A new sensitive isotropic-anisotropic separation experiment-SPEED MAS.
A new sensitive 2D isotropic-anisotropic separation experiment that utilizes stroboscopic phase encoding in the evolution dimension (SPEED) under magic angle sample spinning is presented. This 2D experiment consists of a train of 2N - 1 pi pulses that are applied over 2N rotor periods. The pi pulse train effectively reduces the apparent spinning speed in the evolution dimension by a factor of 1 / (2N) from the mechanical spinning speed. Thus, problems commonly associated with magic angle turning such as stable slow spinning, different matching and TPPM proton decoupling conditions are avoided. Data replication similar to the five pi replicated magic angle turning (FIREMAT) and pseudo 2D sideband suppression (P2DSS) experiments transfers resolution from the acquisition dimension to the evolution dimension. Hence, large spectral windows with good digital resolution are obtained with a few evolution increments. Here, slow spinning sideband patterns are extracted from the replicated 2D dataset with TIGER processing. Nevertheless, 2D Fourier transformation is also applicable. The extracted sideband patterns are identical to magic angle turning sideband pattern allowing for easy extraction of principal shift components. Accurate (13)C principal shift components are obtained for 3-methylglutaric acid using SPEED and FIREMAT experiments to validate the method. Furthermore, SPEED spectra for calcium acetate and alpha santonin are reported to show the wide applicability of this new experiment.
Strohmeier
Mark
M
Department of Chemistry, University of Utah, 315 S. 1400 E., Rm 2020, Salt Lake City, UT 84112-0850, USA.
Grant
David M
DM