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Sample records for analytical ultracentrifugation gel

  1. Analytical Ultracentrifugation: Sedimentation Velocity and Sedimentation Equilibrium

    PubMed Central

    Cole, James L.; Lary, Jeffrey W.; Moody, Thomas; Laue, Thomas M.

    2009-01-01

    Analytical ultracentrifugation (AUC) is a versatile and powerful method for the quantitative analysis of macromolecules in solution. AUC has broad applications for the study of biomacromolecules in a wide range of solvents and over a wide range of solute concentrations. Three optical systems are available for the analytical ultracentrifuge (absorbance, interference and fluorescence) that permit precise and selective observation of sedimentation in real time. In particular, the fluorescence system provides a new way to extend the scope of AUC to probe the behavior of biological molecules in complex mixtures and at high solute concentrations. In sedimentation velocity, the movement of solutes in high centrifugal fields is interpreted using hydrodynamic theory to define the size, shape and interactions of macromolecules. Sedimentation equilibrium is a thermodynamic method where equilibrium concentration gradients at lower centrifugal fields are analyzed to define molecule mass, assembly stoichiometry, association constants and solution nonideality. Using specialized sample cells and modern analysis software, researchers can use sedimentation velocity to determine the homogeneity of a sample and define whether it undergoes concentration-dependent association reactions. Subsequently, more thorough model-dependent analysis of velocity and equilibrium experiments can provide a detailed picture of the nature of the species present in solution and their interactions. PMID:17964931

  2. Characterization of polymeric nanomaterials using analytical ultracentrifugation.

    PubMed

    Diaz, Leosveys; Peyrot, Caroline; Wilkinson, Kevin J

    2015-06-16

    The characterization of nanomaterials represents a complex analytical challenge due to their dynamic nature (small size, high reactivity, and instability) and the low concentrations in the environment, often below typical analytical detection limits. Analytical ultracentrifugation (AUC) is especially useful for the characterization of small nanoparticles (1-10 nm), which are often the most problematic for the commonly used techniques such as electron microscopy or dynamic light scattering. In this study, small polymeric nanomaterials (allospheres) that are used commercially to facilitate the distribution of pesticides in agricultural fields were characterized under a number of environmentally relevant conditions. Under most of the studied conditions, the allospheres were shown to have a constant hydrodynamic diameter (dH) of about 7.0 nm. Only small increases in diameter were observed, either at low pH or very high ionic strength or hardness, demonstrating their high physicochemical stability (and thus high mobility in soils). Furthermore, natural organic matter had little effect on the hydrodynamic diameters of the allospheres. The concentration of the nanoparticles was an important parameter influencing their agglomeration-results obtained using dynamic light scattering at high particle concentrations showed large agglomerate sizes and significant particle losses through sedimentation, clearly indicating the importance of characterizing the nanomaterials under environmentally relevant conditions. PMID:25988704

  3. Improved measurement of the rotor temperature in analytical ultracentrifugation.

    PubMed

    Zhao, Huaying; Balbo, Andrea; Metger, Howard; Clary, Robert; Ghirlando, Rodolfo; Schuck, Peter

    2014-04-15

    Sedimentation velocity is a classical method for measuring the hydrodynamic, translational friction coefficient of biological macromolecules. In a recent study comparing various analytical ultracentrifuges, we showed that external calibration of the scan time, radial magnification, and temperature is critically important for accurate measurements (Anal. Biochem. 440 (2013) 81-95). To achieve accurate temperature calibration, we introduced the use of an autonomous miniature temperature logging integrated circuit (Maxim Thermochron iButton) that can be inserted into an ultracentrifugation cell assembly and spun at low rotor speeds. In the current work, we developed an improved holder for the temperature sensor located in the rotor handle. This has the advantage of not reducing the rotor capacity and allowing for a direct temperature measurement of the spinning rotor during high-speed sedimentation velocity experiments up to 60,000rpm. We demonstrated the sensitivity of this approach by monitoring the adiabatic cooling due to rotor stretching during rotor acceleration and the reverse process on rotor deceleration. Based on this, we developed a procedure to approximate isothermal rotor acceleration for better temperature control. PMID:24530285

  4. Improved Measurement of the Rotor Temperature in Analytical Ultracentrifugation

    PubMed Central

    Zhao, Huaying; Balbo, Andrea; Metger, Howard; Clary, Robert; Ghirlando, Rodolfo; Schuck, Peter

    2014-01-01

    Sedimentation velocity is a classical method for measuring the hydrodynamic, translational friction coefficient of biological macromolecules. In a recent study, comparing various analytical ultracentrifuges, we have shown that external calibration of the scan time, radial magnification, and temperature are critically important for accurate measurements (Anal. Biochem., 2013, doi: 10.1016/j.ab.2013.05.011). To achieve accurate temperature calibration, we have introduced the use of an autonomous miniature temperature logging integrated circuit (Maxim Thermochron iButton ™) that can be inserted in an ultracentrifugation cell assembly and spun at low rotor speeds. In the present work, we developed an improved holder for the temperature sensor located in the rotor handle. This has the advantage of not reducing the rotor capacity and allows for a direct temperature measurement of the spinning rotor during high-speed sedimentation velocity experiments up to 60,000 rpm. We demonstrate the sensitivity of this approach by monitoring the adiabatic cooling due to rotor stretching during rotor acceleration, and the reverse process upon rotor deceleration. Based on this, we developed a procedure to approximate isothermal rotor acceleration for better temperature control. PMID:24530285

  5. Modern analytical ultracentrifugation in protein science: a tutorial review.

    PubMed

    Lebowitz, Jacob; Lewis, Marc S; Schuck, Peter

    2002-09-01

    Analytical ultracentrifugation (AU) is reemerging as a versatile tool for the study of proteins. Monitoring the sedimentation of macromolecules in the centrifugal field allows their hydrodynamic and thermodynamic characterization in solution, without interaction with any matrix or surface. The combination of new instrumentation and powerful computational software for data analysis has led to major advances in the characterization of proteins and protein complexes. The pace of new advancements makes it difficult for protein scientists to gain sufficient expertise to apply modern AU to their research problems. To address this problem, this review builds from the basic concepts to advanced approaches for the characterization of protein systems, and key computational and internet resources are provided. We will first explore the characterization of proteins by sedimentation velocity (SV). Determination of sedimentation coefficients allows for the modeling of the hydrodynamic shape of proteins and protein complexes. The computational treatment of SV data to resolve sedimenting components has been achieved. Hence, SV can be very useful in the identification of the oligomeric state and the stoichiometry of heterogeneous interactions. The second major part of the review covers sedimentation equilibrium (SE) of proteins, including membrane proteins and glycoproteins. This is the method of choice for molar mass determinations and the study of self-association and heterogeneous interactions, such as protein-protein, protein-nucleic acid, and protein-small molecule binding. PMID:12192063

  6. Dynamic range multiwavelength particle characterization using analytical ultracentrifugation.

    PubMed

    Walter, Johannes; Peukert, Wolfgang

    2016-03-31

    We demonstrate how a sophisticated data analysis methodology enables us to perform multiwavelength evaluations of dynamic rotor speed gradient experiments obtained by analytical ultracentrifugation equipped with a multiwavelength detector. Our data evaluation tool HDR-MULTIFIT allows for the accurate analysis of sedimentation coefficient distributions which can be converted to particle size distributions. By means of multiwavelength evaluation, species dependent extinction spectra can be determined even for complex mixtures. Moreover, optical and hydrodynamic properties can be correlated for spherical particles of known optical properties applying multiwavelength evaluation and Mie's theory leading to a significant increase in the dynamic range of the experiment. We provide the theoretical background about the operation principle of our methodology and compare the performance of the multiwavelength analysis to the conventional single wavelength analysis as it is applied in turbidity analysis. We validate our technique using NIST traceable reference particles and show that our technique is universally applicable to materials of known and unknown optical properties, thus clearly extending the possibilities of particle analysis. PMID:26837517

  7. Analytical Ultracentrifugation as a Tool for Studying Protein Interactions

    PubMed Central

    2013-01-01

    The last two decades have led to significant progress in the field of analytical ultracentrifugation driven by instrumental, theoretical, and computational methods. This review will highlight key developments in sedimentation equilibrium (SE) and sedimentation velocity (SV) analysis. For SE, this includes the analysis of tracer sedimentation equilibrium at high concentrations with strong thermodynamic non-ideality, and for ideally interacting systems the development of strategies for the analysis of heterogeneous interactions towards global multi-signal and multi-speed SE analysis with implicit mass conservation. For SV, this includes the development and applications of numerical solutions of the Lamm equation, noise decomposition techniques enabling direct boundary fitting, diffusion deconvoluted sedimentation coefficient distributions, and multi-signal sedimentation coefficient distributions. Recently, effective particle theory has uncovered simple physical rules for the co-migration of rapidly exchanging systems of interacting components in SV. This has opened new possibilities for the robust interpretation of the boundary patterns of heterogeneous interacting systems. Together, these SE and SV techniques have led to new approaches to study macromolecular interactions across the entire the spectrum of affinities, including both attractive and repulsive interactions, in both dilute and highly concentrated solutions, which can be applied to single-component solutions of self-associating proteins as well as the study of multi-protein complex formation in multi-component solutions. PMID:23682298

  8. Current Methods in Sedimentation Velocity and Sedimentation Equilibrium Analytical Ultracentrifugation

    PubMed Central

    Zhao, Huaying; Brautigam, Chad A.; Ghirlando, Rodolfo; Schuck, Peter

    2013-01-01

    Significant progress in the interpretation of analytical ultracentrifugation (AUC) data in the last decade has led to profound changes in the practice of AUC, both for sedimentation velocity (SV) and sedimentation equilibrium (SE). Modern computational strategies have allowed for the direct modeling of the sedimentation process of heterogeneous mixtures, resulting in SV size-distribution analyses with significantly improved detection limits and strongly enhanced resolution. These advances have transformed the practice of SV, rendering it the primary method of choice for most existing applications of AUC, such as the study of protein self- and hetero-association, the study of membrane proteins, and applications in biotechnology. New global multi-signal modeling and mass conservation approaches in SV and SE, in conjunction with the effective-particle framework for interpreting the sedimentation boundary structure of interacting systems, as well as tools for explicit modeling of the reaction/diffusion/sedimentation equations to experimental data, have led to more robust and more powerful strategies for the study of reversible protein interactions and multi-protein complexes. Furthermore, modern mathematical modeling capabilities have allowed for a detailed description of many experimental aspects of the acquired data, thus enabling novel experimental opportunities, with important implications for both sample preparation and data acquisition. The goal of the current commentary is to supplement previous AUC protocols, Current Protocols in Protein Science 20.3 (1999) and 20.7 (2003), and 7.12 (2008), and provide an update describing the current tools for the study of soluble proteins, detergent-solubilized membrane proteins and their interactions by SV and SE. PMID:23377850

  9. Studying multiprotein complexes by multisignal sedimentation velocity analytical ultracentrifugation

    PubMed Central

    Balbo, Andrea; Minor, Kenneth H.; Velikovsky, Carlos A.; Mariuzza, Roy A.; Peterson, Cynthia B.; Schuck, Peter

    2005-01-01

    Protein interactions can promote the reversible assembly of multiprotein complexes, which have been identified as critical elements in many regulatory processes in cells. The biophysical characterization of assembly products, their number and stoichiometry, and the dynamics of their interactions in solution can be very difficult. A classical first-principle approach for the study of purified proteins and their interactions is sedimentation velocity analytical ultracentrifugation. This approach allows one to distinguish different protein complexes based on their migration in the centrifugal field without isolating reversibly formed complexes from the individual components. An important existing limitation for systems with multiple components and assembly products is the identification of the species associated with the observed sedimentation rates. We developed a computational approach for integrating multiple optical signals into the sedimentation coefficient distribution analysis of components, which combines the size-dependent hydrodynamic separation with discrimination of the extinction properties of the sedimenting species. This approach allows one to deduce the stoichiometry and to assign the identity of the assembly products without prior assumptions of the number of species and the nature of their interaction. Although chromophoric labels may be used to enhance the spectral resolution, we demonstrate the ability to work label-free for three-component protein mixtures. We observed that the spectral discrimination can synergistically enhance the hydrodynamic resolution. This method can take advantage of differences in the absorbance spectra of interacting solution components, for example, for the study of protein–protein, protein–nucleic acid or protein–small molecule interactions, and can determine the size, hydrodynamic shape, and stoichiometry of multiple complexes in solution. PMID:15613487

  10. Studying multiprotein complexes by multisignal sedimentation velocity analytical ultracentrifugation.

    PubMed

    Balbo, Andrea; Minor, Kenneth H; Velikovsky, Carlos A; Mariuzza, Roy A; Peterson, Cynthia B; Schuck, Peter

    2005-01-01

    Protein interactions can promote the reversible assembly of multiprotein complexes, which have been identified as critical elements in many regulatory processes in cells. The biophysical characterization of assembly products, their number and stoichiometry, and the dynamics of their interactions in solution can be very difficult. A classical first-principle approach for the study of purified proteins and their interactions is sedimentation velocity analytical ultracentrifugation. This approach allows one to distinguish different protein complexes based on their migration in the centrifugal field without isolating reversibly formed complexes from the individual components. An important existing limitation for systems with multiple components and assembly products is the identification of the species associated with the observed sedimentation rates. We developed a computational approach for integrating multiple optical signals into the sedimentation coefficient distribution analysis of components, which combines the size-dependent hydrodynamic separation with discrimination of the extinction properties of the sedimenting species. This approach allows one to deduce the stoichiometry and to assign the identity of the assembly products without prior assumptions of the number of species and the nature of their interaction. Although chromophoric labels may be used to enhance the spectral resolution, we demonstrate the ability to work label-free for three-component protein mixtures. We observed that the spectral discrimination can synergistically enhance the hydrodynamic resolution. This method can take advantage of differences in the absorbance spectra of interacting solution components, for example, for the study of protein-protein, protein-nucleic acid or protein-small molecule interactions, and can determine the size, hydrodynamic shape, and stoichiometry of multiple complexes in solution. PMID:15613487

  11. Analytical ultracentrifugation: A versatile tool for the characterisation of macromolecular complexes in solution.

    PubMed

    Patel, Trushar R; Winzor, Donald J; Scott, David J

    2016-02-15

    Analytical ultracentrifugation, an early technique developed for characterizing quantitatively the solution properties of macromolecules, remains a powerful aid to structural biologists in their quest to understand the formation of biologically important protein complexes at the molecular level. Treatment of the basic tenets of the sedimentation velocity and sedimentation equilibrium variants of analytical ultracentrifugation is followed by considerations of the roles that it, in conjunction with other physicochemical procedures, has played in resolving problems encountered in the delineation of complex formation for three biological systems - the cytoplasmic dynein complex, mitogen-activated protein kinase (ERK2) self-interaction, and the terminal catalytic complex in selenocysteine synthesis. PMID:26555086

  12. [Splitting into two lines: The historical development of the analytical and the gas ultracentrifuge].

    PubMed

    Helmbold, Bernd; Forstner, Christian

    2015-12-01

    In a historical perspective the ultracentrifuge is often taken as perfect example of a research technology according to Shinn and Joerges (Shinn and Joerges 2000, 2002). Research technologies are defined by a generic device, its own metrology and the interstitiality of the historical actors connected with the device. In our paper we give a detailed analysis of the development of the ultracentrifuge and thereby reveal two different lines of development: analytical ultracentrifuges and gas ultra centrifuges used for isotope separation. Surprisingly, we could not find any interstitial and transversal connections for these two lines. The lines end up with two different devices based on two different technical concepts. Moreover, the great majority of the actors stick to one line. These results are in accordance withother authors, who developed the concept of research technologies further and tried to sharpen their definition. PMID:26572680

  13. Sedimentation analysis of von Willebrand and factor VIIIC protein using partition cells in the analytical ultracentrifuge.

    PubMed

    Barlow, G H; Martin, S E; Marder, V J

    1984-04-01

    Sedimentation analysis of factor VIII complex was performed in the analytical ultracentrifuge using partition cells. This method allowed for the calculation of three different sedimentation coefficients from each run: one based on ristocetin agglutination activity for von Willebrand protein, SWF; one based on coagulant activity for factor VIIIC, SVIIIC; and one based on the schlieren or adsorption data for protein concentration, Sconc. In most cases, there was no agreement between the three values calculated from the same run, indicating a heterogeneous system. The calculated functional sedimentation coefficients give values that require the molecules to be highly asymmetric to be consistent with a glycoprotein of high molecular weight, which is in agreement with results observed in electron microscope studies. The dissociation of VIIIC into a smaller form can be demonstrated by this method. Determination of the three sedimentation coefficients in a series of fractions from gel filtration indicates a uniform size for the VIIIC activity but not for the WF activity. These observations are in agreement with the concept of a copolymer between WF and VIIIC and also with the concept of separate polymers for the two activities. PMID:6423013

  14. Analytical Ultracentrifugation and Its Role in Development and Research of Therapeutical Proteins.

    PubMed

    Liu, Jun; Yadav, Sandeep; Andya, James; Demeule, Barthélemy; Shire, Steven J

    2015-01-01

    The historical contributions of analytical ultracentrifugation (AUC) to modern biology and biotechnology drug development and research are discussed. AUC developed by Svedberg was used to show that proteins are actually large defined molecular entities and also provided the first experimental verification for the semiconservative replication model for DNA initially proposed by Watson and Crick. This chapter reviews the use of AUC to investigate molecular weight of recombinant-DNA-produced proteins, complex formation of antibodies, intermolecular interactions in dilute and high concentration protein solution, and their impact on physical properties such as solution viscosity. Recent studies using a "competitive binding" analysis by AUC have been useful in critically evaluating the design and interpretation of surface plasmon resonance measurements and are discussed. The future of this technology is also discussed including prospects for a new higher precision analytical ultracentrifuge. PMID:26412663

  15. Multidimensional analysis of nanoparticles with highly disperse properties using multiwavelength analytical ultracentrifugation.

    PubMed

    Walter, Johannes; Löhr, Konrad; Karabudak, Engin; Reis, Wieland; Mikhael, Jules; Peukert, Wolfgang; Wohlleben, Wendel; Cölfen, Helmut

    2014-09-23

    The worldwide trend in nanoparticle technology toward increasing complexity must be directly linked to more advanced characterization methods of size, shape and related properties, applicable to many different particle systems in science and technology. Available techniques for nanoparticle characterization are predominantly focused on size characterization. However, simultaneous size and shape characterization is still an unresolved major challenge. We demonstrate that analytical ultracentrifugation with a multiwavelength detector is a powerful technique to address multidimensional nanoparticle analysis. Using a high performance optical setup and data acquisition software, information on size, shape anisotropy and optical properties were accessible in one single experiment with unmatched accuracy and resolution. A dynamic rotor speed gradient allowed us to investigate broad distributions on a short time scale and differentiate between gold nanorod species including the precise evaluation of aggregate formation. We report how to distinguish between different species of single-wall carbon nanotubes in just one experiment using the wavelength-dependent sedimentation coefficient distribution without the necessity of time-consuming purification methods. Furthermore, CdTe nanoparticles of different size and optical properties were investigated in a single experiment providing important information on structure-property relations. Thus, multidimensional information on size, density, shape and optical properties of nanoparticulate systems becomes accessible by means of analytical ultracentrifugation equipped with multiwavelength detection. PMID:25130765

  16. Determination of nanoparticle size distribution together with density or molecular weight by 2D analytical ultracentrifugation

    PubMed Central

    Carney, Randy P.; Kim, Jin Young; Qian, Huifeng; Jin, Rongchao; Mehenni, Hakim; Stellacci, Francesco; Bakr, Osman M.

    2011-01-01

    Nanoparticles are finding many research and industrial applications, yet their characterization remains a challenge. Their cores are often polydisperse and coated by a stabilizing shell that varies in size and composition. No single technique can characterize both the size distribution and the nature of the shell. Advances in analytical ultracentrifugation allow for the extraction of the sedimentation (s) and diffusion coefficients (D). Here we report an approach to transform the s and D distributions of nanoparticles in solution into precise molecular weight (M), density (ρP) and particle diameter (dp) distributions. M for mixtures of discrete nanocrystals is found within 4% of the known quantities. The accuracy and the density information we achieve on nanoparticles are unparalleled. A single experimental run is sufficient for full nanoparticle characterization, without the need for standards or other auxiliary measurements. We believe that our method is of general applicability and we discuss its limitations. PMID:21654635

  17. Studying polyglutamine aggregation in Caenorhabditis elegans using an analytical ultracentrifuge equipped with fluorescence detection.

    PubMed

    Kokona, Bashkim; May, Carrie A; Cunningham, Nicole R; Richmond, Lynn; Jay Garcia, F; Durante, Julia C; Ulrich, Kathleen M; Roberts, Christine M; Link, Christopher D; Stafford, Walter F; Laue, Thomas M; Fairman, Robert

    2016-03-01

    This work explores the heterogeneity of aggregation of polyglutamine fusion constructs in crude extracts of transgenic Caenorhabditis elegans animals. The work takes advantage of the recent technical advances in fluorescence detection for the analytical ultracentrifuge. Further, new sedimentation velocity methods, such as the multi-speed method for data capture and wide distribution analysis for data analysis, are applied to improve the resolution of the measures of heterogeneity over a wide range of sizes. The focus here is to test the ability to measure sedimentation of polyglutamine aggregates in complex mixtures as a prelude to future studies that will explore the effects of genetic manipulation and environment on aggregation and toxicity. Using sedimentation velocity methods, we can detect a wide range of aggregates, ranging from robust analysis of the monomer species through an intermediate and quite heterogeneous population of oligomeric species, and all the way up to detecting species that likely represent intact inclusion bodies based on comparison to an analysis of fluorescent puncta in living worms by confocal microscopy. Our results support the hypothesis that misfolding of expanded polyglutamine tracts into insoluble aggregates involves transitions through a number of stable intermediate structures, a model that accounts for how an aggregation pathway can lead to intermediates that can have varying toxic or protective attributes. An understanding of the details of intermediate and large-scale aggregation for polyglutamine sequences, as found in neurodegenerative diseases such as Huntington's Disease, will help to more precisely identify which aggregated species may be involved in toxicity and disease. PMID:26647351

  18. Tools for the Quantitative Analysis of Sedimentation Boundaries Detected by Fluorescence Optical Analytical Ultracentrifugation

    PubMed Central

    Zhao, Huaying; Casillas, Ernesto; Shroff, Hari; Patterson, George H.; Schuck, Peter

    2013-01-01

    Fluorescence optical detection in sedimentation velocity analytical ultracentrifugation allows the study of macromolecules at nanomolar concentrations and below. This has significant promise, for example, for the study of systems of high-affinity protein interactions. Here we describe adaptations of the direct boundary modeling analysis approach implemented in the software SEDFIT that were developed to accommodate unique characteristics of the confocal fluorescence detection system. These include spatial gradients of signal intensity due to scanner movements out of the plane of rotation, temporal intensity drifts due to instability of the laser and fluorophores, and masking of the finite excitation and detection cone by the sample holder. In an extensive series of experiments with enhanced green fluorescent protein ranging from low nanomolar to low micromolar concentrations, we show that the experimental data provide sufficient information to determine the parameters required for first-order approximation of the impact of these effects on the recorded data. Systematic deviations of fluorescence optical sedimentation velocity data analyzed using conventional sedimentation models developed for absorbance and interference optics are largely removed after these adaptations, resulting in excellent fits that highlight the high precision of fluorescence sedimentation velocity data, thus allowing a more detailed quantitative interpretation of the signal boundaries that is otherwise not possible for this system. PMID:24204779

  19. Determination of the lateral dimension of graphene oxide nanosheets using analytical ultracentrifugation.

    PubMed

    Walter, Johannes; Nacken, Thomas J; Damm, Cornelia; Thajudeen, Thaseem; Eigler, Siegfried; Peukert, Wolfgang

    2015-02-18

    In this paper, a method to determine the lateral dimensions of 2D nanosheets directly in suspension by analytical ultracentrifugation (AUC) is shown. The basis for this study is a well-characterized and stable dispersion of graphene oxide (GO) monolayers in water. A methodology is developed to correlate the sedimentation coefficient distribution measured by AUC with the lateral size distribution of the 2D GO nanosheets obtained from atomic force microscopy (AFM). A very high accuracy can be obtained by virtue of counting several thousand sheets, thereby minimizing any coating effects or statistical uncertainties. The AFM statistics are further used to fit the lateral size distribution obtained from the AUC to determine the unknown hydrodynamic sheet thickness or density. It is found that AUC can derive nanosheet diameter distributions with a relative error of the mean sheet diameter of just 0.25% as compared to the AFM analysis for 90 mass% of the particles in the distribution. The standard deviation of the size-dependent error for the total distribution is found to be 3.25%. Based on these considerations, an expression is given to calculate the cut size of 2D nanosheets in preparative centrifugation experiments. PMID:25201557

  20. Simultaneous analysis of hydrodynamic and optical properties using analytical ultracentrifugation equipped with multiwavelength detection.

    PubMed

    Walter, Johannes; Sherwood, Peter J; Lin, Wei; Segets, Doris; Stafford, Walter F; Peukert, Wolfgang

    2015-03-17

    Analytical ultracentrifugation (AUC) has proven to be a powerful tool for the study of particle size distributions, particle shapes, and interactions with high accuracy and unrevealed resolution. In this work we show how the analysis of sedimentation velocity data from the AUC equipped with a multiwavelength detector (MWL) can be used to gain an even deeper understanding of colloidal and macromolecular mixtures. New data evaluation routines have been integrated in the software SEDANAL to allow for the handling of MWL data. This opens up a variety of new possibilities because spectroscopic information becomes available for individual components in mixtures at the same time using MWL-AUC. For systems of known optical properties information on the hydrodynamic properties of the individual components in a mixture becomes accessible. For the first time, the determination of individual extinction spectra of components in mixtures is demonstrated via MWL evaluation of sedimentation velocity data. In our paper we first provide the informational background for the data analysis and expose the accessible parameters of our methodology. We further demonstrate the data evaluation by means of simulated data. Finally, we give two examples which are highly relevant in the field of nanotechnology using colored silica and gold nanoparticles of different size and extinction properties. PMID:25679871

  1. Recent Advances in the Analysis of Macromolecular Interactions Using the Matrix-Free Method of Sedimentation in the Analytical Ultracentrifuge

    PubMed Central

    Harding, Stephen E.; Gillis, Richard B.; Almutairi, Fahad; Erten, Tayyibe; Kök, M. Şamil; Adams, Gary G.

    2015-01-01

    Sedimentation in the analytical ultracentrifuge is a matrix free solution technique with no immobilisation, columns, or membranes required and can be used to study self-association and complex or “hetero”-interactions, stoichiometry, reversibility and interaction strength of a wide variety of macromolecular types and across a very large dynamic range (dissociation constants from 10−12 M to 10−1 M). We extend an earlier review specifically highlighting advances in sedimentation velocity and sedimentation equilibrium in the analytical ultracentrifuge applied to protein interactions and mucoadhesion and to review recent applications in protein self-association (tetanus toxoid, agrin), protein-like carbohydrate association (aminocelluloses), carbohydrate-protein interactions (polysaccharide-gliadin), nucleic-acid protein (G-duplexes), nucleic acid-carbohydrate (DNA-chitosan) and finally carbohydrate-carbohydrate (xanthan-chitosan and a ternary polysaccharide complex) interactions. PMID:25756246

  2. A Multilaboratory Comparison of Calibration Accuracy and the Performance of External References in Analytical Ultracentrifugation

    PubMed Central

    Zhao, Huaying; Ghirlando, Rodolfo; Alfonso, Carlos; Arisaka, Fumio; Attali, Ilan; Bain, David L.; Bakhtina, Marina M.; Becker, Donald F.; Bedwell, Gregory J.; Bekdemir, Ahmet; Besong, Tabot M. D.; Birck, Catherine; Brautigam, Chad A.; Brennerman, William; Byron, Olwyn; Bzowska, Agnieszka; Chaires, Jonathan B.; Chaton, Catherine T.; Cölfen, Helmut; Connaghan, Keith D.; Crowley, Kimberly A.; Curth, Ute; Daviter, Tina; Dean, William L.; Díez, Ana I.; Ebel, Christine; Eckert, Debra M.; Eisele, Leslie E.; Eisenstein, Edward; England, Patrick; Escalante, Carlos; Fagan, Jeffrey A.; Fairman, Robert; Finn, Ron M.; Fischle, Wolfgang; de la Torre, José García; Gor, Jayesh; Gustafsson, Henning; Hall, Damien; Harding, Stephen E.; Cifre, José G. Hernández; Herr, Andrew B.; Howell, Elizabeth E.; Isaac, Richard S.; Jao, Shu-Chuan; Jose, Davis; Kim, Soon-Jong; Kokona, Bashkim; Kornblatt, Jack A.; Kosek, Dalibor; Krayukhina, Elena; Krzizike, Daniel; Kusznir, Eric A.; Kwon, Hyewon; Larson, Adam; Laue, Thomas M.; Le Roy, Aline; Leech, Andrew P.; Lilie, Hauke; Luger, Karolin; Luque-Ortega, Juan R.; Ma, Jia; May, Carrie A.; Maynard, Ernest L.; Modrak-Wojcik, Anna; Mok, Yee-Foong; Mücke, Norbert; Nagel-Steger, Luitgard; Narlikar, Geeta J.; Noda, Masanori; Nourse, Amanda; Obsil, Tomas; Park, Chad K.; Park, Jin-Ku; Pawelek, Peter D.; Perdue, Erby E.; Perkins, Stephen J.; Perugini, Matthew A.; Peterson, Craig L.; Peverelli, Martin G.; Piszczek, Grzegorz; Prag, Gali; Prevelige, Peter E.; Raynal, Bertrand D. E.; Rezabkova, Lenka; Richter, Klaus; Ringel, Alison E.; Rosenberg, Rose; Rowe, Arthur J.; Rufer, Arne C.; Scott, David J.; Seravalli, Javier G.; Solovyova, Alexandra S.; Song, Renjie; Staunton, David; Stoddard, Caitlin; Stott, Katherine; Strauss, Holger M.; Streicher, Werner W.; Sumida, John P.; Swygert, Sarah G.; Szczepanowski, Roman H.; Tessmer, Ingrid; Toth, Ronald T.; Tripathy, Ashutosh; Uchiyama, Susumu; Uebel, Stephan F. W.; Unzai, Satoru; Gruber, Anna Vitlin; von Hippel, Peter H.; Wandrey, Christine; Wang, Szu-Huan; Weitzel, Steven E.; Wielgus-Kutrowska, Beata; Wolberger, Cynthia; Wolff, Martin; Wright, Edward; Wu, Yu-Sung; Wubben, Jacinta M.; Schuck, Peter

    2015-01-01

    Analytical ultracentrifugation (AUC) is a first principles based method to determine absolute sedimentation coefficients and buoyant molar masses of macromolecules and their complexes, reporting on their size and shape in free solution. The purpose of this multi-laboratory study was to establish the precision and accuracy of basic data dimensions in AUC and validate previously proposed calibration techniques. Three kits of AUC cell assemblies containing radial and temperature calibration tools and a bovine serum albumin (BSA) reference sample were shared among 67 laboratories, generating 129 comprehensive data sets. These allowed for an assessment of many parameters of instrument performance, including accuracy of the reported scan time after the start of centrifugation, the accuracy of the temperature calibration, and the accuracy of the radial magnification. The range of sedimentation coefficients obtained for BSA monomer in different instruments and using different optical systems was from 3.655 S to 4.949 S, with a mean and standard deviation of (4.304 ± 0.188) S (4.4%). After the combined application of correction factors derived from the external calibration references for elapsed time, scan velocity, temperature, and radial magnification, the range of s-values was reduced 7-fold with a mean of 4.325 S and a 6-fold reduced standard deviation of ± 0.030 S (0.7%). In addition, the large data set provided an opportunity to determine the instrument-to-instrument variation of the absolute radial positions reported in the scan files, the precision of photometric or refractometric signal magnitudes, and the precision of the calculated apparent molar mass of BSA monomer and the fraction of BSA dimers. These results highlight the necessity and effectiveness of independent calibration of basic AUC data dimensions for reliable quantitative studies. PMID:25997164

  3. A multilaboratory comparison of calibration accuracy and the performance of external references in analytical ultracentrifugation.

    PubMed

    Zhao, Huaying; Ghirlando, Rodolfo; Alfonso, Carlos; Arisaka, Fumio; Attali, Ilan; Bain, David L; Bakhtina, Marina M; Becker, Donald F; Bedwell, Gregory J; Bekdemir, Ahmet; Besong, Tabot M D; Birck, Catherine; Brautigam, Chad A; Brennerman, William; Byron, Olwyn; Bzowska, Agnieszka; Chaires, Jonathan B; Chaton, Catherine T; Cölfen, Helmut; Connaghan, Keith D; Crowley, Kimberly A; Curth, Ute; Daviter, Tina; Dean, William L; Díez, Ana I; Ebel, Christine; Eckert, Debra M; Eisele, Leslie E; Eisenstein, Edward; England, Patrick; Escalante, Carlos; Fagan, Jeffrey A; Fairman, Robert; Finn, Ron M; Fischle, Wolfgang; de la Torre, José García; Gor, Jayesh; Gustafsson, Henning; Hall, Damien; Harding, Stephen E; Cifre, José G Hernández; Herr, Andrew B; Howell, Elizabeth E; Isaac, Richard S; Jao, Shu-Chuan; Jose, Davis; Kim, Soon-Jong; Kokona, Bashkim; Kornblatt, Jack A; Kosek, Dalibor; Krayukhina, Elena; Krzizike, Daniel; Kusznir, Eric A; Kwon, Hyewon; Larson, Adam; Laue, Thomas M; Le Roy, Aline; Leech, Andrew P; Lilie, Hauke; Luger, Karolin; Luque-Ortega, Juan R; Ma, Jia; May, Carrie A; Maynard, Ernest L; Modrak-Wojcik, Anna; Mok, Yee-Foong; Mücke, Norbert; Nagel-Steger, Luitgard; Narlikar, Geeta J; Noda, Masanori; Nourse, Amanda; Obsil, Tomas; Park, Chad K; Park, Jin-Ku; Pawelek, Peter D; Perdue, Erby E; Perkins, Stephen J; Perugini, Matthew A; Peterson, Craig L; Peverelli, Martin G; Piszczek, Grzegorz; Prag, Gali; Prevelige, Peter E; Raynal, Bertrand D E; Rezabkova, Lenka; Richter, Klaus; Ringel, Alison E; Rosenberg, Rose; Rowe, Arthur J; Rufer, Arne C; Scott, David J; Seravalli, Javier G; Solovyova, Alexandra S; Song, Renjie; Staunton, David; Stoddard, Caitlin; Stott, Katherine; Strauss, Holger M; Streicher, Werner W; Sumida, John P; Swygert, Sarah G; Szczepanowski, Roman H; Tessmer, Ingrid; Toth, Ronald T; Tripathy, Ashutosh; Uchiyama, Susumu; Uebel, Stephan F W; Unzai, Satoru; Gruber, Anna Vitlin; von Hippel, Peter H; Wandrey, Christine; Wang, Szu-Huan; Weitzel, Steven E; Wielgus-Kutrowska, Beata; Wolberger, Cynthia; Wolff, Martin; Wright, Edward; Wu, Yu-Sung; Wubben, Jacinta M; Schuck, Peter

    2015-01-01

    Analytical ultracentrifugation (AUC) is a first principles based method to determine absolute sedimentation coefficients and buoyant molar masses of macromolecules and their complexes, reporting on their size and shape in free solution. The purpose of this multi-laboratory study was to establish the precision and accuracy of basic data dimensions in AUC and validate previously proposed calibration techniques. Three kits of AUC cell assemblies containing radial and temperature calibration tools and a bovine serum albumin (BSA) reference sample were shared among 67 laboratories, generating 129 comprehensive data sets. These allowed for an assessment of many parameters of instrument performance, including accuracy of the reported scan time after the start of centrifugation, the accuracy of the temperature calibration, and the accuracy of the radial magnification. The range of sedimentation coefficients obtained for BSA monomer in different instruments and using different optical systems was from 3.655 S to 4.949 S, with a mean and standard deviation of (4.304 ± 0.188) S (4.4%). After the combined application of correction factors derived from the external calibration references for elapsed time, scan velocity, temperature, and radial magnification, the range of s-values was reduced 7-fold with a mean of 4.325 S and a 6-fold reduced standard deviation of ± 0.030 S (0.7%). In addition, the large data set provided an opportunity to determine the instrument-to-instrument variation of the absolute radial positions reported in the scan files, the precision of photometric or refractometric signal magnitudes, and the precision of the calculated apparent molar mass of BSA monomer and the fraction of BSA dimers. These results highlight the necessity and effectiveness of independent calibration of basic AUC data dimensions for reliable quantitative studies. PMID:25997164

  4. Variable-Field Analytical Ultracentrifugation: I. Time-Optimized Sedimentation Equilibrium.

    PubMed

    Ma, Jia; Metrick, Michael; Ghirlando, Rodolfo; Zhao, Huaying; Schuck, Peter

    2015-08-18

    Sedimentation equilibrium (SE) analytical ultracentrifugation (AUC) is a gold standard for the rigorous determination of macromolecular buoyant molar masses and the thermodynamic study of reversible interactions in solution. A significant experimental drawback is the long time required to attain SE, which is usually on the order of days. We have developed a method for time-optimized SE (toSE) with defined time-varying centrifugal fields that allow SE to be attained in a significantly (up to 10-fold) shorter time than is usually required. To achieve this, numerical Lamm equation solutions for sedimentation in time-varying fields are computed based on initial estimates of macromolecular transport properties. A parameterized rotor-speed schedule is optimized with the goal of achieving a minimal time to equilibrium while limiting transient sample preconcentration at the base of the solution column. The resulting rotor-speed schedule may include multiple over- and underspeeding phases, balancing the formation of gradients from strong sedimentation fluxes with periods of high diffusional transport. The computation is carried out in a new software program called TOSE, which also facilitates convenient experimental implementation. Further, we extend AUC data analysis to sedimentation processes in such time-varying centrifugal fields. Due to the initially high centrifugal fields in toSE and the resulting strong migration, it is possible to extract sedimentation coefficient distributions from the early data. This can provide better estimates of the size of macromolecular complexes and report on sample homogeneity early on, which may be used to further refine the prediction of the rotor-speed schedule. In this manner, the toSE experiment can be adapted in real time to the system under study, maximizing both the information content and the time efficiency of SE experiments. PMID:26287634

  5. A short-run new analytical ultracentrifugal micromethod for determining low-density lipoprotein sub-fractions using Schlieren refractometry.

    PubMed

    Bozóky, Z; Fülöp, L; Köhidai, L

    2001-01-01

    We have developed a new analytical ultracentrifugal micromethod for the determination of serum low-density lipoprotein (LDL) subclasses directly from ultracentrifugal Schlieren scans. We have used special software for the analysis of this type of single-spin density-gradient ultracentrifugation. The flotation of LDL patterns was obtained by underlayering a physiological salt solution with serum or isolated lipoprotein fractions raised to a density of 1.3 g/mL in the spinning ultracentrifugation capillary band-forming cell. The repeated analysis of Schlieren curves of the same sample from 10 to 100 microL in the 60-100 min full-speed interval time resulted in quite reproducible results. We obtained quantitative results by measuring the Schlieren areas between the sample curves and the reference baseline curve by using computerised numerical and graphic techniques. The decomposition of the integrated curve was carried out using a nonlinear regression program followed by deconvolution algorithm analysis in order to determine the parameters of the composing Gaussian subclasses. The LDL particle concentrations were calculated from the area under the integral of the Gaussian curve using a calibration data constant. The flotation range of the LDL Schlieren curves in the cell was identified with serum from which LDL had been removed by means of precipitation reagents and with centrifugation of isolated LDL aliquots. With this technique, we measured the concentration of LDL and analysed its polydispersity without the need for preceding sequential isolation of the LDL. On the basis of the Schlieren curves, the LDL samples were either physically paucidisperse, having a symmetrical peak within a narrow density range, or were polydisperse, showing an asymmetrical pattern distributed over a broader density region. The described method proved to be useful for a clear and immediate visual presentation of the concentration values of the LDL and for the identification of the heterogeneity of LDL variants without the need for the preparative isolation of that density class. PMID:11288837

  6. Probing the selectivity of β-hydroxylation reactions in non-ribosomal peptide synthesis using analytical ultracentrifugation.

    PubMed

    Kokona, Bashkim; Winesett, Emily S; Nikolai von Krusenstiern, A; Cryle, Max J; Fairman, Robert; Charkoudian, Louise K

    2016-02-15

    Bacteria and fungi use non-ribosomal peptide synthetases (NRPSs) to produce peptides of broad structural diversity and biological activity, many of which have proven to be of great importance for human health. The impressive diversity of non-ribosomal peptides originates in part from the action of tailoring enzymes that modify the structures of single amino acids and/or the mature peptide. Studying the interplay between tailoring enzymes and the peptidyl carrier proteins (PCPs) that anchor the substrates is challenging owing to the transient and complex nature of the protein-protein interactions. Using sedimentation velocity (SV) methods, we studied the collaboration between the PCPs and cytochrome P450 enzyme that results in the installation of β-hydroxylated amino acid precursors in the biosynthesis of the depsipeptide skyllamycin. We show that SV methods developed for the analytical ultracentrifuge are ideally suited for a quantitative exploration of PCP-enzyme equilibrium interactions. Our results suggest that the PCP itself and the presence of substrate covalently tethered to the PCP together facilitate productive PCP-P450 interactions, thereby revealing one of nature's intricate strategies for installing interesting functionalities using natural product synthetases. PMID:26655390

  7. Analyzing surfactant structures on length and chirality resolved (6,5) single-wall carbon nanotubes by analytical ultracentrifugation.

    PubMed

    Fagan, Jeffrey A; Zheng, Ming; Rastogi, Vinayak; Simpson, Jeffrey R; Khripin, Constantine Y; Silvera Batista, Carlos A; Hight Walker, Angela R

    2013-04-23

    The structure and density of the bound interfacial surfactant layer and associated hydration shell were investigated using analytical ultracentrifugation for length and chirality purified (6,5) single-wall carbon nanotubes (SWCNTs) in three different bile salt surfactant solutions. The differences in the chemical structures of the surfactants significantly affect the size and density of the bound surfactant layers. As probed by exchange of a common parent nanotube population into sodium deoxycholate, sodium cholate, or sodium taurodeoxycholate solutions, the anhydrous density of the nanotubes was least for the sodium taurodeoxycholate surfactant, and the absolute sedimentation velocities greatest for the sodium cholate and sodium taurodeoxycholate surfactants. These results suggest that the thickest interfacial layer is formed by the deoxycholate, and that the taurodeoxycholate packs more densely than either sodium cholate or deoxycholate. These structural differences correlate well to an observed 25% increase in fluorescence intensity relative to the cholate surfactant for deoxycholate and taurodeoxycholate dispersed SWCNTs displaying equivalent absorbance spectra. Separate sedimentation velocity experiments including the density modifying agent iodixanol were used to establish the buoyant density of the (6,5) SWCNT in each of the bile salt surfactants; from the difference in the buoyant and anhydrous densities, the largest hydrated diameter is observed for sodium deoxycholate. Understanding the effects of dispersant choice and the methodology for measurement of the interfacial density and hydrated diameter is critical for rationally advancing separation strategies and applications of nanotubes. PMID:23530719

  8. Analysis of High Affinity Self-Association by Fluorescence Optical Sedimentation Velocity Analytical Ultracentrifugation of Labeled Proteins: Opportunities and Limitations

    PubMed Central

    Zhao, Huaying; Lomash, Suvendu; Glasser, Carla; Mayer, Mark L.; Schuck, Peter

    2013-01-01

    Sedimentation velocity analytical ultracentrifugation (SV) is a powerful first-principle technique for the study of protein interactions, and allows a rigorous characterization of binding stoichiometry and affinities. A recently introduced commercial fluorescence optical detection system (FDS) permits analysis of high-affinity interactions by SV. However, for most proteins the attachment of an extrinsic fluorophore is an essential prerequisite for analysis by FDS-SV. Using the glutamate receptor GluA2 amino terminal domain as a model system for high-affinity homo-dimerization, we demonstrate how the experimental design and choice of fluorescent label can impact both the observed binding constants as well as the derived hydrodynamic parameter estimates for the monomer and dimer species. Specifically, FAM (5,6-carboxyfluorescein) was found to create different populations of artificially high-affinity and low-affinity dimers, as indicated by both FDS-SV and the kinetics of dimer dissociation studied using a bench-top fluorescence spectrometer and Förster Resonance Energy Transfer. By contrast, Dylight488 labeled GluA2, as well as GluA2 expressed as an EGFP fusion protein, yielded results consistent with estimates for unlabeled GluA2. Our study suggests considerations for the choice of labeling strategies, and highlights experimental designs that exploit specific opportunities of FDS-SV for improving the reliability of the binding isotherm analysis of interacting systems. PMID:24358283

  9. Investigation of pH-induced conformational change and hydration of poly(methacrylic acid) by analytical ultracentrifugation.

    PubMed

    Wang, Xiaoyan; Ye, Xiaodong; Zhang, Guangzhao

    2015-07-14

    Analytical ultracentrifugation was performed on poly(methacrylic acid) (PMAA) with a series of weight average molar masses (Mw) in aqueous solutions as a function of pH. The scales of the sedimentation coefficient (s) and the diffusion coefficient (D) to Mw at infinite dilutions were obtained at different pH values, indicating that PMAA chains adopt a collapsed structure at low pH values, and stretch at pH higher than 5.2. Our results show that the sedimentation coefficient exhibits a minimum at pH ∼ 6.0, presumably due to the effect of the conformational change and the hydration state of PMAA chains. When pH increases from 6.0 to 8.5, PMAA chains with high molar mass shrink a little bit, presumably because the sodium ions act as a bridging agent between nonadjacent carboxylate groups. Furthermore, the weight average molar mass of PMAA at pH 8.5 increases by one fold than that at pH 4.0, indicating the condensation of sodium ions and the increase in the number of hydration water molecules around carboxylate groups at high pH values. PMID:26059391

  10. Characterizing the Effect of Salt and Surfactant Concentration on the Counterion Atmosphere around Surfactant Stabilized SWCNTs Using Analytical Ultracentrifugation.

    PubMed

    Lam, Stephanie; Zheng, Ming; Fagan, Jeffrey A

    2016-04-26

    Accurate characterization of dispersed-phase nanoparticle properties such as density, size, solvation, and charge is necessary for their utilization in applications such as medicine, energy, and materials. Herein, analytical ultracentrifugation (AUC) is used to quantify bile salt surfactant adsorption on length sorted (7,6) single-wall carbon nanotubes (SWCNTs) as a function of bulk surfactant concentration and in the presence of varying quantities of a monovalent salt-sodium chloride. These measurements provide high precision adsorbed surfactant density values in the literature for only the second SWCNT structure to date and report the quantity of adsorbed surfactant across a broad range of bulk surfactant concentrations utilized in SWCNT dispersion processing. Second, the measurements presented herein unambiguously demonstrate, via AUC, a direct relation between the size of the counterion cloud around a surfactant-stabilized SWCNT and solution ionic strength. The results show that changes in the size of the counterion cloud around surfactant-stabilized SWCNT are attributable to electrostatic phenomenon and not to changes in the quantity of adsorbed surfactant with salt addition. These results provide important reference values for projecting SWCNT dispersion behavior as a function of solution conditions and extend the range of nanoparticle properties measurable via AUC. PMID:27031248

  11. Characterization of protein detergent complexes by NMR, light scattering, and analytical ultracentrifugation.

    PubMed

    Maslennikov, Innokentiy; Krupa, Martin; Dickson, Christopher; Esquivies, Luis; Blain, Katherine; Kefala, Georgia; Choe, Senyon; Kwiatkowski, Witek

    2009-03-01

    Bottlenecks in expression, solubilization, purification and crystallization hamper the structural study of integral membrane proteins (IMPs). Successful crystallization is critically dependent on the purity, stability and oligomeric homogeneity of an IMP sample. These characteristics are in turn strongly influenced by the type and concentration of the detergents used in IMP preparation. By utilizing the techniques and analytical tools we earlier developed for the characterization of protein-detergent complexes (PDCs) [21], we demonstrate that for successful protein extraction from E. coli membrane fractions, the solubilizing detergent associates preferentially to IMPs rather than to membrane lipids. Notably, this result is contrary to the generally accepted mechanism of detergent-mediated IMP solubilization. We find that for one particular member of the family of proteins studied (E. coli receptor kinases, which is purified in mixed multimeric states and oligomerizes through its transmembrane region), the protein oligomeric composition is largely unaffected by a 10-fold increase in protein concentration, by alteration of micelle properties through addition of other detergents to the PDC sample, or by a 20-fold variation in the detergent concentration used for solubilization of the IMP from the membrane. We observed that the conditions used for expression of the IMP, which impact protein density in the membrane, has the greatest influence on the IMP oligomeric structure. Finally, we argue that for concentrating PDCs smaller than 30 kDa, stirred concentration cells are less prone to over-concentration of detergent and are therefore more effective than centrifugal ultrafiltration devices. PMID:19214777

  12. Measuring agglomerate size distribution and dependence of localized surface plasmon resonance absorbance on gold nanoparticle agglomerate size using analytical ultracentrifugation.

    PubMed

    Zook, Justin M; Rastogi, Vinayak; Maccuspie, Robert I; Keene, Athena M; Fagan, Jeffrey

    2011-10-25

    Agglomeration of nanoparticles during measurements in relevant biological and environmental media is a frequent problem in nanomaterial property characterization. The primary problem is typically that any changes to the size distribution can dramatically affect the potential nanotoxicity or other size-determined properties, such as the absorbance signal in a biosensor measurement. Herein we demonstrate analytical ultracentrifugation (AUC) as a powerful method for measuring two critical characteristics of nanoparticle (NP) agglomerates in situ in biological media: the NP agglomerate size distribution, and the localized surface plasmon resonance (LSPR) absorbance spectrum of precise sizes of gold NP agglomerates. To characterize the size distribution, we present a theoretical framework for calculating the hydrodynamic diameter distribution of NP agglomerates from their sedimentation coefficient distribution. We measure sedimentation rates for monomers, dimers, and trimers, as well as for larger agglomerates with up to 600 NPs. The AUC size distributions were found generally to be broader than the size distributions estimated from dynamic light scattering and diffusion-limited colloidal aggregation theory, an alternative bulk measurement method that relies on several assumptions. In addition, the measured sedimentation coefficients can be used in nanotoxicity studies to predict how quickly the agglomerates sediment out of solution under normal gravitational forces, such as in the environment. We also calculate the absorbance spectra for monomer, dimer, trimer, and larger gold NP agglomerates up to 600 NPs, to enable a better understanding of LSPR biosensors. Finally, we validate a new method that uses these spectra to deconvolute the net absorbance spectrum of an unknown bulk sample and approximate the proportions of monomers, dimers, and trimers in a polydisperse sample of small agglomerates, so that every sample does not need to be measured by AUC. These results demonstrate the potential utility of AUC to characterize NP agglomeration and sedimentation for nanotoxicity and biosensor studies, as well as to characterize NP agglomerate size and absorbance to improve LSPR and surface-enhanced Raman spectroscopy based biosensors. PMID:21888410

  13. Analytical Ultracentrifugation Sedimentation Velocity for the Characterization of Detergent-Solubilized Membrane Proteins Ca++-ATPase and ExbB

    PubMed Central

    Salvay, Andrés G.; Santamaria, Monica; le Maire, Marc

    2008-01-01

    We have investigated the potential of new methods of analysis of sedimentation velocity (SV) analytical ultracentrifugation (AUC) for the characterization of detergent-solubilized membrane proteins. We analyze the membrane proteins Ca++-ATPase and ExbB solubilized with DDM (dodecyl-β-d-maltoside). SV is extremely well suited for characterizing sample heterogeneity. DDM micelles (s20w = 3.1 S) and complexes (Ca++-ATPase: s20w = 7.3 S; ExbB: s20w = 4 S) are easily distinguished. Using different detergent and protein concentrations, SV does not detect any evidence of self-association for the two proteins. An estimate of bound detergent of 0.9 g/g for Ca++-ATPase and 1.5 g/g for ExbB is obtained from the combined analysis of SV profiles obtained using absorbance and interference optics. Combining s20w with values of the hydrodynamic radius, Rs = 5.5 nm for Ca++-ATPase or Rs = 3.4 nm for ExbB, allows the determination of buoyant molar masses, Mb. In view of their Mb and composition, Ca++-ATPase and ExbB are monomers in our experimental conditions. We conclude that one of the main advantages of SV versus other techniques is the possibility to ascertain the homogeneity of the samples and to focus on a given complex even in the presence of other impurities or aggregates. The relative rapidity of SV measurements also allows experiments on unstable samples. PMID:19669527

  14. Resolving the challenge of measuring ligand binding to membrane proteins by combining analytical ultracentrifugation and light scattering photometry.

    PubMed

    Doran, J D; Mohanty, A K; Fox, T

    2012-01-01

    Membrane proteins are attractive therapeutic targets, however the presence of detergents complicates biophysical binding measurements. Difficulties in determining quantitative dissociation constants for problematic membrane proteins were addressed by combining analytical ultracentrifugation and classical light scattering techniques. Validation of the algorithm used to calculate dissociation constants from sedimentation equilibrium experiments was demonstrated by analyzing binding data of the inhibitor Y-27632 to rho-kinase (ROCK). Kd's of 1.3 ± 0.7 and 52 ± 27 µM were calculated for ROCK constructs (S6-R415) and (M71-E379) respectively, consistent with previously published Ki's of 1.4 ± 0.1 and > 30 µM. Extension of the algorithm to membrane proteins required the collection of light scattering data to determine the partial specific volume, ν, for the membrane protein-detergent complex. Vitamin B12 binding to the bacterial protein btuB in octyl β-D-glucopyranoside (β-OG) illustrates the applicability of the method. A ν of 0.781 ml/g was determined for the btuB-β-OG complex. Incorporating this value into the algorithm generated a Kd of 7.0 ± 1.5 µM for the vitamin B12-btuB affinity. A Kd of 9.7 ± 2.7 µM was determined by equilibrium dialysis under similar experimental conditions. Successfully applying AUC to quantifying small-molecule ligand affinities to membrane proteins represents a significant advance to the field. PMID:21922461

  15. Microanalytical ultracentrifuge

    NASA Astrophysics Data System (ADS)

    Moroz, Pavel E.

    1980-09-01

    An ultracentrifuge based on the air turbine of a dental drill attains 400,000-600,000 rpm and a centrifugal force 2 to 3 million ×g. It is used for the examination of cell suspentions and homogenates and can be applied to macromolecular solutions. Microcuvettes with volumes ranging from less than 1 mm3 to 0.001 mm3 (suitable for single cells) are of disk and square capillary form and are made of polycarbonate or glass. A special microscope is used to obtain a stopped image of the rotating cuvette. A new method to preserve the centrifugal state of the contents is tested: deep freezing of a rotating cuvette for subsequent freeze-drying and microscopical examination. Experiments on cells include centrifugal intercellular movement of nuclei and cytoplasmic particles, cell fusion, and homogenization.

  16. Effect of large refractive index gradients on the performance of absorption optics in the Beckman XL-A/I analytical ultracentrifuge: an experimental study.

    PubMed

    González, José Manuel; Rivas, Germán; Minton, Allen P

    2003-02-01

    An analytical centrifuge cell was modified to detect refraction of light transmitted through the cell caused by refractive index gradients formed by sedimenting solute during centrifugation. Sedimentation velocity and sedimentation equilibrium experiments were carried out in this cell on solutions containing high concentrations of protein and polysaccharide in a Beckman-Coulter XLA analytical ultracentrifuge. Analysis of the results indicates that in the absence of an optical artifact easily recognized as a "black band," the dependence of apparent absorbance upon radial position reported by the instrument may be considered a reliable measure of the solute concentration gradient. PMID:12576068

  17. A new data analysis method to determine binding constants of small molecules to proteins using equilibrium analytical ultracentrifugation with absorption optics.

    PubMed

    Arkin, M; Lear, J D

    2001-12-01

    In principle, equilibrium analytical ultracentrifugation (AU) can be used to quantify the binding stoichiometry and affinity between small-molecule ligands and proteins in aqueous solution. We show here that heteromeric binding constants can be determined using a data-fitting procedure which utilizes a postfitting computation of the total amount of each component in the centrifuge cell. The method avoids overconstraining the fitting of the radial concentration profiles, but still permits unique binding constants to be determined using measurements at a single wavelength. The computational program is demonstrated by applying it to data obtained with mixtures of a 500-Da molecule and interleukin-2, a 16-kDa protein. The 1:1 binding stoichiometry and heteromeric dissociation constants (K(ab)) determined from centrifuge data at two different wavelengths are within the 4-9 microM range independently determined from a functional assay. Values for K(ab) have been obtained for ligands with affinities as weak as 500 microM. This AU method is applicable to compounds with significant UV absorbance (approximately 0.2) at concentrations within approximately 5- to 10-fold of their K(ab). The method, which has been incorporated into a user procedure for IgorPro (Wavemetrics, Oswego, OR), is included as supplementary material. PMID:11726190

  18. Sol-Gel Matrices For Direct Colorimetric Detection Of Analytes

    DOEpatents

    Charych, Deborah H.; Sasaki, Darryl; Yamanaka, Stacey

    2002-11-26

    The present invention relates to methods and compositions for the direct detection of analytes using color changes that occur in immobilized biopolymeric material in response to selective binding of analytes to their surface. In particular, the present invention provides methods and compositions related to the encapsulation of biopolymeric material into metal oxide glass using the sol-gel method.

  19. Sol-gel matrices for direct colorimetric detection of analytes

    DOEpatents

    Charych, Deborah H.; Sasaki, Darryl; Yamanaka, Stacey

    2000-01-01

    The present invention relates to methods and compositions for the direct detection of analytes using color changes that occur in immobilized biopolymeric material in response to selective binding of analytes to their surface. In particular, the present invention provides methods and compositions related to the encapsulation of biopolymeric material into metal oxide glass using the sol-gel method.

  20. Extended flexible linker structures in the complement chimaeric conjugate CR2-Ig by scattering, analytical ultracentrifugation and constrained modelling: implications for function and therapy.

    PubMed

    Gilbert, Hannah E; Aslam, Mohammed; Guthridge, Joel M; Holers, V Michael; Perkins, Stephen J

    2006-02-17

    Complement receptor 2 (CR2; CD21) is a membrane-bound regulator of complement activation, being comprised of 15 or 16 short complement repeat (SCR) domains. A recombinant glycosylated human CR2 SCR 1-2 domain pair was engineered with the Fc fragment of a mouse IgG1 antibody to create a chimaera CR2-Ig containing the major ligand binding domains. Such a chimaera has therapeutic potential as a complement inhibitor or immune modulator. X-ray and neutron scattering and analytical ultracentrifugation identified its domain structure in solution, and provided a comparison with controversial folded-back crystal structures for deglycosylated CR2 SCR 1-2. The radius of gyration R(G) of CR2-Ig was determined to be 5.39(+/-0.14) nm and 5.29(+/-0.01) nm by X-ray and neutron scattering, respectively. The maximum dimension of CR2-Ig was determined to be 17 nm. The molecular mass of CR2-Ig ranged between 101,000 Da and 107,000 Da as determined by neutron scattering and sedimentation equilibrium, in good agreement with the sequence-derived value of 106,600 Da. Sedimentation velocity gave a sedimentation coefficient of 4.49(+/-0.11) S. Stereochemically complete models for CR2-Ig were constructed from crystal structures for the CR2 SCR 1-2 and mouse IgG1 Fc fragments. The two SCR domains and the Fc fragment were joined by randomised conformational peptides. The analysis of 35,000 possible CR2-Ig models showed that only those models in which the two SCR domains were arranged in an open V-shape in random orientations about the Fc fragment accounted for the scattering and sedimentation data. It was not possible to define one single conformational family of Fab-like fragment relative to the Fc fragment. This flexibility is attributed to the relatively long linker sequence and the absence of the antibody light chain from CR2-Ig. The modelling also confirmed that the structure of CR2 SCR 1-2 is more extended in solution than in its crystal structure. PMID:16375923

  1. Self-association and active enzyme forms of Naja naja naja and Crotalus atrox phospholipase A2 studied by analytical ultracentrifugation.

    PubMed

    Bukowski, T; Teller, D C

    1986-12-01

    The dimerization of phospholipase A2 (PLPA2) from Naja naja naja (Pakistani cobra) and Crotalus atrox (Western Diamondback rattlesnake) has been studied from pH 2.5 to 11 at 20 degrees C in 1 mM CaCl2, 0.21 M ionic strength. For the C. atrox enzyme, it was found necessary to use a combination of sedimentation equilibrium and fluorescence yield data to analyze the association. Sedimentation equilibrium in the analytical ultracentrifuge sufficed for the study of the N. naja PLPA2. In the region of enzymatic activity at pH 8, the dimerization association constants found were k2 = 2.8 X 10(6) L/mol and k2 = 6.9 X 10(4) L/mol for the C. atrox and N. naja enzymes, respectively. Analytical linked functions are presented which describe the data. Because the associations are linked to Ca2+ as well as the hydrogen ion, no attempt was made to interpret the ionization of residues in terms of the molecular structure. Active-enzyme sedimentation velocity experiments have been used to study the relation between enzymatic activity and association for both the C. atrox and N. naja enzymes. The substrate 1,2-dibutyryl-sn-glycero-3-phosphocholine (diC4PC) did not dissociate the C. atrox PLPA2. The substrate 1,2-dihexanoyl-sn-glycero-3-phosphocholine (diC6PC) at 7.5 mM dissociated the C. atrox PLPA2 when monitored either as the active enzyme or as the Sr2+-inhibited enzyme. At low enzyme concentrations, 40 mM diC4PC had no effect on N. naja PLPA2 dimerization. However, the sedimentation coefficients observed at enzyme concentrations above 0.2 mg/mL in active-enzyme sedimentation velocity experiments were larger than the values predicted from the thermodynamic studies. Sedimentation coefficients observed for the N. naja PLPA2 acting on diC6PC were larger than those of the monomeric protein, which was the form layered on this substrate. The dissociation of the C. atrox PLPA2 effected by diC6PC was analyzed by the thermodynamics of association and the kinetic Michaelis constant. The analysis suffices to account for the observed sedimentation coefficient. The sedimentation behavior of the N. naja PLPA2 acting on diC6PC substrate was analyzed in terms of a protein-lipid complex. With this model, 68 +/- 16 phospholipid molecules per protein monomer were determined. It is proposed that this enzyme has two micelle nucleation sites per monomer. These putative sites promote micelle formation of the substrate on the enzyme below the critical micelle concentration of the lipid alone. PMID:3801457

  2. Lipid Exchange by Ultracentrifugation.

    PubMed

    Drachmann, Nikolaj Düring; Olesen, Claus

    2016-01-01

    Lipids play an important role in maintaining P-type ATPase structure and function, and often they are crucial for ATPase activity. When the P-type ATPases are in the membrane, they are surrounded by a mix of different lipid species with varying aliphatic chain lengths and saturation, and the complex interplay between the lipids and the P-type ATPases are still not well understood. We here describe a robust method to exchange the majority of the lipids surrounding the ATPase after solubilisation and/or purification with a target lipid of interest. The method is based on an ultracentrifugation step, where the protein sample is spun through a dense buffer containing large excess of the target lipid, which results in an approximately 80-85 % lipid exchange. The method is a very gently technique that maintains protein folding during the process, hence allowing further characterization of the protein in the presence of a target lipid of interest. PMID:26695050

  3. Analytical solution for one-dimensional chemo-mechanical coupling behavior of intelligent polymer gel

    NASA Astrophysics Data System (ADS)

    Yang, Qingsheng; Tian, Hui

    2011-11-01

    As an intelligent material, polymer gel is able to respond to external stimulus, including temperature, chemical concentration, pH, etc. The theoretical framework of chemo-mechanical coupling behavior for intelligent polymer gel is emphasized in this paper. Analytical solutions of the displacement and concentration function are found for one dimensional chemo-mechanical coupling problem. It is shown that the present chemo-mechanical theory can be applied to model chemo-mechanical coupling behavior of intelligent polymer gel. This study has important significance to reveal the mechanism of chemo-mechanical coupling behavior of the polymer gel.

  4. Analytical solution for one-dimensional chemo-mechanical coupling behavior of intelligent polymer gel

    NASA Astrophysics Data System (ADS)

    Yang, Qingsheng; Tian, Hui

    2012-04-01

    As an intelligent material, polymer gel is able to respond to external stimulus, including temperature, chemical concentration, pH, etc. The theoretical framework of chemo-mechanical coupling behavior for intelligent polymer gel is emphasized in this paper. Analytical solutions of the displacement and concentration function are found for one dimensional chemo-mechanical coupling problem. It is shown that the present chemo-mechanical theory can be applied to model chemo-mechanical coupling behavior of intelligent polymer gel. This study has important significance to reveal the mechanism of chemo-mechanical coupling behavior of the polymer gel.

  5. "Reverse-staining" of biomolecules in electrophoresis gels: analytical and micropreparative applications.

    PubMed

    Hardy, Eugenio; Castellanos-Serra, Lila R

    2004-05-01

    Negative or reverse staining using imidazole and zinc salts for protein detection in electrophoresis gels was originally introduced in 1990. The method is based on the selective precipitation of zinc imidazolate in the gel except in the zones where proteins are located. The method was later adapted to allow high-sensitivity negative detection of nucleic acids and bacterial lipopolysaccharides. It provides a practically quantitative recovery of intact biomolecules and is a method of choice for micropreparative applications of gel electrophoresis to proteomics and similar structural studies. Zinc-mediated protein fixation in the gel is fully reversible and the eluted biomolecules are neither chemically modified nor contaminated with organic dyes. Here we present a detailed compilation of practical methods for implementing these techniques with emphasis in their analytical or micropreparative applications. PMID:15081901

  6. Analytical gel filtration of dextran for the study of the glomerular barrier function.

    PubMed

    Hagel, L; Hartmann, A; Lund, K

    1993-07-01

    Analytical gel filtration was used for the study of molecular size distribution of clinical dextran in serum and urine for the purpose of evaluations of changes in the human glomerular barrier function. The column was calibrated in terms of solute size using a simple and accurate technique recently described. Only one sample of a dextran possessing a broad molecular mass distribution was necessary for the calibration procedure and the calculations were performed using an ordinary spreadsheet. The accuracy of the calibration, as evaluated by protein samples, is better than 95%. The simplicity makes the method suitable for use in laboratories not normally specializing in analytical gel filtration. Calibration in terms of size is preferably done with respect to viscosity radius to obtain relevant information about the permeability of dextran into porous membranes. PMID:7688752

  7. A Sedimentation Experiment Using a Preparative Ultracentrifuge

    ERIC Educational Resources Information Center

    Boudreau, Raymond E.; And Others

    1975-01-01

    Describes an experiment that illustrates the use of the preparative ultracentrifuge in isolating and purifying bacterial ribosomes, determines the sedimentation coefficients of the ribonucleoprotein particles, and demonstrates the subunit structure of the 70-S ribosome and the role of the magnesium ion in the association of subunits. (Author/GS)

  8. Studies on the bioactivity of radioiodinated highly purified bovine thyrotropin: analytical polyacrylamide gel electrophoresis

    SciTech Connect

    Takai, N.A.; Filetti, S.; Rapoport, B.

    1981-01-01

    Highly purified bovine TSH (stored in solution at -70 C) was radioiodinated by the stoichiometric chloroamine-T method. The iodinated material ws subjected to analytical polyacrylamide disc gel electrophoresis. TSH was eluted from gel slices (1 mm width) and was analyzed for radioactivity and bioactivity. The latter was determined using the cultured thyroid cell cAMP response assay. Radioactivity in the TSH preparation migrated separately from bioactivity, but concordant with the protein bands observed in gels run in parallel. Further studies performed on bovine TSH purified in our laboratory, as well as on a different TSH preparation of exceptionally high potency (both stored as lyophilized powder) revealed a different pattern, with TSH bioactivity and radioactivity eluting concurrently. Iodination of TSH did not alter its electrophoretic migration on disc gel electrophoresis. In all preparations polymorphism of TSH bioactivity was observed, with at least four separate protein bands containing TSH bioactivity being present in our preparation. The relationship between the degree of iodination and retention of TSH bioactivity was examined. Incorporation of /sup 125/I into TSH was greatly different at two different concentrations of chloramine-T. Despite this, however, the progressive loss of TSH bioactivity was similar at both concentrations, indicating that incorporation of iodine into the TSH molecule is not itself responsible for the decrease in bioactivity. These studies indicate variability among different TSH preparations in terms of their retention of bioactivity. Significant loss of TSH bioactivity appears to occur during storage in solution. The damage to the biological activity of TSH during the iodination procedure is more likely related to the oxidation process than to the incorporation of iodine.

  9. An ultracentrifugation analysis of two hundred fish genomes.

    PubMed

    Bucciarelli, Giuseppe; Bernardi, Giacomo; Bernardi, Giorgio

    2002-08-01

    The goal of this study was to provide a comprehensive view of the compositional characteristics of fish genomes. We therefore expanded the number of fish species that we had explored so far in their DNAs by analytical ultracentrifugation in CsCl density gradient from 122 to 201. This study included representatives from three out of nine orders of Elasmobranchs (sharks and rays), both orders of dipnoan lungfishes, and both orders of chondrosteans (sturgeons and bichirs). We also studied 19 out of 38 teleostean orders, which represent all but four (minor) superorders of the subdivision Teleostei, a group comprising about 23,600 species (96% of all extant fishes). This leaves for further studies two subclasses, Holocephali (chimaeras), and Coelacanthimorpha (gombessas). In spite of this substantial increase in the number of species and orders analysed, all average properties (the modal buoyant density, rho(0), the average buoyant density, , the CsCl profile asymmetry, A, and the compositional heterogeneity, H), and all their ranges were unchanged compared to a previous study [J. Mol. Evol. 31 (1990) 265]. This suggests that, in all likelihood, the properties reported in the present paper can be considered as generally valid for all fish genomes. PMID:12354649

  10. Application of Cassette Ultracentrifugation Using Non-labeled Compounds and Liquid Chromatography-Tandem Mass Spectrometry Analysis for High-Throughput Protein Binding Determination.

    PubMed

    Kieltyka, Kasia; McAuliffe, Brian; Cianci, Christopher; Drexler, Dieter M; Shou, Wilson; Zhang, Jun

    2016-03-01

    Membrane-based devices typically used for serum protein binding determination are not fully applicable to highly lipophilic compounds because of nonspecific binding to the device membrane. Ultracentrifugation, however, completely eliminates the issue by using a membrane-free approach, although its wide application has been limited. This lack of utilization is mainly attributed to 2 factors: the high cost in acquiring and handling of radiolabeled compounds and low assay throughput owing to the difficulties in process automation. To overcome these challenges, we report a high-throughput workflow by cassette ultracentrifugation of nonradiolabeled compounds followed by liquid chromatography-tandem mass spectrometry (LC-MS/MS) analysis. Twenty compounds with diverse physicochemical and protein binding properties were selected for the evaluation of the workflow. To streamline the working process, approaches of matrix balancing for all the samples for LC-MS/MS analysis and determining free fraction without analytical calibration curves were adopted. Both the discrete ultracentrifugation of individual compounds and cassette ultracentrifugation of all the test compounds followed by simultaneous LC-MS/MS analysis exhibited a linear correlation with literature values, demonstrating respectively the validity of the ultracentrifugation process and the cassette approach. The cassette ultracentrifugation using nonradiolabeled compounds followed by LC-MS/MS analysis has greatly facilitated its application for high-throughput protein binding screening in drug discovery. PMID:26886323

  11. Separation of colloidal two dimensional materials by density gradient ultracentrifugation

    SciTech Connect

    Kuang, Yun; Song, Sha; Huang, Jinyang; Sun, Xiaoming

    2015-04-15

    Two-dimensional (2D) materials have been made through various approaches but obtaining monodispersed simply by synthesis optimization gained little success, which highlighted the need for introducing nanoseparation methods. Density gradient ultracentrifugation method has emerged as a versatile and scalable method for sorting colloidal 2D nanomaterials. Isopycnic separation was applied on thickness-dependent separation of graphene nanosheets. And rate-zonal separation, as a more versatile separation method, demonstrated its capability in sorting nanosheets of chemically modified single layered graphene, layered double hydroxide, and even metallic Ag. Establishing such density gradient ultracentrifugation method not only achieves monodispersed nanosheets and provides new opportunities for investigation on size dependent properties of 2D materials, but also makes the surface modification possible by introducing “reaction zones” during sedimentation of the colloids. - Graphical abstract: Two-dimensional (2D) materials have been made through various approaches but obtaining monodispersed simply by synthesis optimization gained little success, which highlighted the need for introducing nanoseparation methods. Density gradient ultracentrifugation method has emerged as a versatile and scalable method for sorting colloidal 2D nanomaterials according to their size of thickness difference. Establishing such density gradient ultracentrifugation method not only achieves monodispersed nanosheets and provides new opportunities for investigation on size dependent properties of 2D materials, but also makes the surface modification possible by introducing “reaction zones” during sedimentation of the colloids. - Highlights: • Density gradient ultracentrifugation was applied on size separation of 2D material. • Isopycnic separation was applied on separation of low density materials. • Rate-zonal separation was applied on separation of large density materials. • Size separation lead to investigation on size dependent properties of 2D material. • Mechanism was investigated by introducing “reaction zones” in the gradient.

  12. Analytical QbD: development of a native gel electrophoresis method for measurement of monoclonal antibody aggregates.

    PubMed

    Pathak, Mili; Dutta, Debayon; Rathore, Anurag

    2014-08-01

    This paper presents a quality by design (QbD) based development of a novel native PAGE (N-PAGE) method as a low-cost analytical tool for analysis of aggregates of monoclonal antibodies. Comparability to the present gold standard of SEC has been established. The motivation is the fact that SEC requires relatively expensive equipment and consumables, thus making N-PAGE relevant to those academicians and other small companies involved in early-stage development of biotherapeutics that do not have access to SEC, especially in developing countries. Furthermore, SEC suffers from certain disadvantages including the possibility of secondary interactions between the stationary phase and analyte resulting in higher elution time and therefore underestimation of the analyte size. The proposed N-PAGE method can also serve as an orthogonal analytical method for aggregate analysis. A QbD-based approach has been used for development and optimization of the protocol. First, initial screening studies were carried out with parameters including the running buffer pH, running buffer molarity, gel buffer pH, loading dye, sample concentration, and running voltage. Next, optimization of operating parameters was performed using principles of design of experiments. The final optimized protocol was compared to the traditional SEC method and the results were found to be comparable. While N-PAGE has been in use for protein analysis for several decades, use of N-PAGE for analysis of mAb aggregates with data comparable to SEC such as the case presented here is novel. PMID:24643784

  13. Separation of colloidal two dimensional materials by density gradient ultracentrifugation

    NASA Astrophysics Data System (ADS)

    Kuang, Yun; Song, Sha; Huang, Jinyang; Sun, Xiaoming

    2015-04-01

    Two-dimensional (2D) materials have been made through various approaches but obtaining monodispersed simply by synthesis optimization gained little success, which highlighted the need for introducing nanoseparation methods. Density gradient ultracentrifugation method has emerged as a versatile and scalable method for sorting colloidal 2D nanomaterials. Isopycnic separation was applied on thickness-dependent separation of graphene nanosheets. And rate-zonal separation, as a more versatile separation method, demonstrated its capability in sorting nanosheets of chemically modified single layered graphene, layered double hydroxide, and even metallic Ag. Establishing such density gradient ultracentrifugation method not only achieves monodispersed nanosheets and provides new opportunities for investigation on size dependent properties of 2D materials, but also makes the surface modification possible by introducing "reaction zones" during sedimentation of the colloids.

  14. Thermonuclear dynamo inside ultracentrifuge with supersonic plasma flow stabilization

    NASA Astrophysics Data System (ADS)

    Winterberg, F.

    2016-01-01

    Einstein's general theory of relativity implies the existence of virtual negative masses in the rotational reference frame of an ultracentrifuge with the negative mass density of the same order of magnitude as the positive mass density of a neutron star. In an ultracentrifuge, the repulsive gravitational field of this negative mass can simulate the attractive positive mass of a mini-neutron star, and for this reason can radially confine a dense thermonuclear plasma placed inside the centrifuge, very much as the positive mass of a star confines its plasma by its own attractive gravitational field. If the centrifuge is placed in an externally magnetic field to act as the seed field of a magnetohydrodynamic generator, the configuration resembles a magnetar driven by the release of energy through nuclear fusion, accelerating the plasma to supersonic velocities, with the magnetic field produced by the thermomagnetic Nernst effect insulating the hot plasma from the cold wall of the centrifuge. Because of the supersonic flow and the high plasma density the configuration is stable.

  15. Ultracentrifugal behavior of apolipoprotein A-I of rhesus monkey (Macaca mulatta).

    PubMed

    Barbeau, D L; Scanu, A M

    1976-12-10

    The sedimentation equilibrium and sedimentation velocity of apolipoprotein AI (apo-A-I) from high density lipoproteins of rhesus monkey plasma were studied in aqueous solutions of 0.02 M EDTA, pH 8.6, as a function of protein concentration. The sedimentation equilibrium results showed that, in the concentration range between 9 and 36 muM (0.25 to 1.0 g/liter), apo-A-I behaved as a single species of molecular weight 28,200. This molecular weight corresponds to that of the monomeric form as previously estimated from electrophoretic and chemical data. As the apo-A-I concentration was increased above 36 muM, the log c versus r2 plots from sedimentation equilibrium experiments became curvilinear, suggesting self-association. An analysis of these data generated nonlinear, nonoverlapping molecular weight versus concentration plots pointing at the existence of a heterogeneous population of apo-A-I. By sedimentation velocity studies apo-A-I at concentrations between 68 and 330 muM exhibited two distinct components, with S0/20,w = 1.9 and S0/20,w = 3.9. When separated by gel permeation chromatography, these two components had an identical amino acid composition and retained similar S20,w values as before column fractionation. The slow component had a diffusion coefficient of 8.27 X 10(-7) cm2/s and, assessed by the criteria of sedimentation equilibrium ultracentrifugation, remained monomeric even at concentrations of 125 muM. The fast component, when analyzed by low speed sedimentation equilibrium, behaved as a self-associating system which could best be fitted into a monomer-hexamer model in a rapid equilibrium. The equilibrium constant for this association was found to be 9.5 X 10(23) M(-5). Thus, rhesus apo-A-I, dissolved in 0.02 M EDTA, pH 8.6, consisted of two distinct species, one monomeric over a relatively wide range of concentrations, the other readily self-associating. Their structural relationship remains to be established. This ultracentrifugal behavior of rhesus apo-A-I differs markedly from that reported for human apo-AI (Vitello, L. B., and Scanu, A. M. (1976) J. Biol. Chem. 251, 1131-1136). PMID:826529

  16. Characterization of chick serum lipoproteins isolated by density gradient ultracentrifugation.

    PubMed

    Rodriguez-Vico, F; Lopez, J M; Castillo, M; Zafra, M F; Garcia-Peregrin, E

    1992-01-01

    Serum lipoproteins from 12h fasted male chicks (15-day-old) were separated into 20 fractions by isopycnic density gradient ultracentrifugation. A new procedure was described by collecting the different fractions from the bottom of tube instead of by aspiration from the meniscus of each tube. Analyses of chemical composition of serum lipoproteins have permitted to reevaluate the density limits of major classes: VHDL, d greater than 1.132 g/ml; HDL, d 1.132-1.084 g/ml; LDL, d 1.084-1.038; IDL, d 1.038-1.022; and VLDL d less than 1.022. HDL fractions clearly predominated (approx. 77% of total lipoproteins) while IDL and VLDL were present at low percentage. LDL was the fraction richest in cholesterol; triacylglycerol content clearly increased from HDL to VLDL, while protein content decreased. All the chemical components of chick serum lipoproteins were accumulated in HDL, although triacylglycerol was relatively distributed in all the lipoprotein classes. PMID:1380327

  17. On the general concept of buoyancy in sedimentation and ultracentrifugation.

    PubMed

    Piazza, Roberto; Buzzaccaro, Stefano; Secchi, Eleonora; Parola, Alberto

    2013-08-01

    Gravity or ultracentrifuge settling of colloidal particles and macromolecules usually involves several disperse species, either because natural and industrial colloids display a large size polydispersity, or because additives are put in on purpose to allow for density-based fractionation of the suspension. Such 'macromolecular crowding', however, may have surprising effects on sedimentation, for it strongly affects the buoyant force felt by a settling particle. Here we show that, as a matter of fact, the standard Archimedes' principle is just a limiting law, valid only for mesoscopic particles settling in a molecular fluid, and we obtain a fully general expression for the actual buoyancy force providing a microscopic basis to the general thermodynamic analysis of sedimentation in multi-component mixtures. The effective buoyancy also depends on the particle shape, being much more pronounced for thin rods and discs. Our model is successfully tested on simple colloidal mixtures, and used to predict rather unexpected effects, such as denser particles floating on top of a lighter fluid, which we actually observe in targeted experiments. This 'generalized Archimedes principle' may provide a tool to devise novel separation methods sensitive to particle size and shape. PMID:23913160

  18. SEDFIT-MSTAR: Molecular weight and molecular weight distribution analysis of polymers by sedimentation equilibrium in the ultracentrifuge

    PubMed Central

    Schuck, Peter; Gillis, Richard B.; Besong, Tabot M.D.; Almutairi, Fahad; Adams, Gary G.; Rowe, Arthur J.; Harding, Stephen E.

    2014-01-01

    Sedimentation equilibrium (analytical ultracentrifugation) is one of the most inherently suitable methods for the determination of average molecular weights and molecular weight distributions of polymers, because of its absolute basis (no conformation assumptions) and inherent fractionation ability (without the need for columns or membranes and associated assumptions over inertness). With modern instrumentation it is also possible to run up to 21 samples simultaneously in a single run. Its application has been severely hampered because of difficulties in terms of baseline determination (incorporating estimation of the concentration at the air/solution meniscus) and complexity of the analysis procedures. We describe a new method for baseline determination based on a smart-smoothing principle and built into the highly popular platform SEDFIT for the analysis of the sedimentation behavior of natural and synthetic polymer materials. The SEDFIT-MSTAR procedure – which takes only a few minutes to perform - is tested with four synthetic data sets (including a significantly non-ideal system) a naturally occurring protein (human IgG1) and two naturally occurring carbohydrate polymers (pullulan and λ–carrageenan) in terms of (i) weight average molecular weight for the whole distribution of species in the sample (ii) the variation in “point” average molecular weight with local concentration in the ultracentrifuge cell and (iii) molecular weight distribution. PMID:24244936

  19. The encephalomyelitic activity of myelin isolated by ultracentrifugation.

    PubMed

    LAATSCH, R H; KIES, M W; GORDON, S; ALVORD, E C

    1962-04-01

    A relatively simple preparation of guinea pig brain myelin, free of gross contamination by other cellular elements has been described. Electron microscopic evidence of the predominance of membranous (lamellar) forms was used as the criterion of purity of this fraction. The slight mitochondrial contamination of the myelin fraction was confirmed by its low succinic dehydrogenase activity. Quantitative bio-assay of the encephalitogenic activity of myelin showed it to have a higher specific activity than whole guinea pig brain. The low encephalomyelitic activity of the other subcellular constituents (nuclei and mitochondria) which were removed from myelin by ultracentrifugation in 30 per cent sucrose could be explained by a small amount of myelin contamination. A basic protein of high specific encephalitogenic activity has been isolated from myelin by methods previously applied to whole brain. Although the protein is similar to nuclear histones, the following facts point to certain significant differences. Nuclei prepared by a different procedure from the one developed for the isolation of myelin were found to be non-encephalitogenic. Although basic protein could be extracted readily from these nuclei by dilute HCl, the same extraction procedure yielded little extractable protein from whole myelin. Myelin which had been defatted by cold chloroform-methanol yielded a basic protein which was highly encephalitogenic. The evidence presented thus supports the view that there exists in myelin a new basic protein responsible for the induction of experimental allergic encephalomyelitis, which is distinctly different from nuclear histones. The possible relationship of this protein to myelin structure and function has been discussed. PMID:14461228

  20. Heavy metal adsorptivity of calcium-alginate-modified diethylenetriamine-silica gel and its application to a flow analytical system using flame atomic absorption spectrometry.

    PubMed

    Mori, Masanobu; Suzuki, Toshinobu; Sugita, Tsuyoshi; Nagai, Daisuke; Hirayama, Kazuo; Onozato, Makoto; Itabashi, Hideyuki

    2014-08-20

    This study aimed to evaluate the heavy metal adsorptivity of calcium-alginate-modified diethylenetriamine-silica gel (CaAD) and incorporate this biosorbent into a flow analytical system for heavy metal ions using flame atomic absorption spectrometry (FAAS). The biosorbent was synthesized by electrostatically coating calcium alginate onto diethylenetriamine (dien)-silica gel. Copper ion adsorption tests by a batch method showed that CaAD exhibited a higher adsorption rate compared with other biosorbents despite its low maximum adsorption capacity. Next, CaAD was packed into a 1mL microcolumn, which was connected to a flow analytical system equipped with an FAAS instrument. The flow system quantitatively adsorbed heavy metals and enriched their concentrations. This quantitative adsorption was achieved for pH 3-4 solutions containing 1.0×10(-6) M of heavy metal ions at a flow rate of 5.0 mL min(-1). Furthermore, the metal ions were successfully desorbed from CaAD at low nitric acid concentrations (0.05-0.15 M) than from the polyaminecarboxylic acid chelating resin (Chelex 100). Therefore, CaAD may be considered as a biosorbent that quickly adsorbs and easily desorbs analyte metal ions. In addition, the flow system enhanced the concentrations of heavy metals such as Cu(2+), Zn(2+), and Pb(2+) by 50-fold. This new enrichment system successfully performed the separation and determination of Cu(2+) (5.0×10(-8)M) and Zn(2+) (5.7×10(-8) M) in a river water sample and Pb(2+) (3.8×10(-9) M) in a ground water sample. PMID:25086892

  1. Ultracentrifugation-free chromatography-mediated large-scale purification of recombinant adeno-associated virus serotype 1 (rAAV1)

    PubMed Central

    Tomono, Taro; Hirai, Yukihiko; Okada, Hironori; Adachi, Kumi; Ishii, Akiko; Shimada, Takashi; Onodera, Masafumi; Tamaoka, Akira; Okada, Takashi

    2016-01-01

    Recombinant adeno-associated virus (rAAV) is an attractive tool for gene transfer and shows potential for use in human gene therapies. The current methods for the production and purification of rAAV from the transfected cell lysate are mainly based on cesium chloride and iodixanol density ultracentrifugation, although those are not scalable. Meanwhile, chromatography-based systems are more scalable. Therefore, in this study, we developed a novel method for the production and purification of rAAV serotype 1 (rAAV1) from serum-free culture supernatant based on ion-exchange and gel-filtration chromatography to obtain highly purified products with an ultracentrifugation-free technique towards Good Manufacturing Practice (GMP) production. The purified rAAV1 displayed three clear and sharp bands (VP1, VP2, and VP3) following sodium dodecyl sulfate–polyacrylamide gel electrophoresis, and more than 90% of rAAV1 particles contained fully packaged viral genomes according to negative-stain electron micrographic analysis. Consequently, the resultant genomic titer of the purified rAAV1 was 3.63 × 1013 v.g./ml (the total titer was 4.17 × 1013 v.g.) from the 4 × 109 HEK293 cells. This novel chromatography-based method will facilitate scale-up of manufacturing for clinical applications in gene therapy. PMID:26913289

  2. Differentiation of liquid analytes in gel films by permeability-modulated double-layer chemo-chips.

    PubMed

    Thete, Aniket R; Gross, G Alexander; Koehler, J Michael

    2009-02-01

    A double-layer chemo-chip for the characterization of liquid analytes by rapid fluorimetric imaging is described. The chemo-chip consists of an array of polymeric micro-spots prepared on a glass slide. Each spot is composed of a thin indicator layer made of PVA doped with an immobilized fluorescence dye and a top layer polymer spot with different permeation properties. The analytes can be differentiated by variations in the optical response rate of the indicator dye after its application. Consequently, different cross-linker concentrations were applied using the Nano-Plotter((TM)) which formed top layers of varying permeability. The chemo-chips were tested with the aqueous solutions of two model liquids (aqueous solutions of malonic acid and phenanthroline hydrochloride). It was found that the transition time of response had changed considerably (up to a factor of about 10) depending on different local cross linking degrees. This has resulted in time-dependent fluorescent patterns of the fluorescence images of the micro-array. The response was fast and the transition times were in the range between a few seconds to 30 s. PMID:19173068

  3. ESR studies of spin-labeled membranes aligned by isopotential spin-dry ultracentrifugation: lipid-protein interactions.

    PubMed Central

    Ge, M; Budil, D E; Freed, J H

    1994-01-01

    Electron spin resonance (ESR) studies have been performed on spin-labeled model membranes aligned using the isopotential spin-dry ultracentrifugation (ISDU) method of Clark and Rothschild. This method relies on sedimentation of the membrane fragments onto a gravitational isopotential surface with simultaneous evaporation of the solvent in a vacuum ultracentrifuge to promote alignment. The degree of alignment obtainable using ISDU, as monitored by ESR measurements of molecular ordering for both lipid (16-PC) and cholestane spin labels (CSL), in dipalmitoylphosphatidylcholine (DPPC) model membranes compares favorably with that obtainable by pressure-annealing. The much gentler conditions under which membranes may be aligned by ISDU greatly extends the range of macroscopically aligned membrane samples that may be investigated by ESR. We report the first ESR study of an integral membrane protein, bacteriorhodopsin (BR) in well-aligned multilayers. We have also examined ISDU-aligned DPPC multilayers incorporating a short peptide gramicidin A' (GA), with higher water content than previously studied. 0.24 mol% BR/DPPC membranes with CSL probe show two distinct components, primarily in the gel phase, which can be attributed to bulk and boundary regions of the bilayer. The boundary regions show sharply decreased molecular ordering and spectral effects comparable to those observed from 2 mol% GA/DPPC membranes. The boundary regions for both BR and GA also exhibit increased fluidity as monitored by the rotational diffusion rates. The high water content of the GA/DPPC membranes reduces the disordering effect as evidenced by the reduced populations of the disordered components. The ESR spectra obtained slightly below the main phase transition of DPPC from both the peptide- and protein-containing membranes reveals a new component with increased ordering of the lipids associated with the peptide or protein. This increase coincides with a broad endothermic peak in the DSC, suggesting a disaggregation of both the peptide and the protein before the main phase transition of the lipid. Detailed simulations of the multicomponent ESR spectra have been performed by the latest nonlinear least-squares methods, which have helped to clarify the spectral interpretations. It is found that the simulations of ESR spectra from CSL in the gel phase for all the lipid membranes studied could be significantly improved by utilizing a model with CSL molecules existing as both hydrogen-bonded to the bilayer interface and non-hydrogen-bonded within the bilayer. Images FIGURE 1 PMID:7535112

  4. Improving the Thermal, Radial and Temporal Accuracy of the Analytical Ultracentrifuge through External References

    PubMed Central

    Ghirlando, Rodolfo; Balbo, Andrea; Piszczek, Grzegorz; Brown, Patrick H.; Lewis, Marc S.; Brautigam, Chad A.; Schuck, Peter; Zhao, Huaying

    2013-01-01

    Sedimentation velocity (SV) is a method based on first-principles that provides a precise hydrodynamic characterization of macromolecules in solution. Due to recent improvements in data analysis, the accuracy of experimental SV data emerges as a limiting factor in its interpretation. Our goal was to unravel the sources of experimental error and develop improved calibration procedures. We implemented the use of a Thermochron iButton® temperature logger to directly measure the temperature of a spinning rotor, and detected deviations that can translate into an error of as much as 10% in the sedimentation coefficient. We further designed a precision mask with equidistant markers to correct for instrumental errors in the radial calibration, which were observed to span a range of 8.6%. The need for an independent time calibration emerged with use of the current data acquisition software (Zhao et al., doi 10.1016/j.ab.2013.02.011) and we now show that smaller but significant time errors of up to 2% also occur with earlier versions. After application of these calibration corrections, the sedimentation coefficients obtained from eleven instruments displayed a significantly reduced standard deviation of ∼ 0.7 %. This study demonstrates the need for external calibration procedures and regular control experiments with a sedimentation coefficient standard. PMID:23711724

  5. Improving the thermal, radial, and temporal accuracy of the analytical ultracentrifuge through external references.

    PubMed

    Ghirlando, Rodolfo; Balbo, Andrea; Piszczek, Grzegorz; Brown, Patrick H; Lewis, Marc S; Brautigam, Chad A; Schuck, Peter; Zhao, Huaying

    2013-09-01

    Sedimentation velocity (SV) is a method based on first principles that provides a precise hydrodynamic characterization of macromolecules in solution. Due to recent improvements in data analysis, the accuracy of experimental SV data emerges as a limiting factor in its interpretation. Our goal was to unravel the sources of experimental error and develop improved calibration procedures. We implemented the use of a Thermochron iButton temperature logger to directly measure the temperature of a spinning rotor and detected deviations that can translate into an error of as much as 10% in the sedimentation coefficient. We further designed a precision mask with equidistant markers to correct for instrumental errors in the radial calibration that were observed to span a range of 8.6%. The need for an independent time calibration emerged with use of the current data acquisition software (Zhao et al., Anal. Biochem., 437 (2013) 104-108), and we now show that smaller but significant time errors of up to 2% also occur with earlier versions. After application of these calibration corrections, the sedimentation coefficients obtained from 11 instruments displayed a significantly reduced standard deviation of approximately 0.7%. This study demonstrates the need for external calibration procedures and regular control experiments with a sedimentation coefficient standard. PMID:23711724

  6. Sol-gel approach for fabrication of coated anodized titanium wire for solid-phase microextraction: highly efficient adsorbents for enrichment of trace polar analytes.

    PubMed

    Jia, Jing; Xu, Lili; Wang, Shuai; Wang, Licheng; Liu, Xia

    2014-05-01

    Nanotubular titania film was prepared in situ on titanium wire and was used as the fiber substrate for solid-phase microextraction (SPME) because of its high surface-to-volume ratio, easy preparation, and mechanical stability. Three different functional coatings, ?-cyclodextrin (?-CD), ?-cyclodextrin-co-poly(ethylenepropylene glycol) (?-CD/PEG), and polyethylene glycol (PEG)-based sorbents were chemically bonded to the nanostructured wire surface via sol-gel technology to further enhance the absorbing capability and extraction selectivity. Coupled to gas chromatography-flame ionic detection (GC-FID), the prepared SPME fibers were investigated using diverse compounds. The results indicated that the fibers showed good mechanical strength, excellent thermal stability, and wonderful capacity and selectivity to polar compounds, including polar aromatic compounds, alcohols, and ketones. Combining the superior hydrophilic property of a bonded functional molecule and the highly porous structure of a fiber coating, the prepared PEG-coated SPME fiber showed much higher adsorption affinity to ephedrine and methylephedrine than ?-CD and ?-CD/PEG fibers. The as-established PEG-coated SPME-GC analytical method provided excellent sensitivity (LODs, 0.004 and 0.001 ng mL(-1) for ephedrine and methylephedrine, respectively) and better linear range (0.01-2 000 ?g L(-1)). In addition, it has surprising repeatability and reproducibility. Finally, the present approach was used to analyze ephedrine and methylephedrine from real urine samples, and reliable results were obtained. PMID:24682230

  7. Purification of very high density lipoproteins by differential density gradient ultracentrifugation.

    PubMed

    Haunerland, N H; Ryan, R O; Law, J H; Bowers, W S

    1987-03-01

    Differential density gradient ultracentrifugation procedures, utilizing a vertical rotor, were developed for the preparative purification of very high density lipoproteins (VHDL, density greater than 1.21 g/ml). The VHDLs of several insect species were purified as follows. An initial density gradient ultracentrifugation step removed lipoproteins of lower density from the VHDL-fraction, which partially separated from the nonlipoproteins present in the infranatant. A complete separation was achieved by a second centrifugation step employing a modified gradient system. The use of a vertical rotor and specially designed discontinuous gradients allows a relatively fast, efficient, and economical isolation of the class of very high density lipoproteins. Similar gradient systems should be useful for the detection and purification of VHDLs from other sources. PMID:3578796

  8. Multidimensional proteomic analysis of photosynthetic membrane proteins by liquid extraction-ultracentrifugation-liquid chromatography-mass spectrometry.

    PubMed

    Huber, Christian G; Walcher, Wolfgang; Timperio, Anna-Maria; Troiani, Sonia; Porceddu, Andrea; Zolla, Lello

    2004-12-01

    The membrane protein components of photosystem I (PSI) and II (PSII) from different species were prefractionated by liquid extraction and sucrose gradient ultracentrifugation and subsequently analyzed by reversed-phase high-performance liquid chromatography-electrospray ionization-mass spectrometry (RP-HPLC-ESI-MS) using poly-(styrene-divinylbenzene)-based monolithic capillary columns. The analytical method was shown to be very flexible and enabled the identification of antenna proteins as well as most of the proteins of the reaction center from PSI and PSII in various plant species with few RP-HPLC-ESI-MS analyses necessitating only minor adaptations in the gradients of acetonitrile in 0.05% aqueous trifluoroacetic acid. The membrane proteins, ranging in molecular mass (Mr) from 4196 (I protein) to more than 80,000 (PSI A/B) as well as isoforms were identified on the basis of their intact Mr and comparison with Mr deduced from known DNA or protein sequences. High quality mass spectra enabled the identification and quantitation of the nonphosphorylated and phosphorylated reaction center subunits D1, D2, and CP43 of PSII, containing five to seven membrane-spanning alpha-helices. Because of its high flexibility and suitability for proteins having a very wide range of Mr and hydrophobicities, the method is generally applicable to the analysis of complex mixtures of membrane proteins. PMID:15449339

  9. Size reduction of 3D-polymer-coated single-walled carbon nanotubes by ultracentrifugation

    NASA Astrophysics Data System (ADS)

    Tsutsumi, Yusuke; Fujigaya, Tsuyohiko; Nakashima, Naotoshi

    2015-11-01

    We describe a novel single-walled carbon nanotube (SWNT) cutting method without introducing any structural defects on the tubes; namely, the finding that simple ultracentrifugation at 600 000g for the SWNTs coated with a cross-linked polymer formed by poly(N-isopropylacrylamide) (PNIPAM) or the polyethylene glycol-carrying PNIPAM copolymer provides shortened (<200 nm) SWNTs, which was revealed by dynamic light scattering (DLS) and atomic force microscopy (AFM) measurements. The Raman and absorption measurements of the obtained SWNTs indicated that the graphitic structure and optical properties, such as characteristic absorption and photoluminescence in the near-IR region of the SWNTs, were almost unchanged even after the cutting. The obtained shortened SWNTs were individually solubilized in water and buffer solution due to the remaining cross-linked polymer structures on the SWNTs. The present method is very simple (only ultracentrifugation) and the yield is very high, which are the advantages in the preparation of many shortened isolated SWNTs with specific properties and functions that are applicable in many fields including bioapplications in vivo, such as imaging, NIR-hyperthermic treatment, photodynamic therapy, etc.We describe a novel single-walled carbon nanotube (SWNT) cutting method without introducing any structural defects on the tubes; namely, the finding that simple ultracentrifugation at 600 000g for the SWNTs coated with a cross-linked polymer formed by poly(N-isopropylacrylamide) (PNIPAM) or the polyethylene glycol-carrying PNIPAM copolymer provides shortened (<200 nm) SWNTs, which was revealed by dynamic light scattering (DLS) and atomic force microscopy (AFM) measurements. The Raman and absorption measurements of the obtained SWNTs indicated that the graphitic structure and optical properties, such as characteristic absorption and photoluminescence in the near-IR region of the SWNTs, were almost unchanged even after the cutting. The obtained shortened SWNTs were individually solubilized in water and buffer solution due to the remaining cross-linked polymer structures on the SWNTs. The present method is very simple (only ultracentrifugation) and the yield is very high, which are the advantages in the preparation of many shortened isolated SWNTs with specific properties and functions that are applicable in many fields including bioapplications in vivo, such as imaging, NIR-hyperthermic treatment, photodynamic therapy, etc. Electronic supplementary information (ESI) available: DLS profile of the supernatant after one ultracentrifugation at 600 000g for SWNT/PNIPAM (NIPAM : BIS = 100 : 1). DLS profiles, AFM images and length histograms, average length as a function of the number of repeated centrifugations, Raman spectra, absorption spectra and PL mappings of SWNT/PNIPAM (NIPAM : BIS = 18 : 1). See DOI: 10.1039/c5nr05066a

  10. Rheologic behavior of deoxyhemoglobin S gels.

    PubMed

    Danish, E H; Harris, J W; Moore, C R; Krieger, I M

    1987-07-20

    The physical properties of deoxyhemoglobin S gels formed from solutions at concentrations and temperatures approaching those in vivo have been characterized by stress relaxation using a rotational rheometer. Gels were annealed in the rheometer and then subjected to a constant shear strain; thereafter the stress sustained was followed with time. Gels with solid-like behavior held stress indefinitely, and were characterized by yield temperature (the temperature at which stress decreased). Gels with less solid behavior were unable to hold target stress, and were characterized by yield stress (maximum stress attained) and equilibrium stress (final stress held). The samples were ultracentrifuged to calculate pellet and polymer masses. The solidity of the gels, as measured by yield temperature or yield stress, was related to the initial hemoglobin concentration, pellet and polymer masses, shear history, temperature, and the temperature and time of annealing. Solidity increased significantly with time when gels were annealed at 37 degrees C, whereas, when annealed at 25 degrees C, no or minimal increases in solidity were noted. Studies suggest that polymerization occurs rapidly and is completed early in or before the gel annealing period and that the increase in solidity with time of annealing is mainly due to factors other than polymer mass, i.e. alignment, increasing bond strength, water loss. The chemical activity of deoxyhemoglobin S did not affect the solidity of the formed gels. When the resultant polymer masses were comparable, gels formed from samples with albumin present (higher initial total protein concentration, but lower initial deoxyhemoglobin S concentration), had the same behavior as gels formed from solutions with higher initial hemoglobin S concentration. These findings demonstrate that gel annealing conditions must be standardized when comparing the rheologic behaviors of deoxyhemoglobin S gels and indicate that the gel's physical properties (influenced by polymer mass, shear history, annealing time) must be considered in understanding pathophysiology of sickling disorders. PMID:3656453

  11. Ultracentrifugation and inductively coupled plasma mass spectrometry for metal-protein equilibrium studies

    NASA Astrophysics Data System (ADS)

    Arnquist, Isaac J.; Holcombe, James A.

    2012-10-01

    The coupling of separation by preparative ultracentrifugation and metal detection by inductively coupled plasma mass spectrometry (ICP-MS) has been explored for metal-protein equilibrium determinations. This study characterizes the stoichiometry as well as apparent (Kapp) and intrinsic (Kint) binding affinities of the metal-protein association for a model protein. In particular, the affinity of Cu2 + for the high affinity binding site in bovine serum albumin (BSA) is determined. Once equilibrium is established between Cu2 + and BSA, preparative ultracentrifugation moves the metalloprotein away from the meniscus, leaving unbound equilibrium copper in the protein free solution. Since the initial (total) concentrations of purified BSA and Cu2 + can be determined, the free copper concentration at equilibrium can also be determined by taking a small aliquot above the sedimenting boundary for analysis using ICP-MS. This analysis allows for the determination of free Cu2 + ion, which is identical to the equilibrium concentration prior to ultracentrifugation. From these data Kapp and Kint were determined at two different conditions, 100 mM Tris(hydroxymethyl)aminomethane (Tris) at pH 9.53 and pH 7.93. log Kapp values of 17.6 and 14.6 were determined at pH 9.53 and pH 7.93, respectively. Furthermore, pH-independent log Kint values of - 1.43 and - 1.04 were determined at pH 9.53 and 7.93, respectively. While the log Kint at pH 9.53 was in good agreement with literature values obtained from alternative methods, Kint at pH 7.93 was about 2.5 × larger than previously reported. BSA undergoes a structural rearrangement between pH 7-9, and the generally accepted pH-dependency of protein tertiary structure may be responsible for the variations in the "intrinsic" binding constant. The Cu-BSA binding affinity was also monitored in 100 mM Tris 0.1% sodium dodecyl sulfate (SDS) solution at pH 7.93 in order to determine the effect of a denaturant on metal binding. Results for both log Kapp and log Kint were similar to those obtained in the absence of 0.1% SDS at pH 7.93. Overall, this study validates and shows the efficacy of combining preparative ultracentrifugation with ICP-MS detection for interrogating metal-protein associations while causing minimal equilibrium perturbations as a result of the separation and measurement processes. Advantages and disadvantages of this methodology are discussed as it relates to alternative methods for metal-protein studies.

  12. Combining Ultracentrifugation and Peptide Termini Group-specific Immunoprecipitation for Multiplex Plasma Protein Analysis

    PubMed Central

    Volk, Sonja; Schreiber, Thomas D.; Eisen, David; Wiese, Calvin; Planatscher, Hannes; Pynn, Christopher J.; Stoll, Dieter; Templin, Markus F.; Joos, Thomas O.; Pötz, Oliver

    2012-01-01

    Blood plasma is a valuable source of potential biomarkers. However, its complexity and the huge dynamic concentration range of its constituents complicate its analysis. To tackle this problem, an immunoprecipitation strategy was employed using antibodies directed against short terminal epitope tags (triple X proteomics antibodies), which allow the enrichment of groups of signature peptides derived from trypsin-digested plasma. Isolated signature peptides are subsequently detected using MALDI-TOF/TOF mass spectrometry. Sensitivity of the immunoaffinity approach was, however, compromised by the presence of contaminant peaks derived from the peptides of nontargeted high abundant proteins. A closer analysis of the enrichment strategy revealed nonspecific peptide binding to the solid phase affinity matrix as the major source of the contaminating peptides. We therefore implemented a sucrose density gradient ultracentrifugation separation step into the procedure. This yielded a 99% depletion of contaminating peptides from a sucrose fraction containing 70% of the peptide-antibody complexes and enabled the detection of the previously undetected low abundance protein filamin-A. Assessment of this novel approach using 15 different triple X proteomics antibodies demonstrated a more consistent detection of a greater number of targeted peptides and a significant reduction in the intensity of nonspecific peptides. Ultracentrifugation coupled with immunoaffinity MS approaches presents a powerful tool for multiplexed plasma protein analysis without the requirement for demanding liquid chromatography separation techniques. PMID:22527512

  13. Size reduction of 3D-polymer-coated single-walled carbon nanotubes by ultracentrifugation.

    PubMed

    Tsutsumi, Yusuke; Fujigaya, Tsuyohiko; Nakashima, Naotoshi

    2015-12-14

    We describe a novel single-walled carbon nanotube (SWNT) cutting method without introducing any structural defects on the tubes; namely, the finding that simple ultracentrifugation at 600 000g for the SWNTs coated with a cross-linked polymer formed by poly(N-isopropylacrylamide) (PNIPAM) or the polyethylene glycol-carrying PNIPAM copolymer provides shortened (<200 nm) SWNTs, which was revealed by dynamic light scattering (DLS) and atomic force microscopy (AFM) measurements. The Raman and absorption measurements of the obtained SWNTs indicated that the graphitic structure and optical properties, such as characteristic absorption and photoluminescence in the near-IR region of the SWNTs, were almost unchanged even after the cutting. The obtained shortened SWNTs were individually solubilized in water and buffer solution due to the remaining cross-linked polymer structures on the SWNTs. The present method is very simple (only ultracentrifugation) and the yield is very high, which are the advantages in the preparation of many shortened isolated SWNTs with specific properties and functions that are applicable in many fields including bioapplications in vivo, such as imaging, NIR-hyperthermic treatment, photodynamic therapy, etc. PMID:26538202

  14. Stability, biophysical properties and effect of ultracentrifugation and diafiltration on measles virus and mumps virus.

    PubMed

    Sviben, Dora; Forčić, Dubravko; Kurtović, Tihana; Halassy, Beata; Brgles, Marija

    2016-06-01

    Measles virus and mumps virus (MeV and MuV) are enveloped RNA viruses used for production of live attenuated vaccines for prophylaxis of measles and mumps disease, respectively. For biotechnological production of and basic research on these viruses, the preparation of highly purified and infectious viruses is a prerequisite, and to meet that aim, knowledge of their stability and biophysical properties is crucial. Our goal was to carry out a detailed investigation of the stability of MeV and MuV under various pH, temperature, shear stress, filtration and storage conditions, as well as to evaluate two commonly used purification techniques, ultracentrifugation and diafiltration, with regard to their efficiency and effect on virus properties. Virus titers were estimated by CCID50 assay, particle size and concentration were measured by Nanoparticle tracking analysis (NTA) measurements, and the host cell protein content was determined by ELISA. The results demonstrated the stability of MuV and MeV at pH <9 and above pH 4 and 5, respectively, and aggregation was observed at pH >9. Storage without stabilizer did not result in structural changes, but the reduction in infectivity after 24 hours was significant at +37 °C. Vortexing of the viruses resulted in significant particle degradation, leading to lower virus titers, whereas pipetting had much less impact on virus viability. Diafiltration resulted in higher recovery of both total and infectious virus particles than ultracentrifugation. These results provide important data for research on all upstream and downstream processes on these two viruses regarding biotechnological production and basic research. PMID:26935920

  15. Basic amphipathic model peptides: Structural investigations in solution, studied by circular dichroism, fluorescence, analytical ultracentrifugation and molecular modelling

    NASA Astrophysics Data System (ADS)

    Mangavel, C.; Sy, D.; Reynaud, J. A.

    1999-05-01

    A twenty amino acid residue long amphipathic peptide made of ten leucine and ten lysine residues and four derivatives, in which a tryptophan, as a fluorescent probe, is substituted for a leucine, are studied. The peptides in water are mainly in an unordered conformation (~90%), and undergo a two state reversible transition upon heating, leading to a partially helical conformation (cold denaturation). Time resolved fluorescence results show that fluorescence decay for the four Trp containing peptides is best described by triple fluorescence decay kinetics. In TFE/water mixture, peptides adopt a single α-helix conformation but the Leu-Trp9 substitution leads to an effective helix destabilizing effect. In salted media, the peptides are fully helical and present a great tendency to self associate by bringing the hydrophobic faces of helices into close contact. This proceeds in non-cooperative multisteps leading to the formation of α helix aggregates with various degrees of complexation. Using modelling, the relative hydrophobic surface areas accessible to water molecules in n-mer structures are calculated and discussed. Nous avons étudié un peptide amphipathique composé de dix lysine et dix leucine, ainsi que quatre dérivés comportant un résidu tryptophane pour les études par fluorescence. Dans l'eau, les peptides ne sont pas structurés (~90%), et se structurent partiellement en hélice α par chauffage (dénaturation froide). Les mesures de déclin de fluorescence font apparaître une cinétique à trois temps de vie. Dans un mélange eau/TFE, les peptides adoptent une conformation en hélice α, mais la substitution Leu-Trp9 possède un effet déstabilisant. En mileu salin, les peptides sont totalement hélicoïdaux et ont tendance à s'agréger de façon à regrouper leur face hydrophobe. Ce processus se fait en plusieurs étapes avec des agrégats de taille variable. L'existence de tels agrégats est discutée sur la base de la modélisation moléculaire complétée par des calculs d'accessibilité des surfaces hydrophobes.

  16. Modeling analytical ultracentrifugation experiments with an adaptive space-time finite element solution for multicomponent reacting systems.

    PubMed

    Cao, Weiming; Demeler, Borries

    2008-07-01

    We describe an extension of the adaptive space-time finite element method (ASTFEM) used in the solution of the Lamm equation to the case of multicomponent reacting systems. We use an operator splitting technique to decouple the sedimentation-diffusion process from the reaction process. The former is solved with an ASTFEM approach based on the Petrov-Galerkin method and on adaptive moving grids, and the latter is solved with the implicit midpoint Euler's method. Our solution can effectively eliminate the sedimentation errors for each component or species involved in the reaction, and it is free from oscillation near the cell bottom. It offers second-order accuracy, and guarantees conservation of mass without any additional postprocessing, and it permits modeling of multicomponent, equilibrating systems where the reaction rate can be kinetically controlled between an instantaneous reaction and a noninteracting mixture. The proposed ASTFEM solution provides improved efficiency and accuracy compared to classical approaches, especially when medium-sized and large molecules are modeled. PMID:18390609

  17. Polyelectrolyte gels

    SciTech Connect

    Segalman, D.J.; Witkowski, W.R.

    1995-06-01

    Polyelectrolyte (PE) gels are swollen polymer/solvent networks that undergo a reversible volume collapse/expansion through various types of stimulation. Applications that could exploit this large deformation and solvent expulsion/absorption characteristics include robotic {open_quotes}fingers{close_quotes} and drug delivery systems. The goals of the research were to first explore the feasibility of using the PE gels as {open_quotes}smart materials{close_quotes} - materials whose response can be controlled by an external stimulus through a feedback mechanism. Then develop a predictive capability to simulate the dynamic behavior of these gels. This involved experimentally characterizing the response of well-characterized gels to an applied electric field and other stimuli to develop an understanding of the underlying mechanisms which cause the volume collapse. Lastly, the numerical analysis tool was used to simulate various potential engineering devices based on PE gels. This report discusses the pursuit of those goals through experimental and computational means.

  18. Thickness sorting of two-dimensional transition metal dichalcogenides via copolymer-assisted density gradient ultracentrifugation.

    PubMed

    Kang, Joohoon; Seo, Jung-Woo T; Alducin, Diego; Ponce, Arturo; Yacaman, Miguel Jose; Hersam, Mark C

    2014-01-01

    Two-dimensional transition metal dichalcogenides have emerged as leading successors to graphene due to their diverse properties, which depend sensitively on sample thickness. Although solution-based exfoliation methods hold promise for scalable production of these materials, existing techniques introduce irreversible structural defects and/or lack sufficient control over the sample thickness. In contrast, previous work on carbon nanotubes and graphene has shown that isopycnic density gradient ultracentrifugation can produce structurally and electronically monodisperse nanomaterial populations. However, this approach cannot be directly applied to transition metal dichalcogenides due to their high intrinsic buoyant densities when encapsulated with ionic small molecule surfactants. Here, we overcome this limitation and thus demonstrate thickness sorting of pristine molybdenum disulfide (MoS2) by employing a block copolymer dispersant composed of a central hydrophobic unit flanked by hydrophilic chains that effectively reduces the overall buoyant density in aqueous solution. The resulting solution-processed monolayer MoS2 samples exhibit strong photoluminescence without further chemical treatment. PMID:25391315

  19. An optimized method for high-titer lentivirus preparations without ultracentrifugation

    PubMed Central

    Jiang, Wei; Hua, Rui; Wei, Mengping; Li, Chenhong; Qiu, Zilong; Yang, Xiaofei; Zhang, Chen

    2015-01-01

    Lentiviral technology has proven to be a powerful tool to express exogenous genes in dividing and non-dividing cells. Currently, most protocols for generating high-titer lentivirus require ultracentrifugation, which can be an instrumental barrier for routine operations in a laboratory. In this study, the effect of relative centrifugal force (RCF) on the concentration efficiency of the lentivirus was systematically explored, and it was found that sucrose gradient centrifugation with a relatively low speed (≤10,000 g) robustly produces a high-titer virus (up to 2 × 108 TU/ml). The optimal sucrose concentration is 10%, and the recovery rate of the functional virus is greater than 80%. The infection efficiency of both concentrated and un-concentrated lentivirus decreases rapidly when the viruses are stored at 4 °C (τ ≈ 1.3 days) or subjected to multiple freeze-thaw cycles (τ = 1.1 rounds). In summary, we describe an efficient and easy-to-handle protocol for high-titer lentivirus purification. PMID:26348152

  20. Isolating and Quantifying Plasma HDL Proteins by Sequential Density Gradient Ultracentrifugation and Targeted Proteomics.

    PubMed

    Henderson, Clark M; Vaisar, Tomas; Hoofnagle, Andrew N

    2016-01-01

    The sensitivity and specificity of tandem mass spectrometers have made targeted proteomics the method of choice for the precise simultaneous measurement of many proteins in complex mixtures. Its application to the relative quantification of proteins in high-density lipoproteins (HDL) that have been purified from human plasma has revealed potential mechanisms to explain the atheroprotective effects of HDL. We describe a moderate throughput method for isolating HDL from human plasma that uses sequential density gradient ultracentrifugation, the traditional method of HDL purification, and subsequent trypsin digestion and nanoflow liquid chromatography-tandem mass spectrometry to quantify 38 proteins in the HDL fraction of human plasma. To control for the variability associated with digestion, matrix effects, and instrument performance, we normalize the signal from endogenous HDL protein-associated peptides liberated during trypsin digestion to the signal from peptides liberated from stable isotope-labeled apolipoprotein A-I spiked in as an internal standard prior to digestion. The method has good reproducibility and other desirable characteristics for preclinical research. PMID:26867741

  1. Purification of infectious adenovirus in two hours by ultracentrifugation and tangential flow filtration

    SciTech Connect

    Ugai, Hideyo; Yamasaki, Takahito; Hirose, Megumi; Inabe, Kumiko; Kujime, Yukari; Terashima, Miho; Liu, Bingbing |; Tang, Hong |; Zhao, Mujun; Murata, Takehide; Kimura, Makoto; Pan, Jianzhi; Obata, Yuichi; Hamada, Hirofumi; Yokoyama, Kazunari K. . E-mail: kazu@brc.riken.jp

    2005-06-17

    Adenoviruses are excellent vectors for gene transfer and are used extensively for high-level expression of the products of transgenes in living cells. The development of simple and rapid methods for the purification of stable infectious recombinant adenoviruses (rAds) remains a challenge. We report here a method for the purification of infectious adenovirus type 5 (Ad5) that involves ultracentrifugation on a cesium chloride gradient at 604,000g for 15 min at 4 deg C and tangential flow filtration. The entire procedure requires less than two hours and infectious Ad5 can be recovered at levels higher than 64% of the number of plaque-forming units (pfu) in the initial crude preparation of viruses. We have obtained titers of infectious purified Ad5 of 1.35 x 10{sup 10} pfu/ml and a ratio of particle titer to infectious titer of seven. The method described here allows the rapid purification of rAds for studies of gene function in vivo and in vitro, as well as the rapid purification of Ad5.

  2. Fluorescence detection for gel and capillary electrophoresis

    SciTech Connect

    Hogan, B.

    1992-07-21

    First, an indirect fluorescence detection system for the separation of proteins via gel electrophoresis. Quantities as low as 50 nanograms of bovine serum albumin and soybean trypsin inhibitor are separated and detected visually without the need for staining of the analytes. This is very similar to levels of protein commonly separated with gel electrophoresis.

  3. Aerosol gels

    NASA Technical Reports Server (NTRS)

    Sorensen, Christopher M. (Inventor); Chakrabarti, Amitabha (Inventor); Dhaubhadel, Rajan (Inventor); Gerving, Corey (Inventor)

    2010-01-01

    An improved process for the production of ultralow density, high specific surface area gel products is provided which comprises providing, in an enclosed chamber, a mixture made up of small particles of material suspended in gas; the particles are then caused to aggregate in the chamber to form ramified fractal aggregate gels. The particles should have a radius (a) of up to about 50 nm and the aerosol should have a volume fraction (f.sub.v) of at least 10.sup.-4. In preferred practice, the mixture is created by a spark-induced explosion of a precursor material (e.g., a hydrocarbon) and oxygen within the chamber. New compositions of matter are disclosed having densities below 3.0 mg/cc.

  4. The binding of D-gluconohydroximo-1,5-lactone to glycogen phosphorylase. Kinetic, ultracentrifugation and crystallographic studies.

    PubMed Central

    Papageorgiou, A C; Oikonomakos, N G; Leonidas, D D; Bernet, B; Beer, D; Vasella, A

    1991-01-01

    Combined kinetic, ultracentrifugation and X-ray-crystallographic studies have characterized the effect of the beta-glucosidase inhibitor gluconohydroximo-1,5-lactone on the catalytic and structural properties of glycogen phosphorylase. In the direction of glycogen synthesis, gluconohydroximo-1,5-lactone was found to competitively inhibit both the b (Ki 0.92 mM) and the alpha form of the enzyme (Ki 0.76 mM) with respect to glucose 1-phosphate in synergism with caffeine. In the direction of glycogen breakdown, gluconohydroximo-1,5-lactone was found to inhibit phosphorylase b in a non-competitive mode with respect to phosphate, and no synergism with caffeine could be demonstrated. Ultracentrifugation and crystallization experiments demonstrated that gluconohydroximo-1,5-lactone was able to induce dissociation of tetrameric phosphorylase alpha and stabilization of the dimeric T-state conformation. A crystallographic binding study with 100 mM-gluconohydroximo-1,5-lactone at 0.24 nm (2.4 A) resolution showed a major peak at the catalytic site, and no significant conformational changes were observed. Analysis of the electron-density map indicated that the ligand adopts a chair conformation. The results are discussed with reference to the ability of the catalytic site of the enzyme to distinguish between two or more conformations of the glucopyranose ring. PMID:1900987

  5. Comparison of direct and indirect enzyme immunoassays with direct ultracentrifugation before electron microscopy for detection of rotaviruses.

    PubMed Central

    Hammond, G W; Ahluwalia, G S; Barker, F G; Horsman, G; Hazelton, P R

    1982-01-01

    A direct and an indirect enzyme immunoassay (EIA) were evaluated against a standard of electron microscopy after direct ultracentrifugation of the specimen for their performances in detecting rotaviruses. The indirect EIA had variable background activity which influenced test specificity. The indirect EIA control (test system without the detector antibody) plus a regression line (which reflected background noise) improved test specificity. However, the results of direct EIA (Rotazyme; Abbott Laboratories, North Chicago, Ill.) sensitivity (86%) and specificity (96%) were better than those of the indirect EIA in tests on 73 rotavirus-positive and 78 rotavirus-negative specimens. Endpoint titrations of purified SA-11 rotavirus showed greater sensitivity of the direct EIA test. Electron microscopy, performed after direct ultracentrifugation, and direct EIA were approximately 2 log10 more sensitive in the detection of purified SA-11 rotavirus than was electron microscopy with standard methods of unconcentrated specimen preparation. Direct EIA test are potentially sensitive, specific, and practical for the rapid detection of rotaviruses from human clinical specimens. Further studies are needed before EIA methods for detection of human rotaviruses can be equated with the level of reliability of results obtainable with sensitive electron microscopy techniques. PMID:6286720

  6. Enhanced Electrochemical Performance of Ultracentrifugation-Derived nc-Li3VO4/MWCNT Composites for Hybrid Supercapacitors.

    PubMed

    Iwama, Etsuro; Kawabata, Nozomi; Nishio, Nagare; Kisu, Kazuaki; Miyamoto, Junichi; Naoi, Wako; Rozier, Patrick; Simon, Patrice; Naoi, Katsuhiko

    2016-05-24

    Nanocrystalline Li3VO4 dispersed within multiwalled carbon nanotubes (MWCNTs) was prepared using an ultracentrifugation (uc) process and electrochemically characterized in Li-containing electrolyte. When charged and discharged down to 0.1 V vs Li, the material reached 330 mAh g(-1) (per composite) at an average voltage of about 1.0 V vs Li, with more than 50% capacity retention at a high current density of 20 A g(-1). This current corresponds to a nearly 500C rate (7.2 s) for a porous carbon electrode normally used in electric double-layer capacitor devices (1C = 40 mA g(-1) per activated carbon). The irreversible structure transformation during the first lithiation, assimilated as an activation process, was elucidated by careful investigation of in operando X-ray diffraction and X-ray absorption fine structure measurements. The activation process switches the reaction mechanism from a slow "two-phase" to a fast "solid-solution" in a limited voltage range (2.5-0.76 V vs Li), still keeping the capacity as high as 115 mAh g(-1) (per composite). The uc-Li3VO4 composite operated in this potential range after the activation process allows fast Li(+) intercalation/deintercalation with a small voltage hysteresis, leading to higher energy efficiency. It offers a promising alternative to replace high-rate Li4Ti5O12 electrodes in hybrid supercapacitor applications. PMID:27158830

  7. Meningococcal endotoxin in lethal septic shock plasma studied by gas chromatography, mass-spectrometry, ultracentrifugation, and electron microscopy.

    PubMed Central

    Brandtzaeg, P; Bryn, K; Kierulf, P; Ovsteb, R; Namork, E; Aase, B; Jantzen, E

    1992-01-01

    We have compared gas chromatography and mass spectrometry (GC-MS) analysis with the Limulus amebocyte lysate (LAL) assay to quantify native meningococcal lipopolysaccharides (LPS) in five patient plasmas containing greater than 5 micrograms/liter by LAL. 3-Hydroxy lauric acid (3-OH-12:0) was used as a specific lipid A marker of neisserial LPS. The quantitative LAL results were confirmed by GC-MS (r = 0.98, P = 0.006). Seven patient plasmas were centrifuged at 103,000 g and the sedimentation behavior of native LPS compared with reference plasma proteins and with apo A1 and apo B100 representing high and low density lipoproteins. After 15 min of centrifugation, 84 +/- 2% (mean +/- SE) of the recovered LPS were found in the lower one-third of the centrifuged volume, whereas 6 +/- 1% remained in the upper one-third volume, indicating that meningococcal endotoxin circulates as complexes with high sedimentation coefficients. Bacterial outer membrane fragments were detected in the bottom fractions of three patient plasmas examined by means of electron microscopy. In three patient plasmas ultracentrifuged for 60 min at 103,000 g, the levels of apo A1 and apo B100 revealed minor changes, whereas only 1 +/- 1% of the recovered LPS remained in the upper one-third and 91 +/- 2% were found in the lower one-third volume. Few bioreactive LPS appear to be complexed with high and low density lipoproteins in meningococcal septic shock plasma. Images PMID:1541674

  8. Effects of ultracentrifugation on plasma biochemical values of prefledged wild peregrine falcons (Falco peregrinus) in northeastern Illinois.

    PubMed

    Pond, Joel; Thompson, Steve; Hennen, Mary; Pauley, John; Gamble, Kathryn C

    2012-09-01

    Centrifugation is performed on whole blood samples to obtain serum or plasma for biochemical analysis. Although blood samples centrifuged in a microhematocrit tube may maximize recovery of plasma from small-volume samples, plasma biochemical values from such samples have been implicated as causing erroneous results. To compare blood biochemical values obtained by microhematocrit centrifugation and centrifugation with a commercial tilt-rotor machine, blood samples were collected from peregrine falcon (Falco peregrinus) eyases aged 32-40 days (n=51). The samples were separated into 2 equal aliquots with 1 aliquot centrifuged in a tilt-rotor machine and the other aliquot ultracentrifuged in microhematocrit tubes. Separated plasma from both processes was sent to a commercial veterinary reference laboratory for routine clinical biochemical analysis. No significant differences were found in the biochemical results of the paired samples by the 2 centrifugation methods. These results show that the centrifugation method has no effect on the plasma quality for biochemical analysis in young peregrine falcons. PMID:23156975

  9. Characterization of physical properties of tissue factorcontaining microvesicles and a comparison of ultracentrifuge-based recovery procedures

    PubMed Central

    Ettelaie, Camille; Collier, Mary E. W.; Maraveyas, Anthony; Ettelaie, Rammile

    2014-01-01

    Microvesicles were isolated from the conditioned media of 3 cell lines (MDA-MB-231, AsPC-1 and A375) by ultracentrifugation at a range of relative centrifugal forces, and the tissue factor (TF) protein and activity, microvesicle number, size distribution and relative density compared. Also, by expressing TF-tGFP in cells and isolating the microvesicles, the relative density of TF-containing microvesicles was established. Nanoparticle tracking analysis (NTA) indicated that the larger-diameter microvesicles (>200 nm) were primarily sedimented at 100,000g and possessed TF-dependent thrombin and factor Xa generation potential, while in the absence of factor VII, all microvesicles possessed some thrombin generation capacity. Immuno-precipitation of TF-containing microvesicles followed by NTA also indicated the range of these microvesicles to be 200400 nm. Analysis of the microvesicles by gradient density centrifugation showed that lower-density (<1.1 g/ml) microvesicles were mainly present in the samples recovered at 100,000g and were associated with TF antigen and activity. Analysis of these fractions by NTA confirmed that these fractions were principally composed of the larger-diameter microvesicles. Similar analysis of microvesicles from healthy or patient plasma supported those obtained from conditioned media indicating that TF activity was mainly associated with lower-density microvesicles. Furthermore, centrifugation of healthy plasma, supplemented with TF-tGFP-containing microvesicles, resulted in 67% retrieval of the fluorescent microvesicles at 100,000g, but only 26% could be recovered at 20,000g. Pre-centrifugation of conditioned media or plasma at 10,000g improved the speed and yield of recovered TF-containing microvesicles by subsequent centrifugation at either 20,000g or 100,000g. In conclusion, TF appears to be associated with low-density (1.031.08 g/ml), larger-diameter (200350 nm) microvesicles. PMID:25206957

  10. Isolation of Exosomes from Blood Plasma: Qualitative and Quantitative Comparison of Ultracentrifugation and Size Exclusion Chromatography Methods

    PubMed Central

    Baranyai, Tamás; Herczeg, Kata; Onódi, Zsófia; Voszka, István; Módos, Károly; Marton, Nikolett; Nagy, György; Mäger, Imre; Wood, Matthew J.; El Andaloussi, Samir; Pálinkás, Zoltán; Kumar, Vikas; Nagy, Péter; Kittel, Ágnes; Buzás, Edit Irén; Ferdinandy, Péter; Giricz, Zoltán

    2015-01-01

    Background Exosomes are emerging targets for biomedical research. However, suitable methods for the isolation of blood plasma-derived exosomes without impurities have not yet been described. Aim Therefore, we investigated the efficiency and purity of exosomes isolated with potentially suitable methods; differential ultracentrifugation (UC) and size exclusion chromatography (SEC). Methods and Results Exosomes were isolated from rat and human blood plasma by various UC and SEC conditions. Efficiency was investigated at serial UC of the supernatant, while in case of SEC by comparing the content of exosomal markers of various fractions. Purity was assessed based on the presence of albumin. We found that the diameter of the majority of isolated particles fell into the size range of exosomes, however, albumin was also present in the preparations, when 1h UC at 4°C was applied. Furthermore, with this method only a minor fraction of total exosomes could be isolated from blood as deduced from the constant amount of exosomal markers CD63 and TSG101 detected after serial UC of rat blood plasma samples. By using UC for longer time or with shorter sedimentation distance at 4°C, or UC performed at 37°C, exosomal yield increased, but albumin impurity was still observed in the isolates, as assessed by transmission electron microscopy, dynamic light scattering and immunoblotting against CD63, TSG101 and albumin. Efficiency and purity were not different in case of using further diluted samples. By using SEC with different columns, we have found that although a minor fraction of exosomes can be isolated without significant albumin content on Sepharose CL-4B or Sephacryl S-400 columns, but not on Sepharose 2B columns, the majority of exosomes co-eluted with albumin. Conclusion Here we show that it is feasible to isolate exosomes from blood plasma by SEC without significant albumin contamination albeit with low vesicle yield. PMID:26690353

  11. Physical and chemical properties of gels. Application to protein nucleation control in the gel acupuncture technique

    NASA Astrophysics Data System (ADS)

    Moreno, Abel; Juárez-Martínez, Gabriela; Hernández-Pérez, Tomás; Batina, Nikola; Mundo, Manuel; McPherson, Alexander

    1999-09-01

    In this work, we present a new approach using analytical and optical techniques in order to determine the physical and chemical properties of silica gel, as well as the measurement of the pore size in the network of the gel by scanning electron microscopy. The gel acupuncture technique developed by Garcı´a-Ruiz et al. (Mater. Res. Bull 28 (1993) 541) Garcı´a-Ruiz and Moreno (Acta Crystallogr. D 50 (1994) 484) was used throughout the history of crystal growth. Several experiments were done in order to evaluate the nucleation control of model proteins (thaumatin I from Thaumatococcus daniellii, lysozyme from hen egg white and catalase from bovine liver) by the porous network of the gel. Finally, it is shown how the number and the size of the crystals obtained inside X-ray capillaries is controlled by the size of the porous structure of the gel.

  12. Chirality-dependent densities of carbon nanotubes by in situ 2D fluorescence-excitation and Raman characterisation in a density gradient after ultracentrifugation

    NASA Astrophysics Data System (ADS)

    Cambré, Sofie; Muyshondt, Pieter; Federicci, Remi; Wenseleers, Wim

    2015-11-01

    Density gradient ultracentrifugation (DGU) becomes increasingly important for the sorting of nanomaterials according to the particles' density, hence structure and dimensions, which determine their unique properties, but the further development of this separation technique is hindered by the limited precision with which the densities could be characterized. In this work, we determine these densities by position-dependent 2D wavelength-dependent IR fluorescence-excitation and resonant Raman spectroscopy measured directly in the density gradient after ultracentrifugation. We apply this method to study the diameter and chirality-dependent sorting of empty and water-filled single-walled carbon nanotubes coated with two different surfactants, sodium cholate (SC) and sodium deoxycholate (DOC). The results elucidate the long standing contradiction that SC would provide better diameter sorting, while DOC is the most efficient surfactant to solubilise the nanotubes. A more predictable separation is obtained for empty DOC-coated nanotubes since their density is found to vary very smoothly with diameter. The accurate and chirality-dependent densities furthermore provide information on the surfactant coating, which is also important for other separation techniques, and allow to determine the mass percentage of water encapsulated inside the nanotubes.Density gradient ultracentrifugation (DGU) becomes increasingly important for the sorting of nanomaterials according to the particles' density, hence structure and dimensions, which determine their unique properties, but the further development of this separation technique is hindered by the limited precision with which the densities could be characterized. In this work, we determine these densities by position-dependent 2D wavelength-dependent IR fluorescence-excitation and resonant Raman spectroscopy measured directly in the density gradient after ultracentrifugation. We apply this method to study the diameter and chirality-dependent sorting of empty and water-filled single-walled carbon nanotubes coated with two different surfactants, sodium cholate (SC) and sodium deoxycholate (DOC). The results elucidate the long standing contradiction that SC would provide better diameter sorting, while DOC is the most efficient surfactant to solubilise the nanotubes. A more predictable separation is obtained for empty DOC-coated nanotubes since their density is found to vary very smoothly with diameter. The accurate and chirality-dependent densities furthermore provide information on the surfactant coating, which is also important for other separation techniques, and allow to determine the mass percentage of water encapsulated inside the nanotubes. Electronic supplementary information (ESI) available: (1) Density calibration, (2) fraction selection and reproducibility, (3) diffusion of the SWCNTs and (4) experimental RRS spectra and fits at various excitation wavelengths. See DOI: 10.1039/c5nr06020f

  13. Ultracentrifugation-based approaches to study regulation of Sec6/8 (exocyst) complex function during development of epithelial cell polarity.

    PubMed

    Yeaman, Charles

    2003-07-01

    The Sec6/8 (exocyst) complex is an essential component of the exocytic apparatus and plays an evolutionarily conserved role in polarized membrane growth. During development of epithelial cell polarity, this cytosolic protein complex is recruited to plasma membrane sites of cell-cell contact, where it facilitates exocytosis to the lateral membrane domain. However, the identity of membrane binding sites for Sec6/8 complex, mechanisms regulating association of Sec6/8 complex with these sites, and the precise function of the complex in polarized trafficking are not known. Biochemical strategies involving differential, rate-zonal, and isopycnic density gradient ultracentrifugation are providing clues to these questions. PMID:12798134

  14. Sol-Gel Glasses

    NASA Technical Reports Server (NTRS)

    Mukherjee, S. P.

    1985-01-01

    Multicomponent homogeneous, ultrapure noncrystalline gels/gel derived glasses are promising batch materials for the containerless glass melting experiments in microgravity. Hence, ultrapure, homogeneous gel precursors could be used to: (1) investigate the effect of the container induced nucleation on the glass forming ability of marginally glass forming compositions; and (2) investigate the influence of gravity on the phase separation and coarsening behavior of gel derived glasses in the liquid-liquid immiscibility zone of the nonsilicate systems having a high density phase. The structure and crystallization behavior of gels in the SiO2-GeO2 as a function of gel chemistry and thermal treatment were investigated. As are the chemical principles involved in the distribution of a second network former in silica gel matrix being investigated. The procedures for synthesizing noncrystalline gels/gel-monoliths in the SiO2-GeO2, GeO2-PbO systems were developed. Preliminary investigations on the levitation and thermal treatment of germania silicate gel-monoliths in the Pressure Facility Acoustic Levitator were done.

  15. Analytical performance and clinical usefulness of two binding assays for growth hormone binding protein (GHBP) measurement: high performance liquid chromatography (HPLC)-gel filtration and dextran-coated charcoal adsorption.

    PubMed

    Llopis, M A; Granada, M L; Audí, L; Sanmartí, A; Bel, J; Sánchez-Planell, L; Formiguera, X; Marin, F; Corominas, A

    1997-11-28

    We compared two binding assays for growth hormone binding protein (GHBP) measurements, which differ in the method of bound and free GH separation: HPLC-gel filtration or dextran coated-charcoal adsorption (DCC). Two pools of sera (high and medium GHBP activity) were used for quality-control assessment. Moreover, 62 samples from 34 children and 28 adults with different nutritional status were studied. Total, between- and intra-iodination coefficients of variation (CVs) from the two methods were not different. Although percentage binding measured in the pool sera significantly differed, the concentrations assessed by Scatchard plot were comparable. Results obtained by the two methods in the 62 sera were significantly correlated (r = 0.77, P < 0.001). With both methods GHBP activity correlated with chronological age and body mass index (BMI) and differed among groups with different nutritional status. Although HPLC and DCC separation methods for GHBP measurement differ in their practicability, our study demonstrates that performance and the clinical usefulness of the two methods are comparable. PMID:9469251

  16. Staining proteins in gels.

    PubMed

    Sasse, Joachim; Gallagher, Sean R

    2004-02-01

    This unit describes protocols for detecting protein in a gel by either Coomassie blue, silver or fluorescent staining. Alternate rapid staining procedures are provided for each method and a support protocol describes how to photograph stained gels. Fluorescent staining (e.g., with SYPRO Orange or Red) is described as a popular alternative to traditional staining procedures, mainly because it is more sensitive than Coomassie staining, and often as sensitive as silver staining. Staining of proteins in SDS-polyacrylamide gels is described, and an alternate protocol details variations in the procedure for proteins in nondenaturing gels. A final support protocol describes the photography of fluorescently stained proteins. PMID:18432935

  17. Pulse Field Gel Electrophoresis.

    PubMed

    Sharma-Kuinkel, Batu K; Rude, Thomas H; Fowler, Vance G

    2016-01-01

    Pulse Field Gel Electrophoresis (PFGE) is a powerful genotyping technique used for the separation of large DNA molecules (entire genomic DNA) after digesting it with unique restriction enzymes and applying to a gel matrix under the electric field that periodically changes direction. PFGE is a variation of agarose gel electrophoresis that permits analysis of bacterial DNA fragments over an order of magnitude larger than that with conventional restriction enzyme analysis. It provides a good representation of the entire bacterial chromosome in a single gel with a highly reproducible restriction profile, providing clearly distinct and well-resolved DNA fragments. PMID:25682374

  18. CONFORMANCE IMPROVEMENT USING GELS

    SciTech Connect

    Randall S. Seright

    2003-09-01

    This report describes work performed during the second year of the project, ''Conformance Improvement Using Gels.'' The project has two objectives. The first objective is to identify gel compositions and conditions that substantially reduce flow through fractures that allow direct channeling between wells, while leaving secondary fractures open so that high fluid injection and production rates can be maintained. The second objective is to optimize treatments in fractured production wells, where the gel must reduce permeability to water much more than that to oil. Pore-level images from X-ray computed microtomography were re-examined for Berea sandstone and porous polyethylene. This analysis suggests that oil penetration through gel-filled pores occurs by a gel-dehydration mechanism, rather than a gel-ripping mechanism. This finding helps to explain why aqueous gels can reduce permeability to water more than to oil. We analyzed a Cr(III)-acetate-HPAM gel treatment in a production well in the Arbuckle formation. The availability of accurate pressure data before, during, and after the treatment was critical for the analysis. After the gel treatment, water productivity was fairly constant at about 20% of the pre-treatment value. However, oil productivity was stimulated by a factor of 18 immediately after the treatment. During the six months after the treatment, oil productivity gradually decreased to approach the pre-treatment value. To explain this behavior, we proposed that the fracture area open to oil flow was increased substantially by the gel treatment, followed by a gradual closing of the fractures during subsequent production. For a conventional Cr(III)-acetate-HPAM gel, the delay between gelant preparation and injection into a fracture impacts the placement, leakoff, and permeability reduction behavior. Formulations placed as partially formed gels showed relatively low pressure gradients during placement, and yet substantially reduced the flow capacity of fractures (with widths from 1 to 4 mm) during brine and oil flow after placement. Regardless of gel age before placement, very little gel washed out from the fractures during brine or oil flow. However, increased brine or oil flow rate and cyclic injection of oil and water significantly decreased the level of permeability reduction. A particular need exists for gels that can plug large apertures (e.g., wide fractures and vugs). Improved mechanical strength and stability were demonstrated (in 1- to 4-mm-wide fractures) for a gel that contained a combination of high- and low-molecular weight polymers. This gel reduced the flow capacity of 2- and 4-mm-wide fractures by 260,000. In a 1-mm-wide fracture, it withstood 26 psi/ft without allowing any brine flow through the fracture. Cr(III)-acetate-HPAM gels exhibited disproportionate permeability reduction in fractures. The effect was most pronounced when the gel was placed as gelant or partially formed gels. The effect occurred to a modest extent with concentrated gels and with gels that were ''fully formed'' when placed. The effect was not evident in tubes. We explored swelling polymers for plugging fractures. Polymer suspensions were quickly prepared and injected. In concept, the partially dissolved polymer would lodge and swell to plug the fracture. For three types of swelling polymers, behavior was promising. However, additional development is needed before their performance will be superior to that of conventional gels.

  19. CONFORMANCE IMPROVEMENT USING GELS

    SciTech Connect

    Randall S. Seright

    2004-09-30

    This report describes work performed during the third and final year of the project, ''Conformance Improvement Using Gels.'' Corefloods revealed throughput dependencies of permeability reduction by polymers and gels that were much more prolonged during oil flow than water flow. This behavior was explained using simple mobility ratio arguments. A model was developed that quantitatively fits the results and predicts ''clean up'' times for oil productivity when production wells are returned to service after application of a polymer or gel treatment. X-ray computed microtomography studies of gels in strongly water-wet Berea sandstone and strongly oil-wet porous polyethylene suggested that oil penetration through gel-filled pores occurs by a gel-dehydration mechanism, rather than gel-ripping or gel-displacement mechanisms. In contrast, analysis of data from the University of Kansas suggests that the gel-ripping or displacement mechanisms are more important in more permeable, strongly water-wet sandpacks. These findings help to explain why aqueous gels can reduce permeability to water more than to oil under different conditions. Since cement is the most commonly used material for water shutoff, we considered when gels are preferred over cements. Our analysis and experimental results indicated that cement cannot be expected to completely fill (top to bottom) a vertical fracture of any width, except near the wellbore. For vertical fractures with apertures less than 4 mm, the cement slurry will simply not penetrate very far into the fracture. For vertical fractures with apertures greater than 4 mm, the slurry may penetrate a substantial distance into the bottom part of the fracture. However, except near the wellbore, the upper part of the fracture will remain open due to gravity segregation. We compared various approaches to plugging fractures using gels, including (1) varying polymer content, (2) varying placement (extrusion) rate, (3) using partially formed gels, (4) using combinations of high and low molecular weight (Mw) polymers, (5) using secondary crosslinking reactions, (6) injecting un-hydrated polymer particles, and (7) incorporating particulates. All of these methods showed promise in some aspects, but required performance improvements in other aspects. All materials investigated to date showed significant performance variations with fracture width. High pressure gradients and limited distance of penetration are common problems in tight fractures. Gravity segregation and low resistance to breaching are common problems in wide fractures. These will be key issues to address in future work. Although gels can exhibit disproportionate permeability reduction in fractures, the levels of permeability reduction for oil flow are too high to allow practical exploitation in most circumstances. In contrast, disproportionate permeability reduction provided by gels that form in porous rock (adjacent to the fractures) has considerable potential in fractured systems.

  20. CONFORMANCE IMPROVEMENT USING GELS

    SciTech Connect

    Randall S. Seright

    2004-03-01

    This technical progress report describes work performed from September 1, 2003, through February 29, 2004, for the project, ''Conformance Improvement Using Gels.'' We examined the properties of several ''partially formed'' gels that were formulated with a combination of high and low molecular weight HPAM polymers. After placement in 4-mm-wide fractures, these gels required about 25 psi/ft for brine to breach the gel (the best performance to date in fractures this wide). After this breach, stabilized residual resistance factors decreased significantly with increased flow rate. Also, residual resistance factors were up to 9 times greater for water than for oil. Nevertheless, permeability reduction factors were substantial for both water and oil flow. Gel with 2.5% chopped fiberglass effectively plugged 4-mm-wide fractures if a 0.5-mm-wide constriction was present. The ability to screen-out at a constriction appears crucial for particulate incorporation to be useful in plugging fractures. In addition to fiberglass, we examined incorporation of polypropylene fibers into gels. Once dispersed in brine or gelant, the polypropylene fibers exhibited the least gravity segregation of any particulate that we have tested to date. In fractures with widths of at least 2 mm, 24-hr-old gels (0.5% high molecular weight HPAM) with 0.5% fiber did not exhibit progressive plugging during placement and showed extrusion pressure gradients similar to those of gels without the fiber. The presence of the fiber roughly doubled the gel's resistance to first breach by brine flow. The breaching pressure gradients were not as large as for gels made with high and low molecular weight polymers (mentioned above). However, their material requirements and costs (i.e., polymer and/or particulate concentrations) were substantially lower than for those gels. A partially formed gel made with 0.5% HPAM did not enter a 0.052-mm-wide fracture when applying a pressure gradient of 65 psi/ft. This result suggests a lower limit of fracture width for entry of formed or partially formed gels (when reasonable pressure gradients are applied). In unfractured porous rock, we investigated the time dependence of oil and water permeabilities during various cycles of oil and water injection after placement of a Cr(III)-acetate-HPAM gel. Permeability to water stabilized rapidly (within 1 pore volume, PV), while permeability to oil stabilized gradually over the course of 100 PV. The behavior was surprisingly insensitive to core material (strongly water-wet Berea sandstone and strongly oil-wet porous polyethylene), core permeability (740 to 10,000 md), and applied pressure gradient (10 to 100 psi/ft).

  1. Modeling chemoresponsive polymer gels.

    PubMed

    Kuksenok, Olga; Deb, Debabrata; Dayal, Pratyush; Balazs, Anna C

    2014-01-01

    Stimuli-responsive gels are vital components in the next generation of smart devices, which can sense and dynamically respond to changes in the local environment and thereby exhibit more autonomous functionality. We describe recently developed computational methods for simulating the properties of such stimuli-responsive gels in the presence of optical, chemical, and thermal gradients. Using these models, we determine how to harness light to drive shape changes and directed motion in spirobenzopyran-containing gels. Focusing on oscillating gels undergoing the Belousov-Zhabotinksy reaction, we demonstrate that these materials can spontaneously form self-rotating assemblies, or pinwheels. Finally, we model temperature-sensitive gels that encompass chemically reactive filaments to optimize the performance of this system as a homeostatic device for regulating temperature. These studies could facilitate the development of soft robots that autonomously interconvert chemical and mechanical energy and thus perform vital functions without the continuous need of external power sources. PMID:24498954

  2. Analytical testing

    NASA Technical Reports Server (NTRS)

    Flannelly, W. G.; Fabunmi, J. A.; Nagy, E. J.

    1981-01-01

    Analytical methods for combining flight acceleration and strain data with shake test mobility data to predict the effects of structural changes on flight vibrations and strains are presented. This integration of structural dynamic analysis with flight performance is referred to as analytical testing. The objective of this methodology is to analytically estimate the results of flight testing contemplated structural changes with minimum flying and change trials. The category of changes to the aircraft includes mass, stiffness, absorbers, isolators, and active suppressors. Examples of applying the analytical testing methodology using flight test and shake test data measured on an AH-1G helicopter are included. The techniques and procedures for vibration testing and modal analysis are also described.

  3. Effect of Polymer Hydration State on In-Gel Immunoassays.

    PubMed

    Vlassakis, Julea; Herr, Amy E

    2015-11-01

    Applications as diverse as drug delivery and immunoassays require hydrogels to house high concentration macromolecular solutions. Yet, thermodynamic partitioning acts to lower the equilibrium concentration of macromolecules in the hydrogel, as compared to the surrounding liquid phase. For immunoassays that utilize a target antigen immobilized in the hydrogel, partitioning hinders introduction of detection antibody into the gel and, consequently, reduces the in-gel concentration of detection antibody, adversely impacting assay sensitivity. Recently, we developed a single-cell targeted proteomic assay with polyacrylamide gel electrophoresis of single cell lysates followed by an in-gel immunoassay. In the present work, we overcome partitioning that both limits analytical sensitivity and increases consumption of costly detection antibody by performing the immunoassay step after dehydrating the antigen-containing polyacrylamide gel. Gels are rehydrated with a solution of detection antibody. We hypothesized that matching the volume of detection antibody solution with the hydrogel water volume fraction would ensure that, at equilibrium, the detection antibody mass resides in the gel and not in the liquid surrounding the gel. Using this approach, we observe (compared with antibody incubation of hydrated gels): (i) 4-11 fold higher concentration of antibody in the dehydrated gels and in the single-cell assay (ii) higher fluorescence immunoassay signal, with up to 5-fold increases in signal-to-noise-ratio and (iii) reduced detection antibody consumption. We also find that detection antibody signal may be less well-correlated with target protein levels (GFP) using this method, suggesting a trade-off between analytical sensitivity and variation in immunoprobe signal. Our volume-matching approach for introducing macromolecular solutions to hydrogels increases the local in-gel concentration of detection antibody without requiring modification of the hydrogel structure, and thus we anticipate broad applicability to hydrogel-based assays, diagnostics, and drug delivery. PMID:26457450

  4. DNA DAMAGE QUANTITATION BY ALKALINE GEL ELECTROPHORESIS.

    SciTech Connect

    SUTHERLAND,B.M.; BENNETT,P.V.; SUTHERLAND, J.C.

    2004-03-24

    Physical and chemical agents in the environment, those used in clinical applications, or encountered during recreational exposures to sunlight, induce damages in DNA. Understanding the biological impact of these agents requires quantitation of the levels of such damages in laboratory test systems as well as in field or clinical samples. Alkaline gel electrophoresis provides a sensitive (down to {approx} a few lesions/5Mb), rapid method of direct quantitation of a wide variety of DNA damages in nanogram quantities of non-radioactive DNAs from laboratory, field, or clinical specimens, including higher plants and animals. This method stems from velocity sedimentation studies of DNA populations, and from the simple methods of agarose gel electrophoresis. Our laboratories have developed quantitative agarose gel methods, analytical descriptions of DNA migration during electrophoresis on agarose gels (1-6), and electronic imaging for accurate determinations of DNA mass (7-9). Although all these components improve sensitivity and throughput of large numbers of samples (7,8,10), a simple version using only standard molecular biology equipment allows routine analysis of DNA damages at moderate frequencies. We present here a description of the methods, as well as a brief description of the underlying principles, required for a simplified approach to quantitation of DNA damages by alkaline gel electrophoresis.

  5. High Purity and Yield Separation of Semiconducting Single-Walled Carbon Nanotubes Dispersed in Aqueous Solutions with Density Gradient Ultracentrifugation Using Mixed Dispersants of Polysaccharides and Surfactants

    NASA Astrophysics Data System (ADS)

    Tsuchiya, Koji; Uchida, Katsumi; Kaminosono, Yoshiya; Shimizu, Kazushi; Ishii, Tadahiro; Yajima, Hirofumi

    2013-03-01

    The heterogeneity of as-synthesized single-walled carbon nanotubes (SWNTs) prevents their potential applications in high-resolution field-effect transistors, nanoscale sensors, and conductive films. In the present study, we demonstrate the development of a new selective-separation procedure for collecting semiconducting single-walled carbon nanotubes (s-SWNTs) with a high purity from as-synthesized SWNTs individually dispersed with mixed dispersing agents consisting of carboxymethylcellulose (CMC) and sodium dodecyl sulfate (SDS) in water using density gradient ultracentrifugation (DGU). Ultraviolet-visible-near infrared (UV-vis-NIR) absorption, resonance Raman, and NIR photoluminescence spectroscopies revealed that the s-SWNTs were enriched to a purity of more than 97%, and that the recovery was approximately 40% through the DGU treatment. This separation strategy is expected to impact the application fields using s-SWNTs.

  6. Microfluidics with Gel Emulsions

    NASA Astrophysics Data System (ADS)

    Priest, Craig; Surenjav, Enkhtuul; Herminghaus, Stephan; Seemann, Ralf

    2006-03-01

    Microfluidic processing is usually achieved using single phase liquids. Instead, we use monodisperse emulsions to compartment liquids within microchannel geometries. At low continuous phase volume fractions, droplets self-organize to form well-defined arrangements, analogous to foam. While it is well-known that confined geometries can induce rearrangement of foam compartments at the millimeter-scale, similar dynamics are also expected for gel emulsions. We have studied online generation, organization and manipulation of gel emulsions using a variety of microchannel geometries. ``Passive'' reorganization, based on fixed channel geometries, can be supplemented by ``active'' manipulation by incorporating a ferrofluid phase. A ferromagnetic phase facilitates reorganization of liquid compartments on demand using an electromagnetic trigger. Moreover, coalescence between adjacent compartments within a gel emulsion can be induced using electrical potential. Microfluidics using gel emulsions will be well-suited for combinatorial chemistry, DNA sequencing, drug screening and protein crystallizations.

  7. Staining proteins in gels.

    PubMed

    Sasse, Joachim; Gallagher, Sean R

    2003-08-01

    This unit describes protocols for detecting protein in a gel by either Coomassie blue staining or silver staining. The former is easier and more rapid; however, silver staining methods are considerably more sensitive and thus can be used to detect smaller amounts of protein. Alternate rapid staining procedures are provided for each method and a support protocol describes how to photograph stained gels. Fluorescent staining is a popular alternative to traditional staining procedures, mainly because it is more sensitive than Coomassie staining, and often as sensitive as silver staining. Staining of proteins in SDS-polyacrylamide gels is described, and an alternate protocol details variations in the procedure for proteins in nondenaturing gels. A final support protocol describes the photography of fluorescently stained proteins. PMID:18265316

  8. Crystallization from Gels

    NASA Astrophysics Data System (ADS)

    Narayana Kalkura, S.; Natarajan, Subramanian

    Among the various crystallization techniques, crystallization in gels has found wide applications in the fields of biomineralization and macromolecular crystallization in addition to crystallizing materials having nonlinear optical, ferroelectric, ferromagnetic, and other properties. Furthermore, by using this method it is possible to grow single crystals with very high perfection that are difficult to grow by other techniques. The gel method of crystallization provides an ideal technique to study crystal deposition diseases, which could lead to better understanding of their etiology. This chapter focuses on crystallization in gels of compounds that are responsible for crystal deposition diseases. The introduction is followed by a description of the various gels used, the mechanism of gelling, and the fascinating phenomenon of Liesegang ring formation, along with various gel growth techniques. The importance and scope of study on crystal deposition diseases and the need for crystal growth experiments using gel media are stressed. The various crystal deposition diseases, viz. (1) urolithiasis, (2) gout or arthritis, (3) cholelithiasis and atherosclerosis, and (4) pancreatitis and details regarding the constituents of the crystal deposits responsible for the pathological mineralization are discussed. Brief accounts of the theories of the formation of urinary stones and gallstones and the role of trace elements in urinary stone formation are also given. The crystallization in gels of (1) the urinary stone constituents, viz. calcium oxalate, calcium phosphates, uric acid, cystine, etc., (2) the constituents of the gallstones, viz. cholesterol, calcium carbonate, etc., (3) the major constituent of the pancreatic calculi, viz., calcium carbonate, and (4) cholic acid, a steroidal hormone are presented. The effect of various organic and inorganic ions, trace elements, and extracts from cereals, herbs, and fruits on the crystallization of major urinary stone and gallstone constituents are described. In addition, tables of gel-grown organic and inorganic crystals are provided.

  9. Fluorescent staining of gels.

    PubMed

    Buxbaum, Engelbert

    2012-01-01

    Certain transition metal complexes show intensive fluorescence when bound to proteins. They can be used to stain gels after electrophoresis with a sensitivity approaching that of silver staining, but in a much simpler and more reproducible procedure. Stains can be prepared easily and at a fraction of the cost of commercially available reagents.Hydrophobic dyes can be used to stain gels without fixing; they do not interfere with later blotting or electro-elution. PMID:22585519

  10. Conformance Improvement Using Gels

    SciTech Connect

    Seright, Randall S.; Schrader; II Hagstrom, John; Wang, Ying; Al-Dahfeeri, Abdullah; Marin, Amaury

    2002-09-26

    This research project had two objectives. The first objective was to identify gel compositions and conditions that substantially reduce flow through fractures that allow direct channeling between wells, while leaving secondary fractures open so that high fluid injection and production rates can be maintained. The second objective was to optimize treatments in fractured production wells, where the gel must reduce permeability to water much more than that to oil.

  11. Analytical Microscopy

    SciTech Connect

    Not Available

    2006-06-01

    In the Analytical Microscopy group, within the National Center for Photovoltaic's Measurements and Characterization Division, we combine two complementary areas of analytical microscopy--electron microscopy and proximal-probe techniques--and use a variety of state-of-the-art imaging and analytical tools. We also design and build custom instrumentation and develop novel techniques that provide unique capabilities for studying materials and devices. In our work, we collaborate with you to solve materials- and device-related R&D problems. This sheet summarizes the uses and features of four major tools: transmission electron microscopy, scanning electron microscopy, the dual-beam focused-ion-beam workstation, and scanning probe microscopy.

  12. Polyacrylamide gel electrophoresis.

    PubMed

    Chrambach, A; Rodbard, D

    1971-04-30

    Polyacrylamide gel electrophoresis (PAGE) provides a versatile, gentle, high resolution method for fractionation and physical-chemical characterization of molecules on the basis of size, conformation, and net charge. The polymerization reaction can be rigorously controlled to provide uniform gels of reproducible, measurable pore size over a wide range. This makes it possible to obtain reproducible relative mobility (Rf) values as physical-chemical constants. Application and extension of Ogston's (random fiber) model for a gel allows for calculation of molecular volume, surface area, or radius, free mobility, and valence from RJ measurements at several gel concentrations, to calculate gel concentration for optimal resolution, and to predict behavior of macromolecules on gel gradients by computerized methods. Extension of classical moving boundary theory has been used to generate multiphasic buffer systems (providing selective stacking, unstacking, restacking, and preparative steady-state-stacking) with known operating characteristics for any pH at 0 degrees and 25 degrees C. A general strategy for isolation of macromolecules and for macromolecular mapping has been developed. Preparative scale PAGE is operational for milligram loads and feasible for gram quantities. PMID:4927678

  13. Nonlinear Elasticity and Cavitation of a Triblock Copolymer Gel

    NASA Astrophysics Data System (ADS)

    Kundu, Santanu; Hashemnejad, Seyed Meysam; Zabet, Mahla; Mishra, Satish

    2015-03-01

    Polymer gels are subjected to large-strain deformation during their applications. The gel deformation at large-strain is non-linear and can often lead to failure of the material. Here, we report the large-strain deformation behavior of a physically cross-linked, swollen polymer gel, which displays unique strain-stiffening response at large-strain. Investigations were performed using large amplitude oscillatory shear (LAOS) and custom developed cavitation rheology techniques. Gent constitutive model, which considers finite extensibility of midblock, was fitted with the LAOS data, therefore, linking the estimated parameters from LAOS analysis to the structure of the gel. Cavitation experiments were conducted as a function of temperature. Both analytical method and finite-element based modeling have been implemented to capture the pressure response in cavitation experiments. Our results provide a critical understanding of gel failure mechanism at large-strain.

  14. CONFORMANCE IMPROVEMENT USING GELS

    SciTech Connect

    Randall S. Seright

    2002-02-28

    This technical progress report describes work performed from June 20 through December 19, 2001, for the project, ''Conformance Improvement Using Gels''. Interest has increased in some new polymeric products that purport to substantially reduce permeability to water while causing minimum permeability reduction to oil. In view of this interest, we are currently studying BJ's Aqua Con. Results from six corefloods revealed that the Aqua Con gelant consistently reduced permeability to water more than that to oil. However, the magnitude of the disproportionate permeability reduction varied significantly for the various experiments. Thus, as with most materials tested to date, the issue of reproducibility and control of the disproportionate permeability remains to be resolved. Concern exists about the ability of gels to resist washout after placement in fractures. We examined whether a width constriction in the middle of a fracture would cause different gel washout behavior upstream versus downstream of the constriction. Tests were performed using a formed Cr(III)-acetate-HPAM gel in a 48-in.-long fracture with three sections of equal length, but with widths of 0.08-, 0.02-, and 0.08-in., respectively. The pressure gradients during gel extrusion (i.e., placement) were similar in the two 0.08-in.-wide fracture sections, even though they were separated by a 0.02-in.-wide fracture section. The constriction associated with the middle fracture section may have inhibited gel washout during the first pulse of brine injection after gel placement. However, during subsequent phases of brine injection, the constriction did not inhibit washout in the upstream fracture section any more than in the downstream section.

  15. Analytical sedimentology

    SciTech Connect

    Lewis, D.W. . Dept. of Geology); McConchie, D.M. . Centre for Coastal Management)

    1994-01-01

    Both a self instruction manual and a cookbook'' guide to field and laboratory analytical procedures, this book provides an essential reference for non-specialists. With a minimum of mathematics and virtually no theory, it introduces practitioners to easy, inexpensive options for sample collection and preparation, data acquisition, analytic protocols, result interpretation and verification techniques. This step-by-step guide considers the advantages and limitations of different procedures, discusses safety and troubleshooting, and explains support skills like mapping, photography and report writing. It also offers managers, off-site engineers and others using sediments data a quick course in commissioning studies and making the most of the reports. This manual will answer the growing needs of practitioners in the field, either alone or accompanied by Practical Sedimentology, which surveys the science of sedimentology and provides a basic overview of the principles behind the applications.

  16. Spatially resolved multicomponent gels

    NASA Astrophysics Data System (ADS)

    Draper, Emily R.; Eden, Edward G. B.; McDonald, Tom O.; Adams, Dave J.

    2015-10-01

    Multicomponent supramolecular systems could be used to prepare exciting new functional materials, but it is often challenging to control the assembly across multiple length scales. Here we report a simple approach to forming patterned, spatially resolved multicomponent supramolecular hydrogels. A multicomponent gel is first formed from two low-molecular-weight gelators and consists of two types of fibre, each formed by only one gelator. One type of fibre in this ‘self-sorted network’ is then removed selectively by a light-triggered gel-to-sol transition. We show that the remaining network has the same mechanical properties as it would have done if it initially formed alone. The selective irradiation of sections of the gel through a mask leads to the formation of patterned multicomponent networks, in which either one or two networks can be present at a particular position with a high degree of spatial control.

  17. Staining proteins in gels.

    PubMed

    Sasse, Joachim; Gallagher, Sean R

    2009-01-01

    This unit describes protocols for detecting protein in a gel by Coomassie blue, silver, or fluorescent staining. As a general protein stain, Coomassie is easier and more rapid; however, fluorescent and silver staining methods are considerably more sensitive and thus can be used to detect smaller amounts of protein. Fluorescent staining is a popular alternative to traditional staining procedures, mainly because it is more sensitive than Coomassie staining, and often as sensitive as silver staining. Alternate protocols describe rapid Coomassie and silver staining methods, as well as fluorescent stains that are specific for phosphoproteins and glycoproteins. Staining of proteins in SDS-polyacrylamide gels is described; variations for fluorescent staining of proteins in nondenaturing gels are also included. Support protocols describe photography of stained proteins. PMID:19170026

  18. Elastodynamics of gels

    SciTech Connect

    Johnson, D.L.

    1982-08-01

    The mechanical properties of gels are analyzed in terms of models which treat the three-dimensional displacements of solid and fluid parts separately and on an equal footing, with no assumptions regarding smallness of concentration or even weakness of the solid skeleton frame. Thus, a unified description of the normal modes in a gel is presented; parameters deduced from measurement on a given mode are shown to influence the properties of the others. It is still assumed, however, that the fluid and solid components can be described by their bulk densities, elastic moduli, etc. This picture is discussed in light of experimental results. 37 references.

  19. Electroblotting from Polyacrylamide Gels.

    PubMed

    Goldman, Aaron; Ursitti, Jeanine A; Mozdzanowski, Jacek; Speicher, David W

    2015-01-01

    Transferring proteins from polyacrylamide gels onto retentive membranes is now primarily used for immunoblotting. A second application that was quite common up to about a decade ago was electroblotting of proteins for N-terminal and internal sequencing using Edman chemistry. This unit contains procedures for electroblotting proteins from polyacrylamide gels onto a variety of membranes, including polyvinylidene difluoride (PVDF) and nitrocellulose. In addition to the commonly used tank or wet transfer system, protocols are provided for electroblotting using semidry and dry systems. This unit also describes procedures for eluting proteins from membranes using detergents or acidic extraction with organic solvents for specialized applications. 2015 by John Wiley & Sons, Inc. PMID:26521711

  20. Rheology of Active Gels

    NASA Astrophysics Data System (ADS)

    Chen, Daniel

    2015-03-01

    Active networks drive a diverse range of critical processes ranging from motility to division in living cells, yet a full picture of their rheological capabilities in non-cellular contexts is still emerging, e.g., How does the rheological response of a network capable of remodeling under internally-generated stresses differ from that of a passive biopolymer network? In order to address this and other basic questions, we have engineered an active gel composed of microtubules, bidirectional kinesin motors, and molecular depletant that self-organizes into a highly dynamic network of active bundles. The network continually remodels itself under ATP-tunable cycles of extension, buckling, fracturing, and self-healing. Using confocal rheometry we have simultaneously characterized the network's linear and non-linear rheological responses to shear deformation along with its dynamic morphology. We find several surprising and unique material properties for these active gels; most notably, rheological cloaking, the ability of the active gel to drive large-scale fluid mixing over several orders of flow magnitude while maintaining an invariant, solid-like rheological profile and spontaneous flow under confinement, the ability to exert micro-Newton forces to drive persistent directed motion of the rheometer tool. Taken together, these results and others to be discussed highlight the rich stress-structure-dynamics relationships in this class of biologically-derived active gels.

  1. Novel detection schemes and automated image analysis algorithms for planar chromatography and gel electrophoresis

    SciTech Connect

    Koutney, L.B.

    1992-09-09

    After a discussion of charge coupled devices and personal computer capabilities, examples of their applications involving novel analytical techniques are presented: laser-based indirect fluorometric detection in thin-layer chromatography; on-line detection of DNA and proteins in gel electrophoresis by uv absorption; automated image analysis for distortion compensation in sequencing gel electrophoresis; and expert systems for data acquisition to achieve constant signal-to-noise, with application to DNA sequencing slab gels.

  2. Transdermal delivery of paeonol using cubic gel and microemulsion gel

    PubMed Central

    Luo, Maofu; Shen, Qi; Chen, Jinjin

    2011-01-01

    Background The aim of this study was to develop new systems for transdermal delivery of paeonol, in particular microemulsion gel and cubic gel formulations. Methods Various microemulsion vehicles were prepared using isopropyl myristate as an oil phase, polyoxyethylated castor oil (Cremophor® EL) as a surfactant, and polyethylene glycol 400 as a cosurfactant. In the optimum microemulsion gel formulation, carbomer 940 was selected as the gel matrix, and consisted of 1% paeonol, 4% isopropyl myristate, 28% Cremophor EL/polyethylene glycol 400 (1:1), and 67% water. The cubic gel was prepared containing 3% paeonol, 30% water, and 67% glyceryl monooleate. Results A skin permeability test using excised rat skins indicated that both the cubic gel and microemulsion gel formulations had higher permeability than did the paeonol solution. An in vivo pharmacokinetic study done in rats showed that the relative bioavailability of the cubic gel and microemulsion gel was enhanced by about 1.51-fold and 1.28-fold, respectively, compared with orally administered paeonol suspension. Conclusion Both the cubic gel and microemulsion gel formulations are promising delivery systems to enhance the skin permeability of paeonol, in particular the cubic gel. PMID:21904450

  3. Swelling-induced and controlled curving in layered gel beams.

    PubMed

    Lucantonio, A; Nardinocchi, P; Pezzulla, M

    2014-11-01

    We describe swelling-driven curving in originally straight and non-homogeneous beams. We present and verify a structural model of swollen beams, based on a new point of view adopted to describe swelling-induced deformation processes in bilayered gel beams, that is based on the split of the swelling-induced deformation of the beam at equilibrium into two components, both depending on the elastic properties of the gel. The method allows us to: (i) determine beam stretching and curving, once assigned the characteristics of the solvent bath and of the non-homogeneous beam, and (ii) estimate the characteristics of non-homogeneous flat gel beams in such a way as to obtain, under free-swelling conditions, three-dimensional shapes. The study was pursued by means of analytical, semi-analytical and numerical tools; excellent agreement of the outcomes of the different techniques was found, thus confirming the strength of the method. PMID:25383031

  4. Swelling-induced and controlled curving in layered gel beams

    PubMed Central

    Lucantonio, A.; Nardinocchi, P.; Pezzulla, M.

    2014-01-01

    We describe swelling-driven curving in originally straight and non-homogeneous beams. We present and verify a structural model of swollen beams, based on a new point of view adopted to describe swelling-induced deformation processes in bilayered gel beams, that is based on the split of the swelling-induced deformation of the beam at equilibrium into two components, both depending on the elastic properties of the gel. The method allows us to: (i) determine beam stretching and curving, once assigned the characteristics of the solvent bath and of the non-homogeneous beam, and (ii) estimate the characteristics of non-homogeneous flat gel beams in such a way as to obtain, under free-swelling conditions, three-dimensional shapes. The study was pursued by means of analytical, semi-analytical and numerical tools; excellent agreement of the outcomes of the different techniques was found, thus confirming the strength of the method. PMID:25383031

  5. Purification, separation and extraction of inner tubes from double-walled carbon nanotubes by tailoring density gradient ultracentrifugation using optical probes

    PubMed Central

    Rohringer, Philip; Shi, Lei; Liu, Xianjie; Yanagi, Kazuhiro; Pichler, Thomas

    2014-01-01

    We studied the effect of varying sonication and centrifugation parameters on double-walled carbon nanotubes (DWCNT) by measuring optical absorption and photoluminescence (PL) of the samples. We found that by using a low sonication intensity before applying density gradient ultracentrifugation (DGU), only inner tube species with a diameter ⩽0.8 nm can be identified in absorption measurements. This is in stark contrast to the result after sonicating at higher intensities, where also bigger inner tubes can be found. Furthermore, by comparing PL properties of samples centrifugated either with or without a gradient medium, we found that applying DGU greatly enhances the PL intensity, whereas centrifugation at even higher speeds but without a gradient medium results in lower intensities. This can be explained by extraction of inner tubes from their host outer tubes in a two-stage process: the different shearing forces from the sonication treatments result in some DWCNT to be opened, whereas others stay uncut. A subsequent application of DGU leads to the extraction of the inner tubes or not if the host nanotube stayed uncut or no gradient medium was used. This work shows a pathway to avoid this phenomenon to unravel the intrinsic PL from inner tubes of DWCNT. PMID:25843961

  6. Synchrotron radiation for direct analysis of metalloproteins on electrophoresis gels.

    PubMed

    Ortega, Richard

    2009-03-01

    Metalloproteomics requires analytical techniques able to assess and quantify the inorganic species in metalloproteins. The most widely used methods are hyphenated techniques, based on the coupling of a high resolution chromatographic method with a high sensitivity method for metal analysis in solution. An alternative approach is the use of methods for solid sample analysis, combining metalloprotein separation by gel electrophoresis and direct analysis of the gels. Direct methods are based on beam analysis, such as lasers, ion beams or synchrotron radiation beams. The aim of this review article is to present the main features of synchrotron radiation based methods and their applications for metalloprotein analysis directly on electrophoresis gels. Synchrotron radiation X-ray fluorescence has been successfully employed for sensitive metal identification, and X-ray absorption spectroscopy for metal local structure speciation in proteins. Synchrotron based methods will be compared to ion beam and mass spectrometry for direct analysis of metalloproteins in electrophoresis gels. PMID:21305106

  7. Linear electrochemical gel actuators

    NASA Astrophysics Data System (ADS)

    Goswami, Shailesh; McAdam, C. John; Hanton, Lyall R.; Moratti, Stephen C.

    2011-11-01

    By using electroactive monomers it is possible to produce gels that respond to oxidation or reduction by swelling and deswelling in the presence of solvent. By the inclusion of an appropriate biasing element such as a spring, it is possible to produce linear, reversible actuation. The process can be driven electrochemically in a standard cell, with driving voltages under +/- 1 V. For many systems, the intrinsic conductivity of the gel, leading to poor or no performance. This can be overcome by blending conductive carbon nanotubes at 1% concentration, which give reasonable conductivity without affecting mechanical performance. Extensions of up to 40% are possible, against an external pressure of 30 kPa. The process is slow, taking up to 160 minutes per cycle due to slow ionic diffusion. The electrochemical cell can be cycled many times without degradation.

  8. Linear electrochemical gel actuators

    NASA Astrophysics Data System (ADS)

    Goswami, Shailesh; McAdam, C. John; Hanton, Lyall R.; Moratti, Stephen C.

    2012-04-01

    By using electroactive monomers it is possible to produce gels that respond to oxidation or reduction by swelling and deswelling in the presence of solvent. By the inclusion of an appropriate biasing element such as a spring, it is possible to produce linear, reversible actuation. The process can be driven electrochemically in a standard cell, with driving voltages under +/- 1 V. For many systems, the intrinsic conductivity of the gel, leading to poor or no performance. This can be overcome by blending conductive carbon nanotubes at 1% concentration, which give reasonable conductivity without affecting mechanical performance. Extensions of up to 40% are possible, against an external pressure of 30 kPa. The process is slow, taking up to 160 minutes per cycle due to slow ionic diffusion. The electrochemical cell can be cycled many times without degradation.

  9. Unpacking a gel-forming mucin: a view of MUC5B organization after granular release.

    PubMed

    Kesimer, Mehmet; Makhov, Alexander M; Griffith, Jack D; Verdugo, Pedro; Sheehan, John K

    2010-01-01

    Gel-forming mucins are the largest complex glycoprotein macromolecules in the body. They form the matrix of gels protecting all the surface epithelia and are secreted as disulfide-bonded polymeric structures. The mechanisms by which they are formed and organized within cells and thereafter released to form mucus gels are not understood. In particular, the initial rate of expansion of the mucins after release from their secretory granules is very rapid (seconds), but no clear mechanism for how it is achieved has emerged. Our major interest is in lung mucins, but most particularly in MUC5B, which is the major gel-forming mucin in mucus, and which provides its major protective matrix. In this study, using OptiPrep density gradient ultracentrifugation, we have isolated a small amount of a stable form of the recently secreted and expanding MUC5B mucin, which accounts for less than 2% of the total mucin present. It has an average mass of approximately 150 x 10(6) Da and size Rg of 150 nm in radius of gyration. In transmission electron microscopy, this compact mucin has maintained a circular structure that is characterized by flexible chains connected around protein-rich nodes as determined by their ability to bind colloidal gold. The appearance indicates that the assembled mucins in a single granular form are organized around a number of nodes, each attached to four to eight subunits. The organization of the mucins in this manner is consistent with efficient packing of a number of large heavily glycosylated monomers while still permitting their rapid unfolding and hydration. For the first time, this provides some insight into how the carbohydrate regions might be organized around the NH(2)- and COOH-terminal globular protein domains within the granule and also explains how the mucin can expand so rapidly upon its release. PMID:19783639

  10. Simplified sizing of low-density lipoprotein using polyacrylamide gradient gel electrophoresis of plasma.

    PubMed

    Westhuyzen, J; Graham, S D; Rasiah, R L; Saltissi, D

    1997-01-01

    Low-density lipoprotein (LDL) particles can be separated into subfractions according to size by non-denaturing polyacrylamide gradient gel electrophoresis. Established research methods require specialised equipment and are frequently unsuited to the clinical laboratory. In this study, we utilised a colour flat bed scanner in conjunction with shareware image analysis software to compare LDL particle diameters of isolated LDL with LDL in whole plasma. LDL was isolated by ultracentrifugation and electrophoresed on 3-13% gels (Gradipore; Sydney, Australia) for 2400 Volt-hours in parallel with plasma and molecular size standards. Coomassie Blue-stained gels were scanned in reflexive mode using a colour flat-bed scanner and Adobe Photoshop 3.0 software. Density traces of each lane were obtained using NIH Image software (public domain, USA). LDL particle diameters were determined from calibration curves of the log of molecular diameter of standards against migration distance. There was a good correlation between LDL particle diameters obtained using isolated LDL and whole plasma (r = 0.87, P < 0.001; n = 22). However, the group means (+/- S.D.) (24.7 +/- 0.6 and 24.8 +/- 0.5 nm respectively) were statistically different on the paired t-test (P < 0.05). It is unclear whether this numerically small difference is due to alterations in LDL during the longer preparative procedures for LDL, or to matrix effects during electrophoresis of plasma samples. In conclusion, plasma samples stained with Coomassie Blue and scanned with a colour flat bed scanner can conveniently be used for LDL particle sizing by non-denaturing polyacrylamide gradient gel electrophoresis. PMID:9156560

  11. Clarification Procedure for Gels

    NASA Technical Reports Server (NTRS)

    Barber, Patrick G.; Simpson, Norman R.

    1987-01-01

    Procedure developed to obtain transparent gels with consistencies suitable for crystal growth, by replacing sodium ions in silicate solution with potassium ions. Clarification process uses cation-exchange resin to replace sodium ions in stock solution with potassium ions, placed in 1M solution of soluble potassium salt. Slurry stirred for several hours to allow potassium ions to replace all other cations on resin. Supernatant solution decanted through filter, and beads rinsed with distilled water. Rinsing removes excess salt but leaves cation-exchange beads fully charged with potassium ions.

  12. Staining proteins in gels.

    PubMed

    Gallagher, Sean; Chakavarti, Deb

    2008-01-01

    Following separation by electrophoretic methods, proteins in a gel can be detected by several staining methods. This unit describes protocols for detecting proteins by four popular methods. Coomassie blue staining is an easy and rapid method. Silver staining, while more time consuming, is considerably more sensitive and can thus be used to detect smaller amounts of protein. Fluorescent staining is a popular alternative to traditional staining procedures, mainly because it is more sensitive than Coomassie staining, and is often as sensitive as silver staining. Staining of proteins with SYPRO Orange and SYPRO Ruby are also demonstrated here. PMID:19066521

  13. High transparent shape memory gel

    NASA Astrophysics Data System (ADS)

    Gong, Jin; Arai, Masanori; Kabir, M. H.; Makino, Masato; Furukawa, Hidemitsu

    2014-03-01

    Gels are a new material having three-dimensional network structures of macromolecules. They possess excellent properties as swellability, high permeability and biocompatibility, and have been applied in various fields of daily life, food, medicine, architecture, and chemistry. In this study, we tried to prepare new multi-functional and high-strength gels by using Meso-Decoration (Meso-Deco), one new method of structure design at intermediate mesoscale. High-performance rigid-rod aromatic polymorphic crystals, and the functional groups of thermoreversible Diels-Alder reaction were introduced into soft gels as crosslinkable pendent chains. The functionalization and strengthening of gels can be realized by meso-decorating the gels' structure using high-performance polymorphic crystals and thermoreversible pendent chains. New gels with good mechanical properties, novel optical properties and thermal properties are expected to be developed.

  14. Polyacrylamide Gel Electrophoresis for Purification of Large Amounts of RNA.

    PubMed

    Meyer, Mélanie; Masquida, Benoît

    2016-01-01

    Polyacrylamide gel electrophoresis (PAGE) constitutes a powerful technique for the efficient purification of RNA molecules dedicated to applications that require high purity levels. PAGE allows for the fractionation of RNA obtained from cell extracts, chemical or enzymatic synthesis, or modification experiments. Native or denaturing conditions can be chosen for analytical or preparative-scale separations and the nucleotide resolution can be tuned by changing the percentage and reticulation of the gel material. In this protocol, we focus on the preparation of milligram-scale amounts of ~200 nucleotides (nt) RNA molecules that were used in subsequent crystallization experiments. PMID:26227037

  15. Nanoparticle gel electrophoresis: bare charged spheres in polyelectrolyte hydrogels.

    PubMed

    Li, Fei; Hill, Reghan J

    2013-03-15

    Nanoparticle gel electrophoresis has recently emerged as an attractive means of separating and characterizing nanoparticles. Consequently, a theory that accounts for electroosmotic flow in the gel, and coupling of the nanoparticle and hydrogel electrostatics and hydrodynamics, is required, particularly for gels in which the mesh size is comparable to or smaller than the particle radii. Here, we present an electrokinetic model for charged, spherical colloidal particles undergoing electrophoresis in charged (polyelectrolyte) hydrogels: the gel-electrophoresis analogue of Henry's theory for electrophoresis in Newtonian electrolytes. We compare numerically exact solutions of the model with several independent asymptotic approximations, identifying regions in the parameter space where these approximations are accurate or break down. As previously assumed in the literature, Henry's formula, modified by the addition of a constant electroosmotic flow mobility, is accurate only for nanoparticles that are small compared to the hydrogel mesh size. We derived an exact analytical solution of the full model by judiciously modifying the theory of Allison et al. for uncharged gels, drawing on the superposition methodology of Doane et al. to account for hydrogel charge. This furnishes accurate and economical mobility predictions for the entire parameter space. The present model suggests that nanoparticle size separations (with diameters ≲40 nm) are optimal at low ionic strength, with a gel mesh size that is selected according to the particle charging mechanism. For weakly charged particles, optimal size separation is achieved when the Brinkman screening length is matched to the mean particle size. PMID:23153681

  16. Esterase activity (EA), total oxidant status (TOS) and total antioxidant capacity (TAC) in gills of Mytilus galloprovincialis exposed to pollutants: Analytical validation and effects evaluation by single and mixed heavy metal exposure.

    PubMed

    Franco, Lorena; Romero, Diego; García-Navarro, José A; Teles, Mariana; Tvarijonaviciute, Asta

    2016-01-15

    The aims of the present study were to optimize and validate methods for esterase activity (EA), total oxidant status (TOS) and total antioxidant capacity (TAC) determination in mussel' gills, and to establish the relationships between these biomarkers and Pb, Cd and Cu pollution, in single form and ternary mixture. Two different buffers for sample homogenization, the need of ultracentrifugation, and analytical validation were evaluated. Coefficients of variation, when buffer without additives and ultracentrifugation were used, were <15%, and recovery were 97%-109% in all cases. The EA response tends to decrease with treatments, TOS decreased significantly in Cd and ternary groups, while TAC tended to increase in treatments with Pb, Cd and ternary groups. In conclusion, the methods for EA, TOS and TAC measurements in gills of mussel were precise and accurate and could be interesting resources in biomonitoring programmes. PMID:26705576

  17. Supramolecular gels: functions and uses.

    PubMed

    Sangeetha, Neralagatta M; Maitra, Uday

    2005-10-01

    In recent years there has been immense interest in studying gels derived from low molecular mass gelators (supramolecular, or simply molecular gels). The motivation for this is not only to understand the fundamental aggregate structures in the gels at different length scales, but also to explore their potential for futuristic technological applications. Gels have been made sensitive to external stimuli like light and chemical entities by incorporating a spectroscopically active or a receptor unit as part of the gelator molecule. This makes them suitable for applications such as sensing and actuating. The diversity of gel structural architectures has allowed them to be utilized as templates to prepare novel inorganic superstructures for possible applications in catalysis and separation. Gels derived from liquid crystals (anisotropy gels) that can act as dynamically functional materials have been prepared, for example, for (re-writable) information recording. Supramolecular gels can be important in controlled release applications, in oil recovery, for gelling cryogenic fuels etc. They can also serve as media for a range of applications. This tutorial review highlights some of the instructive work done by various groups to develop smart and functional gels, and covers a wide spectrum of scientific interest ranging from medicine to materials science. PMID:16172672

  18. Electrically controlled polymeric gel actuators

    DOEpatents

    Adolf, Douglas B.; Shahinpoor, Mohsen; Segalman, Daniel J.; Witkowski, Walter R.

    1993-01-01

    Electrically controlled polymeric gel actuators or synthetic muscles capable of undergoing substantial expansion and contraction when subjected to changing pH environments, temperature, or solvent. The actuators employ compliant containers for the gels and their solvents. The gels employed may be cylindrical electromechanical gel fibers such as polyacrylamide fibers or a mixture of poly vinyl alcohol-polyacrylic acid arranged in a parallel aggregate and contained in an electrolytic solvent bath such as salt water. The invention includes smart, electrically activated devices exploiting this phenomenon. These devices are capable of being manipulated via active computer control as large displacement actuators for use in adaptive structure such as robots.

  19. Electrically controlled polymeric gel actuators

    DOEpatents

    Adolf, D.B.; Shahinpoor, M.; Segalman, D.J.; Witkowski, W.R.

    1993-10-05

    Electrically controlled polymeric gel actuators or synthetic muscles are described capable of undergoing substantial expansion and contraction when subjected to changing pH environments, temperature, or solvent. The actuators employ compliant containers for the gels and their solvents. The gels employed may be cylindrical electromechanical gel fibers such as polyacrylamide fibers or a mixture of poly vinyl alcohol-polyacrylic acid arranged in a parallel aggregate and contained in an electrolytic solvent bath such as salt water. The invention includes smart, electrically activated devices exploiting this phenomenon. These devices are capable of being manipulated via active computer control as large displacement actuators for use in adaptive structure such as robots. 11 figures.

  20. Gel polymer electrolytes for batteries

    DOEpatents

    Balsara, Nitash Pervez; Eitouni, Hany Basam; Gur, Ilan; Singh, Mohit; Hudson, William

    2014-11-18

    Nanostructured gel polymer electrolytes that have both high ionic conductivity and high mechanical strength are disclosed. The electrolytes have at least two domains--one domain contains an ionically-conductive gel polymer and the other domain contains a rigid polymer that provides structure for the electrolyte. The domains are formed by block copolymers. The first block provides a polymer matrix that may or may not be conductive on by itself, but that can soak up a liquid electrolyte, thereby making a gel. An exemplary nanostructured gel polymer electrolyte has an ionic conductivity of at least 1.times.10.sup.-4 S cm.sup.-1 at 25.degree. C.

  1. Ultracentrifuge for separating fluid mixtures

    DOEpatents

    Lowry, Ralph A.

    1976-01-01

    1. A centrifuge for the separation of fluid mixtures having light and heavy fractions comprising a cylindrical rotor, disc type end-plugs closing the ends of the rotor, means for mounting said rotor for rotation about its cylindrical axis, a housing member enclosing the rotor, a vacuum chamber in said housing about the central portion of the rotor, a collection chamber at each end of the housing, the innermost side of which is substantially formed by the outer face of the end-plug, means for preventing flow of the fluid from the collection chambers to said vacuum chamber, at least one of said end-plugs having a plurality of holes therethrough communicating between the collection chamber adjacent thereto and the inside of the rotor to induce countercurrent flow of the fluid in the centrifuge, means for feeding fluid to be processed into the centrifuge, means communicating with the collection chambers to extract the light and heavy separated fractions of the fluid, and means for rotating the rotor.

  2. Homogeneity of gels and gel-derived glasses

    NASA Technical Reports Server (NTRS)

    Mukherjee, S. P.

    1984-01-01

    The significance and implications of gel preparation procedures in controlling the homogeneity of multicomponent oxide gels are discussed. The role of physicochemical factors such as the structure and chemical reactivities of alkoxides, the formation of double-metal alkoxides, and the nature of solvent(s) are critically analyzed in the context of homogeneity of gels during gelation. Three procedures for preparing gels in the SiO2-B2O3-Na2O system are examined in the context of cation distribution. Light scattering results for glasses in the SiO2-B2O3-Na2O system prepared by both the gel technique and the conventional technique are examined.

  3. Crystallization of steroids in gels

    NASA Astrophysics Data System (ADS)

    Kalkura, S. Narayana; Devanarayanan, S.

    1991-03-01

    The crystal growth and characterization of certain steriods, viz., cholesterol, cholesteryl acetate, β-sitosterol, progesterone and testosterone, in a silica gel medium is discussed. The present study shows that the single test tube diffusion method can be used to grow crystals of steroids in a silica gel medium by the reduction of steroid solubility.

  4. Nanocrystal/sol-gel nanocomposites

    DOEpatents

    Petruska, Melissa A.; Klimov, Victor L.

    2012-06-12

    The present invention is directed to solid composites including colloidal nanocrystals within a sol-gel host or matrix and to processes of forming such solid composites. The present invention is further directed to alcohol soluble colloidal nanocrystals useful in formation of sol-gel based solid composites

  5. Nanocrystal/sol-gel nanocomposites

    DOEpatents

    Petruska, Melissa A.; Klimov, Victor L.

    2007-06-05

    The present invention is directed to solid composites including colloidal nanocrystals within a sol-gel host or matrix and to processes of forming such solid composites. The present invention is further directed to alcohol soluble colloidal nanocrystals useful in formation of sol-gel based solid composites.

  6. Sucrose release from polysaccharide gels.

    PubMed

    Nishinari, Katsuyoshi; Fang, Yapeng

    2016-05-18

    Sucrose release from polysaccharide gels has been studied extensively because it is expected to be useful in understanding flavour release from solid foods and to find a new processing method which produces more palatable and healthier foods. We provide an overview of the release of sucrose and other sugars from gels of agar and related polysaccharides. The addition of sucrose to agar solutions leads to the increase in transparency of the resulting gels and the decrease in syneresis, which is attributed to the decrease in mesh size in gels. The syneresis occurring in the quiescent condition and fluid release induced by compression is discussed. The relationship between the sugar release and the structural, rheological and thermal properties of gels is also discussed. Finally, the future research direction is proposed. PMID:26952168

  7. Living bacteria in silica gels

    NASA Astrophysics Data System (ADS)

    Nassif, Nadine; Bouvet, Odile; Noelle Rager, Marie; Roux, Ccile; Coradin, Thibaud; Livage, Jacques

    2002-09-01

    The encapsulation of enzymes within silica gels has been extensively studied during the past decade for the design of biosensors and bioreactors. Yeast spores and bacteria have also been recently immobilized within silica gels where they retain their enzymatic activity, but the problem of the long-term viability of whole cells in an inorganic matrix has never been fully addressed. It is a real challenge for the development of sol-gel processes. Generic tests have been performed to check the viability of Escherichia coli bacteria in silica gels. Surprisingly, more bacteria remain culturable in the gel than in an aqueous suspension. The metabolic activity of the bacteria towards glycolysis decreases slowly, but half of the bacteria are still viable after one month. When confined within a mineral environment, bacteria do not form colonies. The exchange of chemical signals between isolated bacteria rather than aggregates can then be studied, a point that could be very important for 'quorum sensing'.

  8. Methylthymol blue in Fricke gels

    NASA Astrophysics Data System (ADS)

    Penev, K. I.; Mequanint, K.

    2015-01-01

    The initial trial of methylthymol blue (MTB) as a chelator for ferric iron in Fricke gel dosimeters, used for three-dimensional (3D) dosimetry in cancer radiotherapy, is reported. MTB is a structural analogue of the conventionally used xylenol orange (XO); however, the absorbance spectrum of the ferric-MTB complex is shifted to higher wavelengths, which should allow for lower amount of light scattering during gel scanning. In this study, two gelatin substrates, two sources of XO and one source of MTB have been compared. The MTB- containing gels exhibited similar dose response and diffusion coefficient to the XO-containing gels at their wavelengths of maximum absorption (620 and 585 nm, respectively). In addition, the MTB gels gave an excellent dose response at 633 nm, which is an important wavelength that is already used with other 3D dosimeters.

  9. Bouncing gel balls: Impact of soft gels onto rigid surface

    NASA Astrophysics Data System (ADS)

    Tanaka, Y.; Yamazaki, Y.; Okumura, K.

    2003-07-01

    After being thrown onto a solid substrate, very soft spherical gels bounce repeatedly. Separate rheological measurements suggest that these balls can be treated as nearly elastic. The Hertz contact deformation expected in the static (elastic) limit was observed only at very small impact velocities. For larger velocities, the gel ball deformed into flattened forms like a pancake. We measured the size of the gel balls at the maximal deformation and the contact time as a function of velocities for samples different in the original spherical radius and the Young modulus. The experimental results revealed a number of scaling relations. To interpret these relations, we developed scaling arguments to propose a physical picture.

  10. Gel electrophoresis of linear and star-branched DNA

    NASA Astrophysics Data System (ADS)

    Lau, Henry W.; Archer, Lynden A.

    2011-12-01

    The electrophoretic mobility of double-stranded DNA in polyacrylamide gel is investigated using an activated hopping model for the transport of a charged object within a heterogeneous medium. The model is premised upon a representation of the DNA path through the gel matrix as a series of traps with alternating large and small cross sections. Calculations of the trap dimensions from gel data show that the path imposes varying degrees of confinement upon migrating analytes, which retard their forward motion in a size-dependent manner. An expression derived for DNA mobility is shown to provide accurate predictions for the dynamics of linear DNA (67-622 bp) in gels of multiple concentrations. For star-branched DNA, the incorporation within the model of a length scale previously proposed to account for analyte architecture [Yuan , Anal. Chem.ANCHAM0003-270010.1021/ac060414w 78, 6179 (2006)] leads to mobility predictions that compare well with experimental results for a wide range of DNA shapes and molecular weights.

  11. Mechanical Failure in Colloidal Gels

    NASA Astrophysics Data System (ADS)

    Kodger, Thomas Edward

    When colloidal particles in a dispersion are made attractive, they aggregate into fractal clusters which grow to form a space-spanning network, or gel, even at low volume fractions. These gels are crucial to the rheological behavior of many personal care, food products and dispersion-based paints. The mechanical stability of these products relies on the stability of the colloidal gel network which acts as a scaffold to provide these products with desired mechanical properties and to prevent gravitational sedimentation of the dispersed components. Understanding the mechanical stability of such colloidal gels is thus of crucial importance to predict and control the properties of many soft solids. Once a colloidal gel forms, the heterogeneous structure bonded through weak physical interactions, is immediately subject to body forces, such as gravity, surface forces, such as adhesion to a container walls and shear forces; the interplay of these forces acting on the gel determines its stability. Even in the absence of external stresses, colloidal gels undergo internal rearrangements within the network that may cause the network structure to evolve gradually, in processes known as aging or coarsening or fail catastrophically, in a mechanical instability known as syneresis. Studying gel stability in the laboratory requires model colloidal system which may be tuned to eliminate these body or endogenous forces systematically. Using existing chemistry, I developed several systems to study delayed yielding by eliminating gravitational stresses through density matching and cyclic heating to induce attraction; and to study syneresis by eliminating adhesion to the container walls, altering the contact forces between colloids, and again, inducing gelation through heating. These results elucidate the varied yet concomitant mechanisms by which colloidal gels may locally or globally yield, but then reform due to the nature of the physical, or non-covalent, interactions which form them.

  12. Symmetry breaking in actin gels - Implications for cellular motility

    NASA Astrophysics Data System (ADS)

    John, Karin; Peyla, Philippe; Misbah, Chaouqi

    2007-03-01

    The physical origin of cell motility is not fully understood. Recently minimal model systems have shown, that polymerizing actin itself can produce a motile force, without the help of motor proteins. Pathogens like Shigella or Listeria use actin to propel themselves forward in their host cell. The same process can be mimicked with polystyrene beads covered with the activating protein ActA, which reside in a solution containing actin monomers. ActA induces the growth of an actin gel at the bead surface. Initially the gel grows symmetrically around the bead until a critical size is reached. Subsequently one observes a symmetry breaking and the gel starts to grow asymmetrically around the bead developing a tail of actin at one side. This symmetry breaking is accompanied by a directed movement of the bead, with the actin tail trailing behind the bead. Force generation relies on the combination of two properties: growth and elasticity of the actin gel. We study this phenomenon theoretically within the framework of a linear elasticity theory and linear flux-force relationships for the evolution of an elastic gel around a hard sphere. Conditions for a parity symmetry breaking are identified analytically and illustrated numerically with the help of a phasefield model.

  13. Protein gel staining methods: an introduction and overview.

    PubMed

    Steinberg, Thomas H

    2009-01-01

    Laboratory scientists who encounter protein biochemistry in many of its myriad forms must often ask: is my protein pure? The most frequent response: run a denaturing SDS polyacrylamide gel. Running this gel raises another series of considerations regarding detection, quantitation, and characterization and so the next questions invariably center on suitable protein gel staining and detection methods. A total protein profile can be determined with the colorimetric methods embodied in Coomassie Blue and silver staining methods, or increasingly, with fluorescent stains. Protein quantitation can be done following staining, with fluorescence- and instrumentation-based methods offering the greatest sensitivity and linear dynamic range. Protein posttranslational modifications such as phosphorylation and glycosylation can be reliably determined with several fluorescence-based protocols. Staining and detection with two or more different stains can be done in series to establish relative profiles of modified versus total protein or to assess purity at two levels of quantitative sensitivity. The choice of staining method and protocol depends on the required rigor of detection and quantitation combined with available instrumentation and documentation capabilities. Other considerations for staining methods include intended downstream analytical procedures such as mass spectrometry or peptide sequencing, which preclude some methods. Nonfixative staining methods allow western blotting after gel staining. Laboratory custom and budget or intellectual curiosity may be the ultimate determinate of the chosen gel staining protocol. PMID:19892191

  14. Polyoxometalate-based Supramolecular Gel

    PubMed Central

    He, Peilei; Xu, Biao; Liu, Huiling; He, Su; Saleem, Faisal; Wang, Xun

    2013-01-01

    Self-assemblyings of surfactant-encapsulated Wells-Dawson polyoxometalates (SEPs) nanobuilding blocks in butanone and esters yielded supramolecular gels showing thermo and photo responsive properties. The gels can be further polymerized if unsaturated esters were used and subsequently electrospinned into nanowires and non-woven mats. The as-prepared non-woven mats have a Young's modulus as high as 542.55 MPa. It is believed that this supramolecular gel is a good platform for polyoxometalates processing. PMID:23666013

  15. Adhesive, elastomeric gel impregnating composition

    SciTech Connect

    Shaw, David Glenn; Pollard, John Randolph; Brooks, Robert Aubrey

    2002-01-01

    An improved capacitor roll with alternating film and foil layers is impregnated with an adhesive, elastomeric gel composition. The gel composition is a blend of a plasticizer, a polyol, a maleic anhydride that reacts with the polyol to form a polyester, and a catalyst for the reaction. The impregnant composition is introduced to the film and foil layers while still in a liquid form and then pressure is applied to aid with impregnation. The impregnant composition is cured to form the adhesive, elastomeric gel. Pressure is maintained during curing.

  16. Sol-gel encapsulation for controlled drug release and biosensing

    NASA Astrophysics Data System (ADS)

    Fang, Jonathan

    The main focus of this dissertation is to investigate the use of sol-gel encapsulation of biomolecules for controlled drug release and biosensing. Controlled drug release has advantages over conventional therapies in that it maintains a constant, therapeutic drug level in the body for prolonged periods of time. The anti-hypertensive drug Captopril was encapsulated in sol-gel materials of various forms, such as silica xerogels and nanoparticles. The primary objective was to show that sol-gel silica materials are promising drug carriers for controlled release by releasing Captopril at a release rate that is within a therapeutic range. We were able to demonstrate desired release for over a week from Captopril-doped silica xerogels and overall release from Captopril-doped silica nanoparticles. As an aside, the antibiotic Vancomycin was also encapsulated in these porous silica nanoparticles and desired release was obtained for several days in-vitro. The second part of the dissertation focuses on immobilizing antibodies and proteins in sol-gel to detect various analytes, such as hormones and amino acids. Sol-gel competitive immunoassays on antibody-doped silica xerogels were used for hormone detection. Calibration for insulin and C-peptide in standard solutions was obtained in the nM range. In addition, NASA-Ames is also interested in developing a reagentless biosensor using bacterial periplasmic binding proteins (bPBPs) to detect specific biomarkers, such as amino acids and phosphate. These bPBPs were doubly labeled with two different fluorophores and encapsulated in silica xerogels. Ligand-binding experiments were performed on the bPBPs in solution and in sol-gel. Ligand-binding was monitored by fluorescence resonance energy transfer (FRET) between the two fluorophores on the bPBP. Titration data show that one bPBP has retained its ligand-binding properties in sol-gel.

  17. Microchannel gel electrophoretic separation systems and methods for preparing and using

    SciTech Connect

    Herr, Amy E; Singh, Anup K; Throckmorton, Daniel J

    2015-02-24

    A micro-analytical platform for performing electrophoresis-based immunoassays was developed by integrating photopolymerized cross-linked polyacrylamide gels within a microfluidic device. The microfluidic immunoassays are performed by gel electrophoretic separation and quantifying analyte concentration based upon conventional polyacrylamide gel electrophoresis (PAGE). To retain biological activity of proteins and maintain intact immune complexes, native PAGE conditions were employed. Both direct (non-competitive) and competitive immunoassay formats are demonstrated in microchips for detecting toxins and biomarkers (cytokines, c-reactive protein) in bodily fluids (serum, saliva, oral fluids). Further, a description of gradient gels fabrication is included, in an effort to describe methods we have developed for further optimization of on-chip PAGE immunoassays. The described chip-based PAGE immunoassay method enables immunoassays that are fast (minutes) and require very small amounts of sample (less than a few microliters). Use of microfabricated chips as a platform enables integration, parallel assays, automation and development of portable devices.

  18. Microchannel gel electrophoretic separation systems and methods for preparing and using

    SciTech Connect

    Herr, Amy; Singh, Anup K; Throckmorton, Daniel J

    2013-09-03

    A micro-analytical platform for performing electrophoresis-based immunoassays was developed by integrating photopolymerized cross-linked polyacrylamide gels within a microfluidic device. The microfluidic immunoassays are performed by gel electrophoretic separation and quantifying analyte concentration based upon conventional polyacrylamide gel electrophoresis (PAGE). To retain biological activity of proteins and maintain intact immune complexes, native PAGE conditions were employed. Both direct (non-competitive) and competitive immunoassay formats are demonstrated in microchips for detecting toxins and biomarkers (cytokines, c-reactive protein) in bodily fluids (serum, saliva, oral fluids). Further, a description of gradient gels fabrication is included, in an effort to describe methods we have developed for further optimization of on-chip PAGE immunoassays. The described chip-based PAGE immunoassay method enables immunoassays that are fast (minutes) and require very small amounts of sample (less than a few microliters). Use of microfabricated chips as a platform enables integration, parallel assays, automation and development of portable devices.

  19. Analytics for Education

    ERIC Educational Resources Information Center

    MacNeill, Sheila; Campbell, Lorna M.; Hawksey, Martin

    2014-01-01

    This article presents an overview of the development and use of analytics in the context of education. Using Buckingham Shum's three levels of analytics, the authors present a critical analysis of current developments in the domain of learning analytics, and contrast the potential value of analytics research and development with real world…

  20. Let's Talk... Analytics

    ERIC Educational Resources Information Center

    Oblinger, Diana G.

    2012-01-01

    Talk about analytics seems to be everywhere. Everyone is talking about analytics. Yet even with all the talk, many in higher education have questions about--and objections to--using analytics in colleges and universities. In this article, the author explores the use of analytics in, and all around, higher education. (Contains 1 note.)

  1. Photoactive sol-gel biocoatings

    NASA Astrophysics Data System (ADS)

    Ulatowska-Jarża, A.; Bindig, U.; Podbielska, H.; Hołowacz, I.; Gersonde, I.; Beuthan, J.; Müller, G.; Eichler, H. J.

    2006-02-01

    In this work we investigated the photoactive properties sol-gel biocoatings doped with Protoporphyrin IX (PP IX). It was demonstrated that PP IX entrapped in sol-gel preserves it's chemical activity and may have contact with the external environment. The chemical reactions with zinc cations and pyridine, as well as protonation, occurred quite fast. This indicates, that the interconnected porous network could be easily penetrated by relatively large molecules (e.g. mentioned by pyridine molecule). Further, we observed that PP IX molecules do not leave the pores. Structural changes caused by the addition of PP IX to the sol-gel matrix influence not only on the optical properties, but also on durability of the coatings. The altering of PP IX doped silica sol-gel coatings is quite slow.

  2. Topical Review: Polymer gel dosimetry

    PubMed Central

    Baldock, C; De Deene, Y; Doran, S; Ibbott, G; Jirasek, A; Lepage, M; McAuley, K B; Oldham, M; Schreiner, L J

    2010-01-01

    Polymer gel dosimeters are fabricated from radiation sensitive chemicals which, upon irradiation, polymerize as a function of the absorbed radiation dose. These gel dosimeters, with the capacity to uniquely record the radiation dose distribution in three-dimensions (3D), have specific advantages when compared to one-dimensional dosimeters, such as ion chambers, and two-dimensional dosimeters, such as film. These advantages are particularly significant in dosimetry situations where steep dose gradients exist such as in intensity-modulated radiation therapy (IMRT) and stereotactic radiosurgery. Polymer gel dosimeters also have specific advantages for brachytherapy dosimetry. Potential dosimetry applications include those for low-energy x-rays, high-linear energy transfer (LET) and proton therapy, radionuclide and boron capture neutron therapy dosimetries. These 3D dosimeters are radiologically soft-tissue equivalent with properties that may be modified depending on the application. The 3D radiation dose distribution in polymer gel dosimeters may be imaged using magnetic resonance imaging (MRI), optical-computerized tomography (optical-CT), x-ray CT or ultrasound. The fundamental science underpinning polymer gel dosimetry is reviewed along with the various evaluation techniques. Clinical dosimetry applications of polymer gel dosimetry are also presented. PMID:20150687

  3. Fabrication and Characterization of Polysaccharide Ion Gels with Ionic Liquids and Their Further Conversion into Value-Added Sustainable Materials

    PubMed Central

    Takada, Akihiko; Kadokawa, Jun-ichi

    2015-01-01

    A review of the fabrication of polysaccharide ion gels with ionic liquids is presented. From various polysaccharides, the corresponding ion gels were fabricated through the dissolution with ionic liquids. As ionic liquids, in the most cases, 1-butyl-3-methylimidazolium chloride has been used, whereas 1-allyl-3methylimidazolium acetate was specifically used for chitin. The resulting ion gels have been characterized by suitable analytical measurements. Characterization of a pregel state by viscoelastic measurement provided the molecular weight information. Furthermore, the polysaccharide ion gels have been converted into value-added sustainable materials by appropriate procedures, such as exchange with other disperse media and regeneration. PMID:25793912

  4. Gel-based versus gel-free proteomics: a review.

    PubMed

    Baggerman, Geert; Vierstraete, Evy; De Loof, Arnold; Schoofs, Liliane

    2005-12-01

    With the sequencing of the genome of over 150 organisms, the field of biology has been revolutionised. Instead of studying one gene or protein at the time, it is now possible to study the effect of physiological or pathological changes on the expression of all genes or proteins in the organism. Proteomics aims at the simultaneous analysis of all proteins expressed by a cell, tissue or organism in a specific physiological condition. Because proteins are the effector molecules in all organisms, it is evident that changes in the physiological condition of an organism will be reflected by changes in protein expression and/or processing. Since the formulation of the concept of proteomics in the mid 90's proteomics has relied heavily on 2 dimensional gel electrophoresis (2DGE) for the separation and visualization of proteins. 2DGE, however, has a number of inherent drawbacks. 2DGE is costly, fairly insensitive to low copy proteins and cannot be used for the entire proteome. Therefore, over the years, several gel-free proteomics techniques have been developed to either fill the gaps left by 2DGE or to entirely abolish the gel based techniques. This review summarizes the most important gel-free and gel-based proteomics techniques and compares their advantages and drawbacks. PMID:16464155

  5. A new method for HDL particle sizing by polyacrylamide gradient gel electrophoresis using whole plasma.

    PubMed

    Pérusse, M; Pascot, A; Després, J P; Couillard, C; Lamarche, B

    2001-08-01

    Low plasma levels of HDL cholesterol have been associated with an increased risk of coronary heart disease. HDL particles are heterogeneous with respect to size and apolipoprotein content. The objective of the present study was to develop a method to generate lipid-stainable calibrators that would allow the assessment of HDL particle size from whole plasma, using polyacrylamide gradient gel electrophoresis (PAGGE). Lipid-stainable HDL calibrators were obtained by subjecting isolated red blood cells to hemolysis either by freezing at -20 or -80 degrees C overnight or by rapid exposure to liquid nitrogen and mixing of the hemolysis products with plasma aliquots. All three methods were highly reproducible in producing Sudan black lipid-stainable HDL calibrators ranging from 75 to 200 A. The assessment of HDL particle size with these lipid-stainable HDL calibrators was also highly reproducible, with a coefficient of variation below 5.5%. These lipid-stainable HDL calibrators simplify the assessment of HDL particle size by PAGGE using whole plasma, without the need for costly, time-consuming ultracentrifugation procedures. PMID:11483636

  6. Thixotropic gel for vadose zone remediation

    DOEpatents

    Riha, Brian D.

    2012-07-03

    A thixotropic gel suitable for use in subsurface bioremediation is provided along with a process of using the gel. The thixotropic gel provides a non-migrating injectable substrate that can provide below ground barrier properties. In addition, the gel components provide for a favorable environment in which certain contaminants are preferentially sequestered in the gel and subsequently remediated by either indigenous or introduced microorganisms.

  7. Thixotropic gel for vadose zone remediation

    DOEpatents

    Rhia, Brian D.

    2011-03-01

    A thixotropic gel suitable for use in subsurface bioremediation is provided along with a process of using the gel. The thixotropic gel provides a non-migrating injectable substrate that can provide below ground barrier properties. In addition, the gel components provide for a favorable environment in which certain contaminants are preferentially sequestered in the gel and subsequently remediated by either indigenous or introduced microorganisms.

  8. Thixotropic gel for vadose zone remediation

    SciTech Connect

    Riha, Brian D.; Looney, Brian B.

    2015-10-27

    A thixotropic gel suitable for use in subsurface bioremediation is provided along with a process of using the gel. The thixotropic gel provides a non-migrating injectable substrate that can provide below ground barrier properties. In addition, the gel components provide for a favorable environment in which certain contaminants are preferentially sequestered in the gel and subsequently remediated by either indigenous or introduced microorganisms.

  9. A model of ideal elastomeric gels for polyelectrolyte gels.

    PubMed

    Li, Jianyu; Suo, Zhigang; Vlassak, Joost J

    2014-04-21

    The concept of the ideal elastomeric gel is extended to polyelectrolyte gels and verified using a polyacrylamide-co-acrylic acid hydrogel as a model material system. A comparison between mixing and ion osmosis shows that the mixing osmosis is larger than the ion osmosis for small swelling ratios, while the ion osmosis dominates for large swelling ratios. We show further that the non-Gaussian chain effect becomes important in the elasticity of the polymer network at the very large swelling ratios that may occur under certain conditions of pH and salinity. We demonstrate that the Gent model captures the non-Gaussian chain effect well and that it provides a good description of the free energy associated with the stretching of the network. The model of ideal elastomeric gels fits the experimental data very well. PMID:24647731

  10. Multimedia Analysis plus Visual Analytics = Multimedia Analytics

    SciTech Connect

    Chinchor, Nancy; Thomas, James J.; Wong, Pak C.; Christel, Michael; Ribarsky, Martin W.

    2010-10-01

    Multimedia analysis has focused on images, video, and to some extent audio and has made progress in single channels excluding text. Visual analytics has focused on the user interaction with data during the analytic process plus the fundamental mathematics and has continued to treat text as did its precursor, information visualization. The general problem we address in this tutorial is the combining of multimedia analysis and visual analytics to deal with multimedia information gathered from different sources, with different goals or objectives, and containing all media types and combinations in common usage.

  11. Optical Sensors for Biomolecules Using Nanoporous Sol-Gel Materials

    NASA Technical Reports Server (NTRS)

    Fang, Jonathan; Zhou, Jing C.; Lan, Esther H.; Dunn, Bruce; Gillman, Patricia L.; Smith, Scott M.

    2004-01-01

    An important consideration for space missions to Mars is the ability to detect biosignatures. Solid-state sensing elements for optical detection of biological entities are possible using sol-gel based biologically active materials. We have used these materials as optical sensing elements in a variety of bioassays, including immunoassays and enzyme assays. By immobilizing an appropriate biomolecule in the sol-gel sensing element, we have successfully detected analytes such as amino acids and hormones. In the case of the amino acid glutamate, the enzyme glutamate dehydrogenase was the immobilized molecule, whereas in the case of the hormone cortisol, an anti-cortisol antibody was immobilized in the sensing element. In this previous work with immobilized enzymes and antibodies, excellent sensitivity and specificity were demonstrated in a variety of formats including bulk materials, thin films and fibers. We believe that the sol-gel approach is an attractive platform for bioastronautics sensing applications because of the ability to detect a wide range of entities such as amino acids, fatty acids, hopanes, porphyrins, etc. The sol-gel approach produces an optically transparent 3D silica matrix that forms around the biomolecule of interest, thus stabilizing its structure and functionality while allowing for optical detection. This encapsulation process protects the biomolecule and leads to a more "rugged" sensor. The nanoporous structure of the sol-gel matrix allows diffusion of small target molecules but keeps larger, biomolecules immobilized in the pores. We are currently developing these biologically active sol-gel materials into small portable devices for on-orbit cortisol detection

  12. Analytical Challenges in Biotechnology.

    ERIC Educational Resources Information Center

    Glajch, Joseph L.

    1986-01-01

    Highlights five major analytical areas (electrophoresis, immunoassay, chromatographic separations, protein and DNA sequencing, and molecular structures determination) and discusses how analytical chemistry could further improve these techniques and thereby have a major impact on biotechnology. (JN)

  13. Copolymers For Capillary Gel Electrophoresis

    DOEpatents

    Liu, Changsheng; Li, Qingbo

    2005-08-09

    This invention relates to an electrophoresis separation medium having a gel matrix of at least one random, linear copolymer comprising a primary comonomer and at least one secondary comonomer, wherein the comonomers are randomly distributed along the copolymer chain. The primary comonomer is an acrylamide or an acrylamide derivative that provides the primary physical, chemical, and sieving properties of the gel matrix. The at least one secondary comonomer imparts an inherent physical, chemical, or sieving property to the copolymer chain. The primary and secondary comonomers are present in a ratio sufficient to induce desired properties that optimize electrophoresis performance. The invention also relates to a method of separating a mixture of biological molecules using this gel matrix, a method of preparing the novel electrophoresis separation medium, and a capillary tube filled with the electrophoresis separation medium.

  14. Sol-gel derived sorbents

    DOEpatents

    Sigman, Michael E.; Dindal, Amy B.

    2003-11-11

    Described is a method for producing copolymerized sol-gel derived sorbent particles for the production of copolymerized sol-gel derived sorbent material. The method for producing copolymerized sol-gel derived sorbent particles comprises adding a basic solution to an aqueous metal alkoxide mixture for a pH.ltoreq.8 to hydrolyze the metal alkoxides. Then, allowing the mixture to react at room temperature for a precalculated period of time for the mixture to undergo an increased in viscosity to obtain a desired pore size and surface area. The copolymerized mixture is then added to an immiscible, nonpolar solvent that has been heated to a sufficient temperature wherein the copolymerized mixture forms a solid upon the addition. The solid is recovered from the mixture, and is ready for use in an active sampling trap or activated for use in a passive sampling trap.

  15. Supramolecular Construction of Multifluorescent Gels: Interfacial Assembly of Discrete Fluorescent Gels through Multiple Hydrogen Bonding.

    PubMed

    Ji, Xiaofan; Shi, Bingbing; Wang, Hu; Xia, Danyu; Jie, Kecheng; Wu, Zi Liang; Huang, Feihe

    2015-12-01

    Multifluorescent supramolecular gels with complex structures are constructed from discrete fluorescent gels, which serve as the building blocks, through hydrogen bonding interactions at interfaces. The multifluorescent gel can realize rapid healing within only ?100 s. PMID:26540139

  16. Microbubble tunneling in gel phantoms

    PubMed Central

    Caskey, Charles F.; Qin, Shengping; Dayton, Paul A.; Ferrara, Katherine W.

    2009-01-01

    Insonified microbubbles were observed in vessels within a gel with a Young’s modulus similar to that of tissue, demonstrating shape instabilities, liquid jets, and the formation of small tunnels. In this study, tunnel formulation occurred in the direction of the propagating ultrasound wave, where radiation pressure directed the contact of the bubble and gel, facilitating the activity of the liquid jets. Combinations of ultrasonic parameters and microbubble concentrations that are relevant for diagnostic imaging and drug delivery and that lead to tunnel formation were applied and the resulting tunnel formation was quantified. PMID:19425620

  17. Screening effect on nanostructure of charged gel

    NASA Astrophysics Data System (ADS)

    Sugiyama, Masaaki; Annaka, Masahiko; Hino, Masahiro; Fukunaga, Toshiharu; E. Vigild, Martin; Hara, Kazuhiro

    2004-07-01

    Charge screening effects on nanostructures of N-isopropylacrylamide-sodium acrylate (NIPA-SA) and -acrylic acid (NIPA-AAc) gels are investigated with small-angle neutron scattering. The NIPA-SA and NIPA-AAc gels with low water content exhibit microphase separations with different dimensions. The dehydrated NIPA-SA gel also makes the microphase separation but the dehydrated NIPA-AAc gel does not. These results indicate that ionic circumstance around charged bases strongly affects the nanostructures both of the dehydrated gel and the gel with low water content.

  18. Swelling of cross-linked polyelectrolyte gels

    NASA Astrophysics Data System (ADS)

    Schneider, S.; Linse, P.

    2002-08-01

    A model of a cross-linked polyelectrolyte gel has been examined using Monte Carlo simulations. The simple model contained a charged defect-free network represented by linked charged beads and explicit counterions. Pressure-density relations for the polyelectrolyte gel, a corresponding non-ionic polymer gel, and several partly or fully degraded gels have been determined. The polyelectrolyte gel displayed a very large swelling capacity, in agreement with experiments. The swelling mechanism and chain properties are discussed and foundations of current theories on gel swelling are examined.

  19. Viscoelastic Properties of Particle Gels.

    PubMed

    Yanez; Laarz; Bergström

    1999-01-01

    The effect of strength of attraction and volume fraction on the mechanical properties of alumina particle networks were investigated. Alumina particle gels were formed reversibly and in situ in the rheometer by cooling alumina particle suspensions with adsorbed poly(12-hydroxy stearic acid) suspended in a marginal solvent, hexanol. The collapse of the polymer layer with decreasing solvency (temperature) induces flocculation when the long-range van der Waals force overcomes the remaining steric repulsion. The gelation temperature depends on volume fraction. At the gel temperature, Tgel, the gel becomes predominantly elastic; at temperatures below Tgel, the elasticity increases with decreasing temperature. We find that the elastic modulus data, measured over a wide range of volume fraction (0.2 < φ < 0.425) and temperature (10-14 degreesC), follows: G = G0(φ - φg)s. This scaling suggests the prefactor and exponent to be independent of temperature. We present some arguments for why subjecting a particle gel to a preshear procedure might result in an temperature-dependent prefactor. By invoking such an effect, we are able to rescale and collapse previously published moduli data on presheared suspensions according to the (φ - φg) expression. Copyright 1999 Academic Press. PMID:9878149

  20. Nonlinear elasticity of alginate gels

    NASA Astrophysics Data System (ADS)

    Hashemnejad, Seyed Meysam; Kundu, Santanu

    Alginate is a naturally occurring anionic polysaccharide extracted from brown algae. Because of biocompatibility, low toxicity, and simple gelation process, alginate gels are used in biomedical and food applications. Here, we report the rheological behavior of ionically crosslinked alginate gels, which are obtained by in situ gelation of alginates with calcium salts, in between two parallel plates of a rheometer. Strain stiffening behavior was captured using large amplitude oscillatory shear (LAOS) experiments. In addition, negative normal stress was observed for these gels, which has not been reported earlier for any polysaccharide networks. The magnitude of negative normal stress increases with applied strain and can exceed that of the shear stress at large strain. Rheological results fitted with a constitutive model that considers both stretching and bending of chains indicate that nonlinearity is likely related to the stretching of the chains between the crosslink junctions. The results provide an improved understanding of the deformation mechanism of ionically crosslinked alginate gel and the results will be important in developing synthetic extracellular matrix (ECM) from these materials.

  1. Capillary fracture of soft gels.

    PubMed

    Bostwick, Joshua B; Daniels, Karen E

    2013-10-01

    A liquid droplet resting on a soft gel substrate can deform that substrate to the point of material failure, whereby fractures develop on the gel surface that propagate outwards from the contact line in a starburst pattern. In this paper, we characterize (i) the initiation process, in which the number of arms in the starburst is controlled by the ratio of the surface tension contrast to the gel's elastic modulus, and (ii) the propagation dynamics showing that once fractures are initiated they propagate with a universal power law L[proportional]t(3/4). We develop a model for crack initiation by treating the gel as a linear elastic solid and computing the deformations within the substrate from the liquid-solid wetting forces. The elastic solution shows that both the location and the magnitude of the wetting forces are critical in providing a quantitative prediction for the number of fractures and, hence, an interpretation of the initiation of capillary fractures. This solution also reveals that the depth of the gel is an important factor in the fracture process, as it can help mitigate large surface tractions; this finding is confirmed with experiments. We then develop a model for crack propagation by considering the transport of an inviscid fluid into the fracture tip of an incompressible material and find that a simple energy-conservation argument can explain the observed material-independent power law. We compare predictions for both linear elastic and neo-Hookean solids, finding that the latter better explains the observed exponent. PMID:24229192

  2. Calculating Percent Gel For Process Control

    NASA Technical Reports Server (NTRS)

    Webster, Charles Neal; Scott, Robert O.

    1988-01-01

    Reaction state of thermosetting resin tracked to assure desired properties. Rate of gel determined as function of temperature by measuring time to gel of part of graphite fabric impregnated with Hexcel R120 (or equivalent) phenolic resin.

  3. Polyelectrolyte gel dynamics during volume phase transitions

    NASA Astrophysics Data System (ADS)

    Mitra, Mithun; Hua, Jing; Muthukumar, Murugappan

    2011-03-01

    We will address the dynamics of the elastic modes of a polyelectrolyte gel near the first-order volume phase transition. The role of the neutralizing plasma on the modulus of the polyelectrolyte gel will be discussed.

  4. Science Update: Analytical Chemistry.

    ERIC Educational Resources Information Center

    Worthy, Ward

    1980-01-01

    Briefly discusses new instrumentation in the field of analytical chemistry. Advances in liquid chromatography, photoacoustic spectroscopy, the use of lasers, and mass spectrometry are also discussed. (CS)

  5. Electric-field-induced response of a droplet embedded in a polyelectrolyte gel

    NASA Astrophysics Data System (ADS)

    Mohammadi, Aliasghar

    2013-08-01

    The electric-field induced response of a droplet embedded in a quenched polyelectrolyte gel is calculated theoretically. The response comprises the droplet translation and the electric-field induced flow fields within the droplet. The gel is modeled as a soft, and electrically charged porous solid saturated with a salted Newtonian fluid. The droplet is considered an incompressible Newtonian fluid with no free charge. An analytical solution, using the perturbation methodology and linear superposition, is obtained for the leading-order steady response to a DC electric-field. The fluid within the droplet is driven due to hydrodynamic coupling with the electroosmotic flow. The fluid velocity within the droplet is linearly proportional to the electroosmotic flow. Moreover, the microrheological response function of a droplet within a polyelectrolyte gel is also provided, highlighting the importance of boundary conditions at the droplet-gel interface on microrheological measurements.

  6. Characteristics of platelet gels combined with silk

    PubMed Central

    Pallotta, Isabella; Kluge, Jonathan A.; Moreau, Jodie; Calabrese, Rossella

    2014-01-01

    Platelet gel, a fibrin network containing activated platelets, is widely used in regenerative medicine due the capacity of platelet-derived growth factors to accelerate and direct healing processes. However, limitations to this approach include poor mechanical properties, relatively rapid degradation, and the lack of control of release of growth factors at the site of injection. These issues compromise the ability of platelet gels for sustained function in regenerative medicine. In the present study, a combination of platelet gels with silk fibroin gel was studied to address the above limitations. Mixing sonicated silk gels with platelet gels extended the release of growth factors without inhibiting gel forming ability. The released growth factors were biologically active and their delivery was modified further by manipulation of the charge of the silk protein. Moreover, the silk gel augmented both the rheological properties and compressive stiffness of the platelet gel, tuned by the silk concentration and/or silk/platelet gel ratio. Silk-platelet gel injections in nude rats supported enhanced cell infiltration and blood vessel formation representing a step towards new platelet gel formulations with enhanced therapeutic impact. PMID:24480538

  7. A clarified gel for crystal growth

    NASA Technical Reports Server (NTRS)

    Barber, P. G.; Simpson, N. R.

    1985-01-01

    A procedure for preparing clarified sodium silicate gels suitable for crystal growth is described. In the method described here, the silicate stock is clarified by pretreating it with cation exchange resins before preparing the gels. Also, a modified recipe is proposed for preparing gels to achieve improved transparency.

  8. Spring-loaded polymeric gel actuators

    DOEpatents

    Shahinpoor, Mohsen

    1995-01-01

    Spring-loaded electrically controllable polymeric gel actuators are disclosed. The polymeric gels can be polyvinyl alcohol, polyacrylic acid, or polyacrylamide, and are contained in an electrolytic solvent bath such as water plus acetone. The action of the gel is mechanically biased, allowing the expansive and contractile forces to be optimized for specific applications.

  9. Spring-loaded polymeric gel actuators

    DOEpatents

    Shahinpoor, M.

    1995-02-14

    Spring-loaded electrically controllable polymeric gel actuators are disclosed. The polymeric gels can be polyvinyl alcohol, polyacrylic acid, or polyacrylamide, and are contained in an electrolytic solvent bath such as water plus acetone. The action of the gel is mechanically biased, allowing the expansive and contractile forces to be optimized for specific applications. 5 figs.

  10. Two-dimensional Gel Electrophoresis (2DE)

    NASA Astrophysics Data System (ADS)

    Kłodzińska, Ewa; Buszewski, Bogusław

    The chemical compounds, which are present in the environment, increasingly cause bad effects on health. The most serious effects are tumors and various mutations at the cellular level. Such compounds, from the analytical point of view, can serve the function of biomarkers, constituting measurable changes in the organism's cells and biochemical processes occurring therein. The challenge of the twenty-first century is therefore searching for effective and reliable methods of identification of biomarkers as well as understanding bodily functions, which occur in living organisms at the molecular level. The irreplaceable tool for these examinations is proteomics, which includes both quality and quantity analysis of proteins composition, and also makes it possible to learn their functions and expressions. The success of proteomics examinations lies in the usage of innovative analytical techniques, such as electromigration technique, two-dimensional electrophoresis in polyacrylamide gel (2D PAGE), liquid chromatography, together with high resolution mass spectrometry and bio-informatical data analysis. Proteomics joins together a number of techniques used for analysis of hundreds or thousands of proteins. Its main task is not the examination of proteins inside the particular tissue but searching for the differences in the proteins' profile between bad and healthy tissues. These differences can tell us a lot regarding the cause of the sickness as well as its consequences. For instance, using the proteomics analysis it is possible to find relatively fast new biomarkers of tumor diseases, which in the future will be used for both screening and foreseeing the course of illness. In this chapter we focus on two-dimensional electrophoresis because as it seems, it may be of enormous importance when searching for biomarkers of cancer diseases.

  11. Protein/Arabinoxylans Gels: Effect of Mass Ratio on the Rheological, Microstructural and Diffusional Characteristics

    PubMed Central

    Berlanga-Reyes, Claudia M.; Carvajal-Millan, Elizabeth; Hicks, Kevin B.; Yadav, Madhav P.; Rascón-Chu, Agustín; Lizardi-Mendoza, Jaime; Toledo-Guillén, Alma R.; Islas-Rubio, Alma R.

    2014-01-01

    Wheat bran arabinoxylan (WBAX) gels entrapping standard model proteins at different mass ratios were formed. The entrapment of protein affected the gel elasticity and viscosity values, which decreased from 177 to 138 Pa. The presence of protein did not modify the covalent cross-links content of the gel. The distribution of protein through the network was investigated by confocal laser scanning microscopy. In mixed gels, protein aggregates forming clusters were detected at protein/polysaccharide ratios higher than 0.25. These clusters were not homogeneously distributed, suggesting that WBAX and protein are located in two different phases. The apparent diffusion coefficient (Dm) of proteins during release from mixed gels was investigated for mass ratios of 0.06 and 0.12. For insulin, Dm increased significantly from 2.64 × 10−7 to 3.20 × 10−7 cm2/s as the mass ratio augmented from 0.06 to 0.12. No significant difference was found for Dm values of ovalbumin and bovine serum albumin released from the mixed gels. The results indicate that homogeneous protein/WBAX gels can be formed at low mass ratios, allowing the estimation of Dm by using an analytical solution of the second Fick’s law. PMID:25338049

  12. The Swelling of Olympic Gels

    NASA Astrophysics Data System (ADS)

    Lang, Michael; Fischer, Jakob; Werner, Marco; Sommer, Jens-Uwe

    2014-03-01

    The swelling equilibrium of Olympic gels is studied by Monte Carlo Simulations. We observe that gels consisting of flexible cyclic molecules of a higher degree of polymerization N show a smaller equilibrium swelling degree Q ~N - 0 . 28φ0- 0 . 72 for the same monomer volume fraction φ0 at network preparation. This observation is explained by a disinterpenetration process of overlapping non-concatenated polymers upon swelling. In the limit of a sufficiently large number of concatenations per cyclic molecule we expect that the equilibrium degree of swelling becomes proportional to φ0- 1 / 2 independent of N. Our results challenge current textbook models for the equilibrium degree of swelling of entangled polymer networks. Now at: Bio Systems Analysis Group, Jena Centre for Bioinformatics (JCB) and Department for Mathematics and Computer Sciences, Friedrich Schiller University of Jena, 07743 Jena, Germany.

  13. Nanocrystal/sol-gel nanocomposites

    DOEpatents

    Klimov, Victor L.; Petruska, Melissa A.

    2010-05-25

    The present invention is directed to a process for preparing a solid composite having colloidal nanocrystals dispersed within a sol-gel matrix, the process including admixing colloidal nanocrystals with an amphiphilic polymer including hydrophilic groups selected from the group consisting of --COOH, --OH, --SO.sub.3H, --NH.sub.2, and --PO.sub.3H.sub.2 within a solvent to form an alcohol-soluble colloidal nanocrystal-polymer complex, admixing the alcohol-soluble colloidal nanocrystal-polymer complex and a sol-gel precursor material, and, forming the solid composite from the admixture. The present invention is also directed to the resultant solid composites and to the alcohol-soluble colloidal nanocrystal-polymer complexes.

  14. Multiscale modeling of polyelectrolyte gels

    NASA Astrophysics Data System (ADS)

    Wallmersperger, Thomas; Wittel, Falk K.; Kröplin, Bernd H.

    2006-03-01

    Electrolyte polymer gels are a very attractive class of actuation materials with remarkable electronic and mechanical properties having a great similarity to biological contractile tissues. They consist of a polymer network with ionizable groups and a liquid phase with mobile ions. Absorption and delivery of solvent lead to a considerably large change of volume. Due to this capability, they can be used as actuators for technical applications, where large swelling and shrinkage is desired. In the present work chemically and electrically stimulated polymer gels in a solution bath are investigated. To describe the different complicated phenomena occurring in these gels adequately, the modeling can be conducted on different scales. Therefore, models based on the statistical theory and porous media theory, as well as a multi-field model and a discrete element formulation are derived. A refinement of the different theories from global macroscopic to microscopic are presented in this paper: The statistical theory is a macroscopic theory capable to describe the global swelling or bending e.g. of a gel film, while the general theory of porous media (TPM) is a macroscopic continuum theory which is based on the theory of mixtures extended by the concept of volume fractions. The TPM is a homogenized model, i.e. all geometrical and physical quantities can be seen as statistical averages of the real quantities. The presented chemo-electro-mechanical multi-field formulation is a mesoscopic theory. It is capable of giving the concentrations and the electric potential in the whole domain. Finally the (micromechanical) discrete element (DE) theory is employed. In this case, the continuum is represented by distributed particles with local interaction relations combined with balance equations for the chemical field. This method is predestined for problems involving large displacements, strains and discontinuities. The presented formulations are compared and conclusions on their applicability in engineering practice are finally drawn.

  15. Signals: Applying Academic Analytics

    ERIC Educational Resources Information Center

    Arnold, Kimberly E.

    2010-01-01

    Academic analytics helps address the public's desire for institutional accountability with regard to student success, given the widespread concern over the cost of higher education and the difficult economic and budgetary conditions prevailing worldwide. Purdue University's Signals project applies the principles of analytics widely used in…

  16. Learning Analytics Considered Harmful

    ERIC Educational Resources Information Center

    Dringus, Laurie P.

    2012-01-01

    This essay is written to present a prospective stance on how learning analytics, as a core evaluative approach, must help instructors uncover the important trends and evidence of quality learner data in the online course. A critique is presented of strategic and tactical issues of learning analytics. The approach to the critique is taken through…

  17. Validating Analytical Methods

    ERIC Educational Resources Information Center

    Ember, Lois R.

    1977-01-01

    The procedures utilized by the Association of Official Analytical Chemists (AOAC) to develop, evaluate, and validate analytical methods for the analysis of chemical pollutants are detailed. Methods validated by AOAC are used by the EPA and FDA in their enforcement programs and are granted preferential treatment by the courts. (BT)

  18. Extreme Scale Visual Analytics

    SciTech Connect

    Wong, Pak C.; Shen, Han-Wei; Pascucci, Valerio

    2012-05-08

    Extreme-scale visual analytics (VA) is about applying VA to extreme-scale data. The articles in this special issue examine advances related to extreme-scale VA problems, their analytical and computational challenges, and their real-world applications.

  19. Analytical mass spectrometry. Abstracts

    SciTech Connect

    Not Available

    1990-12-31

    This 43rd Annual Summer Symposium on Analytical Chemistry was held July 24--27, 1990 at Oak Ridge, TN and contained sessions on the following topics: Fundamentals of Analytical Mass Spectrometry (MS), MS in the National Laboratories, Lasers and Fourier Transform Methods, Future of MS, New Ionization and LC/MS Methods, and an extra session. (WET)

  20. Analytical mass spectrometry

    SciTech Connect

    Not Available

    1990-01-01

    This 43rd Annual Summer Symposium on Analytical Chemistry was held July 24--27, 1990 at Oak Ridge, TN and contained sessions on the following topics: Fundamentals of Analytical Mass Spectrometry (MS), MS in the National Laboratories, Lasers and Fourier Transform Methods, Future of MS, New Ionization and LC/MS Methods, and an extra session. (WET)

  1. Gels from rigid rod polymer isocyanate systems

    SciTech Connect

    Lucht, L.M.; Shell, P.K.; Cook, R.C.; Cook, A.R. ); Green, M.M.; Gross, R.A.; Reidy, M. . Dept. of Chemistry)

    1986-05-01

    The rigid rod character of polyisocyanates and polyisonitriles is due primarily to steric forces. This permits alternation of the functionality of the pendant groups and allows the polymer to be engineered to specific applications, such as organic conductors or optically active films. Since under the proper conditions these polymers form gels, they may also be useful as controlled release gels or low density foams. So far, we have shown that crosslinked gels and foams can be made. Details of synthesis and characterization of both crosslinked and uncrosslinked isocyanate gels with a hexyl pendant group and gels with a dodecyl pendant group will be discussed. 14 refs., 1 fig.

  2. Quo vadis, analytical chemistry?

    PubMed

    Valcárcel, Miguel

    2016-01-01

    This paper presents an open, personal, fresh approach to the future of Analytical Chemistry in the context of the deep changes Science and Technology are anticipated to experience. Its main aim is to challenge young analytical chemists because the future of our scientific discipline is in their hands. A description of not completely accurate overall conceptions of our discipline, both past and present, to be avoided is followed by a flexible, integral definition of Analytical Chemistry and its cornerstones (viz., aims and objectives, quality trade-offs, the third basic analytical reference, the information hierarchy, social responsibility, independent research, transfer of knowledge and technology, interfaces to other scientific-technical disciplines, and well-oriented education). Obsolete paradigms, and more accurate general and specific that can be expected to provide the framework for our discipline in the coming years are described. Finally, the three possible responses of analytical chemists to the proposed changes in our discipline are discussed. PMID:26631024

  3. Evaluation of an ambient air sampling system for tritium (as tritiated water vapor) using silica gel adsorbent columns

    SciTech Connect

    Patton, G.W.; Cooper, A.T.; Tinker, M.R.

    1995-08-01

    Ambient air samples for tritium analysis (as the tritiated water vapor [HTO] content of atmospheric moisture) are collected for the Hanford Site Surface Environmental Surveillance Project (SESP) using the solid adsorbent silica gel. The silica gel has a moisture sensitive indicator which allows for visual observation of moisture movement through a column. Despite using an established method, some silica gel columns showed a complete change in the color indicator for summertime samples suggesting that breakthrough had occurred; thus a series of tests was conducted on the sampling system in an environmental chamber. The purpose of this study was to determine the maximum practical sampling volume and overall collection efficiency for water vapor collected on silica gel columns. Another purpose was to demonstrate the use of an impinger-based system to load water vapor onto silica gel columns to provide realistic analytical spikes and blanks for the Hanford Site SESP. Breakthrough volumes (V{sub b}) were measured and the chromatographic efficiency (expressed as the number of theoretical plates [N]) was calculated for a range of environmental conditions. Tests involved visual observations of the change in the silica gel`s color indicator as a moist air stream was drawn through the column, measurement of the amount of a tritium tracer retained and then recovered from the silica gel, and gravimetric analysis for silica gel columns exposed in the environmental chamber.

  4. Large deformation and electrochemistry of polyelectrolyte gels

    NASA Astrophysics Data System (ADS)

    Hong, Wei; Zhao, Xuanhe; Suo, Zhigang

    2010-04-01

    Immersed in an ionic solution, a network of polyelectrolytes imbibes the solution and swells, resulting in a polyelectrolyte gel. The swelling is reversible, and the amount of swelling is regulated by ionic concentrations, mechanical forces, and electric potentials. This paper develops a field theory to couple large deformation and electrochemistry. A specific material model is described, including the effects of stretching the network, mixing the polymers with the solvent and ions, and polarizing the gel. We show that the notion of osmotic pressure in a gel has no experimental significance in general, but acquires a physical interpretation within the specific material model. The theory is used to analyze several phenomena: a gel swells freely in an ionic solution, a gel swells under a constraint of a substrate, electric double layer at the interface between the gel and the external solution, and swelling of a gel of a small size.

  5. Fixed charges in the gel matrix of sensor chips and dissociation in diffusion gradients influence the detection of fast protein-protein interactions.

    PubMed

    Glaser, Ralf W; Schönherr, Roland; Heinemann, Stefan H

    2014-02-01

    In molecular interaction studies based on surface plasmon resonance (SPR) measurements, the ligand is often immobilized in a thin carboxydextran gel matrix. Here we investigated the influence of the charged gel on the results of such SPR measurements. At physiological ionic strength, analytes with a net charge of more than about 5 are considerably enriched or depleted due to the Donnan potential under commonly applied experimental conditions. Below physiological ionic strength, enrichment was found to be even stronger than predicted by Donnan theory. The influence of the gel matrix on the apparent binding is prevented in competition experiments, in which SPR measurements are only used to discriminate between free and complexed analyte while the interaction between analyte and ligand is studied in solution. However, if the analyte-ligand interaction is very fast, thermodynamic equilibrium is disturbed near the interface where free analyte binds to the immobilized ligand due to mass transport limitation. Consequently, the soluble analyte-ligand complex dissociates, which results in an overestimation of free analyte. In experiments of calmodulin binding to fragments of the KCNH1 ion channel protein this mass-transport-induced dissociation led to a systematic underestimation of the affinity. We conclude that the insufficient discrimination between the true analyte-ligand binding and the complex interactions of the analyte with the gel phase may result in systematic errors. The theoretical framework for recognizing and avoiding such errors is provided. PMID:24342363

  6. Smart Polymeric Gels: Redefining the Limits of Biomedical Devices

    PubMed Central

    Chaterji, Somali; Kwon, Il Keun; Park, Kinam

    2007-01-01

    This review describes recent progresses in the development and applications of smart polymeric gels, especially in the context of biomedical devices. The review has been organized into three separate sections: defining the basis of smart properties in polymeric gels; describing representative stimuli to which these gels respond; and illustrating a sample application area, namely, microfluidics. One of the major limitations in the use of hydrogels in stimuli–responsive applications is the diffusion rate limited transduction of signals. This can be obviated by engineering interconnected pores in the polymer structure to form capillary networks in the matrix and by downscaling the size of hydrogels to significantly decrease diffusion paths. Reducing the lag time in the induction of smart responses can be highly useful in biomedical devices, such as sensors and actuators. This review also describes molecular imprinting techniques to fabricate hydrogels for specific molecular recognition of target analytes. Additionally, it describes the significant advances in bottom–up nanofabrication strategies, involving supramolecular chemistry. Learning to assemble supramolecular structures from nature has led to the rapid prototyping of functional supramolecular devices. In essence, the barriers in the current performance potential of biomedical devices can be lowered or removed by the rapid convergence of interdisciplinary technologies. PMID:18670584

  7. Metal-silica sol-gel materials

    NASA Technical Reports Server (NTRS)

    Stiegman, Albert E. (Inventor)

    2002-01-01

    The present invention relates to a single phase metal-silica sol-gel glass formed by the co-condensation of a transition metal with silicon atoms where the metal atoms are uniformly distributed within the sol-gel glass as individual metal centers. Any transition metal may be used in the sol-gel glasses. The present invention also relates to sensor materials where the sensor material is formed using the single phase metal-silica sol-gel glasses. The sensor materials may be in the form of a thin film or may be attached to an optical fiber. The present invention also relates to a method of sensing chemicals using the chemical sensors by monitoring the chromatic change of the metal-silica sol-gel glass when the chemical binds to the sensor. The present invention also relates to oxidation catalysts where a metal-silica sol-gel glass catalyzes the reaction. The present invention also relates to a method of performing oxidation reactions using the metal-silica sol-gel glasses. The present invention also relates to organopolymer metal-silica sol-gel composites where the pores of the metal-silica sol-gel glasses are filled with an organic polymer polymerized by the sol-gel glass.

  8. Synthesis of oligomeric models of coal-derived materials for use with GPC calibration. Quarterly report, June-August 1982. [Gel permeation chromatography

    SciTech Connect

    Baltisberger, R J; Jones, M B

    1982-09-01

    One important facet of the characterization of coal-derived materials is that of molecular weight determination. Number average molecular weight is usually obtained by vapor pressure osmometry measurements. However, no satisfactory method is available for determining weight average molecular weights. The latter values are useful in predicting rheological properties. Gel permeation chromatography (GPC) is a technique which should be most readily adaptable for this measurement. The other techniques of ultracentrifugation and light scattering are not as readily available as GPC. At this time, satisfactory GPC calibration standards which possess chemical structures similar to coal derived mterials are non-existent. The purpose of this study is to develop a useful set of GPC calibration standards for asphaltene and preaspaltene analyses. Our previous results suggest models in which coal derived preasphaltenes and asphaltenes are composed of oligomeric aromatic ethers of both diaryl and furan types. We plan to synthesize a series of model oligomers that are in agreement with the average structural formulas of some selected coal preasphaltenes as determined by pmr, elemental analyses and various oxygen derivatization procedures. These model compounds will be tested for use as calibration standards for both high pressure gel permeation chromatographic and vapor pressure osmometric procedures. Their response and retention times will be compared with coal preasphaltenes to determine the suitability of the model compounds as calibration standards.

  9. Tailoring the properties of supramolecular gels

    NASA Astrophysics Data System (ADS)

    Buerkle, Lauren

    Supramolecular gels created from low molecular weight species (gelators) have gathered wide attention over the past few decades on account of their highly ordered assembly and ability to respond to external stimuli. These properties make such gels highly promising candidates for a diverse range of applications including biomaterials, viscosity modifiers, sensors, and liquid crystalline materials. We have focused on the design and tailoring of guanosine (the ribonucleoside of the nucleobase guanine) hydrogels. It is well known that in an aqueous environment, guanosine forms circular hydrogen-bonded quartets around a monovalent metal ion, most commonly potassium. These quartets then stack to form high-aspect ratio fibers that entangle and branch to form gels. Despite facile gel formation, crystallization of the guanosine molecules out of the gel is a common occurrence that leads to gel collapse within hours of fabrication. In addition, guanosine and related gelators often require a high potassium concentration or acidic pH to gel, which presents limited practical use in our target application of tissue engineering. We have focused on the modification and analysis of guanosine gels via an additive and/or a change in chemical structure to inhibit crystallization and promote gelation at physiological salt concentrations. Additionally, initial cell culture experiments suggest that these gel materials show great potential as an easily accessible and inexpensive tissue engineering scaffold. We also examined the potential for supramolecular gels for use in personal care formulations as electrolyte-resistant rheology modifiers for aqueous systems. Sugar-based gels fit the necessary criteria; however, many of these molecules also crystallize from the gel over time. We achieved lifetime stabilization again via a mixing approach and examined the resulting properties of the stabilized gels.

  10. Enzymes in Analytical Chemistry.

    ERIC Educational Resources Information Center

    Fishman, Myer M.

    1980-01-01

    Presents tabular information concerning recent research in the field of enzymes in analytic chemistry, with methods, substrate or reaction catalyzed, assay, comments and references listed. The table refers to 128 references. Also listed are 13 general citations. (CS)

  11. Analytical techniques: A compilation

    NASA Technical Reports Server (NTRS)

    1975-01-01

    A compilation, containing articles on a number of analytical techniques for quality control engineers and laboratory workers, is presented. Data cover techniques for testing electronic, mechanical, and optical systems, nondestructive testing techniques, and gas analysis techniques.

  12. Extreme Scale Visual Analytics

    SciTech Connect

    Steed, Chad A; Potok, Thomas E; Pullum, Laura L; Ramanathan, Arvind; Shipman, Galen M; Thornton, Peter E

    2013-01-01

    Given the scale and complexity of today s data, visual analytics is rapidly becoming a necessity rather than an option for comprehensive exploratory analysis. In this paper, we provide an overview of three applications of visual analytics for addressing the challenges of analyzing climate, text streams, and biosurveilance data. These systems feature varying levels of interaction and high performance computing technology integration to permit exploratory analysis of large and complex data of global significance.

  13. Development of novel Sol-Gel Indicators (SGI's) for in-situ environmental measurements: Part 1, Program and a new pH Sol-Gel Indicator

    SciTech Connect

    Livingston, R.R.; Baylor, L.; Wicks, G.G.

    1992-11-03

    The feasibility of incorporating analytical indicators into a sol-gel glassy matrix and then coating substrates with this composite material has bee demonstrated. Substrates coated include paper, wood, glass, and the lens of an analytical probe. The first SRTC sol-gel indicator, comprising bromophenol blue dispersed in a silica matrix, was fabricated and successfully used to measure solution pH in the range of pH 3.0 to 7.5. material exhibited a quick response time, as measured by color changes both qualitatively and quantitatively, and the measuring device was reversible or reusable. Additional indicators with responses over other ranges as well as indicators sensitive to the presence of elements of interest, are also under development. The new SGI composites possess promising properties and an excellent potential for performing a variety important in-situ environmental measurements and area discussed in this report.

  14. Photopolymerized diffusion-defined polyacrylamide gradient gels for on-chip protein sizing.

    PubMed

    Lo, Catherine T; Throckmorton, Daniel J; Singh, Anup K; Herr, Amy E

    2008-08-01

    We report on a facile diffusion-based photopatterning technique for generating linear and non-linear decreasing pore-size gradients in cross-linked polyacrylamide gels. Diffusion of low viscosity polymer precursor solutions and a two-step photopatterning process were used to define the decreasing pore-size gradient gels in a microfluidic format, thus eliminating the need for controlled mixing and delivery of polymer precursor solutions. We present an analytical model of the non-steady state diffusion process and numerically evaluate that model for direct comparison with empirical characterizations of the gradient gels. We show that the analytical model provides an effective means to predict the steepness and linearity of a desired gradient gel prior to fabrication. To assess electrophoretic assay performance in the microfluidic gradient gels, on-chip sizing of protein samples (20-116 kDa) was investigated. Baseline resolution of six proteins was demonstrated in 4 s using 3.5% to 10% polyacrylamide gradient gels. The demonstrated ability to conduct efficient protein sizing in ultra-short separation lengths (0.3 cm) means low applied electric potentials are needed to achieve the electric field strengths required for protein separations. The low required electric potentials relax operating constraints on electrical components, as is especially important for translation of the assay into pre-clinical and clinical settings. The gradient gel fabrication method reported is amenable to adaptation to non-sizing protein assays, as well as integration with upstream sample preparation steps and subsequent orthogonal downstream assays. PMID:18651068

  15. Automated apparatus for producing gradient gels

    DOEpatents

    Anderson, Norman L.

    1986-01-01

    Apparatus for producing a gradient gel which serves as a standard medium for a two-dimensional analysis of proteins, the gel having a density gradient along its height formed by a variation in gel composition, with the apparatus including first and second pumping means each including a plurality of pumps on a common shaft and driven by a stepping motor capable of providing small incremental changes in pump outputs for the gel ingredients, the motors being controlled, by digital signals from a digital computer, a hollow form or cassette for receiving the gel composition, means for transferring the gel composition including a filler tube extending near the bottom of the cassette, adjustable horizontal and vertical arms for automatically removing and relocating the filler tube in the next cassette, and a digital computer programmed to automatically control the stepping motors, arm movements, and associated sensing operations involving the filling operation.

  16. Automated apparatus for producing gradient gels

    DOEpatents

    Anderson, N.L.

    1983-11-10

    Apparatus for producing a gradient gel which serves as a standard medium for a two-dimensional analysis of proteins, the gel having a density gradient along its height formed by a variation in gel composition, with the apparatus including first and second pumping means each including a plurality of pumps on a common shaft and driven by a stepping motor capable of providing small incremental changes in pump outputs for the gel ingredients, the motors being controlled, by digital signals from a digital computer, a hollow form or cassette for receiving the gel composition, means for transferring the gel composition including a filler tube extending near the bottom of the cassette, adjustable horizontal and vertical arms for automatically removing and relocating the filler tube in the next cassette, and a digital computer programmed to automatically control the stepping motors, arm movements, and associated sensing operations involving the filling operation.

  17. The Hydration Dynamics of Polyelectrolyte Gels

    NASA Astrophysics Data System (ADS)

    Wolgemuth, Charles; Mogilner, Alex; Oster, George

    2002-03-01

    By combining the physics of gels with the hydrodynamics of two-phase fluids, we construct a set of equations that describe the hydration dynamics of polyelectrolyte gels. Numerical solutions to these equations are consistent with previous theory and experiments on gel swelling, but extend the physics to include the flow of the fluid solvent as well as treating the fluid and solvent equally. We use our equations to derive the effective diffusion constants for neutral and charged spherically distributed gels in terms of more microscopic paramters. We then solve the novel probelm of calculating the swelling of an isotropic, spherical gel with a permeable boundary condition and compare these results to previous experimetns on swelling gels.

  18. GEM printer: 3D gel printer for free shaping of functional gel engineering materials

    NASA Astrophysics Data System (ADS)

    Furukawa, Hidemitsu; Muroi, Hisato; Yamamoto, Kouki; Serizawa, Ryo; Gong, Jin

    2013-04-01

    In the past decade, several high-strength gels have been developed. These gels are expected to use as a kind of new engineering materials in the fields of industry and medical as substitutes to polyester fibers, which are materials of artificial blood vessels. The gels have both low surface friction and well permeability due to a large amount of water absorbed in the gels, which are superiority of the gels compering to the polyester fibers. It is, however, difficult for gels to be forked structure or cavity structure by using cutting or mold. Consequently, it is necessary to develop the additive manufacturing device to synthesize and mode freely gels at the same time. Here we try to develop an optical 3D gel printer that enables gels to be shaped precisely and freely. For the free forming of high-strength gels, the 1st gels are ground to particles and mixed with 2nd pregel solution, and the mixed solution is gelled by the irradiation of UV laser beam through an optical fiber. The use of the optical fiber makes one-point UV irradiation possible. Since the optical fiber is controlled by 3D-CAD, the precise and free molding in XYZ directions is easily realized. We successfully synthesized tough gels using the gel printer.

  19. Characteristics of polyacrylamide gel with THPC and Turnbull Blue gel dosimeters evaluated using optical tomography

    NASA Astrophysics Data System (ADS)

    Pilařová (Vávrů), Kateřina; Kozubíková, Petra; Šolc, Jaroslav; Spěváček, Václav

    2014-11-01

    The purpose of this study was to compare characteristics of radiochromic gel - Turnbull Blue gel (TB gel) with polymer gel - polyacrylamide gel and tetrakis hydroxymethyl phosphonium chloride (PAGAT) using optical tomography. Both types of gels were examined in terms of dose sensitivity, dose response linearity and background value of spectrophotometric absorbance. The calibration curve was obtained for 60Co irradiation performed on Gammacell 220 at predefined gamma dose levels between 0 and 140 Gy for TBG and 0-15 Gy for PAGAT. To measure relative dose distributions from stereotactic irradiation, dosimeters were irradiated on Leksell Gamma Knife Perfexion. The cylindrical glass housings filled with gel were attached to the stereotactic frame. They were exposed with single shot and 16 mm collimator by 65 Gy to a 50% prescription isodose for TB gel and 4 Gy to a 50% prescription isodose for PAGAT. Evaluations of dosimeters were performed on an UV-vis Spectrophotometer Helios β and an optical cone beam homemade tomography scanner with a 16-bit astronomy CCD camera with a set of color filters. The advantages and potential disadvantages for both types of gel dosimeters were summarized. Dose distribution in central slice and measured profiles of 16 mm shot shows excellent correspondence with treatment planning system Leksell GammaPlan® for both PAGAT and Turnbull Blue gels. Gel dosimeters are suitable for steep dose gradient verification. An optical tomography evaluation method is successful. Dose response characteristics of TB gel and PAGAT gel are presented.

  20. Population Dynamics of Chesapeake Bay Virioplankton: Total-Community Analysis by Pulsed-Field Gel Electrophoresis†

    PubMed Central

    Wommack, K. Eric; Ravel, Jacques; Hill, Russell T.; Chun, Jongsik; Colwell, Rita R.

    1999-01-01

    Recognition of viruses as the most abundant component of aquatic microbial communities has stimulated investigations of the impact of viruses on bacterio- and phytoplankton host communities. From results of field studies to date, it is concluded that in most aquatic environments, a reduction in the number of bacteria on a daily basis is caused by viral infection. However, the modest amount of in situ virus-mediated mortality may be less significant than viral infection serving to maintain clonal diversity in the host communities directly, through gene transmission (i.e., transduction), and indirectly, by elimination of numerically dominant host species. If the latter mechanism for controlling community diversity prevails, then the overall structure of aquatic viral communities would be expected to change as well over short seasonal and spatial scales. To determine whether this occurs, pulsed-field gel electrophoresis (PFGE) was used to monitor the population dynamics of Chesapeake Bay virioplankton for an annual cycle (1 year). Virioplankton in water samples collected at six stations along a transect running the length of the bay were concentrated 100-fold by ultrafiltration. Viruses were further concentrated by ultracentrifugation, and the concentrated samples were embedded in agarose. PFGE analysis of virus DNA in the agarose plugs yielded several distinct bands, ranging from 50 to 300 kb. Principal-component and cluster analyses of the virus PFGE fingerprints indicated that changes in virioplankton community structure were correlated with time, geographical location, and extent of water column stratification. From the results of this study, it is concluded that, based on the dynamic nature of the Chesapeake Bay virioplankton community structure, the clonal diversity of bacterio- and phytoplankton host communities is an important component of the virus community. PMID:9872784

  1. Self-Pumping Active Gel

    NASA Astrophysics Data System (ADS)

    Wu, Kun-Ta; Hishamunda, Jean Bernard; Fraden, Seth; Dogic, Zvonimir

    Isotropic active gels are the network which is consist of cross-linked building blocks and the structure of which changes randomly and isotropically with time. Dogic et. al. show that pairs of anti-parallel microtubules form extensile bundles, which merge, extend, and buckle. In an unconfined system, the dynamics of these bundles causes spontaneous turbulent-like flow driven by motion of microscopic molecular motors. We found that confining these active gels in a millimeter sized toroids causes a transition into a new dynamical state characterized by circulation currents persisting for hours until ATP is depleted. We show how toroid dimensions impact the properties of self-organized circular currents, how directions of circulation can be designed by engineering ratchet-shaped boundaries, and how circulations of connected toroids can be either synchronized or antisynchronized. Furthermore, we demonstrate that the flow rate in the circulation is independent of curvature and length of flow path. The flow rate persists for centimeters without decay, disregarding conventional pipe flow resistance. Such findings pave the path to self-pumping pipe transport and performing physical work with biological system.

  2. Microfluidics of soft granular gels

    NASA Astrophysics Data System (ADS)

    Nixon, Ryan; Bhattacharjee, Tapomoy; Sawyer, W. Gregory; Angelini, Thomas E.

    Microfluidic methods for encapsulating cells and particles typically involve drop making with two immiscible fluids. The main materials constraint in this approach is surface tension, creating inherent instability between the two fluids. We can eliminate this instability by using miscible inner and outer phases. This is achieved by using granular micro gels which are chemically miscible but physically do not mix. These microgels are yield stress materials, so they flow as solid plugs far from shear gradients, and fluidize where gradients are generated - near an injection nozzle for example. We have found that tuning the yield stress of the material by varying polymer concentration, device performance can be controlled. The solid like behavior of the gel allows us to produces infinitely stable jets that maintain their integrity and configuration over long distances and times. These properties can be combined and manipulated to produce discrete particulate bunches of an inner phase, flowing inside of an outer phase, well enough even to print a Morse code message suspended within flow chambers about a millimeter in diameter moving at millimeters a second.

  3. Tissue simulating gel for medical research

    NASA Technical Reports Server (NTRS)

    Companion, John A. (Inventor)

    1991-01-01

    A tissue simulating gel and a method for preparing the tissue simulating gel are disclosed. The tissue simulating gel is prepared by a process using water, gelatin, ethylene glycol, and a cross-linking agent. In order to closely approximate the characteristics of the type of tissue being simulated, other material has been added to change the electrical, sound conducting, and wave scattering properties of the tissue simulating gel. The result of the entire process is a formulation that will not melt at the elevated temperatures involved in hyperthermia medical research. Furthermore, the tissue simulating gel will not support mold or bacterial growth, is of a sufficient mechanical strength to maintain a desired shape without a supporting shell, and is non-hardening and non-drying. Substances have been injected into the tissue simulating gel prior to the setting-up thereof just as they could be injected into actual tissue, and the tissue simulating gel is translucent so as to permit visual inspection of its interior. A polyurethane spray often used for coating circuit boards can be applied to the surface of the tissue simulating gel to give a texture similar to human skin, making the tissue simulating gel easier to handle and contributing to its longevity.

  4. Structure of chitosan gels mineralized by sorption

    NASA Astrophysics Data System (ADS)

    Modrzejewska, Z.; Skwarczyńska, A.; Douglas, T. E. L.; Biniaś, D.; Maniukiewicz, W.; Sielski, J.

    2015-10-01

    The paper presents the structural studies of mineralized chitosan hydrogels. Hydrogels produced by using sodium beta-glycerophosphate (Na-β-GP) as a neutralizing agent. Mineralization was performed method "post loading", which consisted in sorption to the gels structure Ca ions. In order to obtain - in the structure of gels - compounds similar to the hydroxyapatites present naturally in bone tissue, gels after sorption were modified in: pH 7 buffer and sodium hydrogen phosphate. In order to determine the structural properties of the gels, the following methods were used: infrared spectroscopy with Fourier transformation, FTIR, X-ray diffractometry, XRD, scanning electron microscopy, SEM.

  5. Ionic liquid based multifunctional double network gel

    NASA Astrophysics Data System (ADS)

    Ahmed, Kumkum; Higashihara, Tomoya; Arafune, Hiroyuki; Kamijo, Toshio; Morinaga, Takashi; Sato, Takaya; Furukawa, Hidemitsu

    2015-04-01

    Gels are a promising class of soft and wet materials with diverse application in tissue engineering and bio-medical purpose. In order to accelerate the development of gels, it is required to synthesize multi-functional gels of high mechanical strength, ultra low surface friction and suitable elastic modulus with a variety of methods and new materials. Among many types of gel ionic gel made from ionic liquids (ILs) could be used for diverse applications in electrochemical devices and in the field of tribology. IL, a promising materials for lubrication, is a salt with a melting point lower than 100 °C. As a lubricant, ILs are characterized by an extremely low vapor pressure, high thermal stability and high ion conductivity. In this work a novel approach of making double network DN ionic gel using IL has been made utilizing photo polymerization process. A hydrophobic monomer Methyl methacrylate (MMA) has been used as a first network and a hydrophobic IL monomer, N,N-diethyl-N-(2-mthacryloylethyl)-N-methylammonium bistrifluoromethylsulfonyl)imide (DEMM-TFSI) has been used as a second network using photo initiator benzophenon and crosslinker triethylene glycol dimethacrylate (TEGDMA). The resulting DN ionic gel shows transparency, flexibility, high thermal stability, good mechanical toughness and low friction coefficient value which can be a potential candidate as a gel slider in different mechanical devices and can open a new area in the field of gel tribology.

  6. Food gels: gelling process and new applications.

    PubMed

    Banerjee, Soumya; Bhattacharya, Suvendu

    2012-01-01

    Food gels are viscoelastic substances and several gelled products are manufactured throughout the world. The gelling agents in foods are usually polysaccharides and proteins. In food gels, the polymer molecules are not cross-linked by covalent bonds with the exception of disulphide bonds in some protein gels. Instead, the molecules are held together by a combination of weak inter-molecular forces like hydrogen bonds, electrostatic forces, Van der Waals forces, and hydrophobic interactions. Polysaccharides including hydrocolloids are strongly hydrated in aqueous medium but they tend to have less ordered structures. The mechanism of gelation depends on the nature of the gelling agent(s) and on the conditions of gel formation like the temperature, the presence of ions, the pH, and the concentration of gelling agents, etc. Characterization of gels can be performed in several ways of which rheological measurements are frequently practiced. Multi-component or mixed gel system is an important area of interest in which two or more gelling components are simultaneously used to achieve certain specific structural and functional characteristics. We here discuss about the different gels and gelling agents, the characterization of gels, and the mechanism of gelation with an emphasis on mixed or multi-component gels that would have significant commercial applications. PMID:22332597

  7. Conducting Polymer Electrodes for Gel Electrophoresis

    PubMed Central

    Bengtsson, Katarina; Nilsson, Sara; Robinson, Nathaniel D.

    2014-01-01

    In nearly all cases, electrophoresis in gels is driven via the electrolysis of water at the electrodes, where the process consumes water and produces electrochemical by-products. We have previously demonstrated that π-conjugated polymers such as poly(3,4-ethylenedioxythiophene) (PEDOT) can be placed between traditional metal electrodes and an electrolyte to mitigate electrolysis in liquid (capillary electroosmosis/electrophoresis) systems. In this report, we extend our previous result to gel electrophoresis, and show that electrodes containing PEDOT can be used with a commercial polyacrylamide gel electrophoresis system with minimal impact to the resulting gel image or the ionic transport measured during a separation. PMID:24586761

  8. Enantioselective component selection in multicomponent supramolecular gels.

    PubMed

    Edwards, William; Smith, David K

    2014-01-22

    We investigate a two-component acid-amine gelation system in which chirality plays a vital role. A carboxylic acid based on a second generation l-lysine dendron interacts with chiral amines and subsequently assembles into supramolecular gel fibers. The chirality of the amine controls the assembly of the resulting diastereomeric complexes, even if this chirality is relatively "poor quality". Importantly, the selective incorporation of one enantiomer of an amine over the other into the gel network has been demonstrated, with the R amine that forms complexes which assemble into the most stable gel being primarily selected for incorporation. Thermodynamic control has been proven by forming a gel exclusively with an S amine, allowing the R enantiomer to diffuse through the gel network, and displacing it from the "solidlike" fibers, demonstrating that these gels adapt and evolve in response to chemical stimuli to which they are exposed. Excess amine, which remains unincorporated within the solidlike gel fiber network, can diffuse out and be reacted with an isocyanate, allowing us to quantify the enantioselectivity of component selection but also demonstrating how gels can act as selective reservoirs of potential reagents, releasing them on demand to undergo further reactions; hence, component-selective gel assembly can be coupled with controlled reactivity. PMID:24400807

  9. New possibilities of accurate particle characterisation by applying direct boundary models to analytical centrifugation

    NASA Astrophysics Data System (ADS)

    Walter, Johannes; Thajudeen, Thaseem; Süß, Sebastian; Segets, Doris; Peukert, Wolfgang

    2015-04-01

    Analytical centrifugation (AC) is a powerful technique for the characterisation of nanoparticles in colloidal systems. As a direct and absolute technique it requires no calibration or measurements of standards. Moreover, it offers simple experimental design and handling, high sample throughput as well as moderate investment costs. However, the full potential of AC for nanoparticle size analysis requires the development of powerful data analysis techniques. In this study we show how the application of direct boundary models to AC data opens up new possibilities in particle characterisation. An accurate analysis method, successfully applied to sedimentation data obtained by analytical ultracentrifugation (AUC) in the past, was used for the first time in analysing AC data. Unlike traditional data evaluation routines for AC using a designated number of radial positions or scans, direct boundary models consider the complete sedimentation boundary, which results in significantly better statistics. We demonstrate that meniscus fitting, as well as the correction of radius and time invariant noise significantly improves the signal-to-noise ratio and prevents the occurrence of false positives due to optical artefacts. Moreover, hydrodynamic non-ideality can be assessed by the residuals obtained from the analysis. The sedimentation coefficient distributions obtained by AC are in excellent agreement with the results from AUC. Brownian dynamics simulations were used to generate numerical sedimentation data to study the influence of diffusion on the obtained distributions. Our approach is further validated using polystyrene and silica nanoparticles. In particular, we demonstrate the strength of AC for analysing multimodal distributions by means of gold nanoparticles.

  10. Stacking gels: A method for maximising output for pulsed-field gel electrophoresis.

    PubMed

    Heng, See Kah; Heng, Chua Kek; Puthucheary, S D

    2009-01-01

    Pulsed field gel electrophoresis (PFGE), the gold standard of molecular typing methods, has a major disadvantage of an unusually long electrophoretic time. From the original protocol of 6 days, it was modified to 3 days and subsequently to a single day. We describe the procedure of stacking five to six gels one on top of another in order to increase and maximize the output in a shorter time without compromising the resolution and reproducibility. All the variables that affect pulsed field gels during electrophoresis were taken into consideration. We firstly optimized the parameters to be used and secondly determined whether stacking of five to six gels had any effect on the molecular separation during electrophoresis in comparison with a single gel run. DNA preparation, restriction, electrophoresis, staining and gel documentation was carried out based on previously published methods. Gels were analysed using BioNumerics and dice coefficient and unweighted pair group methods were used to generate dendrograms based on 1.5% tolerance values. Identical band profiles and band resolution-separation were seen in the PFGE patterns with single gel and multiple stacking gels. Cluster analysis further strengthened the fact that results from stacking gels were reproducible and comparable with a single gel run. This method of stacking gels saves time and maximizes the output at the same time. The run time for a single gel was about 28 hours, but with six stacked gels the run time was 54 hours compared with 28 x 6 = 168 hours if they were run separately as single gels thus saving time of 67.86%. Beside the big factor of saving time, stacking gels save resources (electricity, reagents, water, chemicals and working time) by increasing the sample throughput in a shorter time without compromising on quality of data. But optimization of working parameters is vital depending on the PFGE system used. PMID:19384038

  11. Advances in analytical chemistry

    NASA Technical Reports Server (NTRS)

    Arendale, W. F.; Congo, Richard T.; Nielsen, Bruce J.

    1991-01-01

    Implementation of computer programs based on multivariate statistical algorithms makes possible obtaining reliable information from long data vectors that contain large amounts of extraneous information, for example, noise and/or analytes that we do not wish to control. Three examples are described. Each of these applications requires the use of techniques characteristic of modern analytical chemistry. The first example, using a quantitative or analytical model, describes the determination of the acid dissociation constant for 2,2'-pyridyl thiophene using archived data. The second example describes an investigation to determine the active biocidal species of iodine in aqueous solutions. The third example is taken from a research program directed toward advanced fiber-optic chemical sensors. The second and third examples require heuristic or empirical models.

  12. Terpolymer smart gels: synthesis and characterizations

    NASA Astrophysics Data System (ADS)

    Bag, Dibyendu S.; Alam, Sarfaraz; Mathur, G. N.

    2004-10-01

    Two smart terpolymer gels, MS-1 and MS-2, were synthesized such that the same gel can respond to more than one external environmental condition, such as pH, temperature, solvent composition, electric field. So two terpolymers gels of vinyl monomers such as sodium acrylate, acrylamide and N-isopropyl acrylamide were synthesized by using ammonium persulfate (APS) as an initiator, N,N,N',N'-tetramethyl ethylene diamine (TMEDA) as an accelerator and methylene bisacrylamide as a cross-linker. These terpolymers were characterized by elemental and Fourier transform infrared analysis. The swelling behavior of these terpolymer smart gels was evaluated by changing the pH, temperature and solvent composition. The variation of the swelling behavior with time was evaluated in an aqueous medium at room temperature. The time taken for maximum swelling (tm) was about 20 min for the gel MS-2. However the tm value for the gel MS-1 is higher than that of MS-2. The swelling behavior remains almost unchanged over a temperature range of 22-50 °C for both the gels. The discontinuous volume transitions were observed at pH 7.6 and 8.2 for the two gels, MS-1 and MS-2, respectively. The gel MS-1 suddenly shrinks below and swells above pH 7.6. Correspondingly, the pH is 8.2 for the case of MS-2. Volume transitions in an acetone-water mixture were also observed for these gels. The swelling behaviors of these two smart gels are almost parallel above the 40% acetone concentration.

  13. Frontiers in analytical chemistry

    SciTech Connect

    Amato, I.

    1988-12-15

    Doing more with less was the modus operandi of R. Buckminster Fuller, the late science genius, and inventor of such things as the geodesic dome. In late September, chemists described their own version of this maxim--learning more chemistry from less material and in less time--in a symposium titled Frontiers in Analytical Chemistry at the 196th National Meeting of the American Chemical Society in Los Angeles. Symposium organizer Allen J. Bard of the University of Texas at Austin assembled six speakers, himself among them, to survey pretty widely different areas of analytical chemistry.

  14. Viscoelastic Properties of Vitreous Gel

    NASA Astrophysics Data System (ADS)

    Pirouz Kavehpour, H.; Sharif-Kashani, Pooria

    2010-11-01

    We studied the rheological properties of porcine vitreous humor using a stressed-control shear rheometer. All experiments were performed in a closed environment at body temperature to mimic in-vivo conditions. We modeled the creep deformation using a two-element retardation spectrum model. By associating each element of the model to an individual biopolymeric system in the vitreous gel, a separate response to the applied stress was obtained from each component. The short time scale was associated with the collagen structure, while the longer time scale was related to the microfibrilis and hyaluronan network. We were able to distinguish the role of each main component from the overall rheological properties. Knowledge of this correlation enables us to relate the physical properties of vitreous to its pathology, as well as optimize surgical procedures such as vitrectomy.

  15. Gel integration for microfluidic applications.

    PubMed

    Zhang, Xuanqi; Li, Lingjun; Luo, Chunxiong

    2016-05-21

    Molecular diffusive membranes or materials are important for biological applications in microfluidic systems. Hydrogels are typical materials that offer several advantages, such as free diffusion for small molecules, biocompatibility with most cells, temperature sensitivity, relatively low cost, and ease of production. With the development of microfluidic applications, hydrogels can be integrated into microfluidic systems by soft lithography, flow-solid processes or UV cure methods. Due to their special properties, hydrogels are widely used as fluid control modules, biochemical reaction modules or biological application modules in different applications. Although hydrogels have been used in microfluidic systems for more than ten years, many hydrogels' properties and integrated techniques have not been carefully elaborated. Here, we systematically review the physical properties of hydrogels, general methods for gel-microfluidics integration and applications of this field. Advanced topics and the outlook of hydrogel fabrication and applications are also discussed. We hope this review can help researchers choose suitable methods for their applications using hydrogels. PMID:27086944

  16. A Simple Vertical Slab Gel Electrophoresis Apparatus.

    ERIC Educational Resources Information Center

    Carter, J. B.; And Others

    1983-01-01

    Describes an inexpensive, easily constructed, and safe vertical slab gel kit used routinely for sodium dodecyl sulphate-polyacrylamide gel electrophoresis research and student experiments. Five kits are run from a single transformer. Because toxic solutions are used, students are given plastic gloves and closely supervised during laboratory

  17. 21 CFR 866.4900 - Support gel.

    Code of Federal Regulations, 2014 CFR

    2014-04-01

    ... 21 Food and Drugs 8 2014-04-01 2014-04-01 false Support gel. 866.4900 Section 866.4900 Food and Drugs FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN SERVICES (CONTINUED) MEDICAL DEVICES IMMUNOLOGY AND MICROBIOLOGY DEVICES Immunology Laboratory Equipment and Reagents § 866.4900 Support gel....

  18. 21 CFR 866.4900 - Support gel.

    Code of Federal Regulations, 2011 CFR

    2011-04-01

    ... 21 Food and Drugs 8 2011-04-01 2011-04-01 false Support gel. 866.4900 Section 866.4900 Food and Drugs FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN SERVICES (CONTINUED) MEDICAL DEVICES IMMUNOLOGY AND MICROBIOLOGY DEVICES Immunology Laboratory Equipment and Reagents § 866.4900 Support gel....

  19. 21 CFR 866.4900 - Support gel.

    Code of Federal Regulations, 2012 CFR

    2012-04-01

    ... 21 Food and Drugs 8 2012-04-01 2012-04-01 false Support gel. 866.4900 Section 866.4900 Food and Drugs FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN SERVICES (CONTINUED) MEDICAL DEVICES IMMUNOLOGY AND MICROBIOLOGY DEVICES Immunology Laboratory Equipment and Reagents § 866.4900 Support gel....

  20. 21 CFR 866.4900 - Support gel.

    Code of Federal Regulations, 2013 CFR

    2013-04-01

    ... 21 Food and Drugs 8 2013-04-01 2013-04-01 false Support gel. 866.4900 Section 866.4900 Food and Drugs FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN SERVICES (CONTINUED) MEDICAL DEVICES IMMUNOLOGY AND MICROBIOLOGY DEVICES Immunology Laboratory Equipment and Reagents § 866.4900 Support gel....

  1. 21 CFR 866.4900 - Support gel.

    Code of Federal Regulations, 2010 CFR

    2010-04-01

    ... 21 Food and Drugs 8 2010-04-01 2010-04-01 false Support gel. 866.4900 Section 866.4900 Food and Drugs FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN SERVICES (CONTINUED) MEDICAL DEVICES IMMUNOLOGY AND MICROBIOLOGY DEVICES Immunology Laboratory Equipment and Reagents § 866.4900 Support gel....

  2. Chain Release Behavior of Gellan Gels

    NASA Astrophysics Data System (ADS)

    Hossain, Khandker S.; Nishinari, Katsuyoshi

    The chain release behavior from gellan gels was studied by immersing the gel into water and monitoring the mass loss as a function of time. Concentration of released gellan in the external solution was determined for gels of different sizes using phenol-sulfuric acid method. The chain release process became faster with increasing total surface area and volume. However the concentration of released chain normalized by surface area and volume suggests that the chain release itself is governed not only by the ionic effect and the amount of unassociated chains in gel but other factors such as osmotic pressure may play an important role on the chain release from the gels. The diffusion coefficient was estimated from the chain release process which is in the same order of magnitude reported for an isolated gellan chain by light scattering. Rheological measurements also suggest that the unassociated gellan chains are released out when immersed in pure water while unassociated chains are restricted to release out when immersed in salt solution due to the intrusion of cations which is responsible for further association of the unassociated gellan chains being in agreement with the previously published results. The elastic modulus of gels was increased by immersion of gels in water and in salt solutions, which can be attributed as the stiffening of network chains due to gel swelling and the conversion from free and unassociated chains into network chains, respectively, leading to an increase in elastic modulus with time.

  3. A Simple Vertical Slab Gel Electrophoresis Apparatus.

    ERIC Educational Resources Information Center

    Carter, J. B.; And Others

    1983-01-01

    Describes an inexpensive, easily constructed, and safe vertical slab gel kit used routinely for sodium dodecyl sulphate-polyacrylamide gel electrophoresis research and student experiments. Five kits are run from a single transformer. Because toxic solutions are used, students are given plastic gloves and closely supervised during laboratory…

  4. Flow of colloidal suspensions and gels

    NASA Astrophysics Data System (ADS)

    Zia, Roseanna

    Our recent studies of yield of colloidal gels under shear show that yield in such gels occurs in distinct stages. Under fixed stress, yield follows a finite delay period of slow solid-like creep. Post yield, the gel fluidizes and may undergo long-time viscous flow or, in some cases, may re-solidify. Under imposed strain rate, the transition from equilibrium to long-time flow is characterized by one or more stress overshoots, signifying a yield process here as well. These rheological changes are accompanied by evolution in morphology and dynamics of the gel network. Similar regimes have been observed in gels subjected to gravitational forcing; the gel initially supports its own weight, or perhaps undergoes slow, weak compaction. This may be followed by a sudden transition to rapid compaction or sedimentation. Various models have been put forth to explain these behaviors based on structural evolution, but this detail is difficult to observe in experiment. Here we examine the detailed microstructural evolution and rheology of reversible colloidal gels as they deform under gravity, identifying the critical buoyant force at which yield occurs, the role played by ongoing gel coarsening, and similarities and differences compared to yield under shear. We gratefully acknowledge the support of the NSF XSEDE Computational Resource, the NSF Early CAREER Program, and the Office of Naval Research Young Investigator Program.

  5. Hyperspectral imaging of gel pen inks: an emerging tool in document analysis.

    PubMed

    Reed, G; Savage, K; Edwards, D; Nic Daeid, N

    2014-01-01

    Hyperspectral imaging (HSI) is a useful technique in the examination of writing inks, including gel pen inks, which combines digital imaging with % reflectance spectroscopy. This facilitates the detection of subtle differences between chemically similar inks. This study analysed a variety of blue, red and black gel inks on white office paper using HSI. The potential of the technique for ink discrimination compared to other analytical methods of examination is highlighted. Discriminating powers of 1.00, 0.90 and 0.40 were achieved using HSI for red, blue and black gel inks respectively. The overall discriminating power of 0.76 for the technique combined with its non-destructive nature and minimal sampling requirements demonstrates promise for this type of application. PMID:24438781

  6. Analytical Chemistry Laboratory

    NASA Technical Reports Server (NTRS)

    Anderson, Mark

    2013-01-01

    The Analytical Chemistry and Material Development Group maintains a capability in chemical analysis, materials R&D failure analysis and contamination control. The uniquely qualified staff and facility support the needs of flight projects, science instrument development and various technical tasks, as well as Cal Tech.

  7. FIELD ANALYTICAL METHODS GUIDANCE

    EPA Science Inventory

    The guidance outlines a strategy for dynamic work planning and on-site decision making so that EPA project managers can minimize the number of mobilizations that are involved in reaching site decisions. As part of this process, it describes how field-based analytical methods can...

  8. Analytical Services Management System

    Energy Science and Technology Software Center (ESTSC)

    2005-03-30

    Analytical Services Management System (ASMS) provides sample management services. Sample management includes sample planning for analytical requests, sample tracking for shipping and receiving by the laboratory, receipt of the analytical data deliverable, processing the deliverable and payment of the laboratory conducting the analyses. ASMS is a web based application that provides the ability to manage these activities at multiple locations for different customers. ASMS provides for the assignment of single to multiple samples for standardmore » chemical and radiochemical analyses. ASMS is a flexible system which allows the users to request analyses by line item code. Line item codes are selected based on the Basic Ordering Agreement (BOA) format for contracting with participating laboratories. ASMS also allows contracting with non-BOA laboratories using a similar line item code contracting format for their services. ASMS allows sample and analysis tracking from sample planning and collection in the field through sample shipment, laboratory sample receipt, laboratory analysis and submittal of the requested analyses, electronic data transfer, and payment of the laboratories for the completed analyses. The software when in operation contains business sensitive material that is used as a principal portion of the Kaiser Analytical Management Services business model. The software version provided is the most recent version, however the copy of the application does not contain business sensitive data from the associated Oracle tables such as contract information or price per line item code.« less

  9. Analytical Services Management System

    SciTech Connect

    Church, Shane; Nigbor, Mike; Hillman, Daniel

    2005-03-30

    Analytical Services Management System (ASMS) provides sample management services. Sample management includes sample planning for analytical requests, sample tracking for shipping and receiving by the laboratory, receipt of the analytical data deliverable, processing the deliverable and payment of the laboratory conducting the analyses. ASMS is a web based application that provides the ability to manage these activities at multiple locations for different customers. ASMS provides for the assignment of single to multiple samples for standard chemical and radiochemical analyses. ASMS is a flexible system which allows the users to request analyses by line item code. Line item codes are selected based on the Basic Ordering Agreement (BOA) format for contracting with participating laboratories. ASMS also allows contracting with non-BOA laboratories using a similar line item code contracting format for their services. ASMS allows sample and analysis tracking from sample planning and collection in the field through sample shipment, laboratory sample receipt, laboratory analysis and submittal of the requested analyses, electronic data transfer, and payment of the laboratories for the completed analyses. The software when in operation contains business sensitive material that is used as a principal portion of the Kaiser Analytical Management Services business model. The software version provided is the most recent version, however the copy of the application does not contain business sensitive data from the associated Oracle tables such as contract information or price per line item code.

  10. Analytics: Changing the Conversation

    ERIC Educational Resources Information Center

    Oblinger, Diana G.

    2013-01-01

    In this third and concluding discussion on analytics, the author notes that we live in an information culture. We are accustomed to having information instantly available and accessible, along with feedback and recommendations. We want to know what people think and like (or dislike). We want to know how we compare with "others like me."…

  11. Social Learning Analytics

    ERIC Educational Resources Information Center

    Buckingham Shum, Simon; Ferguson, Rebecca

    2012-01-01

    We propose that the design and implementation of effective "Social Learning Analytics (SLA)" present significant challenges and opportunities for both research and enterprise, in three important respects. The first is that the learning landscape is extraordinarily turbulent at present, in no small part due to technological drivers. Online social…

  12. Analytics: Changing the Conversation

    ERIC Educational Resources Information Center

    Oblinger, Diana G.

    2013-01-01

    In this third and concluding discussion on analytics, the author notes that we live in an information culture. We are accustomed to having information instantly available and accessible, along with feedback and recommendations. We want to know what people think and like (or dislike). We want to know how we compare with "others like me."

  13. Challenges for Visual Analytics

    SciTech Connect

    Thomas, James J.; Kielman, Joseph

    2009-09-23

    Visual analytics has seen unprecedented growth in its first five years of mainstream existence. Great progress has been made in a short time, yet great challenges must be met in the next decade to provide new technologies that will be widely accepted by societies throughout the world. This paper sets the stage for some of those challenges in an effort to provide the stimulus for the research, both basic and applied, to address and exceed the envisioned potential for visual analytics technologies. We start with a brief summary of the initial challenges, followed by a discussion of the initial driving domains and applications, as well as additional applications and domains that have been a part of recent rapid expansion of visual analytics usage. We look at the common characteristics of several tools illustrating emerging visual analytics technologies, and conclude with the top ten challenges for the field of study. We encourage feedback and collaborative participation by members of the research community, the wide array of user communities, and private industry.

  14. Ada & the Analytical Engine.

    ERIC Educational Resources Information Center

    Freeman, Elisabeth

    1996-01-01

    Presents a brief history of Ada Byron King, Countess of Lovelace, focusing on her primary role in the development of the Analytical Engine--the world's first computer. Describes the Ada Project (TAP), a centralized World Wide Web site that serves as a clearinghouse for information related to women in computing, and provides a Web address for

  15. Catalytic control over supramolecular gel formation

    NASA Astrophysics Data System (ADS)

    Boekhoven, Job; Poolman, Jos M.; Maity, Chandan; Li, Feng; van der Mee, Lars; Minkenberg, Christophe B.; Mendes, Eduardo; van Esch, Jan H.; Eelkema, Rienk

    2013-05-01

    Low-molecular-weight gels show great potential for application in fields ranging from the petrochemical industry to healthcare and tissue engineering. These supramolecular gels are often metastable materials, which implies that their properties are, at least partially, kinetically controlled. Here we show how the mechanical properties and structure of these materials can be controlled directly by catalytic action. We show how in situ catalysis of the formation of gelator molecules can be used to accelerate the formation of supramolecular hydrogels, which drastically enhances their resulting mechanical properties. Using acid or nucleophilic aniline catalysis, it is possible to make supramolecular hydrogels with tunable gel-strength in a matter of minutes, under ambient conditions, starting from simple soluble building blocks. By changing the rate of formation of the gelator molecules using a catalyst, the overall rate of gelation and the resulting gel morphology are affected, which provides access to metastable gel states with improved mechanical strength and appearance despite an identical gelator composition.

  16. Generation of inkjet drop of particulate gel

    NASA Astrophysics Data System (ADS)

    Yoo, Hansol; Kim, Chongyoup

    2015-08-01

    The generation of inkjet drops of colloidal gels is studied experimentally. Particle suspensions are prepared by dispersing spherical polystyrene particles of 620 nm in the 1:1 mixture of deionized water and ethylene glycol. The gels are prepared by adding polyethylene oxide to the suspensions by inducing the depletion interaction between particles. It is demonstrated that inkjet drops can be generated by using the colloidal gels. It is found that the ligament extended from the inkjet nozzle is stabilized so that the drop can be generated without satellite droplets behind the main drop and the velocity of the gel drop is faster than that of the polymer solution at the same concentration. The gel drop generation characteristics are found to be sensitive to input voltage.

  17. Intelligent gels and cryogels with entrapped emulsions.

    PubMed

    Komarova, Galina A; Starodubtsev, Sergey G; Lozinsky, Vladimir I; Kalinina, Elena V; Landfester, Katharina; Khokhlov, Alexei R

    2008-05-01

    Smart thermoresponsive gels and cryogels with incorporated emulsions have been synthesized and studied. The gels were obtained by three-dimensional copolymerization of N-isopropylacrylamide and N,N'-methylene-bis-acrylamide or N,N'-bis(acryloyl)cystamine in the presence of dispersion of tetradecane stabilized with sodium dodecylsulfate. Polymerization was performed at room temperature and below the water crystallization temperature. Both composite gels and cryogels were capable of heat-induced collapse. The extent of the collapse of the composite gel prepared at room temperature was much smaller and without squeezing of the lipophilic phase out of the shrunk composite gel. In contrast, shrinking of the composite cryogel was accompanied by release of tetradecane emulsion. PMID:18386880

  18. Dewatering fine coal slurries by gel extraction

    SciTech Connect

    Gehrke, S.H.; Lyu, Lii-Hurng.

    1990-01-01

    A new technology called gel extraction has been evaluated to determine its economic viability in dewatering the fine and ultrafine coal slurries generated upon separation of sulfur and ash from clean coal during the physical coal cleaning process. Water must be removed from such slurries prior to transportation and combustion but the dewatering costs are substantial, especially for the fine particles below 28 mesh (0.6 mm). Gel extraction is a potential breakthrough in slurry dewatering technology. The goal of this project was to acquire the qualitative and quantitative data needed to estimate the potential of gel extraction for dewatering coal slurries. The specific objectives were to determine the maximum extents of dewatering (minimum surface moisture in the coal product), the clarity of the water removed (minimum solids content), the speed of the dewatering cycles, the service lifetime of the gels, and the factors which influence all of these. With the results obtained, an economic analysis of Ohio coal cleaning plant dewatering technologies was carried out. The polymer gel at the heart of this project, poly (N-isopropylacrylamide) (PNIPA), can swell several times its shrunken weight at 32[degrees]C by absorbing water at 25[degrees]C. In gel extraction, a shrunken NIPA gel is contacted with a slurry at ambient temperature or cooler; the gel swells by absorbing water from the slurry. The gel is then removed from the dewatered slurry and warmed above its critical temperature of 33[degrees]C, which returns it to the shrunken state by releasing the absorbed water. The facts that the gel is reusable and the process is simple and driven by low-grade energy (warm temperatures), and not inherently limited by particle size, made the process an attractive possible alternative to centrifugation, screening, filtration, etc. for slurry dewatering.

  19. Generative force of self-oscillating gel.

    PubMed

    Hara, Yusuke; Mayama, Hiroyuki; Morishima, Keisuke

    2014-03-01

    We succeeded in measuring the generative force of a self-oscillating polymer gel in an aqueous solution comprising the three substrates of the Belousov-Zhabotinsky (BZ) reaction (malonic acid, sodium bromate, and nitric acid) under constant temperature. In this study, we developed an apparatus with a microforce sensor for measuring the generative force of small-sized gels (1 mm(3)). The self-oscillating polymer gel directly converts the chemical energy of the BZ reaction into mechanical work. It was determined that the generative force of the self-oscillating gel was 972 Pa, and the period of self-oscillation was 480 s at 18 °C. We demonstrated that the generative force of the gel was about a hundredth the generative force of a muscle in the body. We analyzed the time dependence of the color change in the self-oscillating polymer gel. The color of the gel changed periodically owing to the cyclic change in the redox state of the Ru moiety, induced by the BZ reaction. The peaks of the waveforms of the generative force and color change were almost identical. This result showed that the generative force was synchronized with the periodical change in the oxidation number of the Ru catalytic moiety in the gel. To understand a theoretical basis for the generative force of a self-oscillating gel, we considered a general theory that is based on the volume phase transition of gel and the two-parameter Oregonator model of the BZ reaction. PMID:24524539

  20. Moisture Transport in Silica Gel Particle Beds: I. Theoretical Study

    SciTech Connect

    Pesaran, A. A.; Mills, A. F.

    1986-08-01

    Diffusion mechanisms of moisture within silica gel particles are investigated. It is found that for microporous silica gel surface diffusion is the dominant mechanism of moisture transport, while for macroporous silica gel both Knudsen and surface diffusion are important.

  1. Comparison of BD Vacutainer SST Plus Tubes with BD SST II Plus Tubes for common analytes.

    PubMed

    Bush, V J; Janu, M R; Bathur, F; Wells, A; Dasgupta, A

    2001-04-01

    Serum separator tubes were introduced 25 years ago and are widely used in the clinical laboratory today for routine collection of blood. These tubes have gained widespread acceptance due to the advantage of the barrier gel that facilitates rapid separation of serum from cellular constituents of blood and thus reduces hemolysis. However, there are some limitations associated with gel tubes (i.e., gel stability and analyte incompatibilities). The serum separator BD SST tubes manufactured by BD are widely used in clinical laboratories. Recently, BD has developed a new barrier gel, which is superior to the existing gel. We studied the stability of common analytes when serum specimens were stored in the new BD SST II tubes by comparing the performance with the existing BD SST tubes. We did not observe any significant reduction in concentrations of 42 commonly ordered analytes using the new BD SST II tubes. Significant differences were noted at low serum volumes for estradiol in both tube types over time. We conclude that the new BD SST II tubes are suitable for collection of blood and storage of serum for commonly ordered laboratory tests. PMID:11282105

  2. Electromechanical coupling in polyelectrolyte gels

    NASA Astrophysics Data System (ADS)

    Prudnikova, Katsiaryna I.

    This work concerns the systematic characterization of the electromechanical coupling in polyelectrolyte gels (PGs) in correlation with their structure and physical properties in view of their potential application as pressure sensors. PGs are electroactive polymers that respond with an electrical potential difference to gradients in mechanical stress and vice versa. So far, these materials have mainly been studied as electrical actuators, but they can also be used as mechanical sensors. Polyelectrolyte gels are biocompatible, and could form the basis for incorporating tactile sensitivity into artificial skin systems. However, how PGs respond to mechanical stimuli in relation to their structure and electrochemical properties has not been studied systematically in a quantitative manner. In this work, the physical-electrochemical properties of copolymers of acrylamide and acrylic acid of varying compositions were characterized in terms of their equilibrium swelling degree, elastic modulus and Donnan potential. Experimental results were tested against the theory of large deformation and electrochemistry of PGs recently developed by Hong et al. Systematic characterization of the electromechanical coupling in PGs was carried out using a new quantitative test based on the indentation of a flat polymer sample with a spherical indenter, while the potential was monitored with an array of planar electrodes. The experimental results suggest that electromechanical coupling in soft PGs directly subjected to a pressure gradient can be understood as a pressure modulation of the Donnan potential. The idea of the potential application of PGs as pressure transducers was illustrated by showing the prototype of the PG spatially resolved sensor capable of distinguishing between sharp and blunt loads and the prototype of the PG pressure sensor in a microfluidic chip. Spatial resolution of both prototypes was solely given by the resolution of the patterned electrodes. The design framework of the potential application of PGs as sensing layers was discussed with a view to the limitations imposed by the increased electrical impedance and reduced signal-to-noise ratio of the voltage measurements on small-length scales. These limitations were experimentally verified by quantifying the electromechanical response with an array of planar electrodes of systematically varying size.

  3. Augmentation of Cooling Output by Silica Gel-Water Adsorption Cycle Utilizing the Waste Heat of GHP

    NASA Astrophysics Data System (ADS)

    Homma, Hiroki; Araki, Nobuyuki

    The GHP (Gas engine Heat Pump) system is expected to have high energy-efficiency in utilizing the waste heat exhausted from a gas engine. In summer season, a silica gel-water adsorption cooling unit driven by the exhaust heat is considered as a cooling system for saving energy. In this work, an attempt was made to improve the COP of a silica gel-water adsorption cooling system by enhancing heat and mass transfer in the silica gel adsorption layer. A unit cell was introduced as a simplified model of adsorber for analyzing the phenomena of heat and mass transfer in the adsorbent. This cell was composed of a single tube with a silica gel layer bonded on its external surface. Optimization of heat and mass transfer characteristics for the unit cell was carried out by experimental and analytical approach.

  4. Sampling and Sensing Systems for High Priority Analytes

    SciTech Connect

    Brinker, C.Jeffrey; Frye-Mason, Gregory C.; Kottenstette, Richard J.; Lewis, Patrick R.; Sasaki, Darryl Y.; Sellinger, Alan

    1999-04-01

    This reports summarizes the results from a Laboratory Directed Research and Development effort to develop selective coastings for detecting high priority analytes (HPAs), such as chemical warfare (CW) agents and their precursors, in the presence of common interferents. Accomplishments during this project included synthesis and testing of new derivatized sol-gel coatings for surface acoustic wave sensors (SAWs). Surfactant modified and fluoroalcohol derivatized sol-gel oxides were coated onto SAW devices and tested with volatile organic compounds (VOCs). Theses modified sol-gel coatings improved SAW sensitivity to DMMP by over three orders of magnitude when compared to standard polymeric oatings such as polyisobutylene and by over two orders of magnitude compared with polymers tailor made for enhanced sensitivity to phosphonates. SAW sensors coated with these materials exhibit highly sensitive reversible behavior at elevated temperatures (>90 degree C), possibly leading to low detection levels for semivolatile analytes while remaining insensitive to volatile organic interferants. Additionally, we have investigated the use of reactive polymers for detection of volatile and reactive CW agent precursors (Chemical Weapons Convention Schedule 3 Agents) such as phosphouous oxychloride (POCl(3)). The results obtained in this study find that sensitive and selective responses can be obtained for Schedule 3 agents using commercially available polymers and chemical guidelines from solution phase chemistry.

  5. Sol-gel manufactured energetic materials

    DOEpatents

    Simpson, Randall L.; Lee, Ronald S.; Tillotson, Thomas M.; Hrubesh, Lawrence W.; Swansiger, Rosalind W.; Fox, Glenn A.

    2003-12-23

    Sol-gel chemistry is used for the preparation of energetic materials (explosives, propellants and pyrotechnics) with improved homogeneity, and/or which can be cast to near-net shape, and/or made into precision molding powders. The sol-gel method is a synthetic chemical process where reactive monomers are mixed into a solution, polymerization occurs leading to a highly cross-linked three dimensional solid network resulting in a gel. The energetic materials can be incorporated during the formation of the solution or during the gel stage of the process. The composition, pore, and primary particle sizes, gel time, surface areas, and density may be tailored and controlled by the solution chemistry. The gel is then dried using supercritical extraction to produce a highly porous low density aerogel or by controlled slow evaporation to produce a xerogel. Applying stress during the extraction phase can result in high density materials. Thus, the sol-gel method can be used for precision detonator explosive manufacturing as well as producing precision explosives, propellants, and pyrotechnics, along with high power composite energetic materials.

  6. Electrically driven deformations of nematic gels

    NASA Astrophysics Data System (ADS)

    Urayama, Kenji; Kondo, Hidesato; Arai, Yuko O.; Takigawa, Toshikazu

    2005-05-01

    The electrically driven deformations of side chain nematic networks swollen by nematic solvents (nematic gels) have been investigated. The strains of freely suspended gels between electrodes were measured as a function of field strength (E) . The deformation of the gels composed of a network and solvent with identical signs of dielectric anisotropy (??) is dominated by the electrically induced alignment of the nematogens. As a result, the stretching direction is variable according to the sign of ?? : The gel with positive or negative ?? is elongated parallel or normal to the field axis, respectively. The maximum strain among the samples examined is as large as 20% at E?0.5MV/m . The gels composed of a network and solvent with opposite signs of ?? are compressed along the field axis since the electrostrictive effect becomes dominant because of a large reduction in the mesogen alignment effect due to the discord in the director directions of the constituent nematogens. The gels in the isotropic phase show compressive strains along the field direction in proportion to E2 purely originating from electrostriction, independently of the sign of ?? . The nematic gels are quickly deformed within a second upon field application, while the shape recovery after field removal requires a finite time on the order of 103s , which reflects the structural relaxation in the polydomain texture from the oriented to the random state. The influences of elastic modulus as well as network nematicity on the electrical deformation are also examined.

  7. Sol-Gel Manufactured Energetic Materials

    DOEpatents

    Simpson, Randall L.; Lee, Ronald S.; Tillotson, Thomas M.; Hrubesh, Lawrence W.; Swansiger, Rosalind W.; Fox, Glenn A.

    2005-05-17

    Sol-gel chemistry is used for the preparation of energetic materials (explosives, propellants and pyrotechnics) with improved homogeneity, and/or which can be cast to near-net shape, and/or made into precision molding powders. The sol-gel method is a synthetic chemical process where reactive monomers are mixed into a solution, polymerization occurs leading to a highly cross-linked three dimensional solid network resulting in a gel. The energetic materials can be incorporated during the formation of the solution or during the gel stage of the process. The composition, pore, and primary particle sizes, gel time, surface areas, and density may be tailored and controlled by the solution chemistry. The gel is then dried using supercritical extraction to produce a highly porous low density aerogel or by controlled slow evaporation to produce a xerogel. Applying stress during the extraction phase can result in high density materials. Thus, the sol-gel method can be used for precision detonator explosive manufacturing as well as producing precision explosives, propellants, and pyrotechnics, along with high power composite energetic materials.

  8. Halogen-bonding-triggered supramolecular gel formation

    NASA Astrophysics Data System (ADS)

    Meazza, Lorenzo; Foster, Jonathan A.; Fucke, Katharina; Metrangolo, Pierangelo; Resnati, Giuseppe; Steed, Jonathan W.

    2013-01-01

    Supramolecular gels are topical soft materials involving the reversible formation of fibrous aggregates using non-covalent interactions. There is significant interest in controlling the properties of such materials by the formation of multicomponent systems, which exhibit non-additive properties emerging from interaction of the components. The use of hydrogen bonding to assemble supramolecular gels in organic solvents is well established. In contrast, the use of halogen bonding to trigger supramolecular gel formation in a two-component gel (‘co-gel’) is essentially unexplored, and forms the basis for this study. Here, we show that halogen bonding between a pyridyl substituent in a bis(pyridyl urea) and 1,4-diiodotetrafluorobenzene brings about gelation, even in polar media such as aqueous methanol and aqueous dimethylsulfoxide. This demonstrates that halogen bonding is sufficiently strong to interfere with competing gel-inhibitory interactions and create a ‘tipping point’ in gel assembly. Using this concept, we have prepared a halogen bond donor bis(urea) gelator that forms co-gels with halogen bond acceptors.

  9. Electroacoustics of Particles Dispersed in Polymer Gel

    SciTech Connect

    Bhosale, Prasad S.; Chun, Jaehun; Berg, John C.

    2011-06-27

    This study examines the acoustic electrophoresis of particles dispersed in polymer hydrogels, with the particle size either less than or greater than the gel mesh size. When the particles are smaller than the gel mesh size, their acoustic vibration is resisted by only the background water medium, and the measured dynamic electrophoretic mobility, μd (obtained in terms of colloid vibration current, CVI), is the same as in water. For the case of particles larger than the gel mesh size, μd is decreased due to trapping, and the net decrease depends on the viscoelastic properties of the gel. The gel mesh size was varied by varying its crosslink density, the latter being characterized as the storage modulus, G’. The dependence of mobility on G’, for systems of a given particle size, and on particle size, for gels of a given G’, are investigated. The measured mobility remains constant as G’ is increased (i.e., mesh size is decreased) up to a value of approximately 300 Pa, beyond which it decreases. In the second set of measurements, the trapped particle size was increased in a gel medium of constant mesh size, with G’ approximately 100 Pa. In this case, the measured μd is found to be effectively constant over the particle size range studied (14-120 nm), i.e., it is independent of the degree of trapping as expressed by the ratio of the particle size to the mesh size.

  10. Nuclear analytical chemistry

    SciTech Connect

    Brune, D.; Forkman, B.; Persson, B.

    1984-01-01

    This book covers the general theories and techniques of nuclear chemical analysis, directed at applications in analytical chemistry, nuclear medicine, radiophysics, agriculture, environmental sciences, geological exploration, industrial process control, etc. The main principles of nuclear physics and nuclear detection on which the analysis is based are briefly outlined. An attempt is made to emphasise the fundamentals of activation analysis, detection and activation methods, as well as their applications. The book provides guidance in analytical chemistry, agriculture, environmental and biomedical sciences, etc. The contents include: the nuclear periodic system; nuclear decay; nuclear reactions; nuclear radiation sources; interaction of radiation with matter; principles of radiation detectors; nuclear electronics; statistical methods and spectral analysis; methods of radiation detection; neutron activation analysis; charged particle activation analysis; photon activation analysis; sample preparation and chemical separation; nuclear chemical analysis in biological and medical research; the use of nuclear chemical analysis in the field of criminology; nuclear chemical analysis in environmental sciences, geology and mineral exploration; and radiation protection.

  11. Requirements for Predictive Analytics

    SciTech Connect

    Troy Hiltbrand

    2012-03-01

    It is important to have a clear understanding of how traditional Business Intelligence (BI) and analytics are different and how they fit together in optimizing organizational decision making. With tradition BI, activities are focused primarily on providing context to enhance a known set of information through aggregation, data cleansing and delivery mechanisms. As these organizations mature their BI ecosystems, they achieve a clearer picture of the key performance indicators signaling the relative health of their operations. Organizations that embark on activities surrounding predictive analytics and data mining go beyond simply presenting the data in a manner that will allow decisions makers to have a complete context around the information. These organizations generate models based on known information and then apply other organizational data against these models to reveal unknown information.

  12. Analytical applications of aptamers

    NASA Astrophysics Data System (ADS)

    Tombelli, S.; Minunni, M.; Mascini, M.

    2007-05-01

    Aptamers are single stranded DNA or RNA ligands which can be selected for different targets starting from a library of molecules containing randomly created sequences. Aptamers have been selected to bind very different targets, from proteins to small organic dyes. Aptamers are proposed as alternatives to antibodies as biorecognition elements in analytical devices with ever increasing frequency. This in order to satisfy the demand for quick, cheap, simple and highly reproducible analytical devices, especially for protein detection in the medical field or for the detection of smaller molecules in environmental and food analysis. In our recent experience, DNA and RNA aptamers, specific for three different proteins (Tat, IgE and thrombin), have been exploited as bio-recognition elements to develop specific biosensors (aptasensors). These recognition elements have been coupled to piezoelectric quartz crystals and surface plasmon resonance (SPR) devices as transducers where the aptamers have been immobilized on the gold surface of the crystals electrodes or on SPR chips, respectively.

  13. Avatars in Analytical Gaming

    SciTech Connect

    Cowell, Andrew J.; Cowell, Amanda K.

    2009-08-29

    This paper discusses the design and use of anthropomorphic computer characters as nonplayer characters (NPC’s) within analytical games. These new environments allow avatars to play a central role in supporting training and education goals instead of planning the supporting cast role. This new ‘science’ of gaming, driven by high-powered but inexpensive computers, dedicated graphics processors and realistic game engines, enables game developers to create learning and training opportunities on par with expensive real-world training scenarios. However, there needs to be care and attention placed on how avatars are represented and thus perceived. A taxonomy of non-verbal behavior is presented and its application to analytical gaming discussed.

  14. Analytical caustic surfaces

    NASA Technical Reports Server (NTRS)

    Schmidt, R. F.

    1987-01-01

    This document discusses the determination of caustic surfaces in terms of rays, reflectors, and wavefronts. Analytical caustics are obtained as a family of lines, a set of points, and several types of equations for geometries encountered in optics and microwave applications. Standard methods of differential geometry are applied under different approaches: directly to reflector surfaces, and alternatively, to wavefronts, to obtain analytical caustics of two sheets or branches. Gauss/Seidel aberrations are introduced into the wavefront approach, forcing the retention of all three coefficients of both the first- and the second-fundamental forms of differential geometry. An existing method for obtaining caustic surfaces through exploitation of the singularities in flux density is examined, and several constant-intensity contour maps are developed using only the intrinsic Gaussian, mean, and normal curvatures of the reflector. Numerous references are provided for extending the material of the present document to the morphologies of caustics and their associated diffraction patterns.

  15. Analytical Chemistry Laboratory

    SciTech Connect

    Not Available

    1990-12-01

    This purpose of this report is to summarize the activities of the Analytical Chemistry Laboratory (ACL) at Argonne National Laboratory (ANL) for Fiscal Year 1990. The ACL has four technical groups -- Chemical Analysis, Instrumental Analysis, Organic Analysis, and Environmental Analysis. The Chemical Analysis Group uses wet-chemical and instrumental methods for elemental, compositional, and isotopic analyses of solid, liquid, and gaseous samples and provides specialized analytical services. The Instrumental Analysis Group uses nuclear counting techniques in radiochemical analyses over a wide range of sample types from low-level environmental samples to samples of high radioactivity. The Organic Analysis Group uses a number of complementary techniques to separate and to quantitatively and qualitatively analyze complex organic mixtures and compounds at the trace level, including synthetic fuels, toxic substances, fossil-fuel residues and emissions, pollutants, biologically active compounds, pesticides, and drugs. The Environmental Analysis Group performs analyses of inorganic environmental and hazardous waste and coal samples.

  16. Comparison of dye adsorption by mesoporous hybrid gels: understanding the interactions between dyes and gel surfaces.

    PubMed

    Wu, Zhijian; You, Laijiang; Xiang, Hong; Jiang, Yan

    2006-11-15

    Without using any templating agents, mesoporous hybrid gels were prepared using mixtures of tetraethoxysilane (TEOS) with n-propyltriethoxysilane (PTES), bis(trimethoxysilyl)hexane (TSH), or bis(trimethoxysilylpropyl)amine (TSPA) as precursors. Fourier transform infrared (FTIR), N2 adsorption/desorption, thermogravimetry (TG), point of zero charge (PZC), and water vapor adsorption measurements were used to characterize the gels. The adsorption of methyl orange (MO), methyl red (MR), bromocresol purple (BP), phenol red (PR), neutral red (NR), and brilliant blue FCF (BBF) by the gels in both 0.01 M HCl and 0.01 M NaOH solutions was compared comprehensively. The gel derived from TEOS/TSH (with -(CH2)6- groups, Gel 2) has the largest specific surface area (695 m2 g(-1)), the smallest pore volume (0.564 cm3 g(-1)), and the smallest average pore size (3.7 nm). The gels derived form TEOS/PTES (with -(CH2)2CH3 groups, Gel 1), and TEOS/TSPA (with -(CH2)3NH(CH2)3- groups, Gel 3) have similar textual properties. The PZC of Gels 1, 2, and 3 was estimated to be 6.28, 6.20, and 6.88, respectively. Gel 3 has the highest PZC due to the presence of -NH- groups. In general, Gel 2 shows the highest dye adsorption among all the gels in both acidic and basic solutions. All the dyes except NR have much lower adsorption in basic solutions than in acidic solutions. In acidic solutions Gels 1 and 2 have similar adsorption trends for the dyes, except for BP, with NR having the highest adsorption, and PR the lowest adsorption. Gel 3 presents a different trend from Gels 1 and 2, with BBF having the highest adsorption, and MR the lowest adsorption. In basic solutions the order of dye adsorption by all the gels is shown to follow the sequence NR>MR approximately BBF>MO>BP approximately PR. The adsorption results can be explained by considering the textural properties of the gels and the interactions between the gel surfaces and the dyes, which include hydrogen bonding, electrostatic, and hydrophobic interactions. PMID:16978636

  17. Competing on analytics.

    PubMed

    Davenport, Thomas H

    2006-01-01

    We all know the power of the killer app. It's not just a support tool; it's a strategic weapon. Companies questing for killer apps generally focus all their firepower on the one area that promises to create the greatest competitive advantage. But a new breed of organization has upped the stakes: Amazon, Harrah's, Capital One, and the Boston Red Sox have all dominated their fields by deploying industrial-strength analytics across a wide variety of activities. At a time when firms in many industries offer similar products and use comparable technologies, business processes are among the few remaining points of differentiation--and analytics competitors wring every last drop of value from those processes. Employees hired for their expertise with numbers or trained to recognize their importance are armed with the best evidence and the best quantitative tools. As a result, they make the best decisions. In companies that compete on analytics, senior executives make it clear--from the top down--that analytics is central to strategy. Such organizations launch multiple initiatives involving complex data and statistical analysis, and quantitative activity is managed atthe enterprise (not departmental) level. In this article, professor Thomas H. Davenport lays out the characteristics and practices of these statistical masters and describes some of the very substantial changes other companies must undergo in order to compete on quantitative turf. As one would expect, the transformation requires a significant investment in technology, the accumulation of massive stores of data, and the formulation of company-wide strategies for managing the data. But, at least as important, it also requires executives' vocal, unswerving commitment and willingness to change the way employees think, work, and are treated. PMID:16447373

  18. Industrial Analytics Corporation

    SciTech Connect

    Industrial Analytics Corporation

    2004-01-30

    The lost foam casting process is sensitive to the properties of the EPS patterns used for the casting operation. In this project Industrial Analytics Corporation (IAC) has developed a new low voltage x-ray instrument for x-ray radiography of very low mass EPS patterns. IAC has also developed a transmitted visible light method for characterizing the properties of EPS patterns. The systems developed are also applicable to other low density materials including graphite foams.

  19. Competing on talent analytics.

    PubMed

    Davenport, Thomas H; Harris, Jeanne; Shapiro, Jeremy

    2010-10-01

    Do investments in your employees actually affect workforce performance? Who are your top performers? How can you empower and motivate other employees to excel? Leading-edge companies such as Google, Best Buy, Procter & Gamble, and Sysco use sophisticated data-collection technology and analysis to answer these questions, leveraging a range of analytics to improve the way they attract and retain talent, connect their employee data to business performance, differentiate themselves from competitors, and more. The authors present the six key ways in which companies track, analyze, and use data about their people-ranging from a simple baseline of metrics to monitor the organization's overall health to custom modeling for predicting future head count depending on various "what if" scenarios. They go on to show that companies competing on talent analytics manage data and technology at an enterprise level, support what analytical leaders do, choose realistic targets for analysis, and hire analysts with strong interpersonal skills as well as broad expertise. PMID:20929194

  20. Evaluation of radiochromic gel dosimetry and polymer gel dosimetry in a clinical dose verification

    NASA Astrophysics Data System (ADS)

    Vandecasteele, Jan; De Deene, Yves

    2013-09-01

    A quantitative comparison of two full three-dimensional (3D) gel dosimetry techniques was assessed in a clinical setting: radiochromic gel dosimetry with an in-house developed optical laser CT scanner and polymer gel dosimetry with magnetic resonance imaging (MRI). To benchmark both gel dosimeters, they were exposed to a 6 MV photon beam and the depth dose was compared against a diamond detector measurement that served as golden standard. Both gel dosimeters were found accurate within 4% accuracy. In the 3D dose matrix of the radiochromic gel, hotspot dose deviations up to 8% were observed which are attributed to the fabrication procedure. The polymer gel readout was shown to be sensitive to B0 field and B1 field non-uniformities as well as temperature variations during scanning. The performance of the two gel dosimeters was also evaluated for a brain tumour IMRT treatment. Both gel measured dose distributions were compared against treatment planning system predicted dose maps which were validated independently with ion chamber measurements and portal dosimetry. In the radiochromic gel measurement, two sources of deviations could be identified. Firstly, the dose in a cluster of voxels near the edge of the phantom deviated from the planned dose. Secondly, the presence of dose hotspots in the order of 10% related to inhomogeneities in the gel limit the clinical acceptance of this dosimetry technique. Based on the results of the micelle gel dosimeter prototype presented here, chemical optimization will be subject of future work. Polymer gel dosimetry is capable of measuring the absolute dose in the whole 3D volume within 5% accuracy. A temperature stabilization technique is incorporated to increase the accuracy during short measurements, however keeping the temperature stable during long measurement times in both calibration phantoms and the volumetric phantom is more challenging. The sensitivity of MRI readout to minimal temperature fluctuations is demonstrated which proves the need for adequate compensation strategies.

  1. Critical behavior of modulus of gel

    NASA Astrophysics Data System (ADS)

    Tokita, Masayuki; Niki, Ryoya; Hikichi, Kunio

    1985-09-01

    The critical behavior of the shear modulus of casein gel is studied. The shear modulus of casein gel scales with the conductivity exponent in the immediate vicinity of the sol-gel transition point. The asymptotic behavior of the modulus in the region far above the transition point is governed by a different exponent which is much larger than the conductivity exponent. These results are explainable by the crossover behavior of the percolation process. This study shows that the gelation of the casein micelle solution is a realization of the percolation process.

  2. Muscular Contraction Mimiced by Magnetic Gels

    NASA Astrophysics Data System (ADS)

    Zrínyi, Miklós; Szabó, Dénes

    The ability of magnetic-field-sensitive gels to undergo a quick controllable change of shape can be used to create an artificially designed system possessing sensor- and actuator functions internally in the gel itself. The peculiar magneto-elastic properties may be used to create a wide range of motion and to control the shape change and movement, that are smooth and gentle similar to that observed in muscle. Magnetic field sensitive gels provide attractive means of actuation as artificial muscle for biomechanics and biomimetic applications.

  3. Silver staining techniques of polyacrylamide gels.

    PubMed

    Bartsch, Holger; Arndt, Claudia; Koristka, Stefanie; Cartellieri, Marc; Bachmann, Michael

    2012-01-01

    Although the main application for polyacrylamide gels is the separation and subsequent blotting of proteins for immunodetection, there are tasks that need staining of proteins in the polyacrylamide gel. Several different staining techniques exist for protein staining in SDS gels that differ in their sensitivity, their expenditure of time, and other aspects. Still, silver staining is the most sensitive and reliable staining technique. Because this technique was developed in the 1970s, a huge number of variations exist. Therefore, we will provide herein three methods, which are robust and easy to perform. PMID:22585513

  4. Growth kinetics and structure of fibrin gels

    NASA Astrophysics Data System (ADS)

    Ferri, F.; Greco, M.; Arcovito, G.; Bassi, F. Andreasi; de Spirito, M.; Paganini, E.; Rocco, M.

    2001-03-01

    The structure and kinetics of fibrin gels grown from fibrinogen solutions under quasiphysiological conditions, but in absence of Ca++, were investigated by means of elastic light scattering. By combining classical light scattering and low-angle elastic light scattering, an overall wave-vector range of about three decades was spanned, from q~3×102 to q~3×105 cm-1. The scattered intensity distribution of the gels was measured in absolute units and fitted to a single function, which was able to reproduce accurately the data over the entire wave-vector range. From the fitting, it was possible to estimate the average diameter d of the fibrin fibers, the average crossover length ξ of the gel, and establish the fractal nature of the gel structure, with a measure of its fractal dimension Dm. The measure of the intensity in absolute units also allowed the estimate of the density ρ of the fibrin fibers and provided an independent measure of their size. The kinetics of formation of the gel was described in terms of a simple growth model: the scaffold of the network is formed very early in the course of the gelation process, at a ``networking time,'' tn, which is much smaller than the time required to form the final gel. At times t>tn, the gel structure remains substantially unchanged and the successive growth consists only in a thickening of the gel fibers. Gels prepared under the same physical-chemical conditions, but at different fibrinogen concentrations, exhibited rather similar structures and kinetics, showing that the modalities of the gelation process are mainly governed by the solution conditions, and only secondarily by the fibrinogen concentration. For gels at fibrinogen concentration of ~0.24 mg/ml, the gel parameters were d~130 nm, ξ~27 μm, Dm~1.3, and ρ~0.4 g/cm3. Our d and ρ values are in very good agreement with electron microscopy- and turbidity-derived literature data, respectively, while ξ seems to be related to the mesh size of the initial scaffold formed at tn, rather than to the mesh size of the final aged gel.

  5. Detection of PEGylated proteins in polyacrylamide gels by reverse staining with zinc and imidazole salts.

    PubMed

    Hardy, Eugenio; Ramón, José; Saez, Vivian; Báez, Reynier; Tejeda, Yosbel; Ruiz, Amalia

    2008-06-01

    The reverse staining, with imidazole-SDS-zinc, of PEG-linked proteins separated by SDS-PAGE was studied. Using model conjugates (interferon-alpha 2b (IFN-alpha2b) reacted with either a branched-chain (40,000) PEG (PEG2,40) or a linear monomethoxy PEG polymer (Mr of 12,000) and chromatographically purified monoPEG2,40-IFN-alpha2b), conventional small-format analytical gels (<1 mm thick) showed typical detection patterns (i.e., transparent, colorless bands clearly discernible against a zinc imidazolate-generated white gel background), in less than 20 min. Nonreacted (free) PEG was almost undetected, as expected. The reverse-stained PEGylated IFN-alpha2b patterns were qualitatively indistinguishable from those of parallel gels stained with iodine (I2). The LOD was estimated in the low nanogram range (e.g., at about 7 ng for mono- or bi-PEG2,40 IFN-alpha2b per lane on gradient (4-17%) gels). Also, this stain allowed the visualization of Coomassie blue-undetected PEG-IFN bands, and could be restained with I2. PEGylated species of lysozyme, a low-molecular-weight peptide, ovalbumin, and chymotrypsin were used to demonstrate the generality of this stain. We also show (i) how to counteract the adverse effect of some parameters (e.g., gel thickness above 1 mm, long gel length, low (e.g., 4-6%) acrylamide concentration) on the reverse staining process and (ii) that the properties of the reverse-stained PEGylated proteins remain unchanged, as judged by analyzing both the ion exchange chromatography-based positional isomer separation profile and enzyme-linked immunosorbent response of PEG-IFN recovered from gels. Consequently, this technique may be useful for the rapid analysis or the small-scale preparation of PEGylated proteins. PMID:18449861

  6. Chemical sensing using sol-gel derived planar waveguides and indicator phases

    SciTech Connect

    Yang, L.; Saavedra, S.S.

    1995-04-15

    A new optical sensing platform based on a combination of planar waveguiding and sol-gel processing technologies is described. The sensing element consists of two, submicrometer thick glass layers supported on an optically thick glass substrate; both layers were fabricated using a sol-gel coating method. The lower layer is a densified glass that functions as a planar integrated optical waveguide (IOW). The upper layer is an undensified glass of lower index doped with an optical indicator that is immobilized, yet remains sterically accessible to analytes that diffuse into the pore network. Formation of a complex between the analyte and indicator is detected via attenuated total reflection (ATR) of light guided in the IOW. Feasibility was evaluated by constructing IOW-ATR sensors for Pb{sup 2+} and pH, based on immobilized xylenol orange and bromocresol purple, respectively. The response of both sensors was sensitive and rapid, features that are difficult to achieve simultaneously in monolithic sol-gel glass sensors. In the IOW-ATR geometry, these features are realized simultaneously because the primary axes of light propagation and analyte diffusion are orthogonal. The overall approach is technically simple, inexpensive, and applicable to a wide variety of indicator chemistries. 48 refs., 8 figs.

  7. Novel hybrid sol-gel materials for smart sensor windows

    NASA Astrophysics Data System (ADS)

    Wencel, Dorota; Higgins, Clare; Guckian, Adrian; McDonagh, Colette; MacCraith, Brian D.

    2005-06-01

    Current sensor trends, such as multianalyte capability, miniaturisation and patternability are important drivers for materials requirements in optical chemical sensors. In particular, issues such as enhanced sensitivity and printablity are key in developing optimised sensor materials for smart windows for bioprocessing applications. This study focuses on combining novel sol-gel-based hybrid matrices with engineered luminescent complexes to produce stable luminescence-based optical sensors with enhanced sensitivity for a range of analytes including oxygen, pH and carbon dioxide. As well as optimising sensor performance, issues such as surface modification of the plastic substrate and compatibility with different deposition techniques were addressed. Hybrid sol-gel matrices were developed using a range of precursors including tetraethoxysilane (TEOS), methyltriethoxysilane (MTEOS), ethyltriethoxysilane (ETEOS), n-propyltriethoxysilane (PTEOS), phenyltriethoxysilane (PhTEOS), and n-octyltriethoxysilane (C8TEOS). Oxygen sensing, based on luminescence quenching of ruthenium phenanthroline complexes, has been realised with each of these hybrid materials. Furthermore, the possibility of immobilising pH-indicators for pH and carbon dioxide sensing has been investigated with some success. In the context of in-situ monitoring of bioprocesses, issues such as humidity interference as well as the chemical robustness of the multianalyte platform, were addressed.

  8. Stability measurements of antisense oligonucleotides by capillary gel electrophoresis.

    PubMed

    Bruin, G J; Börnsen, K O; Hüsken, D; Gassmann, E; Widmer, H M; Paulus, A

    1995-08-11

    The approach of using antisense oligonucleotides as potential drugs is based on hybridization of a short chemically-modified oligonucleotide with complementary cellular DNA or RNA sequences. A critical question is the stability of chemically modified antisense oligonucleotides in cellular environments. In a model system, resistance against various nucleases was evaluated by capillary gel electrophoresis (CGE). For some of the samples, matrix assisted laser desorption and ionization mass spectrometry (MALDI-MS) was used as an additional analytical tool to perform stability measurements. Using CGE, the enzymatic degradation of single nucleotides from the oligomer can be followed after different incubation times. 10% T polyacrylamide gels give baseline resolution for oligonucleotides ranging between 5 and 30 bases in length. The kinetic influence of a specific nuclease concentration and the antisense oligonucleotide structure on the cleavage reaction are discussed. Also, a simple desalting method to improve the injection efficiency and sensitivity of the method are described. Examples of measurements of chemically modified antisense 19-mers are presented. PMID:7581844

  9. Deceptive responsive genes in gel-based proteomics.

    PubMed

    Hamzelou, Sara; Askari, Hossein; Nobari, Nona Abolfathi

    2016-04-01

    The standard method of the global quantitative analysis of gene expression at the protein level combines high-resolution two-dimensional gel electrophoresis (2DE) with mass spectrometric identification of protein spots. One of the major concerns with the application of gel-based proteomics is the need for the analytical and biological accuracy of the datasets. We mathematically and empirically simulated the possibility of the technical regulations of gene expression using 2DE. Our developed equation predicted a detectable alteration in the quantity of protein spots in response to a new protein added in, with various amounts. Testing the predictability of the developed equation, we observed that a new protein could form deceptive expression profiles, classified using prevalent tools for the analysis of 2DE results. In spite of the theoretically predicted overall reduction of proteins that resulted from adding the new protein, the empirical data revealed differential amount of proteins when various quantities of the new protein were added to the protein sample. The present work emphasize that employment of 2DE would not be a reliable approach for biological samples with extensive proteome alterations such as the developmental and differentiation stages of cells without depletion of high abundant proteins. PMID:26706775

  10. Energy dependence of Fricke-xylenol orange gel and gel based on Turnbull blue for low-energy photons

    NASA Astrophysics Data System (ADS)

    Šolc, Jaroslav; Sochor, Vladimír; Kozubíková, Petra

    2015-01-01

    The paper describes the energy dependence of two types of radiochromic gels, a Fricke-xylenol orange gel (FX gel) and a gel based on Turnbull blue (TB gel), on low energy photons between 14 and 145 keV. Gel samples were irradiated at reference photon fields at the Czech Metrology Institute and evaluated by two independent optical methods. Measurements revealed that the response of the TB gel is independent on photon energy down to at least 14 keV photons, while the FX gel is energy dependent for photons below roughly 50 keV.

  11. Visual Analytics: How Much Visualization and How Much Analytics?

    SciTech Connect

    Keim, Daniel; Mansmann, Florian; Thomas, James J.

    2009-12-16

    The term Visual Analytics has been around for almost five years by now, but still there are on-going discussions about what it actually is and in particular what is new about it. The core of our view on Visual Analytics is the new enabling and accessible analytic reasoning interactions supported by the combination of automated and visual analytics. In this paper, we outline the scope of Visual Analytics using two problem and three methodological classes in order to work out the need for and purpose of Visual Analytics. Thereby, the respective methods are explained plus examples of analytic reasoning interaction leading to a glimpse into the future of how Visual Analytics methods will enable us to go beyond what is possible when separately using the two methods.

  12. Manual control of catalytic reactions: Reactions by an apoenzyme gel and a cofactor gel

    NASA Astrophysics Data System (ADS)

    Kobayashi, Yuichiro; Takashima, Yoshinori; Hashidzume, Akihito; Yamaguchi, Hiroyasu; Harada, Akira

    2015-11-01

    Enzymes play a vital role in catalysing almost all chemical reactions that occur in biological systems. Some enzymes must form complexes with non-protein molecules called cofactors to express catalytic activities. Although the control of catalytic reactions via apoenzyme-cofactor complexes has attracted significant attention, the reports have been limited to the microscale. Here, we report a system to express catalytic activity by adhesion of an apoenzyme gel and a cofactor gel. The apoenzyme and cofactor gels act as catalysts when they form a gel assembly, but they lose catalytic ability upon manual dissociation. We successfully construct a system with switchable catalytic activity via adhesion and separation of the apoenzyme gel with the cofactor gel. We expect that this methodology can be applied to regulate the functional activities of enzymes that bear cofactors in their active sites, such as the oxygen transport of haemoglobin or myoglobin and the electron transport of cytochromes.

  13. Manual control of catalytic reactions: Reactions by an apoenzyme gel and a cofactor gel

    PubMed Central

    Kobayashi, Yuichiro; Takashima, Yoshinori; Hashidzume, Akihito; Yamaguchi, Hiroyasu; Harada, Akira

    2015-01-01

    Enzymes play a vital role in catalysing almost all chemical reactions that occur in biological systems. Some enzymes must form complexes with non-protein molecules called cofactors to express catalytic activities. Although the control of catalytic reactions via apoenzyme–cofactor complexes has attracted significant attention, the reports have been limited to the microscale. Here, we report a system to express catalytic activity by adhesion of an apoenzyme gel and a cofactor gel. The apoenzyme and cofactor gels act as catalysts when they form a gel assembly, but they lose catalytic ability upon manual dissociation. We successfully construct a system with switchable catalytic activity via adhesion and separation of the apoenzyme gel with the cofactor gel. We expect that this methodology can be applied to regulate the functional activities of enzymes that bear cofactors in their active sites, such as the oxygen transport of haemoglobin or myoglobin and the electron transport of cytochromes. PMID:26537172

  14. Sol-gel deposited electrochromic coatings

    SciTech Connect

    Ozer, N.; Lampert, C.M.

    1995-06-01

    Electrochromic devices have increasing application in display devices, switchable mirrors and smart windows. A variety of vacuum deposition technologies have been used to make electrochromic devices. The sol- gel process offers an alternative approach to the synthesis of optical quality and low cost electrochromic device layers. This study summarizes the developments in sol-gel deposited electrochromic films. The sol-gel process involves the formation of oxide networks upon hydrolysis-condensation of alkoxide precursors. In this study we cover the sol-gel deposited oxides of WO[sub 3], V[sub 2]O[sub 5], TiO[sub 2], Nb[sub 2]O[sub 5], and NiO[sub x].

  15. K-Basin gel formation studies

    SciTech Connect

    Beck, M.A.

    1998-07-23

    A key part of the proposed waste treatment for K Basin sludge is the elimination of reactive uranium metal by dissolution in nitric acid (Fkirnent, 1998). It has been found (Delegard, 1998a) that upon nitric acid dissolution of the sludge, a gel sometimes forms. Gels are known to sometimes impair solid/liquid separation and/or material transfer. The purpose of the work reported here is to determine the cause(s) of the gel formation and to determine operating parameters for the sludge dissolution that avoid formation of gel. This work and related work were planned in (Fkunent, 1998), (Jewett, 1998) and (Beck, 1998a). This report describes the results of the tests in (Beck, 1998a) with non-radioactive surrogates.

  16. Procedure to prepare transparent silica gels

    NASA Technical Reports Server (NTRS)

    Barber, Patrick G. (Inventor); Simpson, Norman R. (Inventor)

    1987-01-01

    This invention relates to the production of silica gels and in particular to a process for the preparation of silica gels which can be used as a crystal growth medium that simulates the convectionless environment of space to produce structurally perfect crystals. Modern utilizations of substances in electronics, such as radio transmitters and high frequency microphones, often require single crystals with controlled purity and structural perfection. The near convectionless environment of silica gel suppresses nucleation, thereby reducing the competitive nature of crystal growth. This competition limits the size and perfection of the crystal; and it is obviously desirable to suppress nucleation until, ideally, only one crystal grows in a predetermined location. A silica gel is not a completely convectionless environment like outer space, but is the closest known environment to that of outer space that can be created on Earth.

  17. Sol-gel antireflective coating on plastics

    SciTech Connect

    Ashley, C.S.; Reed, S.T.

    1990-05-29

    This patent describes an antireflection film made from a reliquified sol-gel hydrolyzation, condensation polymeric reaction product of a silicon, alkoxides and/or metal alkoxides, or mixtures thereof. The film is particularly useful for coating plastics.

  18. Turbidimetric studies of Limulus coagulin gel formation.

    PubMed Central

    Moody, T P; Donovan, M A; Laue, T M

    1996-01-01

    The turbidity during trypsin-induced coagulin gel formation was studied over a range of wavelengths. The range of wavelengths used (686-326 nm) also made it possible to investigate the dependence of turbidity on wavelength (the wavelength exponent). Using the results from that work, and structural information on coagulin and the coagulin gel from other studies, a model gel-forming system was designed that consists of species for which the turbidity can be calculated relatively simply. These species include small particles (small in all dimensions relative to the wavelength of incident light); long rods and long random coils (particles that are large in just one dimension relative to the wavelength of incident light); and reflective regions (aggregated material that is large in more than one dimension relative to the wavelength of incident light). The turbidimetric characteristics of the real coagulin gel-forming system are compared with those of the model system. PMID:8889175

  19. Buckling of paramagnetic chains in soft gels.

    PubMed

    Huang, Shilin; Pessot, Giorgio; Cremer, Peet; Weeber, Rudolf; Holm, Christian; Nowak, Johannes; Odenbach, Stefan; Menzel, Andreas M; Auernhammer, Gnter K

    2015-12-16

    We study the magneto-elastic coupling behavior of paramagnetic chains in soft polymer gels exposed to external magnetic fields. To this end, a laser scanning confocal microscope is used to observe the morphology of the paramagnetic chains together with the deformation field of the surrounding gel network. The paramagnetic chains in soft polymer gels show rich morphological shape changes under oblique magnetic fields, in particular a pronounced buckling deformation. The details of the resulting morphological shapes depend on the length of the chain, the strength of the external magnetic field, and the modulus of the gel. Based on the observation that the magnetic chains are strongly coupled to the surrounding polymer network, a simplified model is developed to describe their buckling behavior. A coarse-grained molecular dynamics simulation model featuring an increased matrix stiffness on the surfaces of the particles leads to morphologies in agreement with the experimentally observed buckling effects. PMID:26463270

  20. Gel pad application for automated breast sonography.

    PubMed

    Kim, Yun Ju; Kim, Sung Hun; Jeh, Su Kyung; Choi, Jae Jeong; Kang, Bong Joo; Song, Byung Joo

    2015-04-01

    The purpose of this study was to describe the technical aspects of gel pad application for automated breast sonography and to show its effects on pain relief, scan coverage, and image quality. Twenty patients underwent 2 sets of automated breast sonography with and without gel pad application and were then asked to provide feedback on the examination-related pain. Scan coverage and image quality were compared quantitatively and qualitatively. The degree of pain was significantly decreased after gel pad application (P < .0001). The scan coverage was expanded particularly at the mid-portion of the breast. Image quality was satisfactory without significant differences between the sets. Gel pad application for automated breast sonography is easy and provides significant pain relief. The scan coverage was expanded, while the image quality was maintained. PMID:25792588

  1. Sol-gel antireflective coating on plastics

    DOEpatents

    Ashley, Carol S.; Reed, Scott T.

    1990-01-01

    An antireflection film made from a reliquified sol-gel hydrolyzation, condensation polymeric reaction product of a silicon, alkoxides and/or metal alkoxides, or mixtures thereof. The film is particularly useful for coating plastics.

  2. Sol-gel antireflective coating on plastics

    DOEpatents

    Ashley, C.S.; Reed, S.T.

    1988-01-26

    An antireflection film made from reliquified sol-gel hydrolyzation, condensation polymeric reaction product of a silicon, alkoxides and/or metal alkoxides, or mixtures thereof. The film is particularly useful for coating plastics.

  3. Prepartially crosslinked gel for retarding fluid flow

    SciTech Connect

    Sandiford, B.B.; Chiou, C.S.

    1987-05-19

    This patent describes a subterranean formation having channels which have a high permeability to the flow of fluids. A process for retarding fluid flow in the channels comprises: providing a gel-forming composition which when substantially completely gelled in the high permeability channels is operable for retarding fluid flow therein. The gel-forming composition comprises: an aqueous solution comprising a first substance selected from the group consisting of polyvinyl alcohol, a polyvinyl alcohol copolymer, and mixtures thereof, and an effective amount of a second substance selected from the group consisting of aldehydes, aldehyde generating substances, acetals, acetal generating substances, and mixtures thereof capable of crosslinking with the first substance through the formation of acetal crosslinkages. The second substance is operable for forming a gel with the aqueous solution when the gel-forming composition is acidic.

  4. Polyelectrolyte gels in poor solvent: Elastic moduli

    NASA Astrophysics Data System (ADS)

    Vilgis, T. A.; Johner, A.; Joanny, J. F.

    2000-11-01

    We study theoretically using scaling arguments the behavior of polyelectrolyte gels in poor solvents. Following the classical picture of Katchalsky, our approach is based on single-chain elasticity but it accounts for the recently proposed pearl necklace structure of polyelectrolytes in poor solvents. The elasticity both of gels at swelling equilibrium and of partially swollen gels is studied when parameters such as the ionic strength or the fraction of charged monomers are varied. Our theory could be useful to interpret recent experiments performed in Strasbourg that show that if identical gel samples are swollen to the same extent at different pH the sample with the highest charge has the lowest shear modulus.

  5. Large deformation analysis of gellan gels

    NASA Astrophysics Data System (ADS)

    Kawai, Shinnosuke; Nitta, Yoko; Nishinari, Katsuyoshi

    2007-08-01

    Gellan gel, a typical polysaccharide gel, is ruptured with different deformation behaviors from gelatin gel or rubber. It exhibits both strain hardening and softening; hardening is observed for moderate strain and softening occurs for larger strain. From the analyses of stress-strain curves of gellan gels, we propose forms of strain energy function. The fit with the proposed equation was excellent, while the existing models fail because they consider only one of hardening or softening effect. Furthermore, these equations are shown to be capable of extracting the hardening and softening effects separately from the observed stress-strain curves. By using these fitting equations, the concentration dependences of hardening and softening are investigated. It is shown that the degrees of hardening and softening both increase with increasing gellan concentration.

  6. Sample collection system for gel electrophoresis

    DOEpatents

    Olivares, Jose A.; Stark, Peter C.; Dunbar, John M.; Hill, Karen K.; Kuske, Cheryl R.; Roybal, Gustavo

    2004-09-21

    An automatic sample collection system for use with an electrophoretic slab gel system is presented. The collection system can be used with a slab gel have one or more lanes. A detector is used to detect particle bands on the slab gel within a detection zone. Such detectors may use a laser to excite fluorescently labeled particles. The fluorescent light emitted from the excited particles is transmitted to low-level light detection electronics. Upon the detection of a particle of interest within the detection zone, a syringe pump is activated, sending a stream of buffer solution across the lane of the slab gel. The buffer solution collects the sample of interest and carries it through a collection port into a sample collection vial.

  7. White gels: an easy way to preserve methylene blue stained gels.

    PubMed

    Soto, Ana Maria; Draper, David

    2012-02-01

    Methylene blue can be used as a stain for visualizing nucleic acids in polyacrylamide gel electrophoresis. However, its relatively low sensitivity and reversible binding make it a temporary stain that diffuses from the gel relatively fast. Here we describe a very simple method for fixing methylene blue bands in nucleic acid polyacrylamide gels. The procedure makes the methylene blue stain permanent and increases the visibility of the bands, also contributing to increasing the sensitivity of methylene blue. PMID:22107889

  8. A method for the direct measurement of glycogen synthase activity on gels after polyacrylamide gel electrophoresis.

    PubMed

    Krisman, C R; Blumenfeld, M L

    1986-05-01

    A method for the detection of glycogen synthase activity after nondenaturing polyacrylamide gel electrophoresis is described. After the electrophoretical run, the gels were incubated in situ with UDP-glucose and glycogen. Labeled or unlabeled UDP-glucose could be used, since similar activity patterns were obtained by autoradiography or iodine staining of the gels. The method here described offers several advantages in terms of speed, sensitivity, and economy when compared with other procedures. PMID:2425655

  9. A Practical Use for FXG Gel Dosimetry

    NASA Astrophysics Data System (ADS)

    Olding, T.; Salomons, G.; Darko, J.; Schreiner, L. J.

    2010-11-01

    In-phantom Fricke-xylenol orange-gelatin (FXG) gel dosimetry yields three dimensional (3D) dose data for intensity modulated radiation therapy (IMRT) treatment plan verification within 18-24 hours from the point of request. The information obtained from a 3% dose difference, 3 mm distance-to-agreement gamma function comparison between treatment plan dose and gel-measured dose then provides a useful secondary 3D quality assurance check of the treatment plan prior to delivery.

  10. Sol-Gels for Optical Sensors

    NASA Astrophysics Data System (ADS)

    Podbielska, Halina; Ulatowska-Jarża, Agnieszka; Müller, Gerhard; Eichler, Hans J.

    Sol-gel process allows for formation of glassy and ceramics materials in temperatures much lower than offered by conventional melting techniques. The first paper on sol-gels was published over 150 years ago by Ebelmen, however, the rapid development of this technology and applications occurred in the last few years. There is a broad range of possible applications of solgel derived materials, what marked this technology as one of the most promising fields of contemporary material sciences

  11. Annular gel reactor for chemical pattern formation

    DOEpatents

    Nosticzius, Zoltan; Horsthemke, Werner; McCormick, William D.; Swinney, Harry L.; Tam, Wing Y.

    1990-01-01

    The present invention is directed to an annular gel reactor suitable for the production and observation of spatiotemporal patterns created during a chemical reaction. The apparatus comprises a vessel having at least a first and second chamber separated one from the other by an annular polymer gel layer (or other fine porous medium) which is inert to the materials to be reacted but capable of allowing diffusion of the chemicals into it.

  12. Protein detection in gels using fixation.

    PubMed

    Echan, Lynn A; Speicher, David W

    2002-11-01

    This unit has been recently updated to include information on preformulated gel stains as well as new protocols for Sypro Ruby and silver staining, and gel imaging methodology. Other previously published protocols are also provided for both rapid and acid-based Coomassie blue staining, and alternate methods for silver staining (i.e., nonammoniacal silver staining, rapid silver staining, and an enhanced-background, two-stage method). PMID:18429221

  13. MERRA Analytic Services

    NASA Astrophysics Data System (ADS)

    Schnase, J. L.; Duffy, D. Q.; McInerney, M. A.; Tamkin, G. S.; Thompson, J. H.; Gill, R.; Grieg, C. M.

    2012-12-01

    MERRA Analytic Services (MERRA/AS) is a cyberinfrastructure resource for developing and evaluating a new generation of climate data analysis capabilities. MERRA/AS supports OBS4MIP activities by reducing the time spent in the preparation of Modern Era Retrospective-Analysis for Research and Applications (MERRA) data used in data-model intercomparison. It also provides a testbed for experimental development of high-performance analytics. MERRA/AS is a cloud-based service built around the Virtual Climate Data Server (vCDS) technology that is currently used by the NASA Center for Climate Simulation (NCCS) to deliver Intergovernmental Panel on Climate Change (IPCC) data to the Earth System Grid Federation (ESGF). Crucial to its effectiveness, MERRA/AS's servers will use a workflow-generated realizable object capability to perform analyses over the MERRA data using the MapReduce approach to parallel storage-based computation. The results produced by these operations will be stored by the vCDS, which will also be able to host code sets for those who wish to explore the use of MapReduce for more advanced analytics. While the work described here will focus on the MERRA collection, these technologies can be used to publish other reanalysis, observational, and ancillary OBS4MIP data to ESGF and, importantly, offer an architectural approach to climate data services that can be generalized to applications and customers beyond the traditional climate research community. In this presentation, we describe our approach, experiences, lessons learned,and plans for the future.; (A) MERRA/AS software stack. (B) Example MERRA/AS interfaces.

  14. Influence of drying conditions of zirconium molybdate gel on performance of (99m)Tc gel generator.

    PubMed

    Davarpanah, M R; Attar Nosrati, S; Fazlali, M; Kazemi Boudani, M; Khoshhosn, H; Ghannadi Maragheh, M

    2009-10-01

    (99m)Tc can be produced from (99)Mo/(99m)Tc gel generators. These gels are part of the generator and the (99)Mo/(99m)Tc gel generator performance is directly related with gel structure. In this work a series of zirconium molybdate gels have been synthesized and dried under different conditions and characterized using thermal analysis (TGA, DTA), SEM, XRD and porosity measurements. It is found that the water content of the gel determines the structure porosity which allows the diffusion of the (99m)TcO(4)(-) ions inside the gel and was directly connected with performance of the (99)Mo/(99m)Tc gel generators. Drying conditions of the gel is as an important factor that influence water content and physical-chemical properties of this gel and must be carefully studied to optimize the properties of the gel generators. PMID:19640723

  15. Cavitation of a Physically Associating Gel

    NASA Astrophysics Data System (ADS)

    Mishra, Satish; Kundu, Santanu

    Self-assembly of block copolymers in selective solvents form ordered structures such as micelles, vesicles, and physically crosslinked gels due to difference in their interaction with solvents. These gels have wide range of applications in tissue engineering, food science and biomedical field due to their tunable properties and responsiveness with changing environmental conditions. Pressurization of a defect inside a physically associating gel can lead to elastic instability (cavitation) leading to failure of the gel. The failure behavior involves dissociation of physical networks. A thermoreversible, physically associating gel with different volume fractions of a triblock copolymer, poly (methyl methacrylate)-poly (n-butyl acrylate)-poly (methyl methacrylate) [PMMA-PnBA-PMMA] in 2-ethyl 1-hexanol, a midblock selective solvent, is considered here. Mechanical properties were investigated using shear rheology and cavitation experiments. The experimental data is fitted with a constitutive model that captures the stiffening behavior followed by softening behavior of a physical gel. Finite element analysis has been performed on cavitation rheology geometry to capture the failure behavior and to calculate energy release rate during cavitation experiments.

  16. Microstructure and rheology of thermoreversible nanoparticle gels.

    PubMed

    Ramakrishnan, S; Zukoski, C F

    2006-08-29

    Naïve mode coupling theory is applied to particles interacting with short-range Yukawa attractions. Model results for the location of the gel line and the modulus of the resulting gels are reduced to algebraic equations capturing the effects of the range and strength of attraction. This model is then applied to thermo reversible gels composed of octadecyl silica particles suspended in decalin. The application of the model to the experimental system requires linking the experimental variable controlling strength of attraction, temperature, to the model strength of attraction. With this link, the model predicts temperature and volume fraction dependencies of gelation and modulus with five parameters: particle size, particle volume fraction, overlap volume of surface hairs, and theta temperature. In comparing model predictions with experimental results, we first observe that in these thermal gels there is no evidence of clustering as has been reported in depletion gels. One consequence of this observation is that there are no additional adjustable parameters required to make quantitative comparisons between experimental results and model predictions. Our results indicate that the naïve mode coupling approach taken here in conjunction with a model linking temperature to strength of attraction provides a robust approach for making quantitative predictions of gel mechanical properties. Extension of model predictions to additional experimental systems requires linking experimental variables to the Yukawa strength and range of attraction. PMID:16922571

  17. Actuation and ion transportation of polyelectrolyte gels

    NASA Astrophysics Data System (ADS)

    Hong, Wei; Wang, Xiao

    2010-04-01

    Consisting of charged network swollen with ionic solution, polyelectrolyte gels are known for their salient characters including ion exchange and stimuli responsiveness. The active properties of polyelectrolyte gels are mostly due to the migration of solvent molecules and solute ions, and their interactions with the fixed charges on the network. In this paper, we extend the recently developed nonlinear field theory of polyelectrolyte gels by assuming that the kinetic process is limited by the rate of the transportation of mobile species. To study the coupled mechanical deformation, ion migration, and electric field, we further specialize the model to the case of a laterally constrained gel sheet. By solving the field equations in two limiting cases: the equilibrium state and the steady state, we calculate the mechanical responses of the gel to the applied electric field, and study the dependency on various parameters. The results recover the behavior observed in experiments in which polyelectrolyte gels are used as actuators, such as the ionic polymer metal composite. In addition, the model reveals the mechanism of the selectivity in ion transportation. Although by assuming specific material laws, the reduced system resembles those in most existing models in the literature, the theory can be easily generalized by using more realistic free-energy functions and kinetic laws. The adaptability of the theory makes it suitable for studying many similar material systems and phenomena.

  18. Actuator device utilizing a conductive polymer gel

    DOEpatents

    Chinn, Douglas A.; Irvin, David J.

    2004-02-03

    A valve actuator based on a conductive polymer gel is disclosed. A nonconductive housing is provided having two separate chambers separated by a porous frit. The conductive polymer is held in one chamber and an electrolyte solution, used as a source of charged ions, is held in the second chamber. The ends of the housing a sealed with a flexible elastomer. The polymer gel is further provide with electrodes with which to apply an electrical potential across the gel in order to initiate an oxidation reaction which in turn drives anions across the porous frit and into the polymer gel, swelling the volume of the gel and simultaneously contracting the volume of the electrolyte solution. Because the two end chambers are sealed the flexible elastomer expands or contracts with the chamber volume change. By manipulating the potential across the gel the motion of the elastomer can be controlled to act as a "gate" to open or close a fluid channel and thereby control flow through that channel.

  19. Basic investigations on LCV micelle gel

    NASA Astrophysics Data System (ADS)

    Ebenezer, S. B.; Rafic, M. K.; Ravindran, P. B.

    2013-06-01

    The aim of this study was to investigate the feasibility of using Leuco Crystal Violet (LCV) based micelle gel dosimeter as a quality assurance tool in radiotherapy applications. Basic properties such as absorption coefficient and diffusion of LCV gel phantom over time were evaluated. The gel formulation consisted of 25 mM Trichloroacetic acid, 1mM LCV, 4 mM Triton X-100, 4% gelatin by mass and distilled water. The advantages of using this gel are its tissue equivalence, easy and less preparation time, lower diffusion rate and it can be read with an optical scanner. We were able to reproduce some of the results of Babic et al. The peak absorption was found to be at 600 nm and hence a matrix of yellow LEDs was used as light source. The profiles obtained from projection images confirmed the diffusion of LCV gel after 6 hours of irradiation. Hence the LCV gel phantom should be read before 6 hours post irradiation to get accurate dose information as suggested previously.

  20. Learning Analytics: Readiness and Rewards

    ERIC Educational Resources Information Center

    Friesen, Norm

    2013-01-01

    This position paper introduces the relatively new field of learning analytics, first by considering the relevant meanings of both "learning" and "analytics," and then by looking at two main levels at which learning analytics can be or has been implemented in educational organizations. Although integrated turnkey systems or…

  1. Quality Indicators for Learning Analytics

    ERIC Educational Resources Information Center

    Scheffel, Maren; Drachsler, Hendrik; Stoyanov, Slavi; Specht, Marcus

    2014-01-01

    This article proposes a framework of quality indicators for learning analytics that aims to standardise the evaluation of learning analytics tools and to provide a mean to capture evidence for the impact of learning analytics on educational practices in a standardised manner. The criteria of the framework and its quality indicators are based on…

  2. Natural gels in the Yucca Mountain Area, Nevada, USA

    SciTech Connect

    Levy, S.S.

    1991-12-31

    Relict gels at Yucca Mountain include pore- and fracture-fillings of silica and zeolite related to diagenetic and hydrothermal alteration of vitric tuffs. Water-rich free gels in fractures at Rainier Mesa consist of smectite with or without silica-rich gel fragments. Gels are being studied for their potential role in transport of radionuclides from a nuclear-waste repository.

  3. Preparation and characterization of lidocaine rice gel for oral application.

    PubMed

    Okonogi, Siriporn; Kaewpinta, Adchareeya; Yotsawimonwat, Songwut; Khongkhunthian, Sakornrat

    2016-01-01

    The objective of the present study was to prepare buccal anesthetic gels using rice as gelling agent. Rice grains of four rice varieties, Jasmine (JM), Saohai (SH), Homnil (HN), and Doisket (DS) were chemically modified. Buccal rice gels, containing lidocaine hydrochloride as local anesthetic drug were formulated using the respective modified rice varieties. The gels were evaluated for outer appearance, pH, color, gel strength, foaming property, adhesion, in vitro drug release and in vivo efficacy. It was found that the developed rice gels possessed good texture. Rice varieties showed influence on gel strength, color, turbidity, adhesive property, release property, and anesthetic efficacy. JM gel showed the lowest turbidity with light transmission of 86.76 ± 1.18% whereas SH gel showed the highest gel strength of 208.78 ± 10.42 g/cm(2). Lidocaine hydrochloride can cause a decrease in pH and adhesive property but an increase in turbidity of the gels. In vitro drug release profile within 60 min of lidocaine SH gel and lidocaine HN gel showed that lidocaine could be better released from SH gel. Evaluation of in vivo anesthetic efficacy in 100 normal volunteers indicates that both lidocaine rice gels have high efficacy but different levels. Lidocaine SH gel possesses faster onset of duration and longer duration of action than lidocaine HN gel. PMID:26781924

  4. Uncertainty in 3D gel dosimetry

    NASA Astrophysics Data System (ADS)

    De Deene, Yves; Jirasek, Andrew

    2015-01-01

    Three-dimensional (3D) gel dosimetry has a unique role to play in safeguarding conformal radiotherapy treatments as the technique can cover the full treatment chain and provides the radiation oncologist with the integrated dose distribution in 3D. It can also be applied to benchmark new treatment strategies such as image guided and tracking radiotherapy techniques. A major obstacle that has hindered the wider dissemination of gel dosimetry in radiotherapy centres is a lack of confidence in the reliability of the measured dose distribution. Uncertainties in 3D dosimeters are attributed to both dosimeter properties and scanning performance. In polymer gel dosimetry with MRI readout, discrepancies in dose response of large polymer gel dosimeters versus small calibration phantoms have been reported which can lead to significant inaccuracies in the dose maps. The sources of error in polymer gel dosimetry with MRI readout are well understood and it has been demonstrated that with a carefully designed scanning protocol, the overall uncertainty in absolute dose that can currently be obtained falls within 5% on an individual voxel basis, for a minimum voxel size of 5 mm3. However, several research groups have chosen to use polymer gel dosimetry in a relative manner by normalizing the dose distribution towards an internal reference dose within the gel dosimeter phantom. 3D dosimetry with optical scanning has also been mostly applied in a relative way, although in principle absolute calibration is possible. As the optical absorption in 3D dosimeters is less dependent on temperature it can be expected that the achievable accuracy is higher with optical CT. The precision in optical scanning of 3D dosimeters depends to a large extend on the performance of the detector. 3D dosimetry with X-ray CT readout is a low contrast imaging modality for polymer gel dosimetry. Sources of error in x-ray CT polymer gel dosimetry (XCT) are currently under investigation and include inherent limitations in dosimeter homogeneity, imaging performance, and errors induced through post-acquisition processing. This overview highlights a number of aspects relating to uncertainties in polymer gel dosimetry.

  5. Analytical capillary isotachophoresis: a routine technique for the analysis of lipoproteins and lipoprotein subfractions in whole serum.

    PubMed

    Schmitz, G; Borgmann, U; Assmann, G

    1985-02-22

    A capillary isotachophoretic separation technique was developed for lipoproteins in native serum which, compared with previous electrophoretic techniques, has negligible molecular sieve effects, does not need gel casting, is suitable for whole serum and has a high discriminative power for lipoprotein subfractions. The technique is based on pre-staining whole serum lipoproteins for 30 min at 4 degrees C before separation of 0.5 microliter of the sample in a free-flow capillary system (0.5 mm I.D.) with discontinuous buffer system. In normolipidaemic sera, high-density (HDL) and low-density lipoproteins (VLDL) are separated into two major subpopulations according to their net electric mobility. The identification of these fractions was confirmed by substitution with ultracentrifugally isolated lipoproteins and by their complete absence from Tangier and abetalipoproteinaemic serum. Triglyceride-rich very low-density lipoproteins (VLDL) revealed a defined zone between the HDL and LDL subpopulations. Our preliminary results indicate that the separation of human whole serum lipoproteins by capillary isotachophoresis is a promising method for the determination of lipoprotein subfractions. PMID:4030932

  6. Hexagonal phase based gel-emulsion (O/H1 gel-emulsion): formation and rheology.

    PubMed

    Alam, Mohammad Mydul; Aramaki, Kenji

    2008-11-01

    The formation, stability, and rheological behavior of a hexagonal phase based gel-emulsion (O/H1 gel-emulsion) have been studied in water/C12EO8/hydrocarbon oil systems. A partial phase behavior study indicates that the oil nature has no effect on the phase sequences in the ternary phase diagram of water/C12EO8/oil systems but the domain size of the phases or the oil solubilization capacity considerably changes with oil nature. Excess oil is in equilibrium with the hexagonal phase (H1) in the ternary phase diagram in the H1+O region. The O/H1 gel-emulsion was prepared (formation) and kept at 25 degrees C to check stability. It has been found that the formation and stability of the O/H1 gel-emulsion depends on the oil nature. After 2 min observation (formation), the results show that short chain linear hydrocarbon oils (heptane, octane) are more apt to form a O/H1 gel-emulsion compared to long chain linear hydrocarbon oils (tetradecane, hexadecane), though the stability is not good enough in either system, that is, oil separates within 24 h. Nevertheless, the formation and stability of the O/H1 gel-emulsion is appreciably increased in squalane and liquid paraffin. It is surmised that the high transition temperature of the H1+O phase and the presence of a bicontinuous cubic phase (V1) might hamper the formation of a gel-emulsion. It has been pointed out that the solubilization of oil in the H1 phase could be related to emulsion stability. On the other hand, the oil nature has little or no effect on the formation and stability of a cubic phase based gel-emulsion (O/I1 gel-emulsion). From rheological measurements, it has found that the rheogram of the O/H1 gel-emulsion indicates gel-type structure and shows shear thinning behavior similar to the case of the O/I1 gel-emulsion. Rheological data infer that the O/I1 gel-emulsion is more viscous than the O/H1 gel-emulsion at room temperature but the O/H1 gel-emulsion shows consistency at elevated temperature. PMID:18847293

  7. Analytical sensor redundancy assessment

    NASA Technical Reports Server (NTRS)

    Mulcare, D. B.; Downing, L. E.; Smith, M. K.

    1988-01-01

    The rationale and mechanization of sensor fault tolerance based on analytical redundancy principles are described. The concept involves the substitution of software procedures, such as an observer algorithm, to supplant additional hardware components. The observer synthesizes values of sensor states in lieu of their direct measurement. Such information can then be used, for example, to determine which of two disagreeing sensors is more correct, thus enhancing sensor fault survivability. Here a stability augmentation system is used as an example application, with required modifications being made to a quadruplex digital flight control system. The impact on software structure and the resultant revalidation effort are illustrated as well. Also, the use of an observer algorithm for wind gust filtering of the angle-of-attack sensor signal is presented.

  8. ANALYTIC MODELING OF STARSHADES

    SciTech Connect

    Cash, Webster

    2011-09-01

    External occulters, otherwise known as starshades, have been proposed as a solution to one of the highest priority yet technically vexing problems facing astrophysics-the direct imaging and characterization of terrestrial planets around other stars. New apodization functions, developed over the past few years, now enable starshades of just a few tens of meters diameter to occult central stars so efficiently that the orbiting exoplanets can be revealed and other high-contrast imaging challenges addressed. In this paper, an analytic approach to the analysis of these apodization functions is presented. It is used to develop a tolerance analysis suitable for use in designing practical starshades. The results provide a mathematical basis for understanding starshades and a quantitative approach to setting tolerances.

  9. Normality in analytical psychology.

    PubMed

    Myers, Steve

    2013-12-01

    Although C.G. Jung's interest in normality wavered throughout his career, it was one of the areas he identified in later life as worthy of further research. He began his career using a definition of normality which would have been the target of Foucault's criticism, had Foucault chosen to review Jung's work. However, Jung then evolved his thinking to a standpoint that was more aligned to Foucault's own. Thereafter, the post Jungian concept of normality has remained relatively undeveloped by comparison with psychoanalysis and mainstream psychology. Jung's disjecta membra on the subject suggest that, in contemporary analytical psychology, too much focus is placed on the process of individuation to the neglect of applications that consider collective processes. Also, there is potential for useful research and development into the nature of conflict between individuals and societies, and how normal people typically develop in relation to the spectrum between individuation and collectivity. PMID:25379262

  10. Interpolating analytic visualizations

    NASA Astrophysics Data System (ADS)

    Trutschl, Marjan; Grinstein, Georges; Cvek, Urska

    2004-06-01

    Several authors have developed automated parameterized visualization generation systems14,15,16. All generate classic visualizations or combinations of such visualizations. A vector space model of visualization was proposed by Hoffman18, leading to the development of new visualizations and the concept of interpolating visualizations. These new visualizations provide alternative representations and insights into data and have been applied successfully in numerous data analysis problems including gene expression, drug discovery, clinical trials, toxicogenomics, and medical informatics23. In this paper we elevate this vector space model to include analytic visualizations, ones with tightly coupled analysis, such as Self-Organizing Maps (SOMs) and Multi-Dimensional Scaling (MDS). We describe our new model and provide an example interpolation of a SOM and a scatterplot with a simple data set (the Fisher Iris data) and a more complex and larger one (microarray gene expression data).

  11. VERDE Analytic Modules

    SciTech Connect

    2008-01-15

    The Verde Analytic Modules permit the user to ingest openly available data feeds about phenomenology (storm tracks, wind, precipitation, earthquake, wildfires, and similar natural and manmade power grid disruptions and forecast power outages, restoration times, customers outaged, and key facilities that will lose power. Damage areas are predicted using historic damage criteria of the affected area. The modules use a cellular automata approach to estimating the distribution circuits assigned to geo-located substations. Population estimates served within the service areas are located within 1 km grid cells and converted to customer counts by conversion through demographic estimation of households and commercial firms within the population cells. Restoration times are estimated by agent-based simulation of restoration crews working according to utility published prioritization calibrated by historic performance.

  12. Normality in Analytical Psychology

    PubMed Central

    Myers, Steve

    2013-01-01

    Although C.G. Jung’s interest in normality wavered throughout his career, it was one of the areas he identified in later life as worthy of further research. He began his career using a definition of normality which would have been the target of Foucault’s criticism, had Foucault chosen to review Jung’s work. However, Jung then evolved his thinking to a standpoint that was more aligned to Foucault’s own. Thereafter, the post Jungian concept of normality has remained relatively undeveloped by comparison with psychoanalysis and mainstream psychology. Jung’s disjecta membra on the subject suggest that, in contemporary analytical psychology, too much focus is placed on the process of individuation to the neglect of applications that consider collective processes. Also, there is potential for useful research and development into the nature of conflict between individuals and societies, and how normal people typically develop in relation to the spectrum between individuation and collectivity. PMID:25379262

  13. VERDE Analytic Modules

    Energy Science and Technology Software Center (ESTSC)

    2008-01-15

    The Verde Analytic Modules permit the user to ingest openly available data feeds about phenomenology (storm tracks, wind, precipitation, earthquake, wildfires, and similar natural and manmade power grid disruptions and forecast power outages, restoration times, customers outaged, and key facilities that will lose power. Damage areas are predicted using historic damage criteria of the affected area. The modules use a cellular automata approach to estimating the distribution circuits assigned to geo-located substations. Population estimates servedmore » within the service areas are located within 1 km grid cells and converted to customer counts by conversion through demographic estimation of households and commercial firms within the population cells. Restoration times are estimated by agent-based simulation of restoration crews working according to utility published prioritization calibrated by historic performance.« less

  14. Evolution of gel structure during thermal processing of Na-geopolymer gels.

    PubMed

    Duxson, Peter; Lukey, Grant C; van Deventer, Jannie S J

    2006-10-10

    The present work examines how the gel structure and phase composition of Na-geopolymers derived from metakaolin with varied Si/Al ratio evolve with exposure to temperatures up to 1000 degrees C. Gels were thermally treated and characterized using quantitative XRD, DTA, and FTIR to elucidate the changes in gel structure, phase composition, and porosity at each stage of heating. It is found that the phase stability, defined by the amount and onset temperature of crystallization, is improved at higher Si/Al ratios. Two different mechanisms of densification have been isolated by FTIR, related to viscous flow and collapse of the highly distributed pore network in the gel. Gels with low Si/Al ratio only experience viscous flow that correlates with low thermal shrinkage. Gels at a higher Si/Al ratio, which have a homogeneous microstructure composed of a highly distributed porosity, undergo both densification processes corresponding to a large extent of thermal shrinkage during densification. This work elucidates the intimate relationship between gel microstructure, chemistry, and thermal evolution of Na-geopolymer gels. PMID:17014113

  15. Application of denaturing gradient gel electrophoresis (DGGE) and temperature gradient gel electrophoresis (TGGE) in microbial ecology.

    PubMed

    Muyzer, G; Smalla, K

    1998-01-01

    Here, the state of the art of the application of denaturing gradient gel electrophoresis (DGGE) and temperature gradient gel electrophoresis (TGGE) in microbial ecology will be presented. Furthermore, the potentials and limitations of these techniques will be discussed, and it will be indicated why their use in ecological studies has become so important. PMID:9602286

  16. Development and characterization of molecularly imprinted sol-gel materials for the selective detection of DDT.

    PubMed

    Graham, Amy L; Carlson, Catherine A; Edmiston, Paul L

    2002-01-15

    Molecularly imprinting sol-gel materials for DDT using both a noncovalent and a covalent approach was examined. A nonpolar porous sol-gel network was created through the use of the bridged polysilsesquioxane, bis-(trimethoxysilylethyl)benzene (BTEB), as the principal sol-gel component. Noncovalent molecular imprinting was deemed unsuccessful, presumably because of the lack of strong intermolecular interactions that can be established between the DDT and the sol-gel precursor. A covalent imprinting strategy was employed by generating a sacrificial spacer through the reaction of two 3-isocyanatopropyltriethoxysilanes with one of two different template molecules: 4,4'-ethylenedianiline (EDA) or 4,4'-ethylidenebisphenol (EBP). After formation of the sol-gel, the bonds linking the spacer template to the matrix were cleaved in a manner that generated a pocket of the appropriate size bordered by amine groups that could aid in the binding of DDT through weak hydrogen bonding interactions. Experiments indicated that DDT could be bound selectively by such an approch. To generate a sensor, an environmentally sensitive fluorescent probe, 7-nitrobenz-2-oxa-1,3-diazole, (NBD) located adjacent to the DDT binding site was used to transduce the binding of analyte. EDA-imprinted sol-gels, deposited as films on glass microscope slides, were shown to quantitatively detect DDT in water to a limit-of-detection of 50 ppt with a response time of <60 s. Repeat measurements could be made with the same sensing films after rinsing with acetone between each measurement. The EDA sensing material was selective for DDT and other structurally similar molecules. However, the sensing film design was limited by the relatively minor changes in fluorescence intensity upon binding DDT. This situation may be remedied by an alternative methodology that can facilitate attachment of the NBD fluorophore in an optimal position proximal to the binding pocket. PMID:11811423

  17. Gel-sol-gel thermo-gelation behavior study of chitosan-inorganic phosphate solutions.

    PubMed

    Li, XingYi; Kong, XiangYe; Wang, XiuHong; Shi, Shuai; Guo, Gang; Luo, Feng; Zhao, Xia; Wei, YuQuan; Qian, ZhiYong

    2010-08-01

    In present study, the feasibility of developing a novel thermo-sensitive hydrogel suitable for injectable formulations based on chitosan and inorganic phosphate was demonstrated. The physicochemical and rheological changes of chitosan/dibasic sodium phosphate solutions as in function with temperature were investigated in order to gain a better understanding of gelation process. According to the result of rheological study, there are two phase transition points as in function with temperature, corresponding to 30 degrees C and 43 degrees C. The system is gel state at approximately 4 degrees C. With the temperature increased to 30 degrees C, the gel-sol transition as well as the decrease in turbidity was observed. The sol-gel transition as well as the increase in turbidity was observed again as the temperature was above 43 degrees C. And the gel obtained at approximately 4 degrees C is reversible, but the gel obtained at approximately 43 degrees C is irreversible. PMID:20434557

  18. Comparison of electrical conductivities of various brain phantom gels: Developing a ‘Brain Gel Model’

    PubMed Central

    Kandadai, Madhuvanthi A.; Raymond, Jason L.; Shaw, George J.

    2012-01-01

    The use of conducting gels to mimic brain and other tissues is of increasing interest in the development of new medical devices. Currently, there are few such models that can be utilized at physiologic temperatures. In this work, the conductivities of agar, agarose and gelatin gels were manipulated by varying NaCl concentration from 0–1 mg/ml. The AC conductivity was measured at room and physiological temperatures (37°C) in the 100–500 Hz frequency range. Conductivity (σ) was nearly independent of frequency but increased linearly with NaCl concentration and was higher at physiological temperatures in these gels. A formula for predicting conductivity as a function of NaCl concentration was derived for each gel type. The overall goal is to develop a ‘brain gel model’, for studying low frequency electrical properties of the brain and other tissues at physiological temperatures. PMID:23139442

  19. Structural Properties of Silk Electro-Gels

    NASA Astrophysics Data System (ADS)

    Tabatabai, A. P.; Urbach, J. S.; Blair, D. L.; Kaplan, D. L.

    2013-03-01

    The interest in Bombyx Mori silk emerges from its biocompatibility and its structural superiority to synthetic polymers. Our particular interest lies in understanding the capabilities of silk electro-gels because of their reversibility and tunable adhesion. We create an electro-gel by applying a DC electric potential across a reconstituted silk fibroin solution derived directly from Bombyx Mori cocoons. This process leads to the intermolecular self-assembly of fibroin proteins into a weak gel. In this talk we will present our results on the effects of applied shear on electro-gels. We quantify the structural properties while dynamically imaging shear induced fiber formation; known as fibrillogenesis. It is observed that the mechanical properties and microstructure of these materials are highly dependent on shear history. We will also discuss the role of surface modification, through micro-patterning, on the observed gel structure. Our results provide an understanding of both the viscoelastiticity and microstucture of reconstituted silks that are being utilized as tissue scaffolds. This work is supported by a grant from the AFOSR FA9550-07-1-0130.

  20. The effective atomic number of dosimetric gels.

    PubMed

    Taylor, M L; Franich, R D; Trapp, J V; Johnston, P N

    2008-06-01

    Radiological properties of gel dosimeters and phantom materials are often compared against each other and against water or tissue by consideration parameters including their effective atomic number, Zeff. Effective atomic numbers have been calculated for a range of ferrous-sulphate and polymeric gel dosimeters using mass attenuation coefficient data over the energy range 10 keV to 10 MeV. Data is presented relative to water to allow direct comparison over a range of energies. These data provide energy specific values of Zeff which improves on the practice of applying a power-law based formula to estimate an energy independent value. For applications that require a single value of Zeff, the data presented here allows the choice of a value appropriate to the energy of the photon source or a spectrum-weighted average. Studying the variation of Zeff, which is equivalent to taking into account the variation of mass attenuation coefficients with photon energy, it is found that gels typically match water better than water matches human tissues. As such, the subtle differences in effective atomic number between water and gels are small and may be considered negligible. Consideration of the mean disparity over a large energy range shows, broadly, BANG-1 to be the most water equivalent gel. PMID:18697704

  1. Continuum Models of Stimuli-responsive Gels

    NASA Astrophysics Data System (ADS)

    Hong, Wei

    Immersed in a solution of small molecules and ions, a network of long-chain polymers may imbibe the solution and swell, resulting in a polymeric gel. Depending on the molecular structure of the polymers, the amount of swelling can be regulated by moisture, mechanical forces, ionic strength, electric field, pH value, and many other types of stimuli. Starting from the basic principles of non-equilibrium thermodynamics, this chapter formulates a field theory of the coupled large deformation and mass transportation in a neutral polymeric gel. The theory is then extended to study polyelectrolyte gels with charge-carrying networks by accounting for the electromechanical coupling and migration of solute ions. While the theoretical framework is adaptable to various types of material models, some representative ones are described through specific free-energy functions and kinetic laws. A specific material law for pH-sensitive gels—a special type of polyelectrolyte gels—is introduced as an example of incorporating chemical reactions in modeling stimuli-responsive gels. Finally, a simplified theory for the equilibrium but inhomogeneous swelling of a polymeric gel is deduced. The theory and the specific material models are illustrated through several examples.

  2. Reconfigurable assemblies of active, autochemotactic gels

    PubMed Central

    Dayal, Pratyush; Kuksenok, Olga; Balazs, Anna C.

    2013-01-01

    Using computational modeling, we show that self-oscillating Belousov–Zhabotinsky (BZ) gels can both emit and sense a chemical signal and thus drive neighboring gel pieces to spontaneously self-aggregate, so that the system exhibits autochemotaxis. To the best of our knowledge, this is the closest system to the ultimate self-recombining material, which can be divided into separated parts and the parts move autonomously to assemble into a structure resembling the original, uncut sample. We also show that the gels’ coordinated motion can be controlled by light, allowing us to achieve selective self-aggregation and control over the shape of the gel aggregates. By exposing the BZ gels to specific patterns of light and dark, we design a BZ gel “train” that leads the movement of its “cargo.” Our findings pave the way for creating reconfigurable materials from self-propelled elements, which autonomously communicate with neighboring units and thereby actively participate in constructing the final structure. PMID:23271807

  3. Ultrathin-layer gel electrophoresis of biopolymers.

    PubMed

    Guttman, A; Rónai, Z

    2000-12-01

    Emerging need for large-scale, high-resolution analysis of biopolymers, such as DNA sequencing polymerase chain reaction, (PCR) product sizing, single nucleotide polymorphism (SNP) hunting and analysis of protein molecules necessitated the development of automated and high-throughput gel electrophoresis based methods enabling rapid, high-performance separations in a wide molecular weight range. Scaling down electric field mediated separation processes supports higher throughput due to the applicability of higher voltages, thus speeding up analysis time. Indeed, efforts in miniaturization resulted in faster, easier, less costly and more convenient analyses, fulfilling the needs of the emerging biotechnology industry for microscale and massively parallel assays. The two primary approaches in miniaturizing electrophoresis dimensions are the capillary and microslab formats. This latter one evolved towards ultrathin-layer gel electrophoresis which is, except from the thickness of the separation platform, slightly in the upper side of the scale, resulting in considerably easier handling. Ultrathin-layer gel electrophoresis combines the advantages of conventional slab-gel electrophoresis (multilane format) and capillary gel electrophoresis (rapid, high-efficiency separations). It is readily automated, automatic versions of it have been extensively used for large-scale DNA sequencing in the Human Genome Project and more recently became popular in high throughput DNA fragment analysis. Ultrathin-layer techniques are the first step towards the wider use of electrophoresis microchips in perfecting a user-friendly interface between the user and the microdevice. PMID:11192118

  4. Biopolymer Gels: Nanostructure and Macroscopic Properties

    NASA Astrophysics Data System (ADS)

    Horkay, Ferenc

    Small-angle neutron scattering (SANS) has been used to investigate the effect of salts (NaCl and CaCl2) on the structure of DNA and polyacrylic acid (PAA) gels. In the absence of salt a distinct correlation peak is observed in the SANS spectra of both systems indicating that electrostatic interactions play an important role in the organization of the polymer chains. When the salt concentration is increased, the peak position shifts to smaller values of the scattering vector q, and progressively vanishes. Osmotic swelling pressure measurements show that Ca ions reduce the swelling pressure and lead to the collapse of these gels. The Ca/Na ion exchange process does not affect the shear modulus of PAA gels. However, the shear modulus of DNA gels decreases with increasing Ca ion concentration at high swelling degrees, and increases at low swelling degrees. The results indicate that changing the ionic composition provides a simple way to control the nanoscale structures and properties in polyelectrolyte gels.

  5. Mucosal effects of tenofovir 1% gel.

    PubMed

    Hladik, Florian; Burgener, Adam; Ballweber, Lamar; Gottardo, Raphael; Vojtech, Lucia; Fourati, Slim; Dai, James Y; Cameron, Mark J; Strobl, Johanna; Hughes, Sean M; Hoesley, Craig; Andrew, Philip; Johnson, Sherri; Piper, Jeanna; Friend, David R; Ball, T Blake; Cranston, Ross D; Mayer, Kenneth H; McElrath, M Juliana; McGowan, Ian

    2015-01-01

    Tenofovir gel is being evaluated for vaginal and rectal pre-exposure prophylaxis against HIV transmission. Because this is a new prevention strategy, we broadly assessed its effects on the mucosa. In MTN-007, a phase-1, randomized, double-blinded rectal microbicide trial, we used systems genomics/proteomics to determine the effect of tenofovir 1% gel, nonoxynol-9 2% gel, placebo gel or no treatment on rectal biopsies (15 subjects/arm). We also treated primary vaginal epithelial cells from four healthy women with tenofovir in vitro. After seven days of administration, tenofovir 1% gel had broad-ranging effects on the rectal mucosa, which were more pronounced than, but different from, those of the detergent nonoxynol-9. Tenofovir suppressed anti-inflammatory mediators, increased T cell densities, caused mitochondrial dysfunction, altered regulatory pathways of cell differentiation and survival, and stimulated epithelial cell proliferation. The breadth of mucosal changes induced by tenofovir indicates that its safety over longer-term topical use should be carefully monitored. PMID:25647729

  6. Structural evolution of Colloidal Gels under Flow

    NASA Astrophysics Data System (ADS)

    Boromand, Arman; Maia, Joao; Jamali, Safa

    Colloidal suspensions are ubiquitous in different industrial applications ranging from cosmetic and food industries to soft robotics and aerospace. Owing to the fact that mechanical properties of colloidal gels are controlled by its microstructure and network topology, we trace the particles in the networks formed under different attraction potentials and try to find a universal behavior in yielding of colloidal gels. Many authors have implemented different simulation techniques such as molecular dynamics (MD) and Brownian dynamics (BD) to capture better picture during phase separation and yielding mechanism in colloidal system with short-ranged attractive force. However, BD neglects multi-body hydrodynamic interactions (HI) which are believed to be responsible for the second yielding of colloidal gels. We envision using dissipative particle dynamics (DPD) with modified depletion potential and hydrodynamic interactions, as a coarse-grain model, can provide a robust simulation package to address the gel formation process and yielding in short ranged-attractive colloidal systems. The behavior of colloidal gels with different attraction potentials under flow is examined and structural fingerprints of yielding in these systems will be discussed.

  7. Analytic integrable systems: Analytic normalization and embedding flows

    NASA Astrophysics Data System (ADS)

    Zhang, Xiang

    In this paper we mainly study the existence of analytic normalization and the normal form of finite dimensional complete analytic integrable dynamical systems. More details, we will prove that any complete analytic integrable diffeomorphism F(x)=Bx+f(x) in (Cn,0) with B having eigenvalues not modulus 1 and f(x)=O(|) is locally analytically conjugate to its normal form. Meanwhile, we also prove that any complete analytic integrable differential system x˙=Ax+f(x) in (Cn,0) with A having nonzero eigenvalues and f(x)=O(|) is locally analytically conjugate to its normal form. Furthermore we will prove that any complete analytic integrable diffeomorphism defined on an analytic manifold can be embedded in a complete analytic integrable flow. We note that parts of our results are the improvement of Moser's one in J. Moser, The analytic invariants of an area-preserving mapping near a hyperbolic fixed point, Comm. Pure Appl. Math. 9 (1956) 673-692 and of Poincaré's one in H. Poincaré, Sur l'intégration des équations différentielles du premier order et du premier degré, II, Rend. Circ. Mat. Palermo 11 (1897) 193-239. These results also improve the ones in Xiang Zhang, Analytic normalization of analytic integrable systems and the embedding flows, J. Differential Equations 244 (2008) 1080-1092 in the sense that the linear part of the systems can be nonhyperbolic, and the one in N.T. Zung, Convergence versus integrability in Poincaré-Dulac normal form, Math. Res. Lett. 9 (2002) 217-228 in the way that our paper presents the concrete expression of the normal form in a restricted case.

  8. Analytical techniques for cell fractions

    SciTech Connect

    Pearson, T.; Anderson, L.

    1980-01-15

    Disposable microimmunoadsorbent columns containing Staphylococcus Protein A and monoclonal antibodies were used to bind antigenic proteins from a mixture. Eluates from these columns were directly analyzed by electrophoresis on two-dimensional (2-D) gels. In this way, biochemical and biophysical information on the bound antigen and on the specific antibody can be obtained simultaneously. The microimmunoadsorbents are easy to handle and in conjunction with multiple 2-D gel systems provide a means for screening large numbers of myeloma hybrids for specificity to antigens in complex mixtures.

  9. A New Standard-Based Polynomial Interpolation (SBPIn) Method to Address Gel-to-Gel Variability for the Comparison of Multiple Denaturing Gradient Gel Electrophoresis Profile Matrices

    PubMed Central

    Valentín-Vargas, Alexis; Chorover, Jon; Maier, Raina M.

    2013-01-01

    The Standard-Based Polynomial Interpolation (SBPIn) method is a new simple three-step protocol proposed to address common gel-to-gel variations for the comparison of sample profiles across multiple DGGE gels. The advantages of this method include no requirement for additional software or modification of the standard DGGE protocol. PMID:23234884

  10. On the scattering properties of polyelectrolyte gels

    NASA Astrophysics Data System (ADS)

    Barrat, Jean-Louis; Joanny, Jean-François; Pincus, Phil

    1992-08-01

    We present a simple model for scattering properties of polyelectrolyte gels at swelling equilibrium. In the weak screening limit where the Debye-Hückel screening length is larger than the mesh size of the gel, the direct electrostatic interactions are negligible and the swelling is driven by the osmotic pressure of the counterions. The tension created by this pressure is transmitted through the crosslinks to the elastic chains which behave as isolated chains with an applied force at their end points. The structure factor of the gel can be split into a frozen component due to the average concentration heterogeneities and a thermodynamic component due to concentration fluctuations. The frozen component has a peak at a wavevector of the order of the mesh size of the gel, the thermodynamic component has a peak at a higher wavevector of the order of the inverse transverse radius of the chains. At infinite times the dynamic structure factor relaxes towards the frozen component of the static structure factor. In the limit of small wavevectors the relaxation is diffusive with a diffusion constant equal to the Stokes diffusion constant of the Pincus blobs of the stretched chains. The diffusion constant shows a minimum at a wavevector of the order of the inverse transverse radius of the chains. Nous présentons un modèle simple pour étudier la diffusion de rayonnement par des gels polylectrolytes à l'équilibre de gonflement. Dans la limite d'écrantage faible où la longueur d'écran de Debye-Hückel est plus grande que la maille du gel, les interactions électrostatiques directes sont négligeables et le gonflement est dû à la pression osmotique des contreions. La tension créée par cette pression est transmise par les noeuds du gel aux chaines élastiques qui se comportent comme des chaines isolées avec une force extérieure appliquée aux extrémités. Le facteur de structure du gel est la somme d'une composante gelée due aux hétérogénéités de concentration figées et d'une composante thermodynamique due aux fluctuations de concentration. la composante gelée a un maximum pour un vecteur d'onde de l'ordre de l'inverse de la maille du gel et la composante thermodynamique a un maximum pour un vecteur d'onde beaucoup plus grand de l'ordre de l'inverse du rayon transverse des chaines. A temps longs, le facteur de structure dynamique relaxe vers la composante gelée du facteur de structure statique. A faible vecteur d'onde, la relaxation est diffusive avec un coefficient de diffusion de l'ordre du coefficient de diffusion de Stokes des blobs de Pincus des chaines étirées. Le coefficient de diffusion est minimal pour un vecteur d'onde de l'ordre de l'inverse du rayon transverse des chaines.

  11. Ultraflexible organic amplifier with biocompatible gel electrodes.

    PubMed

    Sekitani, Tsuyoshi; Yokota, Tomoyuki; Kuribara, Kazunori; Kaltenbrunner, Martin; Fukushima, Takanori; Inoue, Yusuke; Sekino, Masaki; Isoyama, Takashi; Abe, Yusuke; Onodera, Hiroshi; Someya, Takao

    2016-01-01

    In vivo electronic monitoring systems are promising technology to obtain biosignals with high spatiotemporal resolution and sensitivity. Here we demonstrate the fabrication of a biocompatible highly conductive gel composite comprising multi-walled carbon nanotube-dispersed sheet with an aqueous hydrogel. This gel composite exhibits admittance of 100 mS cm(-2) and maintains high admittance even in a low-frequency range. On implantation into a living hypodermal tissue for 4 weeks, it showed a small foreign-body reaction compared with widely used metal electrodes. Capitalizing on the multi-functional gel composite, we fabricated an ultrathin and mechanically flexible organic active matrix amplifier on a 1.2-μm-thick polyethylene-naphthalate film to amplify (amplification factor: ∼200) weak biosignals. The composite was integrated to the amplifier to realize a direct lead epicardial electrocardiography that is easily spread over an uneven heart tissue. PMID:27125910

  12. Gel-Filled Holders For Ultrasonic Transducers

    NASA Technical Reports Server (NTRS)

    Companion, John A.

    1992-01-01

    In new technique, ultrasonic transducer embedded in rubbery, castable, low-loss gel to enable transducer to "look" into surface of test object or human body at any desired angle. Composed of solution of water and ethylene glycol in collagen matrix. Provides total contact of water bath, also used on bodies or objects too large for water baths, even if moving. Also provides look angles of poly(methyl methacrylate) angle block with potential of reduced acoustic impedance and refraction. Custom-tailored to task at hand, and gel sufficiently inexpensive to be discarded upon completion. Easy to couple ultrasound in and out of gel, minimizing losses and artifacts of other types of standoffs employed in ultrasonic testing.

  13. Writing in the granular gel medium

    PubMed Central

    Bhattacharjee, Tapomoy; Zehnder, Steven M.; Rowe, Kyle G.; Jain, Suhani; Nixon, Ryan M.; Sawyer, W. Gregory; Angelini, Thomas E.

    2015-01-01

    Gels made from soft microscale particles smoothly transition between the fluid and solid states, making them an ideal medium in which to create macroscopic structures with microscopic precision. While tracing out spatial paths with an injection tip, the granular gel fluidizes at the point of injection and then rapidly solidifies, trapping injected material in place. This physical approach to creating three-dimensional (3D) structures negates the effects of surface tension, gravity, and particle diffusion, allowing a limitless breadth of materials to be written. With this method, we used silicones, hydrogels, colloids, and living cells to create complex large aspect ratio 3D objects, thin closed shells, and hierarchically branched tubular networks. We crosslinked polymeric materials and removed them from the granular gel, whereas uncrosslinked particulate systems were left supported within the medium for long times. This approach can be immediately used in diverse areas, contributing to tissue engineering, flexible electronics, particle engineering, smart materials, and encapsulation technologies. PMID:26601274

  14. Interaction of Surfactants with Block Polyelectrolyte Gels

    NASA Astrophysics Data System (ADS)

    Crichton, Mark; Bhatia, Surita

    2002-03-01

    We present SANS and rheology for poly(styrene)-poly(acrylic acid) polymers in aqueous solutions. These polymers self-assemble to form spherical micelles in aqueous solutions, and the micelles associate to create elastic, transparent gels at moderate polymer concentrations. The addition of cationic and anionic surfactants (DTAB and SDS) can be used to modify the associative interactions and solution rheology. Addition of an anionic surfactant acts to screen attractive interactions and causes a monotonic decrease in the elastic modulus. However, the addition of a cationic surfactant appears to initially induce a stronger intermicellar attraction, leading to gels with a higher elastic modulus. At higher surfactant concentrations, the cationic surfactant begins to screen intermicellar association, leading to a decrease in the strength of the gel.

  15. Mechanical characterization and computational modeling of gels

    NASA Astrophysics Data System (ADS)

    Santos, Paulo Henrique da Silva

    Soft materials like gels have arisen as key component in a wide range of applications, ranging from rocket propellants to complex materials for biomedical devices and drug delivery. Experimental studies have focused on the characterization of a number of gels involving macromolecules such as proteins and polysaccharides; however the link between the microstructure of these systems with their resulting macroproperties is still lacking. From the experimental point of view, this research describes the rheological behavior of some complex systems using the appropriate rheological constitutive equations. Non-conventional rheological techniques are also considered to describe some fragile systems that are significantly disturbed during testing with conventional instruments. From the computational perspective, this research provides insights on how molecular conformation and interactions affect the rheological properties of colloidal and polymeric gels. Molecular and Brownian Dynamics simulation were performed to get a better understanding on gelation processes and to explore new applications for gelled materials.

  16. Surface patterns in thermally responsive elastomeric gels

    NASA Astrophysics Data System (ADS)

    Chester, Shawn; Anand, Lallit

    2011-03-01

    Many stimulus responsive elastomeric gels operate in non-isothermal, chemically saturated environments in a variety of applications. We have recently developed a three dimensional continuum level theory to describe the coupled fluid permeation and large deformation response of thermally responsive elastomeric materials. In this work, we apply our theory and numerical simulation capability to the specific case of surface wrinkles induced via swelling of a thermally responsive gel bonded on top of a compliant impermeable elastic substrate. We show that we can numerically model the swelling behavior and subsequent surface pattern formation. Also, we examine the effect of substrate thickness by varying the ratio of gel to substrate thickness. Further, we show that it is possible to modulate the amplitude of the surface wrinkles by taking advantage of the thermally responsive nature of this class of materials.

  17. Preparation and characterization of hydrophobic superparamagnetic gel.

    SciTech Connect

    Liu, X.; Kaminski, M. D.; Guan, Y.; Chen, H.; Liu, H.; Rosengart, A. J.; Chemical Engineering; Univ. of Chicago; Pritzker School of Medicine; Chinese Academy of Sciences

    2006-01-01

    The present study describes the preparation and analysis of a highly concentrated hydrophobic oleic acid-coated magnetite gel. By contrast to conventional techniques to prepare magnetic fluids, herein the oleic acid was introduced as a reactant during the initial crystallization phase of magnetite that was obtained by the co-precipitation of Fe(II) and Fe(III) salts by addition of ammonium hydroxide. The resulting gelatinous hydrophobic magnetite was characterized in terms of morphology, particle size, magnetic properties, crystal structure, and hydrophobicity/hydrophilicity. This magnetic gel exhibited superparamagnetism with a saturation magnetization of 46.0 emu/g at room temperature and could be well dispersed both in polar and nonpolar carrier liquids. This protocol produced highly concentrated hydrophobic magnetic gel for biopolymer encapsulations.

  18. Fibroblast migration in fibrin gel matrices.

    PubMed Central

    Brown, L. F.; Lanir, N.; McDonagh, J.; Tognazzi, K.; Dvorak, A. M.; Dvorak, H. F.

    1993-01-01

    In healing wounds and many solid tumors, locally increased microvascular permeability results in extravasation of fibrinogen and its extravascular coagulation to form a fibrin gel, with concomitant covalent cross-linking of fibrin by factor XIIIa. Subsequently, inflammatory cells, fibroblasts, and endothelial cells migrate into the gel and organize it into granulation tissue and later into mature collagenous connective tissue. To gain insight into some of the cell migration events associated with these processes, we developed a quantitative in vitro assay that permits the study of fibroblast migration in fibrin gels. Early passage human or rat fibroblasts were allowed to attach to tissue culture dishes and then were overlaid with a thin layer of fibrinogen that was clotted with thrombin. Fibroblasts began to migrate upwards into the fibrin within 24 hours and their numbers and the distance migrated were quantified over several days. The extent of fibroblast migration was affected importantly by the nature of the fibrin clot. Fibroblasts migrated optimally into gels prepared from fibrinogen at concentrations of -3 mg/ml; ie, near normal plasma fibrinogen levels. Migration was greatly enhanced by extensive cross-linking of the fibrin alpha-chains by factor XIIIa, as occurs when clotting takes place in vivo. When fibrinogen was clotted in Dulbecco's modified Eagle's medium, gamma-chains were cross-linked, but alpha-chain cross-linking was strikingly inhibited, and fibroblasts migrated poorly. Gels prepared from factor XIII-depleted fibrinogen exhibited neither alpha-nor gamma-chain cross-linking and did not support fibroblast migration. Further purification of fibrinogen by anion exchange high pressure liquid chromatography depleted fibrinogen of fibronectin, plasminogen, and other impurities; this purified fibrinogen clotted to form fibrin gels that supported reproducible fibroblast migration. Images Figure 1 Figure 2 Figure 4 Figure 6 PMID:8424460

  19. Reduction of gas and water permeabilities using gels

    SciTech Connect

    Seright, R.S.

    1995-05-01

    The authors investigated how different types of gels reduce permeability to water and gases in porous rock. Five types of gels were studied, including (1) a ``weak`` resorcinol-formaldehyde gel, (2) a ``strong`` resorcinol-formaldehyde gel, (3) a Cr(III)-xanthan gel, (4) a Cr(III)-acetate-HPAM gel, and (5) a colloidal-silica gel. For all gels, extensive coreflood experiments were performed to assess the permeability-reduction characteristics and the stability to repeated water-alternating-gas (WAG) cycles. Studies were performed at pressures up to 1,500 psi using either nitrogen or carbon dioxide as the compressed gas. They developed a coreflood apparatus with an inline high-pressure spectrophotometer that allowed tracer studies to be performed without depressurizing the core. They noted several analogies between the results reported here and those observed during a parallel study of the effects of gel on oil and water permeabilities.

  20. Agarose gel shift assay reveals that calreticulin favors substrates with a quaternary structure in solution.

    PubMed

    Boelt, Sanne Grundvad; Houen, Gunnar; Højrup, Peter

    2015-07-15

    Here we present an agarose gel shift assay that, in contrast to other electrophoresis approaches, is loaded in the center of the gel. This allows proteins to migrate in either direction according to their isoelectric points. Therefore, the presented assay enables a direct visualization, separation, and prefractionation of protein interactions in solution independent of isoelectric point. We demonstrate that this assay is compatible with immunochemical methods and mass spectrometry. The assay was used to investigate interactions with several potential substrates for calreticulin, a chaperone that is involved in different biological aspects through interaction with other proteins. The current analytical assays used to investigate these interactions are mainly spectroscopic aggregation assays or solid phase assays that do not provide a direct visualization of the stable protein complex but rather provide an indirect measure of interactions. Therefore, no interaction studies between calreticulin and substrates in solution have been investigated previously. The results presented here indicate that calreticulin has a preference for substrates with a quaternary structure and primarily β-sheets in their secondary structure. It is also demonstrated that the agarose gel shift assay is useful in the study of other protein interactions and can be used as an alternative method to native polyacrylamide gel electrophoresis. PMID:25908558

  1. A Sol-Gel-Modified Poly(methyl methacrylate) Electrophoresis Microchip with a Hydrophilic Channel Wall

    SciTech Connect

    Chen, Gang; Xu, Xuejiao; Lin, Yuehe; Wang, Joseph

    2007-07-27

    A sol-gel method was employed to fabricate a poly(methyl methacrylate) (PMMA) electrophoresis microchip that contains a hydrophilic channel wall. To fabricate such a device, tetraethoxysilane (TEOS) was injected into the PMMA channel and was allowed to diffuse into the surface layer for 24 h. After removing the excess TEOS, the channel was filled with an acidic solution for 3 h. Subsequently, the channel was flushed with water and was pretreated in an oven to obtain a sol-gel-modified PMMA microchip. The water contact angle for the sol-gel-modified PMMA was 27.4° compared with 66.3° for the pure PMMA. In addition, the electro-osmotic flow increased from 2.13×10-4 cm2 V-1 s-1 for the native-PMMA channel to 4.86×10-4 cm2 V-1 s-1 for the modified one. The analytical performance of the sol-gel-modified PMMA microchip was demonstrated for the electrophoretic separation of several purines, coupled with amperometric detection. The separation efficiency of uric acid increased to 74 882.3 m-1 compared with 14 730.5 m-1 for native-PMMA microchips. The result of this simple modification is a significant improvement in the performance of PMMA for microchip electrophoresis and microfluidic applications.

  2. Dynamic Light Scattering From Colloidal Gels

    NASA Technical Reports Server (NTRS)

    Krall, A. H.; Weitz, David A.

    1996-01-01

    We present a brief, preliminary account of the interpretation of dynamic light scattering from fractal colloidal gels. For small scattering angles, and for high initial colloid particle volume fractions, the correlation functions exhibit arrested decay, reflecting the non-ergodic nature of these systems and allowing us to directly determine the elastic modulus of the gels. For smaller initial volume fractions, the correlation functions decay completely. In all cases, the initial decay is not exponential, but is instead described by a stretched exponential. We summarize the principles of a model that accounts for these data and discuss the scaling behavior of the measured parameters.

  3. Patternable hybrid sol-gel glass

    NASA Astrophysics Data System (ADS)

    Jiang, HongJin; Yuan, XiaoCong; Chan, Yuen Chuen; Lam, Yee Loy

    2000-10-01

    The hybrid sol-gel materials have been extensively studied and widely used in the fabrication of optical devices due to their attractive properties. In this work, the synthesis of the UV sensitive organic- inorganic SiO2/TiO2 sol-gel glass is presented. The effect of the fabrication parameters such as doping concentration, bake temperature and UV light exposure time on the film characteristics (thickness and refractive index) are studied. A simple way of patterning the material by UV light radiation is also introduced. These demonstrate the material possesses high potential application for the micro-optics device fabrication.

  4. Neutron detector using sol-gel absorber

    DOEpatents

    Hiller, John M.; Wallace, Steven A.; Dai, Sheng

    1999-01-01

    An neutron detector composed of fissionable material having ions of lithium, uranium, thorium, plutonium, or neptunium, contained within a glass film fabricated using a sol-gel method combined with a particle detector is disclosed. When the glass film is bombarded with neutrons, the fissionable material emits fission particles and electrons. Prompt emitting activated elements yielding a high energy electron contained within a sol-gel glass film in combination with a particle detector is also disclosed. The emissions resulting from neutron bombardment can then be detected using standard UV and particle detection methods well known in the art, such as microchannel plates, channeltrons, and silicon avalanche photodiodes.

  5. Aggregation-structure-elasticity relationship of gels

    NASA Astrophysics Data System (ADS)

    Ma, Hang-Shing

    Aerogel is a mesoporous, low-density material which is desirable for applications like thermal insulation and low-k interlayer dielectric. However, its lack of mechanical integrity hinders its development. Experiments have shown that aerogels exhibit a scaling relationship E ∝ rho m between modulus E and density rho, with the exponent m usually between 3 and 4. The objective of the dissertation is to use computer modeling to understand how the random aggregation process accounts for the fractal structure and the compliant nature of aerogels. Model gels were created by the diffusion-limited cluster-cluster aggregation (DLCA), which simulates random aggregation leading to the sol-gel transition. Then each resulting structure was modeled as an elastic beam network and numerically compressed using the finite element method (FEM). Analyses showed that the DLCA gels reproduced the scaling relationship after trimming the non-contributive dangling branches from the mechanically efficient looped networks. The dangling bond deflection (DEF) model was therefore developed to model the random rotational movement of the dangling branches and the subsequent loop structure formation. Model gels with extensive loops and negligible dangling branches were simulated by combining the DLCA and DEF models. Representation of the aerogel networks by the DLCADEF models was validated for the resemblance of the fractal geometry and elastic behavior. The lack of mechanical integrity in aerogels is a natural consequence of the random aggregation and the resulting fractal structure. Fractal clusters are created in the early stage of aggregation, each of which is characterized by a dense core and sparse perimeter. These clusters grow in size until they percolate at the gel point by knitting together at the perimeters. The gel structure possesses a "blob-and-link" architecture, with the blobs representing the rigid cores of the fractal clusters, and the links corresponding to the tenuous chains formed between the clusters at percolation. Finite element analysis illustrates that the strain energy always localizes at the links in the DLCADEF gels. Therefore the stiffness of an aerogel is reduced by the presence of these compliant links. The key to synthesizing stiffer gels is to homogenize the distribution and cross-linking of mass during the formation of the network.

  6. Effective Management of FXG Gel Dosimetry

    NASA Astrophysics Data System (ADS)

    Olding, T.; Darko, J.; Schreiner, L. J.

    2010-11-01

    The details of a calibration basis for the Fricke-xylenol orange-gelatin (FXG) gel dosimeter combined with the fast, easily accessible readout tool of cone beam optical computed tomography (CT) are described in this report. With proper controls in place, the results from a test intensity modulated radiation therapy (IMRT) treatment plan evaluation indicate that greater than 95% Low's gamma function agreement between plan and gel-measured dose using 3% dose and 3 mm distance-to-agreement criteria is achievable.

  7. Hybrid sol-gel optical materials

    DOEpatents

    Zeigler, John M.

    1992-01-01

    Hybrid sol-gel materials comprise silicate sols cross-linked with linear polysilane, polygermane, or poly(silane-germane). The sol-gel materials are useful as optical identifiers in tagging and verification applications and, in a different aspect, as stable, visible light transparent non-linear optical materials. Methyl or phenyl silicones, polyaryl sulfides, polyaryl ethers, and rubbery polysilanes may be used in addition to the linear polysilane. The linear polymers cross-link with the sol to form a matrix having high optical transparency, resistance to thermooxidative aging, adherence to a variety of substrates, brittleness, and a resistance to cracking during thermal cycling.

  8. Hybrid sol-gel optical materials

    DOEpatents

    Zeigler, John M.

    1993-01-01

    Hybrid sol-gel materials comprise silicate sols cross-linked with linear polysilane, polygermane, or poly(silane-germane). The sol-gel materials are useful as optical identifiers in tagging and verification applications and, in a different aspect, as stable, visible light transparent non-linear optical materials. Methyl or phenyl silicones, polyaryl sulfides, polyaryl ethers, and rubbery polysilanes may be used in addition to the linear polysilane. The linear polymers cross-link with the sol to form a matrix having high optical transparency, resistance to thermooxidative aging, adherence to a variety of substrates, brittleness, and a resistance to cracking during thermal cycling.

  9. Hybrid sol-gel optical materials

    DOEpatents

    Zeigler, J.M.

    1993-04-20

    Hybrid sol-gel materials comprise silicate sols cross-linked with linear polysilane, polygermane, or poly(silane-germane). The sol-gel materials are useful as optical identifiers in tagging and verification applications and, in a different aspect, as stable, visible light transparent non-linear optical materials. Methyl or phenyl silicones, polyaryl sulfides, polyaryl ethers, and rubbery polysilanes may be used in addition to the linear polysilane. The linear polymers cross-link with the sol to form a matrix having high optical transparency, resistance to thermooxidative aging, adherence to a variety of substrates, brittleness, and a resistance to cracking during thermal cycling.

  10. Advances in biomedical applications of pectin gels.

    PubMed

    Munarin, F; Tanzi, M C; Petrini, P

    2012-11-01

    Pectin, due to its simple and cytocompatible gelling mechanism, has been recently exploited for different biomedical applications including drug delivery, gene delivery, wound healing and tissue engineering. Recent studies involving pectin for the biomedical field are reviewed, with the aim to capture the state of art on current research about pectin gels for biomedical applications, moving outside the traditional fields of application such as the food industry or pharmaceutics. Pectin structure, sources and extraction procedures have been discussed focussing on the properties of the polysaccharide that can be tuned to optimize the gels for a desired application and possess a fundamental role in application of pectin in the biomedical field. PMID:22776748

  11. Alignment and nonlinear elasticity in biopolymer gels

    NASA Astrophysics Data System (ADS)

    Feng, Jingchen; Levine, Herbert; Mao, Xiaoming; Sander, Leonard M.

    2015-04-01

    We present a Landau-type theory for the nonlinear elasticity of biopolymer gels with a part of the order parameter describing induced nematic order of fibers in the gel. We attribute the nonlinear elastic behavior of these materials to fiber alignment induced by strain. We suggest an application to contact guidance of cell motility in tissue. We compare our theory to simulation of a disordered lattice model for biopolymers. We treat homogeneous deformations such as simple shear, hydrostatic expansion, and simple extension, and obtain good agreement between theory and simulation. We also consider a localized perturbation which is a simple model for a contracting cell in a medium.

  12. Analytics for Metabolic Engineering.

    PubMed

    Petzold, Christopher J; Chan, Leanne Jade G; Nhan, Melissa; Adams, Paul D

    2015-01-01

    Realizing the promise of metabolic engineering has been slowed by challenges related to moving beyond proof-of-concept examples to robust and economically viable systems. Key to advancing metabolic engineering beyond trial-and-error research is access to parts with well-defined performance metrics that can be readily applied in vastly different contexts with predictable effects. As the field now stands, research depends greatly on analytical tools that assay target molecules, transcripts, proteins, and metabolites across different hosts and pathways. Screening technologies yield specific information for many thousands of strain variants, while deep omics analysis provides a systems-level view of the cell factory. Efforts focused on a combination of these analyses yield quantitative information of dynamic processes between parts and the host chassis that drive the next engineering steps. Overall, the data generated from these types of assays aid better decision-making at the design and strain construction stages to speed progress in metabolic engineering research. PMID:26442249

  13. Analytics for Metabolic Engineering

    PubMed Central

    Petzold, Christopher J.; Chan, Leanne Jade G.; Nhan, Melissa; Adams, Paul D.

    2015-01-01

    Realizing the promise of metabolic engineering has been slowed by challenges related to moving beyond proof-of-concept examples to robust and economically viable systems. Key to advancing metabolic engineering beyond trial-and-error research is access to parts with well-defined performance metrics that can be readily applied in vastly different contexts with predictable effects. As the field now stands, research depends greatly on analytical tools that assay target molecules, transcripts, proteins, and metabolites across different hosts and pathways. Screening technologies yield specific information for many thousands of strain variants, while deep omics analysis provides a systems-level view of the cell factory. Efforts focused on a combination of these analyses yield quantitative information of dynamic processes between parts and the host chassis that drive the next engineering steps. Overall, the data generated from these types of assays aid better decision-making at the design and strain construction stages to speed progress in metabolic engineering research. PMID:26442249

  14. Effect of gel matrix confinement on the solvent dynamics in supramolecular gels.

    PubMed

    Kowalczuk, Joanna; Rachocki, Adam; Bielejewski, Michał; Tritt-Goc, Jadwiga

    2016-06-15

    Supramolecular gels formed by the sugar gelator of methyl-4,6-O-(p-nitrobenzylidene)-α-d-glucopyranoside (1) with 1,3-propanediol (PG) and 1-butanol (BU) were prepared with different gelator concentrations. The solvent dynamics within gels, characterized by the diffusion coefficient (D) and the spin-lattice relaxation time (T1), was the subject of NMR diffusometry and relaxometry studies. The diffusion was studied as a function of diffusion time and gelator concentrations. The relaxation time was measured as a function of Larmor frequency. The decrease of the diffusion coefficient was observed as a function of diffusion time for both gels and for all studied gelator concentrations. It is indicative of the confinement effect due to the geometrical restrictions of the gel matrix. The relaxation data for PG solvent confined in 1/PG gel revealed the low frequency dispersion (in kHz region) which is a fingerprint of a specific interaction experienced by PG solvents in the presence of the rigid structure of gelator 1 aggregates. The relaxation model, well known from the interpretation of liquid confined in nanopores as reorientations mediated by translational displacements (RMTD), was successfully applied to analyze the data of studied solvents confined in matrices of supramolecular gels. The microstructures of gel matrices were imaged by Polarized Microscopy. PMID:27003500

  15. Gel-expanded to gel-condensed transition in neurofilament networks revealed by direct force measurements

    NASA Astrophysics Data System (ADS)

    Beck, Roy; Deek, Joanna; Jones, Jayna B.; Safinya, Cyrus R.

    2010-01-01

    Neurofilaments (NF)-the principal cytoskeletal constituent of myelinated axons in vertebrates-consist of three molecular-weight subunit proteins NF-L (low), NF-M (medium) and NF-H (high), assembled to form mature filaments with protruding unstructured C-terminus side arms. Liquid-crystal gel networks of side-arm-mediated neurofilament assemblies have a key role in the mechanical stability of neuronal processes. Disruptions of the neurofilament network, owing to neurofilament over-accumulation or incorrect side-arm interactions, are a hallmark of motor-neuron diseases including amyotrophic lateral sclerosis. Using synchrotron X-ray scattering, we report on a direct measurement of forces in reconstituted neurofilament gels under osmotic pressure (P). With increasing pressure near physiological salt and average phosphorylation conditions, NF-LMH, comprising the three subunits near in vivo composition, or NF-LH gels, undergo for P>Pc~10kPa, an abrupt non-reversible gel-expanded to gel-condensed transition. The transition indicates side-arm-mediated attractions between neurofilaments consistent with an electrostatic model of interpenetrating chains. In contrast, NF-LM gels remain in a collapsed state for Pgel-condensed state at P>Pc. These findings, which delineate the distinct roles of NF-M and NF-H in regulating neurofilament interactions, shed light on possible mechanisms for disruptions of optimal mechanical network properties.

  16. Free forming of the gel by 3D gel printer SWIM-ER

    NASA Astrophysics Data System (ADS)

    Okada, Koji; Tase, Taishi; Saito, Azusa; Makino, Masato; Gong, Jin; Kawakami, Masaru; Furukawa, Hidemitsu

    2015-04-01

    Gels, soft and wet materials, have unique properties such as material permeability, biocompatibility and low friction, which are hardly found in hard and dry materials. These superior characteristics of hydrogels promise to expand the medical applications. In recent years, the optical 3D gel printer named SWIM-ER (Soft and Wet Industrial - Easy Realizer) was developed by our team in order to fabricate tough gels with free form. We are aiming to create artificial blood vessel of the gel material by 3D gel printer. Artificial blood vessel is expected to be used for vascular surgery practice. The artificial blood vessel made by 3D gel printer can be create to free form on the basis of the biological data of the patient. Therefore, we believe it is possible to contribute to increasing the success rate and safety of vascular surgery by creating artificial blood vessel with 3D gel printer. The modeling method of SWIM-ER is as follow. Pregel solution is polymerized by one-point UV irradiation with optical fiber. The irradiation area is controlled by computer program, so that exact 3D free forming is realized. In this study, synthesis conditions are re-examined in order to improve the degree of freedom of fabrication. The dimensional accuracy in height direction is improved by increasing the cross linker concentration. We examined the relationship of resolution to the pitch and UV irradiation time in order to improve the modeling accuracy.

  17. New possibilities of accurate particle characterisation by applying direct boundary models to analytical centrifugation.

    PubMed

    Walter, Johannes; Thajudeen, Thaseem; Süss, Sebastian; Segets, Doris; Peukert, Wolfgang

    2015-04-21

    Analytical centrifugation (AC) is a powerful technique for the characterisation of nanoparticles in colloidal systems. As a direct and absolute technique it requires no calibration or measurements of standards. Moreover, it offers simple experimental design and handling, high sample throughput as well as moderate investment costs. However, the full potential of AC for nanoparticle size analysis requires the development of powerful data analysis techniques. In this study we show how the application of direct boundary models to AC data opens up new possibilities in particle characterisation. An accurate analysis method, successfully applied to sedimentation data obtained by analytical ultracentrifugation (AUC) in the past, was used for the first time in analysing AC data. Unlike traditional data evaluation routines for AC using a designated number of radial positions or scans, direct boundary models consider the complete sedimentation boundary, which results in significantly better statistics. We demonstrate that meniscus fitting, as well as the correction of radius and time invariant noise significantly improves the signal-to-noise ratio and prevents the occurrence of false positives due to optical artefacts. Moreover, hydrodynamic non-ideality can be assessed by the residuals obtained from the analysis. The sedimentation coefficient distributions obtained by AC are in excellent agreement with the results from AUC. Brownian dynamics simulations were used to generate numerical sedimentation data to study the influence of diffusion on the obtained distributions. Our approach is further validated using polystyrene and silica nanoparticles. In particular, we demonstrate the strength of AC for analysing multimodal distributions by means of gold nanoparticles. PMID:25789666

  18. An x-ray CT polymer gel dosimetry prototype: II. Gel characterization and clinical application.

    PubMed

    Johnston, H; Hilts, M; Carrick, J; Jirasek, A

    2012-05-21

    This article reports on the dosimetric properties of a new N-isopropylacrylamide, high %T, polymer gel formulation (19.5%T, 23%C), optimized for x-ray computed tomography (CT) polymer gel dosimetry (PGD). In addition, a new gel calibration technique is introduced together with an intensity-modulated radiation therapy (IMRT) treatment validation as an example of a clinical application of the new gel dosimeter. The dosimetric properties investigated include the temporal stability, spatial stability, batch reproducibility and dose rate dependence. The polymerization reaction is found to stabilize after 15 h post-irradiation. Spatial stability investigations reveal a small overshoot in response for gels imaged later than 36 h post-irradiation. Based on these findings, it is recommended that the new gel formulation be imaged between 15-36 h after irradiation. Intra- and inter-batch reproducibility are found to be excellent over the entire range of doses studied (0-28 Gy). A significant dose rate dependence is found for gels irradiated between 100-600 MU min⁻¹. Overall, the new gel is shown to have promising characteristics for CT PGD, however the implication of the observed dose rate dependence for some clinical applications remains to be determined. The new gel calibration method, based on pixel-by-pixel matching of dose and measured CT numbers, is found to be robust and to agree with the previously used region of interest technique. Pixel-by-pixel calibration is the new recommended standard for CT PGD. The dose resolution for the system was excellent, ranging from 0.2-0.5 Gy for doses between 0-20 Gy and 0.3-0.6 Gy for doses beyond 20 Gy. Comparison of the IMRT irradiation with planned doses yields excellent results: gamma pass rate (3%, 3 mm) of 99.3% at the isocentre slice and 93.4% over the entire treated volume. PMID:22547527

  19. Synthesis of porphyrin-introduced silica gels by sol-gel process.

    PubMed

    Tanaka, Hidekazu; Yamada, Toshiyuki; Sugiyama, Shinichiro; Shiratori, Hideo; Hino, Ryozi

    2005-06-15

    Using a hydroxyl group appended free base porphyrin derivative (HP), porphyrin-introduced silica gels were synthesized by a sol-gel process. The HP content in the materials linearly increased with increasing the HP concentration. Meanwhile, free base tetraphenylporphyrin (TPP) with no hydroxyl groups were almost not incorporated into the silica gels. These facts suggested that the interaction between hydroxyl groups of the HP molecules and silica network is considerably strong. The UV-vis characters of HP-introduced materials were almost the same as pure HP molecules. The Beer's plot indicated that the HP molecules in the materials are dispersed. PMID:15897099

  20. Analytical laboratory quality audits

    SciTech Connect

    Kelley, William D.

    2001-06-11

    Analytical Laboratory Quality Audits are designed to improve laboratory performance. The success of the audit, as for many activities, is based on adequate preparation, precise performance, well documented and insightful reporting, and productive follow-up. Adequate preparation starts with definition of the purpose, scope, and authority for the audit and the primary standards against which the laboratory quality program will be tested. The scope and technical processes involved lead to determining the needed audit team resources. Contact is made with the auditee and a formal audit plan is developed, approved and sent to the auditee laboratory management. Review of the auditee's quality manual, key procedures and historical information during preparation leads to better checklist development and more efficient and effective use of the limited time for data gathering during the audit itself. The audit begins with the opening meeting that sets the stage for the interactions between the audit team and the laboratory staff. Arrangements are worked out for the necessary interviews and examination of processes and records. The information developed during the audit is recorded on the checklists. Laboratory management is kept informed of issues during the audit so there are no surprises at the closing meeting. The audit report documents whether the management control systems are effective. In addition to findings of nonconformance, positive reinforcement of exemplary practices provides balance and fairness. Audit closure begins with receipt and evaluation of proposed corrective actions from the nonconformances identified in the audit report. After corrective actions are accepted, their implementation is verified. Upon closure of the corrective actions, the audit is officially closed.

  1. Modeling the dynamics of a tracer particle in an elastic active gel

    NASA Astrophysics Data System (ADS)

    Ben-Isaac, E.; Fodor, É.; Visco, P.; van Wijland, F.; Gov, Nir S.

    2015-07-01

    The internal dynamics of active gels both in artificial (in vitro) model systems and inside the cytoskeleton of living cells has been extensively studied with experiments of recent years. These dynamics are probed using tracer particles embedded in the network of biopolymers together with molecular motors, and distinct nonthermal behavior is observed. We present a theoretical model of the dynamics of a trapped active particle, which allows us to quantify the deviations from equilibrium behavior, using both analytic and numerical calculations. We map the different regimes of dynamics in this system and highlight the different manifestations of activity: breakdown of the virial theorem and equipartition, different elasticity-dependent "effective temperatures," and distinct non-Gaussian distributions. Our results shed light on puzzling observations in active gel experiments and provide physical interpretation of existing observations, as well as predictions for future studies.

  2. Modeling the dynamics of a tracer particle in an elastic active gel.

    PubMed

    Ben-Isaac, E; Fodor, É; Visco, P; van Wijland, F; Gov, Nir S

    2015-07-01

    The internal dynamics of active gels both in artificial (in vitro) model systems and inside the cytoskeleton of living cells has been extensively studied with experiments of recent years. These dynamics are probed using tracer particles embedded in the network of biopolymers together with molecular motors, and distinct nonthermal behavior is observed. We present a theoretical model of the dynamics of a trapped active particle, which allows us to quantify the deviations from equilibrium behavior, using both analytic and numerical calculations. We map the different regimes of dynamics in this system and highlight the different manifestations of activity: breakdown of the virial theorem and equipartition, different elasticity-dependent "effective temperatures," and distinct non-Gaussian distributions. Our results shed light on puzzling observations in active gel experiments and provide physical interpretation of existing observations, as well as predictions for future studies. PMID:26274211

  3. The effective diffusion coefficient of a small molecule in a two-phase gel medium

    NASA Astrophysics Data System (ADS)

    Kingsburry, Christine; Slater, Gary W.

    2009-12-01

    Using simple theoretical arguments and exact numerical lattice calculations, Hickey et al. [J. Chem. Phys. 124, 204903 (2006)] derived and tested an expression for the effective diffusion coefficient of a probe molecule in a two-phase medium consisting of a hydrogel with large gel-free inclusions. Although providing accurate predictions, this expression neglects important characteristics that such two-phase systems can present. In this article, we extend the previously derived expression in order to include local interactions between the gel and the analyte, interfacial effects between the main phase and the inclusions, and finally a possible incomplete separation between the two phases. We test our new, generalized expressions using exact numerical calculations. These generalized equations should be a useful tool for the development of novel multiphase systems for specific applications, such as drug-delivery platforms.

  4. A specific stain for the detection of nonheme iron proteins in polyacrylamide gels.

    PubMed

    Leong, L M; Tan, B H; Ho, K K

    1992-12-01

    Nonheme iron proteins can be visualized as blue bands in native polyacrylamide gels using a staining method that is both simple and rapid. The reaction of potassium ferricyanide with protein-bound iron atoms to form royal blue complexes occurs almost instantaneously and is sensitive enough to detect 1 microgram of analytical-grade ferritin and 2 micrograms of purified ferredoxin from cyanobacteria. No special treatment of reagents or apparatus was necessary. On comparison, this stain was found to be more specific than the Ferene S stain, not detecting bovine serum albumin even when present as a hundredfold excess over ferritin. The method was found to be effective for isoelectric focusing gels as well. PMID:1282787

  5. Gel Permeation Chromatography of Fluoroether Polymers

    NASA Technical Reports Server (NTRS)

    Korus, Roger A.; Rosser, Robert W.

    1978-01-01

    A Method is described for determining the molecular weight distribution of fluorinated polymers by gel permeation chromatography. Porous silica-packed columns are used with Freon 113 as the chromatographic solvent. Fluoroether oligomers are used for column calibration in the molecular weight range of 1400 to 12000.

  6. Electrophoretic Porosimetry of Sol-Gels

    NASA Technical Reports Server (NTRS)

    Snow, L. A.; Smith, D. D.; Sibille, L.; Hunt, A. J.; Ng, J.; Rose, M. Franklin (Technical Monitor)

    2000-01-01

    It has been hypothesized that gravity has an effect on the formation and resulting microstructure of sol-gels. In order to more clearly resolve the effect of gravity, pores may be non-destructively analyzed in the wet gel, circumventing the shrinkage and coarsening associated with the drying procedure. We discuss the development of an electrophoretic technique, analogous to affinity chromatography, for the determination of pore size distribution and its application to silica gels. Specifically a monodisperse charged dye is monitored by an optical densitometer as it moves through the wet gel under the influence of an electric field. The transmittance data (output) represents the convolution of the dye concentration profile at the beginning of the run (input) with the pore size distribution (transfer function), i.e. linear systems theory applies. Because of the practical difficulty in producing a delta function input dye profile we prefer instead to use a step function. Average pore size is then related to the velocity of this dye front, while the pore size distribution is related to the spreading of the front. Preliminary results of this electrophoretic porosimetry and its application to ground and space-grown samples will be discussed.

  7. Non-diffusing radiochromic micelle gel

    NASA Astrophysics Data System (ADS)

    Jordan, Kevin; Sekimoto, Masaya

    2010-11-01

    The addition of Laponite, a synthetic clay nanoparticle material to radiochromic leuco Malachite Green micelle hydrogel eliminates diffusion of the cationic dye by electrostatic binding. The clay nanoparticles also increased dose sensitivity ten-fold relative to the parent gel formulation. This material is a suitable 3D water equivalent dosimeter with optical CT readout.

  8. Simple Cloud Chambers Using Gel Ice Packs

    ERIC Educational Resources Information Center

    Kamata, Masahiro; Kubota, Miki

    2012-01-01

    Although cloud chambers are highly regarded as teaching aids for radiation education, school teachers have difficulty in using cloud chambers because they have to prepare dry ice or liquid nitrogen before the experiment. We developed a very simple and inexpensive cloud chamber that uses the contents of gel ice packs which can substitute for dry

  9. Interrupted Nazarov cyclization on silica gel.

    PubMed

    Dhoro, Francis; Tius, Marcus A

    2005-09-14

    Exposure of a mixture of propargyl vinyl ketone and a nucleophilic primary or secondary amine to activated dry silica gel in the absence of solvent leads to a cascade of reactions that results in the formation of an aminocyclopentenone. The reaction with triethylamine leads to a cross-conjugated cyclopentadienone. PMID:16144378

  10. Gel Filtration Chromatography: A Laboratory Experiment.

    ERIC Educational Resources Information Center

    Hurlbut, Jeffrey A.; Schonbeck, Niels D.

    1984-01-01

    Describes a rapid, visual demonstration of protein separation by gel filtration chromatography. The procedure separates two highly colored proteins of different molecular weights on a Sephadex G-75 in 45 minutes. This time includes packing the column as well. Background information, reagents needed, procedures used, and results obtained are…

  11. Gel bead composition for metal adsorption

    DOEpatents

    Scott, Charles D.; Woodward, Charlene A.; Byers, Charles H.

    1991-01-01

    The invention is a gel bead comprising propylene glycol alginate and bone gelatin and is capable of removing metals such as Sr and Cs from solution without adding other adsorbents. The invention could have application to the nuclear industry's waste removal activities.

  12. Gel bead composition for metal adsorption

    DOEpatents

    Scott, Charles D.; Woodward, Charlene A.; Byers, Charles H.

    1990-01-01

    The invention is a gel bead comprising propylene glycol alginate and bone gelatin and is capable of removing metals such as Sr and Cs from solution without adding other adsorbents. The invention could have application to the nuclear industry's waste removal activities.

  13. Sol-Gel Derived Hafnia Coatings

    NASA Technical Reports Server (NTRS)

    Feldman, Jay D.; Stackpoole, Mairead; Blum, Yigal; Sacks, Michael; Ellerby, Don; Johnson, Sylvia M.; Venkatapathy, Ethiras (Technical Monitor)

    2002-01-01

    Sol-gel derived hafnia coatings are being developed to provide an oxidation protection layer on ultra-high temperature ceramics for potential use in turbine engines (ultra-efficient engine technology being developed by NASA). Coatings using hafnia sol hafnia filler particles will be discussed along with sol synthesis and characterization.

  14. Cell viability in a wet silica gel.

    PubMed

    Nieto, Alejandra; Areva, Sami; Wilson, Timothy; Viitala, Reeta; Vallet-Regi, Maria

    2009-11-01

    A modified two-step sol-gel route using silicon ethoxide (TEOS) has been used to synthesize amorphous sol-gel-derived silica, which has been successfully used as a cell encapsulation matrix for 3T3 mouse fibroblasts and CRL-2595 epithelial cells due to its non-toxicity. The sol-gel procedure comprised a first, low pH hydrolysis step, followed by a neutral condensation-gelation step. A high water-to-TEOS ratio and the addition of d-glucose as a porogen and source of nutrients were chosen to minimize silica dissolution and improve the biocompatibility of the process. Indeed, the cell integrity in the encapsulation process was preserved by alcohol removal from the starting solution. Cells were then added in a buffered medium, causing rapid gelation and entrapment of the cells within a randomly structured siloxane matrix in the shape of a monolith, which was maintained in the wet state. MTT and alamarBlue assays were used to check the cytotoxicity of the silica gels and the viability of entrapped cells at initial times in contact with silica. To improve cell attachment, cell clumping experiments - where groups of cells were formed - were designed, rendering improved viability. The obtained materials are therefore excellent candidates for designing tissue-culture scaffolds and implantable bioreactors for biomedical applications. PMID:19481618

  15. Driven Polymer Translocation into a Crosslinked Gel

    NASA Astrophysics Data System (ADS)

    Sean, David; Slater, Gary

    2015-03-01

    In a typical polymer translocation setup, a thin membrane is used to separate two chambers and a polyelectrolyte is driven by an electric field to translocate from one side of the membrane to the other via a small nanopore. However, the high translocation rate that results from the forces required to drive this process makes optical and/or electrical analysis of the translocating polymer challenging. Using coarse-grained Langevin Dynamics simulations we investigate how the translocation process can be slowed down by placing a crosslinked gel on the trans-side of the membrane. Since the driving electric field is localized in the neighborhood of the nanopore, electrophoretic migration is only achieved by a ``pushing'' action from the polymer segment residing in the nanopore. For the case of a flexible polymer we find that the polymer fills the gel pores via multiple ``herniation'' processes, whereas for a semi-flexible chain in a tight gel there are no hernias and the polymer follows a smooth curvilinear path. Moreover, for the case of a semi-flexible polymer the gel makes the translocation process more uniform by reducing the acceleration at the end of the process.

  16. Sol-Gel Synthesis Of Aluminoborosilicate Powders

    NASA Technical Reports Server (NTRS)

    Bull, Jeffrey; Leiser, Daniel; Selvaduray, Guna

    1992-01-01

    Application of sol-gel process to synthesis of aluminoborosilicate powders shows potential for control of microstructures of materials. Development of materials having enhanced processing characteristics prove advantageous in extending high-temperature endurance of fibrous refractory composite insulation made from ceramic fibers.

  17. Polyelectrolyte gels: Ionic partners split up

    NASA Astrophysics Data System (ADS)

    Colby, Ralph H.

    2007-06-01

    Polyelectrolyte gels are currently used as superabsorbers for polar solvents, such as water. Designing them so that the polyelectrolyte chains and their counterions don't get too close to each other makes them useful for absorbing less-polar solvents, too.

  18. Simple Cloud Chambers Using Gel Ice Packs

    ERIC Educational Resources Information Center

    Kamata, Masahiro; Kubota, Miki

    2012-01-01

    Although cloud chambers are highly regarded as teaching aids for radiation education, school teachers have difficulty in using cloud chambers because they have to prepare dry ice or liquid nitrogen before the experiment. We developed a very simple and inexpensive cloud chamber that uses the contents of gel ice packs which can substitute for dry…

  19. 3D gel printing for soft-matter systems innovation

    NASA Astrophysics Data System (ADS)

    Furukawa, Hidemitsu; Kawakami, Masaru; Gong, Jin; Makino, Masato; Kabir, M. Hasnat; Saito, Azusa

    2015-04-01

    In the past decade, several high-strength gels have been developed, especially from Japan. These gels are expected to use as a kind of new engineering materials in the fields of industry and medical as substitutes to polyester fibers, which are materials of artificial blood vessels. We consider if various gel materials including such high-strength gels are 3D-printable, many new soft and wet systems will be developed since the most intricate shape gels can be printed regardless of the quite softness and brittleness of gels. Recently we have tried to develop an optical 3D gel printer to realize the free-form formation of gel materials. We named this apparatus Easy Realizer of Soft and Wet Industrial Materials (SWIM-ER). The SWIM-ER will be applied to print bespoke artificial organs, including artificial blood vessels, which will be possibly used for both surgery trainings and actual surgery. The SWIM-ER can print one of the world strongest gels, called Double-Network (DN) gels, by using UV irradiation through an optical fiber. Now we also are developing another type of 3D gel printer for foods, named E-Chef. We believe these new 3D gel printers will broaden the applications of soft-matter gels.

  20. Electrochemical impedimetric sensor based on molecularly imprinted polymers/sol-gel chemistry for methidathion organophosphorous insecticide recognition.

    PubMed

    Bakas, Idriss; Hayat, Akhtar; Piletsky, Sergey; Piletska, Elena; Chehimi, Mohamed M; Noguer, Thierry; Rouillon, Régis

    2014-12-01

    We report here a novel method to detect methidathion organophosphorous insecticides. The sensing platform was architected by the combination of molecularly imprinted polymers and sol-gel technique on inexpensive, portable and disposable screen printed carbon electrodes. Electrochemical impedimetric detection technique was employed to perform the label free detection of the target analyte on the designed MIP/sol-gel integrated platform. The selection of the target specific monomer by electrochemical impedimetric methods was consistent with the results obtained by the computational modelling method. The prepared electrochemical MIP/sol-gel based sensor exhibited a high recognition capability toward methidathion, as well as a broad linear range and a low detection limit under the optimized conditions. Satisfactory results were also obtained for the methidathion determination in waste water samples. PMID:25159412

  1. (3-Mercaptopropyl)trimethoxysilane-derived Porous Gel Monolith via Thioacetal Reaction-Assisted Sol-Gel Route

    NASA Astrophysics Data System (ADS)

    Ito, S.; Nishi, M.; Kanamori, K.; Nakanishi, K.; Kurahashi, T.; Matsubara, S.; Shimotsuma, Y.; Miura, K.; Hirao, K.

    2011-10-01

    Porous gel monolith was synthesized by reacting (3-mercaptopropyl)trimethoxysilane (MPTMS) with acetone on acidic conditions. It is known that MPTMS itself is difficult to turn into gel on acidic conditions and instead oligomers are obtained owing to the large mercaptopropyl group. In our system, the gels were obtained since acetone worked as a cross-linker via thioacetal reaction. Additionally, Au ions were selectively adsorbed on the obtained gel. When an obtained white gel was soaked in a chloroauric acid solution, the gel turned brown and was getting dark depending on the soaked time; on the other hand, the color of the solution turned from yellow to colorless.

  2. The Case for Assessment Analytics

    ERIC Educational Resources Information Center

    Ellis, Cath

    2013-01-01

    Learning analytics is a relatively new field of inquiry and its precise meaning is both contested and fluid (Johnson, Smith, Willis, Levine & Haywood, 2011; LAK, n.d.). Ferguson (2012) suggests that the best working definition is that offered by the first Learning Analytics and Knowledge (LAK) conference: "the measurement, collection,…

  3. Analytic Geometry, A Tentative Guide.

    ERIC Educational Resources Information Center

    Helwig, G. Alfred; And Others

    This teacher's guide for a semester course in analytic geometry is based on the text "Analytic Geometry" by W. K. Morrill. Included is a daily schedule of suggested topics and homework assignments. Specific teaching hints are also given. The content of the course includes point and plane vectors, straight lines, point and space vectors, planes,…

  4. Understanding Education Involving Geovisual Analytics

    ERIC Educational Resources Information Center

    Stenliden, Linnea

    2013-01-01

    Handling the vast amounts of data and information available in contemporary society is a challenge. Geovisual Analytics provides technology designed to increase the effectiveness of information interpretation and analytical task solving. To date, little attention has been paid to the role such tools can play in education and to the extent to which…

  5. Synthetic and Biopolymer Gels - Similarities and Difference.

    NASA Astrophysics Data System (ADS)

    Horkay, Ferenc

    2006-03-01

    Ion exchange plays a central role in a variety of physiological processes, such as nerve excitation, muscle contraction and cell locomotion. Hydrogels can be used as model systems for identifying fundamental chemical and physical interactions that govern structure formation, phase transition, etc. in biopolymer systems. Polyelectrolyte gels are particularly well-suited to study ion-polymer interactions because their structure and physical-chemical properties (charge density, crosslink density, etc) can be carefully controlled. They are sensitive to different external stimuli such as temperature, ionic composition and pH. Surprisingly few investigations have been made on polyelectrolyte gels in salt solutions containing both monovalent and multivalent cations. We have developed an experimental approach that combines small angle neutron scattering and osmotic swelling pressure measurements. The osmotic pressure exerted on a macroscopic scale is a consequence of changes occurring at a molecular level. The intensity of the neutron scattering signal, which provides structural information as a function of spatial resolution, is directly related to the osmotic pressure. We have found a striking similarity in the scattering and osmotic behavior of polyacrylic acid gels and DNA gels swollen in nearly physiological salt solutions. Addition of calcium ions to both systems causes a sudden volume change. This volume transition, which occurs when the majority of the sodium counterions are replaced by calcium ions, is reversible. Such reversibility implies that the calcium ions are not strongly bound by the polyanion, but are free to move along the polymer chain, which allows these ions to form temporary bridges between negative charges on adjacent chains. Mechanical measurements reveal that the elastic modulus is practically unchanged in the calcium-containing gels, i.e., ion bridging is qualitatively different from covalent crosslinks.

  6. Effectiveness of Gel Repellents on Feral Pigeons

    PubMed Central

    Stock, Birte; Haag-Wackernagel, Daniel

    2013-01-01

    Simple Summary Feral pigeons live in close association in urban areas. They constitute serious health risks to humans and also lead to high economic loss due to costly damage to buildings, historic monuments, statues and even vegetation. While numerous avian repellent systems are regularly introduced onto the market, scientific proof of efficacy and their use from the point of view of animal welfare is lacking. Therefore, two avian gel repellents were studied on free-living feral pigeons in this study. The focus was set on repellent efficacy and animal welfare concerns. This study’s aim is to contribute to a better understanding of feral pigeon management in our cities. Abstract Millions of feral pigeons (Columba livia) live in close association with the human population in our cities. They pose serious health risks to humans and lead to high economic loss due to damage caused to buildings. Consequently, house owners and city authorities are not willing to allow pigeons on their buildings. While various avian repellents are regularly introduced onto the market, scientific proof of efficacy is lacking. This study aimed at testing the effectiveness of two avian gel repellents and additionally examined their application from animal welfare standpoint. The gels used an alleged tactile or visual aversion of the birds, reinforced by additional sensory cues. We mounted experimental shelves with the installed repellents in a pigeon loft and observed the behavior of free-living feral pigeons towards the systems. Both gels showed a restricted, transient repellent effect, but failed to prove the claimed complete effectiveness. Additionally, the gels’ adhesive effect remains doubtful in view of animal welfare because gluing of plumage presents a risk to feral pigeons and also to other non-target birds. This study infers that both gels lack the promised complete efficacy, conflict with animal welfare concerns and are therefore not suitable for feral pigeon management in urban areas. PMID:26479881

  7. Development of novel Sol-Gel Indicators (SGI`s) for in-situ environmental measurements: Part 1, Program and a new pH Sol-Gel Indicator

    SciTech Connect

    Livingston, R.R.; Baylor, L.; Wicks, G.G.

    1992-11-03

    The feasibility of incorporating analytical indicators into a sol-gel glassy matrix and then coating substrates with this composite material has bee demonstrated. Substrates coated include paper, wood, glass, and the lens of an analytical probe. The first SRTC sol-gel indicator, comprising bromophenol blue dispersed in a silica matrix, was fabricated and successfully used to measure solution pH in the range of pH 3.0 to 7.5. material exhibited a quick response time, as measured by color changes both qualitatively and quantitatively, and the measuring device was reversible or reusable. Additional indicators with responses over other ranges as well as indicators sensitive to the presence of elements of interest, are also under development. The new SGI composites possess promising properties and an excellent potential for performing a variety important in-situ environmental measurements and area discussed in this report.

  8. Sol-Gel Synthesis of Au-Nanoparticle Dispersed Bicontinuous Macroporous Siloxane Gel

    NASA Astrophysics Data System (ADS)

    Hamada, Y.; Nishi, M.; Shimotsuma, Y.; Miura, K.; Hirao, K.

    2011-10-01

    We synthesized Au-nanoparticle dispersed siloxane gel with well-defined bicontinuous macroporous morphologies. We employed methyltrimethoxysilane (MTMS) as a precursor of the gel skeleton, and also employed hydrogen tetrachloroaurate(III) as both a precursor of Au nanoparticles and an acid catalyst for hydrolysis/condensation of methoxysilanes. The effect of adding (3-mercaptopropyl)trimethoxysilane (MPTMS) as a starting material on the obtained structure was also investigated. It is found that Au nanoparticles of 20-30 nm in grain size are uniformly dispersed on the gel surface in the system containing MPTMS; in contrast, Au nanoparticles assembled in the pits in the MPTMS-free system. All the heat-treated MPTMS-containing gels showed surface plasmon absorption, and the peaks shifted from 550 to 520 nm with increasing the calcination temperature.

  9. Encapsulation of nanoclusters in dried gel materials via an inverse micelle/sol gel synthesis

    DOEpatents

    Martino, Anthony; Yamanaka, Stacey A.; Kawola, Jeffrey S.; Showalter, Steven K.; Loy, Douglas A.

    1998-01-01

    A dried gel material sterically entrapping nanoclusters of a catalytically active material and a process to make the material via an inverse micelle/sol-gel synthesis. A surfactant is mixed with an apolar solvent to form an inverse micelle solution. A salt of a catalytically active material, such as gold chloride, is added along with a silica gel precursor to the solution to form a mixture. To the mixture are then added a reducing agent for the purpose of reducing the gold in the gold chloride to atomic gold to form the nanoclusters and a condensing agent to form the gel which sterically entraps the nanoclusters. The nanoclusters are normally in the average size range of from 5-10 nm in diameter with a monodisperse size distribution.

  10. Encapsulation of nanoclusters in dried gel materials via an inverse micelle/sol gel synthesis

    DOEpatents

    Martino, A.; Yamanaka, S.A.; Kawola, J.S.; Showalter, S.K.; Loy, D.A.

    1998-09-29

    A dried gel material sterically entrapping nanoclusters of a catalytically active material and a process to make the material via an inverse micelle/sol-gel synthesis are disclosed. A surfactant is mixed with an apolar solvent to form an inverse micelle solution. A salt of a catalytically active material, such as gold chloride, is added along with a silica gel precursor to the solution to form a mixture. To the mixture are then added a reducing agent for the purpose of reducing the gold in the gold chloride to atomic gold to form the nanoclusters and a condensing agent to form the gel which sterically entraps the nanoclusters. The nanoclusters are normally in the average size range of from 5--10 nm in diameter with a monodisperse size distribution. 1 fig.

  11. Covalent Fusion of layered Incompatible Gels in Immiscible Solvents

    NASA Astrophysics Data System (ADS)

    Biswas, Santidan; Singh, Awaneesh; Matyjaszewski, Krzysztof; Balazs, Anna C.

    We carry out dissipative particle dynamics (DPD) simulations to model a two layered stackable gel where the gels are incompatible and are present in immiscible solvent. The bottom layer of the gel is created first and then a solution of new initiators, monomers and cross-linkers is introduced on top of it. These components then undergo polymerization and form the second gel layer. We study all possible combinations of free radical polymerization (FRP) and atom transfer radical polymerization (ATRP) mechanisms with the two layers of the gel. For example, the bottom layer gel is created via ATRP, whereas the top layer gel follows FRP. Our focus is to do a systematic study of all these combinations and find out the factors responsible for combining two incompatible gels in immiscible solvents.

  12. Electric field-induced deformation of polyelectrolyte gels

    SciTech Connect

    Adolf, D.; Hance, B.G.

    1995-08-01

    Water-swollen polyelectrolyte gels deform in an electric field. We observed that the sign and magnitude of the deformation is dependent on the nature of the salt bath in which the gel is immersed and electrocuted. These results are compatible with a deformation mechanism based upon creation of ion density gradients by the field which, in turn, creates osmotic pressure gradients within the gel. A consistent interpretation results only if gel mobility is allowed as well as free ion diffusion and migration.

  13. Metal-doped organic gels and method thereof

    DOEpatents

    Satcher, Jr., Joe H.; Baumann, Theodore F.

    2007-10-23

    Disclosed herein is a sol-gel polymerization process for synthesizing metal-doped organic gels. The process polymerizes metal salts of hydroxylated benzenes or hydroxylated benzene derivatives with alkyl or aryl aldehydes to form metal-doped, wet, organic gels. The gels can then be dried by supercritical solvent extraction to form metal-doped aerogels or by evaporation to form metal-doped xerogels. The aerogels and xerogels can then be pyrolyzed.

  14. Metal-doped organic gels and method thereof

    DOEpatents

    Satcher, Jr., Joe H.; Baumann, Theodore F.

    2003-09-02

    Disclosed herein is a sol-gel polymerization process for synthesizing metal-doped organic gels. The process polymerizes metal salts of hydroxylated benzenes or hydroxylated benzene derivatives with alkyl or aryl aldehydes to form metal-doped, wet, organic gels. The gels can then be dried by supercritical solvent extraction to form metal-doped aerogels or by evaporation to form metal-doped xerogels. The aerogels and xerogels can then be pyrolyzed.

  15. Methods of Manufacturing Bioactive Gels from Extracellular Matrix Material

    NASA Technical Reports Server (NTRS)

    Kentner, Kimberly A. (Inventor); Stuart, Katherine A. (Inventor); Janis, Abram D. (Inventor)

    2016-01-01

    The present invention is directed to methods of manufacturing bioactive gels from ECM material, i.e., gels which retain bioactivity, and can serve as scaffolds for preclinical and clinical tissue engineering and regenerative medicine approaches to tissue reconstruction. The manufacturing methods take advantage of a new recognition that bioactive gels from ECM material can be created by digesting particularized ECM material in an alkaline environment and neutralizing to provide bioactive gels.

  16. Methods of Manufacturing Bioactive Gels from Extracellular Matrix Material

    NASA Technical Reports Server (NTRS)

    Kentner, Kimberly A. (Inventor); Stuart, Katherine A. (Inventor); Janis, Abram D. (Inventor)

    2015-01-01

    The present invention is directed to methods of manufacturing bioactive gels from ECM material, i.e., gels which retain bioactivity, and can serve as scaffolds for preclinical and clinical tissue engineering and regenerative medicine approaches to tissue reconstruction. The manufacturing methods take advantage of a new recognition that bioactive gels from ECM material can be created by digesting particularized ECM material in an alkaline environment and neutralizing to provide bioactive gels.

  17. Methods of Manufacturing Bioactive Gels from Extracellular Matrix Material

    NASA Technical Reports Server (NTRS)

    Kentner, Kimberly A. (Inventor); Stuart, Katherine A. (Inventor); Janis, Abram D. (Inventor)

    2014-01-01

    The present invention is directed to methods of manufacturing bioactive gels from ECM material, i.e., gels which retain bioactivity, and can serve as scaffolds for preclinical and clinical tissue engineering and regenerative medicine approaches to tissue reconstruction. The manufacturing methods take advantage of a new recognition that bioactive gels from ECM material can be created by digesting particularized ECM material in an alkaline environment and neutralizing to provide bioactive gels.

  18. Gel-forming reagents and uses thereof for preparing microarrays

    DOEpatents

    Golova, Julia; Chernov, Boris; Perov, Alexander

    2010-11-09

    New gel-forming reagents including monomers and cross-linkers, which can be applied to gel-drop microarray manufacturing by using co-polymerization approaches are disclosed. Compositions for the preparation of co-polymerization mixtures with new gel-forming monomers and cross-linker reagents are described herein. New co-polymerization compositions and cross-linkers with variable length linker groups between unsaturated C.dbd.C bonds that participate in the formation of gel networks are disclosed.

  19. An unbreakable on-line approach towards sol-gel capillary microextraction.

    PubMed

    Bagheri, Habib; Piri-Moghadam, Hamed; Es'haghi, Ali

    2011-07-01

    In this work a novel unbreakable sol-gel-based in-tube device for on-line solid phase microextraction (SPME) was developed. The inner surface of a copper tube, intended to be used as a high performance liquid chromatography (HPLC) loop, was electrodeposited by metallic Cu followed by the self assembled monolayers (SAM) of 3-(mercaptopropyl) trimethoxysilane (3MPTMOS). Then, poly (ethyleneglycol) (PEG) was chemically bonded to the -OH sites of the SAM already covering the inner surface of the copper loop using sol-gel technology. The homogeneity and the porous surface structure of the SAM and sol-gel coatings were examined using the scanning electron microscopy (SEM) and adsorption/desorption porosimetry (BET). The prepared loop was used for online in-tube SPME (capillary microextraction) of some selected polycyclic aromatic hydrocarbons (PAHs), as model compounds, from the aquatic media. After extraction, the HPLC mobile phase was used for on-line desorption and elution of the extracted analytes from the loop to the HPLC column. Major parameters affecting the extraction efficiency including the sample flow rate through the copper tube, loading time, desorption time and sample volume were optimized. For investigating the sorbent efficiency, four loops based on the copper tube itself, the copper tube after electrodeposition with Cu and the tubes with the SAMs and SAMs-sol-gel coating were made and compared. The SAMs-sol-gel coated loop clearly shows a prominently lead of at least 20-100 times of higher efficiency. The linearity for the analytes was in the range of 0.01-500 μg L(-1). Limit of detection (LOD) was in the range of 0.005-0.5 μg L(-1) and the RSD% values (n=5) were all below 8.3% at the 5 μg L(-1) level. The developed method was successfully applied to real water samples while the relative recovery percentages obtained for the spiked water samples were from 90 to 104%. The prepared loop exhibited long life time due to its remarkable solvent and mechanical stability. Different solvents such as methanol, acetonitrile and acetone were passed through the loop for many days and it was also used for more than 100 extractions/desorption of the selected analytes and no decrease in the peak areas was observed. PMID:21616492

  20. Low temperature and UV curable sol-gel coatings for long lasting optical fiber biosensors

    NASA Astrophysics Data System (ADS)

    Otaduy, D.; Villar, A.; Gomez-Herrero, E.; Goitandia, A. M.; Gorritxategi, E.; Quintana, I.

    2010-04-01

    The use of optical fibers as sensing element is increasing in clinical, pharmaceutical and industrial applications. Excellent light delivery, long interaction length, low cost and ability not only to excite the target molecules but also to capture the emitted light from the targets are the hallmarks of optical fiber as biosensors. In biosensors based on fiber optics the interaction with the analyte can occur within an element of the optical fiber. One of the techniques for this kind of biosensors is to remove the fiber optic cladding and substitute it for biological coatings that will interact with the parameter to sensorize. The deposition of these layers can be made by sol-gel technology. The sol-gel technology is being increasingly used mainly due to the high versatility to tailor their optical features. Incorporation of suitable chemical and biochemical sensing agents have allowed determining pH, gases, and biochemical species, among others. Nonetheless, the relatively high processing temperatures and short lifetime values mean severe drawbacks for a successful exploitation of sol-gel based coated optical fibres. With regard to the latter, herein we present the design, preparation and characterization of novel sol-gel coated optical fibres. Low temperature and UV curable coating formulations were optimized to achieve a good adhesion and optical performance. The UV photopolymerizable formulation was comprised by glycidoxypropyltrimethoxysilane (GLYMO), Tetraethylorthosilicate (TEOS) and an initiator. While the thermoset coating was prepared by using 3-aminopropyltrimethoxysilane, GLYMO, and TEOS as main reagents. Both curable sol-gel coated fibres were analysed by FTIR, SEM and optical characterization. Furthermore, in the present work a new technique for silica cladding removal has been developed by ultra-short pulses laser processing, getting good dimensional accuracy and surface integrity.

  1. Hyaluronidase polymorphism detected by polyacrylamide gel electrophoresis. Application to hyaluronidases from bacteria, slime molds, bee and snake venoms, bovine testes, rat liver lysosomes, and human serum.

    PubMed

    Fiszer-Szafarz, B

    1984-11-15

    A gel electrophoretic technique which allows detection of hyaluronidase activity in the gel has been devised. The principle is that the high-molecular-weight substrate, hyaluronic acid, is included in the gel, where it cannot move in the electrical field. After the run, the gel is incubated under conditions allowing the enzyme to degrade the substrate. Upon staining with "Stains-all" dye (Eastman Kodak Co., 2718), zones of hyaluronidase activity appear as pink bands in a blue background. The sensitivity limit is less than 3 fkat equivalent to 2.2 NF mU. The method is applicable to all types of hyaluronidases and chondroitinase ABC. It enabled to be shown that some hyaluronidases are polymorphic. This technique also made it possible to detect easily hyaluronidase activity in normal human serum. This analytical method represents a convenient step in the purification of hyaluronidase. PMID:6084966

  2. Formulation and method for preparing gels comprising hydrous cerium oxide

    DOEpatents

    Collins, Jack L; Chi, Anthony

    2013-05-07

    Formulations useful for preparing hydrous cerium oxide gels contain a metal salt including cerium, an organic base, and a complexing agent. Methods for preparing gels containing hydrous cerium oxide include heating a formulation to a temperature sufficient to induce gel formation, where the formulation contains a metal salt including cerium, an organic base, and a complexing agent.

  3. Formulation and method for preparing gels comprising hydrous aluminum oxide

    SciTech Connect

    Collins, Jack L.

    2014-06-17

    Formulations useful for preparing hydrous aluminum oxide gels contain a metal salt including aluminum, an organic base, and a complexing agent. Methods for preparing gels containing hydrous aluminum oxide include heating a formulation to a temperature sufficient to induce gel formation, where the formulation contains a metal salt including aluminum, an organic base, and a complexing agent.

  4. 21 CFR 872.1730 - Electrode gel for pulp testers.

    Code of Federal Regulations, 2014 CFR

    2014-04-01

    ... 21 Food and Drugs 8 2014-04-01 2014-04-01 false Electrode gel for pulp testers. 872.1730 Section... (CONTINUED) MEDICAL DEVICES DENTAL DEVICES Diagnostic Devices § 872.1730 Electrode gel for pulp testers. (a) Identification. An electrode gel for pulp testers is a device intended to be applied to the surface of a...

  5. 21 CFR 872.1730 - Electrode gel for pulp testers.

    Code of Federal Regulations, 2010 CFR

    2010-04-01

    ... 21 Food and Drugs 8 2010-04-01 2010-04-01 false Electrode gel for pulp testers. 872.1730 Section... (CONTINUED) MEDICAL DEVICES DENTAL DEVICES Diagnostic Devices § 872.1730 Electrode gel for pulp testers. (a) Identification. An electrode gel for pulp testers is a device intended to be applied to the surface of a...

  6. 21 CFR 872.1730 - Electrode gel for pulp testers.

    Code of Federal Regulations, 2012 CFR

    2012-04-01

    ... 21 Food and Drugs 8 2012-04-01 2012-04-01 false Electrode gel for pulp testers. 872.1730 Section... (CONTINUED) MEDICAL DEVICES DENTAL DEVICES Diagnostic Devices § 872.1730 Electrode gel for pulp testers. (a) Identification. An electrode gel for pulp testers is a device intended to be applied to the surface of a...

  7. 21 CFR 872.1730 - Electrode gel for pulp testers.

    Code of Federal Regulations, 2013 CFR

    2013-04-01

    ... 21 Food and Drugs 8 2013-04-01 2013-04-01 false Electrode gel for pulp testers. 872.1730 Section... (CONTINUED) MEDICAL DEVICES DENTAL DEVICES Diagnostic Devices § 872.1730 Electrode gel for pulp testers. (a) Identification. An electrode gel for pulp testers is a device intended to be applied to the surface of a...

  8. A low molecular weight hydrogel with unusual gel aging.

    PubMed

    Draper, Emily R; McDonald, Tom O; Adams, Dave J

    2015-04-18

    We describe a dipeptide hydrogel with unusual aging characteristics. Over time, a transformation from a turbid gel to a transparent gel occurs which is initiated from the air-water interface. Here, we investigate this transition and discuss the implications of this aging on the bulk properties of the gel. PMID:25775220

  9. Formulation and method for preparing gels comprising hydrous hafnium oxide

    SciTech Connect

    Collins, Jack L; Hunt, Rodney D; Montgomery, Frederick C

    2013-08-06

    Formulations useful for preparing hydrous hafnium oxide gels contain a metal salt including hafnium, an acid, an organic base, and a complexing agent. Methods for preparing gels containing hydrous hafnium oxide include heating a formulation to a temperature sufficient to induce gel formation, where the formulation contains a metal salt including hafnium, an acid, an organic base, and a complexing agent.

  10. Analysis and simulation of a model of polyelectrolyte gel in one spatial dimension

    NASA Astrophysics Data System (ADS)

    Chen, Haoran; Calderer, Maria-Carme; Mori, Yoichiro

    2014-06-01

    We analyse a model of polyelectrolyte gels that was proposed by the authors in previous work. We first demonstrate that the model can be derived using Onsager's variational principle, a general procedure for obtaining equations in soft condensed matter physics. The model is shown to have a unique steady state under the assumption that a suitably defined mechanical energy density satisfies a convexity condition. We then perform a detailed study of the stability of the steady state in the spatially one-dimensional case, obtaining bounds on the relaxation rate. Numerical simulations for the spatially one-dimensional problem are presented, confirming the analytical calculations on stability.

  11. Carbon Redox-Polymer-Gel Hybrid Supercapacitors.

    PubMed

    Vlad, A; Singh, N; Melinte, S; Gohy, J-F; Ajayan, P M

    2016-01-01

    Energy storage devices that provide high specific power without compromising on specific energy are highly desirable for many electric-powered applications. Here, we demonstrate that polymer organic radical gel materials support fast bulk-redox charge storage, commensurate to surface double layer ion exchange at carbon electrodes. When integrated with a carbon-based electrical double layer capacitor, nearly ideal electrode properties such as high electrical and ionic conductivity, fast bulk redox and surface charge storage as well as excellent cycling stability are attained. Such hybrid carbon redox-polymer-gel electrodes support unprecedented discharge rate of 1,000C with 50% of the nominal capacity delivered in less than 2 seconds. Devices made with such electrodes hold the potential for battery-scale energy storage while attaining supercapacitor-like power performances. PMID:26917470

  12. Droplet Spreading with Sol-Gel Transition

    NASA Astrophysics Data System (ADS)

    Jalaal, Maziyar; Stoeber, Boris; Balmforth, Neil J.

    2014-11-01

    The impact and spreading of liquid droplets on a smooth solid substrate is a classical subject with several industrial applications such as ink-jet printing, spray cooling, coating, and many others. For many of these deposition processes, controlling the final shape of the drop is critical. In the current research, a new technique for controlling the spreading of droplets impacting a substrate is presented. This technique exploits the rheology of a thermo-responsive polymer solution that undergoes a reversible sol/gel transition above a critical temperature. Experiments are conducted using a combination of shadowgraphy and micro-PIV to observe spreading drops. It is shown that the final diameter of a droplet can be controlled through the temperature of the substrate and the tunable sol/gel transition temperature of the fluid.A mathematical model is provided to further elucidate the flow dynamics.

  13. Carbon Redox-Polymer-Gel Hybrid Supercapacitors

    NASA Astrophysics Data System (ADS)

    Vlad, A.; Singh, N.; Melinte, S.; Gohy, J.-F.; Ajayan, P. M.

    2016-02-01

    Energy storage devices that provide high specific power without compromising on specific energy are highly desirable for many electric-powered applications. Here, we demonstrate that polymer organic radical gel materials support fast bulk-redox charge storage, commensurate to surface double layer ion exchange at carbon electrodes. When integrated with a carbon-based electrical double layer capacitor, nearly ideal electrode properties such as high electrical and ionic conductivity, fast bulk redox and surface charge storage as well as excellent cycling stability are attained. Such hybrid carbon redox-polymer-gel electrodes support unprecedented discharge rate of 1,000C with 50% of the nominal capacity delivered in less than 2 seconds. Devices made with such electrodes hold the potential for battery-scale energy storage while attaining supercapacitor-like power performances.

  14. Gel permeation chromatography of coal extracts

    SciTech Connect

    Nosyrev, I.E.; Kuzaev, A.I.; Kochkanyan, R.O.; Baranov, S.N.

    1981-01-01

    In the reported experiments, investigations have been made of the molecular-weight distribution of coal extracts by gel permeation chromatography on a Waters instrument fitted with Styragel columns using tetrahydrofuran as eluent. The molecular-weight composition of organic extracts obtained by the treatment of coals with various solvents has been analyzed and it has been concluded that associates are present in the coal. The parameters of the molecular-weight distribution have been calculated using various calibrations. The possibility has been shown of the preparative separation of coal extracts on the gel Sephadex LH-20. The hypothesis has been put forward that coal consists of an oligomeric polyassociate with an intermolecular interaction of the donor-acceptor type. 9 refs.

  15. Structural Hierarchy Governs Fibrin Gel Mechanics

    PubMed Central

    Piechocka, Izabela K.; Bacabac, Rommel G.; Potters, Max; MacKintosh, Fred C.; Koenderink, Gijsje H.

    2010-01-01

    Abstract Fibrin gels are responsible for the mechanical strength of blood clots, which are among the most resilient protein materials in nature. Here we investigate the physical origin of this mechanical behavior by performing rheology measurements on reconstituted fibrin gels. We find that increasing levels of shear strain induce a succession of distinct elastic responses that reflect stretching processes on different length scales. We present a theoretical model that explains these observations in terms of the unique hierarchical architecture of the fibers. The fibers are bundles of semiflexible protofibrils that are loosely connected by flexible linker chains. This architecture makes the fibers 100-fold more flexible to bending than anticipated based on their large diameter. Moreover, in contrast with other biopolymers, fibrin fibers intrinsically stiffen when stretched. The resulting hierarchy of elastic regimes explains the incredible resilience of fibrin clots against large deformations. PMID:20483337

  16. Ballistic penetration of Perma-Gel

    NASA Astrophysics Data System (ADS)

    Ryckman, Raymond Albert; Powell, David Arthur; Lew, Adrian

    2012-03-01

    In this study a number of experiments were performed by taking high-speed footage of the firing spherical steel bullets at different speeds into Perma-Gel, a new synthetic thermoplastic material touted to exhibit similar properties to ordnance ballistic gelatin. We found that the gel undergoes very large and recoverable elastic deformations, which could strongly affect the dynamics of the temporary cavity formed behind the projectile. As with ordnance ballistic gelatin, the diameter of the temporary cavity can be many times the diameter of the projectile, in contrast with that of the permanent cavity which is several times smaller.We also observed that the closure of the cavity chokes the air inside, which could affect its dynamics in noticeable ways. Finally, one of the experiments suggest that the precise model of material failure may not be important to determine the dynamics of the temporary cavity.

  17. Freezing D2O clay gels.

    PubMed

    Letellier, M

    1998-01-01

    To obtain the T1 surface value in smectites/D2O diluted suspensions or gels, as was obtained on a monolayer deuterated clay, we freeze them. The broad Pake's doublets similar to ice doublets and with the same T1 show that we can separate frozen from unfrozen D2O. The latter exhibits a narrower line and a single T1 and is attributed to the liquid surface water layer in rapid exchange with the nearby supercooled water, the quantity of which diminishes with the lowering of the temperature depending on the gel porosity. It is possible to measure the supercooled water quantity and to correct the T1 measured values to extract the T1 surface. The value extrapolated at room temperature allows the complete clay surface area measurement. The example of a montmorillonite is given and a comparison with laponite is made. PMID:9803898

  18. Carbon Redox-Polymer-Gel Hybrid Supercapacitors

    PubMed Central

    Vlad, A.; Singh, N.; Melinte, S.; Gohy, J.-F.; Ajayan, P.M.

    2016-01-01

    Energy storage devices that provide high specific power without compromising on specific energy are highly desirable for many electric-powered applications. Here, we demonstrate that polymer organic radical gel materials support fast bulk-redox charge storage, commensurate to surface double layer ion exchange at carbon electrodes. When integrated with a carbon-based electrical double layer capacitor, nearly ideal electrode properties such as high electrical and ionic conductivity, fast bulk redox and surface charge storage as well as excellent cycling stability are attained. Such hybrid carbon redox-polymer-gel electrodes support unprecedented discharge rate of 1,000C with 50% of the nominal capacity delivered in less than 2 seconds. Devices made with such electrodes hold the potential for battery-scale energy storage while attaining supercapacitor-like power performances. PMID:26917470

  19. Electrodeposited gels prepared from protein alloys

    PubMed Central

    Lin, Yinan; Wang, Siran; Chen, Ying; Wang, Qianrui; Burke, Kelly A; Spedden, Elise M; Staii, Cristian; Weiss, Anthony S; Kaplan, David L

    2015-01-01

    Aim Silk-tropoelastin alloys, composed of recombinant human tropoelastin and regenerated Bombyx mori silk fibroin, are an emerging, versatile class of biomaterials endowed with tunable combinations of physical and biological properties. Electrodeposition of these alloys provides a programmable means to assemble functional gels with both spatial and temporal controllability. Materials & methods Tropoelastin-modified silk was prepared by enzymatic coupling between tyrosine residues. Hydrogel coatings were electrodeposited using two wire electrodes. Results & discussion Mechanical characterization and in vitro cell culture revealed enhanced adhesive capability and cellular response of these alloy gels as compared with electrogelled silk alone. Conclusion These electro-depositable silk-tropoelastin alloys constitute a suitable coating material for nanoparticle-based drug carriers and offer a novel opportunity for on-demand encapsulation/release of nanomedicine. PMID:25816881

  20. Silver staining of 2D electrophoresis gels.

    PubMed

    Rabilloud, Thierry

    2012-01-01

    Silver staining is used to detect proteins after electrophoretic separation on polyacrylamide gels. It -combines excellent sensitivity (in the low nanogram range) with the use of very simple and cheap equipment and chemicals. For its use in proteomics, two important additional features must be considered, compatibility with mass spectrometry and quantitative response. Both features are discussed in this chapter, and optimized silver staining protocols are proposed. PMID:22665294

  1. Diffusion of polyelectrolytes in polyelectrolyte gels

    NASA Astrophysics Data System (ADS)

    Rahalkar, Anand; Muthukumar, Murugappan

    2015-03-01

    Using dynamic light scattering, we have investigated the diffusion coefficient of sodium poly(styrene sulfonate) in a matrix of poly(acrylamide-co-acrylate) gels. The diffusion coefficient of the probe polyelectrolyte exhibits a crossover behavior from a particle-diffusion to entropic-barrier dominated diffusion, as the molecular weight is increased. The effect of electrostatics, by varying the charge density of the matrix, on probe diffusion constant will be presented.

  2. Ring-Resonator/Sol-Gel Interferometric Immunosensor

    NASA Technical Reports Server (NTRS)

    Bearman, Gregory; Cohen, David

    2007-01-01

    A proposed biosensing system would be based on a combination of (1) a sensing volume containing antibodies immobilized in a sol-gel matrix and (2) an optical interferometer having a ring resonator configuration. The antibodies would be specific to an antigen species that one seeks to detect. In the ring resonator of the proposed system, light would make multiple passes through the sensing volume, affording greater interaction length and, hence, greater antibody- detection sensitivity.

  3. Ultrasensitive fluorescence detection of DNA sequencing gels

    SciTech Connect

    Mathies, R.A.

    1991-01-01

    During the three years of this grant we have: (1) Developed and applied a new theory for optimizing high-sensitivity fluorescence detection. (2) Developed and patented a new high-sensitivity confocal-fluorescence laser-excited gel-scanner. (3) Applied this scanner to the development of a new class of versatile and sensitive fluorescent dyes for DNA detection. (4) Developed methods for the detection of single fluorescent molecules by fluorescence burst detection. 11 refs., 10 figs.

  4. Trends in Analytical Scale Separations.

    ERIC Educational Resources Information Center

    Jorgenson, James W.

    1984-01-01

    Discusses recent developments in the instrumentation and practice of analytical scale operations. Emphasizes detection devices and procedures in gas chromatography, liquid chromatography, electrophoresis, supercritical fluid chromatography, and field-flow fractionation. (JN)

  5. Laboratory Workhorse: The Analytical Balance.

    ERIC Educational Resources Information Center

    Clark, Douglas W.

    1979-01-01

    This report explains the importance of various analytical balances in the water or wastewater laboratory. Stressed is the proper procedure for utilizing the equipment as well as the mechanics involved in its operation. (CS)

  6. Analytic Methods in Investigative Geometry.

    ERIC Educational Resources Information Center

    Dobbs, David E.

    2001-01-01

    Suggests an alternative proof by analytic methods, which is more accessible than rigorous proof based on Euclid's Elements, in which students need only apply standard methods of trigonometry to the data without introducing new points or lines. (KHR)

  7. Analytical Chemistry: A Literary Approach.

    ERIC Educational Resources Information Center

    Lucy, Charles A.

    2000-01-01

    Provides an anthology of references to descriptions of analytical chemistry techniques from history, popular fiction, and film which can be used to capture student interest and frame discussions of chemical techniques. (WRM)

  8. Cautions Concerning Electronic Analytical Balances.

    ERIC Educational Resources Information Center

    Johnson, Bruce B.; Wells, John D.

    1986-01-01

    Cautions chemists to be wary of ferromagnetic samples (especially magnetized samples), stray electromagnetic radiation, dusty environments, and changing weather conditions. These and other conditions may alter readings obtained from electronic analytical balances. (JN)

  9. Liposomes: Technologies and Analytical Applications

    NASA Astrophysics Data System (ADS)

    Jesorka, Aldo; Orwar, Owe

    2008-07-01

    Liposomes are structurally and functionally some of the most versatile supramolecular assemblies in existence. Since the beginning of active research on lipid vesicles in 1965, the field has progressed enormously and applications are well established in several areas, such as drug and gene delivery. In the analytical sciences, liposomes serve a dual purpose: Either they are analytes, typically in quality-assessment procedures of liposome preparations, or they are functional components in a variety of new analytical systems. Liposome immunoassays, for example, benefit greatly from the amplification provided by encapsulated markers, and nanotube-interconnected liposome networks have emerged as ultrasmall-scale analytical devices. This review provides information about new developments in some of the most actively researched liposome-related topics.

  10. Numerical integration of analytic functions

    NASA Astrophysics Data System (ADS)

    Milovanović, Gradimir V.; Tošić, Dobrilo ð.; Albijanić, Miloljub

    2012-09-01

    A weighted generalized N-point Birkhoff-Young quadrature of interpolatory type for numerical integration of analytic functions is considered. Special cases of such quadratures with respect to the generalized Gegenbauer weight function are derived.

  11. Dielectric properties of gel collected from shark electrosensors

    NASA Astrophysics Data System (ADS)

    Hughes, Mary E.; Brown, Brandon R.; Hutchison, John C.; Murray, Royce W.

    2003-03-01

    To investigate the physical mechanism of the electric sense, we present an initial characterization of the dielectric properties of the glycoprotein gel that fills the electrosensitive organs of marine elasmobranches (sharks, skates, and rays). To ascertain the properties of the gel, low-frequency impedance spectroscopy is used. The impedance data collected from a dialyzed sample show large values of static permittivity and a loss peak corresponding to a long relaxation time (about 1 ms). Impedance measurements of the native (nondialyzed) gel reliable to 0.1 Hz will be presented and compared to the dialyzed gel. Ramifications of the gel's dielectric properties for the electric sense will be explored.

  12. Semihumid gels as matrices for laser media

    NASA Astrophysics Data System (ADS)

    Larrue, Denis; Zarzycki, J.; Canva, Michael; Georges, Patrick M.; Brun, Alain

    1992-12-01

    Laser dyes were trapped in SiO2 xerogel host matrices to obtain a solid state dye laser. The evolution of the mechanical properties of two kinds of matrices, 'classic' and 'sono' gels, was followed during drying. A new impregnation process was performed on these xerogels: impregnation with a 'sono' sol. The influence of this treatment on certain physical and mechanical properties of the resulting impregnated gels was studied. The results indicate that impregnation substantially improves hardness, elastic modulus and fracture stress. The samples can then be easily polished to obtain optical quality surfaces and be used in a laser cavity. Moreover, optical properties related to laser emission of these materials such as efficiency, lifetime and longevity are better when the laser dye doped xerogels are impregnated. The organic dye molecule used was sulforhodamine 640, and results were obtained six months after their synthesis, with a pump beam working at a 5 Hz repetition rate with 450 (mu) J/pulse energy level. With the first pump shot on a fixed point of the samples, tunability from 600 to 650 nm, 60 (mu) J threshold, 2600 pump shots lifetime and a 10.5% slope efficiency were achieved using an impregnated 'sono' gel matrix.

  13. Sterilizable gels from thermoresponsive block copolymer worms.

    PubMed

    Blanazs, Adam; Verber, Robert; Mykhaylyk, Oleksandr O; Ryan, Anthony J; Heath, Jason Z; Douglas, C W Ian; Armes, Steven P

    2012-06-13

    Biocompatible hydrogels have many applications, ranging from contact lenses to tissue engineering scaffolds. In most cases, rigorous sterilization is essential. Herein we show that a biocompatible diblock copolymer forms wormlike micelles via polymerization-induced self-assembly in aqueous solution. At a copolymer concentration of 10.0 w/w %, interworm entanglements lead to the formation of a free-standing physical hydrogel at 21 °C. Gel dissolution occurs on cooling to 4 °C due to an unusual worm-to-sphere order-order transition, as confirmed by rheology, electron microscopy, variable temperature (1)H NMR spectroscopy, and scattering studies. Moreover, this thermo-reversible behavior allows the facile preparation of sterile gels, since ultrafiltration of the diblock copolymer nanoparticles in their low-viscosity spherical form at 4 °C efficiently removes micrometer-sized bacteria; regelation occurs at 21 °C as the copolymer chains regain their wormlike morphology. Biocompatibility tests indicate good cell viabilities for these worm gels, which suggest potential biomedical applications. PMID:22582795

  14. Micro-size polyacrylamide gel electrophoresis system

    NASA Astrophysics Data System (ADS)

    Hinson, W. G.; Pipkin, J. L.; Anson, J. F.; Casciano, D. A.; Burns, E. R.

    1987-09-01

    The development and characterization of a micro-size two-dimensional polyacrylamide gel electrophoresis system is described. Some of the techniques which have evolved with use of the system are also discussed. This apparatus has unique features which provide advantages over other small scale units. Up to ten first- and second-dimension gels can be processed simultaneously with excellent resolution of protein regions. Consistent reproducibility is possible from protein samples as small as 400 ng and individual protein regions as small as 1 pg can be visualized by silver staining of the two-dimensional gels. Similar sensitivities are achieved in autoradiographs of 3H-labeled proteins extracted from the nuclei of cultured cells. The application of this system in conjunction with flow cytometric examination of nuclear DNA and electrostatic cell sorting of specific cell nuclei to provide homogeneous sample populations, allows subtle variations in isotope incorporation in proteins to be detected; whereas many times in generalized tissue samples these changes are masked. Also, these techniques elucidate the effects of external stimuli (chemicals, drugs, or environment) on protein synthesis and phosphorylation for analyses and comparison. Fabrication drawings are available upon request.

  15. The formation and structure of Olympic gels

    NASA Astrophysics Data System (ADS)

    Fischer, J.; Lang, M.; Sommer, J.-U.

    2015-12-01

    Different methods for creating Olympic gels are analyzed using computer simulations. First ideal reference samples are obtained from freely interpenetrating semi-dilute solutions and melts of cyclic polymers. The distribution of pairwise concatenations per cyclic molecule is given by a Poisson-distribution and can be used to describe the elastic structure of the gels. Several batches of linear chains decorated with different selectively binding groups at their ends are mixed in the "DNA Origami" technique and network formation is realized. While the formation of cyclic molecules follows mean field predictions below overlap of the precursor molecules, an enhanced ring formation above overlap is found that is not explained by mean field arguments. The "progressive construction" method allows to create Olympic gels with a single reaction step from a concentrated mixture of large compressed rings with a low weight fraction of short chains that are below overlap concentration. This method, however, is limited by the difficulty to obtain a sufficiently high degree of polymerization of the large rings.

  16. Sol-gel method for encapsulating molecules

    DOEpatents

    Brinker, C. Jeffrey; Ashley, Carol S.; Bhatia, Rimple; Singh, Anup K.

    2002-01-01

    A method for encapsulating organic molecules, and in particular, biomolecules using sol-gel chemistry. A silica sol is prepared from an aqueous alkali metal silicate solution, such as a mixture of silicon dioxide and sodium or potassium oxide in water. The pH is adjusted to a suitably low value to stabilize the sol by minimizing the rate of siloxane condensation, thereby allowing storage stability of the sol prior to gelation. The organic molecules, generally in solution, is then added with the organic molecules being encapsulated in the sol matrix. After aging, either a thin film can be prepared or a gel can be formed with the encapsulated molecules. Depending upon the acid used, pH, and other processing conditions, the gelation time can be from one minute up to several days. In the method of the present invention, no alcohols are generated as by-products during the sol-gel and encapsulation steps. The organic molecules can be added at any desired pH value, where the pH value is generally chosen to achieve the desired reactivity of the organic molecules. The method of the present invention thereby presents a sufficiently mild encapsulation method to retain a significant portion of the activity of the biomolecules, compared with the activity of the biomolecules in free solution.

  17. Sample prefractionation in granulated sephadex IEF gels.

    PubMed

    Görg, Angelika; Lück, Carsten; Weiss, Walter

    2008-01-01

    Prefractionation procedures not only aid in reducing sample complexity, but also permit loading of higher protein amounts within the separation range applied to two-dimensional electrophoresis (2-DE) gels and thus facilitate the detection of less abundant protein species. Hence we developed a simple, cheap, and fast prefractionation procedure based on flat-bed isoelectric focusing (IEF) in granulated Sephadex gels, containing chaotropes, zwitterionic detergents and carrier ampholytes. After IEF, up to ten Sephadex gel fractions alongside the pH gradient are obtained, and then applied directly onto the surface of the corresponding narrow pH range immobilized pH gradient (IPG) strips as first dimension of 2-DE. The major advantages of this technology are the highly efficient electrophoretic transfer of the prefractionated proteins from the Sephadex IEF fraction into the IPG strip without any sample dilution, and full compatibility with subsequent 2-DE, because the prefractionated samples have not to be eluted, concentrated or desalted, nor does the amount of the carrier ampholytes in the Sephadex fraction interfere with IEF in IPG strips. This sample prefractionation method has been successfully applied for the separation, detection and identification of low abundance proteins from pro- and eukaryotic samples. PMID:18369869

  18. Sol-gel based optical chemical sensors

    NASA Astrophysics Data System (ADS)

    Lobnik, Aleksandra; Korent Urek, Špela; Turel, Matejka; Frančič, Nina

    2011-05-01

    The growing activity in the field of optical chemical sensors has resulted in numerous sensing schemes, new indicator dyes, various polymeric matrix, size and shapes and highly diversified methods of immobilization. The sensor characteristics are dependent upon the choice of indicator, polymer, immobilization technique, and also size. Sol-gel technology provides a low-temperature method for obtaining porous silicate glass matrices. It enables to obtain material in the form of films, powders, monoliths, fibres or nanoparticles. Organic reagents and molecular receptors can be easily immobilized in the matrices. Moreover, one of the unique features of the sol-gel process is that the properties of the final network structure, such as hydrophobicity, thickness, porosity, flexibility, reactivity and stability can be easily tailored by controlling the process conditions, the type and the size of the precursors and catalysis. Here we will report about several sensor designed over the years based on sol-gel materials for monitoring and controlling different parameters, such as heavy metals, amines, phosphates, organophosphates.

  19. Highly-correlated charges in polyelectrolyte gels

    NASA Astrophysics Data System (ADS)

    Sing, Charles; Zwanikken, Johannes; Olvera de La Cruz, Monica

    2013-03-01

    Polyelectrolyte gels are ubiquitous in polymer physics due to their attractive combination of structural and chemical features that permit the realization of ``environmentally responsive'' systems. The conventional conceptual picture of the volume response of these systems is based on a competition between osmotic and elastic effects. We elaborate on this fundamental understanding by including ion correlations through the use of liquid-state integral equation theory. This allows for a statistical mechanical representation of the state of the system that not only surpasses traditional Poisson-Boltzmann theories but also renders structural features in a highly accurate fashion. In particular, the local ion structure is elucidated, allowing for detailed articulation of charge inversion and condensation effects in the context of gel swelling. The inclusion of correlations has a number of ramifications that become apparent, with enhanced gel collapse and excluded volume competitions that give rise to novel and ion-dependent reentrant swelling effects. We expect this rigorous theory to prove instructive in understanding any number of gelated structures, such as chromosomes or designed synthetic materials for drug delivery.

  20. Gel Electrophoresis of Gold-DNA Nanoconjugates

    DOE PAGESBeta

    Pellegrino, T.; Sperling, R. A.; Alivisatos, A. P.; Parak, W. J.

    2007-01-01

    Gold-DNA conjugates were investigated in detail by a comprehensive gel electrophoresis study based on 1200 gels. A controlled number of single-stranded DNA of different length was attached specifically via thiol-Au bonds to phosphine-stabilized colloidal gold nanoparticles. Alternatively, the surface of the gold particles was saturated with single stranded DNA of different length either specifically via thiol-Au bonds or by nonspecific adsorption. From the experimentally determined electrophoretic mobilities, estimates for the effective diameters of the gold-DNA conjugates were derived by applying two different data treatment approaches. The first method is based on making a calibration curve for the relation between effectivemore » diameters and mobilities with gold nanoparticles of known diameter. The second method is based on Ferguson analysis which uses gold nanoparticles of known diameter as reference database. Our study shows that effective diameters derived from gel electrophoresis measurements are affected with a high error bar as the determined values strongly depend on the method of evaluation, though relative changes in size upon binding of molecules can be detected with high precision. Furthermore, in this study, the specific attachment of DNA via gold-thiol bonds to Au nanoparticles is compared to nonspecific adsorption of DNA. Also, the maximum number of DNA molecules that can be bound per particle was determined.« less

  1. Bucky gel actuators optimization towards haptic applications

    NASA Astrophysics Data System (ADS)

    Bubak, Grzegorz; Ansaldo, Alberto; Ceseracciu, Luca; Hata, Kenji; Ricci, Davide

    2014-03-01

    An ideal plastic actuator for haptic applications should generate a relatively large displacement (minimum 0.2-0.6 mm, force (~50 mN/cm2) and a fast actuation response to the applied voltage. Although many different types of flexible, plastic actuators based on electroactive polymers (EAP) are currently under investigation, the ionic EAPs are the only ones that can be operated at low voltage. This property makes them suitable for applications that require inherently safe actuators. Among the ionic EAPs, bucky gel based actuators are very promising. Bucky gel is a physical gel made by grounding imidazolium ionic liquids with carbon nanotubes, which can then be incorporated in a polymeric composite matrix to prepare the active electrode layers of linear and bending actuators. Anyhow, many conflicting factors have to be balanced to obtain required performance. In order to produce high force a large stiffness is preferable but this limits the displacement. Moreover, the bigger the active electrode the larger the force. However the thicker an actuator is, the slower the charging process becomes (it is diffusion limited). In order to increase the charging speed a thin electrolyte would be desirable, but this increases the probability of pinholes and device failure. In this paper we will present how different approaches in electrolyte and electrode preparation influence actuator performance and properties taking particularly into account the device ionic conductivity (which influences the charging speed) and the electrode surface resistance (which influences both the recruitment of the whole actuator length and its speed).

  2. Visual Analytics Technology Transition Progress

    SciTech Connect

    Scholtz, Jean; Cook, Kristin A.; Whiting, Mark A.; Lemon, Douglas K.; Greenblatt, Howard

    2009-09-23

    The authors provide a description of the transition process for visual analytic tools and contrast this with the transition process for more traditional software tools. This paper takes this into account and describes a user-oriented approach to technology transition including a discussion of key factors that should be considered and adapted to each situation. The progress made in transitioning visual analytic tools in the past five years is described and the challenges that remain are enumerated.

  3. Functionalized magnetic nanoparticle analyte sensor

    DOEpatents

    Yantasee, Wassana; Warner, Maryin G; Warner, Cynthia L; Addleman, Raymond S; Fryxell, Glen E; Timchalk, Charles; Toloczko, Mychailo B

    2014-03-25

    A method and system for simply and efficiently determining quantities of a preselected material in a particular solution by the placement of at least one superparamagnetic nanoparticle having a specified functionalized organic material connected thereto into a particular sample solution, wherein preselected analytes attach to the functionalized organic groups, these superparamagnetic nanoparticles are then collected at a collection site and analyzed for the presence of a particular analyte.

  4. Antimicrobial activity and the mechanism of silver nanoparticle thermosensitive gel

    PubMed Central

    Chen, Meiwan; Yang, Zhiwen; Wu, Hongmei; Pan, Xin; Xie, Xiaobao; Wu, Chuanbin

    2011-01-01

    Purpose The purpose of the present study was to elucidate the antimicrobial activity and mechanism of silver nanoparticles incorporated into thermosensitive gel (S-T-Gel) on Staphylococcus aureus, Escherichia coli, and Pseudomonas aeruginosa. Patients and methods This study investigated the growth, permeability, and morphology of Staphylococcus aureus, Escherichia coli, and Pseudomonas aeruginosa cells in order to observe the action of S-T-Gel on the membrane structure of these three bacteria. The cell morphology of normal and treated bacteria cells was assessed by transmission electron microscopy (TEM), and the effects of S-T-Gel on genome DNA of bacterial cells were evaluated by agarose gel electrophoresis. Results S-T-Gel showed promising activity against Staphylococcus aureus and moderate activity against Escherichia coli and Pseudomonas aeruginosa. The observation with TEM suggested that S-T-Gel may destroy the structure of bacterial cell membranes in order to enter the bacterial cell. S-T-Gel then condensed DNA and combined and coagulated with the cytoplasm of the damaged bacteria, resulting in the leakage of the cytoplasmic component and the eventual death of these three bacteria. In addition, the analysis of agarose gel electrophoresis demonstrated that S-T-Gel could increase the decomposability of genome DNA. Conclusion These results about promising antimicrobial activity and mechanism of S-T-Gel may be useful for further research and development in in-vivo studies. PMID:22131833

  5. Formulation and evaluation of curcumin gel for topical application.

    PubMed

    Patel, Nikunjana A; Patel, Natvar J; Patel, Rakesh P

    2009-01-01

    The aim of the present investigation was to develop and study topical gel delivery of curcumin for its anti-inflammatory effects. Carbopol 934P (CRB) and hydroxypropylcellulose (HPC) were used for the preparation of gels. The penetration enhancing effect of menthol (0-12.5% w/w) on the percutaneous flux of curcumin through the excised rat epidermis from 2% w/w CRB and HPC gel system was investigated. All the prepared gel formulations were evaluated for various properties such as compatibility, drug content, viscosity, in vitro skin permeation, and anti-inflammatory effect. The drug and polymers compatibility was confirmed by Differential scanning calorimetry and infrared spectroscopy. The percutaneous flux and enhancement ratio of curcumin across rat epidermis was enhanced markedly by the addition of menthol to both types of gel formulations. Both types of developed topical gel formulations were free of skin irritation. In anti-inflammatory studies done by carrageenan induced rat paw oedema method in wistar albino rats, anti-inflammatory effect of CRB, HPC and standard gel formulations were significantly different from control group (P < 0.05) whereas this effect was not significantly different for CRB and HPC gels formulations to that of standard (diclofenac gel) formulation (P > 0.05). CRB gel showed better % inhibition of inflammation as compared to HPC gel. PMID:18821270

  6. Modelling of the inhomogeneous interior of polymer gels

    NASA Astrophysics Data System (ADS)

    Shew, Chwen-Yang; Iwaki, Takafumi

    2006-04-01

    A simple model has been investigated to elucidate the mean squared displacement (MSD) of probe molecules in cross-linked polymer gels. In the model, we assume that numerous cavities distribute in the inhomogeneous interior of a gel, and probe molecules are confined within these cavities. The individual probe molecules trapped in a gel are treated as Brownian particles confined to a spherical harmonic potential. The harmonic potential is chosen to model the effective potential experienced by the probe particle in the cavity of a gel. Each field strength is corresponding to the characteristic of one type of effective cavity. Since the statistical distribution of different effective cavity sizes is unknown, several distribution functions are examined. Meanwhile, the calculated averaged MSDs are compared to the experimental data by Nisato et al (2000 Phys. Rev. E 61 2879). We find that the theoretical results of the MSD are sensitive to the shape of the distribution function. For low cross-linked gels, the best fit is obtained when the interior cavities of a gel follow a bimodal distribution. Such a result may be attributed to the presence of at least two distinct classes of cavity in gels. For high cross-linked gels, the cavities in the gel can be depicted by a single-modal uniform distribution function, suggesting that the range of cavity sizes becomes smaller. These results manifest the voids inside a gel, and the shape of distribution functions may provide the insight into the inhomogeneous interior of a gel.

  7. Dynamic light-scattering monitoring of a transient biopolymer gel

    NASA Astrophysics Data System (ADS)

    Kostko, A. F.; Chen, T.; Payne, G. F.; Anisimov, M. A.

    2003-05-01

    We performed dynamic light-scattering (DLS) monitoring and a rheological study to characterize the formation and destruction of a transient (limited lifetime) gel formed from the biopolymers chitosan and gelatin. Gel formation, initiated by the enzyme tyrosinase, is followed by spontaneous gel breakage. Our DLS results demonstrate that this material passes through five stages in which the gel forms, consolidates, “lives”, softens, and eventually breaks. We speculate that the existence of the transient gel is caused by a competition between two processes: a fast-rate chemical reaction leading to formation of a branched-copolymer network and a slow-rate diffusion-like rearrangement of the gelatin branches resulting in eventual gel breakage. Despite a dramatic difference in the characteristic times of the gel formation ( tg) and gel breakage ( tb)-the ratio tb/ tg is of the order 10 3-DLS has revealed an intrinsic monitoring-time symmetry in the formation and destruction of the gel provided that a proper physical choice of the reduced temporal scale is used. In this scale the slow-mode relaxation time for both sides of the process, gel formation and gel destruction, exhibits a power law in the spirit of percolation theory.

  8. Fabrication, modeling and optimization of an ionic polymer gel actuator

    NASA Astrophysics Data System (ADS)

    Jo, Choonghee; Naguib, Hani E.; Kwon, Roy H.

    2011-04-01

    The modeling of the electro-active behavior of ionic polymer gel is studied and the optimum conditions that maximize the deflection of the gel are investigated. The bending deformation of polymer gel under an electric field is formulated by using chemo-electro-mechanical parameters. In the modeling, swelling and shrinking phenomena due to the differences in ion concentration at the boundary between the gel and solution are considered prior to the application of an electric field, and then bending actuation is applied. As the driving force of swelling, shrinking and bending deformation, differential osmotic pressure at the boundary of the gel and solution is considered. From this behavior, the strain or deflection of the gel is calculated. To find the optimum design parameter settings (electric voltage, thickness of gel, concentration of polyion in the gel, ion concentration in the solution, and degree of cross-linking in the gel) for bending deformation, a nonlinear constrained optimization model is formulated. In the optimization model, a bending deflection equation of the gel is used as an objective function, and a range of decision variables and their relationships are used as constraint equations. Also, actuation experiments are conducted using poly(2-acrylamido-2-methylpropane sulfonic acid) (PAMPS) gel and the optimum conditions predicted by the proposed model have been verified by the experiments.

  9. Antioxidant effect of green tea on polymer gel dosimeter

    NASA Astrophysics Data System (ADS)

    Samuel, E. J. J.; Sathiyaraj, P.; Deena, T.; Kumar, D. S.

    2015-01-01

    Extract from Green Tea (GTE) acts as an antioxidant in acrylamide based polymer gel dosimeter. In this work, PAGAT gel was used for investigation of antioxidant effect of GTE.PAGAT was called PAGTEG (Polyacrylamide green tea extract gel dosimeter) after adding GTE. Free radicals in water cause pre polymerization of polymer gel before irradiation. Polyphenols from GTE are highly effective to absorb the free radicals in water. THPC is used as an antioxidant in polymer gel dosimeter but here we were replaced it by GTE and investigated its effect by spectrophotometer. GTE added PAGAT samples response was lower compared to THPC added sample. To increase the sensitivity of the PAGTEG, sugar was added. This study confirmed that THPC was a good antioxidant for polymer gel dosimeter. However, GTE also can be used as an antioxidant in polymer gel if use less quantity (GTE) and add sugar as sensitivity enhancer.

  10. Anion-switchable supramolecular gels for controlling pharmaceutical crystal growth

    NASA Astrophysics Data System (ADS)

    Foster, Jonathan A.; Piepenbrock, Marc-Oliver M.; Lloyd, Gareth O.; Clarke, Nigel; Howard, Judith A. K.; Steed, Jonathan W.

    2010-12-01

    We describe the use of low-molecular-weight supramolecular gels as media for the growth of molecular crystals. Growth of a range of crystals of organic compounds, including pharmaceuticals, was achieved in bis(urea) gels. Low-molecular-weight supramolecular gelators allow access to an unlimited range of solvent systems, in contrast to conventional aqueous gels such as gelatin and agarose. A detailed study of carbamazepine crystal growth in four different bis(urea) gelators, including a metallogelator, is reported. The crystallization of a range of other drug substances, namely sparfloxacin, piroxicam, theophylline, caffeine, ibuprofen, acetaminophen (paracetamol), sulindac and indomethacin, was also achieved in supramolecular gel media without co-crystal formation. In many cases, crystals can be conveniently recovered from the gels by using supramolecular anion-triggered gel dissolution; however, crystals of substances that themselves bind to anions are dissolved by them. Overall, supramolecular gel-phase crystallization offers an extremely versatile new tool in pharmaceutical polymorph screening.

  11. Characterization of the proteasome using native gel electrophoresis.

    PubMed

    Elsasser, Suzanne; Schmidt, Marion; Finley, Daniel

    2005-01-01

    Several features of the proteasome make it an excellent subject for analysis by native gel electrophoresis: its size, the multiplicity of variant complexes having proteasome activity, the ease of in-gel assays for proteasome activity, and even its relatively high cellular abundance. Accordingly, native gels have been used to analyze the composition, assembly, gating activity, and binding characteristics of the proteasome. This chapter describes methods for preparing, running, and developing native gels and the proteasome species that are routinely visualized. Additionally, the use of native gels to resolve proteasome complexes present in lysate and to characterize proteasome ligands are described. Following native gel electrophoresis, secondary analyses can be performed, such as activating the core particle, making specific activity assessments, Western blotting of the native gel, resolving native complexes with subsequent SDS-PAGE, and protein identification by mass spectrometry. PMID:16275342

  12. Spontaneous Motion of Amphoteric Polymer Gels on Water

    NASA Astrophysics Data System (ADS)

    Osada, Yoshihito; Gong, JianPing; Uchida, Makoto; Isogai, Noriharu

    1995-04-01

    We have discovered that cross-linked hydrophobic-hydrophilic copolymer gels swollen in organic solvent undergo spontaneous motion when immersed in water. The mode of motion largely depends on the shape of the gel: a disc-shaped gel exhibits translational motion while a triangular or a square shaped one exhibits rotation. The velocity and duration of gel motion are strongly associated with its size and chemical structure. We consider that the gel, immersed in water, rapidly forms a partially organized structure on its outer surface and gradually shrinks, simultaneously producing high osmotic pressure and hydrostatic pressure. By virtue of these two pressures, the organic solvent is released from the gel and the gel obtains a net reaction force to induce motion, presumably due to its heterogeneous structure.

  13. Experimental investigation of the properties of polyelectrolyte gel

    NASA Astrophysics Data System (ADS)

    Pyschnyi, S.; Rydzewski, R.

    1991-03-01

    A polyelectrolyte gel, e.g. polyacrylamide gel has interesting thermo-mechanical properties. It swells in solution, increasing its volume by large factors and the swelling may be induced by a change of temperature, by the acetone content of the solution or by its acidity. The swelling can be reversed, i.e. the gel may be shrunk back to its original shape. The preparation of the gel is described here and quantitative details of the swelling or shrinking are reported. Particular emphasis is placed on the effect of a load on the properties of the gel. It is shown that a tensile load significantly affects the volume changes induced by changes of acidity of the solution. Some peculiar properties of the gel emerged during the investigation, such as anisotropy in thin gels and a decrease of the electrical resistance as an immediate consequence of both loading and unloading.

  14. Photostimulated structural changes of liquid crystal physical gels

    NASA Astrophysics Data System (ADS)

    Moriyama, Masaya; Mizoshita, Norihiro; Kato, Takashi

    2004-10-01

    Photoresponsive liquid crystal physical gels are formed from a hydrogen-bonded gelator containing photochromic azobenzene moieties and nematic or discotic liquid crystals. The bistable gel structures based on the trans-azobenzene gelator could be achieved by combining the trans-cis photoisomerization of the azobenzene moieties and thermal treat-ment. Upon UV irradiation, the trans-cis photoisomerization causes the transition from the initial gel states to the liquid crystal sol states. The cis-trans back-isomerization causes reaggregation of the trans-gelator in the liquid crystals. This leads to the formation of the second gel states which have the structures reflecting the liquid crystal order. The initial gel states can be reversibly changed to the reformed gel states by photoirradiation and thermal treatments. The photo-induced reversible structural changes of the anisotropic physical gels are applied to rewritable information recordings.

  15. Swelling and dissolution of beta-lactoglobulin gels in alkali.

    PubMed

    Mercadé-Prieto, Ruben; Falconer, Robert J; Paterson, William R; Wilson, D Ian

    2007-02-01

    It is well documented in the literature that during the dissolution of whey protein gels in alkali, the gels swell to a great extent. However, the relevance of the swelling step in the dissolution process of the protein gel remains unknown. In the present article we present a systematic study on the swelling of beta-lactoglobulin gels at different alkaline pH and ionic strengths. The equilibrium swelling degree at different conditions has been modeled using a simple model developed for polyelectrolyte gels, modified to take into account the ionization of the residues in a protein. The model can describe the swelling behavior of the gels over a wide range of conditions, but it underpredicts the equilibrium swelling under conditions close to those when dissolution is observed. Dissolution is only noticeable above pH 11.5-12 and only for those gels that are swollen over a minimum degree, suggesting the existence of a dissolution threshold. PMID:17243763

  16. Phenyl Functionalized Sol-gel Silica Sorbent for Capillary Microextraction and Chromia-Based Sol-gel Ucon Stationary Phase for Capillary Gas Chromatography

    NASA Astrophysics Data System (ADS)

    McLean, Michael M.

    The first chapter of this thesis presents an introduction to sol-gel methodology whose usefulness as a synthetic route will be demonstrated with two applications in chromatography. The first application involves the fabrication of a capillary micro-extraction (CME) device by coating a phenyl functionalized extracting phase on the inner surface of a fused silica capillary for analyte pre-concentration. The device was coupled on-line to a RP-HPLC system and practicality was demonstrated using allergens as target analytes. The allergens chosen as model analytes are typically found in fragrance products and food. Most of the 26 fragrance allergens that are monitored by various government authorities have a phenyl organic moiety (a strong chromophore), thus making them appropriate probes for exploring the extraction efficiency of the coating using a UV detector. The CME device showed ppt level limit of detection which makes it suitable for trace analyses of allergens and similar compounds in a variety of matrices. The second application explores the feasibility of using sol-gel derived chromia-based stationary phase in gas chromatographic columns. The organic moiety of the stationary phase was derived from Ucon 75-H-90,000 while the inorganic backbone was prepared using chromium(III) dichloride hydroxide - methacrylic acid - aqua complex, 40% in isopropanol/acetone . Usefulness of prepared chromia-based GC stationary phase was examined for petrochemical application. Promising results were obtained using aliphatic-aromatics, polyaromatic hydrocarbons, BTEX test mixture, cycloalkanes, branched alkanes and akylbenzenes. The column was able to perform without degradation despite being rinsed multiples times sequentially with the following solvents: dichloromethane, methanol, water and finally methanol again. Maximum theoretical plate number calculated is around 2,400 plates/m. The plate number clearly needs improvement but is a promising result for the newly explored chromia-based stationary phase. The maximum programmable temperature is 250°C which is comparable with similar commercially available polar stationary phases.

  17. Ionogel Electrolytes through Sol-Gel Processing

    NASA Astrophysics Data System (ADS)

    Horowitz, Ariel I.

    Electrical energy needs have intensified due to the ubiquity of personal electronics, the decarbonization of energy services through electrification, and the use of intermittent renewable energy sources. Despite developments in mechanical and thermal methods, electrochemical technologies are the most convenient and effective means of storing electrical energy. These technologies include both electrochemical cells, commonly called batteries, and electrochemical double-layer capacitors, or "supercapacitors", which store energy electrostatically. Both device types require an ion-conducting electrolyte. Current devices use solutions of complex salts in organic solvents, leading to both toxicity and flammability concerns. These drawbacks can be avoided by replacing conventional electrolytes with room-temperature molten salts, known as ionic liquids (ILs). ILs are non-volatile, non-flammable, and offer high conductivity and good electrochemical stability. Device mass can be reduced by combining ILs with a solid scaffold material to form an "ionogel," further improving performance metrics. In this work, sol-gel chemistry is explored as a means of forming ionogel electrolytes. Sol-gel chemistry is a solution-based, industrially-relevant, well-studied technique by which solids such as silica can be formed in situ. Previous works used a simple acid-catalyzed sol-gel reaction to create brittle, glassy ionogels. Here, both the range of products that can be accomplished through sol-gel processing and the understanding of interactions between ILs and the sol-gel reaction network are greatly expanded. This work introduces novel ionogel materials, including soft and compliant silica-supported ionogels and PDMS-supported ionogels. The impacts of the reactive formulation, IL identity, and casting time are detailed. It is demonstrated that variations in formulation can lead to rapid gelation and open pore structures in the silica scaffold or slow gelation and more dense silica morphologies. The IL identity is shown to have an impact on the apparent strength of the acid catalyst, leading to significant shifts in gelation time. Delayed casting is proven to be an optimal technique for avoiding pore blockage when combining ionogels with high surface area electrodes for supercapacitor applications. Finally, a simple recycling process is proposed, establishing that ILs can be easily reclaimed from silica-supported ionogels and reused, thereby validating the reputation of ILs as "green" materials.

  18. Investigation of the Peroxovanadate Sol-Gel Process and Characterization of the Gels

    SciTech Connect

    Craig Joseph Fontenot

    2001-12-31

    In general, the peroxovanadate solution sol-gel process can be thought of as consisting of two parts: (1) the decomposition of the peroxo species and (2) cation hydrolysis leading to gelation. By controlling the synthesis conditions, both layered and amorphous compounds can be created. However, the type of water coordination observed in these gels was found to be identical no matter what the long-range order. The current work clarified many of the discrepancies found in the literature and offered much new valuable information. Highlights include the types of vanadium environments present at various stages of hydration, the role of adsorbed water, oxygen exchange from adsorbed water into the gel sites, and the ability to create metastable VMoO solid solution phases. These results could have a variety of impacts on future catalysis research.

  19. Aligned Human Microvessels Formed in 3D Fibrin Gel by Constraint of Gel Contraction

    PubMed Central

    Morin, Kristen T.; Smith, Annie O.; Davis, George E.; Tranquillo, Robert T.

    2013-01-01

    This study aimed to form microvessels in fibrin gels, which is of interest both for studying the fundamental cell-matrix interactions as well as for tissue engineering purposes, and to align the microvessels, which would provide natural inlet and outlet sides for perfusion. The data reported here demonstrate the formation of highly interconnected microvessels in fibrin gel under defined medium conditions and the ability to align them using two methods, both of which involved anchoring the gel at both ends to constrain the cell-induced compaction. The first method used only defined medium and resulted in moderate alignment. The second method used defined and serum-containing media sequentially to achieve high levels of microvessel alignment. PMID:23938272

  20. The Biophysical Properties of Basal Lamina Gels Depend on the Biochemical Composition of the Gel

    PubMed Central

    Pflieger, Kerstin; Boettcher, Kathrin; Zahler, Stefan; Lieleg, Oliver

    2015-01-01

    The migration of cells within a three-dimensional extracellular matrix (ECM) depends sensitively on the biochemical and biophysical properties of the matrix. An example for a biological ECM is given by reconstituted basal lamina gels purified from the Engelbreth-Holm-Swarm sarcoma of mice. Here, we compare four different commercial variants of this ECM, which have all been purified according to the same protocol. Nevertheless, in those gels, we detect strong differences in the migration behavior of leukocyte cells as well as in the Brownian motion of nanoparticles. We show that these differences correlate with the mechanical properties and the microarchitecture of the gels which in turn arise from small variations in their biochemical composition. PMID:25689062

  1. Investigations on gel forming media for use in low gravity bioseparations research

    NASA Astrophysics Data System (ADS)

    Todd, Paul; Szlag, David C.; Plank, Lindsay D.; Delcourt, Scott G.; Kunze, M. Elaine; Kirkpatrick, Francis H.; Pike, Roland G.

    Microgravity research includes investigations designed to gain insight on methods of separating living cells. During a typical separation certain real-time measurements can be made by optical methods, but some materials must also be subjected to subsequent analyses, sometimes including cultivation of the separated cells. In the absence of on-orbit analytical or fraction collecting procedures, some means is required to ``capture'' cells after separation. The use of solutions that form gels was therefore investigated as a means of maintaining cells and/or macromolecules in the separated state after two types of simple ground-based experiments. Microgravity electrophoresis experiments were simulated by separating model cell types (rat, chicken, human and rabbit erythrocytes) in a vertical density gradient containing low-conductivity buffer, 1.7%-6.5% Ficoll, 6.8-5.0% sucrose, and 1% SeaPrep low-melting temperature agarose and demonstrating that, upon cooling, a gel formed in the column, and cells could be captured in the positions to which they had migrated. Two-phase extraction experiments were simulated by choosing two-polymer solutions in which phase separation occurs in normal saline at temperatures compatible with cell viability and in which one or both phases form a gel upon cooling. Suitable polymers included commercial agaroses (1-2%), maltodextrin (5-7%) and gelatin (5-20%).

  2. Investigation of novel sol-gel hydrophobic surfaces for desorption electrospray ionization-mass spectrometry analysis.

    PubMed

    Penna, Andrea; Elviri, Lisa; Careri, Maria; Mangia, Alessandro; Predieri, Giovanni

    2011-05-01

    Sol-gel-based materials were synthesized, characterized and finally tested as solid supports for desorption electrospray ionization-mass spectrometry (DESI-MS) analysis of a mixture of compounds of different polarity. Films with thickness in the 2-4 μm range were obtained by a dip-coating process using tetraethoxysilane (TEOS) and octyltriethoxysilane (OTES) as sol-gel precursors. Three types of surface with different hydrophobic character were obtained by varying the TEOS/OTES ratio in the sol-gel mixture. Each coating was characterized by atomic force microscopy investigations, gaining insight into homogeneity, smoothness and thickness of the obtained films. To study hydrophobicity of each surface, surface free energy measurements were performed. Different DESI-MS responses were observed when different solvent mixture deposition procedures and solvent spray compositions were investigated. Results were finally compared to those obtained by using commercial polytetrafluoroethylene-coated slides. It was found that surface free energy plays an important role in the desorption/ionization process as a function of the polarity of analytes. PMID:21465099

  3. Excluded volume effects on ionic partitioning in gels and microgels: a simulation study.

    PubMed

    Ahualli, Silvia; Martín-Molina, Alberto; Quesada-Pérez, Manuel

    2014-12-14

    In this work the effect of volume exclusion on ionic partitioning in swollen and moderately collapsed gels has been studied through coarse-grained simulations. Our results show that finite size effects yield deviations from the classical theory of Donnan exclusion. At low or moderate reservoir electrolyte concentration these discrepancies become important if one of the ions has diameters of just a few nanometers. When the reservoir electrolyte concentration grows, volume exclusion can lead to a drastic failure of the ideal Donnan exclusion even for conventional hydrated monoatomic ions. In addition, an approximate analytical expression for the partition coefficient of ionic species including the volume exclusion associated with the polymer network and the neutralizing counterions has been proposed and tested. This theoretical approach also provides an expression for the Donnan potential difference that takes such effects into account. Good agreement between theory and simulations is found for slightly and moderately charged gels (both at low and high reservoir electrolyte concentrations). The theory also works acceptably for highly charged gels at high salt concentrations or for electrolytes with large counterions. PMID:25343312

  4. Dispersion functions and factors that determine resolution for DNA sequencing by gel electrophoresis

    SciTech Connect

    Sutherland, J.C.; Reynolds, K.J.; Fisk, D.J.

    1996-04-01

    The number of bases that can be read in a single run by a DNA sequencing instrument that detects fluorophore labeled DNA arriving at a ``finish-line`` located a fixed distance from the starting wells is influenced by numerous parameters. Strategies for improving the length-of-read of a DNA sequencer can be based on quantitative models of the separation of DNA by gel electrophoresis. The dispersion function of the electrophoretic system--the relationship between molecular contour length and time of arrival at the detector--is useful in characterizing the performance of a DNA sequencer. We adapted analytical representations of dispersion functions, originally developed for snapshot imaging of DNA gels, (samples electrophoresed for constant time), to finish-line imaging, and demonstrated that a logistic-type function with non-integral exponent is required to describe the experimental data. We use this dispersion function to determine the resolution length and resolving power of a LI-COR DNA sequencing system and a custom built capillary gel electrophoresis system, and discuss the factors that presently limit the number of bases that can be determined reliably in a single sequencing run.

  5. Mechanical behaviour of bending bucky-gel actuators and its representation

    NASA Astrophysics Data System (ADS)

    Kruusamäe, Karl; Mukai, Ken; Sugino, Takushi; Asaka, Kinji

    2014-02-01

    Bucky-gel actuators are ionic electromechanically active materials that bend in response to a low-voltage excitation. While bending actuators may offer new approaches in engineering solutions, the characterization of bending poses many challenges in comparison to conventional rotary motion. It is often desired to reduce the bending behaviour to a single parameter, which may lead to the loss of accuracy in modelling. A high-speed laser profilometer is utilized to characterize the bending response of different bucky-gel actuators at their full length and to critically compare the applicability of existing representation tools for bending. The best analytical representation of the bending of a bucky-gel actuator is found to be in the form of a power function. It is also observed that, along the length of the actuator, sections closer to the electrical input clamp exhibit back-relaxation (a common drawback for bending ionic actuators) already when the far end of the bending strip is still in forward motion.

  6. The transfer of analytical procedures.

    PubMed

    Ermer, J; Limberger, M; Lis, K; Wätzig, H

    2013-11-01

    Analytical method transfers are certainly among the most discussed topics in the GMP regulated sector. However, they are surprisingly little regulated in detail. General information is provided by USP, WHO, and ISPE in particular. Most recently, the EU emphasized the importance of analytical transfer by including it in their draft of the revised GMP Guideline. In this article, an overview and comparison of these guidelines is provided. The key to success for method transfers is the excellent communication between sending and receiving unit. In order to facilitate this communication, procedures, flow charts and checklists for responsibilities, success factors, transfer categories, the transfer plan and report, strategies in case of failed transfers, tables with acceptance limits are provided here, together with a comprehensive glossary. Potential pitfalls are described such that they can be avoided. In order to assure an efficient and sustainable transfer of analytical procedures, a practically relevant and scientifically sound evaluation with corresponding acceptance criteria is crucial. Various strategies and statistical tools such as significance tests, absolute acceptance criteria, and equivalence tests are thoroughly descibed and compared in detail giving examples. Significance tests should be avoided. The success criterion is not statistical significance, but rather analytical relevance. Depending on a risk assessment of the analytical procedure in question, statistical equivalence tests are recommended, because they include both, a practically relevant acceptance limit and a direct control of the statistical risks. However, for lower risk procedures, a simple comparison of the transfer performance parameters to absolute limits is also regarded as sufficient. PMID:23978903

  7. Climate Analytics as a Service

    NASA Technical Reports Server (NTRS)

    Schnase, John L.; Duffy, Daniel Q.; McInerney, Mark A.; Webster, W. Phillip; Lee, Tsengdar J.

    2014-01-01

    Climate science is a big data domain that is experiencing unprecedented growth. In our efforts to address the big data challenges of climate science, we are moving toward a notion of Climate Analytics-as-a-Service (CAaaS). CAaaS combines high-performance computing and data-proximal analytics with scalable data management, cloud computing virtualization, the notion of adaptive analytics, and a domain-harmonized API to improve the accessibility and usability of large collections of climate data. MERRA Analytic Services (MERRA/AS) provides an example of CAaaS. MERRA/AS enables MapReduce analytics over NASA's Modern-Era Retrospective Analysis for Research and Applications (MERRA) data collection. The MERRA reanalysis integrates observational data with numerical models to produce a global temporally and spatially consistent synthesis of key climate variables. The effectiveness of MERRA/AS has been demonstrated in several applications. In our experience, CAaaS is providing the agility required to meet our customers' increasing and changing data management and data analysis needs.

  8. Utilizing ATRP to Design Self-Regenerating Polymer Gels

    NASA Astrophysics Data System (ADS)

    Yong, Xin; Averick, Saadyah; Kuksenok, Olga; Matyjaszewski, Krzysztof; Balazs, Anna

    2014-03-01

    Using newly developed computational approaches, we design a gel system capable of re-growth after a substantial section of the material was cut away. Atom transfer radical polymerization (ATRP) is utilized to form gels with preserved ``living'' chain ends and residual unreacted cross-linking groups. When this ``living'' gel is cut, these active species are exposed to a solution containing monomer, crosslinker, initiator and catalyst. A ``repairing'' polymerization occurs from both the new initiators introduced in the outer solution and the reactive chain ends present at the cut site. This new polymerization results in a covalent linkage between the initial living gel and the new gel prepared in the outer solution, and the connection is promoted by the presence of residual cross-linking groups. By measuring the diffusion of the outer solution into the cut gel and characterizing the width and strength of the interface between the initial and new gels, we identify the optimum parameters that yield a strong interface between the gel layers. Our simulations results are in good agreement with our experimental studies. This strategy not only regenerates ``injured'' gels, but also offers a novel means to engineer multi-layered composite gels.

  9. Adsorption of pesticidal compounds bearing a single carboxyl functional group and biogenic amines by humic fraction-immobilized silica gel.

    PubMed

    Chen, Cheng-Sheng; Chen, Shushi

    2013-04-17

    Fractions collected from humic acids under acidic and basic conditions were immobilized on silica gel and used as adsorbents for a variety of agricultural pesticide compounds bearing a single carboxyl functional group and biogenic amines in acetonitrile. Among these compounds examined under the same conditions, the percentage of adsorption varies considerably from 0 to almost 100%. The percentage is found to be highly related to the structure of the analyte and the type of functional group attached to it. The adsorption, better performed on adsorbent immobilized with the fraction collected under acidic conditions, is believed to result from the reversible interaction between the functional moieties of the analyte and humic acids (e.g., amino or carboxyl group of analyte vs carboxyl group of humic acids, etc.) as no adsorption is observed under the same conditions for analytes that are derivatives of alcohol, amide, and ester. Given the nature of the analyte, the time needed to reach the maximum percent of adsorption decreases as the amount of adsorbent is increased. Also, the longer the time that has elapsed, the higher the percentage of analyte adsorbed, thus indicating that the adsorption process is surface-oriented. Factors such as the acidic or basic origin of the additive in the liquid phase of the matrix also affect the percentage of analyte adsorbed. PMID:23521499

  10. Vaginal deployment and tenofovir delivery by microbicide gels.

    PubMed

    Gao, Y; Yuan, A; Chuchuen, O; Ham, A; Yang, K H; Katz, D F

    2015-06-01

    Gels are one of the soft material platforms being evaluated to deliver topically acting anti-HIV drugs (microbicides) to the vaginal environment. For each drug, its loaded concentration, gel properties and applied volume, and frequency of dosing can be designed to optimize PK and, thence, PD. These factors also impact user sensory perceptions and acceptability. Deterministic compartmental modeling of vaginal deployment and drug delivery achieved by test gels can help delineate how multiple parameters characterizing drug, vehicle, vaginal environment, and dosing govern details of PK and PD and also gel leakage from the canal. Such microbicide delivery is a transport process combining convection, e.g., from gel spreading along the vaginal canal, with drug diffusion in multiple compartments, including gel, mucosal epithelium, and stroma. The present work builds upon prior models of gel coating flows and drug diffusion (without convection) in the vaginal environment. It combines and extends these initial approaches in several key ways, including: (1) linking convective drug transport due to gel spreading with drug diffusion and (2) accounting for natural variations in dimensions of the canal and the site of gel placement therein. Results are obtained for a leading microbicide drug, tenofovir, delivered by three prototype microbicide gels, with a range of rheological properties. The model includes phosphorylation of tenofovir to tenofovir diphosphate (which manifests reverse transcriptase activity in host cells), the stromal concentration distributions of which are related to reference prophylactic values against HIV. This yields a computed summary measure related to gel protection ("percent protected"). Analyses illustrate tradeoffs amongst gel properties, drug loading, volume and site of placement, and vaginal dimensions, in the time and space history of gel distribution and tenofovir transport to sites of its anti-HIV action and concentrations and potential prophylactic actions of tenofovir diphosphate therein. PMID:25874971

  11. Sol-gel processing to form doped sol-gel monoliths inside hollow core optical fiber and sol-gel core fiber devices made thereby

    NASA Technical Reports Server (NTRS)

    Shaw, Harry C. (Inventor); Ott, Melanie N. (Inventor); Manuel, Michele V. (Inventor)

    2002-01-01

    A process of fabricating a fiber device includes providing a hollow core fiber, and forming a sol-gel material inside the hollow core fiber. The hollow core fiber is preferably an optical fiber, and the sol-gel material is doped with a dopant. Devices made in this manner includes a wide variety of sensors.

  12. Analytical Chemistry of Nitric Oxide

    PubMed Central

    Hetrick, Evan M.

    2013-01-01

    Nitric oxide (NO) is the focus of intense research, owing primarily to its wide-ranging biological and physiological actions. A requirement for understanding its origin, activity, and regulation is the need for accurate and precise measurement techniques. Unfortunately, analytical assays for monitoring NO are challenged by NO’s unique chemical and physical properties, including its reactivity, rapid diffusion, and short half-life. Moreover, NO concentrations may span pM to µM in physiological milieu, requiring techniques with wide dynamic response ranges. Despite such challenges, many analytical techniques have emerged for the detection of NO. Herein, we review the most common spectroscopic and electrochemical methods, with special focus on the fundamentals behind each technique and approaches that have been coupled with modern analytical measurement tools or exploited to create novel NO sensors. PMID:20636069

  13. Analytical approximations for spiral waves

    SciTech Connect

    Löber, Jakob Engel, Harald

    2013-12-15

    We propose a non-perturbative attempt to solve the kinematic equations for spiral waves in excitable media. From the eikonal equation for the wave front we derive an implicit analytical relation between rotation frequency Ω and core radius R{sub 0}. For free, rigidly rotating spiral waves our analytical prediction is in good agreement with numerical solutions of the linear eikonal equation not only for very large but also for intermediate and small values of the core radius. An equivalent Ω(R{sub +}) dependence improves the result by Keener and Tyson for spiral waves pinned to a circular defect of radius R{sub +} with Neumann boundaries at the periphery. Simultaneously, analytical approximations for the shape of free and pinned spirals are given. We discuss the reasons why the ansatz fails to correctly describe the dependence of the rotation frequency on the excitability of the medium.

  14. Big Data Analytics in Healthcare

    PubMed Central

    Belle, Ashwin; Thiagarajan, Raghuram; Soroushmehr, S. M. Reza; Navidi, Fatemeh; Beard, Daniel A.; Najarian, Kayvan

    2015-01-01

    The rapidly expanding field of big data analytics has started to play a pivotal role in the evolution of healthcare practices and research. It has provided tools to accumulate, manage, analyze, and assimilate large volumes of disparate, structured, and unstructured data produced by current healthcare systems. Big data analytics has been recently applied towards aiding the process of care delivery and disease exploration. However, the adoption rate and research development in this space is still hindered by some fundamental problems inherent within the big data paradigm. In this paper, we discuss some of these major challenges with a focus on three upcoming and promising areas of medical research: image, signal, and genomics based analytics. Recent research which targets utilization of large volumes of medical data while combining multimodal data from disparate sources is discussed. Potential areas of research within this field which have the ability to provide meaningful impact on healthcare delivery are also examined. PMID:26229957

  15. Analytical models of dipolarization fronts

    NASA Astrophysics Data System (ADS)

    Vasko, Ivan; Artemyev, Anton

    Dipolarization fronts (DFs) are mesoscale structures generated during the transient magnetic reconnection in the Earth's magnetotail. Spacecraft often observe these structures propagating toward the Earth with velocities 300-100 km/s. Modern multispacecraft observations allow reconstruction of 3D configuration of electromagnetic fields of DF: front is strongly curved in the XY plane and spatially localized along the Z axis (in GSM coordinate system). DFs play important role in plasma heating and charged particle acceleration. Thus, the simplified analytical models of 2D and 3D configuration of DF are necessary to model charge particle interaction with fronts. In the present report we propose 3D analytical model of DF. For several given distributions of B _{z} magnetic field component we have found analytical expressions for magnetic fields B _{x}, B _{y} and electric fields E _{x}, E _{y}. We also discuss distribution of electric field, which is due to the polarization of plasma in the vicinity of DF.

  16. Platelet gel for healing cutaneous chronic wounds.

    PubMed

    Crovetti, Giovanni; Martinelli, Giovanna; Issi, Marwan; Barone, Marilde; Guizzardi, Marco; Campanati, Barbara; Moroni, Marco; Carabelli, Angelo

    2004-04-01

    Wound healing is a specific host immune response for restoration of tissue integrity. Experimental studies demonstrated an alteration of growth factors activity due to their reduced synthesis, increased degradation and inactivation. In wound healing platelets play an essential role since they are rich of alpha-granules growth factors (platelet derived growth factor--PDGF; transforming growth factor-beta--TGF-beta; vascular endothelial growth factor--VEGF). Topical use of platelet gel (PG), hemocomponent obtained from mix of activated platelets and cryoprecipitate, gives the exogenous and in situ adding of growth factors (GF). The hemocomponents are of autologous or homologous origin. We performed a technique based on: multicomponent apheretic procedure to obtain plasma rich platelet and cryoprecipitate; manual processing in an open system, in sterile environment, for gel activation. Every step of the gel synthesis was checked by a quality control programme. The therapeutic protocol consists of the once-weekly application of PG. Progressive reduction of the wound size, granulation tissue forming, wound bed detersion, regression and absence of infective processes were considered for evaluating clinical response to hemotherapy. 24 patients were enrolled. They had single or multiple cutaneous ulcers with different ethiopathogenesis. Only 3 patients could perform autologous withdrawal; in the others homologous hemocomponent were used, always considering suitability and traceability criteria for transfusional use of blood. Complete response was observed in 9 patients, 2 were subjected to cutaneous graft, 4 stopped treatment, 9 had partial response and are still receiving the treatment. In each case granulation tissue forming increased following to the first PG applications, while complete re-epithelization was obtained later. Pain was reduced in every treated patient. Topical haemotherapy with PG may be considered as an adjuvant treatment of a multidisciplinary process, useful to enhance therapy of cutaneous ulcers. PMID:15062754

  17. Platelet gel: applications in dental regenerative surgery

    PubMed Central

    Forni, Franco; Marzagalli, Massimo; Tesei, Patrizia; Grassi, Alessandra

    2013-01-01

    Background Platelet growth factors obtained from platelet-rich plasma (PRP) are used in prosthetic and periodontal regenerative therapy in dentistry. Increased microvascular proliferation in the first 20 days is followed by enhanced osteoblast activity and immature osteoid formation within 3–6 weeks, improving the quality and quantity of newly formed bone tissue. The aim of this study was to evaluate, through three-dimensional X-ray monitoring, the amount of bone obtained after bone regeneration treatment with platelet gel from autologous PRP. Materials and methods Patients eligible for regenerative treatment of atrophic alveolar bone of the maxilla or mandible were studied. The patients’ autologous whole blood was collected at the Department of Immunology and Transfusion of San Matteo Hospital for the preparation of platelet gel. The bone at the treated sites was analysed prior to and 4 months after the treatment using the three-dimensional X-ray system Galileos. Results Over a period of 6 years, 133 patients were treated: 304 implants were inserted and there were five cases of failure. The regenerated bone area consisted of histologically immature osteoid tissue composed of thin trabeculae of vital bone and nuclei of osteocytes, associated with fibro-connective tissue. Discussion This co-operative trial between the Transfusion Centre, for standardised production and validation of the platelet gel, and the Dental Surgery room for its application showed that the technique appears effective and safe. Although difficulties were encountered because of the small sample size and the inability to carry out long-term histological controls, the use of small amounts of PRP (5–10%) combined with autologous bone (15–20%) and alloplastic material appears to reduce the need for bone grafting. PMID:22790266

  18. Analytical Applications of NMR: Summer Symposium on Analytical Chemistry.

    ERIC Educational Resources Information Center

    Borman, Stuart A.

    1982-01-01

    Highlights a symposium on analytical applications of nuclear magnetic resonance spectroscopy (NMR), discussing pulse Fourier transformation technique, two-dimensional NMR, solid state NMR, and multinuclear NMR. Includes description of ORACLE, an NMR data processing system at Syracuse University using real-time color graphics, and algorithms for…

  19. Hybrid slab-microchannel gel electrophoresis system

    DOEpatents

    Balch, Joseph W.; Carrano, Anthony V.; Davidson, James C.; Koo, Jackson C.

    1998-01-01

    A hybrid slab-microchannel gel electrophoresis system. The hybrid system permits the fabrication of isolated microchannels for biomolecule separations without imposing the constraint of a totally sealed system. The hybrid system is reusable and ultimately much simpler and less costly to manufacture than a closed channel plate system. The hybrid system incorporates a microslab portion of the separation medium above the microchannels, thus at least substantially reducing the possibility of non-uniform field distribution and breakdown due to uncontrollable leakage. A microslab of the sieving matrix is built into the system by using plastic spacer materials and is used to uniformly couple the top plate with the bottom microchannel plate.

  20. Fuel oil classification by gel permeation chromatography

    SciTech Connect

    Lenda, K.

    1982-01-01

    The use of the gel permeation chromatography (GPC) in the petrochemical laboratory is demonstrated by experimental optimization of the separation, detection and results calculation for fuel oil samples. A chromatographic response based on the fuel oil GPC separation and detection is compared with results of Conradson carbon residue (CCR) determination - which is one of the standard petrochemical tests for residue fuel. The linear relationship between the results of both tests was confirmed. Comparison of refractive and UV detection for fuel oil classification is presented. 3 refs.