Magnetic beads are ideal for protein purification from dilute supernatants and for pull-down experiments. PureCube MagBeads are ferrimagnetic agarose beads coupled to a chelating ligand (IDA or NTA) coordinating nickel, cobalt, or other ions. In addition, the novel INDIGO ligand provides optimal performance even in the presence of 20 mM EDTA and DTT.
Both ligand-metal systems efficiently bind histidine-tagged proteins. The agarose surface is identical to that of PureCube Agarose, making them an ideal combination for small-scale screening and upscale reactions.All PureCube His Affinity MagBeads are delivered as a 25% suspension.
PureCube His Affinity MagBeads provide:
- Binding capacity of up to 80 mg/mL (for Ni-NTA)
- Low unspecific binding
- Purification of proteins expressed at low levels or from diluted solutions
- Highly reproducible, careful in-house production
Table 1: Features of commercially available His affinity magnetic beads.
| ||Cube Biotech||Supplier G||Supplier Q|
||Magnetite (Fe3O4) beads coated with 6% cross-linked agarose
||Highly cross-linked spherical agarose including magnetite
||Agarose beads with magnetic particles
||INDIGO, Ni-NTA, Co-NTA, NTA Cu-NTA, Al-NTA, Zn-NTA Ni-IDA, IDA
||63 or 37-100 µm
||up to 80 mg His-tagged protein/mL of settled beads
||50 mg His-tagged protein/mL of settled beads
||2 mg His-tagged protein/ml suspension (40 mg/ml settled beads)
||25% slurry in 20% ethanol
||10 or 5% slurry in 20% ethanol
||5% slurry in 30% ethanol
IDA vs NTA
As depicted in Figure 1, the chelating ligands iminodiacetic acid (IDA) and nitrilotriacetic acid (NTA) support similar interaction between nickel and the imidazole rings of the histidine tag. The ligands differ in size on the one hand; the smaller IDA couples to the resin at a higher density and therefore has higher binding capacity. On othe other hand, IDA coordinates the nickel ion with one less valency than NTA (orange circles). As a result, more metal ions may leach from IDA resins giving a less pure eluted protein. Learn more
Fig.1: NTA vs. IDA. Chelating ligands nitrilotriacetic acid (NTA) and iminodiacetic acid (IDA) support similar interaction between Ni2+ and imidiazole rings of a polyhistidine tag, but NTA coordinates the Ni2+ with 4 valencies and IDA with only 3 (orange circles). This difference impacts the quality of the resulting purified protein fraction.