Solid-phase synthesis of the native sequence of horse heart cytochrome c-(66–104)-nonatriacontapeptide and of a C-terminal carboxyamide analog selectively modified at Met-80

The peptide corresponding to the (66–104) sequence of horse heart cytochrome c and its carboxyamide analog, selectively modified at the critical Met⁸⁰ residue, have been synthesized by stepwise solid-phase methods on PAM and BHA resins respectively. The correctness of the growing peptide chain as well as the homogeneity of the final products have been monitored by several analytical methods including quantitative Edman degradation. After HF cleavage both peptides were purified by semipreparative HPLC. The overall yields were 24% for the native (66–104) and 10% for the carboxyamide analog. The homogeneity of the purified synthetic peptides have been determined by different criteria including HPLC, amino acid composition, Edman degradation, electrophoresis, and tryptic peptide mapping. The synthetic fragments have been utilized for preliminary semisynthesis experiments with the native [Hse〉⁶⁵](1–65)H heme-sequence.