An open and shut case

A powerful new NMR technique applied to the ubiquitous Ca2+ sensor, calmodu lin, reveals significant conformational flexibility within each globular do main, which contributes to its ability to bind a wide range of targets. The se measurements of residual dipolar couplings between nuclear spins demonst rate a fast and accurate method for pinpointing structural features that ca nnot be delineated reliably by traditional NOE analysis.