The Thermo Scientific Pierce Monomeric Avidin UltraLink Resin is ideal for affinity purification of biotinylated proteins, peptides and other molecules. Immobiliziation of avidin monomers results in a purification resin with a much lower biotin-binding affinity than native tetrameric avidin, enabling recovery of biotinylated molecules using mild elution conditions.
The Immobilized Monomeric Avidin protein binds biotin with high specificity and moderate affinity, allowing non-biotin molecules to be washed away and then the bound biotin-labeled molecules to be competitively eluted using 2 mM biotin in phosphate buffered saline (PBS). This technique provides the gentlest elution conditions for biotinylated protein purification and avoids the contamination and other problems associated with traditional avidin and streptavidin methods. The monomeric avidin column can then be regenerated by using 0.1M glycine to strip the column of residual bound biotin without losing the ability to bind another biotinylated sample.
With typical avidin or streptavidin, the biotin-binding affinity (Kd = 10-15M) is so great that purification with these traditional media require denaturing conditions for elution, such as 8M Guanidine·HCl at pH 1.5 or boiling in reducing SDS-PAGE sample loading buffer. In addition to their adverse effects on the biotinylated protein of interest, such harsh elution conditions typically cause extraneous proteins (i.e., the avidin or streptavidin subunits) to strip from the resin and co-elute with the desired purification product. By contrast, when avidin is coupled to a resin (e.g., crosslinked beaded agarose or UltraLink Resin) as the subunit monomer, its specificity for biotin is retained, but its biotin-binding affinity decreases to a level (Kd = 10-8M) that is conducive to subsequent elution.