Experimental evidence for CH⋯π interaction-mediated stabilization of the square form in phenylglycine-incorporated ascidiacyclamide.

ABSTRACT: Ascidiacyclamide [cyclo(-Ile-oxazoline-D-Val-thiazole-)₂] is a cytotoxic cyclic peptide from ascidian. We examined the potential of the CH⋯π interaction at the diagonal position of ascidiacyclamide by comparing the interactions of Ile, Val, Abu (2-aminobutyric acid) or Ala with Ile, Chg (cyclohexylglycine) or Phg (phenylglycine). In solution, ascidiacyclamides are in a conformational equilibrium between square and folded forms. The CH⋯π interaction is expected to contribute to stabilization of the square form, which enhances the peptides' cytotoxicity. The distances between the alkyl side chain of Xaa and the π-plane of Phg were estimated from the crystal structures. The conformational free energies (ΔG°) determined through NMR-based quantitation indicated remarkable stab

SUBMITTER: Asano A 

PROVIDER: S-EPMC9854340 | biostudies-literature | 2023 Jan

REPOSITORIES: biostudies-literature