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Background One of the major challenges in environmental science is how to assess the toxicity and risk of complex pollutant mixtures. However, only a few studies have pointed out that there is a significant difference between the toxicities of chemicals on genetically modified strains and wild-type organisms and there are few reports of the differences in the toxicity of chemical mixtures. Therefore, six chemicals, two substituted phenols (4-chlorophenol and 4-nitrophenol), two pesticides (dichlorvos and glyphosate) and two ionic liquids (1-butylpyridinium chloride and 1-butylpyridinium bromide), were selected to construct a six-component mixture system, the lethality of various mixtures on the genetically modified Caenorhabditis elegans strain mtl-2::GFP (MTL-2) at 12 and 24 h were determined, and differences in toxicity to other strains were compared. Results Although the toxicity of 4-chlorophenol on MTL-2 was not significantly different from that on N2 wild-type Caenorhabditis elegans (N2), the toxicities of the other five chemicals on MTL-2 were greater than those on N2. The toxicities of six single chemicals and nine mixture rays on MTL-2 increased with time, which is consistent with the effect on N2 and on the genetically modified strain sod-3::GFP Caenorhabditis elegans (SOD-3). The toxicological interactions of various mixtures in MTL-2 at 12 h were half antagonistic (ANT) and half additive (ADD), while at 24 h, they were mainly synergistic (SYN). The toxicological interactions of various mixtures in MTL-2 change from ANT/ADD to primarily SYN with time, which is different from the change from ANT to ADD in SOD-3 and from SYN to ADD in N2. Conclusions The toxicity and toxicity interactions of chemical mixtures on different Caenorhabditis elegans strains are different. Therefore, it is necessary to examine the effect of genetic factors on the toxicological interaction of mixtures to avoid underestimating or overestimating the mixture risk.

Background The weak magnetic field (WMF) can enhance the ability to remove target pollutants in wastewater, which drives us to consider whether WMF could give rise to the hormesis or not. In our previous study, it was found that polymyxin B sulfate (POL) can induce weak hormesis on Vibrio qinghaiensis sp.-Q67 (Q67). To this end, we set up four different WMF treatments during Q67 culture and POL exposure process, having no WMF in all cases (NW), adding WMF all the time (AW), exerting WMF only during the bacterial culture (BW), and exerting WMF only in POL exposure period (EW). Results It was shown that the concentration–response curves (CRCs) of POL in four WMF treatments at the exposure times of 6, 9, and 12 h are non-monotonic hormetic curves where the maximum stimulative effects (Emin) of POL in BW and EW are obviously larger than those in AW and NW. The maximum Emin is 26.8% occurring in EW and 20.7% in BW at 6 h, while the max Emin is 14.6% in NW at 9 h, it means that stimulations of POL in BW and EW are earlier and stronger than those in NW. These findings first indicated that WMF can enhance the hormesis of POL. Conclusions This study showed that WMF as a key factor may influence the maximum stimulation effect of hormesis. The characteristic of biphasic (hormetic effect) challenges the traditional classical threshold model that is close to chemical risk assessment. But the mechanism of hormesis even now is inconclusive. WMF as a novelty and neglected factor has the potential to support the further development of hormesis mechanism.

Diabetes remains a life-threatening disease. The clinical profile of diabetic subjects is often worsened by the presence of several long-term complications, for example neuropathy, nephropathy, retinopathy, and cataract. Comparative molecular field analysis (CoMFA) and comparative molecular similarity indices analysis (CoMSIA) were performed on a series of 2,4-thiazolidinediones derivatives as aldose reductase (ALR2) inhibitors. Molecular ligand superimposition on a template structure was finished by the database alignment method. The 3D-QSAR models resulted from 44 molecules gave q 2 values of 0.773 and 0.817, r 2 values of 0.981 and 0.979 for CoMFA and CoMSIA, respectively. The contour maps from the models indicated that a large volume group next to the R-substituent will increase the ALR2 inhibitory activity. In fact, adding a -CH2COOH substituent at the R-position would generate a new compound with higher predicted activity.

Molecular electronegativity distance vector (MEDV) derived directly from the molecular topological structures was used to describe the structures of 122 nonionic organic compounds (NOCs) and a quantitative relationship between the MEDV descriptors and the bioconcentration factors (BCF) of NOCs in fish was developed using the variable selection and modeling based on prediction (VSMP). It was found that some main structural factors influencing the BCFs of NOCs are the substructures expressed by four atomic types of nos. 2, 3, 5, and 13, i.e., atom groups −CH2− or =CH−, −CH< or =C

Quantitative structure-retention relationship (QSRR) studies have proved to be a valuable approach in the prediction of the gas chromatographic relative retention time (GC-RRT) of organic chemicals. Polybrominated diphenyl ether (PBDE) congeners are now ubiquitous environmental pollutants. Of the 209 possible PBDE congeners, 126 have been synthesized and their retention-time data on seven different stationary phases has been determined [Korytar et al.:J Chromatography A 1065:239–249, (2005)]. To estimate and predict the GC-RRT values of all 209 PBDEs on different stationary phases, 17 molecular descriptors from the semi-experience algorithm in MOPAC program and the topological structures of PBDE molecules were calculated. By means of the VSMP (variable selection and modeling based on prediction) program [Liu et al.:J Chem Inf Comput Sci 43:964–969, (2003)], six optimal descriptors were selected to develop a QSRR model for the prediction of GC-RRT of PBDE. The descriptors contain some energy information (such as the energy of the lowest unoccupied molecular orbital and highest occupied molecular orbital) and topological information (the number of ortho-, meta-, and para- substituted bromine atoms) as well as the molecular weight (lnM W ). All the models developed were cross-validated using leave-one-out (LOO). For seven GC stationary phases, the estimated correlation coefficients (r 2 ) are all more than 0.985 but for the column CP-Sil 19 (r 2 = 0.9392) and LOO-validated correlation coefficients (q 2 ) all more than 0.985 but for the column CP-Sil 19 (q 2 = 0.9345).

Polybrominated diphenyl ethers (PBDEs) have been used extensively over the past two decades as flame or fire retardants added into many products such as textiles, electronic equipment and insulation material. PBDEs are now ubiquitous environmental pollutants and have been detected in biotic and abiotic matrices that include fish, birds, sediments, air, marine mammals, and human plasma and milk. The purpose of the paper is to develop some models which can predict the gas chromatographic relative retention time of PBDEs on seven stationary phases. The molecular electronegativity distance vector based on 13 atomic types (MEDV-13) were employed to describe the structural changes of PBDEs. Using the variables selection and modeling based on the prediction (VSMP), some four-variable linear equations from 80 PBDEs in the training sets with the correlation coefficient (r 2) >0.98 and the root mean square errors of estimation