Self‐association of the neuroregulatory peptide substance P and its C‐terminal sequences

Abstract

Self‐association of substance P and its C‐terminal partial peptide sequences was studied by CD, quasi‐electric light scattering, and sedimentation experiments. CD spectra of these peptides are strongly influenced by self‐association. They exhibit strong characteristic negative ellipticities, suggesting the formation of a presumably B‐type ordered structure. The tendency to form multimers depends on chain length and constitution and has its maximum at the octapeptide (SP 8). The peptide multimers have a broad distribution of sizes in the range of 30‐ and 800‐nm diameter. Subdivision of this distribution into two size classes gives mean diameters of 60–100 nm (predominating)/200–800 nm for substance P and 30–50 nm/200–800 nm for SP 8 multimers.