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Particulate nitrate (pNO3 –) has often been found to be the major component of fine particles in urban air-sheds in China, the United States, and Europe during winter haze episodes in recent years. However, there is a lack of knowledge regarding the experimentally determined contribution of different chemical pathways to the formation of pNO3 –. Here, for the first time, we combine ground and tall-tower observations to quantify the chemical formation of pNO3 – using observationally constrained model approach based on direct observations of OH and N2O5 for the urban air-shed. We find that the gas-phase oxidation pathway (OH+NO2) during the daytime is the dominant channel over the nocturnal uptake of N2O5 during pollution episodes, with percentages of 74% in urban areas and 76% in suburban areas. This is quite different from previous studies in some regions of the US, in which the uptake of N2O5 was concluded to account for a larger contribution in winter. These results indicate that the driving factor of nitrate pollution in Beijing and different regions of the US is different, as are the mitigation strategies for particulate nitrate.

(-)-Daphnilongeranin B and (-)-daphenylline are two hexacyclic Daphniphyllum alkaloids, each containing a complex cagelike backbone. Described herein are the first asymmetric total synthesis of (-)-daphnilongeranin B and a bioinspired synthesis of (-)-daphenylline with an unusual E ring embedded in a cagelike framework. The key features include an intermolecular [3+2] cycloaddition, a late-stage aldol cyclization to install the F ring of daphnilongeranin B, and a bioinspired cationic rearrangement leading to the tetrasubstituted benzene ring of daphenylline.

The three compounds exhibited different permeability due to different diffusion process and cellular uptake. The toxicity of vanadium complexes on Caco-2 monolayer involved F-actin-related change of tight junction and impairment of microvilli. The toxicity was also related to elevated intracellular reactive oxygen species (ROS) and their cellular accumulation.

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In this study, the antiproliferative effect of bis(acetylacetonato)-oxidovanadium(IV) and sodium metavanadate and the underlying mechanisms were investigated in human pancreatic cancer cell line AsPC-1. The results showed that both exhibited an antiproliferative effect through inducing G2/M cell cycle arrest and can also cause elevation of reactive oxygen species (ROS) levels in cells. Moreover, the two vanadium compounds induced the activation of both PI3K/AKT and MAPK/ERK signaling pathways dose- and time-dependently, which could be counteracted with the antioxidant N-acetylcysteine. In the presence of MEK-1 inhibitor, the degradation of Cdc25C, inactivation of Cdc2 and accumulation of p21 were relieved. However, the treatment of AKT inhibitor did not cause any significant effect. Therefore, it demonstrated that the ROS-induced sustained MAPK/ERK activation rather than AKT contributed to vanadium compounds-induced G2/M cell cycle arrest. The current results also exhibited that the two vanadium compounds did not induce a sustained increase of ROS generation, but the level of ROS reached a plateau instead. The results revealed that an intracellular feedback loop may be against the elevated ROS level induced by vanadate or VO(acac), evidenced by the increased GSH content, the unchanged level at the expression of antioxidant enzymes. Therefore, vanadium compounds can be regarded as a novel type of anticancer drugs through the prolonged activation of MAPK/ERK pathway but retained AKT activity. The present results provided a proof-of-concept evidence that vanadium-based compounds may have the potential as both antidiabetic and antipancreatic cancer agents to prevent or treat patients suffering from both diseases.

This chapter is an overview of recent progress in the design of Pt(IV) prodrugs. These kinetically-inert octahedral prodrugs can be reduced in cancer cells to active squareplanar Pt(II) complexes, for example by intracellular reducing agents such as glutathione or by photoexcitation. The additional axial ligands in Pt(IV) complexes which are released on reduction, allow bioactive molecules to be delivered which can act synergistically with Pt(II) in killing cancer cells, or act as targeting vectors, allow attachment to polymer and nanoparticle delivery systems, or labelling with fluorescent probes. Pt(IV) prodrugs have yet to be approved for clinical use, although some offer the promise of increased efficacy and reduced side effects.