Cyclic Oligomers Research Articles

Properdin: An Immune System Regulator That Can Be a Therapeutic Target of the Complement System

Properdin, a serum glycoprotein, is involved in the immune system regulation, particularly in alternative pathways beginning the complement system. Properdin is made up of cyclic oligomers of monomeric subunits and is generated by various leukocyte subsets. Properdin promotes complement activation, which results in changes withinside the cell milieu that makes contributions to innate and adaptive immunological responses, such as the generation of pro-inflammatory cytokines, immune cell recruitment, and the development of immune cells involved in antigen presentation. Despite the presence of potential inhibitors (properdin) in serum and the formation of non-physiological aggregates in pure properdin preparations, properdin has emerged as a critical component in a variety of inflammatory illness models. Using the properdin-deficient murine model has aided in the knowledge of how properdin participates in diseases pathophysiology promotion or prevention. Pharmaceutical therapy for complement-dependent damage such as properdin is possible for a variety of acute and chronic problems, fluctuating from entrenched medicines for rare conditions to prospective future therapies for large patient groups such as the pandemic coronavirus-virus disease 2019. The basics of properdin biology are discussed, with a focus on the main hurdles that devour hampered the analysis of outcomes as of properdin-targeted studies.

Advanced analytical, chemometric, and genomic tools to identify polymer degradation products and potential microbial consumers in wastewater environments

The worldwide growth in the production of plastics and lack of appropriate waste management has led to unsustainable environmental pollution of global concern. Hence, determining the key drivers characterizing the degradation of polymers in water is a rising topic. Here we propose a workflow based on advanced high throughput data analysis and processing tools aiming at the characterization of (a) the degradation products of polymers exposed to an aquatic environment, and (b) the taxonomical composition of the potential microbial consumers' consortia. To test this approach, polycaprolactonediol (PCLD) polymer probes were exposed to different wastewater environments (influent, aerobic, and anaerobic denitrifying reactors) in four different wastewater treatment plants (WWTPs). Probes were extracted and analyzed by non-target liquid chromatography-high resolution mass spectrometry (LC-HRMS) and the acquired data were processed using advanced chemometric tools (Regions of Interest-Multivariate Curve Resolution-Alternate Least Squares, ROIMCR-ALS). Up to 26 components explaining ca. 69% of the variance were resolved, and 20 of these were further identified. Degradation was dominated by two processes: (a) hydrolysis of the ester groups present in PCLD and (b) formation of cyclic polycaprolactone oligomers. These transformation pathways occurred regardless of what were the WWTPs and the treatment stages, varying only the respective concentrations of the formed by-products. The composition of the microbial communities attached to the polymer and free-living in the surrounding water was characterized by 16S rDNA amplicon sequencing analysis. The two communities showed taxonomic differences and were unique in each WWTP treatment stage. Polymer-attached communities were tentatively proposed as potential consumers.

Cyclodextrin-Based Nanosponges: Overview and Opportunities.

Nanosponges are solid cross-linked polymeric nano-sized porous structures. This broad concept involves, among others, metal organic frameworks and hydrogels. The focus of this manuscript is on cyclodextrin-based nanosponges. Cyclodextrins are cyclic oligomers of glucose derived from starch. The combined external hydrophilicity with the internal hydrophobic surface constitute a unique “microenvironment”, that confers cyclodextrins the peculiar ability to form inclusion host‒guest complexes with many hydrophobic substances. These complexes may impart beneficial modifications of the properties of guest molecules such as solubility enhancement and stabilization of labile guests. These properties complemented with the possibility of using different crosslinkers and high polymeric surface, make these sponges highly suitable for a large range of applications. Despite that, in the last 2 decades, cyclodextrin-based nanosponges have been developed for pharmaceutical and biomedical applications, taking advantage of the nontoxicity of cyclodextrins towards humans. This paper provides a critical and timely compilation of the contributions involving cyclodextrins nanosponges for those areas, but also paves the way for other important applications, including water and soil remediation and catalysis.

Molecular simulations of the structure-property relationships of N-A-S-H gels

A good understanding of the relationship between the micro- and macroscopic properties of N-A-S-H gel is crucial for designing and developing geopolymer binders. This paper develops molecular models for N-A-S-H gels based on aluminosilicate oligomers with different Si/Al ratios and configurations. Our models mimic the geopolymerization process through a poly-condensation reaction between hydroxyls, generating water and forming the aluminosilicate network. The simulation results indicate that more than 50% of the hydroxyls in oligomers are reacted, reflecting the geopolymerization degree. The oligomers with a higher Si/Al ratio and linear configuration exhibit a higher reaction degree, while those with cyclic configurations exhibit a higher complexity for network structure. Decreasing the Si/Al ratio narrows the bond angle distribution and reduces the skeleton stability of N-A-S-H gel structure. This also decreases the dynamic water mobility due to the higher restriction of hydrogen atoms. Chains’ breakage and the associated hydrolysis reaction at their ends are observed with the consumption of almost 2.5% of the generated water molecules. Furthermore, the enhancement in tensile strength is mainly attributed to increased bridge oxygen numbers, especially for those in Si-O-Si bonds. The elastic modulus is mainly influenced by the amount of hydroxyl and network complexity. In addition, increasing the Si/Al ratio increases the number of Si-O-Si bonds and decreases the hydroxyls, enhancing the tensile strength and elastic modulus of N-A-S-H gels. N-A-S-H gels constructed with cyclic oligomers show around 20% higher tensile strength than those with linear oligomers. Thus, this study will provide valuable insights on the molecular structure understanding and design optimization of geopolymer materials.

Theoretical Investigation on the Oligomerization of Methylglyoxal and Glyoxal in Aqueous Atmospheric Aerosol Particles

Secondary organic aerosol (SOA) is the main component of atmospheric particulate matter with wide implications for air quality, human health, and climate change. However, the formation mechanism of SOA has not been fully understood. Methylglyoxal (MGLY) and glyoxal (GLY) are ubiquitous dicarbonyls in the atmosphere and have been considered as important precursors for SOA formation, especially through the oligomerization in the atmospheric aqueous phase. In this paper, the oligomer formation mechanism through the self-oligomerization of MGLY and GLY, and especially their cross-reactions in the atmospheric aqueous phase were investigated by density functional theory (DFT) calculations. Carbenium ions play a key role in the oligomerization, and all of the reactions take place barrierless under acidic conditions. First-generation oligomers (dimers) lead to the formation of chain and cyclic (including five- and six-membered) oligomers, among which five-membered cyclic oligomers are the dominant products. The products identified and described by the energetics of their formation pathways are discussed in view of available experimental findings from the literature. Many of the products were actually measured and assigned. In addition, the diffusion rate constants (kD) of the nucleophilic addition were determined to estimate the formation rate of oligomers in the aqueous phase, and the calculated kD’s are in the range of 1.20–1.31 × 1010 L mol–1 s–1. All of these findings will help us to gain a better understanding of the oligomerization of the dicarbonyl compounds in the atmospheric aqueous aerosol particles, and thus to provide a scientific support toward controlling and reducing SOA formation.

Thermoplastic matrix‐based composites produced by resin transfer molding: A review

AbstractThe recycling of thermoset‐based composites is challenging. The replacement of thermosetting resins with thermoplastics is an initial step to address this issue, together with the use of green reinforcements. Owing to the recent development of low‐viscosity thermoplastic resins, it is possible to produce thermoplastic matrix composites using the resin transfer molding (RTM) technique, which was originally conceived for the production of thermosetting matrix composites. These resins are based on cyclic esters, methyl methacrylate, and cyclic (butylene terephthalate) oligomers. This review presents the state‐of‐the‐art works reported on the production of thermoplastic matrix composites via a thermoplastic RTM (TP‐RTM) process, from the in situ polymerization of the resins through the optimization of the TP‐RTM parameters for the evaluation of the composite properties.

Non-targeted screening of extracts from polyester-phenolic can coatings: Identification of new aldehyde molecules from resole-based resins

Phenolic and substituted phenol based resoles are commonly used in the formulation of can coatings. However, migration analyses of these coatings are very little described compared to other coating technologies. While epoxy and polyester have well known migrants with defined formation mechanisms, Non-Intentionally Added Substances (NIAS) specifically related to the phenolic resin are hardly studied in the literature. The goal of the publication is to further explore the influence of the phenolic resole, used in the formulation of can coatings, on extracted NIAS's nature. Six different model polyester-phenolic can coatings were formulated each with a specific phenol, cresol or tertbutylphenol-based resole. Can coating films were extracted for 24 h at 40 °C in acetonitrile before analysis. NIAS identification was done using gas chromatography separation coupled to high resolution mass spectrometry (HRMS) and nuclear magnetic resonance (NMR) spectroscopy analyses. Cyclic polyester oligomers were found in all extracts, with oligomers found in a range of 10 μg/dm2 to 226 μg/dm2, without specific influence of the resole used in formulation. While very few or no peaks were detected from cresol- and phenol-based resoles, 48 peaks were specifically observed in coating extracts of formulas with tertbutylphenol-based resoles as well as in their respective resoles. The most intense peaks were identified as aldehyde compounds by HRMS and NMR analysis. These aldehydes were semi-quantified in similar proportions as polyester oligomers. The presence of such aldehydes has never been reported in the literature regarding NIAS in can coatings. Further study will then be needed to better understand the aldehyde formation mechanism and assess the toxicological profile of such chemicals.

Chiral Supramolecular Polymer Formed via Host-Guest Complexation of an Octaphosphonate Biscavitand and a Chiral Diammonium Guest

Abstract Chiral supramolecular polymers were constructed through the host-guest complexation of an octaphosphonate biscavitand and a chiral diammonium guest. Isothermal titration calorimetry determined that host-guest complexation was enthalpy- and entropy-favored with high binding constants. Diffusion-ordered NMR spectroscopy and viscometry of the host-guest solution revealed that supramolecular polymerization occurred, which most likely followed a ring-chain mechanism. The cyclic oligomers and the supramolecular polymer chains were visualized by atomic force microscopy. Circular dichroism was observed when the octaphosphonate biscavitand and the chiral diammonium guest were mixed, which suggested that chirally twisted supramolecular polymers were formed.

Comparative study of cyclic polyaniline oligomers with linear and bent structures

In the present work, Grimme’s D3 dispersion corrected density functional theory (DFT-D3) is used for the comparative study of cyclic polyaniline oligomers with linear and bent structures, for the first time. Molecular design and spectral characterisation of these compounds are performed at the B3LYP-D3/6-311G(d,p) and the B3LYP-D3/6-311++G(d,p) levels of theory. The formation mechanism of cyclic polyaniline oligomers compared to the linear and bent structures is discussed. Molecular orbital (MO) calculations are applied to study the electronic structure, and estimate the energy gap between the highest occupied (HOMO) and the lowest unoccupied (LUMO) molecular orbitals. The density of states (DOS) diagrams are used to evaluate the nature of valence and conduction bands and investigate the electrical conductivity. The calculated infrared (IR), ultraviolet-visible (UV-Vis) and nitrogen-15 nuclear magnetic resonance (15N NMR) spectra of these compounds are compared to the theoretical and experimental spectra of polyaniline. Results show that cyclic polyanilines are nonpolar in comparison to the linear and bent structures. The band gap of these molecules is larger than the linear and bent ones. The band gap of cyclic oligomers increases with the increasing size of the rings. These results provide useful information for the characterisation of these novel compounds.

Liquid chromatography-mass spectrometry method for the determination of polyethylene terephthalate and polybutylene terephthalate cyclic oligomers in blood samples.

Food contact materials (FCM) polyethylene terephthalate (PET) and polybutylene terephthalate (PBT) used extensively in food packaging may contain cyclic oligomers which may migrate into food and thus cause toxic effects on human health. A simple, fast, and sensitive ultra-high-performance liquid chromatography method quadrupole time-of-flight mass spectrometer was developed for the analysis of 7 cyclic oligomers in post-mortem blood samples. The targeted analytes were separated on a Waters BEH C18 (150 × 2.1mm, 1.7µm) analytical column by gradient elution. Calibration curves were constructed based on standard solutions and blood samples and Student's t-test was applied to evaluate the matrix effect. The LODs ranged from 1.7 to 16.7μgmL-1, while the method accuracy was assessed by recovery experiments and resulting within the range 84.2-114.6%. Such an analytical method for the determination of PET and PBT cyclic oligomers in biological samples is reported for the first time. The developed methodology allows the determination of these oligomers in blood providing a useful analytical tool to assess the exposure and thus the potential hazard and health risks associated with these non-intentionally added substances (NIAS) from PET and PBT FCM through food consumption. The method was validated and successfully applied to the analysis of 34 post-mortem whole blood samples. Polyethylene terephthalate trimer was detected in four of them, for the first time in literature.

Mono- and dinuclear zirconocene(iv) amide complexes for the catalytic dehydropolymerisation of phenylsilane.

The dehydropolymerisation of phenylsilane is investigated using group 4 metallocene amide complexes as catalysts. The dinuclear zirconocene amide complex Cp2Zr(NMe2)(μ-Me3SiC3SiMe3)Zr(NMe2)Cp2 (2) (Cp = η5-cyclopentadienyl) shows high activity in dehydrocoupling reactions, producing polyphenylsilanes with molecular weights ranging from 200 to 3000 g mol−1 and linear-to-cyclic product ratios of up to 80 : 20. Likewise, different ratios of oligomers and polymers with different tacticities could be described. Ansa-zirconocene amide complexes possessing the ebthi (ebthi = 1,2-ethylene-1,1′-bis(η5-tetrahydroindenyl)) ligand systems were prepared and evaluated for catalytic dehydropolymerisation in comparison to the dinuclear catalyst system.

Nickel-catalysed cycloaddition oligomerisation of 1,6-diynes to medium-size cyclic polyenes

A nickel-catalysed reaction of 1,6-diynes produced cyclic polyene oligomers with a narrow PDI. Their thermal isomerization gave the regio-isomeric cyclic polyenes consisting of trans-disubstituted alkenes.

Characteristics and Hole Transporting Properties of Cyclic Oligomers Consisting of 4-Octyltriphenylamine

Characteristics and Hole Transporting Properties of Cyclic Oligomers Consisting of 4-Octyltriphenylamine

Cyclic (phenylene sulfide) treated carbon fiber for facile preparation of high performance PEEK based anti-wear composites

Improving the surface activity of carbon fiber (CF) via a sizing agent is an efficient approach to enhance the performance of CF reinforced polymer composites. However, the conventional sizing agents usually readily decompose at high temperature. In this work, a novel heat resistant sizing agent is coated directly on the CF surface by in-situ thermal ring-opening polymerization of cyclic phenylene sulfide oligomers (CPS) in air. Studies indicate that the novel sizing agent is oxygenated poly (phenylene sulfide) (PPS), possessing high temperature stability. Properties of the PPS sized CF (CF-CT) filled PEEK based composite are investigated by using the original CF/PEEK composite as a reference. The results reveal that the CF-CT composite exhibit significantly higher tensile strength, lower average friction coefficient and wear rate when CF content exceeds 20 wt%. It is reasonably ascribed to the stronger interface interaction between the PPS sized CF and PEEK, which effectively promotes the enhancement effect of CF in the composite material.

Optically Active Cyclic Oligomers Based on Planar Chiral [2.2]Paracyclophane.

Optically active cyclic dimer, trimer, and tetramer, in which the p-arylene-ethynylenes were stacked, were prepared using enantiopure 4,7,12,15-tetrasubstituted [2.2]paracyclophane as the chiral building block. All molecules exhibited clear Cotton effects in their absorption bands with mirror image spectra, and the signals of the longest wavelengths of the (Rp )- and (Sp )-isomers were positive and negative, respectively. Their circularly polarized luminescence (CPL) signs corresponded with the those of the first Cotton effect. For all molecules, molecular orbitals were localized in one of the stacked p-arylene-ethynylenes in the excited states, resulting in a similar photoluminescence behavior. Although the cyclic dimer did not emit CPL, the cyclic trimer and tetramer exhibited intense CPL emissions with a relatively high dissymmetry factor in the order of 10-3 . Their optical and chiroptical properties were reproduced by time-dependent density functional theory calculations.

Fabrication of h-BN Filled Epoxy-Based Thermally Conductive Adhesive Tapes Containing Cyclic Carbonate-Terminated Oligomers

Fabrication of h-BN Filled Epoxy-Based Thermally Conductive Adhesive Tapes Containing Cyclic Carbonate-Terminated Oligomers

Simultaneous determination of cyclic PET and PBT oligomers migrated from laminated steel cans for food

In this paper, three commonly used PET and PBT copolymers films as inner gauge materials of laminated steel were screened and identified, and then 6 kinds of cyclic PET and PBT oligomers that could be obtained as commercially available standards were selected from the screening results for research. An ultra-high-performance liquid chromatography-quadrupole time-of-flight mass spectrometry (UPLC-QTOF-MS) technique for simultaneous detection of cyclic PET and PBT oligomers in laminated steel cans was first developed. Four different laminated steel metal cans were selected to carry out the migration tests at 40 °C for 10 days in three food simulants of 10% ethanol, 50% ethanol and isooctane. Then commercially acquired cyclic PET dimer to pentamer, cyclic PBT dimer and trimer were used as external standards, and the six oligomers in the migration solutions were quantitatively analyzed by UPLC-QTOF-MS technology. The results showed that all oligomers could be separated well with good linear relationship and high limit of detection. The recoveries of cyclic PET and PBT oligomers ranged from 80.00% to 105.18%, which indicated that UPLC-QTOF-MS was an effective method for simultaneous determination of cyclic PET and PBT oligomers in laminated steel cans. Among the six oligomers tested, cyclic PET trimers and cyclic PET tetramers had the most migration. In addition, the total content of the six oligomers for every can was all the largest in isooctane simulant, meanwhile the content of oligomers in 50% ethanol simulant was far greater than that in 10% ethanol simulant. Moreover, the influence on the amount of oligomers migration by comparing the sterilization and non-sterilization process was studied to find that high sterilization temperature produced more migration and the test methods prescribed by the EU and China standard regulations may cause an underestimate of the amount of oligomer migration.

Exploring the Assembly of Resorc[4]arenes for the Construction of Supramolecular Nano-Aggregates.

Many biologically active compounds feature low solubility in aqueous media and, thus, poor bioavailability. The formation of the host-guest complex by using calixarene-based macrocycles (i.e., resorcinol-derived cyclic oligomers) with a good solubility profile can improve solubilization of hydrophobic drugs. Herein, we explore the ability of resorc[4]arenes to self-assemble in polar solutions, to form supramolecular aggregates, and to promote water-solubility of an isoflavone endowed with anti-cancer activity, namely Glabrescione B (GlaB). Accordingly, we synthesized several architectures featuring a different pattern of substitution on the upper rim including functional groups able to undergo acid dissociation (i.e., carboxyl and hydroxyl groups). The aggregation phenomenon of the amphiphilic resorc[4]arenes has been investigated in a THF/water solution by UV–visible spectroscopy, at different pH values. Based on their ionization properties, we demonstrated that the supramolecular assembly of resorc[4]arene-based systems can be modulated at given pH values, and thus promoting the solubility of GlaB.

Extraction of Cyclic Oligomer and Their Influence on Polyester Dyeing in a Silicone Waterless Dyeing System.

As a promising new dyeing process without using water, the non-aqueous medium dyeing of polyester has attracted people’s attention and some progress has been made in related research. However, the oligomers of polyester fiber can affect the dyeing of polyester during the use of a silicone waterless dyeing system. Based on this point, the oligomer problem in the silicone waterless dyeing system was investigated. The oligomers of some different types of polyester were extracted by solvent extraction. A treatment method with little influence on the fiber was used to reduce the oligomer content in polyester. The improvement of the dyeing effect of polyester after treatment in silicone medium was studied, and the influence of the oligomer on polyester dyeing was also analyzed. For the dyeing of disperse blue 366, the dye exhaustion was increased by 3.25–3.71%, and the color depth of the dyed sample was increased by 6–13%. Moreover, the colorfastness to rubbing was also improved. In the comparison, the changes in thermal properties and crystallization properties of polyester were tested by differential scanning calorimetry (DSC), dynamic mechanical analysis (DMA), and X-ray diffraction analysis (XRD). The results showed that the thermal and crystalline properties of polyester fiber were not changed before and after solvent extraction.

Metathesis of P=C Bonds Catalyzed by N-Heterocyclic Carbenes.

The catalytic metathesis of C=C bonds is a textbook reaction that has no parallel in the widely studied area of multiple bonds involving heavier p-block elements. A high-yielding P=C bond metathesis of phosphaalkenes (ArP=CPh2 , Ar=Mes, o-Tol, Ph) has been discovered that is catalyzed by N-heterocyclic carbenes (NHC=Me2 IMe, Me2 Ii Pr). The products are cyclic oligomers formally derived from ArP=PAr [i. e. cyclo-(ArP)n ; n=3, 4, 5, 6] and Ph2 C=CPh2 . Preliminary mechanistic studies of this remarkable transformation have established NHC=PAr (Ar=Mes, o-Tol, Ph) as key phosphinidene transfer agents. In addition, novel cyclic intermediates, such as, cyclo-(ArP)2 CPh2 and cyclo-(ArP)4 CPh2 have also been observed. This work represents a rare application of non-metal-based catalysts for transformations involving main-group elements.