Hetero- and homonuclear backbone and sidechain correlations are essential for NMR assignments in multiply labeled peptides and proteins in the immobilized state. Correlations are usually retrieved from multi-dimensional ('H, 13C'I 'N) correlation experiments. We demonstrate that, alternatively, a small number of one-dimensional experiments employing selective and efficient heteronuclear polarization transfer can be used for backbone assignments. We also show how this approach can be extended for sidechain assignments using homonuclear through-bond, through space or proton-mediated transfer techniques. In particular, we investigate the polarization transfer dynamics in (NH, Cal Cp) subsystems of a tripeptide and compare our results to theoretical predictions in multi-spin systems. These experimental protocols can be employed at arbitrary MAS frequencies and are very forgiving with respect to the size of the applied r. f. fields.
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