Synthetic peptides with SgII-related proposed active face residues indicated.

For structure-activity purposes, interatomic distances have been measured between six atoms of the proposed active face residues using molecular models in silico. Twenty peptides provided the observed (O) distances for a chi-squared hypothesis test of SgII-relatedness, with the expected (E) interatomic distances from EPL143, a contiguous version of sSgII-14 (Fig 1). χ2 = Σ (O–E)2/E; dof = degrees of freedom; P = probability; E-5 = x10-5 etc. The righthand column shows the accessibility for receptor binding of active face aa side chains, each tri-residue module viewed clockwise and counter-clockwise. Control tri-residues: MK7xxP/NxVxxxF (EPL010); K3MxxxxxxP/N5xxxxxxVF (EPL030); & K3xMxxxxxP/N4xxxxxxxVF (EPL040). NA = not applicable.