Molybdenum Bioavailability and Asymbiotic Nitrogen Fixation in Soils are Raised by Iron (Oxyhydr)oxide-Mediated Free Radical Production.

Nitrogen (N) fixation in soils is closely linked to microbially mediated molybdenum (Mo) cycling. Therefore, elucidating the mechanisms and factors that affect Mo bioavailability is crucial for understanding N fixation. Here, we demonstrate that long-term (26 years) manure fertilization increased microbial diversity and content of short-range ordered iron (oxyhydr)oxides that raised Mo bioavailability (by 2.8 times) and storage (by ∼30%) and increased the abundance of nifH genes (by ∼14%) and nitrogenase activity (by ∼60%). Nanosized iron (oxyhydr)oxides (ferrihydrite, goethite, and hematite nanoparticles) play a dual role in soil Mo cycling: (i) in concert with microorganisms, they raise Mo bioavailability by catalyzing hydroxyl radical (HO•) production via the Fenton reactions and (ii) they increase Mo retention by association with the nanosized iron (oxyhydr)oxides. In summary, long-term manure fertilization raised the stock and bioavailability of Mo (and probably also of other micronutrients) by increasing iron (oxyhydr)oxide reactivity and intensified asymbiotic N fixation through an increased abundance of nifH genes and nitrogenase activity. This work provides a strategy for increasing biological N fixation in agricultural ecosystems.

Adverse Psychological Reactions and Psychological Aids for Medical Staff During the COVID-19 Outbreak in China.

Background: The outbreak of the novel coronavirus disease COVID-19 caused panic and psychological stress throughout the World. We investigated the extent of adverse psychological reactions in two medical staff groups in China, and explored the importance of online psychological assistance for them. Methods: A cross-sectional online survey including Hospital Anxiety and Depression Scale (HADS) and Insomnia Severity Index (ISI) was utilized to assess anxiety, depression, and insomnia. Propensity score matching (PSM) was applied to match sex and age between the two groups. Differences in the prevalence of adverse psychological reactions between the two groups were compared by a Chi-square test. A multivariate logistic regression analysis was utilized to search for associated adverse psychological reaction factors of two groups. Results: A total of 2,920 medical staff took part in the survey, including 470 frontline and 2,450 non-frontline medical staff. The risk of the frontline group experiencing anxiety, depression, insomnia-early, insomnia-middle, and insomnia-late were 1.16, 1.28, 1.26, 1.22, 1.28 times those of the non-frontline group after PSM. For frontline medical staff, the spinsterhood state (OR = 1.23, 95% CI: 1.00-1.51; P = 0.05) was a risk factor for anxiety. Bachelor or college degree (OR = 2.23, 95% CI: 1.24-4.02, P = 0.01) and a contact history with COVID-19 patients (OR = 1.62, 95% CI: 1.10-2.40; P = 0.02) were risk factors for insomnia. For non-frontline medical staff, being a woman (OR = 1.49, 95% CI: 1.08-2.06, P = 0.01) was a risk factor for anxiety, whilst being in a middle age group was a protective factor for anxiety (OR = 0.70, 95% CI: 0.50-0.99, P = 0.04) and depression (OR = 0.65, 95% CI: 0.45-0.93, P = 0.02). Being a woman (OR = 1.47, 95% CI: 1.14-1.89, P = 0.003) and working in a COVID-19 unit (OR = 1.31, 95% CI: 1.11-1.54, P = 0.001) were risk factors for insomnia, whilst the spinsterhood state (OR = 0.80, 95% CI: 0.67-0.95; P = 0.01) was a protective factor for insomnia. Online forms of psychological aid were all popular with medical staff. Conclusions: The prevalence of anxiety, depression, and insomnia in frontline medical staff was significantly higher than in the non-frontline group. Appropriate intervention methods should be adopted according to the different influencing factors of the two groups. Online psychological aid was the preferred mechanism for relieving psychological problems.

Intrinsic enzyme-like activity of magnetite particles is enhanced by cultivation with Trichoderma guizhouense.

Fungal-mineral interactions can produce large amounts of biogenic nano-size (~ 1-100 nm) minerals, yet their influence on fungal physiology and growth remains largely unexplored. Using Trichoderma guizhouense NJAU4742 and magnetite (Mt) as a model fungus and mineral system, we have shown for the first time that biogenic Mt nanoparticles formed during fungal-mineral cultivation exhibit intrinsic peroxidase-like activity. Specifically, the average peroxidase-like activity of Mt nanoparticles after 72 h cultivation was ~ 2.4 times higher than that of the original Mt. Evidence from high resolution X-ray photoelectron spectroscopy analyses indicated that the unique properties of magnetite nanoparticles largely stemmed from their high proportion of surface non-lattice oxygen, through occupying surface oxygen-vacant sites, rather than Fe redox chemistry, which challenges conventional Fenton reaction theories that assume iron to be the sole redox-active centre. Nanoscale secondary ion mass spectrometry with a resolution down to 50 nm demonstrated that a thin (< 1 µm) oxygen-film was present on the surface of fungal hyphae. Furthermore, synchrotron radiation-based micro-FTIR spectra revealed that surface oxygen groups corresponded mainly to organic OH, mineral OH and carbonyl groups. Together, these findings highlight an important, but unrecognized, catalytic activity of mineral nanoparticles produced by fungal-mineral interactions and contribute substantially to our understanding of mineral nanoparticles in natural ecosystems.

Biological removal of cadmium from biogas residues during vermicomposting, and the effect of earthworm hydrolysates on Trichoderma guizhouense sporulation.

The removal efficiency of Cd from biogas residues (BR) by earthworms (Eisenia fetida) during vermicomposting and the optimum addition of earthworm hydrolysates for production of Trichoderma guizhouense NJAU 4742 spores were determined. The results showed that vermicomposting could effectively remove Cd (up to 18.9%) from the BR. Synchrotron radiation based FTIR spectromicroscopy demonstrated a weakened correlation between functional groups after vermicomposting, suggesting that the activity of earthworms affects the binding sites and bioavailability of heavy metals. Under optimum conditions, the hydrolysis rate of earthworms was ~97% and the removal efficiency of Cd was up to 93%. Furthermore, addition of 20% of earthworm hydrolysate promoted the largest production of Trichoderma sporulation (~2.95 × 108 cfu/g straw), indicating the possibility of earthworm hydrolysates promoting the growth of Trichoderma guizhouense is a suitable way to recycle earthworms after vermicomposting.

Mechanisms of Adsorption of Heavy Metal Cations from Waters by an Amino Bio-Based Resin Derived from Rosin.

Rosin derived from conifer trees is used as the basis for a novel environmentally-friendly adsorbent prepared from a sustainable resource. After treatment with ethylenediamine, ethylenediamine rosin-based resin (EDAR) is produced, which possesses cation exchange capacity that is comparable to that of the best commercial synthetic resins. This is demonstrated by its application to the removal of Pb, Cd, and Cu from water, in single and multicomponent systems. Maximum uptake was obtained at pH 5 and in the order Pb(II) > Cd(II) > Cu(II). The maximum adsorption of Pb was ~1.8 mmol/g, but the adsorption process resembled the Freundlich isotherm, whereas the adsorption of Cd(II) and Cu(II) followed the Langmuir isotherm. In the multicomponent systems, there was direct competition between Pb and Cd for sorption sites, whereas the results with Cu indicated it had a preference for different types of sites compared to Pb and Cd. The EDAR resin could be efficiently regenerated and used repeatedly with only a small decrease in performance. Characterization of EDAR, and investigations of its adsorption mechanisms using physical, spectroscopic, and theoretical techniques, including fourier transform infrared spectroscopy (FTIR), 13C nuclear magnetic resonance (13C NMR), scanning electron microscope (SEM), Brunauer Emmett Teller (BET) method, elemental analysis, thermogravimetric analysis (TGA), and molecular dynamics calculations, showed that amino groups have a critical role in determining the cation adsorption properties. We conclude that this new adsorbent derived from an abundant natural material has the potential to make valuable contributions to the routine removal of heavy metal ions (HMs) from drinking water and wastewater.

Adsorption of phenolic compounds from water by a novel ethylenediamine rosin-based resin: Interaction models and adsorption mechanisms.

This study describes the adsorption performance of a novel ethylenediamine rosin-based resin (EDAR) for several industrially-important phenolic compounds. Its removal of 4-nitrophenol (4-NP) from water was comparable to or better than many commercial resins, although it was less effective with other phenols (i. e., phenol, 2,4-dichlorophenol, 4-chlorophenol, and 4-methylphenol). Experimental conditions for batch adsorption of 4-NP by EDAR are evaluated, the adsorption kinetics is well described by the pseudo-second-order model (R2 > 0.99) and isotherm follows the Langmuir isotherm model (R2 > 0.99), with the maximum monolayer adsorption capacity of 82 mg g-1 at pH 6.0 and 293 K. The thermodynamic parameters indicate that the adsorption is spontaneous and endothermic. Also, quantum chemistry calculations indicate involvement of hydrogen-bonding between 4-NP and amino groups of EDAR. 4-NP was efficiently desorbed from the loaded EDAR resin by 0.2 M HCl, and the resin could be recycled with only a small decrease in its initial adsorption capacities. Thus, EDAR is a promising adsorbent for the removal of 4-NP during water treatment.

Direct identification of Cu(II) species adsorbed on rosin-derived resins using electron paramagnetic resonance (EPR) spectroscopy.

Resins derived from natural rosin have been described recently as environmentally-friendly adsorbents with potential uses in the clean-up of wastewaters and the treatment of drinking waters. However, in order to improve the design of these products it is important to understand the chemical mechanisms through which they act. We now describe the combined use of EPR spectroscopy and Cu(II) to probe directly the metal coordination environment after uptake by various rosin-derived products. Clear distinctions are demonstrated between the copper bonding in different adsorbent preparations. Furthermore, in the case of nitrogen cross-linked products, the spectral parameters also provide information on the number of nitrogen atoms in the immediate atomic environment of the copper atom when covalent bonding is involved. This methodology works well for adsorption from solutions containing multiple components, because only those that are paramagnetic are detected, and different types of paramagnetic metal ion produce distinctly different EPR spectra.

Performance of a zeolite modified with N,N-dimethyl dehydroabietylamine oxide (DAAO) for adsorption of humic acid assessed in batch and fixed bed columns.

Factors that affect adsorption of a synthetic humic acid (HA) on a zeolite modified with the surfactant N,N-dimethyl dehydroabietylamine oxide (DAAO) (SMZ) were investigated in batch and fixed bed column experiments. Adsorption increased with increasing HA concentrations and contact time, but decreased with increasing pH, temperature, and ionic strength. Adsorption of HA on SMZ was increased by the presence of the cations Ca2+ and Mg2+, whereas anions such as NO3 -, HCO3 -, SO4 2-, and PO4 3- showed the opposite trend, and competed with HA adsorption. HA adsorption on SMZ was well-fitted by pseudo-second order kinetics, and described by the Langmuir isotherm model. The maximum adsorption capacity in batch experiments calculated from the Langmuir adsorption isotherm was about 126 mg g-1. Thermodynamic calculations showed that HA adsorption on the zeolite with bilayer DAAO coverage was spontaneous and exothermic. Optimum desorption was obtained using 0.1 M NaOH with a recovery of 94%. The HA adsorption capacity of SMZ at the breakthrough point was greatly influenced by bed depth, and could be described by the Thomas model. Adsorption mechanisms are interpreted as involving mainly hydrogen bonding and electrostatic interactions.

Understanding the Effects of Roasting on Antioxidant Components of Coffee Brews by Coupling On-line ABTS Assay to High Performance Size Exclusion Chromatography.

INTRODUCTION: Coffee is a widely consumed beverage containing antioxidant active compounds. During roasting the phytochemical composition of the coffee bean changes dramatically and highly polymeric substances are produced. Besides chlorogenic acids that are already present in green coffee beans, melanoidins show antioxidant capacity as well. OBJECTIVE: To employ post-column derivatisation by coupling high performance size exclusion chromatography (HPSEC) to an antioxidant assay to investigate the effect of roasting on the properties of antioxidant active compounds in coffee brews. METHODOLOGY: We have investigated the antioxidant capacity of Coffea arabica (Arabica) and C. canephora (Robusta) beans that were roasted over the full spectrum of roast conditions (four roasting speeds to three roast degrees) by comparing the results from HPSEC coupled on-line to the ABTS assay with those from two batch assays, Folin Ciocalteu (FC) and oxygen radical absorbance capacity (ORAC) assay. RESULTS: The antioxidant capacity showed a general decrease towards slower and darker roasted coffee for all three assays, indicative of heat degradation of active compounds. Hence, low molecular weight (LMW) compounds such as chlorogenic acids (CGAs) decreased progressively already from relatively mild roasting conditions. In contrast, high molecular weight (HMW) compounds (e.g. melanoidins) increased from light to dark roast degrees with lowering magnitude towards slower roasting profiles. CONCLUSION: By coupling HPSEC on-line to the ABTS assay we were able to separately quantify the contribution of HMW and LMW compounds to the total antioxidant capacity, increasing our understanding of the roast process. © 2016 The Authors. Phytochemical Analysis Published by John Wiley & Sons Ltd.

Formation of iodo-trihalomethanes, iodo-acetic acids, and iodo-acetamides during chloramination of iodide-containing waters: Factors influencing formation and reaction pathways.

This study investigated systematically the factors influencing the formation of iodinated disinfection by-products (I-DBPs) during chloramination of I--containing waters, including reaction time, NH2Cl dose, I- concentration, pH, natural organic matter (NOM) concentration, Br-/I- molar ratio, and water matrix. Among the I-DBPs detected, iodoform (CHI3), iodoacetic acid (IAA), diiodoacetic acid (DIAA), triiodoacetic acid (TIAA), and diiodoacetamide (DIAcAm) were the major species produced from reactions between reactive iodine species (HOI/I2) and NOM. A kinetic model involving the reactions of NH2Cl auto-decomposition, iodine species transformation and NOM consumption was developed, which could well describe NH2Cl decay and HOI/I2 evolution. Higher concentrations of CHI3, IAA, DIAA, TIAA, and DIAcAm were observed in chloramination than in chlorination, whereas IO3- was only formed significantly in chlorination. Maximum formation of I-DBPs occurred at pH 8.0, but acidic conditions favored the formation of iodinated haloacetic acids and DIAcAm. Increasing Br-/I- molar ratio from 1 to 10 did not increase the total amount of I-DBPs, but produced more bromine-substituting species. In addition, chloramination of 18 model compounds indicated that low-SUVA254 (specific ultraviolet absorbance at 254nm) NOM generally favored the formation of I-DBPs compared to high-SUVA254 NOM. Finally, potential pathways for I-DBPs formation from chloramination of NOM were proposed.

Effect of Copper on Fatty Acid Profiles in Non- and Semifermented Teas Analyzed by LC-MS-Based Nontargeted Screening.

Unsaturated fatty acids are well-known precursors of aroma compounds, which are considered important for green tea quality. Due to the known copper-induced oxidation of unsaturated fatty acids and the broad variability of the amount of copper present in tea infusions, this paper investigates the influence of copper, added at a nontoxic concentration (300 µM) to non- and semifermented teas, on the degradation of fatty acids and fatty acid hydroperoxides thereof. The abundance of fatty acids in green and oolong tea was determined by means of a nontargeted approach applying high-resolution MS/MS. As a result, most of the fatty acids in green and oolong tea were already oxidized prior to copper addition. Addition of 300 µM CuSO4 to the oolong tea sample resulted in a decrease of 13-hydroperoxy-9Z,11E-octadecadienoic acid, an important flavor precursor, from 0.12 ± 0.02 to 0.05 ± 0.01 µM (p = 0.035), and other oxidized fatty acids decreased as well. However, copper-induced degradation of oxidized fatty acids was less pronounced in green tea compared to oolong tea, most likely due to the formation of copper complexes with low-molecular-weight compounds as evidenced by electron paramagnetic resonance spectroscopy.

Rapid screening for anthocyanins in cane sugars using ESR spectroscopy.

Anthocyanin, which is soluble in water and released into sugar steam during extraction, was investigated in this study. The anthocyanin content in refined sugar, plantation white sugar, soft brown sugar and raw sugar was determined using electron spin resonance (ESR) spectroscopy, which was operated at room temperature, and compared with spectra from standard anthocyanin. The ESR spectra of red and violet anthocyanins was predominantly g ≈ 2.0055, which corresponded to an unpaired electron located in the pyrylium ring. Signals for Fe(III) and Mn(II), which naturally occur in plants, were found in raw sugar, soft brown sugar and standard anthocyanin but were absent from refined sugar and plantation white sugar due to the refining process. In addition, the ESR results were correlated with the apparent colour of the sugar, which was determined using the method of the International Commission for Uniform Methods of Sugar Analysis and inductively coupled plasma optical emission spectroscopy.

Antioxidant Generation during Coffee Roasting: A Comparison and Interpretation from Three Complementary Assays.

Coffee is a major source of dietary antioxidants; some are present in the green bean, whereas others are generated during roasting. However, there is no single accepted analytical method for their routine determination. This paper describes the adaption of three complementary assays (Folin-Ciocalteu (FC), ABTS and ORAC) for the routine assessment of antioxidant capacity of beverages, their validation, and use for determining the antioxidant capacities of extracts from coffee beans at different stages in the roasting process. All assays showed a progressive increase in antioxidant capacity during roasting to a light roast state, consistent with the production of melanoidins having a higher antioxidant effect than the degradation of CGAs. However, the three assays gave different numbers for the total antioxidant capacity of green beans relative to gallic acid (GA), although the range of values was much smaller when chlorogenic acid (CGA) was used as reference. Therefore, although all three assays indicated that there was an increase in antioxidant activity during coffee roasting, and the large differences in responses to GA and CGA illustrate their different sensitivities to different types of antioxidant molecule.

Probing free radical processes during storage of extracts from whole roasted coffee beans: impact of O2 exposure during extraction and storage.

Development of liquid coffee products of good quality with extended shelf lives is hampered by their rapid quality degradation as a result of both physical and flavor instability. One approach that is being considered for extending the shelf lives of liquid coffees is that of supplementing the beverage with a very mild and slow continuous extraction from intact roasted beans that are held within an aluminum can. This paper reports the use of electron paramagnetic resonance (EPR) spectroscopy to examine the effects of key parameters that affect the stability of liquid coffee prepared from aqueous extracts from whole roasted coffee beans, namely, the O2 content of the water and headspace during extraction and the temperature during storage. It was found that the magnitude of the free radical signal was sensitive to the O2 content of the water used for extraction and storage time and temperature, whereas the intensity of the Fe(III) (g = 4.3) signal was affected only by the O2 content of the water and the Mn signal was insensitive to the experimental parameters. The most critical factor was the O2 content of the water used for extraction, and careful control of O2 exposure at the extraction stage could be a crucial factor for generating products with resistance to oxidative processes during storage.

Influence of pH on the speciation of copper(II) in reactions with the green tea polyphenols, epigallocatechin gallate and gallic acid.

Changes in speciation of copper(II) in reactions with epigallocatechin gallate (EGCG) and gallic acid (GA) as a function of pH have been investigated by multifrequency (X- and S-band) EPR spectroscopy in the fluid and frozen states. The EPR spectra show the formation of three distinct mononuclear species with each of the polyphenols, and these are interpreted in terms of one mono- and two bis-complexes. However, di- or polymeric complexes dominate the Cu(II) speciation in the pH range 4-8, and it is only at alkaline pH values that these mononuclear complexes make appreciable contributions to the metal speciation. Each mononuclear complex displays linewidth anisotropy in fluid solution as a consequence of incomplete averaging of the spin Hamiltonian parameters through molecular motion. Rotational correlation times for the individual complexes have been estimated by analysing the lineshape anisotropy of the fluid solution spectra using parameters determined by simulation of the rigid limit spectra. These show that the molecular masses increase with increasing pH, indicating either coordination of increasing numbers of polyphenol molecules as ligands to the copper or the increasing involvement of polyphenol dimers as ligands in the copper coordination sphere.

Antiradical properties of red wine portisins.

The free radical chemistry of two polyphenolic pigments from red wine, belonging to the family of portisins, has been investigated after reaction with O(2)(•-) radicals using electron paramagnetic resonance (EPR) spectroscopy. Two portisins derived from malvidin-3-glucoside and cyanidin-3-glucoside were used for this study. Stable free radicals were detected with both portisins and correspond to unpaired electrons localized on the B as well as F rings of the portisins. Interpretations were confirmed by comparison with the spectra of free radicals formed by oxidation of the model compounds cyanidin-3-glucoside, malvidin-3-glucoside, and catechin. These results concur with previous work reporting the higher antiradical properties of these pigments compared to their anthocyanin precursors.

Is there a redox reaction between Cu(II) and gallic acid?

Interactions between transition metal ions and polyphenols can result in complexation, redox or polymerization, but the relative importance of these reactions is unclear. The present paper reports results from the reaction of gallic acid (GA) with Cu(II) using electron paramagnetic resonance (EPR) and UV/visible spectroscopy for various relative concentrations and pH values. Reduction of Cu(II) by GA does not occur under strongly acidic or strongly alkaline conditions. Di- or polymerization reactions between Cu(II) and carboxylate groups of GA dominate the results at acidic pH, whereas mononuclear complexes increase in importance at higher pH and GA concentrations. There was no evidence for any redox reaction between Cu(II) and GA and free radical formation from GA at high pH was shown to be the consequence of auto-oxidation, which was inhibited by Cu(II). Serious questions are thus raised about the existence of the frequently assumed redox reactions between Cu(II) and polyphenols.

A reinvestigation of EXAFS and EPR spectroscopic measurements of chromium(VI) reduction by coir pith.

New measurements using extended X-ray absorption fine structure (EXAFS) and electron paramagnetic resonance (EPR) techniques are consistent with Cr in the Cr(III) oxidation state as the main product from the adsorption of Cr(VI) on coir pith. These confirm the previous X-ray measurements, but differ from the results of previous EPR studies, which indicated that Cr(V) was the main form of Cr. The reason for this discrepancy is the presence of a broad signal from Cr(III) in an unsymmetrical environment that was missed previously; the Cr(V) component is in fact only a minor reaction product. As a result of this problem with spectral acquisition and interpretation, some simple recommendations are presented for conducting EPR investigations on natural systems.

Free radicals generated during oxidation of green tea polyphenols: electron paramagnetic resonance spectroscopy combined with density functional theory calculations.

Electron paramagnetic resonance spectroscopy and density functional theory calculations have been used to investigate the redox properties of the green tea polyphenols (GTPs) (-)-epigallocatechin gallate (EGCG), (-)-epigallocatechin (EGC), and (-)-epicatechin gallate (ECG). Aqueous extracts of green tea and these individual phenols were autoxidized at alkaline pH and oxidized by superoxide anion (O(2)(-)) radicals in dimethyl sulfoxide. Several new aspects of the free radical chemistry of GTPs were revealed. EGCG can be oxidized on both the B and the D ring. The B ring was the main oxidation site during autoxidation, but the D ring was the preferred site for O(2)(-) oxidation. Oxidation of the D ring was followed by structural degradation, leading to generation of a radical identical to that of oxidized gallic acid. Alkaline autoxidation of green tea extracts produced four radicals that were related to products of the oxidation of EGCG, EGC, ECG, and gallic acid, whereas the spectra from O(2)(-) oxidation could be explained solely by radicals generated from EGCG. Assignments of hyperfine coupling constants were made by DFT calculations, allowing the identities of the radicals observed to be confirmed.

Free radical generation in rosmarinic acid investigated by electron paramagnetic resonance spectroscopy.

Free radical generation as a result of oxidation reactions of rosmarinic acid (RA), a caffeic acid ester with 3,4-dihydroxyphenyllactate, was investigated by electron paramagnetic resonance (EPR) spectroscopy using a variety of oxidation conditions. Limitations and possibilities of using the various methodologies to obtain information about the reaction chemistry of polyphenols are discussed. Three different spectra were detected dependent on the pH and oxidizing agent. Feasible structures for the observed radicals were tested by density functional theory (DFT) calculations and the results indicate that oxidation reactions can occur at both of the catechol groups.