Backbone dynamics in collagen

Peptide backbone motions of collagen have been extensively studied in the past. The experimental results were interpreted using a model of a collagen rod librating about its helix axis. Considering the size of the collagen molecule and the presence of cross-linked molecules, motional amplitudes derived for the helix axis libration were unusually high. Using solid-state NMR 13C chemical shift anisotropy and 2H quadrupolar lineshape analysis for five different isotope labelled collagens we show that motional averaging of the NMR interactions occurs primarily via small-angle librations about internal bond directions. This type of dynamics is compatible with both the presence of cross-links in collagen and the X-ray data, as well as dynamic models used for other proteins.