Polystyrene latex beads

The first study utilizing this method was reported by Schuller in 1966 [65]. Schuller used polystyrene latex beads that were spread on a salt-containing aqueous subphase in order to keep the particles at the interface. tt-A plots of the floating particles were determined, which showed several phase regions with reproducible transition points. The author determined the particle diameters from the A-value, at which a steep rise in the isotherm occurred. Moreover, Schuller also spread millimeter-sized Styropor particles and found isotherms of similar shape [66]. By taking pictures at different surface pressure, he was able to correlate the shape with different states of order in the monolayer. Shortly after that. 

The following protocol for passive adsorption is based on methods reported for use with hydrophobic polymeric particles, such as polystyrene latex beads or copolymers of the same. Other polymer particle types also may be used in this process, provided they have the necessary hydrophobic character to promote adsorption. For particular proteins, conditions may need to be optimized to take into consideration maximal protein stability and activity after adsorption. Some proteins may undergo extensive denaturation after immobilization onto hydrophobic surfaces therefore, covalent methods of coupling onto more hydrophilic particle surfaces may be a better choice for maintaining native protein structure and long-term stability. 

Narrow particle fractions approaching a monodisperse distribution are particularly easy to treat and characterize when the above equations are applied to experimental data. Figure 2 shows an example of the elution profile (fractogram) obtained by running a mixture of four samples of "monodisperse" polystyrene latex beads. It is clear from the figure that a rather precise value of retention volume Vr can be identified with each bead size. With Vr known, it is easy to obtain R and X from Equation 5 and thence particle diameter d from Equation 4. This operation, as noted, yields diameters accurate to approximately 1-3%. 

Figure 2. Fractionation of four samples of Dow polystyrene latex beads by sedimentation FFF. The nominal particle sizes are given in the figure. Flowrate = 12 ml/hr, channel thickness w = 0.0127 cm, void volume V° = 2.0 ml, and field strength G = 193.7 gravities. Reproduced with permission from Ref. 20. Copyright 1980 John Wiley.

Figure 8.6. Separation of polystyrene latex beads of four different diameters (indicated in the figure) by a disc centrifuge operated at 3586 rpm. (From ref. 44. Reprinted with permission from R. M. Holsworth, T. Provder, and J. J. Stansbrey, in T. Provder, Ed., Particle Size Distribution, ACS Symposium Series No. 332, American Chemical Society, Washington, DC, 1987, Chapter 13. Copyright 1987 American Chemical Society.)...

Figure 9.9. Separation of polystyrene latex beads of indicated diameters in the colloidal size range by SdFFF programmed from 1500 to 75rpm at 2mL/min flowrate. (Courtesy of Bhajendra N. Barman, FFFractionation. Inc.)...

The second issue is the extent of the decrease of the van der Waals interaction. Experiment and calculation of the van der Waals interactions between polystyrene latex beads and either a bare glass plane or a polystyrene coated glass plane [17] revealed that the Hamaker constant decreases only by about 25% at complete screening, while the experiments of Petrache et al. for neutral lipid bilayers require a decrease of about 75% (from 1.2kT to OAkT). Such a strong decrease of the van der Waals interaction upon addition of salt would be expected to have strong consequences in the general theory of colloid stability, and not only in the stability of lipid bilayers. 

Fig.23. High-speed separation of seven polystyrene latex beads by steric-S-FFF. Reproduced from [ 14] with kind permission of the American Association for the Advancement of Science...

Colloid characterization is not the classical application of Th-FFF. Nevertheless, Th-FFF was first applied to silica particles suspended in toluene testing a correlation between thermal diffusion and thermal conductivity [397]. Although a weak retention was achieved, no further studies were carried out until the work of Liu and Giddings [398] who fractionated polystyrene latex beads ranging from 90 to 430 nm in acetonitrile applying a low AT of only 17 K. More recently, polystyrene and polybutadiene latexes with particle sizes between 50 pm and 10 pm were also fractionated in aqueous suspensions despite the weak thermal diffusion [215] (see Fig. 30). Th-FFF is also sensitive to the surface composition of colloids (see the work on block copolymer micelles), recent effort in this area has been devoted to analyzing surfaces of colloidal particles [399,400]. 

As model samples for the verification of the conventional SdFFF as a concentration methodology monodisperse polystyrene latex beads (Dow Chemical Co.) with nominal diameters of 0.357 fum (PSl) and 0.481 /Ltm (PS2) were used. They were either used as dispersions containing 10% solids or diluted with the carrier solution (triple-distilled water -r 0.1% (v/v) detergent FL-70 from Fisher Scientific Co. -l- 0.02% (w/w) NaNj) to study sample dilution effects. Diluted samples in which the amount of the polystyrene was held constant (1 /u-L of the 10% solids) while the volume in which it was contained was varied over a 50,000-fold range (from 1 to 50 mL of carrier solution) were introduced into the SdFFF column. During the feeding step, the flow rate was 5.8 mL/h for the PSl polystyrene, and 7.6 mL/h for the polystyrene PS2, and the channel was rotated at 1800 rpm for the PSl sample and at 1400 rpm for the PS2 sample. In the sep-I aration (elution) step, the experimental conditions for the two samples were as follows ... 

Fig. 1 Fractograms of the polystyrene latex beads of 0.357 /xm (PSl) obtained by the direct injection of 1 julL of PSl (a) and by the concentration procedure of the PSl sample diluted in 10 mL of the carrier solution (b) using the conventional SdFFF technique, as well as of the a-Fe203 sample with nominal particle diameter of 0.271 tm diluted in 6 mL of the carrier solution obtained by the PBSdFFF concentration methodology (Ic).

Both Sa and tri are established by logarithmic plots of tr versus d of well-characterized standards such as polystyrene latex beads. The value of tri depends on the field strength and, for sedimentation FFF, also on the particle density. It will be shown later that this dependence makes possible the determination of particle density and porosity values. 

Twenty years later Dworkin [26] demonstrated that a flare of M. xanthus moved towards clumps of potential prey bacteria Micrococcus luteus). However, the same response was obtained with polystyrene latex beads or glass beads, ruling out the possibility that the cells were responding to a concentration gradient of some chemoattractant. Indeed, Dworkin and Eide [29] failed to detect any chemotactic response when various chemicals were examined as potential attractants... 

Sun, H. and N. Hu (2004). Voltammetric studies of hemoglobin-coated polystyrene latex bead films on pyrolytic graphite electrodes. Biophys. Chem.llO, 297-308. 

As model samples for the verification of the conventional SdFFF as a concentration methodology monodisperse polystyrene latex beads (Dow Chemical Co.) with nominal diameters of 0.357 pm (PSl) and 0.481 pm (PS2) were used. They were either used as dispersions containing 10% solids or diluted with the carrier solution [triple-distilled... 

Dalargin (10 to 10" M) stimulated the luminol-dependent chemiluminescence of mouse whole blood during phagocytosis of polystyrene latex beads (0.8 [im in diameter) recorded over 10 s (Ro-govine and Mushtakova 1995). 

Calibration with known size particles (such as polystyrene latex beads) is used to relate the size of the electrical pulse to the size of the particle. So, the particle counter not only detects that a particle has been detected in the fluid but also the size of the particle. The size threshold determines whether the pulse is large enough to be considered a particle detected or if below the threshold then relegated to just background noise. Liquid chemical particle counters are available for the size range of 0.04—20 pm. 

Reaction with agarose cyclic imidocarbonate Adsorption on to nonporous polystyrene latex beads Reaction with agarose cyclic imidocarbonate Reaction with agarose cyclic imidocarbonate... 

Much research has been directed to determine the energetics of the myosin-actin interactions. Polystyrene latex beads were attached to actin hlaments, and the unbinding force needed to rupture the bond to myosin was determined using optical tweezers in the absence of ATP (101). Tlie average unbinding force was found to be 9.2 pN. 

Figure 6.31 shows the real part of the Clausius-Mossoti factor as a function of the frequency clearly showing the crossover frequency. Figure 6.32 shows the crossover frequency of polystyrene latex beads in water as a function of its radius. The modified conductivity Op is used which compares well with the experimental data. 

Sedimentation FFF has been used for the fractionation of polystyrene, latex beads, emulsions, artificial blood, viruses, and aqueous colloids, liposomes, albumin spheres, and DNA. Thermal FFF has been applied to different types of synthetic polymers. A recent development in FFF has been the increase of separation speed to allow fractionation on a minute scale instead of hours. 

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