Using magnetic beads for antibody purification
Magnetic beads coupled with protein A are one of the easiest methods to purify monoclonal and polyclonal antibodies from serum, ascites and hybridoma cell cultures. For small sample volumes this has been the case for a long time. Now, using magnetic agarose beads, such as LOABeads Protein A, it is possible to scale up the sample volumes to 50 ml or even 500 ml. Compared to chromatography, magnetic beads have several advantages.
- Simple to use. No instruments are needed.
- Flexible. Only use the amount of beads you need.
- Parallel handling. Several samples can be handled in parallel – saving time.
Magnetic agarose beads
Magnetic agarose beads combine the highly valued properties of agarose with the simplicity and fast separations of magnetic beads. Traditionally magnetic beads have been solid particles with a magnetic core. This gives them a significantly lower surface area than agarose beads, which are porous, and thus also a lower binding capacity. Agarose beads are larger than the solid beads, which makes them easier to handle and lets them contain more magnetic material, allowing faster separations. The latter property is very important for the possibility to scale up experiments with magnetic beads.
Advantages of magnetic agarose compared to solid magnetic beads:
- Superior binding capacity. Up to 60 mg IgG/ml settled beads.
- Easy to handle. Clearly visible beads and fast separations.
- High specificity. Low non-specific binding gives high purity.
Immuno-affinity purification
Protein A or G beads are in many cases the simplest way to purify antibodies, but for polyclonal antibodies, immuno-affinity purification is often the preferred method. The antigen that the antibodies were raised against is then coupled to activated beads, for example LOABeads AffiAmino. The antibodies will bind to the beads through their affinity for the antigen and they can easily be purified.
How to use magnetic beads
- Mix the magnetic beads with your sample.
- During incubation the antibodies will bind to the beads.
- By the force of an external magnet, you hold the beads to the tube wall while you remove the sample and wash away any remaining impurities.
- After addition of elution buffer, you can collect the purified antibodies. Again you hold the magnetic beads with an external magnet.