Potential cultivation of Hordeum vulgare L. in soils with high mercury background concentrations

Experimental work was carried out under close-to-real conditions to study mercury uptake by Hordeum vulgare L. cultivated in lysimeter experiments. The soil in the lysimeter experiment was obtained from a test plot located near Almadén (Spain) and had a mean mercury content of 22.9 mg kg(-1). A sequence of four crops was sown starting in autumn 2000 and repeated on a yearly basis until 2004. The first crop was grown in the field prior to the extraction of 5 one-cubic-meter lysimeters. The succeeding crops were sown in the lysimeter experiments at the CIEMAT Research Centre (Madrid, Spain). Samples of root and shoot were obtained during the four seasons. Concentrations of mercury at plant maturity in roots vary between I and 3 mg kg(-1) and in straw and grain the concentrations range from 72 to 480 microg kg(-1) and from 5 to 257 microg kg(-1), respectively. In order to assess the potential risk for human health and animal feed, an evaluation of the mercury content in the edible part of the crop has been carried out. According to legislation, there is no human health intoxication risk with a balanced consumption; otherwise, the forage use would have to be controlled.     

The climate change mitigation effect of bioenergy from sustainably managed forests in Central Europe

We compare sustainably managed with unmanaged forests in terms of their contribution to climate change mitigation based on published data. For sustainably managed forests, accounting of carbon (C) storage based on ecosystem biomass and products as required by the United Nations Framework Convention on Climate Change is not sufficient to quantify their contribution to climate change mitigation. The ultimate value of biomass is its use for biomaterials and bioenergy. Taking Germany as an example, we show that the average removals of wood from managed forests are higher than stated by official reports, ranging between 56 and 86 mill. m³ year^?1 due to the unrecorded harvest of firewood. We find that removals from one hectare can substitute 0.87 m³ ha^?1 year^?1 of diesel, or 7.4 MWh ha^?1 year^?1, taking into account the unrecorded firewood, the use of fuel for harvesting and processing, and the efficiency of energy conversion. Energy substitution ranges between 1.9 and 2.2 t CO_{2 equiv.} ha^?1 year^?1 depending on the type of fossil fuel production. Including bioenergy and carbon storage, the total mitigation effect of managed forest ranges between 3.2 and 3.5 t CO_{2 equiv.} ha^?1 year^?1. This is more than previously reported because of the full accounting of bioenergy. Unmanaged nature conservation forests contribute via C storage only about 0.37 t CO_{2 equiv.}  ha^?1 year^?1 to climate change mitigation. There is no fossil fuel substitution. Therefore, taking forests out of management reduces climate change mitigation benefits substantially. There should be a mitigation cost for taking forest out of management in Central Europe. Since the energy sector is rewarded for the climate benefits of bioenergy, and not the forest sector, we propose that a CO₂ tax is used to award the contribution of forest management to fossil fuel substitution and climate change mitigation. This would stimulate the production of wood for products and energy substitution.     

Methods development for diffraction and spectroscopy studies of metalloenzymes at X-ray free-electron lasers

X-ray free-electron lasers (XFELs) open up new possibilities for X-ray crystallographic and spectroscopic studies of radiation-sensitive biological samples under close to physiological conditions. To facilitate these new X-ray sources, tailored experimental methods and data-processing protocols have to be developed. The highly radiation-sensitive photosystem II (PSII) protein complex is a prime target for XFEL experiments aiming to study the mechanism of light-induced water oxidation taking place at a Mn cluster in this complex. We developed a set of tools for the study of PSII at XFELs, including a new liquid jet based on electrofocusing, an energy dispersive von Hamos X-ray emission spectrometer for the hard X-ray range and a high-throughput soft X-ray spectrometer based on a reflection zone plate. While our immediate focus is on PSII, the methods we describe here are applicable to a wide range of metalloenzymes. These experimental developments were complemented by a new software suite, cctbx.xfel. This software suite allows for near-real-time monitoring of the experimental parameters and detector signals and the detailed analysis of the diffraction and spectroscopy data collected by us at the Linac Coherent Light Source, taking into account the specific characteristics of data measured at an XFEL.     

Molecular population genetics of ref(2)P, a locus which confers viral resistance in Drosophila

The ref(2)P locus (2-54.2) is polymorphic for two allelic forms in natural populations of Drosophila melanogaster, ref(2)Po and ref(2)Pp. The latter allele confers resistance to the rhabdovirus sigma infecting wild populations. Previous work, based on a small sample of prescreened restrictive (resistant) and permissive (susceptible) alleles, identified a large number of amino acid replacement changes (7) relative to synonymous changes (1). Such protein variability could be the result of variation-enhancing selection. To further test the selection hypothesis, we have examined the DNA sequences of ten randomly chosen lines of D. melanogaster and one line of D. simulans. Nine of the ten lines are permissive; D. simulans does not harbor the virus. The melanogaster alleles contain 4 synonymous changes, 19 noncoding changes, and 13 amino acid replacement changes, indicating a relatively high level of polymorphism. Three sequenced restrictive alleles have nearly identical sequences, indicating that they are relatively young. Compared to the permissive alleles, they share only a complex deletion at codon 34, CAG-AAT to GGA, which our analysis indicates to be the site conferring the restrictive phenotype. Patterns of polymorphism and divergence differ from neutral predictions by several criteria for the amino terminal region, which contains the complex deletion (codons 1-91), but not the remainder of the protein (codons 92-599). We find a higher rate of evolution on the D. melanogaster lineage than on the D. simulans lineage. The relatively large amount of both replacement and silent polymorphism in the permissive alleles and the lack of divergence between permissive and restrictive alleles suggests that the sigma virus and ref(2)P may be engaged in an evolutionary race in which new restrictive alleles are continually arising but are relatively short-lived.      

Interaction of the peptide CF3-Leu-Ala-NH-C6H4-CF3 (TFLA) with porcine pancreatic elastase. X-ray studies at 1.8 A

The peptide trifluoroacetyl-Leu-Ala-(p-trifluoromethylanilide), is a reversible inhibitor of pancreatic porcine elastase and is characterized by a Km of 2.5 x 10(-8) M. Co-crystals of the 1:1 complex were obtained in an acetate buffer + dimethylformamide solution at pH 5.7. Diffraction data were recorded on films at the LURE synchrotron facility. The inhibitor was localized on difference Fourier maps, and the refinement of the structure was performed by simulated annealing (XPLOR). The current agreement factor is R = 19% (for 13224 observed structure factors and 1.8 A effective resolution). The RMS deviations from ideality of bond distances and angles are 0.02 A and 2 degrees, respectively. The inhibitor molecule was found in the active site, bent around the side chain of Phe-215 in a geometry that resembles the previously reported structure of the CF3-Lys-Ala complex at 2.5 A, in a parallel beta-sheet association with the loop 214-216. The analysis of the close contacts (less than 3.5 A) indicates that the trifluoromethylamide bond interacts with the active site and not the Leu-Ala or Ala-anilide bonds. The two fluorinated groups of the inhibitor exhibit different specificities: the trifluoroacetyl group (N terminus) is tightly stacked between the two chain loops 191-195 and 213-215, while the trifluoromethylanilide (C terminus) shows less specificity and only a single contact.     

Robustness of activity of Calvin cycle enzymes after high light and low temperature conditions in Antarctic vascular plants

Only two vascular plants have naturally colonized the Maritime Antarctic: Colobanthus quitensis and Deschampsia antarctica. We propose that one of the reasons of their success in this environment is the robustness of their CO₂ assimilation machinery. In order to understand the mechanisms involved in the positive photosynthetic rates under stressful conditions, we analyzed changes in the activity of two key Calvin cycle enzymes: Ribulose bisphosphate carboxylase oxygenase (Rubisco) and stromal Fructose-1,6-bisphosphatase after high light and low temperature treatments. Our results show that the activity of both enzymes does not decrease after 48 h high light/low temperature treatments, a feature usually observed in plants adapted to harsh environments. The activation state of both enzymes remained high throughout the treatments. This feature has been related to the redox state of the chloroplast, suggesting that both plants maintain their redox balance under high light and/or low temperature conditions assayed. Both plants differed in their responsiveness to cold acclimation as observed by gas exchange and enzymatic measurements. We propose that these differences may be related to microclimate adaptations to the environment they naturally develop in the Maritime Antarctic.     

Response of cultured IEC-17 normal rat intestinal epithelial cells to X radiation

The growth parameters and radiosensitivity of normal rat intestinal epithelial cells, IEC-17, were studied. The cells were cultured by standard methods and exposed to an array of doses (1-12 Gy) of 250 kVp X rays. The survival curves generated exhibited no initial shoulder and were bimodal. The Do of the first component was about 0.2 Gy and the second component. 5.0 Gy. The ability of this cell line to repair sublethal lesions was examined by fractionation studies; repair was completed within 60 min after the first dose. When Chinese hamster ovary (CHO) cells were grown under the same conditions used for the IEC-17 cells and then irradiated with single doses, a typical survival curve with a Do of 1.4 Gy was obtained. The survival curves obtained for the IEC-17 cell line are consistent with the response of a morphologically distinct single population containing two functionally separate types of cells.