Stimulated echo NMR spectra and their use for heteronuclear two-dimensional shift correlation

NMR spectra are obtained from Fourier transformation of the latter part of a Hahn stimulated echo. The sequence is 90°-τ_a-90°-τ_b-90°-τ_a-digitize versus τ₂. This is demonstrated for transfer RNA in H₂O using the semiselective J ® pulse (90°-τ_p-90°), developed by Plateau and Gueron in place of each 90° pulse. 2D correlation between ¹³N and protons is obtained by applying a 90°-τ₁-90° ¹⁵N sequence during τ_b and ¹⁵N decoupling while digitizing. The second Fourier transform is performed with respect to τ₁ after discarding the imaginary parts of the first transform, to obtain a real 2D map. Such a 2D spectrum has been obtained for 5 mM¹⁵NH₄Cl and several other small molecules. The sequence should be useful for studies of ¹⁵N labeled macromolecules.