Proteomic and molecular analyses to understand the promotive effect of safranal on soybean growth under salt stress.

Safranal is a free radical scavenger and useful as an antioxidant molecule; however, its promotive role in soybean is not explored. Salt stress decreased soybean growth and safranal improved it even if under salt stress. To study the positive mechanism of safranal on soybean growth, a proteomic approach was used. According to functional categorization, oppositely changed proteins were further confirmed using biochemical techniques. Actin and calcium-dependent protein kinase decreased in soybean root and hypocotyl, respectively, under salt stress and increased with safranal application. Xyloglucan endotransglucosylase/ hydrolase increased in soybean root under salt stress but decreased with safranal application. Peroxidase increased under salt stress and further enhanced by safranal application in soybean root. Actin, RuvB-like helicase, and protein kinase domain-containing protein were upregulated under salt stress and further enhanced by safranal application under salt stress. Dynamin GTPase was downregulated under salt stress but recovered with safranal application under salt stress. Glutathione peroxidase and PfkB domain-containing protein were upregulated by safranal application under salt stress in soybean root. These results suggest that safranal improves soybean growth through the regulation of cell wall and nuclear proteins along with reactive­oxygen species scavenging system. Furthermore, it might promote salt-stress tolerance through the regulation of membrane proteins involved in endocytosis and post-Golgi trafficking. SIGNIFICANCE: To study the positive mechanism of safranal on soybean growth, a proteomic approach was used. According to functional categorization, oppositely changed proteins were further confirmed using biochemical techniques. Actin and calcium-dependent protein kinase decreased in soybean root and hypocotyl, respectively, under salt stress and increased with safranal application. Xyloglucan endotransglucosylase/ hydrolase increased in soybean root under salt stress but decreased with safranal application. Peroxidase increased under salt stress and further enhanced by safranal application in soybean root. Actin, RuvB-like helicase, and protein kinase domain-containing protein were upregulated under salt stress and further enhanced by safranal application under salt stress. Dynamin GTPase was downregulated under salt stress but recovered with safranal application under salt stress. Glutathione peroxidase and PfkB domain-containing protein were upregulated by safranal application under salt stress in soybean root. These results suggest that safranal improves soybean growth through the regulation of cell wall and nuclear proteins along with reactive­oxygen species scavenging system. Furthermore, it might promote salt-stress tolerance through the regulation of membrane proteins involved in endocytosis and post-Golgi trafficking.

Colorimetric Aptasensor Based on Fe3O4-Cu2+ Nanozyme with Intrinsic Peroxidase-Like Activity in the Detection of Breast Cancer Exosomes.

Because breast cancer cells such as MCF-7, exhibit vital and developmental signs by exosome secretion, diagnosing them in the blood can provide a good index of the presence of breast cancer. However, accurate and inexpensive detection of exosomes in clinical practice faces challenges. Therefore, in the presents study, an aptasensor based on CD63 aptameriron oxide-copper ion nanozymes (Fe3O4-Cu2+-NZs) was designed with the ability of the CD63 aptamer to interact with the exosome and the release of the Fe3O4-Cu2+-NZs for peroxidase-like activity on the tetramethylbenzidine (TMB). After fabrication of CD63 aptamer-Fe3O4-Cu2+-NZs based on hydrothermal method, their physicochemical properties were investigated with the SEM, TEM, DLS, Zeta, XRD and magnetization. To investigate the interaction of CD63 aptamer-Fe3O4-Cu2+-NZs with exosomes, the required exosomes were extracted from cultured MCF-7 cells. The performance of CD63 aptamer-Fe3O4-Cu2+-NZs on TMB degradation in the presence and absence of exosomes was investigated through UV-vis adsorption and ocular observations based on colour changes on laboratory and real samples. The results show that the absence of exosomes significantly inhibited the peroxidase-like activity of CD63 aptamer-Fe3O4-Cu2+-NZs due to the aptamer coating. Under optimal conditions, the designed CD63 aptamer-Fe3O4-Cu2+-NZs is capable of detecting exosomes in the range of 1.4 × 104-5.6 × 105 particles/µL with a detection limit of 5.91 × 10³ particles/µL. Also, this method showed a satisfactory outcome in detection of cancer cells in real samples. Overall, this colorimetric aptasensor can be used to diagnose breast cancer cells based on a simple and inexpensive approach.

Effects of cadmium stress on growth and physiological characteristics of sassafras seedlings.

The effects of cadmium stress on the growth and physiological characteristics of Sassafras tzumu Hemsl. were studied in pot experiments. Five Cd levels were tested [CT(Control Treatment) : 0 mg/kg, Cd5: 5 mg/kg, Cd20: 20 mg/kg, Cd50: 50 mg/kg, and Cd100: 100 mg/kg]. The growth and physiological characteristics of the sassafras seedlings in each level were measured. The results showed that soil Cd had negative influences on sassafras growth and reduced the net growth of plant height and the biomass of leaf, branch and root. Significant reductions were recorded in root biomass by 18.18%(Cd5), 27.35%(Cd20), 27.57%(Cd50) and 28.95%(Cd100). The contents of hydrogen peroxide decreased first then increased while malondialdehyde showed the opposite trend with increasing cadmium concentration. Decreases were found in hydrogen peroxide contents by 10.96%(Cd5), 11.82%(Cd20) and 7.02%(Cd50); increases were found in malondialdehyde contents by 15.47%(Cd5), 16.07%(Cd20) and 7.85%(Cd50), indicating that cadmium stress had a certain effect on the peroxidation of the inner cell membranes in the seedlings that resulted in damage to the cell membrane structure. Superoxide dismutase activity decreased among treatments by 17.05%(Cd5), 10,68%(Cd20), 20.85%(Cd50) and 8.91%(Cd100), while peroxidase activity increased steadily with increasing cadmium concentration; these results suggest that peroxidase is likely the main protective enzyme involved in the reactive oxygen removal system in sassafras seedlings. Upward trends were observed in proline content by 90.76%(Cd5), 74.36%(Cd20), 99.73%(Cd50) and 126.01%(Cd100). The increase in proline content with increasing cadmium concentration indicated that cadmium stress induced proline synthesis to resist osmotic stress in the seedlings. Compared to that in CT, the soluble sugar content declined under the different treatments by 32.84%(Cd5), 5.85%(Cd20), 25.55%(Cd50) and 38.69%(Cd100). Increases were observed in the soluble protein content by 2.34%(Cd5), 21.36%(Cd20), 53.15%(Cd50) and 24.22%(Cd100). At different levels of cadmium stress, the chlorophyll content in the seedlings first increased and then decreased, and it was higher in the Cd5 and Cd20 treatments than that in the CT treatment. These results reflected that cadmium had photosynthesis-promoting effects at low concentrations and photosynthesis-suppressing effects at high concentrations. The photosynthetic gas exchange parameters and photosynthetic light-response parameters showed downward trends with increasing cadmium concentration compared with those in CT; these results reflected the negative effects of cadmium stress on photosynthesis in sassafras seedlings.

Quantitative Top-Down Proteomics in Complex Samples Using Protein-Level Tandem Mass Tag Labeling.

Labeling approaches using isobaric chemical tags (e.g., isobaric tagging for relative and absolute quantification, iTRAQ and tandem mass tag, TMT) have been widely applied for the quantification of peptides and proteins in bottom-up MS. However, until recently, successful applications of these approaches to top-down proteomics have been limited because proteins tend to precipitate and "crash" out of solution during TMT labeling of complex samples making the quantification of such samples difficult. In this study, we report a top-down TMT MS platform for confidently identifying and quantifying low molecular weight intact proteoforms in complex biological samples. To reduce the sample complexity and remove large proteins from complex samples, we developed a filter-SEC technique that combines a molecular weight cutoff filtration step with high-performance size exclusion chromatography (SEC) separation. No protein precipitation was observed in filtered samples under the intact protein-level TMT labeling conditions. The proposed top-down TMT MS platform enables high-throughput analysis of intact proteoforms, allowing for the identification and quantification of hundreds of intact proteoforms from Escherichia coli cell lysates. To our knowledge, this represents the first high-throughput TMT labeling-based, quantitative, top-down MS analysis suitable for complex biological samples.

Studies on the characteristics and mechanism of aerobic biodegradation of tetrabromobisphenol A by Irpex lacteus F17.

The study investigated the characteristics of aerobic degradation of tetrabromobisphenol A (TBBPA) by Irpex lacteus F17 (I. lacteus F17) under four different cometabolic substrates (phenol, glucose, sodium pyruvate, and sodium citrate). The biodegradation of TBBPA by I. lacteus F17 could be enhanced via cometabolism, and glucose (8 g/L) was confirmed to be the optimum carbon source. For different initial solution pH ranging from 3.0 to 8.0, the results showed that I. lacteus F17 could be applied to biodegrade TBBPA in a wide pH range of 4.0-8.0, and the degradation rate could reach the maximum 75.31%, while the debromination rate reached the maximum 12.40% under pH 5.0. In addition, it has been confirmed that Mn2+ (50 µmol/L) could promote the secretion of manganese peroxidase and TBBPA biodegradation efficiency. Seven intermediates were identified by gas chromatography-mass spectrometry analysis, and the possible degradation pathways were proposed, which indicated the biodegradation of TBBPA might be subjected to debromination, ß-scission, hydroxylation, deprotonation, and oxidation reactions.

Assessment of selected heavy metals and enzyme activity in soils within the zone of influence of various tree species.

The study aimed to evaluate the total content and bioavailable forms of Zn, Cu, Pb and Ni and enzymatic activity (nitro reductase and peroxidases) in the mineral levels of surface soils within the zone of influence of various tree species. The conducted variance analysis confirmed the significant impact of the studied tree habitats on the total content and bioavailable forms of metals and on enzymatic activity. The total content of analysed metals were low and in no case exceeded the possible concentrations. The high bioavailability (AF %) values calculated for habitats of different species compositions (of 53.78% for Zn, 76.82% for Cu, 60.81% for Pb and 44.72% for Ni) may pose a risk of accumulation of these metals in plants. A significant correlation was found between nitrate reduction activity and Pb content (r = 0.510) and Cu (r = 0.678). Principal component analysis allowed two principal components to be distinguished (PC1 and PC2) that accounted for 60.95% of the total change in variance.

Induction of defense in cereals by 4-fluorophenoxyacetic acid suppresses insect pest populations and increases crop yields in the field.

Synthetic chemical elicitors, so called plant strengtheners, can protect plants from pests and pathogens. Most plant strengtheners act by modifying defense signaling pathways, and little is known about other mechanisms by which they may increase plant resistance. Moreover, whether plant strengtheners that enhance insect resistance actually enhance crop yields is often unclear. Here, we uncover how a mechanism by which 4-fluorophenoxyacetic acid (4-FPA) protects cereals from piercing-sucking insects and thereby increases rice yield in the field. Four-FPA does not stimulate hormonal signaling, but modulates the production of peroxidases, H2O2, and flavonoids and directly triggers the formation of flavonoid polymers. The increased deposition of phenolic polymers in rice parenchyma cells of 4-FPA-treated plants is associated with a decreased capacity of the white-backed planthopper (WBPH) Sogatella furcifera to reach the plant phloem. We demonstrate that application of 4-PFA in the field enhances rice yield by reducing the abundance of, and damage caused by, insect pests. We demonstrate that 4-FPA also increases the resistance of other major cereals such as wheat and barley to piercing-sucking insect pests. This study unravels a mode of action by which plant strengtheners can suppress herbivores and increase crop yield. We postulate that this represents a conserved defense mechanism of plants against piercing-sucking insect pests, at least in cereals.

Colorimetric determination of F-, Br- and I- ions by Ehrlich's bio-reagent oxidation over enzyme mimic like gold nanoparticles: Peroxidase-like activity and multivariate optimization.

Citrate and polyvinyl alcohol capped gold nanoparticles (PVA-GNPs) were synthesized via chemical reduction technique and fully characterized by DLS, SEM, EDS, XRD, UV-Vis and FT-IR analysis. A simple and practical colorimetric sensor based on red-ox reaction of p-dimethylaminobenzaldehyde (DABA) as ehrlich's bio-reagent and Au(III) with H2O2 on PVA-GNPs mimic catalyst with enzyme-like activity, has been fabricated for determination of F-, Br- and I- halide anions. Prepared PVA-GNPs, can simultaneously catalyze the disintegration of H2O2, that used to reduce Au(III) ions into co-doped Au-NPs and oxidation of p-dimethylaminobenzaldehyde ehrlich's bio-reagent while in the presence of halide ions Au-X complex can be formed and improved sensor selectivity. Halide ions (F-, Br- and I-) effectively diminishes the catalytic activity of GNPs to disintegrate oxygenated water by the interaction among Au+ and Au0 and suppressing oxidation of p-dimethylaminobenzaldehyde ehrlich's bio-reagent. In this system which contains PVA-GNPs, H2O2, p-dimethylaminobenzaldehyde ehrlich's bio-reagent, and Au(III), increasing the halide ions (F-, Br- and I-) concentration show color changes from deep green to red. In view of this rule, in this work, a novel colorimetric technique for sensitive determination of F-, Br- and I- was developed. This method has the detection limits of 2.60 × 10-6 M, 6.64 × 10-8 M and 9.93 × 10-9 M and linear ranges between 1.98 × 10-5-1.22 × 10-3 M, 1.99 × 10-6-2.0 × 10-4 M and 1.07 × 10-7- 2.86 × 10-5 M for F-, Br- and I-, respectively. Assays are highly selective over other ions. They effectively applied to detection of halide ions in real water samples.

Linkage of typically cytosolic peroxidases to erythrocyte membrane - A possible mechanism of protection in Hereditary Spherocytosis.

Hereditary Spherocytosis (HS) is a non-immune hemolytic anemia associated to oxidative stress (OS), namely to the linkage of cytosolic antioxidant enzymes to the erythrocyte membrane. Our aims were to evaluate erythrocyte OS changes and the membrane linkage of peroxiredoxin 2 (Prx2), glutathione peroxidase (GPx) and catalase (CAT) in unsplenectomized (unspl) and splenectomized (spl) HS patients and to search for associations with clinical severity (in unspl HS patients). We studied 114 HS patients (74 unspl and 40 spl) and 30 healthy individuals and we evaluated membrane bound hemoglobin (MBH), membrane lipid-peroxidation (LPO), enzymatic activities of GPx and CAT and the amounts of membrane bound Prx2, GPx and CAT, as well as, clinical and analytical parameters for characterization of HS. We found that unspl HS patients showed clear signs of anemia and in spl HS, a correction to this anemia was observed; the latter patients presented higher levels of OS biomarkers, namely, MBH and LPO. CAT was detected in the membrane of all individuals (control and HS groups), while GPx and Prx2 were only present in HS patients; moreover, their linkage to the membrane (in HS) appears to be cumulative since membrane bound peroxidases amount was higher as the number of peroxidases detected increased. MBH increased with the number/amount of membrane bound peroxidases, however LPO levels remained similar. In conclusion, our data suggest that the binding of these typically cytosolic peroxidases to erythrocyte membrane may be part of a mechanism of membrane protection to maintain its integrity by possibly regulating LPO.

Dissipation and the effects of thidiazuron on antioxidant enzyme activity and malondialdehyde content in strawberry.

BACKGROUND: Increasing numbers of fruit swelling agents have been used to improve the fruit rate and production yield of strawberries in recent years. The abuse of fruit swelling agents could lead to an increase in the deformation rate and abnormal coloration of strawberry and a decrease in quality at harvest. Therefore, understanding the harmful effects of fruit swelling agents on strawberry will provide guidance for their reasonable use. RESULTS: The residual determination method for measuring thidiazuron (TDZ) in strawberry was developed and validated by liquid chromatography and tandem mass spectrometry (LC-MS/MS). The recoveries of TDZ in strawberry were 97.9-108.5% with relative standard deviations of 0.9% to 5.3%. The dissipation rates of TDZ were different in strawberries cultivated under field and indoor conditions due to the differences in temperature and humidity. The ascorbic acid content increased when TDZ was applied at 2 mg kg-1 . The SOD (superoxide dismutase), POD (peroxidase) and CAT (catalase) activities of strawberry tended to decrease and subsequently increase following the application of TDZ, and the opposite changes occurred on the malondialdehyde (MDA) content of TDZ-treated strawberry. CONCLUSIONS: The analytical method for measuring TDZ in strawberry that was developed was suitable for dissipation studies on this compound. Antioxidant enzyme activities and the MDA content of strawberry were altered, and some reverse effects, such as membrane damage, were inhibited when TDZ was applied. The data obtained in this study might provide suggestions to reduce the adverse effects of TDZ on strawberry and may help to guide the safe and proper use of TDZ in strawberry. © 2019 Society of Chemical Industry.

Cyanobacterial Catalase Activity Prevents Oxidative Stress Induced by Pseudomonas fluorescens DUS1-27 from Inhibiting Brassica napus L. (canola) Growth.

Plant growth-promoting bacteria (PGPB) inhabit the rhizosphere of plants and are capable of enhancing plant growth through a number of mechanisms. A strain of Pseudomonas fluorescens DUS1-27 was identified as a potential PGPB candidate based on its ability to increase the growth of Brassica napus L. (canola) over that of uninoculated control plants in a soil-based system. The same P. fluorescens isolate was found to reduce plant growth in a hydroponic growth system, with plants showing the symptoms of a microbe-associated molecular pattern (MAMP) response to the bacteria. The amperometric quantification of H2O2, fluorescence-based total peroxidase assays, and quantification of catalase gene expression levels using qRT-PCR revealed that oxidative stress reduced plant growth in the hydroponic system. The addition of the cyanobacterium Nostoc punctiforme (known to have high catalase activity levels) in the hydroponic system as a co-inoculant reduced oxidative stress (49.7% decrease in H2O2 concentrations) triggered by the addition of P. fluorescens DUS1-27, thereby enabling plants to grow larger than uninoculated control plants. These results show the advantage of inoculating with multiple bacteria to promote plant growth and, for the first time, demonstrate that N. punctiforme beneficially assists plants under oxidative stress through its catalase activity in planta.

19F PARASHIFT Probes for Magnetic Resonance Detection of H2O2 and Peroxidase Activity.

Elevated levels of reactive oxygen species and peroxidase expression are often associated with inflammation and inflammatory diseases. We developed two novel Co(II) complexes that can be used to detect oxidative activity associated with inflammation using 19F magnetic resonance imaging (MRI). These agents display a large change in 19F chemical shift upon oxidation from Co(II) to Co(III), facilitating selective visualization of both species using chemical shift selective pulse sequences. This large chemical shift change is attributed to a large magnetic anisotropy in the high spin Co(II) complexes. Importantly, the differing reactivity of the two agents allows for detection of either H2O2 production and/or the activity of peroxidase enzymes, providing two useful platforms for 19F MR hot spot imaging of oxidative events associated with biological inflammation.

Assessment of potentially toxic metal (PTM) pollution in mangrove habitats using biochemical markers: A case study on Avicennia officinalis L. in and around Sundarban, India.

Spatial distribution of potentially toxic metals (PTMs) and their accumulation in mangrove Avicennia officinalis L. were studied along 8 locations in and around Sundarban mangrove wetland, India. Among 8 locations, S3 (Chemaguri) and S5 (Ghushighata) showed higher concentration of PTMs (Cd, Cr, Cu, Ni, Pb, Zn) characterized by higher enrichment factors (3.45-10.03), geo-accumulation indices (0.04-1.22), contamination factors (1.14-3.51) and pollution load indices (1.3-1.45) indicating progressive deterioration of estuarine quality and considerable ecotoxicological risk. Metal concentration in A. officinalis leaves showed significant correlation with sediment metals implying elevated level of bioaccumulation. Significant statistical correlation between photosynthetic pigments (Chlorophyll a, Chlorophyll b), antioxidant response (free radical scavenging and reducing ability) and stress enzymatic activity (Peroxidase, Catalase, Super-oxide dismutase) of A. officinalis with increasing metal concentration in the contaminated locations reflects active detoxification mechanism of the plant. The study indicates the potentiality of biomonitoring metal pollution using studied biochemical markers in mangrove habitats.

Bioavailability of Compounds Susceptible to Enzymatic Oxidation Enhances Growth of Shiitake Medicinal Mushroom (Lentinus edodes) in Solid-State Fermentation with Vineyard Prunings.

Grapes are widely produced in northwestern Mexico, generating many wood trimmings (vineyard prunings) that have no further local use. This makes vineyard prunings a very attractive alternative for the cultivation of white-rot medicinal mushrooms such as Lentinus edodes. This type of wood can also offer a model for the evaluation of oxidative enzyme production during the fermentation process. We tested the effect of wood from vineyard prunings on the vegetative growth of and production of ligninolytic enzymes in L. edodes in solid-state fermentation and with wheat straw as the control substrate. The specific growth rate of the fungus was 2-fold higher on vineyard pruning culture (µM = 0.95 day-1) than on wheat straw culture (µM = 0.47 day-1). Laccase-specific production was 4 times higher in the vineyard prunings culture than on wheat straw (0.34 and 0.08 mU · mg protein-1 · ppm CO2-1, respectively), and manganese peroxidase production was 3.7 times higher on wheat straw culture than on vineyard prunings (2.21 and 0.60 mU · mg protein-1 · ppm CO2-1, respectively). To explain accurately these differences in growth and ligninolytic enzyme activity, methanol extracts were obtained from each substrate and characterized. Resveratrol and catechins were the main compounds identified in vineyard prunings, whereas epigallocatechin was the only one detected in wheat straw. Compounds susceptible to enzymatic oxidation are more bioavailable in vineyard prunings than in wheat straw, and thus the highest L. edodes growth rate is associated with the presence of these compounds.

[Effects of different substrates on low temperature fresh ginseng].

The SOD and POD enzyme activities were detected, ginseng saponin content and protein concentration at 4 ℃ preservation on fresh ginseng by different substrates were determined. The results showed that the appearance of the ginseng and the survival ability were good after six months by perlite preservation. It has lower SOD, POD enzyme activity and higher saponins and protein contention. It is the best fresh storing conditions for ginseng by using perlite at 4 ℃ preservation.

Enzymatic Profile of 'Willamette' Raspberry Leaf and Fruit Affected by Prohexadione-Ca and Young Canes Removal Treatments.

The influence of growth regulator prohexadione-Ca (ProCa) concurrently with young canes removal on the modification of photosynthetic pigments content and antioxidant enzymes (peroxidase, POD; catalase, CAT; polyphenol oxidase, PPO; superoxide dismutase, SOD) activities in leaves and fruits of raspberry (Rubus idaeus L.) cultivar 'Willamette' was studied. ProCa increased while canes removal decreased chlorophylls and carotenoids content compared to control. POD, CAT, and PPO activities in leaves after removal of young canes were higher compared to control (2-4 times) which was visually confirmed for POD by isoelectrofocusing. Removal of young canes slithly increased, while ProCa significantly enhanced SOD activity in leaves compared to control (475.10 and 218.38 nkat mg-1 prot, respectively). Pattern of SOD activity in fruit was similar as in leaf with substantial increase compared to control (about 15 times). Combination of implemented measures increased activity of all enzymes in the leaves and fruits. Our study could provide a better knowledge of the ProCa and canes removal influences on the action of enzymes in order to regulate their activities in fruit products.

Detection of manganese peroxidase and other exoenzymes in four isolates of Geastrum (Geastrales) in pure culture.

Knowledge regarding the enzymatic machinery of fungi is decisive to understand their ecological role. The species of the genus Geastrum are known to grow extremely slowly in pure culture, which makes it difficult to evaluate physiological parameters such as enzyme activity. Qualitative assays were performed on isolates of four species of this genus, showing evidence of laccase, cellulase, pectinase, amylase and lipase activity and suggesting that a wide range of carbon sources can be exploited by these species. For the first time in this genus, quantitative assays verified manganese peroxidase activity (up to 0.6mU/g) in 30-day old cultures, as well as laccase, ß-glycosidase and ß-xylosidase activities.

Direct determination of lignin peroxidase released from Phanerochaete chrysosporium by in-capillary enzyme assay using micellar electrokinetic chromatography.

Here we describe the application of an in-capillary enzyme assay using micellar electrokinetic chromatography (MEKC) in the determination of enzyme activity in a crude culture medium containing lignin peroxidase released from Phanerochaete chrysosporium (P. chrysosporium). The method consists of a plug-plug reaction between lignin peroxidase and its substrate, veratryl alcohol, the separation of the product, veratraldehyde, from the other components including the enzyme and the culture medium, and the determination of the enzyme activity from the peak area of veratraldehyde produced by the plug-plug reaction. This method is more sensitive than conventional spectrophotometry since the background originates from the enzyme and the culture medium can be removed via MEKC separation. Veratraldehyde was separated at -10kV in a background electrolyte containing 50mM tartrate buffer (pH 2.5) and 50mM sodium dodecyl sulfate (SDS) after a plug-plug reaction in the capillary for 5min. The calibration curve of veratraldehyde was linear up to 4pmol (500µM) with a limit to quantification of 0.026pmol (3.2µM) (SN=10). The activity of lignin peroxidase was directly measured from the peak area of veratraldehyde. The activity of lignin peroxidase released from P. chrysosporium into the medium for 7 days was successfully determined to be 3.40UL(-1).

Combined effect of Cd and Pb spiked field soils on bioaccumulation, DNA damage, and peroxidase activities in Trifolium repens.

The present study was designed to investigate the combined effects of Cd and Pb on accumulation and genotoxic potential in white clover (Trifolium repens). For this purpose, T. repens was exposed to contaminated soils (2.5-20 mg kg(-1) cadmium (Cd), 250-2000 mg kg(-1) lead (Pb) and a mixture of these two heavy metals) for 3, 10 and 56 days. The resulting bioaccumulation of Cd and Pb, DNA damage (comet assay) and peroxidase activities (APOX and GPOX) were determined. The exposure time is a determinant factor in experiments designed to measure the influence of heavy metal contamination. The accumulation of Cd or Pb resulting from exposure to the two-metal mixture does not appear to depend significantly on whether the white clover is exposed to soil containing one heavy metal or both. However, when T. repens is exposed to a Cd/Pb mixture, the percentage of DNA damage is lower than when the plant is exposed to monometallic Cd. DNA damage is close to that observed in the case of monometallic Pb exposure. Peroxidase activity cannot be associated with DNA damage under these experimental conditions.