Hawkes G E, Randall E W, Bradley C H
Nature. 1975 Oct 30;257(5529):767-72. doi: 10.1038/257767a0.
The low-abundance isotope of nitrogen, 15N, is now accessible to study by the latest high resolution nuclear magnetic resonance techniques. Structure and motion in polypeptides of moderate size may now be usefully investigated in this way.