Proton Dipolar Recoupling in Resin-Bound Peptides under High-Resolution Magic Angle Spinning

Homonuclear Hartmann–Hahn transfer with reduced relaxation losses by use of the MOCCA-XY16 multiple pulse sequence

“…4 of [38] and was also observed in highresolution magic angle spinning experiments using the virtually identical RFDR pulse sequence [39]. Nevertheless, for a more accurate characterization of the isotropic mixing properties coherence transfer curves were recorded on the cyclic pentapeptide D D -Pro-Ala-AlaAla-Ala which we will refer to as PA 4 in the following.…”

Field modulation effects induced by sample spinning: application to high-resolution magic angle spinning NMR

“…The dipolar and the CSA interaction contribute only to a small fraction of the experimental linewidth since the relatively fast dynamics of these systems is sufficient to greatly reduce these two interactions. Compared to real solid samples, the dipolar and the CSA interactions present in HRMAS samples are therefore much weaker and only a residual effect can be observed [21]. Assuming an isotropic molecular orientation, the effect of MAS on heterogeneous quasi-liquid samples can be described as for powder samples.…”

1H–13C INEPT MAS NMR correlation experiments with 1H–1H mediated magnetization exchange to probe organization in lipid biomembranes

“…In the present study, we have utilized the rotor-synchronized radio-frequency dipolar recoupling (RFDR) sequence [37][38][39]47] to re-introduce residual 1 H-1 H dipolar coupling via zeroquantum coherences as a means of magnetization transfer [48]. 1 H-1 H RFDR correlation experiments were recently demonstrated for swollen protein resins [49] and are similar to proton-mediated rare spin correlation experiments developed for protein structure determination in the solid state [50][51][52][53]. Fig.…”

“…10), the magnetization exchange is very similar for the RFDR and the NOE cross-relaxation based experiments. During the RFDR sequence it is known that magnetization transfer can occur both through recoupling and through NOE cross relaxation [49]. It has also been observed that the RFDR sequence may actually accelerate the incoherent NOE cross-relaxation by a process that has been called rotordriven or RF-driven spin diffusion [56,57].…”

“…The difference in the behavior of the 1 H-1 H magnetization exchange under the cross-relaxation (NOE exchange) or the RFDR type mixing periods is more easily understood by measuring the evolution of the 1 H-1 H exchange as a function of s mix . To perform multiple 1 H- 13 C INEPT experiments at different s mix would prove to be extremely time restrictive, but this information can be obtained by using a standard 2D 1 H NOESY MAS NMR correlation experiments [13,14,46,49]. From NOESY exchange experiments the individual 1 H-1 H cross-relaxation rates can be directly measured as shown in Fig.…”