Search Results (38)

In this study, 2-t-butyl-4-arylimino-2,3-dihydroacridylnickel dibromides were synthesized by nickel-template one-pot condensation, and well characterized along with the single-crystal X-ray diffraction to one representative complex, revealing a distorted tetrahedral geometry around nickel. When activated with modified methylaluminoxane (MMAO), all nickel complexes exhibited high activities (up to 1.91 × 10⁶ g mol⁻¹ (Ni) h⁻¹) toward major trimerization of ethylene. When activated with ethylaluminum dichloride (EtAlCl₂), however, the title complexes performed good activities (up to 1.05 × 10⁶ g mol⁻¹ (Ni) h⁻¹) for selective dimerization of ethylene. In comparison to analogous nickel complexes, higher activities were achieved with the substituent of t-butyl group, especially in the rare case of nickel complexes performing trimerization of ethylene. Full article

The plant hormone ethylene is a key regulator of plant growth, development, and stress adaptation. Many ethylene-related responses, such as abscission, seed germination, or ripening, are of great importance to global agriculture. Ethylene perception and response are mediated by a family of integral membrane receptors (ETRs), which form dimers and higher-order oligomers in their functional state as determined by the binding of Cu(I), a cofactor to their transmembrane helices in the ER-Golgi endomembrane system. The molecular structure and signaling mechanism of the membrane-integral sensor domain are still unknown. In this article, we report on the crystallization of transmembrane (TM) and membrane-adjacent domains of plant ethylene receptors by Lipidic Cubic Phase (LCP) technology using vapor diffusion in meso crystallization. The TM domain of ethylene receptors ETR1 and ETR2, which is expressed in E. coli in high quantities and purity, was successfully crystallized using the LCP approach with different lipids, lipid mixtures, and additives. From our extensive screening of 9216 conditions, crystals were obtained from identical crystallization conditions for ETR1 (aa 1-316) and ETR2 (aa 1-186), diffracting at a medium–high resolution of 2–4 Å. However, data quality was poor and not sufficient for data processing or further structure determination due to rotational blur and high mosaicity. Metal ion loading and inhibitory peptides were explored to improve crystallization. The addition of Zn(II) increased the number of well-formed crystals, while the addition of ripening inhibitory peptide NIP improved crystal morphology. However, despite these improvements, further optimization of crystallization conditions is needed to obtain well-diffracting, highly-ordered crystals for high-resolution structural determination. Overcoming these challenges will represent a major breakthrough in structurally determining plant ethylene receptors and promote an understanding of the molecular mechanisms of ethylene signaling. Full article

Electrocatalytic reduction of carbon dioxide (CO₂RR) employs electricity to store renewable energy in the form of reduction products. The activity and selectivity of the reaction depend on the inherent properties of electrode materials. Single-atom alloys (SAAs) exhibit high atomic utilization efficiency and unique catalytic activity, making them promising alternatives to precious metal catalysts. In this study, density functional theory (DFT) was employed to predict stability and high catalytic activity of Cu/Zn (101) and Pd/Zn (101) catalysts in the electrochemical environment at the single-atom reaction site. The mechanism of C2 products (glyoxal, acetaldehyde, ethylene, and ethane) produced by electrochemical reduction on the surface was elucidated. The C-C coupling process occurs through the CO dimerization mechanism, and the formation of the *CHOCO intermediate proves beneficial, as it inhibits both HER and CO protonation. Furthermore, the synergistic effect between single atoms and Zn results in a distinct adsorption behavior of intermediates compared to traditional metals, giving SAAs unique selectivity towards the C2 mechanism. At lower voltages, the Zn (101) single-atom alloy demonstrates the most advantageous performance in generating ethane on the surface, while acetaldehyde and ethylene exhibit significant certain potential. These findings establish a theoretical foundation for the design of more efficient and selective carbon dioxide catalysts. Full article

Quantitative real-time polymerase chain reaction (qPCR) is an important and extensively utilized technique in medical and biotechnological applications. qPCR enables the real-time detection of nucleic acid during amplification, thus surpassing the necessity of post-amplification gel electrophoresis for amplicon detection. Despite being widely employed in molecular diagnostics, qPCR exhibits limitations attributed to nonspecific DNA amplification that compromises the efficiency and fidelity of qPCR. Herein, we demonstrate that poly(ethylene glycol)-engrafted nanosized graphene oxide (PEG-nGO) can significantly improve the efficiency and specificity of qPCR by adsorbing single-stranded DNA (ssDNA) without affecting the fluorescence of double-stranded DNA binding dye during DNA amplification. PEG-nGO adsorbs surplus ssDNA primers in the initial phase of PCR, having lower concentrations of DNA amplicons and thus minimizing the nonspecific annealing of ssDNA and false amplification due to primer dimerization and erroneous priming. As compared to conventional qPCR, the addition of PEG-nGO and the DNA binding dye, EvaGreen, in the qPCR setup (dubbed as PENGO-qPCR) significantly enhances the specificity and sensitivity of DNA amplification by preferential adsorption of ssDNA without inhibiting DNA polymerase activity. The PENGO-qPCR system for detection of influenza viral RNA exhibited a 67-fold higher sensitivity than the conventional qPCR setup. Thus, the performance of a qPCR can be greatly enhanced by adding PEG-nGO as a PCR enhancer as well as EvaGreen as a DNA binding dye to the qPCR mixture, which exhibits a significantly improved sensitivity of the qPCR. Full article

MOFs have attracted widespread attention in the field of catalytic ethylene dimerization. Compared with post-synthetic modification, ion exchange and other methods to introduce external active centers, the direct use of MOF materials as catalysts is still the most convenient and prospective. Herein, the NiBTCs are synthesized using a one-pot method in two kinds of solvent and characterized by XRD, FT–IR, ICP–OES, XPS, TGA and N₂ physical adsorption. After treatment at 150 °C, the catalytic activities of both materials in ethylene dimerization are up to 470.9, and 647.0 g_pro./(g_cat.·h) and the selectivity of 1-butene in all products could reach 83.2% and 81.7%, respectively. Stability testing of the catalysts demonstrated that they do not decompose during the reaction, but their reuse performance is degraded. In addition, a probable Cossee–Arlman–type mechanism is proposed. The NiBTCs are shown to have superior catalytic performance in ethylene dimerization compared to employing Ni(pyz)₂Cl₂ or α–Ni(im)₂ as catalysts. Full article

This work is concerned with polyethylene terephthalate (PET) saponification by different potassium compounds in various polyols as well as biodiesel’s main by-product, crude glycerol. It was established that reaction conditions (initial PET/K+ molar ratio, reaction time, etc.) could control the molecular weight of obtained oligomeric products. In ethylene glycol, depolymerization proceeds rapidly, and already at 10–30 min, PET is completely dissolved in the reaction mixture with the formation of liquid oligomers. Then, these oligomers react with potassium compounds, and after 200 min of the process, there are only solid, low-molecular-weight products (dipotassium terephthalate, monomers, and dimers). At the same time, PET saponification in pure glycerol is less effective, and solid polyether flakes could not fully decompose even after 200 min of the process. Crude glycerol takes the middle position between pure polyols. Based on the obtained data, an improved kinetic model was developed, and rate constants were estimated. This model takes into account PET saponification by potassium salts as well as direct PET glycolysis. Ethylene glycol is formed in situ by transesterification between fatty acid ethylene glycol esters and glycerol in the case of pure and crude glycerol. Full article

Drilling fluid is the blood of drilling engineering. In the polar drilling process, the ultra-low temperature environment puts high demands on the rheological performance of drilling fluids. In this paper, the effects of temperature, ice debris concentration and weighting agent on the rheological properties of drilling fluids were studied. It was found that the lower the temperature and the higher the ice debris concentration, the higher the drilling fluid viscosity, but when the ice debris concentration was below 2%, the drilling fluid rheology hardly changed. Secondly, the low temperature rheological properties of drilling fluid were adjusted by three different methods: base fluid ratio, organoclay, and polymers (dimer acid, polymethacrylate, ethylene propylene copolymer, and vinyl resin). The results showed that the base fluid rheological performance was optimal when the base fluid ratio was 7:3. Compared with polymers, organoclay has the most significant improvement on the low temperature rheological performance of drilling fluid. The main reason is that organoclay can transform the drilling fluid from Newtonian to non-Newtonian fluid, which exhibits excellent shear dilution of drilling fluid. The organoclay is also more uniformly dispersed in the oil, forming a denser weak gel mesh structure, so it is more effective in improving the cuttings carrying and suspension properties of drilling fluids. However, the drilling fluid containing polymer additives is still a Newtonian fluid, which cannot form a strong mesh structure at ultra-low temperatures, and thus cannot effectively improve the low-temperature rheological performance of drilling fluid. In addition, when the amount of organoclay is 2%, the improvement rate of the yield point reaches 250% at −55 °C, which can effectively improve the cuttings carrying and suspension performance of drilling fluid at ultra-low temperature. Full article

Edaravone, acting as a cerebral protective agent, is administered to treat acute brain infarction. Its poor solubility is addressed here by means of optimizing the composition of the aqueous choline chloride (ChCl)-based eutectic solvents prepared with ethylene glycol (EG) or glycerol (GL) in the three different designed solvents compositions. The slurry method was used for spectroscopic solubility determination in temperatures between 298.15 K and 313.15 K. Measurements confirmed that ethaline (ETA = ChCl:EG = 1:2) and glyceline (GLE = ChCl:GL = 1:2) are very effective solvents for edaravone. The solubility at 298.15 K in the optimal compositions was found to be equal x_E = 0.158 (c_E = 302.96 mg/mL) and x_E = 0.105 (c_E = 191.06 mg/mL) for glyceline and ethaline, respectively. In addition, it was documented that wetting of neat eutectic mixtures increases edaravone solubility which is a fortunate circumstance not only from the perspective of a solubility advantage but also addresses high hygroscopicity of eutectic mixtures. The aqueous mixture with 0.6 mole fraction of the optimal composition yielded solubility values at 298.15 K equal to x_E = 0.193 (c_E = 459.69 mg/mL) and x_E = 0.145 (c_E = 344.22 mg/mL) for glyceline and ethaline, respectively. Since GLE is a pharmaceutically acceptable solvent, it is possible to consider this as a potential new liquid form of this drug with a tunable dosage. In fact, the recommended amount of edaravone administered to patients can be easily achieved using the studied systems. The observed high solubility is interpreted in terms of intermolecular interactions computed using the Conductor-like Screening Model for Real Solvents (COSMO-RS) approach and corrected for accounting of electron correlation, zero-point vibrational energy and basis set superposition errors. Extensive conformational search allowed for identifying the most probable contacts, the thermodynamic and geometric features of which were collected and discussed. It was documented that edaravone can form stable dimers stabilized via stacking interactions between five-membered heterocyclic rings. In addition, edaravone can act as a hydrogen bond acceptor with all components of the studied systems with the highest affinities to ion pairs of ETA and GLE. Finally, the linear regression model was formulated, which can accurately estimate edaravone solubility utilizing molecular descriptors obtained from COSMO-RS computations. This enables the screening of new eutectic solvents for finding greener replacers of designed solvents. The theoretical analysis of tautomeric equilibria confirmed that keto-isomer edaravone is predominant in the bulk liquid phase of all considered deep eutectic solvents (DES). Full article

Sulfur LIMitation1 (SLIM1) transcription factor coordinates gene expression in plants in response to sulfur deficiency (−S). SLIM1 belongs to the family of plant-specific EIL transcription factors with EIN3 and EIL1, which regulate the ethylene-responsive gene expression. The EIL domains consist of DNA binding and dimerization domains highly conserved among EIL family members, while the N- and C-terminal regions are structurally variable and postulated to have regulatory roles in this protein family, such that the EIN3 C-terminal region is essential for its ethylene-responsive activation. In this study, we focused on the roles of the SLIM1 C-terminal region. We examined the transactivation activity of the full-length and the truncated SLIM1 in yeast and Arabidopsis. The full-length SLIM1 and the truncated form of SLIM1 with a deletion of C-terminal 106 amino acids (ΔC105) transactivated the reporter gene expression in yeast when they were fused to the GAL4 DNA binding domain, whereas the deletion of additional 15 amino acids to remove the C-terminal 120 amino acids (ΔC120) eliminated such an activity, identifying the necessity of that 15-amino-acid segment for transactivation. In the Arabidopsis slim1-2 mutant, the transcript levels of SULTR1;2 sulfate transporter and the GFP expression derived from the SULTR1;2 promoter-GFP (P_SULTR1;2-GFP) transgene construct were restored under −S by introducing the full-length SLIM1, but not with the C-terminal truncated forms ΔC105 and ΔC57. Furthermore, the transcript levels of −S-responsive genes were restored concomitantly with an increase in glutathione accumulation in the complementing lines with the full-length SLIM1 but not with ΔC57. The C-terminal 57 amino acids of SLIM1 were also shown to be necessary for transactivation of a −S-inducible gene, SHM7/MSA1, in a transient expression system using the SHM7/MSA1 promoter-GUS as a reporter. These findings suggest that the C-terminal region is essential for the SLIM1 activity. Full article

The design of photo-responsive supramolecular hydrogels based on coumarin dimerization and de-dimerization is described. The photo-responsive coumarin unit is chemically incorporated into an oligo(ethylene glycol) (OEG) bis-urea amphiphile that is capable of co-assembling with non-functionalized OEG amphiphile, to form supramolecular fibers. UV light with two different wavelengths (365 nm and 254 nm) is employed to induce a photo-reversible dimerization and de-dimerization process of coumarin units, respectively. The co-assembled solutions could be photo-crosslinked to induce a sol-to-gel transition through dimerization of coumarin with 365 nm UV light, and de-dimerization occurs with 254 nm UV light, to provide a weaker gel. In this system, the mechanical strength of supramolecular hydrogels can be tuned using the irradiation time, providing precise control of gelation in a supramolecular hydrogelator. Full article

Non-invasive brain stimulation (NIBS) interventions are promising for the treatment of psychiatric disorders. Notwithstanding, the NIBS mechanisms of action over the dorsolateral prefrontal cortex (DLPFC), a hub that modulates affective and cognitive processes, have not been completely mapped. We aimed to investigate regional cerebral blood flow (rCBF) changes over the DLPFC and the subgenual anterior cingulate cortex (sgACC) of different NIBS protocols using Single-Photon Emission Computed Tomography (SPECT). A factorial, within-subjects, double-blinded study was performed. Twenty-three healthy subjects randomly underwent four sessions of NIBS applied once a week: transcranial direct current stimulation (tDCS), intermittent theta-burst stimulation (iTBS), combined tDCS + iTBS and placebo. The radiotracer 99m-Technetium-ethylene-cysteine-dimer was injected intravenously during the NIBS session, and SPECT neuroimages were acquired after the session. Results revealed that the combination of tDCS + iTBS increased right sgACC rCBF. Cathodal and anodal tDCS increased and decreased DLPFC rCBF, respectively, while iTBS showed no significant changes compared to the placebo. Our findings suggest that the combined protocol might optimize the activity in the right sgACC and encourage future trials with neuropsychiatric populations. Moreover, mechanistic studies to investigate the effects of tDCS and iTBS over the DLPFC are required. Full article

Nickel (II) complexes stabilized by PNP(NR₂)₂ (L¹: R = Methyl, L²: R = ethyl, L³: R = isopropyl) ligands were synthesized and characterized. A narrow range of products was observed for catalytic systems containing nickel complexes and ethyl aluminum dichloride (EADC). All exhibit considerable activity in the ethylene dimerization to produce 1-butene. Precatalyst 1 is the most conducive for ethylene dimerization, producing 83.4% C₄ (1-C₄ 36.8%) and 103.0 × 10⁵ g/(molNi·h) in terms of its activity under the appropriate conditions. By adjusting the conditions of the catalytic system for precatalyst 2, high C₄ selectivity (88.1%) with reasonable activity (76.9 × 10⁵ g/(molNi·h)) can be obtained. The X-ray single-crystal analysis of complexes presents mononuclear bidentate coordination at the Ni center, and the relationship between certain bite angles may also imply catalytic performance. Full article

Loop-mediated isothermal amplification (LAMP) is a nucleic acid amplification method that allows the simple, quick, and low-cost detection of various viral genes. LAMP assays are susceptible to generating non-specific amplicons, as high concentrations of DNA primers can give rise to primer dimerization and mismatched hybridizations, resulting in false-positive signals. Herein, we reported that poly(ethylene glycol)-engrafted nanosized graphene oxide (PEG-nGO) can significantly enhance the specificity of LAMP, owing to its ability to adsorb single-stranded DNA (ssDNA). By adsorbing surplus ssDNA primers, PEG-nGO minimizes the non-specific annealing of ssDNAs, including erroneous priming and primer dimerization, leading to the enhanced specificity of LAMP. The detection of complementary DNAs transcribed from the hepatitis C virus (HCV) RNA was performed by the PEG-nGO-based LAMP. We observed that the inclusion of PEG-nGO significantly enhances the specificity and sensitivity of the LAMP assay through the augmented difference in fluorescence signals between the target and non-target samples. The PEG-nGO-based LAMP assay greatly facilitates the detection of HCV-positive clinical samples, with superior precision to the conventional quantitative real-time PCR (RT-qPCR). Among the 20 clinical samples tested, all 10 HCV-positive samples are detected as positive in the PEG-nGO-based LAMP, while only 7 samples are detected as HCV-positive in the RT-qPCR. In addition, the PEG-nGO-based LAMP method significantly improves the detection precision for the false-positive decision by 1.75-fold as compared to the LAMP without PEG-nGO. Thus, PEG-nGO can significantly improve the performance of LAMP assays by facilitating the specific amplification of target DNA with a decrease in background signal. Full article

A laccase named LAC-4 was purified from Ganoderma lucidum. Firstly, the enzymatic properties of purified LAC-4 laccase, and the degradation of three chlorophenol pollutants 2,6-dichlorophenol (2,6-DCP), 2,3,6-trichlorophenol (2,3,6-TCP) and 3-chlorophenol (3-CP) by LAC-4 were systematically studied. LAC-4 had a strong ability for 2,6-DCP and 2,3,6-TCP degradation. The degradation ability of LAC-4 to 3-CP was significantly lower than that of 2,6-DCP and 2,3,6-TCP. LAC-4 also had a good degradation effect on the chlorophenol mixture (2,6-DCP + 2,3,6-TCP). The results of kinetics of degradation of chlorophenols by LAC-4 suggested that the affinity of LAC-4 for 2,6-DCP was higher than 2,3,6-TCP. The catalytic efficiency and the catalytic rate of LAC-4 on 2,6-DCP were also significantly higher than 2,3,6-TCP. During degradation of 2,6-DCP and 2,3,6-TCP, LAC-4 had a strong tolerance for high concentrations of different metal salts (such as MnSO₄, ZnSO₄, Na₂SO₄, MgSO₄, CuSO₄, K₂SO₄) and organic solvents (such as ethylene glycol and glycerol). Next, detoxification of chlorophenols by LAC-4 was also systematically explored. LAC-4 treatment had a strong detoxification ability and a good detoxification effect on the phytotoxicity of individual chlorophenols (2,6-DCP, 2,3,6-TCP) and chlorophenol mixtures (2,6-DCP + 2,3,6-TCP). The phytotoxicities of 2,6-DCP, 2,3,6-TCP and chlorophenol mixtures (2,6-DCP + 2,3,6-TCP) treated with LAC-4 were considerably reduced or eliminated. Finally, we focused on the degradation mechanisms and pathways of 2,6-DCP and 2,3,6-TCP degradation by LAC-4. The putative transformation pathway of 2,6-DCP and 2,3,6-TCP catalyzed by laccase was revealed for the first time. The free radicals formed by LAC-4 oxidation of 2,6-DCP and 2,3,6-TCP produced dimers through polymerization. LAC-4 catalyzed the polymerization of 2,6-DCP and 2,3,6-TCP, forming dimer products. LAC-4 catalyzed 2,6-DCP into two main products: 2,6-dichloro-4-(2,6-dichlorophenoxy) phenol and 3,3′,5,5′-tetrachloro-4,4′-dihydroxybiphenyl. LAC-4 catalyzed 2,3,6-TCP into two main products: 2,3,6-trichloro-4-(2,3,6-trichlorophenoxy) phenol and 2,2′,3,3′,5,5′-hexachloro-[1,1′-biphenyl]-4,4′-diol. Full article

The electrochemical reduction of carbon dioxide (CO₂) on copper electrode derived from cupric oxide (CuO), named oxide derived copper (ODCu), was studied thoroughly in the potential range of −1.0 V to −1.5 V versus RHE. The CuO nanoparticles were prepared by the hydrothermal method. The ODCu electrode was used for carbon dioxide reduction and the results revealed that this electrode is highly selective for C₂₊ products with enhanced current density at significantly less overpotential. This catalyst shifts the selectivity towards C₂₊ products with the highest Faradaic efficiency up to 58% at −0.95 V. In addition, C₂ product formation at the lowest onset potential of −0.1 V is achieved with the proposed catalyst. X-ray diffraction and scanning electron microscopy revealed the reduction of CuO to Cu (111) nanoparticles during the CO₂ RR. The intrinsic property of the synthesized catalyst and its surface reduction are suggested to induce sites or edges for facilitating the dimerization and coupling of intermediates to ethanol and ethylene. Full article