Removal of pharmaceuticals and personal care products by two-stage biofiltration for drinking water treatment

Contamination of drinking water with pharmaceuticals and personal care products (PPCPs) is an issue of health concerns. To effectively control the level of PPCPs in drinking water, a pilot study employing two parallel trains of two-stage biofiltration, i.e., a sand/anthracite (SA) biofilter coupled with a biologically-active granular activated carbon (GAC) post-filter contactor, was conducted as a post-treatment after coagulation in a drinking water treatment plant. Results showed the biofiltration process could effectively remove PPCPs with an average removal of 53.4%, where the GAC contactor played the dominant role to remove 48.1% of the total PPCPs. The molecular properties determined the removability of individual PPCPs, i.e., smaller molecules with simpler structure connectivity were more likely to be removed. Based on the quantitative structure-property relationships (QSPRs) analysis, a simple regression model was proposed to predict the removability of each PPCP across the biofiltration process. The drinking water equivalent level (DWEL) quotient method was developed to assess the health risks of detected PPCPs in water samples. The biofiltration process showed efficient capacity to reduce the health risks of PPCPs with an average removal of 79%, and the PPCPs in the effluents generally would not pose adverse health effects. Pearson correlation analysis explored the possible role of nitrogenous PPCPs (N-PPCPs) as the precursors of nitrogenous disinfection byproducts (N-DBPs) in drinking waters. Aromatic nitrogen in PPCPs was found to be a significant descriptor for the formation potential of trichloroacetonitrile (TCAN). In addition, it was found that pre-filter chlorination could slightly improve the biofiltration of PPCPs.

Molecular docking and 3D-QSAR studies on the glucocorticoid receptor antagonistic activity of hydroxylated polychlorinated biphenyls

The glucocorticoid receptor (GR) antagonistic activities of hydroxylated polychlorinated biphenyls (HO-PCBs) were recently characterised. To further explore the interactions between HO-PCBs and the GR, and to elucidate structural characteristics that influence the GR antagonistic activity of HO-PCBs, molecular docking and three-dimensional quantitative structure-activity relationship (3D-QSAR) studies were performed. Comparative molecular similarity indices analysis (CoMSIA) was performed using both ligand- and receptor-based alignment schemes. Results generated from the receptor-based model were found to be more satisfactory, with q(2) of 0.632 and r(2) of 0.931 compared with those from the ligand-based model. Some internal validation strategies (e.g. cross-validation analysis, bootstrapping analysis and Y-randomisation) and an external validation method were used respectively to further assess the stability and predictive ability of the derived model. Graphical interpretation of the model provided some insights into the structural features that affected the GR antagonistic activity of HO-PCBs. Molecular docking studies revealed that some key residues were critical for ligand-receptor interactions by forming hydrogen bonds (Glu540) and hydrophobic interactions with ligands (Ile539, Val543 and Trp577). Although CoMSIA sometimes depends on the alignment of the molecules, the information provided is beneficial for predicting the GR antagonistic activities of HO-PCB homologues and is helpful for understanding the binding mechanisms of HO-PCBs to GR.

Benzotriazole: An overview on its versatile biological behavior

Discovered in late 1960, azoles are heterocyclic compounds class which constitute the largest group of available antifungal drugs. Particularly, the imidazole ring is the chemical component that confers activity to azoles. Triazoles are obtained by a slight modification of this ring and similar or improved activities as well as less adverse effects are reported for triazole derivatives. Consequently, it is not surprising that benzimidazole/benzotriazole derivatives have been found to be biologically active. Since benzimidazole has been widely investigated, this review is focused on defining the place of benzotriazole derivatives in biomedical research, highlighting their versatile biological properties, the mode of action and Structure Activity Relationship (SAR) studies for a variety of antimicrobial, antiparasitic, and even antitumor, choleretic, cholesterol-lowering agents.

Molecular docking and molecular dynamics studies on the interactions of hydroxylated polybrominated diphenyl ethers to estrogen receptor alpha

Environmental estrogens have attracted great concerns. Recent studies have indicated that some hydroxylated polybrominated diphenyl ethers (HO-PBDEs) can interact with estrogen receptor (ER), and exhibit estrogenic activity. However, interactions between HO-PBDEs and ER are not well understood. In this work, molecular docking and molecular dynamics (MD) simulations were performed to characterize interactions of two HO-PBDEs (4'-HO-BDE30 and 4'-HO-BDE121) with ERα. Surflex-Dock was employed to reveal the probable binding conformations of the compounds at the active site of ERα; MD simulation was used to determine the detailed binding process. The driving forces of the binding between HO-PBDEs and ERα were van der Waals and electrostatic interactions. The decomposition of the binding free energy indicated that the hydrogen bonds between the residues Glu353, Gly521 and ligands were crucial for anchoring the ligands into the active site of ERα and stabilizing their conformations. The results showed that different interaction modes and different specific interactions with some residues were responsible for the different estrogenic activities of the two HO-PBDEs.