The purification of avidin and its derivatives on 2-iminobiotin-6-aminohexyl-Sepharose 4B

The pH-dependent interaction between the cyclic guanidino analog of biotin, 2-iminobiotin, and avidin has been used in the design of an efficient affinity isolation system for avidin and its fluorescent and iodinated derivatives. Avidin and its derivatives are retained by a column of 2-iminobiotin-6-aminohexyl-Sepharose 4B at pH values between 9 and 11 and are specifically eluted from the column at pH 4. This affinity isolation procedure overcomes the harsh conditions, i.e., 6 m guanidine-HCl, pH 1.5, required to dissociate avidin from an immobilized biotin column.