Nerve growth factor of very high yield and specific activity.

Nerve growth factor has been isolated from submaxillary glands of mnature male mice at specific activities about a million times, and in yields of biological activity ten million times, greater than best previous results. The major improvement in the isolation is related to the separation of a highly active tosylarginine methyl esterase present in cruder preparations. The new nerve growth factor may be an entity different from the older one, although no gross differences in the qualitative aspects of their actions are apparent on superficial examination of chick ganglia influenced by them.