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Construction of bending magnet beamline at the APS for environmental studies. Progress report, September 1996--September 1997

Description: 'The items that were accomplished during this period are: (1) preparation and submission of the preliminary design report for the bending magnet beamline; (2) construction of the first optical enclosure (FOE) hutch for the BM beamline and ordering of the installation of utilities, in addition to the FOE hutch, the authors have started construction on the experimental hutch, although this is being supported by other funds; (3) the package has been ordered for the shutter assembly and monochromator for the bending magnet beamline, consisting of the monochromator, white beam stop, and bremstrahlung stop, all integrated on a table; (4) the beamline scientist for the bending magnet has been hired and is active on design and construction activities. In summary, the construction of the bending magnet beamline is proceeding as scheduled. The authors have obtained additional funding necessary to complete construction of the beamline and, according to the estimates, this additional funding plus the funding from the EMSP grant should allow us to complete construction of the bending magnet beamline during the three-year tenure of this grant.'
Date: January 1, 1997
Creator: Stern, E.A.
Partner: UNT Libraries Government Documents Department

Chemical Technology Division Unit Operations Section Monthly Progress Report June 1956

Description: The primary objective of this report is the monthly distribution of experimental data as acquired during that period in the course of engineering studies. Much of the data is of preliminary nature and, therefore, reasonable care should be exercised in its application. You are invited to contact the individual authors for substantiation.
Date: June 1, 1956
Creator: Eister, W. K.; Long, J. T.; Nurmi, E. O.; Suddath, J. C. & Watson, C. D.
Partner: UNT Libraries Government Documents Department

Peptide Based Radiopharmaceuticals: Specific Construct Approach

Description: The objective of this project was to develop receptor based peptides for diagnostic imaging and therapy. A series of peptides related to cell adhesion molecules (CAM) and immune regulation were designed for radiolabeling with <sup>99m</sup>Tc and evaluated in animal models as potential diagnostic imaging agents for various disease conditions such as thrombus (clot), acute kidney failure, and inflection/inflammation imaging. The peptides for this project were designed by the industrial partner, Palatin Technologies, (formerly Rhomed, Inc.) using various peptide design approaches including a newly developed rational computer assisted drug design (CADD) approach termed MIDAS (Metal ion Induced Distinctive Array of Structures). In this approach, the biological function domain and the <sup>99m</sup>Tc complexing domain are fused together so that structurally these domains are indistinguishable. This approach allows construction of conformationally rigid metallo-peptide molecules (similar to cyclic peptides) that are metabolically stable in-vivo. All the newly designed peptides were screened in various in vitro receptor binding and functional assays to identify a lead compound. The lead compounds were formulated in a one-step <sup>99m</sup>Tc labeling kit form which were studied by BNL for detailed in-vivo imaging using various animals models of human disease. Two main peptides usingMIDAS approach evolved and were investigated: RGD peptide for acute renal failure and an immunomodulatory peptide derived from tuftsin (RMT-1) for infection/inflammation imaging. Various RGD based metallopeptides were designed, synthesized and assayed for their efficacy in inhibiting ADP-induced human platelet aggregation. Most of these peptides displayed biological activity in the 1-100 ┬ÁM range. Based on previous work by others, RGD-I and RGD-II were evaluated in animal models of acute renal failure. These earlier studies showed that after acute ischemic injury the renal cortex displays RGD receptor with higher density. The results have indicated good diagnostic potential for their use in this clinical situation, as an imaging agent to ...
Date: October 21, 1997
Creator: Som, P; Rhodes, B A & Sharma, S S
Partner: UNT Libraries Government Documents Department

Modeling of cation binding in hydrated 2:1 clay minerals. Progress report, September 15, 1996--September 14, 1997

Description: 'The primary focus of the research is the development of molecular theories of ion binding to clay minerals, with a view toward understanding the mechanism of radionuclide transport through soils. The overall aim of the research and the computational methods employed are essentially unchanged from those originally proposed. The research is split conceptually into three phases, based on the radionuclides considered. The first, cesium phase has an estimated completion time of 1.5 years from the project initiation. This phase is ongoing at this time. The second, strontium and third, uranium phases will be addressed in the second half of the project period. Phase 1 Accomplishments Code Development: A computer simulation code for the treatment of hydrated smectite and vermiculite clays with varying water content has been developed. This version of the code enables calculations under conditions of constant interlayer spacing or constant applied pressure, and for the complete series of interlayer alkali-metal ions. Final development of the code for (i), calculations of exchange free energies, and (ii), calculations at constant water chemical potential should be completed within the next month. This will allow the most important scientific issues of phase 1 to be fully addressed. Hydrated Clay Structure: The molecular structures of Cs{sup +}- and Na{sup +}-montmorillonite (a common swelling clay) have been investigated. The observed layer spacings versus water content of both clays agree well with experimental swelling curves. 1,2 This has provided validation of the simulation models. Comparison of cesium and sodium structures indicate that cesium preferentially forms inner-sphere complexes with the clay surface. The relationship of this structural observation to Na{sup +} Cs{sup +} exchange thermodynamics is presently under investigation. Dry Cs{sup +}-Montmorillonite Structure: It is thought that dry, cesium-substituted montmorillonites exist as mixed-layer structures with both symmetrical (hexagonal cavities overlapping) and non-symmetrical (hexagonal cavities shifted) stacking ...
Date: January 1, 1997
Creator: Smith, D.E.
Partner: UNT Libraries Government Documents Department

In-situ spectroelectrochemical studies of radionuclide contaminated surface films on metals and the mechanism of their formation and dissolution. 1997 annual progress report

Description: 'The incorporation of radioactive contaminants into corrosion product scales on metals is being investigated using in-situ spectroscopic and electrochemical techniques. To facilitate the study, stable isotopes are used initially, while the corrosion films are simulated by electrodeposition of the appropriate oxide (hydroxide) onto a graphite substrate. Synchrotron x-ray absorption spectroscopy (XAS) is used to determine the structure and composition of the host oxide film, as well as the local structure of the impurity ion. Results on the incorporation of Sr and Ce into surface films of Ni(OH){sub 2} and NiOOH are reported. Cathodically deposited Ni(OH){sub 2} was found to be mainly in the {alpha} form while anodically prepared NiOOH consists of Ni{sup +2} and Ni{sup +4} phases. Sr in the films consists mainly of Sr{sup 2+} which appears to be coordinated to oxygen atoms and is likely to exist as small domains of co-precipitated material. Ce in Ni(OH){sub 2} exists mainly as Ce{sup +3} and as a Ce{sup +4} species when co-deposited with NiOOH. The structure of the Ce{sup +4} phase appears similar to a Ce(OH){sub 4} standard. However, x-ray diffraction and laser Raman measurements indicate that the latter chemical formulation is probably incorrect and that the material is more likely to be a disordered hydrous cerium oxide. Ce chemisorbed on Ni(OH){sub 2} and NiOOH films is predominantly in the +3 valency state. Iron oxide films prepared by anodic deposition from borate buffer solution containing Fe{sup +2}, has been found by XAS to consist mainly of {alpha} FeOOH. The latter has been found by others to be the constituent of the corrosion film on iron; this lends credence to the present simulation approach. Future work will involve studies on the incorporation of radioactive Sr, Ce, and Cs, as well as U, into nickel and iron oxide films. Investigations on the ...
Date: September 1, 1997
Creator: Melendres, C.A.; Balasubramanian, M.; Papapanayiotou, D.; Mini, S. & Mansour, A.N.
Partner: UNT Libraries Government Documents Department

Molecular dissection of the cellular mechanisms involved in nickel hyperaccumulation. 1997 annual progress report

Description: 'Phytoremediation, the use of plants for environmental cleanup of pollutants, including toxic metals, holds the potential to allow the economic restoration of heavy metal and radionuclide contaminated sites. A number of terrestrial plants are known to naturally accumulate high levels of metals in their shoots (1--2% dry weight), and these plants have been termed metal-hyperaccumulators. Clearly, the genetic traits that determine metal-hyperaccumulation offers the potential for the development of practical phytoremediation processes. The long-term objective is to rationally design and generate plants ideally suited for phytoremediation using this unique genetic material. Initially, the strategy will focus on isolating and characterizing the key genetic information needed for expression of the metal-hyperaccumulation phenotype. Recently, histidine has been shown to play a major role in Ni hyperaccumulation. Based on this information the authors propose to investigate, at the molecular level, the role of histidine biosynthesis in Ni hyperaccumuIation in Thlaspi goesingense, a Ni hyperaccumulator species.'
Date: October 28, 1997
Creator: Salt, D. E.
Partner: UNT Libraries Government Documents Department

Permanganate treatment of DNAPLs in reactive barriers and source zone flooding schemes. 1997 annual progress report

Description: 'The goals of this study are (1) to elucidate the basic mechanisms by which potassium permanganate oxidizes common chlorinated solvents, various constituents in aqueous solution, and porous-medium solids, and (2) to assess the potential for chemical oxidation by potassium permanganate to serve as a remedial scheme involving either source zone flooding or reactive barriers. The research plan involves a combined experimental/modeling study that builds on the extensive previous work in the area of reactive barrier systems, and modeling of reactive contaminant transport. The experimental studies are being undertaken at The Ohio State University by Dr. Schwartz and his co-workers. The modeling work is being conducted in Albuquerque, NM by Dr. Zhang of Intera, Inc. The workplan for this study is designed around the following four objectives (1) to describe through batch experiments the kinetics and mechanisms by which potassium permanganate oxidizes dissolved tetrachloroethene (PCE), trichloroethene (TCE), and dichloroethene (DCE), (2) to examine using column studies the nature and kinetics of reactions between potassium permanganate, residual DNAPLs (PCE, TCE, and DCE) and porous medium solids, (3) to represent the process understanding in flow and transport models that demonstrate the potential applicability of the approach, and (4) to apply the resulting computer code in the development of appropriate field tests for assessing the approach.'
Date: January 1, 1997
Creator: Schwartz, F.W.
Partner: UNT Libraries Government Documents Department

In-situ characterizations of dense non-aqueous phase liquids using partitioning tracers. Annual progress report, September 15, 1996--September 14, 1997

Description: 'This paper describes laboratory research conducted to investigate the use of partitioning tracers for the detection, volume estimation, and remediation performance assessment of vadose zones contaminated by nonaqueous phase liquids (NAPLs). These laboratory studies used Ottawa sand and field soil packed columns. The columns were saturated, then reduced to residual saturations of water and NAPL, creating a three phase system of air, water, and NAPL. Conservative and partitioning gas tracers were injected into the column and their elutions were analyzed. The method of moments was used to estimate partition coefficients between the air and NAPL phases for each of the tracers. The partition coefficients and retardation factors are used to select appropriate tracers for NAPL detection and volume estimation in the field. This research identified several perfluorocarbon tracers suitable for use in the field and demonstrated the feasibility of using partitioning tracers as a tool for NAPL detection and volume estimation in the vadose zone.'
Date: January 23, 1998
Creator: Pope, G.A.; McKinney, D.C.; Gupta, A.D.; Jackson, R.E. & Jin, M.
Partner: UNT Libraries Government Documents Department

Heavy metal pumps in plants. 1997 annual progress report

Description: 'Plants have been proposed as a bioremediation tool to help remove toxic heavy metals from contaminated land and water. However, little is known about how plants take up heavy metals from the soil and transport them to different parts of the plant. An important long term goal is to understand how heavy metals, such as copper and cadmium, are transported across the plasma membrane of plant cells. The proposed research is focused on a putative heavy metal uptake pump, AXA2p [Arabidopsis X (unknown heavy metal) ATPase, isoform 2 protein], identified in a model plant, Arabidopsis. AXA belongs to a super-family of ion-translocating P-type ATPases and is the first heavy metal pump cloned from plants. AXA2 is most similar to a subfamily of pumps recently identified in bacteria, yeast and humans which appear to pump heavy metals such as copper and cadmium. Three specific aims are proposed: (1) Determine the ion specificity of the AXA2 pump, (2) Determine how pumping activity is regulated, and (3) Determine if an increased uptake of specific heavy metals can be achieved by engineering a transgenic plant with a hyper-active pump. The hypothesis being tested is that AXA2 encodes a high affinity uptake pump for copper, with lower affinity for metals such as cadmium, zinc and nickel. Fundamental research on heavy metal transporters may eventually permit transgenic plants to be engineered with specific heavy metal uptake systems useful for bioremediation. The long term goal of the proposed research is to understand how heavy metals, such as copper and cadmium, are taken up from the soil and translocated throughout the plant. The focus is on a putative heavy metal pump, AXA2p [Arabidopsis X (unknown heavy metal) ATPase, isoform 2 protein], identified in a model plant, Arabidopsis. AXA2 belongs to a large family of ion-translocating P-type ATPases. AXA2p ...
Date: January 1, 1997
Creator: Harper, J.F.
Partner: UNT Libraries Government Documents Department

Mechanisms, chemistry and kinetics of the anaerobic biodegradation of cis-dichloroethylene and vinyl chloride. First annual progress report, September 15, 1996--September 14, 1997

Description: 'This three-year project is to study the anaerobic biological conversion of cis-1,2- dichloroethene (cDCE) and vinyl Chloride (VC) to ethene. The study is being conducted in three separate phases, the first to better understand the mechanisms involved in cDCE and VC biodegradation, the second to evaluate the chemistry of the processes involved, and the third, to study factors affecting reaction kinetics. Major funding is being provided by the US Department of Energy, but the DuPont Chemical Company has also agreed to directly cost-share on the project at a rate of $75,000 per year for the three year period. Tetrachloroethylene (PCE) and trichloroethylene (TCE) are solvents that are among the most widely occurring organic groundwater contaminants. The biological anaerobic reduction-of chlorinated aliphatic hydrocarbons (CAHs) such as PCE and TCE to cDCE and VC in groundwater was reported in the early 1980s. Further reduction of PCE and its intermediates to ethene was reported in 1989. Several pure cultures of anaerobic bacteria have been found to reductively dehalogenate PCE to cDCE Rates of reduction of PCE and TCE to cDCE are high and the need for electron donor addition for the reactions is small. However, the subsequent reduction of cDCE to VC, and then of VC to the harmless end product, ethene, is much slower and only recently has a pure culture been reported that is capable of reducing cDCE to VC or VC to ethene. There are numerous. reports of such conversions in mixed cultures. The reduction of cDCE and VC to ethene is where basic research is most needed and is the subject of this study.'
Date: January 1, 1997
Creator: McCarty, P.L. & Spormann, A.
Partner: UNT Libraries Government Documents Department

Fundamental studies of the removal of contaminants from ground and waste waters via reduction by zero-valent metals. Annual progress report, September 1, 1996--August 31, 1997

Description: 'Contaminated groundwater is a problem throughout the US and the world. In many instances the tvpes of contamination can be directly attributed to man''s actions. For instance, the burial of wastes, casual disposal of solvents in unlined pits, and the development of irrigated agriculture have all contributed to groundwater contamination. The kinds of contaminants include chlorinated solvents and toxic trace elements that are soluble and mobile in soils and aquifers. Oxyanions of selenium. chromium. uranium. arsenic. and chlorine (as perchlorate) are frequently found as contaminants on many DOE sites. In addition. the careless disposal of cleaning solvents. such as carbon tetrachloride and trichloroethylene. has further contaminated many groundwaters at these sites. In agricultural areas of the western US, shallow groundwaters have become contaminated with high levels of selenate, chromate, and uranyl. The management of these waters requires treatment to remove the contaminants before reuse or surface water disposal. In one instance in the Central Valley of California. the discharge of selenate-contaminated shallow groundwater to a wildlife refuge caused catastrophic bird deaths and deformities of embryos. At sites where solid-propellant rocket motors were tested or disposed of, high concentrations of perchlorate and trichloroethylene are being found in the groundwater. A potential remediation method for many of these oxyanions and chlorinated-solvents is to react the contaminated water with zero-valent iron. In this reaction, the iron serves as both an electron source and as a catalyst. Elemental iron is already being used, on an experimental basis, for the reductive dechlorination of solvents and the removal of toxic trace elements. Both in situ reactive barriers and above-ground reactors are being developed for this purpose. However, the design and operation of these treatment systems requires a detailed process-level understanding of the interactions between the contaminants and the iron surfaces. Only limited success has been achieved ...
Date: January 1, 1997
Creator: Yarmoff, J.A. & Amrhein, C.
Partner: UNT Libraries Government Documents Department

Complete detoxification of short chain chlorinated aliphatics: Isolation of halorespiring organisms and biochemical studies of the dehalogenating enzyme systems. 1997 annual progress report

Description: 'The objectives of the research within this grant are: (1) Isolation and characterization of chlororespiring organisms responsible for the complete dehalogenation of chlorinated ethenes and propanes. (2) Development of conditions that yield high cell densities and induce dechlorinating activity. (3) Development of assay systems to detect the dechlorinating activity in cell-free extracts. (4) Purification and characterization of the dehalogenating enzymes. Anaerobic microcosms were obtained from a variety of geographically different sediment samples. In several microcosms complete dechlorination of tetrachloroethene (PCE) to ethene (ETH), and 1,2-dichloropropane ( 1,2-D) and/or 1,2,3-trichloropropane to propene was observed. Upon subsequent transfers to anaerobic medium, sediment-free, methanogenic enrichment cultures were obtained that dechlorinated PCE to ETH, and 1,2-D to propene, respectively. 2-Bromoethanesulfonate (BES), a well known inhibitor of methanogens, did not inhibit the dechlorination of 1,2-D to propene and the dechlorination of PCE to cis-dichloroethene (cis-DCE). However,-the complete dechlorination of PCE to vinyl chloride (VC) and ETH was severely inhibited. The authors could show that BES inhibited the dechlorination of chloroethenes in cultures not containing methanogens. Previous to this study, BES was believed to be aspecific inhibitor of methanogens and the inhibitory effect of BES on declorination was explained by the involvement of methanogens in the dechlorination process. The non-methanogenic cultures obtained after the BES treatment were subsequently transferred to medium riot containing BES and complete dechlorination of PCE to ETH was observed as was in the original microcosms. Subcultures were further enriched with PCE, cis-DCE, VC, or 1,2-D as the only available electron acceptor and acetate, or acetate plus hydrogen as the only available electron donor(s). To date these cultures have undergone up to 45 transfers. Interestingly, two cultures that originally dechlorinated PCE to ETH, but were then enriched with cis-DCE or VC, lost their ability to-dechlorinate PCE or TCE. This finding indicates that different ...
Date: January 1, 1997
Creator: Loeffler, F.E. & Tiedje, J.M.
Partner: UNT Libraries Government Documents Department

Molecular characterization of a novel heavy metal uptake transporter from higher plants and its potential for use in phytoremediation. 1997 annual progress report

Description: 'In the following the author reports on progress on the Department of Energy Grant from the Office of Energy Research and Office of Environmental Management on the topic of Molecular characterization of a novel heavy metal uptake transporter from higher plants and its potential use in phytoremediation. In this research the authors are investigating the following hypotheses: (1) A novel metal transporter cDNA isolated in my lab functions as a plasma membrane heavy metal and uptake transporter in plants roots. (2.) Over-expression of this cDNA in plants can be used to enhance plasma membrane metal uptake into plant tissues.'
Date: January 1, 1997
Creator: Schroeder, J.I.
Partner: UNT Libraries Government Documents Department

The efficacy of oxidative coupling for promoting in-situ immobilization of hydroxylated aromatics in contaminated soil and sediment systems. Progress report, September 15, 1996--September 14, 1997

Description: 'The principal objective for Year 1 of this study has included sorbent collection, preparation and characterization, as well as investigation of the efficacy of abiotic/enzymatic coupling reactions on the irreversible binding of phenolic compounds on natural soils and sediments. In response to a budget reduction request specific modifications were made without compromising the integrity of the proposed work. The modified Phase 1 experimental matrix consists of four natural sorbents and three phenolic sorbates. Preliminary experiments with Chelsea soil indicated excessive release of soil organic matter (SOM) into solution, thereby complicating determination of aqueous phase phenol concentrations. It was therefore decided to substitute Lachine shale for the Chelsea soil. This shale is a well-characterized natural sorbent used previously in the laboratory. Additionally two field soils having similar soil morphology were identified based on their particle size distribution and organic matter content. These soils were located from US Department of Agriculture soil survey data and collected aseptically from a forested and a grassland site. Another deviation from the proposed schedule of tasks was the initiation of work from Phase 2 and Phase 3. In addition to experiments with natural systems, preliminary work with model and engineered systems was initiated earlier than scheduled in order to integrate and relate all three aspects of the study and provide a more robust perspective of field applications of this remediation technology.'
Date: August 25, 1997
Creator: Weber, W.J. Jr. & Bhandari, A.
Partner: UNT Libraries Government Documents Department

The migration and entrapment of DNAPLs in physically and chemically heterogeneous porous media. Annual progress report, September 15, 1996--August 25, 1997

Description: 'The overall objective of this research is to investigate the influence of coupled physical and chemical heterogeneity on the migration and entrapment of DNAPLs in the saturated zone. This research includes laboratory and numerical investigations for a matrix of fluid and solid properties encompassing a range of wettability characteristics. Specific objectives include: (1) quantification of medium wettability and interfacial tensions; (2) determination of hydraulic property relations; (3) two-dimensional infiltration experiments; (4) modification of a continuum based multiphase flow simulator to account for physical heterogeneity, saturation independent and saturation dependent wettability, and concentration dependent wettability and interfacial tension; and (5) utilization of this model to explore the potential influence of coupled physical and chemical heterogeneities on the migration of DNAPLs and the development of innovative remediation schemes. Research conducted during this period was directed primarily towards the accomplishment of goals (1), (2), (4) and (5); specific details are given below. Goal (3) builds upon results from the other objectives and will, therefore, be started in the coming year.'
Date: January 1, 1997
Creator: Abriola, L.M. & Demond, A.H.
Partner: UNT Libraries Government Documents Department

Improved risk estimated from carbon tetrachloride. Annual progress report, October 1, 1996--September 30, 1997

Description: 'Carbon tetrachloride (CCl{sub 4}) has been used extensively within the Department of Energy (DOE) nuclear weapons facilities. Rocky Flats was formerly the largest volume user of CCl{sub 4} in the US, with 5,000 gallons used there in 1977 alone. At the Hanford site, several hundred thousand gallons of CCl{sub 4} were discharged between 1955 and 1973 into underground cribs for storage. Levels of CCl{sub 4} in groundwater at highly contaminated sites at the Hanford. facility have exceeded the drinking water standard of 5 ppb by several orders of magnitude. High levels of CCl{sub 4} at these facilities represent a potential health hazard for workers conducting cleanup operations and for surrounding communities. The level of CCl{sub 4} cleanup required at these sites and associated costs are driven by current human health risk estimates which assume that CCl{sub 4} is a genotoxic carcinogen. The overall purpose of these studies is to improve the scientific basis for assessing the health risk associated with human exposure to CCl{sub 4}. Specifically, the authors will determine the toxicokinetics of inhaled and ingested CCl{sub 4} in F344/Crl rats, B6C3F1 mice, and Syrian hamsters. They will also evaluate species differences in the metabolism of CCl{sub 4} by rats, mice, hamsters, and man. Dose-response relationships will be determined in all these studies. This information will be used to improve the physiologically based pharmacokinetic (PBPK) model for CCl4 originally developed by Paustenbach et al. (1988) and more recently revised by Thrall and Kenny (1996). They will also provide scientific evidence that CCl{sub 4} , like chloroform, is a hepatocarcinogen only when exposure results in cell damage, cell killing, and regenerative cell proliferation. In combination, the studies outlined in this proposal will provide the exact types of information needed to enable refined cancer risk estimates for CCl{sub 4} under the new ...
Date: October 27, 1997
Creator: Benson, J.M.
Partner: UNT Libraries Government Documents Department

Partitioning tracers for in-situ detection and quantification of dense nonaqueous. 1997 annual progress report

Description: 'The overall goal of the proposed project is to explore the use of partitioning tracers to characterize dense nonaqueous phase liquids (DNAPLs) in subsurface systems. Bulk-phase partitioning tracers will be investigated to detect and determine DNAPL saturation, while interface partitioning tracers will be investigated to measure the area of the DNAPL-water interface. The specific objectives that will be addressed to accomplish this goal are: (1) investigate the use of partitioning tracers to detect and determine both the saturation and interfacial area of DNAPLs in saturated porous media; (2) investigate the effect of rate-limited mass transfer on the transport behavior of partitioning tracers; (3) investigate the effect of porous-media heterogeneity on the transport behavior of partitioning tracers; and (4) develop and evaluate mathematical models capable of simulating the transport of partitioning tracers in complex systems.'
Date: November 10, 1997
Creator: Brusseau, M. L.
Partner: UNT Libraries Government Documents Department

Molecular genetics of metal detoxification: Prospects for phytoremediation. 1997 annual progress report

Description: 'The authors proposed to characterize a number of fission yeast mutants that are hypersensitivity to cadmium and deficient in the production of metal-peptide complexes. For each of the mutants the authors sought to clone the gene responsible for the mutant phenotype and more importantly to define the gene function. They summarize the progress made thus far for each of the mutants. Mutants that hypoproduce phytochelatins are: (1) DS12--The gene has been cloned, but a full length cDNA remains to be isolated. They believe the longest clone is short at the 5 feet end by less than 100 bp. This gene encodes sulfite reductase and its function is needed for Pb-induced sulfide production, but not Cd-induced sulfide production. Since this enzyme acts upstream of cysteine biosynthesis, the likely reason that this mutant hypoproduces phytochelatins is that it fails to produce sufficient cysteine during Cd stress. (2) JS563--The gene has been cloned and found to encode a sulfide dehydrogenase. In vitro, the authors found that the protein binds FAD, converts S{sup 2-} to S{sup 0} while reducing quinone. The protein is membrane associated and has been localized to the mitochondria. Its likely function is to detoxify sulfide in the mitochondria resulting from cadmium-induced sulfide production. The sulfide electrons are likely used for the electron transport chain. Cells that have a defect in this enzyme cannot oxidize mitochondrial S{sup 2-} resulting in high toxic levels of S{sup 2-} during Cd stress. In addition, the high S{sup 2-} level precipitates Cd{sup 2-} to form CdS, and the lack of free Cd{sup 2+} fails to induce phytochelatin synthase activity to produce phytochelatin peptides. (3) JS282--The genomic clone that restores Cd tolerance to JS282 has been isolated. Surprisingly, this genomic clone when present in a multicopy vector in a wild type background causes hypersensitivity to Cd ...
Date: October 15, 1997
Creator: Ow, D.W.
Partner: UNT Libraries Government Documents Department

Molecular-level processes governing the interaction of contaminants with iron and manganese oxides. 1997 annual progress report

Description: 'The central tenet of this proposal is that a fundamental understanding of specific mineral surface-site reactivities will substantially improve reactive transport models of contaminants in geologic systems, and will allow more effective remediation schemes to be devised. Most large-scale, macroscopic models employ global chemical reaction kinetics and thermochemistry. However, such models do not incorporate molecular-level input critical to the detailed prediction of how contaminants interact with minerals in the subsurface. A first step leading to the incorporation of molecular-level processes in large-scale macroscopic models is the ability to understand which molecular-level processes will dominate the chemistry at the microscopic grain level of minerals. To this end, the research focuses on the fundamental mechanisms of redox chemistry at mineral surfaces. As much of this chemistry in sediments involves the Fe(III)/Fe(II) and Mn(IV)/Mn(II) couples, the authors focus on mineral phases containing these species. Of particular interest is the effect of the local coordination environment of Fe and Mn atoms on their reactivity toward contaminant species. Studies of the impact of local atomic structure on reactivity in combination with knowledge about the types and amounts of various surfaces on natural grain- size minerals provide the data for statistical models. These models in turn form the basis of the larger-scale macroscopic descriptions of reactivity that are needed for reactive transport models. A molecular-level understanding of these mechanisms will enhance the ability to design much greater performance efficiency, cost effectiveness, and remediation strategies that have minimal negative impact on the local environment. For instance, a comprehensive understanding of how minerals that contain Fe(II) reduce oxyanions and chlorinated organics should enable the design of other Fe(II)-containing remediation materials in a way that is synergistic with existing minerals in the subsurface environment.'
Date: June 1, 1997
Creator: Chambers, S.A. & Brown, G.
Partner: UNT Libraries Government Documents Department

Modeling of cation binding in hydrated 2:1 clay minerals

Description: 'The primary focus of the research is the development of molecular theories of ion exchange on clay minerals, with a view toward understanding the mechanism of radionuclide transport through soils. The specific scientific goals of the study involve using molecular simulation methods to correlate clay-ion binding strengths with interlayer structure and swelling properties. This should build upon the fundamental understanding of clay behavior and allow for improvement in transport modeling of radionuclides in clay-rich soils.'
Date: June 1, 1998
Creator: Smith, D.E.
Partner: UNT Libraries Government Documents Department

Molecular genetics of metal detoxification: Prospects for phytoremediation. 1998 annual progress report

Description: 'The authors seek to define the genes involved in heavy metal tolerance and sequestration. Two complementary approaches were taken: (1) clone and characterize the genes that complement cadmium hypersensitive mutants of fission yeast, specifically those responsible for production of metal-binding complexes, and (2) isolate genes that can confer cadmium hypertolerance to wild type strains of fission yeast. This work summarizes present status of a 3 year project.'
Date: June 1, 1998
Creator: Ow, D.W.
Partner: UNT Libraries Government Documents Department

Molecular profiling of microbial communities from contaminated sources: Use of substractive cloning methods and rDNA spacer sequences. 1997 annual progress report

Description: 'This project is to develop molecular methods for rapid characterization of microbial communities in contaminated ecosystems. The authors are exploring the use of {sup 16}s ribosomal DNA intergenic spacer regions (ISRs) to profile community composition. The choice proves to be a good one: there are 200--550 bases of 1 to 3 variable regions from which to choose species-specific probes, as well as 2--4 stretches of conserved sequence from which to develop universal PCR (polymerase chain reaction) primers. Preliminary community characterization is complete, and several types of arrays are under development to determine the types of bacteria present and the status of the ground water. Profiling the community composition of polluted groundwater will impact the broad field of microbial ecology as well as mixed-waste bioremediation. Results The samples the authors have been analysing were provided by Dr. Fred Brockman from Pacific Northwest Laboratory, and were collected at the US DOE Hanford site, Washington state. The samples were microbial filtrates from ground water polluted with 2 mg/L carbon tetrachloride and 250 mg/L nitrate and subjected to enrichment (acetate + nitrate) and recirculation. This project is described in some detail in PNNL-11113, Accelerated In Situ Bioremediation of Groundwater, by M.J. Truex, B.S. Hooker, and D.B. Anderson, July 1996.'
Date: December 1, 1997
Partner: UNT Libraries Government Documents Department