An ω1-band-selective, ω1-homonuclear decoupled ROESY experiment:: application to the assignment of 1H NMR spectra of difficult-to-assign peptide sequences

Application of an omega(1),-band-selective, omega(1)-homonuclear decoupled ROESY (BASHD-ROESY) experiment to the assignment of H-1 NMR spectra of peptides is demonstrated. Band selection in the omega(1), dimension is achieved with the double pulsed field gradient spin echo (DPFGSE) technique; homonuclear decoupling in the w(1) dimension is achieved by placing a non-selective 180 degrees 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-ArgAla-Ala-Ala-Arg-Arg-Ala-Ala- Arg-Arg-Ala-Ala-Ala-Arg-NH,. Critical to making the assignments was the significantly increased resolution in the C alpha H-NH region of the ROESY spectrum measured with the BASH-DROESY pulse sequence with band selection and homonuclear decoupling in the CalphaH region. NOEs observed for the peptide indicate it has a helical secondary structure in solution. (C) 1998 John Wiley & Sons, Ltd.