Evaluating Cr behaviour in two different polluted soils: Mechanisms and implications for soil functionality.

This work investigates the mechanisms determining Cr speciation and availability in two different soils polluted with two chromium sources (an industrial sludge, highly polluted with Cr, and Cr(VI) solution) and the influence of these parameters on the recovery of the soil functions related with biological quality and plant growth. The experiment was carried out in greenhouse conditions using 36 pots of 17 kg for the growth of Silene vulgaris for 21 months. Logistic Regression Model using Lasso estimator shows that soil organic matter (SOM) and pH control Cr availability in studied soils. In soils treated with the sludge, X ray Absorption spectroscopy showed that Cr was present as Cr(III), biological quality indicators increased and plants were able to grow. However, in soils polluted with Cr(VI), Cr availability was significantly different in the two soils. In the alkaline and poor in organic matter soil, 12% of Cr(VI) remained in the soil leading to the decrease of soil quality indicators and the total inhibition of plant growth. In the neutral soil, Cr(VI) was totally reduced to Cr(III) by soil organic matter (SOM), quality indicators were not affected and plants grown properly. Infrared Spectroscopy showed that different functional groups reacted with Cr in the two soils. This study highlights the importance to understand the mechanisms underlaying Cr redox and adsorption reactions in Cr polluted soils as they determine the potential recovery of the functions related with biological quality indicators and plant growth. The methodology proposed allows this study in complex soil samples at realistic concentrations and may be useful for risk assessment and for the planning of managing strategies in Cr polluted soils.

Antioxidant effect of phenolic compounds (PC) at different concentrations in IEC-6 cells: A spectroscopic analysis.

Phenolic compounds (PC) have been proposed as natural antioxidant agents that protect cells against oxidative stress-related diseases. Nonetheless, their low bioavailability forecasts controversy about mechanisms on their in vivo scavenging activity against reactive oxygen species (ROS). It has been proposed that PC reduce directly ROS concentration. An alternative or complementary action of PC could be the activation of the cell's antioxidant pathway, involving the regulation of gene expression, like that initiated by the Nrf2 transcription factor. To date there is not enough experimental data to support or discard this possibility. In the present study, we evaluated the use of several PC to prevent peroxidation of macromolecules and to elicit the activation of the Nrf2 transcription factor in H2O2-stresed IEC-6 enterocytic cell line. Synchrotron microspectroscopy demonstrated that PC compounds protected proteins, lipids and nucleic acids against oxidation induced by H2O2. Immunofluorescence results showed that treatment with quercetin (Qc), catechin (Cat) and capsaicin (Cap) induced the translocation of Nrf2 into the nucleus, at the same level as did H2O2 treatment, thus mimicking the action of the endogenous cell response to peroxidation. Even though the detailed mechanism still needs to be elucidated, we demonstrated the activation of Nrf2 by PCs in response to oxidative stress.

Diagnosis of ovarian tumour tissues by SR-FTIR spectroscopy: A pilot study.

Ovarian cancer is the seventh most common cancer among women across the world with very high mortality rates. Histology is considered the gold standard for tumour diagnosis. FTIR spectroscopy is relies on registering biochemical differences in the samples analysed, including biological specimens. Therefore, the Synchrotron radiation based-Fourier transform infrared spectroscopy (SR-FTIR) was used for the preliminary investigation of the molecular composition of the human, non-fixed ovarian neoplastic tissues with different type of biological potential. The study that was carried out on thin tissue sections, placed on barium fluoride infrared windows, was focused on investigating spatial distribution of the biochemical markers in various ovarian tumours. Since the structural constituents of tissues accumulate different molecules which may correspond to the specific type of ovarian tumours, the main goal of this study was to check if the mean intensities of the spectral lines of some bio-molecules can be treated as ovarian cancer bio-indicators. Moreover, an attempt to identify and understand the underlying biochemical changes associated with the disease was carried out. The major spectral differences in the frequency and intensities were identified as bonds of lipids, protein massif and nucleic acids. The results obtained suggest that Fourier transform infrared spectroscopy can be used as a supporting tool in the analysis of neoplastic ovarian tissue.

Pools of cadmium in Chlamydomonas reinhardtii revealed by chemical imaging and XAS spectroscopy.

The green micro-alga Chlamydomonas reinhardtii is commonly used as a model to investigate metallic stress in photosynthetic organisms. The aim of this study was to explore processes implemented by three C. reinhardtii strains to cope with cadmium (Cd), and particularly to evidence Cd sequestration in the cell. For that, we used a combination of subcellular fractionation and chemical imaging (micro X-ray fluorescence (µXRF) and transmission electron microscopy (TEM/X-EDS)) to identify subcellular compartments of Cd accumulation, and X-ray absorption spectroscopy (XAS) to determine chemical Cd speciation. C. reinhardtii wild type strain 11/32b (wt), a newly design strain (pcs1) expressing a modified phytochelatin synthase in the chloroplast and a cell wall less strain CC400 (cw15) were exposed to 70 µM Cd. At this Cd concentration, cell vitality was not affected, however, the strains showed various strategies to cope with Cd stress. In wt, most of Cd was diffused in the whole cell, and complexed by thiol ligands, while the other part was associated with phosphate in vacuolar Ca polyphosphate granules. Thiol ligands increased with exposure time, confirming their important role in Cd stress. In pcs1, Cd was also present as vacuolar Ca polyphosphate granules, and diffused in the cell as Cd-thiol complexes. In addition, while it should be regarded with caution, a minor proportion of Cd complexed by carboxyl groups, was potentially provided by starch produced around the pyrenoid and in the chloroplast. Results suggested that pcs1 uses thiol compounds such as PC to a lesser extent for Cd sequestration than wt. In cw15, an excretion of Cd, Ca polyphosphate granules has to be considered. Finally, Cd was detected in the pyrenoid of all strains.

Identifying predation on rodent teeth through structure and composition: A case from Morocco.

Predation by nocturnal birds of prey is one of the most frequent modes leading to the concentration of rodents in fossil assemblages. This mode of accumulation leaves characteristic surface alterations on bones and teeth. In order to evaluate and characterize the effects of these pre-diagenesis alterations on rodent fossil samples, we have carried out microstructural and chemical analyses on incisors collected from present day Moroccan wild animals and owl pellets. The microstructure of both dentine and enamel was well preserved, but chemical changes were evident in pellet samples and depended on the particular tissue and the nature of the predator. The comparison of compositional data obtained from electron microprobe chemical analyses and infrared spectrometry has allowed us to assign a possible predator to an incisor extracted from a pellet of an unknown origin. This method has further implications for the understanding of taphonomy and palaeoecology of archaeological and fossil sites.

Spectroscopic verification of zinc absorption and distribution in the desert plant Prosopis juliflora-velutina (velvet mesquite) treated with ZnO nanoparticles.

The impact of metal nanoparticles (NPs) on biological systems, especially plants, is still not well understood. The aim of this research was to determine the effects of zinc oxide (ZnO) NPs in velvet mesquite (Prosopis juliflora-velutina). Mesquite seedlings were grown for 15 days in hydroponics with ZnO NPs (10 nm) at concentrations varying from 500 to 4000 mg L(-1). Zinc concentrations in roots, stems and leaves were determined by inductively coupled plasma optical emission spectroscopy (ICP-OES). Plant stress was examined by the specific activity of catalase (CAT) and ascorbate peroxidase (APOX); while the biotransformation of ZnO NPs and Zn distribution in tissues was determined by X-ray absorption spectroscopy (XAS) and micro X-ray fluorescence (µXRF), respectively. ICP-OES results showed that Zn concentrations in tissues (2102 ± 87, 1135 ± 56, and 628 ± 130 mg kg(-1) d wt in roots, stems, and leaves, respectively) were found at 2000 mg ZnO NPs L(-1). Stress tests showed that ZnO NPs increased CAT in roots, stems, and leaves, while APOX increased only in stems and leaves. XANES spectra demonstrated that ZnO NPs were not present in mesquite tissues, while Zn was found as Zn(II), resembling the spectra of Zn(NO(3))(2). The µXRF analysis confirmed the presence of Zn in the vascular system of roots and leaves in ZnO NP treated plants.

Arsenic speciation in biological samples using XAS and mixed oxidation state calibration standards of inorganic arsenic.

The speciation of elements without pre-edge features preformed with X-ray absorption near edge structure (XANES) can lead to problems when the energy difference between two species is small. The speciation of arsenic (As) in plant samples was investigated using the mixtures As2S3/As2O5, As2S3/As2O3, or As2O3/As2O5. The data showed that the energy separation (eV) between As2O5 and As2S3 was 5.8, between As2O3 and As2O5 was 3.6, and between As2S3 and As2O3 was 2.1. From the intensity of the white-line feature and the concentration of As species, calibration curves showing a limit of detection of approximately 10% were generated. In addition, an error of +/-10% was determined for the linear combination-XANES (LC-XANES) fitting technique. The difference between the LC-XANES fittings and calculations from the calibration curves was <10%. The data also showed that the speciation of As in a sample can be determined using EXAFS (extended X-ray absorption fine structure). Finally, it was also shown that both EXAFS and XANES of the sample should be examined to determine the true speciation of an element. Even though there is a difference of 2 eV between As(III) bound to O and As(III) bound to S, in the EXAFS region the As(III)-S and As(III)-O ligands are clearly visible. However, distinction between the As(III)-O and As(V)-O ligands in the EXAFS spectra was not clearly visible in this study.

Use of X-ray absorption spectroscopy and biochemical techniques to characterize arsenic uptake and reduction in pea (Pisum sativum) plants.

Arsenite (As(III)) and arsenate (As(V)) uptake by peas was investigated using inductively coupled plasma/optical emission spectroscopy (ICP-OES) at pH below 4 and at pH 5.8. Additionally, total amylolitic activity and alpha-amylase (1,4-alpha-d-glucan glucanohydrolase; EC 3.2.1.1) activity was assayed in plants exposed to arsenic treatments. At pH below 4, the uptake for As(III) and As(V) in roots was 137 and 124 mg As kg(-1) dry weight (d wt), respectively. Translocation of arsenic to the aerial part was relatively low ( approximately 5mg As kg(-1) d wt). The uptake for As(III) and As(V) in roots at pH 5.8 was about 43 and 30 mg As kg(-1) d wt, respectively, and translocation of As to the aerial part was not detectable. None of the arsenic treatments affected the total amylolitic activity in roots; however, the shoots from all treatments showed an increase in the total amylolitic activity. Alpha-amylase activity in the pea leaves was not significantly affected by arsenic treatments. X-ray absorption spectroscopy (XAS) studies showed a reduction of As(V) to As(III) in the roots. From linear combination X-ray absorption near edge structure (LC-XANES) fittings, it was determined that arsenic was present as a mixture of As(III) oxide and sulfide in pea roots.