Long-term kinetics study and quantitative characterization of the antioxidant capacities of humic and humic-like substances

Purpose

Humic substances (HS) play important functions in the environment by radical scavenging in biogeochemical redox reactions, thus influencing behavior of pollutants and preventing damage to cell membranes; this is due to antioxidant properties of HS. Previous studies focused primarily on assessing endpoint antioxidant capacity (AOC) of HS. Our work aimed to estimate long-term kinetics of the antioxidant capacities of humic and humic-like substances under different pH in relation to their specific structural features.

Materials and methods

The 10-h kinetic profiles of four standard HS and two fungi-produced humic-like substances (HLS) were established with Trolox equivalent antioxidant capacity (TEAC) approach using the ABTS decolorization assay. Three pH levels (3.75, 4.25, and 6.80) and a broad range of humic material concentrations (0.5–10 mg L^?1) were examined. The data were divided into intervals and fit using exponential functions to evaluate the endpoint AOCs as well as rate constants for the reaction of humic materials with the ABTS radical cation. To further explore the nature of the antioxidant activities of humic materials, the physicochemical features and antioxidant activities of humic compounds were subjected to correlation analysis.

Results and discussion

Our results demonstrated that during the first 40 min, the determined AOCs did not exceed 50 % of the endpoint AOCs for studies of humic materials, indicating that short-term measures of the AOCs of humic materials provide artificially low values due to the presence of slow-acting antioxidant compounds. Due to the instability of ABTS^?+ at neutral and alkaline pH values, only the fast antioxidant moieties of humic materials can be assessed with ABTS decolorization approach under these conditions. Our results show that at acidic pH, the antioxidant activity of HLS is mainly related to the presence of nitrogen-containing groups rather than phenols. However, for HS, both nitrogen-containing compounds and phenolic compounds should be considered.

Conclusions

To obtain clearer information concerning the AOC of humic materials, kinetic profiles should first be established, and then endpoint measurements should be taken at a time when the reaction has reached, or at least neared, the endpoint.

     

Effect of 1-methylcyclopropene on volatile emission and aroma in cv. Anna apples

The rapidly ripening summer apple cultivar Anna was treated with 0.1 micro L(-1) and 1 microL L(-1) 1-methylcyclopropene (MCP) at harvest and kept at 20 degrees C, or stored for 5 weeks at 0 degrees C and then transferred to 20 degrees C. Total volatiles were not reduced by treatment with 0.1 microL L(-1) MCP, but were 70% lower in fruits treated with 1 microL L(-1) MCP than in untreated fruits. Ethylene production was 50% and 95% inhibited by 0.1 microL L(-1) and 1 microL L(-1) MCP, respectively. The volatiles produced by fruit at harvest were predominantly aldehydes and alcohols, with some acetate esters as well as 2-methyl butyl acetate and beta-damascenone. During ripening, the acetate and butyrate esters increased greatly and alcohols and aldehydes decreased. MCP-treated apples retained more alcohols, aldehydes, and beta-damascenone volatiles than did untreated apples. Sensory evaluation found that control and 0.1 microL L(-1) treated apples developed more fruity, ripe, and overall aromas, but the preference was for the 1 microL L(-1) treated apples with a less ripe aroma.     

A Quantum Statistical Approach to Remediation Effect of Humic Substances

Among various remediation factors, dissolved organic matter including humic substances (HS) has substantial effect on environmental contamination significantly changing the contaminant??s degradation, bioavailability, reactivity, and immobilization. However, the effects strongly depend on HS concentrations and their aromaticity index (AI). To understand underlying phenomena of remediation action of HS, which is revealed to occur within a definite interval of HS concentrations in water solution, a quantum statistical approach is supposed. Developing this approach, a model of protons as Fermi particles in humic substances was advanced for the first time and applied to describe transformations of HS molecules, i.e., multipoles into micelle structures, which in turn provide for mediating effects in water. Sufficiently high concentration of micelle granules in water solution exists if the concentration of HS lies within a definite interval. It was demonstrated applying a grand canonical Gibbs distribution method to a statistical ensemble of HS particles. Our approach allows for understanding and quantifying some biological and physiological processes connected with mediating action of HS, as for example the reversible red cell aggregation influenced by HS, adsorption of HS particles by cancer cells, and effect of HS on human resistibility to inflammatory processes of different kinds. Application of our results to water systems may be helpful to optimize waste processing and disposal.     

The mycological properties of medieval culture layers as a form of soil ‘biological memory’ about urbanization

Background, aim, and scope  The mycological properties of soil can offer information about ancient human–landscape interaction, including urbanization. This preposition has been confirmed in our study of the habitation deposits in the medieval Russian settlements (eighth to fourteenth centuries A.D.). Materials and methods  The mycobiota of profiles of anthropogenically transformed soil of excavated medieval settlements were examined in different climate conditions in the European part of Russia. The fungal biomass and biomass structure were evaluated using luminescent microscopy. The isolation and enumeration of microfungi were performed using the method of serial dilutions of soil samples and plating them out on the number of solid media. The isolation of keratinolytic microfungi was performed by hear-bite technique. Results  It was established that in ancient urban soils, the mycobiota may have properties different from those of zone fungal communities. The examined cultural layers of ancient settlements differ from the horizons of the surrounding natural soils because of a bigger rate of fungal spores in fungal biomass, more mosaic distribution of microfungal communities, different species composition and dominant microfungal species, increased incidence of some ecological, and trophic fungal groups (for example, keratinophilic, potentially pathogenic microfungi). Discussion  The mycological characteristics of anthropogenic deposits in the excavated medieval settlements were found to be mainly similar to mycological properties of modern urban soils. Conclusions  These properties of habitation deposits can be interpreted as a kind of “soil mycological memory” of the ancient urban impact. Recommendations and perspectives  Soil mycological characteristics could be used in paleoecological reconstructions and biomonitoring of urban impacts     

Supplementary feeding with thermally treated cereals in common carp (<Emphasis Type="Italic">Cyprinus carpio</Emphasis> L.) pond farming and its effects on water quality,nutrient budget and zooplankton and zoobenthos assemblages

To test the influence of supplementary feeding with thermally treated cereals on nutrient budget and environmental and biotic variables, three different treatments were applied in four experimental ponds: two with thermally treated cereals, one with raw cereal and a control with no supplementary feeding. Water parameters, zooplankton and zoobenthos were analysed from May to October over two consecutive years (2012 and 2013). In addition, nitrogen and phosphorus budgets were calculated as the difference between input (feed, stocked fish) and output (harvested fish). The results showed that type of supplementary feed had no influence on water quality, aside from water transparency. Ponds with added thermally treated cereal had significantly (P < 0.05) lower turbidity and suspended solids (and increased Secchi depth) compared with control. While no significant differences were observed in zooplankton assemblages between the experimental ponds and the control, macrozoobenthos density and biomass were considerably lower in the control pond. High seasonal fluctuations resulted in significant differences in density in 2012 only. The use of thermally treated cereal led to improved carp growth and nutrient budget, with an increase in carp yield and nutrient removal per hectare of pond surface. This result is a win–win situation with 10 % lower feed conversion ratio, increased profits and lower environmental impact.     

Distribution and status of medicinal leeches (genus Hirudo) in the Western Palaearctic: anthropogenic,ecological, or historical effects?

1. Distribution and status of medicinal leeches were re‐considered in the light of the new taxonomy recognizing four Western Palaearctic species: Hirudo medicinalis, Hirudo verbana, Hirudo orientalis and Hirudo troctina. 2. Recent records and new data obtained on expeditions to Ukraine, Russia, Azerbaijan, Kazakhstan, Uzbekistan and the Western Balkans were mapped to obtain an up‐to‐date overview of the distribution. 3. Three hypotheses explaining the current ranges of all Hirudo species were tested. The ecological hypothesis, suggesting a strong impact of large‐scale environmental factors, received the highest support, while anthropogenic influence was minimal, and no historical patterns of refugia and colonization were detected. 4. Mapped localities of all Hirudo species show extensive, belt‐shaped ranges extending from east to west. H. medicinalis is distributed from Britain and southern Norway to the southern Urals and probably as far as the Altai Mountains, occupying the deciduous arboreal zone. H. verbana has been recorded from Switzerland and Italy to Turkey and Uzbekistan, which largely corresponds to the Mediterranean and sub‐boreal steppe zone. H. orientalis is associated with mountainous areas in the sub‐boreal eremial zone and occurs in Transcaucasian countries, Iran and Central Asia. H. troctina has been found in north‐western Africa and Spain in the Mediterranean zone. 5. Based on the data gathered, and considering real and potential threats, global IUCN category Near Threatened is proposed for H. medicinalis, H. verbana, and H. orientalis, while H. troctina can only be assigned to category Data Deficient. Copyright © 2010 John Wiley & Sons, Ltd.     

S-nitrosylation of parkin regulates ubiquitination and compromises parkin's protective function

Parkin is an E3 ubiquitin ligase involved in the ubiquitination of proteins that are important in the survival of dopamine neurons in Parkinson's disease (PD). We show that parkin is S-nitrosylated in vitro, as well as in vivo in a mouse model of PD and in brains of patients with PD and diffuse Lewy body disease. Moreover, S-nitrosylation inhibits parkin's ubiquitin E3 ligase activity and its protective function. The inhibition of parkin's ubiquitin E3 ligase activity by S-nitrosylation could contribute to the degenerative process in these disorders by impairing the ubiquitination of parkin substrates.     

Effect of sowing date on seedling emergence of species with seeds enclosed in a stony endocarp

The aim of the present study was to investigate the effect of the natural sequence of temperature conditions between the time of seed sowing and their germination on dormancy release of Prunus avium, P. mahaleb, P. divaricata, P. laurocerasus, P. spinosa, Cornus mas, C. sanguinea, and Celtis australis seeds which are enclosed in a hard stony endocarp. According to their collection date, the seeds (with the endocarp) of the above species were sown outdoor in summer, autumn, and winter and the number of emerged seedlings was counted during the following two springs. For all species, the first sowing date was immediately after seed collection and cleaning. In all species, seedling emergence occurred in early spring and dormancy was released only after the exposure of seeds to specific season conditions. The exposure of seeds of all studied species, except C. australis, to a period of warm temperatures prior to winter was necessary for dormancy breaking and germination. Autumn sowing of P. laurocerasus and C. sanguinea seeds, which were collected in summer, and the sowing immediately after seed collection of the rest species, resulted in a maximum percentage of seedling emergence in the following spring.