Noncovalent interactions between aromatic compounds and dissolved humic acid examined by nuclear magnetic resonance spectroscopy

We examined the molecular-level interactions of aromatic compounds with a humic acid that was extensively characterized with one- and two-dimensional nuclear magnetic resonance (NMR) spectroscopy. Interactions of target compounds were evaluated by monitoring their NMR relaxation properties. Solid-state NMR revealed that the humic sample contains paraffinic carbon (31%), substituted aliphatic carbon (30%), and aromatic carbon (28%). The liquid-state experiments further identified amino acids, a range of carbohydrates, methoxylated aromatics (likely derived from lignin), and a series of aliphatic chains. The 13C spin-lattice relaxation time (T1) of site-specifically labeled naphthalene, 1-naphthol, and quinoline was found to decrease with increasing additions of humic acid. The 1H T1 values also were measured and demonstrated that the association with the humic acid was not specific because all the protons acquired the T1 value of the humic acid at the same rate. The lack of a chemical shift change and an increase in signal line broadening indicates that the interaction between these compounds and humic acid is noncovalent. These interactions were detected at low humic concentrations (5 mg C/L) and suggest that low concentrations of humic material, which are prevalent in both aquatic and terrestrial systems, will significantly affect the fate and transport of contaminants in the environment.     

Interaction between carbamazepine and humic substances: a fluorescence spectroscopy study

Carbamazepine is a popular drug that has been detected in natural environments, but little is known about its biogeochemical cycling, influencing factors, and eco-environmental effects in aquatic ecosystems. Interaction between carbamazepine and humic substances, including fulvic and humic acids, was studied using three-dimensional excitation-emission matrix fluorescence spectroscopy and synchronous-scan fluorescence spectroscopy. The intrinsic fluorescence of humic substances was quenched on the addition of carbamazepine, and static quenching was the primary mechanism. The binding parameters on their interaction, including the conditional binding constants (log K) and binding capacities (C(L)), were estimated by the Ryan-Weber nonlinear theory equation. Log K ranged from 3.41 to 5.04 L/mol at 25 degrees C and pH 7.0. The influence of pH on the complexation and the competition between carbamazepine and Cu(II) for fluorescence-binding sites also were discussed. The present results would be helpful in understanding the fate and biogeochemical cycling of other pharmaceuticals and personal care products in aquatic ecosystems.     

The role of the characteristics of humic substances in binding with benzo[h]quinoline

The binding constants (K(DOC)) of the mixture of benzo[h]quinoline and its protonated analog, benzo[h]quinolinium, to four types of humic substances obtained from the International Humic Substances Society were determined by the fluorescence quenching method. A simple mixing model was used to eliminate the fluorescent interference from the minor analog in the solution and to deduce K(mix), which represents the overall binding as the sum of that for the individual analogs. The characteristics of humic substances, especially their hydrophobicity and aromaticity, established by principal component analysis of structural and elemental compositions, were the main determinants of the binding affinity with both benzo[h]quinoline and benzo[h]quinolinium (K(BQ) and K (BQH+) across a range of pH values. The strongest overall affinity of benzo[h]quinoline for humic substances is observed near pH 4 and with more hydrophobic humic substances, which suggests possible choices in attempts at remediation of benzo[h]quinoline containing particles with humic substances.     

Bis-pyrazolines: synthesis, characterization and antiamoebic activity as inhibitors of growth of Entamoeba histolytica

The cyclization of chalcone with N-4 substituted thiosemicarbazides under basic condition led to the formation of new compounds, thiocarbamoyl bis-pyrazoline derivatives. The structure of the compounds were elucidated by UV, IR, (1)H NMR, (13)C NMR and ESI-MS spectral data and thermogravimetric analysis, and their purities were confirmed by elemental analyses. The antiamoebic activity of these complexes was evaluated by microdilution method against HM1:IMSS strain of Entamoeba histolytica and the results were compared with the standard drug, metronidazole. Structure-activity relationship shows that the compound with aromatic substituents at the thiocarbamoyl group was more active than those with the cyclic groups. However, it was clear from the IC(50) values that the compounds 15 and 20 are more active and both showed a structural resemblance having an electron withdrawing groups attached to the phenyl ring. MTT assay showed that all the compounds are non-toxic to human kidney epithelial cell line.     

The use of non-invasive probes and (13)C nuclear magnetic resonance spectroscopy to assess liver metabolism in humans

Two new methods to assess liver metabolism in humans will be discussed, non-invasive probes and (13)C NMR (nuclear magnetic resonance) spectroscopy. Hepatic UDP-glucose and alpha-ketoglutarate can be sampled by non-invasive probes. This method has been used to quantitate the contribution of the indirect pathway to liver glycogen formation and to estimate relative flow rates and carbon exchange in the Krebs cycle. (13)C NMR spectroscopy has been developed to measure liver glycogen concentrations in vivo. Using this method in combination with measurements of whole body glucose production during fasting, the contribution of gluconeogenesis has been calculated.     

饮用水中消毒副产物研究进展

从饮用水中消毒副产物 (DBPS)种类、毒性、流行病学调查以及饮用水中的分布状况 ,综述了DBPS研究的进展 ;并且从相应的卫生标准或限量值的制定以及去除方法等方面 ,综述了管理和治理情况。结果发现 ,经加氯消毒后的饮用水中DBPS 的种类很多 ,饮用水中存在的主要物质为三卤甲烷和卤乙酸类的物质 ,对人体毒性较大的物质是三卤甲烷、卤乙酸、溴酸盐和亚氯酸盐。国内外饮用水中DBPS 卫生标准或限量值在不断修改或补充 ,监测指标在不断增多 ,限量值在不断加严 ,其目的是利用消毒剂消灭病原体的同时 ,将其对人体危害降至最低。     

Structural and functional approach to studying pesticide side-effects on specific soil functions

The microbial communities in the soil are responsible for material cycling and thus also for maintaining the fertility of agricultural soils. In order to assess pesticide side effects on the soil processes, detailed knowledge is required about the structure and function of the soil microflora. Therefore, the degradation and humification of 14C-labeled maize straw was studied in process-oriented microcosms. Apart from a native orthic luvisol, a heat-treated soil was used that has been freed from organic carbon by incineration at 600 degrees C. Microbial communities involved in the turnover of the crop residues were investigated using denaturing gradient gel electrophoresis (DGGE) of 16S rDNA sequences. Both 13C-nuclear magnetic resonance (NMR) spectroscopy and gel permeation chromatography were used to analyze humic acids produced in the microcosms. To evaluate the sensitivity of the microcosms, the influence of the fungicide dithianon was used in a case study at a concentration of 50 mg/kg. Microbial activity was reduced because of the application of the pesticide, especially in the native soils, while mineralization of 14C-labeled maize straw was only slightly affected. The buildup of fungal biomass was inhibited for at least three weeks. Despite these effects on the microbial communities, no significant differences in the humification products after 26 weeks of incubation were observed.     

Identification of mobile aliphatic sorptive domains in soil humin by solid-state 13C nuclear magnetic resonance

Many sorption studies aim to elucidate organic matter structure and contaminant sorption relationships. Through this pursuit, a great deal of insight has been gained about contaminant interactions with humic fractions, namely the fulvic and humic acid isolates. Comparatively, less is known about the structure and environmental reactivity of the humin fraction; however, researchers have reported that the humin fraction consistently produces higher sorption coefficients than the corresponding source material and other humic fractions. In this paper, we report on a study that uses solid-state 13C nuclear magnetic resonance (NMR) to characterize six humin samples extracted from soil. In addition, 1-naphthol sorption was measured for each whole-soil and humin sample. With the exception of the peat sample, the humin samples yielded significantly higher organic carbon-normalized sorption coefficients (K(oc)) compared with the whole-soil samples. The solid-state 13C NMR analysis reveals the presence of amorphous, polymethylene-rich domains in all of the humin samples. Other researchers have indicated that these domains exhibit a high affinity for hydrophobic organic contaminants. Consequently, we hypothesize that the concentration of amorphous, polymethylene-rich domains in soil humin is responsible for the high sorption coefficients reported here and by other researchers.     

Syntheses and evaluation of 3-(3-bromo phenyl)-5-phenyl-1-(thiazolo [4,5-b] quinoxaline-2-yl)-2-pyrazoline derivatives

A variety of 3-(3-bromo phenyl)-5-phenyl-1-(thiazolo [4,5-b] quinoxaline-2-yl)-2-pyrazoline were obtained by the refluxing of 1-N-thiocarbamoyl 3,5-diphenyl-2-pyrazoline with 2,3-dichloroquinoxaline. The chemical structures of the compounds were elucidated by UV, IR, (1)H NMR, and (13)C NMR spectroscopy. The purity of the compounds was confirmed by their elemental analysis. The antiamoebic activity of these compounds was evaluated by microdilution method against HMI:IMSS strain of Entamoeba histolytica and the IC(50) values were compared with the standard drug metronidazole. Some of the quinoxaline derivatives showed less IC(50) values than metronidazole. To elucidate the toxic effect, MTT assay was performed using kidney epithelial cell line. The results showed that all the compounds are non-toxic.     

西安地区14 094名育龄妇女TOX、RV、CMV和 HSVI/II感染的流行病学特征分析

目的 了解西安地区育龄妇女TORCH感染的流行病学特征,为优生优育提供参考依据。方法 应用化学发光免疫法检测14094名育龄妇女TORCH抗体IgM和IgG,从季节、年龄、户籍等方面进行流行病学分析,采用SPSS 20.0软件对数据进行卡方（χ2）检验。结果 TORCH - IgG阳性率大于80%的病毒为CMV（90.90%）、RV（83.59%）、HSV I（82.95%）。TORCH - IgM阳性率分别为 CMV（2.31%）、RV（1.42%）、HSV I（0.22%）、HSV II（0.15%）、TOX（0.12%）。不同年龄组TOX - IgM（χ2 = 8.20,P = 0.017）、CMV - IgM（χ2 = 7.55,P = 0.023）、HSV II - IgM（χ2 = 6.74,P = 0.034）阳性率差异有统计学意义;不同季节组RV - IgM（χ2 = 10.40,P = 0.015）阳性率差异有统计学意义;不同户籍组TOX - IgM（χ2 = 5.13,P = 0.024）、CMV - IgM（χ2 = 5.28,P = 0.022）阳性率差异有统计学意义。结论 RV和HSV I对西安地区育龄妇女威胁较小,而TOX、HSV II和CMV威胁较大;其中,年龄因素影响TOX、CMV、HSV II感染,季节因素影响RV感染,户籍因素影响TOX、CMV感染,因此,为进一步降低新生儿出生缺陷率,需加强该地区育龄妇女TORCH感染筛查。     

Temporal variability in trihalomethane and haloacetic acid concentrations in Massachusetts public drinking water systems

Previous epidemiological studies in Massachusetts have reported a risk of adverse health outcomes in relation to disinfection by-product (DBP) exposures. Measurement error due to the use of indirect exposure surrogates can lead to misclassification bias in epidemiological studies; therefore, it is important to characterize exposure variability in these populations to assess the potential for exposure misclassification. We used 19,944 trihalomethane (THM) samples and 9291 haloacetic acid (HAA) samples collected in 201 public water systems (PWSs) in Massachusetts to examine temporal variability under different drinking water sources and disinfection types. Annual and seasonal variability was also examined in 46 PWSs with complete quarterly THM4 (i.e., the sum of 4 individual THMs) data from 1995 to 2004 and 19 PWSs with complete HAA5 (i.e., the sum of 5 individual HAAs) data from 2001 to 2004. The quarterly ratio of THM4 and HAA5 and correlations between THM4, HAA5 and individual DBP species were examined to determine the adequacy of using different exposure surrogates in epidemiological studies. Individual PWSs were used to examine monthly variability in relation to quarterly averages. Based on all available matched samples (n=9003) from 1995 to 2004 data, we found a correlation of 0.52 for THM4 and HAA5. The correlation was stronger among the 62 ground water systems (r_s=0.62) compared to the 81 surface water (r_s=0.45) and 40 mixed water (r_s=0.39) systems. Mean THM4 levels were fairly stable over the 10-year study period for 46 PWSs including 39 PWSs that did not change disinfection. Large reductions (∼40 μg/L) in mean THM4 data were found among seven systems that switched from chlorination to alternative disinfectants. As expected, the highest mean THM4 values were detected for Quarter 3, while the lowest values were found in Quarter 1. The highest HAA5 values were detected in Quarters 2 and 3 and the lowest was found in Quarter 4. Data from four systems showed mean differences up to 66 μg/L (67% change) in successive months and by 46 μg/L compared to quarterly mean concentrations. Although longer-term disinfection by-product temporality may be minimal in this study population, the use of monthly average concentrations for exposure assessment may be needed for some PWSs to minimize misclassification of narrow critical periods of exposure in epidemiological studies.     

光催化去除流水中邻苯二甲酸二丁酯效果评价

目的研究光催化去除连续流水中邻苯二甲酸二丁酯（DBP）效果。方法设定4种不同流速水流25，65，110，190ml／min。采用4种方式进行处理通O3（经臭氧发生器后产生的气体，流量为0．6L／min）；紫外光（uv）照射；UV照射同时通O3；UV同时通空气。在有光催化剂纳米（TiO2）和无催化剂条件下，进行光解实验，测定水中邻苯二甲酸二丁酯的去除率。结果TiO2能够促进DBP迅速光解，流速在190ml／min时，DBP去除率也可达到88．8％。通空气对UV光降解效果不大。甚至降低去除率。紫外光和臭氧共同处理对DBP的降解有一定的协同作用。结论应用光催化在连续流水中可有效降解水中邻苯二甲酸二丁酯。     

Syntheses, characterization and in vitro antiamoebic activity of new Pd(II) complexes with 1-N-substituted thiocarbamoyl-3,5-diphenyl-2-pyrazoline derivatives

Reaction of neutral NS bidentate ligands, 1-N-substituted thiocarbamoyl-3,5-diphenyl-2-pyrazolines, isolated by cyclization of chalcone with N-4-substituted thiosemicarbazide of aromatic amines (1-8), with [Pd(DMSO)(2)Cl(2)] (DMSO=dimethylsulfoxide) leads to the formation of new complexes of the type [Pd(L)Cl(2)] (1a-8a). The structures of the compounds were elucidated by UV, IR, (1)H NMR, (13)C NMR and ESI-MS spectral data and thermogravimetric analysis and their purities were confirmed by elemental analyses. The antiamoebic activity of these complexes was evaluated by microdilution method against HM1:IMSS strain of Entameoba histolytica and the results were compared with the standard drug, metronidazole. Generally palladium complexes showed better activity than their corresponding ligands. Compound 3a showed better IC(50)=0.05 microM as compared to metronidazole IC(50)=1.82 microM.     

Sources and Properties of Natural Organic Matter (NOM) in Water Along the Dongjiang River (the Source of Hong Kong’s Drinking Water) and Toxicological Assay of Its Chlorination By-Products

The Dongjiang River is the major source of the drinking water supply for Hong Kong and also other parts of the Pearl River Delta in China, and the deterioration in the water quality of this river and the excessive levels of trihalomethanes (THMs) in the tap water of some districts in Hong Kong have become a matter of public concern. The main objective of the present study is to investigate the distribution patterns of natural organic matter (NOM) and their association with THM production in the Dongjiang River. We examined the physicochemical and biological properties of the river water and the corresponding sediment elutriate collected from four sampling sites along the Dongjiang River from upstream to downstream and chlorination experiments were conducted. Algal bioassays were performed in order to test the chlorination effects. The results showed that: (1) upstream NOM was derived from terrestrial input, while that at mid- and downstream was most likely derived from phytoplankton; (2) phytoplankton is a major contributor to NOM in the sediments, whereas sediments seem to be the site for major microbial degradation of NOM, biogeochemical recycling of nutrients and a potential NOM pool for the overlaying water during sediment resuspension; (3) dissolved organic carbon (DOC) in surface water is a good indicator for THM production, whereas ultraviolet (UV) absorbance at 254 nm (UV₂₅₄) is a better predictor for THM formation in the elutriates; (4) the bioassay results showed that toxic compounds other than THMs in the chlorinated water are the major factors causing algal growth inhibition.     

Mechanisms regulating bioavailability of phenanthrene sorbed on a peat soil-origin humic substance

The organic matter-mineral complex plays an important role in regulating the fate of hydrophobic organic compounds (HOCs) in the environment. In the present study, the authors investigated the microbial bioavailability of phenanthrene (PHE) sorbed on the original and demineralized humic acids (HAs) and humin (HM) that were sequentially extracted from a peat soil. Demineralization treatment dramatically decreased the 720-h mineralized percentage of HM-sorbed PHE from 42.5 ± 2.6% to 3.4 ± 1.3%, whereas the influence of this treatment on the biodegradability of HA-associated PHE was much lower. Degradation kinetics of HA- and HM-sorbed PHE showed that its initial degradation rate was negatively correlated with the aromatic carbon content of humic substances (p<0.05). This was attributed to the strong interactions between PHE and the aromatic components of humic substances, which hampered its release and subsequent biodegradation. The 720-h mineralized percentage of PHE was inversely correlated with the estimated thickness of the organic matter layer at the surfaces of HAs and HMs. Therefore, in a relatively long term, diffusion of PHE within the organic matter layer could be an important factor that may limit the bioavailability of PHE to bacteria. Results of the present study highlight the molecular-scaled mechanisms governing bioavailability of PHE sorbed on humic substances.     

Synthesis, spectroscopic characterization and antiproliferative evaluation in vitro of novel Schiff bases related to benzimidazoles

A series of novel benzimidazole substituted Schiff bases were synthesized by reaction of aromatic aldehydes with corresponding 2-aminobenzimidazoles. Their structure has been studied by 1H and 13C NMR, IR and UV/Vis spectroscopy. Majority of prepared Schiff bases were tested on their antiproliferative activity in vitro and exerted non-specific antiproliferative activity on the tested cell lines at the highest tested concentration. Compounds 18 and 19 exerted the strongest non-specific antiproliferative effect on all cell lines and a concentration-dependent effect on HeLa and MCF-7 cell lines at micromolar concentrations but simultaneously being highly cytotoxic on human fibroblasts as well.     

Sorption of polar and nonpolar aromatic compounds to two humic acids with varied structural heterogeneity

The major objective of the present study was to evaluate the correlation between structural nature of humic acids (HAs) and sorption affinity of organic compounds with varied polarity. We compared the sorption behavior of three aromatic compounds-nonpolar phenanthrene (PHEN) and 1,2,4,5-tetrachlorobenzene (TeCB) and highly polar 2,4-dichlorophenol (DCP)-to a solid-phase coal humic acid (CHA) and a soil humic acid (SHA) suspended in aqueous solution. The structural nature of HAs was characterized using elemental analysis, ultraviolet absorbance, diffusive reflectance Fourier-transform infrared, and solid-state 13C nuclear magnetic resonance. The two tested HAs have very different structural properties: CHA consists primarily of poly(methylene)-rich aliphatics with high aromatic content and some COO/N-C=O but low polarity, while SHA consists of young materials of lignin, carbohydrates, and peptides with high polarity. In response to the structural heterogeneity of HAs, sorption of nonpolar and more hydrophobic solutes (PHEN, TeCB) to CHA is much greater than that to SHA because of the predominance of hydrophobic effects; however, disparities in sorption affinity between the two HAs become smaller for polar and less hydrophobic DCP because of the major role played by polar interactions. The influence of pH on the sorption of different solutes to the two HAs was also discussed. The results of the present work highlight the importance of structural heterogeneity of both solutes and HAs in the sorption process.     

Naturally occurring iodine in humic substances in drinking water in Denmark is bioavailable and determines population iodine intake

Iodine intake is important for thyroid function. Iodine content of natural waters is high in some areas and occurs bound in humic substances. Tap water is a major dietary source but bioavailability of organically bound iodine may be impaired. The objective was to assess if naturally occurring iodine bound in humic substances is bioavailable. Tap water was collected at Randers and Skagen waterworks and spot urine samples were collected from 430 long-term Randers and Skagen dwellers, who filled in a questionnaire. Tap water contained 2 microg/l elemental iodine in Randers and 140 microg/l iodine bound in humic substances in Skagen. Median (25; 75 percentile) urinary iodine excretion among Randers and Skagen dwellers not using iodine-containing supplements was 50 (37; 83) microg/24 h and 177 (137; 219) microg/24 h respectively (P < 0.001). The fraction of samples with iodine below 100 microg/24 h was 85.0 % in Randers and 6.5 % in Skagen (P < 0.001). Use of iodine-containing supplements increased urinary iodine by 60 microg/24 h (P < 0.001). This decreased the number of samples with iodine below 100 microg/24 h to 67.3 % and 5.0 % respectively, but increased the number of samples with iodine above 300 microg/24 h to 2.4 % and 16.1 %. Bioavailability of iodine in humic substances in Skagen tap water was about 85 %. Iodine in natural waters may be elemental or found in humic substances. The fraction available suggests an importance of drinking water supply for population iodine intake, although this may not be adequate to estimate population iodine intake.     

Impact of coal structural heterogeneity on the nonideal sorption of organic contaminants

Carbonaceous geosorbents (black carbon, coal, and humin/kerogen) play a primary role in the nonideal sorption (isotherm nonlinearity, hysteresis, and multiphasic kinetics) of hydrophobic organic chemicals by soils and sediments. The present study investigated the impact of coal structural heterogeneity on sorption/desorption of two model monoaromatic compounds (1,3-dichlorobenzene and 1,3-dinitrobenzene). Due to the higher degree of aromaticity and condensation, anthracite showed stronger sorption affinity and nonlinearity and slower sorption kinetics than lignite. Removal of humic substances by alkali extraction and/or mineral fraction by acidification did not much affect organic carbon-normalized sorption coefficient to the coal, suggesting nearly complete accessibility of adsorption sites on the condensed organic carbon. However, the treatments greatly increased sorption kinetics and meanwhile alleviated hysteresis of 1,3-dinitrobenzene, as compared with the original lignite. These observations were attributed to the enhanced exposure of high-energy adsorption sites on the condensed organic carbon after exfoliating the surface coverage by humic substances and minerals. An empirical biphasic pseudo-second-order model consisting of a fast sorption phase and a slow sorption phase adequately quantified the overall sorption kinetics for the coal sorbents. The results indicated that the condensed organic carbon, in combination with other structural components, controls the nonideal sorption of unburned coal.