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1

Critical Sulfhydryl Switches, Diet, and Cancer Prevention Workshop - Executive Summary  

Cancer.gov

Critical Sulfhydryl Switches, Diet, and Cancer Prevention Workshop Executive Summary OPENING REMARKS Welcome Peter Greenwald, Director, Division of Cancer Prevention John Milner, Nutritional Sciences Research Group, Division of Cancer Prevention Peter Greenwald, M.D., Ph.D., Director, Division of Cancer Prevention (DCP), National Cancer Institute (NCI), National Institutes of Health (NIH), welcomed participants and explained that NCI has been working to enhance the field of basic nutritional science and its relationship to cancer prevention.

2

August 28, 2003: Critical Sulfhydryl Switches, Diet, and Cancer Prevention Workshop - Speakers List  

Cancer.gov

Critical Sulfhydryl Switches, Diet, and Cancer Prevention Workshop Speakers List Elizabeth H. Jeffery, Ph.D., Chair Professor Nutritional Sciences Research Group Division of Cancer Prevention National Cancer Institute National Institutes of Health

3

The critical temperature regions in resistive switching  

Microsoft Academic Search

Critical temperature regions for resistive switching were found based on HfAlO resistive switching memory. From 5 K to 300 K, the resistive switching appears at 60 K, and then a reversible bipolar switching between the two states is observed at above 150 K. It is suggested that the resistive switching characteristics of the binary transitional metal oxides are governed by

L. Chen; P. Zhou; Q. Q. Sun; S. J. Ding; A. Q. Jiang; D. W. Zhang

2011-01-01

4

August 28, 2003: Critical Sulfhydryl Switches, Diet, and Cancer Prevention Workshop - Attendee List  

Cancer.gov

Prevention Workshop Attendee List Elizabeth H. Jeffery, Ph.D., Chair Professor Nutritional Sciences Research Group Division of Cancer Prevention National Cancer Institute National Institutes of Health Bethesda, Maryland Daniel E.

5

Dynamic Critical Switching Curve for Uniform Rotational High Speed Switching in Magnetic Thin Films  

Microsoft Academic Search

Dynamic threshold fields for the idealized uniform rotational switching in thin films are studied on the basis of the numerical solutions of the Landau-Lifshitz-Gilbert equation of motion. Dynamic critical switching curves deduced from the numerical solutions calculated up to the near equilibrium state are quite different from the usual critical switching asteroid. A part of am irreversible rotation region associated

Keiichi Kakuno; Yasuo Gondo

1977-01-01

6

PTIP Promotes Chromatin Changes Critical for Immunoglobulin Class Switch Recombination  

PubMed Central

Programmed genetic rearrangements in lymphocytes require transcription at antigen receptor genes to promote accessibility for initiating double-strand break (DSB) formation critical for DNA recombination and repair. Here, we showed that activated B cells deficient in the PTIP component of the MLL3 (mixed-lineage leukemia 3)–MLL4 complex display impaired trimethylation of histone 3 at lysine 4 (H3K4me3) and transcription initiation of downstream switch regions at the immunoglobulin heavy-chain (Igh) locus, leading to defective immunoglobulin class switching. We also showed that PTIP accumulation at DSBs contributes to class switch recombination (CSR) and genome stability independently of Igh switch transcription. These results demonstrate that PTIP promotes specific chromatin changes that control the accessibility of the Igh locus to CSR and suggest a nonredundant role for the MLL3-MLL4 complex in altering antibody effector function.

Daniel, Jeremy A.; Santos, Margarida Almeida; Wang, Zhibin; Zang, Chongzhi; Schwab, Kristopher R.; Jankovic, Mila; Filsuf, Darius; Chen, Hua-Tang; Gazumyan, Anna; Yamane, Arito; Cho, Young-Wook; Sun, Hong-Wei; Ge, Kai; Peng, Weiqun; Nussenzweig, Michel C.; Casellas, Rafael; Dressler, Gregory R.; Zhao, Keji; Nussenzweig, Andre

2010-01-01

7

Mechanisms of Hepatotoxicity Induced by Sulfhydryl Reagents (Mechanismen van Hepatotoxiciteit Geinduceerd door Sulfhydryl Reagentia).  

National Technical Information Service (NTIS)

In the thesis, the importance of sulfhydryl (SH) groups in hepatocyte function was studied by blocking these groups with various types of sulfhydryl reagents. The organic mercurials PCMB, PCMBS and mersalyl, the sulfhydryl-alkylating reagent NEM and disul...

J. H. Boot

1989-01-01

8

Switching dynamics and critical behavior of standard problem No. 4  

SciTech Connect

We report results for {mu}MAG standard problem No. 4, a 500 nm{times}125 nm{times}3 nm rectangle of material with properties to mimic Permalloy. Switching dynamics are calculated for fields applied instantaneously to an initial s state: Field 1 at 170{degree} and Field 2 at 190{degree} ({minus}170{degree}) from the positive long axis. Reversal in Field 1 proceeds by propagation of end domains toward the sample center. Reversal in Field 2 involves rotation of the end domains in one direction while the center of the particle rotates in the opposite direction, resulting in collapsing 360{degree} walls with complex dynamics on fine length scales. Approaching the static coercivity, H{sub c}, in small field steps, we find that the ring down frequency, f, and susceptibility, {chi}, are in approximate agreement with a single spin model that predicts f{proportional_to}(H{sub c}{minus}H){sup 1/4} and {chi}{proportional_to}(H{sub c}{minus}H){sup {minus}1/2}. We show a correlation between the modes of oscillation that become unstable at the critical field and the switching behavior. {copyright} 2001 American Institute of Physics.

McMichael, R. D.; Donahue, M. J.; Porter, D. G.; Eicke, Jason

2001-06-01

9

Chemical engineering of the critical magnetic field for switching ferroelectricity in multiferroic hexaferrites  

Microsoft Academic Search

Multiferroics wherein the magnetic and ferroelectric order parameters coexist with their large cross-coupling effects have promising application potentials for multifunctional devices. To realize various technical exploitations, not only the capability of switching ferroelectricity with low magnetic field but also the tunability of the critical magnetic field (Bc) for the switching is essential. Herein, we report our discovery of a novel

Sae Hwan Chun; Yisheng Chai; So Young Haam; Deepshikha Jaiswal-Nagar; Dong Hak Nam; Yoon Seok Oh; Ingyu Kim; Beom Sung Lee; Kee Hoon Kim; Kyung Tae Ko; Jae Hoon Park; Jae-Ho Chung

2009-01-01

10

3-Terminal pMTJ reduces critical current and switching time  

NASA Astrophysics Data System (ADS)

To realize the potential of magnetic tunnel junctions (MTJs) for high-density non-volatile memory and non-volatile logic, the critical current to switch the magnetization must be lowered. This paper presents a simulation study of a new structure of perpendicular MTJs (pMTJs) which divides the fixed layer into two coupling parts. We investigate the TMR and the critical current density of this new pMTJ by micromagnetic simulation using OOMMF for various cases. The simulation results show that this new structure pMTJ has lower critical current and shorter switching time compared to the conventional three-layer MTJs.

Cheng, Lanting; Khizroev, Sakhrat; Liang, Ping

2014-05-01

11

Effect of asymmetric leads on critical switching current in magnetic nanopillars  

Microsoft Academic Search

Manschot et al. [Appl. Phys. Lett. 85, 3250 (2004)] predicted that the critical current to switch the magnetizations in a ferromagnetic\\/nonmagnetic\\/ferromagnetic nanopillar from parallel to antiparallel could be reduced by up to a factor of 5 by pairing nonmagnetic leads with different effective resistances (resistivity times spin diffusion length). Comparing switching currents for Co\\/Cu\\/Co nanopillars with Pt and AgSn(5%) leads

H. Kurt; M. Alhajdarwish; W. P. Pratt; J. Bass

2006-01-01

12

Dipolar field effects on the critical current for spin transfer switch of iron and permalloy nanoelements  

NASA Astrophysics Data System (ADS)

We report a theoretical study of dipolar effects on the switching current density of soft ferromagnetic elliptical nanoelements. Relevant changes on the critical current value are found according to the orientation of the magnetization and the spin polarization with the major axis. We show that the critical current density may be reduced by as much as 92% for thin nanoelements magnetized along the minor axis direction, using in-plane spin polarization parallel to the magnetization.

Oliveira, L. L.; Dantas, J. T. S.; Souza, R. M.; Carriço, A. S.; Dantas, Ana L.

2014-05-01

13

Sulfhydryl oxidases: sources, properties, production and applications  

Microsoft Academic Search

The formation of disulfide bonds in proteins and small molecules can greatly affect their functionality. Sulfhydryl oxidases\\u000a (SOXs) are enzymes capable of oxidising the free sulfhydryl groups in proteins and thiol-containing small molecules by using\\u000a molecular oxygen as an electron acceptor. SOXs have been isolated from the intracellular compartments of many organisms, but\\u000a also secreted SOXs are known. These latter

Greta Faccio; Outi Nivala; Kristiina Kruus; Johanna Buchert; Markku Saloheimo

2011-01-01

14

Critical current distribution in spin-transfer-switched magnetic tunnel junctions  

Microsoft Academic Search

The spin transfer switching current distribution within a cell was studied in magnetic-tunnel-junction-based structures having alumina barriers with a resistance-area product (RA) of 10-30 Omega mum2 and a tunneling magnetoresistance of ~20%. These were patterned into current perpendicular to plane configured nanopillars having elliptical cross sections of area ~0.02 mum2. The width of the critical current distribution (sigma\\/average of distribution),

Mahendra Pakala; Yiming Huai; Thierry Valet; Yunfei Ding; Zhitao Diao

2005-01-01

15

Generating disulfides with the quiescin sulfhydryl oxidases  

PubMed Central

The Quiescin-sulfhydryl oxidase (QSOX) family of flavoenzymes catalyzes the direct and facile insertion of disulfide bonds into unfolded reduced proteins with concomitant reduction of oxygen to hydrogen peroxide. This review discusses the chemical mechanism of these enzymes and the involvement of thioredoxin and flavin-binding domains in catalysis. The variability of CxxC motifs in the QSOX family is highlighted and attention is drawn to the steric factors that may promote efficient thiol/disulfide exchange during oxidative protein folding. The varied cellular location of these multi-domain sulfhydryl oxidases is reviewed and potential intracellular and extracellular roles are summarized. Finally, this review identifies important unresolved questions concerning this ancient family of sulfhydryl oxidases.

Heckler, Erin J.; Rancy, Pumtiwitt C.; Kodali, Vamsi K.; Thorpe, Colin

2008-01-01

16

Switch from intravenous to enteral moxifloxacin in critically ill patients: a pilot study.  

PubMed

Critically ill patients generally receive moxifloxacin intravenously to achieve rapid bacterial killing. An early switch from intravenous to enteral moxifloxacin may be considered because of its good oral bioavailability in healthy volunteers. Since bioavailability may be altered in critically ill patients due to pathophysiological changes, this study aimed to investigate whether enteral moxifloxacin is bioequivalent to intravenous moxifloxacin in such patients. Blood samples were obtained from 4 critically ill patients before and at serial time-points after intravenous and enteral administration. In all patients, lower maximum plasma concentration (C(max)) and area under the plasma concentration-time curve during the 24-h observation period (AUC(24h)) values were observed after enteral administration compared to those after intravenous administration. This resulted in lower C(max)/minimum inhibitory concentration (MIC) and AUC(24h)/MIC values, which are 2 indices predicting the antibacterial efficacy of moxifloxacin. Despite the limited number of subjects, we conclude that a switch from intravenous to enteral moxifloxacin is not recommended in these patients, because the 2 administration forms are not bioequivalent. PMID:22804100

de Smet, Julie; Colpaert, Kirsten; de Paepe, Peter; van Bocxlaer, Jan; Decruyenaere, Johan; Boussery, Koen

2012-11-01

17

The hidden switches underlying ROR?-mediated circuits that critically regulate uncontrolled cell proliferation.  

PubMed

Prostaglandin E2 (PGE2) is known to have a key role in the development of colorectal cancer, but previous experiments showed its contrasting (i.e. tumor-promoting or tumor-suppressive) roles depending on experimental conditions. To elucidate the mechanisms underlying such contrasting roles of PGE2 in tumorigenesis, we investigated all the previous experiments and found a new signal transduction pathway mediated by retinoic acid receptor-related orphan receptor (ROR)?, in which PGE2/PKC?-dependent phosphorylation of ROR? attenuates Wnt target gene expression in colon cancer cells. From mathematical simulations combined with biochemical experimentation, we revealed that ROR? induces a biphasic response of Wnt target genes to PGE2 stimulation through a regulatory switch formed by an incoherent feedforward loop, which provides a mechanistic explanation on the contrasting roles of PGE2 observed in previous experiments. More interestingly, we found that ROR? constitutes another regulatory switch formed by coupled positive and negative feedback loops, which regulates the hysteretic response of Wnt signaling and eventually converts a proliferative cellular state into an anti-proliferative state in a very delicate way. Our results indicate that ROR? is the key regulator at the center of these hidden switches that critically regulate cancer cell proliferation and thereby being a promising anti-cancer therapeutic target. PMID:24831657

Shin, Dongkwan; Kim, Ik Soo; Lee, Ji Min; Shin, Sung-Young; Lee, Jong-Hoon; Baek, Sung Hee; Cho, Kwang-Hyun

2014-08-01

18

Effect of interlayer exchange coupling parameter on switching time and critical current density in composite free layer  

NASA Astrophysics Data System (ADS)

We investigated the effect of interlayer exchange coupling parameter on switching current density and switching time in the [CoPt-ML]/Ta/CoFeB composite free layer. The fundamental parameters for the micromagnetic model were extracted from experimental results and ab-initio calculations of the Fe/MgO and Fe/Ta interfaces. We found that the critical current density and switching current decrease with decreasing interlayer exchange coupling. It was observed experimentally that perpendicular magnetic anisotropy (PMA) increases with increasing thickness of Ta insertion due to enhancement of CoFeB/MgO interfacial anisotropy, whereas the interlayer exchange coupling strength decreases. Therefore, our modeling and experimental results indicate that the optimized Ta insertion in the composite layer leads to improved thermal stability via combined interface and bulk anisotropies, lower critical current density, and reduced switching time as compared to the composite layer without Ta insertion.

Singh, Amritpal; Gupta, Subhadra; Kuteifan, Majd; Lubarda, Marko; Lomakin, Vitaliy; Mryasov, Oleg

2014-05-01

19

Techniques for the analysis of cysteine sulfhydryls and oxidative protein folding.  

PubMed

Abstract Significance: Modification of cysteine thiols dramatically affects protein function and stability. Hence, the abilities to quantify specific protein sulfhydryl groups within complex biological samples and map disulfide bond structures are crucial to gaining greater insights into how proteins operate in human health and disease. Recent Advances: Many different molecular probes are now commercially available to label and track cysteine residues at great sensitivity. Coupled with mass spectrometry, stable isotope-labeled sulfhydryl-specific reagents can provide previously unprecedented molecular insights into the dynamics of cysteine modification. Likewise, the combined application of modern mass spectrometers with improved sample preparation techniques and novel data mining algorithms is beginning to routinize the analysis of complex protein disulfide structures. Critical Issues: Proper application of these modern tools and techniques, however, still requires fundamental understanding of sulfhydryl chemistry as well as the assumptions that accompany sample preparation and underlie effective data interpretation. Future Directions: The continued development of tools, technical approaches, and corresponding data processing algorithms will, undoubtedly, facilitate site-specific protein sulfhydryl quantification and disulfide structure analysis from within complex biological mixtures with ever-improving accuracy and sensitivity. Fully routinizing disulfide structure analysis will require an equal but balanced focus on sample preparation and corresponding mass spectral dataset reproducibility. Antioxid. Redox Signal. 21, 511-531. PMID:24383618

Borges, Chad R; Sherma, Nisha D

2014-07-20

20

Sulfhydryl oxidases: sources, properties, production and applications.  

PubMed

The formation of disulfide bonds in proteins and small molecules can greatly affect their functionality. Sulfhydryl oxidases (SOXs) are enzymes capable of oxidising the free sulfhydryl groups in proteins and thiol-containing small molecules by using molecular oxygen as an electron acceptor. SOXs have been isolated from the intracellular compartments of many organisms, but also secreted SOXs are known. These latter enzymes are generally active on small compounds and their physiological role is unknown, whereas the intracellular enzymes prefer proteins as substrates and are involved in protein folding. An increasing number of scientific publications and patent applications on SOXs have been published in recent years. The present mini-review provides an up-to-date summary of SOXs from various families, their production and their actual or suggested applications. The sequence features and domain organisation of the characterised SOXs are reviewed, and special attention is paid to the physicochemical features of the enzymes. A review of patents and patent applications regarding this class of enzymes is also provided. PMID:21732243

Faccio, Greta; Nivala, Outi; Kruus, Kristiina; Buchert, Johanna; Saloheimo, Markku

2011-08-01

21

Multidomain flavin-dependent sulfhydryl oxidases.  

PubMed

Eukaryotic flavin-dependent sulfhydryl oxidases catalyze oxidative protein folding with the generation of disulfides and the reduction of oxygen to hydrogen peroxide. This review deals principally with the Quiescinsulfhydryl oxidases (QSOX) that are found in multiple forms in multicellular organisms and singly in a number of protozoan parasites. QSOX is an ancient fusion of thioredoxin domains and an FAD-binding module, ERV1/ALR. Interdomain disulfide exchanges transmit reducing equivalents from substrates to the flavin cofactor and thence to molecular oxygen. The in vitro substrate specificity of avian QSOX1 and the likely substrates of QSOXs in vivo are discussed. The location of QSOX immunoreactivity and mRNA expression levels in human cells and tissues is reviewed. Generally, there is a marked association of QSOX1 expression with cell types that have a high secretory load of disulfide-containing peptides and proteins. The abundance of sulfhydryl oxidases in the islets of Langerhans suggests that oxidative protein folding may directly contribute to the oxidative stress believed to be a factor in the progression to type II diabetes. Finally, the structure and mechanism of QSOX proteins is compared to their smaller stand-alone cousins: yeast ERV1p and ERV2p, the mammalian augmenter of liver regeneration (ALR), and the viral ALR homologs. PMID:16677076

Coppock, Donald L; Thorpe, Colin

2006-01-01

22

Regulation by sulfhydryl groups of glyceollin accumulation in soybean hypocotyls.  

PubMed

Hypocotyls of 5-d-old etiolated soybean seedlings (Glycine max (L.) Merr. cv. Altona) were treated with (a) dithiothreitol (DTT) or one of the sulfhydryl-binding reagents N-ethylmaleimide (NEM), p-hydroxymercuribenzoate (PMB) und p-chloromercuribenzene sulfonic acid (PMBS), (b) one of the sulfhydryl reagents in combination with DTT, (c) sulfhydryl reagent subsequent to treatment with DTT, and (d) PMBS followed by DTT. Glyceollin was extracted 24 and 48 h after initiation of treatment. The order of decreasing glyceollin-eliciting activity was PMBS?DTT>PMB?NEM. Elicitor effectiveness of sulfhydryl reagents and their reactivity with either L-cysteine or sulfhydryl groups in soybean hypocotyls were not strictly correlated. Mixtures of sulfhydryl reagent and DTT, pretreatment of hypocotyls with DTT and subsequent application of either PMB or PMBS, as well as application of PMBS prior to DTT induced less glyceollin than sulfhydryl reagents alone. In contrast, such pretreatment did not appreciably alter glyceollin accumulation elicited by NEM. The results indicate that glyceollin synthesis can be regulated by interaction with sulfhydryl groups located mainly at the outer surface of the plasmalemma. PMID:24258580

Stössel, P

1984-03-01

23

Modification of membrane sulfhydryl groups in bacteriostatic action of nitrite.  

PubMed Central

The mechanism by which nitrite inhibits outgrowing spores of Bacillus cereus T was examined by using techniques developed earlier for nitrite analogs. The morphological stage of inhibition, cooperativity effects, effect of pH on inhibition, kinetics of protection against iodoacetate incorporation into membrane sulfhydryl groups, and protection against the bacteriocidal effect of carboxymethylation by iodoacetate indicate that nitrite acts as a membrane-directed sulfhydryl agent. The mechanism by which nitrite modifies the chemical reactivity of the sulfhydryl group could be either direct covalent modification or inactivation through communication with another modified membrane component. Profiles of pH effects suggest that the active agent is the protonated form of nitrite. The nitrite concentrations which modify membrane sulfhydryl activity coincide with those which have a bacteriostatic effect. These results are consistent with membrane sulfhydryl modification as a component of the mechanism of nitrite-induced bacteriostasis in this aerobic sporeformer.

Buchman, G W; Hansen, J N

1987-01-01

24

Pulse reshaping in photonic crystal waveguides and microcavities with Kerr nonlinearity: Critical issues for all-optical switching  

NASA Astrophysics Data System (ADS)

We delineate critical issues for “controlling light with light” in photonic crystal (PC) waveguides coupled to Kerr-nonlinear microresonators. These arise from (a) fundamental trade-off between switching speed and switching intensity threshold inherent in high-quality Q -factor cavities and (b) the dynamical nonlinear oscillation of such cavities in response to incident light pulses. Using finite-difference time-domain simulations of electromagnetic pulse propagation, we consider both (i) a nonlinear Fabry-Perot microresonator (embedded within a PC waveguide) exhibiting a narrow transmission resonance and (ii) a nonlinear point defect (side-coupled to a PC waveguide) exhibiting a narrow reflection spectrum. We describe self-induced switching from transmission to reflection induced by pulse intensity tuning as well as control of pulse transmission induced by the secondary, continuous (cw) laser field propagating through the same PC waveguide. For the Fabry-Perot microresonator, a well-defined self-switching threshold is obtained. However, this is accompanied by considerable temporal and spectral distortion of the pulse caused by the oscillatory nonlinear response of the microresonator. When the quality factor of the microresonator is increased, the switching intensity threshold can be lowered but the pulse transit (switching) time and the pulse distortion are increased. For the side-coupled microresonator, a gradual (not sharp) self-switching behavior as a function of incident intensity is obtained. For both the Fabry-Perot and side-coupled nonlinear microresonators, control of pulse transmission can be achieved by means of a secondary cw laser field. The cw power required for switching with realistic Kerr nonlinearities is in excess of 1W/?m2 and may cause optical damage to the semiconducting PC backbone. Both instantaneous and noninstantaneous Kerr-response models are considered. Our results underscore the limitations and trade-offs inherent in the possible control of light with light using Kerr-nonlinear microresonators.

Vujic, Dragan; John, Sajeev

2005-07-01

25

Prevention of acrylonitrile-induced gastrointestinal bleeding by sulfhydryl compounds, atropine and cimetidine  

SciTech Connect

We have recently demonstrated that acrylonitrile (VCN) causes acute gastric hemorrhage and mucosal erosions. The current studies were undertaken to investigate the effects of the sulfhydryl-containing compounds, cysteine and cysteamine, the cholinergic blocking agent atropine and the histamine H2 receptor antagonist, cimetidine on the VCN-induced gastrointestinal (GI) bleeding in rats. Our data shows that pretreatment with L-cysteine, cysteamine, atropine or cimetidine has significantly protected rats against the VCN-induced GI bleeding. A possible mechanism of the VCN-induced GI bleeding may involve the interaction of VCN with critical sulfhydryl groups that, in turn, causes alteration of acetylcholine muscarinic receptors to lead to gastric hemorrhagic lesions and bleeding.

Ghanayem, B.I.; Ahmed, A.E.

1986-07-01

26

[Estimation of sulfhydryl groups by laboratory titrator T-201].  

PubMed

A method for estimating sulfhydryl groups by laboratory titrator T-201 is proposed. It consists in culonometric titration of SH-groups by silver ions. The method is highly sensitive and reproducible. PMID:7378573

Aleksidze, N G; Koshoridze, N I

1980-01-01

27

The Ecdysone receptor controls the post-critical weight switch to nutrition-independent differentiation in Drosophila wing imaginal discs  

PubMed Central

Summary In holometabolous insects, a species-specific size, known as critical weight, needs to be reached for metamorphosis to be initiated in the absence of further nutritional input. Previously, we found that reaching critical weight depends on the insulin-dependent growth of the prothoracic glands (PGs) in Drosophila larvae. Because the PGs produce the molting hormone ecdysone, we hypothesized that ecdysone signaling switches the larva to a nutrition-independent mode of development post-critical weight. Wing discs from pre-critical weight larvae [5 hours after third instar ecdysis (AL3E)] fed on sucrose alone showed suppressed Wingless (WG), Cut (CT) and Senseless (SENS) expression. Post-critical weight, a sucrose-only diet no longer suppressed the expression of these proteins. Feeding larvae that exhibit enhanced insulin signaling in their PGs at 5 hours AL3E on sucrose alone produced wing discs with precocious WG, CT and SENS expression. In addition, knocking down the Ecdysone receptor (EcR) selectively in the discs also promoted premature WG, CUT and SENS expression in the wing discs of sucrose-fed pre-critical weight larvae. EcR is involved in gene activation when ecdysone is present, and gene repression in its absence. Thus, knocking down EcR derepresses genes that are normally repressed by unliganded EcR, thereby allowing wing patterning to progress. In addition, knocking down EcR in the wing discs caused precocious expression of the ecdysone-responsive gene broad. These results suggest that post-critical weight, EcR signaling switches wing discs to a nutrition-independent mode of development via derepression.

Mirth, Christen K.; Truman, James W.; Riddiford, Lynn M.

2009-01-01

28

A flavin-dependent sulfhydryl oxidase in bovine milk.  

PubMed

Both metal and flavin-dependent sulfhydryl oxidases catalyze the net generation of disulfide bonds with the reduction of oxygen to hydrogen peroxide. The first mammalian sulfhydryl oxidase to be described was an iron-dependent enzyme isolated from bovine milk whey (Janolino, V.G., and Swaisgood, H.E. (1975) J. Biol. Chem. 250, 2532-2537). This protein was reported to contain 0.5 atoms of iron per 89 kDa subunit and to be completely inhibited by ethylenediaminetetraacetate (EDTA). However the present work shows that a soluble 62 kDa FAD-linked and EDTA-insensitive sulfhydryl oxidase apparently constitutes the dominant disulfide bond-generating activity in skim milk. Unlike the metalloenzyme, the flavoprotein is not associated tightly with skim milk membranes. Sequencing of the purified bovine enzyme (>70% coverage) showed it to be a member of the Quiescin-sulfhydryl oxidase (QSOX) family. Consistent with its solubility, this bovine QSOX1 paralogue lacks the C-terminal transmembrane span of the long form of these proteins. Bovine milk QSOX1 is highly active toward reduced RNase and with the model substrate dithiothreitol. The significance of these new findings is discussed in relation to the earlier reports of metal-dependent sulfhydryl oxidases. PMID:17944490

Jaje, Jennifer; Wolcott, Holly N; Fadugba, Olajumoke; Cripps, Diane; Yang, Austin J; Mather, Ian H; Thorpe, Colin

2007-11-13

29

A Flavin-dependent Sulfhydryl Oxidase in Bovine Milk†  

PubMed Central

Both metal and flavin-dependent sulfhydryl oxidases catalyze the net generation of disulfide bonds with the reduction of oxygen to hydrogen peroxide. The first mammalian sulfhydryl oxidase to be described was an iron-dependent enzyme isolated from bovine milk whey. This protein was reported to contain 0.5 atoms of iron per 89 kDa subunit and to be completely inhibited by ethylenediaminetetraacetate (EDTA). However the present work shows that a soluble 62 kDa FAD-linked and EDTA-insensitive sulfhydryl oxidase apparently constitutes the dominant disulfide bond-generating activity in skim milk. Unlike the metalloenzyme, the flavoprotein is not associated tightly with skim milk membranes. Sequencing of the purified bovine enzyme (< 70% coverage) showed it to be a member of the Quiescin-sulfhydryl oxidase (QSOX) family. Consistent with its solubility, this bovine QSOX1 paralog lacks the C-terminal transmembrane span of the long form of these proteins. Bovine milk QSOX1 is highly active towards reduced RNase and with the model substrate dithiothreitol. The significance of these new findings is discussed in relation to the earlier reports of metal-dependent sulfhydryl oxidases.

Jaje, Jennifer; Wolcott, Holly N.; Fadugba, Olajumoke; Cripps, Diane; Yang, Austin J.; Mather, Ian H.; Thorpe, Colin

2008-01-01

30

Generating disulfides with the Quiescin-sulfhydryl oxidases.  

PubMed

The Quiescin-sulfhydryl oxidase (QSOX) family of flavoenzymes catalyzes the direct and facile insertion of disulfide bonds into unfolded reduced proteins with concomitant reduction of oxygen to hydrogen peroxide. This review discusses the chemical mechanism of these enzymes and the involvement of thioredoxin and flavin-binding domains in catalysis. The variability of CxxC motifs in the QSOX family is highlighted and attention is drawn to the steric factors that may promote efficient thiol/disulfide exchange during oxidative protein folding. The varied cellular location of these multi-domain sulfhydryl oxidases is reviewed and potential intracellular and extracellular roles are summarized. Finally, this review identifies important unresolved questions concerning this ancient family of sulfhydryl oxidases. PMID:17980160

Heckler, Erin J; Rancy, Pumtiwitt C; Kodali, Vamsi K; Thorpe, Colin

2008-04-01

31

Paradoxical effect of reagents for sulfhydryl and disulfide groups on human sperm capacitation and superoxide production  

Microsoft Academic Search

Spermatozoa must undergo capacitation prior to fertilization. In humans, this process appears regulated by oxidoreduction reactions. We investigated the possibility that these reactions involved the sulfhydryl-disulfide pair, which offers a reversible regulation of cellular processes. The effects of reagents targeted for sulfhydryl and disulfide groups on human sperm capacitation, superoxide (O2•?) generation and protein tyrosine phosphorylation were evaluated. The sulfhydryl

Eve de Lamirande; Claude Gagnon

1998-01-01

32

CAT: A Critical-Area-Targeted Test Set Modification Scheme for Reducing Launch Switching Activity in At-Speed Scan Testing  

Microsoft Academic Search

Reducing excessive launch switching activity (LSA) is now mandatory in at-speed scan testing for avoiding test-induced yield loss, and test set modification is preferable for this purpose. However, previous low-LSA test set modification methods may be ineffective since they are not targeted at reducing launch switching activity in the areas around long sensitized paths, which are spatially and temporally critical

K. Enokimoto; Xiaoqing Wen; Yuta Yamato; Kohei Miyase; H. Sone; Seiji Kajihara; M. Aso; Hiroshi Furukawa

2009-01-01

33

Complete Virion Assembly with Scaffolding Proteins Altered in the Ability To Perform a Critical Conformational Switch?  

PubMed Central

In the ?X174 procapsid, 240 external scaffolding proteins form a nonquasiequivalent lattice. To achieve this arrangement, the four structurally unique subunits must undergo position-dependent conformational switches. One switch is mediated by glycine residue 61, which allows a 30° kink to form in ?-helix 3 in two subunits, whereas the helix is straight in the other two subunits. No other amino acid should be able to produce a bend of this magnitude. Accordingly, all substitutions for G61 are nonviable but mutant proteins differ vis-à-vis recessive and dominant phenotypes. As previously reported, amino acid substitutions with side chains larger than valine confer dominant lethal phenotypes. Alone, these mutant proteins appear to have little or no biological activity but rather require the wild-type protein to interact with other structural proteins. Proteins with conservative substitutions for G61, serine and alanine, have now been characterized. Unlike the dominant lethal proteins, these proteins do not require wild-type subunits to interact with other viral proteins and cause assembly defects reminiscent of those conferred by the lethal dominant proteins in concert with wild-type subunits. Although atomic structures suggest that only a glycine residue can provide the proper torsion angle for assembly, mutants that can productively utilize the altered external scaffolding proteins were isolated, and the mutations were mapped to the coat and internal scaffolding proteins. Thus, the ability to isolate strains that could utilize the single mutant D protein species would not have been predicted from past structural analyses.

Cherwa, James E.; Fane, Bentley A.

2009-01-01

34

Free sulfhydryl measurement as an indicator of antibody stability  

Microsoft Academic Search

Monoclonal antibodies are a major subclass of biopharmaceuticals. They are structurally different from other biopharmaceuticals in size and quaternary structure. Here we demonstrate a correlation between chemical stability of antibodies and thermal stability. We show that overall thermal protein stability can be predicted based on the measurement of free sulfhydryl (–SH) content on applying mildly denaturing conditions. We propose that

Eilyn R. Lacy; Margaret Baker; Michael Brigham-Burke

2008-01-01

35

Complete activation of porcine oocytes induced by the sulfhydryl reagent, thimerosal.  

PubMed

Thimerosal (200 microM) triggered Ca2+ oscillations in 56 of 56 mature porcine oocytes. The Ca2+ oscillations were blocked by the sulfhydryl-reducing agent dithiothreitol (DTT), thus supporting the hypothesis that thimerosal acts by oxidizing critical sulfhydryl groups on intracellular Ca2+-release proteins. Thimerosal treatment alone arrested the oocytes in metaphase, probably by oxidizing tubulin sulfhydryl groups and thus destroying the spindle. However, a 10-min exposure to 200 microM thimerosal followed by a 30-min incubation in 8 mM DTT induced complete activation, as 73.8% of the oocytes formed pronuclei. The second polar body was visible in 73.3% (55 of 75) of the activated oocytes. Combined thimerosal/DTT treatment of the oocytes also induced cortical granule exocytosis, as revealed by confocal microscopy, and the subsequent hardening of the zona pellucida. After activation, some oocytes were incubated in vitro, or in vivo in a ligated porcine oviduct, for 6 days. When cultured in vitro, 42.0% (37 of 88) of the oocytes developed to the compact morula or blastocyst stage; the average number of inner cell mass (ICM) and trophectoderm (TE) nuclei in the blastocysts was 8.6 +/- 0.7 and 20.1 +/- 1.3, respectively. Culture in a ligated oviduct resulted in 42.9% development to the compact morula or blastocyst stage, with the blastocysts having a mean number of 12.5 +/- 1.0 ICM and 63.6 +/- 9.2 TE nuclei. PMID:9369179

Macháty, Z; Wang, W H; Day, B N; Prather, R S

1997-11-01

36

Critical roles of Pten in B cell homeostasis and immunoglobulin class switch recombination.  

PubMed

Pten is a tumor suppressor gene mutated in human cancers. We used the Cre-loxP system to generate a B cell-specific mutation of Pten in mice (bPten(flox/flox)mice). bPten(flox/flox) mice showed elevated numbers of B1a cells and increased serum autoantibodies. Among B2 cells in bPten(flox/flox) spleens, numbers of marginal zone B (MZB) cells were significantly increased while those of follicular B (FOB) cells were correspondingly decreased. Pten-deficient B cells hyperproliferated, were resistant to apoptotic stimuli, and showed enhanced migration. The survival kinase PKB/Akt was highly activated in Pten-deficient splenic B cells. In addition, immunoglobulin class switch recombination was defective and induction of activation-induced cytidine deaminase (AID) was impaired. Thus, Pten plays a role in developmental fate determination of B cells and is an indispensable regulator of B cell homeostasis. PMID:12615906

Suzuki, Akira; Kaisho, Tsuneyasu; Ohishi, Minako; Tsukio-Yamaguchi, Manae; Tsubata, Takeshi; Koni, Pandelakis A; Sasaki, Takehiko; Mak, Tak Wah; Nakano, Toru

2003-03-01

37

Complete virion assembly with scaffolding proteins altered in the ability to perform a critical conformational switch.  

PubMed

In the phiX174 procapsid, 240 external scaffolding proteins form a nonquasiequivalent lattice. To achieve this arrangement, the four structurally unique subunits must undergo position-dependent conformational switches. One switch is mediated by glycine residue 61, which allows a 30 degrees kink to form in alpha-helix 3 in two subunits, whereas the helix is straight in the other two subunits. No other amino acid should be able to produce a bend of this magnitude. Accordingly, all substitutions for G61 are nonviable but mutant proteins differ vis-à-vis recessive and dominant phenotypes. As previously reported, amino acid substitutions with side chains larger than valine confer dominant lethal phenotypes. Alone, these mutant proteins appear to have little or no biological activity but rather require the wild-type protein to interact with other structural proteins. Proteins with conservative substitutions for G61, serine and alanine, have now been characterized. Unlike the dominant lethal proteins, these proteins do not require wild-type subunits to interact with other viral proteins and cause assembly defects reminiscent of those conferred by the lethal dominant proteins in concert with wild-type subunits. Although atomic structures suggest that only a glycine residue can provide the proper torsion angle for assembly, mutants that can productively utilize the altered external scaffolding proteins were isolated, and the mutations were mapped to the coat and internal scaffolding proteins. Thus, the ability to isolate strains that could utilize the single mutant D protein species would not have been predicted from past structural analyses. PMID:19474099

Cherwa, James E; Fane, Bentley A

2009-08-01

38

Ascorbic acid-dependent GLUT3 inhibition is a critical step for switching neuronal metabolism.  

PubMed

Intracellular ascorbic acid is able to modulate neuronal glucose utilization between resting and activity periods. We have previously demonstrated that intracellular ascorbic acid inhibits deoxyglucose transport in primary cultures of cortical and hippocampal neurons and in HEK293 cells. The same effect was not seen in astrocytes. Since this observation was valid only for cells expressing glucose transporter 3 (GLUT3), we evaluated the importance of this transporter on the inhibitory effect of ascorbic acid on glucose transport. Intracellular ascorbic acid was able to inhibit (3)H-deoxyglucose transport only in astrocytes expressing GLUT3-EGFP. In C6 glioma cells and primary cultures of cortical neurons, which natively express GLUT3, the same inhibitory effect on (3)H-deoxyglucose transport and fluorescent hexose 2-[N-(7-nitrobenz-2-oxa-1,3-diazol-4-yl)amino]-2-deoxyglucose (2-NBDG) was observed. Finally, knocking down the native expression of GLUT3 in primary cultured neurons and C6 cells using shRNA was sufficient to abolish the ascorbic acid-dependent inhibitory effect on uptake of glucose analogs. Uptake assays using real-time confocal microscopy demonstrated that ascorbic acid effect abrogation on 2-NBDG uptake in cultured neurons. Therefore, ascorbic acid would seem to function as a metabolic switch inhibiting glucose transport in neurons under glutamatergic synaptic activity through direct or indirect inhibition of GLUT3. PMID:21321936

Beltrán, Felipe A; Acuña, Aníbal I; Miró, María Paz; Angulo, Constanza; Concha, Ilona I; Castro, Maite A

2011-12-01

39

G0/G1 switch gene 2 has a critical role in adipocyte differentiation.  

PubMed

Mouse 3T3-L1 preadipocytes differentiate into adipocytes when treated with 3-isobutyl-1-methylxanthine, dexamethasone, and insulin. Although mechanisms of adipogenesis, including transcriptional cascades, are understood, it is still unclear how clonally expanded cells eventually enter the terminal differentiation program. From gene expression profile studies, we identified G0/G1 switch gene 2 (G0s2) as a novel regulator of adipogenesis. The gene was found to be expressed at a higher level in white and brown adipose tissues, and it was induced in 3T3-L1 cells by hormonal treatment. Importantly, G0s2 expression was closely associated with the transition from mitotic clonal expansion to terminal differentiation. Knockdown of G0s2 expression with siRNA inhibited adipocyte differentiation, whereas constitutive overexpression of G0s2 accelerated differentiation of preadipocytes to mature adipocytes. Expression of G0s2 was found to be regulated by peroxisome proliferator-activated receptor ? (PPAR?), which is a well-known regulator of adipocyte differentiation. Absence of either PPAR? or G0s2 expression resulted in apoptotic pathway activation before terminal differentiation. To determine whether G0s2 has a role in vivo, G0s2-knockout mice were generated. The knockout mice were normal in appearance, but they had less adipose mass than wild-type littermates. Mouse embryonic fibroblast cells from G0s2-deficient mice exhibited impaired adipogenesis and contained unusually small intracellular lipid droplets, suggesting that G0s2 has a role in lipid droplet formation. Our studies demonstrate that G0s2 has an important role in adipogenesis and accumulation of triacylglycerol. PMID:24583640

Choi, H; Lee, H; Kim, T-H; Kim, H J; Lee, Y J; Lee, S J; Yu, J H; Kim, D; Kim, K-S; Park, S W; Kim, J-W

2014-07-01

40

Phylogenetics and enzymology of plant quiescin sulfhydryl oxidase.  

PubMed

Quiescin Sulfhydryl Oxidase (QSOX), a catalyst of disulfide bond formation, is found in both plants and animals. Mammalian, avian, and trypanosomal QSOX enzymes have been studied in detail, but plant QSOX has yet to be characterized. Differences between plant and animal QSOXs in domain composition and active-site sequences raise the question of whether these QSOXs function by the same mechanism. We demonstrate that Arabidopsis thaliana QSOX produced in bacteria is folded and functional as a sulfhydryl oxidase but does not exhibit the interdomain electron transfer observed for its animal counterpart. Based on this finding, further exploration into the respective roles of the redox-active sites in plant QSOX and the reason for their concatenation is warranted. PMID:23068612

Limor-Waisberg, Keren; Alon, Assaf; Mehlman, Tevie; Fass, Deborah

2012-11-30

41

Generating disulfides with the Quiescin-sulfhydryl oxidases  

Microsoft Academic Search

The Quiescin-sulfhydryl oxidase (QSOX) family of flavoenzymes catalyzes the direct and facile insertion of disulfide bonds into unfolded reduced proteins with concomitant reduction of oxygen to hydrogen peroxide. This review discusses the chemical mechanism of these enzymes and the involvement of thioredoxin and flavin-binding domains in catalysis. The variability of CxxC motifs in the QSOX family is highlighted and attention

Erin J. Heckler; Pumtiwitt C. Rancy; Vamsi K. Kodali; Colin Thorpe

2008-01-01

42

Chemical modification and reactivity of sulfhydryls and disulfides of rat brain nicotinic-like acetylcholine receptors  

SciTech Connect

Rat central nervous system binding sites for ..cap alpha..-bungarotoxin display considerable biochemical homology with characterized nicotinic acetylcholine receptors from the periphery. They possess a critical disulfide residue(s), which is susceptible to chemical modification and consequent specific alteration in the affinity of the binding site for cholinergic agonists. After reaction with Na/sub 2/S/sub 2/O/sub 5/, as with reaction with dithiothreitol and 5,5'-dithiobis(2-nitrobenzoic acid), the binding site is frozen in a high affinity state toward acetylcholine. After reduction with dithiothreitol and alkylation with a variety of compounds of different molecular configuration or electrical charge, or both, the binding site is frozen in a low affinity state toward acetylcholine. Thus, effects of disulfide/sulfhydryl modification on agonist binding affinity appear to be attributable to the nature of the covalent modification rather than charge or steric alteration at the receptor active site brought about by chemical modification.

Lukas, R.J.; Bennett, E.L.

1980-06-25

43

A critical role for the right fronto-insular cortex in switching between central-executive and default-mode networks.  

PubMed

Cognitively demanding tasks that evoke activation in the brain's central-executive network (CEN) have been consistently shown to evoke decreased activation (deactivation) in the default-mode network (DMN). The neural mechanisms underlying this switch between activation and deactivation of large-scale brain networks remain completely unknown. Here, we use functional magnetic resonance imaging (fMRI) to investigate the mechanisms underlying switching of brain networks in three different experiments. We first examined this switching process in an auditory event segmentation task. We observed significant activation of the CEN and deactivation of the DMN, along with activation of a third network comprising the right fronto-insular cortex (rFIC) and anterior cingulate cortex (ACC), when participants perceived salient auditory event boundaries. Using chronometric techniques and Granger causality analysis, we show that the rFIC-ACC network, and the rFIC, in particular, plays a critical and causal role in switching between the CEN and the DMN. We replicated this causal connectivity pattern in two additional experiments: (i) a visual attention "oddball" task and (ii) a task-free resting state. These results indicate that the rFIC is likely to play a major role in switching between distinct brain networks across task paradigms and stimulus modalities. Our findings have important implications for a unified view of network mechanisms underlying both exogenous and endogenous cognitive control. PMID:18723676

Sridharan, Devarajan; Levitin, Daniel J; Menon, Vinod

2008-08-26

44

Free sulfhydryl measurement as an indicator of antibody stability.  

PubMed

Monoclonal antibodies are a major subclass of biopharmaceuticals. They are structurally different from other biopharmaceuticals in size and quaternary structure. Here we demonstrate a correlation between chemical stability of antibodies and thermal stability. We show that overall thermal protein stability can be predicted based on the measurement of free sulfhydryl (-SH) content on applying mildly denaturing conditions. We propose that this method can be adapted to a high-throughput screening format and used either as an absolute measure of thermal stability or for ranking a panel of possible variants. PMID:18675772

Lacy, Eilyn R; Baker, Margaret; Brigham-Burke, Michael

2008-11-01

45

Critical role of top interface layer on the bipolar resistive switching of Al\\/PEDOT:PSS\\/Al memory device  

Microsoft Academic Search

The role of top interface layer in bipolar resistive switching (BRS) behaviors of Al\\/PEDOT:PSS\\/Al memory devices was investigated via comparison with the Au\\/PEDOT:PSS\\/Al system. The I–V characteristic curves of device with a PEDOT:PSS layer sandwiched between two Al electrodes displayed bipolar resistive switching characteristics, while the device with Au top electrode showed a permanent breakdown in forming process. HRTEM and

Jong Yun Kim; Hu Young Jeong; Jeong Won Kim; Tae Hyun Yoon; Sung-Yool Choi

2011-01-01

46

The Dynamic Disulfide Relay of Quiescin Sulfhydryl Oxidase  

PubMed Central

Protein stability, assembly, localization, and regulation often depend on formation of disulfide cross-links between cysteine side chains. Enzymes known as sulfhydryl oxidases catalyze de novo disulfide formation and initiate intra- and intermolecular dithiol/disulfide relays to deliver the disulfides to substrate proteins1,2. Quiescin sulfhydryl oxidase (QSOX) is a unique, multi-domain disulfide catalyst that is localized primarily to the Golgi apparatus and secreted fluids3 and has attracted attention due to its over-production in tumors4,5. In addition to its physiological importance, QSOX is a mechanistically intriguing enzyme, encompassing functions typically carried out by a series of proteins in other disulfide formation pathways. How disulfides are relayed through the multiple redox-active sites of QSOX and whether there is a functional benefit to concatenating these sites on a single polypeptide are open questions. We determined the first crystal structure of an intact QSOX enzyme, derived from a trypanosome parasite. Notably, sequential sites in the disulfide relay were found more than 40 Å apart in this structure, too far for direct disulfide transfer. To resolve this puzzle, we trapped and crystallized an intermediate in the disulfide hand-off, which showed a 165° domain rotation relative to the original structure, bringing the two active sites within disulfide bonding distance. The comparable structure of a mammalian QSOX enzyme, also presented herein, reveals additional biochemical features that facilitate disulfide transfer in metazoan orthologs. Finally, we quantified the contribution of concatenation to QSOX activity, providing general lessons for the understanding of multi-domain enzymes and the design of novel catalytic relays.

Alon, Assaf; Grossman, Iris; Gat, Yair; Kodali, Vamsi K.; DiMaio, Frank; Mehlman, Tevie; Haran, Gilad; Baker, David; Thorpe, Colin; Fass, Deborah

2012-01-01

47

Micromagnetic simulation of critical current density of spin transfer torque switching in a full-Heusler Co2FeAl0.5Si0.5 alloy spin valve nanopillar  

NASA Astrophysics Data System (ADS)

We investigated the critical current density of spin transfer torque switching in a full-Heusler Co2FeAl0.5Si0.5 alloy spin-valve nanopillar through micromagnetic simulations. The simulations explain the experimental results on the resistance versus external magnetic field and yield good agreement with the measured switching behavior. It is shown that different magnitudes of current densities and directions of external magnetic fields give rise to a shift of resistance hysteretic loop and a variable range of switching. We demonstrated that three critical current densities have different slopes with Gilbert damping constant ? and spin polarization constant ?, indicating that ? and ? have different contributions to the critical current densities. Furthermore, we found that the area of resistance-current hysteretic loop decreases as the nanopillar size decreases. The domain structures indicated that the magnetization reversals have different switching processes between small and large sizes of pillars.

Huang, H. B.; Ma, X. Q.; Liu, Z. H.; Meng, F. Y.; Shi, S. Q.; Chen, L. Q.

2013-03-01

48

The stability of AID and its function in class-switching are critically sensitive to the identity of its nuclear-export sequence.  

PubMed

The carboxyterminal region of activation-induced deaminase (AID) is required for its function in Ig class switch recombination (CSR) and also contains a nuclear-export sequence (NES). Here, based on an extensive fine-structure mutation analysis of the AID NES, as well as from AID chimeras bearing heterologous NESs, we show that while a functional NES is indeed essential for CSR, it is not sufficient. The precise nature of the NES is critical both for AID stabilization and CSR function: minor changes in the NES can perturb stabilization and CSR without jeopardizing nuclear export. The results indicate that the AID NES fulfills a function beyond simply providing a signal for nuclear export and suggest the possibility that the quality of exportin-binding may be critical to the stabilization of AID and its activity in CSR. PMID:19351893

Geisberger, Roland; Rada, Cristina; Neuberger, Michael S

2009-04-21

49

The stability of AID and its function in class-switching are critically sensitive to the identity of its nuclear-export sequence  

PubMed Central

The carboxyterminal region of activation-induced deaminase (AID) is required for its function in Ig class switch recombination (CSR) and also contains a nuclear-export sequence (NES). Here, based on an extensive fine-structure mutation analysis of the AID NES, as well as from AID chimeras bearing heterologous NESs, we show that while a functional NES is indeed essential for CSR, it is not sufficient. The precise nature of the NES is critical both for AID stabilization and CSR function: minor changes in the NES can perturb stabilization and CSR without jeopardizing nuclear export. The results indicate that the AID NES fulfills a function beyond simply providing a signal for nuclear export and suggest the possibility that the quality of exportin-binding may be critical to the stabilization of AID and its activity in CSR.

Geisberger, Roland; Rada, Cristina; Neuberger, Michael S.

2009-01-01

50

Protein Sulfhydryls and Their Role in the Antioxidant Function of Protein S-Thiolation  

Microsoft Academic Search

Protein S-thiolation\\/dethiolation, i.e., the oxidation of protein sulfhydryls to mixed disulfides and their reduction back to sulfhydryls, is an early cellular response to oxidative stress (1-5). This response may be elicited by oxidative phenomena of diverse origins, and the few cases that have been studied extensively give a limited insight into the metabolic roles and the molecular mechanism of the

J. A. Thomas; B. Poland; R. Honzatko

1995-01-01

51

Post-irradiation inactivation, protection, and repair of the sulfhydryl enzyme malate synthase  

Microsoft Academic Search

Summary Malate synthase from baker's yeast, a trimeric sulfhydryl enzyme with one essential sulfhydryl group per subunit, was inactivated by 2 kGy X-irradiation in air-saturated aqueous solution (enzyme concentration: 0.5 mg\\/ml). The radiation induced changes of enzymic activity were registered at about 0, 30, 60 h after irradiation. To elucidate the role of OH·,\\u000a$$O_2^{\\\\bar \\\\cdot } $$\\u000a, and

H. Durchschlag; P. Zipper

1985-01-01

52

Sulfhydryl oxidases: emerging catalysts of protein disulfide bond formation in eukaryotes  

Microsoft Academic Search

Members of the Quiescin-sulfhydryl oxidase (QSOX) family utilize a thioredoxin domain and a small FAD-binding domain homologous to the yeast ERV1p protein to oxidize sulfhydryl groups to disulfides with the reduction of oxygen to hydrogen peroxide. QSOX enzymes are found in all multicellular organisms for which complete genomes exist and in Trypanosoma brucei, but are not found in yeast. The

Colin Thorpe; Karen L Hoober; Sonali Raje; Nicole M Glynn; Joan Burnside; George K Turi; Donald L Coppock

2002-01-01

53

QSOX contains a pseudo-dimer of functional and degenerate sulfhydryl oxidase domains  

Microsoft Academic Search

Quiescin sulfhydryl oxidase (QSOX) catalyzes formation of disulfide bonds between cysteine residues in substrate proteins. Human QSOX1 is a multi-domain, monomeric enzyme containing a module related to the single-domain sulfhydryl oxidases of the Erv family. A partial QSOX1 crystal structure reveals a single-chain pseudo-dimer mimicking the quaternary structure of Erv enzymes. However, one pseudo-dimer “subunit” has lost its cofactor and

Assaf Alon; Erin J. Heckler; Colin Thorpe; Deborah Fass

2010-01-01

54

Inhibition of glutathione synthesis augments lysis of murine tumor cells by sulfhydryl-reactive antineoplastics.  

PubMed Central

GSH plays an important role in cellular defense against a wide variety of toxic electrophiles via the formation of thioether conjugates. We studied the role of GSH in murine tumor cell defense against a novel class of sulfhydryl-reactive antineoplastics, the sesquiterpene lactones (SL). Incubation of P815 mastocytoma cells with any of the four SL tested (vernolepin, helenalin, elephantopin, and eriofertopin) for 1 h resulted in 70-97% depletion of GSH. The importance of GSH resynthesis upon exposure of tumor cells to SL was evaluated with the use of buthionine sulfoximine (BSO), a selective, nontoxic inhibitor of gamma-glutamylcysteine synthetase. Inhibition of GSH synthesis with 0.2 mM BSO markedly enhanced SL-mediated cytolysis of four murine tumor cell lines. A 6- to 34-fold reduction in the amount of SL causing 50% lysis was obtained with BSO. Addition of BSO to P815cells either during or immediately after a 1-h pulse with 10 micrograms/ml of vernolepin increased cytolysis from less than 3% to 78-82%. However, a 1.5-h delay in the addition of BSO to such cells, which allowed for substantial resynthesis of GSH, reduced cytolysis to 30%. Recovery of GSH synthetic capacity after BSO treatment correlated with loss of the synergistic effect of BSO on lysis by vernolepin. BSO did not augment cytolysis by six other antineoplastics (doxorubicin, mitomycin C, vinblastine, cytosine arabinoside, maytansine, and 1,3-bis-[2-chloroethyl]-1-nitrosourea [BCNU]). Of these, only BCNU depleted cellular GSH. Lysis by jatrophone, another GSH-depleting antitumor agent, was increased 21-fold by BSO. Since prolonged incubation with BSO alone results in near-complete GSH depletion without loss of cell viability, SL-mediated cytolysis is probably not a result of GSH depletion. We have demonstrated, however, a critical role for GSH synthetic capacity as a determinant of tumor cell susceptibility to cytolysis by SL. GSH also plays an important role in cellular defense against oxidative injury. Vernolepin, acting as a GSH-depleting agent, markedly sensitized tumor cells to lysis by H2O2 (greater than 6.5-fold increase with 20 micrograms/ml of vernolepin). These findings suggest the possibility that the coordinated deployment of sulfhydryl-reactive antitumor agents, BSO, and oxidative injury might constitute an effective chemotherapeutic strategy.

Arrick, B A; Nathan, C F; Cohn, Z A

1983-01-01

55

Quiescin sulfhydryl oxidase (QSOX) is expressed in the human atheroma core: possible role in apoptosis.  

PubMed

Quiescin sulfhydryl oxidases (QSOXs) catalyze the formation of disulfide bonds in peptides and proteins, and in vertebrates comprise two proteins: QSOX1 and QSOX2. QSOX1, the most extensively studied type, has been implicated in protein folding, production of extracellular matrix, redox regulation, protection from apoptosis, angiogenesis, and cell differentiation. Atherosclerosis is an immunopathological condition in which redox processes, apoptosis, cell differentiation, and matrix secretion/maturation have critical roles. Considering these data, we hypothesized that QSOX1 could be involved in this disease, possibly reducing apoptosis and angiogenesis inside the plaque. QSOX1 labeling in normal human carotid vessels showed predominant expression by endothelium, subendothelium, and adventitia. In atherosclerotic plaques, however, QSOX1 was highly expressed in macrophages at the lipid core. QSOX1 expression was also studied in terms of mRNA and protein in cell types present in plaques under apoptotic or activating stimuli, emulating conditions found in the atherosclerotic process. QSOX1 mRNA increased in endothelial cells and macrophages after the induction of apoptosis. At the protein level, the correlation between apoptosis and QSOX1 expression was not evident in all cell types, possibly because of a rapid secretion of QSOX1. Our results propose for the first time possible roles for QSOX1 in atherosclerosis, being upregulated in endothelial cells and macrophages by apoptosis and cell activation, and possibly controlling these processes, as well as angiogenesis. The quantitative differences in QSOX1 induction may depend on the cell type and also on local factors. PMID:22069028

de Andrade, Claudia R; Stolf, Beatriz S; Debbas, Victor; Rosa, Daniela S; Kalil, Jorge; Coelho, Veronica; Laurindo, Francisco R M

2011-12-01

56

Direct Sulfhydrylation for Methionine Biosynthesis in Leptospira meyeri  

PubMed Central

A gene library of the Leptospira meyeri serovar semaranga strain Veldrat S.173 DNA has been constructed in a mobilizable cosmid with inserts of up to 40 kb. It was demonstrated that a Leptospira DNA fragment carrying metY complemented Escherichia coli strains carrying mutations in metB. The latter gene encodes cystathionine ?-synthase, an enzyme which catalyzes the second step of the methionine biosynthetic pathway. The metY gene is 1,304 bp long and encodes a 443-amino-acid protein with a molecular mass of 45 kDa as determined by sodium dodecyl sulfate-polyacrylamide gel electrophoresis. The deduced amino acid sequence of the Leptospira metY product has a high degree of similarity to those of O-acetylhomoserine sulfhydrylases from Aspergillus nidulans and Saccharomyces cerevisiae. A lower degree of sequence similarity was also found with bacterial cystathionine ?-synthase. The L. meyeri metY gene was overexpressed under the control of the T7 promoter. MetY exhibits an O-acetylhomoserine sulfhydrylase activity. Genetic, enzymatic, and physiological studies reveal that the transsulfuration pathway via cystathionine does not exist in L. meyeri, in contrast to the situation found for fungi and some bacteria. Our results indicate, therefore, that the L. meyeri MetY enzyme is able to perform direct sulfhydrylation for methionine biosynthesis by using O-acetylhomoserine as a substrate.

Belfaiza, J.; Martel, A.; Margarita, D.; Saint Girons, I.

1998-01-01

57

Protein substrate discrimination in the quiescin sulfhydryl oxidase (QSOX) family.  

PubMed

This work explores the substrate specificity of the quiescin sulfhydryl oxidase (QSOX) family of disulfide-generating flavoenzymes to provide enzymological context for investigation of the physiological roles of these facile catalysts of oxidative protein folding. QSOX enzymes are generally unable to form disulfide bonds within well-structured proteins. Use of a temperature-sensitive mutant of ubiquitin-conjugating enzyme 4 (Ubc4') as a model substrate shows that QSOX activity correlates with the unfolding of Ubc4' monitored by circular dichroism. Fusion of Ubc4' with the more stable glutathione-S-transferase domain demonstrates that QSOX can selectively introduce disulfides into the less stable domain of the fusion protein. In terms of intermolecular disulfide bond generation, QSOX is unable to cross-link well-folded globular proteins via their surface thiols. However, the construction of a septuple mutant of RNase A, retaining a single cysteine residue, demonstrates that flexible protein monomers can be directly coupled by the oxidase. Steady- and pre-steady-state kinetic experiments, combined with static fluorescence approaches, indicate that while QSOX is an efficient catalyst for disulfide bond formation between mobile elements of structure, it does not appear to have a significant binding site for unfolded proteins. These aspects of protein substrate discrimination by QSOX family members are rationalized in terms of the stringent steric requirements for disulfide exchange reactions. PMID:22582951

Codding, Jennifer A; Israel, Benjamin A; Thorpe, Colin

2012-05-22

58

Ontogenesis of the sulfhydryl oxidase QSOX expression in rat brain.  

PubMed

The spatiotemporal pattern of distribution of the sulfhydryl oxidase QSOX throughout ontogeny was mapped in rat brain using immunohistochemistry. The enzyme was detected on embryonic day (E) 12 in the dawning mantle layer, but the adult-like pattern was acquired postnatally around day 30 (P30). Throughout ontogenesis, rQSOX was detected in immature and mature neurons, but not in glial cells. The rQSOX developmental pattern can be divided into four periods: on E12 the enzyme was detected in the brainstem, more precisely in motoneurons; later (E16), rQSOX-positive cells were also observed in the forebrain, in the caudoputamen, and the subventricular zone. During late embryogenesis (E18-20), the amount of rQSOX cells considerably increased throughout the brain; they initially appeared in the hippocampus, then in the isocortex. From birth onwards, complex modifications of the rQSOX distribution occurred leading to the adult pattern by P30. Although rQSOX exhibits an overall increasing spatiotemporal pattern of distribution, different expression strategies were distinguished depending on the cell type or brain area. By comparing the rQSOX ontogeny with data on neurogenesis and brain histogenesis, we hypothesize that the enzyme could play a role in guiding migrating cells, their settling, and neuronal maturation, e.g., during outgrowth and synaptogenesis. PMID:15770657

Mairet-Coello, Georges; Tury, Anna; Fellmann, Dominique; Risold, Pierre-Yves; Griffond, Bernadette

2005-04-18

59

Switch of Sensitivity Dynamics Revealed with DyGloSA Toolbox for Dynamical Global Sensitivity Analysis as an Early Warning for System's Critical Transition  

PubMed Central

Systems with bifurcations may experience abrupt irreversible and often unwanted shifts in their performance, called critical transitions. For many systems like climate, economy, ecosystems it is highly desirable to identify indicators serving as early warnings of such regime shifts. Several statistical measures were recently proposed as early warnings of critical transitions including increased variance, autocorrelation and skewness of experimental or model-generated data. The lack of automatized tool for model-based prediction of critical transitions led to designing DyGloSA – a MATLAB toolbox for dynamical global parameter sensitivity analysis (GPSA) of ordinary differential equations models. We suggest that the switch in dynamics of parameter sensitivities revealed by our toolbox is an early warning that a system is approaching a critical transition. We illustrate the efficiency of our toolbox by analyzing several models with bifurcations and predicting the time periods when systems can still avoid going to a critical transition by manipulating certain parameter values, which is not detectable with the existing SA techniques. DyGloSA is based on the SBToolbox2 and contains functions, which compute dynamically the global sensitivity indices of the system by applying four main GPSA methods: eFAST, Sobol's ANOVA, PRCC and WALS. It includes parallelized versions of the functions enabling significant reduction of the computational time (up to 12 times). DyGloSA is freely available as a set of MATLAB scripts at http://bio.uni.lu/systems_biology/software/dyglosa. It requires installation of MATLAB (versions R2008b or later) and the Systems Biology Toolbox2 available at www.sbtoolbox2.org. DyGloSA can be run on Windows and Linux systems, -32 and -64 bits.

Baumuratova, Tatiana; Dobre, Simona; Bastogne, Thierry; Sauter, Thomas

2013-01-01

60

Peroxynitrite inactivation of tyrosine hydroxylase: mediation by sulfhydryl oxidation, not tyrosine nitration.  

PubMed

Tyrosine hydroxylase (TH) is the initial and rate-limiting enzyme in the biosynthesis of dopamine (DA). TH activity is significantly diminished in Parkinson's disease (PD) and by the neurotoxic amphetamines, thereby accentuating the reductions in DA associated with these conditions. Reactive oxygen and nitrogen species have been implicated in the damage to DA neurons seen in PD and in reaction to amphetamine drugs of abuse, so we investigated the hypothesis that peroxynitrite (ONOO(-)) could interfere with TH catalytic function. ONOO(-) caused a concentration-dependent inactivation of TH. The inactivation was associated with tyrosine nitration (maximum of four tyrosine residues nitrated per TH monomer) and extensive sulfhydryl oxidation. Tetranitromethane, which causes sulfhydryl oxidation at pH 6 and 8 but which nitrates tyrosines only at pH 8, inactivated TH equally at either pH. Bicarbonate protected TH from ONOO(-)-induced inactivation and sulfhydryl oxidation but increased significantly tyrosine nitration. PNU-101033 blocked ONOO(-)-induced tyrosine nitration in TH but could not prevent enzyme inactivation or sulfhydryl oxidation. Together, these results indicate that the inactivation of TH by ONOO(-) is mediated by sulfhydryl oxidation. The coincident nitration of tyrosine residues appears to exert little influence over TH catalytic function. PMID:10575026

Kuhn, D M; Aretha, C W; Geddes, T J

1999-12-01

61

Reusable fast opening switch  

DOEpatents

A reusable fast opening switch for transferring energy, in the form of a high power pulse, from an electromagnetic storage device such as an inductor into a load. The switch is efficient, compact, fast and reusable. The switch comprises a ferromagnetic semiconductor which undergoes a fast transition between conductive and insulating states at a critical temperature and which undergoes the transition without a phase change in its crystal structure. A semiconductor such as europium rich europhous oxide, which undergoes a conductor to insulator transition when it is joule heated from its conductor state, can be used to form the switch.

Van Devender, John P. (Albuquerque, NM); Emin, David (Albuquerque, NM)

1986-01-01

62

Reusable fast opening switch  

DOEpatents

A reusable fast opening switch for transferring energy, in the form of a high power pulse, from an electromagnetic storage device such as an inductor into a load. The switch is efficient, compact, fast and reusable. The switch comprises a ferromagnetic semiconductor which undergoes a fast transition between conductive and metallic states at a critical temperature and which undergoes the transition without a phase change in its crystal structure. A semiconductor such as europium rich europhous oxide, which undergoes a conductor to insulator transition when it is joule heated from its conductor state, can be used to form the switch.

Van Devender, J.P.; Emin, D.

1983-12-21

63

THE ROLE OF SULFHYDRYL GROUPS IN THE BLEACHING AND SYNTHESIS OF RHODOPSIN  

PubMed Central

The condensation of retinene1 with opsin to form rhodopsin is optimal at pH about 6, a pH which favors the condensation of retinene1 with sulfhydryl rather than with amino groups. The synthesis of rhodopsin, though unaffected by the less powerful sulfhydryl reagents, monoiodoacetic acid and its amide, is inhibited completely by p-chloromercuribenzoate (PCMB). This inhibition is reversed in part by the addition of glutathione. PCMB does not attack rhodopsin itself, nor does it react with retinene1. Its action in this system is confined to the —SH groups of opsin. Under some conditions the synthesis of rhodopsin is aided by the presence of such a sulfhydryl compound as glutathione, which helps to keep the —SH groups of opsin free and reduced. By means of the amperometric silver titration of Kolthoff and Harris, it is shown that sulfhydryl groups are liberated in the bleaching of rhodopsin, two such groups for each retinene1 molecule that appears. This is true equally of rhodopsin from the retinas of cattle, frogs) and squid. The exposure of new sulfhydryl groups adds an important element to the growing evidence that relates the bleaching of rhodopsin to protein denaturation. The place of sulfhydryl groups in the structure of rhodopsin is still uncertain. They may be concerned directly in binding the chromophore to opsin; or alternatively they may furnish hydrogen atoms for some reductive change by which the chromophore is formed from retinene1. In the amperometric silver titration, the bleaching of rhodopsin yields directly an electrical variation. This phenomenon may have some fundamental connection with the role of rhodopsin in visual excitation, and may provide a model of the excitation process in general.

Wald, George; Brown, Paul K.

1952-01-01

64

Mechanisms of sodium/calcium selectivity in sodium channels probed by cysteine mutagenesis and sulfhydryl modification.  

PubMed Central

A conserved lysine residue in the "P loop" of domain III renders sodium channels highly selective. Conversion of this residue to glutamate, to mimic the homologous position in calcium channels, enables Ca2+ to permeate sodium channels. Because the lysine-to-glutamate mutation converts a positively charged side chain to a negative one, it has been proposed that a positive charge at this position suffices for Na+ selectivity. We tested this idea by converting the critical lysine to cysteine (K1237C) in mu 1 rat skeletal sodium channels expressed in Xenopus oocytes. Selectivity of the mutant channels was then characterized before and after chemical modification to alter side-chain charge. Wild-type channels are highly selective for Na+ over Ca2+ (PCa/PNa < 0.01). The K1237C mutation significantly increases permeability to Ca2+ (PCa/PNa = 0.6) and Sr2+. Analogous mutations in domains I (D400C), II (E755C), and IV (A1529C) did not alter the selectivity for Na+ over Ca2+, nor did any of the domain IV mutations (G1530C, W1531C, and D1532C) that are known to affect monovalent selectivity. Interestingly, the increase in permeability to Ca2+ in K1237C cannot be reversed by simply restoring the positive charge to the side chain by using the sulfhydryl modifying reagent methanethiosulfonate ethylammonium. Single-channel studies confirmed that modified K1237C channels, which exhibit a reduced unitary conductance, remain permeable to Ca2+, with a PCa/PNa of 0.6. We conclude that the chemical identity of the residue at position 1237 is crucial for channel selectivity. Simply rendering the 1237 side chain positive does not suffice to restore selectivity to the channel. Images FIGURE 2 FIGURE 7

Perez-Garcia, M T; Chiamvimonvat, N; Ranjan, R; Balser, J R; Tomaselli, G F; Marban, E

1997-01-01

65

QSOX contains a pseudo-dimer of functional and degenerate sulfhydryl oxidase domains.  

PubMed

Quiescin sulfhydryl oxidase (QSOX) catalyzes formation of disulfide bonds between cysteine residues in substrate proteins. Human QSOX1 is a multi-domain, monomeric enzyme containing a module related to the single-domain sulfhydryl oxidases of the Erv family. A partial QSOX1 crystal structure reveals a single-chain pseudo-dimer mimicking the quaternary structure of Erv enzymes. However, one pseudo-dimer "subunit" has lost its cofactor and catalytic activity. In QSOX evolution, a further concatenation to a member of the protein disulfide isomerase family resulted in an enzyme capable of both disulfide formation and efficient transfer to substrate proteins. PMID:20211621

Alon, Assaf; Heckler, Erin J; Thorpe, Colin; Fass, Deborah

2010-04-16

66

High levels of active quiescin Q6 sulfhydryl oxidase (QSOX) are selectively present in fetal serum.  

PubMed

The participation of thiol-oxidoreductases such as thioredoxin during implantation, embryogenesis and fetal development has been extensively studied. Here, we analyzed the expression of the thioredoxin superfamily enzyme quiescin Q6/sulfhydryl oxidase (QSOX) during development. Results show that QSOX is present in fetal bovine serum (4 months' gestation), but its levels decrease with time after birth (from P1 to P60). We also demonstrate that a sulfhydryl oxidase activity correlates with QSOX expression in such sera, suggesting a putative role in the redox modulation of developmental programs. PMID:16438804

Zanata, S M; Luvizon, A C; Batista, D F; Ikegami, C M; Pedrosa, F O; Souza, E M; Chaves, D F S; Caron, L F; Pelizzari, J V; Laurindo, F R M; Nakao, L S

2005-01-01

67

Long-term inhibitory plasticity in visual cortical layer 4 switches sign at the opening of the critical period  

PubMed Central

Sensory microcircuits are refined by experience during windows of heightened plasticity termed “critical periods” (CPs). In visual cortex the effects of visual deprivation change dramatically at the transition from the pre-CP to the CP, but the cellular plasticity mechanisms that underlie this change are poorly understood. Here we show that plasticity at unitary connections between GABAergic Fast Spiking (FS) cells and Star Pyramidal (SP) neurons within layer 4 flips sign at the transition between the pre-CP and the CP. During the pre-CP, coupling FS firing with SP depolarization induces long-term depression of inhibition at this synapse, whereas the same protocol induces long-term potentiation of inhibition at the opening of the CP. Despite being of opposite sign, both forms of plasticity share expression characteristics—a change in coefficient of variation with no change in paired-pulse ratio—and depend on GABAB receptor signaling. Finally, we show that the reciprocal SP?FS synapse also acquires the ability to undergo long-term potentiation at the pre-CP to CP transition. Thus, at the opening of the CP, there are coordinated changes in plasticity that allow specific patterns of activity within layer 4 to potentiate feedback inhibition by boosting the strength of FS?SP connections.

Lefort, Sandrine; Gray, Annette C.; Turrigiano, Gina G.

2013-01-01

68

Methylmercury artifact formation during solid-phase extraction of water samples using sulfhydryl cotton fiber adsorbent  

Microsoft Academic Search

Preconcentration of methylmercury from dilute water samples by solid-phase extraction on a column packed with sulfhydryl cotton causes methylation of inorganic mercury. The effect is most severe for low concentrations of mercury in deionized water and environmental water samples, such as melted snow or rainwater, with low dissolved organic carbon (DOC) contents, resulting in up to 40% conversion of inorganic

Valbona Celo; Ram V Ananth; Susannah L Scott; David R. S Lean

2004-01-01

69

Abundance of protein-bound sulfhydryl and bisulfide groups at chromosomal nucleolus organizing regions  

Microsoft Academic Search

Silver stainability of the chromosomal nucleolus organizing regions that contain the structural genes for ribosomal RNA can be abolished by proteolytic and oxidative treatments. Histone extraction has no effect. This indicates that reducing groups of non-histone chromosomal proteins are responsible for silver staining. Treatment with fluorescent sulfhydryl and disulfide specific reagents followed by silver staining demonstrates coincidence of silver dots

Charles H. C. M. Buys; Jan Osinga

1980-01-01

70

Effects of sulfhydryl agents on neuromuscular transmission in the presence or absence of cadmium  

Microsoft Academic Search

To test whether thiol groups are involved in neuromuscular transmission and its blockade by cadmium, the influence of sulfhydryl reagents were investigated on neuromuscular transmission, in the presence or absence of cadmium, using isolated mouse phrenic nerve-diaphragm muscles. Cadmium attenuated twitches evoked by indirect shocks but had almost no effect on twitches by direct shocks in the presence of d-tubocurarine

Masakazu Nishimura; Nobuaki Fujise; Osamu Yagasaki

1986-01-01

71

QSOX sulfhydryl oxidase in rat adenohypophysis: localization and regulation by estrogens  

Microsoft Academic Search

The expression of the rat quiescin sulfhydryl oxidase (rQSOX) and its putative regulation by estrogens were investigated in the adenohypophysis. Immunohistochemi- cal observations revealed that rQSOX protein is abun- dantly expressed throughout the anterior lobe of the pituitary, and can be found in almost all the different cell populations. However, as shown by double immunohisto- chemistry, the cells displaying the

A Tury; G Mairet-Coello; F Poncet; C Jacquemard; P Y Risold; D Fellmann; B Griffond

2004-01-01

72

Integrative genomic analysis of CREB defines a critical role for transcription factor networks in mediating the fed/fasted switch in liver  

PubMed Central

Background Metabolic homeostasis in mammals critically depends on the regulation of fasting-induced genes by CREB in the liver. Previous genome-wide analysis has shown that only a small percentage of CREB target genes are induced in response to fasting-associated signaling pathways. The precise molecular mechanisms by which CREB specifically targets these genes in response to alternating hormonal cues remain to be elucidated. Results We performed chromatin immunoprecipitation coupled to high-throughput sequencing of CREB in livers from both fasted and re-fed mice. In order to quantitatively compare the extent of CREB-DNA interactions genome-wide between these two physiological conditions we developed a novel, robust analysis method, termed the ‘single sample independence’ (SSI) test that greatly reduced the number of false-positive peaks. We found that CREB remains constitutively bound to its target genes in the liver regardless of the metabolic state. Integration of the CREB cistrome with expression microarrays of fasted and re-fed mouse livers and ChIP-seq data for additional transcription factors revealed that the gene expression switches between the two metabolic states are associated with co-localization of additional transcription factors at CREB sites. Conclusions Our results support a model in which CREB is constitutively bound to thousands of target genes, and combinatorial interactions between DNA-binding factors are necessary to achieve the specific transcriptional response of the liver to fasting. Furthermore, our genome-wide analysis identifies thousands of novel CREB target genes in liver, and suggests a previously unknown role for CREB in regulating ER stress genes in response to nutrient influx.

2013-01-01

73

Synthesis of sulfhydryl cross-linking poly(ethylene glycol)-peptides and glycopeptides as carriers for gene delivery.  

PubMed

Sulfhydryl cross-linking poly(ethylene glycol) (PEG)-peptides and glycopeptides were prepared and tested for spontaneous polymerization by disulfide bond formation when bound to plasmid DNA, resulting in stable PEG-peptide and glycopeptide DNA condensates. A 20 amino acid synthetic peptide possessing a single sulfhydryl group on the N-terminal cysteine, with two or five internal acetamidomethyl (Acm)-protected cysteine residues, was reacted with either PEG vinyl sulfone or iodoacetamide tyrosinamide triantennary N-glycan. Following RP-HPLC purification, Acm groups were removed by silver tetrafluoroborate to generate sulfhydryl cross-linking PEG-peptides and glycopeptide that were characterized by either (1)H NMR or LC-MS. Sulfhydryl cross-linking PEG-peptides and glycopeptides were found to bind to plasmid DNA and undergo disulfide cross-linking resulting in stable DNA condensates with potential utility for in vivo gene delivery. PMID:11906260

Park, Youmie; Kwok, Kai Y; Boukarim, Chawki; Rice, Kevin G

2002-01-01

74

Changes in Sulfhydryl Groups of Honeybee Glyceraldehyde Phosphate Dehydrogenase Associated with Generation of the Intermediate Plateau in Its Saturation Kinetics.  

National Technical Information Service (NTIS)

Honeybee and rabbit muscle GPDH were studied to obtain information at the chemical level regarding anomolous saturation kinetics of the honeybee enzyme. Results demonstrate that the enzyme's sulfhydryl groups are implicated in the process. Measured by DTN...

W. G. Gelb J. F. Brandts J. H. Nordin

1973-01-01

75

Progress Report on the Use of Sulfhydryl Oxidase to Improve the Storage Stability and Flavor of Milk.  

National Technical Information Service (NTIS)

Progress is reported on a project studying sulfhydryl oxidase for eventual incorporation in an on-stream immobilized enzyme reactor for milk processing to improve storage stability and to eliminate the heated flavor imparted by sterilization. The preparat...

H. E. Swaisgood H. R. Horton

1974-01-01

76

Comparative Behavioral Toxicity of Four Sulfhydryl Radioprotective Compounds in Mice: WR2721, Cysteamine, Diethyldithiocarbamate, and N-Acetylcysteine,  

National Technical Information Service (NTIS)

A number of sulfhydryl compounds have been shown to protect against ionizing radiation. One of the most effective radioprotectors is S-2(3-aminopropylamino)ethylphosphorothioic acid, also known aas ethiofos, gammaphos, or WR-2721 (Davidson, 1980; Giambarr...

M. R. Landauer H. D. Davis J. A. Dominitz J. F. Weiss

1988-01-01

77

The mitochondrial tricarboxylate carrier of silver eel: chemical modification by sulfhydryl reagents.  

PubMed

The tricarboxylate (or citrate) carrier was purified from eel liver mitochondria and functionally reconstituted into liposomes. Incubation of the proteoliposomes with various sulfhydryl reagents led to inhibition of the reconstituted citrate transport activity. Preincubation of the proteoliposomes with reversible SH reagents, such as mercurials and methanethiosulfonates, protected the eel liver tricarboxylate carrier against inactivation by the irreversible reagent N-(1-pyrenyl)maleimide (PM). Citrate and L-malate, two substrates of the tricarboxylate carrier, protected the protein against inactivation by sulfhydryl reagents and decreased the fluorescent PM bound to the purified protein. These results suggest that the eel liver tricarboxylate carrier requires a single population of free cysteine(s) in order to manifest catalytic activity. The reactive cysteine(s) is most probably located at or near the substrate binding site of the carrier protein. PMID:15479612

Capobianco, Loredana; Impagnatiello, Tecla; Ferramosca, Alessandra; Zara, Vincenzo

2004-09-30

78

Agarose gel electrophoretic evidence for domains of nuclear DNA linked with bonds cleavable with sulfhydryl molecules.  

PubMed

Complexes of intact nuclear DNA with proteins undissociable by 2.0 M NaCl and nonionic detergents were analyzed by agarose gel electrophoresis following physical or enzymatic fragmentation. Sulfhydryl molecules converted these DNAs (but not the bacteriophage lambda DNA) into smaller-Mr forms. Following limited restriction endonuclease digestion of complexes with PstI most of the nuclear DNA formed a high-molecular-mass band in the 60-110 kbp range. These 60-110 kbp fragments, releasable from the rest of nuclei by sulfhydryl molecules, have similar sizes to nuclear DNA loops detected by other techniques and may derive from supranucleosomal organizational units in the chromatin complex. PMID:4054300

Ta?, S; De Larco, J; Altiok, E

1985-10-21

79

Enhanced cytosolic delivery of plasmid DNA by a sulfhydryl-activatable listeriolysin O\\/protamine conjugate utilizing cellular reducing potential  

Microsoft Academic Search

Listeriolysin O (LLO), a sulfhydryl-activated pore-forming protein from Listeria monocytogenes, was tested and utilized for promoting plasmid DNA (pDNA) delivery into the cytosol of cells in culture. To render pDNA-complexing capability to LLO, the unique cysteine 484 of LLO was conjugated to polycationic peptide protamine (PN) at a 1:1 molar ratio through a reversible, endosome-labile disulfide bond. The sulfhydryl-oxidized LLO

G Saito; G L Amidon; K-D Lee

2003-01-01

80

Identification and expression of a new splicing variant of FAD-sulfhydryl oxidase in adult rat brain  

Microsoft Academic Search

Flavoproteins of the quiescin\\/sulfhydryl oxidase (QSOX) family catalyze oxidation of peptide and protein thiols to disulfides with the reduction of oxygen to hydrogen peroxide. We report here the molecular cloning of a new putative sulfhydryl oxidase cDNA, rQSOX-L (GenBank Accession no AY623665), from adult rat brain and its expression studied by RT-PCR, Northern and Western blots in rat tissues. DNA-sequencing

Jean Radom; Didier Colin; Franck Thiebault; Mai Dognin-Bergeret; Georges Mairet-Coello; Annick Esnard-Feve; Dominique Fellmann; Michèle Jouvenot

2006-01-01

81

A dominant sulfhydryl-containing protein in the outer membrane of Neisseria gonorrhoeae.  

PubMed Central

By using a method that labels sulfhydryl-containing proteins in situ, we have detected a major outer membrane protein of Neisseria gonorrhoeae at 41 kDa. A protein of this molecular mass has not previously been shown to be a major outer membrane protein in gonococci. In addition, a minor protein rich in cysteinyl residues was detected at 31.5 kDa. Images

Norrod, E P; Browne, S L; Feldweg, A; Leonard, J

1993-01-01

82

Erv1p from Saccharomyces cerevisiae is a FAD-linked sulfhydryl oxidase  

Microsoft Academic Search

The yeast ERV1 gene encodes a small polypeptide of 189 amino acids that is essential for mitochondrial function and for the viability of the cell. In this study we report the enzymatic activity of this protein as a flavin-linked sulfhydryl oxidase catalyzing the formation of disulfide bridges. Deletion of the amino-terminal part of Erv1p shows that the enzyme activity is

Jeung-Eun Lee; Götz Hofhaus; Thomas Lisowsky

2000-01-01

83

Electrochemical Sensor Detecting Free Sulfhydryl Groups: Evaluation of Milk Heat Treatment  

Microsoft Academic Search

We describe a new and rapid method for the evalua- tion of reactive sulfhydryl groups in whey proteins ob- tained after precipitation of casein by acetic acid at pH 4.6. The procedure is based on the use of a wire tungsten electrode operating at ?0.2 V versus saturated calomel electrode in flow injection analysis. The method was applied to raw

M. S. Cosio; S. Mannino; S. Buratti

2000-01-01

84

Erv2p: characterization of the redox behavior of a yeast sulfhydryl oxidase.  

PubMed

The FAD prosthetic group of the ERV/ALR family of sulfhydryl oxidases is housed at the mouth of a 4-helix bundle and communicates with a pair of juxtaposed cysteine residues that form the proximal redox active disulfide. Most of these enzymes have one or more additional distal disulfide redox centers that facilitate the transfer of reducing equivalents from the dithiol substrates of these oxidases to the isoalloxazine ring where the reaction with molecular oxygen occurs. The present study examines yeast Erv2p and compares the redox behavior of this ER luminal protein with the augmenter of liver regeneration, a sulfhydryl oxidase of the mitochondrial intermembrane space, and a larger protein containing the ERV/ALR domain, quiescin-sulfhydryl oxidase (QSOX). Dithionite and photochemical reductions of Erv2p show full reduction of the flavin cofactor after the addition of 4 electrons with a midpoint potential of -200 mV at pH 7.5. A charge-transfer complex between a proximal thiolate and the oxidized flavin is not observed in Erv2p consistent with a distribution of reducing equivalents over the flavin and distal disulfide redox centers. Upon coordination with Zn2+, full reduction of Erv2p requires 6 electrons. Zn2+ also strongly inhibits Erv2p when assayed using tris(2-carboxyethyl)phosphine (TCEP) as the reducing substrate of the oxidase. In contrast to QSOX, Erv2p shows a comparatively low turnover with a range of small thiol substrates, with reduced Escherichia coli thioredoxin and with unfolded proteins. Rapid reaction studies confirm that reduction of the flavin center of Erv2p is rate-limiting during turnover with molecular oxygen. This comparison of the redox properties between members of the ERV/ALR family of sulfhydryl oxidases provides insights into their likely roles in oxidative protein folding. PMID:17298084

Wang, Wenzhong; Winther, Jakob R; Thorpe, Colin

2007-03-20

85

Erv2p: characterization of the redox behavior of a yeast sulfhydryl oxidase†  

PubMed Central

The FAD prosthetic group of the ERV/ALR family of sulfhydryl oxidases is housed at the mouth of a 4-helix bundle and communicates with a pair of juxtaposed cysteine residues that form the proximal redox active disulfide. Most of these enzymes have one or more additional distal disulfide redox centers that facilitate the transfer of reducing equivalents from the dithiol substrates of these oxidases to the isoalloxazine ring where the reaction with molecular oxygen occurs. The present study examines yeast Erv2p and compares the redox behavior of this ER luminal protein with the augmenter of liver regeneration, a sulfhydryl oxidase of the mitochondrial intermembrane space, and a larger protein containing the ERV/ALR domain, quiescin-sulfhydryl oxidase (QSOX). Dithionite and photochemical reductions of Erv2p show full reduction of the flavin cofactor after the addition of 4-electrons with a mid-point potential of -200 mV at pH 7.5. A charge-transfer complex between a proximal thiolate and the oxidized flavin is not observed in Erv2p consistent with a distribution of reducing equivalents over the flavin and distal disulfide redox centers. Upon coordination with Zn2+, full reduction of Erv2p requires 6-electrons. Zn2+ also strongly inhibits Erv2p when assayed using tris(2-carboxyethyl)phosphine (TCEP) as the reducing substrate of the oxidase. In contrast to QSOX, Erv2p shows a comparatively low turnover with a range of small thiol substrates, with reduced Escherichia coli thioredoxin and with unfolded proteins. Rapid reaction studies confirm that reduction of the flavin center of Erv2p is rate-limiting during turnover with molecular oxygen. This comparison of the redox properties between members of the ERV/ALR family of sulfhydryl oxidases provides insights into their likely roles in oxidative protein folding.

Wang, Wenzhong; Winther, Jakob R.; Thorpe, Colin

2008-01-01

86

Tissue distribution of quiescin Q6\\/sulfhydryl oxidase (QSOX) in developing mouse  

Microsoft Academic Search

Quiescin Q6\\/sulfhydryl oxidases (QSOX) are revisited thiol oxidases considered to be involved in the oxidative protein folding,\\u000a cell cycle control and extracellular matrix remodeling. They contain thioredoxin domains and introduce disulfide bonds into\\u000a proteins and peptides, with the concomitant hydrogen peroxide formation, likely altering the redox environment. Since it is\\u000a known that several developmental processes are regulated by the redox

Kelly F. Portes; Cecília M. Ikegami; Joselito Getz; Ana P. Martins; Lucia de Noronha; Luciana F. Zischler; Giseli Klassen; Anamaria A. Camargo; Silvio M. Zanata; Estela Bevilacqua; Lia S. Nakao

2008-01-01

87

The reactivity of sulfhydryl groups of yeast DNA dependent RNA polymerase I.  

PubMed Central

The number of reactive cysteine residues of yeast RNA polymerase I was determined and their function was studied using parachloromercury benzoate (pCMB), dithiobisnitrobenzoate (DTNB) and N-ethyl-maleimide (NEM) as modifying agents. By treatment with DTNB about 45 sulfhydryl groups react in the presence of 8M urea. Under non-denaturing conditions only 20 sulfhydryl groups are reactive with pCMB and DTNB. Both reagents completely inactivate the enzyme and this effect can be reversed by reducing agents. The sedimentation coefficient and the subunit composition are not affected when the enzyme is inactivated. Two of the most reactive sulfhydryl groups are necessary for activity. The modification of these groups is partially protected by substrates and DNA, suggesting that they are involved either in catalysis or in the maintenance of the conformation of the active site. Experiments with 14C-NEM indicate that the most reactive groups are located in subunits of 185,000, 137,000 and 41,000 daltons. Images

Bull, P; Wyneken, U; Valenzuela, P

1982-01-01

88

Structure of a Baculovirus Sulfhydryl Oxidase, a Highly Divergent Member of the Erv Flavoenzyme Family ?  

PubMed Central

Genomes of nucleocytoplasmic large DNA viruses (NCLDVs) encode enzymes that catalyze the formation of disulfide bonds between cysteine amino acid residues in proteins, a function essential for the proper assembly and propagation of NCLDV virions. Recently, a catalyst of disulfide formation was identified in baculoviruses, a group of large double-stranded DNA viruses considered phylogenetically distinct from NCLDVs. The NCLDV and baculovirus disulfide catalysts are flavin adenine dinucleotide (FAD)-binding sulfhydryl oxidases related to the cellular Erv enzyme family, but the baculovirus enzyme, the product of the Ac92 gene in Autographa californica multiple nucleopolyhedrovirus (AcMNPV), is highly divergent at the amino acid sequence level. The crystal structure of the Ac92 protein presented here shows a configuration of the active-site cysteine residues and bound cofactor similar to that observed in other Erv sulfhydryl oxidases. However, Ac92 has a complex quaternary structural arrangement not previously seen in cellular or viral enzymes of this family. This novel assembly comprises a dimer of pseudodimers with a striking 40-degree kink in the interface helix between subunits. The diversification of the Erv sulfhydryl oxidase enzymes in large double-stranded DNA viruses exemplifies the extreme degree to which these viruses can push the boundaries of protein family folds.

Hakim, Motti; Mandelbaum, Amitai; Fass, Deborah

2011-01-01

89

Oxidative Protein Folding and the Quiescin-Sulfhydryl Oxidase Family of Flavoproteins  

PubMed Central

Abstract Flavin-linked sulfhydryl oxidases participate in the net generation of disulfide bonds during oxidative protein folding in the endoplasmic reticulum. Members of the Quiescin-sulfhydryl oxidase (QSOX) family catalyze the facile direct introduction of disulfide bonds into unfolded reduced proteins with the reduction of molecular oxygen to generate hydrogen peroxide. Current progress in dissecting the mechanism of QSOX enzymes is reviewed, with emphasis on the CxxC motifs in the thioredoxin and Erv/ALR domains and the involvement of the flavin prosthetic group. The tissue distribution and intra- and extracellular location of QSOX enzymes are discussed, and suggestions for the physiological role of these enzymes are presented. The review compares the substrate specificity and catalytic efficiency of the QSOX enzymes with members of the Ero1 family of flavin-dependent sulfhydryl oxidases: enzymes believed to play key roles in disulfide generation in yeast and higher eukaryotes. Finally, limitations of our current understanding of disulfide generation in metazoans are identified and questions posed for the future. Antioxid. Redox Signal. 13, 1217–1230.

Kodali, Vamsi K.

2010-01-01

90

Oxidative protein folding and the Quiescin-sulfhydryl oxidase family of flavoproteins.  

PubMed

Flavin-linked sulfhydryl oxidases participate in the net generation of disulfide bonds during oxidative protein folding in the endoplasmic reticulum. Members of the Quiescin-sulfhydryl oxidase (QSOX) family catalyze the facile direct introduction of disulfide bonds into unfolded reduced proteins with the reduction of molecular oxygen to generate hydrogen peroxide. Current progress in dissecting the mechanism of QSOX enzymes is reviewed, with emphasis on the CxxC motifs in the thioredoxin and Erv/ALR domains and the involvement of the flavin prosthetic group. The tissue distribution and intra- and extracellular location of QSOX enzymes are discussed, and suggestions for the physiological role of these enzymes are presented. The review compares the substrate specificity and catalytic efficiency of the QSOX enzymes with members of the Ero1 family of flavin-dependent sulfhydryl oxidases: enzymes believed to play key roles in disulfide generation in yeast and higher eukaryotes. Finally, limitations of our current understanding of disulfide generation in metazoans are identified and questions posed for the future. PMID:20136510

Kodali, Vamsi K; Thorpe, Colin

2010-10-01

91

Electric Switches  

NSDL National Science Digital Library

In this activity, learners incorporate a simple switch into a battery/bulb circuit. Learners will use their knowledge of circuits to design and make their own switches using common materials. Learners will also identify switches found in common appliances. Note: This activity is designed to be done under the supervision of an educator familiar with electrical and electronic concepts.

Ieee

2013-07-08

92

Homocysteine and other sulfhydryl compounds enhance the binding of lipoprotein(a) to fibrin: a potential biochemical link between thrombosis, atherogenesis, and sulfhydryl compound metabolism.  

PubMed Central

We have previously shown that lipoprotein(a) [Lp(a)], an atherogenic lipoprotein that contains apolipoprotein(a), which shares partial structural homology to plasminogen, binds to a plasmin-modified fibrin surface, and we have postulated that this interaction may be atherogenic. Moderate elevations in blood homocysteine, a relatively common condition, predispose to premature atherosclerosis. The reasons for this are not established. We now report that homocysteine, at concentrations as low as 8 microM, significantly increases the affinity of Lp(a) for fibrin. Homocysteine induces a 20-fold increase in the affinity between Lp(a) and plasmin-treated fibrin and a 4-fold increase with unmodified fibrin. Lp(a) binding is inhibited by epsilon-aminocaproic acid, indicating lysine binding site specificity. Homocysteine does not enhance the binding of Lp(a) to other surface-bound proteins. Cysteine, glutathione, and N-acetylcysteine also increase the affinity between Lp(a) and fibrin. Homocysteine does not affect the binding of low density lipoprotein or plasminogen to fibrin, nor does it alter the gel-filtration elution pattern of Lp(a). Immunoblot analysis documents the fact that homocysteine partially reduces Lp(a). These results suggest that homocysteine alters the intact Lp(a) particle so as to increase the reactivity of the plasminogen-like apolipoprotein(a) portion of the molecule. The observation that sulfhydryl amino acids increase Lp(a) binding to fibrin suggests a biochemical relationship between sulfhydryl compound metabolism, thrombosis, and atherogenesis. Images

Harpel, P C; Chang, V T; Borth, W

1992-01-01

93

Corynebacterium glutamicum Utilizes both Transsulfuration and Direct Sulfhydrylation Pathways for Methionine Biosynthesis  

PubMed Central

A direct sulfhydrylation pathway for methionine biosynthesis in Corynebacterium glutamicum was found. The pathway was catalyzed by metY encoding O-acetylhomoserine sulfhydrylase. The gene metY, located immediately upstream of metA, was found to encode a protein of 437 amino acids with a deduced molecular mass of 46,751 Da. In accordance with DNA and protein sequence data, the introduction of metY into C. glutamicum resulted in the accumulation of a 47-kDa protein in the cells and a 30-fold increase in O-acetylhomoserine sulfhydrylase activity, showing the efficient expression of the cloned gene. Although disruption of the metB gene, which encodes cystathionine ?-synthase catalyzing the transsulfuration pathway of methionine biosynthesis, or the metY gene was not enough to lead to methionine auxotrophy, an additional mutation in the metY or the metB gene resulted in methionine auxotrophy. The growth pattern of the metY mutant strain was identical to that of the metB mutant strain, suggesting that both methionine biosynthetic pathways function equally well. In addition, an Escherichia coli metB mutant could be complemented by transformation of the strain with a DNA fragment carrying corynebacterial metY and metA genes. These data clearly show that C. glutamicum utilizes both transsulfuration and direct sulfhydrylation pathways for methionine biosynthesis. Although metY and metA are in close proximity to one another, separated by 143 bp on the chromosome, deletion analysis suggests that they are expressed independently. As with metA, methionine could also repress the expression of metY. The repression was also observed with metB, but the degree of repression was more severe with metY, which shows almost complete repression at 0.5 mM methionine in minimal medium. The data suggest a physiologically distinctive role of the direct sulfhydrylation pathway in C. glutamicum.

Hwang, Byung-Joon; Yeom, Hye-Jin; Kim, Younhee; Lee, Heung-Shick

2002-01-01

94

Role of sulfhydryl groups in transfection? A case study with chitosan-NAC nanoparticles.  

PubMed

This study investigated the use of chitosan-N-acetylcysteine (NAC) as a non-viral gene carrier. In particular, we aimed to elucidate whether the advantage of thiolation was more pronounced in the stabilization of particles or in the effect of nonspecific sulfhydryl reduction of the target cells. Low-viscosity chitosan was modified by covalent binding of NAC. The resulting conjugate displayed 1.35 mM SH/g polymer. Particles produced via self-assembly of chitosan conjugate and pDNA had a mean particle size of 113.7 nm and a positive zeta-potential. Sulfhydryl group content on the particle surface was investigated by Ellman's test and papain reactivation assay, with the result of about 100 nM SH groups/mL nanoparticle suspension. An oxidation step was performed to stabilize polyplexes via disulfide bonds. The enhanced stability of oxidized particles against both polyanion heparin and alkaline pH was proven by a gel retardation assay. The stabilization was demonstrated to be reversible by treatment with glutathione. Further, the effect of immobilized SH groups and of supplementation with free NAC on transfection efficacy on Caco-2 cells was investigated. The expression of the transgene was raised 2.5-fold and 10-fold with nonoxidized thiomer polyplexes in comparison to polyplexes of unmodified chitosan and oxidized chitosan-NAC, respectively. The impact of sulfhydryl reduction on transfection was assessed via thiol group inactivation with 5,5'-dithiobis-(2-nitrobenzoic acid) (DNTB). This inactivation resulted in a decrease of transfection efficacy. In conclusion, chitosan-NAC conjugate was demonstrated to be beneficial for transfection, either for stabilization via disulfide bonds or for raising the expression of transgene via shifting the redox potential of the target cells. PMID:17552491

Loretz, Brigitta; Thaler, Marlene; Bernkop-Schnürch, Andreas

2007-01-01

95

Sulfhydryl alkylating agents induce calcium current in skeletal muscle fibers of a crustacean (Atya lanipes).  

PubMed

Voltage-clamp experiments using the three-microelectrode voltage clamp technique were performed on ventroabdominal flexor muscles of the crustacean Atya lanipes. Potassium and chloride currents were found to underlie the normal, passive response of the muscle. Blocking potassium currents with tetraethylammonium and replacing chloride ions with methanesulfonate did not unmask an inward current. By treating the muscle with the sulfhydryl-alkylating agent 4-cyclopentene-1,3-dione an inward current was detected. The current induced by the agent is carried by Ca2+, since it is abolished in Ca(2+)-free solutions. The induced Ca2+ current is detected at about -40 mV and reaches a mean maximum value of -78 microA/cm2 at ca. -10 mV. At this potential the time to peak is close to 15 msec. The induced Ca2+ current inactivated with 1-sec prepulses which did not elicit detectable Ca2+ current; the fitted hx curve had a midpoint of -38 mV and a steepness of 5.0 mV. Measurements of isometric tension were performed in small bundles of fibers, and the effects of the sulfhydryl-alkylating agents 4-cyclopentene-1,3-dione and N-ethylmaleimide were investigated. Tetanic tension was enhanced in a strictly Ca(2+)-dependent manner by 4-cyclopentene-1,3-dione. The amplitude of K+ contractures increased after treatment with N-ethylmaleimide. It is concluded that Ca2+ channels are made functional by the sulfhydryl-specific reagents and that the increase in tension is probably mediated by an increase in Ca2+ influx through the chemically induced Ca2+ channels. PMID:1331464

Lizardi, L; Garcia, M C; Sanchez, J A; Zuazaga, C

1992-08-01

96

Avian sulfhydryl oxidase is not a metalloenzyme: adventitious binding of divalent metal ions to the enzyme.  

PubMed

Metal- and flavin-dependent sulfhydryl oxidases catalyze the generation of disulfide bonds with reduction of oxygen to hydrogen peroxide. The mammalian skin enzyme has been reported to be copper-dependent, but a recent protein sequence shows it belongs to the Quiescin/sulfhydryl oxidase (QSOX) flavoprotein family. This work demonstrates that avian QSOX is not a metalloenzyme, and that copper and zinc ions inhibit the oxidation of reduced pancreatic ribonuclease by the enzyme. Studies with Zn(2+), as a redox inactive surrogate for copper, show that one Zn(2+) binds to four-electron-reduced QSOX by diverting electrons away from the flavin and into two of the three redox active disulfide bridges in the enzyme. The resulting zinc complex is modestly air-stable, reverting to a spectrum of the native protein with a t(1/2) of 40 min, whereas the four-electron-reduced native QSOX is reoxidized in less than a second under comparable conditions. Using tris(2-carboxyethyl)phosphine hydrochloride (TCEP), an alternate substrate of QSOX that binds Zn(2+) relatively weakly (unlike dithiothreitol), allows rapid inhibition of oxidase activity to be demonstrated at low micromolar metal levels. Zinc binding was followed by rapid-scanning spectrophotometry. Copper also binds the four-electron-reduced form of QSOX with a visible spectrum suggestive of active site occupancy. In addition to interactions with the reduced enzyme, dialysis experiments show that multiple copper and zinc ions can bind to the oxidized enzyme without the perturbation of the flavin spectrum seen earlier. These data suggest that a reinvestigation of the metal content of skin sulfhydryl oxidases is warranted. The redox-modulated binding of zinc to QSOX is considered in light of evidence for a role of zinc-thiolate interactions in redox signaling and zinc mobilization. PMID:12974644

Brohawn, Stephen G; Miksa, Irina Rudik; Thorpe, Colin

2003-09-23

97

Generation of calcium action potentials in crustacean muscle fibers following exposure to sulfhydryl reagents.  

PubMed

The ventroabdominal flexor muscles of the crustacean Atya lanipes, which are normally completely inexcitable, generate trains of overshooting calcium action potentials after exposure to the sulfhydryl reagents known as alpha, beta-unsaturated carbonyl compounds. The chemically induced action potentials are abolished by protein reagents specific for guanidino and amino groups. Attempts to induce excitability by the use of agents that block potassium conductance were without success. It is proposed that calcium channels are made functional by the covalent modification of a calcium protochannel, via the interaction between the introduced carbonyl group and existing arginine residues. PMID:2866914

Zuazaga, C; del Castillo, J

1985-01-01

98

Ethernet Switching  

NSDL National Science Digital Library

Created by Tony Castro of the Information and Communications Technologies Center (ICT), this simulation demonstrates ethernet switching. The animation depicts three separate local area networks connecting to an ethernet hub. The animation also includes descriptive text. This resource would be a helpful addition to any course on information and communications technologies as it allows students to see exactly how ethernet switching works.

Castro, Tony

2012-10-25

99

Changes in sulfhydryl groups of honeybee glyceraldehyde phosphate dehydrogenase associated with generation of the intermediate plateau in its saturation kinetics  

NASA Technical Reports Server (NTRS)

Honeybee and rabbit muscle GPDH were studied to obtain information at the chemical level regarding anomolous saturation kinetics of the honeybee enzyme. Results demonstrate that the enzyme's sulfhydryl groups are implicated in the process. Measured by DTNB titration, native honeybee GPDH has one less active SH than the native rabbit muscle enzyme and displays changes in overall sulfhydryl reactivity after preincubation with G-3-P or G-3-P plus NAD+. The total DTNB reactive sulfhydryls of rabbit muscle GPDH are not changed by preincubation with NAD+ or G-3-P; honeybee GPDH, under certain conductions of preincubation with these ligands, shows a decrease of two total DTNB reactive SH groups. This difference has been confirmed by an independent experiment in which the two enzymes were carboxymethylated with C-14 bromoacetic acid.

Gelb, W. G.; Brandts, J. F.; Nordin, J. H.

1973-01-01

100

Switching Amplifiers  

NSDL National Science Digital Library

Created by Work-Ready Electronics, a project of the Advanced Technological Education, this module walks visitors through switching amplifiers. The site content is divided up into four sections: Switching Amplifiers Introduction, Class D Switching Amplifiers, Switching RF Power Amplifiers, and Troubleshooting. There is a quiz for each section to test what students learned in the module in the Knowledge Probe section, and the Learning Resources section contains four activities to help cement student understanding. There are also further resources - both print and Web based - for more information and two Questor games, a Flash quiz that reiterates the material covered. The Notebook function allows visitors to take notes and review them at any time. This is an excellent resource students and educators in electronics technician programs to introduce and explore switching amplifiers.

2008-09-04

101

Frequency dependence of critical switching asteroid of CoCrPt-SiO2 granular film under 50-ns microwave impulse  

NASA Astrophysics Data System (ADS)

Understanding the dynamic process of microwave-assisted magnetization reversal (MAMR) in a dipole-dipole coupled granular perpendicular medium is essential for its application to future magnetic storage devices. We experimentally investigated the magnetization reversal process in CoCrPt-SiO2 granular films in terms of the dependence of the switching field on the strength of an applied in-plane radio-frequency magnetic field. The reversal process changed from non-uniform rotation to uniform rotation when the frequency increased toward the ferromagnetic resonance frequency. In the resonant condition, the switching field agreed well with a model assuming uniform rotation of the magnetization in each grain. The agreement suggests that the decoherence of ferromagnetic resonance due to a dynamic dipolar field is weak in adequately exchange-coupled granular films with a saturation magnetization of 415 emu/cm3. This finding is significant for the development of the practical medium necessary for MAMR writing.

Ishida, N.; Soeno, Y.; Sekiguchi, K.; Nozaki, Y.

2013-07-01

102

Hydrogen Sulfide Inhibits L-Type Calcium Currents Depending upon the Protein Sulfhydryl State in Rat Cardiomyocytes  

PubMed Central

Hydrogen sulfide (H2S) is a novel gasotransmitter that inhibits L-type calcium currents (I Ca, L). However, the underlying molecular mechanisms are unclear. In particular, the targeting site in the L-type calcium channel where H2S functions remains unknown. The study was designed to investigate if the sulfhydryl group could be the possible targeting site in the L-type calcium channel in rat cardiomyocytes. Cardiac function was measured in isolated perfused rat hearts. The L-type calcium currents were recorded by using a whole cell voltage clamp technique on the isolated cardiomyocytes. The L-type calcium channel containing free sulfhydryl groups in H9C2 cells were measured by using Western blot. The results showed that sodium hydrosulfide (NaHS, an H2S donor) produced a negative inotropic effect on cardiac function, which could be partly inhibited by the oxidant sulfhydryl modifier diamide (DM). H2S donor inhibited the peak amplitude of I Ca, L in a concentration-dependent manner. However, dithiothreitol (DTT), a reducing sulfhydryl modifier markedly reversed the H2S donor-induced inhibition of I Ca, L in cardiomyocytes. In contrast, in the presence of DM, H2S donor could not alter cardiac function and L type calcium currents. After the isolated rat heart or the cardiomyocytes were treated with DTT, NaHS could markedly alter cardiac function and L-type calcium currents in cardiomyocytes. Furthermore, NaHS could decrease the functional free sulfhydryl group in the L-type Ca2+ channel, which could be reversed by thiol reductant, either DTT or reduced glutathione. Therefore, our results suggest that H2S might inhibit L-type calcium currents depending on the sulfhydryl group in rat cardiomyocytes.

Tsai, Haojan; Tang, Chaoshu; Jin, Hongfang; Du, Junbao

2012-01-01

103

Structure of Yeast Sulfhydryl Oxidase Erv1 Reveals Electron Transfer of the Disulfide Relay System in the Mitochondrial Intermembrane Space*  

PubMed Central

The disulfide relay system in the mitochondrial intermembrane space drives the import of proteins with twin CX9C or twin CX3C motifs by an oxidative folding mechanism. This process requires disulfide bond transfer from oxidized Mia40 to a substrate protein. Reduced Mia40 is reoxidized/regenerated by the FAD-linked sulfhydryl oxidase Erv1 (EC 1.8.3.2). Full-length Erv1 consists of a flexible N-terminal shuttle domain (NTD) and a conserved C-terminal core domain (CTD). Here, we present crystal structures at 2.0 ? resolution of the CTD and at 3.0 ? resolution of a C30S/C133S double mutant of full-length Erv1 (Erv1FL). Similar to previous homologous structures, the CTD exists as a homodimer, with each subunit consisting of a conserved four-helix bundle that accommodates the isoalloxazine ring of FAD and an additional single-turn helix. The structure of Erv1FL enabled us to identify, for the first time, the three-dimensional structure of the Erv1NTD, which is an amphipathic helix flanked by two flexible loops. This structure also represents an intermediate state of electron transfer from the NTD to the CTD of another subunit. Comparative structural analysis revealed that the four-helix bundle of the CTD forms a wide platform for the electron donor NTD. Moreover, computational simulation combined with multiple-sequence alignment suggested that the amphipathic helix close to the shuttle redox enter is critical for the recognition of Mia40, the upstream electron donor. These findings provide structural insights into electron transfer from Mia40 via the shuttle domain of one subunit of Erv1 to the CTD of another Erv1 subunit.

Guo, Peng-Chao; Ma, Jin-Di; Jiang, Yong-Liang; Wang, Shu-Jie; Bao, Zhang-Zhi; Yu, Xiao-Jie; Chen, Yuxing; Zhou, Cong-Zhao

2012-01-01

104

Preparation and characterization of singly-substituted sulfhydryl derivatives of cytochrome c  

SciTech Connect

Sulfydryl derivatives of horse heart cytochrome c have been prepared by reaction with sulfosuccinimidyl-2-(biotinamido) ethyl-1,3'-dithiopropionate, which modifies lysine epsilon - amino groups. The mixture of products containing cytochromes c derivatized at different lysines was resolved by HPLC using a cation exchange column. The resulting purified mono-derivatives were identified as follows: the sulfhydryl group of the modified lysine was alkylated using (/sup 3/H)-iodoacetic acid, this alkylated derivative was digested with chymotrypsin, and the labeled peptide was isolated by HPLC and its amino acid composition determined. Kinetic analysis of each derivative's reactivity with cytochrome c oxidase revealed a pattern of inhibition similar to that observed for the carboxydinitrophenyl-derivatives of horse heart cytochrome c. By reacting the sulfhydryl group with N-(iodoethyl)trifluoroacetamide, the original charge of the cytochrome c is restored. The effects on the reactivity of cytochrome c with cytochrome c oxidase caused by the change in dipole and by steric hindrance from the derivatization can then be distinguished. These derivatives have the advantage that various labels (photoaffinity, fluorescent, etc.) can readily be attached specifically to each of the modified lysines, and are being used in variety of studies.

Theodorakis, J.L.; Armes, L.G.; Margoliash, E.

1986-05-01

105

Competitive Adsorption of Three Human Plasma Proteins onto Sulfhydryl-to-sulfonate Gradient Surfaces†  

PubMed Central

Competitive adsorption of three human plasma proteins: albumin (HSA), fibrinogen (Fgn), and immunoglobulin G (IgG) from their ternary solution mixtures onto a sulfhydryl-to-sulfonate gradient surface was investigated using spatially-resolved total internal reflection fluorescence (TIRF) and autoradiography. The concentration of each protein in the ternary solution mixture was kept at an equivalent of 1/100 of its physiological concentration in blood plasma. The three proteins displayed different adsorption and desorption characteristics. Each protein adsorbed less to the sulfonate region than to the sulfhydryl region of the gradient. The adsorption-desorption kinetics revealed large differences in the adsorption and desorption rates of three proteins. By fitting the experimental data to a simple model of competitive protein adsorption, the affinity of each protein to the surface at the gradient center position was ranked as: Fgn > HSA ? IgG. Competitive exchange of adsorbed proteins was related to the magnitude of desorption rate constants. Such competitive adsorption of the three major human plasma proteins illustrates the complex dynamics of blood proteins – biomaterials interactions.

Ding, Yong-Xue; Hlady, Vladimir

2012-01-01

106

Sulfhydryl-group modifications of Torpedo Californica acetylcholine receptor: subunit localization and effects on function  

SciTech Connect

The effects of thiol-group modification on acetylcholine receptor (ACHR) function were measured using purified Torpedo ACHR reconstituted into soybean lipid vesicles. N-Phenyl-maleimide (NPM) was used to modify sulfhydryl groups in ACHR in the absence of any prior reduction by dithiotheitol. Modification by NPM led to the inhibition of ion channel activity without a detectable effect on ligand binding. The ion flux inhibition by NPM primarily affected channel activation, since the initial rates of activation decreased over a wide range of carbamylcholine concentrations. The /sup 3/H-NPM subunit labelling pattern of ACHR (a multisubunit membrane protein with ..cap alpha../sub 2/..beta gamma..delta stoichiometry) revealed preferential labelling of the ..gamma.. subunit. At high NPM concentration, the number of sulfhydryl groups on the ..gamma.. subunit that could be modified with NPM was two. Detergent was required during labelling for functionally relevant thiol group modifications, and most of the label was protected from protease digestion in the reconstituted membranes. These results are consistent with the presence of the NPM modification in a bilayer and/or cytoplasmic domain. Analysis of cyanogen bromide and trypsin fragments indicates that the labeled cysteines may be located in the postulated amphipathic helix region of the ..gamma.. subunit.

McNamee, M.G.; Yee, A.S.

1986-05-01

107

Oxidation of proximal protein sulfhydryls by phenanthraquinone, a component of diesel exhaust particles.  

PubMed

Diesel exhaust particles (DEP) contain quinones that are capable of catalyzing the generation of reactive oxygen species in biological systems, resulting in induction of oxidative stress. In the present study, we explored sulfhydryl oxidation by phenanthraquinone, a component of DEP, using thiol compounds and protein preparations. Phenanthraquinone reacted readily with dithiol compounds such as dithiothreitol (DTT), 2,3-dimercapto-1-propanol (BAL), and 2,3-dimercapto-1-propanesulfonic acid (DMPS), resulting in modification of the thiol groups, whereas minimal reactivities of this quinone with monothiol compounds such as GSH, 2-mercaptoethanol, and N-acetyl-L-cysteine were seen. The modification of DTT dithiol caused by phenanthraquinone proceeded under anaerobic conditions but was accelerated by molecular oxygen. Phenanthraquinone was also capable of modifying thiol groups in pulmonary microsomes from rats and total membrane preparation isolated from bovine aortic endothelial cells (BAEC), but not bovine serum albumin (BSA), which has a Cys34 as a reactive monothiol group. A comparison of the thiol alkylating agent N-ethylmaleimide (NEM) with that of phenanthraquinone indicates that the two mechanisms of thiol modification are distinct. Studies revealed that thiyl radical intermediates and reactive oxygen species were generated during interaction of phenanthraquinone with DTT. From these findings, it is suggested that phenanthraquinone-mediated destruction of protein sulfhydryls appears to involve the oxidation of presumably proximal thiols and the reduction of molecular oxygen. PMID:11952333

Kumagai, Yoshito; Koide, Sachie; Taguchi, Keiko; Endo, Akiko; Nakai, Yumi; Yoshikawa, Toshikazu; Shimojo, Nobuhiro

2002-04-01

108

Sulfhydryl oxidases: emerging catalysts of protein disulfide bond formation in eukaryotes.  

PubMed

Members of the Quiescin-sulfhydryl oxidase (QSOX) family utilize a thioredoxin domain and a small FAD-binding domain homologous to the yeast ERV1p protein to oxidize sulfhydryl groups to disulfides with the reduction of oxygen to hydrogen peroxide. QSOX enzymes are found in all multicellular organisms for which complete genomes exist and in Trypanosoma brucei, but are not found in yeast. The avian QSOX is the best understood enzymatically: its preferred substrates are peptides and proteins, not monothiols such as glutathione. Mixtures of avian QSOX and protein disulfide isomerase catalyze the rapid insertion of the correct disulfide pairings in reduced RNase. Immunohistochemical studies of human tissues show a marked and highly localized concentration of QSOX in cell types associated with heavy secretory loads. Consistent with this role in the formation of disulfide bonds, QSOX is typically found in the cell in the endoplasmic reticulum and Golgi and outside the cell. In sum, this review suggests that QSOX enzymes play a significant role in oxidative folding of a large variety of proteins in a wide range of multicellular organisms. PMID:12176051

Thorpe, Colin; Hoober, Karen L; Raje, Sonali; Glynn, Nicole M; Burnside, Joan; Turi, George K; Coppock, Donald L

2002-09-01

109

Silencing an Anopheles gambiae catalase and sulfhydryl oxidase increases mosquito mortality after a blood meal.  

PubMed

Catalase is a potent antioxidant, likely involved in post-blood meal homeostasis in mosquitoes. This enzyme breaks down H2O2, preventing the formation of the hydroxyl radical (HO*). Quiescins are newly classified sulfhydryl oxidases that bear a thioredoxin motif at the N-terminal and an ERV1-like portion at the C-terminal. These proteins have a major role in generating disulfides in intra- or extracellular environments, and thus participate in redox reactions. In the search for molecules to serve as targets for novel anti-mosquito strategies, we have silenced a catalase and a putative quiescin/sulfhydryl oxidase (QSOX), from the African malaria vector Anopheles gambiae, through RNA interference (RNAi) experiments. We observed that the survival of catalase- and QSOX-silenced insects was reduced over controls following blood digestion, most likely due to the compromised ability of mosquitoes to scavenge and/or prevent damage caused by blood meal-derived oxidative stress. The higher mortality effect was more accentuated in catalase-silenced mosquitoes, where catalase activity was reduced to low levels. Lipid peroxidation was higher in QSOX-silenced mosquitoes suggesting the involvement of this protein in redox homeostasis following a blood meal. This study points to the potential of molecules involved in antioxidant response and redox metabolism to serve as targets of novel anti-mosquito strategies and offers a screening methodology for finding targetable mosquito molecules. PMID:18454489

Magalhaes, T; Brackney, D E; Beier, J C; Foy, B D

2008-07-01

110

Silencing an Anopheles gambiae Catalase and Sulfhydryl Oxidase Increases Mosquito Mortality After a Blood Meal  

PubMed Central

Catalase is a potent antioxidant, likely involved in post-blood meal homeostasis in mosquitoes. This enzyme breaks down H2O2, preventing the formation of the hydroxyl radical (HO•). Quiescins are newly classified sulfhydryl oxidases that bear a thioredoxin motif at the N-terminal and an ERV1-like portion at the C-terminal. These proteins have a major role in generating disulfides in intra- or extracellular environments, and thus participate in redox reactions. In the search for molecules to serve as targets for novel anti-mosquito strategies, we have silenced a catalase and a putative quiescin/sulfhydryl oxidase (QSOX), from the African malaria vector Anopheles gambiae, through RNA interference (RNAi) experiments. We observed that the survival of catalase- and QSOX-silenced insects was reduced over controls following blood digestion, most likely due to the compromised ability of mosquitoes to scavenge and/or prevent damage caused by blood meal-derived oxidative stress. The higher mortality effect was more accentuated in catalase-silenced mosquitoes, where catalase activity was reduced to low levels. Lipid peroxidation was higher in QSOX-silenced mosquitoes suggesting the involvement of this protein in redox homeostasis following a blood meal. This study points to the potential of molecules involved in antioxidant response and redox metabolism to serve as targets of novel anti-mosquito strategies and offers a screening methodology for finding targetable mosquito molecules.

Magalhaes, T.; Brackney, D.E.; Beier, J.C.; Foy, B.D.

2009-01-01

111

Exploring ORFan Domains in Giant Viruses: Structure of Mimivirus Sulfhydryl Oxidase R596  

PubMed Central

The mimivirus genome contains many genes that lack homologs in the sequence database and are thus known as ORFans. In addition, mimivirus genes that encode proteins belonging to known fold families are in some cases fused to domain-sized segments that cannot be classified. One such ORFan region is present in the mimivirus enzyme R596, a member of the Erv family of sulfhydryl oxidases. We determined the structure of a variant of full-length R596 and observed that the carboxy-terminal region of R596 assumes a folded, compact domain, demonstrating that these ORFan segments can be stable structural units. Moreover, the R596 ORFan domain fold is novel, hinting at the potential wealth of protein structural innovation yet to be discovered in large double-stranded DNA viruses. In the context of the R596 dimer, the ORFan domain contributes to formation of a broad cleft enriched with exposed aromatic groups and basic side chains, which may function in binding target proteins or localization of the enzyme within the virus factory or virions. Finally, we find evidence for an intermolecular dithiol/disulfide relay within the mimivirus R596 dimer, the first such extended, intersubunit redox-active site identified in a viral sulfhydryl oxidase.

Hakim, Motti; Ezerina, Daria; Alon, Assaf; Vonshak, Ohad; Fass, Deborah

2012-01-01

112

QSOX sulfhydryl oxidase in rat adenohypophysis: localization and regulation by estrogens.  

PubMed

The expression of the rat quiescin sulfhydryl oxidase (rQSOX) and its putative regulation by estrogens were investigated in the adenohypophysis. Immunohistochemical observations revealed that rQSOX protein is abundantly expressed throughout the anterior lobe of the pituitary, and can be found in almost all the different cell populations. However, as shown by double immunohisto-chemistry, the cells displaying the strongest rQSOX labeling belong to a subset of gonadotrophs. Immunoelectron microscopy showed that, in adenohypophyseal cells, the protein is linked to the membranes of the rough endoplasmic reticulum, the Golgi apparatus and to dense-core secretory granules. These results are consistent with the secretion of the protein and its presumed role in the extracellular matrix. According to its sulfhydryl oxidase function, rQSOX could also participate in the intracellular folding of secreted proteins or hormones like LH and FSH and act as an endogenous redox modulator of hormonal secretion. A semiquantitative RT-PCR analysis of rQSOX level across the estrous cycle and the fact that chronic administration of 17 beta-estradiol to ovariectomized rats led to a sustained up-regulation of rQSOX in the pituitary suggest that rQSOX expression is controlled by sex hormone levels. Further investigations are needed in order to elucidate its precise roles in that gland and the mechanisms of its regulation. PMID:15531723

Tury, A; Mairet-Coello, G; Poncet, F; Jacquemard, C; Risold, P Y; Fellmann, D; Griffond, B

2004-11-01

113

Gene Switches  

NSDL National Science Digital Library

In this activity, learners explore how genetic switches function and the role of genetic switches in the process of evolution. To make these concepts less abstract and more understandable, learners first view a series of video clips and animations from the HHMI DVD (or online) "Evolution: Constant Change and Common Threads." Then, learners construct a model of a gene switch using craft materials or FridgiGears (magnetic gears). This activity can be done as a demonstration, a student inquiry activity, or a combination of the two.

Colvard, Mary

2010-01-01

114

Extraction of methylmercury and ethylmercury from aqueous solution using surface sulfhydryl-functionalized magnetic mesoporous silica nanoparticles.  

PubMed

Surface sulfhydryl-functionalized magnetic mesoporous silica nanoparticles were prepared, aiming to extract trace alkylmercury from aqueous solution. The prepared nanoparticles were characterized by TEM, ED, EDX, DLS, FTIR, and SERS. Compare with that the non-sulfhydryl-functionalized Fe3O4@SiO2 exhibited almost no affinity for CH3Hg(+) and CH3CH2Hg(+); the sulfhydryl-functionalized Fe3O4@SiO2 exhibited high adsorption affinity for them, resulting from chelating interaction by surface sulfhydryl group, and the adsorption was not significantly impacted by pH within the range of 3.5-9.0 or coexisting metal ions. The monolayer adsorption on surface of Fe3O4@SiO2-RSH could reach equilibrium in 2 min. Moreover, the CH3Hg(+) and CH3CH2Hg(+) adsorbed on Fe3O4@SiO2-RSH could be quickly separated from the matrix in a magnetic field and desorbed easily by acetonitrile and l-cysteine aqueous solution or HCl solution, and the recoveries were more than 80%. Findings of the present work highlight the potential for using Fe3O4@SiO2-RSH magnetic nanoparticles as effective and reusable adsorbents for extraction of ultra trace alkylmercury from environmental water samples. PMID:24767508

Li, Guangzhu; Liu, Miao; Zhang, Zhuqing; Geng, Chao; Wu, Zhongbo; Zhao, Xin

2014-06-15

115

Effects of Redox and Sulfhydryl Reagents on the Bioelectric Properties of the Giant Axon of the Squid.  

National Technical Information Service (NTIS)

The effects of internally and externally applied sulfhydryl reagents on the bioelectric properties of the giant axon of the squid Loligo pealeii and Dosidicus gigas were studied. Cysteine-HCl (400 mM, pH 7.3) was used to remove axoplasm from the perfusion...

F. Huneeus-Cox H. L. Fernandez B. H. Smith

1965-01-01

116

Role of Sulfhydryl Sites on Bacterial Cell Walls in the Biosorption, Mobility and Bioavailability of Mercury and Uranium  

SciTech Connect

The goal of this exploratory study is to provide a quantitative and mechanistic understanding of the impact of bacterial sulfhydryl groups on the bacterial uptake, speciation, methylation and bioavailability of Hg and redox changes of uranium. The relative concentration and reactivity of different functional groups present on bacterial surfaces will be determined, enabling quantitative predictions of the role of biosorption of Hg under the physicochemical conditions found at contaminated DOE sites.The hypotheses we propose to test in this investigation are as follows- 1) Sulfhydryl groups on bacterial cell surfaces modify Hg speciation and solubility, and play an important role, specifically in the sub-micromolar concentration ranges of metals in the natural and contaminated systems. 2) Sulfhydryl binding of Hg on bacterial surfaces significantly influences Hg transport into the cell and the methylation rates by the bacteria. 3) Sulfhydryls on cell membranes can interact with hexavalent uranium and convert to insoluble tetravalent species. 4) Bacterial sulfhydryl surface groups are inducible by the presence of metals during cell growth. Our studies focused on the first hypothesis, and we examined the nature of sulfhydryl sites on three representative bacterial species: Bacillus subtilis, a common gram-positive aerobic soil species; Shewanella oneidensis, a facultative gram-negative surface water species; and Geobacter sulfurreducens, an anaerobic iron-reducing gram-negative species that is capable of Hg methylation; and at a range of Hg concentration (and Hg:bacterial concentration ratio) in which these sites become important. A summary of our findings is as follows- ? Hg adsorbs more extensively to bacteria than other metals. Hg adsorption also varies strongly with pH and chloride concentration, with maximum adsorption occurring under circumneutral pH conditions for both Cl-bearing and Cl-free systems. Under these conditions, all bacterial species tested exhibit almost complete removal of Hg from the experimental solutions at relatively low bacterial concentrations. ? Synchrotron based X-ray spectroscopic studies of these samples indicate that the structure and the coordination environment of Hg surface complexes on bacterial cell walls change dramatically- with sulfhydryls as the dominant Hg-binding groups in the micromolar and submicromolar range, and carboxyls and phosphoryls dominating at high micromolar concentrations. ? Hg interactions change from a trigonal or T-shaped HgS{sub 3} complex to HgS or HgS{sub 2} type complexes as the Hg concentration increases in the submicromolar range. Although all bacterial species studied exhibited the same types of coordination environments for Hg, the relative concentrations of the complexes change as a function of Hg concentration.

Myneni, Satish C.; Mishra, Bhoopesh; Fein, Jeremy

2009-04-01

117

Nucleotide-Protectable Labeling of Sulfhydryl Groups in Subunit I of the ATPhase from Halobacterium Saccharovorum  

NASA Technical Reports Server (NTRS)

A membrane-bound ATPase from the archaebacterium Halobacterium saccharovorum is inhibited by N-ethyl-maleimide in a nucleotide-protectable manner. When the enzyme was incubated with N-[C-14]jethylmaleimide, the bulk of radioactivity was as- sociated with the 87,000-Da subunit (subunit 1). ATP, ADP, or AMP reduced incorporation of the inhibitor. No charge shift of subunit I was detected following labeling with N-ethylmaleimide, indicating an electroneutral reaction. The results are consistent with the selective modification of sulfhydryl groups in subunit I at or near the catalytic site and are further evidence of a resemblance between this archaebacterial ATPase and the vacuolar-type ATPases.

Sulzner, Michael; Stan-Lotter, Helga; Hochstein, Lawrence I.

1992-01-01

118

Olfactory epithelium destruction by ZnSO4 modified sulfhydryl oxidase expression in mice.  

PubMed

Experimental destruction of olfactory neurons stimulates proliferation and differentiation of local neural precursors and is used as a model to study in vivo mechanisms for degeneration and regeneration of the nervous system. Quiescin-sulfhydryl oxidases (QSOX) have a potential role in the control of the cell cycle or growth regulation and have recently been described in the central nervous system. In mice, we show an expression of QSOX in olfactory mucosa. Northern- and western-blot analysis show that the destruction of olfactory epithelium is associated with a reversible reduction in QSOX expression. Interestingly, QSOX is not localized in olfactory neurons (ON) but in cells of the lamina propria, suggesting that olfactory epithelium destruction may act as a signal of down-regulation of QSOX expression. PMID:15671873

Bon, Karine; Adami, Pascale; Esnard, Frédéric; Jouvenot, Michèle; Versaux-Bottéri, Claudine

2005-02-01

119

Intracellular catalysis of disulfide bond formation by the human sulfhydryl oxidase, QSOX1  

PubMed Central

The discovery that the flavoprotein oxidase, Erv2p, provides oxidizing potential for disulfide bond formation in yeast, has led to investigations into the roles of the mammalian homologues of this protein. Mammalian homologues of Erv2p include QSOX (sulfhydryl oxidases) from human lung fibroblasts, guinea-pig endometrial cells and rat seminal vesicles. In the present study we show that, when expressed in mammalian cells, the longer version of human QSOX1 protein (hQSOX1a) is a transmembrane protein localized primarily to the Golgi apparatus. We also present the first evidence showing that hQSOX1a can act in vivo as an oxidase. Overexpression of hQSOX1a suppresses the lethality of a complete deletion of ERO1 (endoplasmic reticulum oxidase 1) in yeast and restores disulfide bond formation, as assayed by the folding of the secretory protein carboxypeptidase Y.

Chakravarthi, Seema; Jessop, Catherine E.; Willer, Martin; Stirling, Colin J.; Bulleid, Neil J.

2007-01-01

120

Intracellular catalysis of disulfide bond formation by the human sulfhydryl oxidase, QSOX1.  

PubMed

The discovery that the flavoprotein oxidase, Erv2p, provides oxidizing potential for disulfide bond formation in yeast, has led to investigations into the roles of the mammalian homologues of this protein. Mammalian homologues of Erv2p include QSOX (sulfhydryl oxidases) from human lung fibroblasts, guinea-pig endometrial cells and rat seminal vesicles. In the present study we show that, when expressed in mammalian cells, the longer version of human QSOX1 protein (hQSOX1a) is a transmembrane protein localized primarily to the Golgi apparatus. We also present the first evidence showing that hQSOX1a can act in vivo as an oxidase. Overexpression of hQSOX1a suppresses the lethality of a complete deletion of ERO1 (endoplasmic reticulum oxidase 1) in yeast and restores disulfide bond formation, as assayed by the folding of the secretory protein carboxypeptidase Y. PMID:17331072

Chakravarthi, Seema; Jessop, Catherine E; Willer, Martin; Stirling, Colin J; Bulleid, Neil J

2007-06-15

121

Peroxynitrite inactivates tryptophan hydroxylase via sulfhydryl oxidation. Coincident nitration of enzyme tyrosyl residues has minimal impact on catalytic activity.  

PubMed

Tryptophan hydroxylase, the initial and rate-limiting enzyme in serotonin biosynthesis, is inactivated by peroxynitrite in a concentration-dependent manner. This effect is prevented by molecules that react directly with peroxynitrite such as dithiothreitol, cysteine, glutathione, methionine, tryptophan, and uric acid but not by scavengers of superoxide (superoxide dismutase), hydroxyl radical (Me(2)SO, mannitol), and hydrogen peroxide (catalase). Assuming simple competition kinetics between peroxynitrite scavengers and the enzyme, a second-order rate constant of 3.4 x 10(4) M(-1) s(-1) at 25 degrees C and pH 7.4 was estimated. The peroxynitrite-induced loss of enzyme activity was accompanied by a concentration-dependent oxidation of protein sulfhydryl groups. Peroxynitrite-modified tryptophan hydroxylase was resistant to reduction by arsenite, borohydride, and dithiothreitol, suggesting that sulfhydryls were oxidized beyond sulfenic acid. Peroxynitrite also caused the nitration of tyrosyl residues in tryptophan hydroxylase, with a maximal modification of 3.8 tyrosines/monomer. Sodium bicarbonate protected tryptophan hydroxylase from peroxynitrite-induced inactivation and lessened the extent of sulfhydryl oxidation while causing a 2-fold increase in tyrosine nitration. Tetranitromethane, which oxidizes sulfhydryls at pH 6 or 8, but which nitrates tyrosyl residues at pH 8 only, inhibited tryptophan hydroxylase equally at either pH. Acetylation of tyrosyl residues with N-acetylimidazole did not alter tryptophan hydroxylase activity. These data suggest that peroxynitrite inactivates tryptophan hydroxylase via sulfhydryl oxidation. Modification of tyrosyl residues by peroxynitrite plays a relatively minor role in the inhibition of tryptophan hydroxylase catalytic activity. PMID:10514446

Kuhn, D M; Geddes, T J

1999-10-15

122

Sulfhydryl oxidation reduces hippocampal susceptibility to hypoxia-induced spreading depression by activating BK channels.  

PubMed

The cytosolic redox status modulates ion channels and receptors by oxidizing/reducing their sulfhydryl (SH) groups. We therefore analyzed to what degree SH modulation affects hippocampal susceptibility to hypoxia. In rat hippocampal slices, severe hypoxia caused a massive depolarization of CA1 neurons and a negative shift of the extracellular DC potential, the characteristic sign of hypoxia-induced spreading depression (HSD). Oxidizing SH groups by 5,5'-dithiobis 2-nitrobenzoic acid (DTNB, 2 mM) postponed HSD by 30%, whereas their reduction by 1,4-dithio-dl-threitol (DTT, 2 mM) or alkylation by N-ethylmaleimide (500 microM) hastened HSD onset. The DTNB-induced postponement of HSD was not affected by tolbutamide (200 microM), dl-2-amino-5-phosphonovaleric acid (150 microM), or 6-cyano-7-nitroquinoxaline-2,3-dione (25 microM). It was abolished, however, by Ni2+ (2 mM), withdrawal of extracellular Ca2+, charybdotoxin (25 nM), and iberiotoxin (50 nM). In CA1 neurons DTNB induced a moderate hyperpolarization, blocked spontaneous spike discharges and postponed the massive hypoxic depolarization. DTT induced burst firing, depolarized glial cells, and hastened the onset of the massive hypoxic depolarization. Schaffer-collateral/CA1 synapses were blocked by DTT but not by DTNB; axonal conduction remained intact. Mitochondria did not markedly respond to DTNB or DTT. While the targets of DTT are less clear, the postponement of HSD by DTNB indicates that sulfhydryl oxidation increases the tolerance of hippocampal tissue slices against hypoxia. We identified as the underlying mechanism the activation of BK channels in a Ca(2+)-sensitive manner. Accordingly, ionic disregulation and the loss of membrane potential occur later or might even be prevented during short-term insults. Therefore well-directed oxidation of SH groups could mediate neuroprotection. PMID:15872065

Hepp, Sebastian; Gerich, Florian J; Müller, Michael

2005-08-01

123

Spatial proximity and sequence localization of the reactive sulfhydryls of porphobilinogen synthase.  

PubMed Central

The zinc metalloenzyme porphobilinogen synthase (PBGS) contains several functionally important, but previously unidentified, reactive sulfhydryl groups. The enzyme has been modified with the reversible sulfhydryl-specific nitroxide spin label derivative of methyl methanethiosulfonate (MMTS), (1-oxyl-2,2,5,5-tetramethyl-delta 3-pyrroline-3-methyl)methanethiosulfonate (SL-MMTS) (Berliner, L. J., Grunwald, J., Hankovszky, H. O., & Hideg, K., 1982, Anal. Biochem. 119, 450-455). EPR spectra show that SL-MMTS labels three groups per PBGS subunit (24 per octamer), as does MMTS. EPR signals reflecting nitroxides of different mobilities are observed. Two of the three modified cysteines have been identified as Cys-119 and Cys-223 by sequencing peptides produced by an Asp-N protease digest of the modified protein. Because MMTS-reactive thiols have been implicated as ligands to the required Zn(II), EPR spectroscopy has been used to determine the spatial proximity of the modified cysteine residues. A forbidden (delta m = 2) EPR transition is observed indicating a through-space dipolar interaction between at least two of the nitroxides. The relative intensity of the forbidden and allowed transitions show that at least two of the unpaired electrons are within at most 7.6 A of each other. SL-MMTS-modified PBGS loses all Zn(II) and cannot catalyze product formation. The modified enzyme retains the ability to bind one of the two substrates at each active site. Binding of this substrate has no influence on the EPR spectral properties of the spin-labeled enzyme, or on the rate of release of the nitroxides when 2-mercaptoethanol is added.(ABSTRACT TRUNCATED AT 250 WORDS)

Markham, G. D.; Myers, C. B.; Harris, K. A.; Volin, M.; Jaffe, E. K.

1993-01-01

124

Optical switch  

DOEpatents

An optical switching device (10) is provided whereby light from a first glass fiber (16) or a second glass fiber (14) may be selectively transmitted into a third glass fiber (18). Each glass fiber is provided with a focusing and collimating lens system (26, 28, 30). In one mode of operation, light from the first glass fiber (16) is reflected by a planar mirror (36) into the third glass fiber (18). In another mode of operation, light from the second glass fiber (14) passes directly into the third glass fiber (18). The planar mirror (36) is attached to a rotatable table (32) which is rotated to provide the optical switching.

Reedy, Robert P. (Livermore, CA) [Livermore, CA

1987-01-01

125

Optical switch  

DOEpatents

An optical switching device is provided whereby light from a first glass fiber or a second glass fiber may be selectively transmitted into a third glass fiber. Each glass fiber is provided with a focusing and collimating lens system. In one mode of operation, light from the first glass fiber is reflected by a planar mirror into the third glass fiber. In another mode of operation, light from the second glass fiber passes directly into the third glass fiber. The planar mirror is attached to a rotatable table which is rotated to provide the optical switching. 3 figs.

Reedy, R.P.

1987-11-10

126

Information Switching Processor (ISP) contention analysis and control  

NASA Technical Reports Server (NTRS)

In designing a satellite system with on-board processing, the selection of a switching architecture is often critical. The on-board switching function can be implemented by circuit switching or packet switching. Destination-directed packet switching has several attractive features, such as self-routing without on-board switch reconfiguration, no switch control memory requirement, efficient bandwidth utilization for packet switched traffic, and accommodation of circuit switched traffic. Destination-directed packet switching, however, has two potential concerns: (1) contention and (2) congestion. And this report specifically deals with the first problem. It includes a description and analysis of various self-routing switch structures, the nature of contention problems, and contention and resolution techniques.

Inukai, Thomas

1995-01-01

127

Information Switching Processor (ISP) contention analysis and control  

NASA Astrophysics Data System (ADS)

In designing a satellite system with on-board processing, the selection of a switching architecture is often critical. The on-board switching function can be implemented by circuit switching or packet switching. Destination-directed packet switching has several attractive features, such as self-routing without on-board switch reconfiguration, no switch control memory requirement, efficient bandwidth utilization for packet switched traffic, and accommodation of circuit switched traffic. Destination-directed packet switching, however, has two potential concerns: (1) contention and (2) congestion. And this report specifically deals with the first problem. It includes a description and analysis of various self-routing switch structures, the nature of contention problems, and contention and resolution techniques.

Inukai, Thomas

1995-07-01

128

Flipping the switch: integrin switching provides metastatic competence.  

PubMed

Integrin switching plays a critical role in the progression to metastatic disease, but the mechanism by which it contributes remains poorly understood. In the 11 February 2014 issue of Science Signaling, Truong et al. identified a transforming growth factor-?-mediated, prometastatic switch that is activated by ?1 integrin inhibition in triple-negative breast cancers (TNBCs). Their work provides insight into the complex signaling changes that arise from integrin switching. Further characterization of ?-integrin switching will require elucidation of the distribution of specific ?-? integrin heterodimers and the role of ligand binding. Identifying the nature of the molecular interactions and the influence of a specific oncogenic context, including the status of driver mutations such as those in Myc and p53, will define the next phase in integrin cancer biology. PMID:24667375

Madamanchi, Aasakiran; Zijlstra, Andries; Zutter, Mary M

2014-03-25

129

Switched matrix accelerator  

SciTech Connect

We describe a new concept for a microwave circuit functioning as a charged-particle accelerator at mm wavelengths, permitting an accelerating gradient higher than conventional passive circuits can withstand consistent with cyclic fatigue. The device provides acceleration for multiple bunches in parallel channels, and permits a short exposure time for the conducting surface of the accelerating cavities. Our analysis includes scalings based on a smooth transmission line model and a complementary treatment with a coupled-cavity simulation. We also provide an electromagnetic design for the accelerating structure, arriving at rough dimensions for a seven-cell accelerator matched to standard waveguide and suitable for bench tests at low power in air at 91.392 GHz. A critical element in the concept is a fast mm-wave switch suitable for operation at high power, and we present the considerations for implementation in an H-plane tee. We discuss the use of diamond as the photoconductor switch medium.

Whittum, David H.; Tantawi, Sami G.

2001-01-01

130

Diversification of Quiescin sulfhydryl oxidase in a preserved framework for redox relay  

PubMed Central

Background The enzyme family Quiescin Sulfhydryl Oxidase (QSOX) is defined by the presence of an amino-terminal thioredoxin-fold (Trx) domain and a carboxy-terminal Erv family sulfhydryl oxidase domain. QSOX enzymes, which generate disulfide bonds and transfer them to substrate proteins, are present in a wide variety of eukaryotic species including metazoans and plants, but are absent from fungi. Plant and animal QSOXs differ in their active-site amino acid sequences and content of non-catalytic domains. The question arises, therefore, whether the Trx-Erv fusion has the same mechanistic significance in all QSOX enzymes, and whether shared features distinguish the functional domains of QSOX from other instances in which these domains occur independently. Through a study of QSOX phylogeny and an analysis of QSOX sequence diversity in light of recently determined three-dimensional structures, we sought insight into the origin and evolution of this multi-domain redox alliance. Results An updated collection of QSOX enzymes was used to confirm and refine the differences in domain composition and active-site sequence motif patterns of QSOXs belonging to various eukaryotic phyla. Beyond the expected phylogenetic distinction of animal and plant QSOX enzymes, trees based on individual redox-active QSOX domains show a particular distinction of the Trx domain early in plant evolution. A comparison of QSOX domains with Trx and Erv domains from outside the QSOX family revealed several sequence and structural features that clearly differentiate QSOXs from other enzymes containing either of these domains. Notably, these features, present in QSOXs of various phyla, localize to the interface between the Trx and Erv domains observed in structures of QSOX that model interdomain redox communication. Conclusions The infrastructure for interdomain electron relay, previously identified for animal and parasite QSOXs, is found broadly across the QSOX family, including the plant enzymes. We conclude that the conserved three-dimensional framework of the QSOX catalytic domains accommodates lineage-specific differences and paralog diversification in the amino acid residues surrounding the redox-active cysteines. Our findings indicate that QSOX enzymes are characterized not just by the presence of the two defining domain folds but also by features that promote coordinated activity.

2013-01-01

131

Flavin-linked Erv-family sulfhydryl oxidases release superoxide anion during catalytic turnover†  

PubMed Central

Typically, simple flavoprotein oxidases couple the oxidation of their substrates with the formation of hydrogen peroxide without release of significant levels of the superoxide ion. However, two evolutionarily-related single-domain sulfhydryl oxidases (Erv2p; a yeast endoplasmic reticulum resident protein and augmenter of liver regeneration, ALR, an enzyme predominantly found in the mitochondrial intermembrane) release up to ~30% of the oxygen they reduce as the superoxide ion. Both enzymes oxidize dithiol substrates via a redox-active disulfide adjacent to the flavin cofactor within the helix-rich Erv domain. Subsequent reduction of the flavin is followed by transfer of reducing equivalents to molecular oxygen. Superoxide release was initially detected using tris(3-hydroxypropyl)phosphine (THP) as an alternative reducing substrate to dithiothreitol (DTT). THP, and other phosphines, showed anomalously high turnover numbers with Erv2p and ALR in the oxygen electrode but oxygen consumption was drastically suppressed upon the addition of superoxide dismutase. The superoxide ion initiates a radical chain reaction promoting the aerobic oxidation of phosphines with the formation of hydrogen peroxide. Use of a known flux of superoxide generated by the xanthine/xanthine oxidase system showed that one superoxide ion stimulates the reduction of 27 and 4.5 molecules of oxygen using THP and tris(2-carboxyethyl)phosphine (TCEP) respectively. This superoxide-dependent amplification of oxygen consumption by phosphines provides a new kinetic method for the detection of superoxide. Superoxide release was also observed by a standard chemiluminescence method using a luciferin analog (MCLA) when 2 mM DTT was employed as a substrate of Erv2p and ALR. The percentage of superoxide released from Erv2p increased to ~65% when monomeric mutants of the normally homodimeric enzyme were used. In contrast, monomeric multi-domain Quiescin-sulfhydryl oxidase enzymes that also contain an Erv FAD-binding fold release only 1-5% of their total reduced oxygen species as the superoxide ion. Aspects of the mechanism and possible physiological significance of superoxide release from these Erv-domain flavoproteins are discussed.

Daithankar, Vidyadhar N.; Wang, Wenzhong; Trujillo, Joliene R.; Thorpe, Colin

2011-01-01

132

Production and characterisation of AoSOX2 from Aspergillus oryzae , a novel flavin-dependent sulfhydryl oxidase with good pH and temperature stability  

Microsoft Academic Search

Sulfhydryl oxidases have found application in the improvement of both dairy and baking products due to their ability to oxidise\\u000a thiol groups in small molecules and cysteine residues in proteins. A genome mining study of the available fungal genomes had\\u000a previously been performed by our group in order to identify novel sulfhydryl oxidases suitable for industrial applications\\u000a and a representative

Greta Faccio; Kristiina Kruus; Johanna Buchert; Markku Saloheimo

2011-01-01

133

Oxidative burst and electrolyte leakage induced by sulfhydryl blockers and by membrane permeabilizing reagents in different organs of Egeria densa  

Microsoft Academic Search

Summary Sulfhydryl blockers, such as N-ethylmaleimide, iodoacetate and heavy metals induce a transitory stimulation of O2 consumption and H2O2 production (oxidative burst) and a rapid release of electrolytes in leaves of various aquatic plants. The correlation between these two responses to N-ethylmaleimide or to Ag+ in separate organs and stages of leaf development was investigated inEgeria densa. Only adult leaves

E. Amicucci; F. Albergoni; M. Manzoni; L. Zingarelli; M. T. Marrè

1998-01-01

134

Hydrogen peroxide-induced reduction of delayed rectifier potassium current in hippocampal neurons involves oxidation of sulfhydryl groups.  

PubMed

This study examined the effect of H2O2 on the delayed rectifier potassium current (IKDR) in isolated hippocampal neurons. Whole-cell voltage-clamp experiments were performed on freshly dissociated hippocampal CA1 neurons of SD rats before and after treatment with H2O2. To reveal the mechanism behind H2O2-induced changes in IKDR, cells were treated with different oxidizing and reducing agents. External application of membrane permeable H2O2 reduced the amplitude and voltage-dependence of IKDR in a concentration dependent manner. Desferoxamine (DFO), an iron-chelator that prevents hydroxyl radical (OH) generation, prevented H2O2-induced reduction in IKDR. Application of the sulfhydryl-oxidizing agent 5,5 dithio-bis-nitrobenzoic acid (DTNB) mimicked the effect of H2O2. Sulfhydryl-reducing agents dithiothreitol (DTT) and glutathione (GSH) alone did not affect IKDR; however, DTT and GSH reversed and prevented the H2O2-induced inhibition of IKDR, respectively. Membrane impermeable agents GSH and DTNB showed effects only when added intracellularly identifying intracellular sulfhydryl groups as potential targets for hydroxyl-mediated oxidation. However, the inhibitory effects of DTNB and H2O2 at the positive test potentials were completely and partially abolished by DTT, respectively, suggesting an additional mechanism of action for H2O2, that is not shared by DTNB. In summary, this study provides evidence for the redox modulation of IKDR, identifies hydroxyl radical as an intermediate oxidant responsible for the H2O2-induced decrease in current amplitude and identifies intracellular sulfhydryl groups as an oxidative target. PMID:23688542

Hasan, Sonia M K; Redzic, Zoran B; Alshuaib, Waleed B

2013-07-01

135

Sulfhydryl-disulfide changes in storage proteins of developing wheat grain: influence on the SDS-unextractable glutenin polymer formation  

Microsoft Academic Search

To understand more precisely the function of free glutenin SH and SS groups in glutenins of developing wheat for UPP formation, a specific sulfhydryl probe, monobromobimane (mBBr), was used for an in vitro protein labeling. By applying this procedure to two varieties of wheat differing in high molecular weight glutenin subunit composition (2*, 7+8, 5+10 and 0, 6+8, 2+12, respectively,

L. Rhazi; R. Cazalis; T. Aussenac

2003-01-01

136

The conserved baculovirus protein p33 (Ac92) is a flavin adenine dinucleotide-linked sulfhydryl oxidase  

SciTech Connect

Open reading frame 92 of the Autographa californica baculovirus (Ac92) is one of about 30 core genes present in all sequenced baculovirus genomes. Computer analyses predicted that the Ac92 encoded protein (called p33) and several of its baculovirus orthologs were related to a family of flavin adenine dinucleotide (FAD)-linked sulfhydryl oxidases. Alignment of these proteins indicated that, although they were highly diverse, a number of amino acids in common with the Erv1p/Alrp family of sulfhydryl oxidases are present. Some of these conserved amino acids are predicted to stack against the isoalloxazine and adenine components of FAD, whereas others are involved in electron transfer. To investigate this relationship, Ac92 was expressed in bacteria as a His-tagged fusion protein, purified, and characterized both spectrophotometrically and for its enzymatic activity. The purified protein was found to have the color (yellow) and absorption spectrum consistent with it being a FAD-containing protein. Furthermore, it was demonstrated to have sulfhydryl oxidase activity using dithiothreitol and thioredoxin as substrates.

Long, C.M. [Department of Biochemistry and Biophysics, Oregon State University, Corvallis, OR 97331 (United States); Rohrmann, G.F. [Department of Microbiology, Oregon State University, Corvallis, OR 97331 (United States); Merrill, G.F., E-mail: merrillg@onid.orst.ed [Department of Biochemistry and Biophysics, Oregon State University, Corvallis, OR 97331 (United States)

2009-06-05

137

The effect of sulfhydryl groups and disulphide linkage in the thermal aggregation of Z19 alpha-zein.  

PubMed

Zeins are the major storage proteins in corn seeds organized in protein bodies located in the endosperm. They are soluble in alcoholic solution and depict a high tendency to aggregation. The Z19 alpha-zein aggregates obtained by heating show a particular and interesting temperature-dependent behavior. This work was aimed at determining not only the effect of temperature on the aggregation behavior, but also the effect of the sulfhydryl groups and disulphide bonds on the thermal aggregation process under non-aqueous conditions. Z19 alpha-zein was chemically modified to obtain different sulfhydryl groups and disulphide-bonds content. Far-UV CD, ANS emission fluorescence, and dynamic light scattering, as well as differential scanning calorimetry, were performed to characterize this protein. Removal of these disulphide-bonds and alkylation of all the sulfhydryl groups in the protein promoted the lowest T(m) of 57.36 degrees C, eliminated aggregation, enhanced protein flexibility, and diminished thermal stability. These results suggest that the disulphide linkage could be the driving force for the Z19 alpha-zein aggregation. PMID:18466780

Cabra, Vanessa; Vázquez-Contreras, Edgar; Moreno, Abel; Arreguin-Espinosa, Roberto

2008-01-01

138

Phenylethynyl-butyltellurium inhibits the sulfhydryl enzyme Na+, K+ -ATPase: an effect dependent on the tellurium atom.  

PubMed

Organotellurium compounds are known for their toxicological effects. These effects may be associated with the chemical structure of these compounds and the oxidation state of the tellurium atom. In this context, 2-phenylethynyl-butyltellurium (PEBT) inhibits the activity of the sulfhydryl enzyme, ?-aminolevulinate dehydratase. The present study investigated on the importance of the tellurium atom in the PEBT ability to oxidize mono- and dithiols of low molecular weight and sulfhydryl enzymes in vitro. PEBT, at high micromolar concentrations, oxidized dithiothreitol (DTT) and inhibited cerebral Na(+), K(+)-ATPase activity, but did not alter the lactate dehydrogenase activity. The inhibition of cerebral Na(+), K(+)-ATPase activity was completely restored by DTT. By contrast, 2-phenylethynyl-butyl, a molecule without the tellurium atom, neither oxidized DTT nor altered the Na(+), K(+)-ATPase activity. In conclusion, the tellurium atom of PEBT is crucial for the catalytic oxidation of sulfhydryl groups from thiols of low molecular weight and from Na(+), K(+)-ATPase. PMID:23955422

Quines, Caroline B; Rosa, Suzan G; Neto, José S S; Zeni, Gilson; Nogueira, Cristina W

2013-11-01

139

Reset Switching Probability of Resistive Switching Devices  

Microsoft Academic Search

The reset switching probability of resistive switching devices is characterized in array testing. The measured switching probability can be quantitatively explained based on the mecha- nism of a thermally activated reset process. An analytical model of switching probability is developed to describe the dependence of reset probability on operation parameters, including applied voltage, selection transistor gate voltage, and pulsewidth. The

An Chen; Ming-Ren Lin

2011-01-01

140

Protein Substrate Discrimination in the Quiescin-sulfhydryl Oxidase (QSOX) Family†  

PubMed Central

This work explores the substrate specificity of the Quiescin-sulfhydryl oxidase (QSOX) family of disulfide-generating flavoenzymes to provide enzymological context for investigation of the physiological roles of these facile catalysts of oxidative protein folding. QSOX enzymes are generally unable to form disulfide bonds within well-structured proteins. Use of a temperature-sensitive mutant of ubiquitin-conjugating enzyme 4 (Ubc4?) as a model substrate shows that QSOX activity correlates with the unfolding of Ubc4? monitored by circular dichroism. Fusion of Ubc4? with the more stable glutathione-S-transferase domain demonstrates that QSOX can selectively introduce disulfides into the less stable domain of the fusion protein. In terms of intermolecular disulfide bond generation, QSOX is unable to crosslink well-folded globular proteins via their surface thiols. However, the construction of a septuple mutant of RNase A, retaining a single cysteine residue, demonstrates that flexible protein monomers can be directly coupled by the oxidase. Steady- and pre-steady state kinetic experiments, combined with static fluorescence approaches, indicate that while QSOX is an efficient catalyst for disulfide bond formation between mobile elements of structure, it does not appear to have a significant binding site for unfolded proteins. These aspects of protein substrate discrimination by QSOX family members are rationalized in terms of the stringent steric requirements for disulfide exchange reactions.

Codding, Jennifer A.; Israel, Benjamin A.; Thorpe, Colin

2012-01-01

141

Position of the sulfhydryl group and the disulfide bonds of human glucocerebrosidase.  

PubMed

Purified human glucocerebrosidase isolated from placenta was modified with [14C]-iodoacetic acid without reduction and digested with both protease-V8 at pH 4.0 followed by alpha-chymotrypsin at pH 7.5. The majority of radioactivity was found in a peptide that contained the [14C]-carboxymethylated-cysteine identified as CM-Cys18. Direct sequencing of the N-terminus of the intact labeled protein confirmed the modification of Cys18. For identification of disulfide bond-containing peptides, another portion of glucocerebrosidase was alkylated with nonlabeled iodoacetic acid and then digested with protease V8 and alpha-chymotrypsin as before. Twenty-eight HPLC fragments were collected. These purified peaks were then reduced with beta-mercaptoethanol followed by S-carboxymethylation with [14C]-iodoacetic acid. Three peptides among these 28 peptides generated two radioactive daughter peptides. These peptides were sequenced and the position of the radioactive CM-cysteines identified. The locations of these disulfides are Cys4-Cys16, Cys23-Cys342, and Cys126-Cys248. Attempts to reproduce the free sulfhydryl labeling experiments using the glucocerebrosidase isolated from Ceredase proved unsuccessful. No label was incorporated by this enzyme prior to reduction. This result suggests that the form of the protein used in the clinic differs from the native protein. PMID:7576080

Lee, Y; Kinoshita, H; Radke, G; Weiler, S; Barranger, J A; Tomich, J M

1995-04-01

142

Tissue distribution of quiescin Q6/sulfhydryl oxidase (QSOX) in developing mouse.  

PubMed

Quiescin Q6/sulfhydryl oxidases (QSOX) are revisited thiol oxidases considered to be involved in the oxidative protein folding, cell cycle control and extracellular matrix remodeling. They contain thioredoxin domains and introduce disulfide bonds into proteins and peptides, with the concomitant hydrogen peroxide formation, likely altering the redox environment. Since it is known that several developmental processes are regulated by the redox state, here we assessed if QSOX could have a role during mouse fetal development. For this purpose, an anti-recombinant mouse QSOX antibody was produced and characterized. In E(13.5), E(16.5) fetal tissues, QSOX immunostaining was confined to mesoderm- and ectoderm-derived tissues, while in P1 neonatal tissues it was slightly extended to some endoderm-derived tissues. QSOX expression, particularly by epithelial tissues, seemed to be developmentally-regulated, increasing with tissue maturation. QSOX was observed in loose connective tissues in all stages analyzed, intra and possibly extracellularly, in agreement with its putative role in oxidative folding and extracellular matrix remodeling. In conclusion, QSOX is expressed in several tissues during mouse development, but preferentially in those derived from mesoderm and ectoderm, suggesting it could be of relevance during developmental processes. PMID:18034316

Portes, Kelly F; Ikegami, Cecília M; Getz, Joselito; Martins, Ana P; de Noronha, Lucia; Zischler, Luciana F; Klassen, Giseli; Camargo, Anamaria A; Zanata, Silvio M; Bevilacqua, Estela; Nakao, Lia S

2008-04-01

143

Kinetics of ferroelectric switching in ultrathin films  

NASA Astrophysics Data System (ADS)

The kinetics of polarization switching in ultrathin ferroelectric polymer films exhibit a critical behavior; there is a pronounced slowing just above the coercive field and just below the critical temperature. The critical slowing is observed in the switching kinetics of ferroelectric Langmuir-Blodgett films of 70% vinylidene-fluoride and 30% trifluoroethylene copolymer with thickness up to 30 ML. Thicker films exhibit an exponential dependence on the field and temperature that is normally associated with extrinsic switching by domain nucleation and growth. We show that the critical behavior arises naturally from the dynamics of homogeneous intrinsic switching in the context of mean-field theory. These results have important implications for the modeling and control of the ferroelectric films in nonvolatile computer memories and solid-state data storage media.

Vizdrik, G.; Ducharme, S.; Fridkin, V. M.; Yudin, S. G.

2003-09-01

144

Ferroelectric switching of elastin.  

PubMed

Ferroelectricity has long been speculated to have important biological functions, although its very existence in biology has never been firmly established. Here, we present compelling evidence that elastin, the key ECM protein found in connective tissues, is ferroelectric, and we elucidate the molecular mechanism of its switching. Nanoscale piezoresponse force microscopy and macroscopic pyroelectric measurements both show that elastin retains ferroelectricity at 473 K, with polarization on the order of 1 ?C/cm(2), whereas coarse-grained molecular dynamics simulations predict similar polarization with a Curie temperature of 580 K, which is higher than most synthetic molecular ferroelectrics. The polarization of elastin is found to be intrinsic in tropoelastin at the monomer level, analogous to the unit cell level polarization in classical perovskite ferroelectrics, and it switches via thermally activated cooperative rotation of dipoles. Our study sheds light onto a long-standing question on ferroelectric switching in biology and establishes ferroelectricity as an important biophysical property of proteins. This is a critical first step toward resolving its physiological significance and pathological implications. PMID:24958890

Liu, Yuanming; Cai, Hong-Ling; Zelisko, Matthew; Wang, Yunjie; Sun, Jinglan; Yan, Fei; Ma, Feiyue; Wang, Peiqi; Chen, Qian Nataly; Zheng, Hairong; Meng, Xiangjian; Sharma, Pradeep; Zhang, Yanhang; Li, Jiangyu

2014-07-01

145

The viral oncogene Np9 acts as a critical molecular switch for co-activating ?-catenin, ERK, Akt and Notch1 and promoting the growth of human leukemia stem/progenitor cells.  

PubMed

HERV-K (human endogenous retrovirus type K) type 1-encoded Np9 is a tumor-specific biomarker, but its oncogenic role and targets in human leukemia remain elusive. We first identified Np9 as a potent viral oncogene in human leukemia. Silencing of Np9 inhibited the growth of myeloid and lymphoblastic leukemic cells, whereas expression of Np9 significantly promoted the growth of leukemia cells in vitro and in vivo. Np9 not only activated ERK, AKT and Notch1 pathways but also upregulated ?-catenin essential for survival of leukemia stem cells. In human leukemia, Np9 protein level in leukemia patients was substantially higher than that in normal donors (56% vs 4.5%). Moreover, Np9 protein level was correlated with the number of leukemia stem/progenitor cells but not detected in normal CD34(+) hematopoietic stem cells. In addition, Np9-positive samples highly expressed leukemia-specific pol-env polyprotein, env and transmembrane proteins as well as viral particles. Thus, the viral oncogene Np9 is a critical molecular switch of multiple signaling pathways regulating the growth of leukemia stem/progenitor cells. These findings open a new perspective to understand the etiology of human common leukemia and provide a novel target for treating leukemia. PMID:23307033

Chen, T; Meng, Z; Gan, Y; Wang, X; Xu, F; Gu, Y; Xu, X; Tang, J; Zhou, H; Zhang, X; Gan, X; Van Ness, C; Xu, G; Huang, L; Zhang, X; Fang, Y; Wu, J; Zheng, S; Jin, J; Huang, W; Xu, R

2013-07-01

146

Metformin exhibits radiation countermeasures efficacy when used alone or in combination with sulfhydryl containing drugs.  

PubMed

Metformin, a biguanide drug used in the treatment of type II diabetes, was evaluated alone and in combination with amifostine, captopril, MESNA or N-acetyl-cysteine (NAC) for its ability to protect when administered 24 h after irradiation. Mouse embryo fibroblasts (MEF), human microvascular endothelial cells (HMEC) and SA-NH mouse sarcoma cells were exposed to 4 Gy in vitro. C3H mice were exposed to 7 Gy and evaluated utilizing an endogenous spleen colony assay system. Amifostine and WR1065, administered 30 min prior to irradiation, were used as positive controls. Treatment of MEF, HMEC and SA-NH cells with metformin elevated survival levels by 1.4-, 1.5- and 1.3-fold compared to 1.9-, 1.8- and 1.6-fold for these same cells treated with WR1065, respectively. Metformin (250 mg/kg) was effective in protecting splenic cells from a 7 Gy dose in vivo (protection factor = 1.8). Amifostine (400 mg/kg), administered 30 min prior to irradiation resulted in a 2.6-fold survival elevation, while metformin administered 24 h after irradiation in combination with NAC (400 mg/kg), MESNA (300 mg/kg) or captopril (200 mg/kg) enhanced survival by 2.6-, 2.8- and 2.4-fold, respectively. Each of these agents has been approved by the FDA for human use and each has a well characterized human safety profile. Metformin alone or in combination with selected sulfhydryl agents possesses radioprotective properties when administered 24 h after radiation exposure comparable to that observed for amifostine administered 30 min prior to irradiation making it a potentially useful agent for radiation countermeasures use. PMID:24754562

Miller, Richard C; Murley, Jeffrey S; Grdina, David J

2014-05-01

147

Human Quiescin-sulfhydryl Oxidase, QSOX1: Probing Internal Redox Steps by Mutagenesis†  

PubMed Central

The flavoprotein Quiescin-sulfhydryl oxidase (QSOX) rapidly inserts disulfide bonds into unfolded, reduced proteins with the concomitant reduction of oxygen to hydrogen peroxide. This study reports the first heterologous expression and enzymological characterization of a human QSOX1 isoform. Like QSOX isolated from avian egg white, recombinant HsQSOX1 is highly active towards reduced ribonuclease A (RNase) and dithiothreitol but shows a >100-fold lower kcat/Km for reduced glutathione. Previous studies on avian QSOX led to a model in which reducing equivalents were proposed to relay through the enzyme from the first thioredoxin domain (C70–C73) to a distal disulfide (C509–C512), then across the dimer interface to the FAD-proximal disulfide (C449–C452), and finally to the FAD. The present work shows that, unlike the native avian enzyme, HsQSOX1 is monomeric. The recombinant expression system enabled construction of the first cysteine mutants for mechanistic dissection of this enzyme family. Activity assays with mutant HsQSOX1 indicated that the conserved distal C509–C512 disulfide is dispensable for the oxidation of reduced RNase or dithiothreitol. The four other cysteine residues chosen for mutagenesis, C70, C73, C449, and C452, are all crucial for efficient oxidation of reduced RNase. C452, of the proximal disulfide, is shown to be the charge-transfer donor to the flavin ring of QSOX, and its partner, C449, is expected to be the interchange thiol, forming a mixed disulfide with C70 in the thioredoxin domain. These data demonstrate that all the internal redox steps occur within the same polypeptide chain of mammalian QSOX and commence with a direct interaction between the reduced thioredoxin domain and the proximal disulfide of the Erv/ALR domain.

Heckler, Erin J.; Alon, Assaf; Fass, Deborah; Thorpe, Colin

2013-01-01

148

Human quiescin-sulfhydryl oxidase, QSOX1: probing internal redox steps by mutagenesis.  

PubMed

The flavoprotein quiescin-sulfhydryl oxidase (QSOX) rapidly inserts disulfide bonds into unfolded, reduced proteins with the concomitant reduction of oxygen to hydrogen peroxide. This study reports the first heterologous expression and enzymological characterization of a human QSOX1 isoform. Like QSOX isolated from avian egg white, recombinant HsQSOX1 is highly active toward reduced ribonuclease A (RNase) and dithiothreitol but shows a >100-fold lower k cat/ K m for reduced glutathione. Previous studies on avian QSOX led to a model in which reducing equivalents were proposed to relay through the enzyme from the first thioredoxin domain (C70-C73) to a distal disulfide (C509-C512), then across the dimer interface to the FAD-proximal disulfide (C449-C452), and finally to the FAD. The present work shows that, unlike the native avian enzyme, HsQSOX1 is monomeric. The recombinant expression system enabled construction of the first cysteine mutants for mechanistic dissection of this enzyme family. Activity assays with mutant HsQSOX1 indicated that the conserved distal C509-C512 disulfide is dispensable for the oxidation of reduced RNase or dithiothreitol. The four other cysteine residues chosen for mutagenesis, C70, C73, C449, and C452, are all crucial for efficient oxidation of reduced RNase. C452, of the proximal disulfide, is shown to be the charge-transfer donor to the flavin ring of QSOX, and its partner, C449, is expected to be the interchange thiol, forming a mixed disulfide with C70 in the thioredoxin domain. These data demonstrate that all the internal redox steps occur within the same polypeptide chain of mammalian QSOX and commence with a direct interaction between the reduced thioredoxin domain and the proximal disulfide of the Erv/ALR domain. PMID:18393449

Heckler, Erin J; Alon, Assaf; Fass, Deborah; Thorpe, Colin

2008-04-29

149

The reactivity of the gamma-aminobutyric acid transporter GAT-1 toward sulfhydryl reagents is conformationally sensitive. Identification of a major target residue.  

PubMed

The gamma-aminobutyric acid (GABA) transporter GAT-1 is a prototype of neurotransmitter transporters that maintain low synaptic levels of the transmitter. Transport by GAT-1 is sensitive to the polar sulfhydryl reagent 2-aminoethyl methanethiosulfonate. Following replacement of endogenous cysteines to other residues by site-directed mutagenesis, we have identified cysteine 399 as the major determinant of the sensitivity of the transporter to sulfhydryl modification. Cysteine-399 is located in the intracellular loop connecting putative transmembrane domains eight and nine. Binding of both sodium and chloride leads to a reduced sensitivity to sulfhydryl reagents, whereas subsequent binding of GABA increases it. Strikingly binding of the nontransportable GABA analogue SKF100330A gives rise to a marked protection against sulfhydryl modification. These effects were not observed in C399S transporters. Under standard conditions GAT-1 is almost insensitive toward the impermeant 2-(trimethylammonium)ethyl methanethiosulfonate. However, in a chloride-free medium, addition of SKF100330A renders wild type GAT-1, but not C399S, very sensitive to this impermeant reagent. These observations indicate that the accessibility of cysteine 399 is highly dependent on the conformation of GAT-1. Consequently, topological assignments based on accessibility of endogeneous or engineered cysteines to small polar sulfhydryl reagents need to be interpreted with extreme caution. PMID:10438469

Golovanevsky, V; Kanner, B I

1999-08-13

150

Bioassay-guided isolation of an anti-ulcer diterpenoid from Croton reflexifolius: role of nitric oxide, prostaglandins and sulfhydryls.  

PubMed

Croton reflexifolius H. B. K (Euphorbiaceae) is a very common medicinal plant in the Huastecan region of Mexico that, according to local folk medicine, is considered useful in the treatment of gastritis and gastric ulcer. We have aimed to test the validity of this practice by using the experimental model of an ethanol-induced gastric ulcer in male Wistar rats. The results showed that C. reflexifolius had gastroprotector activity, that the hexane extract had the highest protective activity (64.38+/-7.72%), and that polyalthic acid isolated from this extract was the main active gastroprotector agent. Rats treated orally with polyalthic acid showed a gastroprotective effect similar to that elicited by carbenoxolone. As with carbenoxolone, the effect elicited by polyalthic acid was attenuated by pretreatment with either N(G)-nitro-L-arginine methyl ester (70 mgkg(-1), i.p.), a nitric oxide (NO) synthase inhibitor, or N-ethylmaleimide (10 mgkg(-1), s.c.), a blocker of sulfhydryl groups. This suggested that the gastroprotective mechanism of this diterpenoid involved the participation of both NO and endogenous sulfhydryl groups. Contrary to carbenoxolone, the gastroprotective effect of polyalthic acid was not affected by the inhibition of prostaglandin synthesis with indometacin (10 mgkg(-1), s. c.). In conclusion, Croton reflexifolius contains compounds with gastroprotector activity. Polyalthic acid, which was isolated from this plant, was the main compound with gastroprotector activity, having effectiveness similar to that found with the use of carbenoxolone. Whereas NO and sulfhydryl groups were involved in the mechanisms of gastroprotective action of polyalthic acid, prostaglandins were not. PMID:18549681

Reyes-Trejo, Benito; Sánchez-Mendoza, María Elena; Becerra-García, Anabel Ariana; Cedillo-Portugal, Ernestina; Castillo-Henkel, Carlos; Arrieta, Jesús

2008-07-01

151

Sulfhydryl Modification Induces Calcium Entry through IP3-Sensitive Store-Operated Pathway in Activation-Dependent Human Neutrophils  

PubMed Central

As the first line of host defense, neutrophils are stimulated by pro-inflammatory cytokines from resting state, facilitating the execution of immunomodulatory functions in activation state. Sulfhydryl modification has a regulatory role in a wide variety of physiological functions through mediation of signaling transductions in various cell types. Recent research suggested that two kinds of sulfhydryl modification, S-nitrosylation by exogenous nitric oxide (NO) and alkylation by N-ethylmaleimide (NEM), could induce calcium entry through a non-store-operated pathway in resting rat neutrophils and DDT1MF-2 cells, while in active human neutrophils a different process has been observed by us. In the present work, data showed that NEM induced a sharp rising of cytosolic calcium concentration ([Ca2+]c) without external calcium, followed by a second [Ca2+]c increase with readdition of external calcium in phorbol 12-myristate 13-acetate (PMA)-activated human neutrophils. Meanwhile, addition of external calcium did not cause [Ca2+]c change of Ca2+-free PMA-activated neutrophils before application of NEM. These data indicated that NEM could induce believable store-operated calcium entry (SOCE) in PMA-activated neutrophils. Besides, we found that sodium nitroprusside (SNP), a donor of exogenous NO, resulted in believable SOCE in PMA-activated human neutrophils via S-nitrosylation modification. In contrast, NEM and SNP have no effect on [Ca2+]c of resting neutrophils which were performed in suspension. Furthermore, 2-Aminoethoxydiphenyl borate, a reliable blocker of SOCE and an inhibitor of inositol 1,4,5-trisphosphate (IP3) receptor, evidently abolished SNP and NEM-induced calcium entry at 75 µM, while preventing calcium release in a concentration-dependent manner. Considered together, these results demonstrated that NEM and SNP induced calcium entry through an IP3-sensitive store-operated pathway of human neutrophils via sulfhydryl modification in a PMA-induced activation-dependent manner.

Pan, Leiting; Wu, Xian; Zhao, Dan; Hessari, Nason Ma'ani; Lee, Imshik; Zhang, Xinzheng; Xu, Jingjun

2011-01-01

152

Identification and expression of a new splicing variant of FAD-sulfhydryl oxidase in adult rat brain.  

PubMed

Flavoproteins of the quiescin/sulfhydryl oxidase (QSOX) family catalyze oxidation of peptide and protein thiols to disulfides with the reduction of oxygen to hydrogen peroxide. We report here the molecular cloning of a new putative sulfhydryl oxidase cDNA, rQSOX-L (GenBank Accession no ), from adult rat brain and its expression studied by RT-PCR, Northern and Western blots in rat tissues. DNA-sequencing demonstrated the existence of two cDNAs in rat cortex, corresponding to a long transcript (rQSOX-L) and a short transcript (rQSOX-S) which differed by 851 nucleotides due to alternative splicing. The new transcript, rQSOX-L (3356 nucleotides), was specifically expressed in brain, hypophysis, heart, testis and seminal vesicle. The distribution of this variant is not homogeneous in the different tissues studied and suggests a complex gene regulation. The full-length rQSOX-L cDNA has an open reading frame of 2250-bp encoding a protein of 750 amino acids that contains a signal peptide sequence, a protein-disulfide-isomerase-type thioredoxin and ERV1-ALR domains and a long form specific C-terminal extension. The rQSOX-L protein is highly homologous to members of the sulfhydryl oxidase/Quiescin family and contains particularly two potential sites for N-glycosylation. This protein isoform was specifically detected in rat brain tissues in opposition to the low molecular form that was ubiquitous. Matrix-assisted laser desorption/ionization time of flight mass spectrometry analysis of the immunoprecipitate tryptic fragments allowed the identification of rQSOX-L protein. PMID:16806532

Radom, Jean; Colin, Didier; Thiebault, Franck; Dognin-Bergeret, Mai; Mairet-Coello, Georges; Esnard-Feve, Annick; Fellmann, Dominique; Jouvenot, Michèle

2006-05-01

153

Redox Factor-1 Activates Endothelial SIRTUIN1 through Reduction of Conserved Cysteine Sulfhydryls in Its Deacetylase Domain  

PubMed Central

Apurinic/Apyrmidinic Endonuclease 1/Redox Factor-1 (APE1/Ref-1) is a reductant which is important for vascular homeostasis. SIRTUIN1 (SIRT1) is a lysine deacetylase that also promotes endothelium-dependent vasorelaxation. We asked if APE1/Ref-1 governs the redox state and activity of SIRT1, and whether SIRT1 mediates the effect of APE1/Ref-1 on endothelium-dependent vascular function. APE1/Ref-1 maintains sulfhydryl (thiol) groups of cysteine residues in SIRT1 in the reduced form and promotes endothelial SIRT1 activity. APE1/Ref-1 stimulates SIRT1 activity by targeting highly conserved vicinal thiols 371 and 374 which form a zinc tetra-thiolate motif in the deacetylase domain of SIRT1. Cysteine residues in the N-terminal redox domain of APE1/Ref-1 are essential for reducing SIRT1 and stimulating its activity. APE1/Ref-1 protects endothelial SIRT1 from hydrogen peroxide-induced oxidation of sulfhydryls and from inactivation. APE1/Ref-1 also promotes lysine deacetylation of the SIRT1 target endothelial nitric oxide synthase (eNOS). SIRT1 mutated at cysteines 371 and 374, which renders it non-reducible by APE1/Ref-1, prevents lysine deacetylation of eNOS by APE1/Ref-1. SIRT1 free thiol (reduced sulfhydryl) content and deacetylase activity are diminished in all examined tissues of APE1/Ref-1+/? mice, including the vasculature. Overexpression of SIRT1 in aortas of APE1/Ref-1+/? mice restores endothelium-dependent vasorelaxation and bioavailable nitric oxide (NO) to levels similar to those observed in wild-type mice. Thus, APE1/Ref-1, by maintaining functionally important cysteine sulfhydryls in SIRT1 in the reduced form, promotes endothelial SIRT1 activity. This reductive activation of endothelial SIRT1 by APE1/Ref-1 mediates the effect of APE1/Ref-1 on eNOS acetylation, promoting endothelium-derived NO and endothelium-dependent vasorelaxation.

Naqvi, Asma; Yamamori, Tohru; Kumar, Santosh; Kumar, Ajay; Irani, Kaikobad

2013-01-01

154

Regulatory role of glutathione and soluble sulfhydryl groups in the toxicity of adriamycin.  

PubMed

Adriamycin (ADR) has been shown to produce free radicals in NADPH microsomal systems, to increase oxygen consumption of both hepatic microsomes and heart sarcosomes and to stimulate superoxide formation in cardiac, submitochondria particles. These reactive products could produce the cardiotoxicity of ADR by oxidizing various membrane structures, especially if the heart lacks sufficient protective reducing substances such as thiols. We examined 1) the effect of ADR on reduced glutathione (G-SH) levels in various tissues including heart, 2) the ability of the sulfhydryl (SH) donor, cysteamine, to alter soluble SH levels in heart tissue after ADR administration and 3) the effects of SH donors (cysteamine and N-acetyl cysteine and G-SH depletion by diethyl maleate on ADR-induced lethality in Swiss ICR-HA mice. A single injection of ADR (15 mg/kg i.p.) elicited a statistically significant fall in liver (P < .05), heart (P < .02) and erythrocyte (P < .01) G-SH levels. Treatment with cysteamine protected against the fall in soluble SH groups in heart tissue. Cysteamine (50 mg/kg, i.p., every 8 hr for 6 days) or N-acetylcysteine (100 mg/kg, i.p., 1 hr before and 7 hr after ADR) protected against ADR-induced lethality and decreased the appearance of microscopic myocardial lesions. When endogenous levels of G-SH were depleted by diethyl maleate (300 mg/kg i.p., every 8 hr for 4 days), ADR lethality was markedly potentiated. Diethyl maleate alone did not cause death. We conclude 1) ADR significantly lowers G-SH levels in erythrocytes, liver and heart tissue, 2) the lowering of cardiac SH groups by ADR can be prevented by cysteamine and 3) ADR toxicity can be potentiated by diethyl maleate, a G-SH depletor, and reduced by cysteamine or N-acetyl cysteine, SH donors. These results suggest that the G-SH system may be involved in the modulation of ADR-induced toxicity. PMID:7441509

Olson, R D; MacDonald, J S; vanBoxtel, C J; Boerth, R C; Harbison, R D; Slonim, A E; Freeman, R W; Oates, J A

1980-11-01

155

Human augmenter of liver regeneration: probing the catalytic mechanism of a flavin-dependent sulfhydryl oxidase.  

PubMed

Augmenter of liver regeneration is a member of the ERV family of small flavin-dependent sulfhydryl oxidases that contain a redox-active CxxC disulfide bond in redox communication with the isoalloxazine ring of bound FAD. These enzymes catalyze the oxidation of thiol substrates with the reduction of molecular oxygen to hydrogen peroxide. This work studies the catalytic mechanism of the short, cytokine form of augmenter of liver regeneration (sfALR) using model thiol substrates of the enzyme. The redox potential of the proximal disulfide in sfALR was found to be approximately 57 mV more reducing than the flavin chromophore, in agreement with titration experiments. Rapid reaction studies show that dithiothreitol (DTT) generates a transient mixed disulfide intermediate with sfALR signaled by a weak charge-transfer interaction between the thiolate of C145 and the oxidized flavin. The subsequent transfer of reducing equivalents to the flavin ring is relatively slow, with a limiting apparent rate constant of 12.4 s(-1). However, reoxidation of the reduced flavin by molecular oxygen is even slower (2.3 s(-1) at air saturation) and thus largely limits turnover at 5 mM DTT. The nature of the charge-transfer complexes observed with DTT was explored using a range of simple monothiols to mimic the initial nucleophilic attack on the proximal disulfide. While ?-mercaptoethanol is a very poor substrate of sfALR (?0.3 min(-1) at 100 mM thiol), it rapidly generates a mixed disulfide intermediate allowing the thiolate of C145 to form a strong charge-transfer complex with the flavin. Unlike the other monothiols tested, glutathione is unable to form charge-transfer complexes and is an undetectable substrate of the oxidase. These data are rationalized on the basis of the stringent steric requirements for thiol-disulfide exchange reactions. The inability of the relatively bulky glutathione to attain the in-line geometry required for efficient disulfide exchange in sfALR may be physiologically important in preventing the oxidase from catalyzing the potentially harmful oxidation of intracellular glutathione. PMID:24147449

Schaefer-Ramadan, Stephanie; Gannon, Shawn A; Thorpe, Colin

2013-11-19

156

Fast superconducting magnetic field switch  

SciTech Connect

The superconducting magnetic switch or fast kicker magnet is employed with an electron stream or a bunch of electrons to rapidly change the direction of flow of the electron stream or bunch of electrons. The apparatus employs a beam tube which is coated with a film of superconducting material. The tube is cooled to a temperature below the superconducting transition temperature and is subjected to a constant magnetic field which is produced by an external dc magnet. The magnetic field produced by the dc magnet is less than the critical field for the superconducting material, thus, creating a Meissner Effect condition. A controllable fast electromagnet is used to provide a magnetic field which supplements that of the dc magnet so that when the fast magnet is energized the combined magnetic field is now greater than the critical field and the superconducting material returns to its normal state allowing the magnetic field to penetrate the tube. This produces an internal field which effects the direction of motion and of the electron stream or electron bunch. The switch can also operate as a switching mechanism for charged particles. Magnetic switches and particularly fast kicker magnets are used in the accelerator industry to quickly deflect particle beams into and out of various transport lines, storage rings, dumps, and specifically to differentially route individual bunches of particles from a train of bunches which are injected or ejected from a given ring.

Goren, Y.; Mahale, N.K.

1995-12-31

157

Latching relay switch assembly  

DOEpatents

A latching relay switch assembly which includes a coil section and a switch or contact section. The coil section includes at least one permanent magnet and at least one electromagnet. The respective sections are, generally, arranged in separate locations or cavities in the assembly. The switch is latched by a permanent magnet assembly and selectively switched by an overriding electromagnetic assembly.

Duimstra, Frederick A. (Anaheim Hills, CA)

1991-01-01

158

A Sulfhydryl Reagent Modulates Systemic Signaling for Wound-Induced and Systemin-Induced Proteinase Inhibitor Synthesis.  

PubMed Central

The sulfhydryl group reagent p-chloromecuribenzene sulfonic acid (PCMBS), an established inhibitor of active apoplastic phloem loading of sucrose in several plant species, is shown to be a powerful inhibitor of wound-induced and systemin-induced activation of proteinase inhibitor synthesis and accumulation in leaves of tomato plants (Lycopersicon esculentum cv Castlemart). PCMBS, supplied to young tomato plants through their cut stems, blocks accumulation of proteinase inhibitors in leaves in response to wounding. The application of systemin directly to fresh wounds enhances systemic accumulation of proteinase inhibitors to levels higher than wounding alone. Placed on fresh wounds, PCMBS severely inhibits systemic induction of proteinase inhibitors, in both the presence and absence of exogenous systemin. PCMBS inhibition can be reversed by cysteine, dithiothreitol, and glutathione. Radiolabeled systemin placed on fresh wounds is readily transported from the wounded leaves to upper leaves. However, in the presence of PCMBS, radiolabeled systemin is not transported away from wound sites. Induction of proteinase inhibitor I synthesis by oligouronides (degree of polymerization [almost equal to] 20), linolenic acid, or methyl jasmonate was not inhibited by PCMBS. The cumulative data support a possible role for sulfhydryl groups in mediating the translocation of systemin from wound sites to distal receptor sites in tomato plants and further support a role for systemin as a systemic wound signal.

Narvaez-Vasquez, J.; Orozco-Cardenas, M. L.; Ryan, C. A.

1994-01-01

159

Modulating the activity of avian pancreatic lipases by an alkyl chain reacting with an accessible sulfhydryl group.  

PubMed

Both turkey (TPL) and chicken (CPL) pancreatic lipases possess only one exposed sulfhydryl residue (Cystein114). After preincubation with the lipase, the sulfhydryl reagent C12 -TNB was found to be a powerful inhibitor of TPL whereas it had no effect on the CPL activity. Based on the 3D structure modelling and the molecular dynamics, the bulky dodecyl chain might hamper the lid movement of the TPL leading to the lipase inhibition upon reaction with C12 -TNB. Meanwhile, the predicted position of the C12 chain linked to Cystein114 of CPL could not block the lid opening mechanism which explains the absence of inhibition by C12 -TNB. Surprisingly, when added during the substrate hydrolysis, C12 -TNB activated the TPL but not the CPL that was slightly inhibited under these conditions. The 3D structure model generated for the open forms of C12 -TPL and C12 -CPL complexes showed that Cystein114 is still accessible and might react with C12 -TNB. Our models clearly explain the activation of TPL and the partial inhibition of CPL after the binding of the C12 chain to the enzyme. PMID:17624306

Fendri, Ahmed; Frikha, Fakher; Miled, Nabil; Ben Bacha, Abir; Gargouri, Youssef

2007-09-01

160

Automatic fault diagnosis of a switching regulator  

NASA Astrophysics Data System (ADS)

This paper describes a microprocessor-based system for the automatic fault diagnosis of a switching regulator. It covers the system from a test philosophy to a working breadboard that correctly identifies single simulated faults in the switching regulator. In addition to open circuit, short circuit, and stuck at faults, the system is capable of diagnosing faults due to excessive leakage, drift in critical components, and system instability.

Nienhaus, H. A.; Palmer, D. E.

161

Temporal switching jitter in photoconductive switches  

SciTech Connect

This paper reports on a recent comparison made between the Air Force Research Laboratory (AFRL) gallium arsenide, optically-triggered switch test configuration and the Sandia National Laboratories (SNL) gallium arsenide, optically-triggered switch test configuration. The purpose of these measurements was to compare the temporal switch jitter times. It is found that the optical trigger laser characteristics are dominant in determining the PCSS jitter.

GAUDET,JOHN A.; SKIPPER,MICHAEL C.; ABDALLA,MICHAEL D.; AHERN,SEAN M.; MAR,ALAN; LOUBRIEL,GUILLERMO M.; ZUTAVERN,FRED J.; O'MALLEY,MARTIN W.; HELGESON,WESLEY D.; ROMERO,SAMUEL P.

2000-04-13

162

RF MEMS switches and switch circuits  

Microsoft Academic Search

MEMS switches are devices that use mechanical movement to achieve a short circuit or an open circuit in the RF transmission line. RF MEMS switches are the specific micromechanical switches that are designed to operate at RF-to-millimeter-wave frequencies (0.1 to 100 GHz). The forces required for the mechanical movement can be obtained using electrostatic, magnetostatic, piezoelectric, or thermal designs. To

G. M. Rebeiz; J. B. Muldavin

2001-01-01

163

Selective labeling of the erythrocyte hexose carrier with a maleimide derivative of glucosamine: Relationship of an exofacial sulfhydryl to carrier conformation and structure  

SciTech Connect

Sulfhydryl-reactive derivatives of glucosamine were synthesized as potentially transportable affinity labels of the human erythrocyte hexose carrier. N-maleoylglycyl derivatives of either 6- or 2-amino-2-deoxy-D-glucopyranose were the most potent inhibitors of 3-O-methylglucose uptake, with concentrations of half-maximal irreversible inhibition of about 1 mM. Surprisingly, these derivatives were very poorly transported into erythrocytes. They reacted rather with an exofacial sulfhydryl on the carrier following a reversible binding step, the latter possibly to the exofacial substrate binding site. However, their reactivity was determined primarily by access to the exofacial sulfhydryl, which, as predicted by the one-site model of transport, required a carrier conformation with the exofacial substrate binding site exposed. Once reacted, the carrier was locked in a conformation unable to reorient inwardly and bind cytochalasin B. In intact erythrocytes the N-maleoylglycyl derivative of 2-({sup 3}H)glucosamine labeled predominantly an M{sub r} 45,000-66,000 protein on gel electrophoresis in a quantitative and cytochalasin B inhibitable fashion. By use of changes in carrier conformation induced by competitive transport inhibitors in a double differential labeling method, virtually complete selectivity of labeling of the carrier protein was achieved, the latter permitting localization of the reactive exofacial sulfhydryl to an M{sub r} 18,000-20,000 tryptic fragment of the carrier.

May, J.M. (Vanderbilt Univ. School of Medicine, Nashville, TN (USA))

1989-02-21

164

The bit-error rate performance of a satellite microwave matrix switch  

NASA Technical Reports Server (NTRS)

The matrix switch is a critical element of communications satellites employing multiple beam antennas and on-board switching. Two proof-of-concept models of a microwave matrix switch have been developed under NASA-sponsored contracts. These switches have undergone extensive testing at NASA Lewis Research Center to determine their operating characteristics in a system environment. The results of these tests indicate the effect of the matrix switch on the overall system operation.

Kerczewski, Robert J.

1988-01-01

165

The bit-error rate performance of a satellite microwave matrix switch  

NASA Technical Reports Server (NTRS)

The matrix switch is a critical element of communications satellites using multiple-beam antennas and on-board switching. Two proof-of-concept models of a microwave matrix switch have been developed under NASA-sponsored contracts. These switches have undergone extensive testing at NASA Lewis Research Center to determine their operating characteristics in a system environment. The results of these tests indicate the effect of the matrix switch on the overall system operation.

Kerczewski, Robert J.

1988-01-01

166

P5-type sulfhydryl oxidoreductase promotes the sorting of proteins to protein body I in rice endosperm cells  

PubMed Central

In rice (Oryza sativa) endosperm cells, oxidative protein folding is necessary for the sorting of storage proteins to protein bodies, PB-I and PB-II. Here we examined the role of sulfhydryl oxidoreductase PDIL2;3 (a human P5 ortholog) in the endoplasmic reticulum (ER), using GFP-AB, a PB-I marker in which the N-terminal region (AB) of ?-globulin is fused to green fluorescent protein (GFP). RNAi knockdown of PDIL2;3 inhibited the accumulation of GFP-AB in PB-I and promoted its exit from the ER. We discuss the role of PDIL2;3 in retaining proteins within the ER and specifying their localization to PB-I through disulfide bond formation.

Onda, Yayoi; Kawagoe, Yasushi

2013-01-01

167

Optical switching: Capillary action  

Microsoft Academic Search

Controlling light in optical systems quickly and easily is crucial for all-optical switching. An approach that does this by exploiting the condensation of gases in a porous structure could open up new avenues in the switching field.

Yuri Kivshar

2007-01-01

168

Remote switch actuator  

DOEpatents

The invention provides a device and method for actuating electrical switches remotely. The device is removably attached to the switch and is actuated through the transfer of a user's force. The user is able to remain physically removed from the switch site obviating need for protective equipment. The device and method allow rapid, safe actuation of high-voltage or high-current carrying electrical switches or circuit breakers.

Haas, Edwin Gerard; Beauman, Ronald; Palo, Jr., Stefan

2013-01-29

169

Fast superconducting magnetic field switch  

DOEpatents

The superconducting magnetic switch or fast kicker magnet is employed with electron stream or a bunch of electrons to rapidly change the direction of flow of the electron stream or bunch of electrons. The apparatus employs a beam tube which is coated with a film of superconducting material. The tube is cooled to a temperature below the superconducting transition temperature and is subjected to a constant magnetic field which is produced by an external dc magnet. The magnetic field produced by the dc magnet is less than the critical field for the superconducting material, thus, creating a Meissner Effect condition. A controllable fast electromagnet is used to provide a magnetic field which supplements that of the dc magnet so that when the fast magnet is energized the combined magnetic field is now greater that the critical field and the superconducting material returns to its normal state allowing the magnetic field to penetrate the tube. This produces an internal field which effects the direction of motion and of the electron stream or electron bunch. The switch can also operate as a switching mechanism for charged particles.

Goren, Yehuda (Mountain View, CA); Mahale, Narayan K. (The Woodlands, TX)

1996-01-01

170

Fast superconducting magnetic field switch  

DOEpatents

The superconducting magnetic switch or fast kicker magnet is employed with electron stream or a bunch of electrons to rapidly change the direction of flow of the electron stream or bunch of electrons. The apparatus employs a beam tube which is coated with a film of superconducting material. The tube is cooled to a temperature below the superconducting transition temperature and is subjected to a constant magnetic field which is produced by an external dc magnet. The magnetic field produced by the dc magnet is less than the critical field for the superconducting material, thus, creating a Meissner Effect condition. A controllable fast electromagnet is used to provide a magnetic field which supplements that of the dc magnet so that when the fast magnet is energized the combined magnetic field is now greater that the critical field and the superconducting material returns to its normal state allowing the magnetic field to penetrate the tube. This produces an internal field which effects the direction of motion and of the electron stream or electron bunch. The switch can also operate as a switching mechanism for charged particles. 6 figs.

Goren, Y.; Mahale, N.K.

1996-08-06

171

Alarm toe switch  

Microsoft Academic Search

An alarm toe switch inserted within a shoe for energizing an alarm circuit in a covert manner includes an insole mounting pad into which a miniature reed switch is fixedly molded. An elongated slot perpendicular to the reed switch is formed in the bottom surface of the mounting pad. A permanent cylindrical magnet positioned in the forward portion of the

Ganyard

1982-01-01

172

Alarm toe switch  

Microsoft Academic Search

An alarm toe switch inserted within a shoe for energizing an alarm circuit n a covert manner includes an insole mounting pad into which a miniature reed switch is fixedly molded. An elongated slot perpendicular to the reed switch is formed in the bottom surface of the mounting pad. A permanent cylindrical magnet positioned in the forward portion of the

Ganyard; Floyd P

1982-01-01

173

Latching type optical switch  

NASA Astrophysics Data System (ADS)

An optical switch on yttrium orthoferrite crystal is developed. The switch is of latching type and has an operating time of 100 ns. Matrices of switches are feasible due to the dimensions of the optical rotator of less than 2 mm3.

Didosyan, Y. S.; Hauser, H.; Fiala, W.; Nicolics, J.; Toriser, W.

2002-05-01

174

Triggered plasma opening switch  

DOEpatents

A triggerable opening switch for a very high voltage and current pulse includes a transmission line extending from a source to a load and having an intermediate switch section including a plasma for conducting electrons between transmission line conductors and a magnetic field for breaking the plasma conduction path and magnetically insulating the electrons when it is desired to open the switch.

Mendel, Clifford W. (Albuquerque, NM)

1988-01-01

175

Rotating flow transition related to surface switching  

NASA Astrophysics Data System (ADS)

We have investigated quantitatively the recently reported phenomena called "surface switching" that occurs in the flow driven by a rotating disk in an open cylindrical vessel [1]. The deformed free surface abruptly changes from an axisymmetric to a non-axisymmetric shape accompanying with a vertical oscillation at irregular intervals. We have studied the flow transition quantitatively using ultrasonic velocity profiling (UVP). The turbulent intensity shows a transition at the same Reynolds number as that for the surface switching. We find that the fluid-air interface becomes unstable at a smaller Reynolds number than the critical Reynolds number for the surface switching. Effects of the material of the rotating disk on the surface switching is discussed.

Tasaka, Yuji; Iima, Makoto; Ito, Kentaro

2008-11-01

176

Critical pulse power components  

SciTech Connect

Critical components for pulsed power conditioning systems will be reviewed. Particular emphasis will be placed on those components requiring significant development efforts. Capacitors, for example, are one of the weakest elements in high-power pulsed systems, especially when operation at high-repetition frequencies for extended periods of time are necessary. Switches are by far the weakest active components of pulse power systems. In particular, opening switches are essentially nonexistent for most applications. Insulaton in all systems and components requires development and improvement. Efforts under way in technology base development of pulse power components will be discussed.

Sarjeant, W.J.; Rohwein, G.J.

1981-01-01

177

Premature switching in graphene Josephson transistors  

Microsoft Academic Search

We investigate electronic transport in single layer graphene coupled to superconducting electrodes. In these Josephson transistors, we observe significant suppression in the critical current Ic and large variations in the product IcRn in comparison to theoretical predictions in the ballistic limit. We show that the depression of Ic can be explained by premature switching in underdamped Josephson junctions described within

Feng Miao; Wenzhong Bao; Hang Zhang; Chun Ning Lau

2009-01-01

178

High temperature superconductor resistive switch characteristics  

Microsoft Academic Search

High Temperature Superconductor (HTSc) will switch from the superconducting state to the normal resistive state when an intrinsic critical current density is exceeded. We have measured the transition characteristics for HTSc thin films forced into transition by the application of voltage driven overcurrents. These thin films were used in the development of prototype HTSc fault current limiting devices. The prototype

T. J. Scholz; John P. Barber

1997-01-01

179

Effective switching frequency multiplier inverter  

DOEpatents

A switching frequency multiplier inverter for low inductance machines that uses parallel connection of switches and each switch is independently controlled according to a pulse width modulation scheme. The effective switching frequency is multiplied by the number of switches connected in parallel while each individual switch operates within its limit of switching frequency. This technique can also be used for other power converters such as DC/DC, AC/DC converters.

Su, Gui-Jia (Oak Ridge, TN); Peng, Fang Z. (Okemos, MI)

2007-08-07

180

Quiescin sulfhydryl oxidase from Trypanosoma brucei: catalytic activity and mechanism of a QSOX family member with a single thioredoxin domain.  

PubMed

Quiescin sulfhydryl oxidase (QSOX) flavoenzymes catalyze the direct, facile, insertion of disulfide bonds into reduced unfolded proteins with the reduction of oxygen to hydrogen peroxide. To date, only QSOXs from vertebrates have been characterized enzymatically. These metazoan sulfhydryl oxidases have four recognizable domains: a redox-active thioredoxin (Trx) domain containing the first of three CxxC motifs (C(I)-C(II)), a second Trx domain with no obvious redox-active disulfide, a helix-rich domain, and then an Erv/ALR domain. This last domain contains the FAD moiety, a proximal C(III)-C(IV) disulfide, and a third CxxC of unknown function (C(V)-C(VI)). Plant and protist QSOXs lack the second Trx domain but otherwise appear to contain the same complement of redox centers. This work presents the first characterization of a single-Trx QSOX. Trypanosoma brucei QSOX was expressed in Escherichia coli using a synthetic gene and found to be a stable, monomeric, FAD-containing protein. Although evidently lacking an entire domain, TbQSOX shows catalytic activity and substrate specificity similar to the vertebrate QSOXs examined previously. Unfolded reduced proteins are more than 200-fold more effective substrates on a per thiol basis than glutathione and some 10-fold better than the parasite bisglutathione analogue, trypanothione. These data are consistent with a role for the protist QSOX in oxidative protein folding. Site-directed mutagenesis of each of the six cysteine residues (to serines) shows that the CxxC motif in the single-Trx domain is crucial for efficient catalysis of the oxidation of both reduced RNase and the model substrate dithiothreitol. As expected, the proximal disulfide C(III)-C(IV), which interacts with the flavin, is catalytically crucial. However, as observed with human QSOX1, the third CxxC motif shows no obvious catalytic role during the in vitro oxidation of reduced RNase or dithiothreitol. Pre-steady-state kinetics demonstrates that turnover in TbQSOX is limited by an internal redox step leading to 2-electron reduction of the FAD cofactor. In sum, the single-Trx domain QSOX studied here shows a striking similarity in enzymatic behavior to its double-Trx metazoan counterparts. PMID:20121244

Kodali, Vamsi K; Thorpe, Colin

2010-03-01

181

Quiescin Sulfhydryl Oxidase from Trypanosoma brucei: Catalytic Activity and Mechanism of a QSOX Family Member with a Single Thioredoxin Domain†  

PubMed Central

Quiescin-sulfhydryl oxidase (QSOX) flavoenzymes catalyze the direct, facile, insertion of disulfide bonds into reduced unfolded proteins with the reduction of oxygen to hydrogen peroxide. To date, only QSOXs from vertebrates have been characterized enzymatically. These metazoan sulfhydryl oxidases have 4 recognizable domains: a redox-active thioredoxin (Trx) domain containing the first of three CxxC motifs (CI-CII), a second Trx domain with no obvious redox-active disulfide, a helix-rich domain, and then an Erv/ALR domain. This last domain contains the FAD moiety, a proximal CIII-CIV disulfide and a third CxxC of unknown function (CV-CVI). Plant and protist QSOXs lack the second Trx domain, but otherwise appear to contain the same complement of redox centers. This work presents the first characterization of a single-Trx QSOX. Trypanosoma brucei QSOX was expressed in Escherichia coli using a synthetic gene and found to be a stable, monomeric, FAD-containing protein. Although evidently lacking an entire domain, TbQSOX shows catalytic activity and substrate specificity similar to the vertebrate QSOXs examined previously. Unfolded reduced proteins are more than 200-fold more effective substrates on a per-thiol basis than glutathione, and some 10-fold better than the parasite bis-glutathione analog, trypanothione. These data are consistent with a role for the protist QSOX in oxidative protein folding. Site-directed mutagenesis of each of the 6 cysteine residues (to serines) show that the CxxC motif in the single Trx domain is crucial for efficient catalysis of the oxidation of both reduced RNase and the model substrate dithiothreitol. As expected, the proximal disulfide CIII-CIV, which interacts with the flavin, is catalytically crucial. However, as observed with human QSOX1, the third CxxC motif shows no obvious catalytic role during the in vitro oxidation of reduced RNase or dithiothreitol. Pre-steady state kinetics demonstrates that turnover in TbQSOX is limited by an internal redox step leading to 2-electron reduction of the FAD cofactor. In sum, the single-Trx domain QSOX studied here shows a striking similarity in enzymatic behavior to its double-Trx metazoan counterparts.

Kodali, Vamsi K.; Thorpe, Colin

2010-01-01

182

An acoustic switch.  

PubMed

The benefits derived from the development of acoustic transistors which act as switches or amplifiers have been reported in the literature. Here we propose a model of acoustic switch. We theoretically demonstrate that the device works: the input signal is totally restored at the output when the switch is on whereas the output signal nulls when the switch is off. The switch, on or off, depends on a secondary acoustic field capable to manipulate the main acoustic field. The model relies on the attenuation effect of many oscillating bubbles on the main travelling wave in the liquid, as well as on the capacity of the secondary acoustic wave to move the bubbles. This model evidences the concept of acoustic switch (transistor) with 100% efficiency. PMID:23816529

Vanhille, Christian; Campos-Pozuelo, Cleofé

2014-01-01

183

Solid state switch  

DOEpatents

A solid state switch, with reverse conducting thyristors, is designed to operate at 20 kV hold-off voltage, 1500 A peak, 1.0 .mu.s pulsewidth, and 4500 pps, to replace thyratrons. The solid state switch is more reliable, more economical, and more easily repaired. The switch includes a stack of circuit card assemblies, a magnetic assist and a trigger chassis. Each circuit card assembly contains a reverse conducting thyristor, a resistor capacitor network, and triggering circuitry.

Merritt, Bernard T. (Livermore, CA); Dreifuerst, Gary R. (Livermore, CA)

1994-01-01

184

AC magnetohydrodynamic microfluidic switch  

SciTech Connect

A microfluidic switch has been demonstrated using an AC Magnetohydrodynamic (MHD) pumping mechanism in which the Lorentz force is used to pump an electrolytic solution. By integrating two AC MHD pumps into different arms of a Y-shaped fluidic circuit, flow can be switched between the two arms. This type of switch can be used to produce complex fluidic routing, which may have multiple applications in {micro}TAS.

Lemoff, A V; Lee, A P

2000-03-02

185

The 11?-hydroxysteroid dehydrogenase type 2 activity in human placental microsomes is inactivated by zinc and the sulfhydryl modifying reagent N-ethylmaleimide  

Microsoft Academic Search

Proper glucocorticoid exposure in utero is vital to normal fetal organ growth and maturation. The human placental 11?-hydroxysteroid dehydrogenase type 2 enzyme (11?-HSD2) catalyzes the unidirectional conversion of cortisol to its inert metabolite cortisone, thereby controlling fetal exposure to maternal cortisol. The present study examined the effect of zinc and the relatively specific sulfhydryl modifying reagent N-ethylmaleimide (NEM) on the

P Niu; K Yang

2002-01-01

186

Revealing the role of defects in ferroelectric switching with atomic resolution  

Microsoft Academic Search

Ferroelectric materials are characterized by a spontaneous polarization, which can be reoriented with an applied electric field. The switching between polarized domains is mediated by nanoscale defects. Understanding the role of defects in ferroelectric switching is critical for practical applications such as non-volatile memories. This is especially the case for ferroelectric nanostructures and thin films in which the entire switching

Peng Gao; Christopher T. Nelson; Jacob R. Jokisaari; Seung-Hyub Baek; Chung Wung Bark; Yi Zhang; Enge Wang; Darrell G. Schlom; Chang-Beom Eom; Xiaoqing Pan

2011-01-01

187

Alarm toe switch  

DOEpatents

An alarm toe switch inserted within a shoe for energizing an alarm circuit n a covert manner includes an insole mounting pad into which a miniature reed switch is fixedly molded. An elongated slot perpendicular to the reed switch is formed in the bottom surface of the mounting pad. A permanent cylindrical magnet positioned in the forward portion of the slot with a diameter greater than the pad thickness causes a bump above the pad. A foam rubber block is also positioned in the slot rearwardly of the magnet and holds the magnet in normal inoperative relation. A non-magnetic support plate covers the slot and holds the magnet and foam rubber in the slot. The plate minimizes bending and frictional forces to improve movement of the magnet for reliable switch activation. The bump occupies the knuckle space beneath the big toe. When the big toe is scrunched rearwardly the magnet is moved within the slot relative to the reed switch, thus magnetically activating the switch. When toe pressure is released the foam rubber block forces the magnet back into normal inoperative position to deactivate the reed switch. The reed switch is hermetically sealed with the magnet acting through the wall so the switch assembly S is capable of reliable operation even in wet and corrosive environments.

Ganyard, Floyd P. (Albuquerque, NM)

1982-01-01

188

Production and characterisation of AoSOX2 from Aspergillus oryzae, a novel flavin-dependent sulfhydryl oxidase with good pH and temperature stability.  

PubMed

Sulfhydryl oxidases have found application in the improvement of both dairy and baking products due to their ability to oxidise thiol groups in small molecules and cysteine residues in proteins. A genome mining study of the available fungal genomes had previously been performed by our group in order to identify novel sulfhydryl oxidases suitable for industrial applications and a representative enzyme was produced, AoSOX1 from Aspergillus oryzae (Faccio et al. BMC Biochem 11:31, 2010). As a result of the study, a second gene coding for a potentially secreted sulfhydryl oxidase, AoSOX2, was identified in the genome of A. oryzae. The protein AoSOX2 was heterologously expressed in Trichoderma reesei and characterised with regard to both biochemical properties as well as preliminary structural analysis. AoSOX2 showed activity on dithiothreitol and glutathione, and to a lesser extent on D/L-cysteine and beta-mercaptoethanol. AoSOX2 was a homodimeric flavin-dependent protein of approximately 78 kDa (monomer 42412 Da) and its secondary structure presents alpha-helical elements. A. oryzae AoSOX2 showed a significant stability to pH and temperature. PMID:21327412

Faccio, Greta; Kruus, Kristiina; Buchert, Johanna; Saloheimo, Markku

2011-05-01

189

Omeprazole, a specific inhibitor of gastric (H/sup +/-K/sup +/)-ATPase, is a H/sup +/-activated oxidizing agent of sulfhydryl groups  

SciTech Connect

Omeprazole (5-methoxy-2-(((4-methoxy-3,5- dimethylpyridinyl)methyl)sulfinyl)-1H-benzimidazole) appeared to inhibit gastric (H/sup +/-K/sup +/)-ATPase by oxidizing its essential sulfhydryl groups, since the gastric ATPase inactivated by the drug in vivo or in vitro recovered its K+-dependent ATP hydrolyzing activity upon incubation with mercaptoethanol. Biological reducing agents like cysteine or glutathione, however, were unable to reverse the inhibitory effect of omeprazole. Moreover, acidic environments enhanced the potency of omeprazole. The chemical reactivity of omeprazole with mercaptans is also consistent with the biological action of omeprazole. The N-sulfenylated compound reacted at neutral pH with another stoichiometric amount of ethyl mercaptan to produce omeprazole sulfide quantitatively. The gastric polypeptides of 100 kilodaltons representing (H/sup +/-K/sup +/)-ATPase in the rat gastric mucosa or isolated hog gastric membranes were covalently labeled with (/sup 14/C)omeprazole. The radioactive label bound to the ATPase, however, could not be displaced by mercaptoethanol under the identical conditions where the ATPase activity was fully restored. These observations suggest that the essential sulfhydryl groups which reacted with omeprazole did not form a stable covalent bond with the drug, but rather that they further reacted with adjacent sulfhydryl groups to form disulfides which could be reduced by mercaptoethanol.

Im, W.B.; Sih, J.C.; Blakeman, D.P.; McGrath, J.P.

1985-04-25

190

The Role of Sulfhydryl Reactivity of Small Molecules for the Activation of the KEAP1/NRF2 Pathway and the Heat Shock Response  

PubMed Central

The KEAP1/NRF2 pathway and the heat shock response are two essential cytoprotective mechanisms that allow adaptation and survival under conditions of oxidative, electrophilic, and thermal stress by regulating the expression of elaborate networks of genes with versatile protective functions. The two pathways are independently regulated by the transcription factor nuclear factor-erythroid 2 p45-related factor 2 (NRF2) and heat shock factor 1 (HSF1), respectively. The activity of these transcriptional master regulators increases during conditions of stress and also upon encounter of small molecules (inducers), both naturally occurring as well as synthetically produced. Inducers have a common chemical property: the ability to react with sulfhydryl groups. The protein targets of such sulfhydryl-reactive compounds are equipped with highly reactive cysteine residues, which serve as sensors for inducers. The initial cysteine-sensed signal is further relayed to affect the expression of large networks of genes, which in turn can ultimately influence complex cell fate decisions such as life and death. The paper summarizes the multiple lines of experimental evidence demonstrating that the reactivity with sulfhydryl groups is a major determinant of the mechanism of action of small molecule dual activators of the KEAP1/NRF2 pathway and the heat shock response.

Dinkova-Kostova, Albena T.

2012-01-01

191

30 GHz tuned MEMS switches  

Microsoft Academic Search

This paper demonstrates the use of resonant tuning in high-isolation reflective MEMS electrostatic switches. Tuned switches can achieve higher isolation and a lower pulldown voltage than a comparable single element switch. An equivalent circuit model was developed for individual shunt capacitive membrane switches and then implemented in tuned circuits. The novel cross switch was developed on a high resistivity silicon.

Jeremy B. Muldavin; Gabriel M. Rebeiz

1999-01-01

192

Visually Activated Switch System (VASS).  

National Technical Information Service (NTIS)

The Visually Activated Switching System (VASS) provides a simple means for control system switching during 'hands-on' flight. Switching is accomplished by looking at a cockpit switch and operating a single trigger switch on the stick or throttle. A helmet...

E. Potter P. Burkott J. Gordon

1976-01-01

193

Effects of redox and sulfhydryl reagents on the bioelectric properties of the giant axon of the squid.  

PubMed

The effects of internally and externally applied sulfhydryl reagents on the bioelectric properties of the giant axon of the squid Loligo pealeii and Dosidicus gigas were studied. Cysteine-HCl (400 mM, pH 7.3) was used to remove axoplasm from the perfusion channel. Oxidizing agents (1 to 60 mM) tended to increase the duration of the action potential and had a slow, irreversible blocking effect when perfused internally; the membrane potential was little affected. Reducing agents applied internally caused a decrease in the spike duration without affecting its height or the membrane potential, although at high concentrations there was reversible deterioration of the action potential. Both external and internal perfusion of mercaptide-forming reagents caused deterioration in the action and membrane potentials with conduction block occurring in 5 to 45 min. 2-mercaptoethanol reversed the effects. Thiol alkylating reagents, iodoacetate and iodoacetamide, were without effect. N-ethylmaleimide did, however, block. Tests with chelating agents for nonheme iron in the membrane brought about no change in the electrical parameters. The implications of the present findings with regard to the macromolecular mechanism of excitation are discussed. PMID:5970570

Huneeus-Cox, F; Fernandez, H L; Smith, B H

1966-09-01

194

Effects of Redox and Sulfhydryl Reagents on the Bioelectric Properties of the Giant Axon of the Squid  

PubMed Central

The effects of internally and externally applied sulfhydryl reagents on the bioelectric properties of the giant axon of the squid Loligo pealeii and Dosidicus gigas were studied. Cysteine-HCl (400 mM, pH 7.3) was used to remove axoplasm from the perfusion channel. Oxidizing agents (1 to 60 mM) tended to increase the duration of the action potential and had a slow, irreversible blocking effect when perfused internally; the membrane potential was little affected. Reducing agents applied internally caused a decrease in the spike duration without affecting its height or the membrane potential, although at high concentrations there was reversible deterioration of the action potential. Both external and internal perfusion of mercaptide-forming reagents caused deterioration in the action and membrane potentials with conduction block occurring in 5 to 45 min. 2-mercaptoethanol reversed the effects. Thiol alkylating reagents, iodoacetate and iodoacetamide, were without effect. N-ethylmaleimide did, however, block. Tests with chelating agents for nonheme iron in the membrane brought about no change in the electrical parameters. The implications of the present findings with regard to the macromolecular mechanism of excitation are discussed. ImagesFigure 1

Huneeus-Cox, F.; Fernandez, H. L.; Smith, B. H.

1966-01-01

195

Surface modification of titanium substrates with silver nanoparticles embedded sulfhydrylated chitosan/gelatin polyelectrolyte multilayer films for antibacterial application.  

PubMed

To develop Ti implants with potent antibacterial activity, a novel "sandwich-type" structure of sulfhydrylated chitosan (Chi-SH)/gelatin (Gel) polyelectrolyte multilayer films embedding silver (Ag) nanoparticles was coated onto titanium substrate using a spin-assisted layer-by-layer assembly technique. Ag ions would be enriched in the polyelectrolyte multilayer films via the specific interactions between Ag ions and -HS groups in Chi-HS, thus leading to the formation of Ag nanoparticles in situ by photo-catalytic reaction (ultraviolet irradiation). Contact angle measurement and field emission scanning electron microscopy equipped with energy dispersive X-ray spectroscopy were employed to monitor the construction of Ag-containing multilayer on titanium surface, respectively. The functional multilayered films on titanium substrate [Ti/PEI/(Gel/Chi-SH/Ag) n /Gel] could efficiently inhibit the growth and activity of Bacillus subtitles and Escherichia coli onto titanium surface. Moreover, studies in vitro confirmed that Ti substrates coating with functional multilayer films remained the biological functions of osteoblasts, which was reflected by cell morphology, cell viability and ALP activity measurements. This study provides a simple, versatile and generalized methodology to design functional titanium implants with good cyto-compatibility and antibacterial activity for potential clinical applications. PMID:24664672

Li, Wen; Xu, Dawei; Hu, Yan; Cai, Kaiyong; Lin, Yingcheng

2014-06-01

196

Sulfhydryl Reactivity: Mechanism of Action of Several Antiviral Compounds--Selenocystine, 4-(2-Propinyloxy)-?-Nitrostyrene, and Acetylaranotin  

PubMed Central

The addition of 5 mM dithiothreitol to a cell-free assay system for influenza ribonucleic acid (RNA) polymerase activity reverses the inhibitory activity otherwise possessed by three established antiviral compounds: selenocystine, 4-(2-propinyloxy)-?-nitrostyrene, and acetylaranotin. Although 50% or greater enzyme inhibitory activity is repeatedly achieved for these compounds at a concentration of approximately 50 ?g/ml (0.1 to 0.25 mM) in the absence of dithiothreitol, no inhibition is seen in its presence at inhibitor concentrations as high as 200 ?g/ml. Against the deoxyribonucleic acid-directed RNA polymerases of Escherichia coli and chicken embryo cells, acetylaranotin and 4-(2-propinyloxy)-?-nitrostyrene caused very little inhibition. Only selenocystine significantly inhibited these two enzymes in the absence of reducing agent, but to an extent substantially less than that obtained against the viral enzyme. These results appear to suggest that influenza RNA polymerase is uniquely sensitive to a variety of structurally diverse antiviral compounds as a consequence of their sulfhydryl reactivity—a fact which might aid in the search for and development of more potent chemotherapeutic agents.

Billard, William; Peets, Edwin

1974-01-01

197

Cinitapride protects against ethanol-induced gastric mucosal injury in rats: role of 5-hydroxytryptamine, prostaglandins and sulfhydryl compounds.  

PubMed

This study was designed to determine the gastroprotective properties of cinitapride (CNT), a novel prokinetic benzamide derivative agonist of 5-HT4 and 5-HT1 receptors and 5-HT2 antagonist, on mucosal injury produced by 50% (v/v) ethanol. Results were compared with those for 5-hydroxytryptamine (5-HT: 10 mg kg-1). The possible involvements of gastric mucus secretion, endogenous prostaglandins (PGs) and sulfhydryl compounds (SH) in the protection mediated by CNT were also examined. Intraperitoneal administration of CNT (0.50 and 1 mg kg-1), 30 min before ethanol, significantly prevented gastric ulceration and increased the hexosamine content of gastric mucus. CNT (1 mg kg-1) also produced a significant increase in gastric mucosal levels of PGE2, but did not induce any significant changes in SH values. On the contrary, pretreatment with 5-HT worsened ethanol-induced erosions, however, did not affect gastric mucus secretion, glycoprotein content or PGE2 levels, although the non-protein SH fraction was significantly decreased. The present results demonstrate that the gastroprotective effects of CNT could be partly explained by a complex PG dependent mechanism. We suggest that 5-HT dependent mechanisms through 5-HT2 receptor blockade and 5-HT1 receptor activation could be also involved. PMID:9211565

Alarcón-de-la-Lastra Romero, C; López, A; Martín, M J; la Casa, C; Motilva, V

1997-04-01

198

Tl(+) showed negligible interaction with inner membrane sulfhydryl groups of rat liver mitochondria, but formed complexes with matrix proteins.  

PubMed

The effects of Tl(+) on protein sulfhydryl (SH) groups, swelling, and respiration of rat liver mitochondria (RLM) were studied in a medium containing TlNO3 and sucrose, or TlNO3 and KNO3 as well as glutamate plus malate, or succinate plus rotenone. Detected with Ellman's reagent, an increase in the content of the SH groups was found in the inner membrane fraction, and a simultaneous decline was found in the content of the matrix-soluble fraction for RLM, incubated and frozen in 25-75 mM TlNO3 . This increase was greater in the medium containing KNO3 regardless of the presence of Ca(2+) . It was eliminated completely for RLM injected in the medium containing TlNO3 and then washed and frozen in the medium containing KNO3 . Calcium-loaded RLM showed increased swelling and decreased respiration. These results suggest that a ligand interaction of Tl(+) with protein SH groups, regardless of the presence of calcium, may underlie the mechanism of thallium toxicity. PMID:24436107

Korotkov, Sergey M; Brailovskaya, Irina V; Kormilitsyn, Boris N; Furaev, Viktor V

2014-04-01

199

FAD-linked sulfhydryl oxidase QSOX: topographic, cellular, and subcellular immunolocalization in adult rat central nervous system.  

PubMed

The distribution of the sulfhydryl oxidase QSOX in the rat brain was mapped using immunohistochemistry. QSOX is specifically expressed by neurons throughout the rostrocaudal extent of the brain as well as in the spinal cord. Although a majority of neurons express QSOX, different intensities of labeling were observed depending on the area: the strongest labeling was observed in the olfactory bulbs, isocortex, hippocampus, basal telencephalon, several thalamic and hypothalamic nuclei, cerebellum, and numerous brainstem nuclei. This study also describes the ultrastructural localization of QSOX in neuronal cells and demonstrates that the enzyme is associated with the Golgi apparatus. Finally, selected double immunohistochemistry showed that in the hypothalamus the highest levels of QSOX labeling were colocalized in neuron populations that express disulfide-bounded neuropeptides. These observations are consistent with a role of the enzyme in secreted peptide/protein folding. Data presented herein will serve as a basis for further investigations of the physiological function of QSOX in the central nervous system. PMID:15116395

Mairet-Coello, Georges; Tury, Anna; Esnard-Feve, Annick; Fellmann, Dominique; Risold, Pierre-Yves; Griffond, Bernadette

2004-05-31

200

Identification of the reactive sulfhydryl group of 1-aminocyclopropane-1-carboxylate deaminase.  

PubMed

1-Aminocyclopropane-1-carboxylate (ACC) deaminase, a pyridoxal phosphate enzyme that catalyzes cyclopropane ring-opening and deamination of ACC, formed a quinoid intermediate with D-alanine, as shown by the appearance of a 510-nm absorption band. The presence of D-alanine also stimulated the inactivation of ACC deaminase with iodoacetamide. The increase of absorbance at 510 nm and the stimulation of the enzyme inactivation were temperature-dependent with a critical point at around 20 degrees C, indicating a conformational change of the enzyme. To identify a reactive thiol group, this stimulated inactivation and an iodoacetamide derivative, N-(iodoacetamidoethyl)-1-aminonaphthalene-5- sulfonic acid were used. The residue that was modified by the specific reagent was monitored by absorbance at 350 nm through the digestion by lysylendopeptidase and the fractionation of peptides, and it was located at Cys-162 near the midpoint of the whole peptide chain of the ACC deaminase. PMID:7764364

Honma, M; Kawai, J; Yamada, M

1993-12-01

201

Premature switching in graphene Josephson transistors  

NASA Astrophysics Data System (ADS)

We investigate electronic transport in single layer graphene coupled to superconducting electrodes. In these Josephson transistors, we observe significant suppression in the critical current Ic and large variations in the product IcRn in comparison to theoretical predictions in the ballistic limit. We show that the depression of Ic can be explained by premature switching in underdamped Josephson junctions described within the resistively and capacitively shunted junction (RCSJ) model. By considering the effect of premature switching and dissipation, the calculated gate dependence of product IcRn agrees with experimental data. Our discovery underscores the crucial role of thermal fluctuations in electronic transport in graphene Josephson transistors.

Miao, Feng; Bao, Wenzhong; Zhang, Hang; Lau, Chun Ning

2009-07-01

202

Optical pseudospark switch  

Microsoft Academic Search

This patent discloses a high voltage, high current, multichannel, optically-triggered switch with the potential for improved lifetime of operation. Triggering of the switch is accomplished by ultraviolet illumination of multiple cathode apertures via fiber optic cables. The trigger optics for each channel, being composed of a fiber-optic cable terminated by some collimating optics, are protected from damaging metalization by enclosing

Michael G. Grothaus; Jack S. Bernardes; David C. Stoudt

1995-01-01

203

Optical Switching Devices.  

National Technical Information Service (NTIS)

An optical switching device employs a rare earth bis-phthalocyanine having third-order nonlinear susceptibilities. In a preferred optical switch, the rare earth bis-phthalocyanine is employed as a nonlinear optical material body that fills the space betwe...

M. E. Boyle J. S. Shirk

1991-01-01

204

Chin Activated Switch.  

National Technical Information Service (NTIS)

The patent application relates to a chin activated switch which is used in directing the movement of a binocular microscope or other surgical equipment and has particular utility in vitreous surgery. A chin activated switch for use in adjusting the moveme...

C. J. McCarthy S. Charles D. M. Eichenbaum

1975-01-01

205

The Electrical Switch  

NSDL National Science Digital Library

This activity is inquiry-based in that students will perform the activity before they formally learn about how a switch works. They will use a multimeter to discover the different settings on a triple-throw switch. The teacher should show the students how

Horton, Michael

2009-05-30

206

Reflective HTS switch  

DOEpatents

A HTS switch includes a HTS conductor for providing a superconducting path for an electrical signal and an serpentine wire actuator for controllably heating a portion of the conductor sufficiently to cause that portion to have normal, and not superconducting, resistivity. Mass of the portion is reduced to decrease switching time.

Martens, Jon S. (Albuquerque, NM); Hietala, Vincent M. (Placitas, NM); Hohenwarter, Gert K. G. (Madison, WI)

1994-01-01

207

Reflective HTS switch  

DOEpatents

A HTS (High Temperature Superconductor) switch includes a HTS conductor for providing a superconducting path for an electrical signal and an serpentine wire actuator for controllably heating a portion of the conductor sufficiently to cause that portion to have normal, and not superconducting, resistivity. Mass of the portion is reduced to decrease switching time. 6 figs.

Martens, J.S.; Hietala, V.M.; Hohenwarter, G.K.G.

1994-09-27

208

Paying Customers to Switch  

Microsoft Academic Search

This paper studies the business practice of offering discounts to new customers in markets with switching costs. In a two-period homogeneous-good duopoly model, it is shown that the equilibrium amount of discounts increases continuously in the expected switching costs of a typical consumer. In equilibrium, firms offer the same prices and discounts in a mature market even if they have

Yongmin Chen

1997-01-01

209

High energy semiconductor switch  

NASA Astrophysics Data System (ADS)

The objective was a controller for electric motors. By operating standard Nema B induction motors at variable speed a great deal of energy is saved. This is especially true in pumping and air conditioning applications. To allow wider use of variable speed AC drives, and to provide improved performance, a better semiconductor switch was sought. This was termed the High Energy Semiconductor Switch.

Risberg, R. L.

1989-02-01

210

Binary Switch Key.  

National Technical Information Service (NTIS)

The code key provides an information code pattern for a switching network. The code key is a portable self contained switch setting device employing spring loaded key pins, protected by a retractable skirt and a positive locking plate for securing the pin...

E. C. Bean C. J. Creveling

1965-01-01

211

A Novel Molecular Switch  

PubMed Central

Transcriptional regulation is a fundamental process for regulating the flux of all metabolic pathways. For the last several decades, the lac operon has served as a valuable model for studying transcription. More recently, the switch that controls the operon has also been successfully adapted to function in mammalian cells. Here we describe how, using directed evolution, we have created a novel switch that recognizes an asymmetric operator sequence. The new switch has a repressor with altered headpiece domains for operator recognition, and a redesigned dimer interface to create a heterodimeric repressor. Quite unexpectedly, the heterodimeric switch functions better than the natural system. It can repress more tightly than the naturally occurring switch of the lac operon; it is less leaky and can be induced more efficiently. Ultimately these novel repressors could be evolved to recognize eukaryotic promoters and used to regulate gene expression in mammalian systems.

Daber, Robert; Lewis, Mitchell

2009-01-01

212

Sequestration-based bistability enables tuning of the switching boundaries and design of a latch  

PubMed Central

Natural biological systems have evolved a diverse array of switches to realize their strategies for environmental response and development. Emerging applications of synthetic biology have begun to exploit such switches to achieve increasingly sophisticated designed behaviors. However, not all switch architectures allow facile design of the switching and memory properties. Furthermore, not all designs are built from components for which large families of variants exist, a requirement for building many orthogonal switch variants. Therefore, there is a critical need from genetic engineers for scalable strategies that yield custom bistable switches. Here, we use a sigma factor and its cognate anti-sigma factor to experimentally verify that ultrasensitivity from sequestration combined with positive feedback is sufficient to build a bistable switch. We show that sequestration allows us to predictably tune the switching boundaries, and we can easily tune our switch to function as a set–reset latch that can be toggled between two states by a pulse of inducer input.

Chen, David; Arkin, Adam P

2012-01-01

213

Investigations of conductance of photochromic switching molecules  

NASA Astrophysics Data System (ADS)

Recent experimental work has confirmed a dramatic conductance enhancement of more than two orders of magnitude after the optical switching between two molecular isomers of a dithienylethene-derivative on gold. To determine which dithienylethene-derivative may be the optimal candidate for use as an optical molecular switch, it is necessary to understand the nature of the conductance switching. To this end, a variety of theoretical tools were employed to study the critical aspects of this unique metal-molecule-metal junction. A plane wave based density functional method revealed marked differences between the two isomers with regard to the line-up of the molecular states and the contact states. A local orbital based density functional method was used to generate a tractable Hamiltonian for a Landauer based transport calculation. Three different derivatives are analyzed to determine which may be an appropriate candidate in a molecular electronic device.

Speyer, Gil; Li, Jun; Sankey, Otto F.

2004-08-01

214

Divergent Molecular Evolution of the Mitochondrial Sulfhydryl:Cytochrome c Oxidoreductase Erv in Opisthokonts and Parasitic Protists*  

PubMed Central

Mia40 and the sulfhydryl:cytochrome c oxidoreductase Erv1/ALR are essential for oxidative protein import into the mitochondrial intermembrane space in yeast and mammals. Although mitochondrial protein import is functionally conserved in the course of evolution, many organisms seem to lack Mia40. Moreover, except for in organello import studies and in silico analyses, nothing is known about the function and properties of protist Erv homologues. Here we compared Erv homologues from yeast, the kinetoplastid parasite Leishmania tarentolae, and the non-related malaria parasite Plasmodium falciparum. Both parasite proteins have altered cysteine motifs, formed intermolecular disulfide bonds in vitro and in vivo, and could not replace Erv1 from yeast despite successful mitochondrial protein import in vivo. To analyze its enzymatic activity, we established the expression and purification of recombinant full-length L. tarentolae Erv and compared the mechanism with related and non-related flavoproteins. Enzyme assays indeed confirmed an electron transferase activity with equine and yeast cytochrome c, suggesting a conservation of the enzymatic activity in different eukaryotic lineages. However, although Erv and non-related flavoproteins are intriguing examples of convergent molecular evolution resulting in similar enzyme properties, the mechanisms of Erv homologues from parasitic protists and opisthokonts differ significantly. In summary, the Erv-mediated reduction of cytochrome c might be highly conserved throughout evolution despite the apparent absence of Mia40 in many eukaryotes. Nevertheless, the knowledge on mitochondrial protein import in yeast and mammals cannot be generally transferred to all other eukaryotes, and the corresponding pathways, components, and mechanisms remain to be analyzed.

Eckers, Elisabeth; Petrungaro, Carmelina; Gross, Dominik; Riemer, Jan; Hell, Kai; Deponte, Marcel

2013-01-01

215

Oxidative protein folding in vitro: a study of the cooperation between quiescin-sulfhydryl oxidase and protein disulfide isomerase.  

PubMed

The flavin-dependent quiescin-sulfhydryl oxidase (QSOX) inserts disulfide bridges into unfolded reduced proteins with the reduction of molecular oxygen to form hydrogen peroxide. This work investigates how QSOX and protein disulfide isomerase (PDI) cooperate in vitro to generate native pairings in two unfolded reduced proteins: ribonuclease A (RNase, four disulfide bonds and 105 disulfide isomers of the fully oxidized protein) and avian riboflavin binding protein (RfBP, nine disulfide bonds and more than 34 million corresponding disulfide pairings). Experiments combining avian or human QSOX with up to 200 muM avian or human reduced PDI show that the isomerase is not a significant substrate of QSOX. Both reduced RNase and RfBP can be efficiently refolded in an aerobic solution containing micromolar concentrations of reduced PDI and nanomolar levels of QSOX without any added oxidized PDI or glutathione redox buffer. Refolding of RfBP is followed continuously using the complete quenching of the fluorescence of free riboflavin that occurs on binding to apo-RfBP. The rate of refolding is half-maximal at 30 muM reduced PDI when the reduced client protein (1 muM) is used in the presence of 30 nM QSOX. The use of high concentrations of PDI, in considerable excess over the folding protein client, reflects the concentration prevailing in the lumen of the endoplasmic reticulum and allows the redox poise of these in vitro experiments to be set with oxidized and reduced PDI. In the absence of either QSOX or redox buffer, the fastest refolding of RfBP is accomplished with excess reduced PDI and just enough oxidized PDI to generate nine disulfides in the protein client. These in vitro experiments are discussed in terms of current models for oxidative folding in the endoplasmic reticulum. PMID:18937500

Rancy, Pumtiwitt C; Thorpe, Colin

2008-11-18

216

Oxidative Protein Folding in vitro: a Study of the Cooperation between Quiescin-sulfhydryl Oxidase and Protein Disulfide Isomerase  

PubMed Central

The flavin-dependent Quiescin-sulfhydryl oxidase (QSOX) inserts disulfide bridges into unfolded reduced proteins with the reduction of molecular oxygen to form hydrogen peroxide. This work investigates how QSOX and protein disulfide isomerase (PDI) cooperate in vitro to generate native pairings in two unfolded reduced proteins: ribonuclease A (RNase: 4 disulfide bonds and 105 disulfide isomers of the fully oxidized protein) and avian riboflavin binding protein (RfBP: 9 disulfide bonds and greater than 34 million corresponding disulfide pairings). Experiments combining avian or human QSOX with up to 200 ?M of avian or human reduced PDI show that the isomerase is not a significant substrate of QSOX. Both reduced RNase and RfBP can be efficiently refolded in an aerobic solution containing micromolar concentrations of reduced PDI and nanomolar levels of QSOX without any added oxidized PDI or glutathione redox buffer. Refolding of RfBP is followed continuously using the complete quenching of the fluorescence of free riboflavin that occurs on binding to apo-RfBP. The rate of refolding is half-maximal at 30 ?M reduced PDI when 1 ?M of the reduced client protein is used in the presence of 30 nM QSOX. The use of high concentrations of PDI, in considerable excess over the folding protein client, reflect the concentration prevailing in the lumen of the endoplasmic reticulum and allow the redox poise of these in vitro experiments to be set with oxidized and reduced PDI. In the absence of either QSOX or redox buffer, the fastest refolding of RfBP is accomplished with excess reduced PDI and just enough oxidized PDI to generate 9- disulfides in the protein client. These in vitro experiments are discussed in terms of current models for oxidative folding in the endoplasmic reticulum.

Rancy, Pumtiwitt C.; Thorpe, Colin

2010-01-01

217

Anomalous resistive switching phenomenon  

NASA Astrophysics Data System (ADS)

Resistive switching was observed in Pt/SrTiO3/Pt capacitor devices. The switching depends on both the amplitude and polarity of the applied voltage and cannot be described as either bipolar or unipolar resistive switching. We term this behavior antipolar due to the opposite polarity of the set voltage relative to the previous reset voltage. A model based on electron injection by tunneling at interfaces and a Poole-Frenkel mechanism through the bulk is proposed. This model is quantified by use of a simple mathematical equation to simulate the experimental results.

Mojarad, Shahin A.; Goss, J. P.; Kwa, Kelvin S. K.; Petrov, Peter K.; Zou, Bin; Alford, Neil; O'Neill, Anthony

2012-12-01

218

Photoconductive switch package  

DOEpatents

A photoconductive switch is formed of a substrate that has a central portion of SiC or other photoconductive material and an outer portion of cvd-diamond or other suitable material surrounding the central portion. Conducting electrodes are formed on opposed sides of the substrate, with the electrodes extending beyond the central portion and the edges of the electrodes lying over the outer portion. Thus any high electric fields produced at the edges of the electrodes lie outside of and do not affect the central portion, which is the active switching element. Light is transmitted through the outer portion to the central portion to actuate the switch.

Ca[rasp, George J

2013-10-22

219

ISS of Switched Systems and Applications to Switching Adaptive Control  

Microsoft Academic Search

In this paper we prove that a switched nonlinear system has several useful ISS-type properties under average dwell-time switching signals if each constituent dynamical system is ISS. This extends available results for switched linear systems. We apply our result to stabilization of uncertain nonlinear systems via switching supervisory control, and show that the plant states can be kept bounded in

L. Vu; D. Chatterjee; D. Liberzon

2005-01-01

220

Switch Actuator Mechanism.  

National Technical Information Service (NTIS)

The switch actuator mechanism has utility as a circuit arming device in bombs which are dropped from aircraft. The mechanism includes a plunger having a sleeve mounted thereon, spring detent mechanism cooperating with the sleeve whereby the sleeve is mova...

S. Yerkovich

1965-01-01

221

Solar array switching unit  

NASA Technical Reports Server (NTRS)

A solar array switching (SASU) unit (22) according to the present invention includes a control system (24), a solar cell array (26) and switch circuits (28). The SASU unit (22) is associated with a power card (30) for receiving an output from the array (26). The array (26) has a number (0.5Y) of rows (38) each of which includes a pair of cell strings (42) separated by one of the switch circuits (28). Each of the strings (42) includes a number (X) of cells in electrical series. The SASU (22) switches the array (26) between a short string configuration where the array (26) effectively includes Y strings of X length, and a long string configuration where the array (26) effectively includes 0.5Y strings of 2X length. The SASU (22) thereby facilitates the use of solar power for space missions where solar intensity, operating temperature or other factors vary significantly.

Craig, Jr., Calvin L. (Inventor)

2000-01-01

222

Basics of Safety Switches  

NSDL National Science Digital Library

This course is one of the quickStep series offered by Siemens in Safety Switches. These are FREE on-line industrial knowledge building tutorials. quickSTEPs are a great start for industry novices moving into technical jobs or staff in operational support rolls. They can also be very effectively used as out of class assignments for review or to build fundamental skills. Each course includes: an online tutorial organized as a number of units, lessons with self check quiz questions, a glossary of terms, a self-check final exam with scoring, an extensive downloadable PDF study guide. This course offers: current protection, fuses, enclosures, switch design, switch terminology, safety switches, a final exam, a glossary and a 72 page study guide.

2008-11-25

223

An optical switch  

DOEpatents

The invention is a gas mixture for a diffuse discharge switch having an electron attaching gas wherein electron attachment is brought about by indirect excitation of molecules to long live states by exposure to laser light. 3 figs.

Christophorou, L.G.; Hunter, S.R.

1987-04-30

224

Optical Switch Evaluation Support.  

National Technical Information Service (NTIS)

Extensive testing has been done on nonlinear interface optical switch (NIOS) devices fabricated from laser deposited nonstoichiometric tungsten oxide films. A Fresnel coefficient formalism for evaluating the indices of refraction of the films has been dev...

J. Chaiken

1993-01-01

225

Plasmonic enhanced ultrafast switch.  

SciTech Connect

Ultrafast electronic switches fabricated from defective material have been used for several decades in order to produce picosecond electrical transients and TeraHertz radiation. Due to the ultrashort recombination time in the photoconductor materials used, these switches are inefficient and are ultimately limited by the amount of optical power that can be applied to the switch before self-destruction. The goal of this work is to create ultrafast (sub-picosecond response) photoconductive switches on GaAs that are enhanced through plasmonic coupling structures. Here, the plasmonic coupler primarily plays the role of being a radiation condenser which will cause carriers to be generated adjacent to metallic electrodes where they can more efficiently be collected.

Subramania,Ganapathi Subramanian; Reno, John Louis; Passmore, Brandon Scott; Harris, Tom.; Shaner, Eric Arthur; Barrick, Todd A.

2009-09-01

226

Switching power supply filter  

NASA Technical Reports Server (NTRS)

A filter for a switching power supply. The filter includes a common mode inductor with coil configurations allowing differential mode current from a dc source to pass through but attenuating common mode noise from the power supply so that the noise does not reach the dc source. The invention also includes the use of feed through capacitors at the switching power supply input terminals to provide further high-frequency noise attenuation.

Kumar, Prithvi R. (Inventor); Abare, Wayne (Inventor)

1989-01-01

227

Improved optical pseudospark switch  

Microsoft Academic Search

Disclosed is a high-voltage, high-current, multichannel, optically-triggered switch with the potential for improved lifetime of operation. Triggering of the switch is accomplished by ultraviolet illumination of multiple cathode apertures via fiber-optic cables. The trigger optics for each channel, being composed of a fiber-optic cable terminated by some collimating optics, are protected from damaging metalization by enclosing them in an angled

Michael G. Grothaus; Jack S. Bernardes; David C. Stoudt

1993-01-01

228

uv preilluminated gas switches  

SciTech Connect

We have designed, built, and characterized uv preilluminated gas switches for a trigger circuit and a low inductance discharge circuit. These switches have been incorporated into a 54 x 76 x 150 cm pulser module to produce a 1 Ma output current rising at 5 x 10/sup 12/ amps/sec with 1 ns jitter. Twenty such modules will be used on the Nova Inertial Confinement Fusion Laser System for plasma retropulse shutters.

Bradley, L.P.; Orham, E.L.; Stowers, I.F.; Braucht, J.R.

1980-06-03

229

Switch Card Apparatus and Methods.  

National Technical Information Service (NTIS)

Switch card apparatus are disclosed. In one embodiment, a circuit includes a first portion having a first switch adapted to be coupled to a first voltage, a second portion including a second switch, and a third portion including a third switch. The first ...

G. H. Smith H. N. Nguyen R. A. Kubinski T. T. Phan

2004-01-01

230

Age-related decrease in high-density lipoproteins antioxidant activity is due to an alteration in the PON1's free sulfhydryl groups.  

PubMed

The aim of this study was to evaluate the antioxidant activity of HDL with aging and to investigate the implication of PON1 in this process. The study involved 54 healthy subjects distributed in two age groups, young (20-25 years) and elderly (65-85 years). Lipid peroxidation was induced by *OH and O2*- oxygen free radicals produced by gamma-radiolysis of water. LDL oxidation was followed by the measurement of conjugated diene (CD), lipid peroxide (LP) and malondialdehyde (MDA) formation. PON1 was purified separately from young (Y-PON1) and elderly subjects (E-PON1). PON1 activity and structure was followed by measurement of PON1 paraoxonase (p.ase) activity, titration of the SH groups, and electrophoretic mobility by SDS-PAGE. Our results show a significant decrease in the HDL antioxidant activity: percentage of protection against CD formation=27.70% (p<0.01) for E-HDL versus 73.08% (p<0.001) for Y-HDL. Moreover, E-PON1 showed a lower antioxidant activity when compared to Y-PON1 47.08% versus 78.14%, respectively (p<0.0001). Exposition of PON1 to *OH and O2*- oxygen free radicals induced a significant decrease in PON1 p.ase activity as well as a reduction in the number of PON1's free sulfhydryl groups. Moreover, our results show a close association between PON1's free sulfhydryl groups and its capacity to protect LDL against lipid peroxidation. There was a significant decrease in the number of free sulfhydryls between Y-PON1 and E-PON1 with respect to cysteine-284 amino acid residues (p<0.0092). PMID:16026789

Jaouad, Leila; de Guise, Chantal; Berrougui, Hicham; Cloutier, Martin; Isabelle, Maxim; Fulop, Tamas; Payette, Hélène; Khalil, Abdelouahed

2006-03-01

231

Relationship of membrane-bound sulfhydryl groups to vitamin D-stimulated uptake of ( sup 75 Se)Selenite by the brush border membrane vesicles from chick duodenum  

SciTech Connect

The uptake of selenite by purified brush border membrane vesicles isolated from duodena of rachitic or vitamin D-treated chicks was studied by using radioactive selenite and a rapid filtration technique. Cholecalciferol treatment (500 IU at 72 h) significantly enhanced selenite uptake, a response that decreased when the vesicles were stored at room temperature for 2.5 h prior to the uptake measurement. Preincubation of the vesicles in 1.0 mmol/L H2O2 reduced (75Se)selenite uptake, indicating the involvement of oxidizable groups in the uptake reaction. Iodoacetic acid (IAA), a sulfhydryl-blocking reagent, at 1-2 mmol/L concentration eliminated the difference in selenite uptake due to cholecalciferol and had no effect on vesicles from rachitic animals. A higher concentration of IAA (10 mmol/L) enhanced selenite uptake manyfold and increased the absolute difference due to cholecalciferol treatment. Single intravenous doses of 100 IU cholecalciferol, 100 IU ergocalciferol, or 0.1 micrograms 1,25-dihydroxycholecalciferol also stimulated selenite uptake, suggesting a general response to vitamin D compounds. Normal animals given a single dose of 1,25-dihydroxycholecalciferol 12 h prior to killing also responded. Treatments that enhanced the uptake of (75Se)selenite also increased the amount of membrane-bound sulfhydryl groups, suggesting the involvement of membrane-bound sulfhydryl groups in the vitamin D response. A significant increase in selenite uptake by intravenous 1,25-dihydroxycholecalciferol occurred within 10 min. This rapid effect provides a new tool to probe early biochemical effects of vitamin D on intestinal epithelium.

Mykkanen, H.M.; Wasserman, R.H. (Cornell Univ., Ithaca, NY (USA))

1990-08-01

232

A radiation hard vacuum switch  

DOEpatents

A vacuum switch with an isolated trigger probe which is not directly connected to the switching electrodes. The vacuum switch within the plasmatron is triggered by plasma expansion initiated by the trigger probe which travels through an opening to reach the vacuum switch elements. The plasma arc created is directed by the opening to the space between the anode and cathode of the vacuum switch to cause conduction. 3 figs.

Boettcher, G.E.

1988-07-19

233

Amifostine (Wr-2721) Prevents Indomethacin-Induced Gastric Damage in Rats: Role of Non-Protein Sulfhydryl Groups and Leukocyte Adherence  

Microsoft Academic Search

This study was designed to evaluate the protective effect of amifostine on indomethacin-induced gastric damage, and the role\\u000a of increased gastric non-protein sulfhydryl groups (NP-SH) and decreased leukocyte adherence in this event. Wistar rats were\\u000a pretreated with amifostine (10, 30, or 90 mg\\/kg intraperitoneal (i.p.) or subcutaneous (s.c.)) or saline. After 30 min, the\\u000a rats received indomethacin (20 mg\\/kg, by gavage) and were

José Maurício S. C. Mota; Pedro M. G. Soares; Álvaro A. J. Menezes; Henrique P. Lemos; Fernando Q. Cunha; Gerly Anne C. Brito; Ronaldo A. Ribeiro; Marcellus H. L. P. de Souza

2007-01-01

234

Synergism of organic zinc salts and sulfhydryl compounds (thiols) in the protection of mice against acute ethanol toxicity, and protective effects of various metal salts.  

PubMed

Organic zinc salts such as zinc aspartate, zinc orotate, zinc histidine and zinc acetate protected mice against the lethality of an acute intraperitoneal challenge with ethanol. A similar activity was also provided by salts of cobalt, zirconium, lithium and magnesium. Organic zinc salts acted synergistically with sulfhydryl compounds in protecting the mice and potentiation between the two categories of agents was seen. The results are in analogy to radioprotective effects by zinc and thiols and imply that organic zinc salts may, alone or in conjunction with thiols, reduce in a wider context tissue injury caused by free radical-mediated mechanisms. PMID:3630856

Floersheim, G L

1987-06-01

235

Circuit Techniques for Improving the Switching Loci of Transistor Switches in Switching Regulators  

Microsoft Academic Search

The use of switching regulator circuits at high power levels and high frequencies requires careful examination and control of the power dissipation during switching, which may be the dominant loss. In this paper it is shown that it is possible to remove most of the switching losses from the switching transistor with two networks, each containing three components: an inductor

E. T. Calkin; B. H. Hamilton

1976-01-01

236

Energy losses in switches  

SciTech Connect

The authors experiments show energy losses between 2 and 10 times that of the resistive time predictions. The experiments used hydrogen, helium, air, nitrogen, SF{sub 6} polyethylene, and water for the switching dielectric. Previously underestimated switch losses have caused over predicting the accelerator outputs. Accurate estimation of these losses is now necessary for new high-efficiency pulsed power devices where the switching losses constitute the major portion of the total energy loss. They found that the switch energy losses scale as (V{sub peak}I{sub peak}){sup 1.1846}. When using this scaling, the energy losses in any of the tested dielectrics are almost the same. This relationship is valid for several orders of magnitude and suggested a theoretical basis for these results. Currents up to .65 MA, with voltages to 3 MV were applied to various gaps during these experiments. The authors data and the developed theory indicates that the switch power loss continues for a much longer time than the resistive time, with peak power loss generally occurring at peak current in a ranging discharge instead of the early current time. All of the experiments were circuit code modeled after developing a new switch loss version based on the theory. The circuit code predicts switch energy loss and peak currents as a function of time. During analysis of the data they noticed slight constant offsets between the theory and data that depended on the dielectric. They modified the plasma conductivity for each tested dielectric to lessen this offset.

Martin, T.H.; Seamen, J.F.; Jobe, D.O.

1993-07-01

237

Elevated Transcription of the Gene QSOX1 Encoding Quiescin Q6 Sulfhydryl Oxidase 1 in Breast Cancer  

PubMed Central

The q arm of chromosome 1 is frequently amplified at the gene level in breast cancer. Since the significance of this is unclear we investigated whether 1q genes are overexpressed in this disease. The cDNA levels of 1q-located genes were analysed in a search for overexpressed genes. 26 genes mapping to the 1q arm show highly significant (P?0.01) overexpression of transcripts in breast cancer compared to normal breast tissue. Amongst those showing the highest levels of overexpression in both expressed sequence tag (EST) and serial analysis of gene expression (SAGE) databases was enzyme quiescin Q6 sulfhydryl oxidase 1 (QSOX1). We investigated QSOX1 cDNA derived from T47D breast carcinoma cells by RT-PCR and 3?-RACE PCR and identified a novel extended form of QSOX1 transcript, containing a long 3?UTR, nearly double the size of the previously reported QSOX1 cDNA, and confirmed its 3? end nucleotide sequence using RACE-PCR. We also used quantitative real-time PCR to analyse a panel of cDNAs derived from 50 clinically-graded normal and malignant breast tissue samples for the expression of QSOX1 mRNAs. QSOX1 transcription was elevated in an increasing proportion in the grade 2 and grade 3 tumours (graded according to the Nottingham prognostic index), with 10 of the 15 grade 3 tumours (67%) examined exceeding the normal range. There was a significant correlation between relative transcript level and clinical grade (P?0.01) for all qPCR primer sets tested. QSOX1 mRNA levels, based on SAGE expression data, did not correlate with either Estrogen Receptor (ER) or Epidermal Growth Factor Receptor 2 (ErbB-2 or HER2/neu) expression. Our data indicate that QSOX1 is a potential new prognostic marker which may prove of use in the staging of breast tumours and the stratification of breast cancer patients.

Soloviev, Mikhail; Esteves, Michelle P.; Amiri, Fakhria; Crompton, Mark R.; Rider, Christopher C.

2013-01-01

238

Novel synchronization technique for two parallel connected sparkgap switches  

NASA Astrophysics Data System (ADS)

In this article a novel way of synchronizing two parallel connected sparkgap switches with accuracies of 1-5 ns for high frequency pulsed power applications is described. The circuit design of a synchronized sparkgap switch circuit is discussed. The circuit uses a combination of one master sparkgap and a set of inductor and capacitors to synchronize two sparkgaps and can be controlled via an IGBT switch. Critical issues for circuit design are presented together with analytical calculations and simulations. Experimental verification of the novel topology is carried out in a prototype experimental setup. Results showing nanosecond level of accuracy in synchronization are reported in this paper along with simulations and analysis.

Kumar, Rohit; Mitra, S.; Patel, A.; Dwivedi, Rajesh; Kolge, T.; Sharma, Ranjeet Archana; Chakravarthy, D. P.

2012-08-01

239

Dynamical switching characteristics of a bistable injection laser  

SciTech Connect

The switching characteristics of a bistable injection laser with very large hysteresis is examined. Switch-on delays are shown to exhibit a ''critical'' part and a ''noncritical'' part, both of which can be reduced by increasing the overdrive current. It is possible to obtain fairly fast switching time (<20 ns) with a strong overdrive. Nominal delays of 100--200 ns result under moderate overdrives. These long time scales are due to long carrier lifetimes in the carrier-depleted absorption section, a property intrinsic to these bistable injection lasers.

Lau, K.Y.; Harder, C.; Yariv, A.

1982-02-01

240

Fast deterministic switching in orthogonal spin torque devices via the control of the relative spin polarizations  

NASA Astrophysics Data System (ADS)

We model 100 ps pulse switching dynamics of orthogonal spin transfer (OST) devices that employ an out-of-plane polarizer and an in-plane polarizer. Simulation results indicate that increasing the spin polarization ratio, CP = PIPP/POPP, results in deterministic switching of the free layer without over-rotation (360° rotation). By using spin torque asymmetry to realize an enhanced effective PIPP, we experimentally demonstrate this behavior in OST devices in parallel to anti-parallel switching. Modeling predicts that decreasing the effective demagnetization field can substantially reduce the minimum CP required to attain deterministic switching, while retaining low critical switching current, Ip ˜ 500 ?A.

Park, Junbo; Ralph, D. C.; Buhrman, R. A.

2013-12-01

241

Purification of gastroprotective triterpenoids from the stem bark of Amphipterygium adstringens; role of prostaglandins, sulfhydryls, nitric oxide and capsaicin-sensitive neurons.  

PubMed

In this investigation three bioactive compounds, responsible for the gastroprotective property of Amphipterygium adstringens, were purified from an active dichloromethane fraction. These compounds were 3alpha-hydroxymasticadienonic acid, beta-sitosterol and 3- epi-oleanolic acid. The latter was the most active compound (88.8 % of gastroprotection) followed by 3alpha-hydroxymasticadienoic acid and beta-sitosterol (69.8 and 42.5 % of gastroprotection, respectively). Carbenoxolone was used as positive control and it showed 88.4 % of gastroprotection. Masticadienonic acid was also isolated from the active fraction, but it was unable to inhibit the ethanol-induced gastric lesions. The gastroprotection of the methanol extract was completely inhibited by the pretreatment with l-NAME and attenuated by pretreatment with indomethacin and N-ethylmaleimide. These results suggest that endogenous nitric oxide plays an important role in the gastroprotection of A. adstringens methanol extract on ethanol-induced gastric mucosal lesions and that there is partial participation by prostaglandins and endogenous sulfhydryls. The effect of 3alpha-hydroxymasticadienonic acid was attenuated only by pretreatment with N-ethylmaleimide, indicating that endogenous sulfhydryls (thiols) participate in its gastroprotective mechanism. Capsaicin-sensitive afferent neurons do not participate in the gastroprotection of either the methanol extract or 3alpha-hydroxymasticadienoic acid. PMID:14648392

Arrieta, Jesús; Benitez, Javier; Flores, Edith; Castillo, Carlos; Navarrete, Andrés

2003-10-01

242

The 3-(bromoacetamido)-propylamine hydrochloride: A novel sulfhydryl reagent and its future potential in the configurational study of S1-myosin  

NASA Technical Reports Server (NTRS)

Configurational study of S1-Myosin is an important step towards understanding force generation in muscle contraction. Previously reported NMR studies were corroborated. A new compound was synthesized, 3-(Bromoacetamido)-propylamine hydrochloride. Its potential as a sulfhydryl reagent provides an indirect but elegant approach towards future structural elucidation of S1-Myosin. The preliminary investigation has shown that this compound, BAAP, reacted with S1 in the absence of MgADP. The modified enzyme had a 2-fold increase in CaATPase activity and no detectable K-EDTA ATPase activity. Reaction of BAAP with S1 in the presence of MgADP resulted in a modified enzyme which retained a Ca-ATPase activity that was about 60 percent of the unmodified S1 and had essentially zero K-EDTA ATPase activity. Sulfhydryl titration indicated that about 1.5 and 3.5 SH groups per S1 molecule were blocked by BAAP in the absence and presence of MgADP, respectively. When coupled to a carboxyl group of EDTA, the resulting reagent could become a useful SH reagent in which chelated paramagnetic or luminescent lanthanide ions can be exploited to probe S1 conformation.

Sharma, Prasanta; Cheung, Herbert C.

1989-01-01

243

Switching power supply  

DOEpatents

The invention is a repratable capacitor charging, switching power supply. A ferrite transformer steps up a dc input. The transformer primary is in a full bridge configuration utilizing power MOSFETs as the bridge switches. The transformer secondary is fed into a high voltage, full wave rectifier whose output is connected directly to the energy storage capacitor. The transformer is designed to provide adequate leakage inductance to limit capacitor current. The MOSFETs are switched to the variable frequency from 20 to 50 kHz to charge a capacitor from 0.6 kV. The peak current in a transformer primary and secondary is controlled by increasing the pulse width as the capacitor charges. A digital ripple counter counts pulses and after a preselected desired number is reached an up-counter is clocked.

Mihalka, A.M.

1984-06-05

244

Thermionic gas switch  

DOEpatents

A temperature responsive thermionic gas switch having folded electron emitting surfaces. An ionizable gas is located between the emitter and an interior surface of a collector, coaxial with the emitter. In response to the temperature exceeding a predetermined level, sufficient electrons are derived from the emitter to cause the gas in the gap between the emitter and collector to become ionized, whereby a very large increase in current in the gap occurs. Due to the folded emitter surface area of the switch, increasing the "on/off" current ratio and adjusting the "on" current capacity is accomplished.

Hatch, George L. (San Francisco, CA); Brummond, William A. (Livermore, CA); Barrus, Donald M. (San Jose, CA)

1986-01-01

245

Magnetic switches and circuits  

SciTech Connect

This report outlines the use of saturable inductors as switches in lumped-element, magnetic-pulse compression circuits is discussed and the characteristic use of each is defined. In addition, the geometric constraints and magnetic pulse compression circuits used in short-pulse, low-inductance systems are considered. The scaling of presaturation leakage currents, magnetic energy losses, and switching times with geometrical and material parameters are developed to aid in evaluating magnetic pulse compression systems in a particular application. Finally, a scheme for increasing the couping coefficient in saturable stripline transformers is proposed to enable their use in the short-pulse, high-voltage regime.

Nunnally, W.C.

1982-05-01

246

Bearingless switched reluctance motor  

NASA Technical Reports Server (NTRS)

A switched reluctance motor has a stator with a first set of poles directed toward levitating a rotor horizontally within the stator. A disc shaped portion of a hybrid rotor is affected by the change in flux relative to the current provided at these levitation poles. A processor senses the position of the rotor and changes the flux to move the rotor toward center of the stator. A second set of poles of the stator are utilized to impart torque upon a second portion of the rotor. These second set of poles are driven in a traditional switched reluctance manner by the processor.

Morrison, Carlos R. (Inventor)

2004-01-01

247

The Role of CuAlO Interface Layer for Switching Behavior of Al\\/ \\/Cu Memory Device  

Microsoft Academic Search

The interface layer between a reactive electrode and switching metal oxide is quite critical to improve the switching characteristics, but the intrinsic roles of this interfacial layer as oxygen reservoir or switching layer are still controversial. In this letter, we investigated the switching behavior of CuxO-based device by fully removing the top insulating Cu2O layer, with lower conductive gradient CuxO

Hangbing Lv; Tingao Tang

2010-01-01

248

49 CFR 236.6 - Hand-operated switch equipped with switch circuit controller.  

Code of Federal Regulations, 2013 CFR

...2013-10-01 2013-10-01 false Hand-operated switch equipped with switch...Instructions: All Systems General § 236.6 Hand-operated switch equipped with switch circuit controller. Hand-operated switch equipped...

2013-10-01

249

High Power Optical Microwave Switches  

NASA Astrophysics Data System (ADS)

The RF distribution and pulse compression systems of the Next Linear Collider could benefit from a microwave switch that could handle few hundred megawatts^1. We present a rigorous analysis form an abstract point of view for the design of high power microwave switches. In our analysis we show how the design can be made to accomplish three goals. First, when the switch is off, the electric fields on the active elements are low. Second, when the switch is on, the losses in the active elements should be below a certain level, finally, one needs to limit the switching time to satisfy the application at hand. We first study the case of a single switch, and then expand our analysis to the case of multiple switches. We also give a design example. ^1 Sami G. Tantawi et. al. "Active radio frequency pulse compression using switched resonant delay lines," Nuclear Instruments and Methods in Physics Research A. Vol. 370 , 1996, pp. 297-302

Tantawi, S. G.; Ruth, R. D.; Vlieks, A. E.

1997-05-01

250

Remotely-Actuated Biomedical Switch.  

National Technical Information Service (NTIS)

The report describes an implantable electronic switch that may be remotely actuated by an rf impulse to operate low-voltage bioinstrumentation attached to or also implanted in the monitored subject. This switching circuitry's unique characteristic lies in...

1969-01-01

251

Kiowa Creek Switching Station  

SciTech Connect

The Western Area Power Administration (Western) proposes to construct, operate, and maintain a new Kiowa Creek Switching Station near Orchard in Morgan County, Colorado. Kiowa Creek Switching Station would consist of a fenced area of approximately 300 by 300 feet and contain various electrical equipment typical for a switching station. As part of this new construction, approximately one mile of an existing 115-kilovolt (kV) transmission line will be removed and replaced with a double circuit overhead line. The project will also include a short (one-third mile) realignment of an existing line to permit connection with the new switching station. In accordance with the Council on Environmental Quality (CEQ) regulations for implementing the procedural provisions of the National Environmental Policy Act of 1969 (NEPA), 40 CFR Parts 1500--1508, the Department of Energy (DOE) has determined that an environmental impact statement (EIS) is not required for the proposed project. This determination is based on the information contained in this environmental assessment (EA) prepared by Western. The EA identifies and evaluates the environmental and socioeconomic effects of the proposed action, and concludes that the advance impacts on the human environment resulting from the proposed project would not be significant. 8 refs., 3 figs., 1 tab.

Not Available

1990-03-01

252

Public digital switching systems  

Microsoft Academic Search

INCE the‘ expansion of telephony to cover long distances, an extensive network of compatible switching nodes, transmission terminals and facilities, and signaling protocols have been developed and deployed the world over. Today one may call over this integrated network to reach any of over 500 million telephone stations. The telephone today is as it was intended by Alexander Graham Bell-a

1983-01-01

253

Switched fragmented aperture antennas  

Microsoft Academic Search

This paper introduces a reconfigurable aperture concept derived from fragmented aperture design where the configuration of the fragmented aperture may be switched by the user to obtain different functionalities. A fragmented aperture antenna is a patchwork of discrete conducting and dielectric units distributed over the specified aperture. The arrangement of the units is determined using an efficient, multistage procedure that

James C. Maloney; Morris P. Kesler; Lisa M. Lust; Lon N. Pringle; T. Lynn Fountain; Paul H. Harms; Glenn S. Smith

2000-01-01

254

High Speed Packet Switching.  

National Technical Information Service (NTIS)

This document constitutes the final report prepared by Proteon, Inc. of Westborough, Massachusetts under contract NAS 5-30629 entitled High-Speed Packet Switching (SBIR 87-1, Phase 2) prepared for NASA-Greenbelt, Maryland. The primary goal of this researc...

1991-01-01

255

A Cdse Bistable Switch.  

National Technical Information Service (NTIS)

Under certain conditions of synthesis, cadmium selenide (CdSe) shows a hysteresis effect in its current-voltage relationship. The material, therefore, has been of interest for use as a switch to control the electroluminescent (EL) emission of a solid stat...

S. A. Harper, L. J. Nicastro

1967-01-01

256

Transparent electrode for optical switch  

DOEpatents

The invention relates generally to optical switches and techniques for applying a voltage to an electro-optical crystal, and more particularly, to transparent electodes for an optical switch. System architectures for very large inertial confinement fusion (ICF) lasers require active optical elements with apertures on the order of one meter. Large aperture optical switches are needed for isolation of stages, switch-out from regenerative amplifier cavities and protection from target retroreflections.

Goldhar, J.; Henesian, M.A.

1984-10-19

257

Switching field distributions with spin transfer torques in perpendicularly magnetized spin-valve nanopillars  

NASA Astrophysics Data System (ADS)

We present switching field distributions of spin-transfer-assisted magnetization reversal in perpendicularly magnetized Co/Ni multilayer spin-valve nanopillars at room temperature. Switching field measurements of the Co/Ni free layer of spin-valve nanopillars with a 50 nm×300 nm ellipse cross section were conducted as a function of current. The validity of a model that assumes a spin-current-dependent effective barrier for thermally activated reversal is tested by measuring switching field distributions under applied direct currents. We show that the switching field distributions deviate significantly from the double exponential shape predicted by the effective barrier model, beginning at applied currents as low as half of the zero field critical current. Barrier heights extracted from switching field distributions for currents below this threshold are a monotonic function of the current. However, the thermally induced switching model breaks down for currents exceeding the critical threshold.

Gopman, D. B.; Bedau, D.; Mangin, S.; Fullerton, E. E.; Katine, J. A.; Kent, A. D.

2014-04-01

258

Component Processes in Task Switching.  

ERIC Educational Resources Information Center

Studied task switching in 4 experiments involving 111 Israeli undergraduates. Results show the preparation for a task switch is not a by-product of general preparation by phasic alertness or predicting target onset and establish reconfiguration as a separate preparatory process. Suggests that there are at least three components of task switching

Meiran, Nachshon; Chorev, Ziv; Sapir, Ayelet

2000-01-01

259

Alarm toe switch. [Patent application  

Microsoft Academic Search

An alarm toe switch inserted within a shoe for energizing an alarm circuit in a covert manner includes an insole mounting pad into which a miniature reed switch is fixedly molded. An elongated slot perpendicular to the reed switch is formed in the bottom surface of the mounting pad. A permanent cylindrical magnet positioned in the forward portion of the

Ganyard

1980-01-01

260

Organic Materials For Optical Switching  

NASA Technical Reports Server (NTRS)

Equations predict properties of candidate materials. Report presents results of theoretical study of nonlinear optical properties of organic materials. Such materials used in optical switching devices for computers and telecommunications, replacing electronic switches. Optical switching potentially offers extremely high information throughout in compact hardware.

Cardelino, Beatriz H.

1993-01-01

261

Semiconductor ac static power switch  

NASA Technical Reports Server (NTRS)

Semiconductor ac static power switch has long life and high reliability, contains no moving parts, and operates satisfactorily in severe environments, including high vibration and shock conditions. Due to their resistance to shock and vibration, static switches are used where accidental switching caused by mechanical vibration or shock cannot be tolerated.

Vrancik, J.

1968-01-01

262

Language Switching and Language Competition  

ERIC Educational Resources Information Center

This study examined the asymmetrical language switching cost in a word reading task (Experiment 1) and in a categorization task (Experiment 2 and 3). In Experiment 1, Spanish-English bilinguals named words in first language (L1) and second language (L2) in a switching paradigm. They were slower to switch from their weaker L2 to their more dominant…

Macizo, Pedro; Bajo, Teresa; Paolieri, Daniela

2012-01-01

263

A 35 GHz Latching Switch  

Microsoft Academic Search

This paper describes the development of a lightweight fast-switching 35 GHz latching ferrite circulator, with an instantaneous bandwidth of 5%, and a switching time of less the 0.30 microseconds. The device is designed for use over the temperature range of -60° C to +100° C under dynamic operating conditions. It is particularly well suited for use as a switching element

William C. Passaro; James W. McManus

1966-01-01

264

A delay model for noise-induced bi-directional switching.  

PubMed

Many biological systems can switch between two distinct states. Once switched, the system remains stable for a period of time and may switch back to its original state. A gene network with bistability is usually required for the switching and stochastic effect in the gene expression may induce such switching. A typical bistable system allows one-directional switching, in which the switch from the low state to the high state or from the high state to the low state occurs under different conditions. It is usually difficult to enable bi-directional switching such that the two switches can occur under the same condition. Here, we present a model consisting of standard positive feedback loops and an extra negative feedback loop with a time delay to study its capability to produce bi-directional switching induced by noise. We find that the time delay in the negative feedback is critical for robust bi-directional switching and the length of delay affects its switching frequency. PMID:20592956

Lei, Jinzhi; He, Guowei; Liu, Haoping; Nie, Qing

2009-12-01

265

Advances in integrated photonic circuits for packet-switched interconnection  

NASA Astrophysics Data System (ADS)

Sustained increases in capacity and connectivity are needed to overcome congestion in a range of broadband communication network nodes. Packet routing and switching in the electronic domain are leading to unsustainable energy- and bandwidth-densities, motivating research into hybrid solutions: optical switching engines are introduced for massive-bandwidth data transport while the electronic domain is clocked at more modest GHz rates to manage routing. Commercially-deployed optical switching engines using MEMS technologies are unwieldy and too slow to reconfigure for future packet-based networking. Optoelectronic packet-compliant switch technologies have been demonstrated as laboratory prototypes, but they have so far mostly used discretely pigtailed components, which are impractical for control plane development and product assembly. Integrated photonics has long held the promise of reduced hardware complexity and may be the critical step towards packet-compliant optical switching engines. Recently a number of laboratories world-wide have prototyped optical switching circuits using monolithic integration technology with up to several hundreds of integrated optical components per chip. Our own work has focused on multi-input to multi-output switching matrices. Recently we have demonstrated 8×8×8? space and wavelength selective switches using gated cyclic routers and 16×16 broadband switching chips using monolithic multi-stage networks. We now operate these advanced circuits with custom control planes implemented with FPGAs to explore real time packet routing in multi-wavelength, multi-port test-beds. We review our contributions in the context of state of the art photonic integrated circuit technology and packet optical switching hardware demonstrations.

Williams, Kevin A.; Stabile, Ripalta

2014-03-01

266

High gain GaAs photoconductive semiconductor switches: Switch longevity  

SciTech Connect

Optically activated, high gain GaAs switches are being tested for many different pulsed power applications that require long lifetime (longevity). The switches have p and n contact metallization (with intentional or unintentional dopants) configured in such a way as to produce p-i-n or n-i-n switches. The longevity of the switches is determined by circuit parameters and by the ability of the contacts to resist erosion. This paper will describe how the switches performed in test-beds designed to measure switch longevity. The best longevity was achieved with switches made with diffused contacts, achieving over 50 million pulses at 10 A and over 2 million pulses at 80 A.

Loubriel, G.M.; Zutavern, F.J.; Mar, A. [and others

1998-07-01

267

Effects of sulfhydryl regents on the activity of lambda Ser/Thr phosphoprotein phosphatase and inhibition of the enzyme by zinc ion.  

PubMed

Sulfhydryl reagents, such as dithiothreitol (DTT), affected the activity of Ser/Thr phosphoprotein phosphatases. Addition of DTT to the assay buffer increased the affinity of lambda Ser/Thr phosphoprotein phosphatase (lambda-PPase) for its Mn2+ cofactor. On the other hand, the enzyme was found to be inactivated simply by dilution in Tris buffer. The inactivation could be completely prevented by the presence of DTT or Mn2+ in the buffer. Further studies showed that oxidation or reduction of cysteine residues in lambda-PPase may not be the cause of the change in the enzyme activity. Without exception, mutation of all cysteine residues in lambda-PPase to serine did not convert the enzyme into a thiol-insensitive mutant. By careful examination of the effects of different sulfhydryl reagents, metal ion cofactors and substrates on lambda-PPase, it was found that the role of sulfhydryl reagents was the chelation of small amounts of inhibitory metal ions, which were present in plastic laboratory ware, such as disposable cuvets and tubes, with prevention of the enzyme from inactivation. One of the main contaminants found in plastic cuvets was Zn2+, which is a potent inhibitor of lambda-PPase. The inhibition of lambda-PPase by Zn2+ was characterized. Pre-treatment of the enzyme (1-4 nM) with 1 microM of ZnCl2 almost completely inhibited the enzymatic activity in response to 2 mM Mn2+. However, no significant inhibition was found when the enzyme was added to the assay mixture containing 1 microM Zn2+ and 2 mM Mn2+ . This confirms the sensitivity of the holoenzyme to inhibitory metal ions in vitro. The kinetic analysis indicated that the inhibitory metal ion might compete with Mn2+ to bind to the active site of lambda-PPase. This was further supported by the mutation of metal cofactor binding amino acid residues of the enzyme. Mutants which have less affinity for Mn2+ are also less sensitive to Zn2+. Our results suggest that inhibitory metal ions may induce a different structural conformation for lambda-PPase. PMID:9543006

Zhuo, S; Dixon, J E

1997-12-01

268

Dynamically-Allocated Multi-Queue Buffers for VLSI Communication Switches  

Microsoft Academic Search

Small n*n switches are key components of interconnection networks used in multiprocessors and multicomputers. The architecture of these n*n switches, particularly their internal buffers, is critical for achieving high-throughput low-latency communication with cost-effective implementations. Several buffer structures are discussed and compared in terms of implementation complexity, inter-switch handshaking requirements, and their ability to deal with variations in traffic patterns and

Yuval Tamir; Gregory L. Frazier

1992-01-01

269

Magnetization switching of an MgO/Co/Pt layer by in-plane current injection  

NASA Astrophysics Data System (ADS)

We demonstrate magnetization switching of a perpendicularly magnetized MgO/Co/Pt trilayer by application of an in-plane current and a constant in-plane magnetic field of small amplitude. Switching occurs due to an effective torque generated by spin-orbit coupling intrinsic to the trilayer structure. We investigate the dependence of the critical switching current on the current pulse width, showing that magnetization reversal in the dc limit is assisted by thermal fluctuations.

Onur Avci, Can; Garello, Kevin; Mihai Miron, Ioan; Gaudin, Gilles; Auffret, Stéphane; Boulle, Olivier; Gambardella, Pietro

2012-05-01

270

Efficiency considerations of load side soft-switching inverters for electric vehicle applications  

Microsoft Academic Search

This paper critically evaluates the efficiency of load side soft-switching inverters for electric vehicle (EV) drive applications. Five types of load side soft-switching inverters are studied, including the auxiliary resonant commutated pole inverter (ARCP), the zero-current-transition (ZCT) inverter, the zero-voltage-transition (ZVT) inverter with coupled inductors (ZVTCI), the ZVT inverter with a single switch (ZVTSS), and the ZVT inverter with a

Wei Dong; Jae-Young Choi; Yong Li; Huijie Yu; Jason Lai; Dusan Boroyevich; Fred C. Lee

2000-01-01

271

High-speed solution switching using piezo-based micropositioning stages  

Microsoft Academic Search

Motion-induced vibration is a critical limitation in high-speed micropositioning stages used to achieve solution switching. Controlled rapid solution switching is used to study the fast activation and deactivation kinetics of ligand-gated ion-channel populations isolated in excised membrane patches-such studies are needed to understand fundamental mechanisms that mediate synaptic elicitation and inhibition in the central nervous system. However, as the solution-switching

Shane Stilson; Annette McClellan; Santosh Devasia

2001-01-01

272

Future large broadband switched satellite communications networks  

NASA Technical Reports Server (NTRS)

Critical technical, market, and policy issues relevant to future large broadband switched satellite networks are summarized. Our market projections for the period 1980 to 2000 are compared. Clusters of switched satellites, in lieu of large platforms, etc., are shown to have significant advantages. Analysis of an optimum terrestrial network architecture suggests the proper densities of ground stations and that link reliabilities 99.99% may entail less than a 10% cost premium for diversity protection at 20/30 GHz. These analyses suggest that system costs increase as the 0.6 power of traffic. Cost estimates for nominal 20/30 GHz satellite and ground facilities suggest optimum system configurations might employ satellites with 285 beams, multiple TDMA bands each carrying 256 Mbps, and 16 ft ground station antennas. A nominal development program is outlined.

Staelin, D. H.; Harvey, R. R.

1979-01-01

273

49 CFR 213.135 - Switches.  

Code of Federal Regulations, 2013 CFR

...switch point shall fit its stock rail properly, with the switch...vertical movement of a stock rail in the switch plates or of a switch plate on a tie shall not adversely affect the...the switch point to the stock rail. Broken or cracked switch...

2013-10-01

274

Critical Flows.  

National Technical Information Service (NTIS)

Models of critical flow in pipes are reviewed. The single phase flow; balance equations for two phase flows; two component critical flows; and one component critical flows are considered. Lackme's (1979, 80) model of critical flow of flashing liquids is i...

M. Giot

1986-01-01

275

Nanoelectromechanics of Polarization Switching in Piezoresponse Force Microscopy  

SciTech Connect

Nanoscale polarization switching in ferroelectric materials by piezoresponse force microscopy in weak and strong indentation limits is analyzed using exact solutions for coupled electroelastic fields under the tip. Tip-induced domain switching is mapped on the Landau theory of phase transitions, with domain size as an order parameter. For a point charge interacting with a ferroelectric surface, switching by both first and the second order processes is possible, depending on the charge-surface separation. For a realistic tip, the domain nucleation process is first order in charge magnitude and polarization switching occurs only above a certain critical tip bias. In pure ferroelectric or ferroelastic switching, the late stages of the switching process can be described using a point charge model and arbitrarily large domains can be created. However, description of domain nucleation and the early stages of growth process when the domain size is comparable with the tip curvature radius (weak indentation) or the contact radius (strong indentation) requires the exact field structure. For higher order ferroic switching (e.g., ferroelectroelastic), the domain size is limited by the tip-sample contact area, thus allowing precise control of domain size.

Kalinin, Sergei V [ORNL; Gruverman, A. [North Carolina State University; Rodriguez, Brian J [ORNL; Shin, Junsoo [ORNL; Baddorf, Arthur P [ORNL; Karapetian, E. [Suffolk University, Boston; Kachanov, M. [Tifts University, Medford, MA

2005-01-01

276

The structure of Plasmodium falciparum serine hydroxymethyltransferase reveals a novel redox switch that regulates its activities.  

PubMed

Plasmodium falciparum serine hydroxymethyltransferase (PfSHMT), an enzyme in the dTMP synthesis cycle, is an antimalarial target because inhibition of its expression or function has been shown to be lethal to the parasite. As the wild-type enzyme could not be crystallized, protein engineering of residues on the surface was carried out. The surface-engineered mutant PfSHMT-F292E was successfully crystallized and its structure was determined at 3?Å resolution. The PfSHMT-F292E structure is a good representation of PfSHMT as this variant revealed biochemical properties similar to those of the wild type. Although the overall structure of PfSHMT is similar to those of other SHMTs, unique features including the presence of two loops and a distinctive cysteine pair formed by Cys125 and Cys364 in the tetrahydrofolate (THF) substrate binding pocket were identified. These structural characteristics have never been reported in other SHMTs. Biochemical characterization and mutation analysis of these two residues confirm that they act as a disulfide/sulfhydryl switch to regulate the THF-dependent catalytic function of the enzyme. This redox switch is not present in the human enzyme, in which the cysteine pair is absent. The data reported here can be further exploited as a new strategy to specifically disrupt the activity of the parasite enzyme without interfering with the function of the human enzyme. PMID:24914963

Chitnumsub, Penchit; Ittarat, Wanwipa; Jaruwat, Aritsara; Noytanom, Krittikar; Amornwatcharapong, Watcharee; Pornthanakasem, Wichai; Chaiyen, Pimchai; Yuthavong, Yongyuth; Leartsakulpanich, Ubolsree

2014-06-01

277

The structure of Plasmodium falciparum serine hydroxymethyltransferase reveals a novel redox switch that regulates its activities  

PubMed Central

Plasmodium falciparum serine hydroxymethyltransferase (PfSHMT), an enzyme in the dTMP synthesis cycle, is an antimalarial target because inhibition of its expression or function has been shown to be lethal to the parasite. As the wild-type enzyme could not be crystallized, protein engineering of residues on the surface was carried out. The surface-engineered mutant PfSHMT-F292E was successfully crystallized and its structure was determined at 3?Å resolution. The PfSHMT-F292E structure is a good representation of PfSHMT as this variant revealed biochemical properties similar to those of the wild type. Although the overall structure of PfSHMT is similar to those of other SHMTs, unique features including the presence of two loops and a distinctive cysteine pair formed by Cys125 and Cys364 in the tetrahydrofolate (THF) substrate binding pocket were identified. These structural characteristics have never been reported in other SHMTs. Biochemical characterization and mutation analysis of these two residues confirm that they act as a disulfide/sulfhydryl switch to regulate the THF-dependent catalytic function of the enzyme. This redox switch is not present in the human enzyme, in which the cysteine pair is absent. The data reported here can be further exploited as a new strategy to specifically disrupt the activity of the parasite enzyme without interfering with the function of the human enzyme.

Chitnumsub, Penchit; Ittarat, Wanwipa; Jaruwat, Aritsara; Noytanom, Krittikar; Amornwatcharapong, Watcharee; Pornthanakasem, Wichai; Chaiyen, Pimchai; Yuthavong, Yongyuth; Leartsakulpanich, Ubolsree

2014-01-01

278

Plasma opening switch  

DOEpatents

A command triggered plasma opening switch assembly using an amplification stage. The assembly surrounds a coaxial transmission line and has a main plasma opening switch (POS) close to the load and a trigger POS upstream from the main POS. The trigger POS establishes two different current pathways through the assembly depended on whether it has received a trigger current pulse. The initial pathway has both POS's with plasma between their anodes and cathodes to form a short across the transmission line and isolating the load. The final current pathway is formed when the trigger POS receives a trigger current pulse which energizes its fast coil to push the conductive plasma out from between its anode and cathode, allowing the main transmission line current to pass to the fast coil of the main POS, thus pushing its plasma out the way so as to establish a direct current pathway to the load.

Savage, Mark E. (Albuquerque, NM); Mendel, Jr., Clifford W. (Albuquerque, NM)

2001-01-01

279

Quantized conductance atomic switch.  

PubMed

A large variety of nanometre-scale devices have been investigated in recent years that could overcome the physical and economic limitations of current semiconductor devices. To be of technological interest, the energy consumption and fabrication cost of these 'nanodevices' need to be low. Here we report a new type of nanodevice, a quantized conductance atomic switch (QCAS), which satisfies these requirements. The QCAS works by controlling the formation and annihilation of an atomic bridge at the crossing point between two electrodes. The wires are spaced approximately 1 nm apart, and one of the two is a solid electrolyte wire from which the atomic bridges are formed. We demonstrate that such a QCAS can switch between 'on' and 'off' states at room temperature and in air at a frequency of 1 MHz and at a small operating voltage (600 mV). Basic logic circuits are also easily fabricated by crossing solid electrolyte wires with metal electrodes. PMID:15635405

Terabe, K; Hasegawa, T; Nakayama, T; Aono, M

2005-01-01

280

Switched optoelectronic microwave load  

NASA Astrophysics Data System (ADS)

The paper presents the analysis of a switched optoelectronic microwave load which can work either as a laser-controlled, matched or adjustable, resistive load or as a high-speed optoelectronic microwave switch. The device consists of a GaAs microstrip section controlled by a pulse-operated laser diode via substrate-edge-excitation. The exponential decay of photoconductivity across a longitudinal section of the microstrip forms a laser-induced electron-hole plasma wedge that works as a lossy tapered transmission-line section. The specific microwave power distribution within the excited region is derived in detail, as is the total input reflection coefficient under two special operating conditions (open-ended section and matched section). Numerical results are presented for a 906 nm excitation.

Platte, W.

1982-10-01

281

The quantum cryptographic switch  

NASA Astrophysics Data System (ADS)

We illustrate the principle of a cryptographic switch for a quantum scenario, in which a third party (Charlie) can control to a continuously varying degree the amount of information the receiver (Bob) receives, after the sender (Alice) has sent her information through a quantum channel. Suppose Charlie transmits a Bell state to Alice and Bob. Alice uses dense coding to transmit two bits to Bob. Only if the 2-bit information corresponding to the choice of the Bell state is made available by Charlie to Bob can the latter recover Alice's information. By varying the amount of information Charlie gives, he can continuously alter the information recovered by Bob. The performance of the protocol as subjected to the squeezed generalized amplitude damping channel is considered. We also present a number of practical situations where a cryptographic switch would be of use.

Srinatha, N.; Omkar, S.; Srikanth, R.; Banerjee, Subhashish; Pathak, Anirban

2014-01-01

282

Cryogenic switched MOSFET characterization  

NASA Technical Reports Server (NTRS)

Both p channel and n channel enhancement mode MOSFETs can be readily switched on and off at temperatures as low as 2.8 K so that switch sampled readout of a VLWIR Ge:Ga focal plane is electronically possible. Noise levels as low as 100 rms electrons per sample (independent of sample rate) can be achieved using existing p channel MOSFETs, at overall rates up to 30,000 samples/second per multiplexed channel (e.g., 32 detectors at a rate of almost 1,000 frames/second). Run of the mill devices, including very low power dissipation n channel FETs would still permit noise levels of the order of 500 electrons/sample.

1981-01-01

283

Future switching satellites  

NASA Technical Reports Server (NTRS)

Communications satellites of the future are likely to use much narrower beams in order to increase the uplink G/T and the downlink EIRP so that small earth terminals of the VSAT class can achieve full mesh connectivity. These satellites will need onboard switches to route traffic from originating upbeams to destination downbeams. This paper presents a new approach to accomplishing this rerouting using destination-directed packets that inherently carry the information needed to control the onboard switch connections and to adjust the traffic flow among the beams and the stations. The method also inherently provides channel multiplication and DAMA advantages which result in maximally efficient utilization of the space segment resource.

Campanella, S. Joseph; Pontano, Benjamin A.; Chalmers, Harvey

1988-01-01

284

Switching Power Supplies  

NSDL National Science Digital Library

Created by Work-Ready Electronics, a project of the Advanced Technological Education program, this module walks visitors through the basics of switching power supplies. The content of the site is divided into four areas: SMPS Basics and Switching Regulators; DC-DC Converters: Charge Pumps, Forwards Converters and Flyback Converters; Inverters, UPS and Hysteresis Curve, and SMPS: Advantages, Disadvantages and Troubleshooting. There is a quiz for each area in the Knowledge Probe area, and the Learning Resources section contains five activities to help cement student understanding. There are also further resources - both print and Web based - for more information and two Questors, a Flash trivia game. The Notebook function allows visitors to take notes and review them at any time. This is an excellent resource students and educators in electronics technician programs.

2008-09-05

285

Prevention of ethanol-induced vascular injury and gastric mucosal lesions by sucralfate and its components: possible role of endogenous sulfhydryls  

SciTech Connect

The authors tested the hypothesis that sucralfate, which contains eight sulfate and aluminum molecules on a sucrose and its other components might decrease ethanol-induced vascular injury and hemorrhagic mucosal lesions through a sulfhydryl (SH)-sensitive process. Experiments performed in rats revealed that the entire sucralfate molecule is not a prerequisite for protection against ethanol-induced mucosal vascular injury and erosions. It appears that sulfate and sucrose octasulfate are potent components of sucralfate, although an equimolar amount of sucralfate is at least twice as effective in gastroprotection than its components. The SH alkylator N-ethylmaleimide abolished the gastroprotection by sucralfate, suggesting SH-sensitive process in the mucosal protection which seems to be associated with the prevention of rapidly developing vascular injury in the stomach of rats given ethanol.

Szabo, S.; Brown, A.

1987-09-01

286

Evaluation of the modifying influence of arecanut on the garlic-modulated hepatic detoxication system enzymes, sulfhydryl content, and lipid peroxidation in mice.  

PubMed

This paper evaluates the potential effects of arecanut (Areca catechu, L.), an important ingredient of betel quid, on the garlic (Allium sativum, L.)-modulated activities of hepatic detoxication system enzymes, acid soluble sulfhydryl content, and lipid peroxidation in mice. Mice were fed on either a normal diet or a diet containing 0.25%, 0.5%, or 1% (w/w) arecanut for 45 days. During the last 10 days of treatment oral administration of garlic at the dose level of 20 or 100 mg/kg body weight/day was supplemented. Significant modulation in the activities of phase I and phase II enzymes, -SH content, and malondialdehyde (MDA) level by garlic was observed. Garlic-modulated alterations in glutathione S-transferase (GST) activity and -SH content were decreased, while cytochrome b5, cytochrome P-450, and MDA levels were further augmented by the arecanut plus garlic treatments. PMID:8584984

Singh, A; Rao, A R

1995-01-01

287

Effect of arecanut on the black mustard (Brassica niger, L.)-modulated detoxication enzymes and sulfhydryl content in the liver of mice.  

PubMed

The modulatory potential of arecanut, a popular masticatory, was assessed on the black mustard-induced changes in hepatic detoxication system in mice. The modulatory effect was assessed on glutathione S-transferase (GST), cytochrome b5 (Cyt. b5) and cytochrome P-450 (Cyt. P-450) and acid-soluble sulfhydryl (-SH) content. Mice were fed on either normal diet or diet containing 0.25%, 0.5% or 1% (w/w) arecanut for 45 days. During the last 10 days of treatment the feed was supplemented with 0.5% or 1% black mustard, the popular condiment. Dietary feeding of mustard could significantly enhance the studied phase I and phase II enzymes as well as -SH content in murine liver. However, black mustard-induced alterations in GST and -SH content were lower, while Cyt. b5 and Cyt. P-450 levels were much higher in mice receiving arecanut treatment than controls. PMID:8402573

Singh, A; Rao, A R

1993-08-16

288

Composite Material Switches  

NASA Technical Reports Server (NTRS)

A device to protect electronic circuitry from high voltage transients is constructed from a relatively thin piece of conductive composite sandwiched between two conductors so that conduction is through the thickness of the composite piece. The device is based on the discovery that conduction through conductive composite materials in this configuration switches to a high resistance mode when exposed to voltages above a threshold voltage.

Javadi, Hamid (Inventor)

2001-01-01

289

Composite Material Switches  

NASA Technical Reports Server (NTRS)

A device to protect electronic circuitry from high voltage transients is constructed from a relatively thin piece of conductive composite sandwiched between two conductors so that conduction is through the thickness of the composite piece. The device is based on the discovery that conduction through conductive composite materials in this configuration switches to a high resistance mode when exposed to voltages above a threshold voltage.

Javadi, Hamid (Inventor)

2002-01-01

290

CREE: Making the Switch  

ScienceCinema

CREE, with the help of ARPA-E funding, has developed a Silicon Carbide (SIC) transistor which can be used to create solid state transformers capable of meeting the unique needs of the emerging smart grid. SIC transistors are different from common silicon computer chips in that they handle grid scale voltages with ease and their high frequency switching is well suited to the intermittent nature of renewable energy generation.

Grider, David; Palmer, John

2014-04-09

291

Optical switch fabric design for gigabit switching router  

NASA Astrophysics Data System (ADS)

One of the key issues of high performance IP Gigabit Switching Router (GSR) design is about switching fabrics. In the traditional bus-based router architectures, the data transfer rate of copper backplanes will soon reach the speed limit because of connector reflections and crosstalk. An alternative optical switching fabric technology is necessary in order to satisfy the demand for high switching bandwidth. In this paper we firstly present a novel all-optical broadcasting switch fabric design scheme based on broadcasting bus architecture. In this section we also illustrate the advantages and disadvantages of this kind of architecture and demonstrate that this kind of switching fabric architecture have no interior block as well as none I/O block. Second, we discuss such implementation scheme of all-optical broadcasting switch fabric architecture as queuing, scheduling and multicasting. Finally, we get a conclusion that all-optical broadcasting switch fabric is one of the cost-effective solutions to design high-speed, scalable and simple switch fabrics compared with those complicated electric crossbar switch fabrics in GSR design.

Wei, Wei; Zeng, QingJi

2001-10-01

292

Simultaneous switching noise suppression for high speed systems using embedded decoupling  

Microsoft Academic Search

High performance computing systems are driving towards higher clock speeds, more switching circuits, and lower operating voltages. Simultaneous switching noise (SSN) will greatly affect signal integrity in such complex future mixed signal systems. It has been reported that in addition to inductance effects, power plane bounce also becomes a critical factor for packages containing many power and ground vias in

Joseph M. Hobbs; Hitesh Windlass; Venky Sundaram; Sungjun Chun; George E. White; Madhavan Swaminathan; Rao R. Tummala

2001-01-01

293

Ultrafast gas switching experiments  

SciTech Connect

We describe recent experiments which studied the physics of ultrafast gas breakdown under the extreme overvoltages which occur when a high pressure gas switch is pulse charged to hundreds of kV in 1 ns or less. The highly overvolted peaking gaps produce powerful electromagnetic pulses with risetimes < 100 ps which can be used for ultrawideband radar systems, particle accelerators, laser drivers, bioelectromagnetic studies, electromagnetic effects testing, and for basic studies of gas breakdown physics. We have produced and accurately measured pulses with 50 to 100 ps risetimes to peak levels of 75 to 160 kV at pulse repetition frequencies (PRF) to I kHz. A unique gas switch was developed to hold off hundreds of kV with parasitic inductance less than I nH. An advanced diagnostic system using Fourier compensation was developed to measure single-shot risetimes below 35 ps. The complete apparatus is described and wave forms are presented. The measured data are compared with a theoretical model which predicts key features including dependence on gas species and pressure. We have applied this technology to practical systems driving ultrawideband radiating antennas and bounded wave simulators. For example, we have developed a thyristor/pulse transformer based system using a highly overvolted cable switch. This pulser driving a Sandia- designed TEM cell, provides an ultra wideband impulse with < 200 ps risetime to the test object at a PRF > 1 kHz at > 100 kV/m E field.

Frost, C.A.; Martin, T.H.; Patterson, P.E.; Rinehart, L.F.; Rohwein, G.J.; Roose, L.D.; Aurand, J.F.; Buttram, M.T.

1996-11-01

294

Organic optical bistable switch  

NASA Astrophysics Data System (ADS)

We demonstrate an organic optical bistable switch by integrating an efficient organic photodetector on top of a transparent electrophosphorescent organic light-emitting diode (TOLED). The bistability is achieved with an external field-effect transistor providing positive feedback. In the ``LOW'' state, the TOLED is off and the current in the photodetector is solely its dark current. In the ``HIGH'' state, the TOLED emits light that is directly coupled into the integrated photodetector through the transparent cathode. The photocurrent then is fed back to the TOLED, maintaining it in the HIGH state. The green electrophosphorescent material, fac tris(2-phenylpyridine) iridium [Ir(ppy)3] doped into a 4,4'-N,N'-dicarbazole-biphenyl host was used as the luminescent material in the TOLED, while alternating thin layers of copper phthalocyanine and 3,4,9,10-perylenetetracarboxylic bis-benzimidazole were used as the active region of the organic photodetector. The circuit has a 3 dB bandwidth of 25 kHz, and can be switched between HIGH and LOW using pulses as narrow as 60 ns. The bistable switch can be both electrically and optically reset, making it a candidate for image-retaining displays (e.g., electronic paper) and other photonic logic applications. The integrated organic device also has broad use as a linear circuit element in applications such as automatic brightness control.

Xue, Jiangeng; Forrest, Stephen R.

2003-01-01

295

Inter-domain redox communication in flavoenzymes of the quiescin/sulfhydryl oxidase family: role of a thioredoxin domain in disulfide bond formation.  

PubMed

Flavoproteins of the quiescin/sulfhydryl oxidase (QSOX) family catalyze oxidation of peptide and protein thiols to disulfides with the reduction of oxygen to hydrogen peroxide. QSOX family members contain several domains, including an N-terminal thioredoxin domain (Trx) and an FAD-binding-domain (ERV) toward the C-terminus. Partial proteolysis of avian QSOX leads to two fragments, designated 30 and 60 kDa from their apparent mobilities on SDS-PAGE. The 30 kDa fragment is a monomer under nondenaturing conditions and contains a Trx domain with a CxxC sequence typical of protein disulfide isomerase (WCGHC). This QSOX fragment is not detectably glycosylated, contains no detectable FAD, and shows undetectable sulfhydryl oxidase activity. In contrast, the 60 kDa fragment is a dimeric glycoprotein that binds FAD tightly and oxidizes dithiothreitol about 1000-fold slower than intact QSOX. Reduced RNase is not a significant substrate of the 60 kDa fragment. The redox behavior of the 60 kDa flavoprotein fragment is profoundly different from that of intact QSOX. Thus, dithionite or photochemical reduction of the 60 kDa fragment leads to two-electron reduction of the FAD without subsequent reduction of the other two CxxC motifs or the appearance of a thiolate to flavin charge-transfer complex. Further characterization of the fragments and insights gained from the crystal structure of yeast ERV2p (Gross, E., Sevier, C. S., Vala, A., Kaiser, C. A., and Fass, D. (2002) Nat. Struct. Biol. 9, 61-67) suggest that the flow of reducing equivalents in intact avian QSOX is dithiol substrate --> C80/83 --> C519/522 --> C459/462 --> FAD --> oxygen. The ancient fusion of thioredoxin domains to a catalytically more limited ERV domain has produced an efficient catalyst for the direct introduction of disulfide bonds into a wide range of proteins and peptides in multicellular organisms. PMID:12693953

Raje, Sonali; Thorpe, Colin

2003-04-22

296

Delays and Q Switching in Semiconductor Lasers--Still an Open Question.  

National Technical Information Service (NTIS)

A critical review is made of the available experimental data and the proposed theoretical explanations regarding long delays and Q switching in semiconductor lasers. It is shown that no model is completely satisfactory in explaining all the available data...

J. E. Ripper J. A. Rossi

1973-01-01

297

6H-SiC Photoconductive Switches Triggered at Below Bandgap Wavelengths.  

National Technical Information Service (NTIS)

Semi-insulating Silicon Carbide (SiC) is an attractive material to use to construct high voltage, compact, photoconducting semiconductor switches (PCSS) due to its large bandgap, high critical electric field strength, high electron saturation velocity, an...

J. R. Stanley J. S. Sullivan

2006-01-01

298

Influence of capping layer on the current-induced magnetization switching in magnetic nanopillars  

NASA Astrophysics Data System (ADS)

Taking into account the thermal effect, we verify that the strong spin relaxation in the capping layer of a magnetic nanopillar significantly affects the current-induced magnetization switching behavior by reducing the critical switching current density. Theoretical calculations reveal that increasing the spin relaxation in the capping layer enhances the spin-polarized current while suppresses the contribution of the spin accumulation to the magnetization switching. The results suggest that the spin-polarized current, rather than the spin accumulation, dominates the current-induced magnetization switching.

Yang, T.; Hirohata, A.; Kimura, T.; Otani, Y.

2006-04-01

299

Monolithic integrated analog switching arrays  

Microsoft Academic Search

The reduction of the chip area of low ON-resistance transistor switches in n-channel metal oxide semiconductor-Si-gate technology to obtain higher density of monolithic integrated analog switching arrays is outlined. The applicability of the scaling principle, the reduction of the gate poly-Si line width and the use of a double diffusion process were studied. Transistor switches with two micron channel length

E. Baechle; J. Hersener; J. Koehne; M. Kuisl; K. Schlueter; A. Stuermer

1983-01-01

300

DNA-controlled excitonic switches.  

PubMed

Fluorescence resonance energy transfer (FRET) is a promising means of enabling information processing in nanoscale devices, but dynamic control over exciton pathways is required. Here, we demonstrate the operation of two complementary switches consisting of diffusive FRET transmission lines in which exciton flow is controlled by DNA. Repeatable switching is accomplished by the removal or addition of fluorophores through toehold-mediated strand invasion. In principle, these switches can be networked to implement any Boolean function. PMID:22401838

Graugnard, Elton; Kellis, Donald L; Bui, Hieu; Barnes, Stephanie; Kuang, Wan; Lee, Jeunghoon; Hughes, William L; Knowlton, William B; Yurke, Bernard

2012-04-11

301

Power transistor switching characterization  

NASA Technical Reports Server (NTRS)

The switching properties of power transistors are investigated. The devices studied were housed in IO-3 cases and were of an n(+)-p-n(-)-n(+) vertical dopant structure. The effects of the magnitude of the reverse-base current and temperature on the reverse-bias second breakdown characteristics are discussed. Brief discussions of device degradation due to second breakdown and of a constant voltage turn-off circuit are included. A description of a vacuum tube voltage clamp circuit which reduces clamped collector voltage overshoot is given.

Blackburn, D. L.

1981-01-01

302

A terahertz molecular switch.  

PubMed

We present time-dependent results describing the current through a molecular device, modeled as a complex with two active centers connected to leads under bias. We show that, at a properly adjusted external voltage, a passing terahertz electromagnetic pulse may cause a transition between states of finite and negligible current, suggesting that the system might be useful as a nanoscopic switch in the terahertz range. A phase diagram defining the bias region in which the transition takes place within a short time is given. As described, the physical processes involved are of an entirely different nature than those in ordinary photodetectors. PMID:12786110

Orellana, P; Claro, F

2003-05-01

303

Neutron activated switch  

DOEpatents

A switch for reacting quickly to a neutron emission. A rod consisting of fissionable material is located inside a vacuum tight body. An adjustable contact is located coaxially at an adjustable distance from one end of the rod. Electrical leads are connected to the rod and to the adjustable contact. With a vacuum drawn inside the body, a neutron bombardment striking the rod causes it to heat and expand longitudinally until it comes into contact with the adjustable contact. This circuit closing occurs within a period of a few microseconds.

Barton, David M. (Espanola, NM)

1991-01-01

304

Biological switches and clocks  

PubMed Central

To introduce this special issue on biological switches and clocks, we review the historical development of mathematical models of bistability and oscillations in chemical reaction networks. In the 1960s and 1970s, these models were limited to well-studied biochemical examples, such as glycolytic oscillations and cyclic AMP signalling. After the molecular genetics revolution of the 1980s, the field of molecular cell biology was thrown wide open to mathematical modellers. We review recent advances in modelling the gene–protein interaction networks that control circadian rhythms, cell cycle progression, signal processing and the design of synthetic gene networks.

Tyson, John J.; Albert, Reka; Goldbeter, Albert; Ruoff, Peter; Sible, Jill

2008-01-01

305

Composite Thermal Switch  

NASA Technical Reports Server (NTRS)

Lithium primary and lithium ion secondary batteries provide high specific energy and energy density. The use of these batteries also helps to reduce launch weight. Both primary and secondary cells can be packaged as high-rate cells, which can present a threat to crew and equipment in the event of external or internal short circuits. Overheating of the cell interior from high current flows induced by short circuits can result in exothermic reactions in lithium primary cells and fully charged lithium ion secondary cells. Venting of the cell case, ejection of cell components, and fire have been reported in both types of cells, resulting from abuse, cell imperfections, or faulty electronic control design. A switch has been developed that consists of a thin layer of composite material made from nanoscale particles of nickel and Teflon that conducts electrons at room temperature and switches to an insulator at an elevated temperature, thus interrupting current flow to prevent thermal runaway caused by internal short circuits. The material is placed within the cell, as a thin layer incorporated within the anode and/or the cathode, to control excess currents from metal-to-metal or metal-to-carbon shorts that might result from cell crush or a manufacturing defect. The safety of high-rate cells is thus improved, preventing serious injury to personnel and sensitive equipment located near the battery. The use of recently available nanoscale particles of nickel and Teflon permits an improved, homogeneous material with the potential to be fine-tuned to a unique switch temperature, sufficiently below the onset of a catastrophic chemical reaction. The smaller particles also permit the formation of a thinner control film layer (<50 m), which can be incorporated into commercial high-rate lithium primary and secondary cells. The innovation permits incorporation in current lithium and lithium-ion cell designs with a minimal impact on cell weight and volume. The composite thermal switch (CTS(TradeMark)) coating can be incorporated in either the anode or cathode or both. The coating can be applied in a variety of different processes that permits incorporation in the cell and electrode manufacturing processes. The CTS responds quickly and halts current flow in the hottest parts of the cell first. The coating can be applied to metal foil and supplied as a cell component onto which the active electrode materials are coated.

McDonald, Robert; Brawn, Shelly; Harrison, Katherine; O'Toole, Shannon; Moeller, Michael

2011-01-01

306

Critical Thinking vs. Critical Consciousness  

ERIC Educational Resources Information Center

This article explores four kinds of critical thinking. The first is found in Socratic dialogues, which employ critical thinking mainly to reveal logical fallacies in common opinions, thus cleansing superior minds of error and leaving philosophers free to contemplate universal verities. The second is critical interpretation (hermeneutics) which…

Doughty, Howard A.

2006-01-01

307

Guaranteed scheduling for switches with configuration overhead  

Microsoft Academic Search

In this paper, we present three algorithms that provide performance guarantees for scheduling switches, such as optical switches, with configuration overhead. Each algorithm emulates an unconstrained (zero overhead) switch by accumulating a batch of configuration requests and generating a corresponding schedule for a constrained switch. Speedup is required both to cover the configuration overhead of the switch and to compensate

Brian Towles; William J. Dally

2003-01-01

308

Switching efficiency improvement in spin torque majority gates  

NASA Astrophysics Data System (ADS)

Spin torque majority gate (STMG) is one of the promising options for beyond complementary metal-oxide-semiconductor logic. Improvement of its performance—switching speed vs. required current—is critical for its competitiveness. In this paper, (a) we identify an optimized layout of the gate comprised of thin magnetic wires with in-plane magnetization; (b) we optimize geometries of perpendicular magnetization spin torque majority gates. Micromagnetic simulations demonstrate an improvement in switching current for in-plane magnetization (with less than 1 ns switching time) from 6 mA in the original scheme to 1.5 mA in the present one. Additionally, failures of switching caused by vortex formation are eliminated and desired output magnetization is achieved. Various geometries of STMG with perpendicular magnetization are explored. The scheme with a straight cross proves to be the most advantageous. It is predicted to operate with the switching current of 50 ?A and less than 4 ns switching time.

Nikonov, Dmitri E.; Manipatruni, Sasikanth; Young, Ian A.

2014-05-01

309

Ferroelastic switching for nanoscale non-volatile magnetoelectric devices  

SciTech Connect

Multiferroics, where (anti-) ferromagnetic, ferroelectric, and ferroelastic order parameters coexist [1-5], enables manipulation of magnetic ordering by electric field through switching of the electric polarization [6-9]. It has been shown that realization of magnetoelectric coupling in single-phase multiferroic such as BiFeO3 requires ferroelastic (71o, 109o) rather than ferroelectric (180o) domain switching [6]. However, the control of such ferroleastic switching in a singlephase system has been a significant challenge as elastic interactions tend to destabilize small switched volumes, resulting in subsequent ferroelastic backswitching at zero electric field, thus disappearance of nonvolatile information storage [10, 11]. Guided by our phase-field simulations, we here report an approach to stabilize ferroelastic switching by eliminating the stress-induced instability responsible for back-switching using isolated monodomain BiFeO3islands. This work demonstrates a critical step to control and utilize nonvolatile magnetoelectric coupling at the nanoscale. Beyond magnetoelectric coupling, it provides a framework for exploring a route to control multiple order parameters coupled to ferroelastic order in other low-symmetry materials.

Baek, S. H.; Jang, H. W.; Folkman, C. M.; Li, Yulan; Winchester, B.; Zhang, J. X.; He, Q.; Chu, Y. H.; Nelson, C. T.; Rzchowski, M. S.; Pan, X. Q.; Ramesh, R.; Chen , L.Q.; Eom, C.B.

2010-04-01

310

Tuning the temperature dependence for switching in dithienylethene photochromic switches.  

PubMed

Diarylethene photochromic switches use light to drive structural changes through reversible electrocyclization reactions. High efficiency in dynamic photoswitching is a prerequisite for applications, as is thermal stability and the selective addressability of both isomers ring-opened and -closed diarylethenes. These properties can be optimized readily through rational variation in molecular structure. The efficiency with regard to switching as a function of structural variation is much less understood, with the exception of geometric requirements placed on the reacting atoms. Ultimately, increasing the quantum efficiency of photochemical switching in diarylethenes requires a detailed understanding of the excited-state potential energy surface(s) and the mechanisms involved in switching. Through studies of the temperature dependence, photoswitching and theoretical studies demonstrate the occurrence or absence of thermal activation barriers in three constitutional isomers that bear distinct ?-conjugated systems. We found that a decrease in the thermal barriers correlates with an increase in switching efficiency. The origin of the barriers is assigned to the decrease in ?-conjugation that is concomitant with the progress of the photoreaction. Furthermore, we show that balanced molecular design can minimize the change in the extent of ?-conjugation during switching and lead to optimal bidirectional switching efficiencies. Our findings hold implications for future structural design of diarylethene photochromic switches. PMID:23889496

Kudernac, Tibor; Kobayashi, Takao; Uyama, Ayaka; Uchida, Kingo; Nakamura, Shinichiro; Feringa, Ben L

2013-08-29

311

EDITORIAL: Molecular switches at surfaces Molecular switches at surfaces  

NASA Astrophysics Data System (ADS)

In nature, molecules exploit interaction with their environment to realize complex functionalities on the nanometer length scale. Physical, chemical and/or biological specificity is frequently achieved by the switching of molecules between microscopically different states. Paradigmatic examples are the energy production in proton pumps of bacteria or the signal conversion in human vision, which rely on switching molecules between different configurations or conformations by external stimuli. The remarkable reproducibility and unparalleled fatigue resistance of these natural processes makes it highly desirable to emulate nature and develop artificial systems with molecular functionalities. A promising avenue towards this goal is to anchor the molecular switches at surfaces, offering new pathways to control their functional properties, to apply electrical contacts, or to integrate switches into larger systems. Anchoring at surfaces allows one to access the full range from individual molecular switches to self-assembled monolayers of well-defined geometry and to customize the coupling between molecules and substrate or between adsorbed molecules. Progress in this field requires both synthesis and preparation of appropriate molecular systems and control over suitable external stimuli, such as light, heat, or electrical currents. To optimize switching and generate function, it is essential to unravel the geometric structure, the electronic properties and the dynamic interactions of the molecular switches on surfaces. This special section, Molecular Switches at Surfaces, collects 17 contributions describing different aspects of this research field. They analyze elementary processes, both in single molecules and in ensembles of molecules, which involve molecular switching and concomitant changes of optical, electronic, or magnetic properties. Two topical reviews summarize the current status, including both challenges and achievements in the field of molecular switches on metal surfaces, focusing on electronic and vibrational spectroscopy in one case and scanning tunneling microscopy studies in the other. Original research articles describe results in many aspects of the field, including: Self-assembly, self-organization, and controlled growth of molecular layers on various substrates. Highly-ordered arrays provide model systems with extraordinary structural properties, allowing one to adjust interactions between molecules and between molecule and substrate, and can be robustly prepared from solution, an essential prerequisite for applications. Conformational or electronic switching of molecules adsorbed at metal and semiconductor surfaces. These studies highlight the elementary processes governing molecular switching at surfaces as well as the wide range of possible stimuli. Carbon-based substrates such as graphene or carbon nanotubes. These substrates are attractive due to their effective two-dimensionality which implies that switching of adsorbed molecules can effect a significant back-action on the substrate. Mechanisms of conformational switching. Several contributions study the role of electron-vibron coupling and heating in current-induced conformational switching. We hope that the collection of articles presented here will stimulate and encourage researchers in surface physics and interfacial chemistry to contribute to the still emerging field of molecular switches at surfaces. We wish to acknowledge the support and input from many colleagues in preparing this special section. A significant part of this work has been conducted in the framework of the Sonderforschungsbereich 658 Elementary Processes in Molecular Switches at Surfaces of the Deutsche Forschungsgemeinschaft, to which we are grateful for financial support. Molecular surfaces at switches contents Molecular switches at surfacesMartin Weinelt and Felix von Oppen Optically and thermally induced molecular switching processes at metal surfacesPetra Tegeder Effects of electron-vibration coupling in transport through single moleculesKatharina J Franke and Jose Ignaci

Weinelt, Martin; von Oppen, Felix

2012-10-01

312

High current photoconductive semiconductor switches  

SciTech Connect

Photoconductive Semiconductor Switches (PCSS) are a completely different type of switch than those currently used in pulsed power applications. The most important attributes of PCSS are jitter-free triggering, low inductance, fast rise time, fast recovery (opening time), and high repetition rate. The most important limitation of the PCSS is the higher laser power required to activate them and the low-electric fields that they switch. These two issues are related because, for a given voltage that needs to be switched, a low field implies a large ''gap'' and, hence, a very large laser energy. This is especially troublesome since the laser energy required to reach a given switch resistance is proportional to the square of the gap spacing. In this paper we descibe major advances in PCSS. The first section describes how we are able to switch higher fields. Si can be used to switch fields of up to 82 kV/cm (a voltage of 123 kV across 1.5 cm), more than a factor of two higher than the 36 kV/cm that we reported a year ago. The development of PCSS for use in pulsed power application requires the ability to switch both high voltages and large currents. Having made signifcant progress in voltage standoff and switched fields, we are now concentrating on the current density issue. The second section describes the devlopment of two-impedance systems to test the maximum currents that the samples can switch. Presently the best we can switch corresponds to 4.0 kA (distributed over 2.1 cm) or 3.2 kA/cm (a current of 800 A distributed over a width of 0.25 cm) for GaAs in our sub-/OMEGA/ impedance test system. The third section focuses on the lock-on phenomenon first reported by our laboratory a year ago. 12 refs., 6 figs., 2 tabs.

Loubriel, G. M.; O'Malley, M. W.; Zutavern, F. J.; McKenzie, B. B.; Conley, W. R.; Hjalmarson, H. P.

1988-01-01

313

Study of optoelectronic switch for satellite-switched time-division multiple access  

NASA Technical Reports Server (NTRS)

The use of optoelectronic switching for satellite switched time division multiple access will improve the isolation and reduce the crosstalk of an IF switch matrix. The results are presented of a study on optoelectronic switching. Tasks include literature search, system requirements study, candidate switching architecture analysis, and switch model optimization. The results show that the power divided and crossbar switching architectures are good candidates for an IF switch matrix.

Su, Shing-Fong; Jou, Liz; Lenart, Joe

1987-01-01

314

Switch evaluation test system for the National Ignition Facility  

SciTech Connect

Flashlamp pumped lasers use pulsed power switches to commute energy stored in capacitor banks to the flashlamps. The particular application in which the authors are interested is the National Ignition Facility (NIF), being designed by Lawrence Livermore National Laboratory, Los Alamos National Laboratory, and Sandia National Laboratories (SNL). To lower the total cost of these switches, SNL has a research program to evaluate large closing switches. The target value of the energy switched by a single device is 1.6 MJ, from a 6 mF, 24kV capacitor bank. The peak current is 500 kA. The lifetime of the NIF facility is 24,000 shots. There is no switch today proven at these parameters. Several short-lived switches (100`s of shots) exist that can handle the voltage and current, but would require maintenance during the facility life. Other type devices, notably ignitrons, have published lifetimes in excess of 20,000 shots, but at lower currents and shorter pulse widths. The goal of the experiments at SNL is to test switches with the full NIF wave shape, and at the correct voltage. The SNL facility can provide over 500 kA at 24 kV charge voltage. the facility has 6.4 mF total capacitance, arranged in 25 sub-modules. the modular design makes the facility more flexible (for possible testing at lower current) and safer. For pulse shaping (the NIF wave shape is critically damped) there is an inductor and resistor for each of the 25 modules. Rather than one large inductor and resistor, this lowers the current in the pulse shaping components, and raises their value to those more easily attained with lumped inductors and resistors. The authors show the design of the facility, and show results from testing conducted thus far. They also show details of the testing plan for high current switches.

Savage, M.E.; Simpson, W.W. [Sandia National Labs., Albuquerque, NM (United States). High Energy Plasma Physics Dept.; Sharpe, R.A. [Sandia National Labs., Albuquerque, NM (United States). High Energy Plasma Physics Dept.]|[Ktech Corp., Albuquerque, NM (United States); Reynolds, F.D. [Sandia National Labs., Albuquerque, NM (United States). High Energy Plasma Physics Dept.]|[Tektronix, Inc., Albuquerque, NM (United States)

1997-07-01

315

Switching of ultrashort pulses in nonlinear high-birefringence two-core optical fibers  

NASA Astrophysics Data System (ADS)

We analyze the switching characteristics of ultrashort pulses in a nonlinear high-birefringence two-core optical fiber by solving a set of four generalized coupled nonlinear Schrödinger equations. In such a fiber, the critical power required for activating switching changes significantly with the polarization angle of the input pulse and, as a result, a pulse at a proper power level can be switched between the two cores of the fiber by changing the input polarization angle. This provides a simple mechanism of achieving optical switching with the fiber. We also study the effects of the group-delay difference (GDD) between the two polarization components and the coupling-coefficient dispersion (CCD) in the fiber on the switching characteristics. The GDD tends to break up the two polarization components in the input pulse and thus leads to an increase in the switching power. A larger GDD, however, can give a sharper switching contrast when the input polarization angle is varied. The CCD tends to break up the input pulse and cause pulse distortion, regardless of the polarization, so it also leads to an increase in the switching power. Unlike the GDD, a large CCD always reduces the switching contrast. To achieve high-quality switching, the fiber should have a small CCD.

Li, Jin Hua; Chiang, Kin Seng; Chow, Kwok Wing

2014-05-01

316

Investigation of critical slowing down in a bistable S-SEED  

Microsoft Academic Search

A simulation of S-SEED switching based upon experimental data is developed that includes the effect of critical slowing down. The simulation's accuracy is demonstrated by close agreement with the results from experimental S-SEED switching. The simulation is subsequently used to understand how the phenomenon of critical slowing down applies to switching of an S-SEED and how the effect on photonic

B. A. Clare; K. A. Corbett; K. J. Grant; P. B. Atanackovic; W. Marwood; J. Munch

2003-01-01

317

Distribution of supercurrent switching in graphene under the proximity effect.  

PubMed

We study the stochastic nature of switching current in hysteretic current-voltage characteristics of superconductor-graphene-superconductor junctions. We find that the dispersion of the switching current distribution scales with temperature as ?(I) proportional to T(?(G)) with ?(G) as low as 1/3. This observation is in sharp contrast to the known Josephson junction behavior where ?(I) proportional to T(?(J)) with ?(J)=2/3. We propose an explanation using a generalized version of Kurkijärvi's theory for the flux stability in rf-SQUID and attribute this anomalous effect to the temperature dependence of the critical current which persists down to low temperatures. PMID:22463661

Coskun, U C; Brenner, M; Hymel, T; Vakaryuk, V; Levchenko, A; Bezryadin, A

2012-03-01

318

Forced commutation performance of vacuum switches for HVDC breaker applications  

SciTech Connect

Tests were conducted to determine performance limits for vacuum switches under forced commutation conditions associated with a highvoltage dc (HVDC) breaker. Circuit parameters were varied and both linear and saturable reactors were used. Single as well as two series breaks were tested. Both ac- and dc recovery voltages were applied. Results confirm that the critical parameters are the current to be interrupted and the time to drive the switch current to zero. A linear reactor works nearly as well as a saturable reactor. Also, the magnitude of current injection need not be matched to the fault current; excess charges preferred.

Premerlani, W.J.

1982-08-01

319

Bistable solitons and optical switching  

Microsoft Academic Search

Using a particular nonlinearity (the 'linear + smooth step' model) as an illustrative example, it is demonstrated numerically that cyclic switching between bistable soliton states of the highly-nonlinear (generalized) Schroedinger equation can occur. Some important aspects of the switching process, including the nature and role of the intermediate states, are discussed. This numerical simulation may serve as a model of

Richard H. Enns; Sadanand S. Rangnekar

1987-01-01

320

IP switching and gigabit routers  

Microsoft Academic Search

To cope with the growth in the Internet and corporate IP networks, we require IP routers capable of much higher performance than is possible with existing architectures. This article examines two approaches to the design of a high-performance router, the gigabit router and the IP switch, and then provides some detail on the implementation of an IP switch and the

P. Newman; G. Minshall; T. Lyon; L. Huston

1997-01-01

321

Broadband Latching Switches and Circulators.  

National Technical Information Service (NTIS)

Work during this period was concentrated on reducing the switching energy of the 1.0 - 2.0 GHz and the 2.0 - 4.0 GHz latching circulators. Several external return path configurations were developed to lower the switching energy while maintaining maximum b...

J. W. Simon W. K. Alverson J. E. Pippin J. K. Parks

1968-01-01

322

Battery switch for downhole tools  

SciTech Connect

An electrical circuit for a downhole tool may include a battery, a load electrically connected to the battery, and at least one switch electrically connected in series with the battery and to the load. The at least one switch may be configured to close when a tool temperature exceeds a selected temperature.

Boling, Brian E. (Sugar Land, TX)

2010-02-23

323

Vacuum Cut-off Switch.  

National Technical Information Service (NTIS)

The vacuum cut-off switch is shown in a system including an evacuation chamber, a pump, an electric motor, a battery and conduits connecting the components. A pressure responsive detecting device is associated with the switch for controlling the operation...

J. E. Coyle

1964-01-01

324

Criticality Model  

SciTech Connect

The ''Disposal Criticality Analysis Methodology Topical Report'' (YMP 2003) presents the methodology for evaluating potential criticality situations in the monitored geologic repository. As stated in the referenced Topical Report, the detailed methodology for performing the disposal criticality analyses will be documented in model reports. Many of the models developed in support of the Topical Report differ from the definition of models as given in the Office of Civilian Radioactive Waste Management procedure AP-SIII.10Q, ''Models'', in that they are procedural, rather than mathematical. These model reports document the detailed methodology necessary to implement the approach presented in the Disposal Criticality Analysis Methodology Topical Report and provide calculations utilizing the methodology. Thus, the governing procedure for this type of report is AP-3.12Q, ''Design Calculations and Analyses''. The ''Criticality Model'' is of this latter type, providing a process evaluating the criticality potential of in-package and external configurations. The purpose of this analysis is to layout the process for calculating the criticality potential for various in-package and external configurations and to calculate lower-bound tolerance limit (LBTL) values and determine range of applicability (ROA) parameters. The LBTL calculations and the ROA determinations are performed using selected benchmark experiments that are applicable to various waste forms and various in-package and external configurations. The waste forms considered in this calculation are pressurized water reactor (PWR), boiling water reactor (BWR), Fast Flux Test Facility (FFTF), Training Research Isotope General Atomic (TRIGA), Enrico Fermi, Shippingport pressurized water reactor, Shippingport light water breeder reactor (LWBR), N-Reactor, Melt and Dilute, and Fort Saint Vrain Reactor spent nuclear fuel (SNF). The scope of this analysis is to document the criticality computational method. The criticality computational method will be used for evaluating the criticality potential of configurations of fissionable materials (in-package and external to the waste package) within the repository at Yucca Mountain, Nevada for all waste packages/waste forms. The criticality computational method is also applicable to preclosure configurations. The criticality computational method is a component of the methodology presented in ''Disposal Criticality Analysis Methodology Topical Report'' (YMP 2003). How the criticality computational method fits in the overall disposal criticality analysis methodology is illustrated in Figure 1 (YMP 2003, Figure 3). This calculation will not provide direct input to the total system performance assessment for license application. It is to be used as necessary to determine the criticality potential of configuration classes as determined by the configuration probability analysis of the configuration generator model (BSC 2003a).

A. Alsaed

2004-09-14

325

Ferroelectric Liquid Crystal Optical Interconnect Switching Systems.  

National Technical Information Service (NTIS)

This grant explored the possible use of ferroelectric liquid crystals (FLC's) in the reamization of photonic switching fabrics. Problems addressed included device fabrication, switch architectures, and switch performance. Experimental versions of most arc...

J. W. Goodman

1993-01-01

326

Alterable Magnetic Gratings for Fiber Optic Switching.  

National Technical Information Service (NTIS)

Optical mode switching of fiber light can enhance the capability of fiber optic communications systems by eliminating opto-electronic-opto converters at switching nodes and by performing the switching even on crosstalk-prone high data rate channels. Durin...

G. F. Sauter J. A. Krawczak G. L. Nelson F. G. Hewitt

1982-01-01

327

Expression of quiescin sulfhydryl oxidase 1 is associated with a highly invasive phenotype and correlates with a poor prognosis in Luminal B breast cancer  

PubMed Central

Introduction Quiescin sulfhydryl oxidase 1 (QSOX1) oxidizes sulfhydryl groups to form disulfide bonds in proteins. Tumor specific expression of QSOX1 has been reported for numerous tumor types. In this study, we investigate QSOX1 as a marker of breast tumor progression and evaluate the role of QSOX1 as it relates to breast tumor growth and metastasis. Methods Correlation of QSOX1 expression with breast tumor grade, subtype and estrogen receptor (ER) status was gathered through informatic analysis using the "Gene expression based Outcome for Breast cancer Online" (GOBO) web-based tool. Expression of QSOX1 protein in breast tumors tissue microarray (TMA) and in a panel of breast cancer cell lines was used to confirm our informatics analysis. To investigate malignant cell mechanisms for which QSOX1 might play a key role, we suppressed QSOX1 protein expression using short hairpin (sh) RNA in ER+ Luminal A-like MCF7, ER+ Luminal B-like BT474 and ER- Basal-like BT549 breast cancer cell lines. Results GOBO analysis revealed high levels of QSOX1 RNA expression in ER+ subtypes of breast cancer. In addition, Kaplan Meyer analyses revealed QSOX1 RNA as a highly significant predictive marker for both relapse and poor overall survival in Luminal B tumors. We confirmed this finding by evaluation of QSOX1 protein expression in breast tumors and in a panel of breast cancer cell lines. Expression of QSOX1 in breast tumors correlates with increasing tumor grade and high Ki-67 expression. Suppression of QSOX1 protein slowed cell proliferation as well as dramatic inhibition of MCF7, BT474 and BT549 breast tumor cells from invading through Matrigel™ in a modified Boyden chamber assay. Inhibition of invasion could be rescued by the exogenous addition of recombinant QSOX1. Gelatin zymography indicated that QSOX1 plays an important role in the function of MMP-9, a key mediator of breast cancer invasive behavior. Conclusions Taken together, our results suggest that QSOX1 is a novel biomarker for risk of relapse and poor survival in Luminal B breast cancer, and has a pro-proliferative and pro-invasive role in malignant progression partly mediated through a decrease in MMP-9 functional activity.

2013-01-01

328

Affective modulation of attentional switching.  

PubMed

Affective modulation of attentional switching may have developed early in evolution and may therefore have primacy over other affective influences. This behavioral study investigated the influence of affect on attentional switching between emotionally neutral stimuli, whether limited-capacity control processes are involved, and whether attentional flexibility should be distinguished from attentional broadening. Experiment 1 showed that suboptimally presented happy faces facilitated switching from an automatized response routine, whereas angry faces had the opposite effect. In Experiment 2, participants with a dominant global (i.e., broad) or local (i.e., narrow) spatial bias switched more easily to the opposite bias after suboptimal happy faces than after neutral primes but less easily after angry faces. Affective modulation of attentional switching was probably incorporated during evolution in many more complex forms of information processing. PMID:23858953

Heerebout, Bram T; Todorovi?, Ana; Smedinga, Hilde E; Phaf, R Hans

2013-01-01

329

Defect-mediated polarization switching in ferroelectrics and related materials: from mesoscopic mechanisms to atomistic control  

SciTech Connect

The plethora of lattice and electronic behaviors in ferroelectric and multiferroic materials and heterostructures opens vistas into novel physical phenomena including magnetoelectric coupling and ferroelectric tunneling. The development of new classes of electronic, energy-storage, and information-technology devices depends critically on understanding and controlling field-induced polarization switching. Polarization reversal is controlled by defects that determine activation energy, critical switching bias, and the selection between thermodynamically equivalent polarization states in multiaxial ferroelectrics. Understanding and controlling defect functionality in ferroelectric materials is as critical to the future of oxide electronics and solid-state electrochemistry as defects in semiconductors are for semiconductor electronics. Here, recent advances in understanding the defect-mediated switching mechanisms, enabled by recent advances in electron and scanning probe microscopy, are discussed. The synergy between local probes and structural methods offers a pathway to decipher deterministic polarization switching mechanisms on the level of a single atomically defined defect.

Kalinin, Sergei V [ORNL; Rodriguez, Brian J [ORNL; Baddorf, Arthur P [ORNL; Balke, Nina [ORNL; Borisevich, Albina Y [ORNL; Chang, Hye Jung [ORNL; Chen, Long-Qing [Pennsylvania State University; Jesse, Stephen [ORNL; Maksymovych, Petro [ORNL; Nikiforov, Maxim [ORNL; Pennycook, Stephen J [ORNL

2010-01-01

330

Optimized scalable network switch  

DOEpatents

In a massively parallel computing system having a plurality of nodes configured in m multi-dimensions, each node including a computing device, a method for routing packets towards their destination nodes is provided which includes generating at least one of a 2m plurality of compact bit vectors containing information derived from downstream nodes. A multilevel arbitration process in which downstream information stored in the compact vectors, such as link status information and fullness of downstream buffers, is used to determine a preferred direction and virtual channel for packet transmission. Preferred direction ranges are encoded and virtual channels are selected by examining the plurality of compact bit vectors. This dynamic routing method eliminates the necessity of routing tables, thus enhancing scalability of the switch.

Blumrich, Matthias A. (Ridgefield, CT) [Ridgefield, CT; Chen, Dong (Croton On Hudson, NY) [Croton On Hudson, NY; Coteus, Paul W. (Yorktown Heights, NY) [Yorktown Heights, NY; Gara, Alan G. (Mount Kisco, NY) [Mount Kisco, NY; Giampapa, Mark E. (Irvington, NY) [Irvington, NY; Heidelberger, Philip (Cortlandt Manor, NY) [Cortlandt Manor, NY; Steinmacher-Burow, Burkhard D. (Mount Kisco, NY) [Mount Kisco, NY; Takken, Todd E. (Mount Kisco, NY) [Mount Kisco, NY; Vranas, Pavlos M. (Bedford Hills, NY) [Bedford Hills, NY

2007-12-04

331

High voltage coaxial switch  

DOEpatents

A coaxial high voltage, high current switch having a solid cylindrical cold cathode coaxially surrounded by a thin hollow cylindrical inner electrode and a larger hollow cylindrical outer electrode. A high voltage trigger between the cathode and the inner electrode causes electrons to be emitted from the cathode and flow to the inner electrode preferably through a vacuum. Some of the electrons penetrate the inner electrode and cause a volumetric discharge in the gas (which may be merely air) between the inner and outer electrodes. The discharge provides a low impedance path between a high voltage charge placed on the outer electrode and a load (which may be a high power laser) coupled to the inner electrode. For high repetition rate the gas between the inner and outer electrodes may be continuously exchanged or refreshed under pressure. 3 figs.

Rink, J.P.

1983-07-19

332

High voltage coaxial switch  

DOEpatents

A coaxial high voltage, high current switch having a solid cylindrical cold cathode coaxially surrounded by a thin hollow cylindrical inner electrode and a larger hollow cylindrical outer electrode. A high voltage trigger between the cathode and the inner electrode causes electrons to be emitted from the cathode and flow to the inner electrode preferably through a vacuum. Some of the electrons penetrate the inner electrode and cause a volumetric discharge in the gas (which may be merely air) between the inner and outer electrodes. The discharge provides a low impedance path between a high voltage charge placed on the outer electrode and a load (which may be a high power laser) coupled to the inner electrode. For high repetition rate the gas between the inner and outer electrodes may be continuously exchanged or refreshed under pressure.

Rink, John P. (Los Alamos, NM)

1983-07-19

333

"Smart" watchdog safety switch  

DOEpatents

A method and apparatus for monitoring a process having a periodic output so that the process equipment is not damaged in the event of a controller failure, comprising a low-pass and peak clipping filter, an event detector that generates an event pulse for each valid change in magnitude of the filtered periodic output, a timing pulse generator, a counter that increments upon receipt of any timing pulse and resets to zero on receipt of any event pulse, an alarm that alerts when the count reaches some preselected total count, and a set of relays that opens to stop power to process equipment. An interface module can be added to allow the switch to accept a variety of periodic output signals.

Kronberg, James W. (353 Church Rd., Beech Island, SC 29842)

1991-01-01

334

''Smart'' watchdog safety switch  

DOEpatents

A method and apparatus for monitoring a process having a periodic output so that the process equipment is not damaged in the event of a controller failure, comprising a low-pass and peak clipping filter, an event detector that generates an event pulse for each valid change in magnitude of the filtered periodic output, a timing pulse generator, a counter that increments upon receipt of any timing pulse and resets to zero on receipt of any event pulse, an alarm that alerts when the count reaches some preselected total count, and a set of relays that opens to stop power to process equipment. An interface module can be added to allow the switch to accept a variety of periodic output signals. 21 figures.

Kronberg, J.W.

1991-10-01

335

Quantum switches and circuits  

US Patent & Trademark Office Database

Quantum switches, referred to as trisistors, operate on the basis of interactions between two elementary particles (EP), such as photons, electrons, phonons, etc. A first EP is used as a control input to the trisistor and interacts with a second EP, thereby inducing a detectable state change in the second EP that determines the trisistor's output value. The physical property which determines the particular EP state could be, for example, polarization, spin direction or energy level. The trisistors are connected primarily in series rather than in parallel as in previous quantum computing devices. The trisistors can be combined to form various types of logic gates, circuits, and other computer components. To implement the changes of state of the trisistors, one preferred embodiment employs nonlinear optics using a thin section of crystal.

2004-11-16

336

The Respiratory Burst and Electrolyte Leakage Induced by Sulfhydryl Blockers in Egeria densa Leaves Are Associated with H2O2 Production and Are Dependent on Ca 21 Influx1  

Microsoft Academic Search

In leaves of Egeria densa Planchon, N-ethylmaleimide (NEM) and other sulfhydryl-binding reagents induce a temporary increase in nonmitochondrial respiration (DQO2) that is inhibited by diphe- nylene iodonium and quinacrine, two known inhibitors of the plasma membrane NADPH oxidase, and are associated with a rel- evant increase in electrolyte leakage (M. Bellando, S. Sacco, F. Albergoni, P. Rocco, M.T. Marre ´

Enrica Amicucci; Luisa Zingarelli; Francesco Albergoni

1998-01-01

337

Anti-ulcerogenic mechanisms of the sesquiterpene lactone onopordopicrin-enriched fraction from Arctium lappa L. (Asteraceae): role of somatostatin, gastrin, and endogenous sulfhydryls and nitric oxide.  

PubMed

Arctium lappa L. has been used in folk medicine as a diuretic, depurative, and digestive stimulant and in dermatological conditions. The mechanisms involved in the anti-ulcerogenic activity of the sesquiterpene onopordopicrin (ONP)-enriched fraction (termed the ONP fraction), obtained from A. lappa leaves, were studied. The gastroprotective mechanism of the ONP fraction was evaluated in experimental in vivo models in rodents, mimicking this disease in humans. ONP fraction (50?mg/kg, p.o.) significantly inhibited the mucosal injury induced by ethanol/HCl solution (75%), indomethacin/bethanecol (68.9%), and stress (58.3%). When the ONP fraction was investigated in pylorus ligature, it did not induce alteration in the gastric volume but did modify the pH and total acid concentration of gastric juice. ONP fraction significantly increased serum somatostatin levels (82.1±4.1 vs. control group 12.7±4?pmol/L) and decreased serum gastrin levels (62.6±6.04 vs. control group 361.5±8.2??U/mL). Mucus production was not significantly altered by the ONP fraction. Gastroprotection by the ONP fraction was completely inhibited by N-ethylmaleimide treatment and did not modify the effect in the animals pretreated with l-N(G)-nitroarginine methyl ester. These results suggest an antisecretory mechanism involved with the antiulcerogenic effect of the ONP fraction. However, only endogenous sulfhydryls play an important role in gastroprotection of the ONP fraction. PMID:22191571

de Almeida, Ana Beatriz Albino; Luiz-Ferreira, Anderson; Cola, Maíra; Di Pietro Magri, Luciana; Batista, Leonia Maria; de Paiva, Joseilson Alves; Trigo, José Roberto; Souza-Brito, Alba R M

2012-04-01

338

Effect of excess dietary iron as ferrous sulfate and excess dietary ascorbic acid on liver zinc, copper and sulfhydryl groups and the ovary  

SciTech Connect

Female guinea pigs of the NIH 13/N strain, weighing between 475 and 512 g, were fed diets supplemented with 50 to 2500 mg of iron per kg of diet as ferrous sulfate and 0.2 to 8.0 g of ascorbic acid per kg of diet. A significant effect was observed on tissue copper and zinc, ovary weight and liver protein sulfhydryl groups. The mean ovary weight for guinea pigs fed 2500 mg of iron was significantly less than that of animals fed 50 mg of iron, 0.045 +/- 0.012 g and 0.061 +/- 0.009 g, respectively. Liver zinc content of animals fed 2500 mg of iron and 200 mg of ascorbic acid per kg of diet was significantly less than that of animals fed 50 mg of iron and 200 mg of ascorbic acid, 16.3 +/- 3.3 ..mu..g and 19.6 +/- 1.6 ..mu..g, respectively. There was no difference in liver copper due to dietary iron, but when dietary ascorbic acid was increased to 8 g per kg of diet, there was a significant decrease (from 22.8 +/- 8.1 ..mu..g to 10.5 +/- 4.8 ..mu..g) in liver copper. Excess dietary ascorbic acid decreased ovarian zinc significantly when increased to 8 g per kg of diet, 2929 +/- 919 ..mu..g vs 1661 +/- 471 ..mu..g, respectively, when compared to the control group.

Edwards, C.H.; Adkins, J.S.; Harrison, B.

1986-03-05

339

Foil fuses as opening switches for slow discharge circuits  

SciTech Connect

Metal foil fuses embedded in various materials are widely used as opening switches in fast discharge circuits (approx.1 ..mu..s). Several technologies of current interest require opening switches in circuits which operate on a much longer time scale (approx.100 ..mu..s). We have investigated the behavior of aluminum and copper foil fuses for conduction times of 100 to 200 ..mu..s. Reliable current interruption is obtained at the end of melting rather than at the end of vaporization. The ratio of initial to final resistance is >100. In general, the performance of slow fuses can be predicted by simple scaling from fast fuse behavior. For applications where the switching function depends critically on the resistivity versus input energy characteristic, the results presented can be used in the selection of proper fuse size and geometry.

Parker, J.V.; Parsons, W.M.

1985-01-01

340

Novel synchronization technique for two parallel connected sparkgap switches.  

PubMed

In this article a novel way of synchronizing two parallel connected sparkgap switches with accuracies of 1-5 ns for high frequency pulsed power applications is described. The circuit design of a synchronized sparkgap switch circuit is discussed. The circuit uses a combination of one master sparkgap and a set of inductor and capacitors to synchronize two sparkgaps and can be controlled via an IGBT switch. Critical issues for circuit design are presented together with analytical calculations and simulations. Experimental verification of the novel topology is carried out in a prototype experimental setup. Results showing nanosecond level of accuracy in synchronization are reported in this paper along with simulations and analysis. PMID:22938319

Kumar, Rohit; Mitra, S; Patel, A; Dwivedi, Rajesh; Kolge, T; Sharma, Ranjeet Archana; Chakravarthy, D P

2012-08-01

341

Alarm toe switch. [Patent application  

DOEpatents

An alarm toe switch inserted within a shoe for energizing an alarm circuit in a covert manner includes an insole mounting pad into which a miniature reed switch is fixedly molded. An elongated slot perpendicular to the reed switch is formed in the bottom surface of the mounting pad. A permanent cylindrical magnet positioned in the forward portion of the slot with a diameter greater than the pad thickness causes a bump above the pad. A foam rubber block is also positioned in the slot rearwardly of the magnet and holds the magnet in normal inoperative relation. A non-magnetic support plate covers the slot and holds the magnet and foam rubber in the slot. The plate minimizes bending and frictional forces to improve movement of the magnet for reliable switch activation. The bump occupies the knuckle space beneath the big toe. When the big toe is scrunched rearwardly the magnet is moved within the slot relative to the reed switch, thus magnetically activating the switch. When toe pressure is released the foam rubber block forces the magnet back into normal inoperative position to deactivate the reed switch.

Ganyard, F.P.

1980-11-18

342

ARTICLES: Polymer passive Q switch  

NASA Astrophysics Data System (ADS)

A study was made of polymer passive Q switches made of polyurethane acrylate colored with a dithiobenzyl complex of nickel. These switches were designed for the use in YAG:Nd3+ lasers. The polymer employed in these switches was elastic in a wide range of temperatures (beginning from -30°C), it adhered well to glass surfaces of the optical grade, and had a high optical strength. The layer structure of these switches improved the transfer of heat from the polymer to the substrate, the thermal conductivity of which was higher, so that the switches could operate stably at radiation intensities up to 16 W/cm2 without any need to move the switch. The photochemical stability of the dye in polyurethane acrylate was 106 pulses at a given point. When the resonator length was reduced to 6 cm and the active element was YAG:Nd3+ , the duration of the single pulses generated using a passive Q switch of this type was ~0.5 nsec and the divergence did not exceed 1 mrad (the corresponding half-width of the beam in the near-field zone was 1.5 mm).

Bezrodny?, V. I.; Tikhonov, E. A.

1986-12-01

343

Switching performance of Nb3Sn persistent current switch  

NASA Astrophysics Data System (ADS)

We designed a persistent current switch consisting of Nb3Sn superconducting wire for Superconducting Magneto-Hydro-Dynamic Propulsion Ship (MHDS). Nb3Sn has Tc higher than NbTi, which is commonly used for the conventional persistent current switch, and thus is expected to show a higher stability against the disturbance. We therefore performed numerical simulations for the heat transfer in a 10kA-class Nb3Sn persistent current switch by using a finite element method. The results of switching performance will be presented based on the computer simulation for temperature distribution during the heating and cooling cycle. We also present the estimated time for the transition from the superconducting to normal state (off-state) and vice versa (on-state).

Tomita, M.; Nemoto, K.; Sugawara, K.; Murakami, M.

344

Bistable solitons and optical switching  

NASA Astrophysics Data System (ADS)

Using a particular nonlinearity (the 'linear + smooth step' model) as an illustrative example, it is demonstrated numerically that cyclic switching between bistable soliton states of the highly-nonlinear (generalized) Schroedinger equation can occur. Some important aspects of the switching process, including the nature and role of the intermediate states, are discussed. This numerical simulation may serve as a model of optical switching between distinctly different soliton states in a nonlinear optical fiber and should simulate the search for the materials and mechanisms with appropriate nonlinearities.

Enns, Richard H.; Rangnekar, Sadanand S.

1987-07-01

345

Switching performance of Nb3Sn persistent current switch  

Microsoft Academic Search

We designed a persistent current switch consisting of Nb3Sn superconducting wire for Superconducting Magneto-Hydro-Dynamic Propulsion Ship (MHDS). Nb3Sn has Tc higher than NbTi, which is commonly used for the conventional persistent current switch, and thus is expected to show a higher stability against the disturbance. We therefore performed numerical simulations for the heat transfer in a 10kA-class Nb3Sn persistent current

M. Tomita; K. Nemoto; K. Sugawara; M. Murakami

2000-01-01

346

Techniques for optical packet switching and optical burst switching  

Microsoft Academic Search

Wavelength-division multiplexing appears to be the solution of choice for providing a faster networking infrastructure that can meet the explosive growth of the Internet. Several differ-ent technologies have been developed so far for the transfer of data over WDM. In this article we survey two new technologies which are still in the experimental stage, optical packet switch-ing and optical burst

Lisong Xu; H. G. Perros; G. Rouskas

2001-01-01

347

Critical Care  

MedlinePLUS

... as complications from surgery, accidents, infections, and severe breathing problems. It involves close, constant attention by a ... center. Monitors, intravenous (IV) tubes, feeding tubes, catheters, breathing machines, and other equipment are common in critical ...

348

Critical Careers.  

ERIC Educational Resources Information Center

Reports the critical shortage of qualified equipment technicians, especially in biomedical equipment. Cites the importance of encouraging careers in this field and describes a source of occupational information. (SK)

Bowles, Roger A.

2001-01-01

349

49 CFR 236.342 - Switch circuit controller.  

Code of Federal Regulations, 2013 CFR

...342 Switch circuit controller. Switch circuit controller connected at the point to switch, derail, or movable-point frog, shall be maintained so that its contacts will not be in position corresponding to switch point closure when switch point...

2013-10-01

350

Compact optical crossbar switch  

US Patent & Trademark Office Database

A planar optical crossbar switch comprising two thin planar substrates, on each of which are recorded or attached two holographic lenses between which light propagates by means of total internal reflection. The first lens is a negative cylindrical lens, used to input the incident light signal to the substrate, and the second lens is a positive cylindrical lens. The two substrates are disposed at right angles to each other in such a way that the positive lenses are positioned one on top of the other with a spatial light modulator sandwiched between them or beneath them. A linear array of detectors collects the output signal from the negative lens on the second substrate. Light from an element in the linear array of sources is spread out, by means of the negative cylindrical holographic lens on the first substrate, across a row of the SLM, and light from a column of the SLM is focused by means of the cylindrical holographic lenses on the second substrate, onto a particular element of the linear array of output detectors. To connect a signal form the ith source in the input array to the jth detector in the output array, the value of the {i,j} pixel of the SLM matrix should be in the ON state.

2001-01-09

351

Heteroleptic Copper Switches  

PubMed Central

Heteroleptic copper compounds have been designed and synthesized on solid supports. Chemical redox agents were used to change the oxidation state of the SiO2-immobilized heteroleptic copper compounds from Cu(I) to Cu(II) and then back to Cu(I). Optical spectroscopy of a dimethyl sulfoxide (DMSO) suspension demonstrated the reversibility of the Cu(I)/Cu(II) SiO2-immobilized compounds by monitoring the metal-to-ligand charge transfer (MLCT) peak at about 450 nm. EPR spectroscopy was used to monitor the isomerization of Cu(I) tetrahedral to Cu(II) square planar. This conformational change corresponds to a 90° rotation of one ligand with respect to the other. Conductive AFM (cAFM) and macroscopic gold electrodes were used to study the electrical properties of a p+ Si-immobilized heteroleptic copper compound where switching between the Cu(I)/Cu(II) states occurred at ?0.8 and +2.3 V.

Kabehie, Sanaz; Xue, Mei; Stieg, Adam Z.; Liong, Monty; Wang, Kang L.

2013-01-01

352

The magnetoelectrochemical switch.  

PubMed

In the field of spintronics, the archetype solid-state two-terminal device is the spin valve, where the resistance is controlled by the magnetization configuration. We show here how this concept of spin-dependent switch can be extended to magnetic electrodes in solution, by magnetic control of their chemical environment. Appropriate nanoscale design allows a huge enhancement of the magnetic force field experienced by paramagnetic molecular species in solutions, which changes between repulsive and attractive on changing the electrodes' magnetic orientations. Specifically, the field gradient force created within a sub-100-nm-sized nanogap separating two magnetic electrodes can be reversed by changing the orientation of the electrodes' magnetization relative to the current flowing between the electrodes. This can result in a breaking or making of an electric nanocontact, with a change of resistance by a factor of up to 10(3). The results reveal how an external field can impact chemical equilibrium in the vicinity of nanoscale magnetic circuits. PMID:25009179

Lunca Popa, Petru; Kemp, Neil T; Majjad, Hicham; Dalmas, Guillaume; Faramarzi, Vina; Andreas, Christian; Hertel, Riccardo; Doudin, Bernard

2014-07-22

353

Switch over from intravenous to oral therapy: A concise overview  

PubMed Central

Majority of the patients admitted to a hospital with severe infections are initially started with intravenous medications. Short intravenous course of therapy for 2-3 days followed by oral medications for the remainder of the course is found to be beneficial to many patients. This switch over from intravenous to oral therapy is widely practiced in the case of antibiotics in many developed countries. Even though intravenous to oral therapy conversion is inappropriate for a patient who is critically ill or who has inability to absorb oral medications, every hospital will have a certain number of patients who are eligible for switch over from intravenous to oral therapy. Among the various routes of administration of medications, oral administration is considered to be the most acceptable and economical method of administration. The main obstacle limiting intravenous to oral conversion is the belief that oral medications do not achieve the same bioavailability as that of intravenous medications and that the same agent must be used both intravenously and orally. The advent of newer, more potent or broad spectrum oral agents that achieve higher and more consistent serum and tissue concentration has paved the way for the popularity of intravenous to oral medication conversion. In this review, the advantages of intravenous to oral switch over therapy, the various methods of intravenous to oral conversion, bioavailability of various oral medications for the switch over program, the patient selection criteria for conversion from parenteral to oral route and application of intravenous to oral switch over through case studies are exemplified.

Cyriac, Jissa Maria; James, Emmanuel

2014-01-01

354

Electromagnetic Activation of Capillary Switches  

NASA Astrophysics Data System (ADS)

By designing coupled droplet pairs with the appropriate length scale to promote surface tension as the dominant force, one can create bi-stable capillary switches. This bi-stability can be triggered by pressure pulses, surface chemistry, electroosmosis, or body forces. To exploit the latter, we designed a capillary switch with electromagnetic activation. The resulting setup consists of a sub-millimeter tube, overfilled with a ferrofluid, surrounded by a wire coil to generate a magnetic field. Evidence of this capillary switching will be presented along with some theoretical basis in fluid- and electro-dynamics. The approach may also be used to investigate other transport phenomena in electromagnetically-coupled microfluidic systems, including the relative effects of translational motion of the ferrofluid (both particles and solvent molecules) versus the rotational effects of the individual magnetic grains. These individually addressable capillary switches offer intriguing applications including high-speed adaptive optics, actuators at the microscale, and possible PCB integration.

Malouin, Bernie; Dayal, Rohan; Parsa, Leila; Hirsa, Amir

2008-11-01

355

Switching characteristics of MINPN devices  

NASA Astrophysics Data System (ADS)

The I- V characteristics of the MINPN devices have been studied with the focus on the physical processes in the switchings. The study consists of computer simulation and experimental measurements, both of which show that these devices can exhibit one-state as well as two-state switchings. Such switchings are attributed to the regenerative process of the avalanche of the reverse PN junction with one or multiple current gains of the two composite NPN and MINP transistors. The MIS minority injection plays an important role in determining the switching characteristics of the device. Experimentally the breakover voltage and the hold-on voltage of this device are observed to be adjustable by applying base voltages. This can be considered as another evidence for the increased minority injection of the MIS structure.

Chang, David C. Y.; Lee, Chung Len; Lei, Tan Fu

1989-03-01

356

Theory of molecular hysteresis switch  

NASA Astrophysics Data System (ADS)

Molecular hysteresis switching has been recently observed in a series of experiments that measured the I-V spectrum of bipyridyl-dinitro oligophenylene-ethylene dithiol (BPDN) based molecular devices [1]. The experimental observations clearly show the presence of Coulomb blockade in single organic molecules that is responsible for the voltage-induced switching. We present the theory of the hysteresis switch which explains the non-linear hysteresis I-V characteristics based on the mechanisms of Coulomb blockade and the existence of two different molecular conformations of neutral and charged states of the molecule. [1] A.S. Blum, J.G. Kushmerick, D.P. Long, C.H. Patterson, J.C. Yang, J.C. Henderson, Y.X. Yao, J.M. Tour, R. Shashidhar, and B.R. Ratna, ``Molecularly inherent voltage-controlled conductance switching'' , Nature Materials 4, 167 (2005).

Kozhushner, Mortko; Oleynik, Ivan

2006-03-01

357

Optical interconnection networks for switching  

NASA Astrophysics Data System (ADS)

An ever-increasing bandwidth demand in computer communication and switching necessitates an efficient interconnection technology. Some of the advanced electronic parallel computer communication architectures may not even be sufficient to meet the ultra-high speed switching requirements of today's applications. The optical signal whether communicated through waveguides or free-space can propagate at the speed of light in the medium and, hence, is independent of the number of components that receive those signals. Optical interconnections are inherently fast, secure, and parallel in nature, which in turn, facilitate high bandwidth computer communication and switching. An attractive means for exploiting optical bema non-interaction property is to use free-space propagation but with focused, i.e., photorefractive volume holographic interconnection technique. In this talk we review a number of different optical interconnection network architectures with an emphasis on photorefractive volume holograms and their possibilities and problems as applied to computer communication switching.

Iftekharuddin, Khan M.

2001-07-01

358

IGBT: a solid state switch.  

National Technical Information Service (NTIS)

A Copper Vapour Laser Power Supply has been designed using a solid state switch consisting in eighteen Isolated Gate Bipolar Transistors (IGBT), -1200 volts, 400 Amps, each-in parallel. This paper presents the Isolated Gate Bipolar Transistor (IGBTs) repl...

D. Chatroux J. Maury B. Hennevin

1993-01-01

359

Single flux quantum crossbar switch  

Microsoft Academic Search

A crossbar switch has been designed using Single Flux Quantum (SFQ) gates exclusively for all internal functions. A 4×4 prototype has been fabricated in our Nb process foundry with Jc of 2000 A\\/cm2. We report on the design and performance of the switch and of an individual crosspoint element at high data rates (⩾1 Gbps). A novel design of a

Qing Ke; Bruce J. Dalrymple; Dale J. Durand; John W. Spargo

1997-01-01

360

High PRF high current switch  

DOEpatents

A triggerable, high voltage, high current, spark gap switch for use in pu power systems. The device comprises a pair of electrodes in a high pressure hydrogen environment that is triggered by introducing an arc between one electrode and a trigger pin. Unusually high repetition rates may be obtained by undervolting the switch, i.e., operating the trigger at voltages much below the self-breakdown voltage of the device.

Moran, Stuart L. (Fredericksburg, VA); Hutcherson, R. Kenneth (College Park, MD)

1990-03-27

361

Electroplated rf MEMS capacitive switches  

Microsoft Academic Search

RF microswitches are newly designed and fabricated with various structural geometry of transmission line, hinge, and movable plate formed by using electroplating techniques, low temperature processes, and dry releasing techniques. In particular, Strontium Titanate Oxide (SrTiO3) with high dielectric constant is investigated for high switching on\\/off ratio and on capacitance as a dielectric layer of a micromechanical capacitive switch. Achieved

Jae Y. Park; Geun H. Kim; Ki W. Chung; Jong U. Bu

2000-01-01

362

Conductance switching in organic monolayers  

Microsoft Academic Search

Self-assembled monolayers of some organic molecules, such as the bipyridyl-dinitro (BPDN) [1], present conductance switching (toggling between ON and OFF states). The switching happens upon crossing fixed threshold values in the applied bias voltage and the device can ``remember'' its previous state; thus, they have potential value as electronic memory devices. We use density-functional theory to elucidate the atomistic origins

Luis Agapito; Sabri Alkis; Jeffrey Krause; Hai-Ping Cheng

2009-01-01

363

Guaranteed Scheduling for Switches with Configuration Overhead  

Microsoft Academic Search

In this paper we present three algorithms that pro- vide performance guarantees for scheduling switches, such as op- tical switches, with configuration overhead. Each algorithm em- ulates an unconstrained (zero overhead) switch by accumulating a batch of configuration requests and generating a correspond- ing schedule for a constrained switch. Speedup is required both to cover the configuration overhead of the

Brian Towles; William J. Dally

2002-01-01

364

Switching activity estimation of CIC filter integrators  

Microsoft Academic Search

In this work, a method for estimation of the switching activity in integrators is presented. To achieve low power, it is always necessary to develop accurate and efficient methods to estimate the switching activity. The switching activities are then used to estimate the power consumption. In our work, the switching activity is first estimated for the general purpose integrators and

Muhammad Abbas; Oscar Gustafsson

2010-01-01

365

A Comparison of High-Voltage Switches  

Microsoft Academic Search

This report summarizes our work on high-voltage switches during the past few years. With joint funding from the Department of Energy (DOE) and the Department of Defense (DOD), we tested a wide variety of switches to a common standard. This approach permitted meaningful comparisons between disparate switches. Most switches were purchased from commercial sources, though some were experimental devices. For

K. W. Chu; G. L. Scott

1999-01-01

366

Characterizing and predicting search engine switching behavior  

Microsoft Academic Search

Search engine switching describes the voluntarily transition from one Web search engine to another. In this paper we present a study of search engine switching behavior that combines large- scale log-based analysis and survey data. We characterize aspects of switching behavior, and develop and evaluate predictive mod- els of switching behavior using features of the active query, the current session,

Ryen W. White; Susan T. Dumais

2009-01-01

367

Zero voltage switching approach for flyback converter  

Microsoft Academic Search

A zero voltage switched flyback power converter which realizes soft switching for every semiconductor is proposed. The sinusoidal resonant current flows through the secondary side rectifier diode and zero current switching of the diode is realized. Diode recovery is not generated. The proposed converter can operate with constant frequency pulse width modulation. High frequency switching and low noise are achieved

K. Yoshida; T. Ishii; N. Nagagata

1992-01-01

368

Research on control type soft switching converters  

Microsoft Academic Search

Paper clarifies the definition of control type soft switching and presents five characteristics for control type soft switching topologies. The theory of five characteristics is verified in the existing control type soft switching topologies, and a series of new control type soft switching topologies, such as buck, boost, buck-boost, cuk, zeta, sepic, flyback, and forward are constructed. A 200 kHz

Yilei Gu; Lijun Hang; Shijie Chen; Yu Du; Zhengyu Lu; Zhaoming Qian

2004-01-01

369

Mapping L1 Ligase ribozyme conformational switch  

PubMed Central

L1 Ligase (L1L)molecular switch is an in vitro optimized synthetic allosteric ribozyme that catalyzes the regioselective formation of a 5’-to-3’ phosphodiester bond, a reaction for which there is no known naturally occurring RNA catalyst. L1L serves as a proof of principle that RNA can catalyze a critical reaction for prebiotic RNA self-replication according to the RNA World hypothesis. L1L crystal structure captures two distinct conformations that differ by a re-orientation of one of the stems by around 80 Å and are presumed to correspond to the active and inactive state, respectively. It is of great interest to understand the nature of these two states in solution, and the pathway for their interconversion. In this study, we use explicit solvent molecular simulation together with a novel enhanced sampling method that utilizes concepts from network theory to map out the conformational transition between active and inactive states of L1L. We find that the overall switching mechanism can be described as a 3-state/2-step process. The first step involves a large-amplitude swing that re-orients stem C. The second step involves the allosteric activation of the catalytic site through distant contacts with stem C. Using a conformational space network representation of the L1L switch transition, it is shown that the connection between the three states follows different topographical patterns: the stem C swing step passes through a narrow region of the conformational space network, whereas the allosteric activation step covers a much wider region and a more diverse set of pathways through the network.

Giambasu, George M.; Lee, Tai-Sung; Scott, William G.; York, Darrin M.

2012-01-01

370

K-Band Latching Switches  

NASA Technical Reports Server (NTRS)

Design, development, and tests are described for two single-pole-double-throw latching waveguide ferrite switches: a K-band switch in WR-42 waveguide and a Ka-band switch in WR-28 waveguide. Both switches have structurally simple junctions, mechanically interlocked without the use of bonding materials; they are impervious to the effects of thermal, shock, and vibration stresses. Ferrite material for the Ka-band switch with a proper combination of magnetic and dielectric properties was available and resulted in excellent low loss, wideband performance. The high power handling requirement of the K-band switch limited the choice of ferrite to nickel-zinc compositions with adequate magnetic properties, but with too low relative dielectric constant. The relative dielectric constant determines the junction dimensions for given frequency responses. In this case the too low value unavoidably leads to a larger than optimum junction volume, increasing the insertion loss and restricting the operating bandwidth. Efforts to overcome the materials-related difficulties through the design of a composite junction with increased effective dielectric properties efforts to modify the relative dielectric constant of nickel-zinc ferrite are examined.

Piotrowski, W. S.; Raue, J. E.

1984-01-01

371

Origin of immunoglobulin isotype switching  

PubMed Central

Summary Background From humans to frogs, immunoglobulin class switching introduces different effector functions to antibodies through an intrachromsomal DNA recombination process at the heavy chain locus. Although there are two conventional antibody classes (IgM, IgW) in sharks, their heavy chains are encoded by 20 to >100 miniloci. These representatives of the earliest jawed vertebrates possess a primordial immunoglobulin gene organization where each gene cluster is autonomous and contains a few rearranging gene segments (VH-D1-D2-JH) with one constant region, ? or ?. Results V(D)J rearrangement always takes place within the ? cluster, but here we show that the VDJ can be expressed with constant regions from different clusters, although IgH genes are spatially distant, at >120 kb. Moreover, reciprocal exchanges take place between Ig? and Ig? genes. Switching is augmented with deliberate immunization and is concomitant with somatic hypermutation activity. Since switching occurs independently of the partners’ linkage position, some events involve transchromosomal recombination. The switch sites consist of direct joins between two genes in the 3? intron flanking JH. Conclusions Our data are consistent with a mechanism of cutting/joining of distal DNA lesions initiated by activation-induced cytidine deaminase (AID), in the absence of mammalian-type switch regions. We suggest that, in shark, with its many autonomous IgH targeted by programmed DNA breakage, factors predisposing broken DNA ends to translocate configured the earliest version of class switch recombination.

Zhu, Catherine; Lee, Victor; Finn, Alyssa; Senger, Kate; Zarrin, Ali A.; Pasquier, Louis Du; Hsu, Ellen

2012-01-01

372

Electronic logic for enhanced switch reliability  

DOEpatents

A logic circuit is used to enhance redundant switch reliability. Two or more switches are monitored for logical high or low output. The output for the logic circuit produces a redundant and fail-safe representation of the switch outputs. When both switch outputs are high, the output is high. Similarly, when both switch outputs are low, the logic circuit's output is low. When the output states of the two switches do not agree, the circuit resolves the conflict by memorizing the last output state which both switches were simultaneously in and produces the logical complement of this output state. Thus, the logic circuit of the present invention allows the redundant switches to be treated as if they were in parallel when the switches are open and as if they were in series when the switches are closed. A failsafe system having maximum reliability is thereby produced.

Cooper, J.A.

1984-01-20

373

Architecture of IP switch based on optical crossbar switching network with feedback loops  

Microsoft Academic Search

This paper proposes a novel optical crossbar switching architecture. The proposed IP switch is based on an optical crossbar switching system, which take full use of advantages of electronics and photonics to face the challenge of the terabits per second IP switching. Group interconnect network is regarded as an ideal switching structure for its low blocking and excellent scalability. We

Xinjun Zhou; Mingcui Cao; Jiangdong Wu; Fengguang Luo; Jun Xu

2001-01-01

374

Influence of switching regimes on dielectric strength of high current triggered vacuum switches  

Microsoft Academic Search

Switching conditions influence on dielectric strength of internal insulation of high-current triggered vacuum switches with trapezoidal-rod electrode system is investigated. Investigations were carried out for two switching regimes. In the first regime electrode erosion occurs mainly in a vapor phase where the electrode surface remains smooth after switching. In the other switching regime a drop phase of electrode erosion prevails

V. A. Sidorov; D. F. Alferov; N. I. Korobova

1999-01-01

375

Optimized switching algorithm for synchronized switch damping for multimodal excitation  

NASA Astrophysics Data System (ADS)

Shunted piezoceramics can be used to dissipate vibration energy of a host structure and therefore reduce vibration amplitudes. The piezoceramic converts a portion of the mechanical energy into electric energy which is then dissipated in an electric network. One semi-active control technique is the synchronized switch damping on inductance (SSDI), which has a good damping performance and can adapt to a wide range of excitation frequencies. In the standard SSDI a switch is closed during maximum deformation for one half of the electrical period time. This results in an inversion of the electrical charge. For the rest of the half-period the switch is opened and the charge remains constant. This results in a nearly rectangular voltage signal, which is in antiphase with the deformation velocity. In case of multimodal excitation, more sophisticated switching laws are developed with the aim to extract vibration energy from higher modes (i.e. Richard). This paper describes a novel multimodal switching law for vibration damping. An observer is designed to obtain an estimation of the first two vibration modes, which are used to determine the switching times. In simulations the increase in energy dissipation is evaluated and compared to the standard SSDI technique. With the new switching algorithm an improvement in energy dissipation is observed. The theoretical results are validated by measurements carried out on a clamped-free beam. The location of the piezoceramics is chosen to optimize the electro-mechanical coupling with the first vibration mode of the beam. The modal observer is realized in a realtime environment. Measurements show a good agreement with the theoretical results.

Schwarzendahl, Sebastian M.; Han, Xu; Neubauer, Marcus; Wallaschek, Jörg

2010-03-01

376

Neural correlates of establishing, maintaining, and switching brain states  

PubMed Central

Although the study of brain states is an old one in neuroscience, there has been growing interest in brain state specification owing to MRI studies tracing brain connectivity at rest. In this review, we summarize recent research on three relatively well-described brain states: the resting, alert, and meditation states. We explore the neural correlates of maintaining a state or switching between states, and argue that the anterior cingulate cortex and striatum play a critical role in state maintenance, whereas the insula has a major role in switching between states. Brain state may serve as a predictor of performance in a variety of perceptual, memory, and problem solving tasks. Thus, understanding brain states is critical for understanding human performance.

Tang, Yi-Yuan; Rothbart, Mary K.; Posner, Michael I.

2012-01-01

377

Enabling Technology for Multiple Input Multiple Output (MIMO) Systems on Mobile Military Platforms: Antennas, Switches, and Packaging.  

National Technical Information Service (NTIS)

This project has addressed a number of critical and practical challenges facing the direct integration of RF MEMS switches with reconfigurable antennas. Current designs have been adjusted to account for limitations presented by fabrication techniques avai...

J. T. Bernhard

2011-01-01

378

Inverting ZCS Switched-Capacitor Bidirectional Converter  

Microsoft Academic Search

The proposed inverting type zero-current switching switched-capacitor (ZCS SC) DC\\/DC converters are a new type of bi-directional power flow control conversion schemes. They possess high efficiency, low EMI emission and current stress features for the proposed quasi-resonant switched-capacitor inverting converters. A family of inverting type zero-current switching switched-capacitor bi-directional converters is presented, which can improve the current stress problem during

Yaung-Shung Lee; Yin-Yuan Chiu; Ming-Wang Cheng

2006-01-01

379

Non-latching relay switch assembly  

DOEpatents

A non-latching relay switch assembly which includes a coil section and a switch or contact section. The coil section includes a permanent magnet and an electromagnet. The respective sections are arranged in separate locations or cavities in the assembly. The switch has a "normal" position and is selectively switched by an overriding electromagnetic assembly. The switch returns to the "normal" position when the overriding electromagnetic assembly is inactive.

Duimstra, Frederick A. (Anaheim Hills, CA)

1991-01-01

380

4 × 4 optical-gate matrix switch  

Microsoft Academic Search

An optical gate-based matrix switch is proposed and a switching function in a 4 × 4 experimental switch is demonstrated. The experimental switch is composed of fiber-type splitters, a lantham-modified lead zirconate-titanate solid solution (PLZT) optical-gate array, and fiber-type combiners. The switch has a broad bandwidth of 400 Mbit\\/s for nonreturn-to-zero (NRZ) optical signal transmission. A possible maximum matrix size

AKIRA HIMENO; MORIO KOBAYASHI

1985-01-01

381

Guided-wave optical gate matrix switch  

Microsoft Academic Search

An optical gate matrix switch that is made by integrating InGaAsP laser diode gates with high-silica guided-wave splitter and combiner circuits in a hybrid fashion is proposed and demonstrated. It provides point-to-multipoint switching. A preliminary experiment for a 4×4 matrix switch shows that the switch is capable of more than 400-Mb\\/s bandwidth signal switching

Akira Himeno; Hiroshi Terui; Morio Kobayashi

1988-01-01

382

Switch-on shocks. [steepening of oblique nonlinear plane MHD waves  

NASA Technical Reports Server (NTRS)

It is argued that parallel propagating Alfven waves steepen to second order in the wave amplitude, rather than first order, as is the case for oblique MHD waves. An analytical solution for the structure of weak switch-on shocks is derived. The Rankine-Hugoniot relations for finite amplitude switch-on shocks are obtained in a compact form. The differential equation for resistive switch-on shocks is solved, and the resistive critical Mach number is obtained. The differential equation for resistive switch-on shocks with finite ion inertia is identical to the one obtained in the pure resistive case. It is argued that efficient electron heat conduction can significantly extend the range of upstream parameters for which switch-on shocks are expected.

Kennel, C. F.; Edmiston, J. P.

1988-01-01

383

Diode pumped Q-switched and mode locked lasers  

Microsoft Academic Search

The simultaneous Q-Switching and Mode Locking (QML) regime provides the generation of relatively high peak power picosecond pulses train with energies of a few muJ each in a simple resonator. The critical review of QML methods and results including our investigations is given in the first part of presentation. The application of several types of saturable crystalline absorbers (Cr4+:YAG, V3+:YAG,

Jan K. Jabczynski; Waldemar Zendzian; Jacek Kwiatkowski

2005-01-01

384

Effect of Asymmetric Leads on Switching Currents in Magnetic Nanopillars  

Microsoft Academic Search

Manschot et al.[1] predicted that the critical current for switching from parallel (P) to antiparallel (AP) magnetic states in ferromagnetic\\/nonmagnetic\\/ferromagnetic (F\\/N\\/F) nanopillars could be reduced by as much as an order of magnitude via asymmetric nonmagnetic leads with different effective resistances (resistivity times spin diffusion length). They proposed sandwiching the nanopillar between high effective resistance Cu (next to the free

Jack Bass; Albert Fert

2005-01-01

385

Current-induced magnetization switching in magnetic tunnel junctions  

Microsoft Academic Search

Current-induced magnetization switching (CIMS) in low-resistance magnetic tunnel junctions was shown at average critical current densities (Jc=1.33×106 A\\/cm2). When large vertical currents pass through the junctions, spin-transfer torque, and vortex fields can rotate the magnetization of the free layer from the initial parallel state to a vortex state, resulting in 10.8% CIMS resistance change at zero-bias current, which is about

Yaowen Liu; Zongzhi Zhang; P. P. Freitas; J. L. Martins

2003-01-01

386

The Role of Sulfhydryl Groups on the Impaired Hepatic 3?,3,5-Triiodothyronine Generation from Thyroxine in the Hypothyroid, Starved, Fetal, and Neonatal Rodent  

PubMed Central

The role of nonprotein sulfhydryl groups (NPSH) in the decreased in vitro hepatic 3?,3,5-triiodothyronine (T3) generation from thyroxine (T4) in the starved, hypothyroid, fetal and 1- to 4-d-old neonatal rat and dwarf mouse was assessed. NPSH were measured in fresh 25% liver homogenates prepared in 0.1 M PO4/10 mM EDTA buffer. As compared with values in adult male rats, NPSH concentration was decreased in the 2-d-starved (1.1±0.04 (mean±SE) vs. 2.2±0.15 mmol/250 g wet liver weight, P < 0.001), fetal (1.0±0.04 vs. 3.2±0.08, P < 0.001), 1-d-old neonatal (1.1±0.03 vs. 2.1±0.04, P < 0.001), and hypothyroid (thyroidectomized 60 d) (1.4±0.06 vs. 2.2±0.15 P < 0.001) rat. NPSH were also decreased in the hypothyroid, hypopituitary dwarf mouse as compared with values in their normal litter mates (1.3±0.03 vs. 2.0±0.2, P < 0.01). Chronic administration of T3 (0.5 ?g/100 g body wt per d) markedly increased hepatic T3 generation from T4 in the thyroidectomized rat and in the dwarf mouse to values similar to those observed in the normal rodent without affecting NPSH concentration. In contrast, T3 administration to the starved rat did not alter either hepatic T3 generation from T4 or NPSH. Reduced glutathione concentration was also markedly decreased in the starved rat (fed; 1.05±0.075 mmol/250 g wet tissue vs. starved 0.38±0.02, P < 0.001). Dithiothreitol (DTT), a thiol reducing agent, increased hepatic T3 generation from T4 in the normal adult male rat by 45±5% in six experiments. When compared to DTT-stimulated control homogenates, the addition of DTT completely restored hepatic T3 generation in starved rats, partially restored T3 generation in 1- and 4-d-old neonates, but had little or no effect in the fetal and hypothyroid rat and dwarf mouse. Liver homogenates stored for 6 mo at ?20°C lost their capacity to generate T3 from T4. NPSH concentrations in the frozen homogenates decreased progressively with increasing storage and were absent by 6 mo. 5?-Deiodinase activity correlated with NPSH concentration in the stored homogenates (r = 0.95, P < 0.005). Addition of DTT partially restored hepatic T3 generation in the frozen homogenate. It is concluded that NPSH are important for the action of the liver 5?-deiodinase. The decreased hepatic T3 generation in the starved rat is associated with decreased NPSH but not with a decrease in the absolute quantity of 5?-deiodinase because provision of sulfhydryl groups restored hepatic T3 generation to normal. In contrast, the decreased hepatic T3 generation in the adult hypothyroid rodent and in the fetal rat is probably due to a decrease in the enzyme concentration per se. In the 1- and 4-d neonatal rat, the decrease in hepatic T3 generation is secondary to a decrease in NPSH and the deiodinating enzyme.

Harris, Arthur R. C.; Fang, Shih-Lieh; Hinerfeld, Lee; Braverman, Lewis E.; Vagenakis, Apostolos G.

1979-01-01

387

Switching friction with thermal- responsive gels.  

PubMed

The thermosensitive graphene oxide (GO)/poly(N-isopropyl acrylamide) (pNIPAM) composite hydrogels are prepared, and their tribological properties in response to external stimuli are evaluated. The frictional coefficient of the hydrogels is closely related to the gel composition and ambient temperature. When the gel is in swelling state below the low critical solution temperature (LCST), it shows ultra-low friction and exhibits high friction at a shrunk state above the LCST. The huge difference of frictional coefficient under two states can be reversibly switched many times by altering the temperature. The incorporation of a nonthermal sensitive monomer into pNIPAM could change the LCST and thus the transformation point of frictional coefficient can be altered. These reversible and tunable frictional hydrogels have potential application in the design of intelligent control equipment. PMID:24249089

Wu, Yang; Cai, Meirong; Pei, Xiaowei; Liang, Yongmin; Zhou, Feng

2013-11-01

388

Ad Critic  

NSDL National Science Digital Library

Ad Critic strives to enter every television advertisement into its database of online commercials, which can be downloaded for free and viewed with QuickTime. A complete list of advertisements is indexed by company and by ad title. There are, however, also indexes of newly added ads, most-downloaded ads, movie trailers, and music found in ads, making it easier for users to search for a new or favorite advertisement. Ad Critic includes a section on advertising news and commentary and provides services for advertising agencies including online market research and detailed viewer statistics.

389

The yin of exofacial protein sulfhydryls and the yang of intracellular glutathione in in vitro transfection with SS14 bioreducible lipoplexes.  

PubMed

Although redox-sensitive transfectants have been considered hitherto as the Holy Grail of gene delivery because of their ability to restrict the release of nucleic acids to intracellular compartments, the reasons for their sometimes lackluster performance do not seem likewise clear. To ascertain the possible influence of extracellular soluble thiols, exofacial protein sulfhydryls (EPTs) and glutathione (GSH) on the overall efficacy of bioreducible lipoplexes, we utilized a cationic gemini surfactant--SS14--in which the two single-chain amphiphiles are held together by a suitable redox-sensitive linkage. We herein draw a big picture whereby the interaction of bioreducible lipoplexes with cells and their internalization are tightly coupled events that ultimately do affect transfection. Specifically, we provide evidence that EPTs entail the reduction-triggered disruption of SS14 lipoplexes in plain Dulbecco's Modified Eagle Medium (DMEM), thereby resulting in a considerable waste (ca. 30%) of nucleic acids and low transgene expression. The DNA release from bioreducible lipoplexes can be blunted to ca. 16% by transfecting cells in complete medium and fully reverted by preincubating them for 1h before delivery in the same culture supernatant (i.e. preconditioning), thus significantly increasing transfection by ca. 3-fold and 10-fold, respectively. These results lead to the proposal of the protein corona as the central mediator in shielding SS14 bioreducible lipoplexes from the action of EPTs in the early phase of delivery and provide a smart solution as to how to increase their efficacy. Besides, we pinpoint associations between intracellular GSH levels and the extent of transfection. All these issues were unique to bioreducible lipoplexes. PMID:23123189

Pezzoli, Daniele; Zanda, Matteo; Chiesa, Roberto; Candiani, Gabriele

2013-01-10

390

Conformationally sensitive reactivity to permeant sulfhydryl reagents of cysteine residues engineered into helical hairpin 1 of the glutamate transporter GLT-1.  

PubMed

In the central nervous system, glutamate transporters terminate the actions of this neurotransmitter by concentrating it into cells surrounding the synapse by a process involving sodium and proton cotransport followed by countertransport of potassium. These transporters contain two oppositely oriented helical hairpins 1 and 2. Hairpin 1 originates from the cytoplasm, but its tip is close to that of hairpin 2, which enters the transporter's lumen from the extracellular side. Here we address the question of whether hairpin 1 and/or domains surrounding it undergo conformational changes during the transport cycle. Therefore, we probed the reactivity of cysteines introduced into hairpin 1 and the cytoplasmic ends of transmembrane domains 6, 7, and 8 of the GLT-1 transporter to membrane-permeant N-ethylmaleimide. In each domain, except for transmembrane domain 6, cysteine mutants were found in which the inhibition of d-[(3)H]aspartate transport by the sulfhydryl reagent was increased when external sodium was replaced by potassium, a condition expected to increase the proportion of cytoplasmic-facing transporters. Conversely, the nontransportable blocker kainate protected against the inhibition in several of these mutants, presumably by locking the transporter in an outward-facing conformation. Moreover, external potassium decreased the oxidative cross-linking of two cysteines, each introduced at the tip of each hairpin. Our results are consistent with a model based on the crystal structure of an archeal homolog. According to this model, the inward movement of hairpin 1 results in the opening of a pathway between the binding pocket and the cytoplasm, lined by parts of transmembrane domains 7 and 8. PMID:17272682

Shlaifer, Irina; Kanner, Baruch I

2007-05-01

391

Distinct Roles of Protein Disulfide Isomerase and P5 Sulfhydryl Oxidoreductases in Multiple Pathways for Oxidation of Structurally Diverse Storage Proteins in Rice[W][OA  

PubMed Central

In the rice (Oryza sativa) endosperm, storage proteins are synthesized on the rough endoplasmic reticulum (ER), in which prolamins are sorted to protein bodies (PBs) called type-I PB (PB-I). Protein disulfide isomerase (PDI) family oxidoreductase PDIL2;3, an ortholog of human P5, contains a conserved structural disulfide in the redox-inactive thioredoxin-like (TRX) domain and was efficiently targeted to the surface of PB-I in a redox active site–dependent manner, whereas PDIL1;1, an ortholog of human PDI, was localized in the ER lumen. Complementation analyses using PDIL1;1 knockout esp2 mutant indicated that the a and a? TRX domains of PDIL1;1 exhibited similar redox activities and that PDIL2;3 was unable to perform the PDIL1;1 functions. PDIL2;3 knockdown inhibited the accumulation of Cys-rich 10-kD prolamin (crP10) in the core of PB-I. Conversely, crP10 knockdown dispersed PDIL2;3 into the ER lumen. Glutathione S-transferase-PDIL2;3 formed a stable tetramer when it was expressed in Escherichia coli, and the recombinant PDIL2;3 tetramer facilitated ?-globulin(C79F) mutant protein to form nonnative intermolecular disulfide bonds in vitro. These results indicate that PDIL2;3 and PDIL1;1 are not functionally redundant in sulfhydryl oxidations of structurally diverse storage proteins and play distinct roles in PB development. We discuss PDIL2;3-dependent and PDIL2;3-independent oxidation pathways that sustain disulfide bonds of crP10 in PB-I.

Onda, Yayoi; Nagamine, Ai; Sakurai, Mutsumi; Kumamaru, Toshihiro; Ogawa, Masahiro; Kawagoe, Yasushi

2011-01-01

392

PERFORMANCE ANALYSIS OF THE KNOCKOUT SWITCH UNDER BURSTY TRAFFIC BASED ON A STOCHASTIC ACTIVITY NETWORK MODEL  

Microsoft Academic Search

The possibility of ATM-based B-ISDNs has made desirable the integration of diverse services like voice, data, and multi-media. The success of these high-speed networks is critically dependent on the availability of fast packet switches (FPS), with the capacity to switch and route at high speeds and provide the required quality of service (QoS). The diversity of the applications, however, leads

Latha Kant; William H. Sanders

393

Flight control computer operational flight program development for the control laws switching mechanism  

Microsoft Academic Search

All new flight control law and flight control computer developments have historically been an extremely expensive and time-consuming proposition specially in a flight-critical system. To reduce and avoid these kind of problems, the switching mechanism method has been addressed. Here the switching mechanism needs two computers. One is a basic(or primary) computer already customized to the production airframe and the

Sang-Seon Park; In-Je Cho; Seung-Ha Ryu; Sang-Soo Lim

2007-01-01

394

Internet Switching by Satellite: An Ultra Fast Processor with Radio Burst Switching.  

National Technical Information Service (NTIS)

This paper introduces a new switching approach for satellites involved in routing statistical traffic, such as Internet Protocol (IP) data. Inherited from the optical domain, Radio Burst Switching (RBS) can combine a coarse switching granularity (such as ...

C. Haardt N. Couville

2005-01-01

395

Staying Critical  

ERIC Educational Resources Information Center

In this article, the two authors of "Becoming Critical: education, knowledge and action research" look back at the book's history since its publication 20 years ago. We describe how the book was originally written, and the diverse responses and reactions that it has produced. We identify some of the book's inadequacies and limitations, and…

Carr, Wilfred; Kemmis, Stephen

2005-01-01

396

Critical Thinking  

Microsoft Academic Search

The process of critical thinking enables students to explore, analyze, and evaluate problems, theories, and interventions from divergent views and varying frames of reference. It requires a certain amount of skepticism and curiosity that will reflect upon accepted doctrines and protocols, in order to ascertain their credibility and utility in working with clients. This article presents the obstacles to acquiring

Sondra Burman

2000-01-01

397

Critical Load  

NSDL National Science Digital Library

In this activity, learners explore the concepts of structural engineering and how to measure the critical load, or the maximum weight a structure can bear. Learners investigate basic structures, how to reinforce, materials selection, and working as a team, design and build a prototype structure to hold increasingly greater weights.

Ieee

2014-05-22

398

Critical Thinking  

ERIC Educational Resources Information Center

True excellence in technology implementation emerges when IT, administrative, and academic leaders link IT to mission-critical institutional objectives, investing in hardware and software to serve an explicit purpose and a distinct population of users. This article illustrates that at public institutions of higher education in New Hampshire as…

Villano, Matt

2006-01-01

399

High speed packet switching  

NASA Technical Reports Server (NTRS)

This document constitutes the final report prepared by Proteon, Inc. of Westborough, Massachusetts under contract NAS 5-30629 entitled High-Speed Packet Switching (SBIR 87-1, Phase 2) prepared for NASA-Greenbelt, Maryland. The primary goal of this research project is to use the results of the SBIR Phase 1 effort to develop a sound, expandable hardware and software router architecture capable of forwarding 25,000 packets per second through the router and passing 300 megabits per second on the router's internal busses. The work being delivered under this contract received its funding from three different sources: the SNIPE/RIG contract (Contract Number F30602-89-C-0014, CDRL Sequence Number A002), the SBIR contract, and Proteon. The SNIPE/RIG and SBIR contracts had many overlapping requirements, which allowed the research done under SNIPE/RIG to be applied to SBIR. Proteon funded all of the work to develop new router interfaces other than FDDI, in addition to funding the productization of the router itself. The router being delivered under SBIR will be a fully product-quality machine. The work done during this contract produced many significant findings and results, summarized here and explained in detail in later sections of this report. The SNIPE/RIG contract was completed. That contract had many overlapping requirements with the SBIR contract, and resulted in the successful demonstration and delivery of a high speed router. The development that took place during the SNIPE/RIG contract produced findings that included the choice of processor and an understanding of the issues surrounding inter processor communications in a multiprocessor environment. Many significant speed enhancements to the router software were made during that time. Under the SBIR contract (and with help from Proteon-funded work), it was found that a single processor router achieved a throughput significantly higher than originally anticipated. For this reason, a single processor router was developed and the final delivery under this contract will include a single processor CNX-500 router. The router and its interface boards (2 FDDIs and 2 dual-ethernets) are all product-quality components.

1991-01-01

400

Optimized Switch Allocation to Improve the Restoration Energy in Distribution Systems  

NASA Astrophysics Data System (ADS)

In distribution networks switching devices play critical role in energy restoration and improving reliability indices. This paper presents a novel objective function to optimally allocate switches in electric power distribution systems. Identifying the optimized location of the switches is a nonlinear programming problem (NLP). In the proposed objective function a new auxiliary function is used to simplify the calculation of the objective function. The output of the auxiliary function is binary. The genetic algorithm (GA) optimization method is used to solve this optimization problem. The proposed method is applied to a real distribution network and the results reveal that the method is successful.

Dezaki, Hamed H.; Abyaneh, Hossein A.; Agheli, Ali; Mazlumi, Kazem

2012-01-01

401

Turn-on spread determines the size of the switching region in an avalanche transistor  

NASA Astrophysics Data System (ADS)

It has been shown recently that only a small part of the emitter-base interface in a Si bipolar junction transistor participates in short-pulsing avalanche switching. This lateral current shrinkage attributed to the ``winner takes all'' effect reduces the transistor switching size from 1600 to ~100 ?m, still remaining much larger than the transistor structure thickness. We show using quasi-3-D transient modelling that the size of the operating perimeter, which is critically important for switching efficiency and device reliability, is determined by competition between lateral turn-on shrinkage and spread. The latter has never been demonstrated in avalanche transistors before.

Duan, Guoyong; Vainshtein, Sergey; Kostamovaara, Juha

2012-05-01

402

Actively Q-switched fiber lasers: Switching dynamics and nonlinear processes  

Microsoft Academic Search

The Q-switching characteristics of actively Q-switched fiber lasers, especially the inconsistency of experimental observations with traditional Q-switching theory, are reviewed first in this paper. Based on a few typical high-power Q-switched rare-earth-doped fiber lasers, the switching dynamics in the linear and ring fiber cavities is then systematically illustrated under different fiber, pumping and switching conditions by using the traveling wave

Yong Wang; Chang-Qing Xu

2007-01-01

403

All-Optical Switch with Switch-Off Time Unrestricted by Carrier Lifetime  

Microsoft Academic Search

We propose a symmetric Mach-Zehnder-type all-optical switch which is based on the nonlinear refractive index change induced in semiconductors. Unlike most all-optical switches, the switch-off time, as well as the switch-on time, of this novel device is not limited by the usually slow carrier lifetime, allowing a very fast switching speed. Its switching characteristics are theoretically examined under various conditions.

Kazuhito Tajima

1993-01-01

404

High power solid state switches  

NASA Astrophysics Data System (ADS)

We have successfully produced an optically triggered thyristor based in Gallium Arsenide, developed a model for breakdown, and are developing two related devices, including a Gallium Arsenide based static inductor thyristor. We are getting at the basic limitations of Gallium Arsenide for these applications, and are developing models for the physical processes that will determine device limitations. The previously supported gas phase work - resulting in the back-lighted thyratron (BLT) - has actually resulted in a very changed view of how switching can be accomplished, and this is impacting the design of important machines. The BLT is being studied internationally: in Japan for laser fusion and laser isotope separation. ITT has built a BLT that has switched 30 kA at 60 kV in testing at NSWC Dahlgren and the device is being commercialized by another American company. Versions of the switch are now being tested for excimer laser and other applications. Basically, the switch, which arose from pulse power physics studies at USC, can switch more current faster (higher di/dt), with less housekeeping, and with other advantageous properties. There are a large number of other new applications, include kinetic energy weapons, pulsed microwave sources and R.F. accelerators.

Gundersen, Martin

1991-11-01

405

Binary switching in a 'symmetric' potential landscape  

PubMed Central

A binary switch is the basic building block for information processing. The potential energy profile of a bistable binary switch is a ‘symmetric' double well. The traditional method of switching it from one state (one well) to the other is to tilt the profile towards the desired state. Here, we present a case, where no such tilting is necessary to switch successfully, even in the presence of thermal noise. This happens because of the built-in dynamics inside the switch itself. It differs from the general perception on binary switching that in a ‘symmetric' potential landscape, the switching probability is 50% in the presence of thermal noise. Our results, considering the complete three-dimensional potential landscape, demonstrate intriguing phenomena on binary switching mechanism. With experimentally feasible parameters, we theoretically demonstrate such intriguing possibility in electric field induced magnetization switching of a shape-anisotropic single-domain magnetostrictive nanomagnet with two stable states at room-temperature.

Roy, Kuntal; Bandyopadhyay, Supriyo; Atulasimha, Jayasimha

2013-01-01

406

Binary switching in a 'symmetric' potential landscape.  

PubMed

A binary switch is the basic building block for information processing. The potential energy profile of a bistable binary switch is a 'symmetric' double well. The traditional method of switching it from one state (one well) to the other is to tilt the profile towards the desired state. Here, we present a case, where no such tilting is necessary to switch successfully, even in the presence of thermal noise. This happens because of the built-in dynamics inside the switch itself. It differs from the general perception on binary switching that in a 'symmetric' potential landscape, the switching probability is 50% in the presence of thermal noise. Our results, considering the complete three-dimensional potential landscape, demonstrate intriguing phenomena on binary switching mechanism. With experimentally feasible parameters, we theoretically demonstrate such intriguing possibility in electric field induced magnetization switching of a shape-anisotropic single-domain magnetostrictive nanomagnet with two stable states at room-temperature. PMID:24154561

Roy, Kuntal; Bandyopadhyay, Supriyo; Atulasimha, Jayasimha

2013-01-01

407

HOLLOTRON switch for megawatt lightweight space inverters  

NASA Technical Reports Server (NTRS)

The feasibility of satisfying the switching requirements for a megawatt ultralight inverter system using HOLLOTRON switch technology was determined. The existing experimental switch hardware was modified to investigate a coaxial HOLLOTRON switch configuration and the results were compared with those obtained for a modified linear HOLLOTRON configuration. It was concluded that scaling the HOLLOTRON switch to the current and voltage specifications required for a megawatt converter system is indeed feasible using a modified linear configuration. The experimental HOLLOTRON switch operated at parameters comparable to the scaled coaxial HOLLOTRON. However, the linear HOLLOTRON data verified the capability for meeting all the design objectives simultaneously including current density (greater than 2 A/sq cm), voltage (5 kV), switching frequency (20 kHz), switching time (300 ns), and forward voltage drop (less than or equal to 20 V). Scaling relations were determined and a preliminary design was completed for an engineering model linear HOLLOTRON switch to meet the megawatt converter system specifications.

Poeschel, R. L.; Goebel, D. M.; Schumacher, R. W.

1991-01-01

408

Critical Information at Critical Moments  

ERIC Educational Resources Information Center

On a daily basis, administrators are reminded of the potential, perhaps the likelihood, of violence or natural crises on their campuses. Comprehensive studies have been conducted and point to recommendations and best practices for planning, preparing, responding to, and recovering from critical incidents. The International Association of Campus…

Fierman, Ben; Thrower, Raymond H., Jr.

2011-01-01

409

System for automatically switching transformer coupled lines  

NASA Technical Reports Server (NTRS)

A system is presented for automatically controlling transformer coupled alternating current electric lines. The secondary winding of each transformer is provided with a center tap. A switching circuit is connected to the center taps of a pair of secondary windings and includes a switch controller. An impedance is connected between the center taps of the opposite pair of secondary windings. The switching circuit has continuity when the AC lines are continuous and discontinuity with any disconnect of the AC lines. Normally open switching means are provided in at least one AC line. The switch controller automatically opens the switching means when the AC lines become separated.

Dwinell, W. S. (inventor)

1979-01-01

410

The arterial switch operation before Jatene.  

PubMed

Attempts at the arterial switch operation predated the Senning and the Mustard venous switch procedures. No patients survived the earlier arterial switch methods. Therefore, from the 1960s to the 1980s, venous switch surgeries became the dominant treatment method for transposition of the great arteries. The Brazilian cardiac surgeon, Adib Jatene, reported the first successful arterial switch in 1975. The history of the earlier arterial switches performed in the 1950s and 1960s is not well known. This article discusses that early history. PMID:18709398

Evans, W N

2009-02-01

411

Pulsed power compression by plasma opening switch  

NASA Astrophysics Data System (ADS)

Inductive-energy-storage pulsed experiments using plasma opening switches have been carried out on a pulsed power generator (REIDEN IV-H). The plasma opening switch is an opening switch which operates on a nanosecond timescale. The experimental data show that the impedance of the switch increased up to 200 omega, a high voltage (6.4MV) and short pulse width (10nsec) output are obtained. The comparison between experimental data and analytic calculations indicates that the faster opening of the switch operation is obtained by increasing the plasma injection velocity and the self magnetic pressure effect mainly affects the final stage of the switch operation.

Yugami, N.; Miyamoto, S.; Fujita, H.; Ozaki, T.; Akiba, T.; Imasaki, K.; Nakai, S.; Yamanaka, C.

1985-10-01

412

Auxiliary power supply switching set  

SciTech Connect

A control circuit and auxiliary power supply and a switching means for connecting the load selectively to the auxiliary power supply and the main power supply. The main power supply may be a public utility power line, and the auxiliary power supply is a windmill, a motor and generator all connected together on a common shaft. A control means senses the output voltage of the generator or output frequency and controls the switch to eithe connect the load to the power line or the auxiliary power supply. A battery is supplied for storing excess windmill power and for driving the motor and generator during periods of low wind.

Baker, C.R.

1984-05-01

413

A piezoelectric cryogenic heat switch.  

PubMed

We have measured the thermal conductance of a mechanical heat switch actuated by a piezoelectric positioner, the PZHS (PieZo electric Heat Switch), at cryogenic temperatures. The thermal conductance of the PZHS was measured between 4 K and 10 K, and on/off conductance ratios of about 100-200 at lowest and highest measures temperature were achieved when the positioner applied its maximum force of 8 N, respectively. We discuss the advantages of using this system in cryogenic applications, and estimate the ultimate performance of an ideal PZHS. PMID:24985863

Jahromi, Amir E; Sullivan, Dan F

2014-06-01

414

Optical Switch Using Risley Prisms  

DOEpatents

An optical switch using Risley prisms and rotary microactuators to independently rotate the wedge prisms of each Risley prism pair is disclosed. The optical switch comprises an array of input Risley prism pairs that selectively redirect light beams from a plurality of input ports to an array of output Risley prism pairs that similarly direct the light beams to a plurality of output ports. Each wedge prism of each Risley prism pair can be independently rotated by a variable-reluctance stepping rotary microactuator that is fabricated by a multi-layer LIGA process. Each wedge prism can be formed integral to the annular rotor of the rotary microactuator by a DXRL process.

Sweatt, William C. (Albuquerque, NM); Christenson, Todd R. (Albuquerque, NM)

2005-02-22

415

Intragenic Suppressor Mutations Restore GTPase and Translation Functions of a Eukaryotic Initiation Factor 5B Switch II Mutant?  

PubMed Central

Structural studies of GTP-binding proteins identified the Switch I and Switch II elements as contacting the ?-phosphate of GTP and undergoing marked conformational changes upon GTP versus GDP binding. Movement of a universally conserved Gly at the N terminus of Switch II is thought to trigger the structural rearrangement of this element. Consistently, we found that mutation of this Gly in the Switch II element of the eukaryotic translation initiation factor 5B (eIF5B) from Saccharomyces cerevisiae impaired cell growth and the guanine nucleotide-binding, GTPase, and ribosomal subunit joining activities of eIF5B. In a screen for mutations that bypassed the critical requirement for this Switch II Gly in eIF5B, intragenic suppressors were identified in the Switch I element and at a residue in domain II of eIF5B that interacts with Switch II. The intragenic suppressors restored yeast cell growth and eIF5B nucleotide-binding, GTP hydrolysis, and subunit joining activities. We propose that the Switch II mutation distorts the geometry of the GTP-binding active site, impairing nucleotide binding and the eIF5B domain movements associated with GTP binding. Accordingly, the Switch I and domain II suppressor mutations induce Switch II to adopt a conformation favorable for nucleotide binding and hydrolysis and thereby reestablish coupling between GTP binding and eIF5B domain movements.

Shin, Byung-Sik; Acker, Michael G.; Maag, David; Kim, Joo-Ran; Lorsch, Jon R.; Dever, Thomas E.

2007-01-01

416

Method and apparatus for multiplexing switch signals  

NASA Technical Reports Server (NTRS)

Apparatus for multiplexing switch state signals comprises a plurality of switches and parallel weighted resistors connected in series between circuit ground and a node at a utilization device. The resistors are weighted as a function of a power of the same base, such as the power of the base 2, for coding the multiplexed switch state signals. A constant current source connected between the node and circuit ground drives current over a single cable conductor through the resistor. Each switch may be independently closed to change the switch state voltage signals multiplexed to the node. An analog-to-digital converter connected between the node and circuit ground demultiplexes the switch state signals received at the node and provides a switch state signal at each analog-to-digital output corresponding to the state of the switches at the moment. A potentiometer may replace a resistor and bypass switch combination in a position where the potentiometer has a maximum value of the lowest power of the base in order to multiplex a true analog voltage signal while switch state signals are unambiguously coded and multiplexed. The potentiometer in the least significant position permits the analog value to be in the range from 0 to a maximum corresponding to the least significant position of the switch state encoding. The invention may be used in redundancy systems by duplicating the invention with corresponding switches in each duplication ganged to open and close simultaneously upon operation of a pushbutton switch.

Hannaford, Blake (Inventor)

1989-01-01

417

Photoconductive Semiconductor Switches for pulsed power applications  

SciTech Connect

Photoconductive Semiconductor Switches (PCSS) are being used in, or tested for, many different pulsed power applications as diverse as ultrawideband (UWB) transmitters and high current pulsers. Some aspects of the switches that are relevant to most of the applications are: switch lifetime (longevity), switch opening time (related to the lifetime of carriers in the semiconductor), switching jitter, and the required laser energy. This paper will emphasize the results that we have obtained with Si switches for UWB applications. These include: measurement of switch longevity (a total of 80 Coulombs or 40 C/cm for a 2 cm wide switch and 18.4 Coulombs or 73 Coulombs/cm for a 0.25 cm wide switch), switching at high repetition rates (up to 540 Hz), measurement of carrier lifetime decay rates (a fast one of a few {mu}s, and a slow one of about 330 {mu}s), and measurements on the effect of neutron irradiation on carrier lifetimes. The total charge switched seems to be the highest ever reported for a PCSS. We have used these Si switches in a variety of circuits to produce: a monocycle with a period of about 10 ns corresponding to a center frequency of about 84 MHz, and ringing (many pulse) waveforms with periods of about 1 ns and 7.5 ns corresponding to center frequencies of 770 MHz and 133 MHz. We will also discuss recent studies on the switching properties of GaP.

Loubriel, G.M.; Zutavern, F.J.; Denison, G.J.; Helgeson, W.D.; McLaughlin, D.L.; O`Malley, M.W.; Buttram, M.T.

1993-08-01

418

Structure of the human sulfhydryl oxidase augmenter of liver regeneration and characterization of a human mutation causing an autosomal recessive myopathy†, ‡  

PubMed Central

The sulfhydryl oxidase augmenter of liver regeneration (ALR) binds FAD in a helix-rich domain that presents a CxxC disulfide proximal to the isoalloxazine ring of the flavin. Head-to-tail interchain disulfide bonds link subunits within the homodimer of both the short, cytokine-like, form of ALR (sfALR), and a longer form (lfALR) which resides in the mitochondrial intermembrane space (IMS). lfALR has an 80-residue N-terminal extension with an additional CxxC motif required for the reoxidation of reduced Mia40 during oxidative protein folding within the IMS. Recently Di Fonzo et al. (Di Fonzo, A., Ronchi, D., Lodi, T., Fassone, E., Tigano, M., Lamperti, C., Corti, S., Bordoni, A., Fortunato, F., Nizzardo, M., Napoli, L., Donadoni, C., Salani, S., Saladino, F., Moggio, M., Bresolin, N., Ferrero, I., and Comi, G. P. (2009) Am. J. Hum. Genet. 84, 594–604) described an R194H mutation of human ALR that led to cataract, progressive muscle hypotonia, and hearing loss in three children. The current work presents a structural and enzymological characterization of the human R194H mutant in lf- and sfALR. A crystal structure of human sfALR was determined by molecular replacement using the rat sfALR structure. R194 is located at the subunit interface of sfALR, close to the intersubunit disulfide bridges. The R194 guanidino moiety participates in three H-bonds: two main-chain carbonyl oxygen atoms (from R194 itself, and from C95 of the intersubunit disulfide of the other protomer) and with the 2' OH of the FAD ribose. The R194H mutation has minimal effect on the enzyme activity using model and physiological substrates of short and long ALR forms. However the mutation adversely affects the stability of both ALR forms: e.g. by decreasing the melting temperature by about 10 °C, by increasing the rate of dissociation of FAD from the holoenzyme by about 45-fold, and by strongly enhancing the susceptibility of sfALR to partial proteolysis and to reduction of its intersubunit disulfide bridges by glutathione. Finally, a comparison of the TROSY-HSQC 2D NMR spectra of wild type sfALR and its R194H mutant reveal a significant increase in conformational flexibility in the mutant protein. In sum, these in vitro data document the major impact of the seemingly conservative R194H mutation on the stability of dimeric ALR and complement the in vivo observations of Di Fonzo et al.

Daithankar, Vidyadhar N.; Schaefer, Stephanie A.; Dong, Ming; Bahnson, Brian J.; Thorpe, Colin

2010-01-01

419

Design and characterization of molecular nonlinear optical switches.  

PubMed

Nanoscale structures, including molecules, supramolecules, polymers, functionalized surfaces, and crystalline/amorphous solids, can commute between two or more forms, displaying contrasts in their nonlinear optical (NLO) properties. Because of this property, they have high potential for applications in data storage, signal processing, and sensing. As potential candidates for integration into responsive materials, scientists have been intensely studying organic and organometallic molecules with switchable first hyperpolarizability over the past two decades. As a result of this, researchers have been able to synthesize and characterize several families of molecular NLO switches that differ by the stimulus used to trigger the commutation. These stimuli can include light irradiation, pH variation, redox reaction, and ion recognition, among others. The design of multistate (including several switchable units) and multifunctional (triggered with different stimuli) systems has also motivated a large amount of work, aiming at the improvement of the storage capacity of optical memories or the diversification of the addressability of the devices. In complement to the synthesis of the compounds and the characterization of their NLO responses by means of hyper-Rayleigh scattering, quantum chemical calculations play a key role in the design of molecular switches with high first hyperpolarizability contrasts. Through the latter, we can gain a fundamental understanding of the various factors governing the efficiency of the switches. These are not easily accessible experimentally, and include donor/acceptor contributions, frequency dispersion, and solvent effects. In this Account, we illustrate the similarities of the experimental and theoretical tools to design and characterize highly efficient NLO switches but also the difficulties in comparing them. After providing a critical overview of the different theoretical approaches used for evaluating the first hyperpolarizabilities, we report two case studies in which theoretical simulations have provided guidelines to design NLO switches with improved efficiencies. The first example presents the joint theoretical/experimental characterization of a new family of multi-addressable NLO switches based on benzazolo-oxazolidine derivatives. The second focuses on the photoinduced commutation in merocyanine-spiropyran systems, where the significant NLO contrast could be exploited for metal cation identification in a new generation of multiusage sensing devices. Finally, we illustrate the impact of environment on the NLO switching properties, with examples based on the keto-enol equilibrium in anil derivatives. Through these representative examples, we demonstrate that the rational design of molecular NLO switches, which combines experimental and theoretical approaches, has reached maturity. Future challenges consist in extending the investigated objects to supramolecular architectures involving several NLO-responsive units, in order to exploit their cooperative effects for enhancing the NLO responses and contrasts. PMID:23865890

Castet, Frédéric; Rodriguez, Vincent; Pozzo, Jean-Luc; Ducasse, Laurent; Plaquet, Aurélie; Champagne, Benoît

2013-11-19

420

Working memory costs of task switching.  

PubMed

Although many accounts of task switching emphasize the importance of working memory as a substantial source of the switch cost, there is a lack of evidence demonstrating that task switching actually places additional demands on working memory. The present study addressed this issue by implementing task switching in continuous complex span tasks with strictly controlled time parameters. A series of 4 experiments demonstrate that recall performance decreased as a function of the number of task switches and that the concurrent load of item maintenance had no influence on task switching. These results indicate that task switching induces a cost on working memory functioning. Implications for theories of task switching, working memory, and resource sharing are addressed. PMID:18444750

Liefooghe, Baptist; Barrouillet, Pierre; Vandierendonck, André; Camos, Valérie

2008-05-01

421

Bilateral, Zero-Impedance Static Semiconductor Switch  

NASA Technical Reports Server (NTRS)

Static semiconductor switching circuit eliminates the undesirable features of electromechanical relays and conventional semiconductor switching circuits. There is a net zero voltage drop at the terminals and thus a zero impedance for bilateral currents there.

Doughman, C. L.

1968-01-01

422

High-Explosive Driven Crowbar Switch.  

National Technical Information Service (NTIS)

The patent application relates to a compact explosive driven switch for use as a low resistance, low inductance crowbar switch. A high-explosive charge extrudes a deformable conductive metallic plate through a polyethylene insulating layer to achieve a ha...

R. S. Dike R. W. Kewish

1974-01-01

423

High-Explosive Driven Crowbar Switch.  

National Technical Information Service (NTIS)

The disclosure relates to a compact explosive driven switch for use as a low resistance, low inductance crowbar switch. A high-explosive charge extrudes a deformable conductive metallic plate through a polyethylene insulating layer to achieve a hard curre...

R. S. Dike R. W. Kewish

1976-01-01

424

14 CFR 25.1145 - Ignition switches.  

Code of Federal Regulations, 2013 CFR

...STANDARDS: TRANSPORT CATEGORY AIRPLANES Powerplant Powerplant Controls and Accessories § 25.1145...a) Ignition switches must control each engine ignition circuit...switches or by a master ignition control. (c) Each group...

2014-01-01

425

Ultrafast Beam Switching Using Coupled VCSELs  

NASA Technical Reports Server (NTRS)

We propose a new approach to performing ultrafast beam switching using two coupled Vertical-Cavity Surface-Emitting Lasers (VCSELs). The strategy is demonstrated by numerical simulation, showing a beam switching of 10 deg at 42 GHz.

Ning, Cun-Zheng; Goorjian, Peter

2001-01-01

426

High voltage MOSFET switching circuit  

DOEpatents

The problem of source lead inductance in a MOSFET switching circuit is compensated for by adding an inductor to the gate circuit. The gate circuit inductor produces an inductive spike which counters the source lead inductive drop to produce a rectangular drive voltage waveform at the internal gate-source terminals of the MOSFET. 2 figs.

McEwan, T.E.

1994-07-26

427

High voltage MOSFET switching circuit  

DOEpatents

The problem of source lead inductance in a MOSFET switching circuit is compensated for by adding an inductor to the gate circuit. The gate circuit inductor produces an inductive spike which counters the source lead inductive drop to produce a rectangular drive voltage waveform at the internal gate-source terminals of the MOSFET.

McEwan, Thomas E. (Livermore, CA)

1994-01-01

428

Anode initiated surface flashover switch  

DOEpatents

A high voltage surface flashover switch has a pair of electrodes spaced by an insulator. A high voltage is applied to an anode, which is smaller than the opposing, grounded, cathode. When a controllable source of electrons near the cathode is energized, the electrons are attracted to the anode where they reflect to the insulator and initiate anode to cathode breakdown.

Brainard, John P. (Albuquerque, NM); Koss, Robert J. (Albuquerque, NM)

2003-04-29

429

Intrinsic nanofilamentation in resistive switching  

NASA Astrophysics Data System (ADS)

Resistive switching materials are promising candidates for nonvolatile data storage and reconfiguration of electronic applications. Intensive studies have been carried out on sandwiched metal-insulator-metal structures to achieve high density on-chip circuitry and non-volatile memory storage. Here, we provide insight into the mechanisms that govern highly reproducible controlled resistive switching via a nanofilament by using an asymmetric metal-insulator-semiconductor structure. In-situ transmission electron microscopy is used to study in real-time the physical structure and analyze the chemical composition of the nanofilament dynamically during resistive switching. Electrical stressing using an external voltage was applied by a tungsten tip to the nanosized devices having hafnium oxide (HfO2) as the insulator layer. The formation and rupture of the nanofilaments result in up to three orders of magnitude change in the current flowing through the dielectric during the switching event. Oxygen vacancies and metal atoms from the anode constitute the chemistry of the nanofilament.

Wu, Xing; Cha, Dongkyu; Bosman, Michel; Raghavan, Nagarajan; Migas, Dmitri B.; Borisenko, Victor E.; Zhang, Xi-Xiang; Li, Kun; Pey, Kin-Leong

2013-03-01

430

Fast latching type optical switch  

NASA Astrophysics Data System (ADS)

A magneto-optical latching switch with a yttrium orthoferrite optical rotator is described. The crystal remains in a given magnetic state for unlimited duration without energy supply. The response time is about 20 ns and the aperture of the optical rotator is 350 ?m.

Didosyan, Yuri S.; Hauser, Hans; Reider, Georg A.; Toriser, Walter

2004-06-01

431

A 35GHz Latching Switch  

Microsoft Academic Search

The development of a fast switching, small, lightweight latching three-port ferrite circulator is outlined. Geometrical configurations, as relating to the toroidal ferrite element and their apparent effects on operating characteristics, are presented. Considerations relating to the proper selection of ferromagnetic materials, compatible with latching applications, are discussed. The finalized device operates at 35 GHz with an instantaneous bandwidth of 5

W. C. Passaro; J. W. McManus

1966-01-01

432

High power ferrite microwave switch  

Microsoft Academic Search

A high power ferrite microwave switch was developed along with associated electronic driver circuits for operation in a spaceborne high power microwave transmitter in geostationary orbit. Three units were built and tested in a space environment to demonstrate conformance to the required performance characteristics. Each unit consisted of an input magic-tee hybrid, two non-reciprocal latching ferrite phase shifters, an out

I. Bardash; N. K. Roschak

1975-01-01

433

Towards a switched current FPAA  

Microsoft Academic Search

It is presented an implementation, at the transistor level, of a field programmable analog array using the switched current technique (SI). Programmable macro-cell blocks are designed using the class AB grounded gate memory cell which performances have been already improved regarding to SNR and bandwidth. The configurable blocks can be sampled up to 40 MHz. The proposed programmable block necessitates

Mourad FAKHFAKH; Siwar MASMOUDI; Mourad LOULOU

2007-01-01

434

Graphene-photonic crystal switch  

NASA Astrophysics Data System (ADS)

We have designed and analyzed a graphene-based photonic crystal directional coupler working as a switch, which is embedded in a SOI photonic crystal slab with triangular lattice of dielectric rods. The directional coupler has two W1 (one missing row of dielectric rods) waveguides and the coupling region is coated with a graphene nanoribbon with width W=50 nm.

Wirth Lima, A.; Sombra, A. S. B.

2014-06-01

435

Fast all-optical switch  

NASA Technical Reports Server (NTRS)

An apparatus and method wherein polarization rotation in alkali vapors or other mediums is used for all-optical switching and digital logic and where the rate of operation is proportional to the amplitude of the pump field. High rates of speed are accomplished by Rabi flopping of the atomic states using a continuously operating monochromatic atomic beam as the pump.

Shay, Thomas M. (Inventor); Poliakov, Evgeni Y. (Inventor); Hazzard, David A. (Inventor)

2001-01-01

436

Tetris Models for Multicast Switches  

Microsoft Academic Search

This paper presents a unified approach to the analysis of schedulers for input-queued multicast ATM switches. It is shown that the general multicast scheduling problem can be mapped onto a variation of the popular blockpacking game Tetris. Within this common framework, one is able to describe and analyze any multicast scheduling policy in an intuitive and geometric fashion. One such

Balaji Prabhakar; Nick Mckeown; Jean Mairesse

1996-01-01

437

Leverless limit switch improves plant operations  

SciTech Connect

This paper describes improved plant operations at the Diablo Canyon nuclear power plant by the installation of a leverless limit switch. The package consists of a stainless steel mounting bracket, ferrous target, mounting hardware, and two switches. It can be fitted to existing holes in the valve yoke. By replacing a traditional limit switch with a leverless switch, engineers solved a problem with determining valve position.

Hansen, T. [ed.

1996-05-01

438

Spark gap switch with spiral gas flow  

SciTech Connect

A spark gap switch having a contaminate removal system using an injected gas. An annular plate concentric with an electrode of the switch defines flow paths for the injected gas which form a strong spiral flow of the gas in the housing which is effective to remove contaminates from the switch surfaces. The gas along with the contaminates is exhausted from the housing through one of the ends of the switch.

Brucker, John P. (Espanola, NM)

1989-01-01

439

Alternator-driven, magnetically switched modulator  

Microsoft Academic Search

The technique of magnetically switching high-power pulses was recently revitalized with the development of amorphous magnetic alloys and the new power conditioning requirements of pulsed lasers and high-brightness particle accelerators. The most common magnetic switching technique for generating high-repetition-rate pulses consists of a dc power supply, a triggered switch (thyratron or solid-state), and a repeated network of magnetic switches and

R. Kihara; H. C. Kirbie

1986-01-01

440

Switching to “lighter” cigarettes and quitting smoking  

Microsoft Academic Search

Objective:Smokers who switch to “lighter” cigarettes may be diverted from quitting smoking. We assessed factors associated with switching and the association between switching and (1) making a quit attempt, and (2) recent quitting, yielding a measure of net quitting (attempts × recent quitting).Design:In 2003, a total of 30 800 ever-smokers who smoked in the past year provided history of switching

H A Tindle; S Shiffman; A M Hartman; J E Bost

2009-01-01

441

Switching inverters and converters for power conversion  

US Patent & Trademark Office Database

A switching inverter having two single-ended EF.sub.2 inverter sections coupled together with a shared ground and partially shared tunable resonant network that is coupled to at least one load, wherein each inverter section comprises a switching section, and wherein the shared tunable network section allows independent tuning of an impedance seen by the corresponding switching section thereby independently tuning even and odd harmonics of the switching frequency.

2011-04-12

442

Micromagnetic analysis of fast precessional switching  

NASA Astrophysics Data System (ADS)

The precessional switching process in magnetic recording thin films is investigated by means of micromagnetic simulations. The uniform mode theory is used to predict the right time instant to switch off the field and the time tolerance which still allows successful switching. This analysis is performed for different values of applied field and anisotropy constant. We verified that the uniform mode theory provides accurate information about the tolerance on the switching time for moderately soft materials.

d'Aquino, M.; Scholz, W.; Schrefl, T.; Serpico, C.; Fidler, J.

2005-04-01

443

Energy loss in spark gap switches  

NASA Astrophysics Data System (ADS)

The paper reports on numerical study of the energy loss in spark gap switches. The operation of the switches is analyzed using the Braginsky model which allows calculation of the time dependence of the spark channel resistance. The Braginsky equation is solved simultaneously with generator circuit equations for different load types. Based on the numerical solutions, expressions which determine both the energy released in a spark gap switch and the switching time are derived.

Oreshkin, V. I.; Lavrinovich, I. V.

2014-04-01

444

A novel MEMS LTCC switch matrix  

Microsoft Academic Search

A novel planar 4×4 switch matrix using microelectromechanical system (MEMS) switches and low temperature cofired ceramic (LTCC) substrate is presented for the first time. Together a 9-layer LTCC substrate and 32 MEMS switches are integrated to create a non-blocking 4×4 switch matrix functionality with excellent RF performance up to 7 GHz. An accurate model for predicting the interconnect circuit and

Bahram Yassini; Savio Choi; A. Zybura; Ming Yu; R. E. Mihailovich; J. F. DeNatale

2004-01-01

445

Correlated randomness and switching phenomena  

NASA Astrophysics Data System (ADS)

One challenge of biology, medicine, and economics is that the systems treated by these serious scientific disciplines have no perfect metronome in time and no perfect spatial architecture-crystalline or otherwise. Nonetheless, as if by magic, out of nothing but randomness one finds remarkably fine-tuned processes in time and remarkably fine-tuned structures in space. Further, many of these processes and structures have the remarkable feature of “switching” from one behavior to another as if by magic. The past century has, philosophically, been concerned with placing aside the human tendency to see the universe as a fine-tuned machine. Here we will address the challenge of uncovering how, through randomness (albeit, as we shall see, strongly correlated randomness), one can arrive at some of the many spatial and temporal patterns in biology, medicine, and economics and even begin to characterize the switching phenomena that enables a system to pass from one state to another. Inspired by principles developed by A. Nihat Berker and scores of other statistical physicists in recent years, we discuss some applications of correlated randomness to understand switching phenomena in various fields. Specifically, we present evidence from experiments and from computer simulations supporting the hypothesis that water’s anomalies are related to a switching point (which is not unlike the “tipping point” immortalized by Malcolm Gladwell), and that the bubbles in economic phenomena that occur on all scales are not “outliers” (another Gladwell immortalization). Though more speculative, we support the idea of disease as arising from some kind of yet-to-be-understood complex switching phenomenon, by discussing data on selected examples, including heart disease and Alzheimer disease.

Stanley, H. E.; Buldyrev, S. V.; Franzese, G.; Havlin, S.; Mallamace, F.; Kumar, P.; Plerou, V.; Preis, T.

2010-08-01

446

49 CFR 236.817 - Switch, electro-pneumatic.  

Code of Federal Regulations, 2013 CFR

...2013-10-01 2013-10-01 false Switch, electro-pneumatic. 236.817 Section 236...APPLIANCES Definitions § 236.817 Switch, electro-pneumatic. A switch operated by an electro-pneumatic switch-and-lock...