Comparison of several hetero-nuclear dipolar recoupling NMR methods to be used in MAS HMQC/HSQC

3D 1H–13C–14N correlation solid-state NMR spectrum

“…If the matching curve is narrow, one loses signal from end parts of the rotor experiencing lower B 1 field out of matching condition. R4 2 1 R4 À2 1 is more robust due to a larger matching breadth always covering most of B 1 distribution along the rotor [24]. Second, compared to other symmetry based methods, such as the recently used R20 9 5 [25], the basic cycle of this technique only lasts two rotor periods, which allows short transfer times of 100-200 ls, often the optimum for 1 H-14 N coupling of directly bonded NH.…”

“…Additionally, smaller coil diameters allow for stronger rf-fields, which are especially important to manipulate efficiently broad powder sample spectra such as that of 14 N nucleus [27]. Moreover, more efficient hetero-nuclear dipolar recoupling techniques, such as SFAM 2 may be used, especially at fast or ultrafast spinning speed [24]. In addition, 1 H resolution may be enhanced by a homo-nuclear 1 H decoupling scheme such as FSLG [28], PMLG [29], eDUMBO [30], or RN v n [31] at moderate m R or SAM [32] at fast or ultra-fast spinning speeds.…”

Enhanced resolution in proton solid-state NMR with very-fast MAS experiments

“…This approach has already been successful in the case of hetero-nuclear dipolar re-introduction under MAS using SFAM 1,2 [29,30]. We name this sequence SAMn after smooth amplitude modulation.…”

High-resolution 14N-edited 1H–13C correlation NMR experiment to study biological solids

“…We propose here a new magic angle spinning (MAS) 14 N-edited method for 1 H-13 C through-space HETCOR spectra to obtain high-resolution in both dimensions. We combine latest hetero-recoupling (Simultaneous Frequency and Amplitude Modulation: SFAM 2 ) [16,17] and homo-decoupling (Smooth Amplitude Modulation: SAM 3 ) [18] techniques along with a filter based on 13 C-14 N D-HMQC experiment.…”