Evolution of aerosol chemistry in Xi'an during the spring dust storm periods: Implications for heterogeneous formation of secondary organic aerosols on the dust surface.

TSP and 9-stage size-segregated samples were simultaneously collected in Xi'an during the spring of 2013 and analyzed for organic aerosols (OA) on a molecular level. n-Alkanes were the dominant compound class during the whole campaign, followed by fatty acids. High molecular weight (HMW) n-alkanes and fatty acids dominated in the coarse mode particles (>1.1 µm) during the dust event, indicating they were mostly originated from surface soil and plants in the upwind regions. Low-volatile anthropogenic compounds such as benzo(e)pyrene (BeP) and bisphenol A (BPA) dominated in the fine mode particles during the whole campaign. In contrast, semi-volatile anthropogenic compounds such as phenanthrene (Phe) and di-n-butyl phthalates (DBP) showed a bimodal size distribution with a significant increase in the coarse mode during the dust event due to their vaporization from the fine mode particles and the subsequent adsorption on the dust surface. Secondary organic aerosols (SOA) in Xi'an during the dust storm period were predominantly enriched on the coarse particles, which can be ascribed to the adsorption and subsequent oxidation of gas-phase hydrophilic organics on the aqueous-phase of hygroscopic dust surface (e.g., mirabilite). Our work suggested an important role of multiphase reaction in evolution of aerosol chemistry during the dust long-range transport process.

[Characteristics of water-soluble organic nitrogen of PM2.5 in Xi'an during wintertime non-haze and haze periods].

High-volume PM2.5 samples were collected hourly from 4 December to 13 December 2012 at an urban site in Xi'an and analyzed for organic carbon (OC), elemental carbon (EC), water-soluble organic carbon (WSOC), water-soluble total nitrogen (WSTN), water-soluble organic nitrogen (WSON) and inorganic ions to investigate the sources and formation mechanism of WSON. The results showed that during the sampling period the averaged hourly concentration of WSON was (12 +/- 9.4) microg x m(-3) and maximized at 31 microg x m(-3), accounting for 47% +/- 9.8% of WSTN with NH4(+) -N and NO3(-) -N being 29% +/- 8.5% and 23% +/- 8.1%, respectively. WSON: WSOC (N: C) mass ratios ranged from 0.04 to 0.65 with an average of 0.31 +/- 0.13 during the observation period. WSON was (1.6 +/- 0.9) microg x m(-3), (6.5 +/- 3.9) microg x m(-3) and (23 +/- 4.7) microg x m(-3) in non-haze days (visibility > 10 km), light haze days (5 km < visibility < 10 km) and heavy haze days (visibility < 5 km), respectively. WSOC/OC mass ratio throughout the observation period showed no significant change, but WSON/WSOC(N: C) mass ratio increased significantly from a lower value of 0.2 +/- 0.1 in non-haze days to 0.3 +/- 0.1 on light haze days and 0.4 +/- 0.1 on heavy haze days, in consistence with the enhanced acidity of the fine particles. In addition, during the whole sampling period, WSON was strongly correlated with NH4(+), SO4(2-) and NO3(-) (R2 > 0.80), and negatively correlated with cation-anion equivalent ratio (R2 = 0.53). These phenomena can be mainly ascribed to a gas-particle conversion of gaseous water-soluble nitrogen-containing organic compounds like amines via acid-base reactions, which was sharply increased under the favorable meteorological conditions (e.g., low temperature and high humidity) during the heavy haze days.

[Immunogenicities and comparison of DNA vaccines encoding pol genes derived from B`/C and A/E recombinant HIV-1 strains].

OBJECTIVE: To construct and compare the immunogenicities of DNA vaccines expressing pol genes derived from B`/C and A/E recombinant subtypes of HIV-1 in China. METHODS: Two DNA vaccines were constructed by inserting the codon optimized pol genes derived from B'/C and A/E subtypes of HIV-1 into mammalian expression vector pSV1.0. In vitro expression efficiencies of the two DNA vaccines were determined by Western blotting and their immunogenicities were compared by i.m. immunizing female BALB/c mice. After immunization, mice splenocytes were isolated sterilely and IFN-γ based enzyme linked immunospot assay (ELISPOT) was employed to read out the specific T cell immunity. RESULTS: The constructed DNA vaccines were validated by restriction enzyme digestion and DNA sequencing. Western blotting result showed both of the two DNA vaccines could be expressed at appreciable levels in vitro. Under the stimulation of Consensus B Pol peptide pools, specific T cell frequency elicited by pSVAE-Pol was (636±178) SFCs/10(6) splenocytes; specific T cell frequency elicited by pSVCN-Pol was (468±265)SFCs/10(6) splenocytes (P=0.412). Under the stimulation of HIV-1 AE2f Pol peptide pools, specific T cell frequency elicited by pSVAE-Pol was (1378±611) SFCs/10(6) splenocytes; specific T cell frequency elicited by pSVCN-Pol was (713±61) SFCs/10(6) splenocytes (P=0.134). Further analysis suggested pSVAE-Pol induced specific T cell responses mainly focused on Pol 1 peptide pool, while, in addition to induce Pol 1 specific T cell responses, pSVCN-Pol could also elicit T cell responses against consensus B Pol 2 peptide pool. CONCLUSION: Although pSVAE-Pol was more immunogenic, pSVCN-Pol could induce T cell responses against broader epitope spectrum. Rational vaccine design may need combine them together.

Apoptosis induced by genipin in human leukemia K562 cells: involvement of c-Jun N-terminal kinase in G2/M arrest.

AIM: To investigate the effect of genipin on apoptosis in human leukemia K562 cells in vitro and elucidate the underlying mechanisms. METHODS: The effect of genipin on K562 cell viability was measured using trypan blue dye exclusion and cell counting. Morphological changes were detected using phase-contrast microscopy. Apoptosis was analyzed using DNA ladder, propidium iodide (PI)-labeled flow cytometry (FCM) and Hoechst 33258 staining. The influence of genipin on cell cycle distribution was determined using PI staining. Caspase 3 activity was analyzed to detect apoptosis at different time points. Protein levels of phospho-c-Jun, phosphor-c-Jun N-terminal kinase (p-JNK), phosphor-p38, Fas-L, p63, and Bax and the release of cytochrome c were detected using Western blot analysis. RESULTS: Genipin reduced the viability of K562 cells with an IC(50) value of approximately 250 µmol/L. Genipin 200-400 µmol/L induced formation of typical apoptotic bodies and DNA fragmentation. Additionally, genipin 400 µmol/L significantly increased the caspase 3 activity from 8-24 h and arrested the cells in the G2/M phase. After stimulation with genipin 500 µmol/L, the levels of p-JNK, p-c-Jun, Fas-L, Bax, and cytochrome c were remarkably upregulated, but there were no obvious changes of p-p38. Genipin 200-500 µmol/L significantly upregulated the Fas-L expression and downregulated p63 expression. Dicoumarol 100 µmol/L, a JNK1/2 inhibitor, markedly suppressed the formation of apoptotic bodies and JNK activation induced by genipin 400 µmol/L. CONCLUSION: These results suggest that genipin inhibits the proliferation of K562 cells and induces apoptosis through the activation of JNK and induction of the Fas ligand.