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Abstract:
Using a recently-built very high speed MAS probe capable of spinning at rates of at least 20 kHz, we have shown that it is possible to obtain 1H signals with line widths in the range of 25-30 Hz, an improvement of three orders of magnitude. To establish that it is possible to obtain distance restraints between nuclei, we have
performed 1D nuclear Overhauser effect (NOE) experiments on gramicidin A. The build-up curves for these NOEs clearly show that one can obtain the same sort of distance restraints for peptides in membrane bilayers as are obtained in well established
solution NMR studies. This is a crucial step in demonstrating that high
resolution solution NMR techniques can be applied to structure determination in membrane systems. Extending this to two dimensions, we have performed a series of 2D-NOESY experiments which establish unambiguously that gramicidin A adopts the same conformation in muitilamellar dispersions as that reported in SDS micelles by Arseniev et al. [Biol. Membr. (1986) 3(5), 437-462]. The 1H MAS
NMR technique that we have developed is therefore potentially capable of determining the complete 3D structure of a membrane spanning peptide.