Probing interaction of a fluorescent ligand with HIV TAR RNA.

Trans-activator of Transcription (Tat) antagonists could block the interaction between Tat protein and its target, trans-activation responsive region (TAR) RNA, to inhibit Tat function and prevent human immunodeficiency virus type 1 (HIV-1) replication. For the first time, a small fluorescence ligand, ICR 191, was found to interact with TAR RNA at the Tat binding site and compete with Tat. It was also observed that the fluorescence of ICR 191 could be quenched when binding to TAR RNA and recovered when discharged via competition with Tat peptide or a well-known Tat inhibitor, neomycin B. The binding parameters of ICR 191 to TAR RNA were determined through theoretical calculations. Mass spectrometry, circular dichroism and molecular docking were used to further confirm the interaction of ICR 191 with TAR RNA. Inspired by these discoveries, a primary fluorescence model for the discovery of Tat antagonists was built using ICR 191 as a fluorescence indicator and the feasibility of this model was evaluated. This ligand-RNA interaction could provide a new strategy for research aimed at discovering Tat antagonists.

[Bioremediation of river water quality by consecutively adjustable submerged vegetation net].

A series of consecutively adjustable submerged vegetation nets were constructed in a polluted shallow river with a length of about 200 m and nearby the water resource protection area of Taihu Lake in East China, forming an aquatic vegetation consisted of submerged plant species Cabomba caroliniana, Vallisneria natans, Elodea nuttallii, Hydrilla verticillata, and Potamogeton crispus. The water quality indices including total nitrogen (TN), ammonium nitrogen (NH4(+)-N), nitrite nitrogen (NO2(-)-N), nitrate nitrogen (NO3(-)-N), total phosphorus (TP), and phosphate (PO4(3-)-P) were monitored, and the bioremediation effect of the vegetation nets was evaluated. After setting up the vegetation nets, the Secchi depth (SD) of the river changed from 0.5 m to 1.7-1.8 m, and the TN and TP concentrations 15 and 20 days after the nets constructed decreased by 35.6% and 66.3%, and 29.4% and 63.2%, respectively. After five months, the concentrations of NH4(+)-N, NO2(-)-N, NO3(-)-N, TN, TP, and PO4(3-)-P decreased by 92.4%, 76.8%, 72.7%, 73.9%, 90.5%, and 92.0%, respectively. This study showed that consecutively adjustable submerged vegetation net could be a potential approach for treating polluted river waters, particularly for the bioremediation of polluted small landscape shallow water bodies.

[Bioremediation efficiency of applying Daphnia magna and submerged plants: a case study in Dishui Lake of Shanghai, China].

From April 2007 to January 2008, a bioremediation experiment was conducted in a diversion channel of D-port pilot area of Dishui Lake (the channel length is 950 m, and its water volume is 10000 m3). Daphnia magna was first introduced to filter the high biomass of phytoplankton and other particulate organic matter, and then, five submerged plant species Elodea canadensis, Vallisneria spiralis, Hydrilla verticillata, Potamogeton lucens, and Potamogeton crispus were transplanted. Water samples were collected monthly to monitor the water quality and to investigate the bioremediation efficiency. Ten months monitoring data showed that in the remediation area, the water body's total nitrogen (TN), ammonium nitrogen (NH4(+)-N), nitrate nitrogen (NO3(-)-N), nitrite nitrogen (NO2(-)-N), total phosphorus (TP), and reactive phosphate (PO4(3-)-P) concentrations and chemical oxygen demand (COD) were significantly lower (P < 0.01), dissolved oxygen (DO) was increased by 50.4%, and the Secchi depth (SD) reached to an average of 3.4-3.7 m. Overall, the water quality was up to grades II or III of state water quality standards for surface water. In March 2008, the established submerged plant community was used to test its effectiveness in improving the eutrophicated water body from Dishui Lake, and the results showed that after 7-day treatment, except biological oxygen demand (BOD), the TN, TP, NO3(-)-N, NO2(-)-N, NH4(+)-N, and PO4(3-)-P concentrations and COD of the eutrophicated water were all decreased significantly, the DO was increased by 17.98%, and the SD was increased by 30 cm. The present study demonstrated the effectiveness of introducing D. magna and transplanting submerged plants in improving the water quality of Dishui Lake.