Magic angle sample spinning in inhomogeneously broadened biological systems

Recent advances in magic angle sample spinning experiments now permit observation of dilute spin high resolution n.m.r. spectra of arbitrary powder samples. In the 'slow-spinning' régime, for which the spinning rate is less than the size of the interaction that is being averaged, the spectra exhibit rotational side bands whose intensities contain information on chemical shift anisotropies. A technique for extracting shift anisotropies from side band intensities is discussed. Since many biologically interesting systems are solid or semi-solid in nature, this technique should find wide application to biological systems. Two illustrations of the point are given in this paper, namely, n.m.r. studies of membranes and of the phosphate-containing phases of bone.