Pollution characteristics, ecological and health risks of herbicides in a drinking water source and its inflowing rivers in North China.

This study measured the pollution characteristics and ecological and health risks of 19 herbicides found in drinking water sources and their inflowing rivers. The targeted herbicides were prevalent in the study area, but most concentrations were well below 10 ng L-1. Acetochlor and atrazine were the dominant herbicides, although their levels were much lower than previously reported. Total herbicide residual levels were greater in April than in December and increased from upstream to downstream, resulting in the highest pollution levels found in the reservoirs, likely due to herbicides delivered from upstream and dense agricultural planting in the surrounding areas. Only atrazine and ametryn presented moderate ecological risks, while the summed risk quotients (ΣRQs) of each sample were >0.1, indicated that the total herbicide levels represented a moderate risk in all samples. For the human health risks, the risk quotients (RQ) of all target herbicides, the total RQs of each sample, and estimated life-stage RQs were far smaller than the 0.2 threshold, indicating the absence of human health risks when the water was consumed at any stage of life. However, early life stages exhibited 3-6 times higher RQ values than adulthood and should not be overlooked. And crucially, the synergistic or antagonistic effects of mixed herbicides are not well understood, and further research is needed to understand the impact of these herbicides on the ecosystem and human health, particularly possible affects in early life stages, such as infants and children.

Characterizing the Specific Recognition of Xanthurenic Acid by GEP1 and GEP1-GCα Interactions in cGMP Signaling Pathway in Gametogenesis of Malaria Parasites.

Gametogenesis is an essential step for malaria parasite transmission and is activated in mosquito by signals including temperature drop, pH change, and mosquito-derived xanthurenic acid (XA). Recently, a membrane protein gametogenesis essential protein 1 (GEP1) was found to be responsible for sensing these signals and interacting with a giant guanylate cyclase α (GCα) to activate the cGMP-PKG-Ca2+ signaling pathway for malaria parasite gametogenesis. However, the molecular mechanisms for this process remain unclear. In this study, we used AlphaFold2 to predict the structure of GEP1 and found that it consists of a conserved N-terminal helical domain and a transmembrane domain that adopts a structure similar to that of cationic amino acid transporters. Molecular docking results showed that XA binds to GEP1 via a pocket similar to the ligand binding sites of known amino acid transporters. In addition, truncations of this N-terminal sequence significantly enhanced the expression, solubility, and stability of GEP1. In addition, we found that GEP1 interacts with GCα via its C-terminal region, which is interrupted by mutations of a few conserved residues. These findings provide further insights into the molecular mechanism for the XA recognition by GEP1 and the activation of the gametogenesis of malaria parasites through GEP1-GCα interaction.

Identification of a novel substrate motif of yeast separase and deciphering the recognition specificity using AlphaFold2 and molecular dynamics simulation.

Separase is a giant cysteine protease and has multiple crucial functions. The most well-known substrate of separase is the kleisin subunit of cohesin, the cleavage of which triggers chromosome segregation during cell division (Uhlmann et al., 1999; Kamenz and Hauf, 2016) [1,2]. Recently, separase has also been found to cleave MCL-1 or BCL-XL proteins to trigger apoptosis (Hellmuth and Stemmann, 2020) [3]. Although substrate recognition through a short sequence right upstream of the cleavage site is well established, recent studies suggested that sequence elements outside this minimum cleavage site are required for optimal cleavage activity and specificity (Rosen et al., 2019; Uhlmann et al., 2000) [4,5]. However, the sequences and their underlying mechanism are largely unknown. To further explore the substrate determinants and recognition mechanism, we carried out sequence alignments and found a conserved motif downstream of the cleavage site in budding yeast. Using Alphafold2 and molecular dynamics simulations, we found this motif is recognized by separase in a conserved cleft near the binding groove of its inhibitor securin. Their binding is mutually exclusive and requires conformation changes of separase. These findings provide deeper insights into substrate recognition and activation of separase, and paved the way for discovering more substrates of separase.

A Guided Vehicle under Fire Conditions Based on a Modified Ultrasonic Obstacle Avoidance Technology.

Low visibility and hot smoke environment under fire conditions can largely hamper the related fire rescue processes. Ultrasound obstacle avoidance technology is then useful for guidance. However, the biggest challenge of adopting ultrasound technology comes from accurate distance measurements under the disturbances of high temperature and soot particle concentration. It is critical to measure the propagation speed under the complicated fire conditions. Therefore, in this study, a baffle calibration method was proposed to improve the accuracy of distance measurement of an obstacle. The method is based on two ultrasound measurement systems, while one is used to calibrate the propagation speed of ultrasound based on the fixed distanced baffle and the other is for the dynamic measurement of obstacle distance based on the calibrated speed. The viability of this method on the guided vehicle was confirmed based on the experiments. From its comparison to those existing methods, such as constant speed and temperature compensation methods, it was known from that the proposed baffle calibration method provides the best prediction. It was obtained that the maximum errors based on the baffle calibration method are 2.75% and 2.62% under the two representative fire scenarios, respectively, which are much lower than those of constant speed (7.81% and 8.4%) and temperature compensation methods (10.4% and 5.12%).