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Precision solid liner experiments on Pegasus II

Description: Pulsed power systems have been used in the past to drive solid liner implosions for a variety of applications. In combination with a variety of target configurations, solid liner drivers can be used to compress working fluids, produce shock waves, and study material properties in convergent geometry. The utility of such a driver depends in part on how well-characterized the drive conditions are. This, in part, requires a pulsed power system with a well-characterized current wave form and well understood electrical parameters. At Los Alamos, the authors have developed a capacitively driven, inductive store pulsed power machine, Pegasus, which meets these needs. They have also developed an extensive suite of diagnostics which are capable of characterizing the performance of the system and of the imploding liners. Pegasus consists of a 4.3 MJ capacitor bank, with a capacitance of 850 {micro}f fired with a typical initial bank voltage of 90 kV or less. The bank resistance is about 0.5 m{Omega}, and bank plus power flow channel has a total inductance of about 24 nH. In this paper the authors consider the theory and modeling of the first precision solid liner driver fielded on the LANL Pegasus pulsed power facility.
Date: September 1, 1995
Creator: Bowers, R.L.; Brownell, J.H. & Lee, H.
Partner: UNT Libraries Government Documents Department

Criticality benchmark results for the ENDF60 library with MCNP{trademark}

Description: The continuous-energy neutron data library ENDF60, for use with the Monte Carlo N-Particle radiation transport code MCNP4A, was released in the fall of 1994. The ENDF60 library is comprised of 124 nuclide data files based on the ENDF/B-VI (B-VI) evaluations through Release 2. Fifty-two percent of these B-VI evaluations are translations from ENDF/B-V (B-V). The remaining forty-eight percent are new evaluations which have sometimes changed significantly. Among these changes are greatly increased use of isotopic evaluations, more extensive resonance-parameter evaluations, and energy-angle correlated distributions for secondary particles. In particular, the upper energy limit for the resolved resonance region of {sup 235}U, {sup 238}U and {sup 239}Pu has been extended from 0.082, 4.0, and 0.301 keV to 2..25, 10.0, and 2.5 keV respectively. As regulatory oversight has advanced and performing critical experiments has become more difficult, there has been an increased reliance on computational methods. For the criticality safety community, the performance of the combined transport code and data library is of interest. The purpose of this abstract is to provide benchmarking results to aid the user in determining the best data library for their application.
Date: July 1, 1995
Creator: Keen, N.D.; Frankle, S.C. & MacFarlane, R.E.
Partner: UNT Libraries Government Documents Department

Preliminary analysis of core capsule x-ray spectroscopy and image results for medium-to-high growth factor implosions

Description: Recent capsule implosions using indirect drive on NOVA have probed core and near-core capsule T{sub e}, {rho} and mix structure using non-trivial pulse shapes (i.e. with a foot). These experiments have been performed using smooth as well as artificially roughened capsules. They have been performed using basically 3 non-trivial pulse-shapes with 3 different types of capsules with correspondingly different growth regimes for Rayleigh-Taylor instabilities. These experiments have employed time-dependent spectroscopy, gated imaging and absolutely calibrated time-integrated imaging as x-ray diagnostics. The authors compare nominal and {open_quotes}modified{close_quotes} 1D calculations with the spectroscopic and time-integrated image results. They find that the core T{sub e} is less than calculated (not surprising), but also that the T{sub e} of the inner pusher is substantially higher (at least 20%) than predicted, with perhaps some enhanced mix of the PVA layer towards the core.
Date: September 1, 1995
Creator: Pollak, G.; Delamater, N. & Landen, N.
Partner: UNT Libraries Government Documents Department

Laboratory studies of radionuclide migration in tuff

Description: The movement of selected radionuclides has been observed in crushed tuff, intact tuff, and fractured tuff columns. Retardation factors and dispersivities were determined from the elution profiles. Retardation factors have been compared with those predicted on the basis of batch sorption studies. This comparison forms a basis for either validating distribution coefficients or providing evidence of speciation, including colloid formation. Dispersivities measured as a function of velocity provide a means of determining the effect of sorption kinetics or mass transfer on radionuclide migration. Dispersion is also being studied in the context of scaling symmetry to develop a basis for extrapolating from the laboratory scale to the field. 21 refs., 6 figs., 2 tabs.
Date: October 1, 1989
Creator: Rundberg, R.S.; Mitchell, A.J.; Ott, M.A.; Thompson, J.L. & Triay, I.R.
Partner: UNT Libraries Government Documents Department

Manganese-oxide minerals in fractures of the Crater Flat Tuff in drill core USW G-4, Yucca Mountain, Nevada

Description: The Crater Flat Tuff is almost entirely below the water table in drill hole USW G-4 at Yucca Mountain, Nevada. Manganese-oxide minerals from the Crater Flat Tuff in USW G-4 were studied using optical, scanning electron microscopic, electron microprobe, and x-ray powder diffraction methods to determine their distribution, mineralogy, and chemistry. Manganese-oxide minerals coat fractures in all three members of the Crater Flat Tuff (Prow Pass, Bullfrog, and Tram), but they are most abundant in fractures in the densely welded devitrified intervals of these members. The coatings are mostly of the cryptomelane/hollandite mineral group, but the chemistry of these coatings varies considerably. Some of the chemical variations, particularly the presence of calcium, sodium, and strontium, can be explained by admixture with todorokite, seen in some x-ray powder diffraction patterns. Other chemical variations, particularly between Ba and Pb, demonstrate that considerable substitution of Pb for Ba occurs in hollandite. Manganese-oxide coatings are common in the 10-m interval that produced 75% of the water pumped from USW G-4 in a flow survey in 1983. Their presence in water-producing zones suggests that manganese oxides may exert a significant chemical effect on groundwater beneath Yucca Mountain. In particular, the ability of the manganese oxides found at Yucca Mountain to be easily reduced suggests that they may affect the redox conditions of the groundwater and may oxidize dissolved or suspended species. Although the Mn oxides at Yucca Mountain have low exchange capacities, these minerals may retard the migration of some radionuclides, particularly the actinides, through scavenging and coprecipitation. 23 refs., 21 figs., 2 tabs.
Date: July 1, 1990
Creator: Carlos, B.A.; Bish, D.L. & Chipera, S.J.
Partner: UNT Libraries Government Documents Department

Confinement Vessel Dynamic Analysis

Description: A series of hydrodynamic and structural analyses of a spherical confinement vessel has been performed. The analyses used a hydrodynamic code to estimate the dynamic blast pressures at the vessel's internal surfaces caused by the detonation of a mass of high explosive, then used those blast pressures as applied loads in an explicit finite element model to simulate the vessel's structural response. Numerous load cases were considered. Particular attention was paid to the bolted port connections and the O-ring pressure seals. The analysis methods and results are discussed, and comparisons to experimental results are made.
Date: August 1, 1999
Creator: Stevens, R. Robert & Rojas, Stephen P.
Partner: UNT Libraries Government Documents Department

Wildlife use of NPDES outfalls at Los Alamos National Laboratory

Description: From July through October of 1991, the Biological Resources Evaluation Team (BRET) surveyed 133 of the 140 National Pollutant Discharge and Elimination System outfalls at Los Alamos National Laboratory (LANL). The purpose of the survey was to determine the use of these wastewater outfalls by wildlife. BRET observed wildlife or evidence of wildlife (scat, tracks, or bedding) by 35 vertebrate species in the vicinity of the outfalls, suggesting these animals could be using water from outfalls. Approximately 56% of the outfalls are probably used or are suitable for use by large mammals as sources of drinking water. Additionally, hydrophytic vegetation grows in association with approximately 40% of the outfalls-a characteristic that could make these areas eligible for wetland status. BRET recommends further study to accurately characterize the use of outfalls by small and medium-sized mammals and amphibians. The team also recommends systematic aquatic macroinvertebrate studies to provide information on resident communities and water quality. Wetland assessments may be necessary to ensure compliance with wetland regulations if LANL activities affect any of the outfalls supporting hydrophytic vegetation.
Date: September 1, 1995
Creator: Foxx, T. & Blea-Edeskuty, B.
Partner: UNT Libraries Government Documents Department

Biomedical Research Group, Health Division annual report 1954

Description: This report covers the activities of the Biomedical Research Group (H-4) of the Health Division during the period January 1 through December 31, 1954. Organizationally, Group H-4 is divided into five sections, namely, Biochemistry, Radiobiology, Radiopathology, Biophysics, and Organic Chemistry. The activities of the Group are summarized under the headings of the various sections. The general nature of each section`s program, publications, documents and reports originating from its members, and abstracts and summaries of the projects pursued during the year are presented.
Date: December 1955
Creator: Langham, W. H. & Storer, J. B.
Partner: UNT Libraries Government Documents Department

Assembly and testing of a composite heat pipe thermal intercept for HTS current leads

Description: We are building high temperature superconducting (HTS) current leads for a demonstration HTS-high gradient magnetic separation (HGMS) system cooled by a cryocooler. The current leads are entirely conductively cooled. A composite nitrogen heat pipe provides efficient thermal communication, and simultaneously electrical isolation, between the lead and an intermediate temperature heat sink. Data on the thermal and electrical performance of the heat pipe thermal intercept are presented. The electrical isolation of the heat pipe was measured as a function of applied voltage with and without a thermal load across the heat pipe. The results show the electrical isolation with evaporation, condensation and internal circulation taking place in the heat pipe.
Date: September 1, 1995
Creator: Daugherty, M.A.; Daney, D.E.; Prenger, F.C.; Hill, D.D.; Williams, P.M. & Boenig, H.J.
Partner: UNT Libraries Government Documents Department

The Cold War is over. What now?

Description: As you might imagine, the end of the Cold War has elicited an intense reexamination of the roles and missions of institutions such as the Los Alamos National Laboratory. During the past few years, the entire defense establishment has undergone substantial consolidation, with a concomitant decrease in support for research and development, including in areas such as materials. The defense industry is down-sizing at a rapid pace. Even universities have experienced significant funding cutbacks from the defense community. I view this as a profound time in history, bringing changes encompassing much more than just the defense world. In fact, support for science and technology is being reexamined across the board more completely than at any other time since the end of World War II.
Date: May 1995
Creator: Hecker, S. S.
Partner: UNT Libraries Government Documents Department

1995 verification flow testing of the HDR reservoir at Fenton Hill, New Mexico

Description: Recent flow testing of the Fenton Hill HDR reservoir has demonstrated that engineered geothermal systems can be shut-in for extended periods of d= with apparently no adverse effects. However, when this particular reservoir at Venton Hill was shut-in for 2 years in a pressurized condition, natural convection within the open-jointed reservoir region appears to have leveled out the preexisting temperature gradient so that the gradient has now approached a condition more typical of liquid-dominated hydrothermal reservoirs which air invariably almost isothermal due to natural convection. As a result of the sudden flow impedance reduction that led to an almost 50% increase in Production flow new the end of the Second Phase of the LTFR in May 1993, we were uncertain as to the state of the reservoir after being shut-in for 2 years. The flow performance observed during the current testing was found to be intermediate between that at-the end of the Second Phase of the LTFT and that following, the subsequent sudden flow increase, implying that whatever caused the sudden reduction in impedance in the first place is probably somehow associated with the cooldown of the reservoir near the injection interval, since temperature recovery at the surfaces of the surrounding open joints is the most obvious phenomenon expected to occur over time within the reservoir.
Date: January 1, 1995
Creator: Brown, D.
Partner: UNT Libraries Government Documents Department

Strong interaction physics with pions at LAMPF: Report of the study group on future opportunities at LAMPF

Description: The LAMPF accelerator, with its high-intensity teams of pions and array of high-resolution spectrometers, provides opportunities for investigations of nuclear structure as well as of strong-interaction hadron dynamics. During operation of LAMPF as a national users facility, Nuclear Physics has undergone an evolution in the way it pictures nuclei: from a system of nucleons interacting through potentials to a system of mutually coupled nucleons, {Delta}(1232)`s, and mesons. While nuclear physics is in the midst of yet another shift of paradigm, with quarks and gluons playing a central role, the traditional picture still has great predictive power, and LAMPF has new opportunities to contribute to solving problems of current interest. At the same time, LAMPF is poised to make important contributions to the evolving area of nonperturbative QCD, where we will be learning how to connect phenomena at large momentum transfer to those at lower momentum scales. where the physically observable hadrons are the natural degrees of freedom. Within the traditional area, exploration of nuclei having extreme ratios of neutron/proton number is of growing interest in a variety of contexts, including astrophysics. Pion double charge exchange (the ({pi}{sup {plus_minus}}, {pi}{sup {plus_minus}}) processes) can produce proton-rich nuclei such as {sup 9}C, {sup 10}C, and {sup 11}N as well as neutron-rich nuclei such as {sup 10}He, {sup 11}Li, {sup 14}Be, and {sup 17}B. With spectrometers available for analyzing the outgoing pion spectra, one can study interesting and controversial modes of motion (soft-dipole modes) and obtain angular distributions that explore the spatial extent of neutron halos.
Date: July 1, 1995
Creator: Johnson, M.B. & Matthews, J.L.
Partner: UNT Libraries Government Documents Department

Advanced Recovery and Integrated Extraction System (ARIES) Fiscal Year 1996 Annual Report

Description: President Clinton issued Nonprolferation and Export Control Policy in September 1993 in response to the growing threat of nuclear proliferation. Four months later, in January 1994, President Clinton and Russia's President Yeltsin issued a Joint Statement Between the United States and Russia on Nonprollfieration of Weapons of Mass Destruction and the Means of Their Delivery. President Clinton announced on 1 March 1995, that approximately 200 metric tons of US- origin weapons-usable fissile materials had been declared surplus to US defense needs. The Advanced Recovery and Integrated Extraction System (ARIES) Demonstration Project is one part of the scientific response to President Clinton's promise to reduce the nuclear weapons stockpile. The work accomplished on the ARIES Demonstration Project during fiscal year 1996, 10ctober 1995 through 30 September 1996, is described in this report. The Department of Energy (DOE), by forming the Office of Fissile Materials Disposition (OFMD), has initiated a Fissile Materials Disposition Program. The first step is the disassembly and conversion of weapons pits. Of the 200 metric tons of US surplus fissile material, approximately 50 tons are weapons plutonium, and of these 50 tons, 2/3 is contained in pits. Weapons plutonium wili be extracted from pits, rendered to an unclassified form, and converted to oxide. The plutonium oxide will then be dispositioned either by immobilization in a ceramic matrix or blended with uranium oxide, fabricated into ceramic pellets of mixed oxide (MOX) fuel, and "burned" in a commercial light water reactor. The purpose of ARIES is to demonstrate two major activities: (1) dismantlement of nuclear weapons, and (2) conversion of weapons-grade plutonium into a form required for long-term storage or in preparation for the disposition (immobilization m MOX fuel) that allows for international inspection and verification, and in accordance with safeguards regimes. Plutonium does not have to be declassified before ...
Date: October 1, 1998
Creator: Dennison, David; Massey, Pamela W. & Nelson, Timothy O.
Partner: UNT Libraries Government Documents Department

Basaltic volcanic episodes of the Yucca Mountain region

Description: The purpose of this paper is to summarize briefly the distribution and geologic characteristics of basaltic volcanism in the Yucca Mountain region during the last 10--12 Ma. This interval largely postdates the major period of silicic volcanism and coincides with and postdates the timing of major extensional faulting in the region. Field and geochronologic data for the basaltic rocks define two distinct episodes. The patterns in the volume and spatial distribution of these basaltic volcanic episodes in the central and southern part of the SNVF are used as a basis for forecasting potential future volcanic activity in vicinity of Yucca Mountain. 33 refs., 2 figs.
Date: March 1, 1990
Creator: Crowe, B.M.
Partner: UNT Libraries Government Documents Department

Electrical resistivity measurements of a dense aluminum plasma

Description: In this paper the authors report results of experiments to measure the electrical resistivity for a dense strongly coupled aluminum plasma. These plasmas cover the density and temperature range from near solid density and room temperature to .03x solid and 40 eV. These conditions give values of {Lambda} = 5--6. The results indicate the resistivity is higher in this regime than most theories. Only the results of some density functional calculations give results consistent with the data.
Date: September 1, 1995
Creator: Benage, J.F. Jr.; Shanahan, W.R. & Murillo, M.S.
Partner: UNT Libraries Government Documents Department

Radionuclide Concentrations in Soils and Vegetation at Low-Level Radioactive Waste Disposal Area G during the 1997 Growing Season

Description: Soil and overstory and understory vegetation (washed and unwashed) collected at eight locations within and around Area G-a low-level radioactive solid-waste disposal facility at Los Alamos National Laboratory-were analyzed for 3H, 238Pu, 239Pu, 137CS, 234U, 235U, 228AC, Be, 214Bi, 60Co, 40& 54Mn, 22Na, 214Pb and 208Tl. In general, most radionuclide concentrations, with the exception of 3Ef and ~9Pu, in soils and overstory and understory vegetation collected from within and around Area G were within upper (95'%) level background concentrations. Although 3H concentrations in vegetation from most sites were significantly higher than background (>2 pCi mL-l), concentrations decreased markedly in comparison to last year's results. The highest `H concentration in vegetation was detected from a juniper tree that was growing over tritium shaft /+150; it contained 530,000 pCi 3H mL-l. Also, as in the pas~ the transuranic waste pad area contained the highest levels of 239Pu in soils and in understory vegetation as compared to other areas at Area G.
Date: August 1, 1998
Creator: L. Naranjo, Jr.; Fresquez, P. R. & Wechsler, R. J.
Partner: UNT Libraries Government Documents Department

An overview of the US Department of Energy Plant Lifetime Improvement Program

Description: This paper provides a brief summary of the U.S. Department of Energy`s (USDOE`s) cooperative effort with the nuclear industry to develop technology to manage the effects of material degradation in systems, structures and components (SSCs) that impact plant safety or can significantly improve plant performance/economics and to establish and demonstrate the license renewal process. Also included are efforts to reduce decontamination/decommission costs, and reduce the uncertainty in long-term service-life decision making. During 1995, the Plant Lifetime Improvement (PLIM) Program was renamed the Commercial Operating Light Water Reactor (COLWR) Program activities are focused on sustaining the LWR option for domestic electricity generation by supporting operation of existing LWRs as long as they are safe, efficient, and economical. The status of the key projects is discussed in this paper.
Date: August 1, 1995
Creator: Moonka, A.K. & Harrison, D.L.
Partner: UNT Libraries Government Documents Department

Tritium production from a low voltage deuterium discharge on palladium and other metals

Description: Over the past year the authors have been able to demonstrate that a plasma loading method produces an exciting and unexpected amount of tritium from small palladium wires. In contrast to electrochemical hydrogen or deuterium loading of palladium, this method yields a reproducible tritium generation rate when various electrical and physical conditions are met. Small diameter wires (100--250 microns) have been used with gas pressures above 200 torr at voltages and currents of about 2,000 V at 3--5 A. By carefully controlling the sputtering rate of the wire, runs have been extended to hundreds of hours allowing a significant amount (> 10`s nCi) of tritium to accumulate. they show tritium generation rates for deuterium-palladium foreground runs that are up to 25 times larger than hydrogen-palladium control experiments using materials from the same batch. They illustrate the difference between batches of annealed palladium and as received palladium from several batches as well as the effect of other metals (Pt, Ni, Nb, Zr, V, W, Hf) to demonstrate that the tritium generation rate can vary greatly from batch to batch.
Date: September 1, 1995
Creator: Claytor, T.N.; Jackson, D.D. & Tuggle, D.G.
Partner: UNT Libraries Government Documents Department

Microstructural properties of high level waste concentrates and gels with raman and infrared spectroscopies. 1997 annual progress report

Description: 'Monosodium aluminate, the phase of aluminate found in waste tanks, is only stable over a fairly narrow range of water vapor pressure (22% relative humidity at 22 C). As a result, aluminate solids are stable at Hanford (seasonal average RH {approximately}20%) but are not be stable at Savannah River (seasonal average RH {approximately}40%). Monosodium aluminate (MSA) releases water upon precipitation from solution. In contrast, trisodium aluminate (TSA) consumes water upon precipitation. As a result, MSA precipitates gradually over time while TSA undergoes rapid accelerated precipitation, often gelling its solution. Raman spectra reported for first time for monosodium and trisodium aluminate solids. Ternary phase diagrams can be useful for showing effects of water removal, even with concentrated waste. Kinetics of monosodium aluminate precipitation are extremely slow (several months) at room temperature but quite fast (several hours) at 60 C. As a result, all waste simulants that contain aluminate need several days of cooking at 60 C in order to truly represent the equilibrium state of aluminate. The high level waste (HLW) slurries that have been created at the Hanford and Savannah River Sites over that last fifty years constitute a large fraction of the remaining HLW volumes at both sites. In spite of the preponderance of these wastes, very little quantitative information is available about their physical and chemical properties other than elemental analyses.'
Date: 1997-23~
Creator: Agnew, S.F.; Coarbin, R.A. & Johnston, C.T.
Partner: UNT Libraries Government Documents Department

A predictive ocean oil spill model

Description: This is the final report of a two-year, Laboratory-Directed Research and Development (LDRD) project at the Los Alamos National Laboratory (LANL). Initially, the project focused on creating an ocean oil spill model and working with the major oil companies to compare their data with the Los Alamos global ocean model. As a result of this initial effort, Los Alamos worked closely with the Eddy Joint Industry Project (EJIP), a consortium oil and gas producing companies in the US. The central theme of the project was to use output produced from LANL`s global ocean model to look in detail at ocean currents in selected geographic areas of the world of interest to consortium members. Once ocean currents are well understood this information could be used to create oil spill models, improve offshore exploration and drilling equipment, and aid in the design of semi-permanent offshore production platforms.
Date: July 1, 1996
Creator: Sanderson, J.; Barnette, D.; Papodopoulos, P.; Schaudt, K. & Szabo, D.
Partner: UNT Libraries Government Documents Department

Dynamical hierarchies - A summary

Description: This paper summarizes some of the problems associated with the generation of higher order emergent structures in formal dynamical systems. In biological systems, higher order hyperstructures occur both in an intuitive and a formal sense: monomers, polymers, membranes, organelles, cells, tissues, organs, etc. constitute an observable hierarchy, apparently generated by the underlying biomolecular process. However, in models and simulations of these systems, it has turned out to be quite difficult to produce higher order emergent structures from first principles. The first problem is to agree on what a higher order structure is. An emergent structure can be defined through an introduction of an observational function. If a property can be observed in the dynamics, but not at the level of the fundamental first order interacting structures, we define it to be emergent. It is well known that second order structures occur relatively easy in simulation, so the problem is how to proceed to third and higher order without external interference. A third order structure is defined through the interaction of second order structures forming a new observable not found at the lower levels.
Date: April 1, 1996
Creator: Rasmussen, S.; Barrett, C.L. & Olesen, M.W.
Partner: UNT Libraries Government Documents Department

Hard chaos, quantum billiards, and quantum dot computers

Description: This is the final report of a three-year, Laboratory-Directed Research and Development (LDRD) project at the Los Alamos National Laboratory (LANL). Research was performed in analytic and computational techniques for dealing with hard chaos, especially the powerful tool of cycle expansions. This work has direct application to the understanding of electrons in nanodevices, such as junctions of quantum wires, or in arrays of dots or antidots. We developed a series of techniques for computing the properties of quantum systems with hard chaos, in particular the flow of electrons through nanodevices. These techniques are providing the insight and tools to design computers with nanoscale components. Recent efforts concentrated on understanding the effects of noise and orbit pruning in chaotic dynamical systems. We showed that most complicated chaotic systems (not just those equivalent to a finite shift) will develop branch points in their cycle expansion. Once the singularity is known to exist, it can be removed with a dramatic increase in the speed of convergence of quantities of physical interest.
Date: July 1, 1996
Creator: Mainieri, R.; Cvitanovic, P. & Hasslacher, B.
Partner: UNT Libraries Government Documents Department

Materials analysis of deposits made by the directed-light fabrication process

Description: This is the final report of a one-year, Laboratory-Directed Research and Development (LDRD) project at the Los Alamos National Laboratory (LANL). The directed-light fabrication (DLF) process is a unique method of forming three-dimensional objects by fusing airborne powders in the focus of a laser beam. This process bypasses conventional ingot processing steps of casting, homogenization, extrusion, forging, and possibly some or all of the required machining. It provides a new ``near-net-shape`` fabrication technology for difficult-to-fabricate materials such as refractory metals, metal composites, intermetallics, ceramics, and possibly superconductors. This project addresses the solidification behavior during DLF processing to characterize the technique in terms of solid/liquid interface characteristics, cooling rates, and growth rates. Materials studied were Ag-Cu, Fe-Ni, 316SS, and Al-Cu.
Date: July 1, 1996
Creator: Lewis, G.; Nemec, R. & Thoma, D.
Partner: UNT Libraries Government Documents Department

Fast events in protein folding

Description: The primary objective of this work was to develop a molecular understanding of how proteins achieve their native three-dimensional (folded) structures. This requires the identification and characterization of intermediates in the protein folding process on all relevant timescales, from picoseconds to seconds. The short timescale events in protein folding have been entirely unknown. Prior to this work, state-of-the-art experimental approaches were limited to milliseconds or longer, when much of the folding process is already over. The gap between theory and experiment is enormous: current theoretical and computational methods cannot realistically model folding processes with lifetimes longer than one nanosecond. This unique approach to employ laser pump-probe techniques that combine novel methods of laser flash photolysis with time-resolved vibrational spectroscopic probes of protein transients. In this scheme, a short (picosecond to nanosecond) laser photolysis pulse was used to produce an instantaneous pH or temperature jump, thereby initiating a protein folding or unfolding reaction. Structure-specific, time-resolved vibrational probes were then used to identify and characterize protein folding intermediates.
Date: April 1, 1996
Creator: Woodruff, W.; Callender, R.; Causgrove, T.; Dyer, R. & Williams, S.
Partner: UNT Libraries Government Documents Department