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Abstract: Efficient sampling of signals is a key issue for multiple-dimensional NMR experiments to establish the best ratio between experiment time and spectral quality. Focussing on the most widely used sampling strategy using standard rectangular sampling and data analysis by Fourier transformation, a central question is concerned with determining the optimal maximum sampling time in the individual dimensions. The spectral resolution depends directly on this choice, as do the overall experiment times when addressing the indirect dimensions. We present a theoretical, numerical, and experimental analysis of the sampling space problem and propose approaches to efficient sampling for typical cases. [Copyright &y& Elsevier]

Based on exact numerical simulations, taking into account isotropic and conformation-dependent anisotropic nuclear spin interactions, we systematically analyse the prospects for high-resolution solid-state NMR on large isotope-labeled membrane proteins macroscopically oriented in phospholipid bilayers. Using the known X-ray structures of rhodopsin and porin as models for large membrane proteins with typical α-helical and β-barrel structural motifs, the analysis considers all possible one- to six-dimensional spectra comprised of frequency dimensions with evolution under any combination of amide 1H, amide 15N, and carbonyl 13C chemical shifts as well as 1H-15N dipole-dipole couplings. Under consideration of typical nuclear spin interaction and experimental line-shape parameters, the analysis provides new insight into the resolution capability and orientation-dependent transfer efficiency of existing experiments as well as guidelines as to improved experimental approaches for the study of large uniformly 15N- and [13C,15N]-labeled membrane proteins. On basis of these results and numerical optimizations of coherence-transfer efficiencies, we propose several new high-resolution experiments for sequential protein backbone assignment and structure determination. [ABSTRACT FROM AUTHOR]

We present a bimodal Floquet analysis of the recently introduced refocused continuous wave ( r CW) solid-state NMR heteronuclear dipolar decoupling method and compare it with the similar looking X-inverse X (XiX) scheme. The description is formulated in the rf interaction frame and is valid for both finite and ideal π pulse r CW irradiation that forms the refocusing element in the r CW scheme. The effective heteronuclear dipolar coupling Hamiltonian up to first order is described. The analysis delineates the difference between the two sequences to different orders of their Hamiltonians for both diagonal and off-diagonal parts. All the resonance conditions observed in experiments and simulations have been characterised and their influence on residual line broadening is highlighted. The theoretical comparison substantiates the numerical simulations and experimental results to a large extent. [ABSTRACT FROM AUTHOR]

Abstract: Refocused continuous wave (rCW) decoupling is presented as an efficient and robust means to obtain well-resolved magic-angle-spinning solid-state NMR spectra of low-γ spins, such as 13C dipolar coupled to fluorine. The rCW decoupling sequences, recently introduced for 1H decoupling, are very robust towards large isotropic and anisotropic shift ranges as often encountered for 19F spins. In rCW decoupling, the so-called refocusing pulses inserted into the CW irradiation eliminate critical residual second- and third-order dipolar coupling and dipolar-coupling against chemical shielding anisotropy cross-terms in the effective Hamiltonian through time-reversal (i.e. refocusing). As important additional assets, the rCW decoupling sequences are robust towards variations in rf amplitudes, operational at low to high spinning speeds, and easy to set-up for optimal performance experimentally. These aspects are demonstrated analytically/numerically and experimentally in comparison to state-of-the-art decoupling sequences such as TPPM, SPINAL-64, and frequency-swept variants of these. [Copyright &y& Elsevier]

Abstract: We present a historical recollection on the development of the software package SIMPSON (SIMulation Package for SOlid-state Nmr). This covers a brief description of the underlying ideas and events leading to creation of SIMPSON and numerous auxiliary programs as well as comments on its impact on the development and application of solid-state NMR in research laboratories world-wide. [Copyright &y& Elsevier]

We present new non-rotor-synchronized variants of the recently introduced refocused continuous wave ( r CW) heteronuclear decoupling method significantly improving the performance relative to the original rotor-synchronized variants. Under non-rotor-synchronized conditions the r CW decoupling sequences provide more efficient decoupling, are easier to setup, and prove more robust towards experimental parameters such as radio frequency (rf) field amplitude and spinning frequency. This is demonstrated through numerical simulations substantiated with experimental results under different sample spinning and rf field amplitude conditions for powder samples of U- 13 C-glycine and U- 13 C- L -histidine·HCl·H 2 O. [ABSTRACT FROM AUTHOR]

Highlights: [•] We developed a method of high yield production of recombinant human amylin. [•] Fibril growth and cytotoxicity of recombinant amylin was demonstrated. [•] Recombinant amylin is a well suited material for structural investigations by NMR. [Copyright &y& Elsevier]

Abstract: Polarization transfer between spin-1/2 nuclei and quadrupolar spin-1 nuclei such as N in solid-state NMR is severely challenged by the typical presence of large quadrupole coupling interactions. This has effectively prevented the use of the abundant N spin as a probe to structural information and its use as an element in multi-dimensional solid-state NMR correlation experiments for assignment and structural characterization. In turn, this has been a contributing factor to the extensive use of isotope labeling in biological solid-state NMR, where N is replaced with N. The alternative strategy of using the abundant N spins calls for methods enabling efficient polarization transfer between N and its binding partners. This work demonstrates that the recently introduced CP transfer method can be optimized to achieve efficient H N polarization transfer under magic angle spinning conditions. The method is demonstrated numerically and experimentally on powder samples of NH4NO3 and l-alanine. [Copyright &y& Elsevier]

Highlights: [•] A modification of the basic Two-Pulse Phase-Modulation (TPPM) heteronuclear decoupling is proposed. [•] The design of the new scheme, rTPPM, is similar to that of the recently introduced rCW schemes. [•] The decoupling efficiency of the new sequence is tested with simulations and corroborated with experimental findings. [•] The robustness of the newly introduced scheme is compared to that of a few related decoupling methods. [ABSTRACT FROM AUTHOR]

Highlights: [•] Heteronuclear polarization transfer by adiabatic RESPIRATIONCP. [•] Increased transfer efficiency and robustness towards rf inhomogeneity. [•] Demonstrated improved performance for 13C→ 15N polarization transfer in proteins. [ABSTRACT FROM AUTHOR]

Abstract: We present a novel sampling strategy, interleaving acquisition of multiple NMR spectra by exploiting initial polarization subsequently from 1H and 2H spins, taking advantage of their different T 1 relaxation times. Different 1H- and 2H-polarization based spectra are in this way simultaneously recorded improving either information content or sensitivity by adding spectra. The so-called Relaxation-optimized Acquisition of Proton Interleaved with Deuterium (RAPID) 1H→ 13C/2H→ 13C CP/MAS multiple-acquisition method is demonstrated by 1D and 2D experiments using a uniformly 2H, 15N,13C-labeled α-spectrin SH3 domain sample with all or 30% back-exchanged labile 2H to 1H. It is demonstrated how 1D 13C CP/MAS or 2D 13C–13C correlation spectra initialized with polarization from either 1H or 2H may be recorded simultaneously with flexibility to be added or used individually for spectral editing. It is also shown how 2D 13C–13C correlation spectra may be recorded interleaved with 2H–13C correlation spectra to obtain 13C–13C correlations along with information about dynamics from 2H sideband patterns. [Copyright &y& Elsevier]