Synthesis and activity-detection of photoswitchable ligands with fipronil to insect.

BACKGROUND: Ionotropic γ-aminobutyric acid (GABA) receptor (GABAR) in an insect is the major inhibitory receptor and is one of the most important targets for insecticides. Due to the high spatiotemporal resolution of GABAR, the photopharmacological ligands acting on it in vertebrates but not insect have been developed. RESULTS: In this study, two types of photochromic ligands (PCLs) including DTFIPs (DTFIP1 and DTFIP2) and ABFIPs (p-, m-, and o-ABFIP) were synthesized by incorporating photoswitch azobenzene or dithienylethene into fipronil (FIP), which is the antagonist of insect GABAR. Their photomodulation was measured by mosquito larval behavior, and their potential action mechanism was explored by the two-electrode voltage clamp (TEVC) technique in vitro. DTFIP1 and m-ABFIP exhibited the most significant difference of insecticidal activity by about 90- and 5-fold to mosquito larvae between non-irradiated and irradiated formation, respectively, and allowed for optical control of mosquito swimming activity. TEVC assay results indicated that m-ABFIP and DTFIP1 enable optical control over the homomeric LsRDL-type GABAR, which is achieved by regulating the chloride channel of resistance to dieldrin (RDL)-type GABAR by photoisomerization. CONCLUSION: Our results suggested that PCLs synthesized from fipronil provide an alternative and precise tool for studying insect ionotropic GABARs and GABA-dependent behavior. © 2022 Society of Chemical Industry.

Variations of drought and its trend in the Loess Plateau from 1986 to 2019.

As one of the extreme climatic events, the frequency and intensity of drought have great impacts on regional water resource. Water is a main limiting factor for plant growth in arid and semi-arid regions. Therefore, it is of great scientific significance to explore the spatiotemporal variations and future tendency of drought for the ecological environment in the Loess Plateau. Based on grid data of monthly precipitation and temperature from 1986 to 2019, we calculated standardized precipitation evapotranspiration index (SPEI) and drought frequency. The spatiotemporal patterns and its variations were analyzed at the seasonal and annual scales in the Loess Plateau using the Mann-Kendall test and Sen's slope estimation method. Finally, the future trend of drought was analyzed in the Loess Plateau by the NAR neural network combined with Hurst index. Results showed that the trend of aridification became more significant in the Loess Plateau, and that the frequency of droughts events exhibited great spatial variations at the interannual and seasonal scales during the study period. Specifically, the highest frequency of drought in the interannual, spring and winter was found in the southeast and west of the Loess Plateau, whereas the frequency of drought in summer and autumn was higher in the northwest. The frequency of moderate drought was the highest in summer compared with other seasons while the frequency of slight drought was the highest in interannual and other seasons. The Loess Plateau showed a trend of aridification in spring and summer, but this trend in autumn and winter became weaker in most areas of the study area. The SPEI value in the interannual, spring, and summer exhibited a decline trend in a future period in the Loess Plateau. The aridification would be enhanced. The Hurst index value was the largest and the persis-tence of its change remained stronger in summer. The possibility of continuous drought in summer would be higher than that in other seasons in the future.