High-sensitivity sapphire cells for high pressure NMR spectroscopy on proteins.

High pressure NMR spectroscopy is a most exciting method for studying the structural anisotropy and conformational dynamics of proteins. The restricted volume of the high pressure glass cells causes a poor signal to noise ratio which up to now renders the application of most of the multidimensional NMR experiments impossible. The method presented here using high strength single crystal sapphire cells doubles the signal-to-noise ratio and allows to perform high pressure NMR measurements more easily. As a first application the difference of partial molar volumes caused by cis-trans-isomerisation of a prolyl peptide bond in the tetrapeptide Gly-Gly-Pro-Ala could be determined as 0.25 ml mol(-1) at 305 K.