1. Protein Binding Capacity

The protein binding capacity is ~40 mg protein per mL of settled beads, as determined by purification of 6xHis-tagged GFP protein from E.coli cleared lysates, and quantified via spectrophotometry.

2. Compatibility

PureCube NTA MagBeads XL are very stable and can resist the following conditions in most situations: pH 2-4, 100% methanol, 100% ethanol, 8 M urea, 6 M guanidinium hydrochloride, 30% (v/v) acetonitrile.

3. Different metal ions confer different binding affinity and specificity

His-tag purification is based on ionic interactions of a coupled metal ion and the Poly-His-tag. Therefore other metal ions can also fullfill the function of Nickel. Figure 1 shows the most frequently used metal ions for His-tag purification. Depending on the used metal ion the balance between the specificity and the affinity of the metal ion to the His-tag shifts. Nickel is a balanced choice between both extremes. Copper has the highest affinity, but Cobalt is the choice for the most pure His-tag purifications.

Fig. 1: Depending on which metal ion is coupled to NTA the balance between protein yield and purification specificity shifts. Nickel is a very balanced choice between the two extremes.