A series of benzofuro-fused 7-deazapurine (6H-furo[2,3-e]pyrimido[4,5-b]indole) 2’-deoxyribo- and ribonucleosides was designed and synthesized. The synthesis of key 10-chloro-6H-furo[2,3-e]pyrimido[4,5-b]indole was based on the Negishi cross-coupling of iodobenzofurane with zincated 4,6-dichloropyrimidine followed by azidation and photochemical cyclization. Glycosylation of the heterocycle with either Hoffer’s chlorodeoxyribose or protected ribose followed by cross-coupling or substitution reactions at position 10 gave the desired two sets of final nucleosides that showed moderate to weak cytostatic activity and interesting fluorescence properties.
Equilibrium and Non‐equilibrium Reaction Schemes for Prebiotic Polymerization of Ribonucleotides
The RNA World theory for the origin of life requires polymers to be generated initially by abiotic reactions. Experiments have studied polymerization of 5′-monophosphates, 2′,3′-cyclic phosphates, and 5′-triphosphates. We consider theoretical models of polymerization in solution illustrating the differences between these cases. We consider (i) a basic model where all monomers undergo reversible joining and breaking; (ii) a model where 2′,3′-cyclic phosphates can join, and breaking regenerates the cyclic phosphate; (iii) a model where 5′-triphosphates can join irreversibly, in addition to the joining and breaking of 2′,3′-cyclic phosphates. In cases (i) and (ii) there is an equilibrium steady state with balance between making and breaking bonds. In case (iii) there is a circular reaction flux in which monomers are activated by an external phosphate source, activated monomers form polymers, and polymers break to release non-activated monomers. The mean length can be calculated as a function of concentration. In case (iii), the mean length switches from a low-concentration regime controlled by the 5′-triphosphates to a high-concentration regime controlled by the 2′,3′-cyclic phosphates. The circular reaction flux is reminiscent of a metabolism. If formation of 5’-triphosphates was already in place for RNA synthesis, ATP could subsequently been co-opted for metabolism.
Ag‐Doped Free‐Standing 2D TiO2 Sheets: Electronic, Optical, Magnetic, and Self‐Healing Behaviour
Beyond a critical doping level, Ag - 2D TiO2 sheets (ATO) are deemed to be a flexible transparent conductor, useful for visible-range functional photonic/optoelectronic devices/sensors, sunlight-sensitive catalysis, and light-activated resistive switching. Due to the lack of control of surface energy which often leads to the formation of structural defects and even dimensionality crossover (2D to 0D) of materials during doping reaction, it is challenging to obtain ATO with a controlled doping level. Gauging the urgency, therefore we report the surface energy-controlled synthesis of ATO employing liquid phase exfoliation of TiO2 and subsequent hydrothermal Ag-doping in the presence of Hexamethylenetetramine (HMTA). Electron microscopy and atomic force microscopy reveal ATO sheets with large lateral dimensions. 6-fold, 4-fold, and strain-mediated crystallographic phases of 2D ATO have been revealed by high-resolution electron imaging. Successful tuning of the band gap down to ~ 2 eV with Ag doping up to ~ 10% is obtained. Synthesized 2D ATO have been investigated for their electrical, optical, optoelectronic, photoluminescence, and ferromagnetic behaviour. Visible light-sensitive thermally/structurally robust semiconductor/conductor via tuneable doping will pave the way for their flexible as well as wearable device applications. Self-healing effect of AFM tip-generated mechanical stress has also been demonstrated.
Room Temperature Aerobic Oxidation of Amines to Nitriles over Ruthenium Oxide Supported on CeO2 Derived from MOFs
Heterogenous BPDC-RuO2-CeO2 catalyst derived from Ce-BPDC MOFs can successfully enable the oxidation of amines to nitriles under mild conditions (1 atm O2, H2O as a solvent, room temperature). The catalytic system has the good compatibility with benzylic and aliphatic amines. Lewis acid-base pair [Ru–O–Ce-Vö] formed by the combination of acidic oxygen vacancy and basic oxygen pair Ru–O–Ce on the surface of the catalyst is the key factor for the catalytic activity. The mechanical experiments indicate that amines adopt the step-by-step dehydrogenation process to nitriles in this transformation. Moreover, the catalyst could be recycled up to six times without the evident loss of catalytic activity and the change of morphology.
Green approach for the synthesis of chalcogenyl‐2,3‐dihydrobenzofuran derivatives through allyl‐phenols/naphthols and their potential as MAO‐B inhibitors
This work presents the design, synthesis, and MAO-B inhibitor activity of a series of chalcogenyl-2,3-dihydrobenzofurans derivatives. Using solvent- and metal-free methodology, a series of chalcogen-containing dihydrobenzofurans 7–9 was obtained with yields ranging from 40% to 99%, using an I2/DMSO catalytic system. All compounds were fully structurally characterized using 1H and 13C NMR analysis, and the unprecedented compounds were additionally analyzed using high-resolution mass spectrometry (HRMS). In addition, the mechanistic proposal that iodide is the most likely species to act in the transfer of protons along the reaction path was studied through theoretical calculations. Finally, the compounds 7b–e, 8a–e, and 9a showed great promise as inhibitors against MAO-B activity.
Surface Modification Driven Initial Coulombic Efficiency and Rate Performance Enhancement of Li1.2Mn0.54Ni0.13Co0.13O2 Cathode
Due to its high energy density and low cost, Li-rich Mn-based layered oxides are considered potential cathode materials for next generation Li-ion batteries. However, they still suffer from serious obstacles of low initial Coulombic efficiency, which is detrimental to their practical application. Here, an efficient surface modification method via NH4H2PO4 assisted pyrolysis is performed to improve the Coulombic efficiency of Li1.2Mn0.54Ni0.13Co0.13O2, where appropriate oxygen vacancies, Li3PO4 and spinel phase are synchronously generated in the surface layer of LMR microspheres. Under the synergistic effect of the oxygen vacancies and spinel phase, the unavoidable oxygen release in the cycling process was effectively suppressed. Moreover, the induced Li3PO4 nanolayer could boost the lithium-ion diffusion and mitigate the dissolution of transition metal ions, especially manganese ions, in the material. The optimally modified sample yielded an impressive initial Coulombic efficiency and outstanding rate performance.
Single Atom Catalysts for Photoelectrochemical Water Splitting
Single atom catalysts (SACs) have attracted increasing attention in electrocatalysis due to their unprecedented catalytic activity with excellent atomic utilization efficiency derived from unique electronic states and coordination environments. In photoelectrochemical (PEC) water splitting, atomically dispersed metal catalysts anchored to photoelectrodes offer the breakthrough to outperform the conventional thin-film PEC catalysts by enlarging the catalytic sites and facilitating photogenerated charge carrier kinetics. Herein, we present a comprehensive review of SAC-incorporated photoelectrodes for efficient PEC water splitting. Firstly, the representative characterization techniques for the identification of SACs and investigations in respect of photogenerated charge carrier kinetics and photon-to-current efficiency will be discussed. Then, we will introduce the state-of-the-art PEC-SACs classified into noble metal, non-noble metal, and dual metal SACs. Finally, critical outlooks to realize the full potential of SACs in photoelectrocatalysis will be highlighted.
Multi‐Functional Organofluoride Catalysts for Polyesters Production and Upcycling Degradation
The production and degradation of polyesters are two crucial processes in polyester materials’life cycle. In this work, multi-functional organocatalysts based on fluorides for both processes are described. Organofluorides were developed as catalysts for ring-opening polymerization of lactide (lactone). Compared with a series of organohalides, organofluoride performed the best catalytic reactivity because of the hydrogen bond interaction between F– and alcohol initiator. The Mn values of polyester products could be up to 72 kg mol–1. With organofluoride catalysts, the ring-opening copolymerization between various anhydrides and epoxides could be established. Furthermore, terpolymerization of anhydride, epoxide, and lactide could be constructed by the self-switchable organofluoride catalyst to yield a block polymer with a strictly controlled polymerization sequence. Organofluorides were also efficient catalysts for upcycling polyester plastic wastes via alcoholysis. Mixed polyester materials could also be hierarchically recycled.
Role of TLR4 signaling pathway in the mitigation of damaged lung by low‐dose gamma irradiation
Abstract
Organisms frequently suffer negative effects from large doses of ionizing radiation. However, radiation is not as hazardous at lower doses as was once believed. The current study aims to evaluate the possible radio-adaptive effect induced by low-dose radiation (LDR) in modulating high-dose radiation (HDR) and N-nitrosodiethylamine (NDEA)-induced lung injury in male albino rats. Sixty-four male rats were randomly divided into four groups: Group 1 (control): normal rats; Group 2 (D): rats given NDEA in drinking water; Group 3 (DR): rats administered with NDEA then exposed to fractionated HDR; and Group 4 (DRL): rats administered with NDEA then exposed to LDR + HDR. In the next stage, malondialdehyde (MDA), glutathione reduced (GSH), catalase (CAT), and superoxide dismutase (SOD) levels in the lung tissues were measured. Furthermore, the enzyme-linked immunoassay analysis technique was performed to assess the Toll-like receptor 4 (TLR4), interleukin-1 receptor-associated kinase 4 (IRAK4), and mitogen-activated protein kinases (MAPK) expression levels. Histopathological and DNA fragmentation analyses in lung tissue, in addition to hematological and apoptosis analyses of the blood samples, were also conducted. Results demonstrated a significant increase in antioxidant defense and a reduction in MDA levels were observed in LDR-treated animals compared to the D and DR groups. Additionally, exposure to LDR decreased TLR4, IRAK4, and MAPK levels, decreased apoptosis, and restored all the alterations in the histopathological, hematological parameters, and DNA fragmentation, indicating its protective effects on the lung when compared with untreated rats. Taken together, LDR shows protective action against the negative effects of subsequent HDR and NDEA. This impact may be attributable to the adaptive response induced by LDR, which decreases DNA damage in lung tissue and activates the antioxidative, antiapoptotic, and anti-inflammatory systems in the affected animals, enabling them to withstand the following HDR exposure.
The role of single‐walled carbon nanotubes functionalized with gold to increase radiosensitivity of cancer cells to X‐ray radiation
The application of high Z-based metallic nanomaterials as radiosensitizers is limited due to some challenges such as non-ideal selection for the target tissue. In this work, we prepared BSA-FA functionalized O-SWCNTs-Au nanosystems as a targeted radiosensitizer for breast cancer therapy in the 4T1 mouse model. The MTT assay was used to investigate the therapeutic effects of nanoparticles in the presence and absence of X-rays so that cancer cells experienced less survival after receiving O-SWCNTs-Au-BSA-FA + 8 G.
The improvement of high-Z-based metallic nanostructures as radiosensitizers with high monolithicity and versatility by superadditive therapeutic track and the good protective effect is considerable, but they are limited by some problems such as nonideal selectivity for the target tissue. In this study, nanosystems were developed to enhance the efficacy of radiotherapy and reduce cancer cell survival based on innovative gold (Au) functionalized oxygen-single-walled carbon nanotubes (O-SWCNTs). We illustrate the use of folic acid (FA) as a targeting agent and bovine serum albumin (BSA) to stabilize the physiological environment and increase durability. The physical and chemical properties of the nanosystems were evaluated using transmission electron microscopy (TEM), selected area electron diffraction (SAED), dynamic light scattering (DLS), zeta potential, X-ray diffraction (XRD), ultraviolet–visible (UV–Visible), and Fourier transform infrared (FTIR) techniques. Finally, the MTT assay was used to investigate the therapeutic effects of nanoparticles in the 4 T1 mouse breast cancer model in the presence and absence of X-rays. So, the cancer cells experienced a more effective reduction in survival after receiving O-SWCNTs-Au-BSA-FA + 8 Gy than O-SWCNTs-BSA, Au-BSA-FA, and O-SWCNTs-Au-BSA + 8 Gy groups.