Fig. 4.

Site-specific ¹H^N total linewidth Δ^tot as well as its homogeneous component Δ^homo in fully protonated ubiquitin at 126 kHz MAS (a) within a confidence interval of 95% as determined by a Monte-Carlo based error analysis (Sawilowsky and Fahoome 2003). Δ^homo was obtained from site-specific R₂′ relaxation rate constants measured in a series of 2D experiments with different echo delay times where the coherence decay was subsequently fitted to a mono-exponential decay using FitTrace of INFOS (Smith 2017). In addition to the median given in the figure, the mean value of Δ^homo is 100 ± 28 Hz. The Δ^tot was obtained by fitting the 2D spectrum (processed without apodization or window function) using the fitting program INFOS (Smith 2017). In (b) the inhomogeneous contribution Δ^inhomo = Δ^tot − Δ^homo is shown. Secondary structural elements for ubiquitin are displayed at the top and are indicated by grey areas