Magnetic bead

Micro- and nanobeads with magnetic properties have recently become popular since these tools can be manipulated, e.g., collected in the region of interest. Magnetite nanoparticles are introduced in order to render the polymeric beads magnetic. Preparation and application of magnetic beads will be discussed in more detail in Sect 5.5. 

Key Words FACS lymphocyte beads magnetic separation enrichment fluorescent cell marker. 

Magnetically attractable polyacrylamide-agarose beads Magnetically attractable ferric oxide particles Magnetically attractable plastic coated beads ... 

Application of the Solid Phase (Bead) Magnetic Processing System ... 

Stable expanded-bed operations promise the ability to handle whole broths efficiently, all the while maintaining plug-flow characteristics. Magnetically stabihzed fluidized beds have been shown to work effectively for bioproduct separations, but are not yet used commercially. A commerci y available process uses well-designed beads of appropriate densities and sizes to enable bed fluidization and stable operation without appreciable recirculation. 

B. Polymeric Urea [Benzene, diethenyl-, polymer with ethenylbenzene, [[[[(1 methylethyl)amino]carbonyt]amino]methyl] deriv.] A 10.0-g. portion of benzylamine polymer beads prepared as in Part A and 125 ml. of tetrahydrofuran (Note 6) are combined in a 300-ml., three-necked, round-bottomed flask equipped with a magnetic stirrer, a dropping funnel, and a condenser fitted with a gas-inlet tube A nitrogen atmosphere is established in the system, and the slurry is stirred while 1.35 g. (0.0159 mole) of isopropyl isocyanate [Propane, 2-isocyanato-] is added. This causes an exothermic reaction, which subsides after about 20 minutes. The mixture is then stirred at room temperature for 22 hours and at reflux for an additional 4 hours. The beads are collected by filtration, washed with 150-ml. portions of tetrahydrofuran (Note 6) and methanol, and dried under reduced pressure over calcium chloride to yield 9.09 g, of the isopropyl urea polymer. 

Mixtures containing polystyrene resins should either be shaken or stirred with a mechanical stirrer. Stirring with a magnetic stir bar results in destruction of resin beads and the resulting debris can clog frits during filtrations. 

The preparation of novel triazole-containing 20-22 membered macrocyclic azacrown ether-thioethers was reported <96JCR(S)182> and the first selective synthetic method fra the synthesis of dicyanotriazolehemiporhyrazines was published <96JOC6446>. 1,2,4-Triazole-containing polyimide beads were prepared and employed as Mo(VI) epoxidation catalyst supports, liie 1,2,4-nitronyl nitroxide 29 was also synthesized and found to have remarkable magnetic properties <96AM60>. 

Ansell, RJ Mosbach, K, Magnetic Molecularly Imprinted Polymer Beads for Drug Radioligand Binding Assay, Analyst 123, 1611, 1998. 

Fig. 6.5 Schematic representation of a bioelectronic protocol for detection of DNA hybridization (A) binding of the target to magnetic beads (B) hybridization with CdS-labeled probe (C) dissolution of CdS tag (D) potentiometric stripping detection at a mercury-film electrode. (Reprinted from [136], Copyright 2009, with permission from Elsevier)...

When the bacteria to be detected are less than 1% of the total population in a sample, IFAs cannot be used because of interference from unrelated particles that are concentrated when large volumes of sample are filtered. To overcome this problem, the organism of interest may be concentrated by immunomagnetic separation.10,51 62 For this procedure magnetic beads coated with monoclonal or polyclonal antibodies are mixed with the sample. The beads are collected with a magnet, and the cells attached to the beads then are removed, enumerated, and identified by IFAs. 

DNA,83 which produces one million or more copies of amplified DNA in a short time. For identification of bacteria, PCR can be used to amplify DNA either after extraction from a sample or after lysis of the cells.83,84 Methods using washing, filtration, or magnetic beads with specific antibodies can be used to collect bacterial cells for PCR.85,86 PCR can be modified for the detection of bacteria from various sources32 and can even amplify DNA from dead cells.87... 

Girault, S. Chassaing, G. Blais, J. C. Brunot, A. Bolbach, G. Coupling of MALDI-TOF mass analysis to the separation of biotinylated peptides by magnetic strepta-vidin beads. Anal. Chem. 1996, 68, 2122-2126. 

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