Supercycled homonuclear dipolar decoupling sequences in solid-state NMR

Homonuclear dipolar decoupling under fast MAS: Resolution patterns and simple optimization strategy

“…Again, the decoupling efficiency can be easily assessed based on the echo intensity, although the effect of offset varies across each spectrum. Small offsets are preferred, which is in agreement with earlier results obtained using windowed PMLG5 xx mm sequence and MAS rates of 7-14 kHz [27].…”

“…The suppression of 1 H homonuclear dipolar interactions renders the 1 H-13 C spin pairs equivalent to the AX system in solution [24,25], providing a sensitive probe of the decoupling efficiency and a good estimate of the scaling factor through the observation of J-multiplets. A more direct method involves acquisition of high-resolution 1D or 2D 1 H-1 H spectra of a reference sample, usually glycine, which allows for optimization of the amplitude of the RF magnetic field m RF and the s c /s R ratio [13,17,18,21,22,26,27], calibration of the effective field [26] and the scaling factor [23,26,27], optimization of the resonance offset, the pulse imperfections and the spectral artifacts [13,21,27,28].…”

1H line width dependence on MAS speed in solid state NMR – Comparison of experiment and simulation

“…1D 1 H spectra of the dipeptide were obtained over a range of spinning frequencies (x r /2p) between 15 and 100 kHz (±50 Hz). A spin-echo experiment was employed to improve the spectral baseline, with a total echo length (2s) of 24 rotor periods [32]. Spin-echo experiments were also performed at different spinning frequencies in the range between 15 and 100 kHz to measure, for each proton in the dipeptide, the transverse dephasing time in the absence of inhomogeneous broadening (T 2 0 ) [40].…”

“…On the other hand, CRAMPS methods achieved a remarkable feat of efficient averaging of the 1 H-1 H dipolar couplings even under moderate spinning frequencies [16][17][18][19][20][21][22][23][24][25]. Thanks to this, investigations on uniformly protonated compounds have become increasingly popular in the recent years [18,21,[26][27][28][29][30][31][32][33][34]. However, to obtain the optimum performance for CRAMPS techniques effects of pulse imperfections, specifics of hardware, details of irradiation schemes, intricacies of windowed acquisition and related artifacts, etc.…”

A large geometric distortion in the first photointermediate of rhodopsin, determined by double-quantum solid-state NMR

“…The duration of each the t 1 /2 half-intervals was incremented stepwise from 0 to a full rotor period. In practice we used a PMLG-5 pulse scheme that comprises ten radiofrequency pulses of flip angle p/2 and equal duration s p (Paul et al 2009). For the DAF experiments, 8 increments were fitted into a single rotor period s r = 178.6 ls (spinning speed 5,600 Hz) using the PMLG-5 pulse duration s p = 2.55 ls.…”