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Magnetic Beads
Magnetic beads are spherical, nanometer sized particles, often made of a magnetite and iron oxide core and coated with a specific chemical functional group. This functionalization helps the magnetic beads to specifically target molecules or cells within a complex biological sample. In terms of affinity chromatography, solid phase immunoassays, and similar procedures, magnetic beads act as the solid support matrix to which the target molecules latch onto. In particular, the large surface area to volume ratio that magnetic beads exhibit allows for an extremely efficient capture when compared to other support systems. Magnetic bead technologies additionally offer high-throughput capabilities, scalability from benchtop to industrial sized applications, and the results or products of a procedure are highly reproducible if techniques are well optimized. Because of the many advantages, the possible applications for magnetic bead technologies are extensive. To name a few, some common techniques include:
- Targeted cell separation
- DNA/RNA extraction and purification
- Use in amplification and genotyping efforts like PCR, qPCR, NGS, and ddPCR
- Flow cytometry, including MACS
- Immunodiagnostics
- Industrial protein or peptide production
Latex Microspheres
Latex microspheres, or latex beads, are colloidal particles composed of amorphous polymer, capable of reacting with amines on nucleic acids, proteins, antibodies, and a variety of other molecules. Our latex microspheres are available in a wide variety of sizes, ranging from 80-300nm. Importantly, physical properties of all beads change slightly with size. Larger beads have lower surface to volume ratios, stronger attraction to a magnetic force, and are suitable when the target molecules are also large to allow for un-cluttered binding. Smaller beads are often preferred when unspecific binding is agreeable, but more efficient separation times are needed. These beads will also remain in suspension longer, meaning they have more time to bind with their target. As a general rule of thumb, you want to match the magnetic bead size to the target molecules; use larger beads for larger proteins or cells and smaller beads for nucleic acids. Our latex microspheres also come prepared at a relatively high concentration (10%). Generally, as bead concentration increases so does the separation process because beads are closer together and can form chain-like structures. This is an important consideration to avoid aggregation in suspensions. These microspheres can be used in lateral flow and other colorimetric applications.
Streptavidin Magnetic Beads
The binding between streptavidin and biotin is an incredibly strong non-covalent interaction, widely used to propagate protein-ligand interactions. Streptavidin has a neutral isoelectric point and does not contain any carbohydrate chains; these features result in lower nonspecific binding allowing for greater assay selectivity and sensitivity. Each molecule of streptavidin has four biotin-specific binding sites, making this affinity binding couple especially favorable. Biotin is often used as the label for detection and quantification of tagged antigens, antibodies, and nucleic acids, the attachment of which rarely interferes with the biological activity of a molecule. Other attributes that make streptavidin magnetic beads an especially favorable choice for use in amplification efforts include its increased resilience to pH changes, temperature, and denaturants.
ReadiPrep™ Protein G Magnetic Agarose Beads
Protein G is an immunoglobulin (IgG) binding protein that can be used to bind antigens to antibodies when coated on magnetic beads. Protein G binds a wider variety of antibodies compared to protein A, including the majority of human, mouse, and rat IgG subclasses. Because protein G exhibits such strong affinity for IgGs in magnetic bead-antibody binding, dissociation of the ligate from the beads and recovery of the target molecule is generally performed in buffers with pH values <3. Due to its strong binding efficiency, protein G magnetic agarose beads are very well suited when looking to directly isolate antibodies from serum, tissue extracts, or cell culture supernatants for immunoprecipitation and coimmunoprecipitation. Our ReadyPrep Protein G magnetic agarose beads are also available, and ready to use, at a relatively high concentration (25%). At this concentration, the beads will exhibit a relatively high binding capacity and only a small volume of magnetic beads are needed in most experiments.
Oligo(dT) Magnetic Beads
Immobilized oligo-deoxythymidine (oligo(dT)) ligands are often used to capture messenger RNA (mRNA). The ability of oligo(dT) magnetic beads to target mRNA relies on the binding between adenylated mRNA, more specifically the poly-A tail, and oligo(dT) sequences on the magnetic beads under high-salt conditions. When the solution is transitioned to a lower salt concentration the complex is destabilized and mRNA is released freely in solution. The capture and purification of mRNA is particularly useful for industrial mRNA production. As of recent, mRNA-based platforms have found much use in therapeutics, gene therapy, oncology, and in vaccines. Although traditional methods of mRNA capture and purification have relied on chromatographic purification, like ion exchange (IEC), size-exclusion (SEC) and hydrophobic interaction chromatography (HIC), the use of oligo(dT) magnetic bead-based approaches offer greater simplicity and speed in operation, especially at larger production-sized scales. At 0.7 μm, our oligo(dT) magnetic beads come prepared ideal for the capture of mRNA and are available in a range of volumes.
Tosyl-Activated Magnetic Beads
Tosyl groups are organic compounds that consist of a toluene molecule and a sulfonyl group. At neutral pHs and standard incubation temperatures, tosyl-activated magnetic beads readily form amine bonds with many different types of proteins. In creation of the tosyl-activated magnetic bead the carbon chain that links the magnetic bead to the sulfonyl group can be of variable lengths. Long carbon linkages allow for beads to swiftly couple to small molecules while also negating issues related to steric hindrance. Also due to these advantages, tosyl-activated magnetic beads are especially well-suited for the isolation and purification of rare cells, fragile molecules, or those that may be present at low concentrations within a sample.
ReadiPrep™ Ni-TED Magnetic Agarose Beads
Ni-TED magnetic agarose beads specifically bind to His-tags on proteins. His-tags are used to facilitate protein purification experiments as they can increase experimental efficiency, protein expression, and protein solubility. Because of which, His-tags are often used in the industrial production of recombinant proteins, offering lower costs and shorter reaction times than traditional methods. Each of the TED (tris(carboxymethyl)ethylene diamine) chelating groups on the magnetic bead provides one binding site for a polyhistidine tag (His-tag). Interestingly, Ni-TED magnetic agarose beads can couple to His-tagged proteins in denaturing as well as nondenaturing conditions, reductants, and chelating conditions. Our ReadiPrep Ni-TED magnetic agarose beads can effortlessly be used on even the most complex biological samples, including microbial lysates, serums, and ascites.
Ordering Information
Table 1. Magnetic Beads
| Cat# ▲ ▼ | Product Name ▲ ▼ | Bead Size ▲ ▼ | Concentration ▲ ▼ | Unit Size ▲ ▼ |
| V105000 | Latex Microsphere | 80 nm | 10% (100 mg/mL) | 10 mL |
| V105010 | Latex Microsphere | 100 nm | 10% (100 mg/mL) | 10 mL |
| V105020 | Latex Microsphere | 120 nm | 10% (100 mg/mL) | 10 mL |
| V105030 | Latex Microsphere | 150 nm | 10% (100 mg/mL) | 10 mL |
| V105040 | Latex Microsphere | 200 nm | 10% (100 mg/mL) | 10 mL |
| V105050 | Latex Microsphere | 300 nm | 10% (100 mg/mL) | 10 mL |
| V105060 | Streptavidin Magnetic Beads | 0.6 µm | 1% (10 mg/mL) | 1 mL |
| V105061 | Streptavidin Magnetic Beads | 0.6 µm | 1% (10 mg/mL) | 5 mL |
| V105070 | Streptavidin Magnetic Beads | 1 µm | 1% (10 mg/mL) | 1 mL |
| V105071 | Streptavidin Magnetic Beads | 1 µm | 1% (10 mg/mL) | 5 mL |