Circular dichroism (CD) studies on biological activity of mast cell degranulating (MCD) peptide analogs

Analogs of MCD peptide were synthesized by solid‐phase methods. Positive charges were deleted at the N‐and/or C‐terminus, including the helical portion of the molecule. Four peptides were prepared by removing residues 16–18 (Arg‐Lys‐Ile), 1–2 (Lys), 1–2 and 16–18 and by acetylation of the amino end (Ile). Analogs were tested on mast cells for histamine‐releasing activity. Although the helicity of these derivatives, determined by circular dichroism (CD), was not significantly different from the native MCD peptide, two analogs with C‐terminal deletions showed a 5‐ to 10‐fold decrease in activity. These findings suggest that the C‐terminus is more important than the N‐terminus in determining bioactivity of MCD peptide.