Bioactive peptides: X-ray and NMR conformational study of (Aib5,6-D-Ala8)cyclolinopeptide A

X-ray diffraction and nuclear magnetic resonance spectroscopy were used in undertaking a conformational analysis of (Aib5,6-D-Ala8)cyclolinopeptide A in solid state and in solution. The findings reveal five intramolecular N-H-O=C hydrogen bonds, one C17 ring structure, one alpha-turn, one gamma-turn and two beta-turns in the orthorhombic form of the peptide. Moreover, spectrum analysisindicates that the peptide is conformationally homogeneous even at room temperature.