Influence of humic substance adsorptive fractionation on pyrene partitioning to dissolved and mineral-associated humic substances

Changes in pyrene binding by dissolved and mineral-associated humic substances (HS) due to HS adsorptive fractionation processes were examined in model environmental systems using purified Aldrich humic acid (PAHA) and Suwannee River fulvic acid (SRFA). For PAHA, carbon-normalized pyrene binding coefficients for nonadsorbed, residual fractions (Koc(res)) were different from the original dissolved PAHA Koc value (Koc(orig)) prior to contact with the mineral suspensions. A strong positive correlation between pyrene log Koc(res) and log weight-average molecular weight (MWw) for residual PAHA fractions was observed, which was relatively independent of the specific mineral adsorbent used and hypothesized fractionation processes. A strong positive correlation between log Koc(ads) and log MWw was also found for PAHA fractions adsorbed to kaolinite at low mass fraction organic carbon levels, although the relationship was statistically different from the one found with residual PAHA fractions. The same trends and correlations found for PAHA were not observed with SRFA, suggesting that the impacts of HS adsorptive fractionation on changes in hydrophobic organic contaminants binding are also influenced by the source and other biogeochemical characteristics of HS.     

Solid-phase microextraction (SPME) as a tool to predict the bioavailability and toxicity of pyrene to the springtail, Folsomia candida, under various soil conditions

The porewater concentrations of pyrene were estimated by a negligible depletive solid-phase microextraction (SPME) method. The effects of organic matter (OM) and soil aging on the bioavailability of pyrene in soil were investigated by generation of reproductive effect concentrations (EC50) for the euedaphic springtail, Folsomia candida, under various test conditions. The soil used was a sandy loam soil with natural OM content of 2.6% (Askov soil). It was enriched with increasing organic matter concentrations of 5%, 10%, and 20% and was aged for 0, 56, and 112 days. The EC50 values of the springtails increased with increasing OM and aging of the soil. The increase of the OM content in the soil reduced the extractability of pyrene by SPME, as well as the toxicity of pyrene. An aging effect was demonstrated in Askov soil, EC50 values increased with increased contact time. The amounts of pyrene extracted by SPME were significantly affected by the soil concentration. Porewater concentrations determined by SPME decreased with increasing OM and aging. However, the pyrene EC50 porewater concentration remained largely constant at approximately 23 microg L(-1). The results demonstrated that the SPME method is a useful indicator for bioavailability to soil microarthropods.     

Binding of mercury(II) to aquatic humic substances: influence of pH and source of humic substances

Conditional distribution coefficients (K(DOM')) for Hg(II) binding to seven dissolved organic matter (DOM) isolates were measured at environmentally relevant ratios of Hg(II) to DOM. The results show that K(DOM') values for different types of samples (humic acids, fulvic acids, hydrophobic acids) isolated from diverse aquatic environments were all within 1 order of magnitude (10(22.5 +/-1.0)-10(23.5 +/- 1.0)) L kg(-1)), suggesting similar Hg(ll) binding environments, presumably involving thiol groups, for the different isolates. K(DOM') values decreased at low pHs (4) compared to values at pH 7, indicating proton competition for the strong Hg(II) binding sites. Chemical modeling of Hg(II)-DOM binding at different pH values was consistent with bidentate binding of Hg(II) by one thiol group (pK(a) = 10.3) and one other group (pK(a) = 6.3) in the DOM, which is in agreement with recent results on the structure of Hg(II)-DOM bonds obtained by extended X-ray absorption fine structure spectroscopy (EXAFS).     

Sorption of very hydrophobic organic compounds (VHOCs) on dissolved humic organic matter (DOM). 2. Measurement of sorption and application of a Flory-Huggins concept to interpret the data

Sorption phenomena of very hydrophobic compounds (VHOCs, log K(OW) > 5) on dissolved humic organic matter (DOM) are overwhelmingly based on partitioning processes. In this respect, DOM is very similar to "rubbery" soil/sediment OM. To exclude system adsorption effects, the DOM sorption coefficients (K(DOM)) of VHOCs were determined using a dynamic approach based on the VHOCs' aqueous solubility enhancement in the presence of DOM. Partition coefficients are strongly correlated to the analytes' Kow across the alkane, PAH, and PCB groups under study. These three "families" are regarded to be good models of hydrophobic partitioning. On the basis of a uniform one-parameter concept characterizing sorption on amorphous polymers, Hildebrand solubility parameters of amorphous polymeric sorbents, including DOM, and of sorbates can be calculated on the basis of partition coefficients. Likewise, partition coefficients can be estimated using Hildebrand solubility parameters. Literature-based partition coefficients on DOM fit very well in this universal one-parameter concept. On using our own sorption data of PAHs, PCBs, and alkanes on DOM, an almost identical solubility parameter for the DOM polymer under study is obtained. The concept is also very useful in understanding both waterborne and airborne bioconcentration processes, which are considered to be partitioning phenomena.     

Antimony(III) binding to humic substances: influence of pH and type of humic acid

Conditional distribution coefficients (Dom) for Sb(III) binding to three commercial humic acids (terrestrial, coal, and aquatic) were measured at environmentally relevant Sb(III)/DOC ratios and as a function of pH using an equilibrium dialysis method. Maximum binding of Sb(III) was observed around pH 6 for two of the humic acids. The third humic acid showed constant Dom values up to pH 6 and decreasing Dom values for pH > 6. Sb(III)/DOC ratio was found to be important for Dom (20 times higher Dom for 60 times lower Sb(III)/DOC ratio). Moreover, Dom depends on the individual humic acid, suggesting that different functional groups are involved and/or different degrees of stabilization by chelation or H-bridges. Chemical modeling of Sb(III)-humics binding at different pH values is consistent with two binding sites involving (i) a phenolic entity forming a neutral complex and (ii) a carboxylic entity forming a negatively charged complex. Under environmentally relevant conditions, over 30% of total Sb(III) may be bound to natural organic matter.     

Carbohydrate polymers of chirata (Swertia chirata) leaves: Structural features, in vitro anti-oxidant activity and fluorescence quenching study

Chirata (Swertia chirata) is widely used in Indian folk medicine for the prevention of various disorders. Herein, we analyzed the water-extracted carbohydrate polymer (WECP) of this herb using chemical, chromatographic, and spectroscopic methods. The anti-oxidant capacity of this fraction was studied by ferric reducing anti-oxidant power (FRAP) and DPPH radical assays. Effect of WECP on bovine serum albumin spectrum (BSA) was determined using excitation wavelength of 282 nm. Anion exchange chromatography of WECP yielded 5 fractions (F1–F5) with different chemical compositions. The major fraction (F5) was homogeneous, had an apparent molecular mass of 4.5 kDa, and contains both carbohydrates (57%) and phenolics (34%). The anti-oxidant capacities of WECP and F5 were comparable to standard anti-oxidants. Notably, activities of the carbohydrate polymers (F1–F5) correlate with their phenolics content. Fluorescence quenching measurement suggests that F5 can form complex with BSA and the value of the binding constant is K=6.28×10⁵/M.     

Potential function of added minerals as nucleation sites and effect of humic substances on mineral formation by the nitrate-reducing Fe(II)-oxidizer Acidovorax sp. BoFeN1

The mobility of toxic metals and the transformation of organic pollutants in the environment are influenced and in many cases even controlled by iron minerals. Therefore knowing the factors influencing iron mineral formation and transformation by Fe(II)-oxidizing and Fe(III)-reducing bacteria is crucial for understanding the fate of contaminants and for the development of remediation technologies. In this study we followed mineral formation by the nitrate-reducing Fe(II)-oxidizing strain Acidovorax sp. BoFeN1 in the presence of the crystalline Fe(III) (oxyhydr)oxides goethite, magnetite and hematite added as potential nucleation sites. M?ssbauer spectroscopy analysis of minerals precipitated by BoFeN1 in (57)Fe(II)-spiked microbial growth medium showed that goethite was formed in the absence of mineral additions as well as in the presence of goethite or hematite. The presence of magnetite minerals during Fe(II) oxidation induced the formation of magnetite in addition to goethite, while the addition of humic substances along with magnetite also led to goethite but no magnetite. This study showed that mineral formation not only depends on the aqueous geochemical conditions but can also be affected by the presence of mineral nucleation sites that initiate precipitation of the same underlying mineral phases.     

Sorption of Eu(III) on humic acid or fulvic acid bound to hydrous alumina studied by SEM-EDS, XPS, TRLFS, and batch techniques

To identify the effect of humic acid (HA) and fulvic acid (FA) on the sorption mechanism of Eu(III) on organic--inorganic colloids in the environment at a molecular level, surface adsorbed/ complexed Eu(III) on hydrous alumina, HA-, and FA-hydrous alumina hybrids were characterized by using X-ray photoelectron spectroscopy (XPS) and time-resolved laser fluorescence spectroscopy (TRLFS). The experiments were performed in 0.1 mol/L KNO3 or 0.1 mol/L NaClO4 under ambient conditions. The pH values were varied between 2 and 11 at a fixed Eu(III) concentration of 6.0 x 10(-7) mol/L and 4.3 x 10(-5) mol/L. The different Eu(III)/FA(HA)/hydrous alumina complexes were characterized by their fluorescence emission spectra ((5D0-F1)/ (5D0 --> 7F2)) and binding energy of Eu(III). Inner-sphere surface complexation may contribute mainly to Eu(III) sorption on hydrous alumina, and a ternary surface complex is formed at the HA/ FA-hydrous alumina hybrid surfaces. The sorption and species of Eu(III) in ternary Eu-HA/FA-hydrous alumina systems are not dominated by either HA/FA or hydrous alumina, but are dominated by both HA/FA and hydrous alumina. The results are important for understanding the sorption mechanisms and the nature of surface adsorbed Eu(III) species and trivalent chemical homologues of Eu(III) in the natural environment.     

现代分析测试技术在印染行业的应用(十八)——分析测试技术在纺织纤维材料鉴别中的应用

对各种新型和传统纺织纤维材料的结构、性能进行分析，提出了一些对新型纺织纤维材料进行鉴别的思路和方法，包括纤维素纤维、动物蛋白质纤维和合成纤维的鉴别。     

Collagenase activity and protein hydrolysis as related to spoilage of iced cod (Gadus morhua)

Collagenase activity and changes in muscular protein of iced Atlantic cod stored for 9 days were studied. The crude fish muscle extract showed maximum collagenase-like activity against bovine insoluble tendon collagen at 48 h of incubation at 37 °C. Collagenase activity against synthetic substrate increased (P<0.05), especially for fish in initial and advanced stages of decomposition. These results suggest that endogenous collagenases and other proteases may be responsible for the destruction of fine collagenous fibrils in the skeletal muscle of cod. The content of titin 1 decreased when decomposition was advanced. Moreover, a progressive degradation of sarcoplasmic proteins with a molecular weight of 100, 94, 85 and 80 kDa was observed. Results suggest that softening of cod muscle during iced storage is caused more by collagenase activity than by proteolysis of myofibrils.     

现代分析测试技术在印染行业的应用(十七)——织物风格的客观评定体系及其计算方法的进展与应用

阐述了织物风格的客观评定体系及其计算方法的研究进展；介绍了KES-F和FAST织物风格仪；分析比较了当前研究织物风格的几种重要方法：基于神经网络的织物风格识别系统、灰度关联分析法和物理仿真技术等。     

Chemotherapy of fascioliasis. II. 4-cyano-2-iodo-6-nitrophenol (nitroxynil) and related compounds

A series of halogenated nitro- and cyano-phenols has been synthesised for structure-activity studies against the liver fluke, Fasciola hepatica. Hie functional groups of the most effective compound, 4-cyano- 2-iodo-6-nitrophenol (nitroxynil), have been modified in several ways.     

Metal flux and dynamic speciation at (bio)interfaces. Part I: Critical evaluation and compilation of physicochemical parameters for complexes with simple ligands and fulvic/humic substances

In the computation of metal flux in aquatic systems, at consuming surfaces like organism membranes, diffusion processes of metal ions, ligands, and complex species, as well as the kinetic and thermodynamic aspects of their chemical interactions, must be considered. The properties of many natural ligands, however, are complicated (formation of successive complexes for simple ligands, polyelectrolytic properties and chemical heterogeneity for macromolecular ligands, large size distribution and fractal structure for suspended aggregates). These properties should be properly modeled to get the correct values of the chemical rate constants and diffusion coefficients required for flux computations. The selection of the most appropriate models and parameter values is far from straightforward. This series of papers discusses the various models and compiles the parameters needed for the three most important types of complexants found in aquatic systems: the small, simple ligands, the fulvic and humic compounds, and the colloidal "particles" or aggregates. In particular, new approaches are presented to compute the rate constants of metal complex formation, with both fulvics/humics and particles/aggregates. The method to include the site distribution of fulvics/humics and the size distribution of particles/aggregates in metal flux computation at consuming interfaces is also discussed in detail. These models and parameters are discussed critically and presented in the same framework, forthe computation of metal flux in presence of any of the above complexants or mixtures. Such parameters, largely spread in the literature, are gathered here and selected specifically for environmental applications. The focus in Part I of the series is on simple ligands and fulvic/humic compounds. Part II deals with particulate and aggregate complexants.     

现代分析测试技术在印染行业的应用(十六)——织物起毛起球的成因、测试方法及改善途径

从纤维性能和纱线结构、织物的组织结构等方面分析不同织物起毛起球的原因,系统介绍了有关织物起毛起球的测试方法（如马丁代尔法,箱式法,随机乱翻法,圆轨迹法）及其适用范围,并就如何改善织物起毛起球性能提出建议。     

Collaborative Longitudinal Evaluation of Keratoconus (CLEK) Study: methods and findings to date.

PURPOSE: To describe baseline and longitudinal findings of the Collaborative Longitudinal Evaluation of Keratoconus (CLEK) Study. METHODS: The CLEK Study is an 8-year, multi-center, natural history study of 1209 patients with keratoconus who were examined annually for 8 years. Its goals are to prospectively characterize changes in vision, corneal curvature, corneal status, and vision-specific quality of life. RESULTS: CLEK Study subjects had a mean age at baseline of 39.3+/-10.9 years. At study entry, 65% of the patients wore rigid contact lenses, and 14% reported a family history of the disease. Subjects exhibited a 7-year decrease in high- (2.03 letters) and low- (4.06 letters) contrast, best-corrected visual acuity, with 19% demonstrating decreases of 10 or more letters in high-contrast, best-corrected acuity and 31% of subjects demonstrating decreases of 10 or more letters in low-contrast, best-corrected acuity in at least one eye. Subjects exhibited an average 8-year increase in corneal curvature of 1.60D in the flat corneal meridian, with 24% demonstrating increases of 3.00D or more. The 8-year incidence of corneal scarring was 20%, with younger age, corneal staining, steeper baseline corneal curvature, contact lens wear, and poorer low-contrast visual acuity predictive of corneal scarring. Data from the National Eye Institute Visual Function Questionnaire suggest that the effect of keratoconus on vision-specific quality of life is disproportionate to its low prevalence and clinical severity. CONCLUSION: Although we report measures of disease severity and visual function across the CLEK sample, clinicians can begin to envisage the course of keratoconus in individual patients by determining whether factors predictive of disease progression are present in those patients.     

Technological properties of chickpea (Cicer arietinum): Production of snacks and health benefits related to type-2 diabetes

Chickpea (Cicer arietinum) is one of the most consumed pulses worldwide (over 2.3 million tons enter the world market annually). Some chickpea components have shown, in preclinical and clinical studies, several health benefits, including antioxidant capacity, and antifungal, antibacterial, analgesic, anticancer, antiinflammatory, and hypocholesterolemic properties, as well as angiotensin I-converting enzyme inhibition. In the United States, chickpea is consumed mostly in the form of hummus. However, the development of new products with value-added bioactivity is creating new opportunities for research and food applications. Information about bioactive compounds and functional properties of chickpea ingredients in the development of new products is needed. The objective of this review was to summarize available scientific information, from the last 15 years, on chickpea production, consumption trends, applications in the food industry in the elaboration of plant-based snacks, and on its bioactive compounds related to type 2 diabetes (T2D). Areas of opportunity for future research and new applications of specific bioactive compounds as novel food ingredients are highlighted. Research is key to overcome the main processing obstacles and sensory challenges for the application of chickpea as ingredient in snack preparations. The use of chickpea bioactive compounds as ingredient in food products is also a promising area for accessibility of their health benefits, such as the management of T2D.     

Free amino acids and peptides as related to antioxidant properties in protein hydrolysates of mackerel (Scomber austriasicus)

Mackerel (Scomber austriasicus) hydrolysates were prepared by an autolytic process and accelerated hydrolysis with a commercial enzyme, Protease N. Changes in the levels and compositions of free amino acids and small peptides during hydrolysis were investigated to find out their relationships with antioxidant activities. Increased levels of free amino acids, anserine, carnosine and other peptides of the hydrolysates obtained with protease were much higher than those by autolysis. Different antioxidant measurements including the inhibition of linoleic acid autoxidation, the scavenging effect on ,-diphenyl-β-picrylhydrazyl free radical, and the reducing power showed that mackerel hydrolysates possessed noticeable antioxidant activities. A good correlation existed between the amount of peptides and antioxidant activity. Three peptide fractions were separated from the hydrolysate by size exclusion chromatography. Results revealed that the peptide with molecular weight of approximately 1400 Da possessed a stronger in vitro antioxidant activity than that of the 900 and 200 Da peptides.     

Alleviation of Cu and Pb rhizotoxicities in cowpea (Vigna unguiculata) as related to ion activities at root-cell plasma membrane surface

Cations, such as Ca and Mg, are generally thought to alleviate toxicities of trace metals through site-specific competition (as incorporated in the biotic ligand model, BLM). Short-term experiments were conducted with cowpea (Vigna unguiculata L. Walp.) seedlings in simple nutrient solutions to examine the alleviation of Cu and Pb toxicities by Al, Ca, H, Mg, and Na. For Cu, the cations depolarized the plasma membrane (PM) and reduced the negativity of ψ(0)(o) (electrical potential at the outer surface of the PM) and thereby decreased {Cu(2+)}(0)(o) (activity of Cu(2+) at the outer surface of the PM). For Pb, root elongation was generally better correlated to the activity of Pb(2+) in the bulk solution than to {Pb(2+)}(0)(o). However, we propose that the addition of cations resulted in a decrease in {Pb(2+)}(0)(o) but a simultaneous increase in the rate of Pb uptake (due to an increase in the negativity of E(m,surf), the difference in potential between the inner and outer surfaces of the PM) thus offsetting the decrease in {Pb(2+)}(0)(o). In addition, Ca was found to alleviate Pb toxicity through a specific effect. Although our data do not preclude site-specific competition (as incorporated in the BLM), we suggest that electrostatic effects have an important role.