Chain Length Research Articles

A new homologous series of semi-conducting liquid crystals based on phenyl-anthracene: synthesis and effect of the alkyloxy terminal chain on charge transport and photoconductive properties.

π-Conjugated systems are the key to the charge transport properties of organic semiconductors. Four multifunctional mesogenic materials were designed and synthesised from 2-amino anthracene and para-hydroxybenzaldehyde. Each material contains a central, rigid phenyl-anthracene core and one flexible alkyloxy chain with different lengths based on the concept of combining liquid crystal (LC) materials featuring facile processability, highly ordered alignment, and effective charge transport. (E)-N-(Anthracen-2-yl)-1-(4-(alkyloxy)phenyl) methanimine (n-OPIA) with n = 8, 10, 12, and 16 was chemically characterized by nuclear magnetic resonance spectroscopy and high-resolution mass spectrometry. Their thermal behaviours were performed by means of differential scanning calorimetry and polarised optical microscopy and showed differences in mesomorphic behaviours with respect to the alkyloxy chain length. Concerning their frontier molecular energy levels, they were studied by optical spectroscopy and cyclic voltammetry and compared to values obtained via ab initio density-functional theory (DFT) calculations. LC field-effect transistors (LC-FETs) using a solvent vapour enhanced drop casting based n-OPIA material showed efficient electrical parameters and interesting photoconductive properties, indicating their potential applications in multifunctional integrated devices. As the alkyloxy chain length of the n-OPIA compounds increased, the hole mobility, on/off current ratio, and responsivity decreased. The 8-OPIA homologue exhibits a mobility one order of magnitude larger than the previously studied homologue, namely 10-OPIA.

Modulating the Amine-CO2 Interaction Strength: Toward Efficient Carbon Capture.

This study contributes to a comprehensive understanding of the interactions between CO2 and amines at the molecular level by exploring the rotational spectra of binary complexes between CO2 and eight different amines through pulsed-jet Fourier transform microwave spectroscopy and quantum chemical calculations. The findings reveal a consistent pattern in which CO2 is bonded to the amino group, primarily through a C···N tetrel bond, while being supported by C-H···O/C hydrogen bonds. Notably, the binding energies increase from primary through tertiary amines and with increasing chain length of the alkyl groups. These groups are found to enhance the electron density at the amino group significantly, thereby facilitating the formation of stronger C···N tetrel bonds. The insights provided into how the interaction strength is modulated by the geometries of amines are deemed essential for the design of more effective CO2 adsorption materials, thus advancing carbon capture technologies.

An Integrated Module Performs Selective 'Online' Epoxidation in the Biosynthesis of the Antibiotic Mupirocin.

The delineation of the complex biosynthesis of the potent antibiotic mupirocin, which consists of a mixture of pseudomonic acids (PAs) isolated from Pseudomonas fluorescens NCIMB 10586, presents significant challenges, and the timing and mechanisms of several key transformations remain elusive. Particularly intriguing are the steps that process the linear backbone from the initial polyketide assembly phase to generate the first cyclic intermediate PA-B. These include epoxidation as well as incorporation of the tetrahydropyran (THP) ring and fatty acid side chain required for biological activity. Herein, we show that the mini-module MmpE performs a rare online (ACP-substrate) epoxidation and is integrated ('in-cis') into the polyketide synthase via a docking domain. A linear polyketide fragment with six asymmetric centres was synthesised using a convergent approach and used to demonstrate substrate flux via an atypical KS0 and a previously unannotated ACP (MmpE_ACP). MmpE_ACP-bound synthetic substrates were critical in demonstrating successful epoxidation in vitro by the purified MmpE oxidoreductase domain. Alongside feeding studies, these results confirm the timing as well as chain length dependence of this selective epoxidation. These mechanistic studies pinpoint the location and nature of the polyketide substrate prior to the key formation of the THP ring and esterification that generate PA-B.

Fatty Acid β-Oxidation May Be Associated with the Erythropoietin Resistance Index in Stable Patients Undergoing Haemodialysis.

Lipid metabolism and adiponectin modulate erythropoiesis in vitro and in general population studies and may also affect responsiveness to erythropoietin in patients undergoing haemodialysis (HD). However, little is known about the impact of lipid-associated biomarkers on reticulocyte production and erythropoietin resistance index (ERI) in patients undergoing HD. Therefore, we aimed to investigate their impacts in 167 stable patients undergoing HD. Pre-dialysis blood samples were collected and analysed for reticulocyte counts and serum lipid profiles by routine analyses and serum carnitine profiles (C0-C18) by LC-MS/MS. ERI was calculated as erythropoietin dose/kg/week normalized for haemoglobin levels. The independent positive determinants of reticulocyte count were log [Triglyceride (TG)] and logC18:1. A large proportion of longer-chain acylcarnitines was positively correlated with reticulocyte counts, possibly resulting from the accumulation of acylcarnitines in mitochondria undergoing fateful exocytosis from reticulocytes. These results indicate a possible association between reticulocyte formation and reduced β-oxidation, which occurs during the peripheral phase of erythroblast enucleation. Total cholesterol (TC) and log [C2/(C16 + C18:1)] as a putative marker of β-oxidation efficiency were negative independent determinants of ERI. Moreover, acyl chain length had a significantly positive impact on the correlation coefficients of individual acylcarnitines with ERI, suggesting that enhanced β-oxidation may be associated with reduced ERI. Finally, adiponectin had no independent association with reticulocyte counts or ERI despite its negative association with HDL-C levels. Enhanced fatty acid β-oxidation and higher TC levels may be associated with lower ERI, whereas higher TG levels and longer acylcarnitines may be related to the latest production of reticulocytes in stable patients undergoing HD.

Polymer Brushes Synthesized by the "Grafting-through" Approach: Characterization and Scaling Analysis.

In this study, a combined morphological and scaling analysis of brushes synthesized by the "grafting-through" method was performed, and the possibility of regulation of the thickness was revealed on an example of polyacrylamide brushes. The chemical composition of the surface in the proposed three-step approach was analyzed by photoelectron and infrared spectroscopy. It was shown that the thickness of the dried brush can be tuned in a controlled manner by varying the polymerization temperature. The scaling dependence of the thickness of the dried brushes d on the length of the polymer d ∼ Lv was obtained by comparing reflectometry and dynamic light scattering data. The value of the exponent v = 0.82 corresponds to a rather high grafting density, exceeding the density of mushroom-like (ν ∼ 1/3) brushes and approaching the value for stretched polymer brushes (ν ∼ 1). A 10-fold increase in the polymer molecular weight leads to a slight decrease in grafting density by a factor of 2, which suggests that the "grafting-through" approach allows obtaining brushes with a high grafting density independently of attached polymer chain length. Herein, the possibility of attachment of uniform polymer brush on large substrates with this approach was demonstrated, which means the scalability of the "grafting-through" technique. The considered approach opens up a simple way for surface modification with polymer nanolayers of controlled thickness.

Synthesis and Magnetic Properties of Spherical Maghemite Nanoparticles with Tunable Size and Surface Chemistry.

We report the synthesis of uniform populations of spherical maghemite nanoparticles by thermal decomposition of iron precursors with tunable diameters centered at 3.3, 7.5, and 12.0 nm and tunable surface chemistry. The three stabilizing ligands were fatty acids with three different alkyl chain lengths (18, 12, and 8 carbon atoms). The unprecedented accurate control of the surface chemistry is made possible by the use of three types of iron complexes, that is, iron oleate (C18), iron dodecanoate (C12), and iron octanoate (C8), associated with fatty acid ligands having the same alkyl chain length, that is, oleic acid (C18), dodecanoic acid (C12), and octanoic acid (C8). Since the thermal decomposition of the iron precursor varies with the chain length, no general rules can be applied to control the nanoparticle size, but optimal synthesis conditions have been investigated to induce the growth of nanoparticles with three different surface chemistries, keeping the diameters centered at 3.3, 7.5, and 12.0 nm. Finally, structural characterization of the nine populations of maghemite nanoparticles was performed by transmission electron microscopy and X-ray diffraction, and magnetic properties were determined by using SQUID magnetometry.

Photocatalytic Cascade Trifluoromethylation/Cyclization : Selective Synthesis of Trifluoroethylated Benzopyran and Benzopyranone Derivatives

We have realized the photocatalytic radical cascade cyclization reaction, enabling the one‐step synthesis of rare trifluoroethyl benzopyran derivatives with a wide variety of structures and excellent yields. Furthermore, the approach exhibits low catalyst load, strong regional control and wide applicability under mild conditions. The selectivity of this transformation is influenced by the length of the carbon chain of the benzaldehyde, as demonstrated by the density functional theory calculations. Additionally, scaling up the photocatalytic process can be easily accomplished.

Seven undescribed meroterpenoids from Sargassum siliquastrum and their inhibitory activity against amyloid β aggregation.

The inhibition of amyloid β (Aβ) aggregation and degradation of Aβ aggregates are promising approaches for treating and preventing Alzheimer's disease. In our search for Aβ42 aggregation inhibitors, we isolated seven undescribed meroterpenoids, sargasilides A (1)‒G (7), from brown alga (Sargassum siliquastrum) collected at Noto Peninsula in Japan. We structurally elucidated the isolated meroterpenoids using spectroscopic data and evaluated their activities using Thioflavin T assay and transmission electron microscopy. Among the seven compounds isolated, sargasilide B had the strongest inhibitory activity. From the comparison of structure and activity, the geometric isomerism of olefins and length of isoprene side chains are important for the activity of meroterpenoids isolated from brown alga.

Experimental and theoretical studies of physicochemical properties of Gemini imidazolium ionic liquids: hydroxyl group in spacer chain and alkyl chain length of cation

Experimental and theoretical studies of physicochemical properties of Gemini imidazolium ionic liquids: hydroxyl group in spacer chain and alkyl chain length of cation

Precision Design of Sequence‐Defined Polyurethanes: Exploring Controlled Folding Through Computational Design

AbstractThis study presents the exploration of sequence‐defined polyurethanes (PUs) as a new class of heteropolymers capable of precise conformational control. Utilizing molecular dynamics simulations, the folding behavior of polyurethane chains is investigated of varying lengths (11, 20, and 50 monomers) in both vacuum and aqueous environments. The simulations reveal that the heterogeneous chains systematically refold to approach the designed target structures better than non‐designed chains or chains with artificially disrupted hydrogen‐bond networks. The subsequent synthesis of an optimized 11‐mer sequence (P1) is achieved through solid‐phase chemistry, with thorough characterization via NMR, MS, and SEC confirming the accuracy of the predicted sequence and its controlled chain length. Solubility tests showed favorable results across multiple solvents, highlighting the versatility of the designed polymer. This research underscores the potential of sequence‐defined polyurethanes to emulate the structural and functional attributes of biological macromolecules, opening new pathways for their application in catalysis, drug delivery, and advanced material design. The findings illustrate a promising direction for the development of synthetic polymers with tailored properties, emphasizing the transformative impact of sequence control in polymer chemistry.

Visualizing and Understanding the Ionic Liquid-Mediated Polybromide Electrochemistry for Aqueous Zinc-Bromine Redox Batteries.

Aqueous zinc-bromine redox systems possess multiple merits for scalable energy storage. Applying bromine complexing agents shows effectiveness in alleviating the key challenge of ubiquitous crossover of reactive liquid bromine species, while the underlying microscopic mechanism requires a deep understanding to engineer better complexing electrochemistry. Herein, taking a series of quaternary ammonium ionic liquids (methyl4NBr, ethyl4NBr, propyl4NBr, and butyl4NBr) as a redox mediator model, operando optical monitoring was used to visualize the dynamic electrochemical behaviors, unveiling the ionic liquid-mediated polybromide electrochemistry with a distinct chain length effect. A longer chain length possesses a stronger electrostatic interaction in the complexing product to effectively capture Br2. Operando results reveal the liquid nature of the reversibly electrogenerated polybromide microdroplets in the butyl4NBr-added redox system, which promoted the Br3-/Br- conversion kinetics and alleviated the self-discharge for improved battery performance. This work provides direct evidence and new insights into complexing electrochemistry for advancing Zn-Br2 batteries.

Quaternary Ammonium Salt-Based Intrinsic Antibacterial Polyurethanes: Optimizing the Antibacterial Activity via Cationic Main- or Side-Chain Design in Hard Segments.

Thermoplastic polyurethanes (TPUs) are one of the most appealing materials with extensive applications in biomedical fields due to their versatile mechanical properties and excellent biocompatibility. In response to the escalating challenges of bacterial infections, it is desirable to obtain TPUs with intrinsic antibacterial activity, particularly for application in biomedical devices and public places. Herein, a cationic main-/side-chain structure regulation strategy in the TPU hard segment was adopted to introduce and optimize the antibacterial activity. This was achieved by synthesizing two types of quaternary ammonium salts (QAS)-containing chain extenders, i.e., N-methyl-N-alkyl-N,N-bis(2-hydroxyethyl) ammonium bromide (Mn, where n represents the N-alkyl chain length) and N,N-dimethyl-N-alkyl-N-2,3-propylene glycol (Dn), from N-methyldiethanolamine (MDEA) and 3-dimethylamino-1,2-propanediol (DMAD), respectively. Given the structural differences between Mn and Dn, main-chain-type PU-Mn and side-chain-type PU-Dn were subsequently obtained with QAS groups in the hard segment. The N-alkyl chain length, QAS content, and main-/side-chain types were systematically investigated to optimize bactericidal properties. The results revealed that a long N-alkyl chain (from C6 to C14) increased the antibacterial activity of the chain extenders and corresponding TPU films. Besides, side-chain-type PU-Dn films showed higher contact-active antibacterial activity than that exerted by the main-chain-type PU-Mn films. Remarkably, almost 100% of Staphylococcus aureus(S. aureus) could be killed by the PU-D14 film with a low QAS content (1.6 wt %). All the TPUs showed good thermal stability with a degradation temperature of 5% mass loss (Td,5%) above 300 °C. Moreover, the TPU films displayed excellent mechanical properties with the tensile strength at break varying from 20.7 to 47.5 MPa and ultimate elongation above 1000%. All of the intrinsic antibacterial films showed negligible hemolytic activities.

Thermodynamic properties and structure of interfacial boundaries in nonionic fluids from the multilayer quasichemical model

The interfacial properties and structure of nonuniform fluids containing complex chainlike molecules and associating species are very much needed in a variety of different fields, including enhanced oil recovery, drug delivery, pharmacy, cosmetics, food processing, etc.Recently, we described the Multilayer Quasichemical Model (MQuM) of a nonuniform fluid that provides a remarkably detailed structural information, including the local concentration and orientation of functional groups of the molecules, the orientation profiles of the chemical bonds in molecular chains and the orientation profiles of the hydrogen bonds in the mixture.In this work, we focus on the description of thermodynamic properties with the aid of MQuM, including the interfacial tension and the profiles of normal and transverse pressures. Before proceeding to more complex systems, a test is performed through comparison with the previously known results from the Scheutjens-Fleer theory for the planar liquid–vapor interface and spherical droplet in one-component fluid of nonpolar monomeric molecules. The model is applied then for planar interfaces between the liquid phases in mixtures of water with n-alkanes of different chain length and for spherical drops in model systems that contain an associating solvent, a nonpolar chain and a nonionic amphiphile. Our theoretical results are compared with experiment, predictions from iSAFT and MD simulation data from the literature. For the spherical droplets, we discuss the model description of the dependence of the interfacial tension on the curvature and estimate the Tolman length. For the planar interface between the equilibrium liquid phases in water – n-alkane mixtures, the interfacial tensions predicted from the model are in good agreement with experiment.

Removal of Per- and Polyfluoroalkyl Substances (PFAS) in fixed bed anion exchange reactors: Factors determining PFAS uptake capacity and models predicting PFAS breakthrough

Per- and polyfluoroalkyl substances (PFAS) are widespread contaminants with adverse environmental and public health effects. Anion exchange (IX) processes can effectively remove many PFAS from water. Objectives of this research were to (1) quantify the effects of PFAS structure and background water matrix constituents [dissolved organic matter (DOM) and major inorganic anions (bicarbonate, chloride, sulfate, and nitrate)] on PFAS uptake capacity of IX resins (KIX), and (2) develop models that predict PFAS breakthrough in packed bed IX columns from PFAS structure and background water matrix characteristics. Rapid small-scale column tests were conducted with two IX resins and 18 water matrices to determine breakthrough curves and KIX values for 23 PFAS. A quantitative structure-property relationship (QSPR) was developed that predicts KIX for different PFAS from a newly developed concept, the normalized chain length (NCL). NCL for each PFAS was calculated using a group contribution method, in which the contributions of PFAS structural fragments to NCL were normalized to that of -CF2-, which was assigned a value of 1.00. Relative to -CF2-, contributions of the structural fragments -O-, -CH2-, >CF-CF3, -CHF-, and -SO3H to NCL for the purposes of KIX prediction were 0.34, -1.87, 1.70, 0.00, and 3.65, respectively. DOM and nitrate adversely impacted PFAS removal, while chloride, sulfate, and bicarbonate, when added at concentrations of up to 3 meq/L above native background levels, had negligible effects on KIX. Based on the obtained water matrix effects, pseudo-single solute models were developed for the two tested IX resins, with which PFAS breakthrough curves for fixed bed IX columns can be predicted using only the NCL and the total organic carbon and nitrate concentrations of the influent water.

Chain relaxation of carborane segments with tailored chain length at high temperatures

High-performance thermoset polymers have good thermal stability due to their highly crosslinked network, while also represent topological constraints that restrict cooperative segmental motion, making it difficult to relax stresses even at high temperatures. Failure of most thermoset polymers at high temperatures is due to ineffective stress relaxation, which limits the use of thermoset polymers in harsh environments. Herein, we employed a cyclosiloxane hybrid polymer (CHP) containing o-carborane segments with tailored carbon chain length to relieve internal stress. The introduction of o-carborane and lengthening of carbon chain both increased the CHP fractional free volume, and reduced the activation energy required in the later stages of the curing process. The carbon chain changed the conformation to achieve chain relaxation by stretching and rotating the carbon–carbon bonds at high temperatures, which avoided cracking and increased the failure temperature of the CHP. Furthermore, the adhesion strength of the o-carborane modified CHP reached a maximum of 2.15 MPa, surpassing 1.23 MPa of the neat CHP. The o-carborane modified CHP with the longest carbon chain exhibited good stability while supporting 1 kg load for 5 min when subjected to ablation, whereas the neat CHP failed after only 47 s. The o-carborane-modified CHP exhibited enhanced high-temperature properties through chain relaxation to inhibit cracking and in situ generation of boron oxide at high temperatures to protect the resin matrix.

Perfluoroalkyl acid precursor or weakly fluorinated organic compound? A proof of concept for oxidative fractionation of PFAS and organofluorines.

Organofluorine mass balance approaches are increasingly applied to investigate the occurrence of per- and polyfluoroalkyl substances (PFAS) and other organofluorines in environmental samples more comprehensively. Usually, complex samples prevent the identification and quantification of every fluorine-containing molecule. Consequently, large unidentified fractions between fluorine sum parameters such as extractable organic fluorine (EOF) and the sum of quantified analytes are frequently reported. We propose using oxidative conversion to separate (unidentified) weakly fluorinated compounds (e.g., pesticides, pharmaceuticals) from PFAA-precursors (perfluoroalkyl chain lengths ≥ C6). We show with three organofluorine model substances (flufenamic acid, diflufenican, pantoprazole) that CF3-groups or aromatic fluorine can be quantitatively converted to inorganic fluoride and trifluoroacetic acid (TFA) by applying PhotoTOP oxidation (UV/TiO2). The principle of fluorine separation in mixtures is demonstrated by the oxidation of the three weakly fluorinated compounds together with the PFAA-precursor 6:2/6:2 fluorotelomer mercaptoalkyl phosphate diester (FTMAP). After oxidation, the products F- and TFA were separated from PFCAs (> C4) by SPE, and the fractions were analyzed individually. Closed mass balances both with and without the addition of organic matrix were achieved. Eventually, the fluorine balance was verified by total fluorine measurements with combustion ion chromatography (CIC). The proposed methods should be considered a proof of concept to potentially explain unidentified fractions of the EOF, especially if compounds with low fluorine content such as pesticides, pharmaceuticals, and their transformation products contribute largely to the EOF. Future studies are needed to show the applicability to the complexity of environmental samples.

Polysaccharide-based hydrogels for cartilage regeneration.

Cartilage defect is one of the common tissue defect clinical diseases and may finally lead to osteoarthritis (OA) which threat patients' physical and psychological health. Polysaccharide is the main component of extracellular matrix (ECM) in cartilage tissue. In the past decades, polysaccharide-based hydrogels have shown great potential for cartilage regeneration considering unique qualities such as biocompatibility, enhanced cell proliferation, drug delivery, low toxicity, and many others. Structures such as chain length and chain branching make polysaccharides have different physical and chemical properties. In this review, cartilage diseases and current treatment options of polysaccharide-based hydrogels for cartilage defection repair were illustrated. We focus on how components and structures of recently developed materials affect the performance. The challenges and perspectives for polysaccharide-based hydrogels in cartilage repair and regeneration were also discussed in depth.

Crowder Chain Length Variability and Excluded Volume Effect on the Phase Separation Behavior of Mucin.

Phase separation within cellular membranes, a critical process underpinning diverse cellular functions, is significantly influenced by transmembrane proteins. Therefore, elucidating the behavior of a transmembrane protein in its phase-separated state is of utmost importance. Our study explores mucin behavior in the cellular milieu, aiming to determine the role of crowder chain length and excluded volume in phase separation. Confocal microscopy images demonstrate the strong partitioning of mucin into the condensed phase influenced by hydrophobic and electrostatic interactions. Fluorescence recovery after photobleaching analysis revealed increased mobility in the presence of shorter chain length crowders, indicating the dynamic behavior of protein within condensed phases. Excluded volume calculation using the theoretical model emphasizes its importance in mucin phase separation under crowded conditions. Our findings underscore the ability of mucin to phase-separate under crowded conditions, highlighting the crucial role of excluded volume and enhancing our understanding of its involvement in cancer progression.

Generalised Gabriel-Roiter measure and thin representations

For Dynkin and Euclidean quivers, it is shown that Gabriel-Roiter measures of thin representations equal the induced chain length functions on the corresponding system of subquivers. This allows a combinatorial procedure to find GR filtrations of thin representations, showing that GR measures of thin representations are field-independent. It is proved that an indecomposable filtration of a thin representation is a GR filtration for a suitable choice of a length function on the category of finite-dimensional representations.

Intrinsic Synergy and Selectivity for the Inhibition of Cancer Cell Growth Generated by a Polymer Ligand of Proximal Enzymes.

A fundamental understanding of the design of polymer ligands of proximal enzymes is essential for the precise targeting of cancer cells, but it is still in its infancy. In this study, we systematically investigated the contribution of the chain length, ligand density, and ligand ratio of proximal enzyme-targeted polymers to the efficacy, synergy, and selectivity for the inhibition of cancer cell proliferation. The results revealed that employing a moderate chain length as a scaffold allowed for an intrinsically high efficacy and synergy of proximal enzyme-targeted polymers, in contrast to single enzyme-targeted polymers that prefer longer chain length for efficacy. The synergy obtained in proximal enzyme targeting was not provided by the combination of the corresponding small molecules. Moreover, the maturation of the synergistic efficacy of the proximal enzyme-targeted polymers also improved selectivity. This study proposes a rational design for polymer inhibitors and/or ligands for cancer cells with a high efficacy and selectivity.