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At least 451 records · Page 25
All sourcesNASA NTRSDOE OSTI
DOE OSTI2024

A hidden demethylation pathway removes mercury from rice plants and mitigates mercury flux to food chains

Dietary exposure to methylmercury (MeHg) causes irreversible damage to human cognition and is mitigated by photolysis and microbial demethylation of MeHg. Rice (Oryza sativa L.) has been identified as a major dietary source of MeHg. However, it remains unknown what drives the process within plants for MeHg to make its way from soils to rice and the subsequent human dietary exposure to Hg. Here we report a hidden pathway of MeHg demethylation independent of light and microorganisms in rice plants. This natural pathway is driven by reactive oxygen species generated in vivo, rapidly transforming MeHg to inorganic Hg and then eliminating Hg from plants as gaseous Hg°. MeHg concentrations in rice grains would increase by 2.4- to 4.7-fold without this pathway, which equates to intelligence quotient losses of 0.01–0.51 points per newborn in major rice-consuming countries, corresponding to annual economic losses of US$30.7–84.2 billion globally. Importantly, this discovered pathway effectively removes Hg from human food webs, playing an important role in exposure mitigation and global Hg cycling.

59 BASIC BIOLOGICAL SCIENCES↗
DOE OSTI2024

An iterative method to deblend AGN-Host contributions for Integral Field spectroscopic observations

ABSTRACT We present a new iterative deblending method to separate the host galaxy (HG) and their Active Galactic Nuclei (AGNs) emission with the use of Integral Field spectroscopic (IFS) data. The method decomposes the resolved HG emission from the unresolved AGN emission by modelling the two-dimensional surface brightness (SB) profile of the point-spread function (PSF) and the two-dimensional SB HG continuum simultaneously per each monochromatic slide. Our method does not require any prior information about the observed SB profile or a detailed fitting of the PSF, making it ideal for the automatic analysis of large galaxy samples. In this work, we test the quality of our method, its advantages, and its disadvantages. We test our method by using a set of IFS mock data cubes to quantify the reliability of our deblending process and further compare our method with the qdblend3d analysis tool. Furthermore, we applied our method to three data cubes selected from the MaNGA survey according to the dominance of either its HG or its AGN. We show that our deblending method is capable of disengaging the bright, non-resolved AGN emission from the HG continuum and its narrow emission lines. However, the decoupling depends on how well the IFS spatially resolves the PSF, and on the relative flux intensity of the HG-AGN. Therefore, the method is ideal for disentangling the bright-flux contribution from AGN-dominated spectra.

Ibarra-Medel, H. (ORCID:0000000297906313)↗
DOE OSTI2023

Acetylation of homogalacturonan and rhamnogalacturonan‐I is catalyzed by a suite of trichome birefringence‐like proteins

SUMMARY Plant cell wall polysaccharides, including xylan, mannan, xyloglucan, and pectins, are often acetylated and members of the domain of unknown function 231 (DUF231)/trichome birefringence‐like (TBL) family have been shown to beO‐acetyltransferases mediating the acetylation of xylan, mannan, and xyloglucan. However, little is known about theO‐acetyltransferases responsible for pectin acetylation. In this report, we biochemically characterized a suite of Arabidopsis DUF231/TBL proteins for their roles in pectin acetylation. We generated 24 TBL recombinant proteins in mammalian cells and demonstrated that 10 of them were able to transfer acetyl groups from acetyl‐CoA onto the pectins homogalacturonan (HG) or rhamnogalacturonan‐I (RG‐I), and thus were named pectinO‐acetyltransferase 1 to 10 (POAT1 to 10). It was found that POAT2,4,9,10 specifically acetylated HG and POAT5,6 acetylated RG‐I, whereas POAT1,3,7,8 could act on both HG and RG‐I. The acetylation of HG and RG‐I by POATs was further corroborated by hydrolysis with pectin acetylesterases and by nuclear magnetic resonance spectroscopy. In addition, mutations of the conserved GDS and DXXH motifs in POAT3 and POAT8 were shown to lead to a loss of their ability to acetylate HG and RG‐I. Furthermore, simultaneous RNA interference downregulation ofPOAT1,3,6,7,8resulted in reduced cell expansion, impaired plant growth, and decreased pectin acetylation. Together, our findings indicate that these POATs are pectinO‐acetyltransferases involved in acetylation of the pectin polysaccharides HG and RG‐I.

Plant Sciences↗
DOE OSTI2020

Multi-Scale Modeling Framework for Mercury Biogeochemistry

Multi-Scale modeling of mercury (Hg) geochemical speciation and reactions has been performed by integrating atomistic quantum chemical calculations with continuum scale speciation models. Major progress has been made in the improvement of quantum chemical models to calculate critical thermodynamic data for Hg complexes in aquatic environments. Rapid and reliable quantum chemical approaches have been developed for calculating acid dissociation constants (pK a ) and stability constants (log K), with calculated mean unsigned errors of 0.5 and 1.5 log units, respectively for ligand molecules and Hg complexes. At the continuum scale, systematic analysis of uncertainty propagation in mercury (Hg) speciation modeling has been conducted and was used to identify environmental conditions under which thermodynamic constant uncertainties are significant and recommended to be accounted for. The integrated framework for multi-scale modeling of mercury geochemistry is open to the research community through the web-based multiscale modeling aqueous speciation resource, AQUA-MER. The improved quantum chemical approaches for thermodynamic constant calculations are accessible through AQUA-MER and can be used to provide the missing constants in the continuum scale speciation calculations. In addition to low molecular mass Hg complex speciation, modeling natural aquatic environments also involve the transport of high molecular weight dissolved organic matter (DOM) in reactive flows simultaneously with equilibrium and kinetic reactions. To this end, atomistic MD simulations were performed to capture the details of aggregation, mechanisms and distribution of functional groups in DOM at the molecular level. The elemental composition and calculated bulk properties of the DOM models are in close agreement with experimental measurements. A travel-time based reactive transport model in the hyporheic zone of stream corridors was established for the multicomponent Hg-DOM-S system and implemented through PFLOTRAN.

54 ENVIRONMENTAL SCIENCES↗
DOE OSTI2021

Defense Waste Processing Facility Nitric-Glycolic Flowsheet Chemical Process Cell Chemistry: Part 2

The conversions of nitrite to nitrate, the destruction of glycolate, and the conversion of glycolate to formate and oxalate were modeled for the Nitric-Glycolic flowsheet using data from Chemical Process Cell (CPC) simulant runs conducted by Savannah River National Laboratory (SRNL) from 2011 to 2016. The goal of this work was to develop empirical correlation models to predict these values from measurable variables from the chemical process so that these quantities could be predicted a-priori from the sludge or simulant composition and measurable processing variables. The need for these predictions arises from the need to predict the REDuction/OXidation (REDOX) state of the glass from the Defense Waste Processing Facility (DWPF) melter. This report summarizes the work on these correlations based on the aforementioned data. Previous work on these correlations was documented in a technical report covering data from 2011-2015. This current report supersedes this previous report. Further refinement of the models as additional data are collected is recommended. The glass REDOX depends on the concentrations of nitrate and manganese (oxidants), and of glycolate, formate, oxalate, carbon, and antifoam (reductants) in the melter feed. The waste sludge contains nitrite, nitrate, manganese (Mn), and oxalate. Virtually all of the nitrite is converted to nitrate or NO+NO 2 +N 2 O gases in the CPC. The portion of the nitrite converted to nitrate increases the amount of nitrate in the sludge. The amount of glycolate in the final melter feed depends on the amount of the glycolic acid feed that is destroyed. Similarly, the amounts of formate and oxalate formed during the decomposition of glycolic acid are required. The material balance on carbon was found to not close in most cases. Generally, there was less carbon at the end of testing compared to the inputs. The most uncertain product variable was glycolate, so material balances were performed where the glycolate concentration was adjusted, usually upward, to close the balance. Correlation versus the original, as-measured, data was generally poor, but correlation against the material balance adjusted values was greatly improved. It was also shown that the correlation of the measured REDOX versus the predicted REDOX was much better when the material balance adjusted glycolate values were used. Three data series were primarily used during the regressions of the data; these series were 1) Sludge Batch 9 NG flowsheet simulant runs NG51-62 (SB9-NG); 2) Scaled Runs + Bounding Hydrogen Runs (SR+BH); and 3) Runs GN43-50 and 57 (43-50,57). The glycolate destruction was found to correlate with acid stoichiometry (AS), percent reducing acid (PRA), and for some data series, headspace to simulant volume ratio (HSV), mercury (Hg), and nitrate. Although glycolate destruction for pairs of data series (e.g., [SB9-NG] and [SR+BH]) were found to depend on HSV, the combination of all three data series was not found to have significant dependence on this variable. The best model for glycolate destruction depended on AS, nitrate, and Hg. This model predicted the product glycolate compositions of the data to within 92-106%. The conversion of glycolate to formate was high when noble metals and Hg were not present, with values up to 100%. When noble metals and Hg were present, this conversion ranged from zero to 7%, and was dependent on AS. Lower AS gave higher conversions to formate. The conversion to oxalate was found to depend on the AS and the initial concentration of nitrite. An alternative fit versus AS and the form of ruthenium (Ru) used is a possible alternative. This fit was somewhat less statistically significant. This second model predicts that more oxalate is formed when Ru-nitrosyl nitrate is used rather than Ru chloride. The conversion of glycolate to oxalate ranged from zero to 6%. The conversion of nitrite to nitrate depended primarily on AS and PRA, with HSV and Hg being significant when these variables were varied. For multiple series of data, nitrite was also needed to SRNL-STI-2017-00172 5HYLVLRQ viL distinguish between data series, and the effect of HSV became insignificant. The best model for nitrite to nitrate conversion depended on AS, PRA, nitrite, and Hg. The 95% confidence intervals on the predicted values of glycolate destruction, glycolate to oxalate conversion, and nitrite to nitrate conversion were used to determine the uncertainty in the predicted REDOX when starting with only the composition of the sludge, AS, and PRA. Using the 95% confidences on an individual value (that is the confidence in getting a particular value for one single test as opposed to what the mean would be for multiple tests), the uncertainty in the predicted REDOX was calculated. The uncertainty in the actual product composition glycolate, oxalate, formate, and nitrate concentrations translated to an uncertainty in the REDOX value of ±0.1,which is approximately the uncertainty claimed in the REDOX model itself.

12 MANAGEMENT OF RADIOACTIVE AND NON-RADIOACTIVE W↗
DOE OSTI2020

Materials Data on Ca3Hg2 by Materials Project

Ca3Hg2 crystallizes in the tetragonal P4/mbm space group. The structure is three-dimensional. there are two inequivalent Ca sites. In the first Ca site, Ca is bonded in a square co-planar geometry to four equivalent Hg atoms. All Ca–Hg bond lengths are 3.33 Å. In the second Ca site, Ca is bonded to six equivalent Hg atoms to form a mixture of distorted edge, face, and corner-sharing CaHg6 pentagonal pyramids. There are two shorter (3.22 Å) and four longer (3.31 Å) Ca–Hg bond lengths. Hg is bonded in a 8-coordinate geometry to eight Ca atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Mg5Hg3 by Materials Project

Mg5Hg3 crystallizes in the hexagonal P6_3/mcm space group. The structure is three-dimensional. there are two inequivalent Mg sites. In the first Mg site, Mg is bonded in a 5-coordinate geometry to five equivalent Hg atoms. There are a spread of Mg–Hg bond distances ranging from 2.85–3.14 Å. In the second Mg site, Mg is bonded in a 6-coordinate geometry to six equivalent Hg atoms. All Mg–Hg bond lengths are 2.98 Å. Hg is bonded in a 9-coordinate geometry to nine Mg atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on BaSnHg by Materials Project

BaHgSn is hexagonal omega structure-derived structured and crystallizes in the hexagonal P6_3/mmc space group. The structure is three-dimensional. Ba is bonded to six equivalent Hg and six equivalent Sn atoms to form a mixture of edge and face-sharing BaSn6Hg6 cuboctahedra. All Ba–Hg bond lengths are 3.78 Å. All Ba–Sn bond lengths are 3.78 Å. Hg is bonded in a 9-coordinate geometry to six equivalent Ba and three equivalent Sn atoms. All Hg–Sn bond lengths are 2.89 Å. Sn is bonded in a 9-coordinate geometry to six equivalent Ba and three equivalent Hg atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Sr3Hg2 by Materials Project

Sr3Hg2 crystallizes in the tetragonal P4/mbm space group. The structure is three-dimensional. there are two inequivalent Sr sites. In the first Sr site, Sr is bonded in a square co-planar geometry to four equivalent Hg atoms. All Sr–Hg bond lengths are 3.49 Å. In the second Sr site, Sr is bonded to six equivalent Hg atoms to form a mixture of distorted face, edge, and corner-sharing SrHg6 pentagonal pyramids. There are two shorter (3.46 Å) and four longer (3.53 Å) Sr–Hg bond lengths. Hg is bonded in a 8-coordinate geometry to eight Sr atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Li3Hg by Materials Project

Li3Hg is alpha bismuth trifluoride structured and crystallizes in the cubic Fm-3m space group. The structure is three-dimensional. there are two inequivalent Li sites. In the first Li site, Li is bonded to four equivalent Li and four equivalent Hg atoms to form a mixture of distorted corner, edge, and face-sharing LiLi4Hg4 tetrahedra. All Li–Li bond lengths are 2.84 Å. All Li–Hg bond lengths are 2.84 Å. In the second Li site, Li is bonded in a 8-coordinate geometry to eight equivalent Li and six equivalent Hg atoms. All Li–Hg bond lengths are 3.27 Å. Hg is bonded in a body-centered cubic geometry to fourteen Li atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on CaHgPb by Materials Project

CaHgPb is hexagonal omega structure-derived structured and crystallizes in the hexagonal P6_3/mmc space group. The structure is three-dimensional. Ca is bonded to six equivalent Hg and six equivalent Pb atoms to form a mixture of edge and face-sharing CaHg6Pb6 cuboctahedra. All Ca–Hg bond lengths are 3.52 Å. All Ca–Pb bond lengths are 3.52 Å. Hg is bonded in a 9-coordinate geometry to six equivalent Ca and three equivalent Pb atoms. All Hg–Pb bond lengths are 2.97 Å. Pb is bonded in a 9-coordinate geometry to six equivalent Ca and three equivalent Hg atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Hg5(ClO2)2 by Materials Project

Hg5(O2Cl)2 crystallizes in the orthorhombic Ibam space group. The structure is three-dimensional. there are three inequivalent Hg2+ sites. In the first Hg2+ site, Hg2+ is bonded in a distorted linear geometry to two equivalent O2- and four equivalent Cl1- atoms. Both Hg–O bond lengths are 2.11 Å. There are a spread of Hg–Cl bond distances ranging from 2.98–3.23 Å. In the second Hg2+ site, Hg2+ is bonded in a 2-coordinate geometry to four equivalent O2- and two equivalent Cl1- atoms. There are two shorter (2.08 Å) and two longer (2.79 Å) Hg–O bond lengths. Both Hg–Cl bond lengths are 3.38 Å. In the third Hg2+ site, Hg2+ is bonded in a 4-coordinate geometry to four equivalent O2- atoms. All Hg–O bond lengths are 2.32 Å. O2- is bonded to four Hg2+ atoms to form a mixture of distorted edge and corner-sharing OHg4 tetrahedra. Cl1- is bonded in a 6-coordinate geometry to six Hg2+ atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Hg5(BrO2)2 by Materials Project

Hg5(O2Br)2 crystallizes in the orthorhombic Ibam space group. The structure is three-dimensional. there are three inequivalent Hg2+ sites. In the first Hg2+ site, Hg2+ is bonded in a distorted linear geometry to two equivalent O2- and four equivalent Br1- atoms. Both Hg–O bond lengths are 2.13 Å. There are a spread of Hg–Br bond distances ranging from 3.06–3.25 Å. In the second Hg2+ site, Hg2+ is bonded in a 2-coordinate geometry to four equivalent O2- and two equivalent Br1- atoms. There are two shorter (2.09 Å) and two longer (2.82 Å) Hg–O bond lengths. Both Hg–Br bond lengths are 3.39 Å. In the third Hg2+ site, Hg2+ is bonded in a 4-coordinate geometry to four equivalent O2- atoms. All Hg–O bond lengths are 2.34 Å. O2- is bonded to four Hg2+ atoms to form a mixture of distorted edge and corner-sharing OHg4 tetrahedra. Br1- is bonded in a 6-coordinate geometry to six Hg2+ atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on NaHg by Materials Project

NaHg is alpha iridium vanadium-like structured and crystallizes in the orthorhombic Cmcm space group. The structure is three-dimensional. there are two inequivalent Na sites. In the first Na site, Na is bonded in a 8-coordinate geometry to eight equivalent Hg atoms. There are a spread of Na–Hg bond distances ranging from 3.23–3.29 Å. In the second Na site, Na is bonded in a 8-coordinate geometry to eight equivalent Hg atoms. There are a spread of Na–Hg bond distances ranging from 3.18–3.44 Å. Hg is bonded in a 8-coordinate geometry to eight Na atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Mg2Hg by Materials Project

Mg2Hg is Cotunnite structured and crystallizes in the orthorhombic Pnma space group. The structure is three-dimensional. there are two inequivalent Mg sites. In the first Mg site, Mg is bonded in a 5-coordinate geometry to five equivalent Hg atoms. There are a spread of Mg–Hg bond distances ranging from 2.97–3.16 Å. In the second Mg site, Mg is bonded in a 4-coordinate geometry to five equivalent Hg atoms. There are a spread of Mg–Hg bond distances ranging from 2.91–3.35 Å. Hg is bonded in a 10-coordinate geometry to ten Mg atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on PrCdHg2 by Materials Project

PrHg2Cd is Heusler structured and crystallizes in the cubic Fm-3m space group. The structure is three-dimensional. Pr is bonded in a body-centered cubic geometry to eight equivalent Hg atoms. All Pr–Hg bond lengths are 3.20 Å. Hg is bonded in a body-centered cubic geometry to four equivalent Pr and four equivalent Cd atoms. All Hg–Cd bond lengths are 3.20 Å. Cd is bonded in a distorted body-centered cubic geometry to eight equivalent Hg atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on CaAgHg2 by Materials Project

CaAgHg2 is Heusler structured and crystallizes in the cubic Fm-3m space group. The structure is three-dimensional. Ca is bonded in a distorted body-centered cubic geometry to six equivalent Ag and eight equivalent Hg atoms. All Ca–Ag bond lengths are 3.61 Å. All Ca–Hg bond lengths are 3.13 Å. Ag is bonded in a 8-coordinate geometry to six equivalent Ca and eight equivalent Hg atoms. All Ag–Hg bond lengths are 3.13 Å. Hg is bonded in a body-centered cubic geometry to four equivalent Ca and four equivalent Ag atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Hg6Cl3O2 by Materials Project

Hg6O2Cl3 crystallizes in the cubic Ia-3d space group. The structure is three-dimensional. Hg+1.17+ is bonded in a distorted single-bond geometry to one O2- and three equivalent Cl1- atoms. The Hg–O bond length is 2.17 Å. There are a spread of Hg–Cl bond distances ranging from 3.04–3.19 Å. O2- is bonded in a distorted trigonal planar geometry to three equivalent Hg+1.17+ atoms. Cl1- is bonded to six equivalent Hg+1.17+ atoms to form a mixture of distorted edge and corner-sharing ClHg6 octahedra. The corner-sharing octahedral tilt angles are 36°.

36 MATERIALS SCIENCE↗