105 K West Cask Transportation Facility Modification Acceptance for Beneficial Use Checklist Project A.5 and A.6 (open access)

105 K West Cask Transportation Facility Modification Acceptance for Beneficial Use Checklist Project A.5 and A.6

The CTFM Subproject of the SNF Project has prepared an ABU checklist per SNF Administrative Procedure (AP) CS-6-019. This checklist identifies the essential documentation needed to operate and maintain the 105 KW CTFM/CLS Structures, Systems, and Components (SSCs) when ownership is transferred from the CTFM Subproject to K Basins Operations. Approval of this supporting document demonstrates an agreement by the approvers as to the documentation required at turnover.
Date: May 5, 2000
Creator: HARRIS, D.L.
Object Type: Report
System: The UNT Digital Library
2007 Nuclear Data Review (open access)

2007 Nuclear Data Review

The results of a review and evaluation of neutron and non-neutron nuclear data published in the scientific literature are presented. The status of new chemical elements is examined. Data on revised values for the isotopic composition of the elements are reviewed and recommended values are presented. Half-lives of very long-lived nuclides are presented, including double beta decay, double electron capture, long-lived alpha decay and long-lived beta decay. Data from new measurements on the very heavy elements (trans-meitnerium elements) are discussed and tabulated. The first observation of the radioactive decay mode of the free neutron is discussed. New measurements that have expanded the neutron drip line for magnesium and aluminum are discussed. Data on recent neutron cross-section and resonance integral measurements are also discussed.
Date: May 5, 2008
Creator: Holden, N. E.
Object Type: Article
System: The UNT Digital Library
2007 Savannah River Site Annual Illness and Injury Surveillance Report (open access)

2007 Savannah River Site Annual Illness and Injury Surveillance Report

The U.S. Department of Energy’s (DOE) commitment to assuring the health and safety of its workers includes the conduct of epidemiologic surveillance activities that provide an early warning system for health problems among workers. The Illness and Injury Surveillance Program monitors illnesses and health conditions that result in an absence of workdays, occupational injuries and illnesses, and disabilities and deaths among current workers.
Date: May 5, 2009
Creator: United States. Department of Energy. Office of Health, Safety, and Security.
Object Type: Report
System: The UNT Digital Library
3D-Simulation Studies of SNS Ring Doublet Magnets (open access)

3D-Simulation Studies of SNS Ring Doublet Magnets

The accumulator ring of the Spallation Neutron Source (SNS) at ORNL employs in its straight sections closely packed quadrupole doublemagnets with large aperture of R=15.1 cm an relatively short iron-to-iron distance of 51.4 cm. These quads have much extended fringe field, and magnetic interferences among them in the doublet assemblies is not avoidable. Though each magnet in the assemblies has been individually mapped to high accuracy of lower than 0.01 percent level, the experimental data including the magnetic interference effect will not be available. We have performed 3D computing simulations on a quadrupole doublet model in order to assess the degree of the interference and to obtain relevant data for the SNS commissioning and operation.
Date: May 5, 2005
Creator: Wang, J. G.; N., Tsoupas & Venturini, M.
Object Type: Article
System: The UNT Digital Library
Adjustable Shock Test Sled for Haversine Pulses at 250 fps (open access)

Adjustable Shock Test Sled for Haversine Pulses at 250 fps

New test requirements were developed by Sandia National Laboratory to simulate a regime of shock testing not previously performed at the Kansas City Plant operated by Honeywell Federal Manufacturing & Technologies. These environments were unique in that they involved amplitude of shock >1000g with relatively long pulse durations (greater 5 ms but less than 10 ms) and involved velocity changes up to 235 ft/sec. Ten months were available to develop, design, manufacture and prove-in this new capability. We designed a new shock sled to deliver this new family of shock environments in a laboratory test. The performance range of the new sled includes five specific shocks (1000 g – 8 ms, 1300 - 6 ms, 1500 g – 5.4 ms, 1950 g – 6 ms, 2250 g – 5.4 ms; all haversine shaped), and it also incorporates adjustability to accommodate new shocks within this range. These shock environments result in velocity changes ranging from 160 fps to 250 fps. The test sled accommodates test articles weighing up to 20 lbs and measuring up to 10” along any axis.
Date: May 5, 2008
Creator: Hartwig, Troy; Hower, Brent & Seaholm, Aaron
Object Type: Article
System: The UNT Digital Library
Advanced Electric and Magnetic Material Models for FDTD Electromagnetic Codes (open access)

Advanced Electric and Magnetic Material Models for FDTD Electromagnetic Codes

The modeling of dielectric and magnetic materials in the time domain is required for pulse power applications, pulsed induction accelerators, and advanced transmission lines. For example, most induction accelerator modules require the use of magnetic materials to provide adequate Volt-sec during the acceleration pulse. These models require hysteresis and saturation to simulate the saturation wavefront in a multipulse environment. In high voltage transmission line applications such as shock or soliton lines the dielectric is operating in a highly nonlinear regime, which require nonlinear models. Simple 1-D models are developed for fast parameterization of transmission line structures. In the case of nonlinear dielectrics, a simple analytic model describing the permittivity in terms of electric field is used in a 3-D finite difference time domain code (FDTD). In the case of magnetic materials, both rate independent and rate dependent Hodgdon magnetic material models have been implemented into 3-D FDTD codes and 1-D codes.
Date: May 5, 2005
Creator: Poole, B. R.; Nelson, S. D. & Langdon, S.
Object Type: Article
System: The UNT Digital Library
ANL pre analysis of the SHEBA/CERES experiments. (open access)

ANL pre analysis of the SHEBA/CERES experiments.

The French and British nuclear programs have prepared a series of natural uranium oxide fuel samples spiked with small amounts of the individual fission products which makeup a large fraction of the total neutron absorption by fission products in spent nuclear fuel. Both programs have utilized these samples in experimental reactors and have inferred the worth of the individual fission products. These results have been used to validate the cross sections used in criticality safety calculations. These measurements constitute a major element in support of spent fuel burnup credit in these countries.
Date: May 5, 2000
Creator: Palmiotti, G.; Smith, M.; Klann, R.; Fujita, E. & Imel, G.
Object Type: Report
System: The UNT Digital Library
Application of Reservoir Characterization and Advanced Technology to Improve Recovery and Economics in a Lower Quality Shallow Shelf San Andres Reservoir. Annual Report: August 3, 2000--August 2, 2001 (open access)

Application of Reservoir Characterization and Advanced Technology to Improve Recovery and Economics in a Lower Quality Shallow Shelf San Andres Reservoir. Annual Report: August 3, 2000--August 2, 2001

The OXY-operated Class 2 Project at West Welch is designed to demonstrate how the use of advanced technology can improve the economics of miscible CO{sub 2} injection projects in lower quality Shallow Shelf Carbonate reservoirs. The research and design phase (Budget Period 1) primarily involved advanced reservoir characterization. The current demonstration phase (Budget Period 2) is the implementation of the reservoir management plan for an optimum miscible CO{sub 2} flood design based on the reservoir characterization. Although Budget Period 1 for the Project officially ended 12/31/96, reservoir characterization and simulation work continued during the Budget Period 2. During the seventh annual reporting period (8/3/00-8/2/01) covered by this report, work continued on interpretation of the interwell seismic data to create porosity and permeability profiles which were distributed into the reservoir geostatistically. The initial interwell seismic CO{sub 2} monitor survey was conducted and the acquired data processed and interpretation started. Only limited well work and facility construction were conducted in the project area. The CO{sub 2} injection initiated in October 1997 was continued, although the operator had to modify the operating plan in response to low injection rates, well performance and changes in CO{sub 2} supply. CO{sub 2} injection was focused in …
Date: May 5, 2003
Creator: Beebe, Tom
Object Type: Report
System: The UNT Digital Library
Assessment of Raman Spectroscopy as a Silicone Pad Production Diagnostic (open access)

Assessment of Raman Spectroscopy as a Silicone Pad Production Diagnostic

Silicone pressure pads are currently deployed in the W80. The mechanical properties of these pads are largely based on the degree of crosslinking between the polymer components that comprise the raw gumstock from which they are formed. Therefore, it is desirable for purposes of both production and systematic study of these materials to have a rapid, reliable means of assaying the extent of crosslinking. The present report describes the evaluation of Raman spectroscopy in this capacity.
Date: May 5, 2005
Creator: Saab, A P; Balazs, G B & Maxwell, R S
Object Type: Report
System: The UNT Digital Library
Association between severity of prescribed burns and subsequent activity of conifer-infesting beetles in stands of longleaf pine (open access)

Association between severity of prescribed burns and subsequent activity of conifer-infesting beetles in stands of longleaf pine

A randomized complete block experiment was performed to measure the effect of prescribed, dormant-season burns of three different levels of severity (measured as fuel consumption and soil surface heating) on subsequent insect infestation and mortality of mature longleaf pine (Pinus palustris Mill.). Multiple-funnel traps baited with a low release rate of turpentine and ethanol were used to monitor activity of certain coniferophagous beetles. Non-aggressive species, including the root beetles Hylastes salebrosus Eichhoff and H. tenuis Eichhoff, the ambrosia beetle Xyleborus pubescens Zimmermann, the reproduction weevil Pachylobius picivorus (Germar), and buprestid borers, were attracted to burned plots in numbers that correlated positively with burn severity. Beetle attraction to burned sites was greatest in the first weeks post-burn and disappeared by the second year. Two potential tree-killing bark beetles, Dendroctonus terebrans (Olivier) and Ips grandicollis (Eichhoff), were trapped in significant numbers but exhibited no attraction to burned plots. Tree mortality correlated significantly with the severity of the burns and amounted to 5% of stems in the hottest burn treatment after 3 years. The majority of the mortality was observed in the second and third years post-burn. Attacks of Ips and Dendroctonus bark beetles were apparent on nearly all dead or dying trees, …
Date: May 5, 2003
Creator: Sullivan, Brian, T; Fettig, C. J.; Otrosina, William, J.; Dalusky, Mark, J. & Berrisford, C.W.
Object Type: Article
System: The UNT Digital Library
Atmospheric Radiation Measurement Program Facilities Newsletter, April 2000 (open access)

Atmospheric Radiation Measurement Program Facilities Newsletter, April 2000

Monthly newsletter discussing news and activities related to the Atmospheric Radiation Measurement Program, articles about weather and atmospheric phenomena, and other related topics.
Date: May 5, 2000
Creator: Atmospheric Radiation Measurement Program (U.S.)
Object Type: Journal/Magazine/Newsletter
System: The UNT Digital Library
ATOMIC LAYER DEPOSITION OF TITANIUM OXIDE THIN FILMS ONNANOPOROUS ALUMINA TEMPLATES FOR MEDICAL APPLICATIONS (open access)

ATOMIC LAYER DEPOSITION OF TITANIUM OXIDE THIN FILMS ONNANOPOROUS ALUMINA TEMPLATES FOR MEDICAL APPLICATIONS

Nanostructured materials may play a significant role in controlled release of pharmacologic agents for treatment of cancer. Many nanoporous polymer materials are inadequate for use in drug delivery. Nanoporous alumina provides several advantages over other materials for use in controlled drug delivery and other medical applications. Atomic layer deposition was used to coat all the surfaces of the nanoporous alumina membrane in order to reduce the pore size in a controlled manner. Both the 20 nm and 100 nm titanium oxide-coated nanoporous alumina membranes did not exhibit statistically lower viability compared to the uncoated nanoporous alumina membrane control materials. In addition, 20 nm pore size titanium oxide-coated nanoporous alumina membranes exposed to ultraviolet light demonstrated activity against Escherichia coli and Staphylococcus aureus bacteria. Nanostructured materials prepared using atomic layer deposition may be useful for delivering a pharmacologic agent at a precise rate to a specific location in the body. These materials may serve as the basis for 'smart' drug delivery devices, orthopedic implants, or self-sterilizing medical devices.
Date: May 5, 2009
Creator: Brigmon, R.
Object Type: Article
System: The UNT Digital Library
Attractor Explosions and Catalyzed Vacuum Decay (open access)

Attractor Explosions and Catalyzed Vacuum Decay

We present a mechanism for catalyzed vacuum bubble production obtained by combining moduli stabilization with a generalized attractor phenomenon in which moduli are sourced by compact objects. This leads straightforwardly to a class of examples in which the Hawking decay process for black holes unveils a bubble of a different vacuum from the ambient one, generalizing the new endpoint for Hawking evaporation discovered recently by Horowitz. Catalyzed vacuum bubble production can occur for both charged and uncharged bodies, including Schwarzschild black holes for which massive particles produced in the Hawking process can trigger vacuum decay. We briefly discuss applications of this process to the population and stability of metastable vacua.
Date: May 5, 2006
Creator: Green, Daniel; Silverstein, Eva & Starr, David
Object Type: Report
System: The UNT Digital Library
Background Radioactivity in River and Reservoir Sediments near Los Alamos, New Mexico (open access)

Background Radioactivity in River and Reservoir Sediments near Los Alamos, New Mexico

As part of its continuing Environmental Surveillance Program, regional river and lake-bottom sediments have been collected annually by Los Alamos National Laboratory (the Laboratory) since 1974 and 1979, respectively. These background samples are collected from three drainage basins at ten different river stations and five reservoirs located throughout northern New Mexico and southern Colorado. Radiochemical analyses for these sediments include tritium, strontium-90, cesium-137, total uranium, plutonium-238, plutonium-239,-240, americium-241, gross alpha, gross beta, and gross gamma radioactivity. Detection-limit radioactivity originates as worldwide fallout from aboveground nuclear weapons testing and satellite reentry into Earth's atmosphere. Spatial and temporal variations in individual analyte levels originate from atmospheric point-source introductions and natural rate differences in airborne deposition and soil erosion. Background radioactivity values on sediments reflect this variability, and grouped river and reservoir sediment samples show a range of statistical distributions that appear to be analyte dependent. Traditionally, both river and reservoir analyte data were blended together to establish background levels. In this report, however, we group background sediment data according to two criteria. These include sediment source (either river or reservoir sediments) and station location relative to the Laboratory (either upstream or downstream). These grouped data are statistically evaluated through 1997, and background …
Date: May 5, 2002
Creator: McLin, Stephen G. & Lyons, Dale W.
Object Type: Report
System: The UNT Digital Library
Beta-cell Assembly for the Quad Gas Sampling Detector (open access)

Beta-cell Assembly for the Quad Gas Sampling Detector

The beta-cells used in the beta-gamma detector have taken time to develop and to standardize the assembly of them. In making the assembly routine it is important to have step by step assembly instructions as well as a list of potential problems and their solutions. This document attempts to accomplish these goals.
Date: May 5, 2008
Creator: Cooper, Matthew W.; Bowyer, Ted W.; McIntyre, Justin I.; Hayes, James C.; Heimbigner, Tom R.; Ripplinger, Michael D. et al.
Object Type: Report
System: The UNT Digital Library
Biodegradation of trichlorofluoromethane by sediment associated anaerobic bacteria from an aquifer contaminated by landfill leachate (open access)

Biodegradation of trichlorofluoromethane by sediment associated anaerobic bacteria from an aquifer contaminated by landfill leachate

The halogenated aliphatic hydrocarbon trichlorofluoromethane has been widely used as a refrigerant and aerosol propellant.
Date: May 5, 2000
Creator: Brigmon, R.L.
Object Type: Article
System: The UNT Digital Library
Biomass Biorefinery for the production of Polymers and Fuels (open access)

Biomass Biorefinery for the production of Polymers and Fuels

The conversion of biomass crops to fuel is receiving considerable attention as a means to reduce our dependence on foreign oil imports and to meet future energy needs. Besides their use for fuel, biomass crops are an attractive vehicle for producing value added products such as biopolymers. Metabolix, Inc. of Cambridge proposes to develop methods for producing biodegradable polymers polyhydroxyalkanoates (PHAs) in green tissue plants as well as utilizating residual plant biomass after polymer extraction for fuel generation to offset the energy required for polymer extraction. The primary plant target is switchgrass, and backup targets are alfalfa and tobacco. The combined polymer and fuel production from the transgenic biomass crops establishes a biorefinery that has the potential to reduce the nation’s dependence on foreign oil imports for both the feedstocks and energy needed for plastic production. Concerns about the widespread use of transgenic crops and the grower’s ability to prevent the contamination of the surrounding environment with foreign genes will be addressed by incorporating and expanding on some of the latest plant biotechnology developed by the project partners of this proposal. This proposal also addresses extraction of PHAs from biomass, modification of PHAs so that they have suitable properties for …
Date: May 5, 2008
Creator: Peoples, Dr. Oliver P.
Object Type: Report
System: The UNT Digital Library
Broken SU(3) antidecuplet for {Theta}{sup +} and {Xi}{sub 3/2} (open access)

Broken SU(3) antidecuplet for {Theta}{sup +} and {Xi}{sub 3/2}

If the narrow exotic baryon resonances {Theta}{sup +}(1540) and {Xi}{sub 3/2} are members of the J{sup P} = 1/2{sup +} antidecuplet with N*(1710), the octet-antidecuplet mixing is required not only by the mass spectrum but also by the decay pattern of N*(1710). This casts doubt on validity of the {Theta}{sup +} mass prediction by the chiral soliton model. While all pieces of the existing experimental information point to a small octet-decuplet mixing, the magnitude of mixing required by the mass spectrum is not consistent with the value needed to account for the hadronic decay rates. The discrepancy is not resolved even after the large experimental uncertainty is taken into consideration. We fail to find an alternative SU(3) assignment even with different spin-parity assignment. When we extend the analysis to mixing with a higher SU(3) multiplet, we find one experimentally testable scenario in the case of mixing with a 27-plet.
Date: May 5, 2004
Creator: Pakvasa, Sandip & Suzuki, Mahiko
Object Type: Article
System: The UNT Digital Library
Calibration and Characterization of Single Photon Counting Cameras for Short-Pulse Laser Experiments (open access)

Calibration and Characterization of Single Photon Counting Cameras for Short-Pulse Laser Experiments

The photon counting efficiency of various CCD based cameras was studied as a function of x-ray energy and exposure. A pair of Spectral Instruments Model 800 CCD cameras fitted with 16 {micro}m thick back-illuminated CCDs were calibrated at low x-ray energy using two well established histogram methods, a standard pixel for pixel histogram and the single pixel event histogram method. In addition, two new thick substrate CCDs were evaluated for use at high energy. One was a commercially available Princeton Instruments LCX1300 deep depletion CCD camera while the other was a custom designed 650 {micro}m thick partially depleted CCD fitted to a SI 800 camera body. It is shown that at high x-ray energy, only a pixel-summing algorithm was able to derive spectral data due to the spreading of x-ray events over many pixels in the thicker substrate CCDs. This paper will describe the different algorithms used to extract spectra and the absolute detection efficiencies using these algorithms. These detectors will be very useful to detect high-energy x-ray photons from high-intensity short pulse laser interactions.
Date: May 5, 2008
Creator: Maddox, B. R.; Park, H.; Remington, B. A. & McKernan, M.
Object Type: Article
System: The UNT Digital Library
Cathodes for Low Temperature Sofc: Issues Concerning Interference From Inert Gas Adsorption and Charge Transfer (open access)

Cathodes for Low Temperature Sofc: Issues Concerning Interference From Inert Gas Adsorption and Charge Transfer

This report summarizes the work done on the project over the duration of the project, from October 1, 2002 through December 31, 2003, which includes a three month no-cost extension. Effort was directed in the following areas: (1) Fabrication of Sr-doped LaCoO3 (LSC) dense and porous samples. (2) Design and construction of a conductivity relaxation apparatus for the estimation of surface exchange coefficient, k{sub chem}, which depends on adsorption, and oxygen chemical diffusion coefficient, {tilde D}{sub 0}, the parameters which are thought to describe the cathodic activation polarization (overall charge transfer) in mixed ionic electronic conducting (MIEC) cathodes. (3) The measurement of and K{sub chem} and {tilde D}{sub 0} on LSC by conductivity relaxation, as a function of temperature and oxygen partial pressure, p{sub O{sub 2}}. (4) Fabrication of YSZ electrolyte discs with patterned LSM and LSC electrodes with three-phase boundary (TPB) length, l{sub TPB}, varying between 50 and 1200 cm{sup -1}. (5) The measurement of charge transfer resistance, R{sub ct}, and estimation of the charge transfer resistivity, {rho}{sub ct}, as a function of temperature and p{sub O{sub 2}}, and the incorporation of the adsorption step in the analysis. (6) Preliminary cell tests with oxidants having different inert gas diluents; …
Date: May 5, 2004
Creator: Virkar, Anil V.
Object Type: Report
System: The UNT Digital Library
Characterization of Dosimetry of the BMRR Horizontal Thimble Tubes and Broad Beam Facility. (open access)

Characterization of Dosimetry of the BMRR Horizontal Thimble Tubes and Broad Beam Facility.

The Brookhaven Medical Research Reactor was a 5 mega-watt, light-water cooled and heavy-graphite moderated research facility. It has two shutter-equipped treatment rooms, three horizontally extended thimble tubes, and an ex-core broad beam facility. The three experimental thimbles, or activation ports, external to the reactor tank were designed for several uses, including the investigations on diagnostic and therapeutic methods using radioactive isotopes of very short half-life, the analysis of radiation exposure on tissue-equivalent materials using a collimated neutron beam, and the evaluation of dose effects on biological cells to improve medical treatment. At the broad beam facility where the distribution of thermal neutrons was essential uniform, a wide variety of mammalian whole-body exposures were studied using animals such as burros or mice. Also studied at the broad beam were whole-body phantom experiments, involving the use of a neutron or photon beam streaming through a screen to obtain the flux spectrum suitable for dose analysis on the sugar-urea-water mixture, a tissue-equivalent material. Calculations of the flux and the dose at beam ports based on Monte Carlo particle-transport code were performed, and measurements conducted at the same tally locations were made using bare or cadmium-covered gold foils. Analytical results, which show good agreement …
Date: May 5, 2008
Creator: Hu, J. P.; Reciniello, R. N. & Holden, N. E.
Object Type: Article
System: The UNT Digital Library
Characterization of Tank 23H Supernate Per Saltstone Waste Acceptance Criteria Analysis Requirements -2005 (open access)

Characterization of Tank 23H Supernate Per Saltstone Waste Acceptance Criteria Analysis Requirements -2005

Variable depth Tank 23H samples (22-inch sample [HTF-014] and 185-inch sample [HTF-013]) were pulled from Tank 23H in February, 2005 for characterization. The characterization of the Tank 23H low activity waste is part of the overall liquid waste processing activities. This characterization examined the species identified in the Saltstone Waste Acceptance Criteria (WAC) for the transfer of waste into the Salt-Feed Tank (SFT). The samples were delivered to the Savannah River National Laboratory (SRNL) and analyzed. Apart from radium-226 with an average measured detection limit of < 2.64E+03 pCi/mL, which is about the same order of magnitude as the WAC limit (< 8.73E+03 pCi/mL), none of the species analyzed was found to approach the limits provided in the Saltstone WAC. The concentration of most of the species analyzed for the Tank 23H samples were 2-5 orders of magnitude lower than the WAC limits. The achievable detection limits for a number of the analytes were several orders of magnitude lower than the WAC limits, but one or two orders of magnitude higher than the requested detection limits. Analytes which fell into this category included plutonium-241, europium-154/155, antimony-125, tin-126, ruthenium/rhodium-106, selenium-79, nickel-59/63, ammonium ion, copper, total nickel, manganese and total organic carbon.
Date: May 5, 2005
Creator: Oji, L
Object Type: Report
System: The UNT Digital Library
Characterizing the Vertical Distribution of Aerosols Over the ARM SGP Site (open access)

Characterizing the Vertical Distribution of Aerosols Over the ARM SGP Site

This project focused on: 1) evaluating the performance of the DOE ARM SGP Raman lidar system in measuring profiles of water vapor and aerosols, and 2) the use of the Raman lidar measurements of aerosol and water vapor profiles for assessing the vertical distribution of aerosols and water vapor simulated by global transport models and examining diurnal variability of aerosols and water vapor. The highest aerosol extinction was generally observed close to the surface during the nighttime just prior to sunrise. The high values of aerosol extinction are most likely associated with increased scattering by hygroscopic aerosols, since the corresponding average relative humidity values were above 70%. After sunrise, relative humidity and aerosol extinction below 500 m decreased with the growth in the daytime convective boundary layer. The largest aerosol extinction for altitudes above 1 km occurred during the early afternoon most likely as a result of the increase in relative humidity. The water vapor mixing ratio profiles generally showed smaller variations with altitude between day and night. We also compared simultaneous measurements of relative humidity, aerosol extinction, and aerosol optical thickness derived from the ARM SGP Raman lidar and in situ instruments on board a small aircraft flown routinely …
Date: May 5, 2009
Creator: Richard Ferrare, Connor Flynn, David Turner
Object Type: Text
System: The UNT Digital Library
Chloroethyinitrosourea-derived ethano cytosine and adenine adducts are substrates for escherichia coli glycosylases excising analogous etheno adducts (open access)

Chloroethyinitrosourea-derived ethano cytosine and adenine adducts are substrates for escherichia coli glycosylases excising analogous etheno adducts

Exocyclic ethano DNA adducts are saturated etheno ring derivatives formed mainly by therapeutic chloroethylnitrosoureas (CNUs), which are also mutagenic and carcinogenic. In this work, we report that two of the ethano adducts, 3,N{sup 4}-ethanocytosine (EC) and 1,N{sup 6}-ethanoadenine (EA), are novel substrates for the Escherichia coli mismatch-specific uracil-DNA glycosylase (Mug) and 3-methyladenine DNA glycosylase II (AlkA), respectively. It has been shown previously that Mug excises 3,N{sup 4}-ethenocytosine ({var_epsilon}C) and AlkA releases 1,N{sup 6}-ethenoadenine ({var_epsilon}A). Using synthetic oligonucleotides containing a single ethano or etheno adduct, we found that both glycosylases had a {approx}20-fold lower excision activity toward EC or EA than that toward their structurally analogous {var_epsilon}C or {var_epsilon}A adduct. Both enzymes were capable of excising the ethano base paired with any of the four natural bases, but with varying efficiencies. The Mug activity toward EC could be stimulated by E. coli endonuclease IV and, more efficiently, by exonuclease III. Molecular dynamics (MD) simulations showed similar structural features of the etheno and ethano derivatives when present in DNA duplexes. However, also as shown by MD, the stacking interaction between the EC base and Phe 30 in the Mug active site is reduced as compared to the {var_epsilon}C base, which could account …
Date: May 5, 2004
Creator: Guliaev, Anton B.; Singer, B. & Hang, Bo
Object Type: Article
System: The UNT Digital Library