Repeating Unit Research Articles

Enhancement of Moisture‐Resistant Performance of Epoxy Resins via Introduction of Hydrophobic and Flexible Chains

AbstractThe introduction of long and flexible polyether chains in epoxy resins is an effective method to improve their toughness. However, using the hydrophilicity/hydrophobicity of polyether chains to tune their moisture resistance has been overlooked currently. In this work, two types of polyether‐based diglycidyl ethers with hydrophilic poly(oxyethylene) (DGEPOE) and relatively hydrophobic poly(oxybutylene) segments (DGEPOB) are synthesized and then binary‐cured with commercial diglycidyl ether of bisphenol A (DGEBA), respectively, yielding the corresponding DGEPOE:DGEBA‐m:ns and DGEPOB:DGEBA‐m:ns based on various ratios. For comparison, pure DGEPOEr, DGEPOBr, and DGEBAr resins are also prepared. Results show that the equilibrium water uptake of DGEPOB:DGEBA‐m:ns is at least less than one‐fifth of that of DGEPOE:DGEBA‐m:ns; meanwhile, the diffusion coefficients of water molecules in DGEPOB:DGEBA‐m:ns are also 1–2 orders of magnitude lower than those in DGEPOE:DGEBA‐m:ns, demonstrating that the incorporation of hydrophobic POB chains can significantly reduce the hygroscopicity of resins. Moreover, DGEPOB:DGEBA‐m:ns not only exhibit superior flexibility and ductility relative to pure DGEBAr, but display exceptional strength and toughness in comparison with pure DGEPOBr. These findings suggest that tuning the hydrophilicity/hydrophobicity of building units of epoxy monomers offers a promising strategy for developing high‐performance epoxy materials, especially suitable for humid environments.

Electronic Structures and Spectra of Donor-Acceptor Conjugated Oligomers.

Narrow band gap donor-acceptor conjugated polymers present excellent paradigms in photonics and optoelectronics due to their chemical tunability, correlated electronic structures, and tunable open-shell electronic configurations. However, rational design for enhancing the properties of these molecular systems remains challenging. In this study, we employed density functional theory (DFT) calculations to investigate prototypical narrow band gap donor-acceptor conjugated oligomers, consisting of alternating cyclopentadithiophene (CPDT) donors paired with benzothiadiazole (BT), benzoselenadiazole (BSe), benzobisthiadiazole (BBT), and thiadiazoloquinoxaline (TQ) acceptors. Analyses of structures, singlet-triplet gaps, and absorption spectra of oligomers with up to ten repeat units have shown that when incorporating the BT, BSe, and TQ acceptors, the backbone curvature resulted in spiral structures that were energetically favored over their linear counterparts, causing differences in the calculated circular dichroism spectra. Oligomers with BBT-based acceptors preferred, however, a linear geometry, consistent with an open-shell electronic structure. Calculated singlet-triplet splittings demonstrated the importance of long chains and specific structures for consistency with the experiment, while effects of the solvent were also quantified. Based on the predicted low-energy conformations, one-photon absorption spectra for the considered oligomers have shown that using the Tamm-Dancoff approximation within time-dependent DFT for the large systems offers good agreement with the first absorption maxima in measured experimental spectra, thus validating the method for large donor-acceptor oligomers. Natural transition orbital analyses provided insights into the excited-state characteristics. Two-photon absorption maxima were accurately predicted, but the cross-sections were overestimated or underestimated, as dependent on the level of theory employed, to be addressed in future work.

Total Syntheses of β- and γ-Naphthocyclinones.

After half a century from their isolation in 1974, we report the first total syntheses of β- and γ-naphthocyclinones, two dimeric pyranonaphthoquinones featuring an unusual bicyclo[3.2.1]-octadienone core. The syntheses were achieved with full stereochemical control and functional group management, relying on 1) enantioselective construction of the bicyclic core by Rh-catalyzed enantioselective 1,4-addition followed by thiolate-mediated reductive cyclization, and 2) judicious design of a common chiral, non-racemic monomer unit that is capable of divergence into the donor and acceptor units, and reunion to construct the bicyclo[3.2.1]octadienone core.

Exploring LCST- and UCST-like Behavior of Branched Molecules Bearing Repeat Units of Elastin-like Peptides as Side Components.

Elastin-like peptides (ELPs) exhibit lower critical solution temperature (LCST)-type behavior, being soluble at low temperatures and insoluble at high temperatures. While the properties of linear, long-chain ELPs are well-studied, short-chain ELPs, especially those with branched architectures, have been less explored. Herein, to obtain further insights into multimeric short ELPs, we investigated the temperature-responsive properties of branched molecules composed of a repeating pentapeptide unit of short ELPs, Phe-Pro-Gly-Val-Gly, as side components and oligo(Glu) as a backbone structure. In turbidimetry experiments, the branched ELPs showed LCST-like behavior similar to conventional ELPs and upper critical solution temperature (UCST)-like behavior, which are rarely observed in ELPs. In addition, the morphological aspects and mechanisms underlying the temperature-responsiveness were investigated. We observed that spherical aggregates formed, and the branched ELPs underwent structural changes through the self-assembly process. This study demonstrates the unique temperature-responsiveness of branched short ELPs, providing new insights into the future development and use of ELPs with tailored properties.

Multifunctional Polymer Synthesis via Sequential Postpolymerization Modification Using a Single Aldehyde Repeat Unit: Allylation and Orthogonal Esterification and Thiol-ene Reaction.

Herein, we present a highly efficient method for synthesizing multifunctional polymers. This method involves the sequential postpolymerization modification (PPM) of a highly reactive aldehyde polymer. We introduce an allylic alcohol functionality into the polymer backbone via Barbier-type allylation, a process facilitated by easy-to-handle indium(0) powder. This step enables the formation of orthogonal pendants, secondary alcohol, and terminal alkene, which can be further functionalized through esterification and thiol-ene click reactions. All of these processes are carried out under mild conditions, ensuring high efficiency and a wide range of functional groups. Our study underscores PPM's operational simplicity and versatility in developing advanced polymer materials and expanding the scope of multifunctional polymer design.

Nanopore sequencing with unique molecular identifiers enables accurate mutation analysis and haplotyping in the complex lipoprotein(a) KIV-2 VNTR.

Repetitive genome regions, such as variable number of tandem repeats (VNTR) or short tandem repeats (STR), are major constituents of the uncharted dark genome and evade conventional sequencing approaches. The protein-coding LPA kringle IV type-2 (KIV-2) VNTR (5.6kb per unit, 1-40 units per allele) is a medically highly relevant example with a particularly intricate structure, multiple haplotypes, intragenic homologies, and an intra-VNTR STR. It is the primary regulator of plasma lipoprotein(a) [Lp(a)] concentrations, an important cardiovascular risk factor. Lp(a) concentrations vary widely between individuals and ancestries. Multiple variants and functional haplotypes in the LPA gene and especially in the KIV-2 VNTR strongly contribute to this variance. We evaluated the performance of amplicon-based nanopore sequencing with unique molecular identifiers (UMI-ONT-Seq) for SNP detection, haplotype mapping, VNTR unit consensus sequence generation, and copy number estimation via coverage-corrected haplotypes quantification in the KIV-2 VNTR. We used 15 human samples and low-level mixtures (0.5 to 5%) of KIV-2 plasmids as a validation set. We then applied UMI-ONT-Seq to extract KIV-2 VNTR haplotypes in 48 multi-ancestry 1000 Genome samples and analyzed at scale a poorly characterized STR within the KIV-2 VNTR. UMI-ONT-Seq detected KIV-2 SNPs down to 1% variant level with high sensitivity, specificity, and precision (0.977 ± 0.018; 1.000 ± 0.0005; 0.993 ± 0.02) and accurately retrieved the full-length haplotype of each VNTR unit. Human variant levels were highly correlated with next-generation sequencing (R2 = 0.983) without bias across the whole variant level range. Six reads per UMI produced sequences of each KIV-2 unit with Q40 quality. The KIV-2 repeat number determined by coverage-corrected unique haplotype counting was in close agreement with droplet digital PCR (ddPCR), with 70% of the samples falling even within the narrow confidence interval of ddPCR. We then analyzed 62,679 intra-KIV-2 STR sequences and explored KIV-2 SNP haplotype patterns across five ancestries. UMI-ONT-Seq accurately retrieves the SNP haplotype and precisely quantifies the VNTR copy number of each repeat unit of the complex KIV-2 VNTR region across multiple ancestries. This study utilizes the KIV-2 VNTR, presenting a novel and potent tool for comprehensive characterization of medically relevant complex genome regions at scale.

Analysis of the Setomimycin Biosynthetic Gene Cluster from Streptomyces nojiriensis JCM3382 and Evaluation of Its α-Glucosidase Inhibitory Activity Using Molecular Docking and Molecular Dynamics Simulations.

The formation of atroposelective biaryl compounds in plants and fungi is well understood; however, polyketide aglycone synthesis and dimerization in bacteria remain unclear. Thus, the biosynthetic gene cluster (BGC) responsible for antibacterial setomimycin production from Streptomyces nojiriensis JCM3382 was examined in comparison with the BGCs of spectomycin, julichromes, lincolnenins, and huanglongmycin. The setomimycin BGC includes post-polyketide synthase (PKS) assembly/cycling enzymes StmD (C-9 ketoreductase), StmE (aromatase), and StmF (thioesterase) as key components. The heterodimeric TcmI-like cyclases StmH and StmK are proposed to aid in forming the setomimycin monomer. In addition, StmI (P-450) is predicted to catalyze the biaryl coupling of two monomeric setomimycin units, with StmM (ferredoxin) specific to the setomimycin BGC. The roles of StmL and StmN, part of the nuclear transport factor 2 (NTF-2)-like protein family and unique to setomimycin BGCs, could particularly interest biochemists and combinatorial biologists. α-Glucosidase, a key enzyme in type 2 diabetes, hydrolyzes carbohydrates into glucose, thereby elevating blood glucose levels. This study aimed to assess the α-glucosidase inhibitory activity of EtOAc extracts of JCM 3382 and setomimycin. The JCM 3382 EtOAc extract and setomimycin exhibited greater potency than the standard inhibitor, acarbose, with IC50 values of 285.14 ± 2.04 μg/mL and 231.26 ± 0.41 μM, respectively. Molecular docking demonstrated two hydrogen bonds with maltase-glucoamylase chain A residues Thr205 and Lys480 (binding energy = -6.8 kcal·mol-1), two π-π interactions with Trp406 and Phe450, and one π-cation interaction with Asp542. Residue-energy analysis highlighted Trp406 and Phe450 as key in setomimycin's binding to maltase-glucoamylase. These findings suggest that setomimycin is a promising candidate for further enzymological research and potential antidiabetic therapy.

Searching of optimal conditions and development of analysis of isocyanate groups in prepolymers

The purpose of the work was to study the options for volumetric analysis of isocyanate groups in prepolymers and to search for factors affecting the accuracy of the analysis in order to identify differences between the values specified by the manufacturer and those obtained in the laboratory.Metods. Intermediate polymerization products based on isocyanates from two or more monomeric units used for the production of polyurethanes, the quality of which is determined by the optimal ratio of isocyanate and hydroxyl groups, were selected as the object of research. The NCO index was determined by the volumetric method based on the interaction of isocyanate groups with diethylamine, with confirmation of the results by methods of mathematical statistics.Results. the work analyzes currently known methods for determining the content of isocyanate groups in prepolymers and identifies differences in the technique of execution. A volumetric method for determining the NCO index based on the interaction of isocyanate groups with diethylamine was used. The solubility of industrial prepolymer samples was evaluated and the dissolution rate was calculated, on the basis of which the optimal volume of the solution and prepolymer samples were determined, providing an accurate determination of the isocyanate number. The adjusted conditions allowed us to reach the required value of the NCO index of the SKU prepolymer, calculated on the basis of static processing of the results and the construction of the Gauss distribution curve. Changes in the methodology make it possible to reach a certified value of the indicator, which allows its use for further calculations in the synthesis of polyurethane.Conclusion. Recommendations for determining the isocyanate index for the analysis of prepolymer by the volumetric method will help to monitor incoming raw materials for compliance with certificates to perform an accurate calculation of raw materials in the synthesis of polyurethane.Key words: prepolymer, polyurethane, isocyanate index, volumetric analysis, diethylamine, solubility.

Expression of a novel NaD1 recombinant antimicrobial peptide enhances antifungal and insecticidal activities

This study aimed to increase the antifungal and insecticidal activities of NaD1, as an antimicrobial peptides (AMP), by improving its interaction with the fungal cell wall and chitin monomeric units in insect midguts. Hence, the chitin-binding domains (CBDs) of wheat germ agglutinin protein (WGA) were fused to either N- or C-terminus of NaD1 generating transgenic Nicotiana tabacum hairy roots (HRs). Molecular assessments confirmed the integration of NaD1 transgenes, their transcription and production of recombinant peptides in the HR lines. Total protein of (CBD)4-NaD1 and NaD1-(CBD)4 transgenic lines inhibited the growth of Pyricularia oryzae mycelium, suggesting that fusion of CBD to NaD1 can increase NaD1 half-life, leading to higher affinity toward cell wall chitin. Furthermore, feeding the third-instar larvae of Chilo suppressalis with both (CBD)4-NaD1 and NaD1-(CBD)4 extracts exhibited a higher mortality rate. Both NaD1-CBDs caused a significant decrease in trypsin (TRY) and chymotrypsin (CTR) activities in the larvae, while enhancing the activity of antioxidant enzymes CAT, POD, APX, and SOD. Therefore, feeding the larvae by total extract of NaD1-(CBD)4 and (CBD)4-NaD1 HR lines probably increased affinity to midgut chitin in C. suppressalis, enhancing insecticidal activities. Overall, the results indicate that recombinant peptides are effective in enhancing fungal and insect resistance.

The influence of myrcene on anionic copolymerization of 1,3-pentadiene and styrene

C5-dienes including 1,3-pentadiene (PD) and isoprene (IP) as by-products of naphtha cracking are important industrial raw materials for the production of thermoplastic elastomers, synthetic rubber and resins. The research on living anionic polymerization (LAP) of myrcene (MY) is also of great significance for the development of new bio-based materials and products. Focusing on the optimal utilization of C5 resources and the high-value utilization of biomass resources and the realization of green chemical production, this article reports the synthesizing of a novel terpolymer by LAP of PD, styrene (ST) and the biomass monomer MY. The discovery of the alternating sequence structure of ST and PD inspires us to further explore the development of copolymers containing this unique sequence structure. The special long branched side chain of MY and its low glass transition temperature are also conducive to the synthesis of new integrated rubbers. The 1H NMR tracking analysis indicates that the polymerization pattern changes from alternating sequence to gradient block sequence with the increase of MY content. Combined with FTIR analysis, the PD monomeric units are mainly trans-1,4 structure and MY monomeric units are predominant cis-1,4 structure. Considering the extremely high polymerization activity of MY compared to ST and PD, the copolymerization rate is significantly dependent on the concentration of the PD monomer. Despite this, due to the interactions between ST and PD ([ST¦PD] intermediate), ST still tends to form alternating segments with PD. The ternary copolymerization can be viewed as a “binary gradient copolymerization” of [ST¦PD] and MY (rMY > r[ST¦PD]).

Photochemical Oxidation of Polyethylene Terephthalate Microplastics Adsorbed on Sand and Silica Surfaces.

The environmental contamination by plastics, microplastics, and related compounds is a major concern. While the detection and release of micro- and nanoparticles from these materials have been widely studied, the formation and release of molecules resulting from their degradation in the environment have been overlooked. This work presents a study of the products released from poly(ethylene terephthalate) (PET) irradiated as pure particles and adsorbed on silica and sand surfaces under different irradiation conditions. The role of oxygen was also evaluated. The products were identified by gas chromatography-mass spectrometry (GC-MS) and liquid chromatography-high resolution mass spectrometry (LC-HRMS). The main released molecules can be accounted for by considering the cleavage of α- and β-bonds next to the ester moiety of the polymer chain. Volatile products such as benzene as well as monomer units of the polymer and related products were identified. In the presence of oxygen, acetic acid and products resulting from hydroxylation at the benzenic ring or at the ethyl moiety were detected. Adsorption on silica and sand has little effect on the photoproduct distributions. The irradiation at 360 nm leads to distributions similar to the ones observed at 257 nm, but the reaction rate is lower. The identified product ethylene terephthalate is a marker of PET plastics and particles and can therefore be used to evaluate the environmental contamination by this polymer material.

Reversible Long-Term Operation of a MK35x Electrolyte-Supported Solid Oxide Cell-Based Stack

High-temperature reversible solid oxide cells (rSOC) combine electrolyzer and fuel cell in one process unit which promises economic advantages with unrivaled high electrical efficiencies. However, large temperature gradients during dynamic rSOC operation can increase the risk of mechanical failure. Here, the degradation behavior of a 10-cell stack of the type “MK35x” with chromium-iron-yttrium (CFY) interconnects and electrolyte-supported cells (ESC) developed at Fraunhofer IKTS was investigated in rSOC operation at DLR. Its degradation was evaluated during nominal rSOC operation for more than 3400 h with 137 switching cycles between solid oxide fuel cell and solid oxide electrolysis cell operation of 24 h reflecting intermittent availability of solar energy. The voltage degradation rates of +0.58%/kh and −1.23%/kh in electrolysis and fuel cell operation, respectively, are among the lowest reported in literature. Comparison to a previously published long-term test in steam electrolysis did not show any indication for an increased degradation. Electrochemical impedance spectroscopy measurements were performed for all repeat units to evaluate the degradation behavior in detail. An overall polarization resistance decrease due to an improvement of the oxygen electrode was observed during electrolysis operation but was absent during fuel cell operation.

PoxtA amplification and mutations in 23S rRNA confer enhanced linezolid resistance in Enterococcus faecalis.

This study aimed to explore the evolutionary patterns and resistance mechanisms of an Enterococcus faecalis strain harbouring poxtA under linezolid exposure. A poxtA-carrying E. faecalis electrotransformant DJH702 with a linezolid minimum inhibitory concentration of 4 mg/L was exposed to increasing concentrations of linezolid (8-64 mg/L). The derived strains growing at 8, 16, 32 and 64 mg/L, designed DJH702_8, DJH702_16, DJH702_32 and DJH702_64, were obtained. The amplification and overexpression of poxtA were measured using sequencing and RT-PCR, the fitness cost by competition assays and the stability of the repeat units by serial passage. In all derived strains, high-level linezolid resistance develops through poxtA amplification. The relative copy numbers and transcription levels of poxtA were significantly increased. However, in the presence of higher linezolid concentrations, DJH702_32 and DJH702_64 showed reduced poxtA copy numbers and transcription levels compared with DJH702_8 and DJH702_16, but additional mutations in the 23S rRNA (G2505A). IS1216E-mediated formation of translocatable units with subsequent tandem amplification of these translocatable units supported the gain of poxtA segments. However, these amplicons were not stable and were lost frequently in the absence of a linezolid selection pressure. The amplification of the poxtA region did not result in a fitness cost, but mutations in 23S rRNA did. poxtA-carrying E. faecalis electrotransformants used two distinct mechanisms to resist linezolid selection pressure: at lower concentrations, strains prioritized increasing poxtA expression levels, while at higher concentrations, a combination of increased poxtA expression and mutations in 23S rRNA was observed.

Degradable polyolefins prepared by integration of disulfides into metathesis polymerizations with 3,6-dihydro-1,2-dithiine.

Disulfide-containing polyolefins were synthesized by ring-opening metathesis polymerization (ROMP) of the 6-membered disulfide-containing cyclic olefin, 3,6-dihydro-1,2-dithiine, which was prepared by ring-closing metathesis of diallyl disulfide. This approach facilitated the production of disulfide-containing unsaturated polyolefins as copolymers with disulfide monomer units embedded within a poly(cyclooctene) or poly(norbornene) framework. The incorporation of disulfides into the polymer backbone imparts redox responsiveness and enables polymer degradation via chemical reduction or thiol-disulfide exchange. This ROMP copolymerization strategy yielded both linear polyolefins, as well as bottlebrush polymers, with degradable segments, thereby broadening the scope of responsive polymer architectures synthesized by ROMP.

In-situ cryogenic X-ray diffraction analysis of Poly(dimethylsiloxane) oil and film

Understanding the phase transitions and crystallographic characteristics of polysiloxane materials poses a significant challenge. To address this issue, a custom cryogenic chamber has been developed and integrated with a laboratory X-ray diffraction apparatus, enabling the execution of in-situ temperature-dependent X-ray diffraction (XRD) analyses across the cooling and heating cycles. Through the utilization of diverse sample holders, the real-time monitoring of crystallization and melting phenomena in both linear poly(dimethylsiloxane) (PDMS) oil and crosslinked PDMS film has been made feasible. Notably, high-quality X-ray diffraction data, encompassing 13 diffraction lines, are successfully acquired for the first time for linear PDMS oil at 153K. Subsequent crystallographic examination has revealed a tetragonal unit cell characterized by lattice parameters a = b = 8.3379 Å, c = 11.9284 Å, and space group I 41, suggesting the adoption of a fourfold helical conformation by two polymer chains, each comprising four monomer units, within the lattice structure. This improved and versatile X-ray instrumentation presents clear advantages over conventional commercial powder X-ray diffractometers, which is anticipated to provide a promising in-situ characterization approach for investigating the low-temperature behaviors of liquid or oil materials.

The dimerization domain of SARS CoV 2 Nucleocapsid protein is partially disordered as a monomer and forms a high affinity dynamic complex.

The SARS-CoV-2 Nucleocapsid (N) is a 419 amino acids protein that drives the compaction and packaging of the viral genome. This compaction is aided not only by protein-RNA interactions, but also by protein-protein interactions that contribute to increasing the valence of the nucleocapsid protein. Here, we focused on quantifying the mechanisms that control dimer formation. Single-molecule Förster Resonance Energy Transfer enabled us to investigate the conformations of the dimerization domain in the context of the full-length protein as well as the energetics associated with dimerization. Under monomeric conditions, we observed significantly expanded configurations of the dimerization domain (compared to the folded dimer structure), which are consistent with a dynamic conformational ensemble. The addition of unlabeled protein stabilizes a folded dimer configuration with a high mean transfer efficiency, in agreement with predictions based on known structures. Dimerization is characterized by a dissociation constant of ~ 12 nM at 23 °C and is driven by strong enthalpic interactions between the two protein subunits, which originate from the coupled folding and binding. Interestingly, the dimer structure retains some of the conformational heterogeneity of the monomeric units, and the addition of denaturant reveals that the dimer domain can significantly expand before being completely destabilized. Our findings suggest that the inherent flexibility of the monomer form is required to adopt the specific fold of the dimer domain, where the two subunits interlock with one another. We proposed that the retained flexibility of the dimer form may favor the capture and interactions with RNA, and that the temperature dependence of dimerization may explain some of the previous observations regarding the phase separation propensity of the N protein.

Simple/commercially‐available Lewis acid in anionic ring‐opening polymerization: powerful compounds with multiple applications in macromolecular engineering

Simple and commercially‐available Lewis acids (LA) are commonly used catalysts in anionic ring‐opening polymerization (AROP) reactions. In particular, for the AROP of epoxides, the addition of a Lewis acid allows the transition from a so‐called end‐chain mechanism to a monomer‐activated mechanism. The presence of the LA simultaneously leads to a decrease in the reactivity of active centers through the formation of a three‐species ate complex and to the activation of the monomer by LA coordination to the oxygen atom of the oxirane ring. These two effects result in both an increase in propagation kinetics and a decrease in transfer reactions, which has enabled the synthesis of high molecular weight polyethers. However, the impact of Lewis acids goes far beyond these classic effects. They have indeed enabled the polymerization of new functional monomers as well as the synthesis of heterotelechelic macromolecules. Also widely used as catalysts in copolymerization reactions (statistical, sequential, or alternating) Lewis acids can strongly influence the composition and sequence of monomer units in macromolecules. Finally, Lewis acids can also significantly influence the architecture of the obtained macromolecules. This review aims to list the various contributions of Lewis acids to macromolecular engineering and illustrate them with well‐chosen examples.

Description of the complete rDNA repeat unit structure of Coturnixjaponica Temminck et Schlegel, 1849 (Aves).

Ribosomal RNA (18S, 5.8S, 28S) gene clusters in genomes form regions that consist of multiple tandem repeats. They are located on a single or several pairs of chromosomes and play an important role in the formation of the nucleolus responsible for the assembly of ribosome subunits. The rRNA gene cluster sequences are widely used for taxonomic studies, however at present, complete information on the avian rDNA repeat unit structure including intergenic spacer sequence is available only for the chicken (Gallusgallusdomesticus Linnaeus, 1758). The GC enrichment and high-order repeats peculiarities within the intergenic spacer described for the chicken rDNA cluster may be responsible for these failures. The karyotype of the Japanese quail (Coturnixjaponica Temminck et Schlegel, 1849) deserves close attention because, unlike most birds, it has three pairs of nucleolar organizer bearing chromosomes, two of which are microchromosomes enriched in repeating elements and heterochromatin that carry translocated terminal nucleolar organizers. Here we assembled and annotated the complete Japanese quail ribosomal gene cluster sequence of 21166 base pairs (GenBank under the registration tag BankIt2509210 CoturnixOK523374). This is the second deciphered avian rDNA cluster after the chicken. Despite the revealed high similarity with the chicken corresponding sequence, it has a number of specific features, which include a slightly lower degree of GC content and the presence of bendable elements in the content of both the transcribed spacer I and the non-transcribed intergenic spacer.

Synthesis and properties of biomass‐based polymethacrylate comprising chitin‐derived 2‐acetamide‐2‐deoxyisosorbide as a repeat unit

AbstractSynthesis and applications of biobased polymers have been extensively studied in order to reduce the use of petroleum‐based polymers and likewise environmental load. Several biobased polymers have been produced on a commercial large scale to date. However, the lineup of biobased high‐performance polymers with transparency and high glass transition temperature is inadequate and their development is a critical issue. In this article, we design a new biobased polymethacrylate comprising rigid cis‐fused bicyclic 2‐acetamide‐2‐deoxyisosorbide (ADI) as a repeat unit. We have recently invented catalytic transformation systems from chitin as a marine biomass to ADI as a new nitrogen‐containing platform chemical. The ADI‐based polymethacrylate is synthesized via free radical polymerization of the methacrylic acid ester of ADI initiated by (NH4)2S2O8 and N,N,N′,N′‐tetramethylethylenediamine in dimethylsulfoxide–H2O mixed solvent. The molecular weight and its dispersity are estimated by size exclusion chromatography on the basis of polymethylmethacrylate standards. UV–visible spectroscopy demonstrates the high transparency of the polymer in the visible wavelength region. Differential scanning calorimetry analysis of the polymer clarifies the remarkably high glass transition temperature, compared with that of polymethylmethacrylate. The thermal decomposition temperature of the polymer is also evaluated by thermogravimetric analysis. On the basis of the favorable properties of the ADI‐based polymer, the present study proposes it as a nitrogen‐containing biobased polymer useful for real‐world applications. © 2024 Society of Chemical Industry.

Importance of Primary and Secondary Hydrogen Bonding Interactions of Polyols on the Plasticization of Chitosan.

Molecular-level interactions between glucosamine and glycerol have shed light on the specific binding motif required for the plasticization of chitosan with glycerol via the gel theory mechanism. Here, we describe a spectroscopic study of the intermolecular interactions between the monomeric repeat unit of chitosan, glucosamine, and simplified 1,2- and 1,3-diol units of glycerol (i.e, 1,3-propanediol and ethylene glycol). The material properties of chitosan films containing these diols at varying concentrations were characterized using ATR-IR, DMA, TGA, and SEM. The combined results indicate that these diols plasticize chitosan via the lubricity theory mechanism, which differs from glycerol that plasticizes via the gel theory mechanism. At low concentrations, this difference in mechanism has a minimal impact on the material properties. However, at high concentrations of the diols, the necessity of a secondary hydrogen bonding interaction for the retention of chitosan plasticization is observed with a significant increase in the Young's modulus of the materials. The impact of hydrophobicity within the diols was also investigated in chitosan films using 1,2-propanediol and 2-methyl-1,3-propanediol. The combined analyses provide strong evidence that both primary and secondary interactions are responsible for determining the mechanism of chitosan plasticization.