Showing papers by "Pacific Northwest National Laboratory published in 1990"

New developments in biochemical mass spectrometry: electrospray ionization

Abstract: The principles, development, and recent application of electrospray ionization-mass spectrometry (ESI-MS) to biological compounds are reviewed. ESI-MS methods now allow determination of accurate molecular weights for proteins extending to over 50,000, and in some cases well over 100,000. Similar capabilities are being developed for oligonucleotides. The instrumentation used for ESI-MS is briefly described and it is shown that, although ionization efficiency appears to be uniformly high, detector sensitivity may be directly correlated with molecular weight. The use of tandem mass spectrometry (e.g., MS/MS) for extending collision-induced dissociation (CID) methods to the structural studies of large molecules is described. For example, effective CID of various albumin species (molecular weight approximately 66,000) can be obtained, far larger than obtainable for singly charged molecular ions. The combination of capillary electrophoresis, in both free solution zone electrophoresis and isotachophoresis formats, as well as microcolumn liquid chromatography with ESI-MS, provides the capability for on-line separation and analysis of subpicomole quantities of proteins. These and other new developments related to ESI-MS are illustrated by a range of examples. Fundamental considerations suggest even more impressive developments may be anticipated related to detection sensitivity and methods for obtaining structural information.

Observations of Thermally Developed Wind Systems in Mountainous Terrain

Abstract: Slope and valley wind systems are local thermally driven circulations that form frequently in complex terrain areas. Recent research has focused on the temperature structure along the slope and valley axes that leads to the wind systems. Two new tools being used in these analyses include the topographic amplification factor, which quantifies the role of the topography in producing bulk temperature gradients along a valley’s axis, and atmospheric heat budgets, which identify key physical processes leading to changes in temperature structure. Both tools are in an early stage of development, are being applied primarily to steady-state nighttime periods, and are leading to new concepts and understanding.

Primary sequence information from intact proteins by electrospray ionization tandem mass spectrometry

Abstract: Tandem mass spectrometry has been used to obtain information related to portions of the primary sequence for an intact protein, bovine ribonuclease A. Multiply charged molecular ions, generated by electrospray ionization, were collisionally dissociated at low energies in a triple quadrupole mass spectrometer to yield singly and multiply charged fragment ions that can be assigned to the known sequence of the protein. Dissociation of the highly charged molecular ions resulted in pairs of complementary product ions. The higher order (gas-phase) protein structure affects the dissociation processes, as observed in comparisons of tandem mass spectra of the native and disulfide-reduced forms of ribonuclease A.

Effect of reducing disulfide-containing proteins on electrospray ionization mass spectra.

Abstract: Electrospray ionization produces multiply charged molecular ions for biomolecules with molecular weights in excess of 100,000. This allows mass spectrometers with limited mass-to-charge range to extend their molecular weight range by a factor equal to the number of charges. The maximum number of observed charges for peptides and smaller proteins correlates well with the number of basic amino acid residues (Arg, Lys, His), except for disulfide-containing molecules, such as lysozyme and bovine albumin. However, reduction of disulfide linkages with 1,4-dithiothreitol (Cleland's reagent) may allow the protein to be in an extended conformation and make "buried" basic residues available for protonation to yield higher charged molecular ions by the electrospray ionization process. For larger proteins reduction of disulfide bridges greatly increases the maximum charge state, but charging of basic amino acid residues remains less efficient than for smaller proteins.

Radiation-induced defects and amorphization in zircon

Abstract: The effects of self-radiation damage as a function of cumulative alpha-decay events in synthetic zircon doped with 238Pu and natural zircons damaged over geologic time are compared and interpreted in terms of the accumulation of both defects and amorphousness. The radiation-induced unit-cell expansion and amorphization result in macroscopic swelling that increases sigmoidally with cumulative decay events and saturates at a fully amorphous state. The derived amorphous fraction as a function of cumulative dose is consistent with models based on the multiple overlap of displacement cascades, indicating that amorphization in zircon occurs as a result of the local accumulation of high defect concentrations rather than directly within a displacement cascade. Annealing of point defects in the natural zircons suppresses initial swelling and delays the onset of amorphization. Full recrystallization of the zircon structure from the amorphous state occurs in two stages, with kinetics and activation energies consistent with the reported thermal stability of the amorphous state. This study further confirms that actinide doping is a viable accelerated technique to study or simulate radiation effects from alpha decay on geologic time scales.

Quantitative Estimates of Soil Ingestion in Normal Children between the Ages of 2 and 7 Years: Population-based Estimates Using Aluminum, Silicon, and Titanium as Soil Tracer Elements

Abstract: This investigation was undertaken to provide quantitative estimates of soil ingestion in young children on a population basis, and to identify demographic and behavioral characteristics that influence the amount of soil ingested. A total of 104 children between the ages of 2 and 7 yr were selected randomly from the population of a three-city area in southeastern Washington State. Using aluminum, silicon, and titanium as tracer elements, a mass-balance approach was employed to assess daily soil ingestion. A duplicate of all food items consumed, all feces, and some urine excreted were collected on 4 consecutive d, along with soil and house dust samples from each child's home. Samples were analyzed by x-ray fluorescence spectrometry. After adjustment of the soil ingestion estimates to account for missing food, excreta samples, and nonfood items consumed, the average daily values based on the three tracer elements were: aluminum, 38.9 mg/d (median = 25.3 mg/d); silicon, 82.4 mg/d (median = 59.4 mg/d)...

Evidence for an effect of ELF electromagnetic fields on human pineal gland function.

Abstract: A study was carried out to determine possible effects of 60-Hz electromagnetic-field exposure on pineal gland function in humans. Overnight excretion of urinary 6-hydroxymelatonin sulfate (6-OHMS), a stable urinary metabolite of the pineal hormone melatonin, was used to assess pineal gland function in 42 volunteers who used standard (conventional) or modified continuous polymer wire (CPW) electric blankets for approximately 8 weeks. Volunteers using conventional electric blankets showed no variations in 6-OHMS excretion as either a group or individuals during the study period. Serving as their own controls, 7 of 28 volunteers using the CPW blankets showed statistically significant changes in their mean nighttime 6-OHMS excretion. The CPW blankets switched on and off approximately twice as often when in service and produced magnetic fields that were 50% stronger than those from the conventional electric blankets. On the basis of these findings, we hypothesize that periodic exposure to pulsed DC or extremely low frequency electric or magnetic fields of sufficient intensity and duration can affect pineal gland function in certain individuals.

Suggestive evidence for the two-neutrino double- beta decay of 76Ge.

Abstract: A dramatic reduction in background was achieved in the latest Pacific Northwest Laboratory--University of South Carolina germanium detectors Two 105-kg natural-isotopic-abundance detectors were operated for 192 kg yr The residual spectrum, after straightforward corrections, has a significant region resembling the theoretical spectrum of the two-neutrino {beta}{beta} decay of {sup 76}Ge A fit to the data yields {ital T}{sub 1/2}{sup 2{nu}}({sup 76}Ge)=(11{sub {minus}03}{sup +06}){times}10{sup 21} yr at the 95% CL, which agrees with shell-model predictions

Hydrogen atom transfer reactions of transition-metal hydrides. Kinetics and mechanism of the hydrogenation of. alpha. -cyclopropylstyrene by metal carbonyl hydrides

Abstract: The hydrogenation of {alpha}-cyclopropylstyrene (CPS) by a series of metal carbonyl hydrides (MH) gives a mixture of the unrearranged hydrogenation product Ph(CH{sub 3})(c-C{sub 3}H{sub 5})CH (UN) and the rearranged hydrogenation product (E)-Ph(CH{sub 3})C{double bond}CHCH{sub 2}CH{sub 3} (RE). With the exception of HCr(CO){sub 3}Cp, second-order kinetics are found, conforming to the rate law {minus}d(CPS)/dt = k(CPS)(MH). The proposed mechanism involves hydrogenation by sequential hydrogen atom transfers from the metal hydride to the organic substrate. The rate-determining step is the first hydrogen atom transfer in which a carbon-centered radical and a metal-centered radical are formed. In the case of HCr(CO){sub 3}Cp at 22{degree}C, the equilibrium constant for this step is K {approximately} 10{sup {minus}12}. The effect of the significant amount of 17-electron {sup {sm bullet}}Cr(CO){sub 3}Cp radical formed in the hydrogenation of CPS by HCr(CO){sub 3}Cp is accommodated by the kinetic analysis. Since the initially formed carbon-centered radical undergoes first-order ring-opening rearrangement in competition with second-order trapping by MH, analysis of the product ratio as a function of (MH) concentration provides relative rates of hydrogen atom transfer from metal hydrides to a carbon-centered radical.

Exposure of mammalian cells to 60-Hz magnetic or electric fields: analysis of DNA repair of induced, single-strand breaks.

Abstract: DNA damage was induced in isolated human peripheral lymphocytes by exposure at 5 Gy to 60Co radiation. Cells were permitted to repair the DNA damage while exposed to 60-Hz fields or while sham-exposed. Exposed cells were subjected to magnetic (B) or electric (E) fields, alone or in combination, throughout their allotted repair time. Repair was stopped at specific times, and the cells were immediately lysed and then analyzed for the presence of DNA single-strand breaks (SSB) by the alkaline-elution technique. Fifty to 75 percent of the induced SSB were repaired 20 min after exposure, and most of the remaining damage was repaired after 180 min. Cells were exposed to a 60-Hz ac B field of 1 mT; an E field of 1 or 20 V/m; or combined E and B fields of 0.2 V/m and 0.05 mT, 6 V/m and 0.6 mT, or 20 V/m and 1 mT. None of the exposures was observed to affect significantly the repair of DNA SSB.

Review and Evaluation of the Effects of Xenobiotic Chemicals on Microorganisms in Soil

Abstract: Publisher Summary This chapter reviews and evaluates the relevance and quality of existing xenobiotic data bases and test methods for evaluating (1) direct and indirect effects (both adverse and beneficial) of xenobiotics on the soil microbial community, (2) direct and indirect effects of the soil microbial community on xenobiotics, and (3) “adequacy of test methods used to evaluate these effects and interactions. The distribution of a xenobiotic between environmental compartments depends on the chemodynamic properties of the compound and on the physicochemical properties of the soil, and it occurs across soil–water and soil–air interfaces and across biological membranes. In assessing the effects of xenobiotic compounds on soil microorganisms, it is necessary to decide which microbial processes or properties should be evaluated. When exposed to xenobiotic compounds, various segments of the soil microbial community are affected to different extents. The degree to which a xenobiotic affects microbial activities is largely dependent on the chemical, its dosage, method of application, and the particular physicochemical characteristics of the soil, such as soil type, temperature, water content, and pH. A systemic examination of those classes of xenobiotics that have not been evaluated for their effects on microorganisms needs to be performed to allow development of a predictive model for environmental risk assessment.

Molecular characterization of X-ray-induced mutations at the HPRT locus in plateau-phase Chinese hamster ovary cells.

Abstract: CHO-K1 cells were irradiated in plateau phase to determine the effects of dose, dose fractionation, and delayed replating on the type, location and frequency of mutations induced by 250 kVp X-rays at the hypoxanthine-guinine phosphoribosyl transferase (HPRT) locus. Independent HPRT-deficient cell lines were isolated from each group for Southern blot analysis using a hamster HPRT cDNA probe. When compared with irradiation with 4 Gy and immediate replating, dose fractionation (2 Gy + 24 h + 2 Gy) and delayed plating (4 Gy + 24 h) appeared to have no effect on the frequency of deletions encompassing the entire gene. Since an increase in survival was noted under these conditions, these data suggest that repair of sublethal and potentially lethal damage acts equally on all premutagenic lesions, regradless of type or location. Differences in the mutation spectrum were noted when cells were irradiated at 2 Gy and replated immediately. The location of the deletion breakpoints was determined in 15 mutants showing partial loss of the HPRT locus. In 12 of these cell lines one or both of the breakpoints appearead to be located near the center of the gene, indicating a nonranrandom distribution of mutaions. These results indicate that damage induced by ionizing radiation results in a nonrandom distribution of genetic damage, suggesting that certain regions of the genome may be acutely sensitive to the mutagenic effect of ionizing radiation.

Iron, radiation, and cancer.

Abstract: Increased iron content of cells and tissue may increase the risk of cancer. In particular, high available iron status may increase the risk of a radiation-induced cancer. There are two possible mechanisms for this effect: iron can catalyze the production of oxygen radicals, and it may be a limiting nutrient to the growth and development of a transformed cell in vivo. Given the high available iron content of the western diet and the fact that the world is changing to the western model, it is important to determine if high iron increases the risk of cancer.

Further reduction of radioactive backgrounds in ultrasensitive germanium spectrometers

Abstract: The radioactive background in two 1.1-kg Ge detectors was significantly reduced by material selection and careful control of fabrication of both the germanium crystals. The isotopes 57,58Co and 65Zn, formed cosmogenically in the crystals, were reduced by minimizing the time between the final between the final zone refinement, crystal growth, installation in the cryostat, and placement underground. An attempt was made to reduce the background from the decay of 68Ge in the detectors by deep mining the ore, rushing it through the refinement, crystal growing, and detector fabrication processes, and storing the germanium underground at all times it was not “in process”. Cosmogenically formed 54Mn, 59Fe, and 56,57,58,60Co in the cryostat were minimized by electroforming the cryostat parts. The ubiquitous background from primordial 40K in electronic components was virtually eliminated by selecting low-background components and by hiding the first-stage preamplifier behind 2.5 cm of 450-yr-old lead in one unit and special low-background lead in the other. Details of the procedures used are discussed.

Complexes containing a C2 bridge between an electron-rich metal and an electron-deficient metal. An agostic interaction in a RuCH2CH2Zr moiety

Abstract: La reaction de (C 5 H 5 )(PMe 3 ) 2 RuC≡CH avec (C 5 H 5 ) 2 Zr(H)(Cl) dans le toluene conduit a la formation de (C 5 H 5 )(PMe 3 ) 2 RuCH=CHZrCl(C 5 H 5 ) 2 qui par hydrolyse donne les complexes [(C 5 H 5 ) 2 ZrCl] 2 O et (C 5 H 5 )(PMe 3 ) 2 RuCH=CH 2 . Ce dernier complexe reagit avec le complexe (C 5 H 5 ) 2 ZrHCl pour donner le complexe (C 5 H 5 )(PMe 3 ) 2 RuCH 2 CH 2 ZrCl(C 5 H 5 ) 2 qui est etudie par diffraction RX

Dynamical low-energy electron-diffraction analysis of bismuth and antimony epitaxy on GaAs(110).

Abstract: The atomic geometry of Bi adsorbed on GaAs(110) is determined using low-energy electron diffraction (LEED) and compared with calculated atomic geometries of GaAs(111)-p(1\ifmmode\times\else\texttimes\fi{}1)-Sb and clean GaAs(110). The analysis of the one-monolayer, epitaxical films is facilitated by comparing LEED intensity data measured for each system under identical experimental conditions and analyzed using a common multiple-scattering model. The overlapping chain geometry, recently proposed as a possible alternative to the previously determined geometry for the GaAs(110)-p(1\ifmmode\times\else\texttimes\fi{}1)-Sb system, was tested for both the Sb and Bi systems. Comprehensive multiple-scattering calculations indicate, however, that the previously determined geometry provides the superior fit to the LEED intensity measurements. Several improvements to the LEED analysis methodology, including simultaneous multidimensional optimization, are described.

Theoretical and experimental studies of optical nonlinearities of haloforms CHX3, X=F, Cl, Br, I

Abstract: In this paper, we present ab initio calculations of static polarizability α and static first and second hyperpolarizabilities β and γ for the haloform series CHX3, where X=F, Cl, Br, and I using the effective core potential (ECP) approach. The microscopic optical nonlinearities α, β, and γ are calculated as the derivatives of the energy with respect to the electric field, with the energy determined by means of the self‐consistent‐field approach (SCF), and nonlinearities calculated by means of the coupled perturbed Hartree–Fock (CPHF) formalism. To test the approximation introduced by the ECP method, nonlinear optical responses for the lighter members of the series CHF3 and CHCl3 are compared with all electron calculations. The effects due to basis set size and inclusion of diffuse and polarization functions of d and f type are examined. The ECP technique is then used to calculate optical nonlinearities for CHBr3 and CHI3. Although very good agreement is found between calculated and experimental polarizabi...

A dynamic reaction coordinate approach to ab initio reaction pathways: Application to the 1,5 hexadiene Cope rearrangement

Abstract: A modified dynamic reaction coordinate algorithm for tracing reaction paths is implemented in the framework of ab initio molecular orbital calculations. This method requires fewer energy and gradient evaluations than the traditional intrinsic reaction coordinate methodology and produces reaction pathways of acceptable accuracy. The approach is applied to the 1,5 hexadiene Cope rearrangement for which we trace the pathways passing through the chair and boat transition states. Analysis of the lowest energy pathway indicates that the rearrangement is concerted and synchronous.

Capillary isotachophoresis with UV and tandem mass spectrometric detection for peptides and proteins.

Abstract: The application of capillary isotachophoresis (CITP) and combined CITP-mass spectrometry (MS) for peptides and proteins is demonstrated. Separation of simple peptide mixtures, as well as enzymatic digets of proteins, is also reported using CITP with UV detection. The potential utility of CITP for proteins is demonstrated. Initial studies of combined CITP-MS of enzymatic digests is also demonstrated, showing the potential for rapid sequence determination.

The development and structure of nocturnal slope winds in a simple valley

Abstract: The results of an observational and modeling study of the nocturnal slope winds in a simple valley are presented. The valley was approximately 225 m deep in the region of the measurements, and featured a uniform slope angle of approximately 23 ° on one of its sidewalls. The wind and temperature structure of the katabatic flows on the valley sidewalls were measured with tower-mounted instruments, and a Doppler sodar and instruments on a tethered balloon and a 61-m tower were used to determine the atmospheric conditions near the center of the valley. The temperature structure of the slope flows was summarized by characteristic scale parameters h and δT for the inversion depth and strength, respectively. On the sidewalls 50 m above the valley floor, the inversion depths were generally smaller and the inversion strengths were weaker than they were on the sidewalls 100 m higher. These results differ significantly from those obtained over a simple slope of an isolated mountain or ridge. The down-valley winds are shown to be important in limiting the strength of the sidewall inversions. The formation of an inversion in the valley also has a pronounced effect on the structure of the slope flows. Numerical simulations suggest that the presence of adiabatic layers in the valley atmosphere is associated with decreases in the slope-flow inversion depth with increasing downslope distance. The simulations also indicate that the length scales that characterize the momentum and inversion depths behave similarly in flows down simple slopes but not in flows down the sidewalls of a valley.

Fish behavior and environmental assessment

Abstract: Studies at the Pacific Northwest Laboratory have evaluated fish behavior and migration in response to gas-supersaturated water, thermal discharge, water-soluble fractions (WSFs) of coal liquids and other environmental stresses. Approaches have included biotelemetry in the field, and avoidance/attraction and predator/prey studies in the laboratory. This article specifically addresses three study examples and integrates the results with those of related studies. Overall, major findings included the following: Thermal discharges (surface water Δts 0->17°C) did not block upstream migration of sonic-tagged adult chinook salmon (Oncorhynchus tschawytscha) and rainbow trout (O. mykiss, formerly Salmo gairdneri) in the Hanford Reach of the Columbia River. Juvenile chinook salmon avoided thermal discharges in the laboratory when Δts exceeded 9 to 11°C above ambient. However, juvenile salmon were more susceptible to predation at 10 to 20% of the thermal dose causing loss of equilibrium. Radio-tagged adult chinook salmon swam deeper in supersaturated water than in normally saturated water in the Snake River and, thereby, avoided the upper, critical zone. Carp (Cyprinus carpio) and black bullhead (Ictalurus melas) did not always avoid lethal gas levels in the laboratory and some fish died in the test apparatus. Fathead minnow (Pimephales promelas) avoided the WSF of a coal liquid at concentrations causing acute effects but not at those causing chronic effects. Rainbow trout did not avoid coal liquid WSFs although they reportedly avoid the major constituent, phenol, tested as a pure compound. Susceptibility to predation of juvenile rainbow trout did not increase until phenol concentrations reached the acute LC50. A conceptual model to link avoidance and toxicological data for environmental assessment is presented.