Evolution of Copolymers of Epoxides and CO2: Catalysts, Monomers, Architectures, and Applications.

The copolymerization of CO2 and epoxides presents a transformative approach to converting greenhouse gases into aliphatic polycarbonates (CO2-PCs), thereby reducing the polymer industry's dependence on fossil resources. Over the past 50 years, a wide array of metallic catalysts, both heterogeneous and homogeneous, have been developed to achieve precise control over polymer selectivity, sequence, regio-, and stereoselectivity. This review details the evolution of metal-based catalysts, with a particular focus on the emergence of organoborane catalysts, and explores how these catalysts effectively address kinetic and thermodynamic challenges in CO2/epoxides copoly2merization. Advances in the synthesis of CO2-PCs with varied sequence and chain architectures through diverse polymerization protocols are examined, alongside the applications of functional CO2-PCs produced by incorporating different epoxides. The review also underscores the contributions of computational techniques to our understanding of copolymerization mechanisms and highlights recent advances in the closed-loop chemical recycling of CO2-sourced polycarbonates. Finally, the industrialization efforts of CO2-PCs are discussed, offering readers a comprehensive understanding of the evolution and future potential of epoxide copolymerization with CO2.

Transcriptome Landscape of Human Folliculogenesis Reveals Oocyte and Granulosa Cell Interactions.

The dynamic transcriptional regulation and interactions of human germlines and surrounding somatic cells during folliculogenesis remain unknown. Using RNA sequencing (RNA-seq) analysis of human oocytes and corresponding granulosa cells (GCs) spanning five follicular stages, we revealed unique features in transcriptional machinery, transcription factor networks, and reciprocal interactions in human oocytes and GCs that displayed developmental-stage-specific expression patterns. Notably, we identified specific gene signatures of two cell types in particular developmental stage that may reflect developmental competency and ovarian reserve. Additionally, we uncovered key pathways that may concert germline-somatic interactions and drive the transition of primordial-to-primary follicle, which represents follicle activation. Thus, our work provides key insights into the crucial features of the transcriptional regulation in the stepwise folliculogenesis and offers important clues for improving follicle recruitment in vivo and restoring fully competent oocytes in vitro.

Small molecule agonist of mitochondrial fusion repairs mitochondrial dysfunction.

Membrane dynamics are important to the integrity and function of mitochondria. Defective mitochondrial fusion underlies the pathogenesis of multiple diseases. The ability to target fusion highlights the potential to fight life-threatening conditions. Here we report a small molecule agonist, S89, that specifically promotes mitochondrial fusion by targeting endogenous MFN1. S89 interacts directly with a loop region in the helix bundle 2 domain of MFN1 to stimulate GTP hydrolysis and vesicle fusion. GTP loading or competition by S89 dislodges the loop from the GTPase domain and unlocks the molecule. S89 restores mitochondrial and cellular defects caused by mitochondrial DNA mutations, oxidative stress inducer paraquat, ferroptosis inducer RSL3 or CMT2A-causing mutations by boosting endogenous MFN1. Strikingly, S89 effectively eliminates ischemia/reperfusion (I/R)-induced mitochondrial damage and protects mouse heart from I/R injury. These results reveal the priming mechanism for MFNs and provide a therapeutic strategy for mitochondrial diseases when additional mitochondrial fusion is beneficial.

Organoboron-mediated polymerizations.

The scientific community has witnessed extensive developments and applications of organoboron compounds as synthetic elements and metal-free catalysts for the construction of small molecules, macromolecules, and functional materials over the last two decades. This review highlights the achievements of organoboron-mediated polymerizations in the past several decades alongside the mechanisms underlying these transformations from the standpoint of the polymerization mode. Emphasis is placed on free radical polymerization, Lewis pair polymerization, ionic (cationic and anionic) polymerization, and polyhomologation. Herein, alkylborane/O2 initiating systems mediate the radical polymerization under ambient conditions in a controlled/living manner by careful optimization of the alkylborane structure or additives; when combined with Lewis bases, the selected organoboron compounds can mediate the Lewis pair polymerization of polar monomers; the bicomponent organoboron-based Lewis pairs and bifunctional organoboron-onium catalysts catalyze ring opening (co)polymerization of cyclic monomers (with heteroallenes, such as epoxides, CO2, CO, COS, CS2, episulfides, anhydrides, and isocyanates) with well-defined structures and high reactivities; and organoboranes initiate the polyhomologation of sulfur ylides and arsonium ylides providing functional polyethylene with different topologies. The topological structures of the produced polymers via these organoboron-mediated polymerizations are also presented in this review mainly including linear polymers, block copolymers, cyclic polymers, and graft polymers. We hope the summary and understanding of how organoboron compounds mediate polymerizations can inspire chemists to apply these principles in the design of more advanced organoboron compounds, which may be beneficial for the polymer chemistry community and organometallics/organocatalysis community.

Ex vivo magnetic resonance imaging of the human fetal brain.

BACKGROUND: The fetal brain undergoes a dynamic process of development during gestation, marked by well-orchestrated events such as neuronal proliferation, migration, axonal outgrowth, and dendritic arborization, mainly elucidated through histological studies. Ex vivo magnetic resonance imaging (MRI) has emerged as a useful tool for 3D visualization of the developing fetal brain, serving as a complementary tool to traditional histology. SUMMARY: In this review, we summarized the commonly employed ex vivo MRI techniques and their advances in fetal brain imaging, as well as a standard protocol for postmortem fetal brain specimen collection and fixation. We then provided an overview of ex vivo MRI-based studies on the fetal brain. KEY MESSAGES: According to our review, ex vivo T1- or T2-weighted structural MRI has contributed to the characterization of the anatomy of transient neuronal proliferative zones, the basal ganglia, and the cortex. Diffusion MRI related techniques, such as diffusion tensor imaging and tractography, have helped to investigate the microstructural patterns of fetal brain tissue, as well as the early emergence and development of neuronal migration pathways and white matter bundles. Ex vivo MRI findings have shown strong histological correlations, supporting the potential of MRI in evaluating the developmental events in the fetal brain. Postmortem MRI examinations have also demonstrated comparable, and in certain cases, superior performance to traditional autopsy in revealing fetal brain abnormalities. In conclusion, ex vivo fetal brain MRI is an invaluable tool that provides unique insights into the early stages of brain development.

HEAT-RESPONSIVE PROTEIN regulates heat stress via fine-tuning ethylene/auxin signaling pathways in cotton.

Plants sense and respond to fluctuating temperature and light conditions during the circadian cycle; however, the molecular mechanism underlying plant adaptability during daytime warm conditions remains poorly understood. In this study, we reveal that the ectopic regulation of a HEAT RESPONSIVE PROTEIN (GhHRP) controls the adaptation and survival of cotton (Gossypium hirsutum) plants in response to warm conditions via modulating phytohormone signaling. Increased ambient temperature promptly enhanced the binding of the phytochrome interacting factor 4 (GhPIF4)/ethylene-insensitive 3 (GhEIN3) complex to the GhHRP promoter to increase its mRNA level. The ectopic expression of GhHRP promoted the temperature-dependent accumulation of GhPIF4 transcripts and hypocotyl elongation by triggering thermoresponsive growth-related genes. Notably, the upregulation of the GhHRP/GhPIF4 complex improved plant growth via modulating the abundance of Arabidopsis thaliana auxin biosynthetic gene YUCCA8 (AtYUC8)/1-aminocyclopropane-1-carboxylate synthase 8 (AtACS8) for fine-tuning the auxin/ethylene interplay, ultimately resulting in decreased ethylene biosynthesis. GhHRP thus protects chloroplasts from photo-oxidative bursts via repressing AtACS8 and AtACS7 and upregulating AtYUC8 and the heat shock transcription factors (HSFA2), heat shock proteins (HSP70 and HSP20). Strikingly, the Δhrp disruption mutant exhibited compromised production of HSP/YUC8 that resulted in an opposite phenotype with the loss of the ability to respond to warm conditions. Our results show that GhHRP is a heat-responsive signaling component that assists plants in confronting the dark phase and modulates auxin signaling to rescue growth under temperature fluctuations.

Cu(II)-Catalyzed Hydroboration Reactions of 1,1-Disubstituted α,ß-Unsaturated Ketones, Esters, and Amides in Pure Water.

Here, a Cu2(OH)2CO3-catalyzed hydroboration reaction of 1,1-disubstituted α,ß-unsaturated compounds has been developed. The reaction was carried out using water as a solvent at room temperature except for N-monosubstituted α,ß-unsaturated amides. This method is applicable to diverse 1,1-disubstituted α,ß-unsaturated ketones, esters, and amides, showing excellent reactivity (up to 98% yield). Gram-scale experiments and functional group transformations further demonstrated the practicality of this method.

Tuning d-orbitals to control spin-orbit coupling in terminated MXenes.

Theory and experiment have revealed that spin-orbit coupling (SOC) strongly depends on the relativistic effect in topological insulators (TIs), while the influence of orbitals is always ignored. Herein, we provide a direct way of controlling effective SOC with the help of orbital effects, reducing the dependence on elements. Taking 5d W2CO2 and 4d Mo2CO2 MXenes as a specific example, we predict that by decreasing the hybridization strength of W atoms with C or O atoms in 2D W2CO2, the nontrivial bandgaps at the Γ-point are directly enhanced. The weak hybridization of W atoms with ligand elements enhances the electron localization of degenerate d-orbitals of three groups under the triangular prism crystal field, inducing stronger on-site Coulomb repulsion that enhances orbital polarization as well as boosts the SOC effect. Meanwhile, similar results have also been observed in 4d Mo2CO2. This implies that the orbital effects are an efficient and straightforward way to control the nontrivial bandgap in 2D MXene TIs. Our work not only provides an alternative perspective on designing large nontrivial bandgaps but also brings a possibility to control the SOC effect for TI devices.

Adolescents' trait mindfulness and psychological stress: The mediating role of attention.

INTRODUCTION: Based on the Combined Cognitive Biases Hypothesis, the current study via two parallel studies aims to explore the potential mediating role of attention biases and attention control regarding the link between trait mindfulness and psychological stress in adolescents. METHODS: For Study 1, we collected self-reported data from 2123 Chinese adolescents (mean age = 15.6 years, SD = 2.37; 52.8% female) in four schools. The participants completed measures of trait mindfulness, perceived stress, and attention bias. Mediation analysis was employed to investigate the potential mediating effect of attention bias. In Study 2, 123 participants (mean age = 17.7 years, SD = 2.68; 41.46% female) completed the attention network task after inducing attention bias. Then, trait mindfulness and perceived stress were measured. Mediation analysis was employed to investigate the potential mediating effect of attention control (alerting, orienting, and conflict monitoring) under attention bias. RESULTS: Study 1 demonstrated a significant mediating effect of negative attention bias ([-0.13, -0.07], p < .05) but not positive attention bias in the relationship between trait mindfulness and psychological stress. Study 2 revealed that conflict monitoring in negative attention bias ([-0.41, -0.16], p < .05), rather than alerting and orienting in negative attention bias, showed a significant mediating effect on the association between trait mindfulness and psychological stress. CONCLUSIONS: Findings from the two studies suggest that conflict monitoring during negative attention bias may be the underlying mechanism through which trait mindfulness helps mitigate psychological stress in adolescents.

Gender Differences in Negative Life Events, Present-Moment Awareness, Problem-Solving, and Perceived Stress Among Rural Adolescents.

Drawing on the stressor-perception-coping-response model of stress, this study examined the associations between negative life events, present-moment awareness, problem-solving, and perceived stress among rural adolescents, focusing specifically on gender differences. Using a cross-sectional design, 3519 Chinese rural adolescents completed measures assessing negative life events, present-moment awareness, problem-solving, and perceived stress. Structural equation modeling was employed to examine the hypothesized serial mediation model. The results revealed a positive association between negative life events and perceived stress in rural adolescents, which was serially mediated by present-moment awareness and problem-solving. Furthermore, significant gender differences were observed. Specifically, girls exhibited larger effects than boys in the overall effect of negative life events on perceived stress, the indirect effect of present-moment awareness, and the serial mediating effect. These findings suggest that present-moment awareness and problem-solving may serve as crucial mechanisms for understanding rural adolescents' perceived stress in response to negative life events, particularly among female rural adolescents.

Temperature-Sensitive Template for Preparation of ZnO/CeO2 Composite Photocatalytic Materials and Its Catalytic Performance.

In this work, a series of thermosensitive ionic liquid functionalized polymers, PNx(IL)y, with controllable morphology and particle size were prepared by free radical polymerization. Then, using the polymer PN64(IL)8 with uniform morphology as a templating agent, the ZnO composite photocatalytic materials doped with rare earth metal Ce were prepared in combination with a microwave-assisted and templated hydrothermal reaction method. Series different Ce-doping amount photocatalytic materials ZnO-Ce-x‱ were characterized by XRD, SEM, TEM, XPS, and other methods. The results demonstrated that the templated materials PN64(IL)8 can prepare ZnO-Ce-2‱ with uniform petaloid ambulacra shape, good distribution of elements, and excellent photocatalytic performance. Photocatalytic degradation experiments of methyl orange (MO) showed that when the Ce-doping amount is only 2‱, the degradation rate of organic dyes can reach 96.5% by reacting the photocatalytic materials in water for 1 h. In addition, this kind of photocatalyst can be used for the degradation of high-concentration MO, as well as being easily recovered and effectively reused by simple filtration. Therefore, the structure of this kind of photocatalyst is controllable in the preparation process with an extremely low Ce-doping amount compared with current reports, and it has a good application prospect in the field of wastewater treatment technology.

Identifying the genetic mechanism of medium-low temperature fluoride-enriched geothermal groundwater by the self-organizing map and evaluating health risk in the Wugongshan area, southeast China.

Fluoride-enriched groundwater is a serious threat for groundwater supply around the world. The medium-low temperature fluoride-enriched geothermal groundwater resource is widely distributed in the circum-Wugongshan area. And the fluoride concentration of all geothermal samples exceeds the WHO permissible limit of 1.5 mg/L. The Self-Organizing Map method, hydrochemical and isotopic analysis are used to decipher the driving factors and genetic mechanism of fluoride-enriched geothermal groundwater. A total of 19 samples collected from the circum-Wugongshan geothermal belt are divided into four clusters by the self-organizing map. Cluster I, Cluster II, Cluster III, and Cluster IV represent the geothermal groundwater with the different degree of fluoride concentration pollution, the different hydrochemical type, and the physicochemical characteristic. The high F- concentration geothermal groundwater is characterized by HCO3-Na with alkalinity environment. The δD and δ18O values indicate that the geothermal groundwater origins from the atmospheric precipitation with the recharge elevation of 1000-2100 m. The dissolution of fluoride-bearing minerals is the main source of fluoride ions in geothermal water. Moreover, groundwater fluoride enrichment is also facilitated by water-rock interaction, cation exchange and alkaline environment. Additionally, the health risk assessment result reveals that the fluorine-enriched geothermal groundwater in the western part of Wugongshan area poses a more serious threat to human health than that of eastern part. The fluoride health risks of geothermal groundwater for different group show differentiation, 100% for children, 94.74% for adult females, and 68.42% for adult males, respectively. Compared with adult females and adult males, children faced the greatest health risks. The results of this study provide scientific evaluation for the utilization of geothermal groundwater and the protection of human health around the Wugongshan area.

Targeted Deletion of Glycoprotein B Gene by CRISPR/Cas9 Nuclease Inhibits Gallid herpesvirus Type 3 in Dually Infected Marek's Disease Virus-Transformed Lymphoblastoid Cell Line MSB-1.

Marek's disease virus (MDV) is a member of the genus Mardivirus in the subfamily Alphaherpesvirinae. There are three different serotypes of MDV designated as MDV-1 (Gallid herpesvirus type 2), MDV-2 (Gallid herpesvirus type 3), and MDV-3 (Meleagrid herpesvirus 1, herpesvirus of turkeys, HVT). MDV-1 is the only serotype that induces Marek's disease (MD), a lymphoproliferative disorder resulting in aggressive T-cell lymphomas and paralytic symptoms. In the lymphomas and lymphoblastoid cell lines (LCL) derived from them, MDV establishes latent infection with limited viral gene expression. The latent viral genome in LCL can be activated by co-cultivation with chicken embryo fibroblast (CEF) monolayers. MSB-1, one of the first MDV-transformed LCL established from the splenic lymphoma, is distinct in harboring both the oncogenic MDV-1 and non-oncogenic MDV-2 viruses. Following the successful application of CRISPR/Cas9 editing approach for precise knockdown of the MDV-1 genes in LCL, we describe here the targeted deletion of MDV-2 glycoprotein B (gB) in MSB-1 cells. Due to the essential nature of gB for infectivity, the production of MDV-2 plaques on CEF was completely abolished in the MDV-2-gB-deleted MSB-1 cells. Our study has demonstrated that the CRISPR/Cas9 system can be used for targeted inactivation of the co-infecting MDV-2 without affecting the MDV-1 in the MSB-1 cell line. Successful inactivation of MDV-2 demonstrated here also points toward the possibility of using targeted gene editing as an antiviral strategy against pathogenic MDV-1 and other viruses infecting chickens. IMPORTANCE Marek's disease (MD) is a lymphoproliferative disease of chickens characterized by rapid-onset lymphomas in multiple organs and by infiltration into peripheral nerves, causing paralysis. Lymphoblastoid cell lines (LCL) derived from MD lymphomas have served as valuable resources to improve understanding of distinct aspects of virus-host interactions in transformed cells including transformation, latency, and reactivation. MDV-transformed LCL MSB-1, derived from spleen lymphoma induced by the BC-1 strain of MDV, has a unique feature of harboring an additional non-pathogenic MDV-2 strain HPRS-24. By targeted deletion of essential gene glycoprotein B from the MDV-2 genome within the MSB-1 cells, we demonstrated the total inhibition of MDV-2 virus replication on co-cultivated CEF, with no effect on MDV-1 replication. The identified viral genes critical for reactivation/inhibition of viruses will be useful as targets for development of de novo disease resistance in chickens to avian pathogens.

Rumination mediates the relationship between childhood trauma and depressive symptoms in schizophrenia patients.

Rumination and childhood trauma are related to depressive symptoms in clinical and non-clinical individuals. This is the first study aimed to test the mediating effect of rumination on the relationship between childhood trauma and depressive symptoms in schizophrenia patients. A total of 313 schizophrenia patients were recruited in the present study. The 17-item Hamilton Depression Rating Scale (HAMD-17) was adopted to evaluate depressive symptoms, the short-form Childhood Trauma Questionnaire (CTQ-SF) and the 10-item Ruminative response scale (RRS-10) were utilized to assess the childhood trauma and rumination in patients, respectively. Our results showed that 168 schizophrenia patients (53.67%) had comorbid depressive symptoms. These patients with depressive symptoms had higher levels of childhood trauma [both CTQ-SF total scores and emotional abuse (EA), emotional neglect (EN), physical neglect (PN) subscale scores] and rumination (both RRS-10 total scores and brooding, reflection subscale scores) compared to patients without depressive symptoms. The stepwise logistic regression analysis identified that EN (OR 1.196, P = 0.003), PN (OR 1.1294, P < 0.001), brooding (OR 1.291, P < 0.001) and reflection (OR 1.481, P < 0.001) could independently predict the depressive symptoms in schizophrenia patients. Moreover, RRS-10 and its subscale scores could mediate the relationship between depressive symptoms and childhood trauma, especially EA, EN and PN in schizophrenia. Our preliminary findings suggest that the rigorous assessment and psychosocial interventions of rumination are important to alleviate the influence of childhood trauma on depressive symptoms in schizophrenia patients.

Application of Chitosan/Poly(vinyl alcohol) Stabilized Copper Film Materials for the Borylation of α, ß-Unsaturated Ketones, Morita-Baylis-Hillman Alcohols and Esters in Aqueous Phase.

A chitosan/poly(vinyl alcohol)-stabilized copper nanoparticle (CP@Cu NPs) was used as a heterogeneous catalyst for the borylation of α, ß-unsaturated ketones, MBH alcohols, and MBH esters in mild conditions. This catalyst not only demonstrated remarkable efficiency in synthesizing organoboron compounds but also still maintained excellent reactivity and stability even after seven recycled uses of the catalyst. This methodology provides a gentle and efficient approach to synthesize the organoboron compounds by efficiently constructing carbon-boron bonds.

Sequence-Reversible Construction of Oxygen-Rich Block Copolymers from Epoxide Mixtures by Organoboron Catalysts.

Switchable catalysis, in combination with epoxide-involved ring-opening (co)polymerization, is a powerful technique that can be used to synthesize various oxygen-rich block copolymers. Despite intense research in this field, the sequence-controlled polymerization from epoxide congeners has never been realized due to their similar ring-strain which exerts a decisive influence on the reaction process. Recently, quaternary ammonium (or phosphonium)-containing bifunctional organoboron catalysts have been developed by our group, showing high efficiency for various epoxide conversions. Herein, we, for the first time, report an operationally simple pathway to access well-defined polyether-block-polycarbonate copolymers from mixtures of epoxides by switchable catalysis, which was enabled through thermodynamically and kinetically preferential ring-opening of terminal epoxides or internal epoxides under different atmospheres (CO2 or N2) using one representative bifunctional organoboron catalyst. This strategy shows a broad substrate scope as it is suitable for various combinations of terminal epoxides and internal epoxides, delivering corresponding well-defined block copolymers. NMR, MALDI-TOF, and gel permeation chromatography analyses confirmed the successful construction of polyether-block-polycarbonate copolymers. Kinetic studies and density functional theory calculations elucidate the reversible selectivity between different epoxides in the presence/absence of CO2. Moreover, by replacing comonomer CO2 with cyclic anhydride, the well-defined polyether-block-polyester copolymers can also be synthesized. This work provides a rare example of sequence-controlled polymerization from epoxide mixtures, broadening the arsenal of switchable catalysis that can produce oxygen-rich polymers in a controlled manner.

All-in-One Luminescent Lanthanide Coordination Polymer Nanoprobe for Facile Detection of Protein Kinase Activity.

This study developed a novel luminescent assay for kinase activity using metal-organic coordination polymer nanoparticles (Tb/ATP-Zn) as the probe. Tb/ATP-Zn, self-assembled by adenosine triphosphate (ATP), Zn2+, and Tb3+, is non-luminescent. Protein kinase A (PKA) can catalyze the transformation of ATP within Tb/ATP-Zn nanoparticles to adenosine diphosphate (ADP), which in turn effectively sensitizes the luminescence of Tb3+. Based on this mechanism, Tb/ATP-Zn can realize the facile luminescent "turn-on" sensing of protein kinase activity without the use of external ATP and substrate peptide. Under optimized conditions, the fluorescence intensities of Tb/ATP-Zn at 550 nm are linear with the PKA activity within a range of 0.3-1.5 U·µL-1. The LOD (S/N = 3) of this method is down to 0.001 U·µL-1. The presented assay also features high selectivity, long-term stability, fast response, and convenient operation. Furthermore, Tb/ATP-Zn was successfully employed for monitoring PKA activity in cell lysis solutions. Probe Tb/ATP-Zn is thus expectable to be a powerful tool for the practical study of PKA in relevant biological events.

Modular Organoboron Catalysts Enable Transformations with Unprecedented Reactivity.

ConspectusElectron-deficient boron-based catalysts with metal-free but metallomimetic characteristics provide a versatile platform for chemical transformations. However, their catalytic performance is usually lower than that of the corresponding metal-based catalysts. Furthermore, many elaborate organoboron compounds are produced via time-consuming multistep syntheses with low yields, presenting a formidable challenge for large-scale applications of these catalysts. Given this context, the development of organoboron catalysts with the combined advantages of high efficiency and easy preparation is of critical importance.Therefore, we envisioned that the construction of a dynamic Lewis multicore system (DLMCS) by integrating the Lewis acidic boron center(s) and a Lewis basic ammonium salt in one molecule would be particularly efficient for on-demand applications because of the intramolecular synergistic effect. This Account summarizes our recent efforts in developing modular organoboron catalysts with unprecedented activities for several chemical transformations. A series of mono-, di-, tri-, and tetranuclear organoboron catalysts was readily designed and prepared in nearly quantitative yields over two steps using commercially available feedstocks. Notably, these catalysts can be modularly tailored by fine control over the electrophilic property of the Lewis acidic boron center(s), electronic and steric effects of the electropositive ammonium cation, linker length between the boron center and the ammonium cation, the number of boron centers, and the nucleophilic anion. This modular design allows systematic manipulation of the reactivity and efficacy of the catalysts, thus optimizing suitable catalysts for versatile chemical transformations. These include the coupling of CO2 and epoxides, copolymerization of CO2 and epoxides, ring-opening polymerization (ROP) of epoxides, and ring-opening copolymerization (ROCOP) of epoxides and cyclic anhydrides.The utilization of mononuclear organoboron catalysts provided a turnover frequency of 11050 h-1 for the CO2/propylene oxide coupling reaction, an unprecedented efficiency of 5.0 kg of polymer/g of catalyst for the copolymerization of CO2 and cyclohexene oxide, and a record-breaking catalytic efficiency of 7.4 kg of polymer/g of catalyst for the ROCOP of epoxides with cyclic anhydrides. A turnover number of 56500 was observed at a catalyst loading of 10 ppm for the ROP of epoxides using the dinuclear catalysts. The tetranuclear organoboron catalysts realized the previously intractable task of the copolymerization of CO2 and epichlorohydrin, producing poly(chloropropylene carbonate) with the highest molecular weight of 36.5 kg/mol reported to date.Furthermore, the study revealed that the interaction between the dynamic Lewis multicore, that is, the intramolecular synergistic effect between the boron center(s) and the quaternary ammonium salt, plays a key role in mediating the catalytic activity and selectivity. This was based on investigations of the crystal structures of the catalysts, key intermediates, reaction kinetics, and density functional theory calculations. The modular tactics for the construction of organoboron catalysts presented in this Account should inspire more advanced catalyst designs.

Enhancement of linalool production in Saccharomyces cerevisiae by utilizing isopentenol utilization pathway.

BACKGROUND: Linalool is a monoterpenoid, also a vital silvichemical with commercial applications in cosmetics, flavoring ingredients, and medicines. Regulation of mevalonate (MVA) pathway metabolic flux is a common strategy to engineer Saccharomyces cerevisiae for efficient linalool production. However, metabolic regulation of the MVA pathway is complex and involves competition for central carbon metabolism, resulting in limited contents of target metabolites. RESULTS: In this study, first, a truncated linalool synthase (t26AaLS1) from Actinidia arguta was selected for the production of linalool in S. cerevisiae. To simplify the complexity of the metabolic regulation of the MVA pathway and increase the flux of isopentenyl pyrophosphate (IPP) and dimethylallyl pyrophosphate (DMAPP), we introduced the two-step isopentenyl utilization pathway (IUP) into S. cerevisiae, which could produce large amounts of IPP/DMAPP. Further, the S. cerevisiae IDI1 (ecoding isopentenyl diphosphate delta-isomerase) and ERG20F96W-N127W (encoding farnesyl diphosphate synthase) genes were integrated into the yeast genome, combined with the strategies of copy number variation of the t26AaLS1 and ERG20F96W-N127W genes to increase the metabolic flux of the downstream IPP, as well as optimization of isoprenol and prenol concentrations, resulting in a 4.8-fold increase in the linalool titer. Eventually, under the optimization of carbon sources and Mg2+ addition, a maximum linalool titer of 142.88 mg/L was obtained in the two-phase extractive shake flask fermentation. CONCLUSIONS: The results show that the efficient synthesis of linalool in S. cerevisiae could be achieved through a two-step pathway, gene expression adjustment, and optimization of culture conditions. The study may provide a valuable reference for the other monoterpenoid production in S. cerevisiae.

Insights into Thiourea-Based Bifunctional Catalysts for Efficient Conversion of CO2 to Cyclic Carbonates.

The bifunctional thiourea catalyst system with both electrophilic and nucleophilic centers has been certified to be effective for fixing CO2 under mild reaction conditions; however, many questions remain, especially concerning the relationship between structure and performance. Herein, we systematically studied a series of such bifunctional catalysts with different chain lengths, nucleophilic anions, and substituents, which impact obvious influence on the catalytic performance. The activation energies of catalysts with different chain lengths are calculated via in situ IR. On this basis, we disclosed for the first time that the spacer length of tetramethylene -(CH2)6- is the optimal spatial effect for the coupling of epoxides and CO2. Particularly, the single crystal X-ray diffraction analysis of the molecular structures of the bifunctional catalyst C8 indicated the discovery of the existence of interaction force between the sulfur atom on the thiourea group and one hydrogen atom on the benzene ring, as well as the intermolecular hydrogen bonding interaction of the bromide (Br-) and two NH groups on the thiourea group. The catalyst structure performance, direct observation of the crystal structure, the thermodynamic study, and a wide range of substrates (12 examples) should be informative on the optimization of the existing catalysts or the design of new catalysts in the future.