Characterization of low populated peptide helical structures in solution by means of NMR proton conformational shifts

A NOE independent NMR method is proposed to characterize unambiguously residues involved in low populated isolated peptide helices. The method is based on the comparison of amide and H alpha chemical shift changes originated upon the addition of stabilizing or denaturing agents with true helical conformational shifts that have been measured for the first time using an isolated model peptide helix, the one formed by Ac-(Leu-Lys-Lys-Leu)3-NHEt in aqueous solution.