Streptavidin-coated magnetic beads

Figure 11 The basic principle of ECL immunoassay using streptavidin-coated magnetic beads, and labels based on Ru(bpy)32+.

Figure 8 Chemiluminescent (A and B) and bioluminescent (C) detections for immobilized hybridizations of PCR product. Dg, digoxigenin Bt, biotin Ad, avidin. Procedure A [30] Biotin moiety is incorporated into PCR products during the amplification reaction, using one 5 -biotinylated primer. The product is hybridized with a Dg-labeled probe and is immobilized on streptavidin-coated magnetic beads. This capture reaction is carried out for 30 min at 37°C. A permanent magnet is used to sediment the beads during washing to remove unbound DNA. By incubation with the washed beads for 45 min at 37°C, anti-Dg antibody conjugated to HRP enzyme is bound to the Dg-labeled probe, and luminol reaction is performed for CL detection. Procedure B [31] Wells of apolystyrene microtiter plate are activated with l-ethyl-3-(3-dimethylaminopropyl)-carbodiimide, and then coated with a labeled cDNA probe complementary to an internal region of the target DNA.

ECL has also been applied to the analysis of polymerase chain reaction (PCR) products [53,55], PCR is first used to amplify the specific genes by use of two primers, one of which is biotinylated. The double-stranded DNA is then captured on streptavidin-coated magnetic beads and washed with an alkaline solution to denature and separate the strands. The particle-bound, single-strand DNA is used to capture products hybridized with Ru-labeled complementary... 

In addition to the attempts at unraveling the modification site, Dive and coworkers also constructed two biotinylated A/BPs, 22 and 23 (Scheme 3c), and used these to study the difference in affinity- and photoaffinity MMP enrichment from a complex proteome [57]. For this, tumor extracts were spiked with hMMP-12 and hMMP-8, after which compounds 22 and 23 were applied, followed by streptavidin-coated magnetic beads for MMP pull-down. Affinity-based labeling with 23 appeared superior to photoaffinity-based labeling with 22 in terms of quantity of captured MMPs and identification of the tryptic fragments by mass spectrometry. 

Fig. 1. Preparation of ssDNA from biotinylated PCR-amplified DNA. (a) DNA is amplified using one primer that has a biotin molecule (B) at the 5 end and one primer that lacks biotin, (b) Double-stranded amplified DNA is captured on a streptavidin-coated magnetic bead via the biotin molecule, (c) The dsDNA is denatured, with the biotinylated strand remaining attached to the streptavidin-coated magnetic bead and the nonbiotinylated strand being released into the supernatant, (d) The nonbiotinylated strand is used as an ssDNA sequencing template.

A DNA optical sensor system was proposed by Cass and co-workers [35] based on the combination of sandwich solution hybridization, magnetic bead capture, flow injection and chemiluminescence for the rapid detection of DNA hybridization. Sandwich solution hybridization uses two sets of DNA probes, one labelled with biotin, the other with an enzyme marker and hybridization is performed in solution where the mobility is greater and the hybridization process is faster, rather than on a surface. The hybrids were bound to the streptavidin-coated magnetic beads through biotin-streptavidin binding reaction. A chemiluminescence fibre-optic biosensor for the detection of hybridization of horseradish peroxidase-labelled complementary DNA to covalent immobilized DNA probes was developed by Zhou and co-workers [36]. 

FK506-FKBP system. The first, by McPherson et al,294 biotinylated FK506 (81) through the secondary hydroxyl in 3% overall yield and used streptavidin-coated magnetic beads for immobilization and after just three rounds of selection, the library converged onto a single clone for FKBPla. 

Streptavidin-coated magnetic beads (Dynabeads M280-SA, Invitrogen, 6.7 x 108beads/mL, 1 mg beads binds 700 pmoles free biotin). 

Figure 5 Biopanning on magnetic beads. The binding of the library to biotinylated target in solution is followed by capture of phages on streptavidin-coated magnetic beads and by selection of bound phages through a magnetic field.

Streptavidin-coated magnetic bead 5 biotinylated 29-mer aptamer... 

The approach using PNA hybridisation probes for MALDI-TOF mass spectrometric analysis is comprised of the following steps (Figure lb) immobilisation of biotinylated target DNA (e.g. a PCR amplicon) by binding to streptavidin coated magnetic beads dissociation and removal of the non-biotinylated... 

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