Conformation of cyclic heptapeptides: solid and solution state conformation of yunnanin A

Abstract

The solid and solution state conformation of yunnamin A, a cyclic heptapeptide, cyclo(-Gly-Tyr-Gly-Pro-Phe-Pro-), isolated from the roots of Stellaria yunnanensis were studied. The X-ray diffraction studies showed that the crystal of yunnanin A [orthorhombic form from a ethanol-methanol mixture, a=11.754 (10), b=12.576 (7), c=30.731 (6) Å, space group P222 1 z=4] had three intramolecular hydrogen bonds forming one type II, one type II′ β-turns and a classical β-bulge unit with all trans amide bonds. The dominant solution conformation analyzed by NMR spectroscopy, Monte Carlo (MC) are restrained molecular dynamics (MD) calculations implemented in MacroModel/Batchmin (Ver. 4.5) was homologous to that in the solid state.