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Sample records for affinity constant km

  1. Automatic gesture analysis using constant affine velocity.

    PubMed

    Cifuentes, Jenny; Boulanger, Pierre; Pham, Minh Tu; Moreau, Richard; Prieto, Flavio

    2014-01-01

    Hand human gesture recognition has been an important research topic widely studied around the world, as this field offers the ability to identify, recognize, and analyze human gestures in order to control devices or to interact with computer interfaces. In particular, in medical training, this approach is an important tool that can be used to obtain an objective evaluation of a procedure performance. In this paper, some obstetrical gestures, acquired by a forceps, were studied with the hypothesis that, as the scribbling and drawing movements, they obey the one-sixth power law, an empirical relationship which connects path curvature, torsion, and euclidean velocity. Our results show that obstetrical gestures have a constant affine velocity, which is different for each type of gesture and based on this idea this quantity is proposed as an appropriate classification feature in the hand human gesture recognition field. PMID:25570332

  2. Determination of proton affinities and acidity constants of sugars.

    PubMed

    Feng, Shuting; Bagia, Christina; Mpourmpakis, Giannis

    2013-06-20

    Proton transfer reactions play a key role in the conversion of biomass derived sugars to chemicals. In this study, we employ high level ab initio theoretical methods, in tandem with solvation effects to calculate the proton affinities (PA) and acidity constants (pKa) of various d-glucose and d-fructose tautomers (protonation-deprotonation processes). In addition, we compare the theoretically derived pH values of sugar solutions against experimentally measured pH values in our lab. Our results demonstrate that the protonation of any of the O atoms of the sugars is thermodynamically preferred without any significant variation in the PA values. Intramolecular hydrogen transfers, dehydration reactions, and ring-opening processes were observed, resulting from the protonation of specific hydroxyl groups on the sugars. Regarding the deprotonation processes (pKa), we found that the sugars' anomeric hydroxyls exhibit the highest acidity. The theoretically calculated pH values of sugar solutions are in excellent agreement with experimental pH measurements at low sugar concentrations. At higher sugar concentrations the calculations predict less acidic solutions than the experiments. In this case, we expect the sugars to act as solvents increasing the proton solvation energy and the acidity of the solutions. We demonstrated through linear relationships that the pKa values are correlated with the relative stability of the conjugate bases. The latter is related to hydrogen bonding and polarization of the C-O(-) bond. A plausible explanation for the good performance of the direct method in calculating the pKa values of sugars can be the presence of intramolecular hydrogen bonds on the conjugate base. Both theory and experiments manifest that fructose is a stronger acid than glucose, which is of significant importance in self-catalyzed biomass-relevant dehydration reactions. PMID:23706015

  3. The Case for a Hubble Constant of 30 km s-1 Mpc-1.

    PubMed

    Bartlett, J G; Blanchard, A; Silk, J; Turner, M S

    1995-02-17

    Although recent determinations of the distance to the Virgo cluster based on Cepheid variable stars represent an important step in pinning down the Hubble constant, after 65 years a definitive determination of the Hubble constant still eludes cosmologists. At present, most of the observational determinations place the Hubble constant between 40 and 90 kilometers per second per megaparsec (km s(-1) Mpc(-1)). The case is made here for a Hubble constant that is even smaller than the lower bound of the accepted range on the basis of the great advantages, all theoretical in nature, of a Hubble constant of around 30 kilometers per second per megaparsec. Such a value for the Hubble cures all of the ills of the current theoretical orthodoxy, that is, a spatially flat universe composed predominantly of cold dark matter. PMID:17811436

  4. The Case for a Hubble Constant of 30 km s-1 Mpc-1.

    PubMed

    Bartlett, J G; Blanchard, A; Silk, J; Turner, M S

    1995-02-17

    Although recent determinations of the distance to the Virgo cluster based on Cepheid variable stars represent an important step in pinning down the Hubble constant, after 65 years a definitive determination of the Hubble constant still eludes cosmologists. At present, most of the observational determinations place the Hubble constant between 40 and 90 kilometers per second per megaparsec (km s(-1) Mpc(-1)). The case is made here for a Hubble constant that is even smaller than the lower bound of the accepted range on the basis of the great advantages, all theoretical in nature, of a Hubble constant of around 30 kilometers per second per megaparsec. Such a value for the Hubble cures all of the ills of the current theoretical orthodoxy, that is, a spatially flat universe composed predominantly of cold dark matter.

  5. The fundamental constants of orthotropic affine plate/slab equations

    NASA Technical Reports Server (NTRS)

    Brunelle, E. J.

    1984-01-01

    The global constants associated with orthotropic slab/plate equations are discussed, and the rotational behavior of the modulus/compliance components associated with orthotropic slabs/plates are addressed. It is concluded that one cluster constant is less than or equal to unity for all physically possible materials. Rotationally anomalous behavior is found in two materials, and a simple inequality which can be used to identify regular or anomalous behavior is presented and discussed in detail.

  6. Binding of ionic species: a general approach to measuring binding constants and assessing affinities.

    PubMed

    Roelens, Stefano; Vacca, Alberto; Venturi, Chiara

    2009-03-01

    Bound together: The association of receptors with ionic species cannot be assimilated to the binding of neutral guests. When dealing with salts, both ion pairing and binding to the free and the ion-paired ionic guest determine the actual association pattern (see figure). The general issue of measuring association constants and assessing affinities for ions is addressed and validated in two cases of anion binding.A general approach to the largely underestimated issue of measuring binding constants and assessing affinities in the binding of ionic species is described. The approach is based on a rigorous, nongraphical determination of binding constants in multiequilibrium systems by nonlinear regression of chemical shift data from NMR titrations and on the use of the BC(50) descriptor for assessing affinities and ranking the binding ability of receptors on a common scale. The approach has been validated with two tripodal anion-binding receptors, namely, a ureidic (1) and a pyrrolic (2) receptor, binding to tetramethylammonium chloride in CDCl(3)/CD(3)CN (80:20). A set of five and six formation constants could be measured for 1 and 2, respectively, including, in addition to the ion pair, complexes of the free and the ion-paired anion. The BC(50) values calculated from the measured constants allowed a quantitative assessment of each receptor's binding affinity towards the chloride anion, the pyrrolic receptor showing a 15-fold larger affinity over the ureidic receptor, a figure that quantifies the improvement obtained by replacing the amido-pyrrolic for ureidic binding groups on the tripodal scaffold of the receptor. The results have shown that, in contrast to common practice, neither of the two systems could be appropriately described by a 1:1 association with the anion only, but required the ion-pairing and ion-pair binding equilibria to be taken into account because these contribute substantially to the complexation process. The BC(50) descriptor has also been shown

  7. Determination of stability constants of complexes of neutral analytes with charged cyclodextrins by affinity capillary electrophoresis.

    PubMed

    Beneš, Martin; Zusková, Iva; Svobodová, Jana; Gaš, Bohuslav

    2012-03-01

    A novel procedure for the determination of stability constants in systems with neutral analytes and charged complexation agents by affinity capillary electrophoresis was established. This procedure involves all necessary corrections to achieve precise and reliable data. Temperature, ionic strength, and viscosity corrections were applied. Based on the conductivity measurements, the average temperature of the background electrolyte in the capillary was kept at the constant value of 25°C by decreasing the temperature of the cooling medium. The viscosity correction was performed using the viscosity ratio determined by an external viscosimeter. The electrophoretical measurements were performed, at first, at constant ionic strength. In this case, the increase of ionic strength caused by increasing complexation agent concentration was compensated by changing of the running buffer concentration. Subsequently the dependence of the analyte effective mobility on the complexation agent concentration was measured without the ionic strength compensation (at variable ionic strength). The new procedure for determination of the stability constants even from such data was established. These stability constants are in a very good agreement with those obtained at the constant ionic strength. The established procedure was applied for determination of the thermodynamic stability constants of (R, R)-(+)- and (S, S)-(-)-hydrobenzoin and R- and S-(3-bromo-2-methylpropan-1-ol) complexing with 6-monodeoxy-6-mono(3-hydroxy)propylamino-β-cyclodextrin hydrochloride.

  8. Bayesian Estimation of the Active Concentration and Affinity Constants Using Surface Plasmon Resonance Technology.

    PubMed

    Feng, Feng; Kepler, Thomas B

    2015-01-01

    Surface plasmon resonance (SPR) has previously been employed to measure the active concentration of analyte in addition to the kinetic rate constants in molecular binding reactions. Those approaches, however, have a few restrictions. In this work, a Bayesian approach is developed to determine both active concentration and affinity constants using SPR technology. With the appropriate prior probabilities on the parameters and a derived likelihood function, a Markov Chain Monte Carlo (MCMC) algorithm is applied to compute the posterior probability densities of both the active concentration and kinetic rate constants based on the collected SPR data. Compared with previous approaches, ours exploits information from the duration of the process in its entirety, including both association and dissociation phases, under partial mass transport conditions; do not depend on calibration data; multiple injections of analyte at varying flow rates are not necessary. Finally the method is validated by analyzing both simulated and experimental datasets. A software package implementing our approach is developed with a user-friendly interface and made freely available. PMID:26098764

  9. The universal statistical distributions of the affinity, equilibrium constants, kinetics and specificity in biomolecular recognition.

    PubMed

    Zheng, Xiliang; Wang, Jin

    2015-04-01

    We uncovered the universal statistical laws for the biomolecular recognition/binding process. We quantified the statistical energy landscapes for binding, from which we can characterize the distributions of the binding free energy (affinity), the equilibrium constants, the kinetics and the specificity by exploring the different ligands binding with a particular receptor. The results of the analytical studies are confirmed by the microscopic flexible docking simulations. The distribution of binding affinity is Gaussian around the mean and becomes exponential near the tail. The equilibrium constants of the binding follow a log-normal distribution around the mean and a power law distribution in the tail. The intrinsic specificity for biomolecular recognition measures the degree of discrimination of native versus non-native binding and the optimization of which becomes the maximization of the ratio of the free energy gap between the native state and the average of non-native states versus the roughness measured by the variance of the free energy landscape around its mean. The intrinsic specificity obeys a Gaussian distribution near the mean and an exponential distribution near the tail. Furthermore, the kinetics of binding follows a log-normal distribution near the mean and a power law distribution at the tail. Our study provides new insights into the statistical nature of thermodynamics, kinetics and function from different ligands binding with a specific receptor or equivalently specific ligand binding with different receptors. The elucidation of distributions of the kinetics and free energy has guiding roles in studying biomolecular recognition and function through small-molecule evolution and chemical genetics. PMID:25885453

  10. The Universal Statistical Distributions of the Affinity, Equilibrium Constants, Kinetics and Specificity in Biomolecular Recognition

    PubMed Central

    Zheng, Xiliang; Wang, Jin

    2015-01-01

    We uncovered the universal statistical laws for the biomolecular recognition/binding process. We quantified the statistical energy landscapes for binding, from which we can characterize the distributions of the binding free energy (affinity), the equilibrium constants, the kinetics and the specificity by exploring the different ligands binding with a particular receptor. The results of the analytical studies are confirmed by the microscopic flexible docking simulations. The distribution of binding affinity is Gaussian around the mean and becomes exponential near the tail. The equilibrium constants of the binding follow a log-normal distribution around the mean and a power law distribution in the tail. The intrinsic specificity for biomolecular recognition measures the degree of discrimination of native versus non-native binding and the optimization of which becomes the maximization of the ratio of the free energy gap between the native state and the average of non-native states versus the roughness measured by the variance of the free energy landscape around its mean. The intrinsic specificity obeys a Gaussian distribution near the mean and an exponential distribution near the tail. Furthermore, the kinetics of binding follows a log-normal distribution near the mean and a power law distribution at the tail. Our study provides new insights into the statistical nature of thermodynamics, kinetics and function from different ligands binding with a specific receptor or equivalently specific ligand binding with different receptors. The elucidation of distributions of the kinetics and free energy has guiding roles in studying biomolecular recognition and function through small-molecule evolution and chemical genetics. PMID:25885453

  11. The universal statistical distributions of the affinity, equilibrium constants, kinetics and specificity in biomolecular recognition.

    PubMed

    Zheng, Xiliang; Wang, Jin

    2015-04-01

    We uncovered the universal statistical laws for the biomolecular recognition/binding process. We quantified the statistical energy landscapes for binding, from which we can characterize the distributions of the binding free energy (affinity), the equilibrium constants, the kinetics and the specificity by exploring the different ligands binding with a particular receptor. The results of the analytical studies are confirmed by the microscopic flexible docking simulations. The distribution of binding affinity is Gaussian around the mean and becomes exponential near the tail. The equilibrium constants of the binding follow a log-normal distribution around the mean and a power law distribution in the tail. The intrinsic specificity for biomolecular recognition measures the degree of discrimination of native versus non-native binding and the optimization of which becomes the maximization of the ratio of the free energy gap between the native state and the average of non-native states versus the roughness measured by the variance of the free energy landscape around its mean. The intrinsic specificity obeys a Gaussian distribution near the mean and an exponential distribution near the tail. Furthermore, the kinetics of binding follows a log-normal distribution near the mean and a power law distribution at the tail. Our study provides new insights into the statistical nature of thermodynamics, kinetics and function from different ligands binding with a specific receptor or equivalently specific ligand binding with different receptors. The elucidation of distributions of the kinetics and free energy has guiding roles in studying biomolecular recognition and function through small-molecule evolution and chemical genetics.

  12. The oxygen affinity of cytochrome bo' in Escherichia coli determined by the deoxygenation of oxyleghemoglobin and oxymyoglobin: Km values for oxygen are in the submicromolar range.

    PubMed Central

    D'Mello, R; Hill, S; Poole, R K

    1995-01-01

    Apparent oxygen affinities for Escherichia coli cells and membranes containing a terminal oxidase with only one type of ligand-binding heme, cytochrome o', were measured with oxyleghemoglobin and oxymyoglobin as sensitive oxygen reporters. Two Km values (0.15 to 0.35 microM and 0.016 to 0.085 microM) were detected, well below values determined for the purified oxidase by insensitive electrode methods. PMID:7836332

  13. Comparison of three distinct ELLA protocols for determination of apparent affinity constants between Con A and glycoproteins.

    PubMed

    Mislovičová, D; Katrlík, J; Paulovičová, E; Gemeiner, P; Tkac, J

    2012-06-01

    A procedure for determination of apparent affinity constants K(D)(app) between Concanavalin A (Con A) and naturally d-mannose containing glycoproteins using enzyme-linked lectin assay (ELLA) is reported. Three distinct ELLA protocols are compared to each other with 3 different fitting models used (Liliom, Hill with and without a cooperativity factor). The glycoproteins were physisorbed on a highly charged polystyrene solid surface of immunoassay plates and the amount of lectin bound to the glycoproteins was determined by photometry. The interactions of Con A with five mannose-containing glycoproteins, invertase (INV), glucoamylase (GA), glucose oxidase (GOx), ovalbumin (OVA), and transferrin (TRF) were quantified with apparent affinity constant being in the range 2×10(-7) to 9×10(-6)M. The strength of interaction between Con A and glycoproteins is discussed on the basis of glycan structure/exposure on the protein backbone for each glycoprotein.

  14. The role of human cytochrome P450 enzymes in the formation of 2-hydroxymetronidazole: CYP2A6 is the high affinity (low Km) catalyst.

    PubMed

    Pearce, Robin E; Cohen-Wolkowiez, Michael; Sampson, Mario R; Kearns, Gregory L

    2013-09-01

    Despite metronidazole's widespread clinical use since the 1960s, the specific enzymes involved in its biotransformation have not been previously identified. Hence, in vitro studies were conducted to identify and characterize the cytochrome P450 enzymes involved in the formation of the major metabolite, 2-hydroxymetronidazole. Formation of 2-hydroxymetronidazole in human liver microsomes was consistent with biphasic, Michaelis-Menten kinetics. Although several cDNA-expressed P450 enzymes catalyzed 2-hydroxymetronidazole formation at a supratherapeutic concentration of metronidazole (2000 μM), at a "therapeutic concentration" of 100 μM only CYPs 2A6, 3A4, 3A5, and 3A7 catalyzed metronidazole 2-hydroxylation at rates substantially greater than control vector, and CYP2A6 catalyzed 2-hydroxymetronidazole formation at rates 6-fold higher than the next most active enzyme. Kinetic studies with these recombinant enzymes revealed that CYP2A6 has a Km = 289 μM which is comparable to the Km for the high-affinity (low-Km) enzyme in human liver microsomes, whereas the Km values for the CYP3A enzymes corresponded with the low-affinity (high-Km) component. The sample-to-sample variation in 2-hydroxymetronidazole formation correlated significantly with CYP2A6 activity (r ≥ 0.970, P < 0.001) at substrate concentrations of 100 and 300 μM. Selective chemical inhibitors of CYP2A6 inhibited metronidazole 2-hydroxylation in a concentration-dependent manner and inhibitory antibodies against CYP2A6 virtually eliminated metronidazole 2-hydroxylation (>99%). Chemical and antibody inhibitors of other P450 enzymes had little or no effect on metronidazole 2-hydroxylation. These results suggest that CYP2A6 is the primary catalyst responsible for the 2-hydroxylation of metronidazole, a reaction that may function as a marker of CYP2A6 activity both in vitro and in vivo.

  15. Jacalin interaction with human immunoglobulin A1 and bovine immunoglobulin G1: affinity constant determined by piezoelectric biosensoring.

    PubMed

    Pedroso, Mariele M; Pesquero, Naira C; Thomaz, Sandra M O; Roque-Barreira, Maria C; Faria, Ronaldo C; Bueno, Paulo R

    2012-03-01

    The affinity of the D-galactose-binding lectin from Artocarpus heterophyllus lectin, known as jacalin, with immonuglobulins (Igs) was determined by biofunctionalization of a piezoelectric transducer. This piezoelectric biofunctionalized transducer was used as a mass-sensitive analytical tool, allowing the real-time binding analysis of jacalin-human immunoglobulin A1 (IgA(1)) and jacalin-bovine IgG(1) interactions from which the apparent affinity constant was calculated. The strategy was centered in immobilizing jacalin on the gold electrode's surface of the piezoelectric crystal resonator using appropriate procedures based on self-assembling of 11-mercaptoundecanoic acid and 2-mercaptoethanol thiol's mixture, a particular immobilization strategy by which it was possible to avoid cross-interaction between the proteins over electrode's surface. The apparent affinity constants obtained between jacalin-human IgA(1) and jacalin-bovine IgG(1) differed by 1 order of magnitude [(8.0 ± 0.9) 10(5) vs (8.3 ± 0.1) 10(6) L mol(-1)]. On the other hand, the difference found between human IgA(1) and human IgA(2) interaction with jacalin, eight times higher for IgA(1), was attributed to the presence of O-linked glycans in the IgA(1) hinge region, which is absent in IgA(2). Specific interaction of jacalin with O-glycans, proved to be present in the human IgA(1) and hypothetically present in bovine IgG(1) structures, is discussed as responsible for the obtained affinity values.

  16. Thermodynamics of Calcium binding to the Calmodulin N-terminal domain to evaluate site-specific affinity constants and cooperativity.

    PubMed

    Beccia, Maria Rosa; Sauge-Merle, Sandrine; Lemaire, David; Brémond, Nicolas; Pardoux, Romain; Blangy, Stéphanie; Guilbaud, Philippe; Berthomieu, Catherine

    2015-07-01

    Calmodulin (CaM) is an essential Ca(II)-dependent regulator of cell physiology. To understand its interaction with Ca(II) at a molecular level, it is essential to examine Ca(II) binding at each site of the protein, even if it is challenging to estimate the site-specific binding properties of the interdependent CaM-binding sites. In this study, we evaluated the site-specific Ca(II)-binding affinity of sites I and II of the N-terminal domain by combining site-directed mutagenesis and spectrofluorimetry. The mutations had very low impact on the protein structure and stability. We used these binding constants to evaluate the inter-site cooperativity energy and compared it with its lower limit value usually reported in the literature. We found that site I affinity for Ca(II) was 1.5 times that of site II and that cooperativity induced an approximately tenfold higher affinity for the second Ca(II)-binding event, as compared to the first one. We further showed that insertion of a tryptophan at position 7 of site II binding loop significantly increased site II affinity for Ca(II) and the intra-domain cooperativity. ΔH and ΔS parameters were studied by isothermal titration calorimetry for Ca(II) binding to site I, site II and to the entire N-terminal domain. They showed that calcium binding is mainly entropy driven for the first and second binding events. These findings provide molecular information on the structure-affinity relationship of the individual sites of the CaM N-terminal domain and new perspectives for the optimization of metal ion binding by mutating the EF-hand loops sequences.

  17. Determination of the kinetic rate constant of cyclodextrin supramolecular systems by high-performance affinity chromatography.

    PubMed

    Zhang, Jiwen; Li, Haiyan; Sun, Lixin; Wang, Caifen

    2015-01-01

    The kinetics of the association and dissociation are fundamental kinetic processes for the host-guest interactions (such as the drug-target and drug-excipient interactions) and the in vivo performance of supramolecules. With advantages of rapid speed, high precision and ease of automation, the high-performance affinity chromatography (HPAC) is one of the best techniques to measure the interaction kinetics of weak to moderate affinities, such as the typical host-guest interactions of drug and cyclodextrins by using a cyclodextrin-immobilized column. The measurement involves the equilibration of the cyclodextrin column, the upload and elution of the samples (non-retained substances and retained solutes) at different flow rates on the cyclodextrin and control column, and data analysis. It has been indicated that cyclodextrin-immobilized chromatography is a cost-efficient high-throughput tool for the measurement of (small molecule) drug-cyclodextrin interactions as well as the dissociation of other supramolecules with relatively weak, fast, and extensive interactions. PMID:25749964

  18. Photodetachment of an electron from selenide ion - The electron affinity and spin-orbit coupling constant for SeH.

    NASA Technical Reports Server (NTRS)

    Smyth, K. C.; Brauman, J. I.

    1972-01-01

    The relative cross section for the gas phase photodetachment of an electron from SeH(-) was determined in the wavelength region 428 to 578 nm. An ion cyclotron resonance spectrometer was used to generate, trap, and detect the negative ions, and a 1000-W xenon arc lamp with a grating monochromator was employed as the light source. The cross section exhibited two sharp thresholds, whose positions remained unchanged for the photodetachment of SeD(-). As a result of these thresholds, the electron affinity and the spin-orbit coupling constant were evaluated.

  19. Evaluation of equilibrium constants for the interaction of lactate dehydrogenase isoenzymes with reduced nicotinamide-adenine dinucleotide by affinity chromatography.

    PubMed Central

    Brinkworth, R I; Masters, C J; Winzor, D J

    1975-01-01

    Rabbit muscle lactate dehydrogenase was subjected to frontal affinity chromatography on Sepharose-oxamate in the presence of various concentrations of NADH and sodium phosphate buffer (0.05 M, pH 6.8) containing 0.5 M-NaCl. Quantitative interpretation of the results yields an intrinsic association constant of 9.0 x 10 (4)M-1 for the interaction of enzyme with NADH at 5 degrees C, a value that is confirmed by equilibrium-binding measurements. In a second series of experiments, zonal affinity chromatography of a mouse tissue extract under the same conditions was used to evaluate assoication constants of the order 2 x 10(5)M-1, 3 x 10(5)M-1, 4 x 10(5)M-1, 7 x 10(5)M-1 and 2 x 10(6)M-1 for the interaction of NADH with the M4, M3H, M2H2, MH3 and H4 isoenzymes respectively of lactate dehydrogenase. PMID:175784

  20. SNAP-Tag Technology: A Useful Tool To Determine Affinity Constants and Other Functional Parameters of Novel Antibody Fragments.

    PubMed

    Niesen, Judith; Sack, Markus; Seidel, Melanie; Fendel, Rolf; Barth, Stefan; Fischer, Rainer; Stein, Christoph

    2016-08-17

    Antibody derivatives, such as the single chain fragment variable (scFv), can be developed as diagnostic and therapeutic tools in cancer research, especially in the form of fusion proteins. Such derivatives are easier to produce and modify than monoclonal antibodies (mAbs) and achieve better tissue/tumor penetration. The genetic modification of scFvs is also much more straightforward than the challenging chemical modification of mAbs. Therefore, we constructed two scFvs derived from the approved monoclonal antibodies cetuximab (scFv2112) and panitumumab (scFv1711), both of which are specific for the epidermal growth factor receptor (EGFR), a well-characterized solid tumor antigen. Both scFvs were genetically fused to the SNAP-tag, an engineered version of the human DNA repair enzyme O(6)-alkylguanine DNA alkyltransferase that allows the covalent coupling of benzylguanine (BG)-modified substrates such as fluorescent dyes. The SNAP-tag achieves controllable and irreversible protein modification and is an important tool for experimental studies in vitro and in vivo. The affinity constant of a scFv is a key functional parameter, especially in the context of a fusion protein. Therefore, we developed a method to define the affinity constants of scFv-SNAP fusion proteins by surface plasmon resonance (SPR) spectroscopy. We could confirm that both scFvs retained their functionality after fusion to the SNAP-tag in a variety of procedures and assays, including ELISA, flow cytometry, and confocal microscopy. The experimental procedures described herein, and the new protocol for affinity determination by SPR spectroscopy, are suitable for the preclinical evaluation of diverse antibody formats and derivatives. PMID:27391930

  1. The estimation of affinity constants for the binding of model peptides to DNA by equilibrium dialysis.

    PubMed Central

    Standke, K C; Brunnert, H

    1975-01-01

    The binding of lysine model peptides of the type Lys-X-Lys, Lys-X-X-Lys and Lys-X-X-X-Lys (X = different aliphatic and aromatic amino acids) has been studied by equilibrium dialysis. It was shown that the strong electrostatic binding forces generated by protonated amino groups of lysine can be distinguished from the weak forces stemming from neutral and aromatic spacer amino acids. The overall binding strength of the lysine model peptides is modified by these weak binding forces and the apparent binding constants are influenced more by the hydrophobic character of the spacer amino acid side chains than by the chainlength of the spacers. PMID:1187347

  2. Estimation of apparent binding constant of complexes of selected acyclic nucleoside phosphonates with β-cyclodextrin by affinity capillary electrophoresis.

    PubMed

    Šolínová, Veronika; Mikysková, Hana; Kaiser, Martin Maxmilián; Janeba, Zlatko; Holý, Antonín; Kašička, Václav

    2016-01-01

    Affinity capillary electrophoresis (ACE) has been applied to estimation of apparent binding constant of complexes of (R,S)-enantiomers of selected acyclic nucleoside phosphonates (ANPs) with chiral selector β-cyclodextrin (βCD) in aqueous alkaline medium. The noncovalent interactions of five pairs of (R,S)-enantiomers of ANPs-based antiviral drugs and their derivatives with βCD were investigated in the background electrolyte (BGE) composed of 35 or 50 mM sodium tetraborate, pH 10.0, and containing variable concentration (0-25 mM) of βCD. The apparent binding constants of the complexes of (R,S)-enantiomers of ANPs with βCD were estimated from the dependence of effective electrophoretic mobilities of (R,S)-enantiomers of ANPs (measured simultaneously by ACE at constant reference temperature 25°C inside the capillary) on the concentration of βCD in the BGE using different nonlinear and linear calculation methodologies. Nonlinear regression analysis provided more precise and accurate values of the binding constants and a higher correlation coefficient as compared to the regression analysis of the three linearized plots of the effective mobility dependence on βCD concentration in the BGE. The complexes of (R,S)-enantiomers of ANPs with βCD have been found to be relatively weak - their apparent binding constants determined by the nonlinear regression analysis were in the range 13.3-46.4 L/mol whereas the values from the linearized plots spanned the interval 12.3-55.2 L/mol. PMID:26426398

  3. Asymmetry in inward- and outward-affinity constant of transport explain unidirectional lysine flux in Saccharomyces cerevisiae.

    PubMed

    Bianchi, Frans; Klooster, Joury S van 't; Ruiz, Stephanie J; Luck, Katja; Pols, Tjeerd; Urbatsch, Ina L; Poolman, Bert

    2016-01-01

    The import of basic amino acids in Saccharomyces cerevisiae has been reported to be unidirectional, which is not typical of how secondary transporters work. Since studies of energy coupling and transport kinetics are complicated in vivo, we purified the major lysine transporter (Lyp1) of yeast and reconstituted the protein into lipid vesicles. We show that the Michaelis constant (KM) of transport from out-to-in is well in the millimolar range and at least 3 to 4-orders of magnitude higher than that of transport in the opposite direction, disfavoring the efflux of solute via Lyp1. We also find that at low values of the proton motive force, the transport by Lyp1 is comparatively slow. We benchmarked the properties of eukaryotic Lyp1 to that of the prokaryotic homologue LysP and find that LysP has a similar KM for transport from in-to-out and out-to-in, consistent with rapid influx and efflux. We thus explain the previously described unidirectional nature of lysine transport in S. cerevisiae by the extraordinary kinetics of Lyp1 and provide a mechanism and rationale for previous observations. The high asymmetry in transport together with secondary storage in the vacuole allow the cell to accumulate basic amino acids to very high levels. PMID:27550794

  4. Asymmetry in inward- and outward-affinity constant of transport explain unidirectional lysine flux in Saccharomyces cerevisiae

    PubMed Central

    Bianchi, Frans; Klooster, Joury S. van ‘t; Ruiz, Stephanie J.; Luck, Katja; Pols, Tjeerd; Urbatsch, Ina L.; Poolman, Bert

    2016-01-01

    The import of basic amino acids in Saccharomyces cerevisiae has been reported to be unidirectional, which is not typical of how secondary transporters work. Since studies of energy coupling and transport kinetics are complicated in vivo, we purified the major lysine transporter (Lyp1) of yeast and reconstituted the protein into lipid vesicles. We show that the Michaelis constant (KM) of transport from out-to-in is well in the millimolar range and at least 3 to 4-orders of magnitude higher than that of transport in the opposite direction, disfavoring the efflux of solute via Lyp1. We also find that at low values of the proton motive force, the transport by Lyp1 is comparatively slow. We benchmarked the properties of eukaryotic Lyp1 to that of the prokaryotic homologue LysP and find that LysP has a similar KM for transport from in-to-out and out-to-in, consistent with rapid influx and efflux. We thus explain the previously described unidirectional nature of lysine transport in S. cerevisiae by the extraordinary kinetics of Lyp1 and provide a mechanism and rationale for previous observations. The high asymmetry in transport together with secondary storage in the vacuole allow the cell to accumulate basic amino acids to very high levels. PMID:27550794

  5. Determination of binding constants by affinity capillary electrophoresis, electrospray ionization mass spectrometry and phase-distribution methods

    PubMed Central

    Chen, Zhi; Weber, Stephen G.

    2008-01-01

    Many methods for determining intermolecular interactions have been described in the literature in the past several decades. Chief among them are methods based on spectroscopic changes, particularly those based on absorption or nuclear magnetic resonance (NMR) [especially proton NMR (1H NMR)]. Recently, there have been put forward several new methods that are particularly adaptable, use very small quantities of material, and do not place severe requirements on the spectroscopic properties of the binding partners. This review covers new developments in affinity capillary electrophoresis, electrospray ionization mass spectrometry (ESI-MS) and phasetransfer methods. PMID:19802330

  6. Inhibition of ionotropic neurotransmitter receptors by antagonists: strategy to estimate the association and the dissociation rate constant of antagonists with very strong affinity to the receptors.

    PubMed

    Aoshima, H; Inoue, Y; Hori, K

    1992-10-01

    Since binding of an agonist to an ionotropic neurotransmitter receptor causes not only channel opening, but also desensitization of the receptor, inhibition of the receptor by the antagonist sometimes becomes very complicated. The transient state kinetics of ligand association and dissociation, and desensitization of the receptor were considered on the basis of the minimal model proposed by Hess' group, and the following possibilities were proposed. 1) When an agonist is simultaneously applied to the receptor with an antagonist whose affinity to the receptor is extremely strong and different from that of the agonist, it is usually impossible to estimate the real inhibition constant exactly from the responses because desensitization of the receptor proceeds before the equilibrium of the ligand binding. Simultaneous addition of the antagonist with strong affinity to the receptor may apparently accelerate inactivation (desensitization) of the receptor. The association rate constant of the antagonist can be estimated by analyses of the rate of the inactivation in the presence and the absence of the antagonist. 2) A preincubated antagonist with a slow dissociation rate constant, i.e., a very effective inhibitor, may cause apparent noncompetitive inhibition of the receptor, since the receptor is desensitized by an agonist as soon as the antagonist dissociates from the receptor and the dissociation of the antagonist from the receptor becomes the rate-determining step. A nicotinic acetylcholine receptor (nAChR) was expressed in Xenopus oocytes by injecting mRNA prepared from Electrophorus electricus electroplax and used for the experiments on inhibition by an antagonist.(ABSTRACT TRUNCATED AT 250 WORDS) PMID:1337082

  7. Structure-based model profiles affinity constant of drugs with hPEPT1 for rapid virtual screening of hPEPT1's substrate.

    PubMed

    Sun, L; Meng, S

    2016-08-01

    The human proton-coupled peptide transporter (hPEPT1) with broad substrates is an important route for improving the pharmacokinetic performance of drugs. Thus, it is essential to predict the affinity constant between drug molecule and hPEPT1 for rapid virtual screening of hPEPT1's substrate during lead optimization, candidate selection and hPEPT1 prodrug design. Here, a structure-based in silico model for 114 compounds was constructed based on eight structural parameters. This model was built by the multiple linear regression method and satisfied all the prerequisites of the regression models. For the entire data set, the r(2) and adjusted r(2) values were 0.74 and 0.72, respectively. Then, this model was used to perform substrate/non-substrate classification. For 29 drugs from DrugBank database, all were correctly classified as substrates of hPEPT1. This model was also used to perform substrate/non-substrate classification for 18 drugs and their prodrugs; this QSAR model also can distinguish between the substrate and non-substrate. In conclusion, the QSAR model in this paper was validated by a large external data set, and all results indicated that the developed model was robust, stable, and can be used for rapid virtual screening of hPEPT1's substrate in the early stage of drug discovery. PMID:27586363

  8. Km as an Apparent Dissociation Constant.

    ERIC Educational Resources Information Center

    Cohlberg, Jeffrey A.

    1979-01-01

    An approach to enzyme kinetics which emphasizes similarities between equilibrium binding and steady state kinetics is outlined. It is intended for use in teaching biochemistry to beginning students. (Author/SA)

  9. Structure of a human IgA1 Fab fragment at 1.55 Å resolution: potential effect of the constant domains on antigen-affinity modulation.

    PubMed

    Correa, Agustin; Trajtenberg, Felipe; Obal, Gonzalo; Pritsch, Otto; Dighiero, Guillermo; Oppezzo, Pablo; Buschiazzo, Alejandro

    2013-03-01

    Despite being the most abundant class of immunoglobulins in humans and playing central roles in the adaptive immune response, high-resolution structural data are still lacking for the antigen-binding region of human isotype A antibodies (IgAs). The crystal structures of a human Fab fragment of IgA1 in three different crystal forms are now reported. The three-dimensional organization is similar to those of other Fab classes, but FabA1 seems to be more rigid, being constrained by a hydrophobic core in the interface between the variable and constant domains of the heavy chain (VH-CH1) as well as by a disulfide bridge that connects the light and heavy chains, influencing the relative heavy/light-chain orientation. The crystal structure of the same antibody but with a G-isotype CH1 which is reported to display different antigen affinity has also been solved. The differential structural features reveal plausible mechanisms for constant/variable-domain long-distance effects whereby antibody class switching could alter antigen affinity.

  10. Correct pK values for dissociation constant of carbonic acid lower the reported Km values of ribulose bisphosphate carboxylase to half. Presentation of a nomograph and an equation for determining the pK values.

    PubMed

    Yokota, A; Kitaoka, S

    1985-09-30

    In the assay of ribulose 1,5-bisphosphate carboxylase/oxygenase (Rubisco) in vitro, the concentration of CO2, the substrate of the enzyme, has been calculated from the amount of sodium bicarbonate added to the assay mixture with a dissociation constant of carbonic acid in pure water, 6.35 to 6.37. However, Rubisco is generally assayed at ionic strength of 0.1 to 0.2 M, where the dissociation constant decreases up to 6.06. The decrease of this level of the constant reduces the calculated CO2 concentration in the assay mixture to about half and accordingly the Kms of Rubisco for CO2 reported so far are not correct. The present report presents a nomograph and an equation, from which dissociation constants of carbonic acid in the presence of various concentrations of salts can be easily calculated. PMID:3931642

  11. Affinity Chromatography.

    ERIC Educational Resources Information Center

    Gray, Gary R.

    1980-01-01

    Presents selected recent advances in immobilization chemistry which have important connections to affinity chromatography. Discusses ligand immobilization and support modification. Cites 51 references. (CS)

  12. Neutrophil haptotaxis induced by the lectin KM+.

    PubMed

    Ganiko, L; Martins, A R; Espreáfico, E M; Roque-Barreira, M C

    1998-05-01

    KM+ is a D-mannose binding lectin from Artocarpus integrifolia that induces neutrophil migration in vitro and in vivo. This attractant activity was shown to be caused by haptotaxis rather than chemotaxis. The inhibition by D-mannose of the neutrophil attraction exerted by KM+, both in vitro and in vivo, supports the idea that haptotaxis is triggered in vivo by the sugar binding sites interacting with glycoconjugates located on the neutrophil surface and in the extracellular matrix. In the present study an in vivo haptotaxis assay was performed by intradermally (i.d.) injecting 125I-KM+ (200 ng), which led to a selective staining of loose connective tissue and vascular endothelium. The radiolabelled area exhibited a maximum increase (five-fold) in neutrophil infiltration 3 h after injection, relative to i.d. 200 ng 125I-BSA. We characterized the ex vivo binding of KM+ to tissue elements by immunohistochemistry, using paraformaldehyde-fixed, paraffin-embedded, untreated rat skin. Bound KM+ was detected with an affinity-purified rabbit IgG anti-KM+ and visualized with an alkaline phosphatase based system. KM+ binding to connective tissue and vascular endothelium was inhibited by preincubating KM+ with 0.4 mM D-mannose and was potentiated by heparan sulfate (100 microg ml(-1)). An in vitro assay carried out in a Boyden microchamber showed that heparan sulfate potentiated the attractant effect of 10 microg KM+ by 34%. The present data suggest that KM+ induces neutrophil migration in vivo by haptotaxis and that the haptotactic gradient could be provided by the interaction of the KM+ carbohydrate recognition site(s) with mannose-containing glycoconjugate(s) in vascular endothelium and connective tissue. Heparan sulfate would act as an accessory molecule, enhancing the KM+ tissue binding and potentiating the induced neutrophil haptotaxis.

  13. A comparison of affinity constants for muscarine-sensitive acetylcholine receptors in guinea-pig atrial pacemaker cells at 29 degrees C and in ileum at 29 degrees C and 37 degrees C.

    PubMed Central

    Barlow, R B; Berry, K J; Glenton, P A; Nilolaou, N M; Soh, K S

    1976-01-01

    1 The affinity of 17 compounds for muscarine-sensitive acetylcholine receptors in atrial pacemaker cells and ileum of the guinea-pig has been measured at 29 degrees C in Ringer-Locke solution. Measurements were also made at 37 degrees C with 7 of them. 2 Some of the compounds had much higher affinity for the receptors in the ileum than for those in the atria. For the most selective compound, 4-diphenylacetoxy-N-methylpiperidine methiodide, the difference was approximately 20-fold. The receptors in the atria are therefore different the structure from those in the ileum. 3 The effect of temperature on affinity are not the same for all the compounds, tested indicating different enthalpies and entropies of adsorption and accounting for some of the difficulty experienced in predicting the affinity of new compounds. PMID:1000135

  14. Concurrent low- and high-affinity sulfate reduction kinetics in marine sediment

    NASA Astrophysics Data System (ADS)

    Harder Tarpgaard, Irene; Røy, Hans; Jørgensen, Bo Barker

    Bacterial sulfate reduction in marine sediments generally occurs in the presence of high millimolar concentrations of sulfate. Published data indicate that low sulfate concentrations may limit sulfate reduction rates below 0.2-2 mM. Yet, high sulfate reduction rates occur in the 1-100 μM range in freshwater sediments and at the sulfate-methane transition in marine sediments. Through a combination of 35S-tracer experiments, including initial velocity experiments and time course experiments, we searched for different sulfate affinities in the mixed community of sulfate reducers in a marine sediment. We supported the radiotracer experiments with a highly sensitive ion chromatographic technique for sulfate with a detection limit of 0.15 μM SO 42- in marine pore water. Our results showed that high and low affinities for sulfate co-occur and that the applied experimental approach may determine the observed apparent half saturation constant, Km. Our experimental and model data both show that sulfate reduction in the studied marine sediment could be explained by two dominating affinities for sulfate: a low affinity with a mean half saturation constant, Km, of 430 μM SO 42- and a high affinity with a mean Km of 2.6 μM SO 42-. The high-affinity sulfate reduction was thermodynamically un-constrained down to <1 μM SO 42-, both in our experiments and under in situ conditions. The reduction of radio-labeled sulfate was partly reversible due to concurrent re-oxidation of sulfide by Fe(III) and possibly due to a reversibility of the enzymatic pathway of sulfate reduction. A literature survey of apparent Km values for sediments and pure cultures is presented and discussed.

  15. Report: Affinity Chromatography.

    ERIC Educational Resources Information Center

    Walters, Rodney R.

    1985-01-01

    Supports, affinity ligands, immobilization, elution methods, and a number of applications are among the topics considered in this discussion of affinity chromatography. An outline of the basic principles of affinity chromatography is included. (JN)

  16. Temperature Structure of the 80 Km to 120 Km Region

    NASA Technical Reports Server (NTRS)

    Forbes, J. M.

    1985-01-01

    Between 80 and 120 km the CIRA 1972 model is based heavily on NASA Meteorological Sounding Rocket Program (MSRP) data collected prior to 1967. Since about 1970 an abundance of E-region (100-130 km) temperature data from the incoherent scatter facilities at Arecibo, Millstone Hill, and St. Santin have also become available. The present study examines the temperature structure of the 80 to 120 km region given considerable additional MSRP rocket data, thus providing better seasonal, latitudinal, and longitudinal coverage in the 80 to 100 km region, and a combination of incoherent scatter and rocket data in the 100 to 120 km region which allows a much improved delineation of lower thermosphere temperature structue. Although some individual station comparisons indicate measurable asymmetries in longitude and latitude, data are still insufficient to separate these effects. Specific recommendations of the new CIRA are given.

  17. Are Fundamental Constants Really Constant?

    ERIC Educational Resources Information Center

    Swetman, T. P.

    1972-01-01

    Dirac's classical conclusions, that the values of e2, M and m are constants and the quantity of G decreases with time. Evoked considerable interest among researchers and traces historical development by which further experimental evidence points out that both e and G are constant values. (PS)

  18. KM Education in LIS Programs

    ERIC Educational Resources Information Center

    Rehman, Sajjad ur; Chaudhry, Abdus Sattar

    2005-01-01

    This paper investigates the perceptions of the heads of 12 Library and Information Science (LIS) schools on Knowledge Management (KM) education. These heads from North America, Europe and the Pacific region had either been offering KM courses or had an apparent interest in such programs. Data about perceptions were gathered on the nature of their…

  19. KM3NeT

    SciTech Connect

    Jong, M. de; Collaboration: KM3NeT Collaboration

    2015-07-15

    KM3NeT is a large research infrastructure, that will consist of a network of deep-sea neutrino telescopes in the Mediterranean Sea. The main objective of KM3NeT is the discovery and subsequent observation of high-energy neutrino sources in the Universe. A further physics perspective is the measurement of the mass hierarchy of neutrinos. A corresponding study, ORCA, is ongoing within KM3NeT. A cost effective technology for (very) large water Cherenkov detectors has been developed based on a new generation of low price 3-inch photo-multiplier tubes. Following the successful deployment and operation of two prototypes, the construction of the KM3NeT research infrastructure has started. The prospects of the different phases of the implementation of KM3NeT are summarised.

  20. KM3NeT

    NASA Astrophysics Data System (ADS)

    de Jong, M.

    2015-07-01

    KM3NeT is a large research infrastructure, that will consist of a network of deep-sea neutrino telescopes in the Mediterranean Sea. The main objective of KM3NeT is the discovery and subsequent observation of high-energy neutrino sources in the Universe. A further physics perspective is the measurement of the mass hierarchy of neutrinos. A corresponding study, ORCA, is ongoing within KM3NeT. A cost effective technology for (very) large water Cherenkov detectors has been developed based on a new generation of low price 3-inch photo-multiplier tubes. Following the successful deployment and operation of two prototypes, the construction of the KM3NeT research infrastructure has started. The prospects of the different phases of the implementation of KM3NeT are summarised.

  1. Computational and ESR studies of electron attachment to decafluorocyclopentane, octafluorocyclobutane, and hexafluorocyclopropane: electron affinities of the molecules and the structures of their stable negative ions as determined from 13C and 19F hyperfine coupling constants.

    PubMed

    ElSohly, Adel M; Tschumper, Gregory S; Crocombe, Richard A; Wang, Jih Tzong; Williams, Ffrancon

    2005-08-01

    High-resolution ESR spectra of the ground-state negative ions of hexafluorocyclopropane (c-C3F6*-), octafluorocyclobutane (c-C4F8*-), and decafluorocyclopentane (c-C5F10*-) are reported and their isotropic 19F hyperfine coupling constants (hfcc) of 198.6 +/- 0.4 G, 147.6 +/- 0.4 G, and 117.9 +/- 0.4 G, respectively, are in inverse ratio to the total number of fluorine atoms per anion. Together with the small value of 5.2 +/- 0.4 G determined for the isotropic 13C hfcc of c-C4F8*-, these results indicate that in each case the singly occupied molecular orbital (SOMO) is delocalized over the equivalent fluorines and possesses a nodal plane through the carbon atoms of a time-averaged D(nh) structure. A series of quantum chemical computations were carried out to further characterize these anions and their neutral counterparts. Both the B3LYP density functional and second-order Møller-Plesset perturbation theory (MP2) indicate that c-C3F6*- adopts a D(3h) geometry and a (2)A2'' ground electronic state, that c-C4F8*- adopts a D(4h) geometry and a (2)A2u ground electronic state, and that c-C5F10*- adopts a C(s) structure and a (2)A' electronic state. Moreover, the 19F hyperfine coupling constants computed with the MP2 method and a high quality triple-zeta basis set are within 1% of the experimental values. Also, the values computed for the 13C hfcc of c-C4F8*- are consistent with the experimental value of 5.2 G. Therefore, in keeping with the ESR results, these negative ions derived from first-row elements can be characterized as pi* species. In addition, the hypervalency of these perfluorocycloalkane radical anions has been clarified.

  2. Imaging Resolution of the 410-km and 660-km Discontinuities

    NASA Astrophysics Data System (ADS)

    Deng, K.; Zhou, Y.

    2014-12-01

    Structure of seismic discontinuities at depths of about 410 km and 660 km provides important constraints on mantle convection as the associated phase transformations in the transition zone are sensitive to thermal perturbations. Teleseismic P-to-S receiver functions have been widely used to map the depths of the two discontinuities. In this study, we investigate the resolution of receiver functions in imaging topographic variations of the 410-km and 660-km discontinuities based on wave propagation simulations using the Spectral Element Method (SEM). We investigate finite-frequency effects of direct P waves as well as P-to-S converted waves by varying the length scale of discontinuity topography in the transition zone. We show that wavefront healing effects are significant in broadband receiver functions. For example, at a period of 10 to 20 seconds, the arrival anomaly in P-to-S converted waves is about 50% of what predicted by ray theory when the topography length scale is in the order of 400 km. The observed arrival anomaly further reduces to 10-20% when the topography length scale reduces to about 200 km. We calculate 2-D boundary sensitivity kernels for direct P waves as well as receiver functions based on surface wave mode summation and confirm that finite frequency-effects can be properly accounted for. Three-dimensional wavespeed structure beneath seismic stations can also introduce significant artifacts in transition zone discontinuity topography if time corrections are not applied, and, the effects are dependent on frequency.

  3. Imaging Resolution of 410-km and 660-km Discontinuities

    NASA Astrophysics Data System (ADS)

    Deng, Kai; Zhou, Ying

    2014-05-01

    Seismic discontinuities in the mantle transition zone at depths of about 410 and 660 km are associated with olivine phase transformations. The depths of the discontinuities provide important constraints on the thermal structure of the mid mantle. Teleseismic receiver functions as well as PP and SS precursors have been widely used in imaging topographic variations of the 410 and 660 discontinuities. Ray-theory based migration and stacking methods are often used to enhance signals of the converted and reflected waves, assuming that the effects of 3-D structure in wavespeed can be averaged out. In this study, we investigate the resolution of traditional methods in imaging the 410-km and 660-km discontinuity topography based on wave propagation simulations using the Spectral Element Method (SEM). We calculate synthetic seismograms in laterally heterogeneous wavespeed models with lateral variations in the 410-km and 660-km discontinuity depths. The SEM synthetics are processed following standard migration and stacking techniques to image the discontinuities. We show that 3-D wave speed structure beneath seismic stations can introduce significant artifacts in transition zone discontinuity topography. We also investigate finite-frequency effects of P-to-S converted waves as well as PP and SS precursors in imaging the discontinuities by varying the length scale of depth variations in the 410-km and 660-km discontinuities in SEM simulations, and show that wave front healing effects depend on the length scale of the depth variation as well as epicentral distances. Finally we compare receiver function delay times with calculations based on finite frequency sensitivity and show that wave front healing effects can be properly accounted for.

  4. Association constants of Pb2+ with binding sites of fungal biomass using metal-based titrations.

    PubMed

    Naja, G; Mustin, C; Volesky, B; Berthelin, J

    2006-01-01

    Biosorption is perceived as an alternative method for toxic heavy metal removal/recovery from aqueous effluents. This work focused on derivation of some key quantitative physico-chemical characteristics of a representative biosorbent material required for its further effective exploitation. The newly developed acid-base and metal-based titrator allowed the characterization of the chemisorption active sites of Rhizopus arrhizus biomass and the study of their metal affinity. This experimental approach, combined with an analytical method consisting of transforming the initial data enabled the calculation of the number and capacity of the reactive sites (Qads) and the metal affinity constants (Km) for lead sorption by R. arrhizus biomass. The pKm values for Rhizopus biomass varied between -3 and -6 for sites releasing no protons, -1 and 1 for sites releasing one proton, and > 8 for sites releasing two protons - combined with the Pb precipitation phenomenon. At low temperatures, the active binding site number was lower at lower lead concentrations whereas the precipitation was promoted at higher lead concentration values. Lead adsorption contributed modestly (11%) to its overall uptake and occurred at low lead concentrations onto strong and medium affinity binding sites. Micro-precipitation quickly commenced around active binding sites distinguished by their weak affinity whenever the solution lead concentrations reached 10(-6) or 10(-5) M and represented more than 85% of the total sorbed metal quantity. The work also demonstrated the usefulnes of the methodology reported here for characterizing complex biosorbent materials.

  5. BC(50): a generalized, unifying affinity descriptor.

    PubMed

    Vacca, Alberto; Francesconi, Oscar; Roelens, Stefano

    2012-12-01

    Assessing binding affinities is an unavoidable step that we come across any time interactions between binding species are investigated. A quantitative evaluation of binding affinities relies on the determination of binding constants but, whilst the binding constant fully defines the affinity of a reagent for a ligand when only one complex species is formed, the same is not true when the interacting partners form more than one complex of different stoichiometry, because all complexes contribute to the overall binding affinity. Unfortunately, this situation is the rule rather than the exception in chemical systems, but a generally accepted solution for this issue has not yet been settled. In this Personal Account, we describe the evolution, from the initial idea to a fully developed stage, of a binding descriptor that has been developed with the aim of filling this gap, thereby providing scientists in all fields of chemistry with a unifying tool for the assessment of binding affinities based on the knowledge of the binding constants in systems that involve any number of complex species.

  6. Affine projective Osserman structures

    NASA Astrophysics Data System (ADS)

    Gilkey, P.; Nikčević, S.

    2013-08-01

    By considering the projectivized spectrum of the Jacobi operator, we introduce the concept of projective Osserman manifold in both the affine and in the pseudo-Riemannian settings. If M is an affine projective Osserman manifold, then the deformed Riemannian extension metric on the cotangent bundle is both spacelike and timelike projective Osserman. Since any rank-1-symmetric space is affine projective Osserman, this provides additional information concerning the cotangent bundle of a rank-1 Riemannian symmetric space with the deformed Riemannian extension metric. We construct other examples of affine projective Osserman manifolds where the Ricci tensor is not symmetric and thus the connection in question is not the Levi-Civita connection of any metric. If the dimension is odd, we use methods of algebraic topology to show the Jacobi operator of an affine projective Osserman manifold has only one non-zero eigenvalue and that eigenvalue is real.

  7. Special Report: Affinity Chromatography.

    ERIC Educational Resources Information Center

    Parikh, Indu; Cuatrecasas, Pedro

    1985-01-01

    Describes the nature of affinity chromatography and its use in purifying enzymes, studying cell interactions, exploring hormone receptors, and other areas. The potential the technique may have in treating disease is also considered. (JN)

  8. Affine group formulation of the Standard Model coupled to gravity

    SciTech Connect

    Chou, Ching-Yi; Ita, Eyo; Soo, Chopin

    2014-04-15

    In this work we apply the affine group formalism for four dimensional gravity of Lorentzian signature, which is based on Klauder’s affine algebraic program, to the formulation of the Hamiltonian constraint of the interaction of matter and all forces, including gravity with non-vanishing cosmological constant Λ, as an affine Lie algebra. We use the hermitian action of fermions coupled to gravitation and Yang–Mills theory to find the density weight one fermionic super-Hamiltonian constraint. This term, combined with the Yang–Mills and Higgs energy densities, are composed with York’s integrated time functional. The result, when combined with the imaginary part of the Chern–Simons functional Q, forms the affine commutation relation with the volume element V(x). Affine algebraic quantization of gravitation and matter on equal footing implies a fundamental uncertainty relation which is predicated upon a non-vanishing cosmological constant. -- Highlights: •Wheeler–DeWitt equation (WDW) quantized as affine algebra, realizing Klauder’s program. •WDW formulated for interaction of matter and all forces, including gravity, as affine algebra. •WDW features Hermitian generators in spite of fermionic content: Standard Model addressed. •Constructed a family of physical states for the full, coupled theory via affine coherent states. •Fundamental uncertainty relation, predicated on non-vanishing cosmological constant.

  9. The Hubble constant.

    PubMed

    Tully, R B

    1993-06-01

    Five methods of estimating distances have demonstrated internal reproducibility at the level of 5-20% rms accuracy. The best of these are the cepheid (and RR Lyrae), planetary nebulae, and surface-brightness fluctuation techniques. Luminosity-line width and Dn-sigma methods are less accurate for an individual case but can be applied to large numbers of galaxies. The agreement is excellent between these five procedures. It is determined that Hubble constant H0 = 90 +/- 10 km.s-1.Mpc-1 [1 parsec (pc) = 3.09 x 10(16) m]. It is difficult to reconcile this value with the preferred world model even in the low-density case. The standard model with Omega = 1 may be excluded unless there is something totally misunderstood about the foundation of the distance scale or the ages of stars. PMID:11607391

  10. The Hubble constant.

    PubMed Central

    Tully, R B

    1993-01-01

    Five methods of estimating distances have demonstrated internal reproducibility at the level of 5-20% rms accuracy. The best of these are the cepheid (and RR Lyrae), planetary nebulae, and surface-brightness fluctuation techniques. Luminosity-line width and Dn-sigma methods are less accurate for an individual case but can be applied to large numbers of galaxies. The agreement is excellent between these five procedures. It is determined that Hubble constant H0 = 90 +/- 10 km.s-1.Mpc-1 [1 parsec (pc) = 3.09 x 10(16) m]. It is difficult to reconcile this value with the preferred world model even in the low-density case. The standard model with Omega = 1 may be excluded unless there is something totally misunderstood about the foundation of the distance scale or the ages of stars. PMID:11607391

  11. Calculation of antibody affinity in homogeneous and heterogeneous systems.

    PubMed

    Chalquest, R R

    1988-12-01

    Antibody affinity is an important determinant of all antibody-antigen reactions. A new computer program, AFCRV, was developed to calculate binding constants with data from a radioimmunoassay on most microcomputers in the laboratory by using constant-ratio dilution curves. Evaluation of a homogeneous or heterogeneous antibody in the presence of a single antigen can be accomplished.

  12. Affinity purification of aprotinin from bovine lung.

    PubMed

    Xin, Yu; Liu, Lanhua; Chen, Beizhan; Zhang, Ling; Tong, Yanjun

    2015-05-01

    An affinity protocol for the purification of aprotinin from bovine lung was developed. To simulate the structure of sucrose octasulfate, a natural specific probe for aprotinin, the affinity ligand was composed of an acidic head and a hydrophobic stick, and was then linked with Sepharose. The sorbent was then subjected to adsorption analysis with pure aprotinin. The purification process consisted of one step of affinity chromatography and another step of ultrafiltration. Then purified aprotinin was subjected to sodium dodecyl sulfate polyacrylamide gel electrophoresis, trypsin inhibitor activity, gel-filtration, and thin-layer chromatography analysis. As calculated, the theoretical maximum adsorption (Qmax ) of the affinity sorbent was 25,476.0 ± 184.8 kallikrein inactivator unit/g wet gel; the dissociation constant of the complex "immobilized ligand-aprotinin" (Kd ) was 4.6 ± 0.1 kallikrein inactivator unit/mL. After the affinity separation of bovine lung aprotinin, reducing sodium dodecyl sulfate polyacrylamide gel electrophoresis analysis and gel-filtration chromatography revealed that the protein was a single polypeptide, and the purities were ∼ 97 and 100%, respectively; the purified peptide was also confirmed with aprotinin standard by gel-filtration chromatography and thin-layer chromatography. After the whole purification process, protein, and bioactivity recoveries were 2.2 and 92.6%, respectively; and the specific activity was up to 15,907.1 ± 10.2 kallikrein inactivator unit/mg. PMID:25677462

  13. Critical factors governing the difference in antizyme-binding affinities between human ornithine decarboxylase and antizyme inhibitor.

    PubMed

    Liu, Yen-Chin; Liu, Yi-Liang; Su, Jia-Yang; Liu, Guang-Yaw; Hung, Hui-Chih

    2011-01-01

    Both ornithine decarboxylase (ODC) and its regulatory protein, antizyme inhibitor (AZI), can bind with antizyme (AZ), but the latter has a higher AZ-binding affinity. The results of this study clearly identify the critical amino acid residues governing the difference in AZ-binding affinities between human ODC and AZI. Inhibition experiments using a series of ODC mutants suggested that residues 125 and 140 may be the key residues responsible for the differential AZ-binding affinities. The ODC_N125K/M140K double mutant demonstrated a significant inhibition by AZ, and the IC(50) value of this mutant was 0.08 µM, three-fold smaller than that of ODC_WT. Furthermore, the activity of the AZ-inhibited ODC_N125K/M140K enzyme was hardly rescued by AZI. The dissociation constant (K(d)) of the [ODC_N125K/M140K]-AZ heterodimer was approximately 0.02 µM, which is smaller than that of WT_ODC by approximately 10-fold and is very close to the K(d) value of AZI_WT, suggesting that ODC_N125K/M140K has an AZ-binding affinity higher than that of ODC_WT and similar to that of AZI. The efficiency of the AZI_K125N/K140M double mutant in the rescue of AZ-inhibited ODC enzyme activity was less than that of AZI_WT. The K(d) value of [AZI_K125N/K140M]-AZ was 0.18 µM, nine-fold larger than that of AZI_WT and close to the K(d) value of ODC_WT, suggesting that AZI_K125N/K140M has an AZ-binding affinity lower than that of AZI_WT and similar to that of ODC. These data support the hypothesis that the differences in residues 125 and 140 in ODC and AZI are responsible for the differential AZ-binding affinities. PMID:21552531

  14. Affinity purification of metalloprotease from marine bacterium using immobilized metal affinity chromatography.

    PubMed

    Li, Shangyong; Wang, Linna; Yang, Juan; Bao, Jing; Liu, Junzhong; Lin, Shengxiang; Hao, Jianhua; Sun, Mi

    2016-06-01

    In this study, an efficient affinity purification protocol for an alkaline metalloprotease from marine bacterium was developed using immobilized metal affinity chromatography. After screening and optimization of the affinity ligands and spacer arm lengths, Cu-iminmodiacetic acid was chosen as the optimal affinity ligand, which was coupled to Sepharose 6B via a 14-atom spacer arm. The absorption analysis of this medium revealed a desorption constant Kd of 21.5 μg/mL and a theoretical maximum absorption Qmax of 24.9 mg/g. Thanks to this affinity medium, the enzyme could be purified by only one affinity purification step with a purity of approximately 95% pure when analyzed by high-performance liquid chromatography and reducing sodium dodecyl sulfate polyacrylamide gel electrophoresis. The recovery of the protease activity reached 74.6%, which is much higher than the value obtained by traditional protocols (8.9%). These results contribute to the industrial purifications and contribute a significant reference for the purification of other metalloproteases. PMID:27058973

  15. Affinity driven social networks

    NASA Astrophysics Data System (ADS)

    Ruyú, B.; Kuperman, M. N.

    2007-04-01

    In this work we present a model for evolving networks, where the driven force is related to the social affinity between individuals of a population. In the model, a set of individuals initially arranged on a regular ordered network and thus linked with their closest neighbors are allowed to rearrange their connections according to a dynamics closely related to that of the stable marriage problem. We show that the behavior of some topological properties of the resulting networks follows a non trivial pattern.

  16. Two bradykinin binding sites with picomolar affinities

    SciTech Connect

    Manning, D.C.; Vavrek, R.; Stewart, J.M.; Snyder, S.H.

    1986-05-01

    Bradykinin (BK) and related peptides exert a wide range of effects on several organ systems. We have attempted to sort out these effects by studying the binding interaction of (/sup 3/H)BK at the membrane level with in vitro receptor binding techniques. High specific activity (/sup 3/H)BK and an enzyme inhibitor cocktail has enabled us to label two BK binding sites with different affinity and peptide specificity in several guinea-pig tissues. In the guinea-pig ileum the high-affinity site has an equilibrium dissociation constant (Kd) for (/sup 3/H)BK of 13 pM and a maximal number of binding sites of 8.3 pmol/g of tissue wet weight. The low-affinity guinea-pig ileum site displays a Kd of 910 pM, a maximum number of binding sites of 14 pmol/g of tissue wet weight and shows a greater selectivity for BK analogs over Lysyl-BK analogs. Two similar sites can also be discriminated in kidney and heart. The potencies of a series of BK analogs at the high-affinity guinea-pig ileum site correlate well with their potencies in contracting ileal smooth muscle. The binding of (/sup 3/H)BK in the guinea-pig ileum is inhibited by physiological concentrations of monovalent and divalent cations.

  17. Analysis of sex differences in open-water ultra-distance swimming performances in the FINA World Cup races in 5 km, 10 km and 25 km from 2000 to 2012

    PubMed Central

    2014-01-01

    Background The present study investigated the changes in swimming speeds and sex differences for elite male and female swimmers competing in 5 km, 10 km and 25 km open-water FINA World Cup races held between 2000 and 2012. Methods The changes in swimming speeds and sex differences across years were analysed using linear, non-linear, and multi-level regression analyses for the annual fastest and the annual ten fastest competitors. Results For the annual fastest, swimming speed remained stable for men and women in 5 km (5.50 ± 0.21 and 5.08 ± 0.19 km/h, respectively), in 10 km (5.38 ± 0.21 and 5.05 ± 0.26 km/h, respectively) and in 25 km (5.03 ± 0.32 and 4.58 ± 0.27 km/h, respectively). In the annual ten fastest, swimming speed remained constant in 5 km in women (5.02 ± 0.19 km/h) but decreased significantly and linearly in men from 5.42 ± 0.03 km/h to 5.39 ± 0.02 km/h. In 10 km, swimming speed increased significantly and linearly in women from 4.75 ± 0.01 km/h to 5.74 ± 0.01 km/h but remained stable in men at 5.36 ± 0.21 km/h. In 25 km, swimming speed decreased significantly and linearly in women from 4.60 ± 0.06 km/h to 4.44 ± 0.08 km/h but remained unchanged at 4.93 ± 0.34 km/h in men. For the annual fastest, the sex difference in swimming speed remained unchanged in 5 km (7.6 ± 3.0%), 10 km (6.1 ± 2.5%) and 25 km (9.0 ± 3.7%). For the annual ten fastest, the sex difference remained stable in 5 km at 7.6 ± 0.6%, decreased significantly and linearly in 10 km from 7.7 ± 0.7% to 1.2 ± 0.3% and increased significantly and linearly from 4.7 ± 1.4% to 9.6 ± 1.5% in 25 km. Conclusions To summarize, elite female open-water ultra-distance swimmers improved in 10 km but impaired in 25 km leading to a linear decrease in sex difference in 10 km and a linear increase in sex difference in 25 km. The linear changes in sex differences

  18. Heparin affin regulatory peptide modulates the endogenous anticoagulant activity of heparin and heparan sulphate mimetics.

    PubMed

    Mejdoubi-Charef, Najet; Courty, José; Sineriz, Fernando; Papy-Garcia, Dulce; Charef, Said

    2012-11-01

    Pleiotrophin, also known as heparin affin regulatory peptide (HARP), is a growth factor expressed in various tissues and cell lines. In this work, HARP was tested for its capacity to modulate the anticoagulant activity of heparin and heparan sulphate mimetics (OTR4120). We used both in vitro and in vivo assays. HARP was found to be differently effective for neutralization of the anticoagulant activity of the mimetic heparan sulphate (OTR4120) and heparin in purified system and human plasma. HARP was shown to compete with both antithrombin and thrombin for binding to heparin and to OTR4120, respectively. In the presence of OTR4120, the V(max) was constant and the calculated maximum velocity was 1.56 U/min; the thrombin Km value (0.011 nM) was affected by HARP concentrations. The Km (HARP) value was 0.085 nM, which is consistent with high affinity of HARP to OTR4120. Under the same conditions, initial velocity patterns for antithrombin-heparin were determined in the presence or in the absence of HARP. The antithrombin value Km (0.022 nM) was affected by HARP (0.077 nM). HARP exhibits efficacy equivalent to or greater than protamine. Interestingly, intraperitoneally administered HARP decreased the anticoagulant activity of heparin and of OTR4120 in mice. Taken together, these data provide the first evidence for a physiological role of HARP in the modulation of anticoagulant activity of heparin and heparin-like material.

  19. PHARMACEUTICAL AND BIOMEDICAL APPLICATIONS OF AFFINITY CHROMATOGRAPHY: RECENT TRENDS AND DEVELOPMENTS

    PubMed Central

    Hage, David S.; Anguizola, Jeanethe A.; Bi, Cong; Li, Rong; Matsuda, Ryan; Papastavros, Efthimia; Pfaunmiller, Erika; Vargas, John; Zheng, Xiwei

    2012-01-01

    Affinity chromatography is a separation technique that has become increasingly important in work with biological samples and pharmaceutical agents. This method is based on the use of a biologically-related agent as a stationary phase to selectively retain analytes or to study biological interactions. This review discusses the basic principles behind affinity chromatography and examines recent developments that have occurred in the use of this method for biomedical and pharmaceutical analysis. Techniques based on traditional affinity supports are discussed, but an emphasis is placed on methods in which affinity columns are used as part of HPLC systems or in combination with other analytical methods. General formats for affinity chromatography that are considered include step elution schemes, weak affinity chromatography, affinity extraction and affinity depletion. Specific separation techniques that are examined include lectin affinity chromatography, boronate affinity chromatography, immunoaffinity chromatography, and immobilized metal ion affinity chromatography. Approaches for the study of biological interactions by affinity chromatography are also presented, such as the measurement of equilibrium constants, rate constants, or competition and displacement effects. In addition, related developments in the use of immobilized enzyme reactors, molecularly imprinted polymers, dye ligands and aptamers are briefly considered. PMID:22305083

  20. Affine differential geometry analysis of human arm movements.

    PubMed

    Flash, Tamar; Handzel, Amir A

    2007-06-01

    Humans interact with their environment through sensory information and motor actions. These interactions may be understood via the underlying geometry of both perception and action. While the motor space is typically considered by default to be Euclidean, persistent behavioral observations point to a different underlying geometric structure. These observed regularities include the "two-thirds power law", which connects path curvature with velocity, and "local isochrony", which prescribes the relation between movement time and its extent. Starting with these empirical observations, we have developed a mathematical framework based on differential geometry, Lie group theory and Cartan's moving frame method for the analysis of human hand trajectories. We also use this method to identify possible motion primitives, i.e., elementary building blocks from which more complicated movements are constructed. We show that a natural geometric description of continuous repetitive hand trajectories is not Euclidean but equi-affine. Specifically, equi-affine velocity is piecewise constant along movement segments, and movement execution time for a given segment is proportional to its equi-affine arc-length. Using this mathematical framework, we then analyze experimentally recorded drawing movements. To examine movement segmentation and classification, the two fundamental equi-affine differential invariants-equi-affine arc-length and curvature are calculated for the recorded movements. We also discuss the possible role of conic sections, i.e., curves with constant equi-affine curvature, as motor primitives and focus in more detail on parabolas, the equi-affine geodesics. Finally, we explore possible schemes for the internal neural coding of motor commands by showing that the equi-affine framework is compatible with the common model of population coding of the hand velocity vector when combined with a simple assumption on its dynamics. We then discuss several alternative explanations

  1. Adjoint affine fusion and tadpoles

    NASA Astrophysics Data System (ADS)

    Urichuk, Andrew; Walton, Mark A.

    2016-06-01

    We study affine fusion with the adjoint representation. For simple Lie algebras, elementary and universal formulas determine the decomposition of a tensor product of an integrable highest-weight representation with the adjoint representation. Using the (refined) affine depth rule, we prove that equally striking results apply to adjoint affine fusion. For diagonal fusion, a coefficient equals the number of nonzero Dynkin labels of the relevant affine highest weight, minus 1. A nice lattice-polytope interpretation follows and allows the straightforward calculation of the genus-1 1-point adjoint Verlinde dimension, the adjoint affine fusion tadpole. Explicit formulas, (piecewise) polynomial in the level, are written for the adjoint tadpoles of all classical Lie algebras. We show that off-diagonal adjoint affine fusion is obtained from the corresponding tensor product by simply dropping non-dominant representations.

  2. News from KM3NeT

    SciTech Connect

    Katz, Ulrich F.; Collaboration: KM3NeT Collaboration

    2014-11-18

    KM3NeT is a future research infrastructure in the Mediterranean Sea, hosting a multi-cubic-kilometre neutrino telescope and nodes for Earth and Sea sciences. In this report we shortly summarise the genesis of the KM3NeT project and present key elements of its technical design. The physics objectives of the KM3NeT neutrino telescope and some selected sensitivity estimates are discussed. Finally, some first results from prototype operations and the next steps towards implementation – in particular the first construction phase in 2014/15 – are described.

  3. Fact Sheet for KM200 Front-end Electronics

    SciTech Connect

    Ianakiev, Kiril Dimitrov; Iliev, Metodi; Swinhoe, Martyn Thomas

    2015-07-08

    The KM200 device is a versatile, configurable front-end electronics boards that can be used as a functional replacement for Canberra’s JAB-01 boards based on the Amptek A-111 hybrid chip, which continues to be the preferred choice of electronics for large number of the boards in junction boxes of multiplicity counters that process the signal from an array of 3He detectors. Unlike the A-111 chip’s fixed time constants and sensitivity range, the shaping time and sensitivity of the new KM200 can be optimized for demanding applications such as spent fuel, and thus could improve the safeguards measurements of existing systems where the A-111 or PDT electronics does not perform well.

  4. Real Km-synthesis via generalized Popov multipliers

    NASA Technical Reports Server (NTRS)

    Chiang, R. Y.; Safonov, M. G.

    1992-01-01

    The authors refine their H-infinity control designs presented at the 1990 and 1991 American Control Conference by introducing a new real Km-synthesis technique involving the use of generalized Popov multipliers. This multiplier technique substantially reduces, and in some cases may even eliminate altogether, the conservativeness associated with traditional Km-synthesis solutions in which all uncertainties are treated as complex, even when they arise from real parameters such as the masses and spring constants in the benchmark problem. The design results demonstrate how this approach permits a very precise analysis of the intrinsic tradeoffs between robustness, performance, and control energy requirements. Also included is an open-loop H-infinity prefilter design that makes it possible to address the command response shaping issue. The design concept has been applied to the benchmark problem no. 4 and successfully removes the initial undesired transient and cuts down the percent overshoot.

  5. Status of KM3NeT

    NASA Astrophysics Data System (ADS)

    Riccobene, G.

    2016-07-01

    The recent observation of cosmic neutrinos by IceCube has pushed the quest towards the identification of cosmic sources of high-energy particles. The KM3NeT Collaboration is now ready to launch the massive construction of detection units to be installed in deep sea to build a km-cubic size neutrino telescope. The main elements of the detector, the status of the project and the expected perfomances are briefly reported.

  6. A MEMS Dielectric Affinity Glucose Biosensor

    PubMed Central

    Huang, Xian; Li, Siqi; Davis, Erin; Li, Dachao; Wang, Qian; Lin, Qiao

    2013-01-01

    Continuous glucose monitoring (CGM) sensors based on affinity detection are desirable for long-term and stable glucose management. However, most affinity sensors contain mechanical moving structures and complex design in sensor actuation and signal readout, limiting their reliability in subcutaneously implantable glucose detection. We have previously demonstrated a proof-of-concept dielectric glucose sensor that measured pre-mixed glucose-sensitive polymer solutions at various glucose concentrations. This sensor features simplicity in sensor design, and possesses high specificity and accuracy in glucose detection. However, lack of glucose diffusion passage, this device is unable to fulfill real-time in-vivo monitoring. As a major improvement to this device, we present in this paper a fully implantable MEMS dielectric affinity glucose biosensor that contains a perforated electrode embedded in a suspended diaphragm. This capacitive-based sensor contains no moving parts, and enables glucose diffusion and real-time monitoring. The experimental results indicate that this sensor can detect glucose solutions at physiological concentrations and possesses good reversibility and reliability. This sensor has a time constant to glucose concentration change at approximately 3 min, which is comparable to commercial systems. The sensor has potential applications in fully implantable CGM that require excellent long-term stability and reliability. PMID:24511215

  7. A new affinity method for purification of bovine testicular hyaluronidase enzyme and an investigation of the effects of some compounds on this enzyme.

    PubMed

    Kaya, Mustafa Oguzhan; Arslan, Oktay; Guler, Ozen Ozensoy

    2015-01-01

    In this study, a new affinity gel for the purification of bovine testicular hyaluronidase (BTH) was synthesized. L-Tyrosine was added as the extension arm to the Sepharose-4B activated with cyanogen bromide. m-Anisidine is a specific inhibitor of BTH enzyme. m-Anisidine was clamped to the newly formed Sepharose-4B-L-tyrosine as a ligand. As a result, an affinity gel having the chemical structure of Sepharose-4B-L-tyrosine-m-anisidine was obtained. BTH purified by ammonium sulfate precipitation and affinity chromatography was obtained with a 16.95% yield and 881.78 degree of purity. The kinetic constants K(M) and V(Max) for BTH were determined by using hyaluronic acid as a substrate. K(M) and V(Max) values obtained from the Lineweaver-Burk graph were found to be 2.23 mM and 19.85 U/mL, respectively. In vitro effects of some chemicals were determined on purified BTH enzyme. Some chemically active ingredients were 1,1-dimethyl piperidinium chloride, β-naphthoxyacetic acid and gibberellic acid. Gibberellic acid showed the best inhibition effect on BTH. PMID:25373501

  8. Affinity chromatography: a historical perspective.

    PubMed

    Hage, David S; Matsuda, Ryan

    2015-01-01

    Affinity chromatography is one of the most selective and versatile forms of liquid chromatography for the separation or analysis of chemicals in complex mixtures. This method makes use of a biologically related agent as the stationary phase, which provides an affinity column with the ability to bind selectively and reversibly to a given target in a sample. This review examines the early work in this method and various developments that have lead to the current status of this technique. The general principles of affinity chromatography are briefly described as part of this discussion. Past and recent efforts in the generation of new binding agents, supports, and immobilization methods for this method are considered. Various applications of affinity chromatography are also summarized, as well as the influence this field has played in the creation of other affinity-based separation or analysis methods. PMID:25749941

  9. Affine conformal vectors in space-time

    NASA Astrophysics Data System (ADS)

    Coley, A. A.; Tupper, B. O. J.

    1992-05-01

    All space-times admitting a proper affine conformal vector (ACV) are found. By using a theorem of Hall and da Costa, it is shown that such space-times either (i) admit a covariantly constant vector (timelike, spacelike, or null) and the ACV is the sum of a proper affine vector and a conformal Killing vector or (ii) the space-time is 2+2 decomposable, in which case it is shown that no ACV can exist (unless the space-time decomposes further). Furthermore, it is proved that all space-times admitting an ACV and a null covariantly constant vector (which are necessarily generalized pp-wave space-times) must have Ricci tensor of Segré type {2,(1,1)}. It follows that, among space-times admitting proper ACV, the Einstein static universe is the only perfect fluid space-time, there are no non-null Einstein-Maxwell space-times, and only the pp-wave space-times are representative of null Einstein-Maxwell solutions. Otherwise, the space-times can represent anisotropic fluids and viscous heat-conducting fluids, but only with restricted equations of state in each case.

  10. Origins of the 520-km discontinuity

    NASA Astrophysics Data System (ADS)

    Vinnik, Lev

    2016-04-01

    The 520-km discontinuity is often explained by the phase transition from wadsleyite to ringwoodite, although the theoretical impedance of this transition is so small that the related converted and reflected seismic phases could hardly be seen in the seismograms. At the same time there are numerous reports on observations of a large discontinuity at this depth, especially in the data on SS precursors and P-wave wide-angle reflections. Revenaugh and Jordan (1991) argued that this discontinuity is related to the garnet/post-garnet transformation. Gu et al. (1998) preferred very deep continental roots extending into the transition zone. Deuss and Woodhouse proposed splitting of the 520-km discontinuity into two discontinuities, whilst Bock (1994) denied evidence of the 520-km discontinuity in the SS precursors. Our approach to this problem is based on the analysis of S and P receiver functions. Most of our data are related to hot-spots in and around the Atlantic where the appropriate converted phases are often comparable in amplitude with P410s and S410p. Both S and P receiver functions provide strong evidence of a low S velocity in a depth range from 450 km to 510 km at some locations. The 520-km discontinuity appears to be the base of this low-velocity layer. Our observations of the low S velocity in the upper transition zone are very consistent with the indications of a drop in the solidus temperature of carbonated peridotite in the same pressure range (Keshav et al. 2011), and this phenomenon provides a viable alternative to the other explanations of the 520-km discontinuity.

  11. The 1% concordance Hubble constant

    SciTech Connect

    Bennett, C. L.; Larson, D.; Weiland, J. L.; Hinshaw, G.

    2014-10-20

    The determination of the Hubble constant has been a central goal in observational astrophysics for nearly a hundred years. Extraordinary progress has occurred in recent years on two fronts: the cosmic distance ladder measurements at low redshift and cosmic microwave background (CMB) measurements at high redshift. The CMB is used to predict the current expansion rate through a best-fit cosmological model. Complementary progress has been made with baryon acoustic oscillation (BAO) measurements at relatively low redshifts. While BAO data do not independently determine a Hubble constant, they are important for constraints on possible solutions and checks on cosmic consistency. A precise determination of the Hubble constant is of great value, but it is more important to compare the high and low redshift measurements to test our cosmological model. Significant tension would suggest either uncertainties not accounted for in the experimental estimates or the discovery of new physics beyond the standard model of cosmology. In this paper we examine in detail the tension between the CMB, BAO, and cosmic distance ladder data sets. We find that these measurements are consistent within reasonable statistical expectations and we combine them to determine a best-fit Hubble constant of 69.6 ± 0.7 km s{sup –1} Mpc{sup –1}. This value is based upon WMAP9+SPT+ACT+6dFGS+BOSS/DR11+H {sub 0}/Riess; we explore alternate data combinations in the text. The combined data constrain the Hubble constant to 1%, with no compelling evidence for new physics.

  12. The Influence of Organizational Culture on Affinity for Knowledge Management Practices of Registered Nurses

    ERIC Educational Resources Information Center

    Allen, Gregory

    2013-01-01

    This study addressed the problems of hospitals' duplicated effort and ad hoc knowledge management (KM) practices. The purpose of this quantitative study was to examine the focus and type of organizational culture in order to describe and predict the relationship between organizational culture and the affinity for KM of nurses working in health…

  13. On the Khinchin Constant

    NASA Technical Reports Server (NTRS)

    Bailey, David H.; Borwein, Jonathan M.; Crandall, Richard E.; Craw, James M. (Technical Monitor)

    1995-01-01

    We prove known identities for the Khinchin constant and develop new identities for the more general Hoelder mean limits of continued fractions. Any of these constants can be developed as a rapidly converging series involving values of the Riemann zeta function and rational coefficients. Such identities allow for efficient numerical evaluation of the relevant constants. We present free-parameter, optimizable versions of the identities, and report numerical results.

  14. Affine generalization of the Komar complex of general relativity

    NASA Astrophysics Data System (ADS)

    Mielke, Eckehard W.

    2001-02-01

    On the basis of the ``on shell'' Noether identities of the metric-affine gauge approach of gravity, an affine superpotential is derived which comprises the energy- and angular-momentum content of exact solutions. In the special case of general relativity (GR) or its teleparallel equivalent, the Komar or Freud complex, respectively, are recovered. Applying this to the spontaneously broken anti-de Sitter gauge model of McDowell and Mansouri with an induced Euler term automatically yields the correct mass and spin of the Kerr-AdS solution of GR with a (induced) cosmological constant without the factor two discrepancy of the Komar formula.

  15. The hubble constant.

    PubMed

    Huchra, J P

    1992-04-17

    The Hubble constant is the constant of proportionality between recession velocity and distance in the expanding universe. It is a fundamental property of cosmology that sets both the scale and the expansion age of the universe. It is determined by measurement of galaxy The Hubble constant is the constant of proportionality between recession velocity and development of new techniques for the measurements of galaxy distances, both calibration uncertainties and debates over systematic errors remain. Current determinations still range over nearly a factor of 2; the higher values favored by most local measurements are not consistent with many theories of the origin of large-scale structure and stellar evolution. PMID:17743107

  16. The cosmological constant

    NASA Technical Reports Server (NTRS)

    Carroll, Sean M.; Press, William H.; Turner, Edwin L.

    1992-01-01

    The cosmological constant problem is examined in the context of both astronomy and physics. Effects of a nonzero cosmological constant are discussed with reference to expansion dynamics, the age of the universe, distance measures, comoving density of objects, growth of linear perturbations, and gravitational lens probabilities. The observational status of the cosmological constant is reviewed, with attention given to the existence of high-redshift objects, age derivation from globular clusters and cosmic nuclear data, dynamical tests of Omega sub Lambda, quasar absorption line statistics, gravitational lensing, and astrophysics of distant objects. Finally, possible solutions to the physicist's cosmological constant problem are examined.

  17. Beyond the Hubble Constant

    NASA Astrophysics Data System (ADS)

    1995-08-01

    about the distances to galaxies and thereby about the expansion rate of the Universe. A simple way to determine the distance to a remote galaxy is by measuring its redshift, calculate its velocity from the redshift and divide this by the Hubble constant, H0. For instance, the measured redshift of the parent galaxy of SN 1995K (0.478) yields a velocity of 116,000 km/sec, somewhat more than one-third of the speed of light (300,000 km/sec). From the universal expansion rate, described by the Hubble constant (H0 = 20 km/sec per million lightyears as found by some studies), this velocity would indicate a distance to the supernova and its parent galaxy of about 5,800 million lightyears. The explosion of the supernova would thus have taken place 5,800 million years ago, i.e. about 1,000 million years before the solar system was formed. However, such a simple calculation works only for relatively ``nearby'' objects, perhaps out to some hundred million lightyears. When we look much further into space, we also look far back in time and it is not excluded that the universal expansion rate, i.e. the Hubble constant, may have been different at earlier epochs. This means that unless we know the change of the Hubble constant with time, we cannot determine reliable distances of distant galaxies from their measured redshifts and velocities. At the same time, knowledge about such change or lack of the same will provide unique information about the time elapsed since the Universe began to expand (the ``Big Bang''), that is, the age of the Universe and also its ultimate fate. The Deceleration Parameter q0 Cosmologists are therefore eager to determine not only the current expansion rate (i.e., the Hubble constant, H0) but also its possible change with time (known as the deceleration parameter, q0). Although a highly accurate value of H0 has still not become available, increasing attention is now given to the observational determination of the second parameter, cf. also the Appendix at the

  18. The estimation of 550 km x 550 km mean gravity anomalies. [from free atmosphere gravimetry data

    NASA Technical Reports Server (NTRS)

    Williamson, M. R.; Gaposchkin, E. M.

    1975-01-01

    The calculation of 550 km X 550 km mean gravity anomalies from 1 degree X 1 degree mean free-air gravimetry data is discussed. The block estimate procedure developed by Kaula was used, and estimates for 1452 of the 1654 blocks were obtained.

  19. Large Circular Basin - 1300-km diameter

    NASA Technical Reports Server (NTRS)

    1974-01-01

    Close-up view of one-half of a 1300-km diameter circular basin the largest observed on Mercury. The other half is hidden beyond the terminator to the left. Hills and valleys extend in a radial fashion outward from the main ring. Interior of the large basin is completely flooded by plains materials; adjacent lowlands are also partially flooded and superimposed on the plains are bowl shaped craters. Wrinkle ridges are abundant on the plains materials. The area shown is 1008 miles (1600 km) from the top to the bottom of the picture. Sun's illumination is from the right. Blurred linear lines extending across the picture near bottom are missing data lines that have been filled in by the computer. Mariner 10 encountered Mercury on Friday, March 29th, 1974, passing the planet on the darkside 431 miles (690-km) from the surface.

    The Mariner 10 mission, managed by the Jet Propulsion Laboratory for NASA's Office of Space Science, explored Venus in February 1974 on the way to three encounters with Mercury-in March and September 1974 and in March 1975. The spacecraft took more than 7,000 photos of Mercury, Venus, the Earth and the Moon.

    NOTE: This image was scanned from physical media.

  20. Km3Net Italy - Seafloor network

    NASA Astrophysics Data System (ADS)

    Papaleo, Riccardo

    2016-04-01

    The KM3NeT European project aims to construct a large volume underwater neutrino telescope in the depths of the Mediterranean Sea. INFN and KM3NeT collaboration, thanks to a dedicated funding of 21.000.000 € (PON 2007-2013), are committed to build and deploy the Phase 1 of the telescope, composed of a network of detection units: 8 towers, equipped with single photomultiplier optical modules, and 24 strings, equipped with multi-photomultipliers optical modules. All the towers and strings are connected to the main electro optical cable by means of a network of junction boxes and electro optical interlink cables. Each junction box is an active node able to provide all the necessary power to the detection units and to guarantee the data transmission between the detector and the on-shore control station. The KM3NeT Italia project foresees the realization and the installation of the first part of the deep sea network, composed of three junction boxes, one for the towers and two for the strings. In July 2015, two junction boxes have been deployed and connected to the new cable termination frame installed during the same sea campaign. The third and last one will be installed in November 2015. The status of the deep sea network is presented together with technical details of the project.

  1. Fundamental Physical Constants

    National Institute of Standards and Technology Data Gateway

    SRD 121 CODATA Fundamental Physical Constants (Web, free access)   This site, developed in the Physics Laboratory at NIST, addresses three topics: fundamental physical constants, the International System of Units (SI), which is the modern metric system, and expressing the uncertainty of measurement results.

  2. Calculation of magnetostriction constants

    NASA Astrophysics Data System (ADS)

    Tatebayashi, T.; Ohtsuka, S.; Ukai, T.; Mori, N.

    1986-02-01

    The magnetostriction constants h1 and h2 for Ni and Fe metals and the anisotropy constants K1 and K2 for Fe metal are calculated on the basis of the approximate d bands obtained by Deegan's prescription, by using Gilat-Raubenheimer's method. The obtained results are compared with the experimental ones.

  3. Thermodynamic mixing of molecular states of the epidermal growth factor receptor modulates macroscopic ligand binding affinity.

    PubMed Central

    Holbrook, M R; Slakey, L L; Gross, D J

    2000-01-01

    The epidermal growth factor receptor (EGFr), when expressed on the cell surface, has long been known to display two distinct affinities for epidermal growth factor (EGF) binding. In addition, the treatment of cells expressing the EGFr with phorbol esters has been shown to cause a loss of the high-affinity binding capacity of the receptor. In the present study, point mutations that alter acidic or phosphorylation sites have been made in an intracellular domain near Tyr-992 (residues 988-992) of the EGFr. Equilibrium (125)I-EGF binding studies demonstrate that the conversion of Tyr-992 into glutamate induces a 4-fold decrease in the EGFr apparent low-affinity dissociation constant, whereas the mutation of two acidic residues, Asp-988 and Glu-991, or the conversion of Tyr-992 into phenylalanine does not alter EGFr affinity. Phorbol ester treatment of EGFr-expressing Chinese hamster ovary cells results in a loss of high-affinity binding and an increase in the apparent low-affinity dissociation constant of the receptor, similar to the effect of a truncation mutant in which the C-terminal 190 residues are deleted. These results are examined in the context of a new model for regulation of the affinity of the EGFr for EGF in which a cytosolic particle stabilizes the high-affinity conformation of the EGFr and a rapid equilibrium exists between EGFr high-affinity and low-affinity conformations. This model demonstrates that the macroscopic affinities of the EGFr can differ from the affinities of individual EGFr molecules and provides a theoretical framework whereby the measured affinities of the EGFr are modulated by intracellular interactions. PMID:11062062

  4. Separate Einstein-Eddington Spaces and the Cosmological Constant

    NASA Astrophysics Data System (ADS)

    Azri, Hemza

    2016-07-01

    In affine variational principle, a symmetric linear connection is taken as a fundamental field. The metric tensor is generated dynamically, and it appears as a canonically conjugate to the connection. From this picture, Einstein's gravity with a cosmological constant can be obtained by a covariant Legendre transformation of the affine Lagrangian. In this talk, we apply this formalism (first proposed by Kijowski) to product spaces and the cosmological constant problem. From pure affine variational principle, we derive the separate Einstein space described by its Ricci tensor. The derived equations spite into two field equations of motion that describe two maximally symmetric spaces with two non independent cosmological constants. We propose that the invariance of the bi-field equations under projections on the separate spaces, may render one of the cosmological constants to zero. We also formulate the model in the presence of matter fields. The resulted separate Einstein-Eddington spaces maybe considered as two states that describe the universe before and after inflation. A possibly interesting affine action for a general perfect fluid is also proposed. It turns out that the condition which leads to zero cosmological constant in the vacuum case, eliminates here the effects of the gravitational mass density of the perfect fluid, and the dynamic of the universe in its final state is governed by only the inertial mass density of the fluid. We present no new solutions to the problems associated with inflation.

  5. High-affinity Cyclic Peptide Matriptase Inhibitors*

    PubMed Central

    Quimbar, Pedro; Malik, Uru; Sommerhoff, Christian P.; Kaas, Quentin; Chan, Lai Y.; Huang, Yen-Hua; Grundhuber, Maresa; Dunse, Kerry; Craik, David J.; Anderson, Marilyn A.; Daly, Norelle L.

    2013-01-01

    The type II transmembrane serine protease matriptase is a key activator of multiple signaling pathways associated with cell proliferation and modification of the extracellular matrix. Deregulated matriptase activity correlates with a number of diseases, including cancer and hence highly selective matriptase inhibitors may have therapeutic potential. The plant-derived cyclic peptide, sunflower trypsin inhibitor-1 (SFTI-1), is a promising drug scaffold with potent matriptase inhibitory activity. In the current study we have analyzed the structure-activity relationships of SFTI-1 and Momordica cochinchinensis trypsin inhibitor-II (MCoTI-II), a structurally divergent trypsin inhibitor from Momordica cochinchinensis that also contains a cyclic backbone. We show that MCoTI-II is a significantly more potent matriptase inhibitor than SFTI-1 and that all alanine mutants of both peptides, generated using positional scanning mutagenesis, have decreased trypsin affinity, whereas several mutations either maintain or result in enhanced matriptase inhibitory activity. These intriguing results were used to design one of the most potent matriptase inhibitors known to date with a 290 pm equilibrium dissociation constant, and provide the first indication on how to modulate affinity for matriptase over trypsin in cyclic peptides. This information might be useful for the design of more selective and therapeutically relevant inhibitors of matriptase. PMID:23548907

  6. Cesium cation affinities and basicities

    NASA Astrophysics Data System (ADS)

    Gal, Jean-François; Maria, Pierre-Charles; Massi, Lionel; Mayeux, Charly; Burk, Peeter; Tammiku-Taul, Jaana

    2007-11-01

    This review focuses on the quantitative data related to cesium cation interaction with neutral or negatively charged ligands. The techniques used for measuring the cesium cation affinity (enthalpies, CCA), and cesium cation basicities (Gibbs free energies, CCB) are briefly described. The quantum chemical calculations methods that were specifically designed for the determination of cesium cation adduct structures and the energetic aspects of the interaction are discussed. The experimental results, obtained essentially from mass spectrometry techniques, and complemented by thermochemical data, are tabulated and commented. In particular, the correlations between cesium cation affinities and lithium cation affinities for the various kinds of ligands (rare gases, polyatomic neutral molecules, among them aromatic compounds and negative ions) serve as a basis for the interpretation of the diverse electrostatic modes of interaction. A brief account of some recent analytical applications of ion/molecule reactions with Cs+, as well as other cationization approaches by Cs+, is given.

  7. Space Shuttle astrodynamical constants

    NASA Technical Reports Server (NTRS)

    Cockrell, B. F.; Williamson, B.

    1978-01-01

    Basic space shuttle astrodynamic constants are reported for use in mission planning and construction of ground and onboard software input loads. The data included here are provided to facilitate the use of consistent numerical values throughout the project.

  8. The cosmological constant problem

    SciTech Connect

    Dolgov, A.D.

    1989-05-01

    A review of the cosmological term problem is presented. Baby universe model and the compensating field model are discussed. The importance of more accurate data on the Hubble constant and the Universe age is stressed. 18 refs.

  9. "Clickable" agarose for affinity chromatography.

    PubMed

    Punna, Sreenivas; Kaltgrad, Eiton; Finn, M G

    2005-01-01

    Successful purification of biological molecules by affinity chromatography requires the attachment of desired ligands to biocompatible chromatographic supports. The Cu(I)-catalyzed cycloaddition of azides and alkynes-the premier example of "click chemistry"-is an efficient way to make covalent connections among diverse molecules and materials. Both azide and alkyne units are highly selective in their reactivity, being inert to most chemical functionalities and stable to wide ranges of solvent, temperature, and pH. We show that agarose beads bearing alkyne and azide groups can be easily made and are practical precursors to functionalized agarose materials for affinity chromatography.

  10. Constant potential pulse polarography

    USGS Publications Warehouse

    Christie, J.H.; Jackson, L.L.; Osteryoung, R.A.

    1976-01-01

    The new technique of constant potential pulse polarography, In which all pulses are to be the same potential, is presented theoretically and evaluated experimentally. The response obtained is in the form of a faradaic current wave superimposed on a constant capacitative component. Results obtained with a computer-controlled system exhibit a capillary response current similar to that observed In normal pulse polarography. Calibration curves for Pb obtained using a modified commercial pulse polarographic instrument are in good accord with theoretical predictions.

  11. Laboratory 20-km cycle time trial reproducibility.

    PubMed

    Zavorsky, G S; Murias, J M; Gow, J; Kim, D J; Poulin-Harnois, C; Kubow, S; Lands, L C

    2007-09-01

    This study evaluated the reproducibility of laboratory based 20-km time trials in well trained versus recreational cyclists. Eighteen cyclists (age = 34 +/- 8 yrs; body mass index = 23.1 +/- 2.2 kg/m (2); VO(2max) = 4.19 +/- 0.65 L/min) completed three 20-km time trials over a month on a Velotron cycle ergometer. Average power output (PO) (W), speed, and heart rate (HR) were significantly lower in the first time trial compared to the second and third time trial. The coefficients of variation (CV) between the second and third trial of the top eight performers for average PO, time to completion, and speed were 1.2 %, 0.6 %, 0.5 %, respectively, compared to 4.8 %, 2.0 %, and 2.3 % for the bottom ten. In addition, the average HR, VO(2), and percentage of VO(2max) were similar between trials. This study demonstrated that (1) a familiarization session improves the reliability of the measurements (i.e., average PO, time to completion and speed), and (2) the CV was much smaller for the best performers.

  12. Global modeling with GEOS-5 from 50-km to 1-km with a single unified GCM

    NASA Astrophysics Data System (ADS)

    Putman, William; Suarez, Max; Molod, Andrea; Barahona, Donifan

    2015-04-01

    The Goddard Earth Observing System model (GEOS-5) of the Global Modeling and Assimilation Office (GMAO) at NASA Goddard Space Flight Center is uniquely designed to adapt to increasing resolution. This supports application of GEOS-5 for decadal scale climate simulation and reanalysis with a horizontal resolution of 50-kilometers (km), high-resolution numerical weather prediction at 25- to 14-km, and global mesoscale modeling at resolutions of 7- to 1.5-km. Resolution-aware parameterizations and dynamics support this diverse portfolio of applications within a single unified GEOS-5 GCM code-base. We will discuss the adaptation of physics parameterizations with increasing resolution. This includes the role of deep convective parameterization, the move to an improved two-moment microphysics scheme, the need for shallow convective parameterization, and the role of non-hydrostatic dynamics and implicit/explicit damping. Parameterization and dynamics evaluation are explored not only in global integrations with GEOS-5 but with radiative convective equilibrium tests that permit the rapid exploration of high-resolution simulations in a smaller doubly periodic Cartesian domain. Simulation results will highlight intercomparisons of model biases in cloud forcing and precipitation from the 30-year 50-km MERRA-2 reanalysis, 50- to 25-km free-running AMIP simulations, a 2-year 7-km global mesoscale simulation, and monthly global simulations at 3.5-km. A global 1.5-km simulation with GEOS-5 highlights our pursuit of truly convection permitting global simulations with GEOS-5. The tuning evaluation for this simulation using doubly periodic radiative convective equilibrium experiments will be discussed.

  13. Overview of affinity tags for protein purification.

    PubMed

    Kimple, Michelle E; Brill, Allison L; Pasker, Renee L

    2013-01-01

    Addition of an affinity tag is a useful method for differentiating recombinant proteins expressed in bacterial and eukaryotic expression systems from the background of total cellular proteins, as well as for detecting protein-protein interactions. This overview describes the historical basis for the development of affinity tags, affinity tags that are commonly used today, how to choose an appropriate affinity tag for a particular purpose, and several recently developed affinity tag technologies that may prove useful in the near future. PMID:24510596

  14. Coenzyme-like ligands for affinity isolation of cholesterol oxidase.

    PubMed

    Xin, Yu; Lu, Liushen; Wang, Qing; Zhang, Ling; Tong, Yanjun; Wang, Wu

    2016-05-15

    Two coenzyme-like chemical ligands were designed and synthesized for affinity isolation of cholesterol oxidase (COD). To simulate the structure of natural coenzyme of COD (flavin adenine dinucleotide (FAD)), on Sepharose beads, 5-aminouracil, cyanuric chloride and 1, 4-butanediamine were composed and then modified. The COD gene from Brevibacterium sp. (DQ345780) was expressed in Escherichia coli BL21 (DE3), and then the sorbents were applied to adsorption analysis with the pure enzyme. Subsequently, the captured enzyme was applied to SDS-PAGE and activity analysis. As calculated, the theoretical maximum adsorption (Qmax) of the two affinity sorbents (RL-1 and RL-2) were ∼83.5 and 46.3mg/g wet gel; and the desorption constant Kd of the two sorbents were ∼6.02×10(-4) and 1.19×10(-4)μM. The proteins after cell lysis were applied to affinity isolation, and then after one step of affinity binding on the two sorbents, the protein recoveries of RL-1 and RL-2 were 9.2% and 9.7%; the bioactivity recoveries were 92.7% and 91.3%, respectively. SDS-PAGE analysis revealed that the purities of COD isolated with the two affinity sorbents were approximately 95%. PMID:26856529

  15. Fluorogen-Activating-Proteins as Universal Affinity Biosensors for Immunodetection

    PubMed Central

    Gallo, Eugenio; Vasilev, Kalin V.; Jarvik, Jonathan

    2014-01-01

    Fluorogen-activating-proteins (FAPs) are a novel platform of fluorescence biosensors utilized for protein discovery. The technology currently demands molecular manipulation methods that limit its application and adaptability. Here, we highlight an alternative approach based on universal affinity reagents for protein detection. The affinity reagents were engineered as bi-partite fusion proteins, where the specificity moiety is derived from IgG-binding proteins –Protein-A or Protein-G – and the signaling element is a FAP. In this manner, primary antibodies provide the antigenic selectivity against a desired protein in biological samples, while FAP affinity reagents target the constant region (Fc) of antibodies and provide the biosensor component of detection. Fluorescence results using various techniques indicate minimal background and high target specificity for exogenous and endogenous proteins in mammalian cells. Additionally, FAP-based affinity reagents provide enhanced properties of detection previously absent using conventional affinity systems. Distinct features explored in this report include: (1) unfixed signal wavelengths (excitation and emission) determined by the particular fluorogen chosen, (2) real-time user controlled fluorescence on-set and off-set, (3) signal wavelength substitution while performing live analysis, and (4) enhanced resistance to photobleaching. PMID:24122476

  16. Ribulose Diphosphate Carboxylase from Freshly Ruptured Spinach Chloroplasts Having an in Vivo Km[CO(2)].

    PubMed

    Bahr, J T; Jensen, R G

    1974-01-01

    The properties of a form of ribulose diphosphate carboxylase having a high affinity for CO(2) have been studied. Its apparent Km(HCO(3) (-)) of 0.5 to 0.8 mm (pH 7.8) and calculated Km(CO(2)) of 11 to 18 mum are comparable to the values exhibited by intact chloroplasts during photosynthesis. This form of the enzyme was released from chloroplasts in hypotonic media and was unstable, rapidly converting to a form having a high Km(HCO(3) (-)) of 20 to 25 mm similar to that for the purified enzyme. Incubation of the enzyme with MgCl(2) and HCO(3) (-) yielded a third form with an intermediate Km(HCO(3) (-)) of 2.5 to 3.0 mm.The low Km form had sufficient activity both at air levels of CO(2) and at saturating CO(2) to account for the rates of photosynthesis by intact chloroplasts. The low Km form could be stabilized in the presence of ribose 5-phosphate, adenosine triphosphate, and MgCl(2), at low temperatures for up to 2 hours.

  17. Quantifying Affinity among Chinese Dialects.

    ERIC Educational Resources Information Center

    Cheng, Chin-Chuan

    A study of the relationships between Chinese dialects based on a quantitative measure of dialect affinity is summarized. First, tone values in all the dialect localities available in the early 1970s were used to calculate the dialectal differences in terms of tone height with respect to the "yin and yang" split. In the late 1970s, calculations of…

  18. Affine Contractions on the Plane

    ERIC Educational Resources Information Center

    Celik, D.; Ozdemir, Y.; Ureyen, M.

    2007-01-01

    Contractions play a considerable role in the theory of fractals. However, it is not easy to find contractions which are not similitudes. In this study, it is shown by counter examples that an affine transformation of the plane carrying a given triangle onto another triangle may not be a contraction even if it contracts edges, heights or medians.…

  19. Improved Blocking at 25km Resolution?

    NASA Astrophysics Data System (ADS)

    Schiemann, R.; Demory, M. E.; Mizielinski, M.; Roberts, M.; Shaffrey, L.; Strachan, J.; Vidale, P. L.; Matsueda, M.

    2014-12-01

    It has been suggested that relatively coarse resolution of atmospheric general circulation models (AGCMs) limits their ability to represent mid-latitude blocking. Assessing the role of model resolution for blocking is computationally expensive, as multi-decadal simulations at the desired resolution are necessary for a robust estimation of blocking statistics. Here, we use an ensemble of three atmosphere-only global models for which simulations that fulfil this requirement are available at resolutions of roughly 25km horizontal grid spacing in the mid-latitudes. This corresponds to about a fourfold increase in resolution over the highest-resolution CMIP5 (Coupled Model Intercomparison Project, Phase 5) models. The three models are (i) the ECMWF model (IFS) as used in the project Athena, (ii) the MRI-AGCM 3.2, and (iii) our own HadGEM3-GA3 simulations obtained in the UPSCALE project (UK on PrACE - weather-resolving Simulations of Climate for globAL Environmental risk). We use a two-dimensional blocking index to assess the representation of blocking in these simulations and in three reanalyses (ERA-Interim, ERA-40, MERRA). We evaluate the spatial distribution of climatological blocking frequency, the interannual variability of blocking occurrence as well as the persistence of blocking events. Furthermore, the degree to which blocking biases are associated with mean-state biases is quantified in the different models. We find that the representation of blocking remains very sensitive to atmospheric resolution as the grid spacing is reduced to about 25km. The simulated blocking frequency increases with resolution, mostly so as to reduce the model bias, yet there is considerable variation between the results obtained for different models, seasons, and for the Atlantic and Pacific regions.

  20. Variation of Fundamental Constants

    NASA Astrophysics Data System (ADS)

    Flambaum, V. V.

    2006-11-01

    Theories unifying gravity with other interactions suggest temporal and spatial variation of the fundamental ``constants'' in expanding Universe. The spatial variation can explain a fine tuning of the fundamental constants which allows humans (and any life) to appear. We appeared in the area of the Universe where the values of the fundamental constants are consistent with our existence. We present a review of recent works devoted to the variation of the fine structure constant α, strong interaction and fundamental masses. There are some hints for the variation in quasar absorption spectra. Big Bang nucleosynthesis, and Oklo natural nuclear reactor data. A very promising method to search for the variation of the fundamental constants consists in comparison of different atomic clocks. Huge enhancement of the variation effects happens in transition between accidentally degenerate atomic and molecular energy levels. A new idea is to build a ``nuclear'' clock based on the ultraviolet transition between very low excited state and ground state in Thorium nucleus. This may allow to improve sensitivity to the variation up to 10 orders of magnitude! Huge enhancement of the variation effects is also possible in cold atomic and molecular collisions near Feshbach resonance.

  1. Elastic constants of calcite

    USGS Publications Warehouse

    Peselnick, L.; Robie, R.A.

    1962-01-01

    The recent measurements of the elastic constants of calcite by Reddy and Subrahmanyam (1960) disagree with the values obtained independently by Voigt (1910) and Bhimasenachar (1945). The present authors, using an ultrasonic pulse technique at 3 Mc and 25??C, determined the elastic constants of calcite using the exact equations governing the wave velocities in the single crystal. The results are C11=13.7, C33=8.11, C44=3.50, C12=4.82, C13=5.68, and C14=-2.00, in units of 1011 dyncm2. Independent checks of several of the elastic constants were made employing other directions and polarizations of the wave velocities. With the exception of C13, these values substantially agree with the data of Voigt and Bhimasenachar. ?? 1962 The American Institute of Physics.

  2. The Hubble constant

    NASA Technical Reports Server (NTRS)

    Huchra, John P.

    1992-01-01

    The Hubble constant is the constant of proportionality between recession velocity and distance in the expanding universe. It is a fundamental property of cosmology that sets both the scale and the expansion age of the universe. It is determined by measurement of galaxy radial velocities and distances. Although there has been considerable progress in the development of new techniques for the measurements of galaxy distances, both calibration uncertainties and debates over systematic errors remain. Current determinations still range over nearly a factor of 2; the higher values favored by most local measurements are not consistent with many theories of the origin of large-scale structure and stellar evolution.

  3. 45 Km Horizontal Path Optical Link Experiment

    NASA Technical Reports Server (NTRS)

    Biswas, A.; Ceniceros, J.; Novak, M.; Jeganathan, M.; Portillo, A.; Erickson, D.; Depew, J.; Sanii, B.; Lesh, J. R.

    2000-01-01

    Mountain-top to mountain-top optical link experiments have been initiated at JPL, in order to perform a systems level evaluation of optical communications. Progress made so far is reported. ne NASA, JPL developed optical communications demonstrator (OCD) is used to transmit a laser signal from Strawberry Peak (SP), located in the San Bernadino mountains of California. This laser beam is received by a 0.6 m aperture telescope at JPL's Table Mountain Facility (TMF), located in Wrightwood, California. The optical link is bi-directional with the TMF telescope transmitting a continuous 4-wave (cw) 780 run beacon and the OCD sending back a 840 nm, 100 - 500 Mbps pseudo noise (PN) modulated, laser beam. The optical link path is at an average altitude of 2 km above sea level, covers a range of 46.8 km and provides an atmospheric channel equivalent to approx. 4 air masses. Average received power measured at either end fall well within the uncertainties predicted by link analysis. The reduction in normalized intensity variance (sigma(sup 2, sub I)) for the 4-beam beacon, compared to each individual beam, at SP, was from approx. 0.68 to 0.22. With some allowance for intra-beam mis-alignment, this is consistent with incoherent averaging. The sigma(sup2, sub I) measured at TMF approx. 0.43 +/- 0.22 exceeded the expected aperture averaged value of less than 0.1, probably because of beam wander. The focused spot sizes of approx. 162 +/- 6 microns at the TMF Coude and approx. 64 +/- 3 microns on the OCD compare to the predicted size range of 52 - 172 microns and 57 - 93 microns, respectively. This is consistent with 4 - 5 arcsec of atmospheric "seeing". The preliminary evaluation of OCD's fine tracking indicates that the uncompensated tracking error is approx. 3.3 micro rad compared to approx. 1.7 micro rad observed in the laboratory. Fine tracking performance was intermittent, primarily due to beacon fades on the OCD tracking sensor. The best bit error rates observed while

  4. Compassion is a constant.

    PubMed

    Scott, Tricia

    2015-11-01

    Compassion is a powerful word that describes an intense feeling of commiseration and a desire to help those struck by misfortune. Most people know intuitively how and when to offer compassion to relieve another person's suffering. In health care, compassion is a constant; it cannot be rationed because emergency nurses have limited time or resources to manage increasing demands.

  5. XrayOpticsConstants

    2005-06-20

    This application (XrayOpticsConstants) is a tool for displaying X-ray and Optical properties for a given material, x-ray photon energy, and in the case of a gas, pressure. The display includes fields such as the photo-electric absorption attenuation length, density, material composition, index of refraction, and emission properties (for scintillator materials).

  6. Compassion is a constant.

    PubMed

    Scott, Tricia

    2015-11-01

    Compassion is a powerful word that describes an intense feeling of commiseration and a desire to help those struck by misfortune. Most people know intuitively how and when to offer compassion to relieve another person's suffering. In health care, compassion is a constant; it cannot be rationed because emergency nurses have limited time or resources to manage increasing demands. PMID:26542898

  7. Teleportation of entanglement over 143 km.

    PubMed

    Herbst, Thomas; Scheidl, Thomas; Fink, Matthias; Handsteiner, Johannes; Wittmann, Bernhard; Ursin, Rupert; Zeilinger, Anton

    2015-11-17

    As a direct consequence of the no-cloning theorem, the deterministic amplification as in classical communication is impossible for unknown quantum states. This calls for more advanced techniques in a future global quantum network, e.g., for cloud quantum computing. A unique solution is the teleportation of an entangled state, i.e., entanglement swapping, representing the central resource to relay entanglement between distant nodes. Together with entanglement purification and a quantum memory it constitutes a so-called quantum repeater. Since the aforementioned building blocks have been individually demonstrated in laboratory setups only, the applicability of the required technology in real-world scenarios remained to be proven. Here we present a free-space entanglement-swapping experiment between the Canary Islands of La Palma and Tenerife, verifying the presence of quantum entanglement between two previously independent photons separated by 143 km. We obtained an expectation value for the entanglement-witness operator, more than 6 SDs beyond the classical limit. By consecutive generation of the two required photon pairs and space-like separation of the relevant measurement events, we also showed the feasibility of the swapping protocol in a long-distance scenario, where the independence of the nodes is highly demanded. Because our results already allow for efficient implementation of entanglement purification, we anticipate our research to lay the ground for a fully fledged quantum repeater over a realistic high-loss and even turbulent quantum channel.

  8. Teleportation of entanglement over 143 km

    PubMed Central

    Herbst, Thomas; Scheidl, Thomas; Fink, Matthias; Handsteiner, Johannes; Wittmann, Bernhard; Ursin, Rupert; Zeilinger, Anton

    2015-01-01

    As a direct consequence of the no-cloning theorem, the deterministic amplification as in classical communication is impossible for unknown quantum states. This calls for more advanced techniques in a future global quantum network, e.g., for cloud quantum computing. A unique solution is the teleportation of an entangled state, i.e., entanglement swapping, representing the central resource to relay entanglement between distant nodes. Together with entanglement purification and a quantum memory it constitutes a so-called quantum repeater. Since the aforementioned building blocks have been individually demonstrated in laboratory setups only, the applicability of the required technology in real-world scenarios remained to be proven. Here we present a free-space entanglement-swapping experiment between the Canary Islands of La Palma and Tenerife, verifying the presence of quantum entanglement between two previously independent photons separated by 143 km. We obtained an expectation value for the entanglement-witness operator, more than 6 SDs beyond the classical limit. By consecutive generation of the two required photon pairs and space-like separation of the relevant measurement events, we also showed the feasibility of the swapping protocol in a long-distance scenario, where the independence of the nodes is highly demanded. Because our results already allow for efficient implementation of entanglement purification, we anticipate our research to lay the ground for a fully fledged quantum repeater over a realistic high-loss and even turbulent quantum channel. PMID:26578764

  9. Teleportation of entanglement over 143 km.

    PubMed

    Herbst, Thomas; Scheidl, Thomas; Fink, Matthias; Handsteiner, Johannes; Wittmann, Bernhard; Ursin, Rupert; Zeilinger, Anton

    2015-11-17

    As a direct consequence of the no-cloning theorem, the deterministic amplification as in classical communication is impossible for unknown quantum states. This calls for more advanced techniques in a future global quantum network, e.g., for cloud quantum computing. A unique solution is the teleportation of an entangled state, i.e., entanglement swapping, representing the central resource to relay entanglement between distant nodes. Together with entanglement purification and a quantum memory it constitutes a so-called quantum repeater. Since the aforementioned building blocks have been individually demonstrated in laboratory setups only, the applicability of the required technology in real-world scenarios remained to be proven. Here we present a free-space entanglement-swapping experiment between the Canary Islands of La Palma and Tenerife, verifying the presence of quantum entanglement between two previously independent photons separated by 143 km. We obtained an expectation value for the entanglement-witness operator, more than 6 SDs beyond the classical limit. By consecutive generation of the two required photon pairs and space-like separation of the relevant measurement events, we also showed the feasibility of the swapping protocol in a long-distance scenario, where the independence of the nodes is highly demanded. Because our results already allow for efficient implementation of entanglement purification, we anticipate our research to lay the ground for a fully fledged quantum repeater over a realistic high-loss and even turbulent quantum channel. PMID:26578764

  10. Lectin affinity chromatography of glycolipids

    SciTech Connect

    Torres, B.V.; Smith, D.F.

    1987-05-01

    Since glycolipids (GLs) are either insoluble or form mixed micelles in water, lectin affinity chromatography in aqueous systems has not been applied to their separation. They have overcome this problem by using tetrahydrofuran (THF) in the mobile phase during chromatography. Affinity columns prepared with the GalNAc-specific Helix pomatia agglutinin (HPA) and equilibrated in THF specifically bind the (/sup 3/H)oligosaccharide derived from Forssman GL indicating that the immobilized HPA retained its carbohydrate-binding specificity in this solvent. Intact Forssman GL was bound by the HPA-column equilibrated in THF and was specifically eluted with 0.1 mg/ml GalNAc in THF. Purification of the Forssman GL was achieved when a crude lipid extract of sheep erythrocyte membranes was applied to the HPA-column in THF. Non-specifically bound GLs were eluted from the column using a step gradient of aqueous buffer in THF, while the addition of GalNAc was required to elute the specifically bound GLs. Using this procedure the A-active GLs were purified from a crude lipid extract of type A human erythrocytes in a single chromatographic step. The use of solvents that maintain carbohydrate-binding specificity and lipid solubility will permit the application of affinity chromatography on immobilized carbohydrate-binding proteins to intact GLs.

  11. Wall of fundamental constants

    SciTech Connect

    Olive, Keith A.; Peloso, Marco; Uzan, Jean-Philippe

    2011-02-15

    We consider the signatures of a domain wall produced in the spontaneous symmetry breaking involving a dilatonlike scalar field coupled to electromagnetism. Domains on either side of the wall exhibit slight differences in their respective values of the fine-structure constant, {alpha}. If such a wall is present within our Hubble volume, absorption spectra at large redshifts may or may not provide a variation in {alpha} relative to the terrestrial value, depending on our relative position with respect to the wall. This wall could resolve the contradiction between claims of a variation of {alpha} based on Keck/Hires data and of the constancy of {alpha} based on Very Large Telescope data. We derive the properties of the wall and the parameters of the underlying microscopic model required to reproduce the possible spatial variation of {alpha}. We discuss the constraints on the existence of the low-energy domain wall and describe its observational implications concerning the variation of the fundamental constants.

  12. Varying constants quantum cosmology

    SciTech Connect

    Leszczyńska, Katarzyna; Balcerzak, Adam; Dabrowski, Mariusz P. E-mail: abalcerz@wmf.univ.szczecin.pl

    2015-02-01

    We discuss minisuperspace models within the framework of varying physical constants theories including Λ-term. In particular, we consider the varying speed of light (VSL) theory and varying gravitational constant theory (VG) using the specific ansätze for the variability of constants: c(a) = c{sub 0} a{sup n} and G(a)=G{sub 0} a{sup q}. We find that most of the varying c and G minisuperspace potentials are of the tunneling type which allows to use WKB approximation of quantum mechanics. Using this method we show that the probability of tunneling of the universe ''from nothing'' (a=0) to a Friedmann geometry with the scale factor a{sub t} is large for growing c models and is strongly suppressed for diminishing c models. As for G varying, the probability of tunneling is large for G diminishing, while it is small for G increasing. In general, both varying c and G change the probability of tunneling in comparison to the standard matter content (cosmological term, dust, radiation) universe models.

  13. Multiple GPCR conformations and signalling pathways: implications for antagonist affinity estimates

    PubMed Central

    Baker, Jillian G.; Hill, Stephen J.

    2007-01-01

    Antagonist affinity measurements have traditionally been considered important in characterizing the cell-surface receptors present in a particular cell or tissue. A central assumption has been that antagonist affinity is constant for a given receptor–antagonist interaction, regardless of the agonist used to stimulate that receptor or the downstream response that is measured. As a consequence, changes in antagonist affinity values have been taken as initial evidence for the presence of novel receptor subtypes. Emerging evidence suggests, however, that receptors can possess multiple binding sites and the same receptor can show different antagonist affinity measurements under distinct experimental conditions. Here, we discuss several mechanisms by which antagonists have different affinities for the same receptor as a consequence of allosterism, coupling to different G proteins, multiple (but non-interacting) receptor sites, and signal-pathway-dependent pharmacology (where the pharmacology observed varies depending on the signalling pathway measured). PMID:17629959

  14. General approach for characterizing in vitro selected peptides with protein binding affinity.

    PubMed

    Larsen, Andrew C; Gillig, Annabelle; Shah, Pankti; Sau, Sujay P; Fenton, Kathryn E; Chaput, John C

    2014-08-01

    In vitro selection technologies are important tools for identifying high affinity peptides to proteins of broad medical and biological interest. However, the technological advances that have made it possible to generate long lists of candidate peptides have far outpaced our ability to characterize the binding properties of individual peptides. Here, we describe a low cost strategy to rapidly synthesize, purify, screen, and characterize peptides for high binding affinity. Peptides are assayed in a 96-well dot blot apparatus using membranes that enable partitioning of bound and unbound peptide-protein complexes. We have validated the binding affinity constants produced by this method using known peptide ligands and applied this process to discover five new peptides with nanomolar affinity to human α-thrombin. Given the need for new analytical tools that can accelerate peptide discovery and characterization, we feel that this approach would be useful to a wide range of technologies that utilize high affinity peptides.

  15. Two-parameter twisted quantum affine algebras

    NASA Astrophysics Data System (ADS)

    Jing, Naihuan; Zhang, Honglian

    2016-09-01

    We establish Drinfeld realization for the two-parameter twisted quantum affine algebras using a new method. The Hopf algebra structure for Drinfeld generators is given for both untwisted and twisted two-parameter quantum affine algebras, which include the quantum affine algebras as special cases.

  16. Identification and characterization of a novel high affinity metal-binding site in the hammerhead ribozyme.

    PubMed Central

    Hansen, M R; Simorre, J P; Hanson, P; Mokler, V; Bellon, L; Beigelman, L; Pardi, A

    1999-01-01

    A novel metal-binding site has been identified in the hammerhead ribozyme by 31P NMR. The metal-binding site is associated with the A13 phosphate in the catalytic core of the hammerhead ribozyme and is distinct from any previously identified metal-binding sites. 31P NMR spectroscopy was used to measure the metal-binding affinity for this site and leads to an apparent dissociation constant of 250-570 microM at 25 degrees C for binding of a single Mg2+ ion. The NMR data also show evidence of a structural change at this site upon metal binding and these results are compared with previous data on metal-induced structural changes in the core of the hammerhead ribozyme. These NMR data were combined with the X-ray structure of the hammerhead ribozyme (Pley HW, Flaherty KM, McKay DB. 1994. Nature 372:68-74) to model RNA ligands involved in binding the metal at this A13 site. In this model, the A13 metal-binding site is structurally similar to the previously identified A(g) metal-binding site and illustrates the symmetrical nature of the tandem G x A base pairs in domain 2 of the hammerhead ribozyme. These results demonstrate that 31P NMR represents an important method for both identification and characterization of metal-binding sites in nucleic acids. PMID:10445883

  17. Native Elution of Yeast Protein Complexes Obtained by Affinity Capture.

    PubMed

    LaCava, John; Fernandez-Martinez, Javier; Rout, Michael P

    2016-01-01

    This protocol describes two options for the native (nondenaturing) elution of protein complexes obtained by affinity capture. The first approach involves the elution of complexes purified through a tag that includes a human rhinovirus 3C protease (PreScission protease) cleavage site sequence between the protein of interest and the tag. Incubation with the protease cleaves immobilized complexes from the affinity medium. The second approach involves the release of protein A-tagged protein complexes using a competitive elution reagent called PEGylOx. The degree of purity of the native assemblies eluted is sample dependent and strongly influenced by the affinity capture. It should be noted that the efficiency of native elution is commonly lower than that of elution by a denaturing agent (e.g., SDS) and the release of the complex will be limited by the activity of the protease or the inhibition constant (Ki) of the competitive release agent. However, an advantage of native release is that some nonspecifically bound materials tend to stay adsorbed to the affinity medium, providing an eluted fraction of higher purity. Finally, keep in mind that the presence of the protease or elution peptide could potentially affect downstream applications; thus, their removal should be considered. PMID:27371597

  18. Binding affinities of anti-acetylcholine receptor autoantibodies in myasthenia gravis

    SciTech Connect

    Bray, J.J.; Drachman, D.B.

    1982-01-01

    Antibodies directed against acetylcholine (ACh) receptors are present in the sera of nearly 90% of patients with myasthenia gravis (MG), and are involved in the pathogenesis of this autoimmune disease. However, the antibody titers measured by the standard radioimmunoassay correspond poorly with the clinical severity of the disease. To determine whether this disparity could be accounted for by differences in the binding affinities of anti-ACh receptor antibodies in different patients, we have measured the binding affinities of these autoantibodies in 15 sera from MG patients. The affinity constants (K/sub o/), as determined by Scatchard analysis, were all in the range of 10/sup 10/ M/sup -1/, comparable to the highest values reported in immunized animals. The affinity constants were truly representative of the population of autoantibodies detected by the radioimmunoassay, as shown by the remarkable linearity of the Scatchard plots (r/sup 2/>0.90) and the close correlation between the antibody titers determined by extrapolation of the Scatchard plots and by saturation analysis (r = 0.99; p < 0.001). There was only a 6-fold variation in affinity constants measured in this series of patients despite widely differing antibody titers and severity of the disease. Factors other than the titer and affinity of anti-ACh receptor antibodies may correlate better with the clinical manifestations of MG.

  19. Change is a Constant.

    PubMed

    Lubowitz, James H; Provencher, Matthew T; Brand, Jefferson C; Rossi, Michael J; Poehling, Gary G

    2015-06-01

    In 2015, Henry P. Hackett, Managing Editor, Arthroscopy, retires, and Edward A. Goss, Executive Director, Arthroscopy Association of North America (AANA), retires. Association is a positive constant, in a time of change. With change comes a need for continuing education, research, and sharing of ideas. While the quality of education at AANA and ISAKOS is superior and most relevant, the unique reason to travel and meet is the opportunity to interact with innovative colleagues. Personal interaction best stimulates new ideas to improve patient care, research, and teaching. Through our network, we best create innovation.

  20. Cosmology with varying constants.

    PubMed

    Martins, Carlos J A P

    2002-12-15

    The idea of possible time or space variations of the 'fundamental' constants of nature, although not new, is only now beginning to be actively considered by large numbers of researchers in the particle physics, cosmology and astrophysics communities. This revival is mostly due to the claims of possible detection of such variations, in various different contexts and by several groups. I present the current theoretical motivations and expectations for such variations, review the current observational status and discuss the impact of a possible confirmation of these results in our views of cosmology and physics as a whole.

  1. Complex high affinity interactions occur between MHCI and superantigens

    NASA Technical Reports Server (NTRS)

    Chapes, S. K.; Herpich, A. R.; Spooner, B. S. (Principal Investigator)

    1998-01-01

    Staphylococcal enterotoxins A and C1 (SEA or SEC1) bound to major histocompatibility-I (MHCI) molecules with high affinity (binding constants ranging from 1.1 microM to 79 nM). SEA and SEC1 directly bound MHCI molecules that had been captured by monoclonal antibodies specific for H-2Kk, H-2Dk, or both. In addition, MHCI-specific antibodies inhibited the binding of SEC1 to LM929 cells and SEA competitively inhibited SEC1 binding; indicating that the superantigens bound to MHCI on the cell surface. The affinity and number of superantigen binding sites differed depending on whether MHCI was expressed in the membrane of LM929 cells or whether it was captured. These data support the hypothesis that MHCI molecules can serve as superantigen receptors.

  2. Affinity screening using competitive binding with fluorine-19 hyperpolarized ligands.

    PubMed

    Kim, Yaewon; Hilty, Christian

    2015-04-13

    Fluorine-19 NMR and hyperpolarization form a powerful combination for drug screening. Under a competitive equilibrium with a selected fluorinated reporter ligand, the dissociation constant (K(D)) of other ligands of interest is measurable using a single-scan Carr-Purcell-Meiboom-Gill (CPMG) experiment, without the need for a titration. This method is demonstrated by characterizing the binding of three ligands with different affinities for the serine protease trypsin. Monte Carlo simulations show that the highest accuracy is obtained when about one-half of the bound reporter ligand is displaced in the binding competition. Such conditions can be achieved over a wide range of affinities, allowing for rapid screening of non-fluorinated compounds when a single fluorinated ligand for the binding pocket of interest is known.

  3. Banach frames in the affine synthesis problem

    NASA Astrophysics Data System (ADS)

    Terekhin, Pavel A.

    2009-10-01

    We consider the problem of representing functions f\\in L^p(\\mathbb R^d) by a series in elements of the affine system \\displaystyle \\psi_{j,k}(x)=\\lvert\\det a_j\\rvert^{1/2}\\psi(a_jx-bk), \\qquad j\\in\\mathbb N, \\quad k\\in\\mathbb Z^d. The corresponding representation theorems are established on the basis of the frame inequalities \\displaystyle A\\Vert g\\Vert _q\\le\\Vert\\{(g,\\psi_{j,k})\\}\\Vert _Y\\le B\\Vert g\\Vert _q for the Fourier coefficients \\displaystyle(g,\\psi_{j,k})=\\int_{\\mathbb R^d}g(x)\\psi_{j,k}(x)\\,dx of functions g\\in L^q(\\mathbb R^d), 1/p+1/q=1, where {\\Vert\\cdot\\Vert}_Y is the norm in some Banach space of number families \\{y_{j,k}\\} and 0 are constants. In particular, it is proved that if the integral of a function \\psi\\in L^1\\cap L^p(\\mathbb R^d), 1, is nonzero, so \\displaystyle\\int_{\\mathbb R^d}\\psi(x)\\,dx\

  4. Interpolation method for accurate affinity ranking of arrayed ligand-analyte interactions.

    PubMed

    Schasfoort, Richard B M; Andree, Kiki C; van der Velde, Niels; van der Kooi, Alex; Stojanović, Ivan; Terstappen, Leon W M M

    2016-05-01

    The values of the affinity constants (kd, ka, and KD) that are determined by label-free interaction analysis methods are affected by the ligand density. This article outlines a surface plasmon resonance (SPR) imaging method that yields high-throughput globally fitted affinity ranking values using a 96-plex array. A kinetic titration experiment without a regeneration step has been applied for various coupled antibodies binding to a single antigen. Globally fitted rate (kd and ka) and dissociation equilibrium (KD) constants for various ligand densities and analyte concentrations are exponentially interpolated to the KD at Rmax = 100 RU response level (KD(R100)).

  5. High affinity DNA-microtubule associated protein interaction.

    PubMed

    Marx, K A

    1992-07-01

    We have isolated the MAP/tau proteins from twice-cycled chick brain microtubule preparations and demonstrated that they are responsible for the nitrocellulose DNA binding activity we and others have measured. Using the isolated MAP/tau proteins we then measured the apparent affinity constant K(app) for the homologous chick DNA interaction and found evidence for two equilibrium affinity classes-a K(app) = 6 x 10(7) M-1, responsible for the bulk of the DNA binding activity and a small (less than 10%) higher affinity K(app) = 10(8) - 10(9) M-1, likely due to sequence specific binding protein species. Using the same chick brain MAP-tau protein, a heterologous interaction with D. melanogaster DNA, was found to possess just the lower affinity class-K(app) = 2 x 10(7) M-1. Under stringent binding conditions we carried out equilibrium nitrocellulose filter binding experiments in a ternary reaction mixture at constant MAP/tau protein and 35S radiolabelled chick DNA concentration using increasing and excess concentrations of competitor DNAs of different sources. The order of competitor strengths found was-chick DNA greater than mouse DNA greater than D. melanogaster = E. coli. DNA. These data and specifically the homologous DNA: protein case being the strongest competitor corroborate our previous studies using total microtubule protein and provide new evidence for a conserved interaction of a small DNA sequence class with MAP/tau protein species. Moreover, these data allow us to conclude that the conserved DNA sequence: MAP/tau protein interactions do not critically depend upon any energetic feature co-involving tubulin for their properties since tubulin is absent from these preparations.

  6. About variable constants

    NASA Astrophysics Data System (ADS)

    Blichert-Toft, J.; Albarede, F.

    2011-12-01

    When only modern isotope compositions are concerned, the choice of normalization values is inconsequential provided that their values are universally accepted. No harm is done as long as large amounts of standard reference material with known isotopic differences with respect to the reference value ('anchor point') can be maintained under controlled conditions. For over five decades, the scientific community has been referring to an essentially unavailable SMOW for stable O and H isotopes and to a long-gone belemnite sample for carbon. For radiogenic isotopes, the isotope composition of the daughter element, the parent-daughter ratio, and a particular value of the decay constant are all part of the reference. For the Lu-Hf system, for which the physical measurements of the decay constant have been particularly defective, the reference includes the isotope composition of Hf and the Lu/Hf ratio of an unfortunately heterogeneous chondrite mix that has been successively refined by Patchett and Tatsumoto (1981), Blichert-Toft and Albarede (1997, BTA), and Bouvier et al. (2008, BVP). The \\varepsilonHf(T) difference created by using BTA and BVP is nearly within error (+0.45 epsilon units today and -0.36 at 3 Ga) and therefore of little or no consequence. A more serious issue arises when the chondritic reference is taken to represent the Hf isotope evolution of the Bulk Silicate Earth (BSE): the initial isotope composition of the Solar System, as determined by the indistinguishable intercepts of the external eucrite isochron (Blichert-Toft et al., 2002) and the internal angrite SAH99555 isochron (Thrane et al., 2010), differs from the chondrite value of BTA and BVP extrapolated to 4.56 Ga by ~5 epsilon units. This difference and the overestimated value of the 176Lu decay constant derived from the slopes of these isochrons, have been interpreted as reflecting irradiation of the solar nebula by either gamma (Albarede et al., 2006) or cosmic rays (Thrane et al., 2010) during

  7. Gm and Km immunoglobulin allotypes in Reindeer Chukchi and Siberian Eskimos.

    PubMed

    Sukernik, R I; Osipova, L P

    1982-01-01

    Blood samples from 403 Reindeer Chukchi of inland Chukotka, and 100 samples from Chaplin Eskimos of the Chukot Peninsula were tested for G 1 m (z,a,x,f), G2m (n), G3m (g,b0,b1,b3,b5,s,t), and Km (1) allotypic determinants. An apparent affinity between the Chukchi and the Eskimos could be inferred from similar frequencies of the two common haplotypes, Gmza;g and Gmza;bst, and from very similar frequencies of the Km1 allele. However, none of the Eskimos had Gmzax;g, though it occurred at a low or moderate frequency in the five Chukchi populations studied. It is assumed that Chukchi can be distinguished from adjoining Eskimos by the same G1m (x) outlier, that has been considered as a taxonomic marker useful in differentiating between Eskimos and American Indians. Comparison of North Asian and North American populations with respect to the array and frequencies of Gm haplotypes and the Km1 allele, supports the hypothesis of a nonrandom distribution of the Gmza;bst and Km1 on both sides of the Bering Strait. PMID:6957376

  8. Measurement of the solar constant

    NASA Technical Reports Server (NTRS)

    Crommelynck, D.

    1981-01-01

    The absolute value of the solar constant and the long term variations that exist in the absolute value of the solar constant were measured. The solar constant is the total irradiance of the Sun at a distance of one astronomical unit. An absolute radiometer removed from the effects of the atmosphere with its calibration tested in situ was used to measure the solar constant. The importance of an accurate knowledge of the solar constant is emphasized.

  9. When constants are important

    SciTech Connect

    Beiu, V.

    1997-04-01

    In this paper the authors discuss several complexity aspects pertaining to neural networks, commonly known as the curse of dimensionality. The focus will be on: (1) size complexity and depth-size tradeoffs; (2) complexity of learning; and (3) precision and limited interconnectivity. Results have been obtained for each of these problems when dealt with separately, but few things are known as to the links among them. They start by presenting known results and try to establish connections between them. These show that they are facing very difficult problems--exponential growth in either space (i.e. precision and size) and/or time (i.e., learning and depth)--when resorting to neural networks for solving general problems. The paper will present a solution for lowering some constants, by playing on the depth-size tradeoff.

  10. Unitaxial constant velocity microactuator

    DOEpatents

    McIntyre, Timothy J.

    1994-01-01

    A uniaxial drive system or microactuator capable of operating in an ultra-high vacuum environment. The mechanism includes a flexible coupling having a bore therethrough, and two clamp/pusher assemblies mounted in axial ends of the coupling. The clamp/pusher assemblies are energized by voltage-operated piezoelectrics therewithin to operatively engage the shaft and coupling causing the shaft to move along its rotational axis through the bore. The microactuator is capable of repeatably positioning to sub-manometer accuracy while affording a scan range in excess of 5 centimeters. Moreover, the microactuator generates smooth, constant velocity motion profiles while producing a drive thrust of greater than 10 pounds. The system is remotely controlled and piezoelectrically driven, hence minimal thermal loading, vibrational excitation, or outgassing is introduced to the operating environment.

  11. Unitaxial constant velocity microactuator

    DOEpatents

    McIntyre, T.J.

    1994-06-07

    A uniaxial drive system or microactuator capable of operating in an ultra-high vacuum environment is disclosed. The mechanism includes a flexible coupling having a bore therethrough, and two clamp/pusher assemblies mounted in axial ends of the coupling. The clamp/pusher assemblies are energized by voltage-operated piezoelectrics therewithin to operatively engage the shaft and coupling causing the shaft to move along its rotational axis through the bore. The microactuator is capable of repeatably positioning to sub-nanometer accuracy while affording a scan range in excess of 5 centimeters. Moreover, the microactuator generates smooth, constant velocity motion profiles while producing a drive thrust of greater than 10 pounds. The system is remotely controlled and piezoelectrically driven, hence minimal thermal loading, vibrational excitation, or outgassing is introduced to the operating environment. 10 figs.

  12. Constant attitude orbit transfer

    NASA Astrophysics Data System (ADS)

    Cress, Peter; Evans, Michael

    A two-impulse orbital transfer technique is described in which the spacecraft attitude remains constant for both burns, eliminating the need for attitude maneuvers between the burns. This can lead to significant savings in vehicle weight, cost and complexity. Analysis is provided for a restricted class of applications of this transfer between circular orbits. For those transfers with a plane change less than 30 deg, the total velocity cost of the maneuver is less than twelve percent greater than that of an optimum plane split Hohmann transfer. While this maneuver does not minimize velocity requirement, it does provide a means of achieving necessary transfer while substantially reducing the cost and complexity of the spacecraft.

  13. A Constant Pressure Bomb

    NASA Technical Reports Server (NTRS)

    Stevens, F W

    1924-01-01

    This report describes a new optical method of unusual simplicity and of good accuracy suitable to study the kinetics of gaseous reactions. The device is the complement of the spherical bomb of constant volume, and extends the applicability of the relationship, pv=rt for gaseous equilibrium conditions, to the use of both factors p and v. The method substitutes for the mechanical complications of a manometer placed at some distance from the seat of reaction the possibility of allowing the radiant effects of reaction to record themselves directly upon a sensitive film. It is possible the device may be of use in the study of the photoelectric effects of radiation. The method makes possible a greater precision in the measurement of normal flame velocities than was previously possible. An approximate analysis shows that the increase of pressure and density ahead of the flame is negligible until the velocity of the flame approaches that of sound.

  14. Lectin KM+-induced neutrophil haptotaxis involves binding to laminin.

    PubMed

    Ganiko, Luciane; Martins, Antônio R; Freymüller, Edna; Mortara, Renato A; Roque-Barreira, Maria-Cristina

    2005-01-18

    The lectin KM+ from Artocarpus integrifolia, also known as artocarpin, induces neutrophil migration by haptotaxis. The interactions of KM+ with both the extracellular matrix (ECM) and neutrophils depend on the lectin ability to recognize mannose-containing glycans. Here, we report the binding of KM+ to laminin and demonstrate that this interaction potentiates the KM+-induced neutrophil migration. Labeling of lung tissue by KM+ located its ligands on the endothelial cells, in the basement membrane, in the alveolus, and in the interstitial connective tissue. Such labeling was inhibited by 400 mM D-mannose, 10 mM Manalpha1-3[Manalpha1-6]Man or 10 microM peroxidase (a glycoprotein-containing mannosyl heptasaccharide). Laminin is a tissue ligand for KM+, since both KM+ and anti-laminin antibodies not only reacted with the same high molecular mass components of a lung extract, but also determined colocalized labeling in basement membranes of the lung tissue. The relevance of the KM+-laminin interaction to the KM+ property of inducing neutrophil migration was evaluated. The inability of low concentrations of soluble KM+ to induce human neutrophil migration was reversed by coating the microchamber filter with laminin. So, the interaction of KM+ with laminin promotes the formation of a substrate-bound KM+ gradient that is able to induce neutrophil haptotaxis.

  15. Analysis of free drug fractions in human serum by ultrafast affinity extraction and two-dimensional affinity chromatography.

    PubMed

    Zheng, Xiwei; Podariu, Maria; Matsuda, Ryan; Hage, David S

    2016-01-01

    Ultrafast affinity extraction and a two-dimensional high performance affinity chromatographic system were used to measure the free fractions for various drugs in serum and at typical therapeutic concentrations. Pooled samples of normal serum or serum from diabetic patients were utilized in this work. Several drug models (i.e., quinidine, diazepam, gliclazide, tolbutamide, and acetohexamide) were examined that represented a relatively wide range of therapeutic concentrations and affinities for human serum albumin (HSA). The two-dimensional system consisted of an HSA microcolumn for the extraction of a free drug fraction, followed by a larger HSA analytical column for the further separation and measurement of this fraction. Factors that were optimized in this method included the flow rates, column sizes, and column switching times that were employed. The final extraction times used for isolating the free drug fractions were 333-665 ms or less. The dissociation rate constants for several of the drugs with soluble HSA were measured during system optimization, giving results that agreed with reference values. In the final system, free drug fractions in the range of 0.7-9.5% were measured and gave good agreement with values that were determined by ultrafiltration. Association equilibrium constants or global affinities were also estimated by this approach for the drugs with soluble HSA. The results for the two-dimensional system were obtained in 5-10 min or less and required only 1-5 μL of serum per injection. The same approach could be adapted for work with other drugs and proteins in clinical samples or for biomedical research. PMID:26462924

  16. Neuromuscular characteristics and fatigue during 10 km running.

    PubMed

    Paavolainen, L; Nummela, A; Rusko, H; Häkkinen, K

    1999-11-01

    This study investigated neuromuscular characteristics and fatigue during 10 km running (10 K) performance in well-trained endurance athletes with different distance running capability. Nine high (HC) and ten low (LC) caliber endurance athletes performed the 10 K on a 200 m indoor track, constant velocity lap (CVL, 4.5 m x s(-1)) 5 times during the course of the 10 K and maximal 20 m speed test before (20 m(b)) and after (20 m(a)) the 10 K. Running velocity (V), ground contact times (CT), ground reaction forces (F) and electromyographic activity (EMG) of the leg muscles (vastus lateralis; VL, biceps femoris; BF, gastrocnemius; GA) were measured during 20 m(b), 20 m(a), and CVLs. The 10 K times differed (p<0.001) between HC and LC (36.3+/-1.2 and 39.2+/-2.0 min, respectively) but no differences were observed in 20 m(b) velocity. The 10 K led to significant (p<0.05) decreases in V, F and integrated EMG (IEMG) and increases in CTs of 20 m(a) in both groups. No changes were observed in HC or LC in F and IEMG during the CVLs but HC showed shorter (p<0.05) mean CT of CVLs than LC. A significant correlation (r = -0.56, p<0.05) was observed between the mean CT of CVLs and velocity of 10 K (V10K). Pre-activity of GA in relation to the IEMG of the total contact phase during the CVLs was higher (p<0.05) in HC than LC. The relative IEMGs of VL and GA in the propulsion phase compared to the IEMG of the 20 m(b) were lower (p<0.05) in HC than LC. In conclusion, marked fatigue took place in both HC and LC during the 10 K but the fatigue-induced changes in maximal 20 m run did not differentiate endurance athletes with different V10K. However, a capability to produce force rapidly throughout the 10 K accompanied with optimal preactivation and contact phase activation seem to be important for 10 km running performance in well trained endurance athletes.

  17. The maximal affinity of ligands

    PubMed Central

    Kuntz, I. D.; Chen, K.; Sharp, K. A.; Kollman, P. A.

    1999-01-01

    We explore the question of what are the best ligands for macromolecular targets. A survey of experimental data on a large number of the strongest-binding ligands indicates that the free energy of binding increases with the number of nonhydrogen atoms with an initial slope of ≈−1.5 kcal/mol (1 cal = 4.18 J) per atom. For ligands that contain more than 15 nonhydrogen atoms, the free energy of binding increases very little with relative molecular mass. This nonlinearity is largely ascribed to nonthermodynamic factors. An analysis of the dominant interactions suggests that van der Waals interactions and hydrophobic effects provide a reasonable basis for understanding binding affinities across the entire set of ligands. Interesting outliers that bind unusually strongly on a per atom basis include metal ions, covalently attached ligands, and a few well known complexes such as biotin–avidin. PMID:10468550

  18. Engineering antibody affinity and specificity.

    PubMed

    Webster, D M; Roberts, S; Cheetham, J C; Griest, R; Rees, A R

    1988-01-01

    A combination of ab initio calculations, "knowledge-based prediction", molecular graphics and site-directed mutagenesis has enabled us to probe the molecular details of antibody:antigen recognition and binding and to alter the affinity and specificity of an antibody for its antigen. The significance of electrostatic hydrogen bonding, hydrophilic/hydrophobic patch matching and van der Waals interactions as well as CDR:CDR interactions are discussed in relation to the results of site-directed mutagenesis experiments on the anti-lysozyme antibody Gloop2. The ability to generate reconstructed antibodies, chimeric antibodies, catalytic antibodies and the use of modelled antibodies for the design of drugs is discussed. PMID:3209295

  19. Proton affinities of hydrated molecules

    NASA Astrophysics Data System (ADS)

    Valadbeigi, Younes

    2016-09-01

    Proton affinities (PA) of non-hydrated, M, and hydrated forms, M(H2O)1,2,3, of 20 organic molecules including alcohols, ethers, aldehydes, ketones and amines were calculated by the B3LYP/6-311++G(d,p) method. For homogeneous families, linear correlations were observed between PAs of the M(H2O)1,2,3 and the PAs of the non-hydrated molecules. Also, the absolute values of the hydration enthalpies of the protonated molecules decreased linearly with the PAs. The correlation functions predicted that for an amine with PA < 1100 kJ/mol the PA(M(H2O)) is larger than the corresponding PA, while for an amine with PA > 1100 kJ/mol the PA(M(H2O)) is smaller than the PA.

  20. MODIS 3km Aerosol Product: Algorithm and Global Perspective

    NASA Technical Reports Server (NTRS)

    Remer, L. A.; Mattoo, S.; Levy, R. C.; Munchak, L.

    2013-01-01

    After more than a decade of producing a nominal 10 km aerosol product based on the dark target method, the MODIS aerosol team will be releasing a nominal 3 km product as part of their Collection 6 release. The new product differs from the original 10 km product only in the manner in which reflectance pixels are ingested, organized and selected by the aerosol algorithm. Overall, the 3 km product closely mirrors the 10 km product. However, the finer resolution product is able to retrieve over ocean closer to islands and coastlines, and is better able to resolve fine aerosol features such as smoke plumes over both ocean and land. In some situations, it provides retrievals over entire regions that the 10 km product barely samples. In situations traditionally difficult for the dark target algorithm, such as over bright or urban surfaces the 3 km product introduces isolated spikes of artificially high aerosol optical depth (AOD) that the 10 km algorithm avoids. Over land, globally, the 3 km product appears to be 0.01 to 0.02 higher than the 10 km product, while over ocean, the 3 km algorithm is retrieving a proportionally greater number of very low aerosol loading situations. Based on collocations with ground-based observations for only six months, expected errors associated with the 3 km land product are determined to be greater than for the 10 km product: 0.05 0.25 AOD. Over ocean, the suggestion is for expected errors to be the same as the 10 km product: 0.03 0.05 AOD. The advantage of the product is on the local scale, which will require continued evaluation not addressed here. Nevertheless, the new 3 km product is expected to provide important information complementary to existing satellite-derived products and become an important tool for the aerosol community.

  1. Complex Affine Toda Theories and Soliton Solutions

    NASA Astrophysics Data System (ADS)

    Zhu, Zhiqing

    1995-01-01

    Toda field theories (TFT's) constitute a large class of integrable (1 + 1)-dimensional field theories that are relativistically invariant: included are conformal field theories and integrable deformations away from conformality. Because they are soluble, for example, by the inverse scattering method, and because they are related to many other areas of field theory, they have been studied extensively in recent years. Hirota's method is a straightforward procedure to obtain soliton solutions to non-linear integrable equations. In Hirota's method, one first writes the nonlinear equations in Hirota's bilinear form, and then expands the so called tau-functions as a power series in an arbitrary parameter. The power series terminates at some finite order, thus the solutions obtained are exact. For an N-soliton solution, the number of terms in the expansion grows exponentially with N, making direct calculation of N-soliton solutions difficult. We extend Hirota's one -parameter expansion to an N-parameter expansion. In the new expansion series, many terms are identical to those in the (N - 1)-soliton solutions, and new terms grow only linearly with N. Furthermore, we note that the expansion must terminate at some finite order, thus the vanishing of higher order terms can be used as constraints on these new terms. It turns out that these constraints can be used to determine the new terms completely. We used this extended Hirota's method to find N-soliton solutions for complex affine TFT's based on a simply-laced Kac-Moody algebra. Soliton solutions for non-simply-laced complex ATFT's can be obtained for those of simply-laced complex ATFT's by folding or twisting. Even though some soliton solutions have already been obtained for complex ATFT's by various methods, the physical implications of these solutions have not yet been thoroughly discussed. There are infinitely many distinct topological solitons in any given complex affine Toda field theory and most of them have complex

  2. High affinity of water-soluble cryptophanes for cesium cations.

    PubMed

    Brotin, Thierry; Montserret, Roland; Bouchet, Aude; Cavagnat, Dominique; Linares, Mathieu; Buffeteau, Thierry

    2012-01-20

    Exceptionally high affinity for cesium cations was achieved in aqueous solution using two enantiopure cryptophanes. Complexation of cesium was evidenced by (133)Cs NMR spectroscopy and by electronic circular dichroism (ECD). Binding constants as high as 6 × 10(9) M(-1) have been measured by isothermal titration calorimetry (ITC). Very strong complexation of rubidium cations (K ~10(6) M(-1)) has also been measured. Chiral hosts allowed the detection of the two cations at low concentrations (μM) using ECD.

  3. Modified gravity in three dimensional metric-affine scenarios

    NASA Astrophysics Data System (ADS)

    Bambi, Cosimo; Ghasemi-Nodehi, M.; Rubiera-Garcia, D.

    2015-08-01

    We consider metric-affine scenarios where a modified gravitational action is sourced by electrovacuum fields in a three dimensional space-time. We first study the case of f (R ) theories, finding deviations near the center as compared to the solutions of general relativity. We then consider Born-Infeld gravity, which has raised a lot of interest in the last few years regarding its applications in astrophysics and cosmology, and show that new features always arise at a finite distance from the center. Several properties of the resulting space-times, in particular in presence of a cosmological constant term, are discussed.

  4. Analyzing a kinetic titration series using affinity biosensors.

    PubMed

    Karlsson, Robert; Katsamba, Phinikoula S; Nordin, Helena; Pol, Ewa; Myszka, David G

    2006-02-01

    The classical method of measuring binding constants with affinity-based biosensors involves testing several analyte concentrations over the same ligand surface and regenerating the surface between binding cycles. Here we describe an alternative approach to collecting kinetic binding data, which we call "kinetic titration." This method involves sequentially injecting an analyte concentration series without any regeneration steps. Through a combination of simulation and experimentation, we show that this method can be as robust as the classical method of analysis. In addition, kinetic titrations can be more efficient than the conventional data collection method and allow us to fully characterize analyte binding to ligand surfaces that are difficult to regenerate.

  5. Conformal field theory on affine Lie groups

    SciTech Connect

    Clubok, K.S.

    1996-04-01

    Working directly on affine Lie groups, we construct several new formulations of the WZW model, the gauged WZW model, and the generic affine-Virasoro action. In one formulation each of these conformal field theories (CFTs) is expressed as a one-dimensional mechanical system whose variables are coordinates on the affine Lie group. When written in terms of the affine group element, this formulation exhibits a two-dimensional WZW term. In another formulation each CFT is written as a two-dimensional field theory, with a three- dimensional WZW term, whose fields are coordinates on the affine group. On the basis of these equivalent formulations, we develop a translation dictionary in which the new formulations on the affine Lie group are understood as mode formulations of the conventional formulations on the Lie group. Using this dictionary, we also express each CFT as a three-dimensional field theory on the Lie group with a four-dimensional WZW term. 36 refs.

  6. Characterization of a constant current charge detector.

    PubMed

    Mori, Masanobu; Chen, Yongjing; Ohira, Shin-Ichi; Dasgupta, Purnendu K

    2012-12-15

    Ion exchangers are ionic equivalents of doped semiconductors, where cations and anions are equivalents of holes and electrons as charge carriers in solid state semiconductors. We have previously demonstrated an ion exchange membrane (IEM) based electrolyte generator which behaves similar to a light-emitting diode and a charge detector (ChD) which behaves analogous to a p-i-n photodiode. The previous work on the charge detector, operated at a constant voltage, established its unique ability to respond to the charge represented by the analyte ions regardless of their redox properties, rather than to their conductivities. It also suggested that electric field induced dissociation (EFID) of water occurs at one or both ion exchange membranes. A logical extension is to study the behavior of the same device, operated in a constant current mode (ChD(i)). The evidence indicates that in the present operational mode the device also responds to the charge represented by the analytes and not their conductivity. Injection of a base into a charge detector operated in the constant voltage mode was not previously examined; in the constant current mode, base injection appears to inhibit EFID. The effects of applied current, analyte residence time and outer channel fluid composition were individually examined; analyte ions of different mobilities as well as affinities for the respective IEMs were used. While the exact behavior is somewhat dependent on the applied current, strong electrolytes, both acids and salts, respond the highest and in a near-uniform fashion, weak acids and their salts respond in an intermediate fashion and bases produce the lowest responses. A fundamentally asymmetric behavior is observed. Injected bases but not injected acids produce a poor response; the effects of incorporating a strong base as the electrolyte in the anion exchange membrane (AEM) compartment is far greater than incorporating an acid in the cation exchange membrane (CEM) compartment. These

  7. Differential Mobility Spectrometry: Preliminary Findings on Determination of Fundamental Constants

    NASA Technical Reports Server (NTRS)

    Limero, Thomas; Cheng, Patti; Boyd, John

    2007-01-01

    The electron capture detector (ECD) has been used for 40+ years (1) to derive fundamental constants such as a compound's electron affinity. Given this historical perspective, it is not surprising that differential mobility spectrometry (DMS) might be used in a like manner. This paper will present data from a gas chromatography (GC)-DMS instrument that illustrates the potential capability of this device to derive fundamental constants for electron-capturing compounds. Potential energy curves will be used to provide possible explanation of the data.

  8. Estimation of Land Surface Temperature from 1-km AVHRR data

    NASA Astrophysics Data System (ADS)

    Frey, Corinne

    2016-04-01

    In order to re-process DLRs 1km AVHRR data archive to different geophysical and descriptive parameters of the land surface and the atmosphere, a series of scientific data processors are being developed in the framework of the TIMELINE project. The archive of DLR ranges back to the 80ies. One of the data processors is SurfTemp, which processes L2 LST and emissivity datasets from AVHRR L1b data. The development of the data processor included the selection of statistical procedures suitable for time series processing, including four mono-window and six split window algorithms. For almost all of these algorithms, new constants were generated, which better account for different atmospheric and geometric acquisition situations. The selection of optimal algorithms for SurfTemp is based on a round robin approach, in which the selected mono-window and split window algorithms are tested on the basis of a large number of TOA radiance/LST pairs, which were generated using a radiative transfer model and the SeeBorV5 profile database. The original LSTs are thereby compared to the LSTs derived from the TOA radiances using the mono- and split window algorithms. The algorithm comparison includes measures of precision, as well as the sensitivity of a method to the accuracy of its input data. The results of the round robin are presented, as well as the implementation of selected algorithms into SurfTemp. Further, first cross-validation results between the AVHRR LST and MODIS LST are shown.

  9. Structural determinants of sigma receptor affinity

    SciTech Connect

    Largent, B.L.; Wikstroem, H.G.; Gundlach, A.L.; Snyder, S.H.

    1987-12-01

    The structural determinants of sigma receptor affinity have been evaluated by examining a wide range of compounds related to opioids, neuroleptics, and phenylpiperidine dopaminergic structures for affinity at sigma receptor-binding sites labeled with (+)-(/sup 3/H)3-PPP. Among opioid compounds, requirements for sigma receptor affinity differ strikingly from the determinants of affinity for conventional opiate receptors. Sigma sites display reverse stereoselectivity to classical opiate receptors. Multi-ringed opiate-related compounds such as morphine and naloxone have negligible affinity for sigma sites, with the highest sigma receptor affinity apparent for benzomorphans which lack the C ring of opioids. Highest affinity among opioids and other compounds occurs with more lipophilic N-substituents. This feature is particularly striking among the 3-PPP derivatives as well as the opioids. The butyrophenone haloperidol is the most potent drug at sigma receptors we have detected. Among the series of butyrophenones, receptor affinity is primarily associated with the 4-phenylpiperidine moiety. Conformational calculations for various compounds indicate a fairly wide range of tolerance for distances between the aromatic ring and the amine nitrogen, which may account for the potency at sigma receptors of structures of considerable diversity. Among the wide range of structures that bind to sigma receptor-binding sites, the common pharmacophore associated with high receptor affinity is a phenylpiperidine with a lipophilic N-substituent.

  10. Non-affine deformations in polymer hydrogels

    PubMed Central

    Wen, Qi; Basu, Anindita; Janmey, Paul A.; Yodh, A. G.

    2012-01-01

    Most theories of soft matter elasticity assume that the local strain in a sample after deformation is identical everywhere and equal to the macroscopic strain, or equivalently that the deformation is affine. We discuss the elasticity of hydrogels of crosslinked polymers with special attention to affine and non-affine theories of elasticity. Experimental procedures to measure non-affine deformations are also described. Entropic theories, which account for gel elasticity based on stretching out individual polymer chains, predict affine deformations. In contrast, simulations of network deformation that result in bending of the stiff constituent filaments generally predict non-affine behavior. Results from experiments show significant non-affine deformation in hydrogels even when they are formed by flexible polymers for which bending would appear to be negligible compared to stretching. However, this finding is not necessarily an experimental proof of the non-affine model for elasticity. We emphasize the insights gained from experiments using confocal rheoscope and show that, in addition to filament bending, sample micro-inhomogeneity can be a significant alternative source of non-affine deformation. PMID:23002395

  11. A Novel Vertex Affinity for Community Detection

    SciTech Connect

    Yoo, Andy; Sanders, Geoffrey; Henson, Van; Vassilevski, Panayot

    2015-10-05

    We propose a novel vertex affinity measure in this paper. The new vertex affinity quantifies the proximity between two vertices in terms of their clustering strength and is ideal for such graph analytics applications as community detection. We also developed a framework that combines simple graph searches and resistance circuit formulas to compute the vertex affinity efficiently. We study the properties of the new affinity measure empirically in comparison to those of other popular vertex proximity metrics. Our results show that the existing metrics are ill-suited for community detection due to their lack of fundamental properties that are essential for correctly capturing inter- and intra-cluster vertex proximity.

  12. Structure of classical affine and classical affine fractional W-algebras

    SciTech Connect

    Suh, Uhi Rinn

    2015-01-15

    We introduce a classical BRST complex (See Definition 3.2.) and show that one can construct a classical affine W-algebra via the complex. This definition clarifies that classical affine W-algebras can be considered as quasi-classical limits of quantum affine W-algebras. We also give a definition of a classical affine fractional W-algebra as a Poisson vertex algebra. As in the classical affine case, a classical affine fractional W-algebra has two compatible λ-brackets and is isomorphic to an algebra of differential polynomials as a differential algebra. When a classical affine fractional W-algebra is associated to a minimal nilpotent, we describe explicit forms of free generators and compute λ-brackets between them. Provided some assumptions on a classical affine fractional W-algebra, we find an infinite sequence of integrable systems related to the algebra, using the generalized Drinfel’d and Sokolov reduction.

  13. Picomolar affinity antibodies from a fully synthetic naive library selected and evolved by ribosome display.

    PubMed

    Hanes, J; Schaffitzel, C; Knappik, A; Plückthun, A

    2000-12-01

    Here we applied ribosome display to in vitro selection and evolution of single-chain antibody fragments (scFvs) from a large synthetic library (Human Combinatorial Antibody Library; HuCAL) against bovine insulin. In three independent ribosome display experiments different clusters of closely related scFvs were selected, all of which bound the antigen with high affinity and specificity. All selected scFvs had affinity-matured up to 40-fold compared to their HuCAL progenitors, by accumulating point mutations during the ribosome display cycles. The dissociation constants of the isolated scFvs were as low as 82 pM, which validates the design of the naïve library and the power of this evolutionary method. We have thus mimicked the process of antibody generation and affinity maturation with a synthetic library in a cell-free system in just a few days, obtaining molecules with higher affinities than most natural antibodies.

  14. Directed evolution of antibody fragments with monovalent femtomolar antigen-binding affinity.

    PubMed

    Boder, E T; Midelfort, K S; Wittrup, K D

    2000-09-26

    Single-chain antibody mutants have been evolved in vitro with antigen-binding equilibrium dissociation constant K(d) = 48 fM and slower dissociation kinetics (half-time > 5 days) than those for the streptavidin-biotin complex. These mutants possess the highest monovalent ligand-binding affinity yet reported for an engineered protein by over two orders of magnitude. Optimal kinetic screening of randomly mutagenized libraries of 10(5)-10(7) yeast surface-displayed antibodies enabled a >1,000-fold decrease in the rate of dissociation after four cycles of affinity mutagenesis and screening. The consensus mutations are generally nonconservative by comparison with naturally occurring mouse Fv sequences and with residues that do not contact the fluorescein antigen in the wild-type complex. The existence of these mutants demonstrates that the antibody Fv architecture is not intrinsically responsible for an antigen-binding affinity ceiling during in vivo affinity maturation.

  15. Purification of muscarinic acetylcholine receptors by affinity chromatography.

    PubMed Central

    André, C; De Backer, J P; Guillet, J C; Vanderheyden, P; Vauquelin, G; Strosberg, A D

    1983-01-01

    Calf forebrain homogenates contain 2.8 pM muscarinic acetylcholine receptors per mg of protein. [3H]Antagonist saturation binding experiments under equilibrium conditions revealed a single class of sites with equilibrium dissociation constants of 0.82 nM for [3H]dexetimide and 0.095 nM for [3H]quinuclidinyl benzilate. Displacement binding studies with agonists revealed the presence of low and high affinity sites. Here we describe the solubilization of muscarinic acetylcholine receptors with digitonin and their purification by affinity chromatography using an affinity gel which consisted of dexetimide coupled to Affi-Gel 10 (i.e., carboxy N-hydroxysuccinimide esters linked via a 1 nm spacer arm to agarose beads). Purified proteins were obtained by specific elution with muscarinic drugs, i.e., the antagonist atropine and the irreversible ligand propylbenzilylcholine mustard. SDS-polyacrylamide gel electrophoresis of the radioiodinated purified preparations revealed a major 70-K protein. Images Fig. 3. PMID:6605245

  16. Microphysical Model of the Venus clouds between 40km and 80km

    NASA Astrophysics Data System (ADS)

    McGouldrick, Kevin

    2013-10-01

    I am continuing to adapt the Community Aerosol and Radiation Model for Atmospheres (CARMA) to successfully simulate the multi-layered clouds of Venus. The present version of the one-dimensional model now includes a simple parameterization of the photochemicial production of sulfuric acid around altitudes of 62km, and its thermochemical destruction below cloud base. Photochemical production in the model is limited by the availability of water vapor and insolation. Upper cloud particles are introduced into the model via binary homogeneous nucleation, while the lower and middle cloud particles are created via activation of involatile cloud condensation nuclei. Growth by condensation and coagulation and coalescence are also treated. Mass loadings and particle sizes compare favorably with the in situ observations by the Pioneer Venus Large Probe Particle Size Spectrometer, and mixing ratios of volatiles compare favorably with remotely sensed observations of water vapor and sulfuric acid vapor. This work was supported by the NASA Planetary Atmospheres Program, grant number NNX11AD79G.

  17. Methods for Improving Aptamer Binding Affinity.

    PubMed

    Hasegawa, Hijiri; Savory, Nasa; Abe, Koichi; Ikebukuro, Kazunori

    2016-01-01

    Aptamers are single stranded oligonucleotides that bind a wide range of biological targets. Although aptamers can be isolated from pools of random sequence oligonucleotides using affinity-based selection, aptamers with high affinities are not always obtained. Therefore, further refinement of aptamers is required to achieve desired binding affinities. The optimization of primary sequences and stabilization of aptamer conformations are the main approaches to refining the binding properties of aptamers. In particular, sequence optimization using combined in silico sequence recombinations and in vitro functional evaluations is effective for the improvement of binding affinities, however, the binding affinities of aptamers are limited by the low hydrophobicity of nucleic acids. Accordingly, introduction of hydrophobic moieties into aptamers expands the diversity of interactions between aptamers and targets. Moreover, construction of multivalent aptamers by connecting aptamers that recognize distinct epitopes is an attractive approach to substantial increases in binding affinity. In addition, binding affinities can be tuned by optimizing the scaffolds of multivalent constructs. In this review, we summarize the various techniques for improving the binding affinities of aptamers. PMID:27043498

  18. Improving image segmentation by learning region affinities

    SciTech Connect

    Prasad, Lakshman; Yang, Xingwei; Latecki, Longin J

    2010-11-03

    We utilize the context information of other regions in hierarchical image segmentation to learn new regions affinities. It is well known that a single choice of quantization of an image space is highly unlikely to be a common optimal quantization level for all categories. Each level of quantization has its own benefits. Therefore, we utilize the hierarchical information among different quantizations as well as spatial proximity of their regions. The proposed affinity learning takes into account higher order relations among image regions, both local and long range relations, making it robust to instabilities and errors of the original, pairwise region affinities. Once the learnt affinities are obtained, we use a standard image segmentation algorithm to get the final segmentation. Moreover, the learnt affinities can be naturally unutilized in interactive segmentation. Experimental results on Berkeley Segmentation Dataset and MSRC Object Recognition Dataset are comparable and in some aspects better than the state-of-art methods.

  19. A global benchmark study using affinity-based biosensors.

    PubMed

    Rich, Rebecca L; Papalia, Giuseppe A; Flynn, Peter J; Furneisen, Jamie; Quinn, John; Klein, Joshua S; Katsamba, Phini S; Waddell, M Brent; Scott, Michael; Thompson, Joshua; Berlier, Judie; Corry, Schuyler; Baltzinger, Mireille; Zeder-Lutz, Gabrielle; Schoenemann, Andreas; Clabbers, Anca; Wieckowski, Sebastien; Murphy, Mary M; Page, Phillip; Ryan, Thomas E; Duffner, Jay; Ganguly, Tanmoy; Corbin, John; Gautam, Satyen; Anderluh, Gregor; Bavdek, Andrej; Reichmann, Dana; Yadav, Satya P; Hommema, Eric; Pol, Ewa; Drake, Andrew; Klakamp, Scott; Chapman, Trevor; Kernaghan, Dawn; Miller, Ken; Schuman, Jason; Lindquist, Kevin; Herlihy, Kara; Murphy, Michael B; Bohnsack, Richard; Andrien, Bruce; Brandani, Pietro; Terwey, Danny; Millican, Rohn; Darling, Ryan J; Wang, Liann; Carter, Quincy; Dotzlaf, Joe; Lopez-Sagaseta, Jacinto; Campbell, Islay; Torreri, Paola; Hoos, Sylviane; England, Patrick; Liu, Yang; Abdiche, Yasmina; Malashock, Daniel; Pinkerton, Alanna; Wong, Melanie; Lafer, Eileen; Hinck, Cynthia; Thompson, Kevin; Primo, Carmelo Di; Joyce, Alison; Brooks, Jonathan; Torta, Federico; Bagge Hagel, Anne Birgitte; Krarup, Janus; Pass, Jesper; Ferreira, Monica; Shikov, Sergei; Mikolajczyk, Malgorzata; Abe, Yuki; Barbato, Gaetano; Giannetti, Anthony M; Krishnamoorthy, Ganeshram; Beusink, Bianca; Satpaev, Daulet; Tsang, Tiffany; Fang, Eric; Partridge, James; Brohawn, Stephen; Horn, James; Pritsch, Otto; Obal, Gonzalo; Nilapwar, Sanjay; Busby, Ben; Gutierrez-Sanchez, Gerardo; Gupta, Ruchira Das; Canepa, Sylvie; Witte, Krista; Nikolovska-Coleska, Zaneta; Cho, Yun Hee; D'Agata, Roberta; Schlick, Kristian; Calvert, Rosy; Munoz, Eva M; Hernaiz, Maria Jose; Bravman, Tsafir; Dines, Monica; Yang, Min-Hsiang; Puskas, Agnes; Boni, Erica; Li, Jiejin; Wear, Martin; Grinberg, Asya; Baardsnes, Jason; Dolezal, Olan; Gainey, Melicia; Anderson, Henrik; Peng, Jinlin; Lewis, Mark; Spies, Peter; Trinh, Quyhn; Bibikov, Sergei; Raymond, Jill; Yousef, Mohammed; Chandrasekaran, Vidya; Feng, Yuguo; Emerick, Anne; Mundodo, Suparna; Guimaraes, Rejane; McGirr, Katy; Li, Yue-Ji; Hughes, Heather; Mantz, Hubert; Skrabana, Rostislav; Witmer, Mark; Ballard, Joshua; Martin, Loic; Skladal, Petr; Korza, George; Laird-Offringa, Ite; Lee, Charlene S; Khadir, Abdelkrim; Podlaski, Frank; Neuner, Phillippe; Rothacker, Julie; Rafique, Ashique; Dankbar, Nico; Kainz, Peter; Gedig, Erk; Vuyisich, Momchilo; Boozer, Christina; Ly, Nguyen; Toews, Mark; Uren, Aykut; Kalyuzhniy, Oleksandr; Lewis, Kenneth; Chomey, Eugene; Pak, Brian J; Myszka, David G

    2009-03-15

    To explore the variability in biosensor studies, 150 participants from 20 countries were given the same protein samples and asked to determine kinetic rate constants for the interaction. We chose a protein system that was amenable to analysis using different biosensor platforms as well as by users of different expertise levels. The two proteins (a 50-kDa Fab and a 60-kDa glutathione S-transferase [GST] antigen) form a relatively high-affinity complex, so participants needed to optimize several experimental parameters, including ligand immobilization and regeneration conditions as well as analyte concentrations and injection/dissociation times. Although most participants collected binding responses that could be fit to yield kinetic parameters, the quality of a few data sets could have been improved by optimizing the assay design. Once these outliers were removed, the average reported affinity across the remaining panel of participants was 620 pM with a standard deviation of 980 pM. These results demonstrate that when this biosensor assay was designed and executed appropriately, the reported rate constants were consistent, and independent of which protein was immobilized and which biosensor was used.

  20. New Quasar Studies Keep Fundamental Physical Constant Constant

    NASA Astrophysics Data System (ADS)

    2004-03-01

    Very Large Telescope sets stringent limit on possible variation of the fine-structure constant over cosmological time Summary Detecting or constraining the possible time variations of fundamental physical constants is an important step toward a complete understanding of basic physics and hence the world in which we live. A step in which astrophysics proves most useful. Previous astronomical measurements of the fine structure constant - the dimensionless number that determines the strength of interactions between charged particles and electromagnetic fields - suggested that this particular constant is increasing very slightly with time. If confirmed, this would have very profound implications for our understanding of fundamental physics. New studies, conducted using the UVES spectrograph on Kueyen, one of the 8.2-m telescopes of ESO's Very Large Telescope array at Paranal (Chile), secured new data with unprecedented quality. These data, combined with a very careful analysis, have provided the strongest astronomical constraints to date on the possible variation of the fine structure constant. They show that, contrary to previous claims, no evidence exist for assuming a time variation of this fundamental constant. PR Photo 07/04: Relative Changes with Redshift of the Fine Structure Constant (VLT/UVES) A fine constant To explain the Universe and to represent it mathematically, scientists rely on so-called fundamental constants or fixed numbers. The fundamental laws of physics, as we presently understand them, depend on about 25 such constants. Well-known examples are the gravitational constant, which defines the strength of the force acting between two bodies, such as the Earth and the Moon, and the speed of light. One of these constants is the so-called "fine structure constant", alpha = 1/137.03599958, a combination of electrical charge of the electron, the Planck constant and the speed of light. The fine structure constant describes how electromagnetic forces hold

  1. Exploring the Benefits of KM Education for LIS Professionals

    ERIC Educational Resources Information Center

    Hazeri, Afsaneh; Martin, Bill; Sarrafzadeh, Maryam

    2009-01-01

    It is to be expected that in a new and emerging discipline like knowledge management (KM) there still will be ambivalence among both LIS educational institutions and their students, as to the need to have KM courses. Investigating the benefits of engaging with these programs might help to clear up this ambiguity. The present paper seeks to shed…

  2. 7 CFR 29.1035 - Mixed color (KM).

    Code of Federal Regulations, 2012 CFR

    2012-01-01

    ... 7 Agriculture 2 2012-01-01 2012-01-01 false Mixed color (KM). 29.1035 Section 29.1035 Agriculture Regulations of the Department of Agriculture AGRICULTURAL MARKETING SERVICE (Standards, Inspections, Marketing... Type 92) § 29.1035 Mixed color (KM). Distinctly different colors of the type mingled together....

  3. 7 CFR 29.1035 - Mixed color (KM).

    Code of Federal Regulations, 2013 CFR

    2013-01-01

    ... 7 Agriculture 2 2013-01-01 2013-01-01 false Mixed color (KM). 29.1035 Section 29.1035 Agriculture Regulations of the Department of Agriculture AGRICULTURAL MARKETING SERVICE (Standards, Inspections, Marketing... Type 92) § 29.1035 Mixed color (KM). Distinctly different colors of the type mingled together....

  4. 7 CFR 29.1035 - Mixed color (KM).

    Code of Federal Regulations, 2014 CFR

    2014-01-01

    ... 7 Agriculture 2 2014-01-01 2014-01-01 false Mixed color (KM). 29.1035 Section 29.1035 Agriculture Regulations of the Department of Agriculture AGRICULTURAL MARKETING SERVICE (Standards, Inspections, Marketing... Type 92) § 29.1035 Mixed color (KM). Distinctly different colors of the type mingled together....

  5. 7 CFR 29.1035 - Mixed color (KM).

    Code of Federal Regulations, 2010 CFR

    2010-01-01

    ... 7 Agriculture 2 2010-01-01 2010-01-01 false Mixed color (KM). 29.1035 Section 29.1035 Agriculture Regulations of the Department of Agriculture AGRICULTURAL MARKETING SERVICE (Standards, Inspections, Marketing... Type 92) § 29.1035 Mixed color (KM). Distinctly different colors of the type mingled together....

  6. 7 CFR 29.1035 - Mixed color (KM).

    Code of Federal Regulations, 2011 CFR

    2011-01-01

    ... 7 Agriculture 2 2011-01-01 2011-01-01 false Mixed color (KM). 29.1035 Section 29.1035 Agriculture Regulations of the Department of Agriculture AGRICULTURAL MARKETING SERVICE (Standards, Inspections, Marketing... Type 92) § 29.1035 Mixed color (KM). Distinctly different colors of the type mingled together....

  7. Anion-induced increases in the affinity of colcemid binding to tubulin.

    PubMed

    Ray, K; Bhattacharyya, B; Biswas, B B

    1984-08-01

    Colcemid binds tubulin rapidly and reversibly in contrast to colchicine which binds tubulin relatively slowly and essentially irreversibly. At 37 degrees C the association rate constant for colcemid binding is 1.88 X 10(6) M-1 h-1, about 10 times higher than that for colchicine; this is reflected in the activation energies for binding which are 51.4 kJ/mol for colcemid and 84.8 kJ/mol for colchicine. Scatchard analysis indicates two binding sites on tubulin having different affinities for colcemid. The high-affinity site (Ka = 0.7 X 10(5) M-1 at 37 degrees C) is sensitive to temperature and binds both colchicine and colcemid and hence they are mutually competitive inhibitors. The low-affinity site (Kb = 1.2 X 10(4) M-1) is rather insensitive to temperature and binds only colcemid. Like colchicine, 0.6 mol of colcemid are bound/mol of tubulin dimer (at the high-affinity site) and the reaction is entropy driven (163 J K-1 mol-1). Similar to colchicine, colcemid binding to tubulin is stimulated by certain anions (viz. sulfate and tartrate) but by a different mechanism. Colcemid binding affinity at the lower-affinity site of tubulin is increased in the presence of ammonium sulfate. Interestingly, the lower-affinity site on tubulin for colcemid, even when converted to higher affinity in presence of ammonium sulfate, is not recognized by colchicine. We conclude that tubulin possesses two binding sites, one of which specifically recognized the groups present on the B-ring of colchicine molecule and is effected by the ammonium sulfate, whereas the higher-affinity site, which could accommodate both colchicine and colcemid, possibly recognized the A and C ring of colchicine.

  8. Exploring KM Features of High-Performance Companies

    NASA Astrophysics Data System (ADS)

    Wu, Wei-Wen

    2007-12-01

    For reacting to an increasingly rival business environment, many companies emphasize the importance of knowledge management (KM). It is a favorable way to explore and learn KM features of high-performance companies. However, finding out the critical KM features of high-performance companies is a qualitative analysis problem. To handle this kind of problem, the rough set approach is suitable because it is based on data-mining techniques to discover knowledge without rigorous statistical assumptions. Thus, this paper explored KM features of high-performance companies by using the rough set approach. The results show that high-performance companies stress the importance on both tacit and explicit knowledge, and consider that incentives and evaluations are the essentials to implementing KM.

  9. Marshall Space Flight Center Propulsion Systems Department (PSD) KM Initiative

    NASA Technical Reports Server (NTRS)

    Caraccioli, Paul; Varnadoe, Tom; McCarter, Mike

    2006-01-01

    NASA Marshall Space Flight Center s Propulsion Systems Department (PSD) is four months into a fifteen month Knowledge Management (KM) initiative to support enhanced engineering decision making and analyses, faster resolution of anomalies (near-term) and effective, efficient knowledge infused engineering processes, reduced knowledge attrition, and reduced anomaly occurrences (long-term). The near-term objective of this initiative is developing a KM Pilot project, within the context of a 3-5 year KM strategy, to introduce and evaluate the use of KM within PSD. An internal NASA/MSFC PSD KM team was established early in project formulation to maintain a practitioner, user-centric focus throughout the conceptual development, planning and deployment of KM technologies and capabilities with in the PSD. The PSD internal team is supported by the University of Alabama's Aging Infrastructure Systems Center Of Excellence (AISCE), Intergraph Corporation, and The Knowledge Institute. The principle product of the initial four month effort has been strategic planning of PSD KM implementation by first determining the "as is" state of KM capabilities and developing, planning and documenting the roadmap to achieve the desired "to be" state. Activities undertaken to support the planning phase have included data gathering; cultural surveys, group work-sessions, interviews, documentation review, and independent research. Assessments and analyses have been performed including industry benchmarking, related local and Agency initiatives, specific tools and techniques used and strategies for leveraging existing resources, people and technology to achieve common KM goals. Key findings captured in the PSD KM Strategic Plan include the system vision, purpose, stakeholders, prioritized strategic objectives mapped to the top ten practitioner needs and analysis of current resource usage. Opportunities identified from research, analyses, cultural/KM surveys and practitioner interviews include

  10. Affinity Proteomics in the mountains: Alpbach 2015.

    PubMed

    Taussig, Michael J

    2016-09-25

    The 2015 Alpbach Workshop on Affinity Proteomics, organised by the EU AFFINOMICS consortium, was the 7th workshop in this series. As in previous years, the focus of the event was the current state of affinity methods for proteome analysis, including complementarity with mass spectrometry, progress in recombinant binder production methods, alternatives to classical antibodies as affinity reagents, analysis of proteome targets, industry focus on biomarkers, and diagnostic and clinical applications. The combination of excellent science with Austrian mountain scenery and winter sports engender an atmosphere that makes this series of workshops exceptional. The articles in this Special Issue represent a cross-section of the presentations at the 2015 meeting. PMID:27118167

  11. Aptamers in Affinity Separations: Stationary Separation

    NASA Astrophysics Data System (ADS)

    Ravelet, Corinne; Peyrin, Eric

    The use of DNA or RNA aptamers as tools in analytical chemistry is a very promising field of research because of their capabilities to bind specifically the target molecules with an affinity similar to that of antibodies. Notably, they appear to be of great interest as target-specific ligands for the separation and capture of various analytes in affinity chromatography and related affinity-based methods such as magnetic bead technology. In this chapter, the recent developments of these aptamer-based separation/capture approaches are addressed.

  12. Beyond Vmax and Km: How details of enzyme function influence geochemical cycles

    NASA Astrophysics Data System (ADS)

    Steen, A. D.

    2015-12-01

    Enzymes catalyze the vast majority of chemical reactions relevant to geomicrobiology. Studies of the activities of enzymes in environmental systems often report Vmax (the maximum possible rate of reaction; often proportional to the concentration of enzymes in the system) and sometimes Km (a measure of the affinity between enzymes and their substrates). However, enzyme studies - particularly those related to enzymes involved in organic carbon oxidation - are often limited to only those parameters, and a relatively limited and mixed set of enzymes. Here I will discuss some novel methods to assay and characterize the specific sets of enzymes that may be important to the carbon cycle in aquatic environments. First, kinetic experiments revealed the collective properties of the complex mixtures of extracellular peptidases that occur where microbial communities are diverse. Crystal structures combined with biochemical characterization of specific enzymes can yield more detailed information about key steps in organic carbon transformations. These new techniques have the potential to provide mechanistic grounding to geomicrobiological models.

  13. Pht2;1 encodes a low-affinity phosphate transporter from Arabidopsis.

    PubMed Central

    Daram, P; Brunner, S; Rausch, C; Steiner, C; Amrhein, N; Bucher, M

    1999-01-01

    An Arabidopsis genomic sequence was recently shown to share similarity with bacterial and eukaryotic phosphate (Pi) transporters. We have cloned the corresponding cDNA, which we named Pht2;1, and subsequently performed gene expression studies and functional analysis of the protein product. The cDNA encodes a 61-kD protein with a putative topology of 12 transmembrane (TM) domains interrupted by a large hydrophilic loop between TM8 and TM9. Two boxes of eight and nine amino acids, located in the N- and C-terminal domains, respectively, are highly conserved among species across all kingdoms (eubacteria, archea, fungi, plants, and animals). The Pht2;1 gene is predominantly expressed in green tissue, the amount of transcript staying constant in leaves irrespective of the Pi status of the shoot; in roots, however, there is a marginal increase in mRNA amounts in response to Pi deprivation. Although the protein is highly similar to eukaryotic sodium-dependent Pi transporters, functional analysis of the Pht2;1 protein in mutant yeast cells indicates that it is a proton/Pi symporter dependent on the electrochemical gradient across the plasma membrane. Its fairly high apparent K(m) for Pi (0.4 mM) and high mRNA content in the shoot, especially in leaves, suggest a role for shoot organs in Pi loading. Pht2;1 thus differs from members of the recently described plant Pi transporter family in primary structure, affinity for Pi, and presumed function. PMID:10559441

  14. The KM phase in semi-realistic heterotic orbifold models

    SciTech Connect

    Giedt, Joel

    2000-07-05

    In string-inspired semi-realistic heterotic orbifolds models with an anomalous U(1){sub X},a nonzero Kobayashi-Masakawa (KM) phase is shown to arise generically from the expectation values of complex scalar fields, which appear in nonrenormalizable quark mass couplings. Modular covariant nonrenormalizable superpotential couplings are constructed. A toy Z{sub 3} orbifold model is analyzed in some detail. Modular symmetries and orbifold selection rules are taken into account and do not lead to a cancellation of the KM phase. We also discuss attempts to obtain the KM phase solely from renormalizable interactions.

  15. Constant-Pressure Hydraulic Pump

    NASA Technical Reports Server (NTRS)

    Galloway, C. W.

    1982-01-01

    Constant output pressure in gas-driven hydraulic pump would be assured in new design for gas-to-hydraulic power converter. With a force-multiplying ring attached to gas piston, expanding gas would apply constant force on hydraulic piston even though gas pressure drops. As a result, pressure of hydraulic fluid remains steady, and power output of the pump does not vary.

  16. PRINCIPLES OF AFFINITY-BASED BIOSENSORS

    EPA Science Inventory

    Despite the amount of resources that have been invested by national and international academic, government, and commercial sectors to develop affinity-based biosensor products, little obvious success has been realized through commercialization of these devices for specific applic...

  17. Visualizing Antibody Affinity Maturation in Germinal Centers

    PubMed Central

    Tas, Jeroen M.J.; Mesin, Luka; Pasqual, Giulia; Targ, Sasha; Jacobsen, Johanne T.; Mano, Yasuko M.; Chen, Casie S.; Weill, Jean-Claude; Reynaud, Claude-Agnès; Browne, Edward P.; Meyer-Hermann, Michael; Victora, Gabriel D.

    2016-01-01

    Antibodies somatically mutate to attain high affinity in germinal centers (GCs). There, competition between B cell clones and among somatic mutants of each clone drives an increase in average affinity across the population. The extent to which higher-affinity cells eliminating competitors restricts clonal diversity is unknown. By combining multiphoton microscopy and sequencing, we show that tens to hundreds of distinct B cell clones seed each GC, and that GCs lose clonal diversity at widely disparate rates. Furthermore, efficient affinity maturation can occur in the absence of homogenizing selection, ensuring that many clones can mature in parallel within the same GC. Our findings have implications for development of vaccines in which antibodies with non-immunodominant specificities must be elicited, as is the case for HIV-1 and influenza. PMID:26912368

  18. Protein purification using PDZ affinity chromatography.

    PubMed

    Walkup, Ward G; Kennedy, Mary B

    2015-01-01

    PDZ domains function in nature as protein-binding domains within scaffold and membrane-associated proteins. They comprise approximately 90 residues and undergo specific, high-affinity interactions with complementary C-terminal peptide sequences, other PDZ domains, and/or phospholipids. We have previously shown that the specific, strong interactions of PDZ domains with their ligands make them well suited for use in affinity chromatography. This unit provides protocols for the PDZ affinity chromatography procedure that are applicable for the purification of proteins that contain PDZ domains or PDZ domain-binding ligands, either naturally or introduced by genetic engineering. We detail the preparation of affinity resins composed of PDZ domains or PDZ domain peptide ligands coupled to solid supports. These resins can be used to purify proteins containing endogenous or genetically introduced PDZ domains or ligands, eluting the proteins with free PDZ domain peptide ligands. PMID:25829303

  19. Designing Chaotic Systems by Piecewise Affine Systems

    NASA Astrophysics Data System (ADS)

    Wu, Tiantian; Li, Qingdu; Yang, Xiao-Song

    Based on mathematical analysis, this paper provides a methodology to ensure the existence of homoclinic orbits in a class of three-dimensional piecewise affine systems. In addition, two chaotic generators are provided to illustrate the effectiveness of the method.

  20. Affinity Electrophoresis Using Ligands Attached To Polymers

    NASA Technical Reports Server (NTRS)

    Van Alstine, James M.; Snyder, Robert S.; Harris, J. M.; Brooks, D. E.

    1990-01-01

    In new technique, reduction of electrophoretic mobilities by addition of polyethylene glycol to ligands increases electrophoretic separabilities. In immuno-affinity electrophoresis, modification of ligands extends specificity of electrophoretic separation to particles having surface electric-charge structures otherwise making them electrophoretically inseparable. Modification of antibodies by polyethylene glycol greatly reduces ability to aggregate while enhancing ability to affect electrophoretic mobilities of cells. In hydrophobic-affinity electrophoresis, addition of polyethylene glycol reduces tendency toward aggregation of cells or macromolecules.

  1. Diacylglycerol kinase η1 is a high affinity isozyme for diacylglycerol.

    PubMed

    Komenoi, Suguru; Takemura, Fumika; Sakai, Hiromichi; Sakane, Fumio

    2015-05-01

    Diacylglycerol kinase (DGK) η plays important roles in various patho-physiological events such as oncogenesis. In this study, we performed an enzymological characterization of DGKη splice variant 1 (DGKη1). The Km value for diacylglycerol was 0.14 mol%. Intriguingly, the Km value of DGKη1 for diacylglycerol was at least 9-fold lower than those of other DGK isozymes including DGKα, indicating that DGKη1 is a high affinity isozyme for diacylglycerol. Therefore, DGKη1 is a unique DGK isozyme, which may function at particular membrane sites where only low concentrations of diacylglycerol are supplied.

  2. The -145 km/s Absorption System of Eta Carinae

    NASA Technical Reports Server (NTRS)

    Vieira, G.; Gull, Theodore R.; Danks, A.; Johansson, S.

    2002-01-01

    With the STIS E230H mode (R approx. 118,000), we have identified about twenty absorption components in line of sight from Eta Carinae. Two components, one at -513 km/s and another at -145 km/s, are quite different in character from the others, mostly at intermediate velocities. The -145 km/s component is significantly wider in fwhm, is seen in many more species, and the lower level can be above 20,000/cm, well above the 2000/cm noted in the -513 km/s component. In the spectral region from 2400 to 3160A, approximately 500 absorption lines have been identified. In this poster, we will present line identifications and atomic parameters of the measured lines, hopefully providing insight as to what levels are being excited and by what processes. Observations were accomplished through STScI under proposal 9242. Funding is through the STIS GTO resources.

  3. 4-km body(ies?) embedded in Saturn's Huygens Ringlet

    NASA Astrophysics Data System (ADS)

    Spitale, Joseph N.; Hahn, Joseph M.; Tamayo, Daniel

    2016-05-01

    Saturn's 20-km-wide Huygens ringlet, located ~250 km exterior to the B ring, displays unusual kinematics, as evidenced by a time variable width-relation. The cause of this behavior is not clear, but may be related to the presence of large embedded bodies (Spitale and Hahn 2016). The largest such bodies produce half-propeller-shaped disturbances originating at the inner edge of the ringlet, whose radial widths imply a size of ~4 km, based on simple scaling from A-ring propellers. Here, we show that a numerical N-body model of the ringlet with a 4-km body embedded near the inner edge produces features that are consistent with the observed half propellers.

  4. High energy neutrino detection with KM3NeT

    NASA Astrophysics Data System (ADS)

    Migliozzi, Pasquale; KM3NeT Collaboration

    2016-05-01

    The KM3NeT Collaboration has started the construction of a next generation high-energy neutrino telescope in the Mediterranean Sea: the largest and most sensitive neutrino research infrastructure. The full KM3NeT detector will be a several cubic kilometres distributed, networked infrastructure. In Italy, off the coast of Capo Passero, and in France, off the coast of Toulon. Thanks to its location in the Northern hemisphere and to its large instrumented volume, KM3NeT will be the optimal instrument to search for neutrinos from the Southern sky and in particular from the Galactic plane, thus making it complementary to IceCube. In this work the technologically innovative component of the detector, the status of construction and the first results from prototypes of the KM3NeT detector will be described as well as its capability to discover neutrino sources are reported.

  5. Akeno 20 km (2) air shower array (Akeno Branch)

    NASA Technical Reports Server (NTRS)

    Teshima, M.; Ohoka, H.; Matsubara, Y.; Hara, T.; Hatano, Y.; Hayashida, N.; He, C. X.; Honda, M.; Ishikawa, F.; Kamata, K.

    1985-01-01

    As the first stage of the future huge array, the Akeno air shower array was expanded to about 20 sq. km. by adding 19 scintillation detectors of 2.25 sq m area outside the present 1 sq. km. Akeno array with a new data collection system. These detectors are spaced about 1km from each other and connected by two optical fiber cables. This array has been in partial operation from 8th, Sep. 1984 and full operation from 20th, Dec. 1984. 20 sq m muon stations are planned to be set with 2km separation and one of them is now under construction. The origin of the highest energy cosmic rays is studied.

  6. How does music aid 5 km of running?

    PubMed

    Bigliassi, Marcelo; León-Domínguez, Umberto; Buzzachera, Cosme F; Barreto-Silva, Vinícius; Altimari, Leandro R

    2015-02-01

    This research investigated the effects of music and its time of application on a 5-km run. Fifteen well-trained male long-distance runners (24.87 ± 2.47 years; 78.87 ± 10.57 kg; 178 ± 07 cm) participated in this study. Five randomized experimental conditions during a 5-km run on an official track were tested (PM: motivational songs, applied before 5 km of running; SM: slow motivational songs, applied during 5 km of running; FM: fast and motivational songs, applied during 5 km of running; CS: calm songs, applied after 5 km of running; CO: control condition). Psychophysiological assessments were performed before (functional near-infrared spectroscopy, heart rate variability [HRV], valence, and arousal), during (performance time, heart rate, and rate of perceived exertion [RPE]), and after (mood, RPE, and HRV) tests. The chosen songs were considered pleasurable and capable of activating. Furthermore, they activated the 3 assessed prefrontal cortex (PFC) areas (medial, right dorsolateral, and left dorsolateral) similarly, generating positive emotional consequences by autonomous system analysis. The first 800 m was accomplished faster for SM and FM compared with other conditions (p ≤ 0.05); moreover, there was a high probability of improving running performance when music was applied (SM: 89%; FM: 85%; PM: 39%). Finally, music was capable of accelerating vagal tonus after 5 km of running with CS (p ≤ 0.05). In conclusion, music was able to activate the PFC area, minimize perceptions, improve performance, and accelerate recovery during 5 km of running.

  7. How does music aid 5 km of running?

    PubMed

    Bigliassi, Marcelo; León-Domínguez, Umberto; Buzzachera, Cosme F; Barreto-Silva, Vinícius; Altimari, Leandro R

    2015-02-01

    This research investigated the effects of music and its time of application on a 5-km run. Fifteen well-trained male long-distance runners (24.87 ± 2.47 years; 78.87 ± 10.57 kg; 178 ± 07 cm) participated in this study. Five randomized experimental conditions during a 5-km run on an official track were tested (PM: motivational songs, applied before 5 km of running; SM: slow motivational songs, applied during 5 km of running; FM: fast and motivational songs, applied during 5 km of running; CS: calm songs, applied after 5 km of running; CO: control condition). Psychophysiological assessments were performed before (functional near-infrared spectroscopy, heart rate variability [HRV], valence, and arousal), during (performance time, heart rate, and rate of perceived exertion [RPE]), and after (mood, RPE, and HRV) tests. The chosen songs were considered pleasurable and capable of activating. Furthermore, they activated the 3 assessed prefrontal cortex (PFC) areas (medial, right dorsolateral, and left dorsolateral) similarly, generating positive emotional consequences by autonomous system analysis. The first 800 m was accomplished faster for SM and FM compared with other conditions (p ≤ 0.05); moreover, there was a high probability of improving running performance when music was applied (SM: 89%; FM: 85%; PM: 39%). Finally, music was capable of accelerating vagal tonus after 5 km of running with CS (p ≤ 0.05). In conclusion, music was able to activate the PFC area, minimize perceptions, improve performance, and accelerate recovery during 5 km of running. PMID:25029009

  8. EF5 Is the High-Affinity Mg(2+) Site in ALG-2.

    PubMed

    Tanner, John J; Frey, Benjamin B; Pemberton, Travis; Henzl, Michael T

    2016-09-13

    The penta-EF-hand (PEF) protein ALG-2 (apoptosis-linked gene 2) has been implicated in several important physiological processes, including endoplasmic reticulum-Golgi vesicular transport and endosomal biogenesis/transport. ALG-2 was recently shown to harbor a metal ion-binding site with a high affinity for Mg(2+) and a low affinity for Ca(2+). We herein present the X-ray structure of Mg(2+)-bound ALG-2des23(wt). Although the C(α) trace is nearly indistinguishable from that of the Ca(2+)-free protein, the orientation of the C-terminal helix differs in the two structures. Consistent with that observation, replacement of the +x ligand in EF5, D169, with alanine eliminates high-affinity Mg(2+) binding. It also eliminates the low-affinity Ca(2+) site and lowers the affinity of the remaining Ca(2+)-binding sites, EF3 and EF1. The coordination environment in EF5 approaches ideal Mg(2+) octahedral geometry. The ligand array, consisting of three carboxylates (+x, +y, +z), a backbone carbonyl (-y), and two water molecules (-x, -z), may offer a recipe for a high-affinity, high-selectivity Mg(2+)-binding site. Sequence data for other PEF proteins indicate that select calpain large subunits, notably CAPN1 and CAPN8, may also possess a high-affinity Mg(2+)-binding site. In Mg(2+)-bound ALG-2, the carbonyl of F188 and the C-terminal carboxylate of V191 interact with the ε-ammonium group of K137 in the opposing subunit, suggesting that Mg(2+) binding could have an impact on dimerization. Interestingly, EF1 and EF3 are also occupied in the crystal, despite having modest affinity for Mg(2+). The results of a calorimetry-based analysis indicate that their Mg(2+) binding constants are 2 orders of magnitude lower than that determined for EF5. PMID:27541325

  9. Constants and Variables of Nature

    SciTech Connect

    Sean Carroll

    2009-04-03

    It is conventional to imagine that the various parameters which characterize our physical theories, such as the fine structure constant or Newton’s gravitational constant, are truly “constant”, in the sense that they do not change from place to place or time to time. Recent developments in both theory and observation have led us to re-examine this assumption, and to take seriously the possibility that our supposed constants are actually gradually changing. I will discuss why we might expect these parameters to vary, and what observation and experiment have to say about the issue.

  10. Local fluctuations of ozone from 16 km to 45 km deduced from in situ vertical ozone profile

    NASA Technical Reports Server (NTRS)

    Moreau, G.; Robert, C.

    1994-01-01

    A vertical ozone profile obtained by an in situ ozone sonde from 16 km to 45 km, has allowed to observe local ozone concentration variations. These variations can be observed, thanks to a fast measurement system based on a UV absorption KrF excimer laser beam in a multipass cell. Ozone standard deviation versus altitude calculated from the mean is derived. Ozone variations or fluctuations are correlated with the different dynamic zones of the stratosphere.

  11. Varying Constants, Gravitation and Cosmology

    NASA Astrophysics Data System (ADS)

    Uzan, Jean-Philippe

    2011-12-01

    Fundamental constants are a cornerstone of our physical laws. Any constant varying in space and/or time would reflect the existence of an almost massless field that couples to matter. This will induce a violation of the universality of free fall. Thus, it is of utmost importance for our understanding of gravity and of the domain of validity of general relativity to test for their constancy. We detail the relations between the constants, the tests of the local position invariance and of the universality of free fall. We then review the main experimental and observational constraints that have been obtained from atomic clocks, the Oklo phenomenon, solar system observations, meteorite dating, quasar absorption spectra, stellar physics, pulsar timing, the cosmic microwave background and big bang nucleosynthesis. At each step we describe the basics of each system, its dependence with respect to the constants, the known systematic effects and the most recent constraints that have been obtained. We then describe the main theoretical frameworks in which the low-energy constants may actually be varying and we focus on the unification mechanisms and the relations between the variation of different constants. To finish, we discuss the more speculative possibility of understanding their numerical values and the apparent fine-tuning that they confront us with.

  12. Characterization of methacrylate chromatographic monoliths bearing affinity ligands.

    PubMed

    Černigoj, Urh; Vidic, Urška; Nemec, Blaž; Gašperšič, Jernej; Vidič, Jana; Lendero Krajnc, Nika; Štrancar, Aleš; Podgornik, Aleš

    2016-09-16

    We investigated effect of immobilization procedure and monolith structure on chromatographic performance of methacrylate monoliths bearing affinity ligands. Monoliths of different pore size and various affinity ligands were prepared and characterized using physical and chromatographic methods. When testing protein A monoliths with different protein A ligand densities, a significant nonlinear effect of ligand density on dynamic binding capacity (DBC) for IgG was obtained and accurately described by Langmuir isotherm curve enabling estimation of protein A utilization as a function of ligand density. Maximal IgG binding capacity was found to be at least 12mg/mL exceeding theoretical monolayer adsorption value of 7.8mg/mL assuming hexagonal packing and IgG hydrodynamic diameter of 11nm. Observed discrepancy was explained by shrinkage of IgG during adsorption on protein A experimentally determined through calculated adsorbed IgG layer thickness of 5.4nm from pressure drop data. For monoliths with different pore size maximal immobilized densities of protein A as well as IgG dynamic capacity linearly correlates with monolith surface area indicating constant ligand utilization. Finally, IgGs toward different plasma proteins were immobilized via the hydrazide coupling chemistry to provide oriented immobilization. DBC was found to be flow independent and was increasing with the size of bound protein. Despite DBC was lower than IgG capacity to immobilized protein A, ligand utilization was higher. PMID:27554023

  13. Jen1p: A High Affinity Selenite Transporter in Yeast

    PubMed Central

    McDermott, Joseph R.; Rosen, Barry P.

    2010-01-01

    Selenium is a micronutrient in most eukaryotes, including humans, which is well known for having an extremely thin border between beneficial and toxic concentrations. Soluble tetravalent selenite is the predominant environmental form and also the form that is applied in the treatment of human diseases. To acquire this nutrient from low environmental concentrations as well as to avoid toxicity, a well-controlled transport system is required. Here we report that Jen1p, a proton-coupled monocarboxylate transporter in S. cerevisiae, catalyzes high-affinity uptake of selenite. Disruption of JEN1 resulted in selenite resistance, and overexpression resulted in selenite hypersensitivity. Transport assay showed that overexpression of Jen1p enables selenite accumulation in yeast compared with a JEN1 knock out strain, indicating the Jen1p transporter facilitates selenite accumulation inside cells. Selenite uptake by Jen1p had a Km of 0.91 mM, which is comparable to the Km for lactate. Jen1p transported selenite in a proton-dependent manner which resembles the transport mechanism for lactate. In addition, selenite and lactate can inhibit the transport of each other competitively. Therefore, we postulate selenite is a molecular mimic of monocarboxylates which allows selenite to be transported by Jen1p. PMID:20861301

  14. Solubilization and partial characterization of a microsomal high affinity GTPase

    SciTech Connect

    Nicchitta, C.; Williamson, J.R.

    1987-05-01

    Isolated rat liver microsomes release sequestered Ca/sup 2 +/ following addition of GTP. In contrast to permeabilized cells, GTP dependent microsomal Ca/sup 2 +/ release requires low concentrations of polyethylene glycol (PEG). They have identified a microsomal, PEG-sensitive high affinity GTPase which shares a number of characteristics with the GTP-dependent Ca/sup 2 +/ release system. To aid in further characterization of this activity they have initiated studies on the solubilization and purification of the microsomal GTPases. When microsomes are solubilized under the following conditions (150 mM NaCl, 5 mg protein/ml, 1% Triton X-114) PEG sensitive GTPase activity selectively partitions into the detergent rich phase of the Triton X-114 extract. As observed in intact microsomal membranes the Triton X-114 soluble GTPase is maximally stimulated by 3% PEG. Half maximal stimulation is observed at 1% PEG. PEG increases the Vmax of this activity; no effects on Km were observed. The Km for GTP of the detergent soluble GTPase is 5 ..mu..M. This GTPase is sensitive to inhibition by sulfhydryl reagents. PEG-sensitive GTPase activity was completely inhibited in the presence of 25 ..mu..M p-hydroxymercuribenzoate (PHMB); half maximal inhibition was observed at 5 ..mu..M. Labeling of the Triton X-114 extract with the photosensitive compound (/sup 32/P) 8-azido GTP indicated the presence of two prominent GTP binding proteins of approximate molecular weights 17 and 54 kD.

  15. Advances in affinity ligand-functionalized nanomaterials for biomagnetic separation.

    PubMed

    Fields, Conor; Li, Peng; O'Mahony, James J; Lee, Gil U

    2016-01-01

    The downstream processing of proteins remains the most significant cost in protein production, and is largely attributed to rigorous chromatographic purification protocols, where the stringency of purity for biopharmaceutical products sometimes exceeds 99%. With an ever burgeoning biotechnology market, there is a constant demand for alternative purification methodologies, to ameliorate the dependence on chromatography, while still adhering to regulatory concerns over product purity and safety. In this article, we present an up-to-date view of bioseparation, with emphasis on magnetic separation and its potential application in the field. Additionally, we discuss the economic and performance benefits of synthetic ligands, in the form of peptides and miniaturized antibody fragments, compared to full-length antibodies. We propose that adoption of synthetic affinity ligands coupled with magnetic adsorbents, will play an important role in enabling sustainable bioprocessing in the future.

  16. Advances in affinity ligand-functionalized nanomaterials for biomagnetic separation.

    PubMed

    Fields, Conor; Li, Peng; O'Mahony, James J; Lee, Gil U

    2016-01-01

    The downstream processing of proteins remains the most significant cost in protein production, and is largely attributed to rigorous chromatographic purification protocols, where the stringency of purity for biopharmaceutical products sometimes exceeds 99%. With an ever burgeoning biotechnology market, there is a constant demand for alternative purification methodologies, to ameliorate the dependence on chromatography, while still adhering to regulatory concerns over product purity and safety. In this article, we present an up-to-date view of bioseparation, with emphasis on magnetic separation and its potential application in the field. Additionally, we discuss the economic and performance benefits of synthetic ligands, in the form of peptides and miniaturized antibody fragments, compared to full-length antibodies. We propose that adoption of synthetic affinity ligands coupled with magnetic adsorbents, will play an important role in enabling sustainable bioprocessing in the future. PMID:26032605

  17. The KM3NeT Digital Optical Module

    NASA Astrophysics Data System (ADS)

    Vivolo, Daniele

    2016-04-01

    KM3NeT is a European deep-sea multidisciplinary research infrastructure in the Mediterranean Sea. It will host a km3-scale neutrino telescope and dedicated instruments for long-term and continuous measurements for Earth and Sea sciences. The KM3NeT neutrino telescope is a 3-dimensional array of Digital Optical Modules, suspended in the sea by means of vertical string structures, called Detection Units, supported by two pre-stretched Dyneema ropes, anchored to the seabed and kept taut with a system of buoys. The Digital Optical Module represents the active part of the neutrino telescope. It is composed by a 17-inch, 14 mm thick borosilicate glass (Vitrovex) spheric vessel housing 31 photomultiplier tubes with 3-inch photocathode diameter and the associated front-end and readout electronics. The technical solution adopted for the KM3NeT optical modules is characterized by an innovative design, considering that existing neutrino telescopes, Baikal, IceCube and ANTARES, all use large photomultipliers, typically with a diameter of 8″ or 10″. It offers several advantages: higher sensitive surface (1260 cm2), weaker sensitivity to Earth's magnetic field, better distinction between single-photon and multi-photon events (photon counting) and directional information with an almost isotropic field of view. In this contribution the design and the performance of the KM3NeT Digital Optical Modules are discussed, with a particular focus on enabling technologies and integration procedure.

  18. Gravity Waves Near 300 km Over the Polar Caps

    NASA Technical Reports Server (NTRS)

    Johnson, F. S.; Hanson, W. B.; Hodges, R. R.; Coley, W. R.; Carignan, G. R.; Spencer, N. W.

    1995-01-01

    Distinctive wave forms in the distributions of vertical velocity and temperature of both neutral particles and ions are frequently observed from Dynamics Explorer 2 at altitudes above 250 km over the polar caps. These are interpreted as being due to internal gravity waves propagating in the neutral atmosphere. The disturbances characterized by vertical velocity perturbations of the order of 100 m/s and horizontal wave lengths along the satellite path of about 500 km. They often extend across the entire polar cap. The associated temperature perturbations indicate that the horizontal phase progression is from the nightside to the dayside. Vertical displacements are inferred to be of the order of 10 km and the periods to be of the order of 10(exp 3) s. The waves must propagate in the neutral atmosphere, but they usually are most clearly recognizable in the observations of ion vertical velocity and ion temperature. By combining the neutral pressure calculated from the observed neutral concentration and temperature with the vertical component of the neutral velocity, an upward energy flux of the order of 0.04 erg/sq cm-s at 250 km has been calculated, which is about equal to the maximum total solar ultraviolet heat input above that altitude. Upward energy fluxes calculated from observations on orbital passes at altitudes from 250 to 560 km indicate relatively little attenuation with altitude.

  19. Classification of neocortical interneurons using affinity propagation

    PubMed Central

    Santana, Roberto; McGarry, Laura M.; Bielza, Concha; Larrañaga, Pedro; Yuste, Rafael

    2013-01-01

    In spite of over a century of research on cortical circuits, it is still unknown how many classes of cortical neurons exist. In fact, neuronal classification is a difficult problem because it is unclear how to designate a neuronal cell class and what are the best characteristics to define them. Recently, unsupervised classifications using cluster analysis based on morphological, physiological, or molecular characteristics, have provided quantitative and unbiased identification of distinct neuronal subtypes, when applied to selected datasets. However, better and more robust classification methods are needed for increasingly complex and larger datasets. Here, we explored the use of affinity propagation, a recently developed unsupervised classification algorithm imported from machine learning, which gives a representative example or exemplar for each cluster. As a case study, we applied affinity propagation to a test dataset of 337 interneurons belonging to four subtypes, previously identified based on morphological and physiological characteristics. We found that affinity propagation correctly classified most of the neurons in a blind, non-supervised manner. Affinity propagation outperformed Ward's method, a current standard clustering approach, in classifying the neurons into 4 subtypes. Affinity propagation could therefore be used in future studies to validly classify neurons, as a first step to help reverse engineer neural circuits. PMID:24348339

  20. Classification of neocortical interneurons using affinity propagation.

    PubMed

    Santana, Roberto; McGarry, Laura M; Bielza, Concha; Larrañaga, Pedro; Yuste, Rafael

    2013-01-01

    In spite of over a century of research on cortical circuits, it is still unknown how many classes of cortical neurons exist. In fact, neuronal classification is a difficult problem because it is unclear how to designate a neuronal cell class and what are the best characteristics to define them. Recently, unsupervised classifications using cluster analysis based on morphological, physiological, or molecular characteristics, have provided quantitative and unbiased identification of distinct neuronal subtypes, when applied to selected datasets. However, better and more robust classification methods are needed for increasingly complex and larger datasets. Here, we explored the use of affinity propagation, a recently developed unsupervised classification algorithm imported from machine learning, which gives a representative example or exemplar for each cluster. As a case study, we applied affinity propagation to a test dataset of 337 interneurons belonging to four subtypes, previously identified based on morphological and physiological characteristics. We found that affinity propagation correctly classified most of the neurons in a blind, non-supervised manner. Affinity propagation outperformed Ward's method, a current standard clustering approach, in classifying the neurons into 4 subtypes. Affinity propagation could therefore be used in future studies to validly classify neurons, as a first step to help reverse engineer neural circuits.

  1. Classification of neocortical interneurons using affinity propagation.

    PubMed

    Santana, Roberto; McGarry, Laura M; Bielza, Concha; Larrañaga, Pedro; Yuste, Rafael

    2013-01-01

    In spite of over a century of research on cortical circuits, it is still unknown how many classes of cortical neurons exist. In fact, neuronal classification is a difficult problem because it is unclear how to designate a neuronal cell class and what are the best characteristics to define them. Recently, unsupervised classifications using cluster analysis based on morphological, physiological, or molecular characteristics, have provided quantitative and unbiased identification of distinct neuronal subtypes, when applied to selected datasets. However, better and more robust classification methods are needed for increasingly complex and larger datasets. Here, we explored the use of affinity propagation, a recently developed unsupervised classification algorithm imported from machine learning, which gives a representative example or exemplar for each cluster. As a case study, we applied affinity propagation to a test dataset of 337 interneurons belonging to four subtypes, previously identified based on morphological and physiological characteristics. We found that affinity propagation correctly classified most of the neurons in a blind, non-supervised manner. Affinity propagation outperformed Ward's method, a current standard clustering approach, in classifying the neurons into 4 subtypes. Affinity propagation could therefore be used in future studies to validly classify neurons, as a first step to help reverse engineer neural circuits. PMID:24348339

  2. Quantification of the affinities and kinetics of protein interactions using silicon nanowire biosensors

    PubMed Central

    Duan, Xuexin; Li, Yue; Rajan, Nitin K.; Routenberg, David A.; Modis, Yorgo; Reed, Mark A.

    2014-01-01

    Monitoring the binding affinities and kinetics of protein interactions is important in clinical diagnostics and drug development because such information is used to identify new therapeutic candidates. Surface plasmon resonance is at present the standard method used for such analysis, but this is limited by low sensitivity and low-throughput analysis. Here, we show that silicon nanowire field-effect transistors can be used as biosensors to measure protein–ligand binding affinities and kinetics with sensitivities down to femtomolar concentrations. Based on this sensing mechanism, we develop an analytical model to calibrate the sensor response and quantify the molecular binding affinities of two representative protein–ligand binding pairs. The rate constant of the association and dissociation of the protein–ligand pair is determined by monitoring the reaction kinetics, demonstrating that silicon nanowire field-effect transistors can be readily used as high-throughput biosensors to quantify protein interactions. PMID:22635097

  3. Measurement of affinity of viral monoclonal antibodies by ELISA titration of free antibody in equilibrium mixtures.

    PubMed

    Azimzadeh, A; Van Regenmortel, M H

    1991-08-01

    The binding affinity of a monoclonal antibody (Mab) to tobacco mosaic virus (TMV) was determined by measuring, in an enzyme-linked immunosorbent assay, the amount of free antibody present after ultracentrifugation of virus-antibody complexes at equilibrium. In antibody excess, univalent binding of Mabs was observed and the affinity constant was K = 3.2 +/- 0.4 10(8) l/mol; in antigen excess, bivalent antibody binding was observed and the antibody avidity was about 15 times higher. In antigen excess, it was imperative to correct experimental data for the presence of 0.55% inactive molecules in the immunopurified antibody preparation. Modelling studies suggest that in the case of antibodies of increasing affinity, it becomes increasingly important to correct for the presence of inactive antibody in the binding assay.

  4. Influence of the galloyl moiety in tea catechins on binding affinity for human serum albumin.

    PubMed

    Minoda, Kanako; Ichikawa, Tatsuya; Katsumata, Tomoharu; Onobori, Ken-ichi; Mori, Taiki; Suzuki, Yukiko; Ishii, Takeshi; Nakayama, Tsutomu

    2010-01-01

    The major catechins of green tea extract are (-)-epicatechin (EC), (-)-epigallocatechin (EGC), (-)-epicatechin gallate (ECg), and (-)-epigallocatechin gallate (EGCg). Recent research has indicated that catechins form complexes with human serum albumin (HSA) in blood, and differences in their binding affinity toward HSA are believed to modulate their bioavailability. In this study, we kinetically investigated the interaction between the catechins and HSA immobilized on a quartz-crystal microbalance (QCM). The association constants obtained from the frequency changes of QCM revealed interactions of ECg and EGCg with HSA that are 100 times stronger than those of EC and EGC. Furthermore, comparisons of these catechins by native-gel electrophoresis/blotting with redox-cycling staining revealed that, in a phosphate buffer, ECg and EGCg have a higher binding affinity toward HSA than EC and EGC. These observations indicate that catechins with a galloyl moiety have higher binding affinities toward HSA than catechins lacking a galloyl moiety.

  5. Impedance-derived electrochemical capacitance spectroscopy for the evaluation of lectin-glycoprotein binding affinity.

    PubMed

    Santos, Adriano; Carvalho, Fernanda C; Roque-Barreira, Maria-Cristina; Bueno, Paulo R

    2014-12-15

    Characterization of lectin-carbohydrate binding using label-free methods such as impedance-derived electrochemical capacitance spectroscopy (ECS) is desirable to evaluate specific interactions, for example, ArtinM lectin and horseradish peroxidase (HRP) glycoprotein, used here as a model for protein-carbohydrate binding affinity. An electroactive molecular film comprising alkyl ferrocene as a redox probe and ArtinM as a carbohydrate receptive center to target HRP was successfully used to determine the binding affinity between ArtinM and HRP. The redox capacitance, a transducer signal associated with the alkyl ferrocene centers, was obtained by ECS and used in the Langmuir adsorption model to obtain the affinity constant (1.6±0.6)×10(8) L mol(-1). The results shown herein suggest the feasibility of ECS application for lectin glycoarray characterization. PMID:24994505

  6. One-step surface modification of polyurethane using affinity binding peptides for enhanced fouling resistance.

    PubMed

    Wang, Yibing; Yu, Yong; Zhang, Liting; Qin, Peng; Wang, Ping

    2015-01-01

    Affinity binding peptides were examined for surface fabrication of synthetic polymeric materials. Peptides possessing strong binding affinities toward polyurethane (PU) were discovered via biopanning of M13 phage peptide library. The apparent binding constant (K(app)) was as high as 2.68 × 10(9) M(-1) with surface peptide density exceeded 1.8 μg/cm(2). Structural analysis showed that the ideal peptide had a high content (75%) of H-donor amino acid residues, and that intensified hydrogen bond interaction was the key driving force for the highly stable binding of peptides on PU. PU treated with such affinity peptides promises applications as low-fouling materials, as peptides increased its wettability and substantially reduced protein adsorption and cell adhesion. These results demonstrated a facile but highly efficient one-step strategy for surface property modification of polymeric materials for biotechnological applications. PMID:25732121

  7. Impedance-derived electrochemical capacitance spectroscopy for the evaluation of lectin-glycoprotein binding affinity.

    PubMed

    Santos, Adriano; Carvalho, Fernanda C; Roque-Barreira, Maria-Cristina; Bueno, Paulo R

    2014-12-15

    Characterization of lectin-carbohydrate binding using label-free methods such as impedance-derived electrochemical capacitance spectroscopy (ECS) is desirable to evaluate specific interactions, for example, ArtinM lectin and horseradish peroxidase (HRP) glycoprotein, used here as a model for protein-carbohydrate binding affinity. An electroactive molecular film comprising alkyl ferrocene as a redox probe and ArtinM as a carbohydrate receptive center to target HRP was successfully used to determine the binding affinity between ArtinM and HRP. The redox capacitance, a transducer signal associated with the alkyl ferrocene centers, was obtained by ECS and used in the Langmuir adsorption model to obtain the affinity constant (1.6±0.6)×10(8) L mol(-1). The results shown herein suggest the feasibility of ECS application for lectin glycoarray characterization.

  8. Identity, Affinity, Reality: Making the Case for Affinity Groups in Elementary School

    ERIC Educational Resources Information Center

    Parsons, Julie; Ridley, Kimberly

    2012-01-01

    Affinity groups are places where students build connections and process "ouch" moments from their classes. Children talk about the isolation they sometimes feel. The relationships students gain through race-based affinity groups enable them to feel less alone with their emotions and help them build a stronger sense of self. At the same time,…

  9. Stepparents' Affinity-Seeking and Affinity-Maintaining Strategies with Stepchildren.

    ERIC Educational Resources Information Center

    Ganong, Lawrence; Coleman, Marilyn; Fine, Mark; Martin, Patricia

    1999-01-01

    Examines the strategies that stepparents use to develop and maintain affinity with stepchildren and the effects that these strategies have on the development of stepparent-stepchildren relationships. Thirty-one affinity-seeking strategies are identified. Results show that dyadic activities worked best, but it is important that stepchildren…

  10. Constant fields and constant gradients in open ionic channels.

    PubMed

    Chen, D P; Barcilon, V; Eisenberg, R S

    1992-05-01

    Ions enter cells through pores in proteins that are holes in dielectrics. The energy of interaction between ion and charge induced on the dielectric is many kT, and so the dielectric properties of channel and pore are important. We describe ionic movement by (three-dimensional) Nemst-Planck equations (including flux and net charge). Potential is described by Poisson's equation in the pore and Laplace's equation in the channel wall, allowing induced but not permanent charge. Asymptotic expansions are constructed exploiting the long narrow shape of the pore and the relatively high dielectric constant of the pore's contents. The resulting one-dimensional equations can be integrated numerically; they can be analyzed when channels are short or long (compared with the Debye length). Traditional constant field equations are derived if the induced charge is small, e.g., if the channel is short or if the total concentration gradient is zero. A constant gradient of concentration is derived if the channel is long. Plots directly comparable to experiments are given of current vs voltage, reversal potential vs. concentration, and slope conductance vs. concentration. This dielectric theory can easily be tested: its parameters can be determined by traditional constant field measurements. The dielectric theory then predicts current-voltage relations quite different from constant field, usually more linear, when gradients of total concentration are imposed. Numerical analysis shows that the interaction of ion and channel can be described by a mean potential if, but only if, the induced charge is negligible, that is to say, the electric field is spatially constant.

  11. Constant fields and constant gradients in open ionic channels.

    PubMed Central

    Chen, D P; Barcilon, V; Eisenberg, R S

    1992-01-01

    Ions enter cells through pores in proteins that are holes in dielectrics. The energy of interaction between ion and charge induced on the dielectric is many kT, and so the dielectric properties of channel and pore are important. We describe ionic movement by (three-dimensional) Nemst-Planck equations (including flux and net charge). Potential is described by Poisson's equation in the pore and Laplace's equation in the channel wall, allowing induced but not permanent charge. Asymptotic expansions are constructed exploiting the long narrow shape of the pore and the relatively high dielectric constant of the pore's contents. The resulting one-dimensional equations can be integrated numerically; they can be analyzed when channels are short or long (compared with the Debye length). Traditional constant field equations are derived if the induced charge is small, e.g., if the channel is short or if the total concentration gradient is zero. A constant gradient of concentration is derived if the channel is long. Plots directly comparable to experiments are given of current vs voltage, reversal potential vs. concentration, and slope conductance vs. concentration. This dielectric theory can easily be tested: its parameters can be determined by traditional constant field measurements. The dielectric theory then predicts current-voltage relations quite different from constant field, usually more linear, when gradients of total concentration are imposed. Numerical analysis shows that the interaction of ion and channel can be described by a mean potential if, but only if, the induced charge is negligible, that is to say, the electric field is spatially constant. Images FIGURE 1 PMID:1376159

  12. The -145 km/S Absorption System of Eta Carinae

    NASA Technical Reports Server (NTRS)

    Vieira, G.; Gull, T. R.; Danks, A.; Johansson, S.

    2002-01-01

    With the STIS E230H mode (R-118,000) , we have identified about twenty absorption components in line of sight from Eta Carinae. Two components, one at -513 km/s and another at -145 W s , are quite different in character from the others, mostly at intermediate velocities. The -145 km/s component is significantly wider in fwhm, is seen in many more species, and the lower level can be above 20,000/cm, well above the 2000/cm noted in the -513 km/s component. In the spectral region from 2400 to 3160A, approximately 500 absorption lines have been identified. In this poster, we will present line identifications and atomic parameters of the measured lines, hopefully providing insight as to what levels are being excited and by what processes.

  13. Potential of KM+ lectin in immunization against Leishmania amazonensis infection.

    PubMed

    Teixeira, Clarissa R; Cavassani, Karen A; Gomes, Regis B; Teixeira, Maria Jania; Roque-Barreira, Maria-Cristina; Cavada, Benildo S; da Silva, João Santana; Barral, Aldina; Barral-Netto, Manoel

    2006-04-01

    In the present study we evaluated Canavalia brasiliensis (ConBr), Pisum arvense (PAA) and Artocarpus integrifolia (KM+) lectins as immunostimulatory molecules in vaccination against Leishmania amazonensis infection. Although they induced IFN-gamma production, the combination of the lectins with SLA antigen did not lead to lesion reduction. However, parasite load was largely reduced in mice immunized with KM+ lectin and SLA. KM+ induced a smaller inflammatory reaction in the air pouch model and was able to inhibit differentiation of dendritic cells (BMDC), but to induce maturation by enhancing the expression of MHC II, CD80 and CD86. These observations indicate the modulatory role of plant lectins in leishmaniasis vaccination may be related to their action on the initial innate response.

  14. Effective cosmological constant induced by stochastic fluctuations of Newton's constant

    NASA Astrophysics Data System (ADS)

    de Cesare, Marco; Lizzi, Fedele; Sakellariadou, Mairi

    2016-09-01

    We consider implications of the microscopic dynamics of spacetime for the evolution of cosmological models. We argue that quantum geometry effects may lead to stochastic fluctuations of the gravitational constant, which is thus considered as a macroscopic effective dynamical quantity. Consistency with Riemannian geometry entails the presence of a time-dependent dark energy term in the modified field equations, which can be expressed in terms of the dynamical gravitational constant. We suggest that the late-time accelerated expansion of the Universe may be ascribed to quantum fluctuations in the geometry of spacetime rather than the vacuum energy from the matter sector.

  15. Seismological detection of "730-km" discontinuity beneath Japan subduction zone

    NASA Astrophysics Data System (ADS)

    Liu, Z.; Park, J. J.; Karato, S. I.

    2015-12-01

    Because the mantle transition zone likely contains a large amount of water (Karato, 2011; Pearson et al., 2014), vertical material transport across the transition would cause partial melting that may produce seismic signals above and/or below the transition zone. Schmandt et al. (2014) observed a seismic low-velocity zone (LVZ) at the top of the lower mantle (~730 km) beneath the southwestern US, arguing for dehydration melting due to downward flow across the 670-km discontinuity (670) from the transition zone. These authors further proposed a correlation between seismic velocity reductions and the direction of water transport, in which LVZ at ~730 km indicates materials moving downward from the transition zone, while the lack of LVZ at this depth would suggest an upward flow of mantle materials. Other regions also need to be investigated to confirm the correlation between this seismic feature and mantle water transport. We test their model by detecting "730-km" discontinuity beneath the Japan subduction zone using frequency-dependent receiver functions. In addition, water transport above the 410-km discontinuity (410) also plays an important role in global water circulation (Bercovici and Karato, 2003). Seismological studies (e.g. Courtier and Revenaugh, 2007; Schaeffer and Bostock, 2010) have observed LVZs above the 410, which might be caused by dehydration melting due to the upwelling of hydrated materials across the 410-km discontinuity from the transition zone. In this study, we also detect potential LVZs above 410 to establish a correlation between seismic velocity drop and flow direction. Around the Japan subduction zone, our preliminary results show evidence of low velocity zones below 670 in regions where stagnant slab is present for a substantial amount of time but not in other regions suggesting a variety of vertical mass transport in this region. Key words: transition zone, water transport, subduction zone, melting, receiver functions

  16. Affinity chromatography of bacterial lactate dehydrogenases.

    PubMed Central

    Kelly, N; Delaney, M; O'Carra, P

    1978-01-01

    The affinity system used was the immobilized oxamate derivative previously used to purify mammalian lactate dehydrogenases. The bacterial dehydrogenases specific for the L-stereoisomer of lactate behaved in the same way as the mammalian enzymes, binding strongly in the presence of NADH. The D-lactate-specific enzymes, however, did not show any biospecific affinity for this gel. The L-specific enzymes could be purified to homogeneity in one affinity-chromatographic step. The D-specific enzymes could be efficiently separated from the L-specific ones and could then be further purified on an immobilized NAD derivative. The mechanism of activation of the lactate dehydrogenase from Streptococcus faecalis by fructose 1,6-bisphosphate was investigated by using the immobilized oxamate gel. PMID:666726

  17. Affinity chromatography of bacterial lactate dehydrogenases.

    PubMed

    Kelly, N; Delaney, M; O'Carra, P

    1978-06-01

    The affinity system used was the immobilized oxamate derivative previously used to purify mammalian lactate dehydrogenases. The bacterial dehydrogenases specific for the L-stereoisomer of lactate behaved in the same way as the mammalian enzymes, binding strongly in the presence of NADH. The D-lactate-specific enzymes, however, did not show any biospecific affinity for this gel. The L-specific enzymes could be purified to homogeneity in one affinity-chromatographic step. The D-specific enzymes could be efficiently separated from the L-specific ones and could then be further purified on an immobilized NAD derivative. The mechanism of activation of the lactate dehydrogenase from Streptococcus faecalis by fructose 1,6-bisphosphate was investigated by using the immobilized oxamate gel. PMID:666726

  18. Simulation of CO2 release at 800 km altitude

    NASA Astrophysics Data System (ADS)

    Setayesh, A.

    1993-08-01

    The SOCRATES contamination-interaction code has been used to simulate the reactions of 0 + CO2 yields CO2(v) + O, O + CO2 - CO(v) + O2, and CO2 + H - CO + OH(v) at an altitude of 800 km in both ram and wake directions of the spacecraft. These simulations show that the radiation from these reactions can be measurable for the parameters which have been used in these calculations. The investigation carries out the simulations as much as 30 km from the spacecraft. The radiative intensity of CO(v) and OH(v) show the highest and lowest, respectively.

  19. Cascade sensitivity studies for KM3NeT

    NASA Astrophysics Data System (ADS)

    Fusco, Luigi Antonio

    2016-07-01

    KM3NeT is a future research infrastructure in the deep seas of the Mediterranean housing a large scale neutrino telescope. The first phase of construction of the telescope has started. Next step is an intermediate phase realising a detector volume of about one-third of the final detector volume. We report on calculations of the sensitivity of the KM3NeT detector to showering neutrino events, the strategy to optimise the detector to a cosmic neutrino flux analogous to the one reported by the IceCube Collaboration and the results of this strategy applied to the intermediate phase detector.

  20. From NEMO to KM3NeT-Italy

    NASA Astrophysics Data System (ADS)

    Nicolau, Carlo A.

    2014-04-01

    The KM3NeT-Italy Collaboration has entered the production stage of an 8 tower apparatus that will be deployed at about 100 km off the Sicily coast. The architecture of the system is based on the NEMO Phase2 prototype tower which is taking data since the deployment in March 2013. In order to optimize production costs, power consumption, and usability, some components have been re-engineered by taking advantage of the previously gained experience and technological progress. The aim of this contribution is to give an overview of the main features that characterize the new apparatus.

  1. Development of prediction models for radioactive caesium distribution within the 80-km radius of the Fukushima Daiichi nuclear power plant.

    PubMed

    Kinase, Sakae; Takahashi, Tomoyuki; Sato, Satoshi; Sakamoto, Ryuichi; Saito, Kimiaki

    2014-08-01

    Preliminary prediction models have been studied for the radioactive caesium distribution within the 80-km radius of the Fukushima Daiichi nuclear power plant. The models were represented by exponential functions using ecological half-life of radioactive caesium in the environment. The ecological half-lives were derived from the changes in ambient dose equivalent rates through vehicle-borne surveys. It was found that the ecological half-lives of radioactive caesium were not constant within the 80-km radius of the Fukushima Daiichi nuclear power plant. The ecological half-life of radioactive caesium in forest areas was found to be much larger than that in urban and water areas.

  2. European and international collaboration in affinity proteomics.

    PubMed

    Stoevesandt, Oda; Taussig, Michael J

    2012-06-15

    In affinity proteomics, specific protein-binding molecules (a.k.a. binders), principally antibodies, are applied as reagents in proteome analysis. In recent years, advances in binder technologies have created the potential for an unprecedented view on protein expression and distribution patterns in plasma, cells and tissues and increasingly on protein function. Particular strengths of affinity proteomics methods include detecting proteins in their natural environments of cell or tissue, high sensitivity and selectivity for detection of low abundance proteins and exploiting binding actions such as functional interference in living cells. To maximise the use and impact of affinity reagents, it will be essential to create comprehensive, standardised binder collections. With this in mind, the EU FP7 programme AFFINOMICS (http://www.affinomics.org), together with the preceding EU programmes ProteomeBinders and AffinityProteome, aims to extend affinity proteomics research by generating a large-scale resource of validated protein-binding molecules for characterisation of the human proteome. Activity is directed at producing binders to about 1000 protein targets, primarily in signal transduction and cancer, by establishing a high throughput, coordinated production pipeline. An important aspect of AFFINOMICS is the development of highly efficient recombinant selection methods, based on phage, cell and ribosome display, capable of producing high quality binders at greater throughput and lower cost than hitherto. The programme also involves development of innovative and sensitive technologies for specific detection of target proteins and their interactions, and deployment of binders in proteomics studies of clinical relevance. The need for such binder generation programmes is now recognised internationally, with parallel initiatives in the USA for cancer (NCI) and transcription factors (NIH) and within the Human Proteome Organisation (HUPO). The papers in this volume of New

  3. Displacement phenomena in lectin affinity chromatography.

    PubMed

    Cho, Wonryeon

    2015-10-01

    The work described here examines displacement phenomena that play a role in lectin affinity chromatography and their potential to impact reproducibility. This was achieved using Lycopersicon esculentum lectin (LEL), a lectin widely used in monitoring cancer. Four small identical LEL columns were coupled in series to form a single affinity chromatography system with the last in the series connected to an absorbance detector. The serial affinity column set (SACS) was then loaded with human plasma proteins. At the completion of loading, the column set was disassembled, the four columns were eluted individually, the captured proteins were trypsin digested, the peptides were deglycosylated with PNGase F, and the parent proteins were identified through mass spectral analyses. Significantly different sets of glycoproteins were selected by each column, some proteins appearing to be exclusively bound to the first column while others were bound further along in the series. Clearly, sample displacement chromatography (SDC) occurs. Glycoproteins were bound at different places in the column train, identifying the presence of glycoforms with different affinity on a single glycoprotein. It is not possible to see these phenomena in the single column mode of chromatography. Moreover, low abundance proteins were enriched, which facilitates detection. The great advantage of this method is that it differentiates between glycoproteins on the basis of their binding affinity. Displacement phenomena are concluded to be a significant component of the separation mechanism in heavily loaded lectin affinity chromatography columns. This further suggests that care must be exercised in sample loading of lectin columns to prevent analyte displacement with nonretained proteins. PMID:26348026

  4. The dynamics of metric-affine gravity

    SciTech Connect

    Vitagliano, Vincenzo; Sotiriou, Thomas P.; Liberati, Stefano

    2011-05-15

    Highlights: > The role and the dynamics of the connection in metric-affine theories is explored. > The most general second order action does not lead to a dynamical connection. > Including higher order invariants excites new degrees of freedom in the connection. > f(R) actions are also discussed and shown to be a non- representative class. - Abstract: Metric-affine theories of gravity provide an interesting alternative to general relativity: in such an approach, the metric and the affine (not necessarily symmetric) connection are independent quantities. Furthermore, the action should include covariant derivatives of the matter fields, with the covariant derivative naturally defined using the independent connection. As a result, in metric-affine theories a direct coupling involving matter and connection is also present. The role and the dynamics of the connection in such theories is explored. We employ power counting in order to construct the action and search for the minimal requirements it should satisfy for the connection to be dynamical. We find that for the most general action containing lower order invariants of the curvature and the torsion the independent connection does not carry any dynamics. It actually reduces to the role of an auxiliary field and can be completely eliminated algebraically in favour of the metric and the matter field, introducing extra interactions with respect to general relativity. However, we also show that including higher order terms in the action radically changes this picture and excites new degrees of freedom in the connection, making it (or parts of it) dynamical. Constructing actions that constitute exceptions to this rule requires significant fine tuned and/or extra a priori constraints on the connection. We also consider f(R) actions as a particular example in order to show that they constitute a distinct class of metric-affine theories with special properties, and as such they cannot be used as representative toy theories to

  5. Optical constants of solid methane

    NASA Technical Reports Server (NTRS)

    Khare, Bishun N.; Thompson, W. R.; Sagan, C.; Arakawa, E. T.; Bruel, C.; Judish, J. P.; Khanna, R. K.; Pollack, J. B.

    1989-01-01

    Methane is the most abundant simple organic molecule in the outer solar system bodies. In addition to being a gaseous constituent of the atmospheres of the Jovian planets and Titan, it is present in the solid form as a constituent of icy surfaces such as those of Triton and Pluto, and as cloud condensate in the atmospheres of Titan, Uranus, and Neptune. It is expected in the liquid form as a constituent of the ocean of Titan. Cometary ices also contain solid methane. The optical constants for both solid and liquid phases of CH4 for a wide temperature range are needed for radiative transfer calculations, for studies of reflection from surfaces, and for modeling of emission in the far infrared and microwave regions. The astronomically important visual to near infrared measurements of solid methane optical constants are conspicuously absent from the literature. Preliminary results are presented of the optical constants of solid methane for the 0.4 to 2.6 micron region. K is reported for both the amorphous and the crystalline (annealed) states. Using the previously measured values of the real part of the refractive index, n, of liquid methane at 110 K n is computed for solid methane using the Lorentz-Lorentz relationship. Work is in progress to extend the measurements of optical constants n and k for liquid and solid to both shorter and longer wavelengths, eventually providing a complete optical constants database for condensed CH4.

  6. Affine Invariant Character Recognition by Progressive Removing

    NASA Astrophysics Data System (ADS)

    Iwamura, Masakazu; Horimatsu, Akira; Niwa, Ryo; Kise, Koichi; Uchida, Seiichi; Omachi, Shinichiro

    Recognizing characters in scene images suffering from perspective distortion is a challenge. Although there are some methods to overcome this difficulty, they are time-consuming. In this paper, we propose a set of affine invariant features and a new recognition scheme called “progressive removing” that can help reduce the processing time. Progressive removing gradually removes less feasible categories and skew angles by using multiple classifiers. We observed that progressive removing and the use of the affine invariant features reduced the processing time by about 60% in comparison to a trivial one without decreasing the recognition rate.

  7. Negative Electron Affinity Mechanism for Diamond Surfaces

    NASA Technical Reports Server (NTRS)

    Krainsky, I. L.; Asnin, V. M.

    1998-01-01

    The energy distribution of the secondary electrons for chemical vacuum deposited diamond films with Negative Electron Affinity (NEA) was investigated. It was found that while for completely hydrogenated diamond surfaces the negative electron affinity peak in the energy spectrum of the secondary electrons is present for any energy of the primary electrons, for partially hydrogenated diamond surfaces there is a critical energy above which the peak is present in the spectrum. This critical energy increases sharply when hydrogen coverage of the diamond surface diminishes. This effect was explained by the change of the NEA from the true type for the completely hydrogenated surface to the effective type for the partially hydrogenated surfaces.

  8. Adsorption affinity of anions on metal oxyhydroxides

    NASA Astrophysics Data System (ADS)

    Pechenyuk, S. I.; Semushina, Yu. P.; Kuz'mich, L. F.

    2013-03-01

    The dependences of anion (phosphate, carbonate, sulfate, chromate, oxalate, tartrate, and citrate) adsorption affinity anions from geometric characteristics, acid-base properties, and complex forming ability are generalized. It is shown that adsorption depends on the nature of both the anions and the ionic medium and adsorbent. It is established that anions are generally grouped into the following series of adsorption affinity reduction: PO{4/3-}, CO{3/2-} > C2O{4/2-}, C(OH)(CH2)2(COO){3/3-}, (CHOH)2(COO){2/2-} > CrO{4/2-} ≫ SO{4/2-}.

  9. New unitary affine-Virasoro constructions

    SciTech Connect

    Halpern, M.B.; Kiritsis, E.; Obers, N.A.; Poratti, M. ); Yamron, J.P. )

    1990-06-20

    This paper reports on a quasi-systematic investigation of the Virasoro master equation. The space of all affine-Virasoro constructions is organized by K-conjugation into affine-Virasoro nests, and an estimate of the dimension of the space shows that most solutions await discovery. With consistent ansatze for the master equation, large classes of new unitary nests are constructed, including quadratic deformation nests with continuous conformal weights, and unitary irrational central charge nests, which may dominate unitary rational central charge on compact g.

  10. Screening of high-affinity scFvs from a ribosome displayed library using BIAcore biosensor.

    PubMed

    Yuan, Qing; Wang, Zhongkang; Nian, Siji; Yin, Youping; Chen, Gang; Xia, Yuxian

    2009-02-01

    An experimental protocol was developed to screen high-affinity single-chain Fv antibody fragments (scFvs) from a Xanthomonas axonopodis pv. citri (Xac) immunized ribosome display library using BIAcore biosensor. The screening methods involved immobilizing antigen [lipopolysaccharides (LPS) of Xac] on sensor chip HPA and then unpurified expression products of scFvs flowing over the immobilized sensor chip. The affinity-improved scFvs were selected based on dissociation rate constants (k (d)). Thirty-five enzyme-linked immunosorbent assay-positive scFvs were analyzed by BIAcore, and three of those (scFv A1, B2, and C5) with lower k (d) were screened. To demonstrate the accuracy of the screening method, the three scFvs were expressed in Escherichia coli HB2151 and purified. The purified scFvs were subsequently further identified according to association rate and affinity constants. The results showed that the three scFvs (A1, B2, and C5) had high affinity for LPS of Xac (3.51 x 10(-11), 1.13 x 10(-10), 5.06 x 10(-10) M, respectively). Furthermore, the scFv B2 was highly specific for LPS of Xac and had no any cross-reactions with bovine serum albumin and LPS from Xac-related bacteria. This provided evidence that the information from the BIAcore screening assay could be accurate. PMID:18574567

  11. Superconformal Chern-Simons partition functions of affine D-type quiver from Fermi gas

    NASA Astrophysics Data System (ADS)

    Moriyama, Sanefumi; Nosaka, Tomoki

    2015-09-01

    We consider the partition function of the superconformal Chern-Simons theories with the quiver diagram being the affine D-type Dynkin diagram. Rewriting the partition function into that of a Fermi gas system, we show that the perturbative expansions in 1 /N are summed up to an Airy function, as in the ABJM theory or more generally the theories of the affine A-type quiver. As a corollary, this provides a proof for the previous proposal in the large N limit. For special values of the Chern-Simons levels, we further identify three species of the membrane instantons and also conjecture an exact expression of the overall constant, which corresponds to the constant map in the topological string theory. [Figure not available: see fulltext.

  12. Measurements of relative binding of cohesin and dockerin mutants using an advanced ELISA technique for high-affinity interactions.

    PubMed

    Slutzki, Michal; Barak, Yoav; Reshef, Dan; Schueler-Furman, Ora; Lamed, Raphael; Bayer, Edward A

    2012-01-01

    The cellulosome is a large bacterial extracellular multienzyme complex able to degrade crystalline cellulosic substrates. The complex contains catalytic and noncatalytic subunits, interconnected by high-affinity cohesin-dockerin interactions. In this chapter, we introduce an optimized method for comparative binding among different cohesins or cohesin mutants to the dockerin partner. This assay offers advantages over other methods (such as ELISA, cELIA, SPR, and ITC) for particularly high-affinity binding interactions. In this approach, the high-affinity interaction of interest occurs in the liquid phase during the equilibrated binding step, whereas the interaction with the immobilized phase is used only for detection of the unbound dockerins that remain in the solution phase. Once equilibrium conditions are reached, the change in free energy of binding (ΔΔG(binding)), as well as the affinity constant of mutants, can be estimated against the known affinity constant of the wild-type interaction. In light of the above, we propose this method as a preferred alternative for the relative quantification of high-affinity protein interactions. PMID:22608739

  13. Increased Antibody Affinity Confers Broad In Vitro Protection against Escape Mutants of Severe Acute Respiratory Syndrome Coronavirus

    PubMed Central

    Rani, Mridula; Bolles, Meagan; Donaldson, Eric F.; Van Blarcom, Thomas; Baric, Ralph; Iverson, Brent

    2012-01-01

    Even though the effect of antibody affinity on neutralization potency is well documented, surprisingly, its impact on neutralization breadth and escape has not been systematically determined. Here, random mutagenesis and DNA shuffling of the single-chain variable fragment of the neutralizing antibody 80R followed by bacterial display screening using anchored periplasmic expression (APEx) were used to generate a number of higher-affinity variants of the severe acute respiratory syndrome coronavirus (SARS-CoV)-neutralizing antibody 80R with equilibrium dissociation constants (KD) as low as 37 pM, a >270-fold improvement relative to that of the parental 80R single-chain variable fragment (scFv). As expected, antigen affinity was shown to correlate directly with neutralization potency toward the icUrbani strain of SARS-CoV. Additionally, the highest-affinity antibody fragment displayed 10-fold-increased broad neutralization in vitro and completely protected against several SARS-CoV strains containing substitutions associated with antibody escape. Importantly, higher affinity also led to the suppression of viral escape mutants in vitro. Escape from the highest-affinity variant required reduced selective pressure and multiple substitutions in the binding epitope. Collectively, these results support the hypothesis that engineered antibodies with picomolar dissociation constants for a neutralizing epitope can confer escape-resistant protection. PMID:22696652

  14. Optical constants of solid methane

    NASA Technical Reports Server (NTRS)

    Khare, Bishun N.; Thompson, W. R.; Sagan, C.; Arakawa, E. T.; Bruel, C.; Judish, J. P.; Khanna, R. K.; Pollack, J. B.

    1990-01-01

    Methane is the most abundant simple organic molecule in the outer solar system bodies. In addition to being a gaseous constituent of the atmospheres of the Jovian planets and Titan, it is present in the solid form as a constituent of icy surfaces such as those of Triton and Pluto, and as cloud condensate in the atmospheres of Titan, Uranus, and Neptune. It is expected in the liquid form as a constituent of the ocean of Titan. Cometary ices also contain solid methane. The optical constants for both solid and liquid phases of CH4 for a wide temperature range are needed for radiative transfer calculations, for studies of reflection from surfaces, and for modeling of emission in the far infrared and microwave regions. The astronomically important visual to near infrared measurements of solid methane optical constants are conspicuously absent from the literature. Preliminary results are presented on the optical constants of solid methane for the 0.4 to 2.6 micrometer region. Deposition onto a substrate at 10 K produces glassy (semi-amorphous) material. Annealing this material at approximately 33 K for approximately 1 hour results in a crystalline material as seen by sharper, more structured bands and negligible background extinction due to scattering. The constant k is reported for both the amorphous and the crystalline (annealed) states. Typical values (at absorption maxima) are in the .001 to .0001 range. Below lambda = 1.1 micrometers the bands are too weak to be detected by transmission through the films less than or equal to 215 micrometers in thickness, employed in the studies to date. Using previously measured values of the real part of the refractive index, n, of liquid methane at 110 K, n is computed for solid methane using the Lorentz-Lorenz relationship. Work is in progress to extend the measurements of optical constants n and k for liquid and solid to both shorter and longer wavelengths, eventually providing a complete optical constants database for

  15. Body Composition Measurements of 161-km Ultramarathon Participants

    Technology Transfer Automated Retrieval System (TEKTRAN)

    This study compares body composition characteristics with performance among participants in a 161-km trail ultramarathon. Height, mass, and percent body fat from bioimpedence spectroscopy were measured on 72 starters. Correlation analyses were used to compare body characteristics with finish time, ...

  16. The -145 km/s Absorption System of Eta Carinae

    NASA Astrophysics Data System (ADS)

    Vieira, G. L.; Gull, T. R.; Danks, A. C.; Johansson, S.

    2002-12-01

    With the STIS E230H mode (R 118,000), we have identified about twenty absorption components in line of sight from Eta Carinae. Two components, one at -513 km/s and another at -145 km/s, are quite different in character from the others, mostly at intermediate velocities (See adjacent posters by T. Gull and A. Danks). The -145 km/s component is significantly wider in fwhm, is seen in many more species, and the lower level can be above 20,000 cm-1, well above the 2000 cm-1 noted in the -513 km/s component. In the spectral region from 2400 to 3160A, approximately 500 absorption lines have been identified. In this poster, we will present line identifications and atomic parameters of the measured lines, hopefully providing insight as to what levels are being excited and by what processes. Observations were accomplished through STScI under proposal 9242 (Danks, P.I.). Funding is through the STIS GTO resources.

  17. Models of earth's atmosphere (90 to 2500 km)

    NASA Technical Reports Server (NTRS)

    1973-01-01

    This monograph replaces a monograph on the upper atmosphere which was a computerized version of Jacchia's model. The current model has a range from 90 to 2500 km. In addition to the computerized model, a quick-look prediction method is given that may be used to estimate the density for any time and spatial location without using a computer.

  18. Gravity wave vertical energy flux at 95 km

    NASA Technical Reports Server (NTRS)

    Jacob, P. G.; Jacka, F.

    1985-01-01

    A three-field photometer (3FP) located at Mt. Torrens near Adelaide, is capable of monitoring different airglow emissions from three spaced fields in the sky. A wheel containing up to six different narrow bandpass interference filters can be rotated, allowing each of the filters to be sequentially placed into each of the three fields. The airglow emission of interest is the 557.7 nm line which has an intensity maximum at 95 km. Each circular field of view is located at the apexes of an equilateral triangle centered on zenith with diameters of 5 km and field separations of 13 km when projected to the 95-km level. The sampling period was 30 seconds and typical data lengths were between 7 and 8 hours. The analysis and results from the interaction of gravity waves on the 557.7 nm emission layer are derived using an atmospheric model similar to that proposed by Hines (1960) where the atmosphere is assumed isothermal and perturbations caused by gravity waves are small and adiabatic, therefore, resulting in linearized equations of motion. In the absence of waves, the atmosphere is also considered stationary. Thirteen nights of quality data from January 1983 to October 1984, covering all seasons, are used in this analysis.

  19. Cosmologies with variable gravitational constant

    SciTech Connect

    Narkikar, J.V.

    1983-03-01

    In 1937 Dirac presented an argument, based on the socalled large dimensionless numbers, which led him to the conclusion that the Newtonian gravitational constant G changes with epoch. Towards the end of the last century Ernst Mach had given plausible arguments to link the property of inertia of matter to the large scale structure of the universe. Mach's principle also leads to cosmological models with a variable gravitational constant. Three cosmologies which predict a variable G are discussed in this paper both from theoretical and observational points of view.

  20. Elastic constants for 8-OCB

    NASA Astrophysics Data System (ADS)

    Czechowski, Grzegorz; Zywucki, B.; Jadzyn, Jan

    1993-10-01

    The Frederiks transitions for the n-octyloxycyanobiphenyl (8-OCB) placed in the external magnetic and electric field as a function of the temperature have been studied. On the basis of threshold values Bc and Uc, the elastic constants for splay, bend and twist modes are determined. The magnetic anisotropy of 8-OCB as a function of temperature has been determined. The K11 and K33 elastic constants show the pretransitional nematic- smectic A effect. The values of critical exponents obtained from the temperature dependence of K11 and K33 in the vicinity of N-SA phase transition are discussed.

  1. Selection is more intelligent than design: improving the affinity of a bivalent ligand through directed evolution.

    PubMed

    Ahmad, Kareem M; Xiao, Yi; Soh, H Tom

    2012-12-01

    Multivalent molecular interactions can be exploited to dramatically enhance the performance of an affinity reagent. The enhancement in affinity and specificity achieved with a multivalent construct depends critically on the effectiveness of the scaffold that joins the ligands, as this determines their positions and orientations with respect to the target molecule. Currently, no generalizable design rules exist for construction of an optimal multivalent ligand for targets with known structures, and the design challenge remains an insurmountable obstacle for the large number of proteins whose structures are not known. As an alternative to such design-based strategies, we report here a directed evolution-based method for generating optimal bivalent aptamers. To demonstrate this approach, we fused two thrombin aptamers with a randomized DNA sequence and used a microfluidic in vitro selection strategy to isolate scaffolds with exceptionally high affinities. Within five rounds of selection, we generated a bivalent aptamer that binds thrombin with an apparent dissociation constant (K(d)) <10 pM, representing a ∼200-fold improvement in binding affinity over the monomeric aptamers and a ∼15-fold improvement over the best designed bivalent construct. The process described here can be used to produce high-affinity multivalent aptamers and could potentially be adapted to other classes of biomolecules.

  2. On the binding affinity of macromolecular interactions: daring to ask why proteins interact

    PubMed Central

    Kastritis, Panagiotis L.; Bonvin, Alexandre M. J. J.

    2013-01-01

    Interactions between proteins are orchestrated in a precise and time-dependent manner, underlying cellular function. The binding affinity, defined as the strength of these interactions, is translated into physico-chemical terms in the dissociation constant (Kd), the latter being an experimental measure that determines whether an interaction will be formed in solution or not. Predicting binding affinity from structural models has been a matter of active research for more than 40 years because of its fundamental role in drug development. However, all available approaches are incapable of predicting the binding affinity of protein–protein complexes from coordinates alone. Here, we examine both theoretical and experimental limitations that complicate the derivation of structure–affinity relationships. Most work so far has concentrated on binary interactions. Systems of increased complexity are far from being understood. The main physico-chemical measure that relates to binding affinity is the buried surface area, but it does not hold for flexible complexes. For the latter, there must be a significant entropic contribution that will have to be approximated in the future. We foresee that any theoretical modelling of these interactions will have to follow an integrative approach considering the biology, chemistry and physics that underlie protein–protein recognition. PMID:23235262

  3. Single-experiment displacement assay for quantifying high-affinity binding by isothermal titration calorimetry.

    PubMed

    Krainer, Georg; Keller, Sandro

    2015-04-01

    Isothermal titration calorimetry (ITC) is the gold standard for dissecting the thermodynamics of a biomolecular binding process within a single experiment. However, reliable determination of the dissociation constant (KD) from a single titration is typically limited to the range 100 μM>KD>1 nM. Interactions characterized by a lower KD can be assessed indirectly by so-called competition or displacement assays, provided that a suitable competitive ligand is available whose KD falls within the directly accessible window. However, this protocol is limited by the fact that it necessitates at least two titrations to characterize one high-affinity inhibitor, resulting in considerable consumption of both sample material and time. Here, we introduce a fast and efficient ITC displacement assay that allows for the simultaneous characterization of both a high-affinity ligand and a moderate-affinity ligand competing for the same binding site on a receptor within a single experiment. The protocol is based on a titration of the high-affinity ligand into a solution containing the moderate-affinity ligand bound to the receptor present in excess. The resulting biphasic binding isotherm enables accurate and precise determination of KD values and binding enthalpies (ΔH) of both ligands. We discuss the theoretical background underlying the approach, demonstrate its practical application to metal ion chelation, explore its potential and limitations with the aid of simulations and statistical analyses, and elaborate on potential applications to protein-inhibitor interactions.

  4. High-affinity host-guest chemistry of large-ring cyclodextrins.

    PubMed

    Assaf, Khaleel I; Gabel, Detlef; Zimmermann, Wolfgang; Nau, Werner M

    2016-08-10

    The host-guest chemistry of large-ring cyclodextrins (LRCDs) has been largely unexplored due to the lack of suitable guest molecules that bind with significant affinities to enable potential applications. Herein, we report their complexation with dodecaborate anions (B12X12(2-)), a novel class of guest molecules. The binding constants of the inorganic guests (10(4)-10(6) M(-1)) allow their classification as the first tight binders for LRCDs. PMID:27456317

  5. Modern affinity reagents: Recombinant antibodies and aptamers.

    PubMed

    Groff, Katherine; Brown, Jeffrey; Clippinger, Amy J

    2015-12-01

    Affinity reagents are essential tools in both basic and applied research; however, there is a growing concern about the reproducibility of animal-derived monoclonal antibodies. The need for higher quality affinity reagents has prompted the development of methods that provide scientific, economic, and time-saving advantages and do not require the use of animals. This review describes two types of affinity reagents, recombinant antibodies and aptamers, which are non-animal technologies that can replace the use of animal-derived monoclonal antibodies. Recombinant antibodies are protein-based reagents, while aptamers are nucleic-acid-based. In light of the scientific advantages of these technologies, this review also discusses ways to gain momentum in the use of modern affinity reagents, including an update to the 1999 National Academy of Sciences monoclonal antibody production report and federal incentives for recombinant antibody and aptamer efforts. In the long-term, these efforts have the potential to improve the overall quality and decrease the cost of scientific research.

  6. Fan Affinity Laws from a Collision Model

    ERIC Educational Resources Information Center

    Bhattacharjee, Shayak

    2012-01-01

    The performance of a fan is usually estimated using hydrodynamical considerations. The calculations are long and involved and the results are expressed in terms of three affinity laws. In this paper we use kinetic theory to attack this problem. A hard sphere collision model is used, and subsequently a correction to account for the flow behaviour…

  7. Microcantilever-Based Label-Free Characterization of Temperature-Dependent Biomolecular Affinity Binding

    PubMed Central

    Wang, Bin; Huang, Fengliang; Nguyen, ThaiHuu; Xu, Yong; Lin, Qiao

    2014-01-01

    This paper presents label-free characterization of temperature-dependent biomolecular affinity binding on solid surfaces using a microcantilever-based device. The device consists of a Parylene cantilever one side of which is coated with a gold film and functionalized with molecules as an affinity receptor to a target analyte. The cantilever is located in a poly(dimethylsiloxane) (PDMS) microfluidic chamber that is integrated with a transparent indium tin oxide (ITO) resistive temperature sensor on the underlying substrate. The ITO sensor allows for real-time measurements of the chamber temperature, as well as unobstructed optical access for reflection-based optical detection of the cantilever deflection. To test the temperature-dependent binding between the target and receptor, the temperature of the chamber is maintained at a constant setpoint, while a solution of unlabeled analyte molecules is continuously infused through the chamber. The measured cantilever deflection is used to determine the target-receptor binding characteristics. We demonstrate label-free characterization of temperature-dependent binding kinetics of the platelet-derived growth factor (PDGF) protein with an aptamer receptor. Affinity binding properties including the association and dissociation rate constants as well as equilibrium dissociation constant are obtained, and shown to exhibit significant dependencies on temperature. PMID:24723743

  8. Boltzmann's constant: A laboratory experiment

    NASA Astrophysics Data System (ADS)

    Kruglak, Haym

    1989-03-01

    The mean-square displacement of a latex microsphere is determined from its projection on a TV monitor. The distribution of displacement is shown to be Gaussian. Boltzmann's constant, calculated from the pooled data of several observers, is in excellent agreement with the accepted value. The experiment is designed for one laboratory period in the advanced undergraduate laboratory.

  9. Ten Thousand Solar Constants Radiometer

    NASA Technical Reports Server (NTRS)

    Kendall, J. M., Sr.

    1985-01-01

    "Radiometer for Accurate (+ or - 1%) Measurement of Solar Irradiances Equal to 10,000 Solar Constants," gives additional information on radiometer described elsewhere. Self-calibrating, water-cooled, thermopile radiometer measures irradiance produced in solar image formed by parabolic reflector or by multiple-mirror solar installation.

  10. The constant region affects antigen binding of antibodies to DNA by altering secondary structure.

    PubMed

    Xia, Yumin; Janda, Alena; Eryilmaz, Ertan; Casadevall, Arturo; Putterman, Chaim

    2013-11-01

    We previously demonstrated an important role of the constant region in the pathogenicity of anti-DNA antibodies. To determine the mechanisms by which the constant region affects autoantibody binding, a panel of isotype-switch variants (IgG1, IgG2a, IgG2b) was generated from the murine PL9-11 IgG3 autoantibody. The affinity of the PL9-11 antibody panel for histone was measured by surface plasmon resonance (SPR). Tryptophan fluorescence was used to determine wavelength shifts of the antibody panel upon binding to DNA and histone. Finally, circular dichroism spectroscopy was used to measure changes in secondary structure. SPR analysis revealed significant differences in histone binding affinity between members of the PL9-11 panel. The wavelength shifts of tryptophan fluorescence emission were found to be dependent on the antibody isotype, while circular dichroism analysis determined that changes in antibody secondary structure content differed between isotypes upon antigen binding. Thus, the antigen binding affinity is dependent on the particular constant region expressed. Moreover, the effects of antibody binding to antigen were also constant region dependent. Alteration of secondary structures influenced by constant regions may explain differences in fine specificity of anti-DNA antibodies between antibodies with similar variable regions, as well as cross-reactivity of anti-DNA antibodies with non-DNA antigens.

  11. A larger number of L chains (Tac) enhance the association rate of interleukin 2 to the high affinity site of the interleukin 2 receptor

    PubMed Central

    1988-01-01

    The IL-2-R is composed of at least two proteins, that is, a 55-kD protein (p55, the L chain, or Tac) and a 75-kD protein (p75, the H chain, or converter). The high affinity binding of IL-2 results in the formation of the ternary complex consisting of IL-2, and the L and H chains. To distinguish the affinity conversion model and the binary complex model we have carried out kinetic studies on the IL-2 binding to the high affinity IL-2-R on T lymphocytes expressing various numbers of L chains and a relatively constant number of H chains. We found that expression of a larger number of L chains accelerated the association of IL-2 to the high affinity receptor. The results are not compatible with the binary complex model that assumes a fixed number of high affinity sites determined by the numbers of a limiting chain. Instead, the results are consistent with the prediction of the affinity conversion model that assumes association of IL-2 to the L chain as the first step of the ternary complex formation and they indicate that the possible role of excess L chains is to accelerate the formation of the ternary complex. The reaction rate constants calculated from the affinity conversion model were reasonably constant. PMID:3263463

  12. Variation of fundamental constants: theory

    NASA Astrophysics Data System (ADS)

    Flambaum, Victor

    2008-05-01

    Theories unifying gravity with other interactions suggest temporal and spatial variation of the fundamental ``constants'' in expanding Universe. There are some hints for the variation of different fundamental constants in quasar absorption spectra and Big Bang nucleosynthesis data. A large number of publications (including atomic clocks) report limits on the variations. We want to study the variation of the main dimensionless parameters of the Standard Model: 1. Fine structure constant alpha (combination of speed of light, electron charge and Plank constant). 2. Ratio of the strong interaction scale (LambdaQCD) to a fundamental mass like electron mass or quark mass which are proportional to Higgs vacuum expectation value. The proton mass is propotional to LambdaQCD, therefore, the proton-to-electron mass ratio comes into this second category. We performed necessary atomic, nuclear and QCD calculations needed to study variation of the fundamental constants using the Big Bang Nucleosynthsis, quasar spectra, Oklo natural nuclear reactor and atomic clock data. The relative effects of the variation may be enhanced in transitions between narrow close levels in atoms, molecules and nuclei. If one will study an enhanced effect, the relative value of systematic effects (which are not enhanced) may be much smaller. Note also that the absolute magnitude of the variation effects in nuclei (e.g. in very narrow 7 eV transition in 229Th) may be 5 orders of magnitude larger than in atoms. A different possibility of enhancement comes from the inversion transitions in molecules where splitting between the levels is due to the quantum tunneling amplitude which has strong, exponential dependence on the electron to proton mass ratio. Our study of NH3 quasar spectra has already given the best limit on the variation of electron to proton mass ratio.

  13. Varying Fine-Structure Constant and the Cosmological Constant Problem

    NASA Astrophysics Data System (ADS)

    Fujii, Yasunori

    We start with a brief account of the latest analysis of the Oklo phenomenon providing the still most stringent constraint on time variability of the fine-structure constant α. Comparing this with the recent result from the measurement of distant QSO's appears to indicate a non-uniform time-dependence, which we argue to be related to another recent finding of the accelerating universe. This view is implemented in terms of the scalar-tensor theory, applied specifically to the small but nonzero cosmological constant. Our detailed calculation shows that these two phenomena can be understood in terms of a common origin, a particular behavior of the scalar field, dilaton. We also sketch how this theoretical approach makes it appropriate to revisit non-Newtonian gravity featuring small violation of Weak Equivalence Principle at medium distances.

  14. Glycan:glycan interactions: High affinity biomolecular interactions that can mediate binding of pathogenic bacteria to host cells

    PubMed Central

    Day, Christopher J.; Tran, Elizabeth N.; Semchenko, Evgeny A.; Tram, Greg; Hartley-Tassell, Lauren E.; Ng, Preston S. K.; King, Rebecca M.; Ulanovsky, Rachel; McAtamney, Sarah; Apicella, Michael A.; Tiralongo, Joe; Morona, Renato; Korolik, Victoria; Jennings, Michael P.

    2015-01-01

    Cells from all domains of life express glycan structures attached to lipids and proteins on their surface, called glycoconjugates. Cell-to-cell contact mediated by glycan:glycan interactions have been considered to be low-affinity interactions that precede high-affinity protein–glycan or protein–protein interactions. In several pathogenic bacteria, truncation of surface glycans, lipooligosaccharide (LOS), or lipopolysaccharide (LPS) have been reported to significantly reduce bacterial adherence to host cells. Here, we show that the saccharide component of LOS/LPS have direct, high-affinity interactions with host glycans. Glycan microarrays reveal that LOS/LPS of four distinct bacterial pathogens bind to numerous host glycan structures. Surface plasmon resonance was used to determine the affinity of these interactions and revealed 66 high-affinity host–glycan:bacterial–glycan pairs with equilibrium dissociation constants (KD) ranging between 100 nM and 50 µM. These glycan:glycan affinity values are similar to those reported for lectins or antibodies with glycans. Cell assays demonstrated that glycan:glycan interaction-mediated bacterial adherence could be competitively inhibited by either host cell or bacterial glycans. This is the first report to our knowledge of high affinity glycan:glycan interactions between bacterial pathogens and the host. The discovery of large numbers of glycan:glycan interactions between a diverse range of structures suggests that these interactions may be important in all biological systems. PMID:26676578

  15. Glycan:glycan interactions: High affinity biomolecular interactions that can mediate binding of pathogenic bacteria to host cells.

    PubMed

    Day, Christopher J; Tran, Elizabeth N; Semchenko, Evgeny A; Tram, Greg; Hartley-Tassell, Lauren E; Ng, Preston S K; King, Rebecca M; Ulanovsky, Rachel; McAtamney, Sarah; Apicella, Michael A; Tiralongo, Joe; Morona, Renato; Korolik, Victoria; Jennings, Michael P

    2015-12-29

    Cells from all domains of life express glycan structures attached to lipids and proteins on their surface, called glycoconjugates. Cell-to-cell contact mediated by glycan:glycan interactions have been considered to be low-affinity interactions that precede high-affinity protein-glycan or protein-protein interactions. In several pathogenic bacteria, truncation of surface glycans, lipooligosaccharide (LOS), or lipopolysaccharide (LPS) have been reported to significantly reduce bacterial adherence to host cells. Here, we show that the saccharide component of LOS/LPS have direct, high-affinity interactions with host glycans. Glycan microarrays reveal that LOS/LPS of four distinct bacterial pathogens bind to numerous host glycan structures. Surface plasmon resonance was used to determine the affinity of these interactions and revealed 66 high-affinity host-glycan:bacterial-glycan pairs with equilibrium dissociation constants (K(D)) ranging between 100 nM and 50 µM. These glycan:glycan affinity values are similar to those reported for lectins or antibodies with glycans. Cell assays demonstrated that glycan:glycan interaction-mediated bacterial adherence could be competitively inhibited by either host cell or bacterial glycans. This is the first report to our knowledge of high affinity glycan:glycan interactions between bacterial pathogens and the host. The discovery of large numbers of glycan:glycan interactions between a diverse range of structures suggests that these interactions may be important in all biological systems. PMID:26676578

  16. Experimental High Resolution (3 km) SMAP Soil Moisture Data Fields With Uncertainty Estimates

    NASA Astrophysics Data System (ADS)

    Das, N. N.

    2015-12-01

    NASA's Soil Moisture Active Passive (SMAP) mission was launched on January 31st, 2015. The objective of the mission is global mapping of surface soil moisture and landscape freeze/thaw state. SMAP utilizes an L-band radar and radiometer sharing a rotating 6-meter mesh reflector antenna. The SMAP spacecraft is in a 685-km Sun-synchronous near-polar orbit, and viewing the surface at a constant 40-degree incidence angle with a 1000-km swath width. Merging of the high-resolution active (radar) and coarse-resolution but high-sensitivity passive (radiometer) L-band observations enable an unprecedented combination of accuracy, resolution, coverage and revisit-time for soil moisture and freeze/thaw state retrievals. However, on July 7th, 2015, the SMAP radar encountered an anomaly and is currently inoperable. Efforts are being made to revive the SMAP radar. Due to the present status of the SMAP observatory, nearly ~2.5 months (from the end of In-Orbit-Check April 13th, 2015 to July 7th, 2015) of the SMAP Active Passive product will be available to public through the NASA DAAC at National Snow and Ice Data Center (NSIDC). The baseline L2_SM_AP product is retrieved soil moisture from the disaggregated/downscaled brightness temperature obtained by merging the coarse-resolution (~36 km) radiometer brightness temperature data and the high-resolution (~3 km) radar backscatter data. The baseline product is intermediate scale 9 km global soil moisture information. Experimentally, a much higher resolution global surface soil moisture data set is also produced at 3 km. This experimental product covering the 2.5 Spring/Summer months is the focus of this presentation. We specifically focus on the analysis of errors and reliability of this data set. The errors in disaggregated brightness temperatures and the retrived soil moisture estimates are discussed. In the presentation the accuracies of the SMAP L2-SM_AP soil moisture retrievals will be shown using summary comparisons with in

  17. New Quasar Studies Keep Fundamental Physical Constant Constant

    NASA Astrophysics Data System (ADS)

    2004-03-01

    Very Large Telescope sets stringent limit on possible variation of the fine-structure constant over cosmological time Summary Detecting or constraining the possible time variations of fundamental physical constants is an important step toward a complete understanding of basic physics and hence the world in which we live. A step in which astrophysics proves most useful. Previous astronomical measurements of the fine structure constant - the dimensionless number that determines the strength of interactions between charged particles and electromagnetic fields - suggested that this particular constant is increasing very slightly with time. If confirmed, this would have very profound implications for our understanding of fundamental physics. New studies, conducted using the UVES spectrograph on Kueyen, one of the 8.2-m telescopes of ESO's Very Large Telescope array at Paranal (Chile), secured new data with unprecedented quality. These data, combined with a very careful analysis, have provided the strongest astronomical constraints to date on the possible variation of the fine structure constant. They show that, contrary to previous claims, no evidence exist for assuming a time variation of this fundamental constant. PR Photo 07/04: Relative Changes with Redshift of the Fine Structure Constant (VLT/UVES) A fine constant To explain the Universe and to represent it mathematically, scientists rely on so-called fundamental constants or fixed numbers. The fundamental laws of physics, as we presently understand them, depend on about 25 such constants. Well-known examples are the gravitational constant, which defines the strength of the force acting between two bodies, such as the Earth and the Moon, and the speed of light. One of these constants is the so-called "fine structure constant", alpha = 1/137.03599958, a combination of electrical charge of the electron, the Planck constant and the speed of light. The fine structure constant describes how electromagnetic forces hold

  18. Remote (250 km) Fiber Bragg Grating Multiplexing System

    PubMed Central

    Fernandez-Vallejo, Montserrat; Rota-Rodrigo, Sergio; Lopez-Amo, Manuel

    2011-01-01

    We propose and demonstrate two ultra-long range fiber Bragg grating (FBG) sensor interrogation systems. In the first approach four FBGs are located 200 km from the monitoring station and a signal to noise ratio of 20 dB is obtained. The second improved version is able to detect the four multiplexed FBGs placed 250 km away, offering a signal to noise ratio of 6–8 dB. Consequently, this last system represents the longest range FBG sensor system reported so far that includes fiber sensor multiplexing capability. Both simple systems are based on a wavelength swept laser to scan the reflection spectra of the FBGs, and they are composed by two identical-lengths optical paths: the first one intended to launch the amplified laser signal by means of Raman amplification and the other one is employed to guide the reflection signal to the reception system. PMID:22164101

  19. Remote (250 km) fiber Bragg grating multiplexing system.

    PubMed

    Fernandez-Vallejo, Montserrat; Rota-Rodrigo, Sergio; Lopez-Amo, Manuel

    2011-01-01

    We propose and demonstrate two ultra-long range fiber Bragg grating (FBG) sensor interrogation systems. In the first approach four FBGs are located 200 km from the monitoring station and a signal to noise ratio of 20 dB is obtained. The second improved version is able to detect the four multiplexed FBGs placed 250 km away, offering a signal to noise ratio of 6-8 dB. Consequently, this last system represents the longest range FBG sensor system reported so far that includes fiber sensor multiplexing capability. Both simple systems are based on a wavelength swept laser to scan the reflection spectra of the FBGs, and they are composed by two identical-lengths optical paths: the first one intended to launch the amplified laser signal by means of Raman amplification and the other one is employed to guide the reflection signal to the reception system. PMID:22164101

  20. KM3NeT-ARCA project status and plan

    NASA Astrophysics Data System (ADS)

    Coniglione, R.

    2016-04-01

    The KM3NeT Collaboration aims at building a research infrastructure in the depths of the Mediterranean Sea hosting a cubic kilometre neutrino telescope. The KM3NeT/ARCA detector is the ideal instrument to look for high-energy neutrino sources thanks to the latitude of the detector and to the optical characteristics of the sea water. The detector latitude allows for a wide coverage of the observable sky including the region of the Galactic centre and the optical sea water properties allow for the measure of the neutrino direction with excellent angular resolution also for cascade events. The technologically innovative components of the detector and the status of construction will be presented as well as the capability it offers to discover neutrinos.

  1. Kinematic characteristics of elite men's 50 km race walking.

    PubMed

    Hanley, Brian; Bissas, Athanassios; Drake, Andrew

    2013-01-01

    Race walking is an endurance event which also requires great technical ability, particularly with respect to its two distinguishing rules. The 50 km race walk is the longest event in the athletics programme at the Olympic Games. The aims of this observational study were to identify the important kinematic variables in elite men's 50 km race walking, and to measure variation in those variables at different distances. Thirty men were analysed from video data recorded during a World Race Walking Cup competition. Video data were also recorded at four distances during the European Cup Race Walking and 12 men analysed from these data. Two camcorders (50 Hz) recorded at each race for 3D analysis. The results of this study showed that walking speed was associated with both step length (r=0.54,P=0.002) and cadence (r=0.58,P=0.001). While placing the foot further ahead of the body at heel strike was associated with greater step lengths (r=0.45,P=0.013), it was also negatively associated with cadence (r= -0.62,P<0.001). In the World Cup, knee angles ranged between 175 and 186° at initial contact and between 180 and 195° at midstance. During the European Cup, walking speed decreased significantly (F=9.35,P=0.002), mostly due to a decrease in step length between 38.5 and 48.5 km (t=8.59,P=0.014). From this study, it would appear that the key areas a 50 km race walker must develop and coordinate are step length and cadence, although it is also important to ensure legal walking technique is maintained with the onset of fatigue. PMID:23679143

  2. Towards a 1km resolution global flood risk model

    NASA Astrophysics Data System (ADS)

    Bates, Paul; Neal, Jeff; Sampson, Chris; Smith, Andy

    2014-05-01

    Recent advances in computationally efficient numerical algorithms and new High Performance Computing architectures now make high (1-2km) resolution global hydrodynamic models a realistic proposition. However in many areas of the world the data sets and tools necessary to undertake such modelling do not currently exist. In particular, five major problems need to be resolved: (1) the best globally available terrain data (SRTM) was generated from X-band interferometric radar data which does not penetrate vegetation canopies and which has significant problems in determining ground elevations in urban areas; (2) a global river bathymetry data set does not currently exist; (3) most river channels globally are less than the smallest currently resolvable grid scale (1km) and therefore require a sub-grid treatment; (4) a means to estimate the magnitude of the T year flood at any point along the global river network does not currently exist; and (5) a large proportion of flood losses are generated by off-floodplain surface water flows which are not well represented in current hydrodynamic modelling systems. In this paper we propose solutions to each of these five issues as part of a concerted effort to develop a 1km (or better) resolution global flood hazard model. We describe the new numerical algorithms, computer architectures and computational resources used, and demonstrate solutions to the five previously intractable problems identified above. We conduct a validation study of the modelling against satellite imagery of major flooding on the Mississippi-Missouri confluence plain in the central USA before outlining a proof-of-concept regional study for SE Asia as a step towards a global scale model. For SE Asia we simulate flood hazard for ten different flood return periods over the entire Thailand, Cambodia, Vietnam, Malaysia and Laos region at 1km resolution and show that the modelling produces coherent, consistent and sensible simulations of extent and water depth.

  3. Saqqar: A 34 km diameter impact structure in Saudi Arabia

    NASA Astrophysics Data System (ADS)

    Kenkmann, Thomas; Afifi, Abdulkader M.; Stewart, Simon A.; Poelchau, Michael H.; Cook, Douglas J.; Neville, Allen S.

    2015-11-01

    Here we present the first proof of an impact origin for the Saqqar circular structure in northwestern Saudi Arabia (Neville et al. ), with an apparent diameter of 34 km, centered at 29°35'N, 38°42'E. The structure is formed in Cambrian-Devonian siliciclastics and is unconformably overlain by undeformed Cretaceous and Paleogene sediments. The age of impact is not well constrained and lies somewhere between 410 and 70 Ma. The subsurface structure is constrained by 2-D reflection seismic profiles and six drilled wells. First-order structural features are a central uplift that rises approximately 2 km above regional datums, surrounded by a ring syncline. The crater rim is defined by circumferential normal faults. The central uplift and ring syncline correspond to a Bouguer gravity high and an annular ring-like low, respectively. The wells were drilled within the central uplift, the deepest among them exceed 2 km depth. Sandstone core samples from these wells show abundant indicators of a shock metamorphic overprint. Planar deformation features (PDFs) were measured with orientations along (0001), {101¯3}, and less frequently along {101¯1} and {101¯4}. Planar fractures (PFs) predominantly occur along (0001) and {101¯1}, and are locally associated with feather features (FFs). In addition, some shocked feldspar grains and strongly deformed mica flakes were found. The recorded shock pressure ranges between 5 and 15 GPa. The preserved level of shock and the absence of an allochthonous crater fill suggest that Saqqar was eroded by 1-2 km between the Devonian and Maastrichtian. The documentation of unequivocal shock features proves the formation of the Saqqar structure by a hypervelocity impact event.

  4. Organizations, Paradigms, and People: The Challenge of KM Interventions

    NASA Technical Reports Server (NTRS)

    Bailey, Teresa; Burton, Yvette

    1999-01-01

    This paper presents viewgraphs on Knowledge Management (KM) and how these interventions are put into practice by organizations and society. The topics include: 1) The Multiple Paradigm Tool; 2) Four Paradigms: tool for the Analyzing Organizations; 3) Assumptions About the Nature of Social Science; 4) Assumptions About the Nature of Society; 5) Schools of Sociological and Organizational Theory; 6) Meaning and Metaphors in the Four Paradigms; and 7) Possibilities and Conclusions.

  5. Towards Mapping the Ocean Surface Topography at 1 km Resolution

    NASA Technical Reports Server (NTRS)

    Fu, Lee-Lueng; Rodriquez, Ernesto

    2006-01-01

    We propose to apply the technique of synthetic aperture radar interferometry to the measurement of ocean surface topography at spatial resolution approaching 1 km. The measurement will have wide ranging applications in oceanography, hydrology, and marine geophysics. The oceanographic and related societal applications are briefly discussed in the paper. To meet the requirements for oceanographic applications, the instrument must be flown in an orbit with proper sampling of ocean tides.

  6. The lectin KM+ induces corneal epithelial wound healing in rabbits.

    PubMed

    Chahud, Fernando; Ramalho, Leandra N Z; Ramalho, Fernando S; Haddad, Antonio; Roque-Barreira, Maria C

    2009-04-01

    Neutrophil influx is essential for corneal regeneration (Gan et al. 1999). KM+, a lectin from Artocarpus integrifolia, induces neutrophil migration (Santos-de-Oliveira et al. 1994). This study aims at investigating a possible effect of KM+ on corneal regeneration in rabbits. A 6.0-mm diameter area of debridement was created on the cornea of both eyes by mechanical scraping. The experimental eyes received drops of KM+ (2.5 microg/ml) every 2 h. The control eyes received buffer. The epithelial wounded areas of the lectin-treated and untreated eyes were stained with fluorescein, photographed and measured. The animals were killed 12 h (group 1, n = 5), 24 h (group 2, n = 10) and 48 h (group 3, n = 5) after the scraping. The corneas were analysed histologically (haematoxylin and eosin and immunostaining for proliferation cell nuclear antigen, p63, vascular endothelial growth factor, c-Met and laminin). No significant differences were found at the epithelial gap between treated and control eyes in the group 1. However, the number of neutrophils in the wounded area was significantly higher in treated eyes in this group. Three control and seven treated eyes were healed completely and only rare neutrophils persisted in the corneal stroma in group 2. No morphological distinction was observed between treated and control eyes in group 3. In treated corneas of group 2, there was an increase in immunostaining of factors involved in corneal healing compared to controls. Thus, topical application of KM+ may facilitate corneal epithelial wound healing in rabbits by means of a mechanism that involves increased influx of neutrophils into the wounded area induced by the lectin.

  7. Acceleration of barium ions near 8000 km above an aurora

    NASA Technical Reports Server (NTRS)

    Stenbaek-Nielsen, H. C.; Hallinan, T. J.; Wescott, E. M.; Foeppl, H.

    1984-01-01

    A barium shaped charge, named Limerick, was released from a rocket launched from Poker Flat Research Range, Alaska, on March 30, 1982, at 1033 UT. The release took place in a small auroral breakup. The jet of ionized barium reached an altitude of 8100 km 14.5 min after release, indicating that there were no parallel electric fields below this altitude. At 8100 km the jet appeared to stop. Analysis shows that the barium at this altitude was effectively removed from the tip. It is concluded that the barium was actually accelerated upward, resulting in a large decrease in the line-of-sight density and hence the optical intensity. The parallel electric potential in the acceleration region must have been greater than 1 kV over an altitude interval of less than 200 km. The acceleration region, although presumably auroral in origin, did not seem to be related to individual auroral structures, but appeared to be a large-scale horizontal structure. The perpendicular electric field below, as deduced from the drift of the barium, was temporally and spatially very uniform and showed no variation related to individual auroral structures passing through.

  8. Genetic affinity and admixture of northern Thai people along their migration route in northern Thailand: evidence from autosomal STR loci.

    PubMed

    Kutanan, Wibhu; Kampuansai, Jatupol; Colonna, Vincenza; Nakbunlung, Supaporn; Lertvicha, Pornpilai; Seielstad, Mark; Bertorelle, Giorgio; Kangwanpong, Daoroong

    2011-02-01

    The Khon Mueang (KM) are the largest group of northern Thai people. Our previous mtDNA studies have suggested an admixture process among the KM with the earlier Mon-Khmer-speaking inhabitants of this region. In this study, we evaluate genetic affinities and admixture among 10 KM populations in northern Thailand lying along the historical Yuan migration route, and 10 neighboring populations belonging to 7 additional ethnic groups: Lawa, Mon (Mon-Khmer-speaking groups), Shan, Yuan, Lue, Khuen and Yong (Tai-speaking groups) by analyzing 15 hypervariable autosomal short tandem repeat loci. The KM exhibited close relationships with neighboring populations, especially the Tai-speaking groups, reflecting an admixed origin of the KM. Admixture proportions were observed in all KM populations, which had a higher contribution from the parental Tai than the Mon-Khmer groups. Different admixture patterns of the KM along the migration route might indicate high heterogeneity among the KM. These patterns were not directly associated with geographical proximity, suggesting other factors, like variation in the timing of admixture with the existing populations may have had an important role. More genetic data from different marker systems solely transmitted through the male or female lineages are needed to complete the description of genetic admixture and population history of the KM.

  9. Structure-Affinity Properties of a High-Affinity Ligand of FKBP12 Studied by Molecular Simulations of a Binding Intermediate

    PubMed Central

    Olivieri, Lilian; Gardebien, Fabrice

    2014-01-01

    With a view to explaining the structure-affinity properties of the ligands of the protein FKBP12, we characterized a binding intermediate state between this protein and a high-affinity ligand. Indeed, the nature and extent of the intermolecular contacts developed in such a species may play a role on its stability and, hence, on the overall association rate. To find the binding intermediate, a molecular simulation protocol was used to unbind the ligand by gradually decreasing the biasing forces introduced. The intermediate was subsequently refined with 17 independent stochastic boundary molecular dynamics simulations that provide a consistent picture of the intermediate state. In this state, the core region of the ligand remains stable, notably because of the two anchoring oxygen atoms that correspond to recurrent motifs found in all FKBP12 ligand core structures. Besides, the non-core regions participate in numerous transient intermolecular and intramolecular contacts. The dynamic aspect of most of the contacts seems important both for the ligand to retain at least a part of its configurational entropy and for avoiding a trapped state along the binding pathway. Since the transient and anchoring contacts contribute to increasing the stability of the intermediate, as a corollary, the dissociation rate constant of this intermediate should be decreased, resulting in an increase of the affinity constant . The present results support our previous conclusions and provide a coherent rationale for explaining the prevalence in high-affinity ligands of (i) the two oxygen atoms found in carbonyl or sulfonyl groups of dissimilar core structures and of (ii) symmetric or pseudo-symmetric mobile groups of atoms found as non-core moieties. Another interesting aspect of the intermediate is the distortion of the flexible 80 s loop of the protein, mainly in its tip region, that promotes the accessibility to the bound state. PMID:25502559

  10. Three pion nucleon coupling constants

    NASA Astrophysics Data System (ADS)

    Ruiz Arriola, E.; Amaro, J. E.; Navarro Pérez, R.

    2016-08-01

    There exist four pion nucleon coupling constants, fπ0pp, - fπ0nn, fπ+pn/2 and fπ-np/2 which coincide when up and down quark masses are identical and the electron charge is zero. While there is no reason why the pion-nucleon-nucleon coupling constants should be identical in the real world, one expects that the small differences might be pinned down from a sufficiently large number of independent and mutually consistent data. Our discussion provides a rationale for our recent determination fp2 = 0.0759(4),f 02 = 0.079(1),f c2 = 0.0763(6), based on a partial wave analysis of the 3σ self-consistent nucleon-nucleon Granada-2013 database comprising 6713 published data in the period 1950-2013.

  11. Quaternions as astrometric plate constants

    NASA Technical Reports Server (NTRS)

    Jefferys, William H.

    1987-01-01

    A new method for solving problems in relative astrometry is proposed. In it, the relationship between the measured quantities and the components of the position vector of a star is modeled using quaternions, in effect replacing the plate constants of a standard four-plate-constant solution with the four components of a quaternion. The method allows a direct solution for the position vectors of the stars, and hence for the equatorial coordinates. Distortions, magnitude, and color effects are readily incorporated into the formalism, and the method is directly applicable to overlapping-plate problems. The advantages of the method include the simplicity of the resulting equations, their freedom from singularities, and the fact that trigonometric functions and tangential point transformations are not needed to model the plate material. A global solution over the entire sky is possible.

  12. Three pion nucleon coupling constants

    NASA Astrophysics Data System (ADS)

    Ruiz Arriola, E.; Amaro, J. E.; Navarro Pérez, R.

    2016-08-01

    There exist four pion nucleon coupling constants, fπ0pp, ‑ fπ0nn, fπ+pn/2 and fπ‑np/2 which coincide when up and down quark masses are identical and the electron charge is zero. While there is no reason why the pion-nucleon-nucleon coupling constants should be identical in the real world, one expects that the small differences might be pinned down from a sufficiently large number of independent and mutually consistent data. Our discussion provides a rationale for our recent determination fp2 = 0.0759(4),f 02 = 0.079(1),f c2 = 0.0763(6), based on a partial wave analysis of the 3σ self-consistent nucleon-nucleon Granada-2013 database comprising 6713 published data in the period 1950-2013.

  13. Time-Varying Fundamental Constants

    NASA Astrophysics Data System (ADS)

    Olive, Keith

    2003-04-01

    Recent data from quasar absorption systems can be interpreted as arising from a time variation in the fine-structure constant. However, there are numerous cosmological, astro-physical, and terrestrial bounds on any such variation. These includes bounds from Big Bang Nucleosynthesis (from the ^4He abundance), the Oklo reactor (from the resonant neutron capture cross-section of Sm), and from meteoretic lifetimes of heavy radioactive isotopes. The bounds on the variation of the fine-structure constant are significantly strengthened in models where all gauge and Yukawa couplings vary in a dependent manner, as would be expected in unified theories. Models which are consistent with all data are severly challenged when Equivalence Principle constraints are imposed.

  14. Modal affinities of endplate acetylcholine receptors caused by loop C mutations

    PubMed Central

    Vij, Ridhima; Purohit, Prasad

    2015-01-01

    The time course of the endplate current is determined by the rate and equilibrium constants for acetylcholine receptor (AChR) activation. We measured these constants in single-channel currents from AChRs with mutations at the neurotransmitter-binding sites, in loop C. The main findings are: (a) Almost all perturbations of loop C generate heterogeneity in the channel open probability (“modes”). (b) Modes are generated by different affinities for ACh that can be either higher or lower than in the wild-type receptors. (c) The modes are stable, in so far as each receptor maintains its affinity for at least several minutes. (d) Different agonists show different degrees of modal activity. With the loop C mutation αP197A, there are four modes with ACh but only two with partial agonists. (e) The affinity variations arise exclusively from the αδ-binding site. (f) Substituting four γ-subunit residues into the δ subunit (three in loop E and one in the β5–β5′ linker) reduces modal activity. (g) At each neurotransmitter-binding site, affinity is determined by a core of five aromatic residues. Modes are eliminated by an alanine mutation at δW57 but not at the other aromatics. (h) Modes are eliminated by a phenylalanine substitution at all core aromatics except αY93. The results suggest that, at the αδ agonist site, loop C and the complementary subunit surface can each adopt alternative conformations and interact with each other to influence the position of δW57 with respect to the aromatic core and, hence, affinity. PMID:26503719

  15. Affinity labelling of phenylalanyl-tRNA synthetase from E. coli MRE-600 by E. coli tRNAphe containing photoreactive group.

    PubMed

    Gorshkova, I I; Knorre, D G; Lavrik, O I; Nevinsky, G A

    1976-06-01

    The photoinduced reaction of phenylalanyl-tRNA synthetase (E.C.6.1.1.20) from E.coli MRE-600 with tRNAphe containing photoreative p-N3-C6H4-NHCOCH2-group attached to 4-thiouridine sU8 (azido-tRNAphe) was investigated. The attachment of this group does not influence the dissociation constant of the complex of Phe-tRNAphe with the enzyme, however it results in sevenfold increase of Km in the enzymatic aminoacylation of tRNAphe. Under irradiation at 300 nm at pH 5.8 the covalent binding of [14C]-Phe-azido-tRNAphe to the enzyme takes place 0.3 moles of the reagent being attached per mole of the enzyme. tRNA prevents the reaction. Phenylalanine, ATP,ADP,AMP, adenosine and pyrophosphate (2.5 xx 10(-3) M) don't affect neither the stability of the tRNA-enzyme complex nor the rate of the affinity labelling. The presence of the mixture of either phenylalanine or phenylalaninol with ATP as well as phenylalaninol adenylate exhibits 50% inhibition of the photoinduced reaction. Therefore, the reaction of [14C]-Phe-azido-tRNA with the enzyme is significantly less sensitive to the presence of the ligands than the reaction of chlorambucilyl-tRNA with the reactive group attached to the acceptor end of the tRNA studied in 1. It has been concluded that the kinetics of the affinity labelling does permit to discriminate the influence of the low molecular weight ligands of the enzyme on the different sites of the tRNA enzyme interaction. PMID:8772

  16. An Alcohol Test for Drifting Constants

    NASA Astrophysics Data System (ADS)

    Jansen, P.; Bagdonaite, J.; Ubachs, W.; Bethlem, H. L.; Kleiner, I.; Xu, L.-H.

    2013-06-01

    The Standard Model of physics is built on the fundamental constants of nature, however without providing an explanation for their values, nor requiring their constancy over space and time. Molecular spectroscopy can address this issue. Recently, we found that microwave transitions in methanol are extremely sensitive to a variation of the proton-to-electron mass ratio μ, due to a fortuitous interplay between classically forbidden internal rotation and rotation of the molecule as a whole. In this talk, we will explain the origin of this effect and how the sensitivity coefficients in methanol are calculated. In addition, we set a limit on a possible cosmological variation of μ by comparing transitions in methanol observed in the early Universe with those measured in the laboratory. Based on radio-astronomical observations of PKS1830-211, we deduce a constraint of Δμ/μ=(0.0± 1.0)× 10^{-7} at redshift z = 0.89, corresponding to a look-back time of 7 billion years. While this limit is more constraining and systematically more robust than previous ones, the methanol method opens a new search territory for probing μ-variation on cosmological timescales. P. Jansen, L.-H. Xu, I. Kleiner, W. Ubachs, and H.L. Bethlem Phys. Rev. Lett. {106}(100801) 2011. J. Bagdonaite, P. Jansen, C. Henkel, H.L. Bethlem, K.M. Menten, and W. Ubachs Science {339}(46) 2013.

  17. Smooth big bounce from affine quantization

    NASA Astrophysics Data System (ADS)

    Bergeron, Hervé; Dapor, Andrea; Gazeau, Jean Pierre; Małkiewicz, Przemysław

    2014-04-01

    We examine the possibility of dealing with gravitational singularities on a quantum level through the use of coherent state or wavelet quantization instead of canonical quantization. We consider the Robertson-Walker metric coupled to a perfect fluid. It is the simplest model of a gravitational collapse, and the results obtained here may serve as a useful starting point for more complex investigations in the future. We follow a quantization procedure based on affine coherent states or wavelets built from the unitary irreducible representation of the affine group of the real line with positive dilation. The main issue of our approach is the appearance of a quantum centrifugal potential allowing for regularization of the singularity, essential self-adjointness of the Hamiltonian, and unambiguous quantum dynamical evolution.

  18. Affinity Chromatography in Nonionic Detergent Solutions

    NASA Astrophysics Data System (ADS)

    Robinson, Jack B.; Strottmann, James M.; Wick, Donald G.; Stellwagen, Earle

    1980-10-01

    Anionic dye affinity chromatography is commonly unproductive in the presence of nonionic detergents used to extract particulate proteins. Using lactate dehydrogenase as a model protein, Cibacron blue F3GA as a model dye, and Triton X-100 as a model detergent, we find that the dye is encapsulated in nonionic detergent micelles, rendering the dye incapable of ligation with the enzyme. However, the dye can be liberated from the micelles without altering the nonionic detergent concentration by addition of an anionic detergent, such as deoxycholate or sodium dodecyl sulfate, forming mixed anionic/nonionic micelles that displace the anionic dye. Encapsulation of the anionic detergents prevents their activity as protein denaturants. These observations have been successfully translated to the dye affinity chromatography of a detergent extract of brain particulate cyclic nucleotide phosphodiesterase.

  19. Artificial Affinity Proteins as Ligands of Immunoglobulins

    PubMed Central

    Mouratou, Barbara; Béhar, Ghislaine; Pecorari, Frédéric

    2015-01-01

    A number of natural proteins are known to have affinity and specificity for immunoglobulins. Some of them are widely used as reagents for detection or capture applications, such as Protein G and Protein A. However, these natural proteins have a defined spectrum of recognition that may not fit specific needs. With the development of combinatorial protein engineering and selection techniques, it has become possible to design artificial affinity proteins with the desired properties. These proteins, termed alternative scaffold proteins, are most often chosen for their stability, ease of engineering and cost-efficient recombinant production in bacteria. In this review, we focus on alternative scaffold proteins for which immunoglobulin binders have been identified and characterized. PMID:25647098

  20. Permeability of self-affine rough fractures

    PubMed

    Drazer; Koplik

    2000-12-01

    The permeability of two-dimensional fractures with self-affine fractal roughness is studied via analytic arguments and numerical simulations. The limit where the roughness amplitude is small compared with average fracture aperture is analyzed by a perturbation method, while in the opposite case of narrow aperture, we use heuristic arguments based on lubrication theory. Numerical simulations, using the lattice Boltzmann method, are used to examine the complete range of aperture sizes, and confirm the analytic arguments. PMID:11138092

  1. Comparison of broadband mode arrivals at ranges of 3515 km and 5171 km in the North Pacific

    NASA Astrophysics Data System (ADS)

    Wage, Kathleen E.

    2003-04-01

    The Acoustic Thermometry of Ocean Climate (ATOC) provided an opportunity to observe signals propagating in the low-order modes of the ocean waveguide. Understanding the fluctuations of these mode signals is an important prerequisite to using them for tomography or other applications. In previous work, we characterized the cross-mode coherence and temporal variability of the low-order mode arrivals at 3515 km range [Wage et al., J. Acoust. Soc. Am. (in press)]. This study compares the mode arrivals for two different ranges : 3515 km and 5171 km, using data from the ATOC vertical line arrays at Hawaii and Kiritimati. We discuss the mode intensity and coherence statistics for each of the arrays and examine mean arrival time trends over the year-long deployment. Experimental results are compared to PE simulations of propagation through a realistic background environment perturbed by internal waves of varying strengths. The dependence of mode statistics on the path-dependent changes in the background sound speed and the parameters of the internal wave field is explored. [Work supported by an ONR Ocean Acoustics Young Faculty Award.] a)A. B. Baggeroer, T. G. Birdsall, C. Clark, J. A. Colosi, B. D. Cornuelle, D. Costa, B. D. Dushaw, M. A. Dzieciuch, A. M. G. Forbes, B. M. Howe, D. Menemenlis, J. A. Mercer, K. Metzger, W. H. Munk, R. C. Spindel, P. F. Worcester, and C. Wunsch.

  2. The gall bladder cholecystokinin receptor exists in two guanine nucleotide-binding protein-regulated affinity states

    SciTech Connect

    Molero, X.; Miller, L.J. )

    1991-02-01

    To study proximal events in cholecystokinin (CCK) action on bovine gall bladder smooth muscle, we used the hormone analogue D-Tyr-Gly-((N1e28,31)CCK-26-32)-phenethyl ester (OPE), which has unique biological properties. This fully efficacious agonist differs from native CCK by not expressing supramaximal inhibition of cell shortening, yet it clearly interacts with the same receptor molecule. This was demonstrated in binding and affinity labeling studies, where both peptides label the same Mr 70,000-85,000 protein and both fully compete for binding of the other ligand. Further, its relatively high affinity for the low affinity CCK receptor permits the clear demonstration of two affinity states of a CCK receptor on a membrane preparation and makes possible evaluation of the molecular basis of these affinity states and their regulation. Analysis of homologous and heterologous binding curves performed with both CCK and OPE peptides and radioligands demonstrated the presence of two affinity states, with CCK being able to distinguish them (Kd1 = 0.48 +/- 0.04 nM and Kd2 = 56.5 +/- 7.4 nM) and OPE recognizing them equally (Kd1 = 0.94 +/- 0.31 nM and Kd2 = 0.96 +/- 0.23 nM). In the presence of nonhydrolyzable GTP analogues, there was a shift in distribution of receptors toward the low affinity state, with the total number of receptors and their absolute affinities for each peptide remaining constant. Thus, the gall bladder CCK receptor is a single molecule capable of assuming two interconvertible affinity states, regulated by a guanine nucleotide-binding protein. Two full agonists are capable of interacting with this molecule to yield different biological responses via different molecular events.

  3. On constructing purely affine theories with matter

    NASA Astrophysics Data System (ADS)

    Cervantes-Cota, Jorge L.; Liebscher, D.-E.

    2016-08-01

    We explore ways to obtain the very existence of a space-time metric from an action principle that does not refer to it a priori. Although there are reasons to believe that only a non-local theory can viably achieve this goal, we investigate here local theories that start with Schrödinger's purely affine theory (Schrödinger in Space-time structure. Cambridge UP, Cambridge, 1950), where he gave reasons to set the metric proportional to the Ricci curvature aposteriori. When we leave the context of unified field theory, and we couple the non-gravitational matter using some weak equivalence principle, we can show that the propagation of shock waves does not define a lightcone when the purely affine theory is local and avoids the explicit use of the Ricci tensor in realizing the weak equivalence principle. When the Ricci tensor is substituted for the metric, the equations seem to have only a very limited set of solutions. This backs the conviction that viable purely affine theories have to be non-local.

  4. Overview of affinity biosensors in food analysis.

    PubMed

    Patel, Pradip D

    2006-01-01

    The 4 major driving forces that are expected to lead to increased use of affinity biosensors that meet crucial industrial test specifications, e.g., fast, reliable, cost-effective, and use of low-skilled personnel, are (1) strict legislative framework, e.g., recent changes proposed to the European food safety and hygiene legislation, EC No. 178/2002; (2) industrial shift from quality control to quality assurance procedures, e.g., Hazard Analysis Critical Control Point, ensuring effective positioning in the global competitive trade; (3) just-in-time production resulting in 'right' product every time; and (4) consumer demand for safe and wholesome products. The affinity biosensors field has expanded significantly over the past decade, with a projected global biosensors market growth from $6.1 billion in 2004 to $8.2 billion in 2009, representing major industrial sectors (e.g., Pharma, Medicare, and Food). This brief review is targeted to affinity biosensors developed for the food industry and includes research and development leading to biosensors for microbiological and chemical analytes of industrial concern, commercial biosensors products on the market, and examples of future prospects in this diagnostic field.

  5. Overview of affinity biosensors in food analysis.

    PubMed

    Patel, Pradip D

    2006-01-01

    The 4 major driving forces that are expected to lead to increased use of affinity biosensors that meet crucial industrial test specifications, e.g., fast, reliable, cost-effective, and use of low-skilled personnel, are (1) strict legislative framework, e.g., recent changes proposed to the European food safety and hygiene legislation, EC No. 178/2002; (2) industrial shift from quality control to quality assurance procedures, e.g., Hazard Analysis Critical Control Point, ensuring effective positioning in the global competitive trade; (3) just-in-time production resulting in 'right' product every time; and (4) consumer demand for safe and wholesome products. The affinity biosensors field has expanded significantly over the past decade, with a projected global biosensors market growth from $6.1 billion in 2004 to $8.2 billion in 2009, representing major industrial sectors (e.g., Pharma, Medicare, and Food). This brief review is targeted to affinity biosensors developed for the food industry and includes research and development leading to biosensors for microbiological and chemical analytes of industrial concern, commercial biosensors products on the market, and examples of future prospects in this diagnostic field. PMID:16792079

  6. Phosphopeptide Enrichment by Immobilized Metal Affinity Chromatography.

    PubMed

    Thingholm, Tine E; Larsen, Martin R

    2016-01-01

    Immobilized metal affinity chromatography (IMAC) has been the method of choice for phosphopeptide enrichment prior to mass spectrometric analysis for many years and it is still used extensively in many laboratories. Using the affinity of negatively charged phosphate groups towards positively charged metal ions such as Fe(3+), Ga(3+), Al(3+), Zr(4+), and Ti(4+) has made it possible to enrich phosphorylated peptides from peptide samples. However, the selectivity of most of the metal ions is limited, when working with highly complex samples, e.g., whole-cell extracts, resulting in contamination from nonspecific binding of non-phosphorylated peptides. This problem is mainly caused by highly acidic peptides that also share high binding affinity towards these metal ions. By lowering the pH of the loading buffer nonspecific binding can be reduced significantly, however with the risk of reducing specific binding capacity. After binding, the enriched phosphopeptides are released from the metal ions using alkaline buffers of pH 10-11, EDTA, or phosphate-containing buffers. Here we describe a protocol for IMAC using Fe(3+) for phosphopeptide enrichment. The principles are illustrated on a semi-complex peptide mixture. PMID:26584922

  7. Trematode hemoglobins show exceptionally high oxygen affinity.

    PubMed

    Kiger, L; Rashid, A K; Griffon, N; Haque, M; Moens, L; Gibson, Q H; Poyart, C; Marden, M C

    1998-08-01

    Ligand binding studies were made with hemoglobin (Hb) isolated from trematode species Gastrothylax crumenifer (Gc), Paramphistomum epiclitum (Pe), Explanatum explanatum (Ee), parasitic worms of water buffalo Bubalus bubalis, and Isoparorchis hypselobagri (Ih) parasitic in the catfish Wallago attu. The kinetics of oxygen and carbon monoxide binding show very fast association rates. Whereas oxygen can be displaced on a millisecond time scale from human Hb at 25 degrees C, the dissociation of oxygen from trematode Hb may require a few seconds to over 20 s (for Hb Pe). Carbon monoxide dissociation is faster, however, than for other monomeric hemoglobins or myoglobins. Trematode hemoglobins also show a reduced rate of autoxidation; the oxy form is not readily oxidized by potassium ferricyanide, indicating that only the deoxy form reacts rapidly with this oxidizing agent. Unlike most vertebrate Hbs, the trematodes have a tyrosine residue at position E7 instead of the usual distal histidine. As for Hb Ascaris, which also displays a high oxygen affinity, the trematodes have a tyrosine in position B10; two H-bonds to the oxygen molecule are thought to be responsible for the very high oxygen affinity. The trematode hemoglobins display a combination of high association rates and very low dissociation rates, resulting in some of the highest oxygen affinities ever observed.

  8. Constraints on the gravitational constant at large distances

    NASA Technical Reports Server (NTRS)

    Mikkelsen, D. R.; Newman, M. J.

    1977-01-01

    D. R. Long (1976) and others have speculated that the gravitational force between point masses in the Newtonian regime might not be exactly proportional to 1/r squared. Distance-dependent deviations from the 1/r squared law can be represented by a distance-dependent gravitational 'constant', G(r). Long has summarized the experimental evidence which constrains G(r) to be very nearly constant for 5 cm less than r less than 1 m. This paper presents observational evidence for constancy in the range 1000 km less than r less than 10 to the eighth km, and points out that the value of G(r) identical to Gc in this range has not been experimentally determined. Constraints on G(r) in the intermediate distance range 10 m less than r less than 1 km are so poor that one cannot rule out the possibility that Gc differs greatly from the laboratory value Go. Models of the earth and sun are used to argue that Gc differs from Go by not more than approximately 40%. Methods of improving the determination of Gc are suggested.

  9. Will women outrun men in ultra-marathon road races from 50 km to 1,000 km?

    PubMed

    Zingg, Matthias Alexander; Karner-Rezek, Klaus; Rosemann, Thomas; Knechtle, Beat; Lepers, Romuald; Rüst, Christoph Alexander

    2014-01-01

    It has been assumed that women would be able to outrun men in ultra-marathon running. The present study investigated the sex differences in running speed in ultra-marathons held worldwide from 50 km to 1,000 km. Changes in running speeds and the sex differences in running speeds in the annual fastest finishers in 50 km, 100 km, 200 km and 1,000 km events held worldwide from 1969-2012 were analysed using linear, non-linear and multi-level regression analyses. For the annual fastest and the annual ten fastest finishers, running speeds increased non-linearly in 50 km and 100 km, but not in 200 km and 1,000 km where running speeds remained unchanged for the annual fastest. The sex differences decreased non-linearly in 50 km and 100 km, but not in 200 and 1,000 km where the sex difference remained unchanged for the annual fastest. For the fastest women and men ever, the sex difference in running speed was lowest in 100 km (5.0%) and highest in 50 km (15.4%). For the ten fastest women and men ever, the sex difference was lowest in 100 km (10.0 ± 3.0%) and highest in 200 km (27.3 ± 5.7%). For both the fastest (r(2) = 0.003, p = 0.82) and the ten fastest finishers ever (r(2) = 0.34, p = 0.41) in 50 km, 100 km, 200 km and 1,000 km, we found no correlation between sex difference in performance and running speed. To summarize, the sex differences in running speeds decreased non-linearly in 50 km and 100 km but remained unchanged in 200 km and 1,000 km, and the sex differences in running speeds showed no change with increasing length of the race distance. These findings suggest that it is very unlikely that women will ever outrun men in ultra-marathons held from 50 km to 100 km.

  10. fine structure of 410km discontinuity beneath the Southern Europe

    NASA Astrophysics Data System (ADS)

    Wan, K.; Wan, X.; Ni, S.

    2005-12-01

    In the distance range of 10-14 degrees, P waves from the topside reflection off the 410km discontinuity are very sensitive to the fine structure of the discontinuity. We analyzed 49 broadband seismograms from an earthquake ( May 18, 1998) in Italy (Mw 5.8) , recorded by Orfeus and SZGRF networks. Distances between the source and the stations were from 9° to 19°, and provided a detailed look at the 410km structure. On the other hand, the azimuth of these records were in a narrow range from 334° and 356°, so the differences in azimuth may have little effects on the waveforms. From our observation, P410 phase has little change in amplitude when the distance decreases from 15° to about 11.5°. However, an abrupt termination was observed from distance 11° to 10.5°. These features cannot be explained with PREM model. We calculated several groups of models with F-K method and compared their synthetic seismograms with the observed one. These models are: 1) two-step sharp jump models, with different thickness; 2) linear models; 3) linear-sharp jump models[Tim Melbourne, Don Helmberger, Journal of Geophysical Research, 1998]; 4) models calculated from a mineralogical model[Gaherty, Wang, Geophysical research letters, 1999]; Features in the observed waveform can be well modeled with model 3 and 4 while only parts of them fitted to model 1 or 2. But when we calculated with a less detailed model, seismograms of model 4 should have more noise than model 3. In conclusion, the structure of 410km discontinuity can be considered as a linear-sharp velocity jump, which is consistent with mineralogical models.

  11. Mapping the global land surface using 1 km AVHRR data

    USGS Publications Warehouse

    Lauer, D.T.; Eidenshink, J.C.

    1998-01-01

    The scientific requirements for mapping the global land surface using 1 km advanced very high resolution radiometer (AVHRR) data have been set forth by the U.S. Global Change Research Program; the International Geosphere Biosphere Programme (IGBP); The United Nations; the National Oceanic and Atmospheric Administration (NOAA); the Committee on Earth Observations Satellites; and the National Aeronautics and Space Administration (NASA) mission to planet Earth (MTPE) program. Mapping the global land surface using 1 km AVHRR data is an international effort to acquire, archive, process, and distribute 1 km AVHRR data to meet the needs of the international science community. A network of AVHRR receiving stations, along with data recorded by NOAA, has been acquiring daily global land coverage since April 1, 1992. A data set of over 70,000 AVHRR images is archived and distributed by the United States Geological Survey (USGS) EROS Data Center, and the European Space Agency. Under the guidance of the IGBP, processing standards have been developed for calibration, atmospheric correction, geometric registration, and the production of global 10-day maximum normalized difference vegetation index (NDVI) composites. The major uses of the composites are for the study of surface vegetation condition, mapping land cover, and deriving biophysical characteristics of terrestrial ecosystems. A time-series of 54 10-day global vegetation index composites for the period of April 1, 1992 through September 1993 has been produced. The production of a time-series of 33 10-day global vegetation index composites using NOAA-14 data for the period of February 1, 1995 through December 31, 1995 is underway. The data products are available from the USGS, in cooperation with NASA's MTPE program and other international organizations.

  12. Binding affinities of CRBPI and CRBPII for 9-cis-retinoids

    PubMed Central

    Kane, Maureen A.; Bright, Frank V.; Napoli, Joseph L.

    2014-01-01

    Background Cellular retinol binding-protein I (CRBPI) and cellular retinol binding-protein II (CRBPII) serve as intracellular retinoid chaperones that bind retinol and retinal with high affinity and facilitate substrate delivery to select enzymes that catalyze retinoic acid (RA) and retinyl ester biosynthesis. Recently, 9-cis-RA has been identified in vivo in the pancreas, where it contributes to regulating glucose-stimulated insulin secretion. In vitro, 9-cis-RA activates RXR (retinoid×receptors), which serve as therapeutic targets for treating cancer and metabolic diseases. Binding affinities and structure–function relationships have been well characterized for CRBPI and CRBPII with all-trans-retinoids, but not for 9-cis-retinoids. This study extended current knowledge by establishing binding affinities for CRBPI and CRBPII with 9-cis-retinoids. Methods We have determined apparent dissociation constants, Kd′, through monitoring binding of 9-cis-retinol, 9-cis-retinal, and 9-cis-RA with CRBPI and CRBPII by fluorescence spectroscopy, and analyzing the data with non-linear regression. We compared these data to the data we obtained for all-trans- and 13-cis-retinoids under identical conditions. Results CRBPI and CRBPII, respectively, bind 9-cis-retinol ( Kd′, 11 nM and 68 nM) and 9-cis-retinal ( Kd′, 8 nM and 5 nM) with high affinity. No significant 9-cis-RA binding was observed with CRBPI or CRBPII. Conclusions CRBPI and CRBPII bind 9-cis-retinol and 9-cis-retinal with high affinities, albeit with affinities somewhat lower than for all-trans-retinol and all-trans-retinal. General significance These data provide further insight into structure–binding relationships of cellular retinol binding-proteins and are consistent with a model of 9-cis-RA biosynthesis that involves chaperoned delivery of 9-cis-retinoids to enzymes that recognize retinoid binding-proteins. PMID:21382444

  13. 157km BOTDA with pulse coding and image processing

    NASA Astrophysics Data System (ADS)

    Qian, Xianyang; Wang, Zinan; Wang, Song; Xue, Naitian; Sun, Wei; Zhang, Li; Zhang, Bin; Rao, Yunjiang

    2016-05-01

    A repeater-less Brillouin optical time-domain analyzer (BOTDA) with 157.68km sensing range is demonstrated, using the combination of random fiber laser Raman pumping and low-noise laser-diode-Raman pumping. With optical pulse coding (OPC) and Non Local Means (NLM) image processing, temperature sensing with +/-0.70°C uncertainty and 8m spatial resolution is experimentally demonstrated. The image processing approach has been proved to be compatible with OPC, and it further increases the figure-of-merit (FoM) of the system by 57%.

  14. The relational database system of KM3NeT

    NASA Astrophysics Data System (ADS)

    Albert, Arnauld; Bozza, Cristiano

    2016-04-01

    The KM3NeT Collaboration is building a new generation of neutrino telescopes in the Mediterranean Sea. For these telescopes, a relational database is designed and implemented for several purposes, such as the centralised management of accounts, the storage of all documentation about components and the status of the detector and information about slow control and calibration data. It also contains information useful during the construction and the data acquisition phases. Highlights in the database schema, storage and management are discussed along with design choices that have impact on performances. In most cases, the database is not accessed directly by applications, but via a custom designed Web application server.

  15. An evaluation of the global 1-km AVHRR land dataset

    USGS Publications Warehouse

    Teillet, P.M.; El Saleous, N.; Hansen, M.C.; Eidenshink, Jeffery C.; Justice, C.O.; Townshend, J.R.G.

    2000-01-01

    This paper summarizes the steps taken in the generation of the global 1-km AVHRR land dataset, and it documents an evaluation of the data product with respect to the original specifications and its usefulness in research and applications to date. The evaluation addresses data characterization, processing, compositing and handling issues. Examples of the main scientific outputs are presented and options for improved processing are outlined and prioritized. The dataset has made a significant contribution, and a strong recommendation is made for its reprocessing and continuation to produce a long-term record for global change research.

  16. Measurement of State-Specific Association Constants in Allosteric Sensors through Molecular Stapling and NMR.

    PubMed

    Moleschi, Kody J; Akimoto, Madoka; Melacini, Giuseppe

    2015-08-26

    Allostery is a ubiquitous mechanism to control biological function and arises from the coupling of inhibitory and binding equilibria. The extent of coupling reflects the inactive vs active state selectivity of the allosteric effector. Hence, dissecting allosteric determinants requires quantification of state-specific association constants. However, observed association constants are typically population-averages, reporting on overall affinities but not on allosteric coupling. Here we propose a general method to measure state-specific association constants in allosteric sensors based on three key elements, i.e., state-selective molecular stapling through disulfide bridges, competition binding saturation transfer experiments and chemical shift correlation analyses to gauge state populations. The proposed approach was applied to the prototypical cyclic adenosine monophosphate (cAMP)-dependent protein kinase (PKA-RIα), for which the structures of the inactive and active states are available, as needed to design the state-selective disulfide bridges. Surprisingly, the PKA-RIα state-specific association constants are comparable to those of a structurally homologous domain with ∼10(3)-fold lower cAMP-affinity, suggesting that the affinity difference arises primarily from changes in the position of the dynamic apo inhibitory equilibrium.

  17. Millikan's measurement of Planck's constant

    NASA Astrophysics Data System (ADS)

    Franklin, Allan

    2013-12-01

    Robert Millikan is famous for measuring the charge of the electron. His result was better than any previous measurement and his method established that there was a fundamental unit of charge, or charge quantization. He is less well-known for his measurement of Planck's constant, although, as discussed below, he is often mistakenly given credit for providing significant evidence in support of Einstein's photon theory of light.1 His Nobel Prize citation was "for his work on the elementary electric charge of electricity and the photoelectric effect," an indication of the significance of his work on the photoelectric effect.

  18. Chandra Independently Determines Hubble Constant

    NASA Astrophysics Data System (ADS)

    2006-08-01

    A critically important number that specifies the expansion rate of the Universe, the so-called Hubble constant, has been independently determined using NASA's Chandra X-ray Observatory. This new value matches recent measurements using other methods and extends their validity to greater distances, thus allowing astronomers to probe earlier epochs in the evolution of the Universe. "The reason this result is so significant is that we need the Hubble constant to tell us the size of the Universe, its age, and how much matter it contains," said Max Bonamente from the University of Alabama in Huntsville and NASA's Marshall Space Flight Center (MSFC) in Huntsville, Ala., lead author on the paper describing the results. "Astronomers absolutely need to trust this number because we use it for countless calculations." Illustration of Sunyaev-Zeldovich Effect Illustration of Sunyaev-Zeldovich Effect The Hubble constant is calculated by measuring the speed at which objects are moving away from us and dividing by their distance. Most of the previous attempts to determine the Hubble constant have involved using a multi-step, or distance ladder, approach in which the distance to nearby galaxies is used as the basis for determining greater distances. The most common approach has been to use a well-studied type of pulsating star known as a Cepheid variable, in conjunction with more distant supernovae to trace distances across the Universe. Scientists using this method and observations from the Hubble Space Telescope were able to measure the Hubble constant to within 10%. However, only independent checks would give them the confidence they desired, considering that much of our understanding of the Universe hangs in the balance. Chandra X-ray Image of MACS J1149.5+223 Chandra X-ray Image of MACS J1149.5+223 By combining X-ray data from Chandra with radio observations of galaxy clusters, the team determined the distances to 38 galaxy clusters ranging from 1.4 billion to 9.3 billion

  19. Henry's law constants of polyols

    NASA Astrophysics Data System (ADS)

    Compernolle, S.; Müller, J.-F.

    2014-05-01

    Henry's law constants (HLC) are derived for several polyols bearing between 2 and 6 hydroxyl groups, based on literature data for water activity, vapour pressure and/or solubility. Depending on the case, infinite dilution activity coefficients (IDACs), solid state pressures or activity coefficient ratios are obtained as intermediary results. For most compounds, these are the first values reported, while others compare favourably with literature data in most cases. Using these values and those from a previous work (Compernolle and Müller, 2014), an assessment is made on the partitioning of polyols, diacids and hydroxy acids to droplet and aqueous aerosol.

  20. Combination of isothermal titration calorimetry and time-resolved luminescence for high affinity antibody-ligand interaction thermodynamics and kinetics.

    PubMed

    Aweda, Tolulope A; Meares, Claude F

    2012-02-01

    For experiments using synthetic ligands as probes for biological experiments, it is useful to determine the specificity and affinity of the ligands for their receptors. As ligands with higher affinities are developed (K(A)>10(8)M(-1); K(D)<10(-8)M), a new challenge arises: to measure these values accurately. Isothermal titration calorimetry measures heat produced or consumed during ligand binding, and also provides the equilibrium binding constant. However, as normally practiced, its range is limited. Displacement titration, where a competing weaker ligand is used to lower the apparent affinity of the stronger ligand, can be used to determine the binding affinity as well as the complete thermodynamic data for ligand-antibody complexes with very high affinity. These equilibrium data have been combined with kinetic measurements to yield the rate constants as well. We describe this methodology, using as an example antibody 2D12.5, which captures yttrium S-2-(4-aminobenzyl)-1, 4, 7, 10-tetraazacyclododecanetetraacetate.

  1. Quantum crytography over 14km of installed optical fiber

    SciTech Connect

    Hughes, R.J.; Luther, G.G.; Morgan, G.L.; Simmons, C.

    1995-09-01

    We have made the first demonstration that low error rate quantum cryptography over long distances (14km) of installed optical fiber in a real-world environment, subject to uncontrolled temperature and mechanical influences, representing an important new step towards incorporation of quantum cryptography into existing information security systems. We also point out that the high visibility single-photon interference in our experiment allows us to infer a test of the superposition principle of quantum mechanics: a photon reaching the detector has traveled over 14km of optical fiber in a wavepacket comprising a coherent superposition of two components that are spatially separated by about 2m. In principle, there are decoherence processes (or even possible modifications of quantum mechanics) that could cause the photon`s wavefunction to collapse into one component or the other during propagation, leading to a reduction in visibility. However, our results are consistent with no such loss of quantum coherence during the 67-{mu}s propagation time.

  2. Infrared emission from the atmosphere above 200 km

    NASA Technical Reports Server (NTRS)

    Simpson, J. P.

    1976-01-01

    The infrared radiation over the range from 4 to 1000 microns from atoms and molecules in the earth's atmosphere, between 200 and 400 km, was calculated. Only zenith lines of sight were considered. The excitation of the atoms and molecules is due to collisions with other molecules and to absorption of radiation from the earth and sun. In some cases, the abundances of the molecules had to be estimated. The most important lines are the forbidden lines from atomic oxygen at 63.1 and 147 micron, and the vibration-rotation band of nitric oxide at 5.3 micron. These lines can have intensities as high as a few times 0.001 ergs/sq cm/sec/steradian at 200 km altitude. In addition, the vibration-rotation bands of NO(+) at 4.3 micron and CO at 4.7 micron and the pure rotation lines of NO and NO(+) could be detected by infrared telescopes in space.

  3. KM3NeT/ORCA status and plans

    NASA Astrophysics Data System (ADS)

    Samtleben, Dorothea F. E.

    2016-04-01

    Neutrinos created in interactions of cosmic rays with the atmosphere can serve as a powerful tool to unveil the neutrino mass hierarchy (NMH). At low energies, around a few GeV, matter effects from the transition through the Earth are expected to imprint a distinct but also subtle signature on the oscillation pattern, specific to the ordering of the neutrino masses. KM3NeT/ORCA (Oscillations Research with Cosmics in the Abyss), a densely instrumented building block of the upcoming KM3NeT neutrino telescope, will be designated to measuring this signature in the Mediterranean Sea. Using detailed simulations the sensitivity towards this signature has been evaluated. The multi-PMT detectors allow in the water for an accurate reconstruction of GeV neutrino event signatures and distinction of neutrino flavours. For the determination of the mass hierarchy a median significance of 2-6σ has been estimated for three years of data taking, depending on the actual hierarchy and the oscillation parameters. At the same time the values of several oscillation parameters like θ23 will be determined to unprecedented precision.

  4. Nighttime ionization by energetic particles at Wallops Island in the altitude region 120 to 200 km

    NASA Technical Reports Server (NTRS)

    Voss, H. D.; Smith, L. G.

    1979-01-01

    Five Nike Apache rockets, each including an energetic particle spectrometer and an electron density-electron temperature experiment, have been launched from Wallops Island (L = 2.6) near midnight under varying geomagnetic conditions. On the most recent of these (5 January 1978) an additional spectrometer with a broom magnet, and a 391.4 nm photometer were flown. The data from this flight indicate that the energetic particle flux consists predominantly of protons, neutral hydrogen and possibly other energetic nuclei. The energy spectrum becomes much softer and the flux more intense with increasing Kp for 10-100 keV. The pitch angle distribution at 180 km is asymmetrical with a peak at 90 deg indicating that the majority of particles are near their mirroring altitude. Ionization rates are calculated based on the measured energy spectrum and mirror height distribution. The resulting ionization rate profile is found to be nearly constant with altitude in the region 120 to 200 km. The measured energetic particle flux and calculated ionization rate from the five flights are found to vary with magnetic activity (based on the Kp and Dst indexes) in the same way as the independently derived ionization rates deduced from the electron density profile.

  5. Hybrid fine scale climatology and microphysics of in-cloud icing: From 32 km reanalysis to 5 km mesoscale modeling

    NASA Astrophysics Data System (ADS)

    Lamraoui, Fayçal; Benoit, Robert; Perron, Jean; Fortin, Guy; Masson, Christian

    2015-03-01

    In-cloud icing can impose safety concerns and economic challenges for various industries. Icing climate representations proved beneficial for optimal designs and careful planning. The current study investigates in-cloud icing, its related cloud microphysics and introduces a 15-year time period climatology of icing events. The model was initially driven by reanalysis data from North American Regional Reanalysis and downscaled through a two-level nesting of 10 km and 5 km, using a limited-area version of the Global Environment Multiscale Model of the Canadian Meteorological Center. In addition, a hybrid approach is used to reduce time consuming calculations. The simulation realized exclusively on significant icing days, was combined with non-significant icing days as represented by data from NARR. A proof of concept is presented here for a 1000 km area around Gaspé during January for those 15 years. An increase in the number and intensity of icing events has been identified during the last 15 years. From GEM-LAM simulations and within the atmospheric layer between 10 m and 200 m AGL, supercooled liquid water contents indicated a maximum of 0.4 g m- 3, and 50% of the values are less than 0.05 g m- 3. All values of median volume diameters (MVD) are approximately capped by 70 μm and the typical values are around 15 μm. Supercooled Large Droplets represent approximately 5%. The vertical profile of icing climatology demonstrates a steady duration of icing events until the level of 60 m. The altitudes of 60 m and 100 m indicate substantial icing intensification toward higher elevations. GEM-LAM demonstrated a substantial improvement in the calculation of in-cloud icing, reducing significantly the challenge posed by complex terrains.

  6. Binding affinities and thermodynamics of noncovalent functionalization of carbon nanotubes with surfactants.

    PubMed

    Oh, Hyunkyu; Sim, Jinsook; Ju, Sang-Yong

    2013-09-01

    Binding affinity and thermodynamic understanding between a surfactant and carbon nanotube is essential to develop various carbon nanotube applications. Flavin mononucleotide-wrapped carbon nanotubes showing a large redshift in optical signature were utilized to determine the binding affinity and related thermodynamic parameters of 12 different nanotube chiralities upon exchange with other surfactants. Determined from the midpoint of sigmoidal transition, the equilibrium constant (K), which is inversely proportional to the binding affinity of the initial surfactant-carbon nanotube, provided quantitative binding strengths of surfactants as SDBS > SC ≈ FMN > SDS, irrespective of electronic types of SWNTs. Binding affinity of metallic tubes is weaker than that of semiconducting tubes. The complex K patterns from semiconducting tubes show preference to certain SWNT chiralities and surfactant-specific cooperativity according to nanotube chirality. Controlling temperature was effective to modulate K values by 30% and enables us to probe thermodynamic parameters. Equally signed enthalpy and entropy changes produce Gibbs energy changes with a magnitude of a few kJ/mol. A greater negative Gibbs energy upon exchange of surfactant produces an enhanced nanotube photoluminescence, implying the importance of understanding thermodynamics for designing nanotube separation and supramolecular assembly of surfactant.

  7. Rationally Designing Aptamer Sequences with Reduced Affinity for Controlled Sensor Performance

    PubMed Central

    Schoukroun-Barnes, Lauren R.; White, Ryan J.

    2015-01-01

    The relative ease of predicting the secondary structure of nucleic acid sequences lends itself to the design of sequences to perform desired functions. Here, we combine the utility of nucleic acid aptamers with predictable control over the secondary structure to rationally design sequences with controlled affinity towards a target analyte when employed as the recognition element in an electrochemical sensor. Specifically, we present a method to modify an existing high-gain aptamer sequence to create sequences that, when employed in an electrochemical, aptamer-based sensor, exhibit reduced affinity towards a small molecule analyte tobramycin. Sensors fabricated with the high-gain parent sequence saturate at concentrations much below the therapeutic window for tobramycin (7–18 µM). Accordingly, the rationale behind modifying this high-gain sequence to reduce binding affinity was to tune sensor performance for optimal sensitivity in the therapeutic window. Using secondary structure predictions and analysis of the NMR structure of an aminoglycoside RNA aptamer bound to tobramycin, we are able to successfully modify the aptamer sequence to tune the dissociation constants of electrochemical aptamer-based sensors between 0.17 and 3 µM. The guidelines we present represent a general strategy to lessening binding affinity of sensors employing aptamer-modified electrodes. PMID:25835184

  8. Chemiluminescently labeled aptamers as the affinity probe for interaction analysis by capillary electrophoresis.

    PubMed

    Li, Hong-Yi; Deng, Qin-Pei; Zhang, De-Wen; Zhou, Ying-Lin; Zhang, Xin-Xiang

    2010-07-01

    Aptamers are nucleic acid oligonucleotides, which can recognize targets with high affinity and specificity. Fluorescently labeled aptamers have been used as affinity probes in CE for interaction analysis. In this study, a method of labeling aptamers chemiluminescently with isoluminol isothiocyanate (ILITC) through covalent bonds was proposed and realized. The ILITC-labeled aptamers were characterized by HPLC-MS and purified by HPLC. After desalination, the ILITC-labeled aptamers were employed as the affinity probe for interaction analysis in CE coupled with chemiluminescence detection (CE-CL) by interface of end column reaction mode, the apparatus of which was home-designed and setup. CE-CL experiment conditions, including buffer pH, concentrations of horseradish peroxidase and H(2)O(2), were optimized first. The system of thrombin and its 29-mer aptamer was chosen as the model. Binding parameters, namely the dissociation constant (K(d)) and the binding site number (n), were calculated. The K(d) obtained was 124.0+/-6.9 nM in agreement with the reported values. Thus, interaction analysis method based on chemiluminescently labeled aptamers as the affinity probe in CE-CL has been established. This method can be widely applied due to the ease and universality of the labeling method, simplicity of CE-CL apparatus and combination with aptamers for a wide range of targets.

  9. The low-affinity complex of cytochrome c and its peroxidase

    PubMed Central

    Van de Water, Karen; Sterckx, Yann G. J.; Volkov, Alexander N.

    2015-01-01

    The complex of yeast cytochrome c peroxidase and cytochrome c is a paradigm of the biological electron transfer (ET). Building on seven decades of research, two different models have been proposed to explain its functional redox activity. One postulates that the intermolecular ET occurs only in the dominant, high-affinity protein–protein orientation, while the other posits formation of an additional, low-affinity complex, which is much more active than the dominant one. Unlike the high-affinity interaction—extensively studied by X-ray crystallography and NMR spectroscopy—until now the binding of cytochrome c to the low-affinity site has not been observed directly, but inferred mainly from kinetics experiments. Here we report the structure of this elusive, weak protein complex and show that it consists of a dominant, inactive bound species and an ensemble of minor, ET-competent protein–protein orientations, which summarily account for the experimentally determined value of the ET rate constant. PMID:25944250

  10. Measurements of laser phase fluctuations induced by atmospheric turbulence over 2 km and 17.5 km distances.

    PubMed

    Ridley, Kevin D

    2011-09-10

    A laser heterodyne system was used to measure the phase fluctuations imposed on a 1.5 μm wavelength laser beam when double-passed over long atmospheric paths. Two distances were used: 2 and 17.5 km. Results are given for intensity scintillation, phase fluctuation time series and spectra, and phase structure function. The results are found to agree well with theory: the spectrum of phase fluctuations follows the 8/3 power law predicted for Kolmogorov turbulence over 3 orders of magnitude in frequency. The methods reported here could be used to investigate large-scale temperature variations in the atmosphere. PMID:21946989

  11. Stability constant estimator user`s guide

    SciTech Connect

    Hay, B.P.; Castleton, K.J.; Rustad, J.R.

    1996-12-01

    The purpose of the Stability Constant Estimator (SCE) program is to estimate aqueous stability constants for 1:1 complexes of metal ions with ligands by using trends in existing stability constant data. Such estimates are useful to fill gaps in existing thermodynamic databases and to corroborate the accuracy of reported stability constant values.

  12. Quantification of the Effects of Ionic Strength, Viscosity, and Hydrophobicity on Protein–Ligand Binding Affinity

    PubMed Central

    2014-01-01

    In order to quantify the interactions between molecules of biological interest, the determination of the dissociation constant (Kd) is essential. Estimation of the binding affinity in this way is routinely performed in “favorable” conditions for macromolecules. Crucial data for ligand–protein binding elucidation is mainly derived from techniques (e.g., macromolecular crystallography) that require the addition of high concentration of salts and/or other additives. In this study we have evaluated the effect of temperature, ionic strength, viscosity, and hydrophobicity on the Kd of three previously characterized protein–ligand systems, based on variation in their binding sites, in order to provide insight into how these often overlooked unconventional circumstances impact binding affinity. Our conclusions are as follows: (1) increasing solvent viscosity in general is detrimental to ligand binding, (2) moderate increases in temperature have marginal effects on the dissociation constant, and (3) the degree of hydrophobicity of the ligand and the binding site determines the extent of the influence of cosolvents and salt concentration on ligand binding affinity. PMID:25147617

  13. ANALYSIS OF DRUG INTERACTIONS WITH HIGH DENSITY LIPOPROTEIN BY HIGH-PERFORMANCE AFFINITY CHROMATOGRAPHY

    PubMed Central

    Chen, Sike; Sobansky, Matthew R.; Hage, David S.

    2009-01-01

    Columns containing immobilized lipoproteins were prepared for the analysis of drug interactions with these particles by high-performance affinity chromatography. This approach was evaluated by using it to examine the binding of high density lipoprotein (HDL) to the drugs propranolol or verapamil. HDL was immobilized by the Schiff base method onto silica and gave HPLC columns with reproducible binding to propranolol over four to five days of continuous operation at pH 7.4. Frontal analysis experiments indicated that two types of interactions were occurring between R/S-propranolol and HDL at 37°C: saturable binding with an association equilibrium constant (Ka) of 1.1–1.9 × 105 M−1, and non-saturable binding with an overall affinity constant (n Ka) of 3.7–4.1 × 104 M−1. Similar results were found at 4 and 27°C. Verapamil also gave similar behavior, with a Ka of 6.0 × 104 M−1 at 37°C for the saturable sites and a n Ka value for the non-saturable sites of 2.5 × 104 M−1. These measured affinities gave good agreement with solution-phase values. The results indicated HPAC can be used to study drug interactions with HDL, providing information that should be valuable in obtaining a better description of how drugs are transported within the body. PMID:19833090

  14. Importin {beta}-type nuclear transport receptors have distinct binding affinities for Ran-GTP

    SciTech Connect

    Hahn, Silvia; Schlenstedt, Gabriel

    2011-03-18

    Highlights: {yields} Determination of binding properties of nuclear transport receptor/Ran-GTP complexes. {yields} Biosensor measurements provide constants for dissociation, on-rates, and off-rates. {yields} The affinity of receptors for Ran-GTP is widely divergent. {yields} Dissociation constants differ for three orders of magnitude. {yields} The cellular concentration of yeast Ran is not limiting. -- Abstract: Cargos destined to enter or leave the cell nucleus are typically transported by receptors of the importin {beta} family to pass the nuclear pore complex. The yeast Saccharomyces cerevisiae comprises 14 members of this protein family, which can be divided in importins and exportins. The Ran GTPase regulates the association and dissociation of receptors and cargos as well as the transport direction through the nuclear pore. All receptors bind to Ran exclusively in its GTP-bound state and this event is restricted to the nuclear compartment. We determined the Ran-GTP binding properties of all yeast transport receptors by biosensor measurements and observed that the affinity of importins for Ran-GTP differs significantly. The dissociation constants range from 230 pM to 270 nM, which is mostly based on a variability of the off-rate constants. The divergent affinity of importins for Ran-GTP suggests the existence of a novel mode of nucleocytoplasmic transport regulation. Furthermore, the cellular concentration of {beta}-receptors and of other Ran-binding proteins was determined. We found that the number of {beta}-receptors altogether about equals the amounts of yeast Ran, but Ran-GTP is not limiting in the nucleus. The implications of our results for nucleocytoplasmic transport mechanisms are discussed.

  15. Alpe Arami garnet peridotite from depth >300 km: revisited in 15 years (Invited)

    NASA Astrophysics Data System (ADS)

    Dobrzhinetskaya, L.; Lesher, C. E.; Bozhilov, K. N.; Green, H. W.

    2009-12-01

    In the mid-1990s we recognized that collisional orogenic belts with UHP metamorphic rocks of crustal affinities, might contain mantle peridotites uplifted from depths of >300km (Dobrzhinetsklaya et al., 1996). We proposed that ilmenite rods + chromite flakes in olivine are the result of exsolution, and that they imply high solubility of TiO2 in Ol at high P-T. The conclusion that the Alpe Arami peridotite massif originates from great depth remains controversial despite the subsequent discovery of Cpx inclusions in Grt containing exsolution lamellae of clinoenstatite displaying antiphase domains. The latter observation requires that the originally precipitated pyroxene had a high-pressure C2/c space group structure consistent with an origin from >8 GPa (~250 km) (Bozhilov et al., 1999). We used confocal laser scanning microscopy to obtain quantitative 3D measurements of Ilm abundance in Ol. We find that Ilm rods can reach >1 vol. % in Ol supporting our contention that Ilm rods exsolved from olivine at 9-12 GPa, e.g. >300 km (Bozhilov et al., 2003). Arguments that Ilm rods hosted by Ol are reaction products from the breakdown of Ti-clinohumite (Risold et al., 2003) are unconvincing given that Ti-clinohumite breakdown does not produce Ilm + chromite that are characteristic of Alpe Arami olivine. Likewise, we have confirmed the high solubility of Ti in olivine at high P-T conditions in multianvil experiments (Dobrzhinetskaya et al., 2000) - findings that are strengthened by the experiments of Tinker & Lesher (2001). Using Focused Ion Beam we prepared TEM foils of the later experiments and confirm that the concentration of TiO2 in Ol increases with pressure under nearly isothermal conditions. Two reactions are proposed to account for these observations. If Ti enters the octahedral site of olivine, either an oxide phase must be formed or a phase richer in SiO2 than olivine must be consumed, leading to reaction 1: 6MgSiO3 + 2FeTiO3 = 2Ti△SiO4 + 3Mg2SiO4 + Fe2SiO4 [1

  16. Ultrasonic velocity and elastic constants of Antrim oil shale

    SciTech Connect

    Wallace, W.D.; Tepley, N.; Thomas, R.L.

    1980-01-01

    Ultrasonic velocities have been measured in 30 core samples from well 201. Both longitudinal and shear wave velocities were measured across core diameters at thirty degree intervals around the circumference in 22 of the samples. No significant angular variation of ultrasonic velocity was found in any of these. Plots of the average velocities between 1166 feet and 1486 feet are presented. In the Antrim, which lies between 1179 feet and 1422 km/s and the average shear wave velocity is 2.60 km/s. Actual velocities in the Antrim vary by + - 6% from these averages. Just above and below the Antrim the measured velocities are somewhat greater than the average Antrim values. Mass densities have also been determined for these samples and combined with the velocity data to obtain elastic constants.

  17. Single amino acid exchange in bacteriophage HK620 tailspike protein results in thousand-fold increase of its oligosaccharide affinity.

    PubMed

    Broeker, Nina K; Gohlke, Ulrich; Müller, Jürgen J; Uetrecht, Charlotte; Heinemann, Udo; Seckler, Robert; Barbirz, Stefanie

    2013-01-01

    Bacteriophage HK620 recognizes and cleaves the O-antigen polysaccharide of Escherichia coli serogroup O18A1 with its tailspike protein (TSP). HK620TSP binds hexasaccharide fragments with low affinity, but single amino acid exchanges generated a set of high-affinity mutants with submicromolar dissociation constants. Isothermal titration calorimetry showed that only small amounts of heat were released upon complex formation via a large number of direct and solvent-mediated hydrogen bonds between carbohydrate and protein. At room temperature, association was both enthalpy- and entropy-driven emphasizing major solvent rearrangements upon complex formation. Crystal structure analysis showed identical protein and sugar conformers in the TSP complexes regardless of their hexasaccharide affinity. Only in one case, a TSP mutant bound a different hexasaccharide conformer. The extended sugar binding site could be dissected in two regions: first, a hydrophobic pocket at the reducing end with minor affinity contributions. Access to this site could be blocked by a single aspartate to asparagine exchange without major loss in hexasaccharide affinity. Second, a region where the specific exchange of glutamate for glutamine created a site for an additional water molecule. Side-chain rearrangements upon sugar binding led to desolvation and additional hydrogen bonding which define this region of the binding site as the high-affinity scaffold.

  18. Henry's law constants of some environmentally important aldehydes

    SciTech Connect

    Betterton, E.A.; Hoffmann, M.R.

    1988-12-01

    The Henry's law constants of seven aldehydes have been determined as a function of temperature by bubble-column and by head-space techniques. The compounds were chosen for their potential importance in the polluted troposphere and to allow structure-reactivity patterns to be investigated. The results (at 25/degree/C) are as follows (in units of M atm/sup /minus/1/): chloral, 3.44 /times/ 10/sup 5/; glyoxal, greater than or equal to3 /times/ 10/sup 5/; methylglyoxal, 3.71 /times/ 10/sup 3/; formaldehyde, 2.97 /times/ 10/sup 3/; benzaldehyde, 3.74 /times/ 10/sup 1/; hydroxyacetaldehyde, 4.14 /times/ 10/sup 4/; acetaldehyde, 1.14 /times/ 10/sup 1/. A plot of Taft's parameter, ..sigma..sigma*, vs log H* (the apparent Henry's law constant) gives a straight line with a slope of 1.72. H* for formaldehyde is anomalously high, as expected, but the extremely high value for hydroxyacetaldehyde was unexpected and may indicate that ..cap alpha..-hydroxy-substituted aldehydes could have an usually high affinity for the aqueous phase. The intrinsic Henry's law constants, H, corrected for hydration, do not show a clear structure-reactivity pattern for this series of aldehydes.

  19. Temperature Compensation in Methanosarcina barkeri by Modulation of Hydrogen and Acetate Affinity

    PubMed Central

    Westermann, Peter; Ahring, Birgitte K.; Mah, Robert A.

    1989-01-01

    The affinity of Methanosarcina barkeri 227 for acetate and hydrogen at different incubation temperatures was investigated. Increasing the temperature from 20 to 37°C resulted in a 4.5-fold increase in Km for acetate and a 4.8-fold increase for hydrogen. The corresponding increase in Vmax for acetate was 8.3-fold (5.4-fold for hydrogen). This response implied a decrease in the temperature coefficient (Q10) and hence a decrease in the temperature dependency as a function of decreasing substrate concentration. PMID:16347915

  20. The ion population between 1300 km and 230000 km in the coma of comet P/Halley

    NASA Technical Reports Server (NTRS)

    Altwegg, K.; Balsiger, H.; Geiss, J.; Goldstein, R.; Ip, W. -H.; Meier, A.; Neugebauer, M.; Rosenbauer, H.; Shelley, E.

    1993-01-01

    During the encounter of the spacecraft Giotto with Comet Halley the two sensors of the ion mass spectrometer (IMS), high energy range spectrometer (HERS) and high intensity spectrometer (HIS), measured the mass and the three-dimensional velocity distributions of cometary ions. HIS looked mainly at the cold, slow part of the distribution close to the nucleus, HERS at the more energetic pick-up ions further out. After a thorough recalibration of the HIS flight spare unit and an extensive data analysis we present here continuous ion density-, composition-, velocity-, and temperature profiles for the water group ion (mass range 16-19 amu/e) along Giotto's inbound trajectory from 230,000 to 1300 km from the comet nucleus. The two sensors are in very good agreement in the region where their measurements overlap thus giving an excellent data base for the discussion of theoretical comet models. The most prominent feature where models and observations disagree is the so called pile up region between 8000 and 15,000 km from the nucleus.

  1. Lipid A-based affinity biosensor for screening anti-sepsis components from herbs.

    PubMed

    Yao, Jie; Chen, Yiguo; Wang, Ning; Jiang, Dongneng; Zheng, Jiang

    2014-01-01

    LPS (lipopolysaccharide), an outer membrane component of Gram-negative bacteria, plays an important role in the pathogenesis of sepsis and lipid A is known to be essential for its toxicity. Therefore it could be an effective measure to prevent sepsis by neutralizing or destroying LPS. Numerous studies have indicated that many traditional Chinese medicines are natural antagonists of LPS in vitro and in vivo. The goal of this study is to develop a rapid method to screen anti-sepsis components from Chinese herbs by use of a direct lipid A-based affinity biosensor technology based on a resonant mirror. The detergent OG (n-octyl β-D-glucopyranoside) was immobilized on a planar non-derivatized cuvette which provided an alternative surface to bind the terminal hydrophilic group of lipid A. A total of 78 herbs were screened based on the affinity biosensor with a target of lipid A. The aqueous extract of PSA (Paeonia suffruticosa Andr) was found to possess the highest capability of binding lipid A. Therefore an aqueous extraction from this plant was investigated further by our affinity biosensor, polyamide chromatography and IEC-HPLC. Finally, we obtained a component (PSA-I-3) from Paeonia suffruticosa Andr that was evaluated with the affinity biosensor. We also studied the biological activities of PSA-I-3 against sepsis in vitro and in vivo to further confirm the component we screened with the biosensor. In vitro, we found that PSA-I-3 could decrease TNFα (tumour necrosis factor α) release from RAW264.7 cells induced by LPS in a dose-dependent manner. In vivo, it increased remarkably the survival of KM (KunMing) mice by challenging both lethal-dose LPS and heat-killed Escherichia coli compared with control groups. Our results suggest that the constructed affinity biosensor can successfully screen the anti-sepsis component from Chinese herbs. PMID:24654965

  2. Wintertime density perturbations near 50 km in relation to latitude

    NASA Technical Reports Server (NTRS)

    Quiroz, R. S.

    1977-01-01

    Standard and reference atmospheres which depict the horizontal distribution of air density in the stratosphere and mesosphere are not realistic in that they do not provide information on the large departures from standard that may occur during a given month, nor on the time- and space-scales of atmospheric perturbations responsible for these departures. In the present paper, it is shown how this information can be obtained from a special analysis of satellite radiance measurements. Plots of the mean zonal radiance, obtained with the VTPR instrument, and the corresponding 50-km density show not only the expected strong poleward gradient of density, but also a strong density surge from late December to early January, affecting all latitudes.

  3. Transport System for Delivery Tourists At Altitude 140 km

    NASA Technical Reports Server (NTRS)

    Bolonkin, Alexander

    2002-01-01

    The author offers a new method and installation for flight in space. This method uses the centrifugal force of a rotating circular cable that provides a means for the launch of a payload into outer space, to keep the fixed space stations at high altitudes (up to 200 km). The method may also be useful for landing to space bodies, for launching of the space ships (crafts), and for moving and accelerating other artificial apparatuses. The offered installation may be used as a propulsion system for space ships and/or probes. This system uses the material of any space body (i.e. stones) for acceleration and change of the space vehicle trajectory. The suggested system may be also used as a high capacity energy accumulator.

  4. Estimating worldwide solar radiation resources on a 40km grid

    SciTech Connect

    Maxwell, E.L.; George, R.L.; Brady, E.H.

    1996-11-01

    During 1995, the National Renewable Energy Laboratory (NREL), initiated the Data Grid Task under the auspices of DOE`s Resource Assessment Program. A data grid is a framework of uniformly spaced locations (grid points) for which data are available. Estimates of monthly averages of direct normal, diffuse horizontal, and global horizontal daily-total solar radiation energy (kWh/m{sup 2}) are being made for each point on a grid covering the US, Mexico, the Caribbean, and southern Canada. The grid points are separated by approximately 40 km. Using interpolation methods, the digital data grid can be used to estimate solar resources at any location. The most encouraging result to date has been the location of sources providing worldwide data for most of the input parameters required for modeling daily total solar radiation. This is a multiyear task expected to continue through the rest of this century.

  5. Readout and data acquisition for KM3NeT

    NASA Astrophysics Data System (ADS)

    Belias, Anastasios; Manolopoulos, Konstantinos

    2013-05-01

    In the KM3NeT neutrino telescope design the readout concept is based on a point-to-point network connecting tenthousands of optical modules in the deep sea through a photonic network with the shore station. The time-over-threshold data from each Photo Multiplier Tube (PMT) of each optical module will be send to shore over fibres using dedicated wavelengths. Nanosecond timing accuracy will be schieved using a clock signal embedded in the data stream and measuring the roundtrip time from the shore to each optical module individually. The DAQ software architecture based on the Internet Communications Engine (ICE) will provide a common and uniform software framework for the control of each optical module and the data acquisition of the whole neutrino telescope.

  6. Latest European coelacanth shows Gondwanan affinities.

    PubMed

    Cavin, Lionel; Forey, Peter L; Buffetaut, Eric; Tong, Haiyan

    2005-06-22

    The last European fossil occurrence of a coelacanth is from the Mid-Cretaceous of the English Chalk (Turonian, 90 million years ago). Here, we report the discovery of a coelacanth from Late Cretaceous non-marine rocks in southern France. It consists of a left angular bone showing structures that imply close phylogenetic affinities with some extinct Mawsoniidae. The closest relatives are otherwise known from Cretaceous continental deposits of southern continents and suggest that the dispersal of freshwater organisms from Africa to Europe occurred in the Late Cretaceous.

  7. On the structure of self-affine convex bodies

    SciTech Connect

    Voynov, A S

    2013-08-31

    We study the structure of convex bodies in R{sup d} that can be represented as a union of their affine images with no common interior points. Such bodies are called self-affine. Vallet's conjecture on the structure of self-affine bodies was proved for d = 2 by Richter in 2011. In the present paper we disprove the conjecture for all d≥3 and derive a detailed description of self-affine bodies in R{sup 3}. Also we consider the relation between properties of self-affine bodies and functional equations with a contraction of an argument. Bibliography: 10 titles.

  8. Measuring an antibody affinity distribution molecule by molecule.

    PubMed

    Temirov, Jamshid P; Bradbury, Andrew R M; Werner, James H

    2008-11-15

    Single molecule fluorescence microscopy was used to observe the binding and unbinding of hapten decorated quantum dots to individual surface immobilized antibodies. The fluorescence time history from an individual antibody site can be used to calculate its binding affinity. While quantum dot blinking occurs during these measurements, we describe a simple empirical method to correct the apparent/observed affinity to account for the blinking contribution. The combination of many single molecule affinity measurements from different antibodies yields not only the average affinity, it directly measures the full shape and character of the surface affinity distribution function.

  9. Measuring an antibody affinity distribution molecule by molecule

    SciTech Connect

    Bradbury, Andrew M; Werner, James H; Temirov, Jamshid

    2008-01-01

    Single molecule fluorescence mIcroscopy was used to observe the binding and unbinding of hapten decorated quantum dots with individual surface immobilized antibodies. The fluorescence time history from an individual antibody site can be used to calculate its binding affinity. While quantum dot blinking occurs during these measurements, we describe a simple empirical method to correct the apparent/observed affinity to account for the blinking contribution. The combination of many single molecule affinity measurements from different antibodies yields not only the average affinity, it directly measures the full shape and character of the surface affinity distribution function.

  10. Metal-affinity separations: A new dimension in protein processing

    SciTech Connect

    Arnold, F.H. )

    1991-02-01

    Rapid growth in the preparative and high-resolution analytical applications of metal-affinity chromatography demonstrate the appeal of metal recognition as a basis for protein separations. Stable, inexpensive chelated metals effectively mimic biospecific interactions, providing selective ligands for protein binding. This article reviews recent progress in understanding the mechanisms of metal-protein recognition that underlie metal-affinity separations. Also discussed are schemes for integrating metal-affinity purifications into the expression and bioprocessing of recombinant proteins. Promising future developments include new metal-affinity processes for analytical and preparative-scale separations and a range of techniques for enhancing the selectivity of metal-affinity separations.

  11. Changes in single skinfold thickness in 100 km ultramarathoners

    PubMed Central

    Knechtle, Beat; Baumgartner, Sabrina; Knechtle, Patrizia; Rüst, Christoph Alexander; Rosemann, Thomas; Bescós, Raúl

    2012-01-01

    Background Changes in single skinfold thickness and body fat have been investigated in ultraswimmers and ultracyclists, but not in ultrarunners. The present study investigated the changes in single skinfold thickness during a 100 km ultramarathon. Methods Firstly, we investigated associations between prerace preparation and prerace body composition and, secondly, changes in single skinfold thickness during a 100 km ultramarathon in 219 male ultramarathoners. Changes in fat mass and skeletal muscle were estimated using anthropometric methods. Results Kilometers run weekly prerace and running speed during training were negatively associated with all skinfold thicknesses (P < 0.05) except for the front thigh skinfold. During the race, skinfold thickness at the pectoral (−0.1%), suprailiac (−1.8%), and calf (−0.8%) sites decreased (P < 0.05). The subjects lost 1.9 ± 1.4 kg of body mass (P < 0.001), 0.7 ± 1.0 kg of estimated skeletal muscle mass (P < 0.001), and 0.2 ± 1.3 kg of estimated fat mass (P < 0.05). The decrease in body mass was positively related to the decrease in both estimated skeletal muscle mass (r = 0.21, P = 0.0017) and estimated fat mass (r = 0.41, P < 0.0001). Conclusion Firstly, prerace fat mass and prerace skinfold thickness were associated with both volume and speed in running training. Secondly, during the ultramarathon, skinfold thickness decreased at the pectoral, suprailiac, and calf sites, but not at the thigh site. Percent decreases in skinfold thickness for ultrarunners was lower than the percent decreases in skinfold thickness reported for ultraswimmers and ultracyclists. PMID:24198597

  12. Constraining density and velocity jumps across the 410 km discontinuity

    NASA Astrophysics Data System (ADS)

    Saki, Morvarid; Thomas, Christine; Cobden, Laura; Abreu, Rafael

    2016-04-01

    We investigate the velocity and density structure of the olivine-to-wadsleyite transition using polarities of precursor arrivals to PP seismic waves that reflect off the 410 km discontinuity beneath the Northern Atlantic. Numerous source-receiver combinations have been used in order to collect a dataset of reflection points beneath our investigation area. We analyzed over 1700 seismograms from Mw > 5.8 using array seismology methods to enhance the signal to noise ratio. For each event the polarity of the PP phase is compared to polarity of the precursor signal and we find several events where the polarity of the precursors are opposite to that of PP. There does not seem to be any dependency of the observed polarities on the propagation direction of the seismic waves but interestingly there seems to be a dependency on the distance between source and receiver. The events with epicentral distances greater than 119 degrees mostly show opposite polarities, while for those with smaller epicentral distances the same polarity of the main phase and precursor signal is dominant. Using Zeoppritz equations, we analyzed more than 64 million combinations of density, compressional and shear wave velocities for both layers, above and below the 410 km discontinuity in order to find the best combination of those parameters that can explain the observations. The results are indicating combinations of density, P and S wave velocity exhibiting a smaller contrast compared to those from the pyrolite model (the density jump, however is still positive to provide physically meaningful results). The calculated reductions in both compressional and shear wave velocities go up to 13% but mostly fall within the range of less than 7- 8%. We interpret this reduction in elastic properties and seismic velocity of minerals as the effect of a higher than normal content of water of wadsleyite in this region, while we can exclude a reduction in iron.

  13. Asympotics with positive cosmological constant

    NASA Astrophysics Data System (ADS)

    Bonga, Beatrice; Ashtekar, Abhay; Kesavan, Aruna

    2014-03-01

    Since observations to date imply that our universe has a positive cosmological constant, one needs an extension of the theory of isolated systems and gravitational radiation in full general relativity from the asymptotically flat to asymptotically de Sitter space-times. In current definitions, one mimics the boundary conditions used in asymptotically AdS context to conclude that the asymptotic symmetry group is the de Sitter group. However, these conditions severely restricts radiation and in fact rules out non-zero flux of energy, momentum and angular momentum carried by gravitational waves. Therefore, these formulations of asymptotically de Sitter space-times are uninteresting beyond non-radiative spacetimes. The situation is compared and contrasted with conserved charges and fluxes at null infinity in asymptotically flat space-times.

  14. Henry's law constants of polyols

    NASA Astrophysics Data System (ADS)

    Compernolle, S.; Müller, J.-F.

    2014-12-01

    Henry's law constants (HLC) are derived for several polyols bearing between 2 and 6 hydroxyl groups, based on literature data for water activity, vapour pressure and/or solubility. While deriving HLC and depending on the case, also infinite dilution activity coefficients (IDACs), solid state vapour pressures or activity coefficient ratios are obtained as intermediate results. An error analysis on the intermediate quantities and the obtained HLC is included. For most compounds, these are the first values reported, while others compare favourably with literature data in most cases. Using these values and those from a previous work (Compernolle and Müller, 2014), an assessment is made on the partitioning of polyols, diacids and hydroxy acids to droplet and aqueous aerosol.

  15. Philicities, Fugalities, and Equilibrium Constants.

    PubMed

    Mayr, Herbert; Ofial, Armin R

    2016-05-17

    The mechanistic model of Organic Chemistry is based on relationships between rate and equilibrium constants. Thus, strong bases are generally considered to be good nucleophiles and poor nucleofuges. Exceptions to this rule have long been known, and the ability of iodide ions to catalyze nucleophilic substitutions, because they are good nucleophiles as well as good nucleofuges, is just a prominent example for exceptions from the general rule. In a reaction series, the Leffler-Hammond parameter α = δΔG(⧧)/δΔG° describes the fraction of the change in the Gibbs energy of reaction, which is reflected in the change of the Gibbs energy of activation. It has long been considered as a measure for the position of the transition state; thus, an α value close to 0 was associated with an early transition state, while an α value close to 1 was considered to be indicative of a late transition state. Bordwell's observation in 1969 that substituent variation in phenylnitromethanes has a larger effect on the rates of deprotonation than on the corresponding equilibrium constants (nitroalkane anomaly) triggered the breakdown of this interpretation. In the past, most systematic investigations of the relationships between rates and equilibria of organic reactions have dealt with proton transfer reactions, because only for few other reaction series complementary kinetic and thermodynamic data have been available. In this Account we report on a more general investigation of the relationships between Lewis basicities, nucleophilicities, and nucleofugalities as well as between Lewis acidities, electrophilicities, and electrofugalities. Definitions of these terms are summarized, and it is suggested to replace the hybrid terms "kinetic basicity" and "kinetic acidity" by "protophilicity" and "protofugality", respectively; in this way, the terms "acidity" and "basicity" are exclusively assigned to thermodynamic properties, while "philicity" and "fugality" refer to kinetics

  16. Avoiding degenerate coframes in an affine gauge approach to quantum gravity

    SciTech Connect

    Mielke, E.W.; McCrea, J.D.; Ne`eman, Y.; Hehl, F.W.

    1993-04-01

    This report discusses the following concepts on quantum gravity: The affine gauge approach; affine gauge transformations versus active differomorphisms; affine gauge approach to quantum gravity with topology change.

  17. Vertical profiles of H2O, H2SO4, and sulfuric acid concentration at 45-75 km on Venus

    NASA Astrophysics Data System (ADS)

    Krasnopolsky, Vladimir A.

    2015-05-01

    A method developed by Krasnopolsky and Pollack (Krasnopolsky, V.A., Pollack, J.B. [1994]. Icarus 109, 58-78) to model vertical profiles of H2O and H2SO4 vapors and sulfuric acid concentration in the Venus cloud layer has been updated with improved thermodynamic parameters for H2O and H2SO4 and reduced photochemical production of sulfuric acid. The model is applied to the global-mean conditions and those at the low latitudes and at 60°. Variations in eddy diffusion near the lower cloud boundary are used to simulate variability in the cloud properties and abundances of H2O and H2SO4. The best version of the model for the global-mean condition results in a lower cloud boundary (LCB) at 47.5 km, H2SO4 peak abundance of 7.5 ppm at the LCB, and H2O mixing ratios of 7 ppm at 62 km and 3.5 ppm above 67 km. The model for low latitudes gives LCB at 48.5 km, the H2SO4 peak of 5 ppm, H2O of 8.5 ppm at 62 km and 3 ppm above 67 km. The model for 60° shows LCB at 46 km, the H2SO4 peak of 8.5 ppm, H2O of 9 ppm at 62 km and 4.5 ppm above 67 km. The calculated variability is induced by the proper changes in the production of sulfuric acid (by factors of 1.2 and 0.7 for the low latitudes and 60°, respectively) and reduction of eddy diffusion near 45 km relative to the value at 54 km by factors of 1.1, 3, and 4.5 for the low and middle (global-mean) latitudes and 60°, respectively. Concentration of sulfuric acid at the low and middle latitudes varies from ∼98% near 50 km to ∼80% at 60 km and then is almost constant at 79% at 70 km. Concentration at 60° is 98% at 50 km, 73% at 63 km, and 81% at 70 km. There is a reasonable agreement between the model results and observations except for the sulfuric acid concentration in the lower clouds. Variations of eddy diffusion in the lower cloud layer simulate variations in atmospheric dynamics and may induce strong variations in water vapor near the cloud tops. Variations in temperature may affect abundances of the H2O and H2SO4 vapors

  18. A nuclear data approach for the Hubble constant measurements

    SciTech Connect

    Pritychenko, B.

    2015-06-09

    An extraordinary number of Hubble constant measurements challenges physicists with selection of the best numerical value. The standard U.S. Nuclear Data Program (USNDP) codes and procedures have been applied to resolve this issue. The nuclear data approach has produced the most probable or recommended Hubble constant value of 67.00(770) (km/sec)/Mpc. This recommended value is based on the last 25 years of experimental research and includes contributions from different types of measurements. The present result implies (14.6±1.7) x 109 years as a rough estimate for the age of the Universe. The complete list of recommended results is given and possible implications are discussed.

  19. Probing the affinity of polyanions for acidic fibroblast growth factor by unfolding kinetics.

    PubMed

    Mach, H; Middaugh, C R

    1994-02-15

    The relationship between ligand-protein affinity and the extent of protein stabilization induced by such interactions has been investigated using the binding of polyanions to acidic fibroblast growth factor (aFGF) as a model system. It was found that the experimentally observed unfolding rate constant of aFGF consists of two components: one equal to the unfolding rate constant of the aFGF-ligand complex and the other the product of the unfolding rate constant of free aFGF, the aFGF-ligand dissociation constant (Kd), and the reciprocal of the molar ligand concentration. This reflects the presence of two possible unfolding pathways: at high ligand excess dissociation is suppressed and slow unfolding of the aFGF-ligand complex itself prevails. When lower concentrations of ligand allows equilibrium-driven appearance of free aFGF, a more rapid unfolding of dissociated protein predominates. Existence of a steady state of dissociated aFGF undergoing unfolding was demonstrated by computer simulation of the elementary events, using experimentally determined rate constants. The potential applications of such simulations are outlined. An equation allowing estimation of dissociation constants from equilibrium denaturation curves obtained in the presence of a varying amount of ligand is also proposed. In addition, determination of initial unfolding rates in the presence of excess protein permits the the stoichiometry of the interaction to be determined.

  20. Determination of thermodynamic values of acidic dissociation constants and complexation constants of profens and their utilization for optimization of separation conditions by Simul 5 Complex.

    PubMed

    Riesová, Martina; Svobodová, Jana; Ušelová, Kateřina; Tošner, Zdeněk; Zusková, Iva; Gaš, Bohuslav

    2014-10-17

    In this paper we determine acid dissociation constants, limiting ionic mobilities, complexation constants with β-cyclodextrin or heptakis(2,3,6-tri-O-methyl)-β-cyclodextrin, and mobilities of resulting complexes of profens, using capillary zone electrophoresis and affinity capillary electrophoresis. Complexation parameters are determined for both neutral and fully charged forms of profens and further corrected for actual ionic strength and variable viscosity in order to obtain thermodynamic values of complexation constants. The accuracy of obtained complexation parameters is verified by multidimensional nonlinear regression of affinity capillary electrophoretic data, which provides the acid dissociation and complexation parameters within one set of measurements, and by NMR technique. A good agreement among all discussed methods was obtained. Determined complexation parameters were used as input parameters for simulations of electrophoretic separation of profens by Simul 5 Complex. An excellent agreement of experimental and simulated results was achieved in terms of positions, shapes, and amplitudes of analyte peaks, confirming the applicability of Simul 5 Complex to complex systems, and accuracy of obtained physical-chemical constants. Simultaneously, we were able to demonstrate the influence of electromigration dispersion on the separation efficiency, which is not possible using the common theoretical approaches, and predict the electromigration order reversals of profen peaks. We have shown that determined acid dissociation and complexation parameters in combination with tool Simul 5 Complex software can be used for optimization of separation conditions in capillary electrophoresis.

  1. Practical strategies for the evaluation of high-affinity protein/nucleic acid interactions.

    PubMed

    Altschuler, Sarah E; Lewis, Karen A; Wuttke, Deborah S

    2013-01-01

    The quantitative evaluation of binding interactions between proteins and nucleic acids is highly sensitive to a variety of experimental conditions. Optimization of these conditions is critical for obtaining high quality, reproducible data, particularly in the context of very high affinity interactions. Here, we discuss the practical considerations involved in optimizing the apparent binding constant of an interaction as measured by two common quantitative assays, electrophoretic mobility shift assay and double-filter binding when measuring extremely tight protein/nucleic acid interactions with sub-nanomolar binding affinities. We include specific examples from two telomere end-binding protein systems, Schizo -saccharomyces pombe Pot1 and Saccharomyces cerevisiae Cdc13, to demonstrate potential experimental pitfalls and some useful strategies for optimization.

  2. Practical strategies for the evaluation of high-affinity protein/nucleic acid interactions

    PubMed Central

    Altschuler, Sarah E.; Lewis, Karen A.; Wuttke, Deborah S.

    2014-01-01

    The quantitative evaluation of binding interactions between proteins and nucleic acids is highly sensitive to a variety of experimental conditions. Optimization of these conditions is critical for obtaining high quality, reproducible data, particularly in the context of very high affinity interactions. Here, we discuss the practical considerations involved in optimizing the apparent binding constant of an interaction as measured by two common quantitative assays, electrophoretic mobility shift assay and double-filter binding when measuring extremely tight protein/nucleic acid interactions with sub-nanomolar binding affinities. We include specific examples from two telomere end-binding protein systems, Schizo -saccharomyces pombe Pot1 and Saccharomyces cerevisiae Cdc13, to demonstrate potential experimental pitfalls and some useful strategies for optimization. PMID:25197549

  3. Relationship of nonreturn rates of dairy bulls to binding affinity of heparin to sperm

    SciTech Connect

    Marks, J.L.; Ax, R.L.

    1985-08-01

    The binding of the glycosaminoglycan (3H) heparin to bull spermatozoa was compared with nonreturn rates of dairy bulls. Semen samples from five bulls above and five below an average 71% nonreturn rate were used. Samples consisted of first and second ejaculates on a single day collected 1 d/wk for up to 5 consecutive wk. Saturation binding assays using (TH) heparin were performed to quantitate the binding characteristics of each sample. Scatchard plot analyses indicated a significant difference in the binding affinity for (TH) heparin between bulls of high and low fertility. Dissociation constants were 69.0 and 119.3 pmol for bulls of high and low fertility, respectively. In contrast, the number of binding sites for (TH) heparin did not differ significantly among bulls. Differences in binding affinity of (TH) heparin to bull sperm might be used to predict relative fertility of dairy bulls.

  4. Structure-based Design of Peptides with High Affinity and Specificity to HER2 Positive Tumors

    PubMed Central

    Geng, Lingling; Wang, Zihua; Yang, Xiaoliang; Li, Dan; Lian, Wenxi; Xiang, Zhichu; Wang, Weizhi; Bu, Xiangli; Lai, Wenjia; Hu, Zhiyuan; Fang, Qiaojun

    2015-01-01

    To identify peptides with high affinity and specificity against human epidermal growth factor receptor 2 (HER2), a series of peptides were designed based on the structure of HER2 and its Z(HER2:342) affibody. By using a combination protocol of molecular dynamics modeling, MM/GBSA binding free energy calculations, and binding free energy decomposition analysis, two novel peptides with 27 residues, pep27 and pep27-24M, were successfully obtained. Immunocytochemistry and flow cytometry analysis verified that both peptides can specifically bind to the extracellular domain of HER2 protein at cellular level. The Surface Plasmon Resonance imaging (SPRi) analysis showed that dissociation constants (KD) of these two peptides were around 300 nmol/L. Furthermore, fluorescence imaging of peptides against nude mice xenografted with SKBR3 cells indicated that both peptides have strong affinity and high specificity to HER2 positive tumors. PMID:26284145

  5. Preorganized Peptide Scaffolds as Mimics of Phosphorylated Proteins Binding Sites with a High Affinity for Uranyl.

    PubMed

    Starck, Matthieu; Sisommay, Nathalie; Laporte, Fanny A; Oros, Stéphane; Lebrun, Colette; Delangle, Pascale

    2015-12-01

    Cyclic peptides with two phosphoserines and two glutamic acids were developed to mimic high-affinity binding sites for uranyl found in proteins such as osteopontin, which is believed to be a privileged target of this ion in vivo. These peptides adopt a β-sheet structure that allows the coordination of the latter amino acid side chains in the equatorial plane of the dioxo uranyl cation. Complementary spectroscopic and analytical methods revealed that these cyclic peptides are efficient uranyl chelating peptides with a large contribution from the phosphorylated residues. The conditional affinity constants were measured by following fluorescence tryptophan quenching and are larger than 10(10) at physiological pH. These compounds are therefore promising models for understanding uranyl chelation by proteins, which is relevant to this actinide ion toxicity. PMID:26583259

  6. Phosphatidylserine Reversibly Binds Cu2+ with Extremely High Affinity

    PubMed Central

    Monson, Christopher F.; Cong, Xiao; Robison, Aaron; Pace, Hudson P.; Liu, Chunming; Poyton, Matthew F.; Cremer, Paul S.

    2012-01-01

    Phosphatidylserine (PS) embedded within supported lipid bilayers (SLBs) was found to bind Cu2+ from solution with extraordinarily high affinity. In fact, the equilibrium dissociation constant was in the femtomolar range. The resulting complex formed in a 1:2 Cu2+ to PS ratio and quenches a broad spectrum of lipid-bound fluorophores in a reversible and pH-dependent fashion. At acidic pH values, the fluorophores were almost completely unquenched, while at basic pH values significant quenching (85–90%) was observed. The pH at which the transition occurred was dependent on the PS concentration and ranged from approximately pH 5 to 8. The quenching kinetics was slow at low Cu2+ concentrations and basic values pH (up to several hours), while the unquenching reaction was orders of magnitude more rapid upon lowering the pH. This was consistent with diffusion limited complex formation at basic pH, but rapid dissociation under acidic conditions. The tight binding of Cu2+ to PS may have physiological consequences under certain circumstances. PMID:22548290

  7. Limited proteolysis for assaying ligand binding affinities of nuclear receptors.

    PubMed

    Benkoussa, M; Nominé, B; Mouchon, A; Lefebvre, B; Bernardon, J M; Formstecher, P; Lefebvre, P

    1997-01-01

    The binding of natural or synthetic ligands to nuclear receptors is the triggering event leading to gene transcription activation or repression. Ligand binding to the ligand binding domain of these receptors induces conformational changes that are evidenced by an increased resistance of this domain to proteases. In vitro labeled receptors were incubated with various synthetic or natural agonists or antagonists and submitted to trypsin digestion. Proteolysis products were separated by SDS-PAGE and quantified. The amount of trypsin-resistant fragments was proportional to receptor occupancy by the ligand, and allowed the determination of dissociation constants (kDa). Using the wild-type or mutated human retinoic acid receptor alpha as a model, kDa values determined by classical competition binding assays using tritiated ligands are in agreement with those measured by the proteolytic assay. This method was successfully extended to human retinoic X receptor alpha, glucocorticoid receptor, and progesterone receptor, thus providing a basis for a new, faster assay to determine simultaneously the affinity and conformation of receptors when bound to a given ligand.

  8. Fatigue damage prognosis using affine arithmetic

    NASA Astrophysics Data System (ADS)

    Gbaguidi, Audrey; Kim, Daewon

    2014-02-01

    Among the essential steps to be taken in structural health monitoring systems, damage prognosis would be the field that is least investigated due to the complexity of the uncertainties. This paper presents the possibility of using Affine Arithmetic for uncertainty propagation of crack damage in damage prognosis. The structures examined are thin rectangular plates made of titanium alloys with central mode I cracks and a composite plate with an internal delamination caused by mixed mode I and II fracture modes, under a harmonic uniaxial loading condition. The model-based method for crack growth rates are considered using the Paris Erdogan law model for the isotropic plates and the delamination growth law model proposed by Kardomateas for the composite plate. The parameters for both models are randomly taken and their uncertainties are considered as defined by an interval instead of a probability distribution. A Monte Carlo method is also applied to check whether Affine Arithmetic (AA) leads to tight bounds on the lifetime of the structure.

  9. Exploring Fluorous Affinity by Liquid Chromatography.

    PubMed

    Catani, Martina; Guzzinati, Roberta; Marchetti, Nicola; Pasti, Luisa; Cavazzini, Alberto

    2015-07-01

    Terms such as "fluorous affinity" and "fluorophilicity" have been used to describe the unique partition and sorption properties often exhibited by highly fluorinated organic compounds, that is molecules rich in sp(3) carbon-fluorine bonds. In this work, we made use of a highly fluorinated stationary phase and a series of benzene derivatives to study the effect of one single perfluorinated carbon on the chromatographic behavior and adsorption properties of molecules. For this purpose, the adsorption equilibria of α,α,α-trifluorotoluene, toluene, and other alkylbenzenes have been studied by means of nonlinear chromatography in a variety of acetonitrile/water eluents. Our results reveal that one single perfluorinated carbon is already enough to induce a drastic change in the adsorption properties of molecules on the perfluorinated stationary phase. In particular, it has been found that adsorption is monolayer if the perfluoroalkyl carbon is present but that, when this unit is missing, molecules arrange as multilayer stack structures. These findings can contribute to the understanding of molecular mechanisms of fluorous affinity. PMID:26047527

  10. Quantification of hydrophobic interaction affinity of colloids

    NASA Astrophysics Data System (ADS)

    Saini, G.; Nasholm, N.; Wood, B. D.

    2009-12-01

    Colloids play an important role in a wide variety of disciplines, including water and wastewater treatment, subsurface transport of metals and organic contaminants, migration of fines in oil reservoirs, biocolloid (virus and bacteria) transport in subsurface, and are integral to laboratory transport studies. Although the role of hydrophobicity in adhesion and transport of colloids, particularly bacteria, is well known; there is scarcity of literature regarding hydrophobicity measurement of non-bacterial colloids and other micron-sized particles. Here we detail an experimental approach based on differential partitioning of colloids between two liquid phases (hydrocarbon and buffer) as a measure of the hydrophobic interaction affinity of colloids. This assay, known as Microbial adhesion to hydrocarbons or MATH, is frequently used in microbiology and bacteriology for quantifying the hydrophobicity of microbes. Monodispersed colloids and particles, with sizes ranging from 1 micron to 33 micron, were used for the experiments. A range of hydrophobicity values were observed for different particles. The hydrophobicity results are also verified against water contact angle measurements of these particles. This liquid-liquid partitioning assay is quick, easy-to-perform and requires minimal instrumentation. Estimation of the hydrophobic interaction affinity of colloids would lead to a better understanding of their adhesion to different surfaces and subsequent transport in porous media.

  11. Evaluation of the 7-km GEOS-5 Nature Run

    NASA Technical Reports Server (NTRS)

    Gelaro, Ronald; Putman, William M.; Pawson, Steven; Draper, Clara; Molod, Andrea; Norris, Peter M.; Ott, Lesley; Prive, Nikki; Reale, Oreste; Achuthavarier, Deepthi; Bosilovich, Michael; Buchard, Virginie; Chao, Winston; Coy, Lawrence; Cullather, Richard; da Silva, Arlindo; Darmenov, Anton; Koster, Randal; McCarty, Will; Schubert, Siegfried

    2015-01-01

    This report documents an evaluation by the Global Modeling and Assimilation Office (GMAO) of a two-year 7-km-resolution non-hydrostatic global mesoscale simulation produced with the Goddard Earth Observing System (GEOS-5) atmospheric general circulation model. The simulation was produced as a Nature Run for conducting observing system simulation experiments (OSSEs). Generation of the GEOS-5 Nature Run (G5NR) was motivated in part by the desire of the OSSE community for an improved high-resolution sequel to an existing Nature Run produced by the European Centre for Medium-Range Weather Forecasts (ECMWF), which has served the community for several years. The intended use of the G5NR in this context is for generating simulated observations to test proposed observing system designs regarding new instruments and their deployments. Because NASA's interest in OSSEs extends beyond traditional weather forecasting applications, the G5NR includes, in addition to standard meteorological components, a suite of aerosol types and several trace gas concentrations, with emissions downscaled to 10 km using ancillary information such as power plant location, population density and night-light information. The evaluation exercise described here involved more than twenty-five GMAO scientists investigating various aspects of the G5NR performance, including time mean temperature and wind fields, energy spectra, precipitation and the hydrological cycle, the representation of waves, tropical cyclones and midlatitude storms, land and ocean surface characteristics, the representation and forcing effects of clouds and radiation, dynamics of the stratosphere and mesosphere, and the representation of aerosols and trace gases. Comparisons are made with observational data sets when possible, as well as with reanalyses and other long model simulations. The evaluation is broad in scope, as it is meant to assess the overall realism of basic aspects of the G5NR deemed relevant to the conduct of OSSEs

  12. Nucleic acid binding affinity of fd gene 5 protein in the cooperative binding mode.

    PubMed

    Bobst, A M; Ireland, J C; Bobst, E V

    1984-02-25

    A sensitive ESR method which allows a direct quantitative determination of nucleic acid binding affinities of proteins under physiologically relevant conditions has been applied to the gene 5 protein of bacteriophage fd. This was achieved with two spin-labeled nucleic acids, (ldT, dT)n and (lA,A)n, which served as macro-molecular spin probes in ESR competition experiments. With the two different macromolecular spin probes, it was possible to determine the relative apparent affinity constants, Kapp, over a large affinity domain. In 20 mM Tris X HCl (pH 8.1), 1 mM sodium EDTA, 0.1 mM dithiothreitol, 10% (w/v) glycerol, 0.05% Triton, and 125 mM NaCl, the following affinity relationship was observed: K(dT)napp = 10(3) KfdDNAapp = 2 X 10(4) K(A)napp = 6.6 X 10(4) KrRNAapp = 1.5 X 10(5) KR17RNAapp. Increasing the [NaCl] from 125 to 200 mM caused considerably less tight binding of gene 5 protein to (lA,A)n, and a typical cooperative binding isotherm was observed, whereas at the lower [NaCl] used for the competition experiments, the binding was essentially stoichiometric. A computer fit of the experimental titration data at 200 mM NaCl gave an intrinsic binding constant, Kint, of 1300 M-1 and a cooperativity factor, omega, of 60 (Kint omega = Kapp) for (lA,A)n.

  13. Is There a Cosmological Constant?

    NASA Technical Reports Server (NTRS)

    Kochanek, Christopher; Oliversen, Ronald J. (Technical Monitor)

    2002-01-01

    The grant contributed to the publication of 18 refereed papers and 5 conference proceedings. The primary uses of the funding have been for page charges, travel for invited talks related to the grant research, and the support of a graduate student, Charles Keeton. The refereed papers address four of the primary goals of the proposal: (1) the statistics of radio lenses as a probe of the cosmological model (#1), (2) the role of spiral galaxies as lenses (#3), (3) the effects of dust on statistics of lenses (#7, #8), and (4) the role of groups and clusters as lenses (#2, #6, #10, #13, #15, #16). Four papers (#4, #5, #11, #12) address general issues of lens models, calibrations, and the relationship between lens galaxies and nearby galaxies. One considered cosmological effects in lensing X-ray sources (#9), and two addressed issues related to the overall power spectrum and theories of gravity (#17, #18). Our theoretical studies combined with the explosion in the number of lenses and the quality of the data obtained for them is greatly increasing our ability to characterize and understand the lens population. We can now firmly conclude both from our study of the statistics of radio lenses and our survey of extinctions in individual lenses that the statistics of optically selected quasars were significantly affected by extinction. However, the limits on the cosmological constant remain at lambda < 0.65 at a 2-sigma confidence level, which is in mild conflict with the results of the Type la supernova surveys. We continue to find that neither spiral galaxies nor groups and clusters contribute significantly to the production of gravitational lenses. The lack of group and cluster lenses is strong evidence for the role of baryonic cooling in increasing the efficiency of galaxies as lenses compared to groups and clusters of higher mass but lower central density. Unfortunately for the ultimate objective of the proposal, improved constraints on the cosmological constant, the next

  14. Affinity Crystallography: A New Approach to Extracting High-Affinity Enzyme Inhibitors from Natural Extracts.

    PubMed

    Aguda, Adeleke H; Lavallee, Vincent; Cheng, Ping; Bott, Tina M; Meimetis, Labros G; Law, Simon; Nguyen, Nham T; Williams, David E; Kaleta, Jadwiga; Villanueva, Ivan; Davies, Julian; Andersen, Raymond J; Brayer, Gary D; Brömme, Dieter

    2016-08-26

    Natural products are an important source of novel drug scaffolds. The highly variable and unpredictable timelines associated with isolating novel compounds and elucidating their structures have led to the demise of exploring natural product extract libraries in drug discovery programs. Here we introduce affinity crystallography as a new methodology that significantly shortens the time of the hit to active structure cycle in bioactive natural product discovery research. This affinity crystallography approach is illustrated by using semipure fractions of an actinomycetes culture extract to isolate and identify a cathepsin K inhibitor and to compare the outcome with the traditional assay-guided purification/structural analysis approach. The traditional approach resulted in the identification of the known inhibitor antipain (1) and its new but lower potency dehydration product 2, while the affinity crystallography approach led to the identification of a new high-affinity inhibitor named lichostatinal (3). The structure and potency of lichostatinal (3) was verified by total synthesis and kinetic characterization. To the best of our knowledge, this is the first example of isolating and characterizing a potent enzyme inhibitor from a partially purified crude natural product extract using a protein crystallographic approach. PMID:27498895

  15. Negative homotropic cooperativity and affinity heterogeneity: preparation of yeast glyceraldehyde-3-phosphate dehydrogenase with maximal affinity homogeneity.

    PubMed Central

    Gennis, L S

    1976-01-01

    A three-step procedure including affinity chromatography on NAD+-azobenzamidopropyl-Sepharose has been designed for the purification of yeast glyceraldehyde-3-phosphate dehydrogenase [D-glyceraldehyde-3-phosphate: NAD+ oxidoreductase (phosphorylating), EC 1.2.1.12] with maximized specific activity and maximized homogeneity with respect to affinity for the coenzyme, NAD+.Binding isotherms allow the analysis of cooperativity patterns that disclose both the average ligand affinity in the system and the distribution of ligands among the sites, only for systems with complete affinity homogeneity. The presence of affinity heterogeneity, resulting from multiple oligomeric species differing only in their affinity for coenzyme, gives rise to isotherms which falsely manifest apparent negative cooperativity. A method for distinguishing negative homotropic cooperativity from affinity heterogeneity is suggested. PMID:186779

  16. Survival of Nannochloropsis Phytoplankton in Hypervelocity Impact Events up to Velocities of 6.07 km/s

    NASA Astrophysics Data System (ADS)

    Pasini, D. L. S.; Price, M. C.; Burchell, M. J.; Cole, M. J.

    2013-09-01

    Studies have previously been conducted to verify the survivability of living cells during hypervelocity impact events to test the panspermia and lithopanspermia hypothesis [1], [2]. It has been demonstrated that bacteria survive impacts up to 5.4 km s-1 (approx. shock pressure 30 GPa) - albeit with a low probability of survival [1] whilst larger more complex objects (such as seeds) break up at ~1 km s-1 [2]. The survivability of yeast spores in impacts up to 7.4 km s-1 has also recently been shown [3]. We demonstrate here the survivability of Nannochloropsis Phytoplankton, a eukaryotic photosynthesizing autotroph found in the 'euphotic zone'(sunlit surface layers of oceans) [4] at impact velocities up to 6.07 km s-1. Phytoplankton from a culture sample was frozen and then fired into water (to simulate oceanic impacts, as described in [5]) using a light gas gun (LGG) [6]. The water was then retrieved and placed into a sealed culture vessel and left under a constant light source to check the viability of any remnant organisms.

  17. Characteristics of the interaction of calcium with casein submicelles as determined by analytical affinity chromatography

    SciTech Connect

    Jang, H.D.; Swaisgood, H.E. )

    1990-12-01

    Interaction of calcium with casein submicelles was investigated in CaCl2 and calcium phosphate buffers and with synthetic milk salt solutions using the technique of analytical affinity chromatography. Micelles that had been prepared by size exclusion chromatography with glycerolpropyl controlled-pore glass from fresh raw skim milk that had never been cooled, were dialyzed at room temperature against calcium-free imidazole buffer, pH 6.7. Resulting submicelles were covalently immobilized on succinamidopropyl controlled-pore glass (300-nm pore size). Using 45Ca to monitor the elution retardation, the affinity of free Ca2+ and calcium salt species was determined at temperatures of 20 to 40 degrees C and pH 6.0 to 7.5. Increasing the pH in this range or increasing the temperature strengthened the binding of calcium to submicelles, similar to previous observations with individual caseins. However, the enthalpy change obtained from the temperature dependence was considerably greater than that reported for alpha s1- and beta-caseins. Furthermore, the elution profiles for 45Ca in milk salt solutions were decidedly different from those in CaCl2 or calcium phosphate buffers and the affinities were also greater. For example, at pH 6.7 and 30 degrees C the average dissociation constant for the submicelle-calcium complex is 0.074 mM for CaCl2 and calcium phosphate buffers, vs 0.016 mM for the milk salt solution. The asymmetric frontal boundaries and higher average affinities observed with milk salts may be due to binding of calcium salts with greater affinity in addition to the binding of free Ca2+ in these solutions.

  18. KM3NeT Digital Optical Module electronics

    NASA Astrophysics Data System (ADS)

    Real, Diego

    2016-04-01

    The KM3NeT collaboration is currently building of a neutrino telescope with a volume of several cubic kilometres at the bottom of the Mediterranean Sea. The telescope consists of a matrix of Digital Optical Modules that will detect the Cherenkov light originated by the interaction of the neutrinos in the proximity of the detector. This contribution describes the main components of the read-out electronics of the Digital Optical Module: the Power Board, which delivers all the power supply required by the Digital Optical Molule electronics; the Central Logic Board, the main core of the read-out system, hosting 31 Time to Digital Converters with 1 ns resolution and the White Rabbit protocol embedded in the Central Logic Board Field Programmable Gate Array; the Octopus boards, that transfer the Low Voltage Digital Signals from the PMT bases to the Central Logic Board and finally the PMT bases, in charge of converting the analogue signal produced in the 31 3" PMTs into a Low Voltage Digital Signal.

  19. Stratospheric microbiology at 20 km over the Pacific Ocean

    USGS Publications Warehouse

    Smith, David J.; Griffin, Dale W.; Schuerger, Andrew C.

    2010-01-01

    An aerobiology sampling flight at 20 km was conducted on 28 April 2008 over the Pacific Ocean (36.5° N, 118–149° W), a period of time that coincided with the movement of Asian dust across the ocean. The aim of this study was to confirm the presence of viable bacteria and fungi within a transoceanic, atmospheric bridge and to improve the resolution of flight hardware processing techniques. Isolates of the microbial strains recovered were analyzed with ribosomal ribonucleic acid (rRNA) sequencing to identify bacterial species Bacillus sp., Bacillus subtilis, Bacillus endophyticus, and the fungal genus Penicillium. Satellite imagery and ground-based radiosonde observations were used to measure dust movement and characterize the high-altitude environment at the time of collection. Considering the atmospheric residency time (7–10 days), the extreme temperature regime of the environment (-75°C), and the absence of a mechanism that could sustain particulates at high altitude, it is unlikely that our samples indicate a permanent, stratospheric ecosystem. However, the presence of viable fungi and bacteria in transoceanic stratosphere remains relevant to understanding the distribution and extent of microbial life on Earth.

  20. A 233 km tunnel for lepton and hadron colliders

    SciTech Connect

    Summers, D. J.; Cremaldi, L. M.; Datta, A.; Duraisamy, M.; Luo, T.; Lyons, G. T.

    2012-12-21

    A decade ago, a cost analysis was conducted to bore a 233 km circumference Very Large Hadron Collider (VLHC) tunnel passing through Fermilab. Here we outline implementations of e{sup +}e{sup -}, pp-bar , and {mu}{sup +}{mu}{sup -} collider rings in this tunnel using recent technological innovations. The 240 and 500 GeV e{sup +}e{sup -} colliders employ Crab Waist Crossings, ultra low emittance damped bunches, short vertical IP focal lengths, superconducting RF, and low coercivity, grain oriented silicon steel/concrete dipoles. Some details are also provided for a high luminosity 240 GeV e{sup +}e{sup -} collider and 1.75 TeV muon accelerator in a Fermilab site filler tunnel. The 40 TeV pp-bar collider uses the high intensity Fermilab p-bar source, exploits high cross sections for pp-bar production of high mass states, and uses 2 Tesla ultra low carbon steel/YBCO superconducting magnets run with liquid neon. The 35 TeV muon ring ramps the 2 Tesla superconducting magnets at 9 Hz every 0.4 seconds, uses 250 GV of superconducting RF to accelerate muons from 1.75 to 17.5 TeV in 63 orbits with 71% survival, and mitigates neutrino radiation with phase shifting, roller coaster motion in a FODO lattice.

  1. Nausea is associated with endotoxemia during a 161-km ultramarathon.

    PubMed

    Stuempfle, Kristin J; Valentino, Taylor; Hew-Butler, Tamara; Hecht, Frederick M; Hoffman, Martin D

    2016-09-01

    This study explored possible contributing factors to gastrointestinal distress, including endotoxemia, hyperthermia, dehydration and nutrition, during a 161-km ultramarathon. Thirty runners participated in the study and 20 finished the race. At three checkpoints and the finish, runners were interviewed to assess the incidence and severity of 12 gastrointestinal symptoms and to determine dietary intake. Core temperature was measured at the same locations. Runners were weighed pre-race, at the three checkpoints and the finish to monitor hydration status. Blood markers for endotoxemia (sCD14) and inflammation (interleukin-6 and C-reactive protein) were measured pre- and post-race. Gastrointestinal symptoms were experienced by most runners (80%), with nausea being the most common complaint (60%). Runners with nausea experienced significantly greater (P = 0.02) endotoxemia than those without nausea (sCD14 mean increase 0.7 versus 0.5 µg · mL(-1)). There was a significant positive correlation (r = 0.652, P = 0.005) between nausea severity and endotoxemia level. Inflammatory response, core temperature, hydration level and race diet were similar between runners with and without nausea. This study links endotoxemia to nausea in ultramarathon runners. Other possible contributing factors to nausea such as hyperthermia, dehydration and nutrition did not appear to play a role in the symptomatic runners in this study. PMID:26707127

  2. ASIC design in the KM3NeT detector

    NASA Astrophysics Data System (ADS)

    Gajanana, D.; Gromov, V.; Timmer, P.

    2013-02-01

    In the KM3NeT project [1], Cherenkov light from the muon interactions with transparent matter around the detector, is used to detect neutrinos. Photo multiplier tubes (PMT) used as photon sensor, are housed in a glass sphere (aka Optical Module) to detect single photons from the Cherenkov light. The PMT needs high operational voltage ( ~ 1.5 kV) and is generated by a Cockroft-Walton (CW) multiplier circuit. The electronics required to control the PMT's and collect the signals is integrated in two ASIC's namely: 1) a front-end mixed signal ASIC (PROMiS) for the readout of the PMT and 2) an analog ASIC (CoCo) to generate pulses for charging the CW circuit and to control the feedback of the CW circuit. In this article, we discuss the two integrated circuits and test results of the complete setup. PROMiS amplifies the input charge, converts it to a pulse width and delivers the information via LVDS signals. These LVDS signals carry accurate information on the Time of arrival ( < 2 ns) and Time over Threshold. A PROM block provides unique identification to the chip. The chip communicates with the control electronics via an I2C bus. This unique combination of the ASIC's results in a very cost and power efficient PMT base design.

  3. Development of a sensitive method for selection of affinity ligand for trypsin using quartz crystal microbalance sensor.

    PubMed

    Bayramoglu, Gulay; Yakup Arica, M

    2012-03-01

    In this work, a new methodology is developed for selection of affinity ligands towards the enzyme "trypsin" using quartz crystals microbalance (QCM) technique. To achieve this goal, the surface amination of gold plated QCM crystals was achieved in 13.56 MHz plasma polymerization system by using ethylenediamine. Three different ligands (i.e., 4-aminobenzamidine, 4-aminobenzoic acid, and phenylalanine) were immobilized on the aminated QCM crystals surface via glutaraldehyde coupling. All three ligand immobilized QCM crystals were characterized and compared under different experimental conditions. It was observed that the benzamidine ligand showed higher affinity to trypsin with a dissociation constant on the order of 1.76 × 10(-9) M, which is within the range of 10(-4)-10(-8) M for affinity ligands. Thus, its selectivity was suitable for purification of trypsin from biological fluids. PMID:21853329

  4. Complementary DNA display selection of high-affinity peptides binding the vacuolating toxin (VacA) of Helicobacter pylori.

    PubMed

    Hayakawa, Yumiko; Matsuno, Mitsuhiro; Tanaka, Makoto; Wada, Akihiro; Kitamura, Koichiro; Takei, Osamu; Sasaki, Ryuzo; Mizukami, Tamio; Hasegawa, Makoto

    2015-09-01

    Artificial peptides designed for molecular recognition of a bacterial toxin have been developed. Vacuolating cytotoxin A protein (VacA) is a major virulence factor of Helicobacter pylori, a gram-negative microaerophilic bacterium inhabiting the upper gastrointestinal tract, particularly the stomach. This study attempted to identify specific peptide sequences with high affinity for VacA using systematic directed evolution in vitro, a cDNA display method. A surface plasmon resonance-based biosensor and fluorescence correlation spectroscopy to examine binding of peptides with VacA identified a peptide (GRVNQRL) with high affinity. Cyclization of the peptide by attaching cysteine residues to both termini improved its binding affinity to VacA, with a dissociation constant (Kd ) of 58 nm. This study describes a new strategy for the development of artificial functional peptides, which are promising materials in biochemical analyses and medical applications.

  5. Structure of a High-Affinity

    SciTech Connect

    Saphire, E.O.; Montero, M.; Menendez, A.; Houten, N.E.van; Irving, M.B.; Pantophlet, R.; Swick, M.B.; Parren, P.W.H.I.; Burton, D.R.; Scott, J.K.; Wilson, I.A.; /Scripps Res. Inst. /Simon Fraser U. /British Columbia U.

    2007-07-13

    The human antibody b12 recognizes a discontinuous epitope on gp120 and is one of the rare monoclonal antibodies that neutralize a broad range of primary human immunodeficiency virus type 1 (HIV-1) isolates. We previously reported the isolation of B2.1, a dimeric peptide that binds with high specificity to b12 and competes with gp120 for b12 antibody binding. Here, we show that the affinity of B2.1 was improved 60-fold over its synthetic-peptide counterpart by fusing it to the N terminus of a soluble protein. This affinity, which is within an order of magnitude of that of gp120, probably more closely reflects the affinity of the phage-borne peptide. The crystal structure of a complex between Fab of b12 and B2.1 was determined at 1.8 Angstrom resolution. The structural data allowed the differentiation of residues that form critical contacts with b12 from those required for maintenance of the antigenic structure of the peptide, and revealed that three contiguous residues mediate B2.1's critical contacts with b12. This single region of critical contact between the B2.1 peptide and the b12 paratope is unlikely to mimic the discontinuous key binding residues involved in the full b12 epitope for gp120, as previously identified by alanine scanning substitutions on the gp120 surface. These structural observations are supported by experiments that demonstrate that B2.1 is an ineffective immunogenic mimic of the b12 epitope on gp120. Indeed, an extensive series of immunizations with B2.1 in various forms failed to produce gp120 cross-reactive sera. The functional and structural data presented here, however, suggest that the mechanism by which b12 recognizes the two antigens is very different. Here, we present the first crystal structure of peptide bound to an antibody that was originally raised against a discontinuous protein epitope. Our results highlight the challenge of producing immunogens that mimic discontinuous protein epitopes, and the necessity of combining

  6. Capacitive Cells for Dielectric Constant Measurement

    ERIC Educational Resources Information Center

    Aguilar, Horacio Munguía; Maldonado, Rigoberto Franco

    2015-01-01

    A simple capacitive cell for dielectric constant measurement in liquids is presented. As an illustrative application, the cell is used for measuring the degradation of overheated edible oil through the evaluation of their dielectric constant.

  7. High voltage compliance constant current ballast

    NASA Technical Reports Server (NTRS)

    Rosenthal, L. A.

    1976-01-01

    A ballast circuit employing a constant current diode and a vacuum tube that can provide a constant current over a voltage range of 1000 volts. The simple circuit can prove useful in studying voltage breakdown characteristics.

  8. Temporal variation of coupling constants and nucleosynthesis

    NASA Astrophysics Data System (ADS)

    Oberhummer, H.; Csótó, A.; Fairbairn, M.; Schlattl, H.; Sharma, M. M.

    2003-05-01

    We investigate the triple-alpha process and the Oklo phenomenon to obtain constraints on possible cosmological time variations of fundamental constants. Specifically we study cosmological temporal constraints for the fine structure constant and nucleon and meson masses.

  9. Effectively nonlocal metric-affine gravity

    NASA Astrophysics Data System (ADS)

    Golovnev, Alexey; Koivisto, Tomi; Sandstad, Marit

    2016-03-01

    In metric-affine theories of gravity such as the C-theories, the spacetime connection is associated to a metric that is nontrivially related to the physical metric. In this article, such theories are rewritten in terms of a single metric, and it is shown that they can be recast as effectively nonlocal gravity. With some assumptions, known ghost-free theories with nonsingular and cosmologically interesting properties may be recovered. Relations between different formulations are analyzed at both perturbative and nonperturbative levels, taking carefully into account subtleties with boundary conditions in the presence of integral operators in the action, and equivalences between theories related by nonlocal redefinitions of the fields are verified at the level of equations of motion. This suggests a possible geometrical interpretation of nonlocal gravity as an emergent property of non-Riemannian spacetime structure.

  10. Affinity chromatography with an immobilized RNA enzyme.

    PubMed Central

    Vioque, A; Altman, S

    1986-01-01

    M1 RNA, the catalytic subunit of Escherichia coli RNase P, has been covalently linked at its 3' terminus to agarose beads. Unlike M1 RNA, which is active in solution in the absence of the protein component (C5) of RNase P, the RNA linked to the beads is active only in the presence of C5 protein. Affinity chromatography of crude extracts of E. coli on a column prepared from the beads to which the RNA has been crosslinked results in the purification of C5 protein in a single step. The protein has been purified in this manner from cells that contain a plasmid, pINIIIR20, which includes the gene that codes for C5 protein. A 6-fold amplification of the expression of C5 protein is found in these cells after induction as compared to cells that do not harbor the plasmid. Images PMID:3526344

  11. Wetting on rough self-affine surfaces

    NASA Astrophysics Data System (ADS)

    Palasantzas, George

    1995-05-01

    In this paper, we present a general investigation of the effective potential for complete wetting on self-affine rough surfaces. The roughness effect is investigated by means of the height-height correlation model in Fourier space ~(1+aξ2q2)-1-H. The parameters H and ξ are, respectively, the roughness exponent and the substrate in-plane correlation length. It is observed that the effect of H on the free interface profile is significant for ξ>ξ) regime is characterized by a power-law scaling ~Y-2.

  12. High-affinity neuropeptide Y receptor antagonists.

    PubMed Central

    Daniels, A J; Matthews, J E; Slepetis, R J; Jansen, M; Viveros, O H; Tadepalli, A; Harrington, W; Heyer, D; Landavazo, A; Leban, J J

    1995-01-01

    Neuropeptide Y (NPY) is one of the most abundant peptide transmitters in the mammalian brain. In the periphery it is costored and coreleased with norepinephrine from sympathetic nerve terminals. However, the physiological functions of this peptide remain unclear because of the absence of specific high-affinity receptor antagonists. Three potent NPY receptor antagonists were synthesized and tested for their biological activity in in vitro, ex vivo, and in vivo functional assays. We describe here the effects of these antagonists inhibiting specific radiolabeled NPY binding at Y1 and Y2 receptors and antagonizing the effects of NPY in human erythroleukemia cell intracellular calcium mobilization perfusion pressure in the isolated rat kidney, and mean arterial blood pressure in anesthetized rats. PMID:7568074

  13. Evaluation system of negative electron affinity photocathode

    NASA Astrophysics Data System (ADS)

    Fu, Rongguo; Chang, Benkang; Qian, Yunsheng; Wang, Guihua; Zong, Zhiyuan

    2001-10-01

    This article first describes the background of the research and manufacture of evaluation system of Negative Electron Affinity photocathode. This article designs a set of super high vacuum system for activating NEA photocathode on the base of activation theory, the process of design and debugging is given. The system is composed of three parts: super high vacuum system for GaAs material activation, multi-meter testing system, surface analysis system. The system is used for on-line evaluation of activating of NEA photocathode. The technical parameters and structure of the evaluation system of NEA photocathode are given in the paper. The system is finished and experiments are made. At last the picture of the system is given.

  14. File Specification for the 7-km GEOS-5 Nature Run, Ganymed Release Non-Hydrostatic 7-km Global Mesoscale Simulation

    NASA Technical Reports Server (NTRS)

    da Silva, Arlindo M.; Putman, William; Nattala, J.

    2014-01-01

    This document describes the gridded output files produced by a two-year global, non-hydrostatic mesoscale simulation for the period 2005-2006 produced with the non-hydrostatic version of GEOS-5 Atmospheric Global Climate Model (AGCM). In addition to standard meteorological parameters (wind, temperature, moisture, surface pressure), this simulation includes 15 aerosol tracers (dust, sea-salt, sulfate, black and organic carbon), O3, CO and CO2. This model simulation is driven by prescribed sea-surface temperature and sea-ice, daily volcanic and biomass burning emissions, as well as high-resolution inventories of anthropogenic sources. A description of the GEOS-5 model configuration used for this simulation can be found in Putman et al. (2014). The simulation is performed at a horizontal resolution of 7 km using a cubed-sphere horizontal grid with 72 vertical levels, extending up to to 0.01 hPa (approximately 80 km). For user convenience, all data products are generated on two logically rectangular longitude-latitude grids: a full-resolution 0.0625 deg grid that approximately matches the native cubed-sphere resolution, and another 0.5 deg reduced-resolution grid. The majority of the full-resolution data products are instantaneous with some fields being time-averaged. The reduced-resolution datasets are mostly time-averaged, with some fields being instantaneous. Hourly data intervals are used for the reduced-resolution datasets, while 30-minute intervals are used for the full-resolution products. All full-resolution output is on the model's native 72-layer hybrid sigma-pressure vertical grid, while the reduced-resolution output is given on native vertical levels and on 48 pressure surfaces extending up to 0.02 hPa. Section 4 presents additional details on horizontal and vertical grids. Information of the model surface representation can be found in Appendix B. The GEOS-5 product is organized into file collections that are described in detail in Appendix C. Additional

  15. Kinematics of the New Zealand plate boundary: Relative motion by GPS across networks of 1000 km and 50 km spacing

    NASA Technical Reports Server (NTRS)

    Meertens, Charles M.; Rocken, Christian; Perin, Barbara; Walcott, Richard

    1993-01-01

    The NASA/DOSE 'Kinematics of the New Zealand Plate Boundary' experiment is a four-year cooperative Global Positioning System (GPS) experiment involving 6 universities and institutions in New Zealand and the United States. The investigation covers two scales, the first on the scale of plates (approximately 1000 km) and the second is on the scale of the plate boundary zone (approximately 50 km). In the first portion of the experiment, phase A, the objective is to make direct measurements of tectonic plate motion between the Australian and Pacific plates using GPS in order to determine the Euler vector of this plate pair. The phase A portion of this experiment was initiated in December 1992 with the first-epoch baseline measurements on the large scale network. The network will be resurveyed two years later to obtain velocities. The stations which were observed for phase A are shown and listed. Additional regional stations which will be used for this study are listed and are part of either CIGNET or other global tracking networks. The phase A portion of the experiment is primarily the responsibility of the UNAVCO investigators. Therefore, this report concentrates on phase A. The first year of NASA funding for phase A included only support for the field work. Processing and analysis will take place with the second year of funding. The second part of the experiemnt measured relative motion between the Australian and Pacific plates across the pate boundary zone between Hokitika and Christchurch on the South Island of New Zealand. The extent and rate of deformation will be determined by comparisons with historical, conventional surveys and by repeated GPS measurements to be made in two years. This activity was the emphasis of the LDGO portion of the study. An ancillary experiment, phase C, concentrated on plate boundary deformation in the vicinity of Wellington and was done as part of training during the early portion of the field campaign. Details of the objectives of the

  16. One-step purification of lactoperoxidase from bovine milk by affinity chromatography.

    PubMed

    Atasever, Ali; Ozdemir, Hasan; Gulcin, Ilhami; Irfan Kufrevioglu, O

    2013-01-15

    Sulphanilamide was determined to be a new inhibitor of lactoperoxidase (LPO) with an IC(50) of 0.848.10(-5)M. The K(i) for sulphanilamide was determined to be 3.57.10(-5)M and sulphanilamide showed competitive inhibition, which makes it a suitable ligand for constructing a Sepharose 4B-L-tyrosine affinity matrix. The affinity matrix was synthesised by coupling sulphanilamide as the ligand and L-tyrosine as the spacer arm to a cyanogen bromide (CNBr)-activated-Sepharose 4B matrix. Lactoperoxidase was purified 409-fold from the synthesized affinity matrix in a single step, with a yield of 62.3% and a specific activity of 40.9 EU/mg protein. The enzyme activity was measured using ABTS as a chromogenic substrate (pH 6.0). The degree of LPO purification was monitored by SDS-PAGE and its R(z) (A(412)/A(280)) value. The R(z) value for the purified LPO was found to be 0.7. Maximum binding was achieved and K(m) and V(max) values were determined.

  17. Dye affinity cryogels for plasmid DNA purification.

    PubMed

    Çimen, Duygu; Yılmaz, Fatma; Perçin, Işık; Türkmen, Deniz; Denizli, Adil

    2015-11-01

    The aim of this study is to prepare megaporous dye-affinity cryogel discs for the purification of plasmid DNA (pDNA) from bacterial lysate. Poly(hydroxyethyl methacrylate) [PHEMA] cryogel discs were produced by free radical polymerization initiated by N,N,N',N'-tetramethylene diamine (TEMED) and ammonium persulfate (APS) redox pair in an ice bath. Cibacron Blue F3GA was used as an affinity ligand (loading amount: 68.9μmol/g polymer). The amount of pDNA adsorbed onto the PHEMA-Cibacron Blue F3GA cryogel discs first increased and then reached a plateau value (i.e., 32.5mg/g cryogel) at 3.0mg/mL pDNA concentration. Compared with the PHEMA cryogel (0.11mg/g cryogel), the pDNA adsorption capacity of the PHEMA-Cibacron Blue F3GA cryogel (32.4mg/g polymer) was improved significantly due to the Cibacron Blue 3GA immobilization onto the polymeric matrix. pDNA adsorption amount decreased from 11.7mg/g to 1.1mg/g with the increasing of NaCl concentration. The maximum pDNA adsorption was achieved at 4°C. The overall recovery of pDNA was calculated as 90%. The PHEMA-Cibacron Blue F3GA cryogel discs could be used five times without decreasing the pDNA adsorption capacity significantly. The results show that the PHEMA-Cibacron Blue F3GA cryogel discs promise high selectivity for pDNA. PMID:26249596

  18. A high resolution (1 km) groundwater model for Indonesia

    NASA Astrophysics Data System (ADS)

    Sutanudjaja, Edwin; Verkaik, Jarno; de Graaf, Inge; van Beek, Rens; Erkens, Gilles; Bierkens, Marc

    2015-04-01

    Groundwater is important in many parts of Indonesia. It serves as a primary source of drinking water and industrial activities. During times of drought, it sustains water flows in streams, rivers, lakes and wetlands, and thus support ecosystem habitat and biodiversity as well as preventing hazardous forest fire. Besides its importance, groundwater is known as a vulnerable resource as unsustainable groundwater exploitation and management occurs in many areas of the country. Therefore, in order to ensure sustainable management of groundwater resources, monitoring and predicting groundwater changes in Indonesia are imperative. However, large extent groundwater models to assess these changes on a regional scale are almost non-existent and are hampered by the strong topographical and lithological transitions that characterize Indonesia. In this study, we built an 1 km resolution groundwater model for the entire Indonesian archipelago (total inland area: about 2 million km2). We adopted the approaches of Sutanudjaja et al. (2011, 2014a) and de Graaf et al. (2014) in order to make a MODFLOW (Harbaugh et al., 2000) groundwater model by using only global datasets. Aquifer schematization and properties of the groundwater model were developed from available global lithological maps (e.g. Dürr et al., 2005; Gleeson et al., 2011; Hartmann & Moorsdorf, 2012; Gleeson et al., 2014). We forced the groundwater model with the recent output of global hydrological model PCR-GLOBWB version 2.0 (Sutanudjaja et al., 2014b; van Beek et al., 2011), specifically the long term average of groundwater recharge and average surface water levels derived from channel discharge. Simulation results were promising. The MODFLOW model converged with realistic aquifer properties (i.e. transmissivities) and produced reasonable groundwater head spatial distribution reflecting the positions of major groundwater bodies and surface water bodies in the country. In Vienna, we aim to show and demonstrate these

  19. High Affinity Binding of Indium and Ruthenium Ions by Gastrins.

    PubMed

    Baldwin, Graham S; George, Graham N; Pushie, M Jake

    2015-01-01

    The peptide hormone gastrin binds two ferric ions with high affinity, and iron binding is essential for the biological activity of non-amidated forms of the hormone. Since gastrins act as growth factors in gastrointestinal cancers, and as peptides labelled with Ga and In isotopes are increasingly used for cancer diagnosis, the ability of gastrins to bind other metal ions was investigated systematically by absorption spectroscopy. The coordination structures of the complexes were characterized by extended X-ray absorption fine structure (EXAFS) spectroscopy. Changes in the absorption of gastrin in the presence of increasing concentrations of Ga3+ were fitted by a 2 site model with dissociation constants (Kd) of 3.3 x 10-7 and 1.1 x 10-6 M. Although the absorption of gastrin did not change upon the addition of In3+ ions, the changes in absorbance on Fe3+ ion binding in the presence of indium ions were fitted by a 2 site model with Kd values for In3+ of 6.5 x 10-15 and 1.7 x 10-7 M. Similar results were obtained with Ru3+ ions, although the Kd values for Ru3+ of 2.6 x 10-13 and 1.2 x 10-5 M were slightly larger than observed for In3+. The structures determined by EXAFS all had metal:gastrin stoichiometries of 2:1 but, while the metal ions in the Fe, Ga and In complexes were bridged by a carboxylate and an oxygen with a metal-metal separation of 3.0-3.3 Å, the Ru complex clearly demonstrated a short range Ru-Ru separation, which was significantly shorter, at 2.4 Å, indicative of a metal-metal bond. We conclude that gastrin selectively binds two In3+ or Ru3+ ions, and that the affinity of the first site for In3+ or Ru3+ ions is higher than for ferric ions. Some of the metal ion-gastrin complexes may be useful for cancer diagnosis and therapy.

  20. High Affinity Binding of Indium and Ruthenium Ions by Gastrins

    PubMed Central

    Baldwin, Graham S.; George, Graham N.; Pushie, M. Jake

    2015-01-01

    The peptide hormone gastrin binds two ferric ions with high affinity, and iron binding is essential for the biological activity of non-amidated forms of the hormone. Since gastrins act as growth factors in gastrointestinal cancers, and as peptides labelled with Ga and In isotopes are increasingly used for cancer diagnosis, the ability of gastrins to bind other metal ions was investigated systematically by absorption spectroscopy. The coordination structures of the complexes were characterized by extended X-ray absorption fine structure (EXAFS) spectroscopy. Changes in the absorption of gastrin in the presence of increasing concentrations of Ga3+ were fitted by a 2 site model with dissociation constants (Kd) of 3.3 x 10−7 and 1.1 x 10−6 M. Although the absorption of gastrin did not change upon the addition of In3+ ions, the changes in absorbance on Fe3+ ion binding in the presence of indium ions were fitted by a 2 site model with Kd values for In3+ of 6.5 x 10−15 and 1.7 x 10−7 M. Similar results were obtained with Ru3+ ions, although the Kd values for Ru3+ of 2.6 x 10−13 and 1.2 x 10−5 M were slightly larger than observed for In3+. The structures determined by EXAFS all had metal:gastrin stoichiometries of 2:1 but, while the metal ions in the Fe, Ga and In complexes were bridged by a carboxylate and an oxygen with a metal-metal separation of 3.0–3.3 Å, the Ru complex clearly demonstrated a short range Ru—Ru separation, which was significantly shorter, at 2.4 Å, indicative of a metal-metal bond. We conclude that gastrin selectively binds two In3+ or Ru3+ ions, and that the affinity of the first site for In3+ or Ru3+ ions is higher than for ferric ions. Some of the metal ion-gastrin complexes may be useful for cancer diagnosis and therapy. PMID:26457677

  1. Characterization of the Rhizobium (Sinorhizobium) meliloti high- and low-affinity phosphate uptake systems.

    PubMed Central

    Voegele, R T; Bardin, S; Finan, T M

    1997-01-01

    Genetic studies have suggested that Rhizobium (Sinorhizobium) meliloti contains two distinct phosphate (Pi) transport systems, encoded by the phoCDET genes and the orfA-pit genes, respectively. Here we present data which show that the ABC-type PhoCDET system has a high affinity for Pi (Km, 0.2 microM) and that Pi uptake by this system is severely inhibited by phosphonates. This high-affinity uptake system was induced under Pi-limiting conditions and was repressed in the presence of excess Pi. Uptake via the OrfA-Pit system was examined in (i) a phoC mutant which showed increased expression of the orfA-pit genes as a result of a promoter-up mutation and (ii) a phoB mutant (PhoB is required for phoCDET expression). Pi uptake in both strains exhibited saturation kinetics (Km, 1 to 2 microM) and was not inhibited by phosphonates. This uptake system was active in wild-type cells grown with excess Pi and appeared to be repressed when the cells were starved for Pi. Thus, our biochemical data show that the OrfA-Pit and PhoCDET uptake systems are differentially expressed depending on the state of the cell with respect to phosphate availability. PMID:9393684

  2. A nitrogen-dependent switch in the high affinity ammonium transport in Medicago truncatula.

    PubMed

    Straub, Daniel; Ludewig, Uwe; Neuhäuser, Benjamin

    2014-11-01

    Ammonium transporters (AMTs) are crucial for the high affinity primary uptake and translocation of ammonium in plants. In the model legume Medicago truncatula, the genomic set of AMT-type ammonium transporters comprises eight members. Only four genes were abundantly expressed in young seedlings, both in roots and shoots. While the expression of all AMTs in the shoot was not affected by the nitrogen availability, the dominating MtAMT1;1 gene was repressed by nitrogen in roots, despite that cellular nitrogen concentrations were far above deficiency levels. A contrasting de-repression by nitrogen was observed for MtAMT1;4 and MtAMT2;1, which were both expressed at intermediate level. Weak expression was found for MtAMT1;2 and MtAMT2;3, while the other AMTs were not detected in young seedlings. When expressed from their endogenous promoters, translational fusion proteins of MtAMT1;1 and MtAMT2;1 with green fluorescent protein were co-localized in the plasma membrane of rhizodermal cells, but also detected in cortical root layers. Both transporter proteins similarly functionally complemented a yeast strain that is deficient in high affinity ammonium transport, both at acidic and neutral pH. The uptake into yeast mediated by these transporters saturated with Km AMT1;1 = 89 µM and Km AMT2;1 = 123 µM, respectively. When expressed in oocytes, MtAMT1;1 mediated much larger (15)N-ammonium uptake than MtAMT2;1, but NH4 (+) currents were only recorded for MtAMT1;1. These currents saturated with a voltage-dependent Km = 90 µM at -80 mV. The cellular localization and regulation of the AMTs suggests that MtAMT1;1 encodes the major high affinity ammonium transporter gene in low nitrogen grown young M. truncatula roots and despite the similar localization and substrate affinity, MtAMT2;1 appears functionally distinct and more important at higher nitrogen supply. PMID:25164101

  3. Processing techniques for global land 1-km AVHRR data

    USGS Publications Warehouse

    Eidenshink, Jeffery C.; Steinwand, Daniel R.; Wivell, Charles E.; Hollaren, Douglas M.; Meyer, David

    1993-01-01

    The U.S. Geological Survey's (USGS) Earth Resources Observation Systems (EROS) Data Center (EDC) in cooperation with several international science organizations has developed techniques for processing daily Advanced Very High Resolution Radiometer (AVHRR) 1-km data of the entire global land surface. These techniques include orbital stitching, geometric rectification, radiometric calibration, and atmospheric correction. An orbital stitching algorithm was developed to combine consecutive observations acquired along an orbit by ground receiving stations into contiguous half-orbital segments. The geometric rectification process uses an AVHRR satellite model that contains modules for forward mapping, forward terrain correction, and inverse mapping with terrain correction. The correction is accomplished by using the hydrologic features coastlines and lakes from the Digital Chart of the World. These features are rasterized into the satellite projection and are matched to the AVHRR imagery using binary edge correlation techniques. The resulting coefficients are related to six attitude correction parameters: roll, roll rate, pitch, pitch rate, yaw, and altitude. The image can then be precision corrected to a variety of map projections and user-selected image frames. Because the AVHRR lacks onboard calibration for the optical wavelengths, a series of time-variant calibration coefficients derived from vicarious calibration methods and are used to model the degradation profile of the instruments. Reducing atmospheric effects on AVHRR data is important. A method has been develop that will remove the effects of molecular scattering and absorption from clear sky observations, using climatological measurements of ozone. Other methods to remove the effects of water vapor and aerosols are being investigated.

  4. Gastrointestinal distress is common during a 161-km ultramarathon.

    PubMed

    Stuempfle, Kristin Jean; Hoffman, Martin Dean

    2015-01-01

    This study examined the incidence, severity, and timing of gastrointestinal (GI) symptoms in finishers and non-finishers of the 161-km Western States Endurance Run. A total of 272 runners (71.0% of starters) completed a post-race questionnaire that assessed the incidence and severity (none = 0, mild = 1, moderate = 2, severe = 3, very severe = 4) of 12 upper (reflux/heartburn, belching, stomach bloating, stomach cramps/pain, nausea, vomiting) and lower (intestinal cramps/pain, flatulence, side ache/stitch, urge to defecate, loose stool/diarrhoea, intestinal bleeding/bloody faeces) GI symptoms experienced during each of four race segments. GI symptoms were experienced by most runners (96.0%). Flatulence (65.9% frequency, mean value 1.0, s = 0.6 severity), belching (61.3% frequency, mean value 1.0, s = 0.6 severity), and nausea (60.3% frequency, mean value 1.0, s = 0.7 severity) were the most common symptoms. Among race finishers, 43.9% reported that GI symptoms affected their race performance, with nausea being the most common symptom (86.0%). Among race non-finishers, 35.6% reported that GI symptoms were a reason for dropping out of the race, with nausea being the most common symptom (90.5%). For both finishers and non-finishers, nausea was greatest during the most challenging and hottest part of the race. GI symptoms are very common during ultramarathon running, and in particular, nausea is the most common complaint for finishers and non-finishers. PMID:25716739

  5. Hundred lightcurves of sub-km main-belt asteroids

    NASA Astrophysics Data System (ADS)

    Yoshida, F.; Souami, D.; Bouquillon, S.; Nakamura, T.; Dermawan, B.; Yagi, M.; Souchay, J.

    2014-07-01

    We observed a single sky field near opposition and near the ecliptic plane using the Subaru telescope equipped with the Suprime-Cam. Taking advantage of the wide field of view (FOV) for the Suprime-Cam, the plan was to obtain 100 lightcurves of asteroids at the same time. The total observing time interval was about 8 hours on September 2, 2002, with 2-min exposures. We detected 147 moving objects in the single FOV (34'×27') on the Suprime-Cam (see Figure). Of those, 112 detections corresponded to different objects. We used the R filter during almost the entire observing run, but we took a few images with the B filter at the beginning, the middle, and the end of the run. We classified main-belt asteroids into S- and C-complexes with the B-R color of the object (Yoshida & Nakamura 2007). Although we carefully avoided regions of bright stars, the sky in the images taken by Suprime-Cam were actually crowded with faint objects. Therefore, the asteroids overlapped with background stars very often. Thus, it was very difficult to get lightcurves with high accuracy. We modified the GAIA-GBOT (Ground Based Optical Tracking) PIPELINE to measure the position and brightness of each object (Bouquillon et al. 2012). Once the objects were identified and their positions measured in pixel coordinates, the pipeline proceeded to the astrometric calibration and then to the photometric calibrations with the Guide Star Catalog II (Lasker et al. 2008). The pipeline produced time series of photometry for each object. The average brightness of each lightcurve ranged between 19--24 mag. We then estimated the rotational period from the lightcurve of each object. In our presentation, we will show the spin-period distribution of sub- km main-belt asteroids and compare it with that of large main-belt asteroids obtained from the lightcurve catalogue.

  6. Characterizing low affinity epibatidine binding to α4β2 nicotinic acetylcholine receptors with ligand depletion and nonspecific binding

    PubMed Central

    2011-01-01

    Background Along with high affinity binding of epibatidine (Kd1≈10 pM) to α4β2 nicotinic acetylcholine receptor (nAChR), low affinity binding of epibatidine (Kd2≈1-10 nM) to an independent binding site has been reported. Studying this low affinity binding is important because it might contribute understanding about the structure and synthesis of α4β2 nAChR. The binding behavior of epibatidine and α4β2 AChR raises a question about interpreting binding data from two independent sites with ligand depletion and nonspecific binding, both of which can affect equilibrium binding of [3H]epibatidine and α4β2 nAChR. If modeled incorrectly, ligand depletion and nonspecific binding lead to inaccurate estimates of binding constants. Fitting total equilibrium binding as a function of total ligand accurately characterizes a single site with ligand depletion and nonspecific binding. The goal of this study was to determine whether this approach is sufficient with two independent high and low affinity sites. Results Computer simulations of binding revealed complexities beyond fitting total binding for characterizing the second, low affinity site of α4β2 nAChR. First, distinguishing low-affinity specific binding from nonspecific binding was a potential problem with saturation data. Varying the maximum concentration of [3H]epibatidine, simultaneously fitting independently measured nonspecific binding, and varying α4β2 nAChR concentration were effective remedies. Second, ligand depletion helped identify the low affinity site when nonspecific binding was significant in saturation or competition data, contrary to a common belief that ligand depletion always is detrimental. Third, measuring nonspecific binding without α4β2 nAChR distinguished better between nonspecific binding and low-affinity specific binding under some circumstances of competitive binding than did presuming nonspecific binding to be residual [3H]epibatidine binding after adding a large concentration of

  7. Boronate Affinity-Molecularly Imprinted Biocompatible Probe: An Alternative for Specific Glucose Monitoring.

    PubMed

    Chen, Guosheng; Qiu, Junlang; Fang, Xu'an; Xu, Jianqiao; Cai, Siying; Chen, Qing; Liu, Yan; Zhu, Fang; Ouyang, Gangfeng

    2016-08-19

    A biocompatible probe for specific glucose recognition is based on photoinitiated boronate affinity-molecular imprinted polymers (BA-MIPs). The unique pre-self-assembly between glucose and boronic acids creates glucose-specific memory cavities in the BA-MIPs coating. As a result, the binding constant toward glucose was enhanced by three orders of magnitude. The BA-MIPs probe was applied to glucose determination in serum and urine and implanted into plant tissues for low-destructive and long-term in vivo continuous glucose monitoring. PMID:27411946

  8. Purification of glycolytic enzymes by using affinity-elution chromatography.

    PubMed Central

    Scopes, R K

    1977-01-01

    1. A systematic procedure for the purification of enzymes by affinity-elution chromatography is described. Enzymes are adsorbed on a cation-exchanger, and eluted with ligands specific for the enzyme concerned. 2. All of the glycolytic and some related enzymes present in rabbit muscle can be purified by the affinity-elution technique. The pH range for adsorption and elution of each enzyme was found, and the effects of minor variations of conditions are described. 3. A description of experimental conditions suitable for affinity elution of each enzyme is given, together with special features relevant to each individual enzyme. 4. Theoretical considerations of affinity elution chromatography are discussed, including its limitations, advantages and disadvantages compared with affinity-adsorption chromatography. Possible developments are suggested to cover enzymes which because of their adsorption characteristics are not at present amenable to affinity-elution procedures. PMID:192194

  9. Antibody-based affinity cryo-EM grid.

    PubMed

    Yu, Guimei; Li, Kunpeng; Jiang, Wen

    2016-05-01

    The Affinity Grid technique combines sample purification and cryo-Electron Microscopy (cryo-EM) grid preparation into a single step. Several types of affinity surfaces, including functionalized lipids monolayers, streptavidin 2D crystals, and covalently functionalized carbon surfaces have been reported. More recently, we presented a new affinity cryo-EM approach, cryo-SPIEM, which applies the traditional Solid Phase Immune Electron Microscopy (SPIEM) technique to cryo-EM. This approach significantly simplifies the preparation of affinity grids and directly works with native macromolecular complexes without need of target modifications. With wide availability of high affinity and high specificity antibodies, the antibody-based affinity grid would enable cryo-EM studies of the native samples directly from cell cultures, targets of low abundance, and unstable or short-lived intermediate states.

  10. Prediction of Neutral Salt Elution Profiles for Affinity Chromatography

    NASA Astrophysics Data System (ADS)

    Robinson, Jack B.; Strottmann, James M.; Stellwagen, Earle

    1981-04-01

    Neutral salts exhibit very marked differences as eluants of proteins from affinity columns. We observe: (i) that the relative potencies of neutral salts as eluants are independent of the protein or the affinity ligand in the systems studied, (ii) that the absolute salt concentration necessary to elute any given protein bound to the affinity matrix is proportional to the algebraic sum of a set of elution coefficients defined herein for the separate ions present in the solution, and (iii) that the proportionality between elution potency and elution coefficient is a function of the affinity of the protein for the immobilized ligand. Given the concentration of one neutral salt required for elution of a protein of interest from an affinity column, the elution capability of any neutral salt at any temperature can be quantitatively predicted for that protein. Accordingly, application and elution protocols for affinity chromatography can be designed to optimize the yield and fold purification of proteins.

  11. Coupling Isotachophoresis with Affinity Chromatography for Rapid and Selective Purification with High Column Utilization, Part 1: Theory

    PubMed Central

    2015-01-01

    We present a novel technique that couples isotachophoresis (ITP) with affinity chromatography (AC) to achieve rapid, selective purification with high column utilization. ITP simultaneously preconcentrates an analyte and purifies it, based on differences in mobility of sample components, excluding species that may foul or compete with the target at the affinity substrate. ITP preconcentration accelerates the affinity reaction, reducing assay time, improving column utilization, and allowing for capture of targets with higher dissociation constants. Furthermore, ITP-AC separates the target and contaminants into nondiffusing zones, thus achieving high resolution in a short distance and time. We present an analytical model for spatiotemporal dynamics of ITP-AC. We identify and explore the effect of key process parameters, including target distribution width and height, ITP zone velocity, forward and reverse reaction constants, and probe concentration on necessary affinity region length, assay time, and capture efficiency. Our analytical approach shows collapse of these variables to three nondimensional parameters. The analysis yields simple analytical relations for capture length and capture time in relevant ITP-AC regimes, and it demonstrates how ITP greatly reduces assay time and improves column utilization. In the second part of this two-part series, we will present experimental validation of our model and demonstrate ITP-AC separation of the target from 10,000-fold more-abundant contaminants. PMID:24937679

  12. [Cell-ELA-based determination of binding affinity of DNA aptamer against U87-EGFRvIII cell].

    PubMed

    Tan, Yan; Liang, Huiyu; Wu, Xidong; Gao, Yubo; Zhang, Xingmei

    2013-05-01

    A15, a DNA aptamer with binding specificity for U87 glioma cells stably overexpressing the epidermal growth factor receptor variant III (U87-EGFRvIII), was generated by cell systematic evolution of ligands by exponential enrichment (cell-SELEX) using a random nucleotide library. Subsequently, we established a cell enzyme-linked assay (cell-ELA) to detect the affinity of A15 compared to an EGFR antibody. We used A15 as a detection probe and cultured U87-EGFRvIII cells as targets. Our data indicate that the equilibrium dissociation constants (K(d)) for A15 were below 100 nmol/L and had similar affinity compared to an EGFR antibody for U87-EGFRvIII. We demonstrated that the cell-ELA was a useful method to determine the equilibrium dissociation constants (K(d)) of aptamers generated by cell-SELEX.

  13. Sperm in poor quality semen from bulls during heat stress have a lower affinity for binding hydrogen-3 heparin

    SciTech Connect

    Ax, R.L.; Gilbert, G.R.; Shook, G.E.

    1987-01-01

    Binding assays with (/sup 3/H) heparin were performed using spermatozoa collected prior to, during, and following summer heat stress to dairy bulls. Ejaculates collected in August 1983 after a period of ambient temperatures exceeding 29.4/sup 0/C exhibited a high frequency of abnormal sperm, and motility was reduced in some samples. Sperm in samples collected during heat stress possessed dissociation constants for binding (/sup 3/H) heparin ranging from 134.5 to 163.2 nmol. In contrast, sperm in semen collected prior to and after heat stress had significantly lower dissociation constants (higher affinity) for (/sup 3/H)heparin, 12.9 to 56.4 nmol. The number of binding sites for (/sup 3/H) heparin on sperm did not change among collection periods. It was concluded that the binding affinity for (/sup 3/H) heparin may reflect membrane integrity of bull sperm.

  14. Yeast 3',5'-bisphosphate nucleotidase: an affinity tag for protein purification.

    PubMed

    Yang, Yang; Ma, Jianhui; Yang, Yilin; Zhang, Xiao; Wang, Yanxing; Yang, Ling; Sun, Meihao

    2014-05-01

    Affinity chromatography is one of the most popular methods for protein purification. Each tag method has its advantages and disadvantages, and combination of different tags and developing of new tags had been proposed and performed. Yeast 3',5'-bisphosphate nucleotidase, also known as HAL2, hydrolyzes 3'-phosphoadenosine 5'-phosphate (PAP) with submicromolar Km, which indicated the tight interactions between HAL2 and PAP. In order to explore the feasibility of HAL2 as a protein purification affinity tag, HAL2 was further characterized with PAP as substrate. Results demonstrated that KmPAP and kcatPAP were ∼0.3μM and ∼11s(-)(1), respectively. Kd for PAP was 0.008μM in the presence of Ca(2+). pH was also found to affect interactions between HAL2 and PAP, with tightest binding (Kd∼8nM) at pH 7.5 and 8. The purification protocol was rationally designed based on nanomolar affinity to PAP agarose in the presence of Ca(2+), which could satisfy the metal requirement for PAP binding, prevent hydrolysis of immobilized PAP and could be chelated by ethylene glycol tetraacetic acid (EGTA) for elution. A series of expression vectors were further constructed and Escherichia coli adenosine 5'-phosphosulfate kinase (APSK) was prokaryotically expressed, purified and characterized. Ready to use expression vector with eight commonly used restriction enzyme recognition sites in multiple cloning site was subsequently constructed. By comparing with current popular tags, HAL2 was found to be an efficient and economical tag for prokaryotic protein expression and purification. PMID:24613729

  15. Affinity chromatography for purification of two urokinases from human urine.

    PubMed

    Takahashi, R; Akiba, K; Koike, M; Noguchi, T; Ezure, Y

    2000-05-26

    A new affinity chromatography (hydrophobic-mediated affinity chromatography), which was characterized by the matrix having both affinity site to urokinase and hydrophobic site, was established for the purification of urokinase from human urine. The hydrophobic affinity matrix (tentatively named PAS in the text) was prepared by immobilizing 6-aminocaproic acid on Sepharose CL-6B, followed by a coupling p-aminobenzamidine to a part of the hydrophobic site on the matrix. The PAS matrix was applied to the purification of urokinase from human urine, and high- and low-molecular weight pure urokinases were efficiently obtained in high yield by the present method. PMID:10892585

  16. Predicting Stability Constants for Uranyl Complexes Using Density Functional Theory

    DOE PAGES

    Vukovic, Sinisa; Hay, Benjamin P.; Bryantsev, Vyacheslav S.

    2015-04-02

    The ability to predict the equilibrium constants for the formation of 1:1 uranyl:ligand complexes (log K1 values) provides the essential foundation for the rational design of ligands with enhanced uranyl affinity and selectivity. We also use density functional theory (B3LYP) and the IEFPCM continuum solvation model to compute aqueous stability constants for UO22+ complexes with 18 donor ligands. Theoretical calculations permit reasonably good estimates of relative binding strengths, while the absolute log K1 values are significantly overestimated. Accurate predictions of the absolute log K1 values (root mean square deviation from experiment < 1.0 for log K1 values ranging from 0more » to 16.8) can be obtained by fitting the experimental data for two groups of mono and divalent negative oxygen donor ligands. The utility of correlations is demonstrated for amidoxime and imide dioxime ligands, providing a useful means of screening for new ligands with strong chelate capability to uranyl.« less

  17. Predicting Stability Constants for Uranyl Complexes Using Density Functional Theory

    SciTech Connect

    Vukovic, Sinisa; Hay, Benjamin P.; Bryantsev, Vyacheslav S.

    2015-04-02

    The ability to predict the equilibrium constants for the formation of 1:1 uranyl:ligand complexes (log K1 values) provides the essential foundation for the rational design of ligands with enhanced uranyl affinity and selectivity. We also use density functional theory (B3LYP) and the IEFPCM continuum solvation model to compute aqueous stability constants for UO22+ complexes with 18 donor ligands. Theoretical calculations permit reasonably good estimates of relative binding strengths, while the absolute log K1 values are significantly overestimated. Accurate predictions of the absolute log K1 values (root mean square deviation from experiment < 1.0 for log K1 values ranging from 0 to 16.8) can be obtained by fitting the experimental data for two groups of mono and divalent negative oxygen donor ligands. The utility of correlations is demonstrated for amidoxime and imide dioxime ligands, providing a useful means of screening for new ligands with strong chelate capability to uranyl.

  18. Fundamental Constants and Tests with Simple Atoms

    NASA Astrophysics Data System (ADS)

    Tan, Joseph

    2015-05-01

    Precise measurements with simple atoms provide stringent tests of physical laws, improving the accuracy of fundamental constants--a set of which will be selected to fully define the proposed New International System of Units. This talk focuses on the atomic constants (namely, the Rydberg constant, the fine-structure constant, and the proton charge radius), discussing the impact of the proton radius obtained from the Lamb-shift measurements in muonic hydrogen. Significant discrepancies persist despite years of careful examination: the slightly smaller proton radius obtained from muonic hydrogen requires the Rydberg constant and the fine-structure constant to have values that disagree significantly with the CODATA recommendations. After giving a general overview, I will discuss our effort to produce one-electron ions in Rydberg states, to enable a different test of theory and measurement of the Rydberg constant.

  19. Using the concept of transient complex for affinity predictions in CAPRI rounds 20-27 and beyond.

    PubMed

    Qin, Sanbo; Zhou, Huan-Xiang

    2013-12-01

    Predictions of protein-protein binders and binding affinities have traditionally focused on features pertaining to the native complexes. In developing a computational method for predicting protein-protein association rate constants, we introduced the concept of transient complex after mapping the interaction energy surface. The transient complex is located at the outer boundary of the bound-state energy well, having near-native separation and relative orientation between the subunits but not yet formed most of the short-range native interactions. We found that the width of the binding funnel and the electrostatic interaction energy of the transient complex are among the features predictive of binders and binding affinities. These ideas were very promising for the five affinity-related targets (T43-45, 55, and 56) of CAPRI rounds 20-27. For T43, we ranked the single crystallographic complex as number 1 and were one of only two groups that clearly identified that complex as a true binder; for T44, we ranked the only design with measurable binding affinity as number 4. For the nine docking targets, continuing on our success in previous CAPRI rounds, we produced 10 medium-quality models for T47 and acceptable models for T48 and T49. We conclude that the interaction energy landscape and the transient complex in particular will complement existing features in leading to better prediction of binding affinities.

  20. Prediction and analysis of canonical EF hand loop and qualitative estimation of Ca²⁺ binding affinity.

    PubMed

    Mazumder, Mohit; Padhan, Narendra; Bhattacharya, Alok; Gourinath, Samudrala

    2014-01-01

    The diversity of functions carried out by EF hand-containing calcium-binding proteins is due to various interactions made by these proteins as well as the range of affinity levels for Ca²⁺ displayed by them. However, accurate methods are not available for prediction of binding affinities. Here, amino acid patterns of canonical EF hand sequences obtained from available crystal structures were used to develop a classifier that distinguishes Ca²⁺-binding loops and non Ca²⁺-binding regions with 100% accuracy. To investigate further, we performed a proteome-wide prediction for E. histolytica, and classified known EF-hand proteins. We compared our results with published methods on the E. histolytica proteome scan, and demonstrated our method to be more specific and accurate for predicting potential canonical Ca²⁺-binding loops. Furthermore, we annotated canonical EF-hand motifs and classified them based on their Ca²⁺-binding affinities using support vector machines. Using a novel method generated from position-specific scoring metrics and then tested against three different experimentally derived EF-hand-motif datasets, predictions of Ca²⁺-binding affinities were between 87 and 90% accurate. Our results show that the tool described here is capable of predicting Ca²⁺-binding affinity constants of EF-hand proteins.

  1. 112 Gb/s PM-QPSK transmission up to 6000 km with 200 km amplifier spacing and a hybrid fiber span configuration.

    PubMed

    Downie, John D; Hurley, Jason; Cartledge, John; Bickham, Scott; Mishra, Snigdharaj

    2011-12-12

    We demonstrate transmission of 112 Gb/s PM-QPSK signals over a system with 200 km span lengths. Amplification is provided by hybrid backward-pumped Raman/EDFA amplifiers and reach lengths up to 6000 km for an 8 channel system and 5400 km for a 32 channel system are shown. As a means of maximizing OSNR, a simple hybrid fiber span configuration is used that combines two ultra-low loss fibers, one having very large effective area.

  2. Choline uptake in Agrobacterium tumefaciens by the high-affinity ChoXWV transporter.

    PubMed

    Aktas, Meriyem; Jost, Kathinka A; Fritz, Christiane; Narberhaus, Franz

    2011-10-01

    Agrobacterium tumefaciens is a facultative phytopathogen that causes crown gall disease. For successful plant transformation A. tumefaciens requires the membrane lipid phosphatidylcholine (PC), which is produced via the methylation and the PC synthase (Pcs) pathways. The latter route is dependent on choline. Although choline uptake has been demonstrated in A. tumefaciens, the responsible transporter(s) remained elusive. In this study, we identified the first choline transport system in A. tumefaciens. The ABC-type choline transporter is encoded by the chromosomally located choXWV operon (ChoX, binding protein; ChoW, permease; and ChoV, ATPase). The Cho system is not critical for growth and PC synthesis. However, [14C]choline uptake is severely reduced in A. tumefaciens choX mutants. Recombinant ChoX is able to bind choline with high affinity (equilibrium dissociation constant [KD] of ≈2 μM). Since other quaternary amines are bound by ChoX with much lower affinities (acetylcholine, KD of ≈80 μM; betaine, KD of ≈470 μM), the ChoXWV system functions as a high-affinity transporter with a preference for choline. Two tryptophan residues (W40 and W87) located in the predicted ligand-binding pocket are essential for choline binding. The structural model of ChoX built on Sinorhizobium meliloti ChoX resembles the typical structure of substrate binding proteins with a so-called "Venus flytrap mechanism" of substrate binding. PMID:21803998

  3. Probing high-affinity 11-mer DNA aptamer against Lup an 1 (β-conglutin).

    PubMed

    Nadal, P; Svobodova, M; Mairal, T; O'Sullivan, C K

    2013-11-01

    Aptamers are synthetic nucleic acids with great potential as analytical tools. However, the length of selected aptamers (typically 60-100 bases) can affect affinity, due to the presence of bases not required for interaction with the target, and therefore, the truncation of these selected sequences and identification of binding domains is a critical step to produce potent aptamers with higher affinities and specificities and lowered production costs. In this paper we report the truncation of an aptamer that specifically binds to β-conglutin (Lup an 1), an anaphylactic allergen. Through comparing the predicted secondary structures of the aptamers, a hairpin structure with a G-rich loop was determined to be the binding motif. The highest affinity was observed with a truncation resulting in an 11-mer sequence that had an apparent equilibrium dissociation constant (K D) of 1.7 × 10(-9) M. This 11-mer sequence was demonstrated to have high specificity for β-conglutin and showed no cross-reactivity to other lupin conglutins (α-, δ-, γ-conglutins) and closely related proteins such as gliadin. Finally, the structure of the truncated 11-mer aptamer was preliminarily elucidated, and the GQRS Mapper strongly predicted the presence of a G-quadruplex, which was subsequently corroborated using one-dimensional NMR, thus highlighting the stability of the truncated structure. PMID:24126837

  4. The high-affinity peptidoglycan binding domain of Pseudomonas phage endolysin KZ144

    SciTech Connect

    Briers, Yves; Schmelcher, Mathias; Loessner, Martin J.; Hendrix, Jelle; Engelborghs, Yves; Volckaert, Guido; Lavigne, Rob

    2009-05-29

    The binding affinity of the N-terminal peptidoglycan binding domain of endolysin KZ144 (PBD{sub KZ}), originating from Pseudomonas aeruginosa bacteriophage {phi}KZ, has been examined using a fusion protein of PBD{sub KZ} and green fluorescent protein (PBD{sub KZ}-GFP). A fluorescence recovery after photobleaching analysis of bound PBD{sub KZ}-GFP molecules showed less than 10% fluorescence recovery in the bleached area within 15 min. Surface plasmon resonance analysis confirmed this apparent high binding affinity revealing an equilibrium affinity constant of 2.95 x 10{sup 7} M{sup -1} for the PBD{sub KZ}-peptidoglycan interaction. This unique domain, which binds to the peptidoglycan of all tested Gram-negative species, was harnessed to improve the specific activity of the peptidoglycan hydrolase domain KMV36C. The chimeric peptidoglycan hydrolase (PBD{sub KZ}-KMV36C) exhibits a threefold higher specific activity than the native catalytic domain (KMV36C). These results demonstrate that the modular assembly of functional domains is a rational approach to improve the specific activity of endolysins from phages infecting Gram-negatives.

  5. Complementary metal oxide semiconductor-compatible silicon nanowire biofield-effect transistors as affinity biosensors.

    PubMed

    Duan, Xuexin; Rajan, Nitin K; Izadi, Mohammad Hadi; Reed, Mark A

    2013-11-01

    Affinity biosensors use biorecognition elements and transducers to convert a biochemical event into a recordable signal. They provides the molecule binding information, which includes the dynamics of biomolecular association and dissociation, and the equilibrium association constant. Complementary metal oxide semiconductor-compatible silicon (Si) nanowires configured as a field-effect transistor (NW FET) have shown significant advantages for real-time, label-free and highly sensitive detection of a wide range of biomolecules. Most research has focused on reducing the detection limit of Si-NW FETs but has provided less information about the real binding parameters of the biomolecular interactions. Recently, Si-NW FETs have been demonstrated as affinity biosensors to quantify biomolecular binding affinities and kinetics. They open new applications for NW FETs in the nanomedicine field and will bring such sensor technology a step closer to commercial point-of-care applications. This article summarizes the recent advances in bioaffinity measurement using Si-NW FETs, with an emphasis on the different approaches used to address the issues of sensor calibration, regeneration, binding kinetic measurements, limit of detection, sensor surface modification, biomolecule charge screening, reference electrode integration and nonspecific molecular binding.

  6. High-aluminum-affinity silica is a nanoparticle that seeds secondary aluminosilicate formation.

    PubMed

    Jugdaohsingh, Ravin; Brown, Andy; Dietzel, Martin; Powell, Jonathan J

    2013-01-01

    Despite the importance and abundance of aluminosilicates throughout our natural surroundings, their formation at neutral pH is, surprisingly, a matter of considerable debate. From our experiments in dilute aluminum and silica containing solutions (pH ~ 7) we previously identified a silica polymer with an extraordinarily high affinity for aluminium ions (high-aluminum-affinity silica polymer, HSP). Here, further characterization shows that HSP is a colloid of approximately 2.4 nm in diameter with a mean specific surface area of about 1,000 m(2) g(-1) and it competes effectively with transferrin for Al(III) binding. Aluminum binding to HSP strongly inhibited its decomposition whilst the reaction rate constant for the formation of the β-silicomolybdic acid complex indicated a diameter between 3.6 and 4.1 nm for these aluminum-containing nanoparticles. Similarly, high resolution microscopic analysis of the air dried aluminum-containing silica colloid solution revealed 3.9 ± 1.3 nm sized crystalline Al-rich silica nanoparticles (ASP) with an estimated Al:Si ratio of between 2 and 3 which is close to the range of secondary aluminosilicates such as imogolite. Thus the high-aluminum-affinity silica polymer is a nanoparticle that seeds early aluminosilicate formation through highly competitive binding of Al(III) ions. In niche environments, especially in vivo, this may serve as an alternative mechanism to polyhydroxy Al(III) species binding monomeric silica to form early phase, non-toxic aluminosilicates.

  7. Monoclonal IgM antibody exhibiting high-affinity binding and cryoglobulin properties.

    PubMed Central

    Ballard, D W; Kranz, D M; Voss, E W

    1983-01-01

    A monoclonal IgM antibody (18-2-3) derived from cell fusion of (NZB X NZW) F1 splenocytes following secondary immunization with fluorescein-conjugated keyhole limpet hemocyanin was shown to exhibit high intrinsic binding affinity and cryoinsolubility. Affinity-purified preparations were determined to be IgM by immunochemical, electrophoretic, and chromatographic analyses. An intrinsic association constant (Ka) of 2.9 X 10(10) M-1 (at 2 degrees C) was measured by first-order dissociation-rate analysis. Antibody solubility at low concentration (approximately equal to 50 micrograms/ml) was shown, by absorption spectroscopy, to be temperature dependent between 4 degrees C and 32 degrees C. Insolubility at low temperature (4 degrees C) was reversible in the presence of homologous fluorescyl hapten, indicative of active site involvement in the mechanism of cryoglobulin-18-2-3 complex formation. Characteristics of clone 18-2-3 are discussed in terms of (i) its potential use as a model for examining the mechanism of cryoprecipitation and (ii) the proposed relationship between affinity maturation and the IgM to IgG class switch. Images PMID:6348779

  8. A structure-based benchmark for protein-protein binding affinity.

    PubMed

    Kastritis, Panagiotis L; Moal, Iain H; Hwang, Howook; Weng, Zhiping; Bates, Paul A; Bonvin, Alexandre M J J; Janin, Joël

    2011-03-01

    We have assembled a nonredundant set of 144 protein-protein complexes that have high-resolution structures available for both the complexes and their unbound components, and for which dissociation constants have been measured by biophysical methods. The set is diverse in terms of the biological functions it represents, with complexes that involve G-proteins and receptor extracellular domains, as well as antigen/antibody, enzyme/inhibitor, and enzyme/substrate complexes. It is also diverse in terms of the partners' affinity for each other, with K(d) ranging between 10(-5) and 10(-14) M. Nine pairs of entries represent closely related complexes that have a similar structure, but a very different affinity, each pair comprising a cognate and a noncognate assembly. The unbound structures of the component proteins being available, conformation changes can be assessed. They are significant in most of the complexes, and large movements or disorder-to-order transitions are frequently observed. The set may be used to benchmark biophysical models aiming to relate affinity to structure in protein-protein interactions, taking into account the reactants and the conformation changes that accompany the association reaction, instead of just the final product.

  9. Enzyme activity assay of glycoprotein enzymes based on a boronate affinity molecularly imprinted 96-well microplate.

    PubMed

    Bi, Xiaodong; Liu, Zhen

    2014-12-16

    Enzyme activity assay is an important method in clinical diagnostics. However, conventional enzyme activity assay suffers from apparent interference from the sample matrix. Herein, we present a new format of enzyme activity assay that can effectively eliminate the effects of the sample matrix. The key is a 96-well microplate modified with molecularly imprinted polymer (MIP) prepared according to a newly proposed method called boronate affinity-based oriented surface imprinting. Alkaline phosphatase (ALP), a glycoprotein enzyme that has been routinely used as an indicator for several diseases in clinical tests, was taken as a representative target enzyme. The prepared MIP exhibited strong affinity toward the template enzyme (with a dissociation constant of 10(-10) M) as well as superb tolerance for interference. Thus, the enzyme molecules in a complicated sample matrix could be specifically captured and cleaned up for enzyme activity assay, which eliminated the interference from the sample matrix. On the other hand, because the boronate affinity MIP could well retain the enzymatic activity of glycoprotein enzymes, the enzyme captured by the MIP was directly used for activity assay. Thus, additional assay time and possible enzyme or activity loss due to an enzyme release step required by other methods were avoided. Assay of ALP in human serum was successfully demonstrated, suggesting a promising prospect of the proposed method in real-world applications.

  10. Weak affinity chromatography as a new approach for fragment screening in drug discovery.

    PubMed

    Duong-Thi, Minh-Dao; Meiby, Elinor; Bergström, Maria; Fex, Tomas; Isaksson, Roland; Ohlson, Sten

    2011-07-01

    Fragment-based drug design (FBDD) is currently being implemented in drug discovery, creating a demand for developing efficient techniques for fragment screening. Due to the intrinsic weak or transient binding of fragments (mM-μM in dissociation constant (K(D))) to targets, methods must be sensitive enough to accurately detect and quantify an interaction. This study presents weak affinity chromatography (WAC) as an alternative tool for screening of small fragments. The technology was demonstrated by screening of a selected 23-compound fragment collection of documented binders, mostly amidines, using trypsin and thrombin as model target protease proteins. WAC was proven to be a sensitive, robust, and reproducible technique that also provides information about affinity of a fragment in the range of 1 mM-10 μM. Furthermore, it has potential for high throughput as was evidenced by analyzing mixtures in the range of 10 substances by WAC-MS. The accessibility and flexibility of the technology were shown as fragment screening can be performed on standard HPLC equipment. The technology can further be miniaturized and adapted to the requirements of affinity ranges of the fragment library. All these features of WAC make it a potential method in drug discovery for fragment screening. PMID:21352794

  11. Analysis of Aged Human Serum Albumin Affinity for Doxazosin.

    PubMed

    Chudzik, Mariola; Równicka-Zubik, Joanna; Pożycka, Jadwiga; Pawelczak, Bartosz; Sulkowska, Anna

    2016-01-01

    Structural changes of human serum albumin (HSA) caused by old age and coexisting diseases result in differences in the binding of doxazosin (DOX). DOX is a postsynaptic α1- adrenoreceptor antagonist used for treatment of hypertension and benign prostatic hyperplasia. In elderly people suffering from various renal or hepatic diseases the significant portion of N-form of human serum albumin (normal) is converted to A-form (aged). The differences in binding of doxazosin to N- and Aform of albumin are an important factor, which may determines therapeutic dosage and toxicity of the test drug. To indicate these differences, the technique of fluorescence spectroscopy was used. The association constant (Ka) obtained from fluorescence quenching demonstrated that doxazosin has higher affinity for AHSA than for HSA. In order to describe the cooperativity in binding process, the values of the Hill's coefficient has been analysed. For DOX-HSA system (λex 295 nm) Hill's coefficient is close to 1 and it indicates that there is a single class of binding sites. For DOX-HSA (λex 275 nm) and DOX-AHSA (λex 275 nm and λex 295 nm) systems we observed positive cooperativity (nH>1). A greater red shift of fluorescence emission maximum of AHSA than HSA in the presence of DOX was observed. This suggests that the binding of DOX to AHSA was accompanied by a stronger increase in polarity around the fluorophores in comparison to HSA. The binding interaction between DOX and HSA has been also studied by molecular docking simulation.

  12. The effects of deionization processes on meteor radar diffusion coefficients below 90 km

    NASA Astrophysics Data System (ADS)

    Younger, J. P.; Lee, C. S.; Reid, I. M.; Vincent, R. A.; Kim, Y. H.; Murphy, D. J.

    2014-08-01

    The decay times of VHF radar echoes from underdense meteor trails are reduced in the lower portions of the meteor region. This is a result of plasma neutralization initiated by the attachment of positive trail ions to neutral atmospheric molecules. Decreased echo decay times cause meteor radars to produce erroneously high estimates of the ambipolar diffusion coefficient at heights below 90 km, which affects temperature estimation techniques. Comparisons between colocated radars and satellite observations show that meteor radar estimates of diffusion coefficients are not consistent with estimates from the Aura Microwave Limb Sounder satellite instrument and that colocated radars operating at different frequencies estimate different values of the ambipolar diffusion coefficient for simultaneous detections of the same meteors. Loss of free electrons from meteor trails due to attachment to aerosols and chemical processes were numerically simulated and compared with observations to determine the specific mechanism responsible for low-altitude meteor trail plasma neutralization. It is shown that three-body attachment of positive metal ions significantly reduces meteor radar echo decay times at low altitudes compared to the case of diffusion only that atmospheric ozone plays little part in the evolution of low-altitude underdense meteor trails and that the effect of three-body attachment begins to exceed diffusion in echo decay times at a constant density surface.

  13. Effect of receptor-ligand affinity on the strength of endothelial cell adhesion.

    PubMed Central

    Xiao, Y; Truskey, G A

    1996-01-01

    The objective of this study was to determine the effect of receptor-ligand affinity on the strength of endothelial cell adhesion. Linear and cyclic forms of the fibronectin (Fn) cell-binding domain peptide Arg-Gly-Asp (RGD) were covalently immobilized to glass, and Fn was adsorbed onto glass slides. Bovine aortic endothelial cells attached to the surfaces for 15 min. The critical wall shear stress at which 50% of the cells detached increased nonlinearly with ligand density and was greater with immobilized cyclic RGD than with immobilized linear RGD or adsorbed Fn. To directly compare results for the different ligand densities, the receptor-ligand dissociation constant and force per bond were estimated from data for the critical shear stress and contact area. Total internal reflection fluorescence microscopy was used to measure the contact area as a function of separation distance. Contact area increased with increasing ligand density. Contact areas were similar for the immobilized peptides but were greater on surfaces with adsorbed Fn. The dissociation constant was determined by nonlinear regression of the net force on the cells to models that assumed that bonds were either uniformly stressed or that only bonds on the periphery of the contact region were stressed (peeling model). Both models provided equally good fits for cells attached to immobilized peptides whereas the peeling model produced a better fit of data for cells attached to adsorbed Fn. Cyclic RGD and linear RGD both bind to the integrin alpha v beta 3, but immobilized cyclic RGD exhibited a greater affinity than did linear RGD. Receptor affinities of Fn adsorbed to glycophase glass and Fn adsorbed to glass were similar. The number of bonds was calculated assuming binding equilibrium. The peeling model produced good linear fits between bond force and number of bonds. Results of this study indicate that 1) bovine aortic endothelial cells are more adherent on immobilized cyclic RGD peptide than linear

  14. Affinity ligands for glycoprotein purification based on the multi-component Ugi reaction.

    PubMed

    Chen, Chen; Khoury, Graziella El; Lowe, Christopher R

    2014-10-15

    One challenge facing the purification of therapeutic glycoproteins by affinity chromatography is creating ligands specific for the glycan moiety. Affinity chromatography of glycoproteins is currently conducted with immobilized lectins or boronates, although biomimetic ligands could present a more desirable option. This work describes the rational design and combinatorial synthesis of carbohydrate-binding ligands based on the solid phase multi-component Ugi reaction. An aldehyde-functionalized Sepharose™ solid support constitutes one component (aldehyde) in the four-component reaction, while the other three components (a primary/secondary amine, a carboxylic acid and an isocyanide) are varied in a combinatorial fashion to generate a tri-substituted Ugi scaffold which provides a degree of rigidity and is functionally suitable for interacting with the glycan moiety of glycoproteins. An Ugi library containing 48 ligands was initially screened against glucose oxidase (GOx) as the model glycoprotein to identify a candidate ligand, A13C24I8, which showed affinity to GOx through its carbohydrate moiety. Immobilized ligand A13C24I8 demonstrated a static binding capacity of 16.7mg GOx/ml resin and an apparent dissociation constant (Kd) of 1.45×10(-6)M at pH 7.4. The adsorbent can also bind 8.1mg AGP/ml resin and displays an apparent affinity constant Kd=1.44×10(-5)M. The ligand has a sugar specificity in the following sequence: sorbitol>fructose>mannitol>ribose>arabinose>xylose>galactose>mannose>glucose>fructose; however, it did not display any specificity for sialic acid or methyl α-D-glycosides. A control ligand, generated by substitution of C24 (3-carboxyphenylboronic acid) with C7 (4-hydroxyphenyl acetic acid), failed to show affinity to the carbohydrate moiety, supporting the importance of the role that boronic acid group plays in sugar binding. GOx spiked E. coli samples were loaded onto immobilized ligand A13C24I8, 3-aminophenylboronic acid (APBA) and

  15. Affinity ligands for glycoprotein purification based on the multi-component Ugi reaction.

    PubMed

    Chen, Chen; Khoury, Graziella El; Lowe, Christopher R

    2014-10-15

    One challenge facing the purification of therapeutic glycoproteins by affinity chromatography is creating ligands specific for the glycan moiety. Affinity chromatography of glycoproteins is currently conducted with immobilized lectins or boronates, although biomimetic ligands could present a more desirable option. This work describes the rational design and combinatorial synthesis of carbohydrate-binding ligands based on the solid phase multi-component Ugi reaction. An aldehyde-functionalized Sepharose™ solid support constitutes one component (aldehyde) in the four-component reaction, while the other three components (a primary/secondary amine, a carboxylic acid and an isocyanide) are varied in a combinatorial fashion to generate a tri-substituted Ugi scaffold which provides a degree of rigidity and is functionally suitable for interacting with the glycan moiety of glycoproteins. An Ugi library containing 48 ligands was initially screened against glucose oxidase (GOx) as the model glycoprotein to identify a candidate ligand, A13C24I8, which showed affinity to GOx through its carbohydrate moiety. Immobilized ligand A13C24I8 demonstrated a static binding capacity of 16.7mg GOx/ml resin and an apparent dissociation constant (Kd) of 1.45×10(-6)M at pH 7.4. The adsorbent can also bind 8.1mg AGP/ml resin and displays an apparent affinity constant Kd=1.44×10(-5)M. The ligand has a sugar specificity in the following sequence: sorbitol>fructose>mannitol>ribose>arabinose>xylose>galactose>mannose>glucose>fructose; however, it did not display any specificity for sialic acid or methyl α-D-glycosides. A control ligand, generated by substitution of C24 (3-carboxyphenylboronic acid) with C7 (4-hydroxyphenyl acetic acid), failed to show affinity to the carbohydrate moiety, supporting the importance of the role that boronic acid group plays in sugar binding. GOx spiked E. coli samples were loaded onto immobilized ligand A13C24I8, 3-aminophenylboronic acid (APBA) and

  16. Ligand Affinities Estimated by Quantum Chemical Calculations.

    PubMed

    Söderhjelm, Pär; Kongsted, Jacob; Ryde, Ulf

    2010-05-11

    We present quantum chemical estimates of ligand-binding affinities performed, for the first time, at a level of theory for which there is a hope that dispersion and polarization effects are properly accounted for (MP2/cc-pVTZ) and at the same time effects of solvation, entropy, and sampling are included. We have studied the binding of seven biotin analogues to the avidin tetramer. The calculations have been performed by the recently developed PMISP approach (polarizable multipole interactions with supermolecular pairs), which treats electrostatic interactions by multipoles up to quadrupoles, induction by anisotropic polarizabilities, and nonclassical interactions (dispersion, exchange repulsion, etc.) by explicit quantum chemical calculations, using a fragmentation approach, except for long-range interactions that are treated by standard molecular-mechanics Lennard-Jones terms. In order to include effects of sampling, 10 snapshots from a molecular dynamics simulation are studied for each biotin analogue. Solvation energies are estimated by the polarized continuum model (PCM), coupled to the multipole-polarizability model. Entropy effects are estimated from vibrational frequencies, calculated at the molecular mechanics level. We encounter several problems, not previously discussed, illustrating that we are first to apply such a method. For example, the PCM model is, in the present implementation, questionable for large molecules, owing to the use of a surface definition that gives numerous small cavities in a protein. PMID:26615702

  17. Multiplexed protein profiling by sequential affinity capture

    PubMed Central

    Ayoglu, Burcu; Birgersson, Elin; Mezger, Anja; Nilsson, Mats; Uhlén, Mathias; Nilsson, Peter

    2016-01-01

    Antibody microarrays enable parallelized and miniaturized analysis of clinical samples, and have proven to provide novel insights for the analysis of different proteomes. However, there are concerns that the performance of such direct labeling and single antibody assays are prone to off‐target binding due to the sample context. To improve selectivity and sensitivity while maintaining the possibility to conduct multiplexed protein profiling, we developed a multiplexed and semi‐automated sequential capture assay. This novel bead‐based procedure encompasses a first antigen capture, labeling of captured protein targets on magnetic particles, combinatorial target elution and a read‐out by a secondary capture bead array. We demonstrate in a proof‐of‐concept setting that target detection via two sequential affinity interactions reduced off‐target contribution, while lowered background and noise levels, improved correlation to clinical values compared to single binder assays. We also compared sensitivity levels with single binder and classical sandwich assays, explored the possibility for DNA‐based signal amplification, and demonstrate the applicability of the dual capture bead‐based antibody microarray for biomarker analysis. Hence, the described concept enhances the possibilities for antibody array assays to be utilized for protein profiling in body fluids and beyond. PMID:26935855

  18. Affinity of guanosine derivatives for polycytidylate revisited

    NASA Technical Reports Server (NTRS)

    Kanavarioti, A.; Hurley, T. B.; Baird, E. E.

    1995-01-01

    Evidence is presented for complexation of guanosine 5'-monophosphate 2-methylimidazolide (2-MeImpG) with polycytidylate (poly(C)) at pH 8.0 and 23 degrees C in the presence of 1.0 M NaCl2 and 0.2 M MgCl2 in water. The association of 2-MeImpG with poly(C) was investigated using UV-vis spectroscopy as well as by monitoring the kinetics of the nucleophilic substitution reaction of the imidazole moiety by amines. The results of both methods are consistent with moderately strong poly(C) 2-MeImpG complexation and the spectrophotometric measurements allowed the construction of a binding isotherm with a concentration of 2-MeImpG equal to 5.55 +/- 0.15 mM at half occupancy. UV spectroscopy was employed to establish the binding of other guanosine derivatives on poly(C). These derivatives are guanosine 5'-monophosphate (5'GMP), guanosine 5'-monophosphate imidazolide (ImpG), and guanosine 5'-monophosphate morpholidate (morpG). Within experimental error these guanosine derivatives exhibit the same affinity for poly(C) as 2-MeImpG.

  19. Prostate Cancer and Bone: The Elective Affinities

    PubMed Central

    2014-01-01

    The onset of metastases dramatically changes the prognosis of prostate cancer patients, determining increased morbidity and a drastic fall in survival expectancy. Bone is a common site of metastases in few types of cancer, and it represents the most frequent metastatic site in prostate cancer. Of note, the prevalence of tumor relapse to the bone appears to be increasing over the years, likely due to a longer overall survival of prostate cancer patients. Bone tropism represents an intriguing challenge for researchers also because the preference of prostate cancer cells for the bone is the result of a sequential series of targetable molecular events. Many factors have been associated with the peculiar ability of prostate cancer cells to migrate in bone marrow and to determine mixed osteoblastic/osteolytic lesions. As anticipated by the success of current targeted therapy aimed to block bone resorption, a better understanding of molecular affinity between prostate cancer and bone microenvironment will permit us to cure bone metastasis and to improve prognosis of prostate cancer patients. PMID:24971315

  20. The neonatal Fc receptor (FcRn) binds independently to both sites of the IgG homodimer with identical affinity

    PubMed Central

    Abdiche, Yasmina Noubia; Yeung, Yik Andy; Chaparro-Riggers, Javier; Barman, Ishita; Strop, Pavel; Chin, Sherman Michael; Pham, Amber; Bolton, Gary; McDonough, Dan; Lindquist, Kevin; Pons, Jaume; Rajpal, Arvind

    2015-01-01

    The neonatal Fc receptor (FcRn) is expressed by cells of epithelial, endothelial and myeloid lineages and performs multiple roles in adaptive immunity. Characterizing the FcRn/IgG interaction is fundamental to designing therapeutic antibodies because IgGs with moderately increased binding affinities for FcRn exhibit superior serum half-lives and efficacy. It has been hypothesized that 2 FcRn molecules bind an IgG homodimer with disparate affinities, yet their affinity constants are inconsistent across the literature. Using surface plasmon resonance biosensor assays that eliminated confounding experimental artifacts, we present data supporting an alternate hypothesis: 2 FcRn molecules saturate an IgG homodimer with identical affinities at independent sites, consistent with the symmetrical arrangement of the FcRn/Fc complex observed in the crystal structure published by Burmeister et al. in 1994. We find that human FcRn binds human IgG1 with an equilibrium dissociation constant (KD) of 760 ± 60 nM (N = 14) at 25°C and pH 5.8, and shows less than 25% variation across the other human subtypes. Human IgG1 binds cynomolgus monkey FcRn with a 2-fold higher affinity than human FcRn, and binds both mouse and rat FcRn with a 10-fold higher affinity than human FcRn. FcRn/IgG interactions from multiple species show less than a 2-fold weaker affinity at 37°C than at 25°C and appear independent of an IgG's variable region. Our in vivo data in mouse and rat models demonstrate that both affinity and avidity influence an IgG's serum half-life, which should be considered when choosing animals, especially transgenic systems, as surrogates. PMID:25658443

  1. Striving for Empathy: Affinities, Alliances and Peer Sexuality Educators

    ERIC Educational Resources Information Center

    Fields, Jessica; Copp, Martha

    2015-01-01

    Peer sexuality educators' accounts of their work reveal two approaches to empathy with their students: affinity and alliance. "Affinity-based empathy" rests on the idea that the more commonalities sexuality educators and students share (or perceive they share), the more they will be able to empathise with one another, while…

  2. Tending to Change: Toward a Situated Model of Affinity Spaces

    ERIC Educational Resources Information Center

    Bommarito, Dan

    2014-01-01

    The concept of affinity spaces, a theoretical construct used to analyze literate activity from a spatial perspective, has gained popularity among scholars of literacy studies and, particularly, video-game studies. This article seeks to expand current notions of affinity spaces by identifying key assumptions that have limited researchers'…

  3. High affinity retinoic acid receptor antagonists: analogs of AGN 193109.

    PubMed

    Johnson, A T; Wang, L; Gillett, S J; Chandraratna, R A

    1999-02-22

    A series of high affinity retinoic acid receptor (RAR) antagonists were prepared based upon the known antagonist AGN 193109 (2). Introduction of various phenyl groups revealed a preference for substitution at the para-position relative to the meta-site. Antagonists with the highest affinities for the RARs possessed hydrophobic groups, however, the presence of polar functionality was also well tolerated.

  4. Emergent cosmological constant from colliding electromagnetic waves

    SciTech Connect

    Halilsoy, M.; Mazharimousavi, S. Habib; Gurtug, O. E-mail: habib.mazhari@emu.edu.tr

    2014-11-01

    In this study we advocate the view that the cosmological constant is of electromagnetic (em) origin, which can be generated from the collision of em shock waves coupled with gravitational shock waves. The wave profiles that participate in the collision have different amplitudes. It is shown that, circular polarization with equal amplitude waves does not generate cosmological constant. We also prove that the generation of the cosmological constant is related to the linear polarization. The addition of cross polarization generates no cosmological constant. Depending on the value of the wave amplitudes, the generated cosmological constant can be positive or negative. We show additionally that, the collision of nonlinear em waves in a particular class of Born-Infeld theory also yields a cosmological constant.

  5. Effective elastic constants of polycrystalline aggregates

    NASA Astrophysics Data System (ADS)

    Bonilla, Luis L.

    A METHOD is presented for the determination of the effective elastic constants of a transversely isotropic aggregate of weakly anisotropic crystallites with cubic symmetry. The results obtained generalize those given in the literature for the second and third order elastic constants. In addition, the second moments and the binary angular correlations of the second order stiffnesses are obtained. It is also explained how these moments can be used to find the two-point correlations of the elastic constants.

  6. Constant voltage electro-slag remelting control

    DOEpatents

    Schlienger, Max E.

    1996-01-01

    A system for controlling electrode gap in an electro-slag remelt furnace has a constant regulated voltage and an eletrode which is fed into the slag pool at a constant rate. The impedance of the circuit through the slag pool is directly proportional to the gap distance. Because of the constant voltage, the system current changes are inversely proportional to changes in gap. This negative feedback causes the gap to remain stable.

  7. Constant voltage electro-slag remelting control

    DOEpatents

    Schlienger, M.E.

    1996-10-22

    A system for controlling electrode gap in an electro-slag remelt furnace has a constant regulated voltage and an electrode which is fed into the slag pool at a constant rate. The impedance of the circuit through the slag pool is directly proportional to the gap distance. Because of the constant voltage, the system current changes are inversely proportional to changes in gap. This negative feedback causes the gap to remain stable. 1 fig.

  8. Affinity Regulates Spatial Range of EGF Receptor Autocrine Ligand Binding

    SciTech Connect

    Dewitt, Ann; Iida, Tomoko; Lam, Ho-Yan; Hill, Virginia; Wiley, H S.; Lauffenburger, Douglas A.

    2002-08-08

    Proper spatial localization of EGFR signaling activated by autocrine ligands represents a critical factor in embryonic development as well as tissue organization and function, and ligand/receptor binding affinity is among the molecular and cellular properties suggested to play a role in governing this localization. The authors employ a computational model to predict how receptor-binding affinity affects local capture of autocrine ligand vis-a-vis escape to distal regions, and provide experimental test by constructing cell lines expressing EGFR along with either wild-type EGF or a low-affinity mutant, EGF{sup L47M}. The model predicts local capture of a lower affinity autocrine ligand to be less efficient when the ligand production rate is small relative to receptor appearance rate. The experimental data confirm this prediction, demonstrating that cells can use ligand/receptor binding affinity to regulate ligand spatial distribution when autocrine ligand production is limiting for receptor signaling.

  9. Detection of protein-protein interactions using tandem affinity purification.

    PubMed

    Goodfellow, Ian; Bailey, Dalan

    2014-01-01

    Tandem affinity purification (TAP) is an invaluable technique for identifying interaction partners for an affinity tagged bait protein. The approach relies on the fusion of dual tags to the bait before separate rounds of affinity purification and precipitation. Frequently two specific elution steps are also performed to increase the specificity of the overall technique. In the method detailed here, the two tags used are protein G and a short streptavidin binding peptide; however, many variations can be employed. In our example the tags are separated by a cleavable tobacco etch virus protease target sequence, allowing for specific elution after the first round of affinity purification. Proteins isolated after the final elution step in this process are concentrated before being identified by mass spectrometry. The use of dual affinity tags and specific elution in this technique dramatically increases both the specificity and stringency of the pull-downs, ensuring a low level of background nonspecific interactions.

  10. Affinity Monolith-Integrated Microchips for Protein Purification and Concentration.

    PubMed

    Gao, Changlu; Sun, Xiuhua; Wang, Huaixin; Qiao, Wei; Hu, Bo

    2016-01-01

    Affinity chromatography is a valuable method to purify and concentrate minute amount of proteins. Monoliths with epoxy groups for affinity immobilization were prepared by direct in-situ photopolymerization of glycidyl methacrylate and ethylene glycol dimethacrylate in porogenic solvents consisting of 1-dodecanol and cyclohexanol. By integrating affinity monoliths onto a microfluidic system, targeted biomolecules can be captured and retained on affinity column, while other biomolecules having no specific interactions toward the immobilized ligands flow through the microchannel. Therefore, proteins which remain on the affinity column are purified and concentrated, and then eluted by appropriate solutions and finally, separated by microchip capillary electrophoresis. This integrated microfluidic device has been applied to the purification and separation of specific proteins (FITC-labeled human serum albumin and IgG) in a mixture.

  11. Affinity based information diffusion model in social networks

    NASA Astrophysics Data System (ADS)

    Liu, Hongli; Xie, Yun; Hu, Haibo; Chen, Zhigao

    2014-12-01

    There is a widespread intuitive sense that people prefer participating in spreading the information in which they are interested. The affinity of people with information disseminated can affect the information propagation in social networks. In this paper, we propose an information diffusion model incorporating the mechanism of affinity of people with information which considers the fitness of affinity values of people with affinity threshold of the information. We find that the final size of information diffusion is affected by affinity threshold of the information, average degree of the network and the probability of people's losing their interest in the information. We also explore the effects of other factors on information spreading by numerical simulations and find that the probabilities of people's questioning and confirming the information can affect the propagation speed, but not the final scope.

  12. Affinity Monolith-Integrated Microchips for Protein Purification and Concentration.

    PubMed

    Gao, Changlu; Sun, Xiuhua; Wang, Huaixin; Qiao, Wei; Hu, Bo

    2016-01-01

    Affinity chromatography is a valuable method to purify and concentrate minute amount of proteins. Monoliths with epoxy groups for affinity immobilization were prepared by direct in-situ photopolymerization of glycidyl methacrylate and ethylene glycol dimethacrylate in porogenic solvents consisting of 1-dodecanol and cyclohexanol. By integrating affinity monoliths onto a microfluidic system, targeted biomolecules can be captured and retained on affinity column, while other biomolecules having no specific interactions toward the immobilized ligands flow through the microchannel. Therefore, proteins which remain on the affinity column are purified and concentrated, and then eluted by appropriate solutions and finally, separated by microchip capillary electrophoresis. This integrated microfluidic device has been applied to the purification and separation of specific proteins (FITC-labeled human serum albumin and IgG) in a mixture. PMID:27473483

  13. Metal-Mediated Affinity and Orientation Specificity in a Computationally Designed Protein Homodimer

    SciTech Connect

    Der, Bryan S.; Machius, Mischa; Miley, Michael J.; Mills, Jeffrey L.; Szyperski, Thomas; Kuhlman, Brian

    2015-10-15

    Computationally designing protein-protein interactions with high affinity and desired orientation is a challenging task. Incorporating metal-binding sites at the target interface may be one approach for increasing affinity and specifying the binding mode, thereby improving robustness of designed interactions for use as tools in basic research as well as in applications from biotechnology to medicine. Here we describe a Rosetta-based approach for the rational design of a protein monomer to form a zinc-mediated, symmetric homodimer. Our metal interface design, named MID1 (NESG target ID OR37), forms a tight dimer in the presence of zinc (MID1-zinc) with a dissociation constant <30 nM. Without zinc the dissociation constant is 4 {micro}M. The crystal structure of MID1-zinc shows good overall agreement with the computational model, but only three out of four designed histidines coordinate zinc. However, a histidine-to-glutamate point mutation resulted in four-coordination of zinc, and the resulting metal binding site and dimer orientation closely matches the computational model (C{alpha} rmsd = 1.4 {angstrom}).

  14. Influence of length and flexibility of spacers on the binding affinity of divalent ligands.

    PubMed

    Liese, Susanne; Netz, Roland R

    2015-01-01

    We present a quantitative model for the binding of divalent ligand-receptor systems. We study the influence of length and flexibility of the spacers on the overall binding affinity and derive general rules for the optimal ligand design. To this end, we first compare different polymeric models and determine the probability to simultaneously bind to two neighboring receptor binding pockets. In a second step the binding affinity of divalent ligands in terms of the IC50 value is derived. We find that a divalent ligand has the potential to bind more efficiently than its monovalent counterpart only, if the monovalent dissociation constant is lower than a critical value. This critical monovalent dissociation constant depends on the ligand-spacer length and flexibility as well as on the size of the receptor. Regarding the optimal ligand-spacer length and flexibility, we find that the average spacer length should be equal or slightly smaller than the distance between the receptor binding pockets and that the end-to-end spacer length fluctuations should be in the same range as the size of a receptor binding pocket.

  15. Influence of length and flexibility of spacers on the binding affinity of divalent ligands

    PubMed Central

    Liese, Susanne

    2015-01-01

    Summary We present a quantitative model for the binding of divalent ligand–receptor systems. We study the influence of length and flexibility of the spacers on the overall binding affinity and derive general rules for the optimal ligand design. To this end, we first compare different polymeric models and determine the probability to simultaneously bind to two neighboring receptor binding pockets. In a second step the binding affinity of divalent ligands in terms of the IC50 value is derived. We find that a divalent ligand has the potential to bind more efficiently than its monovalent counterpart only, if the monovalent dissociation constant is lower than a critical value. This critical monovalent dissociation constant depends on the ligand-spacer length and flexibility as well as on the size of the receptor. Regarding the optimal ligand-spacer length and flexibility, we find that the average spacer length should be equal or slightly smaller than the distance between the receptor binding pockets and that the end-to-end spacer length fluctuations should be in the same range as the size of a receptor binding pocket. PMID:26124882

  16. Enhancing ligand-protein binding in affinity thermoprecipitation: elucidation of spacer effects

    PubMed

    Vaidya; Lele; Kulkarni; Mashelkar

    1999-08-20

    Copolymers of N-isopropylacrylamide and N-acryloyl amino acid spacers of varying chain length were synthesized. p-Aminobenzamidine (PABA) was chemically linked to the pendant carboxyl groups of these polymers to obtain thermoprecipitating affinity polymers. The inhibition constant (Ki) of these polymers for trypsin decreased, i. e., the efficiency of PABA-trypsin binding increased with increase in the spacer chain length. The polymer to which PABA was linked through a spacer of five methylene groups exhibited eleven times lower Ki than that of the polymer containing PABA without a spacer. Investigations on model inhibitors N-acyl-p-aminobenzamidines showed that this enhancement in trypsin binding by the polymers was due to the spacer as well as to microenvironmental effects. Recovery and specific activity of the trypsin recovered increased with the spacer chain length. Separation of trypsin from a mixture of trypsin and chymotrypsin was also enhanced with the spacer chain length. The inhibition constants of these affinity polymers were not adversely affected by the crowding effect. Copyright 1999 John Wiley & Sons, Inc. PMID:10397880

  17. Chromium(VI) but not chromium(III) species decrease mitoxantrone affinity to DNA.

    PubMed

    Nowicka, Anna M; Stojek, Zbigniew; Hepel, Maria

    2013-01-31

    Binding of mitoxantrone (MXT) to double-stranded DNA has been investigated as a model drug-DNA binding system to evaluate the effects of various forms of chromium on the binding properties. We have found that Cr(III), which binds strongly to DNA, does not affect the MXT affinity to DNA. In contrast, Cr(VI), in the form of chromate ions CrO(4)(2-), decreases the MXT affinity to DNA despite electrostatic repulsions with phosphate-deoxyribose chains of DNA. The MXT-DNA binding constant was found to decrease from (1.96 ± 0.005) × 10(5) to (0.77 ± 0.018) × 10(5) M(-1) for Cr(VI) concentration changing from 0 to 30 μM. The influence of Cr(VI) on MXT-DNA binding has been attributed to the oxidation of guanine residue, thus interrupting the intercalation of MXT into the DNA double helix at the preferential CpG intercalation site. This supposition is corroborated by the observed increase in the MXT binding site size from 2 bp (base pairs) to 4-6 bp in the presence of Cr(VI). The measurements of the MXT-DNA binding constant and the MXT binding site size on a DNA molecule have been carried out using spectroscopic, voltammetric, and nanogravimetric techniques, providing useful information on the mechanism of the interactions.

  18. ANALYSIS OF DRUG INTERACTIONS WITH VERY LOW DENSITY LIPOPROTEIN BY HIGH PERFORMANCE AFFINITY CHROMATOGRAPHY

    PubMed Central

    Sobansky, Matthew R.; Hage, David S.

    2014-01-01

    High-performance affinity chromatography (HPAC) was utilized to examine the binding of very low density lipoprotein (VLDL) with drugs, using R/S-propranolol as a model. These studies indicated that two mechanisms existed for the binding of R- and S-propranolol with VLDL. The first mechanism involved non-saturable partitioning of these drugs with VLDL, which probably occurred with the lipoprotein's non-polar core. This partitioning was described by overall affinity constants of 1.2 (± 0.3) × 106 M-1 for R-propranolol and 2.4 (± 0.6) × 106 M-1 for S-propranolol at pH 7.4 and 37 °C. The second mechanism occurred through saturable binding by these drugs at fixed sites on VLDL, such as represented by apolipoproteins on the surface of the lipoprotein. The association equilibrium constants for this saturable binding at 37 °C were 7.0 (± 2.3) × 104 M-1 for R-propranolol and 9.6 (± 2.2) × 104 M-1 for S-propranolol. Comparable results were obtained at 20 °C and 27 °C for the propranolol enantiomers. This work provided fundamental information on the processes involved in the binding of R- and S-propranolol to VLDL, while also illustrating how HPAC can be used to evaluate relatively complex interactions between agents such as VLDL and drugs or other solutes. PMID:25103529

  19. Modification of the characteristic gravitational constants

    NASA Astrophysics Data System (ADS)

    Vujičić, V. A.

    2006-08-01

    In the educational and scientific literature the numerical values of gravitational constants are seen as only approximately correct. The numerical values are different in work by various researchers, as also are the formulae and definitions of constants employed. In this paper, on the basis of Newton’s laws and Kepler’s laws we prove that it is necessary to modify the characteristic gravitational constants and their definitions. The formula for the geocentric gravitational constant of the satellites Kosmos N and the Moon are calculated.

  20. The serotonin transporter: Examination of the changes in transporter affinity induced by ligand binding

    SciTech Connect

    Humphreys, C.J.

    1989-01-01

    The plasmalemmal serotonin transporter uses transmembrane gradients of Na{sup +}, Cl{sup {minus}} and K{sup +} to accumulate serotonin within blood platelets. Transport is competitively inhibited by the antidepressant imipramine. Like serotonin transport, imipramine binding requires Na{sup +}. Unlike serotonin, however, imipramine does not appear to be transported. To gain insight into the mechanism of serotonin transport the author have analyzed the influences of Na{sup +} and Cl{sup {minus}}, the two ions cotransported with serotonin, on both serotonin transport and the interaction of imipramine and other antidepressant drugs with the plasmalemmal serotonin transporter of human platelets. Additionally, the author have synthesized, purified and characterized the binding of 2-iodoimipramine to the serotonin transporter. Finally, the author have conducted a preliminary study of the inhibition of serotonin transport and imipramine binding produced by dicyclohexylcarbodiimide. My results reveal many instances of positive heterotropic cooperativity in ligand binding to the serotonin transporter. Na{sup +} binding enhances the transporters affinity for imipramine and several other antidepressant drugs, and also increases the affinity for Cl{sup {minus}}. Cl{sup {minus}} enhances the transporters affinity for imipramine, as well as for Na{sup +}. At concentrations in the range of its K{sub M} for transport serotonin is a competitive inhibitor of imipramine binding. At much higher concentrations, however, serotonin also inhibits imipramines dissociation rate constant. This latter effect which is Na{sup +}-independent and species specific, is apparently produced by serotonin binding at a second, low affinity site on, or near, the transporter complex. Iodoimipramine competitively inhibit both ({sup 3}H)imipramine binding and ({sup 3}H)serotonin transport.

  1. Mannosylerythritol lipid, a yeast extracellular glycolipid, shows high binding affinity towards human immunoglobulin G

    PubMed Central

    Im, Jae Hong; Nakane, Takashi; Yanagishita, Hiroshi; Ikegami, Toru; Kitamoto, Dai

    2001-01-01

    Background There have been many attempts to develop new materials with stability and high affinity towards immunoglobulins. Some of glycolipids such as gangliosides exhibit a high affinity toward immunoglobulins. However, it is considerably difficult to develop these glycolipids into the practical separation ligand due to their limited amounts. We thus focused our attention on the feasible use of "mannosylerythritol lipid A", a yeast glycolipid biosurfactant, as an alternative ligand for immunoglobulins, and undertook the investigation on the binding between mannosylerythritol lipid A (MEL-A) and human immunoglobulin G (HIgG). Results In ELISA assay, MEL-A showed nearly the same binding affinity towards HIgG as that of bovine ganglioside GM1. Fab of human IgG was considered to play a more important role than Fc in the binding of HIgG by MEL-A. The bound amount of HIgG increased depending on the attached amount of MEL-A onto poly (2-hydroxyethyl methacrylate) (polyHEMA) beads, whereas the amount of human serum albumin slightly decreased. Binding-amount and -selectivity of HIgG towards MEL-A were influenced by salt species, salt concentration and pH in the buffer solution. The composite of MEL-A and polyHEMA, exhibited a significant binding constant of 1.43 × 106 (M-1) for HIgG, which is approximately 4-fold greater than that of protein A reported. Conclusions MEL-A shows high binding-affinity towards HIgG, and this is considered to be due to "multivalent effect" based on the binding molar ratio. This is the first report on the binding of a natural human antibody towards a yeast glycolipid. PMID:11604104

  2. Enhanced antigen-antibody binding affinity mediated by an anti-idiotypic antibody

    SciTech Connect

    Sawutz, D.G.; Koury, R.; Homcy, C.J.

    1987-08-25

    The authors previously described the production of four monoclonal antibodies to the ..beta..-adrenergic receptor antagonist alprenolol. One of these antibodies, 5B7 (IgG/sub 2a/, kappa), was used to raise anti-idiotypic antisera in rabbits. In contrast to the expected results, one of the anti-idiotypic antisera (R9) promotes (/sup 125/I)iodocyanopinodolol (ICYP) binding to antibody 5B7. In the presence of R9, the dissociation constant decreases 100-fold from 20 to 0.3 nM. This increase in binding affinity of antibody 5B7 for ICYP is not observed in the presence of preimmune, rabbit anti-mouse or anti-idiotypic antisera generated to a monoclonal antibody of a different specificity. Furthermore, R9 in the absence of 5B7 does not bind ICYP. The F(ab) fragments of 5B7 and T9 behaved in a similar manner, and the soluble complex responsible for the high-affinity interaction with ICYP can be identified by gel filtration chromatography. The elution position of the complex is consistent with a 5B7 F(ab)-R9 F(ab) dimer, indicating that polyvalency is not responsible for the enhanced ligand binding. Kinetic analysis of ICYP-5B7 binding revealed that the rate of ICYP dissociation from 5B7 in the presence of R9 is approximately 100 times slower than in the absence of R9, consistent with the 100-fold change in binding affinity of 5B7 for ICYP. The available data best fit a model in which an anti-idiotypic antibody binds at or near the binding site of the idiotype participating in the formation of a hybrid ligand binding site. This would allow increased contact of the ligand with the idiotype-anti-idiotype complex and result in an enhanced affinity of the ligand interaction.

  3. Achieving high affinity towards a bacterial lectin through multivalent topological isomers of calix[4]arene glycoconjugates.

    PubMed

    Cecioni, Samy; Lalor, Ruth; Blanchard, Bertrand; Praly, Jean-Pierre; Imberty, Anne; Matthews, Susan E; Vidal, Sébastien

    2009-12-01

    A family of seven topologically isomeric calix[4]arene glycoconjugates was prepared through the synthesis of a series of alkyne-derivatised calix[4]arene precursors that are suitable for the attachment of sugar moieties by microwave-assisted copper(I)-catalysed azide-alkyne cycloaddition (CuAAC). The glycoconjugates thus synthesised comprised one mono-functionalised derivative, two 1,2- or 1,3-divalent regioisomers, one trivalent and three tetravalent topoisomers in the cone, partial cone or 1,3-alternate conformations. The designed glycoconjugates were evaluated as ligands for the galactose-binding lectin PA-IL from the opportunistic bacterium Pseudomonas aeruginosa, a major causative agent of lung infections in cystic fibrosis patients. Binding affinities were determined by isothermal titration calorimetry (ITC), and the interaction with the lectin was shown to be strongly dependant on both the valence and the topology. Whereas the trivalent conjugate displayed enhanced affinity when compared to a monosaccharide model, the tetravalent conjugates are to-date the highest-affinity ligands measured by ITC. The topologies presenting carbohydrates on both faces of calixarene are the most potent ones with dissociation constants of approximately 200 nM. Molecular modelling suggests that such a multivalent molecule can efficiently chelate two of the binding sites of the tetrameric lectin; this explains the 800-fold increase of affinity achieved by the tetravalent molecule. Surface plasmon resonance (SPR) experiments confirmed that this glycoconjugate is the strongest inhibitor for binding of PA-IL to galactosylated surfaces for potential applications as an anti-adhesive agent.

  4. Performance of dye-affinity beads for aluminium removal in magnetically stabilized fluidized bed

    PubMed Central

    Yavuz, Handan; Say, Ridvan; Andaç, Müge; Bayraktar, Necmi; Denizli, Adil

    2004-01-01

    Background Aluminum has recently been recognized as a causative agent in dialysis encephalopathy, osteodystrophy, and microcytic anemia occurring in patients with chronic renal failure who undergo long-term hemodialysis. Only a small amount of Al(III) in dialysis solutions may give rise to these disorders. Methods Magnetic poly(2-hydroxyethyl methacrylate) (mPHEMA) beads in the size range of 80–120 μm were produced by free radical co-polymerization of HEMA and ethylene dimethacrylate (EDMA) in the presence of magnetite particles (Fe3O4). Then, metal complexing ligand alizarin yellow was covalently attached onto mPHEMA beads. Alizarin yellow loading was 208 μmol/g. These beads were used for the removal of Al(III) ions from tap and dialysis water in a magnetically stabilized fluidized bed. Results Al(III) adsorption capacity of the beads decreased with an increase in the flow-rate. The maximum Al(III) adsorption was observed at pH 5.0. Comparison of batch and magnetically stabilized fluidized bed (MSFB) maximum capacities determined using Langmuir isotherms showed that dynamic capacity (17.5 mg/g) was somewhat higher than the batch capacity (11.8 mg/g). The dissociation constants for Al(III) were determined using the Langmuir isotherm equation to be 27.3 mM (MSFB) and 6.7 mM (batch system), indicating medium affinity, which was typical for pseudospecific affinity ligands. Al(III) ions could be repeatedly adsorbed and desorbed with these beads without noticeable loss in their Al(III) adsorption capacity. Conclusions Adsorption of Al(III) demonstrate the affinity of magnetic dye-affinity beads. The MSFB experiments allowed us to conclude that this inexpensive sorbent system may be an important alternative to the existing adsorbents in the removal of aluminium. PMID:15329149

  5. Chasing polys: Interdisciplinary affinity and its connection to physics identity

    NASA Astrophysics Data System (ADS)

    Scott, Tyler D.

    This research is based on two motivations that merge by means of the frameworks of interdisciplinary affinity and physics identity. First, a goal of education is to develop interdisciplinary abilities in students' thinking and work. But an often ignored factor is students interests and beliefs about being interdisciplinary. Thus, this work develops and uses a framework called interdisciplinary affinity. It encompasses students interests in making connections across disciplines and their beliefs about their abilities to make those connections. The second motivation of this research is to better understand how to engage more students with physics. Physics identity describes how a student sees themselves in relation to physics. By understanding how physics identity is developed, researchers and educators can identify factors that increase interest and engagement in physics classrooms. Therefore, physics identity was used in conjunction with interdisciplinary affinity. Using a mixed methods approach, this research used quantitative data to identify the relationships interdisciplinary affinity has with physics identity and the physics classroom. These connections were explored in more detail using a case study of three students in a high school physics class. Results showed significant and positive relationships between interdisciplinary affinity and physics identity, including the individual interest and recognition components of identity. It also identified characteristics of physics classrooms that had a significant, positive relationship with interdisciplinary affinity. The qualitative case study highlighted the importance of student interest to the relationship between interdisciplinary affinity and physics identity. It also identified interest and mastery orientation as key to understanding the link between interdisciplinary affinity and the physics classroom. These results are a positive sign that by understanding interdisciplinary affinity and physics identity

  6. Differences in affinity of cardiac beta-adrenergic receptors for (3H)dihydroalprenolol

    SciTech Connect

    Muntz, K.H.; Calianos, T.A.; Vandermolen, D.T.; Willerson, J.T.; Buja, L.M.

    1986-03-01

    We performed quantitative light microscopic autoradiography of (3H)dihydroalprenolol (DHA) binding to frozen sections of canine myocardium to test the hypothesis that there are differences in the density or affinity of beta-adrenergic receptors on various tissue compartments. In one study, with concentrations of (3H)DHA from 0.34 to 5.1 nM, specific binding to cardiac myocytes was saturable, whereas nonspecific binding was linear with ligand concentration. Arterioles had more specific grain counts than muscle cells (P less than 0.0001), and Scatchard analysis showed that the arterioles had a much higher affinity for (3H)DHA than myocytes. In a second study with lower concentrations of (3H)DHA (0.19-1.98 nM), binding to the arterioles saturated, whereas binding to the cardiac myocytes did not. Specific binding to arterioles was significantly higher (P less than 0.0001) than binding to myocytes at all concentrations of (3H)DHA. The dissociation constants for the subendocardial and subepicardial myocytes were 1.57 and 1.71 nM, respectively, while the dissociation constant for the arterioles was 0.26 nM. The maximum number of binding sites was 911 grains/0.9 X 10(-2) mm2 for subepicardial myocytes, 936 for subendocardial myocytes, and 986 for arterioles. The large nerves accompanying an epicardial artery also demonstrated specific (3H)DHA binding. Thus this study has demonstrated major differences in the distribution and affinity of beta-adrenergic receptors, which may help to explain various physiological responses to beta-adrenergic stimulation.

  7. Analysis of free drug fractions in serum by ultrafast affinity extraction and two-dimensional affinity chromatography using α1-acid glycoprotein microcolumns.

    PubMed

    Bi, Cong; Zheng, Xiwei; Hage, David S

    2016-02-01

    In the circulatory system, many drugs are reversibly bound to serum proteins such as human serum albumin (HSA) and alpha1-acid glycoprotein (AGP), resulting in both free and protein-bound fractions for these drugs. This report examined the use of microcolumns containing immobilized AGP for the measurement of free drug fractions by ultrafast affinity extraction and a two-dimensional affinity system. Several drugs known to bind AGP were used as models to develop and evaluate this approach. Factors considered during the creation of this method included the retention of the drugs on the microcolumns, the injection flow rate, the microcolumn size, and the times at which a second AGP column was placed on-line with the microcolumn. The final system had residence times of only 110-830ms during sample passage through the AGP microcolumns and allowed free drug fractions to be determined within 10-20min when using only 3-10μL of sample per injection. This method was used to measure the free fractions of the model drugs at typical therapeutic levels in serum, giving good agreement with the results obtained by ultrafiltration. This approach was also used to estimate the binding constants for each drug with AGP in serum, even for drugs that had significant interactions with both AGP and HSA in such samples. These results indicated that AGP microcolumns could be used with ultrafast affinity extraction to measure free drug fractions in a label-free manner and to study the binding of drugs with AGP in complex samples such as serum. PMID:26797422

  8. Enzyme-gold affinity labelling of cellulose.

    PubMed

    Berg, R H; Erdos, G W; Gritzali, M; Brown, R D

    1988-04-01

    The enzyme-linked colloidal gold affinity labelling technique was tested as a method to localize cellulose on thin sections of plant cell walls and slime mold spores. Commercially available cellulase from cultures of Trichoderma reesei, the main components being cellobiohydrolase I and II (CBH I, CBH II) and endoglucanase (EG), was linked to colloidal gold by using standard techniques and applied as a dilute, buffered suspension to thin sections. After brief exposure, e.g., 15-30 minutes, cellulose exposed on the surface of sections was labelled with the enzyme-gold complex. Poststaining did not appear to have a deleterious effect on the labelled sections. The specificity of labelling was demonstrated by its complete inhibition when carboxymethylcellulose was incorporated in the labelling mixture, by lack of labelling of 1,4-beta-mannans or 1,3-beta-xylans in noncellulosic walls of marine algae, by lack of labelling of 1,4-beta-glucans in chitin, by much lower labelling density when done at 4 degrees C, and by lack of labelling when sections were predigested with cellulase. Labelling with the crude commercial cellulase was compared to labelling with purified CBH I-, CBH II-, and EG-linked colloidal gold, and the labelling pattern was similar. This method was found useful on conventionally fixed material and required no special preparation other than the use of inert (Ni or Au) grids and 0.5% gelatin to reduce nonspecific binding of the gold complex. Labelling was similar in the several embedding resins tested: LR White, Lowicryl K4M, Epon 812, and Spurr's.(ABSTRACT TRUNCATED AT 250 WORDS)

  9. Optimal affine-invariant matching: performance characterization

    NASA Astrophysics Data System (ADS)

    Costa, Mauro S.; Haralick, Robert M.; Shapiro, Linda G.

    1992-04-01

    The geometric hashing scheme proposed by Lamdan and Wolfson can be very efficient in a model-based matching system, not only in terms of the computational complexity involved, but also in terms of the simplicity of the method. In a recent paper, we discussed errors that can occur with this method due to quantization, stability, symmetry, and noise problems. These errors make the original geometric hashing technique unsuitable for use on the factory floor. Beginning with an explicit noise model, which the original Lamdan and Wolfson technique lacks, we derived an optimal approach that overcomes these problems. We showed that the results obtained with the new algorithm are clearly better than the results from the original method. This paper addresses the performance characterization of the geometric hashing technique, more specifically the affine-invariant point matching, applied to the problem of recognizing and determining the pose of sheet metal parts. The experiments indicate that with a model having 10 to 14 points, with 2 points of the model undetected and 10 extraneous points detected, and with the model points perturbed by Gaussian noise of standard deviation 3 (0.58 of range), the average amount of computation required to obtain an answer is equivalent to trying 11 of the possible three-point bases. The misdetection rate, measured by the percentage of correct bases matches that fail to verify, is 0.9. The percentage of incorrect bases that successfully produced a match that did verify (false alarm rate) is 13. And, finally, 2 of the experiments failed to find a correct match and verify it. Results for experiments with real images are also presented.

  10. Affinity Capillary Electrophoresis Applied to Investigation of Valinomycin Complexes with Ammonium and Alkali Metal Ions.

    PubMed

    Štěpánová, Sille; Kašička, Václav

    2016-01-01

    This chapter deals with the application of affinity capillary electrophoresis (ACE) to investigation of noncovalent interactions (complexes) of valinomycin, a macrocyclic dodecadepsipeptide antibiotic ionophore, with ammonium and alkali metal ions (lithium, sodium, potassium, rubidium, and cesium). The strength of these interactions was characterized by the apparent binding (stability, association) constants (K b) of the above valinomycin complexes using the mobility shift assay mode of ACE. The study involved measurements of effective electrophoretic mobility of valinomycin at variable concentrations of ammonium or alkali metal ions in the background electrolyte (BGE). The effective electrophoretic mobilities of valinomycin measured at ambient temperature and variable ionic strength were first corrected to the reference temperature 25 °C and constant ionic strength (10 or 25 mM). Then, from the dependence of the corrected valinomycin effective mobility on the ammonium or alkali metal ion concentration in the BGE, the apparent binding constants of the valinomycin-ammonium or valinomycin-alkali metal ion complexes were determined using a nonlinear regression analysis. Logarithmic form of the binding constants (log K b) were found to be in the range of 1.50-4.63, decreasing in the order Rb(+) > K(+) > Cs(+) > > Na(+) > NH4 (+) ~ Li(+). PMID:27473493

  11. Selectively Promiscuous Opioid Ligands: Discovery of High Affinity/Low Efficacy Opioid Ligands with Substantial Nociceptin Opioid Peptide Receptor Affinity

    PubMed Central

    2015-01-01

    Emerging clinical and preclinical evidence suggests that a compound displaying high affinity for μ, κ, and δ opioid (MOP, KOP, and DOP) receptors and antagonist activity at each, coupled with moderate affinity and efficacy at nociceptin opioid peptide (NOP) receptors will have utility as a relapse prevention agent for multiple types of drug abuse. Members of the orvinol family of opioid ligands have the desired affinity profile but have typically displayed substantial efficacy at MOP and or KOP receptors. In this study it is shown that a phenyl ring analogue (1d) of buprenorphine displays the desired profile in vitro with high, nonselective affinity for the MOP, KOP, and DOP receptors coupled with moderate affinity for NOP receptors. In vivo, 1d lacked any opioid agonist activity and was an antagonist of both the MOP receptor agonist morphine and the KOP receptor agonist ethylketocyclazocine, confirming the desired opioid receptor profile in vivo. PMID:24761755

  12. Varying constant cosmologies and cosmic singularities

    NASA Astrophysics Data System (ADS)

    Dabrowski, Mariusz P.; Marosek, Konrad

    2013-02-01

    We review standard and non-standard cosmological singularities paying special attention onto those which are of a weak type and do not necessarily exhibit geodesic incompletness. Then, we discuss how these singularities can be weakened, strengthened, or avoided due to the time-variation of the physical constants such as the speed of light c and the gravitational constant G.

  13. Developing Knowledge Management (KM): Contributions by Organizational Learning and Total Quality Management (TQM)

    ERIC Educational Resources Information Center

    Hung, Richard Yu-Yuan; Lien, Bella Ya-Hui

    2005-01-01

    Knowledge management is an integral business function for many organizations to manage intellectual resources effectively. From a resource-based perspective, organizational learning and TQM are antecedents that are closely related to KM. The purposes of this study were to explain the contents of KM, and explore the relationship between KM-related…

  14. String theory, cosmology and varying constants

    NASA Astrophysics Data System (ADS)

    Damour, Thibault

    In string theory the coupling `constants' appearing in the low-energy effective Lagrangian are determined by the vacuum expectation values of some (a priori) massless scalar fields (dilaton, moduli). This naturally leads one to expect a correlated variation of all the coupling constants, and an associated violation of the equivalence principle. We review some string-inspired theoretical models which incorporate such a spacetime variation of coupling constants while remaining naturally compatible both with phenomenological constraints coming from geochemical data (Oklo; Rhenium decay) and with present equivalence principle tests. Barring a very unnatural fine-tuning of parameters, a variation of the fine-structure constant as large as that recently `observed' by Webb et al. in quasar absorption spectra appears to be incompatible with these phenomenological constraints. Independently of any model, it is emphasized that the best experimental probe of varying constants are high-precision tests of the universality of free fall, such as MICROSCOPE and STEP.

  15. BIOINTERACTION ANALYSIS BY HIGH-PERFORMANCE AFFINITY CHROMATOGRAPHY: KINETIC STUDIES OF IMMOBILIZED ANTIBODIES

    PubMed Central

    Nelson, Mary Anne; Moser, Annette; Hage, David S.

    2009-01-01

    A system based on high-performance affinity chromatography was developed for characterizing the binding, elution and regeneration kinetics of immobilized antibodies and immunoaffinity supports. This information was provided by using a combination of frontal analysis, split-peak analysis and peak decay analysis to determine the rate constants for antibody-antigen interactions under typical sample application and elution conditions. This technique was tested using immunoaffinity supports that contained monoclonal antibodies for 2,4-dichlorophenoxyacetic acid (2,4-D). Association equilibrium constants measured by frontal analysis for 2,4-D and related compounds with the immobilized antibodies were 1.7–12 × 106 M−1 at pH 7.0 and 25°C. Split-peak analysis gave association rate constants of 1.4–12 × 105 M−1s−1 and calculated dissociation rate constants of 0.01–0.4 s−1 under the application conditions. Elution at pH 2.5 for the analytes from the antibodies was examined by peak decay analysis and gave dissociation rate constants of 0.056–0.17 s−1. A comparison of frontal analysis results after various periods of column regeneration allowed the rate of antibody regeneration to be examined, with the results giving a first-order regeneration rate constant of 2.4 × 10−4 s−1. This combined approach and the information it provides should be useful in the design and optimization of immunoaffinity chromatography and other analytical methods that employ immobilized antibodies. The methods described are not limited to the particular analytes and antibodies employed in this study but should be useful in characterizing other targets, ligands and supports. PMID:19394281

  16. How Structure Defines Affinity in Protein-Protein Interactions

    PubMed Central

    Erijman, Ariel; Rosenthal, Eran; Shifman, Julia M.

    2014-01-01

    Protein-protein interactions (PPI) in nature are conveyed by a multitude of binding modes involving various surfaces, secondary structure elements and intermolecular interactions. This diversity results in PPI binding affinities that span more than nine orders of magnitude. Several early studies attempted to correlate PPI binding affinities to various structure-derived features with limited success. The growing number of high-resolution structures, the appearance of more precise methods for measuring binding affinities and the development of new computational algorithms enable more thorough investigations in this direction. Here, we use a large dataset of PPI structures with the documented binding affinities to calculate a number of structure-based features that could potentially define binding energetics. We explore how well each calculated biophysical feature alone correlates with binding affinity and determine the features that could be used to distinguish between high-, medium- and low- affinity PPIs. Furthermore, we test how various combinations of features could be applied to predict binding affinity and observe a slow improvement in correlation as more features are incorporated into the equation. In addition, we observe a considerable improvement in predictions if we exclude from our analysis low-resolution and NMR structures, revealing the importance of capturing exact intermolecular interactions in our calculations. Our analysis should facilitate prediction of new interactions on the genome scale, better characterization of signaling networks and design of novel binding partners for various target proteins. PMID:25329579

  17. The sodium ion affinities of asparagine, glutamine, histidine and arginine

    NASA Astrophysics Data System (ADS)

    Wang, Ping; Ohanessian, Gilles; Wesdemiotis, Chrys

    2008-01-01

    The sodium ion affinities of the amino acids Asn, Gln, His and Arg have been determined by experimental and computational approaches (for Asn, His and Arg). Na+-bound heterodimers with amino acid and peptide ligands (Pep1, Pep2) were produced by electrospray ionization. From the dissociation kinetics of these Pep1-Na+-Pep2 ions to Pep1-Na+ and Pep2-Na+, determined by collisionally activated dissociation, a ladder of relative affinities was constructed and subsequently converted to absolute affinities by anchoring the relative values to known Na+ affinities. The Na+ affinities of Asn, His and Arg, were calculated at the MP2(full)/6-311+G(2d,2p)//MP2/6-31G(d) level of ab initio theory. The resulting experimental and computed Na+ affinities are in excellent agreement with one another. These results, combined with those of our previous studies, yield the sodium ion affinities of 18 out of the 20 [alpha]-amino acids naturally occurring in peptides and proteins of living systems.

  18. Analysis of biomolecular interactions using affinity microcolumns: a review.

    PubMed

    Zheng, Xiwei; Li, Zhao; Beeram, Sandya; Podariu, Maria; Matsuda, Ryan; Pfaunmiller, Erika L; White, Christopher J; Carter, NaTasha; Hage, David S

    2014-10-01

    Affinity chromatography has become an important tool for characterizing biomolecular interactions. The use of affinity microcolumns, which contain immobilized binding agents and have volumes in the mid-to-low microliter range, has received particular attention in recent years. Potential advantages of affinity microcolumns include the many analysis and detection formats that can be used with these columns, as well as the need for only small amounts of supports and immobilized binding agents. This review examines how affinity microcolumns have been used to examine biomolecular interactions. Both capillary-based microcolumns and short microcolumns are considered. The use of affinity microcolumns with zonal elution and frontal analysis methods are discussed. The techniques of peak decay analysis, ultrafast affinity extraction, split-peak analysis, and band-broadening studies are also explored. The principles of these methods are examined and various applications are provided to illustrate the use of these methods with affinity microcolumns. It is shown how these techniques can be utilized to provide information on the binding strength and kinetics of an interaction, as well as on the number and types of binding sites. It is further demonstrated how information on competition or displacement effects can be obtained by these methods. PMID:24572459

  19. Supernovae and the Hubble Constant (or, Butthead's Revenge)

    NASA Astrophysics Data System (ADS)

    Wheeler, J. C.; Hoflich, P.

    Physical models of Type Ia supernovae (SN Ia) that do not depend on secondary calibrators have indicated that the Hubble Constant must be about 65 km/s/Mpc for well over a decade with the range of uncertainty shrinking with the sophistication of the models. This estimate is in good agreement with those based on HST observations of Cepheid variables and with purely empirical methods based on SN Ia calibrated with Cepheids. The prospects of progress in understanding the physics of the explosion of SN Ia and of their application to measure other cosmological parameters is reviewed. Despite the rather complex nature of their atmospheres, SN Ia may give a more reliable estimate of distances than Type II. The latter depend on remaining uncertainties in the scattering atmospheres, the helium abundance and possible systematic effects due to distortions of the envelope that will not average out even in a large sample.

  20. Cratering and penetration experiments in Teflon targets at velocities from 1 to 7 km/s

    NASA Technical Reports Server (NTRS)

    Hoerz, Friedrich; Bernhard, Ronald P.; Cintala, Mark J.; See, Thomas H.

    1995-01-01

    Approximately 20 sq m of protective thermal blankets, largely composed of Teflon, were retrieved from the Long Duration Exposure Facility (LDEF) after the spacecraft had spent approximately 5.7 years in space. Examination of these blankets revealed that they contained thousands of hypervelocity impact features ranging from micron-sized craters to penetration holes several millimeters in diameter. We conducted impact experiments in an effort to reproduce such features and to -- hopefully -- understand the relationships between projectile size and the resulting crater or penetration-hole diameter over a wide range of impact velocity. Such relationships are needed to derive the size- and mass-frequency distribution and flux of natural and man-made particles in low-Earth orbit. Powder propellant and light-gas guns were used to launch soda-lime glass spheres of 3.175 mm (1/8 inch) nominal diameter (Dp) into pure Teflon FEP targets at velocities ranging from 1 to 7 km/s. Target thickness (T) was varied over more than three orders of magnitude from infinite halfspace targets (Dp/T less than 0.1) to very thin films (Dp/T greater than 100). Cratering and penetration of massive Teflon targets is dominated by brittle failure and the development of extensive spall zones at the target's front and, if penetrated, the target's rear side. Mass removal by spallation at the back side of Teflon targets may be so severe that the absolute penetration-hole diameter (Dh) can become larger than that of a standard crater (Dc) at relative target thicknesses of Dp/T = 0.6-0.9. The crater diameter is infinite halfspace Teflon targets increases -- at otherwise constant impact conditions -- with encounter velocity by a factor of V0.44. In contrast, the penetration-hole size is very thin foils (Dp/T greater than 50) is essentially unaffected by impact velocity. Penetrations at target thicknesses intermediate to these extremes will scale with variable exponents of V. Our experimental matrix is

  1. Cratering and penetration experiments in teflon targets at velocities from 1 to 7 km/s

    NASA Technical Reports Server (NTRS)

    Horz, Friedrich; Cintala, Mark; Bernhard, Ronald P.; Cardenas, Frank; Davidson, William; Haynes, Gerald; See, Thomas H.; Winkler, Jerry; Knight, Jeffrey

    1994-01-01

    Approximately 20 sq m of protective thermal blankets, largely composed of Teflon, were retrieved from the Long Duration Exposure Facility after the spacecraft spent approximately 5.7 years in space. Examination of these blankets revealed that they contained thousands of hypervelocity impact features ranging from micron-sized craters to penetration holes several millimeters in diameter. We conducted impact experiments to reproduce such features and to understand the relationships between projectile size and the resulting crater or penetration hole diameter over a wide range of impact velocities. Such relationships are needed to derive the size and mass frequency distribution and flux of natural and man-made particles in low-earth orbit. Powder propellant and light-gas guns were used to launch soda-lime glass spheres into pure Teflon targets at velocities ranging from 1 to 7 km/s. Target thickness varied over more than three orders of magnitude from finite halfspace targets to very thin films. Cratering and penetration of massive Teflon targets is dominated by brittle failure and the development of extensive spall zones at the target's front and, if penetrated, the target's rear side. Mass removal by spallation at the back side of Teflon targets may be so severe that the absolute penetration hole diameter can become larger than that of a standard crater. The crater diameter in infinite halfspace Teflon targets increases, at otherwise constant impact conditions, with encounter velocity by a factor of V (exp 0.44). In contrast, the penetration hole size in very thin foils is essentially unaffected by impact velocity. Penetrations at target thicknesses intermediate to these extremes will scale with variable exponents of V. Our experimental matrix is sufficiently systematic and complete, up to 7 km/s, to make reasonable recommendations for velocity-scaling of Teflon craters and penetrations. We specifically suggest that cratering behavior and associated equations apply

  2. Directed evolution to low nanomolar affinity of a tumor-targeting epidermal growth factor receptor-binding affibody molecule.

    PubMed

    Friedman, Mikaela; Orlova, Anna; Johansson, Eva; Eriksson, Tove L J; Höidén-Guthenberg, Ingmarie; Tolmachev, Vladimir; Nilsson, Fredrik Y; Ståhl, Stefan

    2008-03-01

    The epidermal growth factor receptor 1 (EGFR) is overexpressed in various malignancies and is associated with a poor patient prognosis. A small, receptor-specific, high-affinity imaging agent would be a useful tool in diagnosing malignant tumors and in deciding upon treatment and assessing the response to treatment. We describe here the affinity maturation procedure for the generation of Affibody molecules binding with high affinity and specificity to EGFR. A library for affinity maturation was constructed by rerandomization of selected positions after the alignment of first-generation binding variants. New binders were selected with phage display technology, using a single oligonucleotide in a single-library effort, and the best second-generation binders had an approximately 30-fold improvement in affinity (K(d)=5-10 nM) for the soluble extracellular domain of EGFR in biospecific interaction analysis using Biacore. The dissociation equilibrium constant, K(d), was also determined for the Affibody with highest affinity using EGFR-expressing A431 cells in flow cytometric analysis (K(d)=2.8 nM). A retained high specificity for EGFR was verified by a dot blot assay showing staining only of EGFR proteins among a panel of serum proteins and other EGFR family member proteins (HER2, HER3, and HER4). The EGFR-binding Affibody molecules were radiolabeled with indium-111, showing specific binding to EGFR-expressing A431 cells and successful targeting of the A431 tumor xenografts with 4-6% injected activity per gram accumulated in the tumor 4 h postinjection. PMID:18207161

  3. Two high-affinity ligand binding states of uterine estrogen receptor distinguished by modulation of hydrophobic environment

    SciTech Connect

    Hutchens, T.W.; Li, C.M.; Zamah, N.M.; Besch, P.K.

    1987-02-10

    The steroid binding function of soluble (cytosolic) estrogen receptors from calf uteri was evaluated under conditions known to modify the extent of hydrophobic interaction with receptor-associated proteins. Receptor preparations were equilibrated into 6 M urea buffers and control buffers by chromatography through small columns of Sephadex G-25 or by dialysis at 0.6 /sup 0/C. Equilibrium dissociation constants (K/sub d/) and binding capacities (n) of experimental and control receptor preparations were determined by 13-point Scatchard analyses using concentrations of 17..beta..-(/sup 3/H)estradiol from 0.05 to 10 nM. Nonspecific binding was determined at each concentration by parallel incubations with a 200-fold molar excess of the receptor-specific competitor diethylstilbestrol. The control receptor population was consistently found to be a single class of binding sites with a high affinity for estradiol which was unaffected by G-25 chromatography, by dialysis, by dilution, or by the presence of 0.4 M KCl. However, equilibration into 6 M urea induced a discrete (10-fold) reduction in receptor affinity to reveal a second, thermodynamically stable, high-affinity binding state. The presence of 0.4 M KCl did not significantly influence the discrete change in receptor affinity induced by urea. The effects of urea on both receptor affinity and binding capacity were reversible, suggesting a lack of covalent modification. These results demonstrate nonenzymatic means by which not only the binding capacity but also the affinity of receptor for estradiol can be reversibly controlled, suggesting that high concentrations of urea might be more effectively utilized during the physicochemical characterization and purification of steroid receptor proteins.

  4. Affinity- and topology-dependent bound on current fluctuations

    NASA Astrophysics Data System (ADS)

    Pietzonka, Patrick; Barato, Andre C.; Seifert, Udo

    2016-08-01

    We provide a proof of a recently conjectured universal bound on current fluctuations in Markovian processes. This bound establishes a link between the fluctuations of an individual observable current, the cycle affinities driving the system into a non-equilibrium steady state, and the topology of the network. The proof is based on a decomposition of the network into independent cycles with both positive affinity and positive stationary cycle current. This formalism allows for a refinement of the bound for systems in equilibrium or with locally vanishing affinities.

  5. Affinity+: Semi-Structured Brainstorming on Large Displays

    SciTech Connect

    Burtner, Edwin R.; May, Richard A.; Scarberry, Randall E.; LaMothe, Ryan R.; Endert, Alexander

    2013-04-27

    Affinity diagraming is a powerful method for encouraging and capturing lateral thinking in a group environment. The Affinity+ Concept was designed to improve the collaborative brainstorm process through the use of large display surfaces in conjunction with mobile devices like smart phones and tablets. The system works by capturing the ideas digitally and allowing users to sort and group them on a large touch screen manually. Additionally, Affinity+ incorporates theme detection, topic clustering, and other processing algorithms that help bring structured analytic techniques to the process without requiring explicit leadership roles and other overhead typically involved in these activities.

  6. Underwater acoustic positioning system for the SMO and KM3NeT - Italia projects

    SciTech Connect

    Viola, S.; Barbagallo, G.; Cacopardo, G.; Calí, C.; Cocimano, R.; Coniglione, R.; Costa, M.; Cuttone, G.; D'Amato, C.; D'Amato, V.; D'Amico, A.; De Luca, V.; Del Tevere, F.; Distefano, C.; Ferrera, F.; Gmerk, A.; Grasso, R.; Imbesi, M.; Larosa, G.; Lattuada, D.; and others

    2014-11-18

    In the underwater neutrino telescopes, the positions of the Cherenkov light sensors and their movements must be known with an accuracy of few tens of centimetres. In this work, the activities of the SMO and KM3NeT-Italia teams for the development of an acoustic positioning system for KM3NeT-Italia project are presented. The KM3NeT-Italia project foresees the construction, within two years, of 8 towers in the view of the several km{sup 3}-scale neutrino telescope KM3NeT.

  7. Straight as an arrow: humpback whales swim constant course tracks during long-distance migration

    PubMed Central

    Horton, Travis W.; Holdaway, Richard N.; Zerbini, Alexandre N.; Hauser, Nan; Garrigue, Claire; Andriolo, Artur; Clapham, Phillip J.

    2011-01-01

    Humpback whale seasonal migrations, spanning greater than 6500 km of open ocean, demonstrate remarkable navigational precision despite following spatially and temporally distinct migration routes. Satellite-monitored radio tag-derived humpback whale migration tracks in both the South Atlantic and South Pacific include constant course segments of greater than 200 km, each spanning several days of continuous movement. The whales studied here maintain these directed movements, often with better than 1° precision, despite the effects of variable sea-surface currents. Such remarkable directional precision is difficult to explain by established models of directional orientation, suggesting that alternative compass mechanisms should be explored. PMID:21508023

  8. Vicinal coupling constants and protein dynamics.

    PubMed

    Hoch, J C; Dobson, C M; Karplus, M

    1985-07-16

    The effects of motional averaging on the analysis of vicinal spin-spin coupling constants derived from proton NMR studies of proteins have been examined. Trajectories obtained from molecular dynamics simulations of bovine pancreatic trypsin inhibitor and of hen egg white lysozyme were used in conjunction with an expression for the dependence of the coupling constant on the intervening dihedral angle to calculate the time-dependent behavior of the coupling constants. Despite large fluctuations, the time-average values of the coupling constants are not far from those computed for the average structure in the cases where fluctuations occur about a single potential well. The calculated differences show a high correlation with the variation in the magnitude of the fluctuations of individual dihedral angles. For the cases where fluctuations involve multiple sites, large differences are found between the time-average values and the average structure values for the coupling constants. Comparison of the simulation results with the experimental trends suggests that side chains with more than one position are more common in proteins than is inferred from X-ray results. It is concluded that for the main chain, motional effects do not introduce significant errors where vicinal coupling constants are used in structure determinations; however, for side chains, the motional average can alter deductions about the structure. Accurately measured coupling constants are shown to provide information concerning the magnitude of dihedral angle fluctuations.

  9. On geometrically unified fields and universal constants

    NASA Astrophysics Data System (ADS)

    Fabbri, Luca

    2013-07-01

    We consider the Cartan extension of Riemann geometry as the basis upon which to build the Sciama-Kibble completion of Einstein gravity, developing the most general theory in which torsion and metric have two independent coupling constants: the main problem of the ESK theory was that torsion, having the Newton constant, was negligible beyond the Planck scale, but in this {ESK}2 theory torsion, with its own coupling constant, may be relevant much further Planck scales; further consequences of these torsionally-induced interactions will eventually be discussed.

  10. The Determination of the Strong Coupling Constant

    NASA Astrophysics Data System (ADS)

    Dissertori, Günther

    2016-10-01

    The strong coupling constant is one of the fundamental parameters of the Standard Theory of particle physics. In this review I will briefly summarise the theoretical framework, within which the strong coupling constant is defined and how it is connected to measurable observables. Then I will give an historical overview of its experimental determinations and discuss the current status and world average value. Among the many different techniques used to determine this coupling constant in the context of quantum chromodynamics, I will focus in particular on a number of measurements carried out at the Large Electron-Positron Collider (LEP) and the Large Hadron Collider (LHC) at CERN.

  11. Laser Propulsion and the Constant Momentum Mission

    NASA Astrophysics Data System (ADS)

    Larson, C. William; Mead, Franklin B.; Knecht, Sean D.

    2004-03-01

    We show that perfect propulsion requires a constant momentum mission, as a consequence of Newton's second law. Perfect propulsion occurs when the velocity of the propelled mass in the inertial frame of reference matches the velocity of the propellant jet in the rocket frame of reference. We compare constant momentum to constant specific impulse propulsion, which, for a given specification of the mission delta V, has an optimum specific impulse that maximizes the propelled mass per unit jet kinetic energy investment. We also describe findings of more than 50 % efficiency for conversion of laser energy into jet kinetic energy by ablation of solids.

  12. Laser Propulsion and the Constant Momentum Mission

    SciTech Connect

    Larson, C. William; Mead, Franklin B. Jr.; Knecht, Sean D.

    2004-03-30

    We show that perfect propulsion requires a constant momentum mission, as a consequence of Newton's second law. Perfect propulsion occurs when the velocity of the propelled mass in the inertial frame of reference matches the velocity of the propellant jet in the rocket frame of reference. We compare constant momentum to constant specific impulse propulsion, which, for a given specification of the mission delta V, has an optimum specific impulse that maximizes the propelled mass per unit jet kinetic energy investment. We also describe findings of more than 50 % efficiency for conversion of laser energy into jet kinetic energy by ablation of solids.

  13. The region of antithrombin interacting with full-length heparin chains outside the high-affinity pentasaccharide sequence extends to Lys136 but not to Lys139.

    PubMed

    Arocas, V; Turk, B; Bock, S C; Olson, S T; Björk, I

    2000-07-25

    The interaction of a well-defined pentasaccharide sequence of heparin with a specific binding site on antithrombin activates the inhibitor through a conformational change. This change increases the rate of antithrombin inhibition of factor Xa, whereas acceleration of thrombin inhibition requires binding of both inhibitor and proteinase to the same heparin chain. An extended heparin binding site of antithrombin outside the specific pentasaccharide site has been proposed to account for the higher affinity of the inhibitor for full-length heparin chains by interacting with saccharides adjacent to the pentasaccharide sequence. To resolve conflicting evidence regarding the roles of Lys136 and Lys139 in this extended site, we have mutated the two residues to Ala or Gln. Mutation of Lys136 decreased the antithrombin affinity for full-length heparin by at least 5-fold but minimally altered the affinity for the pentasaccharide. As a result, the full-length heparin and pentasaccharide affinities were comparable. The reduced affinity for full-length heparin was associated with the loss of one ionic interaction and was caused by both a lower overall association rate constant and a higher overall dissociation rate constant. In contrast, mutation of Lys139 affected neither full-length heparin nor pentasaccharide affinity. The rate constants for inhibition of thrombin and factor Xa by the complexes between antithrombin and full-length heparin or pentasaccharide were unaffected by both mutations, indicating that neither Lys136 nor Lys139 is involved in heparin activation of the inhibitor. Together, these results show that Lys136 forms part of the extended heparin binding site of antithrombin that participates in the binding of full-length heparin chains, whereas Lys139 is located outside this site. PMID:10913257

  14. Comparative Study of Three Methods for Affinity Measurements: Capillary Electrophoresis Coupled with UV Detection and Mass Spectrometry, and Direct Infusion Mass Spectrometry

    NASA Astrophysics Data System (ADS)

    Mironov, Gleb G.; Logie, Jennifer; Okhonin, Victor; Renaud, Justin B.; Mayer, Paul M.; Berezovski, Maxim V.

    2012-07-01

    We present affinity capillary electrophoresis and mass spectrometry (ACE-MS) as a comprehensive separation technique for label-free solution-based affinity analysis. The application of ACE-MS for measuring affinity constants between eight small molecule drugs [ibuprofen, s-flurbiprofen, diclofenac, phenylbutazone, naproxen, folic acid, resveratrol, and 4,4'-(propane-1,3-diyl) dibenzoic acid] and β-cyclodextrin is described. We couple on-line ACE with MS to combine the separation and kinetic capability of ACE together with the molecular weight and structural elucidation of MS in one system. To understand the full potential of ACE-MS, we compare it with two other methods: Direct infusion mass spectrometry (DIMS) and ACE with UV detection (ACE-UV). After the evaluation, DIMS provides less reliable equilibrium dissociation constants than separation-based ACE-UV and ACE-MS, and cannot be used solely for the study of noncovalent interactions. ACE-MS determines apparent dissociation constants for all reacting small molecules in a mixture, even in cases when drugs overlap with each other during separation. The ability of ACE-MS to interact, separate, and rapidly scan through m/z can facilitate the simultaneous affinity analysis of multiple interacting pairs, potentially leading to the high-throughput screening of drug candidates.

  15. Constants and Pseudo-Constants of Coupled Beam Motion in the PEP-II Rings

    SciTech Connect

    Decker, F.J.; Colocho, W.S.; Wang, M.H.; Yan, Y.T.; Yocky, G.; /SLAC

    2011-11-01

    Constants of beam motion help as cross checks to analyze beam diagnostics and the modeling procedure. Pseudo-constants, like the betatron mismatch parameter or the coupling parameter det C, are constant till certain elements in the beam line change them. This can be used to visually find the non-desired changes, pinpointing errors compared with the model.

  16. Afi-Chip: An Equipment-Free, Low-Cost, and Universal Binding Ligand Affinity Evaluation Platform.

    PubMed

    Song, Yanling; Shi, Yuanzhi; Li, Xingrui; Ma, Yanli; Gao, Mingxuan; Liu, Dan; Mao, Yu; Zhu, Zhi; Lin, Hui; Yang, Chaoyong

    2016-08-16

    Binding affinity characterization is of great importance for aptamer screening because the dissociation constant (Kd) value is a key parameter for evaluating molecular interaction. However, conventional methods often require sophisticated equipment and time-consuming processing. Here, we present a portable device, Afi-Chip, as an equipment-free, rapid, low-cost, and universal platform for evaluation of the aptamer affinity. The Afi-Chip displays a distance readout based on the reaction of an enzyme catalyzing the decomposition of H2O2 for gas generation to push the movement of ink bar. Taking advantage of translating the recognition signal to distance signal and realizing the regents mixing and quantitative readout on the chip, we successfully monitored the aptamer evolution process and characterized binding affinity of aptamers against multiple types of targets, including small molecule glucose, cancer biomarker protein EpCAM, and tumor cell SW620. We also applied the Afi-Chip for rapid characterization of the affinity between anti-HCG and HCG to demonstrate the generality for the molecular interaction study. All of the Kd values obtained are comparable to those reported in the literature or obtained by sophisticated instruments such as a flow cytometer. The Afi-Chip offers a new approach for equipment-free investigation of molecular interactions, such as aptamer identification, ligand selection monitoring, and drug screening. PMID:27454185

  17. Synthetic cannabinoids: In silico prediction of the cannabinoid receptor 1 affinity by a quantitative structure-activity relationship model.

    PubMed

    Paulke, Alexander; Proschak, Ewgenij; Sommer, Kai; Achenbach, Janosch; Wunder, Cora; Toennes, Stefan W

    2016-03-14

    The number of new synthetic psychoactive compounds increase steadily. Among the group of these psychoactive compounds, the synthetic cannabinoids (SCBs) are most popular and serve as a substitute of herbal cannabis. More than 600 of these substances already exist. For some SCBs the in vitro cannabinoid receptor 1 (CB1) affinity is known, but for the majority it is unknown. A quantitative structure-activity relationship (QSAR) model was developed, which allows the determination of the SCBs affinity to CB1 (expressed as binding constant (Ki)) without reference substances. The chemically advance template search descriptor was used for vector representation of the compound structures. The similarity between two molecules was calculated using the Feature-Pair Distribution Similarity. The Ki values were calculated using the Inverse Distance Weighting method. The prediction model was validated using a cross validation procedure. The predicted Ki values of some new SCBs were in a range between 20 (considerably higher affinity to CB1 than THC) to 468 (considerably lower affinity to CB1 than THC). The present QSAR model can serve as a simple, fast and cheap tool to get a first hint of the biological activity of new synthetic cannabinoids or of other new psychoactive compounds.

  18. Afi-Chip: An Equipment-Free, Low-Cost, and Universal Binding Ligand Affinity Evaluation Platform.

    PubMed

    Song, Yanling; Shi, Yuanzhi; Li, Xingrui; Ma, Yanli; Gao, Mingxuan; Liu, Dan; Mao, Yu; Zhu, Zhi; Lin, Hui; Yang, Chaoyong

    2016-08-16

    Binding affinity characterization is of great importance for aptamer screening because the dissociation constant (Kd) value is a key parameter for evaluating molecular interaction. However, conventional methods often require sophisticated equipment and time-consuming processing. Here, we present a portable device, Afi-Chip, as an equipment-free, rapid, low-cost, and universal platform for evaluation of the aptamer affinity. The Afi-Chip displays a distance readout based on the reaction of an enzyme catalyzing the decomposition of H2O2 for gas generation to push the movement of ink bar. Taking advantage of translating the recognition signal to distance signal and realizing the regents mixing and quantitative readout on the chip, we successfully monitored the aptamer evolution process and characterized binding affinity of aptamers against multiple types of targets, including small molecule glucose, cancer biomarker protein EpCAM, and tumor cell SW620. We also applied the Afi-Chip for rapid characterization of the affinity between anti-HCG and HCG to demonstrate the generality for the molecular interaction study. All of the Kd values obtained are comparable to those reported in the literature or obtained by sophisticated instruments such as a flow cytometer. The Afi-Chip offers a new approach for equipment-free investigation of molecular interactions, such as aptamer identification, ligand selection monitoring, and drug screening.

  19. Dense Stereo Matching Method Based on Local Affine Model.

    PubMed

    Li, Jie; Shi, Wenxuan; Deng, Dexiang; Jia, Wenyan; Sun, Mingui

    2013-07-01

    A new method for constructing an accurate disparity space image and performing an efficient cost aggregation in stereo matching based on local affine model is proposed in this paper. The key algorithm includes a new self-adapting dissimilarity measurement used for calculating the matching cost and a local affine model used in cost aggregation stage. Different from the traditional region-based methods, which try to change the matching window size or to calculate an adaptive weight to do the aggregation, the proposed method focuses on obtaining the efficient and accurate local affine model to aggregate the cost volume while preserving the disparity discontinuity. Moreover, the local affine model can be extended to the color space. Experimental results demonstrate that the proposed method is able to provide subpixel precision disparity maps compared with some state-of-the-art stereo matching methods. PMID:24163727

  20. On the thermodynamic basis of the affinity decay rate

    NASA Astrophysics Data System (ADS)

    Garcia-Colín, L. S.; Piña, E.; de la Selva, S. M. T.

    1990-03-01

    In the past five years exhaustive studies in chemical reactions have lead to an empirical equation describing how isothermal-isometric homogeneous reactions evolve towards equilibrium independently of their particular mechanism or rate law. Such an equation expresses the time rate of change of the chemical affinity as a linear function of the inverse of time. In this paper we show that by invoking the local equilibrium hypothesis one may provide, a time evolution equation for the chemical affinity that is uniquely given by the solution of the particular rate law of the reaction considered. Consequently such an equation is not of the same functional form for all reactions. On the other hand, integration of Dalton's law under specific initial conditions, together with the local equilibrium assumption and the ideality requirement for the reacting species, exhibits a unique inverse time decay for the chemical affinity. This explains the good fitting of the inverse in time dependence of the chemical affinity with experimental data.

  1. A thermodynamic approach to the affinity optimization of drug candidates.

    PubMed

    Freire, Ernesto

    2009-11-01

    High throughput screening and other techniques commonly used to identify lead candidates for drug development usually yield compounds with binding affinities to their intended targets in the mid-micromolar range. The affinity of these molecules needs to be improved by several orders of magnitude before they become viable drug candidates. Traditionally, this task has been accomplished by establishing structure activity relationships to guide chemical modifications and improve the binding affinity of the compounds. As the binding affinity is a function of two quantities, the binding enthalpy and the binding entropy, it is evident that a more efficient optimization would be accomplished if both quantities were considered and improved simultaneously. Here, an optimization algorithm based upon enthalpic and entropic information generated by Isothermal Titration Calorimetry is presented.

  2. Frontal affinity chromatography (FAC): theory and basic aspects.

    PubMed

    Kasai, Ken-ichi

    2014-01-01

    Frontal affinity chromatography (FAC) is a versatile analytical tool for determining specific interactions between biomolecules and is particularly useful in the field of glycobiology. This article presents its basic aspects, merits, and theory. PMID:25117240

  3. Bidirectional Elastic Image Registration Using B-Spline Affine Transformation

    PubMed Central

    Gu, Suicheng; Meng, Xin; Sciurba, Frank C.; Wang, Chen; Kaminski, Naftali; Pu, Jiantao

    2014-01-01

    A registration scheme termed as B-spline affine transformation (BSAT) is presented in this study to elastically align two images. We define an affine transformation instead of the traditional translation at each control point. Mathematically, BSAT is a generalized form of the affine transformation and the traditional B-Spline transformation (BST). In order to improve the performance of the iterative closest point (ICP) method in registering two homologous shapes but with large deformation, a bi-directional instead of the traditional unidirectional objective / cost function is proposed. In implementation, the objective function is formulated as a sparse linear equation problem, and a sub-division strategy is used to achieve a reasonable efficiency in registration. The performance of the developed scheme was assessed using both two-dimensional (2D) synthesized dataset and three-dimensional (3D) volumetric computed tomography (CT) data. Our experiments showed that the proposed B-spline affine model could obtain reasonable registration accuracy. PMID:24530210

  4. Antibody Affinity Maturation in Fishes—Our Current Understanding

    PubMed Central

    Magor, Brad G.

    2015-01-01

    It has long been believed that fish lack antibody affinity maturation, in part because they were thought to lack germinal centers. Recent research done on sharks and bony fishes indicates that these early vertebrates are able to affinity mature their antibodies. This article reviews the functionality of the fish homologue of the immunoglobulin (Ig) mutator enzyme activation-induced cytidine deaminase (AID). We also consider the protein and molecular evidence for Ig somatic hypermutation and antibody affinity maturation. In the context of recent evidence for a putative proto-germinal center in fishes we propose some possible reasons that observed affinity maturation in fishes often seems lacking and propose future work that might shed further light on this process in fishes. PMID:26264036

  5. Hydride affinities of cumulated, isolated, and conjugated dienes in acetonitrile.

    PubMed

    Zhu, Xiao-Qing; Liang, Hao; Zhu, Yan; Cheng, Jin-Pei

    2008-11-01

    The hydride affinities (defined as the enthalpy changes in this work) of 15 polarized dienes [five phenyl sulfone substituted allenes (1a), the corresponding five isolated dienes (1b), and the corresponding five conjugated dienes (1c)] in acetonitrile solution were determined by titration calorimetry for the first time. The results display that the hydride affinity scales of the 15 dienes in acetonitrile range from -71.6 to -73.9 kcal/mol for 1a, from -46.2 to -49.7 kcal/mol for 1b, and from -45.0 to -46.5 kcal/mol for 1c, which indicates that the hydride-obtaining abilities of the cumulated dienes (1a) are not only much larger than those of the corresponding conjugated dienes (1c) but also much larger than those of the corresponding isolated dienes (1b). The hydrogen affinities of the 15 dienes as well as the hydrogen affinities and the proton affinities of the radical anions of the dienes (1(-*)) in acetonitrile were also evaluated by using relative thermodynamic cycles according to Hess's law. The results show that (i) the hydrogen affinities of the neutral dienes 1 cover a range from -44.5 to -45.6 kcal/mol for 1a, from -20.4 to -21.4 kcal/mol for 1b, and from -17.3 to -18.5 kcal/mol for 1c; (ii) the hydrogen affinities of the radical anions of the dienes (1(-*)) in acetonitrile cover a range from -40.6 to -47.2 kcal/mol for 1a(-*), from -21.6 to -29.6 kcal/mol for 1b(-*), and from -10.0 to -15.4 kcal/mol for 1c(-*); (iii) the proton affinities of the 15 1a(-*) in acetonitrile cover a range from -97.0 to -100.6 kcal/mol for 1a(-*), from -77.8 to -83.4 kcal/mol for 1b(-*), and from -66.2 to -68.9 kcal/mol for 1c(-*). The main reasons for the great difference between the cumulated dienes and the corresponding isolated and conjugated dienes in the hydride affinity, hydrogen affinity, and proton affinity have been examined. It is evident that these experimental results should be quite valuable to facilitate the elucidation of the origins of the especially high

  6. High-affinity nasal extraction of vinyl acetate vapor is carboxylesterase dependent.

    PubMed

    Bogdanffy, M S; Manning, L A; Sarangapani, R

    1999-10-01

    Vinyl acetate induces nasal tumors in rats, but not mice. Species differences in airflow patterns, physiology, and biochemistry complicate extrapolation of nasal dosimetry from rats to humans. Physiologically based pharmacokinetic modeling of vinyl acetate dosimetry in rats suggested the presence of a saturable metabolic removal pathway in rat nasal mucus. We explored the possibility that this pathway is either a cytochrome P-450 2E1 (CYP2E1) or high-affinity carboxylesterase. Nasal extraction of vinyl acetate vapor (150 ppm) was measured in the surgically isolated nasal cavity of anesthetized rats. Vinyl acetate (150 ppm) was extracted with 73% efficiency in controls. Pretreatment of rats with the CYP2E1 inhibitor diallyl sulfide (DAS) had no effect on extraction, despite significantly reducing CYP2E1 activity. Pretreatment with bis(p-nitrophenyl) phosphate (BNPP), a carboxylesterase inhibitor, reduced extraction to approximately 41%. Acetaldehyde production was similarly unaffected by DAS but was reduced to 55% of control by BNPP. Rat nasal mucus carboxylesterase activity had a K(m) value (32 microM) similar, within a factor of 2, to the value predicted by the physiologically based model, although V(max) was significantly lower than the model prediction. Histochemical observations support the inference that the high-affinity carboxylesterase is bound to the luminal plasma membrane of nasal tissue and is not readily released by nasal lavage, providing an explanation for the low V(max) of the lavage enzyme. This high-affinity isoenzyme could be important in the removal of odorants from the sensory cell-rich nasal olfactory epithelium.

  7. Dental affinities of the C-group inhabitants of Hierakonpolis, Egypt: Nubian, Egyptian, or both?

    PubMed

    Irish, J D; Friedman, R

    2010-04-01

    By c. 2050 BC a small community of C-Group Nubians was present deep within Egyptian territory at the city of Hierakonpolis. Their descendants stayed for the next 400 years. Today, the site of Hierakonpolis, 113 km north of Aswan, is known for its Egyptian deposits; however, it also contains a C-Group cemetery, which documents the northernmost occurrence of this culture. Sixty skeletons were excavated. Tombs feature Nubian architecture and goods, including leather garments, although the use of Egyptian mortuary practices and artifacts increased through time. Dates range from the early 11th Dynasty into the Second Intermediate period. During this time the Egyptian empire occupied Lower Nubia, and their state ideology vilified Nubians. Yet, at least in death, the C-Group inhabitants of Hierakonpolis proudly displayed their cultural heritage. Beyond discerning the reason(s) for their presence at the site (e.g., mercenaries, leather-workers, entertainers?), the focus of this report is to estimate their biological affinity. Were they akin to other Nubians, Egyptians, or both? And, was increasing 'Egyptianization' evident in the mortuary ritual accompanied by concomitant genetic influence? To address these queries, up to 36 dental morphological traits in the recovered individuals were compared to those in 26 regional comparative samples. The most influential traits were identified and phenetic affinities were calculated using the mean measure of divergence and other multivariate analyses. Assuming phenetic similarity provides an estimate of genetic relatedness, these affinities suggest the individuals comprising the C-Group sample were, and remained Nubian during their tenure at Hierakonpolis. PMID:20185126

  8. Why Not a Constant Early Lunar Impact Rate?

    NASA Technical Reports Server (NTRS)

    Wilhelms, D. E.

    1985-01-01

    Two distinct episodes of impacting are recorded on the Moon's surface. An early episode marked by an intense barrage that included basin-forming projectiles ended about 3.8 aeons ago when the Orientale basin was created. The second episode, after 3.2 or 3.3 aeons ago, was marked by a much lower impact rate. These very different rates are separated by a short transition period during the Late Imbrian Epoch. It is found that a constant preImbrian impact rate is consistent with all the relevant observations and with the following lunar historical scenario: (1) crustal solidification between about 4.3 and 4.25 aeons ago; (2) formation of Procellarum, South Pole-Aitken, about 22 now-obliterated basins, and about 2,850 now-obliterated 30 to 300 km craters between 4.25 and 4.1 aeons ago; and (3) formation of 39 still-preserved basins, 1,200 still-perserved craters, and 2,200 now-obliterated craters between 4.1 and 3.85 aeons ago. At the constant rate, the amount of mass that impacted the Moon since crustal solidification would not greatly exceed the amount that has left a permanent visible record.

  9. ANALYSIS OF DRUG INTERACTIONS WITH MODIFIED PROTEINS BY HIGH-PERFORMANCE AFFINITY CHROMATOGRAPHY: BINDING OF GLIBENCLAMIDE TO NORMAL AND GLYCATED HUMAN SERUM ALBUMIN

    PubMed Central

    Matsuda, Ryan; Anguizola, Jeanethe; Joseph, K.S.; Hage, David S.

    2012-01-01

    High-performance affinity chromatography (HPAC) was used to examine the changes in binding that occur for the sulfonylurea drug glibenclamide with human serum albumin (HSA) at various stages of glycation for HSA. Frontal analysis on columns containing normal HSA or glycated HSA indicated glibenclamide was interacting through both high affinity sites (association equilibrium constant, Ka, 1.4–1.9 × 106 M−1 at pH 7.4 and 37°C) and lower affinity sites (Ka, 4.4–7.2 × 104 M−1). Competition studies were used to examine the effect of glycation at specific binding sites of HSA. An increase in affinity of 1.7- to 1.9-fold was seen at Sudlow site I with moderate to high levels of glycation. An even larger increase of 4.3- to 6.0-fold in affinity was noted at Sudlow site II for all of the tested samples of glycated HSA. A slight decrease in affinity may have occurred at the digitoxin site, but this change was not significant for any individual glycated HSA sample. These results illustrate how HPAC can be used as tool for examining the interactions of relatively non-polar drugs like glibenclamide with modified proteins and should lead to a more complete understanding of how glycation can alter the binding of drugs in blood. PMID:23092871

  10. Proton affinity of methyl nitrate - Less than proton affinity of nitric acid

    NASA Technical Reports Server (NTRS)

    Lee, Timothy J.; Rice, Julia E.

    1992-01-01

    Several state-of-the-art ab initio quantum mechanical methods were used to investigate the equilibrium structure, dipole moments, harmonic vibrational frequencies, and IR intensities of methyl nitrate, methanol, and several structures of protonated methyl nitrate, using the same theoretical methods as in an earlier study (Lee and Rice, 1992) of nitric acid. The ab initio results for methyl nitrate and methanol were found to be in good agreement with available experimental data. The proton affinity (PA) of methyl nitrate was calculated to be 176.9 +/-5 kcal/mol, in excellent agreement with the experimental value 176 kcal/mol obtained by Attina et al. (1987) and less than the PA value of nitric acid. An explanation of the discrepancy of the present results with those of an earlier study on protonated nitric acid is proposed.

  11. How the cosmological constant affects gravastar formation

    SciTech Connect

    Chan, R.; Silva, M.F.A. da; Rocha, P. E-mail: mfasnic@gmail.com

    2009-12-01

    Here we generalized a previous model of gravastar consisted of an internal de Sitter spacetime, a dynamical infinitely thin shell with an equation of state, but now we consider an external de Sitter-Schwarzschild spacetime. We have shown explicitly that the final output can be a black hole, a ''bounded excursion'' stable gravastar, a stable gravastar, or a de Sitter spacetime, depending on the total mass of the system, the cosmological constants, the equation of state of the thin shell and the initial position of the dynamical shell. We have found that the exterior cosmological constant imposes a limit to the gravastar formation, i.e., the exterior cosmological constant must be smaller than the interior cosmological constant. Besides, we have also shown that, in the particular case where the Schwarzschild mass vanishes, no stable gravastar can be formed, but we still have formation of black hole.

  12. The Solar Constant: A Take Home Lab

    ERIC Educational Resources Information Center

    Eaton, B. G.; And Others

    1977-01-01

    Describes a method that uses energy from the sun, absorbed by aluminum discs, to melt ice, and allows the determination of the solar constant. The take-home equipment includes Styrofoam cups, a plastic syringe, and aluminum discs. (MLH)

  13. Dielectric constant of water in the interface.

    PubMed

    Dinpajooh, Mohammadhasan; Matyushov, Dmitry V

    2016-07-01

    We define the dielectric constant (susceptibility) that should enter the Maxwell boundary value problem when applied to microscopic dielectric interfaces polarized by external fields. The dielectric constant (susceptibility) of the interface is defined by exact linear-response equations involving correlations of statistically fluctuating interface polarization and the Coulomb interaction energy of external charges with the dielectric. The theory is applied to the interface between water and spherical solutes of altering size studied by molecular dynamics (MD) simulations. The effective dielectric constant of interfacial water is found to be significantly lower than its bulk value, and it also depends on the solute size. For TIP3P water used in MD simulations, the interface dielectric constant changes from 9 to 4 when the solute radius is increased from ∼5 to 18 Å.

  14. The Rate Constant for Fluorescence Quenching

    ERIC Educational Resources Information Center

    Legenza, Michael W.; Marzzacco, Charles J.

    1977-01-01

    Describes an experiment that utilizes fluorescence intensity measurements from a Spectronic 20 to determine the rate constant for the fluorescence quenching of various aromatic hydrocarbons by carbon tetrachloride in an ethanol solvent. (MLH)

  15. High-affinity transport of L-glutamine by a plasma membrane preparation from rat brain.

    PubMed

    Roon, R J; Shofner, S A; Koerner, J F

    1989-10-01

    Plasma membrane vesicles prepared from rat brain contain a saturable, high-affinity transport system for L-glutamine that exhibits the following characteristics: (1) The rate of L-glutamine transport is linear up to 200 micrograms/mL membrane protein. (2) Transport of [3H]-L-glutamine is linear with time for at least 10 min, is significantly reduced by lowering the assay temperature to 4 degrees C, and is essentially abolished by the addition of excess unlabeled L-glutamine. (3) The transport rate is optimal in the range of pH 7.4-8.2. (4) The system exhibits a Km for L-glutamine of approximately 1.7 microM and a Vmax of approximately 46 pmol/(min.mg of protein). (5) The system is not highly dependent upon the addition of monovalent or divalent cations. (6) Inhibitor studies reveal that the amino acid amides exhibit the highest affinity for the system and that there is a high specificity for the L-isomers.

  16. High dielectric constant materials: a band line-up problem

    NASA Astrophysics Data System (ADS)

    Fonseca, L.; Tomfohr, J.; Chagarov, E.; Sankey, O. F.; Demkov, A. A.

    2003-03-01

    To insure continuous downscaling of CMOS technology the semiconductor industry must make a transition from the Si-SiO_2-poly-Si triad to a much more complex Si-dielectric-metal system. The dielectric constant of the new gate dielectric is expected to be higher than that of silicon dioxide (4). This will allow maintaining the gate capacitance and therefore the drain-source saturation current without the thickness reduction of the oxide, and thus will cut down the tunneling component of the parasitic gate leakage. The integration of this new stack into the current CMOS flow is one of the most urgent tasks of today's electronics. The oxide's gate action, among other factors, depends on the barrier height (same as band discontinuity) at the oxide-semiconductor and oxide-metal interfaces. The band alignment is often estimated within the so-called metal-induced gap states (MIGS) model. The MIGS model describes both Bardeen and Schottky limits and interpolates between the two in a linear fashion, provided that electron affinities, charge neutralities and the pinning factor are known. We use the complex band structure of several prospective gate dielectrics (SiO_2, SrTiO_3, HfO_2, and Al_2O_3) to calculate their charge neutrality level, and estimate the band offset to Si, Pt, and several other metals. Results of these model calculations are then compared to those obtained with direct electronic structure methods.

  17. Flexible Linker Modulates Glycosaminoglycan Affinity of Decorin Binding Protein A.

    PubMed

    Morgan, Ashli; Sepuru, Krishna Mohan; Feng, Wei; Rajarathnam, Krishna; Wang, Xu

    2015-08-18

    Decorin binding protein A (DBPA) is a glycosaminoglycan (GAG)-binding adhesin found on the surface of the bacterium Borrelia burgdorferi (B. burgdorferi), the causative agent of Lyme disease. DBPA facilitates bacterial adherence to extracellular matrices of human tissues and is crucial during the early stage of the infection process. Interestingly, DBPA from different strains (B31, N40, and PBr) show significant differences in GAG affinities, but the structural basis for the differences is not clear. In this study, we show that GAG affinity of N40 DBPA is modulated in part by flexible segments that control access to the GAG binding site, such that shortening of the linker leads to higher GAG affinity when analyzed using ELISA, gel mobility shift assay, solution NMR, and isothermal titration calorimetry. Our observation that GAG affinity differences among different B. burgdorferi strains can be attributed to a flexible linker domain regulating access to the GAG-binding domain is novel. It also provides a rare example of how neutral amino acids and dynamic segments in GAG binding proteins can have a large influence on GAG affinity and provides insights into why the number of basic amino acids in the GAG-binding site may not be the only factor determining GAG affinity of proteins. PMID:26223367

  18. Effects of training and anthropometric factors on marathon and 100 km ultramarathon race performance

    PubMed Central

    Tanda, Giovanni; Knechtle, Beat

    2015-01-01

    Background Marathon (42 km) and 100 km ultramarathon races are increasing in popularity. The aim of the present study was to investigate the potential associations of anthropometric and training variables with performance in these long-distance running competitions. Methods Training and anthropometric data from a large cohort of marathoners and 100 km ultramarathoners provided the basis of this work. Correlations between training and anthropometric indices of subjects and race performance were assessed using bivariate and multiple regression analyses. Results A combination of volume and intensity in training was found to be suitable for prediction of marathon and 100 km ultramarathon race pace. The relative role played by these two variables was different, in that training volume was more important than training pace for the prediction of 100 km ultramarathon performance, while the opposite was found for marathon performance. Anthropometric characteristics in terms of body fat percentage negatively affected 42 km and 100 km race performance. However, when this factor was relatively low (ie, less than 15% body fat), the performance of 42 km and 100 km races could be predicted solely on the basis of training indices. Conclusion Mean weekly training distance run and mean training pace were key predictor variables for both marathon and 100 km ultramarathon race performance. Predictive correlations for race performance are provided for runners with a relatively low body fat percentage. PMID:25995653

  19. Neutrophil activation induced by the lectin KM+ involves binding to CXCR2.

    PubMed

    Pereira-da-Silva, Gabriela; Moreno, Andréa N; Marques, Fabiana; Oliver, Constance; Jamur, Maria Célia; Panunto-Castelo, Ademilson; Roque-Barreira, Maria Cristina

    2006-01-01

    The lectin KM+ from Artocarpus integrifolia, also known as artocarpin, induces neutrophil migration by haptotaxis. The interactions of KM+ with both neutrophils and the extracellular matrix depend on the lectin's ability to recognize mannose-containing glycans. In the present study, we characterized the binding of KM+ to human neutrophils and the responses stimulated by this binding. Exposure to KM+ results in cell polarization, formation of a lamellipodium, and induction of deep ruffles on the cell surface. By fluorescence microscopy, we observed that KM+ is distributed homogeneously over the cell surface. KM+/ligand complexes are rapidly internalized, reaching maximum intracellular concentrations at 120 min, and decreasing thereafter. Furthermore, KM+ binding to the surface of human neutrophils is inhibited by the specific sugars, d-mannose or mannotriose. KM+-induced neutrophil migration is inhibited by pertussis toxin as well as by inhibition of CXCR2 activity. These results suggest that the KM+ ligand on the neutrophil surface is a G protein-coupled receptor (GPCR). The results also suggest that neutrophil migration induced by KM+ involves binding to CXCR2.

  20. A new estimate of the Hubble constant using the Virgo cluster distance

    NASA Astrophysics Data System (ADS)

    Visvanathan, N.

    The Hubble constant, which defines the size and age of the universe, remains substantially uncertain. Attention is presently given to an improved distance to the Virgo Cluster obtained by means of the 1.05-micron luminosity-H I width relation of spirals. In order to improve the absolute calibration of the relation, accurate distances to the nearby SMC, LMC, N6822, SEX A and N300 galaxies have also been obtained, on the basis of the near-IR P-L relation of the Cepheids. A value for the global Hubble constant of 67 + or 4 km/sec per Mpc is obtained.