Number Of Methylene Groups Research Articles

Structural and electronic tuning of single-benzene fluorophores with simple methylations

Recent advancements in the development of low molecular-weight fluorophores have led to the study of a single-benzene fluorophore (SBF) containing both electron-withdrawing and electron-donating groups within an aromatic ring, resulting in unique photophysical properties. In this study, we explored the modulation of emissions by adjusting the electron-donating properties via the simple methylation of the 2,5-diamino or 2,5-dihydroxy terephthalate structure. Introducing additional functional groups under both symmetrical and unsymmetrical conditions demonstrated changes in the photophysical properties, which was not only owing to the structural variations in the location and number of methyl groups but also due to alterations in the electron-donating properties. The observed effects appeared to be owing to the interactions between the amine and ester groups, as confirmed via single-crystal X-ray diffraction. Finally, hydrolysis of the ester to the corresponding carboxylic acid resulted in various emission wavelengths at different pH values via protonation and deprotonation. This study provides valuable insights for predicting the structural and electronic effects of additional functional groups in SBF.

Symmetrical diynylic N-arylcarbamate molecules with different numbers of CH2 groups in spacers

The photopolymerization of Langmuir-Schaefer films of diacetylene N-arylcarbamate symmetrical molecules containing different numbers of methylene groups in the molecules was studied. The result of diyne films UV irradiation was the effective transition of the films into the stable state of blue phase polydiacetylene. The number of CH2 groups in the molecules affected the efficiency of the monomers film transition into the polymer and the conjugation length of the polymer chains. Studying the morphology of the films using scanning electron microscopy showed the horizontal position of diyne molecules on the substrates in the state of domains, the sizes of which depended on the number of CH2 groups in the molecules.

How the Aliphatic Glycol Chain Length Determines the Pseudoeutectic Composition in Biodegradable Isodimorphic poly(alkylene succinate-ran-caprolactone) Random Copolyesters.

We synthesize four series of novel biodegradable poly(alkylene succinate-ran-caprolactone) random copolyesters using a two-step ring-opening/transesterification and polycondensation process with ε-caprolactone (PCL) as a common comonomer. The second comonomers are succinic acid derivatives, with variations in the number of methylene groups (nCH2) in the glycol segment, nCH2 = 2, 4, 8, and 12. The obtained copolyesters were poly(ethylene succinate-ran-PCL) (ESxCLy), poly(butylene succinate-ran-PCL) (BSxCLy), poly(octamethylene succinate-ran-PCL) (OSxCLy), and poly(dodecylene succinate-ran-PCL) (DSxCLy). We discovered a new mixed isodimorphic/comonomer exclusion crystallization in ESxCLy copolymers. The BSxCLy, OSxCLy, and DSxCLy copolymers display isodimorphic behavior. Our findings revealed a significant variation in the pseudoeutectic point position, from mixed isodimorphism/comonomer exclusion crystallization to isodimorphism with pseudoeutectic point variation from 54% to up to 90%. Moreover, we established a link between the melting temperature depression slope variation and the comonomer inclusion/exclusion balance, providing valuable insights into the complex topic of isodimorphic random copolymers.

Critical Cooling Rate of Fast-Crystallizing Polyesters: The Example of Poly(alkylene trans-1,4-cyclohexanedicarboxylate)

Controlling the cooling rate experienced by a material during a manufacturing process is a challenge and a major issue. Industrial processing techniques are very diverse and may involve a whole range of cooling rates, which are sometimes extremely high for small and/or thin manufactured parts. For polymers, the cooling rate has consequences on both the microstructure and the time-dependent properties. The common cooling rates associated with conventional calorimetric measurements are generally limited to a few tens of degrees per minute. This work combines several calorimetric techniques (DSC, modulated-temperature DSC, stochastically-modulated DSC and Fast Scanning Calorimetry) to estimate the critical cooling rate required to melt-quench fast-crystallizing polyesters to their fully amorphous state, based on the example of a series of poly(alkylene trans-1,4-cyclohexanedicarboxylate) (PCHs) with a number of methylene groups in the main structure of the repeating unit nCH2 varying from 3 to 6. The even-numbered ones require faster cooling rates (about 3000 K s−1 for nCH2 = 4, between 500 and 1000 K s−1 for nCH2 = 6) compared to the odd-numbered ones (between 50 K min−1 and 100 K s−1 for nCH2 = 3, between 10 and 30 K min−1 for nCH2 = 5).

Influence of Linear Diamine Counterions on the Self-Assembly of Glycine-, Alanine-, Valine-, and Leucine-Based Amphiphiles.

Electrical conductimetry and dynamic light scattering (DLS) were used to investigate the aggregation behaviors of four amino acid-based surfactants (AABSs; undecanoyl-glycine, undecanoyl-l-alanine, undecanoyl-l-valine, undecanoyl-l-leucine) in the presence of five linear diamine counterions (1,2-diaminoethane, 1,3-diaminopropane, 1,4-diaminobutane, 1,5-diaminopentane, 1,6-diaminohexane). Electrical conductimetry was used to measure the CMCs for each system, which ranged from 5.1 to 22.5 mM. With respect to counterions, the obtained CMCs decreased with increases in the interamine spacer length; this was attributed to the improved torsional binding flexibility in longer counterions. Strong linear correlations (mean R2 = 0.9443) were observed between the CMCs and predicted surfactant partition coefficients (logP; water/octanol), suggesting that micellization is primarily driven by the AABS's hydrophobicity for these systems. However, significant deviations in this linear relationship were observed for systems containing 1,2-diaminoethane, 1,4-diaminobutane, and 1,6-diaminohexane (p = 0.0774), suggesting altered binding dynamics for these counterions. pH measurements during the CMC determination experiments indicated the full deprotonation of the AABSs but did not give clear insights into the counterion protonation states, thus yielding an inconclusive evaluation of their charge stabilization effects during binding. However, DLS measurements revealed that the micellar size remained largely independent of the counterion length for counterions longer than 1,2-diaminoethane, with hydrodynamic diameters ranging from 2.2 to 2.8 nm. This was explained by the formation of charge-stabilized noncovalent dimers, with each counterion bearing a full +2 charge. Conductimetry-based estimates of the degrees of counterion binding (β) and free energies of micellization (ΔG°M) revealed that bulky AABSs exhibit preferential binding to counterions with an even number of methylene groups. It is proposed that when these counterions form noncovalent dimers, perturbations in their natural geometries result in the formation of a binding pocket that accommodates the AABS steric bulk. While the direct application of these systems remains to be seen, this study provides valuable insights into the structure-property relationships that govern AABS aggregation.

Elution behavior of carbohydrates using core-shell ion-exchange resin St-60 with different numbers of methylene groups in the porous shell and a constant cross-linking degree of 55%

Elution behavior of carbohydrates using core-shell ion-exchange resin St-60 with different numbers of methylene groups in the porous shell and a constant cross-linking degree of 55%

Elucidating effect of dicarboxylate anions on nanostructural organization of dicationic imidazolium-based ionic liquids

This work reports the influence of the dicarboxylate anion (oxalate, malonate succinate, glutarate, adipate, pimelate) on the aggregation process of ionic liquids derived from 1,8-bis(3-methylimidazolium-1-yl)-octane [C8(MIM)2] and 1,10-bis(3-methylimidazolium-1-yl)-decano [C10(MIM)2] in water solution. The aggregation behavior was investigated using electrical conductivity, nuclear magnetic resonance, transmission electron microscopy, atomic force microscopy, and zeta potential. Results showed that the aggregates have a wormlike morphology. The CAC values for [C10(MIM)2]2+ increase in the following order: [Oxa] < [Suc] < [Mal] < [Glu] < [Adi] < [Pim], which indicates a direct relationship with the increase in the number of methylene groups of the dianion spacer. In the case of [C8(MIM)2]2+, there was no relationship between the CAC value and the anion’s alkyl spacer chain length, which was attributed to the flexibility and complexity of the dynamic behavior of the aggregates. Anions on the nanorganized structures of micelles are oriented in the way that carboxylate groups are at the aggregate surface (forming hydrogen bonds with cationic heads and water), and apolar alkyl chains are in the hydrophobic (downshift) region of the micelles making an arrangement where they also adopt the bend conformation of alkyl chains. The aggregation of dicationic ILs with dicarboxylate anions is a very innovative topic of investigation in the literature, and more research on different structures, system conditions, and techniques could be done to gain a better understanding of these systems.

The gut-facial aging axis: A two-sample Mendelian randomization and mediation analysis of gut microbiota, gut microbiota metabolic pathways, and blood metabolites.

Facial aging (FA) is a complex process influenced by both genetic and environmental factors. Gut microbiota (GM), gut microbiota metabolic pathways (GMMPs), and blood metabolites (BMs) have been implicated in the regulation of FA, but the causal and mediating effects of these factors remain unclear. We used summary-level data from genome-wide association studies (GWAS) of 16S rRNA gene sequencing data for GM (n=18 340), GWAS of GMMPs (n=7738), BMs (n=24 925), and GWAS of FA (n=423 999). We applied Mendelian randomization (MR) methods to estimate the causal effects of GM, GMMPs, and BMs on FA. We performed mediation analysis to quantify the proportion of the effects mediated by blood metabolites. We identified nine genus, two phylum, two families of GM, nine GM metabolic pathways, and 73 BMs that showed potential causal effects on FA. After Bonferroni correction, three BMs remained causally associated with FA, including average number of methylene groups per double bond (β, -0.023; 95% CI, -0.032∼-0.014; p=3.120×10-7) and average number of methylene groups in a fatty acid chain (β, -0.031; 95% CI, -0.045∼-0.016; p=2.062×10-5), which had strong negative causal effects on FA, and ratio of bisallylic groups to total fatty acids (β, 0.023; 95% CI, 0.017∼-0.029; p=8.441×10-15), which had a strong positive causal effect on FA. Mediation analysis revealed that histidine, average number of methylene groups in a fatty acid chain, and triglycerides in chylomicrons and largest VLDL particles mediated the effects of anaerofilum and/ or superpathway of Laspartate and Lasparagine biosynthesis on FA. Our study provides novel insights into the causal and mediating effects of GM, GMMPs, and BMs on FA. These findings may have implications for the development of new strategies for preventing or delaying FA.

Structure, morphology, and properties of aliphatic polyurethane elastomers from bio‐based 1,3‐propanediol

AbstractThe utilization of biomass resources in the production of bio‐based or bio‐recycled polyurethanes (PUs) enhances the sustainable development and eco‐friendliness of PU. Herein, a series of new bio‐based aliphatic poly(propylene dicarboxylate) diols were synthesized using bio‐based 1,3‐propanediol (bio‐PDO) and aliphatic dicarboxylic acids with different chain lengths. These bio‐based polyester diols and 1,4‐butanediol (BDO) reacted with 4,4′‐dicyclohexylmethane diisocyanate to produce aliphatic PU elastomers (PUEs). The study aimed to evaluate the impact of the structure of poly(propylene dicarboxylate) diols on the architecture, morphology, mechanical properties, and degradation of PUEs, thereby expanding the application of bio‐PDO. The results indicate a strong correlation between the degree of microphase separation, tensile properties, and degradation behavior of the synthesized PUEs and the number of methylene groups in the repeating unit of the poly(propylene dicarboxylate) diols. Notably, the PUE derived from poly(propylene pimelate) diol demonstrates the highest level of microphase separation and superior elasticity properties because of the high flexibility of the polyester. On the other hand, PUE prepared from poly(propylene succinate) diol exhibits the fastest degradation performance due to its high density of ester groups. Bio‐PDO based polyester diols show significant potential as raw materials for PUEs with biodegradable and adjustable mechanical properties.Highlights Poly(propylene dicarboxylate) diols were prepared from bio‐based 1,3‐propanediol. The poly(propylene dicarboxylate) diols based polyurethane elastomers (PUEs) have high tensile strength (&gt;22 MPa) and elongation at break (&gt;920%). The morphology, mechanical properties and degradation of PUEs are highly related to the structure of the poly(propylene dicarboxylate) diols. The increasing repeating unit length of the poly(propylene dicarboxylate) diols increases elastic recovery of PUEs.

Kinetic Study and Reaction Mechanism of the Gas-Phase Thermolysis Reaction of Methyl Derivatives of 1,2,4,5-Tetroxane.

Tetroxane derivatives are interesting drugs for antileishmaniasis and antimalaric treatments. The gas-phase thermal decomposition of 3,6,-dimethyl-1,2,4,5-tetroxane (DMT) and 3,3,6,6,-tetramethyl-1,2,4,5-tetroxane (acetone diperoxide (ACDP)) was studied at 493-543 K by direct gas chromatography by means of a flow reactor. The reaction is produced in the injector chamber at different temperatures. The resulting kinetics Arrhenius equations were calculated for both tetroxanes. Including the parent compound of the series 1,2,4,5-tetroxane (formaldehyde diperoxide (FDP)), the activation energy and frequency factors decrease linearly with the number of methyl groups. The reaction mechanisms of ACDP and 3,6,6-trimethyl-1,2,4,5-tetroxane (TMT) decomposition have been studied by means of the DFT method with the BHANDHLYP functional. Our calculations confirm that the concerted mechanism should be discarded and that only the stepwise mechanism occurs. The critical points of the singlet and triplet state potential energy surfaces (S- and T-PES) of the thermolysis reaction of both compounds have been determined. The calculated activation energies of the different steps vary linearly with the number of methyl groups of the methyl-tetroxanes series. The mechanism for the S-PES leads to a diradical O···O open structure, which leads to a C···O dissociation in the second step and the production of the first acetaldehyde/acetone molecule. This last one yields a second C···O dissociation, producing O2 and another acetone/acetaldehyde molecule. The O2 molecule is in the singlet state. A quasi-parallel mechanism for the T-PES from the open diradical to products is also found. Most of the critical points of both PES are linear with the number of methyl groups. Reaction in the triplet state is much more exothermic than the singlet state mechanism. Transitions from the singlet ground state, S0 and low-lying singlet states S1-3, to the low-lying triplet excited states, T1-4, (chemical excitation) in the family of methyl tetroxanes are also studied at the CASSCF/CASPT2 level. Two possible mechanisms are possible here: (i) from S0 to T3 by strong spin orbit coupling (SOC) and subsequent fast internal conversion to the excited T1 state and (ii) from S0 to S2 from internal conversion and subsequent S2 to T1 by SOC. From these experimental and theoretical results, the additivity effect of the methyl groups in the thermolysis reaction of the methyl tetroxane derivatives is clearly highlighted. This information will have a great impact for controlling these processes in the laboratory and chemical industries.

Synthesis and Enzymatic Evaluation of a Small Library of Substituted Phenylsulfonamido-Alkyl Sulfamates towards Carbonic Anhydrase II.

A small library of 79 substituted phenylsulfonamidoalkyl sulfamates, 1b-79b, was synthesized starting from arylsulfonyl chlorides and amino alcohols with different numbers of methylene groups between the hydroxyl and amino moieties yielding intermediates 1a-79a, followed by the reaction of the latter with sulfamoyl chloride. All compounds were screened for their inhibitory activity on bovine carbonic anhydrase II. Compounds 1a-79a showed no inhibition of the enzyme, in contrast to sulfamates 1b-79b. Thus, the inhibitory potential of compounds 1b-79b towards this enzyme depends on the substituent and the substitution pattern of the phenyl group as well as the length of the spacer. Bulkier substituents in the para position proved to be better for inhibiting CAII than compounds with the same substituent in the meta or ortho position. For many substitution patterns, compounds with shorter spacer lengths were superior to those with long chain spacers. Compounds with shorter spacer lengths performed better than those with longer chain spacers for a variety of substitution patterns. The most active compound held inhibition constant as low as Ki = 0.67 μM (for 49b) and a tert-butyl substituent in para position and acted as a competitive inhibitor of the enzyme.

Amide solvents for extraction and separation of 1-hexene from n-heptane: Effect of the amount of methyl groups

In this work, the influence mechanism of methyl group in the structure of amide solvent on the extraction and separation of alkene (1-hexene or 1-octene) from n-heptane has been studied by a combination of liquid–liquid equilibrium (LLE) experiments and quantum chemical calculations. For LLE experiments, as the number of methyl groups in the extractant structure increases, its selectivity for alkene (1-hexene or 1-octene) gradually decreases, and the distribution coefficients of alkene (1-hexene or 1-octene) and n-heptane gradually increase. In the interaction between 1-hexene and extractant, the amount and intensity of C-H⋯O interactions, as well as the presence or absence of N/C-H⋯π interactions and their intensities, are all affected by the amount (0,1,2,3) of methyl group introduced into the amide solvent. The existence of the C-H⋯O and N-H⋯π interactions were verified by the infrared spectroscopy. With increasing methyl group amounts in the extractant structure, the dispersion interaction strengthens, while the contribution percentage of electrostatic interaction and ΔEelst/ΔE declines, leading to the increase of distribution coefficient and decrease of selectivity for alkene (1-hexene or 1-octene) respectively.

Causal relationships between circulating metabolites and rheumatoid arthritis: A mendelian randomization study

BackgroundBlood metabolites serve as pivotal indicators in identifying and predicting the course of rheumatoid arthritis (RA). However, empirical substantiation of a direct causal link between these serum biomarkers and the development of RA is still lacking comprehensive support. MethodIn pursuit of a thorough exploration of the causal links between circulating blood metabolites and RA, we deployed a two-sample Mendelian randomization (MR) approach during our initial investigative phase. This method was utilized to examine the potential connections between 249 distinct circulating metabolites and the prevalence of RA. In the validation phase, we conducted replication analyses with a new metabolic dataset consisting of 123 metabolites. Furthermore, we employed the Mendelian randomization based on Bayesian model averaging (MR-BMA) technique to pinpoint key metabolic characteristics that have significant causal implications. ResultsIn our primary analysis, we found that acetate, acetoacetate and pyruvate exhibited a consistent protective causal association with rheumatoid arthritis, while lactate demonstrated a positive correlation with rheumatoid arthritis risk. It is also noteworthy that a substantial subset of traits related to both saturated and unsaturated fatty acids showed causal influences. Subsequent secondary analyses substantiated these observations, revealing that traits associated with the average number of methylene groups in a fatty acid chain exhibited protective effects. Ultimately, our MR-BMA analyses unveiled that the ratio of polyunsaturated fatty acids (PUFAs) to total fatty acids assumes a paramount role in increasing the susceptibility to rheumatoid arthritis. ConclusionsBy employing systemic MR analyses, our study has successfully generated an all-encompassing atlas elucidating the intricate connections between circulating metabolites and the susceptibility to rheumatoid arthritis. Our results indicate the high unsaturation degree is a dominant risk factors correlated with rheumatoid arthritis.

An integrated cofactor and co-substrate recycling pathway for the biosynthesis of 1,5-pentanediol

Background1,5-pentanediol (1,5-PDO) is a linear diol with an odd number of methylene groups, which is an important raw material for polyurethane production. In recent years, the chemical methods have been predominantly employed for synthesizing 1,5-PDO. However, with the increasing emphasis on environmentally friendly production, it has been a growing interest in the biosynthesis of 1,5-PDO. Due to the limited availability of only three reported feasible biosynthesis pathways, we developed a new biosynthetic pathway to form a cell factory in Escherichia coli to produce 1,5-PDO.ResultsIn this study, we reported an artificial pathway for the synthesis of 1,5-PDO from lysine with an integrated cofactor and co-substrate recycling and also evaluated its feasibility in E.coli. To get through the pathway, we first screened aminotransferases originated from different organisms to identify the enzyme that could successfully transfer two amines from cadaverine, and thus GabT from E. coli was characterized. It was then cascaded with lysine decarboxylase and alcohol dehydrogenase from E. coli to achieve the whole-cell production of 1,5-PDO from lysine. To improve the whole-cell activity for 1,5-PDO production, we employed a protein scaffold of EutM for GabT assembly and glutamate dehydrogenase was also validated for the recycling of NADPH and α-ketoglutaric acid (α-KG). After optimizing the cultivation and bioconversion conditions, the titer of 1,5-PDO reached 4.03 mM.ConclusionWe established a novel pathway for 1,5-PDO production through two consecutive transamination reaction from cadaverine, and also integrated cofactor and co-substrate recycling system, which provided an alternative option for the biosynthesis of 1,5-PDO.

Barrier Properties of Biodegradable Aliphatic–Aromatic Copolyesters (PBXT Series)

AbstractIn this study, a series of biodegradable poly(butylene alkylene carboxylate‐co‐terephthalate) copolymers with varying methylene numbers in the alkylene units (0, 2, 4, and 8) are synthesized. These copolymers, namely, poly(butylene oxalate‐co‐terephthalate) (PBOT), poly(butylene succinate‐co‐terephthalate) (PBST), poly(butylene adipate‐co‐terephthalate) (PBAT), and poly(butylene sebacate‐co‐terephthalate) (PBSeT), are prepared with nearly identical structural and molar compositions. The objective of this study is to comprehensively examine the impact of alkylene unit length on the barrier properties of the materials, delving into aspects such as crystallinity, free volume, molecular chain mobility, as well as adsorption and diffusion of gases within the materials. The findings indicate a decrease in crystallinity from 17.2% for PBOT to 10.2% for PBSeT as the alkylene chain length increases, while maintaining the same chemical composition. Concurrently, the fractional free volume increases from 0.9% to 2.6%, and the melt flow activation energy decreases from 106.6 to 52.1 kJ mol−1. Importantly, theoretical calculations are performed, demonstrating that the predominant site for gas adsorption and diffusion is within the material's free volume. These combined observations indicate a gradual decrease in barrier properties as the number of methylene groups increases.

Regulation of Two-Dimensional Platelet Micelles with Tunable Core Composition Distribution via Coassembly Seeded Growth Approach.

Seeded growth termed "living" crystallization-driven self-assembly (CDSA) has been identified as a powerful method to create one- or two-dimensional nanoparticles. Epitaxial crystallization is usually regarded as the growth mechanism for the formation of uniform micelles. From this perspective, the unimer depositing rate is largely related to the crystallization temperature, which is a key factor to determine the crystallization rate and regulate the core composition distribution among nanoparticles. In the present work, the coassembly of two distinct crystallizable polymers is explored in detail in a one-pot seeded growth protocol. Results have shown that polylactone containing a larger number of methylene groups (-CH2-) in their repeating units such as poly(η-octalactone) (POL) has a faster crystallization rate compared to poly(ε-caprolactone) (PCL) with a smaller number of -CH2- at ambient temperature (25 °C), thus a block or blocky platelet structure with heterogeneous composition distribution is formed. In contrast, when the crystallization temperature decreases to 4 °C, the difference of crystallization rate between both cores become negligible. Consequently, a completely random component distribution within 2D platelets is observed. Moreover, we also reveal that the core component of seed micelles is also paramount for the coassembly seeded growth, and a unique structure of flower-like platelet micelle is created from the coassembly of PCL/POL using POL core-forming seeds. This study on the formation of platelet micelles by one-pot seeded growth using two crystallizable components offers a considerable scope for the design of 2D polymer nanomaterials with a controlled core component distribution.

Hyperbranched polyborosilazanes derived SiBCN ceramic for high-temperature wave-transparent performance

Polymer-derived ceramics (PDCs) is a promising way to prepare ceramic-based electromagnetic functional materials, which can conveniently modulate the composition and dielectric properties of the ceramics. In this paper, SiBCN ceramic matrix composites with excellent high-temperature wave-transparent performance were prepared through PDC method. Three hyperbranched polyborosilazanes (PBSZs) were prepared by adjusting the type of chlorosilane monomers containing different numbers of methyl groups. The carbon element of pyrolytic ceramics was tuned by adjusting the molecular structure of the precursor and the pyrolysis temperature. The lower the methyl number and pyrolysis temperature, the lower the dielectric constant of the polymer-derived SiBCN ceramics, which is favorable for electromagnetic wave (EMW) transmittance. The average EMW transmittance of SiBCN-C pyrolyzed from hyperbranched PBSZ using trichlorosilane at 1000 °C was 90.56 % at room temperature. More excitingly, the excellent wave-transparent performance was also maintained in the temperature range of 100–800 °C. At the test temperature of 800 °C, SiBCN-C-1000 still had excellent wave-transparent performance with minimum and average EMW transmittance of 76.13 % and 88.96 %, respectively. This paper provided a new idea for the preparation of high-temperature wave-transparent SiBCN composite ceramics.

The Influence of the Molecular Structure of Compounds on Their Properties and the Occurrence of Chiral Smectic Phases.

We have designed new chiral smectic mesogens with the -CH2O group near the chiral center. We synthesized two unique rod-like compounds. We determined the mesomorphic properties of these mesogens and confirmed the phase identification using dielectric spectroscopy. Depending on the length of the oligomethylene spacer (i.e., the number of methylene groups) in the achiral part of the molecules, the studied materials show different phase sequences. Moreover, the temperature ranges of the observed smectic phases are different. It can be seen that as the length of the alkyl chain increases, the liquid crystalline material shows more mesophases. Additionally, its clearing (isotropization) temperature increases. The studied compounds are compared with the structurally similar smectogens previously synthesized. The helical pitch measurements were performed using the selective reflection method. These materials can be useful and effective as chiral components and dopants in smectic mixtures targeted for optoelectronics and photonics.

Regulating donor configuration to develop AIE-active type I photosensitizers for lipid droplet imaging and high-performance photodynamic therapy under hypoxia.

Type I photodynamic therapy is considered to be a more promising cancer treatment than type II photodynamic therapy due to its non-oxygen-dependent characteristics. In this work, three D-A structure N,N'-dihydrophenazine (DHP)-based photosensitizers DP-CNPY, SMP-CNPY and DMP-CNPY were designed and synthesized by introducing different numbers of methyl groups in the backbone neighbor of DHP as the donor and combined with the typical strong electron acceptor 2-(pyridin-4-yl)acetonitrile. Among the three photosensitizers, SMP-CNPY with one methyl modification showed the best type I ROS (O2-˙, ˙OH) generation capacity and AIE performance. By encapsulation, SMP-CNPY was fabricated into nanoparticles, and SMP-CNPY NPs exhibited lipid droplet targeting ability with near-infrared (NIR) emission. Cell experiments have proved that SMP-CNPY NPs can effectively kill different kinds of cancer cells under normal oxygen conditions. Even under hypoxic and extreme hypoxic conditions, SMP-CNPY NPs can still produce ROS and kill cancer cells. This work holds significant potential in the field of type I AIE-active photosensitizers and provides a new strategy for overcoming the hypoxic dilemma in the malignant tumor microenvironment.

Diversity and functional specialization of H3K9-specific histone methyltransferases.

Histone modifications play a critical role in the control over activities of the eukaryotic genome; among these chemical alterations, the methylation of lysine K9 in histone H3 (H3K9) is one of the most extensively studied. The number of enzymes capable of methylating H3K9 varies greatly across different organisms: in fission yeast, only one such methyltransferase is present, whereas in mammals, 10 are known. If there are several such enzymes, each of them must have some specific function, and they can interact with one another. Thus arises a complex system of interchangeability, "division of labor," and contacts with each other and with diverse proteins. Histone methyltransferases specialize in the number of methyl groups that they attach and have different intracellular localizations as well as different distributions on chromosomes. Each also shows distinct binding to different types of sequences and has a specific set of nonhistone substrates.