Measurement of hetero-nuclear distances using a symmetry-based pulse sequence in solid-state NMR

Abstract

A Symmetry-based Resonance-Echo DOuble-Resonance (S-REDOR) method is proposed for measuring hetero-nuclear dipolar couplings between two different spin-1/2 nuclei, under fast magic-angle spinning. The hetero-nuclear dipolar couplings are restored by employing the SR4 sequence, which requires the rf-field strength to be only twice the spinning frequency. The S-REDOR experiment is extended to S-RESPDOR (Symmetry-based Resonance-Echo Saturation-Pulse DOuble-Resonance) for determining dipolar coupling between a spin-1/2 nucleus (e.g.(13)C) and (14)N. It is demonstrated that S-REDOR and S-RESPDOR methods suppress efficiently the homo-nuclear dipolar interaction of the irradiated nucleus and benefit from high robustness to the rf-field inhomogeneity, chemical shielding and dipolar truncation. Therefore, these methods allow the measurement of (13)C/(14,15)N distances, with (13)C observation, in uniformly (13)C-labeled samples. Furthermore, we provide analytical solutions for the S-REDOR and S-RESPDOR dephasing curves. These solutions facilitate the measurement of hetero-nuclear distances from experimental data.

Distance measurement between a spin-1/2 and a half-integer quadrupolar nuclei by solid-state NMR using exact analytical expressions

“…The R 3 technique has the advantage to be c-encoded and compatible with high MAS frequency [18]. However, R-RESPDOR presents several drawbacks: (i) it is very sensitive to rf-field inhomogeneity [19], (ii) it is influenced by chemical shift anisotropy (CSA) which does not commute with hetero-nuclear dipolar terms [20], (iii) it is sensitive to homo-nuclear dipolar interactions of the observed nuclei, (iv) it suffers from dipolar truncation, which prevents the measurement of medium-and long-range distances [21], and (v) it is not describable by analytical formula in the general case. We have shown very recently that the above limitations of R-RESPDOR can be circumvented by replacing the R 3 recoupling by SR4 2 1 sequence.…”

“…We have shown very recently that the above limitations of R-RESPDOR can be circumvented by replacing the R 3 recoupling by SR4 2 1 sequence. [20,22] This symmetry-based resonance-echo saturationpulse double-resonance (S-RESPDOR) method was applied to determine 13 C-14 N distance in uniformly 13 C-labeled amino acid. [20] In this communication, we demonstrate that S-RESPDOR can also be used to measure distances between spin-1/2 and halfinteger quadrupolar nuclei, and that a general analytical formula describes its dephasing curve for all spin values.…”

Broadband excitation in solid-state NMR using interleaved DANTE pulse trains with N pulses per rotor period

“…This scrambling results in an apparent saturation of the magnetization of a powder sample. This phenomenon has been used for hetero-nuclear distance measurement [40][41][42][43][44][45][46]. Fig.…”

Selective inversion of 1H resonances in solid-state nuclear magnetic resonance: Use of double-DANTE pulse sequence

“…Homonuclear dipolar couplings have been determined providing distances between 13 C spins in a wide range of systems [1][2][3][4][5]. Heteronuclear dipolar couplings have also been determined, for example, focusing on 13 C- 15 N distances in biomolecules [6][7][8]. These measurements have been based on techniques, such as rotational resonance [9], double-quantum recoupling [10,11], and spin echoes combined with off-magic-angle spinning [12].…”