The 125I-labeled M r 80 000 form of neurophysin has been purified from bovine neurohypophysi. Tryptic digests of this species were analyzed, prior to or after treatment with carboxypeptidase B, by high-pressure liquid chromatography followed by isoelectric focusing and the fragments compared with those generated by a similar treatment of reference bovine 1–39 adrenocorticotropin. The ACTH peptides 22–39 and 1–8, as well as the 1–7 derivative of the latter were identified by those two independent criteria. This provides chemical evidence supporting the hypothesis [8] that high M r neurophysin may contain the sequence of ACTH.
