Abstract
The stability of DNP-proline was examined under conditions of hydrolysis with HC1 such as are used in the identification of N-terminal residues of proteins. Two hitherto un-described hydrolytic products of DNP-DL-proline were isolated and details of their general properties given. These products were shown by synthesis to be [alpha]-2:4-dinitrophenylamino- [delta] -chlorovaleric acid and [alpha]-chloro- [delta] -2:4-dinitrophenylaminovaleric acid. A scheme for the identification of N-terminal proline is suggested in the light of these findings.