Fig. 3.

Single-crystal X-ray diffraction of gichigamin A (1). (A) The complete structure of the gichigamin A monomer generated using PyMol. The C-terminal Gly-ol hydroxyl is displayed with the highest occupancy model (73%). (B) N-terminal α-β-motif of 1. Pro₂ is shown coordinating through two hydrogen bonds to the i + 3 and i + 4 residues. (C) A perpendicular view of the unique 3₁₁-P-helical structure resulted from the inclusion of BALA residues in 1. The N- and C-termini were removed for clarity. (D) For the purpose of comparison, a canonical 3₁₀ helix is shown that was generated with Φ- and Ψ-angles of −49° and −29° for poly-Ala dodecamer using the PepMake 1.2 server at pepmake.wishartlab.com/.