Dipolar Waves as NMR maps of helices in proteins.

Dipolar Waves describe the periodic variation in the magnitudes of dipolar couplings in the backbone of a protein as a function of residue number. They provide a direct link between experimental measurements of dipolar couplings in aligned samples and the periodicity inherent in regular secondary structure elements. It is possible to identify the residues in a helix and the type of helix, deviations from ideality, and to orient the helices relative to an external axis in completely aligned samples and relative to each other in a common frame in weakly aligned samples with Dipolar Waves. They provide a tool for accurately describing helices and a step towards high throughput structure determination of proteins.