Science.gov

Sample records for hydrogen-deuterium exchange studies

  1. Dual Studies on a Hydrogen-Deuterium Exchange of Resorcinol and the Subsequent Kinetic Isotope Effect

    ERIC Educational Resources Information Center

    Giles, Richard; Kim, Iris; Chao, Weyjuin Eric; Moore, Jennifer; Jung, Kyung Woon

    2014-01-01

    An efficient laboratory experiment has been developed for undergraduate students to conduct hydrogen-deuterium (H-D) exchange of resorcinol by electrophilic aromatic substitution using D[subscript 2]O and a catalytic amount of H[subscript 2]SO[subscript 4]. The resulting labeled product is characterized by [superscript 1]H NMR. Students also…

  2. Combining size-exclusion chromatography with differential hydrogen-deuterium exchange to study protein conformational changes.

    PubMed

    Makarov, Alexey A; Helmy, Roy

    2016-01-29

    Methods for protein characterization are being actively developed based on the growing importance of protein therapies and applications. The goal of this study was to demonstrate the use of size-exclusion chromatography (SEC) in combination with differential hydrogen-deuterium exchange (HDX) to compare protein global conformational changes at different solution conditions. Using chaotropic mobile phase additive, differential HDX was used to detect a number of solvent accessible labile protons of protein on-column at pH and temperature conditions which provided unrestricted intrinsic H/D exchange (all-or-nothing approach). Varying SEC on-column conditions allowed for protein conformational changes to be observed. Temperature and pressure were independently studied with regards to their effect on the proteins' (insulin, cytochrome C, ubiquitin, and myoglobin) conformational changes in the solution. The obtained ΔHDX profiles revealed protein conformational changes in solution under varied conditions manifested as the difference in the number of protons exchanged to deuterons, or vice-versa. The approach described in this manuscript could prove useful for protein batch-to-batch comparisons, for optimization of chemical reactions with enzyme as catalyst or for protein chemical modification reactions. PMID:26763301

  3. Pulsed hydrogen/deuterium exchange mass spectrometry for time-resolved membrane protein folding studies.

    PubMed

    Khanal, Anil; Pan, Yan; Brown, Leonid S; Konermann, Lars

    2012-12-01

    Kinetic folding experiments by pulsed hydrogen/deuterium exchange (HDX) mass spectrometry (MS) are a well-established tool for water-soluble proteins. To the best of our knowledge, the current study is the first that applies this approach to an integral membrane protein. The native state of bacteriorhodopsin (BR) comprises seven transmembrane helices and a covalently bound retinal cofactor. BR exposure to sodium dodecyl sulfate (SDS) induces partial unfolding and retinal loss. We employ a custom-built three-stage mixing device for pulsed-HDX/MS investigations of BR refolding. The reaction is triggered by mixing SDS-denatured protein with bicelles. After a variable folding time (10 ms to 24 h), the protein is exposed to excess D(2) O buffer under rapid exchange conditions. The HDX pulse is terminated by acid quenching after 24 ms. Subsequent off-line analysis is performed by size exclusion chromatography and electrospray MS. These measurements yield the number of protected backbone N-H sites as a function of folding time, reflecting the recovery of secondary structure. Our results indicate that much of the BR secondary structure is formed quite late during the reaction, on a time scale of 10 s and beyond. It is hoped that in the future it will be possible to extend the pulsed-HDX/MS approach employed here to membrane proteins other than BR. PMID:23280751

  4. Hydrogen-deuterium exchange studies of the rat thyroid transcription factor 1 homeodomain.

    PubMed

    Esposito, G; Fogolari, F; Damante, G; Formisano, S; Tell, G; Leonardi, A; Di Lauro, R; Viglino, P

    1997-06-01

    The 1H NMR solution structure of the rat thyroid transcription factor 1 homeodomain (TTF-1 HD) showed that the molecule folds like classical homeodomains. The C-terminal extension of helix III (fragment 51-59) appeared to adopt a helical geometry, albeit not as rigid as the preceding portion, but the hydrogen-deuterium exchange of backbone amides and the NOE data provided evidence of a discontinuity between the two moieties of helix III at the highly conserved fragment Asn51-His52-Arg53. Analysis of quantitative measurements of isotope exchange rates allows one to recognize the general occurrence, in that region of HD motifs, of opposite effects to helix III stability. Asparagine, histidine and arginine residues occur most frequently at the beginning and end of protein helices. In TTF-1 HD a local fluctuation is observed in the fragment 51-53 which either kinks or tightens the alpha-helix. A search through the protein structure database reveals that the three most common variants of HD fragments 51-53 are often involved in helices and, frequently, in helix initiation or termination. For homeodomains in general, the nature of the fragment 51-53 may be related to the conformational dynamics of their DNA-recognition helix (helix III). Besides the specific results on fragment 51-53, the complete isotope exchange analysis of TTF-1 HD data shows that the partially solvent-exposed recognition helix is stabilized by hydrophobic interactions, like most of the structured regions of the molecule. Hydrophobic stabilization of the contacting regions meets the requirements of a DNA-interaction mechanism which, as shown with other DNA-protein complexes, should entail negative heat capacity variations due to changes in solvent exposure of the nonpolar protein surface. PMID:9255944

  5. Study of the conformational change of adsorbed proteins on biomaterial surfaces using hydrogen-deuterium exchange with mass spectroscopy.

    PubMed

    Kim, Jinku

    2016-05-01

    There is no doubt that protein adsorption plays a crucial role in determining biocompatibility of biomaterials. Despite the information of the identity and composition of blood plasma/serum proteins adsorbed on surfaces of biomaterials to understand which proteins are involved in blood/biomaterial interactions, it still does not provide information about the conformations and orientations of adsorbed protein, which are very important in determining biological responses to biomaterials. Therefore, our laboratory has developed an experimental technology to probe protein conformations on materials that is applicable to mixtures of proteins. Herein, the new application of hydrogen/deuterium (H/D) exchange combined with mass spectrometry was applied to determine conformational changes of adsorbed proteins at biomaterial surfaces. The results suggest that there may be a significant conformational change in adsorbed proteins at 'low' bulk concentrations that leads to a large change in the kinetics of H/D exchange as compared to 'high' bulk concentrations. This technique may eventually be useful for the study of the kinetics of protein conformational changes. PMID:26896658

  6. Using Hydrogen/Deuterium Exchange Mass Spectrometry to Study Conformational Changes in Granulocyte Colony Stimulating Factor upon PEGylation

    PubMed Central

    Wei, Hui; Ahn, Joomi; Yu, Ying Qing; Tymiak, Adrienne; Engen, John R.; Chen, Guodong

    2012-01-01

    PEGylation is the covalent attachment of polyethylene glycol to proteins, and it can be used to alter immunogenicity, circulating half life and other properties of therapeutic proteins. To determine the impact of PEGylation on protein conformation, we applied hydrogen/deuterium exchange mass spectrometry (HDX MS) to analyze Granulocyte Colony Stimulating Factor (G-CSF) upon PEGylation as a model system. The combined use of HDX automation technology and data analysis software allowed reproducible and robust measurements of the deuterium incorporation levels for peptic peptides of both PEGylated and non-PEGylated G-CSF. The results indicated that significant differences in deuterium incorporation were induced by PEGylation of G-CSF, although the overall changes observed were quite small. PEGylation did not result in gross conformational rearrangement of G-CSF. The data complexity often encountered in HDX MS measurements was greatly reduced though a data processing and presentation format designed to facilitate the comparison process. This study demonstrates the practical utility of HDX MS for comparability studies, process monitoring and protein therapeutic characterization in the biopharmaceutical industry. PMID:22227798

  7. Studies of negative ions by collision-induced decomposition and hydrogen-deuterium exchange techniques.

    PubMed Central

    Hunt, D F; Sethi, S K; Shabanowitz, J

    1980-01-01

    Development of two new techniques for studying the gas phase chemistry of negative ions is reported. Collision induced dissociation (CID) of (M-1)- ions has been accomplished in a newly constructed triple stage quadrupole mass spectrometer. This instrument was assembled by adding two additional Finnigan quadrupole mass filters to a Finnigan Model 3200 CI mass spectrometer. Generation of (M-1)- ions is accomplished by allowing OH- and sample to react under CI conditions in the ion source. The first quadrupole mass filter, Q1, is then employed to selectively pass the (M-1)- ion into a second quadrupole filter containing argon or neon at 10(-3) torr. On collision with the inert gas the (M-1)- ions dissociate into fragments which are then mass analyzed in the third quadrupole filter, CID spectra of (M-1)- ions from twelve carbonyl compounds are presented in this paper. Ion molecule isotope exchange reactions in the CI ion source can be used to count the number of hydrogen atoms in many different chemical environments. Collisions between sample (M-1)- ions and deuterium-labeled reagent gases (ND3, D2O, EtOD) facilitate incorporation of deuterium into the negative ion if the basicities of the sample and reagent anions are similar. Thus it is possible to selectively incorporate deuterium into many organic samples by controlling the exothermicity of the acid base, ion-molecule chemistry. PMID:7428745

  8. Morphological and surface studies of ultrasonically treated Raney nickel hydrogen-deuterium exchange catalysts

    SciTech Connect

    Cioffi, E.A. ); Willis, W.S.; Suib, S.L. )

    1990-02-01

    Previous surface studies of ultrasonicated Raney nickel catalysts have shown that ultrasonication leads to reduction of surface Ni species to the metallic state. Surface impurities that may poison the Raney nickel catalyst have also been removed during ultrasonication. Negligible increases in surface area are observed after ultrasound treatment of the catalysts even though their activities and selectivities in {sup 2}H incorporation into carbohydrates and glycosphingolipids are markedly improved. The surface and morphological changes taking place during ultrasonic treatment are the focus of this paper. Cr{sup 3+}- and Mo{sup 6+}-doped Raney Ni catalysts have been studied before and after ultrasonciation with scanning electron microscopy, X-ray photoelectron spectroscopy, and secondary ion mass spectrometry.

  9. Difference in fibril core stability between two tau four-repeat domain proteins: a hydrogen-deuterium exchange coupled to mass spectrometry study.

    PubMed

    Ramachandran, Gayathri; Udgaonkar, Jayant B

    2013-12-10

    One of the signatures of Alzheimer's disease and tauopathies is fibrillization of the microtubule-associated protein tau. The purpose of this study was to compare the high-resolution structure of fibrils formed by two different tau four-repeat domain constructs, tau4RD and tauK18, using hydrogen-deuterium exchange coupled to mass spectrometry as a tool. While the two fibrils are found to be constructed on similar structural principles, the tauK18 fibril has a slightly more stable core. This difference in fibril core stability appears to be reflective of the mechanistic differences in the aggregation pathways of the two proteins. PMID:24256615

  10. Hydrogen-Deuterium Exchange of Meteoritic Dicarboxylic Acids During Aqueous Extraction

    NASA Technical Reports Server (NTRS)

    Fuller, M.; Huang, Y.

    2002-01-01

    This study examines the extent of hydrogen-deuterium exchange on dicarboxylic acids during aqueous extraction. Deuterium enrichment was observed to be a function of diacid structure as well as delta-D. Additional information is contained in the original extended abstract.

  11. Recombinant Nepenthesin II for Hydrogen/Deuterium Exchange Mass Spectrometry.

    PubMed

    Yang, Menglin; Hoeppner, Morgan; Rey, Martial; Kadek, Alan; Man, Petr; Schriemer, David C

    2015-07-01

    The pitcher secretions of the Nepenthes genus of carnivorous plants contain a proteolytic activity that is very useful for hydrogen/deuterium exchange mass spectrometry (HX-MS). Our efforts to reconstitute pitcher fluid activity using recombinant nepenthesin I (one of two known aspartic proteases in the fluid) revealed a partial cleavage profile and reduced enzymatic stability in certain HX-MS applications. We produced and characterized recombinant nepenthesin II to determine if it complemented nepenthesin I in HX-MS applications. Nepenthesin II shares many properties with nepenthesin I, such as fast digestion at reduced temperature and pH, and broad cleavage specificity, but in addition, it cleaves C-terminal to tryptophan. Neither enzyme reproduces the C-terminal proline cleavage we observed in the natural extract. Nepenthesin II is considerably more resistant to chemical denaturants and reducing agents than nepenthesin I, and it possesses a stability profile that is similar to that of pepsin. Higher stability combined with the slightly broader cleavage specificity makes nepenthesin II a useful alternative to pepsin and a more complete replacement for pitcher fluid in HX-MS applications. PMID:25993527

  12. A Hydrogen-Deuterium Exchange Study on Nickel-based Binary-Ternary Amorphous and Crystalline Membranes

    NASA Astrophysics Data System (ADS)

    Adibhatla, Anasuya

    Hydrogen is a major role player in current global sustainable energy scenario. Research around the world is carried out to harness hydrogen from all possible sources. One of these sources is water gas shift reaction after the coal gasification process. Sustainable infrastructure can be viable in countries like USA and Australia, making this process viable. Various methods are used to harness this hydrogen from the water gas. One of these methods is the use of inorganic membranes based on Pd, Ag, Ni, Zr and other transition metals. Pd addition to the membranes makes the membranes more expensive for commercial use. Various bulk properties like hydrogen permeation and absorption are studied on Pd and Pd-based alloys. Alternate alloys based on Ni, V, Ta etc are being studied to substitute the use of Pd making this technology more cost efficient. A current balance in research in this area is fund to exist by coating the non-precious metal membranes with Pd to improve the surface interaction with hydrogen. The nature of membranes used for hydrogen separation is important aspect for the overall performance. Crystalline materials provide better bulk properties, however, are not durable under high temperature and hydrogen pressure. In this research, non-Pd coated Ni-based amorphous membranes were made by melt spin technique, which have been studied for their surface properties. Gas phase H2-D2 exchange reaction has been carried out on the membrane surface. This provides a measure of catalytic activity of the above mentioned membranes. More studies included the crystallographic phase change determination, bulk hydrogen solubility measurements, surface conduction measurements and surface morphological studies. During this research, it has been observed that crystalline materials provide more surface activity for hydrogen than their amorphous counterparts. Ni64Zr36 alloy has been shown to exhibit similar kinetic rates as metallic Ni. Also, microkinetic analysis was performed

  13. Subzero temperature chromatography for reduced back-exchange and improved dynamic range in amide hydrogen/deuterium exchange mass spectrometry.

    PubMed

    Venable, John D; Okach, Linda; Agarwalla, Sanjay; Brock, Ansgar

    2012-11-01

    Amide hydrogen/deuterium exchange is a commonly used technique for studying the dynamics of proteins and their interactions with other proteins or ligands. When coupled with liquid chromatography and mass spectrometry, hydrogen/deuterium exchange provides several unique advantages over other structural characterization techniques including very high sensitivity, the ability to analyze proteins in complex environments, and a large mass range. A fundamental limitation of the technique arises from the loss of the deuterium label (back-exchange) during the course of the analysis. A method to limit loss of the label during the separation stage of the analysis using subzero temperature reversed-phase chromatography is presented. The approach is facilitated by the use of buffer modifiers that prevent freezing. We evaluated ethylene glycol, dimethyl formamide, formamide, and methanol for their freezing point suppression capabilities, effects on peptide retention, and their compatibilities with electrospray ionization. Ethylene glycol was used extensively because of its good electrospray ionization compatibility; however, formamide has potential to be a superior modifier if detrimental effects on ionization can be overcome. It is demonstrated using suitable buffer modifiers that separations can be performed at temperatures as low as -30 °C with negligible loss of the deuterium label, even during long chromatographic separations. The reduction in back-exchange is shown to increase the dynamic range of hydrogen/deuterium exchange mass spectrometry in terms of mixture complexity and the magnitude with which changes in deuteration level can be quantified. PMID:23025328

  14. Conformational dynamics of human FXR-LBD ligand interactions studied by hydrogen/deuterium exchange mass spectrometry: insights into the antagonism of the hypolipidemic agent Z-guggulsterone.

    PubMed

    Yang, Liping; Broderick, David; Jiang, Yuan; Hsu, Victor; Maier, Claudia S

    2014-09-01

    Farnesoid X receptor (FXR) is a member of the nuclear receptor superfamily of transcription factors that plays a key role in the regulation of bile acids, lipid and glucose metabolisms. The regulative function of FXR is governed by conformational changes of the ligand binding domain (LBD) upon ligand binding. Although FXR is a highly researched potential therapeutic target, only a limited number of FXR-agonist complexes have been successfully crystallized and subsequently yielded high resolution structures. There is currently no structural information of any FXR-antagonist complexes publically available. We therefore explored the use of amide hydrogen/deuterium exchange (HDX) coupled with mass spectrometry for characterizing conformational changes in the FXR-LBD upon ligand binding. Ligand-specific deuterium incorporation profiles were obtained for three FXR ligand chemotypes: GW4064, a synthetic non-steroidal high affinity agonist; the bile acid chenodeoxycholic acid (CDCA), the endogenous low affinity agonist of FXR; and Z-guggulsterone (GG), an in vitro antagonist of the steroid chemotype. A comparison of the HDX profiles of their ligand-bound FXR-LBD complexes revealed a unique mode of interaction for GG. The conformational features of the FXR-LBD-antagonist interaction are discussed. PMID:24953769

  15. Using hydrogen deuterium exchange mass spectrometry to engineer optimized constructs for crystallization of protein complexes: Case study of PI4KIIIβ with Rab11

    PubMed Central

    Fowler, Melissa L.; McPhail, Jacob A.; Jenkins, Meredith L.; Masson, Glenn R.; Rutaganira, Florentine U.; Shokat, Kevan M.; Williams, Roger L.

    2016-01-01

    Abstract The ability of proteins to bind and interact with protein partners plays fundamental roles in many cellular contexts. X‐ray crystallography has been a powerful approach to understand protein‐protein interactions; however, a challenge in the crystallization of proteins and their complexes is the presence of intrinsically disordered regions. In this article, we describe an application of hydrogen deuterium exchange mass spectrometry (HDX‐MS) to identify dynamic regions within type III phosphatidylinositol 4 kinase beta (PI4KIIIβ) in complex with the GTPase Rab11. This information was then used to design deletions that allowed for the production of diffraction quality crystals. Importantly, we also used HDX‐MS to verify that the new construct was properly folded, consistent with it being catalytically and functionally active. Structures of PI4KIIIβ in an Apo state and bound to the potent inhibitor BQR695 in complex with both GTPγS and GDP loaded Rab11 were determined. This hybrid HDX‐MS/crystallographic strategy revealed novel aspects of the PI4KIIIβ‐Rab11 complex, as well as the molecular mechanism of potency of a PI4K specific inhibitor (BQR695). This approach is widely applicable to protein‐protein complexes, and is an excellent strategy to optimize constructs for high‐resolution structural approaches. PMID:26756197

  16. Oligomerization Interface of RAGE Receptor Revealed by MS-Monitored Hydrogen Deuterium Exchange

    PubMed Central

    Poznański, Jarosław; Kulma, Magdalena; Dadlez, Michal

    2013-01-01

    Activation of the receptor for advanced glycation end products (RAGE) leads to a chronic proinflammatory signal, affecting patients with a variety of diseases. Potentially beneficial modification of RAGE activity requires understanding the signal transduction mechanism at the molecular level. The ligand binding domain is structurally uncoupled from the cytoplasmic domain, suggesting receptor oligomerization is a requirement for receptor activation. In this study, we used hydrogen-deuterium exchange and mass spectrometry to map structural differences between the monomeric and oligomeric forms of RAGE. Our results indicated the presence of a region shielded from exchange in the oligomeric form of RAGE and led to the identification of a new oligomerization interface localized at the linker region between domains C1 and C2. Based on this finding, a model of a RAGE dimer and higher oligomeric state was constructed. PMID:24098480

  17. Ion Mobility Spectrometry-Hydrogen Deuterium Exchange Mass Spectrometry of Anions: Part 1. Peptides to Proteins

    NASA Astrophysics Data System (ADS)

    Donohoe, Gregory C.; Khakinejad, Mahdiar; Valentine, Stephen J.

    2015-04-01

    Ion mobility spectrometry (IMS) coupled with hydrogen deuterium exchange (HDX)-mass spectrometry (MS) has been used to study the conformations of negatively-charged peptide and protein ions. Results are presented for ion conformers of angiotensin 1, a synthetic peptide (SP), bovine insulin, ubiquitin, and equine cytochrome c. In general, the SP ion conformers demonstrate a greater level of HDX efficiency as a greater proportion of the sites undergo HDX. Additionally, these ions exhibit the fastest rates of exchange. Comparatively, the angiotensin 1 ions exhibit a lower rate of exchange and HDX level presumably because of decreased accessibility of exchange sites by charge sites. The latter are likely confined to the peptide termini. Insulin ions show dramatically reduced HDX levels and exchange rates, which can be attributed to decreased conformational flexibility resulting from the disulfide bonds. For the larger ubiquitin and protein ions, increased HDX is observed for larger ions of higher charge state. For ubiquitin, a conformational transition from compact to more elongated species (from lower to higher charge states) is reflected by an increase in HDX levels. These results can be explained by a combination of interior site protection by compact conformers as well as decreased access by charge sites. The elongated cytochrome c ions provide the largest HDX levels where higher values correlate with charge state. These results are consistent with increased exchange site accessibility by additional charge sites. The data from these enhanced IMS-HDX experiments are described in terms of charge site location, conformer rigidity, and interior site protection.

  18. Kinetics of hydrogen/deuterium exchanges in cometary ices

    NASA Astrophysics Data System (ADS)

    Faure, Mathilde; Quirico, Eric; Faure, Alexandre; Schmitt, Bernard; Theulé, Patrice; Marboeuf, Ulysse

    2015-11-01

    The D/H composition of volatile molecules composing cometary ices brings key constraints on the origin of comets, on the extent of their presolar heritage, as well as on the origin of atmospheres and hydrospheres of terrestrial planets. Nevertheless, the D/H composition may have been modified to various extents in the nucleus when a comet approaches the Sun and experiences deep physical and chemical modifications in its subsurface. We question here the evolution of the D/H ratio of organic species by proton exchanges with water ice. We experimentally studied the kinetics of D/H exchanges on the ice mixtures H2O:CD3OD, H2O:CD3ND2 and D2O:HCN. Our results show that fast exchanges occur on the -OH and -NH2 chemical groups, which are processed through hydrogen bonds exchanges with water and by the molecular mobility triggered by structural changes, such as glass transition or crystallization. D/H exchanges kinetic is best described by a second-order kinetic law with activation energies of 4300 ± 900 K and 3300 ± 100 K for H2O:CD3OD and H2O:CD3ND2 ice mixtures, respectively. The corresponding pre-exponential factors ln(A(s-1)) are 25 ± 7 and 20 ± 1, respectively. No exchange was observed in the case of HCN trapped in D2O ice. These results strongly suggest that upon thermal heating (1) -OH and -NH2 chemical groups of any organic molecules loose their primordial D/H composition and equilibrate with water ice, (2) HCN does not experience proton transfer and keeps a primordial D/H composition and (3) C-H chemical groups are not isotopically modified.

  19. Changes in protein structure monitored by use of gas‐phase hydrogen/deuterium exchange

    PubMed Central

    Beeston, Helen S.; Ault, James R.; Pringle, Steven D.; Brown, Jeffery M.

    2015-01-01

    The study of protein conformation by solution‐phase hydrogen/deuterium exchange (HDX) coupled to MS is well documented. This involves monitoring the exchange of backbone amide protons with deuterium and provides details concerning the protein's tertiary structure. However, undesired back‐exchange during post‐HDX analyses can be difficult to control. Here, gas‐phase HDX‐MS, during which labile hydrogens on amino acid side chains are exchanged in sub‐millisecond time scales, has been employed to probe changes within protein structures. Addition of the solvent 2,2,2‐trifluoroethanol to a protein in solution can affect the structure of the protein, resulting in an increase in secondary and/or tertiary structure which is detected using circular dichroism. Using a Synapt G2‐S ESI‐mass spectrometer modified to allow deuterated ammonia into the transfer ion guide (situated between the ion mobility cell and the TOF analyser), gas‐phase HDX‐MS is shown to reflect minor structural changes experienced by the proteins β‐lactoglobulin and ubiquitin, as observed by the reduction in the level of deuterium incorporation. Additionally, the use of gas‐phase HDX‐MS to distinguish between co‐populated proteins conformers within a solution is demonstrated with the disordered protein calmodulin; the gas‐phase HDX‐MS results correspond directly with complementary data obtained by use of ion mobility spectrometry‐MS. PMID:25603979

  20. Hydrogen-Deuterium exchange monitored by ATR-FTIR spectroscopy

    NASA Astrophysics Data System (ADS)

    Poe, Brent; Del Vecchio, Alessandro; Cestelli Guidi, Mariangela

    2016-04-01

    Measuring the extent of isotopic exchange is a common means for the determination of self-diffusion coefficients in any type of medium (gas, liquid, amorphous solid, crystalline solid). For rapidly diffusing species such as hydrogen in condensed phases, real time methods involving vibrational spectroscopy can be used by taking advantage of the large relative mass difference between 1H and 2H, resulting in large differences in the band positions of their vibrational modes. We demonstrate rapid isotopic exchange between D2O liquid and H2O vapor using ATR (attenuated total reflectance) in a FTIR spectrometer. Over the course of a few minutes several spectra were acquired of a D2O droplet mounted on a diamond crystal. The progressive exchange reaction between the liquid phase and H2O from the atmosphere was monitored by measuring the decreasing absorbance of the D-O-D bending and O-D stretching bands and the increasing absorbance of the D-O-H and H-O-H bending and O-H stretching bands as functions of time. Our results offer some intriguing insights into the structural characteristics of water as inferred by this exchange process.

  1. Analysis of overlapped and noisy hydrogen/deuterium exchange mass spectra.

    PubMed

    Guttman, Miklos; Weis, David D; Engen, John R; Lee, Kelly K

    2013-12-01

    Noisy and overlapped mass spectrometry data hinder the sequence coverage that can be obtained from hydrogen deuterium exchange analysis, and places a limit on the complexity of the samples that can be studied by this technique. Advances in instrumentation have addressed these limits, but as the complexity of the biological samples under investigation increases, these problems are re-encountered. Here we describe the use of binomial distribution fitting with asymmetric linear squares regression for calculating the accurate deuterium content for mass envelopes of low signal or that contain significant overlap. The approach is demonstrated with a test data set of HIV Env gp140 wherein inclusion of the new analysis regime resulted in obtaining exchange data for 42 additional peptides, improving the sequence coverage by 11%. At the same time, the precision of deuterium uptake measurements was improved for nearly every peptide examined. The improved processing algorithms also provide an efficient method for deconvolution of bimodal mass envelopes and EX1 kinetic signatures. All these functions and visualization tools have been implemented in the new version of the freely available software, HX-Express v2. PMID:24018862

  2. Analysis of Overlapped and Noisy Hydrogen/Deuterium Exchange Mass Spectra

    NASA Astrophysics Data System (ADS)

    Guttman, Miklos; Weis, David D.; Engen, John R.; Lee, Kelly K.

    2013-12-01

    Noisy and overlapped mass spectrometry data hinder the sequence coverage that can be obtained from hydrogen deuterium exchange analysis, and places a limit on the complexity of the samples that can be studied by this technique. Advances in instrumentation have addressed these limits, but as the complexity of the biological samples under investigation increases, these problems are re-encountered. Here we describe the use of binomial distribution fitting with asymmetric linear squares regression for calculating the accurate deuterium content for mass envelopes of low signal or that contain significant overlap. The approach is demonstrated with a test data set of HIV Env gp140 wherein inclusion of the new analysis regime resulted in obtaining exchange data for 42 additional peptides, improving the sequence coverage by 11 %. At the same time, the precision of deuterium uptake measurements was improved for nearly every peptide examined. The improved processing algorithms also provide an efficient method for deconvolution of bimodal mass envelopes and EX1 kinetic signatures. All these functions and visualization tools have been implemented in the new version of the freely available software, HX-Express v2.

  3. 2D IR Cross Peaks Reveal Hydrogen-Deuterium Exchange with Single Residue Specificity

    PubMed Central

    Dunkelberger, Emily B.; Woys, Ann Marie; Zanni, Martin T.

    2013-01-01

    A form of chemical exchange, hydrogen-deuterium exchange (HDX), has long been used as a method for studying the secondary and tertiary structure of peptides and proteins using mass spectrometry and NMR spectroscopy. Using 2D IR (two dimensional infrared) spectroscopy, we resolve cross peaks between the amide II band and a 13C18O isotope labeled amide I band, which we show measures HDX with site-specific resolution. By rapidly scanning 2D IR spectra using mid-IR pulse shaping, we monitor the kinetics of HDX exchange on-the-fly. For the antimicrobial peptide, ovispirin, bound to membrane bilayers, we find that the amide II peak decays with a biexponential with rate constants of 0.54 ± 0.02 and 0.12 ± 0.01 min−1, which is a measure of the overall HDX in the peptide. The cross peaks between Ile-10 labeled ovispirin and the amide II mode, which specifically monitor HDX kinetics at Ile-10, decay with a single rate constant of 0.36 ± 0.1 min−1. Comparing this exchange rate to theoretically determined exchange rates of Ile-10 for ovispirin in a solution random coil configuration, the exchange rate at Ile-10 is at least 100 times slower, consistent with the known α-helix structure of ovispirin in bilayers. Because backbone isotope labels produce only a very small shift of the amide II band, site-specific HDX cannot be measured with FTIR spectroscopy, which is why 2D IR spectroscopy is needed for these measurements. PMID:23659731

  4. Localizing Carbohydrate Binding Sites in Proteins Using Hydrogen/Deuterium Exchange Mass Spectrometry

    NASA Astrophysics Data System (ADS)

    Zhang, Jingjing; Kitova, Elena N.; Li, Jun; Eugenio, Luiz; Ng, Kenneth; Klassen, John S.

    2016-01-01

    The application of hydrogen/deuterium exchange mass spectrometry (HDX-MS) to localize ligand binding sites in carbohydrate-binding proteins is described. Proteins from three bacterial toxins, the B subunit homopentamers of Cholera toxin and Shiga toxin type 1 and a fragment of Clostridium difficile toxin A, and their interactions with native carbohydrate receptors, GM1 pentasaccharides (β-Gal-(1→3)-β-GalNAc-(1→4)[α-Neu5Ac-(2→3)]-β-Gal-(1→4)-Glc), Pk trisaccharide (α-Gal-(1→4)-β-Gal-(1→4)-Glc) and CD-grease (α-Gal-(1→3)-β-Gal-(1→4)-β-GlcNAcO(CH2)8CO2CH3), respectively, served as model systems for this study. Comparison of the differences in deuterium uptake for peptic peptides produced in the absence and presence of ligand revealed regions of the proteins that are protected against deuterium exchange upon ligand binding. Notably, protected regions generally coincide with the carbohydrate binding sites identified by X-ray crystallography. However, ligand binding can also result in increased deuterium exchange in other parts of the protein, presumably through allosteric effects. Overall, the results of this study suggest that HDX-MS can serve as a useful tool for localizing the ligand binding sites in carbohydrate-binding proteins. However, a detailed interpretation of the changes in deuterium exchange upon ligand binding can be challenging because of the presence of ligand-induced changes in protein structure and dynamics.

  5. NMR-Based Detection of Hydrogen/Deuterium Exchange in Liposome-Embedded Membrane Proteins

    PubMed Central

    Yao, Xuejun; Dürr, Ulrich H. N.; Gattin, Zrinka; Laukat, Yvonne; Narayanan, Rhagavendran L.; Brückner, Ann-Kathrin; Meisinger, Chris; Lange, Adam; Becker, Stefan; Zweckstetter, Markus

    2014-01-01

    Membrane proteins play key roles in biology. Determination of their structure in a membrane environment, however, is highly challenging. To address this challenge, we developed an approach that couples hydrogen/deuterium exchange of membrane proteins to rapid unfolding and detection by solution-state NMR spectroscopy. We show that the method allows analysis of the solvent protection of single residues in liposome-embedded proteins such as the 349-residue Tom40, the major protein translocation pore in the outer mitochondrial membrane, which has resisted structural analysis for many years. PMID:25375235

  6. Liquid Chromatography Electrospray Ionization Tandem Mass Spectrometric (LC/ESI-MS/MS) Study for the Identification and Characterization of In Vivo Metabolites of Cisplatin in Rat Kidney Cancer Tissues: Online Hydrogen/Deuterium (H/D) Exchange Study

    PubMed Central

    Bandu, Raju; Ahn, Hyun Soo; Lee, Joon Won; Kim, Yong Woo; Choi, Seon Hee; Kim, Hak Jin; Kim, Kwang Pyo

    2015-01-01

    In vivo rat kidney tissue metabolites of an anticancer drug, cisplatin (cis-diamminedichloroplatinum [II]) (CP) which is used for the treatment of testicular, ovarian, bladder, cervical, esophageal, small cell lung, head and neck cancers, have been identified and characterized by using liquid chromatography positive ion electrospray ionization tandem mass spectrometry (LC/ESI-MS/MS) in combination with on line hydrogen/deuterium exchange (HDX) experiments. To identify in vivo metabolites, kidney tissues were collected after intravenous administration of CP to adult male Sprague-Dawley rats (n = 3 per group). The tissue samples were homogenized and extracted using newly optimized metabolite extraction procedure which involves liquid extraction with phosphate buffer containing ethyl acetate and protein precipitation with mixed solvents of methanol-water-chloroform followed by solid-phase clean-up procedure on Oasis HLB 3cc cartridges and then subjected to LC/ESI-HRMS analysis. A total of thirty one unknown in vivo metabolites have been identified and the structures of metabolites were elucidated using LC-MS/MS experiments combined with accurate mass measurements. Online HDX experiments have been used to further support the structural characterization of metabolites. The results showed that CP undergoes a series of ligand exchange biotransformation reactions with water and other nucleophiles like thio groups of methionine, cysteine, acetylcysteine, glutathione and thioether. This is the first research approach focused on the structure elucidation of biotransformation products of CP in rats, and the identification of metabolites provides essential information for further pharmacological and clinical studies of CP, and may also be useful to develop various effective new anticancer agents. PMID:26244343

  7. Liquid Chromatography Electrospray Ionization Tandem Mass Spectrometric (LC/ESI-MS/MS) Study for the Identification and Characterization of In Vivo Metabolites of Cisplatin in Rat Kidney Cancer Tissues: Online Hydrogen/Deuterium (H/D) Exchange Study.

    PubMed

    Bandu, Raju; Ahn, Hyun Soo; Lee, Joon Won; Kim, Yong Woo; Choi, Seon Hee; Kim, Hak Jin; Kim, Kwang Pyo

    2015-01-01

    In vivo rat kidney tissue metabolites of an anticancer drug, cisplatin (cis-diamminedichloroplatinum [II]) (CP) which is used for the treatment of testicular, ovarian, bladder, cervical, esophageal, small cell lung, head and neck cancers, have been identified and characterized by using liquid chromatography positive ion electrospray ionization tandem mass spectrometry (LC/ESI-MS/MS) in combination with on line hydrogen/deuterium exchange (HDX) experiments. To identify in vivo metabolites, kidney tissues were collected after intravenous administration of CP to adult male Sprague-Dawley rats (n = 3 per group). The tissue samples were homogenized and extracted using newly optimized metabolite extraction procedure which involves liquid extraction with phosphate buffer containing ethyl acetate and protein precipitation with mixed solvents of methanol-water-chloroform followed by solid-phase clean-up procedure on Oasis HLB 3cc cartridges and then subjected to LC/ESI-HRMS analysis. A total of thirty one unknown in vivo metabolites have been identified and the structures of metabolites were elucidated using LC-MS/MS experiments combined with accurate mass measurements. Online HDX experiments have been used to further support the structural characterization of metabolites. The results showed that CP undergoes a series of ligand exchange biotransformation reactions with water and other nucleophiles like thio groups of methionine, cysteine, acetylcysteine, glutathione and thioether. This is the first research approach focused on the structure elucidation of biotransformation products of CP in rats, and the identification of metabolites provides essential information for further pharmacological and clinical studies of CP, and may also be useful to develop various effective new anticancer agents. PMID:26244343

  8. Hydrogen/deuterium exchange on aromatic rings during atmospheric pressure chemical ionization mass spectrometry.

    PubMed

    Davies, Noel W; Smith, Jason A; Molesworth, Peter P; Ross, John J

    2010-04-15

    It has been demonstrated that substituted indoles fully labelled with deuterium on the aromatic ring can undergo substantial exchange back to partial and even fully protonated forms during atmospheric pressure chemical ionisation (APCI) liquid chromatography/mass spectrometry (LC/MS). The degree of this exchange was strongly dependent on the absolute quantity of analyte, the APCI desolvation temperature, the nature of the mobile phase, the mobile phase flow rate and the instrument used. Hydrogen/deuterium (H/D) exchange on several other aromatic ring systems during APCI LC/MS was either undetectable (nitrobenzene, aniline) or extremely small (acetanilide) compared to the effect observed for substituted indoles. This observation has major implications for quantitative assays using deuterium-labelled internal standards and for the detection of deuterium-labelled products from isotopically labelled feeding experiments where there is a risk of back exchange to the protonated form during the analysis. PMID:20213724

  9. Probing Conserved Helical Modules of Portal Complexes by Mass Spectrometry based Hydrogen/deuterium Exchange

    PubMed Central

    Kang, Sebyung; Poliakov, Anton; Sexton, Jennifer; Renfrow, Matthew B.; Prevelige, Peter E.

    2008-01-01

    The dsDNA bacteriophage P22 has a ring shaped dodecameric complex composed of the 84 kDa portal protein subunit which forms the central channel of the phage’s DNA packaging motor. The overall morphology of the P22 portal complex is similar to that of the portal complexes of Phi29, SPP1, T3, T7 phages and herpes simplex virus. Secondary structure prediction of P22 portal protein and its threading onto the crystal structure of the Phi29 portal complexes suggested that P22 portal protein complex shares conserved helical modules which were found in the dodecameric interfaces of the Phi29 portal complex. To identify the amino acids involved in inter-subunit contacts in the P22 portal ring complexes and validate the threading model, we performed comparative hydrogen/deuterium exchange analysis of monomeric and in vitro assembled portal proteins of P22 and the dodecameric Phi29 portal. Hydrogen/deuterium exchange experiments provided evidence of inter-subunit interactions in the P22 portal complex similar to those in the Phi29 portal which map to the regions predicted to be conserved helical modules. PMID:18621389

  10. Nepenthesin from monkey cups for hydrogen/deuterium exchange mass spectrometry.

    PubMed

    Rey, Martial; Yang, Menglin; Burns, Kyle M; Yu, Yaping; Lees-Miller, Susan P; Schriemer, David C

    2013-02-01

    Studies of protein dynamics, structure and interactions using hydrogen/deuterium exchange mass spectrometry (HDX-MS) have sharply increased over the past 5-10 years. The predominant technology requires fast digestion at pH 2-3 to retain deuterium label. Pepsin is used almost exclusively, but it provides relatively low efficiency under the constraints of the experiment, and a selectivity profile that renders poor coverage of intrinsically disordered regions. In this study we present nepenthesin-containing secretions of the pitcher plant Nepenthes, commonly called monkey cups, for use in HDX-MS. We show that nepenthesin is at least 1400-fold more efficient than pepsin under HDX-competent conditions, with a selectivity profile that mimics pepsin in part, but also includes efficient cleavage C-terminal to "forbidden" residues K, R, H, and P. High efficiency permits a solution-based analysis with no detectable autolysis, avoiding the complication of immobilized enzyme reactors. Relaxed selectivity promotes high coverage of disordered regions and the ability to "tune" the mass map for regions of interest. Nepenthesin-enriched secretions were applied to an analysis of protein complexes in the nonhomologous end-joining DNA repair pathway. The analysis of XRCC4 binding to the BRCT domains of Ligase IV points to secondary interactions between the disordered C-terminal tail of XRCC4 and remote regions of the BRCT domains, which could only be identified with a nepenthesin-based workflow. HDX data suggest that stalk-binding to XRCC4 primes a BRCT conformation in these remote regions to support tail interaction, an event which may be phosphoregulated. We conclude that nepenthesin is an effective alternative to pepsin for all HDX-MS applications, and especially for the analysis of structural transitions among intrinsically disordered proteins and their binding partners. PMID:23197791

  11. Time-Resolved Pulsed Hydrogen/Deuterium Exchange Mass Spectrometry Probes Gaseous Proteins Structural Kinetics

    NASA Astrophysics Data System (ADS)

    Rajabi, Khadijeh

    2015-01-01

    A pulsed hydrogen/deuterium exchange (HDX) method has been developed for rapid monitoring of the exchange kinetics of protein ions with D2O a few milliseconds after electrospray ionization (ESI). The stepwise gradual evolution of HDX of multiply charged protein ions was monitored using the pulsed HDX mass spectrometry technique. Upon introducing a very short pulse of D2O (in the μs to ms time scale) into the linear ion trap (LIT) of a time-of-flight (TOF) mass spectrometer, bimodal distributions were detected for the ions of cytochrome c and ubiquitin. Mechanistic details of HDX reactions for ubiquitin and cytochrome c in the gas phase were uncovered and the structural transitions were followed by analyzing the kinetics of HDX.

  12. Time-resolved pulsed hydrogen/deuterium exchange mass spectrometry probes gaseous proteins structural kinetics.

    PubMed

    Rajabi, Khadijeh

    2015-01-01

    A pulsed hydrogen/deuterium exchange (HDX) method has been developed for rapid monitoring of the exchange kinetics of protein ions with D2O a few milliseconds after electrospray ionization (ESI). The stepwise gradual evolution of HDX of multiply charged protein ions was monitored using the pulsed HDX mass spectrometry technique. Upon introducing a very short pulse of D2O (in the μs to ms time scale) into the linear ion trap (LIT) of a time-of-flight (TOF) mass spectrometer, bimodal distributions were detected for the ions of cytochrome c and ubiquitin. Mechanistic details of HDX reactions for ubiquitin and cytochrome c in the gas phase were uncovered and the structural transitions were followed by analyzing the kinetics of HDX. PMID:25318698

  13. Hydrogen/Deuterium Exchange Mass Spectrometry Applied to IL-23 Interaction Characteristics: Potential Impact for Therapeutics

    PubMed Central

    Iacob, Roxana E.; Krystek, Stanley R.; Huang, Richard Y.-C.; Wei, Hui; Tao, Li; Lin, Zheng; Morin, Paul E.; Doyle, Michael L.; Tymiak, Adrienne A.; Engen, John R.

    2015-01-01

    Interleukin-23 (IL-23) is an important therapeutic target for the treatment of inflammatory diseases. Adnectins are targeted protein therapeutics that are derived from domain III of human fibronectin, and have similar protein scaffold to antibodies. A specific adnectin (Adnectin 2) was identified to bind to IL-23 and compete with IL-23/IL-23R interaction, being a potential protein therapeutic. Hydrogen/deuterium exchange mass spectrometry (HDX MS) and computational methods were applied to probe the binding interactions between IL-23 and Adnectin2 and to determine the correlation between the two orthogonal methods. This review article summarizes the current structural knowledge about Il-23 and it focuses on the applicability of HDX MS to investigate the higher order structure of proteins, which plays an important role for the discovery of new and improved biotherapeutics. PMID:25711416

  14. Hydrogen, deuterium and tritium in palladium: An eleastic constants study

    SciTech Connect

    Bach, H. T.; Schwarz, R. B.; Tuggle, D. G.

    2004-01-01

    We have used resonant ultrasound spectroscopy to measure the three independent elastic constants of Pd-H, Pd-D, and Pd-T single crystal at 300K as a junction of hydrogen, deuterium, and tritium concentration, respectively. The addition of interstitial H (D, or T) atoms, located at (0, 1/2, 0) in the fcc Pd lattice, affects all three elastic constants C, C{sub 44}, and B. In the mixed (a+{beta}) phase, and with increasing H isotope, the shear modulus C' shows an abnormal softening whereas C{sub 44} and B do not. This is explained in terms of Zener-type anelastic relaxations affecting the shape of the hydride phases in the coherent ({alpha}+{beta}) two-phase mixture In the single {beta}-phase, C' shows a strong isotope dependence whereas C{sub 44} and B show none. This behavior is explained in terms of differences in the excitation of optical phonons. In Pd-T, {sup 3}He is produced by the radioactive decay of tritium. We have measured in situ the swelling and the change in the elastic constants in Pd-T as a function of aging time. Aging ({sup 3}He formation) affects all three elastic constants. These measurements are being used to understand the early stages of {sup 3}H-{sup 3}He clusterformation in aged Pd-T crystal.

  15. Differential Mobility Spectrometry-Hydrogen Deuterium Exchange (DMS-HDX) as a Probe of Protein Conformation in Solution.

    PubMed

    Zhu, Shaolong; Campbell, J Larry; Chernushevich, Igor; Le Blanc, J C Yves; Wilson, Derek J

    2016-06-01

    Differential mobility spectrometry (DMS) is an ion mobility technique that has been adopted chiefly as a pre-filter for small- to medium-sized analytes (<1 000 Da). With the exception of a handful of studies that employ an analogue of DMS-field asymmetric waveform ion mobility spectroscopy (FAIMS)-the application of DMS to intact biomacromolecules remains largely unexplored. In this work, we employ DMS combined with gas-phase hydrogen deuterium exchange (DMS-HDX) to probe the gas-phase conformations generated from proteins that were initially folded, partially-folded, and unfolded in solution. Our findings indicate that proteins with distinct structural features in solution exhibit unique deuterium uptake profiles as function of their optimal transmission through the DMS. Ultimately we propose that DMS-HDX can, if properly implemented, provide rapid measurements of liquid-phase protein structural stability that could be of use in biopharmaceuticals development. Graphical Abstract ᅟ. PMID:26965162

  16. Probing the dynamic regulation of peripheral membrane proteins using hydrogen deuterium exchange-MS (HDX-MS).

    PubMed

    Vadas, Oscar; Burke, John E

    2015-10-01

    Many cellular signalling events are controlled by the selective recruitment of protein complexes to membranes. Determining the molecular basis for how lipid signalling complexes are recruited, assembled and regulated on specific membrane compartments has remained challenging due to the difficulty of working in conditions mimicking native biological membrane environments. Enzyme recruitment to membranes is controlled by a variety of regulatory mechanisms, including binding to specific lipid species, protein-protein interactions, membrane curvature, as well as post-translational modifications. A powerful tool to study the regulation of membrane signalling enzymes and complexes is hydrogen deuterium exchange-MS (HDX-MS), a technique that allows for the interrogation of protein dynamics upon membrane binding and recruitment. This review will highlight the theory and development of HDX-MS and its application to examine the molecular basis of lipid signalling enzymes, specifically the regulation and activation of phosphoinositide 3-kinases (PI3Ks). PMID:26517882

  17. Differential Mobility Spectrometry-Hydrogen Deuterium Exchange (DMS-HDX) as a Probe of Protein Conformation in Solution

    NASA Astrophysics Data System (ADS)

    Zhu, Shaolong; Campbell, J. Larry; Chernushevich, Igor; Le Blanc, J. C. Yves; Wilson, Derek J.

    2016-03-01

    Differential mobility spectrometry (DMS) is an ion mobility technique that has been adopted chiefly as a pre-filter for small- to medium-sized analytes (<1 000 Da). With the exception of a handful of studies that employ an analogue of DMS—field asymmetric waveform ion mobility spectroscopy (FAIMS)—the application of DMS to intact biomacromolecules remains largely unexplored. In this work, we employ DMS combined with gas-phase hydrogen deuterium exchange (DMS-HDX) to probe the gas-phase conformations generated from proteins that were initially folded, partially-folded, and unfolded in solution. Our findings indicate that proteins with distinct structural features in solution exhibit unique deuterium uptake profiles as function of their optimal transmission through the DMS. Ultimately we propose that DMS-HDX can, if properly implemented, provide rapid measurements of liquid-phase protein structural stability that could be of use in biopharmaceuticals development.

  18. Differential Mobility Spectrometry-Hydrogen Deuterium Exchange (DMS-HDX) as a Probe of Protein Conformation in Solution

    NASA Astrophysics Data System (ADS)

    Zhu, Shaolong; Campbell, J. Larry; Chernushevich, Igor; Le Blanc, J. C. Yves; Wilson, Derek J.

    2016-06-01

    Differential mobility spectrometry (DMS) is an ion mobility technique that has been adopted chiefly as a pre-filter for small- to medium-sized analytes (<1 000 Da). With the exception of a handful of studies that employ an analogue of DMS—field asymmetric waveform ion mobility spectroscopy (FAIMS)—the application of DMS to intact biomacromolecules remains largely unexplored. In this work, we employ DMS combined with gas-phase hydrogen deuterium exchange (DMS-HDX) to probe the gas-phase conformations generated from proteins that were initially folded, partially-folded, and unfolded in solution. Our findings indicate that proteins with distinct structural features in solution exhibit unique deuterium uptake profiles as function of their optimal transmission through the DMS. Ultimately we propose that DMS-HDX can, if properly implemented, provide rapid measurements of liquid-phase protein structural stability that could be of use in biopharmaceuticals development.

  19. Peptide-Column Interactions and Their Influence on Back Exchange Rates in Hydrogen/Deuterium Exchange-MS

    NASA Astrophysics Data System (ADS)

    Sheff, Joey G.; Rey, Martial; Schriemer, David C.

    2013-07-01

    Hydrogen/deuterium exchange (HDX) methods generate useful information on protein structure and dynamics, ideally at the individual residue level. Most MS-based HDX methods involve a rapid proteolytic digestion followed by LC/MS analysis, with exchange kinetics monitored at the peptide level. Localizing specific sites of HDX is usually restricted to a resolution the size of the host peptide because gas-phase processes can scramble deuterium throughout the peptide. Subtractive methods may improve resolution, where deuterium levels of overlapping and nested peptides are used in a subtractive manner to localize exchange to smaller segments. In this study, we explore the underlying assumption of the subtractive method, namely, that the measured back exchange kinetics of a given residue is independent of its host peptide. Using a series of deuterated peptides, we show that secondary structure can be partially retained under quenched conditions, and that interactions between peptides and reversed-phase LC columns may both accelerate and decelerate residue HDX, depending upon peptide sequence and length. Secondary structure is induced through column interactions in peptides with a solution-phase propensity for structure, which has the effect of slowing HDX rates relative to predicted random coil values. Conversely, column interactions can orient random-coil peptide conformers to accelerate HDX, the degree to which correlates with peptide charge in solution, and which can be reversed by using stronger ion pairing reagents. The dependency of these effects on sequence and length suggest that subtractive methods for improving structural resolution in HDX-MS will not offer a straightforward solution for increasing exchange site resolution.

  20. Hydrogen-deuterium exchange mass spectrometry for investigation of backbone dynamics of oxidized and reduced cytochrome P450cam.

    PubMed

    Hamuro, Yoshitomo; Molnar, Kathleen S; Coales, Stephen J; OuYang, Bo; Simorellis, Alana K; Pochapsky, Thomas C

    2008-02-01

    Backbone dynamics of the camphor monoxygenase cytochrome P450(cam) (CYP101) as a function of oxidation/ligation state of the heme iron were investigated via hydrogen/deuterium exchange (H/D exchange) as monitored by mass spectrometry. Main chain amide NH hydrogens can exchange readily with solvent and the rate of this exchange depends upon, among other things, dynamic fluctuations in local structural elements. A fluxional region of the polypeptide will exchange more quickly with solvent than one that is more constrained. In most regions of the enzyme, exchange rates were similar between oxidized high-spin camphor-bound and reduced camphor- and CO-bound CYP101 (CYP-S and CYP-S-CO, respectively). However, in regions of the protein that have previously been implicated in substrate access by structural and molecular dynamics investigations, the reduced enzyme shows significantly slower exchange rates than the oxidized CYP-S. This observation corresponds to increased flexibility of the oxidized enzyme relative to the reduced form. Structural features previously found to be perturbed in CYP-S-CO upon binding of the biologically relevant effector and reductant putidaredoxin (Pdx) as determined by nuclear magnetic resonance are also more protected from exchange in the reduced state. To our knowledge, this study represents the first experimental investigation of backbone dynamics within the P450 family using this methodology. PMID:18023482

  1. Start2Fold: a database of hydrogen/deuterium exchange data on protein folding and stability

    PubMed Central

    Pancsa, Rita; Varadi, Mihaly; Tompa, Peter; Vranken, Wim F.

    2016-01-01

    Proteins fulfil a wide range of tasks in cells; understanding how they fold into complex three-dimensional (3D) structures and how these structures remain stable while retaining sufficient dynamics for functionality is essential for the interpretation of overall protein behaviour. Since the 1950's, solvent exchange-based methods have been the most powerful experimental means to obtain information on the folding and stability of proteins. Considerable expertise and care were required to obtain the resulting datasets, which, despite their importance and intrinsic value, have never been collected, curated and classified. Start2Fold is an openly accessible database (http://start2fold.eu) of carefully curated hydrogen/deuterium exchange (HDX) data extracted from the literature that is open for new submissions from the community. The database entries contain (i) information on the proteins investigated and the underlying experimental procedures and (ii) the classification of the residues based on their exchange protection levels, also allowing for the instant visualization of the relevant residue groups on the 3D structures of the corresponding proteins. By providing a clear hierarchical framework for the easy sharing, comparison and (re-)interpretation of HDX data, Start2Fold intends to promote a better understanding of how the protein sequence encodes folding and structure as well as the development of new computational methods predicting protein folding and stability. PMID:26582925

  2. Microsecond pulsed hydrogen/deuterium exchange of electrosprayed ubiquitin ions stored in a linear ion trap.

    PubMed

    Rajabi, Khadijeh

    2015-02-01

    A pulse of D2O vapour on the order of microseconds is allowed to react with the +6 to +9 charge states of ubiquitin confined in a linear ion trap (LIT). Two envelopes of peaks are detected for the ions of ubiquitin, corresponding to the ions that exchange more quickly and more slowly. The deuterium uptake of the protonated sites on ubiquitin ions accounts for the ion population with the fast exchange. The hydrogen/deuterium exchange (HDX) kinetics of ubiquitin ions trapped in the LIT for 200 ms showed comparable structural transitions to those trapped for 300 ms. When ions are trapped for longer, i.e. up to 2000 ms, mainly the slow exchanging ion population is detected. In all experiments the +7 ions exchange the most, suggesting a short distance between the surface protonated sites and nearby charged sites, and concomitantly high accessibility of surface protonated sites towards D2O. The +6 ions are more compact than the +7 ions but have one fewer protonated site, therefore fewer surface availabilities for D2O attack. The data suggest that the +6 ions keep most of their solution-phase contacts intact while the hydrophobic core is slightly interrupted in the +7 ions, possibly due to the exposure of charged His68 that is normally buried in the hydrophobic pocket. The +8 and +9 ions have more protonated sites but are less compact than the +7 ions because of Coulombic repulsion, resulting in a larger distance between the protonated sites and the basic sites. The data indicate that the HDX mechanism of ions with the slower exchange corresponding to the second envelope of peaks is primarily governed via a relay mechanism. The results suggest that the pulsed HDX MS method is sampling a population of ubiquitin ions with a similar backbone fold to the solution. PMID:25553956

  3. Conformational stability of ribonuclease T1 determined by hydrogen-deuterium exchange.

    PubMed Central

    Mullins, L. S.; Pace, C. N.; Raushel, F. M.

    1997-01-01

    The hydrogen-deuterium exchange kinetics of 37 backbone amide residues in RNase T1 have been monitored at 25, 40, 45, and 50 degrees C at pD 5.6 and at 40 and 45 degrees C at pD 6.6. The hydrogen exchange rate constants of the hydrogen-bonded residues varied over eight orders of magnitude at 25 degrees C with 13 residues showing exchange rates consistent with exchange occurring as a result of global unfolding. These residues are located in strands 2-4 of the central beta-pleated sheet. The residues located in the alpha-helix and the remaining strands of the beta-sheet exhibited exchange behaviors consistent with exchange occurring due to local structural fluctuations. For several residues at 25 degrees C, the global free energy change calculated from the hydrogen exchange data was over 2 kcal/mol greater than the free energy of unfolding determined from urea denaturation experiments. The number of residues showing this unexpected behavior was found to increase with temperature. This apparent inconsistency can be explained quantitatively if the cis-trans isomerization of the two cis prolines, Pro-39 and Pro-55, is taken into account. The cis-trans isomerization equilibrium calculated from kinetic data indicates the free energy of the unfolded state will be 2.6 kcal/mol higher at 25 degrees C when the two prolines are cis rather than trans (Mayr LM, Odefey CO, Schutkowski M, Schmid FX. 1996. Kinetic analysis of the unfolding and refolding of ribonuclease T1 by a stopped-flow double-mixing technique. Biochemistry 35: 5550-5561). The hydrogen exchange results are consistent with the most slowly exchanging hydrogens exchanging from a globally higher free energy unfolded state in which Pro-55 and Pro-39 are still predominantly in the cis conformation. When the conformational stabilities determined by hydrogen exchange are corrected for the proline isomerization equilibrium, the results are in excellent agreement with those from an analysis of urea denaturation curves

  4. Methods for the Analysis of High Precision Differential Hydrogen Deuterium Exchange Data

    PubMed Central

    Chalmers, Michael J.; Pascal, Bruce D.; Willis, Scooter; Zhang, Jun; Iturria, Stephen J.; Dodge, Jeffery A.; Griffin, Patrick R.

    2010-01-01

    Hydrogen/deuterium exchange (HDX) mass spectrometry has been widely applied to the characterization of protein dynamics. More recently, differential HDX has been shown to be effective for the characterization of ligand binding. Previously we have described a fully automated HDX system for use as a ligand screening platform. Here we describe and validate the required data analysis workflow to facilitate the use of HDX as a robust approach for ligand screening. Following acquisition of HDX data at a single on-exchange time point (n ≥ 3), one way analysis of variance in conjunction with the Tukey multiple comparison procedure is used to establish the significance of any measured difference. Analysis results are graphed with respect to a single peptide, ligand or group of ligands, or displayed as an overview within a heat map. For the heat map display, only Δ%D values with a Tukey-adjusted P value less than 0.05 are colored. Hierarchical clustering is used to bin compounds with highly similar HDX signatures. The workflow is evaluated with a small data set showing the ligand binding domain (LDB) of the nuclear receptor peroxisome proliferator-activated receptor gamma (PPARγ) screened against 10 functionally selective ligands. More significantly, data for the vitamin D receptor (VDR) in complex with 87 ligands are presented. To highlight the robustness and precision of our automated HDX platform we analyzed the data from 4191 replicate HDX measurements acquired over an eight month timeframe. Ninety six percent of these measurements were within 10 percent of the mean value. Work has begun to integrate these analysis and graphing components within our HDX software suite. PMID:21528013

  5. Optimization and Application of APCI Hydrogen-Deuterium Exchange Mass Spectrometry (HDX MS) for the Speciation of Nitrogen Compounds.

    PubMed

    Acter, Thamina; Cho, Yunju; Kim, Sungji; Ahmed, Arif; Kim, Byungjoo; Kim, Sunghwan

    2015-09-01

    A systematic study was performed to investigate the utility of atmospheric pressure chemical ionization hydrogen-deuterium exchange mass spectrometry (APCI HDX MS) to identify the structures of nitrogen-containing aromatic compounds. First, experiments were performed to determine the optimized experimental conditions, with dichloromethane and CH(3)OD found to be good cosolvents for APCI HDX. In addition, a positive correlation between the heated capillary temperature and the observed HDX signal was observed, and it was suggested that the HDX reaction occurred when molecules were contained in the solvent cluster. Second, 20 standard nitrogen-containing compounds were analyzed to investigate whether speciation could be determined based on the different types of ions produced from nitrogen-containing compounds with various functional groups. The number of exchanges occurring within the compounds correlated well with the number of active hydrogen atoms attached to nitrogen, and it was confirmed that APCI HDX MS could be used to determine speciation. The results obtained by APCI HDX MS were combined with the subsequent investigation of the double bond equivalence distribution and indicated that resins of shale oil extract contained mostly pyridine type nitrogen compounds. This study confirmed that APCI HDX MS can be added to previously reported chemical ionization, electrospray ionization, and atmospheric pressure photo ionization-based HDX methods, which can be used for structural elucidation by mass spectrometry. PMID:26115964

  6. Optimization and Application of APCI Hydrogen-Deuterium Exchange Mass Spectrometry (HDX MS) for the Speciation of Nitrogen Compounds

    NASA Astrophysics Data System (ADS)

    Acter, Thamina; Cho, Yunju; Kim, Sungji; Ahmed, Arif; Kim, Byungjoo; Kim, Sunghwan

    2015-09-01

    A systematic study was performed to investigate the utility of atmospheric pressure chemical ionization hydrogen-deuterium exchange mass spectrometry (APCI HDX MS) to identify the structures of nitrogen-containing aromatic compounds. First, experiments were performed to determine the optimized experimental conditions, with dichloromethane and CH3OD found to be good cosolvents for APCI HDX. In addition, a positive correlation between the heated capillary temperature and the observed HDX signal was observed, and it was suggested that the HDX reaction occurred when molecules were contained in the solvent cluster. Second, 20 standard nitrogen-containing compounds were analyzed to investigate whether speciation could be determined based on the different types of ions produced from nitrogen-containing compounds with various functional groups. The number of exchanges occurring within the compounds correlated well with the number of active hydrogen atoms attached to nitrogen, and it was confirmed that APCI HDX MS could be used to determine speciation. The results obtained by APCI HDX MS were combined with the subsequent investigation of the double bond equivalence distribution and indicated that resins of shale oil extract contained mostly pyridine type nitrogen compounds. This study confirmed that APCI HDX MS can be added to previously reported chemical ionization, electrospray ionization, and atmospheric pressure photo ionization-based HDX methods, which can be used for structural elucidation by mass spectrometry.

  7. Measuring the hydrogen/deuterium exchange of proteins at high spatial resolution by mass spectrometry: overcoming gas-phase hydrogen/deuterium scrambling.

    PubMed

    Rand, Kasper D; Zehl, Martin; Jørgensen, Thomas J D

    2014-10-21

    Proteins are dynamic molecules that exhibit conformational flexibility to function properly. Well-known examples of this are allosteric regulation of protein activity and ligand-induced conformational changes in protein receptors. Detailed knowledge of the conformational properties of proteins is therefore pertinent to both basic and applied research, including drug development, since the majority of drugs target protein receptors and a growing number of drugs introduced to the market are therapeutic peptides or proteins. X-ray crystallography provides a static picture at atomic resolution of the lowest-energy structure of the native ensemble. There is a growing need for sensitive analytical tools to explore all of the significant molecular structures in the conformational landscape of proteins. Hydrogen/deuterium exchange monitored by mass spectrometry (HDX-MS) has recently emerged as a powerful method for characterizing protein conformational dynamics. The basis of this method is the fact that backbone amides in stable hydrogen-bonded structures (e.g., α-helices and β-sheets) are protected against exchange with the aqueous solvent. All protein structures are dynamic, however, and eventually all of the protecting hydrogen bonds will transiently break as the protein--according to thermodynamic principles--cycles through partially unfolded states that correspond to excited free energy levels. As a result, all of the backbone amides will eventually become temporarily solvent-exposed and exchange-competent over time. Consequently, a folded protein in D2O will gradually incorporate deuterium into its backbone amides, and the kinetics of the process can be readily monitored by mass spectrometry. The deuterium uptake kinetics for the intact protein (global exchange kinetics) represents the sum of the exchange kinetics for the individual backbone amides. Local exchange kinetics is typically achieved by using pepsin digestion under quench conditions (i.e., under cold

  8. Characterization of Stress-Exposed Granulocyte Colony Stimulating Factor Using ELISA and Hydrogen/Deuterium Exchange Mass Spectrometry

    NASA Astrophysics Data System (ADS)

    Tsuchida, Daisuke; Yamazaki, Katsuyoshi; Akashi, Satoko

    2014-10-01

    Information on the higher-order structure is important in the development of biopharmaceutical drugs. Recently, hydrogen/deuterium exchange coupled with mass spectrometry (HDX-MS) has been widely used as a tool to evaluate protein conformation, and unique automated systems for HDX-MS are now commercially available. To investigate the potential of this technique for the prediction of the activity of biopharmaceuticals, granulocyte colony stimulating factor (G-CSF), which had been subjected to three different stress types, was analyzed using HDX-MS and through comparison with receptor-binding activity. It was found that HDX-MS, in combination with ion mobility separation, was able to identify conformational changes in G-CSF induced by stress, and a good correlation with the receptor-binding activity was demonstrated, which cannot be completely determined by conventional peptide mapping alone. The direct evaluation of biological activity using bioassay is absolutely imperative in biopharmaceutical development, but HDX-MS can provide the alternative information in a short time on the extent and location of the structural damage caused by stresses. Furthermore, the present study suggests the possibility of this system being a versatile evaluation method for the preservation stability of biopharmaceuticals.

  9. Polar Aprotic Modifiers for Chromatographic Separation and Back-Exchange Reduction for Protein Hydrogen/Deuterium Exchange Monitored by Fourier Transform Ion Cyclotron Resonance Mass Spectrometry

    NASA Astrophysics Data System (ADS)

    Valeja, Santosh G.; Emmett, Mark R.; Marshall, Alan G.

    2012-04-01

    Hydrogen/deuterium exchange monitored by mass spectrometry is an important non-perturbing tool to study protein structure and protein-protein interactions. However, water in the reversed-phase liquid chromatography mobile phase leads to back-exchange of D for H during chromatographic separation of proteolytic peptides following H/D exchange, resulting in incorrect identification of fast-exchanging hydrogens as unexchanged hydrogens. Previously, fast high-performance liquid chromatography (HPLC) and supercritical fluid chromatography have been shown to decrease back-exchange. Here, we show that replacement of up to 40% of the water in the LC mobile phase by the modifiers, dimethylformamide (DMF) and N-methylpyrrolidone (NMP) (i.e., polar organic modifiers that lack rapid exchanging hydrogens), significantly reduces back-exchange. On-line LC micro-ESI FT-ICR MS resolves overlapped proteolytic peptide isotopic distributions, allowing for quantitative determination of the extent of back-exchange. The DMF modified solvent composition also improves chromatographic separation while reducing back-exchange relative to conventional solvent.

  10. Screen-printed digital microfluidics combined with surface acoustic wave nebulization for hydrogen-deuterium exchange measurements.

    PubMed

    Monkkonen, Lucas; Edgar, J Scott; Winters, Daniel; Heron, Scott R; Mackay, C Logan; Masselon, Christophe D; Stokes, Adam A; Langridge-Smith, Patrick R R; Goodlett, David R

    2016-03-25

    An inexpensive digital microfluidic (DMF) chip was fabricated by screen-printing electrodes on a sheet of polyimide. This device was manually integrated with surface acoustic wave nebulization (SAWN) MS to conduct hydrogen/deuterium exchange (HDX) of peptides. The HDX experiment was performed by DMF mixing of one aqueous droplet of angiotensin II with a second containing various concentrations of D2O. Subsequently, the degree of HDX was measured immediately by SAWN-MS. As expected for a small peptide, the isotopically resolved mass spectrum for angiotensin revealed that maximum deuterium exchange was achieved using 50% D2O. Additionally, using SAWN-MS alone, the global HDX kinetics of ubiquitin were found to be similar to published NMR data and back exchange rates for the uncooled apparatus using high inlet capillary temperatures was less than 6%. PMID:26826755

  11. Effective application of bicelles for conformational analysis of G protein-coupled receptors by hydrogen/deuterium exchange mass spectrometry.

    PubMed

    Duc, Nguyen Minh; Du, Yang; Thorsen, Thor S; Lee, Su Youn; Zhang, Cheng; Kato, Hideaki; Kobilka, Brian K; Chung, Ka Young

    2015-05-01

    G protein-coupled receptors (GPCRs) have important roles in physiology and pathology, and 40% of drugs currently on the market target GPCRs for the treatment of various diseases. Because of their therapeutic importance, the structural mechanism of GPCR signaling is of great interest in the field of drug discovery. Hydrogen/deuterium exchange mass spectrometry (HDX-MS) is a useful tool for analyzing ligand binding sites, the protein-protein interaction interface, and conformational changes of proteins. However, its application to GPCRs has been limited for various reasons, including the hydrophobic nature of GPCRs and the use of detergents in their preparation. In the present study, we tested the application of bicelles as a means of solubilizing GPCRs for HDX-MS studies. GPCRs (e.g., β2-adrenergic receptor [β2AR], μ-opioid receptor, and protease-activated receptor 1) solubilized in bicelles produced better sequence coverage (greater than 90%) than GPCRs solubilized in n-dodecyl-β-D-maltopyranoside (DDM), suggesting that bicelles are a more effective method of solubilization for HDX-MS studies. The HDX-MS profile of β2AR in bicelles showed that transmembrane domains (TMs) undergo lower deuterium uptake than intracellular or extracellular regions, which is consistent with the fact that the TMs are highly ordered and embedded in bicelles. The overall HDX-MS profiles of β2AR solubilized in bicelles and in DDM were similar except for intracellular loop 3. Interestingly, we detected EX1 kinetics, an important phenomenon in protein dynamics, at the C-terminus of TM6 in β2AR. In conclusion, we suggest the application of bicelles as a useful method for solubilizing GPCRs for conformational analysis by HDX-MS. PMID:25740347

  12. Effective Application of Bicelles for Conformational Analysis of G Protein-Coupled Receptors by Hydrogen/Deuterium Exchange Mass Spectrometry

    NASA Astrophysics Data System (ADS)

    Duc, Nguyen Minh; Du, Yang; Thorsen, Thor S.; Lee, Su Youn; Zhang, Cheng; Kato, Hideaki; Kobilka, Brian K.; Chung, Ka Young

    2015-05-01

    G protein-coupled receptors (GPCRs) have important roles in physiology and pathology, and 40% of drugs currently on the market target GPCRs for the treatment of various diseases. Because of their therapeutic importance, the structural mechanism of GPCR signaling is of great interest in the field of drug discovery. Hydrogen/deuterium exchange mass spectrometry (HDX-MS) is a useful tool for analyzing ligand binding sites, the protein-protein interaction interface, and conformational changes of proteins. However, its application to GPCRs has been limited for various reasons, including the hydrophobic nature of GPCRs and the use of detergents in their preparation. In the present study, we tested the application of bicelles as a means of solubilizing GPCRs for HDX-MS studies. GPCRs (e.g., β2-adrenergic receptor [β2AR], μ-opioid receptor, and protease-activated receptor 1) solubilized in bicelles produced better sequence coverage (greater than 90%) than GPCRs solubilized in n-dodecyl-β-D-maltopyranoside (DDM), suggesting that bicelles are a more effective method of solubilization for HDX-MS studies. The HDX-MS profile of β2AR in bicelles showed that transmembrane domains (TMs) undergo lower deuterium uptake than intracellular or extracellular regions, which is consistent with the fact that the TMs are highly ordered and embedded in bicelles. The overall HDX-MS profiles of β2AR solubilized in bicelles and in DDM were similar except for intracellular loop 3. Interestingly, we detected EX1 kinetics, an important phenomenon in protein dynamics, at the C-terminus of TM6 in β2AR. In conclusion, we suggest the application of bicelles as a useful method for solubilizing GPCRs for conformational analysis by HDX-MS.

  13. Differential isotopic enrichment to facilitate characterization of asymmetric multimeric proteins using hydrogen/deuterium exchange mass spectrometry

    PubMed Central

    Pascal, Bruce D.; Bauman, Joseph D.; Patel, Disha; Arnold, Eddy; Griffin, Patrick R.

    2015-01-01

    Hydrogen/deuterium exchange (HDX) coupled to mass spectrometry has emerged as a powerful tool for analyzing the conformational dynamics of protein-ligand and protein-protein interactions. Recent advances in instrumentation and methodology have expanded the utility of HDX for the analysis of large and complex proteins; however, asymmetric dimers with shared amino acid sequence present a unique challenge for HDX because assignment of peptides with identical sequence to their subunit of origin remains ambiguous. Here we report the use of differential isotopic labeling to facilitate HDX analysis of multimers using HIV-1 reverse transcriptase (RT) as a model. RT is an asymmetric heterodimer of 51 kDa (p51) and 66 kDa (p66) subunits. The first 440 residues of p51 and p66 are identical. In this study differentially labeled RT was reconstituted from isotopically enriched (15N-labeled) p51 and unlabeled p66. In order to enable detection of 15N-deuterated RT peptides, the software HDX Workbench was modified to follow a 100% 15N model. Our results demonstrated that 15N enrichment of p51 did not affect its conformational dynamics compared to unlabeled p51, but 15N-labeled p51 did show different conformational dynamics than p66 in the RT heterodimer. Differential HDX-MS of isotopically labeled RT in the presence of the nonnucleoside reverse transcriptase inhibitor (NNRTI) efavirenz (EFV) showed subunit-specific perturbation in the rate of HDX consistent with previously published results and the RT-EFV co-crystal structure. PMID:25763479

  14. Analysis of Local Dynamics of Human Insulin and a Rapid-acting Insulin Analog by Hydrogen Deuterium Exchange Mass Spectrometry

    PubMed Central

    Nakazawa, Shiori; Hashii, Noritaka; Hirose, Kenji; Kawasaki, Nana; Ahn, Joomi

    2013-01-01

    Human insulin, used by diabetics to regulate blood sugar, was first introduced as a recombinant therapeutic drug nearly 30 years ago. Human insulin and insulin lispro have identical primary structure, except for the transposition of two amino acids. Lispro is one of the rapid-acting insulin analogs, which has higher tendency to dissociate than human insulin. In this study, we present an analytical workflow to allow us to detect the difference in the oligomeric dynamics using Hydrogen Deuterium Exchange Mass Spectrometry (HDX MS). The HDX analysis on Insulin and Lispro peptides was conducted to identify the location where different deuterium uptakes were observed between human insulin and lispro. The detected areas were illustrated in various formats to help understand their flexibility associated with rapid dissociation of insulin oligomers. Drug products, human insulin (Humulin R) and lispro (Humalog), were reduced and digested online by pepsin. Deuterium labeling, quenching, and injection to on-line pepsin digestion were prepared using a robotic sample manager. Labeling experiments in 0, 0.5, 5, 10, 60, and 180 min interval were duplicated for both samples. The peptic digests were separated on a UPLC system at 0 °C. Q-TOF MS was used to measure the deuterium incorporation of identified peptides. The amount of deuterium was determined by automated HDX data processing software, DynamX 2.0. We obtained 98% of sequence coverage for both human insulin and lispro. From peptide HDX determination, two regions were revealed distinctive different values in deuterium uptakes between human insulin and lispro; the N terminus of chain A, and a region adjacent to the C terminus of chain B. We attributed this localized behavior to the relation of hexamerization and dimerization, respectively. Furthermore, characteristic profiles that showed different deuteration margins between two insulins were determined, which was also consistent with their involvement in hexamer and dimer

  15. Conformational difference in human IgG2 disulfide isoforms revealed by hydrogen/deuterium exchange mass spectrometry.

    PubMed

    Zhang, Aming; Fang, Jing; Chou, Robert Y-T; Bondarenko, Pavel V; Zhang, Zhongqi

    2015-03-17

    Both recombinant and natural human IgG2 antibodies have several different disulfide bond isoforms, which possess different global structures, thermal stabilities, and biological activities. A detailed mapping of the structural difference among IgG2 disulfide isoforms, however, has not been established. In this work, we employed hydrogen/deuterium exchange mass spectrometry to study the conformation of three major IgG2 disulfide isoforms known as IgG2-B, IgG2-A1, and IgG2-A2 in two recombinant human IgG2 monoclonal antibodies. By comparing the protection factors between amino acid residues in isoforms B and A1 (the classical form), we successfully identified several local regions in which the IgG2-B isoform showed more solvent protection than the IgG2-A1 isoform. On the basis of three-dimensional structural models of IgG2, these identified regions were located on the Fab domains, close to the hinge, centered on the side where the two Fab arms faced each other in spatial proximity. We speculated that in the more solvent-protected B isoform, the two Fab arms were brought into contact by the nonclassical disulfide bonds, resulting in a more compact global structure. Loss of Fab domain flexibility in IgG2-B could limit its ability to access cell-surface epitopes, leading to reduced antigen binding potency. The A2 isoform was previously found to have disulfide linkages similar to those of the classical A1 isoform, but with different biophysical behaviors. Our data indicated that, compared to IgG2-A1, IgG2-A2 had less solvent protection in some heavy-chain Fab regions close the hinge, suggesting that the A2 isoform had more flexible Fab domains. PMID:25730439

  16. Investigation of the gas-phase hydrogen/deuterium exchange behavior of aromatic dicarboxylic acids in a quadrupole ion trap

    NASA Astrophysics Data System (ADS)

    Chipuk, Joseph E.; Brodbelt, Jennifer S.

    2007-11-01

    Gas-phase hydrogen/deuterium (H/D) exchange reactions of four deprotonated aromatic dicarboxylic acids (phthalic acid, isophthalic acid, terephthalic acid and 2,6-naphthalic acid) with D2O were performed in a quadrupole ion trap mass spectrometer. Experimental results showed significant differences in the rate and extent of exchange when the relative position of the carboxylic acid groups varied. Spontaneous and near complete exchange of one aromatic hydrogen atom occurred when the carboxylic acid groups were in the meta-position, whereas no additional exchange was observed for either the ortho- or para-isomers or for the structurally similar naphthalic acid. Computational investigations support the participation of several possible exchange mechanisms with the contribution of each relying heavily on the relative orientation of the acid moieties. A relay mechanism that bridges the deprotonation site and the labile hydrogen site appears to be responsible for the H/D exchange of not only the labile hydrogen atom of isophthalic acid, but also for the formation of a stable carbanion and corresponding subsequent exchange of one aromatic hydrogen atom. The impact of hydrogen bonding on the relay mechanism is demonstrated by the reaction of phthalic acid as the extent and rate of reaction are greatly retarded by the favorable interaction of the two carboxylic acid groups. Finally, a flip-flop mechanism is likely responsible for the exchange of both terephthalic acid and 2,6-naphthalic acid where the reactive sites are too remote for exchange via relay.

  17. Simultaneous reduction and digestion of proteins with disulfide bonds for hydrogen/deuterium exchange monitored by mass spectrometry.

    PubMed

    Zhang, Hui-Min; McLoughlin, Shaun M; Frausto, Stephen D; Tang, Hengli; Emmett, Mark R; Marshall, Alan G

    2010-02-15

    Proteolyzed peptides provide the basis for mass-analyzed hydrogen/deuterium exchange (HDX) for mapping solvent access to various segments of solution-phase proteins. Aspergillus saitoi protease type XIII and porcine pepsin can generate peptides of overlapping sequences and high sequence coverage. However, if disulfide bonds are present, proteolysis can be severely limited, particularly in the vicinity of the disulfide linkage(s). Disulfide bonds cannot be reduced before or during the H/D exchange reaction without affecting the protein higher-order structure. Here, we demonstrate simultaneous quench/digestion/reduction following H/D exchange, for subsequent mass analysis. Proteolysis is conducted in the presence of tris(2-carboxyethyl)phosphine hydrochloride (TCEP.HCl) and urea, and all other steps of the H/D exchange and analysis are maintained. This method yields dramatically increased sequence coverage and localization of solvent-exposed segments for mass-analyzed solution-phase H/D exchange of proteins containing disulfide bonds. PMID:20099838

  18. NMR-Based Amide Hydrogen-Deuterium Exchange Measurements for Complex Membrane Proteins: Development and Critical Evaluation

    NASA Astrophysics Data System (ADS)

    Czerski, Lech; Vinogradova, Olga; Sanders, Charles R.

    2000-01-01

    A method for measuring site-specific amide hydrogen-deuterium exchange rates for membrane proteins in bilayers is reported and evaluated. This method represents an adaptation and extension of the approach of Dempsey and co-workers (Biophys. J. 70, 1777-1788 (1996)) and is based on reconstituting 15N-labeled membrane proteins into phospholipid bilayers, followed by lyophilization and rehydration with D2O or H2O (control). Following incubation for a time t under hydrated conditions, samples are again lyophilized and then solubilized in an organic solvent system, where 1H-15N HSQC spectra are recorded. Comparison of spectra from D2O-exposed samples to spectra from control samples yields the extent of the H-D exchange which occurred in the bilayers during time t. Measurements are site specific if specific 15N labeling is used. The first part of this paper deals with the search for a suitable solvent system in which to solubilize complex membrane proteins in an amide "exchange-trapped" form for NMR quantitation of amide peak intensities. The second portion of the paper documents application of the overall procedure to measuring site-specific amide exchange rates in diacylglycerol kinase, a representative integral membrane protein. Both the potential usefulness and the significant limitations of the new method are documented.

  19. Supercritical fluid chromatography coupled with in-source atmospheric pressure ionization hydrogen/deuterium exchange mass spectrometry for compound speciation.

    PubMed

    Cho, Yunju; Choi, Man-Ho; Kim, Byungjoo; Kim, Sunghwan

    2016-04-29

    An experimental setup for the speciation of compounds by hydrogen/deuterium exchange (HDX) with atmospheric pressure ionization while performing chromatographic separation is presented. The proposed experimental setup combines the high performance supercritical fluid chromatography (SFC) system that can be readily used as an inlet for mass spectrometry (MS) and atmospheric pressure photo ionization (APPI) or atmospheric pressure chemical ionization (APCI) HDX. This combination overcomes the limitation of an approach using conventional liquid chromatography (LC) by minimizing the amount of deuterium solvents used for separation. In the SFC separation, supercritical CO2 was used as a major component of the mobile phase, and methanol was used as a minor co-solvent. By using deuterated methanol (CH3OD), AP HDX was achieved during SFC separation. To prove the concept, thirty one nitrogen- and/or oxygen-containing standard compounds were analyzed by SFC-AP HDX MS. The compounds were successfully speciated from the obtained SFC-MS spectra. The exchange ions were observed with as low as 1% of CH3OD in the mobile phase, and separation could be performed within approximately 20min using approximately 0.24 mL of CH3OD. The results showed that SFC separation and APPI/APCI HDX could be successfully performed using the suggested method. PMID:27020885

  20. Recombinant immobilized rhizopuspepsin as a new tool for protein digestion in hydrogen/deuterium exchange mass spectrometry.

    PubMed

    Rey, Martial; Man, Petr; Brandolin, Gérard; Forest, Eric; Pelosi, Ludovic

    2009-11-01

    Hydrogen/deuterium (H/D) exchange coupled to mass spectrometry is nowadays routinely used to probe protein interactions or conformational changes. The method has many advantages, e.g. very low sample consumption, but offers limited spatial resolution. One way to higher resolution leads through the use of different proteases or their combinations. In the present work we describe recombinant production, purification and use of aspartic protease zymogen from Rhizopus chimensis, protease type XVIII (EC 3.4.23.6), commonly referred to as rhizopuspepsinogen (Rpg). The enzyme was expressed in Escherichia coli, refolded and purified to homogeneity. A typical yield was approximately 100 mg of pure enzyme per 1 L of original bacterial culture. The kinetics of protease activation, i.e. removal of the propeptide achieved by autolysis in an acidic environment, was followed by mass spectrometry. The digestion efficiency was tested for the protease in solution as well as for the immobilized enzyme. Apomyoglobin was successfully digested under all conditions tested and the protease displayed very low or no autodigestion. The results outperformed those obtained with commercial protease where the digestion of apomyoglobin was incomplete and accompanied by many contaminating peptides. Taken together, the recombinant protease type XVIII can be considered as a new and highly efficient tool for H/D exchange followed by mass spectrometry. PMID:19827048

  1. Characterization of IgG1 Conformation and Conformational Dynamics by Hydrogen/Deuterium Exchange Mass Spectrometry

    SciTech Connect

    Houde, Damian; Arndt, Joseph; Domeier, Wayne; Berkowitz, Steven; Engen, John R.

    2009-04-22

    Protein function is dictated by protein conformation. For the protein biopharmaceutical industry, therefore, it is important to have analytical tools that can detect changes in protein conformation rapidly, accurately, and with high sensitivity. In this paper we show that hydrogen/deuterium exchange mass spectrometry (H/DX-MS) can play an important role in fulfilling this need within the industry. H/DX-MS was used to assess both global and local conformational behavior of a recombinant monoclonal IgG1 antibody, a major class of biopharmaceuticals. Analysis of exchange into the intact, glycosylated IgG1 (and the Fab and Fc regions thereof) showed that the molecule was folded, highly stable, and highly amenable to analysis by this method using less than a nanomole of material. With improved chromatographic methods, peptide identification algorithms and data-processing steps, the analysis of deuterium levels in peptic peptides produced after labeling was accomplished in 1--2 days. On the basis of peptic peptide data, exchange was localized to specific regions of the antibody. Changes to IgG1 conformation as a result of deglycosylation were determined by comparing exchange into the glycosylated and deglycosylated forms of the antibody. Two regions of the IgG1 (residues 236-253 and 292-308) were found to have altered exchange properties upon deglycosylation. These results are consistent with previous findings concerning the role of glycosylation in the interaction of IgG1 with Fc receptors. Moreover, the data clearly illustrate how H/DX-MS can provide important characterization information on the higher order structure of antibodies and conformational changes that these molecules may experience upon modification.

  2. Hexicon 2: automated processing of hydrogen-deuterium exchange mass spectrometry data with improved deuteration distribution estimation.

    PubMed

    Lindner, Robert; Lou, Xinghua; Reinstein, Jochen; Shoeman, Robert L; Hamprecht, Fred A; Winkler, Andreas

    2014-06-01

    Hydrogen-deuterium exchange (HDX) experiments analyzed by mass spectrometry (MS) provide information about the dynamics and the solvent accessibility of protein backbone amide hydrogen atoms. Continuous improvement of MS instrumentation has contributed to the increasing popularity of this method; however, comprehensive automated data analysis is only beginning to mature. We present Hexicon 2, an automated pipeline for data analysis and visualization based on the previously published program Hexicon (Lou et al. 2010). Hexicon 2 employs the sensitive NITPICK peak detection algorithm of its predecessor in a divide-and-conquer strategy and adds new features, such as chromatogram alignment and improved peptide sequence assignment. The unique feature of deuteration distribution estimation was retained in Hexicon 2 and improved using an iterative deconvolution algorithm that is robust even to noisy data. In addition, Hexicon 2 provides a data browser that facilitates quality control and provides convenient access to common data visualization tasks. Analysis of a benchmark dataset demonstrates superior performance of Hexicon 2 compared with its predecessor in terms of deuteration centroid recovery and deuteration distribution estimation. Hexicon 2 greatly reduces data analysis time compared with manual analysis, whereas the increased number of peptides provides redundant coverage of the entire protein sequence. Hexicon 2 is a standalone application available free of charge under http://hx2.mpimf-heidelberg.mpg.de. PMID:24676893

  3. Hexicon 2: Automated Processing of Hydrogen-Deuterium Exchange Mass Spectrometry Data with Improved Deuteration Distribution Estimation

    NASA Astrophysics Data System (ADS)

    Lindner, Robert; Lou, Xinghua; Reinstein, Jochen; Shoeman, Robert L.; Hamprecht, Fred A.; Winkler, Andreas

    2014-06-01

    Hydrogen-deuterium exchange (HDX) experiments analyzed by mass spectrometry (MS) provide information about the dynamics and the solvent accessibility of protein backbone amide hydrogen atoms. Continuous improvement of MS instrumentation has contributed to the increasing popularity of this method; however, comprehensive automated data analysis is only beginning to mature. We present Hexicon 2, an automated pipeline for data analysis and visualization based on the previously published program Hexicon (Lou et al. 2010). Hexicon 2 employs the sensitive NITPICK peak detection algorithm of its predecessor in a divide-and-conquer strategy and adds new features, such as chromatogram alignment and improved peptide sequence assignment. The unique feature of deuteration distribution estimation was retained in Hexicon 2 and improved using an iterative deconvolution algorithm that is robust even to noisy data. In addition, Hexicon 2 provides a data browser that facilitates quality control and provides convenient access to common data visualization tasks. Analysis of a benchmark dataset demonstrates superior performance of Hexicon 2 compared with its predecessor in terms of deuteration centroid recovery and deuteration distribution estimation. Hexicon 2 greatly reduces data analysis time compared with manual analysis, whereas the increased number of peptides provides redundant coverage of the entire protein sequence. Hexicon 2 is a standalone application available free of charge under http://hx2.mpimf-heidelberg.mpg.de.

  4. Conformational Analysis of Proteins in Highly Concentrated Solutions by Dialysis-Coupled Hydrogen/Deuterium Exchange Mass Spectrometry.

    PubMed

    Houde, Damian; Nazari, Zeinab E; Bou-Assaf, George M; Weiskopf, Andrew S; Rand, Kasper D

    2016-04-01

    When highly concentrated, an antibody solution can exhibit unusual behaviors, which can lead to unwanted properties, such as increased levels of protein aggregation and unusually high viscosity. Molecular modeling, along with many indirect biophysical measurements, has suggested that the cause for these phenomena can be due to short range electrostatic and/or hydrophobic protein-protein interactions. Hydrogen/deuterium exchange mass spectrometry (HDX-MS) is a useful tool for investigating protein conformation, dynamics, and interactions. However, "traditional" continuous dilution labeling HDX-MS experiments have limited utility for the direct analysis of solutions with high concentrations of protein. Here, we present a dialysis-based HDX-MS (di-HDX-MS) method as an alternative HDX-MS labeling format, which takes advantage of passive dialysis rather than the classic dilution workflow. We applied this approach to a highly concentrated antibody solution without dilution or significant sample manipulation, prior to analysis. Such a method could pave the way for a deeper understanding of the unusual behavior of proteins at high concentrations, which is highly relevant for development of biopharmaceuticals in industry. Graphical Abstract ᅟ. PMID:26860088

  5. Ion Mobility Spectrometry-Hydrogen Deuterium Exchange Mass Spectrometry of Anions: Part 3. Estimating Surface Area Exposure by Deuterium Uptake.

    PubMed

    Khakinejad, Mahdiar; Kondalaji, Samaneh Ghassabi; Donohoe, Gregory C; Valentine, Stephen J

    2016-03-01

    Gas-phase hydrogen deuterium exchange (HDX), collision cross section (CCS) measurement, and molecular dynamics simulation (MDS) techniques were utilized to develop and compare three methods for estimating the relative surface area exposure of separate peptide chains within bovine insulin ions. Electrosprayed [M - 3H](3-) and [M - 5H](5-) insulin ions produced a single conformer type with respective collision cross sections of 528 ± 5 Å(2) and 808 ± 2 Å(2). [M - 4H](4-) ions were comprised of more compact (Ω = 676 ± 3 Å(2)) and diffuse (i.e., more elongated, Ω = 779 ± 3 Å(2)) ion conformer types. Ions were subjected to HDX in the drift tube using D2O as the reagent gas. Collision-induced dissociation was used to fragment mobility-selected, isotopically labeled [M - 4H](4-) and [M - 5H](5-) ions into the protein subchains. Deuterium uptake levels of each chain can be explained by limited inter-chain isotopic scrambling upon collisional activation. Using nominal ion structures from MDS and a hydrogen accessibility model, the deuterium uptake for each chain was correlated to its exposed surface area. In separate experiments, the per-residue deuterium content for the protonated and deprotonated ions of the synthetic peptide KKDDDDDIIKIIK were compared. The differences in deuterium content indicated the regional HDX accessibility for cations versus anions. Using ions of similar conformational type, this comparison highlights the complementary nature of HDX data obtained from positive- and negative-ion analysis. PMID:26620531

  6. Ion Mobility Spectrometry-Hydrogen Deuterium Exchange Mass Spectrometry of Anions: Part 3. Estimating Surface Area Exposure by Deuterium Uptake

    NASA Astrophysics Data System (ADS)

    Khakinejad, Mahdiar; Ghassabi Kondalaji, Samaneh; Donohoe, Gregory C.; Valentine, Stephen J.

    2016-03-01

    Gas-phase hydrogen deuterium exchange (HDX), collision cross section (CCS) measurement, and molecular dynamics simulation (MDS) techniques were utilized to develop and compare three methods for estimating the relative surface area exposure of separate peptide chains within bovine insulin ions. Electrosprayed [M - 3H]3- and [M - 5H]5- insulin ions produced a single conformer type with respective collision cross sections of 528 ± 5 Å2 and 808 ± 2 Å2. [M - 4H]4- ions were comprised of more compact (Ω = 676 ± 3 Å2) and diffuse (i.e., more elongated, Ω = 779 ± 3 Å2) ion conformer types. Ions were subjected to HDX in the drift tube using D2O as the reagent gas. Collision-induced dissociation was used to fragment mobility-selected, isotopically labeled [M - 4H]4- and [M - 5H]5- ions into the protein subchains. Deuterium uptake levels of each chain can be explained by limited inter-chain isotopic scrambling upon collisional activation. Using nominal ion structures from MDS and a hydrogen accessibility model, the deuterium uptake for each chain was correlated to its exposed surface area. In separate experiments, the per-residue deuterium content for the protonated and deprotonated ions of the synthetic peptide KKDDDDDIIKIIK were compared. The differences in deuterium content indicated the regional HDX accessibility for cations versus anions. Using ions of similar conformational type, this comparison highlights the complementary nature of HDX data obtained from positive- and negative-ion analysis.

  7. Automated Hydrogen/Deuterium Exchange Electron Transfer Dissociation High Resolution Mass Spectrometry Measured at Single-Amide Resolution

    NASA Astrophysics Data System (ADS)

    Landgraf, Rachelle R.; Chalmers, Michael J.; Griffin, Patrick R.

    2012-02-01

    Hydrogen deuterium exchange mass spectrometry (HDX-MS) is a well established method for the measurement of solution-phase deuterium incorporation into proteins, which can provide insight into protein conformational mobility. However, most HDX measurements are constrained to regions of the protein where pepsin proteolysis allows detection at peptide resolution. Recently, single-amide resolution deuterium incorporation has been achieved by limiting gas-phase scrambling in the mass spectrometer. This was accomplished by employing a combination of soft ionization and desolvation conditions coupled with the radical-driven fragmentation technique electron transfer dissociation (ETD). Here, a hybrid LTQ-Orbitrap XL is systematically evaluated for its utility in providing single-amide deuterium incorporation for differential HDX analysis of a nuclear receptor upon binding small molecule ligands. We are able to show that instrumental parameters can be optimized to minimize scrambling and can be incorporated into an established and fully automated HDX platform making differential single-amide HDX possible for bottom-up analysis of complex systems. We have applied this system to determine differential single amide resolution HDX data for the peroxizome proliferator activated receptor bound with two ligands of interest.

  8. Applications of hydrogen deuterium exchange (HDX) for the characterization of conformational dynamics in light-activated photoreceptors

    PubMed Central

    Lindner, Robert; Heintz, Udo; Winkler, Andreas

    2015-01-01

    Rational design of optogenetic tools is inherently linked to the understanding of photoreceptor function. Structural analysis of elements involved in signal integration in individual sensor domains provides an initial idea of their mode of operation, but understanding how local structural rearrangements eventually affect signal transmission to output domains requires inclusion of the effector regions in the characterization. However, the dynamic nature of these assemblies renders their structural analysis challenging and therefore a combination of high- and low-resolution techniques is required to appreciate functional aspects of photoreceptors. This review focuses on the potential of hydrogen-deuterium exchange coupled to mass spectrometry (HDX-MS) for complementing the structural characterization of photoreceptors. In this respect, the ability of HDX-MS to provide information on conformational dynamics and the possibility to address multiple functionally relevant states in solution render this methodology ideally suitable. We highlight recent examples demonstrating the potential of HDX-MS and discuss how these results can help to improve existing optogenetic systems or guide the design of novel optogenetic tools. PMID:26157802

  9. Conformational Analysis of Proteins in Highly Concentrated Solutions by Dialysis-Coupled Hydrogen/Deuterium Exchange Mass Spectrometry

    NASA Astrophysics Data System (ADS)

    Houde, Damian; Nazari, Zeinab E.; Bou-Assaf, George M.; Weiskopf, Andrew S.; Rand, Kasper D.

    2016-04-01

    When highly concentrated, an antibody solution can exhibit unusual behaviors, which can lead to unwanted properties, such as increased levels of protein aggregation and unusually high viscosity. Molecular modeling, along with many indirect biophysical measurements, has suggested that the cause for these phenomena can be due to short range electrostatic and/or hydrophobic protein-protein interactions. Hydrogen/deuterium exchange mass spectrometry (HDX-MS) is a useful tool for investigating protein conformation, dynamics, and interactions. However, "traditional" continuous dilution labeling HDX-MS experiments have limited utility for the direct analysis of solutions with high concentrations of protein. Here, we present a dialysis-based HDX-MS (di-HDX-MS) method as an alternative HDX-MS labeling format, which takes advantage of passive dialysis rather than the classic dilution workflow. We applied this approach to a highly concentrated antibody solution without dilution or significant sample manipulation, prior to analysis. Such a method could pave the way for a deeper understanding of the unusual behavior of proteins at high concentrations, which is highly relevant for development of biopharmaceuticals in industry.

  10. Imidazole C-2 Hydrogen/Deuterium Exchange Reaction at Histidine for Probing Protein Structure and Function with MALDI Mass Spectrometry

    PubMed Central

    Hayashi, Naoka; Kuyama, Hiroki; Nakajima, Chihiro; Kawahara, Kazuki; Miyagi, Masaru; Nishimura, Osamu; Matsuo, Hisayuki; Nakazawa, Takashi

    2015-01-01

    We present a mass spectrometric method for analyzing protein structure and function, based on the imidazole C-2 or histidine Cε1 hydrogen/deuterium (H/D) exchange reaction, which is intrinsically second order with respect to the concentrations of the imidazolium cation and OD− in D2O. The second-order rate constant (k2) of this reaction was calculated from the pH-dependency of the pseudo-first-order rate constant (kφ) obtained from the change of average mass ΔMr (0 ≤ ΔMr < 1) of a peptide fragment containing a defined histidine residue at incubation time (t) such that kφ = − [ln(1−ΔMr)]/t. We preferred using k2 rather than kφ because k2max (maximal value of k2) was empirically related to pKa as illustrated with a Brønsted plot: logk2max=-0.7pKa+α (α is an arbitrary constant), so that we could analyze the effect of structure on the H/D-exchange rate in terms of log(k2max/k2) representing the deviation of k2 from k2max. In the catalytic site of bovine ribonuclease A, His12 showed much larger change in log(k2max/k2) compared with His119 upon binding with cytidine 3′-monophosphate, as anticipated from the X-ray structures and the possible change in solvent accessibility. However, there is a need of considering the hydrogen bonds of the imidazole group with non-dissociable groups to interpret an extremely slow H/D exchange rate of His48 in partially solvent-exposed situation. PMID:24606199

  11. Analysis of distinct molecular assembly complexes of keratin K8 and K18 by hydrogen-deuterium exchange.

    PubMed

    Premchandar, Aiswarya; Kupniewska, Anna; Tarnowski, Krzysztof; Mücke, Norbert; Mauermann, Monika; Kaus-Drobek, Magdalena; Edelman, Aleksander; Herrmann, Harald; Dadlez, Michał

    2015-12-01

    Keratins are intermediate filament (IF) proteins that form complex filament systems in epithelial cells, thus serving as scaffolding elements and mechanical stress absorbers. The building blocks of keratin IFs are parallel coiled-coil dimers of two distinct sequence-related proteins distinguished as type I and type II keratins. To gain more insight into their structural dynamics, we resorted to hydrogen-deuterium exchange mass spectrometry of keratins K8 and K18, which are characteristic for simple epithelial cells. Using this powerful technique not employed with IFs before, we mapped patterns of protected versus unprotected regions in keratin complexes at various assembly levels. In particular, we localized protein segments exhibiting different hydrogen exchange patterns in tetramers versus filaments. We observed a general pattern of precisely positioned regions of stability intertwining with flexible regions, mostly represented by the non-α-helical segments. Notably, some regions within the coiled-coil domains are significantly more dynamic than others, while the IF-consensus motifs at the end domains of the central α-helical "rod" segment, which mediate the "head-to-tail" dimer-dimer interaction in the filament elongation process, become distinctly more protected upon formation of filaments. Moreover, to gain more insight into the dynamics of the individual keratins, we investigated the properties of homomeric preparations of K8 and K18. The physiological importance of keratins without a partner is encountered in both pathological and experimental situations when one of the two species is present in robust excess or completely absent, such as in gene-targeted mice. PMID:26434626

  12. Hydrogen-deuterium exchange of aromatic amines and amides using deuterated trifluoroacetic acid

    PubMed Central

    Giles, Richard; Lee, Amy; Jung, Erica; Kang, Aaron; Jung, Kyung Woon

    2014-01-01

    The H-D exchange of aromatic amines and amides, including pharmaceutically relevant compounds such as acetaminophen and diclofenac, was investigated using CF3COOD as both the sole reaction solvent and source of deuterium label. The described method is amenable to efficient deuterium incorporation for a wide variety of substrates possessing both electron-donating and electron-withdrawing substituents. Best results were seen with less basic anilines and highly activated acetanilides, reflecting the likelihood of different mechanistic pathways. PMID:25641994

  13. Optimization and application of atmospheric pressure chemical and photoionization hydrogen-deuterium exchange mass spectrometry for speciation of oxygen-containing compounds.

    PubMed

    Acter, Thamina; Kim, Donghwi; Ahmed, Arif; Jin, Jang Mi; Yim, Un Hyuk; Shim, Won Joon; Kim, Young Hwan; Kim, Sunghwan

    2016-05-01

    This paper presents a detailed investigation of the feasibility of optimized positive and negative atmospheric pressure chemical ionization (APCI) mass spectrometry (MS) and atmospheric pressure photoionization (APPI) MS coupled to hydrogen-deuterium exchange (HDX) for structural assignment of diverse oxygen-containing compounds. The important parameters for optimization of HDX MS were characterized. The optimized techniques employed in the positive and negative modes showed satisfactory HDX product ions for the model compounds when dichloromethane and toluene were employed as a co-solvent in APCI- and APPI-HDX, respectively. The evaluation of the mass spectra obtained from 38 oxygen-containing compounds demonstrated that the extent of the HDX of the ions was structure-dependent. The combination of information provided by different ionization techniques could be used for better speciation of oxygen-containing compounds. For example, (+) APPI-HDX is sensitive to compounds with alcohol, ketone, or aldehyde substituents, while (-) APPI-HDX is sensitive to compounds with carboxylic functional groups. In addition, the compounds with alcohol can be distinguished from other compounds by the presence of exchanged peaks. The combined information was applied to study chemical compositions of degraded oils. The HDX pattern, double bond equivalent (DBE) distribution, and previously reported oxidation products were combined to predict structures of the compounds produced from oxidation of oil. Overall, this study shows that APCI- and APPI-HDX MS are useful experimental techniques that can be applied for the structural analysis of oxygen-containing compounds. PMID:26898203

  14. Hydrogen-deuterium exchange on plasma-exposed W and SS surface

    NASA Astrophysics Data System (ADS)

    Takagi, Ikuji; Nomura, Shinji; Minamimoto, Toshihiro; Akiyoshi, Masafumi; Kobayashi, Taishi; Sasaki, Takayuki

    2015-08-01

    The desorption cross section for hydrogen isotopes adsorbed on stainless steel (SS) and tungsten (W) has been evaluated experimentally to provide basic information on tritium exchange. One side of a sample sheet was alternately exposed to H and D plasma, and deuterium density on the surface was repeatedly observed using nuclear reaction analysis (NRA) under continuous plasma exposure. From the time dependent change in the deuterium density, the desorption cross sections for SS and W were estimated to be 6.9 ± 2.3 × 10-23 m2 and 4.6 ± 1.0 × 10-23 m2, respectively. No significant differences in the cross section between H and D plasma were observed. Recombinative desorption was found to dominate the desorption process owing to the low incident energy of hydrogen atoms.

  15. Different conformational dynamics of PDZ1 and PDZ2 in full-length EBP50 analyzed by hydrogen/deuterium exchange mass spectrometry.

    PubMed

    Park, Ji Young; Duc, Nguyen Minh; Kim, Dong Kyun; Lee, Su Youn; Li, Sheng; Seo, Min-Duk; Woods, Virgil L; Chung, Ka Young

    2015-08-01

    Ezrin-radixin-moesin-binding protein 50 (EBP50) is a scaffolding protein expressed in polarized epithelial cells in various organs, including the liver, kidney, and small intestine, in which it regulates the trafficking and targeting cellular proteins. EBP50 contains two postsynaptic density-95/disk-large/ZO-1 homology (PDZ) domains (e.g., PDZ1 and PDZ2) and an ezrin/radixin/moesin-binding (EB) domain. PDZ domains are one of the major scaffolding domains regulating protein-protein interactions with critical biological roles in cell polarity, migration, proliferation, recognition, and cell-cell interaction. PDZ1 and PDZ2 in EBP50 have different ligand selectivity, although several high-resolution structural studies of isolated PDZ1 and PDZ2 showed similar structures. We studied the conformations of full-length EBP50 and isolated PDZ1 and PDZ2 using hydrogen/deuterium exchange mass spectrometry (HDX-MS). The deuterium uptake profiles of isolated PDZ1 and PDZ2 were similar to those of full-length EBP50. Interestingly, PDZ1 was more dynamic than PDZ2, and these PDZ domains underwent different conformational changes upon ligand binding. These results might explain the differences in ligand-selectivity between PDZ1 and PDZ2. PMID:25789870

  16. Conformational studies of the robust 2-Cys peroxiredoxin Salmonella typhimurium AhpC by solution phase hydrogen/deuterium (H/D) exchange monitored by electrospray ionization mass spectrometry.

    PubMed

    Nirudodhi, Sasidhar; Parsonage, Derek; Karplus, P Andrew; Poole, Leslie B; Maier, Claudia S

    2011-04-30

    This is the first comprehensive HX-MS study of a "robust" 2-Cys peroxiredoxin (Prx), namely Salmonella typhimurium AhpC (StAhpC). Prx proteins control intracellular peroxide levels and are abundant antioxidant proteins in eukaryotes, archaea and bacteria. Crystal structural analyses and structure/activity studies of several bacterial and mammalian 2-Cys Prxs have revealed that the activity of 2-Cys Prxs is regulated by redox-dependent oligmerization and a sensitivity of the active site cysteine residue to overoxidation. The propensity to overoxidation is linked to the conformational flexibility of the peroxidatic active site loop. The HX-MS results emphasize the modulation of the conformational motility of the active site loop by disulfide formation. To obtain information on the conformational impact of decamer formation on the active site loop motility, mutants with Thr77 substituted by Ile, a decamer-disrupting mutation or by Val, a decamer-stabilizing mutation, were studied. For the isoleucine mutant, enhanced mobility was observed for regions encompassing the α4 helix located in the dimer-dimer interface and regions surrounding the peroxidatic loop. In contrast, the T77V mutation resulted in an increase in conformational stability in most regions of the protein except for the active site loop and the region encompassing the resolving cysteine. PMID:21516234

  17. Two-Site Evaluation of the Repeatability and Precision of an Automated Dual-Column Hydrogen/Deuterium Exchange Mass Spectrometry Platform.

    PubMed

    Cummins, David J; Espada, Alfonso; Novick, Scott J; Molina-Martin, Manuel; Stites, Ryan E; Espinosa, Juan Felix; Broughton, Howard; Goswami, Devrishi; Pascal, Bruce D; Dodge, Jeffrey A; Chalmers, Michael J; Griffin, Patrick R

    2016-06-21

    Hydrogen/deuterium exchange coupled with mass spectrometry (HDX-MS) is an information-rich biophysical method for the characterization of protein dynamics. Successful applications of differential HDX-MS include the characterization of protein-ligand binding. A single differential HDX-MS data set (protein ± ligand) is often comprised of more than 40 individual HDX-MS experiments. To eliminate laborious manual processing of samples, and to minimize random and gross errors, automated systems for HDX-MS analysis have become routine in many laboratories. However, an automated system, while less prone to random errors introduced by human operators, may have systematic errors that go unnoticed without proper detection. Although the application of automated (and manual) HDX-MS has become common, there are only a handful of studies reporting the systematic evaluation of the performance of HDX-MS experiments, and no reports have been published describing a cross-site comparison of HDX-MS experiments. Here, we describe an automated HDX-MS platform that operates with a parallel, two-trap, two-column configuration that has been installed in two remote laboratories. To understand the performance of the system both within and between laboratories, we have designed and completed a test-retest repeatability study for differential HDX-MS experiments implemented at each of two laboratories, one in Florida and the other in Spain. This study provided sufficient data to do both within and between laboratory variability assessments. Initial results revealed a systematic run-order effect within one of the two systems. Therefore, the study was repeated, and this time the conclusion was that the experimental conditions were successfully replicated with minimal systematic error. PMID:27224086

  18. Structural basis of specific interactions of Lp-PLA2 with HDL revealed by hydrogen deuterium exchange mass spectrometry[S

    PubMed Central

    Cao, Jian; Hsu, Yuan-Hao; Li, Sheng; Woods, Virgil L.; Dennis, Edward A.

    2013-01-01

    Lipoprotein-associated phospholipase A2 (Lp-PLA2), specifically Group VIIA PLA2, is a member of the phospholipase A2 superfamily and is found mainly associated with LDL and HDL in human plasma. Lp-PLA2 is considered as a risk factor, a potential biomarker, a target for therapy in the treatment of cardiovascular disease, and evidence suggests that the level of Lp-PLA2 in plasma is associated with the risk of future cardiovascular and stroke events. The differential location of the enzyme in LDL/HDL lipoproteins has been suggested to affect Lp-PLA2 function and/or its physiological role and an abnormal distribution of the enzyme may correlate with diseases. Although a mutagenesis study suggested that a surface helix (residues 362–369) mediates the association between Lp-PLA2 and HDL, the molecular details and mechanism of association has remained unknown. We have now employed hydrogen deuterium exchange mass spectrometry to characterize the interaction between recombinant human Lp-PLA2 and human HDL. We have found that specific residues 113–120, 192–204, and 360–368 likely mediate HDL binding. In a previous study, we showed that residues 113–120 are important for Lp-PLA2-liposome interactions. We now find that residues 192–204 show a decreased deuteration level when Lp-PLA2 is exposed to apoA-I, but not apoA-II, the most abundant apoproteins in HDL, and additionally, residues 360–368 are only affected by HDL.The results suggest that apoA-I and phospholipid membranes play crucial roles in Lp-PLA2 localization to HDL. PMID:23089916

  19. Different conformational dynamics of β-arrestin1 and β-arrestin2 analyzed by hydrogen/deuterium exchange mass spectrometry

    SciTech Connect

    Yun, Youngjoo; Kim, Dong Kyun; Seo, Min-Duk; Kim, Kyeong-Man; Chung, Ka Young

    2015-01-30

    Highlights: • The conformational dynamics of β-arrestin1 or β-arrestin2 were analyzed by HDX-MS. • β-Strands II through IV were more dynamic in β-arrestin2 than in β-arrestin1. • The middle loop was less dynamic in β-arrestin2 than in β-arrestin1. • Upon pre-activation by the R169E mutation, β-arrestins became more dynamic. • Pre-activation affected a wider region of β-arrestin1 compared to β-arrestin2. - Abstract: Arrestins have important roles in G protein-coupled receptor (GPCR) signaling including desensitization of GPCRs and G protein-independent signaling. There have been four arrestins identified: arrestin1, arrestin2 (e.g. β-arrestin1), arrestin3 (e.g. β-arrestin2), and arrestin4. β-Arrestin1 and β-arrestin2 are ubiquitously expressed and regulate a broad range of GPCRs, while arrestin1 and arrestin4 are expressed in the visual system. Although the functions of β-arrestin1 and β-arrestin2 widely overlap, β-arrestin2 has broader receptor selectivity, and a few studies have suggested that β-arrestin1 and β-arrestin2 have distinct cellular functions. Here, we compared the conformational dynamics of β-arrestin1 and β-arrestin2 by hydrogen/deuterium exchange mass spectrometry (HDX-MS). We also used the R169E mutant as a pre-activation model system. HDX-MS data revealed that β-strands II through IV were more dynamic in β-arrestin2 in the basal state, while the middle loop was more dynamic in β-arrestin1. With pre-activation, both β-arrestin1 and β-arrestin2 became more flexible, but broader regions of β-arrestin1 became flexible compared to β-arrestin2. The conformational differences between β-arrestin1 and β-arrestin2 in both the basal and pre-activated states might determine their different receptor selectivities and different cellular functions.

  20. Automated data reduction for hydrogen/deuterium exchange experiments, enabled by high-resolution Fourier transform ion cyclotron resonance mass spectrometry.

    PubMed

    Kazazic, Sasa; Zhang, Hui-Min; Schaub, Tanner M; Emmett, Mark R; Hendrickson, Christopher L; Blakney, Gregory T; Marshall, Alan G

    2010-04-01

    Mass analysis of proteolytic fragment peptides following hydrogen/deuterium exchange offers a general measure of solvent accessibility/hydrogen bonding (and thus conformation) of solution-phase proteins and their complexes. The primary problem in such mass analyses is reliable and rapid assignment of mass spectral peaks to the correct charge state and degree of deuteration of each fragment peptide, in the presence of substantial overlap between isotopic distributions of target peptides, autolysis products, and other interferant species. Here, we show that at sufficiently high mass resolving power (m/Delta m(50%) > or = 100,000), it becomes possible to resolve enough of those overlaps so that automated data reduction becomes possible, based on the actual elemental composition of each peptide without the need to deconvolve isotopic distributions. We demonstrate automated, rapid, reliable assignment of peptide masses from H/D exchange experiments, based on electrospray ionization FT-ICR mass spectra from H/D exchange of solution-phase myoglobin. Combined with previously demonstrated automated data acquisition for such experiments, the present data reduction algorithm enhances automation (and thus expands generality and applicability) for high-resolution mass spectrometry-based analysis of H/D exchange of solution-phase proteins. PMID:20116280

  1. Investigation of the structural stability of the human acidic fibroblast growth factor by hydrogen-deuterium exchange.

    PubMed

    Chi, Ya-Hui; Kumar, Thallampuranam Krishnaswamy S; Kathir, Karuppanan Muthusamy; Lin, Dong-Hai; Zhu, Guang; Chiu, Ing-Ming; Yu, Chin

    2002-12-24

    The conformational stability of the human acidic fibroblast growth factor (hFGF-1) is investigated using amide proton exchange and temperature-dependent chemical shifts, monitored by two-dimensional NMR spectroscopy. The change in free energy of unfolding (DeltaG(u)) of hFGF-1 is estimated to be 5.00 +/- 0.09 kcal.mol(-)(1). Amide proton-exchange rates of 74 residues (in hFGF-1) have been unambiguously measured, and the exchange process occurs predominately according to the conditions of the EX2 limit. The exchange rates of the fast-exchanging amide protons exposed to the solvent have been measured using the clean SEA-HSQC technique. The amide proton protection factor and temperature coefficient estimates show reasonably good correlation. Residues in beta-strands II and VI appear to constitute the stability core of the protein. Among the 12 beta-strands constituting the beta-barrel architecture of hFGF-1, beta-strand XI, located in the heparin binding domain, exhibits the lowest average protection factor value. Amide protons involved in the putative folding nucleation site in hFGF-1, identified by quench-flow NMR studies, do not represent the slow-exchanging core. Residues in portions of hFGF-1 experiencing high conformational flexibility mostly correspond to those involved in receptor recognition and binding. PMID:12484774

  2. External reflection FTIR of peptide monolayer films in situ at the air/water interface: experimental design, spectra-structure correlations, and effects of hydrogen-deuterium exchange.

    PubMed Central

    Flach, C R; Brauner, J W; Taylor, J W; Baldwin, R C; Mendelsohn, R

    1994-01-01

    A Fourier transform infrared spectrometer has been interfaced with a surface balance and a new external reflection infrared sampling accessory, which permits the acquisition of spectra from protein monolayers in situ at the air/water interface. The accessory, a sample shuttle that permits the collection of spectra in alternating fashion from sample and background troughs, reduces interference from water vapor rotation-vibration bands in the amide I and amide II regions of protein spectra (1520-1690 cm-1) by nearly an order of magnitude. Residual interference from water vapor absorbance ranges from 50 to 200 microabsorbance units. The performance of the device is demonstrated through spectra of synthetic peptides designed to adopt alpha-helical, antiparallel beta-sheet, mixed beta-sheet/beta-turn, and unordered conformations at the air/water interface. The extent of exchange on the surface can be monitored from the relative intensities of the amide II and amide I modes. Hydrogen-deuterium exchange may lower the amide I frequency by as much as 11-12 cm-1 for helical secondary structures. This shifts the vibrational mode into a region normally associated with unordered structures and leads to uncertainties in the application of algorithms commonly used for determination of secondary structure from amide I contours of proteins in D2O solution. PMID:7919013

  3. Hydrogen/Deuterium Exchange Kinetics Demonstrate Long Range Allosteric Effects of Thumb Site 2 Inhibitors of Hepatitis C Viral RNA-dependent RNA Polymerase.

    PubMed

    Deredge, Daniel; Li, Jiawen; Johnson, Kenneth A; Wintrode, Patrick L

    2016-05-01

    New nonnucleoside analogs are being developed as part of a multi-drug regimen to treat hepatitis C viral infections. Particularly promising are inhibitors that bind to the surface of the thumb domain of the viral RNA-dependent RNA polymerase (NS5B). Numerous crystal structures have been solved showing small molecule non-nucleoside inhibitors bound to the hepatitis C viral polymerase, but these structures alone do not define the mechanism of inhibition. Our prior kinetic analysis showed that nonnucleoside inhibitors binding to thumb site-2 (NNI2) do not block initiation or elongation of RNA synthesis; rather, they block the transition from the initiation to elongation, which is thought to proceed with significant structural rearrangement of the enzyme-RNA complex. Here we have mapped the effect of three NNI2 inhibitors on the conformational dynamics of the enzyme using hydrogen/deuterium exchange kinetics. All three inhibitors rigidify an extensive allosteric network extending >40 Å from the binding site, thus providing a structural rationale for the observed disruption of the transition from distributive initiation to processive elongation. The two more potent inhibitors also suppress slow cooperative unfolding in the fingers extension-thumb interface and primer grip, which may contribute their stronger inhibition. These results establish that NNI2 inhibitors act through long range allosteric effects, reveal important conformational changes underlying normal polymerase function, and point the way to the design of more effective allosteric inhibitors that exploit this new information. PMID:27006396

  4. Load-dependent destabilization of the γ-rotor shaft in FOF1 ATP synthase revealed by hydrogen/deuterium-exchange mass spectrometry

    PubMed Central

    Vahidi, Siavash; Bi, Yumin; Dunn, Stanley D.; Konermann, Lars

    2016-01-01

    FoF1 is a membrane-bound molecular motor that uses proton-motive force (PMF) to drive the synthesis of ATP from ADP and Pi. Reverse operation generates PMF via ATP hydrolysis. Catalysis in either direction involves rotation of the γε shaft that connects the α3β3 head and the membrane-anchored cn ring. X-ray crystallography and other techniques have provided insights into the structure and function of FoF1 subcomplexes. However, interrogating the conformational dynamics of intact membrane-bound FoF1 during rotational catalysis has proven to be difficult. Here, we use hydrogen/deuterium exchange mass spectrometry to probe the inner workings of FoF1 in its natural membrane-bound state. A pronounced destabilization of the γ C-terminal helix during hydrolysis-driven rotation was observed. This behavior is attributed to torsional stress in γ, arising from γ⋅⋅⋅α3β3 interactions that cause resistance during γ rotation within the apical bearing. Intriguingly, we find that destabilization of γ occurs only when FoF1 operates against a PMF-induced torque; the effect disappears when PMF is eliminated by an uncoupler. This behavior resembles the properties of automotive engines, where bearings inflict greater forces on the crankshaft when operated under load than during idling. PMID:26884184

  5. Load-dependent destabilization of the γ-rotor shaft in FOF1 ATP synthase revealed by hydrogen/deuterium-exchange mass spectrometry.

    PubMed

    Vahidi, Siavash; Bi, Yumin; Dunn, Stanley D; Konermann, Lars

    2016-03-01

    FoF1 is a membrane-bound molecular motor that uses proton-motive force (PMF) to drive the synthesis of ATP from ADP and Pi. Reverse operation generates PMF via ATP hydrolysis. Catalysis in either direction involves rotation of the γε shaft that connects the α3β3 head and the membrane-anchored cn ring. X-ray crystallography and other techniques have provided insights into the structure and function of FoF1 subcomplexes. However, interrogating the conformational dynamics of intact membrane-bound FoF1 during rotational catalysis has proven to be difficult. Here, we use hydrogen/deuterium exchange mass spectrometry to probe the inner workings of FoF1 in its natural membrane-bound state. A pronounced destabilization of the γ C-terminal helix during hydrolysis-driven rotation was observed. This behavior is attributed to torsional stress in γ, arising from γ⋅⋅⋅α3β3 interactions that cause resistance during γ rotation within the apical bearing. Intriguingly, we find that destabilization of γ occurs only when FoF1 operates against a PMF-induced torque; the effect disappears when PMF is eliminated by an uncoupler. This behavior resembles the properties of automotive engines, where bearings inflict greater forces on the crankshaft when operated under load than during idling. PMID:26884184

  6. Probing the Conformational and Functional Consequences of Disulfide Bond Engineering in Growth Hormone by Hydrogen-Deuterium Exchange Mass Spectrometry Coupled to Electron Transfer Dissociation.

    PubMed

    Seger, Signe T; Breinholt, Jens; Faber, Johan H; Andersen, Mette D; Wiberg, Charlotte; Schjødt, Christine B; Rand, Kasper D

    2015-06-16

    Human growth hormone (hGH), and its receptor interaction, is essential for cell growth. To stabilize a flexible loop between helices 3 and 4, while retaining affinity for the hGH receptor, we have engineered a new hGH variant (Q84C/Y143C). Here, we employ hydrogen-deuterium exchange mass spectrometry (HDX-MS) to map the impact of the new disulfide bond on the conformational dynamics of this new hGH variant. Compared to wild type hGH, the variant exhibits reduced loop dynamics, indicating a stabilizing effect of the introduced disulfide bond. Furthermore, the disulfide bond exhibits longer ranging effects, stabilizing a short α-helix quite distant from the mutation sites, but also rendering a part of the α-helical hGH core slightly more dynamic. In the regions where the hGH variant exhibits a different deuterium uptake than the wild type protein, electron transfer dissociation (ETD) fragmentation has been used to pinpoint the residues responsible for the observed differences (HDX-ETD). Finally, by use of surface plasmon resonance (SPR) measurements, we show that the new disulfide bond does not compromise receptor affinity. Our work highlight the analytical potential of HDX-ETD combined with functional assays to guide protein engineering. PMID:25978680

  7. Hydrogen-deuterium exchange mass spectrometry reveals the interaction of Fenna-Matthews-Olson protein and chlorosome CsmA protein

    PubMed Central

    Huang, Richard Y-C.; Wen, Jianzhong; Blankenship, Robert E.; Gross, Michael L.

    2011-01-01

    In green-sulfur bacterial photosynthesis, excitation energy absorbed by a peripheral antenna structure known as the chlorosome is sequentially transferred through a baseplate protein to the Fenna-Matthews-Olson (FMO) antenna protein and into the reaction center, which is embedded in the cytoplasmic membrane. The molecular details of the optimized photosystem architecture required for efficient energy transfer are only partially understood. We address here the question of how the baseplate interacts with the FMO protein by applying hydrogen/deuterium exchange coupled with enzymatic digestion and mass spectrometry analysis to reveal the binding interface of the FMO antenna protein and the CsmA baseplate protein. Several regions on the FMO protein, represented by peptides consisting of 123-129, 140-149, 150-162, 191-208 and 224-232, show significant decreases of deuterium uptake after CsmA binding. The results indicate that the CsmA protein interacts with the Bchl a #1 side of the FMO protein. A global picture including peptide-level details for the architecture of the photosystem from green sulfur bacteria can now be drawn. PMID:22142245

  8. Identification of pharmacological chaperones for Gaucher disease and characterization of their effects on beta-glucocerebrosidase by hydrogen/deuterium exchange mass spectrometry.

    PubMed

    Tropak, Michael B; Kornhaber, Gregory J; Rigat, Brigitte A; Maegawa, Gustavo H; Buttner, Justin D; Blanchard, Jan E; Murphy, Cecilia; Tuske, Steven J; Coales, Stephen J; Hamuro, Yoshitomo; Brown, Eric D; Mahuran, Don J

    2008-11-01

    Point mutations in beta-glucocerebrosidase (GCase) can result in a deficiency of both GCase activity and protein in lysosomes thereby causing Gaucher Disease (GD). Enzyme inhibitors such as isofagomine, acting as pharmacological chaperones (PCs), increase these levels by binding and stabilizing the native form of the enzyme in the endoplasmic reticulum (ER), and allow increased lysosomal transport of the enzyme. A high-throughput screen of the 50,000-compound Maybridge library identified two, non-carbohydrate-based inhibitory molecules, a 2,4-diamino-5-substituted quinazoline (IC(50) 5 microM) and a 5-substituted pyridinyl-2-furamide (IC(50) 8 microM). They raised the levels of functional GCase 1.5-2.5-fold in N370S or F213I GD fibroblasts. Immunofluorescence confirmed that treated GD fibroblasts had decreased levels of GCase in their ER and increased levels in lysosomes. Changes in protein dynamics, monitored by hydrogen/deuterium-exchange mass spectrometry, identified a domain III active-site loop (residues 243-249) as being significantly stabilized upon binding of isofagomine or either of these two new compounds; this suggests a common mechanism for PC enhancement of intracellular transport. PMID:18972510

  9. Identification of Pharmacological Chaperones for Gaucher Disease and Characterization of Their Effects on β-Glucocerebrosidase by Hydrogen/Deuterium Exchange Mass Spectrometry

    PubMed Central

    Tropak, Michael B.; Kornhaber, Gregory J.; Rigat, Brigitte A.; Maegawa, Gustavo H.; Buttner, Justin D.; Blanchard, Jan E.; Murphy, Cecilia; Tuske, Steven J.; Coales, Stephen J.; Hamuro, Yoshitomo; Brown, Eric D.

    2010-01-01

    Point mutations in β-glucocerebrosidase (GCase) can result in a deficiency of both GCase activity and protein in lysosomes thereby causing Gaucher Disease (GD). Enzyme inhibitors such as isofagomine, acting as pharmacological chaperones (PCs), increase these levels by binding and stabilizing the native form of the enzyme in the endoplasmic reticulum (ER), and allow increased lysosomal transport of the enzyme. A high-throughput screen of the 50 000-compound Maybridge library identified two, non-carbohydrate-based inhibitory molecules, a 2,4-diamino-5-substituted quinazoline (IC50 5 μM) and a 5-substituted pyridinyl-2-furamide (IC50 8 μM). They raised the levels of functional GCase 1.5–2.5-fold in N370S or F213I GD fibroblasts. Immunofluorescence confirmed that treated GD fibroblasts had decreased levels of GCase in their ER and increased levels in lysosomes. Changes in protein dynamics, monitored by hydrogen/deuterium-exchange mass spectrometry, identified a domain III active-site loop (residues 243–249) as being significantly stabilized upon binding of isofagomine or either of these two new compounds; this suggests a common mechanism for PC enhancement of intracellular transport. PMID:18972510

  10. Sites Involved in Intra- and Interdomain Allostery Associated with the Activation of Factor VIIa Pinpointed by Hydrogen-Deuterium Exchange and Electron Transfer Dissociation Mass Spectrometry*

    PubMed Central

    Song, Hongjian; Olsen, Ole H.; Persson, Egon; Rand, Kasper D.

    2014-01-01

    Factor VIIa (FVIIa) is a trypsin-like protease that plays an important role in initiating blood coagulation. Very limited structural information is available for the free, inactive form of FVIIa that circulates in the blood prior to vascular injury and the molecular details of its activity enhancement remain elusive. Here we have applied hydrogen/deuterium exchange mass spectrometry coupled to electron transfer dissociation to pinpoint individual residues in the heavy chain of FVIIa whose conformation and/or local interaction pattern changes when the enzyme transitions to the active form, as induced either by its cofactor tissue factor or a covalent active site inhibitor. Identified regulatory residues are situated at key sites across one continuous surface of the protease domain spanning the TF-binding helix across the activation pocket to the calcium binding site and are embedded in elements of secondary structure and at the base of flexible loops. Thus these residues are optimally positioned to mediate crosstalk between functional sites in FVIIa, particularly the cofactor binding site and the active site. Our results unambiguously show that the conformational allosteric activation signal extends to the EGF1 domain in the light chain of FVIIa, underscoring a remarkable intra- and interdomain allosteric regulation of this trypsin-like protease. PMID:25344622

  11. Hydrogen-deuterium exchange reactions of cis- and trans-cyclopropane derivatives with D(2)O and CD(3)OD in the gas phase

    PubMed

    Li; Liu

    2000-01-01

    Gas-phase hydrogen-deuterium (H/D) exchange reactions involving four isomeric cyclopropane derivatives were investigated under chemical ionization (CI) conditions, using D(2)O and CD(3)OD as reagent gases. There are abundant ions at [M + 1](+), [M + 2](+) and [M + 3](+) in the D(2)O and CD(3)OD positive-ion CI mass spectra of the two isomer pairs 1, 2 and 3, 4. Their CI mass spectra are identical with each pair, and so are the collision-induced dissociation (CID) spectra of ions [M + 1](+), [M + 2](+) and [M + 3](+) of each of the two isomer pairs. The CID spectra of [M + 1](+) ions indicate that they have common D/H exchange reactions within each pair, which take place between molecular ions and deuterium-labeling reagents to form the [M - H + D](+) ions. Those of their [M + 2](+) ions show that they have common D/H exchange reactions within each pair, which form the [M(d1) + H](+) ions. Those of their [M + 3](+) ions show that they have common D/H exchange reactions within each pair, which take place between the [M(d1)] and deuterium-labeling reagents to produce [M(d2) + H](+) for the isomer pair 1, 2 and [M(d1) + D](+) for the isomer pair 3, 4. The number and position, and active order of the active hydrogen atoms of the isomer pairs 1, 2 and 3, 4 were determined. Copyright 2000 John Wiley & Sons, Ltd. PMID:10637425

  12. Structure and Dynamics of NBD1 from CFTR Characterized Using Crystallography and Hydrogen/Deuterium Exchange Mass Spectrometry

    SciTech Connect

    Lewis, H.A.; Wang, C.; Zhao, X.; Hamuro, Y.; Conners, K.; Kearins, M.C.; Lu, F.; Sauder, J.M.; Molnar, K.S.; Coales, S.J.; Maloney, P.C.; Guggino, W.B.; Wetmore, D.R.; Weber, P.C.; Hunt, J.F.

    2012-04-30

    The {Delta}F508 mutation in nucleotide-binding domain 1 (NBD1) of the cystic fibrosis transmembrane conductance regulator (CFTR) is the predominant cause of cystic fibrosis. Previous biophysical studies on human F508 and {Delta}F508 domains showed only local structural changes restricted to residues 509-511 and only minor differences in folding rate and stability. These results were remarkable because {Delta}F508 was widely assumed to perturb domain folding based on the fact that it prevents trafficking of CFTR out of the endoplasmic reticulum. However, the previously reported crystal structures did not come from matched F508 and {Delta}F508 constructs, and the {Delta}F508 structure contained additional mutations that were required to obtain sufficient protein solubility. In this article, we present additional biophysical studies of NBD1 designed to address these ambiguities. Mass spectral measurements of backbone amide {sup 1}H/{sup 2}H exchange rates in matched F508 and {Delta}F508 constructs reveal that {Delta}F508 increases backbone dynamics at residues 509-511 and the adjacent protein segments but not elsewhere in NBD1. These measurements also confirm a high level of flexibility in the protein segments exhibiting variable conformations in the crystal structures. We additionally present crystal structures of a broader set of human NBD1 constructs, including one harboring the native F508 residue and others harboring the {Delta}F508 mutation in the presence of fewer and different solubilizing mutations. The only consistent conformational difference is observed at residues 509-511. The side chain of residue V510 in this loop is mostly buried in all non-{Delta}F508 structures but completely solvent exposed in all {Delta}F508 structures. These results reinforce the importance of the perturbation {Delta}F508 causes in the surface topography of NBD1 in a region likely to mediate contact with the transmembrane domains of CFTR. However, they also suggest that increased

  13. DNA Interactions Probed by Hydrogen-Deuterium Exchange (HDX) Fourier Transform Ion Cyclotron Resonance Mass Spectrometry Confirm External Binding Sites on the Minichromosomal Maintenance (MCM) Helicase.

    PubMed

    Graham, Brian W; Tao, Yeqing; Dodge, Katie L; Thaxton, Carly T; Olaso, Danae; Young, Nicolas L; Marshall, Alan G; Trakselis, Michael A

    2016-06-10

    The archaeal minichromosomal maintenance (MCM) helicase from Sulfolobus solfataricus (SsoMCM) is a model for understanding structural and mechanistic aspects of DNA unwinding. Although interactions of the encircled DNA strand within the central channel provide an accepted mode for translocation, interactions with the excluded strand on the exterior surface have mostly been ignored with regard to DNA unwinding. We have previously proposed an extension of the traditional steric exclusion model of unwinding to also include significant contributions with the excluded strand during unwinding, termed steric exclusion and wrapping (SEW). The SEW model hypothesizes that the displaced single strand tracks along paths on the exterior surface of hexameric helicases to protect single-stranded DNA (ssDNA) and stabilize the complex in a forward unwinding mode. Using hydrogen/deuterium exchange monitored by Fourier transform ion cyclotron resonance MS, we have probed the binding sites for ssDNA, using multiple substrates targeting both the encircled and excluded strand interactions. In each experiment, we have obtained >98.7% sequence coverage of SsoMCM from >650 peptides (5-30 residues in length) and are able to identify interacting residues on both the interior and exterior of SsoMCM. Based on identified contacts, positively charged residues within the external waist region were mutated and shown to generally lower DNA unwinding without negatively affecting the ATP hydrolysis. The combined data globally identify binding sites for ssDNA during SsoMCM unwinding as well as validating the importance of the SEW model for hexameric helicase unwinding. PMID:27044751

  14. A Binding Site on IL-17A for Inhibitory Macrocycles Revealed by Hydrogen/Deuterium Exchange Mass Spectrometry.

    PubMed

    Espada, Alfonso; Broughton, Howard; Jones, Spencer; Chalmers, Michael J; Dodge, Jeffrey A

    2016-03-10

    Computational assessment of the IL-17A structure identified two distinct binding pockets, the β-hairpin pocket and the α-helix pocket. The β-hairpin pocket was hypothesized to be the site of binding for peptide macrocycles. Support for this hypothesis was obtained using HDX-MS which revealed protection to exchange only within the β-hairpin pocket. This data represents the first direct structural evidence of a small molecule binding site on IL-17A that functions to disrupt the interaction with its receptor. PMID:26854023

  15. First-principles study of temperature-dependent diffusion coefficients: Hydrogen, deuterium, and tritium in α-Ti

    NASA Astrophysics Data System (ADS)

    Lu, Yong; Zhang, Ping

    2013-05-01

    We report the prediction of temperature-dependent diffusion coefficients of interstitial hydrogen, deuterium, and tritium atoms in α-Ti using transition state theory. The microscopic parameters in the pre-factor and activation energy of the impurity diffusion coefficients are obtained from first-principles total energy and phonon calculations including the full coupling between the vibrational modes of the diffusing atom with the host lattice. The dual occupancy case of impurity atom in the hcp matrix is considered, and four diffusion paths are combined to obtain the final diffusion coefficients. The calculated diffusion parameters show good agreement with experiments. Our numerical results indicate that the diffusions of deuterium and tritium atoms are slower than that of the hydrogen atom at temperatures above 425 K and 390 K, respectively.

  16. Conformational changes of the glucocorticoid receptor ligand binding domain induced by ligand and cofactor binding, and the location of cofactor binding sites determined by hydrogen/deuterium exchange mass spectrometry

    PubMed Central

    Frego, Lee; Davidson, Walter

    2006-01-01

    HXMS (hydrogen/deuterium exchange mass spectrometry) of the glucocorticoid receptor ligand-binding domain (GR LBD) complexed with the agonist dexamethasone and the antagonist RU-486 is described. Variations in the rates of exchange were observed in regions consistent with the published crystal structures of GR LBD complexed with RU-486 when compared with the GR dexamethasone complex. We also report the HXMS results for agonist-bound GR LBD with the coactivator transcriptional intermediary factor 2 (TIF2) and anatagonist-bound GR LBD with nuclear receptor corepressor (NCoR). Alterations in exchange rates observed for agonist-bound GR LBD with TIF2 present were consistent with the published crystal structural contacts for the complex. Alterations in exchange rates observed for antagonist-bound GR LBD with NCoR were a subset of those observed with TIF2 binding, suggesting a common or overlapping binding site for coactivator and corepressor. PMID:16600964

  17. Comparative hydrogen-deuterium exchange for a mesophilic vs thermophilic dihydrofolate reductase at 25 °C: identification of a single active site region with enhanced flexibility in the mesophilic protein.

    PubMed

    Oyeyemi, Olayinka A; Sours, Kevin M; Lee, Thomas; Kohen, Amnon; Resing, Katheryn A; Ahn, Natalie G; Klinman, Judith P

    2011-09-27

    The technique of hydrogen-deuterium exchange coupled to mass spectrometry (HDX-MS) has been applied to a mesophilic (E. coli) dihydrofolate reductase under conditions that allow direct comparison to a thermophilic (B. stearothermophilus) ortholog, Ec-DHFR and Bs-DHFR, respectively. The analysis of hydrogen-deuterium exchange patterns within proteolytically derived peptides allows spatial resolution, while requiring a series of controls to compare orthologous proteins with only ca. 40% sequence identity. These controls include the determination of primary structure effects on intrinsic rate constants for HDX as well as the use of existing 3-dimensional structures to evaluate the distance of each backbone amide hydrogen to the protein surface. Only a single peptide from the Ec-DHFR is found to be substantially more flexible than the Bs-DHFR at 25 °C in a region located within the protein interior at the intersection of the cofactor and substrate-binding sites. The surrounding regions of the enzyme are either unchanged or more flexible in the thermophilic DHFR from B. stearothermophilus. The region with increased flexibility in Ec-DHFR corresponds to one of two regions previously proposed to control the enthalpic barrier for hydride transfer in Bs-DHFR [Oyeyemi et al. (2010) Proc. Natl. Acad. Sci. U.S.A. 107, 10074]. PMID:21859100

  18. Dimerization of the type IV pilin from Pseudomonas aeruginosa strain K122-4 results in increased helix stability as measured by time-resolved hydrogen-deuterium exchange

    PubMed Central

    Lento, Cristina; Wilson, Derek J.; Audette, Gerald F.

    2015-01-01

    Truncated pilin monomers from Pseudomonas aeruginosa strain K122-4 (ΔK122) have been shown to enter a monomer-dimer equilibrium in solution prior to oligomerization into protein nanotubes. Here, we examine the structural changes occurring between the monomeric and dimeric states of ΔK122 using time-resolved hydrogen-deuterium exchange mass spectrometry. Based on levels of deuterium uptake, the N-terminal α-helix and the loop connecting the second and third strands of the anti-parallel β-sheet contribute significantly to pilin dimerization. Conversely, the antiparallel β-sheet and αβ loop region exhibit increased flexibility, while the receptor binding domain retains a rigid conformation in the equilibrium state. PMID:26798830

  19. Dimerization of the type IV pilin from Pseudomonas aeruginosa strain K122-4 results in increased helix stability as measured by time-resolved hydrogen-deuterium exchange.

    PubMed

    Lento, Cristina; Wilson, Derek J; Audette, Gerald F

    2016-01-01

    Truncated pilin monomers from Pseudomonas aeruginosa strain K122-4 (ΔK122) have been shown to enter a monomer-dimer equilibrium in solution prior to oligomerization into protein nanotubes. Here, we examine the structural changes occurring between the monomeric and dimeric states of ΔK122 using time-resolved hydrogen-deuterium exchange mass spectrometry. Based on levels of deuterium uptake, the N-terminal α-helix and the loop connecting the second and third strands of the anti-parallel β-sheet contribute significantly to pilin dimerization. Conversely, the antiparallel β-sheet and αβ loop region exhibit increased flexibility, while the receptor binding domain retains a rigid conformation in the equilibrium state. PMID:26798830

  20. Isotopic effect study in the LHCD and LHH experiments in hydrogen/deuterium plasmas of the FT-2 tokamak

    SciTech Connect

    Lashkul, S. I.; Altukhov, A. B.; Gusakov, E. Z.; Dyachenko, V. V.; Esipov, L. A.; Irzak, M. A.; Kantor, M. Yu.; Kouprienko, D. V.; Saveliev, A. N.; Shatalin, S. V.; Stepanov, A. Yu.

    2014-02-12

    Results of comparative experimental studies of the efficiency of lower hybrid current drive (LHCD) and lower hybrid heating (LHH) in the FT-2 tokamak in hydrogen and deuterium plasmas are presented. In the new comparative experimental runs in deuterium/hydrogen plasmas suppression of the LHCD and beginning of the interaction of LH waves with ions is controlled by the plasma density rise. Role of parametric instabilities in CD switch-off is considered. In order to analyze the experimentally observed effect of LHCD the GRILL3D and FRTC codes has been used.

  1. Speed of sound in solid molecular hydrogen-deuterium: Quantum Molecular Dynamics Approximation

    NASA Astrophysics Data System (ADS)

    Guerrero, Carlo Luis; Perlado, Jose Manuel

    2016-05-01

    Uniformity of the solid layer is one of the critical points for an efficient ignition of the Deuterium-Tritium (DT) target. During the compression process this layer, perturbations grow as the Rayleigh-Taylor instability. Knowing the mechanical properties of this layer and its thermo-mechanical limits is necessary if we want to control or to minimize these instabilities. In this work we have used a simplified approach, replacing the DT ice system with a mixture of hydrogen-deuterium (HD) because beta decay of tritium complicates the analysis in the former case. Through simulation with ab initio methods we have calculated the elastic constants, the bulk modulus and sound velocity for hydrogen isotopes in solid molecular state. In this work we present the results for hydrogen-deuterium mixtures 50%-50%, at 15 K and with a compression which covers the range of 1 to 15 GPa. This system is interesting for study the early stages of the dynamic compression and provides conditions that are close to the manufacture of DT target in inertial confinement fusion. Discontinuities in the curve that have been observed on pure hydrogen, which are associated with phase transitions and the phase hysteresis.

  2. Longitudinal Lelectroproduction of Charged Pions on Hydrogen, Deuterium, and Helium 3

    SciTech Connect

    David Gaskell

    2001-05-01

    Conventional pictures of nuclear interactions, in which the pion mediates the long/medium range part of the nuclear force, predict an enhancement of the virtual pion cloud in nuclei relative to that in the free nucleon. Jefferson Lab Experiment E91003 measured charged pion electroproduction from Hydrogen, Deuterium, and Helium-3. The longitudinal cross section, which in the limit of pole dominance can be viewed as the quasifree knockout of a virtual pion, was extracted via a Rosenbluth separation. The longitudinal cross sections from Deuterium and Helium-3 were compared to Hydrogen to look for signatures of the nuclear pions.

  3. Computation of hyperfine energies of hydrogen, deuterium and tritium quantum dots

    NASA Astrophysics Data System (ADS)

    Çakır, Bekir; Özmen, Ayhan; Yakar, Yusuf

    2016-01-01

    The hyperfine energies and hyperfine constants of the ground and excited states of hydrogen, deuterium and tritium quantum dots(QDs) are calculated. Quantum genetic algorithm (QGA) and Hartree-Fock-Roothaan (HFR) methods are employed to calculate the unperturbed wave functions and energy eigenvalues. The results show that in the medium and strong confinement regions the hyperfine energy and hyperfine constant are strongly affected by dot radius, impurity charge, electron spin orientation, impurity spin and impurity magnetic moment. Besides, in all dot radii, the hyperfine splitting and hyperfine constant of the confined hydrogen and tritium atoms are approximately equivalent to each other and they are greater than the confined deuterium atom.

  4. The ground state properties of spin-aligned atomic hydrogen, deuterium, and tritium

    NASA Technical Reports Server (NTRS)

    Etters, R. D.; Dugan, J. V., Jr.; Palmer, R. W.

    1975-01-01

    The internal energy, pressure, and compressibility of ground-state, spin-aligned atomic hydrogen, deuterium, and tritium are calculated assuming that all pair interactions occur via the atomic triplet (spin-aligned) potential. The conditions required to obtain atomic hydrogen and its isotopes in bulk are discussed; such a development would be of value in propulsion systems because of the light mass and energetic recombination of atomic hydrogen. Results show that atomic triplet hydrogen and deuterium remain gaseous at 0 K, and that tritium forms a liquid with a binding energy of approximately -0.75 K per atom at a molar volume of 130 cu cm per mole. The pair distribution function for these systems is calculated, and the predicted superfluid behavior of atomic triplet hydrogen and tritium is briefly discussed.

  5. Nano-scaled TiO(OD)2: a time resolved 1H/2D isotope exchange study observed in situ with neutron scattering at 20 °C and 40 °C.

    PubMed

    Legrand, Vincent; Merdrignac-Conanec, Odile; Paulus, Werner

    2013-03-21

    In situ neutron diffraction measurements of the nanocrystalline deuterated oxyhydroxide TiO(OD)(2) compound were performed as a function of time and temperature under NH(3) gas flow in order to study the hydrogen-deuterium exchange mechanism. Data were collected on the instrument D20 at the ILL (France) and the analysis of the kinetics was directly based on the contrast variation of the incoherent neutron cross section of hydrogen and deuterium. The time evolution of the hydrogenated phase fraction was described using the well-known Kolmogorov-Johnson-Mehl-Avrami (KJMA) expression. The H/D exchange reaction is complete within 140 s at 20 °C and within 120 s at 40 °C. The activation energy for the H/D exchange reaction is estimated to be 37 kJ mol(-1). PMID:23328794

  6. Investigation of the role of the micro-porous layer in polymer electrolyte fuel cells with hydrogen deuterium contrast neutron radiography.

    PubMed

    Cho, Kyu Taek; Mench, Matthew M

    2012-03-28

    In this study, the high resolution hydrogen-deuterium contrast radiography method was applied to elucidate the impact of the micro-porous layer (MPL) on water distribution in the porous fuel cell media. At the steady state, deuterium replaced hydrogen in the anode stream, and the large difference in neutron attenuation of the D(2)O produced at the cathode was used to track the produced water. It was found that the water content peaked in the cathode-side diffusion media (DM) for the cell without MPL, but with an MPL on the anode and cathode DM, the peak water amount was pushed toward the anode, resulting in a relatively flattened water profile through components and demonstrating a liquid barrier effect. Additionally, the dynamic water behavior in diffusion media was analyzed to understand the effect of a MPL and operating conditions. The water content in the DM changed with applied current, although there is a significant amount of residual liquid content that does not appear to be part of capillary channels. The effect of the MPL on irreducible saturation in DM and cell performance was also investigated. PMID:22337210

  7. Epitope mapping by epitope excision, hydrogen/deuterium exchange, and peptide-panning techniques combined with in silico analysis.

    PubMed

    Clementi, Nicola; Mancini, Nicasio; Criscuolo, Elena; Cappelletti, Francesca; Clementi, Massimo; Burioni, Roberto

    2014-01-01

    The fine characterization of protective B cell epitopes plays a pivotal role in the development of novel vaccines. The development of epitope-based vaccines, in fact, cannot be possible without a clear definition of the antigenic regions involved in the binding between the protective antibody (Ab) and its molecular target. To achieve this result, different epitope-mapping approaches have been widely described (Clementi et al. Drug Discov Today 18(9-10):464-471, 2013). Nowadays, the best way to characterize an Ab bound region is still the resolution of Ab-antigen (Ag) co-crystal structure. Unfortunately, the crystallization approaches are not always feasible. However, different experimental strategies aimed to predict Ab-Ag interaction and followed by in silico analysis of the results may be good surrogate approaches to achieve this result. Here, we review few experimental techniques followed by the use of "basic" informatics tools for the analysis of the results. PMID:24515481

  8. Hydrogen-deuterium substitution in solid ethanol by surface reactions at low temperatures

    NASA Astrophysics Data System (ADS)

    Oba, Yasuhiro; Osaka, Kazuya; Chigai, Takeshi; Kouchi, Akira; Watanabe, Naoki

    2016-10-01

    Ethanol (CH3CH2OH) is one of the most abundant complex organic molecules in star-forming regions. Despite its detection in the gas phase only, ethanol is believed to be formed by low-temperature grain-surface reactions. Methanol, the simplest alcohol, has been a target for observational, experimental, and theoretical studies in view of its deuterium enrichment in the interstellar medium; however, the deuterium chemistry of ethanol has not yet been an area of focus. Recently, deuterated dimethyl ether, a structural isomer of ethanol, was found in star-forming regions, indicating that deuterated ethanol can also be present in those environments. In this study, we performed laboratory experiments on the deuterium fractionation of solid ethanol at low temperatures through a reaction with deuterium (D) atoms at 10 K. Hydrogen (H)-D substitution, which increases the deuteration level, was found to occur on the ethyl group but not on the hydroxyl group. In addition, when deuterated ethanol (e.g. CD3CD2OD) solid was exposed to H atoms at 10 K, D-H substitution that reduced the deuteration level occurred on the ethyl group. Based on the results, it is likely that deuterated ethanol is present even under H-atom-dominant conditions in the interstellar medium.

  9. Determination of hydrogen/deuterium ratio with neutron measurements on MAST

    SciTech Connect

    Klimek, I. Cecconello, M.; Ericsson, G.; Sharapov, S. E.; Harrison, J.

    2014-11-15

    On MAST, compressional Alfvén eigenmodes can be destabilized by the presence of a sufficiently large population of energetic particles in the plasma. This dependence was studied in a series of very similar discharges in which increasing amounts of hydrogen were puffed into a deuterium plasma. A simple method to estimate the isotopic ratio n{sub H}/n{sub D} using neutron emission measurements is here described. The inferred isotopic ratio ranged from 0.0 to 0.6 and no experimental indication of changes in radial profile of n{sub H}/n{sub D} were observed. These findings are confirmed by TRANSP/NUBEAM simulations of the neutron emission.

  10. Optimum extracted H{sup {minus}} and D{sup {minus}} current densities from gas-pressure-limited high-power hydrogen/deuterium tandem ion sources

    SciTech Connect

    Hiskes, J.R.

    1993-07-14

    The tandem hydrogen/deuterium ion source is modelled for the purpose of identifying the maximum current densities that can be extracted subject to the gas-pressure constraints proposed for contemporary beam-line systems. Optimum useful extracted current densities are found to be in the range of approximately 7 to 10 mA cm{sup {minus}2}. The sensitivity of these current densities is examined subject to uncertainties in the underlying atomic/molecular rate processes; A principal uncertainty remains the quantification of the molecular vibrational distribution following H{sub 3{sup +}} wall collisions.

  11. Radiation Studies with Argentine Ion Exchange Material

    SciTech Connect

    Crawford, C.L.

    2002-06-28

    A recent technology exchange between Argentina Nuclear Energy Commission (CNEA) and the US Department of Energy involved vitrification studies of ion exchange resins. Details of the spent ion exchange resins currently stored at two Argentine nuclear power plants, Atucha I and Embalse, have been presented in earlier reports. The present study examines irradiation of simulant samples of ion exchange resins.

  12. Neopentane and solid acids: direct hydron exchange before cracking.

    PubMed

    Walspurger, Stéphane; Sun, Yinyong; Souna Sido, Abdelkarim Sani; Sommer, Jean

    2006-09-21

    The hydrogen/deuterium exchange reaction of 2,2-dimethylpropane (neopentane) over D(2)O-exchanged zeolites (MOR, FAU, BEA, MFI) using a batch recirculation reactor was studied by means of gas chromatography coupled with mass spectrometer. In the temperature range 473-573 K, H/D exchange proceeds without side reaction such as cracking at short contact times. Indeed the C-H bond has appeared favorably involved in the activation of neopentane compared to the less accessible C-C bond. The transition state allowing hydron exchange is most likely a carbonium species (pentacoordinated carbon) as in the case of the H/D exchange between methane and solid acid. The activation energies of the H/D exchange between neopentane and zeolites are the same for all zeolites indicating a common carbonium ion type transition state. On the basis of previous results in the case of the exchange between methane and liquid superacids, the deuterium exchange rates in neopentane were tentatively related to the acidity of the solids. However the order of activity MOR > MFI > BEA > FAU seems to be related to the size of the pores, which may suggest the involvement of a confinement effect in the zeolites cavities. Moreover we found that H/D exchange takes also place between neopentane and deuterated sulfated zirconia (SZ) emphasizing its strong acidity. PMID:16970460

  13. Tuning a High Transmission Ion Guide to Prevent Gas-Phase Proton Exchange During H/D Exchange MS Analysis.

    PubMed

    Guttman, Miklos; Wales, Thomas E; Whittington, Dale; Engen, John R; Brown, Jeffery M; Lee, Kelly K

    2016-04-01

    Hydrogen/deuterium exchange (HDX) mass spectrometry (MS) for protein structural analysis has been adopted for many purposes, including biopharmaceutical development. One of the benefits of examining amide proton exchange by mass spectrometry is that it can readily resolve different exchange regimes, as evidenced by either binomial or bimodal isotope patterns. By careful analysis of the isotope pattern during exchange, more insight can be obtained on protein behavior in solution. However, one must be sure that any observed bimodal isotope patterns are not artifacts of analysis and are reflective of the true behavior in solution. Sample carryover and certain stationary phases are known as potential sources of bimodal artifacts. Here, we describe an additional undocumented source of deuterium loss resulting in artificial bimodal patterns for certain highly charged peptides. We demonstrate that this phenomenon is predominantly due to gas-phase proton exchange between peptides and bulk solvent within the initial stages of high-transmission conjoined ion guides. Minor adjustments of the ion guide settings, as reported here, eliminate the phenomenon without sacrificing signal intensity. Such gas-phase deuterium loss should be appreciated for all HDX-MS studies using such ion optics, even for routine studies not focused on interpreting bimodal spectra. Graphical Abstract ᅟ. PMID:26810432

  14. Tuning a High Transmission Ion Guide to Prevent Gas-Phase Proton Exchange During H/D Exchange MS Analysis

    NASA Astrophysics Data System (ADS)

    Guttman, Miklos; Wales, Thomas E.; Whittington, Dale; Engen, John R.; Brown, Jeffery M.; Lee, Kelly K.

    2016-04-01

    Hydrogen/deuterium exchange (HDX) mass spectrometry (MS) for protein structural analysis has been adopted for many purposes, including biopharmaceutical development. One of the benefits of examining amide proton exchange by mass spectrometry is that it can readily resolve different exchange regimes, as evidenced by either binomial or bimodal isotope patterns. By careful analysis of the isotope pattern during exchange, more insight can be obtained on protein behavior in solution. However, one must be sure that any observed bimodal isotope patterns are not artifacts of analysis and are reflective of the true behavior in solution. Sample carryover and certain stationary phases are known as potential sources of bimodal artifacts. Here, we describe an additional undocumented source of deuterium loss resulting in artificial bimodal patterns for certain highly charged peptides. We demonstrate that this phenomenon is predominantly due to gas-phase proton exchange between peptides and bulk solvent within the initial stages of high-transmission conjoined ion guides. Minor adjustments of the ion guide settings, as reported here, eliminate the phenomenon without sacrificing signal intensity. Such gas-phase deuterium loss should be appreciated for all HDX-MS studies using such ion optics, even for routine studies not focused on interpreting bimodal spectra.

  15. Conformational changes in oxidatively stressed monoclonal antibodies studied by hydrogen exchange mass spectrometry

    PubMed Central

    Burkitt, William; Domann, Paula; O'Connor, Gavin

    2010-01-01

    Oxidation of methionine residues in biopharmaceuticals is a common and often unwanted modification that frequently occurs during their manufacture and storage. It often results in a lack of stability and biological function of the product, necessitating continuous testing for the modification throughout the product shelf life. A major class of biopharmaceutical products are monoclonal antibodies (mAbs), however, techniques for their detailed structural analysis have until recently been limited. Hydrogen/deuterium exchange mass spectrometry (HXMS) has recently been successfully applied to the analysis of mAbs. Here we used HXMS to identify and localise the structural changes that occurred in a mAb (IgG1) after accelerated oxidative stress. Structural alterations in a number of segments of the Fc region were observed and these related to oxidation of methionine residues. These included a large change in the hydrogen exchange profile of residues 247–253 of the heavy chain, while smaller changes in hydrogen exchange profile were identified for peptides that contained residues in the interface of the CH2 and CH3 domains. PMID:20162626

  16. Quantitative Assessment of Protein Structural Models by Comparison of H/D Exchange MS Data with Exchange Behavior Accurately Predicted by DXCOREX

    NASA Astrophysics Data System (ADS)

    Liu, Tong; Pantazatos, Dennis; Li, Sheng; Hamuro, Yoshitomo; Hilser, Vincent J.; Woods, Virgil L.

    2012-01-01

    Peptide amide hydrogen/deuterium exchange mass spectrometry (DXMS) data are often used to qualitatively support models for protein structure. We have developed and validated a method (DXCOREX) by which exchange data can be used to quantitatively assess the accuracy of three-dimensional (3-D) models of protein structure. The method utilizes the COREX algorithm to predict a protein's amide hydrogen exchange rates by reference to a hypothesized structure, and these values are used to generate a virtual data set (deuteron incorporation per peptide) that can be quantitatively compared with the deuteration level of the peptide probes measured by hydrogen exchange experimentation. The accuracy of DXCOREX was established in studies performed with 13 proteins for which both high-resolution structures and experimental data were available. The DXCOREX-calculated and experimental data for each protein was highly correlated. We then employed correlation analysis of DXCOREX-calculated versus DXMS experimental data to assess the accuracy of a recently proposed structural model for the catalytic domain of a Ca2+-independent phospholipase A2. The model's calculated exchange behavior was highly correlated with the experimental exchange results available for the protein, supporting the accuracy of the proposed model. This method of analysis will substantially increase the precision with which experimental hydrogen exchange data can help decipher challenging questions regarding protein structure and dynamics.

  17. Cryogenic tritium-hydrogen-deuterium and deuterium-tritium layer implosions with high density carbon ablators in near-vacuum hohlraums

    SciTech Connect

    Meezan, N. B. Hopkins, L. F. Berzak; Pape, S. Le; Divol, L.; MacKinnon, A. J.; Döppner, T.; Ho, D. D.; Jones, O. S.; Khan, S. F.; Ma, T.; Milovich, J. L.; Pak, A. E.; Ross, J. S.; Thomas, C. A.; Benedetti, L. R.; Bradley, D. K.; Celliers, P. M.; Clark, D. S.; Field, J. E.; Haan, S. W.; and others

    2015-06-15

    High Density Carbon (or diamond) is a promising ablator material for use in near-vacuum hohlraums, as its high density allows for ignition designs with laser pulse durations of <10 ns. A series of Inertial Confinement Fusion (ICF) experiments in 2013 on the National Ignition Facility [Moses et al., Phys. Plasmas 16, 041006 (2009)] culminated in a deuterium-tritium (DT) layered implosion driven by a 6.8 ns, 2-shock laser pulse. This paper describes these experiments and comparisons with ICF design code simulations. Backlit radiography of a tritium-hydrogen-deuterium (THD) layered capsule demonstrated an ablator implosion velocity of 385 km/s with a slightly oblate hot spot shape. Other diagnostics suggested an asymmetric compressed fuel layer. A streak camera-based hot spot self-emission diagnostic (SPIDER) showed a double-peaked history of the capsule self-emission. Simulations suggest that this is a signature of low quality hot spot formation. Changes to the laser pulse and pointing for a subsequent DT implosion resulted in a higher temperature, prolate hot spot and a thermonuclear yield of 1.8 × 10{sup 15} neutrons, 40% of the 1D simulated yield.

  18. Cryogenic tritium-hydrogen-deuterium and deuterium-tritium layer implosions with high density carbon ablators in near-vacuum hohlraums

    NASA Astrophysics Data System (ADS)

    Meezan, N. B.; Berzak Hopkins, L. F.; Le Pape, S.; Divol, L.; MacKinnon, A. J.; Döppner, T.; Ho, D. D.; Jones, O. S.; Khan, S. F.; Ma, T.; Milovich, J. L.; Pak, A. E.; Ross, J. S.; Thomas, C. A.; Benedetti, L. R.; Bradley, D. K.; Celliers, P. M.; Clark, D. S.; Field, J. E.; Haan, S. W.; Izumi, N.; Kyrala, G. A.; Moody, J. D.; Patel, P. K.; Ralph, J. E.; Rygg, J. R.; Sepke, S. M.; Spears, B. K.; Tommasini, R.; Town, R. P. J.; Biener, J.; Bionta, R. M.; Bond, E. J.; Caggiano, J. A.; Eckart, M. J.; Gatu Johnson, M.; Grim, G. P.; Hamza, A. V.; Hartouni, E. P.; Hatarik, R.; Hoover, D. E.; Kilkenny, J. D.; Kozioziemski, B. J.; Kroll, J. J.; McNaney, J. M.; Nikroo, A.; Sayre, D. B.; Stadermann, M.; Wild, C.; Yoxall, B. E.; Landen, O. L.; Hsing, W. W.; Edwards, M. J.

    2015-06-01

    High Density Carbon (or diamond) is a promising ablator material for use in near-vacuum hohlraums, as its high density allows for ignition designs with laser pulse durations of <10 ns. A series of Inertial Confinement Fusion (ICF) experiments in 2013 on the National Ignition Facility [Moses et al., Phys. Plasmas 16, 041006 (2009)] culminated in a deuterium-tritium (DT) layered implosion driven by a 6.8 ns, 2-shock laser pulse. This paper describes these experiments and comparisons with ICF design code simulations. Backlit radiography of a tritium-hydrogen-deuterium (THD) layered capsule demonstrated an ablator implosion velocity of 385 km/s with a slightly oblate hot spot shape. Other diagnostics suggested an asymmetric compressed fuel layer. A streak camera-based hot spot self-emission diagnostic (SPIDER) showed a double-peaked history of the capsule self-emission. Simulations suggest that this is a signature of low quality hot spot formation. Changes to the laser pulse and pointing for a subsequent DT implosion resulted in a higher temperature, prolate hot spot and a thermonuclear yield of 1.8 × 1015 neutrons, 40% of the 1D simulated yield.

  19. HK97 Maturation Studied by Crystallography and H/[superscript 2]H Exchange Reveals the Structural Basis for Exothermic Particle Transitions

    SciTech Connect

    Gertsman, Ilya; Komives, Elizabeth A.; Johnson, John E.

    2010-03-22

    HK97 is an exceptionally amenable system for characterizing major conformational changes associated with capsid maturation in double-stranded DNA bacteriophage. HK97 undergoes a capsid expansion of {approx}20%, accompanied by major subunit rearrangements during genome packaging. A previous 3.44-{angstrom}-resolution crystal structure of the mature capsid Head II and cryo-electron microscopy studies of other intermediate expansion forms of HK97 suggested that, primarily, rigid-body movements facilitated the maturation process. We recently reported a 3.65-{angstrom}-resolution structure of the preexpanded particle form Prohead II (P-II) and found that the capsid subunits undergo significant refolding and twisting of the tertiary structure to accommodate expansion. The P-II study focused on major twisting motions in the P-domain and on refolding of the spine helix during the transition. Here we extend the crystallographic comparison between P-II and Head II, characterizing the refolding events occurring in each of the four major domains of the capsid subunit and their effect on quaternary structure stabilization. In addition, hydrogen/deuterium exchange, coupled to mass spectrometry, was used to characterize the structural dynamics of three distinct capsid intermediates: P-II, Expansion Intermediate, and the nearly mature Head I. Differences in the solvent accessibilities of the seven quasi-equivalent capsid subunits, attributed to differences in secondary and quaternary structures, were observed in P-II. Nearly all differences in solvent accessibility among subunits disappear after the first transition to Expansion Intermediate. We show that most of the refolding is coupled to this transformation, an event associated with the transition from asymmetric to symmetric hexamers.

  20. Exchange of deeply trapped and interstitial hydrogen in silicon

    SciTech Connect

    Tuttle, B.; Van de Walle, C.G.; Adams, J.B.

    1999-02-01

    Using {ital ab initio} density-functional calculations, we examine possible exchange mechanisms between an interstitial hydrogen atom and a deeply bound H at a silicon-hydrogen bond. We determine a low-energy pathway for exchange, which involves an intermediate, metastable {equivalent_to}SiH{sub 2} complex with both hydrogen atoms strongly bound to the silicon atom. The energy barrier for the exchange process is E{sub ex}{lt}0.2 eV, consistent with observations of hydrogen-deuterium exchange in a-Si:H(D) films. {copyright} {ital 1999} {ital The American Physical Society}

  1. Solidification studies of automotive heat exchanger materials

    NASA Astrophysics Data System (ADS)

    Carlberg, T.; Jaradeh, M.; Kamgou Kamaga, H.

    2006-11-01

    Modifications of the aluminum alloy AA 3003 have been studied to improve and tailorits properties for applications in automotive heat exchangers. Laboratory techniques have been applied to simulate industrial direct-chill casting, and some basic solidification studies have been conducted. The results are coupled to structures observed in industrial-size ingots and discussed in terms of structure-property relations.

  2. NMR and protein folding: equilibrium and stopped-flow studies.

    PubMed Central

    Frieden, C.; Hoeltzli, S. D.; Ropson, I. J.

    1993-01-01

    NMR studies are now unraveling the structure of intermediates of protein folding using hydrogen-deuterium exchange methodologies. These studies provide information about the time dependence of formation of secondary structure. They require the ability to assign specific resonances in the NMR spectra to specific amide protons of a protein followed by experiments involving competition between folding and exchange reactions. Another approach is to use 19F-substituted amino acids to follow changes in side-chain environment upon folding. Current techniques of molecular biology allow assignments of 19F resonances to specific amino acids by site-directed mutagenesis. It is possible to follow changes and to analyze results from 19F spectra in real time using a stopped-flow device incorporated into the NMR spectrometer. PMID:8298453

  3. Exchange Studies as Actor-Networks: Following Korean Exchange Students in Swedish Higher Education

    ERIC Educational Resources Information Center

    Ahn, Song-ee

    2011-01-01

    This article explores how Korean exchange students organized their studies during exchange programs in Swedish higher education. For most students, the programs became a disordered period in relation to their education. The value of exchange studies seems mainly to be extra-curricular. Drawing upon actor network theory, the article argues that the…

  4. Exchange bias studied with polarized neutron reflectivity

    SciTech Connect

    te Velthuis, S. G. E.

    2000-01-05

    The role of Polarized Neutron Reflectivity (PNR) for studying natural and synthetic exchange biased systems is illustrated. For a partially oxidized thin film of Co, cycling of the magnetic field causes a considerable reduction of the bias, which the onset of diffuse neutron scattering shows to be due to the loosening of the ferromagnetic domains. On the other hand, PNR measurements of a model exchange bias junction consisting of an n-layered Fe/Cr antiferromagnetic (AF) superlattice coupled with an m-layered Fe/Cr ferromagnetic (F) superlattice confirm the predicted collinear magnetization in the two superlattices. The two magnetized states of the F (along or opposite to the bias field) differ only in the relative orientation of the F and adjacent AF layer. The possibility of reading clearly the magnetic state at the interface pinpoints the commanding role that PNR is having in solving this intriguing problem.

  5. On the role of atomic metastability in the production of Balmer line radiation from ‘cold’ atomic hydrogen, deuterium and hydrogenic ion impurities in fusion edge plasmas

    NASA Astrophysics Data System (ADS)

    Hey, J. D.

    2012-03-01

    Published arguments, which assign an important role to atomic metastability in the production of ‘narrow’ Zeeman component radiation from the boundary region of fusion plasmas, are examined critically in relation to l-redistribution by proton and electron collisions, and mixing of unperturbed atomic states by the ion microfield and microfield gradient. It is concluded that these important processes indeed severely constrain the contribution from ‘metastable’ states to the generation of the hydrogen Balmer spectra, for electron concentrations above 1012 cm-3, as pointed out before by the present author (Hey et al 1999 J. Phys. B: At. Mol. Opt. Phys. 32 3555). The analysis of collision-induced l-redistribution represents an extension of that used previously (Hey et al 1996 Contrib. Plasma Phys. 36 583), applicable up to higher electron densities. For comparison purposes, we also consider the question of metastability of ionized helium in a low-temperature plasma, and that of some common hydrogenic impurities (C5+ and Ne9+) in a hydrogen (deuterium) fusion plasma. While for low nuclear charge Z the metastability of 2s1/2 levels is quenched by the plasma environment, it is much reduced in high-Z ions owing to the rapid increase with Z of the two-photon electric dipole (2E1) and magnetic dipole (M1) spontaneous transition rates to the ground state, whereas the role of the plasma in these cases is less important. The main new principle elaborated in this work is the sensitivity of atomic line strengths, and hence collision strengths, to perturbation by the plasma environment for transitions between fine-structure sublevels of the same principal quantum number. As the plasma microfield strength grows, ‘allowed’ transitions diminish in strength, while ‘forbidden’ transitions grow. However, owing to violation of the parity selection rule, there is an overall loss of collision strength available to transitions, resulting from the appearance of significant

  6. An antibody binding site on cytochrome c defined by hydrogen exchange and two-dimensional NMR

    SciTech Connect

    Paterson, Y.; Englander, S.W.; Roder, H. )

    1990-08-17

    The interaction of a protein antigen, horse cytochrome c (cyt c), with a monoclonal antibody has been studied by hydrogen-deuterium (H-D) exchange labeling and two-dimensional nuclear magnetic resonance (2D NMR) methods. The H-exchange rate of residues in three discontiguous regions of the cyt c polypeptide backbone was slowed by factors up to 340-fold in the antibody-antigen complex compared with free cyt c. The protected residues, 36 to 38, 59, 60, 64 to 67, 100, and 101, and their hydrogen-bond acceptors, are brought together in the three-dimensional structure to form a contiguous, largely exposed protein surface with an area of about 750 square angstroms. The interaction site determined in this way is consistent with prior epitope mapping studies and includes several residues that were not previously identified. The hydrogen exchange labeling approach can be used to map binding sites on small proteins in antibody-antigen complexes and may be applicable to protein-protein and protein-ligand interactions in general.

  7. Experimental studies of rotating exchange flow

    NASA Astrophysics Data System (ADS)

    Rabe, B.; Smeed, D. A.; Dalziel, S. B.; Lane-Serff, G. F.

    2007-02-01

    Ocean basins are connected by straits and passages, geometrically limiting important heat and salt exchanges which in turn influence the global thermohaline circulation and climate. Such exchange can be modeled in an idealized way by taking into consideration the density-driven two-layer flow along a strait under the influence of rotation. We use a laboratory model of a lock exchange between two reservoirs of different density through a flat-bottom channel with a horizontal narrows, set up on two different platforms: a 1 m diameter turntable, where density interface position was measured by dye attenuation, and the 14 m diameter turntable at Coriolis/LEGI (Grenoble, France), where correlation imaging velocimetry, a particle imaging technique, allowed us to obtain for the first time detailed measurements of the velocity fields in these flows. The influence of rotation is studied by varying a parameter, Bu, a type of Burger number given by the ratio of the Rossby radius to the channel width at the narrows. In addition, a two-layer version of the Miami Isopycnic Coordinate Model (MICOM) is used, to study the cases with low Burger number. Results from experiments by Dalziel [1988. Two-layer hydraulics: maximal exchange flows. Ph.D. Thesis, Department of Applied Mathematics and Theoretical Physics, University of Cambridge, see also ] are also included for comparison. Time-mean exchange fluxes for any Bu are in close agreement with the inviscid zero-potential vorticity theory of Dalziel [1990. Rotating two-layer sill flows. In: Pratt, L.J. (Ed.), The Physical Oceanography of Sea Straits. Kluwer Academic, Dordrecht, pp. 343-371] and Whitehead et al. [1974. Rotating hydraulics of strait and sill flows. Geophysical Fluid Dynamics 6, 101-125], who found that fluxes for Bu>1 mainly vary with channel width, similar to non-rotating flow, but for Bu<1 are only limited by the Rossby radius. We also show

  8. Method for decomposing observed line shapes resulting from multiple causes - Application to plasma charge-exchange-neutral spectra

    NASA Technical Reports Server (NTRS)

    Patch, R. W.

    1979-01-01

    A method is given for decomposing the widths of observed spectral lines resulting from unresolved line splitting, additive kinetic processes of different types, instrumental broadening (slit function), Doppler broadening, etc. all superimposed. The second moments are used as measures of the various widths involved. The method is not applicable if dispersion type (Lorentz) broadening occurs. Application is made to plasma charge-exchange-neutral spectra of hydrogen, deuterium, and helium.

  9. Signatures of the electron saddle swaps mechanism in the photon spectra following charge-exchange collisions

    NASA Astrophysics Data System (ADS)

    Otranto, Sebastian

    2014-10-01

    During the last few years, several experimental and theoretical studies have focused on state selective charge exchange processes between charged ions and alkali metals. These data are of particular importance for the tokamak nuclear fusion reactor program, since diagnostics on the plasma usually rely on charge-exchange spectroscopy. In this sense, alkali metals, have been proposed as potential alternatives to excited hydrogen/deuterium for which laboratory experiments are not feasible at present. In this talk, we present our recent work involving ion collisions with alkali metals. Oscillatory structures in the angular differential charge-exchange cross sections obtained using the MOTRIMS technique are correctly described by classical trajectory Monte Carlo simulations. These oscillations are found to originate from the number of swaps the electron undergoes around the projectile-target potential saddle before capture takes place and are very prominent at impact energies below 10 keV/amu. Moreover, cross sections of higher order of differentiability also indicate that the swaps leave distinctive signatures in the (n,l)-state selective cross sections and in the photon line emission cross sections. Oscillatory structures for the x-ray hardness ratio parameter are also predicted. In collaboration with Ronnie Hoekstra, Zernike Institute for Advanced Materials, University of Groningen and Ronald Olson, Department of Physics, Missouri University of Science and Technology.

  10. Hydrogen Isotope Exchange of Chlorinated Ethylenes in Aqueous Solution: Possibly a Termolecular Liquid Phase Reaction.

    PubMed

    Gabričević, Mario; Lente, Gábor; Fábián, István

    2015-12-24

    This work reports an experimental study of the hydrogen/deuterium exchange in the basic aqueous solutions of trichloroethylene, trans-1,2-dichloroethylene, and cis-1,2-dichloroethylene using (1)H NMR as a monitoring method. 1,1-Dichlorethylene was also investigated but found not to exchange hydrogen isotopes with water. The kinetics of isotope exchange features two different pathways, the first is first order with respect to hydroxide ion, whereas the second is second order. The first pathway is interpreted as a straightforward bimolecular reaction between chloroethylene and hydroxide ion, which leads to the deprotonation of chloroethylene. The second pathway involves a transition state with the association of one molecule of the chloroethylene and two hydroxide ions. It is shown that the second pathway could involve the formation of a precursor complex composed of one chloroethylene molecule and one hydroxide ion, but a direct termolecular elementary reaction is also feasible, which is shown by deriving a theoretical highest limit for the rate constants of termolecular reactions in solution. PMID:26618984

  11. Kinetics of deuterium exchange on resorcinol in D{sub 2}O at high pressure and high temperature

    SciTech Connect

    Bai, S.; Palmer, B.J.; Yonker, C.R.

    2000-01-13

    The kinetics of deuteration of resorcinol in pure D{sub 2}O were studied for the first time using a flow-through capillary tubular reactor with on-line, proton, and deuterium NMR detection at high temperatures and high pressure. The global rate constants for hydrogen/deuterium (H/D) exchange were determined from temperatures of 200--450 C (723 K) at a pressure of {approximately}400 bar (the critical temperature and pressure of water are 374.2 C and 218.3 bar, respectively). The H/D exchange rate in resorcinol (1,3-dihydroxybenzene) under these extreme conditions was determined using proton NMR as a function of the resorcinol residence time in a capillary tubular reactor, which also served as a high-pressure NMR cell. The {sup 1}H and {sup 2}H NMR results indicate that H/D exchange in resorcinol for the ring protons was observed at temperatures as low as 200 C. The kinetics of H/D exchange in resorcinol and the activation energy was extracted from the experimental {sup 1}H NMR data.

  12. Experimental study of ocean-atmosphere exchanges

    SciTech Connect

    Eymard, L.; Weill, A.; Planton, S.

    1994-12-31

    The SOFIA/ASTEX and SEMAPHORE campaigns were performed over open ocean, near the Azores, to study the ocean-atmosphere exchanges at the local and meso-scales, with a particular insight to the spatial variability of fluxes and related processes. In both cases, the experimental strategy involved two research aircraft and an oceanographic vessel, as well as surface buoys. SOFIA/ASTEX was more particularly devoted to the study of boundary layer and cloud properties, including microphysical and radiative aspects, in the framework of the international campaign ASTEX. SEMAPHORE was aimed at the analysis of surface fluxes and interactions with the upper ocean at the mesoscale. It included an important network of ocean circulation and thermal properties, from ships, current meter moorings, current drifters, and drifting buoys. The thermal front associated with the Azores current is an important feature of the ocean circulation and was particularly investigated. The analysis of data from meteorological satellites is also an important aspect of the two campaigns.

  13. EXCHANGE

    SciTech Connect

    Boltz, J.C.

    1992-09-01

    EXCHANGE is published monthly by the Idaho National Engineering Laboratory (INEL), a multidisciplinary facility operated for the US Department of Energy (DOE). The purpose of EXCHANGE is to inform computer users about about recent changes and innovations in both the mainframe and personal computer environments and how these changes can affect work being performed at DOE facilities.

  14. Superacid-promoted ionization of alkanes without carbonium ion formation: a density functional theory study.

    PubMed

    Dinér, Peter

    2012-10-11

    The carbonium ion has been suggested to be the intermediate in superacid-promoted reactions (SbF(5)-HF) such as hydrogen-deuterium exchange and in the electrophilic C-H cleavage into hydrogen and the carbenium ion. In this study, the superacid-promoted C-H cleavage into hydrogen and the carbenium ion was studied using density functional theory (B3LYP and M062X) and ab initio methods (MP2 and CCSD). The calculations suggest that the superacid-promoted C-H cleavage proceeds via a concerted transition state leading to hydrogen (H(2)) and the carbenium ion without the formation of the elusive carbonium ion. The reactivity for the superacid-promoted C-H cleavage decreases upon going from isobutane (tertiary) > propane (secondary) > isobutane (primary) > propane (primary) > ethane > methane. PMID:22998332

  15. Ceramic heat-exchanger applications study

    SciTech Connect

    McFarlin, D.J.; Sgamboti, C.T.; Lessard, R.D.

    1982-10-01

    To put the potential benefits of ceramic heat exchangers (CHX) applications into quantitative perspective, several industrial cogeneration and electric utiity power generation systems were surveyed and evaluated. This study was focused on coal-based fuel fired applications, for which system performance and economic assessments were made. Seven CHX applications in the industrial cogeneration sector were selected for evaluation. These include (1) Gasified Coal-Fired Gas Turbine, (2) Pressurized Fluidized Bed Combustor (PFBC)-Gas Turbine, (3) Atmospheric Fluidized Bed Combustor (AFBC)-Gas Turbine, (4 and 5) AFBC Combined Cycle with and without reheat and (6 and 7) Indirect Coal-Fired Gas Turbine and Combined Cycle. The performance and economics of these cogeneration systems were evaluated and compared with other competing systems (both advanced and State-of-the-Art). For the electric utility power generation sector five applications utilizing a CHX were selected and evaluated; their performance and cost factors were compared to those of a reference pulverized coal-fired steam plant with flue gas desulfurization. These five applications included (1) PFBC-Combined Cycle, (2) AFBC-Combined Cycle, (3) Industrial Coal Gasifier-Combined Cycle, (4) Indirect Coal-Fired Combined Cycle, and (5) Indirect Coal-Fired Simple Cycle. Of the five CHX applications evaluated in the power generation sector, only the AFBC system showed a clear gain over the reference pulverized coal system.

  16. Commercial Ion Exchange Resin Vitrification Studies

    SciTech Connect

    Cicero-Herman, C.A

    2002-06-28

    In the nuclear industry, ion exchange resins are used for purification of aqueous streams. The major contaminants of the resins are usually the radioactive materials that are removed from the aqueous streams. The use of the ion exchange resins creates a waste stream that can be very high in both organic and radioactive constituents. Therefore, disposal of the spent resin often becomes an economic problem because of the large volumes of resin produced and the relatively few technologies that are capable of economically stabilizing this waste. Vitrification of this waste stream presents a reasonable disposal alternative because of its inherent destruction capabilities, the volume reductions obtainable, and the durable product that it produces.

  17. Hydrogenation vs. H-D isotope scrambling during the conversion of ethylene with hydrogen/deuterium catalyzed by platinum under single-collision conditions.

    PubMed

    Dong, Yujung; Ebrahimi, Maryam; Tillekaratne, Aashani; Simonovis, Juan Pablo; Zaera, Francisco

    2016-07-28

    The catalytic hydrogenation of olefins promoted by transition metals, represented here by the conversion of ethylene with platinum, was studied under a unique regime representing pressures in the mTorr range and single-collision conditions. Isotope labeling was used to follow the concurrent H-D exchange steps that occur during this conversion. Multiple isotope substitutions were observed in the resulting ethane products, reflecting the operability of the reversible stepwise mechanism proposed a long time ago by Horiuti and Polanyi. In fact, the ethane isotopologue distributions obtained in these experiments reflect a much higher probability for the dehydrogenation of ethyl intermediates back to the olefin, relative to the hydrogenation to ethane, than typically seen in this catalysis. In addition, a second mechanistic pathway was clearly identified, responsible for most of the dideuteroethane produced. Based on the dependence of the rates of formation of each isotopologue on the fluxes of deuterium and ethylene, it is argued that this second route may be a "reverse" Eley-Rideal step between gas-phase ethylene and two deuterium atoms adsorbed on adjacent sites of the platinum surface. The clear identification of this second pathway is new, and was possible thanks to our ability to explore a new single-collision intermediate pressure regime. PMID:27373226

  18. High temperature heat exchanger studies for applications to gas turbines

    NASA Astrophysics Data System (ADS)

    Min, June Kee; Jeong, Ji Hwan; Ha, Man Yeong; Kim, Kui Soon

    2009-12-01

    Growing demand for environmentally friendly aero gas-turbine engines with lower emissions and improved specific fuel consumption can be met by incorporating heat exchangers into gas turbines. Relevant researches in such areas as the design of a heat exchanger matrix, materials selection, manufacturing technology, and optimization by a variety of researchers have been reviewed in this paper. Based on results reported in previous studies, potential heat exchanger designs for an aero gas turbine recuperator, intercooler, and cooling-air cooler are suggested.

  19. International Exchange as a Transformative Learning Experience: A Case Study

    ERIC Educational Resources Information Center

    Choi, Sheena; Slaubaugh, Michael; Kim, Ae-Sook

    2012-01-01

    This study examines the role of international exchange programs on the transformative learning of English-speaking students. A student exchange program at a South Korean university is used for this case study. It explores how learning experiences are translated by participants onto their perceptions about the host country. An analysis of a pre-…

  20. Protein-like proton exchange in a synthetic host cavity.

    PubMed

    Hart-Cooper, William M; Sgarlata, Carmelo; Perrin, Charles L; Toste, F Dean; Bergman, Robert G; Raymond, Kenneth N

    2015-12-15

    The mechanism of proton exchange in a metal-ligand enzyme active site mimic (compound 1) is described through amide hydrogen-deuterium exchange kinetics. The type and ratio of cationic guest to host in solution affect the rate of isotope exchange, suggesting that the rate of exchange is driven by a host whose cavity is occupied by water. Rate constants for acid-, base-, and water-mediated proton exchange vary by orders of magnitude depending on the guest, and differ by up to 200 million-fold relative to an alanine polypeptide. These results suggest that the unusual microenvironment of the cavity of 1 can dramatically alter the reactivity of associated water by magnitudes comparable to that of enzymes. PMID:26621709

  1. Microscopic insight into role of protein flexibility during ion exchange chromatography by nuclear magnetic resonance and quartz crystal microbalance approaches.

    PubMed

    Hao, Dongxia; Ge, Jia; Huang, Yongdong; Zhao, Lan; Ma, Guanghui; Su, Zhiguo

    2016-03-18

    Driven by the prevalent use of ion exchange chromatography (IEC) for polishing therapeutic proteins, many rules have been formulated to summarize the different dependencies between chromatographic data and various operational parameters of interest based on statically determined interactions. However, the effects of the unfolding of protein structures and conformational stability are not as well understood. This study focuses on how the flexibility of proteins perturbs retention behavior at the molecular scale using microscopic characterization approaches, including hydrogen-deuterium (H/D) exchange detected by NMR and a quartz crystal microbalance (QCM). The results showed that a series of chromatographic retention parameters depended significantly on the adiabatic compressibility and structural flexibility of the protein. That is, softer proteins with higher flexibility tended to have longer retention times and stronger affinities on SP Sepharose adsorbents. Tracing the underlying molecular mechanism using NMR and QCM indicated that an easily unfolded flexible protein with a more compact adsorption layer might contribute to the longer retention time on adsorbents. The use of NMR and QCM provided a previously unreported approach for elucidating the effect of protein structural flexibility on binding in IEC systems. PMID:26896917

  2. Helical structure and stability in human apolipoprotein A-I by hydrogen exchange and mass spectrometry.

    PubMed

    Chetty, Palaniappan Sevugan; Mayne, Leland; Lund-Katz, Sissel; Stranz, David; Englander, S Walter; Phillips, Michael C

    2009-11-10

    Apolipoprotein A-I (apoA-I) stabilizes anti-atherogenic high density lipoprotein particles (HDL) in the circulation and governs their biogenesis, metabolism, and functional interactions. To decipher these important structure-function relationships, it will be necessary to understand the structure, stability, and plasticity of the apoA-I molecule. Biophysical studies show that lipid-free apoA-I contains a large amount of alpha-helical structure but the location of this structure and its properties are not established. We used hydrogen-deuterium exchange coupled with a fragmentation-separation method and mass spectrometric analysis to study human lipid-free apoA-I in its physiologically pertinent monomeric form. The acquisition of approximately 100 overlapping peptide fragments that redundantly cover the 243-residue apoA-I polypeptide made it possible to define the positions and stabilities of helical segments and to draw inferences about their interactions and dynamic properties. Residues 7-44, 54-65, 70-78, 81-115, and 147-178 form alpha-helices, accounting for a helical content of 48 +/- 3%, in agreement with circular dichroism measurements (49%). At 3 to 5 kcal/mol in free energy of stabilization, the helices are far more stable than could be achieved in isolation, indicating mutually stabilizing helix bundle interactions. However the helical structure is dynamic, unfolding and refolding in seconds, allowing facile apoA-I reorganization during HDL particle formation and remodeling. PMID:19850866

  3. Proton Translocation in Cytochrome c Oxidase: Insights from Proton Exchange Kinetics and Vibrational Spectroscopy

    PubMed Central

    Ishigami, Izumi; Hikita, Masahide; Egawa, Tsuyoshi; Yeh, Syun-Ru; Rousseau, Denis L.

    2014-01-01

    Cytochrome c oxidase is the terminal enzyme in the electron transfer chain. It reduces oxygen to water and harnesses the released energy to translocate protons across the inner mitochondrial membrane. The mechanism by which the oxygen chemistry is coupled to proton translocation is not yet resolved owing to the difficulty of monitoring dynamic proton transfer events. Here we summarize several postulated mechanisms for proton translocation, which have been supported by a variety of vibrational spectroscopic studies. We recently proposed a proton translocation model involving proton accessibility to the regions near the propionate groups of the heme a and heme a3 redox centers of the enzyme based by hydrogen/deuterium (H/D) exchange Raman scattering studies (Egawa et al., PLOS ONE 2013). To advance our understanding of this model and to refine the proton accessibility to the hemes, the H/D exchange dependence of the heme propionate group vibrational modes on temperature and pH was measured. The H/D exchange detected at the propionate groups of heme a3 takes place within a few seconds under all conditions. In contrast, that detected at the heme a propionates occurs in the oxidized but not the reduced enzyme and the H/D exchange is pH-dependent with a pKa of ~8.0 (faster at high pH). Analysis of the thermodynamic parameters revealed that, as the pH is varied, entropy/enthalpy compensation held the free energy of activation in a narrow range. The redox dependence of the possible proton pathways to the heme groups is discussed. PMID:25268561

  4. Hydrogen Isotope Separation by Combined Electrolysis Catalytic Exchange Under Reduced Pressure

    SciTech Connect

    Sugiyama, T.; Asakura, Y.; Uda, T.; Abe, Y.; Shiozaki, T.; Enokida, Y.; Yamamoto, I.

    2005-07-15

    At the National Institute for Fusion Science experimental studies on hydrogen isotope separation by a Combined Electrolysis Catalytic Exchange (CECE) process have been carried out in order to apply it to the system of water detritiation for D-D burning experiments of the Large Helical Device. As an improvement of the CECE process, we have developed a reduced-pressure method as a means of enhancing the separation factor. The feasibility of this method is examined through application to a CECE process using a prototype separation column. Hydrogen-deuterium isotope separation experiments are performed in the two cases where column pressures are 12 and 101 kPa, and the separation factors for hydrogen and deuterium are obtained as 6.8 and 5.6, respectively. It is confirmed that the present method is applicable and useful to the CECE process. The values of Height Equivalent to a Theoretical Plate (HETP) are estimated by analyses with the equilibrium stage model. The HETP values are 15 cm at 12 kPa and 13 cm at 101 kPa. The increase of superficial velocity with decreasing pressure may spoil the efficiency of the mass transfer.

  5. Effect of detergent binding on cytochrome P450 2B4 structure as analyzed by X-ray crystallography and deuterium-exchange mass spectrometry.

    PubMed

    Shah, Manish B; Jang, Hyun-Hee; Wilderman, P Ross; Lee, David; Li, Sheng; Zhang, Qinghai; Stout, C David; Halpert, James R

    2016-09-01

    Multiple crystal structures of CYP2B4 have demonstrated the binding of the detergent 5-cyclohexyl-1-pentyl-β-D-maltoside (CYMAL-5) in a peripheral pocket located adjacent to the active site. To explore the consequences of detergent binding, X-ray crystal structures of the peripheral pocket mutant CYP2B4 F202W were solved in the presence of hexaethylene glycol monooctyl ether (C8E6) and CYMAL-5. The structure in the presence of CYMAL-5 illustrated a closed conformation indistinguishable from the previously solved wild-type. In contrast, the F202W structure in the presence of C8E6 revealed a detergent molecule that coordinated the heme-iron and extended to the protein surface through the substrate access channel 2f. Despite the overall structural similarity of these detergent complexes, remarkable differences were observed in the A, A', and H helices, the F-G cassette, the C-D and β4 loop region. Hydrogen-deuterium exchange mass spectrometry (DXMS) was employed to probe these differences and to test the effect of detergents in solution. The presence of either detergent increased the H/D exchange rate across the plastic regions, and the results obtained by DXMS in solution were consistent in general with the relevant structural snapshots. The study provides insight into effect of detergent binding and the interpretation of associated conformational dynamics of CYP2B4. PMID:27280734

  6. HDX Workbench: Software for the Analysis of H/D Exchange MS Data

    NASA Astrophysics Data System (ADS)

    Pascal, Bruce D.; Willis, Scooter; Lauer, Janelle L.; Landgraf, Rachelle R.; West, Graham M.; Marciano, David; Novick, Scott; Goswami, Devrishi; Chalmers, Michael J.; Griffin, Patrick R.

    2012-09-01

    Hydrogen/deuterium exchange mass spectrometry (HDX-MS) is an established method for the interrogation of protein conformation and dynamics. While the data analysis challenge of HDX-MS has been addressed by a number of software packages, new computational tools are needed to keep pace with the improved methods and throughput of this technique. To address these needs, we report an integrated desktop program titled HDX Workbench, which facilitates automation, management, visualization, and statistical cross-comparison of large HDX data sets. Using the software, validated data analysis can be achieved at the rate of generation. The application is available at the project home page http://hdx.florida.scripps.edu.

  7. Ligand exchange in quaternary alloyed nanocrystals--a spectroscopic study.

    PubMed

    Gabka, Grzegorz; Bujak, Piotr; Giedyk, Kamila; Kotwica, Kamil; Ostrowski, Andrzej; Malinowska, Karolina; Lisowski, Wojciech; Sobczak, Janusz W; Pron, Adam

    2014-11-14

    Exchange of initial, predominantly stearate ligands for pyridine in the first step and butylamine (BA) or 11-mercaptoundecanoic acid (MUA) in the second one was studied for alloyed quaternary Cu-In-Zn-S nanocrystals. The NMR results enabled us to demonstrate, for the first time, direct binding of the pyridine labile ligand to the nanocrystal surface as evidenced by paramagnetic shifts of the three signals attributed to its protons to 7.58, 7.95 and 8.75 ppm. XPS investigations indicated, in turn, a significant change in the composition of the nanocrystal surface upon the exchange of initial ligands for pyridine, which being enriched in indium in the 'as prepared' form became enriched in zinc after pyridine binding. This finding indicated that the first step of ligand exchange had to involve the removal of the surface layer enriched in indium with simultaneous exposure of a new, zinc-enriched layer. In the second ligand exchange step (replacement of pyridine with BA or MUA) the changes in the nanocrystal surface compositions were much less significant. The presence of zinc in the nanocrystal surface layer turned out necessary for effective binding of pyridine as shown by a comparative study of ligand exchange in Cu-In-Zn-S, Ag-In-Zn-S and CuInS2, carried out by complementary XPS and NMR investigations. PMID:25252174

  8. A piloted simulation study of data link ATC message exchange

    NASA Technical Reports Server (NTRS)

    Waller, Marvin C.; Lohr, Gary W.

    1989-01-01

    Data link Air Traffic Control (ATC) and Air Traffic Service (ATS) message and data exchange offers the potential benefits of increased flight safety and efficiency by reducing communication errors and allowing more information to be transferred between aircraft and ground facilities. Digital communication also presents an opportunity to relieve the overloading of ATC radio frequencies which hampers message exchange during peak traffic hours in many busy terminal areas. A piloted simulation study to develop pilot factor guidelines and assess potential flight crew benefits and liabilities from using data link ATC message exchange was completed. The data link ATC message exchange concept, implemented on an existing navigation computer Control Display Unit (CDU) required maintaining a voice radio telephone link with an appropriate ATC facility. Flight crew comments, scanning behavior, and measurements of time spent in ATC communication activities for data link ATC message exchange were compared to similar measures for simulated conventional voice radio operations. The results show crew preference for the quieter flight deck environment and a perception of lower communication workload.

  9. Use of SAR in Regional Methane Exchange Studies

    NASA Technical Reports Server (NTRS)

    Morrissey, L. A.; Livingston, G. P.; Durden, S. L.

    1994-01-01

    Significant sources of uncertainty in global trace gas budgets are due to lack of knowledge concerning the areal and temporal extent of source and sink areas. Synthetic aperture radar (SAR) is particularly suited to studies of northern ecosystems because of its all-weather operating capability which enables the acquisition of seasonal data. As key controls on methane exchange, the ability to differentiate major vegetation communities, inundation, and leaf area index (LAI) with satellite and airborne SAR data would increase the accuracy and precision of regional and seasonal estimates of methane exchange. The utility of SAR data for monitoring key controls on methane emissions from Arctic and boreal ecosystems is examined.

  10. TRACER STUDY OF VERTICAL EXCHANGE BY CUMULUS CLOUDS

    EPA Science Inventory

    The exchange of material by convective cloud processes between the mixed layer and the overlying free troposphere is examined. The paper describes results of a field experiment that was conducted in Lexington, Kentucky during the period from July 20 to August 24, 1983 to study th...

  11. Functional studies of split "Arabidopsis" Ca(2+)/H(+) exchangers

    Technology Transfer Automated Retrieval System (TEKTRAN)

    In plants, high capacity tonoplast cation/H (+) antiport is mediated in part by a family of cation exchanger (CAX) transporters. Functional association between CAX1 and CAX3 has previously been shown. In this study, we further examine the interactions between CAX protein domains using nonfunctional ...

  12. Elucidating the sources of upper tropospheric and lower stratospheric humidity through the in situ measurement of hydrogen-deuterium-oxygen and water

    NASA Astrophysics Data System (ADS)

    St. Clair, Jason Michael

    Water in the upper troposphere (UT) and lower stratosphere (LS) plays a central role in the coupled chemistry-climate system through the radiative effects of water vapor and clouds and through stratospheric ozone chemistry. As the atmosphere changes in response to increased concentrations of greenhouse gasses, UT and LS humidity will change in accordance with the climate sensitivity of water transport mechanisms. Identifying and quantifying the transport mechanisms is the first step toward predicting how humidity will be affected by climate change. Water isotopes hold promise as a tracer capable of discerning between water transport mechanisms. Measurements of H2O and H DO that are accurate and precise enough to be used for the quantitative study of water transport in the UT and LS pose an exceptional challenge due to the low concentration of water at the tropopause and the propensity of water to contaminate instrument surfaces. We have built and successfully flown an H2O-deltaD instrument with the sensitivity to operate in the upper troposphere and lower stratosphere by employing a photolysis laser-induced fluorescence technique to measure H2O and H DO concentrations. The instrument (Hoxotope) exhibits the requisite sensitivity, accuracy, time response, and lack of systematic biases necessary to make a credible deltaD measurement and has demonstrated those same attributes both in the laboratory and in flight aboard the NASA WB-57. Data from the Aura Validation Experiment Water Isotope Intercomparison Flights (AVE-WIIF) in Summer 2005 allowed for the intercomparison between Hoxotope water and the established Harvard Water Vapor instrument, as well as between Hoxotope H DO and ICOS H DO. The data show a close agreement between the calibrations of the instruments and they demonstrate the quick time response of Hoxotope. The successful intercomparison validated Hoxotope as a credible source of deltaD data in the upper troposphere and lower stratosphere. Hoxotope AVE

  13. Bayesian Extraction of Deep UV Resonance Raman Signature of Fibrillar Cross-β Sheet Core based on H-D Exchange Data

    NASA Astrophysics Data System (ADS)

    Shashilov, V. A.; Lednev, I. K.

    2007-11-01

    Amyloid fibrils are associated with many neurodegenerative diseases. The application of conventional biophysical techniques including solution NMR and X-ray crystallography for structural characterization of fibrils is limited because they are neither crystalline nor soluble. The Bayesian approach was utilized for extracting the deep UV resonance Raman (DUVRR) spectrum of the lysozyme fibrillar β-sheet based on the hydrogen-deuterium exchange spectral data. The problem was shown to be unsolvable when using blind source separation or conventional chemometrics methods because of the 100% correlation of the concentration profiles of the species under study. Information about the mixing process was incorporated by forcing the columns of the concentration matrix to be proportional to the expected concentration profiles. The ill-conditioning of the matrix was removed by concatenating it to the diagonal matrix with entries corresponding to the known pure spectra (sources). Prior information about the spectral features and characteristic bands of the spectra was taken into account using the Bayesian signal dictionary approach. The extracted DUVRR spectrum of the cross-β sheet core exhibited sharp bands indicating the highly ordered structure. Well resolved sub-bands in Amide I and Amide III regions enabled us to assign the fibril core structure to anti-parallel β-sheet and estimate the amide group facial angle Ψ in the cross-β structure. The elaborated Bayesian approach was demonstrated to be applicable for studying correlated biochemical processes.

  14. Protein Structure-Function Correlation in Living Human Red Blood Cells Probed by Isotope Exchange-based Mass Spectrometry.

    PubMed

    Narayanan, Sreekala; Mitra, Gopa; Muralidharan, Monita; Mathew, Boby; Mandal, Amit K

    2015-12-01

    To gain insight into the underlying mechanisms of various biological events, it is important to study the structure-function correlation of proteins within cells. Structural probes used in spectroscopic tools to investigate protein conformation are similar across all proteins. Therefore, structural studies are restricted to purified proteins in vitro and these findings are extrapolated in cells to correlate their functions in vivo. However, due to cellular complexity, in vivo and in vitro environments are radically different. Here, we show a novel way to monitor the structural transition of human hemoglobin upon oxygen binding in living red blood cells (RBCs), using hydrogen/deuterium exchange-based mass spectrometry (H/DX-MS). Exploiting permeability of D2O across cell membrane, the isotope exchange of polypeptide backbone amide hydrogens of hemoglobin was carried out inside RBCs and monitored using matrix-assisted laser desorption ionization mass spectrometry (MALDI-MS). To explore the conformational transition associated with oxygenation of hemoglobin in vivo, the isotope exchange kinetics was simplified using the method of initial rates. RBC might be considered as an in vivo system of pure hemoglobin. Thus, as a proof-of-concept, the observed results were correlated with structural transition of hemoglobin associated with its function established in vitro. This is the first report on structural changes of a protein upon ligand binding in its endogenous environment. The proposed method might be applicable to proteins in their native state, irrespective of location, concentration, and size. The present in-cell approach opens a new avenue to unravel a plethora of biological processes like ligand binding, folding, and post-translational modification of proteins in living cells. PMID:26531244

  15. Separation of organic ion exchange resins from sludge -- engineering study

    SciTech Connect

    Duncan, J.B.

    1998-08-25

    This engineering study evaluates the use of physical separation technologies to separate organic ion exchange resin from KE Basin sludge prior to nitric acid dissolution. This separation is necessitate to prevent nitration of the organics in the acid dissolver. The technologies under consideration are: screening, sedimentation, elutriation. The recommended approach is to first screen the Sludge and resin 300 microns then subject the 300 microns plus material to elutriation.

  16. Nucleotide-induced conformational changes of tetradecameric GroEL mapped by H/D exchange monitored by FT-ICR mass spectrometry

    PubMed Central

    Zhang, Qian; Chen, Jin; Kuwajima, Kunihiro; Zhang, Hui-Min; Xian, Feng; Young, Nicolas L.; Marshall, Alan G.

    2013-01-01

    Here we employ hydrogen/deuterium exchange mass spectrometry (HDX-MS) to access E. coli chaperonin GroEL conformation. The ~800 kDa tetradecameric GroEL plays an essential role in the proper folding of many proteins. Previous studies of the structural dynamics of GroEL upon ATP binding have been inconsistent, showing either minimal or major allosteric changes. Our results, based on the native, non-mutated, protein under physiological conditions in solution demonstrate substantial changes in conformation and/or flexibility upon ATP binding. We capture the pivotal step in its functional cycle by use of a non-hydrolyzable ATP analog, ATPγS, to mimic the ATP-bound GroEL state. Comparison of HDX-MS results for apo GroEL and GroEL-ATPγS enables the characterization of the nucleotide-regulated conformational changes throughout the entire protein with high sequence resolution. The 14-mer GroEL complex is the largest protein assembly yet accessed by HDX-MS, with sequence resolution of segments of as few as five amino acids. PMID:23409238

  17. Competing Noncovalent Host-guest Interactions and H/D Exchange: Reactions of Benzyloxycarbonyl-Proline Glycine Dipeptide Variants with ND3

    NASA Astrophysics Data System (ADS)

    Miladi, Mahsan; Olaitan, Abayomi D.; Zekavat, Behrooz; Solouki, Touradj

    2015-11-01

    A combination of density functional theory calculations, hydrogen/deuterium exchange (HDX) reactions, ion mobility-mass spectrometry, and isotope labeling tandem mass spectrometry was used to study gas-phase "host-guest" type interactions of a benzyloxycarbonyl (Z)-capped proline (P) glycine (G) model dipeptide (i.e., Z-PG) and its various structural analogues with ND3. It is shown that in a solvent-free environment, structural differences between protonated and alkali metal ion (Na+, K+, or Cs+)-complexed species of Z-PG affect ND3 adduct formation. Specifically, [Z-PG + H]+ and [Z-PG-OCH3 + H]+ formed gas-phase ND3 adducts ([Z-PG (or Z-PG-OCH3) + H + ND3]+) but no ND3 adducts were observed for [Z-PG + alkali metal]+ or [Z-PG + H - CO2]+. Experimentally measured and theoretically calculated collision cross sections (CCSs) of protonated and alkali metal ion-complexed Z-PG species showed similar trends that agreed with the observed structural differences from molecular modeling results. Moreover, results from theoretical ND3 affinity calculations were consistent with experimental HDX observations, indicating a more stable ND3 adduct for [Z-PG + H]+ compared to [Z-PG + alkali metal]+ species. Molecular modeling and experimental MS results for [Z-PG + H]+ and [Z-PG + alkali metal]+ suggest that optimized cation-π and hydrogen bonding interactions of carbonyl groups in final products are important for ND3 adduct formation.

  18. John Locke's seed lists: a case study in botanical exchange.

    PubMed

    Harris, Stephen A; Anstey, Peter R

    2009-12-01

    This paper gives a detailed analysis of four seed lists in the journals of John Locke. These lists provide a window into a fascinating open network of botanical exchange in the early 1680s which included two of the leading botanists of the day, Pierre Magnol of Montpellier and Jacob Bobart the Younger of Oxford. The provenance and significance of the lists are assessed in relation to the relevant extant herbaria and plant catalogues from the period. The lists and associated correspondence provide the main evidence for Locke's own important, though modest contribution to early modern botany, a contribution which he would have regarded as a small part of the broader project of constructing a natural history of plants. They also provide a detailed case study of the sort of open and informal network of knowledge exchange in the early modern period that is widely recognised by historians of science, but all too rarely illustrated. PMID:19917484

  19. Studying Gas-Phase Interconversion of Tautomers Using Differential Mobility Spectrometry

    NASA Astrophysics Data System (ADS)

    Campbell, J. Larry; Yang, Amy Meng-Ci; Melo, Luke R.; Hopkins, W. Scott

    2016-04-01

    In this study, we report on the use of differential mobility spectrometry (DMS) as a tool for studying tautomeric species, allowing a more in-depth interrogation of these elusive isomers using ion/molecule reactions and tandem mass spectrometry. As an example, we revisit a case study in which gas-phase hydrogen-deuterium exchange (HDX)—a probe of ion structure in mass spectrometry—actually altered analyte ion structure by tautomerization. For the N- and O-protonated tautomers of 4-aminobenzoic acid, when separated using DMS and subjected to subsequent HDX with trace levels of D2O, the anticipated difference between the exchange rates of the two tautomers is observed. However, when using higher levels of D2O or a more basic reagent, equivalent and almost complete exchange of all labile protons is observed. This second observation is a result of the interconversion of the N-protonated tautomer to the O-protonated form during HDX. We can monitor this transformation experimentally, with support from detailed molecular dynamics and electronic structure calculations. In fact, calculations suggest the onset of bulk solution phase properties for 4-aminobenzoic acid upon solvation with eight CH3OH molecules. These findings also underscore the need for choosing HDX reagents and conditions judiciously when separating interconvertible isomers using DMS.

  20. Studying Gas-Phase Interconversion of Tautomers Using Differential Mobility Spectrometry.

    PubMed

    Campbell, J Larry; Yang, Amy Meng-Ci; Melo, Luke R; Hopkins, W Scott

    2016-07-01

    In this study, we report on the use of differential mobility spectrometry (DMS) as a tool for studying tautomeric species, allowing a more in-depth interrogation of these elusive isomers using ion/molecule reactions and tandem mass spectrometry. As an example, we revisit a case study in which gas-phase hydrogen-deuterium exchange (HDX)-a probe of ion structure in mass spectrometry-actually altered analyte ion structure by tautomerization. For the N- and O-protonated tautomers of 4-aminobenzoic acid, when separated using DMS and subjected to subsequent HDX with trace levels of D2O, the anticipated difference between the exchange rates of the two tautomers is observed. However, when using higher levels of D2O or a more basic reagent, equivalent and almost complete exchange of all labile protons is observed. This second observation is a result of the interconversion of the N-protonated tautomer to the O-protonated form during HDX. We can monitor this transformation experimentally, with support from detailed molecular dynamics and electronic structure calculations. In fact, calculations suggest the onset of bulk solution phase properties for 4-aminobenzoic acid upon solvation with eight CH3OH molecules. These findings also underscore the need for choosing HDX reagents and conditions judiciously when separating interconvertible isomers using DMS. Graphical Abstract ᅟ. PMID:27094827

  1. Studying Gas-Phase Interconversion of Tautomers Using Differential Mobility Spectrometry

    NASA Astrophysics Data System (ADS)

    Campbell, J. Larry; Yang, Amy Meng-Ci; Melo, Luke R.; Hopkins, W. Scott

    2016-07-01

    In this study, we report on the use of differential mobility spectrometry (DMS) as a tool for studying tautomeric species, allowing a more in-depth interrogation of these elusive isomers using ion/molecule reactions and tandem mass spectrometry. As an example, we revisit a case study in which gas-phase hydrogen-deuterium exchange (HDX)—a probe of ion structure in mass spectrometry—actually altered analyte ion structure by tautomerization. For the N- and O-protonated tautomers of 4-aminobenzoic acid, when separated using DMS and subjected to subsequent HDX with trace levels of D2O, the anticipated difference between the exchange rates of the two tautomers is observed. However, when using higher levels of D2O or a more basic reagent, equivalent and almost complete exchange of all labile protons is observed. This second observation is a result of the interconversion of the N-protonated tautomer to the O-protonated form during HDX. We can monitor this transformation experimentally, with support from detailed molecular dynamics and electronic structure calculations. In fact, calculations suggest the onset of bulk solution phase properties for 4-aminobenzoic acid upon solvation with eight CH3OH molecules. These findings also underscore the need for choosing HDX reagents and conditions judiciously when separating interconvertible isomers using DMS.

  2. Mass Spectrometric Approaches to Study Protein Structure and Interactions in Lyophilized Powders

    PubMed Central

    Topp, Elizabeth M.

    2015-01-01

    Amide hydrogen/deuterium exchange (ssHDX-MS) and side-chain photolytic labeling (ssPL-MS) followed by mass spectrometric analysis can be valuable for characterizing lyophilized formulations of protein therapeutics. Labeling followed by suitable proteolytic digestion allows the protein structure and interactions to be mapped with peptide-level resolution. Since the protein structural elements are stabilized by a network of chemical bonds from the main-chains and side-chains of amino acids, specific labeling of atoms in the amino acid residues provides insight into the structure and conformation of the protein. In contrast to routine methods used to study proteins in lyophilized solids (e.g., FTIR), ssHDX-MS and ssPL-MS provide quantitative and site-specific information. The extent of deuterium incorporation and kinetic parameters can be related to rapidly and slowly exchanging amide pools (Nfast, Nslow) and directly reflects the degree of protein folding and structure in lyophilized formulations. Stable photolytic labeling does not undergo back-exchange, an advantage over ssHDX-MS. Here, we provide detailed protocols for both ssHDX-MS and ssPL-MS, using myoglobin (Mb) as a model protein in lyophilized formulations containing either trehalose or sorbitol. PMID:25938927

  3. An Effective Deuterium Exchange Method for Neutron Crystal Structure Analysis with Unfolding-Refolding Processes.

    PubMed

    Kita, Akiko; Morimoto, Yukio

    2016-02-01

    A method of hydrogen/deuterium (H/D) exchange with an unfolding-refolding process has been applied to hen egg-white lysozyme (HWL), and accurate evaluation of its deuteration was carried out by time-of-flight mass spectroscopy. Neutron crystallography requires a suitable crystal with enough deuterium exchanged in the protein to decrease incoherent scattering from hydrogens. It is very expensive to prepare a fully deuterated protein, and therefore a simple H/D exchange technique is desirable for this purpose. Acid or base addition to protein solutions with heating effectively increased the number of deuterium up to more than 20 % of that of all hydrogen atoms, and refolded structures were determined by X-ray structure analysis at 1.8 Å resolution. Refolded HWL had increased deuterium content in its protein core and its native structure, determined at atomic resolution, was fully preserved. PMID:26718545

  4. Ion temperatures in HIP-1 and SUMMA from charge-exchange neutral optical emission spectra

    NASA Technical Reports Server (NTRS)

    Patch, R. W.; Lauver, M. R.

    1976-01-01

    Ion temperatures were obtained from observations of the H sub alpha, D sub alpha, and He 587.6 nm lines emitted from hydrogen, deuterium, and helium plasmas in the SUMMA and HIP-1 mirror devices at Lewis Research Center. Steady state discharges were formed by applying a radially inward dc electric field between cylindrical or annular anodes and hollow cathodes located at the peaks of the mirrors. The ion temperatures were found from the Doppler broadening of the charge-exchange components of spectral lines. A statistical method was developed for obtaining scaling relations of ion temperature as a function of current, voltage, and magnetic flux density. Derivations are given that take into account triangular monochromator slit functions, loss cones, and superimposed charge-exchange processes. In addition, the Doppler broadening was found to be sensitive to the influence of drift on charge-exchange cross section. The effects of finite ion-cyclotron radius, cascading, and delayed emission are reviewed.

  5. Cation exchange pretreatment studies for high recovery - Yuma desalting plant

    SciTech Connect

    Kaakinen, J.W.; Laverty, P.E.

    1983-10-01

    The main purpose of the High Recovery Test Program was to obtain feasibility design data for cation exchange softening to allow a greater fractional recovery of desalted product water at the YDP(Yuma Desalting Plant). Compared to the original YDP design with 70-percent desalting recovery, additional removal of calcium in the desalting feed would allow recoveries over 90 percent. Pilot plant equipment to test this process was operated at the YDTF(Yuma Desalting Test Facility) and consisted of an IX unit and an electrodialyzer to supply reject-brine regenerant for the IX experiments. Gypsum scale buildup in the resin bed could be avoided by regeneration with a high upward flow rate causing a fluidized bed. Reuse of regenerant was also beneficial. Results show that the ion exchange high recovery pretreatment process is highly feasible, and that it is technically possible to achieve high recovery in the YDP. Numerous recommendations for a plant design are given and future studies are noted.

  6. Protein structural dynamics at the gas/water interface examined by hydrogen exchange mass spectrometry.

    PubMed

    Xiao, Yiming; Konermann, Lars

    2015-08-01

    Gas/water interfaces (such as air bubbles or foam) are detrimental to the stability of proteins, often causing aggregation. This represents a potential problem for industrial processes, for example, the production and handling of protein drugs. Proteins possess surfactant-like properties, resulting in a high affinity for gas/water interfaces. The tendency of previously buried nonpolar residues to maximize contact with the gas phase can cause significant structural distortion. Most earlier studies in this area employed spectroscopic tools that could only provide limited information. Here we use hydrogen/deuterium exchange (HDX) mass spectrometry (MS) for probing the conformational dynamics of the model protein myoglobin (Mb) in the presence of N(2) bubbles. HDX/MS relies on the principle that unfolded and/or highly dynamic regions undergo faster deuteration than tightly folded segments. In bubble-free solution Mb displays EX2 behavior, reflecting the occurrence of short-lived excursions to partially unfolded conformers. A dramatically different behavior is seen in the presence of N(2) bubbles; EX2 dynamics still take place, but in addition the protein shows EX1 behavior. The latter results from interconversion of the native state with conformers that are globally unfolded and long-lived. These unfolded species likely correspond to Mb that is adsorbed to the surface of gas bubbles. N(2) sparging also induces aggregation. To explain the observed behavior we propose a simple model, that is, "semi-unfolded" ↔ "native" ↔ "globally unfolded" → "aggregated". This model quantitatively reproduces the experimentally observed kinetics. To the best of our knowledge, the current study marks the first exploration of surface denaturation phenomena by HDX/MS. PMID:25761782

  7. Protein structural dynamics at the gas/water interface examined by hydrogen exchange mass spectrometry

    PubMed Central

    Xiao, Yiming; Konermann, Lars

    2015-01-01

    Gas/water interfaces (such as air bubbles or foam) are detrimental to the stability of proteins, often causing aggregation. This represents a potential problem for industrial processes, for example, the production and handling of protein drugs. Proteins possess surfactant-like properties, resulting in a high affinity for gas/water interfaces. The tendency of previously buried nonpolar residues to maximize contact with the gas phase can cause significant structural distortion. Most earlier studies in this area employed spectroscopic tools that could only provide limited information. Here we use hydrogen/deuterium exchange (HDX) mass spectrometry (MS) for probing the conformational dynamics of the model protein myoglobin (Mb) in the presence of N2 bubbles. HDX/MS relies on the principle that unfolded and/or highly dynamic regions undergo faster deuteration than tightly folded segments. In bubble-free solution Mb displays EX2 behavior, reflecting the occurrence of short-lived excursions to partially unfolded conformers. A dramatically different behavior is seen in the presence of N2 bubbles; EX2 dynamics still take place, but in addition the protein shows EX1 behavior. The latter results from interconversion of the native state with conformers that are globally unfolded and long-lived. These unfolded species likely correspond to Mb that is adsorbed to the surface of gas bubbles. N2 sparging also induces aggregation. To explain the observed behavior we propose a simple model, that is, “semi-unfolded” ↔ “native” ↔ “globally unfolded” → “aggregated”. This model quantitatively reproduces the experimentally observed kinetics. To the best of our knowledge, the current study marks the first exploration of surface denaturation phenomena by HDX/MS. PMID:25761782

  8. Interlayer diffusion studies of a Laves phase exchange spring superlattice

    NASA Astrophysics Data System (ADS)

    Wang, C.; Kohn, A.; Wang, S. G.; Ward, R. C. C.

    2011-03-01

    Rare earth Laves phase (RFe2) superlattice structures grown at different temperatures are studied using x-ray reflectivity (XRR), x-ray diffraction, and transmission electron microscopy. The optimized molecular beam epitaxy growth condition is matched with the XRR simulation, showing minimum diffusion/roughness at the interfaces. Electron microscopy characterization reveals that the epitaxial growth develops from initial 3D islands to a high quality superlattice structure. Under this optimum growth condition, chemical analysis by electron energy loss spectroscopy with high spatial resolution is used to study the interface. The analysis shows that the interface roughness is between 0.6 and 0.8 nm and there is no significant interlayer diffusion. The locally sharp interface found in this work explains the success of simple structural models in predicting the magnetic reversal behavior of Laves exchange spring superlattices.

  9. Monte Carlo study of double exchange interaction in manganese oxide

    SciTech Connect

    Naa, Christian Fredy; Suprijadi, Viridi, Sparisoma Djamal, Mitra; Fasquelle, Didier

    2015-09-30

    In this paper we study the magnetoresistance properties attributed by double exchange (DE) interaction in manganese oxide by Monte Carlo simulation. We construct a model based on mixed-valence Mn{sup 3+} and Mn{sup 4+} on the general system of Re{sub 2/3}Ae{sub 1/3}MnO{sub 3} in two dimensional system. The conduction mechanism is based on probability of e{sub g} electrons hopping from Mn{sup 3+} to Mn{sup 4+}. The resistivity dependence on temperature and the external magnetic field are presented and the validity with related experimental results are discussed. We use the resistivity power law to fit our data on metallic region and basic activated behavior on insulator region. On metallic region, we found our result agree well with the quantum theory of DE interaction. From general arguments, we found our simulation agree qualitatively with experimental results.

  10. Simulation of Dyadic Exchange: Proposal of a Method to Study Power in Family Relationships.

    ERIC Educational Resources Information Center

    Osmond, Marie W.; Martin, Patricia Y.

    "Reciprocity," a social simulation game based on exchange theory, was developed by the author to study the dynamics of power relationships in the context of marriage and the family. The simulation can be manipulated to test specific aspects of three major exchange formulations: Blau's social exchange formulation; Emerson's power-dependence…

  11. Technology Solutions Case Study: Foundation Heat Exchanger, Oak Ridge, Tennessee

    SciTech Connect

    2014-03-01

    The foundation heat exchanger, developed by Oak Ridge National Laboratory, is a new concept for a cost-effective horizontal ground heat exchanger that can be connected to water-to-water or water-to-air heat pump systems for space conditioning as well as domestic water heating.

  12. Observational Studies of Parameters Influencing Air-sea Gas Exchange

    NASA Astrophysics Data System (ADS)

    Schimpf, U.; Frew, N. M.; Bock, E. J.; Hara, T.; Garbe, C. S.; Jaehne, B.

    A physically-based modeling of the air-sea gas transfer that can be used to predict the gas transfer rates with sufficient accuracy as a function of micrometeorological parameters is still lacking. State of the art are still simple gas transfer rate/wind speed relationships. Previous measurements from Coastal Ocean Experiment in the Atlantic revealed positive correlations between mean square slope, near surface turbulent dis- sipation, and wind stress. It also demonstrated a strong negative correlation between mean square slope and the fluorescence of surface-enriched colored dissolved organic matter. Using heat as a proxy tracer for gases the exchange process at the air/water interface and the micro turbulence at the water surface can be investigated. The anal- ysis of infrared image sequences allow the determination of the net heat flux at the ocean surface, the temperature gradient across the air/sea interface and thus the heat transfer velocity and gas transfer velocity respectively. Laboratory studies were carried out in the new Heidelberg wind-wave facility AELOTRON. Direct measurements of the Schmidt number exponent were done in conjunction with classical mass balance methods to estimate the transfer velocity. The laboratory results allowed to validate the basic assumptions of the so called controlled flux technique by applying differ- ent tracers for the gas exchange in a large Schmidt number regime. Thus a modeling of the Schmidt number exponent is able to fill the gap between laboratory and field measurements field. Both, the results from the laboratory and the field measurements should be able to give a further understanding of the mechanisms controlling the trans- port processes across the aqueous boundary layer and to relate the forcing functions to parameters measured by remote sensing.

  13. Monte Carlo study on exchange bias and coercivity properties in coupled ferromagnetic/antiferromagnetic films

    NASA Astrophysics Data System (ADS)

    Jiang, Liqin; Shen, Shuangjuan; Zhang, Jian-Min; Feng, Qian; Huang, Zhigao

    2015-12-01

    Based on Monte Carlo simulation, a model consisting of an antiferromagnetic (AFM) film coupled to a ferromagnetic (FM) film is developed to study the exchange bias and coercivity phenomenon. It is suggested that exchange bias is a consequence of exchange coupling in the AFM/FM interface, and the AFM anisotropy needs to have a threshold value for the occurrence of exchange bias. Simultaneously, exchange bias and coercivity as functions of the value of anisotropy, exchange coupling and film thickness are studied. By inducing a thickness dependence of the anisotropy in FM film, the coercivity can be reduced or enhanced by choosing suitable magnetic parameters, which can better account for the discrepancies found in previous studies. The results also provide evidence for the absence of a direct correlation between coercivity and exchange bias, which is in agreement with other studies.

  14. Study on heat transfer of heat exchangers in the Stirling engine - Performance of heat exchangers in the test Stirling engine

    NASA Astrophysics Data System (ADS)

    Kanzaka, Mitsuo; Iwabuchi, Makio

    1992-11-01

    The heat transfer performance of the actual heat exchangers obtained from the experimental results of the test Stirling engine is presented. The heater for the test engine has 120 heat transfer tubes that consist of a bare-tube part and a fin-tube part. These tubes are located around the combustion chamber and heated by the combustion gas. The cooler is the shell-and-tube-type heat exchanger and is chilled by water. It is shown that the experimental results of heat transfer performance of the heater and cooler of the test Stirling engine are in good agreement with the results calculated by the correlation proposed in our previous heat transfer study under the periodically reversing flow condition. Our correlation is thus confirmed to be applicable to the evaluation of the heat transfer coefficient and the thermal design of the heat exchangers in the Stirling engine.

  15. Study of transient behavior of finned coil heat exchangers

    NASA Technical Reports Server (NTRS)

    Rooke, S. P.; Elissa, M. G.

    1993-01-01

    The status of research on the transient behavior of finned coil cross-flow heat exchangers using single phase fluids is reviewed. Applications with available analytical or numerical solutions are discussed. Investigation of water-to-air type cross-flow finned tube heat exchangers is examined through the use of simplified governing equations and an up-wind finite difference scheme. The degenerate case of zero air-side capacitance rate is compared with available exact solution. Generalization of the numerical model is discussed for application to multi-row multi-circuit heat exchangers.

  16. Using satellite data for soil cation exchange capacity studies

    NASA Astrophysics Data System (ADS)

    Ghaemi, M.; Astaraei, A. R.; Sanaeinejad, S. H.; Zare, H.

    2013-12-01

    This study was planned to examine the use of LandSat ETM+ images to develop a model for monitoring spatial variability of soil cation exchange capacity in a semi-arid area of Neyshaboor. 300 field data were collected from specific GPS registered points, 277 of which were error free, to be analysed in the soil laboratory.The statistical analysis showed that therewas a small R-Squared value, 0.17, when we used the whole data set. Visual interpretation of the graphs showed a trend among some of the data in the data set. Forty points were filtered based on the trends, and the statistical analysis was repeated for those data. It was discovered that the 40 series were more or less in the same environmental conditions; most of them were located in disturbed soils or abandoned lands with sparse vegetation cover. The soil was classified into high and medium salinity, with variable carbon (1.0 to 1.6%), heavy textured and with high silt and clay. Finally it was concluded that two different models could be fitted in the data based on their spatial dependency. The current models are able to explain spatial variability in almost 45 to 65% of the cases.

  17. Analytical Study on Thermal and Mechanical Design of Printed Circuit Heat Exchanger

    SciTech Connect

    Su-Jong Yoon; Piyush Sabharwall; Eung-Soo Kim

    2013-09-01

    The analytical methodologies for the thermal design, mechanical design and cost estimation of printed circuit heat exchanger are presented in this study. In this study, three flow arrangements of parallel flow, countercurrent flow and crossflow are taken into account. For each flow arrangement, the analytical solution of temperature profile of heat exchanger is introduced. The size and cost of printed circuit heat exchangers for advanced small modular reactors, which employ various coolants such as sodium, molten salts, helium, and water, are also presented.

  18. The Economic Aspect of the Exchange of Duplicates. Time Studies on Books. A Case Study.

    ERIC Educational Resources Information Center

    Ejlersen, Rita

    This report of a 10-month study performed at the Institut Danois des Echanges Internationaux de Publications Scientifiques et Litteraires (IDE) on its exchange program for duplicate monographs provides an analysis of the working methods and time spent on the various phases, i.e., acquisition, processing, and distribution. The major function of the…

  19. Experimental Studies on Coherent Synchrotron Radiation at an Emittance Exchange Beamline

    SciTech Connect

    Thangaraj, J.C.T.; Thurman-Keup, R.; Ruan, J.; Johnson, A.S.; Lumpkin, A.H.; Santucci, J.; /Fermilab

    2012-04-01

    One of the goals of the Fermilab A0 photoinjector is to experimentally investigate the transverse to longitudinal emittance exchange (EEX) principle. Coherent synchrotron radiation in the emittance exchange line could limit the performance of the emittance exchanger at short bunch lengths. In this paper, we present experimental and simulation studies of the coherent synchrotron radiation (CSR) in the emittance exchange line at the A0 photoinjector. We report on time-resolved CSR studies using a skew-quadrupole technique. We also demonstrate the advantages of running the EEX with an energy chirped beam.

  20. Magnetic exchange coupling through superconductors: A trilayer study

    NASA Astrophysics Data System (ADS)

    Sá de Melo, C. A.

    2000-11-01

    The possibility of magnetic exchange coupling between two ferromagnets (F) separated by a superconductor (S) spacer is analyzed using the functional integral method. For this coupling to occur three prima facie conditions need to be satisfied. First, an indirect exchange coupling between the ferromagnets must exist when the superconductor is in its normal state. Second, superconductivity must not be destroyed due to the proximity to ferromagnetic boundaries. Third, roughness of the F/S interfaces must be small. Under these conditions, when the superconductor is cooled to below its critical temperature, the magnetic coupling changes. The appearance of the superconducting gap introduces a new length scale (the coherence length of the superconductor) and modifies the temperature dependence of the indirect exchange coupling existent in the normal state. The magnetic coupling is oscillatory both above and below the the critical temperature of the superconductor, as well as strongly temperature-dependent. However, at low temperatures the indirect exchange coupling decay length is controlled by the coherence length of the superconductor, while at temperatures close to and above the critical temperature of the superconductor the magnetic coupling decay length is controlled by the thermal length.

  1. Analytical Study on Multi-stream Heat Exchanger Include Longitudinal Heat Conduction and Parasitic Heat Loads

    NASA Astrophysics Data System (ADS)

    Zhu, Weiping; Xie, Xiujuan; Yang, Huihui; Li, Laifeng; Gong, Linghui

    High performance heat exchangers are critical component in many cryogenic systems and its performance is typically very sensitive to longitudinal heat conduction, parasitic heat loads and property variations. This paper gives an analytical study on 1-D model for multi-stream parallel-plate fin heat exchanger by using the method of decoupling transformations. The results obtained in the present paper are valuable for the reference on optimization for heat exchanger design.

  2. 77 FR 48491 - Regulatory New Drug Review: Solutions for Study Data Exchange Standards; Notice of Meeting...

    Federal Register 2010, 2011, 2012, 2013, 2014

    2012-08-14

    ... members of the public regarding the advantages and disadvantages of current and emerging open, consensus... Architecture) be a viable study data exchange standard? Please explain advantages and disadvantages. What would... a viable study data exchange standard? Please explain advantages and disadvantages. What would...

  3. Experimental Study of Coherent Synchrotron Radiation in the Emittance Exchange Line at the A0-Photoinjector

    NASA Astrophysics Data System (ADS)

    Thangaraj, Jayakar C. T.; Thurman-Keup, R.; Johnson, A.; Lumpkin, A. H.; Edwards, H.; Ruan, J.; Santucci, J.; Sun, Y. E.; Church, M.; Piot, P.

    2010-11-01

    Next generation accelerators will require a high current, low emittance beam with a low energy spread. Such accelerators will employ advanced beam conditioning systems such as emittance exchangers to manipulate high brightness beams. One of the goals of the Fermilab A0 photoinjector is to investigate the transverse to longitudinal emittance exchange principle. Coherent synchrotron radiation could limit high current operation of the emittance exchanger. In this paper, we report on the preliminary experimental and simulation study of the coherent synchroton radiation (CSR) in the emittance exchange line at the A0 photoinjector.

  4. Feasibility Study of Secondary Heat Exchanger Concepts for the Advanced High Temperature Reactor

    SciTech Connect

    Piyush Sabharwall

    2011-09-01

    The work reported herein represents a significant step in the preliminary design of heat exchanger options (material options, thermal design, selection and evaluation methodology with existing challenges). The primary purpose of this study is to aid in the development and selection of the required heat exchanger for power production using either a subcritical or supercritical Rankine cycle.

  5. Effects of International Student Exchange on Pre-Service Teachers: A Quasi-Experimental Study

    ERIC Educational Resources Information Center

    Leutwyler, Bruno; Meierhans, Claudia

    2016-01-01

    This contribution provides empirical answers to the question of how teaching-specific competencies develop during participation in an international student exchange programme. The quantitative analyses of this quasi-experimental study suggest that, generally speaking, no specific developments occur during an exchange experience. These findings…

  6. HDX workbench: software for the analysis of H/D exchange MS data.

    PubMed

    Pascal, Bruce D; Willis, Scooter; Lauer, Janelle L; Landgraf, Rachelle R; West, Graham M; Marciano, David; Novick, Scott; Goswami, Devrishi; Chalmers, Michael J; Griffin, Patrick R

    2012-09-01

    Hydrogen/deuterium exchange mass spectrometry (HDX-MS) is an established method for the interrogation of protein conformation and dynamics. While the data analysis challenge of HDX-MS has been addressed by a number of software packages, new computational tools are needed to keep pace with the improved methods and throughput of this technique. To address these needs, we report an integrated desktop program titled HDX Workbench, which facilitates automation, management, visualization, and statistical cross-comparison of large HDX data sets. Using the software, validated data analysis can be achieved at the rate of generation. The application is available at the project home page http://hdx.florida.scripps.edu . PMID:22692830

  7. Molecular biological studies of the cardiac sodium-calcium exchanger.

    PubMed

    Kraev, A; Chumakov, I; Carafoli, E

    1996-04-15

    The intron-exon organization of the entire human Na-Ca-exchanger gene NCX1 and of the central part of the related gene NCX2 has been determined. The NCX1 gene is at least 75 kb long and consists of at least 12 exons, the two largest (the 2nd and the 12th) coding for the N-terminal half of the exchanger sequence and for the last three C-terminal transmembrane domains. They also code for the 3.3-kb 3'-untranslated region and account for more than 90% of the length of the mature mRNA. The remainder of the NCX1 (NCX2) gene, coding for a putative cytoplasmic regulatory domain, is split into 9 (7) small exons. In spite of the limited (65%) average homology of the two cDNAs, analogous exons are readily identified within this portion of the two genes based on their high (80-95%) pairwise homology and similar patterns of differential splicing in brain. Human YAC clones have been identified in the CEPH library, which contain the entire NCX1/2 and NCKX1 (retinal rod exchanger) genes, and are used for chromosomal localization of the three genes. A distant homolog of the mammalian NCX genes has been identified in the C. elegans EST database and has been completely sequenced. It encodes a 20% shorter protein, which has an average 55% homology to human NCX1, and lacks most of the region that is known to be encoded by multiple differentially spliced exons in vertebrates. Comparison of available data on the gene structure of the NCX homologs in various species suggests that this protein has emerged in the primitive nervous system and has been subsequently adapted to other cellular environments by the use of novel domains, encoded in additional exons. PMID:8659815

  8. Isotope dilution study of exchangeable oxygen in premium coal samples

    SciTech Connect

    Finseth, D.

    1987-01-01

    A difficulty with improving the ability to quantitate water in coal is that truly independent methods do not always exist. The true value of any analytical parameter is always easier to determine if totally independent methods exist to determine that parameter. This paper describes the possibility of using a simple isotope dilution technique to determine the water content of coal and presents a comparison of these isotope dilution measurements with classical results for the set of Argonne coals from the premium coal sample program. Isotope dilution is a widely used analytical method and has been applied to the analysis of water in matrices as diverse as chicken fat, living humans, and coal. Virtually all of these applications involved the use of deuterium as the diluted isotope. This poses some problems if the sample contains a significant amount of exchangeable organic hydrogen and one is interested in discriminating exchangeable organic hydrogen from water. This is a potential problem in the coal system. To avoid this potential problem /sup 18/O was used as the diluted isotope in this work.

  9. Continuation of Studies on Development of ODS Heat Exchanger Tubing

    SciTech Connect

    Lawrence Brown; David Workman; Bimal Kad; Gaylord Smith; Archie Robertson; Ian Wright

    2008-04-15

    The Department of Energy (DOE), National Energy Technology Center (NETL), has initiated a strategic plan for the development of advanced technologies needed to design and build fossil fuel plants with very high efficiency and environmental performance. These plants, referred to as 'Vision 21' and FutureGen programs by DOE, will produce electricity, chemicals, fuels, or a combination of these products, and possibly secondary products such as steam/heat for industrial use. MA956 is a prime candidate material being considered for a high temperature heat exchanger in the 'Vision 21' and FutureGen programs. This material is an oxide dispersion strengthened (ODS) alloy; however, there are some gaps in the data required to commit to the use of these alloys in a full-size plant. To fill the technology gaps for commercial production and use of the material for 'Advanced Power Generation Systems' this project has performed development activity to significant increase in circumferential strength of MA956 as compared to currently available material, investigated bonding technologies for bonding tube-to-tube joints through joining development, and performed tensile, creep and fire-side corrosion tests to validate the use and fabrication processes of MA956 to heat exchanger tubing applications. Development activities within this projected has demonstrated increased circumferential strength of MA956 tubes through flow form processing. Of the six fabrication technologies for bonding tube-to-tube joints, inertia friction welding (IFW) and flash butt welding (FBW) were identified as processes for joining MA956 tubes. Tensile, creep, and fire-side corrosion test data were generated for both base metal and weld joints. The data can be used for design of future systems employing MA956. Based upon the positive development activities, two test probes were designed and fabricated for field exposure testing at 1204 C ({approx}2200 F) flue gas. The probes contained tube portions with FBW

  10. Two-photon exchange effect studied with neural networks

    SciTech Connect

    Graczyk, Krzysztof M.

    2011-09-15

    An approach to the extraction of the two-photon exchange (TPE) correction from elastic ep scattering data is presented. The cross-section, polarization transfer (PT), and charge asymmetry data are considered. It is assumed that the TPE correction to the PT data is negligible. The form factors and TPE correcting term are given by one multidimensional function approximated by the feedforward neural network (NN). To find a model-independent approximation, the Bayesian framework for the NNs is adapted. A large number of different parametrizations is considered. The most optimal model is indicated by the Bayesian algorithm. The obtained fit of the TPE correction behaves linearly in {epsilon} but it has a nontrivial Q{sup 2} dependence. A strong dependence of the TPE fit on the choice of parametrization is observed.

  11. Study of thermal energy storage using fluidized bed heat exchangers

    NASA Technical Reports Server (NTRS)

    Weast, T. E.; Shannon, L. J.; Ananth, K. P.

    1980-01-01

    The technical and economic feasibility of fluid bed heat exchangers (FBHX) for thermal energy storage (TES) in waste heat recovery applications is assessed by analysis of two selected conceptual systems, the rotary cement kiln and the electric arc furnace. It is shown that the inclusion of TES in the energy recovery system requires that the difference in off-peak and on-peak energy rates be large enough so that the value of the recovered energy exceeds the value of the stored energy by a wide enough margin to offset parasitic power and thermal losses. Escalation of on-peak energy rates due to fuel shortages could make the FBHX/TES applications economically attractive in the future.

  12. Competing noncovalent host-guest interactions and H/D exchange: reactions of benzyloxycarbonyl-proline glycine dipeptide variants with ND3.

    PubMed

    Miladi, Mahsan; Olaitan, Abayomi D; Zekavat, Behrooz; Solouki, Touradj

    2015-11-01

    A combination of density functional theory calculations, hydrogen/deuterium exchange (HDX) reactions, ion mobility-mass spectrometry, and isotope labeling tandem mass spectrometry was used to study gas-phase "host-guest" type interactions of a benzyloxycarbonyl (Z)-capped proline (P) glycine (G) model dipeptide (i.e., Z-PG) and its various structural analogues with ND3. It is shown that in a solvent-free environment, structural differences between protonated and alkali metal ion (Na(+), K(+), or Cs(+))-complexed species of Z-PG affect ND3 adduct formation. Specifically, [Z-PG + H](+) and [Z-PG-OCH3 + H](+) formed gas-phase ND3 adducts ([Z-PG (or Z-PG-OCH3) + H + ND3](+)) but no ND3 adducts were observed for [Z-PG + alkali metal](+) or [Z-PG + H - CO2](+). Experimentally measured and theoretically calculated collision cross sections (CCSs) of protonated and alkali metal ion-complexed Z-PG species showed similar trends that agreed with the observed structural differences from molecular modeling results. Moreover, results from theoretical ND3 affinity calculations were consistent with experimental HDX observations, indicating a more stable ND3 adduct for [Z-PG + H](+) compared to [Z-PG + alkali metal](+) species. Molecular modeling and experimental MS results for [Z-PG + H](+) and [Z-PG + alkali metal](+) suggest that optimized cation-π and hydrogen bonding interactions of carbonyl groups in final products are important for ND3 adduct formation. Graphical Abstract ᅟ. PMID:26289383

  13. Numerical Study on Crossflow Printed Circuit Heat Exchanger for Advanced Small Modular Reactors

    SciTech Connect

    Yoon, Su-Jong; Sabharwall, Piyush; Kim, Eung-Soo

    2014-03-01

    Various fluids such as water, gases (helium), molten salts (FLiNaK, FLiBe) and liquid metal (sodium) are used as a coolant of advanced small modular reactors (SMRs). The printed circuit heat exchanger (PCHE) has been adopted as the intermediate and/or secondary heat exchanger of SMR systems because this heat exchanger is compact and effective. The size and cost of PCHE can be changed by the coolant type of each SMR. In this study, the crossflow PCHE analysis code for advanced small modular reactor has been developed for the thermal design and cost estimation of the heat exchanger. The analytical solution of single pass, both unmixed fluids crossflow heat exchanger model was employed to calculate a two dimensional temperature profile of a crossflow PCHE. The analytical solution of crossflow heat exchanger was simply implemented by using built in function of the MATLAB program. The effect of fluid property uncertainty on the calculation results was evaluated. In addition, the effect of heat transfer correlations on the calculated temperature profile was analyzed by taking into account possible combinations of primary and secondary coolants in the SMR systems. Size and cost of heat exchanger were evaluated for the given temperature requirement of each SMR.

  14. Multivalency in the gas phase: H/D exchange reactions unravel the dynamic "rock 'n' roll" motion in dendrimer-dendrimer complexes.

    PubMed

    Qi, Zhenhui; Schlaich, Christoph; Schalley, Christoph A

    2013-10-25

    Noncovalent dendrimer-dendrimer complexes were successfully ionized by electrospray ionization of partly protonated amino-terminated polypropylene amine (POPAM) and POPAM dendrimers fully functionalized with benzo[21]crown-7 on all branches. Hydrogen/deuterium exchange (HDX) experiments conducted on dendrimer-dendrimer complexes in the high vacuum of a mass spectrometer give rise to a complete exchange of all labile NH hydrogen atoms. As crown ethers represent noncovalent protective groups against HDX reactions on the ammonium group to which they are coordinated, this result provides evidence for a very dynamic binding situation: each crown is mobile enough to move from one ammonium binding site to another. Schematically, one might compare this motion with two rock 'n' roll dancers that swirl around each other without completely losing all contact at any time. Although the multivalent attachment certainly increases the overall affinity, the "microdynamics" of individual site binding and dissociation remains fast. PMID:24105808

  15. Advances and challenges in analytical characterization of biotechnology products: mass spectrometry-based approaches to study properties and behavior of protein therapeutics

    PubMed Central

    Kaltashov, Igor A.; Bobst, Cedric E.; Abzalimov, Rinat R.; Wang, Guanbo; Baykal, Burcu; Wang, Shunhai

    2011-01-01

    Biopharmaceuticals are a unique class of medicines due to their extreme structural complexity. The structure of these therapeutic proteins is critically important for their efficacy and safety, and the ability to characterize it at various levels (from sequence to conformation) is critical not only at the quality control stage, but also throughout the discovery and design stages. Biological mass spectrometry (MS) offers a variety of approaches to study structure and behavior of complex protein drugs and has already become a default tool for characterizing the covalent structure of protein therapeutics, including sequence and post-translational modifications. Recently, MS-based methods have also begun enjoying a dramatic growth in popularity as a means to provide information on higher order structure and dynamics of biotechnology products. In particular, hydrogen/deuterium exchange MS and charge state distribution analysis of protein ions in electrospray ionization (ESI)MS offer a convenient way to assess the integrity of protein conformation. Native ESI MS also allows the interactions of protein drugs with their therapeutic targets and other physiological partners to be monitored using simple model systems. MS-based methods are also applied to study pharmacokinetics of biopharmaceutical products, where they begin to rival traditional immunoassays. MS already provides valuable support to all stages of development of biopharmaceuticals, from discovery to post-approval monitoring, and its impact on the field of biopharmaceutical analysis will undoubtedly continue to grow. PMID:21619926

  16. Preliminary time-of-flight neutron diffraction studies of Escherichia coli ABC transport receptor phosphate-binding protein at the Protein Crystallography Station

    PubMed Central

    Sippel, K. H.; Bacik, J.; Quiocho, F. A.; Fisher, S. Z.

    2014-01-01

    Inorganic phosphate is an essential molecule for all known life. Organisms have developed many mechanisms to ensure an adequate supply, even in low-phosphate conditions. In prokaryotes phosphate transport is instigated by the phosphate-binding protein (PBP), the initial receptor for the ATP-binding cassette (ABC) phosphate transporter. In the crystal structure of the PBP–phosphate complex, the phosphate is completely desolvated and sequestered in a deep cleft and is bound by 13 hydrogen bonds: 12 to protein NH and OH donor groups and one to a carboxylate acceptor group. The carboxylate plays a key recognition role by accepting a phosphate hydrogen. PBP phosphate affinity is relatively consistent across a broad pH range, indicating the capacity to bind monobasic (H2PO4 −) and dibasic (HPO4 2−) phosphate; however, the mechanism by which it might accommodate the second hydrogen of monobasic phosphate is unclear. To answer this question, neutron diffraction studies were initiated. Large single crystals with a volume of 8 mm3 were grown and subjected to hydrogen/deuterium exchange. A 2.5 Å resolution data set was collected on the Protein Crystallography Station at the Los Alamos Neutron Science Center. Initial refinement of the neutron data shows significant nuclear density, and refinement is ongoing. This is the first report of a neutron study from this superfamily. PMID:24915101

  17. Contemporary approaches to studying and mapping of active water exchange zone of ground water

    NASA Astrophysics Data System (ADS)

    Moraru, C. Ye

    2016-03-01

    The article deals with a zone of ground water active exchange. New principles of the zone study and mapping under the platform hydrogeological condition are discussed. The assessment and distribution techniques are suggested for the active water exchange zone under the condition of hydrogeological parameterization uncertainty. The efficiency and significance of the suggested techniques are proved using the example of ground water in the southwest of Black Sea artesian basin.

  18. New data on Cu-exchanged phillipsite: a multi-methodological study

    NASA Astrophysics Data System (ADS)

    Gatta, G. Diego; Cappelletti, Piergiulio; de'Gennaro, Bruno; Rotiroti, Nicola; Langella, Alessio

    2015-10-01

    The cation exchange capacity of a natural phillipsite-rich sample from the Neapolitan Yellow Tuff, Southern Italy (treated in order to obtain a 95 wt% zeolite-rich sample composed mainly of phillipsite and minor chabazite) for Cu was evaluated using the batch exchange method. The sample had previously been exchanged into its monocationic form (Na), and then used for the equilibrium studies of the exchange reaction 2Na+ ⇆ Cu2+. Reversibility ion exchange tests were performed. The isotherm displays an evident hysteresis loop. Interestingly, the final Cu-exchanged polycrystalline material was green-bluish. Natural, Na- and Cu-exchanged forms were analyzed by X-ray powder diffraction, and the Cu-phillipsite was also investigated by transmission electron microscopy (TEM). Structure refinement of Cu-phillipsite was performed by the Rietveld method using synchrotron data, and it indicates a small, but significant, fraction of Cu sharing with Na two-three independent extra-framework sites. The TEM experiment shows sub-spherical nano-clusters of crystalline species (with average size of 5 nm) lying on the surfaces of zeolite crystals or dispersed in the amorphous fraction, with electron diffraction patterns corresponding to those of CuO (tenorite-like structure) and Cu(OH)2 (spertiniite-like structure). X-ray and TEM investigations show that Cu is mainly concentrated in different species (crystalline or amorphous) within the sample, not only in phillipsite. The experimental findings based on X-ray and TEM investigations, along with the hysteresis loop of the ion exchange tests, are discussed and some general considerations about the mechanisms of exchange reactions involving divalent cations with high hydration energy are provided.

  19. In situ NRA study of hydrogen isotope exchange in self-ion damaged tungsten exposed to neutral atoms

    NASA Astrophysics Data System (ADS)

    Markelj, S.; Založnik, A.; Schwarz-Selinger, T.; Ogorodnikova, O. V.; Vavpetič, P.; Pelicon, P.; Čadež, I.

    2016-02-01

    Isotope exchange was studied in-situ by Nuclear Reaction Analysis in the bulk of self-ion damaged tungsten at 600 K. Both variations of isotope exchange of H by D and of D by H were measured. The deuterium isothermal desorption was also studied and evaluated in order to be able to resolve the self-desorption from the isotope exchange at 600 K. The isotope exchange was also studied on the surface by Elastic Recoil Detection Analysis at 480 K and 380 K. The exchange mechanism was effective both on the surface and in the bulk of damaged tungsten. A simple model was introduced to describe the exchange efficiency on the surface and in the bulk obtaining the exchange cross sections on the surface and in bulk. In both cases an isotope effect was observed, where the exchange of H atoms by D atoms was more efficient than for the reverse sequence.

  20. Coming to Canada to Study: Factors that Influence Student's Decisions to Participate in International Exchange

    ERIC Educational Resources Information Center

    Massey, Jennifer; Burrow, Jeff

    2012-01-01

    Increasing numbers of students are participating in study abroad programs. Outcomes associated with these programs have been studied extensively, but relatively little is known about what motivates and influences students to participate. This study investigated factors that motivate and influence students to study on exchange and explored how…

  1. Brillouin light scattering study of spin waves in NiFe/Co exchange spring bilayer films

    SciTech Connect

    Haldar, Arabinda; Banerjee, Chandrima; Laha, Pinaki; Barman, Anjan

    2014-04-07

    Spin waves are investigated in Permalloy(Ni{sub 80}Fe{sub 20})/Cobalt(Co) exchange spring bilayer thin films using Brillouin light scattering (BLS) experiment. The magnetic hysteresis loops measured by magneto-optical Kerr effect show a monotonic decrease in coercivity of the bilayer films with increasing Py thickness. BLS study shows two distinct modes, which are modelled as Damon-Eshbach and perpendicular standing wave modes. Linewidths of the frequency peaks are found to increase significantly with decreasing Py layer thickness. Interfacial roughness causes to fluctuate exchange coupling at the nanoscale regimes and the effect is stronger for thinner Py films. A quantitative analysis of the magnon linewidths shows the presence of strong local exchange coupling field which is much larger compared to macroscopic exchange field.

  2. Teacher Exchanges: Teaching "Billy Budd" as Secondary School Social Studies.

    ERIC Educational Resources Information Center

    Allen, Rodney F.

    The question of why only English teachers and their students study Herman Melville's novel, "Billy Budd," is raised in this paper. The book offers insights and fundamental social questions for students in secondary school social studies. Suggestions are offered as to how social studies teachers (with their perspectives, concerns, and curriculum…

  3. Hydrogen isotope exchange experiments with Mt Mazama ash

    NASA Astrophysics Data System (ADS)

    Nolan, G. S.; Bindeman, I. N.; Palandri, J. L.

    2011-12-01

    minor (~20%) hydroxyl loss. 5) Native ash dried to <3% water and ~-145% ∂2H), and reacted with the 650 % prepared water evinces a much higher rate of 2H incorporation compared to rates with the native ash under all the same conditions. Given linearity of ∂2H exchange through time and modeling the reaction as (pseudo) first order in concentration of deuterium yields the following isotopic half life values: for 70° C 1.43 years, for 40° C 4.1 years, and for 25 °C 12.1 years. An Arrhenius treatment yields an activation energy of 32-38 kjoules. 6) A second order kinetic treatment can be used to follow the reaction. A calculation using the reaction constant k at 25 °C assuming native ash exposed to -60 % ∂2H water indicates it would take 2 years to rise from a starting value of -150 to approximately -100 % ∂2H. Results of these experiments put quantitative limits on reliability of ∂2H in ash in paleo-climate studies that are primarily controlled by the isotopic environments and temperatures. We hypothesize that hydrogen-deuterium exchange occurs in native ash exposed to isotopically labeled water. The effect is mediated through surface correlated water in addition to diffusion with both having a rate determining effect. There is nothing to suggest that deuterium-hydrogen exchange is selective for molecular or SiOH hydrogen in the ash.

  4. Russian studies of the safety of anion exchange in nitric acid

    SciTech Connect

    Hyder, M.L.; Bartenev, S.A.; Lazarev, L.N.

    1997-07-01

    Synthetic ion exchange resins came into use in the Soviet Union in the 1950`s, and domestic anion exchange resins based on quaternary amine groups have long been used in the Russian nuclear industry. These resins are similar to resins used in the West, and include pyridine-based resins, as well as the more conventional aryl polymers with substituted methyl amines. (Slide 1) The sensitivity of these amines to reaction with nitric acid and other oxidants has been a concern in Russia as in the West, and numerous laboratory studies have been conducted on the reactions involved. Several incidents involving pressure or temperature excursions have provided incentives for such studies. (Slide 2) This report briefly summarizes this work. A report by the Russian authors of this paper providing greater detail is to be issued as a U.S. Dept. of Energy document. Additionally, a second report by these authors, describing new studies on anion exchange resin safety, will also be issued as a DOE report. The separation of plutonium, neptunium, etc. from other materials by ion exchange requires rather strong nitric acid (6-8 M). In some systems, such as the processing of {sup 238}Pu, intense ionizing radiation may also be present during ion exchange separation. As a result, it is necessary to consider not only thermal hydrolysis and oxidation and their effects on the resin, but also radiolysis. All of these were investigated in the Russian studies.

  5. A time-resolved study on the interaction of oppositely charged bicelles--implications on the charged lipid exchange kinetics.

    PubMed

    Yang, Po-Wei; Lin, Tsang-Lang; Hu, Yuan; Jeng, U-Ser

    2015-03-21

    Time-resolved small-angle X-ray scattering was applied to study charged lipid exchange between oppositely charged disc-shaped bicelles. The exchange of charged lipids gradually reduces the surface charge density and weakens the electrostatic attraction between the oppositely charged bicelles which form alternately stacked aggregates upon mixing. Initially, at a high surface charge density with almost no free water layer between the stacked bicelles, fast exchange kinetics dominate the exchange process. At a later stage with a lower surface charge density and a larger water gap between the stacked bicelles, slow exchange kinetics take over. The fast exchange kinetics are correlated with the close contact of the bicelles when there is almost no free water layer between the tightly bound bicelles with a charged lipid exchange time constant as short as 20-40 min. When the water gap becomes large enough to have a free water layer between the stacked bicelles, the fast lipid exchange kinetics are taken over by slow lipid exchange kinetics with time constants around 200-300 min, which are comparable to the typical time constant of lipid exchange between vesicles in aqueous solution. These two kinds of exchange mode fit well with the lipid exchange models of transient hemifusion for the fast mode and monomer exchange for the slow mode. PMID:25649711

  6. Experimental study of a novel manifold structure of micro-channel heat exchanger

    NASA Astrophysics Data System (ADS)

    Xu, Bo; Xu, Kunhao; Wei, Wei; Han, Qing; Chen, Jiangping

    2013-07-01

    Refrigerant flow distribution with phase change heat transfer was experimentally studied for a micro-channel heat exchanger having horizontal headers. In order to solve the problem of maldistribution, a novel manifold structure with orifice and bypass tube was proposed and experimentally studied compared to the conventional structure. Tests were conducted with downward flow for mass flux from 70 to 110 kg m-2s-1 (air side flow velocity from 1 to 2ms-1). The surface temperature distribution of the heat exchanger recorded by thermal imager and the square deviation of it were used to judge the uniformity of flow distribution. It is shown that as mass flux increased, better flow distribution is obtained (small square deviation of temperature distribution means better flow distribution: conventional structure from 32 to 27, novel structure from 19 to 14), and flow distribution of the novel structure was much better than that of the conventional one. The heat transfer performances of the two heat exchangers were also studied. The cooling capacity of the novel heat exchanger was 14.8% higher than that of the conventional because of the better flow distribution. And the refrigerant pressure drop was 120% higher because of bigger mass flow and the resistance of the orifice. It's worth noting that the air pressure drop of novel heat exchanger was also higher (about 28.3%)than that of the conventional one, even when they have same fin and flat tube structure. From the pictures of the heat exchanger surfaces, it was found that some surface area of the conventional heat exchanger was not wet because of the low mass flow and high superheat, which leaded to a poor performance and relatively small air pressure drop.

  7. Modeling of temporal behavior of isotopic exchange between gaseous hydrogen and palladium hydride power

    SciTech Connect

    Melius, C F; Foltz, G W

    1987-01-01

    A parametric rate-equation model is described which depicts the time dependent behavior of the isotopic exchange process occurring between the solid and gas phases in gaseous hydrogen (deuterium) flows through packed-powder palladium deuteride (hydride) beds. The exchange mechanism is assumed to be rate-limited by processes taking place on the surface of the powder. The fundamental kinetic parameter of the model is the isotopic exchange probability, p, which is the probability that an isotopic exchange event occurs during a collision of a gas phase atom with the surface. Isotope effects between the gas and solid phases are explicitly included in terms of the isotope separation factor, ..cap alpha... Results of the model are compared with recent experimental measurements of isotope exchange in the ..beta..-phase hydrogen/palladium system and, using a literature value of ..cap alpha.. = 2.4, a good description of the experimental data is obtained for p approx. 10/sup -7/. In view of the importance of the isotope effects in the hydrogen/palladium system and the range of ..cap alpha.. values reported for the ..beta..-phase in the literature, the sensitivity of the model results to a variation in the value of ..cap alpha.. is examined.

  8. Web-Based Exchange of Views Enhances "Global Studies"

    ERIC Educational Resources Information Center

    Ahamer, Gilbert; Kumpfmuller, Karl A.; Hohenwarter, Michaela

    2011-01-01

    Purpose: The aim of this article is to present the development-oriented Master's curriculum "Global Studies" (GS) at the University of Graz, Austria, as an example of interdisciplinary academic training with the purpose of fostering inter-"cultural" understanding. It aims to show that scientific disciplines can be understood as "cultures of…

  9. Heat Exchanger Design Options and Tritium Transport Study for the VHTR System

    SciTech Connect

    Chang H. Oh; Eung S. Kim

    2008-09-01

    This report presents the results of a study conducted to consider heat exchanger options and tritium transport in a very high temperature reactor (VHTR) system for the Next Generation Nuclear Plant Project. The heat exchanger options include types, arrangements, channel patterns in printed circuit heat exchangers (PCHE), coolant flow direction, and pipe configuration in shell-and-tube designs. Study considerations include: three types of heat exchanger designs (PCHE, shell-and-tube, and helical coil); single- and two-stage unit arrangements; counter-current and cross flow configurations; and straight pipes and U-tube designs in shell-and-tube type heat exchangers. Thermal designs and simple stress analyses were performed to estimate the heat exchanger options, and the Finite Element Method was applied for more detailed calculations, especially for PCHE designs. Results of the options study show that the PCHE design has the smallest volume and heat transfer area, resulting in the least tritium permeation and greatest cost savings. It is theoretically the most reliable mechanically, leading to a longer lifetime. The two-stage heat exchanger arrangement appears to be safer and more cost effective. The recommended separation temperature between first and second stages in a serial configuration is 800oC, at which the high temperature unit is about one-half the size of the total heat exchanger core volume. Based on simplified stress analyses, the high temperature unit will need to be replaced two or three times during the plant’s lifetime. Stress analysis results recommend the off-set channel pattern configuration for the PCHE because stress reduction was estimated at up to 50% in this configuration, resulting in a longer lifetime. The tritium transport study resulted in the development of a tritium behavior analysis code using the MATLAB Simulink code. In parallel, the THYTAN code, previously performed by Ohashi and Sherman (2007) on the Peach Bottom data, was revived

  10. Quantitative Synthesis and Component Analysis of Single-Participant Studies on the Picture Exchange Communication System

    ERIC Educational Resources Information Center

    Tincani, Matt; Devis, Kathryn

    2011-01-01

    The "Picture Exchange Communication System" (PECS) has emerged as the augmentative communication intervention of choice for individuals with autism spectrum disorder (ASD), with a supporting body of single-participant studies. This report describes a meta-analysis of 16 single-participant studies on PECS with percentage of nonoverlapping data…

  11. A review of studies on ion thruster beam and charge-exchange plasmas

    NASA Technical Reports Server (NTRS)

    Carruth, M. R., Jr.

    1982-01-01

    Various experimental and analytical studies of the primary beam and charge-exchange plasmas of ion thrusters are reviewed. The history of plasma beam research is recounted, emphasizing experiments on beam neutralization, expansion of the beam, and determination of beam parameters such as electron temperature, plasma density, and plasma potential. The development of modern electron bombardment ion thrusters is treated, detailing experimental results. Studies on charge-exchange plasma are discussed, showing results such as the relationship between neutralizer emission current and plasma beam potential, ion energies as a function of neutralizer bias, charge-exchange ion current collected by an axially moving Faraday cup-RPA for 8-cm and 30-cm ion thrusters, beam density and potential data from a 15-cm ion thruster, and charge-exchange ion flow around a 30-cm thruster. A 20-cm thruster electrical configuration is depicted and facility effects are discussed. Finally, plasma modeling is covered in detail for plasma beam and charge-exchange plasma.

  12. Studies of Tropical/Mid-Latitude Exchange Using UARS Observations

    NASA Technical Reports Server (NTRS)

    Avallone, Linnea

    2001-01-01

    At the time this proposal was submitted, recent publications had suggested an important role for transport of midlatitude air into the tropical lower stratosphere. Most of these studies had employed data that gave only a time-averaged picture, making it difficult to determine the nature of the transport processes responsible for the observed behavior. We proposed to analyze observations of long-lived trace gases, such as nitric acid, methane, nitrous oxide, and chlorofluorocarbons, made from the Upper Atmosphere Research Satellite, to investigate the seasonal behavior of mixing between the midlatitudes and tropics. We planned to construct probability distributions of the concentrations of these species over small altitude ranges and to compare them to expectations based on modeled mean concentrations and knowledge of instrument precision. Differences from expectation were to be analyzed with respect to meteorological parameters to determine whether wave activity may have induced apparent mixing.

  13. Semi-Empirical Study of the Indirect Exchange Interaction in the Rem - Al System

    NASA Astrophysics Data System (ADS)

    Shakarov, Kh. O.

    2016-05-01

    The Ruderman-Kittel-Kasuya-Yosida exchange interaction (RKKY) is semi-empirically studied for the first time in compounds of binary REM - Al systems (REM - rare-earth metals: Gd, Dy, Ho, Er) using experimental values of paramagnetic Curie point (θp) of these compounds. Prediction of the RKKY theory was confirmed, i.e. there is a direct proportional dependence of θp value on de Gennes factor for equiatomic compounds of heavy REM with aluminum, just as in the case of pure REM. Values of the indirect exchange interaction parameter were semi-empirically estimated for the studied compounds. In general, it was established that RKKY-type exchange interaction is typical for REM compounds with aluminum, just as for pure REM.

  14. Benefits and problems of electronic information exchange as perceived by health care professionals: an interview study

    PubMed Central

    2011-01-01

    Background Various countries are currently implementing a national electronic patient record (n-EPR). Despite the assumed positive effects of n-EPRs, their overall adoption remains low and meets resistance from health care providers. This study aims to increase our understanding of health care providers' attitude towards the n-EPR, by investigating their perceptions of the benefits and problems of electronic information exchange in health care and the n-EPR in particular. Methods The study was conducted in three Dutch health care settings: acute care, diabetes care, and ambulatory mental health care. Two health care organisations were included per setting. Between January and June 2010, interviews were conducted with 17 stakeholders working in these organisations. Relevant themes were deduced by means of thematic qualitative analysis. Results Health care providers perceived electronic information exchange to promote the efficiency and quality of care. The problems they perceived in electronic information exchange mainly concerned the confidentiality and safety of information exchange and the reliability and quality of patient data. Many problems perceived by health care providers did not specifically apply to the n-EPR, but to electronic information exchange in general. Conclusions The implementation of the Dutch n-EPR has mainly followed a top-down approach, thereby neglecting the fact that the perceptions and preferences of its users (health care providers) need to be addressed in order to achieve successful implementation. The results of this study provide valuable suggestions about how to promote health care providers' willingness to adopt electronic information exchange, which can be useful for other countries currently implementing an n-EPR. Apart from providing information about the benefits and usefulness of electronic information exchange, efforts should be focused on minimising the problems as perceived by health care providers. The safety and

  15. Unfolding and aggregation of monoclonal antibodies on cation exchange columns: effects of resin type, load buffer, and protein stability.

    PubMed

    Guo, Jing; Carta, Giorgio

    2015-04-01

    The chromatographic behavior of a monoclonal antibody (mAb) that exhibits a pronounced two-peak elution behavior is studied for a range of strong cation exchange resins and with varying load buffer pH and composition. Six stationary phases are considered, including two tentacle-type resins (Fractogel EMD SO3-(M) and Eshmuno S), a resin with grafted polymeric surface extenders (Nuvia S), a resin with a bimodal pore size distribution (POROS HS 50), and two macroporous resins without polymer grafts (Source 30S and UNOsphere Rapid S). The two-peak elution behavior is very pronounced for the tentacle and polymer-grafted resins and for POROS HS 50, but is essentially absent for the two macroporous resins. The extent of this behavior decreases as the buffer pH and concentration increase and, consequently, mAb binding becomes weaker. Replacing sodium with arginine as the buffer counterion, which is expected to decrease the mAb binding strength, nearly completely eliminates the two-peak behavior, while replacing sodium with tetra-n-butylammonium hydroxide, which is expected to increase the mAb binding strength, dramatically exacerbate the effect. As shown by hydrogen-deuterium exchange mass spectrometry (HX-MS), the two-peak elution behavior is related to conformational changes that occur when the mAb binds. These changes result in increased solvent exposure of specific peptides in the Fc-region for either the Fractogel or the Nuvia resin. No significant conformational changes were seen by HX-MS when the mAb was bound to the UNOsphere resin or on the Fractogel resin when arginine was used in lieu of sodium as the load buffer counterion. Experiments with two additional mAbs on the Fractogel resin show that the two-peak elution behavior is dependent on the particular antibody. Circular dichroism suggests that the propensity of different mAbs to either precipitate directly or to form stabilizing intermolecular structures upon exposure to thermal stress can be related to their

  16. Using social exchange theory to guide successful study recruitment and retention.

    PubMed

    McGregor, Lisa; Parker, Karen; LeBlanc, Pamela; King, Kathryn M

    2010-01-01

    Participant attrition (withdrawal or loss after entering a study) is a major threat to the completion of valid studies. It can result in systematic error (selection bias), thus decreasing the statistical power of studies and limiting the generalisability of study findings. This paper demonstrates how key social exchange theory principles form the theoretical context for our practice, which, in turn enables us to form enduring relationships with study participants. PMID:20222281

  17. Transformations of metal species in ageing humic hydrocolloids studied by competitive ligand and metal exchange.

    PubMed

    Burba, Peter; Van den Bergh, Johan

    2004-03-01

    Transformations of metal species (particularly Al, Ca, Fe, Mg, Mn, Zn) in ageing humic hydrocolloids were studied, applying a competitive ligand and metal exchange approach. For this purpose, metal-containing hydrocolloids, freshly collected from humic-rich German bog lake waters (Hohlohsee (HO), Black Forest; Venner Moor (VM), Muensterland; Arnsberger Wald (AW), Northrhine-Westfalia) and conventionally pre-filtered through 0.45 microm membranes, were subjected on-site to an exchange with EDTA and Cu(II) ions, respectively, as a function of time. EDTA complexes gradually formed, metal fractions exchanged by Cu(II) (as well as free Cu(II) concentrations) were operationally discriminated by means of a small time-controlled tangential-flow ultrafiltration unit (nominal cutoff: 1 kDa). Metal and DOM (dissolved organic matter) fractions obtained this way were determined off-site using instrumental methods (AAS, ICP-OES, carbon analyzer). After weeks of storage, the collected hydrocolloids were studied again by this approach. The EDTA availability of colloid-bound metals (particularly Al and Fe) exhibited different ageing trends, dependent on the sample (VM: decrease of Fe availability (98-76%), HO: increase of Fe availability (76-82%)). In contrast, the Cu(II) exchange equilibria of colloid-bound metals revealed merely low availability of Al (16-38%) and Fe (5-11%) towards Cu(II) ions, also dependent on ageing effects. In particular, the conditional copper exchange constants Kex obtained from the exchange between Cu(II) ions and available metal species (such as Ca, Mg, Mn, Zn) exhibited a strong decrease (by a factor of 2-100) during sample storage, indicating considerable non-equilibria complexation of these metal ions in the original bogwaters studied on-site. PMID:15214428

  18. Density functional study on anisotropic magnetic exchange couplings in iron-based superconductors

    NASA Astrophysics Data System (ADS)

    Oh, Hyungju; Choi, Hyoung Joon

    2013-03-01

    Iron-based superconductors exhibit many different antiferromagnetically ordered ground states. An understanding of the magnetic exchange couplings and ground-state Hamiltonian in the parent compounds of these materials is important because such an information could be the basis to unveil the mechanism of unconventional superconductivity. By performing first-principles calculations of the electronic and magnetic properties with non-collinear spin configurations, we study the anisotropic magnetic exchange couplings in iron-based superconductors. We obtain magnetic excitations using the anisotropic magnetic exchange couplings, and compare the results with published inelastic neutron scattering data. This work was supported by the NRF of Korea (Grant No. 2011-0018306). Computational resources have been provided by KISTI Supercomputing Center (Project No. KSC-2012-C2-14).

  19. Semi-aerobic stabilized landfill leachate treatment by ion exchange resin: isotherm and kinetic study

    NASA Astrophysics Data System (ADS)

    Zamri, Mohd Faiz Muaz Ahmad; Kamaruddin, Mohamad Anuar; Yusoff, Mohd Suffian; Aziz, Hamidi Abdul; Foo, Keng Yuen

    2015-03-01

    This study was carried out to investigate the treatability of ion exchange resin (Indion MB 6 SR) for the removal of chromium (VI), aluminium (III), zinc (II), copper (II), iron (II), and phosphate (PO4)3-, chemical oxygen demand (COD), ammonia nitrogen (NH3-N) and colour from semi-aerobic stabilized leachate by batch test. A range of ion exchange resin dosage was tested towards the removal efficiency of leachate parameters. It was observed that equilibrium data were best represented by the Langmuir model for metal ions and Freundlich was ideally fit for COD, NH3-N and colour. Intra particle diffusion model, pseudo first-order and pseudo second-order isotherm models were found ideally fit with correlation of the experimental data. The findings revealed that the models could describe the ion exchange kinetic behaviour efficiently, which further suggests comprehensive outlook for the future research in this field.

  20. Development of a Direct Contact Heat Exchanger, Phase 1 Study Report

    NASA Technical Reports Server (NTRS)

    Manvi, R.

    1978-01-01

    Electric power generation from geothermal brine requires, first, bringing the hot brine to the surface and then converting the heat to electric power. Binary conversion schemes were proposed, with the heat transfer between the brine and the working organic fluid taking place in a conventional tube and shell heat exchanger. If the brine is heavily laden with dissolved solids, however, solids buildup on the heat exchanger surfaces leads to a considerable degree of fouling and an accompanying drop in performance is experienced. A possible solution to this problem is the use of a direct contact exchanger with the secondary fluid power cycle. The proposed concept involves the formation of fluid sheets and bells as heat angles. Results of a study concerning the fluid mechanics of such surfaces are given.

  1. DETERMINING CARBON ISOTOPE SIGNATURES FROM MICROMETEOROLOGICAL MEASUREMENTS: IMPLICATIONS FOR STUDYING BIOSPHERE-ATMOSPHERE EXCHANGE PROCESSES

    Technology Transfer Automated Retrieval System (TEKTRAN)

    In recent years considerable effort has been focused on combining micrometeorological and stable isotope techniques to elucidate and study biosphere-atmosphere exchange processes. At the ecosystem scale, these methods are increasingly being used to address a number of challenging problems, including...

  2. Multicultural Contacts in Education: A Case Study of an Exchange Project between Different Ethnic Groups

    ERIC Educational Resources Information Center

    Schuitema, Jaap; Veugelers, Wiel

    2011-01-01

    One important aim of citizenship education is learning to deal with cultural diversity. To this end, schools organise exchange projects to bring students into contact with different social and cultural groups. The aim of this study is to investigate the effects of intergroup contact in educational settings and to understand what the most…

  3. State Roundtable Case Studies: Idaho and South Dakota. Western Policy Exchange Project.

    ERIC Educational Resources Information Center

    Bender, Louis W.

    These two case studies were commissioned by the Western Interstate Commission for Higher Education (WICHE) as part of its Western Policy Exchange (WPE) Project, in an effort to understand the dynamics and perceived consequences of a "state roundtable" approach to fostering partnerships in education in order to advance systemic change and reforms…

  4. Research on Study Abroad, Mobility, and Student Exchange in Comparative Education Scholarship

    ERIC Educational Resources Information Center

    Streitwieser, Bernhard T.; Le, Emily; Rust, Val

    2012-01-01

    For many years there has been research on study abroad, student mobility and international student exchange; however in the last two decades the volume and scope of this work has increased significantly. There are now specific academic journals, a host of new books each year, expansive reports by international research organizations, and an…

  5. Interpersonal Exchanges in Discussion Forums: A Study of Learning Communities in Distance Learning Settings

    ERIC Educational Resources Information Center

    Scherer Bassani, Patricia B.

    2011-01-01

    Cooperative relationships are the foundation of a model of online learning based on communities. The development of a community depends on the interaction between community members. This study is based on the belief that the dynamics of exchange of thought, from a Piagetian perspective, are one possibility for understanding the process of…

  6. Further studies on vinamidinium salt amine exchange reactions, borohydride reductions and subsequent transformations

    PubMed Central

    Gupton, John T.; Telang, Nakul; Jia, Xin; Giglio, Benjamin C.; Eaton, James E.; Barelli, Peter J.; Hovaizi, Mona; Hall, Kayleigh E.; Welden, R. Scott; Keough, Matthew J.; Worrall, Eric F.; Finzel, Kara L.; Kluball, Emily J.; Kanters, Rene P.F.; Smith, Timothy M.; Smith, Stanton Q.; Nunes, Shane R.; Wright, Mathew T.; Birnstihl, Jennifer M.

    2010-01-01

    Studies directed at the amine exchange reaction of vinamidinium salts followed by sodium borohydride reduction to secondary and tertiary allylic amines are described. The tertiary allylic amines were alkylated and subjected to base mediated rearrangement to yield a variety of highly functionalized tertiary homoallylic amines. PMID:21113324

  7. Structural Studies of NH4-exchanged Natrolites at Ambient Conditions and High Temperature

    SciTech Connect

    Y Lee; D Seoung; Y Jang; J Bai; Y Lee

    2011-12-31

    with larger alkali metal cations such as the K-, Rb-, and Cs-forms. The dehydrated model of the fully NH{sub 4}-exchanged natrolite at 400 C is essentially same as the one reported previously from the sample prepared by direct melt exchange method using sodium-natrolite. Both the hydrated and dehydrated structures of the partially NH{sub 4}-exchanged natrolite at RT and at 400 C, respectively, are characterized by having two separate sites for the ammonium and potassium cations. Comparing the structural models of the monovalent cation forms studied so far, we find that the rotation angle of the natrolite chain is inversely proportional to the cation radius both in the hydrated and dehydrated phases. The distribution pattern of the non-framework species along the natrolite channel also seems to be related to the non-framework cation radius and hence to the chain rotation angle.

  8. Conformations of cationized linear oligosaccharides revealed by FTMS combined with in-ESI H/D exchange.

    PubMed

    Kostyukevich, Yury; Kononikhin, Alexey; Popov, Igor; Nikolaev, Eugene

    2015-10-01

    Previously (Kostyukevich et al. Anal Chem 2014, 86, 2595), we have reported that oligosaccharides anions are produced in the electrospray in two different conformations, which differ by the rate of gas phase hydrogen/deuterium (H/D) exchange reaction. In the present paper, we apply the in-electrospray ionization (ESI) source H/D exchange approach for the investigation of the oligosaccharides cations formed by attaching of metal ions (Na, K) to the molecule. It was observed that the formation of different conformers can be manipulated by varying the temperature of the desolvating capillary of the ESI interphase. Separation of the conformers was performed using gas phase H/D approach. Because the conformers have different rates of the H/D exchange reaction, the deuterium distribution spectrum becomes bimodal. It was found that the conformation corresponding to the slow H/D exchange rate dominates in the spectrum when the capillary temperature is low (~200 °C), and the conformation corresponding to the fast H/D exchange rate dominates at high (~400 °C) temperatures. In the intermediate temperature region, two conformers are present simultaneously. It was also observed that large oligosaccharide requires higher temperature for the formation of another conformer. It was found that the presence of the conformers considerably depends on the solvent used for ESI and the pH. We have compared these results with the previously performed in-ESI source H/D exchange experiments with peptides and proteins. PMID:26456784

  9. Conceptual study of in-tank cesium removal using an inorganic ion exchange material

    SciTech Connect

    Goheen, R.S.; Kurath, D.E.

    1996-04-01

    Presently, the Hanford Site contains approximately 230,000 m{sup 3} of mixed waste stored in 177 underground tanks. Approximately 55,000 m{sup 3} of this waste is sludge, 90,000 m{sup 3} is salt cake, and 80,000 m{sup 3} is supernate. Although the pretreatment and final disposal requirements for the waste have not been entirely defined, it is likely that some supernatant pretreatment will be required to remove {sup 137}Cs and possibly {sup 90}Sr and the transuranic components. The objective of this study was to estimate the number of HLW glass canisters resulting from the use of inorganic ion exchanger materials as in-tank pretreatment technology. The variables in the study were: number of contacts between waste and ion exchange material; ion exchange material; and decontamination requirement. This conceptual study investigates a generic in-tank Cs removal flowsheet using crystalline silico-titanates and IE-96 zeolites, and the impact of each ion exchanger on the number of glass canisters produced. In determining glass formulation, data based on current reference technology was used. Sample calculations from the worksheets and summaries of final calculated results are included at the end of this report.

  10. Lead exchange in teeth and bone--a pilot study using stable lead isotopes.

    PubMed Central

    Gulson, B L; Gillings, B R

    1997-01-01

    Stable lead isotopes and lead concentrations were measured in the enamel and dentine of permanent (n = 37) and deciduous teeth (n = 14) from 47 European immigrants to Australia to determine whether lead exchange occurs in teeth and how it relates to lead exchange in bone. Enamel exhibits no exchange of its European-origin lead with lead from the Australian environment. In contrast, dentine lead exchanges with Australian lead to the extent of approximately 1% per year. In one subject, trabecular bone from the tooth socket exchanged almost all its European lead with Australian lead over a a 15-year period (turnover of approximately 6% per year), similar to the approximately 8% per year proposed for lead turnover in trabecular bone. The repository characteristics of intact circumpulpal dentine were investigated by analyses of four sets of contiguous slices from six teeth: 1) a set consisting of slices with intact circumpulpal dentine and cementum; 2) a set in which these areas were removed; 3) another set consisting of slices with intact circumpulpal dentine and cementum; and 4) a set without cementum. These analyses show relatively small differences in isotopic composition between contiguous slices except that circumpulpal dentine appears to be the dominant control on lead concentration. There is a significant correlation (R2 = 0.19, p = 0.01, n = 34) of dentine lead concentration and rate of exchange with residence time from the country of origin and Australian lead, but there is no such correlation with enamel lead concentration. Analyses of permanent and deciduous teeth of subjects from other countries who have resided in Australia for varying lengths of time should resolve some of the questions arising from this pilot study. Images Figure 1. PMID:9347897

  11. Fragmentation of doubly-protonated peptide ion populations labeled by H/D exchange with CD3OD

    NASA Astrophysics Data System (ADS)

    Herrmann, Kristin A.; Kuppannan, Krishna; Wysocki, Vicki H.

    2006-03-01

    Doubly-protonated bradykinin (RPPGFSPFR) and an angiotensin III analogue (RVYIFPF) were subjected to hydrogen/deuterium (H/D) exchange with CD3OD in a Fourier transform ion cyclotron resonance (FT-ICR) mass spectrometer. A bimodal distribution of deuterium incorporation was present for bradykinin after H/D exchange for 90 s at a CD3OD pressure of 4 × 10-7 Torr, indicating the existence of at least two distinct populations. Bradykinin ion populations corresponding to 0-2 and 5-11 deuteriums (i.e., D0, D1, D2, D5, D6, D7, D8, D9, D10, and D11) were each monoisotopically selected and fragmented via sustained off-resonance irradiation (SORI) collision-induced dissociation (CID). The D0-D2 ion populations, which correspond to the slower exchanging population, consistently require lower SORI amplitude to achieve a similar precursor ion survival yield as the faster-reacting (D5-D11) populations. These results demonstrate that conformation/protonation motif has an effect on fragmentation efficiency for bradykinin. Also, the partitioning of the deuterium atoms into fragment ions suggests that the C-terminal arginine residue exchanges more rapidly than the N-terminal arginine. Total deuterium incorporation in the b1/y8 and b2/y7 ion pairs matches very closely the theoretical values for all ion populations studied, indicating that the ions of a complementary pair are likely formed during the same fragmentation event, or that no scrambling occurs upon SORI. Deuterium incorporation into the y1/a8 pseudo-ion pair does not closely match the expected theoretical values. The other peptide, doubly-protonated RVYIFPF, has a trimodal distribution of deuterium incorporation upon H/D exchange with CD3OD at a pressure of 1 × 10-7 Torr for 600 s, indicating at least three distinct ion populations. After 90 s of H/D exchange where at least two distinct populations are detected, the D0-D7 ion populations were monoisotopically selected and fragmented via SORI-CID over a range of SORI

  12. Gas-phase reactivity and molecular modeling studies on triply protonated dodecapeptides that contain four basic residues.

    PubMed

    Cassady, C J

    1998-07-01

    Gas-phase deprotonation and hydrogen/deuterium (H/D) exchange reactions for ions from three model dodecapeptides were studied by Fourier transform ion cyclotron resonance mass spectrometry. Molecular dynamics calculations were employed to provide information on conformations and Coulomb energies. The peptides, (KGG)4, (K2G4)2, and K4G8, each contain four high basicity lysine residues and eight low basicity glycine residues; however, in the present work only three lysine residues were protonated. Proton transfer reactions with a series of reference amines revealed apparent gas-phase acidities in a narrow range of 207.3-209.6 kcal/mol, with deprotonation efficiencies following the order [K4G8 + 3H]3+ > [(KGG)4 + 3H]3+ > [(K2G4)2 + 3H]3+. The three ions also react similarly with d4-methanol: each exchanged a maximum of 23-25 of their 25 labile hydrogens, with the first 15-17 exchanges occurring at rate constants of (1.6-2.6) x 10(-11) cm3 molecule-1 s-1. The experimental results agree with molecular modeling findings of similar conformations and Coulomb energies for the three peptide ions. The [M + 3H]3+ data are compared to data obtained previously in our laboratory for the "fully" protonated [M + 4H]4+ (Zhang, X.; Ewing, N. P.; Cassady, C. J. Int. J. Mass Spectrom. Ion Phys., in press). For (KGG)4 and (K2G4)2, there is a marked difference in H/D exchange reactivity between 3+ ions and 4+ ions. The 4+ ions, which have diffuse conformations, slowly exchange only 14 hydrogens, whereas their more compact 3+ counterparts exchange 23-25 hydrogens at a 5-times greater rate. In contrast, the 3+ and 4+ ions of K4G8 have similar compact conformations and exchange reactivity. The results indicate that a multiply hydrogen-bonded intermediate between the deuterating reagent and the peptide ion is necessary for facile H/D exchange. The slower, incomplete H/D exchange of [(KGG)4 + 4H]4+ and [(K2G4)2 + 4H]4+ is attributed to the inability of their protonated lysine n

  13. Beyond the Born Approximation: Two Photon Exchange in Nucleon Structure Studies

    NASA Astrophysics Data System (ADS)

    Averett, Todd

    2013-10-01

    Precision measurements of the electric form factor of the proton at Jefferson Lab have revealed a striking difference between Rosenbluth separation and polarization transfer data. Much of this discrepancy has been attributed to two-photon exchange, previously ignored in nucleon structure studies due to lack of precision in the data. Recently, experiments were conducted at Jefferson Lab where unpolarized electrons were scattered from neutrons polarized normal to the electron scattering plane. The polarized neutrons were produced by polarizing 3He nuclei using spin-exchange optical pumping. The single spin asymmetry for inclusive scattering, formed by flipping the target spin direction, is predicted to be exactly zero in the Born approximation by the Christ-Lee theorem. A non-zero asymmetry is an indication of contributions from two-photon exchange. This asymmetry provides a new tool to study the structure of the nucleon and to directly test models of two-photon exchange contributions. Results will be presented from measurements in the quasi-elastic and deep-inelastic regions.

  14. Metallurgical study of a failed heat exchanger in a H-coal/sup (R)/ pilot plant

    SciTech Connect

    Gray, R.J.; Keiser, J.R.; DeVan, J.H.; Searles, R.

    1982-01-01

    On September 20, 1980, operation of the pilot plant was interrupted when a heat exchanger (a reactor effluent vapor/steam thermo syphon reboiler) failed. Three alloy 800 (Fe-32Ni-21Cr) tubes in the bottom return section (cold end) of the heat exchanger blew out of the tubesheet. The system was shut down and a team of investigators began an intense study to determine the cause of the failure. Purpose of the investigation was to determine if the failure was an isolated incident, so that the affected tubes could be plugged and the system continue to operate, or if the failures were more generic so as to require corrective action. After careful examination of the fractured tubes by optical and scanning electron microscopy, a conclusion was made that stress corrosion cracking originating at the exterior surface was the cause of the failure. Other tubes were found that were approaching a state of failure. Photographs of the heat exchanger and photomicrographs of microstructures that supported this study are presented. As the result of the investigation, remedial steps were taken by the plant operator to return the heat exchanger to line operation.

  15. Kinetic Method for Hydrogen-Deuterium-Tritium Mixture Distillation Simulation

    SciTech Connect

    Sazonov, A.B.; Kagramanov, Z.G.; Magomedbekov, E.P.

    2005-07-15

    Simulation of hydrogen distillation plants requires mathematical procedures suitable for multicomponent systems. In most of the present-day simulation methods a distillation column is assumed to be composed of theoretical stages, or plates. However, in the case of a multicomponent mixture theoretical plate does not exist.An alternative kinetic method of simulation is depicted in the work. According to this method a system of mass-transfer differential equations is solved numerically. Mass-transfer coefficients are estimated with using experimental results and empirical equations.Developed method allows calculating the steady state of a distillation column as well as its any non-steady state when initial conditions are given. The results for steady states are compared with ones obtained via Thiele-Geddes theoretical stage technique and the necessity of using kinetic method is demonstrated. Examples of a column startup period and periodic distillation simulations are shown as well.

  16. Diode laser absorption spectroscopy for studies of gas exchange in fruits

    NASA Astrophysics Data System (ADS)

    Persson, L.; Gao, H.; Sjöholm, M.; Svanberg, S.

    2006-07-01

    Gas exchange in fruits, in particular oxygen transport in apples, was studied non-intrusively using wavelength modulation diode laser absorption spectroscopy at about 761 nm, applied to the strongly scattering intact fruit structure. The applicability of the technique was demonstrated by studies of the influence of the skin to regulate the internal oxygen balance and of cling film in modifying it by observing the response of the signal from the internal oxygen gas to a transient change in the ambient gas concentration. Applications within controlled atmosphere fruit storage and modified atmosphere packaging are discussed. The results suggest that the technique could be applied to studies of a large number of problems concerning gas exchange in foods and in food packaging.

  17. Parametric Sensivity Study of Operating and Design Variables in Wellbore Heat Exchangers

    SciTech Connect

    G. Michael Shook; Gopi Nalla; Gregory L. Mines; K. Kit Bloomfield

    2004-05-01

    This report documents the results of an extensive sensitivity study conducted by the Idaho National Engineering and Environmental Laboratory. This study investigated the effects of various operating and design parameters on wellbore heat exchanger performance to determine conditions for optimal thermal energy extraction and evaluate the potential for using a wellbore heat exchanger model for power generation. Variables studied included operational parameters such as circulation rates, wellbore geometries and working fluid properties, and regional properties including basal heat flux and formation rock type. Energy extraction is strongly affected by fluid residence time, heat transfer contact area, and formation thermal properties. Water appears to be the most appropriate working fluid. Aside from minimal tubing insulation, tubing properties are second order effects. On the basis of the sensitivity study, a best case model was simulated and the results compared against existing low-temperature power generation plants. Even assuming ideal work conversion to electric power, a wellbore heat exchange model cannot generate 200 kW (682.4e+3 BTU/h) at the onset of pseudosteady state. Using realistic conversion efficiency, the method is unlikely to generate 50 kW (170.6e+3 BTU/h).

  18. Parametric Sensitivity Study of Operating and Design Variables in Wellbore Heat Exchangers

    SciTech Connect

    Nalla, G.; Shook, G.M.; Mines, G.L.; Bloomfield, K.K.

    2004-05-01

    This report documents the results of an extensive sensitivity study conducted by the Idaho National Engineering and Environmental Laboratory. This study investigated the effects of various operating and design parameters on wellbore heat exchanger performance to determine conditions for optimal thermal energy extraction and evaluate the potential for using a wellbore heat exchanger model for power generation. Variables studied included operational parameters such as circulation rates, wellbore geometries and working fluid properties, and regional properties including basal heat flux and formation rock type. Energy extraction is strongly affected by fluid residence time, heat transfer contact area, and formation thermal properties. Water appears to be the most appropriate working fluid. Aside from minimal tubing insulation, tubing properties are second order effects. On the basis of the sensitivity study, a best case model was simulated and the results compared against existing low-temperature power generation plants. Even assuming ideal work conversion to electric power, a wellbore heat exchange model cannot generate 200 kW (682.4e+3 BTU/h) at the onset of pseudosteady state. Using realistic conversion efficiency, the method is unlikely to generate 50 kW (170.6e+3 BTU/h).

  19. Systematic modeling study of channel waveguide fabrication by thermal silver ion exchange.

    PubMed

    Li, Guangyu; Winick, Kim A; Griffin, Henry C; Hayden, Joseph S

    2006-03-10

    A systematic study of thermal silver ion exchange used for the fabrication of optical channel waveguides is reported in a single-alkali glass. The diffusion equilibrium and diffusion dynamics are experimentally studied, and the concentration-dependent diffusion coefficients are determined. The relationship between the fabrication conditions, i.e., time, temperature, and melt concentration, and the induced waveguide refractive index profile is established. It is demonstrated that the diffusion equation can be solved, without use of any free parameters, to predict the refractive index profiles of both planar and channel waveguides. A 1.6 cm diameter integrated optic ring resonator, with a propagation loss of 0.1 dB/cm, is fabricated in a glass by thermal silver ion exchange. The induced refractive index profile is related to the optical characteristics of the functional device. PMID:16572690

  20. Numerical study of a round tube heat exchanger with louvered fins and delta winglets

    NASA Astrophysics Data System (ADS)

    Huisseune, H.; T'Joen, C.; De Jaeger, P.; Ameel, B.; De Paepe, M.

    2012-11-01

    Louvered fin and round tube heat exchangers are widely used in air conditioning devices and heat pumps. In this study the effect of punching delta winglet vortex generators in the louvered fin surface is studied numerically. The delta winglets are located in a common-flow-down orientation behind each tube of the staggered tube layout. It is shown that the generated vortices significantly reduce the size of the tube wakes. Three important heat transfer enhancement mechanisms can be distinguished: a better flow mixing, boundary layer thinning and a delay in flow separation from the tube surface. The compound heat exchanger has a better thermal hydraulic performance then when only louvers or only delta winglets are used. Comparison to other enhanced fin designs clearly shows its potential, especially for low Reynolds number applications.

  1. Experimental study on corrugated cross-flow air-cooled plate heat exchangers

    SciTech Connect

    Kim, Minsung; Baik, Young-Jin; Park, Seong-Ryong; Ra, Ho-Sang; Lim, Hyug

    2010-11-15

    Experimental study on cross-flow air-cooled plate heat exchangers (PHEs) was performed. The two prototype PHEs were manufactured in a stack of single-wave plates and double-wave plates in parallel. Cooling air flows through the PHEs in a crosswise direction against internal cooling water. The heat exchanger aims to substitute open-loop cooling towers with closed-loop water circulation, which guarantees cleanliness and compactness. In this study, the prototype PHEs were tested in a laboratory scale experiments. From the tests, double-wave PHE shows approximately 50% enhanced heat transfer performance compared to single-wave PHE. However, double-wave PHE costs 30% additional pressure drop. For commercialization, a wide channel design for air flow would be essential for reliable performance. (author)

  2. Repeated Diagnostic Imaging Studies in Ontario and the Impact of Health Information Exchange Systems.

    PubMed

    Welk, Blayne; Liu, Kuan; Al-Jaishi, Ahmed; McArthur, Eric; Jain, Arsh K; Ordon, Michael

    2016-01-01

    Health information exchange systems can link the results of diagnostic imaging tests across hospitals and geographic areas. One of the potential benefits of these systems is a reduction in imaging studies ordered by physicians who do not know about or have access to the previous imaging results. We used administrative data from Ontario, Canada (from the year 2013), to measure how frequently the same cross-sectional imaging study is repeated in a patient. Overall, 12.8% of the specified imaging tests were repeated within 90 days. An area of Southwestern Ontario with a health information exchange system for diagnostic imaging tests had a 13% lower rate of repeat cross-sectional imaging compared with the rest of the province (11.2 vs 12.8%, p < 0.01). The use of linked radiology systems may be able to reduce the number of repeated imaging tests and improve patient safety and hospital efficiency. PMID:27133604

  3. Comparative study of key exchange and authentication methods in application, transport and network level security mechanisms

    NASA Astrophysics Data System (ADS)

    Fathirad, Iraj; Devlin, John; Jiang, Frank

    2012-09-01

    The key-exchange and authentication are two crucial elements of any network security mechanism. IPsec, SSL/TLS, PGP and S/MIME are well-known security approaches in providing security service to network, transport and application layers; these protocols use different methods (based on their requirements) to establish keying materials and authenticates key-negotiation and participated parties. This paper studies and compares the authenticated key negotiation methods in mentioned protocols.

  4. A pilot study of manual chronic partial exchange transfusion in children with sickle disease.

    PubMed

    Aloni, Michel Ntetani; Lê, Phu-Quoc; Heijmans, Catherine; Huybrechts, Sophie; Devalck, Christine; Azzi, Nadira; Ngalula-Mujinga, Malou; Ferster, Alina

    2015-06-01

    Objective Red cell exchange transfusion is frequently used in the management of patients with sickle cell disease (SCD) either electively or chronically to maintain hemoglobin S (HbS) <30%. The purpose of this retrospective study was to evaluate the results of manual chronic partial exchange transfusion (MCPET) on level of Hb and HbS, on iron load and on the need for chelation, on risk of immunization, monitoring transfusion-transmitted viral infection, and clinical outcome. Methods We reviewed the long-term effect of MCPET in 10 children (six men and four women) with SCD and evaluated the iron balance during a median follow-up of 20 months (range: 6-36) in which 248 exchanges were performed. Results The pre-exchange median Hb value was 9.5 g/dl (range: 7.7-10.9 g/dl) and the median post-exchange value was 9.4 g/dl (range: 8.4-11.1 g/dl).The majority of patients reached an HbS of <50% with a median HbS value of 40.04% (range: 30-54). At start of the MCPET program, the median ferritin was 439 ng/ml (range: 80-1704 ng/ml). In the final evaluation, the median value of ferritin was 531 ng/ml (range: 84-3840 ng/ml). The annual calculated iron balance was 0. 28 ± 0.08 mg/kg/day. MCPET was well tolerated, and adverse effects were limited. Discussion MCPET in children with SCD is safe to prevent iron overload, and is effective and easy to use in our cohort. Conclusion Indication for chronic exchange blood transfusion is essential for patients with SCD with recurrent and frequent crises who do not respond to hydroxyurea. However, there is no consensual study for the period at which chronic transfusion can safely be stopped and further research in large population of patients with SCD will need to clarify this question. PMID:25133935

  5. A Study of Jordanian University Students' Perceptions of Using Email Exchanges with Native English Keypals for Improving Their Writing Competency

    ERIC Educational Resources Information Center

    Mahfouz, Safi Mahmoud

    2010-01-01

    English foreign language learners generally tend to consider email exchanges with native speakers (NSs) as an effective tool for improving their foreign language proficiency. This study investigated Jordanian university students' perceptions of using email exchanges with native English keypals (NEKs) for improving their writing competency. A…

  6. Study by XPS of different conditioning processes to improve the cation exchange in clinoptilolite

    NASA Astrophysics Data System (ADS)

    Ruiz-Serrano, D.; Flores-Acosta, M.; Conde-Barajas, E.; Ramírez-Rosales, D.; Yáñez-Limón, J. M.; Ramírez-Bon, R.

    2010-09-01

    We report the X-ray photoelectron spectroscopy (XPS) analysis of natural clinoptilolite from a mine in Sonora, México. From these measurements we determined the chemical state and binding energy of the elements in the zeolite framework and of those in the extra framework sites. The analysis was done on natural clinoptilolite and on cation-exchanged clinoptilolites with Na + and NH4+ ions. Complementary analysis by several experimental techniques was performed to determine the structural, chemical composition and chemical state modifications experimented by clinoptilolite samples processed by the two types of cation exchange. The clinoptilolite samples were studied by X-ray powder diffraction (XRD) and Fourier transform infrared spectroscopy (FTIR) to determine their structural composition, Energy Dispersive Spectroscopy (EDS) to measure the chemical composition and electronic paramagnetic resonance (EPR) spectroscopy to determine the chemical state of iron inside the natural zeolites.

  7. Charge-exchange erosion studies of accelerator grids in ion thrusters

    NASA Technical Reports Server (NTRS)

    Peng, Xiaohang; Ruyten, Wilhelmus M.; Keefer, Dennis

    1993-01-01

    A particle simulation model is developed to study the charge-exchange grid erosion in ion thrusters for both ground-based and space-based operations. Because the neutral gas downstream from the accelerator grid is different for space and ground operation conditions, the charge-exchange erosion processes are also different. Based on an assumption of now electric potential hill downstream from the ion thruster, the calculations show that the accelerator grid erosion rate for space-based operating conditions should be significantly less than experimentally observed erosion rates from the ground-based tests conducted at NASA Lewis Research Center (LeRC) and NASA Jet Propulsion Laboratory (JPL). To resolve this erosion issue completely, we believe that it is necessary to accurately measure the entire electric potential field downstream from the thruster.

  8. Metallurgical study of a failed heat exchanger in a h-coal pilot plant

    SciTech Connect

    Gray, R.J.; Keiser, J.R.; DeVan, J.H.; Searles, R.

    1981-01-01

    The H-Coal Pilot Plant at Catlettsburg, Kentucky, is designed to process 600 tons of coal per day and produce synthetic fuels. On September 20, 1980, operation of the pilot plant was interrupted when a heat exchanger (a reactor effluent vapor/steam thermo syphon reboiler) failed. Three alloy 800 (Fe-32Ni-21Cr) tubes in the bottom return section (cold end) of the heat exchanger blew out of the tubesheet. The system was shut down and a team of investigators began an intense study. After examination of the fractured tubes by optical and scanning electron microscopy, a conclusion was made that stress corrosion cracking originating at the exterior surface was the cause of the failure. Other tubes were found that were approaching a state of failure. 11 figures.

  9. Engineering study for the treatment of spent ion exchange resin resulting from nuclear process applications

    SciTech Connect

    Place, B.G.

    1990-09-01

    This document is an engineering study of spent ion exchange resin treatment processes with the purpose of identifying one or more suitable treatment technologies. Classifications of waste considered include all classes of low-level waste (LLW), mixed LLW, transuranic (TRU) waste, and mixed TRU waste. A total of 29 process alternatives have been evaluated. Evaluation parameters have included economic parameters (both total life-cycle costs and capital costs), demonstrated operability, environmental permitting, operational availability, waste volume reduction, programmatic consistency, and multiple utilization. The results of this study suggest that there are a number of alternative process configurations that are suitable for the treatment of spent ion exchange resin. The determinative evaluation parameters were economic variables (total life-cycle cost or capital cost) and waste volume reduction. Immobilization processes are generally poor in volume reduction. Thermal volume reduction processes tend to have high capital costs. There are immobilization processes and thermal volume reduction processes that can treat all classifications of spent ion exchange resin likely to be encountered. 40 refs., 19 figs., 17 tabs.

  10. Computational Studies of Water-Exchange Rates around Aqueous Mg2+ and Be2+

    SciTech Connect

    Dang, Liem X.

    2014-12-18

    The water-exchange mechanisms occurring around aqueous divalent Mg2+ and Be2+ ions were studied using molecular dynamics simulations and rate theory methods. Properties associated with the water-exchange process, such as ion-water potentials of mean force, time-dependent transmission coefficients, and rate constants, were examined along with transition rate theory and the reactive flux method, which includes the role of solvent friction. The effects of pressure on water-exchange rates and activation volumes also were studied. The simulated activation volume values and mechanism were different for Mg2+ and Be2+ because of the nature of their solvation shells. We found the agreement with experiments was improved up on solvent effects were taken into account. The Division of Chemical Sciences, Geosciences, and Biosciences, Office of Basic Energy Sciences (BES), of the U.S. Department of Energy (DOE) funded this work. Battelle operates Pacific Northwest National Laboratory for DOE. The calculations were carried out using computer resources provided by BES.