Pierce™ Streptavidin Magnetic Beads, 5 mL - FAQs

The streptavidin-biotin interaction is the strongest known non-covalent biological interaction between a protein and a ligand. Binding of biotin and streptavidin is very rapid and, once formed, the complex is unaffected by wide extremes of pH, temperature, organic solvents, and other denaturing agents. Normally, very harsh methods are required to dissociate the biotin from streptavidin, which will be irreversibly denatured by the procedure.

To dissociate biotinylated proteins from streptavidin, boil the beads in 0.1% SDS or SDS-PAGE buffer for 3 mins or incubate them in 8 M guanidinium hydrochloride, pH 1.5.

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There are two methods to dissociate the non-biotinylated DNA from the biotinylated DNA strand. The following protocols are based on using 20 µL of Dynabeads Streptavidin, but are scalable. Both methods may release very small amounts of complementary biotinylated strand from streptavidin. If it is critical that no biotinylated strand is released, either adopt a different biotin modification using dual biotin (two biotin groups in sequence) or covalently bind DNA to e.g., Dynabeads M-270 Carboxylic Acid.

Using heat:

- Wash the DNA coated Dynabeads in 50 µL 1 x SSC.*
- Resuspend the beads in another 50 µL of 1 x SSC Incubate at 95 degrees C for 5 mins.
- Quickly put the tube in magnet stand for 1-2 mins and transfer the supernatant to a new tube.
- The supernatant contains your non-biotinylated DNA strand.

Using NaOH:

- Wash the DNA coated Dynabeads in 50 µL 1 x SSC.*
- Resuspend the beads in 20 µl of freshly prepared 0.15 M NaOH.
- Incubate at room temperature for 10 mins. Put the tube in magnet stand for 1-2 mins and transfer the supernatant to a new tube.
- The supernatant contains your non-biotinylated DNA strand. Neutralize the probe by adding 2.2 µL 10 x TE, pH 7.5 and 1.3 µL 1.25 M acetic acid.

Wash the Dynabeads coated with biotinylated strand once with 50 µL 0.1M NaOH, once with 50 µL of B&W buffer and once with 50 µL TE buffer.

*1 x SSC (0.15 M NaCl, 0.015 M sodium citrate. Dissolve the reagents in 800 mL water. Adjust pH to 7.0 with NaOH. Adjust the volume to 1 liter with water).

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Assay the supernatant for unbound molecules. This will determine the amount of molecule bound to the Dynabeads. For nucleic acids, the concentration can be checked by OD readings, or by running a gel. For proteins, the concentration in the supernatant can be determined by a spectrometer using a protein assay like BCA. Alternatively, you can label the molecule with radioactivity or fluorescence and measure the concentration of molecule directly on the beads (former) or in the supernatant (latter).

Find additional tips, troubleshooting help, and resources within our Dynabeads Nucleic Acid Purification Support Center.

Streptavidin is a protein composed of four identical subunits, each containing a high affinity binding site for biotin (K-D = 10 -15 M) . Streptavidin has the same biotin binding properties as avidin, but it has a low isoelectric point (pI=5) and no carbohydrate groups, resulting in low non-specific binding.

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The streptavidin in Pierce Streptavidin Magnetic Beads is not His-tagged.

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The magnetite content of Pierce Streptavidin Magnetic Beads is 40%.

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The beads have been chemically pre-blocked to provide low background. Up to 0.1% of Tween-20 can also be added to the wash buffer to reduce non-specific binding.

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There are approximately 9.6 x 10^9 particles/mL of beads.

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During the development of Pierce Streptavidin Magnetic Beads, we have not observed any iron leaching. The iron is encapsulated by a proprietary polymer that prevents the exposure of iron to the environment. Currently, we are not aware of any conditions that lead to iron leaching.

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Pierce Streptavidin Magnetic Beads are homogeneous, non-aggregating, pre-blocked, iron oxide, superparamagnetic microparticles encapsulated with a proprietary polymer surface (no exposed iron, bead size of approximately 1 (0.5-1.5) µm, concentration 10 mg/mL). Pierce Streptavidin Magnetic Beads can be used in manual or automated applications (using KingFisher 96 and KingFisher Flex instruments, for example).
MagnaBind Streptavidin Beads are also superparamagnetic particles, but are heterogeneous aggregates made of silanized iron oxide (bead size approximately 1-4 µm, concentration 5 mg/mL). MagnaBind Streptavidin Beads can only be used in manual applications.

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The Pierce Streptavidin Magnetic Beads contain 50-70 µg of streptavidin protein per mg of beads.

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No, centrifuging causes the formation of irreversible aggregates which greatly reduces binding capacity.

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No, freezing or drying will cause the beads to aggregate and lose binding activity. Store the beads only at 4 degrees C.

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Thermo Scientific Streptavidin Magnetic Beads average about 1 micron in daimeter ranging from about 0.5-1.5 microns while MagnaBind Streptavidin Beads are heterogenous averaging 1 - 4 microns.

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No, neither the MagnaBind Streptavidin Beads nor the Thermo Scientific Streptavidin Magnetic Beads are sterilized. However, they are both supplied in solutions containing sodium azide to prevent bacterial growth.

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Thermo Scientific Streptavidin Magnetic Beads are homogenous non-aggregating, pre-blocked, iron oxide, superparamagnetic microparticles encapsulated with proprietary polymer surface (no exposed iron). The MagnaBind Streptavidin Beads on the other hand are also superparamagnetic particles but are hetreogenous aggregates made of silanized iron oxide. The Thermo Scientific Streptavidin Magnetic Beads can be used in manual or automated applications (using Thermo Scientific KingFisher 96 and KingFisher Flex Instruments for example) while MagnaBind Streptavidin Beads can only be used in manual applications.

Find additional tips, troubleshooting help, and resources within our Protein Assays and Analysis Support Center.