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We report that the use of a hydrogen-bonded pyrimidine-macrocycle complex can efficiently facilitate the threading of two bispyridinium ethylenes into four rings, as evidenced by X-ray crystallography of its precursor, offering a rare example of a doubly threaded [6]rotaxane in 91% yield. The unusual architecture is found to be stable with no dethreading despite the large ring size of the macrocycle with respect to the stopper. [ABSTRACT FROM AUTHOR]

Passivation films with different thicknesses were formed on the surface of tinplate by passivation at different electric charge densities to study the effect of surface layer structure on wettability of tinplate. The variation of wettability for the passivated tinplates during the storage in ambient air was analyzed by X-ray photoelectron spectroscopy and water contact angle measurement. The results showed that the relative mass fraction of Cr in the surface layer of passivated tinplate was increased with the increasing of passivation film thickness. As a result, the surface polarity of tinplate was improved and its water contact angle was decreased, indicating that the tinplate had better hydrophilicity. The content of C in the surface layer of tinplate was increased due to the adsorption of organic compounds on tinplate surface from the surrounding atmosphere during storage, resulting in the decrease of surface polarity, and then the switch from hydrophilicity to hydrophobicity. [ABSTRACT FROM AUTHOR]

The xylene is an important hydrophobic volatile organic compound (VOC) widely used as a solvent in different industries. Compared to the conventional bioreactors, the membrane bioreactor is more efficient for the degradation of hydrophobic VOCs. In this work, the degradation of gaseous xylene in a flat composite membrane bioreactor inoculated with activated sludge under different operating conditions was investigated. The maximum elimination capacities, ECv of 289 g/(m3 h) and ECm of 0.145 g/(m2 h) were obtained at the gas residence time of 20 s and the loading rate of 475 g/(m3 h). Moreover, the membrane bioreactor is stable enough to suffer weak shock loading and short intermittent process shutdown. These results indicate that the membrane biotechnology shows great potentials in practical applications for xylene removal. [ABSTRACT FROM AUTHOR]

Objective To investigate the effect of oxidative stress preconditioning on the oxidative stress-induced damage of bone marrow mesenchymal stem cells (BMSCs). Methods BMSCs were isolated and cultured by density gradient centrifugation combined with adherence method. The cells were divided into three groups: control group (control medium), oxidative damage group (treated with 1000 μmol/L H 2 O 2 for 24 hours), and preconditioning group (preincubated with 50 μmol/L H 2 O 2 for 8 hours before treatment with 1000 μmol/L H 2 O 2 for 24 hours). DCFH-DA staining was used to analyze the level of reactive oxygen species (ROS). Mitochondrial membrane potential was measured by JC-1 staining. DNA damage was detected by TUNEL. Malondialdehyde (MDA) content was detected by thiobarbituric acid (TBA) method, and superoxide dismutase (SOD) activity was detected by water soluble tetrazolium-1 (WST-1) assay. CCK-8 assay was used to detect cell viability and flow cytometry to detect cell apoptosis. Results Compared with the oxidative damage group, the preconditioning group had reduced ROS level, reduced DNA damage, higher mitochondrial membrane potential, significantly decreased MDA content, increased SOD activity, increased cell viability, and significantly decreased apoptosis. Conclusion Oxidative stress preconditioning can enhance the anti-oxidative stress ability of BMSCs and promote its survival under oxidative stress.

Objective: To investigate the effect of nicotinamide mononucleotide adenosyl transferase 3 (NMNAT3) on the mitochondrial function and anti-oxidative stress of rabbit bone marrow mesenchymal stem cells (BMSCs) under oxidative stress in vitro by regulating nicotinamide adenine dinucleotide (NAD + ) levels., Methods: The bone marrow of femur and tibia of New Zealand white rabbits were extracted. BMSCs were isolated and cultured in vitro by density gradient centrifugation combined with adherent culture. The third generation cells were identified by flow cytometry and multi-directional induction. Overexpression of NMNAT3 gene was transfected into rabbit BMSCs by enhanced green fluorescent protein (EGFP) labeled lentivirus (BMSCs/Lv-NMNAT3-EGFP), and then the expression of NMNAT3 was detected by real-time fluorescence quantitative PCR (qRT-PCR) and Western blot and cell proliferation by cell counting kit 8 (CCK-8) method. BMSCs transfected with negative lentivirus (BMSCs/Lv-EGFP) and untransfected BMSCs were used as controls. The oxidative stress injury cell model was established by using H 2 O 2 to treat rabbit BMSCs. According to the experimental treatment conditions, they were divided into 4 groups: Group A was normal BMSCs without H 2 O 2 treatment; untransfected BMSCs, BMSCs/Lv-EGFP, and BMSCs/Lv-NMNAT3-EGFP in groups B, C, and D were treated with H 2 O 2 simulated oxidative stress, respectively. The effects of NMNAT3 on the mitochondrial function of BMSCs under oxidative stress [changes of mitochondrial membrane potential, NAD + and adenosine triphosphate (ATP) levels], the changes of anti-oxidative stress ability of BMSCs [reactive oxygen species (ROS) and malondialdehyde (MDA) levels, manganese superoxide dismutase (Mn-SOD) and catalase (CAT) activities], and the effects of BMSCs on senescence and apoptosis [senescence associated-β-galactosidase (SA-β-gal) staining and TUNEL staining] were detected after 24 hours of treatment., Results: The rabbit BMSCs were successfully isolated and cultured in vitro . The stable strain of rabbit BMSCs with high expression of NMNAT3 gene was successfully obtained by lentiviral transfection, and the expressions of NMNAT3 gene and protein significantly increased ( P <0.05). There was no significant difference in the trend of cell proliferation compared with normal BMSCs. After treatment with H 2 O 2 , the function of mitochondria was damaged and apoptosis increased in all groups. However, compared with groups B and C, the group D showed that the mitochondrial function of BMSCs improved, the membrane potential increased, the level of NAD + and ATP synthesis of mitochondria increased; the anti-oxidative stress ability of BMSCs enhanced, the levels of ROS and MDA decreased, and the activities of antioxidant enzymes (Mn-SOD, CAT) increased; and the proportion of SA-β-gal positive cells and the rate of apoptosis decreased. The differences in all indicators between group D and groups B and C were significant ( P <0.05)., Conclusion: NMNAT3 can effectively improve the mitochondrial function of rabbit BMSCs via increasing the NAD + levels, and enhance its anti-oxidative stress and improve the survival of BMSCs under oxidative stress conditions.