Tailoring broadband inversion pulses for MAS solid state NMR.
A simple approach is demonstrated for designing optimised broadband inversion pulses for MAS solid state NMR studies of biological systems. The method involves a two step numerical optimisation procedure and takes into account experimental requirements such as the pulse length, resonance offset range and extent of H(1) inhomogeneity compensation needed. A simulated annealing protocol is used initially to find appropriate values for the parameters that define the well known tanh/tan adiabatic pulse such that a satisfactory spin inversion is achieved with minimum RF field strength. This information is then used in the subsequent stage of refinement where the RF pulse characteristics are further tailored via a local optimisation procedure without imposing any restrictions on the amplitude and frequency modulation profiles. We demonstrate that this approach constitutes a generally applicable tool for obtaining pulses with good inversion characteristics. At moderate MAS frequencies the efficacy of the method is experimentally demonstrated for generating double-quantum NMR spectra via the zero-quantum dipolar recoupling scheme RFDR.
Riedel
Kerstin
K
Research group-Molecular Biophysics/NMR spectroscopy, Leibniz Institute for Age Research, Fritz Lipmann Institute, D-07745, Jena, Germany.
Herbst
Christian
C
Leppert
Jörg
J
Ohlenschläger
Oliver
O
Görlach
Matthias
M
Ramachandran
Ramadurai
R
D002247:Carbon Isotopes; D019906:Nuclear Magnetic Resonance, Biomolecular / Q000379:methods*; D012313:RNA / Q000737:chemistry
D002247:Carbon Isotopes; D012313:RNA