Investigating the quantitative structure-activity relationships for antibody recognition of two immunoassays for polycyclic aromatic hydrocarbons by multiple regression methods.

Polycyclic aromatic hydrocarbons (PAHs) are ubiquitous contaminants found in the environment. Immunoassays represent useful analytical methods to complement traditional analytical procedures for PAHs. Cross-reactivity (CR) is a very useful character to evaluate the extent of cross-reaction of a cross-reactant in immunoreactions and immunoassays. The quantitative relationships between the molecular properties and the CR of PAHs were established by stepwise multiple linear regression, principal component regression and partial least square regression, using the data of two commercial enzyme-linked immunosorbent assay (ELISA) kits. The objective is to find the most important molecular properties that affect the CR, and predict the CR by multiple regression methods. The results show that the physicochemical, electronic and topological properties of the PAH molecules have an integrated effect on the CR properties for the two ELISAs, among which molar solubility (S(m)) and valence molecular connectivity index ((3)χ(v)) are the most important factors. The obtained regression equations for Ris(C) kit are all statistically significant (p < 0.005) and show satisfactory ability for predicting CR values, while equations for RaPID kit are all not significant (p > 0.05) and not suitable for predicting. It is probably because that the Ris(C) immunoassay employs a monoclonal antibody, while the RaPID kit is based on polyclonal antibody. Considering the important effect of solubility on the CR values, cross-reaction potential (CRP) is calculated and used as a complement of CR for evaluation of cross-reactions in immunoassays. Only the compounds with both high CR and high CRP can cause intense cross-reactions in immunoassays.

[Mechanism study on the extraction of nonylphenol by ionic liquids in water through IR spectroscopy and quantum chemical calculation].

The interaction mechanism of the typical ionic liquid (IL) 1-methyl-3-butyl imidazolium hexafluorophosphate ([BMIM][PF6]), imidazolium ionic liquid with hydroxyl group and nonylphenol (NP) was studied through infrared (IR) spectroscopy and quantum chemical calculations for density functional theory. The results indicated the hydrogen bonds could not be found in the IR spectra before and after IL [BMIM][PF6] extracting NP while the absorption peaks of the hydroxyl group of the ILs containing hydroxyl group have red shifts after the ILs extracting NP. It could be seen in the theoretical calculation that the cation [BMIM]+ of [BMIM][PF6] has the C--H...O hydrogen bond interaction with NP. The O--H...O type hydrogen bond could also be formed between the cation [C4H9OHIM]+ of the IL with hydroxyl group and NP. It could be concluded through the two mechanism study methods that the strength of hydrogen bond between the IL with hydroxyl group and NP was bigger than the one between the typical IL [BMIM][PF6] and NP, followed by the bigger extraction efficiency of NP by the former, which coincided with the extraction experiment result.

Predicting the cross-reactivities of polycyclic aromatic hydrocarbons in ELISA by regression analysis and CoMFA methods.

Immunoassays have been regarded as a possible alternative or supplement for measuring polycyclic aromatic hydrocarbons (PAHs) in the environment. Since there are too many potential cross-reactants for PAH immunoassays, it is difficult to determine all the cross-reactivities (CRs) by experimental tests. The relationship between CR and the physical-chemical properties of PAHs and related compounds was investigated using the CR data from a commercial enzyme-linked immunosorbent assay (ELISA) kit test. Two quantitative structure-activity relationship (QSAR) techniques, regression analysis and comparative molecular field analysis (CoMFA), were applied for predicting the CR of PAHs in this ELISA kit. Parabolic regression indicates that the CRs are significantly correlated with the logarithm of the partition coefficient for the octanol-water system (log K(ow)) (r(2) = 0.643, n = 23, P < 0.0001), suggesting that hydrophobic interactions play an important role in the antigen-antibody binding and the cross-reactions in this ELISA test. The CoMFA model obtained shows that the CRs of the PAHs are correlated with the 3D structure of the molecules (r(cv)(2) = 0.663, r(2) = 0.873, F(4,32) = 55.086). The contributions of the steric and electrostatic fields to CR were 40.4 and 59.6%, respectively. Both of the QSAR models satisfactorily predict the CR in this PAH immunoassay kit, and help in understanding the mechanisms of antigen-antibody interaction.

Impact of atrazine and nitrogen fertilizers on the sorption of chlorotoluron in soil and model sorbents.

Sorption of chlorotoluron in ammonium sulfate, urea and atrazine multi-solutes system was investigated by batch experiments. The results showed application of nitrogen fertilizers to the soil could affect the behavior of chlorotoluron. At the same concentration of N, sorption of chlorotoluron decreased as the concentration of atrazine increased on the day 0 and 6 in soil, respectively. The sorption of chlorotoluron increased from 0 to 6 d when soils were preincubated with deionized water, ammonium sulfate and urea solution for 6 d. That indicated incubation time was one of the most important factors for the sorption of chlorotoluron in nitrogen fertilizers treatments. The individual sorption isotherms of chlorotoluron in rubbery polymer and silica were strictly linear in single solute system, but there were competition sorption between pesticides or between pesticides and nitrogen fertilizers. That indicated the sorption taken place by concurrent solid-phase dissolution mechanism and sorption on the interface of water-organic matter or water-mineral matter.

[Photodegradation of nonylphenol polyethoxylates in aqueous solution].

Two lamps, including simulated sunlight lamp and UVA-365 nm lamp, were used to study the kinetics and changes of component distribution of NPEOs mixture in solution during photodegradation, as well as the effect of H2O2 on the photodegradation. LC-MS was used to analyze the products of NPEOs photodegradation. It was found that photodegradation of NPEOs occurred under both simulated sunlight and UVA irradiation, with the degradation rate being 6.20 x 10(-3) micromol/(L x h) and 1.18 x 10(-2) micromol/(L x h), respectively. The component distribution of short chain NPEO(1,3) increased during the photodegradation process under simulated sunlight, while no obvious change was observed under UVA irradiation. The presence of the oxidant, H2O2, was found to be propitious to the photodegradation of NPEOs, especially under the irradiation of simulated sunlight. At different added concentrations of H2O2, the 96 h degradation percentage of NPEOs increased from 20.9% (non-H2O2) to 44.4% (0.01 mmol/L H2O2) and even 91.5% (1.00 mmol/L H2O2), respectively. The analysis for degradation products using LC-MS suggested that CA(3-9)PEC3 might he the major photodegradation products of NPEOs, based on which the reaction mechanism of NPEOs photodegradation was speculated.

[Effects of nitrogen source and aeration mode on algae growth in freshwater].

Aquarium microcosms were used to study the effects of nitrogen source and aeration mode on the growth and species changes of algae in freshwater. Nitrate nitrogen(NO3(-) -N) and ammonia nitrogen(NH4(+) -N) were used as nitrogen sources. For each nitrogen source, four modes of aeration were selected, including control, continuous aeration, aeration during the day, and aeration at night. In the early stage of the experiment, algae in the NH4(+) -N treatment experiment grew well. In the later stage, algae in the NO3(-) -N treatment experiment grew better. For different aeration modes, continuous aeration show varied effects on algae growth in the two nitrogen source treatments. Day-only aeration had little effect on algae growth. Night-only aeration inhibited algae growth considerably. In NH(+) -N treatments, cyanophyta became dominant species easily. In contrast, chlorophyta dominated in NO3(-) -N treatments.

Influences of copper speciation on toxicity to microorganisms in soils.

OBJECTIVE: To investigate the relationship between copper speciation and microbial features (microbial communities and copper tolerance level) in order to determine the adverse effect of different forms of Cu on microorganisms. METHODS: Tessier's sequential extraction procedure was used to qualify the different Cu forms (exchangeable, carbonate bound, Fe/Mn oxide bound, residue and organic matter bound), and the copper tolerance level (expressed as IC50, influence concentration) was measured by the plate-count method. RESULTS: By simple correlation analysis, the IC50 was positively correlated with the concentration of exchangeable Cu (R2 = 0.8204), while weakly correlated with other forms of Cu. CONCLUSION: The bacterial community tolerance increases in the copper-contaminated soil while sensitive bacteria decrease in the copper-contaminated soils. The exchangeable Cu exerts high toxicity to microbial communities.