Dynal’ magnetic beads

Dynabeads M-270 streptaviclin-coated magnetic beads from Dynal (Oslo, Norway)... 

Tosylactivated magnetic beads (MB-Tosyl) (Dynabeads M-280 Prod. No. 142.03, Dynal Biotech ASA, Oslo, Norway). Hydroquinone (Sigma), hydrogen peroxide (Merck, Germany). Bradford solution (Bio-Rad protein assay Catalog No. 500-0006) was purchased from Bio-Rad laboratories GMGH (Munich, Germany). 

Yet another approach for mRNA isolation is the use of oligo(dT)-coated magnetic beads for mRNA isolation (Figure 7.5). Such beads with attached oligo(dT) are available commercially (Dynal, Lake Success, NY). Alternatively, the oligonucleotide can be chemically attached to magnetic beads [29]. 

The basic magnetic-bead patent appears to be the property of Dynal, but Clemente Associates (formerly Quantum Magnetics, Madison, CT) produces Ni-bearing magnetic particles of 3- to 5-pm diameter for... 

Dynabeads anti E. coli 0157 (Dynal Ltd) 0157 — Magnetic beads AFNOR DYN 16/2-0696. ISO EN 16654... 

The international reference method to detect and recover E. coli 0157 (ISO EN 16654, Fig. 1) inclndes a step of Immuno-Magnetic Separation (IMS), which requires the nse of magnetic beads coated with polyclonal antibodies against 0157 antigen (Dynabeads anti E. coli 0157, Dynal Ltd, Norway). The cell bead complexes are recovered from the medinm by the application of a magnetic field causing the complexes to be concentrated in the tnbe, and enabling the bulk medium to be discarded. The concentrated cells are next plated onto CT-SMAC for strain recovery and confirmation. Chapman et al. (1994) fonnd that IMS was 100-fold more sensitive for detection of E. coli 0157 H7 than direct culture on isolation media. 

For the detection and the recovery of specific strains belonging to major STEC sero-groups, IMS can be performed nsing magnetic beads coated with antibodies specific for 026,0111,0103 and 0145 serogronps (commercially available Dynal Ltd, Norway). However, strains recovered with this method must be confirmed for the presence of stx gene to be considered as STEC strains. This methods have not been ISO certified like the IMS for E. coli 0157 H7, but have been employed to help recover STEC strains from food samples (Anvray et al. 2007) or animal faeces (Jenkins et al. 2003). 

Resting CD4 T cells can also be stimulated with antibodies against the CD4 or CXCR4 receptors see Note 5). For conjugation of antibodies to magnetic beads, 10 pg of antibodies is conjugated with 4 x 10 Dynal beads for 30 min at room temperature. Free antibodies are washed away with PBS +... 

Streptavidin-coated magnetic beads (Dynal) with magnetic rack... 

The 5 mL tube is placed in a magnetic field (DYNAL MDC 1) for 2 min, the supernatant is gently removed with a 1 mL disposable polypropylene transfer pipette. Resuspend the beads in 2 mL HBSS/1% BSA and place the tube in the magnetic field again for 2 min. Collect the supernatant, combine the 2 supernatants and centrifuge at 300,g for 10 min. Resuspend the cells in the desired volume of HACM. 

Superparamagnetic beads, with covalently linked streptavidin, are also commercially available (Dynal, Inc., Oslo, Norway, or Great Neck, NY Advanced Magnetics, Inc., Cambridge, MA Promega). Hornes and Korsnes (1990) found that hybridization is complete within a few minutes and that it is not necessary to have a large excess of capture probe (even at 1 1, the efficiency is close to 100%). A typical hybridization procedure, excluding detection step, takes... 

Wash cells with PBS + 0.1% BSA as described earlier to remove unbound antibodies. Resuspend cells in PBS + 0.1% BSA at a concentration of 1 x 10 cells per ml. Add prewashed Dynal beads pan antimouse IgG (four beads per cell) and incubate at 4°C for 20 min with gentle rocking. Place the tube in magnet for 2 min and then transfer cell supernatant to a new tube. Count the number of cells and pellet them by centrifugation as described earlier. 

Preparation of template Typically for a reaction 15-/tl streptavidin-coated paramagnetic beads (Dynal) are washed twice with 2(X) /il each of the B/W buffer (Dynal), suspended in 15 tl B/W buffer and added to the PCR reaction mixture. After incubation for 30 minutes at room temperature, the supernatant was removed through magnetic separation and the beads incubated with 50 pA 100 mM aqueous NaOH for 5 minutes at room temperature to denature the non-biotinylated DNA... 

Selection is carried out by adding the antigenbinding complexes are removed by washing the beads. A magnetic particle concentrator (Dynal MFC) is used to wash and recover the beads carrying bound ARM complexes. 

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