A Facile Approach to Construct Novel Polyesters as Soft Midblock for Thermoplastic Elastomers.

The development of innovative synthetic strategies to create functional polycaprolactones is highly demanded for advanced material applications. In this contribution, we reported a facile synthetic strategy to prepare a class of CL-based monomers (R-TO) derived from epoxides. They readily polymerize via well-controlled ring-opening polymerization (ROP) to afford a series of polyesters P(R-TO) with high molecular weight (Mn up to 350 kDa). Sequential addition copolymerization of MTO and L-lactide (L-LA) allowed to access of a series of ABA triblock copolymers with composition-dependent mechanical properties. Notably, P(L-LA)100-b-P(MTO)500-b-P(L-LA)100 containing the amorphous P(MTO) segment as a soft midblock and crystalline P(L-LA) domain as hard end block behaved as an excellent thermoplastic elastomer (TPE) with high elongation at break (1438 ± 204%), tensile strength (23.5 ± 1.7 MPa), and outstanding elastic recovery (>88%).

Torsional Strain Enabled Ring-Opening Polymerization towards Axially Chiral Semiaromatic Polyesters with Chemical Recyclability.

The development of new chemically recyclable polymers via monomer design would provide a transformative strategy to address the energy crisis and plastic pollution problem. Biaryl-fused cyclic esters were targeted to generate axially chiral polymers, which would impart new material performance. To overcome the non-polymerizability of the biaryl-fused monomer DBO, a cyclic ester Me-DBO installed with dimethyl substitution was prepared to enable its polymerizability via enhancing torsional strain. Impressively, Me-DBO readily went through well-controlled ring-opening polymerization, producing polymer P(Me-DBO) with high glass transition temperature (Tg >100 °C). Intriguingly, mixing these complementary enantiopure polymers containing axial chirality promoted a transformation from amorphous to crystalline material, affording a semicrystalline stereocomplex with a melting transition temperature more than 300 °C. P(Me-DBO) were capable of depolymerizing back to Me-DBO in high efficiency, highlighting an excellent recyclability.

Kinetic Resolution Polymerization Enabled Chemical Synthesis of Perfectly Isotactic Polythioesters.

Isotactic polythioesters (PTEs) that are thioester analogs to natural polyhydroxyalkanoates (PHAs) have attracted growing attention due to their distinct properties. However, the development of chemically synthetic methods for preparing isotactic PTEs has long been an intricate endeavour. Herein, we report the successful synthesis of perfectly isotactic PTEs via stereocontrolled ring-opening polymerization. This binaphthalene-salen aluminium (SalBinam-Al) catalyst promoted a robust polymerization of rac-α-substituted-ß-propiothiolactones (rac-BTL and rac-PTL) with highly kinetic resolution, affording perfectly isotactic P(BTL) and P(PTL) with Mn up to 276 kDa. Impressively, the isotactic P(BTL) formed a supramolecular stereocomplex with improved thermal property (Tm=204 °C). Ultimately, this kinetic resolution polymerization enabled the facile isolation of enantiopure (S)-BTL, which could efficiently convert to an important pharmaceutical building block (S)-2-benzyl-3-mercapto-propanoic acid. Isotactic P(PTL) served as a tough and ductile material comparable to the commercialized polyolefins. This synthetic system allowed to access of isotactic PTEs, establishing a powerful platform for the discovery of sustainable plastics.

Modulating the Crystallinity of a Circular Plastic towards Packaging Material with Outstanding Barrier Properties.

Chemically recyclable polymers have attracted increasing attention since they are promising materials in a circular economy, but such polymers appropriate for packaging applications are scarce. Here a combined thermal, mechanical, and transport (permeability and sorption) study is presented of a circular polymer system based on biobased trans-hexahydrophthalide which, upon polymerization, can lead to amorphous, homochiral crystalline, and nanocrystalline stereocomplex materials. This study uncovers their largely different transport properties of the same polymer but with different stereochemical arrangements and synergistic or conflicting effects of crystallinity on transport properties versus thermal and mechanical properties. Overall, the homocrystalline chiral polymer shows the best performance with an outstanding barrier character to gases and vapors, outperforming commercial poly(ethylene terephthalate) and polyethylene. The results presented herein show that it is possible to modify the crystalline structure of the same polymer to tune the mechanical and transport properties and generate multiple materials of different barrier characters.

Advancing the Development of Recyclable Aromatic Polyesters by Functionalization and Stereocomplexation.

The development of innovative synthetic polymer systems to overcome the trade-offs between the polymer's depolymerizability and performance properties is in high demand for advanced material applications and sustainable development. In this contribution, we prepared a class of aromatic cyclic esters (M1-M5) from thiosalicylic acid and epoxides by facile one-pot synthesis. Ring-opening polymerization of Ms afforded aromatic polyesters P(M)s with high molecular weights and narrow dispersities. The physical and mechanical properties of P(M)s can be modulated by stereocomplexation and regulation of the side-chain flexibility of the polymers, ultimately achieving high-performance properties such as high thermal stability and crystallinity (Tm up to 209 °C), as well as polyolefin-like high mechanical strength, ductility, and toughness. Furthermore, the functionalizable moieties of P(M)s have driven a wide array of post-polymerization modifications toward access to value-added materials. More importantly, the P(M)s were able to selectively depolymerize into monomers in excellent yields, thus establishing its circular life cycle.

Biobased High-Performance Aromatic-Aliphatic Polyesters with Complete Recyclability.

The development of high-performance recyclable polymers represents a circular plastics economy to address the urgent issues of plastic sustainability. Herein, we design a series of biobased seven-membered-ring esters containing aromatic and aliphatic moieties. Ring-opening polymerization studies showed that they readily polymerize with excellent activity (TOF up to 2.1 × 105 h-1) at room temperature and produce polymers with high molecular weight (Mn up to 438 kg/mol). The variety of functionalities allows us to investigate the substitution effect on polymerizability/recyclability of monomers and properties of polymers (such as Tgs from -1 to 79 °C). Remarkably, a stereocomplexed P(M2) exhibited significantly increased Tm and crystallization rate. More importantly, product P(M)s were capable of depolymerizing into their monomers in solution or bulk with high efficiency, thus establishing their circular life cycle.

Catalyst-Sidearm-Induced Stereoselectivity Switching in Polymerization of a Racemic Lactone for Stereocomplexed Crystalline Polymer with a Circular Life Cycle.

Construction of robust, stereocomplexed (sc) crystalline material, based on a recently discovered infinitely recyclable polymer system, requires blending of enantiomeric polymer chains produced from respective enantiopure, fused six-five bicyclic lactones. Herein, the stereoselective polymerization of the racemic monomer by yttrium catalysts bearing tetradentate ligands is reported, where the tethered donor sidearm switches the heteroselectivity of the catalyst to isoselectivity when it is changed from the ß-OMe to ß-NMe2 sidearm. The latter catalyst produces an isotactic stereoblock polymer (Pm up to 0.95) that forms the crystalline sc-material with a Tm of up to 171 °C. This sc-material can be fully depolymerized back to rac-monomer in a quantitative yield and purity, thus establishing its circular life cycle.

Living Coordination Polymerization of a Six-Five Bicyclic Lactone to Produce Completely Recyclable Polyester.

The development of chemically recyclable polymers promises a closed-loop approach towards a circular plastic economy but still faces challenges in structure/property diversity and depolymerization selectivity. Here we report the first successful coordination ring-opening polymerization of 4,5-trans-cyclohexyl-fused γ-butyrolactone (M1) with lanthanide catalysts at room temperature, producing P(M1) with Mn up to 89 kg mol-1 , high thermal stability, and a linear or cyclic topology. The same catalyst also catalyses selective depolymerization of P(M1) back to M1 exclusively at 120 °C. This coordination polymerization is also living, enabling the synthesis of well-defined block copolymer.

Arabidopsis EDT1/HDG11 improves drought and salt tolerance in cotton and poplar and increases cotton yield in the field.

Drought and salinity are two major environmental factors limiting crop production worldwide. Improvement of drought and salt tolerance of crops with transgenic approach is an effective strategy to meet the demand of the ever-growing world population. Arabidopsis ENHANCED DROUGHT TOLERANCE1/HOMEODOMAIN GLABROUS11 (AtEDT1/HDG11), a homeodomain-START transcription factor, has been demonstrated to significantly improve drought tolerance in Arabidopsis, tobacco, tall fescue and rice. Here we report that AtHDG11 also confers drought and salt tolerance in upland cotton (Gossypium hirsutum) and woody plant poplar (Populus tomentosa Carr.). Our results showed that both the transgenic cotton and poplar exhibited significantly enhanced tolerance to drought and salt stress with well-developed root system. In the leaves of the transgenic cotton plants, proline content, soluble sugar content and activities of reactive oxygen species-scavenging enzymes were significantly increased after drought and salt stress compared with wild type. Leaf stomatal density was significantly reduced, whereas stomatal and leaf epidermal cell size were significantly increased in both the transgenic cotton and poplar plants. More importantly, the transgenic cotton showed significantly improved drought tolerance and better agronomic performance with higher cotton yield in the field both under normal and drought conditions. These results demonstrate that AtHDG11 is not only a promising candidate for crops improvement but also for woody plants.

Expression of Shewanella frigidimarina fatty acid metabolic genes in E. coli by CRISPR/cas9-coupled lambda Red recombineering.

OBJECTIVE: To construct a clustered, regularly interspaced, short palindromic repeats (CRISPR)/cas9 system and use this system to obtain a recombinant Escherichia coli strain possessing the fatty acid metabolism genes from a lipid-rich marine bacterium. RESULTS: The fatty acid regulatory transcription factor (fadR), delta9 (Δ(9) desaturase) and acetyl-CoA carboxylase (acc) genes were cloned from Shewanella frigidimarina. The fatty acid regulatory transcription factor (fadD) and phosphoenolpyruvate carboxylase inactivated strains were used to construct the fadR/delta9 and acc knock-in strains, which are both markerless and "scar"-less, and identified the change in fatty acid composition in the recombinant strains. There was no change in fatty acid composition between the wild-type strain and recombinant strains. All strains had 11:0, 12:0, 13:0, 14:0, 15:0, 16:0, 17:1, 17:0 and 18:0 fatty acids, with 16:0 and 18:0 fatty acids being dominant. The total lipid content of each recombinant strain was higher than the wild-type strain, with a maximum of 13.1 %, nearly 5.3 % higher than wild-type strain. CONCLUSION: The CRISPR/cas9 system, in conjunction with λ-Red recombinases, can rapidly and efficiently edit the E. coli genome. The CRISPR/cas9 recombineering machinery can be modified to select biotechnologically-relevant bacteria other than E. coli.

From meso-Lactide to Isotactic Polylactide: Epimerization by B/N Lewis Pairs and Kinetic Resolution by Organic Catalysts.

B/N Lewis pairs have been discovered to catalyze rapid epimerization of meso-lactide (LA) or LA diastereomers quantitatively into rac-LA. The obtained rac-LA is kinetically polymerized into poly(L-lactide) and optically resolved D-LA, with a high stereoselectivity k(L)/k(D) of 53 and an ee of 91% at 50.6% monomer conversion, by newly designed bifunctional chiral catalyst 4 that incorporates three key elements (ß-isocupreidine core, thiourea functionality, and chiral BINAM) into a single organic molecule. The epimerization and enantioselective polymerization can be coupled into a one-pot process for transforming meso-LA directly into poly(L-lactide) and D-LA.

Cloning and characterization of a novel dehydrin gene, SiDhn2, from Saussurea involucrata Kar. et Kir.

Saussurea involucrata Kar. et Kir. is a hardy dicotyledonous plant capable of tolerating severe abiotic stress conditions. In a previous study, we created a cDNA library to determine what factors are associated with the cold acclimation response in S. involucrata. From this, a full-length cDNA of a dehydrin-like gene (SiDhn2) was obtained by RT-PCR. The SiDhn2 gene was characterized in this study. The full-length SiDhn2 cDNA comprised 693 bp containing an open reading frame of 345 bp specifying a protein of 115 amino acids. An alignment of the deduced amino acid sequence showed that SiDhn2 shared 55 % identity with two Brassica dehydrins. Agrobacterium tumefaciens was used to transform RD29A:SiDhn2 and 35S:SiDhn2 constructs into tobacco to investigate the germination and resistance to freezing and drought stress of transgenic plants. The RD29A:SiDhn2 transgenic plants showed greater resistance to freezing and drought stress than 35S:SiDhn2 transgenic plants or the wild-type. This study demonstrates that SiDhn2 confers cold hardiness and drought resistance, and may be a candidate resistance gene for genetic improvement of crops to increase stress resistance.

Reactions of iron carbenes with α,ß-unsaturated esters by using an Umpolung approach: mechanism and applications.

An Umpolung approach, in which a phosphorus ylide moiety was introduced to increase the electron density of the double bond, was developed to activate electron-deficient alkenes for reaction with electrophilic iron carbenes. In tandem with the Wittig reaction, the reactions of α,ß-unsaturated esters with in situ generated Fe-carbene complexes delivered formal C-H insertion products through cyclopropanation/ring-opening reactions. DFT calculations and cross-experiments indicate that, in this process, the ring opening of the cyclopropylmethyl ylide intermediate is rapid and reversible and the subsequent proton transfer is the rate-determining step. Further studies revealed that, based on the choice of the ylide and ester groups, as well as the base, the reaction could be steered towards either the ring-opening pathway or to the production of vinyl cyclopropanes.

Predicting the prognosis of primary orbital lymphoma by clinical characteristics and imaging features.

AIM: To analyze the 5-year disease-free survival (DFS) of primary orbital lymphoma (POL) by clinical characteristics and imaging features. METHODS: A total of 72 patients, 43 males and 29 females, with histologically confirmed POL, were retrospectively recruited between January 2012 and May 2017. The information on clinical characteristics, imaging features, and 5-year DFS was obtained. Univariate and multivariate forward logistic regression analyses were used to identify the variables significantly associated with 5-year DFS. Kaplan-Meier was applied for survival analysis. RESULTS: Univariate analysis revealed that uni- or bilateral orbital involvement, single or multiple lesions, treatment methods, and contrast enhancement pattern on images were significant for 5-year DFS (P=0.022, 0.042, <0.001, and 0.028, respectively), while in multivariate logistic regression analysis, only uni- or bilateral orbital involvement, treatment methods and contrast enhancement pattern on images were significant (r=0.453, 0.897, and 0.556, P=0.038, <0.001 and 0.022, respectively). The survival curves for DFS were obtained. CONCLUSION: The majority of POL are B-cell lymphomas. Unilateral orbital involvement, homogeneous contrast enhancement on images, and the appropriate treatment schemes result to be significant factors for a good prognosis for POL.

Bifunctional thiourea-based organocatalyst promoted kinetic resolution polymerization of racemic lactide to isotactic polylactide.

Here, we prepared a series of thiourea-based organocatalysts 1-7 by combining two stereogenic elements: binaphthyl-amine and cyclohexyl diamine moieties. Catalyst (R,S)-1 facilitated a stereoselective polymerization of rac-LA to afford iso-enriched PDLA with Pm of 0.96 while its enantiomer (S,R)-1 produced PLLA with Pm of 0.96. These iso-enriched PLA contributed to forming a stereocomplexed PLA with a significantly increased Tm of 196 °C.

Insights into substitution strategy towards thermodynamic and property regulation of chemically recyclable polymers.

The development of chemically recyclable polymers serves as an attractive approach to address the global plastic pollution crisis. Monomer design principle is the key to achieving chemical recycling to monomer. Herein, we provide a systematic investigation to evaluate a range of substitution effects and structure-property relationships in the ɛ-caprolactone (CL) system. Thermodynamic and recyclability studies reveal that the substituent size and position could regulate their ceiling temperatures (Tc). Impressively, M4 equipped with a tert-butyl group displays a Tc of 241 °C. A series of spirocyclic acetal-functionalized CLs prepared by a facile two-step reaction undergo efficient ring-opening polymerization and subsequent depolymerization. The resulting polymers demonstrate various thermal properties and a transformation of the mechanical performance from brittleness to ductility. Notably, the toughness and ductility of P(M13) is comparable to the commodity plastic isotactic polypropylene. This comprehensive study is aimed to provide a guideline to the future monomer design towards chemically recyclable polymers.

The preoperative triglyceride-glucose index has a positive effect on predicting the risk of short-term restenosis after carotid artery stenting: a retrospective cohort study.

Background: Increasing evidence suggests that insulin resistance is linked to cardiovascular disease and atherosclerosis. The triglyceride-glucose (TyG) index has proven to be a convincing marker to quantitatively evaluate insulin resistance. However, there is no relevant information about the relationship between the TyG index and restenosis after carotid artery stenting. Methods: A total of 218 patients were enrolled. Carotid ultrasound and computed tomography angiography were used to evaluate in-stent restenosis. A Kaplan-Meier analysis and Cox regression method were performed to analyze the correlation between TyG index and restenosis. Schoenfeld residuals were used to determine the proportional-hazards assumption. A restricted cubic spline method was used to model and visualize the dose-response relationship between the TyG index and the risk of in-stent restenosis. Subgroup analysis was also performed. Results: Thirty-one participants (14.2%) developed restenosis. The preoperative TyG index had a time-varying effect on restenosis. Within 29 months post-surgery, an increasing preoperative TyG index was linked to a significant increased risk of restenosis (hazard ratio: 4.347; 95% confidence interval 1.886-10.023). However, after 29 months, the effect was decreased, although not statistically significant. The subgroup analysis showed that the hazard ratios tended to be higher in the age ≤ 71 years subgroup (p < 0.001) and participants with hypertension (p < 0.001). Conclusion: The preoperative TyG index was significantly associated with the risk of short-term restenosis after CAS within 29 months post-surgery. The TyG index may be employed to stratify patients based on their risk of restenosis after carotid artery stenting.

Seroprevalence of Epizootic Hemorrhagic Disease Virus in Guangdong Cattle Farms during 2013-2017, China.

Epizootic hemorrhagic disease (EHD) is an infectious viral disease caused by epizootic hemorrhagic disease virus (EHDV) and EHDV frequently circulates in wild and domestic ruminants. Sporadic outbreaks of EHD have caused thousands of deaths and stillbirths on cattle farms. However, not much is known about the circulating status of EHDV in Guangdong, southern China. To estimate the seroprevalence of EHDV in Guangdong province, 2886 cattle serum samples were collected from 2013 to 2017 and tested for antibodies against EHDV using a competitive ELISA. The overall seroprevalence of EHDV reached 57.87% and was highest in autumn (75.34%). A subset of positive samples were serotyped by a serum neutralization test, showing that EHDV serotypes 1 and 5-8 were circulating in Guangdong. In addition, EHDV prevalence always peaked in autumn, while eastern Guangdong had the highest EHDV seropositivity over the five-year period, displaying apparent temporal-spatial distribution of EHDV prevalence. A binary logistic model analysis indicated a significant association between cattle with BTV infections and seroprevalence of EHDV (OR = 1.70, p < 0.001). The co-infection of different serotypes of EHDV and BTV raises a high risk of potential genomic reassortment and is likely to pose a significant threat to cattle, thus urging more surveillance to monitor their circulating dynamics in China.

Highly Reactive Cyclic Carbonates with a Fused Ring toward Functionalizable and Recyclable Polycarbonates.

Monomer design plays an important role in the development of polymers with desired thermal properties and chemical recyclability. Here we prepared a class of seven-membered ring carbonates containing trans-cyclohexyl fused rings. These monomers showed excellent activity for ring-opening polymerization (ROP) with turnover frequency (TOF) up to 6 × 105 h-1 and catalyst loading down to 50 ppm, which yielded high-molecular-weight polycarbonates (Mn up to 673 kg/mol) with great thermostability (Td > 300 °C). Ultimately, the resulting polycarbonates can completely depolymerize into their corresponding cyclic dimers that can repolymerize to synthesize the starting polymers in moderate yields, demonstrating a potential route to achieve chemical recycling. Postfunctionalization of the unsaturated polycarbonate was conducted through cross-linking reaction and "click" reaction under UV irradiation.

A High Triglyceride-Glucose Index Value Is Associated With an Increased Risk of Carotid Plaque Burden in Subjects With Prediabetes and New-Onset Type 2 Diabetes: A Real-World Study.

Background: The triglyceride-glucose (TyG) index has been proposed as a convincing indicator of insulin resistance and has been found to be associated with atherosclerosis among diabetic patients. However, the relationship between the TyG index and arteriosclerosis in subjects with prediabetes and new-onset type 2 diabetes (T2D) remains uncertain. The purpose of this study was to assess the degree of carotid plaque burden in patients with prediabetes and new-onset T2D and to investigate the association between the TyG index and the degree of carotid plaque burden in this population. Methods: This was a cross-sectional observational study that included 716 subjects aged 40-70 years old with prediabetes or new-onset T2D. Demographic, anthropometric, and laboratory measurements were collected. Participants underwent carotid arteriosclerosis evaluation by ultrasonography, and the degree of atherosclerosis was evaluated according to the carotid plaque burden. The TyG index was calculated. Results: The population was stratified into high or low TyG index groups according to the median TyG index value. Higher values were associated with a higher BMI and waist circumference as well as higher total cholesterol, triglyceride, low-density lipoprotein cholesterol, plasma glucose, glycated hemoglobin, fasting C-peptide, and C-reactive protein levels (P < 0.001). The high TyG index group had a higher atherosclerotic plaque burden than the low TyG index group (P < 0.001). Multiclassification logistic regression analysis showed that the TyG index was positively associated with a high plaque burden [odds ratio (OR): 16.706, 95% confidence interval (CI): 3.988-69.978, P = 0.000], while no association was found between the TyG index and a low/moderate plaque burden. This association remained consistent in the subgroup analysis. In multiple linear regression analysis, sex, age, and the TyG index were found to be independently associated with carotid plaque burden. For each unit increase in the TyG index, the risk of a high carotid plaque burden increased 1.595-fold. Conclusion: A high TyG index was positively associated with a high carotid plaque burden in subjects with prediabetes and new-onset T2D. Clinicians should pay close attention to the TyG index to help these patients receive the greatest benefit from early intervention.