Optimization of band-selective homonuclear dipolar recoupling in solid-state NMR by a numerical phase search.
Related Articles Optimization of band-selective homonuclear dipolar recoupling in solid-state NMR by a numerical phase search.
J Chem Phys. 2019 Apr 21;150(15):154201
Authors: Zhang Z, Liu H, Deng J, Tycko R, Yang J
Abstract
Spin polarization transfers among aliphatic 13C nuclei, especially 13C?-13C? transfers, permit correlations of their nuclear magnetic resonance (NMR) frequencies that are essential for signal assignments in multidimensional solid-state NMR of proteins. We derive and demonstrate a new radio-frequency (RF) excitation sequence for homonuclear dipolar recoupling that enhances spin polarization transfers among aliphatic 13C nuclei at moderate magic-angle spinning (MAS) frequencies. The phase-optimized recoupling sequence with five ? pulses per MAS rotation period (denoted as PR5) is derived initially from systematic numerical simulations in which only the RF phases are varied. Subsequent theoretical analysis by average Hamiltonian
theory explains the favorable properties of numerically optimized phase schemes. The high efficiency of spin polarization transfers in simulations is preserved in experiments, in part because the RF field amplitude in PR5 is only 2.5 times the MAS frequency so that relatively low 1H decoupling powers are required. Experiments on a microcrystalline sample of the ?1 immunoglobulin binding domain of protein G demonstrate an average enhancement factor of 1.6 for 13C? -> 13C? polarization transfers, compared to the standard 13C-13C spin-diffusion method, implying a two-fold time saving in relevant 2D and 3D experiments.
PMID: 31005077 [PubMed - in process]
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