Search

The deafness-associated m.12201T>C mutation affects the A5-U68 base-pairing within the acceptor stem of mitochondrial tRNAHis. The primary defect in this mutation is an alteration in tRNAHisaminoacylation. Here, we further investigate the molecular mechanism of the deafness-associated tRNAHis12201T>C mutation and test whether the overexpression of the human mitochondrial histidyl-tRNA synthetase gene (HARS2) in cytoplasmic hybrid (cybrid) cells carrying the m.12201T>C mutation reverses mitochondrial dysfunctions. Using molecular dynamics simulations, we demonstrate that the m.12201T>C mutation perturbs the tRNAHisstructure and function, supported by decreased melting temperature, conformational changes, and instability of mutated tRNA. We show that the m.12201T>C mutation-induced alteration of aminoacylation tRNAHiscauses mitochondrial translational defects and respiratory deficiency. We found that the transfer ofHARS2into the cybrids carrying the m.12201T>C mutation raises the levels of aminoacylated tRNAHisfrom 56.3 to 75.0% but does not change the aminoacylation of other tRNAs. Strikingly,HARS2overexpression increased the steady-state levels of tRNAHisand of noncognate tRNAs, including tRNAAla, tRNAGln, tRNAGlu, tRNALeu(UUR), tRNALys, and tRNAMet, in cells bearing the m.12201T>C mutation. This improved tRNA metabolism elevated the efficiency of mitochondrial translation, activities of oxidative phosphorylation complexes, and respiration capacity. Furthermore,HARS2overexpression markedly increased mitochondrial ATP levels and membrane potential and reduced production of reactive oxygen species in cells carrying the m.12201T>C mutation. These results indicate thatHARS2overexpression corrects the mitochondrial dysfunction caused by the tRNAHismutation. These findings provide critical insights into the pathophysiology of mitochondrial disease and represent a step toward improved therapeutic interventions for mitochondrial disorders.

EDTA functionalized magnetic graphene oxide (EDTA-mGO), a good adsorbent for Pb(II), Hg(II) and Cu(II), was synthesized in the present work. It was characterized by SEM, FTIR, BET, XRD, XPS, TGA and zeta potential analysis. Contact time, adsorbent dose, pH and initial concentration were optimized to improve the removal efficiency. Most importantly, EDTA-mGO displayed better adsorption performance than EDTA-GO, EDTA-Fe3O4 and mGO. The adsorption of Pb(II), Hg(II) and Cu(II) mainly depend on the metal chelation of EDTA and the electrostatic attractions of abundant functional groups on GO surface. Besides, good magnetic performance of EDTA-mGO makes it easy to achieve the solid–liquid separation. The magnetic separation process only took 25 s. The adsorption kinetic data described well with the pseudo-second-order model and the equilibrium data fitted well to Freundlich and Temkin isotherms. The maximum adsorption capacity was 508.4 mg g−1 for Pb(II), 268.4 mg g−1 for Hg(II) and 301.2 mg g−1 for Cu(II) from Langmuir isotherm. Thermodynamic studies (ΔG 0, ΔS > 0) implied an endothermic and spontaneous adsorption process in nature. Furthermore, the excellent reproducibility indicated that EDTA-mGO has a promising application in water treatment.

Xanthate functionalized magnetic graphene oxide (Fe3O4-xGO) was successfully synthesized through linking xanthate groups to a kind of graphenes magnetic material (Fe3O4-GS). Fe3O4-xGO was found to be an ideal adsorbent for Hg(II) and methylene blue removal with a higher adsorption capacity. The synthesized adsorbent was characterized by SEM, TEM, FTIR, XRD, and BET respectively. Fe3O4-xGO can be simply recovered from water with magnetic separation at low magnetic field within only 1min. The adsorption capacity was found to be 118.55mg g(-1) for Hg(2+) (contact time for 180min, pH at 7 and temperature at 25°C) and 526.32mg g(-1) for methylene blue (contact time for 120min, pH at 5.5 and temperature at 25°C), respectively. Kinetic data showed good correlation with pseudo-second-order equation and the Langmuir model was found to fit for the isotherm data, which showed the contaminant sorption was accomplished mainly via chelation or ion exchange. The results of thermodynamic studies (ΔG0, ΔH0, ΔS0) illustrate that the adsorption process was endothermic and spontaneous in nature. The experimental results suggest that Fe3O4-xGO has the potential applications in the environmental management.

Magnetic carbonate hydroxyapatite/graphene oxide (M-CHAP/GO) was successfully prepared by loading magnetic carbonate hydroxyapatite (M-CHAP) onto graphene oxide sheets and was found to be an ideal adsorbent for heavy metal (Pb(II)) and dye (methylene blue). The obtained adsorbent was characterized by SEM, FTIR, XRD, BET, TGA, XPS and zeta potential, respectively. M-CHAP/GO nano-particles possessed a favorable and stable morphology. Moreover, the good magnetic properties of M-CHAP/GO made it simple to recover from water with magnetic separation. The equilibrium adsorption capacity was 277.7 mg g−1 for Pb(II) and 546.4 mg g−1 for methylene blue under the optimal conditions. The pseudo-second-order equation and the Langmuir model showed good correlation with the experimental data and explained well the mechanism of adsorption. It was found that the adsorption process was accomplished mainly via chelation and ion exchange. Thermodynamic studies (ΔG 0, ΔS > 0) implied that the adsorption process was endothermic and spontaneous in nature. The other adsorption mechanisms are further researched in this article. All the experimental results show that M-CHAP/GO nano-particles have potential application in the future of environmental management.

In this paper, carboxymethyl functionalized chitosan was used for the synthesis of a magnetic polysaccharide–graphene oxide composite (SCGO). Compared with the magnetic chitosan–graphene oxide composite reported before, adsorption capacity in this research had improved significantly. The calculated maximum adsorption capacity values for methylene blue (MB) and malachite green (MG) were 358.4 mg g−1 and 289.1 mg g−1, respectively. The morphology, chemical properties and physical structure of SCGO were characterized by scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FTIR) and X-ray powder diffraction (XRD). The influence factors which included pH, adsorbent dose, ionic strength and contact time on the adsorption properties of MB and MG onto SCGO were investigated. The adsorption kinetics of MB and MG on SCGO were well-described by pseudo-second order kinetic models. The experimental data of the isotherm followed the Temkin isotherm model and the Langmuir model, respectively. Thermodynamic analysis was also performed to calculate the changes in free energy (ΔG), enthalpy (ΔH), and entropy (ΔS). The results obtained from this research suggested that SCGO was a potential adsorbent for effective removal of methylene blue and malachite green.

Magnetic hydroxypropyl chitosan/graphene oxide (MHCGO) composites have been synthesized and employed as adsorbent for removal of lead ions from aqueous solution. X-ray powder diffraction, Fourier transform infrared spectrum, and scanning electron microscope showed that the MHCGO composites were fabricated successfully. The effects of adsorbent dosage, pH, and contact time on the adsorption of lead ions have been discussed, and the optimal adsorption conditions have been acquired. The results indicated that the adsorption of lead ions on MHCGO was dependent on pH with the optimum pH nearly 5.5. The adsorption process was fairly quick and the time to reach adsorption equilibrium is 100 min. The adsorption kinetics could be described by the pseudo-second-order model very well. Adsorption data fitted well with Freundlich model. The effect of temperature on lead ions adsorption was studied and was shown to be spontaneous.

A novel magnetic nano-composite was synthesized by a simple method of coprecipitation through embedding ferroferric oxide into magnesium hydroxyapatite (MgHAp/Fe3O4) to remove Cu2 + from aqueous solution. The obtained adsorbent was characterized by scanning electron microscopy (SEM), energy dispersive spectrometer (EDS), Brunauer–Emmett–Teller (BET) surface area measurement and Fourier transform infrared spectroscopy (FTIR). Mg2 + and Cu2 + possess the same electrical charge and similar ionic radius, which is especially beneficial to their exchange in hydroxyapatites. Static adsorption experiments indicated that the maximal immobilization capacity of Cu2 + reached to 305 mg/g on the optimum adsorption conditions (dosage of 0.32 mg/mL, contact time for 90 min, pH at 5.9 and temperature at 25 °C). Adsorption kinetics including the pseudo-first order and pseudo-second order kinetic models were researched and the data fitted better with the pseudo-second order kinetic model (R2 = 0.99). For adsorption isotherms, Freundlich isotherm was proved to be the best correlation (R2 > 0.99) compared with the Henry and Langmuir isotherms. The thermodynamic parameters (ΔG

A method of co-precipitation was used to synthesize a novel magnetic nano-composite strontium hydroxyapatite/ferroferric oxide (SrHAp/Fe3O4) by embedding ferroferric oxide into strontium hydroxyapatite and this SrHAp/Fe3O4 was utilized as adsorbent to remove Pb2 + from aqueous solutions. The morphology features at the micro level of the obtained adsorbent were characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM), Brunauer–Emmett–Teller (BET) surface area and Fourier transform infrared (FTIR). The maximal immobilization capacity of Pb2 + reached to 1249 mg/g at the optimum adsorption conditions (dosage of 0.2 mg/mL, contact time for 20 min, pH at 4.5 and temperature at 25 °C). Adsorption of Pb2 + onto SrHAp/Fe3O4 agreed well with the pseudo-second order model (R2 = 0.9997). For adsorption isotherms, the Freundlich isotherm was provided to be the best correlation (R2 = 0.9862) compared to the Henry and Langmuir isotherms. The thermodynamic parameters (ΔG

Magnetic cobalt ferrite (CoFe 2 O 4 )-reduced graphene oxide (rGO) nanocomposites (CoFe 2 O 4 -rGO) were developed as an adsorbent to remove Pb(II) and Hg(II) from aqueous solution. The CoFe 2 O 4 -rGO was prepared by a facile approach and characterized by X-ray diffraction (XRD), Brunauer–Emmett–Teller (BET) surface area and Zeta potential measurement. In this work, contact time, adsorbent dose, and solution pH temperature were optimized. The sorption kinetics and isotherm model fitting studies, demonstrated that data fit well to pseudo-second order kinetics and Langmuir isotherm models. The highest adsorption equilibrium for Pb(II) were 299.4 mg/g at pH of 5.3 and 25 °C; while for Hg(II) were 157.9 mg/g at pH of 4.6 and 25 °C. Due to magnetic property, CoFe 2 O 4 -rGO could be simply recovered from water by magnetic separations at low magnetic field within 2 min.

In order to investigate the effects of flagellin secreted by bacteria associated with pine wood nematode (Bursaphelenchus xylophilus) on pine cells, suspension cells of Pinus thunbergii were treated with flagellin of Pseudomonas fluorescens GcM5-1A, and some physiological indices were determined. Superoxide anions radical (·O2 −) in treated suspension cells increased with prolongation of treatment time, with maximum content of 1,282 μmol g−1 FW at 30 h, but the content of H2O2 gradually decreased as compared with that in the control group. Maximum content of malondialdehyde (MDA) and free proline, which is 1.72 times and 1.49 times of that in the control, respectively, appeared when suspension cells were treated for 12 h, after that both of the contents decreased gradually. The activities of superoxide dismutase (SOD), peroxidase (POD) and catalases (CAT) also increased at the primary stage of treatment and then decreased compared with those of the control.

© 2015 Elsevier B.V. Multifunctional hyperbranched polyamine modified graphene oxide (HPA-GO) was successfully prepared and characterized by Fourier transform infrared spectroscopy (FTIR), thermogravimetric analysis (TGA), X-ray diffraction (XRD), zeta potential and scanning electron microscope (SEM) analyses. HPA-GO exhibited excellent adsorption performance for the removal of a heavy metal (Pb(II)) and a dye (methylene blue (MB)). The equilibrium adsorption capacity was 819.7 mg g-1 for Pb(II) and 740.7 mg g-1 for MB under the optimal conditions. The pseudo-second order equation and the Langmuir model exhibited good correlation with the adsorption kinetic and isotherm data, respectively, for these two pollutants. The thermodynamic results (ΔG0, ΔS>0) implied that the adsorption process of Pb(II) and MB was feasible, endothermic and spontaneous in nature. A possible adsorption mechanism has been proposed where chelation and electrostatic attraction dominated the adsorption of Pb(II) and π-π stacking interactions and electrostatic attraction dominated the adsorption of MB. In addition, the excellent reproducibility endowed HPA-GO with the potential for application in water treatment.

The octavinyl polyhedral oligomeric silsesquioxane (POSS) grafted polypropylene (PP) was first prepared by reactive blending. The structure and properties of physical blending and reactive blending composites of PP/POSS were investigated by wide-angle X-ray diffraction (WAXD), differential scanning calorimetry (DSC), dynamic mechanical analysis (DMA). WAXD analysis shows that the POSS in the reactive blending composites has better compatibility with PP than in the physical blending composites. The β-form crystalline hence disappears even the non-reactive POSS can act as an effective β-nucleating agents. DSC analysis shows the reactive blending composites have higher crystalline temperature while POSS in the physical blending composites have little effect on the crystalline temperature. The modulus of reactive blending composites increases in the presence of POSS, while that of the physical blending composites decreases with increasing POSS content.

Polypropylene (PP)/octavinyl polyhedral oligomeric silsesquioxane (POSS) composites were prepared by two different processing methods: reactive blending and physical blending, and the crystallization behavior of PP and PP/POSS composites was studied by means of differential scanning calorimetry and polarized optical microscope. The results showed that the crystallization of PP in PP/POSS composites was strongly influenced by the different processing methods. POSS particles can act as effective nucleating agent, accelerating the crystallization of PP. The crystallization rate increased more dramatically for the reactive blending composite due to the stronger nucleating effect of PP grafted POSS. © 2008 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 46: 1762–1772, 2008

Carbon black (CB)-filled immisicible thermoplastic/thermosetting polymer blends consisting of polypropylene (PP) and Novolac resin were reported in this paper. The PP/Novolac/CB blends with varied compositions and different processing sequences were prepared by melt-mixing method. The CB distribution, conductive mechanism and the relationship between morphology and electrical properties of the PP/Novolac/CB blends were investigated. Scanning electron microscopy (SEM), optical microscopy and extraction experiment results showed that in PP/Novolac blends CB particles preferentially localized in the Novolac phase, indicating CB has a good affinity with Novolac resin. The incorporation of CB changed the spherical particles of the dispersed Novolac phase into elongated structure. With increasing Novolac content, the elongation deformation of Novolac phase became more obvious and eventually the blends developed into co-continuous structure, which form double percolation and decrease the percolation threshold. When CB was initially blended with PP and followed by the addition of Novolac resin, the partial migration of CB from PP to the Novolac phase was possibly occurred. The addition of Novolac to PP evidently increases the storage modulus G ′, loss modulus G ″ and complex viscosity η ∗ . The addition of CB to PP/Novolac blends further increase η ∗ , and it increases with increasing CB loading, which was related to the change of composite morphology.

The rheological behavior of polypropylene/novolac blends was investigated with special reference to the effects of the blend ratio, compatibilization, and dynamic cure. The polypropylene and all the polypropylene/novolac blends presented evidence of shear-thinning behavior. The novolac, compatibilizer, and dynamic cure had dramatic effects on the rheological behavior of the polypropylene. Various rheological plots, including plots of the viscosity, storage modulus, loss modulus, and loss angle, Han plots, and Cole–Cole plots, were used to analyze the polypropylene/novolac blends. The results showed that the compatibilization together with the dynamic cure could increase the viscosity and modulus because of the formation of a grafting polymer between the maleic anhydride grafted polypropylene and the curing novolac resin. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2007

In this article, the dynamic vulcanization process was applied to polypropylene (PP)/Novolac blends compatibilized with maleic anhydride-grafted PP (MAH-g-PP). The influences of dynamic cure, content of MAH-g-PP, Novolac, and curing agent on mechanical properties of the PP/Novolac blends were investigated. The results showed that the dynamically cured PP/MAH-g-PP/Novolac blend had the best mechanical properties among all PP/Novolac blends. The dynamic cure of Novolac improved the modulus and stiffness of the PP/Novolac blends. The addition of MAH-g-PP into dynamically cured PP/Novolac blend further enhanced the mechanical properties. With increasing Novolac content, tensile strength, flexural modulus, and flexural strength increased significantly, while the elongation at break dramatically deceased. Those blends with hexamethylenetetramine (HMTA) as a curing agent had good mechanical properties at HMTA content of 10 wt %. Scanning electron microscopy (SEM) analysis showed that dynamically cured PP/MAH-g-PP/Novolac blends had finer domains than the PP/MAH-g-PP/Novolac blends. Thermogravimetric analysis (TGA) results indicated that the incorporation of Novolac into PP could improve the thermal stability of PP. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2007

The crystallization, melting behavior, and morphology of Polypropylene (PP) and PP/Novolac blends were studied by scanning electron microscopy, wide angle X-ray diffraction, differential scanning calorimetry, and polarized optical microscope. The results showed that the crystallization of PP in PP/Novolac blends was strongly influenced by crystallization temperature, particles size of Novolac, crosslinking, and compatibilizer maleic anhydride-grafted PP. The Novolac resin could not only affect the crystal structure, but also acted as effective nucleating agents, accelerating the crystallization of PP in the PP/Novolac blends. And the smaller the Novolac particles were, the more effective were the nucleating agent for PP crystallization. Avrami equation was used to analyze the isothermal crystallization kinetics of PP and PP/Novolac blends. The influences of curing and compatibilizer on the crystallization behavior of PP were rather complicated. The crystallization thermodynamics were estimated using the Hoffman theory. The incorporation of cured Novolac and compatibilizer evidently decreased the chain folding energy of PP. © 2006 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 44: 3288–3303, 2006