Broadband RFDR with adiabatic inversion pulses

Abstract

With a view to obtain ¹³C chemical shift correlation spectra of uniformly labelled peptides/proteins at high magnetic fields and high magic angle spinning frequencies (ω_r/2π ≤ 20 kHz), the efficacy of RFDR with adiabatic inversion pulses has been assessed via numerical simulations and experimental measurements employing different adiabatic pulse phasing schemes, shapes and durations. It is demonstrated that homonuclear dipolar recoupling with superior performance under resonance offset and H ₁ inhomogeneity effects and without strong dependence on the ¹³C chemical shift differences can be achieved with adiabatic pulses. It is shown that ¹³C chemical shift correlation spectra in the entire range of carbon chemical shifts can be obtained efficiently with short adiabatic inversion pulses. In situations where correlation spectra of only the aliphatic region are required, the possibility for minimising the interference between the recoupling and decoupling RF fields with long adiabatic pulses, at low recoupling power levels and without compromising the broadband RFDR characteristics, is also indicated.