Evaluation of the inhibition of chlorophenols towards human cytochrome P450 3A4 and differences among various species.

Chlorophenols (CPs) are important pollutants detected frequently in the environment. This study intended to detect the inhibitory effects of fourteen CPs (2-CP, 3-CP, 4-CP, 4C2AP, 4C3MP, 2.4-DCP, 2.3.4-TCP, 2.4.5-TCP, 2.4.6-TCP, 3.4.5-TCP, 2.3.4.5-TECP, 2.3.4.6-TECP, 2.3.5.6-TECP and PCP) towards human liver cytochrome P450 3A4 (CYP3A4). Throughout the tests, testosterone was used as the probe substrate and CPs were used as inhibitors. A series of experiments (enzyme activity assays, preliminary screening tests, inhibition kinetics determination) were conducted to determine the inhibition of CPs towards human liver CYP3A4. CPs with the inhibitory effect >80% were selected for the inhibition evaluation in liver microsomes from different animal species (monkey, rat, dog, pig). The results showed that 2.3.4-TCP, 3.4.5-TCP, and 2.3.4.5-TECP inhibited the activities of CYP3A4 by 80.3%, 93.4%, 91.6%, respectively. Inhibition kinetics type were non-competitive and inhibition kinetics constant (Ki) values were 26.4 µM, 13.5 µM, and 8.8 µM for the inhibition of 2.3.4-TCP, 3.4.5-TCP, and 2.3.4.5-TECP towards human CYP3A4, respectively. Inhibition kinetics type was competitive and Ki value was 4.9 µM for the inhibition of 2.3.4-TCP towards CYP3A4 in Monkey liver microsomes (MyLMs). Inhibition kinetic types were non-competitive and Ki values were 8.1 µM and 28.7 µM for the inhibition of 3.4.5-TCP and 2.3.4.5-TECP towards CYP3A4 in MyLMs. Inhibition kinetic types were non-competitive and Ki values were 13.8 µM, 0.6 µM, and 6.1 µM for the inhibition of 2.3.4-TCP, 3.4.5-TCP, and 2.3.4.5-TECP towards CYP3A4 in Dog liver microsomes (DLMs), respectively. By comparing Ki values and inhibition kinetic types, the dog was the most suitable model to assess the inhibition of 2.3.4-TCP and 2.3.4.5-TECP towards CYP3A4, and monkey was the most suitable model to assess the inhibition of 3.4.5-TCP towards CYP3A4. In conclusion, our recent study on the inhibition of CPs towards CYP3A4 and species differences was important for further toxicological studies of CPs in human bodies.

Health and ecological risk assessment of heavy metals pollution in an antimony mining region: a case study from South China.

In recent years, international research on the toxicity of the heavy metal, antimony, has gradually changed focus from early medical and pharmacological toxicology to environmental toxicology and ecotoxicology. However, little research has been conducted for sources identification and risk management of heavy metals pollution by long-term antimony mining activities. In this study, a large number of investigations were conducted on the temporal and spatial distribution of antimony and related heavy metal contaminants (lead, zinc, and arsenic), as well as on the exposure risks for the population for the Yuxi river basin in the Hunan province, China. The scope of the investigations included mine water, waste rock, tailings, agricultural soil, surface water, river sediments, and groundwater sources of drinking water. Health and ecological risks from exposure to heavy metal pollution were evaluated. The main pollution sources of heavy metals in the Yuxi River basin were analyzed. Remediation programs and risk management strategies for heavy metal pollution were consequently proposed. This article provides a scientific basis for the risk assessment and management of heavy metal pollution caused by antimony basin ore mining.

[Research on removal of tetrabromobisphenol A from synthetic wastewater by nanoscale zero valent iron supported on organobentonite].

The removal of tetrabromobisphenol A (TBBPA) in methanol aqueous solutions by nanoscale zero valent iron supported on organobentonite (NZVI-CMT) was studied. The effects of temperature, initial concentration of TBBPA and the dose of NZVI-CMT on the degradation and debromination of TBBPA were investigated. The removal rate by NZVI-CMT reached 97.5% within 12 hours at 25 degrees C, when the initial concentration of TBBPA was 10 mg x L(-1). And the removal rate of NZVI-CMT was higher than those of two simple materials, namely organobentonite (CMT) and nanoscale zero valent iron (NZVI), as well as the sum of those two simple materials. In addition, NZVI-CMT exhibited a better reusable attribute, and the rate of the materials remained above 90% after being used for 3 times. Based on the identification of degradation products and analysis of the TBBPA removal by NZVI-CMT, the main reaction mechanism was suggested as adsorption and debromination, and higher reaction temperature was preferable for debromination.

The secondary structure of heated whey protein and its hydrolysates antigenicity.

Fourier transform infrared spectroscopy (FTIR) and circular dichroism (CD) were used to investigate the conformational changes of heated whey protein (WP) and the corresponding changes in the hydrolysates immunoreactivity were determined by competitive enzyme-linked immunosorbent assay (ELISA). Results showed that the contents of alpha- helix and beta-sheet of WP did not decrease much under mild heating conditions and the antigenicity was relatively high; when the heating intensity increased (70 degrees for 25 min or 75 degrees C for 20 min), the content of alpha- helix and beta-sheet decreased to the minimum, so was the antigenicity; However, when the WP was heated at even higher temperature and for a longer time, the beta-sheet associated with protein aggregation begun to increase and the antigenicity increased correspondingly. It was concluded that the conformations of heated WP and the antigenicity of its hydrolysates are related and the optimum structure for decreasing the hydrolysates antigeniity is the least content of alpha-helix and beta-sheet. Establishing the relationship between the WP secondary structure and WP hydrolysates antigenicity is significant to supply the reference for antigenicity reduction by enzymolysis.

[Characterization of Cr (VI) removal and total Cr equilibrium adsorption by sulfate reducing granular sludge in stimulant wastewater].

Sulfate reducing granular sludge (SRGS) cultivated in small scale EGSB reactor was used for Cr (VI) removing. Characterization of Cr (VI) removal and total Cr equilibrium adsorption was studied, and the adsorption isotherm was fitted. Results showed that removal of Cr (VI) was in connection with the structure and chemical composition of SRGS and several environmental factors. The Cr (VI) removal rate increased with the dosage of granular sludge; the increasing of oscillation speed and temperature could enhance Cr (VI) removal and total Cr adsorption, but while the oscillation speed reached 150 r x min(-1) or the temperature came to 40 degrees C, the physical structure of granular sludge would be affected and the granular sludge discrete, and total Cr equilibrium adsorption decreased; lower pH value caused higher Cr (VI) removal rate, however the sulfate on the surface of granular sludge was affected by lower pH value easily and would translate into H2S, then total Cr adsorption rate decreased. Cr (VI) removal would be influenced by physical, chemical and biological factors, and the process included reduction and adsorption mainly. The maximum adsorption of total Cr by granular sludge was 6.84 mg x g(-1), and the total Cr adsorbing process fitted in with Langmuir adsorption isotherm.