IMAC gels - metal affinity

[Goran Karlsson]

Hi,
I have looked for information concerning the affinity konstants for IMAC gels, eg IDA/NTA/TED when binding Ca++, Zn++ and Cu++, but have not found much. Does anyone know some literature or web site where this information is listed?

In one book (Protein Purification, by Janson & Ryden) I found out that
IDA does not bind Ca++, which is interesting. I am eager to find all this information, although I realize that not all combinations are possible to use for IMAC chromatography of proteins, when coordination number of ions and the "denate number" of the chelator are considered.

I am grateful for information about this.

Regards,

Goran Karlsson
Octapharma AB
Stockholm
Sweden

[Chris Pohl]

Goran,

You should be able to find at least some data if you look for information available regarding commercially available bulk media. For example, Chelex 100 and Dowex A1 are both iminodiacetate resins which have a significant number of literature citations. For example, in the book: Ion Chromatography on page 53 there is a table listings stability constants relative to zinc; mercury: 1060, copper: 126, nickel: 4.4, cobalt: 0.61, manganese: 0.024 and magnesium: 0.009. Even though there wasn't any data in this particular reference on calcium, you can see you from the relative magnitude of the magnesium data that such resins bind alkaline earth cations much more weakly than transition metal cations.

Another reference: http://www1.dionex.com/en-us/webdocs/ap ... 25_V15.pdf describes the use of the MetPac CC-1 column which is also an iminodiacetate resin. In order to quantitatively retain transition metals while eluting calcium and magnesium, an eluent consisting of two molar ammonium acetate at pH 5.5 is used.