Structure-activity relationship of the ring portion in backbone-cyclic C-terminal hexapeptide analogs of substance P. NMR and molecular dynamics.

The conformations of two backbone-cyclized substance P analogs were derived from homo- and heteronuclear NMR measurements and molecular dynamics simulations carried out in DMSO. The analogs contain subtle variations in the ring chemistry and are compared with biologically active analogs previously examined. The correlation between conformation and activity is used to gain insight into the conformational requirements from the pharmacophore.