New Methods for Affinity Purification of Proteins. Affinity Precipitation: a Review

I. Yu. Galaev^1,2 and B. Mattiasson¹

¹Department of Biotechnology, Center for Chemistry and Chemical Engineering, Lund University, P. O. Box 124, Lund, S-22100, Sweden; fax: (4646) 222-4713; E-mail: igor.galaev@biotek.lu.se

²To whom correspondence should be addressed.

Submitted January 20, 1997.

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A new method of protein purification, affinity precipitation, is based on the use of a macroligand, i.e., a ligand with two or more affinity sites. Macroligands are synthesized either by covalent linking of two common ligands (directly or through a short spacer) or by covalent binding of several ligands to a water-soluble polymer. The complex of the purified protein with macroligand precipitates if the protein has several ligand-binding sites and can form poorly soluble intermolecular aggregates with the macroligand (the homobifunctional variant); the complex also precipitates when small changes in the environment (pH, ionic strength, temperature, presence of specific substances) dramatically decrease the solubility of the polymeric component of the macroligand, resulting in specific co-precipitation of the macroligand-bound protein (the heterobifunctional variant). The purified protein is obtained by elution from the polymeric precipitate after the latter is separated from the supernatant containing contaminating proteins. Affinity precipitation combines high performance and simplicity of precipitation methods with high selectivity that can be achieved in affinity methods of protein purification.

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KEY WORDS: protein purification, affinity precipitation, "clever polymers".

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