I cannot see the difference between these two types of resins that contain iminodiacetic acid as functional groups besides that the IMAC resins contain the metal for the His-tag. Is this the only difference, is marketing stuff, purity? Any help will be much appreciated, because the cost difference is big.
IMAC stands for immobilized metal affinity chromatography. It's a general term, not a specific product. There are a variety of different chemical chelating groups attached to a support resin to bind to the metal ion (usually nickel or cobalt is used for His-tagged protein purification). IDA (iminodiacetic acid) is one such chelating group. You can buy the "uncharged" resin without the metal already bound, which gives you the option of chosing which metal you want to use. You can also buy the resins already charged with metal to save the step of charging them. So, to directly answer your question, there is no difference as far as the chelating aspect is concerned. However, there may be a difference in the chemical structure of the resin that could influence its chromatographic properties, such as maximum tolerated flow rate or backpressure, or particle size, or chemical stability.
There are also meaningful differences between the various chelating moieties that can affect chromatography, such as resistance to the presence of chelators such as EDTA, or to reducing agents.
I can't speak to the chemical basis of the differences, but anecdotally, I seem to get very different results when I use Talon Co2+ resin vs ThermoFisher Co2+ "His-pur" resin vs Ni-NTA resin.
Just a short comment from a chemical point of view:
Nickel (or cobalt) are metal ions with space for six electron pairs, either from the ligand, or from a his-tagged protein.
IDA (iminodiacetic acid) is a tridentate ligand. It binds nickel with three electron pairs and His protein with a further three electron pairs. This means that nickel is not as tightly bound and leaches more easily, and proteins are bound more tightly, but this also means that other proteins are bound and the eluates contain impurities.
NTA (nitrilotriacetic acid) is a tetradentate ligand. Here, nickel is bound more tightly with four electron pairs, and since proteins are only bound to nickel with two electron pairs, the product is more suber than with IDA. For this reason, NTA has largely prevailed over IDA in the 1990s. The disadvantages of Ni-NTA are its low stability towards chelators and reducing agents, which limits its use in mammalian proteins.
Talon is also a tetradentate ligand that works best with cobalt. Here, the manufacturer claims a higher purity, but the binding capacity is significantly lower than with Ni-NTA, and the stability towards e.g. EDTA and DTT is also lower.
New, innovative chelators, such as INDIGO, are higher then tetradentate and combine a firm binding of nickel, low leaching, a high binding capacity, clean elutates with a high stability against chelators, reducing agents and protease inhibitors.
Thanks Roland Fabis !
Mi idea is to work with chelating resins used in mining instead of IMAC ones due to costs and because I want to scale up. My question goes towards that.
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