precatalysts. Upon activation with either EASC or MAO, all nickel complex precatalysts exhibited high activity [up to 8.12 × 106 g PE (mol of Ni)−1 h−1] with single-site behavior toward ethylene polymerization, producing low-molecular weight and unimodal polyethylenes. The resultant polyethylenes possessed high branching with predominant methyl groups and longer chains, along with either internal vinylene or vinyl end groups. The activities of these complex precatalysts were heavily rationalized on the basis of the electronic and steric influences of their 6-R-substituents, with bromides following the order of Ni5 (F) > Ni4 (Cl) > Ni1 (Me) > Ni2 (Et) > Ni3 (iPr) and chlorides following the order of Ni10 (F) > Ni9 (Cl) > Ni6 (Me) > Ni7 (Et) > Ni8 (iPr). DFT calculations revealed the crucial role of agostic interactions (–Ni⋯H–C(Ph2)) between the nickel metal and the hydrogen atom of the ortho bulky group in achieving high catalytic activity and intramolecular hydrogen bonding with the fluoride atom in producing low Mw PE wax. Moreover, the organic compounds and nickel complexes were well characterized, including representative complexes Ni3 and Ni4, via single-crystal X-ray diffraction. [ABSTRACT FROM AUTHOR]

To evaluate bifunctional ligand reactivity involving NH acidic sites in the secondary coordination sphere, complexes where the proton has been substituted with a methyl group (NMe) are often investigated. An alternative strategy involves substitution of the NH group for an O. This contribution considers and compares the merits of these approaches; the synthesis and characterization of cationic square‐planar Rh carbonyl complexes bearing diprotic bispyrazole pyridine ligand L1, and the bis‐methylated pyrazole pyridine ligand L1Me are described. The syntheses and characterization of the novel monoprotic pyrazole isoxazole pyridine ligand L2 and aprotic bisisoxazole pyridine ligand L3, and their corresponding Rh carbonyl complexes are also described. Comparison of the CO stretching frequencies of the four Rh complexes suggest that substitutions of NH with NMe, as well as with O, lead to significant electronic differences. These electronic differences result in different reactivities with respect to ligand addition/substitution of the Rh carbonyl complexes. Overall, the data suggest that electronic differences arising due to the NH substitutions can be significant and should be considered when the NH group is substituted in investigations of the participation of the NH proton in a reaction. [ABSTRACT FROM AUTHOR]

The benzoanellated tricyclic boratirene 2⋅Li(Et2O) was synthesized by reductive dehalogenation of C─borylborirene 1 with Lithium powder, and its distorted structure was determined by X‐ray analysis. The formation of compound 2⋅Li(Et2O) can be described as a result of the insertion of the carbene‐like boron atom into the C─H bond of a methyl group at a duryl ring (duryl ring = 2,3,5,6‐tetramethylphenyl) in the ortho position. This new tricyclic compound contains a highly shielded, formally three‐coordinated boron atom with δ11B = 27 ppm. However, the 11B chemical shift in the range of 65 to 85 ppm is expected for carbon‐bonded three‐coordinated boron atoms. The reason for the high shielding of this boron atom in 2⋅Li(Et2O) is a very strong C─B hyperconjugation. The strained, and negatively charged three‐membered ring in 2⋅Li(Et2O) is an optimal component for a strong hyperconjugative interaction, leading to the formation of a three‐center two‐electron (3c‐2e) σ bond with the empty p orbital of the boron atom, resulting in a strong distortion of the six‐membered ring. [ABSTRACT FROM AUTHOR]

Background: It is generally accepted that methylation status of CpG sites spaced up to 50 bp apart is correlated, and accumulation of locally disordered methylation at adjacent CpG sites is involved in neoplastic transformation, acting in similar way as stochastic accumulation of mutations. Results: We used EPIC microarray data from 596 samples, representing 12 healthy tissue and cell types, as well as 572 blood cancer specimens to analyze methylation status of adjacent CpG sites across human genome, and subsequently validated our findings with NGS and Sanger sequencing. Our analysis showed that there is a subset of the adjacent CpG sites in human genome, with cytosine at one CpG site methylated and the other devoid of methyl group. These loci map to enhancers that are targeted by families of transcription factors involved in cell differentiation. Moreover, our results suggest that the methylation at these loci differ between alleles within a cell, what allows for remarkable level of heterogeneity of methylation patterns. However, different types of specialized cells acquire only one specific and stable pattern of methylation at each of these loci and that pattern is to a large extent lost during neoplastic transformation. Conclusions: We identified a substantial number of adjacent CpG loci in human genome that display remarkably stable and cell type specific methylation pattern. The methylation pattern at these loci appears to reflect different methylation of alleles in cells. Furthermore, we showed that changes of methylation status at those loci are likely to be involved in regulation of the activity of enhancers and contribute to neoplastic transformation. [ABSTRACT FROM AUTHOR]

Approximately two-thirds of the estimated one-billion metric tons of methane produced annually by methanogens is derived from the cleavage of acetate. Acetate is broken down by a Ni-Fe-S-containing A-cluster within the enzyme acetyl-CoA synthase (ACS) to carbon monoxide (CO) and a methyl group (CH3 +). The methyl group ultimately forms the greenhouse gas methane, whereas CO is converted to the greenhouse gas carbon dioxide (CO2) by a Ni-Fe-S-containing C-cluster within the enzyme carbon monoxide dehydrogenase (CODH). Although structures have been solved of CODH/ACS from acetogens, which use these enzymes to make acetate from CO2, no structure of a CODH/ACS from a methanogen has been reported. In this work, we use cryo-electron microscopy to reveal the structure of a methanogenic CODH and CODH/ACS from Methanosarcina thermophila (MetCODH/ACS). We find that the N-terminal domain of acetogenic ACS, which is missing in all methanogens, is replaced by a domain of CODH. This CODH domain provides a channel for CO to travel between the two catalytic Ni-Fe-S clusters. It generates the binding surface for ACS and creates a remarkably similar CO alcove above the A-cluster using residues from CODH rather than ACS. Comparison of our MetCODH/ACS structure with our MetCODH structure reveals a molecular mechanism to restrict gas flow from the CO channel when ACS departs, preventing CO escape into the cell. Overall, these long-awaited structures of a methanogenic CODH/ACS reveal striking functional similarities to their acetogenic counterparts despite a substantial difference in domain organization. [ABSTRACT FROM AUTHOR]

AbstractEpimedium is widely used in traditional Chinese medicine and contains rich bioactive compounds. These compounds often have a methyl group at their 4’-OH position catalyzed by methyltransferases. Therefore, studying methyltransferases in Epimedium plants is of great significance. In this study, a flavonol methyltransferase, EpOMT4, was isolated from Epimedium pseudowushanense B.L. Guo. The recombinant enzyme regiospecifically transferred a methyl group to the 4’-OH position of 8-prenylkaempferol forming icaritin. The study demonstrates that enzymatic methylation of flavonoids in Epimedium plants holds significant potential and could provide a promising alternative method for the biosynthetic production of bioactive methylated prenylflavonoids. [ABSTRACT FROM AUTHOR]

Herein, we obtained two supramolecular assemblies with layered structures from melamine, N-methylmelamine, and hexynyl-cyanuric acid in water. By combination of X-ray diffraction, electron microscopy, and molecular dynamics studies, we found that introducing one methyl group in melamine alters the arrangement of the layers in these structures. [ABSTRACT FROM AUTHOR]

It has been found out that Pd-Co-based catalyst, supported on anodized aluminum, possesses very high activity in combustion reactions of C1–C6 alkanes and toluene. The catalyst characterization has been made by N2-pysisorption, XRD, SEM, XPS, FTIR, TEM, and EPR methods. In view of the great interest, methane combustion was investigated in detail. It is ascertained that the complete oxidation of methane proceeds by dissociative adsorption on PdO and formation of hydroxyl and methyl groups, the former being highly reactive, and it undergoes further reaction to oxygen-containing intermediates, whereupon HCHO is one of them. The presence of Co2+ cations promotes greatly oxygen adsorption. The dissociative adsorption is favored on neighboring Co2+ cations, leading to the formation of bridging peroxides. Further, the oxygen dissociates on the nearest Pd2+ cations. According to the results from the experimental data, instrumental methods, and the observed kinetics and DFT model calculations, it can be concluded that the reaction pathway over Pd+Co/anodic alumina support (AAS) catalyst proceeds most probably through Mars–van Krevelen. The obtained data on the kinetics were used for simulation of the methane combustion in a full-scale adiabatic reactor. [ABSTRACT FROM AUTHOR]

Dichloromethane (DCM), a common hazardous industrial chemical, is anaerobically metabolized by four bacterial genera: Dehalobacter, Dehalobacterium, Ca. Dichloromethanomonas, and Ca. Formimonas. However, the pivotal methyltransferases responsible for DCM transformation have remained elusive. In this study, we investigated the DCM catabolism of Dehalobacterium formicoaceticum strain EZ94, contained in an enriched culture, using a combination of biochemical approaches. Initially, enzymatic assays were conducted with cell-free protein extracts, after protein separation by blue native polyacrylamide gel electrophoresis. In the slices with the highest DCM transformation activity, a high absolute abundance of the methyltransferase MecC was revealed by mass spectrometry. Enzymatic activity assays with heterologously expressed MecB, MecC, and MecE from strain EZ94 showed complete DCM transformation only when all three enzymes were present. Our experimental results, coupled with the computational analysis of MecB, MecC, and MecE sequences, enabled us to assign specific roles in DCM transformation to each of the proteins. Our findings reveal that both MecE and MecC are zinc-dependent methyltransferases responsible for DCM demethylation and re-methylation of a product, respectively. MecB functions as a cobalamin-dependent shuttle protein transferring the methyl group between MecE and MecC. This study provides the first biochemical evidence of the enzymes involved in the anaerobic metabolism of DCM. IMPORTANCE Dichloromethane (DCM) is a priority regulated pollutant frequently detected in groundwater. In this work, we identify the proteins responsible for the transformation of DCM fermentation in Dehalobacterium formicoaceticum strain EZ94 using a combination of biochemical approaches, heterologous expression of proteins, and computational analysis. These findings provide the basis to apply these proteins as biological markers to monitor bioremediation processes in the field. [ABSTRACT FROM AUTHOR]

A family of ten amino‐containing bis(arylimino)acenaphthene‐nickel (II) bromide complexes varied in the electronic properties of para‐substituents (R = Me, iPr, tBu, OMe, Cl, F, NO2) as well as two amino‐free comparators (R = Me, Cl) are synthesized in good yield from their corresponding unsymmetrical N,N'‐ligands. All organic compounds are well characterized by different analysis techniques. On activation with Me2AlCl, all nickel complexes exhibit moderate to high activities with a maximum activity up to 14.19 × 106 g (PE) mol−1 (Ni) h−1 and deliver narrow dispersed polyethylene (PDI: 1.85–2.65) with adjustable molecular weight values (Mw: 5.27–18.49 × 105 g mol−1). The presence of remote fluoro‐ group and (4‐amino‐3,5‐dimethylphenyl)(phenyl)methyl group has their own unique influence on activity due to their different electronic and steric properties. Nevertheless, the latter with higher steric hindrance results in better thermal stability of the current catalytic system. Moreover, all polyethylene is highly branched and exhibits typical characteristics of thermoplastic elastomers, especially good mechanical properties (εb up to 1175%) and elastic recovery rate (up to 86%). [ABSTRACT FROM AUTHOR]

First case of regiospecific formation of indole fused with a triterpene scaffold is observed. Starting from 3‐oxo‐24‐nor‐allobetulin Fischer reaction with phenylhydrazine under the influence of weak acid catalyst led to 3H‐indole (indolenine) 4. This process was accompanied by a change in the configuration of the methyl group at C‐4 that was confirmed by x‐ray diffraction method. On the other hand, 3,2‐indole 5 was synthesized under the influence of strong acid catalyst (using phenylhydrazine hydrochloride in AcOH acid or phenylhydrazine in MeOH with a few drops of HCl). [ABSTRACT FROM AUTHOR]

• The current study focused on the prediction of 5-methylcytosine (m5C) sites in RNA sequence • A novel method of feature generation has been proposed by incorporating statistical moments for features reduction. • The LSTM model revealed the maximum accuracy score in independent set test and k-fold cross validation as well. • A webserver, m5c-iDeep, is freely available online for the enhancement of research in m5C sites detection. 5-Methylcytosine (m5c) is a modified cytosine base which is formed as the result of addition of methyl group added at position 5 of carbon. This modification is one of the most common PTM that used to occur in almost all types of RNA. The conventional laboratory methods do not provide quick reliable identification of m5c sites. However, the sequence data readiness has made it feasible to develop computationally intelligent models that optimize the identification process for accuracy and robustness. The present research focused on the development of in-silico methods built using deep learning models. The encoded data was then fed into deep learning models, which included gated recurrent unit (GRU), long short-term memory (LSTM), and bi-directional LSTM (Bi-LSTM). After that, the models were subjected to a rigorous evaluation process that included both independent set testing and 10-fold cross validation. The results revealed that LSTM-based model, m5c-iDeep, outperformed revealing 99.9 % accuracy while comparing with existing m5c predictors. In order to facilitate researchers, m5c-iDeep was also deployed on a web-based server which is accessible at https://taseersuleman-m5c-ideep-m5c-ideep.streamlit.app/. [ABSTRACT FROM AUTHOR]

This article reports an efficient and practical microwave-assisted MMPP-promoted synthesis of novel pyrazolyl sulfones from the corresponding 4-(alkyl/cycloalkylthio)-1H-pyrazoles. The reaction of 4-(alkyl/cycloalkylthio)-1H-pyrazoles with magnesium bis(monoperoxyphthalate)hexahydrate (MMPP) as an oxidizing agent afforded the corresponding 4-(alkyl/cycloalkylsulfonyl)-1,3-disubstituted-1H-pyrazoles in 85–95% yield. This method's benefits include its straightforward operation, simple workup, and use of an inexpensive, halogen-free MMPP oxidant that is easy to use and reasonably stable. All synthesized pyrazolyl sulfones were examined against bacterial and fungal strains, and notable antimicrobial activity was demonstrated by a few of the compounds. In order to investigate the prospect of connecting compounds with the highest yield and antimicrobial activity with their opto-electronic properties, time-resolved photoluminescence investigations for compounds 5a, 5b, and 5d were conducted. The tunable spectrum was observed in the micro-second time domain in all three cases, with fluorescent lifetime found higher in the compound having methyl group, intermediate with phenyl group, and lowest with the p-nitrophenyl group. Our procedures will encourage additional research into the valuable properties of pyrazolyl sulfones now that they are widely available with the structural complexity illustrated here. [ABSTRACT FROM AUTHOR]

In this study, six compounds were obtained from a methanolic extract of air-dried leaves of Senna alata and one of them, a triterpenoid (secofriedelane) named as 7-(2-carboxyethyl)-3, 4b, 6a, 8, 10a, 12a-hexamethyl-8-vinyloctadecahydrochrysene-3-carboxylic acid (5) was isolated for the first time from this plant. Then, its chemical structure was detailed and characterised by FT-IR, 1H and 13C- NMR and ESI-MS. Besides, two chemical-modified derivatives of secofriedelane (5a, 5b) were synthesised by methylation and allylation reactions, respectively, and their in vitro antibacterial activities were also evaluated. The results revealed that all the triterpenes showed, against gram-positive and -negative bacterial strains, good and moderate antibacterial activities with bactericidal effects that were enhanced by the methyl groups and altered with the allyl ones. Moreover, the molecular docking results of 5, 5a and 5b in the DNA gyrase (2XCT) active site showed that triterpene 5 has a good score very close to reference (ciprofloxacin). [ABSTRACT FROM AUTHOR]

1,4,5,8‐Tetrafluoroacridine was successfully synthesized from 1,4,5,8‐tetrafluoroacridone through transfer hydrogenation using an in‐house ruthenium pincer catalyst followed by in situ dehydration. The synthetic protocol involves the copper‐catalyzed coupling of 2‐amino‐3,6‐difluorobenzoic acid 1 and 1,4‐difluoro‐2‐iodobenzene 2 to obtain 3 followed by cyclization using polyphosphoric acid to get the 1,4,5,8‐tetrafluoroacridone 4. Common synthetic strategies for converting 4 to the 1,4,5,8‐tetrafluoroacridine 5 were unsuccessful and the transfer hydrogenation approach proved to be most fruitful. 1,4,5,8‐Tetrafluoroacridone 4 can be N‐methylated to give 9. The investigation into the photophysical properties of 4, 5, and 9 revealed that the average photoluminescence (PL) lifetime of the acridine derivatives was longer in the aqueous medium than in ethanol and methanol, indicating the influence of the solvent environment on the excited‐state dynamics. To assess their potential therapeutic applications, the cytotoxic activity of these compounds was evaluated against AGS and IMR‐32 cells, and compound 9 showed significant activity. The addition of methyl group to the acridone was found helpful in enhancing the solubility and biological activity. [ABSTRACT FROM AUTHOR]

para‐Nitrophenyl (PNP) ethers of glycosides are important building blocks en route to functional carbohydrates. They are stable in neutral media, however, under basic conditions such as during the Zemplén deacylation of sugars, aryl migration is frequently observed. We have employed a library of O‐PNP‐substituted methyl glycosides of the manno‐, galacto‐, gluco‐ and altro‐series to study the kinetics of aryl migration in MeOH/sodium methoxide using NMR spectroscopy revealing that migration between cis‐oriented OH groups is faster than between trans‐oriented ones. The rate constants of migration decrease in the order of Alt>Man>Gal>Glc and are related to the energy barriers of chair conformation inversion. The energy profile of the 3 to 4‐PNP migration in methyl mannoside was calculated using DFT methods suggesting the Meisenheimer complex is an intermediate of PNP migration and that coordination of the sodium cation has a major impact on the energy profile. [ABSTRACT FROM AUTHOR]

Although many researchers have devoted their much effort to establish the strategy for developing a stimuli‐responsive molecule and tuning of their properties according to the preprogrammed design, it is still challenging to create desired molecules from the scratch. We recently demonstrated that the molecules with a large structural difference between the theoretically optimized structures in the ground and excited states have a potential to exhibit stimuli‐responsive luminescent properties. We defined these molecules as an excitation‐driven molecule and have shown that they are a versatile platform for designing stimuli‐responsive luminescent molecules. Herein, based on the concept of excitation‐driven molecules, we show that the hypervalent tin‐fused azomethine (TAm) compounds possessing aggregation‐induced emission (AIE) properties can be obtained by simple chemical modification with a methyl group although conventional TAm derivatives are well known to be highly luminescent compounds in solution. Furthermore, by combining the solid‐state luminescence property of AIE and the coordination number shifts of the hypervalent tin atom, the thermoresponsive films operating below the freezing point are fabricated with the polymer. In this study, we apply the concept of excitation‐driven molecules to the hypervalent compounds and demonstrate to obtain the novel functional materials. [ABSTRACT FROM AUTHOR]

Non‐centrosymmetric organics are promising nonlinear optical (NLO) candidates, which always exhibit a short UV absorption cutoff edge, and a strong second harmonic generation (SHG) response, but an overlarge birefringence. Here, in order to optimize the birefringence, the methyl modulation of π‐conjugated organic planar units is proposed and implemented with the urea structure as a template. Thus, N‐methylurea and N,N'‐dimethylurea crystals are obtained by partially replacing hydrogen atoms with methyl groups. This replacement reduces hydrogen donors and weakens interchain hydrogen bonds, which facilitates the decreasing density and the parallel arrangement of π‐conjugated planar units. Hence, both N‐methylurea and N,N'‐dimethylurea crystals exhibit not only an optimized birefringence (N‐methylurea ≈0.099 and N,N'‐dimethylurea ≈0.072 at 546 nm) but also an enhanced SHG response (N‐methylurea ≈1.2 × β‐BaB2O4 and N,N'‐dimethylurea ≈1.9 × β‐BaB2O4), while maintaining a short UV absorption cutoff edge. Therefore, this work provides a novel strategy for the structural design and performance modulation of organic NLO crystals. [ABSTRACT FROM AUTHOR]

Irisquinone is a tumor radiotherapy sensitizer and has been found to have broad-spectrum antitumor activity in recent years. The current acquisition method of extracting and purifying from semen irisis has greatly limited its wide application and activity study deeply. In this work an efficient route for the synthesis of the irisquinone was investigated to solve the source of it. The target compound was synthesized by 5-step reactions to Wittig reaction, reduction, oxidation, Wittig reaction, and oxidation using 3,5-dimethoxycarboxaldehyde as the starting material with an overall yield of 48%. The key factors such as the ratio of raw materials, temperatures, solvents, reaction times, and types of base for the main reactions were optimized. In addition, the deprotection and reduction were completed with Pd/C catalytic simultaneously when compound 2 was synthesized from compound 1. In the last reaction, the 3,5-dimethoxybenzene moiety of compound 4 was directly oxidized to 6-methoxy-1,4-benzoquinone by K3 [Fe(CN)6 ]/H2 O2 without the need to selectively remove the methyl protecting group, which were the innovative points in the experimental route design of the irisquinone synthesis. This work has opened new perspectives for the artificial synthesis and the development of irisquinone. [ABSTRACT FROM AUTHOR]

Chalcogen bonds (ChB) are moderately strong, directional, and specific non‐covalent interactions that have garnered substantial interest over the last decades. Specifically, the presence of two σ‐holes offers great potential for crystal engineering, catalysis, biochemistry, and molecular sensing. However, ChB applications are currently hampered by a lack of methods to characterize and control chalcogen bonds. Here, we report on the influence of various substituents (halogens, cyano, and methyl groups) on the observed self‐complementary ChB networks of 2,1,3‐benzoselenadiazoles. From molecular electrostatic potential calculations, we show that the electrostatic surface potentials (ESP) of the σ‐holes on selenium are largely influenced by the electron‐withdrawing character of these substituents. Structural analyses via X‐ray diffraction reveal a variety of ChB geometries and binding modes that are rationalized via the computed ESP maps, although the structure of 5,6‐dimethyl‐2,1,3‐benzoselenadiazole also demonstrates the influence of steric interactions. 77Se solid‐state magic‐angle spinning NMR spectroscopy, in particular the analysis of the selenium chemical shift tensors, is found to be an effective probe able to characterize both structural and electrostatic features of these self‐complementary ChB systems. We find a positive correlation between the value of the ESP maxima at the σ‐holes and the experimentally measured 77Se isotropic chemical shift, while the skew of the chemical shift tensor is established as a metric which is reflective of the ChB binding motif. [ABSTRACT FROM AUTHOR]

Methyltransferases are gaining traction as a method to achieve greener and regioselective methylations of a wide array of substrates. In this work, a halide methyltransferase biomethylation cascade was successfully adapted with the incorporation of a methionine adenosyltransferase to generate the S‐adenosyl‐L‐methionine (SAM) methylation cofactor in situ from less costly ATP and L‐methionine, instead of directly adding SAM to start the cascade. Furthermore, this cascade was applied to achieve novel catechol and tetrahydroisoquinoline methylations with the O‐methyltransferases RnCOMT, MxSafC and NpN4OMT with high conversions and regioselectivities. In addition, the cascade was successfully trialled with the less toxic methyl group donor, methyl tosylate. [ABSTRACT FROM AUTHOR]

exo‐6b2‐Methyl‐substituted pentabenzocorannulene (exo‐PBC‐Me) was synthesized by the palladium‐catalyzed cyclization of 1,2,3‐triaryl‐1H‐cyclopenta[l]phenanthrene. Its bowl‐shaped geometry with an sp3 carbon atom in the backbone and a methyl group located at the convex (exo) face was verified by X‐ray crystallography. According to DFT calculations, the observed conformer is energetically more favorable than the endo one by 39.9 kcal/mol. Compared to the nitrogen‐doped analogs with intact π‐conjugated backbones (see the main text), exo‐PBC‐Me displayed a deeper bowl depth (avg. 1.93 Å), redshifted and broader absorption (250–620 nm) and emission (from 585 to more than 850 nm) bands and a smaller optical HOMO–LUMO gap (2.01 eV). exo‐PBC‐Me formed polar crystals where all bowl‐in‐bowl stacking with close π ⋅ ⋅ ⋅ π contacts is arranged unidirectionally, providing the potential for applications as organic semiconductors and pyroelectric materials. This unusual structural feature, molecular packing, and properties are most likely associated with the assistance of the methyl group and the sp3 carbon atom in the backbone. [ABSTRACT FROM AUTHOR]

6,13‐Diethynylpentacene derivatives with sterically bulky substituents (Tr*, tris(3,5‐di‐tert‐butylphenyl)methyl groups) appended to the ethynyl moieties at the 6‐ and 13‐positions have been synthesized, as well as derivatives with electron‐withdrawing fluorine groups on the 1,2,3,4,8,9,10,11‐positions. These molecules are designed to investigate relationships between steric and electronic effects on the stability of pentacene toward endoperoxide formation via reaction with photosensitized oxygen in solution under ambient light (i. e., ‘laboratory’ conditions). It is evident from the study that stabilization through changes to the electronic characteristics of pentacene are more effective than the incorporation of sterically bulky groups at the acetylenic termini. Selected pentacene derivatives have been made into binary, amorphous films with the fullerene derivative PCBM to investigate the stability imparted by substituents against cycloaddition reactions. Overall, the introduction of steric protection through the incorporation of Tr* groups is not an efficient strategy for enhancing the persistence of pentacenes. Stabilization through fluorination proves successful for extending the lifetime of the pentacene derivatives by an order of magnitude in solution. Notably, the persistence of pentacene derivatives in solution can also be enhanced through the use of ethereal solvents stabilized with butylated hydroxy toluene (BHT) and/or an increased number of trialkylsilyl groups as substituents. [ABSTRACT FROM AUTHOR]

In X‐ray structures of the isomorphic mer‐[IrX3(THT)(CNXyl)2] (X=Cl 1, Br 2; THT=tetrahydrothiophene; Xyl=2,6‐Me2C6H3−) complexes, we revealed short intermolecular contacts between the C‐atom of an isocyanide methyl group and halide ligands of another molecule. Geometrical consideration of the X‐ray data and analysis of appropriate DFT studies allowed the attribution of these contacts to CMe⋅⋅⋅X−IrIII (X=Cl, Br) tetrel bond. Specifically, through the application of DFT calculations and various theoretical models, the presence of tetrel bonding interactions was validated, and the contribution of the CMe⋅⋅⋅X−IrIII interaction was assessed. The reinforcement of the tetrel bond upon the isocyanide coordination to iridium(III) is substantiated by molecular electrostatic potential (MEP) surface calculations. To distinguish the tetrel bonding characteristics of CMe⋅⋅⋅X−IrIII (X=Cl, Br) interactions from conventional hydrogen bonding, we employed multiple computational methodologies, including Natural Bond Orbital (NBO) analysis and Electron Localization Function (ELF) analysis. Additionally, Energy Decomposition Analysis (EDA) was applied to selected model systems to explore the underlying physical nature of these interactions. [ABSTRACT FROM AUTHOR]

DNMT1 is an essential DNA methyltransferase that catalyzes the transfer of methyl groups to CpG islands in DNA and generates a prominent epigenetic mark. The catalytic activity of DNMT1 relies on its conformational plasticity and ability to change conformation from an auto-inhibited to an activated state. Here, we present four cryo-EM reconstructions of apo DNMT1 and DNTM1: non-productive DNA, DNTM1: H3Ub2-peptide, DNTM1: productive DNA complexes. Our structures demonstrate the flexibility of DNMT1's N-terminal regulatory domains during the transition from an apo 'auto-inhibited' to a DNA-bound 'non-productive' and finally a DNA-bound 'productive' state of DNMT1. Furthermore, we address the regulation of DNMT1's methyltransferase activity by a DNMT1-selective small-molecule inhibitor and ubiquitinated histone H3. We observe that DNMT1 binds DNA in a 'non-productive' state despite the presence of the inhibitor and present the cryo-EM reconstruction of full-length DNMT1 in complex with a di-ubiquitinated H3 peptide analogue. Taken together, our results provide structural insights into the reaction cycle of DNMT1. [ABSTRACT FROM AUTHOR]

Functionalization of Si‐bound methyl group provides an efficient access to diverse organosilanes. However, the asymmetric construction of silicon‐stereogenic architectures by functionalization of Si‐bound methyl group has not yet been described despite recent significant progress in producing chiral silicon. Herein, we disclosed the enantioselective silylmethyl functionalization involving the aryl to alkyl 1,5‐palladium migration to access diverse naphthalenes possessing an enantioenriched stereogenic silicon center, which are inaccessible before. It is worthy to note that the realization of asymmetric induction at the step of metal migration itself remains challenging. Our study constitutes the first enantioselective aryl to alkyl 1,5‐palladium migration reaction. The key to the success is the discovery and fine‐tuning of the different substituents of α,α,α,α‐tetraaryl‐1,3‐dioxolane‐4,5‐dimethanol (TADDOL)‐based phosphoramidites, which ensure the enantioselectivity and desired reactivity. [ABSTRACT FROM AUTHOR]

A new azo dye ligand namely ((E)-1-(4-hydroxy-3-(pyridin-3-yldiazenyl)phenyl)ethan-1-one) (HPPE) was synthesized by the coupling reaction of diazoinium salt of 3-aminopyridine and 4-hydroxyacetophenone. The palladium complex was prepared by reacting palladium chloride with the HPPE ligand. These compounds were characterized by different techniques such as mass, 1H-NMR, infrared, UV-Vis spectroscopies. The infrared data reveal that azo ligand reacting as bidentate via oxygen and nitrogen atom of azo group and it reveals the important functions as carbonyl group, methyl group, and azo group in the ligand and the complex such. The palladium complex is square planer. The ligand showed a visible colorimetric pH sensitive chemosensor, fast response time and is fully reversible and exhibited a large wavelength shift more than170 nm accompanied by excellent sensitivity of pH in the range of 3-9. The HPPE ligand and palladium complex showed potential antioxidant activity especially the ligand showed activity so close to the ascorbic acid. [ABSTRACT FROM AUTHOR]

The histone deacetylases (HDACs) are being explored as a promising therapeutic target for the treatment of various diseases. Here, the synthesis of a series of pyrimidine‐based 1,3,4‐oxadiazoles, in which the oxadiazole scaffold is attached to the pyrimidine ring via a methyleneoxy spacer, is described and their HDAC inhibitory activity studied. The target compounds were synthesized by sequence of reactions involving O‐alkylation of 2‐(methylthio)pyrimidin‐4(3H)‐ones with ethyl 2‐bromoethanoate followed by oxidation of the 2‐methylthio group, displacement of the obtained 2‐methylsulfonyl group with amines, hydrazinolysis of the obtained ethyl (2‐amino‐substituted pyrimidin‐4‐yloxy)acetates to give the corresponding hydrazides and their cyclization under the treatment with ethyl O‐ethyl xanthate or carbonyldiimidazole to 1,3,4‐oxadiazole‐2(3H)‐thiones and 1,3,4‐oxadiazol‐2(3H)‐one, correspondingly. In addition, two 1,3,4‐oxadiazole‐2(3H)‐thiones were converted into (N3)‐morpholinomethyl derivatives by the Mannich reaction with formaldehyde and morpholine. The yields of intermediates and target compounds ranged from moderate to excellent. The synthesized compounds were characterized by 1H and 13C NMR spectra and HRMS data, their purity was controlled by TLC. The synthesized pyrimidine‐based 1,3,4‐oxadiazoles (18 compounds) were tested as inhibitors of the HDAC4 and HDAC8 isoforms and their inhibitory activity was compared with that of Vorinostat. Most of the oxadiazolethiones containing methyl group at the position 6 of the pyrimidine moiety were found to be more selective towards HDAC8, while oxadiazolethiones with propyl group in the pyrimidine ring were active against HDAC4. Among the tested compounds, 5‐((2‐(dibutylamino)‐6‐propylpyrimidin‐4‐yloxy)methyl)‐1,3,4‐oxadiazole‐2(3H)‐thione (48) was found to have the strongest inhibitory activity for HDAC4 isoform (IC50 = 4.2 μM vs. IC50 = 59 μM for Vorinostat) while 5‐((2‐(cyclopentylamino)‐6‐propylpyrimidin‐4‐yloxy)methyl)‐1,3,4‐oxadiazole‐2(3H)‐thione (50) was the most potent HDAC8 inhibitor (IC50 = 6.8 μM). [ABSTRACT FROM AUTHOR]

A series of new aromatic substituted indanone and indanol building blocks have been prepared and are anticipated to aid future drug discovery studies. In total, seven compounds (7, 12–17) are expounded on, and all have been fully characterized. In doing so, we have shown multiple examples of highly chemoselective reactions. One example employed an adaptation of Fujioka's chemoselective reduction methodology, allowing an ester to be reduced in the presence of a ketone. In another example, an uncommon benzylic methyl group to aldehyde oxidation was demonstrated for two different compounds. These and other chemoselective interconversions allowed us to identify compound (12) as a remarkably flexible springboard for accessing a diverse array of indan-based building blocks (13–17). [ABSTRACT FROM AUTHOR]

The enhanced emission properties of several cationic dye molecules on the clay surface established as a result of the strong electrostatic interaction and associated molecular flattening leading to either the suppression of non-radiative deactivation processes or the improvement of radiative deactivation processes has been verified, and it is known as surface-fixation induced emission (S-FIE). Here, the differences in the S-FIE properties as well as the self-fluorescence quenching behavior of the dimidium and propidium dyes were compared. Propidium differs from dimidium by the substitution of a propyl (diethyl methylammonium) group at the 5th position instead of the methyl group in dimidium. So, the differences induced by this substitution, which is not even in conjugation with the chromophore part of the dye molecule show a significant impact on the adsorption strength, S-FIE properties, and self-fluorescence quenching behavior. In propidium and dimidium, the suppression of knr was the key factor for emission enhancement on the clay surface. Interestingly, the alkylammonium cation group in the Propidium helped for better adsorption strength as well as to reduce the self-fluorescence quenching behavior on the clay surface as compared to the dimidium. Since the trialkylammonium cation was not in conjugation with the core structure of the molecule and located at a specific distance, it did not interrupt the flattening of the molecule on the clay surface. These results could be beneficial in the construction of efficient photochemical reaction systems, where the molecule having low adsorption strengths can be modified by alkyl ammonium cations, which will not affect molecular planarization. [ABSTRACT FROM AUTHOR]

Samples of propyne trapped in solid parahydrogen show multiple peak structures in their infrared spectra. These structures are attributed to molecules in two distinct kinds of matrix sites. The most intense lines are assigned to propyne molecules executing a slightly hindered methyl rotation, as was extensively studied in our earlier publication from our two groups, and the other set of peaks to propyne trapped in a secondary site where the methyl rotation is quenched and replaced by methyl torsion within the matrix site. The assignment of the various rovibrational transitions is made possible by the observation of nuclear spin conversion (NSC) within the methyl group at long timescales. The NSC rate depends on the site and is much slower in the sites where the methyl rotation is quenched. [ABSTRACT FROM AUTHOR]

Recent metagenomic studies have identified numerous lineages of hydrogen-dependent, obligately methyl-reducing methanogens. Yet, only a few representatives have been isolated in pure culture. Here, we describe six new species with this capability in the family Methanosarcinaceae (order Methanosarcinales), which makes up a substantial fraction of the methanogenic community in arthropod guts. Phylogenomic analysis placed the isolates from cockroach hindguts into the genus Methanimicrococcus (M. hacksteinii, M. hongohii , and M. stummii) and the isolates from millipede hindguts into a new genus, Methanolapillus (M. africanus, M. millepedarum , and M. ohkumae). Members of this intestinal clade, which includes also uncultured representatives from termites and vertebrates, have substantially smaller genomes (1.6–2.2 Mbp) than other Methanosarcinales. Genome reduction was accompanied by the loss of the upper part of the Wood–Ljungdahl pathway, several energy-converting membrane complexes (Fpo, Ech, and Rnf), and various biosynthetic pathways. However, genes involved in the protection against reactive oxygen species (catalase and superoxide reductase) were conserved in all genomes, including cytochrome bd (CydAB), a high-affinity terminal oxidase that may confer the capacity for microaerobic respiration. Since host-associated Methanosarcinales are nested within omnivorous lineages, we conclude that the specialization on methyl groups is an adaptation to the intestinal environment. [ABSTRACT FROM AUTHOR]

Among polymer wastes, poly(ethylene terephthalate) (PET) is the most important commercial thermoplastic polyester. Less than 30% of total PET production is recycled into new products. Therefore, large amounts of waste PET need to be recycled. We describe a feasible approach for the direct application of the glycolysis products of PET (GP-PET), without further purification, for the synthesis of value-added products. It was established that GP-PET is valorized via phosphorylation with phenylphosphonic dichloride (PPD), as well as with trimethyl phosphate (TMP). When PPD is used, a condensation reaction takes place with the evolution of hydrogen chloride. During the interaction between GP-PET and TMP, the following reactions take place simultaneously: a transesterification with the participation of the hydroxyl group of GP-PET and the methoxy group of TMP and an exchange reaction between the ester group of GP-PET and the methyl ester group of TMP. The occurrence of the exchange reaction was confirmed by 1H, 31P, 13C NMR, and GPC analysis. Thermogravimetric analysis (TGA) revealed that the percentage of a carbon residual (CR) implies the possibility of using the end products as flame retardant (FR) additives, especially for polyurethanes as well as thermal stabilizers of polymer materials or Li-ion cells. [ABSTRACT FROM AUTHOR]

In this paper, we demonstrate the use of machine learning to optimize the continuous flow process of a crucial intermediate in the production of Nemonoxacin. Our focus is to achieve the good yield and enantioselectivity in the construction of chiral methyl group utilize the initial 29 experimental datasets and consider six important variables. Employing Single-Objective Bayesian optimization (SOBO), we achieved an impressive predicted yield of up to 89.7%, which is consistent with the experimental results, with a yield of 89.5%. Additionally, A Multi-Objective Bayesian Optimization (MOBO) algorithm, namely qNEHVI, to strike a balance between yield and enantioselectivity in the continuous flow system is applied. The algorithm's prediction, with a yield of 81.8% and enantioselectivity of 97.85%, was experimentally validated, yielding 83.8% and 97.2%, respectively. This study effectively demonstrates that Bayesian optimization is a powerful tool for optimizing the continuous process in the production of active pharmaceutical ingredients (APIs). [ABSTRACT FROM AUTHOR]

3,3,3-Trifluoro-1,2-propanediol undergoes complete defluorination in two distinct steps: first, the conversion into 3,3,3-trifluoropropionaldehyde catalyzed by adenosylcobalamin (coenzyme B 12 )-dependent diol dehydratase; second, non-enzymatic elimination of all three fluorides from this aldehyde to afford malonic semialdehyde (3-oxopropanoic acid), which is decarboxylated to acetaldehyde. Diol dehydratase accepts 3,3,3-trifluoro-1,2-propanediol as a relatively poor substrate, albeit without significant mechanism-based inactivation of the enzyme during catalysis. Optical and electron paramagnetic resonance (EPR) spectra revealed the steady-state formation of cob(II)alamin and a substrate-derived intermediate organic radical (3,3,3-trifluoro-1,2-dihydroxyprop-1-yl). The coenzyme undergoes Co–C bond homolysis initiating a sequence of reaction by the generally accepted pathway via intermediate radicals. However, the greater steric size of trifluoromethyl and especially its negative impact on the stability of an adjacent radical centre compared to a methyl group has implications for the mechanism of the diol dehydratase reaction. Nevertheless, 3,3,3-trifluoropropionaldehyde is formed by the normal diol dehydratase pathway, but then undergoes non-enzymatic conversion into acetaldehyde, probably via 3,3-difluoropropenal and malonic semialdehyde. [ABSTRACT FROM AUTHOR]

The preferential solvation parameters of atenolol in aqueous binary mixtures of propylene glycol (PG) were derived from reported molar solubility values after conversion to mole fractions by using the inverse Kirkwood–Buff integrals method. This drug is sensitive to preferential solvation effects in this binary system. The preferential solvation parameter by PG (δx1,3) is negative in water-rich mixtures but positive in mixtures of 0.20 < x1 < 1.00. It is conjecturable that hydrophobic hydration around the non-polar methyl and phenylene groups of this drug observable in water-rich mixtures could play a relevant role in drug solvation. Otherwise, in mixtures of 0.20 < x1 < 1.00, the preferential solvation by PG could be due to the acidic behaviour of atenolol. [ABSTRACT FROM AUTHOR]

A streamlined one-day protocol is described to produce isotopically methyl-labeled protein with high levels of deuterium for NMR studies. Using this protocol, the D2O and 2H-glucose content of the media and protonation level of ILV labeling precursors (ketobutyrate and ketovalerate) were varied. The relaxation rate of the multiple-quantum (MQ) state that is present during the HMQC-TROSY pulse sequence was measured for different labeling schemes and this rate was used to predict upper limits of molecular weights for various labeling schemes. The use of deuterated solvents (D2O) or deuterated glucose is not required to obtain 1H–13C correlated NMR spectra of a 50 kDa homodimeric protein that are suitable for assignment by mutagenesis. High quality spectra of 100–150 kDa proteins, suitable for most applications, can be obtained without the use of deuterated glucose. The proton on the β-position of ketovalerate appears to undergo partial exchange with deuterium under the growth conditions used in this study. [ABSTRACT FROM AUTHOR]

The response of the brain to radiation is important for cancer patients receiving whole or partial brain irradiation or total body irradiation, those exposed to irradiation as part of a nuclear accident or a nuclear war or terrorism event, and for astronauts during and following space missions. The mechanisms mediating the effects of irradiation on the hippocampus might be associated with alterations in hippocampal DNA methylation. Changes in cytosine methylation involving the addition of a methyl group to cytosine (5 mC) and especially those involving the addition of a hydroxy group to 5 mC (hydroxymethylcytosine or 5 hmC) play a key role in regulating the expression of genes required for hippocampal function. In this review article, we will discuss the effects of radiation on hippocampal DNA methylation and whether these effects are associated with hippocampus-dependent cognitive measures and molecular measures in the hippocampus involved in cognitive measures. We will also discuss whether the radiation-induced changes in hippocampal DNA methylation show an overlap across different doses of heavy ion irradiation and across irradiation with different ions. We will also discuss whether the DNA methylation changes show a tissue-dependent response. [ABSTRACT FROM AUTHOR]

Terahertz molecular motions are often probed by high-frequency molecular oscillators in different types of non-linear vibrational spectroscopy. Recently developed two-dimensional terahertz-infrared-visible spectroscopy allows direct measuring of this coupling and, thus, obtaining site-specific terahertz vibrational spectrum. However, these data are affected by the intensity and phase of the employed laser pulses. In this work, we develop a method of extracting sample response—representing solely physical properties of a material—from experimental spectra. Using dimethyl sulfoxide as a model molecule to verify this method, we measure the coupling between C–H stretch vibration of its methyl groups and terahertz intramolecular twist and wagging modes. [ABSTRACT FROM AUTHOR]

Tetra‐cyano substituted naphthalene diimides (TCNDIs) with calculated LUMO of −5.2 eV, form one of the strongest electron‐acceptors known to date. However, the synthesis and isolation of this class of molecules remain challenging due to its reactivity emanating from its ultra‐electron‐deficiency. Herein we have established an improved synthetic methodology of TCNDIs with cost‐effective reagents and circumventing metallic catalysts. The synthesis is amenable to TCNDIs with the shortest axial alkyl groups, i. e. methyl group and also longer alkyl chains. We also gained insight on how axial alkyl chain lengths influence electron‐deficiency, Meisenheimer complex formation, reactivity, and charge‐transfer of TCNDIs from computation, spectroscopy, and electrochemical studies. The TCNDIs with Me/Et axial groups were found to be more susceptible to moist solvents vis‐à‐vis the TCNDIs with longer alkyl groups. The single crystal structures of the TCNDIs show infinitely π‐stacked structure, and a new C=O ⋅ ⋅ ⋅ C≡N or C≡N ⋅ ⋅ ⋅ π motif is discerned. Finally, toluene‐mediated charge‐transfer properties of TCNDIs in the single crystals as well as in solution have been examined. [ABSTRACT FROM AUTHOR]

Herein, we demonstrate an Oxa‐Diels‐Alder reaction of 3‐trifluoroacetyl‐4‐methyl‐quinolin‐2(1H)‐one with aldehydes in the presence of a base to engineer the functionalized pyrano[3,4‐c]quinolones. This reaction proceeds through an in‐situ generated hetero dendralene intermediate and features perfect stereoselectivity on a wide range of substrates with excellent atom economy. The high electron‐withdrawing nature of CF3‐group is responsible for making the methyl group present in quinolone moiety more acidic to furnish the corresponding hetero dendralene intermediate. [ABSTRACT FROM AUTHOR]

Introducing a methyl group into 1,3-dioxolane (DOL) to obtain a stable cyclic ether, 4-methyl-1,3-dioxolane (4-Me DOL), allows it to be used as an additive in LiPF6-based carbonate electrolytes. The addition of 4-Me DOL can form a stable SEI with good Li+ transport ability, which can simultaneously improve the rate capability and cycling performance of lithium metal batteries. [ABSTRACT FROM AUTHOR]

Associating molecular structure and mechanical properties is important for silicone rubber design. Although silicone rubbers are widely used due to their odourless, non-toxic, and high- and low-temperature resistance advantages, their application and development are still limited by their poor mechanical properties. The mechanical properties of silicone rubbers can be regulated by designing the cross-link density and cross-linking structure, and altering the molar contents of vinyl in the side groups of methyl vinyl silicone rubber (MVQ) leads to different cross-linking structures and cross-linking densities in the vulcanized rubber. Therefore, this study investigated the differences in molecular parameters and molecular chain structures of unprocessed MVQ rubbers with different vinyl contents. The results showed that MVQ rubbers with high vinyl contents were branched polymers, better facilitating the cross-linking reaction than MVQ rubbers with low vinyl contents. In addition, silicone rubbers with different vinyl contents were co-cross-linked to introduce an inhomogeneous cross-linked network in the silicone rubber to improve its mechanical properties. The cross-linked network properties were analysed by the Flory–Rehner model and Mooney–Rivlin plots, and it was found that the long chains in the sparsely cross-linked domains of the network favoured high elongation at break and the short chains in the densely cross-linked domains contributed to high modulus, which could satisfy the functions of reinforcing and toughening the rubber materials at the same time. It was also found by analysing the filler network and aggregate morphology that the inhomogeneous cross-linked network led to an improvement in the dispersion of silica in the rubber and a significant improvement in the mechanical properties of silicone rubber. [ABSTRACT FROM AUTHOR]