RESUMO
SF3B is a multi-protein complex essential for branch site (BS) recognition and selection during pre-mRNA splicing. Several splicing modulators with antitumor activity bind SF3B and thereby modulate splicing. Here we report the crystal structure of a human SF3B core in complex with pladienolide B (PB), a macrocyclic splicing modulator and potent inhibitor of tumor cell proliferation. PB stalls SF3B in an open conformation by acting like a wedge within a hinge, modulating SF3B's transition to the closed conformation needed to form the BS adenosine-binding pocket and stably accommodate the BS/U2 duplex. This work explains the structural basis for the splicing modulation activity of PB and related compounds, and reveals key interactions between SF3B and a common pharmacophore, providing a framework for future structure-based drug design.
Assuntos
Antineoplásicos/farmacologia , Compostos de Epóxi/farmacologia , Macrolídeos/farmacologia , Fosfoproteínas/metabolismo , Fatores de Processamento de RNA/metabolismo , Splicing de RNA/efeitos dos fármacos , Adenosina/metabolismo , Animais , Antineoplásicos/química , Antineoplásicos/metabolismo , Sítios de Ligação , Proteínas de Transporte/metabolismo , Proliferação de Células/efeitos dos fármacos , Desenho de Fármacos , Compostos de Epóxi/química , Compostos de Epóxi/metabolismo , Células HCT116 , Células HeLa , Humanos , Macrolídeos/química , Macrolídeos/metabolismo , Modelos Moleculares , Complexos Multiproteicos , Fosfoproteínas/química , Fosfoproteínas/genética , Ligação Proteica , Conformação Proteica , Precursores de RNA/genética , Precursores de RNA/metabolismo , Fatores de Processamento de RNA/química , Fatores de Processamento de RNA/genética , RNA Mensageiro/genética , RNA Mensageiro/metabolismo , Proteínas de Ligação a RNA , Células Sf9 , Relação Estrutura-Atividade , TransativadoresRESUMO
Somatic mutations in spliceosome proteins lead to dysregulated RNA splicing and are observed in a variety of cancers. These genetic aberrations may offer a potential intervention point for targeted therapeutics. SF3B1, part of the U2 small nuclear RNP (snRNP), is targeted by splicing modulators, including E7107, the first to enter clinical trials, and, more recently, H3B-8800. Modulating splicing represents a first-in-class opportunity in drug discovery, and elucidating the structural basis for the mode of action opens up new possibilities for structure-based drug design. Here, we present the cryogenic electron microscopy (cryo-EM) structure of the SF3b subcomplex (SF3B1, SF3B3, PHF5A, and SF3B5) bound to E7107 at 3.95 Å. This structure shows that E7107 binds in the branch point adenosine-binding pocket, forming close contacts with key residues that confer resistance upon mutation: SF3B1R1074H and PHF5AY36C The structure suggests a model in which splicing modulators interfere with branch point adenosine recognition and supports a substrate competitive mechanism of action (MOA). Using several related chemical probes, we validate the pose of the compound and support their substrate competitive MOA by comparing their activity against both strong and weak pre-mRNA substrates. Finally, we present functional data and structure-activity relationship (SAR) on the PHF5AR38C mutation that sensitizes cells to some chemical probes but not others. Developing small molecule splicing modulators represents a promising therapeutic approach for a variety of diseases, and this work provides a significant step in enabling structure-based drug design for these elaborate natural products. Importantly, this work also demonstrates that the utilization of cryo-EM in drug discovery is coming of age.
Assuntos
Compostos de Epóxi/química , Macrolídeos/química , Fosfoproteínas/química , Fatores de Processamento de RNA/química , Splicing de RNA/efeitos dos fármacos , Spliceossomos/efeitos dos fármacos , Proteínas de Transporte/química , Proteínas de Transporte/genética , Proteínas de Transporte/isolamento & purificação , Microscopia Crioeletrônica , Modelos Moleculares , Mutação , Fosfoproteínas/isolamento & purificação , Precursores de RNA/metabolismo , Fatores de Processamento de RNA/isolamento & purificação , RNA Mensageiro/metabolismo , Proteínas de Ligação a RNA , TransativadoresRESUMO
Here we report the first total synthesis of the marine macrolide salarin C, a potent anticancer agent, and demonstrate the biomimetic oxidation-Wasserman rearrangement to access salarin A. This synthesis relies on L-proline catalysis to install a chlorohydrin function that masks the sensitive C16-C17 epoxide and potentially mimics the biosynthesis of these compounds where a related chlorohydrin may yield both THF- and epoxide-containing salarins. Additional and key features of the synthesis include (i) macrocycle formation via ring-closing metathesis, (ii) macrocyclic substrate-controlled epoxidation of the C12-C13 allylic alcohol, and (iii) a late-stage Julia-Kocienski olefination to install the side chain. Importantly, this work provides a platform for the synthesis of other salarins and analogues of these potentially important anticancer natural products.
Assuntos
Antineoplásicos , Cloridrinas , Estereoisomerismo , Macrolídeos/química , Compostos de Epóxi/químicaRESUMO
Aerocyanidin and amycomicin are two antibiotics derived from long-chain acids with a rare epoxy isonitrile moiety, the complexity of which renders the total synthesis of these two natural products rather challenging. How this functionality is biosynthesized has also remained obscure. While the biosynthetic gene clusters for these compounds have been identified, both appear to be deficient in genes encoding enzymes seemingly necessary for the oxidative modifications observed in these antibiotics. Herein, the biosynthetic pathways of aerocyanidin and amycomicin are fully elucidated. They share a conserved pathway to isonitrile intermediates that involves a bifunctional thioesterase and a nonheme iron α-ketoglutarate-dependent enzyme. In both cases, the isonitrile intermediates are then loaded onto an acyl carrier protein (ACP) catalyzed by a ligase. The isonitrile-tethered ACP is subsequently processed by polyketide synthase(s) to undergo chain extension, thereby assembling a long-chain γ-hydroxy isonitrile acid skeleton. The epoxide is installed by the cupin domain-containing protein AecF to conclude the biosynthesis of aerocyanidin. In contrast, three P450 enzymes AmcB, AmcC, and AmcQ are involved in epoxidation and keto formation to finalize the biosynthesis of amycomicin. These results thus explain the sequence of oxidation events that result in the final structures of aerocyanidin and amycomicin as well as the biosynthesis of the key γ-hydroxy epoxy isonitrile functional group.
Assuntos
Antibacterianos , Nitrilas , Antibacterianos/química , Antibacterianos/biossíntese , Nitrilas/química , Nitrilas/metabolismo , Compostos de Epóxi/química , Compostos de Epóxi/metabolismo , Estrutura MolecularRESUMO
Genetically encoding a proximal reactive warhead into the protein binder/drug has emerged as an efficient strategy for covalently binding to protein targets, enabling broad applications. To expand the reactivity scope for targeting the diverse natural residues under physiological conditions, the development of a genetically encoded reactive warhead with excellent stability and broad reactivity is highly desired. Herein, we reported the genetic encoding of epoxide-containing tyrosine (EPOY) for developing covalent protein drugs. Our study demonstrates that EPOY, when incorporated into a nanobody (KN035), can cross-link with different side chains (mutations) at the same position of PD-L1 protein. Significantly, a single genetically encoded reactive warhead that is capable of covalent and site-specific targeting to 10 different nucleophilic residues was achieved for the first time. This would largely expand the scope of covalent warhead and inspire the development of covalent warheads for both small-molecule drugs and protein drugs. Furthermore, we incorporate the EPOY into a designed ankyrin repeat protein (DarpinK13) to create the covalent binders of KRAS. This covalent KRAS binder holds the potential to achieve pan-covalent targeting of KRAS based on the structural similarity among all oncogenic KRAS mutants while avoiding off-target binding to NRAS/HRAS through a covalent interaction with KRAS-specific residues (H95 and E107). We envision that covalently targeting to H95 will be a promising strategy for the development of covalent pan-KRAS inhibitors in the future.
Assuntos
Compostos de Epóxi , Humanos , Compostos de Epóxi/química , Proteínas Proto-Oncogênicas p21(ras)/genética , Proteínas Proto-Oncogênicas p21(ras)/química , Proteínas Proto-Oncogênicas p21(ras)/antagonistas & inibidores , Proteínas Proto-Oncogênicas p21(ras)/metabolismo , Tirosina/química , Antígeno B7-H1/química , Antígeno B7-H1/metabolismo , Antígeno B7-H1/antagonistas & inibidores , Anticorpos de Domínio Único/química , Anticorpos de Domínio Único/metabolismoRESUMO
Lipids play integral roles in biological processes, with carbon-carbon double bonds (CâC) markedly influencing their structure and function. Precise characterization and quantification of unsaturated lipids are crucial for understanding lipid physiology and discovering disease biomarkers. However, using mass spectrometry for these purposes presents significant challenges. In this study, we developed a microwave-assisted magnesium monoperoxyphthalate hexahydrate (MMPP) epoxidation reaction, coupled with liquid chromatography-tandem mass spectrometry (LC-MS/MS), to analyze unsaturated lipids. Microwave irradiation expedited the MMPP epoxidation, achieving complete derivatization in 10 min without byproducts. A diagnostic ion pair, displaying a 16 Da mass difference, effectively identified the location of the CâC bond in mass spectra. Microwave irradiation also significantly facilitated the epoxidation reaction of polyunsaturated lipids, achieving yields greater than 85% and yielding a complete epoxidation product. This simplifies chromatographic separation and aids in accurate quantification. Additionally, a purification process was implemented to remove excess derivatization reagents, significantly reducing mass spectrometry response suppression and enhancing analytical reproducibility. The method's effectiveness was validated by analyzing unsaturated lipids in rat plasma from a type I diabetes model. We quantified nine unsaturated lipids and characterized 42 fatty acids and glycerophospholipids. The results indicated that unsaturated fatty acids increased in diabetic plasma while unsaturated glycerophospholipids decreased. Furthermore, the relative abundances of Δ9/Δ11 isomer pairs also exhibited a close association with diabetes. In conclusion, microwave-assisted MMPP epoxidation coupled with LC-MS/MS provides an effective strategy for characterization and quantification of polyunsaturated lipids, offering deeper insight into the physiological impact of unsaturated lipids in related diseases.
Assuntos
Micro-Ondas , Espectrometria de Massas em Tandem , Animais , Ratos , Espectrometria de Massas em Tandem/métodos , Compostos de Epóxi/química , Masculino , Ácidos Graxos Insaturados/química , Ácidos Graxos Insaturados/análise , Ácidos Graxos Insaturados/sangue , Cromatografia Líquida/métodos , Ratos Sprague-DawleyRESUMO
5,6-Epoxy-cholesterols has been recently revealed to control metabolic pathway in breast cancer, which makes investigating their binding interaction with human serum albumin (HSA) an attractive field of research. The main aim of this article is to examine the binding interaction of 5,6 α-epoxy-cholesterol (5,6 α EC) and 5,6 ß-epoxy-cholesterol (5,6 ß- EC) with HSA using different spectroscopic methods and molecular modeling. These compounds interact with HSA via hydrophobic interactions and hydrogen bonds with binding constants 6.3 × 105 M-1 for 5,6 α-epoxy-cholesterol and 6.9 × 105 M-1 for 5,6 ß-epoxy-cholesterol besides, the mechanism of the interaction can be attributed to static quenching. Circular dichroism data indicated that the α-helical content of HSA increased from 50.5 to 59.8 and 61.1 % after the addition of 5,6 α-ECs and 5,6 ß-EC, respectively, with a ratio of 1:2. Thermodynamic analysis revealed that binding between 5,6-epoxy-cholesterols and HSA is spontaneous and entropy-driven. The molecular docking and esterase-like activity experiments were performed to envision a link between the experimental and theoretical results. The optimal binding site of 5,6-epoxy-cholesterols with HSA was located in subdomain IIA. Moreover, theoretical calculations were performed using the B3LYP function with the 6-311++G (d,p) basis set, indicating the HOMO-LUMO energy gap of 7.874 eV for 5,6 α-epoxy-cholesterol and 7.873 eV for 5,6 ß-epoxy-cholesterol. The obtained findings are assumed to provide basic data for understanding the binding interactions of HSA with oxysterol compounds, which could help explore the pharmacokinetics and pharmacodynamics of oxysterol compounds.
Assuntos
Colesterol , Simulação de Acoplamento Molecular , Ligação Proteica , Albumina Sérica Humana , Humanos , Albumina Sérica Humana/química , Albumina Sérica Humana/metabolismo , Colesterol/metabolismo , Colesterol/química , Termodinâmica , Interações Hidrofóbicas e Hidrofílicas , Sítios de Ligação , Dicroísmo Circular , Ligação de Hidrogênio , Compostos de Epóxi/química , Compostos de Epóxi/metabolismoRESUMO
Amitriptyline (ATL), a tricyclic antidepressant, has been reported to cause various adverse effects, particularly hepatotoxicity. The mechanisms of ATL-induced hepatotoxicity remain unknown. The study was performed to identify the olefin epoxidation metabolite of ATL and determine the possible toxicity mechanism. Two glutathione (GSH) conjugates (M1 and M2) and two N-acetylcysteine (NAC) conjugates (M3 and M4) were detected in rat liver microsomal incubations supplemented with GSH and NAC, respectively. Moreover, M1/M2 and M3/M4 were respectively found in ATL-treated rat primary hepatocytes and in bile and urine of rats given ATL. Recombinant P450 enzyme incubations demonstrated that CYP3A4 was the primary enzyme involved in the olefin epoxidation of ATL. Treatment of hepatocytes with ATL resulted in significant cell death. Inhibition of CYP3A attenuated the susceptibility to the observed cytotoxicity of ATL. The metabolic activation of ATL most likely participates in the cytotoxicity of ATL.
Assuntos
Amitriptilina , Citocromo P-450 CYP3A , Compostos de Epóxi , Hepatócitos , Microssomos Hepáticos , Ratos Sprague-Dawley , Animais , Amitriptilina/metabolismo , Ratos , Citocromo P-450 CYP3A/metabolismo , Microssomos Hepáticos/metabolismo , Hepatócitos/efeitos dos fármacos , Hepatócitos/metabolismo , Masculino , Compostos de Epóxi/metabolismo , Compostos de Epóxi/toxicidade , Compostos de Epóxi/química , Glutationa/metabolismo , Células CultivadasRESUMO
Peroxyacid synthesis is the first step in Prilezhaev epoxidation, which is an industrial method to form epoxides. Motivated by the development of a kinetic model as a tool for solvent selection, the effect of solvent type and acid chain length on the lipase-catalyzed peroxyacid synthesis was studied. A thermodynamic activity-based ping-pong kinetic expression was successfully applied to predict the effect of the reagent loadings in hexane. The activity-based reaction quotients provided a prediction of solvent-independent equilibrium constants. However, this strategy did not achieve satisfactory estimations of initial rates in solvents of higher polarity. The lack of compliance with some assumptions of this methodology could be confirmed through molecular dynamics calculations i.e. independent solvation energies and lack of solvent interaction with the active site. A novel approach is proposed combining the activity-based kinetic expression and the free binding energy of the solvent with the active site to predict kinetics upon solvent change. Di-isopropyl ether generated a strong interaction with the enzyme's active site, which was detrimental to kinetics. On the other hand, toluene or limonene gave moderate interaction with the active site rendering improved catalytic yield compared with less polar solvents, a finding sharpened when peroctanoic acid was produced.
Assuntos
Lipase , Simulação de Dinâmica Molecular , Solventes , Solventes/química , Lipase/química , Lipase/metabolismo , Cinética , Compostos de Epóxi/química , Compostos de Epóxi/metabolismo , Proteínas Fúngicas/química , Proteínas Fúngicas/metabolismoRESUMO
A "one-step" strategy has been demonstrated for the tunable synthesis of multifunctional aliphatic polycarbonates (APCs) with ethylene oxide (EO), ethylene carbonate (EC), and cyclohexene oxide (CHO) side groups by the copolymerization of 4-vinyl-1-cyclohexene diepoxide with carbon dioxide under an aminotriphenolate iron/PPNBz (PPN = bis(triphenylphosphine)-iminium, Bz = benzoate) binary catalyst. By adjusting the PPNBz-to-iron complex ratio and incorporating auxiliary solvents, the content of functional side groups can be tuned within the ranges of 53-75% for EO, 18-47% for EC, and <1-7% for CHO. The yield and molecular weight distribution of the resulting multifunctional APCs are affected by the viscosity of the polymerization system. The use of tetrahydrofuran as an auxiliary solvent enables the preparation of narrow-distribution polycarbonates at high conversion. This work presents a novel perspective for the preparation of tailorable multifunctional APCs.
Assuntos
Dióxido de Carbono , Cimento de Policarboxilato , Polimerização , Dióxido de Carbono/química , Cimento de Policarboxilato/química , Compostos de Epóxi/química , Óxido de Etileno/química , Cicloexenos/química , Catálise , Viscosidade , DioxolanosRESUMO
Polyglycidol or polyglycerol (PG), a polyether widely used in biomedical applications, has not been extensively studied in its branched cyclic form (bcPG), despite extensive research on hyperbranched PG (HPG). This study explores the biomedical promise of bcPG, particularly its ability to cross the blood-brain barrier (BBB). We evaluate in vitro biocompatibility, endothelial permeability, and formation of branched linear PG (blPG) as topological impurities in the presence of water. Small angle X-ray scattering in solution revealed a fractal dimension of approximately two for bcPG and the mixture bc+blPG, suggesting random branching. Comparisons of cytotoxicity and endothelial permeability between bcPG, bc+blPG, and HPG in a BBB model using hCMEC/D3 cells showed different biocompatibility profiles and higher endothelial permeability for HPG. bcPG showed a tendency to accumulate around cell nuclei, in contrast to the behavior of HPG. This study contributes to the understanding of the influence of polymer topology on biological behavior.
Assuntos
Materiais Biocompatíveis , Barreira Hematoencefálica , Humanos , Barreira Hematoencefálica/metabolismo , Materiais Biocompatíveis/química , Materiais Biocompatíveis/farmacologia , Polimerização , Células Endoteliais/efeitos dos fármacos , Células Endoteliais/metabolismo , Polímeros/química , Polímeros/farmacologia , Glicerol/química , Compostos de Epóxi/química , Linhagem Celular , Permeabilidade , Propilenoglicóis/química , Propanóis/químicaRESUMO
PURPOSE: Joint destruction is a major burden and an unsolved problem in rheumatoid arthritis (RA) patients. We designed an intra-articular mesoporous silica nanosystem (MSN-TP@PDA-GlcN) with anti-inflammatory and joint protection effects. The nanosystem was synthesized by encapsulating triptolide (TP) in mesoporous silica nanoparticles and coating it with pH-sensitive polydopamine (PDA) and glucosamine (GlcN) grafting on the PDA. The nano-drug delivery system with anti-inflammatory and joint protection effects should have good potency against RA. METHODS: A template method was used to synthesize mesoporous silica (MSN). MSN-TP@PDA-GlcN was synthesized via MSN loading with TP, coating with PDA and grafting of GlcN on PDA. The drug release behavior was tested. A cellular inflammatory model and a rat RA model were used to evaluate the effects on RA. In vivo imaging and microdialysis (MD) system were used to analyze the sustained release and pharmacokinetics in RA rats. RESULTS: TMSN-TP@PDA-GlcN was stable, had good biocompatibility, and exhibited sustained release of drugs in acidic environments. It had excellent anti-inflammatory effects in vitro and in vivo. It also effectively repaired joint destruction in vivo without causing any tissue toxicity. In vivo imaging and pharmacokinetics experiments showed that the nanosystem prolonged the residence time, lowered the Cmax value and enhanced the relative bioavailability of TP. CONCLUSIONS: These results demonstrated that MSN-TP@PDA-GlcN sustained the release of drugs in inflammatory joints and produced effective anti-inflammatory and joint protection effects on RA. This study provides a new strategy for the treatment of RA.
Assuntos
Anti-Inflamatórios , Artrite Reumatoide , Diterpenos , Liberação Controlada de Fármacos , Indóis , Nanopartículas , Fenantrenos , Polímeros , Dióxido de Silício , Animais , Dióxido de Silício/química , Artrite Reumatoide/tratamento farmacológico , Nanopartículas/química , Anti-Inflamatórios/administração & dosagem , Anti-Inflamatórios/farmacologia , Anti-Inflamatórios/química , Anti-Inflamatórios/farmacocinética , Fenantrenos/química , Fenantrenos/administração & dosagem , Fenantrenos/farmacocinética , Fenantrenos/farmacologia , Ratos , Diterpenos/administração & dosagem , Diterpenos/química , Diterpenos/farmacocinética , Diterpenos/farmacologia , Indóis/administração & dosagem , Indóis/química , Indóis/farmacocinética , Indóis/farmacologia , Polímeros/química , Porosidade , Masculino , Compostos de Epóxi/química , Compostos de Epóxi/administração & dosagem , Glucosamina/química , Glucosamina/administração & dosagem , Ratos Sprague-Dawley , Portadores de Fármacos/química , Humanos , Camundongos , Preparações de Ação Retardada , Inflamação/tratamento farmacológico , Inflamação/prevenção & controleRESUMO
By performing molecular dynamics (MD), quantum mechanical/molecular mechanical (QM/MM) calculations, and QM cluster calculations, the origin of chemoselectivity of halohydrin dehalogenase (HHDH)-catalyzed ring-opening reactions of epoxide with the nucleophilic reagent NO2- has been explored. Four possible chemoselective pathways were considered, and the computed results indicate that the pathway associated with the nucleophilic attack on the Cα position of epoxide by NO2- is most energetically favorable and has an energy barrier of 12.9 kcal/mol, which is close to 14.1 kcal/mol derived from experimental kinetic data. A hydrogen bonding network formed by residues Ser140, Tyr153, and Arg157 can strengthen the electrophilicity of the active site of the epoxide substrate to affect chemoselectivity. To predict the energy barrier trends of the chemoselective transition states, multiple analyses including distortion analysis and electrophilic Parr function (Pk+) analysis were carried out with or without an enzyme environment. The obtained insights should be valuable for the rational design of enzyme-catalyzed and biomimetic organocatalytic epoxide ring-opening reactions with special chemoselectivity.
Assuntos
Biocatálise , Compostos de Epóxi , Hidrolases , Hidrolases/metabolismo , Hidrolases/química , Compostos de Epóxi/química , Compostos de Epóxi/metabolismo , Simulação de Dinâmica Molecular , Teoria Quântica , Domínio Catalítico , Especificidade por SubstratoRESUMO
Isoprene has the highest atmospheric emissions of any nonmethane hydrocarbon, and isoprene epoxydiols (IEPOX) are well-established oxidation products and the primary contributors forming isoprene-derived secondary organic aerosol (SOA). Highly acidic particles (pH 0-3) widespread across the lower troposphere enable acid-driven multiphase chemistry of IEPOX, such as epoxide ring-opening reactions forming methyltetrol sulfates through nucleophilic attack of sulfate (SO42-). Herein, we systematically demonstrate an unexpected decrease in SOA formation from IEPOX on highly acidic particles (pH < 1). While IEPOX-SOA formation is commonly assumed to increase at low pH when more [H+] is available to protonate epoxides, we observe maximum SOA formation at pH 1 and less SOA formation at pH 0.0 and 0.4. This is attributed to limited availability of SO42- at pH values below the acid dissociation constant (pKa) of SO42- and bisulfate (HSO4-). The nucleophilicity of HSO4- is 100× lower than SO42-, decreasing SOA formation and shifting particulate products from low-volatility organosulfates to higher-volatility polyols. Current model parameterizations predicting SOA yields for IEPOX-SOA do not properly account for the SO42-/HSO4- equilibrium, leading to overpredictions of SOA formation at low pH. Accounting for this underexplored acidity-dependent behavior is critical for accurately predicting SOA concentrations and resolving SOA impacts on air quality.
Assuntos
Aerossóis , Compostos de Epóxi/química , Concentração de Íons de Hidrogênio , Equilíbrio Ácido-BaseRESUMO
Epoxidized natural rubber (ENR) crosslinked using borax, which exhibits self-healing and self-repairing properties, is successfully developed. The crosslink formation of ENR by using borax under neutral and alkaline conditions is investigated. Fourier transform infrared spectroscopy (FTIR) shows that the borate-ester bond is formed in ENR prepared under both neutral and alkaline conditions, whereas boron nuclear magnetic resonance (11 B-NMR) results exhibit that the ENR prepared under alkaline conditions more actively forms crosslink networks with borax. Moreover, the crosslink density and gel content increase significantly with the presence of borax in alkaline conditions. The crosslink density and gel content of ENR with 10 phr borax are higher by 155% and 36%, respectively, than those of neat ENR. Furthermore, the formation of the crosslinking ENR by borax enhances self-healing and self-repairing properties. The healing efficiency significantly increases from 1.09% to 85.90%, when ENR is developed under alkaline conditions with 30 phr borax. These results represent the first successful demonstration of the efficient use of borax as a crosslinker in ENR, which exhibits its promising self-healing and self-repairing properties under atmospheric conditions without the need for external stimuli. The ENR prepared in this work holds great promise for various self-healing rubber applications.
Assuntos
Boratos , Borracha , Borracha/química , Compostos de Epóxi/química , Concentração de Íons de HidrogênioRESUMO
Mechanophoric polymers are an interesting class of smart polymers which contains a special force-sensitive molecular motif that can lead to a chemical change within the polymer network in response to mechanical force. This investigation reports the design of a mechanophoric polymer based on epoxy-functionalized rhodamine via a monomeric approach. In this case, rhodamine (Rh) is modified with glycidyl methacrylate (GMA) through an epoxy-amine reaction to design a vinyl-functionalized multi-armed macromonomer (Rh-GMA), which is reacted with butyl acrylate (BA) to prepare the crosslinked polymeric film. The crosslinked polymeric film demonstrates mechanophoric properties under UV and stretching conditions.
Assuntos
Compostos de Epóxi , Polímeros , Rodaminas , Rodaminas/química , Compostos de Epóxi/química , Polímeros/química , Polímeros/síntese química , Metacrilatos/química , Estrutura Molecular , Acrilatos/químicaRESUMO
Glycidyl ethers are prepared from a series of furan-based diols and cured with a diamine to form thermosets. The furan diols demonstrate lower toxicity than bisphenol-A in a prior study. The diglycidyl ethers show improved thermal stability compared to the parent diols. Cured thermosets are prepared at elevated temperature using isophorone diamine (IPDA). Glass transition temperatures are in the range of 30-54 °C and depend on the structure of the furan diol. Coatings are prepared on steel substrates and show very high hardness, good adhesion, and a range of flexibility. Properties compare favorably with a control based on a bisphenol-A epoxy resin. The study demonstrates that epoxy resins based on furan diols, which have been shown to have lower toxicity than bisphenol-A, can form thermosets having properties comparable to a standard epoxy resin system; and thus, are viable as replacements for bisphenol-A epoxy resins.
Assuntos
Resinas Epóxi , Furanos , Resinas Epóxi/química , Furanos/química , Compostos Benzidrílicos/química , Temperatura , Estrutura Molecular , Compostos de Epóxi/química , Fenóis/químicaRESUMO
Mesoionic N-heterocyclic olefins (mNHOs) have recently emerged as a novel class of highly nucleophilic and super-basic σ-donor compounds. Making use of these properties in synthetic polymer chemistry, it is shown that a combination of a specific mNHO and a Mg-based Lewis acid (magnesium bis(hexamethyldisilazide), Mg(HMDS)2) delivers poly(propylene oxide) in quantitative yields from the polymerization of the corresponding epoxide (0.1 mol% mNHO loading). The initiation mechanism involves monomer activation by the Lewis acid and direct ring-opening of the monomer by nucleophilic attack of the mNHO, forming a zwitterionic propagating species. Modulation of the mNHO properties is thereby a direct tool to impact initiation efficiency, revealing a sterically unencumbered triazole-derivative as particularly useful. The joint application of mNHOs together with borane-type Lewis acids is also outlined, resulting in high conversions and fast polymerization kinetics. Importantly, while molar mass distributions remain relatively broad, indicating faster propagation than initiation, the overall molar masses are significantly lower than found in the case of regular NHOs, underlining the increased nucleophilicity and ensuing improved initiation efficiency of mNHOs.
Assuntos
Alcenos , Compostos de Epóxi , Ácidos de Lewis , Polimerização , Ácidos de Lewis/química , Compostos de Epóxi/química , Alcenos/química , Compostos Heterocíclicos/química , Estrutura Molecular , Polímeros/química , Polímeros/síntese químicaRESUMO
Indole monooxygenases (IMOs) are enzymes from the family of Group E monooxygenases, requiring flavin adenine dinucleotide (FAD) for their activities. IMOs play important roles in both sulfoxidation and epoxidation reactions. The broad substrate range and high selectivity of IMOs make them promising biocatalytic tools for synthesizing chiral compounds. In the present study, quantum chemical calculations using the cluster approach were performed to investigate the reaction mechanism and the enantioselectivity of the IMO from Variovorax paradoxus EPS (VpIndA1). The sulfoxidation of methyl phenyl sulfide (MPS) and the epoxidation of indene were chosen as the representative reactions. The calculations confirmed that the FADOOH intermediate is the catalytic species in the VpIndA1 reactions. The oxidation of MPS adopts a one-step mechanism involving the direct oxygen-transfer from FADOOH to the substrate and the proton transfer from the -OH group back to FAD, while the oxidation of indene follows a stepwise mechanism involving a carbocation intermediate. It was computationally predicted that VpIndA1 prefers the formation of (S)-product for the MPS sulfoxidation and (1S,2R)-product for the indene epoxidation, consistent with the experimental observations. Importantly, the factors controlling the stereo-preference of the two reactions are identified. The findings in the present study provide valuable insights into the VpIndA1-catalyzed reactions, which are essential for the rational design of this enzyme and other IMOs for industrial applications. It is also worth emphasizing that the quantum chemical cluster approach is again demonstrated to be powerful in studying the enantioselectivity of enzymatic reactions.
Assuntos
Oxigenases de Função Mista , Oxirredução , Estereoisomerismo , Oxigenases de Função Mista/metabolismo , Oxigenases de Função Mista/química , Teoria Quântica , Sulfetos/química , Sulfetos/metabolismo , Indóis/química , Indóis/metabolismo , Modelos Químicos , Compostos de Epóxi/química , Compostos de Epóxi/metabolismo , Flavina-Adenina Dinucleotídeo/química , Flavina-Adenina Dinucleotídeo/metabolismo , Modelos MolecularesRESUMO
We report a transformative epoxy system with a microalgae-derived bio-binder from hydrothermal liquefaction processing (HTL). The obtained bio-binder not only served as a curing agent for conventional epoxy resin (e.g., EPON 862), but also acted as a modifying agent to enhance the thermal and mechanical properties of the conventional epoxy resin. This game-changing epoxy/bio-binder system outperformed the conventional epoxy/hardener system in thermal stability and mechanical properties. Compared to the commercial EPON 862/EPIKURE W epoxy product, our epoxy/bio-binder system (35 wt.% bio-binder addition with respect to the epoxy) increased the temperature of 60% weight loss from 394 °C to 428 °C and the temperature of maximum decomposition rate from 382 °C to 413 °C, while the tensile, flexural, and impact performance of the cured epoxy improved in all cases by up to 64%. Our research could significantly impact the USD 38.2 billion global market of the epoxy-related industry by not only providing better thermal and mechanical performance of epoxy-based composite materials, but also simultaneously reducing the carbon footprint from the epoxy industry and relieving waste epoxy pollution.