[Human embryonic haemoglobins. Ac-Ser-Leu-Thr-is the N-terminal sequence of the zeta-chains (author's transl)].

The complete amino acid sequence of the embryonic zeta-chains has been reported in an earlier communication (Aschauer, H., Sanguansermsri, T. & Braunitzer, G. (1981), Hoppe-Seyler's Z. Physiol. Chem. 362, 1159-1162). To elucidate the nature of the N-terminal blocking group, tryptical cleavage of the zeta-chains was carried out and the N-terminal tryptic tetrapeptide was isolated by high performance liquid chromatography on reversed phase (RP 8). The tetrapeptide was digested with pronase and the mixture was subjected to mass spectrometry by chemical ionization. By this method Ac-Ser was found to be the N-terminus. In a second experiment the tetrapeptide was permethylated and analysed by mass spectrometry with electron ionization. The N-terminal sequence was found to be Ac-Ser-Leu-Thr-.