Dichlorprop induced structural changes of LHCâ ¡ chiral macroaggregates associated with enantioselective toxicity to Scnedesmus obliquus.

The enantioselective toxic mechanisms of chiral herbicides in photosynthetic organisms are closely related to the production of reactive oxygen species (ROS) production, however, there are few reports on how the enantioselective production of ROS can be triggered. In suboptimal conditions, photosynthesis is one of the most important processes in the production of ROS, especially in the process of light utilization and electron transfer. In this study, we investigated the interactions between chiral herbicide dichlorprop (DCPP) enantiomers and the chiral macroaggregates of the photosynthetic light-harvesting chlorophyll a/b pigment-protein complexes (LHCII) in Scenedesmus obliquus, which is of great significance in capturing and utilizing sun light, and also in dissipating the excess excitation energy. The results of the circular dichroism indicated that DCPP induced the structural changes of the LHCII chiral macroaggregates in an enantioselective manner and that the (R)-DCPP treated-group showed a bigger change accompanied by a changed enantioselective dissipation of the excitation energy. The excitation energy was excessed in DCPP treated-groups and the degree of excess was enantioselective and the detrimental non-chemical energy triggered the enantioselective production of ROS, that induced the enantioselective toxicity to green algae S. obliquus. Overall, this study has identified that how the enantioselective production of ROS can be triggered in chloroplasts; this can help to reveal the enantioselective mechanisms of chiral herbicides to photosynthetic organisms.

Biopolymer-induced morphology control of brushite for enhanced defluorination of drinking water.

Due to the relatively lower potential health risks as well as the good affinity for fluoride anion, calcium-based minerals have been widely carried out for the adsorption of fluoride. The improvement of adsorption capacity can be accomplished by regulation of particle size, shape and structure. Thus, here we report the controllable synthesis of petal-like nanosheets of brushite by using chitosan as a regulator. The addition of chitosan polymer in calcium precursor not only could serve ideal nucleation sites but also could play a vital role in confining the calcium phosphate aggregates and thus controlling the size of the brushite flakes. When the concentration of chitosan was 0.01wt%, the as-synthesized brushite showed nanosheet-structured with the dimensions ranged from 100 to 200nm and displayed outstanding fluoride adsorption capacity of 231.5mg/g according to the fitted Langmuir model, which was comparatively higher than that of the previously reported calcium-based adsorbents. Moreover, the pH change and common co-existing anions in solution almost presented less negative effect on the F- adsorption onto petal-like brushite nanosheets. We hope that these petal-like nanosheets based on green nanotechnology can help to achieve the intention of safe drinking water.