The cyclic cystine ladder in θ-defensins is important for structure and stability, but not antibacterial activity.

This is a head-to-tail cyclic peptide with a peptide bond between Arg18 and Gly1. Residues 5 and 14 are alpha-aminobutyric acid Aba (B)

[Aba5,14]BTD-2 is an analogue of naturally-occurring BTD-2 from Papio anubis

Head-to-tail (Arg-Gly) cyclic peptide. Residues 5 and 14 are replaced by alpha-aminobuytyric acid.

simulated annealing, torsion angle dynamics

High resolution NMR solution structure of a symmetrical theta-defensin, BTD-2

Brunger, Adams, Clore, Gros, Nilges and Read