Solid-state NMR at natural isotopic abundance for the determination of conformational polymorphism - the case of designed beta-turn peptides containing di-prolines

The proton double quantum-carbon single quantum correlation experiment has been applied to designed peptides in the solid state in natural isotopic abundance. Analogous to nOe studies in solution, through-space double-quantum connectivities have been exploited to obtain the cis-trans conformational polymorphism of diproline residues occurring at beta-turns in the peptides.