Interaction of different chloro-substituted phenylurea herbicides (diuron and chlortoluron) with bovine serum albumin: Insights from multispectral study

In this work, the interaction between different chloro-substituted phenylurea herbicides (diuron (DIU) and chlortoluron (CHL)) and BSA were investigated and compared at three different temperatures (283 K, 298 K and 310 K) adopting UV-vis, fluorescence, and circular dichroism spectra. The quenching mechanism of the interaction was also proposed. The energy transfer between BSA and DIU/CHL was investigated. The binding sites of DIU/CHL and BSA and the variations in the microenvironment of amino acid residues were studied. The changes of the secondary structure of BSA were analyzed. The results indicate that both DIU and CHL can significantly interact with BSA, and the degree of the interaction between DIU/CHL and BSA increases with the increase of the DIU/CHL concentration. The fluorescence quenching of BSA by DIU/CHL results from the combination of static and dynamic quenching. The DIU/CHL has a weak to moderate binding affinity for BSA, and the binding stoichiometry is 1:1. Their binding processes are spontaneous, and hydrophobic interaction, hydrogen bonds and van der Waals forces are the main interaction forces. DIU/CHL has higher affinity for subdomain IIA (Site I) of BSA than subdomain IIIA (Site II), and also interacts with tryptophan more than tyrosine residues. The energy transfer can occur from BSA to DIU/CHL. By comparison, the strength of the interaction of DIU-BSA is always greater than that of CHL-BSA, and DIU can destroy the secondary structure of BSA molecules greater than CHL and thus the potential toxicity of DIU is higher due to DIU with more chlorine substituents than CHL. It is expected that this study on the interaction can offer in-depth insights into the toxicity of phenylurea herbicides, as well as their impact on human and animal health at the molecular level.

A review on co-metabolic degradation of organic micropollutants during anaerobic digestion: Linkages between functional groups and digestion stages

The emerging presence of organic micropollutants (OMPs) in water bodies produced by human activities is a source of growing concern due to their environmental and health issues. Biodegradation is a widely employed treatment method for OMPs in wastewater owing to its high efficiency and low operational cost. Compared to aerobic degradation, anaerobic degradation has numerous advantages, including energy efficiency and superior performance for certain recalcitrant compounds. Nonetheless, the low influent concentrations of OMPs in wastewater treatment plants (WWTPs) and their toxicity make it difficult to support the growth of microorganisms. Therefore, co-metabolism is a promising mechanism for OMP biodegradation in which co-substrates are added as carbon and energy sources and stimulate increased metabolic activity. Functional microorganisms and enzymes exhibit significant variations at each stage of anaerobic digestion affecting the environment for the degradation of OMPs with different structural properties, as these factors substantially influence OMPs' biodegradability and transformation pathways. However, there is a paucity of literature reviews that explicate the correlations between OMPs' chemical structure and specific metabolic conditions. This study provides a comprehensive review of the co-metabolic processes which are favored by each stage of anaerobic digestion and attempts to link various functional groups to their favorable degradation pathways. Furthermore, potential co-metabolic processes and strategies that can enhance co-digestion are also identified, providing directions for future research.

Designed complexes combining brazilein and brazilin with betanidin for dye-sensitized solar cell application: DFT and TD-DFT study

Dye-sensitized solar cells (DSSCs) are promising third-generation photovoltaic cell technology owing to their easy fabrication, flexibility and better performance under diffuse light conditions. Natural pigment sensitizers are abundantly available and environmentally friendliness. However, narrow absorption spectra of natural pigments result in low efficiencies of the DSSCs. Therefore, combining two or more pigments with complementary absorption spectra is considered an appropriate method to broaden the absorption band and boost efficiency. This study reports three complex molecules: brazilin-betanidin-oxane (Braz-Bd-oxane), brazilin-betanidin-ether (Braz-Bd-ether) and brazilein-betanidin-ether (Braze-Bd-ether), obtained from the etherification and bi-etherification reactions of brazilin dye and brazilein dye with betanidin dye. The equilibrium geometrical structure properties, frontier molecular orbital, electrostatic surface potential, reorganization energy, chemical reactivities, and non-linear optical properties of the studied dyes were investigated using density functional theory (DFT)/B3LYP methods, with 6-31+G(d,p) basis sets and LANL2DZ for light atom and heavy atoms respectively. The optical-electronic properties were calculated using TD-DFT/B3LYP/6-31+G(d,p) for isolated dye and TD-DFT/CAM-B3LYP/6-31G(d,p)/LANL2DZ for dyes@(TiO2)9H4. The results reveal that spectra for Braz-Bd-oxane and Braze-Bd-ether complexes red-shifted compared to the individually selected dyes. The simulated absorption spectra of the adsorbed dyes on (TiO2)9H4 are red-shifted compared to the free dye. Moreover, Braz-Bd-oxane and Braz-Bd-ether exhibit better charge transfer and photovoltaic properties than the selected natural dyes forming these complexes. Based on the dyes' optoelectronic properties and photovoltaic properties, the designed molecules Braz-Bd-oxane and Braze-Bd-ether are considered better candidates to be used as photosensitizers in dye solar cells.

Sorption of carbendazim and linuron from aqueous solutions with activated carbon produced from spent coffee grounds: Equilibrium, kinetic and thermodynamic approach

Spent coffee grounds (SCG) have been used for the production of activated carbon (AC) by impregnation with different ratios of phosphoric acid at 600 °C, Xp (H₃PO₄/coffee): 3:1^30%, 4:1^30%, 3:1^50% and 4:1^50%. The obtained AC was characterized by BET, FTIR and SEM. BET surface area corresponds to 803.422 m² g^-1. The influences of the main parameters such as contact time, the pesticides initial concentration, adsorbent dose, pH and temperature on the efficiency of separation process were investigated during the batch operational mode. Results were modeled by adsorption isotherms: Langmuir, Freundlich and Temkin isotherms, which gave satisfactory correlation coefficients. The maximum adsorption capacities calculated from the Langmuir isotherms were 11.918 mg g^-1 for carbendazim and 5.834 mg g^-1 for linuron at room temperature. Adsorption kinetics of carbendazim and linuron have been studied by the pseudo-first-order, the pseudo-second-order and the intraparticle diffusion model. The results of adsorption kinetics have been fitted the best by pseudo-second-order model. The resulted data from FTIR characterization pointed to the presence of many functional groups on the AC surface. SCG adsorbent, as an eco-friendly and low-cost material, showed high potential for the removal of carbendazim and linuron from aqueous solutions.