Pierce's Gentle Ag/Ab Elution Buffer, pH 6.6

An alternative to acid elution during antigen or antibody affinity purification.

Seems to be simply 3.6 M MgCl2.

Evidence:

- 3.6 M MgCl2 has the same density as Pierce product;

- it definitely cointains Mg2+ because it forms precipitate with high phosphate and that precipitate is dissolved by EDTA but not EGTA;

- the manual mentions that it is "high salt" and precipitation with phosphate;

- 3.6 M MgCl2 tested and definitely works just as well as commercial solution;

- Harlow & Lane "Antibodies" book mentions high MgCl2 as an alternative to acid elution.

The advantage over acid elutions:

Many proteins denature irreversibly at low pH but are stable enough in a mild chaotropic solutions such as high MgCl2. Thus, using this buffer allows one to reuse antigen column many times without a risk of destroying it by acid elution. (The column with immobilized denatured protein is "sticky", exhibiting high non-specific binding). Likewise, many eluted antigens are perfectly native after dialysing the high salt out.