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Preparação e estabilização de uma suspensão cerâmica de porcelana de ossos.; Preparation and stabilization for ceramics suspensions of bone porcelain.

Vera Alatrista, Gerardo Augusto
Fonte: Biblioteca Digitais de Teses e Dissertações da USP Publicador: Biblioteca Digitais de Teses e Dissertações da USP
Tipo: Dissertação de Mestrado Formato: application/pdf
Publicado em 31/07/2008 PT
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O estudo da dispersão e estabilização de barbotinas de porcelana de cinza de ossos é uma etapa muito importante no processo de conformação de peças cerâmicas, assim como também a etapa de obtenção da sua principal matéria-prima que é a cinza de ossos, devido a que constitui 50% em peso da porcelana e por ser uma matéria-prima renovável, reciclável e com alto valor agregado na fabricação de porcelana. Neste trabalho se investigou a influência das temperaturas de calcinação dos ossos (700, 800, 900 e 1000 °C) moídos e lavados, no seu tamanho, forma das partículas, composição química, comportamento elétrico superficial das partículas com o meio líquido, grupos funcionais e possíveis contaminantes nas superfícies das partículas dos ossos calcinados, que poderiam prejudicar a preparação de barbotinas de porcelana de ossos. Mostra-se também a dispersão, preparação e a estabilização da mistura de porcelana de ossos (50% cinza de ossos, 25% de caulim, 25% de feldspato) por meio dos ensaios de viscosidade e mobilidade eletroforética, conseguindo dispersar, homogeneizar e estabilizar as suspensões de porcelana de ossos aplicando tempos de envelhecimentos apropriados.; The study of the dispersion and stabilization of slip casting of bone porcelain is a very important stage in the process of preparation of suspensions ceramic...

Cell wall surface properties and flocculence of a Kluyveromyces marxianus strain

Teixeira, J. A.; Oliveira, Rosário; Azeredo, Joana; Sousa, M.; Sil, C.
Fonte: Elsevier Science B.V. Publicador: Elsevier Science B.V.
Tipo: Artigo de Revista Científica
Publicado em 10/11/1995 ENG
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Yeast flocculation is under genetic control and is described as a cell wall interaction. This characteristic of yeast cells has been traditionally used in industrial fermentation processes. The surface characteristics of the cell walls are expected to be a determinant factor in the aggregation mechanism. Results confirming this have been reported for Saccharomyces strains. It is important to extend these studies to other genera. Among them, due to its potential industrial interest, Kluyveromyces strains must be considered. In this work are reported results relating cell wall surface properties (hydrophobicity and electrophoretic mobility) with the flocculation ability of a strain of Kluyveromyces marxianus. The effect of proteolytic enzymes, pH, salts and sugars on flocculation was also studied. The results obtained clearly demonstrate that cell wall hydrophobicity is a major determinant in the flocculation ability of the Kluyveromyces marxianus cells.; Junta Nacional de Investigação Científica e Tecnológica (JNICT)

The surface charge of trypanosomatids

SOUTO-PADRÓN,THAÏS
Fonte: Academia Brasileira de Ciências Publicador: Academia Brasileira de Ciências
Tipo: Artigo de Revista Científica Formato: text/html
Publicado em 01/12/2002 EN
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The surface charge of trypanosomatids was evaluated by means of the binding of cationic particles, as visualized by electron microscopy and by direct measurements of the electrophoretic mobility of cells. The results obtained indicate that most of the trypanosomatids exhibit a negatively charged surface whose value is species specific and varies according to the developmental stages. Sialic acids associated with glycoproteins, glycolipids and phosphate groups are the major components responsible for the net negative surface charge of the trypanosomatids.

The surface charge of trypanosomatids of the genus trypanosoma

Souto Padrón,Thaís; Chiari,Egler; Souza,Wanderley de
Fonte: Instituto Oswaldo Cruz, Ministério da Saúde Publicador: Instituto Oswaldo Cruz, Ministério da Saúde
Tipo: Artigo de Revista Científica Formato: text/html
Publicado em 01/06/1990 EN
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Cell electrophoresis was used for determionation of the electrophoretic mobility (EPM) of epimastigo and trypamastigote forms of several isolates of Trypanosoma cruzi and some stocks of other members of the Schizotrypanum subgenus, such as T. dionisii, T. vespertilionis and T. myoti. The EPM of T. bruceli, T. rangeli, and T. conorhini was also determined. The results obtained show that the EPM values con be useful to distinguish the parasites.

Rapid preparation of single stranded DNA from PCR products by streptavidin induced electrophoretic mobility shift.

Pagratis, N C
Fonte: PubMed Publicador: PubMed
Tipo: Artigo de Revista Científica
Publicado em 15/09/1996 EN
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Streptavidin induced electrophoretic mobility shift was used to prepare single stranded (ss) DNA amplified with the polymerase chain reaction in the presence of a biotinylated and a non-biotinylated primer. A variety of denaturing conditions, including incubation at 95 degrees C in 50% formamide can be used without disrupting the streptavidin-biotinylated-ssDNA complex. Following electrophoresis, pure non-biotinylated DNA can be efficiently recovered from 7 M urea gels because it is well separated from the severely retarded streptavidin-biotinylated-ssDNA complex. Quantitative complexing of biotinylated ssDNA can occur at a streptavidin to DNA molar ratio of 1 or more.

Electrophoretic Mobility of Bacillus subtilis Knockout Mutants with and without Flagella

Okuda, Shujiro; Igarashi, Ryosuke; Kusui, Yusuke; Kasahara, Yasuhiro; Morisaki, Hisao
Fonte: American Society for Microbiology Publicador: American Society for Microbiology
Tipo: Artigo de Revista Científica
Publicado em /07/2003 EN
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Mutants of Bacillus subtilis 168 strain were obtained by inactivation of a specific gene by homologous recombination with the plasmid pMutinT3. The cell surface properties of these strains were characterized by measuring the electrophoretic mobility of the cells as a function of pH and ionic strength. The surface properties were different for the strains possessing flagella on their cells and strain FlgB, having no flagellum, due to knockout of the corresponding gene. The cell surface properties of the strains possessing flagella become similar to those of strain FlgB after acid treatment. It was confirmed that the acid treatment degraded the flagella without causing any apparent structural change on the cell surface via observations made using atomic force microscopy, transmission electron microscopy, and scanning electron microscopy. These results indicate that the flagella are a key factor influencing cell surface properties.

Antibiotic induced electrophoretic mobility shifts of DNA restriction fragments.

Loucks, E; Chaconas, G; Blakesley, R W; Wells, R D; van de Sande, J H
Fonte: PubMed Publicador: PubMed
Tipo: Artigo de Revista Científica
Publicado em //1979 EN
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Several antibiotics, netropsin, distamycin A, actinomycin D, Hoechst 33258 and olivomycin, which demonstrate base specificity in their DNA binding properties have been found to alter the electrophoretic mobility of DNA restriction fragments in native polyacrylamide gels. The antibiotics mostly reduced the migration of larger DNA fragments, but netropsin and Hoechst 33258 were observed to increase the migration rate of several DNA fragments of intermediate size. DNA fragments of similar molecular weight which comigrate as a single gel band can at times be separated as the result of differential mobility shifts promoted by antibiotic DNA complex formations.

DNA chain length markers and the influence of base composition on electrophoretic mobility of oligodeoxyribonucleotides in polyacrylamide-gels.

Frank, R; Köster, H
Fonte: PubMed Publicador: PubMed
Tipo: Artigo de Revista Científica
Publicado em //1979 EN
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The specific influence of the four nucleobases on electrophoretic mobility of oligodeoxyribonucleotides in polyacrylamide-gels under denaturing and nondenaturing conditions has been investigated using homooligomers from the four deoxyribonucleotides as chain length standards. Homooligomers of same chain lengths exhibit remarkable differences in mobility. Specific retardation of any other oligonucleotide investigated was found to be mainly dependent on base composition but not on sequence. A simple procedure is presented for calculating mobilities relative to the standards on denaturing gels. This allows a reliable identification of oligonucleotides on acrylamide-gels by exact chain length determination with respect to base composition and furthermore a detailed interpretation of complex reaction mixtures. The homooligomers also show the same differences in mobility on nondenaturing gels. The significance of this effect for strand separation is discussed.

Pulse time and agarose concentration affect the electrophoretic mobility of cccDNA during PFGE and FIGE [corrected].

Sobral, B W; Atherly, A G
Fonte: PubMed Publicador: PubMed
Tipo: Artigo de Revista Científica
Publicado em 25/09/1989 EN
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Circular DNAs have been shown to migrate in an unusual manner during field inversion gel electrophoresis (FIGE) and orthogonal field alternating gel electrophoresis (OFAGE). We studied the effect of varying pulse time and agarose concentration on the electrophoretic mobility of supercoiled (ccc) DNAs ranging from 2 kbp to 16 kbp during FIGE and contoured homogeneous electric fields (CHEF). Both supercoiled and linear molecules display a minimum mobility as a function of pulse time in a CHEF apparatus. Linear and cccDNAs of the same size are differently affected by pulse time. Pulse-time dependence was observed for cccDNAs in both systems. Pulse-time dependence in FIGE is very small at a 1.0% agarose concentration, but is pronounced in 0.8% or 1.2% gels.

Diffusion and Electrophoretic Mobility of Single-Stranded RNA from Molecular Dynamics Simulations

Yeh, In-Chul; Hummer, Gerhard
Fonte: Biophysical Society Publicador: Biophysical Society
Tipo: Artigo de Revista Científica
Publicado em /02/2004 EN
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Hydrodynamic properties of small single-stranded RNA homopolymers with three and six nucleotides in free solution are determined from molecular dynamics simulations in explicit solvent. We find that the electrophoretic mobility increases with increasing RNA length, consistent with experiment. Diffusion coefficients of RNA, corrected for finite-size effects and solvent viscosity, agree well with those estimated from experiments and hydrodynamic calculations. The diffusion coefficients and electrophoretic mobilities satisfy a Nernst-Einstein relation in which the effective charge of RNA is reduced by the charge of transiently bound counterions. Fluctuations in the counterion atmosphere are shown to enhance the diffusive spread of RNA molecules drifting along the direction of the external electric field. As a consequence, apparent diffusion coefficients measured by capillary zone electrophoresis can be significantly larger than the actual values at certain experimental conditions.

Electrophoretic mobility of human erythrocytes. On the applicability of the charged layer model.

Donath, E; Voigt, A
Fonte: PubMed Publicador: PubMed
Tipo: Artigo de Revista Científica
Publicado em /02/1986 EN
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The limitations of previous linear electrokinetic theories are discussed. A special model of the surface charge distribution, based on the minimum condition of the interfacial electrostatic free energy, is introduced. The model describes the electrophoretic mobility, taking into account the electroosmotic flow through the surface macromolecular layer and the surface conductivity. This nonlinear electrophoretic theory describes experimental data obtained with human erythrocytes. Numerical results for an uniformly distributed space charge are also presented.

Changes in the electrophoretic mobility of mouse lymph node lymphocytes during ontogeny.

Dumont, F; Robert, F
Fonte: PubMed Publicador: PubMed
Tipo: Artigo de Revista Científica
Publicado em /06/1977 EN
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The electrokinetic properties of peripheral lymph node (LN) cells from C3H and nude mice aged 1, 3 or 10 weeks, were investigated by means of preparative and analytical cell electrophoresis. Two groups of cells were distinguishable throughout the age interval examined. The first group, with low-mobility (LM) included the majority of surface-immunoglobulin positive lymphocytes, was predominant in athymic nude mice and is thus likely to represent B cells. The other group, with higher mobility (HM), was sensitive to anti-Thy 1-2 serum, made up the major LN population in C3H mice and normal nude littermates and thus probably corresponds to T cells. In C3H mice, the relative proportion of LM cells was found to increase with age of LN donors (from 9-22%). Moreover, significant alterations in the mean electrophoretic mobility (EPM) of both lymphocyte populations were detected in the course of development. While the EPM of LM cells diminished from 0-81-0-70 micrometer.s-1.V-1.cm, that of HM cells increased from 1-11-1-22 micrometer.s-1.V-1.cm as the animals grew from 1-10 weeks. These observations indicate a relationship between the degree of maturity of peripheral B- and T-cell populations and their electrokinetic properties.

ELECTROPHORETIC MOBILITY AND AGGLUTINABILITY OF RED BLOOD CELLS: A "NEW" POLYMORPHISM IN MICE

Rubinstein, Pablo; Liu, Ngukoy; Streun, Edwin W.; Decary, Francine
Fonte: The Rockefeller University Press Publicador: The Rockefeller University Press
Tipo: Artigo de Revista Científica
Publicado em 01/02/1974 EN
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A quantitative method has been developed to determine agglutinability of mouse red blood cells. Tests with different inbred strains of mice revealed only two phenotypes. The same inbred strains were tested with the cytopherometer to determine the electrophoretic mobility of the corresponding red cells. Again, two phenotypes were uncovered, and faster mobility was found in the red cells that had higher agglutinability. The genetic control of this character is autosomal and codominant, and segregates independently of H-2 and coat color.

THE ELECTROPHORETIC MOBILITY OF HUMAN ERYTHROCYTES—WHOLE CELLS, GHOSTS, AND FRAGMENTS

Byler, W. H.; Rozendaal, H. M.
Fonte: The Rockefeller University Press Publicador: The Rockefeller University Press
Tipo: Artigo de Revista Científica
Publicado em 20/09/1938 EN
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The electrophoretic mobility of human red cell ghosts decreases in the presence of chicken serum. The decrease is not directly due to the presence of adsorbed material but to a change which is catalyzed by the foreign substance. It is suggested that abnormal serum materials resulting from disease may serve as catalysts. Fragments of broken cells have the same mobility as whole cells at first, then decrease even in pure salt suspension, while the whole cells remain essentially unchanged for hours. The results suggest that the slow change of whole cells, the change of ghosts in the presence of foreign serum, and the change of fragments are all manifestations of the same modification of structure or composition of the cell surface.

Simultaneous sizing and electrophoretic mobility measurement of sub-micron particles using Brownian motion

Palanisami, Akilan; Miller, John H.
Fonte: PubMed Publicador: PubMed
Tipo: Artigo de Revista Científica
Publicado em /10/2010 EN
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The size and surface chemistry of micron scale particles are of fundamental importance in studies of biology and air particulate pollution. However, typical electrophoretic measurements of these and other sub-micron scale particles (300 nm – 1 μm) cannot resolve size information within heterogeneous mixtures unambiguously. Using optical microscopy, we monitor electrophoretic motion together with the Brownian velocity fluctuations—using the latter to measure size by either the Green-Kubo relation or by calibration from known size standards. Particle diameters are resolved to ±12% with 95% confidence. Strikingly, the size resolution improves as particle size decreases due to the increased Brownian motion. The sizing ability of the Brownian assessed electrophoresis method described here complements the electrophoretic mobility resolution of traditional capillary electrophoresis.

The ‘Densitometric Image Analysis Software’ and Its Application to Determine Stepwise Equilibrium Constants from Electrophoretic Mobility Shift Assays

van Oeffelen, Liesbeth; Peeters, Eveline; Nguyen Le Minh, Phu; Charlier, Daniël
Fonte: Public Library of Science Publicador: Public Library of Science
Tipo: Artigo de Revista Científica
Publicado em 21/01/2014 EN
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Current software applications for densitometric analysis, such as ImageJ, QuantityOne (BioRad) and the Intelligent or Advanced Quantifier (Bio Image) do not allow to take the non-linearity of autoradiographic films into account during calibration. As a consequence, quantification of autoradiographs is often regarded as problematic, and phosphorimaging is the preferred alternative. However, the non-linear behaviour of autoradiographs can be described mathematically, so it can be accounted for. Therefore, the ‘Densitometric Image Analysis Software’ has been developed, which allows to quantify electrophoretic bands in autoradiographs, as well as in gels and phosphorimages, while providing optimized band selection support to the user. Moreover, the program can determine protein-DNA binding constants from Electrophoretic Mobility Shift Assays (EMSAs). For this purpose, the software calculates a chosen stepwise equilibrium constant for each migration lane within the EMSA, and estimates the errors due to non-uniformity of the background noise, smear caused by complex dissociation or denaturation of double-stranded DNA, and technical errors such as pipetting inaccuracies. Thereby, the program helps the user to optimize experimental parameters and to choose the best lanes for estimating an average equilibrium constant. This process can reduce the inaccuracy of equilibrium constants from the usual factor of 2 to about 20%...

Adenosine dimethylation of 16S ribosomal RNA: effect of the methylgroups on local conformational stability as deduced from electrophoretic mobility of RNA fragments in denaturing polyacrylamide gels.

Van Charldorp, R; Heus, H A; Van Knippenberg, P H
Fonte: PubMed Publicador: PubMed
Tipo: Artigo de Revista Científica
Publicado em 24/01/1981 EN
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The electrophoretic mobility of RNA fragments derived from the 3'-end of 16S rRNA on slabs of polyacrylamide gel in the presence of urea is strongly influenced by dimethylation of the N6-aminogroup of two adjacent adenosines. This is not due to the presence of the methylgroups per se, but must be ascribed to an effect of methylation on long range intramolecular interactions at these denaturing conditions. When it is assumed that the electrophoretic mobilities of the RNA fragments in the polyacrylamide matrix are determined by the conformational state(s) of the fragments, dimethylation of the adenosines leads in the smaller fragments to a less compact average conformation and in the larger fragments to a more compact average conformation. An effort is made to comprehend the effects of adenosine dimethylation in terms of secondary structure based on nucleotide sequence.

Mechanisms of activation of the properdin system. Studies on properdin electrophoretic mobility in agarose activation of the alternative pathway.

Adam, C; Williams, D G; Peters, D K
Fonte: PubMed Publicador: PubMed
Tipo: Artigo de Revista Científica
Publicado em /11/1975 EN
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The electrophoretic mobility of properdin in agarose with and without EDTA examined in sera from normal subjects and from patients with mesangiocapillary glomerulonephritis, systemic lupus erythematosus, rapidly progressive glomerulonephritis, mesangial IgG-IgA disease, minimal change glomerulonephritis and partial lipodystrophy.In 'EDTA agarose", the properdin arc of normal serum was always cathodal (gamma), whereas in non-EDTA agarose it was always (beta), indicating that agarose activated properdin with its consequent conversion from a cathodal to an anodal form. Using this change in the mobility of properdin to investigate activation of the properdin system, it was found that the lower the C3 concentration of diseased sera, the less able were they to support properdin conversion by non-EDTA agarose. This relationship we interpret as a manifestation of the requirement of an intact C3b feedback pathway for properdin activation. This view was supported experimentally by (i) decreasing ability of non-EDTA agarose to shift properdin mobility in normal serum as it was progressively depleted of components of the alternative pathway by cobra venom factor, C3 nehritic factor or Mg2+, and (ii) the inability of non-EDTA agarose to shift properdin in sera depleted of C3 or factor B...

Electrophoretic mobility of a charged colloidal particle: A computer simulation study

Lobaskin, Vladimir; Duenweg, Burkhard; Holm, Christian
Fonte: Universidade Cornell Publicador: Universidade Cornell
Tipo: Artigo de Revista Científica
Publicado em 11/06/2004
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We study the mobility of a charged colloidal particle in a constant homogeneous electric field by means of computer simulations. The simulation method combines a lattice Boltzmann scheme for the fluid with standard Langevin dynamics for the colloidal particle, which is built up from a net of bonded particles forming the surface of the colloid. The coupling between the two subsystems is introduced via friction forces. In addition explicit counterions, also coupled to the fluid, are present. We observe a non-monotonous dependence of the electrophoretic mobility on the bare colloidal charge. At low surface charge density we observe a linear increase of the mobility with bare charge, whereas at higher charges, where more than half of the ions are co-moving with the colloid, the mobility decreases with increasing bare charge.; Comment: 15 pages, 8 figures

Exact expressions for the mobility and electrophoretic mobility of a weakly charged sphere in a simple electrolyte

Lizana, Ludvig; Grosberg, Alexander Y.
Fonte: Universidade Cornell Publicador: Universidade Cornell
Tipo: Artigo de Revista Científica
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We present (asymptotically) exact expressions for the mobility and electrophoretic mobility of a weakly charged spherical particle in an $1:1$ electrolyte solution. This is done by analytically solving the electro and hydrodynamic equations governing the electric potential and fluid flow with respect to an electric field and a nonelectric force. The resulting formulae are cumbersome, but fully explicit and trivial for computation. In the case of a very small particle compared to the Debye screening length ($R \ll r_D$) our results reproduce proper limits of the classical Debye and Onsager theories, while in the case of a very large particle ($R \gg r_D$) we recover, both, the non-monotonous charge dependence discovered by Levich (1958) as well as the scaling estimate given by Long, Viovy, and Ajdari (1996), while adding the previously unknown coefficients and corrections. The main applicability condition of our solution is charge smallness in the sense that screening remains linear.; Comment: 6 pages, 1 figure