Tailoring broadband inversion pulses for MAS Solid state NMR |
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Authors: | Kerstin Riedel Christian Herbst Jörg Leppert Oliver Ohlenschläger Matthias Görlach Ramadurai Ramachandran |
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Affiliation: | (1) Research group-Molecular Biophysics/NMR spectroscopy, Leibniz Institute for Age Research, Fritz Lipmann Institute, D-07745 Jena, Germany |
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Abstract: | 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 H1 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. |
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Keywords: | double-quantum spectroscopy inversion pulses MAS solid state NMR |
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