Conversion of atmospheric CO2 catalyzed by thiolate-based ionic liquids under mild conditions: efficient synthesis of 2-oxazolidinones.

Thiolate-based ionic liquids, specifically the catalyst [TBP][2-Tp], have demonstrated their efficiency in catalyzing the reaction of CO2 with propargylic amine. This novel synthetic method can be used to synthesize various 2-oxazolidinone derivatives with high yields. The catalyst can be easily regenerated and reused without any decline in its catalytic activity. Experimental and spectroscopic investigations have confirmed that the high activity of [TBP][2-Tp] is attributed to the synergistic effect of its S and N sites in activating CO2, rather than depending solely on basicity to activate the amino group of propargylic amine. These findings highlight the significant potential of thiolate-based ionic liquids for applications in CO2 activation and conversion.

Highly Efficient Thiolate-Based Ionic Liquid Catalysts for Reduction of CO2: Selective N-Functionalization of Amines to Form N-Formamides and N-Methylamines.

Developing efficient catalysts to convert CO2 into value-added chemicals is valuable for reducing carbon emissions. Herein, a kind of novel thiolate-based ionic liquid with sulfur as the active site was designed and synthesized, which served as highly efficient catalyst for the reductive N-functionalization of CO2 by amines and hydrosilane. By adjusting the CO2 pressure, various N-formamides and N-methylamines were selectively obtained in high yields. Remarkably, at the catalyst loading of 0.1 mol %, the N-formylation reaction of N-methylaniline exhibited an impressive turnover frequency (TOF) up to 600 h-1, which could be attributed to the roles of the ionic liquids in activating hydrosilane and amine. In addition, control experiments and NMR monitoring experiments provided evidence that the reduction of CO2 by hydrosilane yielded formoxysilane intermediates that subsequently reacted with amines to form N-formylated products. Alternatively, the formoxysilane intermediates could further react with hydrosilane and amine to produce 4-electron-reduced aminal products. These aminal products served as crucial intermediates in the N-methylation reactions.

Visible light regulates anthocyanin synthesis via malate dehydrogenases and the ethylene signaling pathway in plum (Prunus salicina L.).

Light regulates anthocyanins synthesis in plants. Upon exposure to visible light, the inhibition of photosynthetic electron transfer significantly lowered the contents of anthocyanins and the expression levels of key genes involved in anthocyanins synthesis in plum fruit peel. Meanwhile, the expression levels of PsmMDH2 (encoding the malate dehydrogenase in mitochondria) and PschMDH (encoding the malate dehydrogenase in chloroplasts) decreased significantly. The contents of anthocyanins and the levels of the key genes involved in anthocyanin synthesis decreased significantly with the treatment of 1-MCP (an inhibitor of ethylene perception) but were enhanced by the exogenous application of ethylene. The ethylene treatment could also recover the anthocyanin synthesis capacity lowered by the photosynthetic electron transfer inhibition. Silencing PsmMDH2 and PschMDH significantly lowered the contents of anthocyanins in plum fruit. At low temperature, visible light irradiation induced anthocyanin accumulation in Arabidopsis leaves. However, the mmdh, chmdh, and etr1-1 mutants had significantly lower anthocyanins content and expressions of the key genes involved in anthocyanins synthesis compared to wild type. Overall, the present study demonstrates that both photosynthesis and respiration were involved in the regulation of anthocyanin synthesis in visible light. The visible light regulates anthocyanin synthesis by controlling the malate metabolism via MDHs and the ethylene signaling pathway.

Anthocyanin concentration depends on the counterbalance between its synthesis and degradation in plum fruit at high temperature.

Anthocyanin synthesis and degradation processes were analyzed at transcript, enzyme, and metabolite levels to clarify the effects of high temperature on the concentration of anthocyanin in plum fruit (Prunus salicina Lindl.). The transcript levels of PsPAL, PsCHS, and PsDFR decreased while those of PsANS and PsUFGT were similar at 35 °C compared with 20 °C. The activities of the enzymes encoded by these genes were all increased in fruits at 35 °C. The concentrations of anthocyanins were higher at 35 °C on day 5 but then decreased to lower values on day 9 compared with that at 20 °C. Furthermore, high temperature (35 °C) increased the concentration of hydrogen peroxide and the activity of class III peroxidase in the fruit. The concentration of procatechuic acid, a product of the reaction between anthocyanin and hydrogen peroxide, hardly changed at 20 °C but was significantly increased at 35 °C on day 9, indicating that anthocyanin was degraded by hydrogen peroxide, which was catalyzed by class III peroxidase. Based on mathematical modeling, it was estimated that more than 60-70% was enzymatically degraded on day 9 when the temperature increased from 20 °C to 35 °C. We conclude that at the high temperature, the anthocyanin content in plum fruit depend on the counterbalance between its synthesis and degradation.

Photoprotection mechanism in the 'Fuji' apple peel at different levels of photooxidative sunburn.

The xanthophyll cycle, flavonoid metabolism, the antioxidant system and the production of active oxygen species were analyzed in the peel of 'Fuji' apples re-exposed to sunlight after extended periods of fruit bagging treatment, resulting in different levels of photooxidative sunburn. After re-exposing bagged fruits to sunlight, the production of active oxygen species and the photoprotective capacity in apple peels were both significantly enhanced. As sunburn severity increased, the concentration of hydrogen peroxide increased, while xanthophyll cycle pool size decreased. For the key genes involved in flavonoid synthesis, expressions of MdMYB10 and MdPAL were upregulated, whereas the expressions of MdCHS, MdANS, MdFLS and MdUFGT were downregulated in sunburnt fruit peel. Correspondingly, concentrations of both quercetin-3-glycoside and cyanidin-3-galactoside decreased. Total ascorbate concentrations decreased as sunburn severity increased, with the decrease being faster for oxidized than for reduced ascorbate. Transcription levels of MdGMP, MdGME, MdGGP, MdGPP, MdGalDH and MdGalLDH, the genes involved in ascorbate synthesis, were similar in non-sunburnt and sunburnt fruit peels, whereas activities of l-galactose dehydrogenase and l-galactono-1,4-lactone dehydrogenase decreased in severely sunburnt peel. Although activities of superoxide dismutase and ascorbate peroxidase increased, the activities of monodehydroascorbate reductase, dehydroascorbate reductase and glutathione reductase decreased as sunburn severity increased. In summary, the occurrence of photooxidative sunburn in 'Fuji' apple peel is closely associated with a relatively lower xanthophyll cycle pool size, reduced levels of ascorbate reduction and synthesis and reduced flavonoid synthesis. Our data are consistent with the idea that ascorbate plays a key role in protecting apple fruit from photooxidative sunburn.