Saturday, April 01, 2006

JMR, Tim Cross, PISEMA tensors

Journal of Magnetic Resonance
Volume 179, Issue 2 , April 2006, Pages 190-198

Intensity and mosaic spread analysis from PISEMA tensors in solid-state NMR

J.R. Quine, S. Achuthan, T. Asbury, R. Bertram, M.S. Chapmanc, J. Hue and T.A. Cross


The solid-state NMR experiment PISEMA, is a technique for determining structures of proteins, especially membrane proteins, from oriented samples. One method for determining the structure is to find orientations of local molecular frames (peptide planes) with respect to the unit magnetic field direction, B0. This is done using equations that compute the coordinates of this vector in the frames. This requires an analysis of the PISEMA function and its degeneracies. As a measure of the sensitivity of peptide plane orientations to the data, we use these equations to derive a formula for the intensity function in the powder pattern. With this function and other measures, we investigate the effect of small changes in peptide plane orientations depending on the location of the resonances in the powder pattern spectrum. This gives us an indication of the change in lineshape due to mosaic spread and a way to interpret these in terms of an orientational error bar.

Keywords: PISEMA tensors; Solid-state NMR; Powder pattern intensity; Mosaic spread; Lineshapes

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