Improved procedure for the purification of an iodinated protein: beta nerve growth factor.

An improved procedure for the isolation of iodinated beta Nerve Growth Factor (125I-beta NGF) has been devised. Use of Centricon microconcentrators (Amicon) has allowed the facile and efficient recovery of ultrapure 125I-beta NGF in high yields. Centricon microconcentrators are supplied with two molecular weight cutoffs of 10 K and 30 K daltons. beta NGF is a basic protein with a molecular weight of 26 K daltons. It is therefore possible to filter the 125I-beta NGF through the 30 K filter (30 K Filtrate) leaving behind any aggregates or reactants greater than 30 K while the 125I-beta NGF can be retained and concentrated on the 10 K filter (10 K Retentate). Any free 125I is easily removed, passing through the 10 K filter and then being discarded. In this way 125I-beta NGF can be easily purified.