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This research attempts to elucidate the effect of humic acid (HA) on TiO₂ nanoparticle ultrafiltration (UF) membrane fouling, and quantitatively analyze the synergistic membrane fouling mechanisms using interaction energies. The extended Derjaguin-Landau-Verwey-Overbeek (xDLVO) theory was employed to analyze the interaction energies and predict UF membrane fouling. Membrane fouling effects were studied during the dead-end filtration of individual TiO₂ and HA-TiO₂ mixtures using two kinds of polymeric UF membranes. It was found that HA-TiO₂ mixtures lead to greater flux declines than individual TiO₂ . For specific foulant, the hydrophobic PVDF membrane showed relative severe membrane fouling than hydrophilic PES membrane. As for the HA-TiO₂ mixture, much higher irreversible fouling was observed compared with that of individual TiO₂ . Moreover, this study highlights the importance of HA concentration in synergistic fouling effects of the HA-TiO₂ mixture. The increase of HA concentration caused an increase of contact angle and lower interaction energy, thus aggravating membrane fouling. Results illustrated that synergistic membrane fouling by TiO₂ and HA could be successfully explained using the xDLVO analysis. The extent of membrane fouling turned out to be dominated by Lewis acid-base interaction.
The link between the acute toxicity of heavy metals on algae and the bioadsorption capacity of heavy metals by algae has seldom been reported. In the present study, an acute toxicity experiment was carried out to assess the toxic effects of Pb, Cu, and Cd for Chlorella sorokiniana, and the 96 h IC₅₀ values were 0.249 mg/L, 0.485 mg/L, 46.108 mg/L, and 21.00 mg/L for Cu, Cd, Pb (total), and Pb (free ion), respectively, which implied that Chlorella sorokiniana showed high tolerance to Pb compared to Cu and Cd. Pb distribution analysis indicated that 73.40% to 98.15% of free Pb ions were accumulated on the algae cell wall to avoid further intracellular accumulation, resulting in irreversible metabolic disorders. Then the adsorption capacity of Chlorella was explored. It could be found that the Langmuir model (the R² were 0.988 and 0.962 for living and lifelss cells, respectively) was fit to explain the adsorption equilibrium data and the qₑ calculated by this model were 1.54 and 2.97 mg /10¹⁰ cells for living and lifeless cells, respectively, which was consistent with the experimental result. In the competitive adsorption, Chlorella exhibited a greater affinity for Pb with the higher removal rate compared to Cu and Ni. Therefore, the renewable Chlorella sorokiniana and its dramatic resistance to Pb may serve as a potential biosorbent for Pb in the future.
hTERT (human telomerase reverse transcriptase) plays a key role in the process of cell immortalization. Overexpression of hTERT has been implicated in 85% of malignant tumors and offers a specific target for cancer therapy. In this paper, we describe an effective approach using a single-chain variable fragment (scFv) intrabody derived from monoclonal hybridoma directed against hTERT to attenuate the immortalization of human uterine cervix and hepatoma cells. The scFv we constructed had a high affinity to hTERT, and specifically neutralized over 70% of telomere synthesis activity, thereby inhibiting the viability and proliferation of the cancer cells. Our results indicate that this anti-hTERT intrabody is a promising tool to target hTERT and intervene in the immortalization process of cancer cells.
Tobacco-specific nitrosamines (TSNAs) are carcinogenic chemicals found in tobacco plants. The increasing health consciousness of individuals had led to an increased interest in research on reducing TSNAs content. The aim of this study was to use a pot experiment in which exogenous substances were applied to burley tobacco to dissect the mechanism of TSNAs production. The results indicated that spraying the exogenous substances IAA, NAA, SA and combination thereof on burley tobacco after topping decreased TSNAs content by 2.69–29.4 % in upper leaves and 0.23–39.3 % in middle leaves without affecting total sugar, total nitrogen, potassium and chlorine contents. The application of exogenous substances could down-regulate expression of the NR gene and the activity of the NR enzyme, resulting in less accumulation of the TSNAs precursor nitrite. The exogenous substances significantly reduced nicotine accumulation, which was consistent with low enzyme activities and the down-regulated expressions of genes involved in nicotine biosynthesis, especially significant in the case of quinolinate phosphoribosyltransferase. These results suggested that the application of exogenous substances on burley tobacco after topping could reduce TSNAs content which may be attributed to the regulation of exogenous substances on nitrite and nicotine. This also implies one potential improvement to agronomic practices aimed at controlling the accumulation of TSNAs in burley tobacco.
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