Polystyrene Sulfate Research Articles

Electrokinetic characterization and colloidal stability of polystyrene latex particles partially covered by IgG/a-CRP and m-BSA proteins

In this work the competitive coadsorption of immunoglobulin IgG and bovine serum albumin (BSA) proteins on a sulfate polystyrene latex has been studied. The competitive coadsorption experiments were carried out by changing the initial concentration of both proteins ([m-BSA] or [IgG/a-CRP]) in order to cover different possibilities of competition. By changing the pH and the ionic strength during the incubation, it was possible to obtain latex—protein complexes with different degrees of coverage by each protein. These complexes were characterized electrokinetically under several different redispersion conditions and their colloidal stability was also determined. By combining both results it is possible to establish that, at neutral pH, electrostatic repulsion is the main factor governing the colloidal stability. This stability appeared when negatively charged BSA molecules constituted the majority protein on the particle surface. However, the immunoreactivity of the sensitized latexes was sufficient with a partial coverage by IgG molecules. Therefore the properties of the latex—protein complex depended on the percentage of BSA or IgG adsorbed and on the charge state of the proteins at the redispersion pH. By using specific incubation conditions, latexes covered by different percentages of IgG/BSA were obtained, which showed high colloidal stability and good immunoreactivity.

Kinetics of Heterocoagulation

The heterocoagulation of colloids A and B was investigated by computer simulation and through experiments. In simulation, the cluster aggregation ability Å n , and cluster size n were correlated using the equation A n = A 1 n gamma; , and the three situations, γ = -0.5, 0, and 0.5 were investigated. The scaling laws of aggregation kinetics were established and the exponents were expressed as a function of the relative concentration x = [A]/([A] + [B]) of the two latices. A unique master curve represented the correlation between the temporal variations of the weight S( t) and number N( t) average sizes. On the contrary, the correlation between the exponents of the dynamic scaling laws and the relative concentration x depended on x. In the experiments, a particle counter technique was used to determine the aggregate concentration c n ( t) as a function of the aggregate size n, thereby allowing the aggregate average sizes S( t) and N ( t), which were directly compared to those obtained from simulation, to be calculated. In the heterocoagulation experiments, mixtures of polystyrene amidine latex (A) and polystyrene sulfate latex (B) of equal size, which exhibited identical electrophoretic mobility at the pH of the experiments, developed different aggregation modes. For x ⪡ 0.5, the process resembled an irreversible diffusion-limited aggregation. For x equal or close to 0.5, S( t) and N( t) increased with the features of a reversible process. Finally, for x ⪢ 0.5, the rate of the process is enhanced. Our experiments also showed that sulfate latex constituted the core of the aggregate and that the amidine latices were located around them.

Size separation of polystyrene sulfate particles (189 to 1085 nm radius) in solutions of methyl-hydroxypropyl-cellulose of different chain lengths

Polystyrene sulfate particles of 189 to 1,085 nm radius are retarded in their electrophoretic migration in solutions of methyl-hydroxypropyl-cellulose (4,000 and 15,000 cP viscosity for a 2% solution). The retardation is proportional to polymer concentration and increases inversely with particle size. This suggests a separation mechanism based on size-dependent exclusion from the polymer network, as found previously in other liquid polymer media. In the size range of approximately 200 to 600 nm radius, the 4,000 cP polymer exhibits a steeper decrease of retardation with particle size than the 15,000 cP polymer, but fails to exhibit any size dependent retardation beyond that range.

Gel electrophoresis of polystyrene particles in glutaraldehyde crosslinked polyvinyl alcohol

Polystyrene sulfate and carboxylate particles (19-189 nm radius) were subjected to electrophoresis in glutaraldehyde crosslinked polyvinyl alcohol of molecular weight 25.000 and 650.000 Da at various concentrations. The degree of crosslinking is severely limited by the mechanical properties of the gels that deteriorate beyond a glutaraldehyde concentration which decreases with increasing polyvinyl alcohol chain length. The effective fiber radius of the short-chain and long-chain polymer fiber was 45 +/- 25 and 131 +/- 47 nm, respectively. Thus, these media do not significantly exceed the apparent fiber thickness of agarose, are more difficult to prepare--but are well-defined synthetic products rather than natural ones, and have the advantage of carrying no net charge and can therefore be expected to exhibit no electroendosmosis.

Procedures and computer program for deriving the Ferguson plot from electrophoresis in a single pore gradient gel: Application to agarose gel and a polystyrene particle

This study presents a computerized evaluation of pore gradient gel electrophoretograms to arrive at estimates for both the particle-free mobility and retardation coefficient, which is related to particle size. Agarose pore gradient gels ranging from 0.2 to 1.1% agarose were formed. Gel gradients were stabilized during their formation by a density gradient of 0-20% 5-(N-2,3-dihydroxypropylacetamido)- 2,4,6-triiodo-N,N'bis-(2,3-dihydroxypropyl)-isophthalamide (Nycodenz). Densitometry of gelled-in Bromophenol Blue showed that these pore gradients exhibited a linear central segment and were reproducible. Migration distances of polystyrene sulfate microspheres (36.5 nm radius) in agarose pore gradient gel electrophoresis were determined by time-lapse photography at several durations of electrophoresis. These migration distances were evaluated as a function of migration time as previously reported (D. Tietz, Adv. Electrophoresis 1988, 2, 109-169). Although this is not necessarily required, the mathematical approach used in this study assumed linearity of both the pore gradient and the Ferguson plot for reasons of simplicity. The data evaluation on the basis of the extended Ogston model is incorporated in a user-friendly program, GRADFIT, which is designed for personal computers (Macintosh). The results obtained are compared with (1) conventional electrophoresis using several gels of single concentration with and without Nycodenz, and (ii) a different mathematical approach for the analysis of gradient gels (Rodbard et al., Anal. Biochem. 1971, 40, 135-157). Moreover, a simple procedure for evaluating linear pore gradient gels using linear regression analysis is presented. It is concluded that the values of particle-free mobility and retardation coefficient derived from pore gradient gel electrophoresis using the different mathematical methods are statistically indistinguishable from each other. However, these values are different, albeit close, to those obtained from conventional Ferguson plots. One of the possible reasons for this relatively minor discrepancy is that the particle-free mobility changed slightly during electrophoresis, which has a different effect on electrophoresis in homogeneous gels (single time measurement) and pore gradient gels (multiple time measurements). The characterization of particles according to size and charge by pore gradient electrophoresis provides a significant operational simplification and sample economy compared to that requiring the use of several gel concentrations, although at the price of increased requirements of instrumentation.

Electrophoretic size separations in liquified agarose of polystyrene particles and circular DNA

Polystyrene sulfate particles of 0.37 to 1.78 mu in diameter are retarded in their electrophoretic migration in proportion to the concentration of agarose liquified above its gelling temperature. In the concentration range of 0.02 to 0.2% liquified agarose, the degree of this retardation in electrophoresis at 40 degrees C is inversely related to particle size. By contrast, mitochondrial DNA (16 kb), plasmid pBR322 DNA (4 kb) and plasmid PSA509 DNA (3 kb) exhibit under the same conditions a degree of retardation which is proportional to their size. This confirms the existence of two divergent mechanisms of size separation similarly observed in other liquid polymer media, i.e. one based on collisions with the gel fiber (molecular sieving) and one based on exclusion from the fiber network (the electrophoretic equivalent of gel permeation).

Linear Ferguson plots of polystyrene sulfate size standards for the quantitative agarose gel electrophoresis of subcellular particles.

Accurately standardized commercial polystyrene sulfate particles in agarose gel electrophoresis yield linear Ferguson plots at pH 7.4 over a gel concentration range up to 0.9% agarose which do not exhibit any significant sigmoidal curve elements, using either a discontinuous buffer system or a continuous buffer. Ferguson plots of these standard-sized particles were evaluated using alternatively a linear or convex model, by means of a newly developed set of programs (to be used in conjunction with program M-LAB) which (i) is sufficiently user-friendly to allow for quantitative agarose gel electrophoresis of subcellular-sized spherical particles based on their convex Ferguson plots with the same operational simplicity previously available for linear Ferguson plots only; (ii) simultaneously and interactively analyzes the Ferguson plots of all particles under consideration on the basis of an extended Ogston model.

The role of bacterial cell wall hydrophobicity in adhesion

In this study, the adhesion of bacteria differing in surface hydrophobicity was investigated. Cell wall hydrophobicity was measured as the contact angle of water on a bacterial layer collected on a microfilter. The contact angles ranged from 15 to 70 degrees. This method was compared with procedures based upon adhesion to hexadecane and with the partition of cells in a polyethylene glycol-dextran two-phase system. The results obtained with these three methods agreed reasonably well. The adhesion of 16 bacterial strains was measured on sulfated polystyrene as the solid phase. These experiments showed that hydrophobic cells adhered to a greater extent than hydrophilic cells. The extent of adhesion correlated well with the measured contact angles (linear regression coefficient, 0.8).

Characterization by Ellipsometry of polymerized ultra-thin films formed in a two-dimensional solvent on an oxide surface

Surfactants adsorbed onto the surface of suspended mineral oxide particles may be used to position an ultra-thin layer of polymer on the surface of the particles. The polymer layer is formed by what may be viewed as a three-step process. First, solution parameters are varied in such a way as to induce complete coverage of the particle surface with a surfactant bilayer. Monomer introduced into the solution then partitions into the hydrophobic core of the surfactant layer. In situ polymerization is then initiated to form the polymer layer. The surfactant concentration in the bulk is well below the CMC so that solubilization does not occur nor does a latex form. This process was used to construct ultra-thin polymer layers on the surface of glass slides coated with a vacuum deposited aluminum layer, on which an oxide layer had been formed. The films thus constructed consisted of a polystyrene and sodium dodecyl sulfate suprastructure adhereing to the oxide surface. Ellipsometry was employed to calculate: (1) the optical constants of the freshly deposited aluminum, and (2) the thicknesses of the aluminum oxide and polymer layers. In determination of the thicknesses of the aluminum oxide and polymer layers literature values of the refractive indices were used. Under varying reaction conditions, the thickness of the polymer layer could be varied from 3.5 to 13.6 nm. It may be possible to use this process to produce suspensions of greater stability than those obtained by current techniques.

Structure parameters of molecules and media evaluated by chromatographic partition: I. Controlled-pore glasses

Polystyrene, dextran and sodium dodecyl sulphate—protein data for eleven controlled-pore glasses have been used to validate the expression K D = ( b − R e/ R x) 2 derived from a geometrical exclusion model for cylindrical pores. The calculated pore radii ( R x) agreed well with mercury-intrusion values, and the crucial role of Stokes′ radius ( R e) was confirmed by comparison with Casassa's formulations [E.F. Casassa and Y. Tagami, Macromolecules, 2 (1969) 14; E.F. Casassa, J. Polym. Sci., Part B, 5 (1967) 773]. From theory it was demonstrated that for any molecule, R e = A M x where A and x are defined, structure-specific constants. Thus, linear K D( M) functions were derived and tested, by which one is able to distinguish between coils. rods and ellipsoids, ideal and real solvents, and to determine bond lengths, expansion, gyration radii, axial ratios and diffusion coefficients. The characteristic shape of the empirical K D:log M curves derives directly from the linear K D( M) function.

The mechanism of extender action by potassium persulfate in the suspension polymerization of styrene

AbstractThe contribution by potassium persulfate to suspension stability in the bead polymerization of styrene which is stabilized by hydroxyl apatite (tricalcium phosphate) powders has been studied. Potassium persulfate, when used in lieu of an anionic surfactant as the extender, causes the formation of polystyrene sulfate in the aqueous phase. This anion‐active polymer adsorbs on the surface of the hydroxyl apatite crystals and thus alters their wetting characteristics, causing them to become more effective suspension stabilizers. Polystyrene sulfates of molecular weights ranging from 2000 to 100,000 have been synthesized, characterized, and shown to be effective hydroxyl apatite extenders. The capability of polystyrene sulfate to adsorb onto hydroxyl apatite crystals is not strongly dependent upon the molecular weight of the polymeric ester. The tolerance of the system to high molecular weight polystyrene sulfate is relatively high since excess extender is taken up by dissolving in the monomer phase. The tolerance for water‐soluble polystyrene sulfate, on the other hand, is low because excess extender of this type engages in double‐layer adsorption on hydroxyl apatite, which renders the latter too hydrophilic to permit effective suspension stabilization. Use of a water‐soluble polymerization inhibitor in the suspension polymerization system has no effect on suspension stability when sodium dodecylbenzene sulfonate or preformed polystyrene sulfate is used as the extender; however, suspension stability is destroyed when the inhibitor is used with persulfate, because it prevents the formation of polystyrene sulfate. Potassium persulfate is therefore more accurately described as a precursor of the active extender, which is the mono‐ or disulfate ester of polystyrene.