An ω1-band-selective, ω1-homonuclear decoupled ROESY experiment: application to the assignment of1H NMR spectra of difficult-to-assign peptide sequences

Abstract

Application of an ω1-band-selective, ω1-homonuclear decoupled ROESY (BASHD-ROESY) experiment to the assignment of 1H NMR spectra of peptides is demonstrated. Band selection in the ω1 dimension is achieved with the double pulsed field gradient spin echo (DPFGSE) technique; homonuclear decoupling in the ω1 dimension is achieved by placing a non-selective 180° pulse together with the first half of the DPFGSE in the middle of the evolution period. Application of the BASHD-ROESY experiment is demonstrated with the complete assignment of the proton resonances of the synthetic 19 amino acid peptide N-Ac–Ala–Glu–Ala–Ala– Ala–Arg–Ala–Ala–Ala–Arg–Arg–Ala–Ala– Arg–Arg–Ala–Ala–Ala–Arg–NH2. Critical to making the assignments was the significantly increased resolution in the CαH–NH region of the ROESY spectrum measured with the BASHD-ROESY pulse sequence with band selection and homonuclear decoupling in the CαH region. NOEs observed for the peptide indicate it has a helical secondary structure in solution. © 1998 John Wiley & Sons, Ltd.