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Journal of the American Chemical Society Jul 2024The development of intrinsically recyclable cross-linked materials remains challenged by the inherently unfavorable chemical equilibrium that dictates the efficiency of...
The development of intrinsically recyclable cross-linked materials remains challenged by the inherently unfavorable chemical equilibrium that dictates the efficiency of the reversible covalent bonding/debonding chemistry. Rather than having to (externally) manipulate the bonding equilibrium, we here introduce a new reversible chemistry platform based on monosubstituted thiomaleimides that can undergo complete and independent light-activated covalent bonding and on-demand thermal debonding above 120 °C. Specifically, repeated bonding/debonding of a small-molecule thiomaleimide [2 + 2] photodimer is demonstrated over five heat/light cycles with full conversion in both directions, thereby regenerating its initial monothiomaleimide constituents. This motivated the synthesis of multifunctional thiomaleimide reagents as precursors for the design of covalently cross-linked networks that display intrinsic switching between a monomeric and polymeric state. The resulting materials are shown to covalently dissociate and depolymerize upon heating both in solution and in bulk, thus transforming the densely photo-cross-linked material back into a viscous liquid. Temperature-regulated photorheology evidenced the intrinsic recyclability of the thiomaleimide-based thermosets during multiple cycles of UV cross-linking and thermal de-cross-linking. The thermally reversible photodimerization of thiomaleimides presents a new addition to the designer playground of dynamic polymer networks, providing interesting opportunities for the reprocessing and closed-loop recycling of covalently cross-linked materials.
PubMed: 38953610
DOI: 10.1021/jacs.4c04193 -
Dalton Transactions (Cambridge, England... Jul 2024Synthesis and reactivity with carbon dioxide (CO) of divalent samarium in the bis-tris(pyrazolyl)borate ligand environment has been reported. In addition, CO activation...
Synthesis and reactivity with carbon dioxide (CO) of divalent samarium in the bis-tris(pyrazolyl)borate ligand environment has been reported. In addition, CO activation and functionalisation by lanthanide silylamides in the bis-tris(pyrazolyl)borate ligand environment was demonstrated. Reduction of the Sm(III) precursor [Sm(Tp)(OTf)] (Tp = hydrotris(1-pyrazolyl)borate; OTf = triflate) with KC yielded the insoluble Sm(II) multi-metallic coordination polymer [{Sm(Tp)}] 1-Sm. Addition of 1,2-dimethoxyethane (DME) to 1-Sm enabled isolation of the monomeric complex [Sm(Tp)(DME)] 1-Sm(DME). Complex 1-Sm(DME) reduced CO to yield the oxalate-bridged dimeric Sm(III) complex [{Sm(Tp)}(μ-η:η-OCCO)] 2-Sm. The reactions of heteroleptic Ln(III) silylamide complexes [Ln(Tp)(N'')] (Ln = Y, Sm; N'' = N(SiMe)) with CO yielded monomeric Ln(III) silyloxides [Ln(Tp)(OSiMe)] 3-Ln and trimethylsilyl isocyanate (OCNSiMe). Complexes 3-Ln are the first crystallographically characterised examples of Ln(III)-OSiMe bonds accessed CO activation and functionalisation. Full characterisation data are presented for all complexes, including solid-state molecular structure determination by single-crystal X-ray diffraction.
PubMed: 38953525
DOI: 10.1039/d4dt01382d -
Small (Weinheim An Der Bergstrasse,... Jul 2024Polyimide aerogels have been extensively used in thermal protection domain because they possess a combination of intrinsic characteristics of aerogels and unique...
Polyimide aerogels have been extensively used in thermal protection domain because they possess a combination of intrinsic characteristics of aerogels and unique features of polyimide. However, polyimide aerogels still suffer significant thermally induced shrinkage at temperatures above 200 °C, restricting their application at high temperature. Here, a novel "double-phase-networking" strategy is proposed for fabricating a lightweight and mechanically robust polyimide hybrid aerogel by forming silica-zirconia-phase networking skeletons, which possess exceptional dimensional stability in high-temperature environments and superior thermal insulation. The rational mechanism responsible for the formation of double-phase-networking aerogel is further explained, generally attributing to chemical crosslinking reactions and supramolecular hydrogen bond interactions derived from the main chains of polyimide and silane/zirconia precursor/sol. The as-prepared aerogels exhibit excellent high-temperature (270 °C) dimensional stability (5.09% ± 0.16%), anti-thermal-shock properties, and low thermal conductivity. Moreover, the hydrophobic treatment provides aerogels high water resistance with water contact angle of 136.9°, further suggestive of low moisture content of 3.6% after exposure to 70 °C and 85% relative humidity for 64 h. The proposed solution for significantly enhancing high-temperature dimensional stability and thermal insulation provides a great supporting foundation for fabricating high-performance organic aerogels as thermal protection materials in aerospace.
PubMed: 38953403
DOI: 10.1002/smll.202404104 -
Small (Weinheim An Der Bergstrasse,... Jul 2024Constructing dual-site catalysts consisting of atomically dispersed metal single atoms and metal atomic clusters (MACs) is a promising approach to further boost the...
Constructing dual-site catalysts consisting of atomically dispersed metal single atoms and metal atomic clusters (MACs) is a promising approach to further boost the catalytic activity for oxygen reduction reaction (ORR). Herein, a porous Co@SNC featuring the coexistence of Co single-atom sites (CoN) and S-coordinated Co atomic clusters (SCo) in S, N co-doped carbon substrate is successfully synthesized by using porphyrinic metal-organic framework (Co-TPyP MOF) as the precursor. The introduction of the sulfur source creates abundant microstructural defects to anchor Co metal clusters, thus modulating the electronic structure of its surrounding carbon substrate. The synergistic effect between the two types of active sites and structural advantages, in turn, results in high ORR performance of Co@SNC with half-wave potential (E) of 0.86 V and Tafel slope of 50.17 mV dec. Density functional theory (DFT) calculations also support the synergistic effect between CoN and SCo by detailing the catalytic mechanism for the improved ORR performance. The as-fabricated Zn-air battery (ZAB) using Co@SNC demonstrates impressive peak power density of 174.1 mW cm and charge/discharge durability for 148 h. This work provides a facile synthesis route for dual-site catalysts and can be extended to the development of other efficient atomically dispersed metal-based electrocatalysts.
PubMed: 38953346
DOI: 10.1002/smll.202402323 -
Journal of Biomaterials Science.... Jul 2024In this study, to address the defects of sodium alginate (SA), such as its susceptibility to disintegration, silica was coated on the outer layer of sodium alginate...
In this study, to address the defects of sodium alginate (SA), such as its susceptibility to disintegration, silica was coated on the outer layer of sodium alginate hydrogel beads in order to improve its swelling and slow-release properties. Tetraethyl orthosilicate (TEOS) was used as the hydrolyzed precursor, and the solution of silica precursor was prepared by sol-gel reaction under acidic conditions. Then SA-silica hydrogel beads prepared by ionic crosslinking method were immersed into the SiO precursor solution to prepare SA-silica hydrogel beads. The chemical structure and morphology of the hydrogel beads were characterized by XRD, FTIR, and SEM, and the results showed that the surface of SA-silica beads was successfully encapsulated with the outer layer of SiO, and the surface was smooth and dense. The swelling experiments showed that the swelling performance effectively decreased with the increase of TEOS molar concentration, and the maximum swelling ratio of the hydrogel beads decreased from 41.07 to 14.3, and the time to reach the maximum swelling ratio was prolonged from 4 h to 8 h. The sustained-release experiments showed that the SA-silica hydrogel beads possessed a good pH sensitivity, and the time of sustained-release was significantly prolonged in vitro. Hemolysis and cytotoxicity experiments showed that the SA-silica hydrogel beads were biocompatible when the TEOS molar concentration was lower than 0.375 M. The SA-silica-2 hydrogel beads had good biocompatibility, swelling properties, and slow-release properties at the same time.
PubMed: 38953307
DOI: 10.1080/09205063.2024.2368957 -
Zhongguo Yi Xue Ke Xue Yuan Xue Bao.... Jun 2024Alzheimer's disease (AD) is a severe threat to human health and one of the three major causes of human death.Double-stranded RNA-dependent protein kinase (PKR) is an... (Review)
Review
Alzheimer's disease (AD) is a severe threat to human health and one of the three major causes of human death.Double-stranded RNA-dependent protein kinase (PKR) is an interferon-induced protein kinase involved in innate immunity.In the occurrence and development of AD,PKR is upregulated and continuously activated.On the one hand,the activation of PKR triggers an integrated stress response in brain cells.On the other hand,it indirectly upregulates the expression of β-site amyloid precursor protein cleaving enzyme 1 and facilitates the accumulation of amyloid-β protein (Aβ),which could activate PKR activator to further activate PKR,thus forming a sustained accumulation cycle of Aβ.In addition,PKR can promote Tau phosphorylation,thereby reducing microtubule stability in nerve cells.Inflammation in brain tissue,neurotoxicity resulted from Aβ accumulation,and disruption of microtubule stability led to the progression of AD and the declines of memory and cognitive function.Therefore,PKR is a key molecule in the development and progression of AD.Effective PKR detection can aid in the diagnosis and prediction of AD progression and provide opportunities for clinical treatment.The inhibitors targeting PKR are expected to control the activity of PKR,thereby controlling the progression of AD.Therefore,PKR could be a target for the development of therapeutic drugs for AD.
Topics: Alzheimer Disease; Humans; eIF-2 Kinase; Amyloid beta-Peptides; tau Proteins; Phosphorylation; Brain; Amyloid beta-Protein Precursor
PubMed: 38953267
DOI: 10.3881/j.issn.1000-503X.15792 -
Beilstein Journal of Organic Chemistry 2024The synthesis of protected precursors of cyclic β-1,6-oligoglucosamines from thioglycosides as monomers is performed by electrochemical polyglycosylation. The monomer...
The synthesis of protected precursors of cyclic β-1,6-oligoglucosamines from thioglycosides as monomers is performed by electrochemical polyglycosylation. The monomer with a 2,3-oxazolidinone protecting group afforded the cyclic disaccharide exclusively. Cyclic oligosaccharides up to the trisaccharide were obtained using the monomer with a 2-azido-2-deoxy group.
PubMed: 38952959
DOI: 10.3762/bjoc.20.124 -
Frontiers in Neurology 2024Xanthomatosis is a genetic disease inherited in an autosomal recessive manner. The specific phenotypic features are associated with patient's genetic profile. The result... (Review)
Review
Xanthomatosis is a genetic disease inherited in an autosomal recessive manner. The specific phenotypic features are associated with patient's genetic profile. The result of the mutation is disorder of cholesterol synthesis and the accumulation of its precursors in tissues. The characteristic symptoms are progressive cerebellar ataxia, cataract, diarrhea, and the deposition of cholesterol in the tendons. Our objective is to follow-up information to treatment efficacy of 22-year-old patient diagnosed with cerebrotendinous xanthomatosis through 1.5 year observation. In 2012, an 11-year-old patient with a long history of deformed feet and frequent yellowing of the skin, was admitted to the Department of Neurology due to seizures. In 2013, the patient began to suffer from diarrhea, and its frequency was correlated with the concentration of bilirubin in the blood. In the same year cataract was diagnosed. Gradually, the patient starts to complain about progressive difficulties in moving. In 2019, genetic tests confirmed the diagnosis of cerebrotendinous xanthomatosis. Since July 2021, the patient has been treated with chenodeoxycholic acid. The deterioration of patient's mobility has been significantly inhibited, consequently his quality of life has improved. The presented case report underscores the efficacy of CDCA supplementation in halting the progression of CTX, resulting in marked improvements in the patient's quality of life.
PubMed: 38952472
DOI: 10.3389/fneur.2024.1409138 -
MicroRNA (Shariqah, United Arab... Jun 2024Publications reveal different outcomes achieved by genetically knocking out a long non-coding microRNA-host-gene (lncMIRHG) versus the administration of pharma-cologic...
Review of the Different Outcomes Produced by Genetic Knock Out of the Long Non-coding microRNA-host-gene MIR22HG versus Pharmacologic Antagonism of its Intragenic microRNA product miR-22-3p.
BACKGROUND
Publications reveal different outcomes achieved by genetically knocking out a long non-coding microRNA-host-gene (lncMIRHG) versus the administration of pharma-cologic antagomirs specifically targeting the guide strand of such intragenic microRNA. This suggests that lncMIRHGs may perform diverse functions unrelated to their role as intragenic miRNA precursors.
OBJECTIVE
This review synthesizes in silico, in vitro, and in vivo findings from our lab and others to compare the effects of knocking out the long non-coding RNA MIR22HG, which hosts miR-22, versus administering pharmacological antagomirs targeting miR-22-3p.
METHODS
In silico analyses at the gene, pathway, and network levels reveal both distinct and overlapping targets of hsa-miR-22-3p and its host gene, MIR22HG. While pharmacological an-tagomirs targeting miR-22-3p consistently improve various metabolic parameters in cell culture and animal models across multiple studies, genetic knockout of MIR22HG yields inconsistent results among different research groups.
RESULTS
Additionally, MIR22HG functions as a circulating endogenous RNA (ceRNA) or "sponge" that simultaneously modulates multiple miRNA-mRNA interactions by competing for binding to several miRNAs.
CONCLUSIONS
From a therapeutic viewpoint, genetic inactivation of a lncMIRHG and pharmaco-logic antagonism of the guide strand of its related intragenic miRNA produce different results. This should be expected as lncMIRHGs play dual roles, both as lncRNA and as a source for primary miRNA transcripts.
PubMed: 38952162
DOI: 10.2174/0122115366282339240604042154 -
Critical Reviews in Food Science and... Jul 2024The enterolignans, enterolactone and enterodiol, the main metabolites produced from plant lignans by the gut microbiota, have enhanced bioavailability and activity... (Review)
Review
The enterolignans, enterolactone and enterodiol, the main metabolites produced from plant lignans by the gut microbiota, have enhanced bioavailability and activity compared to their precursors, with beneficial effects on metabolic and cardiovascular health. Although extensively studied, the biosynthesis, cardiometabolic effects, and other therapeutic implications of mammalian lignans are still incompletely understood. The aim of this review is to provide a comprehensive overview of these phytoestrogen metabolites based on up-to-date information reported in studies from a wide range of disciplines. Established and novel synthetic strategies are described, as are the various lignan precursors, their dietary sources, and a proposed metabolic pathway for their conversion to enterolignans. The methodologies used for enterolignan analysis and the available data on pharmacokinetics and bioavailability are summarized and their cardiometabolic bioactivity is explored in detail. The special focus given to research on the health benefits of microbial-derived lignan metabolites underscores the critical role of lignan-rich diets in promoting cardiovascular health.
PubMed: 38952149
DOI: 10.1080/10408398.2024.2371939