Construction of a dephosphorylation-mediated chemiluminescent biosensor for multiplexed detection of DNA glycosylases in cancer cells.

DNA glycosylases are engaged in the base excision repair process and play a vital role in maintaining genomic integrity. It remains a challenge for multiplexed detection of DNA glycosylases in cancer cells. Herein, we demonstrate the construction of a dephosphorylation-mediated chemiluminescent biosensor for multiplexed detection of human alkyladenine DNA glycosylase (hAAG) and uracil DNA glycosylase (UDG) in cancer cells. In this biosensor, the generation of chemiluminescence signals relies on the dephosphorylation of 3-(2'-spiroadamantyl)-4-methoxy-4-(3''-phosphoryloxyphenyl)-1,2-dioxetane (AMPPD) catalyzed by alkaline phosphatase (ALP). We design a bifunctional double-stranded DNA (dsDNA) substrate, a biotin-labelled poly-(T) probe, and two capture probes for the hAAG and UDG assay. This assay involves four steps including (1) the cleavage of the bifunctional dsDNA substrate induced by DNA glycosylases, (2) the recognition of the 3'-OH terminus of the primer by TdT and the subsequent TdT-mediated polymerization reaction, (3) the construction of the AuNPs-dsDNA-ALP nanostructures, and (4) the streptavidin-alkaline phosphatase (SA-ALP)-initiated dephosphorylation of AMPPD for the generation of an enhanced chemiluminescence signal. By taking advantage of the unique features of TdT-mediated polymerization and the intrinsic superiority of the ALP-AMPPD-based chemiluminescence system, this biosensor exhibits good specificity and high sensitivity with a detection limit of 1.53 × 10-6 U mL-1 for hAAG and 1.77 × 10-6 U mL-1 for UDG, and it can even quantify multiple DNA glycosylases at the single-cell level. Moreover, this biosensor can be applied for the measurement of kinetic parameters and the screening of DNA glycosylase inhibitors, holding great potential in DNA damage-related biomedical research and disease diagnostics.

[Impacts of ENSO events on forest fire weather of China]. / ENSO事件对中国森林火险天气的影响.

The ENSO events affect climate and fire danger of China. It would be helpful for improving fire danger forecast to understand the impacts of ENSO events on fire weather for various ecological zones in the country. We calculated the fire weather index (FWI) using the daily climatic dataset (V3.0) of international exchange weather stations in China during 1951-2016. The burned areas in forests for each ecological zone in 2001-2016 were derived from MODIS fire products. Temperature, precipitation, FWI and burned areas in fire season were estimated for each ecological zone by ENSO events (weak, medium, strong, and super strong El Niño events and weak, medium, and strong La Niña events). The results showed that there were 19 El Niño events and 14 La Niña events during 1950-2016. The average daily maximum temperature of the spring fire season increased significantly in the northwestern region with the influence of strong or super strong El Niño event, while the temperature reduced significantly in the medium El Niño event for mid-temperate semi-arid grassland. Precipitation in fire season generally increased in El Niño events in southern and southwestern forest regions. It would be reduced in most areas affected by the low and medium intensity La Niña event, but be increased during the strong La Nina event. The fire weather indices of southern forest regions decreased due to the weak El Niño event. The FWI of the northern forest regions increased with the strong or super strong El Niño event, and reduced in the southern and southwestern forest areas. There was a significant spatial difference on the FWI for some ecological zones with the impacts of the El Niño/La Niña events. The burned areas showed a consistent change trend with seasonal severity rating (SSR) during 2001-2016 when the SSR changed significantly for the regions of deciduous broad-leaved forest in humid/semihumid areas of warm temperate zone, broad-leaved forest in the middle north subtropical humid areas, and broad-leaved forest in tropical and subtropical humid areas. The burned areas in the rest regions were not affected by the ENSO events.

[Forest fire risk assessment for China under different climate scenarios.] / å¤šæ°”å€™æƒ æ™¯ä¸‹ä¸­å›½æ£®æž—ç«ç¾é£Žé™©è¯„ä¼°.

Forest fire risk depends on the hazard factors, affected body, and hazard prevention and reduction ability. The integrated risk assessment is the foundation for developing scientific fire mana-gement policies and carrying out the forest fire prevention measures. A forest fire risk assessment model and index system were established based on the classic natural disaster risk model and available data, and the model was used to assess the forest fire risks in past and future. The future climate scenario data included outputs from five global climate models (GFDL-ESM2M, HadGEM2-ES, IPSL-CM5A-LR, MIROC-ESM-CHEM and NorESM1-M) for RCP 2.6, RCP 4.5, RCP 6.0 and RCP 8.5, respectively. Each component index of Fire Weather Index (FWI) system was calculated daily for each grid in 1987-2050 for the historical observations and future climate scenarios according to the maximum temperature, minimum relative humidity, wind speed and daily precipitation. The results showed that areas with high and very high fire danger ratings in 1987-2010 accounted for 21.2% and 6.2%, respectively, which were distributed in Greater Xing'an Mountains and the Changbai Mountain area, most parts of Yunnan, and many fragment areas in southern China. The areas with high and very high burn possibilities were mainly distributed in the northeast and southwest region, accounting for 13.1% and 4.0%, respectively. Compared with the observation period, the areas with high and very high fire danger ratings in 2021-2050 would increase by 0.6%, 5.5%, 2.3%, and 3.5% under RCP 2.6, RCP 4.5, RCP 6.0, and RCP 8.5 respectively, and North China would show significant increase. The regions with high-risk forest fires would also increase due to climate change, with the most significant increase under RCP 8.5 scenario (+1.6%).

[Changes of climate and fire dynamic in China vegetation zone during 1961-2010].

Climate, vegetation and human activities have influences on regional fire regimes. To understand the fire regimes for ecological zones on national scale is the base for carrying on the forest fire management. Daily observed temperature and precipitation data in 1961-2010 were interpolated into grids for China mainland with spatial resolution of 0.250 x 0.250, which was used to analyze their changes in fire season for eight ecological zones. Mann-Kendall test method was used for trend analysis of climate and fire dynamics. The results indicated that the average temperature for the areas with forests showed a significant linear upward trend in 1961-2010, but the precipitation didn't have the tendency. The average temperature in fire season for all the ecological zones increased significantly in the study period, and the most increment occurred in temperate semi-arid/arid steppe regions. There was no significant change in precipitation in fire season for most regions. Forest fire numbers for the mainland showed obvious fluctuations, but the affected forest areas decreased significantly. The curves of fire numbers and affected forest areas showed a bimodal shape for all ecological zones, except those showed a significant increase in the coniferous forest region in the temperate arid areas.

[Carbon emission from forest fires in Daxing' anling region in 2005-2007].

Based on field investigation, the burned areas and consumed fuel loadings in Daxing' anling region caused by forest fires in 2005-2007 were estimated by comparing the normalized difference vegetation index (NDVI) before and after burning. The burned areas were classified with fire intensity, and the carbon emission from the fires was estimated by the fuel consumption and the average carbon content of plants. It was estimated that the total burned area was 436512. 5 hm2, of which, the severe, moderate, and light burned areas occupied 207178.4, 150159.2, and 79159.4 hm2, respectively. The consumed fuel loadings were 3.9 x 10(6) t in total, and the emitted carbon was 1.76 x 10(6) t, with 0.34 x 10(6), 0.83 x 10(6), 0.27 x 10(6), and 0.32 x 10(6) t from larch (Larix gmelini) forest, conifer and broadleaves mixed forest, broad-leaved forest, and grassland, respectively.