The partial sequence of two large peptides from the N-terminal half of heavy chains from normal rabbit immunoglobulin G.

The partial amino acid sequence of two large peptides is described. These were prepared from the N-terminal half of the heavy chain of immunoglobulin G from pooled normal rabbit serum by tryptic digestion after the in-amino groups of the lysine residues had been blocked with S-ethyl trifluorothioacetate. These peptides are believed to account for about 145 residues of fragment C-1, the N-terminal section of rabbit immunoglobulin G heavy chain prepared by cyanogen bromide cleavage. The evidence from the present paper and the preceding paper (Cebra, Givol & Porter, 1968) suggests that it may be possible to deduce a predominant amino acid sequence for most, if not all, of this section of the molecule.