Latex beads

Hydration of Phospholipids with Solutions of Very Low Ionic Strength Very large unilamellar and oligolamellar vesicles can be prepared when a thin lipid film is dispersed in a solution of very low ionic strength (Reeves and Dowben, 1969). The formation of vesicles with diameters up to 300 pm enclosing latex beads with a diameter of 20 pm have been reported (Antanavage et al., 1978). 

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. 

Kusunoki, H. Latiful Bari, M. Kita,T. Sugii, S. Uemura,T. Flow cytometry for the detection of enterohaemorrhagic Escherichia coli 0157 H7 with latex beads sensitized with specific antibody. J. Vet. Med. 2000,47,551-559. 

Fig. 8.5 SEM images of (A) close packed array of latex beads (scale bar= 1 tm) and (B) macroporous aminopropyl-functionalized magnesium phyllosilicate monolith obtained after infiltration and extraction of colloidal template (scale bar= 1 pm).

Polymeric particles traditionally have been called latex beads or spheres, probably from the classic definition of an emulsion of rubber or plastic globules in water . However, due to... 

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. 

Wash particles (e.g., 100 mg of 1 pm carboxylated latex beads) into coupling buffer (i.e., 50 mM MES, pH 6.0 or 50 mM sodium phosphate, pH 7.2 buffers with pH values from pH 4.5 -7.5 may be used with success however, as the pH increases the reaction rate will decrease). Suspend the particles in 5 ml coupling buffer. The addition of a dilute detergent solution may be done to increase particle stability (e.g., final concentration of 0.01 percent sodium dodecyl sulfate (SDS)). Avoid the addition of any components containing carboxylates or amines (such as acetate, glycine, Tris, imidazole, etc.). Also, avoid the presence of thiols (e.g., dithiothreitol (DTT), 2-mercaptoethanol, etc.), as these will react with EDC and effectively inactivate it. 

Translational diffusion coefficients of fluorophores like rhodamine 6G have been determined by FCS and reasonable values of 3 x 10-6 cm2 s 1 were found (Figure 11.12). Tests with latex beads showed good agreement with known values. 

A unique anion-exchange column has been developed that has a thin (non-diffusion limited) anion-exchange phase coated onto a 10-/nm latex bead. When a mobile phase of 0.15 M NaOH is used, neutral carbohydrates are converted into anions, which are separated on the column. Although the resin has low capacity, and probably causes degradation of the carbohydrates, when it is coupled to a triple-pulsed, amperometric detector, the system provides extremely sensitive, high-resolution separations. 

Dunn, P. A. and Tyrer, H. W. (1981) Quantitation of neutrophil phagocytosis, using fluorescent latex beads. Correlation of microscopy and flow cytometry. J. Lab. Clin. Med. 98, 374-381. 

Illumina produces fiberoptic random bead arrays. Latex beads are encoded using different fluorescent dye mixtures that are either adsorbed into the particles or attached to the surfaces. Presynthesized oligonucleotides are attached to selected bead populations so that a single dye or dyerdye ratio identifies the attached oligonucleotide. Populations are mixed in bulk and then loaded onto the tips of a fiberoptic, one end of which has been acid etched to form microscopic nanowells. The nanowells are filled at random with the mixed bead population to create a BeadArray . Such bxmdles can... 

Another example of a delivery system based on microbubbles and ultrasound is the delivery of circulating microparticles (polymer latex beads) or fluorescent red blood cells outside of the capillaries into the surrounding tissues by the action of ultrasound on the co-injected Optison microbubbles [79]. Interestingly, polymer beads and red blood cells could be detected tens of micrometers away from the capillaries where the bubble destruction took place. This may imply that during rapid destruction of a microbubble in a very strong ultrasound field, adjacent microsphere beads in the bloodstream can be propelled deep into the surrounding tissues. 

The first field of application for SdFFF were latex beads, which were used either to test the channels or to produce separation results alternative to other separation techniques. PS nanoparticles used as model surfaces for bioanalytical work have been analyzed by SdFFF [39]. The appealing feature of SdFFF is its ability to characterize particle adlayers—by direct determination of the mass increase performed by observing the differences in retention between the bare and coated particles—with high precision and few error sources the mass of the coating is determined advantageously on a per particle basis. 

Agglutination reactions have many applications in clinical medicine that can be used to type blood cells for transfusion, to identify bacterial cultures, and to detect the presence and relative amount of specific antibody in a patient s serum. For example agglutination of antibody-coated latex beads has become a popular commercial method for the rapid diagnosis of various conditions such as pregnancy and streptococcal infections. 

Of the particulate stimuli certain ones are far more active when they are coated with proteins from serum (opsonized) than when they are not. However, others like latex beads elicit formation of Oj" by PMNs without opsonization DeChatelet et al. found that the production of O by PMNs from man and rabbit was stimulated by opsonized but not unopsonized zymosan (fragments of yeast cell walls). Bacteria alone were found to stimulate the formation of O but in the presence of serum bacteria stimulated the formation of O7 three fold However, the stimulatory effect of bacteria appeared to be caused by changes which the bacteria produced by an interaction with constitutents of serum, because serum itself after exposure to the bacteria stimulated production of O by PMNs. The active component from serum was heat sensitive (100°) and not sedimentable at 105,000 g. Whether this material was derived from the components of serum or from the bacteria is not clear but may have been a protein of the complement system. 

Among the questions which remain unanswered in this illness is the function of O2". The defect in killing of bacteria appears correctable with a means of supplying H2O2 to the interior of the phagosome. The bacterium may do so if it lacks catalase and consequently excretes H2O2 Another particle such as a latex bead to which an enzymic source of H2O2 is attached will also suffice. In either of... 

Fig. 3. Example of an immunochromatographic assay for a Streptococcal antigen (Sa) using antibody to the antigen (ctSa ) linked to a blue-colored latex bead ( ). The downward pointing triangles represent chromatographic migration. Formation of a sandwich linking the antigen between the latex bead and...

The agglutination reaction is another type of precipitation reaction in which one of the components is present in a particulate form. The use of solid support like latex beads on which to coat a soluble antigen for an agglutination reaction with the corresponding antibody has greatly facilitated its ease of use. These assays are easy to perform however, they can give misleading results at low analyte concentration or interference from the sample matrix (48). 

Fig. 52. Scanning with a platinum coated SFM tip over a SAM surface containing terminal azide groups in the presence of H2 leads to the reduction of azide groups to primary amino groups. Derivatization of the resulting amine surface with aldehyde-modified latex beads results in specific labelling of the reduced areas. Reproduced from [469]...

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