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1

Thermodynamics of beta-sheet formation in polyglutamine.  

PubMed

The role of beta-sheets in the early stages of protein aggregation, specifically amyloid formation, remains unclear. Interpretations of kinetic data have led to a specific model for the role of beta-sheets in polyglutamine aggregation. According to this model, monomeric polyglutamine, which is intrinsically disordered, goes through a rare conversion into an ordered, metastable, beta-sheeted state that nucleates aggregation. It has also been proposed that the probability of forming the critical nucleus, a specific beta-sheet conformation for the monomer, increases with increasing chain length. Here, we test this model using molecular simulations. We quantified free energy profiles in terms of beta-content for monomeric polyglutamine as a function of chain length. In accord with estimates from experimental data, the free energy penalties for forming beta-rich states are in the 10-20 kcal/mol range. However, the length dependence of these free energy penalties does not mirror interpretations of kinetic data. In addition, although homodimerization of disordered molecules is spontaneous, the imposition of conformational restraints on polyglutamine molecules does not enhance the spontaneity of intermolecular associations. Our data lead to the proposal that beta-sheet formation is an attribute of peptide-rich phases such as high molecular weight aggregates rather than monomers or oligomers. PMID:19580768

Vitalis, Andreas; Lyle, Nicholas; Pappu, Rohit V

2009-07-01

2

Conformational diversity in prion protein variants influences intermolecular [beta]-sheet formation  

SciTech Connect

A conformational transition of normal cellular prion protein (PrP{sup C}) to its pathogenic form (PrP{sup Sc}) is believed to be a central event in the transmission of the devastating neurological diseases known as spongiform encephalopathies. The common methionine/valine polymorphism at residue 129 in the PrP influences disease susceptibility and phenotype. We report here seven crystal structures of human PrP variants: three of wild-type (WT) PrP containing V129, and four of the familial variants D178N and F198S, containing either M129 or V129. Comparison of these structures with each other and with previously published WT PrP structures containing M129 revealed that only WT PrPs were found to crystallize as domain-swapped dimers or closed monomers; the four mutant PrPs crystallized as non-swapped dimers. Three of the four mutant PrPs aligned to form intermolecular {beta}-sheets. Several regions of structural variability were identified, and analysis of their conformations provides an explanation for the structural features, which can influence the formation and conformation of intermolecular {beta}-sheets involving the M/V129 polymorphic residue.

Lee, Seungjoo; Antony, Lizamma; Hartmann, Rune; Knaus, Karen J.; Surewicz, Krystyna; Surewicz, Witold K.; Yee, Vivien C. (Case Western); (Cleveland Clinic)

2010-04-19

3

Sequence specificity, statistical potentials, and three-dimensional structure prediction with self-correcting distance geometry calculations of beta-sheet formation in proteins.  

PubMed

A statistical analysis of a representative data set of 169 known protein structures was used to analyze the specificity of residue interactions between spatial neighboring strands in beta-sheets. Pairwise potentials were derived from the frequency of residue pairs in nearest contact, second nearest and third nearest contacts across neighboring beta-strands compared to the expected frequency of residue pairs in a random model. A pseudo-energy function based on these statistical pairwise potentials recognized native beta-sheets among possible alternative pairings. The native pairing was found within the three lowest energies in 73% of the cases in the training data set and in 63% of beta-sheets in a test data set of 67 proteins, which were not part of the training set. The energy function was also used to detect tripeptides, which occur frequently in beta-sheets of native proteins. The majority of native partners of tripeptides were distributed in a low energy range. Self-correcting distance geometry (SECODG) calculations using distance constraints sets derived from possible low energy pairing of beta-strands uniquely identified the native pairing of the beta-sheet in pancreatic trypsin inhibitor (BPTI). These results will be useful for predicting the structure of proteins from their amino acid sequence as well as for the design of proteins containing beta-sheets. PMID:10048326

Zhu, H; Braun, W

1999-02-01

4

Amyloid Beta Mediates Memory Formation  

ERIC Educational Resources Information Center

The amyloid precursor protein (APP) undergoes sequential cleavages to generate various polypeptides, including the amyloid [beta] (1-42) peptide (A[beta][1-42]), which is believed to play a major role in amyloid plaque formation in Alzheimer's disease (AD). Here we provide evidence that, in contrast with its pathological role when accumulated,…

Garcia-Osta, Ana; Alberini, Cristina M.

2009-01-01

5

Preferential Cu2+ coordination by His96 and His111 induces beta-sheet formation in the unstructured amyloidogenic region of the prion protein.  

PubMed

The prion protein (PrP) is a Cu(2+) binding cell surface glycoprotein that can misfold into a beta-sheet-rich conformation to cause prion diseases. The majority of copper binding studies have concentrated on the octarepeat region of PrP. However, using a range of spectroscopic techniques, we show that copper binds preferentially to an unstructured region of PrP between residues 90 and 115, outside of the octarepeat domain. Comparison of recombinant PrP with PrP-(91-115) indicates that this prion fragment is a good model for Cu(2+) binding to the full-length protein. In contrast to previous reports we show that Cu(2+) binds to this region of PrP with a nanomolar dissociation constant. NMR and EPR spectroscopy indicate a square-planar or square-pyramidal Cu(2+) coordination utilizing histidine residues. Studies with PrP analogues show that the high affinity site requires both His(96) and His(111) as Cu(2+) ligands, rather than a complex centered on His(96) as has been previously suggested. Our circular dichroism studies indicate a loss of irregular structure on copper coordination with an increase in beta-sheet conformation. It has been shown that this unstructured region, between residues 90 and 120, is vital for prion propagation and different strains of prion disease have been linked with copper binding. The role of Cu(2+) in prion misfolding and disease must now be re-evaluated in the light of these findings. PMID:15145944

Jones, Christopher E; Abdelraheim, Salama R; Brown, David R; Viles, John H

2004-07-30

6

Beating the Heat - Fast Scanning Melts Silk Beta Sheet Crystals  

NASA Astrophysics Data System (ADS)

Beta-pleated-sheet crystals are among the most stable of protein secondary structures, and are responsible for the remarkable physical properties of many fibrous proteins, such as silk, or proteins forming plaques as in Alzheimer's disease. Previous thinking, and the accepted paradigm, was that beta-pleated-sheet crystals in the dry solid state were so stable they would not melt upon input of heat energy alone. Here we overturn that assumption and demonstrate that beta-pleated-sheet crystals melt directly from the solid state to become random coils, helices, and turns. We use fast scanning chip calorimetry at 2,000 K/s and report the first reversible thermal melting of protein beta-pleated-sheet crystals, exemplified by silk fibroin. The similarity between thermal melting behavior of lamellar crystals of synthetic polymers and beta-pleated-sheet crystals is confirmed. Significance for controlling beta-pleated-sheet content during thermal processing of biomaterials, as well as towards disease therapies, is envisioned based on these new findings.

Cebe, Peggy; Hu, Xiao; Kaplan, David L.; Zhuravlev, Evgeny; Wurm, Andreas; Arbeiter, Daniela; Schick, Christoph

2013-01-01

7

Beating the Heat - Fast Scanning Melts Silk Beta Sheet Crystals  

PubMed Central

Beta-pleated-sheet crystals are among the most stable of protein secondary structures, and are responsible for the remarkable physical properties of many fibrous proteins, such as silk, or proteins forming plaques as in Alzheimer's disease. Previous thinking, and the accepted paradigm, was that beta-pleated-sheet crystals in the dry solid state were so stable they would not melt upon input of heat energy alone. Here we overturn that assumption and demonstrate that beta-pleated-sheet crystals melt directly from the solid state to become random coils, helices, and turns. We use fast scanning chip calorimetry at 2,000?K/s and report the first reversible thermal melting of protein beta-pleated-sheet crystals, exemplified by silk fibroin. The similarity between thermal melting behavior of lamellar crystals of synthetic polymers and beta-pleated-sheet crystals is confirmed. Significance for controlling beta-pleated-sheet content during thermal processing of biomaterials, as well as towards disease therapies, is envisioned based on these new findings. PMID:23350037

Cebe, Peggy; Hu, Xiao; Kaplan, David L.; Zhuravlev, Evgeny; Wurm, Andreas; Arbeiter, Daniela; Schick, Christoph

2013-01-01

8

Cooperative deformation of hydrogen bonds in beta-strands and beta-sheet nanocrystals  

E-print Network

Beta-sheet protein domains are stabilized by weak hydrogen bonds, yet materials such as silk—whose ultimate tensile strength is controlled primarily by this secondary structure—can exceed the ultimate tensile strength of ...

Qin, Zhao

9

Evidence for Novel [beta]-Sheet Structures in Iowa Mutant [beta]-Amyloid Fibrils  

SciTech Connect

Asp23-to-Asn mutation within the coding sequence of {beta}-amyloid, called the Iowa mutation, is associated with early onset, familial Alzheimer's disease and cerebral amyloid angiopathy, in which patients develop neuritic plaques and massive vascular deposition predominantly of the mutant peptide. We examined the mutant peptide, D23N-A{beta}40, by electron microscopy, X-ray diffraction, and solid-state NMR spectroscopy. D23N-A{beta}40 forms fibrils considerably faster than the wild-type peptide (k = 3.77 x 10{sup -3} min{sup -1} and 1.07 x 10{sup -4} min{sup -1} for D23N-A{beta}40 and the wild-type peptide WT-A{beta}40, respectively) and without a lag phase. Electron microscopy shows that D23N-A{beta}40 forms fibrils with multiple morphologies. X-ray fiber diffraction shows a cross-{beta} pattern, with a sharp reflection at 4.7 {angstrom} and a broad reflection at 9.4 {angstrom}, which is notably smaller than the value for WT-A{beta}40 fibrils (10.4 {angstrom}). Solid-state NMR measurements indicate molecular level polymorphism of the fibrils, with only a minority of D23N-A{beta}40 fibrils containing the in-register, parallel {beta}-sheet structure commonly found in WT-A{beta}40 fibrils and most other amyloid fibrils. Antiparallel {beta}-sheet structures in the majority of fibrils are indicated by measurements of intermolecular distances through 13C-13C and 15N-13C dipole-dipole couplings. An intriguing possibility exists that there is a relationship between the aberrant structure of D23N-A{beta}40 fibrils and the unusual vasculotropic clinical picture in these patients.

Tycko, Robert; Sciarretta, Kimberly L.; Orgel, Joseph P.R.O.; Meredith, Stephen C.; (IIT); (NIH); (UC)

2009-07-24

10

Bayesian Models and Algorithms for Protein Beta-Sheet Prediction  

E-print Network

architecture, we significantly reduce the search space by heuristics that enforce the amino acid pairs, the interaction types of -strand segment pairs, and amino acid residue interactions also known as contact maps. As the fourth com- ponent of the -sheet formation, a contact map defines the amino acid pairs that make non

Erdogan, Hakan

11

Role of Polyalanine Domains in -Sheet Formation in Spider Silk Block Copolymers  

SciTech Connect

Genetically engineered spider silk-like block copolymers were studied to determine the influence of polyalanine domain size on secondary structure. The role of polyalanine block distribution on {beta}-sheet formation was explored using FT-IR and WAXS. The number of polyalanine blocks had a direct effect on the formation of crystalline {beta}-sheets, reflected in the change in crystallinity index as the blocks of polyalanines increased. WAXS analysis confirmed the crystalline nature of the sample with the largest number of polyalanine blocks. This approach provides a platform for further exploration of the role of specific amino acid chemistries in regulating the assembly of {beta}-sheet secondary structures, leading to options to regulate material properties through manipulation of this key component in spider silks.

Rabotyagova, O.; Cebe, P; Kaplan, D

2010-01-01

12

Events in the kinetic folding pathway of a small, all beta-sheet protein.  

PubMed

The folding of cardiotoxin analogue III (CTX III), a small (60 amino acids), all beta-sheet protein from the venom of the Taiwan Cobra (Naja naja atra) is here investigated. The folding kinetics is monitored by using a variety of techniques such as NMR, fluorescence, and circular dichroism spectroscopy. The folding of the protein is complete within a time scale of 200 ms. The earliest detectable event in the folding pathway of CTX III is the formation of a hydrophobic cluster, which possess strong affinity to bind to nonpolar dye such as 1-anilino-8-napthalene-sulfonic acid. Quenched-flow deuterium-hydrogen exchange experiments indicate that the segment spanning residues 51-55 along with Lys23, Ile39, Val49, Tyr51 and Val52 could constitute the "hydrophobic cluster." Folding kinetics of CTX III based on the amide-protection data reveals that the triple-stranded, antiparallel beta-sheet segment, which is located in the central core of the molecule, appears to fold faster than the double-stranded beta-sheet segment. PMID:9553067

Sivaraman, T; Kumar, T K; Chang, D K; Lin, W Y; Yu, C

1998-04-24

13

Microphase Separation Controlled Beta Sheet Crystallization Kinetics in Silk Fibroin Protein.  

NASA Astrophysics Data System (ADS)

We investigate the mechanism of isothermal crystallization kinetics of beta-sheet crystals in silk multiblock fibrous proteins. The Avrami analysis kinetic theory, for studies of synthetic polymer crystal growth, is for the first time extended to investigate protein self-assembly in beta-sheet rich Bombyx mori silk fibroin samples, using time-resolved Fourier transform infrared spectroscopy, differential scanning calorimetry and synchrotron real-time wide-angle X-ray scattering. Results indicate formation of beta sheet crystals in silk proteins is different from the 3-D spherulitic crystal growth found in synthetic homopolymers. Observations by scanning electron microscopy support the view that the protein structures vary during the different stages of crystal growth, and show a microphase separation pattern after chymotrypsin enzyme biodegradation. We present a model to explain the crystallization of the multiblock silk fibroin protein, by analogy to synthetic block copolymers. This model could be widely applicable in other proteins with multiblock (i.e., crystallizable and non-crystallizable) domains.

Hu, Xiao; Lu, Qiang; Kaplan, David; Cebe, Peggy

2009-03-01

14

Formation of Sprays From Conical Liquid Sheets  

NASA Technical Reports Server (NTRS)

Our objective is to predict droplet size distributions created by fuel injector nozzles in Jet turbines. These results will be used to determine the initial conditions for numerical simulations of the combustion process in gas turbine combustors. To predict the droplet size distribution, we are currently constructing a numerical model to understand the instability and breakup of thin conical liquid sheets. This geometry serves as a simplified model of the liquid jet emerging from a real nozzle. The physics of this process is difficult to study experimentally as the time and length scales are very short. From existing photographic data, it does seem clear that three-dimensional effects such as the formation of streamwise ligaments and the pulling back of the sheet at its edges under the action of surface tension are important.

Peck, Bill; Mansour, N. N.; Koga, Dennis (Technical Monitor)

1999-01-01

15

A recipe for designing water-soluble, beta-sheet-forming peptides.  

PubMed Central

Based on observations of solubility and folding properties of peptide 33-mers derived from the beta-sheet domains of platelet factor-4 (PF4), interleukin-8 (IL-8), and growth related protein (Gro-alpha), as well as other beta-sheet-forming peptides, general guidelines have been developed to aid in the design of water soluble, self-association-induced beta-sheet-forming peptides. CD, 1H-NMR, and pulsed field gradient NMR self-diffusion measurements have been used to assess the degree of folding and state of aggregation. PF4 peptide forms native-like beta-sheet tetramers and is sparingly soluble above pH 6. IL-8 peptide is insoluble between pH 4.5 and pH 7.5, yet forms stable, native-like beta-sheet dimers at higher pH. Gro-alpha peptide is soluble at all pH values, yet displays no discernable beta-sheet structure even when diffusion data indicate dimer-tetramer aggregation. A recipe used in the de novo design of water-soluble beta-sheet-forming peptides calls for the peptide to contain 40-50% hydrophobic residues, usually aliphatic ones (I, L, V, A, M) (appropriately paired and mostly but not always alternating with polar residues in the sheet sequence), a positively charged (K, R) to negatively charged (E, D) residue ratio between 4/2 and 6/2, and a noncharged polar residue (N, Q, T, S) composition of about 20% or less. Results on four de novo designed, 33-residue peptides are presented supporting this approach. Under near physiologic conditions, all four peptides are soluble, form beta-sheet structures to varying degrees, and self-associate. One peptide folds as a stable, compact beta-sheet tetramer, whereas the others are transient beta-sheet-containing aggregates. PMID:8819163

Mayo, K. H.; Ilyina, E.; Park, H.

1996-01-01

16

Diffraction from the beta-sheet crystallites in spider silk  

E-print Network

We analyze the wide angle x-ray scattering from oriented spider silk fibers in terms of a quantitative scattering model, including both structural and statistical parameters of the $\\beta$-sheet crystallites of spider silk in the amorphous matrix. The model is based on kinematic scattering theory and allows for rather general correlations of the positional and orientational degrees of freedom, including the crystallite's size, composition and dimension of the unit cell. The model is evaluated numerically and compared to experimental scattering intensities allowing us to extract the geometric and statistical parameters. We show explicitly that for the experimentally found mosaicity (width of the orientational distribution) inter-crystallite effects are negligible and the data can be analyzed in terms of single crystallite scattering, as is usually assumed in the literature.

Stephan Ulrich; Anja Glišovi?; Tim Salditt; Annette Zippelius

2008-11-25

17

Structural events during the refolding of an all beta-sheet protein.  

PubMed

The refolding kinetics of the 140-residue, all beta-sheet, human fibroblast growth factor (hFGF-1) is studied using a variety of biophysical techniques such as stopped-flow fluorescence, stopped-flow circular dichroism, and quenched-flow hydrogen exchange in conjunction with multidimensional NMR spectroscopy. Urea-induced unfolding of hFGF-1 under equilibrium conditions reveals that the protein folds via a two-state (native <--> unfolded) mechanism without the accumulation of stable intermediates. However, measurement of the unfolding and refolding rates in various concentrations of urea shows that the refolding of hFGF-1 proceeds through accumulation of kinetic intermediates. Results of the quenched-flow hydrogen exchange experiments reveal that the hydrogen bonds linking the N- and C-terminal ends are the first to form during the refolding of hFGF-1. The basic beta-trefoil framework is provided by the simultaneous formation of beta-strands I, IV, IX, and X. The other beta-strands comprising the beta-barrel structure of hFGF-1 are formed relatively slowly with time constants ranging from 4 to 13 s. PMID:11038349

Samuel, D; Kumar, T K; Balamurugan, K; Lin, W Y; Chin, D H; Yu, C

2001-02-01

18

Metalloporphyrins inhibit beta-hematin (hemozoin) formation.  

PubMed

Metal-substituted protoporphyrin IXs (Cr(III)PPIX (1), Co(III)PPIX (2), Mn(III)PPIX (3), Cu(II)PPIX (4), Mg(II)PPIX (5), Zn(II)PPIX (6), and Sn(IV)PPIX (7)) act as inhibitors to beta-hematin (hemozoin) formation, a critical detoxification biopolymer of malarial parasites. The central metal ion plays a significant role in the efficacy of the metalloprotoporphyrins to inhibit beta-hematin formation. The efficacy of these compounds correlates well with the water exchange rate for the octahedral aqua complexes of the porphyrin's central metal ion. Under these in vitro reaction conditions, metalloporphyrins 5, 6 and 7 are as much as six times more efficacious than the free ligand protoporphyrin IX in preventing beta-hematin formation and four times as efficacious as chloroquine, while metalloporphyrins 3 and 4 are three to four times more effective at preventing beta-hematin formation than the free protoporphyrin IX base. In contrast, the relatively exchange inert metalloporphyrins 1 and 2 are only as efficacious as the free ligand and only two-thirds as effective as chloroquine. Aggregation studies of the heme:MPPIX using UV-Vis and fluorescence spectroscopies are indicative of the formation of pi-pi hetero-metalloporphyrin assemblies. Thus, hemozoin inhibition is likely prevented by the formation of heme:MPPIX complexes through pi-stacking interactions. The ramifications of such hetero-metalloporphyrin assemblies, in the context of the emerging structural picture of hemozoin, are discussed. PMID:10766333

Cole, K A; Ziegler, J; Evans, C A; Wright, D W

2000-01-30

19

Propagating structure of alzheimer's {beta}-amyloid is parallel {beta}-sheet with residues in exact register.  

SciTech Connect

The pathognomonic plaques of Alzheimer's disease are composed primarily of the 39- to 43-aa {beta}-amyloid (A{beta}) peptide. Crosslinking of A{beta} peptides by tissue transglutaminase (tTg) indicates that Gln15 of one peptide is proximate to Lys16 of another in aggregated A{beta}. Here we report how the fibril structure is resolved by mapping interstrand distances in this core region of the A{beta} peptide chain with solid-state NMR. Isotopic substitution provides the source points for measuring distances in aggregated A{beta}. Peptides containing a single carbonyl 13C label at Gln15, Lys16, Leu17, or Val18 were synthesized and evaluated by NMR dipolar recoupling methods for the measurement of interpeptide distances to a resolution of 0.2 Angstrom. Analysis of these data establish that this central core of A{beta} consists of a parallel {beta}-sheet structure in which identical residues on adjacent chains are aligned directly, i.e., in register. Our data, in conjunction with existing structural data, establish that the A{beta} fibril is a hydrogen-bonded, parallel {beta}-sheet defining the long axis of the A{beta} fibril propagation.

Benzinger, T. L. S.; Gregory, D. M.; Burkoth, T. S.; Miller-Auer, H.; Lynn, D. G.; Botto, R. E.; Meredith, S. C.; Chemistry; Univ. of Chicago

1998-11-10

20

Conversion of non-fibrillar {beta}-sheet oligomers into amyloid fibrils in Alzheimer's disease amyloid peptide aggregation  

SciTech Connect

A{beta}(1-40) is one of the main components of the fibrils found in amyloid plaques, a hallmark of brains affected by Alzheimer's disease. It is known that prior to the formation of amyloid fibrils in which the peptide adopts a well-ordered intermolecular {beta}-sheet structure, peptide monomers associate forming low and high molecular weight oligomers. These oligomers have been previously described in electron microscopy, AFM, and exclusion chromatography studies. Their specific secondary structures however, have not yet been well established. A major problem when comparing aggregation and secondary structure determinations in concentration-dependent processes such as amyloid aggregation is the different concentration range required in each type of experiment. In the present study we used the dye Thioflavin T (ThT), Fourier-transform infrared spectroscopy, and electron microscopy in order to structurally characterize the different aggregated species which form during the A{beta}(1-40) fibril formation process. A unique sample containing 90 {mu}M peptide was used. The results show that oligomeric species which form during the lag phase of the aggregation kinetics are a mixture of unordered, helical, and intermolecular non-fibrillar {beta}-structures. The number of oligomers and the amount of non-fibrillar {beta}-structures grows throughout the lag phase and during the elongation phase these non-fibrillar {beta}-structures are transformed into fibrillar (amyloid) {beta}-structures, formed by association of high molecular weight intermediates.

Benseny-Cases, Nuria; Cocera, Mercedes [Unitat de Biofisica, Departament de Bioquimica i de Biologia Molecular, i Centre d'Estudis Biofisics, Facultat de Medicina, Universitat Autonoma de Barcelona, 08193 Bellaterra, Barcelona (Spain); Cladera, Josep [Unitat de Biofisica, Departament de Bioquimica i de Biologia Molecular, i Centre d'Estudis Biofisics, Facultat de Medicina, Universitat Autonoma de Barcelona, 08193 Bellaterra, Barcelona (Spain)], E-mail: josep.cladera@uab.cat

2007-10-05

21

Formation of sheeting joints in concave slopes  

Microsoft Academic Search

Sheeting joints are a structural manifestation of the interaction between the topographic surface and the stresses near the surface. Sheeting joints are predicted to open in two-dimensional valleys and ridges where the following inequality holds: Pk > rhog cosbeta, where P is the normal stress parallel to the fall line of the slope, k is the curvature of the slope,

S. J. Martel; P. Larin

2006-01-01

22

FORMATION OF ROLL WAVES IN LAMINAR SHEET FLOW  

E-print Network

functions of the Froude number #12;I. INTRODUCTION Sheet flow is classified as "wide" open channel flow because channel walls do not affect the flow pattern. Wide open channel flow exists when the ratioFORMATION OF ROLL WAVES IN LAMINAR SHEET FLOW by Pierre Y. Julien and David M. Hartley January 1985

Julien, Pierre Y.

23

Numerical simulation of current sheet formation in a quasiseparatrix layer using adaptive mesh refinement  

SciTech Connect

The formation of a thin current sheet in a magnetic quasiseparatrix layer (QSL) is investigated by means of numerical simulation using a simplified ideal, low-{beta}, MHD model. The initial configuration and driving boundary conditions are relevant to phenomena observed in the solar corona and were studied earlier by Aulanier et al. [Astron. Astrophys. 444, 961 (2005)]. In extension to that work, we use the technique of adaptive mesh refinement (AMR) to significantly enhance the local spatial resolution of the current sheet during its formation, which enables us to follow the evolution into a later stage. Our simulations are in good agreement with the results of Aulanier et al. up to the calculated time in that work. In a later phase, we observe a basically unarrested collapse of the sheet to length scales that are more than one order of magnitude smaller than those reported earlier. The current density attains correspondingly larger maximum values within the sheet. During this thinning process, which is finally limited by lack of resolution even in the AMR studies, the current sheet moves upward, following a global expansion of the magnetic structure during the quasistatic evolution. The sheet is locally one-dimensional and the plasma flow in its vicinity, when transformed into a comoving frame, qualitatively resembles a stagnation point flow. In conclusion, our simulations support the idea that extremely high current densities are generated in the vicinities of QSLs as a response to external perturbations, with no sign of saturation.

Effenberger, Frederic [Theoretische Physik IV, Ruhr-Universitaet Bochum, D-44780 Bochum (Germany); Thust, Kay; Grauer, Rainer; Dreher, Juergen [Theoretische Physik I, Ruhr-Universitaet Bochum, D-44780 Bochum (Germany); Arnold, Lukas [Institute for Advanced Simulation, Forschungszentrum Juelich, D-52425 Juelich (Germany)

2011-03-15

24

Thermodynamics of beta-amyloid fibril formation.  

PubMed

Amyloid fibers are aggregates of proteins. They are built out of a peptide called beta-amyloid (Abeta) containing between 41 and 43 residues, produced by the action of an enzyme which cleaves a much larger protein known as the amyloid precursor protein (APP). X-ray diffraction experiments have shown that these fibrils are rich in beta-structures, whereas the shape of the peptide displays an alpha-helix structure within the APP in its biologically active conformation. A realistic model of fibril formation is developed based on the 17 residues Abeta12-28 amyloid peptide, which has been shown to form fibrils structurally similar to those of the whole Abeta peptide. With the help of physical arguments and in keeping with experimental findings, the Abeta12-28 monomer is assumed to be in four possible states (i.e., native helix conformation, beta-hairpin, globular low-energy state, and unfolded state). Making use of these monomeric states, oligomers (dimers, tertramers, and octamers) were constructed. With the help of short, detailed molecular dynamics calculations of the three monomers and of a variety of oligomers, energies for these structures were obtained. Making use of these results within the framework of a simple yet realistic model to describe the entropic terms associated with the variety of amyloid conformations, a phase diagram can be calculated of the whole many-body system, leading to a thermodynamical picture in overall agreement with the experimental findings. In particular, the existence of micellar metastable states seem to be a key issue to determine the thermodynamical properties of the system. PMID:15267752

Tiana, G; Simona, F; Broglia, R A; Colombo, G

2004-05-01

25

Structural characterization of adsorbed helical and beta-sheet peptides  

NASA Astrophysics Data System (ADS)

Adsorbed peptides on surfaces have potential applications in the fields of biomaterials, tissue engineering, peptide microarrays and nanobiotechnology. The surface region, the "biomolecular interface" between a material and the biological environment, plays a crucial role in these applications. As a result, characterization of adsorbed peptide structure, especially with respect to identity, concentration, spatial distribution, conformation and orientation, is important. The present research employs NEXAFS (near-edge X-ray absorption fine structure spectroscopy) and SFG (sum frequency generation spectroscopy) to provide information about the adsorbed peptide structure. Soft X-ray NEXAFS is a synchrotron-based technique which typically utilizes polarized X-rays to interrogate surfaces under ultra-high vacuum conditions. SFG is a non-linear optical technique which utilizes a combination of a fixed visible and a tunable infrared laser beams to generate a surface-vibrational spectrum of surface species. SFG has the added advantage of being able to directly analyze the surface-structure at the solid-liquid interface. The main goals of the present research were twofold: characterize the structure of adsorbed peptides (1) ex situ using soft X-ray NEXAFS, and (2) in situ using non-linear laser spectroscopy (SFG). Achieving the former goal involved first developing a comprehensive characterization of the carbon, nitrogen and oxygen k-edge NEXAFS spectra for amino acids, and then using a series of helical and beta-sheet peptides to demonstrate the sensitivity of polarization-dependent NEXAFS to secondary structure of adsorbed peptides. Characterizing the structure of adsorbed peptides in situ using SFG involved developing a model system to probe the solid-liquid interface in situ; demonstrating the ability to probe the molecular interactions and adsorbed secondary structure; following the time-dependent ordering of the adsorbed peptides; and establishing the ability to obtain high-resolution peptide-surface interactions in situ. The results from the present research establish SFG and NEXAFS as powerful techniques for chemical and structural characterization of surfaces and biomolecules immobilized onto those surfaces.

Samuel, Newton Thangadurai

26

Formation of current sheets in magnetic reconnection  

SciTech Connect

An ideal evolution of magnetic fields in three spatial dimensions tends to cause neighboring field lines to increase their separation exponentially with distance ? along the lines, ?(?)=?(0)e{sup ?(?)}. The non-ideal effects required to break magnetic field line connections scale as e{sup ??}, so the breaking of connections is inevitable for ? sufficiently large—even though the current density need nowhere be large. When the changes in field line connections occur rapidly compared to an Alfvén transit time, the constancy of j{sub ||}/B along the magnetic field required for a force-free equilibrium is broken in the region where the change occurs, and an Alfvénic relaxation of j{sub ||}/B occurs. Independent of the original spatial distribution of j{sub ||}/B, the evolution is into a sheet current, which is stretched by a factor e{sup ?} in width and contracted by a factor e{sup ?} in thickness with the current density j{sub ||} increasing as e{sup ?}. The dissipation of these sheet currents and their associated vorticity sheets appears to be the mechanism for transferring energy from a reconnecting magnetic field to a plasma. Harris sheets, which are used in models of magnetic reconnection, are shown to break up in the direction of current flow when they have a finite width and are in a plasma in force equilibrium. The dependence of the longterm nature of magnetic reconnection in systems driven by footpoint motion can be studied in a model that allows qualitative variation in the nature of that motion: slow or fast motion compared to the Alfvén transit time and the neighboring footpoints either exponentially separating in time or not.

Boozer, Allen H., E-mail: ahb17@columbia.edu [Department of Applied Physics and Applied Mathematics Columbia University, New York, New York 10027 (United States)

2014-07-15

27

Mechanical energy transfer and dissipation in fibrous beta-sheet-rich proteins.  

PubMed

Mechanical properties of structural protein materials are crucial for our understanding of biological processes and disease states. Through utilization of molecular simulation based on stress wave tracking, we investigate mechanical energy transfer processes in fibrous beta-sheet-rich proteins that consist of highly ordered hydrogen bond (H-bond) networks. By investigating four model proteins including two morphologies of amyloids, beta solenoids, and silk beta-sheet nanocrystals, we find that all beta-sheet-rich protein fibrils provide outstanding elastic moduli, where the silk nanocrystal reaches the highest value of ?40 GPa. However, their capacities to dissipate mechanical energy differ significantly and are controlled strongly by the underlying molecular structure of H-bond network. Notably, silk beta-sheet nanocrystals feature a ten times higher energy damping coefficient than others, owing to flexible intrastrand motions in the transverse directions. The results demonstrate a unique feature of silk nanocrystals, their capacity to simultaneously provide extreme stiffness and energy dissipation capacity. Our results could help one to explain the remarkable properties of silks from an atomistic and molecular perspective, in particular its great toughness and energy dissipation capacity, and may enable the design of multifunctional nanomaterials with outstanding stiffness, strength, and impact resistance. PMID:20866443

Xu, Zhiping; Buehler, Markus J

2010-06-01

28

Prediction of parallel and anti-parallel beta-sheets using Conditional Random Fields  

E-print Network

the information, for example, the window based profiles. Our new method has the advantages over previous methods (both parallel and anti-parallel). In some reduced 3-class definitions for protein secondary structures, the beta-bridge, with only one amino acid on each strand, is also counted as sheets. In this paper, we only

Carbonell, Jaime

29

The folding mechanism of a beta-sheet: the WW domain.  

PubMed

The folding thermodynamics and kinetics of the Pin WW domain, a three-stranded antiparallel beta-sheet, have been characterized extensively. Folding and activation free energies were determined as a function of temperature for 16 mutants, which sample all strands and turns of the molecule. The mutational phi value (Phi(m)) diagram is a smooth function of sequence, indicating a prevalence of local interactions in the transition state (TS). At 37 degrees C, the diagram has a single pronounced maximum at turn 1: the rate-limiting step during folding is the formation of loop 1. In contrast, key residues for thermodynamic stability are located in the strand hydrophobic clusters, indicating that factors contributing to protein stability and folding kinetics are not correlated. The location of the TS along the entropic reaction coordinate Phi(T), obtained by temperature-tuning the kinetics, reveals that sufficiently destabilizing mutants in loop 2 or in the Leu7-Trp11-Tyr24-Pro37 hydrophobic cluster can cause a switch to a late TS. Phi(m) analysis is usually applied "perturbatively" (methyl truncation), but with Phi(T) to quantitatively assess TS shifts along a reaction coordinate, more severe mutations can be used to probe regions of the free energy surface beyond the TS. PMID:11478867

Jäger, M; Nguyen, H; Crane, J C; Kelly, J W; Gruebele, M

2001-08-10

30

Promotion of fibroblast activity by coating with hydrophobins in the beta-sheet end state.  

PubMed

Hydrophobins such as SC3 and SC4 of Schizophyllum commune self-assemble into an amphipathic film at hydrophilic/hydrophobic interfaces. These proteins can thus change the nature of surfaces, which makes them attractive candidates to improve physio- and physico-chemical properties of implant surfaces. At a hydrophobic solid, assembly of the hydrophobin is arrested in an intermediate state, called the alpha-helical state. The conversion to the stable beta-sheet end state can be induced by treating the solid at elevated temperatures in the presence of detergent. We here show that SC3 and SC4 in the alpha-helical state homogeneously cover Teflon sheets when coating was performed at 20 degrees C. However, when the protein was adsorbed at 80 degrees C aggregates were shown to bind tightly to the adsorbed hydrophobin film. The transition to the beta-sheet state created pores of about 50 nm in the SC3 and SC4 coatings when coating was performed at 20 degrees C. Cell growth and morphology on SC4 coatings was better than on SC3. In case of both hydrophobins, fibroblast growth and morphology was not influenced by the coating temperature or the conformation of the protein. However, in contrast to the alpha-helical state, the beta-sheet state of both SC3 and SC4 hardly, if at all, affected mitochondrial activity. PMID:14962552

Janssen, M I; van Leeuwen, M B M; van Kooten, T G; de Vries, J; Dijkhuizen, L; Wösten, H A B

2004-06-01

31

Reduction of burn scar formation by halofuginone-eluting silicone gel sheets: a controlled study on nude mice.  

PubMed

Burn scar formations can cause disfiguration and loss of dermal function. The purpose of this study was to examine whether application of modified silicone gel sheets with an antifibrotic drug halofuginone-eluting hybrid surface produce an effect on scar development. There were a total of 2 animal groups. The athymic nude mice (nu/nu) of both groups underwent transplantation of full-thickness human skin grafts onto their backs and setting of partial thickness burn injury. The status of local scar development was observed over a period of 3 months after the application of silicone gel sheets and also after application of surface-modified halofuginone-eluting silicone gel sheets. Subsequently, via real-time polymerase chain reaction, the cDNA levels from key mediators of scar formation (transforming growth factor beta, COL1A1, connective tissue growth factor, fibroblast growth factor 2, matrix metalloproteinase 2, matrix metalloproteinase 9) were established and statistically evaluated. In comparison with uncoated silicone gel sheets, the application of halofuginone-eluting silicone gel sheets lead to a significant difference in gene expression activity in scar tissue. Halofuginone-eluting hybrid surface silicone gel sheets significantly increase the antiscarring effect of adhesive silicone gel sheets by deceleration and downregulation of scar development by normalization of the expression activity. PMID:22356780

Zeplin, Philip H

2012-03-01

32

Blue color formation of cyanobacteria with beta-cyclocitral.  

PubMed

Volatile compounds, such as beta-cyclocitral, geosmin, and 2-methylisoborneol, from cyanobacteria showed a lytic activity against cyanobacteria. Particularly, beta-cyclocitral caused an interesting color change in the culture broth from green to blue during the lysis process. In the present study, the lytic behavior of various cyanobacteria with beta-cyclocitral was investigated, and a mechanism for the blue color formation was developed. beta-Cyclocitral lysed both the laboratory strains of any genera and bloom samples including many species of cyanobacteria, and caused the characteristic color change from green to blue. beta-Cyclocitral provided a characteristic behavior, such that the absorption maxima of chlorophyll-a and beta-carotene disappeared, but that of phycocyanin still remained after 12 h, which indicated that beta-cyclocitral decomposed chlorophyll-a and beta-carotene rapidly, so that the inherent colors from the tolerant water-soluble pigments became observable in the cultured broth. This phenomenon was confirmed by another experiment using Phormidium (NIES-611), which showed a pink color derived from phycoerythrin. beta-Cyclocitral was more easily oxidized when compared with similar aldehyde compounds, so that the pH of the solution quickly decreased to 4.5. An oxidation product of beta-cyclocitral in water solution was isolated and identified as 2,6,6-trimethylcyclohexene-1-carboxylic acid. This study provides support that beta-cyclocitral derived from cyanobacteria plays an important role in the lysis of cyanobacteria and participates in the blue color formation under natural conditions. PMID:19936836

Harada, Ken-Ichi; Ozaki, Keiko; Tsuzuki, Sayaka; Kato, Hajime; Hasegawa, Masateru; Kuroda, Emilia K; Arii, Suzue; Tsuji, Kiyomi

2009-11-01

33

Thermally Induced Alpha-Helix to Beta-Sheet Transition in Regenerated Silk Fibers and Films  

SciTech Connect

The structure of thin films cast from regenerated solutions of Bombyx mori cocoon silk in hexafluoroisopropyl alcohol (HFIP) was studied by synchrotron X-ray diffraction during heating. A solid-state conformational transition from an alpha-helical structure to the well-known beta-sheet silk II structure occurred at a temperature of approximately 140 degrees C. The transition appeared to be homogeneous, as both phases do not coexist within the resolution of the current study. Modulated differential scanning calorimetry (DSC) of the films showed an endothermic melting peak followed by an exothermic crystallization peak, both occurring near 140 degrees C. Oriented fibers were also produced that displayed this helical molecular conformation. Subsequent heating above the structural transition temperature produced oriented beta-sheet fibers very similar in structure to B. mori cocoon fibers. Heat treatment of silk films at temperatures well below their degradation temperature offers a controllable route to materials with well-defined structures and mechanical behavior.

Drummy,L.; Phillips, D.; Stone, M.; Farmer, B.; Naik, R.

2005-01-01

34

Identification of 'molten globule'-like state in all beta-sheet protein.  

PubMed

The cardiotoxin analogue III (CTX III), isolated from the Taiwan Cobra venom (Naja naja atra), is a sixty amino acid, all beta-sheet protein. The 2,2,2-trifluoro ethanol (TFE) induced unfolding of CTX III is studied under acidic conditions (pH 2.5). Using circular dichroism, 1-anilino-8-napthalene sulphonic acid binding and NMR experiments, it is shown that stable, partially structured state(s) ['molten globule'-like state] is formed between 50 and 80% TFE concentrations. The protein was found to exist in an unfolded state in 80% TFE containing 2M urea. The TFE induced unfolding process is shown to be completely reversible. In the 'molten globule' state of CTX III in 80% TFE, though portion(s) of the backbone of the protein assume helical conformation, most of the original beta-sheet secondary structural elements in the protein are intact. In our opinion, this is the first report of the identification of a 'molten globule'-like state in the unfolding pathway of an all beta-sheet monomeric protein. PMID:7864840

Kumar, T K; Jayaraman, G; Lee, C S; Sivaraman, T; Lin, W Y; Yu, C

1995-02-15

35

Formation and dynamical history of the beta Pictoris system  

NASA Astrophysics Data System (ADS)

The structure of the beta Pic disk holds many clues to its formation and dynamical history. In particular there is strong evidence for sculpting by the beta Pic-b planet. For example, a warp in the disk at 80au is thought to be driven by the secular perturbations of that planet, and scattering of comets by beta Pic-b is thought to be the origin of the Falling Evaporating Bodies. A clump in the disk coincident with the warp, also at ~80au, provides clues to the outer planetary system which for now is poorly constrained. One possible origin for the clump is in trapping of comets into resonance with an outer planet currently at ~60au, with an alternative scenario being a giant impact between planetary embryos. This talk will consider the various disk structures and what they tell us about the formation and dynamical history of the beta Pictoris system.

Wyatt, M.

2014-09-01

36

Nanofiber formation of amphiphilic cyclic tri-beta-peptide.  

PubMed

A novel amphiphilic cyclic peptide composed of two beta-glucosamino acids and one trans-2-aminocyclohexylcarboxylic acid was synthesized and investigated on assembly formation. The cyclic tri-beta-peptide was self-assembled into rodlike crystals or nanofibers depending on preparative conditions. The rodlike crystals showed a layer spacing of 4.8 A along the long axis, and columnar spacings of 10.8 and 21.5 A by electron diffraction analysis along the short axis. The former confirms the columnar structure upon molecular stacking, and the latter indicates triple bundle formation of the columnar assemblies. Fourier transform infrared (FT-IR) measurement of the fibrous assembly showed formation of homogeneous hydrogen bonds among amide groups, also supporting the molecular stacking of cyclic beta-peptides. Straight nanofibers with uniform diameter were also uniquely obtained. PMID:20063334

Ishihara, Yusuke; Kimura, Shunsaku

2010-02-01

37

Design and biological activity of {beta}-sheet breaker peptide conjugates  

SciTech Connect

The sequence LPFFD (iA{beta}{sub 5}) prevents amyloid-{beta} peptide (A{beta}) fibrillogenesis and neurotoxicity, hallmarks of Alzheimer's disease (AD), as previously demonstrated. In this study iA{beta}{sub 5} was covalently linked to poly(ethylene glycol) (PEG) and the activity of conjugates was assessed and compared to the activity of the peptide alone by in vitro studies. The conjugates were characterized by MALDI-TOF. Competition binding assays established that conjugates retained the ability to bind A{beta} with similar strength as iA{beta}{sub 5}. Transmission electron microscopy analysis showed that iA{beta}{sub 5} conjugates inhibited amyloid fibril formation, which is in agreement with binding properties observed for the conjugates towards A{beta}. The conjugates were also able to prevent amyloid-induced cell death, as evaluated by activation of caspase 3. These results demonstrated that the biological activity of iA{beta}{sub 5} is not affected by the pegylation process.

Rocha, Sandra [LEPAE, Chemical Engineering Department, Faculty of Engineering, University of Porto, Rua Dr. Roberto Frias, 4200-465 Porto (Portugal)], E-mail: sandra.rocha@fe.up.pt; Cardoso, Isabel [Molecular Neurobiology Unit, Institute for Molecular and Cell Biology, Rua do Campo Alegre 823, 4150-180 Porto (Portugal); Boerner, Hans [Max Planck Institute of Colloids and Interfaces, 14424 Potsdam (Germany); Pereira, Maria Carmo [LEPAE, Chemical Engineering Department, Faculty of Engineering, University of Porto, Rua Dr. Roberto Frias, 4200-465 Porto (Portugal); Saraiva, Maria Joao [Molecular Neurobiology Unit, Institute for Molecular and Cell Biology, Rua do Campo Alegre 823, 4150-180 Porto (Portugal); ICBAS, University of Porto, Largo Prof. Abel Salazar 2, 4099-003 Porto (Portugal); Coelho, Manuel [LEPAE, Chemical Engineering Department, Faculty of Engineering, University of Porto, Rua Dr. Roberto Frias, 4200-465 Porto (Portugal)

2009-03-06

38

Mapping the transition state of the WW domain beta-sheet.  

PubMed

The folding kinetics of a three-stranded antiparallel beta-sheet (WW domain) have been measured by temperature jump relaxation. Folding and activation free energies were determined as a function of temperature for both the wild-type and the mutant domain, W39F, which modifies the beta(2)-beta(3) hydrophobic interface. The folding rate decreases at higher temperatures as a result of the increase in the activation free energy for folding. Phi-Values were obtained for thermal perturbations allowing the primary features of the folding free energy surface to be determined. The results of this analysis indicate a significant shift from an "early" (Phi(T)=0. 4) to a "late" (Phi(T)=0.8) transition state with increasing temperature. The temperature-dependent Phi-value analysis of the wild-type WW domain and of its more stable W39F hydrophobic cluster mutant reveals little participation of residue 39 in the transition state at lower temperature. As the temperature is raised, hydrophobic interactions at the beta(2)-beta(3) interface gain importance in the transition state and the barrier height of the wild-type, which contains the larger tryptophan residue, increases more slowly than the barrier height of the mutant. PMID:10764597

Crane, J C; Koepf, E K; Kelly, J W; Gruebele, M

2000-04-28

39

CURRENT SHEETS FORMATION IN TANGLED CORONAL MAGNETIC FIELDS  

SciTech Connect

We investigate the dynamical evolution of magnetic fields in closed regions of solar and stellar coronae. To understand under which conditions current sheets form, we examine dissipative and ideal reduced magnetohydrodynamic models in Cartesian geometry, where two magnetic field components are present: the strong guide field B{sub 0}, extended along the axial direction, and the dynamical orthogonal field b. Magnetic field lines thread the system along the axial direction that spans the length L and are line-tied at the top and bottom plates. The magnetic field b initially has only large scales, with its gradient (current) length scale of the order of l{sub b}. We identify the magnetic intensity threshold b/B{sub 0} {approx} l{sub b}/L. For values of b below this threshold, field-line tension inhibits the formation of current sheets, while above the threshold they form quickly on fast ideal timescales. In the ideal case, above the magnetic threshold, we show that current sheets thickness decreases in time until it becomes smaller than the grid resolution, with the analyticity strip width {delta} decreasing at least exponentially, after which the simulations become underresolved.

Rappazzo, A. F. [Bartol Research Institute, Department of Physics and Astronomy, University of Delaware, Newark, DE 19716 (United States); Parker, E. N., E-mail: franco.rappazzo@gmail.com, E-mail: parker@oddjob.uchicago.edu [Enrico Fermi Institute, University of Chicago, Chicago, IL 60637 (United States)

2013-08-10

40

Factors contributing to decreased protein stability when aspartic acid residues are in {beta}-sheet regions.  

SciTech Connect

Asp residues are significantly under represented in {beta}-sheet regions of proteins, especially in the middle of {beta}-strands, as found by a number of studies using statistical, modeling, or experimental methods. To further understand the reasons for this under representation of Asp, we prepared and analyzed mutants of a {beta}-domain. Two Gln residues of the immunoglobulin light-chain variable domain (V{sub L}) of protein Len were replaced with Asp, and then the effects of these changes on protein stability and protein structure were studied. The replacement of Q38D, located at the end of a {beta}-strand, and that of Q89D, located in the middle of a {beta}-strand, reduced the stability of the parent immunoglobulin VL domain by 2.0 kcal/mol and 5.3 kcal/mol, respectively. Because the Q89D mutant of the wild-type V{sub L}-Len domain was too unstable to be expressed as a soluble protein, we prepared the Q89D mutant in a triple mutant background, V{sub L}-Len M4L/Y27dD/T94H, which was 4.2 kcal/mol more stable than the wild-type V{sub L}-Len domain. The structures of mutants V{sub L}-Len Q38D and V{sub L}-Len Q89D/M4L/Y27dD/T94H were determined by X-ray diffraction at 1.6 A resolution. We found no major perturbances in the structures of these QD mutant proteins relative to structures of the parent proteins. The observed stability changes have to be accounted for by cumulative effects of the following several factors: (1) by changes in main-chain dihedral angles and in side-chain rotomers, (2) by close contacts between some atoms, and, most significantly, (3) by the unfavorable electrostatic interactions between the Asp side chain and the carbonyls of the main chain. We show that the Asn side chain, which is of similar size but neutral, is less destabilizing. The detrimental effect of Asp within a {beta}-sheet of an immunoglobulin-type domain can have very serious consequences. A somatic mutation of a {beta}-strand residue to Asp could prevent the expression of the domain both in vitro and in vivo, or it could contribute to the pathogenic potential of the protein in vivo.

Pokkuluri, P. R.; Cai, X.; Raffen, R.; Gu, M.; Stevens, F. J.; Schiffer, M.

2002-07-01

41

sup 1 H NMR identification of a. beta. -sheet structure and description of folding topology in putidaredoxin  

SciTech Connect

Putidaredoxin (Pdx), a 106-residue globular protein consisting of a single polypeptide chain and a (2Fe-2S) cluster, is the physiological reductant of P-450{sub cam}, which in turn catalyzes the monohydroxylation of camphor by molecular oxygen. No crystal structure has been obtained for Pdx or for any closely homologous protein. The application of two-dimensional {sup 1}H NMR methods to the problem of structure determination in Pdx is reported. A {beta}-sheet consisting of five short strands and one {beta}-turn has been identified from distinctive nuclear Overhauser effect patterns. All of the backbone resonances and a majority of the side-chain resonances corresponding to protons in the {beta}-sheet have been assigned sequence specifically. The sheet contains one parallel and three antiparallel strand orientations. Hydrophobic side chains in the {beta}-sheet face primarily toward the protein interior, except for a group of three valine side chains that are apparently solvent exposed. The potential significance of this hydrophobic patch in terms of biological activity is discussed. The folding topology, as determined by the constraints of the {beta}-sheet, is compared with that of other (2Fe-2S) proteins for which folding topologies are known.

Pochapsky, T.C.; Ye, Xiao Mei (Brandeis Univ., Waltham, MA (USA))

1991-04-23

42

Reversible hydrogel-solution system of silk with high beta-sheet content.  

PubMed

Silkworm silk has been widely used as a textile fiber, as biomaterials and in optically functional materials due to its extraordinary properties. The ?-sheet-rich natural nanofiber units of about 10-50 nm in diameter are often considered the origin of these properties, yet it remains unclear how silk self-assembles into these hierarchical structures. A new system composed of ?-sheet-rich silk nanofibers about 10-20 nm in diameter is reported here, where these nanofibers formed into "flowing hydrogels" at 0.5-2% solutions and could be transformed back into the solution state at lower concentrations, even with a high ?-sheet content. This is in contrast with other silk processed materials, where significant ?-sheet content negates reversibility between solution and solid states. These fibers are formed by regulating the self-assembly process of silk in aqueous solution, which changes the distribution of negative charges while still supporting ?-sheet formation in the structures. Mechanistically, there appears to be a shift toward negative charges along the outside of the silk nanofibers in our present study, resulting in a higher zeta potential (above -50 mV) than previous silk materials which tend to be below -30 mV. The higher negative charge on silk nanofibers resulted in electrostatic repulsion strong enough to negate further assembly of the nanofibers. Changing silk concentration changed the balance between hydrophobic interactions and electrostatic repulsion of ?-sheet-rich silk nanofibers, resulting in reversible hydrogel-solution transitions. Furthermore, the silk nanofibers could be disassembled into shorter fibers and even nanoparticles upon ultrasonic treatment following the transition from hydrogel to solution due to the increased dispersion of hydrophobic smaller particles, without the loss of ?-sheet content, and with retention of the ability to transition between hydrogel and solution states through reversion to longer nanofibers during self-assembly. These reversible solution-hydrogel transitions were tunable with ultrasonic intensity, time, or temperature. PMID:25056606

Bai, Shumeng; Zhang, Xiuli; Lu, Qiang; Sheng, Weiqin; Liu, Lijie; Dong, Boju; Kaplan, David L; Zhu, Hesun

2014-08-11

43

Microphase Separation Controlled beta-Sheet Crystallization Kinetics in Fibrous Proteins  

SciTech Connect

Silk is a naturally occurring fibrous protein with a multiblock chain architecture. As such, it has many similarities with synthetic block copolymers, including the possibility for e-sheet crystallization restricted within the crystallizable blocks. The mechanism of isothermal crystallization kinetics of e-sheet crystals in silk multiblock fibrous proteins is reported in this study. Kinetics theories, such as Avrami analysis which was established for studies of synthetic polymer crystal growth, are for the first time extended to investigate protein self-assembly in e-sheet rich Bombyx mori silk fibroin samples, using time-resolved Fourier transform infrared spectroscopy (FTIR), differential scanning calorimetry (DSC) and synchrotron real-time wide-angle X-ray scattering (WAXS). The Avrami exponent, n, was close to 2 for all methods and crystallization temperatures, indicating formation of e-sheet crystals in silk proteins is different from the 3-D spherulitic crystal growth found in synthetic polymers. Observations by scanning electron microscopy support the view that the protein structures vary during the different stages of crystal growth, and show a microphase separation pattern after chymotrypsin enzyme biodegradation. We present a model to explain the crystallization of the multiblock silk fibroin protein, by analogy to block copolymers: crystallization of e-sheets occurs under conditions of geometrical restriction caused by phase separation of the crystallizable and uncrystallizable blocks. This crystallization model could be widely applicable in other proteins with multiblock (i.e., crystallizable and noncrystallizable) domains.

Hu, X.; Lu, Q; Kaplan, D; Cebe, P

2009-01-01

44

Amyloid-like fibril formation in an all beta-barrel protein. Partially structured intermediate state(s) is a precursor for fibril formation.  

PubMed

Acidic fibroblast growth factor from newt (Notopthalmus viridescens) is a approximately 15-kDa, all beta-sheet protein devoid of disulfide bonds. In the present study, we investigate the effects of 2,2,2-trifluoroethanol (TFE) on the structure of newt acidic fibroblast growth factor (nFGF-1). The protein aggregates maximally in 10% (v/v) TFE. Congo red and thioflavin T binding experiments suggest that the aggregates induced by TFE have properties resembling the amyloid fibrils. Transmission electron microscopy and x-ray fiber diffraction data show that the fibrils (induced by TFE) are straight, unbranched, and have a cross-beta structure with an average diameter of 10-15 A. Preformed fibrils (induced by TFE) of nFGF-1 are observed to seed amyloid-like fibril formation in solutions containing the protein (nFGF-1) in the native beta-barrel conformation. Fluorescence, far-UV CD, anilino-8-napthalene sulfonate binding, multidimensional NMR, and Fourier transformed infrared spectroscopy data reveal that formation of a partially structured intermediate state(s) precedes the onset of the fibrillation process. The native beta-barrel structure of nFGF-1 appears to be disrupted in the partially structured intermediate state(s). The protein in the partially structured intermediate state(s) is found to be "sticky" with a solvent-exposed non-polar surface(s). Amyloid fibril formation appears to occur due to coalescence of the protein in the partially structured intermediate state(s) through solvent-exposed non-polar surfaces and intermolecular beta-sheet formation among the extended, linear beta-strands in the protein. PMID:12584201

Srisailam, Sampath; Kumar, Thallampuranam Krishnaswamy S; Rajalingam, Dakshinamurthy; Kathir, Karuppanan Muthusamy; Sheu, Hwo-Shuenn; Jan, Fuh-Jyh; Chao, Pei-Chi; Yu, Chin

2003-05-16

45

Strength limit of entropic elasticity in beta-sheet protein domains  

NASA Astrophysics Data System (ADS)

Elasticity and strength of individual beta-sheet protein domains govern key biological functions and the mechanical properties of biopolymers including spider silk, amyloids, and muscle fibers. The worm-like-chain (WLC) model is commonly used to describe the entropic elasticity of polypeptides and other biomolecules. However, force spectroscopy experiments have shown pronounced deviations from the ideal WLC behavior, leading to controversial views about the appropriate elastic description of proteins at nanoscale. Here we report a simple model that explains the physical mechanism that leads to the breakdown of the WLC idealization in experiments by using only two generic parameters of the protein domain, the H-bond energy and the protein backbone’s persistence length. We show that a rupture initiation condition characterized by the free energy release rate of H-bonds characterizes the limit of WLC entropic elasticity of beta-sheet protein domains and the onset of rupture. Our findings reveal that strength and elasticity are coupled and cannot be treated separately. The predictions of the model are compared with atomic force microscopy experiments of protein rupture.

Keten, Sinan; Buehler, Markus J.

2008-12-01

46

A beta-sheet interaction interface directs the tetramerisation of the Miz-1 POZ domain.  

PubMed

The POZ/BTB domain is an evolutionarily conserved motif found in approximately 40 zinc-finger transcription factors (POZ-ZF factors). Several POZ-ZF factors are implicated in human cancer, and POZ domain interaction interfaces represent an attractive target for therapeutic intervention. Miz-1 (Myc-interacting zinc-finger protein) is a POZ-ZF factor that regulates DNA-damage-induced cell cycle arrest and plays an important role in human cancer by virtue of its interaction with the c-Myc and BCL6 oncogene products. The Miz-1 POZ domain mediates both self-association and the recruitment of non-POZ partners. POZ-ZF factors generally function as homodimers, although higher-order associations and heteromeric interactions are known to be physiologically important; crucially, the interaction interfaces in such large complexes have not been characterised. We report here the crystal structure of the Miz-1 POZ domain up to 2.1 A resolution. The tetrameric organisation of Miz-1 POZ reveals two types of interaction interface between subunits; an interface of alpha-helices resembles the dimerisation interface of reported POZ domain structures, whereas a novel beta-sheet interface directs the association of two POZ domain dimers. We show that the beta-sheet interface directs the tetramerisation of the Miz-1 POZ domain in solution and therefore represents a newly described candidate interface for the higher-order homo- and hetero-oligomerisation of POZ-ZF proteins in vivo. PMID:17880999

Stead, Mark A; Trinh, Chi H; Garnett, James A; Carr, Stephen B; Baron, Andrew J; Edwards, Thomas A; Wright, Stephanie C

2007-11-01

47

Conformational diversity in prion protein variants influences intermolecular ?-sheet formation  

PubMed Central

A conformational transition of normal cellular prion protein (PrPC) to its pathogenic form (PrPSc) is believed to be a central event in the transmission of the devastating neurological diseases known as spongiform encephalopathies. The common methionine/valine polymorphism at residue 129 in the PrP influences disease susceptibility and phenotype. We report here seven crystal structures of human PrP variants: three of wild-type (WT) PrP containing V129, and four of the familial variants D178N and F198S, containing either M129 or V129. Comparison of these structures with each other and with previously published WT PrP structures containing M129 revealed that only WT PrPs were found to crystallize as domain-swapped dimers or closed monomers; the four mutant PrPs crystallized as non-swapped dimers. Three of the four mutant PrPs aligned to form intermolecular ?-sheets. Several regions of structural variability were identified, and analysis of their conformations provides an explanation for the structural features, which can influence the formation and conformation of intermolecular ?-sheets involving the M/V129 polymorphic residue. PMID:19927125

Lee, Seungjoo; Antony, Lizamma; Hartmann, Rune; Knaus, Karen J; Surewicz, Krystyna; Surewicz, Witold K; Yee, Vivien C

2010-01-01

48

Computer-Based Redesign of a Beta Sandwich Protein Suggests That Extensive Negative Design is not Required for de novo beta Sheet Design  

SciTech Connect

The de novo design of globular {Beta} sheet proteins remains largely an unsolved problem. It is unclear whether most designs are failing because the designed sequences do not have favorable energies in the target conformations or whether more emphasis should be placed on negative design, that is, explicitly identifying sequences that have poor energies when adopting undesired conformations. We tested whether we could redesign the sequence of a naturally occurring {Beta} sheet protein, tenascin, with a design algorithm that does not include explicit negative design. Denaturation experiments indicate that the designs are significantly more stable than the wild-type protein and the crystal structure of one design closely matches the design model. These results suggest that extensive negative design is not required to create well-folded {Beta} sandwich proteins. However, it is important to note that negative design elements may be encoded in the conformation of the protein backbone which was preserved from the wild-type protein.

Hu, X.; Wang, H; Ke, H; Kuhlman, B

2008-01-01

49

A method to predict edge strands in beta-sheets from protein sequences  

PubMed Central

There is a need for rules allowing three-dimensional structure information to be derived from protein sequences. In this work, consideration of an elementary protein folding step allows protein sub-sequences which optimize folding to be derived for any given protein sequence. Classical mechanics applied to this system and the energy conservation law during the elementary folding step yields an equation whose solutions are taken over the field of rational numbers. This formalism is applied to beta-sheets containing two edge strands and at least two central strands. The number of protein sub-sequences optimized for folding per amino acid in beta-strands is shown in particular to predict edge strands from protein sequences. Topological information on beta-strands and loops connecting them is derived for protein sequences with a prediction accuracy of 75%. The statistical significance of the finding is given. Applications in protein structure prediction are envisioned such as for the quality assessment of protein structure models. PMID:24688737

Guilloux, Antonin; Caudron, Bernard; Jestin, Jean-Luc

2013-01-01

50

A method to predict edge strands in beta-sheets from protein sequences.  

PubMed

There is a need for rules allowing three-dimensional structure information to be derived from protein sequences. In this work, consideration of an elementary protein folding step allows protein sub-sequences which optimize folding to be derived for any given protein sequence. Classical mechanics applied to this system and the energy conservation law during the elementary folding step yields an equation whose solutions are taken over the field of rational numbers. This formalism is applied to beta-sheets containing two edge strands and at least two central strands. The number of protein sub-sequences optimized for folding per amino acid in beta-strands is shown in particular to predict edge strands from protein sequences. Topological information on beta-strands and loops connecting them is derived for protein sequences with a prediction accuracy of 75%. The statistical significance of the finding is given. Applications in protein structure prediction are envisioned such as for the quality assessment of protein structure models. PMID:24688737

Guilloux, Antonin; Caudron, Bernard; Jestin, Jean-Luc

2013-01-01

51

Collective behavior in two-dimensional biological systems: Receptor clustering and beta-sheet aggregation  

NASA Astrophysics Data System (ADS)

We studied two particular biomedical systems which exhibit collective molecular behavior. One is clustering of tumor necrosis factor receptor I (TNFR1), and another is ?-sheet folding and aggregation. Receptor clustering has been shown to be a crucial step in many signaling events but its biological meaning has not been adequately addressed. Here, via a simple lattice model, we show how cells use this clustering machinery to enhance sensitivity as well as robustness. On the other hand, intracellular deposition of aggregated protein rich in ?-sheet is a prominent cytopathological feature of most neurodegenerative diseases. How this aggregation occurs and how it responds to therapy is not completely understood. Here, we started from a reconstruction of the H-bond potential and carry out a full investigation of ?-sheet thermodynamics as well as kinetics. We show that ?-sheet aggregation is most likely due to molecular stacking and found that the minimal length of an aggregate mutant polymer corresponds well with the number observed in adult Huntington's disease. We have also shown that molecular agents such as dendrimers might fail at high-dose therapy; instead, a potential therapy strategy is to block ?-turn formation. Our predictions can be used for future experimental tests and clinical trials.

Guo, Chinlin

52

Induction of helical conformation in all beta-sheet proteins by trifluoroethanol.  

PubMed

The effect of 2,2,2-Trifluoroethanol (TFE) on the structure of five all beta-sheet proteins, isolated from the venom of the Taiwan cobra (Naja naja atra), is studied. In all the toxins used, it is observed that significant amount of alpha-helix is induced at higher concentrations of TFE. In all these proteins, the induction of helical conformation and disruption of the tertiary structure seem to occur simultaneously. The structural transitions induced by TFE in reduced and denatured protein appear to be different from those observed in the native protein(s). In our opinion, the findings reported herein could have significant implications on research in the area of protein folding. PMID:9016415

Arunkumar, A I; Kumar, T K; Jayaraman, G; Samuel, D; Yu, C

1996-12-01

53

Effect of Process Variables on Transformation-Texture Development in Ti-6Al-4V Sheet Following Beta Heat Treatment  

NASA Astrophysics Data System (ADS)

The effect of preheat time, prestrain, cooling rate, and concurrent deformation during cooling on the preferential selection of hcp alpha variants during the decomposition of the high-temperature, bcc beta phase in two-phase titanium alloys was established using Ti-6Al-4V sheet material. For this purpose, sheet tension samples were pre-soaked in the beta phase field for 0 or 10 minutes (to vary the beta grain size), subjected to a prestrain of 0 or 0.1, and cooled at a rate of 11 or 155 K/min (11 or 155 °C/min) under conditions comprising free ends, fixed ends, or concurrent deformation at a strain rate between ~10-5 and 3 × 10-4 s-1. Electron-backscatter diffraction was used to determine the orientations of the alpha variants so formed, from which the underlying high-temperature, beta-grain microstructure and orientations were reconstructed. These measurements revealed that the parent beta texture changed due to grain growth during preheating. A comparison of the alpha- and beta-phase textures indicated that preferential variant selection was most noticeable under conditions involving a slow cooling rate especially when prestrain or concurrent straining was imposed.

Semiatin, S. L.; Kinsel, K. T.; Pilchak, A. L.; Sargent, G. A.

2013-08-01

54

Magnetic quadrupole formation of elliptical sheet electron beams for high-power microwave devices  

Microsoft Academic Search

Sheet electron beams are attractive for high-power microwave sources due to their ability to transport high current, at reduced current density, through thin clearance apertures and in close proximity to walls or RF structures. This paper reports on the theoretical investigation of magnetic quadrupole formation of elliptical sheet electron beams for use in high-power microwave devices. The beam envelope equations

M. A. Basten; J. H. Booske; J. Anderson

1994-01-01

55

Non-Equilibrium and Current Sheet Formation in Line-Tied  

E-print Network

Non-Equilibrium and Current Sheet Formation in Line-Tied Magnetic Fields C. S. Ng and A years Require sharp gradient (current sheets) Line-tying in photosphere Quasi-equilibrium --- most equations #12;Magnetostatic equilibrium J z +[A, J] = 0 ,or B J = 0 with = = 0. c.f. 2D Euler equation

Ng, Chung-Sang

56

Supramolecular structure in full-length Alzheimer's beta-amyloid fibrils: evidence for a parallel beta-sheet organization from solid-state nuclear magnetic resonance.  

PubMed Central

We report constraints on the supramolecular structure of amyloid fibrils formed by the 40-residue beta-amyloid peptide associated with Alzheimer's disease (A beta(1-40)) obtained from solid-state nuclear magnetic resonance (NMR) measurements of intermolecular dipole-dipole couplings between (13)C labels at 11 carbon sites in residues 2 through 39. The measurements are carried out under magic-angle spinning conditions, using the constant-time finite-pulse radiofrequency-driven recoupling (fpRFDR-CT) technique. We also present one-dimensional (13)C magic-angle spinning NMR spectra of the labeled A beta(1-40) samples. The fpRFDR-CT data reveal nearest-neighbor intermolecular distances of 4.8 +/- 0.5 A for carbon sites from residues 12 through 39, indicating a parallel alignment of neighboring peptide chains in the predominantly beta-sheet structure of the amyloid fibrils. The one-dimensional NMR spectra indicate structural order at these sites. The fpRFDR-CT data and NMR spectra also indicate structural disorder in the N-terminal segment of A beta(1-40), including the first nine residues. These results place strong constraints on any molecular-level structural model for full-length beta-amyloid fibrils. PMID:12124300

Balbach, John J; Petkova, Aneta T; Oyler, Nathan A; Antzutkin, Oleg N; Gordon, David J; Meredith, Stephen C; Tycko, Robert

2002-01-01

57

Hybrid modeling of the formation and structure of thin current sheets in the magnetotail  

NASA Technical Reports Server (NTRS)

Hybrid simulations are used to investigate the formation of a thin current sheet inside the plasma sheet of a magnetotail-like configuration. The initial equilibrium is subjected to a driving electric field which is qualitatively similar to what would be expected from solar wind driving. As a result, a new current sheet with the thickness of approximately the ion inertial length is formed. The current density inside the current sheet region is supplied largely by the electrons. Ion acceleration in the cross-tail direction is absent as the driving electric field fails to penetrate into the equatorial region.

Hesse, Michael; Winske, Dan; Birn, Joachim

1996-01-01

58

Occurrence, Formation and Function of Organic Sheets in the Mineral Tube Structures of Serpulidae (Polychaeta, Annelida)  

PubMed Central

A scanning electron microscopy study of organic sheets in serpulid tube mineral structures was carried out to discern their function, formation and evolution. The organic sheets may have some taxonomic value in distinguishing the two major clades of serpulids previously identified. The organic sheets in the mineral tube structure occur only in certain taxa belonging to clade A, but not all species in clade A have them. Organic sheets are best developed in genus Spirobranchus. One could speculate that organic sheets have evolved as an adaption to further strengthen the mechanical properties of the tubes in clade A, which contains serpulids with the most advanced mineral tube microstructures. The organic sheets are presumably secreted with at least some mineral phase. PMID:24116035

Vinn, Olev

2013-01-01

59

Two cylindrical vortex sheets : evolution and singularity formation.  

E-print Network

??Using Rosenhead's point-vortex approximation with correction terms, the evolution of two symmetrical, counter-rotating, initially cylindrical vortex sheets in an incompressible, potential fluid flow is studied.… (more)

Jeremy, Johnson

2012-01-01

60

Responsive gels formed by the spontaneous self-assembly of peptides into polymeric beta-sheet tapes  

Microsoft Academic Search

Molecular self-assembly is becoming an increasingly popular route to new supramolecular structures and molecular materials1-7. The inspiration for such structures is commonly derived from self-assembling systems in biology. Here we show that a biological motif, the peptide beta-sheet, can be exploited in designed oligopeptides that self-assemble into polymeric tapes and with potentially useful mechanical properties. We describe the construction of

A. Aggeli; M. Bell; N. Boden; J. N. Keen; P. F. Knowles; T. C. B. McLeish; M. Pitkeathly; S. E. Radford

1997-01-01

61

Formation and transport of PCM-focused sheet electron beams  

SciTech Connect

Sheet electron beams have the potential to make possible higher power sources of coherent millimeter-wave radiation. Recent studies indicate the feasibility of stable focusing of low-emittance sheet beams using periodically-cusped magnetic (PCM) fields. The authors will discuss progress on the preparation of experiments to study the stability and transport of PCM-focused sheet electron beams. This includes a laboratory method to form sheet beams using magnetic quadrupole lenses, a commercially relevant strip-beam thermionic electron gun design, and a PCM configuration to confine the beam in both transverse dimensions. The experiments will involve a 10 kV, 2 A, 1.6 mm X 36 mm elliptical sheet beam and a PCM array with a 3.5 cm spatial period. Peak midplane magnetic fields of 1.0 kG should be adequate for stable beam focusing. The experimental studies will be complemented by numerical simulations using the MAGIC particle-in-cell code and the TOSCA 3-D magnetic design code.

Basten, M.A.; Booske, J.H.; Anderson, J.; Scharer, J.E. [Univ. of Wisconsin, Madison, WI (United States). Electrical and Computer Engineering Dept.; True, R. [Litton Electron Devices, San Carlos, CA (United States)

1994-12-31

62

Current Sheet Formation in a Conical Theta Pinch Faraday Accelerator with Radio-frequency Assisted Discharge  

NASA Technical Reports Server (NTRS)

Data from an inductive conical theta pinch accelerator are presented to gain insight into the process of inductive current sheet formation in the presence of a preionized background gas produced by a steady-state RF-discharge. The presence of a preionized plasma has been previously shown to allow for current sheet formation at lower discharge voltages and energies than those found in other pulsed inductive accelerator concepts, leading to greater accelerator efficiencies at lower power levels. Time-resolved magnetic probe measurements are obtained for different background pressures and pulse energies to characterize the effects of these parameters on current sheet formation. Indices are defined that describe time-resolved current sheet characteristics, such as the total current owing in the current sheet, the time-integrated total current ('strength'), and current sheet velocity. It is found that for a given electric field strength, maximums in total current, strength, and velocity occur for one particular background pressure. At other pressures, these current sheet indices are considerably smaller. The trends observed in these indices are explained in terms of the principles behind Townsend breakdown that lead to a dependence on the ratio of the electric field to the background pressure. Time-integrated photographic data are also obtained at the same experimental conditions, and qualitatively they compare quite favorably with the time-resolved magnetic field data.

Polzin, Kurt A.; Hallock, Ashley K.; Choueiri, Edgar Y.

2008-01-01

63

Spontaneous formation of electric current sheets and the origin of solar flares  

NASA Technical Reports Server (NTRS)

It is demonstrated that the continuous boundary motion of a sheared magnetic field in a tenuous plasma with an infinite electrical conductivity can induce the formation of multiple electric current sheets in the interior plasma. In response to specific footpoint displacements, the quadrupolar magnetic field considered is shown to require the formation of multiple electric current sheets as it achieves a force-free state. Some of the current sheets are found to be of finite length, running along separatrix lines of force which separate lobes of magnetic flux. It is suggested that current sheets in the form of infinitely thin magnetic shear layers may be unstable to resistive tearing, a process which may have application to solar flares.

Low, B. C.; Wolfson, R.

1988-01-01

64

Plasma Sheet and Ring Current Formation from Solar and Polar Wind Sources  

Microsoft Academic Search

We consider the formation of the plasma sheet and quiet ring current in the framework of collisionless test particle motions in 3D magnetospheric fields obtained from self-consistent MHD simulations. Simulation results are compared with observations of the near-Earth plasma sheet from the Polar spacecraft, during 2001 and 2002. Many particles were initiated in two regions representative of the solar wind

T. E. Moore; M. C. Fok; M. O. Chandler; C. R. Chappell; S. P. Christon; D. C. Delcourt; J. Fedder; M. Huddleston; M. Liemohn; W. K. Peterson; S. Slinker

2004-01-01

65

Plasma Sheet and (non-storm) Ring Current Formation from Solar and Polar Wind Sources  

Microsoft Academic Search

We consider the formation of the plasma sheet and geosynchronous region (non-storm) ring current in the framework of collisionless test particle motions in 3D magnetospheric fields obtained from self-consistent MHD simulations. Simulation results are compared with observations of the near-Earth plasma sheet from the Polar spacecraft, during 2001 and 2002. Many particles were initiated in two regions representative of the

T. E. Moore; M. C. Fok; M. O. Chandler; C. R. Chappell; S. P. Christon; D. C. Delcourt; J. Fedder; M. Huddleston; M. Liemohn; W. K. Peterson; S. Slinker

2004-01-01

66

Plasma sheet and (nonstorm) ring current formation from solar and polar wind sources  

Microsoft Academic Search

We consider the formation of the plasma sheet and geosynchronous region (nonstorm) ring current in the framework of collisionless test particle motions in three-dimensional magnetospheric fields obtained from self-consistent MHD simulations. Simulation results are compared with observations of the near-Earth plasma sheet from the Polar spacecraft during 2001 and 2002. Many particles were initiated in two regions representative of the

T. E. Moore; M.-C. Fok; M. O. Chandler; C. R. Chappell; S. P. Christon; D. C. Delcourt; J. Fedder; M. Huddleston; M. Liemohn; W. K. Peterson; S. Slinker

2005-01-01

67

Ballooning Instability Induced Plasmoid Formation in Near-Earth Plasma Sheet*  

NASA Astrophysics Data System (ADS)

The formation of plasmoids in the near-Earth magnetotail is believed to be a key element of the substorm onset process. The physical mechanism of plasmoid formation in the plasma sheet has remained a subject of considerable interests and investigations. Previous work has identified a new scenario in MHD simulations where the nonlinear evolution of a ballooning instability is able to induce the formation of plasmoids in a generalized Harris sheet with finite normal magnetic component [1]. In present work, we further examine this novel mechanism for plasmoid formation and explore its implications in the context of substorm onset trigger problem. For that purpose, we adopt the generalized Harris sheet as a model proxy to the near-Earth region of magnetotail during the substorm growth phase. In this region the magnetic component normal to the neutral sheet Bn is weak but nonzero. The magnetic field lines are closed and there are no X-lines. Simulation results indicate that in the higher Lundquist number regime, the linear axial tail mode, which is also known as ``two-dimensional resistive tearing mode'', is stabilized by the finite Bn, hence cannot give rise to the formation of X-lines or plasmoids by itself. On the other hand, the linear ballooning mode is unstable in the same regime, and in its nonlinear stage, the tailward stretching of the plasma sheet in the closed field line region due to the growing ballooning finger structures tends to accelerate the thinning of the near-Earth current sheet. This eventually leads to the formation of a series of plasmoid structures in the near-Earth and middle magnetotail regions of plasma sheet. This new scenario of plasmoid formation suggests a critical role of ballooning instability in the near-Earth plasma sheet in triggering the onset of a substorm expansion. [1] P. Zhu and J. Raeder, Plasmoid formation in current sheet with finite normal magnetic component, Phys. Rev. Lett. 110, 235005 (2013). *Supported by NSF grants AGS-0902360 and PHY-0821899.

Zhu, P.; Raeder, J.

2013-12-01

68

Non-Equilibrium and Current Sheet Formation in Line-Tied  

E-print Network

Non-Equilibrium and Current Sheet Formation in Line-Tied Magnetic Fields: Heating of the Solar in a magnetic non-equilibrium Parker's model (1972): Non-equilibrium driven by complex photospheric motions. i.e. surfaces of tangential discontinuities separating regions of quasi-equilibrium · Photospheric motion has

Ng, Chung-Sang

69

Magnetic quadrupole formation of low-voltage sheet electron beams for high-power microwave devices  

SciTech Connect

Sheet electron beams have the potential to make possible higher power sources of microwave radiation due to their ability to transport high currents, at reduced current densities, through a single narrow RF interaction circuit. Possible microwave device applications using sheet electron beams include sheet-beam klystrons, grating TWT`s, and planar FELs. One difficulty with the experimental investigation and implementation of sheet beams is the lack of a satisfactory source for large aspect-ratio beams. An attractive solution is the use of magnetic quadrupoles to transform an initially round beam from a conventional Pierce gun into a highly eccentric elliptical beam. Both 2-D envelope simulations and 3-D envelope and PIC code simulations indicate that this is a viable method of sheet beam formation, particularly for experimental investigations where flexibility and low-cost fabrication is desired. The authors are currently constructing a system to experimentally test this method. Features of the experiment include a low-cost commercially available Pierce gun, a four quadrupole sheet beam-forming system, and a highly elliptical output beam. Results of the 3-D PIC simulations of the beam and 3-D magnetostatic finite-element simulations of the quadrupole fringe fields will be discussed. Details of the experimental design and initial experimental measurements are presented.

Basten, M.A.; Booske, J.H.; Anderson, J.; Joe, J.; Scharer, J.E. [Univ. of Wisconsin, Madison, WI (United States). Dept. of Electrical and Computer Engineering

1995-12-31

70

Tandem beta-enamino ester formation and cyclization with o-alkynyl anilines catalyzed by InBr3: efficient synthesis of beta-(N-indolyl)-alpha,beta-unsaturated esters.  

PubMed

A tandem reaction providing beta-(N-indolyl)-alpha,beta-unsaturated esters from beta-keto esters and o-alkynyl anilines was developed. Z-Alkenes were selectively formed due to the stability of the beta-enamino ester as an intermediate of the reaction. This reaction includes the intermolecular beta-enamino ester formation and intramolecular cyclization catalyzed by InBr(3). PMID:19113947

Murai, Kenichi; Hayashi, Shoko; Takaichi, Nobuhiro; Kita, Yasuyuki; Fujioka, Hiromichi

2009-02-01

71

Formation and stability of the self-consistent one-dimensional tail current sheet  

NASA Technical Reports Server (NTRS)

The paper investigates the formation, the structure, and the stability of self-consistent one-dimensional current sheets in which the ions carry most of the current and momentum (the occurrence of which was suggested by observations of Mitchell et al., 1990; and Sergeev et al., 1990). Results of the analysis showed that, for the case of a cold current sheet, the characteristic thickness lamba equals to about (Bz/B0) exp 4/3 c/omega(p0), where Bz is the normal field component, B0 is the asymptotic magnitude of the reversing field, and c/omega(p0)is the collisionless ion skin depth based on lobe density. A two-dimensional self-consistent dynamical simulation model is developed, which demonstrates that these idealized current sheets are unstable to kink perturbations driven by the anisotropic pressure distribution produced by the chaotic nature of the particle orbits in a field-reversal region.

Pritchett, P. L.; Coroniti, F. V.

1992-01-01

72

Formation and stability of the self-consistent one-dimensional tail current sheet  

NASA Astrophysics Data System (ADS)

The paper investigates the formation, the structure, and the stability of self-consistent one-dimensional current sheets in which the ions carry most of the current and momentum (the occurrence of which was suggested by observations of Mitchell et al., 1990; and Sergeev et al., 1990). Results of the analysis showed that, for the case of a cold current sheet, the characteristic thickness lamba equals to about (Bz/B0) exp 4/3 c/omega(p0), where Bz is the normal field component, B0 is the asymptotic magnitude of the reversing field, and c/omega(p0)is the collisionless ion skin depth based on lobe density. A two-dimensional self-consistent dynamical simulation model is developed, which demonstrates that these idealized current sheets are unstable to kink perturbations driven by the anisotropic pressure distribution produced by the chaotic nature of the particle orbits in a field-reversal region.

Pritchett, P. L.; Coroniti, F. V.

1992-11-01

73

Formation of current sheets and sigmoidal structure by the kink instability of a magnetic loop  

E-print Network

We study dynamical consequences of the kink instability of a twisted coronal flux rope, using the force-free coronal loop model by Titov & D\\'emoulin (1999) as the initial condition in ideal-MHD simulations. When a critical value of the twist is exceeded, the long-wavelength ($m=1$) kink mode develops. Analogous to the well-known cylindrical approximation, a helical current sheet is then formed at the interface with the surrounding medium. In contrast to the cylindrical case, upward-kinking loops form a second, vertical current sheet below the loop apex at the position of the hyperbolic flux tube (generalized X line) in the model. The current density is steepened in both sheets and eventually exceeds the current density in the loop (although the kink perturbation starts to saturate in our simulations without leading to a global eruption). The projection of the field lines that pass through the vertical current sheet shows an S shape whose sense agrees with the typical sense of transient sigmoidal (forward or reverse S-shaped) structures that brighten in soft X rays prior to coronal eruptions. The upward-kinked loop has the opposite S shape, leading to the conclusion that such sigmoids do not generally show the erupting loops themselves but indicate the formation of the vertical current sheet below them that is the central element of the standard flare model.

B. Kliem; V. S. Titov; T. Toeroek

2003-11-09

74

Formation and Reconnection of Three-Dimensional Current Sheets in the Solar Corona  

NASA Technical Reports Server (NTRS)

Current-sheet formation and magnetic reconnection are believed to be the basic physical processes responsible for much of the activity observed in astrophysical plasmas, such as the Sun s corona. We investigate these processes for a magnetic configuration consisting of a uniform background field and an embedded line dipole, a topology that is expected to be ubiquitous in the corona. This magnetic system is driven by a uniform horizontal flow applied at the line-tied photosphere. Although both the initial field and the driver are translationally symmetric, the resulting evolution is calculated using a fully three-dimensional magnetohydrodynamic (3D MHD) simulation with adaptive mesh refinement that resolves the current sheet and reconnection dynamics in detail. The advantage of our approach is that it allows us to apply directly the vast body of knowledge gained from the many studies of 2D reconnection to the fully 3D case. We find that a current sheet forms in close analogy to the classic Syrovatskii 2D mechanism, but the resulting evolution is different than expected. The current sheet is globally stable, showing no evidence for a disruption or a secondary instability even for aspect ratios as high as 80:1. The global evolution generally follows the standard Sweet- Parker 2D reconnection model except for an accelerated reconnection rate at a very thin current sheet, due to the tearing instability and the formation of magnetic islands. An interesting conclusion is that despite the formation of fully 3D structures at small scales, the system remains close to 2D at global scales. We discuss the implications of our results for observations of the solar corona. Subject Headings: Sun: corona Sun: magnetic fields Sun: reconnection

Edmondson, J. K.; Antiochos, S. K.; DeVore, C. R.; Zurbuchen, T. H.

2010-01-01

75

The role of strand 1 of the C beta-sheet in the structure and function of alpha(1)-antitrypsin.  

PubMed

Serpins inhibit cognate serine proteases involved in a number of important processes including blood coagulation and inflammation. Consequently, loss of serpin function or stability results in a number of disease states. Many of the naturally occurring mutations leading to disease are located within strand 1 of the C beta-sheet of the serpin. To ascertain the structural and functional importance of each residue in this strand, which constitutes the so-called distal hinge of the reactive center loop of the serpin, an alanine scanning study was carried out on recombinant alpha(1)-antitrypsin Pittsburgh mutant (P1 = Arg). Mutation of the P10' position had no effect on its inhibitory properties towards thrombin. Mutations to residues P7' and P9' caused these serpins to have an increased tendency to act as substrates rather than inhibitors, while mutations at P6' and P8' positions caused the serpin to behave almost entirely as a substrate. Mutations at the P6' and P8' residues of the C beta-sheet, which are buried in the hydrophobic core in the native structure, caused the serpin to become highly unstable and polymerize much more readily. Thus, P6' and P8' mutants of alpha(1)-antitrypsin had melting temperatures 14 degrees lower than wild-type alpha(1)-antitrypsin. These results indicate the importance of maintaining the anchoring of the distal hinge to both the inhibitory mechanism and stability of serpins, the inhibitory mechanism being particularly sensitive to any perturbations in this region. The results of this study allow more informed analysis of the effects of mutations found at these positions in disease-associated serpin variants. PMID:11714919

Bottomley, S P; Lawrenson, I D; Tew, D; Dai, W; Whisstock, J C; Pike, R N

2001-12-01

76

Calculation of reversible gas formation of hollow shells from the sheet  

Microsoft Academic Search

A finite-element model for calculating the transitions of reversible gas formation with the use of a special puncheon or bush\\u000a in the matrix, allowing one to decrease the polythickness of the wall of the cupola-like shell made of the sheet via the retardation\\u000a and redistribution of the deformation in a specified direction, is developed.

E. M. Seledkin; V. D. Kukhar’; M. A. Tsepin; K. Yu. Apatov

2010-01-01

77

Live spheroid formation recorded with light sheet-based fluorescence microscopy.  

PubMed

We provide a detailed protocol for a three-dimensional long-term live imaging of cellular spheroids with light sheet-based fluorescence microscopy. The protocol allows the recording of all phases of spheroid formation in three dimensions, including cell proliferation, aggregation, and compaction. We employ the human hepatic cell line HepaRG transfected with the fusion protein H2B-GFP, i.e., a fluorescing histone. The protocol allows monitoring the effect of drugs or toxicants. PMID:25391793

Pampaloni, Francesco; Richa, Roli; Ansari, Nariman; Stelzer, Ernst H K

2015-01-01

78

Factors contributing to the formation of sheeting joints: A study of sheeting joints on a dome in Yosemite National Park  

NASA Astrophysics Data System (ADS)

Sheeting joints (shallow, surface-parallel, opening-mode rock fractures) are widespread and have been studied for centuries. They are commonly attributed to removal of overburden by erosion, but erosion alone cannot open a sheeting joint. I test an alternative hypothesis that sheeting joints open in response to surface-parallel compression along a convex topographic surface using field observations, a large-scale fracture map, and analyses of stresses, slopes, and surface-curvatures (derived from aerial laser altimetry data) for a dome along Tenaya Creek in Yosemite National Park. Approximately 90% of the surface of detailed study is convex in at least one direction. Existing stresses and topography there can account for the nature and distribution of sheeting joints on the doubly-convex surfaces. Sheeting joints parallel and constitute the surface where the surface is doubly convex. Elsewhere, sheeting joints daylight, implying the surface has been eroded since the sheeting joints formed. My findings support the hypothesis.

Mitchell, Kelly J.

79

Abnormal lens morphogenesis and ectopic lens formation in the absence of beta-catenin function.  

PubMed

beta-Catenin plays a key role in cadherin-mediated cell adhesion as well as in canonical Wnt signaling. To study the role of beta-catenin during eye development, we used conditional Cre/loxP system in mouse to inactivate beta-catenin in developing lens and retina. Inactivation of beta-catenin does not suppress lens fate, but instead results in abnormal morphogenesis of the lens. Using BAT-gal reporter mice, we show that beta-catenin-mediated Wnt signaling is notably absent from lens and neuroretina throughout eye development. The observed defect is therefore likely due to the cytoskeletal role of beta-catenin, and is accompanied by impaired epithelial cell adhesion. In contrast, inactivation of beta-catenin in the nasal ectoderm, an area with active Wnt signaling, results in formation of crystallin-positive ectopic lentoid bodies. These data suggest that, outside of the normal lens, beta-catenin functions as a coactivator of canonical Wnt signaling to suppress lens fate. PMID:17410548

Kreslova, Jana; Machon, Ondrej; Ruzickova, Jana; Lachova, Jitka; Wawrousek, Eric F; Kemler, Rolf; Krauss, Stefan; Piatigorsky, Joram; Kozmik, Zbynek

2007-04-01

80

Formation and Degradation of Beta-casomorphins in Dairy Processing.  

PubMed

ABSTRACT Milk proteins including casein are sources of peptides with bioactivity. One of these peptides is beta-casomorphin (BCM) which belongs to a group of opioid peptides formed from ?-casein variants. Beta-casomorphin 7 (BCM7) has been demonstrated to be enzymatically released from the A1 or B ?-casein variant. Epidemiological evidence suggests the peptide BCM 7 is a risk factor for development of human diseases, including increased risk of type 1 diabetes and cardiovascular diseases but this has not been thoroughly substantiated by research studies. High performance liquid chromatography coupled to UV-Vis and mass spectrometry detection as well as enzyme-linked immunosorbent assay (ELISA) have been used to analyse BCMs in dairy products. BCMs have been detected in raw cow's milk and human milk and a variety of commercial cheeses, but their presence has yet to be confirmed in commercial yoghurts. The finding that BCMs are present in cheese suggests they could also form in yoghurt, but be degraded during yoghurt processing. Whether BCMs do form in yoghurt and the amount of BCM forming or degrading at different processing steps needs further investigation and possibly will depend on the heat treatment and fermentation process used, but it remains an intriguing unknown. PMID:25077377

Nguyen, D D; Johnson, S K; Busetti, F; Solah, V A

2014-07-31

81

Efficient Traversal of Beta-Sheet Protein Folding Pathways Using Ensemble Models  

NASA Astrophysics Data System (ADS)

Molecular Dynamics (MD) simulations can now predict ms-timescale folding processes of small proteins - however, this presently requires hundreds of thousands of CPU hours and is primarily applicable to short peptides with few long-range interactions. Larger and slower-folding proteins, such as many with extended ?-sheet structure, would require orders of magnitude more time and computing resources. Furthermore, when the objective is to determine only which folding events are necessary and limiting, atomistic detail MD simulations can prove unnecessary. Here, we introduce the program tFolder as an efficient method for modelling the folding process of large ?-sheet proteins using sequence data alone. To do so, we extend existing ensemble ?-sheet prediction techniques, which permitted only a fixed anti-parallel ?-barrel shape, with a method that predicts arbitrary ?-strand/?-strand orientations and strand-order permutations. By accounting for all partial and final structural states, we can then model the transition from random coil to native state as a Markov process, using a master equation to simulate population dynamics of folding over time. Thus, all putative folding pathways can be energetically scored, including which transitions present the greatest barriers. Since correct folding pathway prediction is likely determined by the accuracy of contact prediction, we demonstrate the accuracy of tFolder to be comparable with state-of-the-art methods designed specifically for the contact prediction problem alone. We validate our method for dynamics prediction by applying it to the folding pathway of the well-studied Protein G. With relatively very little computation time, tFolder is able to reveal critical features of the folding pathways which were only previously observed through time-consuming MD simulations and experimental studies. Such a result greatly expands the number of proteins whose folding pathways can be studied, while the algorithmic integration of ensemble prediction with Markovian dynamics can be applied to many other problems.

Shenker, Solomon; O'Donnell, Charles W.; Devadas, Srinivas; Berger, Bonnie; Waldispühl, Jérôme

82

His26 Protonation in Cytochrome c Triggers Microsecond ?-sheet Formation and Heme Exposure: Implications for Apoptosis  

PubMed Central

Cytochrome c unfolds locally and reversibly upon heating at pH 3. UV resonance Raman (UVRR) spectra reveal that instead of producing unordered structure, unfolding converts turns and some helical elements to ?-sheet. It also disrupts the Met80-heme bond, and was earlier shown to induce peroxidase activity. Aromatic residues that are H-bonded to a heme propionate (Trp59 and Tyr48) alter their orientation, indicating heme displacement. T-jump/UVRR measurements give time constants of 0.2, 3.9 and 67 µs for successive phases of ?-sheet formation and concomitant reorientation of Trp59. UVRR spectra reveal protonation of histidines, and specifically of His26, whose H-bond to Pro44 anchors the 40s ? loop; this loop is known to be the least stable ‘foldon’ in the protein. His26 protonation is proposed to disrupt its H-bond with Pro44, triggering the extension of a short ?-sheet segment at the ‘neck’ of the 40s ? loop into the loop itself and back into the 60’s and 70’s helices. The secondary structure change displaces the heme via H-bonds from residues in the growing ?-sheet, thereby exposing it to exogenous ligands, and inducing peroxidase activity. This unfolding mechanism may play a role in cardiolipin peroxidation by cyt c during apoptosis. PMID:23094892

Balakrishnan, Gurusamy; Hu, Ying; Spiro, Thomas G.

2012-01-01

83

World Sheet Commuting beta-gamma CFT and Non-Relativistic StringTheories  

SciTech Connect

We construct a sigma model in two dimensions with Galilean symmetry in flat target space similar to the sigma model of the critical string theory with Lorentz symmetry in 10 flat spacetime dimensions. This is motivated by the works of Gomis and Ooguri[1] and Danielsson et. al.[2, 3]. Our theory is much simpler than their theory and does not assume a compact coordinate. This non-relativistic string theory has a bosonic matter {beta}{gamma} CFT with the conformal weight of {beta} as 1. It is natural to identify time as a linear combination of {gamma} and {bar {gamma}} through an explicit realization of the Galilean boost symmetry. The angle between {gamma} and {bar {gamma}} parametrizes one parameter family of selection sectors. These selection sectors are responsible for having a non-relativistic dispersion relation without a nontrivial topology in the non-relativistic setup, which is one of the major differences from the previous works[1, 2, 3]. This simple theory is the non-relativistic analogue of the critical string theory, and there are many different avenues ahead to be investigated. We mention a possible consistent generalization of this theory with different conformal weights for the {beta}{gamma} CFT. We also mention supersymmetric generalizations of these theories.

Kim, Bom Soo

2007-08-30

84

Magnetic quadrupole formation of elliptical sheet electron beams for high-power microwave devices  

SciTech Connect

Sheet electron beams are attractive for high-power microwave sources due to their ability to transport high current, at reduced current density, through thin clearance apertures and in close proximity to walls or RF structures. This paper reports on the theoretical investigation of magnetic quadrupole formation of elliptical sheet electron beams for use in high-power microwave devices. The beam envelope equations for an initially round beam passing through a physical non-symmetric quadrupole pair in the presence of space-charge, finite beam emittance, and under the effects of third-order field components and longitudinal velocity variations are presented. The presence of space-charge compensates for over-focusing in the thin beam-dimension and allows for the formation of highly elliptic sheet electron beams. As an example, the results of the study were applied to an existing Pierce gun source with a beam radius of 0.6 cm, beam energy of 10 keV and current density of 2.0 A/cm[sup 2]. The authors find that an elliptical beam with major radius r[sub a] = 3.61 cm, minor radius r[sub b] = 0.16 cm and ellipticity (r[sub a]/r[sub b]) of 22.5 can be produced with only modest quadrupole gradients of 64 G/cm and 18 G/cm. Quadrupole formation of elliptical sheet-beams may be particularly suited for experimental research applications since existing round-beam electron guns may be used and changes in beam ellipticity may be made without breaking the vacuum system.

Basten, M.A.; Booske, J.H.; Anderson, J. (Univ. of Wisconsin, Madison, WI (United States). Electrical and Computer Engineering Dept.)

1994-10-01

85

Landscape formation by past continental ice sheets: insights into the subglacial environment  

NASA Astrophysics Data System (ADS)

Glaciers and ice sheets are known as most powerful, climatically driven agents of large-scale sediment redistribution and landscape formation in the Earth system. During the Quaternary, repeated waxing and waning of continental ice sheets contributed to profound reshaping of the Earth surface and set the scene for the development of ecosystems in the post-glacial time. Despite the well-established impact of glaciers on the upper lithosphere the specific processes of glacial erosion, transport and deposition and the formation landforms at the ice-bed interface are contentious. In particular, the relative importance of direct ice impact versus the impact of glacial meltwater is highly controversial. Here, we focus on the southern peripheral area of the Scandinavian Ice Sheet hosting thick successions of soft, deformable sediments and examine some spectacular sediment/landform assemblages found nowadays in both terrestrial and marine settings to illustrate the nature of the subglacial processes. In order to decipher the past ice sheet behavior field, experimental and numerical approaches are combined. It is shown that the strength of the coupling between the ice and the bed that controls the response of the substratum to ice overriding and stress propagation depends primarily on the ability of the glacial system to evacuate meltwater from ice-bed interface. Strong coupling, locally enhanced by subglacial permafrost resulted in deeply rooted (100's of meters) glaciotectonic deformation reflected on the surface as ice-shoved hills whereas weak coupling promoted by water accumulating under the ice triggered the formation of deep (100's of meters) tunnel valley networks. Under the arteries of fast-flowing ice known as palaeo-ice streams, remoulding of soft sediments generated mega-scale glacial lineations and drumlins that hold the key to understanding glacier dynamics. The subglacial environment is envisaged as a four-dimensional mosaic of stable and deforming spots transient in time and space whose impact is embedded in the properties of sediment/landform systems.

Piotrowski, Jan A.

2014-05-01

86

A revised set of potentials for beta-turn formation in proteins.  

PubMed Central

Three thousand eight hundred ninety-nine beta-turns have been identified and classified using a nonhomologous data set of 205 protein chains. These were used to derive beta-turn positional potentials for turn types I' and II' for the first time and to provide updated potentials for formation of the more common types I, II, and VIII. Many of the sequence preferences for each of the 4 positions in turns can be rationalized in terms of the formation of stabilizing hydrogen bonds, preferences for amino acids to adopt a particular conformation in phi, psi space, and the involvement of turn types I' and II' in beta-hairpins. Only 1,632 (42%) of the turns occur in isolation; the remainder have at least 1 residue in common with another turn and have hence been classified as multiple turns. Several types of multiple turn have been identified and analyzed. PMID:7756980

Hutchinson, E. G.; Thornton, J. M.

1994-01-01

87

Alzheimer's beta-peptide oligomer formation at physiologic concentrations.  

PubMed

When diluted from dimethyl sulfoxide or 1,1,1,3,3,3-hexafluoro-2-propanol, synthetic human Abeta(1-42) readily forms oligomeric structures at near physiologic concentrations (1-20 nM). Oligomers 40 kDa are detected in a sandwich enzyme-linked immunosorbant assay where the capture and detection antibodies recognize the same primary sequence epitope. Monomeric peptide with a single epitope does not react in this format. Abeta(1-40) peptide does not oligomerize readily under these conditions. The rate of oligomer formation has a steep linear temperature dependence but is weakly affected by ionic strength up to 0.5M NaCl or KCl. Oligomer formation is inhibited by concentrations of Tween 20 and several other detergents well below their critical micelle concentrations. Once formed, high-molecular-weight oligomers are stabilized by Tween 20. Gel permeation chromatography of an oligomer preparation formed at nanomolar concentrations indicates that the majority of the Abeta(1-42) peptide chromatographs as monomers/dimers of apparent mw approximately 10 kDa. The most abundant oligomers have apparent mobilities corresponding to 220 kDa (48-mer) and higher multiples of this without detectable concentrations of intermediate low-molecular-weight species. Very little immunoreactive peptide appears in the void volume (>1.5 MDa) of a Superose 12 column. The oligomers are stable, rechromatographing at their original position. Abeta(1-42) oligomer formation at physiologic concentrations is a reproducible process that is amenable to kinetic analysis and inhibition. PMID:15519574

LeVine, Harry

2004-12-01

88

Parallel ?-sheet fibril and antiparallel ?-sheet oligomer: new insights into amyloid formation of hen egg white lysozyme under heat and acidic condition from FTIR spectroscopy.  

PubMed

Hen egg white lysozyme (HEWL) is widely used as a model protein for amyloid research. In this study, we aim to use Fourier transform infrared (FTIR) spectroscopy to gain new structural insights into amyloid formation of HEWL under heat and acidic condition. We reveal that the fibril-forming solution of HEWL has the capability to form fibril and oligomer with distinct ?-sheet configurations under different temperatures. Amyloid fibril with parallel ?-sheet configuration is formed at elevated temperature, while oligomer with antiparallel ?-sheet configuration is formed at room temperature. The interplay between fibrillation and oligomerization suggests that the two ?-sheet aggregates consume the same amyloidogenic materials such as peptide fragments and nicked HEWL due to lysozyme hydrolysis under heat and acidic condition. Temperature-dependent FTIR reveals that the oligomer is unstable at elevated temperature, demonstrating its off-pathway nature. The temperature-dependent formation of parallel and antiparallel ?-sheet configurations discovered in lysozyme system is compared with that of amyloid-? and ?-synuclein systems and the implication is discussed. PMID:23537140

Zou, Ye; Li, Yiyi; Hao, Wenying; Hu, Xiaoqian; Ma, Gang

2013-04-18

89

Calcofluor fluorescence assay for wort beta-glucan in a microplate format  

Technology Transfer Automated Retrieval System (TEKTRAN)

The widely-used fluorescent (Calcofluor) flow injection analysis method for determining the concentrations of beta-glucans in Congress worts from barley malts is adapted to microplate format. Adaptation of the Calcofluor assay to use widely available fluorescent microplate readers makes the assay m...

90

The chemical mechanism of beta-haematin formation studied by Mössbauer spectroscopy.  

PubMed Central

Spontaneous formation of beta-haematin (malaria pigment) from haematin in acetate solution follows pseudo-zero-order and not autocatalytic kinetics. Acetate appears to facilitate the reaction by solubilizing the haematin and acting as a phase-transfer catalyst, a role which, in vivo, could be fulfilled by carboxylic acids or amino acids. PMID:8761447

Adams, P A; Egan, T J; Ross, D C; Silver, J; Marsh, P J

1996-01-01

91

Molecular cloud evolution. I. Molecular cloud and thin CNM sheet formation  

E-print Network

We discuss molecular cloud formation by large-scale supersonic compressions in the diffuse warm neutral medium (WNM). Initially, a shocked layer forms, and within it, a thin cold layer. An analytical model and high-resolution 1D simulations predict the thermodynamic conditions in the cold layer. After $\\sim 1$ Myr of evolution, the layer has column density $\\sim 2.5 \\times 10^{19} \\psc$, thickness $\\sim 0.03$ pc, temperature $\\sim 25$ K and pressure $\\sim 6650$ K $\\pcc$. These conditions are strongly reminiscent of those recently reported by Heiles and coworkers for cold neutral medium sheets. In the 1D simulations, the inflows into the sheets produce line profiles with a central line of width $\\sim 0.5 \\kms$ and broad wings of width $\\sim 1 \\kms$. 3D numerical simulations show that the cold layer develops turbulent motions and increases its thickness, until it becomes a fully three-dimensional turbulent cloud. Fully developed turbulence arises on times ranging from $\\sim 7.5$ Myr for inflow Mach number $\\Mr = 2.4$ to $> 80$ Myr for $\\Mr = 1.03$. These numbers should be considered upper limits. The highest-density turbulent gas (HDG, $n > 100 \\pcc$) is always overpressured with respect to the mean WNM pressure by factors 1.5--4, even though we do not include self-gravity. The intermediate-density gas (IDG, $10 CNM sheets may be formed transiently by this mechanism, when the compressions are only weakly supersonic.

Enrique Vazquez-Semadeni; Dongsu Ryu; Thierry Passot; Ricardo F. Gonzalez; Adriana Gazol

2005-09-06

92

Molecular cloud evolution. I. Molecular cloud and thin CNM sheet formation  

E-print Network

We analyze the scenario of molecular cloud formation by large-scale supersonic compressions in the diffuse warm neutral medium (WNM). An analytical model and high-resolution 1D simulations predict that when the inflow Mach number Mr~1, a thin cold layer forms within the shocked gas. After ~1 Myr of evolution, the layer has column density ~2.5x 0^19 cm^-2, thickness ~0.03 pc, temperature ~25 K and pressure ~6650 K cm^-3. In the simulations, the sheets have line profiles with a central line of width ~0.5 km/s and broad wings of width ~1 km/s, which correspond to the inflowing speed of the gas, and do not imply excessively short lifetimes for the sheets. These sheets are reminiscent of those recently observed by Heiles and coworkers. 3D numerical simulations show that at later times the cold layer becomes dynamically unstable, through a nonlinear thin shell-like instability occurring at the boundary of the thin shell. Fully developed turbulence arises on times ranging from ~5 Myr for Mr=2.4 to ~100 Myr for Mr=1....

Vázquez-Semadeni, E; Passot, T; González, R F; Gazol, A; Vazquez-Semadeni, Enrique; Ryu, Dongsu; Passot, Thierry; Gonzalez, Ricardo F.; Gazol, Adriana

2005-01-01

93

Low cost fabrication of sheet structure using a new beta titanium alloy, Ti-15V-3Cr-3Al-3Sn  

NASA Technical Reports Server (NTRS)

Development efforts have been undertaken to improve the processing and structural efficiencies of advanced cold-formable beta Ti alloys, using the standard, hot-formed and rivetted construction of Ti-6Al-4V sheet structures as a basis for comparison. Ti-15V-3Cr-3Al-3Sn (Ti-15-3) beta alloy is formable, brazable and weldable in the solution-treated condition, and after aging displays mechanical properties suitable for postulated service in the -65 to 600 F temperature range. A novel methodology using cold-formed Ti-15-3 stringers and Ti-6Al-4V face sheets that are joined by means of an out-of-furnace isothermal brazing process, followed by low temperature aging, can reduce production costs by as much as 28 per cent. Structural efficiency has been demonstrated in room and elevated temperature crippling tests of small skin-stringer assemblies.

Kaneko, R. S.; Davis, G. W.; Woods, C. A.; Royster, D. M.

1982-01-01

94

Factors of paleosol formation in a Late Cretaceous eolian sand sheet paleoenvironment, Marlia Formation, Southeastern Brazil  

E-print Network

Formation, Southeastern Brazil Patrick Francisco Führ Dal' Bó a, , Giorgio Basilici a , Rômulo Simões), Brazil b IG ­ Universidade Federal do Pará, 66075-110, Belém (PA), Brazil a b s t r a c ta r t i c l e i Late Cretaceous The Marília Formation, which crops out in southeastern Brazil, is interpreted as a Late

Ahmad, Sajjad

95

Effect of secondary structure on the potential of mean force for poly-L-lysine in the alpha-Helix and beta-sheet conformations  

SciTech Connect

Because poly-L-lysine (PLL) can exist in the {alpha}-helix or {beta}-sheet conformation depending on solution preparation and solution conditions, PLL is a suitable candidate to probe the dependence of protein interactions on secondary structure. The osmotic second virial coefficient and weight-average molecular weight are reported from low-angle laser-light scattering measurements for PLL as a function of NaCl concentration, pH, and {alpha}-helix or {beta}-sheet content. Interactions between PLL molecules become more attractive as salt concentration increases due to screening of PLL charge by salt ions and at low salt concentration become more attractive as pH increases due to decreased net charge on PLL. The experimental results show that interactions are stronger for the {beta}-sheet conformation than for the {alpha}-helix conformation. A spherically-symmetric model for the potential of mean force is used to account for specific interactions not described by DLVO theory and to show how differences in secondary structure affect PLL interactions.

Grigsby, J.J.; Blanch, H.W.; Prausnitz, J.M.

2001-10-30

96

Formation and transport of sheet electron beams and multi-beam configurations for high-power microwave devices  

SciTech Connect

Sheet electron beams and configurations with multiple electron beams have the potential to make possible higher power sources of microwave radiation due to their ability to transport high currents, at reduced current densities, through a single RF interaction circuit. Possible microwave device applications using sheet electron beams include sheet-beam klystrons, rectangular grating circuits, and planar FELS. Historically, implementation of sheet beams in microwave devices has been discouraged by their susceptibility to the diocotron instability in solenoidal focusing systems. However, recent theoretical and numerical studies have shown that stable transport of sheet beams is possible, in periodically cusped magnetic (PCM) fields. The use of an offset-pole PCM configuration has been shown analytically to provide side-fields for 2-D focusing of the beam, and this has been recently verified with PIC code simulations. The authors will present further theoretical studies of sheet and multi-beam transport and discuss results from an experimental investigation of the formation, stability and transport of PCM-focused sheet electron beams. This includes a laboratory method of forming an elliptical sheet beam using a magnetic quadrupole pair and a round-beam Pierce gun.

Basten, M.A.; Booske, J.H.; Anderson, J.; Scharer, J.E. [Univ. of Wisconsin, Madison, WI (United States). Dept. of Electrical and Computer Engineering

1995-11-01

97

Amyloid formation and inhibition of an all-beta protein: A study on fungal polygalacturonase  

NASA Astrophysics Data System (ADS)

Theoretically, all proteins can adopt the nanofibrillar structures known as amyloid, which contain cross-beta structures. The all-beta folded proteins are particularly interesting in this regard, since they appear to be naturally more predisposed toward this structural arrangement. In this study, methanol has been used to drive the beta-helix protein polygalacturonase (PG), toward amyloid fibril formation. Congo red absorbance, thioflavin T fluorescence, circular dichroism (CD) and transmission electron microscopy have been used to characterize this process. Similar to other all-beta proteins, PG shows a non-cooperative fibrillation mechanism, but the structural changes that are monitored by CD indicate a different pattern. Furthermore, several compounds containing aromatic components were tested as potential inhibitors of amyloid formation. Another protein predominantly composed of alpha-helices (human serum albumin) was also targeted by these ligands, in order to get an insight into their potential anti-aggregation property toward structurally different proteins. Among tested compounds, silibinin and chlorpropamide were able to considerably affect both proteins fibrillation process.

Chinisaz, Maryam; Ghasemi, Atiyeh; Larijani, Bagher; Ebrahim-Habibi, Azadeh

2014-02-01

98

Epithelial Sheet Folding Induces Lumen Formation by Madin-Darby Canine Kidney Cells in a Collagen Gel  

PubMed Central

Lumen formation is important for morphogenesis; however, an unanswered question is whether it involves the collective migration of epithelial cells. Here, using a collagen gel overlay culture method, we show that Madin-Darby canine kidney cells migrated collectively and formed a luminal structure in a collagen gel. Immediately after the collagen gel overlay, an epithelial sheet folded from the periphery, migrated inwardly, and formed a luminal structure. The inhibition of integrin-?1 or Rac1 activity decreased the migration rate of the peripheral cells after the sheets folded. Moreover, lumen formation was perturbed by disruption of apical-basolateral polarity induced by transforming growth factor-?1. These results indicate that cell migration and cell polarity play an important role in folding. To further explore epithelial sheet folding, we developed a computer-simulated mechanical model based on the rigidity of the extracellular matrix. It indicated a soft substrate is required for the folding movement. PMID:25170757

Ishida, Sumire; Tanaka, Ryosuke; Yamaguchi, Naoya; Ogata, Genki; Mizutani, Takeomi; Kawabata, Kazushige; Haga, Hisashi

2014-01-01

99

Involvement of Streptococcus gordonii Beta-Glucoside Metabolism Systems in Adhesion, Biofilm Formation, and In Vivo Gene Expression  

Microsoft Academic Search

Streptococcus gordonii genes involved in beta-glucoside metabolism are induced in vivo on infected heart valves during experimental endocarditis and in vitro during biofilm formation on saliva-coated hydroxyapatite (sHA). To determine the roles of beta-glucoside metabolism systems in biofilm formation, the loci of these induced genes were analyzed. To confirm the function of genes in each locus, strains were constructed with

Ali O. Kilic; Lin Tao; Yongshu Zhang; Yu Lei; Ali Khammanivong; Mark C. Herzberg

2004-01-01

100

Formation of lobate debris aprons on Mars: Assessment of regional ice sheet collapse and debris-cover armoring  

E-print Network

Formation of lobate debris aprons on Mars: Assessment of regional ice sheet collapse and debris Keywords: Mars, climate Mars, surface Mars, polar geology Mars, polar caps a b s t r a c t Lobate debris aprons undergoing viscous flow, (2) local debris-covered alpine-like glaciers, or (3) remnants

Marchant, David R.

101

Architecture and origin of an amalgamated fluvial sheet sand, lower Castlegate Formation, Book Cliffs, Utah  

Microsoft Academic Search

Amalgamated, fluvial sheet sandstones in the stratigraphic record are often interpreted as the deposits of braided rivers. Alluvial sequence stratigraphic models show these sheet sandstones overlying sequence boundaries and deposited during low rates of base level rise and fall. Since sequence stratigraphic models rely on the balance between creation\\/destruction of accommodation and sediment supply, is the sheet-like nature of these

Brett T. McLaurin; Ron J. Steel

2007-01-01

102

Involvement of Streptococcus gordonii Beta-Glucoside Metabolism Systems in Adhesion, Biofilm Formation, and In Vivo Gene Expression  

PubMed Central

Streptococcus gordonii genes involved in beta-glucoside metabolism are induced in vivo on infected heart valves during experimental endocarditis and in vitro during biofilm formation on saliva-coated hydroxyapatite (sHA). To determine the roles of beta-glucoside metabolism systems in biofilm formation, the loci of these induced genes were analyzed. To confirm the function of genes in each locus, strains were constructed with gene inactivation, deletion, and/or reporter gene fusions. Four novel systems responsible for beta-glucoside metabolism were identified, including three phosphoenolpyruvate-dependent phosphotransferase systems (PTS) and a binding protein-dependent sugar uptake system for metabolizing multiple sugars, including beta-glucosides. Utilization of arbutin and esculin, aryl-beta-glucosides, was defective in some mutants. Esculin and oligochitosaccharides induced genes in one of the three beta-glucoside metabolism PTS and in four other genetic loci. Mutation of genes in any of the four systems affected in vitro adhesion to sHA, biofilm formation on plastic surfaces, and/or growth rate in liquid medium. Therefore, genes associated with beta-glucoside metabolism may regulate S. gordonii in vitro adhesion, biofilm formation, growth, and in vivo colonization. PMID:15205427

Kiliç, Ali O.; Tao, Lin; Zhang, Yongshu; Lei, Yu; Khammanivong, Ali; Herzberg, Mark C.

2004-01-01

103

Formation and transport of low-voltage, space-charge dominated sheet electron beams for high-power microwave devices  

SciTech Connect

Sheet electron beams have the potential to make possible higher power sources of microwave radiation due to their ability to transport high currents, at reduced current densities, through a single narrow RF interaction circuit. The authors will discuss experimental investigations of the formation of an elliptical sheet beam using magnet quadrupoles and a round-beam electron gun. Features of this configuration include a low-cost, commercially available Pierce gun and a lens system consisting of four tunable magnetic quadrupoles with modest field gradients. Three-dimensional envelope and particle-in-cell simulations indicate that this method can generate highly elliptic output beams, with variability in final beam size, for laboratory experiments on sheet beam transport. They also will present the results of particle-in-cell simulations of the transport of sheet beams in long-period offset-pole periodic magnet arrays. While the stability of sheet beams in short-period arrays has previously been established, the extension to longer magnet periods indicate that side-focusing of space-charge dominated sheet beams is more problematic than beam stability. However, long-term (> 20 periods) stable transport is demonstrated for {lambda}{sub m} = 1 cm for a 2 A, 10 kV elliptical beam with a = 2.7 cm and b = 0.05 cm.

Basten, M.A.; Booske, J.H.; Louis, L.J.; Joe, J.; Scharer, J.E. [Univ. of Wisconsin, Madison, WI (United States). Dept. of Electrical and Computer Engineering

1996-12-31

104

Nonlinear evolution of three-dimensional instabilities of thin and thick electron scale current sheets: Plasmoid formation and current filamentation  

SciTech Connect

Nonlinear evolution of three dimensional electron shear flow instabilities of an electron current sheet (ECS) is studied using electron-magnetohydrodynamic simulations. The dependence of the evolution on current sheet thickness is examined. For thin current sheets (half thickness =d{sub e}=c/?{sub pe}), tearing mode instability dominates. In its nonlinear evolution, it leads to the formation of oblique current channels. Magnetic field lines form 3-D magnetic spirals. Even in the absence of initial guide field, the out-of-reconnection-plane magnetic field generated by the tearing instability itself may play the role of guide field in the growth of secondary finite-guide-field instabilities. For thicker current sheets (half thickness ?5?d{sub e}), both tearing and non-tearing modes grow. Due to the non-tearing mode, current sheet becomes corrugated in the beginning of the evolution. In this case, tearing mode lets the magnetic field reconnect in the corrugated ECS. Later thick ECS develops filamentary structures and turbulence in which reconnection occurs. This evolution of thick ECS provides an example of reconnection in self-generated turbulence. The power spectra for both the thin and thick current sheets are anisotropic with respect to the electron flow direction. The cascade towards shorter scales occurs preferentially in the direction perpendicular to the electron flow.

Jain, Neeraj; Büchner, Jörg [Max Planck/Princeton Center for Plasma Physics, Göttingen (Germany); Max Planck Institute for Solar System Research, Justus-Von-Liebig-Weg-3, Göttingen (Germany)

2014-07-15

105

Ability of carbazole salts, inhibitors of Alzheimer beta-amyloid fibril formation, to cross cellular membranes.  

PubMed

Alzheimer's disease is characterized by the presence of beta-amyloid fibril formation. The inhibition of this peptide accumulation may be a prevention method for Alzheimer's disease. Several classes of molecules have been reported to inhibit beta-amyloid fibril formation and among them carbazoles. However, very few studies have been performed to determine the destination of such molecules in vivo and especially if they can pass the blood brain barrier. The aim of this paper is to study whether carbazoles could pass the blood brain barrier, i.e. if they can circumvent ATP Binding Cassette (ABC) transporters such as P-glycoprotein (P-gp) and Multidrug Resistance-associated protein (MRP1) which efficiently limit drug brain uptake. For this purpose we have synthesized a fluorescent derivative of carbazole benzothiazolium iodide 1,2 disubstituted ethylene (referred as carbazole thiazole: CT), which can be easily detected and followed in the pre-trial study phases in cells or in tissue. We use cellular models overexpressing P-gp and MRP1. Our results show that: i) CT is able to cross membranes and to penetrate rapidly inside the cells, ii) CT is a P-gp substrate and consequently its accumulation in P-gp overexpressing cells is very low, iii) CT is a poor MRP1 substrate. In addition once inside the cells, CT rapidly binds to DNA and is then slowly reduced by intracellular reducing agents. In conclusion, the efficiency of carbazole derivatives in inhibiting the beta-amyloid formation in vivo could be highly compromised because, as P-gp substrates, they will probably not cross the blood brain barrier. PMID:17291491

Saengkhae, Chantarawan; Salerno, Milena; Adès, Dominique; Siove, Alain; Le Moyec, Laurence; Migonney, Véronique; Garnier-Suillerot, Arlette

2007-03-22

106

Interchange motion as a transport mechanism for formation of cold-dense plasma sheet  

NASA Astrophysics Data System (ADS)

evaluate whether interchange motion can provide the transport for the formation of the cold-dense plasma sheet in the near-Earth region, we present an event of cold-dense plasma sheet observed by five THEMIS probes after the interplanetary magnetic field turned northward, as well as their comparisons with the simulation results from the Rice Convection Model (RCM) combined with a modified Dungey force-balanced magnetic field solver. The observations of cold-dense plasma at different locations show quite different characteristics: (1) closer to the flank, the appearance is more periodic and exhibits larger fluctuations in plasma moments and magnetic field; (2) further away from the flank, the cold plasma appears later; (3) in the mixture with the cold plasma, the decrease in high-energy particle fluxes becomes less significant further away from the flank; (4) there is energy-dispersion in the cold particles at some locations; and (5) near the magnetopause, the fluctuations have the characteristics of the Kelvin-Helmholtz (K-H) vortices and the colder-denser plasma is likely to have lower entropy. In the RCM simulations, lower entropy plasma consisting of colder-denser ions and electrons was periodically released locally at the outer boundary to represent the plasma created within a K-H vortex. This lower entropy perturbation is interchange unstable and the resulting interchange motion through the magnetosphere-ionosphere coupling pushes the colder-denser plasma radially inward. The simulated particle energy spectrums at different locations qualitatively reproduce the observations, strongly suggesting that the seemingly different characteristics of cold-dense plasma observed by different probes are all a result of the same interchange-related transport mechanism.

Wang, Chih-Ping; Gkioulidou, Matina; Lyons, Larry R.; Xing, Xiaoyan; Wolf, Richard A.

2014-10-01

107

beta-Amyloid Neurotoxicity Requires Fibril Formation and is Inhibited by Congo Red  

Microsoft Academic Search

beta-Amyloid (betaA) is normally produced as a nontoxic soluble peptide. In Alzheimer disease, betaA aggregates and accumulates in the brain as inert diffuse plaques or compact plaques associated with neurodegenerative changes. To determine the relationship of neurotoxicity to the physical state of betaA, we created (i) nonamyloidogenic amorphous aggregates of betaA [amorphous betaA (Am-betaA)] analogous to diffuse plaques and (ii)

Alfredo Lorenzo; Bruce A. Yankner

1994-01-01

108

Formation of a very thin current sheet in the near-earth magnetotail and the explosive growth phase of substorms  

NASA Technical Reports Server (NTRS)

A magnetofricional method is used to construct two-dimensional MHD equilibria of the Earth's magnetosphere for a given distribution of entropy functions(S = pV(exp gamma), where p is the plasma pressure and V is the tube volume per unit magnetic flux. It is found that a very thin current sheet with B (sub zeta) is less than 0.5 nu T and thickness less than 1000 km can be formed in the near-earth magnetotail (x is approximately -8 to -20R(sub e) during the growth phase of substorm. The tail current sheets are found to become thinner as the entropy or the entropy gradient increases. It is suggested that the new entropy anti-diffusion instability associated with plasma transport across field lines leads to magnetic field dipolarization and accelerates the formation of thin current sheet, which may explain the observed explosive growth phase of substorms.

Lee, L. C.; Zhang, L.; Choe, G. S.; Cai, H. J.

1995-01-01

109

Sequence-specific sup 1 H-NMR assignments and identification of two small antiparallel. beta. -sheets in the solution structure of recombinant human transforming growth factor. alpha  

SciTech Connect

Transforming growth factor {alpha} (TGF{alpha}) is a small mitogenic protein with about 35% sequence identity with epidermal growth factor (EGF). TGF{alpha}-like proteins have been proposed to play a role in oncogenesis and wound healing. This report describes sequence-specific {sup 1}H-NMR resonance assignments for recombinant human TGF{alpha} (hTGF{alpha}). These assignments provide the basis for interpreting NMR data which demonstrate that the solution structure of hTGF{alpha} includes an antiparallel {beta}-sheet involving residues Gly-19 to Leu-24 and Lys-29 to Cys-34 and a second, smaller, antiparallel {beta}-sheet involving residues Tyr-38 and Val-39 and His-45 and Ala-46. These data, together with constraints imposed by the disulfide bonds, are combined to construct a molecular model of the polypeptide chain fold for residues Cys-8 to Ala-46. The resulting structure is similar to that of mouse and human EGF. Human TGF{alpha} and mouse EGF, however, differ with respect to their structural dynamics, since amide proton/deuteron exchange is much faster for hTGF{alpha} than for mouse EGF at pH 3.5.

Montelione, G.T.; Wagner, G. (Univ. of Michigan, Ann Arbor (USA)); Winkler, M.E.; Burton, L.E.; Rinderknecht, E. (Genetech, Inc., San Francisco (CA)); Sporn, M.B. (National Institutes of Health, Bethesda, MD (USA))

1989-03-01

110

Dissecting the structural determinants for the difference in mechanical stability of silk and amyloid beta-sheet stacks.  

PubMed

Stacking of ?-sheets results in a protein super secondary structure with remarkable mechanical properties. ?-Stacks are the determinants of a silk fiber's resilience and are also the building blocks of amyloid fibrils. While both silk and amyloid-type crystals are known to feature a high resistance against rupture, their structural and mechanical similarities and particularities are yet to be fully understood. Here, we systematically compare the rupture force and stiffness of amyloid and spider silk poly-alanine ?-stacks of comparable sizes using Molecular Dynamics simulations. We identify the direction of force application as the primary determinant of the rupture strength; ?-sheets in silk are orientated along the fiber axis, i.e. the pulling direction, and consequently require high forces in the several nanoNewton range for shearing ?-strands apart, while ?-sheets in amyloid are oriented vertically to the fiber, allowing a zipper-like rupture at sub-nanoNewton forces. A secondary factor rendering amyloid ?-stacks softer and weaker than their spider silk counterparts is the sub-optimal side-chain packing between ?-sheets due to the sequence variations of amyloid-forming proteins as opposed to the perfectly packed poly-alanine ?-sheets of silk. Taken together, amyloid fibers can reach the stiffness of silk fibers in spite of their softer and weaker ?-sheet arrangement as they are missing a softening amorphous matrix. PMID:23633029

Xiao, Senbo; Xiao, Shijun; Gräter, Frauke

2013-06-14

111

Protein Secondary Structures (alpha-helix and beta-sheet) at a Cellular Levle and Protein Fractions in Relation to Rumen Degradation Behaviours of Protein: A New Approach  

SciTech Connect

Studying the secondary structure of proteins leads to an understanding of the components that make up a whole protein, and such an understanding of the structure of the whole protein is often vital to understanding its digestive behaviour and nutritive value in animals. The main protein secondary structures are the {alpha}-helix and {beta}-sheet. The percentage of these two structures in protein secondary structures influences protein nutritive value, quality and digestive behaviour. A high percentage of {beta}-sheet structure may partly cause a low access to gastrointestinal digestive enzymes, which results in a low protein value. The objectives of the present study were to use advanced synchrotron-based Fourier transform IR (S-FTIR) microspectroscopy as a new approach to reveal the molecular chemistry of the protein secondary structures of feed tissues affected by heat-processing within intact tissue at a cellular level, and to quantify protein secondary structures using multicomponent peak modelling Gaussian and Lorentzian methods, in relation to protein digestive behaviours and nutritive value in the rumen, which was determined using the Cornell Net Carbohydrate Protein System. The synchrotron-based molecular chemistry research experiment was performed at the National Synchrotron Light Source at Brookhaven National Laboratory, US Department of Energy. The results showed that, with S-FTIR microspectroscopy, the molecular chemistry, ultrastructural chemical make-up and nutritive characteristics could be revealed at a high ultraspatial resolution ({approx}10 {mu}m). S-FTIR microspectroscopy revealed that the secondary structure of protein differed between raw and roasted golden flaxseeds in terms of the percentages and ratio of {alpha}-helixes and {beta}-sheets in the mid-IR range at the cellular level. By using multicomponent peak modelling, the results show that the roasting reduced (P <0.05) the percentage of {alpha}-helixes (from 47.1% to 36.1%: S-FTIR absorption intensity), increased the percentage of {beta}-sheets (from 37.2% to 49.8%: S-FTIR absorption intensity) and reduced the {alpha}-helix to {beta}-sheet ratio (from 0.3 to 0.7) in the golden flaxseeds, which indicated a negative effect of the roasting on protein values, utilisation and bioavailability. These results were proved by the Cornell Net Carbohydrate Protein System in situ animal trial, which also revealed that roasting increased the amount of protein bound to lignin, and well as of the Maillard reaction protein (both of which are poorly used by ruminants), and increased the level of indigestible and undegradable protein in ruminants. The present results demonstrate the potential of highly spatially resolved synchrotron-based infrared microspectroscopy to locate 'pure' protein in feed tissues, and reveal protein secondary structures and digestive behaviour, making a significant step forward in and an important contribution to protein nutritional research. Further study is needed to determine the sensitivities of protein secondary structures to various heat-processing conditions, and to quantify the relationship between protein secondary structures and the nutrient availability and digestive behaviour of various protein sources. Information from the present study arising from the synchrotron-based IR probing of the protein secondary structures of protein sources at the cellular level will be valuable as a guide to maintaining protein quality and predicting digestive behaviours.

Yu,P.

2007-01-01

112

Inducing ?-Sheets Formation in Synthetic Spider Silk Fibers by Aqueous Post-Spin Stretching  

PubMed Central

As a promising biomaterial with numerous potential applications, various types of synthetic spider silk fibers have been produced and studied in an effort to produce manmade fibers with mechanical and physical properties comparable to those of native spider silk. In this study, two recombinant proteins based on Nephila clavipes Major ampullate Spidroin 1 (MaSp1) consensus repeat sequence were expressed and spun into fibers. Mechanical test results showed that fiber spun from the higher molecular weight protein had better overall mechanical properties (70 KD versus 46 KD), whereas postspin stretch treatment in water helped increase fiber tensile strength significantly. Carbon-13 solid-state NMR studies of those fibers further revealed that the postspin stretch in water promoted protein molecule rearrangement and the formation of ?-sheets in the polyalanine region of the silk. The rearrangement correlated with improved fiber mechanical properties and indicated that postspin stretch is key to helping the spider silk proteins in the fiber form correct secondary structures, leading to better quality fibers. PMID:21574576

Hinman, Michael B.; Holland, Gregory P.; Yarger, Jeffery L.; Lewis, Randolph V.

2012-01-01

113

Repetitive formation and decay of current sheets in magnetic loops: An origin of diverse magnetic structures  

NASA Astrophysics Data System (ADS)

In this work, evolution of an incompressible, thermally homogeneous, infinitely conducting, viscous magnetofluid is numerically explored as the fluid undergoes repeated events of magnetic reconnection. The initial magnetic field is constructed by a superposition of two linear force-free fields and has similar morphology as the magnetic loops observed in the solar corona. The results are presented for computations with three distinct sets of footpoint geometries. To onset reconnection, we rely on numerical model magnetic diffusivity, in the spirit of implicit large eddy simulation. It is generally expected that in a high Lundquist number fluid, repeated magnetic reconnections are ubiquitous and hence can lead to a host of magnetic structures with considerable observational importance. In particular, the simulations presented here illustrate formations of magnetic islands, rotating magnetic helices and rising flux ropes—depending on the initial footpoint geometry but through the common process of repeated magnetic reconnections. Further, we observe the development of extended current sheets in two case studies, where the footpoint reconnections generate favorable dynamics.

Kumar, Dinesh; Bhattacharyya, R.; Smolarkiewicz, P. K.

2015-01-01

114

Beta-structure in human amylin and two designer beta-peptides: CD and NMR spectroscopic comparisons suggest soluble beta-oligomers and the absence of significant populations of beta-strand dimers.  

PubMed

Intensity variation for the positive far UV CD band was observed for three 'beta-sheet' peptides. In 6% HFIP, an amyloidogenic species (human pancreatic amylin) displays, on standing, an extremely intense 192-nm band which diminishes upon physical agitation. A concurrently formed Tyr sidechain band at 274 nm disappears completely with agitation, linking the enhancement of the 192-nm band to the highly ordered stacking of beta-sheets. NMR studies indicate that the beta-states of the three peptides are oligomeric, not beta dimers. A membrane-forming EAK peptide displays NMR peaks due to the low concentration of 'random coil' monomers present in slow equilibrium with beta-oligomers; solutions of a more hydrophobic ELKA peptide, which displays an intense 195-nm band, contain only oligomeric species. NMR studies at 25% HFIP revealed the structural requirements for inhibition of beta-oligomer formation. PMID:7980582

Cort, J; Liu, Z; Lee, G; Harris, S M; Prickett, K S; Gaeta, L S; Andersen, N H

1994-11-15

115

Inhibitory effects of nisin-coated multi-walled carbon nanotube sheet on biofilm formation from Bacillus anthracis spores.  

PubMed

Multi-walled carbon nanotube (MWCNT) sheet was fabricated from a drawable MWCNT forest and then deposited on poly(methyl methacrylate) film. The film was further coated with a natural antimicrobial peptide nisin. We studied the effects of nisin coating on the attachment of Bacillus anthracis spores, the germination of attached spores, and the subsequent biofilm formation from attached spores. It was found that the strong adsorptivity and the super hydrophobicity of MWCNTs provided an ideal platform for nisin coating. Nisin coating on MWCNT sheets decreased surface hydrophobicity, reduced spore attachment, and reduced the germination of attached spores by 3.5 fold, and further inhibited the subsequent biofilm formation by 94.6% compared to that on uncoated MWCNT sheet. Nisin also changed the morphology of vegetative cells in the formed biofilm. The results of this study demonstrated that the anti-adhesion and antimicrobial effect of nisin in combination with the physical properties of carbon nanotubes had the potential in producing effective anti-biofilm formation surfaces. PMID:25499501

Dong, Xiuli; McCoy, Eric; Zhang, Mei; Yang, Liju

2014-12-01

116

Formation of intermetallic compound layer in multi-laminated Ni-(TiB2/Al) composite sheets during annealing treatment.  

PubMed

Solid-state reactive diffusion between Ni and Al was investigated during annealing at 650°C by employing multi-laminated Ni-(TiB(2)/Al) composite sheets. In multi-laminated Ni-(TiB(2)/Al) composite sheets annealed up to 5min NiAl(3) was the only phase observed in the diffusion zone, and Ni(2)Al(3) appeared after longer annealing time. Most grains of Ni(2)Al(3) showed equiaxed morphology rather than columnar microstructures like NiAl(3), due to the low concentration gradients of Al and Ni at the Ni/NiAl(3) interface. The preferential formation of this intermetallic compound NiAl(3) in multi-laminated Ni-(TiB(2)/Al) composite sheets was predicted using an effective heat of formation model. The present work indicated that both Ni and Al interdiffused, and the formation of NiAl(3) was a reaction-diffusion process. PMID:23266224

Wang, Q W; Fan, G H; Geng, L; Zhang, J; Zhang, Y Z; Cui, X P

2013-02-01

117

In situ Atomic Force Microscopy Study of Alzheimer's ? -amyloid Peptide on Different Substrates: New Insights into Mechanism of ? -sheet Formation  

NASA Astrophysics Data System (ADS)

We have applied in situ atomic force microscopy to directly observe the aggregation of Alzheimer's ? -amiloid peptide (A?) in contact with two model solid surfaces: hydrophilic mica and hydrophobic graphite. The time course of aggregation was followed by continuous imaging of surfaces remaining in contact with 10-500 ? M solutions of A? in PBS (pH 7.4). Visualization of fragile nanoscale aggregates of A? was made possible by the application of a tapping mode of imaging, which minimizes the lateral forces between the probe tip and the sample. The size and the shape of A? aggregates, as well as the kinetics of their formation, exhibited pronounced dependence on the physicochemical nature of the surface. On hydrophilic mica, A? formed particulate, pseudomicellar aggregates, which at higher A? concentration had the tendency to form linear assemblies, reminiscent of protofibrillar species described recently in the literature. In contrast, on hydrophobic graphite A? formed uniform, elongated sheets. The dimensions of those sheets were consistent with the dimensions of ? -sheets with extended peptide chains perpendicular to the long axis of the aggregate. The sheets of A? were oriented along three directions at 120 degrees to each other, resembling the crystallographic symmetry of a graphite surface. Such substrate-templated self-assembly may be the distinguishing feature of ? -sheets in comparison with ? -helices. These studies show that in situ atomic force microscopy enables direct assessment of amyloid aggregation in physiological fluids and suggest that A? fibril formation may be driven by interactions at the interface of aqueous solutions and hydrophobic substrates, as occurs in membranes and lipoprotein particles in vivo.

Kowalewski, Tomasz; Holtzman, David M.

1999-03-01

118

Antifibrillizing agents catalyze the formation of unstable intermediate aggregates of beta-amyloid.  

PubMed

Although Alzheimer's disease (AD) is characterized by the extracellular deposition of fibrillar aggregates of beta-amyloid (Abeta), transient oligomeric species of Abeta are increasingly implicated in the pathogenesis of AD. Natively unfolded monomeric Abeta can misfold and progressively assemble into fibrillar aggregates, following a well-established "on pathway" seeded-nucleation mechanism. Here, we show that three simple saccharides, mannose, sucrose, and raffinose, alter Abeta aggregation kinetics and morphology. The saccharides inhibit formation of Abeta fibrils but promote formation of various oligomeric aggregate species through different "off pathway" aggregation mechanisms at 37 degrees C but not at 60 degrees C. The various oligomeric Abeta aggregates formed when coincubated with the different saccharides are morphologically distinct but all are toxic toward SH-SY5Y human neuroblastoma cells, increasing the level of toxicity and greatly prolonging toxicity compared with Abeta alone. As a wide variety of anti-Abeta aggregation strategies are being actively pursued as potential therapeutics for AD, these studies suggest that care must be taken to ensure that the therapeutic agents also block toxic oligomeric Abeta assembly as well as inhibit fibril formation. PMID:20306540

Wang, Min S; Boddapati, Shanta; Sierks, Michael R

2010-01-01

119

Regional and temporal variations in the formation of supraglacial melt ponds on the Greenland Ice Sheet  

NASA Astrophysics Data System (ADS)

Surface melt ponds form seasonally in the ablation zone of the Greenland Ice Sheet and they have been shown to provide the sites for the hydrofracture initiation of the moulins required for supraglacial meltwater to reach the bed of the Greenland Ice Sheet (Das et al., 2008). Studies to date have been restricted to a region of large surface lakes surrounding the Jakobshavn Isbrae catchment area (Box and Ski, 2007). However, large surface lakes also develop seasonally in other areas of the ice sheet, especially in the northern regions. We have developed a high temporal resolution dataset of lake evolution and drainage in all of the regions of the Greenland Ice Sheet where large surface lakes develop during summer. This study spans the period 2001-2008 using approximately 200 MODIS scenes per melt season per region. We show that there are significant regional differences in the supraglacial hydrology of the ice sheet, which could cause spatial variations in the role of melt water in ice dynamics across Greenland as it responds to the warming climate. Das, S., Joughin, M., Behn, M., Howat, I., King, M., Lizarralde, D., Bhatia, M., 2008. Fracture propagation to the base of the Greenland Ice Sheet during supra-glacial lake drainage, Science, 5877, p.778-781. Box, J., and Ski, K., 2007. Remote sounding of Greenland supraglacial melt lakes: implications for subglacial hydraulics. J. Glaciol., 53(181), p. 257-265.

Selmes, N.; Murray, T.; James, T. D.

2009-04-01

120

Specific collapse followed by slow hydrogen-bond formation of ?-sheet in the folding of single-chain monellin  

PubMed Central

Characterization of the conformational landscapes for proteins with different secondary structures is important in elucidating the mechanism of protein folding. The folding trajectory of single-chain monellin composed of a five-stranded ?-sheet and a helix was investigated by using a pH-jump from the alkaline unfolded to native state. The kinetic changes in the secondary structures and in the overall size and shape were measured by circular dichroism spectroscopy and small-angle x-ray scattering, respectively. The formation of the tertiary structure was monitored by intrinsic and extrinsic fluorescence. A significant collapse was observed within 300 ?s after the pH-jump, leading to the intermediate with a small amount of secondary and tertiary structures but with an overall oblate shape. Subsequently, the stepwise formation of secondary and tertiary structures was detected. The current observation was consistent with the theoretical prediction that a more significant collapse precedes the formation of secondary structures in the folding of ?-sheet proteins than that of helical proteins [Shea, J. E., Onuchic, J. N. & Brooks, C. L., III (2002) Proc. Natl. Acad. Sci. USA 99, 16064–16068]. Furthermore, it was implied that the initial collapse was promoted by the formation of some specific structural elements, such as tight turns, to form the oblate shape. PMID:15710881

Kimura, Tetsunari; Uzawa, Takanori; Ishimori, Koichiro; Morishima, Isao; Takahashi, Satoshi; Konno, Takashi; Akiyama, Shuji; Fujisawa, Tetsuro

2005-01-01

121

Efficiently engineered cell sheet using a complex of polyethylenimine–alginate nanocomposites plus bone morphogenetic protein 2 gene to promote new bone formation  

PubMed Central

Regeneration of large bone defects is a common clinical problem. Recently, stem cell sheet has been an emerging strategy in bone tissue engineering. To enhance the osteogenic potential of stem cell sheet, we fabricated bone morphogenetic protein 2 (BMP-2) gene-engineered cell sheet using a complex of polyethylenimine–alginate (PEI–al) nanocomposites plus human BMP-2 complementary(c)DNA plasmid, and studied its osteogenesis in vitro and in vivo. PEI–al nanocomposites carrying BMP-2 gene could efficiently transfect bone marrow mesenchymal stem cells. The cell sheet was made by culturing the cells in medium containing vitamin C for 10 days. Assays on the cell culture showed that the genetically engineered cells released the BMP-2 for at least 14 days. The expression of osteogenesis-related gene was increased, which demonstrated that released BMP-2 could effectively induce the cell sheet osteogenic differentiation in vitro. To further test the osteogenic potential of the cell sheet in vivo, enhanced green fluorescent protein or BMP-2-producing cell sheets were treated on the cranial bone defects. The results indicated that the BMP-2-producing cell sheet group was more efficient than other groups in promoting bone formation in the defect area. Our results suggested that PEI–al nanocomposites efficiently deliver the BMP-2 gene to bone marrow mesenchymal stem cells and that BMP-2 gene-engineered cell sheet is an effective way for promoting bone regeneration. PMID:24855355

Jin, Han; Zhang, Kai; Qiao, Chunyan; Yuan, Anliang; Li, Daowei; Zhao, Liang; Shi, Ce; Xu, Xiaowei; Ni, Shilei; Zheng, Changyu; Liu, Xiaohua; Yang, Bai; Sun, Hongchen

2014-01-01

122

Semaphorin 3A blocks the formation of pathologic choroidal neovascularization induced by transforming growth factor beta  

PubMed Central

Objective Choroidal neovascularization (CNV) is a major cause of vision loss in retinal diseases such as age-related macular degeneration (AMD). Previously, we demonstrated that semaphorin3A (Sema3A), which is a chemorepellent guidance molecule, inhibited the formation of retina neovascularization. In the present study, we investigated the antiangiogenic effects of Sema3A on transforming growth factor beta (TGF-?) in vitro and in vivo. Methods Enzyme-linked immunosorbent assays (ELISAs) were used to measure the TGF-? levels in the vitreous humor of patients with AMD and controls. Human umbilical vein endothelial cells (HUVECs) were used for the in vitro study, and a laser-induced CNV mouse model was prepared for the in vivo study. The HUVECs were incubated with TGF-? and Sema3A. The proliferation, migration, apoptosis, and tube formation of the cells were then measured using BrdU, Transwell, flow cytometry, and Matrigel assays, respectively, and the SMAD2/3 signaling pathways were analyzed using western blot analysis. The C57BL/6J mouse retina was exposed to a laser to induce choroidal neovascularization (CNV), and Sema3A was injected intravitreously. After 14 days, fundus fluorescein angiography was performed to evaluate the leakage area of the CNV. The vascular endothelial growth factor (VEGF) and TGF-? concentrations in the retina-choroid complex were measured with ELISA. Components of the p38 mitogen-activated protein kinase (MAPK), extracellular signal-regulated kinase-1/2 (ERK1/2), c-Jun NH2-terminal kinase (JNK), and SMAD2/3 signaling pathways in the Sema3A-treated groups were analyzed using western blotting. Results In this study, we first verified that the vitreous TGF-? level was higher in patients with neovascular AMD than in the controls. We also showed that Sema3A inhibited TGF-?-induced HUVEC proliferation, migration, and tube formation and inhibited the downstream SMAD2/3 signaling pathway. Sema3A also induced TGF-?-stimulated HUVEC apoptosis and inhibited the response of TGF-? in vitro. In vivo, the TGF-? level was increased in the CNV mouse model. Sema3A not only inhibited laser-induced CNV formation but also inhibited the uptake of VEGF and TGF-?. In the western blot analysis, Sema3A was shown to inhibit the phosphorylation of p38 MAPK, ERK1/2, and JNK and to inhibit the SMAD2/3 signaling pathway after Sema3A treatment in CNV mice. Conclusions Sema3A can be applied as a useful, adjunctive therapeutic strategy for preventing CNV formation. PMID:25352735

Bai, Yujing; Liang, Shuting; Zhao, Min; Huang, Lvzhen; Zhao, Mingwei; Li, Xiaoxin

2014-01-01

123

Formation of current sheets and sigmoidal structure by the kink instability of a magnetic loop  

E-print Network

We study dynamical consequences of the kink instability of a twisted coronal flux rope, using the force-free coronal loop model by Titov & D\\'emoulin (1999) as the initial condition in ideal-MHD simulations. When a critical value of the twist is exceeded, the long-wavelength ($m=1$) kink mode develops. Analogous to the well-known cylindrical approximation, a helical current sheet is then formed at the interface with the surrounding medium. In contrast to the cylindrical case, upward-kinking loops form a second, vertical current sheet below the loop apex at the position of the hyperbolic flux tube (generalized X line) in the model. The current density is steepened in both sheets and eventually exceeds the current density in the loop (although the kink perturbation starts to saturate in our simulations without leading to a global eruption). The projection of the field lines that pass through the vertical current sheet shows an S shape whose sense agrees with the typical sense of transient sigmoidal (forward...

Kliem, B; Toeroek, T

2004-01-01

124

Formation of lobate debris aprons on Mars: Assessment of regional ice sheet collapse and debris-cover armoring  

NASA Astrophysics Data System (ADS)

Lobate debris aprons (LDA) are lobate-shaped aprons surrounding scarps and isolated massifs that are concentrated in the vicinity of the northern Dichotomy Boundary on Mars. LDAs have been interpreted as (1) ice-cemented talus aprons undergoing viscous flow, (2) local debris-covered alpine-like glaciers, or (3) remnants of the collapse of a regional retreating ice sheet. We investigate the plausibility that LDAs are remnants of a more extensive regional ice sheet by modeling this process. We find that as a regional ice sheet collapses, the surface drops below cliff and massif bedrock margins, exposing bedrock and regolith, and initiating debris deposition on the surface of a cold-based glacier. Reduced sublimation due to debris-cover armoring of the proto-LDA surface produces a surface slope and consequent ice flow that carries the armoring debris away from the rock outcrops. As collapse and ice retreat continue the debris train eventually reaches the substrate surface at the front of the glacier, leaving the entire LDA armored by debris cover. Using a simplified ice flow model we are able to characterize the temperature and sublimation rate that would be necessary to produce LDAs with a wide range of specified lateral extents and thicknesses. We then apply this method to a database of documented LDA parameters (height, lateral extent) from the Dichotomy Boundary region, and assess the implications for predicted climate conditions during their formation and the range of formation times implied by the model. We find that for the population examined here, typical temperatures are in the range of -85 to -40 °C and typical sublimation rates lie in the range of 6-14 mm/a. Lobate debris apron formation times (from the point of bedrock exposure to complete debris cover) cluster near 400-500 ka. These results show that LDA length and thickness characteristics are consistent with climate conditions and a formation scenario typical of the collapse of a regional retreating ice sheet and exposure of bedrock cliffs. This scenario helps resolve many of the unusual characteristics of lobate debris aprons (LDA) and lineated valley fill (LVF). For example, the distribution of LVF is very consistent with extensive flow of glacial ice from plateau icefields, and the acquisition of a debris cover in the waning stages of retreat of the regional cover as the bedrock scarps are exposed. The typical concentric development of LDA around massifs is much more consistent with ice sheet retreat than insolation-related local accumulation and flow. We thus conclude that the retreating ice-sheet model is robust and should be investigated and tested in more detail. In addition, these results clearly show that the lobate debris aprons in the vicinity of the Dichotomy Boundary could not have attained temperatures near or above the ice melting point and retained their current shape, a finding that supports subzero temperatures for the last several hundred million years, the age of the LDA surfaces. A further implication is that the LDA ice has been preserved for at least several hundred million years, and could potentially contain the record of the climate of Mars, preserved since that time below a sublimation lag deposit.

Fastook, James L.; Head, James W.; Marchant, David R.

2014-01-01

125

Stemness and transdifferentiation of adipose-derived stem cells using L-ascorbic acid 2-phosphate-induced cell sheet formation.  

PubMed

Cell sheet technology has emerged as an important tissue engineering approach. Adipose-derived stem cells (ASCs) have valuable applications in regenerative medicine, but their stemness and differentiation capabilities in the cell sheet format have not been well investigated. In this study, we found that l-ascorbate 2-phosphate (A2-P), a stable form of ascorbic acid, significantly enhanced ASC proliferation and induced ASC sheet fabrication in 7 days with abundant extracellular matrix deposition. Importantly, A2-P treatment significantly enhanced expression of pluripotent markers Sox-2, Oct-4 and Nanog, but treating ASCs with antioxidants other than A2-P revealed no stemness enhancement. Moreover, ASC treatment with A2-P and a collagen synthesis inhibitor, L-2-azetidine carboxylic acid or cis-4-hydroxy-d-proline, significantly inhibited the A2-P-enhanced expression of stemness markers. These findings demonstrated that A2-P enhances stemness of ASCs through collagen synthesis and cell sheet formation. We also showed that A2-P-stimulated collagen synthesis in ASCs may be mediated through ERK1/2 pathway. By culturing the ASC sheets in proper induction media, ASC transdifferentiation capabilities into neuron and hepatocyte-like cells were significantly enhanced after cell sheet formation, while adipogenic and osteogenic differentiation capacities were still maintained. Using a murine model of healing-impaired cutaneous wound, faster wound healing was noted in the group that received ASC sheet treatment, and we observed significantly more engrafted ASCs with evidence of differentiation toward endothelial and epidermal lineages in the cutaneous wound tissue. Therefore, A2-P-mediated ASC sheet formation enhanced ASC stemness and transdifferentiation capabilities, thereby representing a promising approach for applications in regenerative medicine. PMID:24462360

Yu, Jiashing; Tu, Yuan-Kun; Tang, Yueh-Bih; Cheng, Nai-Chen

2014-04-01

126

Double layer formation during current sheet disruptions in a reconnection experiment  

NASA Technical Reports Server (NTRS)

When the current density in the center of a neutral sheet is increased to a critical value spontaneous current disruptions are observed. The release of stored magnetic field energy results in a large inductive voltage pulse which drops off inside the plasma in the form of a potential double layer. Particles are energized, microinstabilities are generated, the plasma is thinned, and the current flow is redirected. These laboratory observations qualitatively support recent models of magnetic substorms and solar flares.

Stenzel, R. L.; Gekelman, W.; Wild, N.

1982-01-01

127

Characteristics of chip formation in the micro-drilling of multi-material sheets  

Microsoft Academic Search

In order to meet the requirements of electronic product miniaturisation, the use of thinner and smaller printed circuit boards (PCBs) will be required. To achieve this, many more micro-holes must be drilled in a smaller area than before. PCBs are anisotropic multi-material sheets consisting of a dielectric layer (resin\\/glass fibre cloth) and a high purity metal conductor (copper foil). It

Lijuan Zheng; Chengyong Wang; Lipeng Yang; Yuexian Song; Lianyu Fu

128

Formation of the Maturín Foreland Basin, eastern Venezuela: Thrust sheet loading or subduction dynamic topography  

NASA Astrophysics Data System (ADS)

The Maturín Basin in eastern Venezuela is considered a good example of a peripheral foreland basin. Earthquake and tomographic data indicate that eastern Venezuela is affected by the oblique subduction of the South American Plate underneath the Caribbean Plate. New forward flexural isostatic modeling of eastern Venezuela has been carried out in order to determine whether the Maturín Basin was generated purely by thrust sheet loading from the Serranía and Monagas Foreland Thrust Belts. A sequence of forward models from middle Miocene to Present was generated for 3 profiles across the Serranía del Interior Thrust Belt, the Monagas Foreland Thrust Belt, and the Maturín Foreland Basin. The predictions of these models are constrained using seismic reflection and well data. The flexural isostatic modeling shows that thrust sheet loading associated with the Serranía del Interior and Monagas Foreland thrust belts is insufficient to generate the observed subsidence within the Maturín Basin. Dynamic fluid flow modeling of subduction related dynamic topography of eastern Venezuela has been used to investigate the influence of South American Plate subduction on the generation of the accommodation space observed in the Maturín Basin. Fluid flow modeling of subduction related dynamic topography suggests that the subduction of the South American lithospheric mantle caused downward deflection of the South American crust affecting the Maturín Basin and the Serranía Thrust Belt. This modeling suggests that the Maturín Basin subsidence has two components: 55% related to thrust sheet loading and 45% driven by continental subduction.

JáCome, Maria I.; Kusznir, Nick; Audemard, Felipe; Flint, Steve

2003-10-01

129

Design study of the geometry of the blanking tool to predict the burr formation of Zircaloy-4 sheet  

SciTech Connect

In this work, we investigated factors that influence burr formation for zircaloy-4 sheet used for spacer grids of nuclear fuel roads. Factors we considered are geometric factors of punch. We changed clearance and velocity in order to consider the failure parameters, and we changed shearing angle and corner radius of L-shaped punch in order to consider geometric factors of punch. First, we carried out blanking test with failure parameter of GTN model using L-shaped punch. The tendency of failure parameters and geometric factors that affect burr formation by analyzing sheared edges is investigated. Consequently, geometric factor's influencing on the burr formation is also high as failure parameters. Then, the sheared edges and burr formation with failure parameters and geometric factors is investigated using FE analysis model. As a result of analyzing sheared edges with the variables, we checked geometric factors more affect burr formation than failure parameters. To check the reliability of the FE model, the blanking force and the sheared edges obtained from experiments are compared with the computations considering heat transfer.

Ha, Jisun, E-mail: nskim@sogang.ac.kr; Lee, Hyungyil, E-mail: nskim@sogang.ac.kr; Kim, Dongchul, E-mail: nskim@sogang.ac.kr; Kim, Naksoo, E-mail: nskim@sogang.ac.kr [Sogang University, Department of Mechanical Engineering, Seoul, 121-742 (Korea, Republic of)

2013-12-16

130

The effects of temperature on benzo[a]pyrene metabolism and adduct formation in the gulf toadfish, Opsanus beta  

Microsoft Academic Search

In order to examine the effects of temperature on benzo[a]pyrene (BaP) metabolism and adduct formation in the absence of the effects of temperature on uptake, gulf toadfish,Opsanus beta, were given a dose of 0.05 mg\\/kg3H-BaPvia caudal vein cannulae at their acclimation temperatures. (18 or 28°C) or following an acute temperature change (18 to 28°C or 28 to 18°C). After 72h,

Christopher J. Kennedy; Patrick J. Walsh

1991-01-01

131

Beta4 integrin is required for hemidesmosome formation, cell adhesion and cell survival  

PubMed Central

The integrin heterodimer alpha 6 beta 4 is expressed in many epithelia and in Schwann cells. In stratified epithelia, alpha 6 beta 4 couple with BPAG1-e and BPAG2 to form hemidesmosomes, attaching externally to laminin and internally to the keratin cytoskeleton. To explore the function of this atypical integrin, and its relation to conventional actin-associated integrins, we targeted the removal of the beta 4 gene in mice. Tissues that express alpha 6 beta 4 are grossly affected. Stratified tissues are devoid of hemidesmosomes, display only a very fragile attachment to the basal lamina, and exhibit signs of degeneration and tissue disorganization. Simple epithelia which express alpha 6 beta 4 are also defective in adherence, even though they do not form hemidesmosomes. In the absence of beta 4, alpha 6 is dramatically downregulated, and other integrins do not appear to compensate for the loss of this heterodimer. These data have important implications for understanding integrin function in cell-substratum adhesion, cell survival and differentiation, and for understanding the role of alpha 6 beta 4 in junctional epidermolysis bullosa, an often lethal human disorder with pathology similar to our mice. PMID:8707838

1996-01-01

132

Pulmonary surfactant-associated polypeptide C in a mixed organic solvent transforms from a monomeric alpha-helical state into insoluble beta-sheet aggregates.  

PubMed Central

In the 35-residue pulmonary surfactant-associated lipopolypeptide C (SP-C), the stability of the valyl-rich alpha-helix comprising residues 9-34 has been monitored by circular dichroism, nuclear magnetic resonance, and Fourier transform infrared spectroscopy in both a mixed organic solvent and in phospholipid micelles. The alpha-helical form of SP-C observed in freshly prepared solutions in a mixed solvent of CHCl3/CH3OH/0.1 M HCl 32:64:5 (v/v/v) at 10 degrees C undergoes within a few days an irreversible transformation to an insoluble aggregate that contains beta-sheet secondary structure. Hydrogen exchange experiments revealed that this conformational transition proceeds through a transition state with an Eyring free activation enthalpy of about 100 kJ mol(-1), in which the polypeptide segment 9-27 largely retains a helical conformation. In dodecylphosphocholine micelles, the helical form of SP-C was maintained after seven weeks at 50 degrees C. The alpha-helical form of SP-C thus seems to be the thermodynamically most stable state in this micellar environment, whereas its presence in freshly prepared samples in the aforementioned mixed solvent is due to a high kinetic barrier for unfolding. These observations support a previously proposed pathway for in vivo synthesis of SP-C through proteolytic processing from a 21-kDa precursor protein. PMID:9865947

Szyperski, T.; Vandenbussche, G.; Curstedt, T.; Ruysschaert, J. M.; Wüthrich, K.; Johansson, J.

1998-01-01

133

A systematic study of the effect of physiological factors on beta2-microglobulin amyloid formation at neutral pH.  

PubMed

Beta(2)-microglobulin (beta(2)m) forms amyloid fibrils that deposit in the musculo-skeletal system in patients undergoing long-term hemodialysis. How beta(2)m self-assembles in vivo is not understood, since the monomeric wild-type protein is incapable of forming fibrils in isolation in vitro at neutral pH, while elongation of fibril-seeds made from recombinant protein has only been achieved at low pH or at neutral pH in the presence of detergents or cosolvents. Here we describe a systematic study of the effect of 11 physiologically relevant factors on beta(2)m fibrillogenesis at pH 7.0 without denaturants. By comparing the results obtained for the wild-type protein with those of two variants (DeltaN6 and V37A), the role of protein stability in fibrillogenesis is explored. We show that DeltaN6 forms low yields of amyloid-like fibrils at pH 7.0 in the absence of seeds, suggesting that this species could initiate fibrillogenesis in vivo. By contrast, high yields of amyloid-like fibrils are observed for all proteins when assembly is seeded with fibril-seeds formed from recombinant protein at pH 2.5 stabilized by the addition of heparin, serum amyloid P component (SAP), apolipoprotein E (apoE), uremic serum, or synovial fluid. The results suggest that the conditions within the synovium facilitate fibrillogenesis of beta(2)m and show that different physiological factors may act synergistically to promote fibril formation. By comparing the behavior of wild-type beta(2)m with that of DeltaN6 and V37A, we show that the physiologically relevant factors enhance fibrillogenesis by stabilizing fibril-seeds, thereby allowing fibril extension by rare assembly competent species formed by local unfolding of native monomers. PMID:16475820

Myers, Sarah L; Jones, Susan; Jahn, Thomas R; Morten, Isobel J; Tennent, Glenys A; Hewitt, Eric W; Radford, Sheena E

2006-02-21

134

Formation of sheet plumes, current coils, and helical magnetic fields in a spherical magnetohydrodynamic dynamo  

SciTech Connect

Aiming at understanding of magnetic field generation process in rapidly rotating stars and planets represented by the Earth, computer simulations of magnetohydrodynamic (MHD) dynamo were performed in a rotating spherical shell geometry. Thermal convection and dynamo process with Ekman number of the order of 10{sup -7} were studied. New structures of convection motion, dynamo-generated electrical current, and magnetic field are found. The flow is organized as a set of thin, sheet-like plumes. The current is made of small-scale coil structure with magnetic flux tubes within each of the coil. These flux tubes are connected each other to form a large scale helical magnetic field structure.

Miyagoshi, Takehiro [Japan Agency for Marine-Earth Science and Technology, Yokohama 236-0001 (Japan); Kageyama, Akira [Graduate School of System Informatics, Kobe University, Kobe 657-8501 (Japan); Sato, Tetsuya [Graduate School of Simulation Studies, University of Hyogo, Kobe 650-0047 (Japan)

2011-07-15

135

Molecular cloning of pigeon UDP-galactose:beta-D-galactoside alpha1,4-galactosyltransferase and UDP-galactose:beta-D-galactoside beta1,4-galactosyltransferase, two novel enzymes catalyzing the formation of Gal alpha1-4Gal beta1-4Gal beta1-4GlcNAc sequence.  

PubMed

We previously found that pigeon IgG possesses unique N-glycan structures that contain the Gal alpha1-4Gal beta1-4Gal beta1-4GlcNAc sequence at their nonreducing termini. This sequence is most likely produced by putative alpha1,4- and beta1,4-galactosyltransferases (GalTs), which are responsible for the biosynthesis of the Gal alpha1-4Gal and Gal beta1-4Gal sequences on the N-glycans, respectively. Because no such glycan structures have been found in mammalian glycoproteins, the biosynthetic enzymes that produce these glycans are likely to have distinct substrate specificities from the known mammalian GalTs. To study these enzymes, we cloned the pigeon liver cDNAs encoding alpha4GalT and beta4GalT by expression cloning and characterized these enzymes using the recombinant proteins. The deduced amino acid sequence of pigeon alpha4GalT has 58.2% identity to human alpha4GalT and 68.0 and 66.6% identity to putative alpha4GalTs from chicken and zebra finch, respectively. Unlike human and putative chicken alpha4GalTs, which possess globotriosylceramide synthase activity, pigeon alpha4GalT preferred to catalyze formation of the Gal alpha1-4Gal sequence on glycoproteins. In contrast, the sequence of pigeon beta4GalT revealed a type II transmembrane protein consisting of 438 amino acid residues, with no significant homology to the glycosyltransferases so far identified from mammals and chicken. However, hypothetical proteins from zebra finch (78.8% identity), frogs (58.9-60.4%), zebrafish (37.1-43.0%), and spotted green pufferfish (43.3%) were similar to pigeon beta4GalT, suggesting that the pigeon beta4GalT gene was inherited from the common ancestors of these vertebrates. The sequence analysis revealed that pigeon beta4GalT and its homologs form a new family of glycosyltransferases. PMID:19959475

Suzuki, Noriko; Yamamoto, Kazuo

2010-02-19

136

Formation of a quasi-one-dimensional current sheet in the laboratory experiment and in the Earth's magnetotail  

NASA Astrophysics Data System (ADS)

Two-dimensional current sheets (CSs) generated in the CS-3D laboratory device are considered. Results obtained in the laboratory experiment are compared with spacecraft observations of CSs in the Earth's magnetotail. The longitudinal and transverse CS structures, as well as CS evolution during the thinning process are studied. It is demonstrated that the CSs obtained in the laboratory experiments and those observed by spacecraft possess common properties: they have the same dimensionless spatial scales, similar distributions of the normal component of the magnetic field along the sheet, and similar ratios between the current density and the normal component of the magnetic field. The results of comparison allow one to guess some details of the structure and dynamics of the Earth's magnetotail CS. In particular, on the basis of the laboratory experiment, it is concluded that the formation of a quasi-one-dimensional CS in the magnetotail at distances of x ˜ -15 R E from the Earth (where R E is the Earth' radius) is accompanied by the growth of the amplitude B 0 of the tangential component of the magnetic field and that the field B 0 in the quasi-stationary state increases tailward. The critical value of the current density is likely equal to , where N e is the electron density and is the ion thermal velocity. The current density cannot substantially exceed this value. Moreover, the CS thickness cannot be substantially smaller then the ion Larmor radius or the ion inertial length.

Yushkov, E. V.; Frank, A. G.; Artemyev, A. V.; Petrukovich, A. A.; Vasko, I. Y.

2015-01-01

137

From Boron Cluster to Two-Dimensional Boron Sheet on Cu(111) Surface: Growth Mechanism and Hole Formation  

PubMed Central

As attractive analogue of graphene, boron monolayers have been theoretically predicted. However, due to electron deficiency of boron atom, synthesizing boron monolayer is very challenging in experiments. Using first-principles calculations, we explore stability and growth mechanism of various boron sheets on Cu(111) substrate. The monotonic decrease of formation energy of boron cluster BN with increasing cluster size and low diffusion barrier for a single B atom on Cu(111) surface ensure continuous growth of two-dimensional (2D) boron cluster. During growth process, hexagonal holes can easily arise at the edge of a 2D triangular boron cluster and then diffuse entad. Hence, large-scale boron monolayer with mixed hexagonal-triangular geometry can be obtained via either depositing boron atoms directly on Cu(111) surface or soft landing of small planar BN clusters. Our theoretical predictions would stimulate further experiments of synthesizing boron sheets on metal substrates and thus enrich the variety of 2D monolayer materials. PMID:24241341

Liu, Hongsheng; Gao, Junfeng; Zhao, Jijun

2013-01-01

138

Physics Resource Reference Sheet  

NSDL National Science Digital Library

This reference sheet, presented by the National Nanotechnology Infrastructure Network provides a valuable physics reference sheet for high school students. Definition of terms, diagrams, abbreviations, mathematical notations, force diagrams, and other useful information is provided in an easy to use format. Included in this lesson are the front and back sides of this reference sheet.

139

Chemistry Reference Sheets  

NSDL National Science Digital Library

This reference sheet, presented by the National Nanotechnology Infrastructure Network provides a valuable chemistry reference sheet for high school students. Definition of terms, diagrams, abbreviations, mathematical notations, the periodic table, and other useful information is provided in an easy to use format. Included in this lesson are the front and back sides of this reference sheet.

140

Physical Science Reference Sheets  

NSDL National Science Digital Library

This reference sheet, presented by the National Nanotechnology Infrastructure Network provides a valuable physical science reference sheet for high school students. Definition of terms, diagrams, abbreviations, mathematical notations, the periodic table, and other useful information is provided in an easy to use format. Included in this lesson are the front and back sides of this reference sheet.

141

Kelvin-Helmholtz vortices around the magnetotail and cold plasma sheet formation: Insight as a multiscale phenomenon  

NASA Astrophysics Data System (ADS)

The magnetopause of the Earth's magnetosphere is a key region in magnetospheric physics, especially in the sense of multiscale coupling from global large-scale phenomena to microscale physics. The velocity shear across the magnetopause is believed to cause Kelvin-Helmholtz instability (KHI) on both the dawn and dusk sides when the interplanetary magnetic field (IMF) points northward; magnetic reconnection and some secondary instabilities are likely to occur in the vortical structure induced by KHI and to play a significant role in solar wind entry across the magnetopause as well as plasma mixing there. This is a manifestation of multiscale coupling; that is, large-scale KH instability may induce micro-scale phenomenon in the rolled-up vortices and resultant formation of the cold plasma sheet in a wide region of the near-Earth magnetotail. Here we show a nice simultaneous measurement of solar wind entry associated with KHI on both sides of the magnetosphere under prolonged northward IMF. In the event that we have found, Cluster on the dawnside and Geotail on the duskside had an opportunity to stay around the magnetopause simultaneously on the opposite side to each other for more than several hours. Proton distribution function on the magnetosphere side of the magnetopause presents dawn-dusk asymmetry, which means that different plasma mixing processes are actually taking place on both sides. Using the Grad-Shafranov reconstruction (GSR) technique that can visualize ambient plasma and field around spacecraft, we clarify that vortical structures due to KHI indeed developed on both sides. These observations and reconstruction analysis suggest that vortical structures induced by KHI result in dawn-dusk asymmetry of plasma mixing around the magnetopause and formation of the cold plasma sheet in a wide region of the near-Earth magnetotail.

Nishino, Masaki N.; Hasegawa, Hiroshi; Fujimoto, Masaki; Mukai, Toshifumi; Saito, Yoshifumi; Reme, Henri; Retino, Alessandro; Nakamura, Rumi; Lucek, Elizabeth

142

Graphene Carrier Control and Band Gap Formation through Stacked Graphene Sheets  

NASA Astrophysics Data System (ADS)

Graphene's use in RF transistors and frequency doublers is attractive since its high mobility and high saturation velocity translate into operation at high frequencies while utilizing little power. However, further graphene development for device applications is hindered by high metal contact resistance, poor control of channel conductivity, and the absence of a band gap. In this talk, I will present our efforts at NRL to address these challenges using two strategies: 1) substitutional insertion of group III-V atoms into graphene's lattice to control the carriers and 2) through a synthetic means to create bilayer graphene with a band gap. Substitutional incorporation of atoms into graphene can result in doping, if their concentration does not drastically affect the ?-network. Using selective oxidation to remove C atoms from the graphene lattice, we are able to backfill the C vacancies using molecular beam deposition of dopants with controllable ultra-low fluxes. We will show that boron and phosphorus dopants can provide extra holes and electrons to the graphene ?-network, respectively, modifying the carrier concentration in transport measurements. Bernal-stacked graphene bilayers have a relatively small band gap (˜few meV). However, if the symmetry of the system is broken by the application of a large applied electric field, the band gap can be increased (˜250 meV). Alternatively, we find it is possible to obtain such large built-in electric fields when graphene sheets of opposite doping are stacked. By bonding a p-type, CVD-grown graphene monolayer transferred from Cu to an n-type, epitaxially grown graphene monolayer on SiC, we formed a p-n graphene bilayer. Transport measurements and modeling of the resulting electric field generated by opposite doping of the graphene sheets indicate the creation of a 100-300 meV band gap in the synthetic bilayer.

Jernigan, Glenn

2012-02-01

143

Formation of a long-lived hot field reversed configuration by dynamically merging two colliding high-{beta} compact toroids  

SciTech Connect

A high temperature field reversed configuration (FRC) has been produced in the newly built, world's largest compact toroid (CT) facility, C-2, by colliding and merging two high-{beta} CTs produced using the advanced field-reversed {theta}-pinch technology. This long-lived, stable merged state exhibits the following key properties: (1) apparent increase in the poloidal flux from the first pass to the final merged state, (2) significantly improved confinement compared to conventional {theta}-pinch FRCs with flux decay rates approaching classical values in some cases, (3) strong conversion from kinetic energy into thermal energy with total temperature (T{sub e} + T{sub i}) exceeding 0.5 keV, predominantly into the ion channel. Detailed modeling using a new 2-D resistive magnetohydrodynamic (MHD) code, LamyRidge, has demonstrated, for the first time, the formation, translation, and merging/reconnection dynamics of such extremely high-{beta} plasmas.

Guo, H. Y.; Binderbauer, M. W.; Barnes, D.; Putvinski, S.; Rostoker, N.; Sevier, L.; Tuszewski, M.; Anderson, M. G.; Andow, R.; Bonelli, L.; Brown, R.; Bui, D. Q.; Bystritskii, V.; Clary, R.; Cheung, A. H.; Conroy, K. D.; Deng, B. H.; Dettrick, S. A.; Douglass, J. D.; Feng, P. [Tri Alpha Energy, Inc., P.O. Box 7010, Rancho Santa Margarita, California 92688 (United States)

2011-05-15

144

Wnt-5/pipetail functions in vertebrate axis formation as a negative regulator of Wnt/beta-catenin activity.  

PubMed

We provide genetic evidence defining a role for noncanonical Wnt function in vertebrate axis formation. In zebrafish, misexpression of Wnt-4, -5, and -11 stimulates calcium (Ca2+) release, defining the Wnt/Ca2+ class. We describe genetic interaction between two Wnt/Ca2+ members, Wnt-5 (pipetail) and Wnt-11 (silberblick), and a reduction of Ca2+ release in Wnt-5/pipetail. Embryos genetically depleted of both maternal and zygotic Wnt-5 product exhibit cell movement defects as well as hyperdorsalization and axis-duplication phenotypes. The dorsalized phenotypes result from increased beta-catenin accumulation and activation of downstream genes. The Wnt-5 loss-of-function defect is consistent with Ca2+ modulation having an antagonistic interaction with Wnt/beta-catenin signaling. PMID:12952939

Westfall, Trudi A; Brimeyer, Ryan; Twedt, Jen; Gladon, Jean; Olberding, Andrea; Furutani-Seiki, Makoto; Slusarski, Diane C

2003-09-01

145

Global Simulations of Differentially Rotating Magnetized Disks Formation of Low-$\\beta$ Filaments and Structured Corona  

E-print Network

We present the results of three-dimensional global magnetohydrodynamic (MHD) simulations of the Parker-shearing instability in a differentially rotating torus initially threaded by toroidal magnetic fields. An equilibrium model of magnetized torus is adopted as an initial condition. When $\\beta_0 = P_{\\rm gas}/P_{\\rm mag} \\sim 1$ at the initial state, magnetic flux buoyantly escapes from the disk and creates loop-like structures similar to those in the solar corona. Inside the torus, growth of non-axisymmetric magneto-rotational (or Balbus & Hawley) instability generates magnetic turbulence. Magnetic field lines are tangled in small scale but in large scale they show low azimuthal wave number spiral structure. After several rotation period, the system oscillates around a state with $\\beta \\sim 5$. We found that magnetic pressure dominated ($\\beta < 1$) filaments are created in the torus. The volume filling factor of the region where $\\beta \\leq 0.3$ is 2-10%. Magnetic energy release in such low-$\\beta$...

Machida, M; Matsumoto, R; Hayashi, Mitsuru R

1999-01-01

146

Does Long-Term Administration of a Beta-Blocker (Timolol) Induce Fibril-Based Cataract Formation In-vivo?  

PubMed Central

Timolol is a non-selective beta-adrenergic receptor antagonist administered for treating glaucoma, heart attacks and hypertension. In the present study, we set out to determine whether or not timolol can provoke cataract formation, thus the influence of timolol on the amyloid-type aggregation of crystallin was investigated. We then provided experimental evidence of crystallin aggregation and its induction by timolol using different spectroscopic measurements. Turbidimetric measurements as well as ThT fluorescence data indicated that timolol induce extent of crystallin amyloid formation. The kinetic of protein aggregation was also changed in presence of increasing concentrations of the drug suggesting that long-term drug administration may contribute to the development of cataract. Since the consequence of timolol-crystallin interaction has yet to be identified, additional data on it may help us to postpone amyloid cataract formation. PMID:25237356

Nikbakht, Mohammad Reza; Ashrafi-Kooshk, Mohammad Reza; Jaafari, Morteza; Ghasemi, Moosa; Khodarahmi, Reza

2014-01-01

147

Promotion of intestinal tumor formation by inulin is associated with an accumulation of cytosolic beta-catenin in Min mice.  

PubMed

Inulin, polydisperse beta (2-1) fructan, has been suggested to protect against colon carcinogenesis and is currently used in a number of food applications. However, the data regarding the role of inulin in intestinal carcinogenesis remains controversial since the results of our previous study suggested that inulin promotes intestinal tumor formation in Min mice, an animal model for intestinal cancer with a mutation in the Apc tumor suppressor gene (Carcinogenesis 2000;21:1167-73). In our present study, we further examined the effects of inulin on intestinal tumor formation in Min mice by carefully analyzing beta-catenin expression and cellular localization at 3 different time points during the tumorigenic process. Min mice were fed a high-fat inulin-enriched (10% w/w) diet or the high-fat diet without any added fiber from the age of 6 weeks to the ages of 9, 12 or 15 weeks. The results showed that inulin significantly increased the number (by 20%) and especially the size (by 44%) of adenomas in the small intestine. At week 15, the promotion of tumor development was accompanied by an accumulation of cytosolic beta-catenin in the adenoma tissue. In the normal appearing mucosa, levels of membrane beta-catenin and PCNA were reduced in the inulin-fed mice, possibly indicating impaired enterocyte migration. These data do not support the earlier suggestions on the cancer preventive effects of inulin and emphasize the need for further research and evaluation where health claims for inulin are concerned. PMID:12866023

Pajari, Anne-Maria; Rajakangas, Johanna; Päivärinta, Essi; Kosma, Veli-Matti; Rafter, Joseph; Mutanen, Marja

2003-09-20

148

Global Simulations of Differentially Rotating Magnetized Disks : Formation of Low-Beta Filaments and Structured Corona  

E-print Network

We present the results of three-dimensional global magnetohydrodynamic (MHD) simulations of the Parker-shearing instability in a differentially rotating torus initially threaded by toroidal magnetic fields. An equilibrium model of magnetized torus is adopted as an initial condition. When $\\beta_0 = P_{\\rm gas}/P_{\\rm mag} \\sim 1$ at the initial state, magnetic flux buoyantly escapes from the disk and creates loop-like structures similar to those in the solar corona. Inside the torus, growth of non-axisymmetric magneto-rotational (or Balbus & Hawley) instability generates magnetic turbulence. Magnetic field lines are tangled in small scale but in large scale they show low azimuthal wave number spiral structure. After several rotation period, the system oscillates around a state with $\\beta \\sim 5$. We found that magnetic pressure dominated ($\\beta gas disks.

M. Machida; MITSURU R. Hayashi; R. Matsumoto

1999-11-16

149

Solution structure of the plant disease resistance-triggering protein NIP1 from the fungus Rhynchosporium secalis shows a novel beta-sheet fold.  

PubMed

Activation of the disease resistance response in a host plant frequently requires the interaction of a plant resistance gene product with a corresponding, pathogenderived signal encoded by an avirulence gene. The products of resistance genes from diverse plant species show remarkable structural similarity. However, due to the general paucity of information on pathogen avirulence genes the recognition process remains in most cases poorly understood. NIP1, a small protein secreted by the fungal barley pathogen Rhynchosporium secalis, is one of only a few fungal avirulence proteins identified and characterized to date. The defense-activating activity of NIP1 is mediated by barley resistance gene Rrs1. In addition, a role of the protein in fungal virulence is suggested by its nonspecific toxicity in leaf tissues of host and non-host cereals as well as its resistance gene-independent stimulatory effect on the plant plasma membrane H+-ATPase. Four naturally occurring NIP1 isoforms are characterized by single amino acid alterations that affect the different activities in a similar way. As a step toward unraveling the signal perception/transduction mechanism, the solution structure of NIP1 was determined. The protein structure is characterized by a novel fold. It consists of two parts containing beta-sheets of two and three anti-parallel strands, respectively. Five intramolecular disulfide bonds, comprising a novel disulfide bond pattern, stabilize these parts and their position with respect to each other. A comparative analysis of the protein structure with the properties of the NIP1 isoforms suggests two loop regions to be crucial for the resistance-triggering activity of NIP1. PMID:12944393

van't Slot, Klaas A E; van den Burg, Harrold A; Kloks, Cathelijne P A M; Hilbers, Cornelis W; Knogge, Wolfgang; Papavoine, Christina H M

2003-11-14

150

Separation of drug stereoisomers by the formation of. beta. -cyclodextrin inclusion complexes  

Microsoft Academic Search

For many drugs, only racemic mixtures are available for clinical use. Because different stereoisomers of drugs often cause different physiological responses, the use of pure isomers could elicit more exact therapeutic effects. Differential complexation of a variety of drug stereoisomers by immobilized ..beta..-cyclodextrin was investigated. Chiral recognition and racemic resolution were observed with a number of compounds from such clinically

D. W. Armstrong; T. J. Ward; R. D. Armstrong; T. E. Beesley

1986-01-01

151

A simplified vortex sheet roll-up method for formation flight  

E-print Network

This thesis studies the influence of the roll-up of a wake on the benefits in induced drag and rolling moment experienced by a close formation of two elliptically loaded wings. The roll-up of the leading wake is computed ...

Denis, Amandine, 1981-

2004-01-01

152

Formation of nanopore in a suspended graphene sheet with argon cluster bombardment: A molecular dynamics simulation study  

NASA Astrophysics Data System (ADS)

Formation of a nanopore in a suspended graphene sheet using an argon gas beam was simulated using molecular dynamics (MD) method. The Lennard-Jones (LJ) two-body potential and Tersoff-Brenner empirical potential energy function are applied in the MD simulations for different interactions between particles. The simulation results demonstrated that the incident energy and cluster size played a crucial role in the collisions. Simulation results for the Ar55-graphene collisions show that the Ar55 cluster bounces back when the incident energy is less than 11 eV/atom, the argon cluster penetrates when the incident energy is greater than 14 eV/atom. The two threshold incident energies, i.e., threshold incident energy of defect formation in graphene and threshold energy of penetration argon cluster were observed in the simulation. The threshold energies were found to have relatively weak negative power law dependence on the cluster size. The number of sputtered carbon atoms is obtained as a function of the kinetic energy of the cluster.

Zabihi, Zabiholah; Araghi, Houshang

2015-01-01

153

Enzymes involved in the formation of 3 beta, 7 beta-dihydroxy-12-oxo-5 beta-cholanic acid from dehydrocholic acid by Ruminococcus sp. obtained from human intestine.  

PubMed

Ruminococcus sp. PO1-3 from human intestinal flora reduced dehydrocholic acid to 3 beta-hydroxy-7,12-dioxo-5 beta-cholanic acid by means of the enzyme 3 beta-hydroxysteroid dehydrogenase (Akao, T., Akao, T., Hattori, M., Namba, T. and Kobashi, K. (1986) J. Biochem. (Tokyo) 99, 1425-1431). This bacterium and its crude extract gave rise to another product, showing a lower RF value on TLC, from dehydrocholic acid. The product was identified as 3 beta, 7 beta-dihydroxy-12-oxo-5 beta-cholanic acid. The crude extract reduced 7-ketolithocholic acid and its methyl ester, but not 6-ketolithocholic acid and 12-ketochenodeoxycholic acid, in the presence of NADPH, and oxidized ursodeoxycholic acid and beta-muricholic acid, but not cholic acid, chenodeoxycholic acid, deoxycholic acid and hydrocholic acid, in the presence of NADP+. Therefore, besides 3 beta-hydroxysteroid dehydrogenase, 7 beta-hydroxysteroid dehydrogenase was shown to be present in this bacterium. The two dehydrogenases were clearly separated from each other by butyl-Toyopearl 650 M column chromatography. From dehydrocholic acid, 7 beta-hydroxy-3,12-dioxo-5 beta-cholanic acid was produced by 7 beta-hydroxysteroid dehydrogenase and 3 beta, 7 beta-dihydroxy-12-oxo-5 beta-cholanic acid was produced by combination of two enzymes, 7 beta- and 3 beta-hydroxysteroid dehydrogenase. PMID:3477291

Akao, T; Akao, T; Hattori, M; Namba, T; Kobashi, K

1987-09-25

154

Unfolding Simulations of Holomyoglobin from Four Mammals: Identification of Intermediates and ?-Sheet Formation from Partially Unfolded States  

PubMed Central

Myoglobin (Mb) is a centrally important, widely studied mammalian protein. While much work has investigated multi-step unfolding of apoMb using acid or denaturant, holomyoglobin unfolding is poorly understood despite its biological relevance. We present here the first systematic unfolding simulations of holoMb and the first comparative study of unfolding of protein orthologs from different species (sperm whale, pig, horse, and harbor seal). We also provide new interpretations of experimental mean molecular ellipticities of myoglobin intermediates, notably correcting for random coil and number of helices in intermediates. The simulated holoproteins at 310 K displayed structures and dynamics in agreement with crystal structures (Rg ?1.48–1.51 nm, helicity ?75%). At 400 K, heme was not lost, but some helix loss was observed in pig and horse, suggesting that these helices are less stable in terrestrial species. At 500 K, heme was lost within 1.0–3.7 ns. All four proteins displayed exponentially decaying helix structure within 20 ns. The C- and F-helices were lost quickly in all cases. Heme delayed helix loss, and sperm whale myoglobin exhibited highest retention of heme and D/E helices. Persistence of conformation (RMSD), secondary structure, and ellipticity between 2–11 ns was interpreted as intermediates of holoMb unfolding in all four species. The intermediates resemble those of apoMb notably in A and H helices, but differ substantially in the D-, E- and F-helices, which interact with heme. The identified mechanisms cast light on the role of metal/cofactor in poorly understood holoMb unfolding. We also observed ?-sheet formation of several myoglobins at 500 K as seen experimentally, occurring after disruption of helices to a partially unfolded, globally disordered state; heme reduced this tendency and sperm-whale did not display any sheet propensity during the simulations. PMID:24386077

Dasmeh, Pouria; Kepp, Kasper P.

2013-01-01

155

Unfolding simulations of holomyoglobin from four mammals: identification of intermediates and ?-sheet formation from partially unfolded states.  

PubMed

Myoglobin (Mb) is a centrally important, widely studied mammalian protein. While much work has investigated multi-step unfolding of apoMb using acid or denaturant, holomyoglobin unfolding is poorly understood despite its biological relevance. We present here the first systematic unfolding simulations of holoMb and the first comparative study of unfolding of protein orthologs from different species (sperm whale, pig, horse, and harbor seal). We also provide new interpretations of experimental mean molecular ellipticities of myoglobin intermediates, notably correcting for random coil and number of helices in intermediates. The simulated holoproteins at 310 K displayed structures and dynamics in agreement with crystal structures (R g ~1.48-1.51 nm, helicity ~75%). At 400 K, heme was not lost, but some helix loss was observed in pig and horse, suggesting that these helices are less stable in terrestrial species. At 500 K, heme was lost within 1.0-3.7 ns. All four proteins displayed exponentially decaying helix structure within 20 ns. The C- and F-helices were lost quickly in all cases. Heme delayed helix loss, and sperm whale myoglobin exhibited highest retention of heme and D/E helices. Persistence of conformation (RMSD), secondary structure, and ellipticity between 2-11 ns was interpreted as intermediates of holoMb unfolding in all four species. The intermediates resemble those of apoMb notably in A and H helices, but differ substantially in the D-, E- and F-helices, which interact with heme. The identified mechanisms cast light on the role of metal/cofactor in poorly understood holoMb unfolding. We also observed ?-sheet formation of several myoglobins at 500 K as seen experimentally, occurring after disruption of helices to a partially unfolded, globally disordered state; heme reduced this tendency and sperm-whale did not display any sheet propensity during the simulations. PMID:24386077

Dasmeh, Pouria; Kepp, Kasper P

2013-01-01

156

Optimal Scaling in Solids Undergoing Ductile Fracture by Void Sheet Formation  

NASA Astrophysics Data System (ADS)

This work is concerned with the derivation of optimal scaling laws, in the sense of matching lower and upper bounds on the energy, for a solid undergoing ductile fracture. The specific problem considered concerns a material sample in the form of an infinite slab of finite thickness subjected to prescribed opening displacements on its two surfaces. The solid is assumed to obey deformation-theory of plasticity and, in order to further simplify the analysis, we assume isotropic rigid-plastic deformations with zero plastic spin. When hardening exponents are given values consistent with observation, the energy is found to exhibit sublinear growth. We regularize the energy through the addition of nonlocal energy terms of the strain-gradient plasticity type. This nonlocal regularization has the effect of introducing an intrinsic length scale into the energy. Under these assumptions, ductile fracture emerges as the net result of two competing effects: whereas the sublinear growth of the local energy promotes localization of deformation to failure planes, the nonlocal regularization stabilizes this process, thus resulting in an orderly progression towards failure and a well-defined specific fracture energy. The optimal scaling laws derived here show that ductile fracture results from localization of deformations to void sheets, and that it requires a well-defined energy per unit fracture area. In particular, fractal modes of fracture are ruled out under the assumptions of the analysis. The optimal scaling laws additionally show that ductile fracture is cohesive in nature, that is, it obeys a well-defined relation between tractions and opening displacements. Finally, the scaling laws supply a link between micromechanical properties and macroscopic fracture properties. In particular, they reveal the relative roles that surface energy and microplasticity play as contributors to the specific fracture energy of the material.

Fokoua, Landry; Conti, Sergio; Ortiz, Michael

2014-04-01

157

Reconnection and Current Sheet Formation in Line-Tied Magnetic Flux Tubes: Energetics and Stability  

NASA Astrophysics Data System (ADS)

Line-tied magnetic fields play a central role in Parker's model of coronal heating [E. N. Parker, Astrophys. J., 174, 499, 1972]. Our previous result [C. S. Ng and A. Bhattacharjee, Phys. Plasmas, 5, 4028, 1998] shows that this model can be realized if a line-tied magnetic equilibrium produced by a smooth footpoint mapping becomes unstable and relaxes to a state with current sheets, leading to magnetic reconnection and heating. A flux-tube tectonics model driven by random footpoint motion [E. R. Priest, J. F. Heyvaerts, and A. M. Title, Astrophys. J., 576, 533, 2002] is revisited. It is shown that if the magnetic field is driven to a statistically steady state, a large current density inversely proportional to the square root of resistivity can fill the whole volume and thus results in a heating rate independent of resistivity. However, the field structures are likely to become unstable and reconnect before they can reach the statistically steady state. The three-dimensional line-tied island coalescence instability -- a possible instability in such systems -- is studied with numerical simulations. Magnetic reconnection in this configuration, which contains neither magnetic nulls nor closed field lines, is discussed. A generalization of the concept of quasi-separatrix layers and a new criterion for the detection of such layers is developed. The new criterion is shown to correlate strongly with reconnection sites. Scaling results from higher resolution simulations will be discussed. This research is supported by a National Science Foundation grant AST-0434322 and by the National Aeronautics and Space Administration.

Ng, C.; Bhattacharjee, A.

2006-12-01

158

The geologic mapping of Venus using C-1 format: Sheets 75N254, 60N263  

NASA Technical Reports Server (NTRS)

The results of geologic mapping of Venus, produced on the base of Magellan images, are presented. We submit two C-1 format geologic maps with the appropriate legend. The mapping territory was taken from Venera 15 and 16 missions and geologic maps were composed. Magellan images allow us to divide some types of the plains units to determine the lava flow direction and to map with better accuracy.

Shalimov, I. V.

1992-01-01

159

Bone formation at a rabbit skull defect by autologous bone marrow cells combined with gelatin microspheres containing TGF-beta1.  

PubMed

The objective of the present study is to investigate the addition effect of transforming growth factor (TGF)-beta1 on the bone formation at a rabbit skull defect induced by autologous bone marrow (BM). Following application of gelatin microspheres containing TGF-beta1, with or without BM cells to skull bone defects, bone formation at the defect was assessed by soft X-ray, dual energy X-ray absorptometry (DEXA), and histological examinations. After implantation for 6 weeks, gelatin microspheres containing 0.05 microg of TGF-beta1 plus 10(6) of BM cells induced bone formation at the 6 mm diameter bone defect. The defect was histologically closed by newly formed bone tissue, whilst both gelatin microspheres containing 0.05 microg of TGF-beta1, and 10(6) and 10(7) of BM cells were ineffective. A DEXA experiment revealed that combination of gelatin microspheres containing TGF-beta1 with BM cells enhanced the bone mineral density at the skull defect to a significantly greater extent than other agents. These findings indicate that a combination of gelatin microspheres containing TGF-beta1 enabled BM cells to enhance the osteoinductive ability, resulting in bone formation even at the cell number at which BM cells alone were ineffective. PMID:11211099

Tabata, Y; Hong, L; Miyamoto, S; Miyao, M; Hashimoto, N; Ikada, Y

2000-01-01

160

Spontaneous Formation of Oligomers and Fibrils in Large-Scale Molecular Dynamics Simulations of A-beta Peptides  

NASA Astrophysics Data System (ADS)

Protein aggregation is associated with serious and eventually-fatal neurodegenerative diseases including Alzheimer's and Parkinson's. While atomic resolution molecular dynamics simulations have been useful in this regard, they are limited to examination of either oligomer formation by a small number of peptides or analysis of the stability of a moderate number of peptides placed in trial or known experimental structures. We describe large scale intermediate-resolution molecular dynamics simulations of the spontaneous formation of fibrils by systems containing large numbers ( 48) of peptides including A-beta (16-22), and A-beta ( 17-42) peptides. We trace out the aggregation process from an initial configuration of random coils to proto-filaments with cross-? structures and demonstrate how kinetics dictates the structural details of the fully formed fibril. Fibrillization kinetics depends strongly on the temperature. Nucleation and templated growth via monomer addition occur at and near a transition temperature above which fibrils are unlikely to form. Oligomeric merging and structural rearrangement are observed at lower temperatures.

Hall, Carol

2013-03-01

161

Inhibition of beta-amyloid aggregation by fluorescent dye labels  

NASA Astrophysics Data System (ADS)

The fluorescence decay of beta-amyloid's (A?) intrinsic fluorophore tyrosine has been used for sensing the oligomer formation of dye-labelled A? monomers and the results compared with previously studied oligomerization of the non-labelled A? peptides. It has been demonstrated that two different sized, covalently bound probes 7-diethylaminocoumarin-3-carbonyl and Hilyte Fluor 488 (HLF), alter the rate and character of oligomerization to different extents. The ability of HLF to inhibit formation of highly ordered structures containing beta-sheets was also shown. The implications of our findings for using fluorescence methods in amyloidosis research are discussed and the advantages of this auto-fluorescence approach highlighted.

Amaro, Mariana; Wellbrock, Thorben; Birch, David J. S.; Rolinski, Olaf J.

2014-02-01

162

{beta}-Ti(M) solid solution formation and its thermal stability in a NiAl-Cr(Mo)-(Hf,Ti) near eutectic alloy  

SciTech Connect

The effects of combined additions of Ti and Hf to NiAl-Cr(Mo) eutectics on the as-cast microstructure and its thermal stability are investigated through SEM, EDS and TEM, with focus on the formation mechanism of {beta}-Ti(M, M = Hf,Cr,Ni) solid solution phase and its thermal stability after short-term heat treatment. The results show that, due to the presence of large concentrations of {beta}-phase forming and stabilizing elements dissolved into the Ti solid solution phase during solidification, the thermodynamically metastable {beta}-phase was preserved at room temperature. With respect to its thermal stability, within the experimental range examined, the {beta}-Ti(M) solid solution phase, is not influenced. From the practical application point of view, this {beta}-Ti(M) solid solution phase may offer application as a strengthening phase for the design of NiAl-Cr(Mo)-Hf based alloys.

Li Hutian [Key Laboratory of Electromagnetic Processing of Materials, Ministry of Education, Northeastern University, Shenyang 110004 (China); Institute of Metal Research, Chinese Academy of Sciences, Shenyang 110016 (China)], E-mail: htli@imr.ac.cn; Wang Qiang; He Jicheng [Key Laboratory of Electromagnetic Processing of Materials, Ministry of Education, Northeastern University, Shenyang 110004 (China); Guo Jianting; Ye Hengqiang [Institute of Metal Research, Chinese Academy of Sciences, Shenyang 110016 (China)

2008-10-15

163

Glial uptake of amyloid beta induces NLRP3 inflammasome formation via cathepsin-dependent degradation of NLRP10.  

PubMed

The NLRP3 inflammasome forms in response to a diverse range of stimuli and is responsible for the processing and release of interleukin-1? (IL-1?) from the immunocompetent cells of the brain. The pathological peptide of Alzheimer's disease, amyloid beta (A?), induces formation of the NLRP3 inflammasome in a manner dependent on the family of proteases, cathepsins; however, the pathway by which cathepsins induce formation of the inflammasome has not yet been elucidated. In this study, we show that A? treatment of primary rat glial cultures increases cathepsin activation in the cytosol, formation of the NLRP3 inflammasome, caspase 1 activation and IL-1? release. We also show that a second NOD-like protein, NLRP10, is found bound to apoptosis-associated speck-like protein under resting conditions; however, with A? treatment, both in vitro and in vivo, NLRP10 is decreased. Further to these data, we show that cathepsins are capable of degrading NLRP10 and that treatment of glial cultures with recombinant NLRP10 reduces A?-induced caspase 1 activation and IL-1? release. We propose that A?-induced cathepsin released into the cytosol degrades NLRP10, thus allowing dissociation of NLRP3 and formation of the inflammasome. PMID:24197756

Murphy, Niamh; Grehan, Belinda; Lynch, Marina A

2014-03-01

164

Astrocyte transforming growth factor beta 1 promotes inhibitory synapse formation via CaM kinase II signaling.  

PubMed

The balance between excitatory and inhibitory synaptic inputs is critical for the control of brain function. Astrocytes play important role in the development and maintenance of neuronal circuitry. Whereas astrocytes-derived molecules involved in excitatory synapses are recognized, molecules and molecular mechanisms underlying astrocyte-induced inhibitory synapses remain unknown. Here, we identified transforming growth factor beta 1 (TGF-?1), derived from human and murine astrocytes, as regulator of inhibitory synapse in vitro and in vivo. Conditioned media derived from human and murine astrocytes induce inhibitory synapse formation in cerebral cortex neurons, an event inhibited by pharmacologic and genetic manipulation of the TGF-? pathway. TGF-?1-induction of inhibitory synapse depends on glutamatergic activity and activation of CaM kinase II, which thus induces localization and cluster formation of the synaptic adhesion protein, Neuroligin 2, in inhibitory postsynaptic terminals. Additionally, intraventricular injection of TGF-?1 enhanced inhibitory synapse number in the cerebral cortex. Our results identify TGF-?1/CaMKII pathway as a novel molecular mechanism underlying astrocyte control of inhibitory synapse formation. We propose here that the balance between excitatory and inhibitory inputs might be provided by astrocyte signals, at least partly achieved via TGF-?1 downstream pathways. Our work contributes to the understanding of the GABAergic synapse formation and may be of relevance to further the current knowledge on the mechanisms underlying the development of various neurological disorders, which commonly involve impairment of inhibitory synapse transmission. PMID:25042347

Diniz, Luan Pereira; Tortelli, Vanessa; Garcia, Matheus Nunes; Araújo, Ana Paula Bérgamo; Melo, Helen M; Silva, Gisele S Seixas da; Felice, Fernanda G De; Alves-Leon, Soniza Vieira; Souza, Jorge Marcondes de; Romão, Luciana Ferreira; Castro, Newton Gonçalves; Gomes, Flávia Carvalho Alcantara

2014-12-01

165

Chimeric DNA-RNA hammerhead ribozyme targeting transforming growth factor-beta 1 mRNA inhibits neointima formation in rat carotid artery after balloon injury.  

PubMed

We designed and synthesized a chimeric DNA-RNA hammerhead ribozyme targeting transforming growth factor (TGF)-beta 1 mRNA and found that this ribozyme effectively and specifically inhibited growth of vascular smooth muscle cells. We examined the effects of the chimeric DNA-RNA hammerhead ribozyme targeting TGF-beta 1 mRNA on neointima formation and investigated the underlying mechanism to develop a possible gene therapy for coronary artery restenosis after percutaneous transluminal coronary angioplasty. Expression of mRNAs encoding TGF-beta 1, p27kip1, and connective tissue growth factor (CTGF) in carotid artery increased after balloon injury. Fluorescein-isothiocyanate (FITC)-labeled ribozyme was taken up into the midlayer smooth muscle of the injured carotid artery. Both 2 and 5 mg of ribozyme reduced neointima formation by 65% compared to that of controls. Ribozyme markedly decreased expression of TGF-beta 1 mRNA and protein in injured vessel. Mismatch ribozyme had no effect on expression of TGF-beta 1 mRNA protein in injured vessel. Ribozyme markedly decreased expression of fibronectin, p27kip1, and CTGF mRNAs in injured vessel, whereas a mismatch ribozyme had no effect on these mRNAs. These findings indicate that the chimeric DNA-RNA hammerhead ribozyme targeting TGF-beta 1 mRNA inhibits neointima formation in rat carotid artery after balloon injury with suppression of TGF-beta 1 and inhibition of extracellular matrix and CTGF. In conclusion, the hammerhead ribozyme against TGF-beta 1 may have promise as a therapy for coronary artery restenosis after percutaneous transluminal coronary angioplasty. PMID:14729108

Ando, Hideyuki; Fukuda, Noboru; Kotani, Motoko; Yokoyama, Shin ichiro; Kunimoto, Satoshi; Matsumoto, Koichi; Saito, Satoshi; Kanmatsuse, Katsuo; Mugishima, Hideo

2004-01-12

166

Inhibition of beta-amylase activity, starch degradation and sucrose formation by indole-3-acetic acid during banana ripening.  

PubMed

In order to observe the effect of indole-3-acetic acid (IAA) on carbohydrate metabolism, unripe banana (Musa acuminata AAA, cv. Nanicão) slices were infiltrated with the hormone and left to ripen under controlled conditions. The climacteric respiration burst was reduced by the action of IAA, and starch degradation and sucrose formation were delayed. Sucrose synthase (SuSy; EC 2.4.1.13) and sucrose-phosphate synthase (SPS; EC 2.4.1.14) activities and transcript levels were not affected, indicating that prevention of sucrose accumulation was not related to sucrose-metabolizing enzymes. Impairment of sucrose synthesis could be a consequence of lack of substrate, since starch degradation was inhibited. The increase in activity and transcript level of beta-amylase was delayed, indicating that this enzyme could be important in starch-to-sucrose metabolism in bananas and that it might be, at least partially, controlled at the transcriptional level. This is the first report showing that IAA can delay starch degradation, possibly affecting the activity of hydrolytic enzymes such as beta-amylase (EC 3.2.1.2). PMID:11346957

Purgatto, E; Lajolo, F M; do Nascimento, J R; Cordenunsi, B R

2001-04-01

167

Nanospace-confined formation of flattened Sn sheets in pre-seeded graphenes for lithium ion batteries.  

PubMed

Flattened Sn sheets are prepared from the pre-seeded Sn salt in the interlayer nanospace of a graphene membrane, which acts as a template to shape Sn crystals and prevent the aggregation. The sandwich structure clamping Sn sheets accommodates the volume change during charge/discharge. We show that the hybrid possesses excellent rate performance and cycling stability as an anode for lithium ion batteries. PMID:24993388

Li, Zhengjie; Lv, Wei; Zhang, Chen; Qin, Jiwen; Wei, Wei; Shao, Jiao-Jing; Wang, Da-Wei; Li, Baohua; Kang, Feiyu; Yang, Quan-Hong

2014-08-21

168

Biology Reference Sheets  

NSDL National Science Digital Library

This reference sheet, presented by the National Nanotechnology Infrastructure Network provides a valuable list biology reference material for high school students in the life sciences. Definition of terms, diagrams, abbreviations, mathematical notations, and other useful information is provided in an easy to use format. Included in this lesson are the front and back sides of this reference sheet.

169

Inhibition of islet amyloid polypeptide fibril formation by selenium-containing phycocyanin and prevention of beta cell apoptosis.  

PubMed

Human islet amyloid polypeptide (hIAPP) fibril is the major constituent of amyloid deposits in pancreatic islets of type 2 diabetes. Misfolding and hIAPP fibril formation are thought to be important in the pathogenesis of diabetes. Studies have showed that selenium-containing phycocyanin (Se-PC) inhibited the fibrillation of hIAPP to form nanoscale particles, which is mainly by interfering with the combination between hIAPP. Small nanoscale oligomers tended to grow into larger nanoparticles and the size of nanoparticles increased with the incubation time. By interfering with the fibrillation of hIAPP and altering the structure, Se-PC alleviated hIAPP-induced cell apoptosis. Meantime, generation of ROS produced during the fibrillation process was inhibited, which was proposed to be the main factor for the hIAPP-cytotoxicity in beta cells. Taken together, Se-PC inhibited hIAPP fibrillation, thus suppressed the formation of ROS to show protective effect on hIAPP mediated cell apoptosis. Our studies provide useful information for our understanding of the interaction mechanisms of Se-PC on hIAPP structure and protective mechanisms on hIAPP cytotoxicity, presenting useful candidate for anti-diabetes drug development. PMID:25034964

Li, Xiaoling; Ma, Lijuan; Zheng, Wenjie; Chen, Tianfeng

2014-10-01

170

Natalizumab plus interferon beta-1a reduces lesion formation in relapsing multiple sclerosis.  

PubMed

The SENTINEL study showed that the addition of natalizumab improved outcomes for patients with relapsing multiple sclerosis (MS) who had experienced disease activity while receiving interferon beta-1a (IFNbeta-1a) alone. Previously unreported secondary and tertiary magnetic resonance imaging (MRI) measures are presented here. Patients received natalizumab 300 mg (n=589) or placebo (n=582) intravenously every 4 weeks plus IFNbeta-1a 30 microg intramuscularly once weekly. Annual MRI scans allowed comparison of a range of MRI end points versus baseline. Over 2 years, 67% of patients receiving natalizumab plus IFNbeta-1a remained free of new or enlarging T2-lesions compared with 30% of patients receiving IFNbeta-1a alone. The mean change from baseline in T2 lesion volume over 2 years decreased in patients receiving natalizumab plus IFNbeta-1a and increased in those receiving IFNbeta-1a alone (-277.5mm(3) versus 525.6mm(3); p<0.001). Compared with IFNbeta-1a alone, add-on natalizumab therapy resulted in a smaller increase in mean T1-hypointense lesion volume after 2 years (1821.3mm(3) versus 2210.5mm(3); p<0.001), a smaller mean number of new T1-hypointense lesions over 2 years (2.3 versus 4.1; p<0.001), and a slower rate of brain atrophy during the second year of therapy (-0.31% versus -0.40%; p=0.020). Natalizumab add-on therapy reduced gadolinium-enhancing, T1-hypointense, and T2 MRI lesion activity and slowed brain atrophy progression in patients with relapsing MS who experienced disease activity despite treatment with IFNbeta-1a alone. PMID:20236661

Radue, Ernst-Wilhelm; Stuart, William H; Calabresi, Peter A; Confavreux, Christian; Galetta, Steven L; Rudick, Richard A; Lublin, Fred D; Weinstock-Guttman, Bianca; Wynn, Daniel R; Fisher, Elizabeth; Papadopoulou, Athina; Lynn, Frances; Panzara, Michael A; Sandrock, Alfred W

2010-05-15

171

A 9-cis beta-carotene-enriched diet inhibits atherogenesis and fatty liver formation in LDL receptor knockout mice.  

PubMed

Our aim was to study the effect of 9-cis beta-carotene-rich powder of the alga Dunaliella bardawil on lipid profile, atherogenesis, and liver steatosis in high-fat diet-fed LDL receptor knockout mice. In 4 sets of experiments, mice were distributed into the following groups: control, fed an unfortified diet; Dunaliella 50, fed a diet composed of 50% 9-cis and 50% all-trans beta-carotene; Dunaliella 25, fed a diet containing 25% 9-cis and 75% all-trans beta-carotene; beta-carotene-deficient Dunaliella, fed beta-carotene-deficient Dunaliella powder; and all-trans beta-carotene, fed a synthetic all-trans beta-carotene. All fortified diets contained 0.6% total beta-carotene. Algal 9-cis beta-carotene was absorbed by the mice and accumulated in the liver. Synthetic all-trans beta-carotene was not converted to 9-cis beta-carotene. Dunaliella 50 inhibited high-fat diet-induced plasma cholesterol elevation by 40-63% and reduced cholesterol concentrations in the atherogenic VLDL and LDL. Atherosclerotic lesion area in mice treated with Dunaliella 50 was 60-83% lower compared with mice fed the high-fat diet alone. beta-Carotene-deficient Dunaliella did not influence plasma cholesterol and atherogenesis, suggesting that beta-carotene is essential for a Dunaliella protective effect. Moreover, by administrating Dunaliella powder containing different levels of 9-cis and all-trans beta-carotene isomers, we found that the effect on plasma cholesterol concentration and atherogenesis is 9-cis-dependent. Dunaliella 50 also inhibited fat accumulation and inflammation in the livers of mice fed a high-fat diet, which was accompanied by reduced mRNA levels of inflammatory genes. These results in mice suggest that 9-cis beta-carotene may have the potential to inhibit atherogenesis in humans. PMID:18806102

Harari, Ayelet; Harats, Dror; Marko, Daniella; Cohen, Hofit; Barshack, Iris; Kamari, Yehuda; Gonen, Ayelet; Gerber, Yariv; Ben-Amotz, Ami; Shaish, Aviv

2008-10-01

172

Investigation on the formation and the determination of gamma-glutamyl-beta-alanylhistidine and related isopeptide in the macromolecular fraction of beef soup stock.  

PubMed

To confirm the formation of gamma-glutamyl-beta-alanylhistidine and related peptide, a model solution (amide-containing amino acids and carnosine) has been heated, and the products are investigated. Spectroscopical analysis indicates that the major product from asparagine and carnosine is beta-aspartyl-beta-alanylhistidine, and that from glutamine and carnosine is gamma-glutamyl-beta-alanylhistidine. Furthermore, to confirm the increase of the above peptides during the heating process of food, an HPLC method for the determination of these isopeptides in food protein is constructed. The isopeptides are liberated by proteolytic digestion and fractionated by solid-phase extraction using Toyopack IC-SP cartridges. The fraction containing the isopeptides is derivatized with phenylisothiocyanate (PITC) and separated and quantified by HPLC using an octadecyl-silica column. As a result of quantification, an increase of the gamma-glutamyl-beta-alanylhistidine isopeptide in the macromolecular fraction of heated beef soup stock solution has been observed. These results suggest that the formation of the isopeptide occurs in the heating of various foods containing carnosine. PMID:11312803

Kuroda, M; Ohtake, R; Suzuki, E; Harada, T

2000-12-01

173

The integrin alpha6beta1 modulation of PI3K and Cdc42 activities induces dynamic filopodium formation in human platelets.  

PubMed

Platelets are an ideal model for studying a rapid morphological change in response to various signal transduction systems. Morphological changes via the activation of integrin alphaIIbbeta3 in platelets have been investigated intensively. In contrast, activation via integrin alpha6beta1 is less well studied. Here, we provide the first biochemical evidence that integrins alpha6beta1 and alphaIIbbeta3 of platelets are associated with different membrane proteins. We also demonstrate that platelets activated by integrin alpha6beta1 show dynamic change by actively forming filopodia and never fully spreading over a period of more than an hour. In addition, platelets activated by integrin alpha6beta1 are different from those activated by integrin alphaIIbbeta3 in terms of cell-substrate contact and in their distribution pattern of actin, Arp2/3 and various phosphotyrosine proteins. The morphological appearance of platelets produced through integrin alpha6beta1 activation is highly dependent on PI3 kinase (PI3K) but less dependent on Src kinase. Suppression of PI3K activity in integrin alpha6beta1 activated platelets induces an increase in Cdc42 activity and more filopodium formation. However, both Cdc42 and PI3K activity are higher in platelets activated by integrin alpha6beta1 than in those activated by integrin alphaIIbbeta3. Taken together, this study demonstrates that the signals induced by integrin alpha6beta1 modulate at the level of PI3K and Cdc42 activity to allow platelets to actively form filopodia. PMID:16228294

Chang, Jui-Chin; Chang, Hsin-Hou; Lin, Chien-Ting; Lo, Szecheng J

2005-12-01

174

Exploring the Influence of Carbon Nanoparticles on the Formation of ?-Sheet-Rich Oligomers of IAPP22–28 Peptide by Molecular Dynamics Simulation  

PubMed Central

Recent advances in nanotechnologies have led to wide use of nanomaterials in biomedical field. However, nanoparticles are found to interfere with protein misfolding and aggregation associated with many human diseases. It is still a controversial issue whether nanoparticles inhibit or promote protein aggregation. In this study, we used molecular dynamics simulations to explore the effects of three kinds of carbon nanomaterials including graphene, carbon nanotube and C60 on the aggregation behavior of islet amyloid polypeptide fragment 22–28 (IAPP22–28). The diverse behaviors of IAPP22–28 peptides on the surfaces of carbon nanomaterials were studied. The results suggest these nanomaterials can prevent ?-sheet formation in differing degrees and further affect the aggregation of IAPP22–28. The ?–? stacking and hydrophobic interactions are different in the interactions between peptides and different nanoparticles. The subtle differences in the interaction are due to the difference in surface curvature and area. The results demonstrate the adsorption interaction has competitive advantages over the interactions between peptides. Therefore, the fibrillation of IAPP22–28 may be inhibited at its early stage by graphene or SWCNT. Our study can not only enhance the understanding about potential effects of nanomaterials to amyloid formation, but also provide valuable information to develop potential ?-sheet formation inhibitors against type II diabetes. PMID:23755253

Guo, Jingjing; Li, Jiazhong; Zhang, Yan; Jin, Xiaojie; Liu, Huanxiang; Yao, Xiaojun

2013-01-01

175

Nanospace-confined formation of flattened Sn sheets in pre-seeded graphenes for lithium ion batteries  

NASA Astrophysics Data System (ADS)

Flattened Sn sheets are prepared from the pre-seeded Sn salt in the interlayer nanospace of a graphene membrane, which acts as a template to shape Sn crystals and prevent the aggregation. The sandwich structure clamping Sn sheets accommodates the volume change during charge/discharge. We show that the hybrid possesses excellent rate performance and cycling stability as an anode for lithium ion batteries.Flattened Sn sheets are prepared from the pre-seeded Sn salt in the interlayer nanospace of a graphene membrane, which acts as a template to shape Sn crystals and prevent the aggregation. The sandwich structure clamping Sn sheets accommodates the volume change during charge/discharge. We show that the hybrid possesses excellent rate performance and cycling stability as an anode for lithium ion batteries. Electronic supplementary information (ESI) available: Details of the preparation and characterization of G/Sn-F, G/Sn-L and G/Sn-S. See DOI: 10.1039/c4nr01924e

Li, Zhengjie; Lv, Wei; Zhang, Chen; Qin, Jiwen; Wei, Wei; Shao, Jiao-Jing; Wang, Da-Wei; Li, Baohua; Kang, Feiyu; Yang, Quan-Hong

2014-07-01

176

Architectural variability of confined turbidite sheet-sands: facies, geometry and infill of associated elementary channels. Examples from the Trois Evêchés Basin, Annot Sandstone Formation, SE France  

NASA Astrophysics Data System (ADS)

The worldwide known Annot Sandstone Formation has been considered as a reference of confined siliciclastic turbidite system. This formation crops out in SE France and represents the Upper Eocene to Lower Oligocene gravitary infill of complex foreland basins, developed in front of the Alpine thrusts. This system can be assimilated as a sand-rich turbidite ramp, sourced by multiple fan deltas leading to topographically complex sub-basins. Highly bypassing channelized systems dominate in the most proximal and most confined areas. They distally evolve to relatively less confined areas, in which sedimentary bodies appear to be more continuous and homogenous on a regional scale. These last architectural elements, defined as sheet-sands or depositional lobes, have been the focus of this study in poorly documented areas. From an important dataset made of very high resolution outcrop correlations (gathered mainly in the Trois Evêchés and Lauzanier sub-basins), we have quantified the complex distribution of sedimentary facies and structures, grain-size and key surfaces in sand-rich sheets. This was done to understand their variability from depositional event to architectural element scales and to better characterize dimensions and characteristics of their components. Six main types of architectural elements were defined, composed of both channelized and unchannelized elements. Channelized units show a high variability in terms of facies, geometry and patterns of infill that are related to multiple erosional and depositional processes, which will be discussed. We notably relate some evidences of sinuous channels, represented by lateral accretion deposits in the channel complex axis and by low angle cross-bedded facies. We interpret this particular facies as the result of flow deconfinement and overbanks above channel margins. The stratigraphic analysis of elementary objects allows us to propose a genetic model and a spatial distribution model of sheet-sand architectural elements. The latter provides their longitudinal repartition, from proximal vertically stacked internal channels to distal compensating sheets. Those features have not been accurately described in relatively distal sand-rich turbidite deposits so far and this high internal variability necessarily implies heterogeneities both in terms of petrophysical characteristics and reservoir connection. Besides, it also implies reconsidering sedimentary processes involved in these environments. Key Words: Annot Sandstones, Confined Systems, Reservoir Heterogeneities, Turbidite Sheet-sands.

Etienne, S.; Mulder, T.; Pace, A.; Bez, M.; Desaubliaux, G.

2012-04-01

177

Application of beta-galactosidase enzyme complementation technology as a high throughput screening format for antagonists of the epidermal growth factor receptor.  

PubMed

We have applied enzyme complementation technology to develop a screen for antagonists of the epidermal growth factor (EGF) receptor. Chimeric proteins containing two weakly complementing deletion mutants of Escherichia coli beta-galactosidase (beta-gal), each fused to the EGF receptor extracellular and transmembrane domains, have been stably expressed in C2C12 cells. In this cell line, formation of active beta-gal is dependent on agonist-stimulated dimerization of the EGF receptor. We have developed a homogenous 384-well assay protocol and have applied this to characterize the pharmacology of the receptor and to develop a high throughput screen (HTS) for EGF receptor antagonists. The assay is tolerant to DMSO concentrations of up to 2% and, across 21 passages in culture, exhibits an EC(50) for EGF of 5.4 +/- 3.6 ng/ml (n = 11) and a Z' of 0.55 +/- 0.13 (n = 11). A random set of 1,280 compounds was screened in duplicate at 11 microM to examine the robustness of enzyme complementation technology and to characterize the false-positive hit rate in the assay. Using a cutoff of 40% inhibition of EGF-promoted beta-gal activity, the hit rate on day 1 was 2.5% and on day 2 was 1.9%. After retesting the active compounds, the hit rate was reduced to 0.4%, of which one of the compounds was identified as a beta-gal inhibitor and the remainder appeared to be nonspecific inhibitors in the assay. This technology is amenable to automated screen workstations, there are highly sensitive chemiluminescent and fluorescent beta-gal assay reagents amenable to detection in miniaturized plate formats, and the assay benefits from a low false-positive hit rate. Enzyme complementation technology may have wide application within the HTS environment for the detection of modulators of receptor activation or inhibitors of protein-protein interactions in mammalian cells. PMID:11788058

Graham, D L; Bevan, N; Lowe, P N; Palmer, M; Rees, S

2001-12-01

178

Double Mantle Plume Upwelling—A Possible Formation Mechanism of Beta Plateau and Devana Chasma,Venus  

NASA Astrophysics Data System (ADS)

Ning Ding,Zuoxun Zeng,China University of Geosciences,Wuhan,430074,China NingDing.eagle@gmail.com Introduction:Venus represents a‘one plate planet’[1],and the uplift,fractures and volcanism in Beta Regio on Venus are considered to be formed by lithosphere uplift driven by a hot plume[2]. Based on the double peaking saddle landform,we suggest the tectonic pattern of double mantle plume upwelling to interpret the formation mechanism of Beta Plateau and Devana Chasma.We take a physical modeling to validate this possibility. Model:There is no ductile shear in Venus[3],so we use quartz sands to simulate the crust of Venus.We use two wood stickes 1.5cm in diameter rising from the rubber canvas slowly and straight till about half of the model,then falling down slowly and straight.The base is a hard rubber plate,in the center of which,there are two holes 3cm in diameter,and the distance between them is 5cm.The holes are covered by rubber canvas.We use the quartz sands in colours of white, red and black with particle size of 70 mess as the model materials. Result:Fig.1:At the beginning of the wood stickes upwelling,only fine radial cracks are formed above the upwelling from central to outside.With the upwelling continue,surface energy of the fine radial cracks increase and make the cracks unstable,finally,the fine radial cracks connect each other and form a fracture zone.And then the two mantle plume downwelling,the fracture zone is developed to form a chasma at the end. Fig.2:The four profiles all form reverse faults outside and normal faults inside.But the difference is the faults in the middle of the chasma goes deeper than others.It is the pattern of Beta Plateau where the tectonic rising is cut by Devana Chasma zone in the topographic features. Fig.3:From the tow fig., we can see two points similar:a.the elevation is high and distribution area is large around the area of two upwelling and it is high around the area of chasma,but the distribution area is small;b.both of them shows saddle shape and two highland connectting bya chasma. Discussion:Based on the‘Geology Map of V-17’,two highlands of Northern part of Devana Chasma,but the material Unit of North and South highland are different.The material Units of North highland are the oldest unit tt and t,the material Unit of South highland is pl and the material Unit of rift is r are both the youngest unit.From the Magellan SAR mosaic[5],we can clearly see Devana Chasma cut the material Unit of tt and pl.So the two highlands of Northern part of Devana Chasma are simultaneous formed.The younger material Unit of South highland of Northern part of Devana Chasma is because of the volcanic eruption of Theia Mons. Conclusion:The physical modeling validates the model of the double plume upwelling is a possible explanation. Acknowledgements:This research was supported by the National Teaching Bases For Geology(CUG)foundation funded. References:[1]I.López,Icarus2008[2]A.T.Basilevsky,Icarus2007[3]J.C.Aubele,2009,LPSC[4]A.V.Vezolainen,2003,Journalofgeophysicalres5earch[5]http://planetarynames.wr.usgs.gov/images/v17_comp&v29_comp.pdf Fig.1 Fig.2 Fig.3a,3b

Ding, N.

2009-12-01

179

Environment-independent 14-helix formation in short beta-peptides: striking a balance between shape control and functional diversity.  

PubMed

We report a significant and unanticipated advance in the study of beta-amino acid-based foldamers: a small proportion of highly preorganized residues can impart high stability to a specific helical secondary structure in water. Most of the residues in these beta-peptides (2 and 3) are intrinsically flexible. Flexible beta-amino acids can be readily and enantiospecifically prepared in functionally diverse forms, but preorganized residues with side chains are rare and challenging to synthesize. Our findings demonstrate that interspersing a few copies of an unfunctionalized but rigid residue among a larger number of flexible residues with diverse side chains is a viable strategy for creating beta-peptides that adopt the 14-helix conformation and therefore display side chains in a predictable spatial arrangement. These results are significant because they enhance the prospects of developing beta-peptides with useful activities. PMID:12733872

Raguse, Tami L; Lai, Jonathan R; Gellman, Samuel H

2003-05-14

180

Ion mobility-mass spectrometry reveals a conformational conversion from random assembly to ?-sheet in amyloid fibril formation  

NASA Astrophysics Data System (ADS)

Amyloid cascades that lead to peptide ?-sheet fibrils and plaques are central to many important diseases. Recently, intermediate assemblies of these cascades were identified as the toxic agents that interact with cellular machinery. The location and cause of the transformation from a natively unstructured assembly to the ?-sheet oligomers found in all fibrils is important in understanding disease onset and the development of therapeutic agents. Largely, research on this early oligomeric region was unsuccessful because all the traditional techniques measure only the average oligomer properties of the ensemble. We utilized ion-mobility methods to deduce the peptide self-assembly mechanism and examined a series of amyloid-forming peptides clipped from larger peptides or proteins associated with disease. We provide unambiguous evidence for structural transitions in each of these fibril-forming peptide systems and establish the potential of this method for the development of therapeutic agents and drug evaluation.

Bleiholder, Christian; Dupuis, Nicholas F.; Wyttenbach, Thomas; Bowers, Michael T.

2011-02-01

181

Wetlands Fact Sheets  

NSDL National Science Digital Library

The U.S. Environmental Protection Agency has provided an extensive list of over 40 fact sheets relating to various aspects of wetlands. Most are provided in a low resoluion format for viewing or a high resolution format for printing. A great deal of basic information regarding the definition, values, and functions of wetlands is provided.

182

Stability of single sheet GNNQQNY aggregates analyzed by replica exchange molecular dynamics: Antiparallel versus parallel association  

SciTech Connect

Protein and peptide aggregation into amyloid plaques is associated with a large variety of neurodegenerative diseases. The definition of the molecular bases of these pathologies is hampered by the transient nature of pre-fibrillar small-oligomers that are considered the toxic species. The ability of the peptide GNNQQNY to form amyloid-like structures makes it a good model to investigate the complex processes involved into amyloid fiber formation. By employing full atomistic replica exchange molecular dynamics simulations, we constructed the free energy surface of small assemblies of GNNQQNY to gain novel insights into the fiber formation process. The calculations suggest that the peptide exhibits a remarkable tendency to form both parallel and antiparallel {beta}-sheets. The data show that GNNQQNY preference for parallel or antiparallel {beta}-sheets is governed by a subtle balance of factors including assemblies' size, sidechain-sidechain interactions and pH. The samplings analysis provides a rationale to the observed trends.

Vitagliano, Luigi; Esposito, Luciana; Pedone, Carlo [Istituto di Biostrutture e Bioimmagini, CNR via Mezzocannone 16, I-80134 Napoli (Italy); De Simone, Alfonso [Department of Chemistry, University of Cambridge, Lensfield Road CB2 1EW, Cambridge (United Kingdom)], E-mail: ad491@cam.ac.uk

2008-12-26

183

Differential expression of prostaglandin endoperoxide H synthase-2 and formation of activated beta-catenin-LEF-1 transcription complex in mouse colonic epithelial cells contrasting in Apc.  

PubMed

Mutations in Apc underlie the intestinal lesions in familial adenomatous polyposis and are found in >85% of sporadic colon cancers. They are frequently associated with overexpression of prostaglandin endoperoxide H synthase-2 (PGHS-2) in colonic adenomas. It has been suggested that Apc mutations are linked mechanistically to increased PGHS-2 expression by elevated nuclear accumulation of beta-catenin-Tcf-LEF transcription complex. In the present study, we show that PGHS-2 is differentially expressed in mouse colonic epithelial cells with distinct Apc status. Cells with a mutated Apc expressed markedly higher levels of PGHS-2 mRNA and protein and produced significantly more prostaglandin E2 than cells with normal Apc. Using electrophoretic mobility shift assays, we demonstrate that DNA-beta-catenin-LEF-1 complex formation is differentially induced in these two cell lines in an Apc-dependent manner. Our data indicate that the differential induction of beta-catenin-LEF-1 complex correlates closely with differential expression of PGHS-2. These findings support the hypothesis that the differential expression of PGHS-2 is mediated through the proposed beta-catenin/Tcf-LEF signaling pathway. PMID:10223208

Mei, J M; Hord, N G; Winterstein, D F; Donald, S P; Phang, J M

1999-04-01

184

Assessment sheets  

NSDL National Science Digital Library

This website offers assessment sheets on humans, plants, habitats, materials, light, earth and beyond, sound, forces, electricity, and science. The sheets tell you what the student should know from each objective.

2007-09-11

185

Formation of {beta}-nickel hydroxide plate-like structures under mild conditions and their optical properties  

SciTech Connect

Nanostructural {beta}-nickel hydroxide ({beta}-Ni(OH){sub 2}) plates were prepared using the microwave-hydrothermal (MH) method at a low temperature and short reaction times. An ammonia solution was employed as the coordinating agent, which reacts with [Ni(H{sub 2}O){sub 6}]{sup 2+} to control the growth of {beta}-Ni(OH){sub 2} nuclei. A trigonal {beta}-Ni(OH){sub 2} single phase was observed by X-ray diffraction (XRD) analyses, and the crystal cell was constructed with structural parameters and atomic coordinates obtained from Rietveld refinement. Field emission scanning electron microscopy (FE-SEM) images revealed that the samples consisted of hexagonal-shaped nanoplates with a different particle size distribution. Broad absorption bands assigned as transitions of Ni{sup 2+} in oxygen octahedral sites were revealed by UV-vis spectra. Photoluminescence (PL) properties observed with a maximum peak centered in the blue-green region were attributed to different defects, which were produced during the nucleation process. We present a growth process scheme of the {beta}-Ni(OH){sub 2} nanoplates. - Graphical abstract: Nanostructural {beta}-Ni(OH){sub 2} crystalline powders were prepared by rapid microwave-hydrothermal method for 1, 8 and 32 min. The hexagonal-shaped nanoplates obtained presented PL emission in the blue-green region and each decomposed component represents a different type of electronic transition, which can be linked to the structural arrangement or surface defects. Highlights: > Ammonia solution to control the growth of {beta}-Ni(OH){sub 2} nuclei. > Regular plates-shape related to crystallization-dissolution-recrystallization. > The surface states and lattice defects generated in growth mechanism of crystals. > Different defects produced in the growth process responsible by photoluminescence. > Each component of photoluminescence curve linked to structural arrangement or surface defects.

Moura, A.P. de [Universidade Estadual Paulista, Instituto de Quimica, CEP 14800-900 Araraquara, SP (Brazil); Lima, R.C., E-mail: rclima@iqufu.ufu.br [Universidade Federal de Uberlandia, Instituto de Quimica, CEP 38400-902 Uberlandia, MG (Brazil); Paris, E.C. [Embrapa, Empresa Brasileira de Pesquisas Agropecuarias, CEP 13560-970 Sao Carlos, SP (Brazil); Li, M.S. [Universidade de Sao Paulo, Instituto de Fisica de Sao Carlos, CEP 13566590 Sao Carlos, SP (Brazil); Varela, J.A. [Universidade Estadual Paulista, Instituto de Quimica, CEP 14800-900 Araraquara, SP (Brazil); Longo, E., E-mail: elson@iq.unesp.br [Universidade Estadual Paulista, Instituto de Quimica, CEP 14800-900 Araraquara, SP (Brazil)

2011-10-15

186

Ice Sheets  

NSDL National Science Digital Library

This educational brief describes the nature and properties of the Greenland and Antarctica ice sheets. Topics include the thickness and aereal extent of the ice sheets, volume of water contained in them, mass balance, and the mechanisms by which ice is lost from or accumulated by the ice sheets.

187

Cell-cell contact formation governs Ca2+ signaling by TRPC4 in the vascular endothelium: evidence for a regulatory TRPC4-beta-catenin interaction.  

PubMed

TRPC4 is well recognized as a prominent cation channel in the vascular endothelium, but its contribution to agonist-induced endothelial Ca(2+) entry is still a matter of controversy. Here we report that the cellular targeting and Ca(2+) signaling function of TRPC4 is determined by the state of cell-cell adhesions during endothelial phenotype transitions. TRPC4 surface expression in human microvascular endothelial cells (HMEC-1) increased with the formation of cell-cell contacts. Epidermal growth factor recruited TRPC4 into the plasma membrane of proliferating cells but initiated retrieval of TRPC4 from the plasma membrane in quiescent, barrier-forming cells. Epidermal growth factor-induced Ca(2+) entry was strongly promoted by the formation of cell-cell contacts, and both siRNA and dominant negative knockdown experiments revealed that TRPC4 mediates stimulated Ca(2+) entry exclusively in proliferating clusters that form immature cell-cell contacts. TRPC4 co-precipitated with the junctional proteins beta-catenin and VE-cadherin. Analysis of cellular localization of fluorescent fusion proteins provided further evidence for recruitment of TRPC4 into junctional complexes. Analysis of TRPC4 function in the HEK293 expression system identified beta-catenin as a signaling molecule that enables cell-cell contact-dependent promotion of TRPC4 function. Our results place TRPC4 as a Ca(2+) entry channel that is regulated by cell-cell contact formation and interaction with beta-catenin. TRPC4 is suggested to serve stimulated Ca(2+) entry in a specific endothelial state during the transition from a proliferating to a quiescent phenotype. Thus, TRPC4 may adopt divergent, as yet unappreciated functions in endothelial Ca(2+) homeostasis and emerges as a potential key player in endothelial phenotype switching and tuning of cellular growth factor signaling. PMID:19996314

Graziani, Annarita; Poteser, Michael; Heupel, Wolfgang-Moritz; Schleifer, Hannes; Krenn, Martin; Drenckhahn, Detlev; Romanin, Christoph; Baumgartner, Werner; Groschner, Klaus

2010-02-01

188

Polyalanine and Abeta Aggregation Kinetics: Probing Intermediate Oligomer Formation and Structure Using Computer Simulations  

NASA Astrophysics Data System (ADS)

The aggregation of proteins into stable, well-ordered structures known as amyloid fibrils has been associated with many neurodegenerative diseases. Amyloid fibrils are long straight, and un-branched structures containing several proto-filaments, each of which exhibits "cross beta structure," -- ribbon-like layers of large beta sheets whose strands run perpendicular to the fibril axis. It has been suggested in the literature that the pathway to fibril formation has the following steps: unfolded monomers associate into transient unstable oligomers, the oligomers undergo a rearrangement into the cross-beta structure and form into proto-filaments, these proto-filaments then associate and grow into fully formed fibrils. Recent experimental studies have determined that the unstable intermediate structures are toxic to cells and that their presence may play a key role in the pathogenesis of the amyloid diseases. Many efforts have been made to determine the structure of intermediate oligomer aggregates that form during the fibrillization process. The goal of this work is to provide details about the structure and formation kinetics of the unstable oligomers that appear in the fibril formation pathway. The specific aims of this work are to determine the steps in the fibril formation pathway and how the kinetics of fibrillization changes with variations in temperature and concentration. The method used is the application of discontinuous molecular dynamics to large systems of peptides represented with an intermediate resolution model, PRIME, that was previously developed in our group. Three different peptide sequences are simulated: polyalanine (KA14K), Abeta17-40, and Abeta17-42; the latter two are truncated sequences of the Alzheimer's peptide. We simulate the spontaneous assembly of these peptide chains from a random initial configuration of random coils. We investigate aggregation kinetics and oligomer formation of a system of 192 polyalanine (KA14K) chains over a variety of temperatures and concentrations. The fibril formation pathway has the following steps: free monomers associate into small amorphous aggregates, those small amorphous aggregates grow, the amorphous aggregates rearrange into beta-sheets, and finally the beta-sheets stack into small fibrillar structures. The rate of fibril formation increases as concentration increases and temperature decreases; this faster fibril formation is the combination of several effects, including increased amorphous aggregate formation from free monomers, increased amorphous aggregate rearrangement into beta-sheets, and increased stacking into small fibrils. There is a competition between enthalpy and entropy that determine the behavior of the final structure in the system. At low temperature, enthalpy is dominant and the system produces multiple large fibrils, while at high temperature entropy is dominant and the system produces one or no large fibrils. As temperature increases and concentration decreases the intermediate structures that form, such as beta-sheets and large independent amorphous aggregates, are more stabilized which leads to slower fibril formation and fewer chains in the large final fibrillar structure. We study the formation of beta-sheets and small fibrillar structures for both Abeta17-40 and Abeta17-42 to determine the difference between the two sequences in aggregation kinetics and oligomer structure as a function of temperature. We observe that at low temperatures, both Abeta17-40 and Abeta17-42 form large amorphous aggregates with a small amount of beta-sheet character, at intermediate temperatures the peptides form a mixture of beta-sheets and fibrils that are surrounded by amorphous aggregates, and at high temperatures the peptides form small amorphous aggregates or remain isolated as free monomers. Abeta 17-42 forms fibrils over a larger temperature range than Abeta 17-40. The structure of the beta-sheets changes as temperature increases through the range conducive to fibril formation. Abeta17-42 goes through the transition from predominantly intr

Phelps, Erin Melissa

2011-12-01

189

Disintegration of liquid sheets  

NASA Technical Reports Server (NTRS)

The development, stability, and disintegration of liquid sheets issuing from a two-dimensional air-assisted nozzle is studied. Detailed measurements of mean drop size and velocity are made using a phase Doppler particle analyzer. Without air flow the liquid sheet converges toward the axis as a result of surface tension forces. With airflow a quasi-two-dimensional expanding spray is formed. The air flow causes small variations in sheet thickness to develop into major disturbances with the result that disruption starts before the formation of the main break-up region. In the two-dimensional variable geometry air-blast atomizer, it is shown that the air flow is responsible for the formation of large, ordered, and small chaotic 'cell' structures.

Mansour, Adel; Chigier, Norman

1990-01-01

190

A calorimetric determination of the enthalpy of formation and a description of the defect structure of the ordered beta-phase /Ni, Cu/ /1-x/ Al/x/  

NASA Technical Reports Server (NTRS)

In order to describe thermodynamically the defect structure of an ordered B-Hume-Rothery phase, the heat of formation of (Ni,Cu)(1-x)Al(x) was measured at 1100 K as a function of concentration in the range x (sub Al) = 0.4 and 0.55 for three substitution rations x (sub Ni)/x (sub Cu) = infinity; 11; 5. The heat of formation of the NiAl beta-phase is strongly negative. For the stoichiometric composition it is -72.2 kJ/g-atom. On both the nickel-rich side and the aluminum-rich side the magnitude of the enthalpy of formation decreases linearly with concentration. Substitution of nickel for copper decreases the magnitude of the enthalpy of formation over the entire homogeneity range for the phase (Ni,Cu)(1-x)Al(x). The curve for the enthalpy of formation as well as the literature values for the chemical potential of aluminum are described with great accuracy by the disorder model of Wagner-Schottky.

Henig, E. T.; Lukas, H. L.

1988-01-01

191

Synthesis of porous sheet-like Co{sub 3}O{sub 4} microstructure by precipitation method and its potential applications in the thermal decomposition of ammonium perchlorate  

SciTech Connect

Porous sheet-like cobalt oxide (Co{sub 3}O{sub 4}) were successfully synthesized by precipitation method combined with calcination of cobalt hydroxide precursors. The structure, morphology and porosity properties of the products were characterized by X-ray powder diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM) and nitrogen adsorption-desorption measurement. The as-prepared sheet-like microstructures were approximately 2-3 {mu}m in average diameter, and the morphology of the cobalt hydroxide precursors was retained after the calcination process. However, it appeared a large number of uniform pores in the sheets after calcination. In order to calculate the potential catalytic activity, the thermal decomposition of ammonium perchlorate (AP) has been analyzed, in which cobalt oxide played a role of an additive and the porous sheet-like Co{sub 3}O{sub 4} microstructures exhibited high catalytic performance and considerable decrease in the thermal decomposition temperature of AP. Moreover, a formation mechanism for the sheet-like microstructures has been discussed. - Graphical abstract: Porous sheet-like Co{sub 3}O{sub 4} were synthesized by facile precipitation method combined with calcination of {beta}-Co(OH){sub 2} precursors. Thermogravimetric-differential scanning calorimetric analysis indicates potential catalytic activity in the thermal decomposition of ammonium perchlorate. Highlights: Black-Right-Pointing-Pointer Synthesis of sheet-like {beta}-Co(OH){sub 2} precursors by precipitation method. Black-Right-Pointing-Pointer Porous sheet-like Co{sub 3}O{sub 4} were obtained by calcining {beta}-Co(OH){sub 2} precursors. Black-Right-Pointing-Pointer The possible formation mechanism of porous sheet-like Co{sub 3}O{sub 4} has been discussed. Black-Right-Pointing-Pointer Porous sheet-like Co{sub 3}O{sub 4} decrease the thermal decomposition temperature of ammonium perchlorate.

Lu Shanshan; Jing Xiaoyan; Liu Jingyuan [Key Laboratory of Superlight Materials and Surface Technology, Ministry of Education, Harbin Engineering University, Harbin 150001 (China); Wang Jun, E-mail: zhqw1888@sohu.com [Key Laboratory of Superlight Materials and Surface Technology, Ministry of Education, Harbin Engineering University, Harbin 150001 (China); Institute of Advanced Marine Materials, Harbin Engineering University, Harbin 150001 (China); Liu Qi; Zhao Yanhua; Jamil, Saba; Zhang Milin [Key Laboratory of Superlight Materials and Surface Technology, Ministry of Education, Harbin Engineering University, Harbin 150001 (China); Liu Lianhe [Institute of Advanced Marine Materials, Harbin Engineering University, Harbin 150001 (China)

2013-01-15

192

The unexpected formation of the stable beta phase of L-glutamic acid during pH-shift precipitation  

NASA Astrophysics Data System (ADS)

Rapid pre-mixing of solutions of sodium L-glutamate and of sulphuric acid enabled the creation of a high supersaturation ratio 4-22 for pH-shift precipitation of L-glutamic acid. In post-mixed samples the prismatic crystals of the metastable alpha polymorph formed in accordance with Ostwald's rule. However, from non-post-mixed samples spherulite-like crystals of the stable beta polymorph were obtained. Without agitation, crystals were observed later than in agitated samples. The mechanism proposed to explain these results assumes that both polymorphs nucleate concomitantly. Both forms nucleate slowly but the beta form nucleates at the highest rate. Without post-mixing the large number of beta crystals depletes most of the supersaturation although the few alpha crystals grow faster. With post-mixing, the fast-growing alpha crystals first reach the critical size for attrition. From that moment attrition generates a large number of secondary alpha nuclei that rapidly deplete the solution.

Roelands, C. P. M.; ter Horst, Joop H.; Kramer, Herman J. M.; Jansens, Peter J.

2005-02-01

193

Beta-D-glucosyl and alpha-D-galactosyl Yariv reagents: syntheses from p-nitrophenyl-D-glycosides by transfer reduction using ammonium formate.  

PubMed

Yariv beta-D-glucosyl (4a) and Yariv alpha-d-galactosyl (4b) reagents are multivalent phenylglycosides. The beta-D-glucosyl reagent is considered diagnostic for arabinogalactan proteins (AGPs) to which it can reversibly bind, stain, and precipitate. The alpha-D-galactosyl reagent does not bind AGPs and is used as a control. In a new strategy, we accomplished the large scale synthesis of the Yariv reagents in one continuous step by a transfer reduction method and without a need for any specialized apparatus. As the starting material, p-nitrophenyl-D-glycosides (1) were reduced to p-aminophenyl-D-glycosides (2) using ammonium formate as the hydrogen donor. The excess formate was converted to formic acid and ammonia, which then were removed from the reaction by simple distillation. Without isolation, p-aminophenyl-D-glycosides were diazotized (3) and coupled to phloroglucinol to give the Yariv reagents in approximately 40% yield. AGPs are a major component of gum arabic, an emulsifying agent widely used in the food and pharmaceutical industries. Increasing interest in AGPs prompted the development of a relatively easy and inexpensive method for the synthesis of these reagents. PMID:15675787

Basile, Dominick V; Ganjian, Iraj

2004-12-15

194

Hydrogen- Facts Sheet  

NSDL National Science Digital Library

This fact sheet provides some basic information about hydrogen. Hydrogen's history, physical and chemical properties, the production of hydrogen, details on how it is stored, safety tips for working with hydrogen and reasons for using hydrogen are outlined. This document may be downloaded in PDF file format.

2011-12-26

195

The effect of glutamic acid side chain on acidity constant of lysine in beta-sheet: A density functional theory study  

NASA Astrophysics Data System (ADS)

In this work, the possibility of proton transfer between side chain of lysine and glutamic acid in peptide of Glu--Ala-Lys+ was demonstrated using density functional theory (DFT). We have shown that the proton transfer takes place between side chain of glutamic and lysine residues through the hydrogen bond formation. The structures of transition state for proton transfer reaction were detected in gas and solution phases. Our kinetic studies show that the proton transfer reaction rate in gas phase is higher than solution phase. The ionization constant (p K a) value of lysine residue in peptide was estimated 1.039 which is lower than intrinsic p K a of lysine amino acid.

Sargolzaei, M.; Afshar, M.; Sadeghi, M. S.; Kavee, M.

2014-07-01

196

Protein structure. Born to be beta.  

PubMed

The beta-sheet-forming propensities of amino acids have been measured in a new model system. The origins of observed variations in the propensities are unclear, but the results provide a useful tool for protein design. PMID:7953549

Regan, L

1994-07-01

197

Self-Assembled Hydrogels from Poly[N-(2-hydroxypropyl)methacrylamide] Grafted with ?-Sheet Peptides  

PubMed Central

A new hybrid hydrogel based on poly[N-(2-hydroxypropyl)methacrylamide] grafted with a ?-sheet peptide, Beta11, was designed. Circular dichroism spectroscopy indicated that the folding ability of ?-sheet peptide was retained in the hybrid system, whereas the sensitivity of the peptide towards temperature and pH variations was hindered. The polymer backbone also prevented the twisting of the fibrils that resulted from the antiparallel arrangement of the ?-strands, as proved by Fourier transform infrared spectroscopy. Thioflavin T binding experiments and transmission electron microscopy showed fibril formation with minimal lateral aggregation. As a consequence, the graft copolymer self-assembled into a hydrogel in aqueous environment. This process was mediated by association of ?-sheet domains. Scanning electron microscopy revealed a particular morphology of the network, characterized by long-range order and uniformly aligned lamellae. Microrheology results confirmed that concentration-dependent gelation occurred. PMID:19591463

Radu-Wu, Larisa C.; Yang, Jiyuan; Wu, Kuangshi; Kope?ek, Jind?ich

2009-01-01

198

Fibrillogenesis in Alzheimer's disease of amyloid beta peptides and apolipoprotein E.  

PubMed Central

A central event in Alzheimer's disease is the conformational change from normally circulating soluble amyloid beta peptides (A beta) and tau proteins into amyloid fibrils, in the form of senile plaques and neurofibrillary tangles respectively. The apolipoprotein E (apoE) gene locus has recently been associated with late-onset Alzheimer's disease. It is not know whether apoE plays a direct role in the pathogenesis of the disease. In the present work we have investigated whether apoE can affect the known spontaneous in vitro formation of amyloid-like fibrils by synthetic A beta analogues using a thioflavine-T assay for fibril formation, electron microscopy and Congo Red staining. Our results show that, under the conditions used, apoE directly promotes amyloid fibril formation, increasing both the rate of fibrillogenesis and the total amount of amyloid formed. ApoE accelerated fibril formation of both wild-type A beta-(1-40) and A beta-(1-40A), an analogue created by the replacement of valine with alanine at residue 18, which alone produces few amyloid-like fibrils. However, apoE produced only a minimal effect on A beta-(1-40Q), found in the Dutch variant of Alzheimer's disease. When recombinant apoE isoforms were used, apoE4 was more efficient than apoE3 at enhancing amyloid formation. These in vitro observations support the hypothesis that apoE acts as a pathological chaperone, promoting the beta-pleated-sheet conformation of soluble A beta into amyloid fibres, and provide a possible explanation for the association of the apoE4 genetic isoform with Alzheimer's disease. Images Figure 2 Figure 4 PMID:7534068

Castano, E M; Prelli, F; Wisniewski, T; Golabek, A; Kumar, R A; Soto, C; Frangione, B

1995-01-01

199

Bayesian models and algorithms for protein ?-sheet prediction.  

PubMed

Prediction of the 3D structure greatly benefits from the information related to secondary structure, solvent accessibility, and nonlocal contacts that stabilize a protein's structure. We address the problem of \\beta-sheet prediction defined as the prediction of \\beta--strand pairings, interaction types (parallel or antiparallel), and \\beta-residue interactions (or contact maps). We introduce a Bayesian approach for proteins with six or less \\beta-strands in which we model the conformational features in a probabilistic framework by combining the amino acid pairing potentials with a priori knowledge of \\beta-strand organizations. To select the optimum \\beta-sheet architecture, we significantly reduce the search space by heuristics that enforce the amino acid pairs with strong interaction potentials. In addition, we find the optimum pairwise alignment between \\beta-strands using dynamic programming in which we allow any number of gaps in an alignment to model \\beta-bulges more effectively. For proteins with more than six \\beta-strands, we first compute \\beta-strand pairings using the BetaPro method. Then, we compute gapped alignments of the paired \\beta-strands and choose the interaction types and \\beta--residue pairings with maximum alignment scores. We performed a 10-fold cross-validation experiment on the BetaSheet916 set and obtained significant improvements in the prediction accuracy. PMID:21233522

Aydin, Zafer; Altunbasak, Yucel; Erdogan, Hakan

2011-01-01

200

Beta amyloid and hyperphosphorylated tau deposits in the pancreas in type 2 diabetes  

SciTech Connect

Strong epidemiologic evidence suggests an association between Alzheimer disease (AD) and type 2 diabetes. To determine if amyloid beta (A{beta}) and hyperphosphorylated tau occurs in type 2 diabetes, pancreas tissues from 21 autopsy cases (10 type 2 diabetes and 11 controls) were analyzed. APP and tau mRNAs were identified in human pancreas and in cultured insulinoma beta cells (INS-1) by RT-PCR. Prominent APP and tau bands were detected by Western blotting in pancreatic extracts. Aggregated A{beta}, hyperphosphorylated tau, ubiquitin, apolipoprotein E, apolipoprotein(a), IB1/JIP-1 and JNK1 were detected in Langerhans islets in type 2 diabetic patients. A{beta} was co-localized with amylin in islet amyloid deposits. In situ beta sheet formation of islet amyloid deposits was shown by infrared microspectroscopy (SIRMS). LPS increased APP in non-neuronal cells as well. We conclude that A{beta} deposits and hyperphosphorylated tau are also associated with type 2 diabetes, highlighting common pathogenetic features in neurodegenerative disorders, including AD and type 2 diabetes and suggesting that A{beta} deposits and hyperphosphorylated tau may also occur in other organs than the brain.

Miklossy, J.; Miller, L.; Qing, H.; Radenovic, A.; Kis, A.; Vileno, B.; Laszlo, F.; Martins, R.N.; Waeber, G.; Mooser, V.; Bosman, F.; Khalili, K.; Darbinian, N.; McGeer, P.L.

2008-08-25

201

Beef induces and rye bran prevents the formation of intestinal polyps in Apc(Min) mice: relation to beta-catenin and PKC isozymes.  

PubMed

Epidemiological studies suggest that high consumption of red meat and saturated fat and low consumption of fiber are associated with an increased risk of colon cancer. Therefore, we studied whether diets high in red meat or high in different grain fibers as well as inulin, polydisperse beta(2-->1) fructan, could affect the formation of intestinal polyps in Apc(Min) mice. Min mice were fed the following high-fat (40% of energy) diets for 5-6 weeks; a high-beef diet and a casein-based diet without added fiber or casein-based diet with 10% (w/w) oat, rye or wheat bran, or 2.5% (w/w) inulin. One group had a normal low-fat AIN93-G diet. The mice fed the rye-bran diet had the lowest number of polyps in the distal small intestine [15.4 +/- 8.7 (mean +/- SD)], and in the entire intestine (26.4 +/- 12.1). The rye-bran group differed significantly (P = 0. 001-0.004) from the beef group (36.6 +/- 9.4 and 52.8 +/- 13.2). In addition, the beef group differed significantly from the AIN93-G group (P = 0.009) and also from the wheat-bran group (21.0 +/- 6.1 and 35.0 +/- 8.2; P = 0.02) in the distal small intestine. The inulin group (32.9 +/- 14.3 and 49.3 +/- 16.3), on the other hand, was close to the beef group and it differed significantly from the rye-bran group in the distal small intestine. The number of animals bearing tumors in the colon + caecum was only 33% in the rye-bran group when compared with 89% in the beef and 100% in the inulin groups. The mice fed the rye-bran and beef diets had the lowest levels of cytosolic beta-catenin (0.60 +/- 0.42 and 0.67 +/- 0.26) and they differed significantly (P = 0.040 and 0.062) from the mice fed the oat-bran diet (1.46 +/- 0.43). No differences between groups in expression of protein kinase C (PKC) alpha, betaII, delta and zeta were found. The four PKC isozymes were positively correlated with cytosolic beta-catenin levels (r = 0.62-0.68; P < 0.0001). PMID:10837006

Mutanen, M; Pajari, A M; Oikarinen, S I

2000-06-01

202

Interaction of the Molecular Chaperone DNAJB6 with Growing Amyloid-beta 42 (A?42) Aggregates Leads to Sub-stoichiometric Inhibition of Amyloid Formation*  

PubMed Central

The human molecular chaperone protein DNAJB6 was recently found to inhibit the formation of amyloid fibrils from polyglutamine peptides associated with neurodegenerative disorders such as Huntington disease. We show in the present study that DNAJB6 also inhibits amyloid formation by an even more aggregation-prone peptide (the amyloid-beta peptide, A?42, implicated in Alzheimer disease) in a highly efficient manner. By monitoring fibril formation using Thioflavin T fluorescence and far-UV CD spectroscopy, we have found that the aggregation of A?42 is retarded by DNAJB6 in a concentration-dependent manner, extending to very low sub-stoichiometric molar ratios of chaperone to peptide. Quantitative kinetic analysis and immunochemistry studies suggest that the high inhibitory efficiency is due to the interactions of the chaperone with aggregated forms of A?42 rather than the monomeric form of the peptide. This interaction prevents the growth of such species to longer fibrils and inhibits the formation of new amyloid fibrils through both primary and secondary nucleation. A low dissociation rate of DNAJB6 from A?42 aggregates leads to its incorporation into growing fibrils and hence to its gradual depletion from solution with time. When DNAJB6 is eventually depleted, fibril proliferation takes place, but the inhibitory activity can be prolonged by introducing DNAJB6 at regular intervals during the aggregation reaction. These results reveal the highly efficacious mode of action of this molecular chaperone against protein aggregation, and demonstrate that the role of molecular chaperones can involve interactions with multiple aggregated species leading to the inhibition of both principal nucleation pathways through which aggregates are able to form. PMID:25217638

Månsson, Cecilia; Arosio, Paolo; Hussein, Rasha; Kampinga, Harm H.; Hashem, Reem M.; Boelens, Wilbert C.; Dobson, Christopher M.; Knowles, Tuomas P. J.; Linse, Sara; Emanuelsson, Cecilia

2014-01-01

203

Interaction of the molecular chaperone DNAJB6 with growing amyloid-beta 42 (A?42) aggregates leads to sub-stoichiometric inhibition of amyloid formation.  

PubMed

The human molecular chaperone protein DNAJB6 was recently found to inhibit the formation of amyloid fibrils from polyglutamine peptides associated with neurodegenerative disorders such as Huntington disease. We show in the present study that DNAJB6 also inhibits amyloid formation by an even more aggregation-prone peptide (the amyloid-beta peptide, A?42, implicated in Alzheimer disease) in a highly efficient manner. By monitoring fibril formation using Thioflavin T fluorescence and far-UV CD spectroscopy, we have found that the aggregation of A?42 is retarded by DNAJB6 in a concentration-dependent manner, extending to very low sub-stoichiometric molar ratios of chaperone to peptide. Quantitative kinetic analysis and immunochemistry studies suggest that the high inhibitory efficiency is due to the interactions of the chaperone with aggregated forms of A?42 rather than the monomeric form of the peptide. This interaction prevents the growth of such species to longer fibrils and inhibits the formation of new amyloid fibrils through both primary and secondary nucleation. A low dissociation rate of DNAJB6 from A?42 aggregates leads to its incorporation into growing fibrils and hence to its gradual depletion from solution with time. When DNAJB6 is eventually depleted, fibril proliferation takes place, but the inhibitory activity can be prolonged by introducing DNAJB6 at regular intervals during the aggregation reaction. These results reveal the highly efficacious mode of action of this molecular chaperone against protein aggregation, and demonstrate that the role of molecular chaperones can involve interactions with multiple aggregated species leading to the inhibition of both principal nucleation pathways through which aggregates are able to form. PMID:25217638

Månsson, Cecilia; Arosio, Paolo; Hussein, Rasha; Kampinga, Harm H; Hashem, Reem M; Boelens, Wilbert C; Dobson, Christopher M; Knowles, Tuomas P J; Linse, Sara; Emanuelsson, Cecilia

2014-11-01

204

A biased probe analysis of potential well formation in an electron only, low beta Polywell magnetic field  

SciTech Connect

Orbital limited motion theory has been applied to two biased probes in a low beta Polywell. The cases studied include electron injection, magnetic field scaling, Polywell bias scaling, and radial position profiles. Langmuir's original orbital limited motion results for a monoenergetic electron beam are shown to be in excellent agreement for electron injection into the Polywell. A distribution function is proposed for the electron plasma characteristics in the centre of the magnetic null and confirmed with experimental results. A translational stage was used to measure the radial plasma potential profile. In other experiments, two probes were used to simultaneously measure the profiles in both the null and a position halfway along a corner cusp. The results confirm a radial potential well created by electron trapping in the device. In addition, we present preliminary results of the potential well scaling with the magnetic field, Polywell bias voltage, and the injected beam current. The electron population was found to maintain non-equilibrium in all cases studied.

Carr, Matthew; Khachan, Joe [Department of Plasma Physics, School of Physics A28, University of Sydney NSW 2006 (Australia)] [Department of Plasma Physics, School of Physics A28, University of Sydney NSW 2006 (Australia)

2013-05-15

205

A biased probe analysis of potential well formation in an electron only, low beta Polywell magnetic field  

NASA Astrophysics Data System (ADS)

Orbital limited motion theory has been applied to two biased probes in a low beta Polywell. The cases studied include electron injection, magnetic field scaling, Polywell bias scaling, and radial position profiles. Langmuir's original orbital limited motion results for a monoenergetic electron beam are shown to be in excellent agreement for electron injection into the Polywell. A distribution function is proposed for the electron plasma characteristics in the centre of the magnetic null and confirmed with experimental results. A translational stage was used to measure the radial plasma potential profile. In other experiments, two probes were used to simultaneously measure the profiles in both the null and a position halfway along a corner cusp. The results confirm a radial potential well created by electron trapping in the device. In addition, we present preliminary results of the potential well scaling with the magnetic field, Polywell bias voltage, and the injected beam current. The electron population was found to maintain non-equilibrium in all cases studied.

Carr, Matthew; Khachan, Joe

2013-05-01

206

Structural model of the amyloid fibril formed by beta(2)-microglobulin #21-31 fragment based on vibrational spectroscopy.  

PubMed

A structural model of amyloid fibril formed by the #21-31 fragment of beta2-microglobulin is proposed from microscope IR measurements on specifically 13C-labeled peptide fibrils and Raman spectra of the dispersed fibril solution. The 13C-shifted amide frequency indicated the secondary structure of the labeled residues. The IR spectra have demonstrated that the region between F22 and V27 forms the core part with the extended beta-sheet structure. Raman spectra indicated the formation of a dimer with a disulfide bridge between C25 residues. PMID:15926803

Hiramatsu, Hirotsugu; Goto, Yuji; Naiki, Hironobu; Kitagawa, Teizo

2005-06-01

207

Study on the Formation and Characterization of the Intermetallics in Friction Stir Welding of Aluminum Alloy to Coated Steel Sheet Lap Joint  

NASA Astrophysics Data System (ADS)

Multimaterial fabrication such as joining of steel and aluminum is currently prominent in a variety of industries. Friction stir welding is a novel solid-state welding process that causes good joint strength between steel and aluminum. However, the phenomenon contributing significant strength at the interface is not yet clear. In the present study, the interface of the friction stir lap-welded aluminum and coated steel sheet having joint strength maximum (71.4 pct of steel base metal) and minimum, respectively, under two parameter combinations, i.e., 1000 rpm 50 mm min-1 and 500 rpm 100 mm min-1, was exclusively characterized by X-ray diffraction, transmission electron microscopy (TEM), concentration profile, and elemental mapping by electron-probe microanalysis. A TEM-assisted EDS study identifies the morphologies of large size Al13Fe4 and small size Fe3Al-type intermetallic compounds at the interface. The diffusion-induced intermetallic growth (thickness) measured from a backscattered image and concentration profile agreed well with the numerically calculated one. The growth of these two phases at 1000 rpm 50 mm min-1 is attributed to the slower cooling rate (~3.5 K/s) with higher diffusion time (44 seconds) along the interface in comparison to the same for 500 rpm 100 mm min-1 with faster cooling rate (~10 K/s) and less diffusion time (13.6 seconds). The formation of thermodynamically stable and hard intermetallic phase Al13Fe4 at 1000 rpm and travel speed 50 mm min-1 in amounts higher than 500 rpm and a travel speed of 100 mm min-1 results in better joint strength, i.e., 71.4 pct, of the steel base metal.

Das, H.; Ghosh, R. N.; Pal, T. K.

2014-10-01

208

Ensemble modeling of [beta]-sheet proteins  

E-print Network

Our ability to characterize protein structure and dynamics is vastly outpaced by the speed of modern genetic sequencing, creating a growing divide between our knowledge of biological sequence and structure. Structural ...

O'Donnell, Charles William

2011-01-01

209

Oncoprotein E7 from beta human papillomavirus 38 induces formation of an inhibitory complex for a subset of p53-regulated promoters.  

PubMed

Our previous studies on cutaneous beta human papillomavirus 38 (HPV38) E6 and E7 oncoproteins highlighted a novel activity of I?B kinase beta (IKK?) in the nucleus of human keratinocytes, where it phosphorylates and stabilizes ?Np73?, an antagonist of p53/p73 functions. Here, we further characterize the role of the IKK? nuclear form. We show that IKK? nuclear translocation and ?Np73? accumulation are mediated mainly by HPV38 E7 oncoprotein. Chromatin immunoprecipitation (ChIP)/Re-ChIP experiments showed that ?Np73? and IKK? are part, together with two epigenetic enzymes DNA methyltransferase 1 (DNMT1) and the enhancer of zeste homolog 2 (EZH2), of a transcriptional regulatory complex that inhibits the expression of some p53-regulated genes, such as PIG3. Recruitment to the PIG3 promoter of EZH2 and DNMT1 resulted in trimethylation of histone 3 on lysine 27 and in DNA methylation, respectively, both events associated with gene expression silencing. Decreases in the intracellular levels of HPV38 E7 or ?Np73? strongly affected the recruitment of the inhibitory transcriptional complex to the PIG3 promoter, with consequent restoration of p53-regulated gene expression. Finally, the ?Np73?/IKK?/DNMT1/EZH2 complex appears to bind a subset of p53-regulated promoters. In fact, the complex is efficiently recruited to several promoters of genes encoding proteins involved in DNA repair and apoptosis, whereas it does not influence the expression of the prosurvival factor Survivin. In summary, our data show that HPV38 via E7 protein promotes the formation of a multiprotein complex that negatively regulates the expression of several p53-regulated genes. PMID:24006445

Saidj, Djamel; Cros, Marie-Pierre; Hernandez-Vargas, Hector; Guarino, Francesca; Sylla, Bakary S; Tommasino, Massimo; Accardi, Rosita

2013-11-01

210

Molecular basis for amyloid-[beta] polymorphism  

SciTech Connect

Amyloid-beta (A{beta}) aggregates are the main constituent of senile plaques, the histological hallmark of Alzheimer's disease. A{beta} molecules form {beta}-sheet containing structures that assemble into a variety of polymorphic oligomers, protofibers, and fibers that exhibit a range of lifetimes and cellular toxicities. This polymorphic nature of A{beta} has frustrated its biophysical characterization, its structural determination, and our understanding of its pathological mechanism. To elucidate A{beta} polymorphism in atomic detail, we determined eight new microcrystal structures of fiber-forming segments of A{beta}. These structures, all of short, self-complementing pairs of {beta}-sheets termed steric zippers, reveal a variety of modes of self-association of A{beta}. Combining these atomic structures with previous NMR studies allows us to propose several fiber models, offering molecular models for some of the repertoire of polydisperse structures accessible to A{beta}. These structures and molecular models contribute fundamental information for understanding A{beta} polymorphic nature and pathogenesis.

Colletier, Jacques-Philippe; Laganowsky, Arthur; Landau, Meytal; Zhao, Minglei; Soriaga, Angela B.; Goldschmidt, Lukasz; Flot, David; Cascio, Duilio; Sawaya, Michael R.; Eisenberga, David (UCLA); (ESRF)

2011-10-19

211

Assembling amyloid fibrils from designed structures containing a significant amyloid beta-peptide fragment.  

PubMed Central

The amyloid plaque, consisting of amyloid beta-peptide (Abeta) fibrils surrounded by dystrophic neurites, is an invariable feature of Alzheimer's disease. The determination of the molecular structure of Abeta fibrils is a significant goal that may lead to the structure-based design of effective therapeutics for Alzheimer's disease. Technical challenges have thus far rendered this goal impossible. In the present study, we develop an alternative methodology. Rather than determining the structure directly, we design conformationally constrained peptides and demonstrate that only certain 'bricks' can aggregate into fibrils morphologically identical to Abeta fibrils. The designed peptides include variants of a decapeptide fragment of Abeta, previously shown to be one of the smallest peptides that (1) includes a pentapeptide sequence necessary for Abeta-Abeta binding and aggregation and (2) can form fibrils indistinguishable from those formed by full-length Abeta. The secondary structure of these bricks is monitored by CD spectroscopy, and electron microscopy is used to study the morphology of the aggregates formed. We then made various residue deletions and substitutions to determine which structural features are essential for fibril formation. From the constraints, statistical analysis of side-chain pair correlations in beta-sheets and experimental data, we deduce a detailed model of the peptide strand alignment in fibrils formed by these bricks. Our results show that the constrained decapeptide dimers rapidly form an intramolecular, antiparallel beta-sheet and polymerize into amyloid fibrils at low concentrations. We suggest that the formation of an exposed beta-sheet (e.g. an Abeta dimer formed by interaction in the decapeptide region) could be a rate-limiting step in fibril formation. A theoretical framework that explains the results is presented in parallel with the data. PMID:12023906

Tjernberg, Lars O; Tjernberg, Agneta; Bark, Niklas; Shi, Yuan; Ruzsicska, Bela P; Bu, Zimei; Thyberg, Johan; Callaway, David J E

2002-01-01

212

Synergistic Action of Fibroblast Growth Factor-2 and Transforming Growth Factor-beta1 Enhances Bioprinted Human Neocartilage Formation  

PubMed Central

Bioprinting as a promising but unexplored approach for cartilage tissue engineering has the advantages of high throughput, digital control, and highly accurate placement of cells and biomaterial scaffold to the targeted 3D locations with simultaneous polymerization. This study tested feasibility of using bioprinting for cartilage engineering and examined the influence of cell density, growth and differentiation factors. Human articular chondrocytes were printed at various densities, stimulated transiently with growth factors and subsequently with chondrogenic factors. Samples were cultured for up to 4 weeks to evaluate cell proliferation and viability, mechanical properties, mass swelling ratio, water content, gene expression, ECM production, DNA content, and histology. Bioprinted samples treated with FGF-2/TGF-?1 had the best chondrogenic properties among all groups apparently due to synergistic stimulation of cell proliferation and chondrogenic phenotype. ECM production per chondrocyte in low cell density was much higher than that in high cell seeding density. This finding was also verified by mechanical testing and histology. In conclusion, cell seeding density that is feasible for bioprinting also appears optimal for human neocartilage formation when combined with appropriate growth and differentiation factors. PMID:22508498

Cui, Xiaofeng; Breitenkamp, Kurt; Lotz, Martin; D’Lima, Darryl

2012-01-01

213

STATE AUTHORITIES SUPERANNUATION SCHEME (SASS) FACT SHEET FACT SHEET FACT SHEET FACT SHEET FACT SH  

E-print Network

STATE AUTHORITIES SUPERANNUATION SCHEME (SASS) FACT SHEET FACT SHEET FACT SHEET FACT SHEET FACT SH superannuation and tax legislation. STC has published this Fact Sheet. STC is not licensed to provide financial in this Fact Sheet and nothing in it is intended to be or should be regarded as personal advice

University of Technology, Sydney

214

Isotactic N-alkyl acrylamide oligomers assume self-assembled sheet structure: first unequivocal evidence from crystal structures.  

PubMed

Herein we present the first unequivocal evidence of the ability of isotactic N-alkyl acrylamide oligomers to assume self-assembled sheet-like structures that are reminiscent of protein beta-sheets. PMID:17009453

Kendhale, Amol; Gonnade, Rajesh; Rajamohanan, Pattuparampil R; Sanjayan, Gangadhar J

2006-07-14

215

Two-dimensional structure of {beta}-Amyloid(10-35) fibrils.  

SciTech Connect

{beta}-Amyloid (A{beta}) peptides are the main protein component of the pathognomonic plaques found in the brains of patients with Alzheimer's disease. These heterogeneous peptides adopt a highly organized fibril structure both in vivo and in vitro. Here we use solid-state NMR on stable, homogeneous fibrils of A{beta}{sub (10-35)}. Specific interpeptide distance constraints are determined with dipolar recoupling NMR on fibrils prepared from a series of singly labeled peptides containing {sup 13}C-carbonyl-enriched amino acids, and skipping no more than three residues in the sequence. From these studies, we demonstrate that the peptide adopts the structure of an extended parallel {beta}-sheet in-register at pH 7.4. Analysis of DRAWS data indicates interstrand distances of 5.3 {+-} 0.3 {angstrom} (mean {+-} standard deviation) throughout the entire length of the peptide, which is compatible only with a parallel {beta}-strand in-register. Intrastrand NMR constraints, obtained from peptides containing labels at two adjacent amino acids, confirm the secondary structural findings obtained using DRAWS. Using peptides with {sup 13}C incorporated at the carbonyl position of adjacent amino acids, structural transitions from {alpha}-helix to {beta}-sheet were observed at residues 19 and 20, but using similar techniques, no evidence for a turn could be found in the putative turn region comprising residues 25-29. Implications of this extended parallel organization for A{beta}{sub (10-35)} for overall fibril formation, stability, and morphology based upon specific amino acid contacts are discussed.

Benzinger, T. L. S.; Gregory, D. M.; Burkoth, T. S.; Miller-Auer, H.; Lynn, D. G.; Botto, R. E.; Meredith, S. C.; Chemistry; Univ. of Chicago

2000-03-28

216

New three-component reaction: novel formation of a seven-membered ring by the unexpected reaction at the gamma-position of the beta-keto ester.  

PubMed

[reaction: see text] The novel three-component reaction of aromatic aldehydes, ethylenediamine, and beta-keto esters is described. In this reaction, beta-keto esters react at the gamma-position which is generally unreactive to produce the seven-membered ring compounds. Products have secondary amines and beta-enamino esters, which can serve in further functionalizations to produce molecular diversity. PMID:17408279

Fujioka, Hiromichi; Murai, Kenichi; Kubo, Ozora; Ohba, Yusuke; Kita, Yasuyuki

2007-04-26

217

Genetic immunization with the free human chorionic gonadotropin beta subunit elicits cytotoxic T lymphocyte responses and protects against tumor formation in mice.  

PubMed

The free beta subunit of human chorionic gonadotropin (hCG beta) is produced and secreted by human lung, bladder, and pancreatic tumors. We attempted to generate cytotoxic T lymphocytes (CTL) with activity against free hCG beta-producing tumors by genetic immunization using a construct containing a beta subunit expressing cDNA. To assess CTL activity in vivo, a cloned syngeneic SP2/O myeloma call line was established that constitutively expresses the free hCG beta protein. Inoculation of this cell line into BALB/c mice produced large tumors within 2 weeks. However, mice immunized with the free hCG beta expression construct demonstrated a marked reduction of tumor size and weight compared with animals immunized with mock DNA ("empty" plasmid). Indeed, 30% of immunized mice were tumor-free after 3 months and thus considered long-term survivors. Inhibition of tumor growth was strongly associated with the level of CTL activity present in CD8+ cells derived from the spleen. In addition, immunized mice developed high titer anti-hCG beta antibodies that neutralized the biologic effects of the intact hCG glycoprotein hormone on its cellular receptor as well. These results illustrate that substantial cellular and humoral immune responses to the free hCG beta subunit may be generated by DNA immunization. This study thus presents a potential approach to inhibiting growth of human tumor cells that produce and secrete the free hCG beta protein. PMID:9194861

Geissler, M; Wands, G; Gesien, A; de la Monte, S; Bellet, D; Wands, J R

1997-06-01

218

In vitro cartilage formation using TGF-beta-immobilized magnetic beads and mesenchymal stem cell-magnetic bead complexes under magnetic field conditions.  

PubMed

We evaluated the efficacy of transforming growth factor (TGF)-beta-immobilized magnetic beads for chondrogenesis in vitro using a mesenchymal stem cell (MSC) delivery system and an external magnetic force (EMF). MSCs isolated from the bone marrow of Sprague Dawley rats were mixed with carboxyl group-combined magnetic beads (Ferri Sphere 100C) coated with anti-rat CD44 mouse monoclonal antibodies. TGF-beta3 (10 and 1 ng/mL) was attached magnetically to such other Ferri Sphere 100C beads via an amide bond formed between a primary amino group on the TGF-beta3 and the carboxyl groups on the surface of the beads. MSC-magnetic bead complexes were centrifuged to form a pellet and cultured in chondrogenic differentiation medium (CDM) supplemented with either 10 or 1 ng/mL TGF-beta-immobilized magnetic beads (10 or 1 ng/mL TGF-beta-immobilized magnetic bead groups) or in CDM supplemented with 1 or 10 ng/mL TGF-beta (1 or 10 ng/mL TGF-beta group). TGF-beta-immobilized magnetic beads were gathered effectively under an EMF. Chondrogenesis was achieved from the MSC-magnetic bead complexes in the presence of 1 ng/mL TGF-beta-immobilized magnetic beads. PMID:19172619

Motoyama, Mitsuru; Deie, Masataka; Kanaya, Atsushi; Nishimori, Makoto; Miyamoto, Ayato; Yanada, Shinobu; Adachi, Nobuo; Ochi, Mitsuo

2010-01-01

219

Localization of soluble beta-carbonic anhydrase in the marine diatom Phaeodactylum tricornutum. Sorting to the chloroplast and cluster formation on the girdle lamellae.  

PubMed

A beta-carbonic anhydrase (CA) in the marine diatom Phaeodactylum tricornutum (PtCA1) is encoded by the nuclear genome. This enzyme was previously found to be important for the operation of photosynthesis with a high affinity for dissolved inorganic carbon. A cDNA sequence that encodes PtCA1 (ptca1) was shown to possess a presequence of 138 bp (pre138), which encodes an N-terminal sequence of 46 amino acids (Pre46AA) that does not exist in the mature PtCA1. In this study, pre138 was ligated with the enhanced green fluorescent protein (GFP) gene (egfp), and introduced into P. tricornutum by microprojectile bombardment. Subsequently, the expressed Pre46AA-GFP fusion was shown to be localized in the chloroplast stroma, whereas the expressed GFP without Pre46AA was localized in the cytoplasm. Insertion of the DNA sequence, encoding a mature region of ptca1 (mptca1) between pre138 and egfp, resulted in the formation of particles with concentrated GFP fluorescence in the stroma of P. tricornutum. These particles, 0.3 to 3.0 mum in size, were shown to be distinct from the mitochondria and localized on the surface of the putative girdle lamella. The attachment of the initial one-half of the pre138 to the mptca1-egfp fusion caused the expressed GFP fusion to accumulate in areas surrounding the chloroplast, presumably due to the presence of the endoplasmic reticulum signal encoded by the initial half-sequence and to the absence of the chloroplast transit sequence. These results indicate that PtCA1 is targeted to the stroma by the bipartite sequences of Pre46AA and that the observed GFP particles are formed specifically in the stroma due to the function of the mptca1. PMID:15849303

Tanaka, Yuji; Nakatsuma, Daisuke; Harada, Hisashi; Ishida, Maki; Matsuda, Yusuke

2005-05-01

220

Glacial landforms on German Bank, Scotian Shelf: evidence for Late Wisconsinan ice-sheet dynamics and implications for the formation of De Geer moraines  

USGS Publications Warehouse

The extent and behaviour of the southeast margin of the Laurentide Ice Sheet in Atlantic Canada is of significance in the study of Late Wisconsinan ice sheet-ocean interactions. Multibeam sonar imagery of subglacial, ice-marginal and glaciomarine landforms on German Bank, Scotian Shelf, provides evidence of the pattern of glacial-dynamic events in the eastern Gulf of Maine. Northwest-southeast trending drumlins and megaflutes dominate northern German Bank. On southern German Bank, megaflutes of thin glacial deposits create a distinct northwest-southeast grain. Lobate regional moraines (>10km long) are concave to the northwest, up-ice direction and strike southwest-northeast, normal to the direction of ice flow. Ubiquitous, overlying De Geer moraines (

Todd, Brian J.; Valentine, Page C.; Longva, Oddvar; Shaw, John

2007-01-01

221

Effect of formation and state of interface on joint strength in friction stir spot welding for advanced high strength steel sheets  

NASA Astrophysics Data System (ADS)

The tensile shear strength and cross tension strength of friction stir spot welded joints were evaluated in the cases of lap joints of 270 N/mm2 grade and 980 N/mm2 grade cold rolled steel sheets with respect to the stir zone area, hardness distribution, and interface condition between the sheets. The results suggested that both the tensile shear strength and cross tension strength were based on the stir zone area and its hardness in both grades of steel. The "hook" shape of the interface also affected the joint strength. However, the joining that occurred across the interfaces had a significant influence on the value of the joint strength in the case of the 270 N/mm2 grade steel.

Taniguchi, Koichi; Matsushita, Muneo; Ikeda, Rinsei; Oi, Kenji

2014-08-01

222

Camera data sheet for pictorial electronic still cameras  

Microsoft Academic Search

A data sheet is presented outlining the performance and characteristics of a Kodak DCS 200mi camera. In addition to providing information on this camera, the format and content of the data sheet could serve as a guide in the organization and display of pertinent information on electronic still cameras in general. Such data sheets are already common in silver halide

Sabine Susstrunk; Jack M. Holm

1995-01-01

223

An abnormal fibrinogen Fukuoka II (Gly-B beta 15-->Cys) characterized by defective fibrin lateral association and mixed disulfide formation.  

PubMed

A dysfibrinogenemia was attributable to a single amino acid substitution from glycine to cysteine at residue 15 of the B beta chain in a fibrinogen molecule designated as fibrinogen Fukuoka II. The fibrinogen Fukuoka II showed prolonged thrombin and reptilase times and impaired fibrinopeptide B release by thrombin, resulting in abolition of fibrin monomer repolymerization under physiological conditions. Repolymerization of the des-(B beta 1-42)-fibrin monomers, however, was not distinguished from the normal pattern of des-(B beta 1-42)-fibrin monomers, suggesting that no other abnormality existed in fibrinogen Fukuoka II. Although an additional cysteine was substituted at residue 15 of the B beta chain, fibrinogen Fukuoka II had no free sulfhydryl group within the molecule. Instead, fibrinogen Fukuoka II formed a disulfide bond with cysteine, albumin, another mutated B beta chain within the same molecule, or intermolecular dimeric fibrinogen Fukuoka II. The mutation in fibrinogen Fukuoka II was the same as that in fibrinogen Ise published previously (Yoshida, N., Wada, H., Morita, K., Hirata, H., Matsuda, M., Yamazumi, K., Asakura, S., and Shirakawa, S. (1991) Blood 77, 1958-1963). Fibrinogen Ise, however, has been described as having prolonged thrombin time but normal reptilase time. Reasons for the discrepancy were not clear. Analysis of the B beta 1-42 fragment showed that fibrinogen was heterogeneous at position 31 of the B beta chain with respect to proline or hydroxyproline. PMID:7493975

Kamura, T; Tsuda, H; Yae, Y; Hattori, S; Ohga, S; Shibata, Y; Kawabata, S; Hamasaki, N

1995-12-01

224

Secondary structure formation in peptide amphiphile micelles  

NASA Astrophysics Data System (ADS)

Peptide amphiphiles (PAs) are capable of self-assembly into micelles for use in the targeted delivery of peptide therapeutics and diagnostics. PA micelles exhibit a structural resemblance to proteins by having folded bioactive peptides displayed on the exterior of a hydrophobic core. We have studied two factors that influence PA secondary structure in micellar assemblies: the length of the peptide headgroup and amino acids closest to the micelle core. Peptide length was systematically varied using a heptad repeat PA. For all PAs the addition of a C12 tail induced micellization and secondary structure. PAs with 9 amino acids formed beta-sheet interactions upon aggregation, whereas the 23 and 30 residue peptides were displayed in an apha-helical conformation. The 16 amino acid PA experienced a structural transition from helix to sheet, indicating that kinetics play a role in secondary structure formation. A p53 peptide was conjugated to a C16 tail via various linkers to study the effect of linker chemistry on PA headgroup conformation. With no linker the p53 headgroup was predominantly alpha helix and a four alanine linker drastically changed the structure of the peptide headgroup to beta-sheet, highlighting the importance of hydrogen boding potential near the micelle core.

Tirrell, Matthew

2012-02-01

225

Beta Thalassemia  

MedlinePLUS

... 1 Beta thalassemia is found in people of Mediterranean, Middle Eastern, African, South Asian (Indian, Pakistani, etc.), ... is commonly found in people of African or Mediterranean ancestry, such as Africans, Italians, Greeks, Turks, and ...

226

Two-Dimensional Infrared (2DIR) Spectroscopy of the Peptide Beta3s Folding  

PubMed Central

Probing underlying free energy landscape, pathways, and mechanism is the key for understanding protein folding in theory and experiment. Recently time-resolved two-dimensional infrared (2DIR) with femtosecond laser pulses, has emerged as a promising tool for investigating the protein folding dynamics on faster timescales than possible by NMR. We have employed molecular dynamics simulations to compute 2DIR spectra of the folding process of a peptide, Beta3s. Simulated non-chiral and chiral 2DIR signals illustrate the variation of the spectra as the peptide conformation evolves along the free energy landscape. Chiral spectra show stronger changes than the non-chiral signals because cross peaks caused by the formation of the ?-sheet are clearly resolved. Chirality-induced 2DIR may be used to detect the folding of ?-sheet proteins with high spectral and temporal resolution. PMID:23956818

Lai, Zaizhi; Preketes, Nicholas K; Jiang, Jun; Mukamel, Shaul; Wang, Jin

2013-01-01

227

Experimental Study of Lower-hybrid Drift Turbulence in a Reconnecting Current Sheet  

SciTech Connect

The role of turbulence in the process of magnetic reconnection has been the subject of a great deal of study and debate in the theoretical literature. At issue in this debate is whether turbulence is essential for fast magnetic reconnection to occur in collisionless current sheets. Some theories claim it is necessary in order to provide anomalous resistivity, while others present a laminar fast reconnection mechanism based on the Hall term in the generalized Ohm's law. In this work, a thorough study of electrostatic potential fluctuations in the current sheet of the Magnetic Reconnection Experiment (MRX) [M. Yamada et al., Phys. Plasmas 4, 1936 (1997)] was performed in order to ascertain the importance of turbulence in a laboratory reconnection experiment. Using amplified floating Langmuir probes, broadband fluctuations in the lower hybrid frequency range (fLH approximately 5-15 MHz) were measured which arise with the formation of the current sheet in MRX. The frequency spectrum, spatial amplitude profile, and spatial correlation characteristics of the measured turbulence were examined carefully, finding consistency with theories of the lower-hybrid drift instability (LHDI). The LHDI and its role in magnetic reconnection has been studied theoretically for decades, but this work represents the first detection and detailed study of the LHDI in a laboratory current sheet. The observation of the LHDI in MRX has provided the unique opportunity to uncover the role of this instability in collisionless reconnection. It was found that: (1) the LHDI fluctuations are confined to the low-beta edge of current sheets in MRX; (2) the LHDI amplitude does not correlate well in time or space with the reconnection electric field, which is directly related to the rate of reconnection; and (3) significant LHDI amplitude persists in high collisionality current sheets where the reconnection rate is classical. These findings suggest that the measured LHDI fluctuations do not play an essential role in determining the reconnection rate in MRX.

T.A. Carter, M. Yamada, H. Ji, R.M. Kulsrud, and F. Trintchouk

2002-06-18

228

Electron Diffraction Evidence for the Ordering of Excess Nickel Atoms by Relation to Stoichiometry in Nickel-Rich Beta'-Nial Formation of a Nickel-Aluminum (Ni2al) Superlattices  

NASA Technical Reports Server (NTRS)

In electron diffraction patterns of nickel-rich beta-NiAl alloys, many anomalies are observed. One of these is the appearance of diffuse intensity maxima between the reflexions of the B2 structure. This is explained by the short-range ordering of the excess nickel atoms on the simple cubic sublattice occupied only by aluminum atoms in the stoichiometric, perfectly ordered NiAl alloy. After annealing Ni 37.5 atomic percent Al and Ni 37.75 atomic percent Al for 1 week at 300 and 400 C, the diffuse intensity maxima transformed into sharp superstructure reflexions. These reflexions are explained by the formation of the four possible variants of an ordered hexagonal superstructure corresponding to the Ni2Al composition. This structure is closely related to the Ni2Al3 structure (same space group) formed by the ordering of vacancies on the nickel sublattice in aluminum-rich beta-NiAl alloys.

Reynaud, F.

1988-01-01

229

Identification, classification, and analysis of beta-bulges in proteins.  

PubMed Central

A beta-bulge is a region of irregularity in a beta-sheet involving two beta-strands. It usually involves two or more residues in the bulged strand opposite to a single residue on the adjacent strand. These irregularities in beta-sheets were identified and classified automatically, extending the definition of beta-bulges given by Richardson et al. (Richardson, J.S., Getzoff, E.D., & Richardson, D.C., 1978, Proc. Natl. Acad. Sci. USA 75, 2574-2578). A set of 182 protein chains (170 proteins) was used, and a total of 362 bulges were extracted. Five types of beta-bulges were found: classic, G1, wide, bent, and special. Their characteristic amino acid preferences were found for most classes of bulges. Basically, bulges occur frequently in proteins; on average there are more than two bulges per protein. In general, beta-bulges produce two main changes in the structure of a beta-sheet: (1) disrupt the normal alternation of side-chain direction; (2) accentuate the twist of the sheet, altering the direction of the surrounding strands. PMID:8251933

Chan, A. W.; Hutchinson, E. G.; Harris, D.; Thornton, J. M.

1993-01-01

230

Minimalist design of water-soluble cross-[beta] architecture  

SciTech Connect

Demonstrated successes of protein design and engineering suggest significant potential to produce diverse protein architectures and assemblies beyond those found in nature. Here, we describe a new class of synthetic protein architecture through the successful design and atomic structures of water-soluble cross-{beta} proteins. The cross-{beta} motif is formed from the lamination of successive {beta}-sheet layers, and it is abundantly observed in the core of insoluble amyloid fibrils associated with protein-misfolding diseases. Despite its prominence, cross-{beta} has been designed only in the context of insoluble aggregates of peptides or proteins. Cross-{beta}'s recalcitrance to protein engineering and conspicuous absence among the known atomic structures of natural proteins thus makes it a challenging target for design in a water-soluble form. Through comparative analysis of the cross-{beta} structures of fibril-forming peptides, we identified rows of hydrophobic residues ('ladders') running across {beta}-strands of each {beta}-sheet layer as a minimal component of the cross-{beta} motif. Grafting a single ladder of hydrophobic residues designed from the Alzheimer's amyloid-{beta} peptide onto a large {beta}-sheet protein formed a dimeric protein with a cross-{beta} architecture that remained water-soluble, as revealed by solution analysis and x-ray crystal structures. These results demonstrate that the cross-{beta} motif is a stable architecture in water-soluble polypeptides and can be readily designed. Our results provide a new route for accessing the cross-{beta} structure and expanding the scope of protein design.

Biancalana, Matthew; Makabe, Koki; Koide, Shohei (UC)

2010-08-13

231

Gender-related effects of 17-{beta}-estradiol and B-hexachlorocyclohexane on liver tumor formation in medaka (Oryzias latipes)  

SciTech Connect

When medaka were acutely exposed to diethylnitrosamine (DEN), greater incidence of hepatocarcinoma was seen in female versus male fish. This is possibly related to elevated female endogenous estrogens, which increase liver weight and production of vitellogenin. To examine roles of estrogens in tumor modulation, 21-day old medaka were exposed to DEN (200 ppm for 24 hr.), then fed purified diets containing the estrogenic compound {beta}-hexachlorocyclohexane ({beta}-HCH) or 17-{beta}estradiol (E2) for 6 months. Incidences of basophilic preneoplastic foci of cellular alteration in females receiving DEN and 0.01, 0.1, or 1.0 ppm E2 were three times the incidences in similarly-treated males. Also, incidences of basophilic foci in DEN + 0.1 ppm E2 males were significantly increased over DEN-only males and were equal to incidences in DEN-only females. Liver weights and hepatosomatic indices of males given 0.1 ppm E2 were not significantly different than females fed control diet. Females fed 0.01-10.0 ppm {beta}-HCH after DEN had 4--5 times greater incidences of basophilic foci as males. Gender-related effects on kinetics of growth rates and volumes of foci are being examined.

Cooke, J.B.; Hinton, D.E. [Univ. of California, Davis, CA (United States)

1994-12-31

232

In-situ time-of-flight neutron diffraction of ErD2 (beta phase) formation during D2 loading.  

SciTech Connect

In an effort to better understand the structural changes occurring during hydrogen loading of erbium target materials, we have performed D{sub 2} loading of erbium metal (powder) with simultaneous neutron diffraction analysis. This experiment tracked the conversion of Er metal to the {alpha} erbium deuteride (solid-solution) phase and then on to the {beta} (fluorite) phase. Complete conversion to ErD{sub 2.0} was accomplished at 10 Torr D{sub 2} pressure with deuterium fully occupying the tetrahedral sites in the fluorite lattice. Increased D{sub 2} pressure (up to 500 Torr at 450 C) revealed {approx}10 % deuterium occupation of the octahedral sites. Subsequent vacuum pumping of the sample at 450 C removed octahedral site occupancy while maintaining tetrahedral deuterium occupancy, thereby yielding stoichiometric ErD{sub 2.0} {beta} phase.

Browning, James Frederick (Oak Ridge National Laboratory, Oak Ridge, TN); Llobet, Anna (Los Alamos National Laboratory, Los Alamos, NM); Snow, Clark Sheldon; Rodriguez, Mark Andrew; Wixom, Ryan R.

2008-06-01

233

The majority of potassium ions in muscle cells is adsorbed on beta- and gamma-carboxyl groups of myosin: potassium-ion-adsorbing carboxyl groups on myosin heads engage in cross-bridge formation during contraction.  

PubMed

High-molecular weight poly(ethylene glycol) (PEG-8000) in the bathing medium prolongs the survival of 2-mm-wide frog muscle segments with open ends. In a PEG-8000-containing medium Rb+, K+, and Na+ in the muscle segments reached new diffusion equilibrium in 2-4 hours. At this new equilibrium, the cell's preference of K+ over Na+ was preserved but very much weakened. Studies of the influence of pH on the equilibrium distribution of labelled Na+ in 2-mm-wide muscle segments confirmed the prediction that beta- and gamma-carboxyl groups, carried respectively on aspartic and glutamic acid residues of intracellular proteins, adsorb K+, Na+ and other monovalent cations. These carboxyl groups have a characteristic pKa between 3.65 and 4.25. A pKa of 3.85 was observed. These findings, when seen in the light of other relevant information available, led to the conclusion that beta- and gamma-carboxyl groups on myosin molecules adsorb--in a close contact one-ion-one-site fashion--the majority (67% to 80%) of K+ in resting muscle cells. Other evidence suggests that in muscle contraction, the K(+)-adsorbing beta- and gamma-carboxyl groups on myosin heads form salt linkages with cationic sites on actin, displacing and releasing the adsorbed K+. Present and earlier findings together offer support for an earlier suggestion that the formation and dissociation of these salt-linkages may underlie the force-generating, cyclic formation and dissociation of cross-bridges during muscle contraction. PMID:1775537

Ling, G N; Ochsenfeld, M M

1991-01-01

234

Formation of gamma'-Ni3Al via the Peritectoid Reaction: gamma plus beta (+Al2O3) equals gamma'(+Al2O3)  

NASA Technical Reports Server (NTRS)

The activities of Al and Ni were measured using multi-cell Knudsen effusion-cell mass spectrometry (multi-cell KEMS), over the composition range 8 - 32 at.%Al and temperature range T = 1400 - 1750 K in the Ni-Al-O system. These measurements establish that equilibrium solidification of gamma'-Ni3Al-containing alloys occurs by the eutectic reaction, L (+ Al2O3) = gamma + beta (+ Al2O3), at 1640 plus or minus 1 K and a liquid composition of 24.8 plus or minus 0.2 at.%Al (at an unknown oxygen content). The {gamma + beta + Al2O3} phase field is stable over the temperature range 1633 - 1640 K, and gamma'-Ni3Al forms via the peritectiod, gamma + beta (+ Al2O3) = gamma'(+ Al2O3), at 1633 plus or minus 1 K. This behavior is inconsistent with the current Ni-Al phase diagram and a new diagram is proposed. This new Ni-Al phase diagram explains a number of unusual steady state solidification structures reported previously and provides a much simpler reaction scheme in the vicinity of the gamma'-Ni3Al phase field.

Copland, Evan

2008-01-01

235

Formation of gamma(sup prime)-Ni3Al via the Peritectoid Reaction: gamma + beta (+ Al2O3)=gamma(sup prime)(+ Al2O3)  

NASA Technical Reports Server (NTRS)

The activities of Al and Ni were measured using multi-cell Knudsen effusion-cell mass spectrometry (multi-cell KEMS), over the composition range 8-32 at.%Al and temperature range T=1400-1750 K in the Ni-Al-O system. These measurements establish that equilibrium solidification of gamma(sup prime)-Ni3Al-containing alloys occurs by the eutectic reaction, L (+ Al2O3)=gamma + Beta(+ Al2O3), at 1640 +/- 1 K and a liquid composition of 24.8 +/- 0.2 at.%al (at an unknown oxygen content). The {gamma + Beta (+Al2O3} phase field is stable over the temperature range 1633-1640 K, and gamma(sup prime)-Ni3Al forms via the peritectoid, gamma + Beta (+ Al2O3)=gamma(sup prime) (+ Al2O3), at 1633 +/- 1 K. This behavior is consistent with the current Ni-Al phase diagram and a new diagram is proposed. This new Ni-Al phase diagram explains a number of unusual steady-state solidification structures reported previously and provides a much simpler reaction scheme in the vicinity of the gamma(sup prime)-Ni2Al phase field.

Copeland, Evan

2008-01-01

236

THE DEPENDENCE OF MAGNETIC RECONNECTION ON PLASMA {beta} AND MAGNETIC SHEAR: EVIDENCE FROM SOLAR WIND OBSERVATIONS  

SciTech Connect

We address the conditions for the onset of magnetic reconnection based on a survey of 197 reconnection events in solar wind current sheets observed by the Wind spacecraft. We report the first observational evidence for the dependence of the occurrence of reconnection on a combination of the magnetic field shear angle, {theta}, across the current sheet and the difference in the plasma {beta} values on the two sides of the current sheet, {Delta}{beta}. For low {Delta}{beta}, reconnection occurred for both low and high magnetic shears, whereas only large magnetic shear events were observed for large {Delta}{beta}: Events with shears as low as 11{sup 0} were observed for {Delta}{beta} < 0.1, but for {Delta}{beta} > 1.5 only events with {theta} > 100{sup 0} were detected. Our observations are in quantitative agreement with a theoretical prediction that reconnection is suppressed in high {beta} plasmas at low magnetic shears due to super-Alfvenic drift of the X-line caused by plasma pressure gradients across the current sheet. The magnetic shear-{Delta}{beta} dependence could account for the high occurrence rate of reconnection observed in current sheets embedded within interplanetary coronal mass ejections, compared to those in the ambient solar wind. It would also suggest that reconnection could occur at a substantially higher rate in solar wind current sheets closer to the Sun than at 1 AU and thus may play an important role in the generation and heating of the solar wind.

Phan, T. D.; Pasma, C.; Oeieroset, M.; Larson, D.; Lin, R. P.; Davis, M. S. [SSL, University of California, Berkeley, CA 94720 (United States); Gosling, J. T. [University of Colorado, Boulder, CO (United States); Paschmann, G. [MPE, Garching (Germany); Drake, J. F., E-mail: phan@ssl.berkeley.ed [University of Maryland, College Park, MD (United States)

2010-08-20

237

Rangeland Sheet 6 Soil Quality Information Sheet  

E-print Network

Rangeland Sheet 6 Soil Quality Information Sheet Rangeland Soil Quality--Organic Matter USDA plant nutrients Physically Decades · Enhances soil structure, protected porosity, and the water penetration and reducing runoff and erosion; · enhances soil fertility and plant productivity by improving

238

Interpeting Data Sheets  

NSDL National Science Digital Library

This resource helps to teach students how to interpret TI or other component manufacturer's data sheets. It is quite extensive, mainly covering the TI Logic Data Sheet. Illustrative material is also included. The document may be downloaded as a PDF.

Nolan, Stephen M.

239

The iA{beta}5p {beta}-breaker peptide regulates the A{beta}(25-35) interaction with lipid bilayers through a cholesterol-mediated mechanism  

SciTech Connect

Highlights: Black-Right-Pointing-Pointer iA{beta}5p shows a significant tendency to deeply penetrates the hydrophobic core of lipid membrane. Black-Right-Pointing-Pointer A{beta}(25-35) locates in the external region of the membrane causing a re-positioning of CHOL. Black-Right-Pointing-Pointer iA{beta}5p withholds cholesterol in the inner hydrophobic core of the lipid membrane. Black-Right-Pointing-Pointer iA{beta}5p prevents the A{beta}(25-35) release from the lipid membrane. -- Abstract: Alzheimer's disease is characterized by the deposition of aggregates of the {beta}-amyloid peptide (A{beta}) in the brain. A potential therapeutic strategy for Alzheimer's disease is the use of synthetic {beta}-sheet breaker peptides, which are capable of binding A{beta} but unable to become part of a {beta}-sheet structure, thus inhibiting the peptide aggregation. Many studies suggest that membranes play a key role in the A{beta} aggregation; consequently, it is strategic to investigate the interplay between {beta}-sheet breaker peptides and A{beta} in the presence of lipid bilayers. In this work, we focused on the effect of the {beta}-sheet breaker peptide acetyl-LPFFD-amide, iA{beta}5p, on the interaction of the A{beta}(25-35) fragment with lipid membranes, studied by Electron Spin Resonance spectroscopy, using spin-labeled membrane components (either phospholipids or cholesterol). The ESR results show that iA{beta}5p influences the A{beta}(25-35) interaction with the bilayer through a cholesterol-mediated mechanism: iA{beta}5p withholds cholesterol in the inner hydrophobic core of the bilayer, making the interfacial region more fluid and capable to accommodate A{beta}(25-35). As a consequence, iA{beta}5p prevents the A{beta}(25-35) release from the lipid membrane, which is the first step of the {beta}-amyloid aggregation process.

Vitiello, Giuseppe [Department of Chemistry, University of Naples 'Federico II', Naples (Italy) [Department of Chemistry, University of Naples 'Federico II', Naples (Italy); CSGI (Consorzio per lo Sviluppo dei Sistemi a Grande Interfase), Florence (Italy)] [Consorzio per lo Sviluppo dei Sistemi a Grande Interfase; Italy; Grimaldi, Manuela; D'Ursi, Anna Maria [Department of Pharmaceutical Science, University of Salerno, Fisciano (Italy)] [Department of Pharmaceutical Science, University of Salerno, Fisciano (Italy); D'Errico, Gerardino, E-mail: gerardino.derrico@unina.it [Department of Chemistry, University of Naples 'Federico II', Naples (Italy) [Department of Chemistry, University of Naples 'Federico II', Naples (Italy); CSGI (Consorzio per lo Sviluppo dei Sistemi a Grande Interfase), Florence (Italy)] [Consorzio per lo Sviluppo dei Sistemi a Grande Interfase; Italy

2012-01-06

240

Effect of Strand Symmetry on the Nanostructure and Material Properties in Beta-Hairpin Peptide Hydrogels  

NASA Astrophysics Data System (ADS)

Hydrogels have been established as promising biomaterials for applications such as scaffolds for tissue engineering, controlled drug delivery and cell encapsulation. De novo designed beta hairpin peptides, capable of undergoing self assembly and hydrogel formation, were investigated that contain asymmetric beta strand arms surrounding a turn sequence. The stimuli responsive self assembly of the hydrogels occurs via an intramolecular folding and strand interdigitation mechanism. CD and FTIR indicate a beta sheet secondary structure. WAXS shows a fibril structure reminiscent of the cross beta spine. SANS has been employed to globally quantify the local structure as being rod-like. Modification of the strand registry results in fibrils with non-twisting, laminated vs. twisted nanostructure. Fibril dimensions as measured by TEM and AFM corroborate the interdigitated assembly. Bulk material properties of these hydrogels studied using oscillatory rheology vary significantly for the different morphologies. Differences in the peptide registry that drive hydrogel nanostructure and the consequent material properties can be potentially utilized for usage in specific biomaterial applications.

Hule, Rohan; Pochan, Darrin; Nagarkar, Radhika; Schneider, Joel

2007-03-01

241

L6E9 myoblasts are deficient of myostatin and additional TGF-beta members are candidates to developmentally control their fiber formation.  

PubMed

This work provides evidence that the robust myoblast differentiation observed in L6E9 cells is causally linked to deficiency of myostatin, which, conversely, has been found to be expressed in C2C12 cells. However, despite the absence of endogenous myostatin, L6E9 myoblasts expressed functional Activin receptors type II (ActRIIs) and follistatin as well as the highly related TGF-beta members Activins and GDF11, suggesting that in this cell line the regulation of fiber size might be under the control of multiple regulators regardless of myostatin. In line with this hypothesis, delivery of a dominant-negative ActRIIb form or the increase of follistatin, as obtained via Trichostatin treatment or stable transfection of a short human follistatin form, enhanced the L6E9 cell differentiation and further increased the size of myotubes, suggesting that L6E9 myoblasts provide a spontaneous myostatin knock-out in vitro model to study TGF-beta ligands involved in developmental regulation of fiber size. PMID:20396675

Rossi, Stefania; Stoppani, Elena; Gobbo, Massimiliano; Caroli, Anna; Fanzani, Alessandro

2010-01-01

242

W-Band Sheet Beam Klystron Design  

SciTech Connect

Sheet beam devices provide important advantages for very high power, narrow bandwidth RF sources like accelerator klystrons [1]. Reduced current density and increased surface area result in increased power capabi1ity, reduced magnetic fields for focusing and reduced cathode loading. These advantages are offset by increased complexity, beam formation and transport issues and potential for mode competition in the ovennoded cavities and drift tube. This paper will describe the design issues encountered in developing a 100 kW peak and 2 kW average power sheet beam k1ystron at W-band including beam formation, beam transport, circuit design, circuit fabrication and mode competition.

Scheitrum, G.; Caryotakis, G.; Burke, A.; Jensen, A.; Jongewaard, E.a Krasnykh, A.; Neubauer, M.; Phillips, R.; Rauenbuehler, K.; /SLAC

2011-11-11

243

Internal hydrogen embrittlement of high-strength beta-alpha titanium alloys  

NASA Astrophysics Data System (ADS)

Potential problems and uncertainties are associated with the complex nature of fracture in solution treated and aged (STA) beta-titanium (beta-Ti) alloys, as well as the potential for long-term alloy degradation due to hydrogen embrittlement. This research characterizes the effects of predissolved hydrogen and microstructural conditions on the fracture resistance of two solution treated and aged (STA) high strength beta-titanium alloys, Low Cost Beta (LCB) and Ti-15-3, in sheet form. Rising-CMOD fracture test results demonstrate that STA beta-Ti alloys are severely embrittled at room temperature and a slow displacement rate above a relatively low threshold hydrogen concentration. Hydrogen concentrations of 400 and 500 wppm reduce the threshold stress intensity at the onset of hydrogen cracking to 50% of the air fracture toughness in STA LCB, and Ti-15-3, respectively. Significant embrittlement for both alloys is triggered at concentrations in excess of 750 wppm, with reductions in threshold stress intensity to an asymptotic value equal to 25% of the air fracture toughness. Reductions in crack growth resistance with increasing hydrogen concentrations are accompanied by significant increases in subcritical crack growth rates. Changes in fracture mode are concurrent with reduced in fracture resistance. With increasing hydrogen concentration, the fracture mode changes from microvoid coalescence to transgranular hydrogen-assisted alpha/beta interface cracking. Two mechanisms of internal hydrogen embrittlement in STA metastable beta-Ti alloys, bond decohesion and hydride formation are proposed to occur at alpha/beta interfaces. A critical isothermal aging time must be exceeded to render Ti-15-3 susceptible to internal hydrogen embrittlement. This is attributed to a critical alpha volume fraction and the associated stress and hydrogen concentration. The internal hydrogen embrittlement of STA Ti-15-3 is a time dependent phenomenon. Experimental results and crack tip strain rate calculations demonstrate that embrittlement will persist in STA Ti-15-3 to loading rates of approximately 0.5 MPa?m/s. As such, hydrogen redistribution to the crack tip is a critical component of internal hydrogen embrittlement. Local transport of hydrogen in intra-alpha beta to susceptible alpha/beta interfaces, and possibly growth kinetics of gamma-TiH2, in the fracture process zone are consistent with the observed kinetics and appear to govern the time dependence.

Hayes, Sean Paul

244

A mechanism for the formation of knots, kinks and disconnection events in the plasma tail of comets  

NASA Astrophysics Data System (ADS)

The growth rates and eigenmodes of the streaming sausage, kink and tearing instabilities in the plasma tail of comets are investigated. The results show that both the sausage and kink modes can be excited by the sheared plasma flow, which is low at the center of the plasma sheet and high on the two sides of the plasma sheet. The streaming sausage mode grows faster than the streaming kink mode when beta(L) is below 1.5. When beta(L) is above 1.5, the streaming kink instability has a higher growth rate. In the presence of a finite resistivity, the streaming sausage mode evolves into the streaming tearing mode, which leads to the formation of magnetic islands. Some of the knots, kinks and disconnection events observed in the plasma tail of comets may be associated with the streaming sausage, kink and tearing instabilities, respectively.

Wang, S.

1991-03-01

245

Dynamic Formation of a Hot Field Reversed Configuration with Improved Confinement by Supersonic Merging of Two Colliding High-{beta} Compact Toroids  

SciTech Connect

A hot stable field-reversed configuration (FRC) has been produced in the C-2 experiment by colliding and merging two high-{beta} plasmoids preformed by the dynamic version of field-reversed {theta}-pinch technology. The merging process exhibits the highest poloidal flux amplification obtained in a magnetic confinement system (over tenfold increase). Most of the kinetic energy is converted into thermal energy with total temperature (T{sub i}+T{sub e}) exceeding 0.5 keV. The final FRC state exhibits a record FRC lifetime with flux confinement approaching classical values. These findings should have significant implications for fusion research and the physics of magnetic reconnection.

Binderbauer, M. W.; Guo, H. Y.; Tuszewski, M.; Putvinski, S.; Sevier, L.; Barnes, D.; Rostoker, N.; Anderson, M. G.; Andow, R.; Bonelli, L.; Brown, R.; Bui, D. Q.; Bystritskii, V.; Clary, R.; Cheung, A. H.; Conroy, K. D.; Deng, B. H.; Dettrick, S. A.; Douglass, J. D.; Feng, P. [Tri Alpha Energy, Inc., Post Office Box 7010, Rancho Santa Margarita, California 92688 (United States)

2010-07-23

246

Formation of decarboxylated betacyanins in heated purified betacyanin fractions from red beet root (Beta vulgaris L.) monitored by LC-MS/MS.  

PubMed

Mixtures of mono-, bi-, and tridecarboxylated betacyanins together with their corresponding neobetacyanins obtained from Beta vulgaris L. root juice as heating degradation products of betacyanins were identified by high-performance liquid chromatography with tandem mass spectrometry (LC-MS/MS) and diode-array (LC-DAD) detection. Two monodecarboxy-betacyanin pairs of diastereomers were detected after the decarboxylation in ethanolic and aqueous solutions. Generation of 17-decarboxy-betacyanins and 2-decarboxy-betacyanins was suggested, the latter so far never having been attributed to betacyanin thermal degradation products. Other main products of decarboxylation were 2,17-bidecarboxybetanin, its isoform, and 14,15-dehydrogenated (neobetacyanin) derivatives of all the decarboxylated betacyanins. The results of this research are crucial in determining betacyanin degradation mechanisms in juices or extracts of B. vulgaris L. roots and other products containing these pigments. PMID:15853391

Wybraniec, S?awomir

2005-05-01

247

Ellagic acid promotes A{beta}42 fibrillization and inhibits A{beta}42-induced neurotoxicity  

SciTech Connect

Smaller, soluble oligomers of {beta}-amyloid (A{beta}) play a critical role in the pathogenesis of Alzheimer's disease (AD). Selective inhibition of A{beta} oligomer formation provides an optimum target for AD therapy. Some polyphenols have potent anti-amyloidogenic activities and protect against A{beta} neurotoxicity. Here, we tested the effects of ellagic acid (EA), a polyphenolic compound, on A{beta}42 aggregation and neurotoxicity in vitro. EA promoted A{beta} fibril formation and significant oligomer loss, contrary to previous results that polyphenols inhibited A{beta} aggregation. The results of transmission electron microscopy (TEM) and Western blot displayed more fibrils in A{beta}42 samples co-incubated with EA in earlier phases of aggregation. Consistent with the hypothesis that plaque formation may represent a protective mechanism in which the body sequesters toxic A{beta} aggregates to render them harmless, our MTT results showed that EA could significantly reduce A{beta}42-induced neurotoxicity toward SH-SY5Y cells. Taken together, our results suggest that EA, an active ingredient in many fruits and nuts, may have therapeutic potential in AD.

Feng, Ying [Department of Histology and Embryology, College of Basic Medical Science, China Medical University, Shenyang 110001 (China) [Department of Histology and Embryology, College of Basic Medical Science, China Medical University, Shenyang 110001 (China); Tsinghua University School of Medicine, Haidian District, Beijing 100084 (China); Yang, Shi-gao; Du, Xue-ting; Zhang, Xi; Sun, Xiao-xia; Zhao, Min [Tsinghua University School of Medicine, Haidian District, Beijing 100084 (China)] [Tsinghua University School of Medicine, Haidian District, Beijing 100084 (China); Sun, Gui-yuan, E-mail: sungy2004@sohu.com [Department of Histology and Embryology, College of Basic Medical Science, China Medical University, Shenyang 110001 (China)] [Department of Histology and Embryology, College of Basic Medical Science, China Medical University, Shenyang 110001 (China); Liu, Rui-tian, E-mail: rtliu@tsinghua.edu.cn [Tsinghua University School of Medicine, Haidian District, Beijing 100084 (China)] [Tsinghua University School of Medicine, Haidian District, Beijing 100084 (China)

2009-12-25

248

The Arabidopsis P4-ATPase ALA3 localizes to the golgi and requires a beta-subunit to function in lipid translocation and secretory vesicle formation.  

PubMed

Vesicle budding in eukaryotes depends on the activity of lipid translocases (P(4)-ATPases) that have been implicated in generating lipid asymmetry between the two leaflets of the membrane and in inducing membrane curvature. We show that Aminophospholipid ATPase3 (ALA3), a member of the P(4)-ATPase subfamily in Arabidopsis thaliana, localizes to the Golgi apparatus and that mutations of ALA3 result in impaired growth of roots and shoots. The growth defect is accompanied by failure of the root cap to release border cells involved in the secretion of molecules required for efficient root interaction with the environment, and ala3 mutants are devoid of the characteristic trans-Golgi proliferation of slime vesicles containing polysaccharides and enzymes for secretion. In yeast complementation experiments, ALA3 function requires interaction with members of a novel family of plant membrane-bound proteins, ALIS1 to ALIS5 (for ALA-Interacting Subunit), and in this host ALA3 and ALIS1 show strong affinity for each other. In planta, ALIS1, like ALA3, localizes to Golgi-like structures and is expressed in root peripheral columella cells. We propose that the ALIS1 protein is a beta-subunit of ALA3 and that this protein complex forms an important part of the Golgi machinery required for secretory processes during plant development. PMID:18344284

Poulsen, Lisbeth Rosager; López-Marqués, Rosa Laura; McDowell, Stephen C; Okkeri, Juha; Licht, Dirk; Schulz, Alexander; Pomorski, Thomas; Harper, Jeffrey F; Palmgren, Michael Gjedde

2008-03-01

249

Molecular dynamics studies of hexamers of amyloid-beta peptide (16-35) and its mutants: influence of charge states on amyloid formation.  

PubMed

To study the early stage of amyloid-beta peptide (Abeta) aggregation, hexamers of the wild-type (WT) Abeta(16-35) and its mutants with amyloid-like conformations have been studied by molecular dynamics simulations in explicit water for a total time of 1.7 micros. We found that the amyloid-like structures in the WT oligomers are destabilized by the solvation of ionic D23/K28 residues, which are buried in the fibrils. This means that the desolvation of D23/K28 residues may contribute to the kinetic barrier of aggregation in the early stage. In the E22Q/D23N, D23N/K28Q, and E22Q/D23N/K28Q mutants, hydration becomes much less significant because the mutated residues have neutral amide side-chains. These amide side-chains can form linear cross-strand hydrogen bond chains, or "polar zippers", if dehydrated. These "polar zippers" increase the stability of the amyloid-like conformation, reducing the barrier for the early-stage oligomerization. This is in accord with experimental observations that both the D23/K28 lactamization and the E22Q/D23N mutation promote aggregation. We also found that the E22Q/D23N mutant prefers an amyloid-like conformation that differs from the one found for WT Abeta. This suggests that different amyloid structures may be formed under different conditions. PMID:17115426

Han, Wei; Wu, Yun-Dong

2007-02-15

250

Complex formation of beta-cyclodextrin in aqueous media with poly(N,N-dimethylacrylamide)containing pendent perfluorooctanesulfonamido groups. Final Report, September 15, 1998 - September 14, 1999  

SciTech Connect

The effect of time on the viscosity of solutions of 0.50--1.0 weight % polyacrylamide copolymers containing 2-(N-ethylperfluorooctanesulfonamido)ethyl acrylate (FOSA) comonomer units was monitored at constant shear rates varying from 0.60 to 3.0 sec{sup {minus}1}. The viscosities decreased to a plateau over a period of about thirty minutes. The copolymer solutions sheared at much higher shear rates of 24 sec{sup {minus}1} showed pronounced shear thinning but regained most of their original viscosities after standing for 20 minutes. Heating the solutions less than one hour caused an increase in the low shear viscosity whereas longer heating times decreased solution viscosities presumably due to hydrolysis of the acrylate groups. Addition of beta-cyclodextrin to solutions of the hydrophobically modified polyacrylamide resulted in sharply decreased copolymer viscosities at cyclodextrin concentrations on the order of about 10{sup {minus}3} M. The above is consistent with competitive hydrophobic association of the perfluorocarbon groups of the copolymer with the cyclodextrin disrupting the mutual association of the perfluorocarbon groups.

Dr. Thieo Hogen-Esch

1999-11-01

251

Emittance Measurements for a Thin Liquid Sheet Flow  

NASA Technical Reports Server (NTRS)

The Liquid Sheet Radiator (LSR) is an external flow radiator that uses a triangular-shaped flowing liquid sheet as the radiating surface. It has potentially much lower mass than solid wall radiators such as pumped loop and heat pipe radiators, along with being nearly immune to micrometeoroid penetration. The LSR has an added advantage of simplicity. Surface tension causes a thin (100-300 microns) liquid sheet to coalesce to a point, causing the sheet flow to have a triangular shape. Such a triangular sheet is desirable since it allows for simple collection of the flow at a single point. A major problem for all external flow radiators is the requirement that the working fluid be of very low (approx. 10(sup -8) torr) vapor pressure to keep evaporative losses low. As a result, working fluids are limited to certain oils (such as used in diffusion pumps) for low temperatures (300-400 K) and liquid metals for higher temperatures. Previous research on the LSR has been directed at understanding the fluid mechanics of thin sheet flows and assessing the stability of such flows, especially with regard to the formation of holes in the sheet. Taylor studied extensively the stability of thin liquid sheets both theoretically and experimentally. He showed that thin sheets in a vacuum are stable. The latest research has been directed at determining the emittance of thin sheet flows. The emittance was calculated from spectral transmittance data for the Dow Corning 705 silicone oil. By experimentally setting up a sheet flow, the emittance was also determined as a function of measurable quantities, most importantly, the temperature drop between the top of the sheet and the temperature at the coalescence point of the sheet. Temperature fluctuations upstream of the liquid sheet were a potential problem in the analysis and were investigated.

Englehart, Amy N.; McConley, Marc W.; Chubb, Donald L.

1996-01-01

252

In silico and in vitro studies to elucidate the role of Cu2+ and galanthamine as the limiting step in the amyloid beta (1–42) fibrillation process  

PubMed Central

The formation of fibrils and oligomers of amyloid beta (A?) with 42 amino acid residues (A?1–42) is the most important pathophysiological event associated with Alzheimer's disease (AD). The formation of A? fibrils and oligomers requires a conformational change from an ?-helix to a ?-sheet conformation, which is encouraged by the formation of a salt bridge between Asp 23 or Glu 22 and Lys 28. Recently, Cu2+ and various drugs used for AD treatment, such as galanthamine (Reminyl®), have been reported to inhibit the formation of A? fibrils. However, the mechanism of this inhibition remains unclear. Therefore, the aim of this work was to explore how Cu2+ and galanthamine prevent the formation of A?1–42 fibrils using molecular dynamics (MD) simulations (20 ns) and in vitro studies using fluorescence and circular dichroism (CD) spectroscopies. The MD simulations revealed that A?1–42 acquires a characteristic U-shape before the ?-helix to ?-sheet conformational change. The formation of a salt bridge between Asp 23 and Lys 28 was also observed beginning at 5 ns. However, the MD simulations of A?1?42 in the presence of Cu2+ or galanthamine demonstrated that both ligands prevent the formation of the salt bridge by either binding to Glu 22 and Asp 23 (Cu2+) or to Lys 28 (galanthamine), which prevents A?1?42 from adopting the U-characteristic conformation that allows the amino acids to transition to a ?-sheet conformation. The docking results revealed that the conformation obtained by the MD simulation of a monomer from the 1Z0Q structure can form similar interactions to those obtained from the 2BGE structure in the oligomers. The in vitro studies demonstrated that A? remains in an unfolded conformation when Cu2+ and galanthamine are used. Then, ligands that bind Asp 23 or Glu 22 and Lys 28 could therefore be used to prevent ? turn formation and, consequently, the formation of A? fibrils. PMID:23904252

Hernández-Rodríguez, Maricarmen; Correa-Basurto, José; Benitez-Cardoza, Claudia G; Resendiz-Albor, Aldo Arturo; Rosales-Hernández, Martha C

2013-01-01

253

Graphene sheets fabricated from disposable paper cups as a catalyst support material for fuel cells  

E-print Network

Graphene sheets fabricated from disposable paper cups as a catalyst support material for fuel cells Hong Zhao and T. S. Zhao* Disposable paper-cups are used for the formation of graphene sheets with Fe2+ as a catalyst. The proposed synthesis strategy not only enables graphene sheets to be produced in high yield

Zhao, Tianshou

254

The East Antarctic Ice Sheet and the Gamburtsev Subglacial Mountains (Invited)  

Microsoft Academic Search

Models of the onset of glaciation in Antarctica routinely document the early growth of the ice sheet on the summit of the Gamburtsev Subglacial Mountains in the center of the East Antarctic Craton. While ice sheet models replicate the formation of the East Antarctic ice sheet 35 million years ago, the age, evolution and structure of the Gamburtsev Mountains remain

R. E. Bell; M. Studinger; F. Ferraccioli; D. Damaske; C. Finn; D. A. Braaten; M. A. Fahnestock; T. A. Jordan; H. Corr; S. Elieff; N. Frearson; A. E. Block; K. Rose

2009-01-01

255

Beta beta homodimers exist in native rabbit skeletal muscle tropomyosin and increase after denaturation-renaturation.  

PubMed

Native tropomyosin from rabbit skeletal muscle (RSTm) consists mainly of alpha alpha and alpha beta coiled coils (alpha/beta approximately 3-4/1). In some extant studies, no beta beta molecules have been found. In this study, RSTm from several different preparations was disulfide cross-linked, both preparation and cross-linking being done under nondenaturing conditions. The cross-linked product was assayed for the presence of beta beta molecules cross-linked at both C36 and C190 (beta = beta). In such cross-linked RSTm, 3-8% beta = beta is detected by sodium dodecyl sulfate polyacrylamide gel electrophoresis, C4 reversed-phase high-performance liquid chromatography, and a free-solution capillary electrophoresis experiment. This percentage becomes approximately 4-10% beta beta when corrected for incomplete double cross-linking and is independent of protein concentration (0.1-10.0 mg/mL), indicating that the observed beta beta species are not artifacts due to intermolecular cross-linking. Upon denaturation and subsequent renaturation either by heating to 55 degrees C or by incubating at 45 degrees C followed by quenching to room temperature, or by guanidine hydrochloride exposure followed by phased renaturation by dialysis, the fraction of beta beta increases, indicating that the reassociation favors homodimer formation somewhat over random association. This result differs from the random association observed when the sulfhydryl on one of the chains is carboxyamidomethylated (Holtzer, M.E., Breiner, T., & Holtzer, A., 1984, Biopolymers 23, 1811-1833), and from the overwhelming heterodimer preferences reported for tropomyosins from other organisms (Lehrer, S.S., Qian, Y., & Hvidt, S., 1989, Science 246, 926-928; Lehrer, S.S. & Qian, Y., 1990, J. Biol. Chem. 265, 1134-1138). PMID:1304342

Holtzer, M E; Kidd, S G; Crimmins, D L; Holtzer, A

1992-03-01

256

Beta beta homodimers exist in native rabbit skeletal muscle tropomyosin and increase after denaturation-renaturation.  

PubMed Central

Native tropomyosin from rabbit skeletal muscle (RSTm) consists mainly of alpha alpha and alpha beta coiled coils (alpha/beta approximately 3-4/1). In some extant studies, no beta beta molecules have been found. In this study, RSTm from several different preparations was disulfide cross-linked, both preparation and cross-linking being done under nondenaturing conditions. The cross-linked product was assayed for the presence of beta beta molecules cross-linked at both C36 and C190 (beta = beta). In such cross-linked RSTm, 3-8% beta = beta is detected by sodium dodecyl sulfate polyacrylamide gel electrophoresis, C4 reversed-phase high-performance liquid chromatography, and a free-solution capillary electrophoresis experiment. This percentage becomes approximately 4-10% beta beta when corrected for incomplete double cross-linking and is independent of protein concentration (0.1-10.0 mg/mL), indicating that the observed beta beta species are not artifacts due to intermolecular cross-linking. Upon denaturation and subsequent renaturation either by heating to 55 degrees C or by incubating at 45 degrees C followed by quenching to room temperature, or by guanidine hydrochloride exposure followed by phased renaturation by dialysis, the fraction of beta beta increases, indicating that the reassociation favors homodimer formation somewhat over random association. This result differs from the random association observed when the sulfhydryl on one of the chains is carboxyamidomethylated (Holtzer, M.E., Breiner, T., & Holtzer, A., 1984, Biopolymers 23, 1811-1833), and from the overwhelming heterodimer preferences reported for tropomyosins from other organisms (Lehrer, S.S., Qian, Y., & Hvidt, S., 1989, Science 246, 926-928; Lehrer, S.S. & Qian, Y., 1990, J. Biol. Chem. 265, 1134-1138). PMID:1304342

Holtzer, M. E.; Kidd, S. G.; Crimmins, D. L.; Holtzer, A.

1992-01-01

257

Signaling through the TGF Beta-Activin Receptors ALK4/5/7 Regulates Testis Formation and Male Germ Cell Development  

PubMed Central

The developing testis provides an environment that nurtures germ cell development, ultimately ensuring spermatogenesis and fertility. Impacts on this environment are considered to underlie aberrant germ cell development and formation of germ cell tumour precursors. The signaling events involved in testis formation and male fetal germ cell development remain largely unknown. Analysis of knockout mice lacking single Tgf? family members has indicated that Tgf?'s are not required for sex determination. However, due to functional redundancy, it is possible that additional functions for these ligands in gonad development remain to be discovered. Using FACS purified gonadal cells, in this study we show that the genes encoding Activin's, TGF?'s, Nodal and their respective receptors, are expressed in sex and cell type specific patterns suggesting particular roles in testis and germ cell development. Inhibition of signaling through the receptors ALK4, ALK5 and ALK7, and ALK5 alone, demonstrated that TGF? signaling is required for testis cord formation during the critical testis-determining period. We also show that signaling through the Activin/NODAL receptors, ALK4 and ALK7 is required for promoting differentiation of male germ cells and their entry into mitotic arrest. Finally, our data demonstrate that Nodal is specifically expressed in male germ cells and expression of the key pluripotency gene, Nanog was significantly reduced when signaling through ALK4/5/7 was blocked. Our strategy of inhibiting multiple Activin/NODAL/TGF? receptors reduces the functional redundancy between these signaling pathways, thereby revealing new and essential roles for TGF? and Activin signaling during testis formation and male germ cell development. PMID:23342175

Stringer, Jessica M.; van den Bergen, Jocelyn A.; Wilhelm, Dagmar; Sinclair, Andrew H.; Western, Patrick S.

2013-01-01

258

New particle formation during alpha- and beta-pinene oxidation by O3, OH and NO3, and the influence of water vapour: particle size distribution studies  

Microsoft Academic Search

New particle formation during the oxidation of a- and b-pinene (C10H16) by ozone, OH and NO3 was studied by measuring the particle size distributions with a scanning mobility particle sizer (TSI 3936). The results indicate a drastically higher nucleation potential of the ozonolysis than in the reaction with either OH or NO3. On the contrary, the contribution of the individual

B. Bonn; G. K. Moortgat

2002-01-01

259

Interhemispheric ice-sheet synchronicity during the Last Glacial Maximum.  

PubMed

The timing of the last maximum extent of the Antarctic ice sheets relative to those in the Northern Hemisphere remains poorly understood. We develop a chronology for the Weddell Sea sector of the East Antarctic Ice Sheet that, combined with ages from other Antarctic ice-sheet sectors, indicates that the advance to and retreat from their maximum extent was within dating uncertainties synchronous with most sectors of Northern Hemisphere ice sheets. Surface climate forcing of Antarctic mass balance would probably cause an opposite response, whereby a warming climate would increase accumulation but not surface melting. Our new data support teleconnections involving sea-level forcing from Northern Hemisphere ice sheets and changes in North Atlantic deep-water formation and attendant heat flux to Antarctic grounding lines to synchronize the hemispheric ice sheets. PMID:22144623

Weber, Michael E; Clark, Peter U; Ricken, Werner; Mitrovica, Jerry X; Hostetler, Steven W; Kuhn, Gerhard

2011-12-01

260

Current status of liquid sheet radiator research  

NASA Astrophysics Data System (ADS)

Initial research on the external flow, low mass liquid sheet radiator (LSR), has been concentrated on understanding its fluid mechanics. The surface tension forces acting at the edges of the sheet produce a triangular planform for the radiating surface of width, W, and length, L. It has been experimentally verified that (exp L)/W agrees with the theoretical result, L/W = (We/8)exp 1/2, where We is the Weber number. Instability can cause holes to form in regions of large curvature such as where the edge cylinders join the sheet of thickness, tau. The W/tau limit that will cause hole formation with subsequent destruction of the sheet has yet to be reached experimentally. Although experimental measurements of sheet emissivity have not yet been performed because of limited program scope, calculations of the emissivity and sheet lifetime is determined by evaporation losses were made for two silicon based oils; Dow Corning 705 and Me(sub 2). Emissivities greater than 0.75 are calculated for tau greater than or equal to 200 microns for both oils. Lifetimes for Me(sub 2) are much longer than lifetimes for 705. Therefore, Me(sub 2) is the more attractive working fluid for higher temperatures (T greater than or equal to 400 K).

Chubb, Donald L.; Calfo, Frederick D.; McMaster, Matthew S.

1993-01-01

261

Locating current sheets in the solar corona  

E-print Network

Current sheets are essential for energy dissipation in the solar corona, in particular by enabling magnetic reconnection. Unfortunately, sufficiently thin current sheets cannot be resolved observationally and the theory of their formation is an unresolved issue as well. We consider two predictors of coronal current concentrations, both based on geometrical or even topological properties of a force free coronal magnetic field. First, there are separatrices related to magnetic nulls. Through separatrices the magnetic connectivity changes discontinuously. Coronal magnetic nulls are, however, very rare. At second, inspired by the concept of generalized magnetic reconnection without nulls, quasi-separatrix layers (QSL) were suggested. Through QSL the magnetic connectivity changes continuously, though strongly. The strength of the connectivity change can be quantified by measuring the squashing of the flux tubes which connect the magnetically conjugated photospheres. We verify the QSL and separatrix concepts by comparing the sites of magnetic nulls and enhanced squashing with the location of current concentrations in the corona. Due to the known difficulties of their direct observation we simulated the coronal current sheets by numerically calculating the response of the corona to energy input from the photosphere heating a simultaneously observed EUV Bright Point. We did not find coronal current sheets not at the separatrices but at several QSL locations. The reason is that although the geometrical properties of force free extrapolated magnetic fields can indeed, hint at possible current concentrations, a necessary condition for current sheet formation is the local energy input into the corona.

Joerg Buechner

2007-02-18

262

Silicon sheet surface studies  

NASA Technical Reports Server (NTRS)

Several activities were performed in the area of silicon sheet surface studies. An interferometry technique was developed for measuring residual stresses in short, thin silicon sheets. Simulation of abrasion of silicon by diamond and by scrating and indentation tests was carried out. The wear rate in silicon was correlated with a wear model.

Danyluk, S.

1984-01-01

263

Quahog Fact Sheet  

NSDL National Science Digital Library

This Rhode Island Sea Grant Fact Sheet describes quahogs, a type of shellfish, and their role in commercial fishery. It includes information about quahog physical description, habitat preference, and the rise of quahog harvests in Rhode Island. The Fact Sheet concludes with a section describing how to dig up your own quahogs, shuck (open) them, and eat them.

Ely, Eleanor; Grant, Rhode I.

264

In-situ Pb isotope analysis of Fe-Ni-Cu sulphides by laser ablation multi-collector ICPMS: New insights into ore formation in the Sudbury impact melt sheet  

NASA Astrophysics Data System (ADS)

Laser-ablation (LA) multi-collector inductively coupled plasma mass spectrometry (MC-ICPMS) is ideally suited to in situ determination of isotope ratios in sulphide minerals. Using samples of magmatic sulphide ore from the Sudbury impact structure, we test LA-MC-ICPMS analytical protocols that aim to meet a range of analytical challenges in the analysis of Pb isotopes. These include: potential matrix sensitive isotopic fractionation; interferences on Pb isotopes; low melting points of many sulphide minerals; the availability of standards. Magmatic sulphides of wide ranging mineralogy (pyrrhotite, pentlandite, chalcopyrite, pyrite and sphalerite) were analysed for Pb isotopic composition, using the silicate glass NIST SRM 610 as an external standard to correct for instrumental mass-fractionation. Despite matrix sensitive melting and re-deposition around ablation pits, several lines of evidence indicate that all analyses are accurate, within typical analytical uncertainties of 0.003-2% (2?), and that the defined approach is insensitive to compositional diversity in sample matrix: (a) laser ablation and dissolution based measurements of sulphide powders are in agreement; (b) analyses from each sample define isochron ages within uncertainty of the known crystallization age (1850 Ma); (c) the results of sulphide measurements by laser ablation are consistent with age-corrected feldspar analyses from the same samples. The results have important implications for ore formation in Sudbury. The Pb isotope data regressions are consistent with age corrected feldspar analyses from each respective sample, which together with time integrated Th/U ratios that match whole rock values (3.1, 4.0 and 6.1 for the Worthington, Copper Cliff and Parkin Offset Dykes, respectively) indicate chemical equilibrium between the silicate and sulphide systems during ore formation. The sulphides within each respective sample have indistinguishable model initial Pb isotope ratios (207Pb/204Pbm), irrespective of mineralogy or texture, indicating a common origin for ores within each of three different Offset Dykes. Furthermore, variations between Offset Dykes (e.g., 207Pb/204Pbm = 15.514 ± 0.012, 15.399 ± 0.009 and 15.275 ± 0.003) show that the ores have differing crustal sources on previously unrecognized scales. Mass balance considerations, particularly for MgO, Ni and Cu, indicate that the spatial distribution of mafic target rocks played a significant role in controlling the mineralization potential in different parts of the melt sheet.

Darling, J. R.; Storey, C. D.; Hawkesworth, C. J.; Lightfoot, P. C.

2012-12-01

265

Nuclear Data Sheets for A = 193  

SciTech Connect

The present revision of the properties for the nuclides belonging to the A = 193 mass chain contains many improvements, corrections and additions to the material presented in previous evaluations (1998Ar07, Nucl. Data Sheets 83, 921 (1998); 1990Sh30, Nucl, Data Sheets 61, 519 (1990)). Among these are measurement results for quadrupole moments, angular distribution coefficients, half-lives and g-factors, for both previously known and new transitions and levels. In addition, major changes to the previously known status of this mass chain consist in the inclusion of data for new superdeformed bands in {sup 193}Pb, and the creation of level schemes for {sup 193}Bi, {sup 193}Po and {sup 193}At. The latter were previously unavailable, except for a very limited attempt in the case of {sup 193}Po, which was not confirmed in later work. Furthermore, the {sup 193}Os beta decay was re-evaluated in order to account for new absolute intensity measurements.

Achterberg, E. [Laboratorio TANDAR, Departamento de Fisica, Comision Nacional de Energia Atomica, Buenos Aires (Argentina); Capurro, O.A. [Laboratorio TANDAR, Departamento de Fisica, Comision Nacional de Energia Atomica, Buenos Aires (Argentina); Marti, G.V. [Laboratorio TANDAR, Departamento de Fisica, Comision Nacional de Energia Atomica, Buenos Aires (Argentina); Vanin, V.R. [Lab. do Acelerador Linear, Universidade de San Paulo, Sao Paulo, SP (Brazil); Castro, R.M. [Lab. do Acelerador Linear, Universidade de San Paulo, Sao Paulo, SP (Brazil); Instituto de Estudos Avancados - IEAv, Centro Tecnico Aerospacial - CTA, Sao Jose dos Campos, SP (Brazil)

2006-01-15

266

Synthetic peptide homologous to. beta. protein from Alzheimer's disease forms amyloid-like fibrils in vitro  

SciTech Connect

Progressive amyloid deposition in senile plaques and cortical blood vessels may play a central role in the pathogenesis of Alzheimer's disease. The authors have used x-ray diffraction and electron microscopy to study the molecular organization and morphology of macromolecular assemblies formed by three synthetic peptides homologous to ..beta.. protein of brain amyloid: ..beta..-(1-28), residues 1-28 of the ..beta.. protein; (Ala/sup 1 -/..beta..-(1-28), ..beta..-(1-28) with alanine substituted for lysine at position 16; and ..beta..-(18-28), residues 18-28 of the ..beta.. protein. ..beta..-(1-28) readily formed fibrils in vitro that were similar in ultrastructure to the in vivo amyloid and aggregated into large bundles resembling those of senile plaque cores. X-ray patterns from partially dried, oriented pellets showed a cross-..beta..-conformation. (Ala/sup 16/)..beta..-(1-28) formed ..beta..-pleated sheet assemblies that were dissimilar to in vivo fibrils. The width of the 10-A spacing indicated stacks of about six sheets. Thus, substitution of the uncharged alanine for the positively charged lysine in the ..beta..-strand region enhances the packing of the sheets and dramatically alters the type of macromolecular aggregate formed. BETA-(18-28) formed assemblies that had even a greater number of stacked sheets. The findings on these homologous synthetic assemblies help to define the specific sequence that is required to form Alzheimer's-type amyloid fibrils, thus providing an in vitro model of age-related cerebral amyloidogenesis.

Kirschner, D.A.; Inouye, H.; Duffy, L.K.; Sinclair, A.; Lind, M.; Selkoe, D.J.

1987-10-01

267

Cereal beta-glucans  

Technology Transfer Automated Retrieval System (TEKTRAN)

Cereal beta-glucans occur predominantly in oats and barley, but can be found in other cereals. Beta-glucan structure is a mixture of single beta-1,3-linkages and consecutive beta-1,4-linkages, and cellotriosyl and cellotetraosyl units typically make up 90-95% of entire molecule. Lichenase can hydr...

268

A Logical OR Redundancy within the Asx-Pro-Asx-Gly Type 1 {Beta}-Turn Motif  

SciTech Connect

Turn secondary structure is essential to the formation of globular protein architecture. Turn structures are, however, much more complex than either {alpha}-helix or {beta}-sheet, and the thermodynamics and folding kinetics are poorly understood. Type I {beta}-turns are the most common type of reverse turn, and they exhibit a statistical consensus sequence of Asx-Pro-Asx-Gly (where Asx is Asp or Asn). A comprehensive series of individual and combined Asx mutations has been constructed within three separate type I 3:5 G1 bulge {beta}-turns in human fibroblast growth factor-1, and their effects on structure, stability, and folding have been determined. The results show a fundamental logical OR relationship between the Asx residues in the motif, involving H-bond interactions with main-chain amides within the turn. These interactions can be modulated by additional interactions with residues adjacent to the turn at positions i + 4 and i + 6. The results show that the Asx residues in the turn motif make a substantial contribution to the overall stability of the protein, and the Asx logical OR relationship defines a redundant system that can compensate for deleterious point mutations. The results also show that the stability of the turn is unlikely to be the prime determinant of formation of turn structure in the folding transition state.

Lee, Jihun; Dubey, Vikash Kumar; Longo, Lian M.; Blaber, Michael (FSU)

2008-04-19

269

Divergent effects of 17-{beta}-estradiol on human vascular smooth muscle and endothelial cell function diminishes TNF-{alpha}-induced neointima formation  

SciTech Connect

Highlights: Black-Right-Pointing-Pointer TNF-{alpha} augments neointimal hyperplasia in human saphenous vein. Black-Right-Pointing-Pointer TNF-{alpha} induces detrimental effects on endothelial and smooth muscle cell function. Black-Right-Pointing-Pointer Estradiol exerts modulatory effects on TNF-induced vascular cell functions. Black-Right-Pointing-Pointer The modulatory effects of estradiol are discriminatory and cell-type specific. -- Abstract: Coronary heart disease (CHD) is a condition characterized by increased levels of proinflammatory cytokines, including tumor necrosis factor-{alpha} (TNF-{alpha}). TNF-{alpha} can induce vascular endothelial cell (EC) and smooth muscle cell (SMC) dysfunction, central events in development of neointimal lesions. The reduced incidence of CHD in young women is believed to be due to the protective effects of estradiol (E2). We therefore investigated the effects of TNF-{alpha} on human neointima formation and SMC/EC functions and any modulatory effects of E2. Saphenous vein (SV) segments were cultured in the presence of TNF-{alpha} (10 ng/ml), E2 (2.5 nM) or both in combination. Neointimal thickening was augmented by incubation with TNF-{alpha}, an effect that was abolished by co-culture with E2. TNF-{alpha} increased SV-SMC proliferation in a concentration-dependent manner that was optimal at 10 ng/ml (1.5-fold increase), and abolished by E2 at all concentrations studied (1-50 nM). Surprisingly, E2 itself at low concentrations (1 and 5 nM) stimulated SV-SMC proliferation to a level comparable to that of TNF-{alpha} alone. SV-EC migration was significantly impaired by TNF-{alpha} (42% of control), and co-culture with E2 partially restored the ability of SV-EC to migrate and repair the wound. In contrast, TNF-{alpha} increased SV-SMC migration by 1.7-fold, an effect that was completely reversed by co-incubation with E2. Finally, TNF-{alpha} potently induced ICAM-1 and VCAM-1 expression in both SV-EC and SV-SMC. However there was no modulation by E2 in either cell-type. In conclusion, TNF-{alpha} induced SV neointima formation, increased SMC proliferation and migration, impaired SV-EC migration and increased expression of adhesion molecules. E2 exerted distinct cell-type and function-specific modulation, the mechanisms underlying which are worthy of further detailed study.

Nintasen, Rungrat [Division of Cardiovascular Medicine, Leeds Institute of Genetics, Health and Therapeutics, University of Leeds, Leeds LS2 9JT (United Kingdom) [Division of Cardiovascular Medicine, Leeds Institute of Genetics, Health and Therapeutics, University of Leeds, Leeds LS2 9JT (United Kingdom); Multidisciplinary Cardiovascular Research Center (MCRC), University of Leeds, Leeds LS2 9JT (United Kingdom); Department of Tropical Pathology, Faculty of Tropical Medicine, Mahidol University (Thailand); Riches, Kirsten; Mughal, Romana S. [Division of Cardiovascular Medicine, Leeds Institute of Genetics, Health and Therapeutics, University of Leeds, Leeds LS2 9JT (United Kingdom) [Division of Cardiovascular Medicine, Leeds Institute of Genetics, Health and Therapeutics, University of Leeds, Leeds LS2 9JT (United Kingdom); Multidisciplinary Cardiovascular Research Center (MCRC), University of Leeds, Leeds LS2 9JT (United Kingdom); Viriyavejakul, Parnpen; Chaisri, Urai; Maneerat, Yaowapa [Department of Tropical Pathology, Faculty of Tropical Medicine, Mahidol University (Thailand)] [Department of Tropical Pathology, Faculty of Tropical Medicine, Mahidol University (Thailand); Turner, Neil A. [Division of Cardiovascular Medicine, Leeds Institute of Genetics, Health and Therapeutics, University of Leeds, Leeds LS2 9JT (United Kingdom) [Division of Cardiovascular Medicine, Leeds Institute of Genetics, Health and Therapeutics, University of Leeds, Leeds LS2 9JT (United Kingdom); Multidisciplinary Cardiovascular Research Center (MCRC), University of Leeds, Leeds LS2 9JT (United Kingdom); Porter, Karen E., E-mail: medkep@leeds.ac.uk [Division of Cardiovascular Medicine, Leeds Institute of Genetics, Health and Therapeutics, University of Leeds, Leeds LS2 9JT (United Kingdom); Multidisciplinary Cardiovascular Research Center (MCRC), University of Leeds, Leeds LS2 9JT (United Kingdom)

2012-04-20

270

Absorption of Beta Particles in Different Materials: An Undergraduate Experiment  

ERIC Educational Resources Information Center

The absorption of beta rays from a radioactive source in different materials was investigated by the use of a simple setup based on a Geiger counter and a set of absorber sheets. The number of electrons traversing the material was measured as a function of its thickness. Detailed GEANT simulations were carried out to reproduce the obtained…

La Rocca, Paola; Riggi, Francesco

2009-01-01

271

Effects of mutations in the {beta} subunit hinge domain on ATP synthase F{sub 1} sector rotation: Interaction between Ser 174 and Ile 163  

SciTech Connect

A complex of {gamma}, {epsilon}, and c subunits rotates in ATP synthase (F{sub o}F{sub 1}) coupling with proton transport. Replacement of {beta}Ser174 by Phe in {beta}-sheet4 of the {beta} subunit ({beta}S174F) caused slow {gamma} subunit revolution of the F{sub 1} sector, consistent with the decreased ATPase activity [M. Nakanishi-Matsui, S. Kashiwagi, T. Ubukata, A. Iwamoto-Kihara, Y. Wada, M. Futai, Rotational catalysis of Escherichia coli ATP synthase F1 sector. Stochastic fluctuation and a key domain of the {beta} subunit, J. Biol. Chem. 282 (2007) 20698-20704]. Modeling of the domain including {beta}-sheet4 and {alpha}-helixB predicted that the mutant {beta}Phe174 residue undergoes strong and weak hydrophobic interactions with {beta}Ile163 and {beta}Ile166, respectively. Supporting this prediction, the replacement of {beta}Ile163 in {alpha}-helixB by Ala partially suppressed the {beta}S174F mutation: in the double mutant, the revolution speed and ATPase activity recovered to about half of the levels in the wild-type. Replacement of {beta}Ile166 by Ala lowered the revolution speed and ATPase activity to the same levels as in {beta}S174F. Consistent with the weak hydrophobic interaction, {beta}Ile166 to Ala mutation did not suppress {beta}S174F. Importance of the hinge domain [phosphate-binding loop (P-loop)/{alpha}-helixB/loop/{beta}-sheet4, {beta}Phe148-{beta}Gly186] as to driving rotational catalysis is discussed.

Kashiwagi, Sachiko [Department of Biochemistry, Faculty of Pharmaceutical Sciences, Iwate Medical University, Iwate 028-3694 (Japan); Futai Special Laboratory, Microbial Chemistry Research Center, Shinagawa-ku, Tokyo 141-002 (Japan); Iwamoto-Kihara, Atsuko [Department of Bioscience, Nagahama Institute of Bioscience and Technology, Nagahama, Shiga 526-0829 (Japan); Kojima, Masaki; Nonaka, Takamasa [Department of Biochemistry, Faculty of Pharmaceutical Sciences, Iwate Medical University, Iwate 028-3694 (Japan); Futai, Masamitsu [Department of Biochemistry, Faculty of Pharmaceutical Sciences, Iwate Medical University, Iwate 028-3694 (Japan); Futai Special Laboratory, Microbial Chemistry Research Center, Shinagawa-ku, Tokyo 141-002 (Japan)], E-mail: futaim@iwate-med.ac.jp; Nakanishi-Matsui, Mayumi [Department of Biochemistry, Faculty of Pharmaceutical Sciences, Iwate Medical University, Iwate 028-3694 (Japan); Futai Special Laboratory, Microbial Chemistry Research Center, Shinagawa-ku, Tokyo 141-002 (Japan)

2008-01-11

272

The thermographic nondestructive evaluation of iron aluminide green sheet  

NASA Astrophysics Data System (ADS)

The recent development of manufacturing techniques for the fabrication of thin iron aluminide sheet requires advanced quantitative methods for on-line inspection. An understanding of the mechanisms responsible for flaws and the development of appropriate flaw detection methods are key elements in an effective quality management system. The first step in the fabrication of thin FeAl alloy sheet is the formation of a green sheet by cold rolling FeAl powder mixed with organic binding agents. The green sheet composite has a bulk density, which is typically less than about 3.6 g/cc. The finished sheet, with a density of about 6.1 g/cc, is obtained using a series of process steps involving binder elimination, densification, sintering, and annealing. Non-uniformities within the green sheet are the major contributor to material failure in subsequent sheet processing and the production of non-conforming finished sheet. The production environment and physical characteristics of the composite provide for unique challenges in developing a rapid nondestructive inspection capability. The method must be non-contact due to the fragile nature of the composite. Limited access to the material also demands a one-sided inspection technique. An active thermographic method providing for 100% on-line inspection within an industrial, process has been developed. This approach is cost competitive with alternative technologies, such as x-ray imaging systems, and provides the required sensitivity to the variations in material composition. The mechanism of flaw formation and the transformation of green sheet flaws into defects that appear in intermediate and finished sheet products are described. A mathematical model which describes the green sheet heat transfer propagation, in the context of the inspection technique and the compact heterogeneity, is also presented. The potential for feedback within the production process is also discussed.

Watkins, Michael Lee

273

Liquid sheet radiator  

NASA Technical Reports Server (NTRS)

A new external flow radiator concept, the liquid sheet radiator (LSR), is introduced. The LSR sheet flow is described and an expression for the length/width (l/w), ratio is presented. A linear dependence of l/w on velocity is predicted that agrees with experimental results. Specific power for the LSR is calculated and is found to be nearly the same as the specific power of a liquid droplet radiator, (LDR). Several sheet thicknesses and widths were experimentally investigated. In no case was the flow found to be unstable.

Chubb, Donald L.; White, K. Alan, III

1987-01-01

274

Liquid sheet radiator  

NASA Technical Reports Server (NTRS)

A new external flow radiator concept, the liquid sheet radiator (LSR), is introduced. The LSR sheet flow is described and an expression for the length/width (l/w) ratio is presented. A linear dependence of l/w on velocity is predicted that agrees with experimental results. Specific power for the LSR is calculated and is found to be nearly the same as the specific power of a liquid droplet radiator (LDR). Several sheet thicknesses and widths were experimentally investigated. In no case was the flow found to be unstable.

Chubb, Donald L.; White, K. Allan, III

1987-01-01

275

Physicochemical properties and interactions of Escherichia coli ribonucleic acid polymerase holoenzyme, core enzyme, subunits, and subassembly alpha 2 beta.  

PubMed

We have investigated several physicochemical properties of Escherichia coli DNA-dependent RNa polymerase, its constituent subunits alpha, beta, beta', and sigma, and the subassembly alpha 2 beta. These included ultraviolet (UV) absorption, isoelectric points, sulfhydryl content, extinction coefficients, and circular dichroism (CD). Among the most notable results is the observation, based on CD measurements, that the sigma subunit, free and combined in holoenzyme, is a highly structured protein with approximately 75% of its residues folded in alpha-helical conformation and little or no detectable beta sheet. No secondary structure changes in either sigma or core accompany formation of holoenzyme. In contrast to the conformational independence of the subunits in assembly of holoenzyme, the protein and its components exhibit conformational flexibility as glycerol concentration is varied and in their interaction with DNA. The effect of glycerol on the conformation of sigma, core, and holoenzyme was monitored by circular dichroism measurements. In the far-ultraviolet, the residue ellipticity at 220 nm ([theta]220) increased approximately 15% from 0 to 10% glycerol for both core and holoenzyme. In the near-ultraviolet, the residue ellipticity at a peak near 280 nm also varied with glycerol concentration, decreasing in intensity by about 50% with holoenzyme, when glycerol was raised from 5 to 10%, then increasing at still higher glycerol contents. Electrophoretic and molecular sieve anaysis showed core and sigma to have greater affinity for each other in 50% glycerol than in 10% glycerol. The presence of 10% glycerol in the assay buffer increased the activity of the enzyme. The effect of various DNA templates on the conformations of core, holoenzyme, alpha 2 beta subassembly, and beta' subunit was also monitored by far-ultraviolet circular dichroism. All the protein samples showed between 10 and 20% decrease in secondary structure upon the addition of the DNA. PMID:7000184

Levine, B J; Orphanos, P D; Fischmann, B S; Beychok, S

1980-10-14

276

Ferulic acid destabilizes preformed {beta}-amyloid fibrils in vitro  

SciTech Connect

Inhibition of the formation of {beta}-amyloid fibrils (fA{beta}), as well as the destabilization of preformed fA{beta} in the CNS, would be attractive therapeutic targets for the treatment of Alzheimer's disease (AD). We reported previously that curcumin (Cur) inhibits fA{beta} formation from A{beta} and destabilizes preformed fA{beta} in vitro. Using fluorescence spectroscopic analysis with thioflavin T and electron microscopic studies, we examined the effects of ferulic acid (FA) on the formation, extension, and destabilization of fA{beta} at pH 7.5 at 37 deg C in vitro. We next compared the anti-amyloidogenic activities of FA with Cur, rifampicin, and tetracycline. Ferulic acid dose-dependently inhibited fA{beta} formation from amyloid {beta}-peptide, as well as their extension. Moreover, it destabilized preformed fA{beta}s. The overall activity of the molecules examined was in the order of: Cur > FA > rifampicin = tetracycline. FA could be a key molecule for the development of therapeutics for AD.

Ono, Kenjiro [Department of Neurology and Neurobiology of Aging, Kanazawa University Graduate School of Medical Science, Kanazawa 920-8640 (Japan); Hirohata, Mie [Department of Neurology and Neurobiology of Aging, Kanazawa University Graduate School of Medical Science, Kanazawa 920-8640 (Japan); Yamada, Masahito [Department of Neurology and Neurobiology of Aging, Kanazawa University Graduate School of Medical Science, Kanazawa 920-8640 (Japan)]. E-mail: m-yamada@med.kanazawa-u.ac.jp

2005-10-21

277

Importance of peroxisomes in the formation of chenodeoxycholic acid in human liver. Metabolism of 3 alpha,7 alpha-dihydroxy-5 beta-cholestanoic acid in Zellweger syndrome.  

PubMed

Infantile Zellweger syndrome belongs to the group of peroxisomal disorders that lack peroxisomes. Both trihydroxycoprostanic acid (THCA), the precursor to cholic acid, and dihydroxycoprostanic acid (DHCA), the precursor to chenodeoxycholic acid, accumulate in this disease. In previous studies, we have shown that liver peroxisomes are required for the conversion of THCA into cholic acid both in vitro and in vivo by measuring a defective conversion in infants with Zellweger syndrome. In our present study, the conversion of DHCA into chenodeoxycholic acid has been measured in an infant with Zellweger syndrome to evaluate the importance of liver peroxisomes for the formation of chenodeoxycholic acid. Coprostanic acidemia was present from the second day of life with high levels of THCA and only trace amounts of DHCA. The conversion of i.v. administered [3H]DHCA into chenodeoxycholic acid was only 7% compared with the 80% conversion in an analogous study in an adult. There was, however, a rapid incorporation of 3H into biliary THCA and, after a lag phase, the 3H was incorporated into biliary cholic acid. After 72 h, 15% of [3H]DHCA was converted to cholic acid. The pool size of DHCA was 1.2 mg/m2 and the pool size of both cholic acid and chenodeoxycholic acid was markedly reduced. The renal excretion of cholic acid was more efficient than that of the less polar chenodeoxycholic acid. More polar metabolites of DHCA and THCA are formed in alternative metabolic pathways facilitating renal excretion of these toxic intermediates. We conclude that liver peroxisomes are essential for a normal conversion of DHCA into chenodeoxycholic acid. PMID:2000261

Kase, B F; Pedersen, J I; Wathne, K O; Gustafsson, J; Björkhem, I

1991-01-01

278

Gas Grill Fact Sheet  

MedlinePLUS

... attempt to sell or resell a recalled product. Gas Grill [ Fact Sheet ] U.S. Consumer Product Safety Commission ... outlet. TIPS FOR PURCHASING A GRILL OR LP GAS CONTAINER n ? Buy grills and containers that bear ...

279

Seat Belt Fact Sheet  

MedlinePLUS

Travel & Motor Vehicle Safety Seat Belt Fact Sheet Safety belts are the most effective means of reducing deaths and serious injuries ... than 90 people die every day in motor vehicle crashes When lap and shoulder belts are used ...

280

Sheet electron beam tester  

NASA Astrophysics Data System (ADS)

The DARPA HiFIVE project uses a pulsed electron sheet beam gun to power a traveling wave tube amplifier operating at 220 GHz. Presented is a method for characterizing the high current density 0.1 mm by 1 mm sheet electron beam. A tungsten tipped probe was scanned through the cross section of the sheet electron beam inside of a vacuum vessel. The probe was controlled with sub-micron precision using stepper motors and LabView computer control while boxcar averaging hardware sampled the pulsed beam. Matlab algorithms were used to interpret the data, calculate beam dimensions and current density, and create 2-dimensional cross section images. Full characterization of two separate HiFIVE sheet electron guns was accomplished and is also presented.

Spear, Alexander Grenbeaux

281

Avian Fact Sheet  

SciTech Connect

OAK-B135 After conducting four national research meetings, producing a document guiding research: Metrics and Methods for Determining or Monitoring Potential Impacts on Birds at Existing and Proposed Wind Energy Sites, 1999, and another paper, Avian Collisions with Wind Turbines: A Summary of Existing Studies and Comparisons to Other Sources of Avian Collision Mortality in the United States, 2001, the subcommittee recognized a need to summarize in a short fact sheet what is known about avian-wind interaction and what questions remain. This fact sheet attempts to summarize in lay terms the result of extensive discussion about avian-wind interaction on land. This fact sheet does not address research conducted on offshore development. This fact sheet is not intended as a conclusion on the subject; rather, it is a summary as of Fall/Winter 2002.

NWCC Wildlife Work Group

2004-12-01

282

Global ice sheet modeling  

SciTech Connect

The University of Maine conducted this study for Pacific Northwest Laboratory (PNL) as part of a global climate modeling task for site characterization of the potential nuclear waste respository site at Yucca Mountain, NV. The purpose of the study was to develop a global ice sheet dynamics model that will forecast the three-dimensional configuration of global ice sheets for specific climate change scenarios. The objective of the third (final) year of the work was to produce ice sheet data for glaciation scenarios covering the next 100,000 years. This was accomplished using both the map-plane and flowband solutions of our time-dependent, finite-element gridpoint model. The theory and equations used to develop the ice sheet models are presented. Three future scenarios were simulated by the model and results are discussed.

Hughes, T.J.; Fastook, J.L. [Univ. of Maine, Orono, ME (United States). Institute for Quaternary Studies

1994-05-01

283

Viscous Sheet Retraction  

E-print Network

We present the results of a combined theoretical and numerical investigation of the rim-driven retraction of flat fluid sheets in both planar and circular geometries. Particular attention is given to the influence of the ...

Savva, Nikos

284

Viscous fluid sheets  

E-print Network

We present a general theory for the dynamics of thin viscous sheets. Employing concepts from differential geometry and tensor calculus we derive the governing equations in terms of a coordinate system that moves with the ...

Savva, Nikos

2007-01-01

285

Monoatomically thin polarizable sheets  

E-print Network

We consider a flat lattice of dipoles modeled by harmonic oscillators interacting with the electromagnetic field in dipole approximation. Eliminating the variables from the coupled equations of motion, we come to effective Maxwell equations. These allow for taking the lattice spacing $a$ to zero. As a result, we obtain reflection coefficients for the scattering of electromagnetic waves off the sheet. These are a generalization of that known from the hydrodynamic model. For instance, we get a non trivial scattering for polarizability perpendicular to the sheet. Also we show that the case of a sheet polarizable parallel to the sheet can be obtained in a natural way from a plasma layer of finite thickness. As an alternative approach we discuss the elimination of the electromagnetic fields resulting in effective equations for the oscillators. These show, for $a\\to 0$, divergent behavior, resulting from the electrostatic interaction of the dipoles.

M. Bordag

2014-04-18

286

Domoic Acid Fact Sheet  

NSDL National Science Digital Library

This online fact sheet illustrates the transfer of domoic acid through the food web. Domoic acid is a nerve toxin produced by a naturally occurring Harmful Algal Bloom (HAB) usually (but not always) of the genus Pseudonitzchia. The sheet explains what to do if you find a sick or dead animal and includes contact information for injured/sick/entangled animal rescue networks in California.

Sanctuary, Channel I.

287

Biodiesel Basics (Fact Sheet)  

SciTech Connect

This fact sheet provides a brief introduction to biodiesel, including a discussion of biodiesel blends, which blends are best for which vehicles, where to buy biodiesel, how biodiesel compares to diesel fuel in terms of performance, how biodiesel performs in cold weather, whether biodiesel use will plug vehicle filters, how long-term biodiesel use may affect engines, biodiesel fuel standards, and whether biodiesel burns cleaner than diesel fuel. The fact sheet also dismisses the use of vegetable oil as a motor fuel.

Not Available

2014-06-01

288

Energy information sheets  

SciTech Connect

The National Energy Information Center (NEIC), as part of its mission, provides energy information and referral assistance to Federal, State, and local governments, the academic community, business and industrial organizations, and the public. The Energy Information Sheets was developed to provide general information on various aspects of fuel production, prices, consumption, and capability. Additional information on related subject matter can be found in other Energy Information Administration (EIA) publications as referenced at the end of each sheet.

NONE

1995-07-01

289

Synthesis of alpha-cyclopropyl-beta-homoprolines.  

PubMed

1-(2-Pyrrolidinyl)cyclopropanecarboxylic acids (alpha-cyclopropyl-beta-homoprolines) were prepared by 1,3-dipolar cycloadditions of cyclic nitrones onto bicyclopropylidene followed by trifluoroacetic acid induced thermal fragmentative rearrangement. With the use of enantiopure pyrroline N-oxides derived from easily available chiral pool molecules, beta-homoprolines were formed with high stereocontrol. The incorporation of one of these new cyclic beta-amino acids into a simple tripeptide was also evaluated. In particular, the sterically hindered nitrogen atom of the highly substituted pyrrolidine 30 was smoothly acylated through the intermediate formation of a mixed anhydride. PMID:19413279

Cordero, Franca M; Salvati, Maria; Vurchio, Carolina; de Meijere, Armin; Brandi, Alberto

2009-06-01

290

Low-Temperature Forming of Beta Titanium Alloys  

NASA Technical Reports Server (NTRS)

Low cost methods for titanium structural fabrication using advanced cold-formable beta alloys were investigated for application in a Mach 2.7 supersonic cruise vehicle. This work focuses on improving processing and structural efficiencies as compared with standard hot formed and riveted construction of alpha-beta alloy sheet structure. Mechanical property data and manufacturing parameters were developed for cold forming, brazing, welding, and processing Ti-15V-3Cr-3Sn-3Al sheet, and Ti-3Al-8V-6Cr-4Zr on a more limited basis. Cost and structural benefits were assessed through the fabrication and evaluation of large structural panels. The feasibility of increasing structural efficiency of beta titanium structure by selective reinforcement with metal matrix composite was also explored.

Kaneko, R. S.; Woods, C. A.

1983-01-01

291

Singular Solutions and Pattern Formation in Aggregation Equations  

E-print Network

singularity formation in vortex-sheet motion by a spectrallypreviously, the motion of the vortex sheet is governed byvortex patches in incompressible inviscid fluids and swarm patches, which both exhibit rotational motion

Sun, Hui

2013-01-01

292

Beta-strand flipping and slipping triggered by turn replacement reveal the opportunistic nature of beta-strand pairing.  

PubMed

We investigated how the register between adjacent beta-strands is specified using a series of mutants of the single-layer beta-sheet (SLB) in Borrelia OspA. The single-layer architecture of this system eliminates structural restraints imposed by a hydrophobic core, enabling us to address this question. A critical turn (turn 9/10) in the SLB was replaced with a segment with an intentional structural mismatch. Its crystal structure revealed a one-residue insertion into the central beta-strand (strand 9) of the SLB. This insertion triggered a surprisingly large-scale structural rearrangement: (i) the central strand (strand 9) was shifted by one residue, causing the strand to flip with respect to the adjacent beta-strands and thus completely disrupting the native side-chain contacts; (ii) the three-residue turn located on the opposite end of the beta-strand (turn 8/9) was pushed into its preceding beta-strand (strand 8); (iii) the register between strands 8 and 9 was shifted by three residues. Replacing the original sequence for turn 8/9 with a stronger turn motif restored the original strand register but still with a flipped beta-strand 9. The stability differences of these distinct structures were surprisingly small, consistent with an energy landscape where multiple low-energy states with different beta-sheet configurations exist. The observed conformations can be rationalized in terms of maximizing the number of backbone H-bonds. These results suggest that adjacent beta-strands "stick" through the use of factors that are not highly sequence specific and that beta-strands could slide back and forth relatively easily in the absence of external elements such as turns and tertiary packing. PMID:17985889

Makabe, Koki; Yan, Shude; Tereshko, Valentina; Gawlak, Grzegorz; Koide, Shohei

2007-11-28

293

Core binding factor beta (Cbf?) controls the balance of chondrocyte proliferation and differentiation by upregulating Indian hedgehog (Ihh) expression and inhibiting parathyroid hormone-related protein receptor (PPR) expression in postnatal cartilage and bone formation.  

PubMed

Core binding factor beta (Cbf?) is essential for embryonic bone morphogenesis. Yet the mechanisms by which Cbf? regulates chondrocyte proliferation and differentiation as well as postnatal cartilage and bone formation remain unclear. Hence, using paired-related homeobox transcription factor 1-Cre (Prx1-Cre) mice, mesenchymal stem cell-specific Cbf?-deficient (Cbf?(f/f) Prx1-Cre) mice were generated to study the role of Cbf? in postnatal cartilage and bone development. These mutant mice survived to adulthood but exhibited severe sternum and limb malformations. Sternum ossification was largely delayed in the Cbf?(f/f) Prx1-Cre mice and the xiphoid process was noncalcified and enlarged. In newborn and 7-day-old Cbf?(f/f) Prx1-Cre mice, the resting zone was dramatically elongated, the proliferation zone and hypertrophic zone of the growth plates were drastically shortened and disorganized, and trabecular bone formation was reduced. Moreover, in 1-month-old Cbf?(f/f) Prx1-Cre mice, the growth plates were severely deformed and trabecular bone was almost absent. In addition, Cbf? deficiency impaired intramembranous bone formation both in vivo and in vitro. Interestingly, although the expression of Indian hedgehog (Ihh) was largely reduced, the expression of parathyroid hormone-related protein (PTHrP) receptor (PPR) was dramatically increased in the Cbf?(f/f) Prx1-Cre growth plate, indicating that that Cbf? deficiency disrupted the Ihh-PTHrP negative regulatory loop. Chromatin immunoprecipitation (ChIP) analysis and promoter luciferase assay demonstrated that the Runx/Cbf? complex binds putative Runx-binding sites of the Ihh promoter regions, and also the Runx/Cbf? complex directly upregulates Ihh expression at the transcriptional level. Consistently, the expressions of Ihh target genes, including CyclinD1, Ptc, and Pthlh, were downregulated in Cbf?-deficient chondrocytes. Taken together, our study reveals not only that Cbf? is essential for chondrocyte proliferation and differentiation for the growth and maintenance of the skeleton in postnatal mice, but also that it functions in upregulating Ihh expression to promoter chondrocyte proliferation and osteoblast differentiation, and inhibiting PPR expression to enhance chondrocyte differentiation. PMID:24821091

Tian, Fei; Wu, Mengrui; Deng, Lianfu; Zhu, Guochun; Ma, Junqing; Gao, Bo; Wang, Lin; Li, Yi-Ping; Chen, Wei

2014-07-01

294

Beta Thalassemia (For Parents)  

MedlinePLUS

Thalassemias Thalassemias are a group of blood disorders that affect the way the body makes hemoglobin, a ... results in that type of thalassemia. About Beta Thalassemia Beta thalassemia occurs when the gene that controls ...

295

Beta-carotene  

MedlinePLUS

... seem to reduce the risk of esophageal cancer. Pancreatic cancer. Taking beta-carotene supplements alone or in combination ... doesn't seem to reduce the risk of pancreatic cancer. Side effects from chemotherapy. Increasing beta-carotene from ...

296

Gamma, Beta, Erf  

NSDL National Science Digital Library

This page includes the encyclopedia entries for gamma, beta and erf functions including factorials, binomials, gamma functions and inverses, differentiated gamma functions, beta functions and inverses, probability integrals and inverses, Frensnel integrals and exponential integrals.

297

Average plasma properties in the central plasma sheet  

SciTech Connect

Using four months of tail data obtained by the three-dimensional plasma instrument on board the AMPTE/IRM satellite in 1986, the authors have done a statistical survey on the behavior of ion and electron moments in the central plasma sheet. Almost 80,000 spin averages of plasma density, ion bulk velocity, ion and electron temperature, and plasma {beta} were analyzed with respect to differences between their values in the inner and outer central plasma sheet as well as their dependence on magnetic activity. The ion temperature increases with increasing magnetic activity while the ion density decreases during disturbed intervals, except in the neutral sheet neighborhood at smaller radial distances. The ion and electron temperatures in the central plasma sheet are highly correlated, with T{sub i}/T{sub e} being constant over a wide range of temperatures and about twice as large as in the distant tail. The average ion flow speeds in the central plasma sheet are below 100 km/s and nearly identical to those found in the plasma sheet boundary layer, although the distribution functions usually are quite different. High-speed flows do occur, but in bursts of most often less than 1 min duration with intermittent intervals of nearly stagnant plasma. The distribution of flow directions strongly favors sunward flow for velocities above 300 km/s, indicating that a near-earth neutral line is rarely, if ever, located inside of X{sub GSM} = {minus} 19 R{sub E}.

Baumjohann, W.; Paschmann, G. (Max-Planck-Institut fuer Physik und Astrophysik, Garching (West Germany)); Cattell, C.A. (Univ. of California, Berkeley (USA))

1989-06-01

298

Raman and AFM study of gamma irradiated plastic bottle sheets  

SciTech Connect

In this investigation, the effects of gamma irradiation on the structural properties of plastic bottle sheet are studied. The Plastic sheets were exposed with 1.25MeV {sup 60}Co gamma rays source at various dose levels within the range from 0-670 kGy. The induced modifications were followed by micro-Raman and atomic force microscopy (AFM). The Raman spectrum shows the decrease in Raman intensity and formation of unsaturated bonds with an increase in the gamma dose. AFM image displays rough surface morphology after irradiation. The detailed Raman analysis of plastic bottle sheets is presented here, and the results are correlated with the AFM observations.

Ali, Yasir; Kumar, Vijay; Dhaliwal, A. S. [Department of Physics, Sant Longowal Institute of Engineering and Technology Longowal, Punjab-148106 (India); Sonkawade, R. G. [School of Physical Sciences, Babasaheb Bhimrao Ambedkar University, Lucknow-226025 (India)

2013-02-05

299

Genetics Home Reference: Beta thalassemia  

MedlinePLUS

... Beta thalassemia occurs most frequently in people from Mediterranean countries, North Africa, the Middle East, India, Central ... do people use for beta thalassemia? erythroblastic anemia mediterranean anemia microcytemia, beta type thalassemia, beta type For ...

300

Characteristics of liquid sheets formed by splash plate nozzles  

NASA Astrophysics Data System (ADS)

An experimental study was conducted to identify the effect of viscosity on the characteristics of liquid sheets formed by a splash plate nozzle. Various mixtures of corn syrup and water are used to obtain viscosities in the range 1-170 mPa.s. Four different splash plates with nozzle diameters of 0.5, 0.75, 1, and 2 mm, with a constant plate angle of 55° were tested. Liquid sheets formed under various operating conditions were directly visualized. The sheet atomization process for the range of parameters studied here is governed by two different mechanisms: Rayleigh-Plateau (R-P) and Rayleigh-Taylor (R-T) instabilities. R-P occurs at the rim and R-T occurs on the thin sheet. The rim instability can be laminar or turbulent, depending on the jet Reynolds number. The R-T instability of the sheet is observed at the outer edges of the radially spreading sheet, where the sheet is the thinnest. It can also occur inside the sheet, due to formation of holes and ruptures.

Ahmed, M.; Amighi, A.; Ashgriz, N.; Tran, H. N.

2008-01-01

301

5. Historic American Buildings Survey Taken from drawing sheet, SHEET ...  

Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

5. Historic American Buildings Survey Taken from drawing sheet, SHEET #21, Showing the house as restored since Survey. (Dormer windows omitted as not authentic) - Samuel des Marest House, River Road, New Milford, Bergen County, NJ

302

Sheet Music Consortium  

NSDL National Science Digital Library

For those who love everything from Sousa to show tunes, the Sheet Music Consortium is a fabulous find. The Consortium is comprised of a number of member libraries (including UCLA) who are interested in building "an open collection of digitized sheet music." Their work has been supported by the Institute of Museum and Library Services and currently offers cross collection searching of 22 sheet music collections, with a total of 226,000 items. Visitors can click on the Virtual Collection to get started with offerings such as "Texas Cowboy Songs" and "The Titanic." The Browse feature is a great way to get a sense of the materials here. Finally, the Activity Stream provides an updated list of the most recently added items for general consumption. [KMG

2013-02-15

303

California Sheet Music Project  

NSDL National Science Digital Library

With oversight provided by Professor Mary Kay Duggan of the University of California at Berkeley, the California Sheet Music Project provides online access to some 2000 pieces of sheet music published in California between 1852 and 1900. The project was funded by the U.S. Institute of Museum and Library Services, and also contains interesting ephemera ranging from a music publisher's catalog from 1872, advertisements, and photographs. The entire database may be searched or browsed by image subject (from the frontispiece of each composition) or by the subject addressed by each piece of music. Some of the songs included in the archive deal with beggars ("Just One Penny to Buy Bread," babies ("Baby's Asleep"), and politicians ("Horace Greeley's Grand March"). Finally the site also has several musical performances of pieces from the collection for the listening pleasure of those compelled to visit this interesting tribute to the sheet music of the Golden State.

Duggan, Mary Kay

304

Historic American Sheet Music  

NSDL National Science Digital Library

Duke University's Historic American Sheet Music Project (HASM) presents digital images of 3,042 pieces of sheet music from Duke's collections, published between 1850 and 1920. Highlights of the collection include "antebellum Southern music, Confederate imprints, and Civil war songs." The search capabilities at the site are sophisticated, allowing users to look for music by publisher name, composer, title, performer, and many other terms. There is online help for searching and a glossary of subject headings. Much of the sheet music is illustrated, and it is possible to search for pictures by "illustration type" (theme), allowing access to the subjects of the illustrations as well as the music itself. It is also possible to browse all the cover illustrations. HASM was originally funded by Ameritech as part of the ongoing Library of Congress/Ameritech Digital Library Competition; it will soon be part of the American Memory Collections at the Library of Congress (described in the November 6, 1998 Scout Report).

1999-01-01

305

Kepler Mission Fact Sheet  

NSDL National Science Digital Library

This 2-page color fact sheet briefly describes NASA's Kepler mission, its instruments, and ground system. Also included are tables listing the instrument parameters and the major institutions involved. Kepler is a spaceborne telescope specifically designed to survey our region of the Milky Way galaxy to detect and characterize hundreds of Earth-size and smaller planets in or near the habitable zone. The habitable zone encompasses the distances from a star where liquid water can exist on a planet's surface. Note: The fact sheets states that the Kepler Telescope was launched in 2007 but did not launch until 2009.

306

Energy information sheets  

SciTech Connect

The National Energy Information Center (NEIC), as part of its mission, provides energy information and referral assistance to Federal, State, and local governments, the academic community, business and industrial organizations, and the general public. Written for the general public, the EIA publication Energy Information Sheets was developed to provide information on various aspects of fuel production, prices, consumption and capability. The information contained herein pertains to energy data as of December 1991. Additional information on related subject matter can be found in other EIA publications as referenced at the end of each sheet.

Not Available

1993-12-02

307

Environmental Data Sheet ENVIRONMENTAL DATA SHEET Dell Inc.  

E-print Network

Environmental Data Sheet Page 1 ENVIRONMENTAL DATA SHEET Dell Inc. PRODUCT: Latitude D520 www change without notice; please note the revision number on the last page. #12;Environmental Data Sheet · The cables may use PVC as an insulating material to ensure product safety · The case material is PC

Fiebig, Peter

308

beta(2)-microglobulin: from physiology to amyloidosis.  

PubMed

beta(2)-microglobulin (beta(2)m) is capable of forming amyloid in osteoarticular structures in kidney failure patients that undergo chronic hemodialysis treatment. Although sophisticated analytical methods have yielded comprehensive data about the conformation of the native protein both as a monomer and as the light chain of the type I major histocompatibility complex, the cause and mechanisms leading to the transformation of beta(2)m into amyloid deposits in patients with dialysis-related amyloidosis are unsettled. The impact on conformational stability of various truncations, cleavages, amino acid substitutions, and divalent cations, especially Cu(2+), however, are highly relevant for understanding beta(2)m unfolding pathways leading to amyloid formation. This review describes the current knowledge about such conformationally destabilizing and amyloidogenic factors and links these to the structure and function of beta(2)m in normal physiology and pathology. Tables listing modifications of beta(2)m found in amyloid from patients and a systematic overview of laboratory conditions conducive to beta(2)m-fibrillogenesis are also included. PMID:19657763

Heegaard, Niels H H

2009-01-01

309

Latent TGF-[beta] structure and activation  

SciTech Connect

Transforming growth factor (TGF)-{beta} is stored in the extracellular matrix as a latent complex with its prodomain. Activation of TGF-{beta}1 requires the binding of {alpha}v integrin to an RGD sequence in the prodomain and exertion of force on this domain, which is held in the extracellular matrix by latent TGF-{beta} binding proteins. Crystals of dimeric porcine proTGF-{beta}1 reveal a ring-shaped complex, a novel fold for the prodomain, and show how the prodomain shields the growth factor from recognition by receptors and alters its conformation. Complex formation between {alpha}v{beta}6 integrin and the prodomain is insufficient for TGF-{beta}1 release. Force-dependent activation requires unfastening of a 'straitjacket' that encircles each growth-factor monomer at a position that can be locked by a disulphide bond. Sequences of all 33 TGF-{beta} family members indicate a similar prodomain fold. The structure provides insights into the regulation of a family of growth and differentiation factors of fundamental importance in morphogenesis and homeostasis.

Shi, Minlong; Zhu, Jianghai; Wang, Rui; Chen, Xing; Mi, Lizhi; Walz, Thomas; Springer, Timothy A. (Harvard-Med)

2011-09-16

310

Fact Sheet on Dirty Bombs  

MedlinePLUS

... Sheet on Dirty Bombs Fact Sheet on Dirty Bombs Printable Version Background A "dirty bomb" is one ... the terrorists’ major objectives. Impact of a Dirty Bomb The extent of local contamination would depend on ...

311

Functional polymer sheet patterning using microfluidics.  

PubMed

Poly(dimethylsiloxane) (PDMS)-based microfluidics provide a novel approach to advanced material synthesis. While PDMS has been successfully used in a wide range of industrial applications, due to the weak mechanical property channels generally possess low aspect ratios (AR) and thus produce microparticles with similarly low ARs. By increasing the channel width to nearly 1 cm, AR to 267, and implementing flow lithography, we were able to establish the slit-channel lithography. Not only does this allow us to synthesize sheet materials bearing multiscale features and tunable chemical anisotropy but it also allows us to fabricate functional layered sheet structures in a one-step, high-throughput fashion. We showcased the technique's potential role in various applications, such as the synthesis of planar material with micro- and nanoscale features, surface morphologies, construction of tubular and 3D layered hydrogel tissue scaffolds, and one-step formation of radio frequency identification (RFID) tags. The method introduced offers a novel route to functional sheet material synthesis and sheet system fabrication. PMID:24967616

Li, Minggan; Humayun, Mouhita; Kozinski, Janusz A; Hwang, Dae Kun

2014-07-22

312

The charge delocalised beta,beta-carotene dication--preparation, structure elucidation by NMR and reactions with nucleophiles.  

PubMed

The reaction between beta,beta-carotene and BF3-etherates has been investigated, leading to structural elucidation of the blue product, formed in appropriate organic solvents, as a symmetrical charge delocalised dication (lambda(max) 985 nm at room temperature in CHCl3) with considerable stability. The reaction, monitored by EPR studies at -25 degrees C, occurred via free radical intermediates. A C40H56BF3 intermediate was captured by EIMS. The detailed structure of the dication was established by COSY, HSQC, HMBC and 1D and 2D ROESY NMR techniques (600 MHz, CDCl3, -20 degrees C) leading to complete assignments of 1H and 13C chemical shifts and 3J(H,H) coupling constants. The effects of the two delocalised charges on chemical shift (charge distribution) and bond distance (3J(H,H)) were considered. The results are consistent with charge delocalisation mainly in the C-5-C-9 and C-5'-C-9' regions and with bond inversion to retro shifted double bonds in the central C-13-C-13' region. A convention for denoting the charge delocalisation and bond types is presented. The experimental results are discussed relative to previous theoretical calculations of the beta,beta-carotene dication structure. (All-E) and (15-Z)-beta,beta-carotene provided the same dication. The NIR spectra and stability of dications prepared in the same manner from the related carotenes 20,20'-dinor-beta,beta-carotene, heptapreno-beta,beta-carotene and nonapreno-beta,beta-carotene were examined for comparison. Reactions of the beta,beta-carotene dication with selected nucleophiles provided products including isocryptoxanthin, isocarotene and mutatochrome with H2O as nucleophile, and isocryptoxanthin methyl ether, 8-methoxy-7,8-dihydro-beta,beta-carotene and isocarotene with CH3ONa as nucleophile. The formation of these products is rationalised from the structure assigned to the dication. PMID:14664396

Lutnaes, Bjart Frode; Bruås, Liv; Kildahl-Andersen, Geir; Krane, Jostein; Liaaen-Jensen, Synnøve

2003-11-21

313

Skill Sheets for Agricultural Mechanics.  

ERIC Educational Resources Information Center

This set of 33 skill sheets for agricultural mechanics was developed for use in high school and vocational school agricultural mechanics programs. Some sheets teach operational procedures while others are for simple projects. Each skill sheet covers a single topic and includes: (1) a diagram, (2) a step-by-step construction or operational…

Iowa State Univ. of Science and Technology, Ames. Dept. of Agricultural Education.

314

US Geological Survey Fact Sheets  

NSDL National Science Digital Library

The US Geological Survey (USGS) Fact Sheets Web site summarizes research and investigations done by the agency and provides details about particular activities. The sheets are organized by theme, including resources, hazards, environment, information management, by individual state, and by scientific discipline. The fact sheets give basic summations of the research and provide links to more detailed pages for those seeking further information.

315

Insulation Fact Sheet.  

ERIC Educational Resources Information Center

Heating and cooling account for 50-70% of the energy consumed in the average American home. Heating water accounts for another 20%. A poorly insulated home loses much of this energy, causing drafty rooms and high energy bills. This fact sheet discusses how to determine if your home needs more insulation, the additional thermal resistance (called…

Conservation and Renewable Energy Inquiry and Referral Service (DOE), Silver Spring, MD.

316

Risk Assessment Fact Sheet  

E-print Network

Risk Assessment ® Fact Sheet U.S. Army Corps of Engineers Building Strong ® Buffalo District June 2012 Risk Assessment A risk assessment is performed for hazardous, toxic, and radioactive waste sites to estimate the potential risks to human health and the environment posed by radioactive substances

US Army Corps of Engineers

317

Materials Safety Data Sheets  

E-print Network

Materials Safety Data Sheets (MSDS) MSDS contain chemical hazard information about substances compounds and solvents. MSDS data can be accessed from the following URLs http://www.ehs.umass.edu/ http://www.chem.umass.edu/Safety with which you work. It is the law that laboratory workers have access to MSDS on materials with which

Schweik, Charles M.

318

Software Fact Sheet Description  

E-print Network

Software Fact Sheet Description Display & Analysis Software Data Access Software www.unidata.ucar.edu/software, and multidisciplinary integration, Unidata provides a rich set of software tools to access and visualize Earth with the aid of three tools: the LDM, RAMADDA and the TDS. Data Management Software Unidata facilitates

319

Quick Information Sheets.  

ERIC Educational Resources Information Center

This compilation of "Trace Quick Sheets" provides descriptions, prices, and ordering information for products and services that assist with communication, control, and computer access for disabled individuals. Product descriptions or product sources are included for: adaptive toys and toy modifications; head pointers, light pointers, and…

Wisconsin Univ., Madison. Trace Center.

320

GED Testing Fact Sheet  

ERIC Educational Resources Information Center

This GED Testing fact sheet provides information on: (1) GED[R] Tests; (2) Versions and Editions of the GED Tests; (3) Earning a Credential; (4) GED Testing Service[R]; (5) History of the GED Tests; (6) Who Accepts the GED Credential; (7) Public/Private Partnership of GEDTS; (8) Renowned GED Credential Recipients; (9) GED Testing Numbers for 2008;…

GED Testing Service, 2009

2009-01-01

321

Fabrication of cylindrical shells from welded sheet billets via superplastic forming  

Microsoft Academic Search

Two alternative production flowcharts for the fabrication of cylindrical shells from titanium alloys in the superplasticity\\u000a (SP) state, namely, the formation of the sheet into a rectangular matrix and the free formation of a package consisting of\\u000a two sheets welded along a rectangular contour by diffusion welding, are considered. It is stated by comparative analysis that,\\u000a for the free formation

T. M. Zagirov; A. A. Kruglov; F. U. Enikeev

2011-01-01

322

Immunolocalization of alpha-keratins and feather beta-proteins in feather cells and comparison with the general process of cornification in the skin of mammals.  

PubMed

The maturation of the corneous material of feathers is a special case of cornification in vertebrate epidermis and is believed to occur mainly by the accumulation of small proteins of about 100 amino acids and a central beta-pleated sheet region known as feather keratins. The present immunocytochemical study carried out using double-labeling immunogold shows that a small amount of alpha-keratins of intermediate filament type form the early keratin clumps in barb and barbule cells. These initial nuclei of formation of corneous material are rapidly coated by the deposition of large amounts of small feather keratin-associated beta-proteins (feather keratins). The latter proteins turn the keratin bundles of barb and barbule cells into a compact and apparently amorphous mass of corneous material where no sign of intermediate filaments are seen. Feather beta-proteins however form an irregular filamentous network of 2-3nm thick electron-pale filaments and produce the characteristic feather X-ray pattern due to their prevalent amount over any other protein present in feather cells. The modality of cornification in feathers is discussed in relation to the process of formation of corneous material in the skin of vertebrates in general that occurs by the association of intermediate filament proteins and keratin-associated proteins. PMID:23228339

Alibardi, L

2013-03-01

323

Synchrotron-based Infrared and X-ray Imaging Shows Focalized Accumulation of Cu and Zn Co-localized With Beta-amyloid Deposits in Alzheimer's Disease  

SciTech Connect

Alzheimer's disease (AD) is characterized by the misfolding and plaque-like accumulation of a naturally occurring peptide in the brain called amyloid beta (Abeta). Recently, this process has been associated with the binding of metal ions such as iron (Fe), copper (Cu), and zinc (Zn). It is thought that metal dyshomeostasis is involved in protein misfolding and may lead to oxidative stress and neuronal damage. However, the exact role of the misfolded proteins and metal ions in the degenerative process of AD is not yet clear. In this study, we used synchrotron Fourier transform infrared micro-spectroscopy (FTIRM) to image the in situ secondary structure of the amyloid plaques in brain tissue of AD patients. These results were spatially correlated with metal ion accumulation in the same tissue sample using synchrotron X-ray fluorescence (SXRF) microprobe. For both techniques, a spatial resolution of 5-10 microm was achieved. FTIRM results showed that the amyloid plaques have elevated beta-sheet content, as demonstrated by a strong amide I absorbance at 1625cm(-1). Using SXRF microprobe, we find that AD tissue also contains 'hot spots' of accumulated metal ions, specifically Cu and Zn, with a strong spatial correlation between these two ions. The 'hot spots' of accumulated Zn and Cu were co-localized with beta-amyloid plaques. Thus for the first time, a strong spatial correlation has been observed between elevated beta-sheet content in Abeta plaques and accumulated Cu and Zn ions, emphasizing an association of metal ions with amyloid formation in AD.

Miller,L.; Wang, Q.; Telivala, T.; Smith, R.; Lanzirotti, A.; Miklossy, J.

2006-01-01

324

Plastic bronchitis in beta thalassemia minor.  

PubMed

Plastic bronchitis is a rare pulmonary disorder associated with various conditions like cystic fibrosis, asthma, pulmonary infection and characterized by formation and expectoration of cast which assumes the shape of the bronchial tree. We report a case of a 33-year-old woman with beta thalassemia minor who developed plastic bronchitis. PMID:24049256

Yadav, Makaresh; Tirpude, Sneha; Joshi, Jyotsna M

2013-07-01

325

Sheet Music from Canada's Past  

NSDL National Science Digital Library

The National Library of Canada has recently updated their collection of historical Canadian sheet music. Sheet Music from Canada's Past (see the November 17, 2000 Scout Report for an earlier mention) has updated their collection of sheet music from the World War I era with sheet music published before the Confederation in 1867. One can search the entire collection or search the World War I and pre-Confederation collections separately. The site also features articles devoted to describing each collection, and the posted music may be printed out from the site. Future plans include digitizing sheet music published between 1867 and 1913.

2001-01-01

326

Imperfect World of $\\beta\\beta$-decay Nuclear Data Sets  

E-print Network

The precision of double-beta ($\\beta\\beta$) decay experimental half lives and their uncertainties is reanalyzed. The method of Benford's distributions has been applied to nuclear reaction, structure and decay data sets. First-digit distribution trend for $\\beta\\beta$-decay T$_{1/2}^{2\

Pritychenko, B

2015-01-01

327

One-way transparent sheets  

E-print Network

In this paper we introduce the concept of metasurfaces which are fully transparent when looking from one of the two sides of the sheet and have controllable functionalities for waves hitting the opposite side (one-way transparent sheets). We address the question on what functionalities are allowed, considering limitations due to reciprocity and passivity. In particular, we have found that it is possible to realize one-way transparent sheets which have the properties of a twist-polarizer in reflection or transmission when illuminated from the other side. Also one-way transparent sheets with controllable co-polarized reflection and transmission from the opposite side are feasible. We show that particular non-reciprocal magneto-electric coupling inside the sheet is necessary to realize lossless non-active transparent sheets. Furthermore, we derive the required polarizabilities of constituent dipole particles such that the layers composed of them form one-way transparent sheets. We conclude with design and simula...

Ra'di, Younes; Tretyakov, Sergei

2013-01-01

328

Locating current sheets in the solar corona  

E-print Network

Current sheets are essential for energy dissipation in the solar corona, in particular by enabling magnetic reconnection. Unfortunately, sufficiently thin current sheets cannot be resolved observationally and the theory of their formation is an unresolved issue as well. We consider two predictors of coronal current concentrations, both based on geometrical or even topological properties of a force free coronal magnetic field. First, there are separatrices related to magnetic nulls. Through separatrices the magnetic connectivity changes discontinuously. Coronal magnetic nulls are, however, very rare. At second, inspired by the concept of generalized magnetic reconnection without nulls, quasi-separatrix layers (QSL) were suggested. Through QSL the magnetic connectivity changes continuously, though strongly. The strength of the connectivity change can be quantified by measuring the squashing of the flux tubes which connect the magnetically conjugated photospheres. We verify the QSL and separatrix concepts by com...

Buechner, J

2006-01-01

329

High Beta Tokamaks  

SciTech Connect

Perhaps the ideal tokamak would have high {beta} ({beta} {approx}> 1) and classical confinement. Such a tokamak has not been found, and we do not know if one does exist. We have searched for such a possibility, so far without success. In 1990, we obtained analytic equilibrium solutions for large aspect ratio tokamaks at {beta} {approx} {Omicron}(1) [1]. These solutions and the extension at high {beta} poloidal to finite aspect ratio [2] provided a basis for the study of high {beta} tokamaks. We have shown that these configurations can be stable to short scale MHD modes [3], and that they have reduced neoclassical transport [4]. Microinstabilities (such as the {del}T{sub i} mode) seem to be stabilized at high {beta} [5] - this is due to the large local shear [3] and the magnetic well. We have some concerns about modes associated with the compressional branch which may appear at high {beta}. Bill Dorland and Mike Kotschenreuther have studied this issue and our concerns may be unfounded. It is certainly tantalizing, especially given the lowered neoclassical transport values, that these configurations could have no microinstabilities and, one could assume, no anomalous transport. Unfortunately, while this work is encouraging, the key question for high {beta} tokamaks is the stability to large scale kink modes. The MHD {beta} limit (Troyon limit) for kink modes at large aspect ratio is problematically low. There is ample evidence from computations that the limit exists. However, it is not known if stable equilibria exist at much higher {beta}--none have been found. We have explored this question in the asymptotic high {beta} poloidal limit. Unfortunately, we are unable to find stable equilibrium and also unable to show that they don't exist. The results of these calculations will be published when a more definitive answer is found.

Cowley, S.

1998-11-14

330

Dynamics of charged current sheets at high-latitude magnetopause  

NASA Astrophysics Data System (ADS)

E. Amata (2), L. Zelenyi (1), M. Dunlop (3), M. Andre (4), P. Song (5), J. Blecki (6), J. Buechner (7), J.L Rauch, J.G. Trotignon (8), G. Consolini, F. Marcucci (2), B. Nikutowski (7), A. Skalsky, S. Romanov, E. Panov (1) (2) IFSI, Roma, Italy, (3) RAL, UK, (4) IRFU, Uppsala, Sweden, (5) U. Mass. Lowell, USA, (6) SRC, Warsaw, Poland, (7) MPAe, Germany, (8) LPCE, Orleans, France; We study dynamics of thin current sheets over polar cusps from data of Interball-1 and Cluster. At the high-beta magnetopause current sheet width often reaches ion gyroradius scales, that leads to their Hall dynamics in the presence of local surface charges. Respective perpendicular electric fields provide the means for momentum coupling through the current sheets and are able to accelerate ions with gyroradius of the order or larger than the sheet width. At borders of large diamagnetic cavities this mechanism is able to support mass exchange and accelerate/ heat incoming magnetosheath particles. At larger scales the inhomogeneous electric fields at the current sheet borders can accelerate incident plasma downtail along magnetopause via inertial drift. It serves to move external plasma away for dynamic equilibrium supporting. Farther away from magnetopause similar nonlinear electric field wave trains, selfconsistently produced by interaction of reflected from the obstacle waves with magnetosheath fluctuations, destroy the incident flux into accelerated magnetosonic jets and decelerated Alfvenic flows and generate small-scale current sheets due to different sign of electron and ion inertial drift in the nonlinear electric field bursts. We suggest that this direct kinetic energy transformation creates current sheets with anomalous statistics of field rotation angles in the turbulent boundary layer in front of magnetopause, which have been attributed earlier to an intermittent turbulence. We compare measured spectra with a model of nonlinear system with intermittent chaotic behavior. Work was supported by INTAS grant 03-51-4872.

Savin, S.; Amata, E.; Zelenyi, L.; Dunlop, M.; Andre, M.; Song, P.; Blecki, J.; Buechner, J.; Rauch, J. L.; Skalsky, A.

331

Irish Sheet Music Archives  

NSDL National Science Digital Library

Based out of Milwaukee, the Ward Irish Music Archives were established in 1992 and is dedicated to the preservation of Irish and Irish-American music in all of its forms. Visitors to this remarkable site can browse over 5,000 pieces of Irish and Irish-American sheet music. While some of these ditties are not in the public domain, the collection can be narrowed down by filtering for only publicly available items. The History section contains a topical history of sheet music from the days of the broadside to the more challenging days of the early 21st century when digital versions became dominant. The Galleries are another great feature, containing additional information about cover artists, composers, and themes. It's an amazing collection and one that will inspire a few sing-a-longs from Dublin to Boston.

332

Clean Cities Fact Sheet  

SciTech Connect

This fact sheet explains the Clean Cities Program and provides contact information for all coalitions and regional offices. It answers key questions such as: What is the Clean Cities Program? What are alternative fuels? How does the Clean Cities Program work? What sort of assistance does Clean Cities offer? What has Clean Cities accomplished? What is Clean Cities International? and Where can I find more information?

Not Available

2004-01-01

333

Between the Sheets: Accounting  

NSDL National Science Digital Library

This guide from the British Website BizEd helps users understand the ways to use spreadsheets in accounting. The tutorial starts with general information: introductions for both students and teachers, a guide to downloadable spreadsheets, a guide to using spreadsheets, and a glossary of important terms. The guide offers a collection of spreadsheets that require Microsoft Excel 97. Also featured is an introduction to balance sheets and income statements, budgeting, and cost volume profit analysis.

2007-05-14

334

Kepler Mission Fact Sheet  

NSDL National Science Digital Library

This 2-page color fact sheet briefly describes NASAâs Kepler mission, its instruments, and ground system. Also included are tables listing the instrument parameters and the major institutions involved. Kepler is a spaceborne telescope specifically designed to survey our region of the Milky Way galaxy to detect and characterize hundreds of Earth-size and smaller planets in or near the habitable zone. The habitable zone encompasses the distances from a star where liquid water can exist on a planet's surface.

2007-01-01

335

Biomolecular Science (Fact Sheet)  

SciTech Connect

A brief fact sheet about NREL Photobiology and Biomolecular Science. The research goal of NREL's Biomolecular Science is to enable cost-competitive advanced lignocellulosic biofuels production by understanding the science critical for overcoming biomass recalcitrance and developing new product and product intermediate pathways. NREL's Photobiology focuses on understanding the capture of solar energy in photosynthetic systems and its use in converting carbon dioxide and water directly into hydrogen and advanced biofuels.

Not Available

2012-04-01

336

BETA GAUGE OPERATION MANUAL  

EPA Science Inventory

This manual provides description and operating instructions for a redesigned Beta Gauge for measuring particles from vehicle exhaust. The improvements and a new control system including a control unit which is radically different from the prior unit, are described. Complete Beta ...

337

Beta Coin Experiment  

NSDL National Science Digital Library

This resource consists of a Java applet and expository text. The applet illustrates Bayesian estimation of the probability of heads for a coin. The prior beta distribution, true probability of heads, and the sample size can be specified. The applet shows the posterior beta distribution.

Siegrist, Kyle

338

MOON for neutrino-less {beta}{beta} decays and {beta}{beta} nuclear matrix elements  

SciTech Connect

The MOON project aims at spectroscopic 0v{beta}{beta} studies with the v-mass sensitivity of 100-30 meV by measuring two beta rays from {sup 100}Mo and/or {sup 82}Se. The detector is a compact super-module of multi-layer PL scintillator plates. R and D works made by the pro to-type MOON-1 and the small PL plate show the possible energy resolution of around {sigma}{approx}2.2%, as required for the mass sensitivity. Nuclear matrix elements M{sup 2v} for 2v{beta}{beta} are shown to be given by the sum {sigma}{sub L}M{sub k} of the 2v{beta}{beta} matrix elements M{sub k} through intermediate quasi-particle states in the Fermi-surface, where Mi is obtained experimentally by using the GT(J{sup {pi}} = 1{sup +}) matrix elements of M{sub i}(k) and M{sub f}(k) for the successive single-{beta} transitions through the k-th intermediate state.

Ejiri, H. [Research Center for Nuclear Physics, Osaka University, Osaka 567-0047 (Japan)

2009-11-09

339

Conversion of rice husk ash to zeolite beta.  

PubMed

White rice husk ash (RHA), an agriculture waste containing crystalline tridymite and alpha-cristobalite, was used as a silica source for zeolite Beta synthesis. The crystallization of zeolite Beta from RHA at 150 degrees C in the presence of tetraethylammonium hydroxide was monitored by XRD, FTIR and (29)Si MAS NMR techniques. It was found that zeolite Beta started to form after 12h and the complete crystallization of zeolite Beta phase was achieved after 2d. XRD, (29)Si MAS NMR and solid yield studies indicate that the transformation mechanism of silica present in RHA to zeolite Beta involves dissolution of the ash, formation of an amorphous aluminosilicate after 6h of crystallization, followed by dissolution in the mother liquor and final transformation to pure zeolite Beta crystals. PMID:16274981

Prasetyoko, Didik; Ramli, Zainab; Endud, Salasiah; Hamdan, Halimaton; Sulikowski, Bogdan

2006-01-01

340

Beta-ensembles with covariance  

E-print Network

This thesis presents analytic samplers for the [beta]-Wishart and [beta]-MANOVA ensembles with diagonal covariance. These generalize the [beta]-ensembles of Dumitriu-Edelman, Lippert, Killip-Nenciu, Forrester-Rains, and ...

Dubbs, Alexander

2014-01-01

341

MAGNETIC RECONNECTION IN THE SOLAR WIND AT CURRENT SHEETS ASSOCIATED WITH EXTREMELY SMALL FIELD SHEAR ANGLES  

SciTech Connect

Using Wind 3 s plasma and magnetic field data, we have identified nine reconnection exhausts within a solar wind disturbance on 1998 October 18-20 driven by a moderately fast interplanetary coronal mass ejection (ICME). Three of the exhausts within the ICME were associated with current sheets having local field shear angles, {theta}, ranging from 4 Degree-Sign to 9 Degree-Sign , the smallest reported values of {theta} yet associated with reconnection exhausts in a space plasma. They were observed in plasma characterized by extremely low (0.02-0.04) plasma {beta}, and very high (281-383 km s{sup -1}) Alfven speed, V{sub A}. Low {beta} allows reconnection to occur at small {theta} and high V{sub A} leads to exhaust jets that are fast enough relative to the surrounding solar wind to be readily identified. Very small-{theta} current sheets are common in the solar wind at 1 AU, but typically are not associated with particularly low plasma {beta} or high V{sub A}. On the other hand, small-{theta} current sheets should be common in the lower solar corona, a plasma regime of extremely low {beta} and extremely high V{sub A}. Our observations lend credence to models that predict that reconnection at small-{theta} current sheets is primarily responsible for coronal heating.

Gosling, J. T. [Laboratory for Atmospheric and Space Physics, University of Colorado, 3665 Discovery Drive, Boulder, CO 80303 (United States); Phan, T. D., E-mail: jack.gosling@lasp.colorado.edu [Space Sciences Laboratory, University of California, Berkeley, CA 94720 (United States)

2013-02-01

342

The quantitative inspection of iron aluminide green sheet using transient thermography  

NASA Astrophysics Data System (ADS)

The recent development of manufacturing techniques for the fabrication of thin iron aluminide, FeAl, sheet requires advanced quantitative methods for on-line inspection. An understanding of the mechanisms responsible for flaws and the development of appropriate flaw detection methods are key elements in an effective quality management system. The first step in the fabrication of thin FeAl alloy sheet is the formation of a green sheet, either by cold rolling or tape casting FeAl powder mixed with organic binding agents. The finished sheet is obtained using a series of process steps involving binder elimination, densification, sintering, and annealing. Non-uniformities within the green sheet are the major contributor to material failure in subsequent sheet processing and the production of non-conforming finished sheet. Previous work has demonstrated the advantages of using active thermography to detect the flaws and heterogeneity within green powder composites (1)(2)(3). The production environment and physical characteristics of these composites provide for unique challenges in developing a rapid nondestructive inspection capability. Thermography is non-contact and minimizes the potential damage to the fragile green sheet. Limited access to the material also demands a one-sided inspection technique. In this paper, we will describe the application of thermography for 100% on-line inspection within an industrial process. This approach is cost competitive with alternative technologies, such as x-ray imaging systems, and provides the required sensitivity to the variations in material composition. The formation of green sheet flaws and their transformation into defects within intermediate and finished sheet products will be described. A green sheet conformance criterion will be presented which would significantly reduce the probability of processing poor quality green sheet which contributes to higher waste and inferior bulk alloy sheet.

Watkins, Michael L.; Hinders, Mark K.; Scorey, Clive; Winfree, William

1999-12-01

343

Improving radiation safety hazard communication through nuclide safety data sheets.  

PubMed

Providing nuclide-specific radiation safety information to radioactive material users constitutes a primary role for the institutional health physicist. Often radioactive material vendors' safety literature fills this need, but may leave out key information (e.g., site-specific requirements) that the radiation safety program would like to convey. Instead, time Nuclide Safety Data Sheet concept provides this safety information using a hazard communication medium and format--the Material Safety Data Sheet--that is well established in the workplace. In addition to allowing institutions to customize time information provided to radioactive material users, the Nuclide Safety Data Sheet also gives workers a familiar format in which to view radiation hazard communication information. PMID:11797904

Edwards, Ben

2002-02-01

344

{alpha}-Lipoic acid exhibits anti-amyloidogenicity for {beta}-amyloid fibrils in vitro  

SciTech Connect

Inhibition of the formation of {beta}-amyloid fibrils (fA{beta}), as well as the destabilization of preformed fA{beta} in the CNS would be attractive therapeutic targets for the treatment of Alzheimer's disease (AD). Using fluorescence spectroscopic analysis with thioflavin T and electron microscopic studies, we examined the effects of {alpha}-lipoic acid (LA) and the metabolic product of LA, dihydrolipoic acid (DHLA), on the formation, extension, and destabilization of fA{beta} at pH 7.5 at 37 {sup o}C in vitro. LA and DHLA dose-dependently inhibited fA{beta} formation from amyloid {beta}-protein, as well as their extension. Moreover, they destabilized preformed fA{beta}s. LA and DHLA could be key molecules for the development of therapeutics for AD.

Ono, Kenjiro [Department of Neurology and Neurobiology of Aging, Kanazawa University Graduate School of Medical Science, Kanazawa 920-8640 (Japan); Hirohata, Mie [Department of Neurology and Neurobiology of Aging, Kanazawa University Graduate School of Medical Science, Kanazawa 920-8640 (Japan); Yamada, Masahito [Department of Neurology and Neurobiology of Aging, Kanazawa University Graduate School of Medical Science, Kanazawa 920-8640 (Japan)]. E-mail: m-yamada@med.kanazawa-u.ac.jp

2006-03-24

345

Texture Development and Drawability of Frictionally Rolled AA 5052 AL Alloy Sheet  

NASA Astrophysics Data System (ADS)

The microstructure, pole figure and r-value of the frictionally rolled and subsequently heat treated AA 5052 Al sheets were investigated by optical microscopy, x-ray diffractometer and tensile tester, respectively. Frictionally rolled AA 5052 Al specimens showed a fine grain size. After subsequently heat treated specimens, the ND//<111> texture component was increased. The r-values of the frictionally rolled and subsequently heat treated Al alloy sheets were about two times higher than those of the original Al sheets. These could be related to the formation of ND//<111> texture components through frictional rolling in and subsequent heat treatment of AA 5052 Al sheet.

Kim, Insoo; Akramov, Saidmurod; Jeong, Hae Bong; No, Tae Kyoung

346

Method for heating a glass sheet  

DOEpatents

A method for heating a glass sheet includes the steps of heating a glass sheet to a first predetermined temperature and applying microwave energy to the glass sheet to heat the glass sheet to at least a second predetermined temperature to allow the glass sheet to be formed. 5 figs.

Boaz, P.T.

1998-07-21

347

Method for heating a glass sheet  

DOEpatents

A method for heating a glass sheet includes the steps of heating a glass sheet to a first predetermined temperature and applying microwave energy to the glass sheet to heat the glass sheet to at least a second predetermined temperature to allow the glass sheet to be formed.

Boaz, Premakaran Tucker (Livonia, MI)

1998-01-01

348

STATE SupErAnnuATion SchEmE (SSS) FACT SHEET FACT SHEET FACT SHEET FACT SHEET FACT SH  

E-print Network

STATE SupErAnnuATion SchEmE (SSS) FACT SHEET FACT SHEET FACT SHEET FACT SHEET FACT SH www. The Scheme is also subject to Commonwealth superannuation and tax legislation. STC has published this Fact been taken in producing the information in this Fact Sheet and nothing in it is intended

University of Technology, Sydney

349

Mammalian ciliary-body epithelial cells in culture produce transforming growth factor-beta  

Microsoft Academic Search

Transforming growth factor-beta (TGF-beta) has recently been found in the aqueous humor. The present study was initiated to test whether the ciliary-body epithelium, the site of aqueous humor formation, is capable of producing TGF-beta. Human, rat and bovine ciliary epithelial cells were grown in tissue culture and their supernatants were tested for TGF-beta using a bioassay. After acid activation of

Horst Helbig; Karen L. Kittredge; Miguel Coca-Prados; Janet Davis; Alan G. Palestine; Robert B. Nussenblatt

1991-01-01

350

Physics 416 Quiz Sheet Name: ___________________________________  

E-print Network

Physics 416 Quiz Sheet Quiz 1 Name: ___________________________________ "Homonyms" are either homophones which are words that sound alike, but have different meanings and spellings, or homographs which

Hart, Gus

351

Active volcanism beneath the West Antarctic ice sheet and implications for ice-sheet stability  

USGS Publications Warehouse

IT is widely understood that the collapse of the West Antarctic ice sheet (WAIS) would cause a global sea level rise of 6 m, yet there continues to be considerable debate about the detailed response of this ice sheet to climate change1-3. Because its bed is grounded well below sea level, the stability of the WAIS may depend on geologically controlled conditions at the base which are independent of climate. In particular, heat supplied to the base of the ice sheet could increase basal melting and thereby trigger ice streaming, by providing the water for a lubricating basal layer of till on which ice streams are thought to slide4,5. Ice streams act to protect the reservoir of slowly moving inland ice from exposure to oceanic degradation, thus enhancing ice-sheet stability. Here we present aerogeophysical evidence for active volcanism and associated elevated heat flow beneath the WAIS near the critical region where ice streaming begins. If this heat flow is indeed controlling ice-stream formation, then penetration of ocean waters inland of the thin hot crust of the active portion of the West Antarctic rift system could lead to the disappearance of ice streams, and possibly trigger a collapse of the inland ice reservoir.

Blankenship, D.D.; Bell, R.E.; Hodge, S.M.; Brozena, J.M.; Behrendt, J.C.; Finn, C.A.

1993-01-01

352

Soil Quality Information Sheet Rangeland Soil Quality--Infiltration  

E-print Network

the infiltration rate. Runoff can cause soil erosion and the formation of gullies. It also carries nutrientsSoil Quality Information Sheet Rangeland Soil Quality--Infiltration USDA, Natural Resources into the soil is infiltration. "Infiltration rate" is simply how fast water enters the soil and is usually

353

Europa Fact Sheet  

NSDL National Science Digital Library

The Galileo spacecraft provided images of Europa, one of Jupiter's moons. The images showed signs of a possible ocean on the surface of the moon. NASA's Europa Fact Sheet provides information and images on this Jovian moon. This site covers one of the top ten scientific breakthroughs of 1997, compiled in the December 19, 1997 issue of Science. The top scientific breakthrough of 1997 was the cloning of a sheep, resulting in a lamb named Dolly. The nine runners up were: the Pathfinder mission to Mars, synchrotrons, biological clock genes, gamma ray bursts, Neandertal DNA, nanotubes, Europa's ocean, whole genome sequencing, and neurons.

354

Planetary Fact Sheets  

NSDL National Science Digital Library

Offered by the National Space Science Data Center of NASA, the Planetary Fact Sheets Web site contains helpful information for students studying astronomy. The site lists links to all of the planets, their satellites, and their rings, as well as to tables comparing all the planets. The planet pages contain a photograph and a simple list of dozens of facts such as mass, volume, distance to the earth, temperature, and much more. Although not flashy, the information provided by this site can be very useful to anyone wanting to learn more about our solar system.

1969-12-31

355

Engineering Research Center Fact Sheets  

NSDL National Science Digital Library

Curious about the latest developments in bioengineering, microelectronics, or earthquake hazard reduction? Wondering what type of research your tax dollars support? Then have a look at this recent posting from the National Science Foundation's (NSF's) Engineering Research Centers (ERC) Program which supports university research in partnership with industry. Here, users can access project descriptions from a variety of laboratories associated with the ERC. Examples of centers featured include Georgia Tech/ Emory Center for the Engineering of Living Tissues, Pacific Earthquake Engineering Research Center, Center for Neuromorphic Systems Engineering, and Center for Advanced Engineering Fibers and Films, to name a few. The research pages, available in either HTML or .pdf formats, present research goals, collaborating institutions, facility overviews, technology transfer initiatives, educational outreach projects, and links to contacts. At many of the pages, color photographs and illustrations accompany text. So the next time you are taking a break from work, peruse the NSF's Engineering Research Centers Fact Sheets and get the latest news about federally funded research and technology.

2001-01-01

356

Iron(II) binding by cereal beta-glucan.  

PubMed

Beta-glucan is a dietary fiber, which possesses several health benefits, such as cholesterol lowering, however this fiber is easily degraded in the presence of Fenton reagents. In the present study, the iron binding capacity of oat beta-glucan and barley beta-glucan was evaluated by investigating the kinetics of the Fenton reaction at pH 2.7 and 4.7 using stopped flow spectroscopy. The rate constant of the Fenton reaction is not affected by the presence of the beta-glucans in a solution pH 2.7, hence none of the beta-glucans bind iron(II) at this pH. However, at pH 4.7, the kinetics of the Fenton reaction vary between acetate buffer (k=2.8×10(2)M(-1)s(-1)), barley beta-glucan (k=2.2×10(2)M(-1)s(-1)) and oat beta-glucan (k=1.2×10(2)M(-1)s(-1)), which demonstrates that barley beta-glucan and oat beta-glucan form complexes with iron(II). Moreover, oat beta-glucan shows a stronger affinity for iron(II) than barley beta-glucan, and may thereby reduce the formation of hydroxyl radicals and diminish the rate of viscosity loss of the oat beta-glucan solution, as shown by the ESR and rheological data. The results presented in this study suggest that cereal beta-glucans can potentially reduce the bioavailability of iron. PMID:25439956

Faure, Audrey M; Koppenol, Willem H; Nyström, Laura

2015-01-22

357

Preformed {beta}-amyloid fibrils are destabilized by coenzyme Q{sub 10} in vitro  

SciTech Connect

Inhibition of the formation of {beta}-amyloid fibrils (fA{beta}), as well as the destabilization of preformed fA{beta} in the CNS, would be attractive therapeutic targets for the treatment of Alzheimer's disease (AD). We reported previously that nordihydroguaiaretic acid (NDGA) and wine-related polyphenol, myricetin (Myr), inhibit fA{beta} formation from A{beta} and destabilize preformed fA{beta} in vitro. Using fluorescence spectroscopic analysis with thioflavin T and electron microscopic studies, we examined the effects of coenzyme Q{sub 10} (CoQ{sub 10}) on the formation, extension, and destabilization of fA{beta} at pH 7.5 at 37 deg C in vitro. We next compared the anti-amyloidogenic activities of CoQ{sub 10} with NDGA and Myr. CoQ{sub 10} dose-dependently inhibited fA{beta} formation from amyloid {beta}-peptide (A{beta}), as well as their extension. Moreover, it destabilized preformed fA{beta}s. The anti-amyloidogenic effects of CoQ{sub 10} were slightly weaker than those of NDGA and Myr. CoQ{sub 10} could be a key molecule for the development of therapeutics for AD.

Ono, Kenjiro [Department of Neurology and Neurobiology of Aging, Kanazawa University Graduate School of Medical Science, Kanazawa 920-8640 (Japan); Hasegawa, Kazuhiro [Department of Pathology, Fukui University, Fukui 910-1193, CREST of Japan Science and Technology Corporation, Kawaguchi 332-0012 (Japan); Naiki, Hironobu [Department of Pathology, Fukui University, Fukui 910-1193, CREST of Japan Science and Technology Corporation, Kawaguchi 332-0012 (Japan); Yamada, Masahito [Department of Neurology and Neurobiology of Aging, Kanazawa University Graduate School of Medical Science, Kanazawa 920-8640 (Japan)]. E-mail: m-yamada@med.kanazawa-u.ac.jp

2005-04-29

358

Characteristics of the aluminum alloy sheets for forming and application examples  

NASA Astrophysics Data System (ADS)

In this paper, the characteristics and application examples of aluminum alloy sheets developed for automotive parts by Sumitomo Light Metal are described. For the automotive closure panels (ex., hood, back-door), an Al-Mg-Si alloy sheet having an excellent hemming performance was developed. The cause of the occurrence and the propagation of cracks by bending were considered to be the combined effect of the shear bands formed across several crystal grains and the micro-voids formed around the second phase particles. By reducing the shear band formation during bending by controlling the crystallographic texture, the Al-Mg-Si alloy sheets showed an excellent hemming performance. For the automotive outer panels (ex., roof, fender, trunk-lid), an Al-Mg alloy sheet, which has both a good hot blow formability and excellent surface appearance after hot blow forming was developed, and hot blow forming technology was put to practical use using this developed Al-Mg alloy sheet. For automotive heat insulators, a high ductile Al-Fe alloy sheet was developed. The heat insulator, which integrated several panels, was put into practical use using this developed Al-Fe alloy sheet. The textured sheet was often used as a heat insulator in order to reduce the thickness of the aluminum alloy sheet and obtain good press formability. The new textured sheet, which has both high rigidity and good press formability for heat insulators, was developed by FE analysis.

Uema, Naoyuki; Asano, Mineo

2013-12-01

359

Beta Estimate Experiment  

NSDL National Science Digital Library

This resource consists of a Java applet and expository text. The applet simulates a random sample from a beta distribution, and computes standard point estimates of the left and right parameters. The bias and mean square error are also computed.

Siegrist, Kyle

360

Ice sheets and nitrogen  

PubMed Central

Snow and ice play their most important role in the nitrogen cycle as a barrier to land–atmosphere and ocean–atmosphere exchanges that would otherwise occur. The inventory of nitrogen compounds in the polar ice sheets is approximately 260 Tg N, dominated by nitrate in the much larger Antarctic ice sheet. Ice cores help to inform us about the natural variability of the nitrogen cycle at global and regional scale, and about the extent of disturbance in recent decades. Nitrous oxide concentrations have risen about 20 per cent in the last 200 years and are now almost certainly higher than at any time in the last 800 000 years. Nitrate concentrations recorded in Greenland ice rose by a factor of 2–3, particularly between the 1950s and 1980s, reflecting a major change in NOx emissions reaching the background atmosphere. Increases in ice cores drilled at lower latitudes can be used to validate or constrain regional emission inventories. Background ammonium concentrations in Greenland ice show no significant recent trend, although the record is very noisy, being dominated by spikes of input from biomass burning events. Neither nitrate nor ammonium shows significant recent trends in Antarctica, although their natural variations are of biogeochemical and atmospheric chemical interest. Finally, it has been found that photolysis of nitrate in the snowpack leads to significant re-emissions of NOx that can strongly impact the regional atmosphere in snow-covered areas. PMID:23713125

Wolff, Eric W.

2013-01-01

361

Twisting of sheet metals  

NASA Astrophysics Data System (ADS)

Twisting of metallic sheets is one particular mode of springback that occurs after drawing of elongated parts, i.e. with one dimension much larger than the two others. In this study, a dedicated device for drawing of elongated part with a U-shaped section has been designed on purpose, in order to obtain reproducible data. Very thin metallic sheet, of thickness 0.15 mm, has been used, so that the maximum length of the part is 100 mm. Two different orientations of the part with respect to the tools have been chosen: either aligned with the tools, or purposefully misaligned by 2°. Several samples were drawn for each configuration, leading to the conclusion that almost no twisting occurs in the first case whereas a significant one can be measured for the second one. In a second step, 2D and 3D numerical simulations within the implicit framework for drawing and springback were carried out. A mixed hardening law associated to von Mises yield criterion represents accurately the mechanical behavior of the material. This paper highlights a comparison of numerical predictions with experiments, e.g. the final shape of the part and the twisting parameter.

Pham, C. H.; Thuillier, S.; Manach, P. Y.

2013-12-01

362

Beta-thalassemia  

Microsoft Academic Search

Beta-thalassemias are a group of hereditary blood disorders characterized by anomalies in the synthesis of the beta chains of hemoglobin resulting in variable phenotypes ranging from severe anemia to clinically asymptomatic individuals. The total annual incidence of symptomatic individuals is estimated at 1 in 100,000 throughout the world and 1 in 10,000 people in the European Union. Three main forms

Renzo Galanello; Raffaella Origa

2010-01-01

363

Effects of au plating on small-scale resistance spot welding of thin-sheet nickel  

NASA Astrophysics Data System (ADS)

The effects of Au plating on joint formation and joint strength in small-scale resistance spot welding (SSRSW) of Ni sheets have been investigated using tensile-shear testing, optical microscopy, scanning electron microscopy (SEM), and energy-dispersive X-ray spectroscopy (EDX). The results show that the mechanisms of the joint formation during the welding of Au-plated Ni sheets involve solid-state bonding, brazing, and fusion welding. The comparison between SSRSW of Au-plated Ni and bare Ni sheets and large-scale resistance spot welding (LSRSW) of Zn-coated steels is also discussed.

Tan, W.; Zhou, Y.; Kerr, H. W.

2002-08-01

364

Creation of Prompt and Thin-Sheet Splashing by Varying Surface Roughness or Increasing Air Pressure  

NASA Astrophysics Data System (ADS)

A liquid drop impacting a solid surface may splash either by emitting a thin liquid sheet that subsequently breaks apart or by promptly ejecting droplets from the advancing liquid-solid contact line. Using high-speed imaging, we show that surface roughness and air pressure influence both mechanisms. Roughness inhibits thin-sheet formation even though it also increases prompt splashing at the advancing contact line. If the air pressure is lowered, droplet ejection is suppressed not only during thin-sheet formation but also for prompt splashing.

Latka, Andrzej; Strandburg-Peshkin, Ariana; Driscoll, Michelle M.; Stevens, Cacey S.; Nagel, Sidney R.

2012-08-01

365

Infiltration into inclined fibrous sheets  

Microsoft Academic Search

The flow from line and point sources through an inclined fibrous sheet is studied experimentally and theoretically for wicking from a saturated region and flow from a constant-flux source. Wicking from a saturated line generates a wetted region whose length grows diffusively, linearly or tends to a constant, depending on whether the sheet is horizontal or inclined downwards or upwards.

M. L ANDERYOU; A. C OTTENDEN

2005-01-01

366

IMMUNIZATION COVER SHEET HEALTH SERVICES  

E-print Network

IMMUNIZATION COVER SHEET HEALTH SERVICES 327 HIGH STREET MIDDLETOWN, CT 06459 University Health of adequate immunization against measles, mumps, rubella (MMR) and, for student beginning in the fall term as proof of adequate immunization or the exemption that applies to your situation Send this cover sheet

Royer, Dana

367

Electromechanical Resonators from Graphene Sheets  

Microsoft Academic Search

Nanoelectromechanical systems were fabricated from single- and multilayer graphene sheets by mechanically exfoliating thin sheets from graphite over trenches in silicon oxide. Vibrations with fundamental resonant frequencies in the megahertz range are actuated either optically or electrically and detected optically by interferometry. We demonstrate room-temperature charge sensitivities down to 8 × 10–4 electrons per root hertz. The thinnest resonator consists

J. Scott Bunch; Arend M. Van der Zande; Scott S. Verbridge; Ian W. Frank; David M. Tanenbaum; Jeevak M. Parpia; Harold G. Craighead; Paul L. McEuen

2007-01-01

368

Beta-cardiotoxin: a new three-finger toxin from Ophiophagus hannah (king cobra) venom with beta-blocker activity.  

PubMed

Snake venoms have provided a number of novel ligands with therapeutic potential. We have constructed a partial cDNA library from the mRNA of Ophiophagus hannah (king cobra) venom gland tissue and identified five new genes encoding proteins belonging to the three-finger toxin family of snake venom proteins. We have isolated and characterized one of these beta-sheet containing proteins with a mass of 7012.43 +/- 0.91 Da from the venom. The protein was nonlethal up to a dose of 10 mg/kg when injected intraperitoneally into Swiss albino mice. However, it induces labored breathing and death at a dose of 100 mg/kg. It does not show any hemolytic or anticoagulant activity. It caused a dose-dependent decrease of heart rate in vivo (anesthetized Sprague-Dawley rats) and also ex vivo (Langendorff isolated rat heart). This is in contrast to classical cardiotoxins from snake venom that increase the heart rate in animals. Radioligand displacement studies showed that this protein targets beta-adrenergic receptors with a binding affinity (Ki) of 5.3 and 2.3 microM toward beta1 and beta2 subtypes, respectively, to bring about its effect, and hence, it was named as beta-cardiotoxin. This is the first report of a natural exogenous beta-blocker. PMID:17616557

Rajagopalan, Nandhakishore; Pung, Yuh Fen; Zhu, Yi Zhun; Wong, Peter Tsun Hon; Kumar, Prakash P; Kini, R Manjunatha

2007-11-01

369

Vertically scanned laser sheet microscopy  

NASA Astrophysics Data System (ADS)

Laser sheet microscopy is a widely used imaging technique for imaging the three-dimensional distribution of a fluorescence signal in fixed tissue or small organisms. In laser sheet microscopy, the stripe artifacts caused by high absorption or high scattering structures are very common, greatly affecting image quality. To solve this problem, we report here a two-step procedure which consists of continuously acquiring laser sheet images while vertically displacing the sample, and then using the variational stationary noise remover (VSNR) method to further reduce the remaining stripes. Images from a cleared murine colon acquired with a vertical scan are compared with common stitching procedures demonstrating that vertically scanned light sheet microscopy greatly improves the performance of current light sheet microscopy approaches without the need for complex changes to the imaging setup and allows imaging of elongated samples, extending the field of view in the vertical direction.

Dong, Di; Arranz, Alicia; Zhu, Shouping; Yang, Yujie; Shi, Liangliang; Wang, Jun; Shen, Chen; Tian, Jie; Ripoll, Jorge

2014-10-01

370

Windows Media Player 6.2 Beta  

NSDL National Science Digital Library

With the Windows Media Player 6.2 Beta, Microsoft enters the high quality, compressed digital music fray. Not only does Microsoft's new media player support numerous media formats, but it also has several novel features. It supports the new MS Audio 4.0 format, which claims to provide MP3-quality sound at half the size of MP3 files, and it offers "intelligent streaming," which increases the probability of a smooth streamed media experience. Somewhat less wonderful for the end-user may be its support for the Windows Media Rights Manager, which provides piracy protection and license control. Though similar to RealPlayer, the Windows Media Player 6.2 Beta's interesting and unique features make it worth checking out. The player runs on Win95/98/NT and is free to download and use.

371

Ganges Chasma Sand Sheet  

NASA Technical Reports Server (NTRS)

[figure removed for brevity, see original site]

Our topic for the weeks of April 4 and April 11 is dunes on Mars. We will look at the north polar sand sea and at isolated dune fields at lower latitudes. Sand seas on Earth are often called 'ergs,' an Arabic name for dune field. A sand sea differs from a dune field in two ways: 1) a sand sea has a large regional extent, and 2) the individual dunes are large in size and complex in form.

Today's sand sheet is located in the Ganges Chasma portion of Valles Marineris. As with yesterday's image, note that the dune forms are seen only at the margin and that the interior of the sand sheet at this resolution appears to completely lack dune forms.

Image information: VIS instrument. Latitude -6.4, Longitude 310.7 East (49.3 West). 19 meter/pixel resolution.

Note: this THEMIS visual image has not been radiometrically nor geometrically calibrated for this preliminary release. An empirical correction has been performed to remove instrumental effects. A linear shift has been applied in the cross-track and down-track direction to approximate spacecraft and planetary motion. Fully calibrated and geometrically projected images will be released through the Planetary Data System in accordance with Project policies at a later time.

NASA's Jet Propulsion Laboratory manages the 2001 Mars Odyssey mission for NASA's Office of Space Science, Washington, D.C. The Thermal Emission Imaging System (THEMIS) was developed by Arizona State University, Tempe, in collaboration with Raytheon Santa Barbara Remote Sensing. The THEMIS investigation is led by Dr. Philip Christensen at Arizona State University. Lockheed Martin Astronautics, Denver, is the prime contractor for the Odyssey project, and developed and built the orbiter. Mission operations are conducted jointly from Lockheed Martin and from JPL, a division of the California Institute of Technology in Pasadena.

2005-01-01

372

Identification and characterization of an equilibrium intermediate in the unfolding pathway of an all beta-barrel protein.  

PubMed

The guanidinium hydrochloride (GdnHCl)-induced unfolding of an all beta-sheet protein, the human acidic fibroblast growth factor (hFGF-1), is studied using a variety of biophysical techniques including multidimensional NMR spectroscopy. The unfolding of hFGF-1 in GdnHCl is shown to involve the formation of a stable equilibrium intermediate. Size exclusion chromotagraphy using fast protein liquid chromatography shows that the intermediate accumulates maximally at 0.96 m GdnHCl. 1-Anilinonapthalene 8-sulfonate binding, one-dimensional (1)H NMR, and limited proteolytic digestion experiments suggest that the intermediate has characteristics resembling a molten globule state. Chemical shift perturbation and hydrogen-deuterium exchange monitored by (1)H-(15)N heteronuclear single quantum coherence spectra reveal that profound structural changes in the intermediate state (in 0.96 m GdnHCl) occur in the C-terminal, heparin binding region of the protein molecule. Additionally, results of the stopped flow fluorescence experiments suggest that the kinetic refolding of hFGF-1 proceeds through the accumulation of an intermediate at low concentrations of the denaturant. To our knowledge, the present study is the first report wherein an equilibrium intermediate is characterized in detail in an all beta-barrel protein. PMID:10950956

Samuel, D; Kumar, T K; Srimathi, T; Hsieh, H; Yu, C

2000-11-10

373

Synthesis and thermal stability of polycrystalline new divalent [beta][double prime]- and [beta]-ferrites prepared by ion exchange  

SciTech Connect

Using ion-exchange chemistry the divalent cations Ba[sup 2+], Sr[sup 2+], Ca[sup 2+], Mg[sup 2+], Cd[sup 2+], Pb[sup 2+], Co[sup 2+], Zn[sup 2+], Mn[sup 2+], Fe[sup 2+], and Sn[sup 2+] have been substituted for K[sup +] in polycrystalline CdO-stabilized K-[beta][double prime]-ferrite samples. Ba, Sr, Ca, Mg, Pb, and Cd ion exchange led to the synthesis of new materials, the divalent M[sup 2+]-[beta][double prime]-ferrites (M = Ba, Sr, Ca, Mg) and M[sup 2+]-[beta]-ferrites (M = Cd, Pb), respectively. Co[sup 2+]-diffusion resulted in the formation of a spinel-type Co-ferrite. In the case of Zn, Mn, Fe, and Sn the samples decomposed to [alpha]-Fe[sub 2]O[sub 3]. The thermal stability of the new divalent [beta][double prime]- and [beta]-ferrites was studied either by high-temperature exchange reactions or by air annealing of the exchanged products. Ba- and Sr-[beta][double prime]-ferrites and Pb-[beta]-ferrite converted to M-type hexagonal ferrites with the magnetoplumbite structure, Mg-[beta][double prime]-ferrite decomposed to a spinel-type Mg-ferrite, and Ca-[beta][double prime]-ferrite and Cd-[beta]-ferrite decomposed to [alpha]-Fe[sub 2]O[sub 3]. Composition, lattice parameters, SEM photographs, and magnetic properties of the ferrites formed are given. The magnetic susceptibilities of the divalent [beta][double prime]- or [beta]-ferrites have values between 0.63 and 1.14 [times] 10[sup [minus]4] emu/g[center dot]Oe at room temperature. 41 refs., 1 fig., 4 tabs.

Kalogirou, O. (Univ. of Hamburg (Germany) Aristotle Univ., Thessaloniki (Greece))

1993-02-01

374

Penguin Fact Sheet.  

ERIC Educational Resources Information Center

Presents factual information on penguins using an outline format. Includes descriptions of physical characteristics, behavioral mechanisms, geographical distribution, and physiological processes. Provides separate bibliographies for teachers and students. (ML)

Flotsam and Jetsam: A Newsletter for Massachusetts Marine Educators, 1985

1985-01-01

375

Prediction and Fourier-transform infrared-spectroscopy estimation of the secondary structure of a recombinant beta-glucosidase from Streptomyces sp. (ATCC 11238).  

PubMed Central

The secondary structure of a recombinant beta-glucosidase (EC 3.2.1.21) from Streptomyces sp. (ATCC 11238) has been predicted by computer algorithms and also estimated by Fourier-transform IR spectroscopy. From curve fitting of the deconvoluted IR spectra, the most probable distribution of the secondary-structural classes appears to be about 34% alpha-helix, 30% beta-sheet, 25% reverse turns and 11% non-ordered structures. These data showed a good agreement with data from computer prediction (35% alpha-helix, 23% beta-sheet, 31% reverse turns and 11% non-ordered structures). PMID:8948434

Perez-Pons, J A; Padros, E; Querol, E

1995-01-01

376

The current-voltage relationship in auroral current sheets  

NASA Technical Reports Server (NTRS)

The current-voltage relation within narrow auroral current sheets is examined through the use of high-resolution data from the high altitude Dynamics Explorer 1 satellite. The north-south perpendicular electric field and the east-west magnetic field are shown for three cases in which there are large amplitude, oppositely directed paired electric fields and narrow current sheets. These data are shown to indicate that there is a linear Ohm's law relationship between the current density and the parallel potential drop within the narrow current sheets. This linear relationship had previously been verified for large-scale auroral formations greater than 20 km wide at the ionosphere. The evidence shown here extends our knowledge down to the scale size of discrete auroral arcs.

Weimer, D. R.; Gurnett, D. A.; Goertz, C. K.; Menietti, J. D.; Burch, J. L.

1987-01-01

377

Systematic study of plasma flow during plasma sheet thinnings  

NASA Technical Reports Server (NTRS)

On the basis of a study of Imp 6 measurements of plasma flow, it is concluded that there is no clear indication of a predominance of tailward plasma flow beyond about X = -15 R sub E in the midnight sector of the plasma sheet during the expansive phase of a substorm. In fact, it is shown statistically that sunward plasma flow is more frequently observed in the midnight sector within about 30 R sub E from the earth than in any other direction during plasma sheet thinning at the substorm expansion. This result supports the conclusion that there is no definite evidence for the formation of a reconnection neutral line in the near-earth plasma sheet during most substorms.

Lui, A. T. Y.; Frank, L. A.; Ackerson, K. L.; Meng, C.-I.; Akasofu, S.-I.

1977-01-01

378

The presence of a novel protein in calf serum that recognizes beta amyloid in the formalin-fixed section.  

PubMed Central

Here we report on a monoclonal antibody, H6-33, that labels various beta-amyloid plaques, including diffuse plaques in the formalin-fixed, paraffin-embedded section from the brain affected with Alzheimer's disease (AD), without formic acid pretreatment. H6-33 also labels some neurofibrillary tangles and all kuru plaques in Gerstmann-Sträussler-Scheinker disease. In sharp contrast, H6-33 did not stain beta amyloid in the leptomeningeal vessel. For specific staining, H6-33 required the presence of fetal calf serum and it was necessary for beta amyloid to be formalin fixed. These results suggest that a novel protein in the calf serum, CSX, binds formalin-fixed beta amyloid, followed by H6-33 binding. The detection of beta amyloid by CSX was nullified by formic acid pretreatment of the tissue section. In accordance with this, CSX reacted only with a polymer form of synthetic beta peptide after fixation, but not with native beta-protein or beta-peptide monomer. These observations strongly suggest that 1) meningovascular beta amyloid should have a beta-pleated sheet structure somewhat dissimilar to that of beta-amyloid cores; and 2) most, if not all, of beta-protein immunoreactivities of diffuse plaques in AD sections are presumably derived from small amounts of amyloid fibrils scattered in the normal-looking neurohil. Images Figure 1 Figure 2 Figure 3 Figure 4 Figure 5 PMID:1698030

Kanemaru, K.; Hasegawa, M.; Shimada, H.; Ihara, Y.

1990-01-01

379

Magnetic Reconnection in the Solar Wind at Current Sheets Associated with Extremely Small Field Shear Angles  

NASA Astrophysics Data System (ADS)

Using Wind 3-s plasma and magnetic field data, we have identified three reconnection exhausts within a large magnetic flux rope embedded within an interplanetary coronal mass ejection in the solar wind on 19 October 1998. These exhausts were associated with current sheets having local field shear angles ranging from 4.1 to 9.3 degrees, the smallest field shear angles (strongest guide fields) yet associated with identified reconnection exhausts in a space plasma. They were observed in plasma characterized by extremely low (<0.01) proton beta and very high (281 - 383 km/s) Alfvén speed. The very low external plasma beta in these events minimized the effect of diamagnetic drift of the X-line and thus allowed reconnection to occur in a sustained fashion. And, the very high external Alfvén speed translated into sufficiently fast (> 10 km/s) exhaust jets that could be adequately resolved by the Wind 3DP plasma experiment. Thin, very small field shear-angle current sheets are common in the solar wind, but typically are not associated with particularly low plasma beta or particularly high Alfvén speeds. On the other hand, small field shear angle current sheets must also be dominant in topologically complex environments such as the solar corona where the plasma beta is often less than 0.01 and the Alfvén speed is high. Our observations thus suggest that reconnection at thin, low field shear angle current sheets should commonly occur in the corona, and lend some credence to models that suggest that reconnection at low field shear angle current sheets contributes substantially to coronal heating.

Gosling, J. T.; Phan, T. D.

2012-12-01

380

Digitalis purpurea P5 beta R2, encoding steroid 5 beta-reductase, is a novel defense-related gene involved in cardenolide biosynthesis.  

PubMed

The stereospecific 5 beta-reduction of progesterone is a required step for cardiac glycoside biosynthesis in foxglove plants. Recently, we have isolated the gene P5 beta R, and here we investigate the function and regulation of P5 beta R2, a new progesterone 5 beta-reductase gene from Digitalis purpurea. P5 beta R2 cDNA was isolated from a D. purpurea cDNA library and further characterized at the biochemical, structural and physiological levels. Like P5 beta R, P5 beta R2 catalyzes the 5 beta-reduction of the Delta(4) double bond of several steroids and is present in all plant organs. Under stress conditions or on treatment with chemical elicitors, P5 beta R expression does not vary, whereas P5 beta R2 is highly responsive. P5 beta R2 expression is regulated by ethylene and hydrogen peroxide. The correlation between P5 beta R2 expression and cardenolide formation demonstrates the key role of this gene in cardenolide biosynthesis, and therefore in the chemical defense of foxglove plants. PMID:19895417

Pérez-Bermúdez, Pedro; García, Aurelio A Moya; Tuñón, Iñaki; Gavidia, Isabel

2010-02-01

381

Global ice-sheet system interlocked by sea level  

SciTech Connect

Denton and Hughes postulated that sea level linked a global ice-sheet system with both terrestrial and grounded marine components during later Quaternary ice ages. Summer temperature changes near Northern Hemisphere melting margins initiated sea-level fluctuations that controlled marine components in both polar hemispheres. It was further proposed that variations of this ice-sheet system amplified and transmitted Milankovitch summer half-year insolation changes between 45 and 75/sup 0/N into global climatic changes. New tests of this hypothesis implicate sea level as a major control of the areal extent of grounded portions of the Antarctic Ice Sheet. But factors other than areal changes of the grounded Antarctic Ice Sheet may have strongly influenced Southern Hemisphere climate and terminated the last ice age simultaneously in both polar hemispheres. Atmospheric carbon dioxide linked to high-latitude oceans is the most likely candidate, but another potential influence was high-frequency climatic oscillations. It is postulated that variations in atmospheric carbon dioxide acted through an Antarctic ice shelf linked to the grounded ice sheet to produce and terminate Southern Hemisphere ice-age climate. It is further postulated that Milankovitch summer insolation combined with a warm-high frequency oscillation caused marked recession of Northern Hemisphere ice-sheet melting margins and the North Atlantic polar front about 14,000 /sup 14/C yr B.P. This permitted renewed formation of North Atlantic Deep Water, which could well have controlled atmospheric carbon dioxide. Combined melting and consequent sea-level rise from the three warming factors initiated irreversible collapse of the interlocked global ice-sheet system, which was at its largest but most vulnerable configuration.

Denton, G.H.; Hughes, T.J.; Karlen, W.

1986-01-01

382

Toolbox Safety Talk Safety Data Sheets (SDS)  

E-print Network

to as "Material Safety Data Sheets" (MSDS), communicate important information regarding the hazards of chemicalToolbox Safety Talk Safety Data Sheets (SDS) Environmental Health & Safety Facilities Safety Safety Data Sheets (SDS) for all chemicals produced. "Safety Data Sheets", previously referred

Pawlowski, Wojtek

383

Computing Vortex Sheet Motion Robert Krasny  

E-print Network

Computing Vortex Sheet Motion Robert Krasny Department of Mathematics, University of Michigan, Ann discontinuity. Vortex sheet motion belongs to thefieldof vortex dynamics, one of the main approaches of vortex sheets. Difficulties arise in computing vortex sheet motion due to short wavelength instability

Krasny, Robert

384

Encapsulation of olive leaf extract in beta-cyclodextrin.  

PubMed

Olive leaf extract, rich in oleuropein, formed an inclusion complex with beta-cyclodextrin (beta-CD) upon mixing of the components in aqueous media and subsequent freeze-drying. Inclusion complex formation was confirmed by differential scanning calorimetry (DSC). DSC thermograms indicated that the endothermic peaks of both the olive leaf extract and the physical mixture of olive leaf extract with beta-CD, attributed to the melting of crystals of the extract, were absent in DSC thermogram of inclusion complex. Moreover, DSC studies under oxidative conditions indicated that the complex of olive leaf extract with beta-CD was protected against oxidation, since it remained intact at temperatures where the free olive leaf extract was oxidized. Phase solubility studies afforded A L type diagrams, 1:1 complex stoichiometry, a moderate binding constant ( approximately 300 M (-1)), and an increase of the aqueous solubility by approximately 50%. The formation of the inclusion complex was also confirmed by nuclear magnetic resonance (NMR) studies of beta-CD solutions in the presence of both pure oleuropein and olive leaf extract. The NMR data have established the formation of a 1:1 complex with beta-CD that involves deep insertion of the dihydroxyphenethyl moiety inside the cavity from its secondary side. PMID:17764146

Mourtzinos, Ioannis; Salta, Fotini; Yannakopoulou, Konstantina; Chiou, Antonia; Karathanos, Vaios T

2007-10-01

385

Evidence that. beta. -amyloid protein in Alzheimer's disease is not derived by normal processing  

SciTech Connect

The {beta}-amyloid protein ({beta}/A4), derived from a larger amyloid precursor protein (APP), is the principal component of senile plaques in Alzheimer's disease. APP is an integral membrane glycoprotein and is secreted as a carboxyl-terminal truncated molecule. APP cleavage, which is a membrane-associated event, occurred at a site located within the {beta}/A4 region. This suggests that an intact amyloidogenic {beta}/A4 fragment is not generated during normal APP catabolism. Therefore, an early event in amyloid formation may involve altered APP processing that results in the release and subsequent deposition of intact {beta}/A4.

Sisodia, S.S.; Koo, E.H.; Price, D.L. (Johns Hopkins Univ. School of Medicine, Baltimore, MD (USA)); Beyreuther, K. (Univ. of Heidelberg (West Germany)); Unterbeck, A. (Molecular Therapeutics, West Haven, CT (USA))

1990-04-27

386

Sheet Music From Canada's Past  

NSDL National Science Digital Library

If you love Canadian history and music, you will most find this site most fetching. Created by the Library and Archives Canada, the site brings together intriguing and historically important sheet music from the past 150 years. The collection exists due to the diligence of Helmut Kallmann, a young CBC music librarian who began to collect sheet music in the early 1950s. Today, the archives contain over 20,000 pieces of sheet music, many of which are available online. In addition, the site offers a handful of musical clips that represent pre-1921 Canadian musicality. Visitors can Search Sheet Music to get started or browse the Gallery area. Here visitors can look around via themes, including Colleges, Flowers, Summer Sports, and Winter. It is worth noting that although we reviewed the English site, the archives are also available in French.

387

State Fact Sheets on COPD  

MedlinePLUS

... page: About CDC.gov . Chronic Obstructive Pulmonary Disease (COPD) Share Compartir Fact Sheets The map below depicts quartiles of age-adjusted COPD prevalence (%). Select a state or territory from the ...

388

Measurements and Characterization (Fact Sheet)  

SciTech Connect

Capabilities fact sheet for the National Center for Photovoltaics: Measurements and Characterization that includes scope, core competencies and capabilities, and contact/web information for Analytical Microscopy, Electro-Optical Characterization, Surface Analysis, and Cell and Module Performance.

Not Available

2011-06-01

389

Concentrating Solar Power (Fact Sheet)  

SciTech Connect

Fact sheet describing the overall capabilities of the NREL CSP Program: collector/receiver characterization, advanced reflector and absorber materials, thermal storage and advanced heat transfer fluids, and CSP modeling and analysis.

Not Available

2010-08-01

390

The effect of tachykinin neuropeptides on amyloid {beta} aggregation  

SciTech Connect

Research highlights: {yields} Mechanistic explanation of how tachykinin neuropeptides reduce A{beta}-induced neurotoxicity. {yields} Biophysical studies suggest that tachykinins do not modulate the distribution of A{beta} oligomeric states, but rather may incorporate into the fibrils. {yields} A possible strategy to inhibit toxicity of amyloid fibrils. -- Abstract: A hallmark of Alzheimer's disease is production of amyloid {beta} peptides resulting from aberrant cleavage of the amyloid precursor protein. Amyloid {beta} assembles into fibrils under physiological conditions, through formation of neurotoxic intermediate oligomers. Tachykinin peptides are known to affect amyloid {beta} neurotoxicity in cells. To understand the mechanism of this effect, we studied how tachykinins affect A{beta}(1-40) aggregation in vitro. Fibrils grown in the presence of tachykinins exhibited reduced thioflavin T (ThT) fluorescence, while their morphology, observed in transmission electron microscopy (TEM), did not alter. Cross linking studies revealed that the distribution of low molecular weight species was not affected by tachykinins. Our results suggest that there may be a specific interaction between tachykinins and A{beta}(1-40) that allows them to co-assemble. This effect may explain the reduction of A{beta}(1-40) neurotoxicity in cells treated with tachykinins.

Flashner, Efrat [The Institute of Chemistry, The Hebrew University of Jerusalem, Edmond J. Safra Campus, Givat Ram, Jerusalem 91904 (Israel)] [The Institute of Chemistry, The Hebrew University of Jerusalem, Edmond J. Safra Campus, Givat Ram, Jerusalem 91904 (Israel); Raviv, Uri, E-mail: raviv@chem.ch.huji.ac.il [The Institute of Chemistry, The Hebrew University of Jerusalem, Edmond J. Safra Campus, Givat Ram, Jerusalem 91904 (Israel)] [The Institute of Chemistry, The Hebrew University of Jerusalem, Edmond J. Safra Campus, Givat Ram, Jerusalem 91904 (Israel); Friedler, Assaf, E-mail: assaf@chem.ch.huji.ac.il [The Institute of Chemistry, The Hebrew University of Jerusalem, Edmond J. Safra Campus, Givat Ram, Jerusalem 91904 (Israel)] [The Institute of Chemistry, The Hebrew University of Jerusalem, Edmond J. Safra Campus, Givat Ram, Jerusalem 91904 (Israel)

2011-04-01

391

Energy information sheets, September 1996  

SciTech Connect

The National Energy Information Center (NEIC), as part of its mission, provides energy information and referral assistance to Federal, State, and local governments, the academic community, business and industrial organizations, and the public. The Energy Information Sheets was developed to provide general information on various aspects of fuel production, prices, consumption, and capability. Additional information on related subject matter can be found in other Energy Information Administration (EIA) publications as referenced at the end of each sheet.

NONE

1996-09-01

392

Energy information sheets, July 1998  

SciTech Connect

The National Energy Information Center (NEIC), as part of its mission, provides energy information and referral assistance to Federal, State, and local governments, the academic community, business and industrial organizations, and the public. The Energy Information Sheets was developed to provide general information on various aspects of fuel production, prices, consumption, and capability. Additional information on related subject matter can be found in other Energy Information Administration (EIA) publications as referenced at the end of each sheet.

NONE

1998-07-01

393

Applied Beta Dosimetry  

SciTech Connect

Measurements of beta and/or nonpenetrating exposure results is complicated and past techniques and capabilities have resulted in significant inaccuracies in recorded results. Current developments have resulted in increased capabilities which make the results more accurate and should result in less total exposure to the work force. Continued development of works in progress should provide equivalent future improvements.

Rich, B.L.

1986-01-01

394

ChemTeacher: Beta Decay  

NSDL National Science Digital Library

ChemTeacher compiles background information, videos, articles, demonstrations, worksheets and activities for high school teachers to use in their classrooms. The Beta Decay page includes resources for teaching students about the discovery and applications of beta decay.

2011-01-01

395

Fuel Cells Fact Sheet  

NSDL National Science Digital Library

This document provides a basic introduction to fuel cells: how they work, the different types of fuel cells (PEM, AFC, PAFC, DMFC, MCFC and SOFC) and the advantages and disadvantages of using fuel cells. Two useful graphic representations of fuel cells are also included. This document may be downloaded in PDF file format.

2012-09-18

396

Horizontal electromagnetic casting of thin metal sheets  

DOEpatents

Thin metal sheets are cast by magnetically suspending molten metal deposited within a ferromagnetic yoke and between AC conducting coils and linearly displacing the magnetically levitated liquid metal while it is being cooled to form a solid metal sheet. Magnetic flux increases as the molten metal sheet moves downward and decreases as the molten metal sheet moves upward to stabilize the sheet and maintain it in equilibrium as it is linearly displaced and solidified by cooling gases. A conducting shield is electrically coupled to the molten metal sheet by means of either metal sheet engaging rollers or brushes on the solidified metal, and by means of an electrode in the vessel containing the molten metal thereby providing a return path for the eddy currents induced in the metal sheet by the AC coil generated magnetic flux. Variation in the geometry of the conducting shield allows the magnetic flux between the metal sheet and the conducting shield to be varied and the thickness in surface quality of the metal sheet to be controlled. Side guards provide lateral containment for the molten metal sheet and stabilize and shape the magnetic field while a leader sheet having electromagnetic characteristics similar to those of the metal sheet is used to start the casting process and precedes the molten metal sheet through the magnet and forms a continuous sheet therewith. The magnet may be either U-shaped with a single racetrack coil or may be rectangular with a pair of facing bedstead coils.

Hull, John R. (Hinsdale, IL); Lari, Robert J. (Aurora, IL); Praeg, Walter F. (Palos Park, IL); Turner, Larry R. (Naperville, IL)

1988-01-01

397

Horizontal electromagnetic casting of thin metal sheets  

DOEpatents

Thin metal sheets are cast by magnetically suspending molten metal deposited within a ferromagnetic yoke and between AC conducting coils and linearly displacing the magnetically levitated liquid metal while it is being cooled to form a solid metal sheet. Magnetic flux increases as the molten metal sheet moves downward and decreases as the molten metal sheet moves upward to stabilize the sheet and maintain it in equilibrium as it is linearly displaced and solidified by cooling gases. A conducting shield is electrically coupled to the molten metal sheet by means of either metal sheet engaging rollers or brushes on the solidified metal, and by means of an electrode in the vessel containing the molten metal thereby providing a return path for the eddy currents induced in the metal sheet by the AC coil generated magnetic flux. Variation in the geometry of the conducting shield allows the magnetic flux between the metal sheet and the conducting shield to be varied and the thickness in surface quality of the metal sheet to be controlled. Side guards provide lateral containment for the molten metal sheet and stabilize and shape the magnetic field while a leader sheet having electromagnetic characteristics similar to those of the metal sheet is used to start the casting process and precedes the molten metal sheet through the magnet and forms a continuous sheet therewith. The magnet may be either U-shaped with a single racetrack coil or may be rectangular with a pair of facing bedstead coils.

Hull, John R. (Hinsdale, IL); Lari, Robert J. (Aurora, IL); Praeg, Walter F. (Palos Park, IL); Turner, Larry R. (Naperville, IL)

1987-01-01

398

Structure-based design of non-natural amino-acid inhibitors of amyloid fibril formation  

SciTech Connect

Many globular and natively disordered proteins can convert into amyloid fibrils. These fibrils are associated with numerous pathologies as well as with normal cellular functions, and frequently form during protein denaturation. Inhibitors of pathological amyloid fibril formation could be useful in the development of therapeutics, provided that the inhibitors were specific enough to avoid interfering with normal processes. Here we show that computer-aided, structure-based design can yield highly specific peptide inhibitors of amyloid formation. Using known atomic structures of segments of amyloid fibrils as templates, we have designed and characterized an all-D-amino-acid inhibitor of the fibril formation of the tau protein associated with Alzheimer's disease, and a non-natural L-amino-acid inhibitor of an amyloid fibril that enhances sexual transmission of human immunodeficiency virus. Our results indicate that peptides from structure-based designs can disrupt the fibril formation of full-length proteins, including those, such as tau protein, that lack fully ordered native structures. Because the inhibiting peptides have been designed on structures of dual-{beta}-sheet 'steric zippers', the successful inhibition of amyloid fibril formation strengthens the hypothesis that amyloid spines contain steric zippers.

Sievers, Stuart A.; Karanicolas, John; Chang, Howard W.; Zhao, Anni; Jiang, Lin; Zirafi, Onofrio; Stevens, Jason T.; Münch, Jan; Baker, David; Eisenberg, David (UCLA); (UWASH); (UL); (Kansas); (Ulm)

2011-09-20

399

Structural consequences of chromophore formation and exploration of conserved lid residues amongst naturally occurring fluorescent proteins  

NASA Astrophysics Data System (ADS)

Computational methods were used to generate the lowest energy conformations of the immature precyclized forms of the 28 naturally occurring GFP-like proteins deposited in the pdb. In all 28 GFP-like proteins, the beta-barrel contracts upon chromophore formation and becomes more rigid. Our prior analysis of over 260 distinct naturally occurring GFP-like proteins revealed that most of the conserved residues are located in the top and bottom of the barrel in the turns between the ?-sheets (Ong et al. 2011) [1]. Structural analyses, molecular dynamics simulations and the Anisotropic Network Model were used to explore the role of these conserved lid residues as possible folding nuclei. Our results are internally consistent and show that the conserved residues in the top and bottom lids undergo relatively less translational movement than other lid residues, and a number of these residues may play an important role as hinges or folding nuclei in the fluorescent proteins.

Zimmer, Matthew H.; Li, Binsen; Shahid, Ramza; Peshkepija, Paola; Zimmer, Marc

2014-01-01

400

THE EFFECTS OF PLASMA BETA AND ANISOTROPY INSTABILITIES ON THE DYNAMICS OF RECONNECTING MAGNETIC FIELDS IN THE HELIOSHEATH  

SciTech Connect

The plasma {beta} (the ratio of the plasma pressure to the magnetic pressure) of a system can have a large effect on its dynamics as high {beta} enhances the effects of pressure anisotropies. We investigate the effects of {beta} in a system of stacked current sheets that break up into magnetic islands due to magnetic reconnection, which is analogous to the compressed heliospheric current sheet in the heliosheath. We find significant differences between systems with low and high initial values of {beta}. At low {beta}, growing magnetic islands are modestly elongated and become round as contraction releases magnetic stress and reduces magnetic energy. At high {beta}, the increase of the parallel pressure in contracting islands causes saturation of modestly elongated islands as island cores approach the marginal firehose condition. Only highly elongated islands reach finite size. The anisotropy within these islands prevents full contraction, leading to a final state of highly elongated islands in which further reconnection is suppressed. The elongation of islands at finite {beta} is further enhanced by reducing the electron-to-ion mass ratio to more realistic values. The results are directly relevant to reconnection in the sectored region of the heliosheath where there is evidence that elongated islands are present, and possibly to other high-{beta} systems such as astrophysical accretion flows and the magnetosphere of Saturn.

Schoeffler, K. M.; Drake, J. F.; Swisdak, M. [Institute for Research in Electronics and Applied Physics, University of Maryland, College Park, MD 20742-3511 (United States)

2011-12-10

401

Toxicological Profile Information Sheet  

NSDL National Science Digital Library

The Agency for Toxic Substances and Disease Registry (ATSDR) is continually assembling toxicological profiles for hazardous substances. This site contains 256 online profiles listed alphabetically by chemical name. Each profile begins with a non-technical public health statement discussing the chemical, its environmental and health effects, and risk of human exposure. A more technical version of this information can also be downloaded in Adobe Acrobat (.pdf) format.

2008-08-28

402

alpha-DNA X: alpha and beta tetrathymidilates covalently linked to oxazolopyridocarbazolium (OPC): comparative stabilization of oligo beta-[dT]:oligo beta-[dA] and oligo alpha-[dT]:oligo beta-[dA] duplexes by the intercalating agent.  

PubMed Central

The influence of the intercalating oxazolopyridocarbazolium (HOPC) on the stabilization of modified oligonucleotides: alpha-T4c5OPC or beta-T4c5OPC associated to beta-oligo (dA) was studied. It appears that the situation is different from what has been observed for the interaction of these modified oligonucleotides with poly (rA). The higher free energy of formation of the alpha-T4c5OPC :beta-oligo(dA), when compared to beta-T4c5OPC, is essentially due to the overall stability added to this system by the intercalator. This enhanced stability comes from a higher number of binding sites of HOPC for the alpha:beta duplex together with a lower van't Hoff energy of formation of the alpha:beta duplex. PMID:2798125

Bazile, D; Gautier, C; Rayner, B; Imbach, J L; Paoletti, C; Paoletti, J

1989-01-01

403

TURBULENT DYNAMICS IN SOLAR FLARE SHEET STRUCTURES MEASURED WITH LOCAL CORRELATION TRACKING  

SciTech Connect

High-resolution observations of the Sun's corona in extreme ultraviolet and soft X-rays have revealed a new world of complexity in the sheet-like structures connecting coronal mass ejections (CMEs) to the post-eruption flare arcades. This article presents initial findings from an exploration of dynamic flows in two flares observed with Hinode/XRT and SDO/AIA. The flows are observed in the hot ({approx}> 10 MK) plasma above the post-eruption arcades and measured with local correlation tracking. The observations demonstrate significant shears in velocity, giving the appearance of vortices and stagnations. Plasma diagnostics indicate that the plasma {beta} exceeds unity in at least one of the studied events, suggesting that the coronal magnetic fields may be significantly affected by the turbulent flows. Although reconnection models of eruptive flares tend to predict a macroscopic current sheet in the region between the CME and the flare arcade, it is not yet clear whether the observed sheet-like structures are identifiable as the current sheets or 'thermal halos' surrounding the current sheets. Regardless, the relationship between the turbulent motions and the embedded magnetic field is likely to be complicated, involving dynamic fluid processes that produce small length scales in the current sheet. Such processes may be crucial for triggering, accelerating, and/or prolonging reconnection in the corona.

McKenzie, D. E., E-mail: mckenzie@physics.montana.edu [Department of Physics, Montana State University, P.O. Box 173840, Bozeman, MT 59717-3840 (United States)

2013-03-20

404

Amyloid fibril formation by a partially structured intermediate state of alpha-chymotrypsin.  

PubMed

Here we investigated the effects of 2,2,2-trifluoroethanol (TFE) on the structure of alpha-chymotrypsin. The protein aggregates maximally in 35% (v/v) TFE. Congo red and thioflavin-T binding experiments suggest that the aggregates induced by TFE have amyloid-like properties, and transmission electron microscopy data show that these aggregates have a fibrilar morphology. Fluorescence, circular dichroism, anilino-8-napthalene sulfonate binding, and Fourier-transformed infrared spectroscopy data suggest that formation of a partially structured intermediate state precedes the onset of the aggregation process. The native beta-barrel structure of alpha-chymotrypsin appears to be disrupted in the partially structured intermediate state in favour of a non-native extended beta-sheet conformation with exposed hydrophobic surfaces. The protein becomes "sticky" under these conditions and aggregates into amyloid-like structures. The data support the hypothesis that amyloid formation involves the ordered self-assembly of partially folded species that are critical soluble precursors of fibrilar aggregates. PMID:15313627

Pallarès, Irantzu; Vendrell, Josep; Avilés, Francesc X; Ventura, Salvador

2004-09-01

405

Thermophilic Beta-Glycosidase  

NASA Technical Reports Server (NTRS)

Report describes identification of thermophilic Beta-glycosidase enzyme from isolate of Sulfolobus solfataricus, sulfur-metabolizing archaebacteria growing aerobically and heterotrophically to relatively high cell yields. Enzyme useful in enzymatic conversion of cellulose to D-glucose and important in recycling of biomass. Used for removal of lactose from milk products. Offers promise as model substance for elucidation of basic principles of structural stabilization of proteins.

Grogan, Dennis W.

1992-01-01

406

Thymosin {beta}4 promotes the migration of endothelial cells without intracellular Ca{sup 2+} elevation  

SciTech Connect

Numerous studies have demonstrated the effects of T{beta}4 on cell migration, proliferation, apoptosis and inflammation after exogenous treatment, but the mechanism by which T{beta}4 functions is still unclear. Previously, we demonstrated that incubation of endothelial cells with T{beta}4 induced synthesis and secretion of various proteins, including plasminogen activator inhibitor type 1 and matrix metaloproteinases. We also showed that T{beta}4 interacts with Ku80, which may operate as a novel receptor for T{beta}4 and mediates its intracellular activity. In this paper, we provide evidence that T{beta}4 induces cellular processes without changes in the intracellular Ca{sup 2+} concentration. External treatment of HUVECs with T{beta}4 and its mutants deprived of the N-terminal tetrapeptide AcSDKP (T{beta}4{sub AcSDKPT/4A}) or the actin-binding sequence KLKKTET (T{beta}4{sub KLKKTET/7A}) resulted in enhanced cell migration and formation of tubular structures in Matrigel. Surprisingly, the increased cell motility caused by T{beta}4 was not associated with the intracellular Ca{sup 2+} elevation monitored with Fluo-4 NW or Fura-2 AM. Therefore, it is unlikely that externally added T{beta}4 induces HUVEC migration via the surface membrane receptors known to generate Ca{sup 2+} influx. Our data confirm the concept that externally added T{beta}4 must be internalized to induce intracellular mechanisms supporting endothelial cell migration.

Selmi, Anna [Department of Molecular and Medical Biophysics, Medical University of Lodz, 92-215 Lodz (Poland)] [Department of Molecular and Medical Biophysics, Medical University of Lodz, 92-215 Lodz (Poland); Malinowski, Mariusz [Institute of Medical Biology, Polish Academy of Sciences, Lodz (Poland)] [Institute of Medical Biology, Polish Academy of Sciences, Lodz (Poland); Brutkowski, Wojciech [Nencki Institute of Experimental Biology, Polish Academy of Sciences, 02-093 Warsaw (Poland)] [Nencki Institute of Experimental Biology, Polish Academy of Sciences, 02-093 Warsaw (Poland); Bednarek, Radoslaw [Department of Molecular and Medical Biophysics, Medical University of Lodz, 92-215 Lodz (Poland)] [Department of Molecular and Medical Biophysics, Medical University of Lodz, 92-215 Lodz (Poland); Cierniewski, Czeslaw S., E-mail: czeslaw.cierniewski@umed.lodz.pl [Department of Molecular and Medical Biophysics, Medical University of Lodz, 92-215 Lodz (Poland); Institute of Medical Biology, Polish Academy of Sciences, Lodz (Poland)

2012-08-15

407

Experimental studies and sheet beam transport for low-voltage, grating TWT amplifiers  

Microsoft Academic Search

Summary form only given, as follows. Spontaneous emission and linear gain measurements for a low-voltage sheet-beam-compatible, grating TWT amplifier are presented. Results of analyses of a sheet beam formation by magnetic quadrupoles from a round beam and staple transport in a periodic cusp magnetic field are also discussed. A round “probe” beam from a 10 kV, 0.25 A Pierce gun

J. E. Scharer; J. H. Booske; J. Joe; M. A. Basten; J. Anderson; K. Wagner

1995-01-01

408

(1,3)-beta-glucans activate both dectin-1 and NLRP3 inflammasome in human macrophages.  

PubMed

beta-Glucans are naturally occurring polysaccharides that are the major cell wall components of fungi. Recognition of beta-glucans is mediated through a membrane-bound pattern recognition receptor called dectin-1, and gene knock-out studies have shown that dectin-1 plays an important role in antifungal immune response in vivo. In this report, we have studied the effect of large particulate (1,3)-beta-glucans, including curdlan, glucan from baker's yeast, paramylon, and zymosan, on inflammatory response in human macrophages. We show that beta-glucans activate the transcription of the proinflammatory cytokine IL-1beta through a dectin-1-dependent pathway in human macrophages. Moreover, dectin-1 receptor associated Syk tyrosine kinase was essential for beta-glucan induced IL-1beta mRNA expression. In contrast to LPS, beta-glucans also strongly activated the secretion of IL-1beta. This beta-glucan triggered IL-1beta release was abolished by cytochalasin D, an inhibitor of phagocytosis, demonstrating that cytosolic recognition of beta-glucans is required for IL-1beta response in human macrophages. RNA interference-mediated gene knockdown experiments demonstrated that cytoplasmic NLRP3 inflammasome is essential for beta-glucan-induced IL-1beta secretion. Moreover, our results suggest that beta-glucan-induced NLRP3 inflammasome activation is dependent on the dectin-1/Syk signaling pathway. Furthermore, our results suggest that the lysosomal cathepsin B protease, the formation of reactive oxygen species, and the efflux of potassium are needed for beta-glucan-induced NLRP3 inflammasome activation. In conclusion, our results show that beta-glucans are recognized by membrane-associated dectin-1 and cytoplasmic NLRP3 inflammasome resulting in IL-1beta gene transcription and IL-1beta secretion in human macrophages, respectively. PMID:20421639

Kankkunen, Päivi; Teirilä, Laura; Rintahaka, Johanna; Alenius, Harri; Wolff, Henrik; Matikainen, Sampsa

2010-06-01

409

Fifty Years Later: The Sequence, Structure and Function of Lacewing Cross-beta Silk  

SciTech Connect

Classic studies of protein structure in the 1950s and 1960s demonstrated that green lacewing egg stalk silk possesses a rare native cross-beta sheet conformation. We have identified and sequenced the silk genes expressed by adult females of a green lacewing species. The two encoded silk proteins are 109 and 67 kDa in size and rich in serine, glycine and alanine. Over 70% of each protein sequence consists of highly repetitive regions with 16-residue periodicity. The repetitive sequences can be fitted to an elegant cross-beta sheet structural model with protein chains folded into regular 8-residue long beta strands. This model is supported by wide-angle X-ray scattering data and tensile testing from both our work and the original papers. We suggest that the silk proteins assemble into stacked beta sheet crystallites bound together by a network of cystine cross-links. This hierarchical structure gives the lacewing silk high lateral stiffness nearly threefold that of silkworm silk, enabling the egg stalks to effectively suspend eggs and protect them from predators.

Weisman, Sarah; Okada, Shoko; Mudie, Stephen T.; Huson, Mickey G.; Trueman, Holly E.; Sriskantha, Alagacone; Haritos, Victoria S.; Sutherland, Tara D.; (CSIRO/MSE); (CSIRO)

2009-12-01

410

Polymeric Beta-Hydroxyalkanoates from Environmental Samples and Bacillus megaterium  

PubMed Central

The procaryotic endogenous storage polymer known as poly-beta-hydroxybutyrate is actually a mixed polymer of short-chain beta-hydroxy fatty acids. A method for the quantitative recovery of this mixed polymer, called poly-beta-hydroxyalkanoate (PHA), with analysis by capillary gas-liquid chromatography, showed the presence of at least 11 short-chain beta-hydroxy acids in polymers extracted from marine sediments. Polymers extracted from Bacillus megaterium monocultures were also a complex mixture of beta-hydroxy acids with chain lengths between four and eight carbons. Lyophilized sediments were extracted in a modified Soxhlet extractor, and the polymer was purified with ethanol and diethyl ether washes. The purified polymer was treated with ethanol-chloroform-hydrochloric acid (8.5:2.5:1) for 4 h at 100°C, a treatment which resulted in the formation of the ethyl esters of the constituent beta-hydroxy acids. Subsequent assay of the products by gas-liquid chromatography indicated excellent reproducibility and sensitivity (detection limit, 100 fmol). Disturbing sediments mechanically or adding natural chelators increased all major PHA components relative to the bacterial biomass. Gardening of sedimentary microbes by Clymenella sp., an annelid worm, induced decreases in PHA, with changes in the relative proportion of component beta-hydroxy acids. The concentration of PHA relative to the bacterial biomass can reflect the recent metabolic status of the microbiota. PMID:16346184

Findlay, Robert H.; White, David C.

1983-01-01

411

Root-growth-inhibiting sheet  

DOEpatents

In accordance with this invention, a porous sheet material is provided at intervals with bodies of a polymer which contain a 2,6-dinitroaniline. The sheet material is made porous to permit free passage of water. It may be either a perforated sheet or a woven or non-woven textile material. A particularly desirable embodiment is a non-woven fabric of non-biodegradable material. This type of material is known as a geotextile'' and is used for weed control, prevention of erosion on slopes, and other landscaping purposes. In order to obtain a root repelling property, a dinitroaniline is blended with a polymer which is attached to the geotextile or other porous material.

Burton, F.G.; Cataldo, D.A.; Cline, J.F.; Skiens, W.E.; Van Voris, P.

1993-01-26

412

Root-growth-inhibiting sheet  

DOEpatents

In accordance with this invention, a porous sheet material is provided at intervals with bodies of a polymer which contain a 2,6-dinitroaniline. The sheet material is made porous to permit free passage of water. It may be either a perforated sheet or a woven or non-woven textile material. A particularly desirable embodiment is a non-woven fabric of non-biodegradable material. This type of material is known as a "geotextile" and is used for weed control, prevention of erosion on slopes, and other landscaping purposes. In order to obtain a root repelling property, a dinitroaniline is blended with a polymer which is attached to the geotextile or other porous material.

Burton, Frederick G. (Stansbury Park, UT); Cataldo, Dominic A. (Kennewick, WA); Cline, John F. (Prosser, WA); Skiens, W. Eugene (Wilsonville, OR); Van Voris, Peter (Richland, WA)

1993-01-01

413

Adhesion Transition of Flexible Sheets  

E-print Network

Intermolecular forces are known to precipitate adhesion events between solid bodies. Inspired by a macro-scale experiment showing the hysteretic adhesion of a piece of flexible tape over a plastic substrate, we develop here a model of far-field dry adhesion between two flexible sheets interacting via a power-law potential. We show that phase transitions from unadhered to adhered states occur as dictated by a dimensionless bending parameter representing the ratio of interaction strength to bending stiffness. The order of the adhesion transitions, as well as their hysteretic nature, is shown to depend on the form of the interaction potential between the flexible sheets. When three or more sheets interact, additional geometrical considerations determine the hierarchical or sequential nature of the adhesion transitions.

Arthur A. Evans; Eric Lauga

2009-05-31

414

Optimal swimming of a sheet  

NASA Astrophysics Data System (ADS)

Propulsion at microscopic scales is often achieved through propagating traveling waves along hairlike organelles called flagella. Taylor's two-dimensional swimming sheet model is frequently used to provide insight into problems of flagellar propulsion. We derive numerically the large-amplitude wave form of the two-dimensional swimming sheet that yields optimum hydrodynamic efficiency: the ratio of the squared swimming speed to the rate-of-working of the sheet against the fluid. Using the boundary element method, we show that the optimal wave form is a front-back symmetric regularized cusp that is 25% more efficient than the optimal sine wave. This optimal two-dimensional shape is smooth, qualitatively different from the kinked form of Lighthill's optimal three-dimensional flagellum, not predicted by small-amplitude theory, and different from the smooth circular-arc-like shape of active elastic filaments.

Montenegro-Johnson, Thomas D.; Lauga, Eric

2014-06-01

415

Modulation of beta-amyloid aggregation by engineering the sequence connecting beta-strand forming domains.  

PubMed

Aggregation of beta-amyloid (A?) into oligomers and fibrils is associated with the pathology of Alzheimer's disease. The major structural characteristics of A? fibrils include the presence of ? sheet-loop-? sheet conformations. Several lines of study suggested a potentially important role of the A? loop forming sequence (referred to as the A? linker region) in A? aggregation. Effects of mutations in several charged residues within the A? linker region on aggregation have been extensively studied. However, little is known about oligomerization effects of sequence variation in other residues within the A? linker region. Moreover, modulation effects of the A? linker mutants on A? aggregation have yet to be characterized. Here, we created and characterized A? linker variants containing sequences preferentially found in specific ? turn conformations. Our results indicate that a propensity to form oligomers may be changed by local sequence variation in the A? linker region without mutating the charged residues. Strikingly, one A? linker variant rapidly formed protofibrillar oligomers, which did not convert to fibrillar aggregates in contrast to A? aggregating to fibrils under similar incubation conditions. Moreover, our results suggest that molecular forces critical in oligomerization and fibrillization may differ at least for those involved in the linker region. When co-incubated with A?, some A? linker variants were found to induce accumulation of A? oligomers. Our results suggest that engineering of the A? linker region as described in this paper may represent a novel approach to control A? oligomerization and create A? oligomerization modulators. PMID:22709576

Hu, Yang; Zheng, HeQiu; Su, Baihao; Hernandez, Michael; Kim, Jin Ryoun

2012-10-01

416

ENVIRONMENTAL AND GENETIC VARIATION OF BETA-CONGLYCININ AND GLYCININ CONTENT IN BRAZILIAN SOYBEAN CULTIVARS  

Technology Transfer Automated Retrieval System (TEKTRAN)

Beta-conglycinin (7S) and glycinin (11S) protein fractions have different functional properties related to gel formation, thermal stability and emulsification. Heat and calcium induced coagulum (tofu gel), made from the 11S fraction is harder than that from the 7S fraction. Beta-conglycinin is the...

417

Photovoltaic Reliability and Engineering (Revised) (Fact Sheet)  

SciTech Connect

Capabilities fact sheet for the National Center for Photovoltaics: Photovoltaic Reliability and Engineering. One-sided sheet that includes Scope, Core Competencies and Capabilities, and Contact/Web information.

Not Available

2011-06-01

418

21 CFR 878.4025 - Silicone sheeting.  

... FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN SERVICES (CONTINUED) MEDICAL DEVICES GENERAL AND PLASTIC SURGERY DEVICES Surgical Devices § 878.4025 Silicone sheeting. (a) Identification. Silicone sheeting is...

2014-04-01